Forest fires in Pennsylvania.

Treesearch

Donald A. Haines; William A. Main; Eugene F. McNamara

1978-01-01

Describes factors that contribute to forest fires in Pennsylvania. Includes an analysis of basic statistics; distribution of fires during normal, drought, and wet years; fire cause, fire activity by day-of-week; multiple-fire day; and fire climatology.

Fire suppression has led to greater drought-sensitivity in dry conifer forests: tree-ring carbon isotope evidence from Central Oregon

NASA Astrophysics Data System (ADS)

Voelker, S.; Merschel, A. G.; Meinzer, F. C.; Spies, T. A.; Still, C. J.

2016-12-01

Mortality events of economically and ecologically important conifers have been widespread across Western North America over recent decades. Many of these events have been linked to "global change-type droughts" characterized by greater temperatures and evaporative demand. In parallel, since the early to mid- 20th century, increasing atmospheric [CO2] has been shown to increase the water use efficiency (WUE) of trees worldwide while conifer forests in western North America have become denser after the advent of modern fire suppression efforts. Therefore, competing hypotheses include that conifer forests have experienced 1) less drought stress due to water savings from increased WUE, 2) more drought stress due to increased demand for water in dense forests with greater leaf area index, or 3) unchanging stress because these two factors have cancelled each other out. To provide a test of these hypotheses we used inter-annual latewood carbon isotope discrimination, Δ13C, across a dry mixed-conifer forest landscape of central Oregon in the rain shadow of the Cascade Mountains. The forests are dominated by old-growth ponderosa pines (Pinus ponderosa) and younger and fire-intolerant grand firs (Abies grandis). Dendrochronological dating of tree establishment and fires scars established sharp declines in fire frequency and associated increases in the densities of grand fir since the early 1900s. Δ13C data for ponderosa pine and grand fir spanned 1830-2013 and 1900-2013, respectively. For our analyses these years were split into periods of high fire frequency (1830-1900), moderate fire frequency (1901-1956) and fire-exclusion (1957-2013). Comparisons of Δ13C to reconstructed Palmer Drought Severity Index values for the same years revealed that leaf gas exchange of both species has been more sensitive to drought during the recent fire-exclusion period compared to previous periods when surface fires kept tree densities much lower. Similar research is needed elsewhere to provide additional tests. However, this initial evidence suggests that despite CO2-driven increases in WUE, conifer forests in western North America have experienced greater drought stress and been made more susceptible to mortality events due to progressive increases in tree densities and competition for water over the past century.

Abrupt Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions

NASA Technical Reports Server (NTRS)

Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.;

Abrupt increases in Amazonian tree mortality due to drought-fire interactions.

PubMed

Brando, Paulo Monteiro; Balch, Jennifer K; Nepstad, Daniel C; Morton, Douglas C; Putz, Francis E; Coe, Michael T; Silvério, Divino; Macedo, Marcia N; Davidson, Eric A; Nóbrega, Caroline C; Alencar, Ane; Soares-Filho, Britaldo S

2014-04-29

Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

Is Managed Wildfire Protecting Yosemite National Park from Drought?

NASA Astrophysics Data System (ADS)

Boisrame, G. F. S.; Thompson, S. E.; Stephens, S.; Collins, B.; Kelly, M.; Tague, N.

2016-12-01

Fire suppression in many dry forest types has left a legacy of dense, homogeneous forests. Such landscapes have high water demands and fuel loads, and when burned can result in catastrophically large fires. These characteristics are undesirable in the face of projected warming and drying in the Western US. This project explores the potential of managed wildfire - a forest management strategy in which fires caused by lightning are allowed to burn naturally as long as certain safety parameters are met - to reverse the effects of fire suppression. The Illilouette Creek Basin in Yosemite National Park has experienced 40 years of managed wildfire, reducing forest cover and increasing meadow and shrubland areas. We have collected evidence from field measurements and remote sensing which suggest that managed wildfire increases landscape and hydrologic heterogeneity, and likely improves resilience to disturbances such as fire and drought. Vegetation maps created from aerial photos show an increase in landscape heterogeneity following the introduction of managed wildfire. Soil moisture observations during the drought years of 2013-2016 suggest that transitions from dense forest to shrublands or meadows can increase summer soil moisture. In the winter of 2015-2016, snow depth measurements showed deeper spring snowpacks in burned areas compared to dense forests. Our study provides a unique view of relatively long-term effects of managed wildfire on vegetation change, ecohydrology, and drought resistance. Understanding these effects is increasingly important as the use of managed wildfire becomes more widely accepted, and as the likelihood of both drought and wildfire increases.

Compounding nonlinearities in the climate and wildfire system contribute to high uncertainty in estimates of future burned area in the western United State

NASA Astrophysics Data System (ADS)

Williams, P.

2015-12-01

Ecological studies are increasingly recognizing the importance of atmospheric vapor-pressure deficit (VPD) as a driver of forest drought stress and disturbance processes such as wildfire. Because of the nonlinear Clausius-Clapeyron relationship between temperature and saturation vapor pressure, small variations in temperature can have large impacts on VPD, and therefore drought, particularly in warm, dry areas and particularly during the warm season. It is also clear that VPD and drought affect forest fire nonlinearly, as incremental drying leads to increasingly large burned areas. Forest fire is also affected by fuel amount and connectivity, which are promoted by vegetation growth in previous years, which is in turn promoted by lack of drought, highlighting the importance of nuances in the sequencing of natural interannual climate variations in modulating the impacts of drought on wildfire. The many factors affecting forest fire, and the nonlinearities embedded within the climate and wildfire systems, cause interannual variability in forest-fire area and frequency to be wildly variable and strongly affected by internal climate variability. In addition, warming over the past century has produced a background increase in forest fire frequency and area in many regions. In this talk I focus on the western United States and will explore whether the relationships between internal climate variability on forest fire area have been amplified by the effects of warming as a result of the compounding nonlinearities described above. I will then explore what this means for future burned area in the western United States and make the case that uncertainties in the future global greenhouse gas emissions trajectory, model projections of mean temperatures, model projections of precipitation, and model projections of natural climate variability translate to very large uncertainties in the effects of future climate variability on forest fire area in the United States and globally.

An Evaluation of Historical Fire Occurrence, Drought and the El Niño Southern Oscillation in the Southcentral United States

NASA Astrophysics Data System (ADS)

Rooney, M.; Stambaugh, M. C.

2016-12-01

Wildfire occurrence in the forested ecosystems of the southcentral United States is driven by conditions of drought. Historically, fire intervals varied temporally and spatially - forced by climate, humans, and environmental conditions. Thus, proxy records are required to assess the relationships between fire occurrence, drought, and the El Niño Southern Oscillation (ENSO). Fire scar data from tree-rings are well-suited to assess historical fire regimes in this region, paired with reconstructions of drought and ENSO that have been developed from networks of ring-width chronologies across the United States. This study combines fire-scar data from twelve different sites in the southcentral United States, including two new fire-history reconstructions. Fire data incorporates 665 fires across Eastern Oklahoma and Northern Texas from 1637-2014. These robust reconstructions of post oak (Quercus stellata) evaluate the variability in fire activity and its association to drought and ENSO. Climate-explained growth variance in post-oak chronologies is strong in this region, providing powerful proxy information in the derived chronologies. In general, most fires occur during the La Niña portion of the ENSO cycle. Many severe fires correspond with drought, and results from super-posed epoch analysis suggest a significant relationship between fire event years and drought conditions in the full period of record. Analysis reveals differences in the relationships of fire, drought and ENSO through time, corresponding to changes in human settlement in the region. Understanding the spatial and temporal relationships that exist between fire occurrence, drought, and ENSO aid in quantifying disturbance characteristics and their associations to climate in the forested ecosystems of the southcentral United States.

Fire, climate and vegetation linkages in the Bolivian Chiquitano seasonally dry tropical forest.

PubMed

Power, M J; Whitney, B S; Mayle, F E; Neves, D M; de Boer, E J; Maclean, K S

2016-06-05

South American seasonally dry tropical forests (SDTFs) are critically endangered, with only a small proportion of their original distribution remaining. This paper presents a 12 000 year reconstruction of climate change, fire and vegetation dynamics in the Bolivian Chiquitano SDTF, based upon pollen and charcoal analysis, to examine the resilience of this ecosystem to drought and fire. Our analysis demonstrates a complex relationship between climate, fire and floristic composition over multi-millennial time scales, and reveals that moisture variability is the dominant control upon community turnover in this ecosystem. Maximum drought during the Early Holocene, consistent with regional drought reconstructions, correlates with a period of significant fire activity between 8000 and 7000 cal yr BP which resulted in a decrease in SDTF diversity. As fire activity declined but severe regional droughts persisted through the Middle Holocene, SDTFs, including Anadenanthera and Astronium, became firmly established in the Bolivian lowlands. The trend of decreasing fire activity during the last two millennia promotes the idea among forest ecologists that SDTFs are threatened by fire. Our analysis shows that the Chiquitano seasonally dry biome has been more resilient to Holocene changes in climate and fire regime than previously assumed, but raises questions over whether this resilience will continue in the future under increased temperatures and drought coupled with a higher frequency anthropogenic fire regime.This article is part of the themed issue 'The interaction of fire and mankind'. © 2016 The Author(s).

Fire, climate and vegetation linkages in the Bolivian Chiquitano seasonally dry tropical forest

PubMed Central

Power, M. J.; Whitney, B. S.; Mayle, F. E.; Neves, D. M.; de Boer, E. J.; Maclean, K. S.

2016-01-01

South American seasonally dry tropical forests (SDTFs) are critically endangered, with only a small proportion of their original distribution remaining. This paper presents a 12 000 year reconstruction of climate change, fire and vegetation dynamics in the Bolivian Chiquitano SDTF, based upon pollen and charcoal analysis, to examine the resilience of this ecosystem to drought and fire. Our analysis demonstrates a complex relationship between climate, fire and floristic composition over multi-millennial time scales, and reveals that moisture variability is the dominant control upon community turnover in this ecosystem. Maximum drought during the Early Holocene, consistent with regional drought reconstructions, correlates with a period of significant fire activity between 8000 and 7000 cal yr BP which resulted in a decrease in SDTF diversity. As fire activity declined but severe regional droughts persisted through the Middle Holocene, SDTFs, including Anadenanthera and Astronium, became firmly established in the Bolivian lowlands. The trend of decreasing fire activity during the last two millennia promotes the idea among forest ecologists that SDTFs are threatened by fire. Our analysis shows that the Chiquitano seasonally dry biome has been more resilient to Holocene changes in climate and fire regime than previously assumed, but raises questions over whether this resilience will continue in the future under increased temperatures and drought coupled with a higher frequency anthropogenic fire regime. This article is part of the themed issue ‘The interaction of fire and mankind’. PMID:27216522

Measuring and modeling carbon balance in mountainous Northern Rocky mixed conifer forests

NASA Astrophysics Data System (ADS)

Hudiburg, T. W.; Berardi, D.; Stenzel, J.

2016-12-01

Drought and wildfire caused by changing precipitation patterns, increased temperatures, increased fuel loads, and decades of fire suppression are reducing forest carbon uptake from local to continental scales. This trend is especially widespread in Idaho and the intermountain west and has important implications for climate change and forest management options. Given the key role of forests in climate regulation, understanding forest response to drought and the feedbacks to the atmosphere is a key research and policy-relevant priority globally. As temperature, fire, and precipitation regimes continue to change and there is increased risk of forest mortality, measurements and modeling at temporal and spatial scales that are conducive to understanding the impacts and underlying mechanisms of carbon and nutrient cycling become critically important. Until recently, sub-daily measurements of ecosystem carbon balance have been limited in remote, mountainous terrain (e.g Northern Rocky mountain forests). Here, we combine new measurement technology and state-of-the-art ecosystem modeling to determine the impact of drought on the total carbon balance of a mature, mixed-conifer forest in Northern Idaho. Our findings indicate that drought had no impact on aboveground NPP, despite early growing season reductions in soil moisture and fine root biomass compared to non-drought years in the past. Modeled estimates of net ecosystem production (NEP) suggest that a simultaneous reduction in heterotrophic respiration increased the carbon sink for this forest. This has important implications for forest management, such as thinning where the objectives are to increase forest resilience to fire and drought, but may decrease NEP.

Forest health in the Blue Mountains: a management strategy for fire-adapted ecosystems.

Treesearch

R.W. Mutch; S.F. Arno; J.K. Brown; C.E. Carlson; R.D. Ottmar; J.L. Peterson

1993-01-01

The fire-adapted forests of the Blue Mountains are suffering from a forest health problem of catastrophic proportions. Contributing to the decline of forest health are such factors as the extensive harvesting of the western larch and ponderosa pine overstory during the 1900s, attempted exclusion of fire from a fire-dependent ecosystem, and the continuing drought. The...

Forest biogeochemistry in response to drought.

PubMed

Schlesinger, William H; Dietze, Michael C; Jackson, Robert B; Phillips, Richard P; Rhoades, Charles C; Rustad, Lindsey E; Vose, James M

2016-07-01

Trees alter their use and allocation of nutrients in response to drought, and changes in soil nutrient cycling and trace gas flux (N2 O and CH4 ) are observed when experimental drought is imposed on forests. In extreme droughts, trees are increasingly susceptible to attack by pests and pathogens, which can lead to major changes in nutrient flux to the soil. Extreme droughts often lead to more common and more intense forest fires, causing dramatic changes in the nutrient storage and loss from forest ecosystems. Changes in the future manifestation of drought will affect carbon uptake and storage in forests, leading to feedbacks to the Earth's climate system. We must improve the recognition of drought in nature, our ability to manage our forests in the face of drought, and the parameterization of drought in earth system models for improved predictions of carbon uptake and storage in the world's forests. © 2015 John Wiley & Sons Ltd.

A Drought Index for Forest Fire Control

Treesearch

John J. Keetch; George M. Byram

1968-01-01

The moisture content of the upper soil, as well as that of the covering layer of duff, has an important effect on the fire suppression effort in forest and wildland areas. In certain forested areas of the United States, fires in deep duff fuels are of particular concern to the fire control manager. When these fuels are dry, fires burn deeply, dam-age is excessive, and...

Abrupt increases in Amazonian tree mortality due to drought–fire interactions

PubMed Central

Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silvério, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nóbrega, Caroline C.; Alencar, Ane; Soares-Filho, Britaldo S.

2014-01-01

Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW⋅m−1). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change. PMID:24733937

Thinning, tree-growth, and resistance to multi-year drought in a mixed-conifer forest of northern California

USGS Publications Warehouse

Vernon, Michael J.; Sherriff, Rosemary L.; van Mantgem, Phillip; Kane, Jeffrey M.

2018-01-01

Drought is an important stressor in forest ecosystems that can influence tree vigor and survival. In the U.S., forest managers use two primary management techniques to promote resistance and resilience to drought: prescribed fire and mechanical thinning. Generally applied to reduce fuels and fire hazard, treatments may also reduce competition for resources that may improve tree-growth and reduce mortality during drought. A recent severe and prolonged drought in California provided a natural experiment to investigate tree-growth responses to fuel treatments and climatic stress. We assessed tree-growth from 299 ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) in treated and untreated stands during severe drought from 2012 to 2015 in the mixed-conifer forests of Whiskeytown National Recreation Area (WNRA) in northern California. The treatment implemented at WNRA removed 34% of live basal area through mechanical thinning with a subsequent pile burning of residual fuels. Tree-growth was positively associated with crown ratio and negatively associated with competition and a 1-year lag of climate water deficit, an index of drought. Douglas-fir generally had higher annual growth than ponderosa pine, although factors affecting growth were the same for both species. Drought resistance, expressed as the ratio between mean growth during drought and mean growth pre-drought, was higher in treated stands compared to untreated stands during both years of severe drought (2014 and 2015) for ponderosa pine but only one year (2014) for Douglas-fir. Thinning improved drought resistance, but tree size, competition and species influenced this response. On-going thinning treatments focused on fuels and fire hazard reduction are likely to be effective at promoting growth and greater drought resistance in dry mixed-conifer forests. Given the likelihood of future droughts, land managers may choose to implement similar treatments to reduce potential impacts.

Managing Fire Risk During Drought: The Influence of Certification and El Nino on Fire-Driven Forest Conversion for Oil Palm in Southeast Asia

NASA Technical Reports Server (NTRS)

Noojipady, Praveen; Morton, Douglas C.; Schroeder, Wilfrid; Carlson, Kimberly M.; Huang, Chengquan; Gibbs, Holly K.; Burns, David; Walker, Nathalie F.; Prince, Stephen D.

2017-01-01

Indonesia and Malaysia have emerged as leading producers of palm oil in the past several decades, expanding production through the conversion of tropical forests to industrial plantations. Efforts to produce "sustainable" palm oil, including certification by the Roundtable on Sustainable Palm Oil (RSPO), include guidelines designed to reduce the environmental impact of palm oil production. Fire-driven deforestation is prohibited by law in both countries and a stipulation of RSPO certification, yet the degree of environmental compliance isunclear, especially during El Niño events when drought conditions increase fire risk. Here, we used time series of satellite data to estimate the spatial and temporal patterns of fire-driven deforestation on and around oil palm plantations. In Indonesia, fire-driven deforestation accounted for one-quarter of total forest losses on both certified and noncertified plantations. After the first plantations in Indonesia received RSPO certification in 2009,forest loss and fire-driven deforestation declined on certified plantations but did not stop altogether. Oil palm expansion in Malaysia rarely involved fire; only 5 % of forest loss on certified plantations had coincident activefire detections. Interannual variability in fire detections was strongly influenced by El Nino and the timing of certification. Fire activity during the 2002, 2004, and 2006 El Nino events was similar among oil palm plantations in Indonesia that would later become certified, noncertified plantations, and surrounding areas. However, total fire activity was 75% and 66% lower on certified plantations than noncertified plantations during the 2009 and 2015 El Nino events, respectively. The decline in fire activity on certified plantations, including during drought periods, highlights the potential for RSPO certification to safeguard carbon stocks in peatlands and remaining forests in accordance with legislation banning fires. However, aligning certification standards with satellite monitoring capabilities will be critical to realize sustainable palm oil production and meet industry commitments to zero forestation.

Temperate forest health in an era of emerging megadisturbance

Treesearch

C. I. Millar; N. L. Stephenson

2015-01-01

Although disturbances such as fire and native insects can contribute to natural dynamics of forest health, exceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability. Interactions from increasing temperatures, drought, native insects and pathogens, and uncharacteristically...

Managing fire risk during drought: the influence of certification and El Niño on fire-driven forest conversion for oil palm in Southeast Asia

NASA Astrophysics Data System (ADS)

Noojipady, Praveen; Morton, Douglas C.; Schroeder, Wilfrid; Carlson, Kimberly M.; Huang, Chengquan; Gibbs, Holly K.; Burns, David; Walker, Nathalie F.; Prince, Stephen D.

2017-08-01

Indonesia and Malaysia have emerged as leading producers of palm oil in the past several decades, expanding production through the conversion of tropical forests to industrial plantations. Efforts to produce sustainable palm oil, including certification by the Roundtable on Sustainable Palm Oil (RSPO), include guidelines designed to reduce the environmental impact of palm oil production. Fire-driven deforestation is prohibited by law in both countries and a stipulation of RSPO certification, yet the degree of environmental compliance is unclear, especially during El Niño events when drought conditions increase fire risk. Here, we used time series of satellite data to estimate the spatial and temporal patterns of fire-driven deforestation on and around oil palm plantations. In Indonesia, fire-driven deforestation accounted for one-quarter of total forest losses on both certified and noncertified plantations. After the first plantations in Indonesia received RSPO certification in 2009, forest loss and fire-driven deforestation declined on certified plantations but did not stop altogether. Oil palm expansion in Malaysia rarely involved fire; only 5 % of forest loss on certified plantations had coincident active fire detections. Interannual variability in fire detections was strongly influenced by El Niño and the timing of certification. Fire activity during the 2002, 2004, and 2006 El Niño events was similar among oil palm plantations in Indonesia that would later become certified, noncertified plantations, and surrounding areas. However, total fire activity was 75 % and 66 % lower on certified plantations than noncertified plantations during the 2009 and 2015 El Niño events, respectively. The decline in fire activity on certified plantations, including during drought periods, highlights the potential for RSPO certification to safeguard carbon stocks in peatlands and remaining forests in accordance with legislation banning fires. However, aligning certification standards with satellite monitoring capabilities will be critical to realize sustainable palm oil production and meet industry commitments to zero deforestation.

Bending the carbon curve: fire management for carbon resilience under climate change

Treesearch

E. L. Loudermilk; R. M. Scheller; P. J. Weisberg; Alec Kretchun

2017-01-01

Forest landscapes are increasingly managed for fire resilience, particularly in the western US which has recently experienced drought and widespread, high-severity wildfires. Fuel reduction treatments have been effective where fires coincide with treated areas. Fuel treatments also have the potential to reduce drought-mortality if tree density is...

Working forests, forest health and management challenges in the redwood region

Treesearch

Ken Pimlott

2017-01-01

As California continues into a fifth year of drought, tree mortality enhanced by the unprecedented bark beetle epidemic contributes to wildfires that continue to increase in frequency and severity. Recent fires have posed increasing fire suppression challenges, life safety concerns, post fire watershed impacts and lasting damage to forested landscapes. The ability of...

Modeling Forest Understory Fires in an Eastern Amazonian Landscape

NASA Technical Reports Server (NTRS)

Alencar, A. A. C.; Solorzano, L. A.; Nepstad, D. C.

2004-01-01

Forest understory fires are an increasingly important cause of forest impoverishment in Ammonia, but little is known of the landscape characteristics and climatic phenomena that determine their occurrence. We developed empirical functions relating the occurrence of understory fires to landscape features near Paragominas, a 35- yr-old ranching and logging center in eastern Ammonia. An historical sequence of maps of forest understory fire was created based on field interviews With local farmers and Landsat TM images. Several landscape features that might explain spatial variations in the occurrence of understory fires were also mapped and co-registered for each of the sample dates, including: forest fragment size and shape, forest impoverishment through logging and understory fires, source of ignition (settlements and charcoal pits), roads, forest edges, and others. The spatial relationship between forest understory fire and each landscape characteristic was tested by regression analyses. Fire probability models were then developed for various combinations of landscape characteristics. The analyses were conducted separately for years of the El Nino Southern Oscillation (ENSO), which are associated with severe drought in eastern Amazonia, and non-ENS0 years. Most (91 %) of the forest area that burned during the 10-yr sequence caught fire during ENSO years, when severe drought may have increased both forest flammability and the escape of agricultural management fires. Forest understory fires were associated with forest edges, as reported in previous studies from Ammonia. But the strongest predictor of forest fire was the percentage of the forest fragment that had been previously logged or burned. Forest fragment size, distance to charcoal pits, distance to agricultural settlement, proximity to forest edge, and distance to roads were also correlated with forest understory fire. Logistic regression models using information on fragment degradation and distance to ignition sources accurately predicted the location of lss than 80% of the forest fires observed during the ENSO event of 1997- 1998. In this Amazon landscape, forest understory fire is a complex function of several variables that influence both the flammability and ignition exposure of the forest.

The influences of drought and humans on the fire regimes of northern Pennsylvania, USA

Treesearch

Patrick H. Brose; Daniel C. Dey; Richard P. Guyette; Joseph M. Marschall; Michael C. Stambaugh

2013-01-01

Understanding past fire regimes is necessary to justify and implement restoration of disturbance-associated forests via prescribed fire programs. In eastern North America, the characteristics of many presettlement fire regimes are unclear because of the passage of time. To help clarify this situation, we developed a 435-year fire history for the former conifer forests...

The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States

Treesearch

James S. Clark; Louis Iverson; Christopher W. Woodall; Craig D. Allen; David M. Bell; Don C. Bragg; Anthony W. D' Amato; Frank W. Davis; Michelle H. Hersh; Ines Ibanez; Stephen T. Jackson; Stephen Matthews; Neil Pederson; Matthew Peters; Mark W. Schwartz; Kristen M. Waring; Niklaus E. Zimmermann

2016-01-01

We synthesize insights from current understanding of drought impacts at stand-to-biogeographic scales, including management options, and we identify challenges to be addressed with new research. Large stand-level shifts underway in western forests already are showing the importance of interactions involving drought, insects, and fire. Diebacks, changes in composition...

A perfect storm: multiple stressors interact to drive postfire regeneration failure of lodgepole pine and Douglas-fir forests in Yellowstone

NASA Astrophysics Data System (ADS)

Hansen, W. D.; Braziunas, K. H.; Rammer, W.; Seidl, R.; Turner, M. G.

2017-12-01

Twenty-first century forests will experience increased stress as environmental conditions and disturbance regimes change. Whether forests retain their structure or transitions to alternate states, particularly when affected by multiple stressors, remains unresolved. Subalpine forests in Yellowstone National Park, WY experience large severe wildfires, and postfire-tree regeneration is necessary to assure resilience. Drying is projected, causing frequent larger wildfires that could reduce seed supply and drought that could constrain postfire-seedling establishment. We asked what combinations of warming-drying conditions, increased fire frequency, and increased burned-patch size cause postfire tree-regeneration failure in Yellowstone? We conducted a simulation experiment to identify combinations of fire frequency, fire size, postfire climate, substrate type, and elevation where lodgepole-pine and Douglas-fir regeneration failed. We expected postfire densities to be reduced if burned-patch sizes exceeded effective dispersal distance, sequential fires burned before trees reached reproductive maturity, or drought occurred after fire. We also expected regeneration failure only where multiple stressors occurred simultaneously at low elevation or on poor substrates.Douglas-fir stands were most vulnerable to regeneration failure. 98% of simulated Douglas-fir stands located in the middle of large burned patches failed to regenerate 30 years post fire. Lodgepole-pine stands in the middle of large burned patches failed to regenerate if they were also located at low elevations (93%) or at higher elevations on soils with poor water retention (73%). Stands of serotinous lodgepole (i.e., trees with closed cones that open when heated) also failed to regenerate if fire recurred before trees were reproductively mature (82%). Drought constrained postfire regeneration, yet, enhanced establishment due to release from cold-temperatures during mid-to-late 21st century often outweighed drought effects. Postfire tree regeneration arises from the interplay between multiple factors; some constraining establishment and others enhancing it. To understand 21st-century climate and fire effects on postfire tree regeneration and forest resilience, a reductionist approach is insufficient.

North Carolina's Emerging Forest Threats: Management Options for Healthy Forests

Treesearch

Lisa Jennings; Emrys Treasure; Jennifer Moore Myers; Steve McNulty; Sean Brogan; David Jones

2012-01-01

Forest landowners are seeing increased pressure from threats like fire, insects, disease, extreme weather, and drought on their land and resources. The last decade has brought record droughts to North Carolina, increasing wildfires, expanding insect and plant invasions, and more intense hurricane and tornado events. Scientists predict increases in temperature and...

Landscape fragmentation, severe drought, and the new Amazon forest fire regime.

PubMed

Alencar, Ane A; Brando, Paulo M; Asner, Gregory P; Putz, Francis E

2015-09-01

Changes in weather and land use are transforming the spatial and temporal characteristics of fire regimes in Amazonia, with important effects on the functioning of dense (i.e., closed-canopy), open-canopy, and transitional forests across the Basin. To quantify, document, and describe the characteristics and recent changes in forest fire regimes, we sampled 6 million ha of these three representative forests of the eastern and southern edges of the Amazon using 24 years (1983-2007) of satellite-derived annual forest fire scar maps and 16 years of monthly hot pixel information (1992-2007). Our results reveal that changes in forest fire regime properties differentially affected these three forest types in terms of area burned and fire scar size, frequency, and seasonality. During the study period, forest fires burned 15% (0.3 million ha), 44% (1 million ha), and 46% (0.6 million ha) of dense, open, and transitional forests, respectively. Total forest area burned and fire scar size tended to increase over time (even in years of average rainfall in open canopy and transitional forests). In dense forests, most of the temporal variability in fire regime properties was linked to El Nino Southern Oscillation (ENSO)-related droughts. Compared with dense forests, transitional and open forests experienced fires twice as frequently, with at least 20% of these forests' areas burning two or more times during the 24-year study period. Open and transitional forests also experienced higher deforestation rates than dense forests. During drier years, the end of the dry season was delayed by about a month, which resulted in larger burn scars and increases in overall area burned later in the season. These observations suggest that climate-mediated forest flammability is enhanced by landscape fragmentation caused by deforestation, as observed for open and transitional forests in the Eastern portion of the Amazon Basin.

A Mega-fire event in Central Russia: fire weather, radiative, and optical properties of the atmosphere, and consequences for subboreal forest plants

Treesearch

Nataly Y. Chubarova; Nickolay G. Prilepsky; Alexei N. Rublev; Allen R. Riebau

2009-01-01

In 2002, a major drought and prolonged high temperatures occurred in central Russia that resulted in unprecedented wildland fires. These fires occurred under extreme fire danger conditions and were impossible for the Russian authorities to extinguish. It is perhaps somewhat unique that the fires were first burning peat bogs and later forests, causing very massive smoke...

Topographic variation in structure of mixed-conifer forests under an active-fire regime

Treesearch

Jamie Lydersen; Malcolm North

2012-01-01

Management efforts to promote forest resiliency as climate changes have often used historical forest conditions to provide general guidance for fuels reduction and forest restoration treatments. However, it has been difficult to identify what stand conditions might be fire and drought resilient because historical data and reconstruction studies are generally limited to...

Simulated Net Ecosystem Carbon Balance of Western US Forests Under Contemporary Climate and Management

NASA Astrophysics Data System (ADS)

Yang, Z.; Law, B. E.; Jones, M. O.

2015-12-01

Previous projections of the contemporary forest carbon balance in the western US showed uncertainties associated with impacts of climate extremes and a coarse spatio-temporal resolution implemented over heterogeneous mountain regions. We modified the Community Land Model (CLM) 4.5 to produce 4km resolution forest carbon changes with drought, fire and management in the western US. We parameterized the model with species data using local plant trait observations for 30 species. To quantify uncertainty, we evaluated the model with data from flux sites, inventories and ancillary data in the region. Simulated GPP was lower than the measurements at our AmeriFlux sites by 17-22%. Simulated burned area was generally higher than Landsat observations, suggesting the model overestimates fire emissions with the new fire model. Landsat MTBS data show high severity fire represents only a small portion of the total burnt area (12-14%), and no increasing trend from 1984 to 2011. Moderate severity fire increased ~0.23%/year due to fires in the Sierra Nevada (Law & Waring 2014). Oregon, California, and Washington were a net carbon sink, and net ecosystem carbon balance (NECB) declined in California over the past 15 years, partly due to drought impacts. Fire emissions were a small portion of the regional carbon budget compared with the effect of harvest removals. Fossil fuel emissions in CA are more than 3x that of OR and WA combined, but are lower per capita. We also identified forest regions that are most vulnerable to climate-driven transformations and to evaluate the effects of management strategies on forest NECB. Differences in forest NECB among states are strongly influenced by the extent of drought (drier longer in the SW) and management intensity (higher in the PNW).

A new forest fire paradigm: The need for high-severity fires

Treesearch

Monica L. Bond; Rodney B. Siegel; Richard L. Hutto; Victoria A. Saab; Stephen A. Shunk

2012-01-01

Bond, Monica L.; Siegel, Rodney B.; Hutto, Richard L.; Saab, Victoria A.; Shunk, Stephen A. 2012. A new forest fire paradigm: The need for high-severity fires. The Wildlife Professional. Winter 2012: 46-49. During the 2012 fire season from June through August, wildfires in the drought-stricken western and central United States burned more than 3.6 million acres of...

Are Northeastern U.S. forests vulnerable to extreme drought?

Treesearch

Adam P. Coble; Matthew A. Vadeboncoeur; Z. Carter Berry; Katie A. Jennings; Cameron D. McIntire; John L. Campbell; Lindsey E. Rustad; Pamela H. Templer; Heidi Asbjornsen

2017-01-01

In the Northeastern U.S., drought is expected to increase in frequency over the next century, and therefore, the responses of trees to drought are important to understand. There is recent debate about whether land-use change or moisture availability is the primary driver of changes in forest species composition in this region. Some argue that fire suppression from the...

Land cover change interacts with drought severity to change fire regimes in Western Amazonia.

PubMed

Gutiérrez-Vélez, Víctor H; Uriarte, María; DeFries, Ruth; Pinedo-Vásquez, Miguel; Fernandes, Katia; Ceccato, Pietro; Baethgen, Walter; Padoch, Christine

Fire is becoming a pervasive driver of environmental change in Amazonia and is expected to intensify, given projected reductions in precipitation and forest cover. Understanding of the influence of post-deforestation land cover change on fires in Amazonia is limited, even though fires in cleared lands constitute a threat for ecosystems, agriculture, and human health. We used MODIS satellite data to map burned areas annually between 2001 and 2010. We then combined these maps with land cover and climate information to understand the influence of land cover change in cleared lands and dry-season severity on fire occurrence and spread in a focus area in the Peruvian Amazon. Fire occurrence, quantified as the probability of burning of individual 232-m spatial resolution MODIS pixels, was modeled as a function of the area of land cover types within each pixel, drought severity, and distance to roads. Fire spread, quantified as the number of pixels burned in 3 × 3 pixel windows around each focal burned pixel, was modeled as a function of land cover configuration and area, dry-season severity, and distance to roads. We found that vegetation regrowth and oil palm expansion are significantly correlated with fire occurrence, but that the magnitude and sign of the correlation depend on drought severity, successional stage of regrowing vegetation, and oil palm age. Burning probability increased with the area of nondegraded pastures, fallow, and young oil palm and decreased with larger extents of degraded pastures, secondary forests, and adult oil palm plantations. Drought severity had the strongest influence on fire occurrence, overriding the effectiveness of secondary forests, but not of adult plantations, to reduce fire occurrence in severely dry years. Overall, irregular and scattered land cover patches reduced fire spread but irregular and dispersed fallows and secondary forests increased fire spread during dry years. Results underscore the importance of land cover management for reducing fire proliferation in this landscape. Incentives for promoting natural regeneration and perennial crops in cleared lands might help to reduce fire risk if those areas are protected against burning in early stages of development and during severely dry years.

Rapid increase in log populations in drought-stressed mixed-conifer and ponderosa pine forests in northern Arizona

Treesearch

Joseph L. Ganey; Scott C. Vojta

2012-01-01

Down logs provide important ecosystem services in forests and affect surface fuel loads and fire behavior. Amounts and kinds of logs are influenced by factors such as forest type, disturbance regime, forest man-agement, and climate. To quantify potential short-term changes in log populations during a recent global- climate-change type drought, we sampled logs in mixed-...

Forest fire danger index based on modifying Nesterov Index, fuel, and anthropogenic activities using MODIS TERRA, AQUA and TRMM satellite datasets

NASA Astrophysics Data System (ADS)

Suresh Babu, K. V.; Roy, Arijit; Ramachandra Prasad, P.

2016-05-01

Forest fire has been regarded as one of the major causes of degradation of Himalayan forests in Uttarakhand. Forest fires occur annually in more than 50% of forests in Uttarakhand state, mostly due to anthropogenic activities and spreads due to moisture conditions and type of forest fuels. Empirical drought indices such as Keetch-Byram drought index, the Nesterov index, Modified Nesterov index, the Zhdanko index which belongs to the cumulative type and the Angstrom Index which belongs to the daily type have been used throughout the world to assess the potential fire danger. In this study, the forest fire danger index has been developed from slightly modified Nesterov index, fuel and anthropogenic activities. Datasets such as MODIS TERRA Land Surface Temperature and emissivity (MOD11A1), MODIS AQUA Atmospheric profile product (MYD07) have been used to determine the dew point temperature and land surface temperature. Precipitation coefficient has been computed from Tropical Rainfall measuring Mission (TRMM) product (3B42RT). Nesterov index has been slightly modified according to the Indian context and computed using land surface temperature, dew point temperature and precipitation coefficient. Fuel type danger index has been derived from forest type map of ISRO based on historical fire location information and disturbance danger index has been derived from disturbance map of ISRO. Finally, forest fire danger index has been developed from the above mentioned indices and MODIS Thermal anomaly product (MOD14) has been used for validating the forest fire danger index.

78 FR 2947 - Manti-La Sal National Forest, Utah; Maverick Point Forest Health Project

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-15

... class structure via use of timber harvesting and prescribed fire. Project activities also seek to.... Over the last 20 years drought conditions have increased; fire size, severity, and total acres burned... fire regimes have been significantly altered from their historical range. The risk of losing key...

Deconstructing the King Megafire.

PubMed

Coen, Janice L; Stavros, E Natasha; Fites-Kaufman, Josephine A

2018-05-24

Hypotheses that megafires - very large, high impact fires - are caused by either climate effects such as drought or fuel accumulation due to fire exclusion with accompanying changes to forest structure have long been alleged and guided policy but their physical basis remains untested. Here, unique airborne observations and microscale simulations using a coupled weather - wildland fire behavior model allowed a recent megafire, the King Fire, to be deconstructed and the relative impacts of forest structure, fuel load, weather, and drought on fire size, behavior, and duration to be separated. Simulations reproduced observed details including the arrival at an inclined canyon, a 25-km run, and later slower growth and features. Analysis revealed that fire-induced winds that equaled or exceeded ambient winds and fine-scale airflow undetected by surface weather networks were primarily responsible for the fire's rapid growth and size. Sensitivity tests varied fuel moisture and amount across wide ranges and showed that both drought and fuel accumulation effects were secondary, limited to sloped terrain where they compounded each other, and, in this case, unable to significantly impact the final extent. Compared to standard data, fuel models derived solely from remote sensing of vegetation type and forest structure improved simulated fire progression, notably in disturbed areas, and the distribution of burn severity. These results point to self-reinforcing internal dynamics rather than external forces as a means of generating this and possibly other outlier fire events. Hence, extreme fires need not arise from extreme fire environment conditions. Kinematic models used in operations do not capture fire-induced winds and dynamic feedbacks so can underestimate megafire events. The outcomes provided a nuanced view of weather, forest structure, fuel accumulation, and drought impacts on landscape-scale fire behavior - roles that can be misconstrued using correlational analyses between area burned and macroscale climate data or other exogenous factors. A practical outcome is that fuel treatments should be focused on sloped terrain, where factors multiply, for highest impact. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Metastability for discontinuous dynamical systems under Lévy noise: Case study on Amazonian Vegetation.

PubMed

Serdukova, Larissa; Zheng, Yayun; Duan, Jinqiao; Kurths, Jürgen

2017-08-24

For the tipping elements in the Earth's climate system, the most important issue to address is how stable is the desirable state against random perturbations. Extreme biotic and climatic events pose severe hazards to tropical rainforests. Their local effects are extremely stochastic and difficult to measure. Moreover, the direction and intensity of the response of forest trees to such perturbations are unknown, especially given the lack of efficient dynamical vegetation models to evaluate forest tree cover changes over time. In this study, we consider randomness in the mathematical modelling of forest trees by incorporating uncertainty through a stochastic differential equation. According to field-based evidence, the interactions between fires and droughts are a more direct mechanism that may describe sudden forest degradation in the south-eastern Amazon. In modeling the Amazonian vegetation system, we include symmetric α-stable Lévy perturbations. We report results of stability analysis of the metastable fertile forest state. We conclude that even a very slight threat to the forest state stability represents L´evy noise with large jumps of low intensity, that can be interpreted as a fire occurring in a non-drought year. During years of severe drought, high-intensity fires significantly accelerate the transition between a forest and savanna state.

Drought and Fragmentation Impacts on Forest Evapotranspiration in Southwestern Amazonia

NASA Astrophysics Data System (ADS)

Numata, I.; Khand, K.; Kjaersgaard, J.

2017-12-01

We assessed the effects of forest fragmentation and drought on forest evapotranspiration (ET) estimated using the energy balance-based model METRIC with Landsat imagery in Rondônia and Acre in the southwestern Amazon. Forest ET estimates were produced for the dry seasons (June-August) of 2009-2011 thus including the 2010 drought period to quantify its impact by comparing to pre- and post-drought years. Furthermore, we tested forest edge distance, edge density, shape index, and area/edge ratio of forest fragments as fragmentation variables. The 2010 drought year showed the lowest monthly forest ET in August and September in both Rondônia and Acre within the study time period. However, part of the decline of forest ET in Acre during this period appeared to be due to less incoming solar radiation caused by atmospheric contamination from fires in addition to inadequate moisture availability. Lingering impacts of the drought on forest ET were observed in 2011, the post-drought year. Both sites showed lower forest ET in the late dry season in 2011 compared to 2009, the pre-drought year. Among forest fragmentation variables, edge distance presented significant impacts on forest ET in the drought and post-drought years (p<0.05), whereas the other variables were not significant. The magnitude of ET changes along edge distance becomes even greater in the drought year (2010) and the post-drought year (2011) in the month of August.

Forest Understory Fire in the Brazilian Amazon in ENSO and Non-ENSO Years: Area Burned and Committed Carbon Emissions

NASA Technical Reports Server (NTRS)

Alencar, A.; Nepstad, D.; Ver-Diaz, M. Del. C.

2004-01-01

"Understory fires" that burn the floor of standing forests are one of the most important types of forest impoverishment in the Amazon, especially during the severe droughts of El Nino Southern Oscillation (ENSO) episodes. However, we are aware of no estimates of the areal extent of these fires for the Brazilian Amazon and, hence, of their contribution to Amazon carbon fluxes to the atmosphere. We calculated the area of forest understory fires for the Brazilian Amazon region during an El Nino (1998) and a non El Nino (1995) year based on forest fire scars mapped with satellite images for three locations in eastern and southern Amazon, where deforestation is concentrated. The three study sites represented a gradient of both forest types and dry season severity. The burning scar maps were used to determine how the percentage of forest that burned varied with distance from agricultural clearings. These spatial functions were then applied to similar forest/climate combinations outside of the study sites to derive an initial estimate for the Brazilian Amazon. Ninety-one percent of the forest area that burned in the study sites was within the first kilometer of a clearing for the non ENSO year and within the first four kilometers for the ENSO year. The area of forest burned by understory forest fire during the severe drought (ENSO) year (3.9 millions of hectares) was 13 times greater than the area burned during the average rainfall year (0.2 million hectares), and twice the area of annual deforestation rate. Dense forest was, proportionally, the forest area most affected by understory fires during the El Nino year, while understory fires were concentrated in transitional forests during the year of average rainfall. Our estimate of aboveground tree biomass killed by fire ranged from 0.06 Pg to 0.38 Pg during the ENSO and from 0,004 Pg to 0,024 Pg during the non ENSO.

Western forest, fire risk, and climate change

Treesearch

Valerie Rapp

2004-01-01

Climate warming may first show up in forests as increased growth, which occurs as warmer temperatures, increased carbon dioxide, and more precipitation encourage higher rates of photosynthesis. The second way that climate change may show up in forests is through changes in disturbance regimes—the long-term patterns of fire, drought, insects, and diseases that are basic...

Western forests, fire risk, and climate change.

Treesearch

Valerie Rapp

2004-01-01

Climate warming may first show up in forests as increased growth, which occurs as warmer temperatures, increased carbon dioxide, and more precipitation encourage higher rates of photosynthesis. The second way that climate change may show up in forests is through changes in disturbance regimes—the long-term patterns of fire, drought, insects, and diseases that are basic...

Soil organic matter composition and quality across fire severity gradients in coniferous and deciduous forests of the southern boreal region

Treesearch

Jessica R. Miesel; William C. Hockaday; Randy Kolka; Philip A. Townsend

2015-01-01

Recent patterns of prolonged regional drought in southern boreal forests of the Great Lakes region, USA, suggest that the ecological effects of disturbance by wildfire may become increasingly severe. Losses of forest soil organic matter (SOM) during fire can limit soil nutrient availability and forest regeneration. These processes are also influenced by the composition...

Persistent effects of a severe drought on Amazonian forest canopy.

PubMed

Saatchi, Sassan; Asefi-Najafabady, Salvi; Malhi, Yadvinder; Aragão, Luiz E O C; Anderson, Liana O; Myneni, Ranga B; Nemani, Ramakrishna

2013-01-08

Recent Amazonian droughts have drawn attention to the vulnerability of tropical forests to climate perturbations. Satellite and in situ observations have shown an increase in fire occurrence during drought years and tree mortality following severe droughts, but to date there has been no assessment of long-term impacts of these droughts across landscapes in Amazonia. Here, we use satellite microwave observations of rainfall and canopy backscatter to show that more than 70 million hectares of forest in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy structure and moisture. Remarkably, and despite the gradual recovery in total rainfall in subsequent years, the decrease in canopy backscatter persisted until the next major drought, in 2010. The decline in backscatter is attributed to changes in structure and water content associated with the forest upper canopy. The persistence of low backscatter supports the slow recovery (>4 y) of forest canopy structure after the severe drought in 2005. The result suggests that the occurrence of droughts in Amazonia at 5-10 y frequency may lead to persistent alteration of the forest canopy.

Post-Disturbance Plant Community Dynamics following a Rare Natural-Origin Fire in a Tsuga canadensis Forest

PubMed Central

Murray, Bryan D.; Holmes, Stacie A.; Webster, Christopher R.; Witt, Jill C.

2012-01-01

Opportunities to directly study infrequent forest disturbance events often lead to valuable information about vegetation dynamics. In mesic temperate forests of North America, stand-replacing crown fire occurs infrequently, with a return interval of 2000–3000 years. Rare chance events, however, may have profound impacts on the developmental trajectories of forest ecosystems. For example, it has been postulated that stand-replacing fire may have been an important factor in the establishment of eastern hemlock (Tsuga canadensis) stands in the northern Great Lakes region. Nevertheless, experimental evidence linking hemlock regeneration to non-anthropogenic fire is limited. To clarify this potential relationship, we monitored vegetation dynamics following a rare lightning-origin crown fire in a Wisconsin hemlock-hardwood forest. We also studied vegetation in bulldozer-created fire breaks and adjacent undisturbed forest. Our results indicate that hemlock establishment was rare in the burned area but moderately common in the scarified bulldozer lines compared to the reference area. Early-successional, non-arboreal species including Rubus spp., Vaccinium angustifolium, sedges (Carex spp.), grasses, Epilobium ciliatum, and Pteridium aquilinium were the most abundant post-fire species. Collectively, our results suggest that competing vegetation and moisture stress resulting from drought may reduce the efficacy of scarification treatments as well as the usefulness of fire for preparing a suitable seedbed for hemlock. The increasing prevalence of growing-season drought suggests that silvicultural strategies based on historic disturbance regimes may need to be reevaluated for mesic species. PMID:22928044

A heuristic expert system for forest fire guidance in Greece.

PubMed

Iliadis, Lazaros S; Papastavrou, Anastasios K; Lefakis, Panagiotis D

2002-07-01

Forests and forestlands are common inheritance for all Greeks and a piece of the national wealth that must be handed over to the next generations in the best possible condition. After 1974, Greece faces a severe forest fire problem and forest fire forecasting is the process that will enable the Greek ministry of Agriculture to reduce the destruction. This paper describes the basic design principles of an Expert System that performs forest fire forecasting (for the following fire season) and classification of the prefectures of Greece into forest fire risk zones. The Expert system handles uncertainty and uses heuristics in order to produce scenarios based on the presence or absence of various qualitative factors. The initial research focused on the construction of a mathematical model which attempted to describe the annual number of forest fires and burnt area in Greece based on historical data. However this has proven to be impossible using regression analysis and time series. A closer analysis of the fire data revealed that two qualitative factors dramatically affect the number of forest fires and the hectares of burnt areas annually. The first is political stability and national elections and the other is drought cycles. Heuristics were constructed that use political stability and drought cycles, to provide forest fire guidance. Fuzzy logic was applied to produce a fuzzy expected interval for each prefecture of Greece. A fuzzy expected interval is a narrow interval of values that best describes the situation in the country or a part of the country for a certain time period. A successful classification of the prefectures of Greece in forest fire risk zones was done by the system, by comparing the fuzzy expected intervals to each other. The system was tested for the years 1994 and 1995. The testing has clearly shown that the system can predict accurately, the number of forest fires for each prefecture for the following year. The average accuracy was as high as 85.25% for 1995 and 80.89% for 1994. This makes the Expert System a very important tool for forest fire prevention planning.

Climatic influences on fire regimes in montane forests of the southern Cascades, California, USA

Treesearch

A. H. Taylor; V. Trouet; C. N. Skinner

2008-01-01

he relationship between climate variability and fire extent was examined in montane and upper montane forests in the southern Cascades. Fire occurrence and extent were reconstructed for seven sites and related to measures of reconstructed climate for the period 1700 to 1900. The climate variables included the Palmer Drought Severity Index (PDSI), summer temperature (...

Climate effects on fire regimes and tree recruitment in Black Hills ponderosa pine forests.

PubMed

Brown, Peter M

2006-10-01

Climate influences forest structure through effects on both species demography (recruitment and mortality) and disturbance regimes. Here, I compare multi-century chronologies of regional fire years and tree recruitment from ponderosa pine forests in the Black Hills of southwestern South Dakota and northeastern Wyoming to reconstructions of precipitation and global circulation indices. Regional fire years were affected by droughts and variations in both Pacific and Atlantic sea surface temperatures. Fires were synchronous with La Niñas, cool phases of the Pacific Decadal Oscillation (PDO), and warm phases of the Atlantic Multidecadal Oscillation (AMO). These quasi-periodic circulation features are associated with drought conditions over much of the western United States. The opposite pattern (El Niño, warm PDO, cool AMO) was associated with fewer fires than expected. Regional tree recruitment largely occurred during wet periods in precipitation reconstructions, with the most abundant recruitment coeval with an extended pluvial from the late 1700s to early 1800s. Widespread even-aged cohorts likely were not the result of large crown fires causing overstory mortality, but rather were caused by optimal climate conditions that contributed to synchronous regional recruitment and longer intervals between surface fires. Synchronous recruitment driven by climate is an example of the Moran effect. The presence of abundant fire-scarred trees in multi-aged stands supports a prevailing historical model for ponderosa pine forests in which recurrent surface fires affected heterogenous forest structure, although the Black Hills apparently had a greater range of fire behavior and resulting forest structure over multi-decadal time scales than ponderosa pine forests of the Southwest that burned more often.

Disentangling the contribution of multiple land covers to fire-mediated carbon emissions in Amazonia during the 2010 drought.

PubMed

Anderson, Liana Oighenstein; Aragão, Luiz E O C; Gloor, Manuel; Arai, Egídio; Adami, Marcos; Saatchi, Sassan S; Malhi, Yadvinder; Shimabukuro, Yosio E; Barlow, Jos; Berenguer, Erika; Duarte, Valdete

2015-10-01

In less than 15 years, the Amazon region experienced three major droughts. Links between droughts and fires have been demonstrated for the 1997/1998, 2005, and 2010 droughts. In 2010, emissions of 510 ± 120 Tg C were associated to fire alone in Amazonia. Existing approaches have, however, not yet disentangled the proportional contribution of multiple land cover sources to this total. We develop a novel integration of multisensor and multitemporal satellite-derived data on land cover, active fires, and burned area and an empirical model of fire-induced biomass loss to quantify the extent of burned areas and resulting biomass loss for multiple land covers in Mato Grosso (MT) state, southern Amazonia-the 2010 drought most impacted region. We show that 10.77% (96,855 km 2 ) of MT burned. We estimated a gross carbon emission of 56.21 ± 22.5 Tg C from direct combustion of biomass, with an additional 29.4 ± 10 Tg C committed to be emitted in the following years due to dead wood decay. It is estimated that old-growth forest fires in the whole Brazilian Legal Amazon (BLA) have contributed to 14.81 Tg of C (11.75 Tg C to 17.87 Tg C) emissions to the atmosphere during the 2010 fire season, with an affected area of 27,555 km 2 . Total C loss from the 2010 fires in MT state and old-growth forest fires in the BLA represent, respectively, 77% (47% to 107%) and 86% (68.2% to 103%) of Brazil's National Plan on Climate Change annual target for Amazonia C emission reductions from deforestation.

Mixed-conifer forests of central Oregon: Effects of logging and fire exclusion vary with environment

Treesearch

Andrew G. Merschel; Thomas A. Spies; Emily K. Heyerdahl

2014-01-01

Twentieth-century land management has altered the structure and composition of mixed-conifer forests and decreased their resilience to fire, drought, and insects in many parts of the Interior West. These forests occur across a wide range of environmental settings and historical disturbance regimes, so their response to land management is likely to vary across...

Characterization of the Fire Regime and Drivers of Fires in the West African Tropical Forest

NASA Astrophysics Data System (ADS)

Dwomoh, F. K.; Wimberly, M. C.

2016-12-01

The Upper Guinean forest (UGF), encompassing the tropical regions of West Africa, is a globally significant biodiversity hotspot and a critically important socio-economic and ecological resource for the region. However, the UGF is one of the most human-disturbed tropical forest ecosystems with the only remaining large patches of original forests distributed in protected areas, which are embedded in a hotspot of climate stress & land use pressures, increasing their vulnerability to fire. We hypothesized that human impacts and climate interact to drive spatial and temporal variability in fire, with fire exhibiting distinctive seasonality and sensitivity to drought in areas characterized by different population densities, agricultural practices, vegetation types, and levels of forest degradation. We used the MODIS active fire product to identify and characterize fire activity in the major ecoregions of the UGF. We used TRMM rainfall data to measure climatic variability and derived indicators of human land use from a variety of geospatial datasets. We employed time series modeling to identify the influences of drought indices and other antecedent climatic indicators on temporal patterns of active fire occurrence. We used a variety of modeling approaches to assess the influences of human activities and land cover variables on the spatial pattern of fire activity. Our results showed that temporal patterns of fire activity in the UGF were related to precipitation, but these relationships were spatially heterogeneous. The pattern of fire seasonality varied geographically, reflecting both climatological patterns and agricultural practices. The spatial pattern of fire activity was strongly associated with vegetation gradients and anthropogenic activities occurring at fine spatial scales. The Guinean forest-savanna mosaic ecoregion had the most fires. This study contributes to our understanding of UGF fire regime and the spatio-temporal dynamics of tropical forest fires in response to intense human and climatic drivers.

Climate-Soil-Vegetation Interactions: A Case-Study from the Forest Fire Phenomenon in Southern Switzerland

NASA Astrophysics Data System (ADS)

Reinhard, M.; Alexakis, E.; Rebetez, M.; Schlaepfer, R.

2003-04-01

In Southern Switzerland, we have observed increasing trends in extreme drought and precipitation events, probably linked to global climatic change. These modifications are more important than changes in annual precipitation sums. On the one hand, an increase in extreme drought implies a higher risk for forest fires, impeding the fulfilment of the various forest functions, on the other hand, extreme precipitation events, developing over a short time span, could simultaneously damage the forest ecosystems or destabilise the soil of burned areas, triggering debris flows. Climatic changes might additionally lead to modifications of the current species composition in the forests. Changes are currently observed at lower elevations (laurophiliation), but are still largely unknown at higher elevations. For the time being, forest fires cannot be regarded as natural phenomena in the South of Switzerland because they are mostly anthropogenically triggered. However, the changing climatic patterns, which set new conditions for the forests, may become a new ecological regulator for the forests as well as the forest fires. The social and environmental consequences are important for these issues. The implications for forest planning and management must be further studied and taken into account. Despite uncertainty about the response of forest ecosystems to climate change, planning and management can no longer rely on decadal to century climatic patterns. The increasing importance of changing environmental conditions within the framework of prevention will have to be reconsidered.

Progressive forest canopy water loss during the 2012-2015 California drought.

PubMed

Asner, Gregory P; Brodrick, Philip G; Anderson, Christopher B; Vaughn, Nicholas; Knapp, David E; Martin, Roberta E

2016-01-12

The 2012-2015 drought has left California with severely reduced snowpack, soil moisture, ground water, and reservoir stocks, but the impact of this estimated millennial-scale event on forest health is unknown. We used airborne laser-guided spectroscopy and satellite-based models to assess losses in canopy water content of California's forests between 2011 and 2015. Approximately 10.6 million ha of forest containing up to 888 million large trees experienced measurable loss in canopy water content during this drought period. Severe canopy water losses of greater than 30% occurred over 1 million ha, affecting up to 58 million large trees. Our measurements exclude forests affected by fire between 2011 and 2015. If drought conditions continue or reoccur, even with temporary reprieves such as El Niño, we predict substantial future forest change.

Climate Change and Forest Disturbances

Treesearch

V. H. Dale; L. A. Joyce; S. McNulty; R. P. Neilson; M. P. Ayres; M. D. Flannigan; P. J. Hanson; L. C. Irland; A. E. Lugo; C. J. Peterson; D. Simberloff; F. J. Swanson; B. J. Stocks; B. M. Wotton

2001-01-01

CLIMATE CHANGE CAN AFFECT FORESTS BY ALTERING THE FREQUENCY, INTENSITY, DURATION, AND TIMING OF FIRE, DROUGHT, INTRODUCED SPECIES, INSECT AND PATHOGEN OUTBREAKS, HURRICANES, WINDSTORMS, ICE STORMS, OR LANDSLIDES

Past and future changes in Canadian boreal wildfire activity.

PubMed

Girardin, Martin P; Mudelsee, Manfred

2008-03-01

Climate change in Canadian boreal forests is usually associated with increased drought severity and fire activity. However, future fire activity could well be within the range of values experienced during the preindustrial period. In this study, we contrast 21st century forecasts of fire occurrence (FireOcc, number of large forest fires per year) in the southern part of the Boreal Shield, Canada, with the historical range of the past 240 years statistically reconstructed from tree-ring width data. First, a historical relationship between drought indices and FireOcc is developed over the calibration period 1959-1998. Next, together with seven tree-ring based drought reconstructions covering the last 240 years and simulations from the CGCM3 and ECHAM4 global climate models, the calibration model is used to estimate past (prior to 1959) and future (post 1999) FireOcc. Last, time-dependent changes in mean FireOcc and in the occurrence rate of extreme fire years are evaluated with the aid of advanced methods of statistical time series analysis. Results suggest that the increase in precipitation projected toward the end of the 21st century will be insufficient to compensate for increasing temperatures and will be insufficient to maintain potential evapotranspiration at current levels. Limited moisture availability would cause FireOcc to increase as well. But will future FireOcc exceed its historical range? The results obtained from our approach suggest high probabilities of seeing future FireOcc reach the upper limit of the historical range. Predictions, which are essentially weighed on northwestern Ontario and eastern boreal Manitoba, indicate that, by 2061-2100, typical FireOcc could increase by more than 34% when compared with the past two centuries. Increases in fire activity as projected by this study could negatively affect the implementation in the next century of forest management inspired by historical or natural disturbance dynamics. This approach is indeed feasible only if current and future fire activities are sufficiently low compared with the preindustrial fire activity, so a substitution of fire by forest management could occur without elevating the overall frequency of disturbance. Conceivable management options will likely have to be directed toward minimizing the adverse impacts of the increasing fire activity.

Wildfires Dynamics in Siberian Larch Forests

NASA Technical Reports Server (NTRS)

Ponomarev, Evgenii I.; Kharuk, Viacheslav I.; Ranson, Kenneth J.

2016-01-01

Wildfire number and burned area temporal dynamics within all of Siberia and along a south-north transect in central Siberia (45deg-73degN) were studied based on NOAA/AVHRR (National Oceanic and Atmospheric Administration/ Advanced Very High Resolution Radiometer) and Terra/MODIS (Moderate Resolution Imaging Spectroradiometer) data and field measurements for the period 1996-2015. In addition, fire return interval (FRI) along the south-north transect was analyzed. Both the number of forest fires and the size of the burned area increased during recent decades (p < 0.05). Significant correlations were found between forest fires, burned areas and air temperature (r = 0.5) and drought index (The Standardized Precipitation Evapotranspiration Index, SPEI) (r = 0.43). Within larch stands along the transect, wildfire frequency was strongly correlated with incoming solar radiation (r = 0.91). Fire danger period length decreased linearly from south to north along the transect. Fire return interval increased from 80 years at 62 N to 200 years at the Arctic Circle (6633' N), and to about 300 years near the northern limit of closed forest stands (about 71+ N). That increase was negatively correlated with incoming solar radiation (r = 0.95). Keywords: wildfires; drought index; larch stands; fire return interval; fire frequency; burned area; climate-induced trends in Siberian wildfires

Short-term impact of disturbance on genetic diversity and structure of Indonesian populations of the butterfly Drupadia theda in East Kalimantan.

PubMed

Fauvelot, C; Cleary, D F R; Menken, S B J

2006-07-01

We investigated the short-term impact of disturbance on genetic diversity and structure of the tropical butterfly Drupadia theda Felder (Lepidoptera: Lycaenidae). Populations were sampled from five landscapes in East Kalimantan (Borneo, Indonesia) which were differentially disturbed by selective logging and the 1997/1998 El Niño Southern Oscillation (ENSO)-induced drought and fires. Sampling occurred before (in 1997) and after the forest fires (in 1998, 1999, 2000, and 2004). Drupadia theda populations underwent serious population size reductions following the 1997/1998 ENSO event. For a total of 208 individuals, we sequenced a 509-bp segment of mtDNA containing the control region plus the 5' end of the 12S rDNA gene. Haplotype diversity in D. theda populations ranged from 0.468 to 0.953. Just after the 1997/1998 ENSO event, number of recorded individuals and genetic diversity were very low in D. theda populations sampled in the two severely burned areas and in a small pristine forest fragment that was surrounded by burned forest and thereby affected by drought. Interestingly, higher levels of genetic diversity were observed in logged forest compared to proximate pristine forest. After 1998, the genetic composition within the three ENSO-disturbed areas diverged. In the twice-burned forest, the genetic diversity in 1999 already approached pre-fire levels, while it remained nearly unchanged in proximate once-burned forest. Our data suggest that the 1997/1998 ENSO-induced drought and fires caused massive reductions in the genetic diversity of D. theda and that population recoveries were linked to their geographical position relative to patches of unburned forest (and thus to source populations).

Climatic stress increases forest fire severity across the western United States

USGS Publications Warehouse

van Mantgem, Philip J.; Nesmith, Jonathan C. B.; Keifer, MaryBeth; Knapp, Eric E.; Flint, Alan; Flint, Lorraine

2013-01-01

Pervasive warming can lead to chronic stress on forest trees, which may contribute to mortality resulting from fire-caused injuries. Longitudinal analyses of forest plots from across the western US show that high pre-fire climatic water deficit was related to increased post-fire tree mortality probabilities. This relationship between climate and fire was present after accounting for fire defences and injuries, and appeared to influence the effects of crown and stem injuries. Climate and fire interactions did not vary substantially across geographical regions, major genera and tree sizes. Our findings support recent physiological evidence showing that both drought and heating from fire can impair xylem conductivity. Warming trends have been linked to increasing probabilities of severe fire weather and fire spread; our results suggest that warming may also increase forest fire severity (the number of trees killed) independent of fire intensity (the amount of heat released during a fire).

Woodland-to-forest transition during prolonged drought in Minnesota after ca. AD 1300.

PubMed

Shuman, Bryan; Henderson, Anna K; Plank, Colin; Stefanova, Ivanka; Ziegler, Susy S

2009-10-01

Interactions among multiple causes of ecological perturbation, such as climate change and disturbance, can produce "ecological surprises." Here, we examine whether climate-fire-vegetation interactions can produce ecological changes that differ in direction from those expected from the effects of climate change alone. To do so, we focus on the "Big Woods" of central Minnesota, USA, which was shaped both by climate and fire. The deciduous Big Woods forest replaced regional woodlands and savannas after the severity of regional fire regimes declined at ca. AD 1300. A trend toward wet conditions has long been assumed to explain the forest expansion, but we show that water levels at two lakes within the region (Wolsfeld Lake and Bufflehead Pond) were low when open woodlands were transformed into the Big Woods. Water levels were high instead at ca. 2240-795 BC when regional fire regimes were most severe. Based on the correlation between water levels and fire-regime severity, we infer that prolonged or repeated droughts after ca. AD 1265 reduced the biomass and connectivity of fine fuels (grasses) within the woodlands. As a result, regional fire severity declined and allowed tree populations to expand. Tree-ring data from the region show a peak in the recruitment of key Big Woods tree species during the AD 1930s drought and suggest that low regional moisture balance need not have been a limiting factor for forest expansion. The regional history, thus, demonstrates the types of counterintuitive ecosystem changes that may arise as climate changes in the future.

The pollen record of a 20th century spruce beetle (Dendroctonus rufipennis) outbreak in a Colorado subalpine forest, USA

Treesearch

R. Scott Anderson; Susan J. Smith; Ann M. Lynch; Brian W. Geils

2010-01-01

The frequency and intensity of ecosystem disturbance, including outbreaks of forest insects and forest fires, is expected to increase in the future as a result of higher temperatures and prolonged drought. While many studies have concentrated on the future climatic impacts on fire, little is known about the impact of future climate on insect infestation....

Persistent effects of a severe drought on Amazonian forest canopy

PubMed Central

Saatchi, Sassan; Asefi-Najafabady, Salvi; Malhi, Yadvinder; Aragão, Luiz E. O. C.; Anderson, Liana O.; Myneni, Ranga B.; Nemani, Ramakrishna

2013-01-01

Recent Amazonian droughts have drawn attention to the vulnerability of tropical forests to climate perturbations. Satellite and in situ observations have shown an increase in fire occurrence during drought years and tree mortality following severe droughts, but to date there has been no assessment of long-term impacts of these droughts across landscapes in Amazonia. Here, we use satellite microwave observations of rainfall and canopy backscatter to show that more than 70 million hectares of forest in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy structure and moisture. Remarkably, and despite the gradual recovery in total rainfall in subsequent years, the decrease in canopy backscatter persisted until the next major drought, in 2010. The decline in backscatter is attributed to changes in structure and water content associated with the forest upper canopy. The persistence of low backscatter supports the slow recovery (>4 y) of forest canopy structure after the severe drought in 2005. The result suggests that the occurrence of droughts in Amazonia at 5–10 y frequency may lead to persistent alteration of the forest canopy. PMID:23267086

Vegetation recovery after fire in the Klamath-Siskiyou region, southern Oregon

USGS Publications Warehouse

Hibbs, David; Jacobs, Ruth

2011-01-01

In July 2002, lightning strikes started five forest fires that merged into one massive wildfire in the Klamath-Siskiyou Ecoregion of southern Oregon. Aided by drought, severe weather conditions, dry fuels, and steep topography, the fire grew to more than 200,000 hectares of mostly public forest land. Known as the Biscuit Fire, it was Oregon's largest forest fire in more than 130 years and one of the largest wildfires on record in the United States. Discussions centered around why such a massive fire was happening, how large would it become, who was keeping communities and homes safe, and what would be the final economic and ecological outcome. Weeks later when the fire was out, conversations turned to other questions, including what, if anything, should happen for forest recovery.

Forest disturbances under climate change

NASA Astrophysics Data System (ADS)

Seidl, Rupert; Thom, Dominik; Kautz, Markus; Martin-Benito, Dario; Peltoniemi, Mikko; Vacchiano, Giorgio; Wild, Jan; Ascoli, Davide; Petr, Michal; Honkaniemi, Juha; Lexer, Manfred J.; Trotsiuk, Volodymyr; Mairota, Paola; Svoboda, Miroslav; Fabrika, Marek; Nagel, Thomas A.; Reyer, Christopher P. O.

2017-06-01

Forest disturbances are sensitive to climate. However, our understanding of disturbance dynamics in response to climatic changes remains incomplete, particularly regarding large-scale patterns, interaction effects and dampening feedbacks. Here we provide a global synthesis of climate change effects on important abiotic (fire, drought, wind, snow and ice) and biotic (insects and pathogens) disturbance agents. Warmer and drier conditions particularly facilitate fire, drought and insect disturbances, while warmer and wetter conditions increase disturbances from wind and pathogens. Widespread interactions between agents are likely to amplify disturbances, while indirect climate effects such as vegetation changes can dampen long-term disturbance sensitivities to climate. Future changes in disturbance are likely to be most pronounced in coniferous forests and the boreal biome. We conclude that both ecosystems and society should be prepared for an increasingly disturbed future of forests.

Forest disturbances under climate change

PubMed Central

Seidl, Rupert; Thom, Dominik; Kautz, Markus; Martin-Benito, Dario; Peltoniemi, Mikko; Vacchiano, Giorgio; Wild, Jan; Ascoli, Davide; Petr, Michal; Honkaniemi, Juha; Lexer, Manfred J.; Trotsiuk, Volodymyr; Mairota, Paola; Svoboda, Miroslav; Fabrika, Marek; Nagel, Thomas A.; Reyer, Christopher P. O.

2017-01-01

Forest disturbances are sensitive to climate. However, our understanding of disturbance dynamics in response to climatic changes remains incomplete, particularly regarding large-scale patterns, interaction effects and dampening feedbacks. Here we provide a global synthesis of climate change effects on important abiotic (fire, drought, wind, snow and ice) and biotic (insects and pathogens) disturbance agents. Warmer and drier conditions particularly facilitate fire, drought and insect disturbances, while warmer and wetter conditions increase disturbances from wind and pathogens. Widespread interactions between agents are likely to amplify disturbances, while indirect climate effects such as vegetation changes can dampen long-term disturbance sensitivities to climate. Future changes in disturbance are likely to be most pronounced in coniferous forests and the boreal biome. We conclude that both ecosystems and society should be prepared for an increasingly disturbed future of forests. PMID:28861124

Multi-temporal analysis of forest fire risk driven by environmental and socio-economic change in the Republic of Korea

NASA Astrophysics Data System (ADS)

Kim, S. J.; Lim, C. H.; Kim, G. S.; Lee, W. K.

2017-12-01

Analysis of forest fire risk is important in disaster risk reduction (DRR) since it provides a way to manage forest fires. Climate and socio-economic factors are important in the cause of forest fires, and the role of the socio-economic factors in prevention and preparedness of forest fires is increasing. As most of the forest fires in the Republic of Korea are highly related to human activities, both environmental factors and socio-economic factors were considered into the analysis of forest fire risk. In this study, the Maximum Entropy (MaxEnt) model was used to predict the potential geographical distribution and probability of forest fire occurrence spatially and temporally from 1980s to the 2010s in the Republic of Korea by multi-temporal analysis and analyze the relationship between forest fires and the factors. As a result of the risk analysis, there was an overall increasing trend in forest fire risk from the 1980s to the 2000s, and socio-economic factors were highly correlated with the occurrence of forest fires. The study demonstrates that the socio-economic factors considered as human activities can increase the occurrence of forest fires. The result implies that managing human activities are significant to prevent forest fire occurrence. In addition, timely forest fire prevention and control is necessary as drought index such as Standardized Precipitation Index (SPI) also affected forest fires.

Fire patterns in the Amazonian biome

NASA Astrophysics Data System (ADS)

Aragao, Luiz E. O. C.; Shimabukuro, Yosio E.; Lima, Andre; Anderson, Liana O.; Barbier, Nicolas; Saatchi, Sassan

2010-05-01

This paper aims to provide an overview of our recent findings on the interplay between climate and land use dynamics in defining fire patterns in Amazonia. Understanding these relationships is currently a fundamental concern for assessing the vulnerability of Amazonia to climate change and its potential for mitigating current increases in atmospheric greenhouse gases. Reducing carbon emissions from tropical deforestation and forest degradation (REDD), for instance, could contribute to a cumulative emission reduction of 13-50 billion tons of carbon (GtC) by 2100. In Amazonia, though, forest fires can release similar quantities of carbon to the atmosphere (~0.2 GtC yr-1) as deforestation alone. Therefore, to achieve carbon savings through REDD mechanism there is an urgent need of understanding and subsequently restraining related Amazonian fire drivers. In this study, we analyze satellite-derived monthly and annual time-series of fires, rainfall and deforestation in Amazonia to: (1) quantify the seasonal patterns and relationships between these variables; (2) quantify fire and rainfall anomalies to evaluate the impact of recent drought on fire patterns; (3) quantify recent trends in fire and deforestation to understand how land use affects fire patterns in Amazonia. Our results demonstrate a marked seasonality of fires. The majority of fires occurs along the Arc of Deforestation, the expanding agricultural frontier in southern and eastern Amazonia, indicating humans are the major ignition sources determining fire seasonality, spatial distribution and long-term patterns. There is a marked seasonality of fires, which is highly correlated (p<0.05) with monthly rainfall and deforestation rates. Deforestation and fires reach their highest values three and six months, respectively, after the peak of the rainy season. This result clearly describes the impact of major human activities on fire incidence, which is generally characterized by the slash-and-burn of Amazonian vegetation for implementation of pastures and agricultural fields. The cumulative number of hot pixels is exponentially related to the monthly rainfall, which ultimately defines where and when fire can potentially strike. During the 2005 Amazonian drought, the number of hot pixels increased 33% in relation to mean 1998-2005. However, even with a large fraction of the basin experiencing considerable water deficits, fires have only affect areas with extensive human activity. Our spatially explicit trend analysis on deforestation and fire data revealed that more than half of the area experiencing increased fire occurrence have reduced deforestation rates. This reverse pattern is likely to be associated with the slash-and-burn of secondary forests and the increase of fragmentation and forest edges, favouring the leakage of fires from deforested lands into forests. Finally, our analysis points towards a reduction of fire incidence due to land use intensification in this region. In this study, we demonstrated that anthropogenic forcing, such as deforestation rates, is decisive in determining the seasonality and annual patterns of fire occurrence. Moreover, droughts can significantly increase the number of fires in the region exacerbating human impacts in Amazonia. Due to ongoing deforestation and the predicted intensification of climate change induced droughts, it is anticipated that a large area of forest edge will be under increased risk of fires and carbon savings from REDD may be partially offset by increased emissions following fire events. Improved fire-free land management practices may provide a sustainable solution for reducing emissions from the world's largest rainforest. Acknowledges The first author would like to thank the financial support of the Natural Environment Research Council (NERC-UK/grant NE/F015356/1).

Modeling the Effects of Drought, Fire, Beetles, and Management on Future Carbon Cycling in the Western US

NASA Astrophysics Data System (ADS)

Buotte, P.; Law, B. E.; Hicke, J. A.; Hudiburg, T. W.; Levis, S.; Kent, J.

2017-12-01

Fire and beetle outbreaks can have substantial impacts on forest structure, composition, and function and these types of disturbances are expected to increase in the future. Therefore understanding the ecological impacts of these disturbances into the future is important. We used ecosystem process modeling to estimate the future occurrence of fire and beetle outbreaks and their impacts on forest resilience and carbon sequestration. We modified the Community Land Model (CLM4.5) to better represent forest growth and mortality in the western US through multiple avenues: 1) we increased the ecological resolution to recognize 14 forest types common to the region; 2) we improved CLM4.5's ability to handle drought stress by adding forest type-specific controls on stomatal conductance and increased rates of leaf shed during periods of low soil moisture; 3) we developed and implemented a mechanistic model of beetle population growth and subsequent tree mortality; 4) we modified the current fire module to account for more refined forest types; and 5) we developed multiple scenarios of harvest based on past harvest rates and proposed changes in land management policies. We ran CLM4.5 in offline mode with climate forcing data. We compare future forest growth rates and carbon sequestration with historical metrics to estimate the combined influence of future disturbances on forest composition and carbon sequestration in the western US.

A vicious circle of fire, deforestation and climate change: an integrative study for the Amazon region

NASA Astrophysics Data System (ADS)

Thonicke, K.; Rammig, A.; Gumpenberger, M.; Vohland, K.; Poulter, B.; Cramer, W.

2009-04-01

The Amazon rainforest is threatened by deforestation due to wood extraction and agricultural production leading to increasing forest fragmentation and forest degradation. These changes in land surface characteristics and water fluxes are expected to further reduce convective precipitation. Under future climate change the stability of the Amazon rainforest is likely to decrease thus leading to forest dieback (savannization) or forest degradation (secondarization). This puts the Amazon rainforest at risk to reduce the generation of precipitation, to act as a carbon sink and biodiversity hotspot. Fires increased in the past during drought years and in open vegetation thereby further accelerating forest degradation. Deforestation as a result of socioeconomic development in the Amazon basin is projected to further increase in the 21st century and brings climate-induced changes forward. Combined effects of deforestation vs. climate change on the stability of the Amazon rainforest and the role of fire in this system need to be quantified in an integrated study. We present simulation results from future climate (AR4) and deforestation (SimAmazon) experiments using the LPJmL-SPITFIRE vegetation model. Land use change is the main driving factor of forest degradation before 2050, whereas extreme climate change scenarios lead to forest degradation by the end of 2100. Forest fires increase with increasing drought conditions during the 21st century. The resulting effects on vegetation secondarization and savannization and their feedbacks on fire spread and emissions will be presented. The effect of wildfires and intentional burning on forest degradation under future climate and socioeconomic change will be discussed, and recommendations for an integrated land use and fire management are given.

Modeling Forest Composition and Carbon Dynamics Under Projected Climate-Fire Interactions in the Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Liang, S.; Hurteau, M. D.; Westerling, A. L.

2014-12-01

The Sierra Nevada Mountains are occupied by a diversity of forest types that sort by elevation. The interaction of changing climate and altered disturbance regimes (e.g. fire) has the potential to drive changes in forest distribution as a function of species-specific response. Quantifying the effects of these drivers on species distributions and productivity under future climate-fire interactions is necessary for informing mitigation and adaptation efforts. In this study, we assimilated forest inventory and soil survey data and species life history traits into a landscape model, LANDIS-II, to quantify the response of forest dynamics to the interaction of climate change and large wildfire frequency in the Sierra Nevada. We ran 100-year simulations forced with historical climate and climate projections from three models (GFDL, CNRM and CCSM3) driven by the A2 emission scenario. We found that non-growing season NPP is greatly enhanced by 15%-150%, depending on the specific climate projection. The greatest increase occurs in subalpine forests. Species-specific response varied as a function of life history characteristics. The distribution of drought and fire-tolerant species, such as ponderosa pine, expanded by 7.3-9.6% from initial conditions, while drought and fire-intolerant species, such as white fir, showed little change in the absence of fire. Changes in wildfire size and frequency influence species distributions by altering the successional stage of burned patches. The range of responses to different climate models demonstrates the sensitivity of these forests to climate variability. The scale of climate projections relative to the scale of forest simulations presents a source of uncertainty, particularly at the ecotone between forest types and for identifying topographically mediated climate refugia. Improving simulations will likely require higher resolution climate projections.

Climate Change Transforms Fire Regimes but Does not Eliminate Forest Carbon Sequestration in the Greater Yellowstone Ecosystem

NASA Astrophysics Data System (ADS)

Henne, P. D.; Hawbaker, T. J.; Berryman, E.

2017-12-01

Annual area burned in the Rocky Mountains varies with climatic conditions. However, projecting long-term changes in wildfire presents an enduring challenge because climate also constrains vegetation and fuel availability. We combined an aridity-threshold fire model with the Landis-II dynamic landscape vegetation model (NECN extension) to project climate change impacts on vegetation, area burned, and ecosystem carbon balance in the Greater Yellowstone Ecosystem (GYE). We developed a fire model that relates drought stress to area burned by quantifying an aridity threshold separating large and small years in 15 ecoregions in the Intermountain West. A significant positive correlation (r2 = 0.97) exists between mean fire-season aridity and ecoregion-specific aridity thresholds. We simulated vegetation and fire dynamics in the GYE at 250 m spatial resolution with Landis-II, using projections from five climate models and two emissions scenarios for the period 1980-2100 AD. We determined if each simulation year exceeded the regional aridity threshold, then randomly drew the number of fires and size of individual fires from fire-size distributions from large or small fire years. Burned area increases dramatically in most climate scenarios, especially after 2060, when most years exceed the aridity threshold. Productivity gains due to rising temperatures partially offset biomass lost to fire, but C stocks plateau or decline after 2060 in most simulations as burned area increases, and drought stress causes post-fire regeneration to decline at low elevations. However, species level changes (e.g. expansion by drought-tolerant Pseuodotsuga menziesii) help maintain productivity in sites where water becomes limiting. Fire-adapted Pinus contorta occupies less total area, but a greater proportion of remaining forests, and Picea engelmannii and Abies lasiocarpa significantly decline. Although fire and climate change will alter species distributions and forest structure, our results suggest that the GYE can maintain a C sink through 2100. However, C stocks will likely shift to higher elevations, and forests will be less resilient to disturbance, in a warmer future. Our landscape-level approach identifies regions likely to maintain high conservation value and ecosystem services under multiple climate scenarios.

76 FR 50168 - Coconino and Kaibab National Forests, Arizona, Four-Forest Restoration Initiative

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-12

... disturbances such as insect and disease, fire and climate change (FSM 2020.5). This project is expected to put... changing climatic conditions (drought), fire, insect, and disease. Purpose and Need for Action In contrast... alternative, will be considered. The no-action alternative represents no change and serves as the baseline for...

Forests at risk: integrating risk science into fuel management strategies.

Treesearch

Jonathan Thompson

2008-01-01

The threat from wildland fire continues to grow across many regions of the Western United States. Drought, urbanization, and a buildup of fuels over the last century have contributed to increasing wildfire risk to property and highly valued natural resources. Fuel treatments, including thinning overly dense forests to reduce fuel and lower fire risk, have become a...

Forest Management Shifts in the Western US and Potential Impacts on the Carbon Balance

NASA Astrophysics Data System (ADS)

Law, B. E.; Jones, M. O.; Yang, Z.; Berner, L. T.

