Legacies of precipitation fluctuations on primary production: Theory and data synthesis

USDA-ARS?s Scientific Manuscript database

Variability of aboveground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space, based on multiyear averages for different locations, than through time, based on year to year change at single locations. Here, we p...

Legacies of precipitation fluctuations on primary production: theory and data synthesis

USDA-ARS?s Scientific Manuscript database

Variability of above-ground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space (based on multiyear averages for different locations) than through time (based on year-to-year change at single locations). Here, we...

A landscape-scale assessment of above- and belowground primary production in coastal wetlands: Implications for climate change-induced community shifts

USGS Publications Warehouse

Stagg, Camille L.; Schoolmaster, Donald R.; Piazza, Sarai C.; Snedden, Gregg; Steyer, Gregory D.; Fischenich, Craig J; McComas, Robert W.

2017-01-01

Above- and belowground production in coastal wetlands are important contributors to carbon accumulation and ecosystem sustainability. As sea level rises, we can expect shifts to more salt-tolerant communities, which may alter these ecosystem functions and services. Although the direct influence of salinity on species-level primary production has been documented, we lack an understanding of the landscape-level response of coastal wetlands to increasing salinity. What are the indirect effects of sea-level rise, i.e., how does primary production vary across a landscape gradient of increasing salinity that incorporates changes in wetland type? This is the first study to measure both above- and belowground production in four wetland types that span an entire coastal gradient from fresh to saline wetlands. We hypothesized that increasing salinity would limit rates of primary production, and saline marshes would have lower rates of above- and belowground production than fresher marshes. However, along the Northern Gulf of Mexico Coast in Louisiana, USA, we found that aboveground production was highest in brackish marshes, compared with fresh, intermediate, and saline marshes, and belowground production was similar among all wetland types along the salinity gradient. Multiple regression analysis indicated that salinity was the only significant predictor of production, and its influence was dependent upon wetland type. We concluded that (1) salinity had a negative effect on production within wetland type, and this relationship was strongest in the fresh marsh (0–2 PSU) and (2) along the overall landscape gradient, production was maintained by mechanisms at the scale of wetland type, which were likely related to plant energetics. Regardless of wetland type, we found that belowground production was significantly greater than aboveground production. Additionally, inter-annual variation, associated with severe drought conditions, was observed exclusively for belowground production, which may be a more sensitive indicator of ecosystem health than aboveground production.

Shifting grassland plant community structure drives positive interactive effects of warming and diversity on aboveground net primary productivity.

PubMed

Cowles, Jane M; Wragg, Peter D; Wright, Alexandra J; Powers, Jennifer S; Tilman, David

2016-02-01

Ecosystems worldwide are increasingly impacted by multiple drivers of environmental change, including climate warming and loss of biodiversity. We show, using a long-term factorial experiment, that plant diversity loss alters the effects of warming on productivity. Aboveground primary productivity was increased by both high plant diversity and warming, and, in concert, warming (≈1.5 °C average above and belowground warming over the growing season) and diversity caused a greater than additive increase in aboveground productivity. The aboveground warming effects increased over time, particularly at higher levels of diversity, perhaps because of warming-induced increases in legume and C4 bunch grass abundances, and facilitative feedbacks of these species on productivity. Moreover, higher plant diversity was associated with the amelioration of warming-induced environmental conditions. This led to cooler temperatures, decreased vapor pressure deficit, and increased surface soil moisture in higher diversity communities. Root biomass (0-30 cm) was likewise consistently greater at higher plant diversity and was greater with warming in monocultures and at intermediate diversity, but at high diversity warming had no detectable effect. This may be because warming increased the abundance of legumes, which have lower root : shoot ratios than the other types of plants. In addition, legumes increase soil nitrogen (N) supply, which could make N less limiting to other species and potentially decrease their investment in roots. The negative warming × diversity interaction on root mass led to an overall negative interactive effect of these two global change factors on the sum of above and belowground biomass, and thus likely on total plant carbon stores. In total, plant diversity increased the effect of warming on aboveground net productivity and moderated the effect on root mass. These divergent effects suggest that warming and changes in plant diversity are likely to have both interactive and divergent impacts on various aspects of ecosystem functioning. © 2015 John Wiley & Sons Ltd.

Regional Contingencies in the Relationship between Aboveground Biomass and Litter in the World’s Grasslands

PubMed Central

O’Halloran, Lydia R.; Borer, Elizabeth T.; Seabloom, Eric W.; MacDougall, Andrew S.; Cleland, Elsa E.; McCulley, Rebecca L.; Hobbie, Sarah; Harpole, W. Stan; DeCrappeo, Nicole M.; Chu, Chengjin; Bakker, Jonathan D.; Davies, Kendi F.; Du, Guozhen; Firn, Jennifer; Hagenah, Nicole; Hofmockel, Kirsten S.; Knops, Johannes M. H.; Li, Wei; Melbourne, Brett A.; Morgan, John W.; Orrock, John L.; Prober, Suzanne M.; Stevens, Carly J.

2013-01-01

Based on regional-scale studies, aboveground production and litter decomposition are thought to positively covary, because they are driven by shared biotic and climatic factors. Until now we have been unable to test whether production and decomposition are generally coupled across climatically dissimilar regions, because we lacked replicated data collected within a single vegetation type across multiple regions, obfuscating the drivers and generality of the association between production and decomposition. Furthermore, our understanding of the relationships between production and decomposition rests heavily on separate meta-analyses of each response, because no studies have simultaneously measured production and the accumulation or decomposition of litter using consistent methods at globally relevant scales. Here, we use a multi-country grassland dataset collected using a standardized protocol to show that live plant biomass (an estimate of aboveground net primary production) and litter disappearance (represented by mass loss of aboveground litter) do not strongly covary. Live biomass and litter disappearance varied at different spatial scales. There was substantial variation in live biomass among continents, sites and plots whereas among continent differences accounted for most of the variation in litter disappearance rates. Although there were strong associations among aboveground biomass, litter disappearance and climatic factors in some regions (e.g. U.S. Great Plains), these relationships were inconsistent within and among the regions represented by this study. These results highlight the importance of replication among regions and continents when characterizing the correlations between ecosystem processes and interpreting their global-scale implications for carbon flux. We must exercise caution in parameterizing litter decomposition and aboveground production in future regional and global carbon models as their relationship is complex. PMID:23405103

Regional contingencies in the relationship between aboveground Bbomass and litter in the world’s grasslands

USGS Publications Warehouse

O’Halloran, Lydia R.; Borer, Elizabeth T.; Seabloom, Eric W.; MacDougall, Andrew S.; Cleland, Elsa E.; McCulley, Rebecca L.; Hobbie, Sarah; Harpole, W. Stan; DeCrappeo, Nicole M.; Chu, Cheng-Jin; Bakker, Jonathan D.; Davies, Kendi F.; Du, Guozhen; Firn, Jennifer; Hagenah, Nicole; Hofmockel, Kirsten S.; Knops, Johannes M.H.; Li, Wei; Melbourne, Brett A.; Morgan, John W.; Orrock, John L.; Prober, Suzanne M.; Stevens, Carly J.

2013-01-01

Based on regional-scale studies, aboveground production and litter decomposition are thought to positively covary, because they are driven by shared biotic and climatic factors. Until now we have been unable to test whether production and decomposition are generally coupled across climatically dissimilar regions, because we lacked replicated data collected within a single vegetation type across multiple regions, obfuscating the drivers and generality of the association between production and decomposition. Furthermore, our understanding of the relationships between production and decomposition rests heavily on separate meta-analyses of each response, because no studies have simultaneously measured production and the accumulation or decomposition of litter using consistent methods at globally relevant scales. Here, we use a multi-country grassland dataset collected using a standardized protocol to show that live plant biomass (an estimate of aboveground net primary production) and litter disappearance (represented by mass loss of aboveground litter) do not strongly covary. Live biomass and litter disappearance varied at different spatial scales. There was substantial variation in live biomass among continents, sites and plots whereas among continent differences accounted for most of the variation in litter disappearance rates. Although there were strong associations among aboveground biomass, litter disappearance and climatic factors in some regions (e.g. U.S. Great Plains), these relationships were inconsistent within and among the regions represented by this study. These results highlight the importance of replication among regions and continents when characterizing the correlations between ecosystem processes and interpreting their global-scale implications for carbon flux. We must exercise caution in parameterizing litter decomposition and aboveground production in future regional and global carbon models as their relationship is complex.

Structure, production and resource use in some old-growth spruce/fir forests in the front range of the Rocky Mountains, USA

USGS Publications Warehouse

Binkley, Dan; Olsson, U.; Rochelle, R.; Stohlgren, T.; Nikolov, N.

2003-01-01

Old-growth forests of Engelmann spruce (Picea engelmannii Parry ex. Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) dominate much of the landscape of the Rocky Mountains. We characterized the structure, biomass and production of 18 old-growth (200-450-year-old) spruce/fir forests in Rocky Mountain National Park, Colorado, as well as the stand-level supply and use of light and nitrogen. Stands were chosen to span a broad range of elevation, aspect, and topography. Aboveground tree biomass in these old-growth forests averaged 253 Mg/ha (range 130-488 Mg/ha), with aboveground net primary production of 3700 kg ha-1 yr-1 (range from 2700 to 5200 kg ha-1 yr-1). Within stands, trees >35 cm in diameter accounted for 70% of aboveground biomass, but trees <35 cm contributed 70% of the production of woody biomass. Differences in slope and aspect among sites resulted in a range of incoming light from 58 to 74 TJ ha-1 yr-1, and tree canopies intercepted an average of 71% of incoming light (range 50-90%). Aboveground net primary production (ANPP) of trees did not relate to the supply of light or N, but ANPP correlated strongly with the amount of light and N used (r2 = 0.45-0.54, P < 0.01). Uptake of 1 kg of N was associated with about 260 kg of ANPP, and one TJ of intercepted shortwave radiation produced about 78 kg of ANPP. Across these old-growth stands, stands with greater biomass showed higher rates of both ANPP and resource use; variation in aboveground biomass was associated with 24% of the variation in N use (P = 0.04), 44% of the light use (P = 0.003), and 45% of the ANPP (P = 0.002). ?? 2002 Elsevier Science B.V. All rights reserved.

Estimating aboveground net primary productivity in forest-dominated ecosystems

Treesearch

Brian D. Kloeppel; Mark E. Harmon; Timothy J. Fahey

2007-01-01

The measurement of net primary productivity (NPP) in forest ecosystems presents a variety of challenges because of the large and complex dimensions of trees and the difficulties of quantifying several components of NPP. As summarized by Clark et al. (2001a), these methodological challenges can be overcome, and more reliable spatial and temporal comparisons can be...

Conversion of tropical lowland forest reduces nutrient return through litterfall, and alters nutrient use efficiency and seasonality of net primary production.

PubMed

Kotowska, Martyna M; Leuschner, Christoph; Triadiati, Triadiati; Hertel, Dietrich

2016-02-01

Tropical landscapes are not only rapidly transformed by ongoing land-use change, but are additionally confronted by increasing seasonal climate variation. There is an increasing demand for studies analyzing the effects and feedbacks on ecosystem functioning of large-scale conversions of tropical natural forest into intensively managed cash crop agriculture. We analyzed the seasonality of aboveground litterfall, fine root litter production, and aboveground woody biomass production (ANPP(woody)) in natural lowland forests, rubber agroforests under natural tree cover ("jungle rubber"), rubber and oil palm monocultures along a forest-to-agriculture transformation gradient in Sumatra. We hypothesized that the temporal fluctuation of litter production increases with increasing land-use intensity, while the associated nutrient fluxes and nutrient use efficiency (NUE) decrease. Indeed, the seasonal variation of aboveground litter production and ANPP(woody) increased from the natural forest to the plantations, while aboveground litterfall generally decreased. Nutrient return through aboveground litter was mostly highest in the natural forest; however, it was significantly lower only in rubber plantations. NUE of N, P and K was lowest in the oil palm plantations, with natural forest and the rubber systems showing comparably high values. Root litter production was generally lower than leaf litter production in all systems, while the root-to-leaf ratio of litter C flux increased along the land-use intensity gradient. Our results suggest that nutrient and C cycles are more directly affected by climate seasonality in species-poor agricultural systems than in species-rich forests, and therefore might be more susceptible to inter-annual climate fluctuation and climate change.

Ecosystem vs. community recovery 25 years after grass invasions and fire in a subtropical woodland

USGS Publications Warehouse

D'Antonio, Carla M.; Yelenik, Stephanie G.; Mack, Michelle C.

2017-01-01

Despite a large body of research documenting invasive plant impacts, few studies have followed individual invaded sites over decades to observe how they change, and none have contrasted how compositional impacts from invasion compare to ecosystem-process impacts over a multi-decadal time-scale. Using direct measurements of plant density and composition and of ecosystems processes, we evaluate how ecosystem structure, above-ground net primary production (ANPP), and above-ground and soil nutrient pools compare over 25 years since fire and C4 grass invasions disrupted seasonally dry Hawaiian woodlands. We compare structure and function between primary woodland that has never burned and is largely native species-dominated, with sites that had been the same woodland type but burned in alien-grass-fuelled fires in the 1970s and 1980s. The sites have not experienced fires since 1987. We report here that woody plant composition and structure continue to be dramatically changed by the initial invasions and fires that occurred 25 years ago and invaders continue to dominate in burned sites. This is reflected in continued low plant carbon pools in burned compared to unburned sites. Yet ANPP and N storage, which were dramatically lower in the initial decade after invasive-grass fuelled fires, have increased and are now indistinguishable from values measured in intact woodlands. Soil carbon pools were resilient to both invasion and fire initially and over time. Above-ground net primary production has recovered because of invasion of burned sites by a non-native N-fixing tree rather than because of recovery of native species. This invasive N-fixing tree is unlikely to return C storage of the invaded sites to those of unburned woodland because of its tissue and growth characteristics and its interactions with invasive grasses. It does not facilitate native species but rather promotes a persistent invasive grass/N-fixer savanna. Synthesis. We conclude that fire, an unusual disturbance in this system, has perpetuated the dominance of these sites by invasive species and that despite the dramatic recovery of above-ground net primary production and N pools, the ecosystem continues to be in a distinctly different state than the pre-fire, pre-Melinis community. Thus, despite the absence of further disturbance (fire), there is no evidence that succession towards the original ecosystem is occurring. The fact that N pools and above-ground net primary production recover because of a new invader (Morella faya), highlights the unpredictability of ecosystem trajectories in the face of altered regional species pools.

Biomass yielding potential of naturally regenerated Prosopis juliflora tree stands at three varied ecosystems in southern districts of Tamil Nadu, India.

PubMed

Saraswathi, K; Chandrasekaran, S

2016-05-01

Fuel energy demand is of great concern in recent times due to the depletion of fossil fuel resources. Biomass serves as widely available primary renewable energy source. Hence, a study was performed to assess the above-ground biomass yielding capability of fuel wood tree Prosopis juliflora in three varied ecosystems viz., coastal, fallow land and riparian ecosystems in southern districts of Tamil Nadu. The results showed that the biomass production potential and above-ground net primary productivity of P. juliflora depend on the age of the tree stands and the nature of ecosystem. A higher biomass yield was observed for P. juliflora trees with 5 to 10 years old when compared to less than 5 years of their age. Among the three ecosystems, the maximum biomass production was recorded in riparian ecosystem. The stands with less than 5-year-old P. juliflora trees gave 1.40 t/ha, and 5- to 10-year-old tree stands produced 27.69 t/ha in riparian ecosystem. Above-ground net primary productivity of both the age groups was high in fallow land ecosystem. In riparian ecosystem, the wood showed high density and low sulphur content than the other two ecosystems. Hence, P. juliflora biomass can serve as an environmentally and economically feasible fuel as well as their utilization proffers an effective means to control its invasiveness.

Watching grass grow: Successes and limitations of image-based methods for monitoring grassland phenology

USDA-ARS?s Scientific Manuscript database

Seasonal changes in aboveground primary production (i.e. phenology) are influenced by environmental conditions with implications for land-atmosphere interactions, carbon cycling, and agricultural production. Monitoring phenology and quantifying seasonal patterns across spatially extensive grasslands...

ANPP-precipitation relationships in multi-year drought experiments in natural ecosystems

USDA-ARS?s Scientific Manuscript database

Background/Question/Methods Predicting the effects of a reduction in precipitations on ecosystem productivity confronts an uncertainty: the relationship between aboveground net primary productivity (ANPP) and precipitation differs if the focus is spatial, driven by the climatic mean annual precipi...

Net primary productivity of subalpine meadows in Yosemite National Park in relation to climate variability

USGS Publications Warehouse

Moore, Peggy E.; Van Wagtendonk, Jan W.; Yee, Julie L.; McClaran, Mitchel P.; Cole, David N.; McDougald, Neil K.; Brooks, Matthew L.

2013-01-01

Subalpine meadows are some of the most ecologically important components of mountain landscapes, and primary productivity is important to the maintenance of meadow functions. Understanding how changes in primary productivity are associated with variability in moisture and temperature will become increasingly important with current and anticipated changes in climate. Our objective was to describe patterns and variability in aboveground live vascular plant biomass in relation to climatic factors. We harvested aboveground biomass at peak growth from four 64-m2 plots each in xeric, mesic, and hydric meadows annually from 1994 to 2000. Data from nearby weather stations provided independent variables of spring snow water content, snow-free date, and thawing degree days for a cumulative index of available energy. We assembled these climatic variables into a set of mixed effects analysis of covariance models to evaluate their relationships with annual aboveground net primary productivity (ANPP), and we used an information theoretic approach to compare the quality of fit among candidate models. ANPP in the xeric meadow was negatively related to snow water content and thawing degree days and in the mesic meadow was negatively related to snow water content. Relationships between ANPP and these 2 covariates in the hydric meadow were not significant. Increasing snow water content may limit ANPP in these meadows if anaerobic conditions delay microbial activity and nutrient availability. Increased thawing degree days may limit ANPP in xeric meadows by prematurely depleting soil moisture. Large within-year variation of ANPP in the hydric meadow limited sensitivity to the climatic variables. These relationships suggest that, under projected warmer and drier conditions, ANPP will increase in mesic meadows but remain unchanged in xeric meadows because declines associated with increased temperatures would offset the increases from decreased snow water content.

Analysis of Spatial and Temporal Patterns of Aboveground Net Primary Productivity in the Eurasian Steppe from 1982 to 2013

NASA Astrophysics Data System (ADS)

Jiao, C.; Yu, G.; He, N.; Chen, X.; Zhang, C.; Hu, Z.; Ge, J.

2016-12-01

Aboveground net primary productivity (NPPA) is a key integrator for characterizing vegetation activity and assessing the carbon balance of ecosystem. In this study, we combined datasets of Global Inventory Modeling and Mapping Studies (GIMMS) normalized difference vegetation index (NDVI) and NPPA field observations to propose a remote sensing-based model for NPPA (ENPPAModel) estimation in the Eurasian steppe Region (EASR). About 25% of NPPA field observations were extracted randomly to validate ENPPAModel. ENPPAModel was then used to discuss spatiotemporal dynamics of NPPA in EASR from 1982 to 2013. Validation against field observations showed good performance of ENPPAModel over the study region, with an overall coefficient of determination (R2) of 0.66 and root mean square error (RMSE) of 19.33 g C m-2 yr-1. The annual total aboveground net primary productivity (TNPPA) of EASR was 378.97 Tg C yr-1, accounting for 26.46% of the global grasslands. For 3 subregions in EASR, the Black Sea-Kazakhstan steppe subregion had highest TNPPA, amounting to 45.67% of the EASR. The annual average aboveground net primary productivity (NPPA) was 43.78 g C m-2 yr-1 in EASR, lower than that of global grasslands and higher than that of global temperate grasslands (excluding savannas).NPPA showed apparent spatial variations, which was consistent with geographical patterns of vegetation types, reflecting hydrothermal conditions in EASR. TNPPA displayed an overall increasing trend by 0.49% per year in EASR from 1982 to 2013. TNPPA increasing trend was much greater than that of global average and North America. Temporal trends of TNPPA of EASR were significantly various during three different periods. During 1982-1995, TNPPA of EASR increased obviously due to lengthened growing season associated with warming. In the period of 1996 - 2007, TNPPA of EASR decreased significantly attributed to decreasing spring temperature in the Tibetan Plateau alpine steppe subregion and decreasing summer precipitation in the Mongolian Plateau steppe subregion. During 2008 -2013, TNPPA of EASR increased weakly resulted from increasing summer precipitation in the Mongolian Plateau steppe subregion.

Comparison of modeling approaches for carbon partitioning: Impact on estimates of global net primary production and equilibrium biomass of woody vegetation from MODIS GPP

Treesearch

Takeshi Ise; Creighton M. Litton; Christian P. Giardina; Akihiko Ito

2010-01-01

Partitioning of gross primary production (GPP) to aboveground versus belowground, to growth versus respiration, and to short versus long�]lived tissues exerts a strong influence on ecosystem structure and function, with potentially large implications for the global carbon budget. A recent meta-analysis of forest ecosystems suggests that carbon partitioning...

The relationship between species richness and aboveground biomass in a primary Pinus kesiya forest of Yunnan, southwestern China.

PubMed

Li, Shuaifeng; Lang, Xuedong; Liu, Wande; Ou, Guanglong; Xu, Hui; Su, Jianrong

2018-01-01

The relationship between biodiversity and biomass is an essential element of the natural ecosystem functioning. Our research aims at assessing the effects of species richness on the aboveground biomass and the ecological driver of this relationship in a primary Pinus kesiya forest. We sampled 112 plots of the primary P. kesiya forests in Yunnan Province. The general linear model and the structural equation model were used to estimate relative effects of multivariate factors among aboveground biomass, species richness and the other explanatory variables, including climate moisture index, soil nutrient regime and stand age. We found a positive linear regression relationship between the species richness and aboveground biomass using ordinary least squares regressions. The species richness and soil nutrient regime had no direct significant effect on aboveground biomass. However, the climate moisture index and stand age had direct effects on aboveground biomass. The climate moisture index could be a better link to mediate the relationship between species richness and aboveground biomass. The species richness affected aboveground biomass which was mediated by the climate moisture index. Stand age had direct and indirect effects on aboveground biomass through the climate moisture index. Our results revealed that climate moisture index had a positive feedback in the relationship between species richness and aboveground biomass, which played an important role in a link between biodiversity maintenance and ecosystem functioning. Meanwhile, climate moisture index not only affected positively on aboveground biomass, but also indirectly through species richness. The information would be helpful in understanding the biodiversity-aboveground biomass relationship of a primary P. kesiya forest and for forest management.

The relationship between species richness and aboveground biomass in a primary Pinus kesiya forest of Yunnan, southwestern China

PubMed Central

Li, Shuaifeng; Lang, Xuedong; Liu, Wande; Ou, Guanglong; Xu, Hui

2018-01-01

The relationship between biodiversity and biomass is an essential element of the natural ecosystem functioning. Our research aims at assessing the effects of species richness on the aboveground biomass and the ecological driver of this relationship in a primary Pinus kesiya forest. We sampled 112 plots of the primary P. kesiya forests in Yunnan Province. The general linear model and the structural equation model were used to estimate relative effects of multivariate factors among aboveground biomass, species richness and the other explanatory variables, including climate moisture index, soil nutrient regime and stand age. We found a positive linear regression relationship between the species richness and aboveground biomass using ordinary least squares regressions. The species richness and soil nutrient regime had no direct significant effect on aboveground biomass. However, the climate moisture index and stand age had direct effects on aboveground biomass. The climate moisture index could be a better link to mediate the relationship between species richness and aboveground biomass. The species richness affected aboveground biomass which was mediated by the climate moisture index. Stand age had direct and indirect effects on aboveground biomass through the climate moisture index. Our results revealed that climate moisture index had a positive feedback in the relationship between species richness and aboveground biomass, which played an important role in a link between biodiversity maintenance and ecosystem functioning. Meanwhile, climate moisture index not only affected positively on aboveground biomass, but also indirectly through species richness. The information would be helpful in understanding the biodiversity-aboveground biomass relationship of a primary P. kesiya forest and for forest management. PMID:29324901

Available fuel dynamics in nine contrasting forest ecosystems in North America

Treesearch

Soung-Ryoul Ryu; Jiquan Chen; Thomas R. Crow; Sari C. Saunders

2004-01-01

Available fuel and its dynamics, both of which affect fire behavior in forest ecosystems, are direct products of ecosystem production, decomposition, and disturbances. Using published ecosystem models and equations, we developed a simulation model to evaluate the effects of dynamics of aboveground net primary production (ANPP), carbon allocation, residual slash,...

Plant functional traits improve diversity-based predictions of temporal stability of grassland productivity

USDA-ARS?s Scientific Manuscript database

Aboveground net primary productivity (ANPP) varies in response to temporal fluctuations in weather. Temporal stability (mean/standard deviation) of community ANPP may be increased, on average, by increasing plant species richness, but stability also may differ widely at a given richness level imply...

Contribution of aboveground plant respiration to carbon cycling in a Bornean tropical rainforet

NASA Astrophysics Data System (ADS)

Katayama, Ayumi; Tanaka, Kenzo; Ichie, Tomoaki; Kume, Tomonori; Matsumoto, Kazuho; Ohashi, Mizue; Kumagai, Tomo'omi

2014-05-01

Bornean tropical rainforests have a different characteristic from Amazonian tropical rainforests, that is, larger aboveground biomass caused by higher stand density of large trees. Larger biomass may cause different carbon cycling and allocation pattern. However, there are fewer studies on carbon allocation and each component in Bornean tropical rainforests, especially for aboveground plant respiration, compared to Amazonian forests. In this study, we measured woody tissue respiration and leaf respiration, and estimated those in ecosystem scale in a Bornean tropical rainforest. Then, we examined carbon allocation using the data of soil respiration and aboveground net primary production obtained from our previous studies. Woody tissue respiration rate was positively correlated with diameter at breast height (dbh) and stem growth rate. Using the relationships and biomass data, we estimated woody tissue respiration in ecosystem scale though methods of scaling resulted in different estimates values (4.52 - 9.33 MgC ha-1 yr-1). Woody tissue respiration based on surface area (8.88 MgC ha-1 yr-1) was larger than those in Amazon because of large aboveground biomass (563.0 Mg ha-1). Leaf respiration rate was positively correlated with height. Using the relationship and leaf area density data at each 5-m height, leaf respiration in ecosystem scale was estimated (9.46 MgC ha-1 yr-1), which was similar to those in Amazon because of comparable LAI (5.8 m2 m-2). Gross primary production estimated from biometric measurements (44.81 MgC ha-1 yr-1) was much higher than those in Amazon, and more carbon was allocated to woody tissue respiration and total belowground carbon flux. Large tree with dbh > 60cm accounted for about half of aboveground biomass and aboveground biomass increment. Soil respiration was also related to position of large trees, resulting in high soil respiration rate in this study site. Photosynthesis ability of top canopy for large trees was high and leaves for the large trees accounted for 30% of total, which can lead high GPP. These results suggest that large trees play considerable role in carbon cycling and make a distinctive carbon allocation in the Bornean tropical rainforest.

COMBINING LIDAR ESTIMATES OF BIOMASS AND LANDSAT ESTIMATES OF STAND AGE FOR SPATIALLY EXTENSIVE VALIDATION OF MODELED FOREST PRODUCTIVITY. (R828309)

EPA Science Inventory

Extensive estimates of forest productivity are required to understand the
relationships between shifting land use, changing climate and carbon storage
and fluxes. Aboveground net primary production of wood (NPP_Aw) is a major component
of total NPP and...

Canopy leaf area constrains [CO2]-induced enhancement of productivity and partitioning among aboveground carbon pools.

Treesearch

Heather R. McCarthy; Ram Oren; Adrien C. Finzi; Kurt H. Johnsen

2006-01-01

Net primary productivity (NPP) is enhanced under future atmospheric [CO2] in temperate forests representing a broad range of productivity. Yet questions remain in regard to how elevated [CO2]-induced NPP enhancement may be affected by climatic variations and limiting nutrient resources, as well as how this additional...

[Periodic fluctuation features of air temperature, precipitation, and aboveground net primary production of alpine meadow ecosystem on Qinghai-Tibetan Plateau].

PubMed

Zhang, Fa-wei; Li, Hong-qin; Li, Ying-nian; Li, Yi-kang; Lin, Li

2009-03-01

With Mexican Hat function as mother function, a wavelet analysis was conducted on the periodic fluctuation features of air temperature, precipitation, and aboveground net primary production (ANPP) in the Alpine Meadow Ecosystem Research Station, Chinese Academy of Sciences from 1980 to 2007. The results showed that there was a main period of 13 years for the annual fluctuations of air temperature, precipitation, and ANPP. A secondary period of 2 years for the annual fluctuations of air temperature and ANPP had lesser influence, whereas that of 4 years for the annual fluctuation of precipitation had greater effect. Lagged correlation analysis indicated that the annual fluctuation of ANNP was mainly controlled by the air temperature in a 20 years scale and had a weak 5-9 years lag effect, but there was a less correlation between ANPP and precipitation.

Plant community composition and biomass in Gulf Coast Chenier Plain marshes: Responses to winter burning and structural marsh management

USGS Publications Warehouse

Gabrey, S.W.; Afton, A.D.

2001-01-01

Many marshes in the Gulf Coast Chenier Plain, USA, are managed through a combination of fall or winter burning and structural marsh management (i.e., levees and water control structures; hereafter SMM). The goals of winter burning and SMM include improvement of waterfowl and furbearer habitat, maintenance of historic isohaline lines, and creation and maintenance of emergent wetlands. Although management practices are intended to influence the plant community, effects of these practices on primary productivity have not been investigated. Marsh processes, such as vertical accretion and nutrient cycles, which depend on primary productivity may be affected directly or indirectly by winter burning or SMM. We compared Chenier Plain plant community characteristics (species composition and above- and belowground biomass) in experimentally burned and unburned control plots within impounded and unimpounded marshes at 7 months (1996), 19 months (1997), and 31 months (1998) after burning. Burning and SMM did not affect number of plant species or species composition in our experiment. For all three years combined, burned plots had higher live above-ground biomass than did unburned plots. Total above-ground and dead above-ground biomasses were reduced in burned plots for two and three years, respectively, compared to those in unburned control plots. During all three years, belowground biomass was lower in impounded than in unimpounded marshes but did not differ between burn treatments. Our results clearly indicate that current marsh management practices influence marsh primary productivity and may impact other marsh processes, such as vertical accretion, that are dependent on organic matter accumulation and decay.

Asymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites

NASA Astrophysics Data System (ADS)

Wu, Donghai; Ciais, Philippe; Viovy, Nicolas; Knapp, Alan K.; Wilcox, Kevin; Bahn, Michael; Smith, Melinda D.; Vicca, Sara; Fatichi, Simone; Zscheischler, Jakob; He, Yue; Li, Xiangyi; Ito, Akihiko; Arneth, Almut; Harper, Anna; Ukkola, Anna; Paschalis, Athanasios; Poulter, Benjamin; Peng, Changhui; Ricciuto, Daniel; Reinthaler, David; Chen, Guangsheng; Tian, Hanqin; Genet, Hélène; Mao, Jiafu; Ingrisch, Johannes; Nabel, Julia E. S. M.; Pongratz, Julia; Boysen, Lena R.; Kautz, Markus; Schmitt, Michael; Meir, Patrick; Zhu, Qiuan; Hasibeder, Roland; Sippel, Sebastian; Dangal, Shree R. S.; Sitch, Stephen; Shi, Xiaoying; Wang, Yingping; Luo, Yiqi; Liu, Yongwen; Piao, Shilong

2018-06-01

Field measurements of aboveground net primary productivity (ANPP) in temperate grasslands suggest that both positive and negative asymmetric responses to changes in precipitation (P) may occur. Under normal range of precipitation variability, wet years typically result in ANPP gains being larger than ANPP declines in dry years (positive asymmetry), whereas increases in ANPP are lower in magnitude in extreme wet years compared to reductions during extreme drought (negative asymmetry). Whether the current generation of ecosystem models with a coupled carbon-water system in grasslands are capable of simulating these asymmetric ANPP responses is an unresolved question. In this study, we evaluated the simulated responses of temperate grassland primary productivity to scenarios of altered precipitation with 14 ecosystem models at three sites: Shortgrass steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a rainfall gradient from dry to moist. We found that (1) the spatial slopes derived from modeled primary productivity and precipitation across sites were steeper than the temporal slopes obtained from inter-annual variations, which was consistent with empirical data; (2) the asymmetry of the responses of modeled primary productivity under normal inter-annual precipitation variability differed among models, and the mean of the model ensemble suggested a negative asymmetry across the three sites, which was contrary to empirical evidence based on filed observations; (3) the mean sensitivity of modeled productivity to rainfall suggested greater negative response with reduced precipitation than positive response to an increased precipitation under extreme conditions at the three sites; and (4) gross primary productivity (GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground NPP (BNPP) all showed concave-down nonlinear responses to altered precipitation in all the models, but with different curvatures and mean values. Our results indicated that most models overestimate the negative drought effects and/or underestimate the positive effects of increased precipitation on primary productivity under normal climate conditions, highlighting the need for improving eco-hydrological processes in those models in the future.

Extreme precipitation patterns and reductions of terrestrial ecosystem production across biomes

Treesearch

Yongguang Zhang; M. Susan Moran; Mark A. Nearing; Guillermo E. Ponce Campos; Alfredo R. Huete; Anthony R. Buda; David D. Bosch; Stacey A. Gunter; Stanley G. Kitchen; W. Henry McNab; Jack A. Morgan; Mitchel P. McClaran; Diane S. Montoya; Debra P.C. Peters; Patrick J. Starks

2013-01-01

Precipitation regimes are predicted to shift to more extreme patterns that are characterized by more heavy rainfall events and longer dry intervals, yet their ecological impacts on vegetation production remain uncertain across biomes in natural climatic conditions. This in situ study investigated the effects of these climatic conditions on aboveground net primary...

Decadal-Scale Reduction in Forest Net Ecosystem Production Following Insect Defoliation Contrasts with Short-Term Impacts of Prescribed Fires

Treesearch

Kenneth L. Clark; Heidi J. Renninger; Nicholas Skowronski; Michael Gallagher; Karina V.R.  Schäfer

2018-01-01

Understanding processes underlying forest carbon dynamics is essential for accurately predicting the outcomes of non-stand-replacing disturbance in intermediate-age forests. We quantified net ecosystem production (NEP), aboveground net primary production (ANPP), and the dynamics of major carbon (C) pools before and during the decade following invasive insect...

Shifting plant species composition in response to climate change stabilizes grassland primary production.

PubMed

Liu, Huiying; Mi, Zhaorong; Lin, Li; Wang, Yonghui; Zhang, Zhenhua; Zhang, Fawei; Wang, Hao; Liu, Lingli; Zhu, Biao; Cao, Guangmin; Zhao, Xinquan; Sanders, Nathan J; Classen, Aimée T; Reich, Peter B; He, Jin-Sheng

2018-04-17

The structure and function of alpine grassland ecosystems, including their extensive soil carbon stocks, are largely shaped by temperature. The Tibetan Plateau in particular has experienced significant warming over the past 50 y, and this warming trend is projected to intensify in the future. Such climate change will likely alter plant species composition and net primary production (NPP). Here we combined 32 y of observations and monitoring with a manipulative experiment of temperature and precipitation to explore the effects of changing climate on plant community structure and ecosystem function. First, long-term climate warming from 1983 to 2014, which occurred without systematic changes in precipitation, led to higher grass abundance and lower sedge abundance, but did not affect aboveground NPP. Second, an experimental warming experiment conducted over 4 y had no effects on any aspect of NPP, whereas drought manipulation (reducing precipitation by 50%), shifted NPP allocation belowground without affecting total NPP. Third, both experimental warming and drought treatments, supported by a meta-analysis at nine sites across the plateau, increased grass abundance at the expense of biomass of sedges and forbs. This shift in functional group composition led to deeper root systems, which may have enabled plant communities to acquire more water and thus stabilize ecosystem primary production even with a changing climate. Overall, our study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity.

Climate and bark beetle effects on forest productivity -- linking dendroecology with forest landscape modeling

Treesearch

Alec M. Kretchun; E. Louise Loudermilk; Robert M. Scheller; Matthew D. Hurteau; Soumaya Belmecheri

2016-01-01

In forested systems throughout the world, climate influences tree growth and aboveground net primary productivity (ANPP). The effects of extreme climate events (i.e., drought) on ANPP can be compounded by biotic factors (e.g., insect outbreaks). Understanding the contribution of each of these influences on growth requires information at...

Rain use efficiency across a precipitation gradient on the Tibetan Plateau

USDA-ARS?s Scientific Manuscript database

Rain use efficiency (RUE), commonly described as the ratio of aboveground net primary production (ANPP) to mean annual precipitation (MAP), is a critical indicator for predicting potential responses of grassland ecosystems to changing precipitation regimes. However, current understanding on patterns...

Nutrient cycling in Nothofagus pumilio forests along an altitudinal gradient in Tierra del Fuego, Argentina

Treesearch

Jorge L. Frangi; Marcelo D. Barrera; Laura L. Richter; Ariel E. Lugo

2005-01-01

Nothofagus pumilio (lenga) forests form monocultures from sea level to timberline in Tierra de Fuego, Argentina. Past studies suggested that the life form change from erect forest to krummholz had advantages to forest function. Aboveground net primary productivity (NPP) and organic matter production per unit leaf area and growing season day were higher in krummholz...

Community Level Offset of Rain Use- and Transpiration Efficiency for a Heavily Grazed Ecosystem in Inner Mongolia Grassland

PubMed Central

Gao, Ying Z.; Giese, Marcus; Gao, Qiang; Brueck, Holger; Sheng, Lian X.; Yang, Hai J.

2013-01-01

Water use efficiency (WUE) is a key indicator to assess ecosystem adaptation to water stress. Rain use efficiency (RUE) is usually used as a proxy for WUE due to lack of transpiration data. Furthermore, RUE based on aboveground primary productivity (RUEANPP) is used to evaluate whole plant water use because root production data is often missing as well. However, it is controversial as to whether RUE is a reliable parameter to elucidate transpiration efficiency (TE), and whether RUEANPP is a suitable proxy for RUE of the whole plant basis. The experiment was conducted at three differently managed sites in the Inner Mongolia steppe: a site fenced since 1979 (UG79), a winter grazing site (WG) and a heavily grazed site (HG). Site HG had consistent lowest RUEANPP and RUE based on total net primary productivity (RUENPP). RUEANPP is a relatively good proxy at sites UG79 and WG, but less reliable for site HG. Similarly, RUEANPP is good predictor of transpiration efficiency based on aboveground net primary productivity (TEANPP) at sites UG79 and WG but not for site HG. However, if total net primary productivity is considered, RUENPP is good predictor of transpiration efficiency based on total net primary productivity (TENPP) for all sites. Although our measurements indicate decreased plant transpiration and consequentially decreasing RUE under heavy grazing, productivity was relatively compensated for with a higher TE. This offset between RUE and TE was even enhanced under water limited conditions and more evident when belowground net primary productivity (BNNP) was included. These findings suggest that BNPP should be considered when studies fucus on WUE of more intensively used grasslands. The consideration of the whole plant perspective and “real” WUE would partially revise our picture of system performance and therefore might affect the discussion on the C-sequestration and resilience potential of ecosystems. PMID:24058632

Community level offset of rain use- and transpiration efficiency for a heavily grazed ecosystem in inner Mongolia grassland.

PubMed

Gao, Ying Z; Giese, Marcus; Gao, Qiang; Brueck, Holger; Sheng, Lian X; Yang, Hai J

2013-01-01

Water use efficiency (WUE) is a key indicator to assess ecosystem adaptation to water stress. Rain use efficiency (RUE) is usually used as a proxy for WUE due to lack of transpiration data. Furthermore, RUE based on aboveground primary productivity (RUEANPP) is used to evaluate whole plant water use because root production data is often missing as well. However, it is controversial as to whether RUE is a reliable parameter to elucidate transpiration efficiency (TE), and whether RUEANPP is a suitable proxy for RUE of the whole plant basis. The experiment was conducted at three differently managed sites in the Inner Mongolia steppe: a site fenced since 1979 (UG79), a winter grazing site (WG) and a heavily grazed site (HG). Site HG had consistent lowest RUEANPP and RUE based on total net primary productivity (RUENPP). RUEANPP is a relatively good proxy at sites UG79 and WG, but less reliable for site HG. Similarly, RUEANPP is good predictor of transpiration efficiency based on aboveground net primary productivity (TEANPP) at sites UG79 and WG but not for site HG. However, if total net primary productivity is considered, RUENPP is good predictor of transpiration efficiency based on total net primary productivity (TENPP) for all sites. Although our measurements indicate decreased plant transpiration and consequentially decreasing RUE under heavy grazing, productivity was relatively compensated for with a higher TE. This offset between RUE and TE was even enhanced under water limited conditions and more evident when belowground net primary productivity (BNNP) was included. These findings suggest that BNPP should be considered when studies fucus on WUE of more intensively used grasslands. The consideration of the whole plant perspective and "real" WUE would partially revise our picture of system performance and therefore might affect the discussion on the C-sequestration and resilience potential of ecosystems.

Grazing effects on aboveground primary production and root biomass of early-seral, mid-seral, and undisturbed semiarid grassland

USGS Publications Warehouse

Milchunas, D.G.; Vandever, M.W.

2013-01-01

Annual/perennial and tall/short plant species differentially dominate early to late successional shortgrass steppe communities. Plant species can have different ratios of above-/below-ground biomass distributions and this can be modified by precipitation and grazing. We compared grazing effects on aboveground production and root biomass in early- and mid-seral fields and undisturbed shortgrass steppe. Production averaged across four years and grazed and ungrazed treatments were 246, 134, and 102 g m−2 yr−1 for the early-, mid-seral, and native sites, respectively, while root biomass averaged 358, 560, and 981 g m−2, respectively. Early- and mid-seral communities provided complimentary forage supplies but at the cost of root biomass. Grazing increased, decreased, or had no effect on aboveground production in early-, mid-seral, and native communities, and had no effect on roots in any. Grazing had some negative effects on early spring forage species, but not in the annual dominated early-seral community. Dominant species increased with grazing in native communities with a long evolutionary history of grazing by large herbivores, but had no effects on the same species in mid-seral communities. Effects of grazing in native communities in a region cannot necessarily be used to predict effects at other seral stages.

Shifting plant species composition in response to climate change stabilizes grassland primary production

PubMed Central

Liu, Huiying; Mi, Zhaorong; Lin, Li; Wang, Yonghui; Zhang, Zhenhua; Zhang, Fawei; Wang, Hao; Liu, Lingli; Zhu, Biao; Cao, Guangmin; Zhao, Xinquan; Sanders, Nathan J.; Reich, Peter B.

2018-01-01

The structure and function of alpine grassland ecosystems, including their extensive soil carbon stocks, are largely shaped by temperature. The Tibetan Plateau in particular has experienced significant warming over the past 50 y, and this warming trend is projected to intensify in the future. Such climate change will likely alter plant species composition and net primary production (NPP). Here we combined 32 y of observations and monitoring with a manipulative experiment of temperature and precipitation to explore the effects of changing climate on plant community structure and ecosystem function. First, long-term climate warming from 1983 to 2014, which occurred without systematic changes in precipitation, led to higher grass abundance and lower sedge abundance, but did not affect aboveground NPP. Second, an experimental warming experiment conducted over 4 y had no effects on any aspect of NPP, whereas drought manipulation (reducing precipitation by 50%), shifted NPP allocation belowground without affecting total NPP. Third, both experimental warming and drought treatments, supported by a meta-analysis at nine sites across the plateau, increased grass abundance at the expense of biomass of sedges and forbs. This shift in functional group composition led to deeper root systems, which may have enabled plant communities to acquire more water and thus stabilize ecosystem primary production even with a changing climate. Overall, our study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity. PMID:29666319

Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers

USDA-ARS?s Scientific Manuscript database

The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground net primary production (ANPP) and soil respiration. How the PPT legacy influenc...

Legacy effects of a regional drought on aboveground net primary production in six central US grasslands

USDA-ARS?s Scientific Manuscript database

Global climate models predict increases in the frequency and severity of drought worldwide, directly affecting most ecosystem types. Consequently, drought legacy effects (drought-induced alterations in ecosystem function postdrought) are expected to become more common in ecosystems varying from dese...

Model analysis of grazing effect on above-ground biomass and above-ground net primary production of a Mongolian grassland ecosystem

NASA Astrophysics Data System (ADS)

Chen, Yuxiang; Lee, Gilzae; Lee, Pilzae; Oikawa, Takehisa

2007-01-01

In this study, we have analyzed the productivity of a grassland ecosystem in Kherlenbayan-Ulaan (KBU), Mongolia under non-grazing and grazing conditions using a new simulation model, Sim-CYCLE grazing. The model was obtained by integrating the Sim-CYCLE [Ito, A., Oikawa, T., 2002. A simulation model of carbon cycle in land ecosystems (Sim-CYCLE): a description based on dry-matter production theory and plot-scale validation. Ecological Modeling, 151, pp. 143-176] and a defoliation formulation [Seligman, N.G., Cavagnaro, J.B., Horno, M.E., 1992. Simulation of defoliation effects on primary production of warm-season, semiarid perennial- species grassland. Ecological Modelling, 60, pp. 45-61]. The results from the model have been validated against a set of field data obtained at KBU showing that both above-ground biomass (AB) and above-ground net primary production ( Np,a) decrease with increasing grazing intensity. The simulated maximum AB for a year maintains a nearly constant value of 1.15 Mg DM ha -1 under non-grazing conditions. The AB decreases and then reaches equilibrium under a stocking rate ( Sr) of 0.4 sheep ha -1 and 0.7 sheep ha -1. The AB decreases all the time if Sr is greater than 0.7 sheep ha -1. These results suggest that the maximum sustainable Sr is 0.7 sheep ha -1. A similar trend is also observed for the simulated Np,a. The annual Np,a is about 1.25 Mg DM ha -1 year -1 and this value is also constant under non-grazing conditions. The annual Np,a decreases and then reaches equilibrium under an Sr of 0.4 sheep ha -1 and 0.7 sheep ha -1, but the Np,a decreases all the time when Sr is greater than 0.7 sheep ha -1. It also indicates that the maximum sustainable Sr is 0.7 sheep ha -1. Transpiration ( ET) and evaporation ( EE) rates were determined by the Penman-Monteith method. Simulated results show that ET decreases with increasing Sr, while EE increases with increasing Sr. At equilibrium, the annual mean evapotranspiration ( E) is 189.11 mm year -1 under non-grazing conditions and 187.46 mm year -1 under an Sr of 0.7 sheep ha -1. This indicates that the water budget of the KBU grassland ecosystem is not significantly affected by grazing.

A Model-Data Intercomparison of Carbon Fluxes, Pools, and LAI in the Community Land Model (CLM) and Alternative Carbon Allocation Schemes

NASA Astrophysics Data System (ADS)

Montane, F.; Fox, A. M.; Arellano, A. F.; Alexander, M. R.; Moore, D. J.

2016-12-01

Carbon (C) allocation to different plant tissues (leaves, stem and roots) remains a central challenge for understanding the global C cycle, as it determines C residence time. We used a diverse set of observations (AmeriFlux eddy covariance towers, biomass estimates from tree-ring data, and Leaf Area Index measurements) to compare C fluxes, pools, and Leaf Area Index (LAI) data with the Community Land Model (CLM). We ran CLM for seven temperate forests in North America (including evergreen and deciduous sites) between 1980 and 2013 using different C allocation schemes: i) standard C allocation scheme in CLM, which allocates C to the stem and leaves as a dynamic function of annual net primary productivity (NPP); ii) two fixed C allocation schemes, one representative of evergreen and the other one of deciduous forests, based on Luyssaert et al. 2007; iii) an alternative C allocation scheme, which allocated C to stem and leaves, and to stem and coarse roots, as a dynamic function of annual NPP, based on Litton et al. 2007. At our sites CLM usually overestimated gross primary production and ecosystem respiration, and underestimated net ecosystem exchange. Initial aboveground biomass in 1980 was largely overestimated for deciduous forests, whereas aboveground biomass accumulation between 1980 and 2011 was highly underestimated for both evergreen and deciduous sites due to the lower turnover rate in the sites than the one used in the model. CLM overestimated LAI in both evergreen and deciduous sites because the Leaf C-LAI relationship in the model did not match the observed Leaf C-LAI relationship in our sites. Although the different C allocation schemes gave similar results for aggregated C fluxes, they translated to important differences in long-term aboveground biomass accumulation and aboveground NPP. For deciduous forests, one of the alternative C allocation schemes used (iii) gave more realistic stem C/leaf C ratios, and highly reduced the overestimation of initial aboveground biomass, and accumulated aboveground NPP for deciduous forests by CLM. Our results would suggest using different C allocation schemes for evergreen and deciduous forests. It is crucial to improve CLM in the near future to minimize data-model mismatches, and to address some of the current model structural errors and parameter uncertainties.

Population of North American elk: effects on plant diversity

Treesearch

Kelley M. Stewart; R. Terry Bowyer; John G. Kier; Brian L. Dick; Roger W. Ruess

2009-01-01

We tested for indirect effects of population density of large herbivores on plant species richness and diversity in a montane ecosystem, where increased net aboveground primary productivity (NAPP) in response to low levels of herbivory has been reported. We documented a positive, linear relationship between plant-species diversity and richness with NAPP. Structural...

Linking aboveground net primary productivity to soil carbon and dissolved organic carbon in complex terrain

NASA Astrophysics Data System (ADS)

Peterson, Fox S.; Lajtha, Kate J.

2013-07-01

Factors influencing soil organic matter (SOM) stabilization and dissolved organic carbon (DOC) content in complex terrain, where vegetation, climate, and topography vary over the scale of a few meters, are not well understood. We examined the spatial correlations of lidar and geographic information system-derived landscape topography, empirically measured soil characteristics, and current and historical vegetation composition and structure versus SOM fractions and DOC pools and leaching on a small catchment (WS1) in the H.J. Andrews Experimental Forest, located in the western Cascades Range of Oregon, USA. We predicted that aboveground net primary productivity (ANPP), litter fall, and nitrogen mineralization would be positively correlated with SOM, DOC, and carbon (C) content of the soil based on the principle that increased C inputs cause C stores in and losses from in the soil. We expected that in tandem, certain microtopographical and microclimatic characteristics might be associated with elevated C inputs and correspondingly, soil C stores and losses. We confirmed that on this site, positive relationships exist between ANPP, C inputs (litter fall), and losses (exportable DOC), but we did not find that these relationships between ANPP, inputs, and exports were translated to SOM stores (mg C/g soil), C content of the soil (% C/g soil), or DOC pools (determined with salt and water extractions). We suggest that the biogeochemical processes controlling C storage and lability in soil may relate to longer-term variability in aboveground inputs that result from a heterogeneous and evolving forest stand.

Field-quantified responses of tropical rainforest aboveground productivity to increasing CO2 and climatic stress, 1997-2009

NASA Astrophysics Data System (ADS)

Clark, Deborah A.; Clark, David B.; Oberbauer, Steven F.

2013-06-01

A directional change in tropical-forest productivity, a large component in the global carbon budget, would affect the rate of increase in atmospheric carbon dioxide ([CO2]). One current hypothesis is that "CO2 fertilization" has been increasing tropical forest productivity. Some lines of evidence instead suggest climate-driven productivity declines. Relevant direct field observations remain extremely limited for this biome. Using a unique long-term record of annual field measurements, we assessed annual aboveground net primary productivity (ANPP) and its relation to climatic factors and [CO2] in a neotropical rainforest through 1997-2009. Over this 12 year period, annual productivity did not increase, as would be expected with a dominant CO2 fertilization effect. Instead, the negative responses of ANPP components to climatic stress far exceeded the small positive responses associated with increasing [CO2]. Annual aboveground biomass production was well explained (73%) by the independent negative effects of increasing minimum temperatures and greater dry-season water stress. The long-term records enable a first field-based estimate of the [CO2] response of tropical forest ANPP: 5.24 g m-2 yr-1 yr-1 (the summed [CO2]-associated increases in two of the four production components; the largest component, leaf litterfall, showed no [CO2] association). If confirmed by longer data series, such a small response from a fertile tropical rainforest would indicate that current global models overestimate the benefits from CO2 fertilization for this biome, where most forests' poorer nutrient status more strongly constrains productivity responses to increasing [CO2]. Given the rapidly intensifying warming across tropical regions, tropical forest productivity could sharply decline through coming decades.

Repackaging precipitation into fewer, larger storms reduces ecosystem exchanges of CO2 and H2O in a semiarid steppe

USDA-ARS?s Scientific Manuscript database

Global circulation models predict that precipitation patterns will become more extreme, i.e. seasonal rainfall events tend to be larger in size, but fewer in number. Studies in North American grasslands have shown that above-ground net primary productivity (ANPP) was enhanced by such repackaging of ...

Litterfall in the hardwood forest of a minor alluvial-floodplain

Treesearch

Calvin E. Meier; John A. Stanturf; Emile S. Gardiner

2006-01-01

within mature deciduous forests, annual development of foliar biomass is a major component of aboveground net primary production and nutrient demand. As litterfall, this same foliage becomes a dominant annual transfer of biomass and nutrients to the detritus pathway. We report litterfall transfers of a mature bottomland hardwood forest in a minor alluvial-floodplain...

Linking aboveground net primary productivity to soil carbon and dissolved organic carbon in complex terrain

Treesearch

F.S. Peterson; K. Lajtha

2013-01-01

Factors influencing soil organic matter (SOM) stabilization and dissolved organic carbon (DOC) content in complex terrain, where vegetation, climate, and topography vary over the scale of a few meters, are not well understood. We examined the spatial correlations of lidar and geographic information system-derived landscape topography, empirically measured soil...

Adaptive management for soil ecosystem services

USGS Publications Warehouse

Birge, Hannah E.; Bevans, Rebecca A.; Allen, Craig R.; Angeler, David G.; Baer, Sara G.; Wall, Diana H.

2016-01-01

Ecosystem services provided by soil include regulation of the atmosphere and climate, primary (including agricultural) production, waste processing, decomposition, nutrient conservation, water purification, erosion control, medical resources, pest control, and disease mitigation. The simultaneous production of these multiple services arises from complex interactions among diverse aboveground and belowground communities across multiple scales. When a system is mismanaged, non-linear and persistent losses in ecosystem services can arise. Adaptive management is an approach to management designed to reduce uncertainty as management proceeds. By developing alternative hypotheses, testing these hypotheses and adjusting management in response to outcomes, managers can probe dynamic mechanistic relationships among aboveground and belowground soil system components. In doing so, soil ecosystem services can be preserved and critical ecological thresholds avoided. Here, we present an adaptive management framework designed to reduce uncertainty surrounding the soil system, even when soil ecosystem services production is not the explicit management objective, so that managers can reach their management goals without undermining soil multifunctionality or contributing to an irreversible loss of soil ecosystem services.

Study of Wetland Ecosystem Vegetation Using Satellite Data

NASA Astrophysics Data System (ADS)

Dyukarev, E. A.; Alekseeva, M. N.; Golovatskaya, E. A.

2017-12-01

The normalized difference vegetation index (NDVI) is used to estimate the aboveground net production (ANP) of wetland ecosystems for the key area at the South Taiga zone of West Siberia. The vegetation index and aboveground production are related by linear dependence and are specific for each wetland ecosystem. The NDVI grows with an increase in the ANP at wooded oligotrophic ecosystems. Open oligotrophic bogs and eutrophic wetlands are characterized by an opposite relation. Maps of aboveground production for wetland ecosystems are constructed for each study year and for the whole period of studies. The average aboveground production for all wetland ecosystems of the key area, which was estimated with consideration for the area they occupy and using the data of satellite measurements of the vegetation index, is 305 g C/m2/yr. The total annual carbon accumulation in aboveground wetland vegetation in the key area is 794600 t.

Coherence between woody carbon uptake and net ecosystem productivity at five eddy-covariance sites

NASA Astrophysics Data System (ADS)

Babst, F.; Bouriaud, O.; Papale, D.; Gielen, B.; Janssens, I.; Nikinmaa, E.; Ibrom, A.; Wu, J.; Bernhofer, C.; Koestner, B.; Gruenwald, T.; Seufert, G.; Ciais, P.; Frank, D. C.

2013-12-01

Forest growth ranks amongst the most important processes that determine the carbon balance of terrestrial ecosystems. Quantifications of forest carbon cycling can be made e.g. using biometric and eddy-covariance (EC) techniques. Both offer different perspectives on carbon uptake and attempts to combine them have been inconsistent and variably successful in the past. This contributes to persistent uncertainties regarding carbon allocation in forest ecosystems and complicates precise vegetation model parameterization. Aiming to reconcile assessments of carbon cycling from biometric and EC techniques, we measured radial tree growth and wood density at five long-term EC stations across Europe. The resulting records were used to calculate annual carbon uptake during above-ground wood formation and compared to monthly and seasonal CO2-flux measurements. Efforts were made to identify i) the time periods when EC and tree-ring data correspond best in different parts of Europe and ii) the fraction of eddy-fluxes which is associated with changes in above-ground woody carbon stocks. Biometric measurements and net ecosystem productivity (NEP) proved largely compatible at seasonal time scales while relationships with gross primary productivity (GPP) were often weaker. Results suggest a partitioning of sequestered carbon mainly used for volume increase (January-June) and a combination of cell-wall thickening and storage (July-September). The inter-annual variability in above-ground woody carbon uptake was significantly linked with absolute productivity ranging between 69-366 g C m-2 y-1 at boreal and temperate sites, thereby accounting for 10-25% of GPP, 15-32% of TER, and 25-80% of NEP. These findings from sites representing the major European climate zones and tree species contribute to improved quantification of above-ground carbon allocation in forests. Furthermore, they refine knowledge on processes driving ecosystem productivity important for e.g. vegetation models and provide an enhanced framework for integrative studies linking tree-ring parameters with EC measurements.

Salinity influences on aboveground and belowground net primary productivity in tidal wetlands

USGS Publications Warehouse

Pierfelice, Kathryn N.; Graeme Lockaby, B.; Krauss, Ken W.; Conner, William H.; Noe, Gregory; Ricker, Matthew C.

2017-01-01

Tidal freshwater wetlands are one of the most vulnerable ecosystems to climate change and rising sea levels. However salinification within these systems is poorly understood, therefore, productivity (litterfall, woody biomass, and fine roots) were investigated on three forested tidal wetlands [(1) freshwater, (2) moderately saline, and (3) heavily salt-impacted] and a marsh along the Waccamaw and Turkey Creek in South Carolina. Mean aboveground (litterfall and woody biomass) production on the freshwater, moderately saline, heavily salt-impacted, and marsh, respectively, was 1,061, 492, 79, and 0  g m−2 year−1 versus belowground (fine roots) 860, 490, 620, and 2,128  g m−2 year−1. Litterfall and woody biomass displayed an inverse relationship with salinity. Shifts in productivity across saline sites is of concern because sea level is predicted to continue rising. Results from the research reported in this paper provide baseline data upon which coupled hydrologic/wetland models can be created to quantify future changes in tidal forest functions.

Soil carbon and nitrogen content and stabilization in mid-rotation, intensively managed sweetgum and loblolly stands

Treesearch

Kurt H. Johnsen; Lisa J. Samuelson; Felipe G. Sanchez; Bob Eaton

2013-01-01

Intensive forestry has resulted in considerable increases in aboveground stand productivity including foliar and belowground biomass which are the primary sources of soil organic matter. Soil organic matter is important for the maintenance of soil physical, chemical and biological quality. Additionally, sequestering carbon (C) in soils may provide a means of mitigating...

Remote sensing of biomass and annual net aerial primary productivity of a salt marsh

NASA Technical Reports Server (NTRS)

Hardisky, M. A.; Klemas, V.; Daiber, F. C.; Roman, C. T.

1984-01-01

Net aerial primary productivity is the rate of storage of organic matter in above-ground plant issues exceeding the respiratory use by the plants during the period of measurement. It is pointed out that this plant tissue represents the fixed carbon available for transfer to and consumption by the heterotrophic organisms in a salt marsh or the estuary. One method of estimating annual net aerial primary productivity (NAPP) required multiple harvesting of the marsh vegetation. A rapid nondestructive remote sensing technique for estimating biomass and NAPP would, therefore, be a significant asset. The present investigation was designed to employ simple regression models, equating spectral radiance indices with Spartina alterniflora biomass to nondestructively estimate salt marsh biomass. The results of the study showed that the considered approach can be successfully used to estimate salt marsh biomass.

Radiation-use efficiency and gas exchange responses to water and nutrient availability in irrigated and fertilized stands of sweetgum and sycamore

Treesearch

Christopher B. Allen; Rodney E. Will; Robert C. McGravey; David R. Coyle; Mark D. Coleman

2005-01-01

We investigated how water and nutrient availability affect radiation-use effeciency (e) and assessed leaf gas exchange as a possible mechanism for shifts in e. We measured aboveground net primary production (ANPP) and annual photosynthetically active radiation (PAR) capture to calculate e as well as leaf-level physiological variables (light-saturated net photosynthesis...

Below-ground herbivory limits induction of extrafloral nectar by above-ground herbivores

PubMed Central

Huang, Wei; Siemann, Evan; Carrillo, Juli; Ding, Jianqing

2015-01-01

Background and Aims Many plants produce extrafloral nectar (EFN), and increase production following above-ground herbivory, presumably to attract natural enemies of the herbivores. Below-ground herbivores, alone or in combination with those above ground, may also alter EFN production depending on the specificity of this defence response and the interactions among herbivores mediated through plant defences. To date, however, a lack of manipulative experiments investigating EFN production induced by above- and below-ground herbivory has limited our understanding of how below-ground herbivory mediates indirect plant defences to affect above-ground herbivores and their natural enemies. Methods In a greenhouse experiment, seedlings of tallow tree (Triadica sebifera) were subjected to herbivory by a specialist flea beetle (Bikasha collaris) that naturally co-occurs as foliage-feeding adults and root-feeding larvae. Seedlings were subjected to above-ground adults and/or below-ground larvae herbivory, and EFN production was monitored. Key Results Above- and/or below-ground herbivory significantly increased the percentage of leaves with active nectaries, the volume of EFN and the mass of soluble solids within the nectar. Simultaneous above- and below-ground herbivory induced a higher volume of EFN and mass of soluble solids than below-ground herbivory alone, but highest EFN production was induced by above-ground herbivory when below-ground herbivores were absent. Conclusions The induction of EFN production by below-ground damage suggests that systemic induction underlies some of the EFN response. The strong induction by above-ground herbivory in the absence of below-ground herbivory points to specific induction based on above- and below-ground signals that may be adaptive for this above-ground indirect defence. PMID:25681822

Below-ground herbivory limits induction of extrafloral nectar by above-ground herbivores.

PubMed

Huang, Wei; Siemann, Evan; Carrillo, Juli; Ding, Jianqing

2015-04-01

Many plants produce extrafloral nectar (EFN), and increase production following above-ground herbivory, presumably to attract natural enemies of the herbivores. Below-ground herbivores, alone or in combination with those above ground, may also alter EFN production depending on the specificity of this defence response and the interactions among herbivores mediated through plant defences. To date, however, a lack of manipulative experiments investigating EFN production induced by above- and below-ground herbivory has limited our understanding of how below-ground herbivory mediates indirect plant defences to affect above-ground herbivores and their natural enemies. In a greenhouse experiment, seedlings of tallow tree (Triadica sebifera) were subjected to herbivory by a specialist flea beetle (Bikasha collaris) that naturally co-occurs as foliage-feeding adults and root-feeding larvae. Seedlings were subjected to above-ground adults and/or below-ground larvae herbivory, and EFN production was monitored. Above- and/or below-ground herbivory significantly increased the percentage of leaves with active nectaries, the volume of EFN and the mass of soluble solids within the nectar. Simultaneous above- and below-ground herbivory induced a higher volume of EFN and mass of soluble solids than below-ground herbivory alone, but highest EFN production was induced by above-ground herbivory when below-ground herbivores were absent. The induction of EFN production by below-ground damage suggests that systemic induction underlies some of the EFN response. The strong induction by above-ground herbivory in the absence of below-ground herbivory points to specific induction based on above- and below-ground signals that may be adaptive for this above-ground indirect defence. © 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.

Do non-native plant species affect the shape of productivity-diversity relationships?

USGS Publications Warehouse

Drake, J.M.; Cleland, E.E.; Horner-Devine, M. C.; Fleishman, E.; Bowles, C.; Smith, M.D.; Carney, K.; Emery, S.; Gramling, J.; Vandermast, D.B.; Grace, J.B.

2008-01-01

The relationship between ecosystem processes and species richness is an active area of research and speculation. Both theoretical and experimental studies have been conducted in numerous ecosystems. One finding of these studies is that the shape of the relationship between productivity and species richness varies considerably among ecosystems and at different spatial scales, though little is known about the relative importance of physical and biological mechanisms causing this variation. Moreover, despite widespread concern about changes in species' global distributions, it remains unclear if and how such large-scale changes may affect this relationship. We present a new conceptual model of how invasive species might modulate relationships between primary production and species richness. We tested this model using long-term data on relationships between aboveground net primary production and species richness in six North American terrestrial ecosystems. We show that primary production and abundance of non-native species are both significant predictors of species richness, though we fail to detect effects of invasion extent on the shapes of the relationship between species richness and primary production.

Sensitivity of tropical forest aboveground productivity to climate anomalies in SW Costa Rica

NASA Astrophysics Data System (ADS)

Hofhansl, Florian; Kobler, Johannes; Ofner, Joachim; Drage, Sigrid; Pölz, Eva-Maria; Wanek, Wolfgang

2014-12-01

The productivity of tropical forests is driven by climate (precipitation, temperature, and light) and soil fertility (geology and topography). While large-scale drivers of tropical productivity are well established, knowledge on the sensitivity of tropical lowland net primary production to climate anomalies remains scarce. We here analyze seven consecutive years of monthly recorded tropical forest aboveground net primary production (ANPP) in response to a recent El Niño-Southern Oscillation (ENSO) anomaly. The ENSO transition period resulted in increased temperatures and decreased precipitation during the El Niño dry period, causing a decrease in ANPP. However, the subsequent La Niña wet period caused strong increases in ANPP such that drought-induced reductions were overcompensated. Most strikingly, the climatic controls differed between canopy production (CP) and wood production (WP). Whereas CP showed strong seasonal variation but was not affected by ENSO, WP decreased significantly in response to a 3°C increase in annual maximum temperatures during the El Niño period but subsequently recovered to above predrought levels during the La Niña period. Moreover, the climate sensitivity of tropical forest ANPP components was affected by local topography (water availability) and disturbance history (species composition). Our results suggest that projected increases in temperature and dry season length could impact tropical carbon sequestration by shifting ANPP partitioning toward decreased WP, thus decreasing the carbon storage of highly productive lowland forests. We conclude that the impact of climate anomalies on tropical forest productivity is strongly related to local site characteristics and will therefore likely prevent uniform responses of tropical lowland forests to projected global changes.

Net primary productivity and its partitioning in response to precipitation gradient in an alpine meadow.

PubMed

Zhang, Fangyue; Quan, Quan; Song, Bing; Sun, Jian; Chen, Youjun; Zhou, Qingping; Niu, Shuli

2017-11-09

The dynamics of net primary productivity (NPP) and its partitioning to the aboveground versus belowground are of fundamental importance to understand carbon cycling and its feedback to climate change. However, the responses of NPP and its partitioning to precipitation gradient are poorly understood. We conducted a manipulative field experiment with six precipitation treatments (1/12 P, 1/4 P, 1/2 P, 3/4 P, P, and 5/4 P, P is annual precipitation) in an alpine meadow to examine aboveground and belowground NPP (ANPP and BNPP) in response to precipitation gradient in 2015 and 2016. We found that changes in precipitation had no significant impact on ANPP or belowground biomass in 2015. Compared with control, only the extremely drought treatment (1/12 P) significantly reduced ANPP by 37.68% and increased BNPP at the depth of 20-40 cm by 80.59% in 2016. Across the gradient, ANPP showed a nonlinear response to precipitation amount in 2016. Neither BNPP nor NPP had significant relationship with precipitation changes. The variance in ANPP were mostly due to forbs production, which was ultimately caused by altering soil water content and soil inorganic nitrogen concentration. The nonlinear precipitation-ANPP relationship indicates that future precipitation changes especially extreme drought will dramatically decrease ANPP and push this ecosystem beyond threshold.

The Oldest, Slowest Rainforests in the World? Massive Biomass and Slow Carbon Dynamics of Fitzroya cupressoides Temperate Forests in Southern Chile.

PubMed

Urrutia-Jalabert, Rocio; Malhi, Yadvinder; Lara, Antonio

2015-01-01

Old-growth temperate rainforests are, per unit area, the largest and most long-lived stores of carbon in the terrestrial biosphere, but their carbon dynamics have rarely been described. The endangered Fitzroya cupressoides forests of southern South America include stands that are probably the oldest dense forest stands in the world, with long-lived trees and high standing biomass. We assess and compare aboveground biomass, and provide the first estimates of net primary productivity (NPP), carbon allocation and mean wood residence time in medium-age stands in the Alerce Costero National Park (AC) in the Coastal Range and in old-growth forests in the Alerce Andino National Park (AA) in the Andean Cordillera. Aboveground live biomass was 113-114 Mg C ha(-1) and 448-517 Mg C ha(-1) in AC and AA, respectively. Aboveground productivity was 3.35-3.36 Mg C ha(-1) year(-1) in AC and 2.22-2.54 Mg C ha(-1) year(-1) in AA, values generally lower than others reported for temperate wet forests worldwide, mainly due to the low woody growth of Fitzroya. NPP was 4.21-4.24 and 3.78-4.10 Mg C ha(-1) year(-1) in AC and AA, respectively. Estimated mean wood residence time was a minimum of 539-640 years for the whole forest in the Andes and 1368-1393 years for only Fitzroya in this site. Our biomass estimates for the Andes place these ecosystems among the most massive forests in the world. Differences in biomass production between sites seem mostly apparent as differences in allocation rather than productivity. Residence time estimates for Fitzroya are the highest reported for any species and carbon dynamics in these forests are the slowest reported for wet forests worldwide. Although primary productivity is low in Fitzroya forests, they probably act as ongoing biomass carbon sinks on long-term timescales due to their low mortality rates and exceptionally long residence times that allow biomass to be accumulated for millennia.

The Oldest, Slowest Rainforests in the World? Massive Biomass and Slow Carbon Dynamics of Fitzroya cupressoides Temperate Forests in Southern Chile

PubMed Central

Urrutia-Jalabert, Rocio; Malhi, Yadvinder; Lara, Antonio

2015-01-01

Old-growth temperate rainforests are, per unit area, the largest and most long-lived stores of carbon in the terrestrial biosphere, but their carbon dynamics have rarely been described. The endangered Fitzroya cupressoides forests of southern South America include stands that are probably the oldest dense forest stands in the world, with long-lived trees and high standing biomass. We assess and compare aboveground biomass, and provide the first estimates of net primary productivity (NPP), carbon allocation and mean wood residence time in medium-age stands in the Alerce Costero National Park (AC) in the Coastal Range and in old-growth forests in the Alerce Andino National Park (AA) in the Andean Cordillera. Aboveground live biomass was 113–114 Mg C ha-1 and 448–517 Mg C ha-1 in AC and AA, respectively. Aboveground productivity was 3.35–3.36 Mg C ha-1 year-1 in AC and 2.22–2.54 Mg C ha-1 year-1 in AA, values generally lower than others reported for temperate wet forests worldwide, mainly due to the low woody growth of Fitzroya. NPP was 4.21–4.24 and 3.78–4.10 Mg C ha-1 year-1 in AC and AA, respectively. Estimated mean wood residence time was a minimum of 539–640 years for the whole forest in the Andes and 1368–1393 years for only Fitzroya in this site. Our biomass estimates for the Andes place these ecosystems among the most massive forests in the world. Differences in biomass production between sites seem mostly apparent as differences in allocation rather than productivity. Residence time estimates for Fitzroya are the highest reported for any species and carbon dynamics in these forests are the slowest reported for wet forests worldwide. Although primary productivity is low in Fitzroya forests, they probably act as ongoing biomass carbon sinks on long-term timescales due to their low mortality rates and exceptionally long residence times that allow biomass to be accumulated for millennia. PMID:26353111

Adaptive management for soil ecosystem services.

PubMed

Birgé, Hannah E; Bevans, Rebecca A; Allen, Craig R; Angeler, David G; Baer, Sara G; Wall, Diana H

2016-12-01

Ecosystem services provided by soil include regulation of the atmosphere and climate, primary (including agricultural) production, waste processing, decomposition, nutrient conservation, water purification, erosion control, medical resources, pest control, and disease mitigation. The simultaneous production of these multiple services arises from complex interactions among diverse aboveground and belowground communities across multiple scales. When a system is mismanaged, non-linear and persistent losses in ecosystem services can arise. Adaptive management is an approach to management designed to reduce uncertainty as management proceeds. By developing alternative hypotheses, testing these hypotheses and adjusting management in response to outcomes, managers can probe dynamic mechanistic relationships among aboveground and belowground soil system components. In doing so, soil ecosystem services can be preserved and critical ecological thresholds avoided. Here, we present an adaptive management framework designed to reduce uncertainty surrounding the soil system, even when soil ecosystem services production is not the explicit management objective, so that managers can reach their management goals without undermining soil multifunctionality or contributing to an irreversible loss of soil ecosystem services. Copyright © 2016. Published by Elsevier Ltd.

Vegetation, plant biomass, and net primary productivity patterns in the Canadian Arctic

NASA Astrophysics Data System (ADS)

Gould, W. A.; Raynolds, M.; Walker, D. A.

