Lettuce dieback

USDA-ARS?s Scientific Manuscript database

Two related viruses, Tomato bushy stunt virus (TBSV) and Moroccan pepper virus (MPV) cause a disease known as lettuce dieback in California and Arizona. Lettuce dieback is characterized by yellowing, necrosis, stunting and death of lettuce plants, and often occurs in low lying areas with poor drain...

Research promises earlier warning for grapevine canker diseases

USDA-ARS?s Scientific Manuscript database

When it comes to detecting and treating vineyards for grapevine canker diseases (also called trunk diseases), like Botryosphaeria dieback (Bot canker), Esca, Eutypa dieback and Phomopsis dieback, the earlier the better, says plant pathologist Kendra Baumgartner, with the USDA’s Agricultural Research...

Double pruning to prevent trunk diseases in Washington vineyards

USDA-ARS?s Scientific Manuscript database

Trunk diseases (aka wood-canker diseases) present a serious challenge to vineyard productivity and longevity. There are four main trunk diseases: Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback. The causal fungi (e.g., Eutypa lata, Neofusicoccum parvum) establish chronic infectio...

Comparing cold-stored and freshly lifted water oak (Quercus nigra) seedlings based on physiological parameters

Treesearch

Rosa C. Goodman; Kent G. Apostol; Douglass F. Jacobs; Barrett C. Wilson; Emile S. Gardiner

2007-01-01

Water oak is often used in afforestation projects in the Lower Mississippi Alluvial Valley, but its field performance is often poor due to low survival rates and severe top dieback immediately after planting. The poor physiological quality of planting stock may be a contributing factor to this transplanting problem. In this study, cold storage was investigated to...

Development of Nested PCR, Multiplex PCR, and Loop-Mediated Isothermal Amplification Assays for Rapid Detection of Cylindrocladium scoparium on Eucalyptus.

PubMed

Qiao, Tian-Min; Zhang, Jing; Li, Shu-Jiang; Han, Shan; Zhu, Tian-Hui

2016-10-01

Eucalyptus dieback disease, caused by Cylindrocladium scoparium , has occurred in last few years in large Eucalyptus planting areas in China and other countries. Rapid, simple, and reliable diagnostic techniques are desired for the early detection of Eucalyptus dieback of C. scoparium prior to formulation of efficient control plan. For this purpose, three PCR-based methods of nested PCR, multiplex PCR, loop-mediated isothermal amplification (LAMP) were developed for detection of C. scoparium based on factor 1-alpha (tef1) and beta-tubulin gene in this study. All of the three methods showed highly specific to C. scoparium . The sensitivities of the nested PCR and LAMP were much higher than the multiplex PCR. The sensitivity of multiplex PCR was also higher than regular PCR. C. scoparium could be detected within 60 min from infected Eucalyptus plants by LAMP, while at least 2 h was needed by the rest two methods. Using different Eucalyptus tissues as samples for C. scoparium detection, all of the three PCR-based methods showed much better detection results than regular PCR. Base on the results from this study, we concluded that any of the three PCR-based methods could be used as diagnostic technology for the development of efficient strategies of Eucalyptus dieback disease control. Particularly, LAMP was the most practical method in field application because of its one-step and rapid reaction, simple operation, single-tube utilization, and simple visualization of amplification products.

Development of Nested PCR, Multiplex PCR, and Loop-Mediated Isothermal Amplification Assays for Rapid Detection of Cylindrocladium scoparium on Eucalyptus

PubMed Central

Qiao, Tian-Min; Zhang, Jing; Li, Shu-Jiang; Han, Shan; Zhu, Tian-Hui

2016-01-01

Eucalyptus dieback disease, caused by Cylindrocladium scoparium, has occurred in last few years in large Eucalyptus planting areas in China and other countries. Rapid, simple, and reliable diagnostic techniques are desired for the early detection of Eucalyptus dieback of C. scoparium prior to formulation of efficient control plan. For this purpose, three PCR-based methods of nested PCR, multiplex PCR, loop-mediated isothermal amplification (LAMP) were developed for detection of C. scoparium based on factor 1-alpha (tef1) and beta-tubulin gene in this study. All of the three methods showed highly specific to C. scoparium. The sensitivities of the nested PCR and LAMP were much higher than the multiplex PCR. The sensitivity of multiplex PCR was also higher than regular PCR. C. scoparium could be detected within 60 min from infected Eucalyptus plants by LAMP, while at least 2 h was needed by the rest two methods. Using different Eucalyptus tissues as samples for C. scoparium detection, all of the three PCR-based methods showed much better detection results than regular PCR. Base on the results from this study, we concluded that any of the three PCR-based methods could be used as diagnostic technology for the development of efficient strategies of Eucalyptus dieback disease control. Particularly, LAMP was the most practical method in field application because of its one-step and rapid reaction, simple operation, single-tube utilization, and simple visualization of amplification products. PMID:27721691

Searching for early-warning signals of impending dieback and death in Mediterranean oaks

NASA Astrophysics Data System (ADS)

Colangelo, Michele; Ripullone, Francesco; Julio Camarero, Jesus; De Micco, Veronica; Gazol, Antonio; Gentilesca, Tiziana; Borghetti, Marco

2017-04-01

In recent decades, forest dieback episodes have been recorded worldwide affecting different tree species. In particular, several cases of widespread dieback and increased mortality rates have been described for Mediterranean oak (Quercus spp.) species. These dieback cases are revealing the high vulnerability of Mediterranean oaks, manifested as a loss in tree vigour (leaf shedding, canopy and shoot dieback), growth decline and sometimes tree death, as a consequence of temperatures rising at unprecedented rates and drying trends. However, in the wake of the so-called 'oak decline phenomenon', the attention on these species has generally been limited, perhaps because they are often regarded as well-adapted to the dry conditions typical of Mediterranean areas. Indeed, according to recent studies, the reduced size, the ability to sprout and the anisohydric behavior of Mediterranean oak species (reduced control of water loss and high stomatal conductance rates) would make them better adapted to withstand heat and drought stress then taller and non-sprouting isohydric species (e.g. conifer, with strict control of water loss by closing stomata). Here, we investigated the vulnerability of Mediterranean oaks by comparing neighboring living and recently dead trees in species with low (Q. pubescens), intermediate (Q. cerris, Q. frainetto) and high (Q. robur) sensitivity to water shortage. We analysed changes in tree vigour using tree-ring width and functional wood anatomical traits as proxies to search for early-warning signals of dieback, in connection with the main proposed dieback mechanisms (hydraulic failure and/or carbon starvation). We also modeled the probability of tree death as a function of tree size (diameter, height) by quantifying recent changes in growth and wood anatomy along tree-ring series. Contrary to the general concept that trees tend to experience increasing cavitation risk with increasing height, our studies show that smaller oaks are more prone to die than taller conspecifics. Further, irrespective of differences in drought sensitivity, dead trees showed lower radial-growth rates than surviving trees from 10 to 20 years prior to tree death. Contrastingly, differences in wood anatomical traits (vessel lumen size, vessel density) between dead and living trees were not always significant, being species-dependent. Our findings indicate that: (i) tree height is a proxy of the probability of drought-induced death, and (ii) recent growth trends constitute valuable early-warning signals of impending dieback and death in Mediterranean oak species.

Assessment of Acacia koa forest health across environmental gradients in Hawai'i using fine resolution remote sensing and GIS.

PubMed

Morales, Rodolfo Martinez; Idol, Travis; Friday, James B

2011-01-01

Koa (Acacia koa) forests are found across broad environmental gradients in the Hawai'ian Islands. Previous studies have identified koa forest health problems and dieback at the plot level, but landscape level patterns remain unstudied. The availability of high-resolution satellite images from the new GeoEye1 satellite offers the opportunity to conduct landscape-level assessments of forest health. The goal of this study was to develop integrated remote sensing and geographic information systems (GIS) methodologies to characterize the health of koa forests and model the spatial distribution and variability of koa forest dieback patterns across an elevation range of 600-1,000 m asl in the island of Kaua'i, which correspond to gradients of temperature and rainfall ranging from 17-20 °C mean annual temperature and 750-1,500 mm mean annual precipitation. GeoEye1 satellite imagery of koa stands was analyzed using supervised classification techniques based on the analysis of 0.5-m pixel multispectral bands. There was clear differentiation of native koa forest from areas dominated by introduced tree species and differentiation of healthy koa stands from those exhibiting dieback symptoms. The area ratio of healthy koa to koa dieback corresponded linearly to changes in temperature across the environmental gradient, with koa dieback at higher relative abundance in warmer areas. A landscape-scale map of healthy koa forest and dieback distribution demonstrated both the general trend with elevation and the small-scale heterogeneity that exists within particular elevations. The application of these classification techniques with fine spatial resolution imagery can improve the accuracy of koa forest inventory and mapping across the islands of Hawai'i. Such findings should also improve ecological restoration, conservation and silviculture of this important native tree species.

An economic case for early adoption of preventative practices for management of grapevine trunk diseases

USDA-ARS?s Scientific Manuscript database

The trunk diseases Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback, significantly decrease yields and vineyard longevity in California. Despite high disease prevalence and substantial yield impacts, most growers routinely wait to adopt preventative practices until vineyards are ...

Six-Year Effects of Two Late Spring Frosts on Appalachian Hardwoods

Treesearch

Everette D. Rast; Robert L. Brisbin; Robert L. Brisbin

1987-01-01

Severe late spring frosts can kill new shoots and leaves on commercial tree species at higher elevations. A previous short-term study has shown that the resulting defoliation and dieback does not seriously affect the radial growth or mortality of most species except American beech. In this study we found that defoliation, dieback, and radial growth increment were...

Characterizing the marsh dieback spectral response at the plant and canopy level with hyperspectral and temporal remote sensing data

USGS Publications Warehouse

Ramsey, E.; Rangoonwala, A.

2008-01-01

We describe newly developed remote sensing tools to map the localized occurrences and regional distribution of the marsh dieback in coastal Louisiana (Fig. 1). As a final goal of our research and development, we identified what spectral features accompanied the onset of dieback and could be directly linked to the optical signal measured at the satellite. In order to accomplish our research goal, we carried out two interlinked objectives. First, we determined the spectral features within the hyperspectral spectra of the impacted plant that could be linked to the spectral return. This was accomplished by measuring the differences in leaf optical properties of impacted and non impacted marsh plants in such a way that the measured differences could be linked to the dieback onset and progression. The spectral analyses were constrained to selected wavelengths (bands of reflectance data) historically associated with changes in leaf composition and structure caused by changes in the plant biophysical environment. Second, we determined what changes in the canopy reflectance (canopy signal sensed at the satellite) could be linked to dieback onset and progression. Third, we transformed a suite of six Landsat Thematic Mapper images collected before, during, and in the final stages of dieback to maps of dieback occurrences. ??2008 IEEE.

Phenolic Glycosides in Populus tremuloides and their Effects on Long-Term Ungulate Browsing.

PubMed

Lastra, R A; Kenkel, N C; Daayf, F

2017-10-01

In the aspen-grassland ecotone of Riding Mountain, Manitoba, lightly browsed vigorous clones of trembling aspen (Populus tremuloides Michx.) occur in close proximity to heavily browsed dieback clones. This study examines whether intraspecific variation in the production of phenolic glycosides is correlated with this strong dichotomy in clonal vigor. Individual clones were sampled over four years at three sites located along a gradient of increasing soil moisture stress. At each site, eight aspen clones of similar size and age were sampled: four vigorous and four dieback clones (total of 24 individual clones). The severity of wapiti (elk) browsing was assessed as the ratio of browse-damaged to total branches per aspen ramet. Statistically significant differences in foliar concentrations of the phenolic glycosides salicortin and tremulacin were observed between vigorous and dieback clones: a mean of 14.8% dry mass for lightly browsed (vigorous) clones, versus just 7.0% for heavily browsed (dieback) clones. Mean concentrations of foliar phenolics were also significantly greater in more moisture-stressed sites. These results demonstrate that the strong dichotomy in clonal vigor (vigorous versus dieback clones) is associated with large differences in phenolic glycoside production. Vigorous clone ramets produce high amounts of phenolic glycosides and have low levels of herbivore browsing and low mortality rates, whereas dieback clone ramets have low amounts of phenolic glycosides and much higher herbivore browsing and mortality rates. This suggests that intraspecific variation in phenolic glycosides in trembling aspen is an important predisposing factor leading to ramet mortality, and by extension to the decline of aspen clones.

Making the economic case for early adoption of practices to prevent trunk diseases

USDA-ARS?s Scientific Manuscript database

All California vineyards become infected at some point by one or more of the following trunk diseases: Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback. The symptoms do not become obvious until the vineyard is approximately 6-8 years old. Trunk diseases limit the productive life o...

Identifying economic hurdles of early adoption of preventative practices: The case of trunk diseases in California winegrape vineyards

USDA-ARS?s Scientific Manuscript database

Trunk diseases including Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback, present a serious challenge to grape growers around the world. In California, where approximately 90% of US winegrape production occurs, most vineyards over age 10 are likely infected and yield losses in su...

The role of pest control advisors in managing grapevine trunk diseases: a survey of perceptions of practice efficacy and trends in recommendations

USDA-ARS?s Scientific Manuscript database

Trunk diseases (Botryosphaeria dieback, Esca, Eutypa dieback, Phomopsis dieback) significantly limit vineyard productivity. The causal fungi establish chronic wood infections, which accumulate over time. Symptoms do not become obvious until the vineyard is 6-8 years old. Post-infection practices (vi...

Rebuilding after collapse: evidence for long-term cohort dynamics in the native Hawaiian rain forest

USGS Publications Warehouse

Boehmer, Hans Juergen; Wagner, Helene H.; Jacobi, James D.; Gerrish, Grant C.; Mueller-Dombois, Dieter

2013-01-01

Questions: Do long-term observations in permanent plots confirm the conceptual model of Metrosideros polymorpha cohort dynamics as postulated in 1987? Do regeneration patterns occur independently of substrate age, i.e. of direct volcanic disturbance impact? Location: The windward mountain slopes of the younger Mauna Loa and the older Mauna Kea volcanoes (island of Hawaii, USA). Methods: After widespread forest decline (dieback), permanent plots were established in 1976 in 13 dieback and 13 non-dieback patches to monitor the population structure of M. polymorpha at ca. 5-yr intervals. Within each plot of 20 × 20 m, all trees with DBH >2.5 cm were individually tagged, measured and tree vigour assessed; regeneration was quantified in 16 systematically placed subplots of 3 × 5 m. Data collected in the subplots included the total number of M. polymorpha seedlings and saplings (five stem height classes). Here we analyse monitoring data from six time steps from 1976 to 2003 using repeated measures ANOVA to test specific predictions derived from the 1987 conceptual model. Results: Regeneration was significantly different between dieback and non-dieback plots. In dieback plots, the collapse in the 1970s was followed by a ‘sapling wave’ that by 2003 led to new cohort stands of M. polymorpha. In non-dieback stands, seedling emergence did not result in sapling waves over the same period. Instead, a ‘sapling gap’ (i.e. very few or no M. polymorpha saplings) prevailed as typical for mature stands. Canopy dieback in 1976, degree of recovery by 2003 and the number of living trees in 2003 were unrelated to substrate age. Conclusions: Population development of M. polymorpha supports the cohort dynamics model, which predicts rebuilding of the forest with the same canopy species after dieback. The lack of association with substrate age suggests that the long-term maintenance of cohort structure in M. polymorpha does not depend on volcanic disturbance but may be related to other environmental mechanisms, such as climate anomalies.

Relationship between crown dieback and drought in the southeastern United States

Treesearch

Michael K. Crosby; Zhaofei Fan; Martin A. Spetich; Theodor D. Leininger; Xingang Fan

2012-01-01

Forest Health and Monitoring (FHM) and Palmer's Drought Severity Index (PDSI) data were obtained for 11 states in the southeastern United States to assess the relationship between drought and crown dieback. Correlation analyses were performed at the species group and ecoregion levels within the study area. The results indicate a negative correlation between...

Ash leaf metabolomes reveal differences between trees tolerant and susceptible to ash dieback disease.

PubMed

Sambles, Christine M; Salmon, Deborah L; Florance, Hannah; Howard, Thomas P; Smirnoff, Nicholas; Nielsen, Lene R; McKinney, Lea V; Kjær, Erik D; Buggs, Richard J A; Studholme, David J; Grant, Murray

2017-12-19

European common ash, Fraxinus excelsior, is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus, we performed untargeted metabolomic profiling on leaves from five high-susceptibility and five low-susceptibility F. excelsior individuals identified during Danish field trials. We describe in this study, two datasets. The first is untargeted LC-MS metabolomics raw data from ash leaves with high-susceptibility and low-susceptibility to ADB in positive and negative mode. These data allow the application of peak picking, alignment, gap-filling and retention-time correlation analyses to be performed in alternative ways. The second, a processed dataset containing abundances of aligned features across all samples enables further mining of the data. Here we illustrate the utility of this dataset which has previously been used to identify putative iridoid glycosides, well known anti-herbivory terpenoid derivatives, and show differential abundance in tolerant and susceptible ash samples.

Ash leaf metabolomes reveal differences between trees tolerant and susceptible to ash dieback disease

PubMed Central

Sambles, Christine M.; Salmon, Deborah L.; Florance, Hannah; Howard, Thomas P.; Smirnoff, Nicholas; Nielsen, Lene R.; McKinney, Lea V.; Kjær, Erik D.; Buggs, Richard J. A.; Studholme, David J.; Grant, Murray

2017-01-01

European common ash, Fraxinus excelsior, is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus, we performed untargeted metabolomic profiling on leaves from five high-susceptibility and five low-susceptibility F. excelsior individuals identified during Danish field trials. We describe in this study, two datasets. The first is untargeted LC-MS metabolomics raw data from ash leaves with high-susceptibility and low-susceptibility to ADB in positive and negative mode. These data allow the application of peak picking, alignment, gap-filling and retention-time correlation analyses to be performed in alternative ways. The second, a processed dataset containing abundances of aligned features across all samples enables further mining of the data. Here we illustrate the utility of this dataset which has previously been used to identify putative iridoid glycosides, well known anti-herbivory terpenoid derivatives, and show differential abundance in tolerant and susceptible ash samples. PMID:29257137

Fraxinus nigra (black ash) dieback in Minnesota: Regional variation and potential contributing factors

Treesearch

Brian J. Palik; Michael E. Ostry; Robert C. Venette; Ebrahim Abdela

2011-01-01

Extensive tree dieback is a recurrent issue in many regions. Crown dieback of Fraxinus nigra Marsh. (black ash; brown ash) in the northeastern and north central United States is an example. F. nigra is a widely distributed hardwood that is often the dominant species in wetland forests from Manitoba to Newfoundland and West...

Variation in woody plant mortality and dieback from severe drought among soils, plant groups, and species within a northern Arizona ecotone.

PubMed

Koepke, Dan F; Kolb, Thomas E; Adams, Henry D

2010-08-01

Vegetation change from drought-induced mortality can alter ecosystem community structure, biodiversity, and services. Although drought-induced mortality of woody plants has increased globally with recent warming, influences of soil type, tree and shrub groups, and species are poorly understood. Following the severe 2002 drought in northern Arizona, we surveyed woody plant mortality and canopy dieback of live trees and shrubs at the forest-woodland ecotone on soils derived from three soil parent materials (cinder, flow basalt, sedimentary) that differed in texture and rockiness. Our first of three major findings was that soil parent material had little effect on mortality of both trees and shrubs, yet canopy dieback of trees was influenced by parent material; dieback was highest on the cinder for pinyon pine (Pinus edulis) and one-seed juniper (Juniperus monosperma). Ponderosa pine (Pinus ponderosa) dieback was not sensitive to parent material. Second, shrubs had similar mortality, but greater canopy dieback, than trees. Third, pinyon and ponderosa pines had greater mortality than juniper, yet juniper had greater dieback, reflecting different hydraulic characteristics among these tree species. Our results show that impacts of severe drought on woody plants differed among tree species and tree and shrub groups, and such impacts were widespread over different soils in the southwestern U.S. Increasing frequency of severe drought with climate warming will likely cause similar mortality to trees and shrubs over major soil types at the forest-woodland ecotone in this region, but due to greater mortality of other tree species, tree cover will shift from a mixture of species to dominance by junipers and shrubs. Surviving junipers and shrubs will also likely have diminished leaf area due to canopy dieback.

Bacterial canker on kiwifruit in Italy: anatomical changes in the wood and in the primary infection sites.

PubMed

Renzi, Marsilio; Copini, Paul; Taddei, Anna R; Rossetti, Antonio; Gallipoli, Lorenzo; Mazzaglia, Angelo; Balestra, Giorgio M

2012-09-01

The bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae is a severe threat to kiwifruit production worldwide. Many aspects of P. syringae pv. actinidiae biology and epidemiology still require in-depth investigation. The infection by and spread of P. syringae pv. actinidiae in xylem and phloem was investigated by carrying out artificial inoculation experiments with histological and dendrochronological analyses of naturally diseased plants in Italy. We found that the bacterium can infect host plants by entering natural openings and lesions. In naturally infected kiwifruit plants, P. syringae pv. actinidiae is present in the lenticels as well as in the dead phloem tissue beneath the lenticels, surrounded by a lesion in the periderm which appears to indicate the importance of lenticels to kiwifruit infection. Biofilm formation was observed outside and inside plants. In cases of advanced stages of P. syringae pv. actinidiae infection, neuroses of the phloem occur, which are followed by cambial dieback and most likely by infection of the xylem. Anatomical changes in wood such as reduced ring width, a drastic reduction in vessel size, and the presence of tyloses were observed within several infected sites. In the field, these changes occur only a year after the first leaf symptoms are observed suggesting a significant time lapse between primary and secondary symptoms. It was possible to study the temporal development of P. syringae pv. actinidiae-induced cambial dieback by applying dendrochronology methods which revealed that cambial dieback occurs only during the growing season.

The causes of mangrove death on Yap, Palau, Pohnpei and Kosrae [Chapter II

Treesearch

Phil G. Cannon; Margie Falanruw; Francis Ruegorong; Rich MacKenzie; Katie Friday; Amy L. Ross-Davis; Sara M. Ashiglar; Ned B. Klopfenstein; Zhangfeng Liu; Mohammad Golabi; Chancy Thomas Iyekar

2014-01-01

The area of a massive mangrove dieback in Yinuf Mn Island, Yap, was selected as the first location to study mangrove dieback problems. Seawater and soil samples were collected from plots where the mangrove trees were dead/dying and these samples were analyzed for eight different seawater and soil floor properties. Seawater and soil properties from dead/dying/...

Assessment of Acacia Koa Forest Health across Environmental Gradients in Hawai‘i Using Fine Resolution Remote Sensing and GIS

PubMed Central

Morales, Rodolfo Martinez; Idol, Travis; Friday, James B.

2011-01-01

Koa (Acacia koa) forests are found across broad environmental gradients in the Hawai‘ian Islands. Previous studies have identified koa forest health problems and dieback at the plot level, but landscape level patterns remain unstudied. The availability of high-resolution satellite images from the new GeoEye1 satellite offers the opportunity to conduct landscape-level assessments of forest health. The goal of this study was to develop integrated remote sensing and geographic information systems (GIS) methodologies to characterize the health of koa forests and model the spatial distribution and variability of koa forest dieback patterns across an elevation range of 600–1,000 m asl in the island of Kaua‘i, which correspond to gradients of temperature and rainfall ranging from 17–20 °C mean annual temperature and 750–1,500 mm mean annual precipitation. GeoEye1 satellite imagery of koa stands was analyzed using supervised classification techniques based on the analysis of 0.5-m pixel multispectral bands. There was clear differentiation of native koa forest from areas dominated by introduced tree species and differentiation of healthy koa stands from those exhibiting dieback symptoms. The area ratio of healthy koa to koa dieback corresponded linearly to changes in temperature across the environmental gradient, with koa dieback at higher relative abundance in warmer areas. A landscape-scale map of healthy koa forest and dieback distribution demonstrated both the general trend with elevation and the small-scale heterogeneity that exists within particular elevations. The application of these classification techniques with fine spatial resolution imagery can improve the accuracy of koa forest inventory and mapping across the islands of Hawai‘i. Such findings should also improve ecological restoration, conservation and silviculture of this important native tree species. PMID:22163920

Dieback of Black Walnut Saplings (Pest Alert)

Treesearch

USDA Forest Service

1977-01-01

Top dieback of black walnut has been observed in 3-7 year old plantations in Illinois, Indiana, and North Carolina. In infected plantations, mortality has averaged 30% of the trees in one growing season. The most common symptom is basal sprouting of the affected trees. Other symptoms include wilted leaves, top dieback, and cankers on the main stem. Bark separation and...

Erwinia mallotivora sp., a New Pathogen of Papaya (Carica papaya) in Peninsular Malaysia

PubMed Central

Amin, Noriha Mat; Bunawan, Hamidun; Redzuan, Rohaiza Ahmad; Jaganath, Indu Bala S.

2011-01-01

Erwinia mallotivora was isolated from papaya infected with dieback disease showing the typical symptoms of greasy, water-soaked lesions and spots on leaves. Phylogenetic analysis of 16S rRNA gene sequences showed that the strain belonged to the genus Erwinia and was united in a monophyletic group with E. mallotivora DSM 4565 (AJ233414). Earlier studies had indicated that the causal agent for this disease was E. papayae. However, our current studies, through Koch’s postulate, have confirmed that papaya dieback disease is caused by E. mallotivora. To our knowledge, this is the first new discovery of E. mallotivora as a causal agent of papaya dieback disease in Peninsular Malaysia. Previous reports have suggested that E. mallotivora causes leaf spot in Mallotus japonicus. However, this research confirms it also to be pathogenic to Carica papaya. PMID:21339975

Erwinia mallotivora sp., a new pathogen of papaya (Carica papaya) in Peninsular Malaysia.

PubMed

Amin, Noriha Mat; Bunawan, Hamidun; Redzuan, Rohaiza Ahmad; Jaganath, Indu Bala S

2010-12-24

Erwinia mallotivora was isolated from papaya infected with dieback disease showing the typical symptoms of greasy, water-soaked lesions and spots on leaves. Phylogenetic analysis of 16S rRNA gene sequences showed that the strain belonged to the genus Erwinia and was united in a monophyletic group with E. mallotivora DSM 4565 (AJ233414). Earlier studies had indicated that the causal agent for this disease was E. papayae. However, our current studies, through Koch's postulate, have confirmed that papaya dieback disease is caused by E. mallotivora. To our knowledge, this is the first new discovery of E. mallotivora as a causal agent of papaya dieback disease in Peninsular Malaysia. Previous reports have suggested that E. mallotivora causes leaf spot in Mallotus japonicus. However, this research confirms it also to be pathogenic to Carica papaya.

Assessment of abiotic and biotic factors associated with eastern white pine ( Pinus strobus L.) dieback in the Southern Appalachian Mountains

Treesearch

Ashley N. Schulz; Angela M. Mech; Christopher Asaro; David R. Coyle; Michelle M. Cram; Rima D. Lucardi; Kamal J.K. Gandhi

2018-01-01

A novel and emerging eastern white pine (Pinus strobus L.) dieback phenomenon is occurring in the Southern Appalachian Mountains in the eastern United States. Symptomatic eastern white pine trees exhibit canopy thinning, branch dieback, and cankers on the branches and bole. These symptoms are often associated with the presence of a scale insect, Matsucoccus...

Evaluation of Sugar Maple Dieback in the Upper Great Lakes Region and Development of a Forest Health Youth Education Program

ERIC Educational Resources Information Center

Bal, Tara L.

2013-01-01

Sugar Maple, "Acer saccharum" Marsh., is one of the most valuable trees in the northern hardwood forests. Severe dieback was recently reported by area foresters in the western Upper Great Lakes Region. Sugar Maple has had a history of dieback over the last 100 years throughout its range and different variables have been identified as…

Sweetgum blight and dieback of associated hardwoods on the Beltsville Experimental Forest in Maryland

Treesearch

R. H. Fenton; J. D. Diller

1960-01-01

In 1948, a dieback of sweetgum (Liquidambar styraciflua L.) was first observed and reported at College Park, Md. Since then, surveys made from Maryland southward have shown that the dieback, now termed sweetgum blight, has increased in both distribution and severity and now occurs throughout much of the species range. No pathogenic organism has been found to be...

Mangrove dieback during fluctuating sea levels.

PubMed

Lovelock, Catherine E; Feller, Ilka C; Reef, Ruth; Hickey, Sharyn; Ball, Marilyn C

2017-05-10

Recent evidence indicates that climate change and intensification of the El Niño Southern Oscillation (ENSO) has increased variation in sea level. Although widespread impacts on intertidal ecosystems are anticipated to arise from the sea level seesaw associated with climate change, none have yet been demonstrated. Intertidal ecosystems, including mangrove forests are among those ecosystems that are highly vulnerable to sea level rise, but they may also be vulnerable to sea level variability and extreme low sea level events. During 16 years of monitoring of a mangrove forest in Mangrove Bay in north Western Australia, we documented two forest dieback events, the most recent one being coincident with the large-scale dieback of mangroves in the Gulf of Carpentaria in northern Australia. Diebacks in Mangrove Bay were coincident with periods of very low sea level, which were associated with increased soil salinization of 20-30% above pre-event levels, leading to canopy loss, reduced Normalized Difference Vegetation Index (NDVI) and reduced recruitment. Our study indicates that an intensification of ENSO will have negative effects on some mangrove forests in parts of the Indo-Pacific that will exacerbate other pressures.

Acute salt marsh dieback in the Mississippi River deltaic plain: A drought-induced phenomenon?

USGS Publications Warehouse

McKee, K.L.; Mendelssohn, I.A.; Materne, M.D.

2004-01-01

Aims Extensive dieback of salt marsh dominated by the perennial grass Spartina alterniflora occurred throughout the Mississippi River deltaic plain during 2000. More than 100,000 ha were affected, with 43,000 ha severely damaged. The aim of this work was to determine if sudden dieback could have been caused by a coincident drought and to assess the significance of this event with respect to long-term changes in coastal vegetation. Location Multiple dieback sites and reference sites were established along 150 km of shoreline in coastal Louisiana, USA. Methods Aerial and ground surveys were conducted from June 2000 to September 2001 to assess soil conditions and plant mortality and recovery. Results Dieback areas ranged in size from???300 m2-5 km2 in area with 50-100% mortality of plant shoots and rhizomes in affected zones. Co-occurring species such as Avicennia germinans (black mangrove) and Juncus roemerianus (needlegrass rush) were unaffected. Historical records indicate that precipitation, river discharge, and mean sea level were unusually low during the previous year. Although the cause of dieback is currently unknown, plant and soil characteristics were consistent with temporary soil desiccation that may have reduced water availability, increased soil salinity, and/or caused soil acidification (via pyrite oxidation) and increased uptake of toxic metals such as Fe or Al. Plant recovery 15 months after dieback was variable (0-58% live cover), but recovering plants were vigorous and indicated no longlasting effects of the dieback agent. Main conclusions These findings have relevance for global change models of coastal ecosystems that predict vegetation responses based primarily on long-term increases in sea level and submergence of marshes. Our results suggest that large-scale changes in coastal vegetation may occur over a relatively short time span through climatic extremes acting in concert with sea-level fluctuations and pre-existing soil conditions. ?? 2004 Blackwell Publishing Ltd.

Winter variation in physiological status of cold stored and freshly lifted semi-evergreen quercus nigra seedlings

Treesearch

Rosa C. Goodman; Douglass F. Jacobs; Kent G. Apostol; Barrett C. Wilson; Emile S. Gardiner

2009-01-01

Water oak (Quercus nigra L.) is a tardily deciduous species commonly planted in afforestation projects in the Lower Mississippi River Alluvial Valley, USA. Field performance is often marked by low survival rates and top dieback, which may be associated with poor physiological quality of planting stock.

Field longevity of a-copaene and quercivorol lures for detection of Euwallacea nr. fornicatus in Florida avocado groves

USDA-ARS?s Scientific Manuscript database

Ambrosia beetles in the Euwallacea nr. fornicatus complex vector a fungal pathogen that causes Fusarium dieback, a disease that impacts avocado (Persea americana), woody ornamentals, and native trees in Florida and California. Currently, these pests are detected with quercivorol lures (containing p-...

Strip-bark and Whole-bark Siberian Pine Radial Growth Trends and Implications for Climate Reconstruction

NASA Astrophysics Data System (ADS)

Leland, C.; Cook, E. R.; Andreu-Hayles, L.; Pederson, N.; Hessl, A. E.; Anchukaitis, K. J.; Byambasuren, O.; Nachin, B.; Davi, N. K.; D'Arrigo, R.; Griffin, K. L.; Bishop, D. A.; Rao, M. P.

2017-12-01

Ancient trees can exhibit strip-bark morphology in which a portion of the cambium, the active layer of growth in the stem, dies in response to environmental stress. Partial cambial dieback has been linked to several different ecological and physiological factors, but the causes of dieback vary depending on site conditions. Further, the implications of such morphology on radial growth trends and its importance for tree-ring-based climate reconstructions remain unclear. We investigate the timing and potential environmental drivers of cambial dieback in Pinus sibirica trees from a xeric site in central Mongolia, and compare growth patterns of strip and whole-bark (full cambium) trees over the past 500 years. Cambial dieback occurred primarily on the southern side of trees, and was most common during the cold and dry 19th century. These unfavorable climatic conditions, combined with high exposure to solar radiation, suggested by the orientation of strip bark, might be responsible for cambial dieback. Increasing ring-width trends are gradual in most strip-bark trees, and do not immediately follow dieback dates detected for individual stems. However, a mean ring-width chronology of all strip-bark trees abruptly increases and significantly exceeds ring widths of coeval whole-bark trees in the early 20th century. After standardizing strip and whole-bark series to remove allometric trends, the differences in recent growth trends persist. Before using strip-bark trees for climate reconstruction, we suggest comparing strip and whole-bark ring-width trends in order to determine appropriate methods for removing potential morphology-related growth trends. We extend this study by analyzing stable carbon isotopes in tree rings to evaluate whether there are physiological differences between strip-bark and whole-bark trees, and to determine if δ13C can be used as an additional parameter for climate reconstruction.

Extracellular compounds produced by fungi associated with Botryosphaeria dieback induce differential defence gene expression patterns and necrosis in Vitis vinifera cv. Chardonnay cells.

PubMed

Ramírez-Suero, M; Bénard-Gellon, M; Chong, J; Laloue, H; Stempien, E; Abou-Mansour, E; Fontaine, F; Larignon, P; Mazet-Kieffer, F; Farine, S; Bertsch, C

2014-11-01

Three major grapevine trunk diseases, esca, botryosphaeria dieback and eutypa dieback, pose important economic problems for vineyards worldwide, and currently, no efficient treatment is available to control these diseases. The different fungi associated with grapevine trunk diseases can be isolated in the necrotic wood, but not in the symptomatic leaves. Other factors seem to be responsible for the foliar symptoms and may represent the link between wood and foliar symptoms. One hypothesis is that the extracellular compounds produced by the fungi associated with grapevine trunk diseases are responsible for pathogenicity.In the present work, we used Vitis vinifera cv. Chardonnay cells to test the aggressiveness of total extracellular compounds produced by Diplodia seriata and Neofusicoccum parvum, two causal agents associated with botryosphaeria dieback. Additionally, the toxicity of purified mellein, a characteristic toxin present in the extracellular compounds of Botryosphaeriaceae, was assessed.Our results show that the total extracellular compounds produced by N. parvum induce more necrosis on Chardonnay calli and induce a different defence gene expression pattern than those of D. seriata. Mellein was produced by both fungi in amounts proportional to its aggressiveness. However, when purified mellein was added to the culture medium of calli, only a delayed necrosis and a lower-level expression of defence genes were observed. Extracellular compounds seem to be involved in the pathogenicity of the fungi associated with botryosphaeria dieback. However, the doses of mellein used in this study are 100 times higher than those found in the liquid fungal cultures: therefore, the possible function of this toxin is discussed.

A retrospective, dual-isotope approach reveals individual predispositions to winter-drought induced tree dieback in the southernmost distribution limit of Scots pine.

PubMed

Voltas, Jordi; Camarero, Jesús Julio; Carulla, David; Aguilera, Mònica; Ortiz, Araceli; Ferrio, Juan Pedro

2013-08-01

Winter-drought induced forest diebacks in the low-latitude margins of species' distribution ranges can provide new insights into the mechanisms (carbon starvation, hydraulic failure) underlying contrasting tree reactions. We analysed a winter-drought induced dieback at the Scots pine's southern edge through a dual-isotope approach (Δ(13) C and δ(18) O in tree-ring cellulose). We hypothesized that a differential long-term performance, mediated by the interaction between CO(2) and climate, determined the fates of individuals during dieback. Declining trees showed a stronger coupling between climate, growth and intrinsic water-use efficiency (WUEi) than non-declining individuals that was noticeable for 25 years prior to dieback. The rising stomatal control of water losses with time in declining trees, indicated by negative Δ(13) C-δ(18) O relationships, was likely associated with their native aptitude to grow more and take up more water (suggested by larger tracheid lumen widths) than non-declining trees and, therefore, to exhibit a greater cavitation risk. Freeze-thaw episodes occurring in winter 2001 unveiled such physiological differences by triggering dieback in those trees more vulnerable to hydraulic failure. Thus, WUEi tightly modulated growth responses to long-term warming in declining trees, indicating that co-occurring individuals were differentially predisposed to winter-drought mortality. These different performances were unconnected to the depletion of stored carbohydrates. © 2013 John Wiley & Sons Ltd.

Wood anatomy and carbon-isotope discrimination support long-term hydraulic deterioration as a major cause of drought-induced dieback.

PubMed

Pellizzari, Elena; Camarero, J Julio; Gazol, Antonio; Sangüesa-Barreda, Gabriel; Carrer, Marco

2016-06-01

Hydraulic impairment due to xylem embolism and carbon starvation are the two proposed mechanisms explaining drought-induced forest dieback and tree death. Here, we evaluate the relative role played by these two mechanisms in the long-term by quantifying wood-anatomical traits (tracheid size and area of parenchyma rays) and estimating the intrinsic water-use efficiency (iWUE) from carbon isotopic discrimination. We selected silver fir and Scots pine stands in NE Spain with ongoing dieback processes and compared trees showing contrasting vigour (declining vs nondeclining trees). In both species earlywood tracheids in declining trees showed smaller lumen area with thicker cell wall, inducing a lower theoretical hydraulic conductivity. Parenchyma ray area was similar between the two vigour classes. Wet spring and summer conditions promoted the formation of larger lumen areas, particularly in the case of nondeclining trees. Declining silver firs presented a lower iWUE than conspecific nondeclining trees, but the reverse pattern was observed in Scots pine. The described patterns in wood anatomical traits and iWUE are coherent with a long-lasting deterioration of the hydraulic system in declining trees prior to their dieback. Retrospective quantifications of lumen area permit to forecast dieback in declining trees 2-5 decades before growth decline started. Wood anatomical traits provide a robust tool to reconstruct the long-term capacity of trees to withstand drought-induced dieback. © 2016 John Wiley & Sons Ltd.

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.

Using a GCM analogue model to investigate the potential for Amazonian forest dieback

NASA Astrophysics Data System (ADS)

Huntingford, C.; Harris, P. P.; Gedney, N.; Cox, P. M.; Betts, R. A.; Marengo, J. A.; Gash, J. H. C.

A combined GCM analogue model and GCM land surface representation is used to investigate the influences of climatology and land surface parameterisation on modelled Amazonian vegetation change. This modelling structure (called IMOGEN) captures the main features of the changes in surface climate as estimated by a GCM with enhanced atmospheric greenhouse gas concentrations. Advantage is taken of IMOGEN's computational speed which allows multiple simulations to be carried out to assess the robustness of the GCM results. The timing of forest dieback is found to be sensitive to the initial ``pre-industrial'' climate, as well as uncertainties in the representation of land-atmosphere CO2 exchange. Changing from a Q10 form for plant dark and maintanence respiration (as used in the coupled GCM runs) to a respiration proportional to maximum photosynthesis, reduces the biomass lost from Amazonia in the 21st century. Replacing the GCM control climate (which has about 25% too little rain in the annual mean over Amazonia) with an observed climatology increases the CO2 concentration at which rainfall drops to critical levels, and thereby further delays the dieback. On the other hand, calibration of the canopy photosynthesis model against Amazonian flux data tends to lead to earlier forest dieback. Further advances are required in both GCM rainfall simulation and land-surface process representation before a clearer picture will emerge on the timing of possible Amazonian forest dieback. However, it seems likely that these advances will overall lead to projections of later forest dieback as GCM control climates become more realistic.

Winter drought impairs xylem phenology, anatomy and growth in Mediterranean Scots pine forests.

PubMed

Camarero, J J; Guada, G; Sánchez-Salguero, R; Cervantes, E

2016-12-01

Continental Mediterranean forests face drought but also cold spells and both climate extremes can impair the resilience capacity of these forests. Climate warming could amplify the negative effects of cold spells by inducing premature dehardening. Here we capitalize on a winter drought-induced dieback triggered by a cold spell which occurred in December 2001 affecting Scots pine forests in eastern Spain. We assessed post-dieback recovery by quantifying and comparing radial growth and xylem anatomy of non-declining (ND, crown cover >50%) and declining (D, crown cover ≤50%) trees in two sites (VP, Villarroya de los Pinares; TO, Torrijas). We also characterized xylogenesis in both sites and aboveground productivity in site VP. Dieback caused legacy effects since needle loss, a 60% reduction in litter fall and radial-growth decline characterized D-trees 3 years after dieback symptoms started appearing in spring 2002. D-trees formed collapsed tracheids in the 2002-ring, particularly in the most affected VP site where xylogenesis differences between ND and D trees were most noticeable. The lower growth rates of D-trees were caused by a shorter duration of their major xylogenesis phases. In site VP the radial-enlargement and wall-thickening of tracheids were significantly reduced in D-trees as compared to ND-trees because these xylogenesis phases tended to start earlier and end later in ND-trees. Gompertz models fitted to tracheid production predicted that maximum growth rates occurred 11-12 days earlier in ND than in D-trees. The formation of radially-enlarging tracheids was enhanced by longer days in both study sites and also by wetter conditions in the driest TO site, but xylogenesis sensitivity to climate was reduced in D-trees. Winter-drought dieback impairs xylem anatomy and phenology, aboveground productivity, xylogenesis and growth in Mediterranean Scots pine populations. Affected stands show a costly post-dieback recovery challenging their resilience ability. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Diseases of Pacific Coast conifers. Agriculture handbook

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

Scharpf, R.F.

1993-06-01

The handbook provides basic information needed to identify the common diseases of Pacific Coast conifers. Hosts, distribution, disease cycles, and identifying characteristics are described for more than 150 diseases, including cankers, diebacks, galls, rusts, needle diseases, root diseases, mistletoes, and rots. Diseases in which abiotic factors are involved are also described. For some groups of diseases, a descriptive key to field identification is included.

Early Impact and Control of Aphid (Chaitophorus populicola Thomas) Infestations on Young Cottonwood Plantations in the Mississippi Delta

Treesearch

J.D. Solomon

1999-01-01

A very heavy infestation of the aphid Chaitophorus populicola Thomas developed primarily on growing shoots in commercial cottonwood plantations and caused serious injury to terminals. Terminal mortality in heavily infested fields averaged 92.5 percent, and shoot dieback averaged 4.3 inches. Many of the surviving terminals were weakened to the...

Analysis of ecological thresholds in a temperate forest undergoing dieback

PubMed Central

Newton, Adrian C.; Cantarello, Elena; Evans, Paul M.

2017-01-01

Positive feedbacks in drivers of degradation can cause threshold responses in natural ecosystems. Though threshold responses have received much attention in studies of aquatic ecosystems, they have been neglected in terrestrial systems, such as forests, where the long time-scales required for monitoring have impeded research. In this study we explored the role of positive feedbacks in a temperate forest that has been monitored for 50 years and is undergoing dieback, largely as a result of death of the canopy dominant species (Fagus sylvatica, beech). Statistical analyses showed strong non-linear losses in basal area for some plots, while others showed relatively gradual change. Beech seedling density was positively related to canopy openness, but a similar relationship was not observed for saplings, suggesting a feedback whereby mortality in areas with high canopy openness was elevated. We combined this observation with empirical data on size- and growth-mediated mortality of trees to produce an individual-based model of forest dynamics. We used this model to simulate changes in the structure of the forest over 100 years under scenarios with different juvenile and mature mortality probabilities, as well as a positive feedback between seedling and mature tree mortality. This model produced declines in forest basal area when critical juvenile and mature mortality probabilities were exceeded. Feedbacks in juvenile mortality caused a greater reduction in basal area relative to scenarios with no feedback. Non-linear, concave declines of basal area occurred only when mature tree mortality was 3–5 times higher than rates observed in the field. Our results indicate that the longevity of trees may help to buffer forests against environmental change and that the maintenance of old, large trees may aid the resilience of forest stands. In addition, our work suggests that dieback of forests may be avoidable providing pressures on mature and juvenile trees do not pass critical thresholds. PMID:29240842

Remote measurement of canopy water content in giant sequoias (Sequoiadendron giganteum) during drought

USGS Publications Warehouse

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

2018-01-01

California experienced severe drought from 2012 to 2016, and there were visible changes in the forest canopy throughout the State. In 2014, unprecedented foliage dieback was recorded in giant sequoia (Sequoiadendron giganteum) trees in Sequoia National Park, in the southern California Sierra Nevada mountains. Although visible changes in sequoia canopies can be recorded, biochemical and physiological responses to drought stress in giant sequoia canopies are not well understood. Ground-based measurements provide insight into the mechanisms of drought responses in trees, but are often limited to few individuals, especially in trees of tall stature such as giant sequoia. Recent studies demonstrate that remotely measured forest canopy water content (CWC) is a general indicator of canopy response to drought, but the underpinning leaf- to canopy-level causes of observed variation in CWC remain poorly understood. We combined field and airborne remote sensing measurements taken in 2015 and 2016 to assess the biophysical responses of giant sequoias to drought. In 49 study trees, CWC was related to leaf water potential, but not to the other foliar traits, suggesting that changes in CWC were made at whole-canopy rather than leaf scales. We found a non-random, spatially varying pattern in mapped CWC, with lower CWC values at lower elevation and along the outer edges of the groves. This pattern was also observed in empirical measurements of foliage dieback from the ground, and in mapped CWC across multiple sequoia groves in this region, supporting the hypothesis that drought stress is expressed in canopy-level changes in giant sequoias. The fact that we can clearly detect a relationship between CWC and foliage dieback, even without taking into account prior variability or new leaf growth, strongly suggests that remotely sensed CWC, and changes in CWC, are a useful measure of water stress in giant sequoia, and valuable for assessing and managing these iconic forests in drought.

Water stress exacerbates the severity of Botryosphaeria dieback in grapevines infected by Neofusicoccum parvum

USDA-ARS?s Scientific Manuscript database

Botryosphaeria dieback (causal fungus Neofusicoccum parvum) is a detrimental grapevine trunk disease, causing internal wood degradation, killing shoots, and reducing yields. We examined the interactive effects of drought and N. parvum infection, common vineyard stresses, on wood-lesion development. ...

Distribution and severity of alder phytophthora in Alaska

Treesearch

G.C. Adams; M. Catal; L. Trummer

2010-01-01

In Alaska, an unprecedented dieback and mortality of Alnus incana ssp. tenuifolia has occurred which stimulated an effort to determine causal agents of the disease. In Europe, similar dieback and mortality of Alnus incana and Alnus glutinosa has been attributed to root rot by a spectrum...

Wood-decay abilities of grapevine trunk pathogens Diaporthe ampelina, Diplodia seriata, Eutypa lata, and Neofusicoccum parvum

USDA-ARS?s Scientific Manuscript database

Trunk pathogens are fungi that infect grapevine wood through pruning wounds and destroy fruiting positions, thereby impacting grape production. Neofusicoccum parvum (causal fungus of Botryosphaeria dieback) and Eutypa lata (causal fungus of Eutypa dieback) cause chronic infections (cankers) of the t...

Making the case for early adoption of preventative practices for management of grapevine trunk diseases

USDA-ARS?s Scientific Manuscript database

Experimental trials on prevention of trunk diseases Botryosphaeria dieback, Esca, and Eutypa dieback have shown that delayed pruning, double pruning, and applications of the pruning-wound protectant thiophanate-methyl (Topsin) can reduce pruning-wound infections by 25-75%. Despite this biological e...

Germination and growth of native and invasive plants on soil associated with biological control of Tamarisk (Tamarix spp.)

USDA-ARS?s Scientific Manuscript database

Introductions of biocontrol beetles (tamarisk beetles) are causing dieback of exotic tamarisk in riparian zones across the western U.S., yet factors that determine plant communities that follow tamarisk dieback are poorly understood. Tamarisk-dominated soils are generally higher in nutrients, organi...

Forest Health Monitoring in New Hampshire, 1996-1999

Treesearch

Northeastern Research Station

2002-01-01

New Hampshire has mature forests dominated by hardwood species but with significant softwood resources. The majority of the trees are healthy with full crowns (low transparency, high density), little dieback and little damage. Red maple had higher dieback and more damage than other species. Eastern white pine had lower crown densities and little damage.

Forest Health Monitoring in Massachusetts, 1996-1999

Treesearch

Northeastern Research Station

2002-01-01

Massachusetts has mature forests dominated by hardwood species. Most of the trees are healthy, with full crowns (low transparency, high density), little dieback and little damage. Red maple trees made up almost one quarter of the trees and had slightly higher amounts of dieback, thinner crowns, and more damage than other common tree species.

Latent infection by Fusarium circinatum influences susceptibility of monterey pine seedlings to pitch canker

Treesearch

Cassandra L. Swett; Thomas R. Gordon

2012-01-01

Pitch canker, caused by Fusarium circinatum, is a serious disease affecting Pinus radiata D. Don (Monterey pine) in nurseries, landscapes, and native forests. A typical symptom of pitch canker is canopy dieback resulting from girdling lesions on terminal branches (Gordon et al. 2001). More extensive dieback can result from...

Stress triggered tree diseases, The diebacks and declines

Treesearch

David R. Houston

1981-01-01

Traditionally, dieback and decline diseases of trees have been described in generalities, attributed to unknown or mysterious causes, and thought to be beyond the scope of human intervention. This publication provides a basis for understanding and coping with these diseases. Discussed are concepts relating to: (1) diagnosing the factors that initiate the disease; (2)...

Vascular Streak Dieback of cacao in Southeast Asia detection and Melanesia: in planta detection of the pathogen and a new taxonomy

USDA-ARS?s Scientific Manuscript database

Vascular Streak Dieback (VSD) disease of cacao (Theobroma cacao) in Southeast Asia and Melanesia is caused by a basidiomycete (Ceratobasidiales) fungus described in a monotypic genus as Oncobasidium theobromae (syn. =Thanatephorus theobromae). The symptoms of the disease include green-spotted chloro...

Diurnal patterns of productivity of arbuscular mycorrhizal fungi revealed with the Soil Ecosystem Observatory.

PubMed

Hernandez, Rebecca R; Allen, Michael F

2013-10-01

Arbuscular mycorrhizal (AM) fungi are the most abundant plant symbiont and a major pathway of carbon sequestration in soils. However, their basic biology, including their activity throughout a 24-h day : night cycle, remains unknown. We employed the in situ Soil Ecosystem Observatory to quantify the rates of diurnal growth, dieback and net productivity of extra-radical AM fungi. AM fungal hyphae showed significantly different rates of growth and dieback over a period of 24 h and paralleled the circadian-driven photosynthetic oscillations observed in plants. The greatest rates (and incidences) of growth and dieback occurred between noon and 18:00 h. Growth and dieback events often occurred simultaneously and were tightly coupled with soil temperature and moisture, suggesting a rapid acclimation of the external phase of AM fungi to the immediate environment. Changes in the environmental conditions and variability of the mycorrhizosphere may alter the diurnal patterns of productivity of AM fungi, thereby modifying soil carbon sequestration, nutrient cycling and host plant success. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Diurnal patterns of productivity of arbuscular mycorrhizal fungi revealed with the Soil Ecosystem Observatory

PubMed Central

Hernandez, Rebecca R; Allen, Michael F

2013-01-01

Arbuscular mycorrhizal (AM) fungi are the most abundant plant symbiont and a major pathway of carbon sequestration in soils. However, their basic biology, including their activity throughout a 24-h day : night cycle, remains unknown. We employed the in situ Soil Ecosystem Observatory to quantify the rates of diurnal growth, dieback and net productivity of extra-radical AM fungi. AM fungal hyphae showed significantly different rates of growth and dieback over a period of 24 h and paralleled the circadian-driven photosynthetic oscillations observed in plants. The greatest rates (and incidences) of growth and dieback occurred between noon and 18:00 h. Growth and dieback events often occurred simultaneously and were tightly coupled with soil temperature and moisture, suggesting a rapid acclimation of the external phase of AM fungi to the immediate environment. Changes in the environmental conditions and variability of the mycorrhizosphere may alter the diurnal patterns of productivity of AM fungi, thereby modifying soil carbon sequestration, nutrient cycling and host plant success. PMID:23844990

Forest Health Monitoring in Maine, 1996-1999.

Treesearch

Northeastern Research Station

2002-01-01

Maine has mixed-age forests dominated by softwood species. Most of the trees are healthy, with full crowns (low transparency, high density), little dieback and little damage. Red maple had higher amounts of dieback but seemed to maintain crown fullness. Eastern white pine and northern white cedar had lower densities as well as higher rates of damage.

Forest Health Monitoring in Connecticut, 1996-1999

Treesearch

Northeastern Research Station

2002-01-01

Connecticut has mature forests dominated by hardwoods. Most trees are healthy with full crowns (low transparency and high density), little dieback and little damage. The exception is eastern hemlock, which was in poor condition, with thin crowns, more dieback and more damage, especially broken tops. These conditions are likely the result of attack by the hemlock woolly...

Forest Health Monitoring in New York, 1996-1999

Treesearch

Northeastern Research Station

2002-01-01

New York has mature forests dominated by hardwood species, but with a significant and varied softwood resource. Most of the trees are healthy, with full crowns (low transparency, high density), little dieback and little damage. American beech tends to be in poorer condition, with thin crowns, higher dieback, and more damage, especially broken and dead branches.

History of sugar maple decline

Treesearch

David R. Houston

1999-01-01

Only a few episodes of sugar maple dieback or decline were recorded during the first half of the 20th Century. In contrast, the last 50 years have provided numerous reports of both urban and forest dieback/decline. In the late 1950s, a defoliation-triggered decline, termed maple blight, that occurred in Wisconsin prompted the first comprehensive, multidisciplinary...

Ash dieback in the Northeast

Treesearch

Robert W. Brandt

1961-01-01

A dieback condition among our ash trees is causing great concern among foresters and forest industries in the northeastern United States. There is good cause for concern. For example, a recent survey made by the New York Conservation Department in 18 eastern counties of the State revealed that about 70 percent of the woodland ash trees are dead or dying.

Long-term vegetation changes in a temperate forest impacted by climate change

Treesearch

Lauren E. Oakes; Paul E. Hennon; Kevin L. O' Hara; Rodolfo Dirzo

2014-01-01

Pervasive forest mortality is expected to increase in future decades as a result of increasing temperatures. Climate-induced forest dieback can have consequences on ecosystem services, potentially mediated by changes in forest structure and understory community composition that emerge in response to tree death. Although many dieback events around the world have been...

Grapevine Botryosphaeria dieback fungi have specific aggressiveness factor repertory involved in wood decay and stilbene metabolization.

PubMed

Stempien, Elodie; Goddard, Mary-Lorène; Wilhelm, Kim; Tarnus, Céline; Bertsch, Christophe; Chong, Julie

2017-01-01

Grapevine trunk diseases: Eutypa dieback, esca and Botryosphaeria dieback, which incidence has increased recently, are associated with several symptoms finally leading to the plant death. In the absence of efficient treatments, these diseases are a major problem for the viticulture; however, the factors involved in disease progression are not still fully identified. In order to get a better understanding of Botryosphaeria dieback development in grapevine, we have investigated different factors involved in Botryosphaeriaceae fungi aggressiveness. We first evaluated the activity of the wood-degrading enzymes of different isolates of Neofusicoccum parvum and Diplodia seriata, two major fungi associated with Botryosphaeria dieback. We further examinated the ability of these fungi to metabolize major grapevine phytoalexins: resveratrol and δ-viniferin. Our results demonstrate that Botryosphaeriaceae were characterized by differential wood decay enzymatic activities and have the capacity to rapidly degrade stilbenes. N. parvum is able to degrade parietal polysaccharides, whereas D. seriata has a better capacity to degrade lignin. Growth of both fungi exhibited a low sensitivity to resveratrol, whereas δ-viniferin has a fungistatic effect, especially on N. parvum Bourgogne S-116. We further show that Botryosphaeriaceae are able to metabolize rapidly resveratrol and δ-viniferin. The best stilbene metabolizing activity was measured for D. seriata. In conclusion, the different Botryosphaeriaceae isolates are characterized by a specific aggressiveness repertory. Wood and phenolic compound decay enzymatic activities could enable Botryosphaeriaceae to bypass chemical and physical barriers of the grapevine plant. The specific signature of Botryosphaeriaceae aggressiveness factors could explain the importance of fungi complexes in synergistic activity in order to fully colonize the host.

Survey of Sycamore Plantations for Canker, Leaf Scorch, and Dieback

Treesearch

T. H. Filer; D. T. Cooper; R. J. Collins; R. Wolfe

1975-01-01

Twenty-six sycamore plantations surveyed in Louisiana, Mississippi, Arkansas, and Tennessee in 1973 had leaf scorch symptoms; cankers caused mor tality in six lower Mississippi Delta s tands. Symptoms of the disease are leaf scorch, top diebac k, and trunk canker. No trees under 4 years old had dieback, and none unde r 6 years old had lethal trunk canker.

Draft Genome Sequence of the Phytopathogenic Fungus Fusarium euwallaceae, the Causal Agent of Fusarium Dieback

PubMed Central

Sánchez-Rangel, Diana; Hernández-Domínguez, Eric; Pérez-Torres, Claudia-Anahí; Ortiz-Castro, Randy; Villafán, Emanuel; Alonso-Sánchez, Alexandro; Rodríguez-Haas, Benjamín; López-Buenfil, Abel; García-Avila, Clemente; Ramírez-Pool, José-Abrahán

2017-01-01

ABSTRACT Here, we report the genome of Fusarium euwallaceae strain HFEW-16-IV-019, an isolate obtained from Kuroshio shot hole borer (a Euwallacea sp.). These beetles were collected in Tijuana, Mexico, from elm trees showing typical symptoms of Fusarium dieback. The final assembly consists of 287 scaffolds spanning 48,274,071 bp and 13,777 genes. PMID:28860245

Herbicides implicated as the cause of severe mangrove dieback in the Mackay region, NE Australia: consequences for marine plant habitats of the GBR World Heritage Area.

PubMed

Duke, Norman C; Bell, Alicia M; Pederson, Dan K; Roelfsema, Chris M; Bengtson Nash, Susan

2005-01-01

Herbicides, particularly diuron, were correlated with severe and widespread dieback of the dominant mangrove, Avicennia marina (Forsk.) Vierh. var. eucalyptifolia (Val.) N.C. Duke (Avicenniaceae), its reduced canopy condition, and declines in seedling health within three neighbouring estuaries in the Mackay region of NE Australia. This unusual species-specific dieback, first observed in the early 1990s, had gotten notably worse by 2002 to affect >30 km(2) of mangroves in at least five adjacent estuaries in the region. Over the past century, agricultural production has responded well to the demands of increasing population with improvements in farm efficiency assisted by significant increases in the use of agricultural chemicals. However, with regular and episodic river flow events, these chemicals have sometimes found their way into estuarine and nearshore water and sediments where their effects on marine habitats have been largely unquantified. Investigations over the last three years in the Mackay region provide compelling evidence of diuron, and possibly other agricultural herbicides, as the most likely cause of the severe and widespread mangrove dieback. The likely consequences of such dieback included declines in coastal water quality with increased turbidity, nutrients and sediment deposition, as well as further dispersal of the toxic chemicals. The implications of such findings are immense since they describe not only the serious deterioration of protected and beneficial mangrove habitat but also the potential for significant direct and indirect effects on other highly-valued estuarine and marine habitats in the region, including seagrass beds and coral reefs of the Great Barrier Reef lagoon. This article reviews all key findings and observations to date and describes the essential correlative and causative evidence.

Grapevine Botryosphaeria dieback fungi have specific aggressiveness factor repertory involved in wood decay and stilbene metabolization

PubMed Central

Wilhelm, Kim; Tarnus, Céline; Bertsch, Christophe

2017-01-01

Grapevine trunk diseases: Eutypa dieback, esca and Botryosphaeria dieback, which incidence has increased recently, are associated with several symptoms finally leading to the plant death. In the absence of efficient treatments, these diseases are a major problem for the viticulture; however, the factors involved in disease progression are not still fully identified. In order to get a better understanding of Botryosphaeria dieback development in grapevine, we have investigated different factors involved in Botryosphaeriaceae fungi aggressiveness. We first evaluated the activity of the wood-degrading enzymes of different isolates of Neofusicoccum parvum and Diplodia seriata, two major fungi associated with Botryosphaeria dieback. We further examinated the ability of these fungi to metabolize major grapevine phytoalexins: resveratrol and δ-viniferin. Our results demonstrate that Botryosphaeriaceae were characterized by differential wood decay enzymatic activities and have the capacity to rapidly degrade stilbenes. N. parvum is able to degrade parietal polysaccharides, whereas D. seriata has a better capacity to degrade lignin. Growth of both fungi exhibited a low sensitivity to resveratrol, whereas δ-viniferin has a fungistatic effect, especially on N. parvum Bourgogne S-116. We further show that Botryosphaeriaceae are able to metabolize rapidly resveratrol and δ-viniferin. The best stilbene metabolizing activity was measured for D. seriata. In conclusion, the different Botryosphaeriaceae isolates are characterized by a specific aggressiveness repertory. Wood and phenolic compound decay enzymatic activities could enable Botryosphaeriaceae to bypass chemical and physical barriers of the grapevine plant. The specific signature of Botryosphaeriaceae aggressiveness factors could explain the importance of fungi complexes in synergistic activity in order to fully colonize the host. PMID:29261692

First Report of the Ash Dieback Pathogen Hymenoscyphus fraxineus in Korea

PubMed Central

Han, Jae-Gu; Shrestha, Bhushan; Hosoya, Tsuyoshi; Lee, Kang-Hyo

2014-01-01

In the past two decades, European ash trees (Fraxinus spp.) have been severely damaged due to ash dieback disease, which is caused by the fungal species Hymenoscyphus fraxineus (Chalara fraxinea in the anamorphic stage). Recent molecular phylogenetic and population genetic studies have suggested that this fungus has been introduced from Asia to Europe. During a fungal survey in Korea, H. fraxineus-like apothecia were collected from fallen leaves, rachises, and petioles of Korean ash and Manchurian ash trees. The morphological and ecological traits of these materials are described with the internal transcribed spacer rDNA sequence comparison of H. fraxineus strains collected from Korea, China and Japan. PMID:25606012

Predicting forest dieback in Maine, USA: a simple model based on soil frost and drought

Treesearch

Allan N.D. Auclair; Warren E. Heilman; Blondel Brinkman

2010-01-01

Tree roots of northern hardwoods are shallow rooted, winter active, and minimally frost hardened; dieback is a winter freezing injury to roots incited by frost penetration in the absence of adequate snow cover and exacerbated by drought in summer. High soil water content greatly increases conductivity of frost. We develop a model based on the sum of z-scores of soil...

Detection and classification of ash dieback on large-scale color aerial photographs

Treesearch

Ralph J. Croxton

1966-01-01

Aerial color photographs were taken at two scales over ash stands in New York State that were infected with ash dieback. Three photo interpreters then attempted to distinguish ash trees from other hardwoods and classify their disease condition. The scale of 1:7,920 was too small to permit accurate identification, but accuracy at the scale 1:1,584 was fair (60 to 70...

Evaluating elevated levels of crown dieback among northern white-cedar (Thuja occidentalis L.) trees in Maine and Michigan: a summary of evaluation monitoring

Treesearch

KaDonna Randolph; William A. Bechtold; Randall S. Morin; Stanley J. Zarnoch

2012-01-01

Analysis of crown condition data for the 2006 national technical report of the Forest Health Monitoring (FHM) Program of the Forest Service, U.S. Department of Agriculture, exposed clusters of phase 3 plots (by the Forest Inventory and Analysis [FIA] Program of the Forest Service) with northern white-cedar (Thuja occidentalis L.) crown dieback...

Draft Genome Sequence of the Phytopathogenic Fungus Fusarium euwallaceae, the Causal Agent of Fusarium Dieback.

PubMed

Ibarra-Laclette, Enrique; Sánchez-Rangel, Diana; Hernández-Domínguez, Eric; Pérez-Torres, Claudia-Anahí; Ortiz-Castro, Randy; Villafán, Emanuel; Alonso-Sánchez, Alexandro; Rodríguez-Haas, Benjamín; López-Buenfil, Abel; García-Avila, Clemente; Ramírez-Pool, José-Abrahán

2017-08-31

Here, we report the genome of Fusarium euwallaceae strain HFEW-16-IV-019, an isolate obtained from Kuroshio shot hole borer (a Euwallacea sp.). These beetles were collected in Tijuana, Mexico, from elm trees showing typical symptoms of Fusarium dieback. The final assembly consists of 287 scaffolds spanning 48,274,071 bp and 13,777 genes. Copyright © 2017 Ibarra-Laclette et al.

Climate-induced forest dieback: An escalating global phenomenon?

USGS Publications Warehouse

Allen, Craig D.

2009-01-01

Forests, which today cover 30 percent of the world’s land surface (FAO, 2006), are being rapidly and directly transformed in many areas by the impacts of expanding human populations and economies. Less evident are the pervasive effects of ongoing climatic changes on the condition and status of forests around the world. Recent examples of drought and heat-related forest stress and dieback (defined here as tree mortality noticeably above usual mortality levels) are being documented from all forested continents, making it possible to begin to see global patterns. This article introduces these patterns and considers the possibility that many forests and woodlands today are at increasing risk of climate-induced dieback. A more comprehensive article (Allen et al., 2009) addresses this topic in considerably greater detail. While climate events can damage forests in many ways ranging from ice storms to tornadoes and hurricanes, the emphasis here is on climatic water stress, driven by drought and warm temperatures.

Estimating Amazonian rainforest stability and the likelihood for large-scale forest dieback

NASA Astrophysics Data System (ADS)

Rammig, Anja; Thonicke, Kirsten; Jupp, Tim; Ostberg, Sebastian; Heinke, Jens; Lucht, Wolfgang; Cramer, Wolfgang; Cox, Peter

2010-05-01

Annually, tropical forests process approximately 18 Pg of carbon through respiration and photosynthesis - more than twice the rate of anthropogenic fossil fuel emissions. Current climate change may be transforming this carbon sink into a carbon source by changing forest structure and dynamics. Increasing temperatures and potentially decreasing precipitation and thus prolonged drought stress may lead to increasing physiological stress and reduced productivity for trees. Resulting decreases in evapotranspiration and therefore convective precipitation could further accelerate drought conditions and destabilize the tropical ecosystem as a whole and lead to an 'Amazon forest dieback'. The projected direction and intensity of climate change vary widely within the region and between different scenarios from climate models (GCMs). In the scope of a World Bank-funded study, we assessed the 24 General Circulation Models (GCMs) evaluated in the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR4) with respect to their capability to reproduce present-day climate in the Amazon basin using a Bayesian approach. With this approach, greater weight is assigned to the models that simulate well the annual cycle of rainfall. We then use the resulting weightings to create probability density functions (PDFs) for future forest biomass changes as simulated by the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJmL) to estimate the risk of potential Amazon rainforest dieback. Our results show contrasting changes in forest biomass throughout five regions of northern South America: If photosynthetic capacity and water use efficiency is enhanced by CO2, biomass increases across all five regions. However, if CO2-fertilisation is assumed to be absent or less important, then substantial dieback occurs in some scenarios and thus, the risk of forest dieback is considerably higher. Particularly affected are regions in the central Amazon basin. The range of potential biomass change arising from the weighting of rainfall patterns is smaller than the uncertainty arising from CO2-fertilisation effects, which highlights the importance of reducing the uncertainties in the direct effects of CO2 on tropical ecosystems. Strong biomass changes also imply changes in forest structure and thus, forest stability. Our results display shifts in forest composition from closed rainforest to more open forest or even shrubland. Our probability-based risk analysis could be used to advise regional forest protection.

Biological Control of Mango Dieback Disease Caused by Lasiodiplodia theobromae Using Streptomycete and Non-streptomycete Actinobacteria in the United Arab Emirates

PubMed Central

Kamil, Fatima H.; Saeed, Esam E.; El-Tarabily, Khaled A.; AbuQamar, Synan F.

2018-01-01

Dieback caused by the fungus Lasiodiplodia theobromae is an important disease on mango plantations in the United Arab Emirates (UAE). In this study, 53 actinobacterial isolates were obtained from mango rhizosphere soil in the UAE, of which 35 (66%) were classified as streptomycetes (SA) and 18 (34%) as non-streptomycetes (NSA). Among these isolates, 19 (12 SA and 7 NSA) showed antagonistic activities against L. theobromae associated with either the production of diffusible antifungal metabolites, extracellular cell-wall-degrading enzymes (CWDEs), or both. Using a “novel” mango fruit bioassay, all isolates were screened in vivo for their abilities to reduce lesion severity on fruits inoculated with L. theobromae. Three isolates, two belonging to Streptomyces and one to Micromonospora spp., showed the strongest inhibitory effect against this pathogen in vitro and were therefore selected for tests on mango seedlings. Our results revealed that the antifungal action of S. samsunensis UAE1 was related to antibiosis, and the production of CWDEs (i.e., chitinase) and siderophores; whilst S. cavourensis UAE1 and M. tulbaghiae UAE1 were considered to be associated with antibiotic- and CWDE-production, respectively. Pre-inoculation in greenhouse experiments with the most promising actinobacterial isolates resulted in very high levels of disease protection in mango seedlings subsequently inoculated with the pathogen. This was evident by the dramatic reduction in the estimated disease severity indices of the mango dieback of individual biocontrol agent (BCA) applications compared with the pathogen alone, confirming their potential in the management of mango dieback disease. L. theobromae-infected mango seedlings treated with S. samsunensis showed significantly reduced number of defoliated leaves and conidia counts of L. theobromae by 2- and 4-fold, respectively, in comparison to the other two BCA applications. This indicates that the synergistic antifungal effects of S. samsunensis using multiple modes of action retarded the in planta invasion of L. theobromae. This is the first report of BCA effects against L. theobromae on mango seedlings by microbial antagonists. It is also the first report of actinobacteria naturally existing in the soils of the UAE or elsewhere that show the ability to suppress the mango dieback disease.

Preventative Disease Management and Grower Decision Making: A Case Study of California Wine-Grape Growers.

PubMed

Hillis, Vicken; Lubell, Mark; Kaplan, Jonathan; Baumgartner, Kendra

2017-06-01

Preventative disease management is challenging to farmers because it requires paying immediate costs in the hopes of returning uncertain future benefits. Understanding farmer decision making about prevention has the potential to reduce disease incidence and minimize the need for more costly postinfection practices. For example, the grapevine trunk-disease complex (esca, Botryosphaeria dieback, Eutypa dieback, and Phomopsis dieback) significantly affects vineyard productivity and longevity. Given the chronic nature of the infections and inability to eradicate the fungal pathogens, the preventative practices of delayed pruning, applications of pruning-wound protectants, and double pruning (also known as prepruning) are the most effective means of management. We surveyed wine-grape growers in six regions of California on their use of these three practices. In spite of acknowledging the yield impacts of trunk diseases, a substantial number of respondents either choose not to use preventative practices or incorrectly adopted them in mature vineyards, too late in the disease cycle to be effective. Growers with more negative perceptions of cost efficacy were less likely to adopt preventative practices or were more likely to time adoption incorrectly in mature vineyards. In general, preventative management may require strong intervention in the form of policy or extension to motivate behavioral change.

Effectiveness of several dosage formula of oil and nano emulsion of citronella against vascular streak dieback (VSD) disease on cocoa

NASA Astrophysics Data System (ADS)

Noveriza, R.; Trisno, J.; Rahma, H.; Yuliani, S.; Reflin; Martinius

2018-02-01

The disease of Vascular streak dieback (VSD) is a deadly disease of cocoa plants, because it attacks the vascular tissue of cocoa at growing point of the plant. In West Sumatra the disease was first reported in 2015 with an incidence of disease range 58.82% - 100% and an intensity of disease range 24.29% - 44.7%. The purpose of this study was to examine the effectiveness of dosage application of oil formula and nano emulsion of citronella formula against Vascular streak dieback (VSD) disease on cocoa plants in West Sumatra (in Padang Pariaman District and Limapuluh Kota District). The results showed that the percentage of VSD disease attacks in both testing sites was 100%. The oil and nano emulsion of citronella formulas can reduce the intensity of VSD disease on cocoa plants in West Sumatra, particularly in Padang Pariaman District and Limapuluh Kota District. The reduction of VSD intensity in Padang Pariaman district ranged from 8.32 to 21.13%; while in Limapuluh Kota district ranged from 4.33 to 11.80%. The nano emulsion of citronella formulation is effective to suppress the intensity of VSD disease on cocoa plants at doses 0.1% (≥ 30% of effectiveness level).