2015-12-01

Forest harvest regimes are changing as land managers cope with fires, drought, and insect damage. Thinning on public lands, typically focused on removal of small trees that could act as fuel ladders, is increasing to reduce risk of crown fires and reduce competition for water in crowded stands. On private lands, drought and wildfires could lead to further shortening of harvest cycles (e.g. from 80 to 45 years) or thinning. To examine the effects of potential changes in management regimes vs climate on carbon processes in forests of Oregon, California and Washington, we used data from ancillary plots, inventories, and satellites to parameterize and test the CLM4.5 model. We first examined contemporary biomass loss over the western US to determine the baseline conditions prior to implementing harvest scenarios. Annual biomass mortality from fires and insects increased significantly (1996-2011), and mortality from insects was about twice that of fires. California, Oregon and Idaho were most impacted by fire-related biomass mortality, whereas Colorado, Montana and Washington were most impacted by insects. Harvest scenarios implemented in CLM4.5 include two thinning scenarios to reduce crown fire risk and drought stress, and a salvage scenario to remove trees remaining after recent beetle or fire related mortality; taking into account our previous work showing 70 - 85 % of salvaged biomass is removed and the remainder is left on-site. We simulated the effect of treatments on current and future net ecosystem carbon balance. Challenges of regional modeling of management effects on carbon and other important considerations are addressed.

Shifts in functional traits elevate risk of fire-driven tree dieback in tropical savanna and forest biomes.

PubMed

Pellegrini, Adam F A; Franco, Augusto C; Hoffmann, William A

2016-03-01

Numerous predictions indicate rising CO2 will accelerate the expansion of forests into savannas. Although encroaching forests can sequester carbon over the short term, increased fires and drought-fire interactions could offset carbon gains, which may be amplified by the shift toward forest plant communities more susceptible to fire-driven dieback. We quantify how bark thickness determines the ability of individual tree species to tolerate fire and subsequently determine the fire sensitivity of ecosystem carbon across 180 plots in savannas and forests throughout the 2.2-million km(2) Cerrado region in Brazil. We find that not accounting for variation in bark thickness across tree species underestimated carbon losses in forests by ~50%, totaling 0.22 PgC across the Cerrado region. The lower bark thicknesses of plant species in forests decreased fire tolerance to such an extent that a third of carbon gains during forest encroachment may be at risk of dieback if burned. These results illustrate that consideration of trait-based differences in fire tolerance is critical for determining the climate-carbon-fire feedback in tropical savanna and forest biomes. © 2015 John Wiley & Sons Ltd.

Climatic stress increases forest fire severity across the western United States.

PubMed

van Mantgem, Phillip J; Nesmith, Jonathan C B; Keifer, MaryBeth; Knapp, Eric E; Flint, Alan; Flint, Lorriane

2013-09-01

Pervasive warming can lead to chronic stress on forest trees, which may contribute to mortality resulting from fire-caused injuries. Longitudinal analyses of forest plots from across the western US show that high pre-fire climatic water deficit was related to increased post-fire tree mortality probabilities. This relationship between climate and fire was present after accounting for fire defences and injuries, and appeared to influence the effects of crown and stem injuries. Climate and fire interactions did not vary substantially across geographical regions, major genera and tree sizes. Our findings support recent physiological evidence showing that both drought and heating from fire can impair xylem conductivity. Warming trends have been linked to increasing probabilities of severe fire weather and fire spread; our results suggest that warming may also increase forest fire severity (the number of trees killed) independent of fire intensity (the amount of heat released during a fire). Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Spatial Configuration of Drought Disturbance and Forest Gap Creation across Environmental Gradients

PubMed Central

Andrew, Margaret E.; Ruthrof, Katinka X.; Matusick, George; Hardy, Giles E. St. J.

2016-01-01

Climate change is increasing the risk of drought to forested ecosystems. Although drought impacts are often anecdotally noted to occur in discrete patches of high canopy mortality, the landscape effects of drought disturbances have received virtually no study. This study characterized the landscape configuration of drought impact patches and investigated the relationships between patch characteristics, as indicators of drought impact intensity, and environmental gradients related to water availability to determine factors influencing drought vulnerability. Drought impact patches were delineated from aerial surveys following an extreme drought in 2011 in southwestern Australia, which led to patchy canopy dieback of the Northern Jarrah Forest, a Mediterranean forest ecosystem. On average, forest gaps produced by drought-induced dieback were moderate in size (6.6 ± 9.7 ha, max = 85.7 ha), compact in shape, and relatively isolated from each other at the scale of several kilometers. However, there was considerable spatial variation in the size, shape, and clustering of forest gaps. Drought impact patches were larger and more densely clustered in xeric areas, with significant relationships observed with topographic wetness index, meteorological variables, and stand height. Drought impact patch clustering was more strongly associated with the environmental factors assessed (R2 = 0.32) than was patch size (R2 = 0.21); variation in patch shape remained largely unexplained (R2 = 0.02). There is evidence that the xeric areas with more intense drought impacts are ‘chronic disturbance patches’ susceptible to recurrent drought disturbance. The spatial configuration of drought disturbances is likely to influence ecological processes including forest recovery and interacting disturbances such as fire. Regime shifts to an alternate, non-forested ecosystem may occur preferentially in areas with large or clustered drought impact patches. Improved understanding of drought impacts and their patterning in space and time will expand our knowledge of forest ecosystems and landscape processes, informing management of these dynamic systems in an uncertain future. PMID:27275744

Fire-climate interactions in the Selway-Bitterroot Wilderness area

Treesearch

Kurt F. Kipfmueller; Thomas W. Swetnam

2000-01-01

Tree-ring reconstructed summer drought was examined in relation to the occurrence of 15 fires in the Selway-Bitterroot Wilderness Area (SBW). The ten largest fire years between 1880 and 1995 were selected from historical fire atlas data; five additional fire years were selected from a fire history completed in a subalpine forest within the SBW. Results of the analysis...

Water and Forest Health: Drought Stress as a Core Driver of Forest Disturbances and Tree Mortality in Western North America

NASA Astrophysics Data System (ADS)

Allen, C. D.; Williams, P.

2012-12-01

Increasing warmth and dry climate conditions have affected large portions of western North America in recent years, causing elevated levels of both chronic and acute forest drought stress. In turn, increases in drought stress amplify the incidence and severity of the most significant forest disturbances in this region, including wildfire, drought-induced tree mortality, and outbreaks of damaging insects and diseases. Regional patterns of drought stress and various forest disturbances are reviewed, including interactions among climate and the various disturbance processes; similar global-scale patterns and trends of drought-amplified forest die-off and high-severity wildfire also are addressed. New research is presented that derives a tree-ring-based Forest Drought Stress Index (FDSI) for the three most widespread conifer species (Pinus edulis, Pinus ponderosa, and Pseudotsuga menziesii) in the southwestern US (Arizona, New Mexico), demonstrating nonlinear escalation of FDSI to levels unprecedented in the past 1000 years, in response to both drought and especially recent warming. This new work further highlights strong correlations between drought stress and amplified forest disturbances (fire, bark beetle outbreaks), and projects that by ca. 2050 anticipated regional warming will cause mean FDSI levels to reach extreme levels that may exceed thresholds for the survival of current tree species in large portions of their current range. Given recent trends of forest disturbance and projections for substantially warmer temperatures and greater drought stress for much of western North America in coming years, the growing risks to western forest health are becoming clear. This emerging understanding suggests an urgent need to determine potentials and methods for managing water on-site to maintain the vigor and resilience of western forests in the face of increasing levels of climate-induced water stress.

Response and Resiliency of Wildlife and Vegetation to Large-Scale Wildfires and Climate Change in the North Cascades

NASA Astrophysics Data System (ADS)

Bartowitz, K.; Morrison, P.; Romain-Bondi, K.; Smith, C. W.; Warne, L.; McGill, D.

2016-12-01

Changing climatic patterns have affected the western US in a variety of ways: decreases in precipitation and snowpack, earlier spring snowmelt, and increased lightning strikes have created a drier, more fire-prone system, despite variability in these characteristics. Wildfires are a natural phenomenon, but have been suppressed for much of the past century. Effects of this evolving fire regime on native vegetation and wildlife are not well understood. Increased frequency and intensity of fires coupled with subsequent drought and extreme heat may inhibit or alter recovery of native ecosystems. We are currently investigating how a mega-fire has affected presence of western gray squirrels (Sciurus griseus, WGS) in the North Cascades, and the mortality, survival, and recovery of vegetation following these fires and extreme drought. The Methow Valley in WA experienced a record-breaking wildfire in 2014, which disturbed nearly 50% of priority habitat of the North Cascades population of WGS. WGS were studied at the same pre and post-fire plots. WGS were present at over half of the post-burn plots (58%). There was a significant difference in the number of WGS hair samples collected in different levels of remaining vegetation: the most in moderate, few in low, and none in high. Vegetation recovery was assessed through field data, and a chronosequence of satellite images and aerial photography. 75% of the 2014 fire burned non-forested vegetation. Ponderosa pine forests comprised the rest. The forests experienced about 70% initial mortality. Recovery of the forest appears slower than in the shrub-steppe. First year seedling survival was poor due to an extremely hot, dry summer, while second year survival appears higher due to a cool, moist spring and summer. One year after a large, multi-severity fire we found WGS may be more resilient to disturbance such as fires than previously thought. Future studies of WGS will help elucidate long-term response to large-scale fires, and aid in management of the state-threatened species. The combination of severe fire and extreme heat/drought may result in shifts from shrub-steppe to grass/forb communities, as well as range contraction of ponderosa pine forests. The study reveals the importance of subsequent climatic conditions on vegetation recovery after a fire.

GIS-based probability assessment of natural hazards in forested landscapes of Central and South-Eastern Europe.

PubMed

Lorz, C; Fürst, C; Galic, Z; Matijasic, D; Podrazky, V; Potocic, N; Simoncic, P; Strauch, M; Vacik, H; Makeschin, F

2010-12-01

We assessed the probability of three major natural hazards--windthrow, drought, and forest fire--for Central and South-Eastern European forests which are major threats for the provision of forest goods and ecosystem services. In addition, we analyzed spatial distribution and implications for a future oriented management of forested landscapes. For estimating the probability of windthrow, we used rooting depth and average wind speed. Probabilities of drought and fire were calculated from climatic and total water balance during growing season. As an approximation to climate change scenarios, we used a simplified approach with a general increase of pET by 20%. Monitoring data from the pan-European forests crown condition program and observed burnt areas and hot spots from the European Forest Fire Information System were used to test the plausibility of probability maps. Regions with high probabilities of natural hazard are identified and management strategies to minimize probability of natural hazards are discussed. We suggest future research should focus on (i) estimating probabilities using process based models (including sensitivity analysis), (ii) defining probability in terms of economic loss, (iii) including biotic hazards, (iv) using more detailed data sets on natural hazards, forest inventories and climate change scenarios, and (v) developing a framework of adaptive risk management.

Can Tree Ring Analyses Predict Resilience of Black Spruce Forests to Fire in Interior Alaska?

NASA Astrophysics Data System (ADS)

Walker, X. J.; Johnstone, J. F.; Mack, M. C.

2015-12-01

Climate change has increased the occurrence, severity, and impact of disturbances on forested ecosystems worldwide. As such there is a growing need to identify factors that contribute to an ecosystem's ability to recover from disturbance, commonly referred to as ecosystem resilience. In trees, drought-induced growth declines may signal decreased ecosystem resilience if mature trees are able to survive in stressful environmental conditions that do not permit successful post-disturbance recruitment and survival. Here we explore links between ecosystem resilience and the growth-climate relationships of pre-fire trees, specifically drought stress signals, across topographic moisture gradients within the boreal forest. We sampled 72 recently (2004) burned black spruce stands within interior Alaska and found the proportion of black spruce relative to deciduous trees decreased post-fire, ranging from almost no change to a 90% decrease. The largest shifts in post-fire species composition occurred in sites where trees showed negative growth responses to warm spring temperatures, and shallow post-fire organic layer depths due to dry site conditions or high fire severity. These sites were generally located at warmer and drier landscape positions, suggesting they are less resilient to disturbance than sites at the wetter end of the gradient. Tree growth-climate responses can provide an estimate of stand environmental stress to ongoing climate change and as such are a valuable tool for predicting landscape variations in forest ecosystem resilience and forecasting future forest composition.

Who is in the Driver's Seat? Millennial-Scale Records of Wildfire in the Western USA Reveal a Complex Interplay of Climate, Fire, and Vegetation

NASA Astrophysics Data System (ADS)

Pierce, J. L.; Meyer, G. A.; Bigio, E.; Nelson, N.; Poulos, M. J.; Jenkins, S.; Riley, K. E.; Weppner, K.; Svenson, L.; Fitch, E. P.; Frechette, J.

2015-12-01

A new synthesis of 10 study areas and >480 14C dates of Holocene fire and erosional response are recorded in alluvial fan sediments of the interior western US. Chronologies are from high elevation mixed conifer forests in the N. Rockies, ponderosa and Douglas-fir forests in the N. Rockies and SW, and low elevation sagebrush steppe and piñon-juniper woodlands near the Snake River Plain. Results are as follows: 1) Late Holocene arrivals of ponderosa, lodgepole and piñon pine at Northern Rockies sites correspond with increased fire severity, linking vegetation and fire regime changes. 2) Deposit types vary with environment; sheetfloods are more common in sparsely vegetated sites and in drier Holocene periods with open forests, whereas dense forests and infrequent severe fires often produce debris flows. 3) Climate variability drives ponderosa pine and Douglas-fir forests in both the SW and N. Rockies to burn 'at both ends of the spectrum', where frequent low-severity fires are typical, but higher-severity fires burn during severe droughts following fuel buildup over wet decades. 4) Fires in dry sage steppe are generally fuel-limited, but burn during prolonged wet and variable climates; grazing, land-use, and invasive species, particularly influence modern fires. 5) At moist high-elevation lodgepole and mixed conifer sites in Yellowstone and central Idaho, episodic large debris flows indicate high severity burns, often during severe multidecadal droughts. 6) Regionally coherent peaks exist ca. 200, 500, 900, 1700 and 2600 cal yr BP, but fire activity is not generally synchronous among sites. Differences in climate among sites likely account for some asynchroneity. 7) Recent severe fires have burned in 8 of 10 sites described; erosional response appears particularly anomalous in the SW, where impacts of fire suppression and land use are greatest. Widespread and severe modern fires may herald the arrival of a no-analog era of fire in the western US.

Drought, Fire and Insects in Western US Forests: Observations to Improve Regional Land System Modeling

NASA Astrophysics Data System (ADS)

Law, B. E.; Yang, Z.; Berner, L. T.; Hicke, J. A.; Buotte, P.; Hudiburg, T. W.

2015-12-01

Drought, fire and insects are major disturbances in the western US, and conditions are expected to get warmer and drier in the future. We combine multi-scale observations and modeling with CLM4.5 to examine the effects of these disturbances on forests in the western US. We modified the Community Land Model, CLM4.5, to improve simulated drought-related mortality in forests, and prediction of insect outbreaks under future climate conditions. We examined differences in plant traits that represent species variation in sensitivity to drought, and redefined plant groupings in PFTs. Plant traits, including sapwood area: leaf area ratio and stemwood density were strongly correlated with water availability during the ecohydrologic year. Our database of co-located observations of traits for 30 tree species was used to produce parameterization of the model by species groupings according to similar traits. Burn area predicted by the new fire model in CLM4.5 compares well with recent years of GFED data, but has a positive bias compared with Landsat-based MTBS. Biomass mortality over recent decades increased, and was captured well by the model in general, but missed mortality trends of some species. Comparisons with AmeriFlux data showed that the model with dynamic tree mortality only (no species trait improvements) overestimated GPP in dry years compared with flux data at semi-arid sites, and underestimated GPP at more mesic sites that experience dry summers. Simulations with both dynamic tree mortality and species trait parameters improved estimates of GPP by 17-22%; differences between predicted and observed NEE were larger. Future projections show higher productivity from increased atmospheric CO2 and warming that somewhat offsets drought and fire effects over the next few decades. Challenges include representation of hydraulic failure in models, and availability of species trait and carbon/water process data in disturbance- and drought-impacted regions.

Understorey fire frequency and the fate of burned forests in southern Amazonia.

PubMed

Morton, D C; Le Page, Y; DeFries, R; Collatz, G J; Hurtt, G C

2013-06-05

Recent drought events underscore the vulnerability of Amazon forests to understorey fires. The long-term impact of fires on biodiversity and forest carbon stocks depends on the frequency of fire damages and deforestation rates of burned forests. Here, we characterized the spatial and temporal dynamics of understorey fires (1999-2010) and deforestation (2001-2010) in southern Amazonia using new satellite-based estimates of annual fire activity (greater than 50 ha) and deforestation (greater than 10 ha). Understorey forest fires burned more than 85 500 km(2) between 1999 and 2010 (2.8% of all forests). Forests that burned more than once accounted for 16 per cent of all understorey fires. Repeated fire activity was concentrated in Mato Grosso and eastern Pará, whereas single fires were widespread across the arc of deforestation. Routine fire activity in Mato Grosso coincided with annual periods of low night-time relative humidity, suggesting a strong climate control on both single and repeated fires. Understorey fires occurred in regions with active deforestation, yet the interannual variability of fire and deforestation were uncorrelated, and only 2.6 per cent of forests that burned between 1999 and 2008 were deforested for agricultural use by 2010. Evidence from the past decade suggests that future projections of frontier landscapes in Amazonia should separately consider economic drivers to project future deforestation and climate to project fire risk.

Understorey fire frequency and the fate of burned forests in southern Amazonia

PubMed Central

Morton, D. C.; Le Page, Y.; DeFries, R.; Collatz, G. J.; Hurtt, G. C.

2013-01-01

Recent drought events underscore the vulnerability of Amazon forests to understorey fires. The long-term impact of fires on biodiversity and forest carbon stocks depends on the frequency of fire damages and deforestation rates of burned forests. Here, we characterized the spatial and temporal dynamics of understorey fires (1999–2010) and deforestation (2001–2010) in southern Amazonia using new satellite-based estimates of annual fire activity (greater than 50 ha) and deforestation (greater than 10 ha). Understorey forest fires burned more than 85 500 km2 between 1999 and 2010 (2.8% of all forests). Forests that burned more than once accounted for 16 per cent of all understorey fires. Repeated fire activity was concentrated in Mato Grosso and eastern Pará, whereas single fires were widespread across the arc of deforestation. Routine fire activity in Mato Grosso coincided with annual periods of low night-time relative humidity, suggesting a strong climate control on both single and repeated fires. Understorey fires occurred in regions with active deforestation, yet the interannual variability of fire and deforestation were uncorrelated, and only 2.6 per cent of forests that burned between 1999 and 2008 were deforested for agricultural use by 2010. Evidence from the past decade suggests that future projections of frontier landscapes in Amazonia should separately consider economic drivers to project future deforestation and climate to project fire risk. PMID:23610169

Interactions of forest disturbance-recovery dynamics with a changing climate

NASA Astrophysics Data System (ADS)

Anderson-Teixeira, K. J.; Miller, A. D.; Tepley, A. J.; Bennett, A. C.; Wang, M.

2015-12-01

As the climate changes, altered disturbance-recovery dynamics in forests worldwide are likely to result in significant biogeochemical and biophysical feedbacks to the climate system. Climate shapes forest disturbance events including tree mortality and fire, with consequent climate feedbacks. For instance, in forests globally, drought increases tree mortality rates, having a stronger impact on larger trees and resulting in greater feedbacks to climate change than would occur if drought sensitivities were equal across tree size classes. Forest regeneration and associated biogeochemical and biophysical feedbacks are also shaped by climate: across the tropics the rate of biomass accumulation is faster in everwet than in seasonally dry climates, and in the Klamath region (N California / S Oregon), post-fire vegetation dynamics and microclimate are shaped by aridity. Forest recovery dynamics will be affected by elevated CO2 and climate change; for instance, models predict that forest regeneration rate, successional dynamics, and climate feedbacks will all be altered under elevated CO2. In combination, climatic impacts on disturbance and recovery can result in dramatic shifts in forest cover on the landscape level. For instance, in fire-prone forested landscapes, forest cover decreases with increasing frequency of high-severity fire and decreasing forest recovery rate, both of which could be altered by climate change, producing rapid loss of forest on the landscape level. Such effects may be amplified by the existence of alternative stable states, which can cause systems to experience non-reversible changes in cover type. Critical transitions in landscape-level forest cover would have significant biogeochemical and biophysical feedbacks. Thus, altered disturbance-recovery dynamics under a changing climate may have sudden and dramatic impacts on forest-climate interactions.

Contributions of insects and droughts to growth decline of trembling aspen mixed boreal forest of western Canada.

PubMed

Chen, Lei; Huang, Jian-Guo; Dawson, Andria; Zhai, Lihong; Stadt, Kenneth J; Comeau, Philip G; Whitehouse, Caroline

2018-02-01

Insects, diseases, fire and drought and other disturbances associated with global climate change contribute to forest decline and mortality in many parts of the world. Forest decline and mortality related to drought or insect outbreaks have been observed in North American aspen forests. However, little research has been done to partition and estimate their relative contributions to growth declines. In this study, we combined tree-ring width and basal area increment series from 40 trembling aspen (Populus tremuloides Michx.) sites along a latitudinal gradient (from 52° to 58°N) in western Canada and attempted to investigate the effect of drought and insect outbreaks on growth decline, and simultaneously partition and quantify their relative contributions. Results indicated that the influence of drought on forest decline was stronger than insect outbreaks, although both had significant effects. Furthermore, the influence of drought and insect outbreaks showed spatiotemporal variability. In addition, our data suggest that insect outbreaks could be triggered by warmer early spring temperature instead of drought, implicating that potentially increased insect outbreaks are expected with continued warming springs, which may further exacerbate growth decline and death in North America aspen mixed forests. © 2017 John Wiley & Sons Ltd.

Climate change and fire danger rating in the Northern Rockies

Treesearch

Faith Ann Heinsch; Charles W. McHugh

2010-01-01

Studies have indicated that changes in wildland fire activity are, at least in part, a product of climate change. Fire danger indices, driven by climatology, should reflect these changes. Energy Release Component (ERC) is considered to be an effective indicator of drought conditions and seasonal drying of forest fuels and is often used in fire management planning....

Estimating live fuel status by drought indices: an approach for assessing local impact of climate change on fire danger

NASA Astrophysics Data System (ADS)

Pellizzaro, Grazia; Dubrovsky, Martin; Bortolu, Sara; Ventura, Andrea; Arca, Bachisio; Masia, Pierpaolo; Duce, Pierpaolo

2014-05-01

Mediterranean shrubs are an important component of both Mediterranean vegetation communities and understorey vegetation. They also constitute the surface fuels primarily responsible for the ignition and the spread of wildland fires in Mediterranean forests. Although fire spread and behaviour are dependent on several factors, the water content of live fuel plays an important role in determining fire occurrence and spread, especially in the Mediterranean shrubland, where live fuel is often the main component of the available fuel which catches fire. According to projections on future climate, an increase in risk of summer droughts is likely to take place in Southern Europe. More prolonged drought seasons induced by climatic changes are likely to influence general flammability characteristics of fuel, affecting load distribution in vegetation strata, floristic composition, and live and dead fuel ratio. In addition, variations in precipitation and mean temperature could directly affect fuel water status, and consequently flammability, and length of critical periods of high ignition danger for Mediterranean ecosystems. The main aim of this work was to propose a methodology for evaluating possible impacts of future climate change on moisture dynamic and length of fire danger period at local scale. Specific objectives were: i) evaluating performances of meteorological drought indices in describing seasonal pattern of live fuel moisture content (LFMC), and ii) simulating the potential impacts of future climate changes on the duration of fire danger period. Measurements of LFMC seasonal pattern of three Mediterranean shrub species were performed in North Western Sardinia (Italy) for 8 years. Seasonal patterns of LFMC were compared with the Drought Code of the Canadian Forest Fire Weather Index and the Keetch-Byram Drought Index. Analysis of frequency distribution and cumulative distribution curves were carried out in order to evaluate performance of codes and to identify threshold values of indices useful to determine the end of the potential fire season due to fuel status. A weather generator linked to climate change scenarios derived from 17 available General Circulation Models (GCMs) was used to produce synthetic weather series, representing present and future climates, for four selected sites located in North Sardinia, Italy. Finally, impacts of future climate change on fire season length at local scale were simulated. Results confirmed that the projected climate scenarios over the Mediterranean area will determine an overall increase of the fire season length.

Amazon forests did not green up during the 2005 drought

NASA Astrophysics Data System (ADS)

Samanta, A.; Ganguly, S.; Hashimoto, H.; Devadiga, S.; Vermote, E. F.; Knyazikhin, Y.; Nemani, R. R.; Myneni, R. B.

2009-12-01

The sensitivity of Amazon rainforests to dry-season droughts remains unresolved with reports of enhanced tree mortality and forest fires, on one hand, and, excessive forest green-up, on the other. Here using the latest and improved version of satellite-derived vegetation greenness data - Collection 5 (C5) Enhanced Vegetation Index (EVI) - we report that the there is no evidence of large-scale greening of the Amazon during the 2005 drought - approximately 11%-12% of these forests display greening, while, 28%-29% show browning or no-change, and for the rest the data are not of sufficient quality to characterize any changes. In addition, independent satellite-derived data on precipitation, surface radiation and aerosols do not substantiate underlying assumptions of the hypothesis of enhanced photosynthetic capacity of intact Amazon forests stimulated by increased light availability during a drought. First, interannual changes in dry-season greenness are unrelated to concurrent changes in light availability. Second, the 2005 drought cannot be used as a surrogate for light availability to these rainforests owing to persistently high aerosol loads in the atmosphere. Third, the spatial extent and magnitude of greening do not change systematically with drought severity. Finally, the changes in vegetation activity of these forests during the drought-stricken dry season of 2005 are not unique in comparison to that observed during dry seasons of non-drought years. Our analysis also demonstrates the critical role of biomass burning aerosols in limiting light availability to water stressed Amazon forests during the dry season of 2005. This will have important implications for the sensitivity of these forests to similar droughts in future.

Synergistic effects of drought and fire on the carbon carrying capacity of tropical forests and woodlands

NASA Astrophysics Data System (ADS)

Boer, Matthias; Bradstock, Ross

2014-05-01

More than half of the global forest carbon stock is held in tropical forests. A relatively large proportion of the tropical forest carbon is stored in plant biomass rather than in the soil, making these stocks particularly vulnerable to disturbances such as droughts, fires and cyclones. The frequencies, duration and intensities of such disturbances may change under future climates with poorly resolved but potentially significant (synergistic) effects on the carbon carrying capacity of tropical forests and thereby on global geochemical cycles. In this study we analyse high-resolution global data sets for tropical forest biomass (Saatchi et al., 2011. PNAS) and fire affected areas (GFED4, Giglio et al.,2013. JGR 118), together with climate data (WorldClim, Hijmans et al., 2005. Int. J. Clim. 25), to quantify the sensitivity of tropical forest carbon stocks in South America, Africa and Asia/Australia to seasonal water deficits and fire. Here, the climatic water deficit (D), calculated as the difference between mean annual potential evapotranspiration and actual evapotranspiration, is used as a measure of seasonal water stress (i.e., evaporative demand not met by available water), while the mean annual burned area fraction (1995-2013) of grid cells is used as a measure of average fire activity. Tropical forest carbon stocks are maximal, as expected, where water deficits are negligible. In those densely forested environments fire tends to be extremely rare as fuels are too wet to burn for most of the time. In all three continents, potential tropical forest carbon stocks are well predicted by a non-linear decreasing function of the mean annual climatic water deficit, with a steep drop in carbon stocks at D of 700-800 mm per year. At this threshold in the climatic water deficit we observe a strong increase in fire activity that is indicative of a critical change in vegetation structure (i.e., tree/grass ratio) and associated shift in the dominant climatic constraint on fire activity from fuel dryness to fuel productivity. By comparing predictions of potential forest carbon stocks (i.e., as a function of D only) with actual carbon stocks, we quantify the sensitivity of those stocks to increasing fire activity. Finally, we map the risk of losses in carbon carrying capacity of tropical forests under scenarios of future climate.

Temperate forest health in an era of emerging megadisturbance

USGS Publications Warehouse

Millar, Constance I.; Stephenson, Nathan L.

2015-01-01

Although disturbances such as fire and native insects can contribute to natural dynamics of forest health, exceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability. Interactions from increasing temperatures, drought, native insects and pathogens, and uncharacteristically severe wildfire are resulting in forest mortality beyond the levels of 20th-century experience. Additional anthropogenic stressors, such as atmospheric pollution and invasive species, further weaken trees in some regions. Although continuing climate change will likely drive many areas of temperate forest toward large-scale transformations, management actions can help ease transitions and minimize losses of socially valued ecosystem services.

Estimating evapotranspiration change due to forest treatment and fire at the basin scale in the Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Roche, J. W.; Goulden, M.; Bales, R. C.

2017-12-01

Increased forest evapotranspiration (ET) coupled with snowpack decreases in a warming climate is likely to decrease runoff and increase forest drought stress. Field experiments and modeling suggest that forest thinning can reduce ET and thus increase potential runoff relative to untreated areas. We investigated the potential magnitude and duration of ET decreases resulting from forest-thinning treatments and fire using a robust empirical relation between Landsat-derived mean-annual normalized difference vegetation index (NDVI) and annual ET measured at flux towers. Among forest treatments, the minimum observed NDVI change required to produce a significant departure from control plots with NDVI of about 0.70 was -0.07 units, corresponding to a basal-area reduction of 3.1 m2 ha-1, and equivalent to an estimated ET reduction of -102 mm yr-1. Intensive thinning in highly productive forests that approached pre-fire-exclusion densities reduced basal area by 40-50%, generating estimated ET reductions of 152-216 mm yr-1 over five years following treatment. Between 1990 and 2008, fires in the American River basin generated more than twice the ET reduction per unit area than those in the Kings River basin, corresponding to greater water and energy limitations in the latter and greater fire severity in the former. A rough extrapolation of these results to the entire American River watershed, much of which would have burned naturally during this 19-year period, could result in ET reductions that approach 10% of full natural flows for drought years and 5% averaged over all years. This work demonstrates the potential utility to estimate forest ET change at the patch scale, which in turn may allow managers to estimate thinning benefits in areas lacking detailed hydrologic measurements.

Dynamics of stem water uptake among isohydric and anisohydric species experiencing a severe drought

Treesearch

Koong Yi; Danilo Dragoni; Richard P. Phillips; Daniel Tyler Roman; Kimberly A. Novick

2017-01-01

Predicting the impact of drought on forest ecosystem processes requires an understanding of trees' species-specific responses to drought, especially in the Eastern USA, where species composition is highly dynamic due to historical changes in land use and fire regime. Here, we adapted a framework that classifies trees' water-use strategy along the spectrum of...

Observing The Dynamics Of Wildland Grass Fires: FireFlux -A Field Validation Experiment

Treesearch

Craig B. Clements; Shiyuan Zhong; Scott Goodrick; Ju Li; Xindi Bian; Warren E. Heilman; Joseph J. Charney; Ryan Perna; Meongdo Jang; Daegyun Lee; Monica Patel; Susan Street; Glenn Aumann

2007-01-01

Grass fires, although not as intense as forest fires, present a major threat to life and property during periods of drought in the Great Plains of the United States. Recently, major wildland grass fires in Texas burned nearly 1.6 million acres and destroyed over 730 homes and 1320 other buildings. The fires resulted in the death of 19 people, an estimated loss of 10,...

Determining the dynamics of evapotranspiration from fragmented forests under drought in southwestern Amazonia using Landsat imagery

NASA Astrophysics Data System (ADS)

Numata, I.; Khand, K.; Kjaersgaard, J.; Cochrane, M. A.; Silva, S.

2016-12-01

Deforestation in the Amazon has resulted in massive amounts of forest biomass loss and also in extensive forest fragmentation across the region. Fragmented tropical forests are exposed to abrupt environmental changes and experience several biological and ecological changes across distances from forest edges. Extreme droughts in 2005 and 2010 have caused extensive tree mortality across this region. These events may exacerbate edge effects, where already water stressed forest fragments dry more rapidly potentially enabling other disturbances such as forest fire. We analyzed the effects of forest fragmentation and drought on forest evapotranspiration (ET) estimated using the energy balance-based model METRIC with Landsat imagery in Rondônia State in the southwestern Amazon. Forest ET estimates were produced for the dry seasons (June-August) of 2009-2011 thus including the 2010 drought event and pre- and post-event periods. METRIC ET data were combined with forest edge data with edge distances of 100m, 300m, 500m, 1000m, 5000m and >5000m (core forest), generated from Landsat land cover maps for spatiotemporal analysis of forest ET. METRIC ET estimates had an agreement with flux tower ET data from the field of R2 = 0.72. Within the study time period, the 2010 drought year showed the lowest average ET from core forest (2.5mm/day), followed by 2011 (3.0mm/day) and 2009 (3.6mm/day) in the month of August, the mid dry season, while no significant differences were noted among three study years earlier in the dry seasons. In terms of edge effects, the major changes in forest ET occur up to 300 m from the forest edges, with ET decreasees of 30 % at 100 m as compared to further distances. The magnitude of edge-related ET changes became even greater during August of the drought year (2010) and the post-drought year (2011). Annual (drought and non-drought) and seasonal (June-August) forest ET variations were highly significant (p<0.001), while the impact of distance from edge on forest ET was significant only in the drought year (p<0.05).

Resilience Through Disturbance: Effects of Wildfire on Vegetation and Water Balance in the Sierra Nevadas

NASA Astrophysics Data System (ADS)

Boisrame, G. F. S.; Thompson, S. E.; Stephens, S.; Collins, B.; Tague, N.

2015-12-01

A century of fire suppression in the Western United States has drastically altered the historically fire-adapated ecology in California's Sierra Nevada Mountains. Fire suppression is understood to have increased the forest cover, as well as the stem density, canopy cover and water demand of montane forests, reducing resilience of the forests to drought, and increasing the risk of catastrophic fire by drying the landscape and increasing fuel loads. The potential to reverse these trends by re-introducing fire into the Sierra Nevada is highly promising, but the likely effects on vegetation structure and water balance are poorly quantified. The Illilouette Creek Basin in Yosemite National Park represents a unique experiment in the Sierra Nevada, in which managers have moved from fire suppression to allowing a near-natural fire regime to prevail since 1972. Changes in vegetation structure in the Illilouette since the restoration of natural burning provides a unique opportunity to examine how frequent, mixed severity fires can reshape the Sierra Nevada landscape. We characterize these changes from 1969 to the present using a combination of Landsat products and high-resolution aerial imagery. We describe how the landscape structure has changed in terms of vegetation composition and its spatial organization, and explore the drivers of different post-fire vegetation type transitions (e.g. forest to shrubland vs. forest to meadow). By upscaling field data using vegetation maps and Landsat wetness indices, we explore how these vegetation transitions have impacted the water balance of the Illilouette Creek Basin, potentially increasing its resilience in the face of drought, climate change, and catastrophic fire. In a region that is adapted to frequent disturbance from fire, this work helps us understand how allowing such natural disturbances to take place can increase the sustainability of diverse landscapes in the long term.

Ecological responses to el Niño-induced surface fires in central Brazilian Amazonia: management implications for flammable tropical forests.

PubMed Central

Barlow, Jos; Peres, Carlos A

2004-01-01

Over the past 20 years the combined effects of El Niño-induced droughts and land-use change have dramatically increased the frequency of fire in humid tropical forests. Despite the potential for rapid ecosystem alteration and the current prevalence of wildfire disturbance, the consequences of such fires for tropical forest biodiversity remain poorly understood. We provide a pan-tropical review of the current state of knowledge of these fires, and include data from a study in a seasonally dry terra firme forest of central Brazilian Amazonia. Overall, this study supports predictions that rates of tree mortality and changes in forest structure are strongly linked to burn severity. The potential consequences for biomass loss and carbon emissions are explored. Despite the paucity of data on faunal responses to tropical forest fires, some trends are becoming apparent; for example, large canopy frugivores and understorey insectivorous birds appear to be highly sensitive to changes in forest structure and composition during the first 3 years after fires. Finally, we appraise the management implications of fires and evaluate the viability of techniques and legislation that can be used to reduce forest flammability, prevent anthropogenic ignition sources from coming into contact with flammable forests and aid the post-fire recovery process. PMID:15212091

The Amazon Basin in transition

Treesearch

Eric A. Davidson; Alessandro C. de Araujo; Paulo Artaxo; Jennifer K. Balch; I. Foster Brown; Mercedes M.C. Bustamente; Michael T. Coe; Ruth S. DeFriess; Michael Keller; Marcos Longo; J. William Munger; Wilfrid Schroeder; Britaldo Soares-Filho; Carlos M. Souza, Jr.; Steven C. Wofsy

2012-01-01

Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional...

Managing the unexpected in prescribed fire and fire use operations: a workshop on the High Reliability Organization

Treesearch

Paul (tech. ed.) Keller

2004-01-01

Fire management, and forest and rangeland fuels management, over the past century have altered the wildland fire situation dramatically, thus also altering the institutional approach to how to deal with the changing landscape. Also, climate change, extended drought, increased insect and disease outbreaks, and invasions of exotic plant species have added complications...

Diversity in Southwesterners' views of Forest Service fire management

Treesearch

P.L. Winter; G.T. Cvetkovich

2007-01-01

The risk of wildland fires is of significant concern in the southwestern United States. Although the Southwest has a long hi story as a fire· prone ecosystem, years of drought and insect infestation have increased fire risk. Paired with these ecological forces is the increased risk caused by the concentration of populations in the wildland urban interface (WUl),...

A study of forest fire danger district division in Lushan Mountain based on RS and GIS

NASA Astrophysics Data System (ADS)

Xiao, Jinxiang; Huang, Shu-E.; Zhong, Anjian; Zhu, Biqin; Ye, Qing; Sun, Lijun

2009-09-01

The study selected 9 factors, average maximum temperature, average temperature, average precipitation, average the longest days of continuous drought and average wind speed during fire prevention period, vegetation type, altitude, slope and aspect as the index of forest fire danger district division, which has taken the features of Lushan Mountain's forest fire history into consideration, then assigned subjective weights to each factor according to their sensitivity to fire or their fire-inducing capability. By remote sensing and GIS, vegetation information layer were gotten from Landsat TM image and DEM with a scale of 1:50000 was abstracted from the digital scanned relief map. Topography info. (elevation, slope, aspect) layers could be gotten after that. A climate resource databank that contained the data from the stations of Lushan Mountain and other nearby 7 stations was built up and extrapolated through the way of grid extrapolation in order to make the distribution map of climate resource. Finally synthetical district division maps were made by weighing and integrating all the single factor special layers,and the study area were divided into three forest fire danger district, include special fire danger district, I-fire danger district and II-fire danger district. It could be used as a basis for developing a forest fire prevention system, preparing the annual investment plan, allocating reasonably the investment of fire prevention, developing the program of forest fire prevention and handle, setting up forest fire brigade, leaders' decisions on forest fire prevention work.

Global warming accelerates drought-induced forest death

ScienceCinema

McDowell, Nathan; Pockman, William

2018-05-16

Many southwestern forests in the United States will disappear or be heavily altered by 2050, according to a series of joint Los Alamos National Laboratory-University of New Mexico studies. Nathan McDowell, a Los Alamos plant physiologist, and William Pockman, a UNM biology professor, explain that their research, and more from scientists around the world, is forecasting that by 2100 most conifer forests should be heavily disturbed, if not gone, as air temperatures rise in combination with drought. "Everybody knows trees die when there's a drought, if there's bark beetles or fire, yet nobody in the world can predict it with much accuracy." McDowell said. "What's really changed is that the temperature is going up," thus the researchers are imposing artificial drought conditions on segments of wild forest in the Southwest and pushing forests to their limit to discover the exact processes of mortality and survival. The study is centered on drought experiments in woodlands at both Los Alamos and the Sevilleta National Wildlife Refuge in central New Mexico. Both sites are testing hypotheses about how forests die on mature, wild trees, rather than seedlings in a greenhouse, through the ecosystem-scale removal of 50 percent of yearly precipitation through large water-diversion trough systems.

Are post-fire silvicultural treatments a useful tool to fight the climate change threat in terms of plant diversity?

NASA Astrophysics Data System (ADS)

Hedo de Santiago, Javier; Esteban Lucasr Borja, Manuel; de las Heras, Jorge

2016-04-01

Adaptative forest management demands a huge scientific knowledge about post-fire vegetation dynamics, taking into account the current context of global change. We hypothesized that management practices should be carry out taking into account the climate change effect, to obtain better results in the biodiversity maintenance across time. All of this with respect to diversity and species composition of the post-fire naturally regenerated Aleppo pine forests understory. The study was carried out in two post-fire naturally regenerated Aleppo pine forests in the Southeastern of the Iberian Peninsula, under contrasting climatic conditions: Yeste (Albacete) shows a dry climate and Calasparra (Murcia) shows a semiarid climate. Thinning as post-fire silvicultural treatment was carried out five years after the wildfire event, in the year 1999. An experiment of artificial drought was designed to evacuate 15% of the natural rainfall in both sites, Yeste and Calasparra, to simulate climate change. Taking into account all the variables (site, silvicultural treatment and artificial drought), alpha diversity indices including species richness, Shannon and Simpson diversity indices, and plant cover, were analyzed as a measure of vegetation abundance. The results showed that plant species were affected by thinning, whereas induced drought affected total cover and species, with lower values at Yeste. Significant site variation was also observed in soil properties, species richness and total plant cover, conversely to the plant species diversity indices. We conclude that the plant community shows different responses to a simulated environment of climate change depending on the experimental site.

The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States.

PubMed

Clark, James S; Iverson, Louis; Woodall, Christopher W; Allen, Craig D; Bell, David M; Bragg, Don C; D'Amato, Anthony W; Davis, Frank W; Hersh, Michelle H; Ibanez, Ines; Jackson, Stephen T; Matthews, Stephen; Pederson, Neil; Peters, Matthew; Schwartz, Mark W; Waring, Kristen M; Zimmermann, Niklaus E

2016-07-01

We synthesize insights from current understanding of drought impacts at stand-to-biogeographic scales, including management options, and we identify challenges to be addressed with new research. Large stand-level shifts underway in western forests already are showing the importance of interactions involving drought, insects, and fire. Diebacks, changes in composition and structure, and shifting range limits are widely observed. In the eastern US, the effects of increasing drought are becoming better understood at the level of individual trees, but this knowledge cannot yet be confidently translated to predictions of changing structure and diversity of forest stands. While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought. Throughout the continental United States, the combination of projected large climate-induced shifts in suitable habitat from modeling studies and limited potential for the rapid migration of tree populations suggests that changing tree and forest biogeography could substantially lag habitat shifts already underway. Forest management practices can partially ameliorate drought impacts through reductions in stand density, selection of drought-tolerant species and genotypes, artificial regeneration, and the development of multistructured stands. However, silvicultural treatments also could exacerbate drought impacts unless implemented with careful attention to site and stand characteristics. Gaps in our understanding should motivate new research on the effects of interactions involving climate and other species at the stand scale and how interactions and multiple responses are represented in models. This assessment indicates that, without a stronger empirical basis for drought impacts at the stand scale, more complex models may provide limited guidance. © 2016 John Wiley & Sons Ltd.

Holocene vegetation and fire history of the mountains of northern Sicily (Italy)

USGS Publications Warehouse

Tinner, Willy; Vescovi, Elisa; Van Leeuwen, Jacqueline; Colombaroli, Daniele; Henne, Paul; Kaltenrieder, Petra; Morales-Molino, Cesar; Beffa, Giorgia; Gnaegi, Bettina; Van der Knaap, Pim W O; La Mantia, Tommaso; Pasta, Salvatore

2016-01-01

Knowledge about vegetation and fire history of the mountains of Northern Sicily is scanty. We analysed five sites to fill this gap and used terrestrial plant macrofossils to establish robust radiocarbon chronologies. Palynological records from Gorgo Tondo, Gorgo Lungo, Marcato Cixé, Urgo Pietra Giordano and Gorgo Pollicino show that under natural or near natural conditions, deciduous forests (Quercus pubescens, Q. cerris, Fraxinus ornus, Ulmus), that included a substantial portion of evergreen broadleaved species (Q. suber, Q. ilex, Hedera helix), prevailed in the upper meso-mediterranean belt. Mesophilous deciduous and evergreen broadleaved trees (Fagus sylvatica, Ilex aquifolium) dominated in the natural or quasi-natural forests of the oro-mediterranean belt. Forests were repeatedly opened for agricultural purposes. Fire activity was closely associated with farming, providing evidence that burning was a primary land use tool since Neolithic times. Land use and fire activity intensified during the Early Neolithic at 5000 bc, at the onset of the Bronze Age at 2500 bc and at the onset of the Iron Age at 800 bc. Our data and previous studies suggest that the large majority of open land communities in Sicily, from the coastal lowlands to the mountain areas below the thorny-cushion Astragalus belt (ca. 1,800 m a.s.l.), would rapidly develop into forests if land use ceased. Mesophilous Fagus-Ilex forests developed under warm mid Holocene conditions and were resilient to the combined impacts of humans and climate. The past ecology suggests a resilience of these summer-drought adapted communities to climate warming of about 2 °C. Hence, they may be particularly suited to provide heat and drought-adaptedFagus sylvatica ecotypes for maintaining drought-sensitive Central European beech forests under global warming conditions.

Effect of prior disturbances on the extent and severity of wildfire in Colorado subalpine forests.

PubMed

Kulakowski, Dominik; Veblen, Thomas T

2007-03-01

Disturbances are important in creating spatial heterogeneity of vegetation patterns that in turn may affect the spread and severity of subsequent disturbances. Between 1997 and 2002 extensive areas of subalpine forests in northwestern Colorado were affected by a blowdown of trees, bark beetle outbreaks, and salvage logging. Some of these stands were also affected by severe fires in the late 19th century. During a severe drought in 2002, fires affected extensive areas of these subalpine forests. We evaluated and modeled the extent and severity of the 2002 fires in relation to these disturbances that occurred over the five years prior to the fires and in relation to late 19th century stand-replacing fires. Occurrence of disturbances prior to 2002 was reconstructed using a combination of tree-ring methods, aerial photograph interpretation, field surveys, and geographic information systems (GIS). The extent and severity of the 2002 fires were based on the normalized difference burn ratio (NDBR) derived from satellite imagery. GIS and classification trees were used to analyze the effects of prefire conditions on the 2002 fires. Previous disturbance history had a significant influence on the severity of the 2002 fires. Stands that were severely blown down (> 66% trees down) in 1997 burned more severely than other stands, and young (approximately 120 year old) postfire stands burned less severely than older stands. In contrast, prefire disturbances were poor predictors of fire extent, except that young (approximately 120 years old) postfire stands were less extensively burned than older stands. Salvage logging and bark beetle outbreaks that followed the 1997 blowdown (within the blowdown as well as in adjacent forest that was not blown down) did not appear to affect fire extent or severity. Conclusions regarding the influence of the beetle outbreaks on fire extent and severity are limited, however, by spatial and temporal limitations associated with aerial detection surveys of beetle activity. Thus, fire extent in these forests is largely independent of prefire disturbance history and vegetation conditions. In contrast, fire severity, even during extreme fire weather and in conjunction with a multiyear drought, is influenced by prefire stand conditions, including the history of previous disturbances.

Effects of Climate Variability and Accelerated Forest Thinning on Watershed-Scale Runoff in Southwestern USA Ponderosa Pine Forests

PubMed Central

Robles, Marcos D.; Marshall, Robert M.; O'Donnell, Frances; Smith, Edward B.; Haney, Jeanmarie A.; Gori, David F.

2014-01-01

The recent mortality of up to 20% of forests and woodlands in the southwestern United States, along with declining stream flows and projected future water shortages, heightens the need to understand how management practices can enhance forest resilience and functioning under unprecedented scales of drought and wildfire. To address this challenge, a combination of mechanical thinning and fire treatments are planned for 238,000 hectares (588,000 acres) of ponderosa pine (Pinus ponderosa) forests across central Arizona, USA. Mechanical thinning can increase runoff at fine scales, as well as reduce fire risk and tree water stress during drought, but the effects of this practice have not been studied at scales commensurate with recent forest disturbances or under a highly variable climate. Modifying a historical runoff model, we constructed scenarios to estimate increases in runoff from thinning ponderosa pine at the landscape and watershed scales based on driving variables: pace, extent and intensity of forest treatments and variability in winter precipitation. We found that runoff on thinned forests was about 20% greater than unthinned forests, regardless of whether treatments occurred in a drought or pluvial period. The magnitude of this increase is similar to observed declines in snowpack for the region, suggesting that accelerated thinning may lessen runoff losses due to warming effects. Gains in runoff were temporary (six years after treatment) and modest when compared to mean annual runoff from the study watersheds (0–3%). Nonetheless gains observed during drought periods could play a role in augmenting river flows on a seasonal basis, improving conditions for water-dependent natural resources, as well as benefit water supplies for downstream communities. Results of this study and others suggest that accelerated forest thinning at large scales could improve the water balance and resilience of forests and sustain the ecosystem services they provide. PMID:25337823

Effects of climate variability and accelerated forest thinning on watershed-scale runoff in southwestern USA ponderosa pine forests.

PubMed

Robles, Marcos D; Marshall, Robert M; O'Donnell, Frances; Smith, Edward B; Haney, Jeanmarie A; Gori, David F

2014-01-01

The recent mortality of up to 20% of forests and woodlands in the southwestern United States, along with declining stream flows and projected future water shortages, heightens the need to understand how management practices can enhance forest resilience and functioning under unprecedented scales of drought and wildfire. To address this challenge, a combination of mechanical thinning and fire treatments are planned for 238,000 hectares (588,000 acres) of ponderosa pine (Pinus ponderosa) forests across central Arizona, USA. Mechanical thinning can increase runoff at fine scales, as well as reduce fire risk and tree water stress during drought, but the effects of this practice have not been studied at scales commensurate with recent forest disturbances or under a highly variable climate. Modifying a historical runoff model, we constructed scenarios to estimate increases in runoff from thinning ponderosa pine at the landscape and watershed scales based on driving variables: pace, extent and intensity of forest treatments and variability in winter precipitation. We found that runoff on thinned forests was about 20% greater than unthinned forests, regardless of whether treatments occurred in a drought or pluvial period. The magnitude of this increase is similar to observed declines in snowpack for the region, suggesting that accelerated thinning may lessen runoff losses due to warming effects. Gains in runoff were temporary (six years after treatment) and modest when compared to mean annual runoff from the study watersheds (0-3%). Nonetheless gains observed during drought periods could play a role in augmenting river flows on a seasonal basis, improving conditions for water-dependent natural resources, as well as benefit water supplies for downstream communities. Results of this study and others suggest that accelerated forest thinning at large scales could improve the water balance and resilience of forests and sustain the ecosystem services they provide.

Regional forest landscape restoration priorities: Integrating historical conditions and an uncertain future in the northern Rocky Mountains

Treesearch

Barry L. Bollenbacher; Russell T. Graham; Keith M. Reynolds

2014-01-01

National law and policy direct the management of the National Forests, with restoring resilient forest conditions being an overarching theme. Climate is a major driver of disturbances that affect ecosystems, especially those with vegetation that show large departures from historical conditions. Drought, fire, insects, and diseases are common forest stressors whose...

Climate change and the eco-hydrology of fire: Will area burned increase in a warming western USA?

PubMed

McKenzie, Donald; Littell, Jeremy S

2017-01-01

Wildfire area is predicted to increase with global warming. Empirical statistical models and process-based simulations agree almost universally. The key relationship for this unanimity, observed at multiple spatial and temporal scales, is between drought and fire. Predictive models often focus on ecosystems in which this relationship appears to be particularly strong, such as mesic and arid forests and shrublands with substantial biomass such as chaparral. We examine the drought-fire relationship, specifically the correlations between water-balance deficit and annual area burned, across the full gradient of deficit in the western USA, from temperate rainforest to desert. In the middle of this gradient, conditional on vegetation (fuels), correlations are strong, but outside this range the equivalence hotter and drier equals more fire either breaks down or is contingent on other factors such as previous-year climate. This suggests that the regional drought-fire dynamic will not be stationary in future climate, nor will other more complex contingencies associated with the variation in fire extent. Predictions of future wildfire area therefore need to consider not only vegetation changes, as some dynamic vegetation models now do, but also potential changes in the drought-fire dynamic that will ensue in a warming climate. © 2016 by the Ecological Society of America.

Influences of prior wildfires on vegetation response to subsequent fire in a reburned Southwestern landscape.

PubMed

Coop, Jonathan D; Parks, Sean A; McClernan, Sarah R; Holsinger, Lisa M

2016-03-01

Large and severe wildfires have raised concerns about the future of forested landscapes in the southwestern United States, especially under repeated burning. In 2011, under extreme weather and drought conditions, the Las Conchas fire burned over several previous burns as well as forests not recently exposed to fire. Our purpose was to examine the influences of prior wildfires on plant community composition and structure, subsequent burn severity, and vegetation response. To assess these relationships, we used satellite-derived measures of burn severity and a nonmetric multidimensional scaling of pre- and post- Las Conchas field samples. Earlier burns were associated with shifts from forested sites to open savannas and meadows, oak scrub, and ruderal communities. These non-forested vegetation types exhibited both resistance to subsequent fire, measured by reduced burn severity, and resilience to reburning, measured by vegetation recovery relative to forests not exposed to recent prior fire. Previous shifts toward non-forested states were strongly reinforced by reburning. Ongoing losses of forests and their ecological values confirm the need for restoration interventions. However, given future wildfire and climate projections, there may also be opportunities presented by transformations toward fire-resistant and resilient vegetation types within portions of the landscape.

The role of climate and vegetation change in shaping past and future fire regimes in the northwestern US and the implications for ecosystem management

USGS Publications Warehouse

Whitlock, C.; Shafer, S.L.; Marlon, J.

2003-01-01

Fire is an important part of the disturbance regimes of northwestern US forests and its role in maintaining and altering forest vegetation is evident in the paleoecological record of the region. Long-term reconstructions of Holocene fire regimes, provided by the analysis of charcoal, pollen, and other fire proxies in a network of lake records, indicate that the Pacific Northwest and summer-dry regions of the northern Rocky Mountains experienced their highest fire activity in the early Holocene (11,000-7000 years ago) and during the Medieval Warm Period (ca. 1000 years ago) when drought conditions were more severe than today. In contrast, in summer-wet areas of the northern Rocky Mountains, the period of highest fire activity was registered in the last 7000 years when dry woodland vegetation developed. When synthesized across the entire northwestern US, the paleoecological record reveals that past and present fire regimes are strongly controlled by climate changes occurring on multiple time scales. The scarcity of fires in the 20th century in some northwestern US ecosystems may be the result of successful fire suppression policies, but in wetter forests this absence is consistent with long-term fire regime patterns. In addition, simulations of potential future climate and vegetation indicate that future fire conditions in some parts of the northwestern US could be more severe than they are today. The Holocene record of periods of intensified summer drought is used to assess the nature of future fire-climate-vegetation linkages in the region. ?? 2003 Elsevier Science B.V. All rights reserved.

Massive mortality of aspen following severe drought along the southern edge of the Canadian boreal forest

PubMed Central

Michaelian, Michael; Hogg, Edward H; Hall, Ronald J; Arsenault, Eric

2011-01-01

Drought-induced, regional-scale dieback of forests has emerged as a global concern that is expected to escalate under model projections of climate change. Since 2000, drought of unusual severity, extent, and duration has affected large areas of western North America, leading to regional-scale dieback of forests in the southwestern US. We report on drought impacts on forests in a region farther north, encompassing the transition between boreal forest and prairie in western Canada. A central question is the significance of drought as an agent of large-scale tree mortality and its potential future impact on carbon cycling in this cold region. We used a combination of plot-based, meteorological, and remote sensing measures to map and quantify aboveground, dead biomass of trembling aspen (Populus tremuloides Michx.) across an 11.5 Mha survey area where drought was exceptionally severe during 2001–2002. Within this area, a satellite-based land cover map showed that aspen-dominated broadleaf forests occupied 2.3 Mha. Aerial surveys revealed extensive patches of severe mortality (>55%) resembling the impacts of fire. Dead aboveground biomass was estimated at 45 Mt, representing 20% of the total aboveground biomass, based on a spatial interpolation of plot-based measurements. Spatial variation in percentage dead biomass showed a moderately strong correlation with drought severity. In the prairie-like, southern half of the study area where the drought was most severe, 35% of aspen biomass was dead, compared with an estimated 7% dead biomass in the absence of drought. Drought led to an estimated 29 Mt increase in dead biomass across the survey area, corresponding to 14 Mt of potential future carbon emissions following decomposition. Many recent, comparable episodes of drought-induced forest dieback have been reported from around the world, which points to an emerging need for multiscale monitoring approaches to quantify drought effects on woody biomass and carbon cycling across large areas.

Field measurements of trace gases emitted by prescribed fires in southeastern US pine forests using an open-path FTIR system

Treesearch

Sheryl K. Akagi; Ian R. Burling; A. Mendoza; Timothy J. Johnson; M. Cameron; David W. T. Griffith; C. Paton-Walsh; David R. Weise; James Reardon; Robert J. Yokelson

2014-01-01

We report trace-gas emission factors from three pine-understory prescribed fires in South Carolina, US measured during the fall of 2011. The fires were more intense than many prescribed burns because the fuels included mature pine stands not subjected to prescribed fire in decades that were lit following an extended drought. Emission factors were measured with a fixed...

Field measurements of trace gases emitted by prescribed fires in southeastern US pine forests using an open-path FTIR system

Treesearch

S. K. Akagi; I. R. Burling; A. Mendoza; T. J. Johnson; M. Cameron; D. W. T. Griffith; C. Paton-Walsh; D. R. Weise; J. Reardon; R. J. Yokelson

2013-01-01

We report trace-gas emission factors from three pine-understory prescribed fires in South Carolina, US measured during the fall of 2011. The fires were more intense than many prescribed burns because the fuels included mature pine stands not subjected to prescribed fire in decades that were lit following an extended drought. The emission factors were measured...

Cordilleran forest scaling dynamics and disturbance regimes quantified by aerial LiDAR

Treesearch

Tyson L. Swetnam

2013-01-01

Semi-arid forests are in a period of rapid transition as a result of unprecedented landscape scale fires, insect outbreaks, drought, and anthropogenic land use practices. Understanding how historically episodic disturbances led to coherent forest structural and spatial patterns that promoted resilience and resistance is a critical part of addressing change. Here my...

Mixed-severity fire history at a forest-grassland ecotone in west central British Columbia, Canada.

PubMed

Harvey, Jill E; Smith, Dan J; Veblen, Thomas T

2017-09-01

This study examines spatially variable stand structure and fire-climate relationships at a low elevation forest-grassland ecotone in west central British Columbia, Canada. Fire history reconstructions were based on samples from 92 fire-scarred trees and stand demography from 27 plots collected over an area of about 7 km 2 . We documented historical chronologies of widespread fires and localized grassland fires between AD 1600 and 1900. Relationships between fire events, reconstructed values of the Palmer Drought Severity Index, and annual precipitation were examined using superposed epoch and bivariate event analyses. Widespread fires occurred during warm, dry years and were preceded by multiple anomalously dry, warm years. Localized fires that affected only grassland-proximal forests were more frequent than widespread fires. These localized fires showed a lagged, positive relationship with wetter conditions. The landscape pattern of forest structure provided further evidence of complex fire activity with multiple plots shown to have experienced low-, mixed-, and/or high-severity fires over the last four centuries. We concluded that this forest-grassland ecotone was characterized by fires of mixed severity, dominated by frequent, low-severity fires punctuated by widespread fires of moderate to high severity. This landscape-level variability in fire-climate relationships and patterns in forest structure has important implications for fire and grassland management in west central British Columbia and similar environments elsewhere. Forest restoration techniques such as prescribed fire and thinning are oftentimes applied at the forest-grassland ecotone on the basis that historically high frequency, low-severity fires defined the character of past fire activity. This study provides forest managers and policy makers with important information on mixed-severity fire activity at a low elevation forest-grassland ecotone, a crucial prerequisite for the effective management of these complex ecosystems. © 2017 by the Ecological Society of America.

Forest response and recovery following disturbance in upland forests of the Atlantic Coastal Plain.

PubMed

Schäfer, Karina V R; Renninger, Heidi J; Carlo, Nicholas J; Vanderklein, Dirk W

2014-01-01

Carbon and water cycling of forests contribute significantly to the Earth's overall biogeochemical cycling and may be affected by disturbance and climate change. As a larger body of research becomes available about leaf-level, ecosystem and regional scale effects of disturbances on forest ecosystems, a more mechanistic understanding is developing which can improve modeling efforts. Here, we summarize some of the major effects of physical and biogenic disturbances, such as drought, prescribed fire, and insect defoliation, on leaf and ecosystem-scale physiological responses as well as impacts on carbon and water cycling in an Atlantic Coastal Plain upland oak/pine and upland pine forest. During drought, stomatal conductance and canopy stomatal conductance were reduced, however, defoliation increased conductance on both leaf-level and canopy scale. Furthermore, after prescribed fire, leaf-level stomatal conductance was unchanged for pines but decreased for oaks, while canopy stomatal conductance decreased temporarily, but then rebounded the following growing season, thus exhibiting transient responses. This study suggests that forest response to disturbance varies from the leaf to ecosystem level as well as species level and thus, these differential responses interplay to determine the fate of forest structure and functioning post disturbance.

The role of fire in the boreal carbon budget

USGS Publications Warehouse

Harden, J.W.; Trumbore, S.E.; Stocks, B.J.; Hirsch, A.; Gower, S.T.; O'Neill, K. P.; Kasischke, E.S.

2000-01-01

To reconcile observations of decomposition rates, carbon inventories, and net primary production (NPP), we estimated long-term averages for C exchange in boreal forests near Thompson, Manitoba. Soil drainage as defined by water table, moss cover, and permafrost dynamics, is the dominant control on direct fire emissions. In upland forests, an average of about 10-30% of annual NPP was likely consumed by fire over the past 6500 years since these landforms and ecosystems were established. This long-term, average fire emission is much larger than has been accounted for in global C cycle models and may forecast an increase in fire activity for this region. While over decadal to century times these boreal forests may be acting as slight net sinks for C from the atmosphere to land, periods of drought and severe fire activity may result in net sources of C from these systems.

Global warming accelerates drought-induced forest death

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDowell, Nathan; Pockman, William

2013-07-09

Many southwestern forests in the United States will disappear or be heavily altered by 2050, according to a series of joint Los Alamos National Laboratory-University of New Mexico studies. Nathan McDowell, a Los Alamos plant physiologist, and William Pockman, a UNM biology professor, explain that their research, and more from scientists around the world, is forecasting that by 2100 most conifer forests should be heavily disturbed, if not gone, as air temperatures rise in combination with drought. "Everybody knows trees die when there's a drought, if there's bark beetles or fire, yet nobody in the world can predict it withmore » much accuracy." McDowell said. "What's really changed is that the temperature is going up," thus the researchers are imposing artificial drought conditions on segments of wild forest in the Southwest and pushing forests to their limit to discover the exact processes of mortality and survival. The study is centered on drought experiments in woodlands at both Los Alamos and the Sevilleta National Wildlife Refuge in central New Mexico. Both sites are testing hypotheses about how forests die on mature, wild trees, rather than seedlings in a greenhouse, through the ecosystem-scale removal of 50 percent of yearly precipitation through large water-diversion trough systems.« less

Air pollution increases forest susceptibility to wildfires: a case study for the San Bernardino Mountains in southern California

Treesearch

N.E. Grulke; R.A. Minnich; T. Paine; P. Riggan

2010-01-01

Many factors increase susceptibility of forests to wildfire. Among them are increases in human population, changes in land use, fire suppression, and frequent droughts. These factors have been exacerbating forest susceptibility to wildfires over the last century in southern California. Here we report on the significant role that air pollution has on increasing forest...

Tropical North Atlantic ocean-atmosphere interactions synchronize forest carbon losses from hurricanes and Amazon fires

NASA Astrophysics Data System (ADS)

Chen, Yang; Randerson, James T.; Morton, Douglas C.

2015-08-01

We describe a climate mode synchronizing forest carbon losses from North and South America by analyzing time series of tropical North Atlantic sea surface temperatures (SSTs), landfall hurricanes and tropical storms, and Amazon fires during 1995-2013. Years with anomalously high tropical North Atlantic SSTs during March-June were often followed by a more active hurricane season and a larger number of satellite-detected fires in the southern Amazon during June-November. The relationship between North Atlantic tropical cyclones and southern Amazon fires (r = 0.61, p < 0.003) was stronger than links between SSTs and either cyclones or fires alone, suggesting that fires and tropical cyclones were directly coupled to the same underlying atmospheric dynamics governing tropical moisture redistribution. These relationships help explain why seasonal outlook forecasts for hurricanes and Amazon fires both failed in 2013 and may enable the design of improved early warning systems for drought and fire in Amazon forests.

Major losses of nutrients following a severe drought in a boreal forest.

PubMed

Houle, Daniel; Lajoie, Geneviève; Duchesne, Louis

2016-11-28

Because of global warming, the frequency and severity of droughts are expected to increase, which will have an impact on forest ecosystem health worldwide 1 . Although the impact of drought on tree growth and mortality is being increasingly documented 2-4 , very little is known about the impact on nutrient cycling in forest ecosystems. Here, based on long-term monitoring data, we report nutrient fluxes in a boreal forest before, during and following a severe drought in July 2012. During and shortly after the drought, we observed high throughfall (rain collected below the canopy) concentrations of nutrient base cations (potassium, calcium and magnesium), chlorine, phosphorus and dissolved organic carbon (DOC), differing by one to two orders of magnitude relative to the long-term normal, and resulting in important canopy losses. The high throughfall fluxes had repercussions in the soil solution at a depth of 30 cm, leading to high DOC, chlorine and potassium concentrations. The net potassium losses (atmospheric deposition minus leaching losses) following the drought were especially important, being the equivalent of nearly 20 years of net losses under 'normal' conditions. Our data show that droughts have unexpected impacts on nutrient cycling through impacts on tree canopy and soils and may lead to important episodes of potassium losses from boreal forest ecosystems. The potassium losses associated with drought will add to those originating from tree harvesting and from forest fires and insect outbreaks 5-7 (with the last two being expected to increase in the future as a result of climate change), and may contribute to reduced potassium availability in boreal forests in a warming world.

A stand-replacing fire history in upper montane forests of the southern Rocky Mountains

USGS Publications Warehouse

Margolis, E.Q.; Swetnam, T.W.; Allen, Craig D.

2007-01-01

Dendroecological techniques were applied to reconstruct stand-replacing fire history in upper montane forests in northern New Mexico and southern Colorado. Fourteen stand-replacing fires were dated to 8 unique fire years (1842–1901) using four lines of evidence at each of 12 sites within the upper Rio Grande Basin. The four lines of evidence were (i) quaking aspen (Populus tremuloides Michx.) inner-ring dates, (ii) fire-killed conifer bark-ring dates, (iii) tree-ring width changes or other morphological indicators of injury, and (iv) fire scars. The annual precision of dating allowed the identification of synchronous stand-replacing fire years among the sites, and co-occurrence with regional surface fire events previously reconstructed from a network of fire scar collections in lower elevation pine forests across the southwestern United States. Nearly all of the synchronous stand-replacing and surface fire years coincided with severe droughts, because climate variability created regional conditions where stand-replacing fires and surface fires burned across ecosystems. Reconstructed stand-replacing fires that predate substantial Anglo-American settlement in this region provide direct evidence that stand-replacing fires were a feature of high-elevation forests before extensive and intensive land-use practices (e.g., logging, railroad, and mining) began in the late 19th century.

Protection against fire in the mountainous forests of Greece case study: forest complex of W. Nestos

NASA Astrophysics Data System (ADS)

Drosos, Vasileios C.; Giannoulas, Vasileios J.; Stergiadou, Anastasia; Karagiannis, Evaggelos; Doukas, Aristotelis-Kosmas G.

2014-08-01

Forest fires are an ancient phenomenon. Appear, however, with devastating frequency and intensity over the last 30 years. In our country, the climatic conditions in combination with the intense relief, favor their rapid spread. Considering the fact that environmental conditions provided for decades even worse (increased temperature, drought and vegetation), then the problem of forest fires in our country, is expected to become more intense. The work focuses on the optimization model of the opening up of the forest mountain areas taking into account the prevention and suppression of forest fires. Research area is the mountain forest complex of W. Nestos of Drama Prefecture. The percentage of forest protection area is examined under the light whether the total hose length corresponds to the actual operational capacity to reach a fire source. For this reason are decided to present a three case study concerning area of the forest being protected by fire extinguishing vehicles. The first one corresponds to a fire suppression bandwidth (buffer zone) with a capacity radius of 150m uphill and 250m downhill from the origin point where the fire extinguishing vehicle stands. The second one corresponds to a fire suppression capacity of 200m uphill and 400m downhill and the third one corresponds to a fire suppression capacity of 300m uphill and 500m downhill. The most important forest technical infrastructures to prevent fire are roads network (opening up) for fire protection and buffer zones. Patrols of small and agile 4 × 4 appropriately equipped (pipe length of 500 meters and putting pressure on uphill to 300 meters) for the first attack of the fire in the summer months coupled with early warning of fire observatories adequately cover the forest protection of W. Nestos complex. But spatial distribution needed improvements to a road density of the optimum economic Dec, both forest protection and for better management (skidding) of woody capital.

Patterns of mortality in an old-growth mixed-conifer forest of the Southern Sierra Nevada, California

Treesearch

Thomas F. Smith; David M. Rizzo; Malcolm North

2005-01-01

Mortality patterns in an old-growth, mixed-conifer forest, in the absence of wildfire, were investigated at the Teakettle Experimental Forest from 2000 to 2002. We tested the hypothesis that after a century of fire suppression, pathogen- and insect-associated mortality (between episodic droughts) would be significantly greater on ingrowth trees (i.e., smaller-diameter...

Tree mortality from fires, bark beetles, and timber harvest during a hot and dry decade in the western United States (2003-2012)

NASA Astrophysics Data System (ADS)

Berner, Logan T.; Law, Beverly E.; Meddens, Arjan J. H.; Hicke, Jeffrey A.

2017-06-01

High temperatures and severe drought contributed to extensive tree mortality from fires and bark beetles during the 2000s in parts of the western continental United States. Several states in this region have greenhouse gas (GHG) emission targets and would benefit from information on the amount of carbon stored in tree biomass killed by disturbance. We quantified mean annual tree mortality from fires, bark beetles, and timber harvest from 2003-2012 for each state in this region. We estimated tree mortality from fires and beetles using tree aboveground carbon (AGC) stock and disturbance data sets derived largely from remote sensing. We quantified tree mortality from harvest using data from US Forest Service reports. In both cases, we used Monte Carlo analyses to track uncertainty associated with parameter error and temporal variability. Regional tree mortality from harvest, beetles, and fires (MORTH+B+F) together averaged 45.8 ± 16.0 Tg AGC yr-1 (±95% confidence interval), indicating a mortality rate of 1.10 ± 0.38% yr-1. Harvest accounted for the largest percentage of MORTH+B+F (˜50%), followed by beetles (˜32%), and fires (˜18%). Tree mortality from harvest was concentrated in Washington and Oregon, where harvest accounted for ˜80% of MORTH+B+F in each state. Tree mortality from beetles occurred widely at low levels across the region, yet beetles had pronounced impacts in Colorado and Montana, where they accounted for ˜80% of MORTH+B+F. Tree mortality from fires was highest in California, though fires accounted for the largest percentage of MORTH+B+F in Arizona and New Mexico (˜50%). Drought and human activities shaped regional variation in tree mortality, highlighting opportunities and challenges to managing GHG emissions from forests. Rising temperatures and greater risk of drought will likely increase tree mortality from fires and bark beetles during coming decades in this region. Thus, sustained monitoring and mapping of tree mortality is necessary to inform forest and GHG management.

A Global Perspective on Warmer Droughts as a Key Driver of Forest Disturbances and Tree Mortality (Invited)

NASA Astrophysics Data System (ADS)

Allen, C. D.

2013-12-01

Recent global warming, in concert with episodic droughts, is causing elevated levels of both chronic and acute forest water stress across large regions. Such increases in water stress affect forest dynamics in multiple ways, including by amplifying the incidence and severity of many significant forest disturbances, particularly drought-induced tree mortality, wildfire, and outbreaks of damaging insects and diseases. Emerging global-scale patterns of drought-related forest die-off are presented, including a newly updated map overview of documented drought- and heat-induced tree mortality events from around the world, demonstrating the vulnerability of all major forest types to forest drought stress, even in typically wet environments. Comparative patterns of drought stress and associated forest disturbances are reviewed for several regions (southwestern Australia, Inner Asia, western North America, Mediterranean Basin), including interactions among climate and various disturbance processes. From the Southwest USA, research is presented that derives a tree-ring-based Forest Drought Stress Index (FDSI) for the most regionally-widespread conifer species (Pinus edulis, Pinus ponderosa, and Pseudotsuga menziesii), demonstrating recent escalation of FDSI to extreme levels relative to the past 1000 years, due to both drought and especially warming. This new work further highlights strong correlations between drought stress and amplified forest disturbances (fire, bark beetle outbreaks), and projects that by CE 2050 anticipated regional warming will cause mean FDSI values to reach historically unprecedented levels that may exceed thresholds for the survival of current tree species in large portions of their current range in the Southwest. Similar patterns of recent climate-amplified forest disturbance risk are apparent from a variety of relatively dry regions across this planet, and given climate projections for substantially warmer temperatures and greater drought stress for many areas globally, the growing water-stress risks to forest health in such regions are becoming clearer. However, the effects of drought stress on forest dynamics are ameliorated through diverse compensatory and resilience-enhancing mechanisms and processes which operate at scales ranging from intracellular tree physiologies and individual tree developmental and morphological adjustments to species population-level demographic and genetic responses to forest stand-level structural and compositional responses up to landscape-scale tree host-insect pest outbreak dynamics and forest-climate ecohydrological feedbacks. In addition, significant uncertainties exist regarding how various other global atmospheric changes (e.g., CO2 enrichment, increased N deposition, and elevated surface-level ozone) will interact with the world's diverse spectrum of tree species to also affect global forest dynamics. Research efforts to address such core scientific uncertainties associated with modeling drought-induced tree mortality and resultant forest dynamics will be discussed.

Strengthening community participation in reducing GHG emission from forest and peatland fire

NASA Astrophysics Data System (ADS)

Thoha, A. S.; Saharjo, B. H.; Boer, R.; Ardiansyah, M.

2018-02-01

Strengthening community participation is needed to find solutions to encourage community more participate in reducing Green House Gas (GHG) from forest and peatland fire. This research aimed to identify stakeholders that have the role in forest and peatland fire control and to formulate strengthening model of community participation through community-based early warning fire. Stakeholder mapping and action research were used to determine stakeholders that had potential influence and interest and to formulate strengthening model of community participation in reducing GHG from forest and peatland fire. There was found that position of key players in the mapping of stakeholders came from the government institution. The existence of community-based fire control group can strengthen government institution through collaborating with stakeholders having strong interest and influence. Moreover, it was found several local knowledge in Kapuas District about how communities predict drought that have potential value for developing the community-based early warning fire system. Formulated institutional model in this research also can be further developed as a model institution in the preservation of natural resources based on local knowledge. In conclusion, local knowledge and community-based fire groups can be integrated within strengthening model of community participation in reducing GHG from forest and peatland fire.

Ancient charcoal as a natural archive for paleofire regime and vegetation change in the Mayumbe, Democratic Republic of the Congo

NASA Astrophysics Data System (ADS)

Hubau, Wannes; Van den Bulcke, Jan; Kitin, Peter; Mees, Florias; Baert, Geert; Verschuren, Dirk; Nsenga, Laurent; Van Acker, Joris; Beeckman, Hans

2013-09-01

Charcoal was sampled in four soil profiles at the Mayumbe forest boundary (DRC). Five fire events were recorded and 44 charcoal types were identified. One stratified profile yielded charcoal assemblages around 530 cal yr BP and > 43.5 cal ka BP in age. The oldest assemblage precedes the period of recorded anthropogenic burning, illustrating occasional long-term absence of fire but also natural wildfire occurrences within tropical rainforest. No other charcoal assemblages older than 2500 cal yr BP were recorded, perhaps due to bioturbation and colluvial reworking. The recorded paleofires were possibly associated with short-lived climate anomalies. Progressively dry climatic conditions since ca. 4000 cal yr BP onward did not promote paleofire occurrence until increasing seasonality affected vegetation at the end of the third millennium BP, as illustrated by a fire occurring in mature rainforest that persisted until around 2050 cal yr BP. During a drought episode coinciding with the 'Medieval Climate Anomaly', mature rainforest was locally replaced by woodland savanna. Charcoal remains from pioneer forest indicate that fire hampered forest regeneration after climatic drought episodes. The presence of pottery shards and oil-palm endocarps associated with two relatively recent paleofires suggests that the effects of climate variability were amplified by human activities.

Estimation of Wild Fire Risk Area based on Climate and Maximum Entropy in Korean Peninsular

NASA Astrophysics Data System (ADS)

Kim, T.; Lim, C. H.; Song, C.; Lee, W. K.

2015-12-01

The number of forest fires and accompanying human injuries and physical damages has been increased by frequent drought. In this study, forest fire danger zone of Korea is estimated to predict and prepare for future forest fire hazard regions. The MaxEnt (Maximum Entropy) model is used to estimate the forest fire hazard region which estimates the probability distribution of the status. The MaxEnt model is primarily for the analysis of species distribution, but its applicability for various natural disasters is getting recognition. The detailed forest fire occurrence data collected by the MODIS for past 5 years (2010-2014) is used as occurrence data for the model. Also meteorology, topography, vegetation data are used as environmental variable. In particular, various meteorological variables are used to check impact of climate such as annual average temperature, annual precipitation, precipitation of dry season, annual effective humidity, effective humidity of dry season, aridity index. Consequently, the result was valid based on the AUC(Area Under the Curve) value (= 0.805) which is used to predict accuracy in the MaxEnt model. Also predicted forest fire locations were practically corresponded with the actual forest fire distribution map. Meteorological variables such as effective humidity showed the greatest contribution, and topography variables such as TWI (Topographic Wetness Index) and slope also contributed on the forest fire. As a result, the east coast and the south part of Korea peninsula were predicted to have high risk on the forest fire. In contrast, high-altitude mountain area and the west coast appeared to be safe with the forest fire. The result of this study is similar with former studies, which indicates high risks of forest fire in accessible area and reflects climatic characteristics of east and south part in dry season. To sum up, we estimated the forest fire hazard zone with existing forest fire locations and environment variables and had meaningful result with artificial and natural effect. It is expected to predict future forest fire risk with future climate variables as the climate changes.

Fire-induced erosion and millennial-scale climate change in northern ponderosa pine forests.

PubMed

Pierce, Jennifer L; Meyer, Grant A; Jull, A J Timothy

2004-11-04

Western US ponderosa pine forests have recently suffered extensive stand-replacing fires followed by hillslope erosion and sedimentation. These fires are usually attributed to increased stand density as a result of fire suppression, grazing and other land use, and are often considered uncharacteristic or unprecedented. Tree-ring records from the past 500 years indicate that before Euro-American settlement, frequent, low-severity fires maintained open stands. However, the pre-settlement period between about ad 1500 and ad 1900 was also generally colder than present, raising the possibility that rapid twentieth-century warming promoted recent catastrophic fires. Here we date fire-related sediment deposits in alluvial fans in central Idaho to reconstruct Holocene fire history in xeric ponderosa pine forests and examine links to climate. We find that colder periods experienced frequent low-severity fires, probably fuelled by increased understory growth. Warmer periods experienced severe droughts, stand-replacing fires and large debris-flow events that comprise a large component of long-term erosion and coincide with similar events in sub-alpine forests of Yellowstone National Park. Our results suggest that given the powerful influence of climate, restoration of processes typical of pre-settlement times may be difficult in a warmer future that promotes severe fires.

Forest Products Laboratory research program on small-diameter material.

Treesearch

2000-01-01

Forests in the United States contain a significant amount of small-diameter and underutilized material. These overstocked stands not only increase the risk of insect, disease, fire, and drought damage, but also are costly to remove. Finding economical and marketable uses for small-diameter and underutilized material would alleviate these problems while improving...

History of Piedmont Forests: Implications For Current Pine Management

Treesearch

D.H. Van Lear; R.A. Harper; P.R. Kapeluck; W.D. Carroll

2004-01-01

Piedmont forests were maintained for millennia in an open condition by anthropogenic- and lightning-ignited fires. After European settlement, row-crop agriculture caused serious soil erosion, making Piedmont soils less capable of supplying moisture and nutrients during drought periods. Dense stands of pine, both naturally and artificially regenerated over the past 70...

Forest processes [Chapter 3

Treesearch

Michael G. Ryan; James M. Vose; Paul J. Hanson; Louis R. Iverson; Chelcy F. Miniat; Charles H. Luce; Lawrence E. Band; Steven L. Klein; Don McKenzie; David N. Wear

2014-01-01

Some of the changes to U.S. forests will be directly caused by the effects of an altered climate, such as increases in atmospheric carbon dioxide (CO2) temperature (T), and nitrogen (N) deposition on tree growth, mortality, and regeneration. Other changes will be indirectly caused by climate-induced changes in disturbances, such as droughts, fire, insect outbreaks,...