2003-01-01

We have developed maps of dominant vegetation types, plant functional types, percent vegetation cover, aboveground plant biomass, and above and belowground annual net primary productivity for Canada north of the northern limit of trees. The area mapped covers 2.5 million km2 including glaciers. Ice-free land covers 2.3 million km2 and represents 42% of all ice-free land in the Circumpolar Arctic. The maps combine information on climate, soils, geology, hydrology, remotely sensed vegetation classifications, previous vegetation studies, and regional expertise to define polygons drawn using photo-interpretation of a 1:4,000,000 scale advanced very high resolution radiometer (AVHRR) color infrared image basemap. Polygons are linked to vegetation description, associated properties, and descriptive literature through a series of lookup tables in a graphic information systems (GIS) database developed as a component of the Circumpolar Arctic Vegetation Map (CAVM) project. Polygons are classified into 20 landcover types including 17 vegetation types. Half of the region is sparsely vegetated (<50% vegetation cover), primarily in the High Arctic (bioclimatic subzones A-C). Whereas most (86%) of the estimated aboveground plant biomass (1.5 × 1015 g) and 87% of the estimated above and belowground annual net primary productivity (2.28 × 1014 g yr-1) are concentrated in the Low Arctic (subzones D and E). The maps present more explicit spatial patterns of vegetation and ecosystem attributes than have been previously available, the GIS database is useful in summarizing ecosystem properties and can be easily updated and integrated into circumpolar mapping efforts, and the derived estimates fall within the range of current published estimates.

Facilitation and inhibition: changes in plant nitrogen and secondary metabolites mediate interactions between above-ground and below-ground herbivores.

PubMed

Huang, Wei; Siemann, Evan; Yang, Xuefang; Wheeler, Gregory S; Ding, Jianqing

2013-09-22

To date, it remains unclear how herbivore-induced changes in plant primary and secondary metabolites impact above-ground and below-ground herbivore interactions. Here, we report effects of above-ground (adult) and below-ground (larval) feeding by Bikasha collaris on nitrogen and secondary chemicals in shoots and roots of Triadica sebifera to explain reciprocal above-ground and below-ground insect interactions. Plants increased root tannins with below-ground herbivory, but above-ground herbivory prevented this increase and larval survival doubled. Above-ground herbivory elevated root nitrogen, probably contributing to increased larval survival. However, plants increased foliar tannins with above-ground herbivory and below-ground herbivory amplified this increase, and adult survival decreased. As either foliar or root tannins increased, foliar flavonoids decreased, suggesting a trade-off between these chemicals. Together, these results show that plant chemicals mediate contrasting effects of conspecific larval and adult insects, whereas insects may take advantage of plant responses to facilitate their offspring performance, which may influence population dynamics.

Rising Mean Annual Temperature Increases Carbon Flux and Alters Partitioning, but Does Not Change Ecosystem Carbon Storage in Hawaiian Tropical Montane Wet Forest

NASA Astrophysics Data System (ADS)

Litton, C. M.; Giardina, C. P.; Selmants, P.

2014-12-01

Terrestrial ecosystem carbon (C) storage exceeds that in the atmosphere by a factor of four, and represents a dynamic balance among C input, allocation, and loss. This balance is likely being altered by climate change, but the response of terrestrial C cycling to warming remains poorly quantified, particularly in tropical forests which play a disproportionately large role in the global C cycle. Over the past five years, we have quantified above- and belowground C pools and fluxes in nine permanent plots spanning a 5.2°C mean annual temperature (MAT) gradient (13-18.2°C) in Hawaiian tropical montane wet forest. This elevation gradient is unique in that substrate type and age, soil type, soil water balance, canopy vegetation, and disturbance history are constant, allowing us to isolate the impact of long-term, whole ecosystem warming on C input, allocation, loss and storage. Across the gradient, soil respiration, litterfall, litter decomposition, total belowground C flux, aboveground net primary productivity, and estimates of gross primary production (GPP) all increase linearly and positively with MAT. Carbon partitioning is dynamic, shifting from below- to aboveground with warming, likely in response to a warming-induced increase in the cycling and availability of soil nutrients. In contrast to observed patterns in C flux, live biomass C, soil C, and total ecosystem C pools remained remarkably constant with MAT. There was also no difference in soil bacterial taxon richness, phylogenetic diversity, or community composition with MAT. Taken together these results indicate that in tropical montane wet forests, increased temperatures in the absence of water limitation or disturbance will accelerate C cycling, will not alter ecosystem C storage, and will shift the products of photosynthesis from below- to aboveground. These results agree with an increasing number of studies, and collectively provide a unique insight into anticipated warming-induced changes in tropical forest C cycling.

Aboveground Net Primary Productivity in a Riparian Wetland Following Restoration of Hydrology

PubMed Central

Koontz, Melissa; Lundberg, Christopher; Lane, Robert; Day, John; Pezeshki, Reza

2016-01-01

This research presents the initial results of the effects of hydrological restoration on forested wetlands in the Mississippi alluvial plain near Memphis, Tennessee. Measurements were carried out in a secondary channel, the Loosahatchie Chute, in which rock dikes were constructed in the 1960s to keep most flow in the main navigation channel. In 2008–2009, the dikes were notched to allow more flow into the secondary channel. Study sites were established based on relative distance downstream of the notched dikes. Additionally, a reference site was established north of the Loosahatchie Chute where the dikes remained unnotched. We compared various components of vegetation composition and productivity at sites in the riparian wetlands for two years. Salix nigra had the highest Importance Value at every site. Species with minor Importance Values were Celtis laevigata, Acer rubrum, and Plantanus occidentalis. Productivity increased more following the introduction of river water in affected sites compared to the reference. Aboveground net primary productivity was highest at the reference site (2926 ± 458.1 g·m−2·year−1), the intact site; however, there were greater increase at the sites in the Loosahatchie Chute, where measurements ranged from 1197.7 ± 160.0 g m−2·year−1·to 2874.2 ± 794.0 g·m−2·year−1. The site furthest from the notching was the most affected. Pulsed inputs into these wetlands may enhance forested wetland productivity. Continued monitoring will quantify impacts of restored channel hydrology along the Mississippi River. PMID:26861409

Aboveground Net Primary Productivity in a Riparian Wetland Following Restoration of Hydrology.

PubMed

Koontz, Melissa; Lundberg, Christopher; Lane, Robert; Day, John; Pezeshki, Reza

2016-02-04

This research presents the initial results of the effects of hydrological restoration on forested wetlands in the Mississippi alluvial plain near Memphis, Tennessee. Measurements were carried out in a secondary channel, the Loosahatchie Chute, in which rock dikes were constructed in the 1960s to keep most flow in the main navigation channel. In 2008-2009, the dikes were notched to allow more flow into the secondary channel. Study sites were established based on relative distance downstream of the notched dikes. Additionally, a reference site was established north of the Loosahatchie Chute where the dikes remained unnotched. We compared various components of vegetation composition and productivity at sites in the riparian wetlands for two years. Salix nigra had the highest Importance Value at every site. Species with minor Importance Values were Celtis laevigata, Acer rubrum, and Plantanus occidentalis. Productivity increased more following the introduction of river water in affected sites compared to the reference. Aboveground net primary productivity was highest at the reference site (2926 ± 458.1 g·m(-2)·year(-1)), the intact site; however, there were greater increase at the sites in the Loosahatchie Chute, where measurements ranged from 1197.7 ± 160.0 g m(-2)·year(-1)·to 2874.2 ± 794.0 g·m(-2)·year(-1). The site furthest from the notching was the most affected. Pulsed inputs into these wetlands may enhance forested wetland productivity. Continued monitoring will quantify impacts of restored channel hydrology along the Mississippi River.

Net primary production and phenology on a southern Appalachian watershed

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

Day, F.P. Jr.; Monk, C.D.

1977-01-01

Net primary production (NPP) is an important function of plant communities which has not often been examined seasonally in a forested ecosystem. The major objective of the study was to measure above-ground NPP seasonally and relate it to phenological activity on a hardwood forest watershed at Coweeta Hydrologic Laboratory, North Carolina. NPP was estimated as the increase in biomass, estimated from regression equations on diameter. Diameter increases were measured by venier tree bands. Phenological observations were made on bud break, leaf emergence, flowering, mature fruit, leaf senescence, and leaf fall. The species studied intensively were Acer rubrum, Quercus prinus, Caryamore » glabra, Cornus florida, and Liriodendron tulipifera. Liriodendron was found to be the most productive species per individual, but Quercus prinus was the most productive per unit ground area. The total watershed estimate of aboveground NPP was 8,754 kg ha/sup -1/yr/sup -1/ and included 47.9 percent leaves, 33.2 percent wood, 7.8 percent bark, 4.8 percent reproductive tissues, 4.2 percent loss to consumers, and 2.1 percent twigs. Increases in leaf biomass were most rapid in the spring, but woody tissue production peaked in June and continued through August. Since leaf production peaked in the spring, the plants' photosynthetic machinery was activated early in the growing season to support woody tissue production, which followed the period of rapid leaf growth, and reproductive activity. Flowering occurred during the leaf expansion period except for Acer rubrum, which flowered before leaf emergence. Fruit maturation occurred during late summer to early fall, when there were no additional biomass increases. Acer rubrum was an exception as its fruit matured during the period of leaf expansion.« less

Net primary production and phenology on a southern Appalachian watershed

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

Day, F.P. Jr.; Monk, C.D.

1977-10-01

Net primary production (NPP) is an important function of plant communities which has not often been examined seasonally in a forested ecosystem. The major objective of the study was to measure above-ground NPP seasonally and relate it to phenological activity on a hardwood forest watershed at Coweeta Hydrologic Laboratory, North Carolina. NPP was estimated as the increase in biomass, estimated from regression equations on diameter. Diameter increases were measured by vernier tree bands. Phenological observations were made on bud break, leaf emergence, flowering, mature fruit, leaf senescence, and leaf fall. The species studied intensively were Acer rubrum, Quercus prinus, Caryamore » glabra, Cornus florida, and Liriodendron tulipifera. Liriodendron was found to be the most productive species per individual, but Quercus prinus was the most productive per unit ground area. The total watershed estimate of aboveground NPP was 8,754 kg ha/sup -1/ yr/sup -1/ and included 47.9% leaves, 33.2% wood, 7.8% bark, 4.8% reproductive tissues, 4.2% loss to consumers, and 2.1% twigs. Increases in leaf biomass were most rapid in the spring, but woody tissue production peaked in June and continued through August. Since leaf production peaked in the spring, the plants' photosynthetic machinery was activated early in the growing season to support woody tissue production, which followed the period of rapid leaf growth, and reproductive activity. Flowering ocurred during the leaf expansion period except for Acer rubrum, which flowered before leaf emergence. Fruit maturation occurred during late summer to early fall, when there were no additional biomass increases. Acer rubrum was an exception as its fruit matured during the period of leaf expansion.« less

Ecosystem carbon partitioning: aboveground net primary productivity correlates with the root carbon input in different land use types of Southern Alps

NASA Astrophysics Data System (ADS)

Rodeghiero, Mirco; Martinez, Cristina; Gianelle, Damiano; Camin, Federica; Zanotelli, Damiano; Magnani, Federico

2013-04-01

Terrestrial plant carbon partitioning to above- and below-ground compartments can be better understood by integrating studies on biomass allocation and estimates of root carbon input based on the use of stable isotopes. These experiments are essential to model ecosystem's metabolism and predict the effects of global change on carbon cycling. Using in-growth soil cores in conjunction with the 13C natural abundance method we quantified net plant-derived root carbon input into the soil, which has been pointed out as the main unaccounted NPP (net primary productivity) component. Four land use types located in the Trentino Region (northern Italy) and representing a range of aboveground net primary productivity (ANPP) values (155-868 gC m-2 y-1) were investigated: conifer forest, apple orchard, vineyard and grassland. Cores, filled with soil of a known C4 isotopic signature were inserted at 18 sampling points for each site and left in place for twelve months. After extraction, cores were analysed for %C and d13C, which were used to calculate the proportion of new plant-derived root C input by applying a mass balance equation. The GPP (gross primary productivity) of each ecosystem was determined by the eddy covariance technique whereas ANPP was quantified with a repeated inventory approach. We found a strong and significant relationship (R2 = 0.93; p=0.03) between ANPP and the fraction of GPP transferred to the soil as root C input across the investigated sites. This percentage varied between 10 and 25% of GPP with the grassland having the lowest value and the apple orchard the highest. Mechanistic ecosystem carbon balance models could benefit from this general relationship since ANPP is routinely and easily measured at many sites. This result also suggests that by quantifying site-specific ANPP, root carbon input can be reliably estimated, as opposed to using arbitrary root/shoot ratios which may under- or over-estimate C partitioning.

Do ungulates accelerate or decelerate nitrogen cycling?

USGS Publications Warehouse

Singer, F.J.; Schoenecker, K.A.

2003-01-01

Nitrogen (N) is an essential nutrient for plants and animals, and N may be limiting in many western US grassland and shrubland ungulate winter ranges. Ungulates may influence N pools and they may alter N inputs and outputs (losses) to the ecosystem in a number of ways. In this paper we compare the ecosystem effects of ungulate herbivory in two western national parks, Rocky Mountain National Park (RMNP), Colorado, and Yellowstone National Park (YNP), Wyoming. We compare ungulate herbivory effects on N pools, N fluxes, N yields, and plant productivity in the context of the accelerating and decelerating nutrient cycling scenarios [Ecology 79 (1998) 165]. We concluded that the YNP grasslands fit the accelerating nutrient cycling scenario for ungulate herbivory: in response to grazing, grassland plant species abundance was largely unaltered, net annual aboveground primary productivity (NAPP) was stimulated (except during drought), consumption of key N-rich forages by ungulates was moderate and their abundance was sustained, soil N mineralization rates doubled, N pools increased, aboveground N yield increased, and N concentrations increased in most grassland plant species. Grazing in grasslands in RMNP resulted in no consistent detectable acceleration or deceleration of nutrient cycling. Grazing effects in short willow and aspen vegetation types in RMNP fit the decelerating nutrient cycling scenario of Ritchie et al. [Ecology 79 (1998) 165]. Key N-rich forages declined due to herbivory (willows, aspen, herbaceous vegetation). Aboveground production declined, soil N mineralization rates declined, N pools declined (NO3− pools were 30% that of ungrazed controls), and aboveground N yield declined. We believe that the higher ungulate densities and rates of plant consumption in RMNP, large declines in N-rich forage plants, and possibly a tendency of ungulates to move N from willow and aspen vegetation types to other types in RMNP, contributed to deceleration of nutrient cycling in two vegetation types in RMNP compared to acceleration in grasslands in YNP.

Comparison of Growth Efficiency of Mature Longleaf and Slash Pine Trees

Treesearch

Steven B. Jack; Mary Carol P. Sheffield; Daniel J. McConville

2002-01-01

Variation in aboveground biomass partitioning (between the stem, branches, and foliage) of mature trees is a key determinant of growth potential. Investment of photosynthate in crown components generally results in greater overall biomass production of longer duration. The increased production of crown components may be an investment in longterm aboveground production...

The importance of forest structure for carbon fluxes of the Amazon rainforest

NASA Astrophysics Data System (ADS)

Rödig, Edna; Cuntz, Matthias; Rammig, Anja; Fischer, Rico; Taubert, Franziska; Huth, Andreas

2018-05-01

Precise descriptions of forest productivity, biomass, and structure are essential for understanding ecosystem responses to climatic and anthropogenic changes. However, relations between these components are complex, in particular for tropical forests. We developed an approach to simulate carbon dynamics in the Amazon rainforest including around 410 billion individual trees within 7.8 million km2. We integrated canopy height observations from space-borne LIDAR in order to quantify spatial variations in forest state and structure reflecting small-scale to large-scale natural and anthropogenic disturbances. Under current conditions, we identified the Amazon rainforest as a carbon sink, gaining 0.56 GtC per year. This carbon sink is driven by an estimated mean gross primary productivity (GPP) of 25.1 tC ha‑1 a‑1, and a mean woody aboveground net primary productivity (wANPP) of 4.2 tC ha‑1 a‑1. We found that successional states play an important role for the relations between productivity and biomass. Forests in early to intermediate successional states are the most productive, and woody above-ground carbon use efficiencies are non-linear. Simulated values can be compared to observed carbon fluxes at various spatial resolutions (>40 m). Notably, we found that our GPP corresponds to the values derived from MODIS. For NPP, spatial differences can be observed due to the consideration of forest successional states in our approach. We conclude that forest structure has a substantial impact on productivity and biomass. It is an essential factor that should be taken into account when estimating current carbon budgets or analyzing climate change scenarios for the Amazon rainforest.

Facilitation and inhibition: changes in plant nitrogen and secondary metabolites mediate interactions between above-ground and below-ground herbivores

PubMed Central

Huang, Wei; Siemann, Evan; Yang, Xuefang; Wheeler, Gregory S.; Ding, Jianqing

2013-01-01

To date, it remains unclear how herbivore-induced changes in plant primary and secondary metabolites impact above-ground and below-ground herbivore interactions. Here, we report effects of above-ground (adult) and below-ground (larval) feeding by Bikasha collaris on nitrogen and secondary chemicals in shoots and roots of Triadica sebifera to explain reciprocal above-ground and below-ground insect interactions. Plants increased root tannins with below-ground herbivory, but above-ground herbivory prevented this increase and larval survival doubled. Above-ground herbivory elevated root nitrogen, probably contributing to increased larval survival. However, plants increased foliar tannins with above-ground herbivory and below-ground herbivory amplified this increase, and adult survival decreased. As either foliar or root tannins increased, foliar flavonoids decreased, suggesting a trade-off between these chemicals. Together, these results show that plant chemicals mediate contrasting effects of conspecific larval and adult insects, whereas insects may take advantage of plant responses to facilitate their offspring performance, which may influence population dynamics. PMID:23902902

Annual Removal of Aboveground Plant Biomass Alters Soil Microbial Responses to Warming

PubMed Central

Xue, Kai; Yuan, Mengting M.; Xie, Jianping; Li, Dejun; Qin, Yujia; Wu, Liyou; Deng, Ye; He, Zhili; Van Nostrand, Joy D.; Luo, Yiqi; Tiedje, James M.

2016-01-01

ABSTRACT Clipping (i.e., harvesting aboveground plant biomass) is common in agriculture and for bioenergy production. However, microbial responses to clipping in the context of climate warming are poorly understood. We investigated the interactive effects of grassland warming and clipping on soil properties and plant and microbial communities, in particular, on microbial functional genes. Clipping alone did not change the plant biomass production, but warming and clipping combined increased the C4 peak biomass by 47% and belowground net primary production by 110%. Clipping alone and in combination with warming decreased the soil carbon input from litter by 81% and 75%, respectively. With less carbon input, the abundances of genes involved in degrading relatively recalcitrant carbon increased by 38% to 137% in response to either clipping or the combined treatment, which could weaken long-term soil carbon stability and trigger positive feedback with respect to warming. Clipping alone also increased the abundance of genes for nitrogen fixation, mineralization, and denitrification by 32% to 39%. Such potentially stimulated nitrogen fixation could help compensate for the 20% decline in soil ammonium levels caused by clipping alone and could contribute to unchanged plant biomass levels. Moreover, clipping tended to interact antagonistically with warming, especially with respect to effects on nitrogen cycling genes, demonstrating that single-factor studies cannot predict multifactorial changes. These results revealed that clipping alone or in combination with warming altered soil and plant properties as well as the abundance and structure of soil microbial functional genes. Aboveground biomass removal for biofuel production needs to be reconsidered, as the long-term soil carbon stability may be weakened. PMID:27677789

Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests

NASA Astrophysics Data System (ADS)

Montané, Francesc; Fox, Andrew M.; Arellano, Avelino F.; MacBean, Natasha; Alexander, M. Ross; Dye, Alex; Bishop, Daniel A.; Trouet, Valerie; Babst, Flurin; Hessl, Amy E.; Pederson, Neil; Blanken, Peter D.; Bohrer, Gil; Gough, Christopher M.; Litvak, Marcy E.; Novick, Kimberly A.; Phillips, Richard P.; Wood, Jeffrey D.; Moore, David J. P.

2017-09-01

How carbon (C) is allocated to different plant tissues (leaves, stem, and roots) determines how long C remains in plant biomass and thus remains a central challenge for understanding the global C cycle. We used a diverse set of observations (AmeriFlux eddy covariance tower observations, biomass estimates from tree-ring data, and leaf area index (LAI) measurements) to compare C fluxes, pools, and LAI data with those predicted by a land surface model (LSM), the Community Land Model (CLM4.5). We ran CLM4.5 for nine temperate (including evergreen and deciduous) forests in North America between 1980 and 2013 using four different C allocation schemes: i. dynamic C allocation scheme (named "D-CLM4.5") with one dynamic allometric parameter, which allocates C to the stem and leaves to vary in time as a function of annual net primary production (NPP); ii. an alternative dynamic C allocation scheme (named "D-Litton"), where, similar to (i), C allocation is a dynamic function of annual NPP, but unlike (i) includes two dynamic allometric parameters involving allocation to leaves, stem, and coarse roots; iii.-iv. a fixed C allocation scheme with two variants, one representative of observations in evergreen (named "F-Evergreen") and the other of observations in deciduous forests (named "F-Deciduous"). D-CLM4.5 generally overestimated gross primary production (GPP) and ecosystem respiration, and underestimated net ecosystem exchange (NEE). In D-CLM4.5, initial aboveground biomass in 1980 was largely overestimated (between 10 527 and 12 897 g C m-2) for deciduous forests, whereas aboveground biomass accumulation through time (between 1980 and 2011) was highly underestimated (between 1222 and 7557 g C m-2) for both evergreen and deciduous sites due to a lower stem turnover rate in the sites than the one used in the model. D-CLM4.5 overestimated LAI in both evergreen and deciduous sites because the leaf C-LAI relationship in the model did not match the observed leaf C-LAI relationship at our sites. Although the four C allocation schemes gave similar results for aggregated C fluxes, they translated to important differences in long-term aboveground biomass accumulation and aboveground NPP. For deciduous forests, D-Litton gave more realistic Cstem / Cleaf ratios and strongly reduced the overestimation of initial aboveground biomass and aboveground NPP for deciduous forests by D-CLM4.5. We identified key structural and parameterization deficits that need refinement to improve the accuracy of LSMs in the near future. These include changing how C is allocated in fixed and dynamic schemes based on data from current forest syntheses and different parameterization of allocation schemes for different forest types. Our results highlight the utility of using measurements of aboveground biomass to evaluate and constrain the C allocation scheme in LSMs, and suggest that stem turnover is overestimated by CLM4.5 for these AmeriFlux sites. Understanding the controls of turnover will be critical to improving long-term C processes in LSMs.

Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests

DOE PAGES

Montané, Francesc; Fox, Andrew M.; Arellano, Avelino F.; ...

2017-09-22

How carbon (C) is allocated to different plant tissues (leaves, stem, and roots) determines how long C remains in plant biomass and thus remains a central challenge for understanding the global C cycle. We used a diverse set of observations (AmeriFlux eddy covariance tower observations, biomass estimates from tree-ring data, and leaf area index (LAI) measurements) to compare C fluxes, pools, and LAI data with those predicted by a land surface model (LSM), the Community Land Model (CLM4.5). We ran CLM4.5 for nine temperate (including evergreen and deciduous) forests in North America between 1980 and 2013 using four different C allocationmore » schemes: i. dynamic C allocation scheme (named "D-CLM4.5") with one dynamic allometric parameter, which allocates C to the stem and leaves to vary in time as a function of annual net primary production (NPP); ii. an alternative dynamic C allocation scheme (named "D-Litton"), where, similar to (i), C allocation is a dynamic function of annual NPP, but unlike (i) includes two dynamic allometric parameters involving allocation to leaves, stem, and coarse roots; iii.–iv. a fixed C allocation scheme with two variants, one representative of observations in evergreen (named "F-Evergreen") and the other of observations in deciduous forests (named "F-Deciduous"). D-CLM4.5 generally overestimated gross primary production (GPP) and ecosystem respiration, and underestimated net ecosystem exchange (NEE). In D-CLM4.5, initial aboveground biomass in 1980 was largely overestimated (between 10 527 and 12 897 g C m -2) for deciduous forests, whereas aboveground biomass accumulation through time (between 1980 and 2011) was highly underestimated (between 1222 and 7557 g C m -2) for both evergreen and deciduous sites due to a lower stem turnover rate in the sites than the one used in the model. D-CLM4.5 overestimated LAI in both evergreen and deciduous sites because the leaf C–LAI relationship in the model did not match the observed leaf C–LAI relationship at our sites. Although the four C allocation schemes gave similar results for aggregated C fluxes, they translated to important differences in long-term aboveground biomass accumulation and aboveground NPP. For deciduous forests, D-Litton gave more realistic C stem/C leaf ratios and strongly reduced the overestimation of initial aboveground biomass and aboveground NPP for deciduous forests by D-CLM4.5. We identified key structural and parameterization deficits that need refinement to improve the accuracy of LSMs in the near future. These include changing how C is allocated in fixed and dynamic schemes based on data from current forest syntheses and different parameterization of allocation schemes for different forest types. Our results highlight the utility of using measurements of aboveground biomass to evaluate and constrain the C allocation scheme in LSMs, and suggest that stem turnover is overestimated by CLM4.5 for these AmeriFlux sites. Understanding the controls of turnover will be critical to improving long-term C processes in LSMs.« less

Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests

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

Montané, Francesc; Fox, Andrew M.; Arellano, Avelino F.

How carbon (C) is allocated to different plant tissues (leaves, stem, and roots) determines how long C remains in plant biomass and thus remains a central challenge for understanding the global C cycle. We used a diverse set of observations (AmeriFlux eddy covariance tower observations, biomass estimates from tree-ring data, and leaf area index (LAI) measurements) to compare C fluxes, pools, and LAI data with those predicted by a land surface model (LSM), the Community Land Model (CLM4.5). We ran CLM4.5 for nine temperate (including evergreen and deciduous) forests in North America between 1980 and 2013 using four different C allocationmore » schemes: i. dynamic C allocation scheme (named "D-CLM4.5") with one dynamic allometric parameter, which allocates C to the stem and leaves to vary in time as a function of annual net primary production (NPP); ii. an alternative dynamic C allocation scheme (named "D-Litton"), where, similar to (i), C allocation is a dynamic function of annual NPP, but unlike (i) includes two dynamic allometric parameters involving allocation to leaves, stem, and coarse roots; iii.–iv. a fixed C allocation scheme with two variants, one representative of observations in evergreen (named "F-Evergreen") and the other of observations in deciduous forests (named "F-Deciduous"). D-CLM4.5 generally overestimated gross primary production (GPP) and ecosystem respiration, and underestimated net ecosystem exchange (NEE). In D-CLM4.5, initial aboveground biomass in 1980 was largely overestimated (between 10 527 and 12 897 g C m -2) for deciduous forests, whereas aboveground biomass accumulation through time (between 1980 and 2011) was highly underestimated (between 1222 and 7557 g C m -2) for both evergreen and deciduous sites due to a lower stem turnover rate in the sites than the one used in the model. D-CLM4.5 overestimated LAI in both evergreen and deciduous sites because the leaf C–LAI relationship in the model did not match the observed leaf C–LAI relationship at our sites. Although the four C allocation schemes gave similar results for aggregated C fluxes, they translated to important differences in long-term aboveground biomass accumulation and aboveground NPP. For deciduous forests, D-Litton gave more realistic C stem/C leaf ratios and strongly reduced the overestimation of initial aboveground biomass and aboveground NPP for deciduous forests by D-CLM4.5. We identified key structural and parameterization deficits that need refinement to improve the accuracy of LSMs in the near future. These include changing how C is allocated in fixed and dynamic schemes based on data from current forest syntheses and different parameterization of allocation schemes for different forest types. Our results highlight the utility of using measurements of aboveground biomass to evaluate and constrain the C allocation scheme in LSMs, and suggest that stem turnover is overestimated by CLM4.5 for these AmeriFlux sites. Understanding the controls of turnover will be critical to improving long-term C processes in LSMs.« less

A global analysis of fine root production as affected by soil nitrogen and phosphorus.

PubMed

Yuan, Z Y; Chen, Han Y H

2012-09-22

Fine root production is the largest component of belowground production and plays substantial roles in the biogeochemical cycles of terrestrial ecosystems. The increasing availability of nitrogen (N) and phosphorus (P) due to human activities is expected to increase aboveground net primary production (ANNP), but the response of fine root production to N and P remains unclear. If roots respond to nutrients as ANNP, fine root production is anticipated to increase with increasing soil N and P. Here, by synthesizing data along the nutrient gradient from 410 natural habitats and from 469 N and/or P addition experiments, we showed that fine root production increased in terrestrial ecosystems with an average increase along the natural N gradient of up to 0.5 per cent with increasing soil N. Fine root production also increased with soil P in natural conditions, particularly at P < 300 mg kg(-1). With N, P and combined N + P addition, fine root production increased by a global average of 27, 21 and 40 per cent, respectively. However, its responses differed among ecosystems and soil types. The global average increases in fine root production are lower than those of ANNP, indicating that above- and belowground counterparts are coupled, but production allocation shifts more to aboveground with higher soil nutrients. Our results suggest that the increasing fertilizer use and combined N deposition at present and in the future will stimulate fine root production, together with ANPP, probably providing a significant influence on atmospheric CO(2) emissions.

Herbivore effects on productivity vary by guild: cattle increase mean productivity while wildlife reduce variability.

PubMed

Charles, Grace K; Porensky, Lauren M; Riginos, Corinna; Veblen, Kari E; Young, Truman P

2017-01-01

Wild herbivores and livestock share the majority of rangelands worldwide, yet few controlled experiments have addressed their individual, additive, and interactive impacts on ecosystem function. While ungulate herbivores generally reduce standing biomass, their effects on aboveground net primary production (ANPP) can vary by spatial and temporal context, intensity of herbivory, and herbivore identity and species richness. Some evidence indicates that moderate levels of herbivory can stimulate aboveground productivity, but few studies have explicitly tested the relationships among herbivore identity, grazing intensity, and ANPP. We used a long-term exclosure experiment to examine the effects of three groups of wild and domestic ungulate herbivores (megaherbivores, mesoherbivore wildlife, and cattle) on herbaceous productivity in an African savanna. Using both field measurements (productivity cages) and satellite imagery, we measured the effects of different herbivore guilds, separately and in different combinations, on herbaceous productivity across both space and time. Results from both productivity cage measurements and satellite normalized difference vegetation index (NDVI) demonstrated a positive relationship between mean productivity and total ungulate herbivore pressure, driven in particular by the presence of cattle. In contrast, we found that variation in herbaceous productivity across space and time was driven by the presence of wild herbivores (primarily mesoherbivore wildlife), which significantly reduced heterogeneity in ANPP and NDVI across both space and time. Our results indicate that replacing wildlife with cattle (at moderate densities) could lead to similarly productive but more heterogeneous herbaceous plant communities in rangelands. © 2016 by the Ecological Society of America.

Belowground impacts of perennial grass cultivation for sustainable biofuel feedstock production in the tropics

DOE PAGES

Sumiyoshi, Yudai; Crow, Susan E.; Litton, Creighton M.; ...

2016-07-08

Perennial grasses can sequester soil organic carbon (SOC) in sustainably managed biofuel systems, directly mitigating atmospheric CO 2 concentrations while simultaneously generating biomass for renewable energy. Our objective was to quantify SOC accumulation and identify the primary drivers of belowground C dynamics in a zero-tillage production system of tropical perennial C4 grasses grown for biofuel feedstock in Hawaii. Specifically, the quantity, quality, and fate of soil C inputs were determined for eight grass accessions – four varieties each of napier grass and guinea grass. Carbon fluxes (soil CO 2 efflux, aboveground net primary productivity, litterfall, total belowground carbon flux, rootmore » decay constant), C pools (SOC pool and root biomass), and C quality (root chemistry, C and nitrogen concentrations, and ratios) were measured through three harvest cycles following conversion of a fallow field to cultivated perennial grasses. A wide range of SOC accumulation occurred, with both significant species and accession effects. Aboveground biomass yield was greater, and root lignin concentration was lower for napier grass than guinea grass. Structural equation modeling revealed that root lignin concentration was the most important driver of SOC pool: varieties with low root lignin concentration, which was significantly related to rapid root decomposition, accumulated the greatest amount of SOC. Roots with low lignin concentration decomposed rapidly, but the residue and associated microbial biomass/by-products accumulated as SOC. In general, napier grass was better suited for promoting soil C sequestration in this system. Further, high-yielding varieties with low root lignin concentration provided the greatest climate change mitigation potential in a ratoon system. By understanding the factors affecting SOC accumulation and the net greenhouse gas trade-offs within a biofuel production system will aid in crop selection to meet multiple goals toward environmental and economic sustainability.« less

Canopy carbon net assimilation of an urban, naturally assembled brownfield forest

NASA Astrophysics Data System (ADS)

Schafer, K. V.; Wadhwa, S.; Tripathee, R.; Gallagher, F. J.

2010-12-01

In this study, we have been investigating an urban brownfield at Liberty State Park that has been abandoned approximately for 40 years. Natural colonization has taken place that allowed a pioneer forest to grow with primarily Betula populifera and Populus spec. Despite soil metal contamination this urban forest exhibits moderate annual productivity and serves as a carbon sink. Diameters at breast height (DBH, 1.35 m above ground) of all trees in a study plot were measured. Aboveground biomass equations were determined for both species through destructive sampling. Aboveground net primary production was about 770 gC m-2 a-1 in 2009. Canopy net assimilation (AnC) was modeled with the canopy conductance constrained assimilation (4CA) model using measured sapflux derived conductance and photosynthetic parameters measured with a LICOR 6400. Annual AnC in 2009 was approximately 1500 gC m-2 a-1 thus with a partitioning of biomass and respiration in the same range of most natural forest with less anthropogenic induced stress. Urban brownfields thus can serve as C sinks and provide phytostabilization of contaminants.

Simulating carbon stocks and fluxes of an African tropical montane forest with an individual-based forest model.

PubMed

Fischer, Rico; Ensslin, Andreas; Rutten, Gemma; Fischer, Markus; Schellenberger Costa, David; Kleyer, Michael; Hemp, Andreas; Paulick, Sebastian; Huth, Andreas

2015-01-01

Tropical forests are carbon-dense and highly productive ecosystems. Consequently, they play an important role in the global carbon cycle. In the present study we used an individual-based forest model (FORMIND) to analyze the carbon balances of a tropical forest. The main processes of this model are tree growth, mortality, regeneration, and competition. Model parameters were calibrated using forest inventory data from a tropical forest at Mt. Kilimanjaro. The simulation results showed that the model successfully reproduces important characteristics of tropical forests (aboveground biomass, stem size distribution and leaf area index). The estimated aboveground biomass (385 t/ha) is comparable to biomass values in the Amazon and other tropical forests in Africa. The simulated forest reveals a gross primary production of 24 tcha(-1) yr(-1). Modeling above- and belowground carbon stocks, we analyzed the carbon balance of the investigated tropical forest. The simulated carbon balance of this old-growth forest is zero on average. This study provides an example of how forest models can be used in combination with forest inventory data to investigate forest structure and local carbon balances.

The effects of prescribed fire and silvicultural thinning on the aboveground carbon stocks and net primary production of overstory trees in an oak-hickory ecosystem in southern Ohio

Treesearch

Jyh-Min Chiang; Ryan W. McEwan; Daniel A. Yaussy; Kim J. Brown

2008-01-01

More than 70 years of fire suppression has influenced forest dynamics and led to the accumulation of fuels in many forests of the United States. To address these changes, forest managers increasingly seek to restore historical ecosystem structure and function through the reintroduction of fire and disturbance processes that mimic fire such as silvicultural thinning. In...

Urbanization effects on leaf litter decomposition, foliar nutrient dynamics and aboveground net primary productivity in the subtropics

Treesearch

Heather A. Enloe; B. Graeme Lockaby; Wayne C. Zipperer; Greg L. Somers

2015-01-01

Urbanization can alter nutrient cycling. This research evaluated how urbanization affected nutrient dynamics in the subtropics. We established 17–0.04 ha plots in five different land cover types—slash pine (Pinus elliottii) plantations (n=3), rural natural pine forests (n= 3), rural natural oak forests (n=4), urban pine forests (n=3) and urban oak forests (n=4) in the...

Early spring, severe frost events, and drought induce rapid carbon loss in high elevation meadows.

PubMed

Arnold, Chelsea; Ghezzehei, Teamrat A; Berhe, Asmeret Asefaw

2014-01-01

By the end of the 20th century, the onset of spring in the Sierra Nevada mountain range of California has been occurring on average three weeks earlier than historic records. Superimposed on this trend is an increase in the presence of highly anomalous "extreme" years, where spring arrives either significantly late or early. The timing of the onset of continuous snowpack coupled to the date at which the snowmelt season is initiated play an important role in the development and sustainability of mountain ecosystems. In this study, we assess the impact of extreme winter precipitation variation on aboveground net primary productivity and soil respiration over three years (2011 to 2013). We found that the duration of snow cover, particularly the timing of the onset of a continuous snowpack and presence of early spring frost events contributed to a dramatic change in ecosystem processes. We found an average 100% increase in soil respiration in 2012 and 2103, compared to 2011, and an average 39% decline in aboveground net primary productivity observed over the same time period. The overall growing season length increased by 57 days in 2012 and 61 days in 2013. These results demonstrate the dependency of these keystone ecosystems on a stable climate and indicate that even small changes in climate can potentially alter their resiliency.

Climatic controls of aboveground net primary production in semi-arid grasslands along a latitudinal gradient portend low sensitivity to warming

USGS Publications Warehouse

Mowll, Whitney; Blumenthal, Dana M.; Cherwin, Karie; Smith, Anine; Symstad, Amy J.; Vermeire, Lance; Collins, Scott L.; Smith, Melinda D.; Knapp, Alan K.

2015-01-01

Although climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary production (ANPP) in most grasslands. Conversely, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming? We evaluated climate and multi-year ANPP data (67 years) from eight western US grasslands arrayed along mean annual temperature (MAT; ~7-14 °C) and mean annual precipitation (MAP; ~250-500 mm) gradients. Weused regression and analysis of covariance to assess relationships between ANPP and temperature, as well as precipitation (annual and growing season) to evaluate temperature sensitivity of ANPP. We also related ANPP to the standardized precipitation evaporation index (SPEI), which combines precipitation and evapotranspiration to better represent moisture available for plant growth. Regression models indicated that variation in growing season temperature was negatively related to total and graminoid ANPP, but precipitation was a stronger predictor than temperature. Growing season temperature was also a significant parameter in more complex models, but again precipitation was consistently a stronger predictor of ANPP. Surprisingly, neither annual nor growing season SPEI were as strongly related to ANPP as precipitation. We conclude that forecasted warming likely will affect ANPP in these grasslands, but that predicting temperature effects from natural climatic gradients is difficult. This is because, unlike precipitation, warming effects can be positive or negative and moderated by shifts in the C3/C4 ratios of plant communities.

Primary productivity of angiosperm and macroalgae dominated habitats in a New England Salt Marsh: a Comparative analysis

NASA Astrophysics Data System (ADS)

Roman, C. T.; Able, K. W.; Lazzari, M. A.; Heck, K. L.

1990-01-01

Net primary productivity estimates were made for the major macrophyte dominated habitats of the Nauset Marsh system, Cape Cod, Massachusetts. Above-ground primary productivity of short form Spartina alterniflora, the dominant habitat of the system, was 664 g m -2 y -1. Productivity of the other dominant angiosperm ( Zostera marina) was estimated to range from 444-987 g m -2 y -1. The marsh creekbank habitat was dominated by an intertidal zone of fucoid algae ( Ascophyllum nodosum ecad. scorpioides, 1179 g m -2 y -1; Fucus vesiculosus, 426 g m -2 y -1), mixed intertidal filamentous algae (91 g m -2 y -1), and a subtidal zone of assorted macroalgae (68 g m -2 y -1). Intertidal mudflats were dominated by Cladophora gracilis, with net production ranging from 59-637 g m -2 y -1. These angiosperm and macrophyte and macrophyte dominated habitats produce over 3 × 10 6 kg y -1 of biomass (1·2 × 10 6 kg carbon y -1). Twenty-eight per cent (28%) of this carbon production is derived from the Zostera and macroalgae habitats. Although S. alterniflora is considered the major macrophyte primary producer in Nauset Marsh and other north temperate salt marshes, it is concluded that other habitats also contribute significantly to total system carbon production.

Primary productivity of angiosperm and macroalgae dominated habitats in a New England salt marsh: a comparative analysis

USGS Publications Warehouse

Roman, C.T.; Able, K.W.; Lazzari, M.A.; Heck, K.L.

1990-01-01

Net primary productivity estimates were made for the major macrophyte dominated habitats of the Nauset Marsh system, Cape Cod, Massachusetts. Above-ground primary productivity of short form Spartina alterniflora, the dominant habitat of the system, was 664 g m-2 y-1. Productivity of the other dominant angiosperm (Zostera marina) was estimated to range from 444?987 g m-2 y-1. The marsh creekbank habitat was dominated by an intertidal zone of fucoid algae (Ascophyllum nodosum ecad. scorpioides, 1179 g m-2 y-1; Fucus vesiculosus, 426 g m-2 y-1), mixed intertidal filamentous algae (91 g m-2 y-1), and a subtidal zone of assorted macroalgae (68 g m-2 y-1). Intertidal mudflats were dominated by Cladophora gracilis, with net production ranging from 59?637 g m-2 y-1. These angiosperm and macrophyte and macrophyte dominated habitats produce over 3 ? 106 kg y-1 of biomass (1?2 ? 106 kg carbon y-1). Twenty-eight per cent (28%) of this carbon production is derived from the Zostera and macroalgae habitats. Although S. alterniflora is considered the major macrophyte primary producer in Nauset Marsh and other north temperate salt marshes, it is concluded that other habitats also contribute significantly to total system carbon production.

Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system.

PubMed

Charbonnier, Fabien; Roupsard, Olivier; le Maire, Guerric; Guillemot, Joannès; Casanoves, Fernando; Lacointe, André; Vaast, Philippe; Allinne, Clémentine; Audebert, Louise; Cambou, Aurélie; Clément-Vidal, Anne; Defrenet, Elsa; Duursma, Remko A; Jarri, Laura; Jourdan, Christophe; Khac, Emmanuelle; Leandro, Patricia; Medlyn, Belinda E; Saint-André, Laurent; Thaler, Philippe; Van Den Meersche, Karel; Barquero Aguilar, Alejandra; Lehner, Peter; Dreyer, Erwin

2017-08-01

In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees. © 2017 John Wiley & Sons Ltd.

Genetic basis of aboveground productivity in two native Populus species and their hybrids.

PubMed

Lojewski, Nathan R; Fischer, Dylan G; Bailey, Joseph K; Schweitzer, Jennifer A; Whitham, Thomas G; Hart, Stephen C

2009-09-01

Demonstration of genetic control over riparian tree productivity has major implications for responses of riparian systems to shifting environmental conditions and effects of genetics on ecosystems in general. We used field studies and common gardens, applying both molecular and quantitative techniques, to compare plot-level tree aboveground net primary productivity (ANPP(tree)) and individual tree growth rate constants in relation to plant genetic identity in two naturally occurring Populus tree species and their hybrids. In field comparisons of four cross types (Populus fremontii S. Wats., Populus angustifolia James, F(1) hybrids and backcross hybrids) across 11 natural stands, productivity was greatest for P. fremontii trees, followed by hybrids and lowest in P. angustifolia. A similar pattern was observed in four common gardens across a 290 m elevation and 100 km environmental gradient. Despite a doubling in productivity across the common gardens, the relative differences among the cross types remained constant. Using clonal replicates in a common garden, we found ANPP(tree) to be a heritable plant trait (i.e., broad-sense heritability), such that plant genetic factors explained between 38% and 82% of the variation in ANPP(tree). Furthermore, analysis of the genetic composition among individual tree genotypes using restriction fragment length polymorphism molecular markers showed that genetically similar trees also exhibited similar ANPP(tree). These findings indicate strong genetic contributions to natural variation in ANPP with important ecological implications.

Long-term effects of fuel treatments on aboveground biomass accumulation in ponderosa pine forests of the northern Rocky Mountains

Treesearch

Kate A. Clyatt; Christopher R. Keyes; Sharon M. Hood

2017-01-01

Fuel treatments in ponderosa pine forests of the northern Rocky Mountains are commonly used to modify fire behavior, but it is unclear how different fuel treatments impact the subsequent production and distribution of aboveground biomass, especially in the long term. This research evaluated aboveground biomass responses 23 years after treatment in two silvicultural...

Shifts in biomass and productivity for a subtropical dry forest in response to simulated elevated hurricane disturbances

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

Holm, Jennifer A.; Van Bloem, Skip J.; Larocque, Guy R.

Caribbean tropical forests are subject to hurricane disturbances of great variability. In addition to natural storm incongruity, climate change can alter storm formation, duration, frequency, and intensity. This model -based investigation assessed the impacts of multiple storms of different intensities and occurrence frequencies on the long-term dynamics of subtropical dry forests in Puerto Rico. Using the previously validated individual-based gap model ZELIG-TROP, we developed a new hurricane damage routine and parameterized it with site- and species-specific hurricane effects. A baseline case with the reconstructed historical hurricane regime represented the control condition. Ten treatment cases, reflecting plausible shifts in hurricane regimes,more » manipulated both hurricane return time (i.e. frequency) and hurricane intensity. The treatment-related change in carbon storage and fluxes were reported as changes in aboveground forest biomass (AGB), net primary productivity (NPP), and in the aboveground carbon partitioning components, or annual carbon accumulation (ACA). Increasing the frequency of hurricanes decreased aboveground biomass by between 5% and 39%, and increased NPP between 32% and 50%. Decadal-scale biomass fluctuations were damped relative to the control. In contrast, increasing hurricane intensity did not create a large shift in the long-term average forest structure, NPP, or ACA from that of historical hurricane regimes, but produced large fluctuations in biomass. Decreasing both the hurricane intensity and frequency by 50% produced the highest values of biomass and NPP. For the control scenario and with increased hurricane intensity, ACA was negative, which indicated that the aboveground forest components acted as a carbon source. However, with an increase in the frequency of storms or decreased storms, the total ACA was positive due to shifts in leaf production, annual litterfall, and coarse woody debris inputs, indicating a carbon sink into the forest over the long-term. The carbon loss from each hurricane event, in all scenarios, always recovered over sufficient time. Our results suggest that subtropical dry forests will remain resilient to hurricane disturbance. However carbon stocks will decrease if future climates increase hurricane frequency by 50% or more.« less

Shifts in biomass and productivity for a subtropical dry forest in response to simulated elevated hurricane disturbances

NASA Astrophysics Data System (ADS)

Holm, Jennifer A.; Van Bloem, Skip J.; Larocque, Guy R.; Shugart, Herman H.

2017-02-01

Caribbean tropical forests are subject to hurricane disturbances of great variability. In addition to natural storm incongruity, climate change can alter storm formation, duration, frequency, and intensity. This model-based investigation assessed the impacts of multiple storms of different intensities and occurrence frequencies on the long-term dynamics of subtropical dry forests in Puerto Rico. Using the previously validated individual-based gap model ZELIG-TROP, we developed a new hurricane damage routine and parameterized it with site- and species-specific hurricane effects. A baseline case with the reconstructed historical hurricane regime represented the control condition. Ten treatment cases, reflecting plausible shifts in hurricane regimes, manipulated both hurricane return time (i.e. frequency) and hurricane intensity. The treatment-related change in carbon storage and fluxes were reported as changes in aboveground forest biomass (AGB), net primary productivity (NPP), and in the aboveground carbon partitioning components, or annual carbon accumulation (ACA). Increasing the frequency of hurricanes decreased aboveground biomass by between 5% and 39%, and increased NPP between 32% and 50%. Decadal-scale biomass fluctuations were damped relative to the control. In contrast, increasing hurricane intensity did not create a large shift in the long-term average forest structure, NPP, or ACA from that of historical hurricane regimes, but produced large fluctuations in biomass. Decreasing both the hurricane intensity and frequency by 50% produced the highest values of biomass and NPP. For the control scenario and with increased hurricane intensity, ACA was negative, which indicated that the aboveground forest components acted as a carbon source. However, with an increase in the frequency of storms or decreased storms, the total ACA was positive due to shifts in leaf production, annual litterfall, and coarse woody debris inputs, indicating a carbon sink into the forest over the long-term. The carbon loss from each hurricane event, in all scenarios, always recovered over sufficient time. Our results suggest that subtropical dry forests will remain resilient to hurricane disturbance. However carbon stocks will decrease if future climates increase hurricane frequency by 50% or more.

Shifts in biomass and productivity for a subtropical dry forest in response to simulated elevated hurricane disturbances

DOE PAGES

Holm, Jennifer A.; Van Bloem, Skip J.; Larocque, Guy R.; ...

2017-02-07

Caribbean tropical forests are subject to hurricane disturbances of great variability. In addition to natural storm incongruity, climate change can alter storm formation, duration, frequency, and intensity. This model -based investigation assessed the impacts of multiple storms of different intensities and occurrence frequencies on the long-term dynamics of subtropical dry forests in Puerto Rico. Using the previously validated individual-based gap model ZELIG-TROP, we developed a new hurricane damage routine and parameterized it with site- and species-specific hurricane effects. A baseline case with the reconstructed historical hurricane regime represented the control condition. Ten treatment cases, reflecting plausible shifts in hurricane regimes,more » manipulated both hurricane return time (i.e. frequency) and hurricane intensity. The treatment-related change in carbon storage and fluxes were reported as changes in aboveground forest biomass (AGB), net primary productivity (NPP), and in the aboveground carbon partitioning components, or annual carbon accumulation (ACA). Increasing the frequency of hurricanes decreased aboveground biomass by between 5% and 39%, and increased NPP between 32% and 50%. Decadal-scale biomass fluctuations were damped relative to the control. In contrast, increasing hurricane intensity did not create a large shift in the long-term average forest structure, NPP, or ACA from that of historical hurricane regimes, but produced large fluctuations in biomass. Decreasing both the hurricane intensity and frequency by 50% produced the highest values of biomass and NPP. For the control scenario and with increased hurricane intensity, ACA was negative, which indicated that the aboveground forest components acted as a carbon source. However, with an increase in the frequency of storms or decreased storms, the total ACA was positive due to shifts in leaf production, annual litterfall, and coarse woody debris inputs, indicating a carbon sink into the forest over the long-term. The carbon loss from each hurricane event, in all scenarios, always recovered over sufficient time. Our results suggest that subtropical dry forests will remain resilient to hurricane disturbance. However carbon stocks will decrease if future climates increase hurricane frequency by 50% or more.« less

Individual tree size inequality enhances aboveground biomass in homegarden agroforestry systems in the dry zone of Sri Lanka.

PubMed

Ali, Arshad; Mattsson, Eskil

2017-01-01

Individual tree size variation, which is generally quantified by variances in tree diameter at breast height (DBH) and height in isolation or conjunction, plays a central role in ecosystem functioning in both controlled and natural environments, including forests. However, none of the studies have been conducted in homegarden agroforestry systems. In this study, aboveground biomass, stand quality, cation exchange capacity (CEC), DBH variation, and species diversity were determined across 45 homegardens in the dry zone of Sri Lanka. We employed structural equation modeling (SEM) to test for the direct and indirect effects of stand quality and CEC, via tree size inequality and species diversity, on aboveground biomass. The SEM accounted for 26, 8, and 1% of the variation in aboveground biomass, species diversity and DBH variation, respectively. DBH variation had the strongest positive direct effect on aboveground biomass (β=0.49), followed by the non-significant direct effect of species diversity (β=0.17), stand quality (β=0.17) and CEC (β=-0.05). There were non-significant direct effects of CEC and stand quality on DBH variation and species diversity. Stand quality and CEC had also non-significant indirect effects, via DBH variation and species diversity, on aboveground biomass. Our study revealed that aboveground biomass substantially increased with individual tree size variation only, which supports the niche complementarity mechanism. However, aboveground biomass was not considerably increased with species diversity, stand quality and soil fertility, which might be attributable to the adaptation of certain productive species to the local site conditions. Stand structure shaped by few productive species or independent of species diversity is a main determinant for the variation in aboveground biomass in the studied homegardens. Maintaining stand structure through management practices could be an effective approach for enhancing aboveground biomass in these dry zone homegarden agroforestry systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of grassland cutting frequency on soil carbon storage - a case study on public lawns in three Swedish cities

NASA Astrophysics Data System (ADS)

Poeplau, C.; Marstorp, H.; Thored, K.; Kätterer, T.

2016-04-01

Soils contain the largest terrestrial carbon pool and thus play a crucial role in the global carbon cycle. Grassland soils have particularly high soil organic carbon (SOC) stocks. In Europe (EU 25), grasslands cover 22 % of the land area. It is therefore important to understand the effects of grassland management and management intensity on SOC storage. City lawns constitute a unique study system in this context, since they provide a high functional diversity and thus a wide range of different management intensities per unit area. In this study we investigated frequently mown (on average eight times per season) utility lawns and rarely mown (once per season) meadow-like lawns at three multi-family housing areas in each of three Swedish cities: Uppsala, Malmö, and Gothenburg. The two different lawn types were compared regarding their aboveground net primary production (NPP) and SOC storage. In addition, root biomass was determined in Uppsala. We found significantly higher aboveground NPP and SOC concentrations and significantly lower soil C : N ratio for the utility lawns compared with the meadow-like lawns. On average, aboveground NPP was 24 % or 0.7 Mg C ha-1 yr-1 higher and SOC was 12 % or 7.8 Mg ha-1 higher. Differences in SOC were well explained by differences in aboveground NPP (R2 = 0.39), which indicates that the increase in productivity due to more optimum CO2-assimilating leaf area, leading to higher carbon input to the soil, was the major driver for soil carbon sequestration. Differences in soil C : N ratio indicated a more closed N cycle in utility lawns, which might have additionally affected SOC dynamics. We did not find any difference in root biomass between the two management regimes, and concluded that cutting frequency most likely only exerts an effect on SOC when cuttings are left on the surface.

Global-scale impacts of nitrogen deposition on tree carbon sequestration in tropical, temperate, and boreal forests: A meta-analysis.

PubMed

Schulte-Uebbing, Lena; de Vries, Wim

2018-02-01

Elevated nitrogen (N) deposition may increase net primary productivity in N-limited terrestrial ecosystems and thus enhance the terrestrial carbon (C) sink. To assess the magnitude of this N-induced C sink, we performed a meta-analysis on data from forest fertilization experiments to estimate N-induced C sequestration in aboveground tree woody biomass, a stable C pool with long turnover times. Our results show that boreal and temperate forests responded strongly to N addition and sequestered on average an additional 14 and 13 kg C per kg N in aboveground woody biomass, respectively. Tropical forests, however, did not respond significantly to N addition. The common hypothesis that tropical forests do not respond to N because they are phosphorus-limited could not be confirmed, as we found no significant response to phosphorus addition in tropical forests. Across climate zones, we found that young forests responded more strongly to N addition, which is important as many previous meta-analyses of N addition experiments rely heavily on data from experiments on seedlings and young trees. Furthermore, the C-N response (defined as additional mass unit of C sequestered per additional mass unit of N addition) was affected by forest productivity, experimental N addition rate, and rate of ambient N deposition. The estimated C-N responses from our meta-analysis were generally lower that those derived with stoichiometric scaling, dynamic global vegetation models, and forest growth inventories along N deposition gradients. We estimated N-induced global C sequestration in tree aboveground woody biomass by multiplying the C-N responses obtained from the meta-analysis with N deposition estimates per biome. We thus derived an N-induced global C sink of about 177 (112-243) Tg C/year in aboveground and belowground woody biomass, which would account for about 12% of the forest biomass C sink (1,400 Tg C/year). © 2017 John Wiley & Sons Ltd.

Regional contingencies in the relationship between aboveground biomass and litter in the world’s grasslands

Treesearch

L.R. O' Halloran; E.T. Borer; E.W. Seabloom; A.S. MacDougall; E.E. Cleland; R.L. McCulley; S. Hobbie; S. Harpole; N.M. DeCrappeo; C.-J. Chu; J.D. Bakker; K.F. Davies; G. Du; J. Firn; N. Hagenah; K.S. Hofmockel; J.M.H. Knops; W. Li; B.A. Melbourne; J.W. Morgan; J.L. Orrock; S.M. Prober; C.J. Stevens

2013-01-01

Based on regional-scale studies, aboveground production and litter decomposition are thought to positively covary, because they are driven by shared biotic and climatic factors. Until now we have been unable to test whether production and decomposition are generally coupled across climatically dissimilar regions, because we lacked replicated data collected within a...

Final Harvest of Above-Ground Biomass and Allometric Analysis of the Aspen FACE Experiment

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

Mark E. Kubiske

The Aspen FACE experiment, located at the US Forest Service Harshaw Research Facility in Oneida County, Wisconsin, exposes the intact canopies of model trembling aspen forests to increased concentrations of atmospheric CO2 and O3. The first full year of treatments was 1998 and final year of elevated CO2 and O3 treatments is scheduled for 2009. This proposal is to conduct an intensive, analytical harvest of the above-ground parts of 24 trees from each of the 12, 30 m diameter treatment plots (total of 288 trees) during June, July & August 2009. This above-ground harvest will be carefully coordinated with themore » below-ground harvest proposed by D.F. Karnosky et al. (2008 proposal to DOE). We propose to dissect harvested trees according to annual height growth increment and organ (main stem, branch orders, and leaves) for calculation of above-ground biomass production and allometric comparisons among aspen clones, species, and treatments. Additionally, we will collect fine root samples for DNA fingerprinting to quantify biomass production of individual aspen clones. This work will produce a thorough characterization of above-ground tree and stand growth and allocation above ground, and, in conjunction with the below ground harvest, total tree and stand biomass production, allocation, and allometry.« less

[Simulation study on the effects of climate change on aboveground biomass of plantation in southern China: Taking Moshao forest farm in Huitong Ecological Station as an example].

PubMed

Dai, Er Fu; Zhou, Heng; Wu, Zhuo; Wang, Xiao-Fan; Xi, Wei Min; Zhu, Jian Jia

2016-10-01

Global climate warming has significant effect on territorial ecosystem, especially on forest ecosystem. The increase in temperature and radiative forcing will significantly alter the structure and function of forest ecosystem. The southern plantation is an important part of forests in China, its response to climate change is getting more and more intense. In order to explore the responses of southern plantation to climate change under future climate scenarios and to reduce the losses that might be caused by climate change, we used climatic estimated data under three new emission scenarios, representative concentration pathways (RCPs) scenarios (RCP2.6 scenario, RCP4.5 scenario, and RCP8.5 scenario). We used the spatially dynamic forest landscape model LANDIS-2, coupled with a forest ecosystem process model PnET-2, to simulate the impact of climate change on aboveground net primary production (ANPP), species' establishment probability (SEP) and aboveground biomass of Moshao forest farm in Huitong Ecological Station, which located in Hunan Province during the period of 2014-2094. The results showed that there were obvious differences in SEP and ANPP among different forest types under changing climate. The degrees of response of SEP to climate change for different forest types were shown as: under RCP2.6 and RCP4.5, artificial coniferous forest>natural broadleaved forest>artificial broadleaved forest. Under RCP8.5, natural broadleaved forest>artificial broadleaved forest>artificial coniferous forest. The degrees of response of ANPP to climate change for different forest types were shown as: under RCP2.6, artificial broadleaved forest> natural broadleaved forest>artificial coniferous forest. Under RCP4.5 and RCP8.5, natural broadleaved forest>artificial broadleaved forest>artificial coniferous forest. The aboveground biomass of the artificial coniferous forest would decline at about 2050, but the natural broadleaved forest and artificial broadleaved forest showed a rising trend in general. During the period of 2014-2094, the total aboveground biomass under RCP2.6, RCP4.5 and RCP8.5 scenarios increased by 68.2%, 79.3% and 72.6%, respectively. The total aboveground biomass under various climatic scenarios sort as: RCP4.5>RCP8.5>RCP2.6. We thought that an appropriate temperature might be beneficial to the biomass accumulation in this study area. However, overextended temperature might hinder the sustainable development of forest production and ecological function.

Using a Multi-Trait Approach to Manipulate Plant Functional Diversity in a Biodiversity-Ecosystem Function Experiment

PubMed Central

Schittko, Conrad; Hawa, Mahmoud; Wurst, Susanne

2014-01-01

A frequent pattern emerging from biodiversity-ecosystem function studies is that functional group richness enhances ecosystem functions such as primary productivity. However, the manipulation of functional group richness goes along with major disadvantages like the transformation of functional trait data into categories or the exclusion of functional differences between organisms in the same group. In a mesocosm study we manipulated plant functional diversity based on the multi-trait Functional Diversity (FD)-approach of Petchey and Gaston by using database data of seven functional traits and information on the origin of the species in terms of being native or exotic. Along a gradient ranging from low to high FD we planted 40 randomly selected eight-species mixtures under controlled conditions. We found a significant positive linear correlation of FD with aboveground productivity and a negative correlation with invasibility of the plant communities. Based on community-weighted mean calculations for each functional trait, we figured out that the traits N-fixation and species origin, i.e. being native or exotic, played the most important role for community productivity. Our results suggest that the identification of the impact of functional trait diversity and the relative contributions of relevant traits is essential for a mechanistic understanding of the role of biodiversity for ecosystem functions such as aboveground biomass production and resistance against invasion. PMID:24897501

Current ozone levels threaten gross primary production and yield of Mediterranean annual pastures and nitrogen modulates the response

NASA Astrophysics Data System (ADS)

Calvete-Sogo, Héctor; Elvira, Susana; Sanz, Javier; González-Fernández, Ignacio; García-Gómez, Héctor; Sánchez-Martín, Laura; Alonso, Rocío; Bermejo-Bermejo, Victoria

2014-10-01

Pastures are among the most important ecosystems in Europe considering their biodiversity and distribution area. However, their response to increasing tropospheric ozone (O3) and nitrogen (N) deposition, two of the main drivers of global change, is still uncertain. A new Open-Top Chamber (OTC) experiment was performed in central Spain, aiming to study annual pasture response to O3 and N in close to natural growing conditions. A mixture of six species of three representative families was sowed in the field. Plants were exposed for 40 days to four O3 treatments: filtered air, non-filtered air (NFA) reproducing ambient levels and NFA supplemented with 20 and 40 nl l-1 O3. Three N treatments were considered to reach the N integrated doses of “background”, +20 or +40 kg N ha-1. Ozone significantly reduced green and total aboveground biomass (maximum reduction 25%) and increased the senescent biomass (maximum increase 40%). Accordingly, O3 decreased community Gross Primary Production due to both a global reduction of ecosystem CO2 exchange and an increase of ecosystem respiration. Nitrogen could partially counterbalance O3 effects on aboveground biomass when the levels of O3 were moderate, but at the same time O3 exposure reduced the fertilization effect of higher N availability. Therefore, O3 must be considered as a stress factor for annual pastures in the Mediterranean areas.

Simulating Carbon Stocks and Fluxes of an African Tropical Montane Forest with an Individual-Based Forest Model

PubMed Central

Fischer, Rico; Ensslin, Andreas; Rutten, Gemma; Fischer, Markus; Schellenberger Costa, David; Kleyer, Michael; Hemp, Andreas; Paulick, Sebastian; Huth, Andreas

2015-01-01

Tropical forests are carbon-dense and highly productive ecosystems. Consequently, they play an important role in the global carbon cycle. In the present study we used an individual-based forest model (FORMIND) to analyze the carbon balances of a tropical forest. The main processes of this model are tree growth, mortality, regeneration, and competition. Model parameters were calibrated using forest inventory data from a tropical forest at Mt. Kilimanjaro. The simulation results showed that the model successfully reproduces important characteristics of tropical forests (aboveground biomass, stem size distribution and leaf area index). The estimated aboveground biomass (385 t/ha) is comparable to biomass values in the Amazon and other tropical forests in Africa. The simulated forest reveals a gross primary production of 24 tcha-1yr-1. Modeling above- and belowground carbon stocks, we analyzed the carbon balance of the investigated tropical forest. The simulated carbon balance of this old-growth forest is zero on average. This study provides an example of how forest models can be used in combination with forest inventory data to investigate forest structure and local carbon balances. PMID:25915854

Responses of plant community composition and biomass production to warming and nitrogen deposition in a temperate meadow ecosystem.

PubMed

Zhang, Tao; Guo, Rui; Gao, Song; Guo, Jixun; Sun, Wei

2015-01-01

Climate change has profound influences on plant community composition and ecosystem functions. However, its effects on plant community composition and biomass production are not well understood. A four-year field experiment was conducted to examine the effects of warming, nitrogen (N) addition, and their interactions on plant community composition and biomass production in a temperate meadow ecosystem in northeast China. Experimental warming had no significant effect on plant species richness, evenness, and diversity, while N addition highly reduced the species richness and diversity. Warming tended to reduce the importance value of graminoid species but increased the value of forbs, while N addition had the opposite effect. Warming tended to increase the belowground biomass, but had an opposite tendency to decrease the aboveground biomass. The influences of warming on aboveground production were dependent upon precipitation. Experimental warming had little effect on aboveground biomass in the years with higher precipitation, but significantly suppressed aboveground biomass in dry years. Our results suggest that warming had indirect effects on plant production via its effect on the water availability. Nitrogen addition significantly increased above- and below-ground production, suggesting that N is one of the most important limiting factors determining plant productivity in the studied meadow steppe. Significant interactive effects of warming plus N addition on belowground biomass were also detected. Our observations revealed that environmental changes (warming and N deposition) play significant roles in regulating plant community composition and biomass production in temperate meadow steppe ecosystem in northeast China.

Effects of water table position and plant functional group on plant community, aboveground production, and peat properties in a peatland mesocosm experiment (PEATcosm)

Treesearch

Lynette R. Potvin; Evan S. Kane; Rodney A. Chimner; Randall K. Kolka; Erik A. Lilleskov

2015-01-01

Aims Our objective was to assess the impacts of water table position and plant functional type on peat structure, plant community composition and aboveground plant production. Methods We initiated a full factorial experiment with 2 water table (WT) treatments (high and low) and 3 plant functional groups (PFG: sedge, Ericaceae,...

Experimentally increased nutrient availability at the permafrost thaw front selectively enhances biomass production of deep-rooting subarctic peatland species.

PubMed

Keuper, Frida; Dorrepaal, Ellen; van Bodegom, Peter M; van Logtestijn, Richard; Venhuizen, Gemma; van Hal, Jurgen; Aerts, Rien

2017-10-01

Climate warming increases nitrogen (N) mineralization in superficial soil layers (the dominant rooting zone) of subarctic peatlands. Thawing and subsequent mineralization of permafrost increases plant-available N around the thaw-front. Because plant production in these peatlands is N-limited, such changes may substantially affect net primary production and species composition. We aimed to identify the potential impact of increased N-availability due to permafrost thawing on subarctic peatland plant production and species performance, relative to the impact of increased N-availability in superficial organic layers. Therefore, we investigated whether plant roots are present at the thaw-front (45 cm depth) and whether N-uptake ( 15 N-tracer) at the thaw-front occurs during maximum thaw-depth, coinciding with the end of the growing season. Moreover, we performed a unique 3-year belowground fertilization experiment with fully factorial combinations of deep- (thaw-front) and shallow-fertilization (10 cm depth) and controls. We found that certain species are present with roots at the thaw-front (Rubus chamaemorus) and have the capacity (R. chamaemorus, Eriophorum vaginatum) for N-uptake from the thaw-front between autumn and spring when aboveground tissue is largely senescent. In response to 3-year shallow-belowground fertilization (S) both shallow- (Empetrum hermaphroditum) and deep-rooting species increased aboveground biomass and N-content, but only deep-rooting species responded positively to enhanced nutrient supply at the thaw-front (D). Moreover, the effects of shallow-fertilization and thaw-front fertilization on aboveground biomass production of the deep-rooting species were similar in magnitude (S: 71%; D: 111% increase compared to control) and additive (S + D: 181% increase). Our results show that plant-available N released from thawing permafrost can form a thus far overlooked additional N-source for deep-rooting subarctic plant species and increase their biomass production beyond the already established impact of warming-driven enhanced shallow N-mineralization. This may result in shifts in plant community composition and may partially counteract the increased carbon losses from thawing permafrost. © 2017 John Wiley & Sons Ltd.

Annual Removal of Aboveground Plant Biomass Alters Soil Microbial Responses to Warming

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

Xue, Kai; Yuan, Mengting M.; Xie, Jianping

Clipping (i.e., harvesting aboveground plant biomass) is common in agriculture and for bioenergy production. However, microbial responses to clipping in the context of climate warming are poorly understood. We investigated the interactive effects of grassland warming and clipping on soil properties and plant and microbial communities, in particular, on microbial functional genes. Clipping alone did not change the plant biomass production, but warming and clipping combined increased the C4 peak biomass by 47% and belowground net primary production by 110%. Clipping alone and in combination with warming decreased the soil carbon input from litter by 81% and 75%, respectively. Withmore » less carbon input, the abundances of genes involved in degrading relatively recalcitrant carbon increased by 38% to 137% in response to either clipping or the combined treatment, which could weaken long-term soil carbon stability and trigger positive feedback with respect to warming. Clipping alone also increased the abundance of genes for nitrogen fixation, mineralization, and denitrification by 32% to 39%. Such potentially stimulated nitrogen fixation could help compensate for the 20% decline in soil ammonium levels caused by clipping alone and could contribute to unchanged plant biomass levels. Moreover, clipping tended to interact antagonistically with warming, especially with respect to effects on nitrogen cycling genes, demonstrating that single-factor studies cannot predict multifactorial changes. These results revealed that clipping alone or in combination with warming altered soil and plant properties as well as the abundance and structure of soil microbial functional genes. Aboveground biomass removal for biofuel production needs to be reconsidered, as the long-term soil carbon stability may be weakened. IMPORTANCE Global change involves simultaneous alterations, including those caused by climate warming and land management practices (e.g., clipping). Data on the interactive effects of warming and clipping on ecosystems remain elusive, particularly in microbial ecology. This study found that clipping alters microbial responses to warming and demonstrated the effects of antagonistic interactions between clipping and warming on microbial functional genes. Clipping alone or combined with warming enriched genes degrading relatively recalcitrant carbon, likely reflecting the decreased quantity of soil carbon input from litter, which could weaken long-term soil C stability and trigger positive warming feedback. These results have important implications in assessing and predicting the consequences of global climate change and indicate that the removal of aboveground biomass for biofuel production may need to be reconsidered.« less

Annual Removal of Aboveground Plant Biomass Alters Soil Microbial Responses to Warming

DOE PAGES

Xue, Kai; Yuan, Mengting M.; Xie, Jianping; ...

2016-09-27

Clipping (i.e., harvesting aboveground plant biomass) is common in agriculture and for bioenergy production. However, microbial responses to clipping in the context of climate warming are poorly understood. We investigated the interactive effects of grassland warming and clipping on soil properties and plant and microbial communities, in particular, on microbial functional genes. Clipping alone did not change the plant biomass production, but warming and clipping combined increased the C4 peak biomass by 47% and belowground net primary production by 110%. Clipping alone and in combination with warming decreased the soil carbon input from litter by 81% and 75%, respectively. Withmore » less carbon input, the abundances of genes involved in degrading relatively recalcitrant carbon increased by 38% to 137% in response to either clipping or the combined treatment, which could weaken long-term soil carbon stability and trigger positive feedback with respect to warming. Clipping alone also increased the abundance of genes for nitrogen fixation, mineralization, and denitrification by 32% to 39%. Such potentially stimulated nitrogen fixation could help compensate for the 20% decline in soil ammonium levels caused by clipping alone and could contribute to unchanged plant biomass levels. Moreover, clipping tended to interact antagonistically with warming, especially with respect to effects on nitrogen cycling genes, demonstrating that single-factor studies cannot predict multifactorial changes. These results revealed that clipping alone or in combination with warming altered soil and plant properties as well as the abundance and structure of soil microbial functional genes. Aboveground biomass removal for biofuel production needs to be reconsidered, as the long-term soil carbon stability may be weakened. IMPORTANCE Global change involves simultaneous alterations, including those caused by climate warming and land management practices (e.g., clipping). Data on the interactive effects of warming and clipping on ecosystems remain elusive, particularly in microbial ecology. This study found that clipping alters microbial responses to warming and demonstrated the effects of antagonistic interactions between clipping and warming on microbial functional genes. Clipping alone or combined with warming enriched genes degrading relatively recalcitrant carbon, likely reflecting the decreased quantity of soil carbon input from litter, which could weaken long-term soil C stability and trigger positive warming feedback. These results have important implications in assessing and predicting the consequences of global climate change and indicate that the removal of aboveground biomass for biofuel production may need to be reconsidered.« less

Estimating forest and woodland aboveground biomass using active and passive remote sensing

USGS Publications Warehouse

Wu, Zhuoting; Dye, Dennis G.; Vogel, John M.; Middleton, Barry R.

2016-01-01

Aboveground biomass was estimated from active and passive remote sensing sources, including airborne lidar and Landsat-8 satellites, in an eastern Arizona (USA) study area comprised of forest and woodland ecosystems. Compared to field measurements, airborne lidar enabled direct estimation of individual tree height with a slope of 0.98 (R2 = 0.98). At the plot-level, lidar-derived height and intensity metrics provided the most robust estimate for aboveground biomass, producing dominant species-based aboveground models with errors ranging from 4 to 14Mg ha –1 across all woodland and forest species. Landsat-8 imagery produced dominant species-based aboveground biomass models with errors ranging from 10 to 28 Mg ha –1. Thus, airborne lidar allowed for estimates for fine-scale aboveground biomass mapping with low uncertainty, while Landsat-8 seems best suited for broader spatial scale products such as a national biomass essential climate variable (ECV) based on land cover types for the United States.

Fine Root Dynamics and Forest Production Across a Calcium Gradient in Northern Hardwood and Conifer Ecosystems

Treesearch

Byung Bae Park; Ruth D. Yanai; Timothy J. Fahey; Scott W. Bailey; Thomas G. Siccama; James B. Shanley; Natalie L. Cleavitt

2008-01-01

Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither aboveground biomass and...

Reconciling inconsistencies in precipitation-productivity relationships: implications for climate change.