Estimating Coextinction Risks from Epidemic Tree Death: Affiliate Lichen Communities among Diseased Host Tree Populations of Fraxinus excelsior

PubMed Central

Jönsson, Mari T.; Thor, Göran

2012-01-01

At least 10% of the world’s tree species are threatened with extinction and pathogens are increasingly implicated in tree threats. Coextinction and threats to affiliates as a consequence of the loss or decline of their host trees is a poorly understood phenomenon. Ash dieback is an emerging infectious disease causing severe dieback of common ash Fraxinus excelsior throughout Europe. We utilized available empirical data on affiliate epiphytic lichen diversity (174 species and 17,800 observations) among 20 ash dieback infected host tree populations of F. excelsior on the island Gotland in the Baltic Sea, Sweden. From this, we used structured scenario projections scaled with empirical data of ash dieback disease to generate probabilistic models for estimating local and regional lichen coextinction risks. Average coextinction probabilities (Ā) were 0.38 (95% CI ±0.09) for lichens occurring on F. excelsior and 0.14 (95% CI ±0.03) when considering lichen persistence on all tree species. Ā was strongly linked to local disease incidence levels and generally increasing with lichen host specificity to F. excelsior and decreasing population size. Coextinctions reduced affiliate community viability, with significant local reductions in species richness and shifts in lichen species composition. Affiliates were projected to become locally extirpated before their hosts, illuminating the need to also consider host tree declines. Traditionally managed open wooded meadows had the highest incidence of ash dieback disease and significantly higher proportions of affiliate species projected to go extinct, compared with unmanaged closed forests and semi-open grazed sites. Most cothreatened species were not previously red-listed, which suggest that tree epidemics cause many unforeseen threats to species. Our analysis shows that epidemic tree deaths represent an insidious, mostly overlooked, threat to sessile affiliate communities in forested environments. Current conservation and management strategies must account for secondary extinctions associated with epidemic tree death. PMID:23049840

Intracellular calcium release through IP3R or RyR contributes to secondary axonal degeneration.

PubMed

Orem, Ben C; Pelisch, Nicolas; Williams, Joshua; Nally, Jacqueline M; Stirling, David P

2017-10-01

Severed CNS axons often retract or dieback away from the injury site and fail to regenerate. The precise mechanisms underlying acute axonal dieback and secondary axonal degeneration remain poorly understood. Here we investigate the role of Ca 2+ store mediated intra-axonal Ca 2+ release in acute axonal dieback and secondary axonal degeneration. To differentiate between primary (directly transected) and "bystander" axonal injury (axons spared by the initial injury but then succumb to secondary degeneration) in real-time we use our previously published highly focal laser-induced spinal cord injury (LiSCI) ex vivo model. Ascending spinal cord dorsal column axons that express YFP were severed using an 800 nm laser pulse while being imaged continuously using two-photon excitation microscopy. We inhibited two major intra-axonal Ca 2+ store channels, ryanodine receptors (RyR) and IP 3 R, with ryanodine or 2-APB, respectively, to individually determine their role in axonal dieback and secondary axonal degeneration. Each antagonist was dissolved in artificial CSF and applied 1h post-injury alone or in combination, and continuously perfused for the remainder of the imaging session. Initially following LiSCI, transected axons retracted equal distances both distal and proximal to the lesion. However, by 4h after injury, the distal axonal segments that are destined for Wallerian degeneration had significantly retracted further than their proximal counterparts. We also found that targeting either RyR or IP 3 R using pharmacological and genetic approaches significantly reduced proximal axonal dieback and "bystander" secondary degeneration of axons compared to vehicle controls at 6h post-injury. Combined treatment effects on secondary axonal degeneration were similar to either drug in isolation. Together, these results suggest that intra-axonal Ca 2+ store mediated Ca 2+ release through RyR or IP 3 R contributes to secondary axonal degeneration following SCI. Copyright © 2017 Elsevier Inc. All rights reserved.

Isotope signals and anatomical features in tree rings suggest a role for hydraulic strategies in diffuse drought-induced die-back of Pinus nigra.

PubMed

Petrucco, Laura; Nardini, Andrea; von Arx, Georg; Saurer, Matthias; Cherubini, Paolo

2017-04-01

The 2003 and 2012 summer seasons were among the warmest and driest of the last 200 years over southeastern Europe, and in particular in the Karst region (northeastern Italy). Starting from winter-spring 2013, several black pines (Pinus nigra J.F. Arnold) suffered crown die-back. Declining trees occurred nearby individuals with no signs of die-back, raising hypotheses about the occurrence of individual-specific hydraulic strategies underlying different responses to extreme drought. We investigated possible processes driving black pine decline by dendrochronological and wood anatomical measurements, coupled with analysis of tree-ring carbon (δ13C) and oxygen (δ18O) isotopic composition in healthy trees (H) and trees suffering die-back (D). Die-back trees showed higher growth rates than H trees at the beginning of the last century, but suffered important growth reduction following the dry summers in 2003 and 2012. After the 2012 drought, D trees produced tracheids with larger diameter and greater vulnerability to implosion than H ones. Healthy trees had significantly higher wood δ13C than D trees, reflecting higher water-use efficiency for the surviving trees, i.e., less water transpired per unit carbon gain, which could be related to lower stomatal conductance and a more conservative use of water. Relatively high δ18O for D trees indicates that they were strongly dependent on shallow water sources, or that they sustained higher transpiration rates than H trees. Our results suggest that H trees adopted a more conservative water-use strategy under drought stress compared with D trees. We speculate that this diversity might have a genotypic basis, but other possible explanations, like different rooting depth, cannot be ruled out. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

First report of Albizia lebbeck dieback caused by Scytalidium dimidiatum in Oman.

PubMed

Elshafie, Abdulkadir E; Ba-Omar, Taher

2002-01-01

Over 200 Albizia lebbeck trees at Sultan Qaboos University campus wilted and died. The symptoms were dieback of large branches due to infection by Scytalidium dimidiatum. The fungus has also infected Ficus benghalensis, F. carica, F. retusa, Thespesia populnea, Delonix regia and Peltophorum petrocarpum. This is the first report of the fungus in Oman and on A. lebbeck, T. populnea, D. regia and P. petrocarpum. The strain of this fungus has not been found to cause human disease in Oman.

Amazon collapse in the next century: exploring the sensitivity to climate and model formulation uncertainties

NASA Astrophysics Data System (ADS)

Booth, B.; Collins, M.; Harris, G.; Chris, H.; Jones, C.

2007-12-01

A number of recent studies have highlighted the risk of abrupt dieback of the Amazon Rain Forest as the result of climate changes over the next century. The recent 2005 Amazon drought brought wider acceptance of the idea that that climate drivers will play a significant role in future rain forest stability, yet that stability is still subject to considerable degree of uncertainty. We present a study which seeks to explore some of the underlying uncertainties both in the climate drivers of dieback and in the terrestrial land surface formulation used in GCMs. We adopt a perturbed physics approach which forms part of a wider project which is covered in an accompanying abstract submitted to the multi-model ensembles session. We first couple the same interactive land surface model to a number of different versions of the Hadley Centre atmosphere-ocean model that exhibit a wide range of different physical climate responses in the future. The rainforest extent is shown to collapse in all model cases but the timing of the collapse is dependent on the magnitude of the climate drivers. In the second part, we explore uncertainties in the terrestrial land surface model using the perturbed physics ensemble approach, perturbing uncertain parameters which have an important role in the vegetation and soil response. Contrasting the two approaches enables a greater understanding of the relative importance of climatic and land surface model uncertainties in Amazon dieback.

Understanding the drivers of extensive plant damage in boreal and Arctic ecosystems: Insights from field surveys in the aftermath of damage.

PubMed

Bjerke, Jarle W; Treharne, Rachael; Vikhamar-Schuler, Dagrun; Karlsen, Stein R; Ravolainen, Virve; Bokhorst, Stef; Phoenix, Gareth K; Bochenek, Zbigniew; Tømmervik, Hans

2017-12-01

The exact cause of population dieback in nature is often challenging to identify retrospectively. Plant research in northern regions has in recent decades been largely focussed on the opposite trend, namely increasing populations and higher productivity. However, a recent unexpected decline in remotely-sensed estimates of terrestrial Arctic primary productivity suggests that warmer northern lands do not necessarily result in higher productivity. As large-scale plant dieback may become more frequent at high northern latitudes with increasing frequency of extreme events, understanding the drivers of plant dieback is especially urgent. Here, we report on recent extensive damage to dominant, short, perennial heath and tundra plant populations in boreal and Arctic Norway, and assess the potential drivers of this damage. In the High-Arctic archipelago of Svalbard, we recorded that 8-50% of Cassiope tetragona and Dryas octopetala shoots were dead, and that the ratios of dead shoots increased from 2014 to 2015. In boreal Norway, 38-63% of Calluna vulgaris shoots were dead, while Vaccinium myrtillus had damage to 91% of shoots in forested sites, but was healthy in non-forested sites. Analyses of numerous sources of environmental information clearly point towards a winter climate-related reason for damage to three of these four species. In Svalbard, the winters of 2011/12 and 2014/15 were documented to be unusually severe, i.e. insulation from ambient temperature fluctuation by snow was largely absent, and ground-ice enforced additional stress. In boreal Norway, the 2013/14 winter had a long period with very little snow combined with extremely low precipitation rates, something which resulted in frost drought of uncovered Calluna plants. However, extensive outbreaks of a leaf-defoliating geometrid moth were identified as the driver of Vaccinium mortality. These results suggest that weather and biotic extreme events potentially have strong impacts on the vegetation state of northern lands. Copyright © 2017 Elsevier B.V. All rights reserved.

Monitoring Spatial Variability and Temporal Dynamics of Phragmites Using Unmanned Aerial Vehicles

PubMed Central

Tóth, Viktor R.

2018-01-01

Littoral zones of freshwater lakes are exposed to environmental impacts from both terrestrial and aquatic sides, while substantial anthropogenic pressure also affects the high spatial, and temporal variability of the ecotone. In this study, the possibility of monitoring seasonal and spatial changes in reed (Phragmites australis) stands using an unmanned aerial vehicle (UAV) based remote sensing technique was examined. Stands in eutrophic and mesotrophic parts of Lake Balaton including not deteriorating (stable) and deteriorating (die-back) patches, were tracked throughout the growing season using a UAV equipped with a Normalized Difference Vegetation Index (NDVI) camera. Photophysiological parameters of P. australis were also measured with amplitude modulated fluorescence. Parameters characterizing the dynamics of seasonal changes in NDVI data were used for phenological comparison of eutrophic and mesotrophic, stable and die-back, terrestrial and aquatic, mowed and not-mowed patches of reed. It was shown that stable Phragmites plants from the eutrophic part of the lake reached specific phenological stages up to 3.5 days earlier than plants from the mesotrophic part of the lake. The phenological changes correlated with trophic (total and nitrate-nitrite nitrogen) and physical (organic C and clay content) properties of the sediment, while only minor relationships with air and water temperature were found. Phenological differences between the stable and die-back stands were even more pronounced, with ~34% higher rates of NDVI increase in stable than die-back patches, while the period of NDVI increase was 16 days longer. Aquatic and terrestrial parts of reed stands showed no phenological differences, although intermediate areas (shallow water parts of stands) were found to be less vigorous. Winter mowing of dried Phragmites sped up sprouting and growth of reed in the spring. This study showed that remote sensing-derived photophysiological and phenological variability within and between reed stands may provide valuable early indicators of environmental stress. The flexibility of the method makes it usable for mapping fine-scale temporal variability and spatial zonation within a stand, revealing ecophysiological hotspots that might require particular attention, and obtaining information vital for conservation and management of plants in the littoral zones. PMID:29915608

Widespread Dieback of Forests in North America under Rapid Global Warming: Response to the VINCERA Future Climate Scenarios Simulated by the MC1 DGVM

NASA Astrophysics Data System (ADS)

Lenihan, J.; Neilson, R.; Bachelet, D.; Drapek, R.

2005-12-01

The VINCERA project is an intercomparison among three dynamic general vegetation models (DGVMs) simulating the response of North American ecosystems to six new future climate scenarios. The scenarios were produced by three general circulation models, each using two different future trace gas emissions scenarios. All of the scenarios are near the warmer end of the Intergovernmental Panel on Climate Change's projected future temperature range. Here we present results from the MC1 DGVM. All major forested ecosystems in North America exhibit carbon sequestration until the late 20th or early 21st century, followed by a drought induced decline and loss of carbon to levels below those at 1900 in the absence of fire suppression. By the end of the 21st century, the entire continent will have lost from 10 to 30 Pg of carbon, depending on the scenario. However, fire suppression can significantly mitigate carbon losses and ecosystem declines, producing a net change in carbon from a loss of about 5 Pg to a gain of about 8 Pg under the different scenarios. Most of the suppression benefits are obtained by forests in the western U.S. Suppression also mitigates carbon losses and conversions to savanna or grassland in the eastern U.S., but forest decline still occurs in the east under all scenarios. Dieback is triggered by two mechanisms. Reduced regional precipitation, variable among the scenarios, is one. The second more pervasive mechanism is the influence of rising temperatures on evapotranspiration. Even with the benefits of enhanced water use efficiency from elevated CO2 and slight increases in precipitation, dramatic increases in temperature can produce widespread forest dieback, and increases in fire severity. The eastern United States appear to be particularly vulnerable, as does the central Canadian boreal forest because of the relative flatness of climate gradients near ecotones. Under some scenarios, dieback is also driven by both increasing temperatures and decreasing precipitation, most notably the southeastern and northwestern United States. Following a period of gradual carbon sequestration, the enhanced evapotranspiration appears to overtake the 'greening' processes producing a rapid dieback. The point of turnaround from greenup to dieback occurs about now for the temperate forests and about a decade from now in the boreal forests, initiating an extended period of rapid losses of ecosystem carbon. These results underscore the critical importance of addressing uncertainties with respect to ecosystem water balance and the direct effects of elevated CO2 concentrations.

Satellite Image Mapping of Tree Mortality in the Sierra Nevada Region of California from 2013 to 2016

NASA Technical Reports Server (NTRS)

Potter, Christopher S.

2017-01-01

Extreme drought from 2013 to 2015 has been linked to extensive tree dieback in the Sierra-Nevada region of California. Landsat satellite imagery was analysed for the region from Lake Tahoe to the southern Sequoia National Forest with the objective of understanding the patterns of tree mortality in the years of 2013 to 2015 and into the near-normal precipitation year of 2016. The main mapping results for Landsat moisture index differences from year-to-year showed that the highest coverage of tree dieback was located in the Sierra and Sequoia National Forests, at four to five times greater area each year than within any other National Park or National Forest unit. Since 2013, over 50% of the Sierra Nevada forest dieback area was detected in the mid elevation zone of 1000-2000 m. The total area of tree mortality in the lower elevation zone of 500-1000 m did not grow notably from 2015 to 2016. Within the largest California river drainages in the Sierra region, new tree mortality in 2015 was detected mainly below 1200 m elevation, whereas new tree mortality in 2016 was detected mainly at higher elevations, up to about 2200 m. In three out of the four years studied, results showed that about 60% of all new tree mortality areas were located on north-facing hill slopes.

Phylogeny and pathogenicity of Lasiodiplodia species associated with dieback of mango in Peru.

PubMed

Rodríguez-Gálvez, Edgar; Guerrero, Pakita; Barradas, Carla; Crous, Pedro W; Alves, Artur

2017-04-01

Mango, which is an important tropical fruit crop in the region of Piura (Peru), is known to be prone to a range of diseases caused by Lasiodiplodia spp. The aim of this study was to evaluate the incidence and prevalence of mango dieback in the region of Piura, and to identify the species of Lasiodiplodia associated with the disease and evaluate their pathogenicity towards mango. Mango dieback was present in all orchards surveyed but incidence varied with location. Identification of fungal isolates was based on morphological and cultural characteristics as well as sequence data of the rDNA internal transcribed spacer region (ITS) and translation elongation factor 1-alpha gene (tef1-α). The following Lasiodiplodia species were identified: Lasiodiplodia brasiliense, Lasiodiplodia egyptiacae (for which the new combination Lasiodiplodia laeliocattleyae is introduced), Lasiodiplodia iraniensis, Lasiodiplodia pseudotheobromae, Lasiodiplodia theobromae, and a Lasiodiplodia sp. Individual and combined gene genealogies suggest that this Lasiodiplodia sp. is possibly a hybrid of Lasiodiplodia citricola and Lasiodiplodia parva. Apart from Lasiodiplodia theobromae, which was the most prevalent species, all other species are newly reported from Peru. Moreover, L. iraniensis is reported for the first time on mango. Inoculation trials of mango plants confirmed Koch's postulates, and revealed differences in aggressiveness among species and isolates. Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Are Scots pine forest edges particularly prone to drought-induced mortality?

NASA Astrophysics Data System (ADS)

Buras, Allan; Schunk, Christian; Zeiträg, Claudia; Herrmann, Corinna; Kaiser, Laura; Lemme, Hannes; Straub, Christoph; Taeger, Steffen; Gößwein, Sebastian; Klemmt, Hans-Joachim; Menzel, Annette

2018-02-01

Climate change is expected to exacerbate the frequency of drought-induced tree mortality world-wide. To better predict the associated change of species composition and forest dynamics on various scales and develop adequate adaptation strategies, more information on the mechanisms driving the often observed patchiness of tree die-back is needed. Although forest-edge effects may play an important role within the given context, only few corresponding studies exist. Here, we investigate the regional die-back of Scots pine in Franconia, Germany, after a hot and dry summer in 2015, thereby emphasizing possible differences in mortality between forest edge and interior. By means of dendroecological investigations and close-range remote sensing, we assess long-term growth performance and current tree vitality along five different forest-edge distance gradients. Our results clearly indicate a differing growth performance between edge and interior trees, associated with a higher vulnerability to drought, increased mortality rates, and lower tree vitality at the forest edge. Prior long-lasting growth decline of dead trees compared to live trees suggests depletion of carbon reserves in course of a long-term drought persisting since the 1990s to be the cause of regional Scots pine die-back. These findings highlight the forest edge as a potential focal point of forest management adaptation strategies in the context of drought-induced mortality.

The potential influence of the annual invasive plant, Impatiens glandulifera (Himalayan Balsam), on the hydro-geomorphic functioning of inland river systems

NASA Astrophysics Data System (ADS)

Kuhn, N. J.; Greenwood, P.; Fister, W.

2014-12-01

The invasive plant, Impatiens glandulifera (Himalayan Balsam), is now found in most European countries, as well as across large parts of North America and on some Australasian islands. It favours damp, nutrient-rich soils that experience frequent natural disturbance, such as riparian zones. Its ability to out-compete native vegetation and tendency to suffer rapid dieback during cold weather has led to speculation that it may promote soil erosion, particularly along riverbanks. Despite the strong implication, its ability to promote erosion has only recently been shown during an investigation over one dieback and regrowth cycle along a small watercourse in northwest Switzerland. This presentation now benefits from additional results covering further dieback and regrowth cycles obtained from the same watercourse as above, and from a different river system in southwest UK. These additional results support the original conclusion that I. glandulifera promotes soil erosion along riverbanks and the riparian zone. Importantly, the equivalent ground surface retreat from each group of contaminated locations over the three dieback and regrowth cycles are comparable with erosion in regions where high magnitude events are often recorded. Given these very high erosion rates, albeit over three monitoring phases, it is hypothesised that I. glandulifera may act as a catalyst for repeat cycles of colonisation, dieback and extreme erosion. Aside from the deleterious effect of large quantities of nutrient-rich sediment entering into watercourses, high magnitude soil loss such as this could result in reach-scale sections of riverbank undergoing profound morphological changes and reduced structural stability. Dynamic modifications such as those could ultimately impede the ability of riverbanks to moderate stream flow and offer flood protection, as well as hamper the capacity of riparian zones to buffer and retain sediment and associated contaminants during their passage from terrestrial to aquatic environments. Given the dearth of effective intervention measures to halt, or even slow, the spread of I. glandulifera, the impact of extreme erosion driven by this invasive plant could eventually affect the ecohydromorphic functioning of whole river systems, thus making their management extremely difficult and complex.

The potential influence of the invasive plant, Impatiens glandulifera (Himalayan Balsam), on the ecohydromorphic functioning of inland river systems

NASA Astrophysics Data System (ADS)

(Phil) Greenwood, Philip; Fister, Wolfgang; Kuhn, Nikolaus

2014-05-01

The invasive plant, Impatiens glandulifera (common English name: Himalayan Balsam), is now found in most temperate European countries, as well as across large parts of North America and on some Australasian islands. As a ruderal species, it favours damp, nutrient-rich soils that experience frequent natural disturbance, such as riparian zones. Its ability to out-compete native vegetation and tendency to suffer rapid dieback during cold weather has led to repeated speculation that it may promote soil erosion, particularly along riverbanks. Despite the strong implication, its ability to promote erosion has only recently been empirically proven during an investigation over one dieback and regrowth cycle along a small watercourse in northwest Switzerland. This presentation now benefits from additional results covering further dieback and regrowth cycles obtained from the same watercourse as above, and from a different river system in southwest UK. These additional results support the original conclusion that I. glandulifera promotes soil erosion along riverbanks and the riparian zone. Importantly, the equivalent ground surface retreat from each group of contaminated locations over the three dieback and regrowth cycles are comparable with erosion in regions where high magnitude events are often recorded. Given these very high erosion rates, albeit over three monitoring phases, it is hypothesised that I. glandulifera may act as a catalyst for repeat cycles of colonisation, dieback and extreme erosion. Aside from the deleterious effect of large quantities of nutrient-rich sediment entering into watercourses, high magnitude soil loss such as this could result in reach-scale sections of riverbank undergoing profound morphological changes and reduced structural stability. Dynamic modifications such as those could ultimately impede the ability of riverbanks to moderate stream flow and offer flood protection, as well as hamper the capacity of riparian zones to buffer and retain sediment and associated contaminants during their passage from terrestrial to aquatic environments. Given the dearth of effective intervention measures to halt, or even slow, the spread of I. glandulifera, the impact of extreme erosion driven by this invasive plant could eventually affect the ecohydromorphic functioning of whole river systems, thus making their management extremely difficult and complex.

Novel Hydraulic Vulnerability Proxies for a Boreal Conifer Species Reveal That Opportunists May Have Lower Survival Prospects under Extreme Climatic Events.

PubMed

Rosner, Sabine; Světlík, Jan; Andreassen, Kjell; Børja, Isabella; Dalsgaard, Lise; Evans, Robert; Luss, Saskia; Tveito, Ole E; Solberg, Svein

2016-01-01

Top dieback in 40-60 years old forest stands of Norway spruce [Picea abies (L.) Karst.] in southern Norway is supposed to be associated with climatic extremes. Our intention was to learn more about the processes related to top dieback and in particular about the plasticity of possible predisposing factors. We aimed at (i) developing proxies for P 50 based on anatomical data assessed by SilviScan technology and (ii) testing these proxies for their plasticity regarding climate, in order to (iii) analyze annual variations of hydraulic proxies of healthy looking trees and trees with top dieback upon their impact on tree survival. At two sites we selected 10 tree pairs, i.e., one healthy looking tree and one tree with visual signs of dieback such as dry tops, needle shortening and needle yellowing (n = 40 trees). Vulnerability to cavitation (P 50) of the main trunk was assessed in a selected sample set (n = 19) and we thereafter applied SilviScan technology to measure cell dimensions (lumen (b) and cell wall thickness (t)) in these specimen and in all 40 trees in tree rings formed between 1990 and 2010. In a first analysis step, we searched for anatomical proxies for P 50. The set of potential proxies included hydraulic lumen diameters and wall reinforcement parameters based on mean, radial, and tangential tracheid diameters. The conduit wall reinforcement based on tangential hydraulic lumen diameters ((t/b ht)(2)) was the best estimate for P 50. It was thus possible to relate climatic extremes to the potential vulnerability of single annual rings. Trees with top dieback had significantly lower (t/b ht)(2) and wider tangential (hydraulic) lumen diameters some years before a period of water deficit (2005-2006). Radial (hydraulic) lumen diameters showed however no significant differences between both tree groups. (t/b ht)(2) was influenced by annual climate variability; strongest correlations were found with precipitation in September of the previous growing season: high precipitation in previous September resulted in more vulnerable annual rings in the next season. The results are discussed with respect to an "opportunistic behavior" and genetic predisposition to drought sensitivity.

Temporal variability in the life history and reproductive biology of female dugongs in Torres Strait: The likely role of sea grass dieback

NASA Astrophysics Data System (ADS)

Marsh, Helene; Kwan, Donna

2008-09-01

The extensive sea grass meadows in Torres Strait enable it to be a globally important habitat for the dugong, Dugong dugon, a marine mammal of cultural and dietary significance to Torres Strait Islanders and the basis for the substantial island-based fishery in the Torres Strait Protected Zone. Torres Strait sea grass communities are subjected to episodic diebacks which are now believed to be largely natural events. Information on dugong life history was obtained from specimens obtained from female dugongs as they were butchered for food by Indigenous hunters at two major dugong hunting communities in Torres Strait: Daru (9.04°S, 143.21°E) in 1978-1982 (a time of sea grass dieback and recovery) and Mabuiag Island (9.95°S, 142.15°E) in 1997-1999 (when sea grasses were abundant). Dugongs sampled in 1997-1999 had their first calf at younger ages (minimum of 6 cf. 10 years), and more frequently (interbirth interval based on all possible pregnancies 2.6±0.4 (S.E.) yr cf. 5.8±1.0 yr) than the dugongs sampled in 1978-1982. Pregnancy rates increased monotonically during 1978-1982, coincident with sea grass recovery. The age distribution of the female dugongs collected in 1997-1999 also suggested a low birth rate between 1973 and 1983 and/or or a high level of mortality for animals born during this period. These results add to the evidence from other regions that the life history and reproductive rate of female dugongs are adversely affected by sea grass loss, the effect of which cannot be separated from a possible density-dependent response to changes in dugong population size. Many green turtles in Torres Strait were also in poor body condition coincident with the 1970s sea grass dieback. The impacts of future sea grass diebacks need to be anticipated when management options for the traditional Torres Strait fisheries for dugongs and green turtles are evaluated.

The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming

NASA Astrophysics Data System (ADS)

Betts, R. A.; Cox, P. M.; Collins, M.; Harris, P. P.; Huntingford, C.; Jones, C. D.

A suite of simulations with the HadCM3LC coupled climate-carbon cycle model is used to examine the various forcings and feedbacks involved in the simulated precipitation decrease and forest dieback. Rising atmospheric CO2 is found to contribute 20% to the precipitation reduction through the physiological forcing of stomatal closure, with 80% of the reduction being seen when stomatal closure was excluded and only radiative forcing by CO2 was included. The forest dieback exerts two positive feedbacks on the precipitation reduction; a biogeophysical feedback through reduced forest cover suppressing local evaporative water recycling, and a biogeochemical feedback through the release of CO2 contributing to an accelerated global warming. The precipitation reduction is enhanced by 20% by the biogeophysical feedback, and 5% by the carbon cycle feedback from the forest dieback. This analysis helps to explain why the Amazonian precipitation reduction simulated by HadCM3LC is more extreme than that simulated in other GCMs; in the fully-coupled, climate-carbon cycle simulation, approximately half of the precipitation reduction in Amazonia is attributable to a combination of physiological forcing and biogeophysical and global carbon cycle feedbacks, which are generally not included in other GCM simulations of future climate change. The analysis also demonstrates the potential contribution of regional-scale climate and ecosystem change to uncertainties in global CO2 and climate change projections. Moreover, the importance of feedbacks suggests that a human-induced increase in forest vulnerability to climate change may have implications for regional and global scale climate sensitivity.

Outbreaks of Yuzu Dieback in Goheung Area: Possible Causes Deduced from Weather Extremes.

PubMed

Kim, Kwang-Hyung; Kim, Gyoung Hee; Son, Kyeong In; Koh, Young Jin

2015-09-01

Starting in 2012, severe diebacks usually accompanied by abundant gum exudation have occurred on yuzu trees in Goheung-gun, Jeonnam Province, where severely affected trees were occasionally killed. On-farm surveys were conducted at 30 randomly-selected orchards located at Pungyang-myeon, Goheung-gun, and the resulting disease incidences were 18.5% and 39.6% for dieback and gumming symptoms, respectively. Black spots on branches and leaves also appeared on infected trees showing a typical dieback symptom. Morphological and molecular identifications of the isolated fungal organisms from lesions on the symptomatic leaves and branches revealed that they are identical to Phomopsis citri, known to cause gummosis. In order to find the reason for this sudden epidemic, we investigated the weather conditions that are exclusively distinct from previous years, hypothesizing that certain weather extremes might have caused the severe induction of pre-existing disease for yuzu. There were two extreme temperature drops beyond the yuzu's cold hardiness limit right after an abnormally-warm-temperature-rise during the winter of 2011-12, which could cause severe frost damage resulting in mechanical injuries and physiological weakness to the affected trees. Furthermore, there was an increased frequency of strong wind events, seven times in 2012 compared to only a few times in the previous years, that could also lead to extensive injuries on branches. In conclusion, we estimated that the possible damages by severe frost and frequent strong wind events during 2012 could cause the yuzu trees to be vulnerable to subsequent fungal infection by providing physical entries and increasing plant susceptibility to infections.

Germination and growth of native and invasive plants on soil associated with biological control of tamarisk (Tamarix spp.)

USGS Publications Warehouse

Sherry, Rebecca A.; Shafroth, Patrick B.; Belnap, Jayne; Ostoja, Steven M.; Reed, Sasha C.

2016-01-01

Introductions of biocontrol beetles (tamarisk beetles) are causing dieback of exotic tamarisk in riparian zones across the western United States, yet factors that determine plant communities that follow tamarisk dieback are poorly understood. Tamarisk-dominated soils are generally higher in nutrients, organic matter, and salts than nearby soils, and these soil attributes might influence the trajectory of community change. To assess physical and chemical drivers of plant colonization after beetle-induced tamarisk dieback, we conducted separate germination and growth experiments using soil and litter collected beneath defoliated tamarisk trees. Focal species were two common native (red threeawn, sand dropseed) and two common invasive exotic plants (Russian knapweed, downy brome), planted alone and in combination. Nutrient, salinity, wood chip, and litter manipulations examined how tamarisk litter affects the growth of other species in a context of riparian zone management. Tamarisk litter, tamarisk litter leachate, and fertilization with inorganic nutrients increased growth in all species, but the effect was larger on the exotic plants. Salinity of 4 dS m−1 benefitted Russian knapweed, which also showed the largest positive responses to added nutrients. Litter and wood chips generally delayed and decreased germination; however, a thinner layer of wood chips increased growth slightly. Time to germination was lengthened by most treatments for natives, was not affected in exotic Russian knapweed, and was sometimes decreased in downy brome. Because natives showed only small positive responses to litter and fertilization and large negative responses to competition, Russian knapweed and downy brome are likely to perform better than these two native species following tamarisk dieback.

Can forest dieback and tree death be predicted by prior changes in wood anatomy?

NASA Astrophysics Data System (ADS)

Colangelo, Michele; Julio Camarero, Jesus; De Micco, Veronica; Borghetti, Marco; Gentilesca, Tiziana; Sanchez-Salguero, Raul; Ripullone, Francesco

2017-04-01

Climate warming is expected to amplify drought stress resulting in more intense and widespread dieback episodes and increasing mortality rates. Studies on quantitative wood anatomy and dendrochronology have demonstrated their potential to supply useful information on the causes of tree decline, although this approach is basically observational and retrospective. Moreover, the long-term reconstruction of wood anatomical features, strictly linked to the evolution of xylem anatomy plasticity through time, allow investigating hydraulic adjustments of trees. In this study, we analyzed wood-anatomical variables in two Italian oak forests where recent episodes of dieback and mortality have been reported. We analyzed in coexisting now-dead and living trees the following wood-anatomical variables: annual tree-ring area, earlywood (EW) and latewood (LW) areas, absolute and relative (%) areas occupied by vessels in the EW and LW, EW and LW vessel areas, EW and LW vessel density and vessel diameter classification. We also calculated the hydraulic diameter (Dh) for all vessels measured within each ring by weighting individual conduit diameters to correspond to the average Hagen-Poiseuille lumen theoretical hydraulic conductivity for a vessel size. Wood-anatomical analyses showed that declining and dead trees were more sensitive to drought stress compared to non declining trees, indicating different susceptibility to water shortage between trees. Dead trees did not form earlywood vessels with smaller lumen diameter than surviving trees but tended to form wider latewood vessels with a higher percentage of vessel area. We discuss the results and implications focusing on those proved more sensitive to the phenomena of decline and mortality.

Genome sequence and genetic diversity of European ash trees.

PubMed

Sollars, Elizabeth S A; Harper, Andrea L; Kelly, Laura J; Sambles, Christine M; Ramirez-Gonzalez, Ricardo H; Swarbreck, David; Kaithakottil, Gemy; Cooper, Endymion D; Uauy, Cristobal; Havlickova, Lenka; Worswick, Gemma; Studholme, David J; Zohren, Jasmin; Salmon, Deborah L; Clavijo, Bernardo J; Li, Yi; He, Zhesi; Fellgett, Alison; McKinney, Lea Vig; Nielsen, Lene Rostgaard; Douglas, Gerry C; Kjær, Erik Dahl; Downie, J Allan; Boshier, David; Lee, Steve; Clark, Jo; Grant, Murray; Bancroft, Ian; Caccamo, Mario; Buggs, Richard J A

2017-01-12

Ash trees (genus Fraxinus, family Oleaceae) are widespread throughout the Northern Hemisphere, but are being devastated in Europe by the fungus Hymenoscyphus fraxineus, causing ash dieback, and in North America by the herbivorous beetle Agrilus planipennis. Here we sequence the genome of a low-heterozygosity Fraxinus excelsior tree from Gloucestershire, UK, annotating 38,852 protein-coding genes of which 25% appear ash specific when compared with the genomes of ten other plant species. Analyses of paralogous genes suggest a whole-genome duplication shared with olive (Olea europaea, Oleaceae). We also re-sequence 37 F. excelsior trees from Europe, finding evidence for apparent long-term decline in effective population size. Using our reference sequence, we re-analyse association transcriptomic data, yielding improved markers for reduced susceptibility to ash dieback. Surveys of these markers in British populations suggest that reduced susceptibility to ash dieback may be more widespread in Great Britain than in Denmark. We also present evidence that susceptibility of trees to H. fraxineus is associated with their iridoid glycoside levels. This rapid, integrated, multidisciplinary research response to an emerging health threat in a non-model organism opens the way for mitigation of the epidemic.

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.

Compensatory axon sprouting for very slow axonal die-back in a transgenic model of spinal muscular atrophy type III.

PubMed

Udina, Esther; Putman, Charles T; Harris, Luke R; Tyreman, Neil; Cook, Victoria E; Gordon, Tessa

2017-03-01

Smn +/- transgenic mouse is a model of the mildest form of spinal muscular atrophy. Although there is a loss of spinal motoneurons in 11-month-old animals, muscular force is maintained. This maintained muscular force is mediated by reinnervation of the denervated fibres by surviving motoneurons. The spinal motoneurons in these animals do not show an increased susceptibility to death after nerve injury and they retain their regenerative capacity. We conclude that the hypothesized immaturity of the neuromuscular system in this model cannot explain the loss of motoneurons by systematic die-back. Spinal muscular atrophy (SMA) is a common autosomal recessive disorder in humans and is the leading genetic cause of infantile death. Patients lack the SMN1 gene with the severity of the disease depending on the number of copies of the highly homologous SMN2 gene. Although motoneuron death in the Smn +/- transgenic mouse model of the mildest form of SMA, SMA type III, has been reported, we have used retrograde tracing of sciatic and femoral motoneurons in the hindlimb with recording of muscle and motor unit isometric forces to count the number of motoneurons with intact neuromuscular connections. Thereby, we investigated whether incomplete maturation of the neuromuscular system induced by survival motoneuron protein (SMN) defects is responsible for die-back of axons relative to survival of motoneurons. First, a reduction of ∼30% of backlabelled motoneurons began relatively late, at 11 months of age, with a significant loss of 19% at 7 months. Motor axon die-back was affirmed by motor unit number estimation. Loss of functional motor units was fully compensated by axonal sprouting to retain normal contractile force in four hindlimb muscles (three fast-twitch and one slow-twitch) innervated by branches of the sciatic nerve. Second, our evaluation of whether axotomy of motoneurons in the adult Smn +/- transgenic mouse increases their susceptibility to cell death demonstrated that all the motoneurons survived and they sustained their capacity to regenerate their nerve fibres. It is concluded the systematic die-back of motoneurons that innervate both fast- and slow-twitch muscle fibres is not related to immaturity of the neuromuscular system in SMA. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Novel Hydraulic Vulnerability Proxies for a Boreal Conifer Species Reveal That Opportunists May Have Lower Survival Prospects under Extreme Climatic Events

PubMed Central

Rosner, Sabine; Světlík, Jan; Andreassen, Kjell; Børja, Isabella; Dalsgaard, Lise; Evans, Robert; Luss, Saskia; Tveito, Ole E.; Solberg, Svein

2016-01-01

Top dieback in 40–60 years old forest stands of Norway spruce [Picea abies (L.) Karst.] in southern Norway is supposed to be associated with climatic extremes. Our intention was to learn more about the processes related to top dieback and in particular about the plasticity of possible predisposing factors. We aimed at (i) developing proxies for P50 based on anatomical data assessed by SilviScan technology and (ii) testing these proxies for their plasticity regarding climate, in order to (iii) analyze annual variations of hydraulic proxies of healthy looking trees and trees with top dieback upon their impact on tree survival. At two sites we selected 10 tree pairs, i.e., one healthy looking tree and one tree with visual signs of dieback such as dry tops, needle shortening and needle yellowing (n = 40 trees). Vulnerability to cavitation (P50) of the main trunk was assessed in a selected sample set (n = 19) and we thereafter applied SilviScan technology to measure cell dimensions (lumen (b) and cell wall thickness (t)) in these specimen and in all 40 trees in tree rings formed between 1990 and 2010. In a first analysis step, we searched for anatomical proxies for P50. The set of potential proxies included hydraulic lumen diameters and wall reinforcement parameters based on mean, radial, and tangential tracheid diameters. The conduit wall reinforcement based on tangential hydraulic lumen diameters ((t/bht)2) was the best estimate for P50. It was thus possible to relate climatic extremes to the potential vulnerability of single annual rings. Trees with top dieback had significantly lower (t/bht)2 and wider tangential (hydraulic) lumen diameters some years before a period of water deficit (2005–2006). Radial (hydraulic) lumen diameters showed however no significant differences between both tree groups. (t/bht)2 was influenced by annual climate variability; strongest correlations were found with precipitation in September of the previous growing season: high precipitation in previous September resulted in more vulnerable annual rings in the next season. The results are discussed with respect to an “opportunistic behavior” and genetic predisposition to drought sensitivity. PMID:27375672

Extreme weather impacts on tropical mangrove forests in the Eastern Brazil Marine Ecoregion.

PubMed

Servino, Ricardo Nogueira; Gomes, Luiz Eduardo de Oliveira; Bernardino, Angelo Fraga

2018-07-01

Extreme weather events are likely to become more frequent in the 21st century bringing significant impacts to coastal ecosystems. However, the capacity to detect and measure those impacts are still limited, with effects largely unstudied. In June 2016, a hailstorm with wind gusts of over 100 km·h -1 caused an unprecedented mangrove dieback on Eastern Brazil. To quantify the scale of impact and short-term recovery of mangroves (15-mo), we used satellite imagery and field sampling to evaluate changes in forest structure in control and impacted areas after the hailstorm. Satellite imagery revealed mangrove dieback in over 500 ha, corresponding to 29.3% of the total forest area suddenly impacted after the hailstorm. Fifteen months after the hailstorm, some impacted areas show an initial recovery, while others continued to degrade. The El Niño years of 2014-2016 created mild drought conditions in Eastern Brazil. As observed in wetlands of semi-arid regions during the same period, mangrove recovery may have been impaired by continued physiological stress and climate change effects. Economic losses in the study site from typical mangrove ecosystem services including food provision, climate regulation, raw materials and nurseries are estimated to at least US$ 792,624 yr -1 . This is the first evidence of an extreme weather impact on mangroves in Brazil that typically provide unique ecological and economic subsistence to coastal populations. Our results reveal that there is a pressing need for long-term monitoring and climate change adaptation actions for coastal wetlands in Brazil, and to provide broad estimates of ecosystem values associated with these ecosystems given many areas are already experiencing chronic stress from local impacts, drought and high temperatures. Copyright © 2018 Elsevier B.V. All rights reserved.

The effect of Phytophthora ramorum on the physiology and xylem function of young tanoak trees

Treesearch

Elizabeth Stamm; Jennifer Parke

2013-01-01

Tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, C.H. Cannon & S. H. Oh) is highly susceptible to Phytophthora ramorum. Symptoms include stem cankers, shoot dieback, and foliar blight. The mechanism by which P. ramorum kills the trees is not known, however. In this study we aimed to...

The Role of Pest Control Advisers in Preventative Management of Grapevine Trunk Diseases.

PubMed

Hillis, Vicken; Lubell, Mark; Kaplan, Jonathan; Doll, David; Baumgartner, Kendra

2016-04-01

Vineyards with trunk diseases (Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback) can have negative returns in the long run. Minimizing economic impacts depends on effective management, but adopting a preventative practice after infection occurs may not improve yields. Pest control advisers may reduce grower uncertainty about the efficacy of and need for prevention, which often entails future and unobservable benefits. Here, we surveyed advisers in California to examine their influence over grower decision-making, in the context of trunk diseases, which significantly limit grape production and for which curative practices are unavailable. Our online survey revealed adviser awareness of high disease incidence, and reduced yields and vineyard lifespan. Advisers rated both preventative and postinfection practices positively. Despite higher cost estimates given to postinfection practices, advisers did not recommend preventative practices at higher rates. High recommendation rates were instead correlated with high disease incidence for both preventative and postinfection practices. Recommendation rates declined with increasing cost for preventative, but not for postinfection, practices. Our findings suggest that even when advisers acknowledge the risks of trunk diseases, they may not recommend preventative practices before infection occurs. This underscores the importance of clear outreach, emphasizing both the need for prevention and its long-term cost efficacy.

Climate change and the ash dieback crisis

PubMed Central

Goberville, Eric; Hautekèete, Nina-Coralie; Kirby, Richard R.; Piquot, Yves; Luczak, Christophe; Beaugrand, Grégory

2016-01-01

Beyond the direct influence of climate change on species distribution and phenology, indirect effects may also arise from perturbations in species interactions. Infectious diseases are strong biotic forces that can precipitate population declines and lead to biodiversity loss. It has been shown in forest ecosystems worldwide that at least 10% of trees are vulnerable to extinction and pathogens are increasingly implicated. In Europe, the emerging ash dieback disease caused by the fungus Hymenoscyphus fraxineus, commonly called Chalara fraxinea, is causing a severe mortality of common ash trees (Fraxinus excelsior); this is raising concerns for the persistence of this widespread tree, which is both a key component of forest ecosystems and economically important for timber production. Here, we show how the pathogen and climate change may interact to affect the future spatial distribution of the common ash. Using two presence-only models, seven General Circulation Models and four emission scenarios, we show that climate change, by affecting the host and the pathogen separately, may uncouple their spatial distribution to create a mismatch in species interaction and so a lowering of disease transmission. Consequently, as climate change expands the ranges of both species polewards it may alleviate the ash dieback crisis in southern and occidental regions at the same time. PMID:27739483

Developing publicly acceptable tree health policy: public perceptions of tree-breeding solutions to ash dieback among interested publics in the UK.

PubMed

Jepson, Paul R; Arakelyan, Irina

2017-07-01

The UK needs to develop effective policy responses to the spread of tree pathogens and pests. This has been given the political urgency following the media and other commentary associated with the arrival of a disease that causes 'dieback' of European Ash ( Fraxinus excelsior ) - a tree species with deep cultural associations. In 2014 the UK government published a plant biosecurity strategy and linked to this invested in research to inform policy. This paper reports the findings of a survey of informed UK publics on the acceptability of various potential strategies to deal with ash dieback, including "no action". During the summer of 2015, we conducted a face-to-face survey of 1152 respondents attending three major countryside events that attract distinct publics interested in the countryside: landowners & land managers; naturalists and gardeners. We found that UK publics who are likely to engage discursively and politically (through letter writing, petitions etc.) with the issue of ash dieback a) care about the issue, b) want an active response, c) do not really distinguish between ash trees in forestry or ecological settings, and d) prefer traditional breeding solutions. Further that e) younger people and gardeners are open to GM breeding techniques, but f) the more policy-empowered naturalists are more likely to be anti-GM. We suggest that these findings provide three 'steers' for science and policy: 1) policy needs to include an active intervention component involving the breeding of disease-tolerant trees, 2) that the development of disease tolerance using GM-technologies could be part of a tree-breeding policy, and 3) there is a need for an active dialogue with publics to manage expectations on the extent to which science and policy can control tree disease or, put another way, to build acceptability for the prospect that tree diseases may have to run their course.

Chronic N enrichment and drought alter plant cover and community composition in a Mediterranean-type semi-arid shrubland.

PubMed

Vourlitis, George L

2017-05-01

Anthropogenic nitrogen (N) deposition has caused a decline in native plant species and an increase in exotic plant species in many terrestrial ecosystems; however, vegetation change depends on the rate and/or duration of N input, individual species responses, interactions with other resources, and ecosystem properties such as species richness and canopy cover, soil texture, pH, and/or disturbance regime. Native shrub and exotic forb responses to N enrichment were evaluated over a 13-year field experiment in a mature coastal sage scrub (CSS) shrubland of southern California to test the hypothesis that dry-season N input will cause a decline in native shrubs and an increase in exotic annuals. Nitrogen enrichment caused the dominant native shrubs, Artemisia californica and Salvia mellifera, to respond differently, with A. californica initially increasing with N input but declining thereafter and S. mellifera declining consistently over the 13-year-period. Both species exhibited higher canopy dieback during drought conditions, especially in N plots. Brassica nigra, an exotic annual, invaded N plots significantly more than control plots, but only after 10 years of N addition and a prolonged drought, which increased native shrub canopy dieback. These results indicate a possible synergism between N enrichment and drought on native shrub and exotic forb abundance, which would have important implications for plant diversity in semi-arid shrublands of southwest US that are anticipated to experience an increase in anthropogenic N enrichment and the frequency and duration of drought.

The reconstruction of Lymantria dispar outbreaks by dendrochronological methods in the South Urals

Treesearch

Sergei Kucherov

1991-01-01

Interest in investigating the influence of extreme ecological factors on the radial growth of oak (Quercus robur L.) is bound up with oak dieback in the South Urals during the last decade. Factors contributing to this problem in the study area are hard winter frosts, late spring frosts, and Lymantria dispar L. outbreaks. To...

Geochemical factors promoting die-back gap formation in colonizing patches of Spartina densiflora in an irregularly flooded marsh

NASA Astrophysics Data System (ADS)

Mirlean, Nicolai; Costa, Cesar S. B.

2017-04-01

Circular (RP) and ring-shape (RP) patches of vegetation in intertidal flats have been associated with the radial expansion of tussock growth forms and die-back gap in older central stands, respectively. RP formation has not yet been sufficiently explained. We accomplished a comparative geochemical study of CP and RP structures of Spartina densiflora within a single saltmarsh in a microtidal estuary (<0.5 m). The pore water under these structures demonstrated distinctive physical-chemical properties by marked seasonal changing in water level and salinity. During high-water period dissolved H2S was frequently low in pore waters of S. densiflora structures due to reactive-Fe, which scavenge the sulfide from solution and form solid sulfides. During less flooded-brackish water period, pore water pH goes down below 4 inside the vegetated bordering areas of RP. In these locations the concentration of soluble sulfides dramatically increases up to 140 μM L-1. The high concentration of protons in pore water is the result of solid sulfides atmospheric oxidation to sulfuric acid. High dissolution of H2S, along with the low pH, creates a toxic environment for S. densiflora and die-back central gap formation in RP. CP structure was 5 cm higher in the intertidal than RP but shows frequent presence of a water layer, less severe oxidation of sulfides and limited building-up of toxic condition to plants. Development of S. densiflora RP probably indicates the uplift of sediment by this bioengineer grass and/or periodic lowering of the water surface below a certain critical level.

Know your limits? Climate extremes impact the range of Scots pine in unexpected places

PubMed Central

Julio Camarero, J.; Gazol, Antonio; Sancho-Benages, Santiago; Sangüesa-Barreda, Gabriel

2015-01-01

Background and Aims Although extreme climatic events such as drought are known to modify forest dynamics by triggering tree dieback, the impact of extreme cold events, especially at the low-latitude margin (‘rear edge’) of species distributional ranges, has received little attention. The aim of this study was to examine the impact of one such extreme cold event on a population of Scots pine (Pinus sylvestris) along the species’ European southern rear-edge range limit and to determine how such events can be incorporated into species distribution models (SDMs). Methods A combination of dendrochronology and field observation was used to quantify how an extreme cold event in 2001 in eastern Spain affected growth, needle loss and mortality of Scots pine. Long-term European climatic data sets were used to contextualize the severity of the 2001 event, and an SDM for Scots pine in Europe was used to predict climatic range limits. Key Results The 2001 winter reached record minimum temperatures (equivalent to the maximum European-wide diurnal ranges) and, for trees already stressed by a preceding dry summer and autumn, this caused dieback and large-scale mortality. Needle loss and mortality were particularly evident in south-facing sites, where post-event recovery was greatly reduced. The SDM predicted European Scots pine distribution mainly on the basis of responses to maximum and minimum monthly temperatures, but in comparison with this the observed effects of the 2001 cold event at the southerly edge of the range limit were unforeseen. Conclusions The results suggest that in order to better forecast how anthropogenic climate change might affect future forest distributions, distribution modelling techniques such as SDMs must incorporate climatic extremes. For Scots pine, this study shows that the effects of cold extremes should be included across the entire distribution margin, including the southern ‘rear edge’, in order to avoid biased predictions based solely on warmer climatic scenarios. PMID:26292992

Amazonian forest dieback under climate-carbon cycle projections for the 21st century

NASA Astrophysics Data System (ADS)

Cox, P. M.; Betts, R. A.; Collins, M.; Harris, P. P.; Huntingford, C.; Jones, C. D.

The first GCM climate change projections to include dynamic vegetation and an interactive carbon cycle produced a very significant amplification of global warming over the 21st century. Under the IS92a ``business as usual'' emissions scenario CO2 concentrations reached about 980ppmv by 2100, which is about 280ppmv higher than when these feedbacks were ignored. The major contribution to the increased CO2 arose from reductions in soil carbon because global warming is assumed to accelerate respiration. However, there was also a lesser contribution from an alarming loss of the Amazonian rainforest. This paper describes the phenomenon of Amazonian forest dieback under elevated CO2 in the Hadley Centre climate-carbon cycle model.

Flowering as the Most Highly Sensitive Period of Grapevine (Vitis vinifera L. cv Mourvèdre) to the Botryosphaeria Dieback Agents Neofusicoccum parvum and Diplodia seriata Infection

PubMed Central

Spagnolo, Alessandro; Larignon, Philippe; Magnin-Robert, Maryline; Hovasse, Agnès; Cilindre, Clara; Van Dorsselaer, Alain; Clément, Christophe; Schaeffer-Reiss, Christine; Fontaine, Florence

2014-01-01

Botryosphaeria dieback is a fungal grapevine trunk disease that currently represents a threat for viticulture worldwide because of the important economical losses due to reduced yield of affected plants and their premature death. Neofusicoccum parvum and Diplodia seriata are among the causal agents. Vine green stems were artificially infected with N. parvum or D. seriata at the onset of three different phenological stages (G stage (separated clusters), flowering and veraison). Highest mean lesion lengths were recorded at flowering. Major proteome changes associated to artificial infections during the three different phenological stages were also reported using two dimensional gel electrophoresis (2D)-based analysis. Twenty (G stage), 15 (flowering) and 13 (veraison) differentially expressed protein spots were subjected to nanoLC-MS/MS and a total of 247, 54 and 25 proteins were respectively identified. At flowering, a weaker response to the infection was likely activated as compared to the other stages, and some defense-related proteins were even down regulated (e.g., superoxide dismutase, major latex-like protein, and pathogenesis related protein 10). Globally, the flowering period seemed to represent the period of highest sensitivity of grapevine to Botryosphaeria dieback agent infection, possibly being related to the high metabolic activity in the inflorescences. PMID:24886812

Ecological Relationships between Meloidogyne spartinae and Salt Marsh Grasses in Connecticut

PubMed Central

Elmer, W. H.

2008-01-01

Healthy specimens of selected grasses were collected from salt marshes and grown in the greenhouse. Plants were inoculated with Meloidogyne spartinae to determine the host range of this nematode. After 12 weeks, Spartina alterniflora plants formed root galls in response to infection and increased M. spartinae populations. Spartina patens, Spartina cynosuroides, Juncus gerardii and Distichlis spicata were non-hosts. In order to determine the natural distribution of M. spartinae in dieback areas, S. alterniflora plants were sampled from transects adjacent to dieback areas in Madison, CT, at low tide. Plants were sampled at the top or the creek and at 1-m intervals to the lowest area of plant growth at the low tide water's edge. Five samples were taken over an elevation drop of 90 cm. Two transects were taken each day on 21 June and 5 July 2007, and one transect was taken on 31 October 2007. Meloidogyne spartinae galls per gram root were higher at the higher elevations. In late June and early July 2007, M. spartinae developed more quickly in the higher elevations, perhaps because peat and sediments were drier and warmer away from low tide water levels. The effects of M. spartinae on S. alterniflora and the role of the nematode in marsh decline and dieback in the northeast United States remain to be determined. PMID:19440262

Biogeochemical processes in an urban, restored wetland of San Francisco Bay, California, 2007-2009; methods and data for plant, sediment and water parameters

USGS Publications Warehouse

Windham-Myers, Lisamarie; Marvin-DiPasquale, Mark C.; Agee, Jennifer L.; Kieu, Le H.; Kakouros, Evangelos; Erikson, Li H.; Ward, Kristen

2010-01-01

The restoration of 18 acres of historic tidal marsh at Crissy Field has had great success in terms of public outreach and visibility, but less success in terms of revegetated marsh sustainability. Native cordgrass (Spartina foliosa) has experienced dieback and has failed to recolonize following extended flooding events during unintended periodic closures of its inlet channel, which inhibits daily tidal flushing. We examined the biogeochemical impacts of these impoundment events on plant physiology and on sulfur and mercury chemistry to help the National Park Service land managers determine the relative influence of these inlet closures on marsh function. In this comparative study, we examined key pools of sulfur, mercury, and carbon compounds both during and between closure events. Further, we estimated the net hydrodynamic flux of methylmercury and total mercury to and from the marsh during a 24-hour diurnal cycle. This report documents the methods used and the data generated during the study.

Mississippi and Louisiana Estuarine Areas. Freshwater Diversion to Lake Pontchartrain Basin and Mississippi Sound. Feasibility Study. Volume 4. Public Views and Responses.

DTIC Science & Technology

1984-04-01

looked at carefully. He said he recognized the dieback in the Louisiana marshes because of levee systems and the displacement of fishermen after seeing...noted these systems were created and Ined by great river systems like the Mississippi and Amazon Rivers. - huition to productivity extends far out to

A broad survey of hydraulic and mechanical safety in the xylem of conifers

Treesearch

Pauline S. Bouche; Maximilien Larter; Jean-Christophe Domec; Regis Burlett; Peter Gasson; Steven Jansen; Sylvain Delzon

2014-01-01

Drought-induced forest dieback has been widely reported over the last decades, and the evidence for a direct causal link between survival and hydraulic failure (xylem cavitation) is now well known. Because vulnerability to cavitation is intimately linked to the anatomy of the xylem, the main objective of this study was to better understand the xylem anatomical...

From detection monitoring to evaluation monitoring - a case study involving crown dieback in northern white-cedar

Treesearch

KaDonna Randolph; William Bechtold; Randall Morin; Stanley Zarnoch

2009-01-01

The Forest Inventory and Analysis (FIA) Phase 3 plot network is a crucial part of the U.S. Forest Health Monitoring program's detection monitoring system, where select indicators are monitored for signals that may indicate deteriorating forest health. When a negative signal is identified, evaluation monitoring provides a mechanism whereby a potential problem can...

Patterns of northern red oak growth and mortality in western Pennsylvania

Treesearch

J. R. McClenahen; R. J. Hutnik; D. D. Davis

1997-01-01

This study evaluates the extent and cause(s) of an observed decline of northern red oak (Quercus rubra L.) on a 50-km portion of a major anticlinal ridge in west central Pennsylvania, and illustrates an approach for evaluating tree declines. Long term annual observations of forest health revealed the onset of crown dieback in 1983, chiefly among red...

European Ash (Fraxinus excelsior L.) dieback: Disintegrating forest in the mountain protected areas, Czech Republic

Treesearch

Stanislav Vacek; Zdenek Vacek; Daniel Bulusek; Tereza Putalova; Murat Sarginci; Otakar Schwarz; Petr Srutka; Vilem Podrazsky; W. Keith Moser

2015-01-01

European ash (Fraxinus excelsior) is an important tree species in most temperate forests in Europe. Its future is threatened however, especially by an invasive fungus, Hymenoscyphus fraxineus (Hymenoscyphus pseudoalbidus, Chalara fraxinea). The current study is focused on the health of ash in the Krkonoše Mountains National Park, Czech Republic. On permanent...

Effect of simulated insect damage on growth and survival of northern red oak (Quercus rubra L.) seedlings

Treesearch

Susan L. Wright; Richard W. Hall; John W. Peacock

1989-01-01

Effects of simulated insect damage—artificial defoliation and root damage in combination with two levels of watering—were studied to determine the potential effect on northern red oak seedlings (Quercus rubra L.). Treatments and treatment combinations caused significant differences in stem diameter, percentage of stem dieback, and mortality....

Friend or foe? Biological and ecological traits of the European ash dieback pathogen Hymenoscyphus fraxineus in its native environment

NASA Astrophysics Data System (ADS)

Cleary, Michelle; Nguyen, Diem; Marčiulynienė, Diana; Berlin, Anna; Vasaitis, Rimvys; Stenlid, Jan

2016-02-01

Hymenoscyphus fraxineus, an introduced ascomycete fungus and primary causal agent of European ash dieback, was investigated on Fraxinus mandshurica trees in its native range in Primorye region of Far East Russia. This evidence is the first report of H. fraxineus on healthy, asymptomatic F. mandshurica trees. High-throughput sequencing revealed 49 distinct fungal taxa associated with leaves of F. mandshurica, 12 of which were identified to species level. Phyllosphere fungal assemblages were similar among sites despite being largely geographically distant. Many organisms comprising the foliar fungal community on F. mandshurica in Far East Russia have similarity to those reported inhabiting F. excelsior in Europe based on previous studies. However, Mycosphaerella sp., the most dominant species in this study and detected in nearly all samples, was associated only with F. mandshurica. Genetic diversity of H. fraxineus was significantly higher in the Far East Russian population than in Europe. In contrast to its aggressive behaviour on Fraxinus excelsior in Europe, H. fraxineus appears to be a benign associate of indigenous F. mandshurica that initially induces quiescent and asymptomatic infections in healthy trees prior to active host colonization normally associated with modification of host tissue during senescence.

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

Durako, M.J.; Carlson, P.R.; Barber, T.R.

The study was conducted to (1) quantify the successional dynamics of seagrass beds experiencing active die-back, and (2) to determine the capacity of healthy and diseased Thalassia to avoid hypoxic stress and sulfide toxicity. A general trend towards recolonization, at the individual patch level was observed. However, basin level observation of frequency of occurrence, abundance, and density revealed that recovery of Thalassia in the most severely affected basin (Rankin Lake) was being outstripped by rapid recolonization of the pioneering species, Halodule wrightii. Measurements of oxygen transport rates through healthy and diseased shoots indicated that the higher porosity of sick shootsmore » is offset by lower conductance. As a result, sick Thalassia may be less able to supply oxygen to their belowground tissue, and this deficiency may contribute to the die-back phenomenon. In an attempt to assess the susceptibility of Thalassia to sediment sulfide toxicity, a series of transplant studies were conducted using both seedlings and apical rhizome segments with at least three short-shoots. Overall poor survival of transplant material indicated that Thalassia does not have the vigor of a pioneer species like Halodules. Rather, as a climax species, it is much more easily disrupted.« less

Gene flow of common ash (Fraxinus excelsior L.) in a fragmented landscape.

PubMed

Semizer-Cuming, Devrim; Kjær, Erik Dahl; Finkeldey, Reiner

2017-01-01

Gene flow dynamics of common ash (Fraxinus excelsior L.) is affected by several human activities in Central Europe, including habitat fragmentation, agroforestry expansion, controlled and uncontrolled transfer of reproductive material, and a recently introduced emerging infectious disease, ash dieback, caused by Hymenoscyphus fraxineus. Habitat fragmentation may alter genetic connectivity and effective population size, leading to loss of genetic diversity and increased inbreeding in ash populations. Gene flow from cultivated trees in landscapes close to their native counterparts may also influence the adaptability of future generations. The devastating effects of ash dieback have already been observed in both natural and managed populations in continental Europe. However, potential long-term effects of genetic bottlenecks depend on gene flow across fragmented landscapes. For this reason, we studied the genetic connectivity of ash trees in an isolated forest patch of a fragmented landscape in Rösenbeck, Germany. We applied two approaches to parentage analysis to estimate gene flow patterns at the study site. We specifically investigated the presence of background pollination at the landscape level and the degree of genetic isolation between native and cultivated trees. Local meteorological data was utilized to understand the effect of wind on the pollen and seed dispersal patterns. Gender information of the adult trees was considered for calculating the dispersal distances. We found that the majority of the studied seeds (55-64%) and seedlings (75-98%) in the forest patch were fathered and mothered by the trees within the same patch. However, we determined a considerable amount of pollen flow (26-45%) from outside of the study site, representing background pollination at the landscape level. Limited pollen flow was observed from neighbouring cultivated trees (2%). Both pollen and seeds were dispersed in all directions in accordance with the local wind directions. Whereas there was no positive correlation between pollen dispersal distance and wind speed, the correlation between seed dispersal distance and wind speed was significant (0.71, p < 0.001), indicating that strong wind favours long-distance dispersal of ash seeds. Finally, we discussed the implications of establishing gene conservation stands and the use of enrichment planting in the face of ash dieback.

Gene flow of common ash (Fraxinus excelsior L.) in a fragmented landscape

PubMed Central

Kjær, Erik Dahl; Finkeldey, Reiner

2017-01-01

Gene flow dynamics of common ash (Fraxinus excelsior L.) is affected by several human activities in Central Europe, including habitat fragmentation, agroforestry expansion, controlled and uncontrolled transfer of reproductive material, and a recently introduced emerging infectious disease, ash dieback, caused by Hymenoscyphus fraxineus. Habitat fragmentation may alter genetic connectivity and effective population size, leading to loss of genetic diversity and increased inbreeding in ash populations. Gene flow from cultivated trees in landscapes close to their native counterparts may also influence the adaptability of future generations. The devastating effects of ash dieback have already been observed in both natural and managed populations in continental Europe. However, potential long-term effects of genetic bottlenecks depend on gene flow across fragmented landscapes. For this reason, we studied the genetic connectivity of ash trees in an isolated forest patch of a fragmented landscape in Rösenbeck, Germany. We applied two approaches to parentage analysis to estimate gene flow patterns at the study site. We specifically investigated the presence of background pollination at the landscape level and the degree of genetic isolation between native and cultivated trees. Local meteorological data was utilized to understand the effect of wind on the pollen and seed dispersal patterns. Gender information of the adult trees was considered for calculating the dispersal distances. We found that the majority of the studied seeds (55–64%) and seedlings (75–98%) in the forest patch were fathered and mothered by the trees within the same patch. However, we determined a considerable amount of pollen flow (26–45%) from outside of the study site, representing background pollination at the landscape level. Limited pollen flow was observed from neighbouring cultivated trees (2%). Both pollen and seeds were dispersed in all directions in accordance with the local wind directions. Whereas there was no positive correlation between pollen dispersal distance and wind speed, the correlation between seed dispersal distance and wind speed was significant (0.71, p < 0.001), indicating that strong wind favours long-distance dispersal of ash seeds. Finally, we discussed the implications of establishing gene conservation stands and the use of enrichment planting in the face of ash dieback. PMID:29053740

Foliicolous fungi from Arctostaphylos pungens in Mexico.

PubMed

Moreno-Rico, Onésimo; Groenewald, Johannes Z; Crous, Pedro W

2014-06-01

Arctostaphylos pungens "Manzanita" is an important shrub in the southwestern USA, and northern and central Mexico. Manzanita bears apple-like fruit that is utilised for a range of edible products. Over the past two years, several foliar disease problems were noted on this host in the San José de Gracia region of Mexico. The aim of the present study was to elucidate their identity through the analysis of morphological characters and DNA phylogeny (based on the large subunit nuclear ribosomal RNA gene and the ITS spacers and the intervening 5.8S rRNA gene of the nrDNA operon) of the fungi associated with these disease symptoms. Three species are newly described: Phaeococcomyces mexicanus sp. nov., a presumed epiphyte, and two species associated with leaf spots and defoliation, namely Coccomyces arctostaphyloides sp. nov. and Passalora arctostaphyli sp. nov. A fourth species is also associated with leaf spots and tip dieback is Harknessia arctostaphyli, for which an epitype is designated. All species can co-occur on the same shrub, which adds to the stress experienced by the plant, leading to further defoliation and dieback.

Effect of drought and defoliation on the susceptibility of eucalypts to cankers caused by Endothia gyrosa and Botryosphaeria ribis

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

Old, K.M.; Gibbs, R.; Craig, I.

1990-01-01

Seedlings, saplings and mature eucalypts were susceptible to infection by Endothia gyrosa and Botryosphaeria ribis. Eucalyptus regnans and E. delegatensis were more susceptible than E. grandis and E. saligna. In trees not subjected to stress, cankers were limited in extent and often healed. When trees were defoliated, either manually or by severe insect attack, stem concentrations of both starch and soluble carbohydrates were reduced and canker development in some pathogen/host combinations was increased. Seedlings subjected to water stress were not predisposed to canker formation. The association of E. gyrosa with branch dieback of rural eucalypts suffering from chronic defoliation suggestsmore » that canker fungi contribute to the crown dieback syndrome in south-eastern Australia.« less

Are Scots pine forest edges particularly prone to drought-stress?

NASA Astrophysics Data System (ADS)

Buras, Allan; Schunk, Christian; Taeger, Steffen; Lemme, Hannes; Gößwein, Sebastian; Menzel, Annette

2017-04-01

In 2016, Scots pine (Pinus sylvestris L.) forests experienced a pronounced dieback in several regions across Germany. Being an economically important tree species, a thorough identification of the reasons for this dieback is of high interest. The dieback is likely to be associated with a record drought event which occurred in summer 2015. However, visual observations indicate that forest edges were particularly affected. This observation is supported by a study from Sweden which showed that Scots pine trees growing at a north-facing forest edge expressed a higher water use if compared to trees from the interior (Cienciala et al., 2002). We therefore hypothesize that Scots pine trees are more prone to drought-stress induced dieback when growing at the forest edge. To test this hypothesis, we investigated the growth performance of Scots pine across three affected stands in Franconia, southern Germany. The stands were selected to represent differing conditions along a gradient of forest fragmentation, ranging from the forest interior, over a forest edge situation, to a small forest island. By means of dendroclimatology and UAV-borne remote sensing, Scots pine growth performance and vitality was compared among the three stands. Our results revealed differing Scots pine growth reactions between the forest interior and forest edge as indicated by the identification of different responder groups (Buras et al., 2016). The forest edge and the forest island expressed significantly higher correlations with the drought-index SPEI (Vicente-Serrano et al., 2009) if compared to the forest interior. Moreover, NDVI of Scots Pine canopies significantly decreased towards the forest edge, this indicating lower vitality of corresponding trees. In conclusion, our results highlight Scots pine to be more prone to drought-stress when growing at the forest edge. This finding has important implications for forest management activities in the context of climate change adaptation, since foresters may need to revise concepts of Scots pine management at forest edges and in forest islands under an increasingly warmer and drier climate. 1. Cienciala, E. et al. The effect of a north-facing forest edge on tree water use in a boreal Scots pine stand. Can. J. For. Res. 32, 693-702 (2002). 2. Buras, A. et al. Tuning the Voices of a Choir: Detecting Ecological Gradients in Time-Series Populations. PLOS ONE 11, e0158346 (2016). 3. Vicente-Serrano, S. M., Beguería, S. & López-Moreno, J. I. A Multiscalar Drought Index Sensitive to Global Warming: The Standardized Precipitation Evapotranspiration Index. J. Climate 23, 1696-1718 (2009).

A remote sensing-assisted risk rating study to predict oak decline and recovery in the Missouri Ozark Highlands, USA

Treesearch

Cuizhen Wang; Hong S. He; John M. Kabrick

2008-01-01

Forests in the Ozark Highlands underwent widespread oak decline affected by severe droughts in 1999-2000. In this study, the differential normalized difference water index was calculated to detect crown dieback. A multi-factor risk rating system was built to map risk levels of stands. As a quick response to drought, decline in 2000 mostly occurred in stands at low to...

The effects of pruning treatments and initial seedling morphology on northern red oak seedling growth

Treesearch

Donald J. Kaczmarek; Phillip E. Pope

1993-01-01

Northern red oak (Quercus rubra L.) seedlings exhibit relatively high survival rates following planting, but their growth rates are often slow and extensive stem dieback can occur. This study was designed to investigate the growth responses of northern red oak seedlings planted with or without root-pruning or shoot-pruning. One-year-old (1-0) northern red oak nursery...

Biology of Leptoypha hospita (Hemiptera: Tingidae), a Potential Biological Control Agent of Chinese Privet

Treesearch

Yanzhuo Zhang; James L. Hanula; Scott Horn; Kristine Braman; Jianghua Sun

2011-01-01

The biology of Leptoypha hospita Drake et Poor (Hemiptera: Tingidae), a potential biological control agent from China for Chinese privet, Ligustrum sinense Lour., was studied in quarantine in the United States. Both nymphs and adults feed on Chinese privet mesophyll cells that lead to a bleached appearance of leaves and dieback of branch tips. L. hospita has five...

Reexamination of effects of paraformaldehyde on tissues around tapholes in sugar maple trees

Treesearch

David R. Houston; J. Chris Fagan

1997-01-01

Pellets containing paraformaldehyde (PFA) are sometimes placed behind spouts in tapped sugar maples to prolong sapflow and increase the yield of sap used to make maple syrup.The practice is controversial because the chemical has been shown to promote decay and is reported to cause cambial dieback around tapholes.This study reexamined the effects of PFA on tapped sugar...

Forest Health Monitoring in Pennsylvania 1998-1999

Treesearch

Northeastern Research Station

2002-01-01

Pennsylvania has mature forests dominated by hardwood species. Red maple was common in all size classes. Most trees are healthy, with full crowns (low transparency, high density), little dieback, and little damage.

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.

Carbon isotope discrimination and water stress in trembling aspen following variable retention harvesting.

PubMed

Bladon, Kevin D; Silins, Uldis; Landhäusser, Simon M; Messier, Christian; Lieffers, Victor J

2007-07-01

Variable retention harvesting (VRH) has been proposed as a silvicultural practice to maintain biodiversity and ecosystem integrity. No previous study has examined tree carbon isotope discrimination to provide insights into water stress that could lead to dieback and mortality of trees following VRH. We measured and compared the carbon isotope ratios (delta(13)C) in stem wood of trembling aspen (Populus tremuloides Michx.) before and after VRH. Eight trees were sampled from isolated residual, edge and control (interior of unharvested stand) positions from each of seven plots in three regions (Calling Lake and Drayton Valley, Alberta and Lac Duparquet, Québec). After VRH, the general trend in mean delta(13)C was residual > edge > control trees. Although this trend is indicative of water stress in residual trees, it also suggests that edge trees received some sheltering effect, reducing their stress compared with that of residuals. A strong inverse relationship was found between the delta(13)C values and the mean annual precipitation in each region. The trend in mean delta(13)C signature was Calling Lake > Drayton Valley > Lac Duparquet trees. These results suggest that residual or edge trees in drier regions are more likely to suffer water stress following VRH. We also observed a trend of greater delta(13)C in stout trees compared with slender trees, both before and after VRH. The evidence of greater water stress in stout trees likely occurred because of a positive relationship between stem diameter and crown volume per basal area. Our results provide evidence that water stress could be the driving mechanism leading to dieback and mortality of residual trees shortly after VRH. Additionally, the results from edge trees indicate that leaving hardwood residuals in larger patches or more sheltered landscape positions could reduce the water stress to which these trees are subjected, thereby reducing dieback and mortality.

The effects of defoliation and thinning on the dieback, mortality, and growth of sugar maple in the Tug Hill Region of New York

Treesearch

Robert A. Wink; Douglas C. Allen

1999-01-01

Some recent literature suggests that thinning should not be conducted immediately prior to, during, or immediately following an outbreak of defoliating insects. Although the individual effects of both defoliation and thinning are well documented in the literature, no study has assessed the combined effect of these two stressors. An outbreak of forest tent caterpillar...