Fire-induced Carbon Emissions and Regrowth Uptake in Western U.S. Forests: Documenting Variation Across Forest Types, Fire Severity, and Climate Regions

NASA Technical Reports Server (NTRS)

Ghimire, Bardan; Williams, Christopher A.; Collatz, George James; Vanderhoof, Melanie

2012-01-01

The forest area in the western United States that burns annually is increasing with warmer temperatures, more frequent droughts, and higher fuel densities. Studies that examine fire effects for regional carbon balances have tended to either focus on individual fires as examples or adopt generalizations without considering how forest type, fire severity, and regional climate influence carbon legacies. This study provides a more detailed characterization of fire effects and quantifies the full carbon impacts in relation to direct emissions, slow release of fire-killed biomass, and net carbon uptake from forest regrowth. We find important variations in fire-induced mortality and combustion across carbon pools (leaf, live wood, dead wood, litter, and duff) and across low- to high-severity classes. This corresponds to fire-induced direct emissions from 1984 to 2008 averaging 4 TgC/yr and biomass killed averaging 10.5 TgC/yr, with average burn area of 2723 sq km/yr across the western United States. These direct emission and biomass killed rates were 1.4 and 3.7 times higher, respectively, for high-severity fires than those for low-severity fires. The results show that forest regrowth varies greatly by forest type and with severity and that these factors impose a sustained carbon uptake legacy. The western U.S. fires between 1984 and 2008 imposed a net source of 12.3 TgC/yr in 2008, accounting for both direct fire emissions (9.5 TgC/yr) and heterotrophic decomposition of fire-killed biomass (6.1 TgC yr1) as well as contemporary regrowth sinks (3.3 TgC/yr). A sizeable trend exists toward increasing emissions as a larger area burns annually.

Dynamics, Patterns and Causes of Fires in Northwestern Amazonia

PubMed Central

Armenteras, Dolors; Retana, Javier

2012-01-01

According to recent studies, two widespread droughts occurred in the Amazon basin, one during 2005 and one during 2010. The drought increased the prevalence of climate-driven fires over most of the basin. Given the importance of human-atmosphere-vegetation interactions in tropical rainforests, these events have generated concerns over the vulnerability of this area to climate change. This paper focuses on one of the wettest areas of the basin, Northwestern Amazonia, where the interactions between the climate and fires are much weaker and where little is known about the anthropogenic drivers of fires. We have assessed the response of fires to climate over a ten-year period, and analysed the socio-economic and demographic determinants of fire occurrence. The patterns of fires and climate and their linkages in Northwestern Amazonia differ from the enhanced fire response to climate variation observed in the rest of Amazonia. The highest number of recorded fires in Northwestern Amazonia occurred in 2004 and 2007, and this did not coincide with the periods of extreme drought experienced in Amazonia in 2005 and 2010. Rather, during those years, Northwestern Amazonia experienced a relatively small numbers of fire hotspots. We have shown that fire occurrence correlated well with deforestation and was determined by anthropogenic drivers, mainly small-scale agriculture, cattle ranching (i.e., pastures) and active agricultural frontiers (including illegal crops). Thus, the particular climatic conditions for air convergence and rainfall created by proximity to the Andes, coupled with the presence of one of the most active colonisation fronts in the region, make this region differently affected by the general drought-induced fire patterns experienced by the rest of the Amazon. Moreover, the results suggest that, even in this wet region, humans are able to modify the frequency of fires and impact these historically well preserved forests. PMID:22523580

Dynamics, patterns and causes of fires in Northwestern Amazonia.

PubMed

Armenteras, Dolors; Retana, Javier

2012-01-01

According to recent studies, two widespread droughts occurred in the Amazon basin, one during 2005 and one during 2010. The drought increased the prevalence of climate-driven fires over most of the basin. Given the importance of human-atmosphere-vegetation interactions in tropical rainforests, these events have generated concerns over the vulnerability of this area to climate change. This paper focuses on one of the wettest areas of the basin, Northwestern Amazonia, where the interactions between the climate and fires are much weaker and where little is known about the anthropogenic drivers of fires. We have assessed the response of fires to climate over a ten-year period, and analysed the socio-economic and demographic determinants of fire occurrence. The patterns of fires and climate and their linkages in Northwestern Amazonia differ from the enhanced fire response to climate variation observed in the rest of Amazonia. The highest number of recorded fires in Northwestern Amazonia occurred in 2004 and 2007, and this did not coincide with the periods of extreme drought experienced in Amazonia in 2005 and 2010. Rather, during those years, Northwestern Amazonia experienced a relatively small numbers of fire hotspots. We have shown that fire occurrence correlated well with deforestation and was determined by anthropogenic drivers, mainly small-scale agriculture, cattle ranching (i.e., pastures) and active agricultural frontiers (including illegal crops). Thus, the particular climatic conditions for air convergence and rainfall created by proximity to the Andes, coupled with the presence of one of the most active colonisation fronts in the region, make this region differently affected by the general drought-induced fire patterns experienced by the rest of the Amazon. Moreover, the results suggest that, even in this wet region, humans are able to modify the frequency of fires and impact these historically well preserved forests.

Depopulation of rural landscapes exacerbates fire activity in the western Amazon.

PubMed

Uriarte, María; Pinedo-Vasquez, Miquel; DeFries, Ruth S; Fernandes, Katia; Gutierrez-Velez, Victor; Baethgen, Walter E; Padoch, Christine

2012-12-26

Destructive fires in Amazonia have occurred in the past decade, leading to forest degradation, carbon emissions, impaired air quality, and property damage. Here, we couple climate, geospatial, and province-level census data, with farmer surveys to examine the climatic, demographic, and land use factors associated with fire frequency in the Peruvian Amazon from 2000 to 2010. Although our results corroborate previous findings elsewhere that drought and proximity to roads increase fire frequency, the province-scale analysis further identifies decreases in rural populations as an additional factor. Farmer survey data suggest that increased burn scar frequency and size reflect increased flammability of emptying rural landscapes and reduced capacity to control fire. With rural populations projected to decline, more frequent drought, and expansion of road infrastructure, fire risk is likely to increase in western Amazonia. Damage from fire can be reduced through warning systems that target high-risk locations, coordinated fire fighting efforts, and initiatives that provide options for people to remain in rural landscapes.

Depopulation of rural landscapes exacerbates fire activity in the western Amazon

PubMed Central

Uriarte, María; Pinedo-Vasquez, Miquel; DeFries, Ruth S.; Fernandes, Katia; Gutierrez-Velez, Victor; Baethgen, Walter E.; Padoch, Christine

2012-01-01

Destructive fires in Amazonia have occurred in the past decade, leading to forest degradation, carbon emissions, impaired air quality, and property damage. Here, we couple climate, geospatial, and province-level census data, with farmer surveys to examine the climatic, demographic, and land use factors associated with fire frequency in the Peruvian Amazon from 2000 to 2010. Although our results corroborate previous findings elsewhere that drought and proximity to roads increase fire frequency, the province-scale analysis further identifies decreases in rural populations as an additional factor. Farmer survey data suggest that increased burn scar frequency and size reflect increased flammability of emptying rural landscapes and reduced capacity to control fire. With rural populations projected to decline, more frequent drought, and expansion of road infrastructure, fire risk is likely to increase in western Amazonia. Damage from fire can be reduced through warning systems that target high-risk locations, coordinated fire fighting efforts, and initiatives that provide options for people to remain in rural landscapes. PMID:23236144

Virtual Special Issue Preface: Forest Response to Environmental Stress: Impacts and Adaptation

Treesearch

Steven McNulty; Enzai Du; Elena Paoletti

2017-01-01

The current distribution of forest typeswas largely established at the beginning of the Holocene epoch (approximately 12,000 BCE), but forests are constantly in flux. Many regional scale stresses (e.g., drought, heat, fire, and insect) and even a few multi-regional or global stresses (e.g., 8200 BCE cooling, or the medievalwarming period) have occurred over the past 12...

Drought Legacy and the Impacts on the Amazon Forest Carbon Exchange

NASA Astrophysics Data System (ADS)

Saatchi, S. S.

2015-12-01

Sassan Saatchi1,2, Yifan Yu1, Xiang Xu2, Luiz Aragao3, Liana Anderson31Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA2Institute of Environment and Sustainability, University of California, Los Angeles, CA 90045. USA3 Remote Sensing Division, National Institute for Space Research, São José dos Campos, Brazil, 12227-010, BrazilRecent Amazonian droughts have drawn attention to the vulnerability of tropical forests to climate perturbations. Ground and satellite observations of 2005 and 2010 mega-droughts have shown an increase in fire occurrence and tree mortality during the period of drought. Here, we use a combination of satellite observations over a period of about 15 years to examine the legacy of the droughts in terms of impacts on the ecological structure and function of the forests in years following the droughts and the subsequent carbon exchange. Using data from microwave satellite sensors of rainfall, canopy backscatter (2000-2014) and GRACE and GOSAT, we show that the 2005 drought has a legacy of 2-5 years in western Amazonia, by increasing the disturbance in canopy trees and impacting the gross primary production of the forest significantly. Amazonian forests, particularly in the southern region were again impacted by the 2010 mega-drought, causing a legacy of 2-4 years with potential decrease in GPP and productivity observed by GOSAT fluorescence. The persistent of low canopy water content observed by a joint QSCAT and OceanSAT observations were linked to a delay in recharging of the hydrological system observed by GRACE over a period of 2-5 years. The results suggest that Amazonian forests with distinct dry seasons in southern and western regions of the basin are potentially more vulnerable to droughts compared to regions with less seasonality. The long recovery time from the 2005 and 2010 droughts suggests that the occurence of droughts in Amazonia at 5-10 year frequency may lead to long-term alteration of the forest structure and function. Keywords: Amazonia, drought, carbon exchange, biomass loss, GPP

Forest-climate interactions in fragmented tropical landscapes.

PubMed

Laurance, William F

2004-03-29

In the tropics, habitat fragmentation alters forest-climate interactions in diverse ways. On a local scale (less than 1 km), elevated desiccation and wind disturbance near fragment margins lead to sharply increased tree mortality, thus altering canopy-gap dynamics, plant community composition, biomass dynamics and carbon storage. Fragmented forests are also highly vulnerable to edge-related fires, especially in regions with periodic droughts or strong dry seasons. At landscape to regional scales (10-1000 km), habitat fragmentation may have complex effects on forest-climate interactions, with important consequences for atmospheric circulation, water cycling and precipitation. Positive feedbacks among deforestation, regional climate change and fire could pose a serious threat for some tropical forests, but the details of such interactions are poorly understood.

Drought and Burn Scars in Southeastern Australia

NASA Image and Video Library

2003-03-05

More than 2 million acres were consumed by hundreds of fires between December 2002 and February 2003 in southeastern Australia national parks, forests, foothills and city suburbs as seen by NASA Terra spacecraft.

Daily fire occurrence in northern Eurasia from 2002 to 2009

Treesearch

W. M. Hao; H. M. Eissinger; A. Petkov; B. L. Nordgren; Shawn Urbanski

2010-01-01

Northern Eurasia, covering 20% of the global land mass and containing 70% of boreal forest, is extremely sensitive to climate changes. Warmer temperatures in this region have led to less snowfall, earlier spring, longer growing season, and reduced moisture for soil and vegetation in summer. Recently, severe drought and record high temperatures caused catastrophic fires...

Wildfire in the valley of the wild roses

Treesearch

Linda Moon Stumpff

2015-01-01

Santa Clara Indian Pueblo lands are adjacent to the Jemez National Forest, Bandelier National Monument and Valles Caldera National Preserve. This paper explores Pueblo vulnerability and resilience after repeated and devastating fires in this century as a result of drought and climate change. Santa Clara Pueblo holds a rich store of traditional knowledge about the fire-...

Historical dominance of low-severity fire in dry and wet mixed-conifer forest habitats of the endangered terrestrial Jemez Mountains salamander (Plethodon neomexicanus)

USGS Publications Warehouse

Margolis, Ellis; Malevich, Steven B.

2016-01-01

Anthropogenic alteration of ecosystem processes confounds forest management and conservation of rare, declining species. Restoration of forest structure and fire hazard reduction are central goals of forest management policy in the western United States, but restoration priorities and treatments have become increasingly contentious. Numerous studies have documented changes in fire regimes, forest stand structure and species composition following a century of fire exclusion in dry, frequent-fire forests of the western U.S. (e.g., ponderosa pine and dry mixed-conifer). In contrast, wet mixed-conifer forests are thought to have historically burned infrequently with mixed- or high-severity fire—resulting in reduced impacts from fire exclusion and low restoration need—but data are limited. In this study we quantified the current forest habitat of the federally endangered, terrestrial Jemez Mountains salamander (Plethodon neomexicanus) and compared it to dendroecological reconstructions of historical habitat (e.g., stand structure and composition), and fire regime parameters along a gradient from upper ponderosa pine to wet mixed-conifer forests. We found that current fire-free intervals in Jemez Mountains salamander habitat (116–165 years) are significantly longer than historical intervals, even in wet mixed-conifer forests. Historical mean fire intervals ranged from 10 to 42 years along the forest gradient. Low-severity fires were historically dominant across all forest types (92 of 102 fires). Although some mixed- or highseverity fire historically occurred at 67% of the plots over the last four centuries, complete mortality within 1.0 ha plots was rare, and asynchronous within and among sites. Climate was an important driver of temporal variability in fire severity, such that mixed- and high-severity fires were associated with more extreme drought than low-severity fires. Tree density in dry conifer forests historically ranged from open (90 trees/ha) to moderately dense (400 trees/ha), but has doubled on average since fire exclusion. Infill of fire-sensitive tree species has contributed to the conversion of historically dry mixedconifer to wet mixed-conifer forest. We conclude that low-severity fire, which has been absent for over a century, was a critical ecosystem process across the forest gradient in Jemez Mountains salamander habitat, and thus is an important element of ecosystem restoration, resilience, and rare species recovery.

Fire regime in a Mexican forest under indigenous resource management.

PubMed

Fulé, Peter Z; Ramos-Gómez, Mauro; Cortés-Montaño, Citlali; Miller, Andrew M

2011-04-01

The Rarámuri (Tarahumara) people live in the mountains and canyons of the Sierra Madre Occidental of Chihuahua, Mexico. They base their subsistence on multiple-use strategies of their natural resources, including agriculture, pastoralism, and harvesting of native plants and wildlife. Pino Gordo is a Rarámuri settlement in a remote location where the forest has not been commercially logged. We reconstructed the forest fire regime from fire-scarred trees, measured the structure of the never-logged forest, and interviewed community members about fire use. Fire occurrence was consistent throughout the 19th and 20th centuries up to our fire scar collection in 2004. This is the least interrupted surface-fire regime reported to date in North America. Studies from other relict sites such as nature reserves in Mexico or the USA have all shown some recent alterations associated with industrialized society. At Pino Gordo, fires recurred frequently at the three study sites, with a composite mean fire interval of 1.9 years (all fires) to 7.6 years (fires scarring 25% or more of samples). Per-sample fire intervals averaged 10-14 years at the three sites. Approximately two-thirds of fires burned in the season of cambial dormancy, probably during the pre-monsoonal drought. Forests were dominated by pines and contained many large living trees and snags, in contrast to two nearby similar forests that have been logged. Community residents reported using fire for many purposes, consistent with previous literature on fire use by indigenous people. Pino Gordo is a valuable example of a continuing frequent-fire regime in a never-harvested forest. The Rarámuri people have actively conserved this forest through their traditional livelihood and management techniques, as opposed to logging the forest, and have also facilitated the fire regime by burning. The data contribute to a better understanding of the interactions of humans who live in pine forests and the fire regimes of these ecosystems, a topic that has been controversial and difficult to assess from historical or paleoecological evidence.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehleringer, James; Randerson, James; Lai, Chun-Ta

The objective of the proposed research was to collect data and develop models to improve our understanding of the role of drought and fire impacts on the terrestrial carbon cycle in the western US, including impacts associated with urban systems as they impacted regional carbon cycles. Using data we collected and a synthesis of other measurements, we developed new ways (a) to evaluate the representation of drought stress and fire emissions in the Community Land Model, (b) to model net ecosystem exchange combining ground level atmospheric observations with boundary layer theory, (c) to model upstream impacts of fire and fossilmore » fuel emissions on atmospheric carbon dioxide observations, and (d) to model carbon dioxide observations within urban systems and at the urban-wildland interfaces of forest ecosystems.« less

Queensland, Australia

NASA Image and Video Library

1994-09-30

STS068-253-045 (30 September-11 October 1994) --- Forest fires in southeastern Queensland, Australia. The smoke is blowing to the east. This is the southeastern edge of the Darling Downs, a wheat-growing and sheep pasture region just west of the Great Dividing Range, southwest of Brisbane. An extensive summer drought made the forests of the range highly susceptible to wildfire.

Drought-driven disturbance history characterizes a southern Rocky Mountain subalpine forest

Treesearch

R. Justin DeRose; James N. Long

2012-01-01

The view that subalpine forest vegetation dynamics in western North America are "driven" by a particular disturbance type (i.e., fire) has shaped our understanding of their disturbance regimes. In the wake of a recent (1990s) landscape- extent spruce beetle (Dendroctonus rufipennis Kirby) outbreak in the southern Rocky Mountains, we re-examined the temporal...

Post Fire Vegetation Recovery in Portugal

NASA Astrophysics Data System (ADS)

Gouveia, Celia; Bastos, Ana; DaCamara, Carlos; Trigo, Ricardo M.

2011-01-01

Fires in Portugal, as in the Mediterranean ecosystems, have a complex effect on vegetation regeneration due to the different responses of vegetation to the variety of fire regimes and to the complexity of landscape structures. A thorough evaluation of vegetation recovery after fire events becomes therefore crucial in land management. In 2005, Portugal suffered a strong damage from forest fires that damaged an area of 300 000 ha of forest and shrub. This year are particularly interesting because it is associated the severe drought of 2005. The aim of the present study is to identify large burnt scars in Portugal during the 2005 fire seasons and monitoring vegetation behaviour throughout the pre and the post fire periods. The mono-parametric model developed by Gouveia et al. (2010), based on monthly values of NDVI, at the 1km×1km spatial scale, as obtained from the VEGETATION-SPOT5 instrument, from 1999 to 2009, was used.

Floodplains as an Achilles’ heel of Amazonian forest resilience

PubMed Central

Flores, Bernardo M.; Holmgren, Milena; van Nes, Egbert H.; Jakovac, Catarina C.; Mesquita, Rita C. G.; Scheffer, Marten

2017-01-01

The massive forests of central Amazonia are often considered relatively resilient against climatic variation, but this view is challenged by the wildfires invoked by recent droughts. The impact of such fires that spread from pervasive sources of ignition may reveal where forests are less likely to persist in a drier future. Here we combine field observations with remotely sensed information for the whole Amazon to show that the annually inundated lowland forests that run through the heart of the system may be trapped relatively easily into a fire-dominated savanna state. This lower forest resilience on floodplains is suggested by patterns of tree cover distribution across the basin, and supported by our field and remote sensing studies showing that floodplain fires have a stronger and longer-lasting impact on forest structure as well as soil fertility. Although floodplains cover only 14% of the Amazon basin, their fires can have substantial cascading effects because forests and peatlands may release large amounts of carbon, and wildfires can spread to adjacent uplands. Floodplains are thus an Achilles’ heel of the Amazon system when it comes to the risk of large-scale climate-driven transitions. PMID:28396440

[Forest fire division by using MODIS data based on the temporal-spatial variation law].

PubMed

He, Cheng; He, Cheng; Gong, Yin-xi; Zhang, Si-yu; He, Teng-fei; Chen, Feng; Sun, Yu; Feng, Zhong-ke

2013-09-01

Forest fires are harmful to the ecological environment, which have induced global attention. In the present paper fire activities extracted from MODIS and burned areas were compared, and it was found that the wave band of 8-9 extracted from MOD14A1 was useful for fire monitoring, and the data accorded with field investigation with goodness of fit reaching up to 0. 83. Through combining this wave band and the relative data to make the time and space analysis of the forest fires for 11 years, from 2000 to 2010, the study showed that the fire occurred most frequently in the spring, the autumn took the second place, and in the summer there was almost no fire occurrence unless drought. Through the analysis of the research area, the burned areas of the coniferous forest and temperate mixed forest were 53.68% and 44%, respectively, while the grassland was only 2.32%. Da Hinggan Ling region was the main combustion area, the burned areas were 64.7% and that for Xiao Hinggan Ling was about 23.49%, while those for other areas were less than 5%. The majority of forest land of burned areas has a gentle slope (< or =5 percent), and is in the middle altitude between 200 and 500 m. So, using satellite remote sensing to analyze the time series of burned areas in forests would make the relationship between the fire activities, climate change, topography and vegetation type clear and it is also helpful to predicting the risk level of the fire areas.

Mitigating Wildfire Risk in the Wildland Urban Interface: The Role of Regulations

Treesearch

Cheryl R. Renner; Margaret Reams; Terry Haines

2006-01-01

The growth of residential communities within forest areas throughout the country, and particularly in the West, has increased the danger to life and property from uncontrolled wildfire. The conflict of permanent residential settlements built next to a fire-adapted ecosystem has been further exacerbated by 100 years of fire suppression and an extended drought in the...

The dynamics and drivers of fuel and fire in the Portuguese public forest.

PubMed

Fernandes, Paulo M; Loureiro, Carlos; Guiomar, Nuno; Pezzatti, Gianni B; Manso, Filipa T; Lopes, Luís

2014-12-15

The assumption that increased wildfire incidence in the Mediterranean Basin during the last decades is an outcome of changes in land use warrants an objective analysis. In this study we examine how annual area burned (BA) in the Portuguese public forest varied in relation to environmental and human-influenced drivers during the 1943-2011 period. Fire behaviour models were used to describe fuel hazard considering biomass removal, cover type changes, area burned, post-disturbance fuel accumulation, forest age-classes distribution and fuel connectivity. Biomass removal decreased rapidly beyond the 1940s, which, along with afforestation, increased fuel hazard until the 1980s; a subsequent decline was caused by increased fire activity. Change point analysis indicates upward shifts in BA in 1952 and in 1973, both corresponding to six-fold increases. Fire weather (expressed by the 90th percentile of the Canadian FWI during summer) increased over the study period, accounting for 18 and 36% of log(BA) variation before 1974 and after 1973, respectively. Regression modelling indicates that BA responds positively to fire weather, fuel hazard and number of fires in descending order of importance; pre-summer and 2-year lagged precipitation respectively decrease and increase BA, but the effects are minor and non-significant when both variables are included in the model. Land use conflicts (expressed through more fires) played a role, but it was afforestation and agricultural abandonment that supported the fire regime shifts, explaining weather-drought as the current major driver of BA as well. We conclude that bottom-up factors, i.e. human-induced changes in landscape flammability and ignition density, can enhance or override the influence of weather-drought on the fire regime in Mediterranean humid regions. A more relevant role of fuel control in fire management policies and practices is warranted by our findings. Copyright © 2014 Elsevier Ltd. All rights reserved.

Contingent Pacific-Atlantic Ocean influence on multicentury wildfire synchrony over western North America.

PubMed

Kitzberger, Thomas; Brown, Peter M; Heyerdahl, Emily K; Swetnam, Thomas W; Veblen, Thomas T

2007-01-09

Widespread synchronous wildfires driven by climatic variation, such as those that swept western North America during 1996, 2000, and 2002, can result in major environmental and societal impacts. Understanding relationships between continental-scale patterns of drought and modes of sea surface temperatures (SSTs) such as El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) may explain how interannual to multidecadal variability in SSTs drives fire at continental scales. We used local wildfire chronologies reconstructed from fire scars on tree rings across western North America and independent reconstructions of SST developed from tree-ring widths at other sites to examine the relationships of multicentury patterns of climate and fire synchrony. From 33,039 annually resolved fire-scar dates at 238 sites (the largest paleofire record yet assembled), we examined forest fires at regional and subcontinental scales. Since 1550 CE, drought and forest fires covaried across the West, but in a manner contingent on SST modes. During certain phases of ENSO and PDO, fire was synchronous within broad subregions and sometimes asynchronous among those regions. In contrast, fires were most commonly synchronous across the West during warm phases of the AMO. ENSO and PDO were the main drivers of high-frequency variation in fire (interannual to decadal), whereas the AMO conditionally changed the strength and spatial influence of ENSO and PDO on wildfire occurrence at multidecadal scales. A current warming trend in AMO suggests that we may expect an increase in widespread, synchronous fires across the western U.S. in coming decades.

Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements

NASA Astrophysics Data System (ADS)

Gatti, L. V.; Gloor, M.; Miller, J. B.; Doughty, C. E.; Malhi, Y.; Domingues, L. G.; Basso, L. S.; Martinewski, A.; Correia, C. S. C.; Borges, V. F.; Freitas, S.; Braz, R.; Anderson, L. O.; Rocha, H.; Grace, J.; Phillips, O. L.; Lloyd, J.

2014-02-01

Feedbacks between land carbon pools and climate provide one of the largest sources of uncertainty in our predictions of global climate. Estimates of the sensitivity of the terrestrial carbon budget to climate anomalies in the tropics and the identification of the mechanisms responsible for feedback effects remain uncertain. The Amazon basin stores a vast amount of carbon, and has experienced increasingly higher temperatures and more frequent floods and droughts over the past two decades. Here we report seasonal and annual carbon balances across the Amazon basin, based on carbon dioxide and carbon monoxide measurements for the anomalously dry and wet years 2010 and 2011, respectively. We find that the Amazon basin lost 0.48+/-0.18 petagrams of carbon per year (PgCyr-1) during the dry year but was carbon neutral (0.06+/-0.1PgCyr-1) during the wet year. Taking into account carbon losses from fire by using carbon monoxide measurements, we derived the basin net biome exchange (that is, the carbon flux between the non-burned forest and the atmosphere) revealing that during the dry year, vegetation was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25+/-0.14PgCyr-1, which is roughly consistent with the mean long-term intact-forest biomass sink of 0.39+/-0.10PgCyr-1 previously estimated from forest censuses. Observations from Amazonian forest plots suggest the suppression of photosynthesis during drought as the primary cause for the 2010 sink neutralization. Overall, our results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net biome exchange by drought.

Hydrological extremes in the media: The 2015 drought event in Germany

NASA Astrophysics Data System (ADS)

Zink, Matthias; Samaniego, Luis; Kumar, Rohini; Thober, Stephan; Mai, Juliane; Schäfer, David; Marx, Andreas

2017-04-01

The 2003 drought event had major implications on many societal sectors, including energy production, health, forestry and agriculture. The reduced availability of water accompanied by high temperatures led to substantial economic losses in Germany on the order of 1.5 Billion Euros, in agriculture alone. Furthermore, soil droughts have considerable impacts on ecosystems, forest fires and water management. In 2015, another drought event impacted Germany which had impacts on inland navigation, forest fire risk and agriculture among others. Due to this drought event, corn yield reduced by 22% compared to the preceding 5 years. This drought event was tracked by the 2014 implemented German Drought Monitor, a near real-time, online soil water monitoring platform (Zink et al., 2016). This platform uses an high resolution, operational modeling system which delivers easy to understand maps of soil drought conditions that are published on a daily basis on www.ufz.de/droughtmonitor. During the 2015 event, the German Drought Monitor was used by several regional to national newspapers as well as by television to inform the public about the recent status of soil moisture conditions. Next to publishing the drought maps, we were asked to comment the drought development and especially the severity of the ongoing drought event. On the one hand, this gave us the opportunity to inform the public about different types and the characterization of droughts. On the other hand, some journalists just tried to invoke statements such as "this is the most severe drought event ever recorded" to get a good headline. Further the secondmost pressing question of the journalists was, if the current event could be directly attributed to climate change. A clear answer to this question could not be given since the drought monitor is based on only a 65 year period of data. Depending on the media company, different depths of information and knowledge was finally transferred to the newsletter article and thus the public. In conclusion, the German Drought Monitor is the most objective instrument to assess agricultural droughts in Germany.

Major atmospheric emissions from peat fires in Southeast Asia during non-drought years: evidence from the 2013 Sumatran fires

PubMed Central

Gaveau, David L. A.; Salim, Mohammad A.; Hergoualc'h, Kristell; Locatelli, Bruno; Sloan, Sean; Wooster, Martin; Marlier, Miriam E.; Molidena, Elis; Yaen, Husna; DeFries, Ruth; Verchot, Louis; Murdiyarso, Daniel; Nasi, Robert; Holmgren, Peter; Sheil, Douglas

2014-01-01

Trans-boundary haze events in Southeast Asia are associated with large forest and peatland fires in Indonesia. These episodes of extreme air pollution usually occur during drought years induced by climate anomalies from the Pacific (El Niño Southern Oscillation) and Indian Oceans (Indian Ocean Dipole). However, in June 2013 – a non-drought year – Singapore's 24-hr Pollutants Standards Index reached an all-time record 246 (rated “very unhealthy”). Here, we show using remote sensing, rainfall records and other data, that the Indonesian fires behind the 2013 haze followed a two-month dry spell in a wetter-than-average year. These fires were short-lived (one week) and limited to a localized area in Central Sumatra (1.6% of Indonesia): burning an estimated 163,336 ha, including 137,044 ha (84%) on peat. Most burning was confined to deforested lands (82%; 133,216 ha). The greenhouse gas (GHG) emissions during this brief, localized event were considerable: 172 ± 59 Tg CO2-eq (or 31 ± 12 Tg C), representing 5–10% of Indonesia's mean annual GHG emissions for 2000–2005. Our observations show that extreme air pollution episodes in Southeast Asia are no longer restricted to drought years. We expect major haze events to be increasingly frequent because of ongoing deforestation of Indonesian peatlands. PMID:25135165

Major atmospheric emissions from peat fires in Southeast Asia during non-drought years: evidence from the 2013 Sumatran fires

NASA Astrophysics Data System (ADS)

Gaveau, David L. A.; Salim, Mohammad A.; Hergoualc'h, Kristell; Locatelli, Bruno; Sloan, Sean; Wooster, Martin; Marlier, Miriam E.; Molidena, Elis; Yaen, Husna; Defries, Ruth; Verchot, Louis; Murdiyarso, Daniel; Nasi, Robert; Holmgren, Peter; Sheil, Douglas

2014-08-01

Trans-boundary haze events in Southeast Asia are associated with large forest and peatland fires in Indonesia. These episodes of extreme air pollution usually occur during drought years induced by climate anomalies from the Pacific (El Niño Southern Oscillation) and Indian Oceans (Indian Ocean Dipole). However, in June 2013 - a non-drought year - Singapore's 24-hr Pollutants Standards Index reached an all-time record 246 (rated ``very unhealthy''). Here, we show using remote sensing, rainfall records and other data, that the Indonesian fires behind the 2013 haze followed a two-month dry spell in a wetter-than-average year. These fires were short-lived (one week) and limited to a localized area in Central Sumatra (1.6% of Indonesia): burning an estimated 163,336 ha, including 137,044 ha (84%) on peat. Most burning was confined to deforested lands (82%; 133,216 ha). The greenhouse gas (GHG) emissions during this brief, localized event were considerable: 172 +/- 59 Tg CO2-eq (or 31 +/- 12 Tg C), representing 5-10% of Indonesia's mean annual GHG emissions for 2000-2005. Our observations show that extreme air pollution episodes in Southeast Asia are no longer restricted to drought years. We expect major haze events to be increasingly frequent because of ongoing deforestation of Indonesian peatlands.

Major atmospheric emissions from peat fires in Southeast Asia during non-drought years: evidence from the 2013 Sumatran fires.

PubMed

Gaveau, David L A; Salim, Mohammad A; Hergoualc'h, Kristell; Locatelli, Bruno; Sloan, Sean; Wooster, Martin; Marlier, Miriam E; Molidena, Elis; Yaen, Husna; DeFries, Ruth; Verchot, Louis; Murdiyarso, Daniel; Nasi, Robert; Holmgren, Peter; Sheil, Douglas

2014-08-19

Trans-boundary haze events in Southeast Asia are associated with large forest and peatland fires in Indonesia. These episodes of extreme air pollution usually occur during drought years induced by climate anomalies from the Pacific (El Niño Southern Oscillation) and Indian Oceans (Indian Ocean Dipole). However, in June 2013--a non-drought year--Singapore's 24-hr Pollutants Standards Index reached an all-time record 246 (rated "very unhealthy"). Here, we show using remote sensing, rainfall records and other data, that the Indonesian fires behind the 2013 haze followed a two-month dry spell in a wetter-than-average year. These fires were short-lived (one week) and limited to a localized area in Central Sumatra (1.6% of Indonesia): burning an estimated 163,336 ha, including 137,044 ha (84%) on peat. Most burning was confined to deforested lands (82%; 133,216 ha). The greenhouse gas (GHG) emissions during this brief, localized event were considerable: 172 ± 59 Tg CO2-eq (or 31 ± 12 Tg C), representing 5-10% of Indonesia's mean annual GHG emissions for 2000-2005. Our observations show that extreme air pollution episodes in Southeast Asia are no longer restricted to drought years. We expect major haze events to be increasingly frequent because of ongoing deforestation of Indonesian peatlands.

Long-term persistence and fire resilience of oak shrubfields in dry conifer forests of northern New Mexico

USGS Publications Warehouse

Guiterman, Christopher H.; Margolis, Ellis; Allen, Craig D.; Falk, Donald A.; Swetnam, Thomas W.

2017-01-01

Extensive high-severity fires are creating large shrubfields in many dry conifer forests of the interior western USA, raising concerns about forest-to-shrub conversion. This study evaluates the role of disturbance in shrubfield formation, maintenance and succession in the Jemez Mountains, New Mexico. We compared the environmental conditions of extant Gambel oak (Quercus gambelii) shrubfields with adjoining dry conifer forests and used dendroecological methods to determine the multi-century fire history and successional dynamics of five of the largest shrubfields (76–340 ha). Across the study area, 349 shrubfields (5–368 ha) occur in similar topographic and climate settings as dry conifer forests. This suggests disturbance, rather than other biophysical factors, may explain their origins and persistence. Gambel oak ages and tree-ring fire scars in our sampled shrubfields indicate they historically (1664–1899) burned concurrently with adjoining conifer forests and have persisted for over 115 years in the absence of fire. Aerial imagery from 1935 confirmed almost no change in sampled shrubfield patch sizes or boundaries over the twentieth century. The largest shrubfield we identified is less than 4% the size of the largest conifer-depleted and substantially shrub-dominated area recently formed in the Jemez following extensive high-severity wildfires, indicating considerable departure from historical patterns and processes. Projected hotter droughts and increasingly large high-severity fires could trigger more forest-to-shrub transitions and maintain existing shrubfields, inhibiting conifer forest recovery. Restoration of surface fire regimes and associated historical forest structures likely could reduce the rate and patch size of dry conifer forests being converted to shrubfields.

Is the western United States running out of trees?

Treesearch

J. Shaw; J. Long

2014-01-01

During the past 2 decades, the forests of the Interior West of the United States have been impacted by drought, insects, disease, and fire. When considered over periods of 5-10 years, many forest types have experienced periods of negative net growth, meaning that mortality exceeded gross growth at the population scale. While many of these changes have been attributed...

Climate and wildfires in the North American boreal forest.

PubMed

Macias Fauria, Marc; Johnson, E A

2008-07-12

The area burned in the North American boreal forest is controlled by the frequency of mid-tropospheric blocking highs that cause rapid fuel drying. Climate controls the area burned through changing the dynamics of large-scale teleconnection patterns (Pacific Decadal Oscillation/El Niño Southern Oscillation and Arctic Oscillation, PDO/ENSO and AO) that control the frequency of blocking highs over the continent at different time scales. Changes in these teleconnections may be caused by the current global warming. Thus, an increase in temperature alone need not be associated with an increase in area burned in the North American boreal forest. Since the end of the Little Ice Age, the climate has been unusually moist and variable: large fire years have occurred in unusual years, fire frequency has decreased and fire-climate relationships have occurred at interannual to decadal time scales. Prolonged and severe droughts were common in the past and were partly associated with changes in the PDO/ENSO system. Under these conditions, large fire years become common, fire frequency increases and fire-climate relationships occur at decadal to centennial time scales. A suggested return to the drier climate regimes of the past would imply major changes in the temporal dynamics of fire-climate relationships and in area burned, a reduction in the mean age of the forest, and changes in species composition of the North American boreal forest.

A comparative study of fire weather indices in a semiarid south-eastern Europe region. Case of study: Murcia (Spain).

PubMed

Pérez-Sánchez, Julio; Senent-Aparicio, Javier; Díaz-Palmero, José María; Cabezas-Cerezo, Juan de Dios

2017-07-15

Forest fires are an important distortion in forest ecosystems, linked to their development and whose effects proceed beyond the destruction of ecosystems and material properties, especially in semiarid regions. Prevention of forest fires has to lean on indices based on available parameters that quantify fire risk ignition and spreading. The present study was conducted to compare four fire weather indices in a semiarid region of 11,314km 2 located in southern Spain, characterised as being part of the most damaged area by fire in the Iberian Peninsula. The studied period comprises 3033 wildfires in the region during 15years (2000-2014), of which 80% are >100m 2 and 14% >1000m 2 , resulting around 40km 2 of burnt area in this period. The indices selected have been Angström Index, Forest Fire Drought Index, Forest Moisture Index and Fire Weather Index. Likewise, four selection methods have been applied to compare the results of the studied indices: Mahalanobis distance, percentile method, ranked percentile method and Relative Operating Characteristic curves (ROC). Angström index gives good results in the coastal areas with higher temperatures, low rainfall and wider range of variations while Fire Weather Index has better results in inland areas with higher rainfall, dense forest mass and fewer changes in meteorological conditions throughout the year. ROC space rejects all the indices except Fire Weather Index with good performance all over the region. ROC analysis ratios can be used to assess the success (or lack thereof) of fire indices; thus, it benefits operational wildfire predictions in semiarid regions similar to that of the case study. Copyright © 2017 Elsevier B.V. All rights reserved.

Interactions between rainfall, deforestation and fires during recent years in the Brazilian Amazonia.

PubMed

Aragão, Luiz Eduardo O C; Malhi, Yadvinder; Barbier, Nicolas; Lima, Andre; Shimabukuro, Yosio; Anderson, Liana; Saatchi, Sassan

2008-05-27

Understanding the interplay between climate and land-use dynamics is a fundamental concern for assessing the vulnerability of Amazonia to climate change. In this study, we analyse satellite-derived monthly and annual time series of rainfall, fires and deforestation to explicitly quantify the seasonal patterns and relationships between these three variables, with a particular focus on the Amazonian drought of 2005. Our results demonstrate a marked seasonality with one peak per year for all variables analysed, except deforestation. For the annual cycle, we found correlations above 90% with a time lag between variables. Deforestation and fires reach the highest values three and six months, respectively, after the peak of the rainy season. The cumulative number of hot pixels was linearly related to the size of the area deforested annually from 1998 to 2004 (r2=0.84, p=0.004). During the 2005 drought, the number of hot pixels increased 43% in relation to the expected value for a similar deforested area (approx. 19000km2). We demonstrated that anthropogenic forcing, such as land-use change, is decisive in determining the seasonality and annual patterns of fire occurrence. Moreover, droughts can significantly increase the number of fires in the region even with decreased deforestation rates. We may expect that the ongoing deforestation, currently based on slash and burn procedures, and the use of fires for land management in Amazonia will intensify the impact of droughts associated with natural climate variability or human-induced climate change and, therefore, a large area of forest edge will be under increased risk of fires.

Temporal and Spatial Wildfire Dynamics of Northern Siberia: Larch Forests and Insect Outbreak Areas

NASA Astrophysics Data System (ADS)

Kharuk, Viacheslav; Antamoshkina, Olga; Ponomarev, Eugene

2017-04-01

Wildfire number and burned area temporal dynamics within all of Siberia and along a south-north transect in central Siberia (45 - 73°N) were studied based on NOAA/AVHRR and Terra/MODIS data and field measurements for the period since 1996. In addition, fire return interval along the south-north transect was analyzed. Third, pest outbreak (Siberian silkmoth) impact on the wildfires was studied. Both, number of forest fires and burned area in Siberia increased during recent decades. Significant correlations were found between forest fires, burned areas and air temperature (r = 0.5) and drought index (SPEI) (r = -0.43). Within larch stands along the transect wildfire frequency was strongly correlated with incoming solar radiation (r = 0.91). Fire danger period length decreased linearly from south to north along the transect. Fire return interval increased from 80 years at 62°N to 200 years at the Arctic Circle (66°33'N), and to about 300 years near the northern limit of closed forest stands ( 71+°N). That increase was negatively correlated with incoming solar radiation (r = -0.95). Siberian silkmoth outbreaks leads to an order of magnitude increase in burned area and fire frequency. Multiple fires turns former "dark needle conifer" taiga into grass and bush communities for decades.

Future climate change drives increases in forest fires and summertime OC concentrations in the Western U.S.

NASA Astrophysics Data System (ADS)

Spracklen, D. V.; Logan, J. A.; Mickley, L. J.; Park, R. J.; Flannigan, M. D.; Westerling, A. L.

2006-12-01

Increased forest fire activity in the Western United States appears to be driven by increasing spring and summer temperatures. Here we make a first estimate of how climate-driven changes in fire activity will influence summertime organic carbon (OC) concentrations in the Western US. We use output from a general circulation model (GCM) combined with area burned regressions to predict how area burned will change between present day and 2050. Calculated area burned is used to create future emission estimates for the Western U.S. and we use a global chemical transport model (CTM) to predict future changes in OC concentrations. Stepwise linear regression is used to determine the best relationships between observed area burned for 1980- 2004 and variables chosen from temperature, relative humidity, wind speed, rainfall and drought indices from the Candaian Fire Weather Index Model. Best predictors are ecosytem dependent but typically include mean summer temperature and mean drought code. In forest ecosystems of the Western U.S. our regressions explain 50-60% of the variance in annual area burned. Between 2000 and 2050 increases in temperature and reductions in precipitation, as predicted by the GISS GCM, cause mean area burned in the western U.S. to increase by 30-55%. We use the GEOS-Chem CTM to show that these increased emissions result in an increase in summertime western U.S. OC concentrations by 55% over current concentrations. Our results show that the predicted increase in future wild fires will have important consequences for western US air quality and visibility.

Impact of a drier Early-Mid-Holocene climate upon Amazonian forests.

PubMed

Mayle, Francis E; Power, Mitchell J

2008-05-27

This paper uses a palaeoecological approach to examine the impact of drier climatic conditions of the Early-Mid-Holocene (ca 8000-4000 years ago) upon Amazonia's forests and their fire regimes. Palaeovegetation (pollen data) and palaeofire (charcoal) records are synthesized from 20 sites within the present tropical forest biome, and the underlying causes of any emergent patterns or changes are explored by reference to independent palaeoclimate data and present-day patterns of precipitation, forest cover and fire activity across Amazonia. During the Early-Mid-Holocene, Andean cloud forest taxa were replaced by lowland tree taxa as the cloud base rose while lowland ecotonal areas, which are presently covered by evergreen rainforest, were instead dominated by savannahs and/or semi-deciduous dry forests. Elsewhere in the Amazon Basin there is considerable spatial and temporal variation in patterns of vegetation disturbance and fire, which probably reflects the complex heterogeneous patterns in precipitation and seasonality across the basin, and the interactions between climate change, drought- and fire susceptibility of the forests, and Palaeo-Indian land use. Our analysis shows that the forest biome in most parts of Amazonia appears to have been remarkably resilient to climatic conditions significantly drier than those of today, despite widespread evidence of forest burning. Only in ecotonal areas is there evidence of biome replacement in the Holocene. From this palaeoecological perspective, we argue against the Amazon forest 'dieback' scenario simulated for the future.

NASA's AVIRIS Instrument Sheds New Light on Southern California Wildfires

NASA Image and Video Library

2017-12-08

NASA's Airborne Visible Infrared Imaging Spectrometer instrument (AVIRIS), flying aboard a NASA Armstrong Flight Research Center high-altitude ER-2 aircraft, flew over the wildfires burning in Southern California on Dec. 5, 2017 and acquired this false-color image. Active fires are visible in red, ground surfaces are in green and smoke is in blue. AVIRIS is an imaging spectrometer that observes light in visible and infrared wavelengths, measuring the full spectrum of radiated energy. Unlike regular cameras with three colors, AVIRIS has 224 spectral channels from the visible through the shortwave infrared. This permits mapping of fire temperatures, fractional coverage, and surface properties, including how much fuel is available for a fire. Spectroscopy is also valuable for characterizing forest drought conditions and health to assess fire risk. AVIRIS has been observing fire-prone areas in Southern California for many years, forming a growing time series of before/after data cubes. These data are helping improve scientific understanding of fire risk and how ecosystems respond to drought and fire. https://photojournal.jpl.nasa.gov/catalog/PIA11243

The ecology and management of moist mixed-conifer forests in eastern Oregon and Washington: a synthesis of the relevant biophysical science and implications for future land management

Treesearch

Peter Stine; Paul Hessburg; Thomas Spies; Marc Kramer; Christopher J. Fettig; Andrew Hansen; John Lehmkuhl; Kevin O' Hara; Karl Polivka; Peter Singleton; Susan Charnley; Andrew Merschel; Rachel White

2014-01-01

Land managers in the Pacific Northwest have reported a need for updated scientific information on the ecology and management of mixed-conifer forests east of the Cascade Range in Oregon and Washington. Of particular concern are the moist mixed-conifer forests, which have become drought-stressed and vulnerable to high-severity fire after decades of human disturbances...

Fire history and fire-climate relationships in upper elevation forests of the southwestern United States

NASA Astrophysics Data System (ADS)

Margolis, Ellis Quinn

Fire history and fire-climate relationships of upper elevation forests of the southwestern United States are imperative for informing management decisions in the face of increased crown fire occurrence and climate change. I used dendroecological techniques to reconstruct fires and stand-replacing fire patch size in the Madrean Sky Islands and Mogollon Plateau. Reconstructed patch size (1685-1904) was compared with contemporary patch size (1996-2004). Reconstructed fires at three sites had stand-replacing patches totaling > 500 ha. No historical stand-replacing fire patches were evident in the mixed conifer/aspen forests of the Sky Islands. Maximum stand-replacing fire patch size of modern fires (1129 ha) was greater than that reconstructed from aspen (286 ha) and spruce-fir (521 ha). Undated spruce-fir patches may be evidence of larger (>2000ha) stand-replacing fire patches. To provide climatological context for fire history I used correlation and regionalization analyses to document spatial and temporal variability in climate regions, and El-Nino Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation (AMO) teleconnections using 273 tree-ring chronologies (1732-1979). Four regions were determined by common variability in annual ring width. The component score time series replicate spatial variability in 20th century droughts (e.g., 1950's) and pluvials (e.g., 1910's). Two regions were significantly correlated with instrumental SOI and AMO, and three with PDO. Sub-regions within the southwestern U.S. varied geographically between the instrumental (1900-1979) and the pre-instrumental periods (1732-1899). Mapped correlations between ENSO, PDO and AMO, and tree-ring indices illustrate detailed sub-regional variability in the teleconnections. I analyzed climate teleconnections, and fire-climate relationships of historical upper elevation fires from 16 sites in 8 mountain ranges. I tested for links between Palmer Drought Severity Index and tree-ring reconstructed ENSO, PDO and AMO phases (1905-1978 and 1700-1904). Upper elevation fires (115 fires, 84 fire years, 1623-1904) were compared with climate indices. ENSO, PDO, and AMO affected regional PDSI, but AMO and PDO teleconnections changed between periods. Fire occurrence was significantly related to inter-annual variability in PDSI, precipitation, ENSO, and phase combinations of ENSO and PDO, but not AMO (1700-1904). Reduced upper elevation fire (1785-1840) was coincident with a cool AMO phase.

Integration of climatic water deficit and fine-scale physiography in process-based modeling of forest landscape resilience to large-scale tree mortality

NASA Astrophysics Data System (ADS)

Yang, J.; Weisberg, P.; Dilts, T.

2016-12-01

Climate warming can lead to large-scale drought-induced tree mortality events and greatly affect forest landscape resilience. Climatic water deficit (CWD) and its physiographic variations provide a key mechanism in driving landscape dynamics in response to climate change. Although CWD has been successfully applied in niche-based species distribution models, its application in process-based forest landscape models is still scarce. Here we present a framework incorporating fine-scale influence of terrain on ecohydrology in modeling forest landscape dynamics. We integrated CWD with a forest landscape succession and disturbance model (LANDIS-II) to evaluate how tree species distribution might shift in response to different climate-fire scenarios across an elevation-aspect gradient in a semi-arid montane landscape of northeastern Nevada, USA. Our simulations indicated that drought-intolerant tree species such as quaking aspen could experience greatly reduced distributions in the more arid portions of their existing ranges due to water stress limitations under future climate warming scenarios. However, even at the most xeric portions of its range, aspen is likely to persist in certain environmental settings due to unique and often fine-scale combinations of resource availability, species interactions and disturbance regime. The modeling approach presented here allowed identification of these refugia. In addition, this approach helped quantify how the direction and magnitude of fire influences on species distribution would vary across topoclimatic gradients, as well as furthers our understanding on the role of environmental conditions, fire, and inter-specific competition in shaping potential responses of landscape resilience to climate change.

Soil organic matter composition and quality across fire severity gradients in coniferous and deciduous forests of the southern boreal region

NASA Astrophysics Data System (ADS)

Miesel, Jessica R.; Hockaday, William C.; Kolka, Randall K.; Townsend, Philip A.

2015-06-01

Recent patterns of prolonged regional drought in southern boreal forests of the Great Lakes region, USA, suggest that the ecological effects of disturbance by wildfire may become increasingly severe. Losses of forest soil organic matter (SOM) during fire can limit soil nutrient availability and forest regeneration. These processes are also influenced by the composition of postfire SOM. We sampled the forest floor layer (i.e., full organic horizon) and 0-10 cm mineral soil from stands dominated by coniferous (Pinus banksiana Lamb.) or deciduous (Populus tremuloides Michx.) species 1-2 months after the 2011 Pagami Creek wildfire in northern Minnesota. We used solid-state 13C NMR to characterize SOM composition across a gradient of fire severity in both forest cover types. SOM composition was affected by fire, even when no statistically significant losses of total C stocks were evident. The most pronounced differences in SOM composition between burned and unburned reference areas occurred in the forest floor for both cover types. Carbohydrate stocks in forest floor and mineral horizons decreased with severity level in both cover types, whereas pyrogenic C stocks increased with severity in the coniferous forest floor and decreased in only the highest severity level in the deciduous forest floor. Loss of carbohydrate and lignin pools contributed to a decreased SOM stability index and increased decomposition index. Our results suggest that increases in fire severity expected to occur under future climate scenarios may lead to changes in SOM composition and dynamics with consequences for postfire forest recovery and C uptake.

Resistance of the boreal forest to high burn rates.

PubMed

Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

2014-09-23

Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30-500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks.

Resistance of the boreal forest to high burn rates

PubMed Central

Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

2014-01-01

Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30–500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks. PMID:25201981

The role of disturbance severity and canopy closure on standing crop of understory plant species in ponderosa pine stands in northern Arizona, USA

Treesearch

Kyla E. Sabo; Carolyn Hull Sieg; Stephen C. Hart; John Duff Bailey

2009-01-01

Concerns about the long-term sustainability of overstocked dry conifer forests in western North America have provided impetus for treatments designed to enhance their productivity and native biodiversity. Dense forests are increasingly prone to large stand-replacing fires; yet, thinning and burning treatments, especially combined with other disturbances such as drought...

Climate Change and Your National Forest: Assessing the potential effects of climate change on the El Yunque National Forest

Treesearch

L.N. Jennings; E.A. Treasure; S.G. McNulty

2013-01-01

Forestlands across the world are experiencing increased threats from fire, insect and plant invasions, disease, extreme weather, and drought. Scientists project increases in temperature and changes in rainfall patterns that can make these threats occur more often, with more intensity, and/or for longer durations. Although many of the effects of future changes are...

Response of native Hawaiian woody species to lava-ignited wildfires in tropical forests and shrublands

Treesearch

Alison Ainsworth; J. Boone Kauffman

2009-01-01

Wildfires are rare in the disturbance history of Hawaiian forests but may increase in prevalence due to invasive species and global climate change. We documented survival rates and adaptations facilitating persistence of native woody species following 2002–2003 wildfires in Hawaii Volcanoes National Park, Hawaii. Fires occurred during an El Niño drought and were...

Rapid warming accelerates tree growth decline in semi-arid forests of Inner Asia.

PubMed

Liu, Hongyan; Park Williams, A; Allen, Craig D; Guo, Dali; Wu, Xiuchen; Anenkhonov, Oleg A; Liang, Eryuan; Sandanov, Denis V; Yin, Yi; Qi, Zhaohuan; Badmaeva, Natalya K

2013-08-01

Forests around the world are subject to risk of high rates of tree growth decline and increased tree mortality from combinations of climate warming and drought, notably in semi-arid settings. Here, we assess how climate warming has affected tree growth in one of the world's most extensive zones of semi-arid forests, in Inner Asia, a region where lack of data limits our understanding of how climate change may impact forests. We show that pervasive tree growth declines since 1994 in Inner Asia have been confined to semi-arid forests, where growing season water stress has been rising due to warming-induced increases in atmospheric moisture demand. A causal link between increasing drought and declining growth at semi-arid sites is corroborated by correlation analyses comparing annual climate data to records of tree-ring widths. These ring-width records tend to be substantially more sensitive to drought variability at semi-arid sites than at semi-humid sites. Fire occurrence and insect/pathogen attacks have increased in tandem with the most recent (2007-2009) documented episode of tree mortality. If warming in Inner Asia continues, further increases in forest stress and tree mortality could be expected, potentially driving the eventual regional loss of current semi-arid forests. © 2013 John Wiley & Sons Ltd.

Spatial and temporal dimensions of fire activity in the fire-prone eastern Canadian taiga.

PubMed

Erni, Sandy; Arseneault, Dominique; Parisien, Marc-André; Bégin, Yves

2017-03-01

The forest age mosaic is a fundamental attribute of the North American boreal forest. Given that fires are generally lethal to trees, the time since last fire largely determines the composition and structure of forest stands and landscapes. Although the spatiotemporal dynamics of such mosaics has long been assumed to be random under the overwhelming influence of severe fire weather, no long-term reconstruction of mosaic dynamics has been performed from direct field evidence. In this study, we use fire length as a proxy for fire extent across the fire-prone eastern Canadian taiga and systematically reconstruct the spatiotemporal variability of fire extent and fire intervals, as well as the resulting forest age along a 340-km transect for the 1840-2013 time period. Our results indicate an extremely active fire regime over the last two centuries, with an overall burn rate of 2.1% of the land area yr -1 , mainly triggered by seasonal anomalies of high temperature and severe drought. However, the rejuvenation of the age mosaic was strongly patterned in space and time due to the intrinsically lower burn rates in wetland-dominated areas and, more importantly, to the much-reduced likelihood of burning of stands up to 50 years postfire. An extremely high burn rate of ~5% yr -1 would have characterized our study region during the last century in the absence of such fuel age effect. Although recent burn rates and fire sizes are within their range of variability of the last 175 years, a particularly severe weather event allowed a 2013 fire to spread across a large fire refuge, thus shifting the abundance of mature and old forest to a historic low. These results provide reference conditions to evaluate the significance and predict the spatiotemporal dynamics and impacts of the currently strengthening fire activity in the North American boreal forest. © 2016 John Wiley & Sons Ltd.

Sensitivity of woody carbon stocks to bark investment strategy in Neotropical savannas and forests

NASA Astrophysics Data System (ADS)

Trugman, Anna T.; Medvigy, David; Hoffmann, William A.; Pellegrini, Adam F. A.

2018-01-01

Fire frequencies are changing in Neotropical savannas and forests as a result of forest fragmentation and increasing drought. Such changes in fire regime and climate are hypothesized to destabilize tropical carbon storage, but there has been little consideration of the widespread variability in tree fire tolerance strategies. To test how aboveground carbon stocks change with fire frequency and composition of plants with different fire tolerance strategies, we update the Ecosystem Demography model 2 (ED2) with (i) a fire survivorship module based on tree bark thickness (a key fire-tolerance trait across woody plants in savannas and forests), and (ii) plant functional types representative of trees in the region. With these updates, the model is better able to predict how fire frequency affects population demography and aboveground woody carbon. Simulations illustrate that the high survival rate of thick-barked, large trees reduces carbon losses with increasing fire frequency, with high investment in bark being particularly important in reducing losses in the wettest sites. Additionally, in landscapes that frequently burn, bark investment can broaden the range of climate and fire conditions under which savannas occur by reducing the range of conditions leading to either complete tree loss or complete grass loss. These results highlight that tropical vegetation dynamics depend not only on rainfall and changing fire frequencies but also on tree fire survival strategy. Further, our results indicate that fire survival strategy is fundamentally important in regulating tree size demography in ecosystems exposed to fire, which increases the preservation of aboveground carbon stocks and the coexistence of different plant functional groups.

The potential predictability of fire danger provided by ECMWF forecast

NASA Astrophysics Data System (ADS)

Di Giuseppe, Francesca

2017-04-01

The European Forest Fire Information System (EFFIS), is currently being developed in the framework of the Copernicus Emergency Management Services to monitor and forecast fire danger in Europe. The system provides timely information to civil protection authorities in 38 nations across Europe and mostly concentrates on flagging regions which might be at high danger of spontaneous ignition due to persistent drought. The daily predictions of fire danger conditions are based on the US Forest Service National Fire Danger Rating System (NFDRS), the Canadian forest service Fire Weather Index Rating System (FWI) and the Australian McArthur (MARK-5) rating systems. Weather forcings are provided in real time by the European Centre for Medium range Weather Forecasts (ECMWF) forecasting system. The global system's potential predictability is assessed using re-analysis fields as weather forcings. The Global Fire Emissions Database (GFED4) provides 11 years of observed burned areas from satellite measurements and is used as a validation dataset. The fire indices implemented are good predictors to highlight dangerous conditions. High values are correlated with observed fire and low values correspond to non observed events. A more quantitative skill evaluation was performed using the Extremal Dependency Index which is a skill score specifically designed for rare events. It revealed that the three indices were more skilful on a global scale than the random forecast to detect large fires. The performance peaks in the boreal forests, in the Mediterranean, the Amazon rain-forests and southeast Asia. The skill-scores were then aggregated at country level to reveal which nations could potentiallty benefit from the system information in aid of decision making and fire control support. Overall we found that fire danger modelling based on weather forecasts, can provide reasonable predictability over large parts of the global landmass.

Deforestation fires versus understory fires in the Amazon Basin: What can we learn from satellite-based CO measurements?

NASA Astrophysics Data System (ADS)

Martinez-Alonso, S.; Deeter, M. N.; Worden, H. M.; Gille, J. C.; Clerbaux, C.; George, M.

2014-12-01

Deforestation fires in the Amazon Basin abound during the dry season (July to October) and are mostly associated with "slash and burn" agricultural practices. Understory fires occur when fires escape from deforested areas into neighboring standing forests; they spread slowly below the canopy, affecting areas that may be comparable or even larger than clear-cut areas. The interannual variabilities of understory fires and deforestation rates appear to be uncorrelated. Areas burned in understory fires are particularly extensive during droughts. Because they progress below a canopy of living trees, understory fires and their effects are not as easily identifiable from space as deforestation fires. Here we analyze satellite remote sensing products for CO and fire to investigate differences between deforestation fires and understory fires in the Amazon Basin under varying climatic conditions. The MOPITT (Measurements Of Pollution In The Troposphere) instrument on board NASA's Terra satellite has been measuring tropospheric CO since 2000, providing the longest global CO record to date. IASI (the Infrared Atmospheric Sounding Interferometer) A and B are two instruments on board METOP-A and -B, respectively, measuring, among others, CO since 2006 and 2012. MODIS (the Moderate Resolution Imaging Spectroradiometer) instruments on board NASA's Terra and Aqua satellites provide, among other products, a daily record of fires and their effects since 2000 and 2002, respectively. The temporal extent of all these datasets allows for the detailed analysis of drought versus non-drought years. Initial results indicate that MOPITT CO emissions during the dry season peaked in 2005, 2007, and 2010. Those were draught years and coincide with peaks in area affected by understory fires.

Seasonal Forecasting of Fires across Southern Borneo, 1997-2010

NASA Astrophysics Data System (ADS)

Spessa, Allan; Field, Robert; Kaiser, Johannes; Langner, Andreas; Moore, Jonathan; Pappenberger, Florian; Siegert, Florian; Weber, Ulrich

2014-05-01

Wildfire is a fundamental Earth System process, affecting almost all biogeochemical cycles, and all vegetated biomes. Fires are naturally rare in humid tropical forests, and tropical trees are generally killed by even low-intensity fires. However, fire activity in the tropics has increased markedly over the past 15-20 years, especially in Indonesia, Amazonia, and more recently, central Africa also. Since fire is the prime tool for clearing land in the tropics, it not surprising that the increase in fire activity is strongly associated with increased levels of deforestation, which is driven mainly by world-wide demand for timber and agricultural commodities. The consequences of deforestation fires for biodiversity conservation and emissions of greenhouse gases and aerosols are enormous. For example, carbon emissions from tropical biomass burning are around 20% of annual average global fossil fuel emissions. The destructive fires in Indonesia during the exceptionally strong El Niño-induced drought in late 1997 and early 1998 rank as some of the largest peak emissions events in recorded history. Past studies estimate about 1Gt of carbon was released to the atmosphere from the Indonesian fires in 1997 (which were mostly concentrated in carbon-rich forested peatlands). This amount is equivalent to about 14% of the average global annual fossil fuel emissions released during the 1990s. While not as large as the 1997-98 events, significant emissions from biomass burning have also been recorded in other (less severe) El Niño years across Indonesia, in particular, 2002, 2004, 2006 and 2009-2010. Recent climate modelling studies indicate that the frequency of El Niño events may increase under future climate change, affecting many tropical countries, including Indonesia. An increased drought frequency plus a projected increase in population and land use pressures in Indonesia, imply there will be even more fires and emissions in future across the region. However, while several studies using historical data have established negative relationships between fires and antecedent rainfall, and/or positive relationships between fires and deforestation in regions affected by El Nino, comparatively little work has attempted to predict fires and emissions in such regions. Ensemble seasonal climate forecasts issued with several months lead-time have been applied to support risk assessment systems in many fields, notably agricultural production and natural disaster management of flooding, heat waves, drought and fire. The USA, for example, has a long-standing seasonal fire danger prediction system. Fire danger monitoring systems have been operating in Indonesia for over a decade, but, as of yet, no fire danger prediction systems exist. Given the effort required to mobilise suppression and prevention measures in Indonesia, one could argue that high fire danger periods must be anticipated months in advance for mitigation and response measures to be effective. To address this need, the goal of our work was to examine the utility of seasonal rainfall forecasts in predicting severe fires in Indonesia more than one month in advance, using southern Borneo (comprising the bulk of Kalimantan) as a case study. Here we present the results of comparing seasonal forecasts of monthly rainfall from ECMWF's System 4 against i) observed rainfall (GPCP), and ii) burnt area and deforestation (MODIS, AVHRR and Landsat) across southern Borneo for the period 1997-2010. Our results demonstrate the utility of using ECMWF's seasonal climate forecasts for predicting fire activity in the region. Potential applications include improved fire mitigation and responsiveness, and improved risk assessments of biodiversity and carbon losses through fire. These are important considerations for forest protection programmes (e.g. REDD+), forest carbon markets and forest (re)insurance enterprises.

Evaluating and monitoring forest fuel treatments using remote sensing applications in Arizona, U.S.A.

USGS Publications Warehouse

Petrakis, Roy; Villarreal, Miguel; Wu, Zhuoting; Hetzler, Robert; Middleton, Barry R.; Norman, Laura M.

2018-01-01

The practice of fire suppression across the western United States over the past century has led to dense forests, and when coupled with drought has contributed to an increase in large and destructive wildfires. Forest management efforts aimed at reducing flammable fuels through various fuel treatments can help to restore frequent fire regimes and increase forest resilience. Our research examines how different fuel treatments influenced burn severity and post-fire vegetative stand dynamics on the San Carlos Apache Reservation, in east-central Arizona, U.S.A. Our methods included the use of multitemporal remote sensing data and cloud computing to evaluate burn severity and post-fire vegetation conditions as well as statistical analyses. We investigated how forest thinning, commercial harvesting, prescribed burning, and resource benefit burning (managed wildfire) related to satellite measured burn severity (the difference Normalized Burn Ratio – dNBR) following the 2013 Creek Fire and used spectral measures of post-fire stand dynamics to track changes in land surface characteristics (i.e., brightness, greenness and wetness). We found strong negative relationships between dNBR and post-fire greenness and wetness, and a positive non-linear relationship between dNBR and brightness, with greater variability at higher severities. Fire severity and post-fire surface changes also differed by treatment type. Our results showed harvested and thinned sites that were not treated with prescribed fire had the highest severity fire. When harvesting was followed by a prescribed burn, the sites experienced lower burn severity and reduced post-fire changes in vegetation greenness and wetness. Areas that had previously experienced resource benefit burns had the lowest burn severities and the highest post-fire greenness measurements compared to all other treatments, except for where the prescribed burn had occurred. These results suggest that fire treatments may be most effective at reducing the probability of hazardous fire and increasing post-fire recovery. This research demonstrates the utility of remote sensing and spatial data to inform forest management, and how various fuel treatments can influence burn severity and post-fire vegetation response within ponderosa pine forests across the southwestern U.S.

Effects of Natural and Experimental Drought on Growth and Water Use Efficiency in Amazon trees

NASA Astrophysics Data System (ADS)

Vadeboncoeur, M. A.; Brum, M., Jr.; Oliveira, R. S.; Moutinho, V. H. P.; Flores, C. F.; Llerena, C. A.; Palace, M. W.; Asbjornsen, H.

2016-12-01

Severe regional droughts in the Amazon basin, mostly associated with El Nino events, have attracted considerable attention over the past decade, especially with regard to their effects on tree mortality, vulnerability to fire, and changes in the terrestrial budgets of carbon, water, and energy. Understanding the complex responses of forest ecosystems to such droughts is key to predicting how these globally critical forest ecosystems will respond to a changing climate with higher temperatures and greater precipitation variability. Though tree rings are not formed by all tropical tree species, they offer a unique retrospective approach for investigating patterns of climatic responses in both carbon cycling (primary production inferred from diameter growth) and water cycling (water use efficiency calculated from stable C isotope ratios). We sampled increment cores from 40 tree species at the Tapajos National Forest in Brazil, as well as the Cocha Cashu Biological Station in Peru, for an isotopic dendrochronological investigation into the effects of past droughts on the growth and water-use efficiency of canopy and mid-story tree species. We found that many but not all trees responded to drought years with periods of reduced growth lasting 2-3 years. Forthcoming data on carbon isotope ratios will allow us to compare the sensitivity of species and sites in terms of water use under drought conditions.

Natural disturbance production functions

Treesearch

Jeffrey P. Prestemon; D. Evan Mercer; John M. Pye

2008-01-01

Natural disturbances in forests are driven by physical and biological processes. Large, landscape scale disturbances derive primarily from weather (droughts, winds, ice storms, and floods), geophysical activities (earthquakes, volcanic eruptions), fires, insects, and diseases. Humans have invented ways to minimize their negative impacts and reduce their rates of...

Simulating fire regimes in the Amazon in response to climate change and deforestation.

PubMed

Silvestrini, Rafaella Almeida; Soares-Filho, Britaldo Silveira; Nepstad, Daniel; Coe, Michael; Rodrigues, Hermann; Assunção, Renato

2011-07-01

Fires in tropical forests release globally significant amounts of carbon to the atmosphere and may increase in importance as a result of climate change. Despite the striking impacts of fire on tropical ecosystems, the paucity of robust spatial models of forest fire still hampers our ability to simulate tropical forest fire regimes today and in the future. Here we present a probabilistic model of human-induced fire occurrence for the Amazon that integrates the effects of a series of anthropogenic factors with climatic conditions described by vapor pressure deficit. The model was calibrated using NOAA-12 night satellite hot pixels for 2003 and validated for the years 2002, 2004, and 2005. Assessment of the fire risk map yielded fitness values > 85% for all months from 2002 to 2005. Simulated fires exhibited high overlap with NOAA-12 hot pixels regarding both spatial and temporal distributions, showing a spatial fit of 50% within a radius of 11 km and a maximum yearly frequency deviation of 15%. We applied this model to simulate fire regimes in the Amazon until 2050 using IPCC's A2 scenario climate data from the Hadley Centre model and a business-as-usual (BAU) scenario of deforestation and road expansion from SimAmazonia. Results show that the combination of these scenarios may double forest fire occurrence outside protected areas (PAs) in years of extreme drought, expanding the risk of fire even to the northwestern Amazon by midcentury. In particular, forest fires may increase substantially across southern and southwestern Amazon, especially along the highways slated for paving and in agricultural zones. Committed emissions from Amazon forest fires and deforestation under a scenario of global warming and uncurbed deforestation may amount to 21 +/- 4 Pg of carbon by 2050. BAU deforestation may increase fires occurrence outside PAs by 19% over the next four decades, while climate change alone may account for a 12% increase. In turn, the combination of climate change and deforestation would boost fire occurrence outside PAs by half during this period. Our modeling results, therefore, confirm the synergy between the two Ds of REDD (Reducing Emissions from Deforestation and Forest Degradation in Developing Countries).

Temporal and spatial climatic controls on Holocene fire-related erosion and sedimentation, Jemez Mountains, New Mexico

NASA Astrophysics Data System (ADS)

Fitch, Erin P.; Meyer, Grant A.

2016-01-01

In the Jemez Mountains, tree-ring data indicate that low-severity fires characterized the 400 yr before Euro-American settlement, and that subsequent fire suppression promoted denser forests, recent severe fires, and erosion. Over longer timescales, climate change may alter fire regimes; thus, we used fire-related alluvial deposits to assess the timing of moderate- to high-severity fires, their geomorphic impact, and relation to climate over the last 4000 yr. Fire-related sedimentation does not clearly follow millennial-scale climatic changes, but probability peaks commonly correspond with severe drought, e.g., within the interval 1700-1400 cal yr BP, and ca. 650 and ca. 410 cal yr BP. The latter episodes were preceded by prolonged wet intervals that could promote dense stands. Estimated recurrence intervals for fire-related sedimentation are 250-400 yr. Climatic differences with aspect influenced Holocene post-fire response: fire-related deposits constitute 77% of fan sediments from north-facing basins but only 39% of deposits from drier southerly aspects. With sparser vegetation and exposed bedrock, south aspects can generate runoff and sediment when unburned, whereas soil-mantled north aspects produce minor sediment unless severely burned. Recent channel incision appears unprecedented over the last 2300 yr, suggesting that fuel loading and extreme drought produced an anomalously severe burn in 2002.

Mesoscale disturbance and ecological response to decadal climatic variability in the American Southwest

USGS Publications Warehouse

Swetnam, T.W.; Betancourt, J.L.

1998-01-01

Ecological responses to climatic variability in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and tree demography reveal climatic effects across scales, from annual to decadal, and from local (<102 km2) to mesoscale (104-106 km2). Climate-disturbance relations are more variable and complex than previously assumed. During the past three centuries, mesoscale outbreaks of the western spruce budworm (Choristoneura occidentalis) were associated with wet, not dry episodes, contrary to conventional wisdom. Regional fires occur during extreme droughts but, in some ecosystems, antecedent wet conditions play a secondary role by regulating accumulation of fuels. Interdecadal changes in fire-climate associations parallel other evidence for shifts in the frequency or amplitude of the Southern Oscillation (SO) during the past three centuries. High interannual, fire-climate correlations (r = 0.7 to 0.9) during specific decades (i.e., circa 1740-80 and 1830-60) reflect periods of high amplitude in the SO and rapid switching from extreme wet to dry years in the Southwest, thereby entraining fire occurrence across the region. Weak correlations from 1780 to 1830 correspond with a decrease in SO frequency or amplitude inferred from independent tree-ring width, ice core, and coral isotope reconstructions. Episodic dry and wet episodes have altered age structures and species composition of woodland and conifer forests. The scarcity of old, living conifers established before circa 1600 suggests that the extreme drought of 1575-95 had pervasive effects on tree populations. The most extreme drought of the past 400 years occurred in the mid-twentieth century (1942-57). This drought resulted in broadscale plant dieoffs in shrublands, woodlands, and forests and accelerated shrub invasion of grasslands. Drought conditions were broken by the post-1976 shift to the negative SO phase and wetter cool seasons in the Southwest. The post-1976 period shows up as an unprecedented surge in tree-ring growth within millennia-length chronologies. This unusual episode may have produced a pulse in tree recruitment and improved rangeland conditions (e.g., higher grass production), though additional study is needed to disentangle the interacting roles of land use and climate. The 1950s drought and the post-1976 wet period and their aftermaths offer natural experiments to study long-term ecosystem response to interdecadal climate variability.Ecological responses to climatic variability in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and tree demography reveal climatic effects across scales, from annual to decadal, and from local (<102 km2) to mesoscale (104-106 km2). Climate-disturbance relations are more variable and complex than previously assumed. During the past three centuries, mesoscale outbreaks of the western spruce budworm (Choristoneura occidentalis) were associated with wet, not dry episodes, contrary to conventional wisdom. Regional fires occur during extreme droughts but, in some ecosystems, antecedent wet conditions play a secondary role by regulating accumulation of fuels. Interdecadal changes in fire-climate associations parallel other evidence for shifts in the frequency or amplitude of the Southern Oscillation (SO) during the past three centuries. High interannual, fire-climate correlations (r = 0.7 to 0.9) during specific decades (i.e., circa 1740-80 and 1830-60) reflect periods of high amplitude in the SO and rapid switching from extreme wet to dry years in the Southwest, thereby entraining fire occurrence across the region. Weak correlations from 1780 to 1830 correspond with a decrease in SO frequency or amplitude inferred from independent tree-ring width, ic

Fire, Fuel Composition and Resilience Threshold in Subalpine Ecosystem

PubMed Central

Blarquez, Olivier; Carcaillet, Christopher

2010-01-01

Background Forecasting the effects of global changes on high altitude ecosystems requires an understanding of the long-term relationships between biota and forcing factors to identify resilience thresholds. Fire is a crucial forcing factor: both fuel build-up from land-abandonment in European mountains, and more droughts linked to global warming are likely to increase fire risks. Methods To assess the vegetation response to fire on a millennium time-scale, we analyzed evidence of stand-to-local vegetation dynamics derived from sedimentary plant macroremains from two subalpine lakes. Paleobotanical reconstructions at high temporal resolution, together with a fire frequency reconstruction inferred from sedimentary charcoal, were analyzed by Superposed Epoch Analysis to model plant behavior before, during and after fire events. Principal Findings We show that fuel build-up from arolla pine (Pinus cembra) always precedes fires, which is immediately followed by a rapid increase of birch (Betula sp.), then by ericaceous species after 25–75 years, and by herbs after 50–100 years. European larch (Larix decidua), which is the natural co-dominant species of subalpine forests with Pinus cembra, is not sensitive to fire, while the abundance of Pinus cembra is altered within a 150-year period after fires. A long-term trend in vegetation dynamics is apparent, wherein species that abound later in succession are the functional drivers, loading the environment with fuel for fires. This system can only be functional if fires are mainly driven by external factors (e.g. climate), with the mean interval between fires being longer than the minimum time required to reach the late successional stage, here 150 years. Conclusion Current global warming conditions which increase drought occurrences, combined with the abandonment of land in European mountain areas, creates ideal ecological conditions for the ignition and the spread of fire. A fire return interval of less than 150 years would threaten the dominant species and might override the resilience of subalpine forests. PMID:20814580

Interactions between atmospheric circulation, nutrient deposition, and tropical forest primary production (Invited)

NASA Astrophysics Data System (ADS)

Randerson, J. T.; Chen, Y.; Rogers, B. M.; Morton, D. C.; van der Werf, G.; Mahowald, N. M.

2010-12-01

Tropical forests influence regional and global climate by means of several pathways, including by modifying surface energy exchange and by forming clouds. High levels of precipitation, leaching, and soil weathering limit nutrient availability in these ecosystems. Phosphorus (P) is a key element limiting net primary production, and in some areas, including forests recovering from prior disturbance, nitrogen (N) also may limit some components of production. Here we quantified atmospheric P and N inputs to these forests from fires using satellite-derived estimates of emissions and atmospheric models. In Africa and South America, cross-biome transport of fire-emitted aerosols and reactive N gases from savannas and areas near the deforestation frontier increased deposition of P and N in interior forests. Equatorward atmospheric transport during the dry (fire) season in one hemisphere was linked with surface winds moving toward the inter-tropical convergence zone (ITCZ) in the other hemisphere. Deposition levels were higher in tropical forests in Africa than in South America because of large savanna areas with high levels of fire emissions in both southern and northern Africa. We conclude by describing a potential feedback loop by which equatorward transport of fire emissions, dust, and spores sustains the productivity of tropical forests. We specifically assessed evidence that savanna-to-forest atmospheric transport of nutrients increases forest productivity, height, and rates of evapotranspiration (ET). In parallel, we examined the degree to which increases in ET and surface roughness in tropical forests have the potential to strengthen several components of the Hadley circulation, including deep convection, equatorward return flow (near the surface), and the intensity of seasonal drought in the subtropics (thereby increasing fires). These interactions are important for understanding biogeochemical - climate interactions on millennial timescales and for quantifying how contemporary changes in fire activity and land use are changing the global carbon cycle.

The 2007 southern California wildfires: Lessons in complexity

USGS Publications Warehouse

Keeley, J.E.; Safford, H.; Fotheringham, C.J.; Franklin, J.; Moritz, M.

2009-01-01

The 2007 wildfire season in southern California burned over 1,000,000 ac (400,000 ha) and included several megafires. We use the 2007 fires as a case study to draw three major lessons about wildfires and wildfire complexity in southern California. First, the great majority of large fires in southern California occur in the autumn under the influence of Santa Ana windstorms. These fires also cost the most to contain and cause the most damage to life and property, and the October 2007 fires were no exception because thousands of homes were lost and seven people were killed. Being pushed by wind gusts over 100 kph, young fuels presented little barrier to their spread as the 2007 fires reburned considerable portions of the area burned in the historic 2003 fire season. Adding to the size of these fires was the historic 2006-2007 drought that contributed to high dead fuel loads and long distance spotting. As in 2003, young chaparral stands and fuel treatments were not reliable barriers to fire in October 2007. Second, the Zaca Fire in July and August 2007 showed that other factors besides high winds can sometimes combine to create conditions for large fires in southern California. Spring and summer fires in southern California chaparral are usually easily contained because of higher fuel moisture and the general lack of high winds. However, the Zaca Fire burned in a remote wilderness area of rugged terrain that made access difficult. In addition, because of its remoteness, anthropogenic ignitions have been low and stand age and fuel loads were high. Coupled with this was severe drought that year that generated fuel moisture levels considerably below normal for early summer. A third lesson comes from 2007 conifer forest fires in the southern California mountains. In contrast to lower elevation chaparral, fire suppression has led to major increases in conifer forest fuels that can lead to unnaturally severe fires when ignitions escape control. The Slide and Grass Valley Fires of October 2007 occurred in forests that had been subject to extensive fuel treatment, but fire control was complicated by a patchwork of untreated private properties and mountain homes built of highly flammable materials. In a fashion reminiscent of other recent destructive conifer fires in California, burning homes themselves were a major source of fire spread. These lessons suggest that the most important advances in fire safety in this region are to come from advances in fire prevention, fire preparedness, and land-use planning that includes fire hazard patterns.

Climate change impacts on forest fires: the stakeholders' perspective

NASA Astrophysics Data System (ADS)

Giannakopoulos, C.; Roussos, A.; Karali, A.; Hatzaki, M.; Xanthopoulos, G.; Chatzinikos, E.; Fyllas, N.; Georgiades, N.; Karetsos, G.; Maheras, G.; Nikolaou, I.; Proutsos, N.; Sbarounis, T.; Tsaggari, K.; Tzamtzis, I.; Goodess, C.

2012-04-01

In this work, we present a synthesis of the presentations and discussions which arose during a workshop on 'Impacts of climate change on forest fires' held in September 2011 at the National Observatory of Athens, Greece in the framework of EU project CLIMRUN. At first, a general presentation about climate change and extremes in the Greek territory provided the necessary background to the audience and highlighted the need for data and information exchange between scientists and stakeholders through climate services within CLIMRUN. Discussions and presentations that followed linked climate with forest science through the use of a meteorological index for fire risk and future projections of fire danger using regional climate models. The current situation on Greek forests was also presented, as well as future steps that should be taken to ameliorate the situation under a climate change world. A time series analysis of changes in forest fires using available historical data on forest ecosystems in Greece was given in this session. This led to the topic of forest fire risk assessment and fire prevention, stating all actions towards sustainable management of forests and effective mechanisms to control fires under climate change. Options for a smooth adaptation of forests to climate change were discussed together with the lessons learned on practical level on prevention, repression and rehabilitation of forest fires. In between there were useful interventions on sustainable hunting and biodiversity protection and on climate change impacts on forest ecosystems dynamics. The importance of developing an educational program for primary/secondary school students on forest fire management was also highlighted. The perspective of forest stakeholders on climate change and how this change can affect their current or future activities was addressed through a questionnaire they were asked to complete. Results showed that the majority of the participants consider climate variability to be important or very important and to influence their activities. Extreme climate events, desertification and drought were regarded as the most important environmental problems along with loss of biodiversity. Most of the participants answered that they use historical data for research, and would welcome climate data and services targeted to their sector if offered. Acknowledgement: This work was supported by the EU project CLIMRUN under contract FP7-ENV-2010- 265192.