PubMed

Knapp, Alan K; Ciais, Philippe; Smith, Melinda D

2017-04-01

Contents 41 I. 41 II. 42 III. 43 IV. 44 V. 45 Acknowledgements 46 References 46 SUMMARY: Precipitation (PPT) is a primary climatic determinant of plant growth and aboveground net primary production (ANPP) over much of the globe. Thus, PPT-ANPP relationships are important both ecologically and to land-atmosphere models that couple terrestrial vegetation to the global carbon cycle. Empirical PPT-ANPP relationships derived from long-term site-based data are almost always portrayed as linear, but recent evidence has accumulated that is inconsistent with an underlying linear relationship. We review, and then reconcile, these inconsistencies with a nonlinear model that incorporates observed asymmetries in PPT-ANPP relationships. Although data are currently lacking for parameterization, this new model highlights research needs that, when met, will improve our understanding of carbon cycle dynamics, as well as forecasts of ecosystem responses to climate change. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Responses of Plant Community Composition and Biomass Production to Warming and Nitrogen Deposition in a Temperate Meadow Ecosystem

PubMed Central

Gao, Song; Guo, Jixun; Sun, Wei

2015-01-01

Climate change has profound influences on plant community composition and ecosystem functions. However, its effects on plant community composition and biomass production are not well understood. A four-year field experiment was conducted to examine the effects of warming, nitrogen (N) addition, and their interactions on plant community composition and biomass production in a temperate meadow ecosystem in northeast China. Experimental warming had no significant effect on plant species richness, evenness, and diversity, while N addition highly reduced the species richness and diversity. Warming tended to reduce the importance value of graminoid species but increased the value of forbs, while N addition had the opposite effect. Warming tended to increase the belowground biomass, but had an opposite tendency to decrease the aboveground biomass. The influences of warming on aboveground production were dependent upon precipitation. Experimental warming had little effect on aboveground biomass in the years with higher precipitation, but significantly suppressed aboveground biomass in dry years. Our results suggest that warming had indirect effects on plant production via its effect on the water availability. Nitrogen addition significantly increased above- and below-ground production, suggesting that N is one of the most important limiting factors determining plant productivity in the studied meadow steppe. Significant interactive effects of warming plus N addition on belowground biomass were also detected. Our observations revealed that environmental changes (warming and N deposition) play significant roles in regulating plant community composition and biomass production in temperate meadow steppe ecosystem in northeast China. PMID:25874975

Response of NDVI, biomass, and ecosystem gas exchange to long-term warming and fertilization in wet sedge tundra.

PubMed

Boelman, Natalie T; Stieglitz, Marc; Rueth, Heather M; Sommerkorn, Martin; Griffin, Kevin L; Shaver, Gaius R; Gamon, John A

2003-05-01

This study explores the relationship between the normalized difference vegetation index (NDVI), aboveground plant biomass, and ecosystem C fluxes including gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem production. We measured NDVI across long-term experimental treatments in wet sedge tundra at the Toolik Lake LTER site, in northern Alaska. Over 13 years, N and P were applied in factorial experiments (N, P and N + P), air temperature was increased using greenhouses with and without N + P fertilizer, and light intensity (photosynthetically active photon flux density) was reduced by 50% using shade cloth. Within each treatment plot, NDVI, aboveground biomass and whole-system CO(2) flux measurements were made at the same sampling points during the peak-growing season of 2001. We found that across all treatments, NDVI is correlated with aboveground biomass ( r(2)=0.84), GEP ( r(2)=0.75) and ER ( r(2)=0.71), providing a basis for linking remotely sensed NDVI to aboveground biomass and ecosystem carbon flux.

Soil Communities Promote Temporal Stability and Species Asynchrony in Experimental Grassland Communities

PubMed Central

Pellkofer, Sarah; van der Heijden, Marcel G. A.; Schmid, Bernhard; Wagg, Cameron

2016-01-01

Background Over the past two decades many studies have demonstrated that plant species diversity promotes primary productivity and stability in grassland ecosystems. Additionally, soil community characteristics have also been shown to influence the productivity and composition of plant communities, yet little is known about whether soil communities also play a role in stabilizing the productivity of an ecosystem. Methodology/Principal Findings Here we use microcosms to assess the effects of the presence of soil communities on plant community dynamics and stability over a one-year time span. Microcosms were filled with sterilized soil and inoculated with either unaltered field soil or field soil sterilized to eliminate the naturally occurring soil biota. Eliminating the naturally occurring soil biota not only resulted in lower plant productivity, and reduced plant species diversity, and evenness, but also destabilized the net aboveground productivity of the plant communities over time, which was largely driven by changes in abundance of the dominant grass Lolium perenne. In contrast, the grass and legumes contributed more to net aboveground productivity of the plant communities in microcosms where soil biota had been inoculated. Additionally, the forbs exhibited compensatory dynamics with grasses and legumes, thus lowering temporal variation in productivity in microcosms that received the unaltered soil inocula. Overall, asynchrony among plant species was higher in microcosms where an unaltered soil community had been inoculated, which lead to higher temporal stability in community productivity. Conclusions/Significance Our results suggest that soil communities increase plant species asynchrony and stabilize plant community productivity by equalizing the performance among competing plant species through potential antagonistic and facilitative effects on individual plant species. PMID:26829481

Asymmetric Responses of Primary Productivity to Altered Precipitation Simulated by Land Surface Models across Three Long-term Grassland Sites

NASA Astrophysics Data System (ADS)

Wu, D.; Ciais, P.; Viovy, N.; Knapp, A.; Wilcox, K.; Bahn, M.; Smith, M. D.; Ito, A.; Arneth, A.; Harper, A. B.; Ukkola, A.; Paschalis, A.; Poulter, B.; Peng, C.; Reick, C. H.; Hayes, D. J.; Ricciuto, D. M.; Reinthaler, D.; Chen, G.; Tian, H.; Helene, G.; Zscheischler, J.; Mao, J.; Ingrisch, J.; Nabel, J.; Pongratz, J.; Boysen, L.; Kautz, M.; Schmitt, M.; Krohn, M.; Zeng, N.; Meir, P.; Zhang, Q.; Zhu, Q.; Hasibeder, R.; Vicca, S.; Sippel, S.; Dangal, S. R. S.; Fatichi, S.; Sitch, S.; Shi, X.; Wang, Y.; Luo, Y.; Liu, Y.; Piao, S.

2017-12-01

Changes in precipitation variability including the occurrence of extreme events strongly influence plant growth in grasslands. Field measurements of aboveground net primary production (ANPP) in temperate grasslands suggest a positive asymmetric response with wet years resulting in ANPP gains larger than ANPP declines in dry years. Whether land surface models used for historical simulations and future projections of the coupled carbon-water system in grasslands are capable to simulate such non-symmetrical ANPP responses remains an important open research question. In this study, we evaluate the simulated responses of grassland primary productivity to altered precipitation with fourteen land surface models at the three sites of Colorado Shortgrass Steppe (SGS), Konza prairie (KNZ) and Stubai Valley meadow (STU) along a rainfall gradient from dry to wet. Our results suggest that: (i) Gross primary production (GPP), NPP, ANPP and belowground NPP (BNPP) show nonlinear response curves (concave-down) in all the models, but with different curvatures and mean values. In contrast across the sites, primary production increases and then saturates along increasing precipitation with a flattening at the wetter site. (ii) Slopes of spatial relationships between modeled primary production and precipitation are steeper than the temporal slopes (obtained from inter-annual variations). (iii) Asymmetric responses under nominal precipitation range with modeled inter-annual primary production show large uncertainties, and model-ensemble median generally suggests negative asymmetry (greater declines in dry years than increases in wet years) across the three sites. (iv) Primary production at the drier site is predicted to more sensitive to precipitation compared to wetter site, and median sensitivity consistently indicates greater negative impacts of reduced precipitation than positive effects of increased precipitation under extreme conditions. This study implies that most models overemphasize the drought effects or underestimate the watering impacts on primary production in the normal-state, with the direct consequence that carbon-water interactions need to be improved in future model generations with improved mechanistic representations.

Stand structural diversity rather than species diversity enhances aboveground carbon storage in secondary subtropical forests in Eastern China

NASA Astrophysics Data System (ADS)

Ali, Arshad; Yan, En-Rong; Chen, Han Y. H.; Chang, Scott X.; Zhao, Yan-Tao; Yang, Xiao-Dong; Xu, Ming-Shan

2016-08-01

Stand structural diversity, typically characterized by variances in tree diameter at breast height (DBH) and total height, plays a critical role in influencing aboveground carbon (C) storage. However, few studies have considered the multivariate relationships of aboveground C storage with stand age, stand structural diversity, and species diversity in natural forests. In this study, aboveground C storage, stand age, tree species, DBH and height diversity indices, were determined across 80 subtropical forest plots in Eastern China. We employed structural equation modelling (SEM) to test for the direct and indirect effects of stand structural diversity, species diversity, and stand age on aboveground C storage. The three final SEMs with different directions for the path between species diversity and stand structural diversity had a similar goodness of fit to the data. They accounted for 82 % of the variation in aboveground C storage, 55-59 % of the variation in stand structural diversity, and 0.1 to 9 % of the variation in species diversity. Stand age demonstrated strong positive total effects, including a positive direct effect (β = 0.41), and a positive indirect effect via stand structural diversity (β = 0.41) on aboveground C storage. Stand structural diversity had a positive direct effect on aboveground C storage (β = 0.56), whereas there was little total effect of species diversity as it had a negative direct association with, but had a positive indirect effect, via stand structural diversity, on aboveground C storage. The negligible total effect of species diversity on aboveground C storage in the forests under study may have been attributable to competitive exclusion with high aboveground biomass, or a historical logging preference for productive species. Our analyses suggested that stand structural diversity was a major determinant for variations in aboveground C storage in the secondary subtropical forests in Eastern China. Hence, maintaining tree DBH and height diversity through silvicultural operations might constitute an effective approach for enhancing aboveground C storage in these forests.

Indirect quantification of fine root production in a near tropical wet mountainous region

NASA Astrophysics Data System (ADS)

Lu, X.; Zhang, J.; Huang, C.

2016-12-01

The main functions of fine root (defined as diameter <= 2 mm) are water and nutrient transports. Besides being a carbon (C) storage pool, it also provides a C flux pathway through soil and plant. Fine root takes up a small portion, normally 5%, of biomass in forest ecosystems, but 30% to 70% of total net primary production. Therefore, quantifying fine root productivity is important to study the forest C budget. Presumably, belowground growth can be indirectly estimated by the more accessible aboveground vegetation structure dynamics. To verify the relationship with fine root productivity, we take internal (floristic) and external (environmental) factors into account, including litter production, canopy density (leaf area index), leaf nutrients (N, K, Ca, Mg, P), weather and/or soil physical conditions (air temperature, humidity, precipitation, solar radiation and soil moisture). The study was conducted in near tropical broadleaf (700 m asl) and conifer (1700 m asl) forests in northeastern Taiwan, generally receiving more than 4000 mm of precipitation per year. For each site, 16 50-cm long minirhizotron tubes were installed. Fine root images were acquired every three weeks. Growth and decline, newly presence and absence of fine roots were delineated by image processing algorithms to derive fine-root productivity through time. Aforementioned internal and external attributes were simultaneously collected as well. Some of these variables were highly correlated and were detrended using principal component analysis. We found that these transformed variables (mainly associated with litter production, precipitation and solar radiation) can delineate the spatiotemporal dynamics of root production well (r2 = 0.87, p = 0.443). In conclusion, this study demonstrated the feasibility of utilized aboveground variables to indirectly assess fine root growth, which could be further developed for the regional scale mapping with aid of remote sensing.

Biomass, production and woody detritus in an old coast redwood (Sequoia sempervirens) forest

USGS Publications Warehouse

Busing, R.T.; Fujimori, T.

2005-01-01

We examined aboveground biomass dynamics, aboveground net primary production (ANPP), and woody detritus input in an old Sequoia sempervirens stand over a three-decade period. Our estimates of aboveground biomass ranged from 3300 to 5800 Mg ha-1. Stem biomass estimates ranged from 3000 to 5200 Mg ha-1. Stem biomass declined 7% over the study interval. Biomass dynamics were patchy, with marked declines in recent tree-fall patches <0.05 ha in size. Larger tree-fall patches approaching 0.2 ha in size were observed outside the study plot. Our estimates of ANPP ranged from 6 to 14 Mg ha -1yr-1. Estimates of 7 to 10 Mg ha-1yr -1 were considered to be relatively accurate. Thus, our estimates based on long-term data corroborated the findings of earlier short-term studies. ANPP of old, pure stands of Sequoia was not above average for temperate forests. Even though production was potentially high on a per stem basis, it was moderate at the stand level. We obtained values of 797 m3 ha -1 and 262 Mg ha-1 for coarse woody detritus volume and mass, respectively. Fine woody detritus volume and mass were estimated at 16 m3 ha-1 and 5 Mg ha-1, respectively. Standing dead trees (or snags) comprised 7% of the total coarse detritus volume and 8% of the total mass. Coarse detritus input averaged 5.7 to 6.9 Mg ha -1yr-1. Assuming steady-state input and pool of coarse detritus, we obtained a decay rate constant of 0.022 to 0.026. The old-growth stand of Sequoia studied had extremely high biomass, but ANPP was moderate and the amount of woody detritus was not exceptionally large. Biomass accretion and loss were not rapid in this stand partly because of the slow population dynamics and low canopy turnover rate of Sequoia at the old-growth stage. Nomenclature: Hickman (1993). ?? Springer 2005.

Contrasting impacts of continuous moderate drought and episodic severe droughts on the aboveground-biomass increment and litterfall of three coexisting Mediterranean woody species.

PubMed

Liu, Daijun; Ogaya, Romà; Barbeta, Adrià; Yang, Xiaohong; Peñuelas, Josep

2015-11-01

Climate change is predicted to increase the aridity in the Mediterranean Basin and severely affect forest productivity and composition. The responses of forests to different timescales of drought, however, are still poorly understood because extreme and persistent moderate droughts can produce nonlinear responses in plants. We conducted a rainfall-manipulation experiment in a Mediterranean forest dominated by Quercus ilex, Phillyrea latifolia, and Arbutus unedo in the Prades Mountains in southern Catalonia from 1999 to 2014. The experimental drought significantly decreased forest aboveground-biomass increment (ABI), tended to increase the litterfall, and decreased aboveground net primary production throughout the 15 years of the study. The responses to the experimental drought were highly species-specific. A. unedo suffered a significant reduction in ABI, Q. ilex experienced a decrease during the early experiment (1999-2003) and in the extreme droughts of 2005-2006 and 2011-2012, and P. latifolia was unaffected by the treatment. The drought treatment significantly increased branch litterfall, especially in the extremely dry year of 2011, and also increased overall leaf litterfall. The drought treatment reduced the fruit production of Q. ilex, which affected seedling recruitment. The ABIs of all species were highly correlated with SPEI in early spring, whereas the branch litterfalls were better correlated with summer SPEIs and the leaf and fruit litterfalls were better correlated with autumn SPEIs. These species-specific responses indicated that the dominant species (Q. ilex) could be partially replaced by the drought-resistant species (P. latifolia). However, the results of this long-term study also suggest that the effect of drought treatment has been dampened over time, probably due to a combination of demographic compensation, morphological and physiological acclimation, and epigenetic changes. However, the structure of community (e.g., species composition, dominance, and stand density) may be reordered when a certain drought threshold is reached. © 2015 John Wiley & Sons Ltd.

Long-term above-ground biomass production in a red oak-pecan agroforestry system

USDA-ARS?s Scientific Manuscript database

Agroforestry systems have widely been recognized for their potential to foster long-term carbon sequestration in woody perennials. This study aims to determine the above-ground biomass in a 16-year-old red oak (Quercus rubra) - pecan (Carya illinoinensis) silvopastoral planting (141 and 53 trees ha-...

Comparison between remote sensing and a dynamic vegetation model for estimating terrestrial primary production of Africa.

PubMed

Ardö, Jonas

2015-12-01

Africa is an important part of the global carbon cycle. It is also a continent facing potential problems due to increasing resource demand in combination with climate change-induced changes in resource supply. Quantifying the pools and fluxes constituting the terrestrial African carbon cycle is a challenge, because of uncertainties in meteorological driver data, lack of validation data, and potentially uncertain representation of important processes in major ecosystems. In this paper, terrestrial primary production estimates derived from remote sensing and a dynamic vegetation model are compared and quantified for major African land cover types. Continental gross primary production estimates derived from remote sensing were higher than corresponding estimates derived from a dynamic vegetation model. However, estimates of continental net primary production from remote sensing were lower than corresponding estimates from the dynamic vegetation model. Variation was found among land cover classes, and the largest differences in gross primary production were found in the evergreen broadleaf forest. Average carbon use efficiency (NPP/GPP) was 0.58 for the vegetation model and 0.46 for the remote sensing method. Validation versus in situ data of aboveground net primary production revealed significant positive relationships for both methods. A combination of the remote sensing method with the dynamic vegetation model did not strongly affect this relationship. Observed significant differences in estimated vegetation productivity may have several causes, including model design and temperature sensitivity. Differences in carbon use efficiency reflect underlying model assumptions. Integrating the realistic process representation of dynamic vegetation models with the high resolution observational strength of remote sensing may support realistic estimation of components of the carbon cycle and enhance resource monitoring, providing suitable validation data is available.

Decreases in net primary production and net ecosystem production along a repeated-fires induced forest/grassland gradient

NASA Astrophysics Data System (ADS)

Cheng, C. H.; Huang, Y. H.; Chung-Yu, L.; Menyailo, O.

2016-12-01

Fire is one of the most important disturbances in ecosystems. Fire rapidly releases stored carbon into atmosphere and also plays critical roles on soil properties, light and moisture regimes, and plant structures and communities. With the interventions of climate change and human activities, fire regimes become more severe and frequent. In many parts of world, forest fire regimes can be further altered by grass invasion because the invasive grasses create a positive feedback cycle through their rapid recovery after fires and their high flammability during dry periods and allow forests to be burned repeatedly in a relatively short time. For such invasive grass-fire cycle, a great change of native vegetation community can occur. In this study, we examined a C4 invasive grass () fire-induced forest/grassland gradient to quantify the changes of net primary production (NPP) and net ecosystem production (NEP) from an unburned forest to repeated fire grassland. Our results demonstrated negative effects of repeated fires on NPP and NEP. Within 4 years of the onset of repeated fires on the unburned forest, NPP declined by 14%, mainly due to the reduction in aboveground NPP but offset by increase of belowground NPP. Subsequent fires cumulatively caused reductions in both aboveground and belowground NPP. A total of 40% reduction in the long-term repeated fire induced grassland was found. Soil respiration rate were not significantly different along the forest/grassland gradient. Thus, a great reduction in NEP were shown in grassland, which shifted from 4.6 Mg C ha-1 yr-1 in unburnt forest to -2.6 Mg C ha-1 yr-1. Such great losses are critical within the context of forest carbon cycling and long-term sustainability. Forest management practices that can effectively reduce the likelihood of repeated fires and consequent likelihood of establishment of the grass fire cycle are essential for protecting the forest.

Biomass production in experimental grasslands of different species richness during three years of climate warming

NASA Astrophysics Data System (ADS)

de Boeck, H. J.; Lemmens, C. M. H. M.; Zavalloni, C.; Gielen, B.; Malchair, S.; Carnol, M.; Merckx, R.; van den Berge, J.; Ceulemans, R.; Nijs, I.

2008-04-01

Here we report on the single and combined impacts of climate warming and species richness on the biomass production in experimental grassland communities. Projections of a future warmer climate have stimulated studies on the response of terrestrial ecosystems to this global change. Experiments have likewise addressed the importance of species numbers for ecosystem functioning. There is, however, little knowledge on the interplay between warming and species richness. During three years, we grew experimental plant communities containing one, three or nine grassland species in 12 sunlit, climate-controlled chambers in Wilrijk, Belgium. Half of these chambers were exposed to ambient air temperatures (unheated), while the other half were warmed by 3°C (heated). Equal amounts of water were added to heated and unheated communities, so that warming would imply drier soils if evapotranspiration was higher. Biomass production was decreased due to warming, both aboveground (-29%) and belowground (-25%), as negative impacts of increased heat and drought stress in summer prevailed. Complementarity effects, likely mostly through both increased aboveground spatial complementarity and facilitative effects of legumes, led to higher shoot and root biomass in multi-species communities, regardless of the induced warming. Surprisingly, warming suppressed productivity the most in 9-species communities, which may be attributed to negative impacts of intense interspecific competition for resources under conditions of high abiotic stress. Our results suggest that warming and the associated soil drying could reduce primary production in many temperate grasslands, and that this will not necessarily be mitigated by efforts to maintain or increase species richness.

Aboveground vertebrate and invertebrate herbivore impacts on net N mineralization in subalpine grasslands

Treesearch

Anita C. Risch; Martin Schutz; Martijn L. Vandegehuchte; Wim H. van der Putten; Henk Duyts; Ursina Raschein; Dariusz J. Gwiazdowicz; Matt D. Busse; Deborah S. Page-Dumroese; Stephan Zimmerman

2015-01-01

Aboveground herbivores have strong effects on grassland nitrogen (N) cycling. They can accelerate or slow down soil net N mineralization depending on ecosystem productivity and grazing intensity. Yet, most studies only consider either ungulates or invertebrate herbivores, but not the combined effect of several functionally different vertebrate and invertebrate...

Response of AM fungi spore population to elevated temperature and nitrogen addition and their influence on the plant community composition and productivity

PubMed Central

Zhang, Tao; Yang, Xue; Guo, Rui; Guo, Jixun

2016-01-01

To examine the influence of elevated temperature and nitrogen (N) addition on species composition and development of arbuscular mycorrhizal fungi (AMF) and the effect of AMF on plant community structure and aboveground productivity, we conducted a 5-year field experiment in a temperate meadow in northeast China and a subsequent greenhouse experiment. In the field experiment, N addition reduced spore population diversity and richness of AMF and suppressed the spore density and the hyphal length density (HLD). Elevated temperature decreased spore density and diameter and increased the HLD, but did not affect AMF spore population composition. In the greenhouse experiment, AMF altered plant community composition and increased total aboveground biomass in both elevated temperature and N addition treatments; additionally, AMF also increased the relative abundance and aboveground biomass of the grasses Leymus chinensis (Poaceae) and Setaria viridis (Gramineae) and significantly reduced the relative abundance and aboveground biomass of the Suaeda corniculata (Chenopodiaceae). Although elevated temperature and N addition can affect species composition or suppress the development of AMF, AMF are likely to play a vital role in increasing plant diversity and productivity. Notably, AMF might reduce the threat of climate change induced degradation of temperate meadow ecosystems. PMID:27098761

Response of AM fungi spore population to elevated temperature and nitrogen addition and their influence on the plant community composition and productivity

NASA Astrophysics Data System (ADS)

Zhang, Tao; Yang, Xue; Guo, Rui; Guo, Jixun

2016-04-01

To examine the influence of elevated temperature and nitrogen (N) addition on species composition and development of arbuscular mycorrhizal fungi (AMF) and the effect of AMF on plant community structure and aboveground productivity, we conducted a 5-year field experiment in a temperate meadow in northeast China and a subsequent greenhouse experiment. In the field experiment, N addition reduced spore population diversity and richness of AMF and suppressed the spore density and the hyphal length density (HLD). Elevated temperature decreased spore density and diameter and increased the HLD, but did not affect AMF spore population composition. In the greenhouse experiment, AMF altered plant community composition and increased total aboveground biomass in both elevated temperature and N addition treatments; additionally, AMF also increased the relative abundance and aboveground biomass of the grasses Leymus chinensis (Poaceae) and Setaria viridis (Gramineae) and significantly reduced the relative abundance and aboveground biomass of the Suaeda corniculata (Chenopodiaceae). Although elevated temperature and N addition can affect species composition or suppress the development of AMF, AMF are likely to play a vital role in increasing plant diversity and productivity. Notably, AMF might reduce the threat of climate change induced degradation of temperate meadow ecosystems.

Relating seasonal patterns of the AVHRR vegetation index to simulated photosynthesis and transpiration of forests in different climates

NASA Technical Reports Server (NTRS)

Running, Steven W.; Nemani, Ramakrishna R.

1988-01-01

Weekly AVHRR Normalized Difference Vegetation Index (NDVI) values for 1983-1984 for seven sites of diverse climate in North America were correlated with results of an ecosystem simulation model of a hypothetical forest stand for the corresponding period at each site. The tendency of raw NDVI data to overpredict photosynthesis and transpiration on water limited sites was shown to be partially corrected by using an aridity index of annual radiation/annual precipitation. The results suggest that estimates of vegetation productivity using the global vegetation index are only accurate as annual integrations, unless unsubsampled local area coverage NDVI data can be tested against forest photosynthesis, transpiration and aboveground net primary production data measured at shorter time intervals.

Lianas reduce carbon accumulation and storage in tropical forests.

PubMed

van der Heijden, Geertje M F; Powers, Jennifer S; Schnitzer, Stefan A

2015-10-27

Tropical forests store vast quantities of carbon, account for one-third of the carbon fixed by photosynthesis, and are a major sink in the global carbon cycle. Recent evidence suggests that competition between lianas (woody vines) and trees may reduce forest-wide carbon uptake; however, estimates of the impact of lianas on carbon dynamics of tropical forests are crucially lacking. Here we used a large-scale liana removal experiment and found that, at 3 y after liana removal, lianas reduced net above-ground carbon uptake (growth and recruitment minus mortality) by ∼76% per year, mostly by reducing tree growth. The loss of carbon uptake due to liana-induced mortality was four times greater in the control plots in which lianas were present, but high variation among plots prevented a significant difference among the treatments. Lianas altered how aboveground carbon was stored. In forests where lianas were present, the partitioning of forest aboveground net primary production was dominated by leaves (53.2%, compared with 39.2% in liana-free forests) at the expense of woody stems (from 28.9%, compared with 43.9%), resulting in a more rapid return of fixed carbon to the atmosphere. After 3 y of experimental liana removal, our results clearly demonstrate large differences in carbon cycling between forests with and without lianas. Combined with the recently reported increases in liana abundance, these results indicate that lianas are an important and increasing agent of change in the carbon dynamics of tropical forests.

Does biodiversity make a difference? Relationships between species richness, evolutionary diversity, and aboveground live tree biomass across US forests

Treesearch

Kevin M. Potter; Christopher W. Woodall

2014-01-01

Biodiversity conveys numerous functional benefits to forested ecosystems, including community stability and resilience. In the context of managing forests for climate change mitigation/adaptation, maximizing and/or maintaining aboveground biomass will require understanding the interactions between tree biodiversity, site productivity, and the stocking of live trees....

Modeling and Mapping Agroforestry Aboveground Biomass in the Brazilian Amazon Using Airborne Lidar Data

Treesearch

Qi Chen; Dengsheng Lu; Michael Keller; Maiza dos-Santos; Edson Bolfe; Yunyun Feng; Changwei Wang

2015-01-01

Agroforestry has large potential for carbon (C) sequestration while providing many economical, social, and ecological benefits via its diversified products. Airborne lidar is considered as the most accurate technology for mapping aboveground biomass (AGB) over landscape levels. However, little research in the past has been done to study AGB of agroforestry systems...

Earlier snowmelt and warming lead to earlier but not necessarily more plant growth.

PubMed

Livensperger, Carolyn; Steltzer, Heidi; Darrouzet-Nardi, Anthony; Sullivan, Patrick F; Wallenstein, Matthew; Weintraub, Michael N

2016-01-01

Climate change over the past ∼50 years has resulted in earlier occurrence of plant life-cycle events for many species. Across temperate, boreal and polar latitudes, earlier seasonal warming is considered the key mechanism leading to earlier leaf expansion and growth. Yet, in seasonally snow-covered ecosystems, the timing of spring plant growth may also be cued by snowmelt, which may occur earlier in a warmer climate. Multiple environmental cues protect plants from growing too early, but to understand how climate change will alter the timing and magnitude of plant growth, experiments need to independently manipulate temperature and snowmelt. Here, we demonstrate that altered seasonality through experimental warming and earlier snowmelt led to earlier plant growth, but the aboveground production response varied among plant functional groups. Earlier snowmelt without warming led to early leaf emergence, but often slowed the rate of leaf expansion and had limited effects on aboveground production. Experimental warming alone had small and inconsistent effects on aboveground phenology, while the effect of the combined treatment resembled that of early snowmelt alone. Experimental warming led to greater aboveground production among the graminoids, limited changes among deciduous shrubs and decreased production in one of the dominant evergreen shrubs. As a result, we predict that early onset of the growing season may favour early growing plant species, even those that do not shift the timing of leaf expansion. Published by Oxford University Press on behalf of the Annals of Botany Company.

Net Primary Productivity and Edaphic Fertility in Two Pluvial Tropical Forests in the Chocó Biogeographical Region of Colombia

PubMed Central

Quinto-Mosquera, Harley

2017-01-01

The net primary productivity (NPP) of tropical forests is a key process of the carbon cycle and therefore for the mitigation of global climate change. It has been proposed that NPP is limited by the availability of soil nutrients in lowland tropical forests and that belowground NPP decreases as edaphic fertility increases. This hypothesis was evaluated in two localities (Opogodó and Pacurita) of the Chocó Biogeographical region, one of the rainiest of the world, where the aboveground (litter and wood) and belowground (fine and coarse roots) components of NPP were measured. Fertility parameters (pH, nutrients, and texture) were also determined and related to NPP. Total NPP was similar between locations (23.7 vs. 24.2 t ha-1 year-1 for Opogodó and Pacurita, respectively). However, components of NPP showed differences: in Pacurita, with steeper topography, NPP of wood and coarse roots were higher; therefore, differences of topography and drainage between localities probably affected the NPP of wood. On the other hand, soils of Opogodó, where NPP of fine roots was higher, showed higher contents of sand, N+, and organic matter (OM). With the increase of pH, OM, N+, K, Mg, and sand, the NPP of leaves and fine roots as well as the percentage of NPP belowground also increased, which suggests NPP limitation by multiple nutrients. The increase of NPP belowground with the availability of edaphic nutrients evidenced a redistribution of the aboveground and belowground components of NPP with the increase of soil fertility in oligotrophic systems, probably as a mechanism to improve the capture of resources. PMID:28114418

Net Primary Productivity and Edaphic Fertility in Two Pluvial Tropical Forests in the Chocó Biogeographical Region of Colombia.

PubMed

Quinto-Mosquera, Harley; Moreno, Flavio

2017-01-01

The net primary productivity (NPP) of tropical forests is a key process of the carbon cycle and therefore for the mitigation of global climate change. It has been proposed that NPP is limited by the availability of soil nutrients in lowland tropical forests and that belowground NPP decreases as edaphic fertility increases. This hypothesis was evaluated in two localities (Opogodó and Pacurita) of the Chocó Biogeographical region, one of the rainiest of the world, where the aboveground (litter and wood) and belowground (fine and coarse roots) components of NPP were measured. Fertility parameters (pH, nutrients, and texture) were also determined and related to NPP. Total NPP was similar between locations (23.7 vs. 24.2 t ha-1 year-1 for Opogodó and Pacurita, respectively). However, components of NPP showed differences: in Pacurita, with steeper topography, NPP of wood and coarse roots were higher; therefore, differences of topography and drainage between localities probably affected the NPP of wood. On the other hand, soils of Opogodó, where NPP of fine roots was higher, showed higher contents of sand, N+, and organic matter (OM). With the increase of pH, OM, N+, K, Mg, and sand, the NPP of leaves and fine roots as well as the percentage of NPP belowground also increased, which suggests NPP limitation by multiple nutrients. The increase of NPP belowground with the availability of edaphic nutrients evidenced a redistribution of the aboveground and belowground components of NPP with the increase of soil fertility in oligotrophic systems, probably as a mechanism to improve the capture of resources.

On the relationship between sea level and Spartina alterniflora production

USGS Publications Warehouse

Kirwan, Matthew L.; Christian, Robert R.; Blum, Linda K.; Brinson, Mark M.

2012-01-01

A positive relationship between interannual sea level and plant growth is thought to stabilize many coastal landforms responding to accelerating rates of sea level rise. Numerical models of delta growth, tidal channel network evolution, and ecosystem resilience incorporate a hump-shaped relationship between inundation and plant primary production, where vegetation growth increases with sea level up to an optimum water depth or inundation frequency. In contrast, we use decade-long measurements of Spartina alterniflora biomass in seven coastal Virginia (USA) marshes to demonstrate that interannual sea level is rarely a primary determinant of vegetation growth. Although we find tepid support for a hump-shaped relationship between aboveground production and inundation when marshes of different elevation are considered, our results suggest that marshes high in the intertidal zone and low in relief are unresponsive to sea level fluctuations. We suggest existing models are unable to capture the behavior of wetlands in these portions of the landscape, and may underestimate their vulnerability to sea level rise because sea level rise will not be accompanied by enhanced plant growth and resultant sediment accumulation.

Contrasting above- and belowground sensitivity of three Great Plains grasslands to altered rainfall regimes.

PubMed

Wilcox, Kevin R; von Fischer, Joseph C; Muscha, Jennifer M; Petersen, Mark K; Knapp, Alan K

2015-01-01

Intensification of the global hydrological cycle with atmospheric warming is expected to increase interannual variation in precipitation amount and the frequency of extreme precipitation events. Although studies in grasslands have shown sensitivity of aboveground net primary productivity (ANPP) to both precipitation amount and event size, we lack equivalent knowledge for responses of belowground net primary productivity (BNPP) and NPP. We conducted a 2-year experiment in three US Great Plains grasslands--the C4-dominated shortgrass prairie (SGP; low ANPP) and tallgrass prairie (TGP; high ANPP), and the C3-dominated northern mixed grass prairie (NMP; intermediate ANPP)--to test three predictions: (i) both ANPP and BNPP responses to increased precipitation amount would vary inversely with mean annual precipitation (MAP) and site productivity; (ii) increased numbers of extreme rainfall events during high-rainfall years would affect high and low MAP sites differently; and (iii) responses belowground would mirror those aboveground. We increased growing season precipitation by as much as 50% by augmenting natural rainfall via (i) many (11-13) small or (ii) fewer (3-5) large watering events, with the latter coinciding with naturally occurring large storms. Both ANPP and BNPP increased with water addition in the two C4 grasslands, with greater ANPP sensitivity in TGP, but greater BNPP and NPP sensitivity in SGP. ANPP and BNPP did not respond to any rainfall manipulations in the C3 -dominated NMP. Consistent with previous studies, fewer larger (extreme) rainfall events increased ANPP relative to many small events in SGP, but event size had no effect in TGP. Neither system responded consistently above- and belowground to event size; consequently, total NPP was insensitive to event size. The diversity of responses observed in these three grassland types underscores the challenge of predicting responses relevant to C cycling to forecast changes in precipitation regimes even within relatively homogeneous biomes such as grasslands. © 2014 John Wiley & Sons Ltd.

Amazon forest carbon dynamics predicted by profiles of canopy leaf area and light environment

Treesearch

S. C. Stark; V. Leitold; J. L. Wu; M. O. Hunter; C. V. de Castilho; F. R. C. Costa; S. M. McMahon; G. G. Parker; M. Takako Shimabukuro; M. A. Lefsky; M. Keller; L. F. Alves; J. Schietti; Y. E. Shimabukuro; D. O. Brandao; T. K. Woodcock; N. Higuchi; P. B de Camargo; R. C. de Oliveira; S. R. Saleska

2012-01-01

Tropical forest structural variation across heterogeneous landscapes may control above-ground carbon dynamics. We tested the hypothesis that canopy structure (leaf area and light availability) – remotely estimated from LiDAR – control variation in above-ground coarse wood production (biomass growth). Using a statistical model, these factors predicted biomass growth...

Analysis of biophysical and anthropogenic variables and their relation to the regional spatial variation of aboveground biomass illustrated for North and East Kalimantan, Borneo.

PubMed

Van der Laan, Carina; Verweij, Pita A; Quiñones, Marcela J; Faaij, André Pc

2014-12-01

Land use and land cover change occurring in tropical forest landscapes contributes substantially to carbon emissions. Better insights into the spatial variation of aboveground biomass is therefore needed. By means of multiple statistical tests, including geographically weighted regression, we analysed the effects of eight variables on the regional spatial variation of aboveground biomass. North and East Kalimantan were selected as the case study region; the third largest carbon emitting Indonesian provinces. Strong positive relationships were found between aboveground biomass and the tested variables; altitude, slope, land allocation zoning, soil type, and distance to the nearest fire, road, river and city. Furthermore, the results suggest that the regional spatial variation of aboveground biomass can be largely attributed to altitude, distance to nearest fire and land allocation zoning. Our study showed that in this landscape, aboveground biomass could not be explained by one single variable; the variables were interrelated, with altitude as the dominant variable. Spatial analyses should therefore integrate a variety of biophysical and anthropogenic variables to provide a better understanding of spatial variation in aboveground biomass. Efforts to minimise carbon emissions should incorporate the identified factors, by 1) the maintenance of lands with high AGB or carbon stocks, namely in the identified zones at the higher altitudes; and 2) regeneration or sustainable utilisation of lands with low AGB or carbon stocks, dependent on the regeneration capacity of the vegetation. Low aboveground biomass densities can be found in the lowlands in burned areas, and in non-forest zones and production forests.

Ecosystem carbon exchange in response to locust outbreaks in a temperate steppe.

PubMed

Song, Jian; Wu, Dandan; Shao, Pengshuai; Hui, Dafeng; Wan, Shiqiang

2015-06-01

It is predicted that locust outbreaks will occur more frequently under future climate change scenarios, with consequent effects on ecological goods and services. A field manipulative experiment was conducted to examine the responses of gross ecosystem productivity (GEP), net ecosystem carbon dioxide (CO2) exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) to locust outbreaks in a temperate steppe of northern China from 2010 to 2011. Two processes related to locust outbreaks, natural locust feeding and carcass deposition, were mimicked by clipping 80 % of aboveground biomass and adding locust carcasses, respectively. Ecosystem carbon (C) exchange (i.e., GEP, NEE, ER, and SR) was suppressed by locust feeding in 2010, but stimulated by locust carcass deposition in both years (except SR in 2011). Experimental locust outbreaks (i.e., clipping plus locust carcass addition) decreased GEP and NEE in 2010 whereas they increased GEP, NEE, and ER in 2011, leading to neutral changes in GEP, NEE, and SR across the 2 years. The responses of ecosystem C exchange could have been due to the changes in soil ammonium nitrogen, community cover, and aboveground net primary productivity. Our findings of the transient and neutral changes in ecosystem C cycling under locust outbreaks highlight the importance of resistance, resilience, and stability of the temperate steppe in maintaining reliable ecosystem services, and facilitate the projections of ecosystem functioning in response to natural disturbance and climate change.

BOREAS TE-6 Allometry Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Gower, Stith T.; Vogel, Jason G.

2000-01-01

The BOREAS TE-6 team collected several data sets in support of its efforts to characterize and interpret information on the plant biomass, allometry, biometry, sapwood, leaf area index, net primary production, soil temperature, leaf water potential, soil CO2 flux, and multivegetation imagery of boreal vegetation. This data set includes tree measurements conducted on the above-ground biomass of trees in the BOREAS NSA and SSA during the growing seasons of 1994 and 1995 and the derived allometric relationships/equations. The data are stored in ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distrobuted Activity Archive Center (DAAC).

Aboveground tree growth varies with belowground carbon allocation in a tropical rainforest environment

Treesearch

J.W. Raich; D.A. Clark; L. Schwendenmann; Tana Wood

2014-01-01

Young secondary forests and plantations in the moist tropics often have rapid rates of biomass accumulation and thus sequester large amounts of carbon. Here, we compare results from mature forest and nearby 15–20 year old tree plantations in lowland Costa Rica to evaluate differences in allocation of carbon to aboveground production and root systems. We found that the...

Aboveground tree biomass on productive forest land in Alaska.

Treesearch

John Yarie; Delbert Mead

1982-01-01

Total aboveground woody biomass of trees on forest land that can produce 1.4 cubic m eters per hectare per year of industrial wood in Alaska is 1.33 billion metric tons green weight. The estimated energy value of the standing woody biomass is 11.9 x 10'5 Btu's. Statewide tables of biomass and energy values for softwoods, hardwoods, and species groups are...

Differences in ecosystem carbon distribution and nutrient cycling linked to forest tree species composition in a mid-successional boreal forest

USGS Publications Warehouse

Melvin, April M.; Mack, Michelle C.; Johnstone, Jill F.; McGuire, A. David; Genet, Helene; Schuur, Edward A.G.

2015-01-01

In the boreal forest of Alaska, increased fire severity associated with climate change is expanding deciduous forest cover in areas previously dominated by black spruce (Picea mariana). Needle-leaf conifer and broad-leaf deciduous species are commonly associated with differences in tree growth, carbon (C) and nutrient cycling, and C accumulation in soils. Although this suggests that changes in tree species composition in Alaska could impact C and nutrient pools and fluxes, few studies have measured these linkages. We quantified C, nitrogen, phosphorus, and base cation pools and fluxes in three stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a single fire event in 1958. Paper birch consistently displayed characteristics of more rapid C and nutrient cycling, including greater aboveground net primary productivity, higher live foliage and litter nutrient concentrations, and larger ammonium and nitrate pools in the soil organic layer (SOL). Ecosystem C stocks (aboveground + SOL + 0–10 cm mineral soil) were similar for the two species; however, in black spruce, 78% of measured C was found in soil pools, primarily in the SOL, whereas aboveground biomass dominated ecosystem C pools in birch forest. Radiocarbon analysis indicated that approximately one-quarter of the black spruce SOL C accumulated prior to the 1958 fire, whereas no pre-fire C was observed in birch soils. Our findings suggest that tree species exert a strong influence over C and nutrient cycling in boreal forest and forest compositional shifts may have long-term implications for ecosystem C and nutrient dynamics.

Vertebrate herbivory in managed coastal wetlands: A manipulative experiment

USGS Publications Warehouse

Johnson, L.A.; Foote, A.L.

1997-01-01

Structural marsh management and nutria herbivory are both believed to strongly influence plant production in the brackish, deltaic marshes of coastal Louisiana, USA. Previous studies have tested the effects of structural management on aboveground biomass after implementing management, but very few studies have collected data before and after management. Thus, to test the effects of structural marsh management on Spartina patens (Ait.) Muhl. and Scirpus americanus Pers., the aboveground biomass of both species was estimated before and after the construction of shallow, leveed impoundments. The water level in each impoundment was managed with a single flap-gated culvert fitted with a variable crest weir. Additionally, the influence of nutria grazing on aboveground biomass was measured by nondestructively sampling fenced (ungrazed) and unfenced (grazed) plots in both managed and unmanaged areas. While there was no significant difference in S. patens production between managed and unmanaged areas, marsh management negatively affected Sc. americanus production the two species also differed in their responses to grazing. Grazing dramatically reduced the sedge, Sc. americanus, while the grass, S. patens, remained at similar biomass levels in grazed and ungrazed plant stands. These findings support the belief that herbivory has a strong influence on plant production, but do not support the claim that management increases plant production in the deltaic marshes of Louisiana.

Carbon stocks and fluxes in managed peatlands in northern Borneo

NASA Astrophysics Data System (ADS)

Arn Teh, Yit; Manning, Frances; Cook, Sarah; Zin Zawawi, Norliyana; Sii, Longwin; Hill, Timothy; Page, Susan; Whelan, Mick; Evans, Chris; Gauci, Vincent; Chocholek, Melanie; Khoon Kho, Lip

2017-04-01

Oil palm is the largest agricultural crop in the tropics and accounts for 13 % of current tropical land area. Patterns of land-atmosphere exchange from oil palm ecosystems therefore have potentially important implications for regional and global C budgets due to the large scale of land conversion. This is particularly true for oil palm plantations on peat because of the large C stocks held by tropical peat soils that are potential sensitivity to human disturbance. Here we report preliminary findings on C stocks and fluxes from a long-term, multi-scale project in Sarawak, Malaysia that aims to quantify the impacts of oil palm conversion on C and greenhouse gas fluxes from oil palm recently established on peat. Land-atmosphere fluxes were determined using a combination of top-down and bottom-up methods (eddy covariance, canopy/stem and soil flux measurements, net primary productivity). Fluvial fluxes were determined by quantifying rates of dissolved and particulate organic C export. Ecosystem C dynamics were determined using the intensive C plot method, which quantified all major C stocks and fluxes, including plant and soil stocks, leaf litterfall, aboveground biomass production, root production, stem/canopy respiration, root-rhizosphere respiration, and heterotrophic soil respiration. Preliminary analysis indicates that vegetative aboveground biomass in these 7 year old plantations was 8.9-11.9 Mg C ha-1, or approximately one-quarter of adjacent secondary forest. Belowground biomass was 5.6-6.5 Mg C ha-1; on par with secondary forests. Soil C stocks in the 0-30 cm depth was 233.1-240.8 Mg C ha-1, or 32-36% greater than soil C stocks in secondary forests at the same depth (176.8 Mg C ha-1). Estimates of vegetative aboveground and belowground net primary productivity were 1.3-1.7 Mg C ha-1 yr-1 and 0.8-0.9 Mg C ha-1 yr-1, respectively. Fruit brunch production was approximately 67 Mg C ha-1over 7 yearsor 9.6 Mg C ha-1 yr-1. Total soil respiration rates were 18 Mg C ha-1 yr-1, with 26 % accounted for by root-rhizosphere respiration and 74 % from heterotrophic soil respiration. This translates to a peat mineralization rate of 10 to 17 Mg C ha-1 yr-1 in the upper 35 cm soil depth above the water table. Fluvial C fluxes were 1.9 Mg C ha-1yr-1, or roughly three times the flux from secondary forest. Findings from the partitioned soil respiration and fluvial flux measurements indicate that peat mineralization may be occurring. However, it is unclear if this represents a net loss of C from the ecosystem, due to the apparent increase in soil C stocks following land conversion, rather than an expected net reduction in soil C. This unexpected finding implies that other processes may be offsetting C losses from heterotrophic decay and fluvial exchange.

Effects of herbage removal on productivity of selected high-Sierra meadow community types

USGS Publications Warehouse

Stohlgren, Thomas J.; DeBenedetti, Steven H.; Parsons, David J.

1989-01-01

We investigated the effects of herbage removal on three subalpine meadow plant communities in the Rock Creek drainage of Sequoia National Park, California, USA. In the xeric Carex exserta Mkze. (short-hair sedge) type, annual aboveground productivity averaged 19 g/m2 in control plots (clipped once after plant senescence in late September) over a five-year period. Annual aboveground productivity was enhanced about 30%–35% when plots in this community type were clipped more frequently (i.e., “additional” herbage removal in the early, mid, and late seasons) during each of four treatment years but was reduced by 13%–19% during a fifth (recovery) year in which all but late September clipping was suspended. In a moderately mesic Eleocharis pauciflora (Lightf.) Link. (few-flowered spike rush)-Calamagrostis breweri Thurb. (short-hair grass) type, control plot productivity averaged 115 g/m2/yr and was reduced by 20–30% by the additional herbage removal. A more mesic Deschampsia caespitosa (L.) Beauv. (tufted hairgrass)-Carex rostrata Stokes, (beaked sedge) type had the greatest mean above-ground productivity (169 g/m2/yr) but also showed damage (i.e., decrease in productivity by 15%–20%) caused by the additional herbage removal. These data suggest that long-term, intensive herbage removal may be more detrimental to moderately mesic and mesic subalpine meadow community types than to xeric types.

Consequences of long-term severe industrial pollution for aboveground carbon and nitrogen pools in northern taiga forests at local and regional scales.

PubMed

Manninen, Sirkku; Zverev, Vitali; Bergman, Igor; Kozlov, Mikhail V

2015-12-01

Boreal coniferous forests act as an important sink for atmospheric carbon dioxide. The overall tree carbon (C) sink in the forests of Europe has increased during the past decades, especially due to management and elevated nitrogen (N) deposition; however, industrial atmospheric pollution, primarily sulphur dioxide and heavy metals, still negatively affect forest biomass production at different spatial scales. We report local and regional changes in forest aboveground biomass, C and N concentrations in plant tissues, and C and N pools caused by long-term atmospheric emissions from a large point source, the nickel-copper smelter in Monchegorsk, in north-western Russia. An increase in pollution load (assessed as Cu concentration in forest litter) caused C to increase in foliage but C remained unchanged in wood, while N decreased in foliage and increased in wood, demonstrating strong effects of pollution on resource translocation between green and woody tissues. The aboveground C and N pools were primarily governed by plant biomass, which strongly decreased with an increase in pollution load. In our study sites (located 1.6-39.7 km from the smelter) living aboveground plant biomass was 76 to 4888 gm(-2), and C and N pools ranged 35-2333 g C m(-2) and 0.5-35.1 g N m(-2), respectively. We estimate that the aboveground plant biomass is reduced due to chronic exposure to industrial air pollution over an area of about 107,200 km2, and the total (aboveground and belowground) loss of phytomass C stock amounts to 4.24×10(13) g C. Our results emphasize the need to account for the overall impact of industrial polluters on ecosystem C and N pools when assessing the C and N dynamics in northern boreal forests because of the marked long-term negative effects of their emissions on structure and productivity of plant communities. Copyright © 2015 Elsevier B.V. All rights reserved.

Hydrologic resilience and Amazon productivity.

PubMed

Ahlström, Anders; Canadell, Josep G; Schurgers, Guy; Wu, Minchao; Berry, Joseph A; Guan, Kaiyu; Jackson, Robert B

2017-08-30

The Amazon rainforest is disproportionately important for global carbon storage and biodiversity. The system couples the atmosphere and land, with moist forest that depends on convection to sustain gross primary productivity and growth. Earth system models that estimate future climate and vegetation show little agreement in Amazon simulations. Here we show that biases in internally generated climate, primarily precipitation, explain most of the uncertainty in Earth system model results; models, empirical data and theory converge when precipitation biases are accounted for. Gross primary productivity, above-ground biomass and tree cover align on a hydrological relationship with a breakpoint at ~2000 mm annual precipitation, where the system transitions between water and radiation limitation of evapotranspiration. The breakpoint appears to be fairly stable in the future, suggesting resilience of the Amazon to climate change. Changes in precipitation and land use are therefore more likely to govern biomass and vegetation structure in Amazonia.Earth system model simulations of future climate in the Amazon show little agreement. Here, the authors show that biases in internally generated climate explain most of this uncertainty and that the balance between water-saturated and water-limited evapotranspiration controls the Amazon resilience to climate change.

The interactive effects of fire and diversity on short-term responses of ecosystem processes in experimental mediterranean grasslands.

PubMed

Dimitrakopoulos, Panayiotis G; Siamantziouras, Akis-Stavros D; Galanidis, Alexandros; Mprezetou, Irene; Troumbis, Andreas Y

2006-06-01

We conducted a field experiment using constructed communities to test whether species richness contributed to the maintenance of ecosystem processes under fire disturbance. We studied the effects of diversity components (i.e., species richness and species composition) upon productivity, structural traits of vegetation, decomposition rates, and soil nutrients between burnt and unburnt experimental Mediterranean grassland communities. Our results demonstrated that fire and species richness had interactive effects on aboveground biomass production and canopy structure components. Fire increased biomass production of the highest-richness communities. The effects of fire on aboveground biomass production at different levels of species richness were derived from changes in both vertical and horizontal canopy structure of the communities. The most species-rich communities appeared to be more resistant to fire in relation to species-poor ones, due to both compositional and richness effects. Interactive effects of fire and species richness were not important for belowground processes. Decomposition rates increased with species richness, related in part to increased levels of canopy structure traits. Fire increased soil nutrients and long-term decomposition rate. Our results provide evidence that composition within richness levels had often larger effects on the stability of aboveground ecosystem processes in the face of fire disturbance than species richness per se.

Aboveground Tree Growth Varies with Belowground Carbon Allocation in a Tropical Rainforest Environment

PubMed Central

Raich, James W.; Clark, Deborah A.; Schwendenmann, Luitgard; Wood, Tana E.

2014-01-01

Young secondary forests and plantations in the moist tropics often have rapid rates of biomass accumulation and thus sequester large amounts of carbon. Here, we compare results from mature forest and nearby 15–20 year old tree plantations in lowland Costa Rica to evaluate differences in allocation of carbon to aboveground production and root systems. We found that the tree plantations, which had fully developed, closed canopies, allocated more carbon belowground - to their root systems - than did mature forest. This increase in belowground carbon allocation correlated significantly with aboveground tree growth but not with canopy production (i.e., leaf fall or fine litter production). In contrast, there were no correlations between canopy production and either tree growth or belowground carbon allocation. Enhanced allocation of carbon to root systems can enhance plant nutrient uptake, providing nutrients beyond those required for the production of short-lived tissues such as leaves and fine roots, and thus enabling biomass accumulation. Our analyses support this deduction at our site, showing that enhanced allocation of carbon to root systems can be an important mechanism promoting biomass accumulation during forest growth in the moist tropics. Identifying factors that control when, where and for how long this occurs would help us to improve models of forest growth and nutrient cycling, and to ascertain the role that young forests play in mitigating increased atmospheric carbon dioxide. PMID:24945351

Shrubland primary production and soil respiration diverge along European climate gradient

PubMed Central

Reinsch, Sabine; Koller, Eva; Sowerby, Alwyn; de Dato, Giovanbattista; Estiarte, Marc; Guidolotti, Gabriele; Kovács-Láng, Edit; Kröel-Dulay, György; Lellei-Kovács, Eszter; Larsen, Klaus S.; Liberati, Dario; Peñuelas, Josep; Ransijn, Johannes; Robinson, David A.; Schmidt, Inger K.; Smith, Andrew R.; Tietema, Albert; Dukes, Jeffrey S.; Beier, Claus; Emmett, Bridget A.

2017-01-01

Above- and belowground carbon (C) stores of terrestrial ecosystems are vulnerable to environmental change. Ecosystem C balances in response to environmental changes have been quantified at individual sites, but the magnitudes and directions of these responses along environmental gradients remain uncertain. Here we show the responses of ecosystem C to 8–12 years of experimental drought and night-time warming across an aridity gradient spanning seven European shrublands using indices of C assimilation (aboveground net primary production: aNPP) and soil C efflux (soil respiration: Rs). The changes of aNPP and Rs in response to drought indicated that wet systems had an overall risk of increased loss of C but drier systems did not. Warming had no consistent effect on aNPP across the climate gradient, but suppressed Rs more at the drier sites. Our findings suggest that above- and belowground C fluxes can decouple, and provide no evidence of acclimation to environmental change at a decadal timescale. aNPP and Rs especially differed in their sensitivity to drought and warming, with belowground processes being more sensitive to environmental change. PMID:28256623

Shrubland primary production and soil respiration diverge along European climate gradient

NASA Astrophysics Data System (ADS)

Reinsch, Sabine; Koller, Eva; Sowerby, Alwyn; de Dato, Giovanbattista; Estiarte, Marc; Guidolotti, Gabriele; Kovács-Láng, Edit; Kröel-Dulay, György; Lellei-Kovács, Eszter; Larsen, Klaus S.; Liberati, Dario; Peñuelas, Josep; Ransijn, Johannes; Robinson, David A.; Schmidt, Inger K.; Smith, Andrew R.; Tietema, Albert; Dukes, Jeffrey S.; Beier, Claus; Emmett, Bridget A.

2017-03-01

Above- and belowground carbon (C) stores of terrestrial ecosystems are vulnerable to environmental change. Ecosystem C balances in response to environmental changes have been quantified at individual sites, but the magnitudes and directions of these responses along environmental gradients remain uncertain. Here we show the responses of ecosystem C to 8-12 years of experimental drought and night-time warming across an aridity gradient spanning seven European shrublands using indices of C assimilation (aboveground net primary production: aNPP) and soil C efflux (soil respiration: Rs). The changes of aNPP and Rs in response to drought indicated that wet systems had an overall risk of increased loss of C but drier systems did not. Warming had no consistent effect on aNPP across the climate gradient, but suppressed Rs more at the drier sites. Our findings suggest that above- and belowground C fluxes can decouple, and provide no evidence of acclimation to environmental change at a decadal timescale. aNPP and Rs especially differed in their sensitivity to drought and warming, with belowground processes being more sensitive to environmental change.

The global potential of bioenergy on abandoned agriculture lands.

PubMed

Campbell, J Elliott; Lobell, David B; Genova, Robert C; Field, Christopher B

2008-08-01

Converting forest lands into bioenergy agriculture could accelerate climate change by emitting carbon stored in forests, while converting food agriculture lands into bioenergy agriculture could threaten food security. Both problems are potentially avoided by using abandoned agriculture lands for bioenergy agriculture. Here we show the global potential for bioenergy on abandoned agriculture lands to be less than 8% of current primary energy demand, based on historical land use data, satellite-derived land cover data, and global ecosystem modeling. The estimated global area of abandoned agriculture is 385-472 million hectares, or 66-110% of the areas reported in previous preliminary assessments. The area-weighted mean production of above-ground biomass is 4.3 tons ha(-1) y(-1), in contrast to estimates of up to 10 tons ha(-1) y(-1) in previous assessments. The energy content of potential biomass grown on 100% of abandoned agriculture lands is less than 10% of primary energy demand for most nations in North America, Europe, and Asia, but it represents many times the energy demand in some African nations where grasslands are relatively productive and current energy demand is low.

Combining Multi-Source Remotely Sensed Data and a Process-Based Model for Forest Aboveground Biomass Updating.

PubMed

Lu, Xiaoman; Zheng, Guang; Miller, Colton; Alvarado, Ernesto

2017-09-08

Monitoring and understanding the spatio-temporal variations of forest aboveground biomass (AGB) is a key basis to quantitatively assess the carbon sequestration capacity of a forest ecosystem. To map and update forest AGB in the Greater Khingan Mountains (GKM) of China, this work proposes a physical-based approach. Based on the baseline forest AGB from Landsat Enhanced Thematic Mapper Plus (ETM+) images in 2008, we dynamically updated the annual forest AGB from 2009 to 2012 by adding the annual AGB increment (ABI) obtained from the simulated daily and annual net primary productivity (NPP) using the Boreal Ecosystem Productivity Simulator (BEPS) model. The 2012 result was validated by both field- and aerial laser scanning (ALS)-based AGBs. The predicted forest AGB for 2012 estimated from the process-based model can explain 31% ( n = 35, p < 0.05, RMSE = 2.20 kg/m²) and 85% ( n = 100, p < 0.01, RMSE = 1.71 kg/m²) of variation in field- and ALS-based forest AGBs, respectively. However, due to the saturation of optical remote sensing-based spectral signals and contribution of understory vegetation, the BEPS-based AGB tended to underestimate/overestimate the AGB for dense/sparse forests. Generally, our results showed that the remotely sensed forest AGB estimates could serve as the initial carbon pool to parameterize the process-based model for NPP simulation, and the combination of the baseline forest AGB and BEPS model could effectively update the spatiotemporal distribution of forest AGB.

Combining Multi-Source Remotely Sensed Data and a Process-Based Model for Forest Aboveground Biomass Updating

PubMed Central

Lu, Xiaoman; Zheng, Guang; Miller, Colton

2017-01-01

Monitoring and understanding the spatio-temporal variations of forest aboveground biomass (AGB) is a key basis to quantitatively assess the carbon sequestration capacity of a forest ecosystem. To map and update forest AGB in the Greater Khingan Mountains (GKM) of China, this work proposes a physical-based approach. Based on the baseline forest AGB from Landsat Enhanced Thematic Mapper Plus (ETM+) images in 2008, we dynamically updated the annual forest AGB from 2009 to 2012 by adding the annual AGB increment (ABI) obtained from the simulated daily and annual net primary productivity (NPP) using the Boreal Ecosystem Productivity Simulator (BEPS) model. The 2012 result was validated by both field- and aerial laser scanning (ALS)-based AGBs. The predicted forest AGB for 2012 estimated from the process-based model can explain 31% (n = 35, p < 0.05, RMSE = 2.20 kg/m2) and 85% (n = 100, p < 0.01, RMSE = 1.71 kg/m2) of variation in field- and ALS-based forest AGBs, respectively. However, due to the saturation of optical remote sensing-based spectral signals and contribution of understory vegetation, the BEPS-based AGB tended to underestimate/overestimate the AGB for dense/sparse forests. Generally, our results showed that the remotely sensed forest AGB estimates could serve as the initial carbon pool to parameterize the process-based model for NPP simulation, and the combination of the baseline forest AGB and BEPS model could effectively update the spatiotemporal distribution of forest AGB. PMID:28885556

The response of aboveground plant productivity to earlier snowmelt and summer warming in an Arctic ecosystem

NASA Astrophysics Data System (ADS)

Livensperger, C.; Steltzer, H.; Darrouzet-Nardi, A.; Sullivan, P.; Wallenstein, M. D.; Weintraub, M. N.

2012-12-01

Plant communities in the Arctic are undergoing changes in structure and function due to shifts in seasonality from changing winters and summer warming. These changes will impact biogeochemical cycling, surface energy balance, and functioning of vertebrate and invertebrate communities. To examine seasonal controls on aboveground net primary production (ANPP) in a moist acidic tundra ecosystem in northern Alaska, we shifted the growing season by accelerating snowmelt (using radiation absorbing shadecloth) and warming air and soil temperature (using 1 m2 open-top chambers), individually and in combination. After three years, we measured ANPP by harvesting up to 16 individual ramets, tillers and rhizomes for each of 7 plant species, including two deciduous shrubs, two graminoids, two evergreen shrubs and one forb during peak season. Our results show that ANPP per stem summed across the 7 species increased when snow melt occurred earlier. However, standing biomass, excluding current year growth, was also greater. The ratio of ANPP/standing biomass decreased in all treatments compared to the control. ANPP per unit standing biomass summed for the four shrub species decreases due to summer warming alone or in combination with early snowmelt; however early snowmelt alone did not lead to lower ANPP for the shrubs. ANPP per tiller or rhizome summed for the three herbaceous species increased in response to summer warming. Understanding the differential response of plants to changing seasonality will inform predictions of future Arctic plant community structure and function.

Grassland productivity limited by multiple nutrients.

PubMed

Fay, Philip A; Prober, Suzanne M; Harpole, W Stanley; Knops, Johannes M H; Bakker, Jonathan D; Borer, Elizabeth T; Lind, Eric M; MacDougall, Andrew S; Seabloom, Eric W; Wragg, Peter D; Adler, Peter B; Blumenthal, Dana M; Buckley, Yvonne M; Chu, Chengjin; Cleland, Elsa E; Collins, Scott L; Davies, Kendi F; Du, Guozhen; Feng, Xiaohui; Firn, Jennifer; Gruner, Daniel S; Hagenah, Nicole; Hautier, Yann; Heckman, Robert W; Jin, Virginia L; Kirkman, Kevin P; Klein, Julia; Ladwig, Laura M; Li, Qi; McCulley, Rebecca L; Melbourne, Brett A; Mitchell, Charles E; Moore, Joslin L; Morgan, John W; Risch, Anita C; Schütz, Martin; Stevens, Carly J; Wedin, David A; Yang, Louie H

2015-07-06

Terrestrial ecosystem productivity is widely accepted to be nutrient limited(1). Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)(2,3), the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized(4-8). However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.

Interrelated effects of mycorrhiza and free-living nitrogen fixers cascade up to aboveground herbivores.

PubMed

Khaitov, Botir; Patiño-Ruiz, José David; Pina, Tatiana; Schausberger, Peter

2015-09-01

Aboveground plant performance is strongly influenced by belowground microorganisms, some of which are pathogenic and have negative effects, while others, such as nitrogen-fixing bacteria and arbuscular mycorrhizal fungi, usually have positive effects. Recent research revealed that belowground interactions between plants and functionally distinct groups of microorganisms cascade up to aboveground plant associates such as herbivores and their natural enemies. However, while functionally distinct belowground microorganisms commonly co-occur in the rhizosphere, their combined effects, and relative contributions, respectively, on performance of aboveground plant-associated organisms are virtually unexplored. Here, we scrutinized and disentangled the effects of free-living nitrogen-fixing (diazotrophic) bacteria Azotobacter chroococcum (DB) and arbuscular mycorrhizal fungi Glomus mosseae (AMF) on host plant choice and reproduction of the herbivorous two-spotted spider mite Tetranychus urticae on common bean plants Phaseolus vulgaris. Additionally, we assessed plant growth, and AMF and DB occurrence and density as affected by each other. Both AMF alone and DB alone increased spider mite reproduction to similar levels, as compared to the control, and exerted additive effects under co-occurrence. These effects were similarly apparent in host plant choice, that is, the mites preferred leaves from plants with both AMF and DB to plants with AMF or DB to plants grown without AMF and DB. DB, which also act as AMF helper bacteria, enhanced root colonization by AMF, whereas AMF did not affect DB abundance. AMF but not DB increased growth of reproductive plant tissue and seed production, respectively. Both AMF and DB increased the biomass of vegetative aboveground plant tissue. Our study breaks new ground in multitrophic belowground-aboveground research by providing first insights into the fitness implications of plant-mediated interactions between interrelated belowground fungi-bacteria and aboveground herbivores.

Resolving model parameter values from carbon and nitrogen stock measurements in a wide range of tropical mature forests using nonlinear inversion and regression trees

USGS Publications Warehouse

Liu, S.; Anderson, P.; Zhou, G.; Kauffman, B.; Hughes, F.; Schimel, D.; Watson, Vicente; Tosi, Joseph

2008-01-01

Objectively assessing the performance of a model and deriving model parameter values from observations are critical and challenging in landscape to regional modeling. In this paper, we applied a nonlinear inversion technique to calibrate the ecosystem model CENTURY against carbon (C) and nitrogen (N) stock measurements collected from 39 mature tropical forest sites in seven life zones in Costa Rica. Net primary productivity from the Moderate-Resolution Imaging Spectroradiometer (MODIS), C and N stocks in aboveground live biomass, litter, coarse woody debris (CWD), and in soils were used to calibrate the model. To investigate the resolution of available observations on the number of adjustable parameters, inversion was performed using nine setups of adjustable parameters. Statistics including observation sensitivity, parameter correlation coefficient, parameter sensitivity, and parameter confidence limits were used to evaluate the information content of observations, resolution of model parameters, and overall model performance. Results indicated that soil organic carbon content, soil nitrogen content, and total aboveground biomass carbon had the highest information contents, while measurements of carbon in litter and nitrogen in CWD contributed little to the parameter estimation processes. The available information could resolve the values of 2-4 parameters. Adjusting just one parameter resulted in under-fitting and unacceptable model performance, while adjusting five parameters simultaneously led to over-fitting. Results further indicated that the MODIS NPP values were compressed as compared with the spatial variability of net primary production (NPP) values inferred from inverse modeling. Using inverse modeling to infer NPP and other sensitive model parameters from C and N stock observations provides an opportunity to utilize data collected by national to regional forest inventory systems to reduce the uncertainties in the carbon cycle and generate valuable databases to validate and improve MODIS NPP algorithms.

Insights into mechanisms governing forest carbon response to nitrogen deposition: a model-data comparison using observed responses to nitrogen addition

NASA Astrophysics Data System (ADS)

Thomas, R. Q.; Bonan, G. B.; Goodale, C. L.

2013-01-01

In many forest ecosystems, nitrogen (N) deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C) sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a~global biogeochemical model (CLM-CN 4.0). We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1) by increasing the aboveground C storage in response to historical N deposition (1850-2004) from 14 to 34 kg C per additional kg N added through deposition and (2) by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m-2 yr-1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss) and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition) and N pulse additions of N over multiple years (N fertilization) allows for greater understanding of the mechanisms governing C-N coupling.

Insights into mechanisms governing forest carbon response to nitrogen deposition: a model-data comparison using observed responses to nitrogen addition

NASA Astrophysics Data System (ADS)

Thomas, R. Q.; Bonan, G. B.; Goodale, C. L.

2013-06-01

In many forest ecosystems, nitrogen (N) deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C) sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a global biogeochemical model (CLM-CN 4.0). We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1) by increasing the aboveground C storage in response to historical N deposition (1850-2004) from 14 to 34 kg C per additional kg N added through deposition and (2) by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m-2 yr-1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss) and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition) and N pulse additions of N over multiple years (N fertilization) allows for greater understanding of the mechanisms governing C-N coupling.

Carbon And Nitrogen Storage Of A Mediterranean-Type Shrubland In Response To Post-Fire Succession And Long-Term Experimental Nitrogen Deposition

NASA Astrophysics Data System (ADS)

Vourlitis, G. L.; Hentz, C. S.

2015-12-01

Mediterranean-type shublands are subject to periodic fire and high levels of atmospheric nitrogen (N) deposition. Little is known how N inputs interact with post-fire secondary succession to affect ecosystem carbon (C) and N storage and cycling. Thus, a field experiment was conducted in a chaparral stand located in NE San Diego County, USA that burned during a wildfire in July 2003 to test the hypotheses that rates of C and N storage would significantly increase in response to experimental N addition. The experimental layout consists of a randomized design where four-10 x 10 m plots received 5 gN m-2 (added N) in the fall of each year since 2003 and four-10 x 10 m plots served as un-manipulated controls. Aboveground biomass C and N pools and fluxes, including biomass and litter C and N pool size, litter production, net primary production (NPP), N uptake, and litter C and N mineralization were measured seasonally (every 3 months) for a period of 10 years. Belowground surface (0-10 cm) soil extractable N, pH, and total soil N and C pools and surface root biomass C and N pools were also measured seasonally for a period of 10 years, while N losses from leaching were measured over a shorted (8 year) period of time. Added N led to a rapid increase in soil extractable N and a decline in soil pH; however, total soil C and N storage have yet to be affected by N input. Added N plots initially had significantly lower C and N storage than control plots; however, rates of aboveground N and C storage became significantly higher added N plots after 4-5 years of exposure. N losses from leaching continue to be significantly higher in added N plots even with an increase in aboveground C and N storage. The impact of N enrichment on ecosystem C and N storage varied depending on the stage of succession, but the eventual N-induced increase in NPP has implications for fuel buildup and future fire intensity. While N enrichment acted to increase aboveground C and N storage, plots exposed to high N inputs lost substantially more N from leaching than control plots. These results indicate that post-fire chaparral shrublands tend to be "leaky" even though they are not yet "N-saturated." Recovering stands in high-N deposition areas will likely be large sources of N to groundwater and/or streams regardless of whether NPP is stimulated by N input.

Fine root dynamics and forest production across a calcium gradient in northern hardwood and conifer ecosystems

USGS Publications Warehouse

Park, B.B.; Yanai, R.D.; Fahey, T.J.; Bailey, S.W.; Siccama, T.G.; Shanley, J.B.; Cleavitt, N.L.

2008-01-01

Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither aboveground biomass and production nor belowground biomass were related to soil Ca or Ca:Al ratios across this gradient. Hardwood stands had 37% higher aboveground biomass (P = 0.03) and 44% higher leaf litter production (P < 0.01) than the conifer stands, on average. Fine root biomass (<2 mm in diameter) in the upper 35 cm of the soil, including the forest floor, was very similar in hardwoods and conifers (5.92 and 5.93 Mg ha-1). The turnover coefficient (TC) of fine roots smaller than 1 mm ranged from 0.62 to 1.86 y-1 and increased significantly with soil exchangeable Ca (P = 0.03). As a result, calculated fine root production was clearly higher in sites with higher soil Ca (P = 0.02). Fine root production (biomass times turnover) ranged from 1.2 to 3.7 Mg ha-1 y-1 for hardwood stands and from 0.9 to 2.3 Mg ha-1 y -1 for conifer stands. The relationship we observed between soil Ca availability and root production suggests that cation depletion might lead to reduced carbon allocation to roots in these ecosystems. ?? 2008 Springer Science+Business Media, LLC.

Cacao Cultivation under Diverse Shade Tree Cover Allows High Carbon Storage and Sequestration without Yield Losses

PubMed Central

Abou Rajab, Yasmin; Leuschner, Christoph; Barus, Henry; Tjoa, Aiyen; Hertel, Dietrich

2016-01-01

One of the main drivers of tropical forest loss is their conversion to oil palm, soy or cacao plantations with low biodiversity and greatly reduced carbon storage. Southeast Asian cacao plantations are often established under shade tree cover, but are later converted to non-shaded monocultures to avoid resource competition. We compared three co-occurring cacao cultivation systems (3 replicate stands each) with different shade intensity (non-shaded monoculture, cacao with the legume Gliricidia sepium shade trees, and cacao with several shade tree species) in Sulawesi (Indonesia) with respect to above- and belowground biomass and productivity, and cacao bean yield. Total biomass C stocks (above- and belowground) increased fivefold from the monoculture to the multi-shade tree system (from 11 to 57 Mg ha-1), total net primary production rose twofold (from 9 to 18 Mg C ha-1 yr-1). This increase was associated with a 6fold increase in aboveground biomass, but only a 3.5fold increase in root biomass, indicating a clear shift in C allocation to aboveground tree organs with increasing shade for both cacao and shade trees. Despite a canopy cover increase from 50 to 93%, cacao bean yield remained invariant across the systems (variation: 1.1–1.2 Mg C ha-1 yr-1). The monocultures had a twice as rapid leaf turnover suggesting that shading reduces the exposure of cacao to atmospheric drought, probably resulting in greater leaf longevity. Thus, contrary to general belief, cacao bean yield does not necessarily decrease under shading which seems to reduce physical stress. If planned properly, cacao plantations under a shade tree cover allow combining high yield with benefits for carbon sequestration and storage, production system stability under stress, and higher levels of animal and plant diversity. PMID:26927428

Cacao Cultivation under Diverse Shade Tree Cover Allows High Carbon Storage and Sequestration without Yield Losses.

PubMed

Abou Rajab, Yasmin; Leuschner, Christoph; Barus, Henry; Tjoa, Aiyen; Hertel, Dietrich

2016-01-01

One of the main drivers of tropical forest loss is their conversion to oil palm, soy or cacao plantations with low biodiversity and greatly reduced carbon storage. Southeast Asian cacao plantations are often established under shade tree cover, but are later converted to non-shaded monocultures to avoid resource competition. We compared three co-occurring cacao cultivation systems (3 replicate stands each) with different shade intensity (non-shaded monoculture, cacao with the legume Gliricidia sepium shade trees, and cacao with several shade tree species) in Sulawesi (Indonesia) with respect to above- and belowground biomass and productivity, and cacao bean yield. Total biomass C stocks (above- and belowground) increased fivefold from the monoculture to the multi-shade tree system (from 11 to 57 Mg ha-1), total net primary production rose twofold (from 9 to 18 Mg C ha-1 yr-1). This increase was associated with a 6fold increase in aboveground biomass, but only a 3.5fold increase in root biomass, indicating a clear shift in C allocation to aboveground tree organs with increasing shade for both cacao and shade trees. Despite a canopy cover increase from 50 to 93%, cacao bean yield remained invariant across the systems (variation: 1.1-1.2 Mg C ha-1 yr-1). The monocultures had a twice as rapid leaf turnover suggesting that shading reduces the exposure of cacao to atmospheric drought, probably resulting in greater leaf longevity. Thus, contrary to general belief, cacao bean yield does not necessarily decrease under shading which seems to reduce physical stress. If planned properly, cacao plantations under a shade tree cover allow combining high yield with benefits for carbon sequestration and storage, production system stability under stress, and higher levels of animal and plant diversity.