AFLP Approach Reveals Variability in Phragmites australis: Implications for Its Die-Back and Evidence for Genotoxic Effects

PubMed Central

Coppi, Andrea; Lastrucci, Lorenzo; Cappelletti, David; Cerri, Martina; Ferranti, Francesco; Ferri, Valentina; Foggi, Bruno; Gigante, Daniela; Venanzoni, Roberto; Viciani, Daniele; Selvaggi, Roberta; Reale, Lara

2018-01-01

Phragmites australis is a subcosmopolitan species typical of wetlands being studied in Europe for its disappearance from natural stands, a phenomenon called reed die-back syndrome (RDBS). Although it is conjectured that low genetic variability contributes to RDBS, this aspect remains neglected to this day. Using a molecular fingerprinting approach and a sequence analysis of the trnT-trnL/rbcL-psaI regions of cpDNA, this study aimed to compare the genetic structure of stable vs. RDBS-affected P. australis stands from five wetlands of central Italy. Beforehand, in order to characterize the health condition of reed populations, the occurrence of the main macromorphological descriptors for RDBS was considered on 40 reed stands. Soil samples were also collected to examine the total content of heavy metals. The current study analyzed cpDNA in 19 samples and AFLP profiles in 381 samples to investigate the genetic structure of Phragmites populations. Based on the multinomial-Dirichlet model, an analysis of candidate loci under selective pressure was also performed. The relationships among AFLP data, RDBS descriptors and chemicals were evaluated with the use of Linear Mixed Models. The analysis of the cpDNA shows the occurrence of the haplotypes M (the most widespread), and K here recorded for the first time in Italy. Three new haplotypes were also described. The DNA fingerprinting analysis has produced a total of 322 loci (98% polymorphic) and shows the medium-to-high amount of genetic diversity. The significant genetic differentiation among wetlands (Fst = 0.337) suggests either low gene flow or small effective population size. Moreover, the low amount of outlier loci (only 5; l.5% of the total), seems to indicate the scarce occurrence of selective pressure upon the reed’s genome. Genetic diversity increased in relationship to the decrease in diameter and of flowering buds of the reed, two of the trends associated with the die-back. The current study rejects the hypothesis that genetic diversity massively contributed to RDBS. Moreover, significant relationships between genetic diversity and the total concentration of some heavy metals (Cr, Cu, and Zn) were highlighted, indicating possible genotoxic effects on P. australis. The current study represents a fact-finding background useful for the conservation of common reed. PMID:29632544

Carry over effects of nutrient addition on the recovery of an invasive seaweed from the winter die-back.

PubMed

Uyà, Marc; Maggi, Elena; Mori, Giovanna; Nuccio, Caterina; Gribben, Paul E; Bulleri, Fabio

2017-05-01

Nutrient enrichment of coastal waters can enhance the invasibility and regrowth of non-native species. The invasive alga Caulerpa cylindracea has two distinct phases: a well-studied fast-growing summer phase, and a winter latent phase. To investigate the effects of nutrient enrichment on the regrowth of the seaweed after the winter resting-phase, a manipulative experiment was carried out in intertidal rockpools in the North-western Mediterranean. Nutrients were supplied under different temporal regimes: press (constant release from January to May), winter pulse (January to March) and spring pulse (March to May). Independently from the temporal characteristics of their addition, nutrients accelerated the re-growth of C. cylindracea after the winter die-back, resulting in increased percentage covers at the peak of the growing season. Nutrient addition did not influence the number and length of fronds and the biomass. Native components of the algal community did not respond to nutrient additions. Our results show that nutrient supply can favour the spread of C. cylindracea even when occurring at a time of the year at which the seaweed is not actively growing. Copyright © 2017 Elsevier Ltd. All rights reserved.

Know your limits? Climate extremes impact the range of Scots pine in unexpected places.

PubMed

Julio Camarero, J; Gazol, Antonio; Sancho-Benages, Santiago; Sangüesa-Barreda, Gabriel

2015-11-01

Although extreme climatic events such as drought are known to modify forest dynamics by triggering tree dieback, the impact of extreme cold events, especially at the low-latitude margin ('rear edge') of species distributional ranges, has received little attention. The aim of this study was to examine the impact of one such extreme cold event on a population of Scots pine (Pinus sylvestris) along the species' European southern rear-edge range limit and to determine how such events can be incorporated into species distribution models (SDMs). A combination of dendrochronology and field observation was used to quantify how an extreme cold event in 2001 in eastern Spain affected growth, needle loss and mortality of Scots pine. Long-term European climatic data sets were used to contextualize the severity of the 2001 event, and an SDM for Scots pine in Europe was used to predict climatic range limits. The 2001 winter reached record minimum temperatures (equivalent to the maximum European-wide diurnal ranges) and, for trees already stressed by a preceding dry summer and autumn, this caused dieback and large-scale mortality. Needle loss and mortality were particularly evident in south-facing sites, where post-event recovery was greatly reduced. The SDM predicted European Scots pine distribution mainly on the basis of responses to maximum and minimum monthly temperatures, but in comparison with this the observed effects of the 2001 cold event at the southerly edge of the range limit were unforeseen. The results suggest that in order to better forecast how anthropogenic climate change might affect future forest distributions, distribution modelling techniques such as SDMs must incorporate climatic extremes. For Scots pine, this study shows that the effects of cold extremes should be included across the entire distribution margin, including the southern 'rear edge', in order to avoid biased predictions based solely on warmer climatic scenarios. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Paper birch decline in the Niobrara River Valley, Nebraska: Weather, microclimate, and birch stand conditions

USGS Publications Warehouse

Stroh, Esther D.; Miller, Joel P.

2009-01-01

The Niobrara River Valley in north-central Nebraska supports scattered stands of paper birch (Betula papyrifera Marsh), a species more typical of boreal forests. These birch stands are considered to be relictual populations that have persisted since the end of the Wisconsin glaciation, when regional flora was more boreal in nature (Wright 1970, Kaul and others, 1988). Dieback of canopy-sized birch has been observed throughout the Niobrara Valley in recent years, although no onset dates are documented. The current dieback event probably started around or after the early 1980’s. The study objectives were to understand microclimatic conditions in birch stands relative to nearby weather stations and historic weather conditions, and to assess current health conditions of individual birch trees. Temperature was measured every half-hour from June 2005 through October 2007 in 12 birch stands and individual birch tree health was measured as expressed by percent living canopy in these and 13 additional stands in spring 2006 and 2007. Birch site microclimate was compared to data from a National Weather Service station in Valentine, Nebraska, and to an automated weather station at The Nature Conservancy Niobrara Valley Preserve 24 kilometers north of Johnstown, Nebraska. Historic weather data from the Valentine station and another National Weather Service Station at Ainsworth, Nebraska, were used to reconstruct minimum and maximum temperature at The Nature Conservancy and one microclimate monitoring station using Kalman filtering and smoothing algorithms. Birch stand microclimate differed from local weather stations as well as among stands. Birch health was associated with annual minimum temperature regimes; those stands whose annual daily minimum temperature regimes were most like The Nature Conservancy station contained smaller proportions of living trees. Frequency of freeze/thaw conditions capable of inducing rootlet injury and subsequent crown dieback significantly have increased in the second one-half of the period of record (1978–2007) as compared to the first one-half (1948–1977). River location was associated with birch health; upper river sites had significantly healthier trees than north bank sites. Localized microclimates in the birch stands have likely facilitated the persistence of the birch populations in a region otherwise unsuitable for the species. These microclimate differences may reduce frequency of thaw/freeze conditions that can induce root injury and potential crown dieback. A large population decline in the context of increased frequency of potentially injurious climatic events would make population recovery much more difficult now than from 1948 to 1977, when thaw/freeze conditions were less frequent. These conditions, combined with little evidence of recruitment of young birch and great geographic distances from potential immigrant sources, make the future persistence of birch in the Niobrara River Valley stands uncertain.

Oak Decline

Treesearch

Philip M. Wargo; David R. Houston; Leon A. LaMadeleine

1983-01-01

Periodic occurrences of decline and death of oaks over widespread areas have been recorded since 1900. These outbreaks, variously named oak decline, oak dieback, or oak mortality, are caused by a complex interaction of environmental stresses and pests and given the name oak decline.

Virulence of Hymenoscyphus albidus and H. fraxineus on Fraxinus excelsior and F. pennsylvanica

PubMed Central

Kowalski, Tadeusz; Bilański, Piotr; Holdenrieder, Ottmar

2015-01-01

European ash (Fraxinus excelsior) is currently battling an onslaught of ash dieback, a disease emerging in the greater part of its native area, brought about by the introduction of the ascomycete Hymenoscyphus fraxineus (= Hymenoscyphus pseudoalbidus). The closely-related fungus Hymenoscyphus albidus, which is indigenous to Europe, is non-pathogenic when in contact with F. excelsior, but could pose a potential risk to exotic Fraxinus species. The North American green ash (Fraxinus pennsylvanica) is planted widely throughout Europe and regenerates naturally within this environment but little is known about the susceptibility of this species to ash dieback. We performed wound inoculations with both fungi (nine strains of H. fraxineus and three strains of H. albidus) on rachises and stems of F. excelsior and F. pennsylvanica under field conditions in Southern Poland. Necrosis formation was evaluated after two months on the rachises and after 12 months on the stems. After inoculation of H. albidus, only small lesions (of up to 1.3 cm in length) developed on the F. excelsior and F. pennsylvanica rachises, but with no significant distinction from the controls. Hymenoscyphus albidus did not cause necrotic lesions on the stems of either Fraxinus species. In contrast, H. fraxineus induced necroses on all inoculated rachises of both ash species with mean lengths of 8.4 cm (F. excelsior) and 1.9 cm (F. pennsylvanica). Necroses also developed on all of the inoculated F. excelsior stems (mean length 18.0 cm), whereas on F. pennsylvanica such lesions only occurred on about 5% of the stems (mean length 1.9 cm). The differences between strains were negligible. No necroses were observed on the control plants. Reisolations of H. albidus were only successful in around 8–11% of the cases, while H. fraxineus was reisolated from 50–70% of the inoculated organs showing necrotic lesions. None of the Hymenoscyphus species were isolated from the control plants. Our data confirm H. fraxineus’ high virulence with regards to F. excelsior and demonstrate a low virulence in relation to F. pennsylvanica under field conditions in Poland. Hymenoscyphus albidus did not express any perceivable pathogenicity on both host species. PMID:26517266

Systematics of Fusaria associated with Ambrosia beetles

USDA-ARS?s Scientific Manuscript database

Here, I summarize research efforts directed at characterizing ambrosia beetle-associated fusaria, including the species responsible for avocado wilt in Israel (Mendel et al., Phytoparasitica 2012) and branch dieback in California (Eskalen et al., Pl. Dis. 2012). Our multilocus molecular phylogenetic...

Genetic structure of the fungal grapevine pathogen Eutypa lata from four continents

USDA-ARS?s Scientific Manuscript database

Deciphering the geographic origins of pathogens and elucidating the population biology of these microscopic organisms are necessary steps to establish effective disease-control strategies. The generalist ascomycete fungus Eutypa lata causes Eutypa dieback of grapevine (Vitis vinifera) worldwide. To ...

Genetic structure of the fungal grapevine pathogen Eutypa lata from four continents

USDA-ARS?s Scientific Manuscript database

The generalist ascomycete fungus Eutypa lata causes Eutypa dieback of grapevine (Vitis vinifera) worldwide. To decipher the cosmopolitan distribution of this fungus, the population genetic structure of 17 geographic samples was investigated from four continental regions (Australia, California, Europ...

Limited Growth Recovery after Drought-Induced Forest Dieback in Very Defoliated Trees of Two Pine Species

PubMed Central

Guada, Guillermo; Camarero, J. Julio; Sánchez-Salguero, Raúl; Cerrillo, Rafael M. Navarro

2016-01-01

Mediterranean pine forests display high resilience after extreme climatic events such as severe droughts. However, recent dry spells causing growth decline and triggering forest dieback challenge the capacity of some forests to recover following major disturbances. To describe how resilient the responses of forests to drought can be, we quantified growth dynamics in plantations of two pine species (Scots pine, black pine) located in south-eastern Spain and showing drought-triggered dieback. Radial growth was characterized at inter- (tree-ring width) and intra-annual (xylogenesis) scales in three defoliation levels. It was assumed that the higher defoliation the more negative the impact of drought on tree growth. Tree-ring width chronologies were built and xylogenesis was characterized 3 years after the last severe drought occurred. Annual growth data and the number of tracheids produced in different stages of xylem formation were related to climate data at several time scales. Drought negatively impacted growth of the most defoliated trees in both pine species. In Scots pine, xylem formation started earlier in the non-defoliated than in the most defoliated trees. Defoliated trees presented the shortest duration of the radial-enlargement phase in both species. On average the most defoliated trees formed 60% of the number of mature tracheids formed by the non-defoliated trees in both species. Since radial enlargement is the xylogenesis phase most tightly related to final growth, this explains why the most defoliated trees grew the least due to their altered xylogenesis phases. Our findings indicate a very limited resilience capacity of drought-defoliated Scots and black pines. Moreover, droughts produce legacy effects on xylogenesis of highly defoliated trees which could not recover previous growth rates and are thus more prone to die. PMID:27066053

Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks.

PubMed

Zemp, Delphine Clara; Schleussner, Carl-Friedrich; Barbosa, Henrique M J; Hirota, Marina; Montade, Vincent; Sampaio, Gilvan; Staal, Arie; Wang-Erlandsson, Lan; Rammig, Anja

2017-03-13

Reduced rainfall increases the risk of forest dieback, while in return forest loss might intensify regional droughts. The consequences of this vegetation-atmosphere feedback for the stability of the Amazon forest are still unclear. Here we show that the risk of self-amplified Amazon forest loss increases nonlinearly with dry-season intensification. We apply a novel complex-network approach, in which Amazon forest patches are linked by observation-based atmospheric water fluxes. Our results suggest that the risk of self-amplified forest loss is reduced with increasing heterogeneity in the response of forest patches to reduced rainfall. Under dry-season Amazonian rainfall reductions, comparable to Last Glacial Maximum conditions, additional forest loss due to self-amplified effects occurs in 10-13% of the Amazon basin. Although our findings do not indicate that the projected rainfall changes for the end of the twenty-first century will lead to complete Amazon dieback, they suggest that frequent extreme drought events have the potential to destabilize large parts of the Amazon forest.

Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks

NASA Astrophysics Data System (ADS)

Zemp, Delphine Clara; Schleussner, Carl-Friedrich; Barbosa, Henrique M. J.; Hirota, Marina; Montade, Vincent; Sampaio, Gilvan; Staal, Arie; Wang-Erlandsson, Lan; Rammig, Anja

2017-03-01

Reduced rainfall increases the risk of forest dieback, while in return forest loss might intensify regional droughts. The consequences of this vegetation-atmosphere feedback for the stability of the Amazon forest are still unclear. Here we show that the risk of self-amplified Amazon forest loss increases nonlinearly with dry-season intensification. We apply a novel complex-network approach, in which Amazon forest patches are linked by observation-based atmospheric water fluxes. Our results suggest that the risk of self-amplified forest loss is reduced with increasing heterogeneity in the response of forest patches to reduced rainfall. Under dry-season Amazonian rainfall reductions, comparable to Last Glacial Maximum conditions, additional forest loss due to self-amplified effects occurs in 10-13% of the Amazon basin. Although our findings do not indicate that the projected rainfall changes for the end of the twenty-first century will lead to complete Amazon dieback, they suggest that frequent extreme drought events have the potential to destabilize large parts of the Amazon forest.

Climate-induced forest dieback as an emergent global phenomenon: Organized oral session at the Ecological Society of America/Society of Ecological Restoration Joint Meeting; San Jose, California, 5-10 August 2007

USGS Publications Warehouse

Allen, Craig D.; Breshears, David D.

2007-01-01

An organized oral session at the annual meeting of the Ecological Society of America in San Jose, Calif., posed this question: Is climate-induced drought stress triggering increasing rates and unusual patterns of forest die-off at a global scale? Twenty-nine researchers representing five continents reported on patterns, mechanisms, and projections of forest mortality.Observations include widespread forest dieback or reductions in tree cover and biodiversity in response to drought and warmer temperatures in the African Sahel (Patrick Gonzalez, The Nature Conservancy), Mediterranean and alpine Europe (Jorge Castro, Universidad de Granada), and Argentinean Patagonia (Thomas Kitzberger, Universidad Nacional del Comahue). In contrast, although much Eucalyptus mortality has resulted from recent droughts in Australia, warming trends have been less pronounced in the Southern Hemisphere and it is unclear if contemporary climate-induced tree mortality differs from previous historical drought impacts (Rod Fensham, Queensland Herbarium).

Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks

PubMed Central

Zemp, Delphine Clara; Schleussner, Carl-Friedrich; Barbosa, Henrique M. J.; Hirota, Marina; Montade, Vincent; Sampaio, Gilvan; Staal, Arie; Wang-Erlandsson, Lan; Rammig, Anja

2017-01-01

Reduced rainfall increases the risk of forest dieback, while in return forest loss might intensify regional droughts. The consequences of this vegetation–atmosphere feedback for the stability of the Amazon forest are still unclear. Here we show that the risk of self-amplified Amazon forest loss increases nonlinearly with dry-season intensification. We apply a novel complex-network approach, in which Amazon forest patches are linked by observation-based atmospheric water fluxes. Our results suggest that the risk of self-amplified forest loss is reduced with increasing heterogeneity in the response of forest patches to reduced rainfall. Under dry-season Amazonian rainfall reductions, comparable to Last Glacial Maximum conditions, additional forest loss due to self-amplified effects occurs in 10–13% of the Amazon basin. Although our findings do not indicate that the projected rainfall changes for the end of the twenty-first century will lead to complete Amazon dieback, they suggest that frequent extreme drought events have the potential to destabilize large parts of the Amazon forest. PMID:28287104

Neuronal responses to an asymmetrical alternating current field can mimic those produced by an imposed direct current field in vitro.

PubMed

Pan, Linjie; Cirillo, John; Borgens, Richard Ben

2012-08-01

The remarkable polarity-dependent growth and anatomical organization of neurons in vitro produced by imposed direct current (DC) voltage gradients (electrical fields; Ef) can be mimicked by another type of electrical cue. This is a properly structured asymmetrical alternating current (AC) electrical field (A-ACEf). Here we provide details on the construction of an AC signal generator in which all components of an AC waveform can be individually controlled. We show that 1) conventional symmetrical AC voltage gradients will not induce growth, guidance, or architectural changes in sympathetic neurons. We also provide the first qualitative and quantitative data showing that an asymmetric AC application can indeed mimic the DC response in chick sympathetic neurons and their growing neurites. This shift in orientation and neuronal anatomy requires dieback of some neurites and the extension of others to produce a preferred orientation perpendicular to the gradient of voltage. Our new results may lead to a noninvasive means to modify nerve growth and organization by magnetic inductive coupling at distance. These data also indicate the possibility of a means to mimic DC-dependent release of drugs or other biologically active molecules from electrically sensitive that can be loaded with these chemical cargos. Copyright © 2012 Wiley Periodicals, Inc.

Climate Warming Threatens Semi-arid Forests in Inner Asia

NASA Astrophysics Data System (ADS)

WU, X.; Liu, H.; Qi, Z.; Li, X.

2014-12-01

A line of evidences reveal an increasing tree growth decline and tree mortality mainly attributable to climate warming and the warming-mediated changes in drought and other processes (such as fire and insect dynamics) in many parts of world tropical, temperate and boreal forests. However, the growth responses to climate change of the widely distributed semi-arid forests are unclear. Here, we synthetically investigate the tree growth patterns during past decades and its interannual response to climate variations in Inner Asia combining the ground truth field survey and samplings, remote sensing observations and climate data. We identified a pervasive tree growth decline since mid-1990s in semi-arid forests in Inner Asia. The widely observed tree growth decline is dominantly attributable to warming-induced water stress during pre- and early growing season. Tree growth of semi-arid forests in Inner Asia is particularly susceptible to spring warming and has been suffering a prolonged growth limitation in recent decades due to spring warming-mediated water conditions. Additionally, we identified a much slower growth rate in younger trees and a lack of tree regeneration in these semi-arid forests. The widely observed forest growth reduction and lack of tree regeneration over semi-arid forests in Inner Asia could predictably exert great effects on forest structure, regionally/globally biophysical and biochemical processes and the feedbacks between biosphere and atmosphere. Notably, further increases in forest stress and tree mortality could be reasonably expected, especially in context of the increase frequency and severity of high temperature and heat waves and changes in forest disturbances, potentially driving the eventual regional loss of current semi-arid forests. Given the potential risks of climate induced forest dieback, increased management attention to adaptation options for enhancing forest resistance and resilience to projected climate stress can be expected. However, the functionally realistic mechanisms beneath the pervasively climate-induced forest decline/dieback still remain unclear. Network-based long-term surveys and experiment studies are urgently needed for further understandings regarding the responses of forest/tree growth to climate warming/variations.

Evaluation of Camellias for zone 6b

USDA-ARS?s Scientific Manuscript database

Recent hybridization of camellias has yielded several selections recognized as cold hardy to USDA Hardiness Zone 6. Several of the cold hardy camellias, in an established camellia evaluation since 2004, were damaged with foliar bronzing and stem dieback after a severe freeze in November 2013 in McMi...

Effect of compensatory growth on Palmer amaranth response to glyphosate.

USDA-ARS?s Scientific Manuscript database

Incomplete weed control can occur after herbicide applications. Death of one or many shoot meristems could remove apical dominance, leading to compensatory growth from once dormant lateral buds. Palmer amaranth (PA) dieback and regrowth in response to POST herbicides has been observed. The objective...

Susceptibility of cultivated and wild Vitis to wood infection by fungal trunk pathogens

USDA-ARS?s Scientific Manuscript database

Cultivars of European grapevine, Vitis vinifera, show varying levels of susceptibility to Eutypa dieback and Esca, in terms of foliar symptoms. However, little is known regarding cultivar susceptibility of their woody tissues to canker formation. Accordingly, we evaluated the relative susceptibility...

Chemical ecology and serendipity: Developing attractants for Florida ambrosia beetle pests

USDA-ARS?s Scientific Manuscript database

Two exotic ambrosia beetles have become established in southern Florida: Xyleborus glabratus, the redbay ambrosia beetle (RAB), and Euwallacea fornicatus, the tea shot hole borer (TSHB). Both pests vector pathogenic fungal symbionts; the former for laurel wilt and the latter for Fusarium dieback d...

Formulating entompathogens for control of boring beetles in avocado orchards

USDA-ARS?s Scientific Manuscript database

A foam formulation of Beauveria bassiana was adapted to control boring beetles in avocado orchards. The two geographically independent avocado growing areas in the United States are threatened by emerging diseases vectored by boring beetles. In the California growing region, Fusarium dieback is vect...

Orchard establishment, precocity, and eco-physiological traits of several pomegranate cultivars

USDA-ARS?s Scientific Manuscript database

California faces many threats to food security, ranging from water limitations resulting from long-term drought to invasive pests and disease. Major tree crops, such as citrus and avocado, are threatened by Citrus Greening and Fusarium Dieback, respectively, posing significant economic threats to gr...

Behavioral assays for evaluating host preferences of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae).

USDA-ARS?s Scientific Manuscript database

In 2010, the exotic ambrosia beetle, Euwallacea nr. fornicatus Eichhoff (Coleoptera: Curculionidae: Scolytinae) was first discovered in Florida avocado groves. Introduction of its symbiotic Fusarium spp. fungi into galleries in the xylem tissue results in Fusarium-dieback disease. Unlike most ambros...

Dissemination of aerial and root infecting Phytophthoras by human vectors

Treesearch

J.F. Webber; J. Rose

2008-01-01

Two new Phytophthora pathogens, Phytophthora kernoviae and P. ramorum, have recently established in parts of the U.K. They are most prevalent in the south west of England where they cause intense episodes of foliar blight and dieback on both ornamental and naturalised rhododendron such as Rhododendron ponticum,...

Pruning Allegheny hardwoods

Treesearch

W. D. Zeedyk; A. F. Hough

1958-01-01

The continuing heavy demand for high-quality Allegheny hardwoods, particularly black cherry and sugar maple, impresses on us the need for more information responses of hardwoods to pruning. Pruning may have beneficial effects: it may increase quality without sacrificing growth. Or it may have detrimental effects: it may cause dieback of cambium, decay, staining and...

A generic risk-based surveying method for invading plant pathogens

USDA-ARS?s Scientific Manuscript database

Invasive plant pathogens are increasing with international trade and travel with damaging environmental and economic consequences. Recent examples include tree diseases such as Sudden Oak Death in the Western US and Ash Dieback in Europe. To control an invading pathogen it is crucial that newly in...

Dispersion of marked Euwallacea nr. fornicatus in Florida avocado groves, and estimation of lure sampling range

USDA-ARS?s Scientific Manuscript database

The shot hole borer, Euwallacea nr. fornicatus Eichhoff (Coleoptera: Curculionidae: Scolytinae), is a significant invasive pest of avocado. Females introduce pathogenic Fusarium fungus into galleries, resulting in a disease called Fusarium die-back. Lures containing either quercivorol or a-copaene a...

Sporulation of Phytophthora ramorum and P. kernoviae on asymptomatic foliage and fruit

Treesearch

S. Denman; E. Moralejo; S.A. Kirk; E. Orton; A. Whybrow

2008-01-01

Phytophthora ramorum and P. kernoviae are newly discovered invasive Phytophthoras causing leaf necrosis, shoot tip dieback (mostly on ornamental and forest understorey host species) and bleeding cankers on tree trunks of a wide range of plant species. Both pathogens are now present in south-west England....

Long-term nitrogen fertilization increases winter injury in montane red spruce foliage (Picea rubens) foliage

Treesearch

T.D. Perkins; G.T. Adams; S.T. Lawson; P.G. Schaberg; S.G. McNulty

2000-01-01

Current-year red spruce (Picea rubens Sarg.) foliage is predisposed to winter injury by one or more types of anthropogenic pollutants, particularly acidic deposition. The resultant defoliation, when severe and repeated, leads to dieback and eventual mortality of affected red spruce individuals

Grower perceptions of preventative practices for management of trunk diseases of grape

USDA-ARS?s Scientific Manuscript database

Trials on prevention of trunk diseases (e.g., Eutypa dieback) show that three practices [delayed pruning, double pruning, pruning-wound protectants] prevent pruning-wound infections by 25-100%. Nonetheless, they are often not adopted until disease incidence is >20% in mature vineyards. There are no ...

A foam formulation of an entomopathogenic fungus for control of boring beetles in avocado orchards

USDA-ARS?s Scientific Manuscript database

A foam formulation of Beauveria bassiana was adapted to control boring beetles in avocado orchards. The two geographically independent avocado growing areas in the United States are threatened by emerging diseases vectored by boring beetles. In the California growing region, Fusarium dieback is vect...

Surface elevation dynamics in a regenerating mangrove forest at Homebush Bay, Australia

USGS Publications Warehouse

Rogers, K.; Saintilan, N.; Cahoon, D.

2005-01-01

Following the dieback of an interior portion of a mangrove forest at Homebush Bay, Australia, surface elevation tables and feldspar marker horizons were installed in the impacted, intermediate and control forest to measure vertical accretion, elevation change, and shallow subsidence. The objectives of the study were to determine current vertical accretion and elevation change rates as a guide to understanding mangrove dieback, ascertain the factors controlling surface elevation change, and investigate the sustainability of the mangrove forest under estimated sea-level rise conditions. The study demonstrates that the influences on surface dynamics are more complex than soil accretion and soil autocompaction alone. During strong vegetative regrowth in the impacted forest, surface elevation increase exceeded vertical accretion apparently as a result of belowground biomass production. In addition, surface elevation in all forest zones was correlated with total monthly rainfall during a severe El Ni?o event, highlighting the importance of rainfall to groundwater recharge and surface elevation. Surface elevation increase for all zones exceeded the 85-year sea level trend for Sydney Harbour. Since mean sea-level also decreased during the El Ni?o event, the decrease in surface elevation did not translate to an increase in inundation frequency or influence the sustainability of the mangrove forest. These findings indicate that subsurface soil processes such as organic matter accumulation and groundwater flux can significantly influence mangrove surface elevation, and contribute to the long-term sustainability of mangrove systems under a scenario of rising sea levels.

Botryosphaeriaceae associated with the die-back of ornamental trees in the Western Balkans.

PubMed

Zlatković, Milica; Keča, Nenad; Wingfield, Michael J; Jami, Fahimeh; Slippers, Bernard

2016-04-01

Extensive die-back and mortality of various ornamental trees and shrubs has been observed in parts of the Western Balkans region during the past decade. The disease symptoms have been typical of those caused by pathogens residing in the Botryosphaeriaceae. The aims of this study were to isolate and characterize Botryosphaeriaceae species associated with diseased ornamental trees in Serbia, Montenegro, Bosnia and Herzegovina. Isolates were initially characterized based on the DNA sequence data for the internal transcribed spacer rDNA and six major clades were identified. Representative isolates from each clade were further characterized using DNA sequence data for the translation elongation factor 1-alpha, β-tubulin-2 and large subunit rRNA gene regions, as well as the morphology of the asexual morphs. Ten species of the Botryosphaeriaceae were identified of which eight, i.e., Dothiorella sarmentorum, Neofusicoccum parvum, Botryosphaeria dothidea, Phaeobotryon cupressi, Sphaeropsis visci, Diplodia seriata, D. sapinea and D. mutila were known taxa. The remaining two species could be identified only as Dothiorella spp. Dichomera syn-asexual morphs of D. sapinea, Dothiorella sp. 2 and B. dothidea, as well as unique morphological characters for a number of the known species are described. Based on host plants and geographic distribution, the majority of Botryosphaeriaceae species found represent new records. The results of this study contribute to our knowledge of the distribution, host associations and impacts of these fungi on trees in urban environments.

Endophytic Association of Trichoderma asperellum within Theobroma cacao Suppresses Vascular Streak Dieback Incidence and Promotes Side Graft Growth

PubMed Central

Nasaruddin, Nasaruddin; Hendarto, Hendarto; Hakkar, Andi Akbar; Agriansyah, Nursalim

2016-01-01

Trichoderma species are able to persist on living sapwood and leaves of cacao (Theobroma cacao) in an endophytic relationship. In this research, we evaluated the ability of Trichodema asperellum introduced at the incision site in the bark for side grafting with the concentration of 4 g/10 mL, 4 g/100 mL, and 4 g/1,000 mL (suspended in water) in suppressing vascular streak dieback (VSD) incidence and promoting growth of side grafts in the field. The incidence of VSD in two local clones of cacao, MCC1 and M04, without application of T. asperellum was 71.2% and 70.1% at 21 wk after grafting, respectively. However, when the two clones were treated with a concentration of 4 g/10 mL T. asperellum, the incidence was 20.6% and 21.7%, respectively, compared to 29.1% and 20.9% at 4 g/100 mL and 18.2% and 15.6% at 4 g/1,000 mL. By comparing to the control, the treatment with the same concentrations of T. asperellum listed above, the total number of stomata in MCC1 decreased by 41.9%, 30.2%, and 14.0% and in M04 by 30.5%, 21.9%, and -2.5% (exception), respectively. Otherwise, the total area of stomata opening increased by 91.4%, 99.7%, and 28.6% in MCC1 and by 203.8%, 253.5%, and 35.9% in M04, respectively. Furthermore, the number of buds and branches treated with a mixture concentration on the the two clones increased by 90.7% and 21.7%, respectively. These data showed that the application of T. asperellum to cacao scions while grafting can decrease VSD incidence in side grafts and increase growth of grafts in addition to decreasing total number of stomata, increasing total area of opened stomata, and increasing number of buds and branches. PMID:27790069

Endophytic Association of Trichoderma asperellum within Theobroma cacao Suppresses Vascular Streak Dieback Incidence and Promotes Side Graft Growth.

PubMed

Rosmana, Ade; Nasaruddin, Nasaruddin; Hendarto, Hendarto; Hakkar, Andi Akbar; Agriansyah, Nursalim

2016-09-01

Trichoderma species are able to persist on living sapwood and leaves of cacao ( Theobroma cacao ) in an endophytic relationship. In this research, we evaluated the ability of Trichodema asperellum introduced at the incision site in the bark for side grafting with the concentration of 4 g/10 mL, 4 g/100 mL, and 4 g/1,000 mL (suspended in water) in suppressing vascular streak dieback (VSD) incidence and promoting growth of side grafts in the field. The incidence of VSD in two local clones of cacao, MCC1 and M04, without application of T. asperellum was 71.2% and 70.1% at 21 wk after grafting, respectively. However, when the two clones were treated with a concentration of 4 g/10 mL T. asperellum , the incidence was 20.6% and 21.7%, respectively, compared to 29.1% and 20.9% at 4 g/100 mL and 18.2% and 15.6% at 4 g/1,000 mL. By comparing to the control, the treatment with the same concentrations of T. asperellum listed above, the total number of stomata in MCC1 decreased by 41.9%, 30.2%, and 14.0% and in M04 by 30.5%, 21.9%, and -2.5% (exception), respectively. Otherwise, the total area of stomata opening increased by 91.4%, 99.7%, and 28.6% in MCC1 and by 203.8%, 253.5%, and 35.9% in M04, respectively. Furthermore, the number of buds and branches treated with a mixture concentration on the the two clones increased by 90.7% and 21.7%, respectively. These data showed that the application of T. asperellum to cacao scions while grafting can decrease VSD incidence in side grafts and increase growth of grafts in addition to decreasing total number of stomata, increasing total area of opened stomata, and increasing number of buds and branches.

a-Copaene and quercivorol lures: Chemical analysis and efficacy for detection of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae)

USDA-ARS?s Scientific Manuscript database

Invasive ambrosia beetles in the Euwallacea nr. fornicatus complex vector a fungal pathogen responsible for Fusarium dieback, a disease that impacts avocado (Persea americana) and numerous native trees in the USA, Israel, and other countries. Currently, these pests are detected with quercivorol lure...

Identification of five new hosts of Phytophthora ramorum in an infested forest in California

Treesearch

S. Rooney-Latham; C.L. Blomquist; A. Williams; E. Gunnison; T. Pastalka

2017-01-01

Phytophthora ramorum causes stem and bole cankers (sudden oak death) and foliar and twig dieback (ramorum blight) of susceptible plants. To date, more than 100 tree, shrub and herbaceous hosts of P. ramorum have been identified. In March 2015, plant samples were submitted to the CDFA Plant Pest Diagnostics...

Tree crown conditions in Missouri, 2000-2003

Treesearch

KaDonna C. Randolph; W. Keith Moser

2009-01-01

The Forest Service, U.S. Department of Agriculture, Forest Inventory and Analysis (FIA) Program uses visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes three FIA tree crown condition indicators (crown dieback, crown density, and foliage transparency) and sapling crown vigor measured in Missouri between 2000...

Forest Health Monitoring in Vermont, 1996-1999

Treesearch

Northeastern Research Station

2002-01-01

Vermont forests vary in size and age class. Trees are distributed evenly between hardwood and softwood species but hardwood dominated the seedling sample. Most of the trees are healthy, with full crowns (low transparency, high density), little dieback and little damage. White and green ash had higher transparencies and lower crown densities possibly explained by the...

Decline of quaking aspen in the Interior West - examples from Utah

Treesearch

Dale L. Bartos; Robert B. Campbell

1998-01-01

Quaking aspen (Populus tremuloides) are unique because, in contrast to most western forest trees, they reproduce primarily by suckering from the parent root system. Generally disturbance or dieback is necessary to stimulate regeneration of aspen stands. These self-regenerating stands have existed for thousands of years. If they are lost from the...

Condition-dependent co-regulation of genomic clusters of virulence factors in the grapevine trunk pathogen Neofusicoccum parvum

USDA-ARS?s Scientific Manuscript database

The ascomycete Neofusicoccum parvum, one of the causal agents of Botryosphaeria dieback, is a destructive wood-infecting fungus and a serious threat to grape production worldwide. The capability of colonizing woody tissue combined with the secretion of phytotoxic compounds is thought to underlie its...

Slow lifelong growth predisposes Populus tremuloides to tree mortality

Treesearch

Kathryn B. Ireland; Margaret M. Moore; Peter Z. Fule; Thomas J. Zegler; Robert E. Keane

2014-01-01

Widespread dieback of aspen forests, sometimes called sudden aspen decline, has been observed throughout much of western North America, with the highest mortality rates in the southwestern United States. Recent aspen mortality has been linked to drought stress and elevated temperatures characteristic of conditions expected under climate change, but the role of...

Calcium status of the forest floor in red spruce forests of the northeastern U.S. - past, present and future

Treesearch

Mark B. David; Gregory B. Lawrence; Walter C. Shortle; Scott W. Bailey

1996-01-01

Dieback and growth decline of red spruce (Picea rubens) in the eastern U.S. coincides with the period of acidic deposition, and has led to much speculation as to whether this decline is caused by decreased root-available Ca in the soil.

Recovery Plan for Phytophthora kernoviae Causing Bleeding Trunk Cankers, Leaf Blight and Stem Dieback in Trees and Shrubs

USDA-ARS?s Scientific Manuscript database

Phytophthora kernoviae, a recently described species of Phytophthora, is an invasive pathogen of forest trees and shrubs such as beech (Fagus sylvatica) and rhododendron (Rhododendron ponticum) that has become established in woodlands and public gardens in Cornwall, United Kingdom. Although the ori...

Descriptive statistics of tree crown condition in the Northeastern United States

Treesearch

KaDonna C. Randolph; Randall S. Morin; Jim Steinman

2010-01-01

The U.S. Forest Service Forest Inventory and Analysis (FIA) Program uses visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes four crown condition indicators (crown dieback, crown density, foliage transparency, and sapling crown vigor) measured in Connecticut, Delaware, Maine, Maryland, Massachusetts, New...

Sycamore diseases

Treesearch

F. I. McCracken

1989-01-01

The canker stain disease, one of several fungi that cause cankers of sycamore, can cause serious loss of sycamores in natural stands, plantations, and urban areas. As many as 35 percent of the trees in some stands may be diseased. Affected trees develop thin crowns, twig dieback, small leaves and epicormic branches. The narrow, elongate, bark covered, flat, spiraling...

A method to detect and quantify Eutypa lata and Diplodia seriata/intermedia complex DNA in grapevine pruning wounds

USDA-ARS?s Scientific Manuscript database

Trunk diseases are factors that limit sustainability of vineyards worldwide. Bot canker and Eutypa dieback are caused by several fungi belonging to the Botryosphaericeae and Diatrypaceae, respectively with Diplodia seriata and Eutypa lata being two of the most common species. Previous information in...

Evaluation of olive as a host of Xylella fastidiosa and associated sharpshooter vectors

USDA-ARS?s Scientific Manuscript database

Olive (Olea europaea L.) trees exhibiting leaf scorch and/or branch dieback symptoms in California were surveyed for the xylem-limited, fastidious bacterium Xylella fastidiosa. Only ~17% of diseased trees tested positive for X. fastidiosa by PCR, and disease symptoms could not be attributed to X. fa...

Estimating the risk of Amazonian forest dieback.

PubMed

Rammig, Anja; Jupp, Tim; Thonicke, Kirsten; Tietjen, Britta; Heinke, Jens; Ostberg, Sebastian; Lucht, Wolfgang; Cramer, Wolfgang; Cox, Peter

2010-08-01

*Climate change will very likely affect most forests in Amazonia during the course of the 21st century, but the direction and intensity of the change are uncertain, in part because of differences in rainfall projections. In order to constrain this uncertainty, we estimate the probability for biomass change in Amazonia on the basis of rainfall projections that are weighted by climate model performance for current conditions. *We estimate the risk of forest dieback by using weighted rainfall projections from 24 general circulation models (GCMs) to create probability density functions (PDFs) for future forest biomass changes simulated by a dynamic vegetation model (LPJmL). *Our probabilistic assessment of biomass change suggests a likely shift towards increasing biomass compared with nonweighted results. Biomass estimates range between a gain of 6.2 and a loss of 2.7 kg carbon m(-2) for the Amazon region, depending on the strength of CO(2) fertilization. *The uncertainty associated with the long-term effect of CO(2) is much larger than that associated with precipitation change. This underlines the importance of reducing uncertainties in the direct effects of CO(2) on tropical ecosystems.

Modelling drought-induced dieback of Aleppo pine at the arid timberline

NASA Astrophysics Data System (ADS)

Wingate, Lisa; Preisler, Yakir; Bert, Didier; Rotenberg, Eyal; Yakir, Dan; Maseyk, Kadmiel; Ogee, Jerome

2016-04-01

During the mid 1960's an ambitious afforestation programme was initiated in the Negev desert of Israel. After five decades enduring harsh growing conditions, the Aleppo pine forest of Yatir is now exhibiting signs of 'drought-induced' dieback. Since 2010, 5-10% of the entire Yatir population have died, however the pattern of mortality is extremely patchy with some areas exhibiting >80% mortality whilst others display none. In this presentation, we reflect on historic climatic and edaphic conditions that have triggered this landscape mosaic of survival and mortality and how physiological and hydraulic traits vary within this patchwork. In addition, we explore how these pine trees have responded physiologically over recent years (1996-2010) to a series of severe drought events using a combined approach that brings together micrometeorological, dendro-isotopic and dendro-climatological datasets alongside process-based modelling. In particular the dataset trends were investigated with the isotope-enabled ecosystem model MuSICA to explore the consequences of subsequent droughts and embolism on modelled carbohydrate and water pool dynamics and their impact on carbon allocation and ecosystem function.

Research frontiers in drought-induced tree mortality: Crossing scales and disciplines

DOE PAGES

Hartmann, Henrik; Adams, Henry D.; Anderegg, William R. L.; ...

2015-01-12

Sudden and widespread forest die-back and die-off (e.g., Huang & Anderegg, 2012) and increased mortality rates (e.g., Peng et al., 2011) in many forest ecosystems across the globe have been linked to drought and elevated temperatures (Allen et al., 2010, Fig. 1). Furthermore, these observations have caused a focus on the physiological mechanisms of drought-induced tree mortality (e.g. McDowell et al., 2008) and many studies, both observational and manipulative, have been carried out to explain tree death during drought from a physiological perspective.

Physiological and morphological response patterns of Populus deltoides to alluvial groundwater

USGS Publications Warehouse

Cooper, D.J.; D'Amico, D.R.; Scott, M.L.

2003-01-01

We examined the physiological and morphological response patterns of plains cottonwood [Populus deltoides subsp. monilifera (Aiton) Eck.] to acute water stress imposed by groundwater pumping. Between 3 and 27 July 1996, four large pumps were used to withdraw alluvial groundwater from a cottonwood forest along the South Platte River, near Denver, Colorado, USA. The study was designed as a stand-level, split-plot experiment with factorial treatments including two soil types (a gravel soil and a loam topsoil over gravel), two water table drawdown depths (∼0.5 m and >1.0 m), and one water table control (no drawdown) per soil type. Measurements of water table depth, soil water potential (Ψs), predawn and midday shoot water potential (Ψpd and Ψmd), and D/H (deuterium/hydrogen) ratios of different water sources were made in each of six 600-m2 plots prior to, during, and immediately following pumping. Two additional plots were established and measured to examine the extent to which surface irrigation could be used to mitigate the effects of deep drawdown on P. deltoides for each soil type. Recovery of tree water status following pumping was evaluated by measuring stomatal conductance (gs) and xylem water potential (Ψxp) on approximately hourly time steps from before dawn to mid-afternoon on 11 August 1996 in watered and unwatered, deep-drawdown plots on gravel soils. P. deltoides responded to abrupt alluvial water table decline with decreased shoot water potential followed by leaf mortality. Ψpd and percent leaf loss were significantly related to the magnitude of water table declines. The onset and course of these responses were influenced by short-term variability in surface and ground water levels, acting in concert with physiological and morphological adjustments. Decreases in Ψpd corresponded with increases in Ψmd, suggesting shoot water status improved in response to stomatal closure and crown dieback. Crown dieback caused by xylem cavitation likely occurred when Ψpd reached −0.4 to −0.8 MPa. The application of surface irrigation allowed trees to maintain favorable water status with little or no apparent cavitation, even in deep-drawdown plots. Two weeks after the partial canopy dieback and cessation of pumping, gs and Ψxp measurements indicated that water stress persisted in unwatered P. deltoides in deep-drawdown plots.

Flowering, die-back and recovery of a semelparous woody bamboo in the Atlantic Forest

NASA Astrophysics Data System (ADS)

Montti, Lía; Campanello, Paula I.; Goldstein, Guillermo

2011-07-01

Chusquea ramosissima is a semelparous woody bamboo growing in the understory of the semideciduous Atlantic Forest that increases in abundance after disturbance and consequently has profound effects on vegetation dynamics. Flowering and death of C. ramosissima may open a window of opportunity leaving space vacant for the recruitment of tree seedlings. We describe the flowering pattern and seedling demography of this species at different spatio-temporal scales between the years 2001 and 2009, and evaluate if tree seedling abundance of canopy species increased after the flowering event. At a landscape scale, flowering sites were interspersed with sites that did not flower. At a local scale, the flowering extended over 5 years, with flowering and non-flowering culms intermingled, also in small patches (i.e., 4 m 2). Seeds germinated soon after flowering and die-back. Four successive seedling cohorts were studied. Mortality rate was high during the first 4 months after seedling emergence but several fast-growing seedlings were able to become established successfully. At the end of the study, 10%-20% of the initial number of bamboo seedlings in each cohort survived. Seedling abundance of tree canopy species was similar in flowering and non-flowering sites. C. ramosissima was able to re-colonize and perpetuate in sites it previously occupied. The coexistence of flowering and non-flowering culms at different spatio-temporal scales and clonal growth by rhizomes, together with the successful bamboo seedlings establishment, enhanced bamboo persistence in gaps and disturbed sites. Flowering and death of C. ramosissima did not facilitate seedling growth of canopy tree species.

Quantitative analysis of contents and volatile emissions from a-copaene and quercivorol lures, and longevity for attraction of Euwallacea nr. fornicatus in Florida

USDA-ARS?s Scientific Manuscript database

Ambrosia beetles in the cryptic species complex Euwallacea nr. fornicatus vector a fungal pathogen responsible for Fusarium dieback, a disease that impacts avocado (Persea americana) and numerous native trees in the USA (California, Florida), Israel, and other countries. Currently, these pests are d...

Xyleborus glabratus attacks and systemic colonization by Raffaelea lauricola associated with dieback of Cinnamomum camphora in the southeastern United States

Treesearch

S. W. Fraedrich; T. C. Harrington; G. S. Best

2014-01-01

Laurel wilt, caused by Raffaelea lauricola, is responsible for extensive mortality of redbay and other American members of the Lauraceae in the southeastern United States. Raffaelea lauricola is a mycangial symbiont of the redbay ambrosia beetle (Xyleborus glabratus), and the beetle and fungus were accidentally...

Mating of Phytophthora ramorum: functionality and consequences

Treesearch

Xavier Boutet; Annelies Vercauteren; Chandelier Heungens; Anne Kurt

2010-01-01

Phytophthora ramorum (Werres, De Cock, Man in’t Veld), which causes “sudden oak death” in the United States and dieback and leaf necrosis in ornamental plants (mainly Rhododendron and Viburnum) in Europe, is a heterothallic species with two mating types, A1 and A2 (Werres and others 2001, Rizzo and...

Potential streamflow changes from forest decline due to air pollution

Treesearch

R. M. Rice; J. Lewis

1988-01-01

In recent years, serious die-back of forest trees has been reported in western Europe and eastern North America. One presumed cause of the forest decline is air pollution and acid deposition. Concern has been expressed that adverse hydrologic responses might occur in forested watersheds as the result of reduced evapotranspiration and increased discharge. According...

Populus tremuloides mortality near the southwestern edge of its range

Treesearch

Thomas J. Zegler; Margaret M. Moore; Mary L. Fairweather; Kathryn B. Ireland; Peter Z. Fule

2012-01-01

Mortality and crown dieback of quaking aspen (Populus tremuloides) were extensive on the Williams Ranger District, Kaibab National Forest in northern Arizona. We collected data from a random sample of 48 aspen sites to determine the relationship of predisposing site and stand factors and contributing agents to ramet mortality. Mortality of overstory (P10.1 cm DBH)...

Crown Health of Reserve Hardwood Trees Following Reproduction Cutting in the Ouachita Mountains

Treesearch

Dale A. Starkey; James M. Guldin

2004-01-01

Abstract - Monitoring the health of reserve hardwood trees is being performed as part of the Ecosystem Management Research Project on the Ouachita and Ozark National Forests in Arkansas. A suite of crown variables (diameter, live crown ratio, density, dieback, and foliage transparency) was used to detect significant changes in reserve tree health...

Diversity of Diaporthe species associated with wood cankers of fruit and nut crops in northern California

USDA-ARS?s Scientific Manuscript database

Diaporthe ampelina, causal agent of Phomopsis cane and leaf spot of grapevine (Vitis vinifera L.), is also frequently isolated from grapevine wood, causing Phomopsis dieback. In California, Diaporthe species cause a wide range of symptoms not only on grape, but also other fruit and nut crops. To bet...

Neofusicoccum parvum colonization of the grapevine woody stem triggers asynchronous host responses at the site of infection and in the leaves

USDA-ARS?s Scientific Manuscript database

Grapevine trunk diseases cause important economic losses in vineyards worldwide. Neofusicoccum parvum, one of the most aggressive causal agents of the trunk disease Botryosphaeria dieback, colonizes cells and tissues of the grapevine wood, leading to the formation of an internal canker. Symptoms the...

Climate, canker, and alder mortality in the Southern Rockies

Treesearch

James J. Worrall

2012-01-01

An increase in dieback and mortality of thinleaf alder (Alnus incana ssp. tenuifolia) raised concern in southern Wyoming and Colorado two decades ago. In 1990, there was concern over extensive mortality of thinleaf alder along Big Laramie River near Jelm, WY, as well as in multiple locations in Colorado.2 Trees of all ages were...

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...

What's Causing the Mortality in Southern Hardwoods?

Treesearch

W. M. Broadfoot; E. R. Toole

1958-01-01

Widespread dieback and mortality of hardwoods has been noted in the South during recent years. In general, losses have been most severe in certain areas of cottonwood, sweetgum, and black willow. Some damage also has been noted in red oaks, especially Nuttall; and in elms, green ash, sycamore, and some less important species. On uplands, mortality has occurred in...

Descriptive statistics of tree crown condition in California, Oregon, and Washington

Treesearch

KaDonna C. Randolph; Sally J. Campbell; Glenn Christensen

2010-01-01

The U.S. Forest Service Forest Inventory and Analysis (FIA) Program uses visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes four tree crown condition indicators (crown dieback, crown density, foliage transparency, and sapling crown vigor) measured in California, Oregon, and Washington between 1996 and 1999....

Descriptive statistics of tree crown condition in the North Central United States

Treesearch

KaDonna C. Randolph; Randall S. Morin; Jim Steinman

2010-01-01

The U.S. Forest Service Forest Inventory and Analysis (FIA) Program uses visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes four crown condition indicators (crown dieback, crown density, foliage transparency, and sapling crown vigor) measured in Illinois, Indiana, Michigan, Minnesota, Missouri, and Wisconsin...

Descriptive statistics of tree crown condition in the United States Interior West

Treesearch

KaDonna C. Randolph; Mike T. Thompson

2010-01-01

The U.S. Forest Service Forest Inventory and Analysis (FIA) Program uses visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes four crown condition indicators (crown dieback, crown density, foliage transparency, and sapling crown vigor) measured in Colorado, Idaho, Nevada, Utah, and Wyoming between 1996 and...

Dogwood Anthracnose and its Spread in the South

Treesearch

Robert L. Anderson; John L. Knighten; Keith Langdon; Floyd Hedrix; Ron Roncadori

In the 15 years since it was first reported in the United States, dogwood anthracnose (caused by Discula destructive sp. nov.) has spread rapidly and caused serious losses among flowering dogwoods (Cornus florida L.), particularly in the South. Infection begins in leaves and spreads to twigs and branches, which dieback. Main-stem infections cause cankers, which kill...

Sudden aspen decline in southwest Colorado: Site and stand factors and a hypothesis on etiology

Treesearch

Jim Worrall; Leanne Egeland; Tom Eager; Roy Mask; Erik Johnson; Phil Kemp; Wayne Shepperd

2008-01-01

An initial assessment of rapid dieback and mortality of aspen in southwest Colorado suggests that it represents a decline disease incited by acute, warm drought. Predisposing factors include low elevation, south and southwest aspects, droughty soils, open stands, and physiological maturity. Contributing factors include Cytospora canker, two bark beetles, poplar borer,...

Effects of Artificial Defoliation on the Growth of Cottonwood: Simulation of Cottonwood Leaf Beetle Defoliation

Treesearch

Steven A. Tucker; T. Evan Nebeker; Michael D. Warriner; William D. Jones; T. Keith Beatty

2004-01-01

Populus are among the fastest growing commercial forest trees but are not without problems. Insects and diseases can take their toll. The cottonwood leaf beetle (Chrysomela scripta F.; CLB) is of concern. Although damage by the CLB can result in terminal dieback, reduction in growth, and potential mortality, the impact on ...

Asian Longhorned Beetle - A New Introduction, Pest Alert

Treesearch

USDA Forest Service, State and Private Forestry, Northeastern Area; Animal and Plant Health Inspection Service

2008-01-01

The Asian longhorned beetle (ALB) has been discovered attacking trees in the United States. Tunneling by beetle larvae girdles tree stems and branches. Repeated attacks lead to dieback of the tree crown and, eventually, death of the tree. ALB probably traveled to the United States inside solid wood packing material from China. The beetle has been intercepted at ports...

Decline of Ohia (Metrosideros polymorpha) in Hawaii: a review

Treesearch

Charles S. Hodges; Ken T. Adee; John D. Stein; Hulton B. Wood; Robert D. Doty

1986-01-01

Portions of the ohia (Metrosideros polymorpha) forests on the windward slopes of Mauna Loa and Mauna Kea on the island of Hawaii began dying in 1952. Little mortality has occurred since 1972. About 50,000 ha are affected by the decline. Individual trees exhibit several symptoms, from slow progressive dieback to rapid death. Seven types of decline...

Characterization of Cytospora isolates from wood cankers of declining grapevine in North America, with the descriptions of two new Cytospora species

USDA-ARS?s Scientific Manuscript database

Cytospora species are ubiquitous pathogens of woody plants, causing dieback and wood cankers in numerous perennial hosts, including agronomic crops (e.g., Prunus), timber trees (e.g., Eucalyptus), and riparian hosts (e.g., Salix). Cytospora chrysosperma, C. cincta, and C. leucostoma have been report...

Two new Cytospora species, Cytospora vinacea sp. nov. and Cytospora viticola sp. nov., from declining vineyards in eastern North America

USDA-ARS?s Scientific Manuscript database

Cytospora species are ubiquitous pathogens of woody plants, causing branch dieback and wood cankers in numerous perennial hosts, including agronomic crops (e.g., Prunus), timber trees (e.g., Eucalyptus), and riparian hosts (e.g., Salix). Cytospora chrysosperma, C. cincta, and C. leucostoma have been...

Digital photography for urban street tree crown conditions

Treesearch

Neil A. Clark; Sang-Mook Lee; William A. Bechtold; Gregory A. Reams

2006-01-01

Crown variables such as height, diameter, live crown ratio, dieback, transparency, and density are all collected as part of the overall crown assessment (USDA 2004). Transparency and density are related to the amount of foliage and thus the photosynthetic potential of the tree. These measurements are both currently based on visual estimates and have been shown to be...

Fusarium symbionts of an ambrosia beetle (Euwallacea sp.) in southern Florida are pathogens of avocado, Persea americana

USDA-ARS?s Scientific Manuscript database

Fusarium dieback, a destructive disease of avocado (Persea americana), was reported in California and Israel in 2012. It is associated with an ambrosia beetle, Euwallacea sp., and damage caused by an unnamed symbiont of the beetle in Clade 3 of the Fusarium solani species complex (FSSC) designated p...

Geographic Variation in Disease Susceptibility of American Sycamore

Treesearch

D. T. Cooper; T. H. Filer; O. O. Wells

1977-01-01

Leaf scorch, top dieback, and lethal bole cankers were found in two progeny tests of sycamore in Mississippi. Both tests indicated that southern seed sources are more disease resistant than northern seed sources and that some progenies within seed source have even greater resistance. Although eight organisms associated with one or more of the disease symptoms were...

Attack pattern of Platypus koryoensis (Coleoptera: Curculionidae: Platypodidae) in relation to crown dieback of Mongolian oak in Korea

Treesearch

Jung-Su Lee; Robert A. Haack; Won Il. Choi

2011-01-01

The ambrosia beetle, Platypus koryoensis (Murayama), vectors the Korean oak wilt (KOW) pathogen, Raffaelea quercus-mongolicae K.H. Kim, Y.J. Choi, & H.D. Shin, in Korea, which is highly lethal to Mongolian oak, Quercus mongolica Fisch., and is considered a major threat to forest ecosystem health. We...

Detection of spatio-temporal changes of Norway spruce forest stands in Ore Mountains using airborne hyperspectral imagery

NASA Astrophysics Data System (ADS)

Misurec, J.; Kopačková, V.; Lhotáková, Z.; Albrechtova, J.; Campbell, P. K. E.

2015-12-01

The Ore Mountains are an example of the region that suffered from severe environmental pollution caused by long-term coal mining and heavy industry leading to massive dieback of the local Norway spruce forests between the 1970's and 1990's. The situation became getting better at the end of 1990's after pollution loads significantly decreased. In 1998 and 2013, airborne hyperspectral data (with sensor ASAS and APEX, respectively) were used to study recovery of the originally damaged forest stands and compared them with those that have been less affected by environmental pollution. The field campaign (needle biochemical analysis, tree defoliation etc.) accompanied hyperspectral imagery acquisition. An analysis was conducted assessing a set of 16 vegetation indices providing complex information on foliage, biochemistry and canopy biophysics and structure. Five of them (NDVI, NDVI705, VOG1, MSR and TCARI/OSAVI) showing the best results were employed to study spatial gradients as well as temporal changes. The detected gradients are in accordance with ground truth data on representative trees. The obtained results indicate that the original significant differences between the damaged and undamaged stands have been generally levelled until 2013, although it is still possible to detect signs of the previous damages in several cases.

Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation

Treesearch

Yong-Jiang Zhang; Frederick C. Meinzer; Guang-You Hao; Fabian G. Scholz; Sandra J. Bucci; Frederico S.C. Takahashi; Randol Villalobos-Vega; Juan P. Giraldo; Kun-Fang Cao; William A. Hoffmann; Guillermo Goldstein

2009-01-01

Size-related changes in hydraulic architecture, carbon allocation, and gas exchange of Sclerolobium paniculatum (Leguminosae), a dominant tree species in Neotropical savannas of central Brazil (Cerrado), were investigated to assess their potential role in the dieback of tall individuals. Trees greater than ~6 m tall exhibited more branch damage,...

Variation in phenotype for resistance to Phytophthora ramorum in a range of species and cultivars of the genus Viburnum

Treesearch

Niklaus J. Grunwald; E. Anne Davis; Robert G. Linderman

2006-01-01

Phytophthora ramorum is a recently introduced plant pathogen causing a range of diseases including sudden oak death, Ramorum shoot dieback and Ramorum blight (Rizzo and others 2002, 2004; Werres and others 2001). P. ramorum also attacks several nursery crops including viburnum and rhododendron (Werres and others 2001). Since its...

A new mechanism for calcium loss in forest-floor soils

Treesearch

Gregory B. Lawrence; Mark B. David; Walter C. Shortle

1995-01-01

Calcium is the fifth most abundant element in trees, and is an essential component for wood formation and the maintenance of cell walls. Depletion of Ca from the rooting zone can result in acidification of soil and surface water and possibly growth decline and dieback of red spruce. During the past six decades, concentrations of root-available Ca (exchangeable and acid...

Effects of defoliation and drought on root food reserves in sugar maple seedlings

Treesearch

Johnson Parker; Johnson Parker

1970-01-01

The artificial defoliation of sugar maple (Acer. saccharum Marsh.) can cause a marked decline in root food reserves, especially starch, and an increase in the levels of the reducing sugars, fructose and glucose. Defoliation can also bring on the dieback-decline syndrome in sugar maples (Parker and Houston 1968). Two experiments designed to examine this question were...

How much older are Appalachian oaks below-ground than above-ground?

Treesearch

Daniel J. Heggenstaller; Eric K. Zenner; Patrick H. Brose; Jerilynn E. Peck

2012-01-01

Young oaks (Quercus spp.) are known to invest more in early root growth than shoot growth, enabling seedlings to tolerate stem die-back and resprouting. The resulting disparity in age between above- and below-ground tissues has been previously demonstrated for seedling-sized stems, but not for successful canopy-ascending trees. We compared the age of stem cross...

Descriptive statistics of tree crown condition in the Southern United States and impacts on data analysis and interpretation

Treesearch

KaDonna C. Randolph

2006-01-01

The U.S. Department of Agriculture Forest Service, Forest Inventory and Analysis Program (FIA) utilizes visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes and discusses distributions of three FIA crown condition indicators (crown density, crown dieback, and foliage transparency) for trees in the Southern...

Cambial dieback and taphole closure in sugar maple after tapping

Treesearch

Carter B. Gibbs; H. Clay Smith

1973-01-01

Dead cambial tissues adjacent to tapholes were found to be elliptical in shape and to average 1.6 inches in length and 0.2 inch in width. Chemical and physical treatments designed to stimulate the growth of callus tissues surrounding tapholes were not successful. Nearly all the tapholes, both treated and untreated, had closed after three growing seasons.

Hardwood vigor and survival following applications of imazapyr in mid-rotation pine plantations

Treesearch

Prabudhda Dahal Dahal; Hal O. Liechty; Bryan Rupar; Conner Fristoe; Eric Heitzman

2006-01-01

Tree vigor, live crown ratios, dieback, and survival of hardwood competition were monitored for 2 years following a fall application (16 ounces per acre) of imazapyr on 4 stands of loblolly pine (Pinus taeda L.) in the Gulf Coastal Plain of Louisiana and Arkansas. Assessments during the first growing season following application indicated that 87 to...

Sugarberry Dieback and Mortality in Southern Louisiana: Cause, Impact, and Prognosis

Treesearch

J.D. Solomon; A. Dan Wilson; Theodor D. Leininger; D.G. Lester; C.S. McCasland; S. Clarke; C. Affeltranger

1997-01-01

A sudden widespread decline of sugarberry trees (Celfis laevigufu) was observed in southern Louisiana during the period between the early fall of 1988 and spring of 1990. Approximately 3 million acres or 5,000 square miles of forested lands were affected by the decline. In addition, sporadic reports of sugarberry decline also were reported at numerous locations in...

Simulating forest productivity along a neotropical elevational transect: temperature variation and carbon use efficiency

NASA Astrophysics Data System (ADS)

Marthews, T.; Malhi, Y.; Girardin, C.; Silva-Espejo, J.; Aragão, L.; Metcalfe, D.; Rapp, J.; Mercado, L.; Fisher, R.; Galbraith, D.; Fisher, J.; Salinas-Revilla, N.; Friend, A.; Restrepo-Coupe, N.; Williams, R.

2012-04-01

A better understanding of the mechanisms controlling the magnitude and sign of carbon components in tropical forest ecosystems is important for reliable estimation of this important regional component of the global carbon cycle. We used the JULES vegetation model to simulate all components of the carbon balance at six sites along an Andes-Amazon transect across Peru and Brazil and compared the results to published field measurements. In the upper montane zone the model predicted a vegetation dieback, indicating a need for better parameterisation of cloud forest vegetation. In the lower montane and lowland zones simulated ecosystem productivity and respiration were predicted with reasonable accuracy, although not always within the error bounds of the observations. Model-predicted carbon use efficiency in this transect surprisingly did not increase with elevation, but remained close to the 'temperate' value 0.5. This may be explained by elevational changes in the balance between growth and maintenance respiration within the forest canopy, as controlled by both temperature- and pressure-mediated processes.

Temporal shifts in top-down vs. bottom-up control of epiphytic algae in a seagrass ecosystem

USGS Publications Warehouse

Whalen, Matthew A.; Duffy, J. Emmett; Grace, James B.

2013-01-01

In coastal marine food webs, small invertebrate herbivores (mesograzers) have long been hypothesized to occupy an important position facilitating dominance of habitat-forming macrophytes by grazing competitively superior epiphytic algae. Because of the difficulty of manipulating mesograzers in the field, however, their impacts on community organization have rarely been rigorously documented. Understanding mesograzer impacts has taken on increased urgency in seagrass systems due to declines in seagrasses globally, caused in part by widespread eutrophication favoring seagrass overgrowth by faster-growing algae. Using cage-free field experiments in two seasons (fall and summer), we present experimental confirmation that mesograzer reduction and nutrients can promote blooms of epiphytic algae growing on eelgrass (Zostera marina). In this study, nutrient additions increased epiphytes only in the fall following natural decline of mesograzers. In the summer, experimental mesograzer reduction stimulated a 447% increase in epiphytes, appearing to exacerbate seasonal dieback of eelgrass. Using structural equation modeling, we illuminate the temporal dynamics of complex interactions between macrophytes, mesograzers, and epiphytes in the summer experiment. An unexpected result emerged from investigating the interaction network: drift macroalgae indirectly reduced epiphytes by providing structure for mesograzers, suggesting that the net effect of macroalgae on seagrass depends on macroalgal density. Our results show that mesograzers can control proliferation of epiphytic algae, that top-down and bottom-up forcing are temporally variable, and that the presence of macroalgae can strengthen top-down control of epiphytic algae, potentially contributing to eelgrass persistence.

Potential Effects of Drought on Tree Dieback in Great Britain and Implications for Forest Management in Adaptation to Climate Change

NASA Astrophysics Data System (ADS)

Yu, Jianjun; Berry, Pam

2017-04-01

The drought and heat stress has alerted the composition, structure and biogeography of forests globally, whilst the projected severe and widespread droughts are potentially increasing. This challenges the sustainable forest management to better cope with future climate and maintain the forest ecosystem functions and services. Many studies have investigated the climate change impacts on forest ecosystem but less considered the climate extremes like drought. In this study, we implement a dynamic ecosystem model based on a version of LPJ-GUESS parameterized with European tree species and apply to Great Britain at a finer spatial resolution of 5*5 km. The model runs for the baseline from 1961 to 2011 and projects to the latter 21st century using 100 climate scenarios generated from MaRIUS project to tackle the climate model uncertainty. We will show the potential impacts of climate change on forest ecosystem and vegetation transition in Great Britain by comparing the modelled conditions in the 2030s and the 2080s relative to the baseline. In particular, by analyzing the modelled tree mortality, we will show the tree dieback patterns in response to drought for various species, and assess their drought vulnerability across Great Britain. We also use species distribution modelling to project the suitable climate space for selected tree species using the same climate scenarios. Aided by these two modelling approaches and based on the corresponding modelling results, we will discuss the implications for adaptation strategy for forest management, especially in extreme drought conditions. The gained knowledge and lessons for Great Britain are considered to be transferable in many other regions.

Spectral Demixing and Spectral Index Correlations for Subpixel Quantification of Land-Cover Components from Coarse Resolution Imagery at Fort Bliss, Texas

DTIC Science & Technology

2003-12-01

Application to Land-Cover Change in the Brazilian Amazon ,” Remote Sensing of Environment, vol 52, pp 137-154. Anderson, G.L., J.D. Hanson, and R.H. Haas...FORTRAN, Cambridge University Press. Price, K.P., D. A. Pyke,and L. Mendes. 1992. “Shrub Dieback in a Semiarid Ecosystem; The Integration of Remote

Remote Sensing of Forest Health Indicators for Assessing Change in Forest Health

Treesearch

Michael K. Crosby; Zhaofei Fan; Martin A. Spetich; Theodor D. Leininger

2012-01-01

Oak decline poses a substantial threat to forest health in the Ozark Highlands of northern Arkansas and southern Missouri, where coupled with diseases and insect infestations, it has damaged large tracts of forest lands. Forest Health Monitoring (FHM) crown health indicators (e.g. crown dieback, etc.), collected by the U.S. Forest Service’s Forest Inventory and...

Fusarium canker of bitternut hickory caused by Fusarium solani in the North-Central and Northeastern United States

Treesearch

J.-H. Park; J. Juzwik

2012-01-01

Multiple annual cankers were observed on the upper main stems of bitternut hickory (Carya cordiformis) exhibiting top dieback in Indiana, Iowa, Minnesota, New York, Ohio, and Wisconsin during a 2006 to 2008 survey of declining hickory. The top-killed trees had normal-sized, green leaves below and the cankers were oval, sunken, and bounded by heavy...

Genetic structure of Notholithocarpus densiflorus(Fagaceae) from the species to the local scale: A review of our knowledge for conservation and replanting

Treesearch

Richard S Dodd; Alejandro Nettel; Jessica W. Wright; Zara Afzal-Rafii

2013-01-01

Tanoak, Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S. H. Oh (Fagaceae), is an important component of mixed-evergreen forests and woodlands in coastal California and Oregon, with incursions into the Sierra Nevada and the Klamath Ranges. Sudden Oak Death (SOD) is causing severe dieback and mortality in tanoak and could...

Assessing Oak Decline Incidence and Distribution in the Southern U.S. Using Forest Inventory and Analysis Data

Treesearch

Steven W. Oak; James R. Steinman; Dale A. Starkey; Edwin K. Yockey

2004-01-01

Forest Inventory and Analysis data for twelve southern states were used to evaluate regional oak decline status. Total host type, vulnerable host type, and affected areas were determined. The attributes used for classification were forest type, predominant stem size class, oak basal area percent, and dieback damage coding. Host type totaled 104.7 million acres in the...

Japanese oak wilt as a newly emerged forest pest in Japan: why does a symbiotic ambrosia fungus kill host trees?

Treesearch

Naoto Kamata; Koujiro Esaki; Kenryu Kato; Hisahito Oana; Yutaka Igeta; Ryotaro Komura

2007-01-01

Japanese oak wilt (JOW) has been known since the 1930s, but in the last 15 years epidemics have intensified and spread to the island's western coastal areas. The symbiotic ambrosia fungus Raffaelea quercivora is the causal agent of oak dieback, and is vectored by Platypus quercivorus (Murayama). This is the first example of an...

Oak mortality associated with crown dieback and oak borer attack in the Ozark Highlands

Treesearch

Zhaofei Fan; John M. Kabrick; Martin A. Spetich; Stephen R. Shifley; Randy G. Jensen

2008-01-01

Oak decline and related mortality have periodically plagued upland oak-hickory forests, particularly oak species in the red oak group, across the Ozark Highlands of Missouri, Arkansas and Oklahoma since the late 1970s. Advanced tree age and periodic drought, as well as Armillaria root fungi and oak borer attack are believed to contribute to oak decline and mortality....

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.

Widespread tree mortality with the ongoing California drought: the roll of water balance and temperature

NASA Astrophysics Data System (ADS)

Goulden, M.; Bales, R. C.

2016-12-01

The southern Sierra Nevada experienced extreme drought, heat and forest dieback from 2012-16, with 50% below average P, 3oC above average T, and tens of millions of trees dying. The drought and dieback were widespread at the Southern Sierra Critical Zone Observatory (SSCZO). The SSCZO provides a rich suite of meteorological, ecological and hydrologic datasets, including many that began around 2010 and include two wet years followed by the intensifying drought. The SSCZO observations span an altitude gradient; this gradient includes a xeric pine and oak forest at 1200 m, which is near the lower ecotone of closed canopy forest, and a mesic pine and fir forest at 2100 m. Findings include: 1) Tree death was greater at 1200-m, following the altitudinal pattern seen across central CA, with dieback focused in the lower parts of species and ecosystem type ranges. 2) Mortality was associated with a year over year depletion of subsurface moisture. The cumulative overdraft (P-ET) at 1200 m exceeded 100 cm; the cumulative P-ET at 2100 m was near zero. 3) Much of the accelerated moisture depletion at 1200-m was associated with warmer temperatures and a greater evaporative demand. The 1200 and 2100 m sites experienced similar annual precipitation, and the rate of ET at comparable temperatures was also similar. The lower site was 5oC warmer on average, which led to 40% greater ET, and a more rapid depletion of belowground moisture. 4) A similar pattern was observed in Landsat and MODIS imagery. Mortality was high below 1600 m and low above 2000m. Mortality decreased rapidly with elevation and cooler temperatures from 1600 to 2000 m. Mortality in the 1600 to 2000 m zone was well correlated with Land Surface Temperature, with greater mortality on warm, southern slopes and less mortality on cool, northern slopes. In combination these findings illustrate the interacting effect of drought and temperature in controlling the patterns of tree death accross the Southern Sierra Nevada.

Using a dune forest as a filtering ecosystem for water produced by a treatment plant - One decade of environmental assessment.

PubMed

Trichet, Pierre; Cheval, Nicolas; Lambrot, Catherine; Maugard, Francis; Reynaud, Virginie; Cornu, Jean-Yves; Denaix, Laurence; Augusto, Laurent

2018-06-04

A dune forest in SW France composed of maritime pines was irrigated with treated wastewater for a decade in an experiment (including irrigated plots versus control plots) to evaluate the environmental impact of applying wastewater on the water table, soil properties, and plants. The amount of treated wastewater (1921 mm yr -1 ) applied was twice the annual precipitation. Nutrient inputs were also very high, particularly nitrogen (N: 539 kg-N ha -1  yr -1 ), phosphorus (P: 102 kg-P ha -1  yr -1 ), and calcium (Ca: 577 kg-Ca ha -1  yr -1 ). Irrigation caused a rise in the water table, and increased its sodium (Na), NO 3 - , potassium (K), and calcium concentrations. Soil properties were affected by irrigation at least down to a depth of 1.2 m. After eight years of irrigation, soil pH had increased by 1.4 units, and soil available P content (P Olsen ) increased nearly 8-fold. In the short-term (i.e. 1-3 years), irrigation with treated wastewater improved growth, standing biomass, and the nutritional status of the vegetation. But tree dieback started in the fourth year of irrigation and worsened until the end of the monitoring period when almost all the irrigated trees were dead or moribund. The understory composition was drastically modified by irrigation, with an increase in α-biodiversity and in the biomass of herbaceous species, and a reduction in woody species abundance. The factor that best explained tree dieback was manganese nutrition (Mn): (i) the Mn content of the tree foliage was negatively affected by irrigation and below the deficiency values reported for pine species, and (ii) soil available Mn (CaCl 2 extraction) decreased by half in the topsoil layer. Manganese deficiency was probably the consequence of the increase in soil pH, which in turn reduced soil Mn availability. Tree dieback was not related to either to a macronutrient deficiency or to toxicity caused by a trace element. Copyright © 2018 Elsevier B.V. All rights reserved.