Reconstructing daily clear-sky land surface temperature for cloudy regions from MODIS data

USDA-ARS?s Scientific Manuscript database

Land surface temperature (LST) is a critical parameter in environmental studies and resource management. The MODIS LST data product has been widely used in various studies, such as drought monitoring, evapotranspiration mapping, soil moisture estimation and forest fire detection. However, cloud cont...

Effectiveness of protected areas in mitigating fire within their boundaries: case study of Chiapas, Mexico.

PubMed

Román-Cuesta, María Rosa; Martínez-Vilalta, Jordi

2006-08-01

Since the severe 1982-1983 El Niño drought, recurrent burning has been reported inside tropical protected areas (TPAs). Despite the key role of fire in habitat degradation, little is known about the effectiveness of TPAs in mitigating fire incidence and burned areas. We used a GPS fire database (1995-2005) (n=3590 forest fires) obtained from the National Forest Commission to compare fire incidence (number of fires) and burned areas inside TPAs and their surrounding adjacent buffer areas in Southern Mexico (Chiapas). Burned areas inside parks ranged from 2% (Palenque) to 45% (Lagunas de Montebello) of a park's area, and the amount burned was influenced by two severe El Niño events (1998 and 2003). These two years together resulted in 67% and 46% of the total area burned in TPAs and buffers, respectively during the period under analysis. Larger burned areas in TPAs than in their buffers were exclusively related to the extent of natural habitats (flammable area excluding agrarian and pasture lands). Higher fuel loads together with access and extinction difficulties were likely behind this trend. A higher incidence of fire in TPAs than in their buffers was exclusively related to anthropogenic factors such as higher road densities and agrarian extensions. Our results suggest that TPAs are failing to mitigate fire impacts, with both fire incidence and total burned areas being significantly higher in the reserves than in adjacent buffer areas. Management plans should consider those factors that facilitate fires in TPAs: anthropogenic origin of fires, sensitivity of TPAs to El Niñio-droughts, large fuel loads and fuel continuity inside parks, and limited financial resources. Consideration of these factors favors lines of action such as alternatives to the use of fire (e.g., mucuna-maize system), climatic prediction to follow the evolution of El Niño, fuel management strategies that favor extinction practices, and the strengthening of local communities and ecotourism.

The Zoning of Forest Fire Potential of Gulestan Province Forests Using Granular Computing and MODIS Images

NASA Astrophysics Data System (ADS)

Jalilzadeh Shadlouei, A.; Delavar, M. R.

2013-09-01

There are many vegetation in Iran. This is because of extent of Iran and its width. One of these vegetation is forest vegetation most prevalent in Northern provinces named Guilan, Mazandaran, Gulestan, Ardebil as well as East Azerbaijan. These forests are always threatened by natural forest fires so much so that there have been reports of tens of fires in recent years. Forest fires are one of the major environmental as well as economic, social and security concerns in the world causing much damages. According to climatology, forest fires are one of the important factors in the formation and dispersion of vegetation. Also, regarding the environment, forest fires cause the emission of considerable amounts of greenhouse gases, smoke and dust into the atmosphere which in turn causes the earth temperature to rise up and are unhealthy to humans, animals and vegetation. In agriculture droughts are the usual side effects of these fires. The causes of forest fires could be categorized as either Human or Natural Causes. Naturally, it is impossible to completely contain forest fires; however, areas with high potentials of fire could be designated and analysed to decrease the risk of fires. The zoning of forest fire potential is a multi-criteria problem always accompanied by inherent uncertainty like other multi-criteria problems. So far, various methods and algorithm for zoning hazardous areas via Remote Sensing (RS) and Geospatial Information System (GIS) have been offered. This paper aims at zoning forest fire potential of Gulestan Province of Iran forests utilizing Remote Sensing, Geospatial Information System, meteorological data, MODIS images and granular computing method. Granular computing is part of granular mathematical and one way of solving multi-criteria problems such forest fire potential zoning supervised by one expert or some experts , and it offers rules for classification with the least inconsistencies. On the basis of the experts' opinion, 6 determinative criterias contributing to forest fires have been designated as follows: vegetation (NDVI), slope, aspect, temperature, humidity and proximity to roadways. By applying these variables on several tentatively selected areas and formation information tables and producing granular decision tree and extraction of rules, the zoning rules (for the areas in question) were extracted. According to them the zoning of the entire area has been conducted. The zoned areas have been classified into 5 categories: high hazard, medium hazard (high), medium hazard (low), low hazard (high), low hazard (low). According to the map, the zoning of most of the areas fall into the low hazard (high) class while the least number of areas have been classified as low hazard (low). Comparing the forest fires in these regions in 2010 with the MODIS data base for forest fires, it is concluded that areas with high hazards of forest fire have been classified with a 64 percent precision. In other word 64 percent of pixels that are in high hazard classification are classified according to MODIS data base. Using this method we obtain a good range of Perception. Manager will reduce forest fire concern using precautionary proceeding on hazardous area.

Atmospheric CO2 measurements reveal strong drought sensitivity of Amazonian carbon balance

NASA Astrophysics Data System (ADS)

Miller, J. B.; Gatti, L.; Gloor, M.; Doughty, C.; Malhi, Y.; Domingues, L. G.; Basso, L. S.; Martinewski, A.; Correia, C.; Borges, V.; Freitas, S. R.; Braz, R.; Anderson, L.; Rocha, H.; Grace, J.; Phillips, O.; Lloyd, J.

2013-12-01

Potential feedbacks between land carbon pools and climate are one of the largest sources of uncertainty for predicting future global climate, but estimates of their sensitivity to climate anomalies in the tropics and determination of underlying mechanisms are either incomplete or strongly model-based. Amazonia alone stores ~150-200 Pg of labile carbon, and has experienced an increasing trend in temperature and extreme floods and droughts over the last two decades. Here we report the first Amazon Basin-wide seasonal and annual carbon balances based on tropospheric greenhouse gas sampling, during an anomalously dry and a wet year, 2010 and 2011, providing the first whole-system assessment of sensitivity to such conditions. During 2010, the Amazon Basin lost 0.5×0.2 PgCyr-1 while in 2011 it was approximately carbon neutral (0.06×0.1 PgCyr-1). Carbon loss via fire was 0.5×0.1 PgCyr-1 in 2010 and 0.3×0.1 PgCyr-1 in 2011, as derived from Basin-wide carbon monoxide (CO) enhancements. Subtracting fire emissions from total carbon flux to derive Basin net biome exchange (NBE) reveals that in 2010 the non-fire regions of the Basin were carbon neutral; in 2011 they were a net carbon sink of -0.3×0.1 PgC yr-1, roughly consistent with a three-decade long intact-forest biomass sink of ~ -0.5×0.3 PgCyr-1 estimated from forest censuses. Altogether, our results suggest that if the recent trend of precipitation extremes persists, the Amazon region may become an increasing carbon source as a result of both emissions from fires and suppression of NBE by drought.

Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements.

PubMed

Gatti, L V; Gloor, M; Miller, J B; Doughty, C E; Malhi, Y; Domingues, L G; Basso, L S; Martinewski, A; Correia, C S C; Borges, V F; Freitas, S; Braz, R; Anderson, L O; Rocha, H; Grace, J; Phillips, O L; Lloyd, J

2014-02-06

Feedbacks between land carbon pools and climate provide one of the largest sources of uncertainty in our predictions of global climate. Estimates of the sensitivity of the terrestrial carbon budget to climate anomalies in the tropics and the identification of the mechanisms responsible for feedback effects remain uncertain. The Amazon basin stores a vast amount of carbon, and has experienced increasingly higher temperatures and more frequent floods and droughts over the past two decades. Here we report seasonal and annual carbon balances across the Amazon basin, based on carbon dioxide and carbon monoxide measurements for the anomalously dry and wet years 2010 and 2011, respectively. We find that the Amazon basin lost 0.48 ± 0.18 petagrams of carbon per year (Pg C yr(-1)) during the dry year but was carbon neutral (0.06 ± 0.1 Pg C yr(-1)) during the wet year. Taking into account carbon losses from fire by using carbon monoxide measurements, we derived the basin net biome exchange (that is, the carbon flux between the non-burned forest and the atmosphere) revealing that during the dry year, vegetation was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25 ± 0.14 Pg C yr(-1), which is roughly consistent with the mean long-term intact-forest biomass sink of 0.39 ± 0.10 Pg C yr(-1) previously estimated from forest censuses. Observations from Amazonian forest plots suggest the suppression of photosynthesis during drought as the primary cause for the 2010 sink neutralization. Overall, our results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net biome exchange by drought.

The Influence of Wildfire on Long-Term Erosion: Insights from the Jemez Mountains, NM and the Western USA

NASA Astrophysics Data System (ADS)

Fitch, E. P.; Meyer, G. A.

2017-12-01

A major influence of wildfire on long-term erosion in the western USA is strongly suggested by extreme postfire debris flows and floods, where fire severity has increased in recent decades due to climate change and land use. Roughly 30% of the ponderosa-mixed conifer forests of the Jemez Mountains has burned in the last 20 yr, much at high severity, whereas tree-ring data indicate mostly lower-severity burns from 1600-1900 CE, before fire suppression and grazing. Fire-related alluvial deposits proximal to hillslopes reflect mostly small to moderate erosional events over the last 4000 yr, compared to thick, bouldery debris-flow deposits from recent severe fires; some modern postfire debris flows appear truly extreme in comparison to Holocene deposits. Recognizable fire-related deposits make up 77% of fans from moist north aspects, as relatively dense vegetation and thick soil yield minor surface runoff unless severely burned. Only 39% of fan sediments from drier south aspects are fire-related, however, as sparser vegetation and exposed bedrock can produce runoff and sediment when unburned. Peaks in fire-related sedimentation at 1800, 650, 410, and 300 cal yr BP coincide with severe droughts, often preceded by wetter decades that could suppress fire activity and promote denser stands. Although the Medieval Climatic Anomaly (MCA, 1050-700 cal yr BP) was marked by generally warmer temperatures and multidecadal episodes of widespread, severe drought in the western USA, fire-related sedimentation was relatively minor in the Jemez Mountains. In contrast, dense subalpine forests of Yellowstone and central Idaho burned less frequently and more severely in the late Holocene, and produced major debris flows in the MCA. Fire accounts for only 30-50% of Holocene fan deposition in these areas, as steep unburned basins also produce large debris flows in extreme storms. The relative importance of fire in erosion depends on topography, bedrock, soil cover, and forest composition and density; potent climatic influence on the latter makes it difficult to generalize about how strongly fire drives long-term erosion rates, as even local aspect is important. Also, our data represent interglacial environments that are uncommon over the Quaternary, such that extrapolation of fire's importance beyond the last 104 yr is unwarranted.

Fire, Drought, and Forest Management Influences on Pine/Hardwood Ecosystems in the Southern Appalachians

Treesearch

J.M. Vose; B.D. Clinton; W.T. Swank

1993-01-01

Establishment and maintenance of pitch pine/hardwood ecosystems in the southern Appalachians depends on intense wildfire. These ecosystems typically have a substantial evergreen shrub component (Kalmia latifolia) which limits regeneration of future overstory species. Wildfires provide microsite conditions conducive to pine regeneration and reduce...

Historical fire and multidecadal drought as context for piñon - Juniper woodland restoration in western Colorado

USGS Publications Warehouse

Shinneman, Douglas J.; Baker, William L.

2009-01-01

Fire is known to structure tree populations, but the role of broad-scale climate variability is less clear. For example, the influence of climatic “teleconnections” (the relationship between oceanic–atmospheric fluctuations and anomalous weather patterns across broad scales) on forest age structure is relatively unexplored. We sampled semiarid piñon–juniper (Pinus edulis–Juniperus osteosperma) woodlands in western Colorado, USA, to test the hypothesis that woodland age structures are shaped by climate, including links to oceanic–atmospheric fluctuations, and by past fires and livestock grazing. Low-severity surface fire was lacking, as fire scars were absent, and did not influence woodland densities, but stand-replacing fires served as long-rotation (>400–600 years), stand-initiating events. Old-growth stands (>300 years old) were found in 75% of plots, consistent with a long fire rotation. Juniper and piñon age structures suggest contrasting responses during the past several centuries to dry and wet episodes linked to the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). Juniper density increased slightly during periods of drought, positive (warm) AMO (after ∼10-year lag), and negative (cool) PDO. In contrast, piñon populations may still be recovering from a long, drought-filled period (AD 1620–1820), with pulses of recovery favored during cool AMO, warm PDO, and above-average moisture periods. Analysis of 20th-century tree establishment and instrumental climate data corroborate the long-term relationships between age structure and climate. After Euro–American settlement (AD 1881), livestock grazing reduced understory grasses and forbs, reducing competition with tree seedlings and facilitating climate-induced increases in piñons. Thus tree populations in these woodlands are in flux, affected by drought and wet periods linked to oceanic–atmospheric variability, Euro–American livestock grazing, and long-rotation, high-severity fires. Reductions in livestock grazing levels may aid ecological restoration efforts. However, given long-term fluctuations in tree density and composition, and expected further drought, thinning or burning to reduce tree populations may be misdirected.

Earth Observation taken during the Expedition 36 mission

NASA Image and Video Library

2013-08-24

ISS036-E-035677 (24 Aug. 2013) --- One of the Expedition 36 crew members aboard the International Space Station used a 50mm lens to record this high oblique view of the massive drought-aided Rim Fire in and around California's Yosemite National Park and the Stanislaus National Forest on Aug. 24. Editor's Note: The fire began on Aug. 17 and, as of Aug. 26, continues to burn. More than 224 square miles have been affected.

Effects of experimental fuel additions on fire intensity and severity: unexpected carbon resilience of a neotropical forest.

PubMed

Brando, Paulo M; Oliveria-Santos, Claudinei; Rocha, Wanderley; Cury, Roberta; Coe, Michael T

2016-07-01

Global changes and associated droughts, heat waves, logging activities, and forest fragmentation may intensify fires in Amazonia by altering forest microclimate and fuel dynamics. To isolate the effects of fuel loads on fire behavior and fire-induced changes in forest carbon cycling, we manipulated fine fuel loads in a fire experiment located in southeast Amazonia. We predicted that a 50% increase in fine fuel loads would disproportionally increase fire intensity and severity (i.e., tree mortality and losses in carbon stocks) due to multiplicative effects of fine fuel loads on the rate of fire spread, fuel consumption, and burned area. The experiment followed a fully replicated randomized block design (N = 6) comprised of unburned control plots and burned plots that were treated with and without fine fuel additions. The fuel addition treatment significantly increased burned area (+22%) and consequently canopy openness (+10%), fine fuel combustion (+5%), and mortality of individuals ≥5 cm in diameter at breast height (dbh; +37%). Surprisingly, we observed nonsignificant effects of the fuel addition treatment on fireline intensity, and no significant differences among the three treatments for (i) mortality of large trees (≥30 cm dbh), (ii) aboveground forest carbon stocks, and (iii) soil respiration. It was also surprising that postfire tree growth and wood increment were higher in the burned plots treated with fuels than in the unburned control. These results suggest that (i) fine fuel load accumulation increases the likelihood of larger understory fires and (ii) single, low-intensity fires weakly influence carbon cycling of this primary neotropical forest, although delayed postfire mortality of large trees may lower carbon stocks over the long term. Overall, our findings indicate that increased fine fuel loads alone are unlikely to create threshold conditions for high-intensity, catastrophic fires during nondrought years. © 2016 John Wiley & Sons Ltd.

Post-fire soil functionality and microbial community structure in a Mediterranean shrubland subjected to experimental drought.

PubMed

Hinojosa, M Belén; Parra, Antonio; Laudicina, Vito Armando; Moreno, José M

2016-12-15

Fire may cause significant alterations in soil properties. Post-fire soil dynamics can vary depending, among other factors, on rainfall patterns. However, little is known regarding variations in response to post-fire drought. This is relevant in arid and semiarid areas with poor soils, like much of the western Mediterranean. Furthermore, climate change projections in such areas anticipate reduced precipitation and longer annual drought periods, together with an increase in fire severity and frequency. This research evaluates the effects of experimental drought after fire on soil dynamics of a Cistus-Erica shrubland (Central Spain). A replicated (n=4) field experiment was conducted in which the total rainfall and its patterns were manipulated by means of a rain-out shelters and irrigation system. The treatments were: environmental control (natural rainfall), historical control (average rainfall, 2months drought), moderate drought (25% reduction of historical control, 5months drought) and severe drought (45% reduction, 7months drought). After one growing season under these rainfall treatments, the plots were burned. One set of unburned plots under natural rainfall served as an additional control. Soils were collected seasonally. Fire increased soil P and N availability. Post-fire drought treatments reduced available soil P but increased N concentration (mainly nitrate). Fire reduced available K irrespective of drought treatments. Fire reduced enzyme activities and carbon mineralization rate, a reduction that was higher in post-fire drought-treated soils. Fire decreased soil microbial biomass and the proportion of fungi, while that of actinomycetes increased. Post-fire drought decreased soil total microbial biomass and fungi, with bacteria becoming more abundant. Our results support that increasing drought after fire could compromise the resilience of Mediterranean ecosystems to fire. Copyright © 2016 Elsevier B.V. All rights reserved.

Increased Drought Impacts on Temperate Rainforests from Southern South America: Results of a Process-Based, Dynamic Forest Model

PubMed Central

Gutiérrez, Alvaro G.; Armesto, Juan J.; Díaz, M. Francisca; Huth, Andreas

2014-01-01

Increased droughts due to regional shifts in temperature and rainfall regimes are likely to affect forests in temperate regions in the coming decades. To assess their consequences for forest dynamics, we need predictive tools that couple hydrologic processes, soil moisture dynamics and plant productivity. Here, we developed and tested a dynamic forest model that predicts the hydrologic balance of North Patagonian rainforests on Chiloé Island, in temperate South America (42°S). The model incorporates the dynamic linkages between changing rainfall regimes, soil moisture and individual tree growth. Declining rainfall, as predicted for the study area, should mean up to 50% less summer rain by year 2100. We analysed forest responses to increased drought using the model proposed focusing on changes in evapotranspiration, soil moisture and forest structure (above-ground biomass and basal area). We compared the responses of a young stand (YS, ca. 60 years-old) and an old-growth forest (OG, >500 years-old) in the same area. Based on detailed field measurements of water fluxes, the model provides a reliable account of the hydrologic balance of these evergreen, broad-leaved rainforests. We found higher evapotranspiration in OG than YS under current climate. Increasing drought predicted for this century can reduce evapotranspiration by 15% in the OG compared to current values. Drier climate will alter forest structure, leading to decreases in above ground biomass by 27% of the current value in OG. The model presented here can be used to assess the potential impacts of climate change on forest hydrology and other threats of global change on future forests such as fragmentation, introduction of exotic tree species, and changes in fire regimes. Our study expands the applicability of forest dynamics models in remote and hitherto overlooked regions of the world, such as southern temperate rainforests. PMID:25068869

Increased drought impacts on temperate rainforests from southern South America: results of a process-based, dynamic forest model.

PubMed

Gutiérrez, Alvaro G; Armesto, Juan J; Díaz, M Francisca; Huth, Andreas

2014-01-01

Increased droughts due to regional shifts in temperature and rainfall regimes are likely to affect forests in temperate regions in the coming decades. To assess their consequences for forest dynamics, we need predictive tools that couple hydrologic processes, soil moisture dynamics and plant productivity. Here, we developed and tested a dynamic forest model that predicts the hydrologic balance of North Patagonian rainforests on Chiloé Island, in temperate South America (42°S). The model incorporates the dynamic linkages between changing rainfall regimes, soil moisture and individual tree growth. Declining rainfall, as predicted for the study area, should mean up to 50% less summer rain by year 2100. We analysed forest responses to increased drought using the model proposed focusing on changes in evapotranspiration, soil moisture and forest structure (above-ground biomass and basal area). We compared the responses of a young stand (YS, ca. 60 years-old) and an old-growth forest (OG, >500 years-old) in the same area. Based on detailed field measurements of water fluxes, the model provides a reliable account of the hydrologic balance of these evergreen, broad-leaved rainforests. We found higher evapotranspiration in OG than YS under current climate. Increasing drought predicted for this century can reduce evapotranspiration by 15% in the OG compared to current values. Drier climate will alter forest structure, leading to decreases in above ground biomass by 27% of the current value in OG. The model presented here can be used to assess the potential impacts of climate change on forest hydrology and other threats of global change on future forests such as fragmentation, introduction of exotic tree species, and changes in fire regimes. Our study expands the applicability of forest dynamics models in remote and hitherto overlooked regions of the world, such as southern temperate rainforests.

Potential changes in forest composition could reduce impacts of climate change on boreal wildfires.

PubMed

Terrier, Aurélie; Girardin, Martin P; Périé, Catherine; Legendre, Pierre; Bergeron, Yves

2013-01-01

There is general consensus that wildfires in boreal forests will increase throughout this century in response to more severe and frequent drought conditions induced by climate change. However, prediction models generally assume that the vegetation component will remain static over the next few decades. As deciduous species are less flammable than conifer species, it is reasonable to believe that a potential expansion of deciduous species in boreal forests, either occurring naturally or through landscape management, could offset some of the impacts of climate change on the occurrence of boreal wildfires. The objective of this study was to determine the potential of this offsetting effect through a simulation experiment conducted in eastern boreal North America. Predictions of future fire activity were made using multivariate adaptive regression splines (MARS) with fire behavior indices and ecological niche models as predictor variables so as to take into account the effects of changing climate and tree distribution on fire activity. A regional climate model (RCM) was used for predictions of future fire risk conditions. The experiment was conducted under two tree dispersal scenarios: the status quo scenario, in which the distribution of forest types does not differ from the present one, and the unlimited dispersal scenario, which allows forest types to expand their range to fully occupy their climatic niche. Our results show that future warming will create climate conditions that are more prone to fire occurrence. However, unlimited dispersal of southern restricted deciduous species could reduce the impact of climate change on future fire occurrence. Hence, the use of deciduous species could be a good option for an efficient strategic fire mitigation strategy aimed at reducing fire Propagation in coniferous landscapes and increasing public safety in remote populated areas of eastern boreal Canada under climate change.

Climate regulation of fire emissions and deforestation in equatorial Asia.

PubMed

van der Werf, G R; Dempewolf, J; Trigg, S N; Randerson, J T; Kasibhatla, P S; Giglio, L; Murdiyarso, D; Peters, W; Morton, D C; Collatz, G J; Dolman, A J; DeFries, R S

2008-12-23

Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire emissions from Indonesia, Malaysia, and Papua New Guinea during 2000-2006. We found that average fire emissions from this region [128 +/- 51 (1sigma) Tg carbon (C) year(-1), T = 10(12)] were comparable to fossil fuel emissions. In Borneo, carbon emissions from fires were highly variable, fluxes during the moderate 2006 El Niño more than 30 times greater than those during the 2000 La Niña (and with a 2000-2006 mean of 74 +/- 33 Tg C yr(-1)). Higher rates of forest loss and larger areas of peatland becoming vulnerable to fire in drought years caused a strong nonlinear relation between drought and fire emissions in southern Borneo. Fire emissions from Sumatra showed a positive linear trend, increasing at a rate of 8 Tg C year(-2) (approximately doubling during 2000-2006). These results highlight the importance of including deforestation in future climate agreements. They also imply that land manager responses to expected shifts in tropical precipitation may critically determine the strength of climate-carbon cycle feedbacks during the 21st century.

Water relations of evergreen and drought-deciduous trees along a seasonally dry tropical forest chronosequence.

PubMed

Hasselquist, Niles J; Allen, Michael F; Santiago, Louis S

2010-12-01

Seasonally dry tropical forests (SDTF) are characterized by pronounced seasonality in rainfall, and as a result trees in these forests must endure seasonal variation in soil water availability. Furthermore, SDTF on the northern Yucatan Peninsula, Mexico, have a legacy of disturbances, thereby creating a patchy mosaic of different seral stages undergoing secondary succession. We examined the water status of six canopy tree species, representing contrasting leaf phenology (evergreen vs. drought-deciduous) at three seral stages along a fire chronosequence in order to better understand strategies that trees use to overcome seasonal water limitations. The early-seral forest was characterized by high soil water evaporation and low soil moisture, and consequently early-seral trees exhibited lower midday bulk leaf water potentials (Ψ(L)) relative to late-seral trees (-1.01 ± 0.14 and -0.54 ± 0.07 MPa, respectively). Although Ψ(L) did not differ between evergreen and drought-deciduous trees, results from stable isotope analyses indicated different strategies to overcome seasonal water limitations. Differences were especially pronounced in the early-seral stage where evergreen trees had significantly lower xylem water δ(18)O values relative to drought-deciduous trees (-2.6 ± 0.5 and 0.3 ± 0.6‰, respectively), indicating evergreen species used deeper sources of water. In contrast, drought-deciduous trees showed greater enrichment of foliar (18)O (∆(18)O(l)) and (13)C, suggesting lower stomatal conductance and greater water-use efficiency. Thus, the rapid development of deep roots appears to be an important strategy enabling evergreen species to overcome seasonal water limitation, whereas, in addition to losing a portion of their leaves, drought-deciduous trees minimize water loss from remaining leaves during the dry season.

Increased susceptibility to drought-induced mortality in Sequoia sempervirens (Cupressaceae) trees under Cenozoic atmospheric carbon dioxide starvation.

PubMed

Quirk, Joe; McDowell, Nate G; Leake, Jonathan R; Hudson, Patrick J; Beerling, David J

2013-03-01

Climate-induced forest retreat has profound ecological and biogeochemical impacts, but the physiological mechanisms underlying past tree mortality are poorly understood, limiting prediction of vegetation shifts with climate variation. Climate, drought, fire, and grazing represent agents of tree mortality during the late Cenozoic, but the interaction between drought and declining atmospheric carbon dioxide ([CO2]a) from high to near-starvation levels ∼34 million years (Ma) ago has been overlooked. Here, this interaction frames our investigation of sapling mortality through the interdependence of hydraulic function, carbon limitation, and defense metabolism. • We recreated a changing Cenozoic [CO2]a regime by growing Sequoia sempervirens trees within climate-controlled growth chambers at 1500, 500, or 200 ppm [CO2]a, capturing the decline toward minimum concentrations from 34 Ma. After 7 months, we imposed drought conditions and measured key physiological components linking carbon utilization, hydraulics, and defense metabolism as hypothesized interdependent mechanisms of tree mortality. • Catastrophic failure of hydraulic conductivity, carbohydrate starvation, and tree death occurred at 200 ppm, but not 500 or 1500 ppm [CO2]a. Furthermore, declining [CO2]a reduced investment in carbon-rich foliar defense compounds that would diminish resistance to biotic attack, likely exacerbating mortality. • Low-[CO2]a-driven tree mortality under drought is consistent with Pleistocene pollen records charting repeated Californian Sequoia forest contraction during glacial periods (180-200 ppm [CO2]a) and may even have contributed to forest retreat as grasslands expanded on multiple continents under low [CO2]a over the past 10 Ma. In this way, geologic intervals of low [CO2]a coupled with drought could impose a demographic bottleneck in tree recruitment, driving vegetation shifts through forest mortality.

Prolonged Effect of Severe Wildfires on Mercury and Other Volatiles in Forest Soils of the Lake Superior Region, USA

NASA Astrophysics Data System (ADS)

Cannon, W. F.; Woodruff, L. G.

2003-12-01

Soils in Isle Royale National Park, Michigan and Voyageurs National Park, Minnesota show spatial patterns of depletion of total Hg, organic C, Se, total S, P, and Pb within areas of severe, stand-replacing wildfires that burned in 1936, approximately 65 years prior to our current study. The fires burned during a regional drought, were of high severity, and likely consumed a high percentage of organic forest-floor material (O-horizon). A "fire factor" is defined by positive correlations among Hg, C, Se, S, P, and Pb. A factor score for this six-element grouping derived from factor analysis was assigned to each sample. The scores show a high spatial correlation with the footprint of the 1936 fires in both parks, particularly for A-horizon soils. Because many of these elements are volatile, and are highly correlated with soil organic matter, observed depletions likely represent instantaneous atmospheric release during combustion of O-horizon soils coupled with decades-long reduction of organic matter on the forest floor and near-surface soils. Nearly complete combustion of the modern O-horizon would release roughly 1 mg Hg/m2 from the forest floor. Decades-long disturbance resulting from destruction of mature forests and gradual regrowth following fire also play an important role in Hg cycling. Destruction of a mature forest results in decreased deposition of Hg from litterfall as well as throughfall, which contributes Hg by wash-off of dry deposited Hg from foliar surfaces. Hg in forest soils may follow a fire-dependent cycle in which sudden Hg loss during fire is followed by a period of continued Hg loss as evasion exceeds sequestration in the early stand-replacement stage, finally to resume gradual buildup in later stages of forest regrowth. In the Lake Superior region this cycle exceeds 65 years in duration and is of the same magnitude as the fire return interval for this region. Forests that are controlled by fire-induced cycles of stand replacement may also be in continuous cycles of Hg sequestration and emission. Fire history appears to be a major determinant in the amount of Hg stored in forest soils. Fire almost certainly releases Hg to the atmosphere as forest floor material is burned and thus contributes to atmospheric Hg loads. Fire also appears to cleanse burned areas of Hg both by the atmospheric release during combustion and longer-term release during post-fire forest reorganization. Fire cleansing appears to persist for decades after severe fires and may ameliorate Hg contamination of aquatic food webs by decreasing the soil Hg load of burned watersheds.

Earth Observation

NASA Image and Video Library

2013-08-26

ISS036-E-037185 (26 Aug. 2013) --- One of the Expedition 36 crew members aboard the International Space Station used a 50mm lens to record this view of the massive drought-aided Rim Fire in and around California's Yosemite National Park and the Stanislaus National Forest on Aug. 26. The fire began on Aug. 17 and, at the time of this photo on Aug. 26, it still continues to burn, as some 3,700 firefighters battle it. More than 224 square miles have been affected.

Ozone distribution in remote ecologically vulnerable terrain of the southern Sierra Nevada, CA.

PubMed

Panek, Jeanne; Saah, David; Esperanza, Annie; Bytnerowicz, Andrzej; Fraczek, Witold; Cisneros, Ricardo

2013-11-01

Ozone concentration spatial patterns remain largely uncharacterized across the extensive wilderness areas of the Sierra Nevada, CA, despite being downwind of major pollution sources. These natural areas, including four national parks and four national forests, contain forest species that are susceptible to ozone injury. Forests stressed by ozone are also more vulnerable to other agents of mortality, including insects, pathogens, climate change, and ultimately fire. Here we analyze three years of passive ozone monitor data from the southern Sierra Nevada and interpolate landscape-scale spatial and temporal patterns during the summer-through-fall high ozone concentration period. Segmentation analysis revealed three types of ozone exposure sub-regions: high, low, and variable. Consistently high ozone exposure regions are expected to be most vulnerable to forest mortality. One high exposure sub-region has been documented elsewhere as being further vulnerable to increased drought and fire potential. Identifying such hot-spots of forest vulnerability has utility for prioritizing management. Copyright © 2013 Elsevier Ltd. All rights reserved.

Tree physiology and bark beetles

Treesearch

Michael G. Ryan; Gerard Sapes; Anna Sala; Sharon Hood

2015-01-01

Irruptive bark beetles usually co-occur with their co-evolved tree hosts at very low (endemic) population densities. However, recent droughts and higher temperatures have promoted widespread tree mortality with consequences for forest carbon, fire and ecosystem services (Kurz et al., 2008; Raffa et al., 2008; Jenkins et al., 2012). In this issue of New Phytologist,...

Vulnerability Assessment of Dust Storms in the United States under a Changing Climate Scenario

EPA Science Inventory

Severe weather events, such as flooding, drought, forest fires, and dust storms can have a serious impact on human health. Dust storm events are not well predicted in the United States, however they are expected to become more frequent as global climate warms through the 21st cen...

Anthropogenic and Climatic Influence on Vegetation Fires in Peatland of Insular Southeast Asia

NASA Astrophysics Data System (ADS)

Liew, S.; Miettinen, J.; Salinas Cortijo, S. V.

2011-12-01

Fire is traditionally used as a tool in land clearing by farmers and shifting cultivators in Southeast Asia. However, the small scale clearing of land is increasingly being replaced by modern large-scale conversion of forests into plantations/agricultural land, usually also by fires. Fires get out of control in periods of extreme drought, especially during the El Nino periods, resulting in severe episodes of transboundary air pollution in the form of smoke haze. We use the MODIS active fires product (hotspots) to establish correlations between the temporal and spatial patterns of vegetation fires with climatic variables, land cover change and soil type (peat or non-peat) in the western part of Insular Southeast Asia for a decade from 2001 to 2010. Fire occurrence exhibits a negative correlation with rainfall, and is more severe overall during the El-Nino periods. However, not all regions are equally affected by El-Nino. In Southern Sumatra and Southern Borneo the correlation with El-Nino is high. However, fires in some regions such as the peatland in Riau, Jambi and Sarawak do not appear to be influenced by El-Nino. These regions are also experiencing rapid conversion of forest to large scale plantations.

Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.

PubMed

Dore, Sabina; Montes-Helu, Mario; Hart, Stephen C; Hungate, Bruce A; Koch, George W; Moon, John B; Finkral, Alex J; Kolb, Thomas E

2012-10-01

Carbon uptake by forests is a major sink in the global carbon cycle, helping buffer the rising concentration of CO 2 in the atmosphere, yet the potential for future carbon uptake by forests is uncertain. Climate warming and drought can reduce forest carbon uptake by reducing photosynthesis, increasing respiration, and by increasing the frequency and intensity of wildfires, leading to large releases of stored carbon. Five years of eddy covariance measurements in a ponderosa pine (Pinus ponderosa)-dominated ecosystem in northern Arizona showed that an intense wildfire that converted forest into sparse grassland shifted site carbon balance from sink to source for at least 15 years after burning. In contrast, recovery of carbon sink strength after thinning, a management practice used to reduce the likelihood of intense wildfires, was rapid. Comparisons between an undisturbed-control site and an experimentally thinned site showed that thinning reduced carbon sink strength only for the first two posttreatment years. In the third and fourth posttreatment years, annual carbon sink strength of the thinned site was higher than the undisturbed site because thinning reduced aridity and drought limitation to carbon uptake. As a result, annual maximum gross primary production occurred when temperature was 3 °C higher at the thinned site compared with the undisturbed site. The severe fire consistently reduced annual evapotranspiration (range of 12-30%), whereas effects of thinning were smaller and transient, and could not be detected in the fourth year after thinning. Our results show large and persistent effects of intense fire and minor and short-lived effects of thinning on southwestern ponderosa pine ecosystem carbon and water exchanges. © 2012 Blackwell Publishing Ltd.

Medium-long term soil resilience against different disturbances: wildfires, silvicultural treatments and climate change

NASA Astrophysics Data System (ADS)

Hedo de Santiago, Javier; Borja, Manuel Esteban Lucas; de las Heras, Jorge

2016-04-01

Soils of semiarid Mediterranean forest ecosystems are very fragile and sensitive to changes due to different anthropogenic and natural disturbances. The increasing vulnerability of semiarid lands within this world framework has generated growing awareness in the field of research, with highly intensified study into soils properties. One of the main problems of Mediterranean forests is wildfire disturbance. Fire should be considered more an ecological factor but, in contrast to the role of fire, it is now a closely related factor to human action. On the other hand, to improve the recovery of forest communities after fire, silvicultural treatments are needed and, for that matter, another disturbance is added to the ecosystem. By last, climate change is also affecting the fire regime increasing fire frequency and burned area, enhancing the destructiveness to Mediterranean ecosystems. After all of these three disturbances, changes in vegetation dynamics and soil properties are expected to occur due to the plant-soil feedback. Soil plays an essential role in the forest ecosystem's fertility and stability and specifically soil microorganisms, which accomplish reactions to release soil nutrients for vegetation development, for that is essential to enlarge knowledge about soil properties resilience in semiarid forest ecosystems. Physico-chemical and microbiological soil properties, and enzyme activities have been studied in two Aleppo pine forest stands that have suffered three disturbances: 1) a wildfire event, 2) silvicultural treatments (thinning) and 3) an artificial drought (simulating climate change) and results showed that soil recovered after 15 years. Final results showed that soils have been recovered from the three disturbances at the medium-long term.

Spatial and Temporal Patterns of Unburned Areas within Fire Perimeters in the Northwestern United States from 1984 to 2014

NASA Astrophysics Data System (ADS)

Meddens, A. J.; Kolden, C.; Lutz, J. A.; Abatzoglou, J. T.; Hudak, A. T.

2016-12-01

Recently, there has been concern about increasing extent and severity of wildfires across the globe given rapid climate change. Areas that do not burn within fire perimeters can act as fire refugia, providing (1) protection from the detrimental effects of the fire, (2) seed sources, and (3) post-fire habitat on the landscape. However, recent studies have mainly focused on the higher end of the burn severity spectrum whereas the lower end of the burn severity spectrum has been largely ignored. We developed a spatially explicit database for 2,200 fires across the inland northwestern USA, delineating unburned areas within fire perimeters from 1984 to 2014. We used 1,600 Landsat scenes with one or two scenes before and one or two scenes after the fires to capture the unburned proportion of the fire. Subsequently, we characterized the spatial and temporal patterns of unburned areas and related the unburned proportion to interannual climate variability. The overall classification accuracy detecting unburned locations was 89.2% using a 10-fold cross-validation classification tree approach in combination with 719 randomly located field plots. The unburned proportion ranged from 2% to 58% with an average of 19% for a select number of fires. We find that using both an immediate post-fire image and a one-year post fire image improves classification accuracy of unburned islands over using just a single post-fire image. The spatial characteristics of the unburned islands differ between forested and non-forested regions with a larger amount of unburned area within non-forest. In addition, we show trends of unburned proportion related primarily to concurrent climatic drought conditions across the entire region. This database is important for subsequent analyses of fire refugia prioritization, vegetation recovery studies, ecosystem resilience, and forest management to facilitate unburned islands through fuels breaks, prescribed burning, and fire suppression strategies.

Holocene vegetation and fire regimes in subalpine and mixed conifer forests, southern Rocky Mountains, USA

USGS Publications Warehouse

Anderson, R. Scott; Allen, Craig D.; Toney, J.L.; Jass, R.B.; Bair, A.N.

2008-01-01

Our understanding of the present forest structure of western North America hinges on our ability to determine antecedent forest conditions. Sedimentary records from lakes and bogs in the southern Rocky Mountains of Colorado and New Mexico provide information on the relationships between climate and vegetation change, and fire history since deglaciation. We present a new pollen record from Hunters Lake (Colorado) as an example of a high-elevation vegetation history from the southern Rockies. We then present a series of six sedimentary records from ???2600 to 3500-m elevation, including sites presently at the alpine?subalpine boundary, within the Picea engelmannii?Abies lasiocarpa forest and within the mixed conifer forest, to determine the history of fire in high-elevation forests there. High Artemisia and low but increasing percentages of Picea and Pinus suggest vegetation prior to 13 500 calendar years before present (cal yr BP) was tundra or steppe, with open spruce woodland to ???11 900 cal yr BP. Subalpine forest (Picea engelmannii, Abies lasiocarpa) existed around the lake for the remainder of the Holocene. At lower elevations, Pinus ponderosa and/or contorta expanded 11 900 to 10 200 cal yr BP; mixed conifer forest expanded ???8600 to 4700 cal yr BP; and Pinus edulis expanded after ???4700 cal yr BP. Sediments from lake sites near the alpine?subalpine transition contained five times less charcoal than those entirely within subalpine forests, and 40 times less than bog sites within mixed conifer forest. Higher fire episode frequencies occurred between ???12 000 and 9000 cal yr BP (associated with the initiation or expansion of south-west monsoon and abundant lightning, and significant biomass during vegetation turnover) and at ???2000?1000 cal yr BP (related to periodic droughts during the long-term trend towards wetter conditions and greater biomass). Fire episode frequencies for subalpine?alpine transition and subalpine sites were on average 5 to 10 fire events/1000 years over the Holocene, corresponding to one fire event every ???100 to 200 years. (5) Our Holocene-length sedimentary charcoal records provide additional evidence for the anomalous nature of the 20th-century fire regime, where fires were largely suppressed as a national policy. ?? IAWF 2008.

Comparison of different methods for the in situ measurement of forest litter moisture content

NASA Astrophysics Data System (ADS)

Schunk, C.; Ruth, B.; Leuchner, M.; Wastl, C.; Menzel, A.

2016-02-01

Dead fine fuel (e.g., litter) moisture content is an important parameter for both forest fire and ecological applications as it is related to ignitability, fire behavior and soil respiration. Real-time availability of this value would thus be a great benefit to fire risk management and prevention. However, the comprehensive literature review in this paper shows that there is no easy-to-use method for automated measurements available. This study investigates the applicability of four different sensor types (permittivity and electrical resistance measuring principles) for this measurement. Comparisons were made to manual gravimetric reference measurements carried out almost daily for one fire season and overall agreement was good (highly significant correlations with 0.792 < = r < = 0.947, p < 0.001). Standard deviations within sensor types were linearly correlated to daily sensor mean values; however, above a certain threshold they became irregular, which may be linked to exceedance of the working ranges. Thus, measurements with irregular standard deviations were considered unusable and relationships between gravimetric and automatic measurements of all individual sensors were compared only for useable periods. A large drift in these relationships became obvious from drought to drought period. This drift may be related to installation effects or settling and decomposition of the litter layer throughout the fire season. Because of the drift and the in situ calibration necessary, it cannot be recommended to use the methods presented here for monitoring purposes and thus operational hazard management. However, they may be interesting for scientific studies when some manual fuel moisture measurements are made anyway. Additionally, a number of potential methodological improvements are suggested.

Predicting moisture dynamics of fine understory fuels in a moist tropical rainforest system: results of a pilot study undertaken to identify proxy variables useful for rating fire danger.

PubMed

Ray, David; Nepstad, Dan; Brando, Paulo

2010-08-01

*The use of fire as a land management tool in the moist tropics often has the unintended consequence of degrading adjacent forest, particularly during severe droughts. Reliable models of fire danger are needed to help mitigate these impacts. *Here, we studied the moisture dynamics of fine understory fuels in the east-central Brazilian Amazon during the 2003 dry season. Drying stations established under varying amounts of canopy cover (leaf area index (LAI) = 0 - 5.3) were subjected to a range of water inputs (5-15 mm) and models were developed to forecast litter moisture content (LMC). Predictions were then compared with independent field data. *A multiple linear regression relating litter moisture content to forest structure (LAI), ambient vapor pressure deficit (VPD(M)) and an index of elapsed time since a precipitation event (d(-1)) was identified as the best-fit model (adjusted R(2) = 0.89). Relative to the independent observations, model predictions were relatively unbiased when the LMC was

An ecosystem services framework for multidisciplinary research in the Colorado River headwaters

USGS Publications Warehouse

Semmens, D.J.; Briggs, J.S.; Martin, D.A.

2009-01-01

A rapidly spreading Mountain Pine Beetle epidemic is killing lodgepole pine forest in the Rocky Mountains, causing landscape change on a massive scale. Approximately 1.5 million acres of lodgepoledominated forest is already dead or dying in Colorado, the infestation is still spreading rapidly, and it is expected that in excess of 90 percent of all lodgepole forest will ultimately be killed. Drought conditions combined with dramatically reduced foliar moisture content due to stress or mortality from Mountain Pine Beetle have combined to elevate the probability of large fires throughout the Colorado River headwaters. Large numbers of homes in the wildland-urban interface, an extensive water supply infrastructure, and a local economy driven largely by recreational tourism make the potential costs associated with such a fire very large. Any assessment of fire risk for strategic planning of pre-fire management actions must consider these and a host of other important socioeconomic benefits derived from the Rocky Mountain Lodgepole Pine Forest ecosystem. This paper presents a plan to focus U.S. Geological Survey (USGS) multidisciplinary fire/beetle-related research in the Colorado River headwaters within a framework that integrates a wide variety of discipline-specific research to assess and value the full range of ecosystem services provided by the Rocky Mountain Lodgepole Pine Forest ecosystem. Baseline, unburned conditions will be compared with a hypothetical, fully burned scenario to (a) identify where services would be most severely impacted, and (b) quantify potential economic losses. Collaboration with the U.S. Forest Service will further yield a distributed model of fire probability that can be used in combination with the ecosystem service valuation to develop comprehensive, distributed maps of fire risk in the Upper Colorado River Basin. These maps will be intended for use by stakeholders as a strategic planning tool for pre-fire management activities and can be updated and improved adaptively on an annual basis as tree mortality, climatic conditions, and management actions unfold. 

User's guide to the douglas-fir beetle impact model. Forest Service general technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsden, M.A.; Eav, B.B.; Thompson, M.K.

1994-09-01

Douglas-fir beetle occurs throughout the range of its principal host, Douglas-fir. At epidemic levels, the beetle causes considerable mortality in large-diameter Douglas-fir trees. Wind storms, drought, fire, and other factors have been reported as precendent conditions for epidemics of Douglas-fir beetle. An impact model has been developed to simulate tree mortality during such epidemics. The model has been linked to the Stand Prognosis Model (Forest Vegetation Simulator). This is a guide for using the model.

Surface Fire Influence on Carbon Balance Components in Scots Pine Forest of Siberia, Russia

NASA Astrophysics Data System (ADS)

Kukavskaya, E.; Ivanova, G. A.; Conard, S. G.; Soja, A. J.

2008-12-01

Wildfire is one of the most important disturbances in boreal forests, and it can have a profound effect on forest-atmosphere carbon exchange. Pinus sylvestris (Scots pine) stands of Siberia are strongly impacted by fires of low to high severity. Biomass distribution in mature lichen/feathermoss Scots pine stands indicates that they are carbon sinks before fire. Fires contribute significantly to the carbon budget resulting in a considerable carbon efflux, initially through direct consumption of forest fuels and later as a result of tree mortality and decomposition of dead material accumulated on the forest floor. In initial postfire years these processes dominate over photosynthetic carbon assimilation, and the ecosystems become a carbon source. Over several postfire years, above-ground carbon in dead biomass tends to increase, with the increase depending significantly on fire severity. High-severity fire enhances dead biomass carbon, while moderate- and low-severity fires have minimal effect on above-ground carbon distribution in Scots pine ecosystems. Dead stand biomass carbon increases, primarily during the first two years following fires, due to tree mortality. This increase can account for up to 12.4% of the total stand biomass after low- and moderate- intensity fires. We found tree dieback following a high-intensity fire is an order of magnitude higher, and thus the dead biomass increases up to 88.1% of total above-ground biomass. Photosynthetic CO2 uptake decreases with increasing tree mortality, and needle foliage and bark are incorporated into the upper layer of the forest floor in the course of years. Ground vegetation and duff carbon were >90, 71-83, and 82% of prefire levels after fires of low, moderate, and high severity, respectively for the first 4 to 5 years after fire. Fires of low and moderate severity caused down woody fuel carbon to increase by 2.1 and 3.6 t ha-1 respectively by four years after burning as compared to the pre-fire values. Climate change and increasing drought length observed in recent decades have increased the probability of high-intensity fire occurrence. Areas burned have increased in extent and severity across Siberia, resulting in increased carbon emissions to the atmosphere from fuel combustion and post fire decomposition.

Comparison of different methods for the in situ measurement of forest litter moisture content

NASA Astrophysics Data System (ADS)

Schunk, C.; Ruth, B.; Leuchner, M.; Wastl, C.; Menzel, A.

2015-06-01

Dead fine fuel (e.g. litter) moisture content is an important parameter for both forest fire and ecological applications as it is related to ignitability, fire behavior as well as soil respiration. However, the comprehensive literature review in this paper shows that there is no easy-to-use method for automated measurements available. This study investigates the applicability of four different sensor types (permittivity and electrical resistance measuring principles) for this measurement. Comparisons were made to manual gravimetric reference measurements carried out almost daily for one fire season and overall agreement was good (highly significant correlations with 0.792 ≦ r ≦ 0.947). Standard deviations within sensor types were linearly correlated to daily sensor mean values; however, above a certain threshold they became irregular, which may be linked to exceedance of the working ranges. Thus, measurements with irregular standard deviations were considered unusable and calibrations of all individual sensors were compared for useable periods. A large drift in the sensor raw value-litter moisture-relationship became obvious from drought to drought period. This drift may be related to installation effects or settling and decomposition of the litter layer throughout the fire season. Because of the drift and the in situ calibration necessary, it cannot be recommended to use the methods presented here for monitoring purposes. However, they may be interesting for scientific studies when some manual fuel moisture measurements are made anyway. Additionally, a number of potential methodological improvements are suggested.

Fine-scale spatial climate variation and drought mediate the likelihood of reburning.

PubMed

Parks, Sean A; Parisien, Marc-André; Miller, Carol; Holsinger, Lisa M; Baggett, Larry Scott

2018-03-01

In many forested ecosystems, it is increasingly recognized that the probability of burning is substantially reduced within the footprint of previously burned areas. This self-limiting effect of wildland fire is considered a fundamental emergent property of ecosystems and is partly responsible for structuring landscape heterogeneity (i.e., mosaics of different age classes), thereby reducing the likelihood of uncharacteristically large fires in regions with active fire regimes. However, the strength and longevity of this self-limiting phenomenon is not well understood in most fire-prone ecosystems. In this study, we quantify the self-limiting effect in terms of its strength and longevity for five fire-prone study areas in western North America and investigate how each measure varies along a spatial climatic gradient and according to temporal (i.e., annual) climatic variation. Results indicate that the longevity (i.e., number of years) of the self-limiting effect ranges between 15 yr in the warm and dry study area in the southwestern United States to 33 yr in the cold, northern study areas in located in northwestern Montana and the boreal forest of Canada. We also found that spatial climatic variation has a strong influence on wildland fire's self-limiting capacity. Specifically, the self-limiting effect within each study area was stronger and lasted longer in areas with low mean moisture deficit (i.e., wetter and cooler settings) compared to areas with high mean moisture deficit (warmer and drier settings). Last, our findings show that annual climatic variation influences wildland fire's self-limiting effect: drought conditions weakened the strength and longevity of the self-limiting effect in all study areas, albeit at varying magnitudes. Overall, our study provides support for the idea that wildland fire contributes to spatial heterogeneity in fuel ages that subsequently mediate future fire sizes and effects. However, our findings show that the strength and longevity of the self-limiting effect varies considerably according to spatial and temporal climatic variation, providing land and fire managers relevant information for effective planning and management of fire and highlighting that fire itself is an important factor contributing to fire-free intervals. © 2017 by the Ecological Society of America.

Investing carbon offsets in woody forests - the best solution for California?

NASA Astrophysics Data System (ADS)

Dass, P.; Houlton, B. Z.; Warlind, D.

2016-12-01

Increasing atmospheric carbon dioxide (CO2) concentrations from fossil fuel combustion, land conversion and biomass burning are principal to climate change and its manifolds risks on human health, the environment and the global economy. Effective mitigation of climate change thereby involves cutting fossil-fuel emissions at the source or capturing CO2 in engineered or natural ecosystem stocks, or both. The lifetime of CO2 in the atmosphere exceeds 100 years; thus, in the case of CO2 sequestration by natural ecosystems, the residence time of soil and vegetation carbon(C) is a critical component of the efficacy of C offsets in the marketplace, particularly in local to global Cap and Trade frameworks. Here we use a land-surface model to analyze trade-offs in C investment into natural forest vs. grassland sinks and the role of fire in driving the most sustained pathways of CO2 sequestration under Cap and Trade policies. We focus on the California Climate Exchange and AB32 as the model system for examining risks of CO2 offset investments by considering model-based scenarios of (a.) natural woody forests (mixture of trees, shrubs and grasslands) or (b.) pure grasslands (no woody vegetation allowed) under conditions of drought and changes in fire frequency. While forests capture more carbon than grasslands, the latter stores a greater fraction of C in below ground stocks, making it less vulnerable to climate-driven disturbances. Preliminary results for simulations carried out for the last century for the state of California corroborate this hypothesis: while trees capture 100 GgCyr-1 more than grasses, CO2 emissions due to fire is less by 20 GgCyr-1 from grasslands when compared to forest environments. Since policies need to regard potential future scenarios, we present results that investigate how the alternate systems of trees and grasses respond to (i.) the environmental conditions of the no-mitigation scenario (RCP 8.5) through the year 2100, (ii.) periods of extended drought and (iii.) environmental conditions favoring higher incidences of fire.

Leaf to landscape responses of giant sequoia to hotter drought: An introduction and synthesis for the special section

USGS Publications Warehouse

Nydick, Koren R.; Stephenson, Nathan L.; Ambrose, Anthony R.; Asner, Gregory P.; Baxter, Wendy L.; Das, Adrian J.; Dawson, Todd E.; Martin, Roberta E.; Paz-Kagan, Tarin

2018-01-01

Hotter droughts are becoming more common as climate change progresses, and they may already have caused instances of forest dieback on all forested continents. Learning from hotter droughts, including where on the landscape forests are more or less vulnerable to these events, is critical to help resource managers proactively prepare for the future. As part of our Leaf to Landscape Project, we measured the response of giant sequoia, the world’s largest tree species, to the extreme 2012–2016 hotter drought in California. The project integrated leaf-level physiology measurements, crown-level foliage dieback surveys, and remotely sensed canopy water content (CWC) to shed light on mechanisms and spatial patterns in drought response. Here we summarize initial findings, present a conceptual model of drought response, and discuss management implications; details are presented in the other four articles of the special section on Giant Sequoias and Drought. Giant sequoias exhibited both leaf- and canopy-level responses that were effective in protecting whole-tree hydraulic integrity for the vast majority of individual sequoias. Very few giant sequoias died during the drought compared to other mixed conifer tree species; however, the magnitude of sequoia drought response varied across the landscape. This variability was partially explained by local site characteristics, including variables related to site water balance. We found that low CWC is an indicator of recent foliage dieback, which occurs when stress levels are high enough that leaf-level adjustments alone are insufficient for giant sequoias to maintain hydraulic integrity. CWC or change in CWC may be useful indicators of drought stress that reveal patterns of vulnerability to future hotter droughts. Future work will measure recovery from the drought and strengthen our ability to interpret CWC maps. Our ultimate goal is to produce giant sequoia vulnerability maps to help target management actions, such as reducing other stressors, increasing resistance to hotter drought through prescribed fire or mechanical thinning, and planting sequoias in projected future suitable habitat, which may occur outside current grove distributions. We suggest that managers compare different types of vulnerability assessments and combine vulnerability maps with other sources of information to inform decisions.

Harvesting systems for western stand health improvement cuttings

Treesearch

Bruce R. Hartsough; Bryce J. Stokes; Joseph F. McNeel; William F. Watson

1995-01-01

A significant percentage of the forested area in the western United States is comprised of stands that have been altered over time by human activities, especially fire suppression, and are now being damaged by droughts, insect attacks, and wildfires. These stands should be returned to a condition where "biotic and abiotic influences do not threaten resource...

Fine-scale spatial climate variation and drought mediate the likelihood of reburning

Treesearch

Sean A. Parks; Marc‐Andre Parisien; Carol Miller; Lisa M. Holsinger; Larry Scott Baggett

2018-01-01

In many forested ecosystems, it is increasingly recognized that the probability of burning is substantially reduced within the footprint of previously burned areas. This self‐limiting effect of wildland fire is considered a fundamental emergent property of ecosystems and is partly responsible for structuring landscape heterogeneity (i.e., mosaics of different age...

Invasive species and disturbances: Current and future roles of Forest Service Research and Development

Treesearch

Jim Slavicek; Allen M. Solomon

2010-01-01

The success of an invasive species is in large part due to favorable conditions resulting from the complex interactions among natural and anthropogenic factors such as native and nonnative pests, fires, droughts, hurricanes, wind storms, ice storms, climate warming, management practices, human travel, and trade. Reducing the negative effects of invasive species and...

Climate regulation of fire emissions and deforestation in equatorial Asia

PubMed Central

van der Werf, G. R.; Dempewolf, J.; Trigg, S. N.; Randerson, J. T.; Kasibhatla, P. S.; Giglio, L.; Murdiyarso, D.; Peters, W.; Morton, D. C.; Collatz, G. J.; Dolman, A. J.; DeFries, R. S.

2008-01-01

Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire emissions from Indonesia, Malaysia, and Papua New Guinea during 2000–2006. We found that average fire emissions from this region [128 ± 51 (1σ) Tg carbon (C) year−1, T = 1012] were comparable to fossil fuel emissions. In Borneo, carbon emissions from fires were highly variable, fluxes during the moderate 2006 El Niño more than 30 times greater than those during the 2000 La Niña (and with a 2000–2006 mean of 74 ± 33 Tg C yr−1). Higher rates of forest loss and larger areas of peatland becoming vulnerable to fire in drought years caused a strong nonlinear relation between drought and fire emissions in southern Borneo. Fire emissions from Sumatra showed a positive linear trend, increasing at a rate of 8 Tg C year−2 (approximately doubling during 2000–2006). These results highlight the importance of including deforestation in future climate agreements. They also imply that land manager responses to expected shifts in tropical precipitation may critically determine the strength of climate–carbon cycle feedbacks during the 21st century. PMID:19075224

A fire history derived from Pinus resinosa Ait. for the Islands of Eastern Lac La Croix, Minnesota, USA.

PubMed

Johnson, Lane B; Kipfmueller, Kurt F

2016-06-01

We reconstructed fire occurrence near a fur-trade era canoe travel corridor (used ca. 1780-1802) in the Quetico-Superior region west of Lake Superior to explore the possibility of human influence on pre-fire suppression rates of fire occurrence. Our research objectives were to (1) examine the spatial and temporal patterns of fire in the study area, (2) test fires' strength of association with regional drought, and (3) assess whether reconstructed fire frequencies could be explained by observed rates of lightning fire ignition over the modern period of record. We developed a 420-year fire history for the eastern portion of Lac La Croix in the Boundary Waters Canoe Area Wilderness (BWCAW). Seventy-one fire-scarred samples were collected from remnant Pinus resinosa Ait. (red pine) stumps and logs from thirteen distinct island and three mainland forest stands. Collectively these samples contained records of 255 individual fire scars representing 79 fire events from 1636 to 1933 (study area mean fire intervals [MFI] 3.8 yr). Reconstructed fires were spatially and temporally asynchronous and not strongly associated with regional drought (P > 0.05). When compared to the conservative, tree-ring reconstructed estimate of historical fire occurrence and modern lightning-caused fires (1929-2012), a noticeable change in the distribution and frequency of fires within the study area was evident with only two lightning-ignited island fires since 1934 in the study area. Our results suggest a high likelihood that indigenous land use contributed to surface fire ignitions within our study area and highlights the importance of examining the potential effects of past indigenous land use when determining modern approaches to fire and wilderness management in fire-adapted ecosystems.

Effects of active forest fire on terrestrial ecosystem production and greenhouse gas emissions

NASA Astrophysics Data System (ADS)

Sannigrahi, Srikanta; Rahmat, Shahid; Bhatt, Sandeep; Rana, Virendra

2017-04-01

The forest fire is one of the most catalysing agents which degrade an ecosystems leading to the loss of net and gross primary productivity (NPP & GPP) and carbon sequestration service. Additionally, it can suppress the efficiency of service providing capacity of an ecosystem throughout the time and space. Remote sensing-based forest fire estimation in a diverse ecosystem is very much essential for mitigating the biodiversity and productivity losses due to the forest fire. Satellite-based Land Surface Temperature (LST) has been calculated for the pre-fire and fire years to identify the burn severity hotspot across all eco-regions in the Lower Himalaya region. Several burn severity indices: Normalized Burn Ratio (NBR), Burnt Area Index (BAI), Normalized Multiband Drought Index (NMDI), Soil Adjusted Vegetation Index (SAVI), Global Environmental Monitoring Index (GEMI), Enhance Vegetation Index (EVI) have been used in this study to quantify the spatial and temporal changes (delta) of the selected indices. Two Light Use Efficiency (LUE) models: Carnegie- Ames-Stanford-Approach (CASA) and Vegetation Photosynthesis Model (VPM) have been used to quantify the terrestrial Net Primary Productivity (NPP) in the pre-fire and fire years across all biomes of the region. A novel approach has been preceded in this field to demonstrate the correlation between forest fire density (FFD) and NPP. A strong positive correlation was found between burn severity indices and predicted NPP: BAI and NPP (r = 0.49), NBR and NPP: (r = 0.58), EVI and NPP: (r = 0.72), SAVI and NPP: (r = 0.67), whereas, a negative association has noted between the NMDI and NPP: (r = -0.36) during the both studied years. Results have shown that the NPP is highly correlated with the forest fire density (R2 = 0.75, RMSE = 5.03 gC m-2 month-1). The estimated LST of the individual fire days has witnessed a sharp temperature increase by > 6oC - 9oC in comparison to the non-fire days clearly indicates high fire risk (in Uttarakhand) due to the subtle water stress condition with lesser soil moisture content into the ground. Among the 13 districts, the maximum net emissions of carbon and nitrogen compounds have been observed in 7 districts (accounting for high biomass and forest cover loss by the 2016 forest fire), whereas, the rest of the 6 districts acts as the sequester of greenhouse compounds. This new approach having the potentiality of quantifying the losses of ecosystem productivity due to forest fires and could be used in broader aspects if more accurate field based observation can be obtained in the near future.

Exploring the likelihood and mechanism of a climate-change-induced dieback of the Amazon rainforest

PubMed Central

Malhi, Yadvinder; Aragão, Luiz E. O. C.; Galbraith, David; Huntingford, Chris; Fisher, Rosie; Zelazowski, Przemyslaw; Sitch, Stephen; McSweeney, Carol; Meir, Patrick

2009-01-01

We examine the evidence for the possibility that 21st-century climate change may cause a large-scale “dieback” or degradation of Amazonian rainforest. We employ a new framework for evaluating the rainfall regime of tropical forests and from this deduce precipitation-based boundaries for current forest viability. We then examine climate simulations by 19 global climate models (GCMs) in this context and find that most tend to underestimate current rainfall. GCMs also vary greatly in their projections of future climate change in Amazonia. We attempt to take into account the differences between GCM-simulated and observed rainfall regimes in the 20th century. Our analysis suggests that dry-season water stress is likely to increase in E. Amazonia over the 21st century, but the region tends toward a climate more appropriate to seasonal forest than to savanna. These seasonal forests may be resilient to seasonal drought but are likely to face intensified water stress caused by higher temperatures and to be vulnerable to fires, which are at present naturally rare in much of Amazonia. The spread of fire ignition associated with advancing deforestation, logging, and fragmentation may act as nucleation points that trigger the transition of these seasonal forests into fire-dominated, low biomass forests. Conversely, deliberate limitation of deforestation and fire may be an effective intervention to maintain Amazonian forest resilience in the face of imposed 21st-century climate change. Such intervention may be enough to navigate E. Amazonia away from a possible “tipping point,” beyond which extensive rainforest would become unsustainable. PMID:19218454

Exploring the likelihood and mechanism of a climate-change-induced dieback of the Amazon rainforest.

PubMed

Malhi, Yadvinder; Aragão, Luiz E O C; Galbraith, David; Huntingford, Chris; Fisher, Rosie; Zelazowski, Przemyslaw; Sitch, Stephen; McSweeney, Carol; Meir, Patrick

2009-12-08

We examine the evidence for the possibility that 21st-century climate change may cause a large-scale "dieback" or degradation of Amazonian rainforest. We employ a new framework for evaluating the rainfall regime of tropical forests and from this deduce precipitation-based boundaries for current forest viability. We then examine climate simulations by 19 global climate models (GCMs) in this context and find that most tend to underestimate current rainfall. GCMs also vary greatly in their projections of future climate change in Amazonia. We attempt to take into account the differences between GCM-simulated and observed rainfall regimes in the 20th century. Our analysis suggests that dry-season water stress is likely to increase in E. Amazonia over the 21st century, but the region tends toward a climate more appropriate to seasonal forest than to savanna. These seasonal forests may be resilient to seasonal drought but are likely to face intensified water stress caused by higher temperatures and to be vulnerable to fires, which are at present naturally rare in much of Amazonia. The spread of fire ignition associated with advancing deforestation, logging, and fragmentation may act as nucleation points that trigger the transition of these seasonal forests into fire-dominated, low biomass forests. Conversely, deliberate limitation of deforestation and fire may be an effective intervention to maintain Amazonian forest resilience in the face of imposed 21st-century climate change. Such intervention may be enough to navigate E. Amazonia away from a possible "tipping point," beyond which extensive rainforest would become unsustainable.

A century of Amazon burning driven by Atlantic climate

NASA Astrophysics Data System (ADS)

Makou, M.; Thompson, L. G.; Davis, M. E.; Eglinton, T. I.

2011-12-01

Very little is known about annual burning trends in the Amazon Basin prior to remote sensing of fires beginning in the late 1970's. Fires reduce Amazon forest biomass and species richness, release pollutant aerosols, and impact the carbon cycle, compelling further investigation of fire-climate dynamics. We measured organic compounds derived from vegetation burning in ice core samples from the Quelccaya Ice Cap in Peru at better than annual resolution to reconstruct wet and dry season burning throughout the Twentieth Century. Variations in the abundance of methyl hexadecanoate, which is produced by thermal alteration of vascular plant alkanoic acids, were used as a proxy for past fire activity. Concentrations of this compound in Quelccaya ice varied strongly on seasonal, interannual, and decadal time scales over the last 100 years, with high-amplitude dry season variability and muted, decadal-scale changes in wet season fire activity. Decade-long periods of repeatedly enhanced burning occurred during the 1930's and 1960's when dry season precipitation was perpetually reduced, as evidenced by low stages of the Rio Negro. These decadal trends suggest that changes in dry season precipitation drive fire activity in the western Amazon and highlight the potential of Amazon forests to undergo repeated strong burning. Fires occurred during years when sea surface temperatures (SSTs) in the north tropical Atlantic were elevated and the north-south tropical Atlantic SST gradient was enhanced; this SST pattern likely displaced the intertropical convergence zone northward, driving subsidence and drought in the western and southern Amazon basin. Thus, our novel ice core record suggests that Amazon forest fire activity during the Twentieth Century was driven primarily by Atlantic climate processes, and future forest health will depend heavily on the evolution of tropical climate.

Fire and Deforestation Dynamics in South America over the Past 50 Years

NASA Astrophysics Data System (ADS)

van Marle, M.; Field, R. D.; van der Werf, G.

2015-12-01

Fires play an important role in the Earth system and are one of the major sources of greenhouse gases and aerosols. Satellites have been key to understand their spatial and temporal variability in space and time, but the most frequently used satellite datasets start only in 1995. There are still large uncertainties about the frequency and intensity of fires in the pre-satellite time period, especially in regions with active deforestation, which may have changed dramatically in intensity in the past decades influencing fire dynamics. We used two datasets to extend the record of fires and deforestation in the Amazon region back in time: 1) annual forest loss rates starting in 1990 derived from Vegetation Optical Depth (VOD), which is a satellite-based vegetation product that can be used as proxy for forest loss, and 2) horizontal visibility as proxy for fire emissions, reported by weather stations and airports in the Amazon, which started around 1940, and having widespread coverage since 1973. We show that these datasets overlap with fire emission estimates from the Global Fire Emissions Database (GFED) enabling us to estimate fire emissions over the last 50 years. We will discuss how fires have varied over time in this region with globally significant emissions, how droughts have influenced fire activity and deforestation rates, and what the impact is of land-use change caused by fire on emissions in the Amazon region.

The relationship of large fire occurrence with drought and fire danger indices in the western USA, 1984-2008: The role of temporal scale

Treesearch

Karin L. Riley; John T. Abatzoglou; Isaac C. Grenfell; Anna E. Klene; Faith Ann Heinsch

2013-01-01

The relationship between large fire occurrence and drought has important implications for fire prediction under current and future climates. This study’s primary objective was to evaluate correlations between drought and fire-danger- rating indices representing short- and long-term drought, to determine which had the strongest relationships with large fire occurrence...

Drought and Fire in the Western United States: Contrasting the Causes, Distributions, and Effects of Drought in the 20th and 21st Centuries with a Multiyear Moisture Deficit Drought Index

NASA Astrophysics Data System (ADS)

Crockett, J.; Westerling, A. L.

2016-12-01

The current drought in California is considered to be most severe drought event of the 20th and 21st century. Climate models forecast increasing temperatures in the Western United States but are less certain regarding precipitation patterns. Here we impose a novel index based on sustained, multiyear moisture deficit anomalies onto a 1/8° grid of the Western United States to investigate 1) whether California's drought is irregular in the recent history of the Western States; 2) how temperature and precipitation affected the development of large drought events; and 3) what impact did drought events have on burn area and severity of fires. Fire records were compiled from the Monitoring Trends in Burn Severity database and compared to drought events since 1984. Results indicate that drought events similar in size and duration to the current drought have occurred in the West since 1918, though previous drought events were not as severe nor centered on California. Six drought events of similar size to the 2012 - 2014 drought were compared: while they were characterized by negative precipitation anomalies, only the 2012 - 2014 event exhibited temperature anomalies that increased over the drought's duration. In addition, we found that large fires ( > 1000 acres) within drought areas had greater total area burned as well as area burned at medium and high severities compared to fires in non-drought areas. Our results suggest that though uncertainty of future precipitation patterns exists, increasing temperatures will exacerbate drought severity when events do occur. In addition, understanding the relationships between droughts and fire can guide land managers to more effective fire management during drought events.

The impact of the 2015-2016 El Niño-Southern Oscillation (ENSO) event on greenhouse gas exchange and surface energy budget in an Indonesian oil palm plantation

NASA Astrophysics Data System (ADS)

Stiegler, Christian; Meijide, Ana; June, Tania; Knohl, Alexander

2017-04-01

The 2015-2016 El Niño-Southern Oscillation (ENSO) event was one of the strongest observed in the last 20 years. Oil palm plantations cover a large fraction of tropical lowlands in Southeast Asia but despite their growing areal extent, measurements and observations of greenhouse gas exchange and surface energy balance are still scarce. In addition, the effects of extreme events such as ENSO on carbon sequestration and the partitioning of surface energy balance components are widely unknown. In this study, we use micrometeorological measurements located in commercial oil palm plantations in the Jambi province (Sumatra, Indonesia) to assess the impact of the 2015-2016 ENSO event and severe forest fires on greenhouse gas exchange and surface energy budget. Continuous measurements are in operation since July 2013 and we assess turbulent fluxes of carbon dioxide (CO2), water vapour and sensible heat using the eddy covariance technique before, during and after the 2015-2016 ENSO event. In the beginning of the ENSO event, the area experienced a strong drought with decreasing soil moisture, increasing air and surface temperatures, and strong atmospheric vapour pressure deficit. During the peak of the drought from August to October 2015, hundreds of forest fires in the area resulted in strong smoke production, decreasing incoming solar radiation by 35% compared to pre-ENSO values and diffuse radiation became almost the sole shortwave radiation flux. During the beginning of the drought, carbon uptake of the oil palm plantation was around 2.1 gC m-2 d-1 and initially increased by 50% due to clear-sky conditions and high incoming photosynthetically active radiation (PAR) but increasing density of smoke turned the oil palm plantation into a source of carbon. The turbulent heat fluxes experienced an increase in sensible heat fluxes due to drought conditions at the cost of latent heat fluxes resulting in an increase in the midday Bowen-ratio from 0.17 to 0.40. Strong smoke generally decreased the magnitude of the turbulent heat fluxes by 45% compared to pre-ENSO values. Overall, the ENSO event forest fires resulted in a major anomaly of exchange processes between the oil palm plantation and the atmosphere.

Seasonal-to-interannual variation in biomass burning over the contiguous United States

NASA Astrophysics Data System (ADS)

Kim, K. M.; Lau, W. K. M.; Ichoku, I.; Pereira, G.; Darmenov, A.; da Silva, A. M., Jr.; Ellison, L.

2017-12-01

The intensity and frequency of wildfires are strongly affected by climatic factors, such as droughts and heat waves, which are governed by weather and climate dynamics. . Climatic impacts on wildfire and biomass burning can be complex involving not only natural variability, but also human activities. In this study, we examine the seasonality of occurrences and intensity of fires and climatic impact as a function of underlying biomes over the CONUS, using fire pixel data from MODIS instruments on-board Terra and Aqua. Results show that there are three distinct fire seasons, i.e., summer (June to August), spring (March-April), and Fall (September-October). In the evergreen needle leaf region where most fires occur, the fire season peaks in mid boreal summer. In this region, fires tend to start early (June) in southern US, and late (August) in northern US. Double peaks are distinctive features in grass land and crop land. Double peaks in crop land (spring and fall) appear to be associated with agricultural practices. However, the two peaks in grass land (spring and summer) are due to natural wildfires, associated with changes in seasonal weather pattern. To better understand the potential climatic impact on fire, we examine relationships between fire weather index (FWI) and fire pixel counts. Fire pixel count has a strong correlation with FWI in evergreen needle leaf forest, deciduous broad leaf forest, and open shrub land. However, no significant linear relations are found in crop land, grass land, and mixed forest. The implications of these findings, and possible impacts of atmospheric teleconnecon on the fire season in the CONUS will also be discussed.

Burned forests impact water supplies.

PubMed

Hallema, Dennis W; Sun, Ge; Caldwell, Peter V; Norman, Steven P; Cohen, Erika C; Liu, Yongqiang; Bladon, Kevin D; McNulty, Steven G

2018-04-10

Wildland fire impacts on surface freshwater resources have not previously been measured, nor factored into regional water management strategies. But, large wildland fires are increasing and raise concerns about fire impacts on potable water. Here we synthesize long-term records of wildland fire, climate, and river flow for 168 locations across the United States. We show that annual river flow changed in 32 locations, where more than 19% of the basin area was burned. Wildland fires enhanced annual river flow in the western regions with a warm temperate or humid continental climate. Wildland fires increased annual river flow most in the semi-arid Lower Colorado region, in spite of frequent droughts in this region. In contrast, prescribed burns in the subtropical Southeast did not significantly alter river flow. These extremely variable outcomes offer new insights into the potential role of wildfire and prescribed fire in regional water resource management, under a changing climate.

Multi-season climate synchronized historical fires in dry forests (1650-1900), northern Rockies, U.S.A.

PubMed

Heyerdahl, Emily K; Morgan, Penelope; Riser, James P

2008-03-01

Our objective was to infer the climate drivers of regionally synchronous fire years in dry forests of the U.S. northern Rockies in Idaho and western Montana. During our analysis period (1650-1900), we reconstructed fires from 9245 fire scars on 576 trees (mostly ponderosa pine, Pinus ponderosa P. & C. Lawson) at 21 sites and compared them to existing tree-ring reconstructions of climate (temperature and the Palmer Drought Severity Index [PDSI]) and large-scale climate patterns that affect modern spring climate in this region (El Niño Southern Oscillation [ENSO] and the Pacific Decadal Oscillation [PDO]). We identified 32 regional-fire years as those with five or more sites with fire. Fires were remarkably widespread during such years, including one year (1748) in which fires were recorded at 10 sites across what are today seven national forests plus one site on state land. During regional-fire years, spring-summers were significantly warm and summers were significantly warm-dry whereas the opposite conditions prevailed during the 99 years when no fires were recorded at any of our sites (no-fire years). Climate in prior years was not significantly associated with regional- or no-fire years. Years when fire was recorded at only a few of our sites occurred under a broad range of climate conditions, highlighting the fact that the regional climate drivers of fire are most evident when fires are synchronized across a large area. No-fire years tended to occur during La Niña years, which tend to have anomalously deep snowpacks in this region. However, ENSO was not a significant driver of regional-fire years, consistent with the greater influence of La Niña than El Niño conditions on the spring climate of this region. PDO was not a significant driver of past fire, despite being a strong driver of modern spring climate and modern regional-fire years in the northern Rockies.

Water relations of evergreen and drought-deciduous trees along a seasonally dry tropical forest chronosequence

PubMed Central

Allen, Michael F.; Santiago, Louis S.

2010-01-01

Seasonally dry tropical forests (SDTF) are characterized by pronounced seasonality in rainfall, and as a result trees in these forests must endure seasonal variation in soil water availability. Furthermore, SDTF on the northern Yucatan Peninsula, Mexico, have a legacy of disturbances, thereby creating a patchy mosaic of different seral stages undergoing secondary succession. We examined the water status of six canopy tree species, representing contrasting leaf phenology (evergreen vs. drought-deciduous) at three seral stages along a fire chronosequence in order to better understand strategies that trees use to overcome seasonal water limitations. The early-seral forest was characterized by high soil water evaporation and low soil moisture, and consequently early-seral trees exhibited lower midday bulk leaf water potentials (ΨL) relative to late-seral trees (−1.01 ± 0.14 and −0.54 ± 0.07 MPa, respectively). Although ΨL did not differ between evergreen and drought-deciduous trees, results from stable isotope analyses indicated different strategies to overcome seasonal water limitations. Differences were especially pronounced in the early-seral stage where evergreen trees had significantly lower xylem water δ18O values relative to drought-deciduous trees (−2.6 ± 0.5 and 0.3 ± 0.6‰, respectively), indicating evergreen species used deeper sources of water. In contrast, drought-deciduous trees showed greater enrichment of foliar 18O (∆18Ol) and 13C, suggesting lower stomatal conductance and greater water-use efficiency. Thus, the rapid development of deep roots appears to be an important strategy enabling evergreen species to overcome seasonal water limitation, whereas, in addition to losing a portion of their leaves, drought-deciduous trees minimize water loss from remaining leaves during the dry season. PMID:20658152

Influence of forest and rangeland management on anadromous fish habitat in Western North America: impacts of natural events.

Treesearch

Douglas N. Swanston

1980-01-01

Natural events affecting vegetative cover and the hydrology and stability of a stream and its parent watershed are key factors influencing the quality of anadromous fish habitat. High intensity storms, drought, soil mass movement, and fire have the greatest impacts. Wind, stream icing, and the influence of insects and disease are important locally...

No genetic adaptation of the Mediterranean keystone shrub Cistus ladanifer in response to experimental fire and extreme drought.

PubMed

Torres, Iván; Parra, Antonio; Moreno, José M; Durka, Walter

2018-01-01

In Mediterranean ecosystems, climate change is projected to increase fire danger and summer drought, thus reducing post-fire recruitment of obligate seeder species, and possibly affecting the population genetic structure. We performed a genome-wide genetic marker study, using AFLP markers, on individuals from one Central Spain population of the obligate post-fire seeder Cistus ladanifer L. that established after experimental fire and survived during four subsequent years under simulated drought implemented with a rainout shelter system. We explored the effects of the treatments on marker diversity, spatial genetic structure and presence of outlier loci suggestive of selection. We found no effect of fire or drought on any of the genetic diversity metrics. Analysis of Molecular Variance showed very low genetic differentiation among treatments. Neither fire nor drought altered the small-scale spatial genetic structure of the population. Only one locus was significantly associated with the fire treatment, but inconsistently across outlier detection methods. Neither fire nor drought are likely to affect the genetic makeup of emerging C. ladanifer, despite reduced recruitment caused by drought. The lack of genetic change suggests that reduced recruitment is a random, non-selective process with no genome-wide consequences on this keystone, drought- and fire tolerant Mediterranean species.

Monitoring the Effects of Forest Restoration Treatments on Post-Fire Vegetation Recovery with MODIS Multitemporal Data

PubMed Central

van Leeuwen, Willem J. D.

2008-01-01

This study examines how satellite based time-series vegetation greenness data and phenological measurements can be used to monitor and quantify vegetation recovery after wildfire disturbances and examine how pre-fire fuel reduction restoration treatments impact fire severity and impact vegetation recovery trajectories. Pairs of wildfire affected sites and a nearby unburned reference site were chosen to measure the post-disturbance recovery in relation to climate variation. All site pairs were chosen in forested uplands in Arizona and were restricted to the area of the Rodeo-Chediski fire that occurred in 2002. Fuel reduction treatments were performed in 1999 and 2001. The inter-annual and seasonal vegetation dynamics before, during, and after wildfire events can be monitored using a time series of biweekly composited MODIS NDVI (Moderate Resolution Imaging Spectroradiometer - Normalized Difference Vegetation Index) data. Time series analysis methods included difference metrics, smoothing filters, and fitting functions that were applied to extract seasonal and inter-annual change and phenological metrics from the NDVI time series data from 2000 to 2007. Pre- and post-fire Landsat data were used to compute the Normalized Burn Ratio (NBR) and examine burn severity at the selected sites. The phenological metrics (pheno-metrics) included the timing and greenness (i.e. NDVI) for the start, peak and end of the growing season as well as proxy measures for the rate of green-up and senescence and the annual vegetation productivity. Pre-fire fuel reduction treatments resulted in lower fire severity, which reduced annual productivity much less than untreated areas within the Rodeo-Chediski fire perimeter. The seasonal metrics were shown to be useful for estimating the rate of post-fire disturbance recovery and the timing of phenological greenness phases. The use of satellite time series NDVI data and derived pheno-metrics show potential for tracking vegetation cover dynamics and successional changes in response to drought, wildfire disturbances, and forest restoration treatments in fire-suppressed forests. PMID:27879809

Post-fire drought effects and their legacy on soil functionality and microbial community structure in a Mediterranean shrubland

NASA Astrophysics Data System (ADS)

Belen Hinojosa, M.; Parra, Antonio; Laudicina, V. Armando; Moreno, José M.