A comparison of two above-ground biomass estimation techniques integrating satellite-based remotely sensed data and ground data for tropical and semiarid forests in Puerto Rico

NASA Astrophysics Data System (ADS)

Iiames, J. S.; Riegel, J.; Lunetta, R.

2013-12-01

Two above-ground forest biomass estimation techniques were evaluated for the United States Territory of Puerto Rico using predictor variables acquired from satellite based remotely sensed data and ground data from the U.S. Department of Agriculture Forest Inventory Analysis (FIA) program. The U.S. Environmental Protection Agency (EPA) estimated above-ground forest biomass implementing methodology first posited by the Woods Hole Research Center developed for conterminous United States (National Biomass and Carbon Dataset [NBCD2000]). For EPA's effort, spatial predictor layers for above-ground biomass estimation included derived products from the U.S. Geologic Survey (USGS) National Land Cover Dataset 2001 (NLCD) (landcover and canopy density), the USGS Gap Analysis Program (forest type classification), the USGS National Elevation Dataset, and the NASA Shuttle Radar Topography Mission (tree heights). In contrast, the U.S. Forest Service (USFS) biomass product integrated FIA ground-based data with a suite of geospatial predictor variables including: (1) the Moderate Resolution Imaging Spectrometer (MODIS)-derived image composites and percent tree cover; (2) NLCD land cover proportions; (3) topographic variables; (4) monthly and annual climate parameters; and (5) other ancillary variables. Correlations between both data sets were made at variable watershed scales to test level of agreement. Notice: This work is done in support of EPA's Sustainable Healthy Communities Research Program. The U.S EPA funded and conducted the research described in this paper. Although this work was reviewed by the EPA and has been approved for publication, it may not necessarily reflect official Agency policy. Mention of any trade names or commercial products does not constitute endorsement or recommendation for use.

Greenhouse gas emissions and carbon sequestration by agroforestry systems in southeastern Brazil.

PubMed

Torres, Carlos Moreira Miquelino Eleto; Jacovine, Laércio Antônio Gonçalves; Nolasco de Olivera Neto, Sílvio; Fraisse, Clyde William; Soares, Carlos Pedro Boechat; de Castro Neto, Fernando; Ferreira, Lino Roberto; Zanuncio, José Cola; Lemes, Pedro Guilherme

2017-12-01

Agrosilvopastoral and silvopastoral systems can increase carbon sequestration, offset greenhouse gas (GHG) emissions and reduce the carbon footprint generated by animal production. The objective of this study was to estimate GHG emissions, the tree and grass aboveground biomass production and carbon storage in different agrosilvopastoral and silvopastoral systems in southeastern Brazil. The number of trees required to offset these emissions were also estimated. The GHG emissions were calculated based on pre-farm (e.g. agrochemical production, storage, and transportation), and on-farm activities (e.g. fertilization and machinery operation). Aboveground tree grass biomass and carbon storage in all systems was estimated with allometric equations. GHG emissions from the agroforestry systems ranged from 2.81 to 7.98 t CO 2 e ha -1 . Carbon storage in the aboveground trees and grass biomass were 54.6, 11.4, 25.7 and 5.9 t C ha -1 , and 3.3, 3.6, 3.8 and 3.3 t C ha -1 for systems 1, 2, 3 and 4, respectively. The number of trees necessary to offset the emissions ranged from 17 to 44 trees ha -1 , which was lower than the total planted in the systems. Agroforestry systems sequester CO 2 from the atmosphere and can help the GHG emission-reduction policy of the Brazilian government.

How drought severity constrains gross primary production(GPP) and its partitioning among carbon pools in a Quercus ilex coppice?

NASA Astrophysics Data System (ADS)

Rambal, S.; Lempereur, M.; Limousin, J. M.; Martin-StPaul, N. K.; Ourcival, J. M.; Rodríguez-Calcerrada, J.

2014-12-01

The partitioning of photosynthates toward biomass compartments plays a crucial role in the carbon (C) sink function of forests. Few studies have examined how carbon is allocated toward plant compartments in drought-prone forests. We analyzed the fate of gross primary production (GPP) in relation to yearly water deficit in an old evergreen Mediterranean Quercus ilex coppice severely affected by water limitations. Carbon fluxes between the ecosystem and the atmosphere were measured with an eddy covariance flux tower running continuously since 2001. Discrete measurements of litterfall, stem growth and fAPAR allowed us to derive annual productions of leaves, wood, flowers and acorns, and an isometric relationship between stem and belowground biomass has been used to estimate perennial belowground growth. By combining eddy covariance fluxes with annual net primary productions (NPP), we managed to close a C budget and derive values of autotrophic, heterotrophic respirations and carbon-use efficiency (CUE; the ratio between NPP and GPP). Average values of yearly net ecosystem production (NEP), GPP and Reco were 282, 1259 and 977 g C m-2. The corresponding aboveground net primary production (ANPP) components were 142.5, 26.4 and 69.6 g C m-2 for leaves, reproductive effort (flowers and fruits) and stems, respectively. NEP, GPP and Reco were affected by annual water deficit. Partitioning to the different plant compartments was also impacted by drought, with a hierarchy of responses going from the most affected - the stem growth - to the least affected - the leaf production. The average CUE was 0.40, which is well in the range for Mediterranean-type forest ecosystems. CUE tended to decrease less drastically in response to drought than GPP and NPP did, probably due to drought acclimation of autotrophic respiration. Overall, our results provide a baseline for modeling the inter-annual variations of carbon fluxes and allocation in this widespread Mediterranean ecosystem, and they highlight the value of maintaining continuous experimental measurements over the long term.

Biomass production efficiency controlled by management in temperate and boreal ecosystems

NASA Astrophysics Data System (ADS)

Campioli, M.; Vicca, S.; Luyssaert, S.; Bilcke, J.; Ceschia, E.; Chapin, F. S., III; Ciais, P.; Fernández-Martínez, M.; Malhi, Y.; Obersteiner, M.; Olefeldt, D.; Papale, D.; Piao, S. L.; Peñuelas, J.; Sullivan, P. F.; Wang, X.; Zenone, T.; Janssens, I. A.

2015-11-01

Plants acquire carbon through photosynthesis to sustain biomass production, autotrophic respiration and production of non-structural compounds for multiple purposes. The fraction of photosynthetic production used for biomass production, the biomass production efficiency, is a key determinant of the conversion of solar energy to biomass. In forest ecosystems, biomass production efficiency was suggested to be related to site fertility. Here we present a database of biomass production efficiency from 131 sites compiled from individual studies using harvest, biometric, eddy covariance, or process-based model estimates of production. The database is global, but dominated by data from Europe and North America. We show that instead of site fertility, ecosystem management is the key factor that controls biomass production efficiency in terrestrial ecosystems. In addition, in natural forests, grasslands, tundra, boreal peatlands and marshes, biomass production efficiency is independent of vegetation, environmental and climatic drivers. This similarity of biomass production efficiency across natural ecosystem types suggests that the ratio of biomass production to gross primary productivity is constant across natural ecosystems. We suggest that plant adaptation results in similar growth efficiency in high- and low-fertility natural systems, but that nutrient influxes under managed conditions favour a shift to carbon investment from the belowground flux of non-structural compounds to aboveground biomass.

Legacies of precipitation fluctuations on primary production: theory and data synthesis.

PubMed

Sala, Osvaldo E; Gherardi, Laureano A; Reichmann, Lara; Jobbágy, Esteban; Peters, Debra

2012-11-19

Variability of above-ground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space (based on multiyear averages for different locations) than through time (based on year-to-year change at single locations). Here, we propose a theory of controls of ANPP based on four hypotheses about legacies of wet and dry years that explains space versus time differences in ANPP-precipitation relationships. We tested the hypotheses using 16 long-term series of ANPP. We found that legacies revealed by the association of current- versus previous-year conditions through the temporal series occur across all ecosystem types from deserts to mesic grasslands. Therefore, previous-year precipitation and ANPP control a significant fraction of current-year production. We developed unified models for the controls of ANPP through space and time. The relative importance of current-versus previous-year precipitation changes along a gradient of mean annual precipitation with the importance of current-year PPT decreasing, whereas the importance of previous-year PPT remains constant as mean annual precipitation increases. Finally, our results suggest that ANPP will respond to climate-change-driven alterations in water availability and, more importantly, that the magnitude of the response will increase with time.

Hydrologic remediation for the Deepwater Horizon incident drove ancillary primary production increase in coastal swamps

USGS Publications Warehouse

Middleton, Beth A.; Johnson, Darren; Roberts, Brian J

2015-01-01

As coastal wetlands subside worldwide, there is an urgency to understand the hydrologic drivers and dynamics of plant production and peat accretion. One incidental test of the effects of high rates of discharge on forested wetland production occurred in response to the 2010 Deepwater Horizon incident, in which all diversions in Louisiana were operated at or near their maximum discharge level for an extended period to keep offshore oil from threatened coastal wetlands. Davis Pond Diversion was operated at six times the normal discharge levels for almost 4 months, so that Taxodium distichum swamps downstream of the diversion experienced greater inundation and lower salinity. After this remediation event in 2010, above-ground litter production increased by 2.7 times of production levels in 2007–2011. Biomass of the leaf and reproductive tissues of several species increased; wood litter was minimal and did not change during this period. Root production decreased in 2010 but subsequently returned to pre-remediation values in 2011. Both litter and root production remained high in the second growing season after hydrologic remediation. Annual tree growth (circumference increment) was not significantly altered by the remediation. The potential of freshwater pulses for regulating tidal swamp production is further supported by observations of higher T. distichum growth in lower salinity and/or pulsed environments across the U.S. Gulf Coast. Usage of freshwater pulses to manage altered estuaries deserves further consideration, particularly because the timing and duration of such pulses could influence both primary production and peat accretion.

Interactions between the flooding regime and floodplain grasslands in the Tana River Delta, in Kenya

NASA Astrophysics Data System (ADS)

Leauthaud, Crystele; Musila, Winfred; Duvail, Stéphanie; Kergoat, Laurent; Hiernaux, Pierre; Grippa, Manuela; Albergel, Jean

2017-04-01

The floodplain grasslands of the Tana River Delta, located on the East African coast in Kenya, form part of an intertwined socio-ecological deltaic system of high biodiversity value that delivers numerous goods and services. Mainly composed of Echinochloa stagnina (Retz) P. Beauv., a high-value forage species, this ecosystem is the major dry-season grazing grounds of the local pastoralist communities. The construction of hydroelectric infrastructure has led to a modification of the flooding regime. The impacts of the resulting reduction of floods in the deltaic zone on ecosystem properties and services still need to be assessed. In such a perspective, this study characterizes the link between the flooding regime of the Tana River and the growth pattern of its floodplain grassland. Aboveground dry phytomass was sampled for 15 months under a wide variety of naturally flooded and non-flooded conditions and controlled irrigation and cutting frequency treatments. Annual aboveground dry phytomass attained high values between 11 T.ha-1 and 32 T.ha-1 and annual net primary production of the grasslands reached 35 T.ha-1.year-1. Growth rates clearly depended on the flooding regime, management and climate conditions and were on average more than twice as fast during, and 50% faster after the floods, relative to pre-flood conditions. A plant growth model allowed testing the effect of different flooding regimes on plant productivity, confirming very low productivity in the absence of floods. These results suggest that rangeland and water management for the Tana River deltaic wetlands are tightly linked. The projected construction of another dam could lead to a reduction of flood extent and period and a decrease of grassland productivity and growth duration. Mitigation of this type of negative impacts, which will have direct and adverse consequences for the pastoralist communities as well as on the delivery of other goods and services, needs to be undertaken.

Soil Respiration in Semiarid Temperate Grasslands under Various Land Management

PubMed Central

Hou, Xiangyang; Schellenberg, Michael P.

2016-01-01

Soil respiration, a major component of the global carbon cycle, is significantly influenced by land management practices. Grasslands are potentially a major sink for carbon, but can also be a source. Here, we investigated the potential effect of land management (grazing, clipping, and ungrazed enclosures) on soil respiration in the semiarid grassland of northern China. Our results showed the mean soil respiration was significantly higher under enclosures (2.17μmol.m−2.s−1) and clipping (2.06μmol.m−2.s−1) than under grazing (1.65μmol.m−2.s−1) over the three growing seasons. The high rates of soil respiration under enclosure and clipping were associated with the higher belowground net primary productivity (BNPP). Our analyses indicated that soil respiration was primarily related to BNPP under grazing, to soil water content under clipping. Using structural equation models, we found that soil water content, aboveground net primary productivity (ANPP) and BNPP regulated soil respiration, with soil water content as the predominant factor. Our findings highlight that management-induced changes in abiotic (soil temperature and soil water content) and biotic (ANPP and BNPP) factors regulate soil respiration in the semiarid temperate grassland of northern China. PMID:26808376

Controls on vegetation – soil moisture coupling in arid shrublands during drought elicited through long-term data

USDA-ARS?s Scientific Manuscript database

Our goal was to quantify variation in ecological responses to sustained period of moisture limitation (ecological drought) across a semiarid ecological landscape in northern Chihuahuan Desert, USA. We obtained long-term meteorological, ecological site, soil moisture and aboveground net primary prod...

Net ecosystem CO2 exchange of a primary tropical peat swamp forest in Sarawak, Malaysia

NASA Astrophysics Data System (ADS)

Tang Che Ing, A.; Stoy, P. C.; Melling, L.

2014-12-01

Tropical peat swamp forests are widely recognized as one of the world's most efficient ecosystems for the sequestration and storage of carbon through both their aboveground biomass and underlying thick deposits of peat. As the peat characteristics exhibit high spatial and temporal variability as well as the structural and functional complexity of forests, tropical peat ecosystems can act naturally as both carbon sinks and sources over their life cycles. Nonetheless, few reports of studies on the ecosystem-scale CO2 exchange of tropical peat swamp forests are available to-date and their present roles in the global carbon cycle remain uncertain. To quantify CO2 exchange and unravel the prevailing factors and potential underlying mechanism regulating net CO2 fluxes, an eddy covariance tower was erected in a tropical peat swamp forest in Sarawak, Malaysia. We observed that the diurnal and seasonal patterns of net ecosystem CO2 exchange (NEE) and its components (gross primary productivity (GPP) and ecosystem respiration (RE)) varied between seasons and years. Rates of NEE declined in the wet season relative to the dry season. Conversely, both the gross primary productivity (GPP) and ecosystem respiration (RE) were found to be higher during the wet season than the dry season, in which GPP was strongly negatively correlated with NEE. The average annual NEE was 385 ± 74 g C m-2 yr-1, indicating the primary peat swamp forest functioned as net source of CO2 to the atmosphere over the observation period.

Phytoremediation of ionic and methylmercury pollution

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

Meagher, Richard B.

2010-04-28

Our long-term goal is to enable highly productive plant species to extract, resist, detoxify, and sequester the toxic elemental pollutants, like the heavy metal mercury. Our current working hypothesis is that transgenic plants controlling the transport, chemical speciation, electrochemical state. volatilization, and aboveground binding of mercury will: a) tolerate mercury and grow rapidly in mercury contaminated environments; b) prevent methylmercury from entering the food chain; c) remove mercury from polluted soil and water; and d) hyperaccumulate mercury in aboveground tissues for later harvest. Progress toward these specific aims is reported: to increase the transport of mercury into roots and tomore » aboveground vegetative organs; to increase biochemical sinks and storage for mercury in leaves; to increase leaf cell vacuolar storage of mercury; and to demonstrate that several stacked transgenes, when functioning in concert, enhance mercury resistance and hyperaccumulation to high levels.« less

Aboveground allometric models for freeze-affected black mangroves (Avicennia germinans): equations for a climate sensitive mangrove-marsh ecotone.

PubMed

Osland, Michael J; Day, Richard H; Larriviere, Jack C; From, Andrew S

2014-01-01

Across the globe, species distributions are changing in response to climate change and land use change. In parts of the southeastern United States, climate change is expected to result in the poleward range expansion of black mangroves (Avicennia germinans) at the expense of some salt marsh vegetation. The morphology of A. germinans at its northern range limit is more shrub-like than in tropical climes in part due to the aboveground structural damage and vigorous multi-stem regrowth triggered by extreme winter temperatures. In this study, we developed aboveground allometric equations for freeze-affected black mangroves which can be used to quantify: (1) total aboveground biomass; (2) leaf biomass; (3) stem plus branch biomass; and (4) leaf area. Plant volume (i.e., a combination of crown area and plant height) was selected as the optimal predictor of the four response variables. We expect that our simple measurements and equations can be adapted for use in other mangrove ecosystems located in abiotic settings that result in mangrove individuals with dwarf or shrub-like morphologies including oligotrophic and arid environments. Many important ecological functions and services are affected by changes in coastal wetland plant community structure and productivity including carbon storage, nutrient cycling, coastal protection, recreation, fish and avian habitat, and ecosystem response to sea level rise and extreme climatic events. Coastal scientists in the southeastern United States can use the identified allometric equations, in combination with easily obtained and non-destructive plant volume measurements, to better quantify and monitor ecological change within the dynamic, climate sensitive, and highly-productive mangrove-marsh ecotone.

Aboveground allometric models for freeze-affected black mangroves (Avicennia germinans): equations for a climate sensitive mangrove-marsh ecotone

USGS Publications Warehouse

Osland, Michael J.; Day, Richard H.; Larriviere, Jack C.; From, Andrew S.

2014-01-01

Across the globe, species distributions are changing in response to climate change and land use change. In parts of the southeastern United States, climate change is expected to result in the poleward range expansion of black mangroves (Avicennia germinans) at the expense of some salt marsh vegetation. The morphology of A. germinans at its northern range limit is more shrub-like than in tropical climes in part due to the aboveground structural damage and vigorous multi-stem regrowth triggered by extreme winter temperatures. In this study, we developed aboveground allometric equations for freeze-affected black mangroves which can be used to quantify: (1) total aboveground biomass; (2) leaf biomass; (3) stem plus branch biomass; and (4) leaf area. Plant volume (i.e., a combination of crown area and plant height) was selected as the optimal predictor of the four response variables. We expect that our simple measurements and equations can be adapted for use in other mangrove ecosystems located in abiotic settings that result in mangrove individuals with dwarf or shrub-like morphologies including oligotrophic and arid environments. Many important ecological functions and services are affected by changes in coastal wetland plant community structure and productivity including carbon storage, nutrient cycling, coastal protection, recreation, fish and avian habitat, and ecosystem response to sea level rise and extreme climatic events. Coastal scientists in the southeastern United States can use the identified allometric equations, in combination with easily obtained and non-destructive plant volume measurements, to better quantify and monitor ecological change within the dynamic, climate sensitive, and highly-productive mangrove-marsh ecotone.

Long-Term Trends in Loblolly Pine Site Productivity and Stand Characteristics Observed at the Impac Research Site in Alachua County, Florida

Treesearch

Timothy A. Martin; Eric J. Jokela

2002-01-01

While nutrient availability is a dominant factor controlling leaf area development and pine productivity in the southeastern USA, few studies have explored the long-term interactions among nutrient inputs, canopy foliage production, and aboveground biomass production. In order to address these questions, the Intensive Management Practices Assessment Center (IMPAC)...

Nitrogen Fertilization Effects on Productivity and Nitrogen Loss in Three Grass-Based Perennial Bioenergy Cropping Systems

PubMed Central

Duran, Brianna E. L.; Duncan, David S.; Oates, Lawrence G.; Kucharik, Christopher J.; Jackson, Randall D.

2016-01-01

Nitrogen (N) fertilization can greatly improve plant productivity but needs to be carefully managed to avoid harmful environmental impacts. Nutrient management guidelines aimed at reducing harmful forms of N loss such as nitrous oxide (N2O) emissions and nitrate (NO3-) leaching have been tailored for many cropping systems. The developing bioenergy industry is likely to make use of novel cropping systems, such as polycultures of perennial species, for which we have limited nutrient management experience. We studied how a switchgrass (Panicum virgatum) monoculture, a 5-species native grass mixture and an 18-species restored prairie responded to annual fertilizer applications of 56 kg N ha-1 in a field-scale agronomic trial in south-central Wisconsin over a 2-year period. We observed greater fertilizer-induced N2O emissions and sub-rooting zone NO3- concentrations in the switchgrass monoculture than in either polyculture. Fertilization increased aboveground net primary productivity in the polycultures, but not in the switchgrass monoculture. Switchgrass was generally more productive, while the two polycultures did not differ from each other in productivity or N loss. Our results highlight differences between polycultures and a switchgrass monoculture in responding to N fertilization. PMID:26991790

Interannual growth dynamics of vegetation in the Kuparuk River watershed, Alaska based on the Normalized Difference Vegetation Index

USGS Publications Warehouse

Hope, A.S.; Boynton, W.L.; Stow, D.A.; Douglas, David C.

2003-01-01

Interannual above-ground production patterns are characterized for three tundra ecosystems in the Kuparuk River watershed of Alaska using NOAA-AVHRR Normalized Difference Vegetation Index (NDVI) data. NDVI values integrated over each growing season (SINDVI) were used to represent seasonal production patterns between 1989 and 1996. Spatial differences in ecosystem production were expected to follow north-south climatic and soil gradients, while interannual differences in production were expected to vary with variations in seasonal precipitation and temperature. It was hypothesized that the increased vegetation growth in high latitudes between 1981 and 1991 previously reported would continue through the period of investigation for the study watershed. Zonal differences in vegetation production were confirmed but interannual variations did not covary with seasonal precipitation or temperature totals. A sharp reduction in the SINDVI in 1992 followed by a consistent increase up to 1996 led to a further hypothesis that the interannual variations in SINDVI were associated with variations in stratospheric optical depth. Using published stratospheric optical depth values derived from the SAGE and SAGE-II satellites, it is demonstrated that variations in these depths are likely the primary cause of SINDVI interannual variability.

Switchgrass ecotypes alter microbial contribution to deep-soil C

USDA-ARS?s Scientific Manuscript database

Switchgrass (Panicum virgatum L.) is a C4, perennial grass that is being developed as a bioenergy crop for the United States. While aboveground biomass production is well documented for switchgrass ecotypes (lowland, upland), little is known about the impact of plant belowground productivity on mic...

The Dynamics of Sediment Oxygenation in Marsh Rhizospheres

NASA Astrophysics Data System (ADS)

Koop-Jakobsen, K.

2014-12-01

Many marsh grasses are capable of internal oxygen transport from aboveground sources to belowground roots and rhizomes, where oxygen may leak across the rhizodermis and oxygenate the surrounding sediment. In the field, the extent of sediment oxygenation in marshes was assessed in the rhizosphere of the marsh grass; Spartina anglica, inserting 70 optical fiber oxygen sensors into the rhizosphere. Two locations with S. anglica growing in different sediment types were investigated. No oxygen was detected in the rhizospheres indicating that belowground sediment oxygenation in S. anglica has a limited effect on the bulk anoxic sediment and is restricted to sediment in the immediate vicinity of the roots. In the laboratory, the presence of 1.5mm wide and 16mm long oxic root zones was demonstrated around root tips of S. anglica growing in permeable sandy sediment using planar optodes recording 2D-images of the oxygen distribution. Oxic root zones in S. anglica growing in tidal flat deposits were significantly smaller. The size of oxic roots zones was highly dynamic and affected by tidal inundations as well as light availability. Atmospheric air was the primary oxygen source for belowground sediment oxygenation, whereas photosynthetic oxygen production only played a minor role for the size of the oxic root zones during air-exposure of the aboveground biomass. During tidal inundations (1.5 h) completely submerging the aboveground biomass cutting off access to atmospheric oxygen, the size of oxic root zones were reduced significantly in the light and oxic root zones were completely eliminated in darkness. Sediment oxygenation in the rhizospheres of marsh grasses is of significant importance for marshes ability to retain inorganic nitrogen before it reaches the coastal waters. The presence of oxic roots zones promotes coupled nitrification-denitrification at depth in the sediment, which can account for more than 80% of the total denitrification in marshes.

Does nitrogen and sulfur deposition affect forest productivity?

Treesearch

Brittany A. Johnson; Kathryn B. Piatek; Mary Beth Adams; John R. Brooks

2010-01-01

We studied the effects of atmospheric nitrogen and sulfur deposition on forest productivity in a 10-year-old, aggrading forest stand at the Fernow Experimental Forest in Tucker County, WV. Forest productivity was expressed as total aboveground wood biomass, which included stem and branch weight of standing live trees. Ten years after stand regeneration and treatment...

Weed management, training, and irrigation practices for organic production of trailing blackberry: III. Accumulation and removal of aboveground biomass, carbon, and nutrients

USDA-ARS?s Scientific Manuscript database

The effects of various production practices on biomass, C, and nutrient content, accumulation, and loss were assessed over 2 years in a mature organic trailing blackberry (Rubus L. subgenus Rubus, Watson) production system. Treatments included two irrigation options (no irrigation after harvest and ...

Root-soil relationships and terroir

NASA Astrophysics Data System (ADS)

Tomasi, Diego

2015-04-01

Soil features, along with climate, are among the most important determinants of a succesful grape production in a certain area. Most of the studies, so far, investigated the above-ground vine response to differente edaphic and climate condition, but it is clearly not sufficient to explain the vine whole behaviour. In fact, roots represent an important part of the terroir system (soil-plant-atmosphere-man), and their study can provide better comprehension of vine responses to different environments. The root density and distribution, the ability of deep-rooting and regenerating new roots are good indicators of root well-being, and represents the basis for an efficient physiological activity of the root system. Root deepening and distribution are strongly dependent and sensitive on soil type and soil properties, while root density is affected mostly by canopy size, rootstock and water availability. According to root well-being, soil management strategies should alleviate soil impediments, improving aeration and microbial activity. Moreover, agronomic practices can impact root system performance and influence the above-ground growth. It is well known, for example, that the root system size is largely diminished by high planting densities. Close vine spacings stimulate a more effective utilization of the available soil, water and nutrients, but if the competition for available soil becomes too high, it can repress vine growth, and compromise vineyard longevity, productivity and reaction to growing season weather. Development of resilient rootstocks, more efficient in terms of water and nutrient uptake and capable of dealing with climate and soil extremes (drought, high salinity) are primary goals fore future research. The use of these rootstocks will benefit a more sustainable use of the soil resources and the preservation and valorisation of the terroir.

Evaluating lidar point densities for effective estimation of aboveground biomass

USGS Publications Warehouse

Wu, Zhuoting; Dye, Dennis G.; Stoker, Jason M.; Vogel, John M.; Velasco, Miguel G.; Middleton, Barry R.

2016-01-01

The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) was recently established to provide airborne lidar data coverage on a national scale. As part of a broader research effort of the USGS to develop an effective remote sensing-based methodology for the creation of an operational biomass Essential Climate Variable (Biomass ECV) data product, we evaluated the performance of airborne lidar data at various pulse densities against Landsat 8 satellite imagery in estimating above ground biomass for forests and woodlands in a study area in east-central Arizona, U.S. High point density airborne lidar data, were randomly sampled to produce five lidar datasets with reduced densities ranging from 0.5 to 8 point(s)/m2, corresponding to the point density range of 3DEP to provide national lidar coverage over time. Lidar-derived aboveground biomass estimate errors showed an overall decreasing trend as lidar point density increased from 0.5 to 8 points/m2. Landsat 8-based aboveground biomass estimates produced errors larger than the lowest lidar point density of 0.5 point/m2, and therefore Landsat 8 observations alone were ineffective relative to airborne lidar for generating a Biomass ECV product, at least for the forest and woodland vegetation types of the Southwestern U.S. While a national Biomass ECV product with optimal accuracy could potentially be achieved with 3DEP data at 8 points/m2, our results indicate that even lower density lidar data could be sufficient to provide a national Biomass ECV product with accuracies significantly higher than that from Landsat observations alone.

Plant uptake of explosives from contaminated soil at the Joliet Army Ammunition Plant

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

Zellmer, S.D.; Schneider, J.F.; Tomczyk, N.A.

1995-04-01

Explosives and their degradation products may enter the animal and human food chains through plants grown on soils contaminated with explosives. Soil and plant samples were collected from the Group 61 area at the Joliet Army Ammunition Plant and analyzed to determine the extent to which 2,4,6-trinitrotoluene (TNT) and its degradation products are taken up by existing vegetation and crops growing on contaminated soils. Neither TNT nor its degradation products was detected in any of the aboveground plant organs of existing vegetation. Oat (Avena sativa L.) and perennial ryegrass (Lolium perenne L.) were planted on TNT-contaminated soils amended with threemore » levels of chopped grass hay. Extractable TNT concentrations in hay-amended soils were monitored for almost 1 year. Crop establishment and growth improved with increased levels of hay amendment, but TNT uptake was not affected or detected in any aboveground crop organs. Evidence was found to indicate that soil manipulation and hay addition may reduce extractable TNT concentration in soils, but the wide variations in TNT concentrations in these soils prevented development of conclusive evidence regarding reduction of extractable TNT concentrations. Results from this study suggest that vegetation grown on TNT-contaminated soils is not a major health concern because TNT and its degradation products were not detected in aboveground plant organs. However, low concentrations of TNT, 4-amino-2,6-dinitrotoluene, and 2-amino-4,6-dinitrotoluene were detected in or on some existing vegetation and crop roots. 21 refs., 10 figs., 26 tabs.« less

Successional change in species composition alters climate sensitivity of grassland productivity.

PubMed

Shi, Zheng; Lin, Yang; Wilcox, Kevin R; Souza, Lara; Jiang, Lifen; Jiang, Jiang; Jung, Chang Gyo; Xu, Xia; Yuan, Mengting; Guo, Xue; Wu, Liyou; Zhou, Jizhong; Luo, Yiqi

2018-05-31

Succession theory predicts altered sensitivity of ecosystem functions to disturbance (i.e., climate change) due to the temporal shift in plant community composition. However, empirical evidence in global change experiments is lacking to support this prediction. Here, we present findings from an 8-year long-term global change experiment with warming and altered precipitation manipulation (double and halved amount). First, we observed a temporal shift in species composition over 8 years, resulting in a transition from an annual C 3 -dominant plant community to a perennial C 4 -dominant plant community. This successional transition was independent of any experimental treatments. During the successional transition, the response of aboveground net primary productivity (ANPP) to precipitation addition magnified from neutral to +45.3%, while the response to halved precipitation attenuated substantially from -17.6% to neutral. However, warming did not affect ANPP in either state. The findings further reveal that the time-dependent climate sensitivity may be regulated by successional change in species composition, highlighting the importance of vegetation dynamics in regulating the response of ecosystem productivity to precipitation change. © 2018 John Wiley & Sons Ltd.

Dormant season fire inhibits sixweeks fescue and enhances forage production in shortgrass steppe

USDA-ARS?s Scientific Manuscript database

In the Great Plains of central North America, fire effects on vegetation vary considerably along an east–to–west gradient of declining mean annual precipitation and aboveground plant productivity. In the western, semiarid region of the Great Plains, recent studies demonstrate that prescribed fire ca...

Meta-analysis as a tool to study crop productivity response to poultry litter application

USDA-ARS?s Scientific Manuscript database

Extensive research on the use of poultry litter (PL) under different agricultural practices in the USA has shown both negative and positive effects on crop productivity (either yield or aboveground biomass). However, these experimental results are substantially dependent on the experimental set-up, ...

Change in soil organic carbon after five years of continuous winter wheat or switchgrass

USDA-ARS?s Scientific Manuscript database

Perennial grasses have been promoted to supply cellulose for ethanol production but possible consequences on soil organic carbon (SOC) should be assessed before adoption in a given region. Specific objectives were to (i) compare above-ground biomass C production and depth distribution of SOC conten...

Root mass, net primary production and turnover in aspen, jack pine and black spruce forests in Saskatchewan and Manitoba, Canada.

PubMed

Steele, Sarah J.; Gower, Stith T.; Vogel, Jason G.; Norman, John M.

1997-01-01

Root biomass, net primary production and turnover were studied in aspen, jack pine and black spruce forests in two contrasting climates. The climate of the Southern Study Area (SSA) near Prince Albert, Saskatchewan is warmer and drier in the summer and milder in the winter than the Northern Study Area (NSA) near Thompson, Manitoba, Canada. Ingrowth soil cores and minirhizotrons were used to quantify fine root net primary production (NPPFR). Average daily fine root growth (m m(-2) day(-1)) was positively correlated with soil temperature at 10-cm depth (r(2) = 0.83-0.93) for all three species, with black spruce showing the strongest temperature effect. At both study areas, fine root biomass (measured from soil cores) and fine root length (measured from minirhizotrons) were less for jack pine than for the other two species. Except for the aspen stands, estimates of NPPFR from minirhizotrons were significantly greater than estimates from ingrowth cores. The core method underestimated NPPFR because it does not account for simultaneous fine root growth and mortality. Minirhizotron NPPFR estimates ranged from 59 g m(-2) year(-1) for aspen stands at SSA to 235 g m(-2) year(-1) for black spruce at NSA. The ratio of NPPFR to total detritus production (aboveground litterfall + NPPFR) was greater for evergreen forests than for deciduous forests, suggesting that carbon allocation patterns differ between boreal evergreen and deciduous forests. In all stands, NPPFR consistently exceeded annual fine root turnover and the differences were larger for stands in the NSA than for stands in the SSA, whereas the difference between study areas was only significant for black spruce. The imbalance between NPPFR and fine root turnover is sufficient to explain the net accumulation of carbon in boreal forest soils.

Aboveground Allometric Models for Freeze-Affected Black Mangroves (Avicennia germinans): Equations for a Climate Sensitive Mangrove-Marsh Ecotone

PubMed Central

Osland, Michael J.; Day, Richard H.; Larriviere, Jack C.; From, Andrew S.

2014-01-01

Across the globe, species distributions are changing in response to climate change and land use change. In parts of the southeastern United States, climate change is expected to result in the poleward range expansion of black mangroves (Avicennia germinans) at the expense of some salt marsh vegetation. The morphology of A. germinans at its northern range limit is more shrub-like than in tropical climes in part due to the aboveground structural damage and vigorous multi-stem regrowth triggered by extreme winter temperatures. In this study, we developed aboveground allometric equations for freeze-affected black mangroves which can be used to quantify: (1) total aboveground biomass; (2) leaf biomass; (3) stem plus branch biomass; and (4) leaf area. Plant volume (i.e., a combination of crown area and plant height) was selected as the optimal predictor of the four response variables. We expect that our simple measurements and equations can be adapted for use in other mangrove ecosystems located in abiotic settings that result in mangrove individuals with dwarf or shrub-like morphologies including oligotrophic and arid environments. Many important ecological functions and services are affected by changes in coastal wetland plant community structure and productivity including carbon storage, nutrient cycling, coastal protection, recreation, fish and avian habitat, and ecosystem response to sea level rise and extreme climatic events. Coastal scientists in the southeastern United States can use the identified allometric equations, in combination with easily obtained and non-destructive plant volume measurements, to better quantify and monitor ecological change within the dynamic, climate sensitive, and highly-productive mangrove-marsh ecotone. PMID:24971938

Potential aboveground biomass in drought-prone forest used for rangeland pastoralism.

PubMed

Fensham, R J; Fairfax, R J; Dwyer, J M

2012-04-01

The restoration of cleared dry forest represents an important opportunity to sequester atmospheric carbon. In order to account for this potential, the influences of climate, soils, and disturbance need to be deciphered. A data set spanning a region defined the aboveground biomass of mulga (Acacia aneura) dry forest and was analyzed in relation to climate and soil variables using a Bayesian model averaging procedure. Mean annual rainfall had an overwhelmingly strong positive effect, with mean maximum temperature (negative) and soil depth (positive) also important. The data were collected after a recent drought, and the amount of recent tree mortality was weakly positively related to a measure of three-year rainfall deficit, and maximum temperature (positive), soil depth (negative), and coarse sand (negative). A grazing index represented by the distance of sites to watering points was not incorporated by the models. Stark management contrasts, including grazing exclosures, can represent a substantial part of the variance in the model predicting biomass, but the impact of management was unpredictable and was insignificant in the regional data set. There was no evidence of density-dependent effects on tree mortality. Climate change scenarios represented by the coincidence of historical extreme rainfall deficit with extreme temperature suggest mortality of 30.1% of aboveground biomass, compared to 21.6% after the recent (2003-2007) drought. Projections for recovery of forest using a mapping base of cleared areas revealed that the greatest opportunities for restoration of aboveground biomass are in the higher-rainfall areas, where biomass accumulation will be greatest and droughts are less intense. These areas are probably the most productive for rangeland pastoralism, and the trade-off between pastoral production and carbon sequestration will be determined by market forces and carbon-trading rules.

Regional assessment of boreal forest productivity using an ecological process model and remote sensing parameter maps.

PubMed

Kimball, J. S.; Keyser, A. R.; Running, S. W.; Saatchi, S. S.

2000-06-01

An ecological process model (BIOME-BGC) was used to assess boreal forest regional net primary production (NPP) and response to short-term, year-to-year weather fluctuations based on spatially explicit, land cover and biomass maps derived by radar remote sensing, as well as soil, terrain and daily weather information. Simulations were conducted at a 30-m spatial resolution, over a 1205 km(2) portion of the BOREAS Southern Study Area of central Saskatchewan, Canada, over a 3-year period (1994-1996). Simulations of NPP for the study region were spatially and temporally complex, averaging 2.2 (+/- 0.6), 1.8 (+/- 0.5) and 1.7 (+/- 0.5) Mg C ha(-1) year(-1) for 1994, 1995 and 1996, respectively. Spatial variability of NPP was strongly controlled by the amount of aboveground biomass, particularly photosynthetic leaf area, whereas biophysical differences between broadleaf deciduous and evergreen coniferous vegetation were of secondary importance. Simulations of NPP were strongly sensitive to year-to-year variations in seasonal weather patterns, which influenced the timing of spring thaw and deciduous bud-burst. Reductions in annual NPP of approximately 17 and 22% for 1995 and 1996, respectively, were attributed to 3- and 5-week delays in spring thaw relative to 1994. Boreal forest stands with greater proportions of deciduous vegetation were more sensitive to the timing of spring thaw than evergreen coniferous stands. Similar relationships were found by comparing simulated snow depth records with 10-year records of aboveground NPP measurements obtained from biomass harvest plots within the BOREAS region. These results highlight the importance of sub-grid scale land cover complexity in controlling boreal forest regional productivity, the dynamic response of the biome to short-term interannual climate variations, and the potential implications of climate change and other large-scale disturbances.

Experimental fire increases soil carbon dioxide efflux in a grassland long-term multifactor global change experiment.

PubMed

Strong, Aaron L; Johnson, Tera P; Chiariello, Nona R; Field, Christopher B

2017-05-01

Numerous studies have demonstrated that soil respiration rates increase under experimental warming, although the long-term, multiyear dynamics of this feedback are not well constrained. Less is known about the effects of single, punctuated events in combination with other longer-duration anthropogenic influences on the dynamics of soil carbon (C) loss. In 2012 and 2013, we assessed the effects of decadal-scale anthropogenic global change - warming, increased nitrogen (N) deposition, elevated carbon dioxide (CO 2 ), and increased precipitation - on soil respiration rates in an annual-dominated Mediterranean grassland. We also investigated how controlled fire and an artificial wet-up event, in combination with exposure to the longer-duration anthropogenic global change factors, influenced the dynamics of C cycling in this system. Decade-duration surface soil warming (1-2 °C) had no effect on soil respiration rates, while +N addition and elevated CO 2 concentrations increased growing-season soil CO 2 efflux rates by increasing annual aboveground net primary production (NPP) and belowground fine root production, respectively. Low-intensity experimental fire significantly elevated soil CO 2 efflux rates in the next growing season. Based on mixed-effects modeling and structural equation modeling, low-intensity fire increased growing-season soil respiration rates through a combination of three mechanisms: large increases in soil temperature (3-5 °C), significant increases in fine root production, and elevated aboveground NPP. Our study shows that in ecosystems where soil respiration has acclimated to moderate warming, further increases in soil temperature can stimulate greater soil CO 2 efflux. We also demonstrate that punctuated short-duration events such as fire can influence soil C dynamics with implications for both the parameterization of earth system models (ESMs) and the implementation of climate change mitigation policies that involve land-sector C accounting. © 2016 John Wiley & Sons Ltd.

Modeling Aboveground Biomass in Hulunber Grassland Ecosystem by Using Unmanned Aerial Vehicle Discrete Lidar

PubMed Central

Wang, Dongliang; Xin, Xiaoping; Shao, Quanqin; Brolly, Matthew; Zhu, Zhiliang; Chen, Jin

2017-01-01

Accurate canopy structure datasets, including canopy height and fractional cover, are required to monitor aboveground biomass as well as to provide validation data for satellite remote sensing products. In this study, the ability of an unmanned aerial vehicle (UAV) discrete light detection and ranging (lidar) was investigated for modeling both the canopy height and fractional cover in Hulunber grassland ecosystem. The extracted mean canopy height, maximum canopy height, and fractional cover were used to estimate the aboveground biomass. The influences of flight height on lidar estimates were also analyzed. The main findings are: (1) the lidar-derived mean canopy height is the most reasonable predictor of aboveground biomass (R2 = 0.340, root-mean-square error (RMSE) = 81.89 g·m−2, and relative error of 14.1%). The improvement of multiple regressions to the R2 and RMSE values is unobvious when adding fractional cover in the regression since the correlation between mean canopy height and fractional cover is high; (2) Flight height has a pronounced effect on the derived fractional cover and details of the lidar data, but the effect is insignificant on the derived canopy height when the flight height is within the range (<100 m). These findings are helpful for modeling stable regressions to estimate grassland biomass using lidar returns. PMID:28106819

Modeling Aboveground Biomass in Hulunber Grassland Ecosystem by Using Unmanned Aerial Vehicle Discrete Lidar.

PubMed

Wang, Dongliang; Xin, Xiaoping; Shao, Quanqin; Brolly, Matthew; Zhu, Zhiliang; Chen, Jin

2017-01-19

Accurate canopy structure datasets, including canopy height and fractional cover, are required to monitor aboveground biomass as well as to provide validation data for satellite remote sensing products. In this study, the ability of an unmanned aerial vehicle (UAV) discrete light detection and ranging (lidar) was investigated for modeling both the canopy height and fractional cover in Hulunber grassland ecosystem. The extracted mean canopy height, maximum canopy height, and fractional cover were used to estimate the aboveground biomass. The influences of flight height on lidar estimates were also analyzed. The main findings are: (1) the lidar-derived mean canopy height is the most reasonable predictor of aboveground biomass ( R ² = 0.340, root-mean-square error (RMSE) = 81.89 g·m -2 , and relative error of 14.1%). The improvement of multiple regressions to the R ² and RMSE values is unobvious when adding fractional cover in the regression since the correlation between mean canopy height and fractional cover is high; (2) Flight height has a pronounced effect on the derived fractional cover and details of the lidar data, but the effect is insignificant on the derived canopy height when the flight height is within the range (<100 m). These findings are helpful for modeling stable regressions to estimate grassland biomass using lidar returns.

Stimulation of the Salicylic Acid Pathway Aboveground Recruits Entomopathogenic Nematodes Belowground

PubMed Central

Filgueiras, Camila Cramer; Willett, Denis S.; Junior, Alcides Moino; Pareja, Martin; Borai, Fahiem El; Dickson, Donald W.; Stelinski, Lukasz L.; Duncan, Larry W.

2016-01-01

Plant defense pathways play a critical role in mediating tritrophic interactions between plants, herbivores, and natural enemies. While the impact of plant defense pathway stimulation on natural enemies has been extensively explored aboveground, belowground ramifications of plant defense pathway stimulation are equally important in regulating subterranean pests and still require more attention. Here we investigate the effect of aboveground stimulation of the salicylic acid pathway through foliar application of the elicitor methyl salicylate on belowground recruitment of the entomopathogenic nematode, Steinernema diaprepesi. Also, we implicate a specific root-derived volatile that attracts S. diaprepesi belowground following aboveground plant stimulation by an elicitor. In four-choice olfactometer assays, citrus plants treated with foliar applications of methyl salicylate recruited S. diaprepesi in the absence of weevil feeding as compared with negative controls. Additionally, analysis of root volatile profiles of citrus plants receiving foliar application of methyl salicylate revealed production of d-limonene, which was absent in negative controls. The entomopathogenic nematode S. diaprepesi was recruited to d-limonene in two-choice olfactometer trials. These results reinforce the critical role of plant defense pathways in mediating tritrophic interactions, suggest a broad role for plant defense pathway signaling belowground, and hint at sophisticated plant responses to pest complexes. PMID:27136916

[Energy accumulation and allocation of main plant populations in Aneurolepidium chinense grassland in Songnen Plain].

PubMed

Qu, Guohui; Wen, Mingzhang; Guo, Jixun

2003-05-01

The calorific value of plants is dependent on their biological characteristics and energy-containing materials. The allocation of calorific value in different organs of Aneurolepidium chinese, Calamagrostic epigejos, Puccinellia tenuiflora and Chloris virgata was inflorescence > leaf > stem > dead standing. The seasonal dynamics of standing crop energy of aboveground part of four plant populations showed single-peak curve, and the energy production was Aneurolepidium chinense > Calamagrostic epigejos > Chloris virgata > Puccinellia tenuiflora. Energy increasing rate showed double-peak curve, with the first peak at heading stage and the second peak at maturing stage of seeds. Energy increasing rate was negative at the final stage of growth. The horizontal distribution of energy of aboveground part was that the allocation ratio of different organs at different growth stages was different. There existed a similar trend for vertical distribution of energy among four plant populations, i.e., was the vertical distribution of energy of aboveground part showed a tower shape, with the maximum value in 10-30 cm height. The vertical distribution of energy of underground part showed an inverted tower shape from soil surface to deeper layer, with the maximum value in 0-10 cm depth. The standing crop energy of underground part was about 3-4 times than that of aboveground part.

Shifts in Aboveground Biomass Allocation Patterns of Dominant Shrub Species across a Strong Environmental Gradient

PubMed Central

Kumordzi, Bright B.; Gundale, Michael J.; Nilsson, Marie-Charlotte; Wardle, David A.

2016-01-01

Most plant biomass allocation studies have focused on allocation to shoots versus roots, and little is known about drivers of allocation for aboveground plant organs. We explored the drivers of within-and between-species variation of aboveground biomass allocation across a strong environmental resource gradient, i.e., a long-term chronosequence of 30 forested islands in northern Sweden across which soil fertility and plant productivity declines while light availability increases. For each of the three coexisting dominant understory dwarf shrub species on each island, we estimated the fraction of the total aboveground biomass produced year of sampling that was allocated to sexual reproduction (i.e., fruits), leaves and stems for each of two growing seasons, to determine how biomass allocation responded to the chronosequence at both the within-species and whole community levels. Against expectations, within-species allocation to fruits was least on less fertile islands, and allocation to leaves at the whole community level was greatest on intermediate islands. Consistent with expectations, different coexisting species showed contrasting allocation patterns, with the species that was best adapted for more fertile conditions allocating the most to vegetative organs, and with its allocation pattern showing the strongest response to the gradient. Our study suggests that co-existing dominant plant species can display highly contrasting biomass allocations to different aboveground organs within and across species in response to limiting environmental resources within the same plant community. Such knowledge is important for understanding how community assembly, trait spectra, and ecological processes driven by the plant community vary across environmental gradients and among contrasting ecosystems. PMID:27270445

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

DOE PAGES

Wagner, Fabien H.; Hérault, Bruno; Bonal, Damien; ...

2016-04-28

Here, the seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positivelymore » to precipitation when rainfall is < 2000 mm yr -1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr -1.« less

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

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

Wagner, Fabien H.; Hérault, Bruno; Bonal, Damien

Here, the seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positivelymore » to precipitation when rainfall is < 2000 mm yr -1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr -1.« less

Improving Lidar-based Aboveground Biomass Estimation with Site Productivity for Central Hardwood Forests, USA

NASA Astrophysics Data System (ADS)

Shao, G.; Gallion, J.; Fei, S.

2016-12-01

Sound forest aboveground biomass estimation is required to monitor diverse forest ecosystems and their impacts on the changing climate. Lidar-based regression models provided promised biomass estimations in most forest ecosystems. However, considerable uncertainties of biomass estimations have been reported in the temperate hardwood and hardwood-dominated mixed forests. Varied site productivities in temperate hardwood forests largely diversified height and diameter growth rates, which significantly reduced the correlation between tree height and diameter at breast height (DBH) in mature and complex forests. It is, therefore, difficult to utilize height-based lidar metrics to predict DBH-based field-measured biomass through a simple regression model regardless the variation of site productivity. In this study, we established a multi-dimension nonlinear regression model incorporating lidar metrics and site productivity classes derived from soil features. In the regression model, lidar metrics provided horizontal and vertical structural information and productivity classes differentiated good and poor forest sites. The selection and combination of lidar metrics were discussed. Multiple regression models were employed and compared. Uncertainty analysis was applied to the best fit model. The effects of site productivity on the lidar-based biomass model were addressed.

Potential for post-closure radionuclide redistribution due to biotic intrusion: aboveground biomass, litter production rates, and the distribution of root mass with depth at material disposal area G, Los Alamos National Laboratory

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

French, Sean B; Christensen, Candace; Jennings, Terry L

2008-01-01

Low-level radioactive waste (LLW) generated at the Los Alamos National Laboratories (LANL) is disposed of at LANL's Technical Area (T A) 54, Material Disposal Area (MDA) G. The ability of MDA G to safely contain radioactive waste during current and post-closure operations is evaluated as part of the facility's ongoing performance assessment (PA) and composite analysis (CA). Due to the potential for uptake and incorporation of radio nuclides into aboveground plant material, the PA and CA project that plant roots penetrating into buried waste may lead to releases of radionuclides into the accessible environment. The potential amount ofcontamination deposited onmore » the ground surface due to plant intrusion into buried waste is a function of the quantity of litter generated by plants, as well as radionuclide concentrations within the litter. Radionuclide concentrations in plant litter is dependent on the distribution of root mass with depth and the efficiency with which radionuclides are extracted from contaminated soils by the plant's roots. In order to reduce uncertainties associated with the PA and CA for MDA G, surveys are being conducted to assess aboveground biomass, plant litter production rates, and root mass with depth for the four prominent vegetation types (grasses, forbs, shrubs and trees). The collection of aboveground biomass for grasses and forbs began in 2007. Additional sampling was conducted in October 2008 to measure root mass with depth and to collect additional aboveground biomass data for the types of grasses, forbs, shrubs, and trees that may become established at MDA G after the facility undergoes final closure, Biomass data will be used to estimate the future potential mass of contaminated plant litter fall, which could act as a latent conduit for radionuclide transport from the closed disposal area. Data collected are expected to reduce uncertainties associated with the PA and CA for MDA G and ultimately aid in the assessment and subsequent prevention of radionuclide transport within the environment from the closed disposal area and potential exposure to site workers and the public.« less

Relationships among net primary productivity, nutrients and climate in tropical rain forest: A pan-tropical analysis

USGS Publications Warehouse

Cleveland, Cory C.; Townsend, Alan R.; Taylor, Philip; Alvarez-Clare, Silvia; Bustamante, Mercedes M.C.; Chuyong, George; Dobrowski, Solomon Z.; Grierson, Pauline; Harms, Kyle E.; Houlton, Benjamin Z.; Marklein, Alison; Parton, William; Porder, Stephen; Reed, Sasha C.; Sierra, Carlos A.; Silver, Whendee L.; Tanner, Edmund V.J.; Wieder, William R.

2011-01-01

Tropical rain forests play a dominant role in global biosphere-atmosphere CO2 exchange. Although climate and nutrient availability regulate net primary production (NPP) and decomposition in all terrestrial ecosystems, the nature and extent of such controls in tropical forests remain poorly resolved. We conducted a meta-analysis of carbon-nutrient-climate relationships in 113 sites across the tropical forest biome. Our analyses showed that mean annual temperature was the strongest predictor of aboveground NPP (ANPP) across all tropical forests, but this relationship was driven by distinct temperature differences between upland and lowland forests. Within lowland forests (< 1000 m), a regression tree analysis revealed that foliar and soil-based measurements of phosphorus (P) were the only variables that explained a significant proportion of the variation in ANPP, although the relationships were weak. However, foliar P, foliar nitrogen (N), litter decomposition rate (k), soil N and soil respiration were all directly related with total surface (0–10 cm) soil P concentrations. Our analysis provides some evidence that P availability regulates NPP and other ecosystem processes in lowland tropical forests, but more importantly, underscores the need for a series of large-scale nutrient manipulations – especially in lowland forests – to elucidate the most important nutrient interactions and controls.

Evaluation of sampling strategies to estimate crown biomass

Treesearch

Krishna P Poudel; Hailemariam Temesgen; Andrew N Gray

2015-01-01

Depending on tree and site characteristics crown biomass accounts for a significant portion of the total aboveground biomass in the tree. Crown biomass estimation is useful for different purposes including evaluating the economic feasibility of crown utilization for energy production or forest products, fuel load assessments and fire management strategies, and wildfire...

Timber volume and aboveground live tree biomass estimations for landscape analyses in the Pacific Northwest

Treesearch

Xiaoping Zhou; Miles A. Hemstrom

2010-01-01

Timber availability, aboveground tree biomass, and changes in aboveground carbon pools are important consequences of landscape management. There are several models available for calculating tree volume and aboveground tree biomass pools. This paper documents species-specific regional equations for tree volume and aboveground live tree biomass estimation that might be...

The contribution of fine roots to peatland stability under changing environmental conditions

NASA Astrophysics Data System (ADS)

Malhotra, A.; Brice, D. J.; Childs, J.; Phillips, J.; Hanson, P. J.; Iversen, C. M.

2017-12-01

Fine-root production and traits are closely linked with ecosystem nutrient and water fluxes, and may regulate these fluxes in response to environmental change. Plant strategies can shift to favoring below- over aboveground biomass allocation when nutrients or moisture are limited. Fine-roots traits such as root tissue density (RTD) or specific root length (SRL) can also adapt to the environment, for example, by maximizing the area of soil exploited by decreasing RTD and increasing SRL during dry conditions. Fine-root trait plasticity could contribute to the stability of peatland carbon function in response to environmental change. However, the extent and mechanisms of peatland fine-root plasticity are unknown. We investigated fine-root growth and traits and their link to environmental factors and aboveground dynamics at SPRUCE (Spruce and Peatland Responses Under Changing Environments), a warming and elevated CO2 (eCO2) experiment in an ombrotrophic peatland. In the first growing season of whole ecosystem warming, fine-root production increased with warming and drying. Above- versus belowground allocation strategies varied by plant functional type (PFT). In shrubs, contrary to our expectation, aboveground- to fine-root production allocation ratio increased with dryer conditions, perhaps as a response to a concurrent increase in nutrients. Trait response hypotheses were largely supported, with RTD decreasing and SRL increasing with warming; however, response varied among PFTs. Once eCO2 was turned on in the second growing season, preliminary results suggest interactive effects of warming and eCO2 on total fine-root production: production decreased or increased with warming in ambient or elevated CO2 plots, respectively. Both trait and production responses to warming and eCO2 varied by microtopography and depth. Our results highlight plasticity of fine-root traits and biomass allocation strategies; the extent and mechanism of which varies by PFT. We will summarize our results using a trait-based approach as a first step toward modeling fine-root contributions to peatland carbon stability in response to environmental change.

Species-specific defence responses facilitate conspecifics and inhibit heterospecifics in above–belowground herbivore interactions

PubMed Central

Huang, Wei; Siemann, Evan; Xiao, Li; Yang, Xuefang; Ding, Jianqing

2014-01-01

Conspecific and heterospecific aboveground and belowground herbivores often occur together in nature and their interactions may determine community structure. Here we show how aboveground adults and belowground larvae of the tallow tree specialist beetle Bikasha collaris and multiple heterospecific aboveground species interact to determine herbivore performance. Conspecific aboveground adults facilitate belowground larvae, but other aboveground damage inhibits larvae or has no effect. Belowground larvae increase conspecific adult feeding, but decrease heterospecific aboveground insect feeding and abundance. Chemical analyses and experiments with plant populations varying in phenolics show that all these positive and negative effects on insects are closely related to root and shoot tannin concentrations. Our results show that specific plant herbivore responses allow herbivore facilitation and inhibition to co-occur, likely shaping diverse aboveground and belowground communities. Considering species-specific responses of plants is critical for teasing apart inter- and intraspecific interactions in aboveground and belowground compartments. PMID:25241651

Response of Plant Height, Species Richness and Aboveground Biomass to Flooding Gradient along Vegetation Zones in Floodplain Wetlands, Northeast China.

PubMed

Lou, Yanjing; Pan, Yanwen; Gao, Chuanyu; Jiang, Ming; Lu, Xianguo; Xu, Y Jun

2016-01-01

Flooding regime changes resulting from natural and human activity have been projected to affect wetland plant community structures and functions. It is therefore important to conduct investigations across a range of flooding gradients to assess the impact of flooding depth on wetland vegetation. We conducted this study to identify the pattern of plant height, species richness and aboveground biomass variation along the flooding gradient in floodplain wetlands located in Northeast China. We found that the response of dominant species height to the flooding gradient depends on specific species, i.e., a quadratic response for Carex lasiocarpa, a negative correlation for Calamagrostis angustifolia, and no response for Carex appendiculata. Species richness showed an intermediate effect along the vegetation zone from marsh to wet meadow while aboveground biomass increased. When the communities were analysed separately, only the water table depth had significant impact on species richness for two Carex communities and no variable for C. angustifolia community, while height of dominant species influenced aboveground biomass. When the three above-mentioned communities were grouped together, variations in species richness were mainly determined by community type, water table depth and community mean height, while variations in aboveground biomass were driven by community type and the height of dominant species. These findings indicate that if habitat drying of these herbaceous wetlands in this region continues, then two Carex marshes would be replaced gradually by C. angustifolia wet meadow in the near future. This will lead to a reduction in biodiversity and an increase in productivity and carbon budget. Meanwhile, functional traits must be considered, and should be a focus of attention in future studies on the species diversity and ecosystem function in this region.

Aboveground carbon in Quebec forests: stock quantification at the provincial scale and assessment of temperature, precipitation and edaphic properties effects on the potential stand-level stocking.

PubMed

Duchesne, Louis; Houle, Daniel; Ouimet, Rock; Lambert, Marie-Claude; Logan, Travis

2016-01-01

Biological carbon sequestration by forest ecosystems plays an important role in the net balance of greenhouse gases, acting as a carbon sink for anthropogenic CO2 emissions. Nevertheless, relatively little is known about the abiotic environmental factors (including climate) that control carbon storage in temperate and boreal forests and consequently, about their potential response to climate changes. From a set of more than 94,000 forest inventory plots and a large set of spatial data on forest attributes interpreted from aerial photographs, we constructed a fine-resolution map (∼375 m) of the current carbon stock in aboveground live biomass in the 435,000 km(2) of managed forests in Quebec, Canada. Our analysis resulted in an area-weighted average aboveground carbon stock for productive forestland of 37.6 Mg ha(-1), which is lower than commonly reported values for similar environment. Models capable of predicting the influence of mean annual temperature, annual precipitation, and soil physical environment on maximum stand-level aboveground carbon stock (MSAC) were developed. These models were then used to project the future MSAC in response to climate change. Our results indicate that the MSAC was significantly related to both mean annual temperature and precipitation, or to the interaction of these variables, and suggest that Quebec's managed forests MSAC may increase by 20% by 2041-2070 in response to climate change. Along with changes in climate, the natural disturbance regime and forest management practices will nevertheless largely drive future carbon stock at the landscape scale. Overall, our results allow accurate accounting of carbon stock in aboveground live tree biomass of Quebec's forests, and provide a better understanding of possible feedbacks between climate change and carbon storage in temperate and boreal forests.

Response of Plant Height, Species Richness and Aboveground Biomass to Flooding Gradient along Vegetation Zones in Floodplain Wetlands, Northeast China

PubMed Central

Lou, Yanjing; Pan, Yanwen; Gao, Chuanyu; Jiang, Ming; Lu, Xianguo; Xu, Y. Jun

2016-01-01

Flooding regime changes resulting from natural and human activity have been projected to affect wetland plant community structures and functions. It is therefore important to conduct investigations across a range of flooding gradients to assess the impact of flooding depth on wetland vegetation. We conducted this study to identify the pattern of plant height, species richness and aboveground biomass variation along the flooding gradient in floodplain wetlands located in Northeast China. We found that the response of dominant species height to the flooding gradient depends on specific species, i.e., a quadratic response for Carex lasiocarpa, a negative correlation for Calamagrostis angustifolia, and no response for Carex appendiculata. Species richness showed an intermediate effect along the vegetation zone from marsh to wet meadow while aboveground biomass increased. When the communities were analysed separately, only the water table depth had significant impact on species richness for two Carex communities and no variable for C. angustifolia community, while height of dominant species influenced aboveground biomass. When the three above-mentioned communities were grouped together, variations in species richness were mainly determined by community type, water table depth and community mean height, while variations in aboveground biomass were driven by community type and the height of dominant species. These findings indicate that if habitat drying of these herbaceous wetlands in this region continues, then two Carex marshes would be replaced gradually by C. angustifolia wet meadow in the near future. This will lead to a reduction in biodiversity and an increase in productivity and carbon budget. Meanwhile, functional traits must be considered, and should be a focus of attention in future studies on the species diversity and ecosystem function in this region. PMID:27097325

Effects of 10-year management regimes on the soil seed bank in saline-alkaline grassland.

PubMed

Ma, Hongyuan; Yang, Haoyu; Liang, Zhengwei; Ooi, Mark K J

2015-01-01

Management regimes for vegetation restoration of degraded grasslands can significantly affect the process of ecological succession. However, few studies have focused on variation in the soil seed bank during vegetation restoration under different management regimes, especially in saline-alkaline grassland habitats. Our aim was to provide insights into the ecological effects of grassland management regimes on soil seed bank composition and vegetation establishment in mown, fenced, transplanted and natural grassland sites, all dominated by the perennial rhizomatous grass Leymus chinensis. We studied species composition and diversity in both the soil seed bank and aboveground vegetation in differently managed grasslands in Northeast China. An NMDS (nonmetric multidimensional scaling) was used to evaluate the relationship between species composition, soil seed banks, aboveground vegetation and soil properties. Fenced and mown grassland sites had high density and species richness in both the soil seed bank and aboveground vegetation. The Transplanted treatment exhibited the highest vegetation growth and seed production of the target species L. chinensis. Seeds of L. chinensis in the soil occurred only in transplanted and natural grassland. Based on the NMDS analysis, the number of species in both the soil seed bank and aboveground vegetation were significantly related to soil Na+, Cl-, RSC (residual sodium carbonate), alkalinity, ESP (exchangeable sodium percentage) and AP (available phosphorus). Soil seed bank composition and diversity in the saline-alkaline grassland were significantly affected by the management regimes implemented, and were also significantly related to the aboveground vegetation and several soil properties. Based on vegetative growth, reproductive output and maintenance of soil seed bank, the transplanting was identified as the most effective method for relatively rapid restoration of the target species L. chinensis. This approach could be beneficial for the restoration of dominant species in a wide range of degraded grassland ecosystems.

Nitrogen Fertilization Effects on Productivity and Nitrogen Loss in Three Grass-Based Perennial Bioenergy Cropping Systems

DOE PAGES

Duran, Brianna E. L.; Duncan, David S.; Oates, Lawrence G.; ...

2016-03-18

Nitrogen (N) fertilization can greatly improve plant productivity but needs to be carefully managed to avoid harmful environmental impacts. Nutrient management guidelines aimed at reducing harmful forms of N loss such as nitrous oxide (N 2O) emissions and nitrate (NO 3 -) leaching have been tailored for many cropping systems. The developing bioenergy industry is likely to make use of novel cropping systems, such as polycultures of perennial species, for which we have limited nutrient management experience. We studied how a switchgrass (Panicum virgatum) monoculture, a 5-species native grass mixture and an 18- species restored prairie responded to annual fertilizermore » applications of 56 kg N ha -1 in a fieldscale agronomic trial in south-central Wisconsin over a 2-year period.We observed greater fertilizer-induced N 2O emissions and sub-rooting zone NO 3 - concentrations in the switchgrass monoculture than in either polyculture. Fertilization increased aboveground net primary productivity in the polycultures, but not in the switchgrass monoculture. Switchgrass was generally more productive, while the two polycultures did not differ from each other in productivity or N loss. In conclusion, our results highlight differences between polycultures and a switchgrass monoculture in responding to N fertilization.« less

Forest Restoration Carbon Analysis of Baseline Carbon Emissions and Removal in Tropical Rainforest at La Selva Central, Peru

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

Patrick Gonzalez; Benjamin Kroll; Carlos R. Vargas

Conversion of tropical forest to agricultural land and pasture has reduced forest extent and the provision of ecosystem services, including watershed protection, biodiversity conservation, and carbon sequestration. Forest conservation and reforestation can restore those ecosystem services. We have assessed forest species patterns, quantified deforestation and reforestation rates, and projected future baseline carbon emissions and removal in Amazon tropical rainforest at La Selva Central, Peru. The research area is a 4800 km{sup 2} buffer zone around the Parque Nacional Yanachaga-Chemillen, Bosque de Proteccion San Matias-San Carlos, and the Reserva Comunal Yanesha. A planned project for the period 2006-2035 would conserve 4000more » ha of forest in a proposed 7000 ha Area de Conservacion Municipale de Chontabamba and establish 5600 ha of natural regeneration and 1400 ha of native species plantations, laid out in fajas de enriquecimiento (contour plantings), to reforest 7000 ha of agricultural land. Forest inventories of seven sites covering 22.6 ha in primary forest and 17 sites covering 16.5 ha in secondary forest measured 17,073 trees of diameter {ge} 10 cm. The 24 sites host trees of 512 species, 267 genera, and 69 families. We could not identify the family of 7% of the trees or the scientific species of 21% of the trees. Species richness is 346 in primary forest and 257 in the secondary forest. In primary forest, 90% of aboveground biomass resides in old-growth species. Conversely, in secondary forest, 66% of aboveground biomass rests in successional species. The density of trees of diameter {ge} 10 cm is 366 trees ha{sup -1} in primary forest and 533 trees ha{sup -1} in secondary forest, although the average diameter is 24 {+-} 15 cm in primary forest and 17 {+-} 8 cm in secondary forest. Using Amazon forest biomass equations and wood densities for 117 species, aboveground biomass is 240 {+-} 30 t ha{sup -1} in the primary sites and 90 {+-} 10 t ha{sup -1} in the secondary sites. Aboveground carbon density is 120 {+-} 15 t ha{sup -1} in primary forest and 40 {+-} 5 t ha{sup -1} in secondary forest. Forest stands in the secondary forest sites range in age from 10 to 42 y. Growth in biomass (t ha{sup -1}) as a function of time (y) follows the relation: biomass = 4.09-0.017 age{sup 2} (p < 0.001). Aboveground biomass and forest species richness are positively correlated (r{sup 2} = 0.59, p < 0.001). Analyses of Landsat data show that the land cover of the 3700 km{sup 2} of non-cloud areas in 1999 was: closed forest 78%; open forest 12%, low vegetation cover 4%, sparse vegetation cover 6%. Deforestation from 1987 to 1999 claimed a net 200 km{sup 2} of forest, proceeding at a rate of 0.005 y{sup -1}. Of those areas of closed forest in 1987, only 89% remained closed forest in 1999. Consequently, closed forests experienced disruption in the time period at double the rate of net deforestation. The three protected areas experienced negligible deforestation or slight reforestation. Based on 1987 forest cover, 26,000 ha are eligible for forest carbon trading under the Clean Development Mechanism, established by the Kyoto Protocol to the United Nations Framework Convention on Climate Change. Principal components analysis showed that distance to nonforest was the factor that best explained observed patterns of deforestation while distance to forest best explained observed patterns of reforestation, more significant than elevation, distance to rivers, distance to roads, slope, and distance to towns of population > 400. Aboveground carbon in live vegetation in the project area decreased from 35 million {+-} 4 million t in 1987 to 34 million {+-} 4 million t in 1999. Projected aboveground carbon in live vegetation would fall to 33 million {+-} 4 million t in 2006, 32 million {+-} 4 million t in 2011, and 29 million {+-} 3 million t in 2035. Projected net deforestation in the research area would total 13,000 {+-} 3000 ha in the period 1999-2011, proceeding at a rate of 0.003 {+-} 0.0007 y{sup -1}, and would total 33,000 {+-} 7000 ha in the period 2006-2035. The proposed 7000 ha of forest conservation could prevent gross baseline deforestation of 100 ha (min. 70 ha, max 150 ha) in the period 2006-2035, averting baseline carbon emissions of 10,000 t (min. 6 000 t, max. 18 000 t). Projected gross reforestation in the research area would total 8500 {+-} 1500 ha in the period 1999-2011, proceeding at a rate of 0.0012 y{sup -1} (min. 0.01 y{sup -1}, max. 0.014 y{sup -1}), and would total 24,000 {+-} 4000 ha in the period 2006-2035. Gross baseline reforestation for the proposed 7000 ha of reforestation would total 2600 {+-} 400 ha in the period 2006-2035, representing a baseline removal from the atmosphere of 73,000 t carbon (min. 30,000 t, max. 120,000 t). The proposed reforestation project could sequester 230,000 t carbon (min. 140,000 t, max. 310,000 t) above baseline removal in the period 2006-2035.« less

Fertilization Increases Below-Ground Carbon Sequestration of Loblolly Pine Plantations

Treesearch

K.H. Johnsen; J.R. Butnor; C. Maier; R. Oren; R. Pangle; L. Samuelson; J. Seiler; S.E. McKeand; H.L. Allen

2001-01-01

The extent of fertilization of southern pine forests is increasing rapidly; industrial fertilization increased from 16,200 ha per year in 1988, to 344,250 ha in 1998. Fertilization increases stand productivity and can increase carbon (C) sequestration by: 1) increasing above-ground standing C; 2) increasing C stored in forest products; and 3) increasing below-ground...

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

Treesearch

Fabien H. Wagner; Bruno Herault; Damien Bonal; Clement Stahl; Liana O. Anderson; Timothy R. Baker; Gabriel Sebastian Becker; Hans Beeckman; Danilo Boanerges Souza; Paulo Cesar Botosso; David M. J. S. Bowman; Achim Brauning; Benjamin Brede; Foster Irving Brown; Jesus Julio Camarero; Plinio Barbosa Camargo; Fernanda C. G. Cardoso; Fabricio Alvim Carvalho; Wendeson Castro; Rubens Koloski Chagas; Jerome Chave; Emmanuel N. Chidumayo; Deborah A. Clark; Flavia Regina Capellotto Costa; Camille Couralet; Paulo Henrique da Silva Mauricio; Helmut Dalitz; Vinicius Resende de Castro; Jacanan Eloisa de Freitas Milani; Edilson Consuelo de Oliveira; Luciano de Souza Arruda; Jean-Louis Devineau; David M. Drew; Oliver Dunisch; Giselda Durigan; Elisha Elifuraha; Marcio Fedele; Ligia Ferreira Fedele; Afonso Figueiredo Filho; Cesar Augusto Guimaraes Finger; Augusto Cesar Franco; Joao Lima Freitas Junior; Franklin Galvao; Aster Gebrekirstos; Robert Gliniars; Paulo Mauricio Lima de Alencastro Graca; Anthony D. Griffiths; James Grogan; Kaiyu Guan; Jurgen Homeier; Maria Raquel Kanieski; Lip Khoon Kho; Jennifer Koenig; Sintia Valerio Kohler; Julia Krepkowski; Jose Pires Lemos-Filho; Diana Lieberman; Milton Eugene Lieberman; Claudio Sergio Lisi; Tomaz Longhi Santos; Jose Luis Lopez Ayala; Eduardo Eijji Maeda; Yadvinder Malhi; Vivian R. B. Maria; Marcia C. M. Marques; Renato Marques; Hector Maza Chamba; Lawrence Mbwambo; Karina Liana Lisboa Melgaco; Hooz Angela Mendivelso; Brett P. Murphy; Joseph O' Brien; Steven F. Oberbauer; Naoki Okada; Raphael Pelissier; Lynda D. Prior; Fidel Alejandro Roig; Michael Ross; Davi Rodrigo Rossatto; Vivien Rossi; Lucy Rowland; Ervan Rutishauser; Hellen Santana; Mark Schulze; Diogo Selhorst; Williamar Rodrigues Silva; Marcos Silveira; Susanne Spannl; Michael D. Swaine; Jose Julio Toledo; Marcos Miranda Toledo; Marisol Toledo; Takeshi Toma; Mario Tomazello Filho; Juan Ignacio Valdez Hernandez; Jan Verbesselt; Simone Aparecida Vieira; Gregoire Vincent; Carolina Volkmer de Castilho; Franziska Volland; Martin Worbes; Magda Lea Bolzan Zanon; Luiz E. O. C. Aragao

2016-01-01

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter...

Post-establishment fertilization of Minnesota hybrid poplar plantations

Treesearch

Mark Coleman; David Tolsted; Tom Nichols; Wendell D. Johnson; Edward G. Wene; Tom Houghtaling

2006-01-01

Experimental plantings were installed at five sites in three locations in western Minnesota. Aboveground biomass production increased 43–82% as a result of three annual applications of urea or balanced nutrient blend fertilizer beginning near canopy closure. There were no production differences between the type of fertilizer used, indicating that N was the major...

Forage composition, productivity, and utilization in the eastern Washington Cascade Range

Treesearch

John F. Lehmkuhl; Andrea L. Lyons; Edd Bracken; Jodi Leingang; William L. Gaines; Erich K. Dodson; Peter H. Singleton

2013-01-01

Provision of forage for wild and domestic ungulates, and the associated impacts of their herbivory, are contentious issues for wildland management in western North America. We quantified the composition, above-ground net production (ANP), and utilization of herbaceous and shrub vegetation in five non-forest and seven forest cover types across the core springsummer-...

Forage composition, productivity, and utilization in the Eastern Washington Cascade Range

Treesearch

John F. Lehmkuhl; Andrea L. Lyons; Edd Bracken; Jodi Leingang; William L. Gaines; Erich Kyle Dodson; Peter H. Singleton

2013-01-01

Provision of forage for wild and domestic ungulates, and the associated impacts of their herbivory, are contentious issues for wildland management in western North America. We quantified the composition, above-ground net production (ANP), and utilization of herbaceous and shrub vegetation in five non-forest and seven forest cover types across the core spring-...