Oak Decline and Red Oak Borer in the Interior Highlands of Arkansas an Missouri: Natural Phenomena, Severe Occurrences

Treesearch

Dale A. Starkey; Forrest Oliveria; Alexander Mangini; Manfred Mielke

2004-01-01

Oak decline is a complex disease resulting in dieback and mortality of oaks. A number of factors are involved and can be classified as predisposing, inciting, or contributing, according to their roles. Decline events have been noted repeatedly during the past century in the eastern U.S. A severe episode of oak decline is occurring in the Interior Highlands region of...

Yellow birch grows better in mixed-wood stands than in northern hardwood old-growth stands

Treesearch

William B. Leak

1961-01-01

Yellow birch, the most valuable timber tree in the northern hardwood forest, is losing ground in northern New England. Birch dieback in the late 1930s and 1940s killed millions of board-feet of yellow birch. Meanwhile, the demand for yellow birch veneer and lumber has increased by leaps and bounds. So industries that depend upon yellow birch are having increasing...

Discovering the Factors Contributing to the Decline and Mortality of Willow Oaks in the D'Arbonne National Wildlife Refuge, LA.

Treesearch

Theodor D. Leininger

1998-01-01

Since the early 1990's, mature willow oaks (Quercus phellos L.) on certain sites in the D'Arbonne National Wildlife Refuge(DNWR), in northeast Louisiana, have shown crown dieback. The die back is progressive with some trees continuing to decline, eventually leading to death, within one to three years. This condition has caused the Refuge forester to...

Frost injury to bitterbrush in eastern California

Treesearch

R. S. Smith; R. F. Scharpf; E. R. Schneegas

1965-01-01

Widespread dieback of Purshia tridentata, on the Inyo National Forest in eastern California in the spring of 1964, was caused by a severe 3-day frost with daily minimums down to 13°F. An unusually warm 9-day period-with temperatures up to 70°F., which preceded the frost by a week, had induced the bitterbrush to break dormancy and start shoot elongation when the frost...

Influence of climate on the growth of quaking aspen (Populus tremuloides) in Colorado and southern Wyoming

Treesearch

M. M. Dudley; Jose Negron; N. A. Tisserat; W. D. Shepperd; W. R. Jacobi

2015-01-01

We analyzed a series of increment cores collected from 260 adult dominant or co-dominant quaking aspen (Populus tremuloides Michx.) trees from national forests across Colorado and southern Wyoming in 2009 and 2010. Half of the cores were collected from trees in stands with a high amount of crown dieback, and half were from lightly damaged stands. We define the level of...

Oak mortality associated with crown dieback and oak borer attack in the Ozark Highlands

Treesearch

Zhaofei Fan; John M. Kabrick; Martin A. Spetich; Stephen R. Shifley; Randy G. Jensen

2008-01-01

Oak decline and related mortality have periodically plagued upland oak–hickory forests, particularly oak species in the red oak group, across the Ozark Highlands of Missouri, Arkansas and Oklahoma since the late 1970s. Advanced tree age and periodic drought, as well as Armillaria root fungi and oak borer attack are believed to contribute to oak decline and mortality....

Tree mortality predicted from drought-induced vascular damage

USGS Publications Warehouse

Anderegg, William R.L.; Flint, Alan L.; Huang, Cho-ying; Flint, Lorraine E.; Berry, Joseph A.; Davis, Frank W.; Sperry, John S.; Field, Christopher B.

2015-01-01

The projected responses of forest ecosystems to warming and drying associated with twenty-first-century climate change vary widely from resiliency to widespread tree mortality1, 2, 3. Current vegetation models lack the ability to account for mortality of overstorey trees during extreme drought owing to uncertainties in mechanisms and thresholds causing mortality4, 5. Here we assess the causes of tree mortality, using field measurements of branch hydraulic conductivity during ongoing mortality in Populus tremuloides in the southwestern United States and a detailed plant hydraulics model. We identify a lethal plant water stress threshold that corresponds with a loss of vascular transport capacity from air entry into the xylem. We then use this hydraulic-based threshold to simulate forest dieback during historical drought, and compare predictions against three independent mortality data sets. The hydraulic threshold predicted with 75% accuracy regional patterns of tree mortality as found in field plots and mortality maps derived from Landsat imagery. In a high-emissions scenario, climate models project that drought stress will exceed the observed mortality threshold in the southwestern United States by the 2050s. Our approach provides a powerful and tractable way of incorporating tree mortality into vegetation models to resolve uncertainty over the fate of forest ecosystems in a changing climate.

Impact of urban environmental pollution on growth, leaf damage, and chemical constituents of Warsaw urban trees

Treesearch

Waldemar Chmielewski; Wojciech Dmuchowski; Stanislaw Suplat

1998-01-01

In the last 10 years, 3.5 percent of the tree population died annually in PolandÕs largest and most polluted cities, which is a problem of economic importance. Dieback of streetside trees in Warsaw is a long term process. It is an effect of biological reactions of trees to unfavorable conditions in the urban environment, particularly air and soil pollution and water...

White Fringetree as a Novel Larval Host for Emerald Ash Borer.

PubMed

Cipollini, Don

2015-02-01

Emerald ash borer is an invasive Asian pest of ash species in North America. All North American species of ash tested so far are susceptible to it, but there are no published reports of this insect developing fully in non-ash hosts in the field in North America. I report here evidence that emerald ash borer can attack and complete development in white fringetree, Chionanthus virginicus L., a species native to the southeastern United States that is also planted ornamentally. Four of 20 mature ornamental white fringetrees examined in the Dayton, Ohio area showed external symptoms of emerald ash borer attack, including the presence of adult exit holes, canopy dieback, and bark splitting and other deformities. Removal of bark from one of these trees yielded evidence of at least three generations of usage by emerald ash borer larvae, several actively feeding live larvae, and a dead adult confirmed as emerald ash borer. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Hymenoscyphus fraxineus vs. Hymenoscyphus albidus – A comparative light microscopic study on the causal agent of European ash dieback and related foliicolous, stroma-forming species

PubMed Central

Baral, Hans-Otto; Bemmann, Martin

2014-01-01

Five species of Hymenoscyphus that fruit on black stromatized parts of dead leaves of deciduous trees are presented, giving details on their morphological and ecological characteristics. Several of these species have previously been misplaced in rutstroemiaceous genera because of the presence of a substratal stroma. However, the heteropolar, scutuloid ascospores with an often hook-like lateral protrusion at the rounded apex and the ascus apical ring of the Hymenoscyphus-type represent two reliable morphological characteristics that, together with molecular data, provide clear evidence for their placement in the genus Hymenoscyphus (Helotiaceae). Among the species treated is Hymenoscyphus fraxineus (=Hymenoscyphus pseudoalbidus), the causal agent of the European ash dieback disease. Since 1992 this species started within Europe to replace the rather uncommon Hymenoscyphus albidus, which is likewise confined to leaves of Fraxinus. Hy. fraxineus has been recorded already since 1990 in Eastern Asia (Japan, Korea, northeast of China), where it had been initially misidentified as Lambertella albida (≡Hy. albidus). In these regions, it occurs as a harmless saprotroph on Fraxinus mandshurica and Fraxinus rhynchophylla, suggesting that those populations are native while the European ash dieback disease has a recent Eastern Asiatic origin. The distinctly higher genetic diversity found in Japanese Hy. fraxineus in contrast to European Hy. fraxineus supports this view. Genetic similarities between Japanese Hy. fraxineus and European Hy. albidus suggest that also Hy. albidus might be a descendant of Asian Hy. fraxineus, though having invaded Europe much earlier. However, consistent genetic deviation between European and Asian Hy. fraxineus at two nucleotide positions of the ITS region indicates that the European ash disease originates from a region different from the presently known areas in Eastern Asia. Our results underline the importance of detailed morphological studies in combination with molecular work. Hy. fraxineus was described from Europe as a cryptic species that differed from Hy. albidus by molecular data alone. However, the Hy. albidus/Hy. fraxineus species complex represents one of many examples within the ascomycetes in which subtle microscopic differences between closely related species, in this case the presence or absence of croziers at the ascus base, are strictly correlated with molecular characteristics. Two species that closely resemble Hy. albidus and Hy. fraxineus form pseudosclerotia in Aesculus leaves and again differ from each other mainly in the ascus base: Hymenoscyphus aesculi on Aesculus hippocastanum from Europe lacks croziers, whereas Hymenoscyphus honshuanus from Japan on Aesculus turbinata possesses croziers. Other taxa treated here include Hymenoscyphus vacini, a European species growing on stromatized net veins of skeletonized leaves of Acer, and Hymenoscyphus torquatus, a Chinese species on unidentified herbaceous stems. An equivalent stroma-forming North American species on leaves of Fraxinus, Rutstroemia longipes (Rutstroemiaceae), is discussed and compared. A key to the Hymenoscyphus species that form a dark stroma on leaves of Acer, Aesculus, Fraxinus, and Picrasma is provided. PMID:25544935

Comparison of FVS projection of oak decline on the Mark Twain National Forest to actual growth and mortality as measured over three FIA inventory cycles

Treesearch

Don Vandendriesche; Linda Haugen

2008-01-01

Oak decline has been recorded on oak forests throughout the Ozark Plateau of Missouri since the 1970s, but severe drought in the late 1990s, combined with the advancing age of the Ozark forests, has intensified the levels of crown dieback and mortality beyond historical levels. The purpose of this project was to determine whether the Forest Vegetation Simulator (FVS)...

Interactions among Amazon land use, forests and climate: prospects for a near-term forest tipping point.

PubMed

Nepstad, Daniel C; Stickler, Claudia M; Filho, Britaldo Soares-; Merry, Frank

2008-05-27

Some model experiments predict a large-scale substitution of Amazon forest by savannah-like vegetation by the end of the twenty-first century. Expanding global demands for biofuels and grains, positive feedbacks in the Amazon forest fire regime and drought may drive a faster process of forest degradation that could lead to a near-term forest dieback. Rising worldwide demands for biofuel and meat are creating powerful new incentives for agro-industrial expansion into Amazon forest regions. Forest fires, drought and logging increase susceptibility to further burning while deforestation and smoke can inhibit rainfall, exacerbating fire risk. If sea surface temperature anomalies (such as El Niño episodes) and associated Amazon droughts of the last decade continue into the future, approximately 55% of the forests of the Amazon will be cleared, logged, damaged by drought or burned over the next 20 years, emitting 15-26Pg of carbon to the atmosphere. Several important trends could prevent a near-term dieback. As fire-sensitive investments accumulate in the landscape, property holders use less fire and invest more in fire control. Commodity markets are demanding higher environmental performance from farmers and cattle ranchers. Protected areas have been established in the pathway of expanding agricultural frontiers. Finally, emerging carbon market incentives for reductions in deforestation could support these trends.

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

Interactions and consequences of silicon, nitrogen, and Fusarium palustre on herbivory and DMSP levels of Spartina alterniflora

NASA Astrophysics Data System (ADS)

Bazzano, Magalí; Elmer, Wade

2017-11-01

Sudden Vegetation Dieback (SVD) has been associated with multiple factors affecting the health of Spartina alterniflora. These include altered nutrition (N, Si and various metals), herbivory from the purple marsh crab, and the association with a fungal pathogen (Fusarium palustre). A metabolite produced by Spartina alterniflora that has been associated with plant health is dimethylsulfoniopropionate (DMSP), but little information exist on how these biotic stressors and nutrition interact to affect DMSP levels. Understanding how these factors might be interrelated might provide insight into the etiology of SVD. Surveys of a marsh affected by SVD confirmed lower levels of DMSP and higher concentrations of Si and other metals were present in Sp. alterniflora when compared to plants from marsh that exhibited no signs of SVD. In repeated greenhouse experiments, the application of Si to Sp. alterniflora had no effect on DMSP concentrations. However, when plants were inoculated with the pathogenic fungus, Fusarium palustre, and then treated with Si, DMSP levels were elevated 27%. Inoculation alone had no effect on DMSP levels. Si application neither favor growth nor suppress the stunting effect of disease by F. palustre. Furthermore, grazing by Sesarma reticulatum, a herbivorous crab, was not affected by Si nutrition. Grazing was increased by nitrogen fertilization and inoculation with F. palustre. Deciphering the role of Si nutrition in Sp. alterniflora and dieback remains unresolved, but no evidence suggests enhancing Si nutrition would directly favor marsh health.

Can vessel dimension explain tolerance toward fungal vascular wilt diseases in woody plants? Lessons from Dutch elm disease and esca disease in grapevine

PubMed Central

Pouzoulet, Jérôme; Pivovaroff, Alexandria L.; Santiago, Louis S.; Rolshausen, Philippe E.

2014-01-01

This review illuminates key findings in our understanding of grapevine xylem resistance to fungal vascular wilt diseases. Grapevine (Vitis spp.) vascular diseases such as esca, botryosphaeria dieback, and eutypa dieback, are caused by a set of taxonomically unrelated ascomycete fungi. Fungal colonization of the vascular system leads to a decline of the plant host because of a loss of the xylem function and subsequent decrease in hydraulic conductivity. Fungal vascular pathogens use different colonization strategies to invade and kill their host. Vitis vinifera cultivars display different levels of tolerance toward vascular diseases caused by fungi, but the plant defense mechanisms underlying those observations have not been completely elucidated. In this review, we establish a parallel between two vascular diseases, grapevine esca disease and Dutch elm disease, and argue that the former should be viewed as a vascular wilt disease. Plant genotypes exhibit differences in xylem morphology and resistance to fungal pathogens causing vascular wilt diseases. We provide evidence that the susceptibility of three commercial V. vinifera cultivars to esca disease is correlated to large vessel diameter. Additionally, we explore how xylem morphological traits related to water transport are influenced by abiotic factors, and how these might impact host tolerance of vascular wilt fungi. Finally, we explore the utility of this concept for predicting which V. vinifera cultivars are most vulnerable of fungal vascular wilt diseases and propose new strategies for disease management. PMID:24971084

Early growth interactions between a mangrove and an herbaceous salt marsh species are not affected by elevated CO2 or drought

NASA Astrophysics Data System (ADS)

Howard, Rebecca J.; Stagg, Camille L.; Utomo, Herry S.

2018-07-01

Increasing atmospheric carbon dioxide (CO2) concentrations are likely to influence future distributions of plants and plant community structure in many regions of the world through effects on photosynthetic rates. In recent decades the encroachment of woody mangrove species into herbaceous marshes has been documented along the U.S. northern Gulf of Mexico coast. These species shifts have been attributed primarily to rising sea levels and warming winter temperatures, but the role of elevated CO2 and water availability may become more prominent drivers of species interactions under future climate conditions. Drought has been implicated as a major factor contributing to salt marsh vegetation dieback in this region. In this greenhouse study we examined the effects of CO2 concentration (∼380 ppm, ∼700 ppm) and water regime (drought, saturated, flooded) on early growth of Avicennia germinans, a C3 mangrove species, and Spartina alterniflora, a C4 grass. Plants were grown in monocultures and in a mixed-species assemblage. We found that neither species responded to elevated CO2 over the 10-month duration of the experiment, and there were few interactions between experimental factors. Two effects of water regime were documented: lower A. germinans pneumatophore biomass under drought conditions, and lower belowground biomass under flooded conditions regardless of planting assemblage. Evidence of interspecific interactions was noted. Competition for aboveground resources (e.g., light) was indicated by lower S. alterniflora stem biomass in mixed-species assemblage compared to biomass in S. alterniflora monocultures. Pneumatophore biomass of A. germinans was reduced when grown in monoculture compared to the mixed-species assemblage, indicating competition for belowground resources. These interactions provide insight into how these species may respond following major disturbance events that lead to vegetation dieback. Site variation in propagule availability and physico-chemical conditions will determine plant community composition and structure following such disturbances when these two species co-occur.

The synergistic use of models and observations: understanding the mechanisms behind observed biomass dynamics at 14 Amazonian field sites and the implications for future biomass change

NASA Astrophysics Data System (ADS)

Levine, N. M.; Galbraith, D.; Christoffersen, B. J.; Imbuzeiro, H. A.; Restrepo-Coupe, N.; Malhi, Y.; Saleska, S. R.; Costa, M. H.; Phillips, O.; Andrade, A.; Moorcroft, P. R.

2011-12-01

The Amazonian rainforests play a vital role in global water, energy and carbon cycling. The sensitivity of this system to natural and anthropogenic disturbances therefore has important implications for the global climate. Some global models have predicted large-scale forest dieback and the savannization of Amazonia over the next century [Meehl et al., 2007]. While several studies have demonstrated the sensitivity of dynamic global vegetation models to changes in temperature, precipitation, and dry season length [e.g. Galbraith et al., 2010; Good et al., 2011], the ability of these models to accurately reproduce ecosystem dynamics of present-day transitional or low biomass tropical forests has not been demonstrated. A model-data intercomparison was conducted with four state-of-the-art terrestrial ecosystem models to evaluate the ability of these models to accurately represent structure, function, and long-term biomass dynamics over a range of Amazonian ecosystems. Each modeling group conducted a series of simulations for 14 sites including mature forest, transitional forest, savannah, and agricultural/pasture sites. All models were run using standard physical parameters and the same initialization procedure. Model results were compared against forest inventory and dendrometer data in addition to flux tower measurements. While the models compared well against field observations for the mature forest sites, significant differences were observed between predicted and measured ecosystem structure and dynamics for the transitional forest and savannah sites. The length of the dry season and soil sand content were good predictors of model performance. In addition, for the big leaf models, model performance was highest for sites dominated by late successional trees and lowest for sites with predominantly early and mid-successional trees. This study provides insight into tropical forest function and sensitivity to environmental conditions that will aid in predictions of the response of the Amazonian rainforest to future anthropogenically induced changes.

Parallel shifts in ecology and natural selection in an island lizard

PubMed Central

Calsbeek, Ryan; Buermann, Wolfgang; Smith, Thomas B

2009-01-01

Background Natural selection is a potent evolutionary force that shapes phenotypic variation to match ecological conditions. However, we know little about the year-to-year consistency of selection, or how inter-annual variation in ecology shapes adaptive landscapes and ultimately adaptive radiations. Here we combine remote sensing data, field experiments, and a four-year study of natural selection to show that changes in vegetation structure associated with a severe drought altered both habitat use and natural selection in the brown anole, Anolis sagrei. Results In natural populations, lizards increased their use of vegetation in wet years and this was correlated with selection on limb length but not body size. By contrast, a die-back of vegetation caused by drought was followed by reduced arboreality, selection on body size, and relaxed selection on limb length. With the return of the rains and recovery of vegetation, selection reverted back to pre-drought pattern of selection acting on limb length but not body size. To test for the impact of vegetation loss on natural selection during the drought, we experimentally removed vegetation on a separate study island in a naturally wet year. The experiment revealed similar inter-annual changes in selection on body size but not limb length. Conclusion Our results illustrate the dynamic nature of ecology driving natural selection on Anolis morphology and emphasize the importance of inter-annual environmental variation in shaping adaptive variation. In addition, results illustrate the utility of using remote sensing data to examine ecology's role in driving natural selection. PMID:19126226

Flood-Ring Formation and Root Development in Response to Experimental Flooding of Young Quercus robur Trees

PubMed Central

Copini, Paul; den Ouden, Jan; Robert, Elisabeth M. R.; Tardif, Jacques C.; Loesberg, Walter A.; Goudzwaard, Leo; Sass-Klaassen, Ute

2016-01-01

Spring flooding in riparian forests can cause significant reductions in earlywood-vessel size in submerged stem parts of ring-porous tree species, leading to the presence of ‘flood rings’ that can be used as a proxy to reconstruct past flooding events, potentially over millennia. The mechanism of flood-ring formation and the relation with timing and duration of flooding are still to be elucidated. In this study, we experimentally flooded 4-year-old Quercus robur trees at three spring phenophases (late bud dormancy, budswell, and internode expansion) and over different flooding durations (2, 4, and 6 weeks) to a stem height of 50 cm. The effect of flooding on root and vessel development was assessed immediately after the flooding treatment and at the end of the growing season. Ring width and earlywood-vessel size and density were measured at 25- and 75-cm stem height and collapsed vessels were recorded. Stem flooding inhibited earlywood-vessel development in flooded stem parts. In addition, flooding upon budswell and internode expansion led to collapsed earlywood vessels below the water level. At the end of the growing season, mean earlywood-vessel size in the flooded stem parts (upon budswell and internode expansion) was always reduced by approximately 50% compared to non-flooded stem parts and 55% compared to control trees. This reduction was already present 2 weeks after flooding and occurred independent of flooding duration. Stem and root flooding were associated with significant root dieback after 4 and 6 weeks and mean radial growth was always reduced with increasing flooding duration. By comparing stem and root flooding, we conclude that flood rings only occur after stem flooding. As earlywood-vessel development was hampered during flooding, a considerable number of narrow earlywood vessels present later in the season, must have been formed after the actual flooding events. Our study indicates that root dieback, together with strongly reduced hydraulic conductivity due to anomalously narrow earlywood vessels in flooded stem parts, contribute to reduced radial growth after flooding events. Our findings support the value of flood rings to reconstruct spring flooding events that occurred prior to instrumental flood records. PMID:27379108

What mediates tree mortality during drought in the southern Sierra Nevada?

USGS Publications Warehouse

Paz-Kagan, Tarin; Brodrick, Philip; Vaughn, Nicholas R.; Das, Adrian J.; Stephenson, Nathan L.; Nydick, Koren R.; Asner, Gregory P.

2017-01-01

Severe drought has the potential to cause selective mortality within a forest, thereby inducing shifts in forest species composition. The southern Sierra Nevada foothills and mountains of California have experienced extensive forest dieback due to drought stress and insect outbreak. We used high-fidelity imaging spectroscopy (HiFIS) and light detection and ranging (LiDAR) from the Carnegie Airborne Observatory (CAO) to estimate the effect of forest dieback on species composition in response to drought stress in Sequoia National Park. Our aims were: (1) to quantify site-specific conditions that mediate tree mortality along an elevation gradient in the southern Sierra Nevada Mountains; (2) to assess where mortality events have a greater probability of occurring; and (3) to estimate which tree species have a greater likelihood of mortality along the elevation gradient. A series of statistical models were generated to classify species composition and identify tree mortality, and the influences of different environmental factors were spatially quantified and analyzed to assess where mortality events have a greater likelihood of occurring. A higher probability of mortality was observed in the lower portion of the elevation gradient, on southwest and west-facing slopes, in areas with shallow soils, on shallower slopes, and at greater distances from water. All of these factors are related to site water balance throughout the landscape. Our results also suggest that mortality is species-specific along the elevation gradient, mainly affecting Pinus ponderosa and Pinus lambertiana at lower elevations. Selective mortality within the forest may drive long-term shifts in community composition along the elevation gradient.

What mediates tree mortality during drought in the southern Sierra Nevada?

PubMed

Paz-Kagan, Tarin; Brodrick, Philip G; Vaughn, Nicholas R; Das, Adrian J; Stephenson, Nathan L; Nydick, Koren R; Asner, Gregory P

2017-12-01

Severe drought has the potential to cause selective mortality within a forest, thereby inducing shifts in forest species composition. The southern Sierra Nevada foothills and mountains of California have experienced extensive forest dieback due to drought stress and insect outbreak. We used high-fidelity imaging spectroscopy (HiFIS) and light detection and ranging (LiDAR) from the Carnegie Airborne Observatory (CAO) to estimate the effect of forest dieback on species composition in response to drought stress in Sequoia National Park. Our aims were (1) to quantify site-specific conditions that mediate tree mortality along an elevation gradient in the southern Sierra Nevada Mountains, (2) to assess where mortality events have a greater probability of occurring, and (3) to estimate which tree species have a greater likelihood of mortality along the elevation gradient. A series of statistical models were generated to classify species composition and identify tree mortality, and the influences of different environmental factors were spatially quantified and analyzed to assess where mortality events have a greater likelihood of occurring. A higher probability of mortality was observed in the lower portion of the elevation gradient, on southwest- and west-facing slopes, in areas with shallow soils, on shallower slopes, and at greater distances from water. All of these factors are related to site water balance throughout the landscape. Our results also suggest that mortality is species-specific along the elevation gradient, mainly affecting Pinus ponderosa and Pinus lambertiana at lower elevations. Selective mortality within the forest may drive long-term shifts in community composition along the elevation gradient. © 2017 by the Ecological Society of America.

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.

Soil solution and sugar maple response to NH(4)NO (3) additions in a base-poor northern hardwood forest of Québec, Canada.

PubMed

Moore, Jean-David; Houle, Daniel

2009-08-01

Nitrogen additions (NH4NO3) at rates of three- and ten-fold ambient atmospheric deposition (8.5 kg ha(-1) year(-1)) were realised in an acid- and base-poor northern hardwood forest of Québec, Canada. Soil solution chemistry, foliar chemistry, crown dieback and basal area growth of sugar maple (Acer saccharum Marsh.) were measured. Except for a transitory increase of NO3 and NH4 concentrations, there was no persistent increase in their level in soil solution 3 years after N treatments, with the exception of one plot out of three, that received the highest N addition, beginning to show persistent and high NO3 concentrations after 2 years of N additions. Three years of N additions have significantly increased the N DRIS index of sugar maple but not N foliar concentration. Potassium, Ca and Mn foliar concentrations, as well as P and Ca DRIS indices, decreased in treated plots after 3 years. No treatment effect was observed for basal area growth and dieback rate. One unexpected result was the significant decrease in foliar Ca even in the treated plots that received low N rates, despite the absence of significant NO3-induced leaching of Ca. The mechanism responsible for the decrease in foliar Ca is not known. Our results, however, clearly demonstrate that increased N deposition at sites with low base saturation may affect Ca nutrition even when clear signs of N saturation are not observed.

Features of Scots pine radial growth in conditions of provenance trial.

NASA Astrophysics Data System (ADS)

Kuzmin, Sergey; Kuzmina, Nina

2013-04-01

Provenance trial of Scots pine in Boguchany forestry of Krasnoyarsk krai is conducted on two different soils - dark-grey loam forest soil and sod-podzol sandy soil. Complex of negative factors for plant growth and development appears in dry conditions of sandy soil. It could results in decrease of resistance to diseases. Sandy soils in different climatic zones have such common traits as low absorbing capacity, poorness of elemental nutrition, low microbiological activity and moisture capacity, very high water permeability. But Scots pine trees growing in such conditions could have certain advantages and perspectives of use. In the scope of climate change (global warming) the study of Scots pine growth on sandy soil become urgent because of more frequent appearance of dry seasons. Purpose of the work is revelation of radial growth features of Scots pine with different origin in dry conditions of sandy soil and assessment of external factors influence. The main feature of radial growth of majority of studied pine provenances in conditions of sandy soil is presence of significant variation of increment with distinct decline in 25-years old with loss of tree rings in a number of cases. The reason of it is complex of factors: deficit of June precipitation and next following outbreak of fungal disease. Found «frost rings» for all trees of studied clymatypes in 1992 are the consequence of temperature decline from May 21 to June 2 - from 23 down to 2 degree Celsius. Perspective climatypes with biggest radial increments and least sensitivity to fungal disease were revealed. Eniseysk and Vikhorevka (from Krasnoyarsk krai and Irkutsk oblast)provenances of pine have the biggest radial increments, the least sensitivity to Cenangium dieback and smallest increments decline. These climatypes are in the group of perspective provenances and in present time they are recommended for wide trial in the region for future use in plantation forest growing. Kandalaksha (Murmansk oblast) climatype from northern taiga with good resistance to pathogen have nonsignificant decline in radial increment during epiphytoty in comparison with local and southern climatypes. Southern Chemal provenance (Altai) after influence of Cenangium dieback has more than others losses of tree rings as the result of nonresistance to this fungal disease.

Ten Years of Land Cover Change on the California Coast Detected using Landsat Satellite Image Analysis

NASA Technical Reports Server (NTRS)

Potter, Christopher S.

2013-01-01

Landsat satellite imagery was analyzed to generate a detailed record of 10 years of vegetation disturbance and regrowth for Pacific coastal areas of Marin and San Francisco Counties. The Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) methodology, a transformation of Tasseled-Cap data space, was applied to detected changes in perennial coastal shrubland, woodland, and forest cover from 1999 to 2009. Results showed several principal points of interest, within which extensive contiguous areas of similar LEDAPS vegetation change (either disturbed or restored) were detected. Regrowth areas were delineated as burned forest areas in the Point Reyes National Seashore (PRNS) from the 1995 Vision Fire. LEDAPS-detected disturbance patterns on Inverness Ridge, PRNS in areas observed with dieback of tanoak and bay laurel trees was consistent with defoliation by sudden oak death (Phytophthora ramorum). LEDAPS regrowth pixels were detected over much of the predominantly grassland/herbaceous cover of the Olema Valley ranchland near PRNS. Extensive restoration of perennial vegetation cover on Crissy Field, Baker Beach and Lobos Creek dunes in San Francisco was identified. Based on these examples, the LEDAPS methodology will be capable of fulfilling much of the need for continual, low-cost monitoring of emerging changes to coastal ecosystems.

Forcings and feedbacks by land ecosystem changes on climate change

NASA Astrophysics Data System (ADS)

Betts, R. A.

2006-12-01

Vegetation change is involved in climate change through both forcing and feedback processes. Emissions of CO{2} from past net deforestation are estimated to have contributed approximately 0.22 0.51 Wm - 2 to the overall 1.46 Wm - 2 radiative forcing by anthropogenic increases in CO{2} up to the year 2000. Deforestation-induced increases in global mean surface albedo are estimated to exert a radiative forcing of 0 to -0.2 Wm - 2, and dust emissions from land use may exert a radiative forcing of between approximately +0.1 and -0.2 Wm - 2. Changes in the fluxes of latent and sensible heat due to tropical deforestation are simulated to have exerted other local warming effects which cannot be quantified in terms of a Wm - 2 radiative forcing, with the potential for remote effects through changes in atmospheric circulation. With tropical deforestation continuing rapidly, radiative forcing by surface albedo change may become less useful as a measure of the forcing of climate change by changes in the physical properties of the land surface. Although net global deforestation is continuing, future scenarios used for climate change prediction suggest that fossil fuel emissions of CO{2} may continue to increase at a greater rate than land use emissions and therefore continue to increase in dominance as the main radiative forcing. The CO{2} rise may be accelerated by up to 66% by feedbacks arising from global soil carbon loss and forest dieback in Amazonia as a consequence of climate change, and Amazon forest dieback may also exert feedbacks through changes in the local water cycle and increases in dust emissions.

Fire-mediated dieback and compositional cascade in an Amazonian forest.

PubMed

Barlow, Jos; Peres, Carlos A

2008-05-27

The only fully coupled land-atmosphere global climate model predicts a widespread dieback of Amazonian forest cover through reduced precipitation. Although these predictions are controversial, the structural and compositional resilience of Amazonian forests may also have been overestimated, as current vegetation models fail to consider the potential role of fire in the degradation of forest ecosystems. We examine forest structure and composition in the Arapiuns River basin in the central Brazilian Amazon, evaluating post-fire forest recovery and the consequences of recurrent fires for the patterns of dominance of tree species. We surveyed tree plots in unburned and once-burned forests examined 1, 3 and 9 years after an unprecedented fire event, in twice-burned forests examined 3 and 9 years after fire and in thrice-burned forests examined 5 years after the most recent fire event. The number of trees recorded in unburned primary forest control plots was stable over time. However, in both once- and twice-burned forest plots, there was a marked recruitment into the 10-20cm diameter at breast height tree size classes between 3 and 9 years post-fire. Considering tree assemblage composition 9 years after the first fire contact, we observed (i) a clear pattern of community turnover among small trees and the most abundant shrubs and saplings, and (ii) that species that were common in any of the four burn treatments (unburned, once-, twice- and thrice-burned) were often rare or entirely absent in other burn treatments. We conclude that episodic wildfires can lead to drastic changes in forest structure and composition, with cascading shifts in forest composition following each additional fire event. Finally, we use these results to evaluate the validity of the savannization paradigm.

When the forest dies: the response of forest soil fungi to a bark beetle-induced tree dieback

PubMed Central

Štursová, Martina; Šnajdr, Jaroslav; Cajthaml, Tomáš; Bárta, Jiří; Šantrůčková, Hana; Baldrian, Petr

2014-01-01

Coniferous forests cover extensive areas of the boreal and temperate zones. Owing to their primary production and C storage, they have an important role in the global carbon balance. Forest disturbances such as forest fires, windthrows or insect pest outbreaks have a substantial effect on the functioning of these ecosystems. Recent decades have seen an increase in the areas affected by disturbances in both North America and Europe, with indications that this increase is due to both local human activity and global climate change. Here we examine the structural and functional response of the litter and soil microbial community in a Picea abies forest to tree dieback following an invasion of the bark beetle Ips typographus, with a specific focus on the fungal community. The insect-induced disturbance rapidly and profoundly changed vegetation and nutrient availability by killing spruce trees so that the readily available root exudates were replaced by more recalcitrant, polymeric plant biomass components. Owing to the dramatic decrease in photosynthesis, the rate of decomposition processes in the ecosystem decreased as soon as the one-time litter input had been processed. The fungal community showed profound changes, including a decrease in biomass (2.5-fold in the litter and 12-fold in the soil) together with the disappearance of fungi symbiotic with tree roots and a relative increase in saprotrophic taxa. Within the latter group, successive changes reflected the changing availability of needle litter and woody debris. Bacterial biomass appeared to be either unaffected or increased after the disturbance, resulting in a substantial increase in the bacterial/fungal biomass ratio. PMID:24671082

Examination of Axonal Injury and Regeneration in Microfluidic Neuronal Culture Using Pulsed Laser Microbeam Dissection

PubMed Central

Hellman, Amy N.; Vahidi, Behrad; Kim, Hyung Joon; Mismar, Wael; Steward, Oswald; Jeon, Noo Li; Venugopalan, Vasan

2010-01-01

We describe the integrated use of pulsed laser microbeams and microfluidic cell culture to examine the dynamics of axonal injury and regeneration in vitro. Microfabrication methods are used to place high purity dissociated central nervous system neurons in specific regions that allow the axons to interact with permissive and inhibitory substrates. Acute injury to neuron bundles is produced via the delivery of single 180 ps duration, λ=532 nm laser pulses. Laser pulse energies of 400 nJ and 800 nJ produce partial and complete transection of the axons, respectively, resulting in elliptical lesions 25 μm and 50 μm in size. The dynamics of the resulting degeneration and regrowth of proximal and distal axonal segments are examined for up to 8 h using time-lapse microscopy. We find the proximal and distal dieback distances from the site of laser microbeam irradiation to be roughly equal for both partial and complete transection of the axons. In addition, distinct growth cones emerge from the proximal neurite segments within 1–2 h post-injury, followed by a uniform front of regenerating axons that originate from the proximal segment and traverse the injury site within 8 h. We also examine the use of EGTA to chelate the extracellular calcium and potentially reduce the severity of the axonal degeneration following injury. While we find the addition of EGTA to reduce the severity of the initial dieback, it also hampers neurite repair and interfere with the formation of neuronal growth cones to traverse the injury site. This integrated use of laser microbeam dissection within a microfluidic cell culture system to produce precise zones of neuronal injury shows potential for high-throughput screening of agents to promote neuronal regeneration. PMID:20532390

Progression of ash canopy thinning and dieback outward from the initial infestation of emerald ash borer (Coleoptera: Buprestidae) in southeastern Michigan.

PubMed

Smitley, David; Davis, Terrance; Rebek, Eric

2008-10-01

Our objective was to characterize the rate at which ash (Fraxinus spp.) trees decline in areas adjacent to the leading edge of visible ash canopy thinning due to emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). Trees in southeastern Michigan were surveyed from 2003 to 2006 for canopy thinning and dieback by comparing survey trees with a set of 11 standard photographs. Freeways stemming from Detroit in all directions were used as survey transects. Between 750 and 1,100 trees were surveyed each year. A rapid method of sampling populations of emerald ash borer was developed by counting emerald ash borer emergence holes with binoculars and then felling trees to validate binocular counts. Approximately 25% of the trees surveyed for canopy thinning in 2005 and 2006 also were sampled for emerald ash borer emergence holes using binoculars. Regression analysis indicates that 41-53% of the variation in ash canopy thinning can be explained by the number of emerald ash borer emergence holes per tree. Emerald ash borer emergence holes were found at every site where ash canopy thinning averaged > 40%. In 2003, ash canopy thinning averaged 40% at a distance of 19.3 km from the epicenter of the emerald ash borer infestation in Canton. By 2006, the point at which ash trees averaged 40% canopy thinning had increased to a distance of 51.2 km away from Canton. Therefore, the point at which ash trees averaged 40% canopy thinning, a state of decline clearly visible to the average person, moved outward at a rate of 10.6 km/yr during this period.

Distribution, Predictors, and Impacts of Emerald Ash Borer (Agrilus planipennis) (Coleoptera: Buprestidae) Infestation of White Fringetree (Chionanthus virginicus).

PubMed

Peterson, Donnie L; Cipollini, Don

2017-02-01

Emerald ash borer, Agrilus planipennis (Fairmaire), is an invasive pest of ash trees (Fraxinus spp.) in North America that was recently found infesting white fringetree (Chionanthus virginicus L.). Initial reports of the infestation of white fringetree by emerald ash borer occurred in southwestern Ohio and Chicago, IL. We examined white fringetrees at additional sites in Illinois, Indiana, Ohio, and Pennsylvania in Summer and Fall 2015 and Winter 2016 for emerald ash borer infestation. Our aim was to examine white fringetrees at a limited number of sites with emerald ash borer infestation and to relate tree size, crown dieback, epicormic sprouting, tree sex, and adjacency to ash or white fringetrees with the likelihood of beetle infestation. A higher proportion of infested trees exhibited epicormic sprouting and the likelihood that a tree was infested increased with increasing crown dieback, variables that may be both predictors and responses to attack. The proportion of trees infested with emerald ash borer increased with increasing tree size. Signs consistent with emerald ash borer infestation were found in 26% of 178 white fringetrees, with at least one host infested at each site in all states. Infestation rates of white fringetrees increased with the density of white fringetrees at each site. The Chicago Botanic Garden site had a significantly lower infestation (3.7%) than other sites, which may be due to proactive management of ash. Overall, these data indicate white fringetree has been utilized by emerald ash borer throughout their overlapping ranges in the United States in ornamental settings likely due to ecological fitting. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Nogo-66 Receptor Antagonist Peptide (NEP1-40) Administration Promotes Functional Recovery and Axonal Growth After Lateral Funiculus Injury in the Adult Rat

PubMed Central

Cao, Y.; Shumsky, J. S.; Sabol, M. A.; Kushner, R. A.; Strittmatter, S.; Hamers, F. P. T.; Lee, D. H. S.; Rabacchi, S. A.; Murray, M.

2010-01-01

Objective The myelin protein Nogo inhibits axon regeneration by binding to its receptor (NgR) on axons. Intrathecal delivery of an NgR antagonist (NEP1-40) promotes growth of injured corticospinal axons and recovery of motor function following a dorsal hemisection. The authors used a similar design to examine recovery and repair after a lesion that interrupts the rubrospinal tract (RST). Methods Rats received a lateral funiculotomy at C4 and NEP1-40 or vehicle was delivered to the cervical spinal cord for 4 weeks. Outcome measures included motor and sensory tests and immunohistochemistry. Results Gait analysis showed recovery in the NEP1-40-treated group compared to operated controls, and a test of forelimb usage also showed a beneficial effect. The density of labeled RST axons increased ipsilaterally in the NEP1-40 group in the lateral funiculus rostral to the lesion and contralaterally in both gray and white matter. Thus, rubrospinal axons exhibited diminished dieback and/or growth up to the lesion site. This was accompanied by greater density of 5 HT and calcitonin gene-related peptide axons adjacent to and into the lesion/matrix site in the NEP1-40 group. Conclusions NgR blockade after RST injury is associated with axonal growth and/or diminished dieback of severed RST axons up to but not into or beyond the lesion/matrix site, and growth of serotonergic and dorsal root axons adjacent to and into the lesion/matrix site. NgR blockade also supported partial recovery of function. The authors’ results indicate that severed rubrospinal axons respond to NEP1-40 treatment but less robustly than corticospinal, raphe-spinal, or dorsal root axons. PMID:18056009

A 10-Year Assessment of Hemlock Decline in the Catskill Mountain Region of New York State Using Hyperspectral Remote Sensing Techniques.

PubMed

Hanavan, Ryan P; Pontius, Jennifer; Hallett, Richard

2015-02-01

The hemlock woolly adelgid is a serious pest of Eastern and Carolina hemlock in the eastern United States. Successfully managing the hemlock resource in the region depends on careful monitoring of the spread of this invasive pest and the targeted application of management options such as biological control, chemical, or silvicultural treatments. To inform these management activities and test the applicability of a landscape-scale remote sensing effort to monitor hemlock condition, hyperspectral collections, and concurrent ground-truthing in 2001 and 2012 of hemlock condition were compared with field metrics spanning a 10-yr survey in the Catskills region of New York. Fine twig dieback significantly increased from 9 to 15% and live crown ratio significantly decreased from 67 to 56% in 2001 and 2012, respectively. We found a significant shift from 59% "healthy" hemlock in 2001 to only 16% in 2012. However, this shift from healthy to declining classifications was mostly a shift to decline class 2 "early decline". These results indicate that while there has been significant increase in decline symptoms as measured in both field and remote sensing assessments, a majority of the declining areas identified in the resulting spatial coverages remain in the "early decline" category and widespread mortality has not yet occurred. While this slow decline across the region stands in contrast to many reports of mortality within 10 yr, the results from this work are in line with other long-term monitoring studies and indicate that armed with the spatial information provided here, continued management strategies can be focused on particular areas to help control the further decline of hemlock in the region. Published by Oxford University Press on behalf of Entomological Society of America 2015. This work is written by US Government employees and is in the public domain in the US.

Diplodia quercivora sp. nov.: a new species of Diplodia found on declining Quercus canariensis trees in Tunisia.

PubMed

Linaldeddu, Benedetto T; Franceschini, Antonio; Alves, Artur; Phillips, Alan J L

2013-01-01

During a study of the species of Botryosphaeriaceae associated with oak decline in Tunisia, a large collection of Diplodia strains were isolated from Quercus afares, Q. canariensis and Q. suber trees showing a progressive dieback of shoots and branches, trunk canker and exudates and collar rot. Most of the isolates were identified as Diplodia corticola, while two isolates from Q. canariensis were morphologically and phylogenetically (ITS and tef1-α sequences data) distinct from all other known species of Diplodia. They are described here as Diplodia quercivora sp. nov. In addition, phylogenetic analyses showed for the first time the existence of two distinct lineages within D. corticola. In artificial inoculation experiments, D. quercivora caused necrotic lesions on bark and wood of three Mediterranean oak species, Q. ilex, Q. pubescens and Q. suber. In particular, among the oak species tested, Q. pubescens was the most susceptible.

Seven-Year Evaluation of Insecticide Tools for Emerald Ash Borer in Fraxinus pennsylvanica (Lamiales: Oleaceae) Trees.

PubMed

Bick, Emily N; Forbes, Nora J; Haugen, Christopher; Jones, Grant; Bernick, Shawn; Miller, Fredric

2018-04-02

Emerald ash borer (EAB), Agrilus planipennis (Fairmaire; Coleoptera: Buprestidae), is decimating ash trees (Fraxinus spp.) in North America. Combatting EAB includes the use of insecticides; however, reported insecticide efficacy varies among published studies. This study assessed the effects of season of application, insecticide active ingredient, and insecticide application rate on green ash (Fraxinus pennsylvanica Marsh.) (Lamiales: Oleaceae) canopy decline caused by EAB over a 5- to 7-yr interval. Data suggested that spring treatments were generally more effective in reducing canopy decline than fall treatments, but this difference was not statistically significant. Lowest rates of decline (<5% over 5 yr) were observed in trees treated with imidacloprid injected annually in the soil during spring (at the higher of two tested application rates; 1.12 g/cm diameter at 1.3 m height) and emamectin benzoate injected biennially into the stem. All tested insecticides (dinotefuran, emamectin benzoate, and imidacloprid) under all tested conditions significantly reduced the rate of increase of dieback.

Connection of Gnomonia intermedia to Discula betulina and its relationship to other taxa in Gnomoniaceae.

PubMed

Green, Sarah; Castlebury, Lisa A

2007-01-01

Discula betulina is a foliar pathogen on birch (Betula) and Gnomonia intermedia is found on overwintered birch leaves. Perithecia of G. intermedia developed in vitro on colonies of D. betulina isolated from birch tissues in late summer, and single ascospores of G. intermedia consistently developed into colonies similar to D. betulina, producing typical D. betulina conidia. Isolates of D. betulina could be grouped into two mating types, which produced fertile perithecia of G. intermedia when mated with each other. Mycelia from single-ascospore and single-conidial isolates were inoculated onto shoots of downy birch, causing lesions and die-back from which D. betulina was consistently isolated. ITS region ribosomal DNA sequence analysis confirmed the results of the morphological and mating studies, and found that the closest known relatives of G. intermedia/D. betulina are Gnomoniella nana and Sirococcus clavigignenti-juglandacearum. The conclusion from these studies is that D. betulina is the anamorph of G. intermedia.

Early growth interactions between a mangrove and an herbaceous salt marsh species are not affected by elevated CO2 or drought

USGS Publications Warehouse

Howard, Rebecca J.; Stagg, Camille L.; Utomo, Herry S.

2018-01-01

Increasing atmospheric carbon dioxide (CO2) concentrations are likely to influence future distributions of plants and plant community structure in many regions of the world through effects on photosynthetic rates. In recent decades the encroachment of woody mangrove species into herbaceous marshes has been documented along the U.S. northern Gulf of Mexico coast. These species shifts have been attributed primarily to rising sea levels and warming winter temperatures, but the role of elevated CO2 and water availability may become more prominent drivers of species interactions under future climate conditions. Drought has been implicated as a major factor contributing to salt marsh vegetation dieback in this region. In this greenhouse study we examined the effects of CO2 concentration (∼380 ppm, ∼700 ppm) and water regime (drought, saturated, flooded) on early growth of Avicennia germinans, a C3 mangrove species, and Spartina alterniflora, a C4 grass. Plants were grown in monocultures and in a mixed-species assemblage. We found that neither species responded to elevated CO2 over the 10-month duration of the experiment, and there were few interactions between experimental factors. Two effects of water regime were documented: lower A. germinanspneumatophore biomass under drought conditions, and lower belowground biomass under flooded conditions regardless of planting assemblage. Evidence of interspecific interactions was noted. Competition for aboveground resources (e.g., light) was indicated by lower S. alterniflora stem biomass in mixed-species assemblage compared to biomass in S. alterniflora monocultures. Pneumatophore biomass of A. germinans was reduced when grown in monoculture compared to the mixed-species assemblage, indicating competition for belowground resources. These interactions provide insight into how these species may respond following major disturbance events that lead to vegetation dieback. Site variation in propagule availability and physico-chemical conditions will determine plant community composition and structure following such disturbances when these two species co-occur.

Vascular Streak Dieback of cacao in Southeast Asia and Melanesia: in planta detection of the pathogen and a new taxonomy.

PubMed

Samuels, Gary J; Ismaiel, Adnan; Rosmana, Ade; Junaid, Muhammad; Guest, David; McMahon, Peter; Keane, Philip; Purwantara, Agus; Lambert, Smilja; Rodriguez-Carres, Marianela; Cubeta, Marc A

2012-01-01

Vascular Streak Dieback (VSD) disease of cacao (Theobroma cacao) in Southeast Asia and Melanesia is caused by a basidiomycete (Ceratobasidiales) fungus Oncobasidium theobromae (syn. =Thanatephorus theobromae). The most characteristic symptoms of the disease are green-spotted leaf chlorosis or, commonly since about 2004, necrotic blotches, followed by senescence of leaves beginning on the second or third flush behind the shoot apex, and blackening of infected xylem in the vascular traces at the leaf scars resulting from the abscission of infected leaves. Eventually the shoot apex is killed and infected branches die. In susceptible cacao the fungus may grow through the xylem down into the main stem and kill a mature cacao tree. Infections in the stem of young plants prior to the formation of the first 3-4 lateral branches usually kill the plant. Basidiospores released from corticioid basidiomata developed on leaf scars or along cracks in the main vein of infected leaves infect young leaves. The pathogen commonly infects cacao but there are rare reports from avocado. As both crops are introduced to the region, the pathogen is suspected to occur asymptomatically in native vegetation. The pathogen is readily isolated but cultures cannot be maintained. In this study, DNA was extracted from pure cultures of O. theobromae obtained from infected cacao plants sampled from Indonesia. The internal transcribed spacer region (ITS), consisting of ITS1, 5.8S ribosomal RNA and ITS2, and a portion of nuclear large subunit (LSU) were sequenced. Phylogenetic analysis of ITS sequences placed O. theobromae sister to Ceratobasidium anastomosis groups AG-A, AG-Bo, and AG-K with high posterior probability. Therefore the new combination Ceratobasidium theobromae is proposed. A PCR-based protocol was developed to detect and identify C. theobromae in plant tissue of cacao enabling early detection of the pathogen in plants. A second species of Ceratobasidium, Ceratobasidium ramicola, identified through ITS sequence analysis, was isolated from VSD-affected cacao plants in Java, and is widespread in diseased cacao collected from Indonesia. Published by Elsevier Ltd.

Wind damage and salinity effects of Hurricanes Katrina and Rita on coastal baldcypress forests of Louisiana: Chapter 6F in Science and the storms-the USGS response to the hurricanes of 2005

USGS Publications Warehouse

Doyle, Thomas W.; Conner, William H.; Day, Richard H.; Krauss, Ken W.; Swarzenski, Christopher M.

2007-01-01

The frequency of hurricane landfall in a given coastal stretch may play a more important role in the ecology of coastal forests than previously thought because of direct and indirect impacts of fallen trees and the introduction of salt water that lingers long after the storm passes. Findings show that surge events can inundate interior freshwater forests many miles from the coast and elevate soil salinities twofold to threefold. These elevated salinities may contribute to delayed mortality of certain tree species and set the stage for eventual forest decline and dieback.

Early warning of climate tipping points

NASA Astrophysics Data System (ADS)

Lenton, Timothy M.

2011-07-01

A climate 'tipping point' occurs when a small change in forcing triggers a strongly nonlinear response in the internal dynamics of part of the climate system, qualitatively changing its future state. Human-induced climate change could push several large-scale 'tipping elements' past a tipping point. Candidates include irreversible melt of the Greenland ice sheet, dieback of the Amazon rainforest and shift of the West African monsoon. Recent assessments give an increased probability of future tipping events, and the corresponding impacts are estimated to be large, making them significant risks. Recent work shows that early warning of an approaching climate tipping point is possible in principle, and could have considerable value in reducing the risk that they pose.

Natural and drought scenarios in an east central Amazon forest: Fidelity of the Community Land Model 3.5 with three biogeochemical models

NASA Astrophysics Data System (ADS)

Sakaguchi, Koichi; Zeng, Xubin; Christoffersen, Bradley J.; Restrepo-Coupe, Natalia; Saleska, Scott R.; Brando, Paulo M.

2011-03-01

Recent development of general circulation models involves biogeochemical cycles: flows of carbon and other chemical species that circulate through the Earth system. Such models are valuable tools for future projections of climate, but still bear large uncertainties in the model simulations. One of the regions with especially high uncertainty is the Amazon forest where large-scale dieback associated with the changing climate is predicted by several models. In order to better understand the capability and weakness of global-scale land-biogeochemical models in simulating a tropical ecosystem under the present day as well as significantly drier climates, we analyzed the off-line simulations for an east central Amazon forest by the Community Land Model version 3.5 of the National Center for Atmospheric Research and its three independent biogeochemical submodels (CASA', CN, and DGVM). Intense field measurements carried out under Large Scale Biosphere-Atmosphere Experiment in Amazonia, including forest response to drought from a throughfall exclusion experiment, are utilized to evaluate the whole spectrum of biogeophysical and biogeochemical aspects of the models. Our analysis shows reasonable correspondence in momentum and energy turbulent fluxes, but it highlights three processes that are not in agreement with observations: (1) inconsistent seasonality in carbon fluxes, (2) biased biomass size and allocation, and (3) overestimation of vegetation stress to short-term drought but underestimation of biomass loss from long-term drought. Without resolving these issues the modeled feedbacks from the biosphere in future climate projections would be questionable. We suggest possible directions for model improvements and also emphasize the necessity of more studies using a variety of in situ data for both driving and evaluating land-biogeochemical models.

Changes in understory species occurrence of a secondary broadleaved forest after mass mortality of oak trees under deer foraging pressure

PubMed Central

2016-01-01

The epidemic of mass mortality of oak trees by Japanese oak wilt has affected secondary deciduous broadleaved forests that have been used as coppices in Japan. The dieback of oak trees formed gaps in the crown that would be expected to enhance the regeneration of shade-intolerant pioneer species. However, foraging by sika deer Cervus nippon has also affected forest vegetation, and the compound effects of both on forest regeneration should be considered when they simultaneously occur. A field study was conducted in Kyôto City, Japan to investigate how these compound effects affected the vegetation of the understory layer of these forests. The presence/absence of seedlings and saplings was observed for 200 quadrats sized 5 m ×5 m for each species in 1992, before the mass mortality and deer encroachment, and in 2014 after these effects. A hierarchical Bayesian model was constructed to explain the occurrence, survival, and colonization of each species with their responses to the gaps that were created, expanded, or affected by the mass mortality of Quercus serrata trees. The species that occurred most frequently in 1992, Eurya japonica, Quercus glauca, and Cleyera japonica, also had the highest survival probabilities. Deer-unpalatable species such as Symplocos prunifolia and Triadica sebifera had higher colonization rates in the gaps, while the deer-palatable species Aucuba japonica had the smallest survival probability. The gaps thus promoted the colonization of deer-unpalatable plant species such as Symplocos prunifolia and Triadica sebifera. In the future, such deer-unpalatable species may dominate gaps that were created, expanded, or affected by the mass mortality of oak trees. PMID:28028480

Changes in understory species occurrence of a secondary broadleaved forest after mass mortality of oak trees under deer foraging pressure.

PubMed

Itô, Hiroki

2016-01-01

The epidemic of mass mortality of oak trees by Japanese oak wilt has affected secondary deciduous broadleaved forests that have been used as coppices in Japan. The dieback of oak trees formed gaps in the crown that would be expected to enhance the regeneration of shade-intolerant pioneer species. However, foraging by sika deer Cervus nippon has also affected forest vegetation, and the compound effects of both on forest regeneration should be considered when they simultaneously occur. A field study was conducted in Kyôto City, Japan to investigate how these compound effects affected the vegetation of the understory layer of these forests. The presence/absence of seedlings and saplings was observed for 200 quadrats sized 5 m ×5 m for each species in 1992, before the mass mortality and deer encroachment, and in 2014 after these effects. A hierarchical Bayesian model was constructed to explain the occurrence, survival, and colonization of each species with their responses to the gaps that were created, expanded, or affected by the mass mortality of Quercus serrata trees. The species that occurred most frequently in 1992, Eurya japonica , Quercus glauca , and Cleyera japonica , also had the highest survival probabilities. Deer-unpalatable species such as Symplocos prunifolia and Triadica sebifera had higher colonization rates in the gaps, while the deer-palatable species Aucuba japonica had the smallest survival probability. The gaps thus promoted the colonization of deer-unpalatable plant species such as Symplocos prunifolia and Triadica sebifera . In the future, such deer-unpalatable species may dominate gaps that were created, expanded, or affected by the mass mortality of oak trees.

Methane Exchange in a Coastal Fen in the First Year after Flooding - A Systems Shift

PubMed Central

Hahn, Juliane; Köhler, Stefan; Glatzel, Stephan; Jurasinski, Gerald

2015-01-01

Background Peatland restoration can have several objectives, for example re-establishing the natural habitat, supporting unique biodiversity attributes or re-initiating key biogeochemical processes, which can ultimately lead to a reduction in greenhouse gas (GHG) emissions. Every restoration measure, however, is itself a disturbance to the ecosystem. Methods Here, we examine an ecosystem shift in a coastal fen at the southern Baltic Sea which was rewetted by flooding. The analyses are based on one year of bi-weekly closed chamber measurements of methane fluxes gathered at spots located in different vegetation stands. During measurement campaigns, we recorded data on water levels, peat temperatures, and chemical properties of peat water. In addition we analyzed the first 20 cm of peat before and after flooding for dry bulk density (DBD), content of organic matter and total amounts of carbon (C), nitrogen (N), sulfur (S), and other nutrients. Results Rewetting turned the site from a summer dry fen into a shallow lake with water levels up to 0.60 m. We observed a substantial die-back of vegetation, especially in stands of sedges (Carex acutiformis Ehrh). Concentrations of total organic carbon and nitrogen in the peat water, as well as dry bulk density and concentrations of C, N and S in the peat increased. In the first year after rewetting, the average annual exchange of methane amounted to 0.26 ± 0.06 kg m-2. This is equivalent to a 190-times increase in methane compared to pre-flooding conditions. Highest methane fluxes occurred in sedge stands which suffered from the heaviest die-back. None of the recorded environmental variables showed consistent relationships with the amounts of methane exchanged. Conclusions Our results suggest that rewetting projects should be monitored not only with regard to vegetation development but also with respect to biogeochemical conditions. Further, high methane emissions that likely occur directly after rewetting by flooding should be considered when forecasting the overall effect of rewetting on GHG exchange. PMID:26461916

Exploring uncertainty of Amazon dieback in a perturbed parameter Earth system ensemble.

PubMed

Boulton, Chris A; Booth, Ben B B; Good, Peter

2017-12-01

The future of the Amazon rainforest is unknown due to uncertainties in projected climate change and the response of the forest to this change (forest resiliency). Here, we explore the effect of some uncertainties in climate and land surface processes on the future of the forest, using a perturbed physics ensemble of HadCM3C. This is the first time Amazon forest changes are presented using an ensemble exploring both land vegetation processes and physical climate feedbacks in a fully coupled modelling framework. Under three different emissions scenarios, we measure the change in the forest coverage by the end of the 21st century (the transient response) and make a novel adaptation to a previously used method known as "dry-season resilience" to predict the long-term committed response of the forest, should the state of the climate remain constant past 2100. Our analysis of this ensemble suggests that there will be a high chance of greater forest loss on longer timescales than is realized by 2100, especially for mid-range and low emissions scenarios. In both the transient and predicted committed responses, there is an increasing uncertainty in the outcome of the forest as the strength of the emissions scenarios increases. It is important to note however, that very few of the simulations produce future forest loss of the magnitude previously shown under the standard model configuration. We find that low optimum temperatures for photosynthesis and a high minimum leaf area index needed for the forest to compete for space appear to be precursors for dieback. We then decompose the uncertainty into that associated with future climate change and that associated with forest resiliency, finding that it is important to reduce the uncertainty in both of these if we are to better determine the Amazon's outcome. © 2017 John Wiley & Sons Ltd.

Structural overshoot of tree growth with climate variability and the global spectrum of drought-induced forest dieback.

PubMed

Jump, Alistair S; Ruiz-Benito, Paloma; Greenwood, Sarah; Allen, Craig D; Kitzberger, Thomas; Fensham, Rod; Martínez-Vilalta, Jordi; Lloret, Francisco

2017-09-01

Ongoing climate change poses significant threats to plant function and distribution. Increased temperatures and altered precipitation regimes amplify drought frequency and intensity, elevating plant stress and mortality. Large-scale forest mortality events will have far-reaching impacts on carbon and hydrological cycling, biodiversity, and ecosystem services. However, biogeographical theory and global vegetation models poorly represent recent forest die-off patterns. Furthermore, as trees are sessile and long-lived, their responses to climate extremes are substantially dependent on historical factors. We show that periods of favourable climatic and management conditions that facilitate abundant tree growth can lead to structural overshoot of aboveground tree biomass due to a subsequent temporal mismatch between water demand and availability. When environmental favourability declines, increases in water and temperature stress that are protracted, rapid, or both, drive a gradient of tree structural responses that can modify forest self-thinning relationships. Responses ranging from premature leaf senescence and partial canopy dieback to whole-tree mortality reduce canopy leaf area during the stress period and for a lagged recovery window thereafter. Such temporal mismatches of water requirements from availability can occur at local to regional scales throughout a species geographical range. As climate change projections predict large future fluctuations in both wet and dry conditions, we expect forests to become increasingly structurally mismatched to water availability and thus overbuilt during more stressful episodes. By accounting for the historical context of biomass development, our approach can explain previously problematic aspects of large-scale forest mortality, such as why it can occur throughout the range of a species and yet still be locally highly variable, and why some events seem readily attributable to an ongoing drought while others do not. This refined understanding can facilitate better projections of structural overshoot responses, enabling improved prediction of changes in forest distribution and function from regional to global scales. © 2017 John Wiley & Sons Ltd.

Structural overshoot of tree growth with climate variability and the global spectrum of drought-induced forest dieback

USGS Publications Warehouse

Jump, Alistair S.; Ruiz-Benito, Paloma; Greenwood, Sarah; Allen, Craig D.; Kitzberger, Thomas; Fensham, Rod; Martínez-Vilalta, Jordi; Lloret, Francisco

2017-01-01

Ongoing climate change poses significant threats to plant function and distribution. Increased temperatures and altered precipitation regimes amplify drought frequency and intensity, elevating plant stress and mortality. Large-scale forest mortality events will have far-reaching impacts on carbon and hydrological cycling, biodiversity, and ecosystem services. However, biogeographical theory and global vegetation models poorly represent recent forest die-off patterns. Furthermore, as trees are sessile and long-lived, their responses to climate extremes are substantially dependent on historical factors. We show that periods of favourable climatic and management conditions that facilitate abundant tree growth can lead to structural overshoot of aboveground tree biomass due to a subsequent temporal mismatch between water demand and availability. When environmental favourability declines, increases in water and temperature stress that are protracted, rapid, or both, drive a gradient of tree structural responses that can modify forest self-thinning relationships. Responses ranging from premature leaf senescence and partial canopy dieback to whole-tree mortality reduce canopy leaf area during the stress period and for a lagged recovery window thereafter. Such temporal mismatches of water requirements from availability can occur at local to regional scales throughout a species geographical range. As climate change projections predict large future fluctuations in both wet and dry conditions, we expect forests to become increasingly structurally mismatched to water availability and thus overbuilt during more stressful episodes. By accounting for the historical context of biomass development, our approach can explain previously problematic aspects of large-scale forest mortality, such as why it can occur throughout the range of a species and yet still be locally highly variable, and why some events seem readily attributable to an ongoing drought while others do not. This refined understanding can facilitate better projections of structural overshoot responses, enabling improved prediction of changes in forest distribution and function from regional to global scales.

Towards quantifying uncertainty in predictions of Amazon 'dieback'.

PubMed

Huntingford, Chris; Fisher, Rosie A; Mercado, Lina; Booth, Ben B B; Sitch, Stephen; Harris, Phil P; Cox, Peter M; Jones, Chris D; Betts, Richard A; Malhi, Yadvinder; Harris, Glen R; Collins, Mat; Moorcroft, Paul

2008-05-27

Simulations with the Hadley Centre general circulation model (HadCM3), including carbon cycle model and forced by a 'business-as-usual' emissions scenario, predict a rapid loss of Amazonian rainforest from the middle of this century onwards. The robustness of this projection to both uncertainty in physical climate drivers and the formulation of the land surface scheme is investigated. We analyse how the modelled vegetation cover in Amazonia responds to (i) uncertainty in the parameters specified in the atmosphere component of HadCM3 and their associated influence on predicted surface climate. We then enhance the land surface description and (ii) implement a multilayer canopy light interception model and compare with the simple 'big-leaf' approach used in the original simulations. Finally, (iii) we investigate the effect of changing the method of simulating vegetation dynamics from an area-based model (TRIFFID) to a more complex size- and age-structured approximation of an individual-based model (ecosystem demography). We find that the loss of Amazonian rainforest is robust across the climate uncertainty explored by perturbed physics simulations covering a wide range of global climate sensitivity. The introduction of the refined light interception model leads to an increase in simulated gross plant carbon uptake for the present day, but, with altered respiration, the net effect is a decrease in net primary productivity. However, this does not significantly affect the carbon loss from vegetation and soil as a consequence of future simulated depletion in soil moisture; the Amazon forest is still lost. The introduction of the more sophisticated dynamic vegetation model reduces but does not halt the rate of forest dieback. The potential for human-induced climate change to trigger the loss of Amazon rainforest appears robust within the context of the uncertainties explored in this paper. Some further uncertainties should be explored, particularly with respect to the representation of rooting depth.

Methane Exchange in a Coastal Fen in the First Year after Flooding--A Systems Shift.

PubMed

Hahn, Juliane; Köhler, Stefan; Glatzel, Stephan; Jurasinski, Gerald

2015-01-01

Peatland restoration can have several objectives, for example re-establishing the natural habitat, supporting unique biodiversity attributes or re-initiating key biogeochemical processes, which can ultimately lead to a reduction in greenhouse gas (GHG) emissions. Every restoration measure, however, is itself a disturbance to the ecosystem. Here, we examine an ecosystem shift in a coastal fen at the southern Baltic Sea which was rewetted by flooding. The analyses are based on one year of bi-weekly closed chamber measurements of methane fluxes gathered at spots located in different vegetation stands. During measurement campaigns, we recorded data on water levels, peat temperatures, and chemical properties of peat water. In addition we analyzed the first 20 cm of peat before and after flooding for dry bulk density (DBD), content of organic matter and total amounts of carbon (C), nitrogen (N), sulfur (S), and other nutrients. Rewetting turned the site from a summer dry fen into a shallow lake with water levels up to 0.60 m. We observed a substantial die-back of vegetation, especially in stands of sedges (Carex acutiformis Ehrh). Concentrations of total organic carbon and nitrogen in the peat water, as well as dry bulk density and concentrations of C, N and S in the peat increased. In the first year after rewetting, the average annual exchange of methane amounted to 0.26 ± 0.06 kg m-2. This is equivalent to a 190-times increase in methane compared to pre-flooding conditions. Highest methane fluxes occurred in sedge stands which suffered from the heaviest die-back. None of the recorded environmental variables showed consistent relationships with the amounts of methane exchanged. Our results suggest that rewetting projects should be monitored not only with regard to vegetation development but also with respect to biogeochemical conditions. Further, high methane emissions that likely occur directly after rewetting by flooding should be considered when forecasting the overall effect of rewetting on GHG exchange.

Lessons from Fraxinus, a crowd-sourced citizen science game in genomics

PubMed Central

Rallapalli, Ghanasyam; Saunders, Diane GO; Yoshida, Kentaro; Edwards, Anne; Lugo, Carlos A; Collin, Steve; Clavijo, Bernardo; Corpas, Manuel; Swarbreck, David; Clark, Matthew; Downie, J Allan; Kamoun, Sophien

2015-01-01

In 2013, in response to an epidemic of ash dieback disease in England the previous year, we launched a Facebook-based game called Fraxinus to enable non-scientists to contribute to genomics studies of the pathogen that causes the disease and the ash trees that are devastated by it. Over a period of 51 weeks players were able to match computational alignments of genetic sequences in 78% of cases, and to improve them in 15% of cases. We also found that most players were only transiently interested in the game, and that the majority of the work done was performed by a small group of dedicated players. Based on our experiences we have built a linear model for the length of time that contributors are likely to donate to a crowd-sourced citizen science project. This model could serve a guide for the design and implementation of future crowd-sourced citizen science initiatives. DOI: http://dx.doi.org/10.7554/eLife.07460.001 PMID:26219214

ʻŌhiʻa Lehua rainforest: born among Hawaiian volcanoes, evolved in isolation: the story of a dynamic ecosystem with relevance to forests worldwide

USGS Publications Warehouse

Mueller-Dombois, Dieter; Jacobi, James D.; Boehmer, Hans Juergen; Price, Jonathan P.

2013-01-01

In the early 1970s, a multidisciplinary team of forest biologists began a study of Hawaiian ecosystems under the International Biological Program (IBP). Research focus was on the intact native ecosystems in and around Hawai'i Volcanoes National Park, in particular the ʻŌhiʻa Lehua rainforest. Patches of dead ʻŌhiʻa stands had been reported from the windward slopes of Mauna Loa and Mauna Kea. Subsequent air photo analyses by a team of US and Hawai'i State foresters discovered rapidly spreading ʻŌhiʻa dieback, also called ʻŌhiʻa forest decline. A killer disease was suspected to destroy the Hawaiian rain forest in the next 15-25 years. Ecological research continued with a focus on the dynamics of the Hawaiian rainforest. This book explains what really happened and why the ʻŌhiʻa rainforest survived in tact as everyone can witness today.

The roles of hydraulic and carbon stress in a widespread climate-induced forest die-off

PubMed Central

Anderegg, William R. L.; Berry, Joseph A.; Smith, Duncan D.; Sperry, John S.; Anderegg, Leander D. L.; Field, Christopher B.

2012-01-01

Forest ecosystems store approximately 45% of the carbon found in terrestrial ecosystems, but they are sensitive to climate-induced dieback. Forest die-off constitutes a large uncertainty in projections of climate impacts on terrestrial ecosystems, climate–ecosystem interactions, and carbon-cycle feedbacks. Current understanding of the physiological mechanisms mediating climate-induced forest mortality limits the ability to model or project these threshold events. We report here a direct and in situ study of the mechanisms underlying recent widespread and climate-induced trembling aspen (Populus tremuloides) forest mortality in western North America. We find substantial evidence of hydraulic failure of roots and branches linked to landscape patterns of canopy and root mortality in this species. On the contrary, we find no evidence that drought stress led to depletion of carbohydrate reserves. Our results illuminate proximate mechanisms underpinning recent aspen forest mortality and provide guidance for understanding and projecting forest die-offs under climate change. PMID:22167807

Phytotoxins Produced by Fungi Associated with Grapevine Trunk Diseases

PubMed Central

Andolfi, Anna; Mugnai, Laura; Luque, Jordi; Surico, Giuseppe; Cimmino, Alessio; Evidente, Antonio

2011-01-01

Up to 60 species of fungi in the Botryosphaeriaceae family, genera Cadophora, Cryptovalsa, Cylindrocarpon, Diatrype, Diatrypella, Eutypa, Eutypella, Fomitiporella, Fomitiporia, Inocutis, Phaeoacremonium and Phaeomoniella have been isolated from decline-affected grapevines all around the World. The main grapevine trunk diseases of mature vines are Eutypa dieback, the esca complex and cankers caused by the Botryospheriaceae, while in young vines the main diseases are Petri and black foot diseases. To understand the mechanism of these decline-associated diseases and the symptoms associated with them, the toxins produced by the pathogens involved in these diseases were isolated and characterised chemically and biologically. So far the toxins of only a small number of these decline fungi have been studied. This paper presents an overview of the toxins produced by the most serious of these vine wood pathogens: Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum and some taxa in the Botryosphaeriaceae family, and examines how these toxins produce decline symptoms. The chemical structure of these metabolites and in some cases their vivotoxin nature are also discussed. PMID:22295177

α-Copaene is an attractant, synergistic with quercivorol, for improved detection of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae)

PubMed Central

Owens, David; Montgomery, Wayne S.; Narvaez, Teresa I.; Bauchan, Gary R.; Schnell, Elena Q.; Tabanca, Nurhayat; Carrillo, Daniel

2017-01-01

The tea shot-hole borer, Euwallacea fornicatus Eichhoff, is an ambrosia beetle endemic to Asia and a pest of commercial tea, Camellia sinensis (L.) Kuntze. Recently, a complex of species morphologically similar to E. fornicatus has been recognized, which includes new pests established in Israel and the USA, both in California and Florida. Collectively termed E. nr. fornicatus, these cryptic species carry symbiotic Fusarium spp. fungi, some of which cause dieback disease in susceptible hosts, which include avocado, Persea americana Miller. Due to the threat to this economically important crop, research was initiated to evaluate efficacy of kairomone-based lures for detection of the beetle in Florida (termed the Florida tea shot hole borer, FL-TSHB). A series of field tests were conducted in 2016 in commercial avocado groves known to have FL-TSHB at various population levels. All tests evaluated lures containing quercivorol (p-menth-2-en-1-ol) and α-copaene, presented separately and in combination; and one test evaluated effect of trap type on beetle captures. In addition, electroantennography (EAG) was used to quantify female olfactory responses to lure emissions. This study identified (-)-α-copaene as a new attractant for FL-TSHB, equivalent in efficacy to quercivorol (the standard lure for Euwallacea detection in the USA); however, the combination of lures captured significantly more FL-TSHB than either lure alone. This combination resulted in synergistic attraction at two field sites and additive attraction at a third site. Sticky panel traps captured more FL-TSHB than comparably-baited Lindgren funnel traps. Females engaged in host-seeking flight from 11:00 to 16:00 hr (EST), with peak numbers observed between 12:00 and 13:00 hr. EAG analyses confirmed olfactory chemoreception of both kairomones, with a higher response elicited with the combination of volatiles. Results indicate that detection of pest E. nr. fornicatus in Florida can be improved by using a two-component lure consisting of p-menth-2-en-1-ol and (-)-α-copaene. PMID:28609448

Recent drought-induced mortality of aspen forests along a water-balance tipping point for ecosystems in western Canada

NASA Astrophysics Data System (ADS)

Hogg, E.