2017-04-01

Climate change in subtropical areas, like the Mediterranean, is projected to decrease precipitation and to lengthen the seasonal drought period. Fire danger is also projected to increase under the most severe conditions. Little is known about the effects of increasing drought and, particularly, its legacy when precipitation resumes to normal, on the recovery of burned ecosystems. Here we studied the effects of post-fire drought and its legacy two years after it stopped on soil microbial community structure and functionality of a Cistus-Erica shrubland. To do this, a manipulative experiment was setup in which rainfall total patterns were modified by means of a rain-out shelters and irrigation system in a fully replicated set of previously burned plots. The treatments were: environmental control (natural rainfall), historical control (average rainfall, 2 months drought), moderate drought (25% reduction of historical control, 5 months drought) and severe drought (45% reduction, 7 months drought). One set of unburned plots under natural rainfall served as an additional control. Availability of the main soil nutrients and microbial community composition and functionality were monitored over 4 years under these rainfall manipulation treatments. Thereafter, treatments were discontinued and plots were subjected to ambient rainfall for two additional years. Post-fire drought had not effect on total C or N. Fire increased soil P and N availability. However, post-fire drought reduced available soil P and increased nitrate in the short term. Post- fire reduction of available K was accentuated by continued drought. Fire significantly reduced soil organic matter, enzyme activities and carbon mineralization, mainly in drought treated soils. Fire also decreased soil microbial biomass and the proportion of fungi, while that of actinomycetes increased in the short term. Post-fire drought accentuated the decrease of soil total microbial biomass and fungi, with bacteria becoming more abundant. After discontinuing the drought treatments, the effect of the previous drought was significant for available P and enzyme activities. Although the microbial biomass did not show a drought legacy effect of the previous drought period, the proportion of fungi was still lower in post-fire drought treatments and the proportion of bacteria (mainly Gram+) higher. Our results show that post-fire drought had an effect on soil functionality and microbial community structure, and that once the drought ceased its effects on some biogeochemical constituents and microbial groups were still visible two years thereafter. The fact that in a lapse of two years some variables had resume to normal while others still differed among drought treatment signifies that the legacies will last for some additional years, impairing during this time the normal functioning of the soil. However, these legacy was related to the magnitude of drought and, although not tested in our study, on the time since the occurrence of the phenomenon, and the sensitivity of the ecological system.

Modeling the effects of throughfall reduction on soil water content in a Brazilian Oxisol under a moist tropical forest

NASA Astrophysics Data System (ADS)

Belk, Elizabeth L.; Markewitz, Daniel; Rasmussen, Todd C.; Carvalho, Eduardo J. Maklouf; Nepstad, Daniel C.; Davidson, Eric A.

2007-08-01

Access to water reserves in deep soil during drought periods determines whether or not the tropical moist forests of Amazonia will be buffered from the deleterious effects of water deficits. Changing climatic conditions are predicted to increase periods of drought in Amazonian forests and may lead to increased tree mortality, changes in forest composition, or greater susceptibility to fire. A throughfall reduction experiment has been established in the Tapajós National Forest of east-central Amazonia (Brazil) to test the potential effects of severe water stress during prolonged droughts. Using time domain reflectometry observations of water contents from this experiment, we have developed a dynamic, one-dimensional, vertical flow model to enhance our understanding of hydrologic processes within these tall-stature forests on well-drained, upland, deep Oxisols and to simulate changes in the distribution of soil water. Simulations using 960 days of data accurately captured mild soil water depletion near the surface after the first treatment year and decreasing soil moisture at depth during the second treatment year. The model is sensitive to the water retention and unsaturated flow equation parameters, specifically the van Genuchten parameters θs, θr, and n, but less sensitive to Ks and α. The low root-mean-square error between observed and predicted volumetric soil water content suggests that this vertical flow model captures the most important hydrologic processes in the upper landscape position of this study site. The model indicates that present rates of evapotranspiration within the exclusion plot have been sustained at the expense of soil water storage.

Anthropogenic Land-use Change and the Dynamics of Amazon Forest Biomass

NASA Technical Reports Server (NTRS)

Laurance, William F.

2004-01-01

This project was focused on assessing the effects of prevailing land uses, such as habitat fragmentation, selective logging, and fire, on biomass and carbon storage in Amazonian forests, and on the dynamics of carbon sequestration in regenerating forests. Ancillary goals included developing GIs models to help predict the future condition of Amazonian forests, and assessing the effects of anthropogenic climate change and ENS0 droughts on intact and fragmented forests. Ground-based studies using networks of permanent plots were linked with remote-sensing data (including Landsat TM and AVHRR) at regional scales, and higher-resolution techniques (IKONOS imagery, videography, LIDAR, aerial photographs) at landscape and local scales. The project s specific goals were quite eclectic and included: Determining the effects of habitat fragmentation on forest dynamics, floristic composition, and the various components of above- and below-ground biomass. Assessing historical and physical factors that affect trajectories of forest regeneration and carbon sequestration on abandoned lands. Extrapolating results from local studies of biomass dynamics in fragmented and regenerating forests to landscape and regional scales in Amazonia, using remote sensing and GIS. Testing the hypothesis that intact Amazonian forests are functioning as a significant carbon sink. Examining destructive synergisms between forest fragmentation and fire. Assessing the short-term impacts of selective logging on aboveground biomass. Developing GIS models that integrate current spatial data on forest cover, deforestation, logging, mining, highway and roads, navigable rivers, vulnerability to wild fires, protected areas, and existing and planned infrastructure projects, in an effort to predict the future condition of Brazilian Amazonian forests over the next 20-25 years. Devising predictive spatial models to assess the influence of varied biophysical and anthropogenic predictors on Amazonian deforestation.

The extreme drought episode of August 2011-May 2012: A scenario for future droughts in Central Europe?

NASA Astrophysics Data System (ADS)

Zahradníček, P.; Trnka, M.; Brázdil, R.; Mozny, M.; Stepanek, P.; Hlavinka, P.; Malý, A.; Dubrovsky, M.

2014-12-01

The weather conditions from August 2011 to May 2012 produced an extreme drought in the eastern Czech Republic (Moravia), whereas the patterns were nearly normal in its western region (Bohemia). The Southern and Central Moravia regions, which represent the most important agricultural areas, were most affected by the drought. The precipitation totals for the studied period were 50% to 70% of the long-term mean, which was calculated for 1961-2000. In autumn 2011, the total precipitation accounted for 10% to 30% of the long-term mean for most of Moravia, increasing to 30% to 50% in spring 2012. Moreover, 7.5% of the Czech Republic experienced a 100-year drought; 20% of the country experienced a 20-year drought. According to the Palmer Drought Severity Index, the 2012 drought was classified as the worst in the past 130 years. The drought patterns were related to the prevailing high-pressure systems over Central Europe and the occurrence of weather types with different precipitation amounts in Bohemia and Moravia. The most substantial drought effects occurred in the agricultural sector. A decrease in cereal yields was observed in the analyzed production areas in Moravia, which was unprecedented in the past 52 years. Moreover, winter crops were affected more than spring crops. An increased risk of fire occurred due to the drought conditions; the largest forest fire in the past 15 years was recorded during this period. Furthermore, signs of hydrological drought were also reported in rivers. The 2011-2012 drought was compared with the significant droughts in 2000, 2003 and 2007. Austria and Slovakia, which neighbor the Czech Republic, experienced a similar drought. This drought analysis can be used as a scenario for future droughts and their impacts in Central Europe due to the global warming projected by GCMs.Acknowledgements:This study was made possible by the generous support of the "Establishment of International Scientific Team Focused on Drought Research" project (no. OP VK CZ.1.07/2.3.00/20.0248).

Experimental drought induces short-term changes in soil functionality and microbial community structure after fire in a Mediterranean shrubland

NASA Astrophysics Data System (ADS)

Hinojosa, M. B.; Parra, A.; Laudicina, V. A.; Moreno, J. M.

2014-10-01

Fire is a major ecosystem driver, causing significant changes in soil nutrients and microbial community structure and functionality. Post-fire soil dynamics can vary depending on rainfall patterns, although variations in response to drought are poorly known. This is particularly important in areas with poor soils and limited rainfall, like arid and semiarid ones. Furthermore, climate change projections in many such areas anticipate reduced precipitation and longer drought, together with an increase in fire severity. The effects of experimental drought and fire were studied on soils in a Mediterranean Cistus-Erica shrubland in Central Spain. A replicated (n = 4) field experiment was carried out in which four levels of rainfall pattern were implemented by means of a rain-out shelters and irrigation system. The treatments were: environmental control (natural rainfall), historical control (long-term average rainfall, 2 months drought), moderate drought (25% reduction of historical control, 5 months drought) and severe drought (45% reduction, 7 months drought). After one growing season, the plots were burned with high fire intensity, except a set of unburned plots that served as control. Soils were collected seasonally during one year and variables related to soil nutrient availability and microbial community structure and functionality were studied. Burned soils increased nutrient availability (P, N, K) with respect to unburned ones, but drought reduced such an increase in P, while it further increased N and K. Such changes in available soil nutrients were short-lived. Drought caused a further decrease of enzyme activities, carbon mineralization rate and microbial biomass. Fire decreased the relative abundance of fungi and actinomycetes. However, fire and drought caused a further reduction in fungi, with bacteria becoming relatively more abundant. Arguably, increasing drought and fires due to climate change will likely shift soil recovery after fire.

Extreme wildfire events are linked to global-change-type droughts in the northern Mediterranean

NASA Astrophysics Data System (ADS)

Ruffault, Julien; Curt, Thomas; Martin-StPaul, Nicolas K.; Moron, Vincent; Trigo, Ricardo M.

2018-03-01

Increasing drought conditions under global warming are expected to alter the frequency and distribution of large and high-intensity wildfires. However, our understanding of the impact of increasing drought on extreme wildfires events remains incomplete. Here, we analyzed the weather conditions associated with the extreme wildfires events that occurred in Mediterranean France during the exceptionally dry summers of 2003 and 2016. We identified that these fires were related to two distinct shifts in the fire weather space towards fire weather conditions that had not been explored before and resulting from specific interactions between different types of drought and different fire weather types. In 2016, a long-lasting press drought intensified wind-driven fires. In 2003, a hot drought combining a heat wave with a press drought intensified heat-induced fires. Our findings highlight that increasing drought conditions projected by climate change scenarios might affect the dryness of fuel compartments and lead to a higher frequency of extremes wildfires events.

Effects of Disturbance on Carbon Sequestration in the New Jersey Pine Barrens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schafer, Karina; Bohrer, Gil

While carbon and water cycling of forests contribute significantly to the Earth's overall biogeochemical cycling, it may be affected by disturbance and climate change. In this research, we contributed to the body of research on leaf-level, ecosystem and regional scale effects of disturbances on forest ecosystems, in an effort to foster more mechanistic understanding, which in turn can improve modeling efforts. Here, we summarize some of the major findings in this research of physical and biogenic disturbances, such as drought, prescribed fire, and insect defoliation, on leaf and ecosystem-scale physiological responses as well as impacts on carbon and water cyclingmore » in an Atlantic Coastal Plain upland oak/pine and upland pine forest. Following we have incorporated some of our findings into a new version of the Finite-element Tree-Crown Hydrodynamics (model version 2) model, which improved timing and hysteresis of transpiration modeling for trees. Furthermore, incorporation of hydrodynamics into modeling transpiration improved latent heat flux estimates. In our study on the physiology of the trees, we showed that during drought, stomatal conductance and canopy stomatal conductance were reduced, however, defoliation increased conductance on both leaf-level and canopy scale. Furthermore, after prescribed fire, leaf-level stomatal conductance was unchanged for pines but decreased for oaks, while canopy stomatal conductance decreased temporarily, but then rebounded the following growing season, thus exhibiting transient responses. This study suggests that forest response to disturbance varies from the leaf to ecosystem level as well as species level and thus, these differential responses interplay to determine the fate of forest structure and functioning post disturbance. Incorporating this responses improves model outcome.« less

Hydro-climate and ecological behaviour of the drought of Amazonia in 2005.

PubMed

Marengo, J A; Nobre, C A; Tomasella, J; Cardoso, M F; Oyama, M D

2008-05-27

In 2005, southwestern Amazonia experienced the effects of an intense drought that affected life and biodiversity. Several major tributaries as well as parts of the main river itself contained only a fraction of their normal volumes of water, and lakes were drying up. The consequences for local people, animals and the forest itself are impossible to estimate now, but they are likely to be serious. The analyses indicate that the drought was manifested as weak peak river season during autumn to winter as a consequence of a weak summertime season in southwestern Amazonia; the winter season was also accompanied by rainfall that sometimes reached 25% of the climatic value, being anomalously warm and dry and helping in the propagation of fires. Analyses of climatic and hydrological records in Amazonia suggest a broad consensus that the 2005 drought was linked not to El Niño as with most previous droughts in the Amazon, but to warming sea surface temperatures in the tropical North Atlantic Ocean.

Tropical savannas and dry forests.

PubMed

Pennington, R Toby; Lehmann, Caroline E R; Rowland, Lucy M

2018-05-07

In the tropics, research, conservation and public attention focus on rain forests, but this neglects that half of the global tropics have a seasonally dry climate. These regions are home to dry forests and savannas (Figures 1 and 2), and are the focus of this Primer. The attention given to rain forests is understandable. Their high species diversity, sheer stature and luxuriance thrill biologists today as much as they did the first explorers in the Age of Discovery. Although dry forest and savanna may make less of a first impression, they support a fascinating diversity of plant strategies to cope with stress and disturbance including fire, drought and herbivory. Savannas played a fundamental role in human evolution, and across Africa and India they support iconic megafauna. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fragmentation, topography, and forest age modulate impacts of drought on a tropical forested landscape in eastern Puerto Rico

NASA Astrophysics Data System (ADS)

Uriarte, M.; Schwartz, N.; Budsock, A.

2017-12-01

Naturally regenerating second-growth forests account for ca. 50% of tropical forest cover and provide key ecosystem services. Understanding climate impacts on these ecosystems is critical for developing effective mitigation programs. Differences in environmental conditions and landscape context from old-growth forests may exacerbate climate impacts on second-growth stands. Nearly 70% of forest regeneration is occurring in hilly, upland, or mountain regions; a large proportion of second-growth forests are also fragmented. The effects of drought at the landscape scale, however, and the factors that modulate landscape heterogeneity in drought impacts remain understudied. Heterogeneity in soil moisture, light, and temperature in fragmented, topographically complex landscapes is likely to influence climate impacts on these forests. We examine impacts of a severe drought in 2015 on a forested landscape in Puerto Rico using two anomalies in vegetation indices. The study landscape is fragmented and topographically complex and includes old- and second-growth forests. We consider how topography (slope, aspect), fragmentation (distance to forest edge, patch size), and forest age (old- vs second-growth) modulate landscape heterogeneity of drought impacts and recovery from drought. Drought impacts were more severe in second-growth forests than in old-growth stands. Both topography and forest fragmentation influences the magnitude of drought impacts. Forest growing in steep areas, south facing slopes, small patches, and closer to forest edges exhibited more marked responses to drought. Forest recovery from drought was greater in second-growth forests and south facing slopes but slower in small patches and closer to forest edges. These findings are congruent with studies of drought impacts on tree growth in the study region. Together these results demonstrate the need for a multi-scalar approach to the study of drought impacts on tropical forests.

Seeing the forest and the trees: USGS scientist links local changes to global scale

USGS Publications Warehouse

Wilson, Jim; Allen, Craig D.

2011-01-01

The recent recipient of two major awards, Craig D. Allen, a research ecologist with the U.S. Geological Survey Fort Collins Science Center, has loved trees since childhood. He is now considered an expert of world renown on the twin phenomena of forest changes and tree mortality resulting from climate warming and drought, and in 2010 was twice recognized for his scientific contributions.In December 2010, Dr. Allen was named a 2010 Fellow of the American Association for the Advancement of Science “for outstanding leadership in the synthesis of global forest responses to climate change, built from worldwide collaboration and a deep understanding of the environmental history of the southwestern United States.”In March 2010, he was honored with the Meritorious Service Award from the U.S. Department of the Interior (DOI) in recognition of his outstanding vision, initiative, and scientific contributions to the USGS, DOI, and U.S. Department of Agriculture in establishing a model science program to support adaptive land management at the new Valles Caldera National Preserve in north-central New Mexico.Dr. Allen has authored more than 85 publications on landscape ecology and landscape change, from fire history and ecology to ecosystem responses to climate change. He has appeared on NOVA discussing fire ecology and on The Discovery Channel and Discovery Canada explaining the links between drought-induced tree mortality and climate warming, in addition to being interviewed and quoted in innumerable newspaper articles on both topics.But how did this unassuming scientist grow from nurturing maple saplings on 40 acres in Wisconsin to understanding forest system stress worldwide?

Earth Observation taken during the Expedition 36 mission

NASA Image and Video Library

2013-08-24

ISS036-E-035685 (24 Aug. 2013) --- One of the Expedition 36 crew members aboard the International Space Station used a 50mm lens to record this high oblique view of the massive drought-aided Rim Fire in and around California's Yosemite National Park and the Stanislaus National Forest on Aug. 24. A portion of a solar array panel on the orbital outpost can be seen in upper left corner of the image. Editor's Note: The fire began on Aug. 17 and, as of Aug. 26, continues to burn. More than 224 square miles have been affected.

Forest resilience to drought varies across biomes.

PubMed

Gazol, Antonio; Camarero, Jesus Julio; Vicente-Serrano, Sergio M; Sánchez-Salguero, Raúl; Gutiérrez, Emilia; de Luis, Martin; Sangüesa-Barreda, Gabriel; Novak, Klemen; Rozas, Vicente; Tíscar, Pedro A; Linares, Juan C; Martín-Hernández, Natalia; Martínez Del Castillo, Edurne; Ribas, Montse; García-González, Ignacio; Silla, Fernando; Camisón, Alvaro; Génova, Mar; Olano, José M; Longares, Luis A; Hevia, Andrea; Tomás-Burguera, Miquel; Galván, J Diego

2018-05-01

Forecasted increase drought frequency and severity may drive worldwide declines in forest productivity. Species-level responses to a drier world are likely to be influenced by their functional traits. Here, we analyse forest resilience to drought using an extensive network of tree-ring width data and satellite imagery. We compiled proxies of forest growth and productivity (TRWi, absolutely dated ring-width indices; NDVI, Normalized Difference Vegetation Index) for 11 tree species and 502 forests in Spain corresponding to Mediterranean, temperate, and continental biomes. Four different components of forest resilience to drought were calculated based on TRWi and NDVI data before, during, and after four major droughts (1986, 1994-1995, 1999, and 2005), and pointed out that TRWi data were more sensitive metrics of forest resilience to drought than NDVI data. Resilience was related to both drought severity and forest composition. Evergreen gymnosperms dominating semi-arid Mediterranean forests showed the lowest resistance to drought, but higher recovery than deciduous angiosperms dominating humid temperate forests. Moreover, semi-arid gymnosperm forests presented a negative temporal trend in the resistance to drought, but this pattern was absent in continental and temperate forests. Although gymnosperms in dry Mediterranean forests showed a faster recovery after drought, their recovery potential could be constrained if droughts become more frequent. Conversely, angiosperms and gymnosperms inhabiting temperate and continental sites might have problems to recover after more intense droughts since they resist drought but are less able to recover afterwards. © 2018 John Wiley & Sons Ltd.

One year monitoring of fire-induced effects on dissolved organic matter and nutrient dynamics under different land-use

NASA Astrophysics Data System (ADS)

Potthast, Karin; Meyer, Stefanie; Crecelius, Anna; Schubert, Ulrich; Michalzik, Beate

2016-04-01

It is supposed that the changing climate will promote extreme weather events that in turn will increase drought periods and the abundance of fire events in temperate climate regions such as Central Europe. The impact of fires on the nutrient budgets of ecosystems is highly diverse and seems to depend on the ecosystem type. For example, little is known about fire effects on water-bound organic matter (OM) and nutrient fluxes in temperate managed forest ecosystems. Fires can strongly alter the distribution (forest floor vs. mineral soil), binding forms (organic vs. inorganic) and availability (solubility by water) of OM and associated nutrients. To elucidate the effects and seasonality of low intensity fires on the mobilization of dissolved organic carbon and nutrients, an experimental ground fire was conducted in November 2014 in the Hainich region, Central Germany. In addition, differences in response patterns between two land-use types (pasture and beech forest) were investigated. Lysimeters (n=5 controls/ 5 fire-manipulated) with topsoil monoliths (0-4 cm), rainfall/throughfall samplers, littertraps as well as temperature and moisture sensors were installed on three sites of each land-use type. During the one year of monitoring (Sep14-Dec15) soil solution, rainfall, and throughfall samples were taken biweekly and analyzed for pH, dissolved and particulate organic carbon (DOC, POC) and nitrogen (DN, PN) as well as for nutrients (e.g. K, Ca, Mg, P, S). Compared to the control sites, the ground fire immediately induced a short-run release peak of DOC in both land-use types. Within two weeks these differences were muted in the post-fire period. The effect of fire was land-use specific with annual DOC fluxes of 82 and 45 kg/(ha*a) for forest and pasture sites, respectively. In contrast, nitrogen fluxes responded differently to the fire event. In the forest, a significant increase in DN concentrations was notable five months after the fire, at the beginning of the vegetation period and lasted until November with DN concentrations in June being 4 times higher compared to the control (82 vs. 18 mg DN/L) and being negatively correlated with pH-values (r=-0.51 p<0.001). Annual DN fluxes from fire manipulated forest plots were two times higher compared to control ones (62 vs. 29 kg DN/(ha*a)) whereas only low impact was found at the pasture with 45 and 38 kg DN/(ha*a) for fire-manipulated plots and control, respectively. In general, the results exhibit highly differing response patterns of elements to fire between the two land-use types and with season. Starting in spring higher DN fluxes following fire event at the forest site could be associated with accelerated activity of soil microbes mineralizing released organic substances from burned forest floor and/or from dead roots. This mineralization process resulted in a significant increase in acidity of the soil solution that may affect important ecosystem functions like nutrient cycling and primary production. Hence, high resolution monitoring following a low intensive fire indicated nutrient losses from the forest ecosystem that could be a hazard for managed forests on nutrient poor soils if fire frequency increases with climate change.

Increased Wildfire Risk Driven by Climate and Development Interactions in the Bolivian Chiquitania, Southern Amazonia.

PubMed

Devisscher, Tahia; Anderson, Liana O; Aragão, Luiz E O C; Galván, Luis; Malhi, Yadvinder

2016-01-01

Wildfires are becoming increasingly dominant in tropical landscapes due to reinforcing feedbacks between land cover change and more severe dry conditions. This study focused on the Bolivian Chiquitania, a region located at the southern edge of Amazonia. The extensive, unique and well-conserved tropical dry forest in this region is susceptible to wildfires due to a marked seasonality. We used a novel approach to assess fire risk at the regional level driven by different development trajectories interacting with changing climatic conditions. Possible future risk scenarios were simulated using maximum entropy modelling with presence-only data, combining land cover, anthropogenic and climatic variables. We found that important determinants of fire risk in the region are distance to roads, recent deforestation and density of human settlements. Severely dry conditions alone increased the area of high fire risk by 69%, affecting all categories of land use and land cover. Interactions between extreme dry conditions and rapid frontier expansion further increased fire risk, resulting in potential biomass loss of 2.44±0.8 Tg in high risk area, about 1.8 times higher than the estimates for the 2010 drought. These interactions showed particularly high fire risk in land used for 'extensive cattle ranching', 'agro-silvopastoral use' and 'intensive cattle ranching and agriculture'. These findings have serious implications for subsistence activities and the economy in the Chiquitania, which greatly depend on the forestry, agriculture and livestock sectors. Results are particularly concerning if considering the current development policies promoting frontier expansion. Departmental protected areas inhibited wildfires when strategically established in areas of high risk, even under drought conditions. However, further research is needed to assess their effectiveness accounting for more specific contextual factors. This novel and simple modelling approach can inform fire and land management decisions in the Chiquitania and other tropical forest landscapes to better anticipate and manage large wildfires in the future.

Increased Wildfire Risk Driven by Climate and Development Interactions in the Bolivian Chiquitania, Southern Amazonia

PubMed Central

Devisscher, Tahia; Anderson, Liana O.; Aragão, Luiz E. O. C.; Galván, Luis; Malhi, Yadvinder

2016-01-01

Wildfires are becoming increasingly dominant in tropical landscapes due to reinforcing feedbacks between land cover change and more severe dry conditions. This study focused on the Bolivian Chiquitania, a region located at the southern edge of Amazonia. The extensive, unique and well-conserved tropical dry forest in this region is susceptible to wildfires due to a marked seasonality. We used a novel approach to assess fire risk at the regional level driven by different development trajectories interacting with changing climatic conditions. Possible future risk scenarios were simulated using maximum entropy modelling with presence-only data, combining land cover, anthropogenic and climatic variables. We found that important determinants of fire risk in the region are distance to roads, recent deforestation and density of human settlements. Severely dry conditions alone increased the area of high fire risk by 69%, affecting all categories of land use and land cover. Interactions between extreme dry conditions and rapid frontier expansion further increased fire risk, resulting in potential biomass loss of 2.44±0.8 Tg in high risk area, about 1.8 times higher than the estimates for the 2010 drought. These interactions showed particularly high fire risk in land used for ‘extensive cattle ranching’, ‘agro-silvopastoral use’ and ‘intensive cattle ranching and agriculture’. These findings have serious implications for subsistence activities and the economy in the Chiquitania, which greatly depend on the forestry, agriculture and livestock sectors. Results are particularly concerning if considering the current development policies promoting frontier expansion. Departmental protected areas inhibited wildfires when strategically established in areas of high risk, even under drought conditions. However, further research is needed to assess their effectiveness accounting for more specific contextual factors. This novel and simple modelling approach can inform fire and land management decisions in the Chiquitania and other tropical forest landscapes to better anticipate and manage large wildfires in the future. PMID:27632528

Effects of high-frequency understorey fires on woody plant regeneration in southeastern Amazonian forests

PubMed Central

Balch, Jennifer K.; Massad, Tara J.; Brando, Paulo M.; Nepstad, Daniel C.; Curran, Lisa M.

2013-01-01

Anthropogenic understorey fires affect large areas of tropical forest, yet their effects on woody plant regeneration post-fire remain poorly understood. We examined the effects of repeated experimental fires on woody stem (less than 1 cm at base) mortality, recruitment, species diversity, community similarity and regeneration mode (seed versus sprout) in Mato Grosso, Brazil. From 2004 to 2010, forest plots (50 ha) were burned twice (B2) or five times (B5), and compared with an unburned control (B0). Stem density recovered within a year after the first burn (initial density: 12.4–13.2 stems m−2), but after 6 years, increased mortality and decreased regeneration—primarily of seedlings—led to a 63 per cent and 85 per cent reduction in stem density in B2 and B5, respectively. Seedlings and sprouts across plots in 2010 displayed remarkable community similarity owing to shared abundant species. Although the dominant surviving species were similar across plots, a major increase in sprouting occurred—almost three- and fourfold greater in B2 and B5 than in B0. In B5, 29 species disappeared and were replaced by 11 new species often present along fragmented forest edges. By 2010, the annual burn regime created substantial divergence between the seedling community and the initial adult tree community (greater than or equal to 20 cm dbh). Increased droughts and continued anthropogenic ignitions associated with frontier land uses may promote high-frequency fire regimes that may substantially alter regeneration and therefore successional processes. PMID:23610167

Attribution of Disturbances Causing Tree Mortality for the Continental U.S.

NASA Astrophysics Data System (ADS)

Wang, M.; Xu, C.; Allen, C. D.; McDowell, N. G.

2016-12-01

Broad-scale tree mortality has been frequently reported and documented to increase with warming climate and human activities. However, there is so far no general method to quantify the relative contributions of different disturbances on observed broad-scale tree mortality. In this study, we presented a framework to investigate the contribution of various disturbances causing tree mortality for 2000-2014 in the continental US. Our work is based on the high-resolution forest-loss data developed by Hansen et al. (2013). Firstly, fire-driven mortality was determined using the data from Monitoring Trends in Burn Severity (MTBS) project. Secondly, a landscape-pattern-recognition approach focusing on the differences of boundary complexity caused by natural and anthropogenic disturbances was developed to attribute harvest-driven mortality patches. Then, a drought threshold was determined through conducting an intensive literature survey for attribution of drought-driven mortality. Our results showed that we can correctly attribute 85% harvest-driven mortality as compared to Forest Inventory and Analysis (FIA) data. Based on Evaporative Stress Index (ESI), our literature survey suggests that most mortality events happened at extreme drought (37.7%), then severe (31.4%) and moderate (23.4%) drought. In total, 92.6% of drought-induced mortality events observed during 2000-2014 occurred at drought conditions of moderate or worse with corresponding ESI values ranging from -0.9 -2.49. Therefore, -0.9 will be used as the threshold to attribute drought-driven tree mortality. Overall, these results imply a great potential for using these methods to identify and attribute disturbances driving tree death at broad spatial scales.

Simulating drought impacts on energy balance in an Amazonian rainforest

NASA Astrophysics Data System (ADS)

Imbuzeiro, H. A.; Costa, M. H.; Galbraith, D.; Christoffersen, B. O.; Powell, T.; Harper, A. B.; Levine, N. M.; Rowland, L.; Moorcroft, P. R.; Benezoli, V. H.; Meir, P.; da Costa, A. C. L.; Brando, P. M.; Malhi, Y.; Saleska, S. R.; Williams, M. D.

2014-12-01

The studies of the interaction between vegetation and climate change in the Amazon Basin indicate that up to half of the region's forests may be displaced by savanna vegetation by the end of the century. Additional analyses suggest that complex interactions among land use, fire-frequency, and episodic drought are driving an even more rapid process of the forest impoverishment and displacement referred here as "savannization". But it is not clear whether surface/ecosystem models are suitable to analyze extreme events like a drought. Long-term simulations of throughfall exclusion experiments has provided unique insights into the energy dynamics of Amazonian rainforests during drought conditions. In this study, we evaluate how well six surface/ecosystem models quantify the energy dynamics from two Amazonian throughfall exclusion experiments. All models were run for the Tapajós and Caxiuanã sites with one control plot using normal precipitation (i.e. do not impose a drought) and then the drought manipulation was imposed for several drought treatments (10 to 90% rainfall exclusion). The sap flow, net radiation (Rn), sensible (H), latent (LE) and ground (G) heat flux are used to analyze if the models are able to capture the dynamics of water stress and what the implications for the energy dynamics are. With respect to the model validation, when we compare the sap flow observed and transpiration simulated, models are more accurate to simulate control plots than drought treatments (50% rainfall exclusion). The results show that the models overestimate the sap flow data during the drought conditions, but they were able to capture the changes in the main energy balance components for different drought treatments. The Rn and LE decreased and H increased with more intensity of drought. The models sensitivity analysis indicate that models are more sensitive to drought when rainfall is excluded for more than 60% and when this reduction occurs during the dry season.

A review of the combination among global change factors in forests, shrublands and pastures of the Mediterranean Region: Beyond drought effects

NASA Astrophysics Data System (ADS)

Doblas-Miranda, E.; Alonso, R.; Arnan, X.; Bermejo, V.; Brotons, L.; de las Heras, J.; Estiarte, M.; Hódar, J. A.; Llorens, P.; Lloret, F.; López-Serrano, F. R.; Martínez-Vilalta, J.; Moya, D.; Peñuelas, J.; Pino, J.; Rodrigo, A.; Roura-Pascual, N.; Valladares, F.; Vilà, M.; Zamora, R.; Retana, J.

2017-01-01

Climate change, alteration of atmospheric composition, land abandonment in some areas and land use intensification in others, wildfires and biological invasions threaten forests, shrublands and pastures all over the world. However, the impacts of the combinations between global change factors are not well understood despite its pressing importance. Here we posit that reviewing global change factors combination in an exemplary region can highlight the necessary aspects in order to better understand the challenges we face, warning about the consequences, and showing the challenges ahead of us. The forests, shrublands and pastures of the Mediterranean Basin are an ideal scenario for the study of these combinations due to its spatial and temporal heterogeneity, increasing and diverse human population and the historical legacy of land use transformations. The combination of multiple global change factors in the Basin shows different ecological effects. Some interactions alter the effects of a single factor, as drought enhances or decreases the effects of atmospheric components on plant ecophysiology. Several interactions generate new impacts: drought and land use changes, among others, alter water resources and lead to land degradation, vegetation regeneration decline, and expansion of forest diseases. Finally, different factors can occur alone or simultaneously leading to further increases in the risk of fires and biological invasions. The transitional nature of the Basin between temperate and arid climates involves a risk of irreversible ecosystem change towards more arid states. However, combinations between factors lead to unpredictable ecosystem alteration that goes beyond the particular consequences of drought. Complex global change scenarios should be studied in the Mediterranean and other regions of the world, including interregional studies. Here we show the inherent uncertainty of this complexity, which should be included in any management strategy.

140-Year Dynamics of a Forest Ecotone Under Climate and Environmental Change

NASA Astrophysics Data System (ADS)

Thorne, J. H.; Kelsey, R.

2006-12-01

Terrestrial plant species live within elevational limits. Response to climate change at the lower edge of a species' range can be quite different from response at its upper limits. Lower edge dynamics can sometimes lead to rapid shifts, if establishment conditions have changed. Under those circumstances, stand replacing disturbances can cause the local extirpation of the species because subsequent recruitment is ineffectual. We examined the position of lower edge of Pinus ponderosa forests in El Dorado County, California, where the tree occupies a broad elevational gradient. We found that over 140 years, this forest had shifted upslope over 500 meters. Minimum monthly air temperatures from stations forming an elevational transect in these mountains have warmed over the past 60 years by over 30 C. In the zone of the shift, this means that now no months are frozen, whereas 60 years ago December, January and February were below 00C. This warming is associated with advancing summer drought conditions, which set the stage for drought stress and reduced competitive abilities in the seedlings. We present an estimate for how much sooner summer drought conditions begin. Potential confounding factors: including grazing, agriculture, fires and urban expansion were found to occupy only 40% of the 540 km2 of forests lost since 1850 in the County. Forest change here is a disturbance initiated, recruitment limited system. Implications of this research include that the lower edge of coniferous systems are sensitive to climate change, via a combination of direct and indirect effects. A possible feedback between this edge and the lower limits of the snowline is discussed.

Holocene Fire, Climate, and Geomorphic Response: Perspectives From the Past and Indications for the Future

NASA Astrophysics Data System (ADS)

Meyer, G. A.; Pierce, J. L.; Frechette, J. D.; New, J.; Jull, A.

2006-12-01

Increased wildfire activity has accompanied late 20th-century to present warming across the diverse conifer forests of western North America. In ponderosa pine forests in particular, large, severe wildfires and ensuing erosion and debris flows appear unprecedented in light of tree-ring fire-scar records, and are often attributed to increased stand density following Euro-American settlement and fire suppression starting in the late 1800s. Yet, presettlement periods in fire-scar records correspond to mostly cooler Little Ice Age climates, when we expect that severe fires may be less probable. AMS 14C dating of fire-related alluvial-fan deposits provides a longer-term context for assessing links between fire, climate, erosion, and anthropogenic change. Infrequent high-severity fire is typical of cool, high-elevation Yellowstone National Park (YNP). Fire-related debris flows were common in YNP 2350-2000 cal yr BP and in Medieval time 1050-650 BP, both relatively warm periods at many sites across the Northern Hemisphere. Drier, low-elevation ponderosa forests in central Idaho also experienced severe fires and debris flows at these times, and ~25% of fan aggradation in the last 4000 yr occurred via postfire debris flows within the 400-yr Medieval period containing widespread, multidecadal droughts (Cook et al. 2004). Few fire-related deposits in YNP date to the Little Ice Age and prior cold episodes ca. 1400 and 2800 BP. At these same times, thin charcoal-bearing deposits indicate frequent low-severity fires in Idaho, where cooler, effectively wetter climates promoted growth of grass and fine fuels that promoted surface fires in the typically dry summers of this region. Initial data from varied forest types in the monsoonal (dry spring, wet summer) climate of the Sacramento Mountains, New Mexico, indicate voluminous fire-related sedimentation 6000-4500 BP, consistent with a warm middle Holocene. Fire-induced debris flows were less frequent in the late Holocene, but indicate that some severe fires affected ponderosa pine-dominated forests. Therefore, modern postfire debris flows are not without precedent in any of these areas, where fire has been an important catalyst for episodic erosion. Each record indicates an increased probability of severe fire with warmer climates. As greenhouse gas increases are virtually assured over the next century, impacts on fire and erosion have likely just begun. Earlier snowmelt accompanying warming lengthens the fire season in much of the Rocky Mountains, including YNP and central Idaho (Westerling et al. 2006). In ponderosa and similar forests where surface fires were suppressed by humans, increased stand density compounds the effect of warming. Increasing temperatures may also heighten precipitation intensity, producing greater postfire erosion. Although Holocene history provides imperfect analogs for a uniquely anthropogenic future, the sensitivity of fire regimes to past warming portends future increases in severe fires and geomorphic change.

Modeling the effects of fire severity and climate warming on active layer and soil carbon dynamics of black spruce forests across the landscape in interior Alaska

USGS Publications Warehouse

Genet, H.; McGuire, Anthony David; Barrett, K.; Breen, A.; Euskirchen, E.S.; Johnstone, J.F.; Kasischke, E.S.; Melvin, A.M.; Bennett, A.; Mack, M.C.; Rupp, T.S.; Schuur, A.E.G.; Turetsky, M.R.; Yuan, F.

2013-01-01

There is a substantial amount of carbon stored in the permafrost soils of boreal forest ecosystems, where it is currently protected from decomposition. The surface organic horizons insulate the deeper soil from variations in atmospheric temperature. The removal of these insulating horizons through consumption by fire increases the vulnerability of permafrost to thaw, and the carbon stored in permafrost to decomposition. In this study we ask how warming and fire regime may influence spatial and temporal changes in active layer and carbon dynamics across a boreal forest landscape in interior Alaska. To address this question, we (1) developed and tested a predictive model of the effect of fire severity on soil organic horizons that depends on landscape-level conditions and (2) used this model to evaluate the long-term consequences of warming and changes in fire regime on active layer and soil carbon dynamics of black spruce forests across interior Alaska. The predictive model of fire severity, designed from the analysis of field observations, reproduces the effect of local topography (landform category, the slope angle and aspect and flow accumulation), weather conditions (drought index, soil moisture) and fire characteristics (day of year and size of the fire) on the reduction of the organic layer caused by fire. The integration of the fire severity model into an ecosystem process-based model allowed us to document the relative importance and interactions among local topography, fire regime and climate warming on active layer and soil carbon dynamics. Lowlands were more resistant to severe fires and climate warming, showing smaller increases in active layer thickness and soil carbon loss compared to drier flat uplands and slopes. In simulations that included the effects of both warming and fire at the regional scale, fire was primarily responsible for a reduction in organic layer thickness of 0.06 m on average by 2100 that led to an increase in active layer thickness of 1.1 m on average by 2100. The combination of warming and fire led to a simulated cumulative loss of 9.6 kgC m−2 on average by 2100. Our analysis suggests that ecosystem carbon storage in boreal forests in interior Alaska is particularly vulnerable, primarily due to the combustion of organic layer thickness in fire and the related increase in active layer thickness that exposes previously protected permafrost soil carbon to decomposition.

Solutions Network Formulation Report. Visible/Infrared Imager/Radiometer Suite and Advanced Microwave Scanning Radiometer Data Products for National Drought Monitor Decision Support

NASA Technical Reports Server (NTRS)

Estep, Leland

2007-01-01

Drought effects are either direct or indirect depending on location, population, and regional economic vitality. Common direct effects of drought are reduced crop, rangeland, and forest productivity; increased fire hazard; reduced water levels; increased livestock and wildlife mortality rates; and damage to wildlife and fish habitat. Indirect impacts follow on the heels of direct impacts. For example, a reduction in crop, rangeland, and forest productivity may result in reduced income for farmers and agribusiness, increased prices for food and timber, unemployment, reduced tax revenues, increased crime, foreclosures on bank loans to farmers and businesses, migration, and disaster relief programs. In the United States alone, drought is estimated to result in annual losses of between $6 - 8 billion. Recent sustained drought in the United States has made decision-makers aware of the impacts of climate change on society and environment. The eight major droughts that occurred in the United States between 1980 and 1999 accounted for the largest percentage of weather-related monetary losses. Monitoring drought and its impact that occurs at a variety of scales is an important government activity -- not only nationally but internationally as well. The NDMC (National Drought Mitigation Center) and the USDA (U.S. Department of Agriculture) RMA (Risk Management Agency) have partnered together to develop a DM-DSS (Drought Monitoring Decision Support System). This monitoring system will be an interactive portal that will provide users the ability to visualize and assess drought at all levels. This candidate solution incorporates atmospherically corrected VIIRS data products, such as NDVI (Normalized Difference Vegetation Index) and Ocean SST (sea surface temperature), and AMSR-E soil moisture data products into two NDMC vegetation indices -- VegDRI (Vegetation Drought Response Index) and VegOUT (Vegetation Outlook) -- which are then input into the DM-DSS.

Response of Amazon Fires to the 2015/2016 El Niño and Evaluation of a Seasonal Fire Season Severity Forecast

NASA Astrophysics Data System (ADS)

Randerson, J. T.

2016-12-01

Recent work has established that year-to-year variability in drought and fire within the Amazon responds to a dual forcing from ocean-atmosphere interactions in the tropical Pacific and North Atlantic. Teleconnections between the Pacific and the Amazon are strongest between October and March, when El Niño contributes to below-average precipitation during the wet season. A reduced build-up of soil moisture during the wet season, in turn, may limit water availability and transpiration in tropical forests during the following dry season, lowering surface humidity, drying fuels, and allowing fires to spread more easily through the understory. The delayed influence of soil moisture through this land - atmosphere coupling provides a means to predict fire season severity 3-6 months before the onset of the dry season. With the aim of creating new opportunities for forest conservation, we have developed an experimental seasonal fire forecasting system for the Amazon. The 2016 fire season severity forecast, released in June by UCI and NASA, predicts unusually high risk across eastern Peru, northern Bolivia, and Brazil. Several surface and satellite data streams confirm that El Niño teleconnections had a significant impact on wet season hydrology within the Amazon. Rainfall observations from the Global Precipitation Climatology Centre provided evidence that cumulative precipitation deficits during August-April were 1 to 2 standard deviations below the long-term mean for most of the basin. These observations were corroborated by strong negative terrestrial water storage anomalies measured by the Gravity Recovery and Climate Experiment, and by fluorescence and vegetation index observations from other sensors that indicated elevated canopy stress. By August 3rd, satellite observations showed above average fire activity in most, but not all, forecast regions. Using additional satellite observations that become available later this year, we plan to describe the full spatial and temporal pattern of fires within the Amazon during the 2016 dry season and evaluate the success of our forecast. As a part of this analysis, we will compare fires from 2016 with other years of extreme drought (i.e., 2005 and 2010), and assess how trends in land use, including regional changes in deforestation, modify El Niño-driven fire risk.

Scientists assess impact of Indonesia fires

NASA Astrophysics Data System (ADS)

Showstack, Randy

The fires burning in Indonesia over the past several months are setting aflame the biomass and wildlife habitat of the tropical forests, spreading a dangerously unhealthy haze across the populous country and nearby nations in southeast Asia, causing transportation hazards, and sending plumes of smoke up into the troposphere.Most of the fires have been set—by big landowners, commercial loggers, and small farmers—in attempts to clear and cultivate the land, as people have done in the past. But this year a drought induced by El Niño limited the rainfall that could help extinguish the flames and wash away the smoke and haze. In addition, some scientists say that smoke could even delay the monsoon, which usually arrives in early November.

Types and rates of forest disturbance in Brazilian Legal Amazon, 2000–2013

PubMed Central

Tyukavina, Alexandra; Hansen, Matthew C.; Potapov, Peter V.; Stehman, Stephen V.; Smith-Rodriguez, Kevin; Okpa, Chima; Aguilar, Ricardo

2017-01-01

Deforestation rates in primary humid tropical forests of the Brazilian Legal Amazon (BLA) have declined significantly since the early 2000s. Brazil’s national forest monitoring system provides extensive information for the BLA but lacks independent validation and systematic coverage outside of primary forests. We use a sample-based approach to consistently quantify 2000–2013 tree cover loss in all forest types of the region and characterize the types of forest disturbance. Our results provide unbiased forest loss area estimates, which confirm the reduction of primary forest clearing (deforestation) documented by official maps. By the end of the study period, nonprimary forest clearing, together with primary forest degradation within the BLA, became comparable in area to deforestation, accounting for an estimated 53% of gross tree cover loss area and 26 to 35% of gross aboveground carbon loss. The main type of tree cover loss in all forest types was agroindustrial clearing for pasture (63% of total loss area), followed by small-scale forest clearing (12%) and agroindustrial clearing for cropland (9%), with natural woodlands being directly converted into croplands more often than primary forests. Fire accounted for 9% of the 2000–2013 primary forest disturbance area, with peak disturbances corresponding to droughts in 2005, 2007, and 2010. The rate of selective logging exploitation remained constant throughout the study period, contributing to forest fire vulnerability and degradation pressures. As the forest land use transition advances within the BLA, comprehensive tracking of forest transitions beyond primary forest loss is required to achieve accurate carbon accounting and other monitoring objectives. PMID:28439536

Monitoring Forest and Rangeland Change in the United States Using Landsat Time Series Data

NASA Astrophysics Data System (ADS)

Vogelmann, J.; Tolk, B.; Xian, G. Z.; Homer, C.

2011-12-01

The LANDFIRE project produces spatial data layers for fire management applications. As part of the project, 2000 vintage Landsat Thematic Mapper and Enhanced Thematic Mapper plus data sets were used to generate detailed vegetation type data sets for the entire United States. We are currently using several approaches to update this information, including incorporation of (1) Landsat-derived historic fire burn information, (2) forest harvest information from Landsat time series data using the Vegetation Change Tracker, and (3) data sets that capture subtle and gradual intra-state disturbances, such as those related to insects and disease as well as succession. The primary focus of this presentation will be on of the detection and characterization of gradual change occurring in forest and rangeland ecosystems, and how to incorporate this information in the LANDFIRE updating process. Landsat data acquired over the previous 25+ years are being used to assess status and trends of forest and rangeland condition. Current study areas are located in the southwestern US, western Nebraska, western Wyoming, western South Dakota, northeastern US and the central Appalachian Mountains. Trends of changing vegetation index values derived from Landsat time series data stacks are the foundation for the gradual change information being developed. Thus far we have found evidence of gradual systematic change in all areas that we have examined. Many of the conifer forests in the southwestern US are showing declining conditions related to insects and drought, and very few of the examined areas are showing evidence of increased canopy cover or greenness. While sagebrush communities are showing decreases in greenness related to fire, mining, and drought, few of these communities are showing evidence of increased greenness or "improving" conditions. However, there is evidence that some forest communities are expanding and that canopy cover density is increasing at some locations. In Nebraska, increases in canopy cover appear to be mostly related to expansion of eastern red cedar. In the White Mountains of New Hampshire, observed increases in forest canopy appear to be related to understory balsam fir expansion, most likely related to release of forest suppression resulting from the thinning of the upper forest canopy. Continued analyses of time series data using multi-spatial scenes and covering multiple years are required in order to develop accurate impressions and representations of the changing ecosystem patterns and trends that are occurring. The approach demonstrates that Landsat time series data can be used operationally for assessing gradual ecosystem change across large areas. This information complements the information derived from other time-series change detection used for LANDFIRE.

Climate Change and water in Southwestern North America special feature: water, climate change, and sustainability in the southwest.

PubMed

MacDonald, Glen M

2010-12-14

The current Southwest drought is exceptional for its high temperatures and arguably the most severe in history. Coincidentally, there has been an increase in forest and woodland mortality due to fires and pathogenic outbreaks. Although the high temperatures and aridity are consistent with projected impacts of greenhouse warming, it is unclear whether the drought can be attributed to increased greenhouse gases or is a product of natural climatic variability. Climate models indicate that the 21st century will be increasingly arid and droughts more severe and prolonged. Forest and woodland mortality due to fires and pathogens will increase. Demography and food security dictate that water demand in the Southwest will remain appreciable. If projected population growth is twinned with suburb-centered development, domestic demands will intensify. Meeting domestic demands through transference from agriculture presents concerns for rural sustainability and food security. Environmental concerns will limit additional transference from rivers. It is unlikely that traditional supply-side solutions such as more dams will securely meet demands at current per-capita levels. Significant savings in domestic usage can be realized through decreased applications of potable water to landscaping, but this is a small fraction of total regional water use, which is dominated by agriculture. Technical innovations, policy measures, and market-based solutions that increase supply and decrease water demand are all needed. Meeting 21st-century sustainability challenges in the Southwest will also require planning, cooperation, and integration that surpass 20th-century efforts in terms of geographic scope, jurisdictional breadth, multisectoral engagement, and the length of planning timelines.

Water, climate change, and sustainability in the southwest

PubMed Central

2010-01-01

The current Southwest drought is exceptional for its high temperatures and arguably the most severe in history. Coincidentally, there has been an increase in forest and woodland mortality due to fires and pathogenic outbreaks. Although the high temperatures and aridity are consistent with projected impacts of greenhouse warming, it is unclear whether the drought can be attributed to increased greenhouse gasses or is a product of natural climatic variability. Climate models indicate that the 21st century will be increasingly arid and droughts more severe and prolonged. Forest and woodland mortality due to fires and pathogens will increase. Demography and food security dictate that water demand in the Southwest will remain appreciable. If projected population growth is twinned with suburb-centered development, domestic demands will intensify. Meeting domestic demands through transference from agriculture presents concerns for rural sustainability and food security. Environmental concerns will limit additional transference from rivers. It is unlikely that traditional supply-side solutions such as more dams will securely meet demands at current per-capita levels. Significant savings in domestic usage can be realized through decreased applications of potable water to landscaping, but this is a small fraction of total regional water use, which is dominated by agriculture. Technical innovations, policy measures, and market-based solutions that increase supply and decrease water demand are all needed. Meeting 21st-century sustainability challenges in the Southwest will also require planning, cooperation, and integration that surpass 20th-century efforts in terms of geographic scope, jurisdictional breadth, multisectoral engagement, and the length of planning timelines. PMID:21149704

Quantifying the Causes and Propogation of the 2015 Washington Wildfires

NASA Astrophysics Data System (ADS)

Engel, R.; Marlier, M. E.; Lettenmaier, D. P.

2017-12-01

In the summer of 2015, Washington state experienced wildfires that burned over 450,000 ha, more than five times the average and more than three times the next-most severe fire season in the 30-year record. We examine the confluence of factors that led to the extreme fire season, and evaluate whether 2015 can be used as a predictor of possible future conditions that will be affected by climate warming. In previous work, we have found that 2015 was an extremely warm summer (nearly 1 degree C warmer than the previous year in the 30-year record) but was not particularly anomalous in terms of many other climatic indicators, including reconstructed soil moisture, the Palmer Drought Severity Index (PDSI), and the Canadian Fire Weather Index. However, according to the Dead Fuel Moisture (DFM), a drying index used by the US Forest Service, 2015 was an extreme year of record. The DFM relies on temperature, precipitation, and relative humidity to establish a daily equilibrium moisture content of dead material. We examine both Washington's 2015 fire season and the 30-year fire record with respect to climatology and other potential drivers of fire (e.g. forest health, ignition). Additionally, we explore the role of land cover with respect to fire propagation through the season. While too many potential causes of extreme fires exist to establish a concrete long-term relationship at such a fine scale, we find that the 2015 fire anomaly was at least partially climatically driven.

Climate change and the future of natural disturbances in the central hardwood region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dale, Virginia H; Hughes, M. Joseph; Hayes, Daniel J

The spatial patterns and ecological processes of the southeastern upland hardwood forests have evolved to reflect past climatic conditions and natural disturbance regimes. Changes in climate can lead to disturbances that exceed their natural range of variation, and the impacts of these changes will depend on the vulnerability or resiliency of these ecosystems. Global Circulation Models generally project annual increases in temperature across the southeastern United States over the coming decades, but changes in precipitation are less consistent. Even more unclear is how climate change might affect future trends in the severity and frequency of natural disturbances, such as severemore » storms, fires, droughts, floods, and insect outbreaks. Here, we use a time-series satellite data record to map the spatial pattern and severity of broad classes of natural disturbances the southeast region. The data derived from this map allow analysis of regional-scale trends in natural and anthropogenic disturbances in the region over the last three decades. Throughout the region, between 5% and 25% of forest land is affected by some sort of disturbance each year since 1985. The time series reveals periodic droughts that themselves are widespread and of low severity but are associated with more localized, high-severity disturbances such as fire and insect outbreaks. The map also reveals extensive anthropogenic disturbance across the region in the form of forest conversion related to resource extraction and urban and residential development. We discuss how changes in climate and disturbance regimes might affect southeastern forests in the future via altering the exposure, sensitivity and adaptive capacity of these ecosystems. Changes in climate are highly likely to expose southeastern forests to more frequent and severe disturbances, but ultimately how vulnerable or resilient southeastern forests are to these changes will depend on their sensitivity and capacity to adapt to these novel conditions.« less

Deforestation and climate feedbacks threaten the ecological integrity of south–southeastern Amazonia

PubMed Central

Coe, Michael T.; Marthews, Toby R.; Costa, Marcos Heil; Galbraith, David R.; Greenglass, Nora L.; Imbuzeiro, Hewlley M. A.; Levine, Naomi M.; Malhi, Yadvinder; Moorcroft, Paul R.; Muza, Michel Nobre; Powell, Thomas L.; Saleska, Scott R.; Solorzano, Luis A.; Wang, Jingfeng

2013-01-01

A mosaic of protected areas, including indigenous lands, sustainable-use production forests and reserves and strictly protected forests is the cornerstone of conservation in the Amazon, with almost 50 per cent of the region now protected. However, recent research indicates that isolation from direct deforestation or degradation may not be sufficient to maintain the ecological integrity of Amazon forests over the next several decades. Large-scale changes in fire and drought regimes occurring as a result of deforestation and greenhouse gas increases may result in forest degradation, regardless of protected status. How severe or widespread these feedbacks will be is uncertain, but the arc of deforestation in south–southeastern Amazonia appears to be particularly vulnerable owing to high current deforestation rates and ecological sensitivity to climate change. Maintaining forest ecosystem integrity may require significant strengthening of forest conservation on private property, which can in part be accomplished by leveraging existing policy mechanisms. PMID:23610166

Deforestation and climate feedbacks threaten the ecological integrity of south-southeastern Amazonia.

PubMed

Coe, Michael T; Marthews, Toby R; Costa, Marcos Heil; Galbraith, David R; Greenglass, Nora L; Imbuzeiro, Hewlley M A; Levine, Naomi M; Malhi, Yadvinder; Moorcroft, Paul R; Muza, Michel Nobre; Powell, Thomas L; Saleska, Scott R; Solorzano, Luis A; Wang, Jingfeng

2013-06-05

A mosaic of protected areas, including indigenous lands, sustainable-use production forests and reserves and strictly protected forests is the cornerstone of conservation in the Amazon, with almost 50 per cent of the region now protected. However, recent research indicates that isolation from direct deforestation or degradation may not be sufficient to maintain the ecological integrity of Amazon forests over the next several decades. Large-scale changes in fire and drought regimes occurring as a result of deforestation and greenhouse gas increases may result in forest degradation, regardless of protected status. How severe or widespread these feedbacks will be is uncertain, but the arc of deforestation in south-southeastern Amazonia appears to be particularly vulnerable owing to high current deforestation rates and ecological sensitivity to climate change. Maintaining forest ecosystem integrity may require significant strengthening of forest conservation on private property, which can in part be accomplished by leveraging existing policy mechanisms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genet, Helene; McGuire, A. David; Barrett, K.

There is a substantial amount of carbon stored in the permafrost soils of boreal forest ecosystems, where it is currently protected from decomposition. The surface organic horizons insulate the deeper soil from variations in atmospheric temperature. The removal of these insulating horizons through consumption by fire increases the vulnerability of permafrost to thaw, and the carbon stored in permafrost to decomposition. In this study we ask how warming and fire regime may influence spatial and temporal changes in active layer and carbon dynamics across a boreal forest landscape in interior Alaska. To address this question, we (1) developed and testedmore » a predictive model of the effect of fire severity on soil organic horizons that depends on landscape-level conditions and (2) used this model to evaluate the long-term consequences of warming and changes in fire regime on active layer and soil carbon dynamics of black spruce forests across interior Alaska. The predictive model of fire severity, designed from the analysis of field observations, reproduces the effect of local topography (landform category, the slope angle and aspect and flow accumulation), weather conditions (drought index, soil moisture) and fire characteristics (day of year and size of the fire) on the reduction of the organic layercaused by fire. The integration of the fire severity model into an ecosystem process-based model allowed us to document the relative importance and interactions among local topography, fire regime and climate warming on active layer and soil carbon dynamics. Lowlands were more resistant to severe fires and climate warming, showing smaller increases in active layer thickness and soil carbon loss compared to drier flat uplands and slopes. In simulations that included the effects of both warming and fire at the regional scale, fire was primarily responsible for a reduction in organic layer thickness of 0.06 m on average by 2100 that led to an increase in active layer thickness of 1.1 m on average by 2100. The combination of warming and fire led to a simulated cumulative loss of 9.6 kgC m 2 on average by 2100. Our analysis suggests that ecosystem carbon storage in boreal forests in interior Alaska is particularly vulnerable, primarily due to the combustion of organic layer thickness in fire and the related increase in active layer thickness that exposes previously protected permafrost soil carbon to decomposition.« less

Long-term Observations of Ecohydrology, Climate, Energy Fluxes, and Eddy Covariance Error in a Large, Semiarid Floodplain

NASA Astrophysics Data System (ADS)

Cleverly, J. R.; Thibault, J. R.; Dahm, C. N.; Allred Coonrod, J. E.; Slusher, M.; Teet, S.; Schuetz, J.

2008-12-01

Some of the highest rates of water and energy fluxes between terrestrial ecosystems and the atmosphere occur over large floodplains in arid and semiarid areas. Often located in high-pressure zones near 35 degrees latitude, abundant radiation and easily accessible groundwater contribute few limitations on growth and production in desert phreatophytes. Desert regions typically undergo cycles of drought and floods, and phreatophytic communities wax or wane in cover, density, and structure with cumulative species responses to timing and severity in these regional weather cycles. The Rio-ET Laboratory at the University of New Mexico has been collecting long-term data from a flux network of riparian monitoring stations, mounted on towers along the Middle Rio Grande. Ongoing measurements of energy, water and carbon dioxide fluxes, groundwater dynamics, meteorology, leaf area index, and community dynamics began at some locations in 1999. Recent reanalysis of the flux dataset was performed in which error correction procedures were compared to each and other and in relation to an irrigated crop under advection. Most riparian sites exhibited stable atmospheric stratification and an energy balance consistent with evaporative cooling. Evaporative cooling was more prominent in the late afternoon and evening, during wet conditions. Reduced latent heat fluxes were observed in a cottonwood forest following restoration and fire, but only in years when the forest floor was not re-vegetated by opportunistic annuals or target removal species. Water use by riparian phreatophytes was 1) non-responsive to drought during the monsoon season (non-native Russian olive and monospecific saltcedar communities), 2) responded negatively to monsoon-season drought (xeroriparian saltcedar and saltgrass mosaic community), or 3) responded positively to monsoon-season drought (cottonwood forests). Water salvage related to ecological restoration is dependent upon restoration strategy, emphasizing the importance of due diligent followup to prevent unintentional re-vegetation of the site. Restoration of monospecific saltcedar provides the greatest opportunity for water salvage although restoration of cottonwood forests through removal of densely-packed non-native understory results in marginal water salvage. Benefits of ecosystem restoration increase with drought and during the period of explosive growth following a period of prolonged drought.

Drought differentially affects the post-fire dynamics of seeders and resprouters in a Mediterranean shrubland.

PubMed

Parra, Antonio; Moreno, José M

2018-06-01

In fire-prone ecosystems, changes in rainfall after fire could differentially affect seeders and resprouters, thus leading to long-lasting impacts on the vegetation. Climate change in the Mediterranean region is projected to reduce precipitation, expand the summer drought and increase fire danger. Understanding the sensitivity to changes in rainfall during the post-fire regeneration stage is critical to anticipate the impacts of climate change on Mediterranean-type areas of the world. Here, we investigated how species differing in post-fire regeneration strategy (seeders vs resprouters) responded to rainfall changes in a Cistus-Erica shrubland of central Spain. Drought treatments were implemented using a system of automatic rainout shelters with an irrigation facility before (one season) and after (four years) burning a set of experimental plots. Treatments applied were: environmental control (natural rainfall), historical control (mimicking the long-term rainfall), moderate drought (-25% rainfall), and severe drought (-45% rainfall). Plant demography and vigour (main woody shrubs), as well as abundance (shrubs and herbs) were monitored during the first four years after fire. The first post-fire year was the key period for the recovery of seeders (Cistus ladanifer and Rosmarinus officinalis), and their recruitment, cover and size significantly decreased with drought. However, density four years after fire was larger than unburned and it was significantly correlated with emergence during the first year, indicating that population controls were more on emergence than on establishment. In contrast, resprouters (Erica arborea, Erica scoparia and Phillyrea angustifolia) were hardly affected by drought. Plant community dynamics in the burned control plots progressively converged with the unburned ones, while that in the drought-treated plots lagged behind them, maintaining a higher cover, richness and diversity of herbs. This post-fire "herbalization" due to drought might facilitate an untimely fire, before seeders would reach sexual maturity, which could have major implications for the maintenance of the community. Copyright © 2018 Elsevier B.V. All rights reserved.

Forest fires and environmental haze in Southeast Asia: using the 'stakeholder' approach to assign costs and responsibilities.

PubMed

Quah, E; Johnston, D

2001-10-01

The 'seasonal haze' problem is one which afflicts large parts of Southeast Asia in years of drought. The major cause is forest, bush and field fires in the states of Kalimantan and Sumatra in Indonesia, and to a lesser extent in Sabah, Sarawak, and other parts of Malaysia. Almost all of these fires now seem preventable, since they are intentionally set to clear land for cultivation. Theoretically, the government authorities at central, provincial and local levels in these countries should be responsible for controlling activities in their territory. In practice, however, air pollution control through regulatory policies and practices is extraordinarily difficult to implement and maintain in a situation of this kind in developing countries, especially at a time of crippling economic setbacks. Moreover, the establishment of legal liability, through an international tribunal or otherwise, hardly seems a politically feasible course of action for the government of an affluent 'victim state' such as Singapore. Faith in the usual solutions--science, regulation, law and diplomacy--is weakened by one's sense of current realities. The purpose of this paper is to review the issues and suggested responses, the cost implications of each, the responsibilities as well as entitlements that might apply to the various stakeholders, and the special role of Singapore as an affluent 'victim state'. We also discuss the incentive mechanisms that would be needed to manage forest fires.

Challenges to Sierra Nevada forests and their local communities: An observational and modeling perspective

NASA Astrophysics Data System (ADS)

Schmidt, Cynthia L.

Global forests are experiencing dramatic changes due to changes in climate as well as anthropogenic activities. Increased warming is causing the advancement of some species upslope and northward, while it is also causing widespread mortality due to increased drought conditions. In addition, increasing human population in mountain regions is resulting in elevated risk of human life and property loss due to larger and more severe wildfires. My research focuses on assessing the current vulnerability of forests and their communities in the Sierra Nevada, and how forests are projected to change in the future based on different climate change scenarios. In the first chapter I use Landsat satellite imagery to identify and attribute cause of forest disturbance between 1985 and 2011, primarily focusing on disturbances due to insect, diseases and drought. The change-detection algorithm, Landtrendr, was successfully used to identify forest disturbance, but identifying cause of disturbance was challenging due to the spectral similarities between disturbance types. Landtrendr was most successful in identifying disturbance due to insect, disease and drought in the San Bernardino National Forest, where there is little forest management activity. In the second chapter, I assess whether state or local land use policies in high-fire prone regions exist to reduce the vulnerability of residential developments to wildfire. Three specific land-use tools associated with reducing wildfire vulnerability are identified: (1) buffers around developments; (2) clustered developments; (3) restricting construction on slopes greater than 25%. The study also determines whether demographic and physical characteristics of selected California counties were related to implementing land use policies related to reducing wildfire vulnerability. Results indicate that land use policies related to preventing wildfire-related losses focus on building materials, road access, water availability and vegetation management, not the three identified land-use tools. San Diego County, the county that has experienced the most devastating fires, had the highest percentage of residential developments with both clustering and buffering. The third chapter focuses on future forest conditions. I used a Dynamic Global Vegetation Model (DGVM) to assess future vegetation dynamics and productivity under changing climate and atmospheric CO2 concentrations in the Sierra Nevada. Model results suggest that Temperate Broadleaved Evergreen Plant Functional Types (PFTs) will move upslope and eastward, replacing Temperate Needleleaved PFTs. Boreal Needleleaved Evergreen PFTs, found primarily at higher elevations, will decline dramatically as temperatures continue to increase. Gross Primary Productivity (GPP) will increase as atmospheric CO2 concentration increases, due primarily to the increase in the more productive broadleaved PFTs. Forest ecosystems play an important role in maintaining climate stability at the regional and global scales as a vital carbon sink, so understanding the role of disturbance and climate change will be vital to both scientists and policy makers in the future.

The influence of prefire tree growth and crown condition on postfire mortality of sugar pine following prescribed fire in Sequoia National Park

USGS Publications Warehouse

Nesmith, Jonathan C. B.; Das, Adrian J.; O'Hara, Kevin L.; van Mantgem, Phillip J.

2015-01-01

Tree mortality is a vital component of forest management in the context of prescribed fires; however, few studies have examined the effect of prefire tree health on postfire mortality. This is especially relevant for sugar pine (Pinus lambertiana Douglas), a species experiencing population declines due to a suite of anthropogenic factors. Using data from an old-growth mixed-conifer forest in Sequoia National Park, we evaluated the effects of fire, tree size, prefire radial growth, and crown condition on postfire mortality. Models based only on tree size and measures of fire damage were compared with models that included tree size, fire damage, and prefire tree health (e.g., measures of prefire tree radial growth or crown condition). Immediately following the fire, the inclusion of different metrics of prefire tree health produced variable improvements over the models that included only tree size and measures of fire damage, as models that included measures of crown condition performed better than fire-only models, but models that included measures of prefire radial growth did not perform better. However, 5 years following the fire, sugar pine mortality was best predicted by models that included measures of both fire damage and prefire tree health, specifically, diameter at breast height (DBH, 1.37 m), crown scorch, 30-year mean growth, and the number of sharp declines in growth over a 30-year period. This suggests that factors that influence prefire tree health (e.g., drought, competition, pathogens, etc.) may partially determine postfire mortality, especially when accounting for delayed mortality following fire.

The role of fire-return interval and season of burn in snag dynamics in a south Florida slash pine forest

USGS Publications Warehouse

Lloyd, John D.; Slater, Gary L.; Snyder, James R.

2012-01-01

Standing dead trees, or snags, are an important habitat element for many animal species. In many ecosystems, fire is a primary driver of snag population dynamics because it can both create and consume snags. The objective of this study was to examine how variation in two key components of the fire regime—fire-return interval and season of burn—affected population dynamics of snags. Using a factorial design, we exposed 1 ha plots, located within larger burn units in a south Florida slash pine (Pinus elliottii var. densa Little and Dorman) forest, to prescribed fire applied at two intervals (approximately 3-year intervals vs. approximately 6-year intervals) and during two seasons (wet season vs. dry season) over a 12- to 13-year period. We found no consistent effect of fire season or frequency on the density of lightly to moderately decayed or heavily decayed snags, suggesting that variation in these elements of the fire regime at the scale we considered is relatively unimportant in the dynamics of snag populations. However, our confidence in these findings is limited by small sample sizes, potentially confounding effects of unmeasured variation in fire behavior and effects (e.g., intensity, severity, synergy with drought cycles) and wide variation in responses within a treatment level. The generalizing of our findings is also limited by the narrow range of treatment levels considered. Future experiments incorporating a wider range of fire regimes and directly quantifying fire intensity would prove useful in identifying more clearly the role of fire in shaping the dynamics of snag populations.

Diverse responses of different structured forest to drought in Southwest China through remotely sensed data

NASA Astrophysics Data System (ADS)

Xu, Peipei; Zhou, Tao; Zhao, Xiang; Luo, Hui; Gao, Shan; Li, Zheng; Cao, Leyao

2018-07-01

Global climate change leads to gradual increases in the frequency, intensity, and duration of extreme drought events. Human activities such as afforestation and deforestation have led to spatial variation in forest structure, causing forests to exhibit an age-spatial structure relationship. Thus, it is of great importance to accurately evaluate the effects of drought stress on forest ecosystems with different forest age structures. Because the spatial heterogeneity varies with drought stress intensity, forest age, there are still a lot of uncertainties in current studies. In this study, based on the field measurement, and the proxy index of stand age (based on forest canopy height from LiDAR and stock volume from inventory) at the regional scale, we analyzed the different drought responses of forest ecosystems with various forest ages across different scales in Yunnan province, southwest China from 2001 to 2014. At the local scale, significant differences in the effects of drought stress were found among forests with various ages, suggesting that older forests suffer more under drought stress than younger forests. At the regional scale, the investigation statistics of forest damage indicated a maximum damage ratio in the forest with tall trees (>32 m), whereas damage was minimal in the forest with short trees (<25 m). The stock volume of the forest exhibited the same pattern, that is, the forest damage ratio increased as the stock volume increased. These data demonstrate that the responses of forest drought could be affected by forest age. Under drought stress, older forests show greater vulnerability and risk of damage, which will require special attention for forest managers, as well as improved risk assessments, in the context of future climate change.

Smoke pollution disrupted biodiversity during the 2015 El Niño fires in Southeast Asia

NASA Astrophysics Data System (ADS)

Y-H Lee, Benjamin P.; Davies, Zoe G.; Struebig, Matthew J.

2017-09-01

Forest and peatland fires during the 2015 El Niño drought were amongst the worst on record in Southeast Asia. They were a major contributor of carbon emissions across the region, with the associated smoke-induced haze causing an air pollution crisis that affected millions of people. We present evidence of air pollution impacts on biodiversity. Using daily acoustic recordings in central Singapore, we monitored the dawn chorus before, during and after the haze event. We demonstrate that levels of ecological community acoustic activity dropped dramatically during the haze, and that this decline was significantly associated with levels of air pollution considered ‘unhealthy’ to the human population. Acoustic disruption was apparent across four common indices of soundscape activity, with only a partial recovery to pre-haze levels observed 16 weeks after the smoke had dissipated. These impacts on ecological communities were likely to be even more severe closer to the fires, where air pollution levels were reported to be 15-fold greater than those recorded in Singapore. Our results indicate that large-scale air pollution crises may have hitherto underestimated and potentially far-reaching impacts on biodiversity, especially in parts of the world prone to extensive forest fires.

Water stress assessment of cork oak leaves and maritime pine needles based on LIF spectra

NASA Astrophysics Data System (ADS)

Lavrov, A.; Utkin, A. B.; Marques da Silva, J.; Vilar, Rui; Santos, N. M.; Alves, B.

2012-02-01

The aim of the present work was to develop a method for the remote assessment of the impact of fire and drought stress on Mediterranean forest species such as the cork oak ( Quercus suber) and maritime pine ( Pinus pinaster). The proposed method is based on laser induced fluorescence (LIF): chlorophyll fluorescence is remotely excited by frequency-doubled YAG:Nd laser radiation pulses and collected and analyzed using a telescope and a gated high sensitivity spectrometer. The plant health criterion used is based on the I 685/ I 740 ratio value, calculated from the fluorescence spectra. The method was benchmarked by comparing the results achieved with those obtained by conventional, continuous excitation fluorometric method and water loss gravimetric measurements. The results obtained with both methods show a strong correlation between them and with the weight-loss measurements, showing that the proposed method is suitable for fire and drought impact assessment on these two species.

Approaches to modeling landscape-scale drought-induced forest mortality

USGS Publications Warehouse

Gustafson, Eric J.; Shinneman, Douglas

2015-01-01

Drought stress is an important cause of tree mortality in forests, and drought-induced disturbance events are projected to become more common in the future due to climate change. Landscape Disturbance and Succession Models (LDSM) are becoming widely used to project climate change impacts on forests, including potential interactions with natural and anthropogenic disturbances, and to explore the efficacy of alternative management actions to mitigate negative consequences of global changes on forests and ecosystem services. Recent studies incorporating drought-mortality effects into LDSMs have projected significant potential changes in forest composition and carbon storage, largely due to differential impacts of drought on tree species and interactions with other disturbance agents. In this chapter, we review how drought affects forest ecosystems and the different ways drought effects have been modeled (both spatially and aspatially) in the past. Building on those efforts, we describe several approaches to modeling drought effects in LDSMs, discuss advantages and shortcomings of each, and include two case studies for illustration. The first approach features the use of empirically derived relationships between measures of drought and the loss of tree biomass to drought-induced mortality. The second uses deterministic rules of species mortality for given drought events to project changes in species composition and forest distribution. A third approach is more mechanistic, simulating growth reductions and death caused by water stress. Because modeling of drought effects in LDSMs is still in its infancy, and because drought is expected to play an increasingly important role in forest health, further development of modeling drought-forest dynamics is urgently needed.

Santa Ana Winds and Fire Regimes of Southern California National Forests

NASA Astrophysics Data System (ADS)

Bendix, J.

2015-12-01

In Southern California, it has long been understood that foehn-type Santa Ana winds are an important factor in the occurrence of large wildfires. Although a variety of anecdotal observations and statistical analyses have confirmed the importance of these winds to wildfire, particularly in the Fall months when Santa Ana winds overlap with dry fuels from summer drought, many of the details of those winds' impacts on fire remain obscure. This paper uses data regarding individual fires from California's Fire and Resource Assessment Program database and a compilation of Santa Ana Wind days (SAW days) published by Abatzoglou et al. in 2013 to assess the relationship of Santa Ana winds to fire occurrence and size in Southern California. The analysis included 474 fires larger than 20 ha (~50 acres).that burned on the four Southern California national forests (Angeles, Cleveland, Los Padres and San Bernardino) between 1948 and 2010. Overall, just 10.3% of the fires started on SAW days, and 14.4% experienced at least one SAW day between start and containment dates. The impact of Santa Ana winds is greater, however, with increasing fire size. For fires > 4000 ha, 18.4% began on SAW days, with 30.4% experiencing at least one SAW day before containment. And 20% of fires > 20000 ha started on SAW days, with 50% including one or more SAW days. Fires beginning on SAW days were larger, with a mean of 6239 ha compared to 2150 ha for fires that began on non-SAW days. Only 2% of the fires that began on SAW days were started by lightning, suggesting that the impact of Santa Ana winds on Southern California fire regimes may be enhanced by humans' role in ignitions.

Adaptive management of forest fires in periurban areas in the Federal District, Brazil: A case study from the Urubu Valley rural community

Treesearch

Gabriel Constantino Zacharias; Renata Marson Teixeira de Andrade

2013-01-01

In a climate change scenario, where global warming increases the critical period of drought, the risk of wildfire is expected to increase. In the Federal District (DF) - Brazil, wildfire in periruban areas have economic, financial, environmental and public health significance, however it is poorly studied. Thus, one wonders if the DF is prepared to deal with the higher...

Forests growing under dry conditions have higher hydrological resilience to drought than do more humid forests.

PubMed

Helman, David; Lensky, Itamar M; Yakir, Dan; Osem, Yagil

2017-07-01

More frequent and intense droughts are projected during the next century, potentially changing the hydrological balances in many forested catchments. Although the impacts of droughts on forest functionality have been vastly studied, little attention has been given to studying the effect of droughts on forest hydrology. Here, we use the Budyko framework and two recently introduced Budyko metrics (deviation and elasticity) to study the changes in the water yields (rainfall minus evapotranspiration) of forested catchments following a climatic drought (2006-2010) in pine forests distributed along a rainfall gradient (P = 280-820 mm yr -1 ) in the Eastern Mediterranean (aridity factor = 0.17-0.56). We use a satellite-based model and meteorological information to calculate the Budyko metrics. The relative water yield ranged from 48% to 8% (from the rainfall) in humid to dry forests and was mainly associated with rainfall amount (increasing with increased rainfall amount) and bedrock type (higher on hard bedrocks). Forest elasticity was larger in forests growing under drier conditions, implying that drier forests have more predictable responses to drought, according to the Budyko framework, compared to forests growing under more humid conditions. In this context, younger forests were shown more elastic than older forests. Dynamic deviation, which is defined as the water yield departure from the Budyko curve, was positive in all forests (i.e., less-than-expected water yields according to Budyko's curve), increasing with drought severity, suggesting lower hydrological resistance to drought in forests suffering from larger rainfall reductions. However, the dynamic deviation significantly decreased in forests that experienced relatively cooler conditions during the drought period. Our results suggest that forests growing under permanent dry conditions might develop a range of hydrological and eco-physiological adjustments to drought leading to higher hydrological resilience. In the context of predicted climate change, such adjustments are key factors in sustaining forested catchments in water-limited regions. © 2016 John Wiley & Sons Ltd.

Tree diversity does not always improve resistance of forest ecosystems to drought.

PubMed

Grossiord, Charlotte; Granier, André; Ratcliffe, Sophia; Bouriaud, Olivier; Bruelheide, Helge; Chećko, Ewa; Forrester, David Ian; Dawud, Seid Muhie; Finér, Leena; Pollastrini, Martina; Scherer-Lorenzen, Michael; Valladares, Fernando; Bonal, Damien; Gessler, Arthur

2014-10-14

Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year (Δδ(13)CS). Δδ(13)CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the drought exposure of the ecosystem. However, the other three forest types were unaffected by tree species diversity. We conclude that higher diversity enhances resistance to drought events only in drought-prone environments. Managing forest ecosystems for high tree species diversity does not necessarily assure improved adaptability to the more severe and frequent drought events predicted for the future.

Avian demographic responses to drought and fire: a community-level perspective.

PubMed

Saracco, James F; Fettig, Stephen M; San Miguel, George L; Mehlman, David W; Albert, Steven K

2018-05-22

Drought stress is an important consideration for wildlife in arid and semiarid regions under climate change. Drought can impact plant and animal populations directly, through effects on their physiology, as well as indirectly through effects on vegetation productivity and resource availability, and by creating conditions conducive to secondary disturbance, such as wildfire. We implemented a novel approach to understanding community-level demographic responses of birds and their habitats to these stressors in the context of climate change at 14 study sites in the Four Corners region of the southwestern United States. A large wildfire affecting three of the sites provided a natural experiment for also examining fire effects on vegetation and the bird community. We assessed (1) trends in drought and end-of-century (2071-2100) predicted average drought conditions under mid-range and high greenhouse gas concentration trajectory scenarios; (2) effects of drought and fire on habitat (vegetation greenness); and (3) effects of drought and fire on community-level avian productivity and adult apparent survival rates. Drought has increased and is expected to increase further at our study sites under climate change. Under spring drought conditions, vegetation greenness and avian productivity declined, while summer drought appeared to negatively affect adult apparent survival rates. Response to fire was mixed; in the year of the fire, avian productivity declined, but was higher than normal for several years post-fire. Our results highlight important links between environmental stressors and avian vital rates that will likely affect population trajectories in this region under climate change. We suggest that the use and continued development of community-level demographic models will provide useful tool for leveraging sparse species-level data to provide multi-species inferences and inform conservation. © 2018 by the Ecological Society of America.

Fire-climate-human interactions during the postglacial period at Sunrise Ridge, Mount Rainier National Park, Washington (USA)

NASA Astrophysics Data System (ADS)

Walsh, Megan K.; Lukens, Michael L.; McCutcheon, Patrick T.; Burtchard, Greg C.

2017-12-01

With the creation of Mount Rainier National Park (MORA) in 1899 came the active management of the park's landscapes and a heavy emphasis on fire suppression. Today, managers at MORA seek to better manage current fire activity; however, this requires an improved understanding of past fire activity on the mountain. In this study high-resolution macroscopic charcoal analysis and pollen analysis of lake sediment records was used to reconstruct the postglacial fire and vegetation history for the Sunrise Ridge area of MORA. Fire activity was lowest during the Late Glacial when vegetation was sparse and climate was cool and dry. Fire activity increased during the early Holocene as the regional climate warmed and dried, and burnable biomass became more abundant. Fire activity continued to increase into the middle Holocene (until ca. 6600 cal yr BP) even as the regional climate became wetter and eventually cooler; the modern-day mesic forest and subalpine meadow landscapes of the park established at this time. Fire activity was generally highest and mean fire return intervals were lowest on Sunrise Ridge during the late Holocene, and are consistent with tree-ring based estimates of fire frequency. The similarity between the Sunrise Ridge and other paleofire records in the Pacific Northwest suggests that broad-scale climatic shifts, such as the retreat of the Cordilleran ice sheet and changes in annual insolation, as well as increased interannual climate variability (i.e., drought) particularly in the middle to late Holocene, were responsible for changes in fire activity during the postglacial period. However, abundant and increasing archaeological evidence from Sunrise Ridge during the middle to late Holocene suggests that humans may have also influenced the landscape at this time. It is likely that fires will continue to increase at MORA as drought becomes a more frequent occurrence in the Pacific Northwest.

Post-fire environments are favourable for plant functioning of seeder and resprouter Mediterranean shrubs, even under drought.