Long-term patterns in tropical reforestation: plant community composition and aboveground biomass accumulation.

Treesearch

E. Mar¡n-Spiotta; R. Ostertag; Silver W. L.

2007-01-01

Primary tropical forests are renowned for their high biodiversity and carbon storage, and considerable research has documented both species and carbon losses with deforestation and agricultural land uses. Economic drivers are now leading to the abandonment of agricultural lands, and the area in secondary forests is increasing. We know little about how long it takes for...

Long-term, patterns in tropical reforestation: plant community composition and aboveground biomass accumulation.

Treesearch

E. MARIN-SPIOTTA; R. OSTERTAG; SILVER W. L.

2007-01-01

Primary tropical forests are renowned for their high biodiversity and carbon storage, and considerable research has documented both species and carbon losses with deforestation and agricultural land uses. Economic drivers are now leading to the abandonment of agricultural lands, and the area in secondary forests is increasing. We know little about how long it takes for...

Recovery of aboveground plant biomass and productivity after fire in mesic and dry black spruce forests of interior Alaska

USGS Publications Warehouse

Mack, M.C.; Treseder, K.K.; Manies, K.L.; Harden, J.W.; Schuur, E.A.G.; Vogel, J.G.; Randerson, J.T.; Chapin, F. S.

2008-01-01

Plant biomass accumulation and productivity are important determinants of ecosystem carbon (C) balance during post-fire succession. In boreal black spruce (Picea mariana) forests near Delta Junction, Alaska, we quantified aboveground plant biomass and net primary productivity (ANPP) for 4 years after a 1999 wildfire in a well-drained (dry) site, and also across a dry and a moderately well-drained (mesic) chronosequence of sites that varied in time since fire (2 to ???116 years). Four years after fire, total biomass at the 1999 burn site had increased exponentially to 160 ?? 21 g m-2 (mean ?? 1SE) and vascular ANPP had recovered to 138 ?? 32 g m-2 y -1, which was not different than that of a nearby unburned stand (160 ?? 48 g m-2 y-1) that had similar pre-fire stand structure and understory composition. Production in the young site was dominated by re-sprouting graminoids, whereas production in the unburned site was dominated by black spruce. On the dry and mesic chronosequences, total biomass pools, including overstory and understory vascular and non-vascular plants, and lichens, increased logarithmically (dry) or linearly (mesic) with increasing site age, reaching a maximum of 2469 ?? 180 (dry) and 4008 ?? 233 g m-2 (mesic) in mature stands. Biomass differences were primarily due to higher tree density in the mesic sites because mass per tree was similar between sites. ANPP of vascular and non-vascular plants increased linearly over time in the mesic chronosequence to 335 ?? 68 g m-2 y -1 in the mature site, but in the dry chronosequence it peaked at 410 ?? 43 g m-2 y-1 in a 15-year-old stand dominated by deciduous trees and shrubs. Key factors regulating biomass accumulation and production in these ecosystems appear to be the abundance and composition of re-sprouting species early in succession, the abundance of deciduous trees and shrubs in intermediate aged stands, and the density of black spruce across all stand ages. A better understanding of the controls over these factors will help predict how changes in climate and fire regime will affect the carbon balance of Interior Alaska. ?? 2008 Springer Science+Business Media, LLC.

Leaf endophytic fungus interacts with precipitation to alter belowground microbial communities in primary successional dunes

PubMed Central

Bell-Dereske, Lukas; Takacs-Vesbach, Cristina; Kivlin, Stephanie N.; Emery, Sarah M.; Rudgers, Jennifer A.

2017-01-01

Abstract Understanding interactions between above- and belowground components of ecosystems is an important next step in community ecology. These interactions may be fundamental to predicting ecological responses to global change because indirect effects occurring through altered species interactions can outweigh or interact with the direct effects of environmental drivers. In a multiyear field experiment (2010–2015), we tested how experimental addition of a mutualistic leaf endophyte (Epichloë amarillans) associated with American beachgrass (Ammophila breviligulata) interacted with an altered precipitation regime (±30%) to affect the belowground microbial community. Epichloë addition increased host root biomass at the plot scale, but reduced the length of extraradical arbuscular mycorrhizal (AM) fungal hyphae in the soil. Under ambient precipitation alone, the addition of Epichloë increased root biomass per aboveground tiller and reduced the diversity of AM fungi in A. breviligulata roots. Furthermore, with Epichloë added, the diversity of root-associated bacteria declined with higher soil moisture, whereas in its absence, bacterial diversity increased with higher soil moisture. Thus, the aboveground fungal mutualist not only altered the abundance and composition of belowground microbial communities but also affected how belowground communities responded to climate, suggesting that aboveground microbes have potential for cascading influences on community dynamics and ecosystem processes that occur belowground. PMID:28334408

MS-Based Metabolite Profiling of Aboveground and Root Components of Zingiber mioga and Officinale.

PubMed

Han, Ji Soo; Lee, Sunmin; Kim, Hyang Yeon; Lee, Choong Hwan

2015-09-03

Zingiber species are members of the Zingiberaceae family, and are widely used for medicinal and food purposes. In this study aboveground and root parts of Zingiber mioga and Zingiber officinale were subjected to metabolite profiling by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) in order to characterize them by species and parts and also to measure bioactivities. Both primary and secondary metabolites showed clear discrimination in the PCA score plot and PLS-DA by species and parts. Tetrahydrocurcumin, diarylheptanoid, 8-gingerol, and 8-paradol were discriminating metabolites between Z. mioga and Z. officinale that were present in different quantities. Eleven flavonoids, six amino acids, six organic acids, four fatty acids, and gingerenone A were higher in the aboveground parts than the root parts. Antioxidant activities were measured and were highest in the root part of Z. officinale. The relatively high contents of tetrahydrocurcumin, diarylheptanoid, and galanganol C in the root part of Z. officinale showed highly positive correlation with bioactivities based on correlation assay. On the basis of these results, we can suggest different usages of structurally different parts of Zingiber species as food plants.

Primary Productivity and Precipitation-Use Efficiency in Temperate Grassland in the Loess Plateau of China

PubMed Central

Jia, Xiaoxu; Xie, Baoni; Shao, Ming’an; Zhao, Chunlei

2015-01-01

Clarifying spatial variations in aboveground net primary productivity (ANPP) and precipitation-use efficiency (PUE) of grasslands is critical for effective prediction of the response of terrestrial ecosystem carbon and water cycle to future climate change. Though the combination use of remote sensing products and in situ ANPP measurements, we quantified the effects of climatic [mean annual precipitation (MAP) and precipitation seasonal distribution (PSD)], biotic [leaf area index (LAI)] and abiotic [slope gradient, aspect, soil water storage (SWS) and other soil physical properties] factors on the spatial variations in ANPP and PUE across different grassland types (i.e., meadow steppe, typical steppe and desert steppe) in the Loess Plateau. Based on the study, ANPP increased exponentially with MAP for the entire temperate grassland; suggesting that PUE increased with increasing MAP. Also PSD had a significant effect on ANPP and PUE; where more even PSD favored higher ANPP and PUE. Then MAP, more than PSD, explained spatial variations in typical steppe and desert steppe. However, PSD was the dominant driving factor of spatial variations in ANPP of meadow steppe. This suggested that in terms of spatial variations in ANPP of meadow steppe, change in PSD due to climate change was more important than that in total annual precipitation. LAI explained 78% of spatial PUE in the entire Loess Plateau temperate grassland. As such, LAI was the primary driving factor of spatial variations in PUE. Although the effect of SWS on ANPP and PUE was significant, it was nonetheless less than that of precipitation and vegetation. We therefore concluded that changes in vegetation structure and consequently in LAI and/or altered pattern of seasonal distribution of rainfall due to global climate change could significantly influence ecosystem carbon and water cycle in temperate grasslands. PMID:26295954

Primary Productivity and Precipitation-Use Efficiency in Temperate Grassland in the Loess Plateau of China.

PubMed

Jia, Xiaoxu; Xie, Baoni; Shao, Ming'an; Zhao, Chunlei

2015-01-01

Clarifying spatial variations in aboveground net primary productivity (ANPP) and precipitation-use efficiency (PUE) of grasslands is critical for effective prediction of the response of terrestrial ecosystem carbon and water cycle to future climate change. Though the combination use of remote sensing products and in situ ANPP measurements, we quantified the effects of climatic [mean annual precipitation (MAP) and precipitation seasonal distribution (PSD)], biotic [leaf area index (LAI)] and abiotic [slope gradient, aspect, soil water storage (SWS) and other soil physical properties] factors on the spatial variations in ANPP and PUE across different grassland types (i.e., meadow steppe, typical steppe and desert steppe) in the Loess Plateau. Based on the study, ANPP increased exponentially with MAP for the entire temperate grassland; suggesting that PUE increased with increasing MAP. Also PSD had a significant effect on ANPP and PUE; where more even PSD favored higher ANPP and PUE. Then MAP, more than PSD, explained spatial variations in typical steppe and desert steppe. However, PSD was the dominant driving factor of spatial variations in ANPP of meadow steppe. This suggested that in terms of spatial variations in ANPP of meadow steppe, change in PSD due to climate change was more important than that in total annual precipitation. LAI explained 78% of spatial PUE in the entire Loess Plateau temperate grassland. As such, LAI was the primary driving factor of spatial variations in PUE. Although the effect of SWS on ANPP and PUE was significant, it was nonetheless less than that of precipitation and vegetation. We therefore concluded that changes in vegetation structure and consequently in LAI and/or altered pattern of seasonal distribution of rainfall due to global climate change could significantly influence ecosystem carbon and water cycle in temperate grasslands.

Energy Balance of Rural Ecosystems In India

NASA Astrophysics Data System (ADS)

Chhabra, A.; Madhava Rao, V.; Hermon, R. R.; Garg, A.; Nag, T.; Bhaskara Rao, N.; Sharma, A.; Parihar, J. S.

2014-11-01

India is predominantly an agricultural and rural country. Across the country, the villages vary in geographical location, area, human and livestock population, availability of resources, agricultural practices, livelihood patterns etc. This study presents an estimation of net energy balance resulting from primary production vis-a-vis energy consumption through various components in a "Rural Ecosystem". Seven sites located in different agroclimatic regions of India were studied. An end use energy accounting "Rural Energy Balance Model" is developed for input-output analysis of various energy flows of production, consumption, import and export through various components of crop, trees outside forest plantations, livestock, rural households, industry or trade within the village system boundary. An integrated approach using field, ancillary, GIS and high resolution IRS-P6 Resourcesat-2 LISS IV data is adopted for generation of various model inputs. The primary and secondary field data collection of various energy uses at household and village level were carried out using structured schedules and questionnaires. High resolution multi-temporal Resourcesat-2 LISS IV data (2013-14) was used for generating landuse/landcover maps and estimation of above-ground Trees Outside Forests phytomass. The model inputs were converted to energy equivalents using country-specific energy conversion factors. A comprehensive geotagged database of sampled households and available resources at each study site was also developed in ArcGIS framework. Across the study sites, the estimated net energy balance ranged from -18.8 Terra Joules (TJ) in a high energy consuming Hodka village, Gujarat to 224.7 TJ in an agriculture, aquaculture and plantation intensive Kollaparru village, Andhra Pradesh. The results indicate that the net energy balance of a Rural Ecosystem is largely driven by primary production through crops and natural vegetation. This study provides a significant insight to policy relevant recommendations for Energy Sustainable Rural India.

Comparison of modeling approaches for carbon partitioning: Impact on estimates of global net primary production and equilibrium biomass of woody vegetation from MODIS GPP

NASA Astrophysics Data System (ADS)

Ise, Takeshi; Litton, Creighton M.; Giardina, Christian P.; Ito, Akihiko

2010-12-01

Partitioning of gross primary production (GPP) to aboveground versus belowground, to growth versus respiration, and to short versus long-lived tissues exerts a strong influence on ecosystem structure and function, with potentially large implications for the global carbon budget. A recent meta-analysis of forest ecosystems suggests that carbon partitioning to leaves, stems, and roots varies consistently with GPP and that the ratio of net primary production (NPP) to GPP is conservative across environmental gradients. To examine influences of carbon partitioning schemes employed by global ecosystem models, we used this meta-analysis-based model and a satellite-based (MODIS) terrestrial GPP data set to estimate global woody NPP and equilibrium biomass, and then compared it to two process-based ecosystem models (Biome-BGC and VISIT) using the same GPP data set. We hypothesized that different carbon partitioning schemes would result in large differences in global estimates of woody NPP and equilibrium biomass. Woody NPP estimated by Biome-BGC and VISIT was 25% and 29% higher than the meta-analysis-based model for boreal forests, with smaller differences in temperate and tropics. Global equilibrium woody biomass, calculated from model-specific NPP estimates and a single set of tissue turnover rates, was 48 and 226 Pg C higher for Biome-BGC and VISIT compared to the meta-analysis-based model, reflecting differences in carbon partitioning to structural versus metabolically active tissues. In summary, we found that different carbon partitioning schemes resulted in large variations in estimates of global woody carbon flux and storage, indicating that stand-level controls on carbon partitioning are not yet accurately represented in ecosystem models.

Contrasting seasonal overlaps between primary and secondary growth are linked to wood anatomy in Mediterranean sub-shrubs.

PubMed

Camarero, J J; Palacio, S; Montserrat-Martí, G

2013-09-01

Whole-plant approaches allow quantification of the temporal overlap between primary and secondary growth. If the amount of time available to grow is short, there may be a high temporal overlap between shoot growth and wood formation. We hypothesise that such overlap depends on the duration of the growing season and relates to wood anatomy. We evaluated wood anatomy, shoot longitudinal and radial growth rates, fine root production and the concentrations of non-structural carbohydrates (NSC) in the wood of six sub-shrub species growing in sites with contrasting climatic conditions (Lepidium subulatum, Linum suffruticosum, Salvia lavandulifolia, Satureja montana, Ononis fruticosa, Echinospartum horridum). Sub-shrub species living in sites with a short growing season displayed a high overlap between aboveground primary and secondary growth and formed wide vessels, whereas species from the warmest and driest sites presented the reverse characteristics. The highest overlap was linked to a rapid shoot extension and thickening through the enhanced hydraulic conductivity provided by wide vessels. The reductions in NSC concentrations when growth peaked were low or moderate, indicating that sub-shrubs accumulate NSC in excess, as do trees. The temporal overlap among primary and secondary growth in woody plants may be connected to the duration and rates of shoot and wood growth, which in turn depend on the vessel lumen area. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

[Structural recovering in Andean successional forests from Porce (Antioquia, Colombia)].

PubMed

Yepes, Adriana P; del Valle, Jorge I; Jaramillo, Sandra L; Orrego, Sergio A

2010-03-01

Places subjected to natural or human disturbance can recover forest through an ecological process called secondary succession. Tropical succession is affected by factors such as disturbances, distance from original forest, surface configuration and local climate. These factors determine the composition of species and the time trend of the succession itself. We studied succession in soils used for cattle ranching over various decades in the Porce Region of Colombia (Andean Colombian forests). A set of twenty five permanent plots was measured, including nine plots (20 x 50 m) in primary forests and sixteen (20 x 25 m) in secondary forests. All trees with diameter > or =1.0 cm were measured. We analyzed stem density, basal area, above-ground biomass and species richness, in a successional process of ca. 43 years, and in primary forests. The secondary forests' age was estimated in previous studies, using radiocarbon dating, aerial photographs and a high-resolution satellite image analysis (7 to >43 years). In total, 1,143 and 1,766 stems were measured in primary and secondary forests, respectively. Basal area (5.7 to 85.4 m2 ha(-1)), above-ground biomass (19.1 to 1,011.5 t ha(-1)) and species richness (4 to 69) directly increased with site age, while steam density decreased (3,180 to 590). Diametric distributions were "J-inverted" for primary forests and even-aged size-class structures for secondary forests. Three species of palms were abundant and exclusive in old secondary forests and primary forests: Oenocarpus mapora, Euterpe precatoria and Oenocarpus bataua. These palms happened in cohorts after forest disturbances. Secondary forest structure was 40% in more than 43 years of forest succession and indicate that many factors are interacting and affecting the forests succession in the area (e.g. agriculture, cattle ranching, mining, etc.).

Simulating forest productivity and surface-atmosphere carbon exchange in the BOREAS study region.

PubMed

Kimball, John S.; Thornton, Peter E.; White, Mike A.; Running, Steven W.

1997-01-01

A process-based, general ecosystem model (BIOME-BGC) was used to simulate daily gross primary production, maintenance and heterotrophic respiration, net primary production and net ecosystem carbon exchange of boreal aspen, jack pine and black spruce stands. Model simulations of daily net carbon exchange of the ecosystem (NEE) explained 51.7% (SE = 1.32 g C m(-2) day(-1)) of the variance in daily NEE derived from stand eddy flux measurements of CO(2) during 1994. Differences between measured and simulated results were attributed to several factors including difficulties associated with measuring nighttime CO(2) fluxes and model assumptions of site homogeneity. However, comparisons between simulations and field data improved markedly at coarser time-scales. Model simulations explained 66.1% (SE = 0.97 g C m(-2) day(-1)) of the variance in measured NEE when 5-day means of daily results were compared. Annual simulations of aboveground net primary production ranged from 0.6-2.4 Mg C ha(-1) year(-1) and were concurrent with results derived from tree increment core measurements and allometric equations. Model simulations showed that all of the sites were net sinks (0.1-4.1 Mg C ha(-1) year(-1)) of atmospheric carbon for 1994. Older conifer stands showed narrow margins between uptake of carbon by net photosynthesis and carbon release through respiration. Younger stands were more productive than older stands, primarily because of lower maintenance respiration costs. However, all sites appeared to be less productive than temperate forests. Productivity simulations were strongly linked to stand morphology and site conditions. Old jack pine and aspen stands showed decreased productivity in response to simulated low soil water contents near the end of the 1994 growing season. Compared with the aspen stand, the jack pine stand appeared better adapted to conserve soil water through lower daily evapotranspiration losses but also exhibited a narrower margin between daily net photosynthesis and respiration. Stands subjected to water stress during the growing season may exist on the edge between being annual sources or sinks for atmospheric carbon.

Aboveground carbon sequestration in dry temperate forests varies with climate not fire regime.

PubMed

Gordon, Christopher E; Bendall, Eli R; Stares, Mitchell G; Collins, Luke; Bradstock, Ross A

2018-06-01

The storage of carbon in plant tissues and debris has been proposed as a method to offset anthropogenic increases in atmospheric [CO 2 ]. Temperate forests represent significant above-ground carbon (AGC) "sinks" because their relatively fast growth and slow decay rates optimise carbon assimilation. Fire is a common disturbance event in temperate forests globally that should strongly influence AGC because: discrete fires consume above-ground biomass releasing carbon to the atmosphere, and the long-term application of different fire-regimes select for specific plant communities that sequester carbon at different rates. We investigated the latter process by quantifying AGC storage at 104 sites in the Sydney Basin Bioregion, Australia, relative to differences in components of the fire regime: frequency, severity and interfire interval. To predict the potential impacts of future climate change on fire/AGC interactions, we stratified our field sites across gradients of mean annual temperature and precipitation and quantified within- and between-factor interactions between the fire and climate variables. In agreement with previous studies, large trees were the primary AGC sink, accounting for ~70% of carbon at sites. Generalised additive models showed that mean annual temperature was the strongest predictor of AGC storage, with a 54% near-linear decrease predicted across the 6.1°C temperature range experienced at sites. Mean annual precipitation, fire frequency, fire severity and interfire interval were consistently poor predictors of total above-ground storage, although there were some significant relationships with component stocks. Our results show resilience of AGC to frequent and severe wildfire and suggest temperature mediated decreases in forest carbon storage under future climate change predictions. © 2018 John Wiley & Sons Ltd.

Impacts of intensive management and genetic improvement on soil CO2 efflux and carbon cycling in managed loblolly pine forests

Treesearch

Chelsea G. Drum; Eric J. Jokela; Jason G. Vogel; Edward A. G. Schuur; Salvador Gezan

2015-01-01

In the southeastern United States, fertilization and weed control treatments, with deployment of genetically improved seedlings planting stock, are routinely used to increase aboveground productivity (Jokela and others 2004).

Plant Diversity Impacts Decomposition and Herbivory via Changes in Aboveground Arthropods

PubMed Central

Ebeling, Anne; Meyer, Sebastian T.; Abbas, Maike; Eisenhauer, Nico; Hillebrand, Helmut; Lange, Markus; Scherber, Christoph; Vogel, Anja; Weigelt, Alexandra; Weisser, Wolfgang W.

2014-01-01

Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ecosystem processes is an important but little studied piece of information. In a grassland biodiversity experiment, we addressed this gap by assessing aboveground decomposer and herbivore communities and linking their abundance and diversity to rates of decomposition and herbivory. Path analyses showed that increasing plant diversity led to higher abundance and diversity of decomposing arthropods through higher plant biomass. Higher species richness of decomposers, in turn, enhanced decomposition. Similarly, species-rich plant communities hosted a higher abundance and diversity of herbivores through elevated plant biomass and C:N ratio, leading to higher herbivory rates. Integrating trophic interactions into the study of biodiversity effects is required to understand the multiple pathways by which biodiversity affects ecosystem functioning. PMID:25226237

Relationship of Aboveground Biomass Production Site Index and Soil Characteristics in a Loblolly Pine Stand

Treesearch

Minyi Zhou; Thomas J. Dean

2004-01-01

As a part of the continuing studies of the Cooperative Research in Sustainable Silviculture and Soil Productivity (CRiSSSP), 24 experimental plots in a loblolly pine (Pinus taeda L.) stand have recently been installed near Natchitoches, LA. The plots were uniformly assigned to 3 blocks based on topography (i.e., up slope, midslope, and down slope)....

Effects of energy development on wetland plants and macroinvertebrate communities in Prairie Pothole Region wetlands

USGS Publications Warehouse

Preston, Todd M.; Ray, Andrew M.

2016-01-01

Energy production in the Williston Basin, USA, results in the coproduction of highly saline, sodium chloride-dominated water (brine). The Prairie Pothole Region (PPR) overlies the northeastern portion of the Williston Basin. Although PPR wetlands span a range of salinity, the dominant salt is sodium sulfate, and salinities are much lower than brine. Introduction of brine to wetlands can result in pronounced water-quality changes; however, the ecological effects of such contamination are poorly understood. We examined the effects of brine contamination on primary productivity, emergent macrophyte tissue chemistry, and invertebrate communities from 10 wetlands in the PPR. Based on a recognized Contamination Index (CI) used to identify brine contamination in the PPR, water-quality samples indicated that six wetlands were uncontaminated while four were contaminated. Across this gradient, we observed a significant decrease in above-ground biomass and a significant increase in tissue chloride concentrations of hardstem bulrush (Schoenoplectus acutus) with increased CI values. Additionally, a significant decrease in macroinvertebrate taxonomic richness with increased CI values was observed. These findings provide needed insight on the biological effects of brine contamination on PPR wetlands.

The Dynamics of sediment oxygenation in Spartina anglica Rhizospheres - a Planar Optode Study

NASA Astrophysics Data System (ADS)

Koop-Jakobsen, Ketil

2013-04-01

The salt marsh grass Spartina anglica have well-developed aerenthyma tissue facilitating a rapid transport of oxygen from the atmosphere to belowground roots and rhizomes, where oxygen can leak out of the root system and oxygenate the surrounding sediment. In this way, oxic microzones are distributed vertically in marsh sediments promoting aerobic microbial activity at depth. In this study, the dynamics of sediment oxygenation in Spartina anglica rhizospheres was investigated, visualizing the belowground oxygen content using planar optode technology. Oxic microzones around roots and rhizomes were monitored in the laboratory under different light conditions and during tidal inundations of the aboveground biomass. Oxic microzones were restricted to the root tips extending up to16mm along the root and 1.5mm into the anoxic bulk sediment from the root surface. The oxygen concentration was highest at the root-surface ranging from 58-85μM. The volume of the oxic microzones did not change significantly with decreasing light availability of the aboveground biomass showing that the atmosphere is the primary source for oxygen transported below ground. Consequently, tidal inundations cutting off the access to atmospheric oxygen resulted in a complete collapse of the oxic microzones after 3 hours of inundation in the light as well as in the dark. However, monitoring oxic microzones during a 24h tidal cycle with diurnal tidal inundations lasting 90min showed a 36% reduction of the oxic microzones in the light in contrast to a complete collapse of the oxic microzones in the dark. Hence, light availability and photosynthetic oxygen production of the aboveground biomass does influence the kinetics of oxic microzone develupment. Belowground sediment oxygenation is of significant importance for the biogeochemical cycles in salt marsh sediment, in particular coupled nitrification-denitrification occurring at depth associated with oxic microzones can account for a significant proportion of the gaseous export of nitrogen from Spartina spp.-dominated marshes. This study shows that tidal inundations have significant impact on belowground biogeochemical conditions and must be taken into account when monitoring tidal marsh processes on a daily basis.

49 CFR 195.307 - Pressure testing aboveground breakout tanks.

Code of Federal Regulations, 2013 CFR

2013-10-01

... aboveground breakout tanks. (a) For aboveground breakout tanks built into API Specification 12F and first placed in service after October 2, 2000, pneumatic testing must be in accordance with section 5.3 of API Specification 12 F (incorporated by reference, see § 195.3). (b) For aboveground breakout tanks built to API...

49 CFR 195.307 - Pressure testing aboveground breakout tanks.

Code of Federal Regulations, 2012 CFR

2012-10-01

... aboveground breakout tanks. (a) For aboveground breakout tanks built into API Specification 12F and first placed in service after October 2, 2000, pneumatic testing must be in accordance with section 5.3 of API Specification 12 F (incorporated by reference, see § 195.3). (b) For aboveground breakout tanks built to API...

49 CFR 195.307 - Pressure testing aboveground breakout tanks.

Code of Federal Regulations, 2011 CFR

2011-10-01

... aboveground breakout tanks. (a) For aboveground breakout tanks built into API Specification 12F and first placed in service after October 2, 2000, pneumatic testing must be in accordance with section 5.3 of API Specification 12 F (incorporated by reference, see § 195.3). (b) For aboveground breakout tanks built to API...

49 CFR 195.307 - Pressure testing aboveground breakout tanks.

Code of Federal Regulations, 2014 CFR

2014-10-01

... aboveground breakout tanks. (a) For aboveground breakout tanks built into API Specification 12F and first placed in service after October 2, 2000, pneumatic testing must be in accordance with section 5.3 of API Specification 12 F (incorporated by reference, see § 195.3). (b) For aboveground breakout tanks built to API...

Intra-annual changes in biomass, carbon, and nitrogen dynamics at 4-year old switchgrass field trials in West Tennessee, USA

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

Garten, Jr, C. T.; Smith, Jeffery L.; Tyler, Donald D.

2010-02-15

Switchgrass is a potential bioenergy crop that could promote soil C sequestration in some environments. We compared four cultivars on a well-drained Alfisol to test for differences in biomass, C, and N dynamics during the fourth growing season. There was no difference (P > 0.05) among cultivars and no significant cultivar x time interaction in analyses of dry mass, C stocks, or N stocks in aboveground biomass and surface litter. At the end of the growing season, mean (±SE) aboveground biomass was 2.1±0.13 kg m-2, and surface litter dry mass was approximately 50% of aboveground biomass. Prior to harvest, themore » live root:shoot biomass ratio was 0.76. There was no difference (P > 0.05) among cultivars for total biomass, C, and N stocks belowground. Total belowground biomass (90-cm soil depth) as well as coarse (greater than or equal to 1 mm diameter) and fine (< 1 mm diameter) live root biomass increased from April to October. Dead roots were less than 7% of live root biomass to a depth of 90 cm. Net production of total belowground biomass (505 ±132 g m-2) occurred in the last half of the growing season. The increase in total live belowground biomass (426 ±139 g m-2) was more or less evenly divided among rhizomes, coarse, and fine roots. The N budget for annual switchgrass production was closely balanced with 6.3 g N m-2 removed by harvest of aboveground biomass and 6.7 g N m-2 supplied by fertilization. At the location of our study in west Tennessee, intra-annual changes in biomass, C, and N stocks belowground were of greater importance to crop management for C sequestration than were differences among cultivars.« less

Plant functional trait diversity regulates the nonlinear response of productivity to regional climate change in Tibetan alpine grasslands.

PubMed

Wu, Jianshuang; Wurst, Susanne; Zhang, Xianzhou

2016-10-19

The biodiversity-productivity relationship is still under debate for alpine grasslands on the Tibetan Plateau. We know little about direct and indirect effects of biotic and abiotic drivers on this relationship, especially in regard to plant functional trait diversity. Here, we examine how aboveground net primary productivity (ANPP) and precipitation use efficiency (PUE) respond to climate, soil and community structure across alpine grasslands on the Northern Tibetan Plateau. We found that both ANPP and PUE showed nonlinear patterns along water availability and site altitude variation, which together accounted for 80.3% and 68.8% of variation in ANPP and PUE, respectively, by optimal generalized additive models. Functional trait divergence (FTD) and community weighted mean (CWM) of plant functional traits were as important as plant species diversity (PSD) for explaining the nonlinear productivity-climate relationship. These findings were confirmed by results from principal component analyses and structural equation models. We also found that FTD was negatively correlated with PSD across different alpine grasslands. Our results implicate: first, the combinatorial influences of temperature and precipitation gradients are important for predicting alpine grassland dynamics; second, the convergence and divergence of plant functional traits may have the potential to elucidate the effect of plant diversity on ecosystem functionality.

Plant functional trait diversity regulates the nonlinear response of productivity to regional climate change in Tibetan alpine grasslands

PubMed Central

Wu, Jianshuang; Wurst, Susanne; Zhang, Xianzhou

2016-01-01

The biodiversity-productivity relationship is still under debate for alpine grasslands on the Tibetan Plateau. We know little about direct and indirect effects of biotic and abiotic drivers on this relationship, especially in regard to plant functional trait diversity. Here, we examine how aboveground net primary productivity (ANPP) and precipitation use efficiency (PUE) respond to climate, soil and community structure across alpine grasslands on the Northern Tibetan Plateau. We found that both ANPP and PUE showed nonlinear patterns along water availability and site altitude variation, which together accounted for 80.3% and 68.8% of variation in ANPP and PUE, respectively, by optimal generalized additive models. Functional trait divergence (FTD) and community weighted mean (CWM) of plant functional traits were as important as plant species diversity (PSD) for explaining the nonlinear productivity-climate relationship. These findings were confirmed by results from principal component analyses and structural equation models. We also found that FTD was negatively correlated with PSD across different alpine grasslands. Our results implicate: first, the combinatorial influences of temperature and precipitation gradients are important for predicting alpine grassland dynamics; second, the convergence and divergence of plant functional traits may have the potential to elucidate the effect of plant diversity on ecosystem functionality. PMID:27759112

DEVELOPMENT AND VERIFICATION OF A SCREENING MODEL FOR SURFACE SPREADING OF PETROLEUM

EPA Science Inventory

Overflows and leakage from aboveground storage tanks and pipelines carrying crude oil and petroleum products occur frequently. The spilled hydrocarbons pose environmental threats by contaminating the surrounding soil and the underlying ground water. Predicting the fate and transp...

Feedbacks between inundation, root production, and shoot growth in a rapidly submerging brackish marsh

USGS Publications Warehouse

Kirwan, Matthew L.; Guntenspergen, Glenn R.

2012-01-01

6.Synthesis. Below-ground responses of marshes to sea level rise are more broadly applicable than above-ground feedbacks because they are consistent among different species and do not depend on the availability of mineral sediment.

Interactions among resource partitioning, sampling effect, and facilitation on the biodiversity effect: a modeling approach.

PubMed

Flombaum, Pedro; Sala, Osvaldo E; Rastetter, Edward B

2014-02-01

Resource partitioning, facilitation, and sampling effect are the three mechanisms behind the biodiversity effect, which is depicted usually as the effect of plant-species richness on aboveground net primary production. These mechanisms operate simultaneously but their relative importance and interactions are difficult to unravel experimentally. Thus, niche differentiation and facilitation have been lumped together and separated from the sampling effect. Here, we propose three hypotheses about interactions among the three mechanisms and test them using a simulation model. The model simulated water movement through soil and vegetation, and net primary production mimicking the Patagonian steppe. Using the model, we created grass and shrub monocultures and mixtures, controlled root overlap and grass water-use efficiency (WUE) to simulate gradients of biodiversity, resource partitioning and facilitation. The presence of shrubs facilitated grass growth by increasing its WUE and in turn increased the sampling effect, whereas root overlap (resource partitioning) had, on average, no effect on sampling effect. Interestingly, resource partitioning and facilitation interacted so the effect of facilitation on sampling effect decreased as resource partitioning increased. Sampling effect was enhanced by the difference between the two functional groups in their efficiency in using resources. Morphological and physiological differences make one group outperform the other; once these differences were established further differences did not enhance the sampling effect. In addition, grass WUE and root overlap positively influence the biodiversity effect but showed no interactions.

Grassland establishment under varying resource availability: a test of positive and negative feedback.

PubMed

Baer, Sara G; Blair, John M

2008-07-01

The traditional logic of carbon (C) and nitrogen (N) interactions in ecosystems predicts further increases or decreases in productivity (positive feedback) in response to high and low fertility in the soil, respectively; but the potential for development of feedback in ecosystems recovering from disturbance is less well understood. Furthermore, this logic has been challenged in grassland ecosystems where frequent fires or grazing may reduce the contribution of aboveground litter inputs to soil organic matter pools and nutrient supply for plant growth, relative to forest ecosystems. Further, if increases in plant productivity increase soil C content more than soil N content, negative feedback may result from increased microbial demand for N making less available for plant growth. We used a field experiment to test for feedback in an establishing grassland by comparing aboveground net primary productivity (ANPP) and belowground pools and fluxes of C and N in soil with enriched, ambient, and reduced N availability. For eight years annual N enrichment increased ANPP, root N, and root tissue quality, but root C:N ratios remained well above the threshold for net mineralization of N. There was no evidence that N enrichment increased root biomass, soil C or N accrual rates, or storage of C in total, microbial, or mineralizable pools within this time frame. However, the net nitrogen mineralization potential (NMP) rate was greater following eight years of N enrichment, and we attributed this to N saturation of the microbial biomass. Grassland developing under experimentally imposed N limitation through C addition to the soil exhibited ANPP, root biomass and quality, and net NMP rate similar to the ambient soil. Similarity in productivity and roots in the reduced and ambient N treatments was attributed to the potentially high nitrogen-use efficiency (NUE) of the dominant C4 grasses, and increasing cover of legumes over time in the C-amended soil. Thus, in a developing ecosystem, positive feedback between soil N supply and plant productivity may promote enhanced long-term N availability and override progressive N limitation as C accrues in plant and soil pools. However, experimentally imposed reduction in N availability did not feed back to reduce ANPP, possibly due to shifts in NUE and functional group composition.

Tropical Soil Carbon Stocks do not Reflect Aboveground Forest Biomass Across Geological and Rainfall Gradients

NASA Astrophysics Data System (ADS)

Cusack, D. F.; Markesteijn, L.; Turner, B. L.

2016-12-01

Soil organic carbon (C) dynamics present a large source of uncertainty in global C cycle models, and inhibit our ability to predict effects of climate change. Tropical wet and seasonal forests exert a disproportionate influence on the global C cycle relative to their land area because they are the most C-rich ecosystems on Earth, containing 25-40% of global terrestrial C stocks. While significant advances have been made to map aboveground C stocks in tropical forests, determining soil C stocks using remote sensing technology is still not possible for closed-canopy forests. It is unclear to what extent aboveground C stocks can be used to predict soil C stocks across tropical forests. Here we present 1-m-deep soil organic C stocks for 42 tropical forest sites across rainfall and geological gradients in Panama. We show that soil C stocks do not correspond to aboveground plant biomass or to litterfall productivity in these humid tropical forests. Rather, soil C stocks were strongly and positively predicted by fine root biomass, soil clay content, and rainfall (R2 = 0.47, p < 0.05). Fine root biomass, in turn, was most strongly predicted by total extractable soil base cations (R2 = 0.24, p < 0.05, negative relationship). Our measures of tropical soil C and its relationships with climatic and soil chemical characteristics form an important basis for improving model estimates of soil C stocks and predictions of climate change effects on tropical C storage.

Liana infestation impacts tree growth in a lowland tropical moist forest

NASA Astrophysics Data System (ADS)

van der Heijden, G. M. F.; Phillips, O. L.

2009-03-01

Stand-level estimates of the effect of lianas on tree growth in mature tropical forests are needed to evaluate the functional impact of lianas and their potential to affect the ability of tropical forests to sequester carbon, but these are currently lacking. Using data collected on tree growth rates, local growing conditions and liana competition in five permanent sampling plots in Amazonian Peru, we present the first such estimates of the effect of lianas on above-ground productivity of trees. By constructing a multi-level linear mixed effect model to predict individual tree diameter growth model using individual tree growth conditions, we were able to estimate stand-level above-ground biomass (AGB) increment in the absence of lianas. We show that lianas, mainly by competing above-ground with trees, reduce tree annual above-ground stand-level biomass by ~10%, equivalent to 0.51 Mg dry weight ha-1 yr-1 or 0.25 Mg C ha-1 yr-1. AGB increment of lianas themselves was estimated to be 0.15 Mg dry weight ha-1 yr-1 or 0.07 Mg C ha-1 yr-1, thus only compensating ~29% of the liana-induced reduction in stand-level AGB increment. Increasing liana pressure on tropical forests may therefore not only reduce their carbon storage capacity, by indirectly promoting tree species with low-density wood, but also their rate of carbon uptake, with potential consequences for the rate of increase in atmospheric carbon dioxide.

Liana infestation impacts tree growth in a lowland tropical moist forest

NASA Astrophysics Data System (ADS)

van der Heijden, G. M. F.; Phillips, O. L.

2009-10-01

Ecosystem-level estimates of the effect of lianas on tree growth in mature tropical forests are needed to evaluate the functional impact of lianas and their potential to affect the ability of tropical forests to sequester carbon, but these are currently lacking. Using data collected on tree growth rates, local growing conditions and liana competition in five permanent sampling plots in Amazonian Peru, we present the first ecosystem-level estimates of the effect of lianas on above-ground productivity of trees. By first constructing a multi-level linear mixed effect model to predict individual-tree diameter growth model using individual-tree growth conditions, we were able to then estimate stand-level above-ground biomass (AGB) increment in the absence of lianas. We show that lianas, mainly by competing above-ground with trees, reduce tree annual above-ground stand-level biomass increment by ~10%, equivalent to 0.51 Mg dry weight ha-1 yr-1 or 0.25 Mg C ha-1 yr-1. AGB increment of lianas themselves was estimated to be 0.15 Mg dry weight ha-1 yr-1 or 0.07 Mg C ha-1 yr-1, thus only compensating ~29% of the liana-induced reduction in ecosystem AGB increment. Increasing liana pressure on tropical forests will therefore not only tend to reduce their carbon storage capacity, by indirectly promoting tree species with low-density wood, but also their rate of carbon uptake, with potential consequences for the rate of increase in atmospheric carbon dioxide.

Biomass resilience of Neotropical secondary forests.

PubMed

Poorter, Lourens; Bongers, Frans; Aide, T Mitchell; Almeyda Zambrano, Angélica M; Balvanera, Patricia; Becknell, Justin M; Boukili, Vanessa; Brancalion, Pedro H S; Broadbent, Eben N; Chazdon, Robin L; Craven, Dylan; de Almeida-Cortez, Jarcilene S; Cabral, George A L; de Jong, Ben H J; Denslow, Julie S; Dent, Daisy H; DeWalt, Saara J; Dupuy, Juan M; Durán, Sandra M; Espírito-Santo, Mario M; Fandino, María C; César, Ricardo G; Hall, Jefferson S; Hernandez-Stefanoni, José Luis; Jakovac, Catarina C; Junqueira, André B; Kennard, Deborah; Letcher, Susan G; Licona, Juan-Carlos; Lohbeck, Madelon; Marín-Spiotta, Erika; Martínez-Ramos, Miguel; Massoca, Paulo; Meave, Jorge A; Mesquita, Rita; Mora, Francisco; Muñoz, Rodrigo; Muscarella, Robert; Nunes, Yule R F; Ochoa-Gaona, Susana; de Oliveira, Alexandre A; Orihuela-Belmonte, Edith; Peña-Claros, Marielos; Pérez-García, Eduardo A; Piotto, Daniel; Powers, Jennifer S; Rodríguez-Velázquez, Jorge; Romero-Pérez, I Eunice; Ruíz, Jorge; Saldarriaga, Juan G; Sanchez-Azofeifa, Arturo; Schwartz, Naomi B; Steininger, Marc K; Swenson, Nathan G; Toledo, Marisol; Uriarte, Maria; van Breugel, Michiel; van der Wal, Hans; Veloso, Maria D M; Vester, Hans F M; Vicentini, Alberto; Vieira, Ima C G; Bentos, Tony Vizcarra; Williamson, G Bruce; Rozendaal, Danaë M A

2016-02-11

Land-use change occurs nowhere more rapidly than in the tropics, where the imbalance between deforestation and forest regrowth has large consequences for the global carbon cycle. However, considerable uncertainty remains about the rate of biomass recovery in secondary forests, and how these rates are influenced by climate, landscape, and prior land use. Here we analyse aboveground biomass recovery during secondary succession in 45 forest sites and about 1,500 forest plots covering the major environmental gradients in the Neotropics. The studied secondary forests are highly productive and resilient. Aboveground biomass recovery after 20 years was on average 122 megagrams per hectare (Mg ha(-1)), corresponding to a net carbon uptake of 3.05 Mg C ha(-1) yr(-1), 11 times the uptake rate of old-growth forests. Aboveground biomass stocks took a median time of 66 years to recover to 90% of old-growth values. Aboveground biomass recovery after 20 years varied 11.3-fold (from 20 to 225 Mg ha(-1)) across sites, and this recovery increased with water availability (higher local rainfall and lower climatic water deficit). We present a biomass recovery map of Latin America, which illustrates geographical and climatic variation in carbon sequestration potential during forest regrowth. The map will support policies to minimize forest loss in areas where biomass resilience is naturally low (such as seasonally dry forest regions) and promote forest regeneration and restoration in humid tropical lowland areas with high biomass resilience.

Modelling basin-wide variations in Amazon forest photosynthesis

NASA Astrophysics Data System (ADS)

Mercado, Lina; Lloyd, Jon; Domingues, Tomas; Fyllas, Nikolaos; Patino, Sandra; Dolman, Han; Sitch, Stephen

2010-05-01

Given the importance of Amazon rainforest in the global carbon and hydrological cycles, there is a need to use parameterized and validated ecosystem gas exchange and vegetation models for this region in order to adequately simulate present and future carbon and water balances. Recent research has found major differences in above-ground net primary productivity (ANPP), above ground biomass and tree dynamics across Amazonia. West Amazonia is more dynamic, with younger trees, higher stem growth rates and lower biomass than central and eastern Amazon (Baker et al. 2004; Malhi et al. 2004; Phillips et al. 2004). A factor of three variation in above-ground net primary productivity has been estimated across Amazonia by Malhi et al. (2004). Different hypotheses have been proposed to explain the observed spatial variability in ANPP (Malhi et al. 2004). First, due to the proximity to the Andes, sites from western Amazonia tend to have richer soils than central and eastern Amazon and therefore soil fertility could possibly be highly related to the high wood productivity found in western sites. Second, if GPP does not vary across the Amazon basin then different patterns of carbon allocation to respiration could also explain the observed ANPP gradient. However since plant growth depends on the interaction between photosynthesis, transport of assimilates, plant respiration, water relations and mineral nutrition, variations in plant gross photosynthesis (GPP) could also explain the observed variations in ANPP. In this study we investigate whether Amazon GPP can explain variations of observed ANPP. We use a sun and shade canopy gas exchange model that has been calibrated and evaluated at five rainforest sites (Mercado et al. 2009) to simulate gross primary productivity of 50 sites across the Amazon basin during the period 1980-2001. Such simulation differs from the ones performed with global vegetation models (Cox et al. 1998; Sitch et al. 2003) where i) single plant functional type parameter values are assigned and assumed invariant with environmental condition but also ii) these models use leaf N as a factor that limit photosynthesis. Instead, since leaf P may also limit photosynthesis of the tropical forest (Reich et al. 2009), we use a more specific description of photosynthetic capacity across the basin based on the model evaluation done in Mercado et al. (2009) in which canopy photosynthetic capacity is related to foliar P but also using the relationships derived between canopy photosynthesis and leaf nutrients (N and P) from measurements in tropical trees (Domingues et al.In review). A study of this kind can inform the global vegetation/climate community as to the need for variability in key model parameters in order to accurately simulate carbon fluxes across the Amazon basin. Baker, T. R., et al. 2004. Increasing biomass in Amazonian forest plots. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences 359 (1443):353-365. Phillips, O. L. et al. 2004. Pattern and process in Amazon tree turnover, 1976-2001. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences 359 (1443):381-407. Malhi, Y. et al. 2004. The above-ground coarse wood productivity of 104 Neotropical forest plots. Global Change Biology 10 (5):563-591. Mercado, L.M. et al. 2009. Impact of changes in diffuse radiation on the global land carbon sink. Nature 458 (7241), 1014. Cox, P. M. et al. 1998. A canopy conductance and photosynthesis model for use in a GCM land surface scheme. Journal of Hydrology 213 (1-4):79-9 Sitch, S. et al. 2003. Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model. Global Change Biology 9 (2):161-185. Reich B. R. et al. 2009. Leaf phosphorus influences the photosynhtesis-nitrogen relation: a cross-biome analysis of 314 species. Oecologia, doi 10.1007/s00442-009-1291-3. Domingues, T. et al. In review. Co-limitation of photosynthetic capacity by nitrogen and phosphorus along a precipitation gradient in West Africa. Plant Cell and Environment.

Quantitative retrieving forest ecological parameters based on remote sensing in Liping County of China

NASA Astrophysics Data System (ADS)

Tian, Qingjiu; Chen, Jing M.; Zheng, Guang; Xia, Xueqi; Chen, Junying

2006-09-01

Forest ecosystem is an important component of terrestrial ecosystem and plays an important role in global changes. Aboveground biomass (AGB) of forest ecosystem is an important factor in global carbon cycle studies. The purpose of this study was to retrieve the yearly Net Primary Productivity (NPP) of forest from the 8-days-interval MODIS-LAI images of a year and produce a yearly NPP distribution map. The LAI, DBH (diameter at breast height), tree height, and tree age field were measured in different 80 plots for Chinese fir, Masson pine, bamboo, broadleaf, mix forest in Liping County. Based on the DEM image and Landsat TM images acquired on May 14th, 2000, the geometric correction and terrain correction were taken. In addition, the "6S"model was used to gain the surface reflectance image. Then the correlation between Leaf Area Index (LAI) and Reduced Simple Ratio (RSR) was built. Combined with the Landcover map, forest stand map, the LAI, aboveground biomass, tree age map were produced respectively. After that, the 8-days- interval LAI images of a year, meteorology data, soil data, forest stand image and Landcover image were inputted into the BEPS model to get the NPP spatial distribution. At last, the yearly NPP spatial distribution map with 30m spatial resolution was produced. The values in those forest ecological parameters distribution maps were quite consistent with those of field measurements. So it's possible, feasible and time-saving to estimate forest ecological parameters at a large scale by using remote sensing.

Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration

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

Swetnam, Tyson L.; Brooks, Paul D.; Barnard, Holly R.

Mountains are vital to ecosystems and human society given their influence on global carbon and water cycles. Yet the extent to which topography regulates montane forest carbon uptake and storage remains poorly understood. To address this knowledge gap, we compared forest aboveground carbon loading to topographic metrics describing energy balance and water availability across three headwater catchments of the Boulder Creek Watershed, Colorado, USA. The catchments range from 1800 to 3500 m above mean sea level with 46–102 cm/yr mean annual precipitation and -1.2° to 12.3°C mean annual temperature. In all three catchments, we found mean forest carbon loading consistentlymore » increased from ridges (27 ± 19 Mg C ha) to valley bottoms (60 ± 28 Mg C ha). Low topographic positions held up to 185 ± 76 Mg C ha, more than twice the peak value of upper positions. Toe slopes fostered disproportionately high net carbon uptake relative to other topographic positions. Carbon storage was on average 20–40 Mg C ha greater on north to northeast aspects than on south to southwest aspects, a pattern most pronounced in the highest elevation, coldest and wettest catchment. Both the peak and mean aboveground carbon storage of the three catchments, crossing an 11°C range in temperature and doubling of local precipitation, defied the expectation of an optimal elevation-gradient climatic zone for net primary production. These results have important implications for models of forest sensitivity to climate change, as well as to predicted estimates of continental carbon reservoirs.« less

Temperate forest fragments maintain aboveground carbon stocks out to the forest edge despite changes in community composition.

PubMed

Ziter, Carly; Bennett, Elena M; Gonzalez, Andrew

2014-11-01

Edge effects are among the primary mechanisms by which forest fragmentation can influence the link between biodiversity and ecosystem processes, but relatively few studies have quantified these mechanisms in temperate regions. Carbon storage is an important ecosystem function altered by edge effects, with implications for climate change mitigation. Two opposing hypotheses suggest that aboveground carbon (AGC) stocks at the forest edge will (a) decrease due to increased tree mortality and compositional shifts towards smaller, lower wood density species (e.g., as seen in tropical systems) or, less often, (b) increase due to light/temperature-induced increases in diversity and productivity. We used field-based measurements, allometry, and mixed models to investigate the effects of proximity to the forest edge on AGC stocks, species richness, and community composition in 24 forest fragments in southern Quebec. We also asked whether fragment size or connectivity with surrounding forests altered these edge effects. AGC stocks remained constant across a 100 m edge-to-interior gradient in all fragment types, despite changes in tree community composition and stem density consistent with expectations of forest edge effects. We attribute this constancy primarily to compensatory effects of small trees at the forest edge; however, it is due in some cases to the retention of large trees at forest edges, likely a result of forest management. Our results suggest important differences between temperate and tropical fragments with respect to mechanisms linking biodiversity and AGC dynamics. Small temperate forest fragments may be valuable in conservation efforts based on maintaining biodiversity and multiple ecosystem services.

Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration

DOE PAGES

Swetnam, Tyson L.; Brooks, Paul D.; Barnard, Holly R.; ...

2017-04-21

Mountains are vital to ecosystems and human society given their influence on global carbon and water cycles. Yet the extent to which topography regulates montane forest carbon uptake and storage remains poorly understood. To address this knowledge gap, we compared forest aboveground carbon loading to topographic metrics describing energy balance and water availability across three headwater catchments of the Boulder Creek Watershed, Colorado, USA. The catchments range from 1800 to 3500 m above mean sea level with 46–102 cm/yr mean annual precipitation and -1.2° to 12.3°C mean annual temperature. In all three catchments, we found mean forest carbon loading consistentlymore » increased from ridges (27 ± 19 Mg C ha) to valley bottoms (60 ± 28 Mg C ha). Low topographic positions held up to 185 ± 76 Mg C ha, more than twice the peak value of upper positions. Toe slopes fostered disproportionately high net carbon uptake relative to other topographic positions. Carbon storage was on average 20–40 Mg C ha greater on north to northeast aspects than on south to southwest aspects, a pattern most pronounced in the highest elevation, coldest and wettest catchment. Both the peak and mean aboveground carbon storage of the three catchments, crossing an 11°C range in temperature and doubling of local precipitation, defied the expectation of an optimal elevation-gradient climatic zone for net primary production. These results have important implications for models of forest sensitivity to climate change, as well as to predicted estimates of continental carbon reservoirs.« less

Precipitation-productivity Relation in Grassland in Northern China: Investigations at Multiple Spatiotemporal Scales

NASA Astrophysics Data System (ADS)

Hu, Z.

2017-12-01

Climate change is predicted to cause dramatic variability in precipitation regime, not only in terms of change in annual precipitation amount, but also in precipitation seasonal distribution and precipitation event characteristics (high frenquency extrem precipitation, larger but fewer precipitation events), which combined to influence productivity of grassland in arid and semiarid regions. In this study, combining remote sensing products with in-situ measurements of aboveground net primary productivity (ANPP) and gross primary productivity (GPP) data from eddy covariance system in grassland of northern China, we quantified the effects of spatio-temporal vairation in precipitation on productivity from local sites to region scale. We found that, for an individual precipitation event, the duration of GPP-response to the individual precipitation event and the maximum absolute GPP response induced by the individual precipitation event increased linearly with the size of precipitation events. Comparison of the productivity-precipitation relationships between multi-sites determined that the predominant characteristics of precipitation events (PEC) that affected GPP differed remarkably between the water-limited temperate steppe and the temperature-limited alpine meadow. The number of heavy precipitation events (>10 mm d-1) was the most important PEC to impact GPP in the temperate steppe through affecting soil moisture at different soil profiles, while precipitation interval was the factor that affected GPP most in the alpine meadow via its effects on temperature. At the region scale, shape of ANPP-precipitation relationship varies with distinct spatial scales, and besides annual precipitation, precipitation seasonal distribution also has comparable impacts on spatial variation in ANPP. Temporal variability in ANPP was lower at both the dry and wet end, and peaked at a precipitation of 243.1±3.5mm, which is the transition region between typical steppe and desert steppe. Our work has important implications to obtain an advanced understanding of productivity-response of grassland ecosystems to altered precipitation regimes.

Necromass production: studies in undisturbed and logged Amazon Forests

Treesearch

MICHAEL PALACE; MICHAEL KELLER; HUDSON SILVA

2008-01-01

Necromass stocks account for up to 20% of carbon stored in tropical forests and have been estimated to be 14–19% of the annual aboveground carbon flux. Both stocks and fluxes of necromass are infrequently measured. In this study, we directly measured the production of fallen coarse necromass (>2 cm diameter) during 4.5 years using repeated surveys in undisturbed...

Assessing evidence for a pervasive alteration in tropical tree communities.

PubMed

Chave, Jérôme; Condit, Richard; Muller-Landau, Helene C; Thomas, Sean C; Ashton, Peter S; Bunyavejchewin, Sarayudh; Co, Leonardo L; Dattaraja, Handanakere S; Davies, Stuart J; Esufali, Shameema; Ewango, Corneille E N; Feeley, Kenneth J; Foster, Robin B; Gunatilleke, Nimal; Gunatilleke, Savitri; Hall, Pamela; Hart, Terese B; Hernández, Consuelo; Hubbell, Stephen P; Itoh, Akira; Kiratiprayoon, Somboon; Lafrankie, James V; Loo de Lao, Suzanne; Makana, Jean-Rémy; Noor, Md Nur Supardi; Kassim, Abdul Rahman; Samper, Cristián; Sukumar, Raman; Suresh, Hebbalalu S; Tan, Sylvester; Thompson, Jill; Tongco, Ma Dolores C; Valencia, Renato; Vallejo, Martha; Villa, Gorky; Yamakura, Takuo; Zimmerman, Jess K; Losos, Elizabeth C

2008-03-04

In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species over slow-growing ones. This pervasive alteration of mature tropical forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16-52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Aboveground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC ha(-1) y(-1), 95% confidence intervals [0.07, 0.39] MgC ha(-1) y(-1)), but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 [0.09, 0.55] % y(-1)) compared with the tree community as a whole (+0.15 % y(-1)); however, this significant trend was due to a single plot. Biomass of slow-growing species increased significantly when calculated over all plots (+0.21 [0.02, 0.37] % y(-1)), and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests.

Variation in stem mortality rates determines patterns of above-ground biomass in Amazonian forests: implications for dynamic global vegetation models.

PubMed

Johnson, Michelle O; Galbraith, David; Gloor, Manuel; De Deurwaerder, Hannes; Guimberteau, Matthieu; Rammig, Anja; Thonicke, Kirsten; Verbeeck, Hans; von Randow, Celso; Monteagudo, Abel; Phillips, Oliver L; Brienen, Roel J W; Feldpausch, Ted R; Lopez Gonzalez, Gabriela; Fauset, Sophie; Quesada, Carlos A; Christoffersen, Bradley; Ciais, Philippe; Sampaio, Gilvan; Kruijt, Bart; Meir, Patrick; Moorcroft, Paul; Zhang, Ke; Alvarez-Davila, Esteban; Alves de Oliveira, Atila; Amaral, Ieda; Andrade, Ana; Aragao, Luiz E O C; Araujo-Murakami, Alejandro; Arets, Eric J M M; Arroyo, Luzmila; Aymard, Gerardo A; Baraloto, Christopher; Barroso, Jocely; Bonal, Damien; Boot, Rene; Camargo, Jose; Chave, Jerome; Cogollo, Alvaro; Cornejo Valverde, Fernando; Lola da Costa, Antonio C; Di Fiore, Anthony; Ferreira, Leandro; Higuchi, Niro; Honorio, Euridice N; Killeen, Tim J; Laurance, Susan G; Laurance, William F; Licona, Juan; Lovejoy, Thomas; Malhi, Yadvinder; Marimon, Bia; Marimon, Ben Hur; Matos, Darley C L; Mendoza, Casimiro; Neill, David A; Pardo, Guido; Peña-Claros, Marielos; Pitman, Nigel C A; Poorter, Lourens; Prieto, Adriana; Ramirez-Angulo, Hirma; Roopsind, Anand; Rudas, Agustin; Salomao, Rafael P; Silveira, Marcos; Stropp, Juliana; Ter Steege, Hans; Terborgh, John; Thomas, Raquel; Toledo, Marisol; Torres-Lezama, Armando; van der Heijden, Geertje M F; Vasquez, Rodolfo; Guimarães Vieira, Ima Cèlia; Vilanova, Emilio; Vos, Vincent A; Baker, Timothy R

2016-12-01

Understanding the processes that determine above-ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. The relationship between stem mortality rates and AGB varies among different regions of Amazonia, indicating that variation in wood density and height/diameter relationships also influences AGB. In contrast to previous findings, we find that woody NPP is not correlated with stem mortality rates and is weakly positively correlated with AGB. Across the four models, basin-wide average AGB is similar to the mean of the observations. However, the models consistently overestimate woody NPP and poorly represent the spatial patterns of both AGB and woody NPP estimated using plot data. In marked contrast to the observations, DGVMs typically show strong positive relationships between woody NPP and AGB. Resolving these differences will require incorporating forest size structure, mechanistic models of stem mortality and variation in functional composition in DGVMs. © 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Contrasting Responses of Ecosystem Carbon Gain (Input) and Soil Carbon Efflux (Output) to Warming and Drought Across a European Aridity Gradient

NASA Astrophysics Data System (ADS)

Cosby, J.; Reinsch, S.; Koehler, E.; de Dato, G.; Estiarte, M.; Guidolotti, G.; Kovacs-Lang, E.; Dukes, J.; Kröel-Dulay, G.; Larsen, K. S.; Lellei-Kovács, E.; Liberati, D.; Ransijn, J.; Schmidt, I. K.; Smith, A. R.; Sowerby, A.; Emmett, B.

2015-12-01

Understanding the relationship between aboveground and belowground processes are crucial to understand if we are to forecast feedbacks between terrestrial carbon (C) dynamics and future climate. To test if climate induced changes in annual aboveground net primary production (ANPP) will drive changes in C loss by soil respiration (Rs) we integrated data across a European temperature and precipitation gradient. Six European shrublands were exposed to year-round, night time warming (+1.5 oC) or repeated drought (-30% annual rain) during the plants growth season for over a decade, using an identical experimental approach. As a result, drought reduced ecosystem C gain as ANPP by 50% (compared to an untreated control) at the driest xeric site with effects reducing in intensity across the aridity gradient to a 15% ANPP-C gain at the wettest hydric site (slope=1.2, R2=0.76). In contrast, reductions in Rs-C loss were of a lower magnitude (0-15%) and increased in intensity across the aridity gradient (slope=-0.44, R2=0.76) if the hydric site was excluded. These results suggest (i) above and belowground C fluxes responses do not track each other in response to drought and (ii) whilst ANPP at our hydric sites follows that predicted from an aridity gradient, Rs responses did not. Results from the warming treatments were generally of lower magnitude and opposite direction indicating different mechanisms were driving responses. Overall, these results suggest that ANPP is more sensitive than Rs to climate stresses and soil respiration C fluxes are not predictable from changes in plant productivity. Indirect effects on soil properties and/or microbial communities need to be explored. As we observed no acclimation of either ANPP or Rs after over a decade of treatments, feedbacks between the terrestrial C cycle and climate may not weaken over decadal timescales at larger, continental scales.

Species richness alters spatial nutrient heterogeneity effects on above-ground plant biomass.

PubMed

Xi, Nianxun; Zhang, Chunhui; Bloor, Juliette M G

2017-12-01

Previous studies have suggested that spatial nutrient heterogeneity promotes plant nutrient capture and growth. However, little is known about how spatial nutrient heterogeneity interacts with key community attributes to affect plant community production. We conducted a meta-analysis to investigate how nitrogen heterogeneity effects vary with species richness and plant density. Effect size was calculated using the natural log of the ratio in plant biomass between heterogeneous and homogeneous conditions. Effect sizes were significantly above zero, reflecting positive effects of spatial nutrient heterogeneity on community production. However, species richness decreased the magnitude of heterogeneity effects on above-ground biomass. The magnitude of heterogeneity effects on below-ground biomass did not vary with species richness. Moreover, we detected no modification in heterogeneity effects with plant density. Our results highlight the importance of species richness for ecosystem function. Asynchrony between above- and below-ground responses to spatial nutrient heterogeneity and species richness could have significant implications for biotic interactions and biogeochemical cycling in the long term. © 2017 The Author(s).

A native plant competitor mediates the impact of above- and belowground damage on an invasive tree.

PubMed

Carrillo, Juli; Siemann, Evan

2016-10-01

Plant competition may mediate the impacts of herbivory on invasive plant species through effects on plant growth and defense. This may predictably depend on whether herbivory occurs above or below ground and on relative plant competitive ability. We simulated the potential impact of above- or belowground damage by biocontrol agents on the growth of a woody invader (Chinese tallow tree, Triadica sebifera) through artificial herbivory, with or without competition with a native grass, little bluestem (Schizachyrium scoparium). We measured two defense responses of Triadica through quantifying constitutive and induced extrafloral nectar production and tolerance of above- and belowground damage (root and shoot biomass regrowth). We examined genetic variation in plant growth and defense across native (China) and invasive (United States) Triadica populations. Without competition, aboveground damage had a greater impact than belowground damage on Triadica performance, whereas with competition and above- and belowground damage impacted Triadica similarly. Whole plant tolerance to damage below ground was negatively associated with tolerance to grass competitors indicating tradeoffs in the ability to tolerate herbivory vs. compete. Competition reduced investment in defensive extrafloral nectar (EFN) production. Aboveground damage inhibited rather than induced EFN production while belowground plant damage did not impact aboveground nectar production. We found some support for the evolution of increased competitive ability hypothesis for invasive plants as United States plants were larger than native China plants and were more plastic in their response to biotic stressors than China plants (they altered their root to shoot ratios dependent on herbivory and competition treatments). Our results indicate that habitat type and the presence of competitors may be a larger determinant of herbivory impact than feeding mode and suggest that integrated pest management strategies including competitive dynamics of recipient communities should be incorporated into biological control agent evaluation at earlier stages. © 2016 by the Ecological Society of America.

Aboveground carbon in Quebec forests: stock quantification at the provincial scale and assessment of temperature, precipitation and edaphic properties effects on the potential stand-level stocking

PubMed Central

Houle, Daniel; Ouimet, Rock; Lambert, Marie-Claude; Logan, Travis

2016-01-01

Biological carbon sequestration by forest ecosystems plays an important role in the net balance of greenhouse gases, acting as a carbon sink for anthropogenic CO2 emissions. Nevertheless, relatively little is known about the abiotic environmental factors (including climate) that control carbon storage in temperate and boreal forests and consequently, about their potential response to climate changes. From a set of more than 94,000 forest inventory plots and a large set of spatial data on forest attributes interpreted from aerial photographs, we constructed a fine-resolution map (∼375 m) of the current carbon stock in aboveground live biomass in the 435,000 km2 of managed forests in Quebec, Canada. Our analysis resulted in an area-weighted average aboveground carbon stock for productive forestland of 37.6 Mg ha−1, which is lower than commonly reported values for similar environment. Models capable of predicting the influence of mean annual temperature, annual precipitation, and soil physical environment on maximum stand-level aboveground carbon stock (MSAC) were developed. These models were then used to project the future MSAC in response to climate change. Our results indicate that the MSAC was significantly related to both mean annual temperature and precipitation, or to the interaction of these variables, and suggest that Quebec’s managed forests MSAC may increase by 20% by 2041–2070 in response to climate change. Along with changes in climate, the natural disturbance regime and forest management practices will nevertheless largely drive future carbon stock at the landscape scale. Overall, our results allow accurate accounting of carbon stock in aboveground live tree biomass of Quebec’s forests, and provide a better understanding of possible feedbacks between climate change and carbon storage in temperate and boreal forests. PMID:26966680

Effects of 10-Year Management Regimes on the Soil Seed Bank in Saline-Alkaline Grassland

PubMed Central

Ma, Hongyuan; Yang, Haoyu; Liang, Zhengwei; Ooi, Mark K. J.

2015-01-01

Background Management regimes for vegetation restoration of degraded grasslands can significantly affect the process of ecological succession. However, few studies have focused on variation in the soil seed bank during vegetation restoration under different management regimes, especially in saline-alkaline grassland habitats. Our aim was to provide insights into the ecological effects of grassland management regimes on soil seed bank composition and vegetation establishment in mown, fenced, transplanted and natural grassland sites, all dominated by the perennial rhizomatous grass Leymus chinensis. Methodology We studied species composition and diversity in both the soil seed bank and aboveground vegetation in differently managed grasslands in Northeast China. An NMDS (nonmetric multidimensional scaling) was used to evaluate the relationship between species composition, soil seed banks, aboveground vegetation and soil properties. Principal Findings Fenced and mown grassland sites had high density and species richness in both the soil seed bank and aboveground vegetation. The Transplanted treatment exhibited the highest vegetation growth and seed production of the target species L. chinensis. Seeds of L. chinensis in the soil occurred only in transplanted and natural grassland. Based on the NMDS analysis, the number of species in both the soil seed bank and aboveground vegetation were significantly related to soil Na+, Cl-, RSC (residual sodium carbonate), alkalinity, ESP (exchangeable sodium percentage) and AP (available phosphorus). Conclusions Soil seed bank composition and diversity in the saline-alkaline grassland were significantly affected by the management regimes implemented, and were also significantly related to the aboveground vegetation and several soil properties. Based on vegetative growth, reproductive output and maintenance of soil seed bank, the transplanting was identified as the most effective method for relatively rapid restoration of the target species L. chinensis. This approach could be beneficial for the restoration of dominant species in a wide range of degraded grassland ecosystems. PMID:25902145

ENZYMES FOR ENHANCING BIOREMEDIATION OF PETROLEUM- CONTAMINATED SOILS: A BRIEF REVIEW

EPA Science Inventory

During the 1950s and 1960s, hundreds of thousands of underground storage tanks (and above-ground storage tanks) containing petroleum products and hazardous chemicals were installed. Many of these tanks either have been abandoned or have exceeded their useful lives and are leakin...

DIRECT ESTIMATION OF ABOVEGROUND FOREST PRODUCTIVITY THROUGH HYPERSPECTRAL REMOTE SENSING OF CANOPY NITROGEN. (R825865)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Flowering in grassland predicted by CO2 and resource effects on species aboveground biomass

USDA-ARS?s Scientific Manuscript database

Ongoing enrichment of atmospheric CO2 concentration may increase plant community productivity by changing plant community composition through direct and indirect effects on light, water, or nutrient availability. CO2 enrichment has been predicted to reduce plant reproductive allocation in herbaceou...

Net carbon exchange across the Arctic tundra-boreal forest transition in Alaska 1981-2000

USGS Publications Warehouse

Thompson, Catharine Copass; McGuire, A.D.; Clein, Joy S.; Chapin, F. S.; Beringer, J.

2006-01-01

Shifts in the carbon balance of high-latitude ecosystems could result from differential responses of vegetation and soil processes to changing moisture and temperature regimes and to a lengthening of the growing season. Although shrub expansion and northward movement of treeline should increase carbon inputs, the effects of these vegetation changes on net carbon exchange have not been evaluated. We selected low shrub, tall shrub, and forest tundra sites near treeline in northwestern Alaska, representing the major structural transitions expected in response to warming. In these sites, we measured aboveground net primary production (ANPP) and vegetation and soil carbon and nitrogen pools, and used these data to parameterize the Terrestrial Ecosystem Model. We simulated the response of carbon balance components to air temperature and precipitation trends during 1981-2000. In areas experiencing warmer and dryer conditions, Net Primary Production (NPP) decreased and heterotrophic respiration (R H ) increased, leading to a decrease in Net Ecosystem Production (NEP). In warmer and wetter conditions NPP increased, but the response was exceeded by an increase in R H ; therefore, NEP also decreased. Lastly, in colder and wetter regions, the increase in NPP exceeded a small decline in R H , leading to an increase in NEP. The net effect for the region was a slight gain in ecosystem carbon storage over the 20 year period. This research highlights the potential importance of spatial variability in ecosystem responses to climate change in assessing the response of carbon storage in northern Alaska over the last two decades. ?? Springer 2005.

Long-term monitoring at multiple trophic levels suggests heterogeneity in responses to climate change in the Canadian Arctic tundra

PubMed Central

Gauthier, Gilles; Bêty, Joël; Cadieux, Marie-Christine; Legagneux, Pierre; Doiron, Madeleine; Chevallier, Clément; Lai, Sandra; Tarroux, Arnaud; Berteaux, Dominique

2013-01-01

Arctic wildlife is often presented as being highly at risk in the face of current climate warming. We use the long-term (up to 24 years) monitoring records available on Bylot Island in the Canadian Arctic to examine temporal trends in population attributes of several terrestrial vertebrates and in primary production. Despite a warming trend (e.g. cumulative annual thawing degree-days increased by 37% and snow-melt date advanced by 4–7 days over a 23-year period), we found little evidence for changes in the phenology, abundance or productivity of several vertebrate species (snow goose, foxes, lemmings, avian predators and one passerine). Only primary production showed a response to warming (annual above-ground biomass of wetland graminoids increased by 123% during this period). We nonetheless found evidence for potential mismatches between herbivores and their food plants in response to warming as snow geese adjusted their laying date by only 3.8 days on average for a change in snow-melt of 10 days, half of the corresponding adjustment shown by the timing of plant growth (7.1 days). We discuss several reasons (duration of time series, large annual variability, amplitude of observed climate change, nonlinear dynamic or constraints imposed by various rate of warming with latitude in migrants) to explain the lack of response by herbivores and predators to climate warming at our study site. We also show how length and intensity of monitoring could affect our ability to detect temporal trends and provide recommendations for future monitoring. PMID:23836788

Net primary productivity and rain-use efficiency as affected by warming, altered precipitation, and clipping in a mixed-grass prairie.

PubMed

Xu, Xia; Sherry, Rebecca A; Niu, Shuli; Li, Dejun; Luo, Yiqi

2013-09-01

Grassland productivity in response to climate change and land use is a global concern. In order to explore the effects of climate change and land use on net primary productivity (NPP), NPP partitioning [fBNPP , defined as the fraction of belowground NPP (BNPP) to NPP], and rain-use efficiency (RUE) of NPP, we conducted a field experiment with warming (+3 °C), altered precipitation (double and half), and annual clipping in a mixed-grass prairie in Oklahoma, USA since July, 2009. Across the years, warming significantly increased BNPP, fBNPP , and RUEBNPP by an average of 11.6%, 2.8%, and 6.6%, respectively. This indicates that BNPP was more sensitive to warming than aboveground NPP (ANPP) since warming did not change ANPP and RUEANPP much. Double precipitation stimulated ANPP, BNPP, and NPP but suppressed RUEANPP , RUEBNPP , and RUENPP while half precipitation decreased ANPP, BNPP, and NPP but increased RUEANPP , RUEBNPP , and RUENPP . Clipping interacted with altered precipitation in impacting RUEANPP , RUEBNPP , and RUENPP , suggesting land use could confound the effects of precipitation changes on ecosystem processes. Soil moisture was found to be a main factor in regulating variation in ANPP, BNPP, and NPP while soil temperature was the dominant factor influencing fBNPP . These findings suggest that BNPP is critical point to future research. Additionally, results from single-factor manipulative experiments should be treated with caution due to the non-additive interactive effects of warming with altered precipitation and land use (clipping). © 2013 John Wiley & Sons Ltd.

NGEE Arctic Plant Traits: Plant Biomass and Traits, Kougarok Road Mile Marker 64, Seward Peninsula, Alaska, beginning 2016

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

Verity Salmon; Colleen Iversen; Amy Breen

Data includes aboveground biomass and plant traits for destructive harvests performed at the Kougarok hill slope located at Kougarok Road, Mile Marker 64. Data collection began in July 2016. Aboveground biomass and aboveground plant traits are available for shrub and understory species found in vegetation plots. Paired observations of aboveground and belowground plant traits are available for select shrub species.

[Effects of drought stress on growth and water use efficiency of two medicinal plants].

PubMed

Chen, Ping; Meng, Ping; Zhang, Jin-Song; He, Chun-Xia; Jia, Chang-Rong; Li, Jian-Zhong

2014-05-01

Growth characteristics, stable carbon isotope discrimination (Delta13C), water use efficiency (WUE), and their correlation of Cassia obtusifolia and Isatis indigotica were measured at three soil water levels, i. e., 30%, 50% and 75% of field water holding capacity (FWHC), and at three growth stages. The growth indices of the two medicinal plants at 75% of FWHC were higher than those at 30% and 50% of FWHC, suggesting that the two medicinal plants could obtain high production under sufficient moisture condition. The Delta13C(A) (aboveground biomass-based Delta13C) and Delta13C(T) (total biomass-based Delta13C) decreased, and the WUE(A) (aboveground biomass-based WUE) and WUE(T) (total biomass-based WUE) of C. obtusifolia and I. indigotica increased with the increasing degree of drought stress. The growth indices of the two medicinal plants had little difference in the different water treatments, which indicated that the two medicinal plants were insensitive to drought stress. Water use efficiency of I. indigotica had significant negative relationships with aboveground biomass and total biomass, while that of C. obtusifolia had a significant positive correlation with the root/shoot ratio.