2009-05-01

In western Canada, the boundary between boreal forest and prairie grasslands marks a dramatic change in nearly all aspects of ecosystem functioning. These include a steep spatial gradient in hydrological characteristics of the landscape (lake level variability, water runoff and stream flow patterns) that coincides with the southern range limit of peatlands and several species of boreal conifers. Previous studies indicate that the forest-grassland boundary in this region represents a critical "tipping point" (Lenton et al. 2008) where long-term water input by precipitation is barely sufficient to satisfy the water use demands of productive, closed-canopy forests. This concept is consistent with the observed, regional gradient in the character of forests dominated by aspen (Populus tremuloides), the most abundant and widespread deciduous tree in North America. Aspen-dominated forests are productive and continuous in the boreal zone, but are stunted and patchy in the boreal-grassland transition zone, often referred to as the aspen parkland. Based on the "tipping point" concept, there are concerns that aspen forests in this region are especially sensitive to the projected trend toward warmer and drier conditions under human-induced climate change. In response to these concerns, a large-scale study was established across west-central Canada in 2000, entitled "Climate Impacts on Productivity and Health of Aspen" (CIPHA). The study has hierarchical sampling design that is aimed at "scaling up" forest-climate responses from individual trees to the region. During 2001-2002, the region was affected by an exceptionally severe drought that subsequently led to massive dieback and mortality of aspen forests within the boreal-grassland transition zone. Drought severity and extent was quantified using a simple climate moisture index (CMI), and drought impacts were quantified using tree-ring analysis, in combination with plot-based and remotely-sensed measures. Results showed that stand-level productivity, dieback and mortality were governed primarily by moisture variation. Furthermore, during and following this drought there was increasing damage by wood-boring insects and elevated, regional-scale mortality of aspen over at least 6 years (2002-2008). Although it is premature to attribute these impacts to anthropogenic climate change, they provide an excellent analog for what may be expected in future, even under a modest trend toward drying over the next few decades. Furthermore, the recent aspen mortality in western Canada shares many features common to other recent episodes of drought-induced forest mortality that have been documented on all of the earth's forested continents. This suggests the need for an integrated, global research and monitoring system that would enable early detection and attribution of large-scale ecosystem changes, especially in climatically-sensitive regions along forest-grassland boundaries around the world.

Intertidal resource use over millennia enhances forest productivity

NASA Astrophysics Data System (ADS)

Trant, Andrew J.; Nijland, Wiebe; Hoffman, Kira M.; Mathews, Darcy L.; McLaren, Duncan; Nelson, Trisalyn A.; Starzomski, Brian M.

2016-08-01

Human occupation is usually associated with degraded landscapes but 13,000 years of repeated occupation by British Columbia's coastal First Nations has had the opposite effect, enhancing temperate rainforest productivity. This is particularly the case over the last 6,000 years when intensified intertidal shellfish usage resulted in the accumulation of substantial shell middens. We show that soils at habitation sites are higher in calcium and phosphorous. Both of these are limiting factors in coastal temperate rainforests. Western redcedar (Thuja plicata) trees growing on the middens were found to be taller, have higher wood calcium, greater radial growth and exhibit less top die-back. Coastal British Columbia is the first known example of long-term intertidal resource use enhancing forest productivity and we expect this pattern to occur at archaeological sites along coastlines globally.

Impact of Austropuccinia psidii (myrtle rust) on Myrtaceae-rich wet sclerophyll forests in south east Queensland.

PubMed

Pegg, Geoff; Taylor, Tamara; Entwistle, Peter; Guymer, Gordon; Giblin, Fiona; Carnegie, Angus

2017-01-01

In April 2010, Austropuccinia psidii (formerly Puccinia psidii) was detected for the first time in Australia on the central coast of New South Wales. The fungus spread rapidly along the east coast and can now be found infecting vegetation in a range of native forest ecosystems with disease impacts ranging from minor leaf spots to severe shoot and stem blight and tree dieback. Localised extinction of some plant species has been recorded. In 2014, the impact of A. psidii was observed for the first time in a wet sclerophyll site with a rainforest understory, dominated by species of Myrtaceae, in Tallebudgera Valley, south east Queensland, Australia. This study aimed to determine the impact of A. psidii on individual species and species composition. Here we provide quantitative and qualitative evidence on the significant impact A. psidii has in native ecosystems, on a broader range of species than previously reported. Archirhodomyrtus beckleri, Decaspermum humile, Gossia hillii and Rhodamnia maideniana are in serious decline, with significant increases in tree mortality over the period of our study. This research further highlights the potential of this invasive pathogen to negatively impact native ecosystems and biodiversity.

Impact of Austropuccinia psidii (myrtle rust) on Myrtaceae-rich wet sclerophyll forests in south east Queensland

PubMed Central

Taylor, Tamara; Entwistle, Peter; Guymer, Gordon; Giblin, Fiona; Carnegie, Angus

2017-01-01

In April 2010, Austropuccinia psidii (formerly Puccinia psidii) was detected for the first time in Australia on the central coast of New South Wales. The fungus spread rapidly along the east coast and can now be found infecting vegetation in a range of native forest ecosystems with disease impacts ranging from minor leaf spots to severe shoot and stem blight and tree dieback. Localised extinction of some plant species has been recorded. In 2014, the impact of A. psidii was observed for the first time in a wet sclerophyll site with a rainforest understory, dominated by species of Myrtaceae, in Tallebudgera Valley, south east Queensland, Australia. This study aimed to determine the impact of A. psidii on individual species and species composition. Here we provide quantitative and qualitative evidence on the significant impact A. psidii has in native ecosystems, on a broader range of species than previously reported. Archirhodomyrtus beckleri, Decaspermum humile, Gossia hillii and Rhodamnia maideniana are in serious decline, with significant increases in tree mortality over the period of our study. This research further highlights the potential of this invasive pathogen to negatively impact native ecosystems and biodiversity. PMID:29161305

Winners and losers as mangrove, coral and seagrass ecosystems respond to sea-level rise in Solomon Islands

NASA Astrophysics Data System (ADS)

Albert, Simon; Saunders, Megan I.; Roelfsema, Chris M.; Leon, Javier X.; Johnstone, Elizabeth; Mackenzie, Jock R.; Hoegh-Guldberg, Ove; Grinham, Alistair R.; Phinn, Stuart R.; Duke, Norman C.; Mumby, Peter J.; Kovacs, Eva; Woodroffe, Colin D.

2017-09-01

A 2007 earthquake in the western Solomon Islands resulted in a localised subsidence event in which sea level (relative to the previous coastal settings) rose approximately 30-70 cm, providing insight into impacts of future rapid changes to sea level on coastal ecosystems. Here, we show that increasing sea level by 30-70 cm can have contrasting impacts on mangrove, seagrass and coral reef ecosystems. Coral reef habitats were the clear winners with a steady lateral growth from 2006-2014, yielding a 157% increase in areal coverage over seven years. Mangrove ecosystems, on the other hand, suffered the largest impact through a rapid dieback of 35% (130 ha) of mangrove forest in the study area after subsidence. These forests, however, had partially recovered seven years after the earthquake albeit with a different community structure. The shallow seagrass ecosystems demonstrated the most dynamic response to relative shifts in sea level with both losses and gains in areal extent at small scales of 10-100 m. The results of this study emphasize the importance of considering the impacts of sea-level rise within a complex landscape in which winners and losers may vary over time and space.

Colletotrichum species associated with jute (Corchorus capsularis L.) anthracnose in southeastern China.

PubMed

Niu, Xiaoping; Gao, Hong; Qi, Jianmin; Chen, Miancai; Tao, Aifen; Xu, Jiantang; Dai, Zhigang; Su, Jianguang

2016-04-28

Anthracnose, caused by the Colletotrichum species of fungi, is one of the most serious diseases affecting jute in China. The disease causes chlorotic regions with black brown sunken necrotic pits on the surfaces of stems. In late stages of disease, plants undergo defoliation, dieback and blight, which make anthracnose a major threat to jute fiber production and quality in China. In this study, 7 strains of Colletotrichum fungi were isolated from diseased jute stems from Zhejiang, Fujian, Guangxi, and Henan plantations in China. Multi-locus sequence (ACT, TUB2, CAL, GS, GAPDH and ITS) analysis coupled with morphological assessment revealed that C. fructicola, C. siamense and C. corchorum-capsularis sp. nov. were associated with jute anthracnose in southeastern China. C. fructicola and C. siamense were previously not associated with jute anthracnose. C. corchorum-capsularis is a new species formally described here. Pathogenicity tests confirmed that all species can infect jute, causing anthracnose, however the virulence of the 3 species differed. This report is the first associating these three species with jute disease worldwide and is the first description of the pathogens responsible for jute anthracnose in China.

Fungi associated with black mould on baobab trees in southern Africa.

PubMed

Cruywagen, Elsie M; Crous, Pedro W; Roux, Jolanda; Slippers, Bernard; Wingfield, Michael J

2015-07-01

There have been numerous reports in the scientific and popular literature suggesting that African baobab (Adansonia digitata) trees are dying, with symptoms including a black mould on their bark. The aim of this study was to determine the identity of the fungi causing this black mould and to consider whether they might be affecting the health of trees. The fungi were identified by sequencing directly from mycelium on the infected tissue as well as from cultures on agar. Sequence data for the ITS region of the rDNA resulted in the identification of four fungi including Aureobasidium pullulans, Toxicocladosporium irritans and a new species of Rachicladosporium described here as Rachicladosporium africanum. A single isolate of an unknown Cladosporium sp. was also found. These fungi, referred to here as black mould, are not true sooty mould fungi and they were shown to penetrate below the bark of infected tissue, causing a distinct host reaction. Although infections can lead to dieback of small twigs on severely infected branches, the mould was not found to kill trees.

Monitoring invasive pathogens in plant nurseries for early-detection and to minimise the probability of escape.

PubMed

Alonso Chavez, Vasthi; Parnell, Stephen; VAN DEN Bosch, Frank

2016-10-21

The global increase in the movement of plant products in recent years has triggered an increase in the number of introduced plant pathogens. Plant nurseries importing material from abroad may play an important role in the introduction and spread of diseases such as ash dieback and sudden oak death which are thought to have been introduced through trade. The economic, environmental and social costs associated with the spread of invasive pathogens become considerably larger as the incidence of the pathogen increases. To control the movement of pathogens across the plant trade network it is crucial to develop monitoring programmes at key points of the network such as plant nurseries. By detecting the introduction of invasive pathogens at low incidence, the control and eradication of an epidemic is more likely to be successful. Equally, knowing the likelihood of having sold infected plants once a disease has been detected in a nursery can help designing tracing plans to control the onward spread of the disease. Here, we develop an epidemiological model to detect and track the movement of an invasive plant pathogen into and from a plant nursery. Using statistical methods, we predict the epidemic incidence given that a detection of the pathogen has occurred for the first time, considering that the epidemic has an asymptomatic period between infection and symptom development. Equally, we calculate the probability of having sold at least one infected plant during the period previous to the first disease detection. This analysis can aid stakeholder decisions to determine, when the pathogen is first discovered in a nursery, the need of tracking the disease to other points in the plant trade network in order to control the epidemic. We apply our method to high profile recent introductions including ash dieback and sudden oak death in the UK and citrus canker and Huanglongbing disease in Florida. These results provide new insight for the design of monitoring strategies at key points of the trade network. Copyright © 2016 Elsevier Ltd. All rights reserved.

Lichen-moss interactions within biological soil crusts

NASA Astrophysics Data System (ADS)

Ruckteschler, Nina; Williams, Laura; Büdel, Burkhard; Weber, Bettina

2015-04-01

Biological soil crusts (biocrusts) create well-known hotspots of microbial activity, being important components of hot and cold arid terrestrial regions. They colonize the uppermost millimeters of the soil, being composed of fungi, (cyano-) bacteria, algae, lichens, bryophytes and archaea in varying proportions. Biocrusts protect the (semi-) arid landscape from wind and water erosion, and also increase water holding capacity and nutrient content. Depending on location and developmental stage, composition and species abundance vary within biocrusts. As species live in close contact, they are expected to influence each other, but only a few interactions between different organisms have so far been explored. In the present study, we investigated the effects of the lichen Fulgensia fulgens whilst growing on the moss Trichostomum crispulum. While 77% of Fulgensia fulgens thalli were found growing associated with mosses in a German biocrust, up to 95% of Fulgensia bracteata thalli were moss-associated in a Swedish biocrust. In 49% (Germany) and in 78% (Sweden) of cases, thalli were observed on the moss T. crispulum and less frequently on four and three different moss species. Beneath F. fulgens and F. bracteata thalli, the mosses were dead and in close vicinity to the lichens the mosses appeared frail, bringing us to the assumption that the lichens may release substances harming the moss. We prepared a water extract from the lichen F. fulgens and used this to water the moss thalli (n = 6) on a daily basis over a time-span of three weeks. In a control setup, artificial rainwater was applied to the moss thalli (n = 6). Once a week, maximum CO2 gas exchange rates of the thalli were measured under constant conditions and at the end of the experiment the chlorophyll content of the moss samples was determined. In the course of the experiment net photosynthesis (NP) of the treatment samples decreased concurrently with an increase in dark respiration (DR). The control samples remained at the same stable level for both NP and DR over time. The chlorophyll content of the treatment samples was significantly lower than that of the controls. This supports our assumption that water extracts of F. fulgens may indeed cause a dieback of the host moss. In a next step of the project, the substances responsible for this detrimental effect on the moss will be identified. The accelerated dieback of the moss probably causes increased CO2 concentrations below the lichen thalli, improving their overall photosynthetic performance. Thus, both dead and living biomass in biocrusts increase upon this association, promoting microbial activity and the growth of vascular plant vegetation.

Environmental mutagenesis during the end-Permian ecological crisis

PubMed Central

Visscher, Henk; Looy, Cindy V.; Collinson, Margaret E.; Brinkhuis, Henk; van Konijnenburg-van Cittert, Johanna H. A.; Kürschner, Wolfram M.; Sephton, Mark A.

2004-01-01

During the end-Permian ecological crisis, terrestrial ecosystems experienced preferential dieback of woody vegetation. Across the world, surviving herbaceous lycopsids played a pioneering role in repopulating deforested terrain. We document that the microspores of these lycopsids were regularly released in unseparated tetrads indicative of failure to complete the normal process of spore development. Although involvement of mutation has long been hinted at or proposed in theory, this finding provides concrete evidence for chronic environmental mutagenesis at the time of global ecological crisis. Prolonged exposure to enhanced UV radiation could account satisfactorily for a worldwide increase in land plant mutation. At the end of the Permian, a period of raised UV stress may have been the consequence of severe disruption of the stratospheric ozone balance by excessive emission of hydrothermal organohalogens in the vast area of Siberian Traps volcanism. PMID:15282373

Intertidal resource use over millennia enhances forest productivity

PubMed Central

Trant, Andrew J.; Nijland, Wiebe; Hoffman, Kira M.; Mathews, Darcy L.; McLaren, Duncan; Nelson, Trisalyn A.; Starzomski, Brian M.

2016-01-01

Human occupation is usually associated with degraded landscapes but 13,000 years of repeated occupation by British Columbia's coastal First Nations has had the opposite effect, enhancing temperate rainforest productivity. This is particularly the case over the last 6,000 years when intensified intertidal shellfish usage resulted in the accumulation of substantial shell middens. We show that soils at habitation sites are higher in calcium and phosphorous. Both of these are limiting factors in coastal temperate rainforests. Western redcedar (Thuja plicata) trees growing on the middens were found to be taller, have higher wood calcium, greater radial growth and exhibit less top die-back. Coastal British Columbia is the first known example of long-term intertidal resource use enhancing forest productivity and we expect this pattern to occur at archaeological sites along coastlines globally. PMID:27572157

Paper birch: Sentinels of climate change in the Niobrara River Valley, Nebraska

USGS Publications Warehouse

Stroh, Esther D.

2011-01-01

The Niobrara River Valley in the northern Great Plains supports scattered stands of paper birch (Betula papyrifera Marsh), a species more typical of boreal forests. These birch stands are considered to be relictual populations that have persisted since the end of the Wisconsin glaciation. Localized summer microclimates have likely facilitated the persistence of birch populations in a region otherwise unsuitable for the species. Dieback of canopy-sized birch has been observed throughout the valley in recent years, although no onset dates are documented. Changes in spring weather patterns may be causing rootlet injury so that trees die in spite of the still-cool summer microclimates. Current weather patterns, combined with little evidence of recruitment of young birch and great geographic distances from potential immigrant sources, make the future persistence of birch in the Niobrara River Valley stands uncertain.

Environmental mutagenesis during the end-Permian ecological crisis.

PubMed

Visscher, Henk; Looy, Cindy V; Collinson, Margaret E; Brinkhuis, Henk; van Konijnenburg-van Cittert, Johanna H A; Kürschner, Wolfram M; Sephton, Mark A

2004-08-31

During the end-Permian ecological crisis, terrestrial ecosystems experienced preferential dieback of woody vegetation. Across the world, surviving herbaceous lycopsids played a pioneering role in repopulating deforested terrain. We document that the microspores of these lycopsids were regularly released in unseparated tetrads indicative of failure to complete the normal process of spore development. Although involvement of mutation has long been hinted at or proposed in theory, this finding provides concrete evidence for chronic environmental mutagenesis at the time of global ecological crisis. Prolonged exposure to enhanced UV radiation could account satisfactorily for a worldwide increase in land plant mutation. At the end of the Permian, a period of raised UV stress may have been the consequence of severe disruption of the stratospheric ozone balance by excessive emission of hydrothermal organohalogens in the vast area of Siberian Traps volcanism. Copyright 2004 The National Academy of Sciencs of the USA

Tropical rainforest response to marine sky brightening climate engineering

NASA Astrophysics Data System (ADS)

Muri, Helene; Niemeier, Ulrike; Kristjánsson, Jón Egill

2015-04-01

Tropical forests represent a major atmospheric carbon dioxide sink. Here the gross primary productivity (GPP) response of tropical rainforests to climate engineering via marine sky brightening under a future scenario is investigated in three Earth system models. The model response is diverse, and in two of the three models, the tropical GPP shows a decrease from the marine sky brightening climate engineering. Partial correlation analysis indicates precipitation to be important in one of those models, while precipitation and temperature are limiting factors in the other. One model experiences a reversal of its Amazon dieback under marine sky brightening. There, the strongest partial correlation of GPP is to temperature and incoming solar radiation at the surface. Carbon fertilization provides a higher future tropical rainforest GPP overall, both with and without climate engineering. Salt damage to plants and soils could be an important aspect of marine sky brightening.

Northern Hemisphere Biome-and Process-Specific Changes in Forest Area and Gross Merchantable Volume: 1890-1990 (DB1017)

DOE Data Explorer

Auclair, A.N.D. [Science and Policy Associates, Inc., Washington, D.C. (United States; Bedford, J.A. [Science and Policy Associates, Inc., Washington, D.C. (United States); Revenga, C. [Science and Policy Associates, Inc., Washington, D.C. (United States); Brenkert, A.L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

1997-01-01

This database lists annual changes in areal extent (Ha) and gross merchantable wood volume (m3) produced by depletion and accrual processes in boreal and temperate forests in Alaska, Canada, Europe, Former Soviet Union, Non-Soviet temperate Asia, and the contiguous United States for the years 1890 through 1990. Forest depletions (source terms for atmospheric CO2) are identified as forest pests, forest dieback, forest fires, forest harvest, and land-use changes (predominantly the conversion of forest, temperate woodland, and shrubland to cropland). Forest accruals (sink terms for atmospheric CO2) are identified as fire exclusion, fire suppression, and afforestation or crop abandonment. The changes in areal extent and gross merchantable wood volume are calculated separately for each of the following biomes: forest tundra, boreal softwoods, mixed hardwoods, temperate softwoods, temperate hardwoods, and temperate wood- and shrublands.

Neuronal matrix metalloproteinase-9 is a determinant of selective neurodegeneration

PubMed Central

Kaplan, Artem; Spiller, Krista J.; Towne, Christopher; Kanning, Kevin C.; Choe, Ginn T.; Geber, Adam; Akay, Turgay; Aebischer, Patrick; Henderson, Christopher E.

2018-01-01

SUMMARY Selective neuronal loss is the hallmark of neurodegenerative diseases. In patients with amyotrophic lateral sclerosis (ALS), most motor neurons die but those innervating extraocular, pelvic sphincter and slow limb muscles exhibit selective resistance. We identified 18 genes that show >10-fold differential expression between resistant and vulnerable motor neurons. One of these, matrix metalloproteinase-9 (MMP-9), is expressed only by fast motor neurons, which are selectively vulnerable. In ALS model mice expressing mutant SOD1, reduction of MMP-9 function using gene ablation, viral gene therapy or pharmacological inhibition significantly delayed muscle denervation. In the presence of mutant SOD1, MMP-9 expressed by fast motor neurons themselves enhances activation of ER stress and is sufficient to trigger axonal die-back. These findings define MMP-9 as a candidate therapeutic target for ALS. The molecular basis of neuronal diversity thus provides novel insights into mechanisms of selective vulnerability to neurodegeneration. PMID:24462097

Cytospora species from Populus and Salix in China with C. davidiana sp. nov.

PubMed

Wang, Yan-Li; Lu, Quan; Decock, Cony; Li, Yong-Xia; Zhang, Xing-Yao

2015-05-01

Poplar and willow plantations have become widespread in China, in order to meet national economic and environmental needs. The emergence of several pathogens is enhanced by climatic change and associated human factors. Species of Cytospora are well-known pathogens on poplar and willow, and cause stem cankers and diebacks. In the present study, we conducted a survey of Cytospora species occurring on Populus spp. and Salix spp. in China. We used morphological examination and phylogenetic inferences, based on the DNA sequence data from the internal transcribed spacer regions (ITS1, 5.8S rDNA, and ITS2) and partial β-tubulin gene, to identify six Cytospora species occurring on poplar and willow. Five of these species belonged to known taxa, viz. Cytospora chrysosperma (asexual state of Valsa sordida), Cytospora translucens (asexual state of Leucostoma translucens), Cytospora fugax (asexual state of Valsa salicina), Cytospora atrocirrhata, and Cytospora kantschavelii. Our study yielded a new species, Cytospora davidiana sp. nov., on poplar. The new species is characterized by typical torsellioid conidiomata. An additional Cytospora sp. 1, which formed a distinct clade in the phylogenetic inferences, remains unnamed; the paucity of available materials prevented phenotypical characterization. Copyright © 2015 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach.

PubMed

Giuggiola, Arnaud; Ogée, Jérôme; Rigling, Andreas; Gessler, Arthur; Bugmann, Harald; Treydte, Kerstin

2016-04-01

Thinning fosters individual tree growth by increasing the availability of water, light and nutrients. At sites where water rather than light is limiting, thinning also enhances soil evaporation and might not be beneficial. Detailed knowledge of the short- to long-term physiological response underlying the growth responses to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models to study the physiological processes underlying long-term growth enhancement of heavily thinned Pinus sylvestris in a xeric forest in Switzerland. This approach allowed us to identify and disentangle thinning-induced changes in stomatal conductance and assimilation rate. At our xeric study site, the increase in stomatal conductance far outweighed the increase in assimilation, implying that growth release in heavily thinned trees is primarily driven by enhanced water availability rather than increased light availability. We conclude that in forests with relatively isohydric species (drought avoiders) that are growing close to their physiological limits, thinning is recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival of forest trees under drought. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Ecosystem heterogeneity determines the ecological resilience of the Amazon to climate change

PubMed Central

Longo, Marcos; Baccini, Alessandro; Phillips, Oliver L.; Lewis, Simon L.; Alvarez-Dávila, Esteban; Segalin de Andrade, Ana Cristina; Brienen, Roel J. W.; Erwin, Terry L.; Feldpausch, Ted R.; Monteagudo Mendoza, Abel Lorenzo; Nuñez Vargas, Percy; Prieto, Adriana; Silva-Espejo, Javier Eduardo; Malhi, Yadvinder; Moorcroft, Paul R.

2016-01-01

Amazon forests, which store ∼50% of tropical forest carbon and play a vital role in global water, energy, and carbon cycling, are predicted to experience both longer and more intense dry seasons by the end of the 21st century. However, the climate sensitivity of this ecosystem remains uncertain: several studies have predicted large-scale die-back of the Amazon, whereas several more recent studies predict that the biome will remain largely intact. Combining remote-sensing and ground-based observations with a size- and age-structured terrestrial ecosystem model, we explore the sensitivity and ecological resilience of these forests to changes in climate. We demonstrate that water stress operating at the scale of individual plants, combined with spatial variation in soil texture, explains observed patterns of variation in ecosystem biomass, composition, and dynamics across the region, and strongly influences the ecosystem’s resilience to changes in dry season length. Specifically, our analysis suggests that in contrast to existing predictions of either stability or catastrophic biomass loss, the Amazon forest’s response to a drying regional climate is likely to be an immediate, graded, heterogeneous transition from high-biomass moist forests to transitional dry forests and woody savannah-like states. Fire, logging, and other anthropogenic disturbances may, however, exacerbate these climate change-induced ecosystem transitions. PMID:26711984

Ecosystem heterogeneity determines the ecological resilience of the Amazon to climate change.

PubMed

Levine, Naomi M; Zhang, Ke; Longo, Marcos; Baccini, Alessandro; Phillips, Oliver L; Lewis, Simon L; Alvarez-Dávila, Esteban; Segalin de Andrade, Ana Cristina; Brienen, Roel J W; Erwin, Terry L; Feldpausch, Ted R; Monteagudo Mendoza, Abel Lorenzo; Nuñez Vargas, Percy; Prieto, Adriana; Silva-Espejo, Javier Eduardo; Malhi, Yadvinder; Moorcroft, Paul R

2016-01-19

Amazon forests, which store ∼ 50% of tropical forest carbon and play a vital role in global water, energy, and carbon cycling, are predicted to experience both longer and more intense dry seasons by the end of the 21st century. However, the climate sensitivity of this ecosystem remains uncertain: several studies have predicted large-scale die-back of the Amazon, whereas several more recent studies predict that the biome will remain largely intact. Combining remote-sensing and ground-based observations with a size- and age-structured terrestrial ecosystem model, we explore the sensitivity and ecological resilience of these forests to changes in climate. We demonstrate that water stress operating at the scale of individual plants, combined with spatial variation in soil texture, explains observed patterns of variation in ecosystem biomass, composition, and dynamics across the region, and strongly influences the ecosystem's resilience to changes in dry season length. Specifically, our analysis suggests that in contrast to existing predictions of either stability or catastrophic biomass loss, the Amazon forest's response to a drying regional climate is likely to be an immediate, graded, heterogeneous transition from high-biomass moist forests to transitional dry forests and woody savannah-like states. Fire, logging, and other anthropogenic disturbances may, however, exacerbate these climate change-induced ecosystem transitions.

New estimates of temperature response of leaf photosynthesis in Amazon forest trees, its acclimation to mean temperature change and consequences for modelling climate response to rain forests.

NASA Astrophysics Data System (ADS)

Kruijt, B.; Jans, W.; Vasconcelos, S.; Tribuzy, E. S.; Felsemburgh, C.; Eliane, M.; Rowland, L.; da Costa, A. C. L.; Meir, P.

2014-12-01

In many dynamic vegetation models, degradation of the tropical forests is induced because they assume that productivity falls rapidly when temperatures rise in the region of 30-40°C. Apart plant respiration, this is due to the assumptions on the temperature optima of photosynthetic capacity, which are low and can differ widely between models, where in fact hardly any empirical information is available for tropical forests. Even less is known about the possibility that photosynthesis will acclimate to changing temperatures. The objective of this study to is to provide better estimates for optima, as well as to determine whether any acclimation to temperature change is to be expected. We present both new and hitherto unpublished data on the temperature response of photosynthesis of Amazon rainforest trees, encompassing three sites, several species and five field campaigns. Leaf photosynthesis and its parameters were determined at a range of temperatures. To study the long-term (seasonal) acclimation of this response, this was combined with an artificial, in situ, multi-season leaf heating experiment. The data show that, on average for all non-heated cases, the photosynthetic parameter Vcmax weakly peaks between 35 and 40 ˚C, while heating does not have a clearly significant effect. Results for Jmax are slightly different, with sharper peaks. Scatter was relatively high, which could indicate weak overall temperature dependence. The combined results were used to fit new parameters to the various temperature response curve functions in a range of DGVMs. The figure shows a typical example: while the default Jules model assumes a temperature optimum for Vcmax at around 33 ˚C, the data suggest that Vcmax keeps rising up to at least 40 ˚C. Of course, calculated photosynthesis, obtained by applying this Vcmax in the Farquhar model, peaks at lower temperature. Finally, the implication of these new model parameters for modelled climate change impact on modelled Amazon forests will be assessed, where it is expected that predicted die-back will be less.

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

NASA Astrophysics Data System (ADS)

Eamus, D.; Zolfaghar, S.; Villalobos-Vega, R.; Cleverly, J.; Huete, A.

2015-10-01

Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs. We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream. We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources. Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.

Molecular and physiological responses of trees to waterlogging stress.

PubMed

Kreuzwieser, Jürgen; Rennenberg, Heinz

2014-10-01

One major effect of global climate change will be altered precipitation patterns in many regions of the world. This will cause a higher probability of long-term waterlogging in winter/spring and flash floods in summer because of extreme rainfall events. Particularly, trees not adapted at their natural site to such waterlogging stress can be impaired. Despite the enormous economic, ecological and social importance of forest ecosystems, the effect of waterlogging on trees is far less understood than the effect on many crops or the model plant Arabidopsis. There is only a handful of studies available investigating the transcriptome and metabolome of waterlogged trees. Main physiological responses of trees to waterlogging include the stimulation of fermentative pathways and an accelerated glycolytic flux. Many energy-consuming, anabolic processes are slowed down to overcome the energy crisis mediated by waterlogging. A crucial feature of waterlogging tolerance is the steady supply of glycolysis with carbohydrates, particularly in the roots; stress-sensitive trees fail to maintain sufficient carbohydrate availability resulting in the dieback of the stressed tissues. The present review summarizes physiological and molecular features of waterlogging tolerance of trees; the focus is on carbon metabolism in both, leaves and roots of trees. © 2014 John Wiley & Sons Ltd.

Colletotrichum species associated with jute (Corchorus capsularis L.) anthracnose in southeastern China

PubMed Central

Niu, Xiaoping; Gao, Hong; Qi, Jianmin; Chen, Miancai; Tao, Aifen; Xu, Jiantang; Dai, Zhigang; Su, Jianguang

2016-01-01

Anthracnose, caused by the Colletotrichum species of fungi, is one of the most serious diseases affecting jute in China. The disease causes chlorotic regions with black brown sunken necrotic pits on the surfaces of stems. In late stages of disease, plants undergo defoliation, dieback and blight, which make anthracnose a major threat to jute fiber production and quality in China. In this study, 7 strains of Colletotrichum fungi were isolated from diseased jute stems from Zhejiang, Fujian, Guangxi, and Henan plantations in China. Multi-locus sequence (ACT, TUB2, CAL, GS, GAPDH and ITS) analysis coupled with morphological assessment revealed that C. fructicola, C. siamense and C. corchorum-capsularis sp. nov. were associated with jute anthracnose in southeastern China. C. fructicola and C. siamense were previously not associated with jute anthracnose. C. corchorum-capsularis is a new species formally described here. Pathogenicity tests confirmed that all species can infect jute, causing anthracnose, however the virulence of the 3 species differed. This report is the first associating these three species with jute disease worldwide and is the first description of the pathogens responsible for jute anthracnose in China. PMID:27121760

PCR-Based Gut Content Analysis to Detect Predation of Eriococcus ironsidei (Hemiptera: Eriococcidae) by Coccinellidae Species in Macadamia Nut Orchards in Hawaii.

PubMed

Gutierrez-Coarite, Rosemary; Yoneishi, Nicole M; Pulakkatu-Thodi, Ishakh; Mollinedo, Javier; Calla, Bernarda; Wright, Mark G; Geib, Scott M

2018-04-02

Macadamia felted coccid, Eriococcus ironsidei (Williams) (Hemiptera: Eriococcidae) was first found infesting macadamia trees in the island of Hawaii in 2005. Macadamia felted coccid infests all above-ground parts of trees to feed and reproduce. Their feeding activity distorts and stunts new growth which causes yellow spotting on older leaves, and when population densities become high, branch dieback occurs. Different predatory beetles have been observed in macadamia nut trees infested by E. ironsidei, the most abundant were Halmus chalybeus, Curinus coeruleus, Scymnodes lividigaster, Rhyzobius forestieri, and Sticholotis ruficeps. To verify predation of E. ironsidei by these beetles, a molecular assay was developed utilizing species-specific primers to determine presence in gut content of predators. Using these primers for PCR analysis, wild predator beetles were screened for the presence of E. ironsidei DNA. Analysis of beetles collected from macadamia orchards revealed predation by H. chalybeus, C. coeruleus, S. lividigaster, R. forestieri, and S. ruficeps on E. ironsidei. This study demonstrates that these beetles may play an important role in controlling the population of E. ironsidei, and these predators may be useful as biocontrol agents for E. ironsidei.

Water and light improvement after thinning at a xeric site: Which weights the most? A dual isotope approach

NASA Astrophysics Data System (ADS)

Giuggiola, Arnaud; Ogée, Jérôme; Gessler, Arthur; Rigling, Andreas; Bugmann, Harald; Treydte, Kerstin

2015-04-01

Reductions in stand density foster individual tree growth due to increases of resources such as water, light and nutrients. Detailed knowledge of the short- to long-term physiological response underlying the growth response to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models such as MuSICA to study the physiological processes underlying growth enhancement in a long-term thinning experiment in a xeric Pinus sylvestris forest in Switzerland. This approach allowed for identifying and disentangling changes in stomatal conductance and assimilation rate. Our results indicate that an increase in stomatal conductance outweighs an increase in assimilation, meaning that the observed growth releases in heavy thinned trees at our xeric site are primarily driven by enhanced water availability rather than by the increase in light availability. We conclude that in areas with isohydric species (drought avoiders) that tend to grow close to their physiological limits, thinning is highly recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival rate of individual trees and forests.

The containment of toxic wastes: I. Long term metal movement in soils over a covered metalliferous waste heap at Parc lead-zinc mine, North Wales.

PubMed

Shu, J; Bradshaw, A D

1995-01-01

In order to stabilise and contain a toxic metalliferous waste heap at Parc Mine, North Wales, it was covered with 30-40 cm layer of quarry waste in 1977-1978, and sown with a grass/clover seed mixture. This study has examined subsequent metal movement in the cover material and its effect on vegetation. The results, especially when compared with previous observations, give no evidence of upward migration of metals by capillarity in the cover material. Sideways movement of leachate, however, appears to be carrying the metals into the cover material on the sloping sides, giving rise to increasing concentrations of heavy metals in the vegetation and dieback in some places. Root growth on the flat top of the heap is greater than on the slope, but the roots have not penetrated the waste and the contents of Pb, Zn and Cd in surface vegetation remain low. Surface covering of toxic waste with coarse materials restricting capillary rise is therefore a valid reclamation technique so long as lateral movement of toxic leachate can be controlled.

Does the invasive plant, Impatiens glandulifera promote soil erosion from riparian zones? An investigation on a small watercourse in northwest Switzerland

NASA Astrophysics Data System (ADS)

Greenwood, Philip; Kuhn, Nikolaus

2013-04-01

Impatiens glandulifera (common English name: Himalayan Balsam) was introduced into Europe in the mid-19th century, whereupon its invasive tendency has facilitated its expansion throughout many mainland European countries. Its rate of expansion can be attributed to certain lifecycle traits that allow it to become rapidly established and crowd-out many native floral species. Its preferred habitat includes damp, nutrient-rich soils that experience frequent natural disturbance, such as along riparian zones. Once present, nearby watercourses then inadvertently act as conduits that facilitate the movement of seeds downstream into un-colonised parts of a catchment. Once established, individual plants form discrete and often mono-cultural stands of dense vegetation that can typically range in area from a few m-2 to > 150 m-2. Impatiens glandulifera is cold-intolerant however, and in temperate countries rapidly dies when exposed to the first frosts of the season. Once die-back occurs, it is hypothesised that a reduction in the protection afforded to the underlying soil by the vegetation canopy will promote the mobilisation of material from areas contaminated with I. glandulifera at a greater rate that areas supporting indigeneous vgetation, due to their increased exposure to erosion processes. An investigation was conducted to test this hypothesis in a contaminated sub-catchment of the Birs River in northwest Switzerland. A measurement technique consisting of erosion pins, an erosion bridge and a digital caliper was employed to quantify changes in the soil profile, as this approach represented the least invasive way of repeatedly measuring through vegetation without undue disturbance. An initial soil surface profile was established at five contaminated sites in late summer 2012 before die-back occurred, as well as at five nearby reference sites where I. glandulifera was absent. All soil surface profiles were re-measured at ca. 25-day intervals and the average net change was quantified for each site and converted to an equivalent soil flux value (i.e. kg m-2) between re-measurements. Net soil loss from contaminated and reference sites were statistically compared in order to determine whether the difference is significant. The preliminary findings suggest that I. glandulifera does play a significant role in promoting soil loss from riparian zones.

The potentiation of zinc toxicity by soil moisture in a boreal forest ecosystem.

PubMed

Owojori, Olugbenga J; Siciliano, Steven D

2015-03-01

Northern boreal forests often experience forest dieback as a result of metal ore mining and smelting. The common solution is to lime the soil, which increases pH, reducing metal toxicity and encouraging recovery. In certain situations, however, such as in Flin Flon, Manitoba, Canada, liming has yielded only moderate benefits, with some locations responding well to liming and other locations not at all. In an effort to increase the effectiveness of the ecorestoration strategy, the authors investigated if these differences in liming responsiveness were linked to differences in toxicity. Toxicity of metal-impacted Flin Flon soils on the oribatid mite Oppia nitens and the collembolan Folsomia candida was assessed, with a view toward identifying the metal of concern in the area. The effects of moisture content on metal sorption, uptake, and toxicity to the invertebrates were also investigated. Toxicity tests with the invertebrates were conducted using either Flin Flon soils or artificial soils with moisture content adjusted to 30%, 45%, 60%, or 75% of the maximum water-holding capacity of the soil samples. The Relative to Cd Toxicity Model identified Zn as the metal of concern in the area, and this was confirmed using validation tests with field contaminated soils. Furthermore, increasing the moisture content in soils increased the amount of mobile Zn available for uptake with the ion exchange resin. Survival and reproduction of both invertebrates were reduced under Zn exposure as moisture level increased. Thus, moisture-collecting landforms, which are often also associated with high Zn concentrations at Flin Flon, have, as a result, higher Zn toxicity to the soil ecosystem because of increases in soil moisture. © 2014 SETAC.

Minimum Irrigation Requirements for Cottonwood (Populus fremontii and P. deltoides) and Willow (Salix gooddingii) Grown in a Desert Environment

NASA Astrophysics Data System (ADS)

Glenn, E. P.; Hartwell, S.; Morino, K.; Nagler, P. L.

2009-12-01

Native tree plots have been established in riverine irrigation districts in the western U.S. to provide habitat for threatened and endangered birds. Information is needed on the minimum effective irrigation requirements of the target species. We summarize preliminary (or unpublished) findings of a study or cottonwood (Populus spp.) and willow (Salix gooddingii) trees that were grown for seven years in an outdoor plot in a desert environment in Tucson, Arizona to determine plant water use. Plants were allowed to achieve a nearly complete canopy cover over the first four years, then were subjected to three summer irrigation schedules: 6.2 mm d-1; 8.26 mm d-1 and 15.7 mm d-1. The lowest irrigation rate was sufficient to maintain growth and high leaf area index for cottonwoods over three years, but willows suffered partial die-back on this rate, and required 8.26 mm d-1 to maintain growth. These irrigation rates were required April 15 - September 15, but only 0.88 mm d-1 was required during the dormant periods of the year. Expressed as a fraction of reference crop evapotranspiration (ET/ETo), annual water requirements were 0.83 ETo for cottonwood and 1.01 ETo for willow, which includes irrigation plus precipitation. Current practices tend to over-irrigate restoration plots, and this study can provide guidelines for more efficient water use.

Improving the Amazonian Hydrologic Cycle in a Coupled Land-Atmosphere, Single Column Model

NASA Astrophysics Data System (ADS)

Harper, A. B.; Denning, S.; Baker, I.; Prihodko, L.; Branson, M.

2006-12-01

We have coupled a land-surface model, the Simple Biosphere Model (SiB3), to a single column of the Colorado State University General Circulation Model (CSU-GCM) in the Amazon River Basin. This is a preliminary step in the broader goal of improved simulation of Basin-wide hydrology. A previous version of the coupled model (SiB2) showed drought and catastrophic dieback of the Amazon rain forest. SiB3 includes updated soil hydrology and root physiology. Our test area for the coupled single column model is near Santarem, Brazil, where measurements from the km 83 flux tower in the Tapajos National Forest can be used to evaluate model output. The model was run for 2001 using NCEP2 Reanalysis as driver data. Preliminary results show that the updated biosphere model coupled to the GCM produces improved simulations of the seasonal cycle of surface water balance and precipitation. Comparisons of the diurnal and seasonal cycles of surface fluxes are also being made.

Alterations in Grapevine Leaf Metabolism Occur Prior to Esca Apoplexy Appearance.

PubMed

Magnin-Robert, Maryline; Adrian, Marielle; Trouvelot, Sophie; Spagnolo, Alessandro; Jacquens, Lucile; Letousey, Patricia; Rabenoelina, Fanja; Harir, Mourad; Roullier-Gall, Chloé; Clément, Christophe; Schmitt-Kopplin, Philippe; Vallat, Armelle; Abou-Mansour, Eliane; Fontaine, Florence

2017-12-01

Esca disease is one of the major grapevine trunk diseases in Europe and the etiology is complex, since several inhabiting fungi are identified to be associated with this disease. Among the foliar symptom expressions, the apoplectic form may be distinguished and characterized by sudden dieback of shoots, leaf drop, and shriveling of grape clusters in a few days that can ultimately induce the plant death. To further understand this drastic event, we conducted transcriptomic and metabolomic analyses to characterize responses of leaves during the period preceding symptom appearance (20 and 7 days before foliar symptom expression) and at the day of apoplexy expression. Transcriptomic and metabolomic analyses provide signatures for the apoplectic leaves and most changes concerning the metabolism of carbohydrates, amino acids, and phenylpropanoids. In deciphering glutathione-S-transferase (GST), its preferential location in phloem, correlated with the upregulation of GST genes and a decrease of the glutathione level, offers further support to the putative role of glutathione during apoplexy expression.

Apparent climatically induced increase of tree mortality rates in a temperate forest

USGS Publications Warehouse

van Mantgem, P.J.; Stephenson, N.L.

2007-01-01

We provide a first detailed analysis of long-term, annual-resolution demographic trends in a temperate forest. After tracking the fates of 21 338 trees in a network of old-growth forest plots in the Sierra Nevada of California, we found that mortality rate, but not the recruitment rate, increased significantly over the 22 years of measurement (1983-2004). Mortality rates increased in both of two dominant taxonomic groups (Abies and Pinus) and in different forest types (different elevational zones). The increase in overall mortality rate resulted from an increase in tree deaths attributed to stress and biotic causes, and coincided with a temperature-driven increase in an index of drought. Our findings suggest that these forests (and by implication, other water-limited forests) may be sensitive to temperature-driven drought stress, and may be poised for die-back if future climates continue to feature rising temperatures without compensating increases in precipitation. ?? 2007 Blackwell Publishing Ltd/CNRS.

Neuronal matrix metalloproteinase-9 is a determinant of selective neurodegeneration.

PubMed

Kaplan, Artem; Spiller, Krista J; Towne, Christopher; Kanning, Kevin C; Choe, Ginn T; Geber, Adam; Akay, Turgay; Aebischer, Patrick; Henderson, Christopher E

2014-01-22

Selective neuronal loss is the hallmark of neurodegenerative diseases. In patients with amyotrophic lateral sclerosis (ALS), most motor neurons die but those innervating extraocular, pelvic sphincter, and slow limb muscles exhibit selective resistance. We identified 18 genes that show >10-fold differential expression between resistant and vulnerable motor neurons. One of these, matrix metalloproteinase-9 (MMP-9), is expressed only by fast motor neurons, which are selectively vulnerable. In ALS model mice expressing mutant superoxide dismutase (SOD1), reduction of MMP-9 function using gene ablation, viral gene therapy, or pharmacological inhibition significantly delayed muscle denervation. In the presence of mutant SOD1, MMP-9 expressed by fast motor neurons themselves enhances activation of ER stress and is sufficient to trigger axonal die-back. These findings define MMP-9 as a candidate therapeutic target for ALS. The molecular basis of neuronal diversity thus provides significant insights into mechanisms of selective vulnerability to neurodegeneration. Copyright © 2014 Elsevier Inc. All rights reserved.

Potential groundwater contribution to Amazon evapotranspiration

NASA Astrophysics Data System (ADS)

Fan, Y.; Miguez-Macho, G.

2010-07-01

Climate and land ecosystem models simulate a dry-season vegetation stress in the Amazon forest, but observations show enhanced growth in response to higher radiation under less cloudy skies, indicating an adequate water supply. Proposed mechanisms include larger soil water store and deeper roots in nature and the ability of roots to move water up and down (hydraulic redistribution). Here we assess the importance of the upward soil water flux from the groundwater driven by capillarity. We present a map of water table depth from observations and groundwater modeling, and a map of potential capillary flux these water table depths can sustain. The maps show that the water table beneath the Amazon can be quite shallow in lowlands and river valleys (<5 m in 36% and <10 m in 60% of Amazonia). The water table can potentially sustain a capillary flux of >2.1 mm day-1 to the land surface averaged over Amazonia, but varies from 0.6 to 3.7 mm day-1 across nine study sites. Current models simulate a large-scale reduction in dry-season photosynthesis under today's climate and a possible dieback under projected future climate with a longer dry season, converting the Amazon from a net carbon sink to a source and accelerating warming. The inclusion of groundwater and capillary flux may modify the model results.

Quantitative Analysis of Land Loss in Coastal Louisiana Using Remote Sensing

NASA Astrophysics Data System (ADS)

Wales, P. M.; Kuszmaul, J.; Roberts, C.

2005-12-01

For the past thirty-five years the land loss along the Louisiana Coast has been recognized as a growing problem. One of the clearest indicators of this land loss is that in 2000 smooth cord grass (spartina alterniflora) was turning brown well before its normal hibernation period. Over 100,000 acres of marsh were affected by the 2000 browning. In 2001 data were collected using low altitude helicopter based transects of the coast, with 7,400 data points being collected by researchers at the USGS, National Wetlands Research Center, and Louisiana Department of Natural Resources. The surveys contained data describing the characteristics of the marsh, including latitude, longitude, marsh condition, marsh color, percent vegetated, and marsh die-back. Creating a model that combines remote sensing images, field data, and statistical analysis to develop a methodology for estimating the margin of error in measurements of coastal land loss (erosion) is the ultimate goal of the study. A model was successfully created using a series of band combinations (used as predictive variables). The most successful band combinations or predictive variables were the braud value [(Sum Visible TM Bands - Sum Infrared TM Bands)/(Sum Visible TM Bands + Sum Infrared TM Bands)], TM band 7/ TM band 2, brightness, NDVI, wetness, vegetation index, and a 7x7 autocovariate nearest neighbor floating window. The model values were used to generate the logistic regression model. A new image was created based on the logistic regression probability equation where each pixel represents the probability of finding water or non-water at that location in each image. Pixels within each image that have a high probability of representing water have a value close to 1 and pixels with a low probability of representing water have a value close to 0. A logistic regression model is proposed that uses seven independent variables. This model yields an accurate classification in 86.5% of the locations considered in the 1997 and 2001 survey locations. When the logistic regression was modeled to the satellite imagery of the entire Louisiana Coast study area a statewide loss was estimated to be 358 mi2 to 368 mi2, from 1997 to 2001, using two different methods for estimating land loss.

Milestones in plant sulfur research on sulfur-induced-resistance (SIR) in Europe

PubMed Central

Bloem, Elke; Haneklaus, Silvia; Schnug, Ewald

2015-01-01

Until the 1970's of the last century sulfur (S) was mainly regarded as a pollutant being the main contributor of acid rain, causing forest dieback in central Europe. When Clean Air Acts came into force at the start of the 1980's SO2 contaminations in the air were consequently reduced within the next years. S changed from an unwanted pollutant into a lacking plant nutrient in agriculture since agricultural fields were no longer “fertilized” indirectly by industrial pollution. S deficiency was first noticed in Brassica crops that display an especially high S demand because of its content of S-containing secondary metabolites, the glucosinolates. In Scotland, where S depositions decreased even faster than in continental Europe, an increasing disease incidence with Pyrenopeziza brassicae was observed in oilseed rape in the beginning 1990's and the concept of sulfur-induced-resistance (SIR) was developed after a relationship between the S status and the disease incidence was uncovered. Since then a lot of research was carried out to unravel the background of SIR in the metabolism of agricultural crops and to identify metabolites, enzymes and reactions, which are potentially activated by the S metabolism to combat fungal pathogens. The S status of the crop is affecting many different plant features such as color and scent of flowers, pigments in leaves, metabolite concentrations and the release of gaseous S compounds which are directly influencing the desirability of a crop for a variety of different organisms from microorganisms, over insects and slugs to the point of grazing animals. The present paper is an attempt to sum up the knowledge about the effect of the S nutritional status of agricultural crops on parameters that are directly related to their health status and by this to SIR. Milestones in SIR research are compiled, open questions are addressed and future projections were developed. PMID:25642233

Expert risk perceptions and the social amplification of risk: A case study in invasive tree pests and diseases.

PubMed

Urquhart, Julie; Potter, Clive; Barnett, Julie; Fellenor, John; Mumford, John; Quine, Christopher P

2017-11-01

The Social Amplification of Risk Framework (SARF) is often used as a conceptual tool for studying diverse risk perceptions associated with environmental hazards. While widely applied, it has been criticised for implying that it is possible to define a benchmark 'real' risk that is determined by experts and around which public risk perceptions can subsequently become amplified. It has been argued that this objectification of risk is particularly problematic when there are high levels of scientific uncertainty and a lack of expert consensus about the nature of a risk and its impacts. In order to explore this further, this paper examines how 'experts' - defined in this case as scientists, policy makers, outbreak managers and key stakeholders - construct and assemble their understanding of the risks associated with two invasive tree pest and disease outbreaks in the UK, ash dieback and oak processionary moth. Through semi-structured interviews with experts in each of the case study outbreaks, the paper aims to better understand the nature of information sources drawn on to construct perceptions of tree health risks, especially when uncertainty is prevalent. A key conclusion is that risk assessment is a socially-mediated, relational and incremental process with experts drawing on a range of official, anecdotal and experiential sources of information, as well as reference to past events in order to assemble the risk case. Aligned with this, experts make attributions about public concern, especially when the evidence base is incomplete and there is a need to justify policy and management actions and safeguard reputation.

Red Reveals Branch Die-back in Norway Maple Acer platanoides

PubMed Central

Sinkkonen, Aki

2008-01-01

Background and Aims Physiological data suggest that autumn leaf colours of deciduous trees are adaptations to environmental stress. Recently, the evolution of autumn colouration has been linked to tree condition and defence. Most current hypotheses presume that autumn colours vary between tree individuals. This study was designed to test if within-tree variation should be taken into account in experimental and theoretical research on autumn colouration. Methods Distribution of red autumn leaf colours was compared between partially dead and vigorous specimens of Norway maple (Acer platanoides) in a 3-year study. In August, the amount of reddish foliage was estimated in pairs of partially dead and control trees. Within-tree variation in the distribution of reddish leaves was evaluated. Leaf nitrogen and carbon concentrations were analysed. Key Results Reddish leaf colours were more frequent in partially dead trees than in control trees. Reddish leaves were evenly distributed in control trees, while patchiness of red leaf pigments was pronounced in partially dead trees. Large patches of red leaves were found beneath or next to dead tree parts. These patches reoccurred every year. Leaf nitrogen concentration was lower in reddish than in green leaves but the phenomenon seemed similar in both partially dead and control trees. Conclusions The results suggest that red leaf colouration and branch condition are interrelated in Norway maple. Early reddish colours may be used as an indication of leaf nitrogen and carbon levels but not as an indication of tree condition. Studies that concentrate on entire trees may not operate at an optimal level to detect the evolutionary mechanisms behind autumnal leaf colour variation. PMID:18567914

Red reveals branch die-back in Norway maple Acer platanoides.

PubMed

Sinkkonen, Aki

2008-09-01

Physiological data suggest that autumn leaf colours of deciduous trees are adaptations to environmental stress. Recently, the evolution of autumn colouration has been linked to tree condition and defence. Most current hypotheses presume that autumn colours vary between tree individuals. This study was designed to test if within-tree variation should be taken into account in experimental and theoretical research on autumn colouration. Distribution of red autumn leaf colours was compared between partially dead and vigorous specimens of Norway maple (Acer platanoides) in a 3-year study. In August, the amount of reddish foliage was estimated in pairs of partially dead and control trees. Within-tree variation in the distribution of reddish leaves was evaluated. Leaf nitrogen and carbon concentrations were analysed. Reddish leaf colours were more frequent in partially dead trees than in control trees. Reddish leaves were evenly distributed in control trees, while patchiness of red leaf pigments was pronounced in partially dead trees. Large patches of red leaves were found beneath or next to dead tree parts. These patches reoccurred every year. Leaf nitrogen concentration was lower in reddish than in green leaves but the phenomenon seemed similar in both partially dead and control trees. The results suggest that red leaf colouration and branch condition are interrelated in Norway maple. Early reddish colours may be used as an indication of leaf nitrogen and carbon levels but not as an indication of tree condition. Studies that concentrate on entire trees may not operate at an optimal level to detect the evolutionary mechanisms behind autumnal leaf colour variation.

Xylella fastidiosa Isolates from Both subsp. multiplex and fastidiosa Cause Disease on Southern Highbush Blueberry (Vaccinium sp.) Under Greenhouse Conditions.

PubMed

Oliver, J E; Cobine, P A; De La Fuente, L

2015-07-01

Xylella fastidiosa is a xylem-limited gram-negative plant pathogen that affects numerous crop species, including grape, citrus, peach, pecan, and almond. Recently, X. fastidiosa has also been found to be the cause of bacterial leaf scorch on blueberry in the southeastern United States. Thus far, all X. fastidiosa isolates obtained from infected blueberry have been classified as X. fastidiosa subsp. multiplex; however, X. fastidiosa subsp. fastidiosa isolates are also present in the southeastern United States and commonly cause Pierce's disease of grapevines. In this study, seven southeastern U.S. isolates of X. fastidiosa, including three X. fastidiosa subsp. fastidiosa isolates from grape, one X. fastidiosa subsp. fastidiosa isolate from elderberry, and three X. fastidiosa subsp. multiplex isolates from blueberry, were used to infect the southern highbush blueberry 'Rebel'. Following inoculation, all isolates colonized blueberry, and isolates from both X. fastidiosa subsp. multiplex and X. fastidiosa subsp. fastidiosa caused symptoms, including characteristic stem yellowing and leaf scorch symptoms as well as dieback of the stem tips. Two X. fastidiosa subsp. multiplex isolates from blueberry caused more severe symptoms than the other isolates examined, and infection with these two isolates also had a significant impact on host mineral nutrient content in sap and leaves. These findings have potential implications for understanding X. fastidiosa host adaptation and expansion and the development of emerging diseases caused by this bacterium.

Tree mortality in mature riparian forest: Implications for Fremont cottonwood conservation in the American southwest

USGS Publications Warehouse

Andersen, Douglas

2015-01-01

Mature tree mortality rates are poorly documented in desert riparian woodlands. I monitored deaths and calculated annual survivorship probability (Ps) in 2 groups of large (27–114 cm DBH), old (≥40 years old) Fremont cottonwood (Populus fremontii Wats.) in a stand along the free-flowing Yampa River in semiarid northwestern Colorado. Ps = 0.993 year-1 in a group (n = 126) monitored over 2003–2013, whereas Ps = 0.985 year-1 in a group (n = 179) monitored over the same period plus 3 earlier years (2000–2003) that included drought and a defoliating insect outbreak. Assuming Ps was the same for both groups during the 10-year postdrought period, the data indicate that Ps = 0.958 year-1 during the drought. I found no difference in canopy dieback level between male and female survivors. Mortality was equal among size classes, suggesting Ps is independent of age, but published longevity data imply that either Ps eventually declines with age or, as suggested in this study, periods with high Ps are interrupted by episodes of increased mortality. Stochastic population models featuring episodes of low Ps suggest a potential for an abrupt decline in mature tree numbers where recruitment is low. The modeling results have implications for woodland conservation, especially for relictual stands along regulated desert rivers.

A broad survey of hydraulic and mechanical safety in the xylem of conifers

PubMed Central

Bouche, Pauline S.; Larter, Maximilien; Domec, Jean-Christophe; Burlett, Régis; Gasson, Peter; Jansen, Steven; Delzon, Sylvain

2014-01-01

Drought-induced forest dieback has been widely reported over the last decades, and the evidence for a direct causal link between survival and hydraulic failure (xylem cavitation) is now well known. Because vulnerability to cavitation is intimately linked to the anatomy of the xylem, the main objective of this study was to better understand the xylem anatomical properties associated with cavitation resistance. An extensive data set of cavitation resistance traits and xylem anatomical properties was developed for 115 conifer species, with special attention given to the micro-morphology of bordered pits. The ratio of torus to pit aperture diameter, so-called torus overlap, increased with increasing cavitation resistance, while the flexibility of the margo does not seem to play a role, suggesting that air-seeding is located at the seal between the aspirated torus and pit aperture. Moreover, punctured tori were reported in various Pinaceae species. Species resistant to cavitation had thicker tracheid walls, while their lumen diameter (conduit size) was only slightly reduced, minimizing the impact on hydraulic conductance. The results also demonstrated (i) the existence of an indirect trade-off between hydraulic safety and mechanical strength; and (ii) a consistency between species distribution and xylem anatomy: species with a wide torus overlap and high valve effects are found in arid environments such as the Mediterranean region. PMID:24916072

An imperative need for global change research in tropical forests.

PubMed

Zhou, Xuhui; Fu, Yuling; Zhou, Lingyan; Li, Bo; Luo, Yiqi

2013-09-01

Tropical forests play a crucial role in regulating regional and global climate dynamics, and model projections suggest that rapid climate change may result in forest dieback or savannization. However, these predictions are largely based on results from leaf-level studies. How tropical forests respond and feedback to climate change is largely unknown at the ecosystem level. Several complementary approaches have been used to evaluate the effects of climate change on tropical forests, but the results are conflicting, largely due to confounding effects of multiple factors. Although altered precipitation and nitrogen deposition experiments have been conducted in tropical forests, large-scale warming and elevated carbon dioxide (CO2) manipulations are completely lacking, leaving many hypotheses and model predictions untested. Ecosystem-scale experiments to manipulate temperature and CO2 concentration individually or in combination are thus urgently needed to examine their main and interactive effects on tropical forests. Such experiments will provide indispensable data and help gain essential knowledge on biogeochemical, hydrological and biophysical responses and feedbacks of tropical forests to climate change. These datasets can also inform regional and global models for predicting future states of tropical forests and climate systems. The success of such large-scale experiments in natural tropical forests will require an international framework to coordinate collaboration so as to meet the challenges in cost, technological infrastructure and scientific endeavor.

Road building, land use and climate change: prospects for environmental governance in the Amazon.

PubMed

Perz, Stephen; Brilhante, Silvia; Brown, Foster; Caldas, Marcellus; Ikeda, Santos; Mendoza, Elsa; Overdevest, Christine; Reis, Vera; Reyes, Juan Fernando; Rojas, Daniel; Schmink, Marianne; Souza, Carlos; Walker, Robert

2008-05-27

Some coupled land-climate models predict a dieback of Amazon forest during the twenty-first century due to climate change, but human land use in the region has already reduced the forest cover. The causation behind land use is complex, and includes economic, institutional, political and demographic factors. Pre-eminent among these factors is road building, which facilitates human access to natural resources that beget forest fragmentation. While official government road projects have received considerable attention, unofficial road building by interest groups is expanding more rapidly, especially where official roads are being paved, yielding highly fragmented forest mosaics. Effective governance of natural resources in the Amazon requires a combination of state oversight and community participation in a 'hybrid' model of governance. The MAP Initiative in the southwestern Amazon provides an example of an innovative hybrid approach to environmental governance. It embodies a polycentric structure that includes government agencies, NGOs, universities and communities in a planning process that links scientific data to public deliberations in order to mitigate the effects of new infrastructure and climate change.

Proposal of Xanthomonas translucens pv. pistaciae pv. nov., pathogenic to pistachio (Pistacia vera).

PubMed

Giblot-Ducray, Danièle; Marefat, Alireza; Gillings, Michael R; Parkinson, Neil M; Bowman, John P; Ophel-Keller, Kathy; Taylor, Cathy; Facelli, Evelina; Scott, Eileen S

2009-12-01

Strains of Xanthomonas translucens have caused dieback in the Australian pistachio industry for the last 15 years. Such pathogenicity to a dicotyledonous woody host contrasts with that of other pathovars of X. translucens, which are characterized by their pathogenicity to monocotyledonous plant families. Further investigations, using DNA-DNA hybridization, gyrB gene sequencing and integron screening, were conducted to confirm the taxonomic status of the X. translucens pathogenic to pistachio. DNA-DNA hybridization provided a clear classification, at the species level, of the pistachio pathogen as a X. translucens. In the gyrB-based phylogeny, strains of the pistachio pathogen clustered among the X. translucens pathovars as two distinct lineages. Integron screening revealed that the cassette arrays of strains of the pistachio pathogen were different from those of other Xanthomonas species, and again distinguished two groups. Together with previously reported pathogenicity data, these results confirm that the pistachio pathogen is a new pathovar of X. translucens and allow hypotheses about its origin. The proposed name is Xanthomonas translucens pv. pistaciae pv. nov.

A new mechanism for calcium loss in forest-floor soils

USGS Publications Warehouse

Lawrence, G.B.; David, M.B.; Shortle, W.C.

1995-01-01

CALCIUM is the fifth most abundant element in trees, and is an essential component for wood formation and the maintenance of cell walls. Depletion of Ca from the rooting zone can result in acidification of soil1 and surface water2 and possibly growth decline and dieback of red spruce3,4. During the past six decades, concentrations of root-available Ca (exchangeable and acid-ex tract able forms) in forest-floor soils have decreased in the northeastern United States5,6. Both net forest growth and acid deposition have been put forth as mechanisms that can account for this Ca depletion5,6. Here, however, we present data collected in red spruce forests in the northeastern United States that are inconsistent with either of these mechanisms. We propose that aluminium, mobilized in the mineral soil by acid deposition, is transported into the forest floor in a reactive form that reduces storage of Ca, and thus its availability for root uptake. This results in potential stress to trees and, by increasing the demand for Ca, also decreases neutralization of drainage waters, thereby leading to acidification of lakes and streams.

Monitoring snow cover and its effect on runoff regime in the Jizera Mountains

NASA Astrophysics Data System (ADS)

Kulasova, Alena

2015-04-01

The Jizera Mountains in the northern Bohemia are known by its rich snow cover. Winter precipitation represents usually a half of the precipitation in the hydrological year. Gradual snow accumulation and melt depends on the course of the particular winter period, the topography of the catchments and the type of vegetation. During winter the snow depth, and especially the snow water equivalent, are affected by the changing character of the falling precipitation, air and soil temperatures and the wind. More rapid snowmelt occurs more on the slopes without forest oriented to the South, while a gradual snowmelt occurs on the locations turned to the North and in forest. Melting snow recharges groundwater and affects water quality in an important way. In case of extreme situation the snowmelt monitoring is important from the point of view of flood protection of communities and property. Therefore the immediate information on the amount of water in snow is necessary. The way to get this information is the continuous monitoring of the snow depth and snow water equivalent. In the Jizera Mountains a regular monitoring of snow cover has been going on since the end of the 19th century. In the 80s of the last century the Jizera Mountains were affected by the increased fallout of pollutants in the air. There followed a gradual dieback of the forest cover and cutting down the upper part of the ridges. In order to get data for the quantification of runoff regime changes in the changing natural environment, the Czech Hydrometeorological Institute (CHMI) founded in the upper part of the Mountains several experimental catchments. One of the activities of the employees of the experimental basis is the regular measurement of snow cover at selected sites from 1982 up to now. At the same time snow cover is being observed using snow pillows, where its mass is monitored with the help of pressure sensors. In order to improve the reliability of the continuous measurement of the snow water equivalent the LDSMS (Libor Danes Snow Measurement System) which uses weighing sensors has been developed. The system contains a novel device precluding the snowbridging (protected by a utility model). Data from manual and automatic measurements are transmitted to the central forecasting service of CHMI in Prague - Komorany (CPP) and to regional forecasting branches (RPP), where they are one of the inputs of the hydrological forecasting models. The contribution deals with the results of the manual snow measurement during the dieback of forest and now, in comparison with the automatic snow measurement in the experimental catchments of CHMI Uhlirska, Jezdecka and with the effect of snowmelt on the water level in the streams.

Stomatal Conductance, Plant Species Distribution, and an Exploration of Rhizosphere Microbes and Mycorrhizae at a Deliberately Leakimg Experimental Carbon Sequestration Field (ZERT)

NASA Astrophysics Data System (ADS)

Sharma, B.; Apple, M. E.; Morales, S.; Zhou, X.; Holben, B.; Olson, J.; Prince, J.; Dobeck, L.; Cunningham, A. B.; Spangler, L.

2010-12-01

One measure to reduce atmospheric CO2 is to sequester it in deep geological formations. Rapid surface detection of any CO2 leakage is crucial. CO2 leakage rapidly affects vegetation above sequestration fields. Plant responses to high CO2 are valuable tools in surface detection of leaking CO2. The Zero Emission Research Technology (ZERT) site in Bozeman, MT is an experimental field for surface detection of CO2 where 0.15 ton/day of CO2 was released (7/19- 8/15/2010) from a 100m horizontal injection well, HIW, 1.5 m underground with deliberate leaks of CO2 at intervals, and from a vertical injector, VI, (6/3-6/24/2010). The vegetation includes Taraxacum officinale (Dandelion), Dactylis glomerata (Orchard Grass), and other herbaceous plants. We collected soil and roots 1, 3 and 5 m from the VI to determine the responses of mycorrhizal fungi and rhizosphere microbes to high CO2. Mycorrhizal fungi obtain C from root exudates, increase N and P availability, and reduce desiccation, while prokaryotic rhizosphere microbes fix atmospheric N and will be examined for abundance and expression of carbon and nitrogen cycling genes. We are quantifying mycorrhizal colonization and the proportion of spores, hyphae, and arbuscules in vesicular-arbuscular mycorrhizae (VAM) in cleared and stained roots. Stomatal conductance is an important measure of CO2 uptake and water loss via transpiration. We used a porometer (5-40°C, 0-90% RH, Decagon) to measure stomatal conductivity in dandelion and orchard grass at 1, 3, and 5 m from the VI and along a transect perpendicular to the HIW. Dandelion conductance was highest close to the VI and almost consistently higher close to hot spots (circular regions with maximum CO2 and leaf dieback) at the HIW, with 23.2 mmol/m2/s proximal to the hot spot, and 10.8 mmol/m2/s distally. Average conductance in grass (50.3 mmol/m2/s) was higher than in dandelion, but grass did not have high conductance near hot spots. Stomata generally close at elevated CO2. Dandelion leaves near hot spots undergo rapid color change from green to red before senescing to a desiccated brown, while xeromorphic grass leaves do not. Species-specific differences in leaf survival following exposure to CO2 may be linked to species-specific differences in stomatal conductance, and to rhizosphere and mycorrhizal responses. Initial survey results of plant species distribution suggest a shift from a dandelion-grass to a grass-dominated community over hot spots. Sudden and long-term shifts in species composition have important ecological implications and may provide a means of surface detection of upwelling CO2.

Global warming and climate change in Amazonia: Climate-vegetation feedback and impacts on water resources

NASA Astrophysics Data System (ADS)

Marengo, José; Nobre, Carlos A.; Betts, Richard A.; Cox, Peter M.; Sampaio, Gilvan; Salazar, Luis

This chapter constitutes an updated review of long-term climate variability and change in the Amazon region, based on observational data spanning more than 50 years of records and on climate-change modeling studies. We start with the early experiments on Amazon deforestation in the late 1970s, and the evolution of these experiments to the latest studies on greenhouse gases emission scenarios and land use changes until the end of the twenty-first century. The "Amazon dieback" simulated by the HadCM3 model occurs after a "tipping point" of CO2 concentration and warming. Experiments on Amazon deforestation and change of climate suggest that once a critical deforestation threshold (or tipping point) of 40-50% forest loss is reached in eastern Amazonia, climate would change in a way which is dangerous for the remaining forest. This may favor a collapse of the tropical forest, with a substitution of the forest by savanna-type vegetation. The concept of "dangerous climate change," as a climate change, which induces positive feedback, which accelerate the change, is strongly linked to the occurrence of tipping points, and it can be explained as the presence of feedback between climate change and the carbon cycle, particularly involving a weakening of the current terrestrial carbon sink and a possible reversal from a sink (as in present climate) to a source by the year 2050. We must, therefore, currently consider the drying simulated by the Hadley Centre model(s) as having a finite probability under global warming, with a potentially enormous impact, but with some degree of uncertainty.

DNA phylogeny, morphology and pathogenicity of Botryosphaeria species on grapevines.

PubMed

van Niekerk, Jan M; Crous, Pedro W; Groenewald, J Z Ewald; Fourie, Paul H; Halleen, Francois

2004-01-01

Several species of Botr yosphaeria are known to occur on grapevines, causing a wide range of disorders including bud mortality, dieback, brown wood streaking and bunch rot. In this study the 11 Botryosphaeria spp. associated with grapevines growing in various parts of the world, but primarily in South Africa, are distinguished based on morphology, DNA sequences (ITS-1, 5.8S, ITS-2 and EF1-α) and pathological data. Botryosphaeria australis, B. lutea, B. obtusa, B. parva, B. rhodina and a Diplodia sp. are confirmed from grapevines in South Africa, while Diplodia porosum, Fusicoccum viticlavatum and F. vitifusiforme are described as new. Although isolates of B. dothidea and B. stevensii are confirmed from grapevines in Portugal, neither of these species occurred in South Africa, nor were any isolates of B. ribis confirmed from grapevines. All grapevine isolates from Portugal, formerly presumed to be B. ribis, are identified as B. parva based on their EF1-α equence data. From artificial inoculations on grapevine shoots, we conclude that B. australis, B. parva, B. ribis and B. stevensii are more virulent than the other species studied. The Diplodia sp. collected from grapevine canes is morphologically similar but phylogenetically distinct from D. sarmentorum. Diplodia sarmentorum is confirmed as anamorph of Otthia spiraeae, the type species of the genus Otthia (Botryosphaeriaceae). A culture identified as O. spiraeae clustered within Botryosphaeria and thus is regarded as probable synonym. These findings confirm earlier suggestions that the generic concept of Botryosphaeria should be expanded to include genera with septate ascospores and Diplodia anamorphs.

High-resolution mycorrhizal hyphae dynamics: temporal variation, biophysical controls, and global environmental change

NASA Astrophysics Data System (ADS)

Hernandez, R. R.; Allen, M. F.

2010-12-01

Soils are the largest terrestrial carbon (C) repository in the global C cycle, storing 4.5 times more C than aboveground vegetation. Mycorrhizal fungi are critical edaphic organisms that influence soil C dynamics at both microscopic and ecosystem scales. Understanding the production and turnover of these organisms is critical for accurate ecosystem C budgets and predictive models incorporating changes in climate. This study seeks to quantify high-resolution mycorrhizal hyphae dynamics at various temporal scales in a mixed conifer forest (UC James Reserve, CA) using novel technologies including automated minirhizotrons, embedded soil sensor networks, and environmental software (i.e., Rootfly). We found that hyphae elongation and dieback rates in May 2009 varied significantly across 6-h diel time intervals and were greatest between 12:00 pm and 6:00 pm, when soil temperature and modeled CO2 flux is maximum. Seasonal dynamics revealed peak hyphae biomass in mid-April and rapid hyphae length decline from mid-April through June. Seasonal hyphae dynamism is tightly coupled with biophysical controls, namely, soil water content, which is positively related to hyphae production, and soil temperature. Interestingly, 14 °C may be a threshold for hyphae growth in this system as soil temperatures exceeding this value are coupled with rapid hyphae mortality. This study suggests that human-mediated changes to biophysical controls may modulate seasonal hyphae growth regimes, possibly reducing growth season duration or initiating early mortality. In this scenario, mycorrhizal hyphae mortality may act as a positive feedback to increasing CO2 levels, by releasing large amounts of CO2 into the atmosphere.