PubMed

Parra, Antonio; Moreno, José M

2017-05-01

Understanding how drought affects seeder and resprouter plants during post-fire regeneration is important for the anticipation of Mediterranean vegetation vulnerability in a context of increasing drought and fire caused by climate change. A Mediterranean shrubland was subjected to various drought treatments (including 45% rainfall reduction, 7 months drought yr -1 ), before and after experimental burning, by means of a rainout-shelter system with an irrigation facility. Predawn shoot water potential (Ψ pd ), relative growth rate (RGR), specific leaf area (SLA) and bulk leaf carbon isotopic composition (δ 13 C) were monitored in the main woody species during the first 3 yr after fire. Cistus ladanifer seedlings showed higher Ψ pd , RGR and SLA, and lower δ 13 C, than unburned plants during the first two post-fire years. Seedlings under drought maintained relatively high Ψ pd , but suffered a decrease in Ψ pd and RGR, and an increase in δ 13 C, relative to control treatments. Erica arborea, E. scoparia and Phillyrea angustifolia resprouts had higher Ψ pd and RGR than unburned plants during the first post-fire year. Resprouters were largely unaffected by drought. Overall, despite marked differences between the two functional groups, post-fire environments were favourable for plant functioning of both seeder and resprouter shrubs, even under the most severe drought conditions implemented. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Cropland management dynamics as a driver of forest cover change in European Russia (Invited)

NASA Astrophysics Data System (ADS)

Tyukavina, A.; Krylov, A.; Potapov, P.; Turubanova, S.; Hansen, M.; McCarty, J. L.

2013-12-01

The European part of Russia spans over 40% of the European subcontinent and comprises most of Europe's temperate and boreal forests. The region has undergone a socio-economic transition during the last two decades that has resulted in radical changes in land management. Large-scale agriculture land abandonment caused massive afforestation in the Central and Northern parts of the region (Alcantara et al. 2012). Afforestation of former croplands is currently not included in the official forestry statistical reports (Potapov et al. 2012), but is likely to have major impacts on regional carbon budgets (Kuemmerle et al. 2009). We employed a complete archive of Landsat TM and ETM+ imagery and automatic data processing algorithm to create regional time-sequential image composites and multi-temporal metrics for 1985-2012. Spectral metrics were used as independent variables to map forest cover and change with help of supervised machine learning algorithms and trend analysis. Forest cover loss was attributed to fires, harvesting, and wind/disease dynamics, while forest cover gain was disaggregated into reforestation and afforestation using pre-1990 TM imagery as baseline data. Special attention was paid to agricultural abandonment. Fire events of the last decade have been further characterized by ignition place, time, and burning intensity using MODIS fire detection data. Change detection products have been validated using field data collected during summer 2012 and 2013 and high resolution imagery. Massive arable land abandonment caused forest area increase within Central agricultural regions. While total logging area decreased after the USSR breakdown, logging and other forms of clearing increased within the Central and Western parts of the region. Gross forest gain and loss were nearly balanced within region; however, the most populated regions of European Russia featured the highest rate of net forest cover loss during the last decade. The annual burned forest area as well as area of windstorms damage significantly increased, especially in the Central regions. Fires predominantly affected pine forests and drained peatlands prone to summer droughts. Fire date and ignition analysis showed that forest fires are not related to extensive spring-time agricultural burning. References: Alcantara, C., T. Kuemmerle, A. V. Prishchepov & V. C. Radeloff. 2012. Mapping abandoned agriculture with multi-temporal MODIS satellite data. 334-347. Remote Sensing of Environment. Kuemmerle, T., O. Chaskovskyy, J. Knorn, V. C. Radeloff, I. Kruhlov, W. S. Keeton & P. Hostert. 2009. Forest cover change and illegal logging in the Ukrainian Carpathians in the transition period from 1988 to 2007. Remote Sensing of Environment, 113, 1194-1207. Potapov, P., S. Turubanova, I. Zhuravleva, M. Hansen, A. Yaroshenko & A. Manisha. 2012. Forest Cover Change within the Russian European North after the Breakdown of Soviet Union (1990-2005) 1-11. International Journal of Forestry Research.

A belowground perspective on the drought sensitivity of forests: Towards improved understanding and simulation

DOE PAGES

Phillips, Richard P.; Ibanez, Ines; D’Orangeville, Loic; ...

2016-09-13

Predicted increases in the frequency and intensity of droughts across the temperate biome have highlighted the need to examine the extent to which forests may differ in their sensitivity to water stress. At present, a rich body of literature exists on how leaf- and stem-level physiology influence tree drought responses; however, less is known regarding the dynamic interactions that occur below ground between roots and soil physical and biological factors. Hence, there is a need to better understand how and why processes occurring below ground influence forest sensitivity to drought. Here, we review what is known about tree species’ belowmore » ground strategies for dealing with drought, and how physical and biological characteristics of soils interact with rooting strategies to influence forest sensitivity to drought. Then, we highlight how a below ground perspective of drought can be used in models to reduce uncertainty in predicting the ecosystem consequences of droughts in forests. Lastly, we describe the challenges and opportunities associated with managing forests under conditions of increasing drought frequency and intensity, and explain how a below ground perspective on drought may facilitate improved forest management.« less

A belowground perspective on the drought sensitivity of forests: Towards improved understanding and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Richard P.; Ibanez, Ines; D’Orangeville, Loic

Predicted increases in the frequency and intensity of droughts across the temperate biome have highlighted the need to examine the extent to which forests may differ in their sensitivity to water stress. At present, a rich body of literature exists on how leaf- and stem-level physiology influence tree drought responses; however, less is known regarding the dynamic interactions that occur below ground between roots and soil physical and biological factors. Hence, there is a need to better understand how and why processes occurring below ground influence forest sensitivity to drought. Here, we review what is known about tree species’ belowmore » ground strategies for dealing with drought, and how physical and biological characteristics of soils interact with rooting strategies to influence forest sensitivity to drought. Then, we highlight how a below ground perspective of drought can be used in models to reduce uncertainty in predicting the ecosystem consequences of droughts in forests. Lastly, we describe the challenges and opportunities associated with managing forests under conditions of increasing drought frequency and intensity, and explain how a below ground perspective on drought may facilitate improved forest management.« less

Competition amplifies drought stress in forests across broad climatic and compositional gradients

USGS Publications Warehouse

Gleason, Kelly; Bradford, John B.; Bottero, Alessandra; D'Amato, Tony; Fraver, Shawn; Palik, Brian J.; Battaglia, Michael; Iverson, Louis R.; Kenefic, Laura; Kern, Christel C.

2017-01-01

Forests around the world are experiencing increasingly severe droughts and elevated competitive intensity due to increased tree density. However, the influence of interactions between drought and competition on forest growth remains poorly understood. Using a unique dataset of stand-scale dendrochronology sampled from 6405 trees, we quantified how annual growth of entire tree populations responds to drought and competition in eight, long-term (multi-decadal), experiments with replicated levels of density (e.g., competitive intensity) arrayed across a broad climatic and compositional gradient. Forest growth (cumulative individual tree growth within a stand) declined during drought, especially during more severe drought in drier climates. Forest growth declines were exacerbated by high density at all sites but one, particularly during periods of more severe drought. Surprisingly, the influence of forest density was persistent overall, but these density impacts were greater in the humid sites than in more arid sites. Significant density impacts occurred during periods of more extreme drought, and during warmer temperatures in the semi-arid sites but during periods of cooler temperatures in the humid sites. Because competition has a consistent influence over growth response to drought, maintaining forests at lower density may enhance resilience to drought in all climates.

Extreme Fire Severity Patterns in Topographic, Convective and Wind-Driven Historical Wildfires of Mediterranean Pine Forests

PubMed Central

Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

2014-01-01

Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme severity wildfires. PMID:24465492

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

PubMed

Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

2014-01-01

Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme severity wildfires.

A 6900-year history of landscape modification by humans in lowland Amazonia

NASA Astrophysics Data System (ADS)

Bush, M. B.; Correa-Metrio, A.; McMichael, C. H.; Sully, S.; Shadik, C. R.; Valencia, B. G.; Guilderson, T.; Steinitz-Kannan, M.; Overpeck, J. T.

2016-06-01

A sedimentary record from the Peruvian Amazon provided evidence of climate and vegetation change for the last 6900 years. Piston cores collected from the center of Lake Sauce, a 20 m deep lake at 600 m elevation, were 19.7 m in length. The fossil pollen record showed a continuously forested catchment within the period of the record, although substantial changes in forest composition were apparent. Fossil charcoal, found throughout the record, was probably associated with humans setting fires. Two fires, at c. 6700 cal BP and 4270 cal BP, appear to have been stand-replacing events possibly associated with megadroughts. The fire event at 4270 cal BP followed a drought that caused lowered lake levels for several centuries. The successional trajectories of forest recovery following these large fires were prolonged by smaller fire events. Fossil pollen of Zea mays (cultivated maize) provided evidence of agricultural activity at the site since c. 6320 cal BP. About 5150 years ago, the lake deepened and started to deposit laminated sediments. Maize agriculture reached a peak of intensity between c. 3380 and 700 cal BP. Fossil diatom data provided a proxy for lake nutrient status and productivity, both of which peaked during the period of maize cultivation. A marked change in land use was evident after c. 700 cal BP when maize agriculture was apparently abandoned at this site. Iriartea, a hyperdominant of riparian settings in western Amazonia, increased in abundance within the last 1100 years, but declined markedly at c. 1070 cal BP and again between c. 80 and -10 cal BP.

The Burning of Surface and Deep Peat during Boreal Forest and Peatland Fires: Implications for Fire Behaviour and Global Carbon Cycling

NASA Astrophysics Data System (ADS)

Turetsky, M. R.

2015-12-01

Fire is increasingly appreciated as a threat to peatlands and their carbon stocks. The global peatland carbon pool exceeds that of global vegetation and is similar to the current atmospheric carbon pool. Under pristine conditions, most of the peat carbon stock is protected from burning, and resistance to fire has increased peat carbon storage in high latitude regions over long time scales. This, in part, is due to the high porosity and storage coefficient of surface peat, which minimizes water table variability and maintains wet conditions even during drought. However, higher levels of disturbance associated with warming and increasing human activities are triggering state changes and the loss of resiliency in some peatland systems. This presentation will summarize information on burn area and severity in peatlands under undisturbed scenarios of hydrologic self-regulation, and will assess the consequences of warming and drying on peatland vegetation and wildfire behaviour. Our goal is to predict where and when peatlands will become more vulnerable to deep smouldering, given the importance of deep peat layers to global carbon cycling, permafrost stability, and a variety of other ecosystem services in northern regions. Results from two major wildfire seasons (2004 in Alaska and 2014 in the Northwest Territories) show that biomass burning in peatlands releases similar amounts of carbon to the atmosphere as patterns of burning in upland forests, but that peatlands are less vulnerable to severe burning that tends to occur in boreal forests during late season fire activity.

Construction of Open Burning Facility Moody Air Force Base, Georgia Environmental Assessment and Finding of No Significant Impact

DTIC Science & Technology

2009-01-01

are smaller and more leathery, and the leaf canopy is less dense. The trees commonly found in the southeastern United States are pines ( Pinus spp...during periods of extreme drought . These periodic fires maintained the pine subclimax forest by controlling hardwood competition, encouraged the growth...cinnamomea), chain fern (Woodwardia virginica), and greenbrier (Smilax spp). In the transition areas from wetlands to uplands, pond pine ( Pinus serotina

An improved method for standardized mapping of drought conditions

Treesearch

Frank H. Koch; William D. Smith; John W. Coulston

2013-01-01

Virtually all U.S. forests experience droughts, although the intensity and frequency of the droughts vary widely between, as well as, within forest ecosystems (Hanson and Weltzin 2000). Generally, forests throughout the Western United States are subject to annual seasonal droughts, while forests in the Eastern United States can be characterized by one of two...

Recent drought conditions in the Conterminous United States

Treesearch

Frank H. Koch; William D. Smith; John W. Coulston

2013-01-01

Droughts are common in virtually all U.S. forests, but their frequency and intensity vary widely both between and within forest ecosystems (Hanson and Weltzin 2000). Forests in the Western United States generally exhibit a pattern of annual seasonal droughts. Forests in the Eastern United States tend to exhibit one of two prevailing patterns: random occasional droughts...

Characterizing Drought and Vegetation Response at the Forest Line in Hawai`i

NASA Astrophysics Data System (ADS)

Frazier, A. G.; Crausbay, S.; Brewington, L.; Giambelluca, T. W.

2016-12-01

Globally, montane treelines are thought to be controlled by low-temperature limitations. The upper limit of cloud forest on Haleakalā, Maui, however, is hypothesized to be controlled by moisture limitations, particularly drought events. Drought in Hawai`i is largely driven by El Niño and future projections show an increased frequency of extreme El Niño events, which may ultimately lower the forest line and threaten biodiversity in Hawai`i. This study aims to characterize the drought regime at the forest line ecotone in Hawai`i since 1920, investigate the role of the El Niño-Southern Oscillation (ENSO), and examine the landscape-scale vegetation responses to drought around the forest line. Drought events were characterized from 1920 to 2014 using the Standardized Precipitation Index (SPI). Two remotely-sensed vegetation indices (VI) were analyzed from the moderate resolution imaging spectroradiometer (MODIS) satellite measurements from 2000 to 2014 to determine vegetation responses to drought events identified using the SPI. The forest line area experienced 28 drought events from 1920 to 2014. A multi-year drought from 2008 to 2014 was the most extreme on record, persisting for 70 consecutive months and resulting in browning both above and below the forest line while the other three drought events since 2000 resulted in overall greening. No clear pattern was found between El Niño event strength and drought severity, and surprisingly almost half of the droughts were associated with La Niña events. This work highlights for the first time the importance of La Niña events for Hawaiian drought and contributes to our understanding of ecological response to drought at the forest line ecotone.

Mapping Live Fuel Moisture and the relation to drought and post fire events for Southern California region

NASA Astrophysics Data System (ADS)

Hatzopoulos, N.; Kim, S. H.; Kafatos, M.; Nghiem, S. V.; Myoung, B.

2016-12-01

Live Fuel Moisture is a dryness measure used by the fire departments to determine how dry is the current situation of the fuels from the forest areas. In order to map Live Fuel Moisture we conducted an analysis with a standardized regressional approach from various vegetation indices derived from remote sensing data of MODIS. After analyzing the results we concluded mapping Live Fuel Moisture using a standardized NDVI product. From the mapped remote sensed product we observed the appearance of extremely high dry fuels to be highly correlated with very dry years based on the overall yearly precipitation. The appearances of the extremely dry mapped fuels tend to have a direct association with fire events and observed to be a post fire indicator. In addition we studied the appearance of extreme dry fuels during critical months when season changes from spring to summer as well as the relation to fire events.

Amazon Forests Response to Droughts: A Perspective from the MAIAC Product

NASA Technical Reports Server (NTRS)

Bi, Jian; Myneni, Ranga; Lyapustin, Alexei; Wang, Yujie; Park, Taejin; Chi, Chen; Yan, Kai; Knyazikhin, Yuri

2016-01-01

Amazon forests experienced two severe droughts at the beginning of the 21st century: one in 2005 and the other in 2010. How Amazon forests responded to these droughts is critical for the future of the Earth's climate system. It is only possible to assess Amazon forests' response to the droughts in large areal extent through satellite remote sensing. Here, we used the Multi-Angle Implementation of Atmospheric Correction (MAIAC) Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation index (VI) data to assess Amazon forests' response to droughts, and compared the results with those from the standard (Collection 5 and Collection 6) MODIS VI data. Overall, the MAIAC data reveal more realistic Amazon forests inter-annual greenness dynamics than the standard MODIS data. Our results from the MAIAC data suggest that: (1) the droughts decreased the greenness (i.e., photosynthetic activity) of Amazon forests; (2) the Amazon wet season precipitation reduction induced by El Niño events could also lead to reduced photosynthetic activity of Amazon forests; and (3) in the subsequent year after the water stresses, the greenness of Amazon forests recovered from the preceding decreases. However, as previous research shows droughts cause Amazon forests to reduce investment in tissue maintenance and defense, it is not clear whether the photosynthesis of Amazon forests will continue to recover after future water stresses, because of the accumulated damages caused by the droughts.

Evaluating multiple causes of persistent low microwave backscatter from Amazon forests after the 2005 drought.

PubMed

Frolking, Steve; Hagen, Stephen; Braswell, Bobby; Milliman, Tom; Herrick, Christina; Peterson, Seth; Roberts, Dar; Keller, Michael; Palace, Michael

2017-01-01

Amazonia has experienced large-scale regional droughts that affect forest productivity and biomass stocks. Space-borne remote sensing provides basin-wide data on impacts of meteorological anomalies, an important complement to relatively limited ground observations across the Amazon's vast and remote humid tropical forests. Morning overpass QuikScat Ku-band microwave backscatter from the forest canopy was anomalously low during the 2005 drought, relative to the full instrument record of 1999-2009, and low morning backscatter persisted for 2006-2009, after which the instrument failed. The persistent low backscatter has been suggested to be indicative of increased forest vulnerability to future drought. To better ascribe the cause of the low post-drought backscatter, we analyzed multiyear, gridded remote sensing data sets of precipitation, land surface temperature, forest cover and forest cover loss, and microwave backscatter over the 2005 drought region in the southwestern Amazon Basin (4°-12°S, 66°-76°W) and in adjacent 8°x10° regions to the north and east. We found moderate to weak correlations with the spatial distribution of persistent low backscatter for variables related to three groups of forest impacts: the 2005 drought itself, loss of forest cover, and warmer and drier dry seasons in the post-drought vs. the pre-drought years. However, these variables explained only about one quarter of the variability in depressed backscatter across the southwestern drought region. Our findings indicate that drought impact is a complex phenomenon and that better understanding can only come from more extensive ground data and/or analysis of frequent, spatially-comprehensive, high-resolution data or imagery before and after droughts.

Evaluating multiple causes of persistent low microwave backscatter from Amazon forests after the 2005 drought

PubMed Central

Hagen, Stephen; Braswell, Bobby; Milliman, Tom; Herrick, Christina; Peterson, Seth; Roberts, Dar; Keller, Michael; Palace, Michael

2017-01-01

Amazonia has experienced large-scale regional droughts that affect forest productivity and biomass stocks. Space-borne remote sensing provides basin-wide data on impacts of meteorological anomalies, an important complement to relatively limited ground observations across the Amazon’s vast and remote humid tropical forests. Morning overpass QuikScat Ku-band microwave backscatter from the forest canopy was anomalously low during the 2005 drought, relative to the full instrument record of 1999–2009, and low morning backscatter persisted for 2006–2009, after which the instrument failed. The persistent low backscatter has been suggested to be indicative of increased forest vulnerability to future drought. To better ascribe the cause of the low post-drought backscatter, we analyzed multiyear, gridded remote sensing data sets of precipitation, land surface temperature, forest cover and forest cover loss, and microwave backscatter over the 2005 drought region in the southwestern Amazon Basin (4°-12°S, 66°-76°W) and in adjacent 8°x10° regions to the north and east. We found moderate to weak correlations with the spatial distribution of persistent low backscatter for variables related to three groups of forest impacts: the 2005 drought itself, loss of forest cover, and warmer and drier dry seasons in the post-drought vs. the pre-drought years. However, these variables explained only about one quarter of the variability in depressed backscatter across the southwestern drought region. Our findings indicate that drought impact is a complex phenomenon and that better understanding can only come from more extensive ground data and/or analysis of frequent, spatially-comprehensive, high-resolution data or imagery before and after droughts. PMID:28873422

Multi-Scale Modeling of Boreal Forest Vegetation Growth Under the Influence of Permafrost and Wildfire Interactions

NASA Astrophysics Data System (ADS)

Foster, A.; Armstrong, A. H.; Shuman, J. K.; Ranson, K.; Shugart, H. H., Jr.; Rogers, B. M.; Goetz, S. J.

2017-12-01

Global temperatures have increased about 0.2°C per decade since 1979, and the high latitudes are warming faster than the rest of the globe. Climate change within Alaska is likely to bring about increased drought and longer fire seasons, as well as increases in the severity and frequency of fires. These changes in disturbance regimes and their associated effects on ecosystem C stocks, including permafrost, may lead to a positive feedback to further climate warming. As of now, it is uncertain how vegetation will respond to ongoing climate change, and the addition of disturbance effects leads to even more complicated and varied scenarios. Through ecological modeling, we have the capacity to examine forest processes at multiple temporal and spatial scales, allowing for the testing of complex interactions between vegetation, climate, and disturbances. The University of Virginia Forest Model Enhanced (UVAFME) is an individual tree-based forest model that has been updated for use in interior boreal Alaska, with a new permafrost model and updated fire simulation. These updated submodels allow for feedback between soils, vegetation, and fire severity through fuels tracking and impact of depth of burn on permafrost dynamics. We present these updated submodels as well as calibration and validation of UVAFME to the Yukon River Basin in Alaska, with comparisons to inventory data. We also present initial findings from simulations of potential future forest biomass, structure, and species composition across the Yukon River Basin under expected changes in precipitation, temperature, and disturbances. We predict changing climate and the associated impacts on wildfire and permafrost dynamics will result in shifts in biomass and species composition across the region, with potential for further feedback to the climate-vegetation-disturbance system. These simulations advance our understanding of the possible futures for the Alaskan boreal forest, which is a valuable part of the global carbon budget.

Assessment of multi-wildfire occurrence data for machine learning based risk modelling

NASA Astrophysics Data System (ADS)

Lim, C. H.; Kim, M.; Kim, S. J.; Yoo, S.; Lee, W. K.

2017-12-01

The occurrence of East Asian wildfires is mainly caused by human-activities, but the extreme drought increased due to the climate change caused wildfires and they spread to large-scale fires. Accurate occurrence location data is required for modelling wildfire probability and risk. In South Korea, occurrence data surveyed through KFS (Korea Forest Service) and MODIS (MODerate-resolution Imaging Spectroradiometer) satellite-based active fire data can be utilized. In this study, two sorts of wildfire occurrence data were applied to select suitable occurrence data for machine learning based wildfire risk modelling. MaxEnt (Maximum Entropy) model based on machine learning is used for wildfire risk modelling, and two types of occurrence data and socio-economic and climate-environment data are applied to modelling. In the results with KFS survey based data, the low relationship was shown with climate-environmental factors, and the uncertainty of coordinate information appeared. The MODIS-based active fire data were found outside the forests, and there were a lot of spots that did not match the actual wildfires. In order to utilize MODIS-based active fire data, it was necessary to extract forest area and utilize only high-confidence level data. In KFS data, it was necessary to separate the analysis according to the damage scale to improve the modelling accuracy. Ultimately, it is considered to be the best way to simulate the wildfire risk by constructing more accurate information by combining two sorts of wildfire occurrence data.

Heightened fire probability in Indonesia in non-drought conditions: the effect of increasing temperatures

NASA Astrophysics Data System (ADS)

Fernandes, Kátia; Verchot, Louis; Baethgen, Walter; Gutierrez-Velez, Victor; Pinedo-Vasquez, Miguel; Martius, Christopher

2017-05-01

In Indonesia, drought driven fires occur typically during the warm phase of the El Niño Southern Oscillation. This was the case of the events of 1997 and 2015 that resulted in months-long hazardous atmospheric pollution levels in Equatorial Asia and record greenhouse gas emissions. Nonetheless, anomalously active fire seasons have also been observed in non-drought years. In this work, we investigated the impact of temperature on fires and found that when the July-October (JASO) period is anomalously dry, the sensitivity of fires to temperature is modest. In contrast, under normal-to-wet conditions, fire probability increases sharply when JASO is anomalously warm. This describes a regime in which an active fire season is not limited to drought years. Greater susceptibility to fires in response to a warmer environment finds support in the high evapotranspiration rates observed in normal-to-wet and warm conditions in Indonesia. We also find that fire probability in wet JASOs would be considerably less sensitive to temperature were not for the added effect of recent positive trends. Near-term regional climate projections reveal that, despite negligible changes in precipitation, a continuing warming trend will heighten fire probability over the next few decades especially in non-drought years. Mild fire seasons currently observed in association with wet conditions and cool temperatures will become rare events in Indonesia.

Interactions across spatial scales among forest dieback, fire, and erosion in northern New Mexico landscapes

USGS Publications Warehouse

Allen, Craig D.

2007-01-01

Ecosystem patterns and disturbance processes at one spatial scale often interact with processes at another scale, and the result of such cross-scale interactions can be nonlinear dynamics with thresholds. Examples of cross-scale pattern-process relationships and interactions among forest dieback, fire, and erosion are illustrated from northern New Mexico (USA) landscapes, where long-term studies have recently documented all of these disturbance processes. For example, environmental stress, operating on individual trees, can cause tree death that is amplified by insect mortality agents to propagate to patch and then landscape or even regional-scale forest dieback. Severe drought and unusual warmth in the southwestern USA since the late 1990s apparently exceeded species-specific physiological thresholds for multiple tree species, resulting in substantial vegetation mortality across millions of hectares of woodlands and forests in recent years. Predictions of forest dieback across spatial scales are constrained by uncertainties associated with: limited knowledge of species-specific physiological thresholds; individual and site-specific variation in these mortality thresholds; and positive feedback loops between rapidly-responding insect herbivore populations and their stressed plant hosts, sometimes resulting in nonlinear “pest” outbreak dynamics. Fire behavior also exhibits nonlinearities across spatial scales, illustrated by changes in historic fire regimes where patch-scale grazing disturbance led to regional-scale collapse of surface fire activity and subsequent recent increases in the scale of extreme fire events in New Mexico. Vegetation dieback interacts with fire activity by modifying fuel amounts and configurations at multiple spatial scales. Runoff and erosion processes are also subject to scale-dependent threshold behaviors, exemplified by ecohydrological work in semiarid New Mexico watersheds showing how declines in ground surface cover lead to non-linear increases in bare patch connectivity and thereby accelerated runoff and erosion at hillslope and watershed scales. Vegetation dieback, grazing, and fire can change land surface properties and cross-scale hydrologic connectivities, directly altering ecohydrological patterns of runoff and erosion. The interactions among disturbance processes across spatial scales can be key drivers in ecosystem dynamics, as illustrated by these studies of recent landscape changes in northern New Mexico. To better anticipate and mitigate accelerating human impacts to the planetary ecosystem at all spatial scales, improvements are needed in our conceptual and quantitative understanding of cross-scale interactions among disturbance processes.

Effects of Climate and Fuels Management on Wildfire Occurrence, Size, Severity and Emissions in the Sierra Nevada

NASA Astrophysics Data System (ADS)

Westerling, A. L.; Fites, J. A.; Keyser, A.

2015-12-01

Annual wildfire burned area in federally managed Sierra Nevada forests has increased by more than 10,000 ha per decade since the early 1970s. At the same time, recent years have seen some extremely large fires compared to the historical record, with significant areas of moderate to high severity fire (e.g., McNally 2002, Rim 2013, King 2014 fires). Changes to fuels and fire regimes due to fire suppression and land use, as well as warming temperatures and the occurrence of drought, are thought to be significant factors contributing to increased risks of large, severe fires in Sierra Nevada forests. Over 70% of the vegetated area in federally managed forests in the Sierra Nevada is classified as having altered fuels and fire regimes, while average annual temperature in the Sierra Nevada has been above the long term mean for all but four years in the past two decades. As climate is expected to continue warming for decades to come, we explored fuels management scenarios as the primary tools available to modify risks of large, severe wildfires. We developed experimental statistical models of fire occurrence, fire size, and high severity burned area, to explore the interaction between climate and altered fuels conditions. These models were applied to historical climate conditions, a sample of future climate projections, and to both current fuels conditions and a range of scenarios for fuels treatments. Emissions from wildfires were estimated using the Fire Inventory from the National Center for Atmospheric Research. Our models project that average annual burned area in the Sierra Nevada will more than double by mid-century. Similarly, particulate and other pollution emissions from Sierra Nevada wildfires are projected to more than double, even if future fire severity does not change. Fuels treatment scenarios significantly reduced simulated future burned area and emissions below untreated projections. High severity burned area responded to both climate and fuels treatments. A sensitivity analysis indicated that in areas where the fraction of highly altered fuels is high, successfully restoring fuels to prehistoric conditions could more than compensate for expected climate change effects on fire severity by mid-century.

Chapter4 - Drought patterns in the conterminous United States and Hawaii.

Treesearch

Frank H. Koch; William D. Smith; John W. Coulston

2014-01-01

Droughts are common in virtually all U.S. forests, but their frequency and intensity vary widely both between and within forest ecosystems (Hanson and Weltzin 2000). Forests in the Western United States generally exhibit a pattern of annual seasonal droughts. Forests in the Eastern United States tend to exhibit one of two prevailing patterns: random occasional droughts...

Modeling the Effects of Drought Events on Forest Ecosystem Functioning Historically and Under Scenarios of Climate Change

NASA Astrophysics Data System (ADS)

Ren, J.; Hanan, E. J.; Kolden, C.; Abatzoglou, J. T.; Tague, C.; Liu, M.; Adam, J. C.

2017-12-01

Drought events have been increasing across the western United States in recent years. Many studies have shown that, in the context of climate change, droughts will continue to be stronger, more frequent, and prolonged in the future. However, the response of forest ecosystems to droughts, particularly multi-year droughts, is not well understood. The objectives of this study are to examine how drought events of varying characteristics (e.g. intensity, duration, frequency, etc.) have affected the functioning of forest ecosystems historically, and how changing drought characteristics (including multi-year droughts) may affect forest functioning in a future climate. We utilize the Regional Hydro-Ecological Simulation System (RHESSys) to simulate impacts of both historical droughts and scenarios of future droughts on forest ecosystems. RHESSys is a spatially-distributed and process-based model that captures the interactions between coupled biogeochemical and hydrologic cycles at catchment scales. Here our case study is the Trail Creek catchment of the Big Wood River basin in Idaho, the Northwestern USA. For historical simulations, we use the gridded meteorological data of 1979 to 2016; for future climate scenarios, we utilize downscaled data from GCMs that have been demonstrated to capture drought events in the Northwest of the USA. From these climate projections, we identify various types of drought in intensity and duration, including multi-year drought events. We evaluate the following responses of ecosystems to these events: 1) evapotranspiration and streamflow; 2) gross primary productivity; 3) the post-drought recovery of plant biomass; and 4) the forest functioning and recovery after multi-year droughts. This research is part of an integration project to examine the roles of drought, insect outbreak, and forest management activities on wildfire activity and its impacts. This project will provide improved information for forest managers and communities in the wild urban interface to adapt to climate change.

Drought impacts on vegetation dynamics in the Mediterranean based on remote sensing and multi-scale drought indices

NASA Astrophysics Data System (ADS)

Trigo, Ricardo; Gouveia, Celia M.; Beguería, Santiago; Vicente-Serrano, Sergio

2015-04-01

A number of recent studies have identified a significant increase in the frequency of drought events in the Mediterranean basin (e.g. Trigo et al., 2013, Vicente-Serrano et al., 2014). In the Mediterranean region, large drought episodes are responsible for the most negative impacts on the vegetation including significant losses of crop yield, increasing risk of forest fires (e.g. Gouveia et al., 2012) and even forest decline. The aim of the present work is to analyze in detail the impacts of drought episodes on vegetation in the Mediterranean basin behavior using NDVI data from (from GIMMS) for entire Mediterranean basin (1982-2006) and the multi-scale drought index (the Standardised Precipitation-Evapotranspiration Index (SPEI). Correlation maps between fields of monthly NDVI and SPEI for at different time scales (1-24 months) were computed in order to identify the regions and seasons most affected by droughts. Affected vegetation presents high spatial and seasonal variability, with a maximum in summer and a minimum in winter. During February 50% of the affected pixels corresponded to a time scale of 6 months, while in November the most frequent time scale corresponded to 3 months, representing more than 40% of the affected region. Around 20% of grid points corresponded to the longer time scales (18 and 24 months), persisting fairly constant along the year. In all seasons the wetter clusters present higher NDVI values which indicates that aridity holds a key role to explain the spatial differences in the NDVI values along the year. Despite the localization of these clusters in areas with higher values of monthly water balance, the strongest control of drought on vegetation activity are observed for the drier classes located over regions with smaller absolute values of water balance. Gouveia C.M., Bastos A., Trigo R.M., DaCamara C.C. (2012) "Drought impacts on vegetation in the pre and post-fire events over Iberian Peninsula". Natural Hazards and Earth System Sciences, 12, 3123-3137, 2012. Trigo R.M., Añel J., Barriopedro D., García-Herrera R., Gimeno L., Nieto R., Castillo R., Allen M.R., Massey N. (2013), The record Winter drought of 2011-12 in the Iberian Peninsula [in "Explaining Extreme Events of 2012 from a Climate Perspective". [Peterson, T. C., M. P. Hoerling, P.A. Stott and S. Herring, Eds.] Bulletin of the American Meteorological Society, 94 (9), S41-S45. Vicente-Serrano S.M., López-Moreno J.I., Beguería S., Lorenzo-Lacruz J., Sanchez-Lorenzo A., García-Ruiz J.M., Azorin-Molina C., Móran-Tejeda E., Revuelto J., Trigo R., Coelho F., Espejo F.: Evidence of increasing drought severity caused by temperature rise in southern Europe. Environmental Research Letters, 9, 044001, 2014. Acknowledgements: This work was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project QSECA (PTDC/AAGGLO/4155/2012).

Wildfire Effects on In-stream Nutrient Processing and Hydrologic Transport

NASA Astrophysics Data System (ADS)

Rhea, A.; Covino, T. P.; Rhoades, C.; Fegel, T.

2017-12-01

In many forests throughout the Western U.S., drought, climate change, and growing fuel loads are contributing to increased fire frequency and severity. Wildfires can influence watershed nutrient retention as they fundamentally alter the biological composition and physical structure in upland landscapes, riparian corridors, and stream channels. While numerous studies have documented substantial short-term increases in stream nutrient concentrations and export (particularly reactive nitrogen, N) following forest fires, the long-term implications for watershed nutrient cycling remain unclear. For example, recent work indicates that nitrate concentrations and export can remain elevated for a decade or more following wildfire, yet the controls on these processes are unknown. In this research, we use empirical observations from nutrient tracer injections, nutrient diffusing substrates, and continuous water quality monitoring to isolate biological and physical controls on nutrient export across a burn-severity gradient. Tracer results demonstrate substantial stream-groundwater exchange, but little biological nutrient uptake in burned streams. This in part explains patterns of elevated nutrient export. Paired nutrient diffusing substrate experiments allow us to further investigate shifts in N, phosphorus, and carbon limitation that may suppress post-fire stream nutrient uptake. By isolating the mechanisms that reduce the capacity of fire-affected streams to retain and transform nutrient inputs, we can better predict dynamics in post-fire water quality and help prioritize upland and riparian restoration.

Echohydrological implications of drought for forests in the United States

Treesearch

James M. Vose; Chelcy Ford Miniat; Charles H. Luce; Heidi Asbjornsen; Peter V. Caldwell; John L. Campbell; Gordon E. Grant; Daniel J. Isaak; Steven P. Loheide; Ge Sun

2016-01-01

The relationships among drought, surface water flow, and groundwater recharge are not straightforward for most forest ecosystems due to the strong role that vegetation plays in the forest water balance. Hydrologic responses to drought can be either mitigated or exacerbated by forest vegetation depending upon vegetation water use and how forest population dynamics...

Assessment of the 1998–2001 drought impact on forest health in southeastern forests: an analysis of drought severity using FHM data

Treesearch

R. J. Klos; G. G. Wang; W. L. Bauerle

2010-01-01

Analyses of forest health indicators monitored through the Forest Health and Monitoring (FHM) program suggested that weather was the most important cause of tree mortality. Drought is of particular importance among weather variables because several global climate change scenarios predicted more frequent and/or intense drought in the Southeastern United States. During...

Evaluation of climate-related carbon turnover processes in global vegetation models for boreal and temperate forests.

PubMed

Thurner, Martin; Beer, Christian; Ciais, Philippe; Friend, Andrew D; Ito, Akihiko; Kleidon, Axel; Lomas, Mark R; Quegan, Shaun; Rademacher, Tim T; Schaphoff, Sibyll; Tum, Markus; Wiltshire, Andy; Carvalhais, Nuno

2017-08-01

Turnover concepts in state-of-the-art global vegetation models (GVMs) account for various processes, but are often highly simplified and may not include an adequate representation of the dominant processes that shape vegetation carbon turnover rates in real forest ecosystems at a large spatial scale. Here, we evaluate vegetation carbon turnover processes in GVMs participating in the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP, including HYBRID4, JeDi, JULES, LPJml, ORCHIDEE, SDGVM, and VISIT) using estimates of vegetation carbon turnover rate (k) derived from a combination of remote sensing based products of biomass and net primary production (NPP). We find that current model limitations lead to considerable biases in the simulated biomass and in k (severe underestimations by all models except JeDi and VISIT compared to observation-based average k), likely contributing to underestimation of positive feedbacks of the northern forest carbon balance to climate change caused by changes in forest mortality. A need for improved turnover concepts related to frost damage, drought, and insect outbreaks to better reproduce observation-based spatial patterns in k is identified. As direct frost damage effects on mortality are usually not accounted for in these GVMs, simulated relationships between k and winter length in boreal forests are not consistent between different regions and strongly biased compared to the observation-based relationships. Some models show a response of k to drought in temperate forests as a result of impacts of water availability on NPP, growth efficiency or carbon balance dependent mortality as well as soil or litter moisture effects on leaf turnover or fire. However, further direct drought effects such as carbon starvation (only in HYBRID4) or hydraulic failure are usually not taken into account by the investigated GVMs. While they are considered dominant large-scale mortality agents, mortality mechanisms related to insects and pathogens are not explicitly treated in these models. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Density-dependent vulnerability of forest ecosystems to drought

USGS Publications Warehouse

Bottero, Alessandra; D'Amato, Anthony W.; Palik, Brian J.; Bradford, John B.; Fraver, Shawn; Battaglia, Mike A.; Asherin, Lance A.

2017-01-01

1. Climate models predict increasing drought intensity and frequency for many regions, which may have negative consequences for tree recruitment, growth and mortality, as well as forest ecosystem services. Furthermore, practical strategies for minimizing vulnerability to drought are limited. Tree population density, a metric of tree abundance in a given area, is a primary driver of competitive intensity among trees, which influences tree growth and mortality. Manipulating tree population density may be a mechanism for moderating drought-induced stress and growth reductions, although the relationship between tree population density and tree drought vulnerability remains poorly quantified, especially across climatic gradients.2. In this study, we examined three long-term forest ecosystem experiments in two widely distributed North American pine species, ponderosa pine Pinus ponderosa (Lawson & C. Lawson) and red pine Pinus resinosa (Aiton), to better elucidate the relationship between tree population density, growth and drought. These experiments span a broad latitude and aridity range and include tree population density treatments that have been purposefully maintained for several decades. We investigated how tree population density influenced resistance (growth during drought) and resilience (growth after drought compared to pre-drought growth) of stand-level growth during and after documented drought events.3. Our results show that relative tree population density was negatively related to drought resistance and resilience, indicating that trees growing at lower densities were less vulnerable to drought. This result was apparent in all three forest ecosystems, and was consistent across species, stand age and drought intensity.4. Synthesis and applications. Our results highlighted that managing pine forest ecosystems at low tree population density represents a promising adaptive strategy for reducing the adverse impacts of drought on forest growth in coming decades. Nonetheless, the broader applicability of our findings to other types of forest ecosystems merits additional investigation.

A cross-scale framework of peatland resilience based on long-term research in interior Alaska and the Northwest Territories, Canada

NASA Astrophysics Data System (ADS)

Turetsky, M. R.; Kane, E. S.; Baltzer, J. L.; Quinton, W. L.; Euskirchen, E. S.; Sonnentag, O.; Waldrop, M. P.; Neumann, R.; Douglas, T.

2017-12-01

Considerable progress has been made in recent decades towards understanding northern ecosystem structure and function in the context of resilience theory. For example, there is increasing understanding that wildfire activity is overwhelming the resilience mechanisms of conifer species, shifting forest composition toward deciduous cover in some boreal regions. Relative to forests and grasslands, we have less knowledge on what governs the response of northern peatlands to disturbance, including drought, wildfire, and permafrost thaw. The majority of peatland research to date has instead focused on ecological and hydrological measurements across fen-to-bog or hummock-to-hollow gradients. It was only recently appreciated that fire serves as an important agent of successional change in northern peatlands, as recent studies show that peat accumulation and the function of peatlands as net carbon sinks requires light to moderate fire activity. In this presentation, we will synthesize results from water table and vegetation manipulation experiments, continuous ecosystem-scale measurements of carbon, energy and water fluxes, and observations across gradients of fire severity and permafrost thaw to derive a mechanistic framework of peatland ecological and hydrological resilience. In particular, we will highlight the past decade of observations made at the Scotty Creek Research Station in the Northwest Territories as well as the Alaska Peatland Experiment (APEX) in interior Alaska. Our research shows that vegetation, particularly deep rooting early successional species and late successional mosses, play a critical role in maintaining nutrient cycling and ecosystem carbon balance in a peat accumulating state. Peatlands also govern how the surrounding landscape responds to drought, fire, and permafrost thaw. Future research needs to consider the resilience of northern ecosystems at a variety of spatio-temporal scales through a combination of ground measurements, remote sensing, and change detection. The goal of this presentation is to advance awareness of the role of peatlands in cross-scale interactions affecting carbon, nutrient and energy exchange.

Short- and long-term efficacy of forest thinning to mitigate drought impacts in mountain forests in the European Alps.

PubMed

Elkin, Ché; Giuggiola, Arnaud; Rigling, Andreas; Bugmann, Harald

2015-06-01

In many regions of the world, drought is projected to increase under climate change, with potential negative consequences for forests and their ecosystem services (ES). Forest thinning has been proposed as a method for at least temporarily mitigating drought impacts, but its general applicability and longer-term impacts are unclear. We use a process-based forest model to upscale experimental data for evaluating the impacts of forest thinning in a drought-susceptible valley in the interior of the European Alps, with the specific aim of assessing (1) when and where thinning may be most effective and (2) the longer-term implications for forest dynamics. Simulations indicate that forests will be impacted by climate-induced increases in drought across a broad elevation range. At lower elevations, where drought is currently prevalent, thinning is projected to temporarily reduce tree mortality, but to have minor impacts on forest dynamics in the longer term. Thinning may be particularly useful at intermediate and higher elevations as a means of temporarily reducing mortality in drought-sensitive species such as Norway spruce and larch, which currently dominate these elevations. However, in the longer term, even intense thinning will likely not be sufficient to prevent a climate change induced dieback of these species, which is projected to occur under even moderate climate change. Thinning is also projected to have the largest impact on long-term forest dynamics at intermediate elevations, with the magnitude of the impact depending on the timing and intensity of thinning. More intense thinning that is done later is projected to more strongly promote a transition to more drought-tolerant species. We conclude that thinning is a viable option for temporarily reducing the negative drought impacts on forests, but that efficient implementation of thinning should be contingent on a site-specific evaluation of the near term risk of significant drought, and how thinning will impact the rate and direction of climate driven forest conversion.

Extreme late-summer drought causes neutral annual carbon balance in southwestern ponderosa pine forests and grasslands

NASA Astrophysics Data System (ADS)

Kolb, Thomas; Dore, Sabina; Montes-Helu, Mario

2013-03-01

We assessed the impacts of extreme late-summer drought on carbon balance in a semi-arid forest region in Arizona. To understand drought impacts over extremes of forest cover, we measured net ecosystem production (NEP), gross primary production (GPP), and total ecosystem respiration (TER) with eddy covariance over five years (2006-10) at an undisturbed ponderosa pine (Pinus ponderosa) forest and at a former forest converted to grassland by intense burning. Drought shifted annual NEP from a weak source of carbon to the atmosphere to a neutral carbon balance at the burned site and from a carbon sink to neutral at the undisturbed site. Carbon fluxes were particularly sensitive to drought in August. Drought shifted August NEP at the undisturbed site from sink to source because the reduction of GPP (70%) exceeded the reduction of TER (35%). At the burned site drought shifted August NEP from weak source to neutral because the reduction of TER (40%) exceeded the reduction of GPP (20%). These results show that the lack of forest recovery after burning and the exposure of undisturbed forests to late-summer drought reduce carbon sink strength and illustrate the high vulnerability of forest carbon sink strength in the southwest US to predicted increases in intense burning and precipitation variability.

What We Have Learned From 20+ Years of Research on Effects of Drought, Fire and Management on Carbon and Water Dynamics of Pacific Northwest Semi-Arid Forests

NASA Astrophysics Data System (ADS)

Law, B. E.; Berner, L. T.; Kwon, H.; Schmidt, A.

2016-12-01

Eco-climatic heterogeneity and proximity to oceans provides endless learning opportunities for eco-physiologists and modelers alike. We have been conducting measurements and modeling of ecosystem responses to climate and disturbance over Oregon's strong climatic gradient since 1990, and in the Metolius semi-arid region. Some of our findings have challenged common assumptions. Our first flux site was the Metolius old-growth ponderosa pine site (established 1996), followed by flux measurements at clusters of different age forests. We found that the old pine site continued to be an annual net carbon sink, contrary to expectations. Twenty years after stand-replacing disturbance, naturally regenerating young ponderosa pine was still a net carbon source, and a young pine plantation with removed debris (lower decomposition) was a weak sink. Physiological sensitivity to climate varies with tree size. Young pine forests responded to seasonal drought sooner and to a more severe degree. During extreme drought years, old pine showed only a small decline in water transport efficiency (11-24%), whereas efficiency declined by 46% in mature pine, and 80% in young pine. Thus, young trees risk hydraulic failure, which may account for higher mortality in young plantations nearby. Carbon uptake (GPP), soil fluxes, and evapotranspiration (calculated from sapflux or eddy flux data) are strongly coupled in the semi-arid ecosystems, suggesting it is feasible to combine sapflux and soil flux data along with water-use efficiency (GPP/LE) from high quality eddy flux data to estimate NEE in the landscape near flux sites or in patches of forests too small for EC measurements. Highlights show our key findings from development and application of multiple models, including SPA, Biome-BGC and CLM, and ideas for future directions.

Constraining Earth System Models in the Tropics with Multiple Satellite Observations

NASA Astrophysics Data System (ADS)

Shi, M.; Liu, J.; Saatchi, S. S.; Chan, S.; Yu, Y.; Zhao, M.

2016-12-01

Because of the impacts of cloud and atmospheric aerosol on spectral observations and the saturation of spectral observations over dense forests, the current spectral observations (e.g., Moderate Resolution Imaging Spectroradiometer) have large uncertainties in the tropics. Nevertheless, the backscatter observations from the SeaWinds Scatterometer onboard QuikSCAT (QSCAT) are sensitive to the variations of canopy water content and structure of forest canopy, and are not affected by clouds and atmospheric aerosols. In addition, the lack of sensitivity of the Soil Moisture Active Passive (SMAP) Level 1C brightness temperature (TB) to soil moisture under dense forest canopies (e.g., forests in tropics) makes the SMAP TB data a direct indicator of canopy properties. In this study, we use a variety of new satellite observations, including the QSCAT backscatter observations, the Gravity Recovery and Climate Experiment (GRACE) satellite's observed temporal gravity field variations, and the SMAP Level 1C TB, to constrain the carbon (C) cycle simulated by the Community Land Model version 4.5 BGC (CLM4.5) for the 2005 Amazonia drought and 2015 El Nino. Our results show that the leaf C pool size simulated by CLM4.5 decreases dramatically in southwest Amazonia in the 2005 drought, and recovers slowly afterward (after about 3 years). This result is consistent with the long-term C-recovery after the 2005 Amazonia drought observed by QSCAT. The slow C pool recovery is associated with large fire disturbance and the slow water storage recovery simulated by CLM4.5 and observed by GRACE. We will also discuss the impact of the 2015 El Nino on the tropical C dynamics constrained by SMAP Level 1C data. This study represents an innovative way of using satellite microwave observations to constrain C cycle in an Earth system model.

Disturbance and the carbon balance of US forests: A quantitative review of impacts from harvests, fires, insects, and droughts

NASA Astrophysics Data System (ADS)

Williams, Christopher A.; Gu, Huan; MacLean, Richard; Masek, Jeffrey G.; Collatz, G. James

2016-08-01

Disturbances are a major determinant of forest carbon stocks and uptake. They generally reduce land carbon stocks but also initiate a regrowth legacy that contributes substantially to the contemporary rate of carbon stock increase in US forestlands. As managers and policy makers increasingly look to forests for climate protection and mitigation, and because of increasing concern about changes in disturbance intensity and frequency, there is a need for synthesis and integration of current understanding about the role of disturbances and other processes in governing forest carbon cycle dynamics, and the likely future of this and other sinks for atmospheric carbon. This paper aims to address that need by providing a quantitative review of the distribution, extent and carbon impacts of the major disturbances active in the US. We also review recent trends in disturbances, climate, and other global environmental changes and consider their individual and collective contributions to the US carbon budget now and in the likely future. Lastly, we identify some key challenges and opportunities for future research needed to improve current understanding, advance predictive capabilities, and inform forest management in the face of these pressures. Harvest is found to be the most extensive disturbance both in terms of area and carbon impacts, followed by fire, windthrow and bark beetles, and lastly droughts. Collectively these lead to the gross loss of about 200 Tg C y- 1 in live biomass annually across the conterminous US. At the same time, the net change in forest carbon stocks is positive (190 Tg C y- 1), indicating not only forest resilience but also an apparently large response to growth enhancements such as fertilization by CO2 and nitrogen. Uncertainty about disturbance legacies, disturbance interactions, likely trends, and global change factors make the future of the US forest carbon sink unclear. While there is scope for management to enhance carbon sinks in US forests, tradeoffs with other values and uses are likely to significantly limit practical implementation. Continued and expanded remote sensing and field-based monitoring capabilities and manipulative experimentation are needed to improve understanding of the US forest carbon sink, and assess how disturbance processes are responding to the pressures of global environmental change. In addition, continued development and application of holistic, decision support tools that consider a range of forest values are needed to enable managers and policy makers to use the best available information for guiding forest resources now and into the future.

Disturbance and the Carbon Balance of US Forests: A Quantitative Review of Impacts from Harvests, Fires, Insects, and Droughts

NASA Technical Reports Server (NTRS)

Williams, Christopher A.; Gu, Huan; MacLean, Richard; Masek, Jeffrey G.; Collatz, G. James

2016-01-01

Disturbances are a major determinant of forest carbon stocks and uptake. They generally reduce land carbon stocks but also initiate a regrowth legacy that contributes substantially to the contemporary rate of carbon stock increase in US forestlands. As managers and policy makers increasingly look to forests for climate protection and mitigation, and because of increasing concern about changes in disturbance intensity and frequency, there is a need for synthesis and integration of current understanding about the role of disturbances and other processes in governing forest carbon cycle dynamics, and the likely future of this and other sinks for atmospheric carbon. This paper aims to address that need by providing a quantitative review of the distribution, extent and carbon impacts of the major disturbances active in the US. We also review recent trends in disturbances, climate, and other global environmental changes and consider their individual and collective contributions to the US carbon budget now and in the likely future. Lastly, we identify some key challenges and opportunities for future research needed to improve current understanding, advance predictive capabilities, and inform forest management in the face of these pressures. Harvest is found to be the most extensive disturbance both in terms of area and carbon impacts, followed by fire, windthrow and bark beetles, and lastly droughts. Collectively these lead to the gross loss of about 200 Tg C y(exp -1) in live biomass annually across the conterminous US. At the same time, the net change in forest carbon stocks is positive (190 Tg C y(exp -1)), indicating not only forest resilience but also an apparently large response to growth enhancements such as fertilization by CO2 and nitrogen. Uncertainty about disturbance legacies, disturbance interactions, likely trends, and global change factors make the future of the US forest carbon sink unclear. While there is scope for management to enhance carbon sinks in US forests, tradeoffs with other values and uses are likely to significantly limit practical implementation. Continued and expanded remote sensing and field-based monitoring capabilities and manipulative experimentation are needed to improve understanding of the US forest carbon sink, and assess how disturbance processes are responding to the pressures of global environmental change. In addition, continued development and application of holistic, decision support tools that consider a range of forest values are needed to enable managers and policy makers to use the best available information for guiding forest resources now and into the future.

An ecohydrological model to quantify the risk of drought-induced forest mortality events across climate regimes

NASA Astrophysics Data System (ADS)

Parolari, A.; Katul, G. G.; Porporato, A. M.

2013-12-01

Regional scale drought-induced forest mortality events are projected to become more frequent under future climates due to changes in rainfall patterns. However, the ability to predict the conditions under which such events occur is currently lacking. To quantify and understand the underlying causes of drought-induced forest mortality, we propose a stochastic ecohydrological model that explicitly couples tree water and carbon use strategies with climate characteristics, such as the frequency and severity of drought. Using the model and results from a controlled drought experiment, we identify the soil, vegetation, and climate factors that underlie tree water and carbon deficits and, ultimately, the risk of drought-induced forest mortality. This mortality risk is then compared across the spectrum of anisohydric-isohydric stomatal control strategies and a range of rainfall regimes. These results suggest certain soil-plant combinations may maximize the survivable drought length in a given climate. Finally, we discuss how this approach can be expanded to estimate the effect of anticipated climate change on drought-induced forest mortality and associated consequences for forest water and carbon balances.

Fire in the Vegetation and Peatlands of Borneo, 1997-2007: Patterns, Drivers and Emissions from Biomass Burning

NASA Astrophysics Data System (ADS)

Spessa, Allan; Weber, Ulrich; Langner, Andreas; Siegert, Florian; Heil, Angelika

2010-05-01

The peatland forests of equatorial SE Asia cover over 20 Mha with most located in Indonesia. Indonesian peatlands are globally one of the largest near-surface reserves of terrestrial organic carbon, with peat deposits of up to 20m thick and an estimated carbon storage of 55-61 Gt. The destructive fires in Indonesia during the exceptionally strong drought of late 1997 and early 1998 mark some of the largest peak emissions events in recorded history of global fires. Past studies estimate that about 1Gt of carbon was released to the atmosphere from the Indonesian fires in 1997- equivalent to 14% of the average global annual fossil fuel emissions released during the 1990s. Previous studies have established a non-linear negative correlation between fires and antecedent rainfall in Borneo, with ENSO-driven droughts being identified as the main cause of below-average rainfall events over the past decade or so. However, while these studies suggest that this non-linear relationship is mediated by ignitions associated with land use and land cover change (LULCC), they have not demonstrated it. A clear link between fires and logging in Borneo has been reported, but this work was restricted to eastern Kalimantan and the period 1997-98. The relationship between fires, emissions, rainfall and LULCC across the island of Borneo therefore remains to be examined using available fine resolution data over a multi-year period. Using rainfall data, up-to-date peat maps and state-of-the art satellite sensor data to determine burnt area and deforestation patterns over the decade 1997-2007, we show at a pixel working resolution of 0.25 degrees the following: Burning across Borneo predominated in southern Kalimantan. Fire activity is negatively and non-linearly correlated to rainfall mainly in pixels that have undergone a significant reduction in forest cover, and that the bigger the reduction, the stronger the correlation. Such pixels occur overwhelmingly in southern Kalimantan. These correlations are noticeably much weaker or absent in Sarawak and Sabah, and central Borneo, where little or no deforestation was observed. Emissions from biomass burning reflect fire activity, and that fires in the carbon-rich peats of southern Kalimantan dominate the emissions profile during the El Nino years of 1997-98, 2002, 2004 and 2006. Previous work in southern Amazon forests demonstrates that recurrent fires promote a change from tree-dominated to grass-dominated ecosystems which, in turn, promotes even more fires. We show that recurrent fire and deforestation are also linked as part of a similar positive feedback process in Kalimantan. Our results support the detailed field work undertaken in 1997-98 in East Kalimantan, and reinforce these findings across time and space. Emissions from fires in Kalimantan peatlands represent a serious perturbation in terms of forcing from trace gases and aerosols on regional and global climate. Several global and regional climate modelling studies have reported that equatorial SE Asia, including Borneo, will experience reduced rainfall in future decades. At the same time, demands for establishing pulp paper and palm oil plantations to replace native rainforests, especially on peatlands where tenure conflicts among land owners tend to be minimal, is forecast to increase. These joint scenarios imply even more fires and emissions in future. It is critical therefore that present efforts to mitigate emissions through reduced deforestation programs in the region works, otherwise the consequences will be disastrous.

Rapid increases and time-lagged declines in amphibian occupancy after wildfire.

PubMed

Hossack, Blake R; Lowe, Winsor H; Corn, Paul Stephen

2013-02-01

Climate change is expected to increase the frequency and severity of drought and wildfire. Aquatic and moisture-sensitive species, such as amphibians, may be particularly vulnerable to these modified disturbance regimes because large wildfires often occur during extended droughts and thus may compound environmental threats. However, understanding of the effects of wildfires on amphibians in forests with long fire-return intervals is limited. Numerous stand-replacing wildfires have occurred since 1988 in Glacier National Park (Montana, U.S.A.), where we have conducted long-term monitoring of amphibians. We measured responses of 3 amphibian species to fires of different sizes, severity, and age in a small geographic area with uniform management. We used data from wetlands associated with 6 wildfires that burned between 1988 and 2003 to evaluate whether burn extent and severity and interactions between wildfire and wetland isolation affected the distribution of breeding populations. We measured responses with models that accounted for imperfect detection to estimate occupancy during prefire (0-4 years) and different postfire recovery periods. For the long-toed salamander (Ambystoma macrodactylum) and Columbia spotted frog (Rana luteiventris), occupancy was not affected for 6 years after wildfire. But 7-21 years after wildfire, occupancy for both species decreased ≥ 25% in areas where >50% of the forest within 500 m of wetlands burned. In contrast, occupancy of the boreal toad (Anaxyrus boreas) tripled in the 3 years after low-elevation forests burned. This increase in occupancy was followed by a gradual decline. Our results show that accounting for magnitude of change and time lags is critical to understanding population dynamics of amphibians after large disturbances. Our results also inform understanding of the potential threat of increases in wildfire frequency or severity to amphibians in the region. ©2012 Society for Conservation Biology.

Rapid increases and time-lagged declines in amphibian occupancy after wildfire

USGS Publications Warehouse

Hossack, Blake R.; Lowe, Winsor H.; Corn, Paul Stephen

2013-01-01

Climate change is expected to increase the frequency and severity of drought and wildfire. Aquatic and moisture-sensitive species, such as amphibians, may be particularly vulnerable to these modified disturbance regimes because large wildfires often occur during extended droughts and thus may compound environmental threats. However, understanding of the effects of wildfires on amphibians in forests with long fire-return intervals is limited. Numerous stand-replacing wildfires have occurred since 1988 in Glacier National Park (Montana, U.S.A.), where we have conducted long-term monitoring of amphibians. We measured responses of 3 amphibian species to fires of different sizes, severity, and age in a small geographic area with uniform management. We used data from wetlands associated with 6 wildfires that burned between 1988 and 2003 to evaluate whether burn extent and severity and interactions between wildfire and wetland isolation affected the distribution of breeding populations. We measured responses with models that accounted for imperfect detection to estimate occupancy during prefire (0-4 years) and different postfire recovery periods. For the long-toed salamander (Ambystoma macrodactylum) and Columbia spotted frog (Rana luteiventris), occupancy was not affected for 6 years after wildfire. But 7-21 years after wildfire, occupancy for both species decreased ≥ 25% in areas where >50% of the forest within 500 m of wetlands burned. In contrast, occupancy of the boreal toad (Anaxyrus boreas) tripled in the 3 years after low-elevation forests burned. This increase in occupancy was followed by a gradual decline. Our results show that accounting for magnitude of change and time lags is critical to understanding population dynamics of amphibians after large disturbances. Our results also inform understanding of the potential threat of increases in wildfire frequency or severity to amphibians in the region.

An assessment of climate and fire danger rating in the Northern Rockies during the 1910 fire season

Treesearch

Charles W. McHugh; Mark A. Finney; Larry S. Bradshaw

2010-01-01

The 1910 fires of western Montana and northern Idaho have received much publicity in the popular media but little scientific attention regarding the factors that contribute to fire behavior and fire danger. Here we present information surrounding the weather, and reconstructed measures of Palmer Drought Severity Index (PDSI), Keetch-Byram Drought Index (KBDI), Energy...

Mortality of resprouting chaparral shrubs after a fire and during a record drought: physiological mechanisms and demographic consequences.

PubMed

Pratt, R Brandon; Jacobsen, Anna L; Ramirez, Aaron R; Helms, Anjel M; Traugh, Courtney A; Tobin, Michael F; Heffner, Marcus S; Davis, Stephen D

2014-03-01

We examined postfire regeneration of chaparral shrubs during an intense drought. This study focused on the demography and physiology of shrub species that resprout from a basal lignotuber following fire. We found significant levels of resprout mortality when intense drought occurred in the year following fire during the period of shrub recovery. Three of the seven sampled resprouting species had the greatest or near greatest levels of mortality ever recorded when compared to previous studies. Most shrub mortality occurred during the drought after individuals had resprouted (i.e. individuals survived fire, resprouted and then subsequently died). Physiological measurements of species with high mortality suggested that resprout stems were highly embolized and xylem hydraulic conductivities were close to zero during the peak of the drought. In addition, lignotubers of two of the three species experiencing high mortality were depleted of starch. Population densities of most shrub species declined after the drought compared with their prefire levels, with the exception of one drought tolerant obligate seeding species. Resprouting shrub species may deplete their carbohydrate reserves during the resprouting process, making them particularly vulnerable to drought because of the need to transpire water to acquire the CO2 that is used to supply energy to a large respiring root system. Drought appears to interact with fire by altering postfire shrub recovery and altering species abundances and composition of chaparral communities. © 2013 John Wiley & Sons Ltd.

Vulnerability to drought-induced embolism of Bornean heath and dipterocarp forest trees.

PubMed

Tyree, Melvin T.; Patiño, Sandra; Becker, Peter

1998-01-01

Occasional droughts may be important in controlling the distribution and structure of forest types in relatively aseasonal north Borneo. The low water retention capacity of the coarse, sandy soils on which tropical heath forest occurs may cause drought to develop more quickly and severely than on the finer textured soils of nearby dipterocarp forest. Resistance to drought-induced embolism is considered an important component of drought tolerance. We constructed embolism vulnerability curves relating loss in hydraulic conductivity to xylem tension by the air-injection method for understory trees of 14 species from both tropical heath and mixed dipterocarp forests in Brunei Darussalam. There was no significant difference (Mann-Whitney U-test, P = 0.11) between forest types in the xylem tension at which 50% loss of hydraulic conductivity occurred. Most species from both forest types were highly vulnerable to embolism compared with species from seasonal tropical forests. We speculate that other mechanisms, such as stomatal control to prevent development of embolism-inducing xylem tensions, are more cost-effective adaptations against occasional drought, but that the attendant reduction in productivity and competitive ability places a greater premium on resistance to embolism when drought is annual and predictable.

The German drought monitor

NASA Astrophysics Data System (ADS)

Zink, Matthias; Samaniego, Luis; Kumar, Rohini; Thober, Stephan; Mai, Juliane; Schäfer, David; Marx, Andreas

2016-07-01

The 2003 drought event in Europe had major implications on many societal sectors, including energy production, health, forestry and agriculture. The reduced availability of water accompanied by high temperatures led to substantial economic losses on the order of 1.5 Billion Euros, in agriculture alone. Furthermore, soil droughts have considerable impacts on ecosystems, forest fires and water management. Monitoring soil water availability in near real-time and at high-resolution, i.e., 4 × 4 km2, enables water managers to mitigate the impact of these extreme events. The German drought monitor was established in 2014 as an online platform. It uses an operational modeling system that consists of four steps: (1) a daily update of observed meteorological data by the German Weather Service, with consistency checks and interpolation; (2) an estimation of current soil moisture using the mesoscale hydrological model; (3) calculation of a quantile-based soil moisture index (SMI) based on a 60 year data record; and (4) classification of the SMI into five drought classes ranging from abnormally dry to exceptional drought. Finally, an easy to understand map is produced and published on a daily basis on www.ufz.de/droughtmonitor. Analysis of the ongoing 2015 drought event, which garnered broad media attention, shows that 75% of the German territory underwent drought conditions in July 2015. Regions such as Northern Bavaria and Eastern Saxony, however, have been particularly prone to drought conditions since autumn 2014. Comparisons with historical droughts show that the 2015 event is amongst the ten most severe drought events observed in Germany since 1954 in terms of its spatial extent, magnitude and duration.

Chemical Results of Laboratory Dry/Rewet Experiments Conducted on Wetland Soils from Two Sites in the Everglades, Florida

USGS Publications Warehouse

Orem, William H.

2008-01-01

Drought and fire are natural environmental factors that have historically impacted and shaped the Everglades ecosystem. For example, drought and fire help to maintain the existing ecosystem biotic assemblage by periodically eradicating invading flora not adapted to living with this normal aspect of Everglades' ecology. Flora native to the Everglades are adapted to withstand normal drought cycles and all but the most intense fire conditions that burn into the peat substrate. Remobilization of nutrients and other elements from wetland soil following drought/fire and rewetting may actually stimulate plant re-growth, assisting in the recovery of the ecosystem from these events, and play a role in maintaining the geochemical balance of the ecosystem. Although drought/fire cycles occur naturally in the Everglades' ecosystem, the frequency, intensity, and duration of these events have been altered by anthropogenic activities. The hydrology of the ecosystem has been changed by the construction of water management structures starting around 1900 and continuing through the 1970s. These structures include canals, levees, and pumping stations around Lake Okeechobee and within the Everglades. In addition, water management practices have preferentially moved water toward agricultural and urban areas and away from the Everglades during periods of low rainfall. One result of these practices has been more severe drought and fire cycles within the ecosystem compared to pre-development activity. A major goal of restoration efforts in the Everglades is to restore a more natural flow of water into the ecosystem to alleviate some of the extreme drought and fire conditions witnessed during the past several decades.

Smokey Bear is Dead: A New Era of Wildfires in the Western U.S

NASA Astrophysics Data System (ADS)

Pierce, J. L.; Duffin, J.; Lindquist, E.; Wuerzer, T.; Pellant, M.

2013-12-01

High fuel densities, combined with increasingly severe drought, make the western US highly susceptible to changes in the timing of snowmelt and increases in the length of the fire season. The forests and rangelands of Idaho are especially prone to wildfire; in 2012, over 1.7 million acres burned across Idaho, more acres than in any other state. Climate change is projected to increase summer temperatures and decrease summer precipitation in Idaho, and a drier, warmer, and more variable climate will increase the risk of stand-replacing fires. While infrastructure and alert systems are in place to warn residents about threats from hurricanes, floods and tornados, there is limited protection for communities in the ';fire-plain.' Part of this lack of preparation may stem from the belief that fires can be prevented or stopped; a perception that has been perpetuated by ';Smokey Bear,' and the generally successful interval of fire suppression during the 1960's-1980's. However, in the mid-1980's, severe drought, rising temperatures, and early snowmelt have brought an era of ';mega-fires' to the American West. Periods of recurring high wildfire activity across the western US are not unprecedented in the paleo-record, but the frequency of large fires (> 400 ha) and the annual area burned have increased in the modern. For example, in the past 10 years in Idaho, 17 fires burned over 100,000 acres each: six of those fires occurred in 2012. Likewise, the size and severity of rangeland fires in the Western U.S. has increased by almost an order of magnitude in recent decades; in the early 1980's, range fire extents over 100,000 acres was unheard of, but has become increasingly common in recent years (Pellant, 2013). Boise State University's departments of Geoscience, Community and Regional Planning, and the Public Policy Center are examining the risks and impacts of fire along the Boise WUI. The research integrates the perspectives of the geosciences and social sciences by combining physically-based fire hazards, effective fire management policies, and Planning in the West.

Seven hundred years of human-driven and climate-influenced fire activity in a British Columbia coastal temperate rainforest

PubMed Central

Gavin, Daniel G.; Starzomski, Brian M.

2016-01-01

While wildland fire is globally most common at the savannah-grassland ecotone, there is little evidence of fire in coastal temperate rainforests. We reconstructed fire activity with a ca 700-year fire history derived from fire scars and stand establishment from 30 sites in a very wet (up to 4000 mm annual precipitation) temperate rainforest in coastal British Columbia, Canada. Drought and warmer temperatures in the year prior were positively associated with fire events though there was little coherence of climate indices on the years of fires. At the decadal scale, fires were more likely to occur after positive El Niño-Southern Oscillation and Pacific Decadal Oscillation phases and exhibited 30-year periods of synchrony with the negative phase of the Arctic Oscillation. Fire frequency was significantly inversely correlated with the distance from former Indigenous habitation sites and fires ceased following cultural disorganization caused by disease and other European impacts in the late nineteenth century. Indigenous people were likely to have been the primary ignition source in this and many coastal temperate rainforest settings. These data are directly relevant to contemporary forest management and discredit the myth of coastal temperate rainforests as pristine landscapes. PMID:27853581

Control of the multimillennial wildfire size in boreal North America by spring climatic conditions

PubMed Central

Ali, Adam A.; Blarquez, Olivier; Girardin, Martin P.; Hély, Christelle; Tinquaut, Fabien; El Guellab, Ahmed; Valsecchi, Verushka; Terrier, Aurélie; Bremond, Laurent; Genries, Aurélie; Gauthier, Sylvie; Bergeron, Yves

2012-01-01

Wildfire activity in North American boreal forests increased during the last decades of the 20th century, partly owing to ongoing human-caused climatic changes. How these changes affect regional fire regimes (annual area burned, seasonality, and number, size, and severity of fires) remains uncertain as data available to explore fire–climate–vegetation interactions have limited temporal depth. Here we present a Holocene reconstruction of fire regime, combining lacustrine charcoal analyses with past drought and fire-season length simulations to elucidate the mechanisms linking long-term fire regime and climatic changes. We decomposed fire regime into fire frequency (FF) and biomass burned (BB) and recombined these into a new index to assess fire size (FS) fluctuations. Results indicated that an earlier termination of the fire season, due to decreasing summer radiative insolation and increasing precipitation over the last 7.0 ky, induced a sharp decrease in FF and BB ca. 3.0 kyBP toward the present. In contrast, a progressive increase of FS was recorded, which is most likely related to a gradual increase in temperatures during the spring fire season. Continuing climatic warming could lead to a change in the fire regime toward larger spring wildfires in eastern boreal North America. PMID:23213207

Fire history, related to climate and land use in three southern Appalachian landscapes in the eastern United States.

PubMed

Flatley, William T; Lafon, Charles W; Grissino-Mayer, Henri D; LaForest, Lisa B

2013-09-01

Fire-maintained ecosystems and associated species are becoming increasingly rare in the southern Appalachian Mountains because of fire suppression policies implemented in the early 20th century. Restoration of these communities through prescribed fire has been hindered by a lack of information on historical fire regimes. To characterize past fire regimes, we collected and absolutely dated the tree rings on cross sections from 242 fire-scarred trees at three different sites in the southern Appalachian Mountains of Tennessee and North Carolina. Our objectives were to (1) characterize the historical frequency of fire in southern Appalachian mixed pine-oak forests, (2) assess the impact of interannual climatic variability on the historical occurrence of fire, and (3) determine whether changes in human culture and land use altered the frequency of fire. Results demonstrate that fires burned frequently at all three sites for at least two centuries prior to the implementation of fire suppression and prevention in the early to mid 20th century. Composite mean fire return intervals were 2-4 yr, and point mean fire return intervals were 9-13 yr. Area-wide fires that burned across multiple stands occurred at 6-13-yr intervals. The majority of fires were recorded during the dormant season. Fire occurrence exhibited little relationship with reconstructed annual drought conditions. Also, fire activity did not change markedly during the transition from Native American to Euro-American settlement or during the period of industrial logging at the start of the 20th century. Fire activity declined significantly, however, during the fire suppression period, with a nearly complete absence of fire during recent decades. The characterization of past fire regimes should provide managers with specific targets for restoration of fire-associated communities in the southern Appalachian Mountains. The fire chronologies reported here are among the longest tree-ring reconstructions of fire history compiled for the eastern United States and support the hypothesis that frequent burning has played a long and important role in the development of forests in the southern Appalachian Mountains.

Climate and hydrological changes in the northeastern United States: recent trends and implications for forested and aquatic ecosystems

USGS Publications Warehouse

Huntington, Thomas G.; Richardson, Andrew D.; McGuire, Kevin J.; Hayhoe, Katharine

2009-01-01

We review twentieth century and projected twenty-first century changes in climatic and hydrologic conditions in the northeastern United States and the implications of these changes for forest ecosystems. Climate warming and increases in precipitation and associated changes in snow and hydrologic regimes have been observed over the last century, with the most pronounced changes occurring since 1970. Trends in specific climatic and hydrologic variables differ in their responses spatially (e.g., coastal vs. inland) and temporally (e.g., spring vs. summer). Trends can differ depending on the period of record analyzed, hinting at the role of decadal-scale climatic variation that is superimposed over the longer-term trend. Model predictions indicate that continued increases in temperature and precipitation across the northeastern United States can be expected over the next century. Ongoing increases in growing season length (earlier spring and later autumn) will most likely increase evapotranspiration and frequency of drought. In turn, an increase in the frequency of drought will likely increase the risk of fire and negatively impact forest productivity, maple syrup production, and the intensity of autumn foliage coloration. Climate and hydrologic changes could have profound effects on forest structure, composition, and ecological functioning in response to the changes discussed here and as described in related articles in this issue of the Journal.

Derivation of burn scar depths and estimation of carbon emissions with LIDAR in Indonesian peatlands

PubMed Central

Ballhorn, Uwe; Siegert, Florian; Mason, Mike; Limin, Suwido

2009-01-01

During the 1997/98 El Niño-induced drought peatland fires in Indonesia may have released 13–40% of the mean annual global carbon emissions from fossil fuels. One major unknown in current peatland emission estimations is how much peat is combusted by fire. Using a light detection and ranging data set acquired in Central Kalimantan, Borneo, in 2007, one year after the severe peatland fires of 2006, we determined an average burn scar depth of 0.33 ± 0.18 m. Based on this result and the burned area determined from satellite imagery, we estimate that within the 2.79 million hectare study area 49.15 ± 26.81 megatons of carbon were released during the 2006 El Niño episode. This represents 10–33% of all carbon emissions from transport for the European Community in the year 2006. These emissions, originating from a comparatively small area (approximately 13% of the Indonesian peatland area), underline the importance of peat fires in the context of green house gas emissions and global warming. In the past decade severe peat fires occurred during El Niño-induced droughts in 1997, 2002, 2004, 2006, and 2009. Currently, this important source of carbon emissions is not included in IPCC carbon accounting or in regional and global carbon emission models. Precise spatial measurements of peat combusted and potential avoided emissions in tropical peat swamp forests will also be required for future emission trading schemes in the framework of Reduced Emissions from Deforestation and Degradation in developing countries. PMID:19940252

Forest fires caused by lightning activity in Portugal

NASA Astrophysics Data System (ADS)

Russo, Ana; Ramos, Alexandre M.; Benali, Akli; Trigo, Ricardo M.

2017-04-01

Wildfires in southern Europe have been causing in the last decades extensive economic and ecological losses and, even human casualties (e.g. Pereira et al., 2011). According to statistics provided by the EC-JRC European Forest Fires Information System (EFFIS) for Europe, the years of 2003 and 2007 represent the most dramatic fire seasons since the beginning of the millennium, followed by the years 2005 and 2012. These extreme years registered total annual burned areas for Europe of over 600.000 ha, reaching 800.000 ha in 2003. Over Iberia and France, the exceptional fire seasons registered in 2003 and 2005 were coincident respectively with one of the most severe heatwaves (Bastos et al., 2014) and droughts of the 20th century (Gouveia et al., 2009). On the other hand, the year 2007 was very peculiar as the area of the Peloponnese was struck by a severe winter drought followed by a subsequent wet spring, being also stricken by three heat heaves during summer and played a major role increasing the susceptibility of the region to wildfires (Gouveia et al., 2016). Some countries have a relatively large fraction of fires caused by natural factors such as lightning, e.g. northwestern USA, Canada, Russia. In contrast, Mediterranean countries such as Portugal has only a small percentage of fire records caused by lightning. Although significant uncertainties remain for the triggering mechanism for the majority of fires registered in the catalog, since they were cataloged without a likely cause. In this work we have used mainly two different databases: 1) the Portuguese Rural Fire Database (PRFD) which is representative of rural fires that have occurred in Continental Portugal, 2002-2009, with the original data provided by the National forestry Authority; 2) lightning discharges location which were extracted from the Portuguese Lightning Location System that has been in service since June of 2002 and is operated by the national weather service - Portuguese Institute for Sea and Atmosphere (IPMA). The main objective of this work was to evaluate and quantify the relations between the wildfires' occurrence and the lightning activity. In particularly we were able to verify if wildfires which were identified as "ignited by lightning" by comparing its location to the lightning discharges location database. Furthermore we have also investigated possible fire ignition by lightning discharges that have not yet been labeled in the PRFD by comparing daily data from both datasets. - Bastos A., Gouveia C.M., Trigo R.M., Running S.W., 2014. Biogeosciences, 11, 3421-3435. - Pereira M.G., B.D. Malamud R.M. Trigo, P.I. Alves, 2011. Nat. Hazards Earth Syst. Sci., 11, 3343-3358. - Gouveia C., Trigo R.M., DaCamara C.C., 2009. Nat. Hazards Earth Syst. Sci., 9, 185-195 - Gouveia C.M., Bistinas I., Liberato M.L.R., Bastos A., Koutsiasd N., Trigo R., 2016. Agricultural and Forest Meteorology, 218-219, 135-145. Acknowledgements Research performed was supported by FAPESP/FCT Project Brazilian Fire-Land-Atmosphere System (BrFLAS) (1389/2014 and 2015/01389-4). Ana Russo thanks FCT for granted support (SFRH/BPD/99757/2014). A. M. Ramos was also supported by a FCT postdoctoral grant (FCT/DFRH/ SFRH/BPD/84328/2012).

Global Burned Area and Biomass Burning Emissions from Small Fires

NASA Technical Reports Server (NTRS)

Randerson, J. T.; Chen, Y.; vanderWerf, G. R.; Rogers, B. M.; Morton, D. C.

2012-01-01

In several biomes, including croplands, wooded savannas, and tropical forests, many small fires occur each year that are well below the detection limit of the current generation of global burned area products derived from moderate resolution surface reflectance imagery. Although these fires often generate thermal anomalies that can be detected by satellites, their contributions to burned area and carbon fluxes have not been systematically quantified across different regions and continents. Here we developed a preliminary method for combining 1-km thermal anomalies (active fires) and 500 m burned area observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) to estimate the influence of these fires. In our approach, we calculated the number of active fires inside and outside of 500 m burn scars derived from reflectance data. We estimated small fire burned area by computing the difference normalized burn ratio (dNBR) for these two sets of active fires and then combining these observations with other information. In a final step, we used the Global Fire Emissions Database version 3 (GFED3) biogeochemical model to estimate the impact of these fires on biomass burning emissions. We found that the spatial distribution of active fires and 500 m burned areas were in close agreement in ecosystems that experience large fires, including savannas across southern Africa and Australia and boreal forests in North America and Eurasia. In other areas, however, we observed many active fires outside of burned area perimeters. Fire radiative power was lower for this class of active fires. Small fires substantially increased burned area in several continental-scale regions, including Equatorial Asia (157%), Central America (143%), and Southeast Asia (90%) during 2001-2010. Globally, accounting for small fires increased total burned area by approximately by 35%, from 345 Mha/yr to 464 Mha/yr. A formal quantification of uncertainties was not possible, but sensitivity analyses of key model parameters caused estimates of global burned area increases from small fires to vary between 24% and 54%. Biomass burning carbon emissions increased by 35% at a global scale when small fires were included in GFED3, from 1.9 Pg C/yr to 2.5 Pg C/yr. The contribution of tropical forest fires to year-to-year variability in carbon fluxes increased because small fires amplified emissions from Central America, South America and Southeast Asia-regions where drought stress and burned area varied considerably from year to year in response to El Nino-Southern Oscillation and other climate modes.

Combining Ecosystem Observations, Manipulations and the Data Assimilation Research Testbed to Provide New Insights into Community Land Model Performance

NASA Astrophysics Data System (ADS)

Foster, A.; Armstrong, A. H.; Shuman, J. K.; Ranson, K.; Shugart, H. H., Jr.; Rogers, B. M.; Goetz, S. J.

2016-12-01

Global temperatures have increased about 0.2°C per decade since 1979, and the high latitudes are warming faster than the rest of the globe. Climate change within Alaska is likely to bring about increased drought and longer fire seasons, as well as increases in the severity and frequency of fires. These changes in disturbance regimes and their associated effects on ecosystem C stocks, including permafrost, may lead to a positive feedback to further climate warming. As of now, it is uncertain how vegetation will respond to ongoing climate change, and the addition of disturbance effects leads to even more complicated and varied scenarios. Through ecological modeling, we have the capacity to examine forest processes at multiple temporal and spatial scales, allowing for the testing of complex interactions between vegetation, climate, and disturbances. The University of Virginia Forest Model Enhanced (UVAFME) is an individual tree-based forest model that has been updated for use in interior boreal Alaska, with a new permafrost model and updated fire simulation. These updated submodels allow for feedback between soils, vegetation, and fire severity through fuels tracking and impact of depth of burn on permafrost dynamics. We present these updated submodels as well as calibration and validation of UVAFME to the Yukon River Basin in Alaska, with comparisons to inventory data. We also present initial findings from simulations of potential future forest biomass, structure, and species composition across the Yukon River Basin under expected changes in precipitation, temperature, and disturbances. We predict changing climate and the associated impacts on wildfire and permafrost dynamics will result in shifts in biomass and species composition across the region, with potential for further feedback to the climate-vegetation-disturbance system. These simulations advance our understanding of the possible futures for the Alaskan boreal forest, which is a valuable part of the global carbon budget.