[Spatial distribution of aboveground biomass of shrubs in Tianlaochi catchment of the Qilian Mountains].

PubMed

Liang, Bei; Di, Li; Zhao, Chuan-Yan; Peng, Shou-Zhang; Peng, Huan-Hua; Wang, Chao

2014-02-01

This study estimated the spatial distribution of the aboveground biomass of shrubs in the Tianlaochi catchment of Qilian Mountains based on the field survey and remote sensing data. A relationship model of the aboveground biomass and its feasibly measured factors (i. e. , canopy perimeter and plant height) was built. The land use was classified by object-oriented technique with the high resolution image (GeoEye-1) of the study area, and the distribution of shrub coverage was extracted. Then the total aboveground biomass of shrubs in the study area was estimated by the relationship model with the distribution of shrub coverage. The results showed that the aboveground biomass of shrubs in the study area was 1.8 x 10(3) t and the aboveground biomass per unit area was 1598.45 kg x m(-2). The distribution of shrubs mainly was at altitudes of 3000-3700 m, and the aboveground biomass of shrubs on the sunny slope (1.15 x 10(3) t) was higher than that on the shady slope (0.65 x 10(3) t).

Height-related trends in leaf xylem anatomy and shoot hydraulic characteristics in a tall conifer: safety versus efficiency in water transport

Treesearch

D.R. Woodruff; F.C. Meinzer; B. Lachenbruch

2008-01-01

Growth and aboveground biomass accumulation follow a common pattern as tree size increases, with productivity peaking when leaf area reaches its maximum and then declining as tree age and size increase. Age- and size-related declines in forest productivity are major considerations in setting the rotational age of commercial forests, and relate to issues of carbon...

C3 and C4 biomass allocation responses to elevated CO2 and nitrogen: contrasting resource capture strategies

USGS Publications Warehouse

White, K.P.; Langley, J.A.; Cahoon, D.R.; Megonigal, J.P.

2012-01-01

Plants alter biomass allocation to optimize resource capture. Plant strategy for resource capture may have important implications in intertidal marshes, where soil nitrogen (N) levels and atmospheric carbon dioxide (CO2) are changing. We conducted a factorial manipulation of atmospheric CO2 (ambient and ambient + 340 ppm) and soil N (ambient and ambient + 25 g m-2 year-1) in an intertidal marsh composed of common North Atlantic C3 and C4 species. Estimation of C3 stem turnover was used to adjust aboveground C3 productivity, and fine root productivity was partitioned into C3-C4 functional groups by isotopic analysis. The results suggest that the plants follow resource capture theory. The C3 species increased aboveground productivity under the added N and elevated CO2 treatment (P 2 alone. C3 fine root production decreased with added N (P 2 (P = 0.0481). The C4 species increased growth under high N availability both above- and belowground, but that stimulation was diminished under elevated CO2. The results suggest that the marsh vegetation allocates biomass according to resource capture at the individual plant level rather than for optimal ecosystem viability in regards to biomass influence over the processes that maintain soil surface elevation in equilibrium with sea level.

Silicon availability modifies nutrient use efficiency and content, C:N:P stoichiometry, and productivity of winter wheat (Triticum aestivum L.)

NASA Astrophysics Data System (ADS)

Neu, Silke; Schaller, Jörg; Dudel, E. Gert

2017-01-01

Silicon (Si) is known as beneficial element for graminaceous plants. The importance of Si for plant functioning of cereals was recently emphasized. However, about the effect of Si availability on biomass production, grain yield, nutrient status and nutrient use efficiency for wheat (Triticum aestivum L.), as one of the most important crop plants worldwide, less is known so far. Consequently, we assessed the effect of a broad range of supply levels of amorphous SiO2 on wheat plant performance. Our results revealed that Si is readily taken up and accumulated basically in aboveground vegetative organs. Carbon (C) and phosphorus (P) status of plants were altered in response to varying Si supply. In bulk straw biomass C concentration decreased with increasing Si supply, while P concentration increased from slight limitation towards optimal nutrition. Thereby, aboveground biomass production increased at low to medium supply levels of silica whereas grain yield increased at medium supply level only. Nutrient use efficiency was improved by Si insofar that biomass production was enhanced at constant nitrogen (N) status of substrate and plants. Consequently, our findings imply fundamental influences of Si on C turnover, P availability and nitrogen use efficiency for wheat as a major staple crop.

Phenological bud bank development of Bouteloua gracilis, Hesperostipa comata, and Pascopyrum smithii during drought in the Northern Great Plains

USDA-ARS?s Scientific Manuscript database

Vegetative reproduction in rangelands relies on tiller recruitment from belowground bud banks. Improved understanding of species-specific bud production and phenology would facilitate timing of aboveground management strategies. Twelve individual plants of the warm season grass (Bouteloua gracilis...

Farming strategies to feed people, facilitate essential soil services, and fuel the economy

USDA-ARS?s Scientific Manuscript database

Perennial cellulosic biomass and food crop residues are important on-farm resources, which have become potential valuable sources of income as a harvestable commodity contributing to biofuel production demands. Inputs of carbon embedded in above-ground plant biomass are a key biological energy sourc...

Switchgrass cultivars alter microbial contribution to deep soil C in Nebraska

USDA-ARS?s Scientific Manuscript database

Switchgrass (Panicum virgatum L.) is a C4, perennial grass that is being developed as a bioenergy crop for the United States. While aboveground biomass production is well documented for switchgrass ecotypes (lowland, upland) and cultivars, there has been little focus on the impact of plant belowgro...

Aboveground tree biomass for Pinus ponderosa in northeastern California

Treesearch

Martin W. Ritchie; Jianwei Zhang; Todd A. Hamilton

2013-01-01

Forest managers need accurate biomass equations to plan thinning for fuel reduction or energy production. Estimates of carbon sequestration also rely upon such equations. The current allometric equations for ponderosa pine (Pinus ponderosa) commonly employed for California forests were developed elsewhere, and are often applied without consideration potential for...

40 CFR 112.1 - General applicability.

Code of Federal Regulations, 2010 CFR

2010-07-01

.... The production, recovery, or recycling of oil is not wastewater treatment for purposes of this... aboveground storage container for purposes of this part. (c) As provided in section 313 of the Clean Water Act... facility is 42,000 U.S. gallons or less of oil. For purposes of this exemption, the completely buried...

40 CFR 112.1 - General applicability.

Code of Federal Regulations, 2011 CFR

2011-07-01

.... The production, recovery, or recycling of oil is not wastewater treatment for purposes of this... aboveground storage container for purposes of this part. (c) As provided in section 313 of the Clean Water Act... facility is 42,000 U.S. gallons or less of oil. For purposes of this exemption, the completely buried...

40 CFR 112.1 - General applicability.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... The production, recovery, or recycling of oil is not wastewater treatment for purposes of this... aboveground storage container for purposes of this part. (c) As provided in section 313 of the Clean Water Act... facility is 42,000 U.S. gallons or less of oil. For purposes of this exemption, the completely buried...

40 CFR 112.1 - General applicability.

Code of Federal Regulations, 2012 CFR

2012-07-01

.... The production, recovery, or recycling of oil is not wastewater treatment for purposes of this... aboveground storage container for purposes of this part. (c) As provided in section 313 of the Clean Water Act... facility is 42,000 U.S. gallons or less of oil. For purposes of this exemption, the completely buried...

Response of aboveground carbon balance to long-term, experimental enhancements in precipitation seasonality is contingent on plant community type in cold-desert rangelands

USGS Publications Warehouse

McAbee, Kathryn; Reinhardt, Keith; Germino, Matthew; Bosworth, Andrew

2017-01-01

Semi-arid rangelands are important carbon (C) pools at global scales. However, the degree of net C storage or release in water-limited systems is a function of precipitation amount and timing, as well as plant community composition. In northern latitudes of western North America, C storage in cold-desert ecosystems could increase with boosts in wintertime precipitation, in which climate models predict, due to increases in wintertime soil water storage that enhance summertime productivity. However, there are few long-term, manipulative field-based studies investigating how rangelands will respond to altered precipitation amount or timing. We measured aboveground C pools and fluxes at leaf, soil, and ecosystem scales over a single growing season in plots that had 200 mm of supplemental precipitation added in either winter or summer for the past 21 years, in shrub- and exotic-bunchgrass-dominated garden plots. At our cold-desert site (298 mm precipitation during the study year), we hypothesized that increased winter precipitation would stimulate the aboveground C uptake and storage relative to ambient conditions, especially in plots containing shrubs. Our hypotheses were generally supported: ecosystem C uptake and long-term biomass accumulation were greater in winter- and summer-irrigated plots compared to control plots in both vegetation communities. However, substantial increases in the aboveground biomass occurred only in winter-irrigated plots that contained shrubs. Our findings suggest that increases in winter precipitation will enhance C storage of this widespread ecosystem, and moreso in shrub- compared to grass-dominated communities.

Response of aboveground carbon balance to long-term, experimental enhancements in precipitation seasonality is contingent on plant community type in cold-desert rangelands.

PubMed

McAbee, Kathryn; Reinhardt, Keith; Germino, Matthew J; Bosworth, Andrew

2017-03-01

Semi-arid rangelands are important carbon (C) pools at global scales. However, the degree of net C storage or release in water-limited systems is a function of precipitation amount and timing, as well as plant community composition. In northern latitudes of western North America, C storage in cold-desert ecosystems could increase with boosts in wintertime precipitation, in which climate models predict, due to increases in wintertime soil water storage that enhance summertime productivity. However, there are few long-term, manipulative field-based studies investigating how rangelands will respond to altered precipitation amount or timing. We measured aboveground C pools and fluxes at leaf, soil, and ecosystem scales over a single growing season in plots that had 200 mm of supplemental precipitation added in either winter or summer for the past 21 years, in shrub- and exotic-bunchgrass-dominated garden plots. At our cold-desert site (298 mm precipitation during the study year), we hypothesized that increased winter precipitation would stimulate the aboveground C uptake and storage relative to ambient conditions, especially in plots containing shrubs. Our hypotheses were generally supported: ecosystem C uptake and long-term biomass accumulation were greater in winter- and summer-irrigated plots compared to control plots in both vegetation communities. However, substantial increases in the aboveground biomass occurred only in winter-irrigated plots that contained shrubs. Our findings suggest that increases in winter precipitation will enhance C storage of this widespread ecosystem, and moreso in shrub- compared to grass-dominated communities.

Plant diversity and functional groups affect Si and Ca pools in aboveground biomass of grassland systems.

PubMed

Schaller, Jörg; Roscher, Christiane; Hillebrand, Helmut; Weigelt, Alexandra; Oelmann, Yvonne; Wilcke, Wolfgang; Ebeling, Anne; Weisser, Wolfgang W

2016-09-01

Plant diversity is an important driver of nitrogen and phosphorus stocks in aboveground plant biomass of grassland ecosystems, but plant diversity effects on other elements also important for plant growth are less understood. We tested whether plant species richness, functional group richness or the presence/absence of particular plant functional groups influences the Si and Ca concentrations (mmol g(-1)) and stocks (mmol m(-2)) in aboveground plant biomass in a large grassland biodiversity experiment (Jena Experiment). In the experiment including 60 temperate grassland species, plant diversity was manipulated as sown species richness (1, 2, 4, 8, 16) and richness and identity of plant functional groups (1-4; grasses, small herbs, tall herbs, legumes). We found positive species richness effects on Si as well as Ca stocks that were attributable to increased biomass production. The presence of particular functional groups was the most important factor explaining variation in aboveground Si and Ca stocks (mmol m(-2)). Grass presence increased the Si stocks by 140 % and legume presence increased the Ca stock by 230 %. Both the presence of specific plant functional groups and species diversity altered Si and Ca stocks, whereas Si and Ca concentration were affected mostly by the presence of specific plant functional groups. However, we found a negative effect of species diversity on Si and Ca accumulation, by calculating the deviation between mixtures and mixture biomass proportions, but in monoculture concentrations. These changes may in turn affect ecosystem processes such as plant litter decomposition and nutrient cycling in grasslands.

Soil nutrient additions increase invertebrate herbivore abundances, but not herbivory, across three grassland systems.

PubMed

La Pierre, Kimberly J; Smith, Melinda D

2016-02-01

Resource availability may influence invertebrate communities, with important consequences for ecosystem function, such as biomass production. We assessed: (1) the effects of experimental soil nutrient additions on invertebrate abundances and feeding rates and (2) the resultant changes in the effects of invertebrates on aboveground plant biomass at three grassland sites spanning the North American Central Plains, across which plant tissue chemistry and biomass vary. Invertebrate communities and rates of herbivory were sampled within a long-term nutrient-addition experiment established at each site along the broad Central Plains precipitation gradient. Additionally, the effects of invertebrates on aboveground plant biomass were determined under ambient and elevated nutrient conditions. At the more mesic sites, invertebrate herbivore abundances increased and their per capita rate of herbivory decreased with nutrient additions. In contrast, at the semi-arid site where plant biomass is low and plant nutrient concentrations are high, invertebrate herbivore abundances did not vary and per capita rates of herbivory increased with nutrient additions. No change in the effect of invertebrate herbivores on aboveground plant biomass was observed at any of the sites. In sum, nutrient additions induced shifts in both plant biomass and leaf nutrient content, which altered invertebrate abundances and feeding rate. However, due to the inverse relationship between changes in herbivore abundance and per capita rates of herbivory, nutrient additions did not alter the effect of invertebrates on aboveground biomass. Overall, we suggest that this inverse response of herbivore abundance and per capita feeding rate may buffer ecosystems against changes in invertebrate damage in response to fluctuations in nutrient levels.

A simple method for estimating gross carbon budgets for vegetation in forest ecosystems.

PubMed

Ryan, Michael G.

1991-01-01

Gross carbon budgets for vegetation in forest ecosystems are difficult to construct because of problems in scaling flux measurements made on small samples over short periods of time and in determining belowground carbon allocation. Recently, empirical relationships have been developed to estimate total belowground carbon allocation from litterfall, and maintenance respiration from tissue nitrogen content. I outline a method for estimating gross carbon budgets using these empirical relationships together with data readily available from ecosystem studies (aboveground wood and canopy production, aboveground wood and canopy biomass, litterfall, and tissue nitrogen contents). Estimates generated with this method are compared with annual carbon fixation estimates from the Forest-BGC model for a lodgepole pine (Pinus contorta Dougl.) and a Pacific silver fir (Abies amabilis Dougl.) chronosequence.

Degraded tropical rain forests possess valuable carbon storage opportunities in a complex, forested landscape.

PubMed

Alamgir, Mohammed; Campbell, Mason J; Turton, Stephen M; Pert, Petina L; Edwards, Will; Laurance, William F

2016-07-20

Tropical forests are major contributors to the terrestrial global carbon pool, but this pool is being reduced via deforestation and forest degradation. Relatively few studies have assessed carbon storage in degraded tropical forests. We sampled 37,000 m(2) of intact rainforest, degraded rainforest and sclerophyll forest across the greater Wet Tropics bioregion of northeast Australia. We compared aboveground biomass and carbon storage of the three forest types, and the effects of forest structural attributes and environmental factors that influence carbon storage. Some degraded forests were found to store much less aboveground carbon than intact rainforests, whereas others sites had similar carbon storage to primary forest. Sclerophyll forests had lower carbon storage, comparable to the most heavily degraded rainforests. Our findings indicate that under certain situations, degraded forest may store as much carbon as intact rainforests. Strategic rehabilitation of degraded forests could enhance regional carbon storage and have positive benefits for tropical biodiversity.

Degraded tropical rain forests possess valuable carbon storage opportunities in a complex, forested landscape

PubMed Central

Alamgir, Mohammed; Campbell, Mason J.; Turton, Stephen M.; Pert, Petina L.; Edwards, Will; Laurance, William F.

2016-01-01

Tropical forests are major contributors to the terrestrial global carbon pool, but this pool is being reduced via deforestation and forest degradation. Relatively few studies have assessed carbon storage in degraded tropical forests. We sampled 37,000 m2 of intact rainforest, degraded rainforest and sclerophyll forest across the greater Wet Tropics bioregion of northeast Australia. We compared aboveground biomass and carbon storage of the three forest types, and the effects of forest structural attributes and environmental factors that influence carbon storage. Some degraded forests were found to store much less aboveground carbon than intact rainforests, whereas others sites had similar carbon storage to primary forest. Sclerophyll forests had lower carbon storage, comparable to the most heavily degraded rainforests. Our findings indicate that under certain situations, degraded forest may store as much carbon as intact rainforests. Strategic rehabilitation of degraded forests could enhance regional carbon storage and have positive benefits for tropical biodiversity. PMID:27435389

Degraded tropical rain forests possess valuable carbon storage opportunities in a complex, forested landscape

NASA Astrophysics Data System (ADS)

Alamgir, Mohammed; Campbell, Mason J.; Turton, Stephen M.; Pert, Petina L.; Edwards, Will; Laurance, William F.

2016-07-01

Tropical forests are major contributors to the terrestrial global carbon pool, but this pool is being reduced via deforestation and forest degradation. Relatively few studies have assessed carbon storage in degraded tropical forests. We sampled 37,000 m2 of intact rainforest, degraded rainforest and sclerophyll forest across the greater Wet Tropics bioregion of northeast Australia. We compared aboveground biomass and carbon storage of the three forest types, and the effects of forest structural attributes and environmental factors that influence carbon storage. Some degraded forests were found to store much less aboveground carbon than intact rainforests, whereas others sites had similar carbon storage to primary forest. Sclerophyll forests had lower carbon storage, comparable to the most heavily degraded rainforests. Our findings indicate that under certain situations, degraded forest may store as much carbon as intact rainforests. Strategic rehabilitation of degraded forests could enhance regional carbon storage and have positive benefits for tropical biodiversity.

Ecosystem responses to warming and watering in typical and desert steppes.

PubMed

Xu, Zhenzhu; Hou, Yanhui; Zhang, Lihua; Liu, Tao; Zhou, Guangsheng

2016-10-10

Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two years, whereas warming manipulation had no significant effect. The soil microbial biomass carbon (MBC) and the soil respiration (SR) were increased by watering in both steppes, but the SR was significantly decreased by warming in the desert steppe only. The inorganic nitrogen components varied irregularly, with generally lower levels in the desert steppe. The belowground traits of soil total organic carbon (TOC) and the MBC were more closely associated with the ANPP in the desert than in the typical steppes. The results showed that the desert steppe with lower productivity may respond strongly to precipitation changes, particularly with warming, highlighting the positive effect of adding water with warming. Our study implies that the habitat- and year-specific responses to warming and watering should be considered when predicting an ecosystem's functional responses under climate change scenarios.

Ecosystem responses to warming and watering in typical and desert steppes

PubMed Central

Xu, Zhenzhu; Hou, Yanhui; Zhang, Lihua; Liu, Tao; Zhou, Guangsheng

2016-01-01

Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two years, whereas warming manipulation had no significant effect. The soil microbial biomass carbon (MBC) and the soil respiration (SR) were increased by watering in both steppes, but the SR was significantly decreased by warming in the desert steppe only. The inorganic nitrogen components varied irregularly, with generally lower levels in the desert steppe. The belowground traits of soil total organic carbon (TOC) and the MBC were more closely associated with the ANPP in the desert than in the typical steppes. The results showed that the desert steppe with lower productivity may respond strongly to precipitation changes, particularly with warming, highlighting the positive effect of adding water with warming. Our study implies that the habitat- and year-specific responses to warming and watering should be considered when predicting an ecosystem’s functional responses under climate change scenarios. PMID:27721480

Ecosystem responses to warming and watering in typical and desert steppes

NASA Astrophysics Data System (ADS)

Xu, Zhenzhu; Hou, Yanhui; Zhang, Lihua; Liu, Tao; Zhou, Guangsheng

2016-10-01

Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two years, whereas warming manipulation had no significant effect. The soil microbial biomass carbon (MBC) and the soil respiration (SR) were increased by watering in both steppes, but the SR was significantly decreased by warming in the desert steppe only. The inorganic nitrogen components varied irregularly, with generally lower levels in the desert steppe. The belowground traits of soil total organic carbon (TOC) and the MBC were more closely associated with the ANPP in the desert than in the typical steppes. The results showed that the desert steppe with lower productivity may respond strongly to precipitation changes, particularly with warming, highlighting the positive effect of adding water with warming. Our study implies that the habitat- and year-specific responses to warming and watering should be considered when predicting an ecosystem’s functional responses under climate change scenarios.

Invader partitions ecological and evolutionary responses to above- and belowground herbivory.

PubMed

Huang, Wei; Carrillo, Juli; Ding, Jianqing; Siemann, Evan

2012-11-01

Interactions between above- and belowground herbivory may, affect plant performance and structure communities. Though many studies have documented interactions of invasive plants and.herbivores, none shows how above- and belowground herbivores interact to affect invasive plant performance. Here, in a common garden in China, we subjected genetically differentiated tallow trees (Triadica sebifera) from native (China) and invaded (United States) ranges to herbivory by aboveground adults and belowground larvae of a specialist beetle, Bikasha collaris. Overall, relative to plants from China, U.S. plants had greater total and aboveground mass, comparable belowground mass, lower resistance to both above- and belowground herbivory, and higher tolerance to aboveground herbivory only. Accordingly, aboveground adults had greater impacts on Chinese plants, but belowground larvae more strongly impacted U.S. plants. These results indicate that the invader may adopt an "aboveground first" strategy, allocating more resources aboveground in response to selection for increased competitive ability, which increases aboveground tolerance to herbivory. Furthermore, we found that adults facilitated larval success, and these feedbacks were stronger for U.S. plants, suggesting that aboveground feeding of adults may be associated with lower defenses and/or higher resources belowground in the invader. Therefore, plants may have evolved different responses to above- and belowground herbivory, which can affect invasion success and herbivore population dynamics. These findings may provide new insights for an effective biological control program against invasive plants.

Modeling aboveground biomass of Tamarix ramosissima in the Arkansas River Basin of Southeastern Colorado, USA

USGS Publications Warehouse

Evangelista, P.; Kumar, S.; Stohlgren, T.J.; Crall, A.W.; Newman, G.J.

2007-01-01

Predictive models of aboveground biomass of nonnative Tamarix ramosissima of various sizes were developed using destructive sampling techniques on 50 individuals and four 100-m2 plots. Each sample was measured for average height (m) of stems and canopy area (m2) prior to cutting, drying, and weighing. Five competing regression models (P < 0.05) were developed to estimate aboveground biomass of T. ramosissima using average height and/or canopy area measurements and were evaluated using Akaike's Information Criterion corrected for small sample size (AICc). Our best model (AICc = -148.69, ??AICc = 0) successfully predicted T. ramosissima aboveground biomass (R2 = 0.97) and used average height and canopy area as predictors. Our 2nd-best model, using the same predictors, was also successful in predicting aboveground biomass (R2 = 0.97, AICc = -131.71, ??AICc = 16.98). A 3rd model demonstrated high correlation between only aboveground biomass and canopy area (R2 = 0.95), while 2 additional models found high correlations between aboveground biomass and average height measurements only (R2 = 0.90 and 0.70, respectively). These models illustrate how simple field measurements, such as height and canopy area, can be used in allometric relationships to accurately predict aboveground biomass of T. ramosissima. Although a correction factor may be necessary for predictions at larger scales, the models presented will prove useful for many research and management initiatives.

Nutrient Distribution Indicated Whole-Tree Harvesting as a Possible Factor Restricting the Sustainable Productivity of a Poplar Plantation System in China

PubMed Central

Ge, Xiaomin; Tian, Ye; Tang, Luozhong

2015-01-01

We evaluated the biomass and contents of five major macronutrients (N, P, K, Ca and Mg) in 10-year-old poplar trees (Populus deltoids Bartr. cv. “Lux”), and determined their nutrient use efficiencies (NUEs) at Zhoushan Forestry Farm (32°20′ N, 119°40′ E), Jiangsu province, in eastern China. The above- and below-ground biomass of poplar trees was 161.7 t ha-1, of which 53.3% was stemwood. The nutrient contents in the aboveground part were as follows: 415.1 kg N ha-1, 29.7 kg P ha-1, 352.0 kg K ha-1, 1083.0 kg Ca ha-1, and 89.8 kg Mg ha-1. The highest nutrient contents were in stembark, followed by branches, roots, stemwood, and foliage. The NUEs of the aboveground parts of poplar for N, P, K, Ca and Mg were 0.313, 4.377, 0.369, 0.120, 1.448 t dry biomass kg-1 nutrient, respectively, while those of stemwood were 1.294, 33.154, 1.253, 0.667, and 3.328 t dry biomass kg-1, respectively. The cycling coefficients, defined as the percentage of annual nutrient return in annual nutrient uptake, of N, P, K, Ca and Mg for the aboveground part were 87, 95, 69, 92, and 84%, respectively. Based on the NUE and nutrient cycling characteristics, shifting from whole-tree harvesting to stemwood-only harvesting and appropriately extending the harvest rotation could prevent site deterioration and support sustainable productivity of poplar plantation systems. PMID:25992549

Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

NASA Astrophysics Data System (ADS)

Armitage, A. R.; Fourqurean, J. W.

2016-01-01

The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50-100 %. Soil carbon content slightly decreased ( ˜ 10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen : phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded an approximate threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m-2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

NASA Astrophysics Data System (ADS)

Armitage, A. R.; Fourqurean, J. W.

2015-10-01

The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50-100 %. Soil carbon content slightly decreased (~ 10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen: phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded a threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m-2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

Community-weighted mean of leaf traits and divergence of wood traits predict aboveground biomass in secondary subtropical forests.

PubMed

Ali, Arshad; Yan, En-Rong; Chang, Scott X; Cheng, Jun-Yang; Liu, Xiang-Yu

2017-01-01

Subtropical forests are globally important in providing ecological goods and services, but it is not clear whether functional diversity and composition can predict aboveground biomass in such forests. We hypothesized that high aboveground biomass is associated with high functional divergence (FDvar, i.e., niche complementarity) and community-weighted mean (CWM, i.e., mass ratio; communities dominated by a single plant strategy) of trait values. Structural equation modeling was employed to determine the direct and indirect effects of stand age and the residual effects of CWM and FDvar on aboveground biomass across 31 plots in secondary forests in subtropical China. The CWM model accounted for 78, 20, 6 and 2% of the variation in aboveground biomass, nitrogen concentration in young leaf, plant height and specific leaf area of young leaf, respectively. The FDvar model explained 74, 13, 7 and 0% of the variation in aboveground biomass, plant height, twig wood density and nitrogen concentration in young leaf, respectively. The variation in aboveground biomass, CWM of leaf nitrogen concentration and specific leaf area, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf explained by the joint model was 86, 20, 13, 7, 2 and 0%, respectively. Stand age had a strong positive direct effect but low indirect positive effects on aboveground biomass. Aboveground biomass was negatively related to CWM of nitrogen concentration in young leaf, but positively related to CWM of specific leaf area of young leaf and plant height, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf. Leaf and wood economics spectra are decoupled in regulating the functionality of forests, communities with diverse species but high nitrogen conservative and light acquisitive strategies result in high aboveground biomass, and hence, supporting both the mass ratio and niche complementarity hypotheses in secondary subtropical forests. Copyright © 2016 Elsevier B.V. All rights reserved.

The sweet side of global change-dynamic responses of non-structural carbohydrates to drought, elevated CO2 and nitrogen fertilization in tree species.

PubMed

Li, Weibin; Hartmann, Henrik; Adams, Henry D; Zhang, Hongxia; Jin, Changjie; Zhao, Chuanyan; Guan, Dexin; Wang, Anzhi; Yuan, Fenghui; Wu, Jiabing

2018-06-11

Non-structural carbohydrates (NSC) play a central role in plant functioning as energy carriers and building blocks for primary and secondary metabolism. Many studies have investigated how environmental and anthropogenic changes, like increasingly frequent and severe drought episodes, elevated CO2 and atmospheric nitrogen (N) deposition, influence NSC concentrations in individual trees. However, this wealth of data has not been analyzed yet to identify general trends using a common statistical framework. A thorough understanding of tree responses to global change is required for making realistic predictions of vegetation dynamics. Here we compiled data from 57 experimental studies on 71 tree species and conducted a meta-analysis to evaluate general responses of stored soluble sugars, starch and total NSC (soluble sugars + starch) concentrations in different tree organs (foliage, above-ground wood and roots) to drought, elevated CO2 and N deposition. We found that drought significantly decreased total NSC in roots (-17.3%), but not in foliage and above-ground woody tissues (bole, branch, stem and/or twig). Elevated CO2 significantly increased total NSC in foliage (+26.2%) and roots (+12.8%), but not in above-ground wood. By contrast, total NSC significantly decreased in roots (-17.9%), increased in above-ground wood (+6.1%), but was unaffected in foliage from N fertilization. In addition, the response of NSC to three global change drivers was strongly affected by tree taxonomic type, leaf habit, tree age and treatment intensity. Our results pave the way for a better understanding of general tree function responses to drought, elevated CO2 and N fertilization. The existing data also reveal that more long-term studies on mature trees that allow testing interactions between these factors are urgently needed to provide a basis for forecasting tree responses to environmental change at the global scale.

Disking Effects of Fifth-Year Volume Production of Four Eastern Cottonwood Clones Established on an Afforestation Site, Sharkey County, Mississippi

Treesearch

Ronald K. Fisher; Emile S. Gardiner; John A. Stanturf; C. Jeffrey Portwood

2002-01-01

In spring 1995, an eastern cottonwood (Populus delfoides) plantation was established on a former agricultural field in Sharkey County, MS to evaluate the effects of clonal variety and mechanical weed control on aboveground biomass production. Four cottonwood clones, ST-66, ST-72, ST-75 and S7C-1 were planted on a 12 foot x 12 foot spacing and subjected to 2...

Steeper declines in forest photosynthesis than respiration explain age-driven decreases in forest growth.

PubMed

Tang, Jianwu; Luyssaert, Sebastiaan; Richardson, Andrew D; Kutsch, Werner; Janssens, Ivan A

2014-06-17

The traditional view of forest dynamics originated by Kira and Shidei [Kira T, Shidei T (1967) Jap J Ecol 17:70-87] and Odum [Odum EP (1969) Science 164(3877):262-270] suggests a decline in net primary productivity (NPP) in aging forests due to stabilized gross primary productivity (GPP) and continuously increased autotrophic respiration (Ra). The validity of these trends in GPP and Ra is, however, very difficult to test because of the lack of long-term ecosystem-scale field observations of both GPP and Ra. Ryan and colleagues [Ryan MG, Binkley D, Fownes JH (1997) Ad Ecol Res 27:213-262] have proposed an alternative hypothesis drawn from site-specific results that aboveground respiration and belowground allocation decreased in aging forests. Here, we analyzed data from a recently assembled global database of carbon fluxes and show that the classical view of the mechanisms underlying the age-driven decline in forest NPP is incorrect and thus support Ryan's alternative hypothesis. Our results substantiate the age-driven decline in NPP, but in contrast to the traditional view, both GPP and Ra decline in aging boreal and temperate forests. We find that the decline in NPP in aging forests is primarily driven by GPP, which decreases more rapidly with increasing age than Ra does, but the ratio of NPP/GPP remains approximately constant within a biome. Our analytical models describing forest succession suggest that dynamic forest ecosystem models that follow the traditional paradigm need to be revisited.

Carbon sequestration in two created riverine wetlands in the midwestern United States.

PubMed

Bernal, Blanca; Mitsch, William J

2013-07-01

Wetlands have the ability to accumulate significant amounts of carbon (C) and thus could provide an effective approach to mitigate greenhouse gas accumulation in the atmosphere. Wetland hydrology, age, and management can affect primary productivity, decomposition, and ultimately C sequestration in riverine wetlands, but these aspects of wetland biogeochemistry have not been adequately investigated, especially in created wetlands. In this study we investigate the ability of created freshwater wetlands to sequester C by determining the sediment accretion and soil C accumulation of two 15-yr-old created wetlands in central Ohio-one planted and one naturally colonized. We measured the amount of sediment and soil C accumulated over the parent material and found that these created wetlands accumulated an average of 242 g C m yr, 70% more than a similar natural wetland in the region and 26% more than the rate estimated for these same wetlands 5 yr before this study. The C sequestration of the naturally colonized wetland was 22% higher than that of the planted wetland (267 ± 17 vs. 219 ± 15 g C m yr, respectively). Soil C accrual accounted for 66% of the aboveground net primary productivity on average. Open water communities had the highest C accumulation rates in both wetlands. This study shows that created wetlands can be natural, cost-effective tools to sequester C to mitigate the effect of greenhouse gas emissions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Fiddler crabs facilitate Spartina alterniflora growth, mitigating periwinkle overgrazing of marsh habitat.

PubMed

Gittman, Rachel K; Keller, Danielle A

2013-12-01

Ecologists have long been interested in identifying and testing factors that drive top-down or bottom-up regulation of communities. Most studies have focused on factors that directly exert top-down (e.g., grazing) or bottom-up (e.g., nutrient availability) control on primary production. For example, recent studies in salt marshes have demonstrated that fronts of Littoraria irrorata periwinkles can overgraze Spartina alterniflora and convert marsh to mudflat. The importance of indirect, bottom-up effects, particularly facilitation, in enhancing primary production has also recently been explored. Previous field studies separately revealed that fiddler crabs, which burrow to depths of more than 30 cm, can oxygenate marsh sediments and redistribute nutrients, thereby relieving the stress of anoxia and enhancing S. alterniflora growth. However, to our knowledge, no studies to date have explored how nontrophic facilitators can mediate top-down effects (i.e., grazing) on primary-producer biomass. We conducted a field study testing whether fiddler crabs can facilitate S. alterniflora growth sufficiently to mitigate overgrazing by periwinkles and thus sustain S. alterniflora marsh. As inferred from contrasts to experimental plots lacking periwinkles and fiddler crabs, periwinkles alone exerted top-down control of total aboveground biomass and net growth of S. alterniflora. When fiddler crabs were included, they counteracted the effects of periwinkles on net S. alterniflora growth. Sediment oxygen levels were greater and S. alterniflora belowground biomass was lower where fiddler crabs were present, implying that fiddler crab burrowing enhanced S. alterniflora growth. Consequently, in the stressful interior S. alterniflora marsh, where subsurface soil anoxia is widespread, fiddler crab facilitation can mitigate top-down control by periwinkles and can limit and possibly prevent loss of biogenically structured marsh habitat and its ecosystem services.

Dry flue gas desulfurization by-product application effects on plant uptake and soil storage changes in a managed grassland.

PubMed

Burgess-Conforti, Jason R; Brye, Kristofor R; Miller, David M; Pollock, Erik D; Wood, Lisa S

2018-02-01

Environmental regulations mandate that sulfur dioxide (SO 2 ) be removed from the flue gases of coal-fired power plants, which results in the generation of flue gas desulfurization (FGD) by-products. These FGD by-products may be a viable soil amendment, but the large amounts of trace elements contained in FGD by-products are potentially concerning. The objective of this study was to evaluate the effects of land application of a high-Ca dry FGD (DFGD) by-product on trace elements in aboveground biomass and soil. A high-Ca DFGD by-product was applied once at a rate of 9 Mg ha -1 on May 18, 2015 to small plots with mixed-grass vegetation. Soil and biomass were sampled prior to application and several times thereafter. Aboveground dry matter and tissue As, Co, Cr, Hg, Se, U, and V concentrations increased (P < 0.05) following application, but did not differ (P > 0.05) from pre-application levels or the unamended control within 3 to 6 months of application. Soil pH in the amended treatment 6 months after application was greater (P < 0.05) than in the unamended control. Soil Ca, S, and Na contents also increased (P < 0.05), following by-product application compared to the unamended control. High-Ca DFGD by-products appear to be useful as a soil amendment, but cause at least a temporary increase in tissue concentrations of trace elements, which may be problematic for animal grazing situations.

Growing Season Carbon Dioxide Exchange in Flooded Non-Mulching and Non-Flooded Mulching Cotton

PubMed Central

Li, Zhi-guo; Zhang, Run-hua; Wang, Xiu-jun; Chen, Fang; Tian, Chang-yan

2012-01-01

There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO2 concentrations. However, limited information exists regarding the potential for increased carbon sequestration of different management strategies. The objective of this study was to quantify and contrast carbon dioxide exchange in traditional non-mulching with flooding irrigation (TF) and plastic film mulching with drip irrigation (PM) cotton (Gossypium hirsutum L.) fields in northwest China. Net primary productivity (NPP), soil heterotrophic respiration (R h) and net ecosystem productivity (NEP) were measured during the growing seasons in 2009 and 2010. As compared with TF, PM significantly increased the aboveground and belowground biomass and the NPP (340 g C m−2 season−1) of cotton, and decreased the R h (89 g C m−2 season−1) (p<0.05). In a growing season, PM had a higher carbon sequestration in terms of NEP of ∼ 429 g C m−2 season−1 than the TF. These results demonstrate that conversion of this type of land use to mulching practices is an effective way to increase carbon sequestration in the short term in cotton systems of arid areas. PMID:23226376

Grazing alters net ecosystem C fluxes and the global warming potential of a subtropical pasture.

PubMed

Gomez-Casanovas, Nuria; DeLucia, Nicholas J; Bernacchi, Carl J; Boughton, Elizabeth H; Sparks, Jed P; Chamberlain, Samuel D; DeLucia, Evan H

2018-03-01

The impact of grazing on C fluxes from pastures in subtropical and tropical regions and on the environment is uncertain, although these systems account for a substantial portion of global C storage. We investigated how cattle grazing influences net ecosystem CO 2 and CH 4 exchange in subtropical pastures using the eddy covariance technique. Measurements were made over several wet-dry seasonal cycles in a grazed pasture, and in an adjacent pasture during the first three years of grazer exclusion. Grazing increased soil wetness but did not affect soil temperature. By removing aboveground biomass, grazing decreased ecosystem respiration (R eco ) and gross primary productivity (GPP). As the decrease in R eco was larger than the reduction in GPP, grazing consistently increased the net CO 2 sink strength of subtropical pastures (55, 219 and 187 more C/m 2 in 2013, 2014, and 2015). Enteric ruminant fermentation and increased soil wetness due to grazers, increased total net ecosystem CH 4 emissions in grazed relative to ungrazed pasture (27-80%). Unlike temperate, arid, and semiarid pastures, where differences in CH 4 emissions between grazed and ungrazed pastures are mainly driven by enteric ruminant fermentation, our results showed that the effect of grazing on soil CH 4 emissions can be greater than CH 4 produced by cattle. Thus, our results suggest that the interactions between grazers and soil hydrology affecting soil CH 4 emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased total net ecosystem CH 4 emissions and removed aboveground biomass, it increased the net storage of C and decreased the global warming potential associated with C fluxes of pasture by increasing its net CO 2 sink strength. © 2017 by the Ecological Society of America.

Climatically induced interannual variability in aboveground production in forest-tundra and northern taiga of central Siberia.

PubMed

Knorre, Anastasia A; Kirdyanov, Alexander V; Vaganov, Eugene A

2006-02-01

To investigate the variability of primary production of boreal forest ecosystems under the current climatic changes, we compared the dynamics of annual increments and productivity of the main components of plant community (trees, shrubs, mosses) at three sites in the north of Siberia (Russia). Annual radial growth of trees and shrubs was mostly defined by summer temperature regime (positive correlation), but climatic response of woody plants was species specific and depends on local conditions. Dynamics of annual increments of mosses were opposite to tree growth. The difference in climatic response of the different vegetation components of the forest ecosystems indicates that these components seem to be adapted to use climatic conditions during the short and severe northern summer, and decreasing in annual production of one component is usually combined with the increase of other component productivity. Average productivity in the northern forest ecosystems varies from 0.05 to 0.14 t ha(-1) year(-1) for trees, from 0.05 to 0.18 t ha(-1) year(-1) for shrubs and from 0.54 to 0.66 t ha(-1) year(-1) for mosses. Higher values of tree productivity combined with lower annual moss productivity were found in sites in northern taiga in comparison with forest-tundra. Different tendencies in the productivity of the dominant species from each vegetation level (trees, shrubs, mosses) were indicated for the last 10 years studied (1990-1999): while productivity of mosses is increasing, productivity of trees is decreasing, but there is no obvious trend in the productivity of shrubs. Our results show that in the long term, the main contribution to changes in annual biomass productivity in forest-tundra and northern taiga ecosystems under the predicted climatic changes will be determined by living ground cover.

Evaluation of non-destructive methods for estimating biomass in marshes of the upper Texas, USA coast

USGS Publications Warehouse

Whitbeck, M.; Grace, J.B.

2006-01-01

The estimation of aboveground biomass is important in the management of natural resources. Direct measurements by clipping, drying, and weighing of herbaceous vegetation are time-consuming and costly. Therefore, non-destructive methods for efficiently and accurately estimating biomass are of interest. We compared two non-destructive methods, visual obstruction and light penetration, for estimating aboveground biomass in marshes of the upper Texas, USA coast. Visual obstruction was estimated using the Robel pole method, which primarily measures the density and height of the canopy. Light penetration through the canopy was measured using a Decagon light wand, with readings taken above the vegetation and at the ground surface. Clip plots were also taken to provide direct estimates of total aboveground biomass. Regression relationships between estimated and clipped biomass were significant using both methods. However, the light penetration method was much more strongly correlated with clipped biomass under these conditions (R2 value 0.65 compared to 0.35 for the visual obstruction approach). The primary difference between the two methods in this situation was the ability of the light-penetration method to account for variations in plant litter. These results indicate that light-penetration measurements may be better for estimating biomass in marshes when plant litter is an important component. We advise that, in all cases, investigators should calibrate their methods against clip plots to evaluate applicability to their situation. ?? 2006, The Society of Wetland Scientists.

Estimating soil organic and aboveground woody carbon stock in a protected dry Miombo ecosystem, Zimbabwe: Landsat 8 OLI data applications

NASA Astrophysics Data System (ADS)

Dube, Timothy; Muchena, Richard; Masocha, Mhosisi; Shoko, Cletah

2018-06-01

Accurate and reliable soil organic carbon stock estimation is critical in understanding forest role to regional carbon cycles. So far, the total carbon pool in dry Miombo ecosystems is often under-estimated. In that regard this study sought to model the relationship between the aboveground woody carbon pool and the soil carbon pool, using both ground-based and remote sensing methods. To achieve this objective, the Ratio Vegetation Index (RVI), Normalized Difference Vegetation Index (NDVI), and the Soil Adjusted Vegetation Index (SAVI) computed from the newly launched Landsat 8 OLI satellite data were used. Correlation and regression analysis were used to relate Soil Organic Carbon (S.O.C), aboveground woody carbon and remotely sensed vegetation indices. Results showed a soil organic carbon in the upper soil layer (0-15 cm) was positively correlated with aboveground woody carbon and this relationship was significant (r = 0.678; P < 0.05) aboveground carbon. However, there were no significant correlations (r = -0.11, P > 0.05) between SOC in the deeper soil layer (15-30 cm) and aboveground woody carbon. These findings imply that (relationship between aboveground woody carbon and S.O.C) aboveground woody carbon stocks can be used as a proxy to estimate S.O.C in the top soil layer (0-15 cm) in dry Miombo ecosystems. Overall, these findings underscore the potential and significance of remote sensing data in understanding savanna ecosystems contribution to the global carbon cycle.

Estimating aboveground biomass of mariola (Parthenium incanum) from plant dimensions

Treesearch

Carlos Villalobos

2007-01-01

The distribution and abundance of plant biomass in space and time are important properties of rangeland ecosystem. Land managers and researchers require reliable shrub weight estimates to evaluate site productivity, food abundance, treatment effects, and stocking rates. Rapid, nondestructive methods are needed to estimate shrub biomass in semi-arid ecosystems. Shrub...

Use of integrated indoor concentrations of tracer gases and volatile organic compounds to distinguish soil sources from above-ground sources

EPA Science Inventory

Vapor intrusion refers to the situation in which harmful chemicals [such as halogenated or chlorinated volatile organic compounds (VOC) or petroleum products] in the groundwater or soil volatilize in the vadose zone and migrate into the indoor environment. These chemicals typical...

Cultivated Lands of Kuban and Features of Their Development

ERIC Educational Resources Information Center

Belyuchenko, Ivan S.

2016-01-01

The basis of cultivated lands consists of the interacting populations of annual and perennial weeds and updated annually cultural annual plants, which have very limited data on the aboveground net production, and even less information about the yield of their underground organs. The aim of the research is scientific and theoretical development of…

Response of a subalpine grassland to simulated grazing: Aboveground productivity along soil phosphorus gradients

Treesearch

C. Thiel-Egenter; A. C. Risch; M. F. Jurgensen; D. S. Page-Dumroese; B. O. Krusi; M. Schutz

2007-01-01

Interactions between grassland ecosystems and vertebrate herbivores are critical for a better understanding of ecosystem processes, but diverge widely in different ecosystems. In this study, we examined plant responses to simulated red deer (Cervus elaphus L.) grazing using clip-plot experiments in a subalpine grassland ecosystem of the Central...

Predicting small-diameter loblolly pine aboveground biomass in naturally regenerated stands

Treesearch

Kristin M. McElligott; Don C. Bragg; Jamie L. Schuler

2015-01-01

There is growing interest in managing southern pine forests for both carbon sequestration and bioenergy. For instance, thinning otherwise unmerchantable trees in naturally regenerated pine-dominated forests should generate biomass without conflicting with more traditional forest products. However, we lack the tools to accurately quantify the biomass in these...

Allometric models for predicting aboveground biomass and carbon stock of tropical perennial C4 grasses in Hawaii

USDA-ARS?s Scientific Manuscript database

Biomass represents a promising renewable energy opportunity that mayprovide a more sustainable alternative to the use of fossil resources by minimizing the net production of greenhouse gases. Yet, allometric models that allow the prediction of biomass, biomass carbon (C) and nitrogen (N) stocks rap...

Composition and species diversity of pine-wiregrass savannas of the Green Swamp, North Carolina

Treesearch

Joan Walker; Robert K. Peet

1983-01-01

Fire-maintained, species-rich pines wiregrass savannas in the Green Swamp, North Carolina were sampled over their natural range of environmental conditions and fire frequencies. Species composition, species richness, diversity (Exp H', I/ C), and aboveground production were documented and fertilization experiments conducted to assess possible mechanisms for the...

Airport cleanup rises above problems

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

Pressly, N.; Lucas, B.; Frumer, B.

Engineers used a treatment combination to improve the in-situ bioremediation system`s efficiency in removing underground fuel leaks at JFK Airport. John F. Kennedy International Airport, in New York City, on Jamaica Bay, has an above-ground storage capacity of about 32 million gallons of jet fuel, which flow through about 50 miles of high-pressure underground pipe to the central terminal area. EAch terminal`s fuel hydrant system was the major source os subsurface contamination at the site. The site is covered by 1 to 1.5 feet of reinforced concrete pavement. Liquid phase jet fuel (free product) was measured on the water tablemore » with true thickness ranging from less than 1 inch to 1 foot. After analysis of core samples, contamination was found adsorbed to the soil with maximum levels at the water table. This article describes the clean up, covering the following topics: microbial conditions during system operation; above-ground treatment challenges: free product emulsification, presence of biomass; evaluation of enhancements: dissolved air floatation, coagulation and flocculation, retention time adjustments; conclusions.« less

A new conceptual model on the fate and controls of fresh and pyrolized plant litter decomposition

USDA-ARS?s Scientific Manuscript database

The leaching of dissolved organic matter (DOM) from fresh and pyrolyzed aboveground plant inputs to the soil is a major pathway by which decomposing aboveground plant material contributes to soil organic matter formation. Understanding how aboveground plant input chemical traits control the partiti...

The Vegetation Nitrogen Content and its Latitudinal Patterns in China

NASA Astrophysics Data System (ADS)

Zhao, Hang; He, Nianpeng; Yu, Guirui; Wang, Qiufeng

2017-04-01

Nitrogen is an essential nutrient element in biological life activities, and plays an important role in plant production and growth. Vegetation nitrogen content can be used as an important component in estimating ecosystem nitrogen storage. In the present study, we used a large amount of data from the database of north-south transects of eastern China and published literatures. We explored the nitrogen content of different components of China terrestrial ecosystems and its latitude pattern at the scales of the plots and of 8 eco-regions. The average nitrogen content of the forest ecosystem was 1.797% in the tree leaves, 0.663% in the tree branch, 0.586% in the tree stem, 0.755% in the tree root. In the shrub layer, the average leaf nitrogen content is 1.845%, the average branch content is 0.968% and the average root nitrogen content is 0.995%. In the herb layer, the average nitrogen content of aboveground is 2.463% and 1.279% for underground. The average nitrogen content of aboveground in grassland ecosystem is 2.006% and 0.994% for underground. The average aboveground nitrogen content in desert ecosystem is 1.911%. The average nitrogen contents of the leaves, stems and roots in wetland ecosystem were 1.669%, 0.741% and 0.659%. There were significant differences in nitrogen content among different organs, and it showed that the nitrogen content of leaves > roots > branches > trunks and aboveground component > underground component. The nitrogen content of different components in China terrestrial ecosystems increased with increasing latitude, especially in leaf. These results demonstrated latitudinal patterns of nitrogen content in Chinese terrestrial ecosystems, based on field-measured data, and provided a reference or standard for regional vegetation nitrogen allocation and storage estimations.

Detecting Below-Ground Processes, Diversity, and Ecosystem Function in a Savanna Ecosystem Using Spectroscopy Across Different Vegetation Layers

NASA Astrophysics Data System (ADS)

Cavender-Bares, J.; Schweiger, A. K.; Madritch, M. D.; Gamon, J. A.; Hobbie, S. E.; Montgomery, R.; Townsend, P. A.

2017-12-01

Above-and below-ground plant traits are important for substrate input to the rhizosphere. The substrate composition of the rhizosphere, in turn, affects the diversity of soil organisms, influences soil biochemistry, and water content, and resource availability for plant growth. This has substantial consequences for ecosystem functions, such as above-ground productivity and stability. Above-ground plant chemical and structural traits can be linked to the characteristics of other plant organs, including roots. Airborne imaging spectroscopy has been successfully used to model and predict chemical and structural traits of the above-ground vegetation. However, remotely sensed images capture, almost exclusively, signals from the top of the canopy, providing limited direct information about understory vegetation. Here, we use a data set collected in a savanna ecosystem consisting of spectral measurements gathered at the leaf, the whole plant, and vegetation canopy level to test for hypothesized linkages between above- and below-ground processes that influence root biomass, soil biochemistry, and the diversity of the soil community. In this environment, consisting of herbaceous vegetation intermixed with shrubs and trees growing at variable densities, we investigate the contribution of different vegetation strata to soil characteristics and test the ability of imaging spectroscopy to detect these in plant communities with contrasting vertical structure.

Vegetative Regeneration Capacities of Five Ornamental Plant Invaders After Shredding

NASA Astrophysics Data System (ADS)

Monty, Arnaud; Eugène, Marie; Mahy, Grégory

2015-02-01

Vegetation management often involves shredding to dispose of cut plant material or to destroy the vegetation itself. In the case of invasive plants, this can represent an environmental risk if the shredded material exhibits vegetative regeneration capacities. We tested the effect of shredding on aboveground and below-ground vegetative material of five ornamental widespread invaders in Western Europe that are likely to be managed by cutting and shredding techniques: Buddleja davidii (butterfly bush, Scrophulariaceae), Fallopia japonica (Japanese knotweed, Polygonaceae), Spiraea × billardii Hérincq (Billard's bridewort, Rosaceae), Solidago gigantea (giant goldenrod, Asteraceae), and Rhus typhina L. (staghorn sumac, Anacardiaceae). We looked at signs of vegetative regeneration and biomass production, and analyzed the data with respect to the season of plant cutting (spring vs summer), the type of plant material (aboveground vs below-ground), and the shredding treatment (shredded vs control). All species were capable of vegetative regeneration, especially the below-ground material. We found differences among species, but the regeneration potential was generally still present after shredding despite a reduction of growth rates. Although it should not be excluded in all cases (e.g., destruction of giant goldenrod and staghorn sumac aboveground material), the use of a shredder to destroy woody alien plant material cannot be considered as a general management option without significant environmental risk.

Vegetative regeneration capacities of five ornamental plant invaders after shredding.

PubMed

Monty, Arnaud; Eugène, Marie; Mahy, Grégory

2015-02-01

Vegetation management often involves shredding to dispose of cut plant material or to destroy the vegetation itself. In the case of invasive plants, this can represent an environmental risk if the shredded material exhibits vegetative regeneration capacities. We tested the effect of shredding on aboveground and below-ground vegetative material of five ornamental widespread invaders in Western Europe that are likely to be managed by cutting and shredding techniques: Buddleja davidii (butterfly bush, Scrophulariaceae), Fallopia japonica (Japanese knotweed, Polygonaceae), Spiraea × billardii Hérincq (Billard's bridewort, Rosaceae), Solidago gigantea (giant goldenrod, Asteraceae), and Rhus typhina L. (staghorn sumac, Anacardiaceae). We looked at signs of vegetative regeneration and biomass production, and analyzed the data with respect to the season of plant cutting (spring vs summer), the type of plant material (aboveground vs below-ground), and the shredding treatment (shredded vs control). All species were capable of vegetative regeneration, especially the below-ground material. We found differences among species, but the regeneration potential was generally still present after shredding despite a reduction of growth rates. Although it should not be excluded in all cases (e.g., destruction of giant goldenrod and staghorn sumac aboveground material), the use of a shredder to destroy woody alien plant material cannot be considered as a general management option without significant environmental risk.

Biomass production in experimental grasslands of different species richness during three years of climate warming

NASA Astrophysics Data System (ADS)

de Boeck, H. J.; Lemmens, C. M. H. M.; Gielen, B.; Malchair, S.; Carnol, M.; Merckx, R.; van den Berge, J.; Ceulemans, R.; Nijs, I.

2007-12-01

Here we report on the single and combined impacts of climate warming and species richness on the biomass production in experimental grassland communities. Projections of a future warmer climate have stimulated studies on the response of terrestrial ecosystems to this global change. Experiments have likewise addressed the importance of species numbers for ecosystem functioning. There is, however, little knowledge on the interplay between warming and species richness. During three years, we grew experimental plant communities containing one, three or nine grassland species in 12 sunlit, climate-controlled chambers in Wilrijk, Belgium. Half of these chambers were exposed to ambient air temperatures (unheated), while the other half were warmed by 3°C (heated). Equal amounts of water were added to heated and unheated communities, so that warming would imply drier soils if evapotranspiration was higher. Biomass production was decreased due to warming, both aboveground (-29%) and belowground (-25%), as negative impacts of increased heat and drought stress in summer prevailed. Increased resource partitioning, likely mostly through spatial complementarity, led to higher shoot and root biomass in multi-species communities, regardless of the induced warming. Surprisingly, warming suppressed productivity the most in 9-species communities, which may be attributed to negative impacts of intense interspecific competition for resources under conditions of high abiotic stress. Our results suggest that warming and the associated soil drying could reduce primary production in many temperate grasslands, and that this will not necessarily be mitigated by efforts to maintain or increase species richness.

Moderate forest disturbance as a stringent test for gap and big-leaf models

NASA Astrophysics Data System (ADS)

Bond-Lamberty, B.; Fisk, J. P.; Holm, J. A.; Bailey, V.; Bohrer, G.; Gough, C. M.

2015-01-01

Disturbance-induced tree mortality is a key factor regulating the carbon balance of a forest, but tree mortality and its subsequent effects are poorly represented processes in terrestrial ecosystem models. It is thus unclear whether models can robustly simulate moderate (non-catastrophic) disturbances, which tend to increase biological and structural complexity and are increasingly common in aging US forests. We tested whether three forest ecosystem models - Biome-BGC (BioGeochemical Cycles), a classic big-leaf model, and the ZELIG and ED (Ecosystem Demography) gap-oriented models - could reproduce the resilience to moderate disturbance observed in an experimentally manipulated forest (the Forest Accelerated Succession Experiment in northern Michigan, USA, in which 38% of canopy dominants were stem girdled and compared to control plots). Each model was parameterized, spun up, and disturbed following similar protocols and run for 5 years post-disturbance. The models replicated observed declines in aboveground biomass well. Biome-BGC captured the timing and rebound of observed leaf area index (LAI), while ZELIG and ED correctly estimated the magnitude of LAI decline. None of the models fully captured the observed post-disturbance C fluxes, in particular gross primary production or net primary production (NPP). Biome-BGC NPP was correctly resilient but for the wrong reasons, and could not match the absolute observational values. ZELIG and ED, in contrast, exhibited large, unobserved drops in NPP and net ecosystem production. The biological mechanisms proposed to explain the observed rapid resilience of the C cycle are typically not incorporated by these or other models. It is thus an open question whether most ecosystem models will simulate correctly the gradual and less extensive tree mortality characteristic of moderate disturbances.

Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

NASA Astrophysics Data System (ADS)

Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

2011-09-01

Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

Decreased summer drought affects plant productivity and soil carbon dynamics in Mediterranean woodland

NASA Astrophysics Data System (ADS)

Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

2011-06-01

Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. The throughfall manipulation experiment started in 2004 and we report data up to the 2009 growing season. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 50 % and 220 %, respectively, as compared to control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction of precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodland. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long term soil C stocks.

Moderate forest disturbance as a stringent test for gap and big-leaf models

DOE PAGES

Bond-Lamberty, Benjamin; Fisk, Justin P.; Holm, Jennifer; ...

2015-01-27

Disturbance-induced tree mortality is a key factor regulating the carbon balance of a forest, but tree mortality and its subsequent effects are poorly represented processes in terrestrial ecosystem models. It is thus unclear whether models can robustly simulate moderate (non-catastrophic) disturbances, which tend to increase biological and structural complexity and are increasingly common in aging US forests. We tested whether three forest ecosystem models – Biome-BGC (BioGeochemical Cycles), a classic big-leaf model, and the ZELIG and ED (Ecosystem Demography) gap-oriented models – could reproduce the resilience to moderate disturbance observed in an experimentally manipulated forest (the Forest Accelerated Succession Experimentmore » in northern Michigan, USA, in which 38% of canopy dominants were stem girdled and compared to control plots). Each model was parameterized, spun up, and disturbed following similar protocols and run for 5 years post-disturbance. The models replicated observed declines in aboveground biomass well. Biome-BGC captured the timing and rebound of observed leaf area index (LAI), while ZELIG and ED correctly estimated the magnitude of LAI decline. None of the models fully captured the observed post-disturbance C fluxes, in particular gross primary production or net primary production (NPP). Biome-BGC NPP was correctly resilient but for the wrong reasons, and could not match the absolute observational values. ZELIG and ED, in contrast, exhibited large, unobserved drops in NPP and net ecosystem production. The biological mechanisms proposed to explain the observed rapid resilience of the C cycle are typically not incorporated by these or other models. It is thus an open question whether most ecosystem models will simulate correctly the gradual and less extensive tree mortality characteristic of moderate disturbances.« less

Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments

DOE PAGES

Wilcox, Kevin R.; Shi, Zheng; Gherardi, Laureano A.; ...

2017-04-02

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitationmore » changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. Here, we used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. Finally, this highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.« less

Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments.

PubMed

Wilcox, Kevin R; Shi, Zheng; Gherardi, Laureano A; Lemoine, Nathan P; Koerner, Sally E; Hoover, David L; Bork, Edward; Byrne, Kerry M; Cahill, James; Collins, Scott L; Evans, Sarah; Gilgen, Anna K; Holub, Petr; Jiang, Lifen; Knapp, Alan K; LeCain, Daniel; Liang, Junyi; Garcia-Palacios, Pablo; Peñuelas, Josep; Pockman, William T; Smith, Melinda D; Sun, Shanghua; White, Shannon R; Yahdjian, Laura; Zhu, Kai; Luo, Yiqi

2017-10-01

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes. © 2017 John Wiley & Sons Ltd.

Effects of nitrogen deposition and cattle grazing on productivity, invasion impact, and soil microbial processes in a serpentine grassland

NASA Astrophysics Data System (ADS)

Pasari, J.; Hernandez, D.; Selmants, P. C.; Keck, D.

2010-12-01

In recent decades, human activities have vastly increased the amount of biologically available nitrogen (N) in the biosphere. The resulting increase in N availability has broadly affected ecosystems through increased productivity, changes in species composition, altered nutrient cycles, and increases in invasion by exotic plant species, especially in systems that were historically low in N. California serpentine grasslands are N-limited ecosystems historically dominated by native species including several threatened and endangered plants and animals. Cattle grazing has emerged as the primary tool for controlling the impact of nitrophilic exotic grasses whose increased abundance has paralleled the regional traffic-derived increase in atmospheric N deposition. We examined the interactive effects of cattle grazing and N deposition on plant community composition, productivity, invasion resistance, and microbial processes in the Bay Area's largest serpentine grassland to determine the efficacy of current management strategies as well as the biogeochemical consequences of exotic species invasion. In the first two years of the study, aboveground net primary productivity decreased in response to grazing and increased in response to nitrogen addition. However, contrary to our hypotheses the change in productivity was not due to an increase in exotic species cover as there was little overall effect of grazing or N addition on species composition. Microbial activity was more responsive to grazing and N. Potential net N mineralization rates increased with N addition, but were not affected by grazing. In contrast, soil respiration rates were inhibited by grazing, but were not affected by N addition; suggesting strong carbon-limitation of soil microbial activity, particularly under grazing. Site differences in soil depth and grazing intensity were often more important than treatment effects. We suspect that the unusually dry conditions in the first two growing seasons inhibited the growth of exotic species and minimized the effects of cattle exclusion and N addition on species composition.

High Throughput Determination of Plant Height, Ground Cover, and Above-Ground Biomass in Wheat with LiDAR

PubMed Central

Jimenez-Berni, Jose A.; Deery, David M.; Rozas-Larraondo, Pablo; Condon, Anthony (Tony) G.; Rebetzke, Greg J.; James, Richard A.; Bovill, William D.; Furbank, Robert T.; Sirault, Xavier R. R.

2018-01-01

Crop improvement efforts are targeting increased above-ground biomass and radiation-use efficiency as drivers for greater yield. Early ground cover and canopy height contribute to biomass production, but manual measurements of these traits, and in particular above-ground biomass, are slow and labor-intensive, more so when made at multiple developmental stages. These constraints limit the ability to capture these data in a temporal fashion, hampering insights that could be gained from multi-dimensional data. Here we demonstrate the capacity of Light Detection and Ranging (LiDAR), mounted on a lightweight, mobile, ground-based platform, for rapid multi-temporal and non-destructive estimation of canopy height, ground cover and above-ground biomass. Field validation of LiDAR measurements is presented. For canopy height, strong relationships with LiDAR (r2 of 0.99 and root mean square error of 0.017 m) were obtained. Ground cover was estimated from LiDAR using two methodologies: red reflectance image and canopy height. In contrast to NDVI, LiDAR was not affected by saturation at high ground cover, and the comparison of both LiDAR methodologies showed strong association (r2 = 0.92 and slope = 1.02) at ground cover above 0.8. For above-ground biomass, a dedicated field experiment was performed with destructive biomass sampled eight times across different developmental stages. Two methodologies are presented for the estimation of biomass from LiDAR: 3D voxel index (3DVI) and 3D profile index (3DPI). The parameters involved in the calculation of 3DVI and 3DPI were optimized for each sample event from tillering to maturity, as well as generalized for any developmental stage. Individual sample point predictions were strong while predictions across all eight sample events, provided the strongest association with biomass (r2 = 0.93 and r2 = 0.92) for 3DPI and 3DVI, respectively. Given these results, we believe that application of this system will provide new opportunities to deliver improved genotypes and agronomic interventions via more efficient and reliable phenotyping of these important traits in large experiments. PMID:29535749

High Throughput Determination of Plant Height, Ground Cover, and Above-Ground Biomass in Wheat with LiDAR.

PubMed

Jimenez-Berni, Jose A; Deery, David M; Rozas-Larraondo, Pablo; Condon, Anthony Tony G; Rebetzke, Greg J; James, Richard A; Bovill, William D; Furbank, Robert T; Sirault, Xavier R R

2018-01-01

Crop improvement efforts are targeting increased above-ground biomass and radiation-use efficiency as drivers for greater yield. Early ground cover and canopy height contribute to biomass production, but manual measurements of these traits, and in particular above-ground biomass, are slow and labor-intensive, more so when made at multiple developmental stages. These constraints limit the ability to capture these data in a temporal fashion, hampering insights that could be gained from multi-dimensional data. Here we demonstrate the capacity of Light Detection and Ranging (LiDAR), mounted on a lightweight, mobile, ground-based platform, for rapid multi-temporal and non-destructive estimation of canopy height, ground cover and above-ground biomass. Field validation of LiDAR measurements is presented. For canopy height, strong relationships with LiDAR ( r 2 of 0.99 and root mean square error of 0.017 m) were obtained. Ground cover was estimated from LiDAR using two methodologies: red reflectance image and canopy height. In contrast to NDVI, LiDAR was not affected by saturation at high ground cover, and the comparison of both LiDAR methodologies showed strong association ( r 2 = 0.92 and slope = 1.02) at ground cover above 0.8. For above-ground biomass, a dedicated field experiment was performed with destructive biomass sampled eight times across different developmental stages. Two methodologies are presented for the estimation of biomass from LiDAR: 3D voxel index (3DVI) and 3D profile index (3DPI). The parameters involved in the calculation of 3DVI and 3DPI were optimized for each sample event from tillering to maturity, as well as generalized for any developmental stage. Individual sample point predictions were strong while predictions across all eight sample events, provided the strongest association with biomass ( r 2 = 0.93 and r 2 = 0.92) for 3DPI and 3DVI, respectively. Given these results, we believe that application of this system will provide new opportunities to deliver improved genotypes and agronomic interventions via more efficient and reliable phenotyping of these important traits in large experiments.

Assessment of forest nutrient pools in view of biomass potentials - a case study from Austria oak stands

NASA Astrophysics Data System (ADS)

Yan, S.; Bruckman, V. J.; Glatzel, G.; Hochbichler, E.

2012-04-01

As one of the renewable energy forms, bio-energy could help to relieve the pressure which is caused by growing global energy demand. In Austria, large area of forests, traditional utilization of biomass and people's desire to live in a sound environment have supported the positive development of bio-energy. Soil nutrient status is in principle linked with the productivity of the aboveground biomass. This study focuses on K, Ca and Mg pools in soils and aboveground biomass in order to learn more on the temporal dynamics of plant nutrients as indicators for biomass potentials in Quercus dominated forests in northeastern Austria. Three soil types (according to WRB: eutric cambisol, calcic chernozem and haplic luvisol) were considered representative for the area and sampled. We selected nine Quercus petraea dominated permanent plots for this study. Exchangeable cations K, Ca and Mg in the soils were quantified in our study plots. Macronutrients pools of K, Ca and Mg in aboveground biomass were calculated according to inventory data and literature review. The exchangeable cations pool in the top 50 cm of the soil were 882 - 1,652 kg ha-1 for K, 2,661 to 16,510 kg ha-1 for Ca and 320 - 1,850 kg ha-1 for Mg. The nutrient pool in aboveground biomass ranged from 29 to 181 kg ha-1 for K, from 56 to 426 kg ha-1 for Ca and from 4 to 26 kg ha-1 for Mg. The underground exchangeable pools of K, Ca and Mg are generally 10, 22 and 58 times higher than aboveground biomass nutrient pools. Our results showed that the nutrient pools in the mineral soil are sufficient to support the tree growth. The levels of soil nutrients in particular K, Ca and Mg in our study areas are reasonably high and do not indicate the necessity for additional fertilization under current silvicultural practices and biomass extraction rate. The forest in our study areas is in favorable condition to supply biomass as raw material for energy utilization.

Climate-suitable planting as a strategy for maintaining forest productivity and functional diversity.

PubMed

Duveneck, Matthew J; Scheller, Robert M

2015-09-01

Within the time frame of the longevity of tree species, climate change will change faster than the ability of natural tree migration. Migration lags may result in reduced productivity and reduced diversity in forests under current management and climate change. We evaluated the efficacy of planting climate-suitable tree species (CSP), those tree species with current or historic distributions immediately south of a focal landscape, to maintain or increase aboveground biomass productivity, and species and functional diversity. We modeled forest change with the LANDIS-II forest simulation model for 100 years (2000-2100) at a 2-ha cell resolution and five-year time steps within two landscapes in the Great Lakes region (northeastern Minnesota and northern lower Michigan, USA). We compared current climate to low- and high-emission futures. We simulated a low-emission climate future with the Intergovernmental Panel on Climate Change (IPCC) 2007 B1 emission scenario and the Parallel Climate Model Global Circulation Model (GCM). We simulated a high-emission climate future with the IPCC A1FI emission scenario and the Geophysical Fluid Dynamics Laboratory (GFDL) GCM. We compared current forest management practices (business-as-usual) to CSP management. In the CSP scenario, we simulated a target planting of 5.28% and 4.97% of forested area per five-year time step in the Minnesota and Michigan landscapes, respectively. We found that simulated CSP species successfully established in both landscapes under all climate scenarios. The presence of CSP species generally increased simulated aboveground biomass. Species diversity increased due to CSP; however, the effect on functional diversity was variable. Because the planted species were functionally similar to many native species, CSP did not result in a consistent increase nor decrease in functional diversity. These results provide an assessment of the potential efficacy and limitations of CSP management. These results have management implications for sites where diversity and productivity are expected to decline. Future efforts to restore a specific species or forest type may not be possible, but CSP may sustain a more general ecosystem service (e.g., aboveground biomass).

Linear and nonlinear effects of temperature and precipitation on ecosystem properties in tidal saline wetlands

USGS Publications Warehouse

Feher, Laura C.; Osland, Michael J.; Griffith, Kereen T.; Grace, James B.; Howard, Rebecca J.; Stagg, Camille L.; Enwright, Nicholas M.; Krauss, Ken W.; Gabler, Christopher A.; Day, Richard H.; Rogers, Kerrylee

2017-01-01

Climate greatly influences the structure and functioning of tidal saline wetland ecosystems. However, there is a need to better quantify the effects of climatic drivers on ecosystem properties, particularly near climate-sensitive ecological transition zones. Here, we used climate- and literature-derived ecological data from tidal saline wetlands to test hypotheses regarding the influence of climatic drivers (i.e., temperature and precipitation regimes) on the following six ecosystem properties: canopy height, biomass, productivity, decomposition, soil carbon density, and soil carbon accumulation. Our analyses quantify and elucidate linear and nonlinear effects of climatic drivers. We quantified positive linear relationships between temperature and above-ground productivity and strong positive nonlinear (sigmoidal) relationships between (1) temperature and above-ground biomass and canopy height and (2) precipitation and canopy height. Near temperature-controlled mangrove range limits, small changes in temperature are expected to trigger comparatively large changes in biomass and canopy height, as mangrove forests grow, expand, and, in some cases, replace salt marshes. However, within these same transition zones, temperature-induced changes in productivity are expected to be comparatively small. Interestingly, despite the significant above-ground height, biomass, and productivity relationships across the tropical–temperate mangrove–marsh transition zone, the relationships between temperature and soil carbon density or soil carbon accumulation were not significant. Our literature review identifies several ecosystem properties and many regions of the world for which there are insufficient data to fully evaluate the influence of climatic drivers, and the identified data gaps can be used by scientists to guide future research. Our analyses indicate that near precipitation-controlled transition zones, small changes in precipitation are expected to trigger comparatively large changes in canopy height. However, there are scant data to evaluate the influence of precipitation on other ecosystem properties. There is a need for more decomposition data across climatic gradients, and to advance understanding of the influence of changes in precipitation and freshwater availability, additional ecological data are needed from tidal saline wetlands in arid climates. Collectively, our results can help scientists and managers better anticipate the linear and nonlinear ecological consequences of climate change for coastal wetlands.

Airborne laser scanner-assisted estimation of aboveground biomass change in a temperate oak-pine forest

Treesearch

Nicholas S. Skowronski; Kenneth L. Clark; Michael Gallagher; Richard A. Birdsey; John L. Hom

2014-01-01

We estimated aboveground tree biomass and change in aboveground tree biomass using repeated airborne laser scanner (ALS) acquisitions and temporally coincident ground observations of forest biomass, for a relatively undisturbed period (2004-2007; ∇07-04), a contrasting period of disturbance (2007-2009; ∇09-07...

Soil moisture mediates alpine life form and community productivity responses to warming.

PubMed

Winkler, Daniel E; Chapin, Kenneth J; Kueppers, Lara M

2016-06-01

Climate change is expected to alter primary production and community composition in alpine ecosystems, but the direction and magnitude of change is debated. Warmer, wetter growing seasons may increase productivity; however, in the absence of additional precipitation, increased temperatures may decrease soil moisture, thereby diminishing any positive effect of warming. Since plant species show individual responses to environmental change, responses may depend on community composition and vary across life form or functional groups. We warmed an alpine plant community at Niwot Ridge, Colorado continuously for four years to test whether warming increases or decreases productivity of life form groups and the whole community. We provided supplemental water to a subset of plots to alleviate the drying effect of warming. We measured annual above-ground productivity and soil temperature and moisture, from which we calculated soil degree days and adequate soil moisture days. Using an information-theoretic approach, we observed that positive productivity responses to warming at the community level occur only when warming is combined with supplemental watering; otherwise we observed decreased productivity. Watering also increased community productivity in the absence of warming. Forbs accounted for the majority of the productivity at the site and drove the contingent community response to warming, while cushions drove the generally positive response to watering and graminoids muted the community response. Warming advanced snowmelt and increased soil degree days, while watering increased adequate soil moisture days. Heated and watered plots had more adequate soil moisture days than heated plots. Overall, measured changes in soil temperature and moisture in response to treatments were consistent with expected productivity responses. We found that available soil moisture largely determines the responses of this forb-dominated alpine community to simulated climate warming. © 2016 by the Ecological Society of America.

Eliciting maize defense pathways aboveground attracts belowground biocontrol agents.