MIP diversity from Trichoderma: Structural considerations and transcriptional modulation during mycoparasitic association with Fusarium solani olive trees

PubMed Central

Lopez, David; Chaar, Hatem; Khouaja, Ali; Pujade-Renaud, Valérie; Fumanal, Boris; Gousset-Dupont, Aurélie; Bronner, Gisèle; Label, Philippe; Julien, Jean-Louis; Triki, Mohamed Ali; Auguin, Daniel

2018-01-01

Major intrinsic proteins (MIP) are characterized by a transmembrane pore-type architecture that facilitates transport across biomembranes of water and a variety of low molecular weight solutes. They are found in all parts of life, with remarkable protein diversity. Very little is known about MIP from fungi. And yet, it can legitimately be stated that MIP are pivotal molecular components in the privileged relationships fungi enjoy with plants or soil fauna in various environments. To date, MIP have never been studied in a mycoparasitism situation. In this study, the diversity, expression and functional prediction of MIP from the genus Trichoderma were investigated. Trichoderma spp. genomes have at least seven aquaporin genes. Based on a phylogenetic analysis of the translated sequences, members were assigned to the AQP, AQGP and XIP subfamilies. In in vitro and in planta assays with T. harzianum strain Ths97, expression analyses showed that four genes were constitutively expressed. In a mycoparasitic context with Fusarium solani, the causative agent of fusarium dieback on olive tree roots, these genes were up-regulated. This response is of particular interest in analyzing the MIP promoter cis-regulatory motifs, most of which are involved in various carbon and nitrogen metabolisms. Structural analyses provide new insights into the possible role of structural checkpoints by which these members transport water, H2O2, glycerol and, more generally, linear polyols across the membranes. Taken together, these results provide the first evidence that MIP may play a key role in Trichoderma mycoparasitism lifestyle. PMID:29543834

Phylogenetic lineages in the Botryosphaeriaceae

PubMed Central

Crous, Pedro W.; Slippers, Bernard; Wingfield, Michael J.; Rheeder, John; Marasas, Walter F.O.; Philips, Alan J.L.; Alves, Artur; Burgess, Treena; Barber, Paul; Groenewald, Johannes Z.

2006-01-01

Botryosphaeria is a species-rich genus with a cosmopolitan distribution, commonly associated with dieback and cankers of woody plants. As many as 18 anamorph genera have been associated with Botryosphaeria, most of which have been reduced to synonymy under Diplodia (conidia mostly ovoid, pigmented, thick-walled), or Fusicoccum (conidia mostly fusoid, hyaline, thin-walled). However, there are numerous conidial anamorphs having morphological characteristics intermediate between Diplodia and Fusicoccum, and there are several records of species outside the Botryosphaeriaceae that have anamorphs apparently typical of Botryosphaeria s.str. Recent studies have also linked Botryosphaeria to species with pigmented, septate ascospores, and Dothiorella anamorphs, or Fusicoccum anamorphs with Dichomera synanamorphs. The aim of this study was to employ DNA sequence data of the 28S rDNA to resolve apparent lineages within the Botryosphaeriaceae. From these data, 12 clades are recognised. Two of these lineages clustered outside the Botryosphaeriaceae, namely Diplodia-like anamorphs occurring on maize, which are best accommodated in Stenocarpella (Diaporthales), as well as an unresolved clade including species of Camarosporium/Microdiplodia. We recognise 10 lineages within the Botryosphaeriaceae, including an unresolved clade (Diplodia/Lasiodiplodia/Tiarosporella), Botryosphaeria s.str. (Fusicoccum anamorphs), Macrophomina, Neoscytalidium gen. nov., Dothidotthia (Dothiorella anamorphs), Neofusicoccum gen. nov. (Botryosphaeria-like teleomorphs, Dichomera-like synanamorphs), Pseudofusicoccum gen. nov., Saccharata (Fusicoccum- and Diplodia-like synanamorphs), “Botryosphaeria” quercuum (Diplodia-like anamorph), and Guignardia (Phyllosticta anamorphs). Separate teleomorph and anamorph names are not provided for newly introduced genera, even where both morphs are known. The taxonomy of some clades and isolates (e.g. B. mamane) remains unresolved due to the absence of ex-type cultures. PMID:18490983

Minesoil grading and ripping affect black walnut growth and survival

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

Josiah, S.J.

In 1980 and 1981, the Botany Department of Southern Illinois University and Sahara Coal Company, Inc. of Harrisburg, Illinois established a series of experimental tree plantings, including black walnut, on a variety of minesoils to explore the effects of different intensities of grading on tree growth. Subsequent walnut stem and root growth were examined during 1985 on five different mine sites: unmined former agricultural land, graded minespoil, replaced (with pan scrapers) topsoil over graded spoil, ripped-graded spoil, and ungraded spoil. Soil bulk density, resistance to penetration, and spoil/soil fertility levels were also measured. The most vigorous trees were found onmore » sites having the lowest soil bulk density and soil strength and lacking horizontal barriers to root growth - the ungraded and ripped sites. Topsoiled sites had the poorest growth and survival, and the greatest stem dieback of any site measured, probably attributable to the confinement of root growth to the upper 15 cm of friable soil above the severely compacted zone. The overall results indicate that most of the minesoil construction techniques examined in this study, which are representative of techniques commonly used in the midwestern US, cause severe minesoil compaction and do not create the proper soil conditions necessary for the survival and vigorous growth of black walnut. Ripping compacted spoil in this and other studies proved to be very effective in alleviating the negative impacts of minesoil compaction. When planning surface mine reclamation activities, ripping should be considered as a possible ameliorative technique when compaction of mined lands is unavoidable and trees are the desired vegetative cover. 4 figures.« less

Transcriptional and microscopic analyses of citrus stem and root responses to Candidatus Liberibacter asiaticus infection.

PubMed

Aritua, Valente; Achor, Diann; Gmitter, Frederick G; Albrigo, Gene; Wang, Nian

2013-01-01

Huanglongbing (HLB) is the most destructive disease that affects citrus worldwide. The disease has been associated with Candidatus Liberibacter. HLB diseased citrus plants develop a multitude of symptoms including zinc and copper deficiencies, blotchy mottle, corky veins, stunting, and twig dieback. Ca. L. asiaticus infection also seriously affects the roots. Previous study focused on gene expression of leaves and fruit to Ca. L. asiaticus infection. In this study, we compared the gene expression levels of stems and roots of healthy plants with those in Ca. L. asiaticus infected plants using microarrays. Affymetrix microarray analysis showed a total of 988 genes were significantly altered in expression, of which 885 were in the stems, and 111 in the roots. Of these, 551 and 56 were up-regulated, while 334 and 55 were down-regulated in the stem and root samples of HLB diseased trees compared to healthy plants, respectively. Dramatic differences in the transcriptional responses were observed between citrus stems and roots to Ca. L. asiaticus infection, with only 8 genes affected in both the roots and stems. The affected genes are involved in diverse cellular functions, including carbohydrate metabolism, cell wall biogenesis, biotic and abiotic stress responses, signaling and transcriptional factors, transportation, cell organization, protein modification and degradation, development, hormone signaling, metal handling, and redox. Microscopy analysis showed the depletion of starch in the roots of the infected plants but not in healthy plants. Collapse and thickening of cell walls were observed in HLB affected roots, but not as severe as in the stems. This study provides insight into the host response of the stems and roots to Ca. L. asiaticus infection.

Transcriptional and Microscopic Analyses of Citrus Stem and Root Responses to Candidatus Liberibacter asiaticus Infection

PubMed Central

Aritua, Valente; Achor, Diann; Gmitter, Frederick G.; Albrigo, Gene; Wang, Nian

2013-01-01

Huanglongbing (HLB) is the most destructive disease that affects citrus worldwide. The disease has been associated with Candidatus Liberibacter. HLB diseased citrus plants develop a multitude of symptoms including zinc and copper deficiencies, blotchy mottle, corky veins, stunting, and twig dieback. Ca. L. asiaticus infection also seriously affects the roots. Previous study focused on gene expression of leaves and fruit to Ca. L. asiaticus infection. In this study, we compared the gene expression levels of stems and roots of healthy plants with those in Ca. L. asiaticus infected plants using microarrays. Affymetrix microarray analysis showed a total of 988 genes were significantly altered in expression, of which 885 were in the stems, and 111 in the roots. Of these, 551 and 56 were up-regulated, while 334 and 55 were down-regulated in the stem and root samples of HLB diseased trees compared to healthy plants, respectively. Dramatic differences in the transcriptional responses were observed between citrus stems and roots to Ca. L. asiaticus infection, with only 8 genes affected in both the roots and stems. The affected genes are involved in diverse cellular functions, including carbohydrate metabolism, cell wall biogenesis, biotic and abiotic stress responses, signaling and transcriptional factors, transportation, cell organization, protein modification and degradation, development, hormone signaling, metal handling, and redox. Microscopy analysis showed the depletion of starch in the roots of the infected plants but not in healthy plants. Collapse and thickening of cell walls were observed in HLB affected roots, but not as severe as in the stems. This study provides insight into the host response of the stems and roots to Ca. L. asiaticus infection. PMID:24058486

Do diurnal patterns of branch carbon uptake and transpiration recover after heat waves? Results from a Mediterranean-type ecosystem experiencing seasonal and exceptional drought

NASA Astrophysics Data System (ADS)

Pivovaroff, A. L.; Pesqueira, A.; Sun, W.; Seibt, U.

2016-12-01

Mediterranean-type ecosystems are biodiversity hotspots, but increasing temperature and changes in precipitation will have significant impacts on vegetation, as evidenced by the current die-back of many woody species in southern California, USA, due to exceptional drought conditions. We installed flow-through chambers on four native woody plant species at Stunt Ranch, a University of California Natural Reserve System site, in order to continuously monitor fluxes of carbon and water at the branch-scale from the growing season through the annual seasonal drought period. Study species included Heteromeles arbutifolia, Malosma laurina, Salvia leucophylla, and Quercus agrifolia. Here we present the results of diurnal flux patterns before, during, and after two extreme heat waves events, when daily maximum temperatures doubled. Under typical summer conditions, which include hot, sunny days, study species exhibited two peaks in carbon assimilation during a diurnal cycle: a peak in the morning and a smaller, secondary peak in the afternoon, separated by a midday depression. During heat wave events, which generally lasted 3 days, species exhibited a small morning peak and no afternoon peak at all. All study species returned to their pre-heat wave diurnal flux patterns, which included the second afternoon peak, when weather conditions returned to normal. Since soil moisture was not affected by the short-term heat wave events, we conclude that the pronounced changes in diurnal patterns, including disappearance of the secondary afternoon peak, are the result of stomatal regulation in response to atmospheric water demand rather than root responses to soil moisture deficits. Our results demonstrate that carbon uptake of native species may be impacted under ongoing climate change when increased temperatures and drought conditions may be sustained.

Calcium isotope systematics in small upland catchments affected by spruce dieback in the period of extreme acid rain (1970-1990)

NASA Astrophysics Data System (ADS)

Novak, Martin; Farkas, Juraj; Holmden, Chris; Hruska, Jakub; Curik, Jan; Stepanova, Marketa; Prechova, Eva; Veselovsky, Frantisek; Komarek, Arnost

2017-04-01

Recently, new isotope tools have become available to study the behavior of nutrients in stressed ecosystems. In this study, we focus on changes in the abundance ratio of calcium (Ca) isotopes accompanying biogeochemical processes in small forested catchments. We monitored del44Ca values in ecosystem pools and fluxes in four upland sites situated in the Czech Republic, Central Europe. A heavily acidified site in the Eagle Mts. (northern Czech Republic) experienced 13 times higher atmospheric Ca inputs, compared to the other three sites, which were less affected by forest decline. Industrial dust was responsible for the elevated Ca input. Del44Ca values of individual poos/fluxes were used to identify Ca sources for the bioavailable Ca soil reservoir and for runoff. The bedrock of the study sites differed (leucogranite, orthogneiss vs. serpentinite and amphibolite). Across the sites, mean del44Ca values increased in the order: spruce bark < fine roots < needles < soil < bedrock < canopy throughfall < open-area precipitation < runoff < soil water. Plant preferentially took up isotopically light Ca, while residual isotopically heavy Ca was sorbed to soil particles or exported via runoff. Even at sites with a low del44Ca values of bedrock, runoff had a high del44Ca value. At the base-poor site, most runoff came from atmospheric deposition and residual Ca following plant uptake. It appeared that bedrock weathering did not supply enough Ca to replenish the bioavailable Ca pool in the soil. Currently, we are analyzing Ca isotope composition of individual rock-forming minerals to better assess the effect of different weathering rates of minerals with low/high radiogenic 40Ca contents on runoff del44Ca.

Limitations on gas exchange recovery following natural drought in Californian oak woodlands.

NASA Astrophysics Data System (ADS)

Ackerly, D.; Skelton, R. P.; Dawson, T.; Thompson, S.; Feng, X.; Weitz, A.; McLaughlin, B.

2017-12-01

Abstract Background/Question/Methods Drought can cause major damage to plant communities, but species damage thresholds and post-drought recovery of forest productivity are not yet predictable. We asked the question how should forest net primary productivity recover following exposure to severe drought? We used a natural drought period to investigate whether drought responses and post-drought recovery of canopy health could be predicted by properties of the water transport system. We aimed to test the hypothesis that recovery of gas exchange and canopy health would be most severely limited by xylem embolism in stems. To do this we monitored leaf level gas exchange and water status for multiple individuals of two deciduous and two evergreen species for four years spanning a severe drought event and following subsequent rehydration. Results/Discussion Severe drought caused major declines in leaf water potential, reduced stomatal conductance and assimilation rates and increased canopy bareness in our four canopy species. Water potential surpassed levels associated with incipient embolism in leaves of most trees. In contrast, due to hydraulic segmentation, water potential only rarely surpassed critical thresholds in the stems of the study trees. Individuals that surpassed critical thresholds of embolism in the stem displayed significant canopy dieback and mortality. Thus, recovery of plant gas exchange and canopy health was predicted by xylem safety margin in stems, but not leaves, providing strong support for stem cavitation vulnerability as an index of damage under natural drought conditions.

Implications of plant acclimation for future climate-carbon cycle feedbacks

NASA Astrophysics Data System (ADS)

Mercado, Lina; Kattge, Jens; Cox, Peter; Sitch, Stephen; Knorr, Wolfgang; Lloyd, Jon; Huntingford, Chris

2010-05-01

The response of land ecosystems to climate change and associated feedbacks are a key uncertainty in future climate prediction (Friedlingstein et al. 2006). However global models generally do not account for the acclimation of plant physiological processes to increased temperatures. Here we conduct a first global sensitivity study whereby we modify the Joint UK land Environment Simulator (JULES) to account for temperature acclimation of two main photosynthetic parameters, Vcmax and Jmax (Kattge and Knorr 2007) and plant respiration (Atkin and Tjoelker 2003). The model is then applied over the 21st Century within the IMOGEN framework (Huntingford et al. 2004). Model simulations will provide new and improved projections of biogeochemical cycling, forest resilience, and thus more accurate projections of climate-carbon cycle feedbacks and the future evolution of the Earth System. Friedlingstein P, Cox PM, Betts R et al. (2006) Climate-carbon cycle feedback analysis, results from the C4MIP model intercomparison. Journal of Climate, 19, 3337-3353. Kattge J and Knorr W (2007): Temperature acclimation in a biochemical model of photosynthesis: a reanalysis of data from 36 species. Plant, Cell and Environment 30, 1176-1190 Atkin O.K and Tjoelker, M. G. (2003): Thermal acclimation and the dynamic response of plant respiration to temperature. Trends in Plant Science 8 (7), 343-351 Huntingford C, et al. (2004) Using a GCM analogue model to investigate the potential for Amazonian forest dieback. Theoretical and Applied Climatology, 78, 177-185.

Fir Decline and Mortality in the Southern Siberian Mountains

NASA Technical Reports Server (NTRS)

Kharuk, Viacheslav I.; Im, Sergei T.; Petrov, Ilya A.; Dvinskaya, Mariya, L.; Fedotova, Elena V.; Ranson, Kenneth J.

2016-01-01

Increased dieback and mortality of dark needle conifer (DNC) stands (composed of fir (Abies sibirica),Siberian pine (Pinus sibirica) and spruce (Picea obovata))were documented in Russia during recent decades. Here we analyzed spatial and temporal patterns of fir decline and mortality in the southern Siberian Mountains based on satellite, in situ and dendrochronological data. The studied stands are located within the boundary between DNC taiga to the north and forest-steppe to the south. Fir decline and mortality were observed to originate where topographic features contributed to maximal water-stress risk, i.e., steep (1825),convex, south-facing slopes with a shallow well-drained root zone. Fir regeneration survived droughts and increased stem radial growth, while upper canopy trees died. Tree ring width(TRW) growth negatively correlated with vapor pressure deficit (VPD), drought index and occurrence of late frosts, and positively with soil water content. Previous year growth conditions (i.e., drought index, VPD, soil water anomalies)have a high impact on current TRW (r 0.600.74). Fir mortality was induced by increased water stress and severe droughts (as a primary factor) in synergy with bark-beetles and fungi attacks (as secondary factors). Dendrochronology data indicated that fir mortality is a periodic process. In a future climate with increased aridity and drought frequency, fir (and Siberian pine) may disappear from portions of its current range (primarily within the boundary with the forest steppe)and is likely to be replaced by drought-tolerant species such as Pinus sylvestris and Larix sibirica.

Gas exchange by the mesic-origin, arid land plantation species Robinia pseudoacacia under annual summer reduction in plant hydraulic conductance.

PubMed

Miyazawa, Yoshiyuki; Du, Sheng; Taniguchi, Takeshi; Yamanaka, Norikazu; Kumagai, Tomo'omi

2018-03-28

The mesic-origin plantation species Robinia pseudoacacia L. has been successfully grown in many arid land plantations around the world but often exhibits dieback and reduced growth due to drought. Therefore, to explore the behavior of this species under changing environmental conditions, we examined the relationship between ecophysiological traits, gas exchange and plant hydraulics over a 3-year period in trees that experienced reduced plant hydraulic conductance (Gp) in summer. We found that the transpiration rate, stomatal conductance (Gs) and minimum leaf water potential (Ψlmin) decreased in early summer in response to a decrease in Gp, and that Gp did not recover until the expansion of new leaves in spring. However, we did not observe any changes in the leaf area index or other ecophysiological traits at the leaf level in response to this reduction in Gp. Furthermore, model simulations based on measured data revealed that the canopy-scale photosynthetic rate (Ac) was 15-25% higher than the simulated Ac when it was assumed that Ψlmin remained constant after spring but almost the same as the simulated Ac when it was assumed that Gp remained high even after spring. These findings indicate that R. pseudoacacia was frequently exposed to a reduced Gp at the study site but offset its effects on Ac by plastically lowering Ψlmin to avoid experiencing any further reduction in Gp or Gs.

Novel taxa in the Fusarium fujikuroi species complex from Pinus spp.

PubMed Central

Herron, D.A.; Wingfield, M.J.; Wingfield, B.D.; Rodas, C.A.; Marincowitz, S.; Steenkamp, E.T.

2015-01-01

The pitch canker pathogen Fusarium circinatum has caused devastation to Pinus spp. in natural forests and non-natives in commercially managed plantations. This has drawn attention to the potential importance of Fusarium species as pathogens of forest trees. In this study, we explored the diversity of Fusarium species associated with diseased Pinus patula, P. tecunumanii, P. kesiya and P. maximinoi in Colombian plantations and nurseries. Plants displaying symptoms associated with a F. circinatum-like infection (i.e., stem cankers and branch die-back on trees in plantations and root or collar rot of seedlings) were sampled. A total of 57 isolates were collected and characterised based on DNA sequence data for the translation elongation factor 1-α and β-tubulin gene regions. Phylogenetic analyses of these data allowed for the identification of more than 10 Fusarium species. These included F. circinatum, F. oxysporum, species within the Fusarium solani species complex and seven novel species in the Fusarium fujikuroi species complex (formerly the Gibberella fujikuroi species complex), five of which are described here as new. Selected isolates of the new species were tested for their pathogenicity on Pinus patula and compared with that of F. circinatum. Of these, F. marasasianum, F. parvisorum and F. sororula displayed levels of pathogenicity to P. patula that were comparable with that of F. circinatum. These apparently emerging pathogens thus pose a significant risk to forestry in Colombia and other parts of the world. PMID:26955193

The interplay of plant and animal disease in a changing landscape: the role of sudden aspen decline in moderating Sin Nombre virus prevalence in natural deer mouse populations.

PubMed

Lehmer, Erin M; Korb, Julie; Bombaci, Sara; McLean, Nellie; Ghachu, Joni; Hart, Lacey; Kelly, Ashley; Jara-Molinar, Edlin; O'Brien, Colleen; Wright, Kimberly

2012-06-01

We examined how climate-mediated forest dieback regulates zoonotic disease prevalence using the relationship between sudden aspen decline (SAD) and Sin Nombre virus (SNV) as a model system. We compared understory plant community structure, small mammal community composition, and SNV prevalence on 12 study sites within aspen forests experiencing levels of SAD ranging from <10.0% crown fade to >95.0% crown fade. Our results show that sites with the highest levels of SAD had reduced canopy cover, stand density, and basal area, and these differences were reflected by reductions in understory vegetation cover. Conversely, sites with the highest levels of SAD had greater understory standing biomass, suggesting that vegetation on these sites was highly clustered. Changes in forest and understory vegetation structure likely resulted in shifts in small mammal community composition across the SAD gradient, as we found reduced species diversity and higher densities of deer mice, the primary host for SNV, on sites with the highest levels of SAD. Sites with the highest levels of SAD also had significantly greater SNV prevalence compared to sites with lower levels of SAD, which is likely a result of their abundance of deer mice. Collectively, results of our research provide strong evidence to show SAD has considerable impacts on vegetation community structure, small mammal density and biodiversity and the prevalence of SNV.

Dynamics of Murray-Darling floodplain forests under multiple stressors: The past, present, and future of an Australian icon

NASA Astrophysics Data System (ADS)

Mac Nally, Ralph; Cunningham, Shaun C.; Baker, Patrick J.; Horner, Gillis J.; Thomson, James R.

2011-12-01

We review the human actions, proximal stressors and ecological responses for floodplain forests Australia's largest river system—the Murray-Darling Basin. A conceptual model for the floodplain forests was built from extensive published information and some unpublished results for the system, which should provide a basis for understanding, studying and managing the ecology of floodplains that face similar environmental stresses. Since European settlement, lowlands areas of the basin have been extensively cleared for agriculture and remnant forests heavily harvested for timber. The most significant human intervention is modification of river flows, and the reduction in frequency, duration and timing of flooding, which are compounded by climate change (higher temperatures and reduced rainfall) and deteriorating groundwater conditions (depth and salinity). This has created unfavorable conditions for all life-history stages of the dominant floodplain tree (Eucalyptus camaldulensis Dehnh.). Lack of extensive flooding has led to widespread dieback across the Murray River floodplain (currently 79% by area). Management for timber resources has altered the structure of these forests from one dominated by large, widely spreading trees to mixed-aged stands of smaller pole trees. Reductions in numbers of birds and other vertebrates followed the decline in habitat quality (hollow-bearing trees, fallen timber). Restoration of these forests is dependent on substantial increases in the frequency and extent of flooding, improvements in groundwater conditions, re-establishing a diversity of forest structures, removal of grazing and consideration of these interacting stressors.

A broad survey of hydraulic and mechanical safety in the xylem of conifers.

PubMed

Bouche, Pauline S; Larter, Maximilien; Domec, Jean-Christophe; Burlett, Régis; Gasson, Peter; Jansen, Steven; Delzon, Sylvain

2014-08-01

Drought-induced forest dieback has been widely reported over the last decades, and the evidence for a direct causal link between survival and hydraulic failure (xylem cavitation) is now well known. Because vulnerability to cavitation is intimately linked to the anatomy of the xylem, the main objective of this study was to better understand the xylem anatomical properties associated with cavitation resistance. An extensive data set of cavitation resistance traits and xylem anatomical properties was developed for 115 conifer species, with special attention given to the micro-morphology of bordered pits. The ratio of torus to pit aperture diameter, so-called torus overlap, increased with increasing cavitation resistance, while the flexibility of the margo does not seem to play a role, suggesting that air-seeding is located at the seal between the aspirated torus and pit aperture. Moreover, punctured tori were reported in various Pinaceae species. Species resistant to cavitation had thicker tracheid walls, while their lumen diameter (conduit size) was only slightly reduced, minimizing the impact on hydraulic conductance. The results also demonstrated (i) the existence of an indirect trade-off between hydraulic safety and mechanical strength; and (ii) a consistency between species distribution and xylem anatomy: species with a wide torus overlap and high valve effects are found in arid environments such as the Mediterranean region. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Spatial distribution of xylem embolisms in the stems of Pinus thunbergii at the threshold of fatal drought stress.

PubMed

Umebayashi, Toshihiro; Morita, Toshimitsu; Utsumi, Yasuhiro; Kusumoto, Dai; Yasuda, Yuko; Haishi, Tomoyuki; Fukuda, Kenji

2016-10-01

Although previous studies have suggested that branch dieback and whole-plant death due to drought stress occur at 50-88% loss of stem hydraulic conductivity (P 50 and P 88 , respectively), the dynamics of catastrophic failure in the water-conducting pathways in whole plants subjected to drought remain poorly understood. We examined the dynamics of drought stress tolerance in 3-year-old Japanese black pine (Pinus thunbergii Parl.). We nondestructively monitored (i) the spatial distribution of drought-induced embolisms in the stem at greater than P 50 and (ii) recovery from embolisms following rehydration. Stem water distributions were visualized by cryo-scanning electron microscopy. The percentages of both embolized area and loss of hydraulic conductivity showed similar patterns of increase, although the water loss in xylem increased markedly at -5.0 MPa or less. One seedling that had reached 72% loss of the water-conducting area survived and the xylem water potential recovered to -0.3 MPa. We concluded that Japanese black pines may need to maintain water-filled tracheids within earlywood of the current-year xylem under natural conditions to avoid disconnection of water movement between the stem and the tops of branches. It is necessary to determine the spatial distribution of embolisms around the point of the lethal threshold to gain an improved understanding of plant survival under conditions of drought. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Radar and optical mapping of surge persistence and marsh dieback along the New Jersey Mid-Atlantic coast after Hurricane Sandy

USGS Publications Warehouse

Rangoonwala, Amina; Enwright, Nicholas M.; Ramsey, Elijah W.; Spruce, Joseph P.

2016-01-01

This study combined a radar-based time series of Hurricane Sandy surge and estimated persistence with optical sensor-based marsh condition change to assess potential causal linkages of surge persistence and marsh condition change along the New Jersey Atlantic Ocean coast. Results based on processed TerraSAR-X and COSMO-SkyMed synthetic aperture radar (SAR) images indicated that surge flooding persisted for 12 h past landfall in marshes from Great Bay to Great Egg Harbor Bay and up to 59 h after landfall in many back-barrier lagoon marshes. Marsh condition change (i.e. loss of green marsh vegetation) was assessed from optical satellite images (Satellite Pour l’Observation de la Terre and Moderate Resolution Imaging Spectroradiometer) collected before and after Hurricane Sandy. High change in condition often showed spatial correspondence, with high surge persistence in marsh surrounding the lagoon portion of Great Bay, while in contrast, low change and high persistence spatial correspondence dominated the interior marshes of the Great Bay and Great Egg Harbor Bay estuaries. Salinity measurements suggest that these areas were influenced by freshwater discharges after landfall possibly mitigating damage. Back-barrier marshes outside these regions exhibited mixed correspondences. In some cases, topographic features supporting longer surge persistence suggested that non-correspondence between radar and optical data-based results may be due to differential resilience; however, in many cases, reference information was lacking to determine a reason for non-correspondence.

Noninvasive Measurement of Vulnerability to Drought-Induced Embolism by X-Ray Microtomography1

PubMed Central

Choat, Brendan; Cochard, Herve; Jansen, Steven

2016-01-01

Hydraulic failure induced by xylem embolism is one of the primary mechanisms of plant dieback during drought. However, many of the methods used to evaluate the vulnerability of different species to drought-induced embolism are indirect and invasive, increasing the possibility that measurement artifacts may occur. Here, we utilize x-ray computed microtomography (microCT) to directly visualize embolism formation in the xylem of living, intact plants with contrasting wood anatomy (Quercus robur, Populus tremula × Populus alba, and Pinus pinaster). These observations were compared with widely used centrifuge techniques that require destructive sampling. MicroCT imaging provided detailed spatial information regarding the dimensions and functional status of xylem conduits during dehydration. Vulnerability curves based on microCT observations of intact plants closely matched curves based on the centrifuge technique for species with short vessels (P. tremula × P. alba) or tracheids (P. pinaster). For ring porous Q. robur, the centrifuge technique significantly overestimated vulnerability to embolism, indicating that caution should be used when applying this technique to species with long vessels. These findings confirm that microCT can be used to assess the vulnerability to embolism on intact plants by direct visualization. PMID:26527655

A deforestation-induced tipping point for the South American monsoon system.

PubMed

Boers, Niklas; Marwan, Norbert; Barbosa, Henrique M J; Kurths, Jürgen

2017-01-25

The Amazon rainforest has been proposed as a tipping element of the earth system, with the possibility of a dieback of the entire ecosystem due to deforestation only of parts of the rainforest. Possible physical mechanisms behind such a transition are still subject to ongoing debates. Here, we use a specifically designed model to analyse the nonlinear couplings between the Amazon rainforest and the atmospheric moisture transport from the Atlantic to the South American continent. These couplings are associated with a westward cascade of precipitation and evapotranspiration across the Amazon. We investigate impacts of deforestation on the South American monsoonal circulation with particular focus on a previously neglected positive feedback related to condensational latent heating over the rainforest, which strongly enhances atmospheric moisture inflow from the Atlantic. Our results indicate the existence of a tipping point. In our model setup, crossing the tipping point causes precipitation reductions of up to 40% in non-deforested parts of the western Amazon and regions further downstream. The responsible mechanism is the breakdown of the aforementioned feedback, which occurs when deforestation reduces transpiration to a point where the available atmospheric moisture does not suffice anymore to release the latent heat needed to maintain the feedback.

A deforestation-induced tipping point for the South American monsoon system

PubMed Central

Boers, Niklas; Marwan, Norbert; Barbosa, Henrique M. J.; Kurths, Jürgen

2017-01-01

The Amazon rainforest has been proposed as a tipping element of the earth system, with the possibility of a dieback of the entire ecosystem due to deforestation only of parts of the rainforest. Possible physical mechanisms behind such a transition are still subject to ongoing debates. Here, we use a specifically designed model to analyse the nonlinear couplings between the Amazon rainforest and the atmospheric moisture transport from the Atlantic to the South American continent. These couplings are associated with a westward cascade of precipitation and evapotranspiration across the Amazon. We investigate impacts of deforestation on the South American monsoonal circulation with particular focus on a previously neglected positive feedback related to condensational latent heating over the rainforest, which strongly enhances atmospheric moisture inflow from the Atlantic. Our results indicate the existence of a tipping point. In our model setup, crossing the tipping point causes precipitation reductions of up to 40% in non-deforested parts of the western Amazon and regions further downstream. The responsible mechanism is the breakdown of the aforementioned feedback, which occurs when deforestation reduces transpiration to a point where the available atmospheric moisture does not suffice anymore to release the latent heat needed to maintain the feedback. PMID:28120928

Climate extremes and predicted warming threaten Mediterranean Holocene firs forests refugia

PubMed Central

Camarero, J. Julio; Carrer, Marco; Gutiérrez, Emilia; Alla, Arben Q.; Andreu-Hayles, Laia; Hevia, Andrea; Koutavas, Athanasios; Martínez-Sancho, Elisabet; Nola, Paola; Papadopoulos, Andreas; Pasho, Edmond; Toromani, Ervin

2017-01-01

Warmer and drier climatic conditions are projected for the 21st century; however, the role played by extreme climatic events on forest vulnerability is still little understood. For example, more severe droughts and heat waves could threaten quaternary relict tree refugia such as Circum-Mediterranean fir forests (CMFF). Using tree-ring data and a process-based model, we characterized the major climate constraints of recent (1950–2010) CMFF growth to project their vulnerability to 21st-century climate. Simulations predict a 30% growth reduction in some fir species with the 2050s business-as-usual emission scenario, whereas growth would increase in moist refugia due to a longer and warmer growing season. Fir populations currently subjected to warm and dry conditions will be the most vulnerable in the late 21st century when climatic conditions will be analogous to the most severe dry/heat spells causing dieback in the late 20th century. Quantification of growth trends based on climate scenarios could allow defining vulnerability thresholds in tree populations. The presented predictions call for conservation strategies to safeguard relict tree populations and anticipate how many refugia could be threatened by 21st-century dry spells. PMID:29109266

A deforestation-induced tipping point for the South American monsoon system

NASA Astrophysics Data System (ADS)

Boers, Niklas; Marwan, Norbert; Barbosa, Henrique M. J.; Kurths, Jürgen

2017-01-01

The Amazon rainforest has been proposed as a tipping element of the earth system, with the possibility of a dieback of the entire ecosystem due to deforestation only of parts of the rainforest. Possible physical mechanisms behind such a transition are still subject to ongoing debates. Here, we use a specifically designed model to analyse the nonlinear couplings between the Amazon rainforest and the atmospheric moisture transport from the Atlantic to the South American continent. These couplings are associated with a westward cascade of precipitation and evapotranspiration across the Amazon. We investigate impacts of deforestation on the South American monsoonal circulation with particular focus on a previously neglected positive feedback related to condensational latent heating over the rainforest, which strongly enhances atmospheric moisture inflow from the Atlantic. Our results indicate the existence of a tipping point. In our model setup, crossing the tipping point causes precipitation reductions of up to 40% in non-deforested parts of the western Amazon and regions further downstream. The responsible mechanism is the breakdown of the aforementioned feedback, which occurs when deforestation reduces transpiration to a point where the available atmospheric moisture does not suffice anymore to release the latent heat needed to maintain the feedback.

Climate extremes and predicted warming threaten Mediterranean Holocene firs forests refugia.

PubMed

Sánchez-Salguero, Raúl; Camarero, J Julio; Carrer, Marco; Gutiérrez, Emilia; Alla, Arben Q; Andreu-Hayles, Laia; Hevia, Andrea; Koutavas, Athanasios; Martínez-Sancho, Elisabet; Nola, Paola; Papadopoulos, Andreas; Pasho, Edmond; Toromani, Ervin; Carreira, José A; Linares, Juan C

2017-11-21

Warmer and drier climatic conditions are projected for the 21st century; however, the role played by extreme climatic events on forest vulnerability is still little understood. For example, more severe droughts and heat waves could threaten quaternary relict tree refugia such as Circum-Mediterranean fir forests (CMFF). Using tree-ring data and a process-based model, we characterized the major climate constraints of recent (1950-2010) CMFF growth to project their vulnerability to 21st-century climate. Simulations predict a 30% growth reduction in some fir species with the 2050s business-as-usual emission scenario, whereas growth would increase in moist refugia due to a longer and warmer growing season. Fir populations currently subjected to warm and dry conditions will be the most vulnerable in the late 21st century when climatic conditions will be analogous to the most severe dry/heat spells causing dieback in the late 20th century. Quantification of growth trends based on climate scenarios could allow defining vulnerability thresholds in tree populations. The presented predictions call for conservation strategies to safeguard relict tree populations and anticipate how many refugia could be threatened by 21st-century dry spells.

Noninvasive Measurement of Vulnerability to Drought-Induced Embolism by X-Ray Microtomography.

PubMed

Choat, Brendan; Badel, Eric; Burlett, Regis; Delzon, Sylvain; Cochard, Herve; Jansen, Steven

2016-01-01

Hydraulic failure induced by xylem embolism is one of the primary mechanisms of plant dieback during drought. However, many of the methods used to evaluate the vulnerability of different species to drought-induced embolism are indirect and invasive, increasing the possibility that measurement artifacts may occur. Here, we utilize x-ray computed microtomography (microCT) to directly visualize embolism formation in the xylem of living, intact plants with contrasting wood anatomy (Quercus robur, Populus tremula × Populus alba, and Pinus pinaster). These observations were compared with widely used centrifuge techniques that require destructive sampling. MicroCT imaging provided detailed spatial information regarding the dimensions and functional status of xylem conduits during dehydration. Vulnerability curves based on microCT observations of intact plants closely matched curves based on the centrifuge technique for species with short vessels (P. tremula × P. alba) or tracheids (P. pinaster). For ring porous Q. robur, the centrifuge technique significantly overestimated vulnerability to embolism, indicating that caution should be used when applying this technique to species with long vessels. These findings confirm that microCT can be used to assess the vulnerability to embolism on intact plants by direct visualization. © 2016 American Society of Plant Biologists. All Rights Reserved.

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.

Dual RNA-Sequencing of Eucalyptus nitens during Phytophthora cinnamomi Challenge Reveals Pathogen and Host Factors Influencing Compatibility

PubMed Central

Meyer, Febé E.; Shuey, Louise S.; Naidoo, Sitha; Mamni, Thandekile; Berger, Dave K.; Myburg, Alexander A.; van den Berg, Noëlani; Naidoo, Sanushka

2016-01-01

Damage caused by Phytophthora cinnamomi Rands remains an important concern on forest tree species. The pathogen causes root and collar rot, stem cankers, and dieback of various economically important Eucalyptus spp. In South Africa, susceptible cold tolerant Eucalyptus plantations have been affected by various Phytophthora spp. with P. cinnamomi considered one of the most virulent. The molecular basis of this compatible interaction is poorly understood. In this study, susceptible Eucalyptus nitens plants were stem inoculated with P. cinnamomi and tissue was harvested five days post inoculation. Dual RNA-sequencing, a technique which allows the concurrent detection of both pathogen and host transcripts during infection, was performed. Approximately 1% of the reads mapped to the draft genome of P. cinnamomi while 78% of the reads mapped to the Eucalyptus grandis genome. The highest expressed P. cinnamomi gene in planta was a putative crinkler effector (CRN1). Phylogenetic analysis indicated the high similarity of this P. cinnamomi CRN1 to that of Phytophthora infestans. Some CRN effectors are known to target host nuclei to suppress defense. In the host, over 1400 genes were significantly differentially expressed in comparison to mock inoculated trees, including suites of pathogenesis related (PR) genes. In particular, a PR-9 peroxidase gene with a high similarity to a Carica papaya PR-9 ortholog previously shown to be suppressed upon infection by Phytophthora palmivora was down-regulated two-fold. This PR-9 gene may represent a cross-species effector target during P. cinnamomi infection. This study identified pathogenicity factors, potential manipulation targets, and attempted host defense mechanisms activated by E. nitens that contributed to the susceptible outcome of the interaction. PMID:26973660

Mapping Chaparral in the Santa Monica Mountains Using Multiple Spectral Mixture Models

NASA Technical Reports Server (NTRS)

Green Robert O.; Roberts, D. A.; Gardner, M.; Church, R.; Ustin, S.; Scheer, G.

1996-01-01

California chaparral is one of the most important natural vegetation communities in Southern California, representing a significant source of species diversity and, through a high susceptibility to fire, playing a major role in ecosystem dynamics. Due to steep topographic gradients, harsh edaphic conditions and variable fire histories, chaparral typically forms a complex mosaic of different species dominants and age classes, each with unique successional responses to fire and canopy characteristics (e.g. moisture content, biomass, fuel load) that modify fire susceptibility. The high human cost of fire and intimate mixing along the urban interface combine to modify the natural fire regime as well as provide additional impetus for a better understanding of how to predict fire and its management. Management problems have been further magnified by nearly seventy years of fire suppression and drought related die-back over the last few years resulting in a large accumulation of highly combustible fuels. Chaparral communities in the Santa Monica Mountains exemplify many of the management challenges associated with fire and biodiversity. A study was initiated in the Santa Monica Mountains to investigate the use of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) for providing improved maps of chaparral coupled with direct estimates of canopy attributes (e.g. biomass, leaf area, fuel load). The Santa Monica Mountains are an east-west trending range located approximately 75 kilometers north of Los Angeles extending westward into Ventura County. Within the Santa Monica Mountains a diverse number of ecosystems are located, including four distinct types of chaparral, wetlands, riparian habitats, woodlands, and coastal sage scrub. In this study we focus on mapping three types of chaparral, oak woodlands and grasslands. Chaparral mapped included coastal sage scrub, chamise chaparral and mixed chaparral that consisted predominantly of two species of Ceanothus.

Responses of riparian cottonwoods to alluvial water table declines

USGS Publications Warehouse

Scott, M.L.; Shafroth, P.B.; Auble, G.T.

1999-01-01

Human demands for surface and shallow alluvial groundwater have contributed to the loss, fragmentation, and simplification of riparian ecosystems. Populus species typically dominate riparian ecosystems throughout arid and semiarid regions of North American and efforts to minimize loss of riparian Populus requires an integrated understanding of the role of surface and groundwater dynamics in the establishment of new, and maintenance of existing, stands. In a controlled, whole-stand field experiment, we quantified responses of Populus morphology, growth, and mortality to water stress resulting from sustained water table decline following in-channel sand mining along an ephemeral sandbed stream in eastern Colorado, USA. We measured live crown volume, radial stem growth, annual branch increment, and mortality of 689 live Populus deltoides subsp. monilifera stems over four years in conjunction with localized water table declines. Measurements began one year prior to mining and included trees in both affected and unaffected areas. Populus demonstrated a threshold response to water table declines in medium alluvial sands; sustained declines ???1 m produced leaf desiccation and branch dieback within three weeks and significant declines in live crown volume, stem growth, and 88% mortality over a three-year period. Declines in live Crown volume proved to be a significant leading indicator of mortality in the following year. A logistic regression of tree survival probability against the prior year's live crown volume was significant (-2 log likelihood = 270, ??2 with 1 df = 232, P < 0.0001) and trees with absolute declines in live crown volume of ???30 during one year had survival probabilities <0.5 in the following year. In contrast, more gradual water table declines of ~0.5 m had no measurable effect on mortality, stem growth, or live crown volume and produced significant declines only in annual branch growth increments. Developing quantitative information on the timing and extent of morphological responses and mortality of Populus to the rate, depth, and duration of water table declines can assist in the design of management prescriptions to minimize impacts of alluvial groundwater depletion on existing riparian Populus forests.

Restoration of estuarine wetlands via "managed realignment": the use of natural analogues.

NASA Astrophysics Data System (ADS)

Cundy, A.

2003-04-01

A proposed management response to rising sea-levels for low-relief coastal areas is the managed-realignment approach, where existing coastal defences are repositioned landward, and protective wetlands allowed to develop on the abandoned land. This technique has been applied with varying degrees of success at a number of coastal sites, and, in the U.K. at least, its use is increasing as coastal management authorities move away from hard engineering approaches towards more "natural" coastal and floodplain management. Studies of the response of low-lying coastal areas to the managed-realignment approach, and the subsequent restoration of intertidal wetlands, have tended to rely on short-term (< 5 years) studies of erosion and accretion, vegetation change, and changes in sediment chemistry. While the short-term response to breaching is important, it is essential to complement these studies with an understanding of the medium-term (decadal) response of low-lying coasts to sudden inundation to allow effective site selection and management. This medium-term response may be assessed using sedimentary and geomorphological studies at coastal sites which have been historically breached and flooded, which provide natural analogues for the managed realignment process. This paper illustrates this approach using data from two contrasting sites in southern England (Pagham Harbour and part of the Hamble estuary), which were flooded in the early 20th century following breaching of flood defences. Sediments at both sites retain a record of environmental change following marine inundation, and sedimentary studies, combined with documentary evidence, have been used to examine post-breaching marsh stability, variations in sediment accumulation rate, and vegetation colonisation and dieback over varying timescales. Historically-breached sites such as Pagham Harbour and the Hamble estuary are relatively common around European coasts, and these provide important natural laboratories within which the medium-term coastal response to managed-realignment schemes can be assessed.

Evaluations of Insecticides and Fungicides for Reducing Attack Rates of a new invasive ambrosia beetle (Euwallacea Sp., Coleoptera: Curculionidae: Scolytinae) in Infested Landscape Trees in California.

PubMed

Eatough Jones, Michele; Kabashima, John; Eskalen, Akif; Dimson, Monica; Mayorquin, Joey S; Carrillo, Joseph D; Hanlon, Christopher C; Paine, Timothy D

2017-08-01

A recently discovered ambrosia beetle with the proposed common name of polyphagous shot hole borer (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae), is reported to attack >200 host tree species in southern California, including many important native and urban landscape trees. This invasive beetle, along with its associated fungi, causes branch dieback and tree mortality in a large variety of tree species including sycamore (Platanus racemosa Nutt.). Due to the severity of the impact of this Euwallacea sp., short-term management tools must include chemical control options for the arboriculture industry and private landowners to protect trees. We examined the effectiveness of insecticides, fungicides, and insecticide-fungicide combinations for controlling continued Euwallacea sp. attacks on previously infested sycamore trees which were monitored for 6 mo after treatment. Pesticide combinations were generally more effective than single pesticide treatments. The combination of a systemic insecticide (emamectin benzoate), a contact insecticide (bifenthrin), and a fungicide (metconazole) provided some level of control when applied on moderate and heavily infested trees. The biological fungicide Bacillus subtilis provided short-term control. There was no difference in the performance of the three triazole fungicides (propiconazole, tebuconazole, and metconazole) included in this study. Although no pesticide combination provided substantial control over time, pesticide treatments may be more effective when trees are treated during early stages of attack by this ambrosia beetle. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Exploring eco-hydrological consequences of the Amazonian ecosystems under climate and land-use changes in the 21st century

NASA Astrophysics Data System (ADS)

Zhang, K.; Castanho, A. D.; Moghim, S.; Bras, R. L.; Coe, M. T.; Costa, M. H.; Levine, N. M.; Longo, M.; McKnight, S.; Wang, J.; Moorcroft, P. R.

2012-12-01

Deforestation and drought have imposed regional-scale perturbations onto Amazonian ecosystems and are predicted to cause larger negative impacts on the Amazonian ecosystems and associated regional carbon dynamics in the 21st century. However, global climate models (GCMs) vary greatly in their projections of future climate change in Amazonia, giving rise to uncertainty in the expected fate of the Amazon over the coming century. In this study, we explore the possible eco-hydrological consequences of the Amazonian ecosystems under projected climate and land-use changes in the 21st century using two state-of-the-art terrestrial ecosystem models—Ecosystem Demography Model 2.1(ED2.1) and Integrated Biosphere Simulator model (IBIS)—driven by three representative, bias-corrected climate projections from three IPCC GCMs (NCARPCM1, NCARCCSM3 and HadCM3), coupled with two land-use change scenarios (a business-as-usual and a strict governance scenario). We also analyze the relative roles of climate change, CO2 fertilization, land-use change and fire in driving the projected composition and structure of the Amazonian ecosystems. Our results show that CO2 fertilization enhances vegetation productivity and above-ground biomass (AGB) in the region, while land-use change and fire cause AGB loss and the replacement of forests by the savanna-like vegetation. The impacts of climate change depend strongly on the direction and severity of projected precipitation changes in the region. In particular, when intensified water stress is superimposed on unregulated deforestation, both ecosystem models predict large-scale dieback of Amazonian rainforests.

The role of Phragmites australis in mediating inland salt marsh migration in a Mid-Atlantic estuary.

PubMed

Smith, Joseph A M

2013-01-01

Many sea level rise adaptation plans emphasize the protection of adjacent uplands to allow for inland salt marsh migration, but little empirical information exists on this process. Using aerial photos from 1930 and 2006 of Delaware Estuary coastal habitats in New Jersey, I documented the rate of coastal forest retreat and the rate of inland salt marsh migration across 101.1 km of undeveloped salt marsh and forest ecotone. Over this time, the amount of forest edge at this ecotone nearly doubled. In addition, the average amount of forest retreat was 141.2 m while the amount of salt marsh inland migration was 41.9 m. Variation in forest retreat within the study area was influenced by variation in slope. The lag between the amount of forest retreat and salt marsh migration is accounted for by the presence of Phragmites australis which occupies the forest and salt marsh ecotone. Phragmites expands from this edge into forest dieback areas, and the ability of salt marsh to move inland and displace Phragmites is likely influenced by salinity at both an estuary-wide scale and at the scale of local subwatersheds. Inland movement of salt marsh is lowest at lower salinity areas further away from the mouth of the estuary and closer to local heads of tide. These results allow for better prediction of salt marsh migration in estuarine landscapes and provide guidance for adaptation planners seeking to prioritize those places with the highest likelihood of inland salt marsh migration in the near-term.

Fir Decline and Mortality in the Southern Siberian Mountains

NASA Technical Reports Server (NTRS)

Kharuk, Viacheslav I.; Im, Sergei T.; Petrov, Ilya A.; Dvinskaya, Mariya, L.; Fedotova, Elena V.; Ranson, Kenneth J.

2016-01-01

Increased dieback and mortality of dark needle conifer (DNC) stands (composed of fir (Abies sibirica),Siberian pine (Pinus sibirica) and spruce (Picea obovata)) were documented in Russia during recent decades. Here we analyzed spatial and temporal patterns of fir decline and mortality in the southern Siberian Mountains based on satellite, in situ and dendrochronological data. The studied stands are located within the boundary between DNC taiga to the north and forest-steppe to the south. Fir decline and mortality were observed to originate where topographic features contributed to maximal water-stress risk, i.e., steep (18 deg to 25 deg), convex, south-facing slopes with a shallow well-drained root zone. Fir regeneration survived droughts and increased stem radial growth, while upper canopy trees died. Tree ring width (TRW) growth negatively correlated with vapor pressure deficit (VPD), drought index and occurrence of late frosts, and positively with soil water content. Previous year growth conditions (i.e., drought index, VPD, soil water anomalies) have a high impact on current TRW (r = 0.60 to 0.74). Fir mortality was induced by increased water stress and severe droughts (as a primary factor) in synergy with bark-beetles and fungi attacks (as secondary factors). Dendrochronology data indicated that fir mortality is a periodic process. In a future climate with increased aridity and drought frequency, fir (and Siberian pine) may disappear from portions of its current range (primarily within the boundary with the forest- steppe) and is likely to be replaced by drought-tolerant species such as Pinus sylvestris and Larix sibirica.

Size matters a lot: tree height and prior growth predict drought-induced tree death in Italian oak forests

NASA Astrophysics Data System (ADS)

Ripullone, F.; Colangelo, M.; Camarero, J. J.; Gazol, A.; Borghetti, M.; Gentilesca, T.

2016-12-01

Climate warming is expected to amplify drought stress resulting in the occurrence of more widespread dieback episodes and increasing mortality rates. This has pushed the search of reliable and robust early-warning indicators of impending drought-triggered tree death. Recent studies highlight how level of defoliation or age of trees strictly coact with drought in leading to forest decline. In addition, tree size and the tree-to-tree competition for water could also contribute to tree death in drought-prone sites. In this regard, it has been predicted that tall trees with isohydric stomatal regulation are most likely to die due to drought stress. Here, we test this hypothesis by analyzing size, age, competition and growth data in a Mediterranean oak species characterized by anisohydric behaviour, showing recent drought-induced mortality in two Italian forest sites. At both study sites, tree height was associated to the probability of dying. However, this association was opposite to published predictions because living trees were taller than dead trees at both sites. Neither age nor competition intensity played significant roles as drivers of tree mortality. Regarding growth data, trends in basal area increment were significantly smaller in dead than in living trees. Differences were most marked at mid (15 years prior to death) than at short (10 years) or long-term (35 year) scales. This is probably not related to intrinsic growth features of the study species but it can be explained because the most severe drought since 1950 occurred in 2000 at the study area, i.e. 15 years prior to the increase of tree mortality and when growth of living and dead trees started diverging. Lastly, we discuss potential factors which may explain why smaller individuals of anisohydric tree species such as Mediterranean oaks are prone to drought-induced tree death.

Vegetation-climate feedback causes reduced precipitation in CMIP5 regional Earth system model simulation over Africa

NASA Astrophysics Data System (ADS)

Wu, Minchao; Smith, Benjamin; Schurgers, Guy; Lindström, Joe; Rummukainen, Markku; Samuelsson, Patrick

2013-04-01

Terrestrial ecosystems have been demonstrated to play a significant role within the climate system, amplifying or dampening climate change via biogeophysical and biogeochemical exchange with the atmosphere and vice versa (Cox et al. 2000; Betts et al. 2004). Africa is particularly vulnerable to climate change and studies of vegetation-climate feedback mechanisms on Africa are still limited. Our study is the first application of A coupled Earth system model at regional scale and resolution over Africa. We applied a coupled regional climate-vegetation model, RCA-GUESS (Smith et al. 2011), over the CORDEX Africa domain, forced by boundary conditions from a CanESM2 CMIP5 simulation under the RCP8.5 future climate scenario. The simulations were from 1961 to 2100 and covered the African continent at a horizontal grid spacing of 0.44°. RCA-GUESS simulates changes in the phenology, productivity, relative cover and population structure of up to eight plant function types (PFTs) in response to forcing from the climate part of the model. These vegetation changes feedback to simulated climate through dynamic adjustments in surface energy fluxes and surface properties. Changes in the net ecosystem-atmosphere carbon flux and its components net primary production (NPP), heterotrophic respiration and emissions from biomass burning were also simulated but do not feedback to climate in our model. Constant land cover was assumed. We compared simulations with and without vegetation feedback switched "on" to assess the influence of vegetation-climate feedback on simulated climate, vegetation and ecosystem carbon cycling. Both positive and negative warming feedbacks were identified in different parts of Africa. In the Sahel savannah zone near 15°N, reduced vegetation cover and productivity, and mortality caused by a deterioration of soil water conditions led to a positive warming feedback mediated by decreased evapotranspiration and increased sensible heat flux between vegetation and the atmosphere. In the equatorial rainforest stronghold region of central Africa, a feedback syndrome characterised by reduced plant production and LAI, a dominance shift from tropical trees to grasses, reduced soil water and reduced rainfall was identified. The likely underlying mechanism was a decline in evaporative water recycling associated with sparser vegetation cover, reminiscent of Earth system model studies in which a similar feedback mechanism was simulated to force dieback of tropical rainforest and reduced precipitation over the Amazon Basin (Cox et al. 2000; Betts et al. 2004; Malhi et al. 2009). Opposite effects are seen in southern Senegal, southern Mali, northern Guinea and Guinea-Bissau, positive evapotranspiration feedback enhancing the cover of trees in forest and savannah, mitigating warming and promoting local moisture recycling as rainfall. We reveal that LAI-driven evapotranspiration feedback may reduced rainfall in parts of Africa, vegetation-climate feedbacks may significantly impact the magnitude and character of simulated changes in climate as well as vegetation and ecosystems in future scenario studies of this region. They should be accounted for in future studies of climate change and its impacts on Africa. Keywords: vegetation-climate feedback, regional climate model, evapotranspiration, CORDEX. References: Betts, R.A., Cox, P.M., Collins, M., Harris, P.P., Huntingford, C. & Jones, C.D. 2004. The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming. Theoretical and Applied Climatology 78: 157-175. Cox, P.M., Betts, R.A., Jones, C.D., Spall, S.A. & Totterdell, I.J. 2000. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature 408: 184-187. Samuelsson, P., Jones, C., Wilĺen, U., Gollvik, S., Hansson, U. and coauthors. 2011. The Rossby Centre Regional Climate Model RCA3:Model description and performance. Tellus 63A, 4-23. Smith, B., Prentice, I. C. and Sykes, M. T. 2001. Representation of vegetation dynamics in modelling of terrestrial ecosystems: comparing two contrasting approaches within European climate space. Global Ecol. Biogeog. 10, 621-637 Smith, B., Samuelsson, P., Wramneby, A. & Rummukainen, M. 2011. A model of the coupled dynamics of climate, vegetation and terrestrial ecosystem biogeochemistry for regional applications. Tellus 63A: 87-106.

Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change?

PubMed

Savi, Tadeja; Bertuzzi, Stefano; Branca, Salvatore; Tretiach, Mauro; Nardini, Andrea

2015-02-01

Urban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Mapping Robinia pseudoacacia forest health in the Yellow River delta by using high-resolution IKONOS imagery and object-based image analysis

NASA Astrophysics Data System (ADS)

Wang, Hong; Lu, Kaiyu; Pu, Ruiliang

2016-10-01

The Robinia pseudoacacia forest in the Yellow River delta of China has been planted since the 1970s, and a large area of dieback of the forest has occurred since the 1990s. To assess the condition of the R. pseudoacacia forest in three forest areas (i.e., Gudao, Machang, and Abandoned Yellow River) in the delta, we combined an estimation of scale parameters tool and geometry/topology assessment criteria to determine the optimal scale parameters, selected optimal predictive variables determined by stepwise discriminant analysis, and compared object-based image analysis (OBIA) and pixel-based approaches using IKONOS data. The experimental results showed that the optimal segmentation scale is 5 for both the Gudao and Machang forest areas, and 12 for the Abandoned Yellow River forest area. The results produced by the OBIA method were much better than those created by the pixel-based method. The overall accuracy of the OBIA method was 93.7% (versus 85.4% by the pixel-based) for Gudao, 89.0% (versus 72.7%) for Abandoned Yellow River, and 91.7% (versus 84.4%) for Machang. Our analysis results demonstrated that the OBIA method was an effective tool for rapidly mapping and assessing the health levels of forest.

Mechanisms controlling the impact of multi-year drought on mountain hydrology.

PubMed

Bales, Roger C; Goulden, Michael L; Hunsaker, Carolyn T; Conklin, Martha H; Hartsough, Peter C; O'Geen, Anthony T; Hopmans, Jan W; Safeeq, Mohammad

2018-01-12

Mountain runoff ultimately reflects the difference between precipitation (P) and evapotranspiration (ET), as modulated by biogeophysical mechanisms that intensify or alleviate drought impacts. These modulating mechanisms are seldom measured and not fully understood. The impact of the warm 2012-15 California drought on the heavily instrumented Kings River basin provides an extraordinary opportunity to enumerate four mechanisms that controlled the impact of drought on mountain hydrology. Two mechanisms intensified the impact: (i) evaporative processes have first access to local precipitation, which decreased the fractional allocation of P to runoff in 2012-15 and reduced P-ET by 30% relative to previous years, and (ii) 2012-15 was 1 °C warmer than the previous decade, which increased ET relative to previous years and reduced P-ET by 5%. The other two mechanisms alleviated the impact: (iii) spatial heterogeneity and the continuing supply of runoff from higher elevations increased 2012-15 P-ET by 10% relative to that expected for a homogenous basin, and iv) drought-associated dieback and wildfire thinned the forest and decreased ET, which increased 2016 P-ET by 15%. These mechanisms are all important and may offset each other; analyses that neglect one or more will over or underestimate the impact of drought and warming on mountain runoff.

El Niño/Southern Oscillation response to global warming

PubMed Central

Latif, M.; Keenlyside, N. S.

2009-01-01

The El Niño/Southern Oscillation (ENSO) phenomenon, originating in the Tropical Pacific, is the strongest natural interannual climate signal and has widespread effects on the global climate system and the ecology of the Tropical Pacific. Any strong change in ENSO statistics will therefore have serious climatic and ecological consequences. Most global climate models do simulate ENSO, although large biases exist with respect to its characteristics. The ENSO response to global warming differs strongly from model to model and is thus highly uncertain. Some models simulate an increase in ENSO amplitude, others a decrease, and others virtually no change. Extremely strong changes constituting tipping point behavior are not simulated by any of the models. Nevertheless, some interesting changes in ENSO dynamics can be inferred from observations and model integrations. Although no tipping point behavior is envisaged in the physical climate system, smooth transitions in it may give rise to tipping point behavior in the biological, chemical, and even socioeconomic systems. For example, the simulated weakening of the Pacific zonal sea surface temperature gradient in the Hadley Centre model (with dynamic vegetation included) caused rapid Amazon forest die-back in the mid-twenty-first century, which in turn drove a nonlinear increase in atmospheric CO2, accelerating global warming. PMID:19060210

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.

Sulawesi cacao (Theobroma cacao, l.) performances under two different agricultural system in east coast of Central Sulawesi

NASA Astrophysics Data System (ADS)

Muslimin; Wijayanti, W.; Anshary, A.; Basri, Z.; Cruz, A. F.; Suwastika, I. N.; Shiina, T.

2018-04-01

Cacao (Theobroma cacao L.) is one major agricultural commodity from central Sulawesi, which is significantly affected by a range of pest and diseases including Cacao Pod Borer (CPB), Pod Rod Diseases (PRD), and Vascular Streak Dieback (VSD). Intensive and extensive approaches, including introduction of various new superior cultivars/clones, and development of eco-friendly agricultural system were implemented in order to overtake that problem. Here, we observed the performance of three different clones (namely: Sulawesi 1, MCC01, and Tadulako-1) in two different locations (Parigi and Poso-which located along east coast of central Sulawesi province), and under two different Agricultural management system (echo-friendly-intensive and Non-Intensive). All clones tested showed their well-adapted and suitable to local conditions. The performance of each clone can be improved by intensive management system. Based on all observed parameters (number of wet bean per pot, bean count, fat and shell percentage, and percentage of infection) it convincingly showed that intensive management system was working well in improving the quality and quantity of cacao beans production, and it fit to commercial requirements. The highest rate of infection was by Phytophthora, and no significant differences on the overall performances. Clones of Sulawesi-1 and MCC01 most likely was better than Tadulako-1.

Impacts of an Extreme Early-Season Freeze Event in the Interior Pacific Northwest (30 October-3 November 2002) on Western Juniper Woodlands.

NASA Astrophysics Data System (ADS)

Knapp, Paul A.; Soulé, Peter T.

2005-07-01

In mid-autumn 2002, an exceptional 5-day cold spell affected much of the interior Pacific Northwest, with minimum temperatures averaging 13°C below long-term means (1953-2002). On 31 October, minimum temperature records occurred at 98 of the 106 recording stations, with records lowered in some locations by 9°C. Calculation of recurrence intervals of minimum temperatures shows that 50% of the stations experienced a >500-yr event. The synoptic conditions responsible were the development of a pronounced high pressure ridge over western Canada and an intense low pressure area centered in the Intermountain West that promoted strong northeasterly winds. The cold spell occurred near the end of the growing season for an ecologically critical and dominant tree species of the interior Pacific Northwest—western juniper—and followed an extended period of severe drought. In spring 2003, it became apparent that the cold had caused high rates of tree mortality and canopy dieback in a species that is remarkable for its longevity and resistance to climatic stress. The cold event altered western juniper dominance in some areas, and this alteration may have long-term impacts on water budgets, fire intensities and frequencies, animal species interrelationships, and interspecific competition among plant species.

Hydraulics play an important role in causing low growth rate and dieback of aging Pinus sylvestris var. mongolica trees in plantations of Northeast China.

PubMed

Liu, Yan-Yan; Wang, Ai-Ying; An, Yu-Ning; Lian, Pei-Yong; Wu, De-Dong; Zhu, Jiao-Jun; Meinzer, Frederick C; Hao, Guang-You

2018-07-01

The frequently observed forest decline in water-limited regions may be associated with impaired tree hydraulics, but the precise physiological mechanisms remain poorly understood. We compared hydraulic architecture of Mongolian pine (Pinus sylvestris var. mongolica) trees of different size classes from a plantation and a natural forest site to test whether greater hydraulic limitation with increasing size plays an important role in tree decline observed in the more water-limited plantation site. We found that trees from plantations overall showed significantly lower stem hydraulic efficiency. More importantly, plantation-grown trees showed significant declines in stem hydraulic conductivity and hydraulic safety margins as well as syndromes of stronger drought stress with increasing size, whereas no such trends were observed at the natural forest site. Most notably, the leaf to sapwood area ratio (LA/SA) showed a strong linear decline with increasing tree size at the plantation site. Although compensatory adjustments in LA/SA may mitigate the effect of increased water stress in larger trees, they may result in greater risk of carbon imbalance, eventually limiting tree growth at the plantation site. Our results provide a potential mechanistic explanation for the widespread decline of Mongolian pine trees in plantations of Northern China. © 2018 John Wiley & Sons Ltd.

El Nino/Southern Oscillation response to global warming.

PubMed

Latif, M; Keenlyside, N S

2009-12-08

The El Niño/Southern Oscillation (ENSO) phenomenon, originating in the Tropical Pacific, is the strongest natural interannual climate signal and has widespread effects on the global climate system and the ecology of the Tropical Pacific. Any strong change in ENSO statistics will therefore have serious climatic and ecological consequences. Most global climate models do simulate ENSO, although large biases exist with respect to its characteristics. The ENSO response to global warming differs strongly from model to model and is thus highly uncertain. Some models simulate an increase in ENSO amplitude, others a decrease, and others virtually no change. Extremely strong changes constituting tipping point behavior are not simulated by any of the models. Nevertheless, some interesting changes in ENSO dynamics can be inferred from observations and model integrations. Although no tipping point behavior is envisaged in the physical climate system, smooth transitions in it may give rise to tipping point behavior in the biological, chemical, and even socioeconomic systems. For example, the simulated weakening of the Pacific zonal sea surface temperature gradient in the Hadley Centre model (with dynamic vegetation included) caused rapid Amazon forest die-back in the mid-twenty-first century, which in turn drove a nonlinear increase in atmospheric CO(2), accelerating global warming.

De novo sequencing, assembly, and analysis of the root transcriptome of Persea americana (Mill.) in response to Phytophthora cinnamomi and flooding.

PubMed

Reeksting, Bianca J; Coetzer, Nanette; Mahomed, Waheed; Engelbrecht, Juanita; van den Berg, Noëlani

2014-01-01

Avocado is a diploid angiosperm containing 24 chromosomes with a genome estimated to be around 920 Mb. It is an important fruit crop worldwide but is susceptible to a root rot caused by the ubiquitous oomycete Phytophthora cinnamomi. Phytophthora root rot (PRR) causes damage to the feeder roots of trees, causing necrosis. This leads to branch-dieback and eventual tree death, resulting in severe losses in production. Control strategies are limited and at present an integrated approach involving the use of phosphite, tolerant rootstocks, and proper nursery management has shown the best results. Disease progression of PRR is accelerated under high soil moisture or flooding conditions. In addition, avocado is highly susceptible to flooding, with even short periods of flooding causing significant losses. Despite the commercial importance of avocado, limited genomic resources are available. Next generation sequencing has provided the means to generate sequence data at a relatively low cost, making this an attractive option for non-model organisms such as avocado. The aims of this study were to generate sequence data for the avocado root transcriptome and identify stress-related genes. Tissue was isolated from avocado infected with P. cinnamomi, avocado exposed to flooding and avocado exposed to a combination of these two stresses. Three separate sequencing runs were performed on the Roche 454 platform and produced approximately 124 Mb of data. This was assembled into 7685 contigs, with 106 448 sequences remaining as singletons. Genes involved in defence pathways such as the salicylic acid and jasmonic acid pathways as well as genes associated with the response to low oxygen caused by flooding, were identified. This is the most comprehensive study of transcripts derived from root tissue of avocado to date and will provide a useful resource for future studies.

De Novo Sequencing, Assembly, and Analysis of the Root Transcriptome of Persea americana (Mill.) in Response to Phytophthora cinnamomi and Flooding

PubMed Central

Reeksting, Bianca J.; Coetzer, Nanette; Mahomed, Waheed; Engelbrecht, Juanita; van den Berg, Noëlani

2014-01-01

Avocado is a diploid angiosperm containing 24 chromosomes with a genome estimated to be around 920 Mb. It is an important fruit crop worldwide but is susceptible to a root rot caused by the ubiquitous oomycete Phytophthora cinnamomi. Phytophthora root rot (PRR) causes damage to the feeder roots of trees, causing necrosis. This leads to branch-dieback and eventual tree death, resulting in severe losses in production. Control strategies are limited and at present an integrated approach involving the use of phosphite, tolerant rootstocks, and proper nursery management has shown the best results. Disease progression of PRR is accelerated under high soil moisture or flooding conditions. In addition, avocado is highly susceptible to flooding, with even short periods of flooding causing significant losses. Despite the commercial importance of avocado, limited genomic resources are available. Next generation sequencing has provided the means to generate sequence data at a relatively low cost, making this an attractive option for non-model organisms such as avocado. The aims of this study were to generate sequence data for the avocado root transcriptome and identify stress-related genes. Tissue was isolated from avocado infected with P. cinnamomi, avocado exposed to flooding and avocado exposed to a combination of these two stresses. Three separate sequencing runs were performed on the Roche 454 platform and produced approximately 124 Mb of data. This was assembled into 7685 contigs, with 106 448 sequences remaining as singletons. Genes involved in defence pathways such as the salicylic acid and jasmonic acid pathways as well as genes associated with the response to low oxygen caused by flooding, were identified. This is the most comprehensive study of transcripts derived from root tissue of avocado to date and will provide a useful resource for future studies. PMID:24563685

Involvement of miR160/miR393 and their targets in cassava responses to anthracnose disease.

PubMed

Pinweha, Nattaya; Asvarak, Thipa; Viboonjun, Unchera; Narangajavana, Jarunya

2015-02-01

Cassava is a starchy root crop for food and industrial applications in many countries around the world. Among the factors that affect cassava production, diseases remain the major cause of yield loss. Cassava anthracnose disease is caused by the fungus Colletotrichum gloeosporioides. Severe anthracnose attacks can cause tip die-backs and stem cankers, which can affect the availability of planting materials especially in large-scale production systems. Recent studies indicate that plants over- or under-express certain microRNAs (miRNAs) to cope with various stresses. Understanding how a disease-resistant plant protects itself from pathogens should help to uncover the role of miRNAs in the plant immune system. In this study, the disease severity assay revealed different response to C. gloeosporioides infection in two cassava cultivars. Quantitative RT-PCR analysis uncovered the differential expression of the two miRNAs and their target genes in the two cassava cultivars that were subjected to fungal infection. The more resistant cultivar revealed the up-regulation of miR160 and miR393, and consequently led to low transcript levels in their targets, ARF10 and TIR1, respectively. The more susceptible cultivar exhibited the opposite pattern. The cis-regulatory elements relevant to defense and stress responsiveness, fungal elicitor responsiveness and hormonal responses were the most prevalent present in the miRNAs gene promoter regions. The possible dual role of these specific miRNAs and their target genes associated with cassava responses to C. gloeosporioides is discussed. This is the first study to address the molecular events by which miRNAs which might play a role in fungal-infected cassava. A better understanding of the functions of miRNAs target genes should greatly increase our knowledge of the mechanism underlying susceptibility and lead to new strategies to enhance disease tolerance in this economically important crop. Copyright © 2014 Elsevier GmbH. All rights reserved.

The Impacts of Amazon Deforestation on Pacific Climate

NASA Astrophysics Data System (ADS)

Lindsey, Leah

Variability in eastern Pacific sea surface temperatures (SSTs) associated with the El Nino Southern Oscillation are known to affect Amazonian precipitation, but to what extent do changing Amazonian vegetation and rainfall impact eastern Pacific SST? The Amazon rainforest is threatened by many factors including climate change and clearing for agricultural reasons. Forest fires and dieback are more likely due to increased frequency and intensity of droughts in the region. It is possible that extensive Amazon deforestation can enhance El Nino conditions by weakening the Walker circulation. Correlations between annual rainfall rates over the Amazon and other atmospheric parameters (global precipitation, surface air temperature, low cloud amount, 500 hPa vertical velocity, surface winds, and 200 hPa winds) over the eastern Pacific indicate strong relationships among these fields. Maps of these correlations (teleconnection maps) reveal that when the Amazon is rainy SSTs in the central and eastern Pacific are cold, rainfall is suppressed over the central and eastern Pacific, low clouds are prominent over the eastern and southeastern Pacific, and subsidence over the central and eastern Pacific is enhanced. Precipitation in the Amazon is also consistent with a strong Walker circulation (La Nina conditions), manifest as strong correlations with the easterly surface and westerly 200 hPa zonal winds. Coupling between Amazon rainfall and these fields are seen in observations and model data. Correlations were calculated using data from observations, reanalysis data, two models under the Coupled Model Intercomparison Project/Atmospheric Model Intercomparison Project (CMIP5/AMIP), and an AMIP run with the model used in this study, the Community Earth System Model (CESM1.1.1). Although the correlations between Amazon precipitation and the aforementioned fields are strong, they do not show causality. In order to investigate the impact of tropical South American deforestation on the Pacific climate, numerical experiments were performed using the CESM. Amazon deforestation was studied in an idealized world where a single continent was covered in forest and then, in a separate simulation, covered in grassland. Four different sets of simulations were carried out: 1) the baseline idealized set-up with prescribed SST, 2) another with an Andes-like mountain range, 3) a simulation with a slab ocean model rather than prescribed SST, and 4) a simulation repeated with the standard Community Atmosphere Model (CAM4) replaced by the Superparameterized version (SP-CAM). The continent in these simulations was compared to the Amazon, and the ocean to the west of the continent was compared to the eastern Pacific. All of the simulations showed a strong warming of around 3-4°C over the continent going from forest to grassland. A notable decrease in precipitation over land of about 1-3 mm day-1 and increase to the west of the continent of about 1-2 mm day-1 was also observed in most of the simulations. The simulations with the slab ocean model showed enhanced precipitation changes with a corresponding decrease of 2-4 mm day-1 over land and increase of 3-5 mm day-1 west of the continent. Simulations that used the SP-CAM showed very small changes in precipitation, which was likely due to the decreased spin-up time allowed for these simulations. The decrease in the surface roughness and reduction in the evapotranspiration for the simulations with grassland contributed to these changes in surface temperature and precipitation. The conversion of forest to grassland in our experiments imply that deforestation can lead to weakening of the Walker circulation by weakening easterly surface winds and westerly upper tropospheric winds. These findings suggest that large-scale Amazon deforestation is capable of enhancing El Nino conditions.