Drought impact on vegetation in pre and post fire events in Iberian Peninsula

NASA Astrophysics Data System (ADS)

Gouveia, C. M.; Bastos, A.; Trigo, R. M.; DaCamara, C.

2012-04-01

In 2004/2005, the Iberian Peninsula was stricken by an exceptional drought that affected more than one third of Portugal and part of southern Spain during more than 9 months. This severe drought had a strong negative impact on vegetation dynamics, as it coincided with the period of high photosynthetic activity (Gouveia et al., 2009). Since water availability is a crucial factor in post-fire vegetation recovery, it is desirable to assess the impact that such water-stress conditions had on fire sensitivity and post-fire vegetation recovery. Fire events in the European Mediterranean areas have become a serious problem and a major ecosystem disturbance, increasing erosion and soil degradation. In Portugal, the years 2003 and 2005 were particularly devastating. In 2003 it was registered the maximal burnt area since 1980, with more than 425000 ha burned, representing about 5% of Portuguese mainland. The 2005 fire season registered the highest number of fire occurrences in Portugal and the second year with the greatest number of fires in Spain. The high number of fire events observed during the summer 2005 in the Iberian Peninsula is linked, in part, to the extreme drought conditions that prevailed during the preceding winter and spring seasons of 2004/2005. Vegetation recovery after the 2003 and 2005 fire seasons was estimated using the mono-parametric model developed by Gouveia et al. (2010), which relies on monthly values of Normalized Difference Vegetation Index (NDVI), from 1999 to 2009, at 1kmresolution, as obtained from the VEGETATION-SPOT5 instrument.. This model was further used to evaluate the effect of drought in pre and post vegetation activity. Besides the standard NDVI, the Normalized Difference Water Index (NDWI) and the Normalized Difference Drought Index (NDDI) were computed in order to evaluate drought intensity. In the case of the burnt scars of 2003, when data corresponding to the months of drought are removed, recovery times are considerably shorter. The extreme water stress conditions to which vegetation is subject during drought events appear, therefore, to delay the regeneration process, which is to be expected since water availability is determinant to primary productivity. On the other hand, in the case of 2005 burnt areas, vegetation is more stressed and dryer in summer than in spring and, in general, fire damage is higher for pixels with higher vegetation density and higher moisture content during the months before the fire. These relationships are also related with the distinct vegetation behavior of the different land covers: in general, shrubland holds less quantity of very dry biomass, while needle leaf presents higher amounts of fairly dry biomass. Gouveia C., Trigo R.M., DaCamara C.C (2009) "Drought and Vegetation Stress Monitoring in Portugal using Satellite Data". Natural Hazards and Earth System Sciences, 9, 1-11 Gouveia C., DaCamara C.C, Trigo R.M. (2010). "Post-fire vegetation dynamics in Portugal". Natural Hazards and Earth System Sciences, 10, 4, 673-684.

Evaluation of last extreme drought events in Amazon basin using remotely sensing data

NASA Astrophysics Data System (ADS)

Panisset, Jéssica S.; Gouveia, Célia M.; Libonati, Renata; Peres, Leonardo; Machado-Silva, Fausto; França, Daniela A.; França, José R. A.

2017-04-01

Amazon basin has experienced several intense droughts among which were highlighted last recent ones in 2005 and 2010. Climate models suggest these events will be even more frequent due to higher concentration of greenhouse gases that are also driven forward by alteration in forest dynamics. Environmental and social impacts demand to identify these intense droughts and the behavior of climate parameters that affect vegetation. This present study also identifies a recent intense drought in Amazon basin during 2015. Meteorological parameters and vegetation indices suggest this event was the most severe already registered in the region. We have used land surface temperature (LST), vegetation indices, rainfall and shortwave radiation from 2000 to 2015 to analyze and compare droughts of 2005, 2010 and 2015. Our results show singularities among the three climate extreme events. The austral winter was the most affected season in 2005 and 2010, but not in 2015 when austral summer presented extreme conditions. Precipitation indicates epicenter of 2005 in west Amazon corroborating with previous studies. In 2010, the west region was strongly affected again together with the northwest and the southeast areas. However, 2015 epicenters were concentrated in the east of the basin. In 2015, shortwave radiation has exceeded the maximum values of 2005 and temperature the maximum value of 2010. Vegetation indices have shown positive and negative anomalies. Despite of heterogenous response of Amazon forest to drought, hybrid vegetation indices using NDVI (Normalized Difference Vegetation Index) and LST highlights the exceptionality of 2015 drought episode that exhibits higher vegetation water stress than the cases of 2010 and 2005. Finally, this work has shown how meteorological parameters influence droughts and the effects on vegetation in Amazon basin. Complexity of climate, ecosystem heterogeneity and high diversity of Amazon forest are response by idiosyncrasies of each drought. All these information improve the predictability of future climate scenarios and their effects in the environment. Research performed was supported by FAPESP/FCT Project Brazilian Fire-Land-Atmosphere System (BrFLAS) (1389/2014 and 2015/01389-4), by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) through a Master grant from PPGM/IGEO/UFRJ (first author), and by Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) through grants E-26/201.521/2014; E-26/101.423/2014; E-26/201.221/2015; and E-26/203.174/2016.

Drought stress and carbon uptake in an Amazon forest measured with spaceborne imaging spectroscopy

PubMed Central

Asner, Gregory P.; Nepstad, Daniel; Cardinot, Gina; Ray, David

2004-01-01

Amazônia contains vast stores of carbon in high-diversity ecosystems, yet this region undergoes major changes in precipitation affecting land use, carbon dynamics, and climate. The extent and structural complexity of Amazon forests impedes ground studies of ecosystem functions such as net primary production (NPP), water cycling, and carbon sequestration. Traditional modeling and remote-sensing approaches are not well suited to tropical forest studies, because (i) biophysical mechanisms determining drought effects on canopy water and carbon dynamics are poorly known, and (ii) remote-sensing metrics of canopy greenness may be insensitive to small changes in leaf area accompanying drought. New spaceborne imaging spectroscopy may detect drought stress in tropical forests, helping to monitor forest physiology and constrain carbon models. We combined a forest drought experiment in Amazônia with spaceborne imaging spectrometer measurements of this area. With field data on rainfall, soil water, and leaf and canopy responses, we tested whether spaceborne hyperspectral observations quantify differences in canopy water and NPP resulting from drought stress. We found that hyperspectral metrics of canopy water content and light-use efficiency are highly sensitive to drought. Using these observations, forest NPP was estimated with greater sensitivity to drought conditions than with traditional combinations of modeling, remote-sensing, and field measurements. Spaceborne imaging spectroscopy will increase the accuracy of ecological studies in humid tropical forests. PMID:15071182

Model-data frameworks for determining greenhouse gas implications of bioenergy landscapes in the US

NASA Astrophysics Data System (ADS)

Hudiburg, T. W.; Kent, J.; DeLucia, E. H.; Law, B. E.

2017-12-01

A sustainable, carbon-negative, bio-based portion of the energy sector may require considerable changes in land use. Perennial grasses have been proposed because of their potential to yield substantial biomass on marginal lands without displacing food and reduce GHG emissions by storing soil carbon. Woody biomass from harvest residues and forest health thinning operations have also been proposed, however the GHG mitigation potential is less clear. Through integration of observations, ecosystem, and economic models we have assessed the potential for a US Renewable Fuel Standard (RFS) to displace gasoline and reduce GHG emissions from the transportation sector, through the use of cellulosic biofuels (e.g. perennial grasses). We found that 2022 US transportation sector GHG emissions are decreased by 7.0 ± 2.5%; an estimate that is 50% less than those unconstrained by economic feasibility. Also, through integration of observations, ecosystem modeling, and life cycle assessment, we investigated potential carbon mitigation by replacing an Oregon coal plant with wood (bio-coal) from harvest residues and thinning operations in forests vulnerable to drought and fire. We found that carbon emissions varied from no change to moderate increases compared to the current emissions from the coal plant depending on transportation distance, energy inputs for conversion to bio-coal, and avoided emissions from fire and drought. Our work indicates that integrated assessment using ecosystem and economic models that are constrained by observations is required to evaluate potential GHG and carbon mitigation scenarios from varied feedstock sources.

Review of broad-scale drought monitoring of forests: Toward an integrated data mining approach

Treesearch

Steve Norman; Frank H. Koch; William W. Hargrove

2016-01-01

Efforts to monitor the broad-scale impacts of drought on forests often come up short. Drought is a direct stressor of forests as well as a driver of secondary disturbance agents, making a full accounting of drought impacts challenging. General impacts  can be inferred from moisture deficits quantified using precipitation and temperature measurements. However,...

In Forests Globally, Large Trees Suffer Most during Drought

NASA Astrophysics Data System (ADS)

Bennett, A. C.; McDowell, N. G.; Allen, C. D.; Anderson-Teixeira, K. J.

2014-12-01

Globally, drought events are increasing in both frequency and intensity. Spatial and temporal variation in water availability is expected to alter the ecophysiology and structure of forests, with consequent feedbacks to climate change. Extensive tree mortality induced by heat and aridity has been documented across a range of latitudes, and several global vegetation models have simulated widespread forest die-off in the future. The impact of drought on forest structure and function will depend on the differential responses of trees of different sizes. Understanding the size-dependence of drought-induced mortality is necessary to predict local and global impacts. Here we show that in forests worldwide, drought has a greater impact on the growth and mortality of large trees compared to smaller trees. This trend holds true for forests ranging from semiarid woodlands to tropical rainforests. This finding contrasts with what would be expected if deep root access to water were the primary determinant of tree drought response. Rather, the greater drought response of larger trees could be driven by greater inherent vulnerability of large trees to hydraulic stress or by canopy position becoming more of a liability under drought, as exposed crowns face higher evaporative demand. These findings imply that future droughts will have a disproportionate effect on large trees, resulting in a larger feedback to climate change than would occur if all tree size classes were equally affected by drought.

Tree species' responses to throughfall removal experiments superimposed on a natural drought event in two contrasting humid temperate forests in New Hampshire, USA

NASA Astrophysics Data System (ADS)

Jennings, Katie; McIntire, Cameron; Coble, Adam; Vandeboncoeur, Matthew; Rustad, Lindsay; Templer, Pamela; Absbjornsen, Heidi

2017-04-01

Climate change is likely to affect Northeastern U.S. forests through the increased frequency and severity of drought events. However, our understanding of how these humid temperate forests will respond to moderate to extreme droughts is limited. Given the important role that these forests play in providing ecosystem services and in supplying forest products, enhancing our knowledge about the impacts of drought is critical to guiding forest management and climate change adaptation efforts. We conducted 50% throughfall removal experiments at two contrasting sites in the Northeastern US (Hubbard Brook Experimental Forest and Thompson Farm, NH, USA), which were superimposed on the severe natural drought occurring in August-September 2016. Preliminary analysis suggests that the two sites respond differently to simulated drought. Pinus strobus trees at Thompson Farm reduced their transpiration rates in response to both the natural and experimental drought, particularly evident during a 5-day period at the height of the drought were transpiration nearly ceased. Both P. strobus and Quercus rubra trees increased their water use efficiency in response to reduced soil water availability, with Q. rubra allowing its midday water potential to reach more negative values, consistent with its more drought tolerant strategy compared to P. strobus. In contrast, we did not detect any significant differences in tree transpiration rates or growth in the dominant tree species, Acer rubrum, in response to the experimental drought treatment at Hubbard Brook. However, both soil respiration and fine root biomass production were lower in the drought treatment plots relative to the control plots at Hubbard Brook. We plan to continue these throughfall removal experiments for at least two more years to better understand the implications of future drought in these humid temperate forests and identify differences in species' physiological adaptations and threshold responses.

Implications of mechanistic modeling of drought effects on growth and competition in forest landscape models

Treesearch

Eric J. Gustafson; Arjan M. G. De Bruijn; Brian R. Miranda; Brian R. Sturtevant; J. Thompson

2016-01-01

The incidence of drought is expected to increase worldwide as a factor structuring forested landscapes. Ecophysiological mechanisms are being added to Forest Landscape Models (FLMs) to increase their robustness to the novel environmental conditions of the future (including drought), but their behavior has not been evaluated for mixed temperate forests. We evaluated...

Impacts of single and recurrent wildfires on topsoil moisture regime

NASA Astrophysics Data System (ADS)

González-Pelayo, Oscar; Malvar, Maruxa; van den Elsen, Erik; Hosseini, Mohammadreza; Coelho, Celeste; Ritsema, Coen; Bautista, Susana; Keizer, Jacob

2017-04-01

The increasing fire recurrence on forest in the Mediterranean basin is well-established by future climate scenarios due to land use changes and climate predictions. By this, shifts on mature pine woodlands to shrub rangelands are of major importance on forest ecosystems buffer functions, since historical patterns of established vegetation help to recover from fire disturbances. This fact, together with the predicted expansion of the drought periods, will affect feedback processes of vegetation patterns since water availability on these seasons are driven by post-fire local soil properties. Although fire impacts of soil properties and water availability has been widely studied using the fire severity as the main factor, little research is developed on post-fire soil moisture patterns, including the fire recurrence as a key explanatory variable. The following research investigated, in pine woodlands of north central Portugal, the short-term consequences (one year after a fire) of wildfire recurrence on the surface soil moisture content (SMC) and on effective soil water (SWEFF, parameter that includes actual daily soil moisture, soil field capacity-FC and permanent wilting point-PWP). The study set-up includes analyses at two fire recurrence scenarios (1x- and 4x-burnt since 1975), at a patch level (shrub patch/interpatch) and at two soil depths (2.5 and 7.5 cm) in a nested approach. Understanding how fire recurrence affects water in soil over space and time is the main goal of this research. The use of soil moisture sensors in a nested approach, the rainfall features and analyses on basic soil properties as soil organic matter, texture, bulk density, pF curves, soil water repellency and soil surface components will establish which factors has the largest role in controlling soil moisture behavior. Main results displayed, in a seasonal and yearly basis, no differences on SMC as increasing fire recurrence (1x- vs 4x-burnt) neither between patch/interpatch microsites at both two soil depths. Otherwise, in a yearly basis and during soil drying cycles, it was found less effective water on soil at the surface layers of the 4x-burnt and between shrub interpatches, based on the worst soil hydrological conditions (PWP) and the increasing percentage of abiotic soil surface components as increasing fire recurrence. Our results suggest that the inclusion of soil hydrological properties, as pF-curves, on the soil water effectiveness calculation seems to be a better indicator of water availability that volumetric SM per se. Otherwise, the use of a nested approach methodology, stresses how fire recurrence, expected increases in the summer drought spells and, the increasing dominance of abiotic soil surface components, are the factors that much influence soil eco-hydrological functioning in fire prone ecosystems. Furthermore, this research point out how post-fire soil structural quality into plant interpatches could provoke looping feedback processes triggering desertification situations also in humid Mediterranean forestlands.

Mapping drought conditions using multi-year windows

Treesearch

Frank H. Koch; John W. Coulston; William D. Smith

2012-01-01

Drought, especially persistent drought, may impact forests in direct and indirect ways. Low to moderate drought stress directly reduces plant growth processes at the cellular level, while more severe stress also substantially diminishes photosynthesis (Kareiva and others 1993, Mattson and Haack 1987). Indirectly, forest communities subjected to drought stress may be...

Wildfires in Chernobyl-contaminated forests and risks to the population and the environment: a new nuclear disaster about to happen?

PubMed

Evangeliou, Nikolaos; Balkanski, Yves; Cozic, Anne; Hao, Wei Min; Møller, Anders Pape

2014-12-01

Radioactive contamination in Ukraine, Belarus and Russia after the Chernobyl accident left large rural and forest areas to their own fate. Forest succession in conjunction with lack of forest management started gradually transforming the landscape. During the last 28 years dead wood and litter have dramatically accumulated in these areas, whereas climate change has increased temperature and favored drought. The present situation in these forests suggests an increased risk of wildfires, especially after the pronounced forest fires of 2010, which remobilized Chernobyl-deposited radioactive materials transporting them thousand kilometers far. For the aforementioned reasons, we study the consequences of different forest fires on the redistribution of (137)Cs. Using the time frequency of the fires that occurred in the area during 2010, we study three scenarios assuming that 10%, 50% and 100% of the area are burnt. We aim to sensitize the scientific community and the European authorities for the foreseen risks from radioactivity redistribution over Europe. The global model LMDZORINCA that reads deposition density of radionuclides and burnt area from satellites was used, whereas risks for the human and animal population were calculated using the Linear No-Threshold (LNT) model and the computerized software ERICA Tool, respectively. Depending on the scenario, whereas between 20 and 240 humans may suffer from solid cancers, of which 10-170 may be fatal. ERICA predicts insignificant changes in animal populations from the fires, whereas the already extreme radioactivity background plays a major role in their living quality. The resulting releases of (137)Cs after hypothetical wildfires in Chernobyl's forests are classified as high in the International Nuclear Events Scale (INES). The estimated cancer incidents and fatalities are expected to be comparable to those predicted for Fukushima. This is attributed to the fact that the distribution of radioactive fallout after the wildfires occurred to the intensely populated Western Europe, whereas after Fukushima it occurred towards the Pacific Ocean. The situation will be exacerbated near the forests not only due to the expected redistribution of refractory radionuclides (also trapped there), but also due to the nutritional habits of the local human and animal population. Copyright © 2014 Elsevier Ltd. All rights reserved.

Temperature as a potent driver of regional forest drought stress and tree mortality

USGS Publications Warehouse

Williams, A. Park; Allen, Craig D.; Macalady, Alison K.; Griffin, Daniel; Woodhouse, Connie A.; Meko, David M.; Swetnam, Thomas W.; Rauscher, Sara A.; Seager, Richard; Grissino-Mayer, Henri D.; Dean, Jeffrey S.; Cook, Edward R.; Gangodagamage, Chandana; Cai, Michael; McDowell, Nathan G.

2012-01-01

s the climate changes, drought may reduce tree productivity and survival across many forest ecosystems; however, the relative influence of specific climate parameters on forest decline is poorly understood. We derive a forest drought-stress index (FDSI) for the southwestern United States using a comprehensive tree-ring data set representing AD 1000-2007. The FDSI is approximately equally influenced by the warm-season vapour-pressure deficit (largely controlled by temperature) and cold-season precipitation, together explaining 82% of the FDSI variability. Correspondence between the FDSI and measures of forest productivity, mortality, bark-beetle outbreak and wildfire validate the FDSI as a holistic forest-vigour indicator. If the vapour-pressure deficit continues increasing as projected by climate models, the mean forest drought-stress by the 2050s will exceed that of the most severe droughts in the past 1,000 years. Collectively, the results foreshadow twenty-first-century changes in forest structures and compositions, with transition of forests in the southwestern United States, and perhaps water-limited forests globally, towards distributions unfamiliar to modern civilization.

A Coupled Model for Simulating Future Wildfire Regimes in the Western U.S.

NASA Astrophysics Data System (ADS)

Bart, R. R.; Kennedy, M. C.; Tague, C.; Hanan, E. J.

2017-12-01

Higher temperatures and larger fuel loads in the western U.S. have increased the size and intensity of wildfires over the past decades. However, it is unclear if this trend will continue over the long-term since increased wildfire activity has the countering effect of reducing landscape fuel loads, while higher temperatures alter the rate of vegetation recovery following fire. In this study, we introduce a coupled ecohydrologic-fire model for investigating how changes in vegetation, forest management, climate, and hydrology may affect future fire regimes. The spatially-distributed ecohydrologic model, RHESSys, simulates hydrologic, carbon and nutrient fluxes at watershed scales; the fire-spread model, WMFire, stochastically propagates fire on a landscape based on conditions in the ecohydrologic model. We use the coupled model to replicate fire return intervals in multiple ecoregions within the western U.S., including the southern Sierra Nevada and southern California. We also examine the sensitivity of fire return intervals to various model processes, including litter production, fire severity, and post-fire vegetation recovery rates. Results indicate that the coupled model is able to replicate expected fire return intervals in the selected locations. Fire return intervals were highly sensitive to the rate of vegetation growth, with longer fire return intervals associated with slower growing vegetation. Application of the model is expected to aid in our understanding of how fuel treatments, climate change and droughts may affect future fire regimes.

Spatio-temporal trends of drought by forest type in the conterminous United States, 1960-2013

Treesearch

Matthew P. Peters; Louis R. Iverson; Stephen N. Matthews

2014-01-01

Droughts are common in virtually all U.S. forests, but their frequency and intensity vary within forest ecosystems (Hanson and Weltzin 2000). Accounting for the long-term influence of droughts within a region is difficult due to variations in the spatial extent and intensities over a period. Therefore, we created a cumulative drought severity index (CDSI) (Fig. 1) for...

Climate and Wildfire in Mountains of the Western United States

NASA Astrophysics Data System (ADS)

Alfaro, E.; Westerling, A. L.; Cayan, D. R.

2004-12-01

Since the mid-1980s, there has been a dramatic increase in the area burned in wildfires in mountain forests of the western United States, with mean annual area burned nearly three and a half times higher compared to the preceding one and a half decades.(1) Concomitant increases in variability in annual area burned and in fire suppression costs pose a serious challenge for land management in the mountainous West. The variance in annual area burned since 1987 is nineteen times its previous level. Since managers must be prepared for the worst possible scenarios in every fire season, increased uncertainty about the scale of the western fire season each year imposes high costs on public agencies. Annual real suppression costs in western forests have more than doubled for the Forest Service since 1987, while the variance in annual suppression costs is over four times higher. Although federal agencies' fire suppression budgets have increased recently, they are still close to what would be spent in an "average" year that seldom occurs, while costs tend to fluctuate between low and high extremes. Modeling area burned and suppression costs as a function of climate variability alone, Westerling (2004, unpublished work) found that the probability of the Forest Service's suppression expenses exceeding the current annual suppression budget has exceeded 50% since 1987, a substantial increase from the one-in-three chance over the preceding 40 years. Recent progress in our understanding of the links between climate and wildfire, and in our ability to forecast some aspects of both climate and wildfire season severity a season or more in advance, offers some hope that these costs might be ameliorated through the integration of climate information into fire and fuels management. In addition to the effects of climate variability on wildfire, long-term biomass accumulations in some western ecosystems have fueled an increasing incidence of large, stand-replacing wildfires where such fires were previously rare. These severe large fires can result in erosion and changes in vegetation type, with consequences for water quality, stream flow, future biological productivity of the affected areas, and habitat loss for endangered species. Apart from their deleterious ecological consequences, severe fires can also dramatically affect amenity values for public lands and for homeowners living in the wildland-urban interface. In the National Fire Plan, land management agencies have committed to reducing fuels on millions of hectares of public lands. The primary means are mechanical removal, prescribed fire and wildland fire use. The Forest Service estimates they will need to spend hundreds of millions of dollars per year to meet their fuel reduction targets, while efforts in recent years have not kept up with the current rate of biomass increase. Use of climate information for targeting resources and scheduling prescribed burns could increase the efficiency of these efforts. In this study we review the fire history since 1970 for western mountain forests, and demonstrate apparent links between regional climate variability and decadal-scale changes in annual area burned. This analysis explores how wildfire size and frequency have varied over the past thirty-five years by elevation and latitude, and how climate indices such as precipitation, temperature, drought indices and the timing of spring runoff vary in importance for fire season severity by elevation in forests around the western United States.

7 CFR 760.302 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... breeding purposes on or before the beginning date of a qualifying drought or fire. Adult beef cow means a... qualifying drought or fire. Adult buffalo and beefalo bull means a male animal of those breeds that was at least 2 years old and used for breeding purposes on or before the beginning date of a qualifying drought...

7 CFR 760.302 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... breeding purposes on or before the beginning date of a qualifying drought or fire. Adult beef cow means a... qualifying drought or fire. Adult buffalo and beefalo bull means a male animal of those breeds that was at least 2 years old and used for breeding purposes on or before the beginning date of a qualifying drought...

7 CFR 760.302 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... breeding purposes on or before the beginning date of a qualifying drought or fire. Adult beef cow means a... qualifying drought or fire. Adult buffalo and beefalo bull means a male animal of those breeds that was at least 2 years old and used for breeding purposes on or before the beginning date of a qualifying drought...

7 CFR 760.304 - Covered livestock.

Code of Federal Regulations, 2013 CFR

2013-01-01

... producer: (i) During the 60 days prior to the beginning date of a qualifying drought or fire: (A) Owned, (B...) Sold or otherwise disposed of due to qualifying drought during: (A) The current production year or (B... qualifying drought or fire; (5) Not have been produced and maintained for reasons other than commercial use...

7 CFR 760.303 - Eligible livestock producer.

Code of Federal Regulations, 2011 CFR

2011-01-01

... must: (1) During the 60 days prior to the beginning date of a qualifying drought or fire, own, cash or... county affected by a qualifying drought during the normal grazing period for the county or (ii) Rangeland... qualifying drought or fire to be eligible for LFP payments. (c) An eligible livestock producer does not...

7 CFR 760.304 - Covered livestock.

Code of Federal Regulations, 2012 CFR

2012-01-01

... producer: (i) During the 60 days prior to the beginning date of a qualifying drought or fire: (A) Owned, (B...) Sold or otherwise disposed of due to qualifying drought during: (A) The current production year or (B... qualifying drought or fire; (5) Not have been produced and maintained for reasons other than commercial use...

7 CFR 760.303 - Eligible livestock producer.

Code of Federal Regulations, 2012 CFR

2012-01-01

... must: (1) During the 60 days prior to the beginning date of a qualifying drought or fire, own, cash or... county affected by a qualifying drought during the normal grazing period for the county or (ii) Rangeland... qualifying drought or fire to be eligible for LFP payments. (c) An eligible livestock producer does not...

7 CFR 760.303 - Eligible livestock producer.

Code of Federal Regulations, 2014 CFR

2014-01-01

... must: (1) During the 60 days prior to the beginning date of a qualifying drought or fire, own, cash or... county affected by a qualifying drought during the normal grazing period for the county or (ii) Rangeland... qualifying drought or fire to be eligible for LFP payments. (c) An eligible livestock producer does not...

7 CFR 760.304 - Covered livestock.

Code of Federal Regulations, 2014 CFR

2014-01-01

... producer: (i) During the 60 days prior to the beginning date of a qualifying drought or fire: (A) Owned, (B...) Sold or otherwise disposed of due to qualifying drought during: (A) The current production year or (B... qualifying drought or fire; (5) Not have been produced and maintained for reasons other than commercial use...

7 CFR 760.303 - Eligible livestock producer.

Code of Federal Regulations, 2010 CFR

2010-01-01

... must: (1) During the 60 days prior to the beginning date of a qualifying drought or fire, own, cash or... county affected by a qualifying drought during the normal grazing period for the county or (ii) Rangeland... qualifying drought or fire to be eligible for LFP payments. (c) An eligible livestock producer does not...

7 CFR 760.304 - Covered livestock.

Code of Federal Regulations, 2011 CFR

2011-01-01

... producer: (i) During the 60 days prior to the beginning date of a qualifying drought or fire: (A) Owned, (B...) Sold or otherwise disposed of due to qualifying drought during: (A) The current production year or (B... qualifying drought or fire; (5) Not have been produced and maintained for reasons other than commercial use...

7 CFR 760.303 - Eligible livestock producer.

Code of Federal Regulations, 2013 CFR

2013-01-01

... must: (1) During the 60 days prior to the beginning date of a qualifying drought or fire, own, cash or... county affected by a qualifying drought during the normal grazing period for the county or (ii) Rangeland... qualifying drought or fire to be eligible for LFP payments. (c) An eligible livestock producer does not...

Forest response to 1,000 years of drought variability in the Southwestern United States

NASA Astrophysics Data System (ADS)

Williams, A. P.; Meko, D. M.; Woodhouse, C. A.; Cook, E.; Swetnam, T. W.; Macalady, A. K.; Allen, C. D.; Rauscher, S. A.; Jiang, X.; Grissino-Mayer, H.; McDowell, N. G.; Cai, M.

2011-12-01

Droughts in the early 1950s and early 2000s significantly accelerated tree mortality rates in the Southwestern United States. During the early 2000s, forest inventory data indicate that the proportion of dead piñon pine, ponderosa pine, and Douglas-fir trees doubled in the Southwest. The 2000s drought peaked in 2002 and was the most severe drought in at least 100 years. In 2011, precipitation, dew-point, and wind data indicate the intensity of the 2002 drought has been surpassed in a number of ways. Measurements of water potential in piñon pine trees in northern New Mexico indicate that, at present, trees have less access to soil moisture than in 2002 when widespread mortality occurred. How do these recent droughts compare to those of the last 1000 years? We used records of annual tree-ring widths from 309 populations of piñon pine, ponderosa pine, and Douglas-fir throughout the Southwestern United States to reconstruct a single record of regional drought stress from 1000-2005 AD. This record indicates that the last Southwestern drought similar in intensity to one in the early 2000s occurred in the late 1600s. Both of these droughts, however, paled in comparison to a mega-drought that occurred from 1575-1595. The emergence from this mega-drought, around 1600 AD, appears to mark a transition period from a time when droughts similar the early 2000s drought were much more common. Tree-age studies indicate a scarcity of Southwestern trees with rings extending back beyond the mega-drought of the late 1500s. This suggests that (1) the late-1500s mega-drought triggered a massive die-off of forests and/or (2) the higher frequency of drought events prior to the mega-drought sustained a much more sparse forest population than the one that has thrived from the 1600s through present. Given this apparent plasticity of Southwestern forests, a change in the forest population should be underway if higher temperatures contribute to forest drought stress. The Southwestern tree-ring record indicates that this is the case. During the 20th century, tree-ring widths correlated very positively with total winter precipitation and very negatively with spring-summer maximum temperature. This indicates that Southwestern forest growth is significantly impacted by both the amount of water delivered before the growing season and temperature during the growing season. We conclude that in the absence of a significant increase in winter precipitation, continued warming should lead to a more sparsely populated Southwestern forest population, similar to the one that appears to have existed during 1000-1600 AD.

Contribution of Near Real Time MODIS-Based Forest Disturbance Detection Products to a National Forest Threat Early Warning System

NASA Astrophysics Data System (ADS)

Spruce, J.; Hargrove, W. W.; Gasser, J.; Smoot, J.; Kuper, P.

2011-12-01

This presentation discusses an effort to compute and post weekly MODIS forest change products for the conterminous US (CONUS), as part of a web-based national forest threat early warning system (EWS) known as the U.S. Forest Change Assessment Viewer (FCAV). The US Forest Service, NASA, USGS, and ORNL are working collaboratively to contribute weekly change products to this EWS. Large acreages of the nation's forests are being disturbed by a growing multitude of biotic and abiotic threats that can act either singularly or in combination. When common at regional scales, such disturbances can pose hazards and threats to floral and faunal bio-diversity, ecosystem sustainability, ecosystem services, and human settlements across the conterminous US. Regionally evident forest disturbances range from ephemeral periodic canopy defoliation to stand replacement mortality events due to insects, disease, fire, hurricanes, tornadoes, ice, hail, and drought. Mandated by the Healthy Forest Restoration Act of 2003, this forest threat EWS has been actively developed since 2006 and on-line since 2010. The FCAV system employs 250-meter MODIS NDVI-based forest change products as a key element of the system, providing regional and CONUS scale products in near real time every 8 days. Each of our forest change products in FCAV is based on current versus historical 24 day composites of NDVI data gridded at 231.66 meter resolution. Current NDVI is derived from USGS eMODIS expedited products. MOD13 NDVI is used for constructing historical baselines. CONUS change products are computed for all forests as % change in the current versus historical NDVI for a given 24 day period. Change products are computed according to previous year, previous 3 year and previous 8 year historical baselines. The use of multiple baselines enables apparent forest disturbance anomalies to be more fully assessed. CONUS forest change products are posted each week on the FCAV, a web mapping service constructed and maintained by the National Environmental Modeling and Analysis Center. The FCAV EWS has been used to aid multiple Federal and State agency forest management activities, including aerial disturbance detection surveys, as well as rapid response preliminary assessments of timber loss due to tornadoes, regional drought studies, and fire damage assessments. The FCAV allows end-users to assess the context of apparent forest vegetation change with respect to ancillary data, such as land cover, topography, hydrology, climate variables, and administrative boundaries. Such change products are being evaluated through case studies involving comparison with higher spatial resolution satellite, aerial, and field data. The presentation will include multiple examples in which regionally evident forest disturbances were successfully detected and monitored with the MODIS-based change products, as part of the FCAV. FCAV's MODIS forest change products enable end-users (e.g., resource managers) to view and monitor forest hazards at regional scales throughout the year and across the nation.

Effects of drought on forests and rangelands in the United States: a comprehensive science synthesis

Treesearch

James Vose; J.S. Clark; Charlie Luce; Toral Patel-Weynand

2016-01-01

This assessment provides input to the reauthorized National Integrated Drought Information System (NIDIS) and the National Climate Assessment (NCA), and it establishes the scientific foundation needed to manage for drought resilience and adaptation. Focal areas include drought characterization; drought impacts on forest processes and disturbances such as insect...

Drought sensitivity changes over the last century at the North American savanna-forest boundary

NASA Astrophysics Data System (ADS)

Heilman, K.; McLachlan, J. S.

2017-12-01

Future environmental changes can affect the sensitivity of tree growth to climate. Theses changes are of particular concern at biome boundaries where tree distribution could shift as a result of changes in both drought and drought sensitivity. One such region is the North American savanna-forest boundary, where increased CO2 and droughts could alter savanna and forest ecosystem distributions in two contrasting ways: 1). More severe droughts may increase drought sensitivity, favoring open savanna ecosystems or, 2). Increases in water use efficiency resulting from higher atmospheric CO2 may decrease drought sensitivity, promoting forest expansion. This study sought to understand whether the past 100 years of climate and CO2 changes have impacted regional tree growth-climate sensitivity. To test for these climate sensitivity changes, we measured the sensitivity of Quercus spp. radial growth to Palmer Drought Severity Index (PDSI). Tree growth sensitivity to climate can vary according to many factors, including: stand structure, available moisture, and tree age. To control for these factors, we sampled tree growth-climate responses at sites in both open and closed forests, and at both low and high annual precipitation. Within each site, we compared growth responses to climate between trees established under high CO2 conditions after 1950 (high CO2 young), and tree established before 1950 under low CO2 levels (low CO2 young). At most sites, low CO2 young have a higher drought sensitivity than higher CO2 young. These changes in the sensitivity to drought are consistent with CO2 enhancement of water use efficiency. Furthermore, these differences in drought sensitivity are higher at sites with high temperature and low precipitation, suggesting that the alleviation of drought is more likely in hot and dry regions. Thus, if CO2 enhancement is indeed occurring in these systems, lower growth sensitivity to drought in hot and dry regions could favor increased forest growth. If changes in drought sensitivity scale to ecosystem level, decreased drought sensitivity may have helped promote regional forest expansion.

Simulating tropical carbon stocks and fluxes in a changing world using an individual-based forest model.

NASA Astrophysics Data System (ADS)

Fischer, Rico; Huth, Andreas

2014-05-01

Large areas of tropical forests are disturbed due to climate change and human influence. Experts estimate that the last remaining rainforests could be destroyed in less than 100 years with strong consequences for both developing and industrial countries. Using a modelling approach we analyse how disturbances modify carbon stocks and carbon fluxes of African rainforests. In this study we use the process-based, individual-oriented forest model FORMIND. The main processes of this model are tree growth, mortality, regeneration and competition. The study regions are tropical rainforests in the Kilimanjaro region and Madagascar. Modelling above and below ground carbon stocks, we analyze the impact of disturbances and climate change on forest dynamics and forest carbon stocks. Droughts and fire events change the structure of tropical rainforests. Human influence like logging intensify this effect. With the presented results we could establish new allometric relationships between forest variables and above ground carbon stocks in tropical regions. Using remote sensing techniques, these relationships would offer the possibility for a global monitoring of the above ground carbon stored in the vegetation.

Northern Forest DroughtNet: A New Framework to Understand Impacts of Precipitation Change on the Northern Forest Ecosystem

NASA Astrophysics Data System (ADS)

Asbjornsen, H.; Rustad, L.; Templer, P. H.; Jennings, K.; Phillips, R.; Smith, M.

2014-12-01

Recent trends and projections for future change for the U.S. northern forests suggest that the region's climate is becoming warmer, wetter, and, ironically, drier, with more precipitation occurring as large events, separated by longer periods with no precipitation. However, to date, precipitation manipulation experiments conducted in forest ecosystems represent only ~5% of all such experiments worldwide, and our understanding of how the mesic-adapted northern forest will respond to greater frequency and intensity of drought in the future is especially poor. Several important challenges have hampered previous research efforts to conduct forest drought experiments and draw robust conclusions, including difficulties in reducing water uptake by deep and lateral tree roots, logistical and financial constraints to establishing and maintaining large-scale field experiments, and the lack of standardized approaches for determining the appropriate precipitation manipulation treatment (e.g., amount and timing of throughfall displacement), designing and constructing the throughfall displacement infrastructure, identifying key response variables, and collecting and analyzing the field data. The overarching goal of this project is to establish a regional research coordination network - Northern Forest DroughtNet - to investigate the impacts of changes in the amount and distribution of precipitation on the hydrology, biogeochemistry, and carbon (C) cycling dynamics of northern temperate forests. Specific objectives include the development of a standard prototype for conducting precipitation manipulation studies in forest ecosystems (in collaboration with the international DroughtNet-RCN) and the implementation of this prototype drought experiment at the Hubbard Brook Experimental Forest. Here, we present the advances made thus far towards achieving the objectives of Northern Forest DroughtNet, plans for future work, and an invitation to the larger scientific community interested in precipitation manipulation experiments in forest ecosystems to participate in the network.

Contribution of Near Real Time MODIS-Based Forest Disturbance Detection Products to a National Forest Threat Early Warning System

NASA Technical Reports Server (NTRS)

Spruce, Joseph P.; Hargrove, William; Glasser, Jerry; Kuper, Philip D.

2011-01-01

This presentation discusses an effort to compute and post weekly MODIS forest change products for the conterminous US (CONUS), as part of national forest threat early warning system (EWS) known as the U.S. Forest Change Assessment Viewer (FCAV). The US Forest Service, NASA, USGS, and ORNL are working collaboratively to contribute weekly change products to this EWS. Large acreages of the nation's forests are being disturbed by a growing multitude of biotic and abiotic threats that can act either singularly or in combination. When common at regional scales, such disturbances can pose hazards and threats to floral and faunal bio-diversity, ecosystem sustainability, ecosystem services, and human settlements across the conterminous US. Regionally evident forest disturbances range from ephemeral periodic canopy defoliation to stand replacement mortality events due to insects, disease, fire, hurricanes, tornadoes, ice, hail, and drought. Mandated by the Healthy Forest Restoration Act of 2003, this forest threat EWS has been actively developed since 2006 and on-line since 2010. This FCAV system employs 250-meter MODIS NDVI-based forest change products as a key element of the system, providing regional and CONUS scale products in near real time every 8 days. Each forest change product in FCAV is based on current versus historical 24 day composite NDVI data gridded at 231.66 meter resolution. Current NDVI is derived from USGS eMODIS expedited products. MOD13 NDVI is used for constructing historical baselines. CONUS change products are computed for all forests as % change in the current versus historical NDVI. Change products are computed according to previous year, previous 3 years and previous 8 year historical baselines. The use of multiple baselines enables disturbance anomaly phenology to be more fully assessed. CONUS forest change products are posted each week on the FCAV, a web mapping service maintained by the National Environmental Modeling and Analysis Center. The FCAV EWS has been used to aid multiple Federal and State agency forest management activities, including aerial disturbance detection surveys, as well as rapid response preliminary assessments of timber loss due to tornadoes, regional drought studies, and fire damage assessments. The FCAV allows end-users to assess the context of apparent forest vegetation change with respect to ancillary data, such as land cover, topography, hydrology, climate variables, and administrative boundaries. Such change products are being evaluated through case studies involving comparison with higher spatial resolution satellite, aerial, and field data. The presentation will include multiple examples in which regionally evident forest disturbances were successfully detected and monitored with the MODIS-based change products, as part of the FCAV. FCAV's MODIS forest change products enable end-users (e.g., resource managers) to monitor forest hazards at regional scales throughout the year and across the nation.

Understanding the Role of Typhoons, Fire, and Climate on the Vegetation Dynamics of Tropical Dry Forests: Looking to the Past to Develop Future Management Solutions

DTIC Science & Technology

2010-04-01

centennial -to millennial scale typhoon reconstructions from the western North Pacific are far more limited. Historical government documents of typhoon... Centennial scale swings from humid to drought conditions have been documented in some tropical locations (Hodell et al., 2001). By looking to the past... depressions with a maximum depth of roughly 12 meters. The lagoon hollows are bounded by sand flats and coral reefs (Fig. 2). Core VC9 was located in the

Multi-index time series monitoring of drought and fire effects on desert grasslands

USGS Publications Warehouse

Villarreal, Miguel; Norman, Laura M.; Buckley, Steven; Wallace, Cynthia S.A.; Coe, Michelle A.

2016-01-01

The Western United States is expected to undergo both extended periods of drought and longer wildfire seasons under forecasted global climate change and it is important to understand how these disturbances will interact and affect recovery and composition of plant communities in the future. In this research paper we describe the temporal response of grassland communities to drought and fire in southern Arizona, where land managers are using repeated, prescribed fire as a habitat restoration tool. Using a 25-year atlas of fire locations, we paired sites with multiple fires to unburned control areas and compare satellite and field-based estimates of vegetation cover over time. Two hundred and fifty Landsat TM images, dating from 1985–2011, were used to derive estimates of Total Vegetation Fractional Cover (TVFC) of live and senescent grass using the Soil-Adjusted Total Vegetation Index (SATVI) and post-fire vegetation greenness using the Normalized Difference Vegetation Index (NDVI). We also implemented a Greenness to Cover Index that is the difference of time-standardized SATVI-TVFC and NDVI values at a given time and location to identify post-fire shifts in native, non-native, and annual plant cover. The results highlight anomalous greening and browning during drought periods related to amounts of annual and non-native plant cover present. Results suggest that aggressive application of prescribed fire may encourage spread of non-native perennial grasses and annual plants, particularly during droughts.

Climate and human influences on historical fire regimes (AD 1400-1900) in the eastern Great Basin (USA)

Treesearch

Stanley G. Kitchen

2015-01-01

High fire activity in western North America is associated with drought. Drought and fire prevail under negative El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) phases in the Southwest and with positive phases in the Northwest. Here, I infer climate effects on historic fire patterns in the geographically intermediate, eastern Great...

Larger trees suffer most during drought in forests worldwide

USGS Publications Warehouse

Bennett, Amy C.; McDowell, Nathan G.; Allen, Craig D.; Anderson-Teixeira, Kristina J.

2015-01-01

The frequency of severe droughts is increasing in many regions around the world as a result of climate change. Droughts alter the structure and function of forests. Site- and region-specific studies suggest that large trees, which play keystone roles in forests and can be disproportionately important to ecosystem carbon storage and hydrology, exhibit greater sensitivity to drought than small trees. Here, we synthesize data on tree growth and mortality collected during 40 drought events in forests worldwide to see whether this size-dependent sensitivity to drought holds more widely. We find that droughts consistently had a more detrimental impact on the growth and mortality rates of larger trees. Moreover, drought-related mortality increased with tree size in 65% of the droughts examined, especially when community-wide mortality was high or when bark beetles were present. The more pronounced drought sensitivity of larger trees could be underpinned by greater inherent vulnerability to hydraulic stress, the higher radiation and evaporative demand experienced by exposed crowns, and the tendency for bark beetles to preferentially attack larger trees. We suggest that future droughts will have a more detrimental impact on the growth and mortality of larger trees, potentially exacerbating feedbacks to climate change.

Vegetation limits the impact of a warm climate on boreal wildfires.

PubMed

Girardin, Martin P; Ali, Adam A; Carcaillet, Christopher; Blarquez, Olivier; Hély, Christelle; Terrier, Aurélie; Genries, Aurélie; Bergeron, Yves

2013-09-01

Strategic introduction of less flammable broadleaf vegetation into landscapes was suggested as a management strategy for decreasing the risk of boreal wildfires projected under climatic change. However, the realization and strength of this offsetting effect in an actual environment remain to be demonstrated. Here we combined paleoecological data, global climate models and wildfire modelling to assess regional fire frequency (RegFF, i.e. the number of fires through time) in boreal forests as it relates to tree species composition and climate over millennial time-scales. Lacustrine charcoals from northern landscapes of eastern boreal Canada indicate that RegFF during the mid-Holocene (6000-3000 yr ago) was significantly higher than pre-industrial RegFF (AD c. 1750). In southern landscapes, RegFF was not significantly higher than the pre-industrial RegFF in spite of the declining drought severity. The modelling experiment indicates that the high fire risk brought about by a warmer and drier climate in the south during the mid-Holocene was offset by a higher broadleaf component. Our data highlight an important function for broadleaf vegetation in determining boreal RegFF in a warmer climate. We estimate that its feedback may be large enough to offset the projected climate change impacts on drought conditions. © 2013 Her Majesty the Queen in Right of Canada New Phytologist © 2013 New Phytologist Trust.

Fires in Non-drought Conditions in Indonesia: the Role of Increasing Temperatures

NASA Astrophysics Data System (ADS)

Fernandes, K.; Verchot, L. V.; Baethgen, W.; Gutierrez-Velez, V.; Pinedo-Vasquez, M.; Martius, C.

2017-12-01

In Indonesia, drought driven fires occur typically during the warm phase of the El Niño Southern Oscillation (ENSO), such as those of 1997 and 2015 that resulted in months-long hazardous atmospheric pollution levels in Equatorial Asia and record greenhouse gas emissions. Nonetheless, anomalously active fire seasons have also been observed in non-drought years. In this work, we investigated whether fires are impacted by temperature anomalies and if so, if the responses differ under contrasting precipitation regimes. Our findings show that when the July-October dry-season is anomalously dry, the sensitivity of fires to temperature anomalies is similar regardless of the sign of the anomalies. In contrast, in wet condition, fire risk increases sharply when the dry season is anomalously warm. We also present a characterization of near-term regional climate projections over the next few decades and the implications of continuing global temperature increase in future fire probability in Indonesia.

Response of Sierra Nevada forests to projected climate-wildfire interactions.

PubMed

Liang, Shuang; Hurteau, Matthew D; Westerling, Anthony LeRoy

2017-05-01

Climate influences forests directly and indirectly through disturbance. The interaction of climate change and increasing area burned has the potential to alter forest composition and community assembly. However, the overall forest response is likely to be influenced by species-specific responses to environmental change and the scale of change in overstory species cover. In this study, we sought to quantify how projected changes in climate and large wildfire size would alter forest communities and carbon (C) dynamics, irrespective of competition from nontree species and potential changes in other fire regimes, across the Sierra Nevada, USA. We used a species-specific, spatially explicit forest landscape model (LANDIS-II) to evaluate forest response to climate-wildfire interactions under historical (baseline) climate and climate projections from three climate models (GFDL, CCSM3, and CNRM) forced by a medium-high emission scenario (A2) in combination with corresponding climate-specific large wildfire projections. By late century, we found modest changes in the spatial distribution of dominant species by biomass relative to baseline, but extensive changes in recruitment distribution. Although forest recruitment declined across much of the Sierra, we found that projected climate and wildfire favored the recruitment of more drought-tolerant species over less drought-tolerant species relative to baseline, and this change was greatest at mid-elevations. We also found that projected climate and wildfire decreased tree species richness across a large proportion of the study area and transitioned more area to a C source, which reduced landscape-level C sequestration potential. Our study, although a conservative estimate, suggests that by late century, forest community distributions may not change as intact units as predicted by biome-based modeling, but are likely to trend toward simplified community composition as communities gradually disaggregate and the least tolerant species are no longer able to establish. The potential exists for substantial community composition change and forest simplification beyond this century. © 2016 John Wiley & Sons Ltd.

Fire carbon emissions over maritime southeast Asia in 2015 largest since 1997.

PubMed

Huijnen, V; Wooster, M J; Kaiser, J W; Gaveau, D L A; Flemming, J; Parrington, M; Inness, A; Murdiyarso, D; Main, B; van Weele, M

2016-05-31

In September and October 2015 widespread forest and peatland fires burned over large parts of maritime southeast Asia, most notably Indonesia, releasing large amounts of terrestrially-stored carbon into the atmosphere, primarily in the form of CO2, CO and CH4. With a mean emission rate of 11.3 Tg CO2 per day during Sept-Oct 2015, emissions from these fires exceeded the fossil fuel CO2 release rate of the European Union (EU28) (8.9 Tg CO2 per day). Although seasonal fires are a frequent occurrence in the human modified landscapes found in Indonesia, the extent of the 2015 fires was greatly inflated by an extended drought period associated with a strong El Niño. We estimate carbon emissions from the 2015 fires to be the largest seen in maritime southeast Asia since those associated with the record breaking El Niño of 1997. Compared to that event, a much better constrained regional total carbon emission estimate can be made for the 2015 fires through the use of present-day satellite observations of the fire's radiative power output and atmospheric CO concentrations, processed using the modelling and assimilation framework of the Copernicus Atmosphere Monitoring Service (CAMS) and combined with unique in situ smoke measurements made on Kalimantan.

Drought in the Rockies

NASA Technical Reports Server (NTRS)

2002-01-01

This image shows the difference between the amount of vegetation in July 2000 and the average July vegetation for North America. Of particular interest are the dry conditions in the western United States. This spring and summer the Rocky Mountains have been relatively dry, and the brown regions stretching from the Canadian to the Mexican border, indicate the effect on the regions' forests. Western Montana and eastern Idaho are particularly parched, and appear darker brown. The dry conditions have contributed to this year's devastating fire season, during which millions of acres have burned in the west. Scientists find that during the growing season, land plants can be used to measure drought. Healthy, thriving plants reflect and absorb visible and near-infrared light differently than plants under stress. These variations in reflectance and absorption can be measured by satellites to produce maps of healthy and stressed vegetation. This image shows Normalized Difference Vegetation Index (NDVI) anomaly, which indicates where vegetation growth was above average (green pixels), below average (brown pixels), or normal (white pixels). For more images and information about measuring vegetation and drought from space visit: Drought and Vegetation Monitoring. Image courtesy NASA Goddard Space Flight Center Biospheric Sciences Branch, based on data from NOAA.

Northern Forest DroughtNet: Initial results from a multi-year throughfall manipulation experiment in New Hampshire

NASA Astrophysics Data System (ADS)

McIntire, C.; Vadeboncoeur, M. A.; Coble, A.; Jennings, K.; Asbjornsen, H.

2016-12-01

Climate change is likely to affect the Northern Forest region through the increased frequency and severity of drought events. However, our understanding of how the Northern Forest, which is adapted to humid temperate conditions, will respond to moderate to extreme droughts is limited. Given the important role that these forests play in protecting ecosystem services and in supplying forest products, enhancing our knowledge about impacts of drought is critical to ensuring effective forest management and adaptation to climate change. The Northern Forest DroughtNet project aims to simulate a four-year severe drought by removing 55% of the incoming throughfall; thus representing the 99th percentile of annual precipitation based on historic precipitation data in Durham, NH. This is accomplished using two replicated 900 m2 throughfall removal structures consisting of a network of gutters that capture and divert incoming precipitation away from the established treatment area. Data presented here will address the ecosystem response to the drought treatment over the course of the first year of the experiment as well as validate the effectiveness and artifacts of the throughfall removal structure. Response variables of interest include soil moisture content, above and below ground biomass production, litterfall, decomposition rates, leaf water potential, foliar gas exchange, and whole tree transpiration rates. Preliminary findings provide insight into the effectiveness of using throughfall manipulation experiments in a temperate forest ecosystem to simulate an extreme drought event, as well as initial tree physiological and growth responses in relation to soil moisture availability and the implications for future climate change impacts.

An assessment of three measures of long-term moisture deficiency before critical fire periods.

Treesearch

Donald A. Haines; Von J. Johnson; William A. Main

1976-01-01

Values of the Palmer Drought Index, the Keetch-Byram Drought Index, and a Buildup Index are calculated for 26 critical fires situations in the north-central and north-eastern states. The paper examines the response characteristics of these indexes, representative of different moisture regimes, relative to fire danger.

Competition amplifies drought stress in forests across broad climatic and compositional gradients

Treesearch

Kelly E. Gleason; John B. Bradford; Alessandra Bottero; Anthony W. D' Amato; Shawn Fraver; Brian J. Palik; Michael A. Battaglia; Louis Iverson; Laura Kenefic; Christel C. Kern

2017-01-01

Forests around the world are experiencing increasingly severe droughts and elevated competitive intensity due to increased tree density. However, the influence of interactions between drought and competition on forest growth remains poorly understood. Using a unique dataset of stand-scale dendrochronology sampled from 6405 trees, we quantified how annual growth of...

Reserves Protect against Deforestation Fires in the Amazon

PubMed Central

Adeney, J. Marion; Christensen, Norman L.; Pimm, Stuart L.

2009-01-01

Background Reserves are the principal means to conserve forests and biodiversity, but the question of whether reserves work is still debated. In the Amazon, fires are closely linked to deforestation, and thus can be used as a proxy for reserve effectiveness in protecting forest cover. We ask whether reserves in the Brazilian Amazon provide effective protection against deforestation and consequently fires, whether that protection is because of their location or their legal status, and whether some reserve types are more effective than others. Methodology/Principal Findings Previous work has shown that most Amazonian fires occur close to roads and are more frequent in El Niño years. We quantified these relationships for reserves and unprotected areas by examining satellite-detected hot pixels regressed against road distance across the entire Brazilian Amazon and for a decade with 2 El Niño-related droughts. Deforestation fires, as measured by hot pixels, declined exponentially with increasing distance from roads in all areas. Fewer deforestation fires occurred within protected areas than outside and the difference between protected and unprotected areas was greatest near roads. Thus, reserves were especially effective at preventing these fires where they are known to be most likely to burn; but they did not provide absolute protection. Even within reserves, at a given distance from roads, there were more deforestation fires in regions with high human impact than in those with low impact. The effect of El Niño on deforestation fires was greatest outside of reserves and near roads. Indigenous reserves, limited-use reserves, and fully protected reserves all had fewer fires than outside areas and did not appear to differ in their effectiveness. Conclusions/Significance Taking time, regional factors, and climate into account, our results show that reserves are an effective tool for curbing destructive burning in the Amazon. PMID:19352423

Climatic and anthropogenic drivers of northern Amazon fires during the 2015-2016 El Niño event.

PubMed

Fonseca, Marisa G; Anderson, Liana O; Arai, Egidio; Shimabukuro, Yosio E; Xaud, Haron A M; Xaud, Maristela R; Madani, Nima; Wagner, Fabien H; Aragão, Luiz E O C

2017-12-01

The strong El Niño Southern Oscillation (ENSO) event that occurred in 2015-2016 caused extreme drought in the northern Brazilian Amazon, especially in the state of Roraima, increasing fire occurrence. Here we map the extent of precipitation and fire anomalies and quantify the effects of climatic and anthropogenic drivers on fire occurrence during the 2015-2016 dry season (from December 2015 to March 2016) in the state of Roraima. To achieve these objectives we first estimated the spatial pattern of precipitation anomalies, based on long-term data from the TRMM (Tropical Rainfall Measuring Mission), and the fire anomaly, based on MODIS (Moderate Resolution Imaging Spectroradiometer) active fire detections during the referred period. Then, we integrated climatic and anthropogenic drivers in a Maximum Entropy (MaxEnt) model to quantify fire probability, assessing (1) the model accuracy during the 2015-2016 and the 2016-2017 dry seasons; (2) the relative importance of each predictor variable on the model predictive performance; and (3) the response curves, showing how each environmental variable affects the fire probability. Approximately 59% (132,900 km 2 ) of the study area was exposed to precipitation anomalies ≤-1 standard deviation (SD) in January and ~48% (~106,800 km 2 ) in March. About 38% (86,200 km 2 ) of the study area experienced fire anomalies ≥1 SD in at least one month between December 2015 and March 2016. The distance to roads and the direct ENSO effect on fire occurrence were the two most influential variables on model predictive performance. Despite the improvement of governmental actions of fire prevention and firefighting in Roraima since the last intense ENSO event (1997-1998), we show that fire still gets out of control in the state during extreme drought events. Our results indicate that if no prevention actions are undertaken, future road network expansion and a climate-induced increase in water stress will amplify fire occurrence in the northern Amazon, even in its humid dense forests. As an additional outcome of our analysis, we conclude that the model and the data we used may help to guide on-the-ground fire-prevention actions and firefighting planning and therefore minimize fire-related ecosystems degradation, economic losses and carbon emissions in Roraima. © 2017 by the Ecological Society of America.

Decadal-scale ecosystem memory reveals interactive effects of drought and insect defoliation on boreal forest productivity

NASA Astrophysics Data System (ADS)

Itter, M.; D'Orangeville, L.; Dawson, A.; Kneeshaw, D.; Finley, A. O.

2017-12-01

Drought and insect defoliation have lasting impacts on the dynamics of the boreal forest. Impacts are expected to worsen under global climate change as hotter, drier conditions forecast for much of the boreal increase the frequency and severity of drought and defoliation events. Contemporary ecological theory predicts physiological feedbacks in tree responses to drought and defoliation amplify impacts potentially causing large-scale productivity losses and forest mortality. Quantifying the interactive impacts of drought and insect defoliation on regional forest health is difficult given delayed and persistent responses to disturbance events. We developed a Bayesian hierarchical model to estimate forest growth responses to interactions between drought and insect defoliation by species and size class. Delayed and persistent responses to past drought and defoliation were quantified using empirical memory functions allowing for improved detection of interactions. The model was applied to tree-ring data from stands in Western (Alberta) and Eastern (Québec) regions of the Canadian boreal forest with different species compositions, disturbance regimes, and regional climates. Western stands experience chronic water deficit and forest tent caterpillar (FTC) defoliation; Eastern stands experience irregular water deficit and spruce budworm (SBW) defoliation. Ecosystem memory to past water deficit peaked in the year previous to growth and decayed to zero within 5 (West) to 8 (East) years; memory to past defoliation ranged from 8 (West) to 12 (East) years. The drier regional climate and faster FTC defoliation dynamics (compared to SBW) likely contribute to shorter ecosystem memory in the West. Drought and defoliation had the largest negative impact on large-diameter, host tree growth. Surprisingly, a positive interaction was observed between drought and defoliation for large-diameter, non-host trees likely due to reduced stand-level competition for water. Results highlight the temporal persistence of drought and defoliation stress on boreal forest growth dynamics and provide an empirical estimate of their interactive effects with explicit uncertainty.

Emission Factors for CO2, CO, CH4, and C2 - C4 Hydrocarbons from the 2011 Great Dismal Swamp, Virginia Fire

NASA Astrophysics Data System (ADS)

Baker, S.; Soja, A. J.; Richardson, M. J.

2012-12-01

With a warming climate, increased dry conditions and drought periods are likely to result in higher fire activity in the wetlands of the eastern and southeastern US. Fires in this fuel type can smolder for months producing significant carbon release and major impacts on air quality. While a comprehensive set of emission factors has been established for most US fuel types, a less complete set is available for emissions where deep layers of organic matter can consume and smolder for days, weeks and months. Lightning started the Lateral West fire in the Great Dismal Swamp National Wildlife Refuge, Virginia on August 4, and it burned slowly through drought-stressed hardwood forest and dry peat soil. The fire produced dense plumes of smoke that mostly dispersed over the Atlantic Ocean, but also affected air quality as far away as Washington, D.C. Fire emissions were sampled August 26, 2011. The fire had burned 6,358 acres. and was smoldering along in the peat, with some brush still igniting. The average emission factors (EF) we measured from the sampling were 1441 g/kg CO2, 192 g/kg CO; and 16.5 g/kg CH4.. Modified combustion efficiency (MCE) was 0.83, produced by the small amount of flaming combustion mixed with smoldering combustion of the peat. The CO2 EF values are similar to those measured from smoldering duff in Alaska in 2003 (1436 g/kg), and the CO EF was lower than Alaska (244 g/kg CO), while the CH4 EF was much higher than Alaska (8.4 g/kg CH4). We will present our complete set of emission factors from the Great Dismal Swamp for CO2, CO, CH4, and C2 - C4 hydrocarbons, and contrast these results with other fuel types. Linear regressions of C1- C4 hydrocarbons vs. CO concentration will presented and compared with other emissions results.

Integrated Mapping of Drought-Impacted Areas in the Sierra-Nevada Foothills Region of California Using Landsat Imagery

NASA Astrophysics Data System (ADS)

Rao, M.

2014-12-01

Drought is a natural disaster with serious implications to environmental, social and economic well-being at local, regional and global scales. In its third year, California's drought condition has seriously impacted not just the agricultural sector, but also the natural resources sector including forestry, wildlife, and fisheries. As of July 15, 2014, the National Weather Service drought monitor shows 81% of California in the category of extreme drought. As future predictions of drought and fire severity become more real in California, there is an increased awareness to pursue innovative and cost-effective solutions that are based on silvicultural treatments and controlled burns to improve forest health and reduce the risk of high-severity wildfires. The main goal of this study is to develop a GIS map of the drought-impacted region of northern and central California using remote sensing data. Specifically, based on a geospatial database for the study region, Landsat imagery in conjunction with field and ancillary data will be analyzed using a combination of supervised and unsupervised classification techniques in addition to spectral indices such as the Modified Perpendicular Drought Index (MPDI). This spectral index basically scales the line perpendicular to the soil line defined in the Red-NIR feature space in conjunction with added information about vegetative fraction derived using NDVI. The image processing will be conducted for two time periods (2001 and 2014) to characterize the severity of the drought. In addition to field data, data collected by state agencies including calforests.org will be used in the classification and accuracy assessment procedures. Visual assessment using high-resolution imagery such as NAIP will be used to further refine the spatial maps. The drought severity maps produced will greatly facilitate site-specific planning efforts aimed at implementing resource management decisions.

Modifying rainfall patterns in a Mediterranean shrubland: system design, plant responses, and experimental burning

NASA Astrophysics Data System (ADS)

Parra, Antonio; Ramírez, David A.; Resco, Víctor; Velasco, Ángel; Moreno, José M.

2012-11-01

Global warming is projected to increase the frequency and intensity of droughts in the Mediterranean region, as well as the occurrence of large fires. Understanding the interactions between drought, fire and plant responses is therefore important. In this study, we present an experiment in which rainfall patterns were modified to simulate various levels of drought in a Mediterranean shrubland of central Spain dominated by Cistus ladanifer, Erica arborea and Phillyrea angustifolia. A system composed of automatic rainout shelters with an irrigation facility was used. It was designed to be applied in vegetation 2 m tall, treat relatively large areas (36 m2), and be quickly dismantled to perform experimental burning and reassembled back again. Twenty plots were subjected to four rainfall treatments from early spring: natural rainfall, long-term average rainfall (2 months drought), moderate drought (25% reduction from long-term rainfall, 5 months drought) and severe drought (45% reduction, 7 months drought). The plots were burned in late summer, without interfering with rainfall manipulations. Results indicated that rainfall manipulations caused differences in soil moisture among treatments, leading to reduced water availability and growth of C. ladanifer and E. arborea in the drought treatments. However, P. angustifolia was not affected by the manipulations. Rainout shelters had a negligible impact on plot microenvironment. Experimental burns were of high fire intensity, without differences among treatments. Our system provides a tool to study the combined effects of drought and fire on vegetation, which is important to assess the threats posed by climate change in Mediterranean environments.

Modifying rainfall patterns in a Mediterranean shrubland: system design, plant responses, and experimental burning.

PubMed

Parra, Antonio; Ramírez, David A; Resco, Víctor; Velasco, Ángel; Moreno, José M

2012-11-01

Global warming is projected to increase the frequency and intensity of droughts in the Mediterranean region, as well as the occurrence of large fires. Understanding the interactions between drought, fire and plant responses is therefore important. In this study, we present an experiment in which rainfall patterns were modified to simulate various levels of drought in a Mediterranean shrubland of central Spain dominated by Cistus ladanifer, Erica arborea and Phillyrea angustifolia. A system composed of automatic rainout shelters with an irrigation facility was used. It was designed to be applied in vegetation 2 m tall, treat relatively large areas (36 m2), and be quickly dismantled to perform experimental burning and reassembled back again. Twenty plots were subjected to four rainfall treatments from early spring: natural rainfall, long-term average rainfall (2 months drought), moderate drought (25% reduction from long-term rainfall, 5 months drought) and severe drought (45% reduction, 7 months drought). The plots were burned in late summer, without interfering with rainfall manipulations. Results indicated that rainfall manipulations caused differences in soil moisture among treatments, leading to reduced water availability and growth of C. ladanifer and E. arborea in the drought treatments. However, P. angustifolia was not affected by the manipulations. Rainout shelters had a negligible impact on plot microenvironment. Experimental burns were of high fire intensity, without differences among treatments. Our system provides a tool to study the combined effects of drought and fire on vegetation, which is important to assess the threats posed by climate change in Mediterranean environments.

On the key role of droughts in the dynamics of summer fires in Mediterranean Europe.

PubMed

Turco, Marco; von Hardenberg, Jost; AghaKouchak, Amir; Llasat, Maria Carmen; Provenzale, Antonello; Trigo, Ricardo M

2017-03-06

Summer fires frequently rage across Mediterranean Europe, often intensified by high temperatures and droughts. According to the state-of-the-art regional fire risk projections, in forthcoming decades climate effects are expected to become stronger and possibly overcome fire prevention efforts. However, significant uncertainties exist and the direct effect of climate change in regulating fuel moisture (e.g. warmer conditions increasing fuel dryness) could be counterbalanced by the indirect effects on fuel structure (e.g. warmer conditions limiting fuel amount), affecting the transition between climate-driven and fuel-limited fire regimes as temperatures increase. Here we analyse and model the impact of coincident drought and antecedent wet conditions (proxy for the climatic factor influencing total fuel and fine fuel structure) on the summer Burned Area (BA) across all eco-regions in Mediterranean Europe. This approach allows BA to be linked to the key drivers of fire in the region. We show a statistically significant relationship between fire and same-summer droughts in most regions, while antecedent climate conditions play a relatively minor role, except in few specific eco-regions. The presented models for individual eco-regions provide insights on the impacts of climate variability on BA, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

Integrated model-experimental framework to assess carbon cycle components in disturbed mountainous terrain

NASA Astrophysics Data System (ADS)

Stenzel, J.; Hudiburg, T. W.; Berardi, D.; McNellis, B.; Walsh, E.

2017-12-01

In forests vulnerable to drought and fire, there is critical need for in situ carbon and water balance measurements that can be integrated with earth system modeling to predict climate feedbacks. Model development can be improved by measurements that inform a mechanistic understanding of the component fluxes of net carbon uptake (i.e., NPP, autotrophic and heterotrophic respiration) and water use, with specific focus on responses to climate and disturbance. By integrating novel field-based instrumental technology, existing datasets, and state-of-the-art earth system modeling, we are attempting to 1) quantify the spatial and temporal impacts of forest thinning on regional biogeochemical cycling and climate 2) evaluate the impact of forest thinning on forest resilience to drought and disturbance in the Northern Rockies ecoregion. The combined model-experimental framework enables hypothesis testing that would otherwise be impossible because the use of new in situ high temporal resolution field technology allows for research in remote and mountainous terrains that have been excluded from eddy-covariance techniques. Our preliminary work has revealed some underlying difficulties with the new instrumentation that has led to new ideas and modified methods to correctly measure the component fluxes. Our observations of C balance following the thinning operations indicate that the recovery period (source to sink) is longer than hypothesized. Finally, we have incorporated a new plant functional type parameterization for Northern Rocky mixed-conifer into our simulation modeling using regional and site observations.

Long-term climate and competition explain forest mortality patterns under extreme drought.

PubMed

Young, Derek J N; Stevens, Jens T; Earles, J Mason; Moore, Jeffrey; Ellis, Adam; Jirka, Amy L; Latimer, Andrew M

2017-01-01

Rising temperatures are amplifying drought-induced stress and mortality in forests globally. It remains uncertain, however, whether tree mortality across drought-stricken landscapes will be concentrated in particular climatic and competitive environments. We investigated the effects of long-term average climate [i.e. 35-year mean annual climatic water deficit (CWD)] and competition (i.e. tree basal area) on tree mortality patterns, using extensive aerial mortality surveys conducted throughout the forests of California during a 4-year statewide extreme drought lasting from 2012 to 2015. During this period, tree mortality increased by an order of magnitude, typically from tens to hundreds of dead trees per km 2 , rising dramatically during the fourth year of drought. Mortality rates increased independently with average CWD and with basal area, and they increased disproportionately in areas that were both dry and dense. These results can assist forest managers and policy-makers in identifying the most drought-vulnerable forests across broad geographic areas. © 2016 John Wiley & Sons Ltd/CNRS.

Characterizing drought for forested landscapes and streams

Treesearch

Charlie Luce; Neil Pederson; John Campbell; Connie Millar; Patrick Kormos; James M. Vose; Ross Woods

2016-01-01

The purpose of this chapter is to explore drought as a hydrometeorological phenomenon and reflect broadly on the characteristics of drought that influence forests, rangelands, and streams. It is a synthesis of understanding about drought processes, hydrology, paleoclimatology, and historical climate variability, and how this understanding can help predict potential...

Forest ecosystems of temperate climatic regions: from ancient use to climate change.

PubMed

Gilliam, Frank S

2016-12-01

871 I. 871 II. 874 III. 875 IV. 878 V. 882 884 References 884 SUMMARY: Humans have long utilized resources from all forest biomes, but the most indelible anthropogenic signature has been the expanse of human populations in temperate forests. The purpose of this review is to bring into focus the diverse forests of the temperate region of the biosphere, including those of hardwood, conifer and mixed dominance, with a particular emphasis on crucial challenges for the future of these forested areas. Implicit in the term 'temperate' is that the predominant climate of these forest regions has distinct cyclic, seasonal changes involving periods of growth and dormancy. The specific temporal patterns of seasonal change, however, display an impressive variability among temperate forest regions. In addition to the more apparent current anthropogenic disturbances of temperate forests, such as forest management and conversion to agriculture, human alteration of temperate forests is actually an ancient phenomenon, going as far back as 7000 yr before present (bp). As deep-seated as these past legacies are for temperate forests, all current and future perturbations, including timber harvesting, excess nitrogen deposition, altered species' phenologies, and increasing frequency of drought and fire, must be viewed through the lens of climate change. © 2016 The Author. New Phytologist © 2016 New Phytologist Trust.

[Relationships of forest fire with lightning in Daxing' anling Mountains, Northeast China].

PubMed

Lei, Xiao-Li; Zhou, Guang-Sheng; Jia, Bing-Rui; Li, Shuai

2012-07-01

Forest fire is an important factor affecting forest ecosystem succession. Recently, forest fire, especially forest lightning fire, shows an increasing trend under global warming. To study the relationships of forest fire with lightning is essential to accurately predict the forest fire in time. Daxing' anling Mountains is a region with high frequency of forest lightning fire in China, and an important experiment site to study the relationships of forest fire with lightning. Based on the forest fire records and the corresponding lightning and meteorological observation data in the Mountains from 1966 to 2007, this paper analyzed the relationships of forest fire with lightning in this region. In the period of 1966-2007, both the lightning fire number and the fired forest area in this region increased significantly. The meteorological factors affecting the forest lighting fire were related to temporal scales. At yearly scale, the forest lightning fire was significantly correlated with precipitation, with a correlation coefficient of -0.489; at monthly scale, it had a significant correlation with air temperature, the correlation coefficient being 0.18. The relationship of the forest lightning fire with lightning was also related to temporal scales. At yearly scale, there was no significant correlation between them; at monthly scale, the forest lightning fire was strongly correlated with lightning and affected by precipitation; at daily scale, a positive correlation was observed between forest lightning fire and lightning when the precipitation was less than 5 mm. According to these findings, a fire danger index based on ADTD lightning detection data was established, and a forest lightning fire forecast model was developed. The prediction accuracy of this model for the forest lightning fire in Daxing' anling Mountains in 2005-2007 was > 80%.

Tree mortality following a drought-year lightning ignition in the Ouachita Mountains, Arkansas: 2 years postburn

Treesearch

Virginia L. McDaniel; James M. Guldin; Nancy E. Koerth; Jason E. Milks; Rebecca J. Finzer; Ben F. Rowland

2016-01-01

Increasingly, fire managers are using natural ignitions in conjunction with prescribed burns to restore and maintain fire-adapted ecosystems. Increased fuel loading from fire suppression and increasing drought indices associated with climate change, however, may cause natural ignitions to burn with greater intensity and severity. Managers must weigh risk factors versus...

Modification of the Fosberg fire weather index to include drought

Treesearch

Scott L. Goodrick

2002-01-01

The Fosberg fire weather index is a simple tool for evaluating the potential influence of weather on a wildland fire based on temperature, relative humidity and wind speed. A modification to this index that includes the impact of precipitation is proposed. The Keetch-Byram drought index is used to formulate a 'fuel availability' factor that modifies the...

Carbon and water fluxes from ponderosa pine forests disturbed by wildfire and thinning.

PubMed

Dore, S; Kolb, T E; Montes-Helu, M; Eckert, S E; Sullivan, B W; Hungate, B A; Kaye, J P; Hart, S C; Koch, G W; Finkral, A

2010-04-01

Disturbances alter ecosystem carbon dynamics, often by reducing carbon uptake and stocks. We compared the impact of two types of disturbances that represent the most likely future conditions of currently dense ponderosa pine forests of the southwestern United States: (1) high-intensity fire and (2) thinning, designed to reduce fire intensity. High-severity fire had a larger impact on ecosystem carbon uptake and storage than thinning. Total ecosystem carbon was 42% lower at the intensely burned site, 10 years after burning, than at the undisturbed site. Eddy covariance measurements over two years showed that the burned site was a net annual source of carbon to the atmosphere whereas the undisturbed site was a sink. Net primary production (NPP), evapotranspiration (ET), and water use efficiency were lower at the burned site than at the undisturbed site. In contrast, thinning decreased total ecosystem carbon by 18%, and changed the site from a carbon sink to a source in the first posttreatment year. Thinning also decreased ET, reduced the limitation of drought on carbon uptake during summer, and did not change water use efficiency. Both disturbances reduced ecosystem carbon uptake by decreasing gross primary production (55% by burning, 30% by thinning) more than total ecosystem respiration (TER; 33-47% by burning, 18% by thinning), and increased the contribution of soil carbon dioxide efflux to TER. The relationship between TER and temperature was not affected by either disturbance. Efforts to accurately estimate regional carbon budgets should consider impacts on carbon dynamics of both large disturbances, such as high-intensity fire, and the partial disturbance of thinning that is often used to prevent intense burning. Our results show that thinned forests of ponderosa pine in the southwestern United States are a desirable alternative to intensively burned forests to maintain carbon stocks and primary production.

Temperature is a potent driver of regional forest drought stress, disturbance, and tree mortality (Invited)

NASA Astrophysics Data System (ADS)

Williams, P.; Allen, C. D.; Macalady, A.; Griffin, D.; Woodhouse, C. A.; Meko, D. M.; Swetnam, T. W.; Rauscher, S.; Seager, R.; Grissino-Mayer, H.; Dean, J.; Cook, E. R.; Gangodagamage, C.; Cai, M.; McDowell, N. G.

2013-12-01

I present a forest drought-stress index (FDSI) for the Southwestern United States using a comprehensive set of regional tree-ring records for AD 1000-2007. Comparing the last century of FDSI data to observed climate records, regional FDSI appears approximately equally influenced by warm-season atmospheric moisture demand (mostly controlled by temperature) and cold-season precipitation, together explaining an astounding 82% of southwestern FDSI variability. When atmospheric moisture demand intensifies, so does forest drought stress. Importantly, intensified moisture demand is not only associated with decreased tree growth; it is also associated with increased mortality. In particular, among a suite of drought-related climate variables, warm-season moisture demand has been the best predictor of annual forest area burned by stand-replacing wildfires since at least 1984. Further, the relationship between moisture demand and burned area is exponential, where incremental increases in moisture demand correspond to increasingly large influences on area burned. Using climate observations to update FDSI through 2013, I show that the current Southwestern drought-stress event, which began in 2000, is the most severe in over 400 years, but not as severe as those that occurred during the infamous 'Megadroughts' of AD 1000-1600. Like the Megadroughts of the past, the current drought will come to an end, but unlike the Megadroughts of the past, the current drought and those that will follow will be superimposed upon a warming-induced trend toward increased moisture demand and intensified forest drought stress, disturbance, and mortality. If atmospheric moisture demand continues increasing as projected by climate models, then mean annual Southwestern US climate by the 2050s will be less suitable for forest growth and survival than it was during the worst years of last millennium's Megadroughts. An intense La-Niña driven drought anomaly superimposed upon mean conditions in the 2050s would lead to forest drought stress, mortality, and wildfire conditions that are far more disastrous than those observed thusfar. These results foreshadow 21st-century transitions of Southwestern forests, and probably forests elsewhere, toward distributions unfamiliar to modern civilization.

Cordilleran forest scaling dynamics and disturbance regimes quantified by aerial lidar

NASA Astrophysics Data System (ADS)

Swetnam, Tyson L.

Semi-arid forests are in a period of rapid transition as a result of unprecedented landscape scale fires, insect outbreaks, drought, and anthropogenic land use practices. Understanding how historically episodic disturbances led to coherent forest structural and spatial patterns that promoted resilience and resistance is a critical part of addressing change. Here my coauthors and I apply metabolic scaling theory (MST) to examine scaling behavior and structural patterns of semi-arid conifer forests in Arizona and New Mexico. We conceptualize a linkage to mechanistic drivers of forest assembly that incorporates the effects of low-intensity disturbance, and physiologic and resource limitations as an extension of MST. We use both aerial LiDAR data and field observations to quantify changes in forest structure from the sub-meter to landscape scales. We found: (1) semi-arid forest structure exhibits MST-predicted behaviors regardless of disturbance and that MST can help to quantitatively measure the level of disturbance intensity in a forest, (2) the application of a power law to a forest overstory frequency distribution can help predict understory presence/absence, (3) local indicators of spatial association can help to define first order effects (e.g. topographic changes) and map where recent disturbances (e.g. logging and fire) have altered forest structure. Lastly, we produced a comprehensive set of above-ground biomass and carbon models for five distinct forest types and ten common species of the southwestern US that are meant for use in aerial LiDAR forest inventory projects. This dissertation presents both a conceptual framework and applications for investigating local scales (stands of trees) up to entire ecosystems for diagnosis of current carbon balances, levels of departure from historical norms, and ecological stability. These tools and models will become more important as we prepare our ecosystems for a future characterized by increased climatic variability with an associated increase in frequency and severity of ecological disturbances.

Drought timing and local climate determine the sensitivity of eastern temperate forests to drought.

PubMed

D'Orangeville, Loïc; Maxwell, Justin; Kneeshaw, Daniel; Pederson, Neil; Duchesne, Louis; Logan, Travis; Houle, Daniel; Arseneault, Dominique; Beier, Colin M; Bishop, Daniel A; Druckenbrod, Daniel; Fraver, Shawn; Girard, François; Halman, Joshua; Hansen, Chris; Hart, Justin L; Hartmann, Henrik; Kaye, Margot; Leblanc, David; Manzoni, Stefano; Ouimet, Rock; Rayback, Shelly; Rollinson, Christine R; Phillips, Richard P

2018-06-01

Projected changes in temperature and drought regime are likely to reduce carbon (C) storage in forests, thereby amplifying rates of climate change. While such reductions are often presumed to be greatest in semi-arid forests that experience widespread tree mortality, the consequences of drought may also be important in temperate mesic forests of Eastern North America (ENA) if tree growth is significantly curtailed by drought. Investigations of the environmental conditions that determine drought sensitivity are critically needed to accurately predict ecosystem feedbacks to climate change. We matched site factors with the growth responses to drought of 10,753 trees across mesic forests of ENA, representing 24 species and 346 stands, to determine the broad-scale drivers of drought sensitivity for the dominant trees in ENA. Here we show that two factors-the timing of drought, and the atmospheric demand for water (i.e., local potential evapotranspiration; PET)-are stronger drivers of drought sensitivity than soil and stand characteristics. Drought-induced reductions in tree growth were greatest when the droughts occurred during early-season peaks in radial growth, especially for trees growing in the warmest, driest regions (i.e., highest PET). Further, mean species trait values (rooting depth and ψ 50 ) were poor predictors of drought sensitivity, as intraspecific variation in sensitivity was equal to or greater than interspecific variation in 17 of 24 species. From a general circulation model ensemble, we find that future increases in early-season PET may exacerbate these effects, and potentially offset gains in C uptake and storage in ENA owing to other global change factors. © 2018 John Wiley & Sons Ltd.

Observed effects of an exceptional drought on tree mortality in a tropical dry forest

NASA Astrophysics Data System (ADS)

Medvigy, D.; Vargas, G.; Xu, X.; Smith, C. M.; Becknell, J.; Brodribb, T.; Powers, J. S.