PubMed

Filgueiras, Camila Cramer; Willett, Denis S; Pereira, Ramom Vasconcelos; Moino Junior, Alcides; Pareja, Martin; Duncan, Larry W

2016-11-04

Plant defense pathways mediate multitrophic interactions above and belowground. Understanding the effects of these pathways on pests and natural enemies above and belowground holds great potential for designing effective control strategies. Here we investigate the effects of aboveground stimulation of plant defense pathways on the interactions between corn, the aboveground herbivore adult Diabrotica speciosa, the belowground herbivore larval D. speciosa, and the subterranean ento-mopathogenic nematode natural enemy Heterorhabditis amazonensis. We show that adult D. speciosa recruit to aboveground herbivory and methyl salicylate treatment, that larval D. speciosa are relatively indiscriminate, and that H. amazonensis en-tomopathogenic nematodes recruit to corn fed upon by adult D. speciosa. These results suggest that entomopathogenicnematodes belowground can be highly attuned to changes in the aboveground parts of plants and that biological control can be enhanced with induced plant defense in this and similar systems.

Elk browsing increases aboveground growth of water-stressed willows by modifying plant architecture.

PubMed

Johnston, Danielle B; Cooper, David J; Hobbs, N Thompson

2007-12-01

In the northern elk wintering range of Yellowstone National Park, USA, wolf (Canis lupus) removal allowed elk (Cervus elaphus) to overbrowse riparian woody plants, leading to the exclusion of beaver (Castor canadensis) and a subsequent water table decline in many small stream valleys. Reduced elk browsing following wolf reintroduction may or may not facilitate willow (Salix sp.) recovery in these areas. To determine if the effect of elk browsing on willow interacts with that of beaver abandonment, we manipulated elk browsing and the water table in a factorial experiment. Under the condition of an ambient (low) water table, elk browsing increased shoot water potential (Psis), photosynthesis per unit leaf area (A), stomatal conductance per unit leaf area (gs), and aboveground current annual growth (CAG) by 50%. Elk browsing occurred entirely during dormancy and did not affect total plant leaf area (L). Improved water balance, photosynthetic rate, and annual aboveground productivity in browsed willows appeared to be due to morphological changes, such as increased shoot diameter and decreased branching, which typically increase plant hydraulic conductivity. An elevated water table increased Psis, A, gs, CAG, and L, and eliminated or lessened the positive effect of browsing on CAG for most species. Because low water tables create conditions whereby high willow productivity depends on the morphological effects of annual elk browsing, removing elk browsing in areas of water table decline is unlikely to result in vigorous willow stands. As large willow standing crops are required by beaver, a positive feedback between water-stressed willow and beaver absence may preclude the reestablishment of historical conditions. In areas with low water table, willow restoration may depend on actions to promote the re-establishment of beaver in addition to reducing elk browsing.

Rapid recovery of gross ecosystem production and ecosystem-level respiration in a semiarid sagebrush shrubland following prescribed fire.

NASA Astrophysics Data System (ADS)

Fellows, A.; Flerchinger, G. N.

2016-12-01

The impact of fire remains a key uncertainty in our understanding of the spatio-temporal dynamics of carbon cycling on Western US rangelands. We, therefore, tracked the recovery of carbon fluxes and vegetative carbon stocks following prescribed fire in a sagebrush shrubland located in the Western US Great Basin. We quantified the change in plant function type, Leaf Area Index (LAI), aboveground carbon stocks, Gross Ecosystem Production (GEP), and Ecosystem-level Respiration (Reco) for 2 years before and 5 years following a prescribed fire that burned in 2007. Recruitment of burned sagebrush shrubland by fast growing grasses and forbs drove a rapid recovery of LAI, GEP, and Reco following fire; LAI, GEP, and Reco recovered within 1-3 years. These findings are consistent with previous measurement and modeling work by Flerchinger that demonstrated rooting depths, soil moisture withdrawal, and evapotranspiration also recovered within a few years of this fire. Live aboveground biomass reached 15% of pre-fire aboveground biomass after 5 years. The rapid recovery of LAI, rooting depth, GEP and Reco may partially reflect conducive environmental conditions at this site and at the time of the fire. In particular, the site was wet for a sagebrush shrubland; annual precipitation averaged 545 mm during the study and large-deep snow drifts formed upslope of the site. Post-fire weather was particularly wet, with the second, third and fourth years following fire receiving 587, 614, and 745 mm of water. Grazing was excluded from the burned area, which limited herbivory and may have facilitated vegetation establishment and growth. Lastly, the fire burned in September after many grasses and herbaceous plants had already senesced.

Disentangling the effects of species diversity, and intraspecific and interspecific tree size variation on aboveground biomass in dry zone homegarden agroforestry systems.

PubMed

Ali, Arshad; Mattsson, Eskil

2017-11-15

The biodiversity - aboveground biomass relationship has been intensively studied in recent decades. However, no consensus has been arrived to consider the interplay of species diversity, and intraspecific and interspecific tree size variation in driving aboveground biomass, after accounting for the effects of plot size heterogeneity, soil fertility and stand quality in natural forest including agroforests. We tested the full, partial and no mediations effects of species diversity, and intraspecific and interspecific tree size variation on aboveground biomass by employing structural equation models (SEMs) using data from 45 homegarden agroforestry systems in Sri Lanka. The full mediation effect of either species diversity or intraspecific and interspecific tree size variation was rejected, while the partial and no mediation effects were accepted. In the no mediation SEM, homegarden size had the strongest negative direct effect (β=-0.49) on aboveground biomass (R 2 =0.65), followed by strong positive direct effect of intraspecific tree size variation (β=0.32), species diversity (β=0.29) and interspecific tree size variation (β=0.28). Soil fertility had a negative direct effect on interspecific tree size variation (β=-0.31). Stand quality had a significant positive total effect on aboveground biomass (β=0.28), but homegarden size had a significant negative total effect (β=-0.62), while soil fertility had a non-significant total effect on aboveground biomass. Similar to the no mediation SEM, the partial mediation SEMs had explained almost similar variation in aboveground biomass because species diversity, and intraspecific and interspecific tree size variation had non-significant indirect effects on aboveground biomass via each other. Our results strongly suggest that a multilayered tree canopy structure, due to high intraspecific and interspecific tree size variation, increases light capture and efficient utilization of resources among component species, and hence, support the niche complementarity mechanism via plant-plant interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

Ecological linkages between aboveground and belowground biota.

PubMed

Wardle, David A; Bardgett, Richard D; Klironomos, John N; Setälä, Heikki; van der Putten, Wim H; Wall, Diana H

2004-06-11

All terrestrial ecosystems consist of aboveground and belowground components that interact to influence community- and ecosystem-level processes and properties. Here we show how these components are closely interlinked at the community level, reinforced by a greater degree of specificity between plants and soil organisms than has been previously supposed. As such, aboveground and belowground communities can be powerful mutual drivers, with both positive and negative feedbacks. A combined aboveground-belowground approach to community and ecosystem ecology is enhancing our understanding of the regulation and functional significance of biodiversity and of the environmental impacts of human-induced global change phenomena.

Introduction to the invited issue on carbon allocation of trees and forests

Treesearch

Daniel Epron; Yann Nouvellon; Michael G. Ryan

2012-01-01

Carbon (C) allocation is a major issue in plant ecology, controlling the flows of C fixed in photosynthesis between respiration and biomass production, and between short- and long-lived and aboveground and belowground tissues. Incomplete knowledge of C allocation currently hinders accurate modelling of tree growth and forest ecosystem metabolism (Friedlingstein et al....

Influences of community composition on biogeochemistry of loblolly pine (Pinus taeda) systems

Treesearch

B.G. Lockaby; J.H. Miller; R.G. Clawson

1995-01-01

Litterfall and decomposition processes were compared among four forest plantations that were dominated by loblolly pine (Pinus taeda L) but that differed.in terms of presence or absence of deciduous and herbaceous components. Based on aboveground litterfall, the pine-only community was the most productive but had the slowest turnover of organic...

Wildfire and post-fire erosion impacts on forest ecosystem carbon and nitrogen: An analysis

Treesearch

D. G. Neary; S. T. Overby

2006-01-01

Many ecosystem processes occurring in soils depend upon the presence of organic matter. Soil organic matter is particularly important for nutrient supply, cation exchange capacity, and water retention, hence its importance in long-term site productivity. However, wildfires consume large amounts of aboveground organic material, and soil heating can consume soil organic...

Nitrogen and Phosphorus Use Efficiency in Stands of Loblolly and Slash Pine

Treesearch

Christopher A. Dicus; Thomas J. Dean

2002-01-01

Nitrogen and phosphorus use efficiency (NUE and PUE, respectively), the annual amount of stemwood produced per unit net N or P used in total aboveground production, were examined in 17-year-old pure stands of unthinned loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Englem.) planted at two spacings. Slash pine stands...

Enhancing composite durability : using thermal treatments

Treesearch

Jerrold E. Winandy; W. Ramsay Smith

2007-01-01

The use of thermal treatments to enhance the moisture resistance and aboveground durability of solid wood materials has been studied for years. Much work was done at the Forest Products Laboratory in the last 15 years on the fundamental process of both short-and long-term exposure to heat on wood materials and its interaction with various treatment chemicals. This work...

Aboveground and belowground responses to elevated ozone in maize lines: Mo17, B73, & B73 x Mo17

USDA-ARS?s Scientific Manuscript database

Today, rising tropospheric ozone concentrations are estimated to reduce maize yields by 10% in the US. Exposure to ozone decreases plant productivity by reducing photosynthesis. As ozone enters the plant, it reacts to form reactive oxygen species that overwhelm the detoxification potential of the le...

Ex situ growth and biomass of Populus bioenergy crops irrigated and fertilized with landfill leachate

Treesearch

Ronald S. Jr. Zalesny; Adam H. Wiese; Edmund O. Bauer; Donald E. Riemenschneider

2009-01-01

Merging traditional intensive forestry with waste management offers dual goals of fiber and bioenergy production, along with environmental benefits such as soil/water remediation and carbon sequestration. As part of an ongoing effort to acquire data about initial genotypic performance, we evaluated: (1) the early aboveground growth of trees belonging to currently...

Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect

PubMed Central

Strengbom, Joachim; Viketoft, Maria; Bommarco, Riccardo

2016-01-01

Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition: Dactylis glomerata L., which is competitively favoured by nitrogen addition, and Festuca rubra L., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage of D. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage of F. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability of F. rubra, and a 23% increase in that of D. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory. D. glomerata remained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion of F. rubra. Belowground herbivory appeared to mitigate the influence of aboveground herbivory, and this mechanism may play a role for plant species coexistence. PMID:27069805

Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect.

PubMed

Borgström, Pernilla; Strengbom, Joachim; Viketoft, Maria; Bommarco, Riccardo

2016-01-01

Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition: Dactylis glomerata L., which is competitively favoured by nitrogen addition, and Festuca rubra L., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage of D. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage of F. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability of F. rubra, and a 23% increase in that of D. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory. D. glomerata remained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion of F. rubra. Belowground herbivory appeared to mitigate the influence of aboveground herbivory, and this mechanism may play a role for plant species coexistence.

Seagrass metabolism across a productivity gradient using the eddy covariance, Eulerian control volume, and biomass addition techniques

NASA Astrophysics Data System (ADS)

Long, Matthew H.; Berg, Peter; Falter, James L.

2015-05-01

The net ecosystem metabolism of the seagrass Thalassia testudinum was studied across a nutrient and productivity gradient in Florida Bay, Florida, using the Eulerian control volume, eddy covariance, and biomass addition techniques. In situ oxygen fluxes were determined by a triangular Eulerian control volume with sides 250 m long and by eddy covariance instrumentation at its center. The biomass addition technique evaluated the aboveground seagrass productivity through the net biomass added. The spatial and temporal resolutions, accuracies, and applicability of each method were compared. The eddy covariance technique better resolved the short-term flux rates and the productivity gradient across the bay, which was consistent with the long-term measurements from the biomass addition technique. The net primary production rates from the biomass addition technique, which were expected to show greater autotrophy due to the exclusion of sediment metabolism and belowground production, were 71, 53, and 30 mmol carbon m-2 d-1 at 3 sites across the bay. The net ecosystem metabolism was 35, 25, and 11 mmol oxygen m-2 d-1 from the eddy covariance technique and 10, -103, and 14 mmol oxygen m-2 d-1 from the Eulerian control volume across the same sites, respectively. The low-flow conditions in the shallow bays allowed for periodic stratification and long residence times within the Eulerian control volume that likely reduced its precision. Overall, the eddy covariance technique had the highest temporal resolution while producing accurate long-term flux rates that surpassed the capabilities of the biomass addition and Eulerian control volume techniques in these shallow coastal bays.

The engineered phytoremediation of ionic and methylmercury pollution 70054yr.2001.doc

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

Meagher, Richard B.

2001-06-01

Our long-term objective is to enable highly productive plant species to extract, resist, detoxify, and/or sequester toxic organic and heavy metal pollutants (Meagher, 2000) applying scientific strategies and technologies from a rapidly developing field called phytoremediation. The phytoremediation of toxic elemental and organic pollutants requires the use relatively different approaches (Meagher, 2000). Our current specific objectives are to use transgenic plants to control the chemical species, electrochemical state, and aboveground binding of mercury to (a) prevent methylmercury from entering the food-chain, (b) remove mercury from polluted sites, and (c) hyperaccumulate mercury in aboveground tissues for later harvest. Various parts ofmore » this strategy are being critically tested by examining different genes in model plants and field species and comparing the results to control plants as recently reviewed (Meagher et al., 2000; Rugh et al., 2000).« less

Aboveground mechanical stimuli affect belowground plant-plant communication.

PubMed

Elhakeem, Ali; Markovic, Dimitrije; Broberg, Anders; Anten, Niels P R; Ninkovic, Velemir

2018-01-01

Plants can detect the presence of their neighbours and modify their growth behaviour accordingly. But the extent to which this neighbour detection is mediated by abiotic stressors is not well known. In this study we tested the acclimation response of Zea mays L. seedlings through belowground interactions to the presence of their siblings exposed to brief mechano stimuli. Maize seedling simultaneously shared the growth solution of touched plants or they were transferred to the growth solution of previously touched plants. We tested the growth preferences of newly germinated seedlings toward the growth solution of touched (T_solution) or untouched plants (C_solution). The primary root of the newly germinated seedlings grew significantly less towards T_solution than to C_solution. Plants transferred to T_solution allocated more biomass to shoots and less to roots. While plants that simultaneously shared their growth solution with the touched plants produced more biomass. Results show that plant responses to neighbours can be modified by aboveground abiotic stress to those neighbours and suggest that these modifications are mediated by belowground interactions.

Development of a data driven process-based model for remote sensing of terrestrial ecosystem productivity, evapotranspiration, and above-ground biomass

NASA Astrophysics Data System (ADS)

El Masri, Bassil

2011-12-01

Modeling terrestrial ecosystem functions and structure has been a subject of increasing interest because of the importance of the terrestrial carbon cycle in global carbon budget and climate change. In this study, satellite data were used to estimate gross primary production (GPP), evapotranspiration (ET) for two deciduous forests: Morgan Monroe State forest (MMSF) in Indiana and Harvard forest in Massachusetts. Also, above-ground biomass (AGB) was estimated for the MMSF and the Howland forest (mixed forest) in Maine. Surface reflectance and temperature, vegetation indices, soil moisture, tree height and canopy area derived from the Moderate Resolution Imagining Spectroradiometer (MODIS), the Advanced Microwave Scanning Radiometer (AMRS-E), LIDAR, and aerial imagery respectively, were used for this purpose. These variables along with others derived from remotely sensed data were used as inputs variables to process-based models which estimated GPP and ET and to a regression model which estimated AGB. The process-based models were BIOME-BGC and the Penman-Monteith equation. Measured values for the carbon and water fluxes obtained from the Eddy covariance flux tower were compared to the modeled GPP and ET. The data driven methods produced good estimation of GPP and ET with an average root mean square error (RMSE) of 0.17 molC/m2 and 0.40 mm/day, respectively for the MMSF and the Harvard forest. In addition, allometric data for the MMSF were used to develop the regression model relating AGB with stem volume. The performance of the AGB regression model was compared to site measurements using remotely sensed data for the MMSF and the Howland forest where the model AGB RMSE ranged between 2.92--3.30 Kg C/m2. Sensitivity analysis revealed that improvement in maintenance respiration estimation and remotely sensed maximum photosynthetic activity as well as accurate estimate of canopy resistance will result in improved GPP and ET predictions. Moreover, AGB estimates were found to decrease as large grid size is used in rasterizing LIDAR return points. The analysis suggested that this methodology could be used as an operational procedure for monitoring changes in terrestrial ecosystem functions and structure brought by environmental changes.

Controls over aboveground forest carbon density on Barro Colorado Island, Panama

NASA Astrophysics Data System (ADS)

Mascaro, J.; Asner, G. P.; Muller-Landau, H. C.; van Breugel, M.; Hall, J.; Dahlin, K.

2011-06-01

Despite the importance of tropical forests to the global carbon cycle, ecological controls over landscape-level variation in live aboveground carbon density (ACD) in tropical forests are poorly understood. Here, we conducted a spatially comprehensive analysis of ACD variation for a continental tropical forest - Barro Colorado Island, Panama (BCI) - and tested site factors that may control such variation. We mapped ACD over 1256 ha of BCI using airborne Light Detection and Ranging (LiDAR), which was well-correlated with ground-based measurements of ACD in Panamanian forests of various ages (r2 = 0.84, RMSE = 17 Mg C ha-1, P < 0.0001). We used multiple regression to examine controls over LiDAR-derived ACD, including slope angle, forest age, bedrock, and soil texture. Collectively, these variables explained 14 % of the variation in ACD at 30-m resolution, and explained 33 % at 100-m resolution. At all resolutions, slope (linked to underlying bedrock variation) was the strongest driving factor; standing carbon stocks were generally higher on steeper slopes. This result suggests that physiography may be more important in controlling ACD variation in Neotropical forests than currently thought. Although BCI has been largely undisturbed by humans for a century, past land-use over approximately half of the island still influences ACD variation, with younger forests (80-130 years old) averaging ~15 % less carbon storage than old-growth forests (>400 years old). If other regions of relatively old tropical secondary forests also store less carbon aboveground than primary forests, the effects on the global carbon cycle could be substantial and difficult to detect with traditional satellite monitoring.

Methods for estimating aboveground biomass and its components for Douglas-fir and lodgepole pine trees

Treesearch

K.P. Poudel; H. Temesgen

2016-01-01

Estimating aboveground biomass and its components requires sound statistical formulation and evaluation. Using data collected from 55 destructively sampled trees in different parts of Oregon, we evaluated the performance of three groups of methods to estimate total aboveground biomass and (or) its components based on the bias and root mean squared error (RMSE) that...

Aboveground tree biomass statistics for Maine: 1982

Treesearch

Eric H. Wharton; Thomas S. Frieswyk; Anne M. Malley

1985-01-01

Traditional measures of volume inadequately describe the total aboveground wood resource. The 1980-82 inventory of Maine included estimates of aboveground tree biomass on timberland. There are nearly 1,504.4 million green tons of wood and bark in all trees above the ground level, or 88.2 green tons per acre of timberland. Most of the biomass is in growing stock, but 49...

Extraction and textural characterization of above-ground areas from aerial stereo pairs: a quality assessment

NASA Astrophysics Data System (ADS)

Baillard, C.; Dissard, O.; Jamet, O.; Maître, H.

Above-ground analysis is a key point to the reconstruction of urban scenes, but it is a difficult task because of the diversity of the involved objects. We propose a new method to above-ground extraction from an aerial stereo pair, which does not require any assumption about object shape or nature. A Digital Surface Model is first produced by a stereoscopic matching stage preserving discontinuities, and then processed by a region-based Markovian classification algorithm. The produced above-ground areas are finally characterized as man-made or natural according to the grey level information. The quality of the results is assessed and discussed.

Coupling of remote sensing, field campaign, and mechanistic and empirical modeling to monitor spatiotemporal carbon dynamics of a Mediterranean watershed in a changing regional climate.

PubMed

Berberoglu, S; Donmez, C; Evrendilek, F

2015-04-01

The aim of this study was to simulate impacts of regional climate change in the 2070s on carbon (C) cycle of a Mediterranean watershed combining field measurements, Envisat MERIS and IKONOS data, and the Carnegie Ames Stanford Approach model. Simulation results indicated that the present total C sink status (1.36 Mt C year(-1)) of Mediterranean evergreen needleleaf forest, grassland and cropland ecosystems is expected to weaken by 7.6% in response to the climate change in the 2070s (Mt=10(12) g). This decreasing trend was mirrored in soil respiration (R H), aboveground and belowground net primary production (NPP), NEP, and net biome production (NBP). The decrease in NEP in the 2070s was the highest (21.9%) for mixed forest where the smallest present C sink of 0.03 Mt C year(-1) was estimated. The average present net ecosystem production (NEP) values were estimated at 110±15, 75±19, and 41±25 g C m(-2) years(-1) in forest, grassland, and cropland, respectively, with a watershed-scale mean of 95±30 g C m(-2) years(-1). The largest present C sink was in grassland, with a total C pool of 0.55 Mt C year(-1), through its greater spatial extent.

Monitoring Forage Production of California Rangeland Using Remote Sensing Observations

NASA Astrophysics Data System (ADS)

Liu, H.; Jin, Y.; Dahlgren, R. A.; O'Geen, A. T.; Roche, L. M.; Smith, A. M.; Flavell, D.

2016-12-01

Pastures and rangeland cover more than 10 million hectares in California's coastal and inland foothill regions, providing feeds to livestock and important ecosystem services. Forage production in California has a large year-to-year variation due to large inter-annual and seasonal variabilities in precipitation and temperature. It also varies spatially due to the variability in climate and soils. Our goal is to develop a robust and cost-effective tool to map the near-real-time and historical forage productivity in California using remote sensing observations from Landsat and MODIS satellites. We used a Monteith's eco-physiological plant growth theory: the aboveground net primary production (ANPP) is determined by (i) the absorbed photosynthetically active radiation (APAR) and the (ii) light use efficiency (LUE): ANPP = APAR * LUEmax * f(T) * f(SM), where LUEmax is the maximum LUE, and f(T) and f(SM) are the temperature and soil moisture constrains on LUE. APAR was estimated with Landsat and MODIS vegetation index (VI), and LUE was calibrated with a statewide point dataset of peak forage production measurements at 75 annual rangeland sites. A non-linear optimization was performed to derive maximum LUE and the parameters for temperature and soil moisture regulation on LUE by minimizing the differences between the estimated and measured ANPP. Our results showed the satellite-derived annual forage production estimates correlated well withcontemporaneous in-situ forage measurements and captured both the spatial and temporal productivity patterns of forage productivity well. This remote sensing algorithm can be further improved as new field measurements become available. This tool will have a great importance in maintaining a sustainable range industry by providing key knowledge for ranchers and the stakeholders to make managerial decisions.

Responses of plant available water and forest productivity to variably layered coarse textured soils

NASA Astrophysics Data System (ADS)

Huang, Mingbin; Barbour, Lee; Elshorbagy, Amin; Si, Bing; Zettl, Julie

2010-05-01

Reforestation is a primary end use for reconstructed soils following oil sands mining in northern Alberta, Canada. Limited soil water conditions strongly restrict plant growth. Previous research has shown that layering of sandy soils can produce enhanced water availability for plant growth; however, the effect of gradation on these enhancements is not well defined. The objective of this study was to evaluate the effect of soil texture (gradation and layering) on plant available water and consequently on forest productivity for reclaimed coarse textured soils. A previously validated system dynamics (SD) model of soil moisture dynamics was coupled with ecophysiological and biogeochemical processes model, Biome-BGC-SD, to simulate forest dynamics for different soil profiles. These profiles included contrasting 50 cm textural layers of finer sand overlying coarser sand in which the sand layers had either a well graded or uniform soil texture. These profiles were compared to uniform profiles of the same sands. Three tree species of jack pine (Pinus banksiana Lamb.), white spruce (Picea glauce Voss.), and trembling aspen (Populus tremuloides Michx.) were simulated using a 50 year climatic data base from northern Alberta. Available water holding capacity (AWHC) was used to identify soil moisture regime, and leaf area index (LAI) and net primary production (NPP) were used as indices of forest productivity. Published physiological parameters were used in the Biome-BGC-SD model. Relative productivity was assessed by comparing model predictions to the measured above-ground biomass dynamics for the three tree species, and was then used to study the responses of forest leaf area index and potential productivity to AWHC on different soil profiles. Simulated results indicated soil layering could significantly increase AWHC in the 1-m profile for coarse textured soils. This enhanced AWHC could result in an increase in forest LAI and NPP. The increased extent varied with soil textures and vegetative types. The simulated results showed that the presence of 50 cm of coarser graded sand overlying 50 cm of finer graded sand is the most effective reclaimed prescription to increase AWHC and forest productivity among the studied soil profiles.

Effects of nitrogen addition and fire on plant nitrogen use in a temperate steppe.

PubMed

Wei, Hai-Wei; Lü, Xiao-Tao; Lü, Fu-Mei; Han, Xing-Guo

2014-01-01

Plant nitrogen (N) use strategies have great implications for primary production and ecosystem nutrient cycling. Given the increasing atmospheric N deposition received by most of the terrestrial ecosystems, understanding the responses of plant N use would facilitate the projection of plant-mediated N cycling under global change scenarios. The effects of N deposition on plant N use would be affected by both natural and anthropogenic disturbances, such as prescribed fire in the grassland. We examined the effects of N addition (5.25 g N m(-2) yr(-1)) and prescribed fire (annual burning) on plant N concentrations and N use characters at both species and community levels in a temperate steppe of northern China. We found that N addition and fire independently affected soil N availability and plant N use traits. Nitrogen addition increased aboveground net primary productivity (ANPP), inorganic N, and N uptake, decreased N response efficiency (NRE), but did not affect biomass-weighed N concentrations at community level. Prescribed fire did not change the community level N concentrations, but largely decreased N uptake efficiency and NRE. At the species level, the effects of N addition and fire on plant N use were species-specific. The divergent responses of plant N use at community and species levels to N addition and fire highlight the importance of the hierarchical responses of plant N use at diverse biological organization levels to the alteration of soil N availability. This study will improve our understanding of the responses of plant-mediated N cycling to global change factors and ecosystem management strategies in the semiarid grasslands.

Does elevated CO 2 alter silica uptake in trees?

DOE PAGES

Fulweiler, Robinson W.; Maguire, Timothy J.; Carey, Joanna C.; ...

2015-01-13

Human activities have greatly altered global carbon (C) and Nitrogen (N) cycling. In fact, atmospheric concentrations of carbon dioxide (CO 2) have increased 40% over the last century and the amount of N cycling in the biosphere has more than doubled. In an effort to understand how plants will respond to continued global CO 2 fertilization, longterm free-air CO 2 enrichment experiments have been conducted at sites around the globe. Here we examine how atmospheric CO 2 enrichment and N fertilization affects the uptake of silicon (Si) in the Duke Forest, North Carolina, a stand dominated by Pinus taeda (loblollymore » pine), and five hardwood species. Specifically, we measured foliar biogenic silica concentrations in five deciduous and one coniferous species across three treatments: CO 2 enrichment, N enrichment, and N and CO 2 enrichment. We found no consistent trends in foliar Si concentration under elevated CO 2, N fertilization, or combined elevated CO 2 and N fertilization. However, two-thirds of the tree species studied here have Si foliar concentrations greater than well-known Si accumulators, such as grasses. Based on net primary production values and aboveground Si concentrations in these trees, we calculated forest Si uptake rates under control and elevated CO 2 concentrations. Due largely to increased primary production, elevated CO 2 enhanced the magnitude of Si uptake between 20 and 26%, likely intensifying the terrestrial silica pump. This uptake of Si by forests has important implications for Si export from terrestrial systems, with the potential to impact C sequestration and higher trophic levels in downstream ecosystems.« less

Plant diversity enhances productivity and soil carbon storage

PubMed Central

Chen, Shiping; Wang, Wantong; Xu, Wenting; Wang, Yang; Wan, Hongwei; Tang, Xuli; Zhou, Guoyi; Xie, Zongqiang; Zhou, Daowei; Shangguan, Zhouping; Huang, Jianhui; Wang, Yanfen; Sheng, Jiandong; Tang, Lisong; Li, Xinrong; Dong, Ming; Wu, Yan; Wang, Qiufeng; Wu, Jianguo; Chapin, F. Stuart; Bai, Yongfei

2018-01-01

Despite evidence from experimental grasslands that plant diversity increases biomass production and soil organic carbon (SOC) storage, it remains unclear whether this is true in natural ecosystems, especially under climatic variations and human disturbances. Based on field observations from 6,098 forest, shrubland, and grassland sites across China and predictions from an integrative model combining multiple theories, we systematically examined the direct effects of climate, soils, and human impacts on SOC storage versus the indirect effects mediated by species richness (SR), aboveground net primary productivity (ANPP), and belowground biomass (BB). We found that favorable climates (high temperature and precipitation) had a consistent negative effect on SOC storage in forests and shrublands, but not in grasslands. Climate favorability, particularly high precipitation, was associated with both higher SR and higher BB, which had consistent positive effects on SOC storage, thus offsetting the direct negative effect of favorable climate on SOC. The indirect effects of climate on SOC storage depended on the relationships of SR with ANPP and BB, which were consistently positive in all biome types. In addition, human disturbance and soil pH had both direct and indirect effects on SOC storage, with the indirect effects mediated by changes in SR, ANPP, and BB. High soil pH had a consistently negative effect on SOC storage. Our findings have important implications for improving global carbon cycling models and ecosystem management: Maintaining high levels of diversity can enhance soil carbon sequestration and help sustain the benefits of plant diversity and productivity. PMID:29666315

Plant diversity enhances productivity and soil carbon storage.

PubMed

Chen, Shiping; Wang, Wantong; Xu, Wenting; Wang, Yang; Wan, Hongwei; Chen, Dima; Tang, Zhiyao; Tang, Xuli; Zhou, Guoyi; Xie, Zongqiang; Zhou, Daowei; Shangguan, Zhouping; Huang, Jianhui; He, Jin-Sheng; Wang, Yanfen; Sheng, Jiandong; Tang, Lisong; Li, Xinrong; Dong, Ming; Wu, Yan; Wang, Qiufeng; Wang, Zhiheng; Wu, Jianguo; Chapin, F Stuart; Bai, Yongfei

2018-04-17

Despite evidence from experimental grasslands that plant diversity increases biomass production and soil organic carbon (SOC) storage, it remains unclear whether this is true in natural ecosystems, especially under climatic variations and human disturbances. Based on field observations from 6,098 forest, shrubland, and grassland sites across China and predictions from an integrative model combining multiple theories, we systematically examined the direct effects of climate, soils, and human impacts on SOC storage versus the indirect effects mediated by species richness (SR), aboveground net primary productivity (ANPP), and belowground biomass (BB). We found that favorable climates (high temperature and precipitation) had a consistent negative effect on SOC storage in forests and shrublands, but not in grasslands. Climate favorability, particularly high precipitation, was associated with both higher SR and higher BB, which had consistent positive effects on SOC storage, thus offsetting the direct negative effect of favorable climate on SOC. The indirect effects of climate on SOC storage depended on the relationships of SR with ANPP and BB, which were consistently positive in all biome types. In addition, human disturbance and soil pH had both direct and indirect effects on SOC storage, with the indirect effects mediated by changes in SR, ANPP, and BB. High soil pH had a consistently negative effect on SOC storage. Our findings have important implications for improving global carbon cycling models and ecosystem management: Maintaining high levels of diversity can enhance soil carbon sequestration and help sustain the benefits of plant diversity and productivity.

Soil CO2 dynamics and fluxes as affected by tree harvest in an experimental sand ecosystem.

Treesearch

C.K. Keller; T.M. White; R. O' Brien; J.L. Smith

2006-01-01

Soil CO2 production is a key process in ecosystem C exchange, and global change predictions require understanding of how ecosystem disturbance affects this process. We monitored CO2 levels in soil gas and as bicarbonate in drainage from an experimental red pine ecosystem, for 1 year before and 3 years after its aboveground...

Environmental parameters affecting inoculum production from lilac leaf pieces infected with Phytophthora ramorum

Treesearch

Nina Shishkoff

2008-01-01

Leaves with lesions caused by Phytophthora ramorum Werres, de Cock & Man in?t Veld often drop off infected plants. Because fallen leaves might serve as sources of inoculum both for the above-ground tissues of host plants and for their roots, this study quantified the inoculum produced by such leaves on the surface of pots when exposed to...

Direct estimation of aboveground forest productivity through hyperspectral remote sensing of canopy nitrogen

Treesearch

Marie-Louise Smith; Scott V. Ollinger; Mary E. Martin; John D. Aber; Richard A. Hallett; Christine L. Goodale

2002-01-01

The concentration of nitrogen in foliage has been related to rates of net photosynthesis across a wide range of plant species and functional groups and thus represents a simple and biologically meaningful link between terrestrial cycles of carbon and nitrogen. Although foliar N is used by ecosystem models to predict rates of leaf-level photosynthesis, it has rarely...

Estimating aboveground tree biomass for beetle-killed lodgepole pine in the Rocky Mountains of northern Colorado

Treesearch

Woodam Chung; Paul Evangelista; Nathaniel Anderson; Anthony Vorster; Hee Han; Krishna Poudel; Robert Sturtevant

2017-01-01

The recent mountain pine beetle (Dendroctonus ponderosae Hopkins) epidemic has affected millions of hectares of conifer forests in the Rocky Mountains. Land managers are interested in using biomass from beetle-killed trees for bioenergy and biobased products, but they lack adequate information to accurately estimate biomass in stands with heavy mortality. We...

Biomass Production and Nitrogen Recovery after Fertilization of Young Loblolly Pines

Treesearch

J. B. Baker; G. L. Switzer; L. E. Nelson

1974-01-01

Ammonium nitrate applied at rates of 112 and 224 kg of N/ha in successive years to different areas of a young loblolly pine (Pinus taeda L.) plantation increased aboveground biomass by 25% and N accumulation by 30%. Fertilization at plantation age 3 resulted in significantly greater biomass and N accumulations in the pine; fertilization at age 4...

Acidic deposition and sustainable forest management in the central Appalachians, USA

Treesearch

Mary Beth Adams

1999-01-01

Long-term productivity of mixed-species forests in the central Appalachian region of the United States may be threatened by changes in base cation availability of the soil. These changes may be due to increased intensity of harvest removals and a shift toward shorter rotations that result in increased removal of calcium and magnesium in aboveground biomass, and through...

An experimental test of the causes of forest growth decline with stand age.

Treesearch

Michael G. Ryan; Dan Binkley; James H. Fownes; Christian Giardina; Randy S. Senock

2004-01-01

The decline in aboveground wood production after canopy closure in even-aged forest stands is a common pattern in forests, but clear evidence for the mechanism causing the decline is lacking. The problem is fundamental to forest biology, commercial forestry (the decline sets the rotation age), and to carbon storage in forests. We tested three hypotheses...

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1997-04-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. 10 figs.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1997-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products.

Response of alpine grassland to elevated nitrogen deposition and water supply in China.

PubMed

Li, Kaihui; Liu, Xuejun; Song, Ling; Gong, Yanming; Lu, Chunfang; Yue, Ping; Tian, Changyan; Zhang, Fusuo

2015-01-01

Species composition and productivity are influenced by water and N availability in semi-arid grasslands. To assess the effects of increased N deposition and water supply on plant species composition and productivity, two field experiments with four N addition treatments, and three N and water combination treatments were conducted in alpine grassland in the mid Tianshan mountains, northwest China. When considering N addition alone, aboveground biomass (AGB) of forbs (F(AGB)) responded less to N addition than AGB of grasses (G(AGB)). G(AGB) increased as an effect of N combined with water addition but F(AGB) did not show such an effect, reflecting a stronger response of grasses to the interaction of water availability and N than forbs. Under all treatments, N allocation to the aboveground tissue did not change for either forbs or grasses. N deposition and water addition did not alter species richness in the present study. These results suggest that N addition generally promoted AGB but had little effect on species richness in wet years. Snowfall in winter combined with rainfall in the early growing season likely plays a critical role in regulating plant growth of the subsequent year in the alpine grassland.

Latitudinal variation in ambient UV-B radiation is an important determinant of Lolium perenne forage production, quality, and digestibility

PubMed Central

Comont, David; Winters, Ana; Gomez, Leonardo D; McQueen-Mason, Simon J; Gwynn-Jones, Dylan

2013-01-01

Few studies to date have considered the responses of agriculturally important forage grasses to UV-B radiation. Yet grasses such as Lolium perenne have a wide current distribution, representing exposure to a significant variation in ambient UV-B. The current study investigated the responses of L. perenne (cv. AberDart) to a simulated latitudinal gradient of UV-B exposure, representing biologically effective UV-B doses at simulated 70, 60, 50, 40, and 30° N latitudes. Aspects of growth, soluble compounds, and digestibility were assessed, and results are discussed in relation to UV-B effects on forage properties and the implications for livestock and bio-ethanol production. Aboveground biomass production was reduced by approximately 12.67% with every 1 kJ m–2 day–1 increase in biologically weighted UV-B. As a result, plants grown in the highest UV-B treatment had a total biomass of just 13.7% of controls. Total flavonoids were increased by approximately 76% by all UV-B treatments, while hydroxycinnamic acids increased in proportion to the UV-B dose. Conversely, the digestibility of the aboveground biomass and concentrations of soluble fructans were reduced by UV-B exposure, although soluble sucrose, glucose, and fructose concentrations were unaffected. These results highlight the capacity for UV-B to directly affect forage productivity and chemistry, with negative consequences for digestibility and bioethanol production. Results emphasize the need for future development and distribution of L. perenne varieties to take UV-B irradiance into consideration. PMID:23580749

Plants as green phones: Novel insights into plant-mediated communication between below- and above-ground insects.

PubMed

Soler, Roxina; Harvey, Jeffrey A; Bezemer, T Martijn; Stuefer, Josef F

2008-08-01

Plants can act as vertical communication channels or 'green phones' linking soil-dwelling insects and insects in the aboveground ecosystem. When root-feeding insects attack a plant, the direct defense system of the shoot is activated, leading to an accumulation of phytotoxins in the leaves. The protection of the plant shoot elicited by root damage can impair the survival, growth and development of aboveground insect herbivores, thereby creating plant-based functional links between soil-dwelling insects and insects that develop in the aboveground ecosystem. The interactions between spatially separated insects below- and aboveground are not restricted to root and foliar plant-feeding insects, but can be extended to higher trophic levels such as insect parasitoids. Here we discuss some implications of plants acting as communication channels or 'green phones' between root and foliar-feeding insects and their parasitoids, focusing on recent findings that plants attacked by root-feeding insects are significantly less attractive for the parasitoids of foliar-feeding insects.

Above-ground biomass of mangrove species. I. Analysis of models

NASA Astrophysics Data System (ADS)

Soares, Mário Luiz Gomes; Schaeffer-Novelli, Yara

2005-10-01

This study analyzes the above-ground biomass of Rhizophora mangle and Laguncularia racemosa located in the mangroves of Bertioga (SP) and Guaratiba (RJ), Southeast Brazil. Its purpose is to determine the best regression model to estimate the total above-ground biomass and compartment (leaves, reproductive parts, twigs, branches, trunk and prop roots) biomass, indirectly. To do this, we used structural measurements such as height, diameter at breast-height (DBH), and crown area. A combination of regression types with several compositions of independent variables generated 2.272 models that were later tested. Subsequent analysis of the models indicated that the biomass of reproductive parts, branches, and prop roots yielded great variability, probably because of environmental factors and seasonality (in the case of reproductive parts). It also indicated the superiority of multiple regression to estimate above-ground biomass as it allows researchers to consider several aspects that affect above-ground biomass, specially the influence of environmental factors. This fact has been attested to the models that estimated the biomass of crown compartments.

Superfund record of decision (EPA Region 10): Elmendorf Air Force Base, Operable Unit 2, source area ST41, Anchorage, AK. (First remedial action), September 1992. Interim report

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

Not Available

1992-09-01

The 13,130-acre Elmendorf Air Force Base (AFB) site is located adjacent to the municipality of Anchorage, Alaska. From 1940 to 1991, Elmendorf AFB used a 20-acre portion of the site, referred to as source area ST41, to store the fuel product JP-4 and aviation gasoline in four 1-million gallon underground tanks. As a result of numerous leaks and above-ground spills since the tanks were installed in the 1940s, USAF conducted investigations through its Installation Restoration Program (IRP). These investigations revealed several hundred thousand gallons of fuel in the ground water and soil. The ROD addresses an interim remedy at Elmendorfmore » AFB. The action is needed to reduce further spread of fuel constituents through the recovery of floating product on the ground water surface, and containment of seeps. Future RODs will include a final remedy for ground water and soil at ST41, as OU2, and will address the other six OUs at the site. The primary contaminants of concern affecting the ground water at ST41 are the compounds in JP-4, especially VOCs such as benzene, toluene, and xylenes. The selected interim remedial action for the site are included.« less

Temperature and rainfall interact to control carbon cycling in tropical forests.

PubMed

Taylor, Philip G; Cleveland, Cory C; Wieder, William R; Sullivan, Benjamin W; Doughty, Christopher E; Dobrowski, Solomon Z; Townsend, Alan R

2017-06-01

Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short-term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer-term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore climate - C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (< 20 °C), high rainfall slowed rates of C cycling, but in warm tropical forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of climate - C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth. © 2017 John Wiley & Sons Ltd/CNRS.

Productivity depends more on the rate than the frequency of N addition in a temperate grassland.

PubMed

Zhang, Yunhai; Feng, Jinchao; Isbell, Forest; Lü, Xiaotao; Han, Xingguo

2015-07-28

Nitrogen (N) is a key limiting resource for aboveground net primary productivity (ANPP) in diverse terrestrial ecosystems. The relative roles of the rate and frequency (additions yr(-1)) of N application in stimulating ANPP at both the community- and species-levels are largely unknown. By independently manipulating the rate and frequency of N input, with nine rates (from 0 to 50 g N m(-2) year(-1)) crossed with two frequencies (twice year(-1) or monthly) in a temperate steppe of northern China across 2008-2013, we found that N addition increased community ANPP, and had positive, negative, or neutral effects for individual species. There were similar ANPP responses at the community- or species-level when a particular annual amount of N was added either twice year(-1) or monthly. The community ANPP was less sensitive to soil ammonium at lower frequency of N addition. ANPP responses to N addition were positively correlated with annual precipitation. Our results suggest that, over a five-year period, there will be similar ANPP responses to a given annual N input that occurs either frequently in small amounts, as from N deposition, or that occur infrequently in larger amounts, as from application of N fertilizers.

A comparison of litter production in young and old baldcypress (Taxodium distichum L.) stands at Caddo Lake, Texas

USGS Publications Warehouse

McCoy, John W.; Draugelis-Dale, Rassa O.; Keeland, Bobby D.; Darville, Roy

2010-01-01

Aboveground primary productivity for cypress forests was assessed from measurements of litter production in two age groups and in two hydrological regimes (standing water and free-flowing). Caddo Lake, located in northeast Texas on the Texas-Louisiana border, offered a unique study site since it is dominated by extensive stands composed entirely of Taxodium distichum (L.) Rich, (baldcypress) in different age groups. Young stands (approximately 100 years old) are found along the shoreline and on shallow flooded islands. Old stands (-150 to 300 years old) are found in deeper water where they were continuously flooded. Litter production over three years from October 1998 to September 2001 was measured. Litter consisting of leaves, twigs, bark, reproductive parts, and Tillandsia usneoides (L.) L. (Spanish moss) was collected monthly using 0.5 m2 floating traps. Tree diameters were measured within 200 m2 circular plots in each stand. The young stands supported densities greater than 2,000 stems/ha and a mean stand basal area of 72.3 m2/ha, whereas old stands supported lower densities of about 500 stems/ha but with a similar mean stand basal area of 73.3 m2/ha. There was a significant difference between old and young stands for overall yearly litter production, averaging about 670 g/m2/yr in the young stands and 460 g/m2/yr in the old stands. Leaves and twigs were significantly greater in the young stands, while reproductive parts were higher in old stands. Litter collections between years or hydrological regimes were not significantly different.

Estimating and mapping forest biomass using regression models and Spot-6 images (case study: Hyrcanian forests of north of Iran).

PubMed

Motlagh, Mohadeseh Ghanbari; Kafaky, Sasan Babaie; Mataji, Asadollah; Akhavan, Reza

2018-05-21

Hyrcanian forests of North of Iran are of great importance in terms of various economic and environmental aspects. In this study, Spot-6 satellite images and regression models were applied to estimate above-ground biomass in these forests. This research was carried out in six compartments in three climatic (semi-arid to humid) types and two altitude classes. In the first step, ground sampling methods at the compartment level were used to estimate aboveground biomass (Mg/ha). Then, by reviewing the results of other studies, the most appropriate vegetation indices were selected. In this study, three indices of NDVI, RVI, and TVI were calculated. We investigated the relationship between the vegetation indices and aboveground biomass measured at sample-plot level. Based on the results, the relationship between aboveground biomass values and vegetation indices was a linear regression with the highest level of significance for NDVI in all compartments. Since at the compartment level the correlation coefficient between NDVI and aboveground biomass was the highest, NDVI was used for mapping aboveground biomass. According to the results of this study, biomass values were highly different in various climatic and altitudinal classes with the highest biomass value observed in humid climate and high-altitude class.

Into the black and back: the ecology of brain investment in Neotropical army ants (Formicidae: Dorylinae)

NASA Astrophysics Data System (ADS)

Bulova, S.; Purce, K.; Khodak, P.; Sulger, E.; O'Donnell, S.

2016-04-01

Shifts to new ecological settings can drive evolutionary changes in animal sensory systems and in the brain structures that process sensory information. We took advantage of the diverse habitat ecology of Neotropical army ants to test whether evolutionary transitions from below- to above-ground activity were associated with changes in brain structure. Our estimates of genus-typical frequencies of above-ground activity suggested a high degree of evolutionary plasticity in habitat use among Neotropical army ants. Brain structure consistently corresponded to degree of above-ground activity among genera and among species within genera. The most above-ground genera (and species) invested relatively more in visual processing brain tissues; the most subterranean species invested relatively less in central processing higher-brain centers (mushroom body calyces). These patterns suggest a strong role of sensory ecology (e.g., light levels) in selecting for army ant brain investment evolution and further suggest that the subterranean environment poses reduced cognitive challenges to workers. The highly above-ground active genus Eciton was exceptional in having relatively large brains and particularly large and structurally complex optic lobes. These patterns suggest that the transition to above-ground activity from ancestors that were largely subterranean for approximately 60 million years was followed by re-emergence of enhanced visual function in workers.

Effect of specific plant-growth-promoting rhizobacteria (PGPR) on growth and uptake of neonicotinoid insecticide thiamethoxam in corn (Zea mays L.) seedlings.

PubMed

Myresiotis, Charalampos K; Vryzas, Zisis; Papadopoulou-Mourkidou, Euphemia

2015-09-01

Corn (Zea mays L.) is one of the most important cereal crops in the world and is used for food, feed and energy. Inoculation with plant-growth-promoting rhizobacteria (PGPR) would reduce the use of chemical fertilisers and pesticides and could be suggested as an alternative practice for sustainable production of corn in modern agricultural systems. In this study, the effect of two Bacillus PGPR formulated products, Companion (B. subtilis GB03) and FZB24 (B. subtilis FZB24), on corn growth and root uptake of insecticide thiamethoxam was investigated. All bacterial treatments enhanced root biomass production by 38-65% compared with the uninoculated control, with no stimulatory effect of PGPR on above-ground biomass of corn. The uptake results revealed that, in plants inoculated with the PGPR B. subtilis FZB24 and B. subtilis GB03, singly or in combination, the uptake and/or systemic translocation of thiamethoxam in the above-ground corn parts was significantly higher at the different growth ages compared with the control receiving no bacterial treatment. The findings suggest that the PGPR-elicited enhanced uptake of thiamethoxam could lead to improved efficiency of thiamethoxam using reduced rates of pesticides in combination with PGPR as an alternative crop protection technique. © 2014 Society of Chemical Industry.

Tassel Removal Positively Affects Biomass Production Coupled with Significantly Increasing Stem Digestibility in Switchgrass

PubMed Central

Zhao, Chunqiao; Fan, Xifeng; Hou, Xincun; Zhu, Yi; Yue, Yuesen; Zhang, Shuang; Wu, Juying

2015-01-01

In this study, tassels of Cave-in-Rock (upland) and Alamo (lowland) were removed at or near tassel emergence to explore its effects on biomass production and quality. Tassel-removed (TR) Cave-in-Rock and Alamo both exhibited a significant (P<0.05) increase in plant heights (not including tassel length), tiller number, and aboveground biomass dry weight (10% and 12%, 30% and 13%, 13% and 18%, respectively by variety) compared to a control (CK) treatment. Notably, total sugar yields of TR Cave-in-Rock and Alamo stems increased significantly (P<0.05 or 0.01) by 19% and 19%, 21% and 14%, 52% and 18%, respectively by variety, compared to those of control switchgrass under 3 treatments by direct enzymatic hydrolysis (DEH), enzymatic hydrolysis after 1% NaOH pretreatment (EHAL) and enzymatic hydrolysis after 1% H2SO4 pretreatment (EHAC). These differences were mainly due to significantly (P<0.05 or 0.01) higher cellulose content, lower cellulose crystallinity indexes (CrI) caused by higher arabinose (Ara) substitution in xylans, and lower S/G ratio in lignin. However, the increases of nitrogen (N) and sulphur (S) concentration negatively affects the combustion quality of switchgrass aboveground biomass. This work provides information for increasing biomass production and quality in switchgrass and also facilitates the inhibition of gene dispersal of switchgrass in China. PMID:25849123

Aboveground vs. Belowground Carbon Stocks in African Tropical Lowland Rainforest: Drivers and Implications.

PubMed

Doetterl, Sebastian; Kearsley, Elizabeth; Bauters, Marijn; Hufkens, Koen; Lisingo, Janvier; Baert, Geert; Verbeeck, Hans; Boeckx, Pascal

2015-01-01

African tropical rainforests are one of the most important hotspots to look for changes in the upcoming decades when it comes to C storage and release. The focus of studying C dynamics in these systems lies traditionally on living aboveground biomass. Belowground soil organic carbon stocks have received little attention and estimates of the size, controls and distribution of soil organic carbon stocks are highly uncertain. In our study on lowland rainforest in the central Congo basin, we combine both an assessment of the aboveground C stock with an assessment of the belowground C stock and analyze the latter in terms of functional pools and controlling factors. Our study shows that despite similar vegetation, soil and climatic conditions, soil organic carbon stocks in an area with greater tree height (= larger aboveground carbon stock) were only half compared to an area with lower tree height (= smaller aboveground carbon stock). This suggests that substantial variability in the aboveground vs. belowground C allocation strategy and/or C turnover in two similar tropical forest systems can lead to significant differences in total soil organic C content and C fractions with important consequences for the assessment of the total C stock of the system. We suggest nutrient limitation, especially potassium, as the driver for aboveground versus belowground C allocation. However, other drivers such as C turnover, tree functional traits or demographic considerations cannot be excluded. We argue that large and unaccounted variability in C stocks is to be expected in African tropical rain-forests. Currently, these differences in aboveground and belowground C stocks are not adequately verified and implemented mechanistically into Earth System Models. This will, hence, introduce additional uncertainty to models and predictions of the response of C storage of the Congo basin forest to climate change and its contribution to the terrestrial C budget.

Aboveground vs. Belowground Carbon Stocks in African Tropical Lowland Rainforest: Drivers and Implications

PubMed Central

Bauters, Marijn; Hufkens, Koen; Lisingo, Janvier; Baert, Geert; Verbeeck, Hans; Boeckx, Pascal

2015-01-01

Background African tropical rainforests are one of the most important hotspots to look for changes in the upcoming decades when it comes to C storage and release. The focus of studying C dynamics in these systems lies traditionally on living aboveground biomass. Belowground soil organic carbon stocks have received little attention and estimates of the size, controls and distribution of soil organic carbon stocks are highly uncertain. In our study on lowland rainforest in the central Congo basin, we combine both an assessment of the aboveground C stock with an assessment of the belowground C stock and analyze the latter in terms of functional pools and controlling factors. Principal Findings Our study shows that despite similar vegetation, soil and climatic conditions, soil organic carbon stocks in an area with greater tree height (= larger aboveground carbon stock) were only half compared to an area with lower tree height (= smaller aboveground carbon stock). This suggests that substantial variability in the aboveground vs. belowground C allocation strategy and/or C turnover in two similar tropical forest systems can lead to significant differences in total soil organic C content and C fractions with important consequences for the assessment of the total C stock of the system. Conclusions/Significance We suggest nutrient limitation, especially potassium, as the driver for aboveground versus belowground C allocation. However, other drivers such as C turnover, tree functional traits or demographic considerations cannot be excluded. We argue that large and unaccounted variability in C stocks is to be expected in African tropical rain-forests. Currently, these differences in aboveground and belowground C stocks are not adequately verified and implemented mechanistically into Earth System Models. This will, hence, introduce additional uncertainty to models and predictions of the response of C storage of the Congo basin forest to climate change and its contribution to the terrestrial C budget. PMID:26599231

Drivers of aboveground wood production in a lowland tropical forest of West Africa: teasing apart the roles of tree density, tree diversity, soil phosphorus, and historical logging.

PubMed

Jucker, Tommaso; Sanchez, Aida Cuni; Lindsell, Jeremy A; Allen, Harriet D; Amable, Gabriel S; Coomes, David A

2016-06-01

Tropical forests currently play a key role in regulating the terrestrial carbon cycle and abating climate change by storing carbon in wood. However, there remains considerable uncertainty as to whether tropical forests will continue to act as carbon sinks in the face of increased pressure from expanding human activities. Consequently, understanding what drives productivity in tropical forests is critical. We used permanent forest plot data from the Gola Rainforest National Park (Sierra Leone) - one of the largest tracts of intact tropical moist forest in West Africa - to explore how (1) stand basal area and tree diversity, (2) past disturbance associated with past logging, and (3) underlying soil nutrient gradients interact to determine rates of aboveground wood production (AWP). We started by statistically modeling the diameter growth of individual trees and used these models to estimate AWP for 142 permanent forest plots. We then used structural equation modeling to explore the direct and indirect pathways which shape rates of AWP. Across the plot network, stand basal area emerged as the strongest determinant of AWP, with densely packed stands exhibiting the fastest rates of AWP. In addition to stand packing density, both tree diversity and soil phosphorus content were also positively related to productivity. By contrast, historical logging activities negatively impacted AWP through the removal of large trees, which contributed disproportionately to productivity. Understanding what determines variation in wood production across tropical forest landscapes requires accounting for multiple interacting drivers - with stand structure, tree diversity, and soil nutrients all playing a key role. Importantly, our results also indicate that logging activities can have a long-lasting impact on a forest's ability to sequester and store carbon, emphasizing the importance of safeguarding old-growth tropical forests.

Evaluating productivity-biodiversity relationship and spectral diversity in prairie grasslands under different fire management treatments using in-situ and remote sensing hyperspectral data

NASA Astrophysics Data System (ADS)

Gholizadeh, H.; Gamon, J. A.; Zygielbaum, A. I.; Schweiger, A. K.; Cavender-Bares, J.; Yang, Y.; Knops, J. M. H.

2017-12-01

Grasslands cover as much as 25% of the Earth's surface and account for approximately 20% of overall terrestrial productivity and contribute to global biodiversity. To optimize the status of grasslands and to counteract their degradation, different management practices have been adopted. Fire has been shown to be an important management practice in the maintenance of grasslands. Our main goals were 1) to evaluate the productivity-biodiversity relationship in grasslands under fire treatment, and 2) to evaluate the capability of hyperspectral remote sensing in estimating biodiversity using spectral data (i.e. spectral diversity). We used above-ground biomass (as a surrogate for productivity), species richness (SR; as a surrogate for biodiversity), and airborne hyperspectral data from a natural grassland with fire treatment (20 plots), and a natural grassland without fire treatment (21 plots), all located at the Cedar Creek Ecosystem Science Reserve in Central Minnesota, USA. The productivity-biodiversity relationship for the fire treatment plots showed a hump-shaped model with adjusted R2=0.37, whereas the relationship for the non-burned plots were non-significant. The relationship between SR and spectral diversity (SD) were positive linear for both treatments; however, the relationship for plots with fire treatment was higher (adjusted R2 = 0.34 vs. 0.19). It is assumed that post-fire foliar nutrients increase soil nitrogen and phosphorus which facilitate post-fire growth and induce higher above-ground biomass and chlorophyll content in plants. Overall, the results of this study showed that management practices affect the productivity-biodiversity relationship and illustrated the effect of fire treatment on remote sensing of biodiversity.

Aboveground vertebrate and invertebrate herbivore impact on net N mineralization in subalpine grasslands.

PubMed

Risch, Anita C; Schotz, Martin; Vandegehuchte, Martijn L; Van Der Putten, Wim H; Duyts, Henk; Raschein, Ursina; Gwiazdowicz, Dariusz J; Busse, Matt D; Page-dumroese, Deborah S; Zimmermann, Stephan

2015-12-01

Aboveground herbivores have strong effects on grassland nitrogen (N) cycling. They can accelerate or slow down soil net N mineralization depending on ecosystem productivity and grazing intensity. Yet, most studies only consider either ungulates or invertebrate herbivores, but not the combined effect of several functionally different vertebrate and invertebrate herbivore species or guilds. We assessed how a diverse herbivore community affects net N mineralization in subalpine grasslands. By using size-selective fences, we progressively excluded large, medium, and small mammals, as well as invertebrates from two vegetation types, and assessed how the exclosure types (ET) affected net N mineralization. The two vegetation types differed in long-term management (centuries), forage quality, and grazing history and intensity. To gain a more mechanistic understanding of how herbivores affect net N mineralization, we linked mineralization to soil abiotic (temperature; moisture; NO3-, NH4+, and total inorganic N concentrations/pools; C, N, P concentrations; pH; bulk density), soil biotic (microbial biomass; abundance of collembolans, mites, and nematodes) and plant (shoot and root biomass; consumption; plant C, N, and fiber content; plant N pool) properties. Net N mineralization differed between ET, but not between vegetation types. Thus, short-term changes in herbivore community composition and, therefore, in grazing intensity had a stronger effect on net N mineralization than long-term management and grazing history. We found highest N mineralization values when only invertebrates were present, suggesting that mammals had a negative effect on net N mineralization. Of the variables included in our analyses, only mite abundance and aboveground plant biomass explained variation in net N mineralization among ET. Abundances of both mites and leaf-sucking invertebrates were positively correlated with aboveground plant biomass, and biomass increased with progressive exclusion. The negative impact of mammals on net N mineralization may be related partially to (1) differences in the amount of plant material (litter) returned to the belowground subsystem, which induced a positive bottom-up effect on mite abundance, and (2) alterations in the amount and/or distribution of dung, urine, and food waste. Thus, our results clearly show that short-term alterations of the aboveground herbivore community can strongly impact nutrient cycling within ecosystems independent of long-term management and grazing history.

Body mass of prefledging Emperor Geese Chen canagica: Large-scale effects of interspecific densities and food availability

USGS Publications Warehouse

Lake, B.C.; Schmutz, J.A.; Lindberg, M.S.; Ely, Craig R.; Eldridge, W.D.; Broerman, F.J.

2008-01-01

We studied body mass of prefledging Emperor Geese Chen canagica at three locations across the Yukon-Kuskokwim Delta, Alaska, during 1990-2004 to investigate whether large-scale variation in body mass was related to interspecific competition for food. From 1990 to 2004, densities of Cackling Geese Branta hutchinsii minima more than doubled and were c. 2-5?? greater than densities of Emperor Geese, which were relatively constant over time. Body mass of prefledging Emperor Geese was strongly related (negatively) to interspecific densities of geese (combined density of Cackling and Emperor Geese) and positively related to measures of food availability (grazing lawn extent and net above-ground primary productivity (NAPP)). Grazing by geese resulted in consumption of ??? 90% of the NAPP that occurred in grazing lawns during the brood-rearing period, suggesting that density-dependent interspecific competition was from exploitation of common food resources. Efforts to increase the population size of Emperor Geese would benefit from considering competitive interactions among goose species and with forage plants. ?? 2008 The Authors.

Multiscale Trend Analysis for Pampa Grasslands Using Ground Data and Vegetation Sensor Imagery

PubMed Central

Scottá, Fernando C.; da Fonseca, Eliana L.

2015-01-01

This study aimed to evaluate changes in the aboveground net primary productivity (ANPP) of grasslands in the Pampa biome by using experimental plots and changes in the spectral responses of similar vegetation communities obtained by remote sensing and to compare both datasets with meteorological variations to validate the transition scales of the datasets. Two different geographic scales were considered in this study. At the local scale, an analysis of the climate and its direct influences on grassland ANPP was performed using data from a long-term experiment. At the regional scale, the influences of climate on the grassland reflectance patterns were determined using vegetation sensor imagery data. Overall, the monthly variations of vegetation canopy growth analysed using environmental changes (air temperature, total rainfall and total evapotranspiration) were similar. The results from the ANPP data and the NDVI data showed the that variations in grassland growth were similar and independent of the analysis scale, which indicated that local data and the relationships of local data with climate can be considered at the regional scale in the Pampa biome by using remote sensing. PMID:26197320

Use of artificially-induced freezing temperatures to identify freeze tolerance in above-ground buds of Saccharum and Erianthus accessions

USDA-ARS?s Scientific Manuscript database

Sugarcane is a crop which is primarily grown between 30oN and 30oS latitude in tropical environments. Small areas of production in sub-tropical regions exist, and there is an increasing desire to produce the crop in colder environments. Cold-tolerant sugarcane is important both to the sub-tropical s...

In Situ Bioremediation of MTBE in Groundwater

DTIC Science & Technology

2003-06-01

by-products (carbon dioxide and water ). Groundwater leaving the down-gradient edge of the treatment zone contains MTBE at concentrations less than... groundwater treatment approaches ineffective or impracticable. Currently, conventional pump and treat (P&T) followed by aboveground water treatment and...carbon dioxide and water ). Groundwater leaving the down gradient edge of the treatment zone contains MTBE at concentrations less than or equal to the

Soil nutrients, aboveground productivity and vegetative diversity after 10 years of experimental acidification and base cation depletion

Treesearch

Mary Beth Adams; James A. Burger

2010-01-01

Soil acidification and base cation depletion are concerns for those wishing to manage central Appalachian hardwood forests sustainably. In this research, 2 experiments were established in 1996 and 1997 in two forest types common in the central Appalachian hardwood forests, to examine how these important forests respond to depletion of nutrients such as calcium and...

Five-year vegetation control effects on aboveground biomass and nitrogen content and allocation in Douglas-fir plantations on three contrasting sites

Treesearch

Warren D. Devine; Timothy B. Harrington; Thomas A. Terry; Robert B. Harrison; Robert A. Slesak; David H. Peter; Constance A. Harrington; Carol J. Shilling; Stephen H. Schoenholtz

2011-01-01

Despite widespread use of intensive vegetation control (VC) in forest management, the effects of VC on allocation of biomass and nutrients between young trees and competing vegetation are not well understood. On three Pacific Northwest sites differing in productivity, soil parent material, and understory vegetation community, we evaluated year-5 effects of presence/...

Hyperspectral sensing of forests

NASA Astrophysics Data System (ADS)

Goodenough, David G.; Dyk, Andrew; Chen, Hao; Hobart, Geordie; Niemann, K. Olaf; Richardson, Ash

2007-11-01

Canada contains 10% of the world's forests covering an area of 418 million hectares. The sustainable management of these forest resources has become increasingly complex. Hyperspectral remote sensing can provide a wealth of new and improved information products to resource managers to make more informed decisions. Research in this area has demonstrated that hyperspectral remote sensing can be used to create more accurate products for forest inventory, forest health, foliar biochemistry, biomass, and aboveground carbon than are currently available. This paper surveys recent methods and results in hyperspectral sensing of forests and describes space initiatives for hyperspectral sensing.

A novel dendrochronological approach reveals drivers of carbon sequestration in tree species of riparian forests across spatiotemporal scales.

PubMed

Rieger, Isaak; Kowarik, Ingo; Cherubini, Paolo; Cierjacks, Arne

2017-01-01

Aboveground carbon (C) sequestration in trees is important in global C dynamics, but reliable techniques for its modeling in highly productive and heterogeneous ecosystems are limited. We applied an extended dendrochronological approach to disentangle the functioning of drivers from the atmosphere (temperature, precipitation), the lithosphere (sedimentation rate), the hydrosphere (groundwater table, river water level fluctuation), the biosphere (tree characteristics), and the anthroposphere (dike construction). Carbon sequestration in aboveground biomass of riparian Quercus robur L. and Fraxinus excelsior L. was modeled (1) over time using boosted regression tree analysis (BRT) on cross-datable trees characterized by equal annual growth ring patterns and (2) across space using a subsequent classification and regression tree analysis (CART) on cross-datable and not cross-datable trees. While C sequestration of cross-datable Q. robur responded to precipitation and temperature, cross-datable F. excelsior also responded to a low Danube river water level. However, CART revealed that C sequestration over time is governed by tree height and parameters that vary over space (magnitude of fluctuation in the groundwater table, vertical distance to mean river water level, and longitudinal distance to upstream end of the study area). Thus, a uniform response to climatic drivers of aboveground C sequestration in Q. robur was only detectable in trees of an intermediate height class and in taller trees (>21.8m) on sites where the groundwater table fluctuated little (≤0.9m). The detection of climatic drivers and the river water level in F. excelsior depended on sites at lower altitudes above the mean river water level (≤2.7m) and along a less dynamic downstream section of the study area. Our approach indicates unexploited opportunities of understanding the interplay of different environmental drivers in aboveground C sequestration. Results may support species-specific and locally adapted forest management plans to increase carbon dioxide sequestration from the atmosphere in trees. Copyright © 2016 Elsevier B.V. All rights reserved.

Distinguishing the vegetation dynamics induced by anthropogenic factors using vegetation optical depth and AVHRR NDVI: A cross-border study on the Mongolian Plateau.

PubMed

Zhou, Xiang; Yamaguchi, Yasushi; Arjasakusuma, Sanjiwana

2018-03-01

Distinguishing the vegetation dynamics induced by anthropogenic factors and identifying the major drivers can provide crucial information for designing actionable and practical countermeasures to restore degraded grassland ecosystems. Based on the residual trend (RESTREND) method, this study distinguished the vegetation dynamics induced by anthropogenic factors from the effects of climate variability on the Mongolian Plateau during 1993-2012 using vegetation optical depth (VOD) and normalized difference vegetation index (NDVI), which measure vegetation water content in aboveground biomass and chlorophyll abundance in canopy cover respectively; afterwards, the major drivers within different agricultural zones and socio-institutional periods were identified by integrating agricultural statistics with statistical analysis techniques. The results showed that grasslands in Mongolia and the grazing zone of Inner Mongolia Autonomous Region (IMAR), China underwent a significant human-induced decrease in aboveground biomass during 1993-2012 and 1993-2000 respectively, which was attributable to the rapid growth of livestock densities stimulated by livestock privatization and market factors; by contrast, grasslands in these two regions did not experience a concurrent human-induced reduction in canopy greenness. Besides, the results indicated that grasslands in the grazing zone of IMAR underwent a significant human-induced increase in aboveground biomass since 2000, which was attributable to the reduced grazing pressure induced by China's ecological restoration programs; concurrently, grasslands in this region also experienced a remarkable increase in canopy greenness, however, this increase was found not directly caused by the decreased stocking densities. Furthermore, the results revealed that the farming and semi-grazing/farming zone of IMAR underwent a significant human-induced increase in both aboveground biomass and canopy greenness since 2000, which was attributable to the intensified grain production stimulated by market factors, open grazing regulation and confined feeding popularization. These findings suggest that China's grassland restoration practice has important implications for Mongolia to reverse the severe and continuous grassland degradation in the future. Copyright © 2017 Elsevier B.V. All rights reserved.

Integration of carbon conservation into sustainable forest management using high resolution satellite imagery: A case study in Sabah, Malaysian Borneo

NASA Astrophysics Data System (ADS)

Langner, Andreas; Samejima, Hiromitsu; Ong, Robert C.; Titin, Jupiri; Kitayama, Kanehiro

2012-08-01

Conservation of tropical forests is of outstanding importance for mitigation of climate change effects and preserving biodiversity. In Borneo most of the forests are classified as permanent forest estates and are selectively logged using conventional logging techniques causing high damage to the forest ecosystems. Incorporation of sustainable forest management into climate change mitigation measures such as Reducing Emissions from Deforestation and Forest Degradation (REDD+) can help to avert further forest degradation by synergizing sustainable timber production with the conservation of biodiversity. In order to evaluate the efficiency of such initiatives, monitoring methods for forest degradation and above-ground biomass in tropical forests are urgently needed. In this study we developed an index using Landsat satellite data to describe the crown cover condition of lowland mixed dipterocarp forests. We showed that this index combined with field data can be used to estimate above-ground biomass using a regression model in two permanent forest estates in Sabah, Malaysian Borneo. Tangkulap represented a conventionally logged forest estate while Deramakot has been managed in accordance with sustainable forestry principles. The results revealed that conventional logging techniques used in Tangkulap during 1991 and 2000 decreased the above-ground biomass by an annual amount of average -6.0 t C/ha (-5.2 to -7.0 t C/ha, 95% confidential interval) whereas the biomass in Deramakot increased by 6.1 t C/ha per year (5.3-7.2 t C/ha, 95% confidential interval) between 2000 and 2007 while under sustainable forest management. This indicates that sustainable forest management with reduced-impact logging helps to protect above-ground biomass. In absolute terms, a conservative amount of 10.5 t C/ha per year, as documented using the methodology developed in this study, can be attributed to the different management systems, which will be of interest when implementing REDD+ that rewards the enhancement of carbon stocks.

Controls over aboveground forest carbon density on Barro Colorado Island, Panama

NASA Astrophysics Data System (ADS)

Mascaro, J.; Asner, G. P.; Muller-Landau, H. C.; van Breugel, M.; Hall, J.; Dahlin, K.

2010-12-01

Despite the importance of tropical forests to the global carbon cycle, ecological controls over landscape-level variation in live aboveground carbon density (ACD) in tropical forests are poorly understood. Here, we conducted a spatially comprehensive analysis of ACD variation for a mainland tropical forest - Barro Colorado Island, Panama (BCI) - and tested site factors that may control such variation. We mapped ACD over 98% of BCI (~1500 ha) using airborne Light Detection and Ranging (LiDAR), which was well-correlated with ground-based measurements of ACD in Panamanian forests of various ages (r2 = 0.77, RMSE = 29 Mg C ha-1, P < 0.0001). We used multiple regression to examine controls over LiDAR-derived ACD, including slope angle, bedrock, soil texture, and forest age. Collectively, these variables explained 14% of the variation in ACD at 30-m resolution, and explained 33% at 100-m resolution. At all resolutions, slope (linked to underlying bedrock variation) was the strongest driving factor; standing carbon stocks were generally higher on steeper slopes, where erosion rates tend to exceed weathering rates, compared to gentle slopes, where weathering in place produces deep, oxic soils. This result suggests that physiography may be more important in controlling ACD variation in Neotropical forests than currently thought. Although BCI has been largely undisturbed by humans for a century, past land-use over approximately half of the island still influences ACD variation, with younger forests (80-130 years old) averaging ~15% less carbon storage than old-growth forests (>400 years old). If other regions of relatively old tropical secondary forests also store less carbon aboveground than primary forests, the effects on the global carbon cycle could be substantial and difficult to detect with satellite monitoring.

Community metabolism during early development of a restored wetland

USGS Publications Warehouse

McKenna, J.E.

2003-01-01

Productivity is an important ecological function of any natural system and may be quite high in wetlands. Restoration of productive wetlands may play a key role in re-establishing ecological function to portions of the vast areas of wetlands (roughly 86%) drained and otherwise altered in the United States over the past two centuries. A restored wetland at the Montezuma National Wildlife Refuge (upstate New York, USA) was examined to determine if ecological function (i.e., productivity), as well as biotic structure, was restored. Physicochemical conditions and both aquatic and terrestrial productivity were measured at the restoration site and compared with rates and conditions in a reference wetland. Gross aquatic community production rates (based on diurnal oxygen curves) were similar at each site (1,679 and 2,311 g O2 · m−2 · yr−1) and within the range expected for the habitat. Terrestrial Net Aboveground Primary Production rates (measured by monthly biomass changes) (2,400 and 2,500 g dry wt. · m−2 · yr−1) were also similar between sites when tree and herb production were combined. Aquatic respiration rates (3,704 and 4,552 g O2 · m−2· yr−1) were also similar but high, typically more than twice as large as gross aquatic production. As a result, net aquatic production rates at both sites were usually negative, indicating that these small wetlands are organic matter sinks that satisfy aquatic respiration by consumption of both autochthonous aquatic production and imported terrestrial production. They enhance diversity of the local landscape by producing populations of aquatic consumers that cannot be supported by aquatic production alone. Typical wetland conditions and processes developed quickly after restoration, but differences in biotic community structure indicate that observed rates of production and respiration at both sites were maintained by flow through different foodweb pathways. Despite the relatively high process rates, and successional progress of the restoration site is expected to be slow.

The positive relationships between plant coverage, species richness, and aboveground biomass are ubiquitous across plant growth forms in semi-steppe rangelands.

PubMed

Sanaei, Anvar; Ali, Arshad; Chahouki, Mohammad Ali Zare

2018-01-01

The positive relationships between biodiversity and aboveground biomass are important for biodiversity conservation and greater ecosystem functioning and services that humans depend on. However, the interaction effects of plant coverage and biodiversity on aboveground biomass across plant growth forms (shrubs, forbs and grasses) in natural rangelands are poorly studied. Here, we hypothesized that, while accounting for environmental factors and disturbance intensities, the positive relationships between plant coverage, biodiversity, and aboveground biomass are ubiquitous across plant growth forms in natural rangelands. We applied structural equation models (SEMs) using data from 735 quadrats across 35 study sites in semi-steppe rangelands in Iran. The combination of plant coverage and species richness rather than Shannon's diversity or species diversity (a latent variable of species richness and evenness) substantially enhance aboveground biomass across plant growth forms. In all selected SEMs, plant coverage had a strong positive direct effect on aboveground biomass (β = 0.72 for shrubs, 0.84 for forbs and 0.80 for grasses), followed by a positive effect of species richness (β = 0.26 for shrubs, 0.05 for forbs and 0.09 for grasses), and topographic factors. Disturbance intensity had a negative effect on plant coverage, whereas it had a variable effect on species richness across plant growth forms. Plant coverage had a strong positive total effect on aboveground biomass (β = 0.84 for shrubs, 0.88 for forbs, and 0.85 for grasses), followed by a positive effect of species richness, and a negative effect of disturbance intensity across plant growth forms. Our results shed light on the management of rangelands that is high plant coverage can significantly improve species richness and aboveground biomass across plant growth forms. We also found that high disturbance intensity due to heavy grazing has a strong negative effect on plant coverage rather than species richness in semi-steppe rangelands. This study suggests that proper grazing systems (e.g. rotational system) based on carrying capacity and stocking rate of a rangeland may be helpful for biodiversity conservation, better grazing of livestock, improvement of plant coverage and enhancement of aboveground biomass. Copyright © 2017 Elsevier Ltd. All rights reserved.