Sensitivity of tropical carbon to climate change constrained by carbon dioxide variability.

PubMed

Cox, Peter M; Pearson, David; Booth, Ben B; Friedlingstein, Pierre; Huntingford, Chris; Jones, Chris D; Luke, Catherine M

2013-02-21

The release of carbon from tropical forests may exacerbate future climate change, but the magnitude of the effect in climate models remains uncertain. Coupled climate-carbon-cycle models generally agree that carbon storage on land will increase as a result of the simultaneous enhancement of plant photosynthesis and water use efficiency under higher atmospheric CO(2) concentrations, but will decrease owing to higher soil and plant respiration rates associated with warming temperatures. At present, the balance between these effects varies markedly among coupled climate-carbon-cycle models, leading to a range of 330 gigatonnes in the projected change in the amount of carbon stored on tropical land by 2100. Explanations for this large uncertainty include differences in the predicted change in rainfall in Amazonia and variations in the responses of alternative vegetation models to warming. Here we identify an emergent linear relationship, across an ensemble of models, between the sensitivity of tropical land carbon storage to warming and the sensitivity of the annual growth rate of atmospheric CO(2) to tropical temperature anomalies. Combined with contemporary observations of atmospheric CO(2) concentration and tropical temperature, this relationship provides a tight constraint on the sensitivity of tropical land carbon to climate change. We estimate that over tropical land from latitude 30° north to 30° south, warming alone will release 53 ± 17 gigatonnes of carbon per kelvin. Compared with the unconstrained ensemble of climate-carbon-cycle projections, this indicates a much lower risk of Amazon forest dieback under CO(2)-induced climate change if CO(2) fertilization effects are as large as suggested by current models. Our study, however, also implies greater certainty that carbon will be lost from tropical land if warming arises from reductions in aerosols or increases in other greenhouse gases.

High-Throughput Chemical Screening Identifies Compounds that Inhibit Different Stages of the Phytophthora agathidicida and Phytophthora cinnamomi Life Cycles.

PubMed

Lawrence, Scott A; Armstrong, Charlotte B; Patrick, Wayne M; Gerth, Monica L

2017-01-01

Oomycetes in the genus Phytophthora are among the most damaging plant pathogens worldwide. Two important species are Phytophthora cinnamomi , which causes root rot in thousands of native and agricultural plants, and Phytophthora agathidicida , which causes kauri dieback disease in New Zealand. As is the case for other Phytophthora species, management options for these two pathogens are limited. Here, we have screened over 100 compounds for their anti-oomycete activity, as a potential first step toward identifying new control strategies. Our screening identified eight compounds that showed activity against both Phytophthora species. These included five antibiotics, two copper compounds and a quaternary ammonium cation. These compounds were tested for their inhibitory action against three stages of the Phytophthora life cycle: mycelial growth, zoospore germination, and zoospore motility. The inhibitory effects of the compounds were broadly similar between the two Phytophthora species, but their effectiveness varied widely among life cycle stages. Mycelial growth was most successfully inhibited by the antibiotics chlortetracycline and paromomycin, and the quaternary ammonium salt benzethonium chloride. Copper chloride and copper sulfate were most effective at inhibiting zoospore germination and motility, whereas the five antibiotics showed relatively poor zoospore inhibition. Benzethonium chloride was identified as a promising antimicrobial, as it is effective across all three life cycle stages. While further testing is required to determine their efficacy and potential phytotoxicity in planta , we have provided new data on those agents that are, and those that are not, effective against P. agathidicida and P. cinnamomi . Additionally, we present here the first published protocol for producing zoospores from P. agathidicida , which will aid in the further study of this emerging pathogen.

Diversity of Phytophthora Species from Declining Mediterranean Maquis Vegetation, including Two New Species, Phytophthora crassamura and P. ornamentata sp. nov.

PubMed Central

Scanu, Bruno; Linaldeddu, Benedetto T.; Deidda, Antonio; Jung, Thomas

2015-01-01

The Mediterranean basin is recognized as a global biodiversity hotspot accounting for more than 25,000 plant species that represent almost 10% of the world’s vascular flora. In particular, the maquis vegetation on Mediterranean islands and archipelagos constitutes an important resource of the Mediterranean plant diversity due to its high rate of endemism. Since 2009, a severe and widespread dieback and mortality of Quercus ilex trees and several other plant species of the Mediterranean maquis has been observed in the National Park of La Maddalena archipelago (northeast Sardinia, Italy). Infected plants showed severe decline symptoms and a significant reduction of natural regeneration. First studies revealed the involvement of the highly invasive wide-host range pathogen Phytophthora cinnamomi and several fungal pathogens. Subsequent detailed research led to a better understanding of these epidemics showing that multiple Phytophthora spp. were involved, some of them unknown to science. In total, nine Phytophthora species were isolated from rhizosphere soil samples collected from around symptomatic trees and shrubs including Asparagus albus, Cistus sp., Juniperus phoenicea, J. oxycedrus, Pistacia lentiscus and Rhamnus alaternus. Based on morphological characters, growth-temperature relations and sequence analysis of the ITS and cox1 gene regions, the isolates were identified as Phytophthora asparagi, P. bilorbang, P. cinnamomi, P. cryptogea, P. gonapodyides, P. melonis, P. syringae and two new Clade 6 taxa which are here described as P. crassamura sp. nov. and P. ornamentata sp. nov. Pathogenicity tests supported their possible involvement in the severe decline that is currently threatening the Mediterranean maquis vegetation in the La Maddalena archipelago. PMID:26649428

Protein accumulation in leaves and roots associated with improved drought tolerance in creeping bentgrass expressing an ipt gene for cytokinin synthesis

PubMed Central

Merewitz, Emily B.; Gianfagna, Thomas; Huang, Bingru

2011-01-01

Cytokinins (CKs) may be involved in the regulation of plant adaptation to drought stress. The objectives of the study were to identify proteomic changes in leaves and roots in relation to improved drought tolerance in transgenic creeping bentgrass (Agrostis stolonifera) containing a senescence-activated promoter (SAG12) and the isopentyl transferase (ipt) transgene that increases endogenous CK content. Leaves of SAG12-ipt bentgrass exhibited less severe senescence under water stress, as demonstrated by maintaining lower electrolyte leakage and lipid peroxidation, and higher photochemical efficiency (Fv/Fm), compared with the null transformant (NT) plants. SAG12-ipt plants had higher root/shoot ratios and lower lipid peroxidation in leaves under water stress than the NT plants. The suppression of drought-induced leaf senescence and root dieback in the transgenic plants was associated with the maintenance of greater antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase). The SAG12-ipt and NT plants exhibited differential protein expression patterns under well-watered and drought conditions in both leaves and roots. Under equivalent leaf water deficit (47% relative water content), SAG12-ipt plants maintained higher abundance of proteins involved in (i) energy production within both photosynthesis and respiration [ribulose 1,5-bisphosphate carboxylase (RuBisCO) and glyceraldehyde phosphate dehydrogenase (GAPDH)]; (ii) amino acid synthesis (methionine and glutamine); (iii) protein synthesis and destination [chloroplastic elongation factor (EF-Tu) and protein disulphide isomerases (PDIs)]; and (iv) antioxidant defence system (catalase and peroxidase) than the NT plants. These results suggest that increased endogenous CKs under drought stress may directly or indirectly regulate protein abundance and enzymatic activities involved in the above-mentioned metabolic processes, thereby enhancing plant drought tolerance. PMID:21831843

Exploring public perceptions of solutions to tree diseases in the UK: Implications for policy-makers.

PubMed

Jepson, Paul; Arakelyan, Irina

2017-10-01

Tree diseases are on the increase in many countries and the implications of their appearance can be political, as well as ecological and economic. Preventative policy approaches to tree diseases are difficult to formulate because dispersal pathways for pest and pathogens are numerous, poorly known and likely to be beyond human management control. Genomic techniques could offer the quickest and most predictable approach to developing a disease tolerant native ash. The population of European Ash ( Fraxinus Excelsi or) has suffered major losses in the last decade, due to the onset of Hymenoscyphus fraxineus (previously called Chalara Fraxinea ) commonly known in the UK as ash dieback. This study presents evidence on the public acceptability of tree-breed solutions to the spread of Chalara , with the main aim to provide science and policy with an up-stream 'steer' on the likely public acceptability of different tree breeding solutions. The findings showed that whilst there was a firm anti-GM and ' we shouldn't tamper with nature ' attitude among UK publics, there was an equally firm and perhaps slightly larger pragmatic attitude that GM (science and technology) should be used if there is a good reason to do so, for example if it can help protect trees from disease and help feed the world. The latter view was significantly stronger among younger age groups (Millennials), those living in urban areas and when the (GM)modified trees were destined for urban and plantation, rather than countryside settings. Overall, our findings suggest that the UK government could consider genomic solutions to tree breeding with more confidence in the future, as large and influential publics appear to be relaxed about the use of genomic techniques to increase tolerance of trees to disease.

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.

Precipitation driven decadal scale decline and recovery of wetlands of Lake Pannon during the Tortonian

PubMed Central

Kern, Andrea K.; Harzhauser, Mathias; Soliman, Ali; Piller, Werner E.; Gross, Martin

2012-01-01

High resolution pollen and dinoflagellate analyses were performed on a continuous 98-cm-long core from Tortonian deposits of Lake Pannon in the Styrian Basin in Austria. The sample distance of 1-cm corresponds to a resolution of roughly one decade, allowing insights into environmental and climatic changes over a millennium of Late Miocene time. Shifts in lake level, surface water productivity on a decadal- to centennial-scale can be explained by variations of rainfall during the Tortonian climatic optimum. Related to negative fine scale shifts of mean annual precipitation, shoreline vegetation belts reacted in an immediate replacement of Poaceae by Cyperaceae as dominant grasses in the marshes fringing the lake. In contrast to such near-synchronous ecosystem-responses to precipitation, a delayed lake level rise of 4–6 decades is evident in the hydrological budget of Lake Pannon. This transgression, caused by a precipitation increase up to > 1200 mm/yr, resulted in a complete dieback of marshes. Simultaneously, “open-water” dinoflagellates, such as Impagidinium, took over in the brackish lagoon and fresh water dinoflagellates disappeared. As soon as the rainfall switched back to moderate levels of ~ 1100–1200 mm/yr, the rise of the lake level slowed down, the marsh plants could keep up again and the former vegetation belts became re-established. Thus, mean annual precipitation, more than temperature, was the main driving force for high-frequency fluctuations in the Tortonian wetlands and surface water conditions of Lake Pannon. Such high resolution studies focusing on Tortonian decadal to centennial climate change will be crucial to test climate models which try to compare the Tortonian models with predictions for future climate change. PMID:23576820

Indirect effects of emerald ash borer-induced ash mortality and canopy gap formation on epigaeic beetles.

PubMed

Gandhi, Kamal J K; Smith, Annemarie; Hartzler, Diane M; Herms, Daniel A

2014-06-01

Exotic herbivorous insects have drastically and irreversibly altered forest structure and composition of North American forests. For example, emerald ash borer (Agrilus planipennis Fairmaire) from Asia has caused wide-scale mortality of ash trees (Fraxinus spp.) in eastern United States and Canada. We studied the effects of forest changes resulting from emerald ash borer invasion on epigaeic or ground beetles (Coleoptera: Carabidae) along a gradient of ash dieback and gap sizes in southeastern Michigan. Ground beetles were sampled in hydric, mesic, and xeric habitats in which black (Fraxinus nigra Marshall), green (Fraxinus pennsylvanica Marshall), and white (Fraxinus americana L.) ash were the most common species, respectively. During 2006-2007, we trapped 2,545 adult ground beetles comprising 52 species. There was a negative correlation between percent ash tree mortality in 2006 and catches of all beetles. Catches of Agonum melanarium Dejean (in 2006) and Pterostichus mutus (Say) (in 2006-2007) were negatively correlated with tree mortality and gap size, respectively. However, catches of Pterostichus corvinus Dejean were positively correlated with gap size in 2006. As ash mortality and average gap size increased from 2006 to 2007, catches of all beetles as well as P. mutus and Pterostichus stygicus (Say) increased (1.3-3.9 times), while species diversity decreased, especially in mesic and xeric stands. Cluster analysis revealed that beetle assemblages in hydric and mesic stand diverged (25 and 40%, respectively) in their composition from 2006 to 2007, and that hydric stands had the most unique beetle assemblages. Overall, epigaeic beetle assemblages were altered in ash stands impacted by emerald ash borer; however, these impacts may dissipate as canopy gaps close.

Origin of the Outbreak in France of Pseudomonas syringae pv. actinidiae Biovar 3, the Causal Agent of Bacterial Canker of Kiwifruit, Revealed by a Multilocus Variable-Number Tandem-Repeat Analysis

PubMed Central

Cunty, A.; Cesbron, S.; Poliakoff, F.; Jacques, M.-A.

2015-01-01

The first outbreaks of bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae biovar 3 were detected in France in 2010. P. syringae pv. actinidiae causes leaf spots, dieback, and canker that sometimes lead to the death of the vine. P. syringae pv. actinidifoliorum, which is pathogenic on kiwi as well, causes only leaf spots. In order to conduct an epidemiological study to track the spread of the epidemics of these two pathogens in France, we developed a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA). MLVA was conducted on 340 strains of P. syringae pv. actinidiae biovar 3 isolated in Chile, China, France, Italy, and New Zealand and on 39 strains of P. syringae pv. actinidifoliorum isolated in Australia, France, and New Zealand. Eleven polymorphic VNTR loci were identified in the genomes of P. syringae pv. actinidiae biovar 3 ICMP 18744 and of P. syringae pv. actinidifoliorum ICMP 18807. MLVA enabled the structuring of P. syringae pv. actinidiae biovar 3 and P. syringae pv. actinidifoliorum strains in 55 and 16 haplotypes, respectively. MLVA and discriminant analysis of principal components revealed that strains isolated in Chile, China, and New Zealand are genetically distinct from P. syringae pv. actinidiae strains isolated in France and in Italy, which appear to be closely related at the genetic level. In contrast, no structuring was observed for P. syringae pv. actinidifoliorum. We developed an MLVA scheme to explore the diversity within P. syringae pv. actinidiae biovar 3 and to trace the dispersal routes of epidemic P. syringae pv. actinidiae biovar 3 in Europe. We suggest using this MLVA scheme to trace the dispersal routes of P. syringae pv. actinidiae at a global level. PMID:26209667

South American Leaf Blight of the Rubber Tree (Hevea spp.): New Steps in Plant Domestication using Physiological Features and Molecular Markers

PubMed Central

Lieberei, Reinhard

2007-01-01

Background Rubber trees (Hevea spp.) are perennial crops of Amazonian origin that have been spread over the whole tropical belt to guarantee worldwide production of natural rubber. This crop plant has found its place in many national economies of producing countries, and although its domestication by selection of suitable genotypes was very slow, it contributes a lot to the welfare of small farmers worldwide. Its development is limited by severe diseases. In South America, the main fungal disease of rubber trees is the South American leaf blight (SALB) caused by the ascomycete Microcyclus ulei. This fungus inhibits natural rubber production on a commercial scale in South and Central America. Scope The disease is still restricted to its continent of origin, but its potential to be distributed around the world rises with every transcontinental airline connection that directly links tropical regions. The need to develop control measures against the disease is an urgent task and must be carried out on an international scale. All control efforts so far taken since 1910 have ended in a miserable failure. Even the use of modern systemic fungicides and use of greatly improved application techniques have failed to prevent large losses and dieback of trees. The results of research dealing with both the disease and the pathosystem over more than 50 years are summarized and placed into perspective. Future Prospects A detailed knowledge of this host–pathogen combination requires understanding of the dynamics of Hevea leaf development, the biochemical potential for cyanide liberation, and molecular data for several types of resistance factors. Resolution of the Hevea–SALB problem may serve as a model for future host–pathogen studies of perennial plants requiring a holistic approach. PMID:17650512

Delayed and reduced carbon uptake in a subarctic peatland following an extreme winter event

NASA Astrophysics Data System (ADS)

Parmentier, F. J. W.; Rasse, D. P.; Lund, M.; Bjerke, J. W.; Drake, B. G.; Weldon, S.; Tømmervik, H. A.; Hansen, G.

2017-12-01

An increase in the frequency of extreme winter events in the Arctic may lead to more widespread damage to shrub-dominated ecosystems, including peatlands. In principle, such damage should reduce carbon uptake in the following summer, but the resilience of northern ecosystems to extreme winter events remains unclear due to a dearth of flux measurements from affected areas. In this talk, therefore, we report CO2 fluxes measured with eddy covariance from a peatland in northern Norway and show that vegetation productivity was delayed and reduced during the summer of 2014, following an extreme winter event. Strong frost and the absence of a protective snow cover in January of that year - its combined intensity unprecedented in the local climate record - led to severe dieback of the shrub species Calluna vulgaris and Empetrum nigrum. Similar vegetation damage was reported at the time along 1000 km of coastal Norway, indicating the widespread impact of this frost drought event. Consequently, gross primary production (GPP) showed a strong delayed response to temperature, from snowmelt up to the peak of summer, potentially reducing carbon uptake by 15 (0-24) g C m-2 ( 13% of GPP in that period). The delayed response of the vegetation was also exhibited in remotely-sensed NDVI values, with a maximum two weeks later than normal and at the lowest level in more than a decade. Photosynthesis was eventually stimulated by the warm and sunny summer, but ecosystem respiration increased as well - which limited net carbon uptake. This study shows that damage from a single extreme winter event can have a profound impact on ecosystem CO2 uptake, and it highlights the importance of including winter-induced shrub damage in terrestrial ecosystem models to accurately predict vegetation and carbon sequestration trends in the arctic and boreal region.

Prolonged Soil Frost Affects Hydraulics and Phenology of Apple Trees

PubMed Central

Beikircher, Barbara; Mittmann, Claudia; Mayr, Stefan

2016-01-01

Restoration of an adequate water supply in spring is a prerequisite for survival of angiosperm trees in temperate regions. Trees must re-establish access to soil water and recover xylem functionality. We thus hypothesized that prolonged soil frost impairs recovery and affects hydraulics and phenology of Malus domestica var. ‘Golden Delicious.’ To test this hypothesis, over two consecutive winters the soil around some trees was insulated to prolong soil frosting, From mid-winter to early summer, the level of native embolism, the water and starch contents of wood, bark and buds were quantified at regular intervals and findings correlated with various phenological parameters, xylogenesis and fine root growth. The findings confirm that prolonged soil frost affects tree hydraulics and phenology but the severity of the effect depends on the climatic conditions. In both study years, percentage loss of hydraulic conductivity (PLC) decreased from about 70% at the end of winter to about 10% in May. Thereby, xylem refilling strongly coincided with a decrease of starch in wood and bark. Also treated trees were able to restore their hydraulic system by May but, in the warm spring of 2012, xylem refilling, the increases in water content and starch depolymerization were delayed. In contrast, in the cold spring of 2013 only small differences between control and treated trees were observed. Prolongation of soil frost also led to a delay in phenology, xylogenesis, and fine root growth. We conclude that reduced water uptake from frozen or cold soils impairs refilling and thus negatively impacts tree hydraulics and growth of apple trees in spring. Under unfavorable circumstances, this may cause severe winter damage or even dieback. PMID:27379146

Prolonged Soil Frost Affects Hydraulics and Phenology of Apple Trees.

PubMed

Beikircher, Barbara; Mittmann, Claudia; Mayr, Stefan

2016-01-01

Restoration of an adequate water supply in spring is a prerequisite for survival of angiosperm trees in temperate regions. Trees must re-establish access to soil water and recover xylem functionality. We thus hypothesized that prolonged soil frost impairs recovery and affects hydraulics and phenology of Malus domestica var. 'Golden Delicious.' To test this hypothesis, over two consecutive winters the soil around some trees was insulated to prolong soil frosting, From mid-winter to early summer, the level of native embolism, the water and starch contents of wood, bark and buds were quantified at regular intervals and findings correlated with various phenological parameters, xylogenesis and fine root growth. The findings confirm that prolonged soil frost affects tree hydraulics and phenology but the severity of the effect depends on the climatic conditions. In both study years, percentage loss of hydraulic conductivity (PLC) decreased from about 70% at the end of winter to about 10% in May. Thereby, xylem refilling strongly coincided with a decrease of starch in wood and bark. Also treated trees were able to restore their hydraulic system by May but, in the warm spring of 2012, xylem refilling, the increases in water content and starch depolymerization were delayed. In contrast, in the cold spring of 2013 only small differences between control and treated trees were observed. Prolongation of soil frost also led to a delay in phenology, xylogenesis, and fine root growth. We conclude that reduced water uptake from frozen or cold soils impairs refilling and thus negatively impacts tree hydraulics and growth of apple trees in spring. Under unfavorable circumstances, this may cause severe winter damage or even dieback.

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.

Convergent structural responses of tropical forests to diverse disturbance regimes.

PubMed

Kellner, James R; Asner, Gregory P

2009-09-01

Size frequency distributions of canopy gaps are a hallmark of forest dynamics. But it remains unknown whether legacies of forest disturbance are influencing vertical size structure of landscapes, or space-filling in the canopy volume. We used data from LiDAR remote sensing to quantify distributions of canopy height and sizes of 434,501 canopy gaps in five tropical rain forest landscapes in Costa Rica and Hawaii. The sites represented a wide range of variation in structure and natural disturbance history, from canopy gap dynamics in lowland Costa Rica and Hawaii, to stages and types of stand-level dieback on upland Mauna Kea and Kohala volcanoes. Large differences in vertical canopy structure characterized these five tropical rain forest landscapes, some of which were related to known disturbance events. Although there were quantitative differences in the values of scaling exponents within and among sites, size frequency distributions of canopy gaps followed power laws at all sites and in all canopy height classes. Scaling relationships in gap size at different heights in the canopy were qualitatively similar at all sites, revealing a remarkable similarity despite clearly defined differences in species composition and modes of prevailing disturbance. These findings indicate that power-law gap-size frequency distributions are ubiquitous features of these five tropical rain forest landscapes, and suggest that mechanisms of forest disturbance may be secondary to other processes in determining vertical and horizontal size structure in canopies.

An evaluation of bur oak (Quercus macrocarpa) decline in the urban forest of Winnipeg, Manitoba, Canada

USGS Publications Warehouse

Catton, H.A.; St., George; Remphrey, W.R.

2007-01-01

Winnipeg, Manitoba, Canada, has a large, indigenous population of bur oak (Quercus macrocarpa Michx.). In the 1980s, many of these trees were showing signs of decline, a disease caused by a complex of abiotic and secondary biotic stressing agents. Potential causal factors were investigated by comparing various aspects of 120 bur oaks visually rated as healthy or declined based on crown dieback levels. The results indicated that many selected bur oak trees predated surrounding urban development and that declined trees were significantly older with more severe stem wounds and competition from surrounding trees than healthy specimens. Average annual growth ring widths of healthy and declined trees were similar in the early part of the 20th century. However, decline actually began decades before symptoms were noticed, coinciding with a period of in tense city-wide urban development, as growth of declined trees was slower than that of healthy trees beginning sporadically in the 1940s and consistently from 1974 to 2001. During the early years of decline, the year-by-year separation in ring width between the two categories was significantly positively related to precipitation levels. This suggested that in wet years, declined trees may have been surrounded by unfavorable water-logged soils, possibly as a result of natural drainage patterns being impeded by urban development. ?? 2007 International Society of Arboriculture.

Comparative Genome Analysis of “Candidatus Phytoplasma australiense” (Subgroup tuf-Australia I; rp-A) and “Ca. Phytoplasma asteris” Strains OY-M and AY-WB▿ †

PubMed Central

Tran-Nguyen, L. T. T.; Kube, M.; Schneider, B.; Reinhardt, R.; Gibb, K. S.

2008-01-01

The chromosome sequence of “Candidatus Phytoplasma australiense” (subgroup tuf-Australia I; rp-A), associated with dieback in papaya, Australian grapevine yellows in grapevine, and several other important plant diseases, was determined. The circular chromosome is represented by 879,324 nucleotides, a GC content of 27%, and 839 protein-coding genes. Five hundred two of these protein-coding genes were functionally assigned, while 337 genes were hypothetical proteins with unknown function. Potential mobile units (PMUs) containing clusters of DNA repeats comprised 12.1% of the genome. These PMUs encoded genes involved in DNA replication, repair, and recombination; nucleotide transport and metabolism; translation; and ribosomal structure. Elements with similarities to phage integrases found in these mobile units were difficult to classify, as they were similar to both insertion sequences and bacteriophages. Comparative analysis of “Ca. Phytoplasma australiense” with “Ca. Phytoplasma asteris” strains OY-M and AY-WB showed that the gene order was more conserved between the closely related “Ca. Phytoplasma asteris” strains than to “Ca. Phytoplasma australiense.” Differences observed between “Ca. Phytoplasma australiense” and “Ca. Phytoplasma asteris” strains included the chromosome size (18,693 bp larger than OY-M), a larger number of genes with assigned function, and hypothetical proteins with unknown function. PMID:18359806

[Hydraulic limitation on photosynthetic rate of old Populus simonii trees in sandy soil of north Shaanxi Province].

PubMed

Zuo, Li-Xiang; Li, Yang-Yang; Chen, Jia-Cun

2014-06-01

'Old and dwarf trees' on the loess plateau region mainly occurred among mature trees rather than among small trees. To elucidate the mechanism of tree age on 'old and dwarf trees' formation, taking Populus simonii, a tree species that accounted for the largest portion of 'old and dwarf trees' on the loess plateau, as an example, the growth, photosynthesis and hydraulic traits of P. simonii trees with different ages (young: 13-15 years, mid-aged: 31-34 years, and old: 49-54 years) were measured. The results showed that the dieback length increased, and net photosynthetic rate, stomatal conductance, transpiration rate, and whole plant hydraulic conductance decreased significantly with the increasing tree age. Both net photosynthetic rate and stomatal conductance measured at different dates were significantly and positively related to the whole plant hydraulic conductance, suggesting that the decreasing photosynthetic rate of old trees was possibly caused by the declined hydraulic conductance. Although the resistance to cavitation in stems and leaves was stronger in old trees than in young and mid-aged trees, there were no differences in midday native stem embolization degree and leaf hydraulic conductance based on the vulnerability curve estimation, suggesting that the increased hydraulic resistance of the soil-root system is probably the most important reason for decreasing the whole plant hydraulic conductance of old trees.

Specific and sensitive detection of the conifer pathogen Gremmeniella abietina by nested PCR

PubMed Central

Zeng, Qing-Yin; Hansson, Per; Wang, Xiao-Ru

2005-01-01

Background Gremmeniella abietina (Lagerb.) Morelet is an ascomycete fungus that causes stem canker and shoot dieback in many conifer species. The fungus is widespread and causes severe damage to forest plantations in Europe, North America and Asia. To facilitate early diagnosis and improve measures to control the spread of the disease, rapid, specific and sensitive detection methods for G. abietina in conifer hosts are needed. Results We designed two pairs of specific primers for G. abietina based on the 18S rDNA sequence variation pattern. These primers were validated against a wide range of fungi and 14 potential conifer hosts. Based on these specific primers, two nested PCR systems were developed. The first system employed universal fungal primers to enrich the fungal DNA targets in the first round, followed by a second round selective amplification of the pathogen. The other system employed G. abietina-specific primers in both PCR steps. Both approaches can detect the presence of G. abietina in composite samples with high sensitivity, as little as 7.5 fg G. abietina DNA in the host genomic background. Conclusion The methods described here are rapid and can be applied directly to a wide range of conifer species, without the need for fungal isolation and cultivation. Therefore, it represents a promising alternative to disease inspection in forest nurseries, plantations and quarantine control facilities. PMID:16280082

Effect of Chipping and Solarization on Emergence and Boring Activity of a Recently Introduced Ambrosia Beetle (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae) in Southern California.

PubMed

Eatough Jones, Michele; Paine, Timothy D

2015-08-01

Polyphagous shot hole borer (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae) has recently invaded southern California. The beetle, along with its associated fungi, Fusarium euwallaceae, Graphium sp., and Acremonium sp., causes branch dieback and tree mortality in a large variety of tree species including avocado (Persea americana Mill.) and box elder (Acer negundo L.). With the spread of the beetle through Los Angeles, Orange, and San Diego Counties in California, there is increasing concern that felled trees and pruned branches infested with polyphagous shot hole borer should receive sanitation treatment to reduce the potential spread of the beetle from the movement of untreated wood. We tested two sanitation methods to reduce beetle populations, chipping with a commercial chipper and solarization by covering logs with clear or black plastic in full sun. Both chipping and solarization decreased beetle emergence and boring activity compared to untreated control logs. Chipping was most effective for chip sizes <5 cm. Solarization was most effective using clear polyethylene sheeting during hot summer months, particularly August, when daily maximum temperatures were ≥35°C. Beetles persisted for 2 mo or more when solarization was applied during the spring or fall. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

CH4 and CO2 exchange of a brackish degraded peatland within the drainage-rewetting sequence - Synthesis from an interdisciplinary multi-year approach

NASA Astrophysics Data System (ADS)

Sachs, T.; Koebsch, F.; Boettcher, M. E.; Glatzel, S.; Liebner, S.; Matthias, W.; Koch, M.; Westphal, J.; Jurasinski, G.

2016-12-01

Rewetting is considered as common measure to stop aerobic peat decomposition and to re-establish the net natural C sink function of peatlands. In this long-term study, we accompanied the development of a degraded brackish peatland from drainage to year-round flooding. Based on eddy covariance measurements of CH4 and CO2 fluxes, remote sensing monitoring of vegetation succession and insights into major dissimilatory pathways, we develop a more differentiated perspective on the greenhouse gas (GHG) effect of rewetting measures conducted in brackish peatlands. Contrary to the common assumption that CH4 production is inhibited in coastal ecosystems, CH4 emissions increased remarkably after rewetting. Despite few local exceptions, sulfate - the major electron acceptor in marine environments - was completely converted to stable organic and metal sulfides. Sulfate depletion in concert with high substrate supply derived from a destabilized peat C pool and the extensive die-back of vegetation fuel CH4 emissions especially in the initial rewetting phase. CH4 fluxes are further interpreted in light of climate variables and vegetation data to differentiate between short-term response to climate variation and long-term trends based on ecosystem succession after flooding. High CH4 emissions in the initial rewetting phase are considered to be (at least partially) compensated as CO2 release by aerobic respiration decreases. However, our results indicate that flooding does not only cease CO2 release by ecosystem respiration, but that also CO2 uptake by canopy photosynthesis is affected to the same degree when vegetation cannot cope with the rapid rise in water level. Our study highlights the importance of a multi-year monitoring to cover the dynamic ecosystem development within the drainage-rewetting sequence. We further emphasize the relevance of interdisciplinary approaches to understand the complex interactions between ecosystem compartments as basic controls for GHG exchange.

Vulnerability and resilience of the carbon exchange of a subarctic peatland to an extreme winter event

NASA Astrophysics Data System (ADS)

Parmentier, Frans-Jan W.; Rasse, Daniel P.; Lund, Magnus; Bjerke, Jarle W.; Drake, Bert G.; Weldon, Simon; Tømmervik, Hans; Hansen, Georg H.

2018-06-01

Extreme winter events that damage vegetation are considered an important climatic cause of arctic browning—a reversal of the greening trend of the region—and possibly reduce the carbon uptake of northern ecosystems. Confirmation of a reduction in CO2 uptake due to winter damage, however, remains elusive due to a lack of flux measurements from affected ecosystems. In this study, we report eddy covariance fluxes of CO2 from a peatland in northern Norway and show that vegetation CO2 uptake was delayed and reduced in the summer of 2014 following an extreme winter event earlier that year. Strong frost in the absence of a protective snow cover—its combined intensity unprecedented in the local climate record—caused severe dieback of the dwarf shrub species Calluna vulgaris and Empetrum nigrum. Similar vegetation damage was reported at the time along ~1000 km of coastal Norway, showing the widespread impact of this event. Our results indicate that gross primary production (GPP) exhibited a delayed response to temperature following snowmelt. From snowmelt up to the peak of summer, this reduced carbon uptake by 14 (0–24) g C m‑2 (~12% of GPP in that period)—similar to the effect of interannual variations in summer weather. Concurrently, remotely-sensed NDVI dropped to the lowest level in more than a decade. However, bulk photosynthesis was eventually stimulated by the warm and sunny summer, raising total GPP. Species other than the vulnerable shrubs were probably resilient to the extreme winter event. The warm summer also increased ecosystem respiration, which limited net carbon uptake. This study shows that damage from a single extreme winter event can have an ecosystem-wide impact on CO2 uptake, and highlights the importance of including winter-induced shrub damage in terrestrial ecosystem models to accurately predict trends in vegetation productivity and carbon sequestration in the Arctic and sub-Arctic.

Indirect facilitation becomes stronger with seedling age in a degraded seasonally dry forest

NASA Astrophysics Data System (ADS)

Torres, Romina C.; Renison, Daniel

2016-01-01

In seasonally dry forests direct facilitation by woody species due to amelioration of harsh abiotic conditions could be important during germination and early establishment of tree seedlings, and under some species but not others. Recent research suggests that at later stages facilitation by woody species may be indirect due to protection of saplings from herbivores, implying that under absence of herbivores reforestation programs may plant saplings in unprotected open sites. We used the native tree Lithraea molleoides from central Argentina as a model species to test this hypothesis. We performed a seeding and planting experiment simulating early and late establishment respectively, which included 234 study plots situated in herbaceous, shrub and tree patches of differing species composition and under two herbivore treatments (grazed and ungrazed) and replicated at three sites. Seedling counts averaged 0.82% of the sown seeds after 6 months, were highest under shrubs and lowest in open patches, and were influenced by woody species composition only in tree patches (all P values < 0.05). At seedling stages we detected no influence of herbivory (P = 0.4) nor of indirect facilitation due to herbivory (herbivory × patch type P = 0.7). Survival of planted saplings was 53% after 3 years and over winter dieback affected 76% of the saplings. At sapling stages we found an increasing importance of indirect facilitation through protection from herbivores, as we recorded the highest sapling survival and growth at tree and shrub patches and the lowest in open patches (all P values < 0.001), and a negative effect of livestock (P < 0.001) mainly on the open patches (herbivory × patch type P = 0.07 and P = 0.001 for survival and growth, respectively). We found no significant influence of woody species composition on sapling survival and growth (all P values > 0.05). We conclude that direct facilitation is involved at all studied stages while indirect facilitation becomes increasingly important at the sapling stage.

Anthropogenic nitrogen deposition alters growth responses of European beech (Fagus sylvativa L.) to climate change.

PubMed

Hess, Carsten; Niemeyer, Thomas; Fichtner, Andreas; Jansen, Kirstin; Kunz, Matthias; Maneke, Moritz; von Wehrden, Henrik; Quante, Markus; Walmsley, David; von Oheimb, Goddert; Härdtle, Werner

2018-02-01

Global change affects the functioning of forest ecosystems and the services they provide, but little is known about the interactive effects of co-occurring global change drivers on important functions such as tree growth and vitality. In the present study we quantified the interactive (i.e. synergistic or antagonistic) effects of atmospheric nitrogen (N) deposition and climatic variables (temperature, precipitation) on tree growth (in terms of tree-ring width, TRW), taking forest ecosystems with European beech (Fagus sylvatica L.) as an example. We hypothesised that (i) N deposition and climatic variables can evoke non-additive responses of the radial increment of beech trees, and (ii) N loads have the potential to strengthen the trees' sensitivity to climate change. In young stands, we found a synergistic positive effect of N deposition and annual mean temperature on TRW, possibly linked to the alleviation of an N shortage in young stands. In mature stands, however, high N deposition significantly increased the trees' sensitivity to increasing annual mean temperatures (antagonistic effect on TRW), possibly due to increased fine root dieback, decreasing mycorrhizal colonization or shifts in biomass allocation patterns (aboveground vs. belowground). Accordingly, N deposition and climatic variables caused both synergistic and antagonistic effects on the radial increment of beech trees, depending on tree age and stand characteristics. Hence, the nature of interactions could mediate the long-term effects of global change drivers (including N deposition) on forest carbon sequestration. In conclusion, our findings illustrate that interaction processes between climatic variables and N deposition are complex and have the potential to impair growth and performance of European beech. This in turn emphasises the importance of multiple-factor studies to foster an integrated understanding and models aiming at improved projections of tree growth responses to co-occurring drivers of global change. Copyright © 2017 Elsevier Ltd. All rights reserved.

Do canopy disturbances drive forest plantations into more natural conditions? — A case study from Can Gio Biosphere Reserve, Viet Nam

NASA Astrophysics Data System (ADS)

Vogt, Juliane; Kautz, Markus; Fontalvo Herazo, Martha Liliana; Triet, Tran; Walther, Denny; Saint-Paul, Ulrich; Diele, Karen; Berger, Uta

2013-11-01

Large areas of mangrove forests were devastated in South Viet Nam during the second Indochina war. After its end in 1975, extensive reforestation with monocultures took place. Can Gio, one of the biggest replanted sites with about 20,000 ha of mangroves mainly Rhizophora apiculata, was declared a biosphere reserve by the UNESCO in 2000. Although this status now enables progressive forest dynamics, there are still drawbacks resulting from the unnatural character of the plantations. For example, the homogeneous size and age structure as well as the regular arrangement of the planted trees make larger forest stands more vulnerable to synchronized collapsing which can be triggered by stronger winds and storms. A transformation into a more natural forest characterized by a heterogeneous age and size structure and a mixed species composition is of urgent need to avoid a synchronized dieback. In this study we test the capability of natural canopy disturbances (e.g. lightning strikes) to facilitate this transformation.Canopy gaps created by lightning strikes were detected and quantified by remote sensing techniques. SPOT satellite images from the years 2003, 2005 and 2007 provided information about the spatial distribution, size, shape, and formation frequency of the gaps. Lightning strike gaps were identified based on their shape and size. They form small openings (mean: 0.025 ha) and their yearly probability of occurrence was determined to be approximately 0.012 per hectare. Selected gaps were surveyed in the field in 2008 to complement the remote sensing data and to provide information upon forest structure and regeneration.Simulation experiments were carried out with the individual-based KiWi mangrove model for quantifying the influence of different lightning regimes on the vertical and horizontal structure of the R. apiculata plantation. In addition, we conducted simulations with a natural and thus randomly generated forest to compare the structure of the two different cultivation types (i.e. plantation and natural forest). The simulation shows that even small disturbances can already partly buffer the risk of cohort senescence of monospecific even-aged plantations. However, after the decline of the plantation, the disturbance regime does not play an important role for further stand development. After the break-up of the initial strongly regular structure of the simulated plantation, a vertical pattern, i.e. height distribution of the trees, similar to the one of the natural forest, emerged quickly. However, the convergence for the horizontal structure i.e. the distance of trees to their nearest neighbor, took twice as long as for the vertical structure. Our results highlight the importance of small disturbances such as lightning strikes to mitigate vulnerability against synchronous windfall in homogenous forest structures. Hence, creating small openings artificially may be an appropriate management measure in areas where the frequency of natural small-scale disturbances is low.

Synergy between land use and climate change increases future fire risk in Amazon forests

NASA Astrophysics Data System (ADS)

Le Page, Yannick; Morton, Douglas; Hartin, Corinne; Bond-Lamberty, Ben; Cardoso Pereira, José Miguel; Hurtt, George; Asrar, Ghassem

2017-12-01

Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, which are common under the current climate in frontier forests, may accelerate Amazon forest losses from climate-driven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactions between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change - Representative Concentration Pathway (RCP) 8.5 - projected understory fires increase in frequency and duration, burning 4-28 times more forest in 2080-2100 than during 1990-2010. In contrast, active climate mitigation and land use contraction in RCP4.5 constrain the projected increase in fire activity to 0.9-5.4 times contemporary burned area. Importantly, if climate mitigation is not successful, land use contraction alone is very effective under low to moderate climate change, but does little to reduce fire activity under the most severe climate projections. These results underscore the potential for a fire-driven transformation of Amazon forests if recent regional policies for forest conservation are not paired with global efforts to mitigate climate change.

Potential contribution of groundwater to dry-season ET in the Amazon

NASA Astrophysics Data System (ADS)

Miguez-Macho, Gonzalo; Fan, Ying

2010-05-01

Climate and land ecosystem models simulate vegetation stress in the Amazon forest in the dry season, but observations show enhanced growth in response to higher radiation under less cloudy skies indicating an adequate water supply. The question is: how does the vegetation obtain sufficient water, and what is missing in the models? Shallow model soil and rooting depth is a factor; the ability of roots to move water up and down (hydraulic redistribution) may be another, but another cause may lie in the buffering effect of the groundwater found in nature but absent in models. We present observational and modeling evidence that the vast groundwater store, consequence of high annual rainfall combined with poor drainage in the Amazon, may provide a stable source for dry-season photosynthesis. The water table beneath the Amazon is sufficiently shallow (38% area <5m and 63% area <10m deep) as to contribute >2mm/day to dry-season evapotranspiration, a non-negligible portion of tower-observed flux of 3-4mm/day, the latter including canopy-interception loss and open-water evaporation. This may have important implications to our understanding of Amazonia ecosystem response and feedback to climate change. Current models, lacking groundwater, predict a significant reduction in dry-season photosynthesis under current climate and large-scale dieback under projected future climate converting the Amazon from a net carbon sink to a net source and accelerating warming. If groundwater is considered in the models, the magnitude of the responses and feedbacks may be reduced.

[Health assessment of individual trees in natural Larix gmelinii forest in Great Xing' an Mountains of China].

PubMed

Zhu, Yu; Liu, Zhao-Gang; Jin, Guang-Ze

2013-05-01

To integrate the health assessment results of individual trees into the health assessment of subcompartment (or stand) scale could improve the accuracy of subcompartment (or stand) scale health assessment, and realize the coupling process between the individual tree scale and the subcompartment (or stand) scale, providing a theoretical basis for the realization of forest health management. Taking the natural Larix gmelinii forest in Great Xing' an Mountains as the object, a health assessment indicators system of individual trees was established, which included root state, canopy defoliation degree, crown transparency, crown overlap, crown dieback ratio, live crown ratio, crown skewness, and vertical competition index. The principal component analysis (PCA) was employed to eliminate the correlations, the entropy value method was adopted to confirm the weight of each indicator, and the health status of individual L. gmelinii was assessed by fuzzy synthetic evaluation (FSE) method. Based on the health assessment results, a prediction model of the individual tree health was established by discriminant analysis (DA) method. The results showed that the trees in sub-healthy gradation were up to 36.7%, and those in healthy gradation only reached 12.9%. The proportion of the trees in unhealthy gradation exceeded that of the trees in healthy gradation, occupying 21.1% of the total. The prediction accuracy of the established model was 86.3%. More rational and effective management measures should be taken to improve the tree health grade.

Dying piece by piece: carbohydrate dynamics in aspen (Populus tremuloides) seedlings under severe carbon stress.

PubMed

Wiley, Erin; Hoch, Günter; Landhäusser, Simon M

2017-11-02

Carbon starvation as a mechanism of tree mortality is poorly understood. We exposed seedlings of aspen (Populus tremuloides) to complete darkness at 20 or 28 °C to identify minimum non-structural carbohydrate (NSC) concentrations at which trees die and to see if these levels vary between organs or with environmental conditions. We also first grew seedlings under different shade levels to determine if size affects survival time under darkness due to changes in initial NSC concentration and pool size and/or respiration rates. Darkness treatments caused a gradual dieback of tissues. Even after half the stem had died, substantial starch reserves were still present in the roots (1.3-3% dry weight), indicating limitations to carbohydrate remobilization and/or transport during starvation in the absence of water stress. Survival time decreased with increased temperature and with increasing initial shade level, which was associated with smaller biomass, higher respiration rates, and initially smaller NSC pool size. Dead tissues generally contained no starch, but sugar concentrations were substantially above zero and differed between organs (~2% in stems up to ~7.5% in leaves) and, at times, between temperature treatments and initial, pre-darkness shade treatments. Minimum root NSC concentrations were difficult to determine because dead roots quickly began to decompose, but we identify 5-6% sugar as a potential threshold for living roots. This variability may complicate efforts to identify critical NSC thresholds below which trees starve. © Society for Experimental Biology 2017.

Extremely low genetic diversity across mangrove taxa reflects past sea level changes and hints at poor future responses.

PubMed

Guo, Zixiao; Li, Xinnian; He, Ziwen; Yang, Yuchen; Wang, Wenqing; Zhong, Cairong; Greenberg, Anthony J; Wu, Chung-I; Duke, Norman C; Shi, Suhua

2018-04-01

The projected increases in sea levels are expected to affect coastal ecosystems. Tropical communities, anchored by mangrove trees and having experienced frequent past sea level changes, appear to be vibrant at present. However, any optimism about the resilience of these ecosystems is premature because the impact of past climate events may not be reflected in the current abundance. To assess the impact of historical sea level changes, we conducted an extensive genetic diversity survey on the Indo-Malayan coast, a hotspot with a large global mangrove distribution. A survey of 26 populations in six species reveals extremely low genome-wide nucleotide diversity and hence very small effective population sizes (N e ) in all populations. Whole-genome sequencing of three mangrove species further shows the decline in N e to be strongly associated with the speed of past changes in sea level. We also used a recent series of flooding events in Yalong Bay, southern China, to test the robustness of mangroves to sea level changes in relation to their genetic diversity. The events resulted in the death of half of the mangrove trees in this area. Significantly, less genetically diverse mangrove species suffered much greater destruction. The dieback was accompanied by a drastic reduction in local invertebrate biodiversity. We thus predict that tropical coastal communities will be seriously endangered as the global sea level rises. Well-planned coastal development near mangrove forests will be essential to avert this crisis. © 2017 John Wiley & Sons Ltd.

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

Van Voris, P.; Cataldo, D.A.; Garland, T.R.

An evaluation of the terrestrial transport, transformations and ecological effects of phosphorus (red phosphorus-butyl rubber (RP/BR)), smoke/obscurant was performed to characterize the effects on: (1) natural vegetation characteristic of US Army training sites in the United States; (2) physical and chemical properties of representative of soils of those sites; and (3) soil microbiological communities. The influence and interactions of smoke/obscurant concentration relative humidity and wind speed was assessed. Toxicity symptoms for plants from repeated or a single exposure included leaf tip burn, leaf curl, leaf abscission and drop, floral abortion, chlorosis, neucrotic spotting, wilting, dessication and dieback for ponderosa pine,more » short needle pine, sagebrush, a native grass (Blando Brome) and bushbean. Soils data suggest an increase in the mobility of selected trace elements after exposure; however, this effect appears to be ameliorated with time. This phenomenon is influenced by soil type, which is a reflection of the buffering capacity of the exposed soil (i.e., Burbank, Quallayute, Shawano, and Yamac) as well as the concentration and duration of exposure. Increased mobility of trace elements is also evidenced in the trace element content of plants grown on soils after exposure to RP/BR smoke. Soil Microbial Community effects show a reduction in the production of nitrate after soil is exposed to RP/BR smoke. This indicates a reduction in ammonium oxidizing bacterial populations, specifically Nitrosomonas and probably Nitrobacter. For the most part most of the plant, soil and soil microbial effects are transient.« less

Vulnerability to Climate Change of Mangroves: Assessment from Cameroon, Central Africa

PubMed Central

Ellison, Joanna C.; Zouh, Isabella

2012-01-01

Intertidal mangrove ecosystems are sensitive to climate change impacts, particularly to associated relative sea level rise. Human stressors and low tidal range add to vulnerability, both characteristics of the Doula Estuary, Cameroon. To investigate vulnerability, spatial techniques were combined with ground surveys to map distributions of mangrove zones, and compare with historical spatial records to quantify change over the last few decades. Low technology techniques were used to establish the tidal range and relative elevation of the mapped mangrove area. Stratigraphic coring and palaeobiological reconstruction were used to show the longer term biological history of mangroves and net sedimentation rate, and oral history surveys of local communities were used to provide evidence of recent change and identify possible causes. Results showed that the seaward edge of mangroves had over two thirds of the shoreline experienced dieback at up to 3 m per year over the last three decades, and an offshore mangrove island had suffered 89% loss. Results also showed low net sedimentation rates under seaward edge mangroves, and restricted intertidal elevation habitats of all mangroves, and Avicennia and Laguncularia in particular. To reduce vulnerability, adaptation planning can be improved by reducing the non-climate stressors on the mangrove area, particularly those resulting from human impacts. Other priorities for adaptation planning in mangrove areas that are located in such low tidal range regions are to plan inland migration areas and strategic protected areas for mangroves, and to undertake management activities that enhance accretion within the mangroves. PMID:24832511

Landscape-scale variation in canopy water content of giant sequoias during drought

USGS Publications Warehouse

Paz-Kagan, Tarin; Vaughn, Nicolas R.; Martin, Roberta E.; Brodrick, Philip G.; Stephenson, Nathan L.; Das, Adrian; Nydick, Koren R.; Asner, Gregory P.

2018-01-01

Recent drought (2012–2016) caused unprecedented foliage dieback in giant sequoias (Sequoiadendron giganteum), a species endemic to the western slope of the southern Sierra Nevada in central California. As part of an effort to understand and map sequoia response to droughts, we studied the patterns of remotely sensed canopy water content (CWC), both within and among sequoia groves in two successive years during the drought period (2015 and 2016). Our aims were: (1) to quantify giant sequoia responses to severe drought stress at a landscape scale using CWC as an indicator of crown foliage status, and (2) to estimate the effect of environmental correlates that mediate CWC change within and among giant sequoia groves. We utilized airborne high fidelity imaging spectroscopy (HiFIS) and light detection and ranging (LiDAR) data from the Carnegie Airborne Observatory to assess giant sequoia foliage status during 2015 and 2016 of the 2012–2016 droughts. A series of statistical models were generated to classify giant sequoias and to map their location in Sequoia and Kings Canyon National Parks (SEKI) and vicinity. We explored the environmental correlates and the spatial patterns of CWC change at the landscape scale. The mapped CWC was highly variable throughout the landscape during the two observation years, and proved to be most closely related to geological substrates, topography, and site-specific water balance. While there was an overall net gain in sequoia CWC between 2015 and 2016, certain locations (lower elevations, steeper slopes, areas more distant from surface water sources, and areas with greater climate water deficit) showed CWC losses. In addition, we found greater CWC loss in shorter sequoias and those growing in areas with lower sequoia stem densities. Our results suggest that CWC change indicates sequoia response to droughts across landscapes. Long-term monitoring of giant sequoia CWC will likely be useful for modeling and predicting their population-level response to future climate change.

Can local adaptation explain varying patterns of herbivory tolerance in a recently introduced woody plant in North America?

PubMed

Long, Randall W; Bush, Susan E; Grady, Kevin C; Smith, David S; Potts, Daniel L; D'Antonio, Carla M; Dudley, Tom L; Fehlberg, Shannon D; Gaskin, John F; Glenn, Edward P; Hultine, Kevin R

2017-01-01

Patterns of woody-plant mortality have been linked to global-scale environmental changes, such as extreme drought, heat stress, more frequent and intense fires, and episodic outbreaks of insects and pathogens. Although many studies have focussed on survival and mortality in response to specific physiological stresses, little attention has been paid to the role of genetic heritability of traits and local adaptation in influencing patterns of plant mortality, especially in non-native species. Tamarix spp. is a dominant, non-native riparian tree in western North America that is experiencing dieback in some areas of its range due to episodic herbivory by the recently introduced northern tamarisk leaf beetle ( Diorhabda carinulata ). We propose that genotype × environment interactions largely underpin current and future patterns of Tamarix mortality. We anticipate that (i) despite its recent introduction, and the potential for significant gene flow, Tamarix in western North America is generally adapted to local environmental conditions across its current range in part due to hybridization of two species; (ii) local adaptation to specific climate, soil and resource availability will yield predictable responses to episodic herbivory; and (iii) the ability to cope with a combination of episodic herbivory and increased aridity associated with climate change will be largely based on functional tradeoffs in resource allocation. This review focusses on the potential heritability of plant carbon allocation patterns in Tamarix , focussing on the relative contribution of acquired carbon to non-structural carbohydrate (NSC) pools versus other sinks as the basis for surviving episodic disturbance. Where high aridity and/or poor edaphic position lead to chronic stress, NSC pools may fall below a minimum threshold because of an imbalance between the supply of carbon and its demand by various sinks. Identifying patterns of local adaptation of traits related to resource allocation will improve forecasting of Tamarix population susceptibility to episodic herbivory.

Origin of the Outbreak in France of Pseudomonas syringae pv. actinidiae Biovar 3, the Causal Agent of Bacterial Canker of Kiwifruit, Revealed by a Multilocus Variable-Number Tandem-Repeat Analysis.

PubMed

Cunty, A; Cesbron, S; Poliakoff, F; Jacques, M-A; Manceau, C

2015-10-01

The first outbreaks of bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae biovar 3 were detected in France in 2010. P. syringae pv. actinidiae causes leaf spots, dieback, and canker that sometimes lead to the death of the vine. P. syringae pv. actinidifoliorum, which is pathogenic on kiwi as well, causes only leaf spots. In order to conduct an epidemiological study to track the spread of the epidemics of these two pathogens in France, we developed a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA). MLVA was conducted on 340 strains of P. syringae pv. actinidiae biovar 3 isolated in Chile, China, France, Italy, and New Zealand and on 39 strains of P. syringae pv. actinidifoliorum isolated in Australia, France, and New Zealand. Eleven polymorphic VNTR loci were identified in the genomes of P. syringae pv. actinidiae biovar 3 ICMP 18744 and of P. syringae pv. actinidifoliorum ICMP 18807. MLVA enabled the structuring of P. syringae pv. actinidiae biovar 3 and P. syringae pv. actinidifoliorum strains in 55 and 16 haplotypes, respectively. MLVA and discriminant analysis of principal components revealed that strains isolated in Chile, China, and New Zealand are genetically distinct from P. syringae pv. actinidiae strains isolated in France and in Italy, which appear to be closely related at the genetic level. In contrast, no structuring was observed for P. syringae pv. actinidifoliorum. We developed an MLVA scheme to explore the diversity within P. syringae pv. actinidiae biovar 3 and to trace the dispersal routes of epidemic P. syringae pv. actinidiae biovar 3 in Europe. We suggest using this MLVA scheme to trace the dispersal routes of P. syringae pv. actinidiae at a global level. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Can local adaptation explain varying patterns of herbivory tolerance in a recently introduced woody plant in North America?

PubMed Central

Bush, Susan E.; Grady, Kevin C.; Smith, David S.; Potts, Daniel L.; D'Antonio, Carla M.; Dudley, Tom L.; Fehlberg, Shannon D.; Gaskin, John F.; Glenn, Edward P.; Hultine, Kevin R.

2017-01-01

Abstract Patterns of woody-plant mortality have been linked to global-scale environmental changes, such as extreme drought, heat stress, more frequent and intense fires, and episodic outbreaks of insects and pathogens. Although many studies have focussed on survival and mortality in response to specific physiological stresses, little attention has been paid to the role of genetic heritability of traits and local adaptation in influencing patterns of plant mortality, especially in non-native species. Tamarix spp. is a dominant, non-native riparian tree in western North America that is experiencing dieback in some areas of its range due to episodic herbivory by the recently introduced northern tamarisk leaf beetle (Diorhabda carinulata). We propose that genotype × environment interactions largely underpin current and future patterns of Tamarix mortality. We anticipate that (i) despite its recent introduction, and the potential for significant gene flow, Tamarix in western North America is generally adapted to local environmental conditions across its current range in part due to hybridization of two species; (ii) local adaptation to specific climate, soil and resource availability will yield predictable responses to episodic herbivory; and (iii) the ability to cope with a combination of episodic herbivory and increased aridity associated with climate change will be largely based on functional tradeoffs in resource allocation. This review focusses on the potential heritability of plant carbon allocation patterns in Tamarix, focussing on the relative contribution of acquired carbon to non-structural carbohydrate (NSC) pools versus other sinks as the basis for surviving episodic disturbance. Where high aridity and/or poor edaphic position lead to chronic stress, NSC pools may fall below a minimum threshold because of an imbalance between the supply of carbon and its demand by various sinks. Identifying patterns of local adaptation of traits related to resource allocation will improve forecasting of Tamarix population susceptibility to episodic herbivory. PMID:28852513

Factors affecting fall down rates of dead aspen (Populus tremuloides) biomass following severe drought in west-central Canada.

PubMed

Ted Hogg, Edward H; Michaelian, Michael

2015-05-01

Increases in mortality of trembling aspen (Populus tremuloides Michx.) have been recorded across large areas of western North America following recent periods of exceptionally severe drought. The resultant increase in standing, dead tree biomass represents a significant potential source of carbon emissions to the atmosphere, but the timing of emissions is partially driven by dead-wood dynamics which include the fall down and breakage of dead aspen stems. The rate at which dead trees fall to the ground also strongly influences the period over which forest dieback episodes can be detected by aerial surveys or satellite remote sensing observations. Over a 12-year period (2000-2012), we monitored the annual status of 1010 aspen trees that died during and following a severe regional drought within 25 study areas across west-central Canada. Observations of stem fall down and breakage (snapping) were used to estimate woody biomass transfer from standing to downed dead wood as a function of years since tree death. For the region as a whole, we estimated that >80% of standing dead aspen biomass had fallen after 10 years. Overall, the rate of fall down was minimal during the year following stem death, but thereafter fall rates followed a negative exponential equation with k = 0.20 per year. However, there was high between-site variation in the rate of fall down (k = 0.08-0.37 per year). The analysis showed that fall down rates were positively correlated with stand age, site windiness, and the incidence of decay fungi (Phellinus tremulae (Bond.) Bond. and Boris.) and wood-boring insects. These factors are thus likely to influence the rate of carbon emissions from dead trees following periods of climate-related forest die-off episodes. © 2014 Her Majesty the Queen in Right of Canada Global Change Biology © 2014 John Wiley & Sons Ltd Reproduced with the permission of the Minister of Natural Resources Canada.

O-GlcNAc Transferase Is Essential for Sensory Neuron Survival and Maintenance

PubMed Central

Su, Cathy

2017-01-01

O-GlcNAc transferase (OGT) regulates a wide range of cellular processes through the addition of the O-GlcNAc sugar moiety to thousands of protein substrates. Because nutrient availability affects the activity of OGT, its role has been broadly studied in metabolic tissues. OGT is enriched in the nervous system, but little is known about its importance in basic neuronal processes in vivo. Here, we show that OGT is essential for sensory neuron survival and maintenance in mice. Sensory neuron-specific knock-out of OGT results in behavioral hyposensitivity to thermal and mechanical stimuli accompanied by decreased epidermal innervation and cell-body loss in the dorsal root ganglia. These effects are observed early in postnatal development and progress as animals age. Cultured sensory neurons lacking OGT also exhibit decreased axonal outgrowth. The effects on neuronal health in vivo are not solely due to disruption of developmental processes, because inducing OGT knock-out in the sensory neurons of adult mice results in a similar decrease in nerve fiber endings and cell bodies. Significant nerve-ending loss occurs before a decrease in cell bodies; this phenotype is indicative of axonal dieback that progresses to neuronal death. Our findings demonstrate that OGT is important in regulating axonal maintenance in the periphery and the overall health and survival of sensory neurons. SIGNIFICANCE STATEMENT We show the importance of O-GlcNAc transferase (OGT) for sensory neuron health and survival in vivo. This study is the first to find that loss of OGT results in neuronal cell death. Moreover, it suggests that aberrant O-GlcNAc signaling can contribute to the development of neuropathy. The sensory neurons lie outside of the blood–brain barrier and therefore, compared to central neurons, may have a greater need for mechanisms of metabolic sensing and compensation. Peripheral sensory neurons in particular are subject to degeneration in diabetes. Our findings provide a foundation for understanding the role of OGT under normal physiological conditions in the peripheral nervous system. This knowledge will be important for gaining greater insight into such disease states as diabetic neuropathy. PMID:28115479

Point of no return: experimental determination of the lethal hydraulic threshold during drought for loblolly pine (Pinus taeda)

NASA Astrophysics Data System (ADS)

Hammond, W.; Yu, K.; Wilson, L. A.; Will, R.; Anderegg, W.; Adams, H. D.

2017-12-01

The strength of the terrestrial carbon sink—dominated by forests—remains one of the greatest uncertainties in climate change modelling. How forests will respond to increased variability in temperature and precipitation is poorly understood, and experimental study to better inform global vegetation models in this area is needed. Necessary for achieving­­­­ this goal is an understanding of how increased temperatures and drought will affect landscape level distributions of plant species. Quantifying physiological thresholds representing a point of no return from drought stress, including thresholds in hydraulic function, is critical to this end. Recent theoretical, observational, and modelling research has converged upon a threshold of 60 percent loss of hydraulic conductivity at mortality (PLClethal). However, direct experimental determination of lethal points in conductivity and cavitation during drought is lacking. We quantified thresholds in hydraulic function in Loblolly pine, Pinus taeda, a commercially important timber species. In a greenhouse experiment, we exposed saplings (n = 96 total) to drought and rewatered treatment groups at variable levels of increasing water stress determined by pre-selected targets in pre-dawn water potential. Treatments also included a watered control with no drought, and drought with no rewatering. We measured physiological responses to water stress, including hydraulic conductivity, native PLC, water potential, foliar color, canopy die-back, and dark-adapted chlorophyll fluorescence. Following the rewatering treatment, we observed saplings for at least two months to determine which survived and which died. Using these data we calculated lethal physiological thresholds in water potential, directly measured PLC, and PLC inferred from water potential using a hydraulic vulnerability curve. We found that PLClethal inferred from water potential agreed with the 60% threshold suggested by previous research. However, directly measured PLC supported a much higher threshold. Beyond PLClethal, some trees survived by basal and epicormic re-sprouting, despite complete top-kill of existing foliage. Additional empirical study of multiple species to represent functional groups is needed to provide lethal thresholds for models presently in development.

An analysis of tree mortality using high resolution remotely-sensed data for mixed-conifer forests in San Diego county

NASA Astrophysics Data System (ADS)

Freeman, Mary Pyott

ABSTRACT An Analysis of Tree Mortality Using High Resolution Remotely-Sensed Data for Mixed-Conifer Forests in San Diego County by Mary Pyott Freeman The montane mixed-conifer forests of San Diego County are currently experiencing extensive tree mortality, which is defined as dieback where whole stands are affected. This mortality is likely the result of the complex interaction of many variables, such as altered fire regimes, climatic conditions such as drought, as well as forest pathogens and past management strategies. Conifer tree mortality and its spatial pattern and change over time were examined in three components. In component 1, two remote sensing approaches were compared for their effectiveness in delineating dead trees, a spatial contextual approach and an OBIA (object based image analysis) approach, utilizing various dates and spatial resolutions of airborne image data. For each approach transforms and masking techniques were explored, which were found to improve classifications, and an object-based assessment approach was tested. In component 2, dead tree maps produced by the most effective techniques derived from component 1 were utilized for point pattern and vector analyses to further understand spatio-temporal changes in tree mortality for the years 1997, 2000, 2002, and 2005 for three study areas: Palomar, Volcan and Laguna mountains. Plot-based fieldwork was conducted to further assess mortality patterns. Results indicate that conifer mortality was significantly clustered, increased substantially between 2002 and 2005, and was non-random with respect to tree species and diameter class sizes. In component 3, multiple environmental variables were used in Generalized Linear Model (GLM-logistic regression) and decision tree classifier model development, revealing the importance of climate and topographic factors such as precipitation and elevation, in being able to predict areas of high risk for tree mortality. The results from this study highlight the importance of multi-scale spatial as well as temporal analyses, in order to understand mixed-conifer forest structure, dynamics, and processes of decline, which can lead to more sustainable management of forests with continued natural and anthropogenic disturbance.

Tephra, trees, and trouble: forest dieback delays landslide response to pyroclastic eruption

NASA Astrophysics Data System (ADS)

Korup, Oliver; Seidemann, Jan; Mohr, Christian

2017-04-01

Large explosive eruptions may substantially transform landscapes by burying topography under thick layers of tephra. The excess pyroclastic sediment that is gradually washed into rivers following such eruptions is responsible for some of the highest specific sediment yields ever documented. The handful of detailed quantitative studies of such catastrophic fluvial response has hardly looked at how hillslopes respond to tephra loads, however. We studied whether three recent eruptions in Chile's Southern Volcanic Zone (SVZ) noticeably changed hillslope erosion rates, and found a strikingly delayed increase in shallow landslide activity. In the case of Chaitén volcano, which erupted in 2008, densely forested hillslopes nearby gained steadily in landslides abundance and area, and most rapidly some eight years after being covered by tephra. In 2016 alone, more than 75 per cent of the volume of all slope failures since the eruption (more than 2 million cubic metres) occurred in an area of 250 square kilometres around the volcano. Neighboring regions of comparable topography, forest cover, rainfall, and lithology have landslide rates at least ten times lower, so that we argue that successive loss of shear strength due to delayed tree-root decay and suppressed vegetation regrowth promotes slope failures near the volcano, especially where pristine rainforests were obliterated by tephra loads. These shallow landslides scrape sediment, soils, and dead wood from hillslopes, and reinforce the supply to rivers with high sediment and organic carbon loads nearly a decade after the eruption. We estimate that 0.1-0.2 Mt C were mobilized by these slope failures, and thus more than 25 per cent of the total post-eruptive organic carbon flux bound for the nearby north Patagonian fjords. Given that explosive eruptions in the SVZ have a mean return period of ca. 275 years, we propose that protracted landslide response of densely forested hillslopes to explosive eruptions plays an important, though largely ignored, part in long-term sediment and organic carbon budgets. Our results also indicate that monitoring of post-eruptive sediment and biogeochemical fluxes should account for lagged landslide response of tephra-covered forested hillslopes to avoid substantial underestimates.

Transcriptome responses of an ungrafted Phytophthora root rot tolerant avocado (Persea americana) rootstock to flooding and Phytophthora cinnamomi.

PubMed

Reeksting, B J; Olivier, N A; van den Berg, N

2016-09-22

Avocado (Persea americana Mill.) is a commercially important fruit crop worldwide. A major limitation to production is the oomycete Phytophthora cinnamomi, which causes root rot leading to branch-dieback and tree death. The decline of orchards infected with P. cinnamomi occurs much faster when exposed to flooding, even if flooding is only transient. Flooding is a multifactorial stress compromised of several individual stresses, making breeding and selection for tolerant varieties challenging. With more plantations occurring in marginal areas, with imperfect irrigation and drainage, understanding the response of avocado to these stresses will be important for the industry. Maintenance of energy production was found to be central in the response to flooding, as seen by up-regulation of transcripts related to glycolysis and induction of transcripts related to ethanolic fermentation. Energy-intensive processes were generally down-regulated, as evidenced by repression of transcripts related to processes such as secondary cell-wall biosynthesis as well as defence-related transcripts. Aquaporins were found to be down-regulated in avocado roots exposed to flooding, indicating reduced water-uptake under these conditions. The transcriptomic response of avocado to flooding and P. cinnamomi was investigated utilizing microarray analysis. Differences in the transcriptome caused by the presence of the pathogen were minor compared to transcriptomic perturbations caused by flooding. The transcriptomic response of avocado to flooding reveals a response to flooding that is conserved in several species. This data could provide key information that could be used to improve selection of stress tolerant rootstocks in the avocado industry.

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 implication of climate process uncertainties within the Earth System Framework

NASA Astrophysics Data System (ADS)

Booth, B.; Lambert, F. H.; McNeal, D.; Harris, G.; Sexton, D.; Boulton, C.; Murphy, J.

2011-12-01

Uncertainties in the magnitude of future climate change have been a focus of a great deal of research. Much of the work with General Circulation Models has focused on the atmospheric response to changes in atmospheric composition, while other processes remain outside these frameworks. Here we introduce an ensemble of new simulations, based on an Earth System configuration of HadCM3C, designed to explored uncertainties in both physical (atmospheric, oceanic and aerosol physics) and carbon cycle processes, using perturbed parameter approaches previously used to explore atmospheric uncertainty. Framed in the context of the climate response to future changes in emissions, the resultant future projections represent significantly broader uncertainty than existing concentration driven GCM assessments. The systematic nature of the ensemble design enables interactions between components to be explored. For example, we show how metrics of physical processes (such as climate sensitivity) are also influenced carbon cycle parameters. The suggestion from this work is that carbon cycle processes represent a comparable contribution to uncertainty in future climate projections as contributions from atmospheric feedbacks more conventionally explored. The broad range of climate responses explored within these ensembles, rather than representing a reason for inaction, provide information on lower likelihood but high impact changes. For example while the majority of these simulations suggest that future Amazon forest extent is resilient to the projected climate changes, a small number simulate dramatic forest dieback. This ensemble represents a framework to examine these risks, breaking them down into physical processes (such as ocean temperature drivers of rainfall change) and vegetation processes (where uncertainties point towards requirements for new observational constraints).

Future drying of the southern Amazon and central Brazil

NASA Astrophysics Data System (ADS)

Yoon, J.; Zeng, N.; Cook, B.

2008-12-01

Recent climate modeling suggests that the Amazon rainforest could exhibit considerable dieback under future climate change, a prediction that has raised considerable interest as well as controversy. To determine the likelihood and causes of such changes, we analyzed the output of 15 models from the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC/AR4) and a dynamic vegetation model VEGAS driven by these climate output. Our results suggest that the core of the Amazon rainforest should remain largely stable. However, the periphery, notably the southern edge, is in danger of drying out, driven by two main processes. First, a decline in precipitation of 24% in the southern Amazon lengthens the dry season and reduces soil moisture, despite of an increase in precipitation during the wet season, due to the nonlinear response in hydrology and ecosystem dynamics. Two dynamical mechanisms may explain the lower dry season precipitation: (1) a stronger north-south tropical Atlantic sea surface temperature gradient; (2) a general subtropical drying under global warming when the dry season southern Amazon is under the control of the subtropical high pressure. Secondly, evaporation will increase due to the general warming, thus also reducing soil moisture. As a consequence, the median of the models projects a reduction of vegetation by 20%, and enhanced fire carbon flux by 10-15% in the southern Amazon, central Brazil, and parts of the Andean Mountains. Because the southern Amazon is also under intense human influence, the double pressure of deforestation and climate change may subject the region to dramatic changes in the 21st century.

Synergy between land use and climate change increases future fire risk in Amazon forests

DOE PAGES

Le Page, Yannick; Morton, Douglas; Hartin, Corinne; ...

2017-12-20

Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, which are common under the current climate in frontier forests, may accelerate Amazon forest losses from climate-driven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactionsmore » between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change – Representative Concentration Pathway (RCP) 8.5 – projected understory fires increase in frequency and duration, burning 4–28 times more forest in 2080–2100 than during 1990–2010. In contrast, active climate mitigation and land use contraction in RCP4.5 constrain the projected increase in fire activity to 0.9–5.4 times contemporary burned area. Importantly, if climate mitigation is not successful, land use contraction alone is very effective under low to moderate climate change, but does little to reduce fire activity under the most severe climate projections. These results underscore the potential for a fire-driven transformation of Amazon forests if recent regional policies for forest conservation are not paired with global efforts to mitigate climate change.« less

Limitations and potential of satellite imagery to monitor environmental response to coastal flooding

USGS Publications Warehouse

Ramsey, Elijah W.; Werle, Dirk; Suzuoki, Yukihiro; Rangoonwala, Amina; Lu, Zhong

2012-01-01

Storm-surge flooding and marsh response throughout the coastal wetlands of Louisiana were mapped using several types of remote sensing data collected before and after Hurricanes Gustav and Ike in 2008. These included synthetic aperture radar (SAR) data obtained from the (1) C-band advance SAR (ASAR) aboard the Environmental Satellite, (2) phased-array type L-band SAR (PALSAR) aboard the Advanced Land Observing Satellite, and (3) optical data obtained from Thematic Mapper (TM) sensor aboard the Land Satellite (Landsat). In estuarine marshes, L-band SAR and C-band ASAR provided accurate flood extent information when depths averaged at least 80 cm, but only L-band SAR provided consistent subcanopy detection when depths averaged 50 cm or less. Low performance of inundation mapping based on C-band ASAR was attributed to an apparent inundation detection limit (>30 cm deep) in tall Spartina alterniflora marshes, a possible canopy collapse of shoreline fresh marsh exposed to repeated storm-surge inundations, wind-roughened water surfaces where water levels reached marsh canopy heights, and relatively high backscatter in the near-range portion of the SAR imagery. A TM-based vegetation index of live biomass indicated that the severity of marsh dieback was linked to differences in dominant species. The severest impacts were not necessarily caused by longer inundation but rather could be caused by repeated exposure of the palustrine marsh to elevated salinity floodwaters. Differential impacts occurred in estuarine marshes. The more brackish marshes on average suffered higher impacts than the more saline marshes, particularly the nearshore coastal marshes occupied by S. alterniflora.

Synergy between land use and climate change increases future fire risk in Amazon forests

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

Le Page, Yannick; Morton, Douglas; Hartin, Corinne

Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, which are common under the current climate in frontier forests, may accelerate Amazon forest losses from climate-driven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactionsmore » between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change – Representative Concentration Pathway (RCP) 8.5 – projected understory fires increase in frequency and duration, burning 4–28 times more forest in 2080–2100 than during 1990–2010. In contrast, active climate mitigation and land use contraction in RCP4.5 constrain the projected increase in fire activity to 0.9–5.4 times contemporary burned area. Importantly, if climate mitigation is not successful, land use contraction alone is very effective under low to moderate climate change, but does little to reduce fire activity under the most severe climate projections. These results underscore the potential for a fire-driven transformation of Amazon forests if recent regional policies for forest conservation are not paired with global efforts to mitigate climate change.« less

BFGF neutralization stimulates VEGF secretion in melanoma B16 cells.