2016-12-01

Climate models predict that the coming century will bring reduced rainfall to Neotropical dry forests. It is unknown how tropical dry forest trees will respond to such rainfall reductions. Will there be increased mortality? If so, what will be the dominant mechanism of mortality? Will certain functional groups or size classes be more susceptible to unusually dry conditions and do functional traits underlie these patterns? With these questions in mind, we analyzed the response of trees from 18 Costa Rican tropical dry forest inventory plots and from additional transects to the exceptional 2015 drought that coincided with a strong ENSO event. We compared stand-level mortality rates observed during pre-drought years (2008-2014) and during the drought year of 2015 in the inventory plots. For both inventory plots and transects, we analyzed whether particular functional groups or size classes experienced exceptional mortality after the drought. We found that mortality rates were two to three times higher during the drought than before the drought. In contrast to observations at moist tropical forests, tree size had little influence on mortality. In terms of functional groups, mortality rates of evergreen oaks growing on nutrient-poor soils particularly increased during drought. Legumes seemed less affected by the drought than non-legumes. However, elevated mortality rates were not clearly correlated with commonly-measured traits like wood density or specific leaf area. Instead, hydraulic traits like P50 or turgor loss point may be better predictors of drought-driven mortality. In addition, trees that died during the drought tended to have smaller relative growth rate prior to the drought than trees that survived the drought.

Tropical forests and the changing earth system.

PubMed

Lewis, Simon L

2006-01-29

Tropical forests are global epicentres of biodiversity and important modulators of the rate of climate change. Recent research on deforestation rates and ecological changes within intact forests, both areas of recent research and debate, are reviewed, and the implications for biodiversity (species loss) and climate change (via the global carbon cycle) addressed. Recent impacts have most likely been: (i) a large source of carbon to the atmosphere, and major loss of species, from deforestation and (ii) a large carbon sink within remaining intact forest, accompanied by accelerating forest dynamism and widespread biodiversity changes. Finally, I look to the future, suggesting that the current carbon sink in intact forests is unlikely to continue, and that the tropical forest biome may even become a large net source of carbon, via one or more of four plausible routes: changing photosynthesis and respiration rates, biodiversity changes in intact forest, widespread forest collapse via drought, and widespread forest collapse via fire. Each of these scenarios risks potentially dangerous positive feedbacks with the climate system that could dramatically accelerate and intensify climate change. Given that continued land-use change alone is already thought to be causing the sixth mass extinction event in Earth's history, should such feedbacks occur, the resulting biodiversity and societal consequences would be even more severe.

Fire carbon emissions over maritime southeast Asia in 2015 largest since 1997

NASA Astrophysics Data System (ADS)

Huijnen, V.; Wooster, M. J.; Kaiser, J. W.; Gaveau, D. L. A.; Flemming, J.; Parrington, M.; Inness, A.; Murdiyarso, D.; Main, B.; van Weele, M.

2016-05-01

In September and October 2015 widespread forest and peatland fires burned over large parts of maritime southeast Asia, most notably Indonesia, releasing large amounts of terrestrially-stored carbon into the atmosphere, primarily in the form of CO2, CO and CH4. With a mean emission rate of 11.3 Tg CO2 per day during Sept-Oct 2015, emissions from these fires exceeded the fossil fuel CO2 release rate of the European Union (EU28) (8.9 Tg CO2 per day). Although seasonal fires are a frequent occurrence in the human modified landscapes found in Indonesia, the extent of the 2015 fires was greatly inflated by an extended drought period associated with a strong El Niño. We estimate carbon emissions from the 2015 fires to be the largest seen in maritime southeast Asia since those associated with the record breaking El Niño of 1997. Compared to that event, a much better constrained regional total carbon emission estimate can be made for the 2015 fires through the use of present-day satellite observations of the fire’s radiative power output and atmospheric CO concentrations, processed using the modelling and assimilation framework of the Copernicus Atmosphere Monitoring Service (CAMS) and combined with unique in situ smoke measurements made on Kalimantan.

Earth observations taken by the Expedition 12 crew

NASA Image and Video Library

2005-11-15

ISS012-E-13692 (2 Jan. 2006) --- A Forest Fire in Ouachita National Wildlife Refuge, Louisiana is featured in this image photographed by an Expedition 12 crew member on the International Space Station. Dry conditions and high winds have led to numerous recent fire outbreaks throughout much of the southwestern and south-central USA. This image captures the smoke plume from a fire in the Upper Ouachita National Wildlife Refuge in northeastern Louisiana. Drought conditions have persisted for much of the past year, leading to an increased fuel load comprised of dried grasses, shrubs, and trees. The combination of high amounts of dry fuel and frequent high winds has stoked small point fires into widespread brush fires. The fires generating this minimum 25-kilometer smoke plume started at approximately 13:00 hours local time. This image was acquired approximately 3.5 hours later as the station passed over the Texas/Louisiana border to the southwest. The extent of the plume reflects the strong westerly winds that drove the fire eastwards and damaged an estimated 200-300 acres of the wildlife refuge. The striking illumination of the plume is caused by a very low sun angle (angle between the horizon and the Sun directly below the space station), but this also results in generally low illumination of other scene features such as agricultural fields.

Climate change and the eco-hydrology of fire: Will area burned increase in a warming western USA?

USGS Publications Warehouse

McKenzie, Donald; Littell, Jeremy

2017-01-01

Wildfire area is predicted to increase with global warming. Empirical statistical models and process-based simulations agree almost universally. The key relationship for this unanimity, observed at multiple spatial and temporal scales, is between drought and fire. Predictive models often focus on ecosystems in which this relationship appears to be particularly strong, such as mesic and arid forests and shrublands with substantial biomass such as chaparral. We examine the drought–fire relationship, specifically the correlations between water-balance deficit and annual area burned, across the full gradient of deficit in the western USA, from temperate rainforest to desert. In the middle of this gradient, conditional on vegetation (fuels), correlations are strong, but outside this range the equivalence hotter and drier equals more fire either breaks down or is contingent on other factors such as previous-year climate. This suggests that the regional drought–fire dynamic will not be stationary in future climate, nor will other more complex contingencies associated with the variation in fire extent. Predictions of future wildfire area therefore need to consider not only vegetation changes, as some dynamic vegetation models now do, but also potential changes in the drought–fire dynamic that will ensue in a warming climate.

Fire carbon emissions over maritime southeast Asia in 2015 largest since 1997

PubMed Central

Huijnen, V.; Wooster, M. J.; Kaiser, J. W.; Gaveau, D. L. A.; Flemming, J.; Parrington, M.; Inness, A.; Murdiyarso, D.; Main, B.; van Weele, M.

2016-01-01

In September and October 2015 widespread forest and peatland fires burned over large parts of maritime southeast Asia, most notably Indonesia, releasing large amounts of terrestrially-stored carbon into the atmosphere, primarily in the form of CO2, CO and CH4. With a mean emission rate of 11.3 Tg CO2 per day during Sept-Oct 2015, emissions from these fires exceeded the fossil fuel CO2 release rate of the European Union (EU28) (8.9 Tg CO2 per day). Although seasonal fires are a frequent occurrence in the human modified landscapes found in Indonesia, the extent of the 2015 fires was greatly inflated by an extended drought period associated with a strong El Niño. We estimate carbon emissions from the 2015 fires to be the largest seen in maritime southeast Asia since those associated with the record breaking El Niño of 1997. Compared to that event, a much better constrained regional total carbon emission estimate can be made for the 2015 fires through the use of present-day satellite observations of the fire’s radiative power output and atmospheric CO concentrations, processed using the modelling and assimilation framework of the Copernicus Atmosphere Monitoring Service (CAMS) and combined with unique in situ smoke measurements made on Kalimantan. PMID:27241616

Long-term droughtiness and drought tolerance of eastern US forests over five decades

Treesearch

Matthew P. Peters; Louis R. Iverson; Stephen N. Matthews

2015-01-01

Droughts can influence forest composition directly by limiting water or indirectly by intensifying other stressors that affect establishment, growth, and mortality. Using community assemblages of eastern US tree species and drought tolerance characteristics assessed from literature, we examine recent drought conditions in relation to the spatial distribution of species...

Woody plant richness and NDVI response to drought events in Catalonian (northeastern Spain) forests.

PubMed

Lloret, F; Lobo, A; Estevan, H; Maisongrande, P; Vayreda, J; Terradas, J

2007-09-01

The role of species diversity on ecosystem resistance in the face of strong environmental fluctuations has been addressed from both theoretical and experimental viewpoints to reveal a variety of positive and negative relationships. Here we explore empirically the relationship between the richness of forest woody species and canopy resistance to extreme drought episodes. We compare richness data from an extensive forest inventory to a temporal series of satellite imagery that estimated drought impact on forest canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in 2003 in relation to records of previous years. We considered five different types of forests that are representative of the main climatic and altitudinal gradients of the region, ranging from lowland Mediterranean to mountain boreal-temperate climates. The observed relationship differed among forest types and interacted with the climate, summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI decreased during the drought. This decrease was stronger in forests with lower richness. In Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI loss, but lower NDVI values were observed in drier localities with lower richness, and in more moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI decreased, mostly due to the drought impact on drier localities, while no relation to species richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with high richness. No effect of drought was observed in the high mountain Pinus uncinata forests. Our results show that a shift on the diversity-stability relationship appears across the regional, climatic gradient. A positive relationship appears in drier localities, supporting a null model where the probability of finding a species able to cope with drier conditions increases with the number of species. However, in more moist localities we hypothesize that the proportion of drought-sensitive species would increase in richer localities, due to a higher likelihood of co-occurrence of species that share moist climatic requirements. The study points to the convenience of considering the causes of disturbance in relation to current environmental gradients and historical environmental constraints on the community.

Drought causes reduced growth of trembling aspen in western Canada.

PubMed

Chen, Lei; Huang, Jian-Guo; Alam, Syed Ashraful; Zhai, Lihong; Dawson, Andria; Stadt, Kenneth J; Comeau, Philip G

2017-07-01

Adequate and advance knowledge of the response of forest ecosystems to temperature-induced drought is critical for a comprehensive understanding of the impacts of global climate change on forest ecosystem structure and function. Recent massive decline in aspen-dominated forests and an increased aspen mortality in boreal forests have been associated with global warming, but it is still uncertain whether the decline and mortality are driven by drought. We used a series of ring-width chronologies from 40 trembling aspen (Populus tremuloides Michx.) sites along a latitudinal gradient (from 52° to 58°N) in western Canada, in an attempt to clarify the impacts of drought on aspen growth by using Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI). Results indicated that prolonged and large-scale droughts had a strong negative impact on trembling aspen growth. Furthermore, the spatiotemporal variability of drought indices is useful for explaining the spatial heterogeneity in the radial growth of trembling aspen. Due to ongoing global warming and rising temperatures, it is likely that severer droughts with a higher frequency will occur in western Canada. As trembling aspen is sensitive to drought, we suggest that drought indices could be applied to monitor the potential effects of increased drought stress on aspen trees growth, achieve classification of eco-regions and develop effective mitigation strategies to maintain western Canadian boreal forests. © 2017 John Wiley & Sons Ltd.

Characterizing interactions between fire and other disturbances and their impacts on tree mortality in western U.S. Forests

USGS Publications Warehouse

Kane, Jeffrey M.; Varner, J. Morgan; Metz, Margaret R.; van Mantgem, Phillip J.

2017-01-01

Increasing evidence that pervasive warming trends are altering disturbance regimes and their interactions with fire has generated substantial interest and debate over the implications of these changes. Previous work has primarily focused on conditions that promote non-additive interactions of linked and compounded disturbances, but the spectrum of potential interaction patterns has not been fully considered. Here we develop and define terminology, expand on the existing conceptual framework and review the patterns and mechanisms of disturbance interactions with a focus on interactions between fire and other forest disturbances and a specific emphasis on resulting tree mortality. The types of interactions reflect the positive, negative, or neutral responses to the incidence, intensity, and effects of the interaction. These types of interactions are not always mutually exclusive, but can be distinct. The collective effect of the interactions will determine the longer-term ecosystem response that can result in a resistant, resilient, or compounded interaction. Our review indicates that the interactions of drought, bark beetles, or pathogens with fire often result in neutral or maintained interactions that do not negatively or positively influence the incidence or intensity following fire. The effect of these disturbance interactions on tree mortality ranged from antagonistic (reduced mortality compared to individual disturbances) to synergistic (greater mortality compared to individual disturbances) within and among disturbance interaction types but often resulted in additive effects (mortality is consistent with the summation of the two disturbances). Synergistic effects on tree mortality have been observed when the severity of the initial disturbance is moderate to high and time between disturbances is relatively short. When the sequence of disturbance interaction is reversed (e.g., fire precedes other disturbances) the conditions can generally promote impeded interactions (lower incidence of interaction), reduced interactions (lower intensity of interaction), and antagonistic interactions (lower tree mortality). While recent research on fire-disturbance interactions has increased over the last decade and provided important insights, more research that identifies the specific thresholds of incidence, intensity, and effects of interaction by region and forest type are needed to better assist management solutions that promote desired outcomes in rapidly changing ecosystems.

Forest tree responses to extreme drought and some biotic events: Towards a selection according to hazard tolerance?

NASA Astrophysics Data System (ADS)

Bréda, Nathalie; Badeau, Vincent

2008-09-01

The aim of this paper is to illustrate how some extreme events could affect forest ecosystems. Forest tree response can be analysed using dendroecological methods, as tree-ring widths are strongly controlled by climatic or biotic events. Years with such events induce similar tree responses and are called pointer years. They can result from extreme climatic events like frost, a heat wave, spring water logging, drought or insect damage… Forest tree species showed contrasting responses to climatic hazards, depending on their sensitivity to water shortage or temperature hardening, as illustrated from our dendrochronological database. For foresters, a drought or a pest disease is an extreme event if visible and durable symptoms are induced (leaf discolouration, leaf loss, perennial organs mortality, tree dieback and mortality). These symptoms here are shown, lagging one or several years behind a climatic or biotic event, from forest decline cases in progress since the 2003 drought or attributed to previous severe droughts or defoliations in France. Tree growth or vitality recovery is illustrated, and the functional interpretation of the long lasting memory of trees is discussed. A coupled approach linking dendrochronology and ecophysiology helps in discussing vulnerability of forest stands, and suggests management advices in order to mitigate extreme drought and cope with selective mortality.

Remotely-sensed detection of effects of extreme droughts on gross primary production.

PubMed

Vicca, Sara; Balzarolo, Manuela; Filella, Iolanda; Granier, André; Herbst, Mathias; Knohl, Alexander; Longdoz, Bernard; Mund, Martina; Nagy, Zoltan; Pintér, Krisztina; Rambal, Serge; Verbesselt, Jan; Verger, Aleixandre; Zeileis, Achim; Zhang, Chao; Peñuelas, Josep

2016-06-15

Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space.

Conversion of natural forest to managed forest plantations decreases tree resistance to prolonged droughts

Treesearch

Jean-Christophe Domec; John S. King; Eric Ward; A. Christopher Oishi; Sari Palmroth; Andrew Radecki; Dave M. Bell; Guofang Miao; Michael Gavazzi; Daniel M. Johnson; Steve G. McNulty; Ge Sun; Asko Noormets

2015-01-01

Throughout the southern US, past forest management practices have replaced large areas of native forests with loblolly pine plantations and have resulted in changes in forest response to extreme weather conditions. However, uncertainty remains about the response of planted versus natural species to drought across the geographical range of these forests. Taking...

Ecosystem heterogeneity and diversity mitigate Amazon forest resilience to frequent extreme droughts.

PubMed

Longo, Marcos; Knox, Ryan G; Levine, Naomi M; Alves, Luciana F; Bonal, Damien; Camargo, Plinio B; Fitzjarrald, David R; Hayek, Matthew N; Restrepo-Coupe, Natalia; Saleska, Scott R; da Silva, Rodrigo; Stark, Scott C; Tapajós, Raphael P; Wiedemann, Kenia T; Zhang, Ke; Wofsy, Steven C; Moorcroft, Paul R

2018-05-22

The impact of increases in drought frequency on the Amazon forest's composition, structure and functioning remain uncertain. We used a process- and individual-based ecosystem model (ED2) to quantify the forest's vulnerability to increased drought recurrence. We generated meteorologically realistic, drier-than-observed rainfall scenarios for two Amazon forest sites, Paracou (wetter) and Tapajós (drier), to evaluate the impacts of more frequent droughts on forest biomass, structure and composition. The wet site was insensitive to the tested scenarios, whereas at the dry site biomass declined when average rainfall reduction exceeded 15%, due to high mortality of large-sized evergreen trees. Biomass losses persisted when year-long drought recurrence was shorter than 2-7 yr, depending upon soil texture and leaf phenology. From the site-level scenario results, we developed regionally applicable metrics to quantify the Amazon forest's climatological proximity to rainfall regimes likely to cause biomass loss > 20% in 50 yr according to ED2 predictions. Nearly 25% (1.8 million km 2 ) of the Amazon forests could experience frequent droughts and biomass loss if mean annual rainfall or interannual variability changed by 2σ. At least 10% of the high-emission climate projections (CMIP5/RCP8.5 models) predict critically dry regimes over 25% of the Amazon forest area by 2100. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Modeling forest mortality caused by drought stress: implications for climate change

Treesearch

Eric J Gustafson; Brian R. Sturtevant

2013-01-01

Climate change is expected to affect forest landscape dynamics in many ways, but it is possible that the most important direct impact of climate change will be drought stress. We combined data from weather stations and forest inventory plots (FIA) across the upper Great Lakes region (USA) to study the relationship between measures of drought stress and mortality for...

Hydrological responses to defoliation and drought of an upland oak/pine forest

Treesearch

K.V.R. Schäfer; H.J. Renninger; K.L. Clark; D. Medvigy

2014-01-01

Hydrologic variability during 2005-2011 was observed and analyzed at an upland oak/pine forest in the New Jersey Pinelands. The forest experienced defoliation by Gypsy moth (Lymantria dispar L.) in 2007, drought conditions in 2006 and a more severe drought in 2010. By using sap flux and eddy covariance measurements, stream discharge data from USGS,...

Frequency and distribution of forest, savanna, and crop fires over tropical regions during PEM-Tropics A

NASA Astrophysics Data System (ADS)

Olson, Jennifer R.; Baum, Bryan A.; Cahoon, Donald R.; Crawford, James H.

1999-03-01

Advanced very high resolution radiometer 1.1 km resolution satellite radiance data were used to locate active fires throughout much of the tropical region during NASA's Global Tropospheric Experiment (GTE) Pacific Exploratory Mission-Tropics (PEM-Tropics A) aircraft campaign, held in September and October 1996. The spatial and temporal distributions of the fires in Australia, southern Africa, and South America are presented here. The number of fires over northern Australia, central Africa, and South America appeared to decrease toward the end of the mission period. Fire over eastern Australia was widespread, and temporal patterns showed a somewhat consistent amount of burning with periodic episodes of enhanced fire counts observed. At least one episode of enhanced fire counts corresponded to the passage of a frontal system which brought conditions conducive to fire to the region, with strong westerlies originating over the hot, dry interior continent. Regions that were affected by lower than normal rainfall during the previous wet season (e.g., northern Australia and southwestern Africa) showed relatively few fires during this period. This is consistent with a drought-induced decrease in vegetation and therefore a decreased availability of fuel for burning. Alternatively, a heavier than normal previous wet season along the southeastern coast of South Africa may have contributed to high fuel loading and an associated relatively heavy amount of burning compared to data from previous years.

Interspecific variation in functional traits of oak seedlings (Quercus ilex, Quercus trojana, Quercus virgiliana) grown under artificial drought and fire conditions.

PubMed

Chiatante, D; Tognetti, R; Scippa, G S; Congiu, T; Baesso, B; Terzaghi, M; Montagnoli, A

2015-07-01

To face summer drought and wildfire in Mediterranean-type ecosystems, plants adopt different strategies that involve considerable rearrangements of biomass allocation and physiological activity. This paper analyses morphological and physiological traits in seedlings of three oak species (Quercus ilex, Quercus trojana and Quercus virgiliana) co-occurring under natural conditions. The aim of this study was to evaluate species-specific characteristics and the response of these oak seedlings to drought stress and fire treatment. Seedlings were kept in a growth chamber that mimicked natural environmental conditions. All three species showed a good degree of tolerance to drought and fire treatments. Differences in specific biomass allocation patterns and physiological traits resulted in phenotypic differences between species. In Q. ilex, drought tolerance depended upon adjustment of the allocation pattern. Q. trojana seedlings undergoing mild to severe drought presented a higher photosystem II (PSII) efficiency than control seedlings. Moreover, Q. trojana showed a very large root system, which corresponded to higher soil area exploitation, and bigger leaf midrib vascular bundles than the other two species. Morphological and physiological performances indicated Q. trojana as the most tolerant to drought and fire. These characteristics contribute to a high recruitment potential of Q. trojana seedlings, which might be the reason for the dominance of this species under natural conditions. Drought increase as a result of climate change is expected to favour Q. trojana, leading to an increase in its spatial distribution.

Assessing fire risk in Portugal during the summer fire season

NASA Astrophysics Data System (ADS)

Dacamara, C. C.; Pereira, M. G.; Trigo, R. M.

2009-04-01

Since 1998, Instituto de Meteorologia, the Portuguese Weather Service has relied on the Canadian Fire Weather Index (FWI) System (van Wagner, 1987) to produce daily forecasts of fire risk. The FWI System consists of six components that account for the effects of fuel moisture and wind on fire behavior. The first three components, i.e. the Fine Fuel Moisture Code (FFMC), the Duff Moisture Code (DMC) and the Drought Code (DC) respectively rate the average moisture content of surface litter, decomposing litter, and organic (humus) layers of the soil. Wind effects are then added to FFMC leading to the Initial Spread Index (ISI) that rates fire spread. The remaining two fuel moisture codes (DMC and DC) are in turn combined to produce the Buildup Index (BUI) that is a rating of the total amount of fuel available for combustion. BUI is finally combined with ISI to produce the Fire Weather Index (FWI) that represents the rate of fire intensity. Classes of fire danger and levels of preparedness are commonly defined on an empirical way for a given region by calibrating the FWI System against wildfire activity as defined by the recorded number of events and by the observed burned area over a given period of time (Bovio and Camia, 1998). It is also a well established fact that distributions of burned areas are heavily skewed to the right and tend to follow distributions of the exponential-type (Cumming, 2001). Based on the described context, a new procedure is presented for calibrating the FWI System during the summer fire season in Portugal. Two datasets were used covering a 28-year period (1980-2007); i) the official Portuguese wildfire database which contains detailed information on fire events occurred in the 18 districts of Continental Portugal and ii) daily values of the six components of the FWI System as derived from reanalyses (Uppala et al., 2005) of the European Centre for Medium-Range Weather Forecasts (ECMWF). Calibration of the FWI System is then performed in two steps; 1) a truncated Weibull distribution is fitted to the sample of burned areas and 2) the quality of the fitted statistical model is improved by incorporating components of the FWI System as covariates. Obtained model allows estimating on a daily basis the probability of occurrence of fires larger than a given threshold as well as producing maps of fire risk. Results as obtained from a prototype currently being developed will be presented and discussed. In particular, it will be shown that results provide additional evidence of the known fact that the extent of burned area in Portugal is controlled by two main atmospheric factors (Pereira et al. 2005): i) a long-term control related to the regime of temperature and precipitation in spring and ii) a short-term control exerted by the occurrence of very intense dry spells in days of extreme synoptic situations. Bovio, G., and A. Camia. 1998. An analysis of large forest fire danger conditions in Europe. In Proc. 3rd Int. Conf. on Forest Fire Research & 14th Conf. on Fire and Forest Meteorology, Viegas, D.X. (Ed.), Luso, 16-20 Nov., ADAI, 975-994. Cumming, S.G., 2001. Parametric models of the fire size distribution. Can J. For. Res., 31, 1297-1303. Pereira, M.G., Trigo, R.M., DaCamara, C.C., Pereira, J.M.C. and Leite, S.M., 2005. Synoptic patterns associated with large summer forest fires in Portugal. Agr. and For. Meteorol., 129 (1-2), 11-25. Uppala, S.M. et al., 2005: The ERA-40 re-analysis. Quart. J. R. Meteorol. Soc., 131, 2961-3012. Van Wagner, C.E., 1987. Development and structure of the Canadian forest fire weather index system. Canadian Forestry Service, Forest Technical Report 35, Ottawa, 37 pp.

Plant water use responses along secondary forest succession during the 2015-2016 El Niño drought in Panama.

PubMed

Bretfeld, Mario; Ewers, Brent E; Hall, Jefferson S

2018-03-05

Tropical forests are increasingly being subjected to hotter, drier conditions as a result of global climate change. The effects of drought on forests along successional gradients remain poorly understood. We took advantage of the 2015-2016 El Niño event to test for differences in drought response along a successional gradient by measuring the sap flow in 76 trees, representing 42 different species, in 8-, 25- and 80-yr-old secondary forests in the 15-km 2 'Agua Salud Project' study area, located in central Panama. Average sap velocities and sapwood-specific hydraulic conductivities were highest in the youngest forest. During the dry season drought, sap velocities increased significantly in the 80-yr-old forest as a result of higher evaporative demand, but not in younger forests. The main drivers of transpiration shifted from radiation to vapor pressure deficit with progressing forest succession. Soil volumetric water content was a limiting factor only in the youngest forest during the dry season, probably as a result of less root exploration in the soil. Trees in early-successional forests displayed stronger signs of regulatory responses to the 2015-2016 El Niño drought, and the limiting physiological processes for transpiration shifted from operating at the plant-soil interface to the plant-atmosphere interface with progressing forest succession. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Drought stress and tree size determine stem CO2 efflux in a tropical forest.

PubMed

Rowland, Lucy; da Costa, Antonio C L; Oliveira, Alex A R; Oliveira, Rafael S; Bittencourt, Paulo L; Costa, Patricia B; Giles, Andre L; Sosa, Azul I; Coughlin, Ingrid; Godlee, John L; Vasconcelos, Steel S; Junior, João A S; Ferreira, Leandro V; Mencuccini, Maurizio; Meir, Patrick

2018-06-01

CO 2 efflux from stems (CO 2_stem ) accounts for a substantial fraction of tropical forest gross primary productivity, but the climate sensitivity of this flux remains poorly understood. We present a study of tropical forest CO 2_stem from 215 trees across wet and dry seasons, at the world's longest running tropical forest drought experiment site. We show a 27% increase in wet season CO 2_stem in the droughted forest relative to a control forest. This was driven by increasing CO 2_stem in trees 10-40 cm diameter. Furthermore, we show that drought increases the proportion of maintenance to growth respiration in trees > 20 cm diameter, including large increases in maintenance respiration in the largest droughted trees, > 40 cm diameter. However, we found no clear taxonomic influence on CO 2_stem and were unable to accurately predict how drought sensitivity altered ecosystem scale CO 2_stem , due to substantial uncertainty introduced by contrasting methods previously employed to scale CO 2_stem fluxes. Our findings indicate that under future scenarios of elevated drought, increases in CO 2_stem may augment carbon losses, weakening or potentially reversing the tropical forest carbon sink. However, due to substantial uncertainties in scaling CO 2_stem fluxes, stand-scale future estimates of changes in stem CO 2 emissions remain highly uncertain. © 2018 The Authors New Phytologist © 2018 New Phytologist Trust.

El Niño drought increased canopy turnover in Amazon forests.

PubMed

Leitold, Veronika; Morton, Douglas C; Longo, Marcos; Dos-Santos, Maiza Nara; Keller, Michael; Scaranello, Marcos

2018-03-25

Amazon droughts, including the 2015-2016 El Niño, may reduce forest net primary productivity and increase canopy tree mortality, thereby altering both the short- and the long-term net forest carbon balance. Given the broad extent of drought impacts, inventory plots or eddy flux towers may not capture regional variability in forest response to drought. We used multi-temporal airborne Lidar data and field measurements of coarse woody debris to estimate patterns of canopy turnover and associated carbon losses in intact and fragmented forests in the central Brazilian Amazon between 2013-2014 and 2014-2016. Average annualized canopy turnover rates increased by 65% during the drought period in both intact and fragmented forests. The average size and height of turnover events was similar for both time intervals, in contrast to expectations that the 2015-2016 El Niño drought would disproportionally affect large trees. Lidar-biomass relationships between canopy turnover and field measurements of coarse woody debris were modest (R 2  ≈ 0.3), given similar coarse woody debris production and Lidar-derived changes in canopy volume from single tree and multiple branch fall events. Our findings suggest that El Niño conditions accelerated canopy turnover in central Amazon forests, increasing coarse woody debris production by 62% to 1.22 Mg C ha -1  yr -1 in drought years . No claim to original US Government works New Phytologist © 2018 New Phytologist Trust.

Extrapolating carbon dynamics of tropical dry forests into future climates: improving simulation models with empirical observations

NASA Astrophysics Data System (ADS)

Medvigy, David; Waring, Bonnie; Vargas, German; Xu, Xiangtao; Smith, Christina; Becknell, Justin; Trierweiler, Annette; Brodribb, Timothy; Powers, Jennifer

2017-04-01

Tropical dry forests occur in areas with warm temperatures and a pronounced dry season with little to no rainfall that lasts 3 to 7 months. The potential area covered by this biome is vast: globally, 47% of all forest occurs in tropical and subtropical latitudes, and of all tropical forests approximately 42% are classified as dry forests. Throughout the last several centuries, the area covered by tropical dry forests has been dramatically reduced through conversion to grazing and croplands, and they are now considered the most threatened tropical biome. However, in many regions, tropical dry forests are now growing back. There is growing concern that this recovery process will be strongly impacted by climate variability and change. Observations show that climate is changing in the seasonal tropics, and climate models forecast that neotropical dry forests will receive significantly less rainfall in the 21st century than in the 20th century. Rates of nitrogen deposition are also changing rapidly in this sector, and the fertility of some soils may still be recovering from past land use. We are engaged in several efforts to understand how water and nutrients limit the productivity of these forests, including manipulative experiments, modeling, and investigation of responses to natural climate variability. In 2015, at a well-characterized site in Guanacaste, Costa Rica, we established a full-factorial fertilization experiment with N and P in diverse mature forest stands. Initial responses highlight stronger ecosystem sensitivity to P addition than to N addition. Intriguingly, pre-experiment numerical simulations with a mechanistic ecosystem model had indicated the reverse. Work is ongoing to use field observations to better represent critical processes in the model, and ultimately to improve the model's sensitivity to nutrients and water. In addition, in 2016, we established a full factorial nutrient addition and drought experiment in plantations. Thus far, soil moisture has been successfully reduced in the drought treatments. Finally, we are investigating the impact of an extreme climatic event, the 2015 drought, on the productivity of this forest. The fingerprint of the drought on tree mortality is very strong. We found that plot-level mortality rates were two to three times higher during the drought than before the drought, and varied from 0 to >50% among species. In contrast to observations at moist tropical forests, tree size had little influence on mortality. In terms of functional groups, mortality rates of evergreen oaks growing on nutrient-poor soils particularly increased during drought. However, elevated mortality rates were not clearly correlated with commonly-measured traits like wood density or specific leaf area. In addition, trees that died during the drought tended to have smaller relative growth rate prior to the drought than trees that survived the drought. Mechanistic models are able to simulate stand-level mortality following the drought, and model-data comparison highlights different tree hydraulic strategies that can mitigate drought effects.

Focused sunlight factor of forest fire danger assessment using Web-GIS and RS technologies

NASA Astrophysics Data System (ADS)

Baranovskiy, Nikolay V.; Sherstnyov, Vladislav S.; Yankovich, Elena P.; Engel, Marina V.; Belov, Vladimir V.

2016-08-01

Timiryazevskiy forestry of Tomsk region (Siberia, Russia) is a study area elaborated in current research. Forest fire danger assessment is based on unique technology using probabilistic criterion, statistical data on forest fires, meteorological conditions, forest sites classification and remote sensing data. MODIS products are used for estimating some meteorological conditions and current forest fire situation. Geonformation technologies are used for geospatial analysis of forest fire danger situation on controlled forested territories. GIS-engine provides opportunities to construct electronic maps with different levels of forest fire probability and support raster layer for satellite remote sensing data on current forest fires. Web-interface is used for data loading on specific web-site and for forest fire danger data representation via World Wide Web. Special web-forms provide interface for choosing of relevant input data in order to process the forest fire danger data and assess the forest fire probability.

Contributing factors for drought in United States forest ecosystems under projected future climates and their uncertainty

Treesearch

Charlie Luce; James M. Vose; Neil Pederson; John Campbell; Connie Millar; Patrick Kormos; Ross Woods

2016-01-01

Observations of increasing global forest die-off related to drought are leading to more questions about potential increases in drought occurrence, severity, and ecological consequence in the future. Dry soils and warm temperatures interact to affect trees during drought; so understanding shifting risks requires some understanding of changes in both temperature...

Hydrological dynamics and fire history of the last 1300 years in western Siberia reconstructed from a high-resolution, ombrotrophic peat archive

NASA Astrophysics Data System (ADS)

Lamentowicz, Mariusz; Słowiński, Michał; Marcisz, Katarzyna; Zielińska, Małgorzata; Kaliszan, Karolina; Lapshina, Elena; Gilbert, Daniel; Buttler, Alexandre; Fiałkiewicz-Kozieł, Barbara; Jassey, Vincent E. J.; Laggoun-Defarge, Fatima; Kołaczek, Piotr

2015-11-01

Siberian peatlands provide records of past changes in the continental climate of Eurasia. We analyzed a core from Mukhrino mire in western Siberia to reconstruct environmental change in this region over the last 1300 years. The pollen analysis revealed little variation of local pine-birch forests. A testate amoebae transfer function was used to generate a quantitative water-table reconstruction; pollen, plant macrofossils, and charcoal were analyzed to reconstruct changes in vegetation and fire activity. The study revealed that Mukhrino mire was wet until the Little Ice Age (LIA), when drought was recorded. Dry conditions during the LIA are consistent with other studies from central and eastern Europe, and with the pattern of carbon accumulation across the Northern Hemisphere. A significant increase in fire activity between ca. AD 1975 and 1990 may be associated with the development of the nearby city of Khanty-Mansiysk, as well as with the prevailing positive Arctic Oscillation.

Carbon Monoxide in Mid-Troposphere over Indonesia Fires, October 2015

NASA Image and Video Library

2015-10-30

Widespread forest fires across Indonesia have burned tens of thousands of acres over three months, causing high levels of pollution, loss of life, and billions of dollars to the Indonesian government. It is estimated that more than 43 million people have been inhaling toxic fumes, and large parts of Indonesia have been placed in a state of emergency. Most of the fires are believed to have been set to clear farmland during the dry season, but a long term drought enhanced by El Niño conditions have contributed to the fires remaining unchecked due to lack of rain. These images made with data acquired by AIRS, the Atmospheric Infrared Sounder on NASA's Aqua Satellite, show the global concentration of carbon monoxide at the 500hPa pressure level, or approximately 18,000 feet (5,500 meters) altitude. The data are an average of measurements taken over three days, from October 14 through 16, and October 26 through 28, and the high concentration and large extent of the fires over Indonesia are quite apparent. While the scale for this image extends to 400 parts per billion, local values of carbon monoxide can be significantly higher. http://photojournal.jpl.nasa.gov/catalog/PIA20042

Condition and fate of logged forests in the Brazilian Amazon.

PubMed

Asner, Gregory P; Broadbent, Eben N; Oliveira, Paulo J C; Keller, Michael; Knapp, David E; Silva, José N M

2006-08-22

The long-term viability of a forest industry in the Amazon region of Brazil depends on the maintenance of adequate timber volume and growth in healthy forests. Using extensive high-resolution satellite analyses, we studied the forest damage caused by recent logging operations and the likelihood that logged forests would be cleared within 4 years after timber harvest. Across 2,030,637 km2 of the Brazilian Amazon from 1999 to 2004, at least 76% of all harvest practices resulted in high levels of canopy damage sufficient to leave forests susceptible to drought and fire. We found that 16+/-1% of selectively logged areas were deforested within 1 year of logging, with a subsequent annual deforestation rate of 5.4% for 4 years after timber harvests. Nearly all logging occurred within 25 km of main roads, and within that area, the probability of deforestation for a logged forest was up to four times greater than for unlogged forests. In combination, our results show that logging in the Brazilian Amazon is dominated by highly damaging operations, often followed rapidly by deforestation decades before forests can recover sufficiently to produce timber for a second harvest. Under the management regimes in effect at the time of our study in the Brazilian Amazon, selective logging would not be sustained.

Condition and fate of logged forests in the Brazilian Amazon

PubMed Central

Asner, Gregory P.; Broadbent, Eben N.; Oliveira, Paulo J. C.; Keller, Michael; Knapp, David E.; Silva, José N. M.

2006-01-01

The long-term viability of a forest industry in the Amazon region of Brazil depends on the maintenance of adequate timber volume and growth in healthy forests. Using extensive high-resolution satellite analyses, we studied the forest damage caused by recent logging operations and the likelihood that logged forests would be cleared within 4 years after timber harvest. Across 2,030,637 km2 of the Brazilian Amazon from 1999 to 2004, at least 76% of all harvest practices resulted in high levels of canopy damage sufficient to leave forests susceptible to drought and fire. We found that 16 ± 1% of selectively logged areas were deforested within 1 year of logging, with a subsequent annual deforestation rate of 5.4% for 4 years after timber harvests. Nearly all logging occurred within 25 km of main roads, and within that area, the probability of deforestation for a logged forest was up to four times greater than for unlogged forests. In combination, our results show that logging in the Brazilian Amazon is dominated by highly damaging operations, often followed rapidly by deforestation decades before forests can recover sufficiently to produce timber for a second harvest. Under the management regimes in effect at the time of our study in the Brazilian Amazon, selective logging would not be sustained. PMID:16901980

Exploring fire dynamics with BFAST approach: case studies in Sardinia, Italy

NASA Astrophysics Data System (ADS)

Quarfeld, Jamie; di Mauro, Biagio; Colombo, Roberto; Verbesselt, Jan

2016-04-01

The synergistic effect of wildfire and extreme post-fire climatic events, (e.g. droughts or torrential rainfall), may result in long windows of disturbance - challenging the overall resilience of Mediterranean ecosystems and communities. The notion that increased fire frequency and severity may reduce ecosystem resilience has received much attention in Mediterranean regions in recent decades. Careful evaluation of vegetation recovery and landscape regeneration after a fire event provides vital information useful in land management. In this study, an extension of Breaks For Additive Seasonal and Trend (BFAST) is proposed as an ideal approach to monitor change and assess fire dynamics at the landscape level based on analysis of the MODerate-resolution Imaging Spectroradiometer (MODIS, TERRA) time series. To this end, satellite images of three vegetation indices (VIs), the Normalized Burn Ratio (NBR), the Enhanced Vegetation Index (EVI) and the Normalized Difference Vegetation Index (NDVI) were used. The analysis was conducted on areas affected by wildfires in the Sardinia region (Italy) between 2007 and 2010. Some land surface (LS) descriptors (i.e. mean and maximum VI) and fire characteristics (e.g. pre-fire trend & VI, change magnitude, current VI) were extracted to characterize the post-fire evolution of each site within a fifteen-year period (2000-2015). Resilience was estimated using a classic linear function, whereby recovery rates were compared to regional climate data (e.g. water balance) and local landscape components (e.g.topography, land use and land cover). The methodology was applied according to land cover type (e.g. mixed forest, maquis, shrubland, pasture) within each fire site and highlighted the challenge of isolating effects and quantifying the role of fire regime characteristics on resilience in a dynamic way when considering large, heterogeneous areas. Preliminary findings can be outlined as follows: I. NBR showed it was most effective at detecting fire occurrence. EVI showed it was more sensitive to the influence of the Savitkzy-Golay smoothing filter than NBR or NDVI; II. The quantitative assessment of resilience for different land covers (maquis, mixed forest, shrubland) allows discrimination of diverse post-fire dynamics. Mixed forest showed an overall lower resilience compared to maquis and shrubland. Detection of post-fire breakpoints appears to occur in a similar time sequence with respect to both year of fire occurrence and land cover. III. The combined use of several climate and landscape components enables characterization of different features of post-fire dynamics in a Mediterranean ecosystem. In summary, the approach used in this study provides useful insight into complex post-fire vegetation dynamics in Mediterranean regions from a remote sensing perspective. Tailoring of the methodologies employed this study can inform a broad spectrum of forest and wildfire management activities, from monitoring and decision support during the fire season to long-term fuel management and landscape planning, with the general goal of reducing fire exposure and losses from future wildfires. Results can be expanded to include additional LS descriptors or soil geological aspects that contribute to a stronger integration of remote sensing data in operational natural resource management plans for ecosystem conservation and natural hazard prevention.

Impacts of Water Stress on Forest Recovery and Its Interaction with Canopy Height.

PubMed

Xu, Peipei; Zhou, Tao; Yi, Chuixiang; Luo, Hui; Zhao, Xiang; Fang, Wei; Gao, Shan; Liu, Xia

2018-06-13

Global climate change is leading to an increase in the frequency, intensity, and duration of drought events, which can affect the functioning of forest ecosystems. Because human activities such as afforestation and forest attributes such as canopy height may exhibit considerable spatial differences, such differences may alter the recovery paths of drought-impacted forests. To accurately assess how climate affects forest recovery, a quantitative evaluation on the effects of forest attributes and their possible interaction with the intensity of water stress is required. Here, forest recovery following extreme drought events was analyzed for Yunnan Province, southwest China. The variation in the recovery of forests with different water availability and canopy heights was quantitatively assessed at the regional scale by using canopy height data based on light detection and ranging (LiDAR) measurements, enhanced vegetation index data, and standardized precipitation evapotranspiration index (SPEI) data. Our results indicated that forest recovery was affected by water availability and canopy height. Based on the enhanced vegetation index measures, shorter trees were more likely to recover than taller ones after drought. Further analyses demonstrated that the effect of canopy height on recovery rates after drought also depends on water availability—the effect of canopy height on recovery diminished as water availability increased after drought. Additional analyses revealed that when the water availability exceeded a threshold (SPEI > 0.85), no significant difference in the recovery was found between short and tall trees ( p > 0.05). In the context of global climate change, future climate scenarios of RCP2.6 and RCP8.5 showed more frequent water stress in Yunnan by the end of the 21st century. In summary, our results indicated that canopy height casts an important influence on forest recovery and tall trees have greater vulnerability and risk to dieback and mortality from drought. These results may have broad implications for policies and practices of forest management.

Five millennia of frozen vegetation and fire dynamics from an ice core in the Mongolian Altai

NASA Astrophysics Data System (ADS)

Brügger, S. O.; Gobet, E.; Sigl, M.; Osmont, D.; Papina, T.; Rudaya, N.; Schwikowski, M.; Tinner, W.

2017-12-01

The steppes of the Altai region in Central Asia are highly vulnerable to e.g. drought and overgrazing. Degradation during the past decades may undermine their resilience under global change conditions. Knowledge about past vegetation and fire dynamics in Mongolian Altai may contribute to a better understanding of future climate and human impact responses, however, paleo records are scarce in the area. Our novel high-alpine ice record from Tsambagarav glacier (48°39.338'N, 90°50.826'E, 4130m asl) in the Mongolian Altai provides unique paleoenvironmental informations at the landscape scale. The site is surrounded by dry steppes with scattered boreal tree stands. We assume that the site collects pollen and spores within several hundred km. The archive provides an exceptional temporal resolution with a sound chronology covering the past 5500 years (Herren et al. 2013). Microfossil analysis allows to reconstruct large-scale fire and vegetation dynamics to gain a better understanding of the timing and causes of late Holocene response variability. We use pollen as proxies for vegetation composition and structure, microscopic charcoal as a proxy for fire activity (Eichler et al. 2011), and spheroidal carbonaceous particles (SCPs or soots) as a proxy for fossil fuel combustion. Here we present the first microscopic charcoal record from Mongolia and link it to vegetation dynamics of the past. The reconstructed mid to late Holocene forest collapses likely in response to climate change underscore the vulnerability of relict forest ecosystems in the Mongolian Altai. Our multiproxy-study suggests that moisture is more important than temperature for forest preservation. The lacking resilience of vegetation to moisture changes in the past emphasizes the vulnerability of large forests in neighboring dry areas such as the Russian Altai, if global warming is associated to moisture declines as future projections forecast (IPCC; Climate Change 2013). References: Eichler et al. (2011). An ice-core based history of Siberian forest fires since AD 1250. Quat Sci Rev 30(9) Herren et al. (2013). The onset of Neoglaciation 6000 years ago in western Mongolia revealed by an ice core from the Tsambagarav mountain range. Quat Sci Rev 69 IPCC; Climate Change (2013): The Physical Science Basis. IPCC Working Group I Contribution to AR5

The Influence of Large-Scale Circulation on Fire Outbreaks in the Amazon Region

NASA Astrophysics Data System (ADS)

Pires, L. B. M.; Romao, M.; Freitas, A. C. V.

2017-12-01

The combination of alterations in land use cover and severe droughts may dramatically increase fire outbreaks. Tropical convection in the Amazon Basin is regulated mainly by large-scale atmospheric systems such as the Walker circulation. Many of the documented drought episodes in the Amazon occurred during intense El Niño events such as those recorded in 1926, 1983, 1997-1998, and 2010. However, not all El Niño events are related to drought in the Amazon. Recent studies have also pointed out the importance of the tropical Atlantic Ocean in the modulation of the Amazonian climate, as observed during the drought episodes in 2005 and 2010. This work investigates the fire outbreak tendency in the Amazon region, and the influence of large-scale circulation on these events. Data from the Fire Program of the Center for Weather Forecasting and Climate Studies (CPTEC/INPE) show a substantial increase in the number of fire outbreaks in the last few years, especially during 2016. However, in the 2017 year a sharp drop in fire outbreaks reaching levels similar to the years prior to 2016 is being noted, already showing a reduction of 54% in relation to the preceding 2016 year. The 2015-2016 period was marked by one of the strongest El Niño in history. This was reflected in the increase of the number of fire outbreaks due to the increase of the drought and temperature elevation period. On the other hand, the 2017 year is being characterized by a condition of neutrality in relation to the El Niño-Southern Oscillation (ENSO) phenomena, and have overall presented positive sea surface temperature (SST) anomalies in the tropical Atlantic. Variations of these systems and their relation to fire outbreaks is demonstrated.

Forest fires and PM10 pollution: the March 2012 case in Northern Spain

NASA Astrophysics Data System (ADS)

Rasilla Álvarez, Domingo; García Codron, Juan Carlos; Carracedo Martín, Virginia

2016-04-01

Forest fires are one of the largest sources of particulate matter, carbon monoxide, volatile organic compounds and other pollutants at regional scale. They significantly impact on local air quality and human health, even far from their original sources. March 2012 was one of the largest fire activity late winter and early spring seasons across northern Spain and Portugal. Official statistics from the Spanish and Portuguese authorities show that, during that month, approximately 35.000 ha were burned, representing the top March season in Cantabria (N. Spain) and the northern distritos of Portugal since 1981, most of them occurring in the mountainous areas, as depicted from the FIRMS database (https://firms.modaps.eosdis.nasa.gov/). At the same time, an analysis of the pollution data (Airbase dataset; http://www.eea.europa.eu/) show an increase in PM10 average values and exceedences of the limit values across the same area simultaneously or immediately after the main fire activity episodes. A comprehensive analysis of this fire and pollution event was undertaken to analyze the possible contribution of forest fires and other sources of PM10 to the high levels of this pollutant at ground level. Besides statistics of fire activity, satellite "hot spots" and ground level pollution data, we have included in our analysis meteorological records (synoptic stations, upper air soundings), backtrajectories (http://ready.arl.noaa.gov/HYSPLIT.php) and dust forecast models (https://www.bsc.es/earth-sciences/mineral-dust/catalogo-datos-dust). The results show a good agreement between the spatial and temporal variability of the levels of PM10 and the direction of the pollution plumes downwind the forest fires. The activity was mostly concentrated during 3 events, the first one between February 25th to March 3rd; the second spanning from 10th to 17th, and the last one, the most severe of the three, at the end of March. The climatological background was favourable, because most of the Iberian Peninsula recorded severe moisture deficits at the end of the winter, as shown by the drought indices. At synoptic time scale, the episodes of generalized burning coincided with warmer and drier than usual conditions, although wind speed was low, in agreement with the prevailing stable atmosphere. Saharian dust advections seem to have an indirect contribution to the high levels of PM10, probably by resuspension of old air masses. Moreover, the possible advection of old polluted layers from Eastern Europe, through a European blocking circulation (cut off high), is also considered.

Drought and tree mortality in tropical rainforest: understanding and differentiating functional responses

NASA Astrophysics Data System (ADS)

Meir, P.; Rowland, L.; da Costa, A. C. L.; Mencuccini, M.; Oliveira, A.; Binks, O.; Christoffersen, B. O.; Eliane, M.; Vasconcelos, S.; Kruijt, B.; Ferreira, L.

2014-12-01

Our understanding of how forests respond to drought is especially constrained with respect to widespread tree mortality events. This limitation is particularly clear for tropical forests, despite the risk of drought to these ecosystems during the coming decades. We present new findings from the only current long-term 'ecosystem-scale' (1 ha) rainfall manipulation experiment in tropical rainforest, the Esecaflor experiment at Caxiuana National Forest, Para State, Brazil. Throughfall has been partially excluded from experimental forest at the Esecaflor experiment for more than a decade. We have previously demonstrated a capacity to model short-term physiological responses well, but longer term physiology and ecological dynamics remain challenging to understand and represent. In particular, high mortality and increased autotrophic respiration following extended drought are poorly understood phenomena, and their interaction with hydraulic responses and limitations needs to be characterised. We present initial data that for the first time combine carbon use and hydraulic metrics, comparing drought-vulnerable and non-vulnerable species that have experienced extended soil moisture deficit, as imposed in the experiment, also considering the response in soil respiration. We also discuss how these findings can be used to develop future empirical and modelling studies aimed at improving our capacity to predict the effects of drought on tropical forest ecosystems in Amazonia and in other tropical forest regions where species characteristics and environmental constraints may influence both short and long-term responses to drought.

On underestimation of global vulnerability to tree mortality and forest die-off from hotter drought in the Anthropocene

USGS Publications Warehouse

Allen, Craig D.; Breshears, David D.; McDowell, Nathan G.

2015-01-01

Patterns, mechanisms, projections, and consequences of tree mortality and associated broad-scale forest die-off due to drought accompanied by warmer temperatures—“hotter drought”, an emerging characteristic of the Anthropocene—are the focus of rapidly expanding literature. Despite recent observational, experimental, and modeling studies suggesting increased vulnerability of trees to hotter drought and associated pests and pathogens, substantial debate remains among research, management and policy-making communities regarding future tree mortality risks. We summarize key mortality-relevant findings, differentiating between those implying lesser versus greater levels of vulnerability. Evidence suggesting lesser vulnerability includes forest benefits of elevated [CO2] and increased water-use efficiency; observed and modeled increases in forest growth and canopy greening; widespread increases in woody-plant biomass, density, and extent; compensatory physiological, morphological, and genetic mechanisms; dampening ecological feedbacks; and potential mitigation by forest management. In contrast, recent studies document more rapid mortality under hotter drought due to negative tree physiological responses and accelerated biotic attacks. Additional evidence suggesting greater vulnerability includes rising background mortality rates; projected increases in drought frequency, intensity, and duration; limitations of vegetation models such as inadequately represented mortality processes; warming feedbacks from die-off; and wildfire synergies. Grouping these findings we identify ten contrasting perspectives that shape the vulnerability debate but have not been discussed collectively. We also present a set of global vulnerability drivers that are known with high confidence: (1) droughts eventually occur everywhere; (2) warming produces hotter droughts; (3) atmospheric moisture demand increases nonlinearly with temperature during drought; (4) mortality can occur faster in hotter drought, consistent with fundamental physiology; (5) shorter droughts occur more frequently than longer droughts and can become lethal under warming, increasing the frequency of lethal drought nonlinearly; and (6) mortality happens rapidly relative to growth intervals needed for forest recovery. These high-confidence drivers, in concert with research supporting greater vulnerability perspectives, support an overall viewpoint of greater forest vulnerability globally. We surmise that mortality vulnerability is being discounted in part due to difficulties in predicting threshold responses to extreme climate events. Given the profound ecological and societal implications of underestimating global vulnerability to hotter drought, we highlight urgent challenges for research, management, and policy-making communities.

Patterns of drought tolerance in major European temperate forest trees: climatic drivers and levels of variability.

PubMed

Zang, Christian; Hartl-Meier, Claudia; Dittmar, Christoph; Rothe, Andreas; Menzel, Annette

2014-12-01

The future performance of native tree species under climate change conditions is frequently discussed, since increasingly severe and more frequent drought events are expected to become a major risk for forest ecosystems. To improve our understanding of the drought tolerance of the three common European temperate forest tree species Norway spruce, silver fir and common beech, we tested the influence of climate and tree-specific traits on the inter and intrasite variability in drought responses of these species. Basal area increment data from a large tree-ring network in Southern Germany and Alpine Austria along a climatic cline from warm-dry to cool-wet conditions were used to calculate indices of tolerance to drought events and their variability at the level of individual trees and populations. General patterns of tolerance indicated a high vulnerability of Norway spruce in comparison to fir and beech and a strong influence of bioclimatic conditions on drought response for all species. On the level of individual trees, low-growth rates prior to drought events, high competitive status and low age favored resilience in growth response to drought. Consequently, drought events led to heterogeneous and variable response patterns in forests stands. These findings may support the idea of deliberately using spontaneous selection and adaption effects as a passive strategy of forest management under climate change conditions, especially a strong directional selection for more tolerant individuals when frequency and intensity of summer droughts will increase in the course of global climate change. © 2014 John Wiley & Sons Ltd.

Global resistance and resilience of primary production following extreme drought are predicted by mean annual precipitation

NASA Astrophysics Data System (ADS)

Stuart-Haëntjens, E. J.; De Boeck, H. J.; Lemoine, N. P.; Gough, C. M.; Kröel-Dulay, G.; Mänd, P.; Jentsch, A.; Schmidt, I. K.; Bahn, M.; Lloret, F.; Kreyling, J.; Wohlgemuth, T.; Stampfli, A.; Anderegg, W.; Classen, A. T.; Smith, M. D.

2017-12-01

Extreme drought is increasing globally in frequency and intensity, with uncertain consequences for the resistance and resilience of key ecosystem functions, including primary production. Primary production resistance, the capacity of an ecosystem to withstand change in primary production following extreme climate, and resilience, the degree to which primary production recovers, vary among and within ecosystem types, obscuring global patterns of resistance and resilience to extreme drought. Past syntheses on resistance have focused climatic gradients or individual ecosystem types, without assessing interactions between the two. Theory and many empirical studies suggest that forest production is more resistant but less resilient than grassland production to extreme drought, though some empirical studies reveal that these trends are not universal. Here, we conducted a global meta-analysis of sixty-four grassland and forest sites, finding that primary production resistance to extreme drought is predicted by a common continuum of mean annual precipitation (MAP). However, grasslands and forests exhibit divergent production resilience relationships with MAP. We discuss the likely mechanisms underlying the mixed production resistance and resilience patterns of forests and grasslands, including different plant species turnover times and drought adaptive strategies. These findings demonstrate the primary production responses of forests and grasslands to extreme drought are mixed, with far-reaching implications for Earth System Models, ecosystem management, and future studies of extreme drought resistance and resilience.

Automated Monitoring of Carbon Fluxes in a Northern Rocky Mountain Forest Indicates Above-Average Net Primary Productivity During the 2015 Western U.S. Drought

NASA Astrophysics Data System (ADS)

Stenzel, J.; Hudiburg, T. W.

2016-12-01

As global temperatures rise in the 21st century, "hotter" droughts will become more intense and persistent, particularly in areas which already experience seasonal drought. Because forests represent a large and persistent terrestrial carbon sink which has previously offset a significant proportion of anthropogenic carbon emissions, forest carbon cycle responses to drought have become a prominent research concern. However, robust mechanistic modeling of carbon balance responses to projected drought effects requires improved observation-driven representations of carbon cycle processes; many such component processes are rarely monitored in complex terrain, are modeled or unrepresented quantities at eddy covariance sites, or are monitored at course temporal scales that are not conducive to elucidating process responses at process time scales. In the present study, we demonstrate the use of newly available and affordable automated dendrometers for the estimation of intra-seasonal Net Primary Productivity (NPP) in a Northern Rocky Mountain conifer forest which is impacted by seasonal drought. Results from our pilot study suggest that NPP was restricted by mid-summer moisture deficit under the extraordinary 2015 Western U.S. drought, with greater than 90% off stand growth occurring prior to August. Examination of growth on an inter-annual scale, however, suggests that the study site experienced above-average NPP during this exceptionally hot year. Taken together, these findings indicate that intensifying mid-summer drought in regional forests has affected the timing but has not diminished the magnitude of this carbon flux. By employing automated instrumentation for the intra-annual assessment of NPP, we reveal that annual NPP in regional forests is largely determined before mid-summer and is therefore surprisingly resilient to intensities of seasonal drought that exceed normal conditions of the 20th century.

Drought characteristics' role in widespread aspen forest mortality across Colorado, USA.

PubMed

Anderegg, Leander D L; Anderegg, William R L; Abatzoglou, John; Hausladen, Alexandra M; Berry, Joseph A

2013-05-01

Globally documented widespread drought-induced forest mortality has important ramifications for plant community structure, ecosystem function, and the ecosystem services provided by forests. Yet the characteristics of drought seasonality, severity, and duration that trigger mortality events have received little attention despite evidence of changing precipitation regimes, shifting snow melt timing, and increasing temperature stress. This study draws upon stand level ecohydrology and statewide climate and spatial analysis to examine the drought characteristics implicated in the recent widespread mortality of trembling aspen (Populus tremuloides Michx.). We used isotopic observations of aspen xylem sap to determine water source use during natural and experimental drought in a region that experienced high tree mortality. We then drew upon multiple sources of climate data to characterize the drought that triggered aspen mortality. Finally, regression analysis was used to examine the drought characteristics most associated with the spatial patterns of aspen mortality across Colorado. Isotopic analysis indicated that aspens generally utilize shallow soil moisture with little plasticity during drought stress. Climate analysis showed that the mortality-inciting drought was unprecedented in the observational record, especially in 2002 growing season temperature and evaporative deficit, resulting in record low shallow soil moisture reserves. High 2002 summer temperature and low shallow soil moisture were most associated with the spatial patterns of aspen mortality. These results suggest that the 2002 drought subjected Colorado aspens to the most extreme growing season water stress of the past century by creating high atmospheric moisture demand and depleting the shallow soil moisture upon which aspens rely. Our findings highlight the important role of drought characteristics in mediating widespread aspen forest mortality, link this aspen die-off to regional climate change trends, and provide insight into future climate vulnerability of these forests. © 2013 Blackwell Publishing Ltd.

Introducing GFWED: The Global Fire Weather Database

NASA Technical Reports Server (NTRS)

Field, R. D.; Spessa, A. C.; Aziz, N. A.; Camia, A.; Cantin, A.; Carr, R.; de Groot, W. J.; Dowdy, A. J.; Flannigan, M. D.; Manomaiphiboon, K.;

Forest biogeochemistry in response to drought

Treesearch

William H. Schlesinger; Michael C. Dietze; Robert B. Jackson; Richard P. Phillips; Charles C. Rhoades; Lindsey E. Rustad; James M. Vose

2015-01-01

Trees alter their use and allocation of nutrients in response to drought, and changes in soil nutrient cycling and trace gas flux (N2O and CH4) are observed when experimental drought is imposed on forests. In extreme droughts, trees are increasingly susceptible to attack by pests and pathogens, which can lead to major changes in nutrient flux to the soil....

Plant hydraulic diversity buffers forest ecosystem responses to drought

NASA Astrophysics Data System (ADS)

Anderegg, W.; Konings, A. G.; Trugman, A. T.; Pacala, S. W.; Yu, K.; Sulman, B. N.; Sperry, J.; Bowling, D. R.

2017-12-01

Drought impacts carbon, water, and energy cycles in forests and may pose a fundamental threat to forests in future climates. Plant hydraulic transport of water is central to tree drought responses, including curtailing of water loss and the risk of mortality during drought. The effect of biodiversity on ecosystem function has typically been examined in grasslands, yet the diversity of plant hydraulic strategies may influence forests' response to drought. In a combined analysis of eddy covariance measurements, remote-sensing data of plant water content variation, model simulations, and plant hydraulic trait data, we test the degree to which plant water stress schemes influence the carbon cycle and how hydraulic diversity within and across ecosystems affects large-scale drought responses. We find that current plant functional types are not well-suited to capture hydraulic variation and that higher hydraulic diversity buffers ecosystem variation during drought. Our results demonstrate that tree functional diversity, particularly hydraulic diversity, may be critical to simulate in plant functional types in current land surface model projections of future vegetation's response to climate extremes.

Monitoring gradual ecosystem change using Landsat time series analyses: case studies in selected forest and rangeland ecosystems

USGS Publications Warehouse

Vogelmann, James E.; Xian, George; Homer, Collin G.; Tolk, Brian

2012-01-01

The focus of the study was to assess gradual changes occurring throughout a range of natural ecosystems using decadal Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM +) time series data. Time series data stacks were generated for four study areas: (1) a four scene area dominated by forest and rangeland ecosystems in the southwestern United States, (2) a sagebrush-dominated rangeland in Wyoming, (3) woodland adjacent to prairie in northwestern Nebraska, and (4) a forested area in the White Mountains of New Hampshire. Through analyses of time series data, we found evidence of gradual systematic change in many of the natural vegetation communities in all four areas. Many of the conifer forests in the southwestern US are showing declines related to insects and drought, but very few are showing evidence of improving conditions or increased greenness. Sagebrush communities are showing decreases in greenness related to fire, mining, and probably drought, but very few of these communities are showing evidence of increased greenness or improving conditions. In Nebraska, forest communities are showing local expansion and increased canopy densification in the prairie–woodland interface, and in the White Mountains high elevation understory conifers are showing range increases towards lower elevations. The trends detected are not obvious through casual inspection of the Landsat images. Analyses of time series data using many scenes and covering multiple years are required in order to develop better impressions and representations of the changing ecosystem patterns and trends that are occurring. The approach described in this paper demonstrates that Landsat time series data can be used operationally for assessing gradual ecosystem change across large areas. Local knowledge and available ancillary data are required in order to fully understand the nature of these trends.

Remotely-sensed detection of effects of extreme droughts on gross primary production

PubMed Central

Vicca, Sara; Balzarolo, Manuela; Filella, Iolanda; Granier, André; Herbst, Mathias; Knohl, Alexander; Longdoz, Bernard; Mund, Martina; Nagy, Zoltan; Pintér, Krisztina; Rambal, Serge; Verbesselt, Jan; Verger, Aleixandre; Zeileis, Achim; Zhang, Chao; Peñuelas, Josep

2016-01-01

Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space. PMID:27301671

The sensitivity of US wildfire occurrence to pre-season soil moisture conditions across ecosystems.

PubMed

Jensen, Daniel; Reager, John T; Zajic, Brittany; Rousseau, Nick; Rodell, Matthew; Hinkley, Everett

2018-01-01

It is generally accepted that year-to-year variability in moisture conditions and drought are linked with increased wildfire occurrence. However, quantifying the sensitivity of wildfire to surface moisture state at seasonal lead-times has been challenging due to the absence of a long soil moisture record with the appropriate coverage and spatial resolution for continental-scale analysis. Here we apply model simulations of surface soil moisture that numerically assimilate observations from NASA's Gravity Recovery and Climate Experiment (GRACE) mission with the US Forest Service's historical Fire-Occurrence Database over the contiguous United States. We quantify the relationships between pre-fire-season soil moisture and subsequent-year wildfire occurrence by land-cover type and produce annual probable wildfire occurrence and burned area maps at 0.25-degree resolution. Cross-validated results generally indicate a higher occurrence of smaller fires when months preceding fire season are wet, while larger fires are more frequent when soils are dry. This result is consistent with the concept of increased fuel accumulation under wet conditions in the pre-season. These results demonstrate the fundamental strength of the relationship between soil moisture and fire activity at long lead-times and are indicative of that relationship's utility for the future development of national-scale predictive capability.

The sensitivity of US wildfire occurrence to pre-season soil moisture conditions across ecosystems

NASA Astrophysics Data System (ADS)

Jensen, Daniel; Reager, John T.; Zajic, Brittany; Rousseau, Nick; Rodell, Matthew; Hinkley, Everett

2018-01-01

It is generally accepted that year-to-year variability in moisture conditions and drought are linked with increased wildfire occurrence. However, quantifying the sensitivity of wildfire to surface moisture state at seasonal lead-times has been challenging due to the absence of a long soil moisture record with the appropriate coverage and spatial resolution for continental-scale analysis. Here we apply model simulations of surface soil moisture that numerically assimilate observations from NASA’s Gravity Recovery and Climate Experiment (GRACE) mission with the USDA Forest Service’s historical Fire-Occurrence Database over the contiguous United States. We quantify the relationships between pre-fire-season soil moisture and subsequent-year wildfire occurrence by land-cover type and produce annual probable wildfire occurrence and burned area maps at 0.25 degree resolution. Cross-validated results generally indicate a higher occurrence of smaller fires when months preceding fire season are wet, while larger fires are more frequent when soils are dry. This is consistent with the concept of increased fuel accumulation under wet conditions in the pre-season. These results demonstrate the fundamental strength of the relationship between soil moisture and fire activity at long lead-times and are indicative of that relationship’s utility for the future development of national-scale predictive capability.

Widespread crown condition decline, food web disruption, and amplified tree mortality with increased climate change-type drought

PubMed Central

Carnicer, Jofre; Coll, Marta; Ninyerola, Miquel; Pons, Xavier; Sánchez, Gerardo; Peñuelas, Josep

2011-01-01

Climate change is progressively increasing severe drought events in the Northern Hemisphere, causing regional tree die-off events and contributing to the global reduction of the carbon sink efficiency of forests. There is a critical lack of integrated community-wide assessments of drought-induced responses in forests at the macroecological scale, including defoliation, mortality, and food web responses. Here we report a generalized increase in crown defoliation in southern European forests occurring during 1987–2007. Forest tree species have consistently and significantly altered their crown leaf structures, with increased percentages of defoliation in the drier parts of their distributions in response to increased water deficit. We assessed the demographic responses of trees associated with increased defoliation in southern European forests, specifically in the Iberian Peninsula region. We found that defoliation trends are paralleled by significant increases in tree mortality rates in drier areas that are related to tree density and temperature effects. Furthermore, we show that severe drought impacts are associated with sudden changes in insect and fungal defoliation dynamics, creating long-term disruptive effects of drought on food webs. Our results reveal a complex geographical mosaic of species-specific responses to climate change–driven drought pressures on the Iberian Peninsula, with an overwhelmingly predominant trend toward increased drought damage. PMID:21220333

Widespread crown condition decline, food web disruption, and amplified tree mortality with increased climate change-type drought.

PubMed

Carnicer, Jofre; Coll, Marta; Ninyerola, Miquel; Pons, Xavier; Sánchez, Gerardo; Peñuelas, Josep

2011-01-25

Climate change is progressively increasing severe drought events in the Northern Hemisphere, causing regional tree die-off events and contributing to the global reduction of the carbon sink efficiency of forests. There is a critical lack of integrated community-wide assessments of drought-induced responses in forests at the macroecological scale, including defoliation, mortality, and food web responses. Here we report a generalized increase in crown defoliation in southern European forests occurring during 1987-2007. Forest tree species have consistently and significantly altered their crown leaf structures, with increased percentages of defoliation in the drier parts of their distributions in response to increased water deficit. We assessed the demographic responses of trees associated with increased defoliation in southern European forests, specifically in the Iberian Peninsula region. We found that defoliation trends are paralleled by significant increases in tree mortality rates in drier areas that are related to tree density and temperature effects. Furthermore, we show that severe drought impacts are associated with sudden changes in insect and fungal defoliation dynamics, creating long-term disruptive effects of drought on food webs. Our results reveal a complex geographical mosaic of species-specific responses to climate change-driven drought pressures on the Iberian Peninsula, with an overwhelmingly predominant trend toward increased drought damage.

Forest-fire models

Treesearch

Haiganoush Preisler; Alan Ager

2013-01-01

For applied mathematicians forest fire models refer mainly to a non-linear dynamic system often used to simulate spread of fire. For forest managers forest fire models may pertain to any of the three phases of fire management: prefire planning (fire risk models), fire suppression (fire behavior models), and postfire evaluation (fire effects and economic models). In...

Spatial and temporal trends of drought effects in a heterogeneous semi-arid forest ecosystem

USGS Publications Warehouse

Assal, Timothy J.; Anderson, Patrick J.; Sibold, Jason

2016-01-01

Drought has long been recognized as a driving mechanism in the forests of western North America and drought-induced mortality has been documented across genera in recent years. Given the frequency of these events are expected to increase in the future, understanding patterns of mortality and plant response to severe drought is important to resource managers. Drought can affect the functional, physiological, structural, and demographic properties of forest ecosystems. Remote sensing studies have documented changes in forest properties due to direct and indirect effects of drought; however, few studies have addressed this at local scales needed to characterize highly heterogeneous ecosystems in the forest-shrubland ecotone. We analyzed a 22-year Landsat time series (1985–2012) to determine changes in forest in an area that experienced a relatively dry decade punctuated by two years of extreme drought. We assessed the relationship between several vegetation indices and field measured characteristics (e.g. plant area index and canopy gap fraction) and applied these indices to trend analysis to uncover the location, direction and timing of change. Finally, we assessed the interaction of climate and topography by forest functional type. The Normalized Difference Moisture Index (NDMI), a measure of canopy water content, had the strongest correlation with short-term field measures of plant area index (R2 = 0.64) and canopy gap fraction (R2 = 0.65). Over the entire time period, 25% of the forested area experienced a significant (p-value < 0.05) negative trend in NDMI, compared to less than 10% in a positive trend. Coniferous forests were more likely to be associated with a negative NDMI trend than deciduous forest. Forests on southern aspects were least likely to exhibit a negative trend while north aspects were most prevalent. Field plots with a negative trend had a lower live density, and higher amounts of standing dead and down trees compared to plots with no trend. Our analysis identifies spatially explicit patterns of long-term trends anchored with ground based evidence to highlight areas of forest that are resistant, persistent or vulnerable to severe drought. The results provide a long-term perspective for the resource management of this area and can be applied to similar ecosystems throughout western North America.

Mean annual precipitation predicts primary production resistance and resilience to extreme drought

DOE PAGES

Stuart-Haëntjens, Ellen; De Boeck, Hans J.; Lemoine, Nathan P.; ...

2018-09-01

Extreme drought is increasing in frequency and intensity in many regions globally, with uncertain consequences for the resistance and resilience of ecosystem functions, including primary production. Primary production resistance, the capacity to withstand change during extreme drought, and resilience, the degree to which production recovers, vary among and within ecosystem types, obscuring generalized patterns of ecological stability. Theory and many observations suggest forest production is more resistant but less resilient than grassland production to extreme drought; however, studies of production sensitivity to precipitation variability indicate that the processes controlling resistance and resilience may be influenced more by mean annual precipitationmore » (MAP) than ecosystem type. Here, we conducted a global meta-analysis to investigate primary production resistance and resilience to extreme drought in 64 forests and grasslands across a broad MAP gradient. We found resistance to extreme drought was predicted by MAP; however, grasslands (positive) and forests (negative) exhibited opposing resilience relationships with MAP. Our findings indicate that common plant physiological mechanisms may determine grassland and forest resistance to extreme drought, whereas differences among plant residents in turnover time, plant architecture, and drought adaptive strategies likely underlie divergent resilience patterns. The low resistance and resilience of dry grasslands suggests that these ecosystems are the most vulnerable to extreme drought – a vulnerability that is expected to compound as extreme drought frequency increases in the future.« less

Mean annual precipitation predicts primary production resistance and resilience to extreme drought.

PubMed

Stuart-Haëntjens, Ellen; De Boeck, Hans J; Lemoine, Nathan P; Mänd, Pille; Kröel-Dulay, György; Schmidt, Inger K; Jentsch, Anke; Stampfli, Andreas; Anderegg, William R L; Bahn, Michael; Kreyling, Juergen; Wohlgemuth, Thomas; Lloret, Francisco; Classen, Aimée T; Gough, Christopher M; Smith, Melinda D

2018-04-27

Extreme drought is increasing in frequency and intensity in many regions globally, with uncertain consequences for the resistance and resilience of ecosystem functions, including primary production. Primary production resistance, the capacity to withstand change during extreme drought, and resilience, the degree to which production recovers, vary among and within ecosystem types, obscuring generalized patterns of ecological stability. Theory and many observations suggest forest production is more resistant but less resilient than grassland production to extreme drought; however, studies of production sensitivity to precipitation variability indicate that the processes controlling resistance and resilience may be influenced more by mean annual precipitation (MAP) than ecosystem type. Here, we conducted a global meta-analysis to investigate primary production resistance and resilience to extreme drought in 64 forests and grasslands across a broad MAP gradient. We found resistance to extreme drought was predicted by MAP; however, grasslands (positive) and forests (negative) exhibited opposing resilience relationships with MAP. Our findings indicate that common plant physiological mechanisms may determine grassland and forest resistance to extreme drought, whereas differences among plant residents in turnover time, plant architecture, and drought adaptive strategies likely underlie divergent resilience patterns. The low resistance and resilience of dry grasslands suggests that these ecosystems are the most vulnerable to extreme drought - a vulnerability that is expected to compound as extreme drought frequency increases in the future. Copyright © 2018. Published by Elsevier B.V.

Mean annual precipitation predicts primary production resistance and resilience to extreme drought

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stuart-Haëntjens, Ellen; De Boeck, Hans J.; Lemoine, Nathan P.

Extreme drought is increasing in frequency and intensity in many regions globally, with uncertain consequences for the resistance and resilience of ecosystem functions, including primary production. Primary production resistance, the capacity to withstand change during extreme drought, and resilience, the degree to which production recovers, vary among and within ecosystem types, obscuring generalized patterns of ecological stability. Theory and many observations suggest forest production is more resistant but less resilient than grassland production to extreme drought; however, studies of production sensitivity to precipitation variability indicate that the processes controlling resistance and resilience may be influenced more by mean annual precipitationmore » (MAP) than ecosystem type. Here, we conducted a global meta-analysis to investigate primary production resistance and resilience to extreme drought in 64 forests and grasslands across a broad MAP gradient. We found resistance to extreme drought was predicted by MAP; however, grasslands (positive) and forests (negative) exhibited opposing resilience relationships with MAP. Our findings indicate that common plant physiological mechanisms may determine grassland and forest resistance to extreme drought, whereas differences among plant residents in turnover time, plant architecture, and drought adaptive strategies likely underlie divergent resilience patterns. The low resistance and resilience of dry grasslands suggests that these ecosystems are the most vulnerable to extreme drought – a vulnerability that is expected to compound as extreme drought frequency increases in the future.« less

Assessing the vegetation condition impacts of the 2011 drought across the U.S. southern Great Plains using the vegetation drought response index (VegDRI)

USGS Publications Warehouse

Tadesse, Tsegaye; Wardlow, Brian D.; Brown, Jesslyn F.; Svoboda, Mark; Hayes, Michael; Fuchs, Brian; Gutzmer, Denise

2015-01-01

The vegetation drought response index (VegDRI), which combines traditional climate- and satellite-based approaches for assessing vegetation conditions, offers new insights into assessing the impacts of drought from local to regional scales. In 2011, the U.S. southern Great Plains, which includes Texas, Oklahoma, and New Mexico, was plagued by moderate to extreme drought that was intensified by an extended period of record-breaking heat. The 2011 drought presented an ideal case study to evaluate the performance of VegDRI in characterizing developing drought conditions. Assessment of the spatiotemporal drought patterns represented in the VegDRI maps showed that the severity and patterns of the drought across the region corresponded well to the record warm temperatures and much-below-normal precipitation reported by the National Climatic Data Center and the sectoral drought impacts documented by the Drought Impact Reporter (DIR). VegDRI values and maps also showed the evolution of the drought signal before the Las Conchas Fire (the largest fire in New Mexico’s history). Reports in the DIR indicated that the 2011 drought had major adverse impacts on most rangeland and pastures in Texas and Oklahoma, resulting in total direct losses of more than $12 billion associated with crop, livestock, and timber production. These severe impacts on vegetation were depicted by the VegDRI at subcounty, state, and regional levels. This study indicates that the VegDRI maps can be used with traditional drought indicators and other in situ measures to help producers and government officials with various management decisions, such as justifying disaster assistance, assessing fire risk, and identifying locations to move livestock for grazing.

Permafrost as an additional driving factor for the extreme fire event in the boreal Baikal region in 2003

NASA Astrophysics Data System (ADS)

Forkel, M.; Thonicke, K.; Beer, C.; Cramer, W.; Bartalev, S.; Schmullius, C.

2012-04-01

Wildfires are a natural and important element in the functioning of boreal forests. However, in some years, fires with extreme spread and severity occur. Such severe fires degrade the forest, affect human values, emit huge amount of carbon and aerosols and alter the land surface albedo. Usually, wind, slope, and dry conditions have been recognized as factors determining fire spread. In the Baikal region, 127,000 km2 burned in 2003, while the annual average burned area is approx. 8100 km2. In average years, 16% of the burned area occurred in the continuous permafrost zone but in 2003, 33% of these burned areas coincide with the existence of permanently frozen grounds. Permafrost and the associated upper active layer, which thaws during summer and refreezes during winter, is an important supply for soil moisture in boreal ecosystems. This leads to the question if permafrost hydrology is a potential additional driving factor for extreme fire events in boreal forests. Using temperature and precipitation data, we calculated the Nesterov index as indicator for fire weather conditions. Further, we used satellite observations of burned area and surface moisture, a digital elevation model, a land cover and a permafrost map to evaluate drivers for the temporal dynamic and spatial variability of surface moisture conditions and burned area in spring 2003. On the basis of time series decomposition, we separated the effect of drivers for fire activity on different time scales. We next computed cross-correlations to identify potential time lags between weather conditions, surface moisture and fire activity. Finally, we assessed the predictive capability of different combinations of driving variables for surface moisture conditions and burned area using multivariate spatial-temporal regression models. The results from this study demonstrate that permafrost in larch-dominated ecosystems regulates the inter-annual variability of surface moisture and thus increases the inter-annual variability of burned area. The drought conditions in spring 2003 were accelerated by the presence of permafrost because less water was stored in the upper active layer from the dry previous summer 2002 and the permafrost table prevents vegetative water uptake from deeper layers. In contrast, weather conditions (precipitation anomaly, Nesterov index) are weaker predictors for the 2003 fire event. Our analysis advances the understanding of complex interactions between the atmosphere, vegetation and soil on how feedback mechanisms can lead to extreme fire events. These findings emphasize the importance of a mechanistic coupling of soil thermodynamics, hydrology, and fire activity in earth system models for projecting climate change impacts over the next century.

Impact of drought on wildfires in Iberia

NASA Astrophysics Data System (ADS)

Russo, Ana; Gouveia, Célia M.; DaCamara, Carlos; Sousa, Pedro; Trigo, Ricardo M.

2015-04-01

Southern European countries, and the Iberian Peninsula (IP) in particular, have been vastly affected by summer wildfires (Trigo et al., 2013). This condition is hampered by the frequent warm and dry meteorological conditions found in summer which play a significant role in the triggering and spreading of wildfires. These meteorological conditions are also particularly important for the onset and end of drought periods, a phenomenon that has recurrently affected the IP (Gouveia et al., 2012). Moreover, the IP corresponds to one of the most sensitive areas to current and future climate change, and recent and future trends towards a dryer and warmer Mediterranean climate (Sousa et al., 2014) will tend to exacerbate these problems. The main scope of this study was to investigate the impact of drought on wildfires' burned areas in the IP. The objective was to examine the correlation between drought, as expressed by both the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) (Vicente-Serrano et al., 2010), and wildfire burned areas. The SPI and SPEI were both calculated for 4 large regions (Northwestern, Northern, Southwestern and Eastern) whose spatial patterns and seasonal fire regimes were shown to be related with constraining factors such as topography, vegetation cover and climate conditions (Trigo et al., 2013). In this study, the drought indices were determined for the time scales of 3 and 6 months for August and for 12 months in September, thus representing the summer and annual drought. The correlation between drought and burned areas during July and August was particularly significant for the 3 months SPEI and SPI relatively to the 6 and 12 time scales, which indicates that drought and fires relation is a small-size scale process. Moreover, the correlation between drought and burned areas during July and August was particularly significant for the Northern and Southwestern regions both for SPEI for 3 and 6 months in August. In the Eastern and Northwestern regions the correlation was most significant for the SPI for 3 and 6 months. Thus, the relation between wildfires and drought is better explained in the Northern and Southwestern regions by the temperature influence and on the Northwestern and Eastern by the precipitation influence. Gouveia C.M., Bastos A., Trigo R.M., DaCamara C.C. (2012) "Drought impacts on vegetation in the pre and post-fire events over Iberian Peninsula". Natural Hazards and Earth System Sciences, 12, 3123-3137, 2012. Vicente-Serrano S.M., Santiago Beguería, Juan I. López-Moreno (2010) "A Multi-scalar drought index sensitive to global warming: The Standardized Precipitation Evapotranspiration Index - SPEI". Journal of Climate 23: 1696-1718. Trigo R.M., Sousa P., Pereira M., Rasilla D., Gouveia C.M. (2013) "Modelling wildfire activity in Iberia with different Atmospheric Circulation Weather Types". International Journal of Climatology, DOI: 10.1002/joc.3749 Sousa PM, Trigo RM, Pereira MG, Bedia J, Gutiérrez JM, 2014. Different approaches to model future burnt area in the Iberian Peninsula. Agricultural and Forest Meteorology 202, 11-25. doi:10.1016/j.agrformet.2014.11.018 Acknowledgements: This work was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project QSECA (PTDC/AAGGLO/4155/2012).