PubMed

Wang, Zhiyong; Wei, Pei; Xiang, Junjian; Wang, Hong

2017-08-01

Fusarium root rot is a major cryptogamic disease in olive trees caused by the soil-borne fungus Fusarium solani. Controlling this disease requires the extensive use of chemicals. However, using BCAs such as some Trichoderma strains may be an opportune alternative to fungicides in protecting olive plantations. A new isolate (Fso14) was isolated from young olive trees showing severe dieback symptoms. The objective of this work was to analyze the biocontrol behavior of a Tunisian strain of T. harzianum (Ths97) on olive trees against Fso14 by assessing both mycoparasitic activity (in planta and in vitro) and ability to locally modulate different gene-related defenses of the plant. Ths97 was found to inhibit Fso14 growth in vitro. Optical microscopic analysis at the confrontation zone between hyphae showed that Ths97 grew alongside Fso14 with numerous contact points suggesting parasitic activity. On olive trees, Ths97 developed a strong protective role against root infestation by Fso14, whether inoculated before or after the pathogenic agent. When inoculated alone, Fso14 and Ths97 did not modulate (or only slightly with inhibitions or inductions, respectively) the expression of genes involved in plant immunity (oxidative stress, phenylpropanoid pathway, PR-proteins and JA/Et-SA hormonal status). However, when Ths97 was inoculated in combination with Fso14, several defense-related genes were highly up-regulated, indicating probable primed-plant events. These promising results provided valuable information on using Ths97 as a beneficial agent to control fusarium root rot disease caused by F. solani in olive trees. Copyright © 2017. Published by Elsevier Ltd.

Mass-wasting triggered by the end-Triassic mass-extinction

NASA Astrophysics Data System (ADS)

van de Schootbrugge, Bas; Vecoli, Marco; Strother, Paul; Lindstrom, Sofie; Oschmann, Wolfgang

2014-05-01

The end-Triassic dieback of tree-forming vegetation across NW Europe and the proliferation of a low-growing herbaceous pioneer vegetation composed of ferns and fern allies, likely had a major impact on weathering and erosion of emerged land masses. In a recently drilled core from northern Germany (Schandelah), palynological analyses provide evidence for this scenario. The uppermost Rhaetian Triletes Beds show increasing amounts of reworked Palaeozoic acritarchs and prasinophytes of up to 30% of the palynomorph fraction. Most of the acritarchs are singletons and can be assigned to Ordovician and Silurian species, such as Ankyrotrochus crispum, Oppilatala eoplanktonica, and Evittia spp. The average age of the reworked acritarch assemblages is observed to increase during the latest Rhaetian, leading to an inverted stratigraphy among Palaeozoic species. Further North, in the Stenlille cores from the Danish Basin, reworked Palaeozoic palynomorphs appear to constitute mainly sphaeromorphic prasinophytes and other Palaeozoic microfossils such as chitinozoans and carboniferous spores. Further south, at Mingolsheim (S Germany) the Triletes Beds contain a clear sign of soil reworking, including mycorrhizal fungal remains and cysts from probable soil organisms. These peculiar changes in palynological assemblages go hand-in-hand with important changes in sedimentology. The reworking of soil and bedrock is occurring in an interval that also contains evidence for earthquake activity in the form of widespread seismites. All these observations may be attributed to a number of mutually non-exclusive mechanisms, including decreased plant cover, an intensified hydrological cycle due to greenhouse warming, and the doming of the Central Atlantic Magmatic Province leading to continental-scale tectonic steepening of basin margins.

Water level fluctuations in a tropical reservoir: the impact of sediment drying, aquatic macrophyte dieback, and oxygen availability on phosphorus mobilization.

PubMed

Keitel, Jonas; Zak, Dominik; Hupfer, Michael

2016-04-01

Reservoirs in semi-arid areas are subject to water level fluctuations (WLF) that alter biogeochemical processes in the sediment. We hypothesized that wet-dry cycles may cause internal eutrophication in such systems when they affect densely vegetated shallow areas. To assess the impact of WLF on phosphorus (P) mobilization and benthic P cycling of iron-rich sediments, we tested the effects of (i) sediment drying and rewetting, (ii) the impact of organic matter availability in the form of dried Brazilian Waterweed (Egeria densa), and (iii) alternating redox conditions in the surface water. In principle, drying led to increased P release after rewetting both in plant-free and in plant-amended sediments. Highest P mobilization was recorded in plant amendments under oxygen-free conditions. After re-establishment of aerobic conditions, P concentrations in surface water decreased substantially owing to P retention by sediments. In desiccated and re-inundated sediments, P retention decreased by up to 30% compared to constantly inundated sediments. We showed that WLF may trigger biochemical interactions conducive to anaerobic P release. Thereby, E. densa showed high P release and even P uptake that was redox-controlled and superimposed sedimentary P cycling. Macrophytes play an important role in the uptake of P from the water but may be also a significant source of P in wet-dry cycles. We estimated a potential for the abrupt release of soluble reactive phosphorus (SRP) by E. densa of 0.09-0.13 g SRP per m(2) after each wet-dry cycle. Released SRP may exceed critical P limits for eutrophication, provoking usage restrictions. Our results have implications for management of reservoirs in semi-arid regions affected by WLF.

Extreme temperatures, foundation species, and abrupt ecosystem change: an example from an iconic seagrass ecosystem.

PubMed

Thomson, Jordan A; Burkholder, Derek A; Heithaus, Michael R; Fourqurean, James W; Fraser, Matthew W; Statton, John; Kendrick, Gary A

2015-04-01

Extreme climatic events can trigger abrupt and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under climate change, the impact of these events on many foundation species and the ecosystems they support remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia--a relatively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit--as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing climate. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the event compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Chelonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the event. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized framework for assessing the vulnerability of ecosystems to abrupt change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contribution to this framework. © 2014 John Wiley & Sons Ltd.

Recent Changes in the Riparian Forest of a Large Regulated Mediterranean River: Implications for Management

NASA Astrophysics Data System (ADS)

González, Eduardo; González-Sanchis, María; Cabezas, Álvaro; Comín, Francisco A.; Muller, Etienne

2010-04-01

The structure of the floodplain forests of the Middle Ebro River (NE Spain) was examined at patch and landscape scales along a three-step chronosequence defined according to the extent of flow regulation-induced hydrogeomorphic changes, with the ultimate purpose of producing baseline information to guide through management and restoration plans. At patch scale, a total of 6,891 stems within 39 plots were registered for species, diameter and health status. The stem density, size class distribution, canopy dieback and mortality were further compared by means of non-parametric tests. At landscape scale, the temporal evolution of the area occupied by forest stands of different ages in the floodplain along the chronosequence was evaluated using four sets of aerial photographs dated in 1927, 1957, 1981 and 2003. The within-patch structure of pioneer forests (<25-30 years old) was characterized by dense and healthy populations of pioneer species ( Populus nigra, Salix alba and Tamarix spp.), but the area occupied by these forest types has progressively decreased (up to 37%) since the intensification of river regulation (ca. 1957). In contrast, non-pioneer forests (>25-30 years old) were characterized by declining and sparse P. nigra- S. alba- Tamarix spp. stands, where late-seral species such as Ulmus minor and Fraxinus angustifolia were frequent, but only as small-size stems. At landscape scale, these type of senescent forests have doubled their surface after river regulation was intensified. Populus alba only appeared in the oldest plots recorded (colonized before 1957), suggesting sexual regeneration failure during the last five decades, but usually as healthy and dense stands. Based on these findings, measures principally aimed at recovering some hydrogeomorphic dynamism are recommended to guarantee the self-sustainability of the floodplain forest ecosystem.

Predicting the retreat and migration of tidal forests along the northern Gulf of Mexico under sea-level rise

USGS Publications Warehouse

Doyle, T.W.; Krauss, K.W.; Conner, W.H.; From, A.S.

2010-01-01

Tidal freshwater forests in coastal regions of the southeastern United States are undergoing dieback and retreat from increasing tidal inundation and saltwater intrusion attributed to climate variability and sea-level rise. In many areas, tidal saltwater forests (mangroves) contrastingly are expanding landward in subtropical coastal reaches succeeding freshwater marsh and forest zones. Hydrological characteristics of these low-relief coastal forests in intertidal settings are dictated by the influence of tidal and freshwater forcing. In this paper, we describe the application of the Sea Level Over Proportional Elevation (SLOPE) model to predict coastal forest retreat and migration from projected sea-level rise based on a proxy relationship of saltmarsh/mangrove area and tidal range. The SLOPE model assumes that the sum area of saltmarsh/mangrove habitat along any given coastal reach is determined by the slope of the landform and vertical tide forcing. Model results indicated that saltmarsh and mangrove migration from sea-level rise will vary by county and watershed but greater in western Gulf States than in the eastern Gulf States where millions of hectares of coastal forest will be displaced over the next century with a near meter rise in relative sea level alone. Substantial losses of coastal forests will also occur in the eastern Gulf but mangrove forests in subtropical zones of Florida are expected to replace retreating freshwater forest and affect regional biodiversity. Accelerated global eustacy from climate change will compound the degree of predicted retreat and migration of coastal forests with expected implications for ecosystem management of State and Federal lands in the absence of adaptive coastal management.

Diversity, Adaptability and Ecosystem Resilience

NASA Astrophysics Data System (ADS)

Keribin, Rozenn; Friend, Andrew

2013-04-01

Our ability to predict climate change and anticipate its impacts depends on Earth System Models (ESMs) and their ability to account for the high number of interacting components of the Earth System and to gauge both their influence on the climate and the feedbacks they induce. The land carbon cycle is a component of ESMs that is still poorly constrained. Since the 1990s dynamic global vegetation models (DGVMs) have become the main tool through which we understand the interactions between plant ecosystems and the climate. While DGVMs have made it clear the impacts of climate change on vegetation could be dramatic, predicting the dieback of rainforests and massive carbon losses from various ecosystems, they are highly variable both in their composition and their predictions. Their treatment of plant diversity and competition in particular vary widely and are based on highly-simplified relationships that do not account for the multiple levels of diversity and adaptability found in real plant ecosystems. The aim of this GREENCYCLES II project is to extend an individual-based DGVM to treat the diversity of physiologies found in plant communities and evaluate their effect if any on the ecosystem's transient dynamics and resilience. In the context of the InterSectoral Impacts Model Intercomparison Project (ISI-MIP), an initiative coordinated by a team at the Potsdam Institute for Climate Impact Research (PIK) that aims to provide fast-track global impact assessments for the IPCC's Fifth Assessment Report, we compare 6 vegetation models including 4 DGVMs under different climate change scenarios and analyse how the very different treatments of plant diversity and interactions from one model to the next affect the models' results. We then investigate a new, more mechanistic method of incorporating plant diversity into the DGVM "Hybrid" based on ecological tradeoffs mediated by plant traits and individual-based competition for light.

Phytotoxic Effects and Phytochemical Fingerprinting of Hydrodistilled Oil, Enriched Fractions, and Isolated Compounds Obtained from Cryptocarya massoy (Oken) Kosterm. Bark.

PubMed

Rolli, Enrico; Marieschi, Matteo; Maietti, Silvia; Guerrini, Alessandra; Grandini, Alessandro; Sacchetti, Gianni; Bruni, Renato

2016-01-01

The hydrodistilled oil of Cryptocarya massoy bark was characterized by GC-FID and GC/MS analyses, allowing the identification of unusual C10 massoia lactone (3, 56.2%), C12 massoia lactone (4, 16.5%), benzyl benzoate (1, 12.7%), C8 massoia lactone (3.4%), δ-decalactone (5, 1.5%), and benzyl salicylate (2, 1.8%) as main constituents. The phytotoxic activities of the oil, three enriched fractions (lactone-rich, ester-rich, and sesquiterpene-rich), and four constituents (compounds 1, 2, 5, and δ-dodecalactone (6)) against Lycopersicon esculentum and Cucumis sativus seeds and seedlings were screened. At a concentration of 1000 μl/l, the essential oil and the massoia lactone-rich fraction caused a complete inhibition of the germination of both seeds, and, when applied on tomato plantlets, they induced an 85 and 100% dieback, respectively. These performances exceeded those of the well-known phytotoxic essential oils of Syzygium aromaticum and Cymbopogon citratus, already used in commercial products for the weed and pest management. The same substances were also evaluated against four phytopathogenic bacteria and ten phytopathogenic fungi, providing EC50 values against the most susceptible strains in the 100-500 μl/l range for the essential oil and in the 10-50 μl/l range for compound 6 and the lactone-rich fraction. The phytotoxic behavior was related mainly to massoia lactones and benzyl esters, while a greater amount of 6 may infer a good activity against some phytopathogenic fungi. Further investigations of these secondary metabolites are warranted, to evaluate their use as natural herbicides. Copyright © 2016 Verlag Helvetica Chimica Acta AG, Zürich.

Above-Ground Dimensions and Acclimation Explain Variation in Drought Mortality of Scots Pine Seedlings from Various Provenances

PubMed Central

Seidel, Hannes; Menzel, Annette

2016-01-01

Seedling establishment is a critical part of the life cycle, thus seedling survival might be even more important for forest persistence under recent and future climate change. Scots pine forests have been disproportionally more affected by climate change triggered forest-dieback. Nevertheless, some Scots pine provenances might prove resilient to future drought events because of the species’ large distributional range, genetic diversity, and adaptation potential. However, there is a lack of knowledge on provenance-specific survival under severe drought events and on how acclimation alters survival rates in Scots pine seedlings. We therefore conducted two drought-induced mortality experiments with potted Scots pine seedlings in a greenhouse. In the first experiment, 760 three-year-old seedlings from 12 different provenances of the south-western distribution range were subjected to the same treatment followed by the mortality experiment in 2014. In the second experiment, we addressed the question of whether acclimation to re-occurring drought stress events and to elevated temperature might decrease mortality rates. Thus, 139 four-year-old seedlings from France, Germany, and Poland were subjected to different temperature regimes (2012–2014) and drought treatments (2013–2014) before the mortality experiment in 2015. Provenances clearly differed in their hazard of drought-induced mortality, which was only partly related to the climate of their origin. Drought acclimation decreased the hazard of drought-induced mortality. Above-ground dry weight and height were the main determinants for the hazard of mortality, i.e., heavier and taller seedlings were more prone to mortality. Consequently, Scots pine seedlings exhibit a considerable provenance-specific acclimation potential against drought mortality and the selection of suitable provenances might thus facilitate seedling establishment and the persistence of Scots pine forest. PMID:27458477

Mining-caused changes to habitat structure affect amphibian and reptile population ecology more than metal pollution.

PubMed

Sasaki, Kiyoshi; Lesbarrères, David; Watson, Glen; Litzgus, Jacqueline

2015-12-01

Emissions from smelting not only contaminate water and soil with metals, but also induce extensive forest dieback and changes in resource availability and microclimate. The relative effects of such co-occurring stressors are often unknown, but this information is imperative in developing targeted restoration strategies. We assessed the role and relative effects of structural alterations of terrestrial habitat and metal pollution caused by century-long smelting operations on amphibian and reptile communities by collecting environmental and time- and area-standardized multivariate abundance data along three spatially replicated impact gradients. Overall, species richness, diversity, and abundance declined progressively with increasing levels of metals (As, Cu, and Ni) and soil temperature (T(s)) and decreasing canopy cover, amount of coarse woody debris (CWD), and relative humidity (RH). The composite habitat variable (which included canopy cover, CWD, T(s), and RH) was more strongly associated with most response metrics than the composite metal variable (As, Cu, and Ni), and canopy cover alone explained 19-74% of the variance. Moreover, species that use terrestrial habitat for specific behaviors (e.g., hibernation, dispersal), especially forest-dependent species, were more severely affected than largely aquatic species. These results suggest that structural alterations of terrestrial habitat and concomitant changes in the resource availability and microclimate have stronger effects than metal pollution per se. Furthermore, much of the variation in response metrics was explained by the joint action of several environmental variables, implying synergistic effects (e.g., exacerbation of metal toxicity by elevated temperatures in sites with reduced canopy cover). We thus argue that the restoration of terrestrial habitat conditions is a key to successful recovery of herpetofauna communities in smelting-altered landscapes.

Recent changes in the riparian forest of a large regulated Mediterranean river: implications for management.

PubMed

González, Eduardo; González-Sanchis, María; Cabezas, Alvaro; Comín, Francisco A; Muller, Etienne

2010-04-01

The structure of the floodplain forests of the Middle Ebro River (NE Spain) was examined at patch and landscape scales along a three-step chronosequence defined according to the extent of flow regulation-induced hydrogeomorphic changes, with the ultimate purpose of producing baseline information to guide through management and restoration plans. At patch scale, a total of 6,891 stems within 39 plots were registered for species, diameter and health status. The stem density, size class distribution, canopy dieback and mortality were further compared by means of non-parametric tests. At landscape scale, the temporal evolution of the area occupied by forest stands of different ages in the floodplain along the chronosequence was evaluated using four sets of aerial photographs dated in 1927, 1957, 1981 and 2003. The within-patch structure of pioneer forests (<25-30 years old) was characterized by dense and healthy populations of pioneer species (Populus nigra, Salix alba and Tamarix spp.), but the area occupied by these forest types has progressively decreased (up to 37%) since the intensification of river regulation (ca. 1957). In contrast, non-pioneer forests (>25-30 years old) were characterized by declining and sparse P. nigra-S. alba-Tamarix spp. stands, where late-seral species such as Ulmus minor and Fraxinus angustifolia were frequent, but only as small-size stems. At landscape scale, these type of senescent forests have doubled their surface after river regulation was intensified. Populus alba only appeared in the oldest plots recorded (colonized before 1957), suggesting sexual regeneration failure during the last five decades, but usually as healthy and dense stands. Based on these findings, measures principally aimed at recovering some hydrogeomorphic dynamism are recommended to guarantee the self-sustainability of the floodplain forest ecosystem.

Histological Examination of Horse Chestnut Infection by Pseudomonas syringae pv. aesculi and Non-Destructive Heat Treatment to Stop Disease Progression

PubMed Central

de Keijzer, Jeroen; van den Broek, Lambertus A. M.; Ketelaar, Tijs; van Lammeren, André A. M.

2012-01-01

Since its emergence in Northwest Europe as a pathogen that infects trunks and branches of Aesculus spp. (the horse chestnuts) approximately one decade ago, Pseudomonas syringae pv. aesculi has rapidly established itself as major threat to these trees. Infected trees exhibit extensive necrosis of phloem and cambium, which can ultimately lead to dieback. The events after host entry leading to extensive necrosis are not well documented. In this work, the histopathology of this interaction is investigated and heat-treatment is explored as method to eradicate bacteria associated with established infections. The early wound-repair responses of A. hippocastanum, both in absence and presence of P. s. pv. aesculi, included cell wall lignification by a distinct layer of phloem and cortex parenchyma cells. The same cells also deposited suberin lamellae later on, suggesting this layer functions in compartmentalizing healthy from disrupted tissues. However, monitoring bacterial ingress, its construction appeared inadequate to constrain pathogen spread. Microscopic evaluation of bacterial dispersal in situ using immunolabelling and GFP-tagging of P. s. pv. aesculi, revealed two discriminative types of bacterial colonization. The forefront of lesions was found to contain densely packed bacteria, while necrotic areas housed bacterial aggregates with scattered individuals embedded in an extracellular matrix of bacterial origin containing alginate. The endophytic localization and ability of P. s. pv aesculi to create a protective matrix render it poorly accessible for control agents. To circumvent this, a method based on selective bacterial lethality at 39°C was conceived and successfully tested on A. hippocastanum saplings, providing proof of concept for controlling this disease by heat-treatment. This may be applicable for curing other tree cankers, caused by related phytopathogens. PMID:22808044

Histological examination of horse chestnut infection by Pseudomonas syringae pv. aesculi and non-destructive heat treatment to stop disease progression.

PubMed

de Keijzer, Jeroen; van den Broek, Lambertus A M; Ketelaar, Tijs; van Lammeren, André A M

2012-01-01

Since its emergence in Northwest Europe as a pathogen that infects trunks and branches of Aesculus spp. (the horse chestnuts) approximately one decade ago, Pseudomonas syringae pv. aesculi has rapidly established itself as major threat to these trees. Infected trees exhibit extensive necrosis of phloem and cambium, which can ultimately lead to dieback. The events after host entry leading to extensive necrosis are not well documented. In this work, the histopathology of this interaction is investigated and heat-treatment is explored as method to eradicate bacteria associated with established infections. The early wound-repair responses of A. hippocastanum, both in absence and presence of P. s. pv. aesculi, included cell wall lignification by a distinct layer of phloem and cortex parenchyma cells. The same cells also deposited suberin lamellae later on, suggesting this layer functions in compartmentalizing healthy from disrupted tissues. However, monitoring bacterial ingress, its construction appeared inadequate to constrain pathogen spread. Microscopic evaluation of bacterial dispersal in situ using immunolabelling and GFP-tagging of P. s. pv. aesculi, revealed two discriminative types of bacterial colonization. The forefront of lesions was found to contain densely packed bacteria, while necrotic areas housed bacterial aggregates with scattered individuals embedded in an extracellular matrix of bacterial origin containing alginate. The endophytic localization and ability of P. s. pv aesculi to create a protective matrix render it poorly accessible for control agents. To circumvent this, a method based on selective bacterial lethality at 39 °C was conceived and successfully tested on A. hippocastanum saplings, providing proof of concept for controlling this disease by heat-treatment. This may be applicable for curing other tree cankers, caused by related phytopathogens.

Acidic fog and temperature effects on stigmatic receptivity in two birch species

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

Hughes, R.N.; Cox, R.M.

Factorial assays were performed to determine the effects of simulated acid fog (SAF) and temperature on stigmatic receptivity in two birch species. Excised reproductive branches were sampled from representative individuals of mountain paper birch (Betula cordifolia Regel.) and paper birch (Betula papyrifera Marsh.) in populations adjacent to the Bay of Fundy, New Brunswick, Canada. Since 1979 these trees have exhibited branch dieback in association with abnormal foliar browning symptoms. This browning has been linked with acidity and nitrate deposited by fog, which is frequent in the area. In general, experimental results indicated that pollen germination increased with temperature, but pHmore » effects were less obvious. Similarly, pollen tube growth responded positively to temperature and was little affected by fog acidity. ANOVA tests indicated a significant difference (P < 0.05) between species in their pollen germination response only at 12{degrees}C, and not at the other three temperatures tested. For pollen tube growth, significant differences between species (P < 0.05) were demonstrated at 12 and 22{degrees}C. A significant pH effect was demonstrated at 27{degrees}C for germination, while pH effects on tube growth were significant at 27 and 12{degrees}C (P < 0.01). A response surface regression analysis indicated that acidity significantly affected pollen germination in mountain paper birch (P < 0.001) but not in paper birch. Temperature was not a significant factor for in vivo pollen germination in either species. For pollen tube growth, however, temperature was more important than pH and produced highly significant effects in both species (P < 0.001). Acidity was also a significant factor in pollen tube growth for paper birch. 39 refs., 4 figs., 3 tabs.« less

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

Van Voris, P.; Ligotke, M.W.; McFadden, K.M.

An evaluation of the terrestrial transport, transformations and ecological effects of phosphorus (red phosphorus-butyl rubber (RP/BR)) smoke obscurant was performed at Pacific Northwest Laboratory. A similar evaluation using white phosphorus (WP) smoke/obscurant is currently proceeding. The objective is to characterize the effects of smokes and obscurants on: (1) natural vegetation characteristic of US Army training sites in the United States; (2) physical and chemical properties of representative of soils of those sites; and (3) soil microbiological communities. The influence and interactions of smoke/obscurant concentration, relative humidity (25%, 60%, 90% and simulated rain) and wind speed of 0.22 to 4.45 m/smore » by smoke is assessed. Five plant species and four soils were exposed to both single and repeated doses of RP/BR smokes in the Pacific Northwest Laboratory ''P-3'' rated recirculating environmental wind tunnel. Detailed results for RP/BR and limited results for WP are presented. Toxicity symptoms for plants exposed for 2, 4, 6, and 8 hours to concentrations of RP/BR ranging from 200 mg/m/sup 3/ included leaf tip burn, leaf curl, leaf abscission and drop, floral abortion, chlorosis, neucrotic spotting, wilting, desiccation and dieback. Grass and bushbean were the most sensitive. The intensity and duration of these effects varied. Soils effects data suggest that there is an increase in the mobility of selected trace elements after exposure; however, this effect appears to be ameliorated with time. Soil microbial community effects show a reduction in the production of nitrate after soil is exposed to RP/BR smoke. Most of the plant, soil and soil microbial effects are transient in nature and are somewhat less intense resulting from repeated exposures; however, there is evidence that some of these environmental impacts may be persistent. 43 refs., 44 figs., 67 tabs.« less

Climate-Induced Boreal Forest Change: Predictions versus Current Observations

NASA Technical Reports Server (NTRS)

Soja, Amber J.; Tchebakova, Nadezda M.; French, Nancy H. F.; Flannigan, Michael D.; Shugart, Herman H.; Stocks, Brian J.; Sukhinin, Anatoly I.; Parfenova, E. I.; Chapin, F. Stuart, III; Stackhouse, Paul W., Jr.

2007-01-01

For about three decades, there have been many predictions of the potential ecological response in boreal regions to the currently warmer conditions. In essence, a widespread, naturally occurring experiment has been conducted over time. In this paper, we describe previously modeled predictions of ecological change in boreal Alaska, Canada and Russia, and then we investigate potential evidence of current climate-induced change. For instance, ecological models have suggested that warming will induce the northern and upslope migration of the treeline and an alteration in the current mosaic structure of boreal forests. We present evidence of the migration of keystone ecosystems in the upland and lowland treeline of mountainous regions across southern Siberia. Ecological models have also predicted a moisture-stress-related dieback in white spruce trees in Alaska, and current investigations show that as temperatures increase, white spruce tree growth is declining. Additionally, it was suggested that increases in infestation and wildfire disturbance would be catalysts that precipitate the alteration of the current mosaic forest composition. In Siberia, five of the last seven years have resulted in extreme fire seasons, and extreme fire years have also been more frequent in both Alaska and Canada. In addition, Alaska has experienced extreme and geographically expansive multi-year outbreaks of the spruce beetle, which had been previously limited by the cold, moist environment. We suggest that there is substantial evidence throughout the circumboreal region to conclude that the biosphere within the boreal terrestrial environment has already responded to the transient effects of climate change. Additionally, temperature increases and warming-induced change are progressing faster than had been predicted in some regions, suggesting a potential non-linear rapid response to changes in climate, as opposed to the predicted slow linear response to climate change.

Phacidiopycnis washingtonensis--a new species associated with pome fruits from Washington State.

PubMed

Xiao, C L; Rogers, J D; Kim, Y K; Liu, Q

2005-01-01

A new species of Phacidiopycnis associated with pome fruits is described. The fungus causes fruit rot on apples during storage and is associated with a twig dieback and canker disease of crabapple trees and dead twigs of pear trees. To characterize the biology of the fungus and compare it with Ph. piri, the type species of the genus, effects of nine media and light on mycelial growth and pycnidial production, mycelial growth in response to temperature and mode of conidial germination in response to nutrient were determined. Apple-juice agar, pear-juice agar, prune-juice agar, potato-dextrose agar (PDA) and malt-extract agar, Czapek-Dox agar and oatmeal agar (OMA) favored mycelial growth. Cornmeal agar (CMA) did not favor mycelial growth. Light effect on pycnidial formation was medium dependent. Abundant pycnidia with mature conidia formed in 14 d old PDA and OMA cultures at 20 C, regardless of light, whereas none or very few pycnidia formed on other media in the dark. Fluorescent light stimulated formation of pycnidia except on CMA. The fungus grew at -3-25 C, with optimum growth at 15-20 C. Conidia germinated either by forming germ tubes or less often by budding. Budding of conidia occurred in 1 and 10% pear-juice solutions but not in 100% pear-juice solution. Six isolates of Ph. washingtonensis from different species of pome fruits had identical ITS sequences. The sizes of the ITS region were the same for both Ph. washingtonensis and Ph. piri, and four polymorphic nucleotide sites were found in the ITS region between Ph. washingtonensis and Ph. piri. The similarity in ITS sequences between these two taxa is confirmatory evidence for the erection of the new species of Phacidiopycnis associated with pome fruits we describe here.

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

Uranga, Carla C., E-mail: curanga@cicese.edu.mx; Beld, Joris, E-mail: joris.beld@drexelmed.edu; Mrse, Anthony, E-mail: amrse@ucsd.edu

The Botryosphaeriaceae are a family of trunk disease fungi that cause dieback and death of various plant hosts. This work sought to characterize fatty acid derivatives in a highly virulent member of this family, Lasiodiplodia theobromae. Nuclear magnetic resonance and gas chromatography-mass spectrometry of an isolated compound revealed (Z, Z)-9,12-ethyl octadecadienoate, (trivial name ethyl linoleate), as one of the most abundant fatty acid esters produced by L. theobromae. A variety of naturally produced esters of fatty acids were identified in Botryosphaeriaceae. In comparison, the production of fatty acid esters in the soil-borne tomato pathogen Fusarium oxysporum, and the non-phytopathogenic fungusmore » Trichoderma asperellum was found to be limited. Ethyl linoleate, ethyl hexadecanoate (trivial name ethyl palmitate), and ethyl octadecanoate, (trivial name ethyl stearate), significantly inhibited tobacco seed germination and altered seedling leaf growth patterns and morphology at the highest concentration (0.2 mg/mL) tested, while ethyl linoleate and ethyl stearate significantly enhanced growth at low concentrations, with both still inducing growth at 98 ng/mL. This work provides new insights into the role of naturally esterified fatty acids from L. theobromae as plant growth regulators with similar activity to the well-known plant growth regulator gibberellic acid. - Highlights: • Lasiodiplodia theobromae produces a wide variety of fatty acid esters in natural substrates. • Ethyl stearate and ethyl linoleate inhibit tobacco germination at 0.2 mg/mL. • Ethyl stearate and ethyl linoleate induce tobacco germination at 98 ng/mL. • Tobacco growth increase in ethyl stearate and ethyl linoleate parallels gibberellic acid. • A role as plant growth regulators is proposed for fatty acid esters.« less

Belowground processes regulate ecosystem nitrogen retention during a multi-year forest dieback event

NASA Astrophysics Data System (ADS)

Nave, L. E.; Le Moine, J.; Gough, C. M.; Vogel, C.; Nadelhoffer, K. J.; Curtis, P.

2013-12-01

In the absence of disturbances, forests typically have strong retention capacity for nitrogen (N), which is internally recycled between soil, microbial and plant pools. However, disturbances that trigger senescence or mortality of forest vegetation may alter internal N cycling processes and lead to the loss of ecosystem N retention capacity. Here, we present an assessment of the role played by belowground processes in governing ecosystem N cycling and retention during an experimental disturbance that killed the dominant canopy taxa in a Great Lakes forest over a 4-year period. After applying stem girdling to hasten the age-related senescence of the dominant taxa (Populus and Betula spp.; ~35% of the basal area), we observed a 38% decrease in stand-level allocation of nonstructural carbohydrates to fine roots, which triggered a tenfold increase in the rate of fine root turnover and increased soil NH4+ and NO3- availability. Elevated soil N availability decreased mycorrhizal hyphal foraging and N uptake, effectively down-regulating the role of symbiotic fungi in the N nutrition of the residual (longer-lived) tree taxa. However, even as residual trees took up less N from mycorrhizal sources, their overall N uptake increased and served to offset the loss of the dominant taxa. The net result of this offset was that canopy N stocks remained constant through the disturbance period and there was no appreciable loss of ecosystem N stocks due to leaching or gaseous export. In sum, the cascade of changes in root, microbial, and soil processes during this experiment indicates that these interdependent components of the belowground system comprised a mechanism responsible for retention and redistribution of ecosystem N stocks during the disturbance period.

Path Dependence of Regional Climate Change

NASA Astrophysics Data System (ADS)

Herrington, Tyler; Zickfeld, Kirsten

2013-04-01

Path dependence of the climate response to CO2 forcing has been investigated from a global mean perspective, with evidence suggesting that long-term global mean temperature and precipitation changes are proportional to cumulative CO2 emissions, and independent of emissions pathway. Little research, however, has been done on path dependence of regional climate changes, particularly in areas that could be affected by tipping points. Here, we utilize the UVic Earth System Climate Model version 2.9, an Earth System Model of Intermediate Complexity. It consists of a 3-dimensional ocean general circulation model, coupled with a dynamic-thermodynamic sea ice model, and a thermodynamic energy-moisture balance model of the atmosphere. This is then coupled with a terrestrial carbon cycle model and an ocean carbon-cycle model containing an inorganic carbon and marine ecosystem component. Model coverage is global with a zonal resolution of 3.6 degrees and meridional resolution of 1.8 degrees. The model is forced with idealized emissions scenarios across five cumulative emission groups (1300 GtC, 2300 GtC, 3300 GtC, 4300 GtC, and 5300 GtC) to explore the path dependence of (and the possibility of hysteresis in) regional climate changes. Emission curves include both fossil carbon emissions and emissions from land use changes, and span a variety of peak and decline scenarios with varying emission rates, as well as overshoot and instantaneous pulse scenarios. Tipping points being explored include those responsible for the disappearance of summer Arctic sea-ice, the irreversible melt of the Greenland Ice Sheet, the collapse of the Atlantic Thermohaline Circulation, and the dieback of the Amazonian Rainforest. Preliminary results suggest that global mean climate change after cessation of CO2 emissions is independent of the emissions pathway, only varying with total cumulative emissions, in accordance with results from earlier studies. Forthcoming analysis will investigate path dependence of regional climate change. Some evidence exists to support the idea of hysteresis in the Greenland Ice Sheet, and since tipping points represent non-linear elements of the climate system, we suspect that the other tipping points might also show path dependence.

The roles of community biomass and species pools in the regulation of plant diversity

USGS Publications Warehouse

Grace, J.B.

2001-01-01

Considerable debate has developed over the importance of community biomass and species pools in the regulation of community diversity. Attempts to explain patterns of plant diversity as a function of community biomass or productivity have been only partially successful and in general, have explained only a fraction of the observed variation in diversity. At the same time studies that have focused on the importance of species pools have led some to conclude that diversity is primarily regulated in the short term by the size of the species pool rather than by biotic interactions. In this paper, I explore how community biomass and species pools may work in combination to regulate diversity in herbaceous plant communities. To address this problem, I employ a simple model in which the dynamics of species richness are a function of aboveground community biomass and environmentally controlled gradients in species pools. Model results lead to two main predictions about the role of biomass regulation: (1) Seasonal dynamics of richness will tend to follow a regular oscillation, with richness rising to peak values during the early to middle portion of the growing season and then declining during the latter part of the season. (2.) Seasonal dieback of aboveground tissues facilitates the long-term maintenance of high levels of richness in the community. The persistence of aboveground tissues and accumulation of litter are especially important in limiting the number of species through the suppression of recruitment. Model results also lead to two main predictions about the role of species pools: (1) The height and position of peak richness relative to community biomass will be influenced by the rate at which the species pool increases as available soil resources increase. (2) Variations in nonresource environmental factors (e.g. soil pH or soil salinity) have the potential to regulate species pools in a way that is uncorrelated with aboveground biomass. Under extreme conditions, such nonresource effects can create a unimodal envelope of biomass-richness values. Available evidence from the literature provides partial support for these predictions, though additional data are needed to provide more convincing tests.

Groundwater-dependent ecosystems: recent insights, new techniques and an ecosystem-scale threshold response

NASA Astrophysics Data System (ADS)

Eamus, D.; Zolfaghar, S.; Villalobos-Vega, R.; Cleverly, J.; Huete, A.

2015-05-01

Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs; and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs. We discuss three methods for identifying GDEs: (1) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration, (2) stable isotope analysis of water sources in the transpiration stream; and (3) remote sensing methods. We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of ET using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the "White method" to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration vs. evaporation (e.g., using stable isotopes) or from groundwater vs. rainwater sources. Groundwater extraction can have severe consequences on structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and discuss the use of C isotope ratios in xylem to reveal past influences of GW extraction. We conclude with a discussion of a depth-to-groundwater threshold in mesic and semi-arid GDEs. Across this threshold, significant changes occur in ecosystem structure and function.

On the relative magnitudes of photosynthesis, respiration, growth and carbon storage in vegetation

NASA Astrophysics Data System (ADS)

van Oijen, M.

2012-04-01

• Background and Aims. The carbon balance of vegetation is dominated by the two large fluxes of photosynthesis (P) and respiration (R). Mechanistic models have attempted to simulate the two fluxes separately, each with their own set of internal and external controls. This has led to model predictions where environmental change causes R to exceed P, with consequent dieback of vegetation. However, empirical evidence suggests that the R:P ratio is constrained to a narrow range of about 0.4-0.5. Physiological explanations for the narrow range are not conclusive. We aim to introduce a novel perspective by theoretical study of the quantitative relationship between the four carbon fluxes of P, R, growth and storage (or its inverse, remobilisation). • Methods. Starting from the law of conservation of mass - in this case carbon - we derive equations for the relative magnitudes of all carbon fluxes which depend on only two parameters: the R:P ratio and the relative rate of storage of carbon into remobilisable reserves. The equations are used to explain observed flux ratios and to analyse incomplete data sets of carbon fluxes. • Key Results. Storage rate is shown to be a freely varying parameter, whereas R:P is narrowly constrained. This explains the constancy of the ratio reported in the literature. With the information thus gained, a data set of R and P in grassland was analysed, and flux estimates could be derived for the periods after cuts in which plant growth is dominated by remobilisation before photosynthesis takes over. • Conclusions. We conclude that the relative magnitudes of photosynthesis, respiration, growth and substrate storage are indeed tightly constrained, but because of mass conservation rather than for physiological reasons. This facilitates analysis of incomplete data sets. Mechanistic models, as the embodiment of physiological mechanisms, need to show consistency with the constraints. • Reference. Van Oijen, M., Schapendonk, A. & Höglind, M. (2010). On the relative magnitudes of photosynthesis, respiration, growth and carbon storage in vegetation. Annals of Botany 105: 793-797.

Temporal trends of bulk precipitation and stream water chemistry (1977-1997) in a small forested area, Krusne hory, northern Bohemia, Czech Republic

USGS Publications Warehouse

Peters, N.E.; Cerny, J.; Havel, M.; Krejci, R.

1999-01-01

The Krusne hory (Erzgebirge or Ore Mountains) has been heavily affected by high atmospheric pollutant deposition caused by fossil fuel combustion in an adjacent Tertiary coal basin. Long-term routine sampling of bulk precipitation (1977-1996) and stream water (1977-1998) in a forested area on the south-eastern slope of the mountains were used to evaluate trends and patterns in solute concentration and flux with respect to controlling processes. From 1977 to 1996, the annual volume-weighted Ca2+ and SO42- concentrations decreased in bulk precipitation. However, after 1989, when a pronounced and continuous decrease occurred in coal production, annual volume-weighted concentrations decreased for most solutes, except H+. The concentration decreases were marked, with 1996 levels at or below 50% of those in 1989. The lack of a trend in H+ is attributed to similar decreases in both acid anions and neutralizing base cations. Stream water concentrations of most solutes, i.e. H+, Ca2+, Mg2+, SO42- and NO3-, were highest at the onset of sampling in 1977, decreased markedly from 1977 to 1983 and decreased more gradually from 1983 to 1998. The spruce forest die-back and removal reduced dry deposition of these solutes by reducing the filtering action, which was provided by the forest canopy. A notable decrease in stream water Ca2+ concentrations occurred after 1995 and may be due to the depletion of Ca2+, which was provided by catchment liming in 1986, 1988 and 1989. Solute flux trends in bulk atmospheric deposition and stream water generally were not significant and the lack of trend is attributed to the large interannual variability in precipitation quantity and runoff, respectively. All solutes except Na+ varied seasonally. The average seasonal concentrations varied between the solutes, but for most solutes were highest in winter and spring and lowest in summer, correlating with the seasonal trend and runoff. For Ca2+, Mg2+ and SO42-, the concentration minimum occurs in September and the maximum occurs in February or March, correlating with the seasonal baseflow. These solutes are primarily controlled by the contribution of soil water and groundwater to stream flow. During snowmelt, the meltwater generally causes concentrations to decrease as soil water and groundwater are diluted. For NO3, average minimum concentrations occur in August at the end of the growing season concurrent with the lowest stream flow, and the maximum occurs in February and March with high stream flow during snowmelt. Seasonal stream water NO3- concentration variations are large compared with the long-term decrease.The Krusne hory (Erzgebirge or Ore Mountains) has been heavily affected by high atmospheric pollutant deposition caused by fossil fuel combustion in an adjacent Tertiary coal basin. Long-term routine sampling of bulk precipitation (1977-1996) and stream water (1977-1998) in a forested area on the south-eastern slope of the mountains were used to evaluate trends and patterns in solute concentration and flux with respect to controlling processes. From 1977 to 1996, the annual volume-weighted Ca2+ and SO42- concentrations decreased in bulk precipitation. However, after 1989, when a pronounced and continuous decrease occurred in coal production, annual volume-weighted concentrations decreased for most solutes, except H+. The concentration decreases were marked, with 1996 levels at or below 50% of those in 1989. The lack of a trend in H+ is attributed to similar decreases in both acid anions and neutralizing base cations. Stream water concentrations of most solutes, i.e. H+, Ca2+, Mg2+, SO42- and NO3-, were highest at the onset of sampling in 1977, decreased markedly from 1977 to 1983 and decreased more gradually from 1983 to 1998. The spruce forest die-back and removal reduced dry deposition of these solutes by reducing the filtering action, which was provided by the forest canopy. A notable decrease in stream water Ca2+ concentrations occurred after 1995 an

The Jena Diversity Model: Towards a Richer Representation of the Terrestrial Biosphere for Earth System Modelling

NASA Astrophysics Data System (ADS)

Pavlick, R.; Reu, B.; Bohn, K.; Dyke, J.; Kleidon, A.

2010-12-01

The terrestrial biosphere is a complex, self-organizing system which is continually both adapting to and altering its global environment. It also exhibits a vast diversity of vegetation forms and functioning. However, the terrestrial biosphere components within current state-of-the-art Earth System Models abstract this diversity in to a handful of relatively static plant functional types. These coarse and static representations of functional diversity might contribute to overly pessimistic projections regarding terrestrial ecosystem responses to scenarios of global change (e.g. Amazonian and boreal forest diebacks). In the Jena Diversity (JeDi) model, we introduce a new approach to vegetation modelling with a richer representation of functional diversity, based not on plant functional types, but on unavoidable plant ecophysiological trade-offs, which we hypothesize should be more stable in time. The JeDi model tests a large number of plant growth strategies. Each growth strategy is simulated using a set of randomly generated parameter values, which characterize its functioning in terms of carbon allocation, ecophysiology, and phenology, which are then linked to the growing conditions at the land surface. The model is constructed in such a way that these parameters inherently lead to ecophysiological trade-offs, which determine whether a growth strategy is able to survive and reproduce under the prevalent climatic conditions. Kleidon and Mooney (2000) demonstrated that this approach is capable of reproducing the geographic distribution of species richness. More recently, we have shown the JeDi model can explain other biogeographical phenomena including the present-day global pattern of biomes (Reu et al., accepted), ecosystem evenness (Kleidon et al. 2009), and possible mechanisms for biome shifts and biodiversity changes under scenarios of global warming (Reu et al., submitted). We have also evaluated the simulated biogeochemical fluxes from JeDi against a variety of site, field, and satellite observations (Pavlick et al., submitted) following a protocol established by the Carbon-Land Model Intercomparison Project (Randerson et al. 2009). We found that the global patterns of biogeochemical fluxes and land surface properties are reasonably well simulated using this bottom-up trade-off approach and compare favorably with other state of the art terrestrial biosphere models. Here, we present some results from JeDi simulations, wherein we varied the modelled functional diversity to quantify its impact on terrestrial biogeochemical fluxes under both present-day conditions and projected scenarios of global change. We also present results from a set of simulations wherein we vary the ability of the modelled ecosystems to adapt through changes in functional composition, leading to different projection responses of the carbon cycle to global warming. This plant functional tradeoff approach sets the foundation for many applications, including exploring the emergence and climatic impacts of major vegetation transitions throughout the last 400 million years as well as quantifying the significance of preserving functional diversity to hedge against uncertain climates in the future.

Vegetation-climate feedback causes reduced precipitation and tropical rainforest cover in CMIP5 regional Earth system model simulation over Africa

NASA Astrophysics Data System (ADS)

Wu, M.; Smith, B.; Samuelsson, P.; Rummukainen, M.; Schurgers, G.

2012-12-01

We applied a coupled regional climate-vegetation model, RCA-GUESS (Smith et al. 2011), over the CORDEX Africa domain, forced by boundary conditions from a CanESM2 CMIP5 simulation under the RCP8.5 future climate scenario. The simulations were from 1961 to 2100 and covered the African continent at a horizontal grid spacing of 0.44°. RCA-GUESS simulates changes in the phenology, productivity, relative cover and population structure of up to eight plant function types (PFTs) in response to forcing from the climate part of the model. These vegetation changes feed back to simulated climate through dynamic adjustments in surface energy fluxes and surface properties. Changes in the net ecosystem-atmosphere carbon flux and its components net primary production (NPP), heterotrophic respiration and emissions from biomass burning were also simulated but do not feed back to climate in our model. Constant land cover was assumed. We compared simulations with and without vegetation feedback switched "on" to assess the influence of vegetation-climate feedback on simulated climate, vegetation and ecosystem carbon cycling. Both positive and negative warming feedbacks were identified in different parts of Africa. In the Sahel savannah zone near 15°N, reduced vegetation cover and productivity, and mortality caused by a deterioration of soil water conditions led to a positive warming feedback mediated by decreased evapotranspiration and increased sensible heat flux between vegetation and the atmosphere. In the equatorial rainforest stronghold region of central Africa, a feedback syndrome characterised by reduced plant production and LAI, a dominance shift from tropical trees to grasses, reduced soil water and reduced rainfall was identified. The likely underlying mechanism was a decline in evaporative water recycling associated with sparser vegetation cover, reminiscent of Earth system model studies in which a similar feedback mechanism was simulated to force dieback of tropical rainforest and reduced precipitation over the Amazon Basin (Cox et al. 2000; Betts et al. 2004; Malhi et al. 2009). Opposite effects are seen in southern Senegal, southern Mali, northern Guinea and Guinea-Bissau, positive evapotranspiration feedback enhancing the cover of trees in forest and savannah, mitigating warming and promoting local moisture recycling as rainfall. Our study, the first application of a coupled Earth system model at regional scale and resolution over Africa, reveals that vegetation-climate feedbacks may significantly impact the magnitude and character of simulated changes in climate as well as vegetation and ecosystems in future scenario studies of this region. They should be accounted for in future studies of climate change and its impacts on Africa.

Climate, streamflow, and legacy effects on growth of riparian Populus angustifolia in the arid San Luis Valley, Colorado

USGS Publications Warehouse

Andersen, Douglas

2016-01-01

Knowledge of the factors affecting the vigor of desert riparian trees is important for their conservation and management. I used multiple regression to assess effects of streamflow and climate (12–14 years of data) or climate alone (up to 60 years of data) on radial growth of clonal narrowleaf cottonwood (Populus angustifolia), a foundation species in the arid, Closed Basin portion of the San Luis Valley, Colorado. I collected increment cores from trees (14–90 cm DBH) at four sites along each of Sand and Deadman creeks (total N = 85), including both perennial and ephemeral reaches. Analyses on trees <110 m from the stream channel explained 33–64% of the variation in standardized growth index (SGI) over the period having discharge measurements. Only 3 of 7 models included a streamflow variable; inclusion of prior-year conditions was common. Models for trees farther from the channel or over a deep water table explained 23–71% of SGI variability, and 4 of 5 contained a streamflow variable. Analyses using solely climate variables over longer time periods explained 17–85% of SGI variability, and 10 of 12 included a variable indexing summer precipitation. Three large, abrupt shifts in recent decades from wet to dry conditions (indexed by a seasonal Palmer Drought Severity Index) coincided with dramatically reduced radial growth. Each shift was presumably associated with branch dieback that produced a legacy effect apparent in many SGI series: uncharacteristically low SGI in the year following the shift. My results suggest trees in locations distant from the active channel rely on the regional shallow unconfined aquifer, summer rainfall, or both to meet water demands. The landscape-level differences in the water supplies sustaining these trees imply variable effects from shifts in winter-versus monsoon-related precipitation, and from climate change versus streamflow or groundwater management.

Population collapse dynamics in Acropora downingi, an Arabian/Persian Gulf ecosystem-engineering coral, linked to rising temperature.

PubMed

Riegl, Bernhard; Johnston, Matthew; Purkis, Sam; Howells, Emily; Burt, John; Steiner, Sascha C C; Sheppard, Charles R C; Bauman, Andrew

2018-03-05

As in the tropical Atlantic, Acropora populations in the southern Persian/Arabian Gulf plummeted within two decades after having been ecosystem engineers on most wave-exposed reefs since the Pleistocene. Since 1996/1998 live coral cover in the Gulf declined by over 90% in many areas, primarily due to bleaching and diseases caused by rising temperatures. In the formerly dominant table-coral species A. downingi, population dynamics corresponding to disturbance regimes was quantified in three transition matrices (lower disturbance pre-1996; moderate disturbance from 1998 to 2010 and 2013 to 2017, disturbed in 1996/1998, 2010/11/12, 2017). Increased disturbance frequency and severity caused progressive reduction in coral size, cover, and population fecundity. Small size-classes were bolstered more by partial colony mortality than sexual recruitment. Some large corals had a size refuge and resisted die-back but were also lost with increasing disturbance. Matrix and biophysical larval flow models suggested one metapopulation. Southern, Arabian, populations could be connected to northern, Iranian, populations but this connectivity was lost under assumptions of pelagic larval duration at rising temperatures shortened to a third. Then, the metapopulation disintegrated into isolated populations. Connectivity required to avoid extinctions increased exponentially with disturbance frequency and correlation of disturbances across the metapopulation. Populations became unsustainable at eight disturbances in 15 years, when even highest theoretical recruitment no longer compensated mortality. This lethal disturbance frequency was 3-fold that of the moderately disturbed monitoring period and 4-fold of the preceding low-disturbance period-suggesting ongoing shortening of the disturbance-free period. Observed population collapse and environmental changes in the Gulf suggest that A. downingi is heading toward at least functional extinction mainly due to increasingly frequent temperature-induced mortality events, clearly linked to climate change. © 2018 John Wiley & Sons Ltd.

Variability in Susceptibility to Anthracnose in the World Collection of Olive Cultivars of Cordoba (Spain).

PubMed

Moral, Juan; Xaviér, Carlos J; Viruega, José R; Roca, Luis F; Caballero, Juan; Trapero, Antonio

2017-01-01

Anthracnose of olive ( Olea europaea ssp. europaea L.), caused by Colletotrichum species, is a serious disease causing fruit rot and branch dieback, whose epidemics are highly dependent on cultivar susceptibility and environmental conditions. Over a period of 10 years, there have been three severe epidemics in Andalusia (southern Spain) that allowed us to complete the assessment of the World Olive Germplasm Bank of Córdoba, one of the most important cultivar collections worldwide.A total of 308 cultivars from 21 countries were evaluated, mainly Spain (174 cvs.), Syria (29 cvs.), Italy (20 cvs.), Turkey (15 cvs.), and Greece (16 cvs.). Disease assessments were performed using a 0-10 rating scale, specifically developed to estimate the incidence of symptomatic fruit in the tree canopy. Also, the susceptibility of five reference cultivars was confirmed by artificial inoculation. Because of the direct relationship between the maturity of the fruit and their susceptibility to the pathogen, evaluations were performed at the end of fruit ripening, which forced coupling assessments according to the maturity state of the trees. By applying the cluster analysis to the 308 cultivars, these were classified as follows: 66 cvs. highly susceptible (21.4%), 83 cvs. susceptible (26.9%), 66 cvs. moderately susceptible (21.4%), 61 cvs. resistant (19.8%), and 32 cvs. highly resistant (10.4%). Representative cultivars of these five categories are "Ocal," "Lechín de Sevilla," "Arbequina," "Picual," and "Frantoio," respectively. With some exceptions, such as cvs. Arbosana, Empeltre and Picual, most of the Spanish cultivars, such as "Arbequina," "Cornicabra," "Hojiblanca," "Manzanilla de Sevilla," "Morisca," "Picudo," "Farga," and "Verdial de Huévar" are included in the categories of moderately susceptible, susceptible or highly susceptible. The phenotypic evaluation of anthracnose reaction is a limiting factor for the selection of olive cultivars by farmers, technicians, and breeders.

MDMA-induced neurotoxicity of serotonin neurons involves autophagy and rilmenidine is protective against its pathobiology.

PubMed

Mercer, Linda D; Higgins, Gavin C; Lau, Chew L; Lawrence, Andrew J; Beart, Philip M

2017-05-01

Toxicity of 3,4-methylenedioxymethamphetamine (MDMA) towards biogenic amine neurons is well documented and in primate brain predominantly affects serotonin (5-HT) neurons. MDMA induces damage of 5-HT axons and nerve fibres and intracytoplasmic inclusions. Whilst its pathobiology involves mitochondrially-mediated oxidative stress, we hypothesised MDMA possessed the capacity to activate autophagy, a proteostatic mechanism for degradation of cellular debris. We established a culture of ventral pons from embryonic murine brain enriched in 5-HT neurons to explore mechanisms of MDMA neurotoxicity and recruitment of autophagy, and evaluated possible neuroprotective actions of the clinically approved agent rilmenidine. MDMA (100 μM-1 mM) reduced cell viability, like rapamycin (RM) and hydrogen peroxide (H 2 O 2 ), in a concentration- and time-dependent manner. Immunocytochemistry revealed dieback of 5-HT arbour: MDMA-induced injury was slower than for RM and H 2 O 2 , neuritic blebbing occurred at 48 and 72 h and Hoechst labelling revealed nuclear fragmentation with 100 μM MDMA. MDMA effected concentration-dependent inhibition of [ 3 H]5-HT uptake with 500 μM MDMA totally blocking transport. Western immunoblotting for microtubule associated protein light chain 3 (LC3) revealed autophagosome formation after treatment with MDMA. Confocal analyses and immunocytochemistry for 5-HT, Hoechst and LC3 confirmed MDMA induced autophagy with abundant LC3-positive puncta within 5-HT neurons. Rilmenidine (1 μM) protected against MDMA-induced injury and image analysis showed full preservation of 5-HT arbours. MDMA had no effect on GABA neurons, indicating specificity of action at 5-HT neurons. MDMA-induced neurotoxicity involves autophagy induction in 5-HT neurons, and rilmenidine via beneficial actions against toxic intracellular events represents a potential treatment for its pathobiology in sustained usage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Purple Pitcher Plant (Sarracenia rosea) Dieback and Partial Community Disassembly following Experimental Storm Surge in a Coastal Pitcher Plant Bog

PubMed Central

Abbott, Matthew J.; Battaglia, Loretta L.

2015-01-01

Sea-level rise and frequent intense hurricanes associated with climate change will result in recurrent flooding of inland systems such as Gulf Coastal pitcher plant bogs by storm surges. These surges can transport salt water and sediment to freshwater bogs, greatly affecting their biological integrity. Purple pitcher plants (Sarracenia rosea) are Gulf Coast pitcher plant bog inhabitants that could be at a disadvantage under this scenario because their pitcher morphology may leave them prone to collection of saline water and sediment after a surge. We investigated the effects of storm surge water salinity and sediment type on S. rosea vitality, plant community structure, and bog soil-water conductivity. Plots (containing ≥1 ramet of S. rosea) were experimentally flooded with fresh or saline water crossed with one of three sediment types (local, foreign, or no sediment). There were no treatment effects on soil-water conductivity; nevertheless, direct exposure to saline water resulted in significantly lower S. rosea cover until the following season when a prescribed fire and regional drought contributed to the decline of all the S. rosea to near zero percent cover. There were also significant differences in plant community structure between treatments over time, reflecting how numerous species increased in abundance and a few species decreased in abundance. However, in contrast to S. rosea, most of the other species in the community appeared resilient to the effects of storm surge. Thus, although the community may be somewhat affected by storm surge, those few species that are particularly sensitive to the storm surge disturbance will likely drop out of the community and be replaced by more resilient species. Depending on the longevity of these biological legacies, Gulf Coastal pitcher plant bogs may be incapable of fully recovering if they become exposed to storm surge more frequently due to climate change. PMID:25874369

Purple pitcher plant (Sarracenia rosea) Dieback and partial community disassembly following experimental storm surge in a coastal pitcher plant bog.

PubMed

Abbott, Matthew J; Battaglia, Loretta L

2015-01-01

Sea-level rise and frequent intense hurricanes associated with climate change will result in recurrent flooding of inland systems such as Gulf Coastal pitcher plant bogs by storm surges. These surges can transport salt water and sediment to freshwater bogs, greatly affecting their biological integrity. Purple pitcher plants (Sarracenia rosea) are Gulf Coast pitcher plant bog inhabitants that could be at a disadvantage under this scenario because their pitcher morphology may leave them prone to collection of saline water and sediment after a surge. We investigated the effects of storm surge water salinity and sediment type on S. rosea vitality, plant community structure, and bog soil-water conductivity. Plots (containing ≥1 ramet of S. rosea) were experimentally flooded with fresh or saline water crossed with one of three sediment types (local, foreign, or no sediment). There were no treatment effects on soil-water conductivity; nevertheless, direct exposure to saline water resulted in significantly lower S. rosea cover until the following season when a prescribed fire and regional drought contributed to the decline of all the S. rosea to near zero percent cover. There were also significant differences in plant community structure between treatments over time, reflecting how numerous species increased in abundance and a few species decreased in abundance. However, in contrast to S. rosea, most of the other species in the community appeared resilient to the effects of storm surge. Thus, although the community may be somewhat affected by storm surge, those few species that are particularly sensitive to the storm surge disturbance will likely drop out of the community and be replaced by more resilient species. Depending on the longevity of these biological legacies, Gulf Coastal pitcher plant bogs may be incapable of fully recovering if they become exposed to storm surge more frequently due to climate change.

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.

A neighborhood analysis of the consequences of Quercus suber decline for regeneration dynamics in Mediterranean forests.

PubMed

Ibáñez, Beatriz; Gómez-Aparicio, Lorena; Stoll, Peter; Ávila, José M; Pérez-Ramos, Ignacio M; Marañón, Teodoro

2015-01-01

In forests, the vulnerable seedling stage is largely influenced by the canopy, which modifies the surrounding environment. Consequently, any alteration in the characteristics of the canopy, such as those promoted by forest dieback, might impact regeneration dynamics. Our work analyzes the interaction between canopy neighbors and seedlings in Mediterranean forests affected by the decline of their dominant species (Quercus suber). Our objective was to understand how the impacts of neighbor trees and shrubs on recruitment could affect future dynamics of these declining forests. Seeds of the three dominant tree species (Quercus suber, Olea europaea and Quercus canariensis) were sown in six sites during two consecutive years. Using a spatially-explicit, neighborhood approach we developed models that explained the observed spatial variation in seedling emergence, survival, growth and photochemical efficiency as a function of the size, identity, health, abundance and distribution of adult trees and shrubs in the neighborhood. We found strong neighborhood effects for all the performance estimators, particularly seedling emergence and survival. Tree neighbors positively affected emergence, independently of species identity or health. Alternatively, seedling survival was much lower in neighborhoods dominated by defoliated and dead Q. suber trees than in neighborhoods dominated by healthy trees. For the two oak species, these negative effects were consistent over the three years of the experimental seedlings. These results indicate that ongoing changes in species' relative abundance and canopy trees' health might alter the successional trajectories of Mediterranean oak-forests through neighbor-specific impacts on seedlings. The recruitment failure of dominant late-successional oaks in the gaps opened after Q. suber death would indirectly favor the establishment of other coexisting woody species, such as drought-tolerant shrubs. This could lead current forests to shift into open systems with lower tree cover. Adult canopy decline would therefore represent an additional factor threatening the recruitment of Quercus forests worldwide.

Seeing the risks of multiple Arctic amplifying feedbacks.

NASA Astrophysics Data System (ADS)

Carter, P.

2014-12-01

There are several potentially very large sources of Arctic amplifying feedbacks that have been identified. They present a great risk to the future as they could become self and inter-reinforcing with uncontrollable knock-on, or cascading risks. This has been called a domino effect risk by Carlos Duarte. Because of already committed global warming and the millennial duration of global warming, these are highly policy relevant. These Arctic feedback processes are now all operant with emissions of carbon dioxide methane and nitrous oxide detected. The extent of the risks from these feedback sources are not obvious or easy to understand by policy makers and the public. They are recorded in the IPCC AR5 as potential tipping points, as is the irreversibility of permafrost thaw. Some of them are not accounted for in the IPCC AR5 global warming projections because of quantitative uncertainty. UNEP issued a 2012 report (Policy Implications of Thawing Permafrost) advising that by omitting carbon feedback emissions from permafrost, carbon budget calculations by err on the low side. There is the other unassessed issue of a global warming safety limit for preventing uncontrollable increasing Arctic feedback emissions. Along with our paper, we provide illustrations of the Arctic feedback sources and processes from satellite imagery and flow charts that allows for their qualitative consideration. We rely on the IPCC assessments, the 2012 paper Possible role of wetlands permafrost can methane hydrates in the methane cycle under future climate change; a review, by Fiona M. O'Connor et al., and build on the WWF 2009 Arctic Climate Feedbacks: Global Implications. The potential sources of Arctic feedback processes identified include: Arctic and Far North snow albedo decline, Arctic summer sea ice albedo decline, Greenland summer ice surface melting albedo loss, albedo decline by replacement of Arctic tundra with forest, tundra fires, Boreal forest fires, Boreal forest die-back, warming subarctic peat rich wetlands (methane), thawing permafrost (carbon dioxide, methane and nitrous oxide), and Arctic subsea floor methane.

Drought response of five conifer species under contrasting water availability suggests high vulnerability of Norway spruce and European larch.

PubMed

Lévesque, Mathieu; Saurer, Matthias; Siegwolf, Rolf; Eilmann, Britta; Brang, Peter; Bugmann, Harald; Rigling, Andreas

2013-10-01

The ability of tree species to cope with anticipated decrease in water availability is still poorly understood. We evaluated the potential of Norway spruce, Scots pine, European larch, black pine, and Douglas-fir to withstand drought in a drier future climate by analyzing their past growth and physiological responses at a xeric and a mesic site in Central Europe using dendroecological methods. Earlywood, latewood, and total ring width, as well as the δ(13) C and δ(18) O in early- and latewood were measured and statistically related to a multiscalar soil water deficit index from 1961 to 2009. At the xeric site, δ(13) C values of all species were strongly linked to water deficits that lasted longer than 11 months, indicating a long-term cumulative effect on the carbon pool. Trees at the xeric site were particularly sensitive to soil water recharge in the preceding autumn and early spring. The native species European larch and Norway spruce, growing close to their dry distribution limit at the xeric site, were found to be the most vulnerable species to soil water deficits. At the mesic site, summer water availability was critical for all species, whereas water availability prior to the growing season was less important. Trees at the mesic were more vulnerable to water deficits of shorter duration than the xeric site. We conclude that if summers become drier, trees growing on mesic sites will undergo significant growth reductions, whereas at their dry distribution limit in the Alps, tree growth of the highly sensitive spruce and larch may collapse, likely inducing dieback and compromising the provision of ecosystem services. However, the magnitude of these changes will be mediated strongly by soil water recharge in winter and thus water availability at the beginning of the growing season. © 2013 John Wiley & Sons Ltd.

Variability in Susceptibility to Anthracnose in the World Collection of Olive Cultivars of Cordoba (Spain)

PubMed Central

Moral, Juan; Xaviér, Carlos J.; Viruega, José R.; Roca, Luis F.; Caballero, Juan; Trapero, Antonio

2017-01-01

Anthracnose of olive (Olea europaea ssp. europaea L.), caused by Colletotrichum species, is a serious disease causing fruit rot and branch dieback, whose epidemics are highly dependent on cultivar susceptibility and environmental conditions. Over a period of 10 years, there have been three severe epidemics in Andalusia (southern Spain) that allowed us to complete the assessment of the World Olive Germplasm Bank of Córdoba, one of the most important cultivar collections worldwide.A total of 308 cultivars from 21 countries were evaluated, mainly Spain (174 cvs.), Syria (29 cvs.), Italy (20 cvs.), Turkey (15 cvs.), and Greece (16 cvs.). Disease assessments were performed using a 0–10 rating scale, specifically developed to estimate the incidence of symptomatic fruit in the tree canopy. Also, the susceptibility of five reference cultivars was confirmed by artificial inoculation. Because of the direct relationship between the maturity of the fruit and their susceptibility to the pathogen, evaluations were performed at the end of fruit ripening, which forced coupling assessments according to the maturity state of the trees. By applying the cluster analysis to the 308 cultivars, these were classified as follows: 66 cvs. highly susceptible (21.4%), 83 cvs. susceptible (26.9%), 66 cvs. moderately susceptible (21.4%), 61 cvs. resistant (19.8%), and 32 cvs. highly resistant (10.4%). Representative cultivars of these five categories are “Ocal,” “Lechín de Sevilla,” “Arbequina,” “Picual,” and “Frantoio,” respectively. With some exceptions, such as cvs. Arbosana, Empeltre and Picual, most of the Spanish cultivars, such as “Arbequina,” “Cornicabra,” “Hojiblanca,” “Manzanilla de Sevilla,” “Morisca,” “Picudo,” “Farga,” and “Verdial de Huévar” are included in the categories of moderately susceptible, susceptible or highly susceptible. The phenotypic evaluation of anthracnose reaction is a limiting factor for the selection of olive cultivars by farmers, technicians, and breeders. PMID:29163612

Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon-juniper woodland.

PubMed

Pangle, Robert E; Limousin, Jean-Marc; Plaut, Jennifer A; Yepez, Enrico A; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Pockman, William T; McDowell, Nate G

2015-04-01

Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between k s and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (E C) and conductance (G C). For both species, we observed significant reductions in plant transpiration (E) and k s under experimentally imposed drought. Conversely, supplemental water additions increased E and k s in both species. Interestingly, both species exhibited similar declines in k s under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant k s also reduced carbon assimilation in both species, as leaf-level stomatal conductance (g s) and net photosynthesis (A n) declined strongly with decreasing k s. Finally, we observed that chronically low whole-plant k s was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy E C and G C. Our data indicate that significant reductions in k s precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon-juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent regional drought in the southwestern United States.

Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon–juniper woodland

PubMed Central

Pangle, Robert E; Limousin, Jean-Marc; Plaut, Jennifer A; Yepez, Enrico A; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Pockman, William T; McDowell, Nate G

2015-01-01

Plant hydraulic conductance (ks) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between ks and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (EC) and conductance (GC). For both species, we observed significant reductions in plant transpiration (E) and ks under experimentally imposed drought. Conversely, supplemental water additions increased E and ks in both species. Interestingly, both species exhibited similar declines in ks under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant ks also reduced carbon assimilation in both species, as leaf-level stomatal conductance (gs) and net photosynthesis (An) declined strongly with decreasing ks. Finally, we observed that chronically low whole-plant ks was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy EC and GC. Our data indicate that significant reductions in ks precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon–juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent regional drought in the southwestern United States. PMID:25937906

Water quality following extensive beetle-induced tree mortality: Interplay of aromatic carbon loading, disinfection byproducts, and hydrologic drivers.

PubMed

Brouillard, Brent M; Dickenson, Eric R V; Mikkelson, Kristin M; Sharp, Jonathan O

2016-12-01

The recent bark beetle epidemic across western North America may impact water quality as a result of elevated organic carbon release and hydrologic shifts associated with extensive tree dieback. Analysis of quarterly municipal monitoring data from 2004 to 2014 with discretization of six water treatment facilities in the Rocky Mountains by extent of beetle impact revealed a significant increasing trend in total organic carbon (TOC) and total trihalomethane (TTHM) production within high (≳50% areal infestation) beetle-impacted watersheds while no or insignificant trends were found in watersheds with lower impact levels. Alarmingly, the TTHM concentration trend in the high impact sites exceeded regulatory maximum contaminant levels during the most recent two years of analysis (2013-14). To evaluate seasonal differences, explore the interplay of water quality and hydrologic processes, and eliminate variability associated with municipal reporting, these treatment facilities were targeted for more detailed surface water sampling and characterization. Surface water samples collected from high impact watersheds exhibited significantly higher TOC, aromatic signatures, and disinfection byproduct (DBP) formation potential than watersheds with lower infestation levels. Spectroscopic analyses of surface water samples indicated that these heightened DBP precursor levels are a function of both elevated TOC loading and increased aromatic character. This association was heightened during precipitation and runoff events in high impact sites, supporting the hypothesis that altered hydrologic flow paths resulting from tree mortality mobilize organic carbon and elevate DBP formation potential for several months after runoff ceases. The historical trends found here likely underestimate the full extent of TTHM shifts due to monitoring biases with the extended seasonal release of DBP precursors increasing the potential for human exposure. Collectively, our analysis suggests that while water quality impacts continue to rise nearly one decade after infestation, significant increases in TOC mobilization and DBP precursors are limited to watersheds that experience extensive tree mortality. Copyright © 2016 Elsevier B.V. All rights reserved.

Biogenic and pedogenic controls on Si distributions and cycling in grasslands of the Santa Cruz soil chronosequence, California

NASA Astrophysics Data System (ADS)

White, Art F.; Vivit, Davison V.; Schulz, Marjorie S.; Bullen, Tom D.; Evett, Rand R.; Aagarwal, Jugdeep

2012-10-01

Biogenic and pedogenic processes control silica cycling in grasslands growing on a soil chronosequence and dominated by strong seasonal variabilities of a Mediterranean climate. Shallow pore water Si, in spite of significant annual uptake and release by plant growth and dieback, exhibits only moderate seasonal fluctuations reflecting strong buffering from labile biogenic Si, dominated by phytoliths and by secondary pedogenic silicates. Long phytolith residence times (340-900 yrs) reflect the seasonally dry climate and high solute Si concentrations. Water-extractable Si is closely associated with Al, indicating seasonal precipitation and dissolution of a highly labile 1:1 hydroxyaluminosilicate (HAS), probably allophane, which transforms in deeper soil into fine grained, poorly crystalline kaolinite. Shallow plant roots extract greater proportions of biogenic Si and deeper plant roots larger amounts pedogenic Si. High pore water Ge/Si in late winter and spring reflects the reinforcing effects of plant fractionation and concurrent dissolution of Ge-enriched HAS. The same processes produce pore waters with depleted 30Si/28Si. In the summer and fall, Ge/Si declines and 30Si/28Si increases, reflecting the cessation of plant uptake, continued dissolution of soil phytoliths and re-precipitation of less soluble HAS. Si inputs from weathering (2-90 mmol m-2 yr-1) and losses from pore water discharge (18-68 mM m-2 yr-1) are comparable for individual soils, decline with soil age and are significantly less than amounts of Si annual cycled through the vegetation (42-171 mM m-2 yr-1). Mobile Si is generally balanced in the soils with upward bio-pumping by the shallow-rooted grasses efficiently competing against downward leaching and pore water discharge. Small net annual increases in Si in the present day soils could not have been maintained over the time scale represented by the chronosequence (65-225 yrs), implying past changes in environmental conditions.

The missing flux in a 35S budget for the soils of a small polluted catchment

USGS Publications Warehouse

Novak, M.; Michel, R.L.; Prechova, E.; Stepanova, M.

2004-01-01

A combination of cosmogenic and artificial 35S was used to assess the movement of sulfur in a steep Central European catchment affected by spruce die-back. The Jezer??i?? catchment, Krus??ne?? Hory Mts. (Czech Republic) is characterized by a large disproportion between atmospheric S input and S output via stream discharge, with S output currently exceeding S input three times. A relatively high natural concentration of cosmogenic 35S (42 mBq L-1) was found in atmospheric deposition into the catchment in winter and spring of 2000. In contrast, stream discharge contained only 2 mBq L-1. Consequently, more than 95% of the deposited S is cycled or retained within the catchment for more than several months, while older S is exported via surface water. In spring, when the soil temperature is above 0 ??C, practically no S from instantaneous rainfall is exported, despite the steepness of the slopes and the relatively short mean residence time of water in the catchment (6.5 months). Sulfur cycling in the soil includes not just adsorption of inorganic sulfate and biological uptake, but also volatilization of S compounds back into the atmosphere. Laboratory incubations of an Orthic Podzol from Jezer??i?? spiked with h 720 kBq of artificial 35S showed a 20% loss of the spike within 18 weeks under summer conditions. Under winter conditions, the 35S loss was insignificant (< 5%). This missing S flux was interpreted as volatilized hydrogen sulfide resulting from intermittent dissimilatory bacterial sulfate reduction. The missing S flux is comparable to the estimated uncertainty in many catchment S mass balances (??10%), or even larger, and should be considered in constructing these mass balances. In severely polluted forest catchments, such as Jezer??i??, sulfur loss to volatilization may exceed 13 kg ha-1 a-1, which is more than the current total atmospheric S input in large parts of North America and Europe. ?? 2004 Kluwer Academic Publishers.