The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo

PubMed Central

MacKenzie, A. R.; Langford, B.; Pugh, T. A. M.; Robinson, N.; Misztal, P. K.; Heard, D. E.; Lee, J. D.; Lewis, A. C.; Jones, C. E.; Hopkins, J. R.; Phillips, G.; Monks, P. S.; Karunaharan, A.; Hornsby, K. E.; Nicolas-Perea, V.; Coe, H.; Gabey, A. M.; Gallagher, M. W.; Whalley, L. K.; Edwards, P. M.; Evans, M. J.; Stone, D.; Ingham, T.; Commane, R.; Furneaux, K. L.; McQuaid, J. B.; Nemitz, E.; Seng, Yap Kok; Fowler, D.; Pyle, J. A.; Hewitt, C. N.

2011-01-01

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity. PMID:22006961

Structural Health Monitoring of Above-Ground Storage Tank Floors by Ultrasonic Guided Wave Excitation on the Tank Wall.

PubMed

Lowe, Premesh S; Duan, Wenbo; Kanfoud, Jamil; Gan, Tat-Hean

2017-11-04

There is an increasing interest in using ultrasonic guided waves to assess the structural degradation of above-ground storage tank floors. This is a non-invasive and economically viable means of assessing structural degradation. Above-ground storage tank floors are ageing assets which need to be inspected periodically to avoid structural failure. At present, normal-stress type transducers are bonded to the tank annular chime to generate a force field in the thickness direction of the floor and excite fundamental symmetric and asymmetric Lamb modes. However, the majority of above-ground storage tanks in use have no annular chime due to a simplified design and/or have a degraded chime due to corrosion. This means that transducers cannot be mounted on the chime to assess structural health according to the present technology, and the market share of structural health monitoring of above-ground storage tank floors using ultrasonic guided wave is thus limited. Therefore, the present study investigates the potential of using the tank wall to bond the transducer instead of the tank annular chime. Both normal and shear type transducers were investigated numerically, and results were validated using a 4.1 m diameter above-ground storage tank. The study results show shear mode type transducers bonded to the tank wall can be used to assess the structural health of the above-ground tank floors using an ultrasonic guided wave. It is also shown that for the cases studied there is a 7.4 dB signal-to-noise ratio improvement at 45 kHz for the guided wave excitation on the tank wall using shear mode transducers.

Structural Health Monitoring of Above-Ground Storage Tank Floors by Ultrasonic Guided Wave Excitation on the Tank Wall

PubMed Central

Kanfoud, Jamil; Gan, Tat-Hean

2017-01-01

There is an increasing interest in using ultrasonic guided waves to assess the structural degradation of above-ground storage tank floors. This is a non-invasive and economically viable means of assessing structural degradation. Above-ground storage tank floors are ageing assets which need to be inspected periodically to avoid structural failure. At present, normal-stress type transducers are bonded to the tank annular chime to generate a force field in the thickness direction of the floor and excite fundamental symmetric and asymmetric Lamb modes. However, the majority of above-ground storage tanks in use have no annular chime due to a simplified design and/or have a degraded chime due to corrosion. This means that transducers cannot be mounted on the chime to assess structural health according to the present technology, and the market share of structural health monitoring of above-ground storage tank floors using ultrasonic guided wave is thus limited. Therefore, the present study investigates the potential of using the tank wall to bond the transducer instead of the tank annular chime. Both normal and shear type transducers were investigated numerically, and results were validated using a 4.1 m diameter above-ground storage tank. The study results show shear mode type transducers bonded to the tank wall can be used to assess the structural health of the above-ground tank floors using an ultrasonic guided wave. It is also shown that for the cases studied there is a 7.4 dB signal-to-noise ratio improvement at 45 kHz for the guided wave excitation on the tank wall using shear mode transducers. PMID:29113058

Aboveground predation by an American badger (Taxidea taxus) on black-tailed prairie dogs (Cynomys ludovicianus)

USGS Publications Warehouse

Eads, D.A.; Biggins, D.E.

2008-01-01

During research on black-tailed prairie dogs (Cynomys ludovicianus), we repeatedly observed a female American badger (Taxidea taxus) hunting prairie dogs on a colony in southern Phillips County, Montana. During 1-14 June 2006, we observed 7 aboveground attacks (2 successful) and 3 successful excavations of prairie dogs. The locations and circumstances of aboveground attacks suggested that the badger improved her probability of capturing prairie dogs by planning the aboveground attacks based on perceptions of speeds, angles, distances, and predicted escape responses of prey. Our observations add to previous reports on the complex and varied predatory methods and cognitive capacities of badgers. These observations also underscore the individuality of predators and support the concept that predators are active participants in predator-prey interactions.

The importance of nitrogen and carbohydrate storage for plant growth of the alpine herb Veratrum album.

PubMed

Kleijn, David; Treier, Urs A; Müller-Schärer, Heinz

2005-05-01

We examined whether nitrogen (N) and carbohydrates reserves allow Veratrum album, an alpine forb, to start spring growth earlier than the neighbouring vegetation and to survive unpredictable disturbances resulting in loss of above-ground biomass. * Seasonal dynamics of plant reserves, soil N availability and vegetation growth were monitored. Veratrum album shoots were experimentally removed when carbohydrate reserves were at a seasonal minimum and the subsequent changes in biomass and reserves were compared with those in control plants. Reserves did not give V. album a competitive advantage in spring; however, they did function as a buffer against the impact of calamities. Shoot removal resulted in significantly lower root dry weight, higher N concentration in rhizome and roots and lower starch concentrations in rhizome and roots but no plant mortality was observed. Veratrum album used stored N reserves to supplement N uptake and establish high leaf N concentrations, which facilitated a rapid refilling of depleted carbohydrate reserves. The primary function of N reserves appears to be to allow V. album to complete the growing cycle in as short a period as possible, thus minimizing exposure to above-ground risks.

Assimilating satellite-based canopy height within an ecosystem model to estimate aboveground forest biomass

NASA Astrophysics Data System (ADS)

Joetzjer, E.; Pillet, M.; Ciais, P.; Barbier, N.; Chave, J.; Schlund, M.; Maignan, F.; Barichivich, J.; Luyssaert, S.; Hérault, B.; von Poncet, F.; Poulter, B.

2017-07-01

Despite advances in Earth observation and modeling, estimating tropical biomass remains a challenge. Recent work suggests that integrating satellite measurements of canopy height within ecosystem models is a promising approach to infer biomass. We tested the feasibility of this approach to retrieve aboveground biomass (AGB) at three tropical forest sites by assimilating remotely sensed canopy height derived from a texture analysis algorithm applied to the high-resolution Pleiades imager in the Organizing Carbon and Hydrology in Dynamic Ecosystems Canopy (ORCHIDEE-CAN) ecosystem model. While mean AGB could be estimated within 10% of AGB derived from census data in average across sites, canopy height derived from Pleiades product was spatially too smooth, thus unable to accurately resolve large height (and biomass) variations within the site considered. The error budget was evaluated in details, and systematic errors related to the ORCHIDEE-CAN structure contribute as a secondary source of error and could be overcome by using improved allometric equations.

Phytoremediation potential of Cd and Zn by wetland plants, Colocasia esculenta L. Schott., Cyperus malaccensis Lam. and Typha angustifolia L. grown in hydroponics.

PubMed

Chayapan, P; Kruatrachue, M; Meetam, M; Pokethitiyook, P

2015-09-01

Cadmium and zinc phytoremediation potential of wetland plants, Colocasia esculenta, Cyperus malaccensis, and Typha angustifolia, was investigated. Plants were grown for 15 days in nutrient solutions containing various concentrations of Cd (0, 5, 10, 20, 50 mg l(-1)) and Zn (0, 10, 20, 50, 100 mg l(-1)). T angustifolia was tolerant to both metals as indicated by high RGR when grown in 50 mg I(-1) Cd and 100 mg I(-1) Zn solutions. All these plants accumulated more metals in their underground parts and > 100 mg kg(-1) in their aboveground with TF values < 1. Only C. esculenta could be considered a Zn hyperaccumulator because it could concentrate > 10,000 mg kg(-1) in its aboveground parts with TF > 1. T angustifolia exhibited highest biomass production and highest Cd and Zn uptake, confirming that this plant is a suitable candidate for treating of Cd contaminated soil/sediments.

[Adaptability of APSIM model in Southwestern China: A case study of winter wheat in Chongqing City].

PubMed

Dai, Tong; Wang, Jing; He, Di; Zhang, Jian-ping; Wang, Na

2015-04-01

Field experimental data of winter wheat and parallel daily meteorological data at four typical stations in Chongqing City were used to calibrate and validate APSIM-wheat model and determine the genetic parameters for 12 varieties of winter wheat. The results showed that there was a good agreement between the simulated and observed growth periods from sowing to emergence, flowering and maturity of wheat. Root mean squared errors (RMSEs) between simulated and observed emergence, flowering and maturity were 0-3, 1-8, and 0-8 d, respectively. Normalized root mean squared errors (NRMSEs) between simulated and observed above-ground biomass for 12 study varieties were less than 30%. NRMSE between simulated and observed yields for 10 varieties out of 12 study varieties were less than 30%. APSIM-wheat model performed well in simulating phenology, aboveground biomass and yield of winter wheat in Chongqing City, which could provide a foundational support for assessing the impact of climate change on wheat production in the study area based on the model.

Opposing effects of floral visitors and soil conditions on the determinants of competitive outcomes maintain species diversity in heterogeneous landscapes.

PubMed

Lanuza, Jose B; Bartomeus, Ignasi; Godoy, Oscar

2018-06-01

Theory argues that both soil conditions and aboveground trophic interactions have equivalent potential to limit or promote plant diversity. However, it remains unexplored how they jointly modify the niche differences stabilising species coexistence and the average fitness differences driving competitive dominance. We conducted a field study in Mediterranean annual grasslands to parameterise population models of six competing plant species. Spatially explicit floral visitor assemblages and soil salinity variation were characterised for each species. Both floral visitors and soil salinity modified species population dynamics via direct changes in seed production and indirect changes in competitive responses. Although the magnitude and sign of these changes were species-specific, floral visitors promoted coexistence at neighbourhood scales, while soil salinity did so over larger scales by changing the superior competitors' identity. Our results show how below and aboveground interactions maintain diversity in heterogeneous landscapes through their opposing effects on the determinants of competitive outcomes. © 2018 John Wiley & Sons Ltd/CNRS.

Phytoremediation of ionic and methylmercury pollution

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

Meagher, Richard B.

2002-06-01

Our long-term objective is to enable highly productive plant species to extract, resist, detoxify, and/or sequester toxic organic and heavy metal pollutants (Meagher, 2000) applying scientific strategies and technologies from a rapidly developing field called phytoremediation. The phytoremediation of toxic elemental and organic pollutants requires the use relatively different approaches (Meagher, 2000). Our current specific objectives are to use transgenic plants to control the chemical species, electrochemical state, and aboveground binding of mercury to (a) prevent methylmercury from entering the food-chain, (b) remove mercury from polluted sites, and (c) hyperaccumulate mercury in aboveground tissues for later harvest. Various parts ofmore » this strategy are being critically tested by examining different genes in model plants and field species and comparing the results to control plants as we recently reviewed (Meagher et al., 2000; Rugh et al., 2000). A positive spin-off from this work on mercury has been a strategy for the phytoremediation of arsenic (Dhankher et al., 2002) and cadmium.« less

Phytoremediation of Ionic and Methyl Mercury Pollution

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

Meagher, Richard B.

Our long-term objective is to enable highly productive plant species to extract, resist, detoxify, and/or sequester toxic organic and heavy metal pollutants by applying scientific strategies and technologies from a rapidly developing field called phytoremediation. The phytoremediation of toxic elemental and organic pollutants employs a variety of different approaches (Meagher, 2000). Our current specific objectives are to use transgenic plants to control the chemical species, electrochemical state, transport, and aboveground binding of mercury to (a) prevent methylmercury from entering the food-chain, (b) remove mercury from polluted sites, and (c) hyperaccumulate mercury in aboveground tissues for later harvest and waste disposal.more » Various parts of this strategy are being critically tested by examining different genes in model plants and field species and comparing the results to control plants, as we reviewed previously (Meagher et al., 2000; Rugh et al., 2000). A positive spin-off from this work on mercury has been a strategy for the phytoremediation of arsenic (Dhankher et al., 2002) and cadmium (Dhankher et al., 2003).« less

Phytoremediation of ionic and methylmercury pollution

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

Meagher, Richard B.

Our long-term objective is to enable highly productive plant species to extract, resist, detoxify, and/or sequester toxic organic and heavy metal pollutants (Meagher, 2000) applying scientific strategies and technologies from a rapidly developing field called phytoremediation. The phytoremediation of toxic elemental and organic pollutants requires the use relatively different approaches (Meagher, 2000). Our current specific objectives are to use transgenic plants to control the chemical species, electrochemical state, and aboveground binding of mercury to (a) prevent methylmercury from entering the food-chain, (b) remove mercury from polluted sites, and (c) hyperaccumulate mercury in aboveground tissues for later harvest. Various parts ofmore » this strategy are being critically tested by examining different genes in model plants and field species and comparing the results to control plants as we recently reviewed (Meagher et al., 2000; Rugh et al., 2000). A positive spin-off from this work on mercury has been a strategy for the phytoremediation of arsenic (Dhankher et al., 2002) and cadmium.« less

Seasonal variation of red clover (Trifolium pratense L., Fabaceae) isoflavones and estrogenic activity

PubMed Central

Booth, Nancy L.; Overk, Cassia R.; Yao, Ping; Totura, Steve; Deng, Yunfan; Hedayat, A. S.; Bolton, Judy L.; Pauli, Guido F.; Farnsworth, Norman R.

2007-01-01

Red clover (Trifolium pratense L., Fabaceae) dietary supplements are currently used to treat menopausal symptoms because of their high content of the mildly estrogenic isoflavones daidzein, genistein, formononetin and biochanin A. These compounds are estrogenic in vitro and in vivo, but little information exists on the best time to harvest red clover fields to maximize content of the isoflavones and thus make an optimal product. Samples of cultivated red clover aboveground parts and flower heads were collected in parallel over one growing season in northeastern Illinois. Generally, autohydrolytic extracts of aboveground parts contained more isoflavones and had more estrogenic activity in Ishikawa endometrial cells, compared with extracts of flower heads. Daidzein and genistein content peaked around June to July, while formononetin and biochanin A content peaked in early September. Flower head and total aboveground parts extracts exhibited differential estrogenic activity in an Ishikawa (endometrial) cell-based alkaline phosphatase (AP) induction assay, whereas nondifferential activity was observed for most extracts tested in an MCF-7 (breast) cell proliferation assay when tested at the same final concentrations. Ishikawa assay results could be mapped onto the extracts’ content of individual isoflavones, but MCF-7 results did not show such a pattern. These results suggest that significant metabolism of isoflavones may occur in MCF-7 cells, but not in Ishikawa cells, and therefore caution is advised in the choice of bioassay used for the biological standardization of botanical dietary supplements. PMID:16478248

Methane and carbon dioxide flux in the profile of wood ant (Formica aquilonia) nests and the surrounding forest floor during a laboratory incubation.

PubMed

Jílková, Veronika; Picek, Tomáš; Šestauberová, Martina; Krištůfek, Václav; Cajthaml, Tomáš; Frouz, Jan

2016-10-01

We compared methane (CH4) and carbon dioxide (CO2) fluxes in samples collected from the aboveground parts of wood ant nests and in the organic and mineral layer of the surrounding forest floor. Gas fluxes were measured during a laboratory incubation, and microbial properties (abundance of fungi, bacteria and methanotrophic bacteria) and nutrient contents (total and available carbon and nitrogen) were also determined. Both CO2 and CH4 were produced from ant nest samples, indicating that the aboveground parts of wood ant nests act as sources of both gases; in comparison, the forest floor produced about four times less CO2 and consumed rather than produced CH4 Fluxes of CH4 and CO2 were positively correlated with contents of available carbon and nitrogen. The methanotrophic community was represented by type II methanotrophic bacteria, but their abundance did not explain CH4 flux. Fungal abundance was greater in ant nest samples than in forest floor samples, but bacterial abundance was similar in both kinds of samples, suggesting that the organic materials in the nests may have been too recalcitrant for bacteria to decompose. The results indicate that the aboveground parts of wood ant nests are hot spots of CO2 and CH4 production in the forest floor. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effects of irrigation and addition of nitrogen fertiliser on net ecosystem carbon balance for a grassland.

PubMed

Moinet, Gabriel Y K; Cieraad, Ellen; Turnbull, Matthew H; Whitehead, David

2017-02-01

The ability to quantify the impacts of changing management practices on the components of net ecosystem carbon balance (N B ) is required to forecast future changes in soil carbon stocks and potential feedbacks on atmospheric CO 2 concentrations. In this study we investigated seasonal changes on the components of net ecosystem carbon balance resulting from the application of irrigation and nitrogen fertiliser to a temperate grassland in New Zealand where we simulated grazing events. We made seasonal measurements of the components of N B using chamber measurements in field plots with and without irrigation and addition of nitrogen fertiliser. We developed models to determine the physiological responses of gross canopy photosynthesis (A), leaf respiration (R L ) and soil respiration (R S ) to soil and air temperature, soil water content and irradiance and we estimated annual N B for the first year after treatments were applied. Overall, irrigation and nitrogen addition had a synergistic effect to increase annual estimates of above-ground components of carbon balance (A, R L and carbon exported through simulated grazing, F export ), but there was no effect from adding nitrogen alone. Annual R S remained unchanged between treatments. The treatments resulted in increases in above-ground biomass production, but, with the high intensity of simulated grazing, these were not sufficient to offset ecosystem carbon losses, so all treatments remained a net source of carbon. There were no significant differences between treatments and annual N B ranged from -540gCm -2 y -1 for the treatment with no irrigation and no nitrogen addition and -284gCm -2 y -1 for the treatment with irrigation and nitrogen addition. Our findings from the first year of the treatments quantify the net benefits of addition of irrigation and nitrogen on increasing above-ground production for animal feed but show that this did not lead to a net increase carbon input to the soil. Copyright © 2016 Elsevier B.V. All rights reserved.

Monitoring grass nutrients and biomass as indicators of rangeland quality and quantity using random forest modelling and WorldView-2 data

NASA Astrophysics Data System (ADS)

Ramoelo, Abel; Cho, M. A.; Mathieu, R.; Madonsela, S.; van de Kerchove, R.; Kaszta, Z.; Wolff, E.

2015-12-01

Land use and climate change could have huge impacts on food security and the health of various ecosystems. Leaf nitrogen (N) and above-ground biomass are some of the key factors limiting agricultural production and ecosystem functioning. Leaf N and biomass can be used as indicators of rangeland quality and quantity. Conventional methods for assessing these vegetation parameters at landscape scale level are time consuming and tedious. Remote sensing provides a bird-eye view of the landscape, which creates an opportunity to assess these vegetation parameters over wider rangeland areas. Estimation of leaf N has been successful during peak productivity or high biomass and limited studies estimated leaf N in dry season. The estimation of above-ground biomass has been hindered by the signal saturation problems using conventional vegetation indices. The objective of this study is to monitor leaf N and above-ground biomass as an indicator of rangeland quality and quantity using WorldView-2 satellite images and random forest technique in the north-eastern part of South Africa. Series of field work to collect samples for leaf N and biomass were undertaken in March 2013, April or May 2012 (end of wet season) and July 2012 (dry season). Several conventional and red edge based vegetation indices were computed. Overall results indicate that random forest and vegetation indices explained over 89% of leaf N concentrations for grass and trees, and less than 89% for all the years of assessment. The red edge based vegetation indices were among the important variables for predicting leaf N. For the biomass, random forest model explained over 84% of biomass variation in all years, and visible bands including red edge based vegetation indices were found to be important. The study demonstrated that leaf N could be monitored using high spatial resolution with the red edge band capability, and is important for rangeland assessment and monitoring.

Testing the responses of four wheat crop models to heat stress at anthesis and grain filling.

PubMed

Liu, Bing; Asseng, Senthold; Liu, Leilei; Tang, Liang; Cao, Weixing; Zhu, Yan

2016-05-01

Higher temperatures caused by future climate change will bring more frequent heat stress events and pose an increasing risk to global wheat production. Crop models have been widely used to simulate future crop productivity but are rarely tested with observed heat stress experimental datasets. Four wheat models (DSSAT-CERES-Wheat, DSSAT-Nwheat, APSIM-Wheat, and WheatGrow) were evaluated with 4 years of environment-controlled phytotron experimental datasets with two wheat cultivars under heat stress at anthesis and grain filling stages. Heat stress at anthesis reduced observed grain numbers per unit area and individual grain size, while heat stress during grain filling mainly decreased the size of the individual grains. The observed impact of heat stress on grain filling duration, total aboveground biomass, grain yield, and grain protein concentration (GPC) varied depending on cultivar and accumulated heat stress. For every unit increase of heat degree days (HDD, degree days over 30 °C), grain filling duration was reduced by 0.30-0.60%, total aboveground biomass was reduced by 0.37-0.43%, and grain yield was reduced by 1.0-1.6%, but GPC was increased by 0.50% for cv Yangmai16 and 0.80% for cv Xumai30. The tested crop simulation models could reproduce some of the observed reductions in grain filling duration, final total aboveground biomass, and grain yield, as well as the observed increase in GPC due to heat stress. Most of the crop models tended to reproduce heat stress impacts better during grain filling than at anthesis. Some of the tested models require improvements in the response to heat stress during grain filling, but all models need improvements in simulating heat stress effects on grain set during anthesis. The observed significant genetic variability in the response of wheat to heat stress needs to be considered through cultivar parameters in future simulation studies. © 2016 John Wiley & Sons Ltd.

Efficacies of designer biochars in improving biomass and nutrient uptake of winter wheat grown in a hard setting subsoil layer.

PubMed

Sigua, G C; Novak, J M; Watts, D W; Johnson, M G; Spokas, K

2016-01-01

In the Coastal Plains region of the United States, the hard setting subsoil layer of Norfolk soils results in low water holding capacity and nutrient retention, which often limits root development. In this region, the Norfolk soils are under intensive crop production that further depletes nutrients and reduces organic carbon (C). Incorporation of pyrolyzed organic residues or "biochars" can provide an alternative recalcitrant C source. However, biochar quality and effect can be inconsistent and different biochars react differently in soils. We hypothesized that addition of different designer biochars will have variable effects on biomass and nutrient uptake of winter wheat. The objective of this study was to investigate the effects of designer biochars on biomass productivity and nutrient uptake of winter wheat (Triticum aestivum L.) in a Norfolk's hard setting subsoil layer. Biochars were added to Norfolk's hard setting subsoil layer at the rate of 40 Mg ha(-1). The different sources of biochars were: plant-based (pine chips, PC); animal-based (poultry litter, PL); 50:50 blend (50% PC:50% PL); 80:20 blend (80% PC:20% PL); and hardwood (HW). Aboveground and belowground biomass and nutrient uptake of winter wheat varied significantly (p⩽0.0001) with the different designer biochar applications. The greatest increase in the belowground biomass of winter wheat over the control was from 80:20 blend of PC:PL (81%) followed by HW (76%), PC (59%) and 50:50 blend of PC:PL (9%). However, application of PL resulted in significant reduction of belowground biomass by about 82% when compared to the control plants. The average uptake of P, K, Ca, Mg, Na, Al, Fe, Cu and Zn in both the aboveground and belowground biomass of winter wheat varied remarkably with biochar treatments. Overall, our results showed promising significance for the treatment of a Norfolk's hard setting subsoil layer since designer biochars did improve both aboveground/belowground biomass and nutrient uptake of winter wheat. Published by Elsevier Ltd.

Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico

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

Buss, Heather; Brantley, S. L.; Scatena, Fred

2013-01-01

Recent work has suggested that weathering processes occurring in the subsurface produce the majority of silicate weathering products discharged to the world s oceans, thereby exerting a primary control on global temperature via the well-known positive feedback between silicate weathering and CO2. In addition, chemical and physical weathering processes deep within the critical zone create aquifers and control groundwater chemistry, watershed geometry and regolith formation rates. Despite this, most weathering studies are restricted to the shallow critical zone (e.g., soils, outcrops). Here we investigate the chemical weathering, fracturing and geomorphology of the deep critical zone in the Bisley watershed inmore » the Luquillo Critical Zone Observatory, Puerto Rico, from two boreholes drilled to 37.2 and 27.0 m depth, from which continuous core samples were taken. Corestones exposed aboveground were also sampled. Weathered rinds developed on exposed corestones and along fracture surfaces on subsurface rocks slough off of exposed corestones once rinds attain a thickness up to ~1 cm, preventing the corestones from rounding due to diffusion limitation. Such corestones at the land surface are assumed to be what remains after exhumation of similar, fractured bedrock pieces that were observed in the drilled cores between thick layers of regolith. Some of these subsurface corestones are massive and others are highly fractured, whereas aboveground corestones are generally massive with little to no apparent fracturing. Subsurface corestones are larger and less fractured in the borehole drilled on a road where it crosses a ridge compared to the borehole drilled where the road crosses the stream channel. Both borehole profiles indicate that the weathering zone extends to well below the stream channel in this upland catchment; hence weathering depth is not controlled by the stream level within the catchment and not all of the water in the watershed is discharged to the stream.« less

Using Lidar and Radar measurements to constrain predictions of forest ecosystem structure and function.

PubMed

Antonarakis, Alexander S; Saatchi, Sassan S; Chazdon, Robin L; Moorcroft, Paul R

2011-06-01

Insights into vegetation and aboveground biomass dynamics within terrestrial ecosystems have come almost exclusively from ground-based forest inventories that are limited in their spatial extent. Lidar and synthetic-aperture Radar are promising remote-sensing-based techniques for obtaining comprehensive measurements of forest structure at regional to global scales. In this study we investigate how Lidar-derived forest heights and Radar-derived aboveground biomass can be used to constrain the dynamics of the ED2 terrestrial biosphere model. Four-year simulations initialized with Lidar and Radar structure variables were compared against simulations initialized from forest-inventory data and output from a long-term potential-vegtation simulation. Both height and biomass initializations from Lidar and Radar measurements significantly improved the representation of forest structure within the model, eliminating the bias of too many large trees that arose in the potential-vegtation-initialized simulation. The Lidar and Radar initializations decreased the proportion of larger trees estimated by the potential vegetation by approximately 20-30%, matching the forest inventory. This resulted in improved predictions of ecosystem-scale carbon fluxes and structural dynamics compared to predictions from the potential-vegtation simulation. The Radar initialization produced biomass values that were 75% closer to the forest inventory, with Lidar initializations producing canopy height values closest to the forest inventory. Net primary production values for the Radar and Lidar initializations were around 6-8% closer to the forest inventory. Correcting the Lidar and Radar initializations for forest composition resulted in improved biomass and basal-area dynamics as well as leaf-area index. Correcting the Lidar and Radar initializations for forest composition and fine-scale structure by combining the remote-sensing measurements with ground-based inventory data further improved predictions, suggesting that further improvements of structural and carbon-flux metrics will also depend on obtaining reliable estimates of forest composition and accurate representation of the fine-scale vertical and horizontal structure of plant canopies.

Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico

USGS Publications Warehouse

Buss, Heather L.; Brantley, Susan L.; Scatena, Fred; Bazilevskaya, Katya; Blum, Alex E.; Schulz, Marjorie S.; Jiménez, Rafael; White, Arthur F.; Rother, G.; Cole, D.

2013-01-01

Recent work has suggested that weathering processes occurring in the subsurface produce the majority of silicate weathering products discharged to the world's oceans, thereby exerting a primary control on global temperature via the well-known positive feedback between silicate weathering and CO2. In addition, chemical and physical weathering processes deep within the critical zone create aquifers and control groundwater chemistry, watershed geometry and regolith formation rates. Despite this, most weathering studies are restricted to the shallow critical zone (e.g. soils, outcrops). Here we investigate the chemical weathering, fracturing and geomorphology of the deep critical zone in the Bisley watershed in the Luquillo Critical Zone Observatory, Puerto Rico, from two boreholes drilled to 37.2 and 27.0 m depth, from which continuous core samples were taken. Corestones exposed aboveground were also sampled. Weathered rinds developed on exposed corestones and along fracture surfaces on subsurface rocks slough off of exposed corestones once rinds attain a thickness up to ~1 cm, preventing the corestones from rounding due to diffusion limitation. Such corestones at the land surface are assumed to be what remains after exhumation of similar, fractured bedrock pieces that were observed in the drilled cores between thick layers of regolith. Some of these subsurface corestones are massive and others are highly fractured, whereas aboveground corestones are generally massive with little to no apparent fracturing. Subsurface corestones are larger and less fractured in the borehole drilled on a road where it crosses a ridge compared with the borehole drilled where the road crosses the stream channel. Both borehole profiles indicate that the weathering zone extends to well below the stream channel in this upland catchment; hence weathering depth is not controlled by the stream level within the catchment and not all of the water in the watershed is discharged to the stream

Assessing the Effects of Land-use Change on Plant Traits, Communities and Ecosystem Functioning in Grasslands: A Standardized Methodology and Lessons from an Application to 11 European Sites

PubMed Central

Garnier, Eric; Lavorel, Sandra; Ansquer, Pauline; Castro, Helena; Cruz, Pablo; Dolezal, Jiri; Eriksson, Ove; Fortunel, Claire; Freitas, Helena; Golodets, Carly; Grigulis, Karl; Jouany, Claire; Kazakou, Elena; Kigel, Jaime; Kleyer, Michael; Lehsten, Veiko; Lepš, Jan; Meier, Tonia; Pakeman, Robin; Papadimitriou, Maria; Papanastasis, Vasilios P.; Quested, Helen; Quétier, Fabien; Robson, Matt; Roumet, Catherine; Rusch, Graciela; Skarpe, Christina; Sternberg, Marcelo; Theau, Jean-Pierre; Thébault, Aurélie; Vile, Denis; Zarovali, Maria P.

2007-01-01

Background and Aims A standardized methodology to assess the impacts of land-use changes on vegetation and ecosystem functioning is presented. It assumes that species traits are central to these impacts, and is designed to be applicable in different historical, climatic contexts and local settings. Preliminary results are presented to show its applicability. Methods Eleven sites, representative of various types of land-use changes occurring in marginal agro-ecosystems across Europe and Israel, were selected. Climatic data were obtained at the site level; soil data, disturbance and nutrition indices were described at the plot level within sites. Sixteen traits describing plant stature, leaf characteristics and reproductive phase were recorded on the most abundant species of each treatment. These data were combined with species abundance to calculate trait values weighed by the abundance of species in the communities. The ecosystem properties selected were components of above-ground net primary productivity and decomposition of litter. Key Results The wide variety of land-use systems that characterize marginal landscapes across Europe was reflected by the different disturbance indices, and were also reflected in soil and/or nutrient availability gradients. The trait toolkit allowed us to describe adequately the functional response of vegetation to land-use changes, but we suggest that some traits (vegetative plant height, stem dry matter content) should be omitted in studies involving mainly herbaceous species. Using the example of the relationship between leaf dry matter content and above-ground dead material, we demonstrate how the data collected may be used to analyse direct effects of climate and land use on ecosystem properties vs. indirect effects via changes in plant traits. Conclusions This work shows the applicability of a set of protocols that can be widely applied to assess the impacts of global change drivers on species, communities and ecosystems. PMID:17085470

Models of reforestation productivity and carbon sequestration for land use and climate change adaptation planning in South Australia.

PubMed

Hobbs, Trevor J; Neumann, Craig R; Meyer, Wayne S; Moon, Travis; Bryan, Brett A

2016-10-01

Environmental management and regional land use planning has become more complex in recent years as growing world population, climate change, carbon markets and government policies for sustainability have emerged. Reforestation and agroforestry options for environmental benefits, carbon sequestration, economic development and biodiversity conservation are now important considerations of land use planners. New information has been collected and regionally-calibrated models have been developed to facilitate better regional land use planning decisions and counter the limitations of currently available models of reforestation productivity and carbon sequestration. Surveys of above-ground biomass of 264 reforestation sites (132 woodlots, 132 environmental plantings) within the agricultural regions of South Australia were conducted, and combined with spatial information on climate and soils, to develop new spatial and temporal models of plant density and above-ground biomass productivity from reforestation. The models can be used to estimate productivity and total carbon sequestration (i.e. above-ground + below-ground biomass) under a continuous range of planting designs (e.g. variable proportions of trees and shrubs or plant densities), timeframes and future climate scenarios. Representative spatial models (1 ha resolution) for 3 reforestation designs (i.e. woodlots, typical environmental planting, biodiverse environmental plantings) × 3 timeframes (i.e. 25, 45, 65 years) × 4 possible climates (i.e. no change, mild, moderate, severe warming and drying) were generated (i.e. 36 scenarios) for use within land use planning tools. Copyright © 2016 Elsevier Ltd. All rights reserved.

Abiotic and biotic determinants of coarse woody productivity in temperate mixed forests.

PubMed

Yuan, Zuoqiang; Ali, Arshad; Wang, Shaopeng; Gazol, Antonio; Freckleton, Robert; Wang, Xugao; Lin, Fei; Ye, Ji; Zhou, Li; Hao, Zhanqing; Loreau, Michel

2018-07-15

Forests play an important role in regulating the global carbon cycle. Yet, how abiotic (i.e. soil nutrients) and biotic (i.e. tree diversity, stand structure and initial biomass) factors simultaneously contribute to aboveground biomass (coarse woody) productivity, and how the relative importance of these factors changes over succession remain poorly studied. Coarse woody productivity (CWP) was estimated as the annual aboveground biomass gain of stems using 10-year census data in old growth and secondary forests (25-ha and 4.8-ha, respectively) in northeast China. Boosted regression tree (BRT) model was used to evaluate the relative contribution of multiple metrics of tree diversity (taxonomic, functional and phylogenetic diversity and trait composition as well as stand structure attributes), stand initial biomass and soil nutrients on productivity in the studied forests. Our results showed that community-weighted mean of leaf phosphorus content, initial stand biomass and soil nutrients were the three most important individual predictors for CWP in secondary forest. Instead, initial stand biomass, rather than diversity and functional trait composition (vegetation quality) was the most parsimonious predictor of CWP in old growth forest. By comparing the results from secondary and old growth forest, the summed relative contribution of trait composition and soil nutrients on productivity decreased as those of diversity indices and initial biomass increased, suggesting the stronger effect of diversity and vegetation quantity over time. Vegetation quantity, rather than diversity and soil nutrients, is the main driver of forest productivity in temperate mixed forest. Our results imply that diversity effect for productivity in natural forests may not be so important as often suggested, at least not during the later stage of forest succession. This finding suggests that as a change of the importance of different divers of productivity, the environmentally driven filtering decreases and competitively driven niche differentiation increases with forest succession. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparative analysis of spectral unmixing and neural networks for estimating small diameter tree above-ground biomass in the State of Mississippi

Treesearch

Moham P. Tiruveedhula; Joseph Fan; Ravi R. Sadasivuni; Surya S. Durbha; David L. Evans

2010-01-01

The accumulation of small diameter trees (SDTs) is becoming a nationwide concern. Forest management practices such as fire suppression and selective cutting of high grade timber have contributed to an overabundance of SDTs in many areas. Alternative value-added utilization of SDTs (for composite wood products and biofuels) has prompted the need to estimate their...

Aboveground biomass responses to organic matter removal, soil compaction, and competing vegetation control on 20-year mixed conifer plantations in California

Treesearch

Jianwei Zhang; Matt D. Busse; David H. Young; Gary O. Fiddler; Joseph W. Sherlock; Jeff D. TenPas

2017-01-01

We measured vegetation growth 5, 10, and 20 years following plantation establishment at 12 Long-term Soil Productivity installations in California’s Sierra Nevada and Southern Cascades. The combined effects of soil compaction (none, moderate, severe), organic matter removal (tree bole only, whole tree, whole tree plus forest floor), and competing vegetation...

Long-term simulations of forest management impacts on carbon storage from loblolly pine plantations in the Southern U.S.

Treesearch

Huei-Jin Wang; Philip J. Radtke; Stephen P. Prisley

2012-01-01

Accounting for forest components in carbon accounting systems may be insufficient when substantial amounts of sequestered carbon are harvested and converted to wood products in use and in landfill. The potential of forest offset – in-woods aboveground carbon storage, carbon stored in harvested wood, and energy offset by burning harvested wood – from loblolly pine...

Effects of organic matter removal, soil compaction and vegetation control on 10th year biomass and foliar nutrition: LTSP continent-wide comparisons

Treesearch

Felix Ponder Jr.; Robert L. Fleming; Shannon Berch; Matt D. Busse; John D. Elioff; Paul W. Hazlett; Richard D. Kabzems; J. Marty Kranabetter; David M. Morris; Deborah Page-Dumroese; Brian J. Palik; Robert F. Powers; Felipe G. Sanchez; D. Andrew Scott; Richard H. Stagg; Douglas M. Stone; David H. Young; Jianwei Zhang; Kim H. Ludovici; Daniel W. McKenney; Debbie S Mossa; Paul T. Sanborn; Richard A. Voldseth

2012-01-01

We examined 10th year above-ground planted tree and total stand biomass, and planted tree foliar N and P concentrations across gradients in soil disturbance at 45 North American Long-Term Soil Productivity (LTSP) installations. While ranging across several climate regions, these installations all share a common experimental design with similar measurement protocols....

Competition along productivity gradients: news from heathlands.

PubMed

Delerue, Florian; Gonzalez, Maya; Achat, David L; Puzos, Luc; Augusto, Laurent

2018-05-01

The importance of competition in low productive habitats is still debated. Studies which simultaneously evaluate preemption of resources and consequences for population dynamics are needed for a comprehensive view of competitive outcomes. We cultivated two emblematic species of European heathlands (Calluna vulgaris and Molinia caerulea) in a nursery for 2 years at two fertility levels, reproducing the productivity gradient found in phosphorus (P)-depleted heathlands in southwest France. The second year, we planted Ulex europaeus seedlings, a ubiquitous heathland species, under the cover of the two species to evaluate its ability to regenerate. Half of the seedlings were placed in tubes for exclusion of competitor roots. We measured the development of the competitors aboveground and belowground and their interception of resources (light, water, inorganic P). Ulex seedlings' growth and survival were also measured. Our results on resources interception were consistent with species distribution in heathlands. Molinia, which dominates rich heathlands, was the strongest competitor for light and water in the rich soil. Calluna, which dominates poor heathlands, increased its root allocation in the poor soil, decreasing water and inorganic P availability. However, the impact of total competition and root competition on Ulex seedlings decreased in the poor soil. Other mechanisms, especially decrease of water stress under neighbouring plant cover, appeared to have more influence on the seedlings' response. We found no formal contradiction between Tilman and Grime's theories. Root competition has a primary role in acquisition of soil resources in poor habitats. However, the importance of competition decreases with decreasing fertility.

Exploring the control of land-atmospheric oscillations over terrestrial vegetation productivity

NASA Astrophysics Data System (ADS)

Depoorter, Mathieu; Green, Julia; Gentine, Pierre; Liu, Yi; van Eck, Christel; Regnier, Pierre; Dorigo, Wouter; Verhoest, Niko; Miralles, Diego

2015-04-01

Vegetation dynamics play an important role in the climate system due to their control on the carbon, energy and water cycles. The spatiotemporal variability of vegetation is regulated by internal climate variability as well as natural and anthropogenic forcing mechanisms, including fires, land use, volcano eruptions or greenhouse gas emissions. Ocean-atmospheric oscillations, affect the fluxes of heat and water over continents, leading to anomalies in radiation, precipitation or temperature at widely separated locations (i.e. teleconnections); an effect of ocean-atmospheric oscillations on terrestrial primary productivity can therefore be expected. While different studies have shown the general importance of internal climate variability for global vegetation dynamics, the control by particular teleconnections over the regional growth and decay of vegetation is still poorly understood. At continental to global scales, satellite remote sensing offers a feasible approach to enhance our understanding of the main drivers of vegetation variability. Traditional studies of the multi-decadal variability of global vegetation have been usually based on the normalized difference vegetation index (NDVI) derived from the Advanced Very High Resolution Radiometer (AVHRR), which extends back to the early '80s. There are, however, some limitations to NDVI observations; arguably the most important of these limitations is that from the plant physiology perspective the index does not have a well-defined meaning, appearing poorly correlated to vegetation productivity. On the other hand, recently developed records from other remotely-sensed properties of vegetation, like fluorescence or microwave vegetation optical depth, have proven a significantly better correspondence to above-ground biomass. To enhance our understanding of the controls of ocean-atmosphere oscillations over vegetation, we propose to explore the link between climate oscillation extremes and net primary productivity over the last two decades. The co-variability of a range of climate oscillation indices and newly-derived records of fluorescence and vegetation optical depth is analyzed using a statistical framework based on correlations, bootstrapping and Empirical Orthogonal Functions (EOFs). Results will enable us to characterize regional hotspots where particular climatic oscillations control vegetation productivity, as well as allowing us to underpin the climatic variables behind this control.

Estimates of Global Rangeland Net Primary Productivity and its Consumption Based on Climate and Livestock Distribution Data

NASA Astrophysics Data System (ADS)

Asrar, G.; Wolf, J.; Rafique, R.; West, T. O.; Ogle, S. M.

2016-12-01

Rangelands play an important role in providing ecosystem services such as food, forage, and fuels in many parts of the world. The net primary productivity (NPP), a difference between CO2 fixed by plants and CO2 lost to autotrophic respiration, is a good indicator of the productivity of rangeland ecosystems, and their contribution to the cycling of carbon in the Earth system. In this study, we estimated the NPP of global rangelands, the consumption thereof by grazing livestock, and associated uncertainties, to better understand and quantify the contribution of rangelands to land-based carbon storage. We estimated rangeland NPP using mean annual precipitation data from Climate Research Unit (CRU), and a regression model based on global observations (Del Grosso et al., 2008). Spatial distributions of annual livestock consumption of rangeland NPP (Wolf et al., 2015) were combined with gridded annual rangeland NPP for the years 2000 - 2011. The uncertainty analysis of these estimates was conducted using a Monte Carlo approach. The rangeland NPP estimates with associated uncertainties were also compared with the total modeled GPP estimates obtained from vegetation dynamic model simulations. Our results showed that mean above-ground NPP of rangelands is 1017.5 MgC/km2, while mean below-ground NPP is 847.6 MgC/km2. The total rangeland NPP represents a significant portion of the total NPP of the terrestrial ecosystem. The livestock area requirements used to geographically distribute livestock spatially are based on optimal pasturage and are low relative to area requirements on less productive land. Even so, ca. 90% of annual livestock consumption of rangeland NPP were met with no adjustment of livestock distributions. Moreover, the results of this study allowed us to explicitly quantify the temporal and spatial variations of rangeland NPP under different climatic conditions. Uncertainty analysis was helpful in identifying the strength and weakness of the methods used to estimate rangeland NPP. Overall, the results from this study are useful in quantifying the contribution of rangelands to the carbon cycle and for providing geospatially distributed carbon fluxes associated with the production and consumption of rangeland biomass.

Proven Alternatives for Aboveground Treatment of Arsenic in Groundwater

EPA Pesticide Factsheets

This issue paper, developed for EPA's Engineering Forum, identifies and summarizes experiences with proven aboveground treatment alternatives for arsenic in groundwater, and provides information on their relative effectiveness and cost.

Estimating Above-Ground Carbon Biomass in a Newly Restored Coastal Plain Wetland Using Remote Sensing

PubMed Central

Riegel, Joseph B.; Bernhardt, Emily; Swenson, Jennifer

2013-01-01

Developing accurate but inexpensive methods for estimating above-ground carbon biomass is an important technical challenge that must be overcome before a carbon offset market can be successfully implemented in the United States. Previous studies have shown that LiDAR (light detection and ranging) is well-suited for modeling above-ground biomass in mature forests; however, there has been little previous research on the ability of LiDAR to model above-ground biomass in areas with young, aggrading vegetation. This study compared the abilities of discrete-return LiDAR and high resolution optical imagery to model above-ground carbon biomass at a young restored forested wetland site in eastern North Carolina. We found that the optical imagery model explained more of the observed variation in carbon biomass than the LiDAR model (adj-R2 values of 0.34 and 0.18 respectively; root mean squared errors of 0.14 Mg C/ha and 0.17 Mg C/ha respectively). Optical imagery was also better able to predict high and low biomass extremes than the LiDAR model. Combining both the optical and LiDAR improved upon the optical model but only marginally (adj-R2 of 0.37). These results suggest that the ability of discrete-return LiDAR to model above-ground biomass may be rather limited in areas with young, small trees and that high spatial resolution optical imagery may be the better tool in such areas. PMID:23840837

MODIS Based Estimation of Forest Aboveground Biomass in China.

PubMed

Yin, Guodong; Zhang, Yuan; Sun, Yan; Wang, Tao; Zeng, Zhenzhong; Piao, Shilong

2015-01-01

Accurate estimation of forest biomass C stock is essential to understand carbon cycles. However, current estimates of Chinese forest biomass are mostly based on inventory-based timber volumes and empirical conversion factors at the provincial scale, which could introduce large uncertainties in forest biomass estimation. Here we provide a data-driven estimate of Chinese forest aboveground biomass from 2001 to 2013 at a spatial resolution of 1 km by integrating a recently reviewed plot-level ground-measured forest aboveground biomass database with geospatial information from 1-km Moderate-Resolution Imaging Spectroradiometer (MODIS) dataset in a machine learning algorithm (the model tree ensemble, MTE). We show that Chinese forest aboveground biomass is 8.56 Pg C, which is mainly contributed by evergreen needle-leaf forests and deciduous broadleaf forests. The mean forest aboveground biomass density is 56.1 Mg C ha-1, with high values observed in temperate humid regions. The responses of forest aboveground biomass density to mean annual temperature are closely tied to water conditions; that is, negative responses dominate regions with mean annual precipitation less than 1300 mm y-1 and positive responses prevail in regions with mean annual precipitation higher than 2800 mm y-1. During the 2000s, the forests in China sequestered C by 61.9 Tg C y-1, and this C sink is mainly distributed in north China and may be attributed to warming climate, rising CO2 concentration, N deposition, and growth of young forests.

MODIS Based Estimation of Forest Aboveground Biomass in China

PubMed Central

Sun, Yan; Wang, Tao; Zeng, Zhenzhong; Piao, Shilong

2015-01-01

Accurate estimation of forest biomass C stock is essential to understand carbon cycles. However, current estimates of Chinese forest biomass are mostly based on inventory-based timber volumes and empirical conversion factors at the provincial scale, which could introduce large uncertainties in forest biomass estimation. Here we provide a data-driven estimate of Chinese forest aboveground biomass from 2001 to 2013 at a spatial resolution of 1 km by integrating a recently reviewed plot-level ground-measured forest aboveground biomass database with geospatial information from 1-km Moderate-Resolution Imaging Spectroradiometer (MODIS) dataset in a machine learning algorithm (the model tree ensemble, MTE). We show that Chinese forest aboveground biomass is 8.56 Pg C, which is mainly contributed by evergreen needle-leaf forests and deciduous broadleaf forests. The mean forest aboveground biomass density is 56.1 Mg C ha−1, with high values observed in temperate humid regions. The responses of forest aboveground biomass density to mean annual temperature are closely tied to water conditions; that is, negative responses dominate regions with mean annual precipitation less than 1300 mm y−1 and positive responses prevail in regions with mean annual precipitation higher than 2800 mm y−1. During the 2000s, the forests in China sequestered C by 61.9 Tg C y−1, and this C sink is mainly distributed in north China and may be attributed to warming climate, rising CO2 concentration, N deposition, and growth of young forests. PMID:26115195

Preliminary study on the relationships between aboveground storage and remotely sensed data at Pingdong plain afforestation land in Southern Taiwan

NASA Astrophysics Data System (ADS)

Wei, C.; Chen, J. M.; Yu, J.; Cheng, C.; Lai, Y.; Chiang, P.; Hong, C.; Chang, C.; Wey, T.; Tsai, M.; Wang, Y.

2013-12-01

This research aims on the relationships between LAI and five vegetation index (BR, SRBR, BD, NDVI and TNDVI) from remotely sensed images, in situ measurements and aboveground storage for 10-11yr old plain afforestation (14 species) located at Wanlong farm of subtropical-tropical region at the southern part of Taiwan which originally governed by Taiwan Sugar Corporation. The preliminary results show the aboveground storage is 14.19×9.19 m3 ha-1 and the correlation coefficient between aboveground storage and BR, SRBR, BD, NDVI and TNDVI is 0.331 (p=0.211), 0.317 (p=0.232), 0.310 (p=0.244), 0.714 (p=0.002) and 0.706 (p=0.002) while NDVI performs the best correlation. LAI value using Fisheye or Tracing Radiation and Architecture of Canopies (TRAC) is 0.76×0.37 and 3.89×2.81, respectively. Besides, CI measured by TRAC is 0.83×0.09 and the correlation coefficient with LAI is 0.868 (p<0.001). It shows feasible to estimate aboveground storage using ground investigation incorporating remotely sensed data for young plain afforestation stand. Due to the mixed-plantation and difference between growing and non-growing season at the sample site, the relationship between aboveground storage, LAI and VI is yet to be developed for independent species and may need to modify due to seasonally and inter-annually variation.

Controls of vegetation structure and net primary production in restored grasslands

USGS Publications Warehouse

Munson, Seth M.; Lauenroth, William K.

2014-01-01

1. Vegetation structure and net primary production (NPP) are fundamental properties of ecosystems. Understanding how restoration practices following disturbance interact with environmental factors to control these properties can provide insight on how ecosystems recover and guide management efforts. 2. We assessed the relative contribution of environmental and restoration factors in controlling vegetation structure, above- and below-ground investment in production across a chronosequence of semiarid Conservation Reserve Program (CRP) fields recovering from dryland wheat cropping relative to undisturbed grassland. Importantly, we determined the role of plant diversity and how seeding either native or introduced perennial grasses influenced the recovery of vegetation properties. 3. Plant basal cover increased with field age and was highest in CRP fields seeded with native perennial grasses. In contrast, fields seeded with introduced perennial grasses had tall-growing plants with relatively low basal cover. These vegetation structural characteristics interacted with precipitation, but not soil characteristics, to influence above-ground NPP (ANPP). Fields enrolled in the CRP program for >7 years supported twice as much ANPP as undisturbed shortgrass steppe in the first wet year of the study, but all CRP fields converged on a common low amount of ANPP in the following dry year and invested less than half as much as the shortgrass steppe in below-ground biomass. 4. ANPP in CRP fields seeded with native perennial grasses for more than 7 years was positively related to species richness, whereas ANPP in CRP fields seeded with introduced perennial grasses were controlled more by dominant species. 5. Synthesis and applications. Seeding with introduced, instead of native, perennial grasses had a strong direct influence on vegetation structure, including species richness, which indirectly affected NPP through time. However, the effects of restoring either native or introduced grasses on NPP were secondary to low water availability. Therefore, restoration strategies that maximize basal cover and below-ground biomass, which promote water acquisition, may lead to high resilience in semiarid and arid regions.

Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

NASA Astrophysics Data System (ADS)

Zhang, Wenmin; Brandt, Martin; Tong, Xiaoye; Tian, Qingjiu; Fensholt, Rasmus

2018-01-01

Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy-rainfall events, longer dry spells, and a shifted timing of the wet season. Yet the aboveground net primary productivity (ANPP) in drylands is usually explained by annual-rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tested the importance of rainfall metrics in the wet season (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days, and heavy-rainfall events) for growing season ANPP. We focused on the Sahel and northern Sudanian region (100-800 mm yr-1) and applied daily satellite-based rainfall estimates (CHIRPS v2.0) and growing-season-integrated normalized difference vegetation index (NDVI; MODIS) as a proxy for ANPP over the study period: 2001-2015. Growing season ANPP in the arid zone (100-300 mm yr-1) was found to be rather insensitive to variations in the seasonal-rainfall metrics, whereas vegetation in the semi-arid zone (300-700 mm yr-1) was significantly impacted by most metrics, especially by the number of rainy days and timing (onset and cessation) of the wet season. We analysed critical breakpoints for all metrics to test if vegetation response to changes in a given rainfall metric surpasses a threshold beyond which vegetation functioning is significantly altered. It was shown that growing season ANPP was particularly negatively impacted after > 14 consecutive dry days and that a rainfall intensity of ˜ 13 mm day-1 was detected for optimum growing season ANPP. We conclude that the number of rainy days and the timing of the wet season are seasonal-rainfall metrics that are decisive for favourable vegetation growth in the semi-arid Sahel and need to be considered when modelling primary productivity from rainfall in the drylands of the Sahel and elsewhere.

Linkages of plant stoichiometry to ecosystem production and carbon fluxes with increasing nitrogen inputs in an alpine steppe.

PubMed

Peng, Yunfeng; Li, Fei; Zhou, Guoying; Fang, Kai; Zhang, Dianye; Li, Changbin; Yang, Guibiao; Wang, Guanqin; Wang, Jun; Yang, Yuanhe

2017-12-01

Unprecedented levels of nitrogen (N) have entered terrestrial ecosystems over the past century, which substantially influences the carbon (C) exchange between the atmosphere and biosphere. Temperature and moisture are generally regarded as the major controllers over the N effects on ecosystem C uptake and release. N-phosphorous (P) stoichiometry regulates the growth and metabolisms of plants and soil organisms, thereby affecting many ecosystem C processes. However, it remains unclear how the N-induced shift in the plant N:P ratio affects ecosystem production and C fluxes and its relative importance. We conducted a field manipulative experiment with eight N addition levels in a Tibetan alpine steppe and assessed the influences of N on aboveground net primary production (ANPP), gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE); we used linear mixed-effects models to further determine the relative contributions of various factors to the N-induced changes in these parameters. Our results showed that the ANPP, GEP, ER, and NEE all exhibited nonlinear responses to increasing N additions. Further analysis demonstrated that the plant N:P ratio played a dominate role in shaping these C exchange processes. There was a positive relationship between the N-induced changes in ANPP (ΔANPP) and the plant N:P ratio (ΔN:P), whereas the ΔGEP, ΔER, and ΔNEE exhibited quadratic correlations with the ΔN:P. In contrast, soil temperature and moisture were only secondary predictors for the changes in ecosystem production and C fluxes along the N addition gradient. These findings highlight the importance of plant N:P ratio in regulating ecosystem C exchange, which is crucial for improving our understanding of C cycles under the scenarios of global N enrichment. © 2017 John Wiley & Sons Ltd.

Maize (Zea mays) seeds can detect above-ground weeds; thiamethoxam alters the view.

PubMed

Afifi, Maha; Lee, Elizabeth; Lukens, Lewis; Swanton, Clarence

2015-09-01

Far red light is known to penetrate soil and delay seed germination. Thiamethoxam as a seed treatment has been observed to enhance seed germination. No previous work has explored the effect of thiamethoxam on the physiological response of buried maize seed when germinating in the presence of above-ground weeds. We hypothesised that the changes in red:far red reflected from above-ground weeds would be detected by maize seed phytochrome and delay seed germination by decreasing the level of GA and increasing ABA. We further hypothesised that thiamethoxam would overcome this delay in germination. Thiamethoxam enhanced seed germination in the presence of above-ground weeds by increasing GA signalling and downregulating DELLA protein and ABA signalling genes. An increase in amylase activity and a degradation of starch were also observed. Far red reflected from the above-ground weeds was capable of penetrating below the soil surface and was detected by maize seed phytochrome. Thiamethoxam altered the effect of far red on seed germination by stimulating GA and inhibiting ABA synthesis. This is the first study to suggest that the mode of action of thiamethoxam involves both GA synthesis and ABA inhibition. © 2014 Society of Chemical Industry.

Linkages between below and aboveground communities: Decomposer responses to simulated tree species loss are largely additive.

Treesearch

Becky A. Ball; Mark A. Bradford; Dave C. Coleman; Mark D. Hunter

2009-01-01

Inputs of aboveground plant litter influence the abundance and activities of belowground decomposer biota. Litter-mixing studies have examined whether the diversity and heterogeneity of litter inputs...

Evaluation and Validation of Aboveground Techniques for Coating Condition Assessment

DOT National Transportation Integrated Search

2006-02-28

The overall objective was to determine the accuracy, resolution, and limitations of equipment typically used for modern aboveground ECDA work with respect to locating holidays and disbondments with commonly used coatings with varying spatial relation...

Biomass of open-grown Virginia pine

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

Madgwick, H.A.I.; Olah, F.D.; Burkhart, H.E.

1977-03-01

Five open-grown Pinus virginiana trees ranging from 1.05 to 15.78 m tall were destructively sampled and the data used to obtain relationships between tree size and biomass to estimate dry matter production. The ratio of foliage to above-ground woody biomass decreased with tree age from 0.4 for a 7-year-old tree to 0.05 for a 39-year-old tree. Needle longevity increased with tree age. 5 references.

Carbon Fluxes at the AmazonFACE Research Site

NASA Astrophysics Data System (ADS)

Norby, R.; De Araujo, A. C.; Cordeiro, A. L.; Fleischer, K.; Fuchslueger, L.; Garcia, S.; Hofhansl, F.; Garcia, M. N.; Grandis, A.; Oblitas, E.; Pereira, I.; Pieres, N. M.; Schaap, K.; Valverde-Barrantes, O.

2017-12-01

The free-air CO2 enrichment (FACE) experiment to be implemented in the Amazon rain forest requires strong pretreatment characterization so that eventual responses to elevated CO2 can be detected against a background of substantial species diversity and spatial heterogeneity. Two 30-m diameter plots have been laid out for initial characterization in a 30-m tall, old-growth, terra firme forest. Intensive measurements have been made of aboveground tree growth, leaf area, litter production, and fine-root production; these data sets together support initial estimates of plot-scale net primary productivity (NPP). Leaf-level measurements of photosynthesis throughout the canopy and over a daily time course in both the wet and dry season, coupled with meterological monitoring, support an initial estimate of gross primary productivity (GPP) and carbon-use efficiency (CUE = NPP/GPP). Monthly monitoring of CO2 efflux from the soil, partitioned into autotrophic and heterotrophic components, supports an estimate of net ecosystem production (NEP). Our estimate of NPP in the two plots (1.2 and 1.4 kg C m-2 yr-1) is 16-38% greater than previously reported for the site, primarily due to our more complete documentation of fine-root production, including root production deeper than 30 cm. The estimate of CUE of the ecosystem (0.52) is greater than most others in Amazonia; this discrepancy reflects large uncertainty in GPP, which derived from just two days of measurement, or to underestimates of the fine-root component of NPP in previous studies. Estimates of NEP (0 and 0.14 kg C m-2 yr-1) are generally consistent with a landscape-level estimate from flux tower data. Our C flux estimates, albeit very preliminary, provide initial benchmarks for a 12-model a priori evaluation of this forest. The model means of GPP, NPP, and NEP are mostly consistent with our field measurements. Predictions of C flux responses to elevated CO2 from the models become hypotheses to be tested in the FACE experiment. Although carbon fluxes on small plots cannot be expected to represent the fluxes across the wider and more diverse region, our integrated measurements, coupled with a model framework, provide a strong foundation for understanding the mechanistic basis of responses and for extending results of experimental CO2 fertilization to the wider region.

Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

NASA Astrophysics Data System (ADS)

Bohn, Friedrich J.; May, Felix; Huth, Andreas

2018-03-01

Rising temperatures due to climate change influence the wood production of forests. Observations show that some temperate forests increase their productivity, whereas others reduce their productivity. This study focuses on how species composition and forest structure properties influence the temperature sensitivity of aboveground wood production (AWP). It further investigates which forests will increase their productivity the most with rising temperatures. We described forest structure by leaf area index, forest height and tree height heterogeneity. Species composition was described by a functional diversity index (Rao's Q) and a species distribution index (ΩAWP). ΩAWP quantified how well species are distributed over the different forest layers with regard to AWP. We analysed 370 170 forest stands generated with a forest gap model. These forest stands covered a wide range of possible forest types. For each stand, we estimated annual aboveground wood production and performed a climate sensitivity analysis based on 320 different climate time series (of 1-year length). The scenarios differed in mean annual temperature and annual temperature amplitude. Temperature sensitivity of wood production was quantified as the relative change in productivity resulting from a 1 °C rise in mean annual temperature or annual temperature amplitude. Increasing ΩAWP positively influenced both temperature sensitivity indices of forest, whereas forest height showed a bell-shaped relationship with both indices. Further, we found forests in each successional stage that are positively affected by temperature rise. For such forests, large ΩAWP values were important. In the case of young forests, low functional diversity and small tree height heterogeneity were associated with a positive effect of temperature on wood production. During later successional stages, higher species diversity and larger tree height heterogeneity were an advantage. To achieve such a development, one could plant below the closed canopy of even-aged, pioneer trees a climax-species-rich understorey that will build the canopy of the mature forest. This study highlights that forest structure and species composition are both relevant for understanding the temperature sensitivity of wood production.

The importance of biodiversity and dominance for multiple ecosystem functions in a human-modified tropical landscape.

PubMed

Lohbeck, Madelon; Bongers, Frans; Martinez-Ramos, Miguel; Poorter, Lourens

2016-10-01

Many studies suggest that biodiversity may be particularly important for ecosystem multifunctionality, because different species with different traits can contribute to different functions. Support, however, comes mostly from experimental studies conducted at small spatial scales in low-diversity systems. Here, we test whether different species contribute to different ecosystem functions that are important for carbon cycling in a high-diversity human-modified tropical forest landscape in Southern Mexico. We quantified aboveground standing biomass, primary productivity, litter production, and wood decomposition at the landscape level, and evaluated the extent to which tree species contribute to these ecosystem functions. We used simulations to tease apart the effects of species richness, species dominance and species functional traits on ecosystem functions. We found that dominance was more important than species traits in determining a species' contribution to ecosystem functions. As a consequence of the high dominance in human-modified landscapes, the same small subset of species mattered across different functions. In human-modified landscapes in the tropics, biodiversity may play a limited role for ecosystem multifunctionality due to the potentially large effect of species dominance on biogeochemical functions. However, given the spatial and temporal turnover in species dominance, biodiversity may be critically important for the maintenance and resilience of ecosystem functions. © 2016 The Authors. Ecology, published by Wiley Periodicals, Inc., on behalf of the Ecological Society of America.

Remote Sensing of a Manipulated Prairie Grassland Experiment to Predict Belowground Processes

NASA Astrophysics Data System (ADS)

Cavender-Bares, J.; Schweiger, A. K.; Hobbie, S. E.; Madritch, M. D.; Wang, Z.; Couture, J. J.; Gamon, J. A.; Townsend, P. A.

2017-12-01

Given the importance of plant biodiversity for providing the ecosystem functions and services on which humans depend, rapid and remote methods of monitoring plant biodiversity across large spatial extents and biological scales are increasingly critical. In North American prairie systems, the ecosystem benefits of diversity are a subject of ongoing investigation and relevance to policy. However, detecting belowground components of ecosystem biodiversity, composition and associated functions are not possible directly through remote sensing. Nevertheless, belowground components of diversity may be linked to aboveground components allowing indirect inferences. Here we test a series of hypotheses about how aboveground functional and chemical diversity and composition of plant communities drive belowground functions, including N mineralization, enzyme activity and microbial biomass, as well as microbial diversity and composition. We hypothesize that the quantity and chemical composition of aboveground inputs to soil drive belowground processes, including decomposition and microbial enzyme activity. We use plant spectra (400 nm to 2500 nm) measured at the leaf and airborne level to determine chemical and functional composition of leaves and canopies in a long-term grassland experiment where diversity is manipulated at the Cedar Creek Ecosystem Science Reserve. We then assess the extent to which belowground chemistry, microbial diversity and composition are predicted from aboveground plant diversity, biomass and chemical composition. We find strong associations between aboveground inputs and belowground enzyme activity and microbial biomass but only weak linkages between aboveground diversity and belowground diversity. We discuss the potential for such approaches and the caveats related to the spatial scale of measurements and spatial resolution of airborne detection.

Standing crop and aboveground biomass partitioning of a dwarf mangrove forest in Taylor River Slough, Florida

USGS Publications Warehouse

Coronado-Molina, C.; Day, J.W.; Reyes, E.; Perez, B.C.

2004-01-01

The structure and standing crop biomass of a dwarf mangrove forest, located in the salinity transition zone ofTaylor River Slough in the Everglades National Park, were studied. Although the four mangrove species reported for Florida occurred at the study site, dwarf Rhizophora mangle trees dominated the forest. The structural characteristics of the mangrove forest were relatively simple: tree height varied from 0.9 to 1.2 meters, and tree density ranged from 7062 to 23 778 stems haa??1. An allometric relationship was developed to estimate leaf, branch, prop root, and total aboveground biomass of dwarf Rhizophora mangle trees. Total aboveground biomass and their components were best estimated as a power function of the crown area times number of prop roots as an independent variable (Y = B ?? Xa??0.5083). The allometric equation for each tree component was highly significant (p<0.0001), with all r2 values greater than 0.90. The allometric relationship was used to estimate total aboveground biomass that ranged from 7.9 to 23.2 ton haa??1. Rhizophora mangle contributed 85% of total standing crop biomass. Conocarpus erectus, Laguncularia racemosa, and Avicennia germinans contributed the remaining biomass. Average aboveground biomass allocation was 69% for prop roots, 25% for stem and branches, and 6% for leaves. This aboveground biomass partitioning pattern, which gives a major role to prop roots that have the potential to produce an extensive root system, may be an important biological strategy in response to low phosphorus availability and relatively reduced soils that characterize mangrove forests in South Florida.

Cadmium uptake in above-ground parts of lettuce (Lactuca sativa L.).

PubMed

Tang, Xiwang; Pang, Yan; Ji, Puhui; Gao, Pengcheng; Nguyen, Thanh Hung; Tong, Yan'an

2016-03-01

Because of its high Cd uptake and translocation, lettuce is often used in Cd contamination studies. However, there is a lack of information on Cd accumulation in the above-ground parts of lettuce during the entire growing season. In this study, a field experiment was carried out in a Cd-contaminated area. Above-ground lettuce parts were sampled, and the Cd content was measured using a flame atomic absorption spectrophotometer (AAS). The results showed that the Cd concentration in the above-ground parts of lettuce increased from 2.70 to 3.62mgkg(-1) during the seedling stage, but decreased from 3.62 to 2.40mgkg(-1) during organogenesis and from 2.40 to 1.64mgkg(-1) during bolting. The mean Cd concentration during the seedling stage was significantly higher than that during organogenesis (a=0.05) and bolting (a=0.01). The Cd accumulation in the above-ground parts of an individual lettuce plant could be described by a sigmoidal curve. Cadmium uptake during organogenesis was highest (80% of the total), whereas that during bolting was only 4.34%. This research further reveals that for Rome lettuce: (1) the highest Cd content of above-ground parts occurred at the end of the seedling phase; (2) the best harvest time with respect to Cd phytoaccumulation is at the end of the organogenesis stage; and (3) the organogenesis stage is the most suitable time to enhance phytoaccumulation efficiency by adjusting the root:shoot ratio. Copyright © 2015 Elsevier Inc. All rights reserved.

Tree allometry and improved estimation of carbon stocks and balance in tropical forests.

PubMed

Chave, J; Andalo, C; Brown, S; Cairns, M A; Chambers, J Q; Eamus, D; Fölster, H; Fromard, F; Higuchi, N; Kira, T; Lescure, J-P; Nelson, B W; Ogawa, H; Puig, H; Riéra, B; Yamakura, T

2005-08-01

Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitative contribution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferring changes from long-term forest inventory plots. Regression models are used to convert inventory data into an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees >or= 5 cm diameter, directly harvested in 27 study sites across the tropics. Proportional relationships between aboveground biomass and the product of wood density, trunk cross-sectional area, and total height are constructed. We also develop a regression model involving wood density and stem diameter only. Our models were tested for secondary and old-growth forests, for dry, moist and wet forests, for lowland and montane forests, and for mangrove forests. The most important predictors of AGB of a tree were, in decreasing order of importance, its trunk diameter, wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5-6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprecedented dataset, these models should improve the quality of tropical biomass estimates, and bring consensus about the contribution of the tropical forest biome and tropical deforestation to the global carbon cycle.

Aboveground Whitefly Infestation Modulates Transcriptional Levels of Anthocyanin Biosynthesis and Jasmonic Acid Signaling-Related Genes and Augments the Cope with Drought Stress of Maize

PubMed Central

Park, Yong-Soon; Bae, Dong-Won; Ryu, Choong-Min

2015-01-01

Up to now, the potential underlying molecular mechanisms by which maize (Zea mays L.) plants elicit defense responses by infestation with a phloem feeding insect whitefly [Bemisia tabaci (Genn.)] have been barely elucidated against (a)biotic stresses. To fill this gap of current knowledge maize plants were infested with whitefly and these plants were subsequently assessed the levels of water loss. To understand the mode of action, plant hormone contents and the stress-related mRNA expression were evaluated. Whitefly-infested maize plants did not display any significant phenotypic differences in above-ground tissues (infested site) compared with controls. By contrast, root (systemic tissue) biomass was increased by 2-fold by whitefly infestation. The levels of endogenous indole-3-acetic acid (IAA), jasmonic acid (JA), and hydrogen peroxide (H2O2) were significantly higher in whitefly-infested plants. The biosynthetic or signaling-related genes for JA and anthocyanins were highly up-regulated. Additionally, we found that healthier plants were obtained in whitefly-infested plants under drought conditions. The weight of whitefly-infested plants was approximately 20% higher than that of control plants at 14 d of drought treatment. The drought tolerance-related genes, ZmbZIP72, ZmSNAC1, and ZmABA1, were highly expressed in the whitefly-infected plants. Collectively, our results suggest that IAA/JA-derived maize physiological changes and correlation of H2O2 production and water loss are modulated by above-ground whitefly infestation in maize plants. PMID:26630288

Biomass is the main driver of changes in ecosystem process rates during tropical forest succession.

PubMed

Lohbeck, Madelon; Poorter, Lourens; Martínez-Ramos, Miguel; Bongers, Frans

2015-05-01

Over half of the world's forests are disturbed, and the rate at which ecosystem processes recover after disturbance is important for the services these forests can provide. We analyze the drivers' underlying changes in rates of key ecosystem processes (biomass productivity, litter productivity, actual litter decomposition, and potential litter decomposition) during secondary succession after shifting cultivation in wet tropical forest of Mexico. We test the importance of three alternative drivers of ecosystem processes: vegetation biomass (vegetation quantity hypothesis), community-weighted trait mean (mass ratio hypothesis), and functional diversity (niche complementarity hypothesis) using structural equation modeling. This allows us to infer the relative importance of different mechanisms underlying ecosystem process recovery. Ecosystem process rates changed during succession, and the strongest driver was aboveground biomass for each of the processes. Productivity of aboveground stem biomass and leaf litter as well as actual litter decomposition increased with initial standing vegetation biomass, whereas potential litter decomposition decreased with standing biomass. Additionally, biomass productivity was positively affected by community-weighted mean of specific leaf area, and potential decomposition was positively affected by functional divergence, and negatively by community-weighted mean of leaf dry matter content. Our empirical results show that functional diversity and community-weighted means are of secondary importance for explaining changes in ecosystem process rates during tropical forest succession. Instead, simply, the amount of vegetation in a site is the major driver of changes, perhaps because there is a steep biomass buildup during succession that overrides more subtle effects of community functional properties on ecosystem processes. We recommend future studies in the field of biodiversity and ecosystem functioning to separate the effects of vegetation quality (community-weighted mean trait values and functional diversity) from those of vegetation quantity (biomass) on ecosystem processes and services.

Growth, allometry and shade tolerance of understory saplings of four subalpine conifers in central Japan.

PubMed

Takahashi, Koichi; Obata, Yoshiko

2014-03-01

The conifers Abies veitchii, A. mariesii, Picea jezoensis var. hondoensis, Tsuga diversifolia dominate in subalpine forests in central Japan. We expected that species differences in shade tolerance and in aboveground and belowground architecture are important for their coexistence. We examined net production and carbon allocation of understory saplings. Although the four species allocated similar amounts of biomass to roots at a given trunk height, the root-zone area of T. diversifolia was greater than that of the three other species. T. diversifolia often dominates shallow soil sites, such as ridge and rocky slopes, and, therefore, a wide spread of lateral roots would be an adaptation to such edaphic conditions. Crown width and leaf and branch mass were greatest for T. diversifolia and A. mariesii, followed in order by A. veitchii and P. jezoensis var. hondoensis. Although leaf mass of P. jezoensis var. hondoensis was lowest among the four species, species differences were not found in the net production per sapling because net production per leaf mass was greatest for P. jezoensis var. hondoensis. The leaf lifespan was longer in the order A. mariesii, T. diversifolia, P. jezoensis var. hondoensis and A. veitchii. The minimum rate of net production per leaf mass required to maintain the current sapling leaf mass (MRNP(LM)) was lowest in A. mariesii and T. diversifolia, and increased in the order of A. veitchii and P. jezoensis var. hondoensis. A. mariesii and T. diversifolia may survive in shade conditions by a lower MRNP(LM) than the two other species. Therefore, species differences in aboveground and belowground architecture and MRNPLM reflected their shade tolerance and regeneration strategies, which contribute to their coexistence.

Sown species richness and realized diversity can influence functioning of plant communities differently.

PubMed

Rychtecká, Terezie; Lanta, Vojtěch; Weiterová, Iva; Lepš, Jan

2014-08-01

Biodiversity-ecosystem functioning experiments (BEF) typically manipulate sown species richness and composition of experimental communities to study ecosystem functioning as a response to changes in diversity. If sown species richness is taken as a measure of diversity and aboveground biomass production as a measure of community functioning, then this relationship is usually found to be positive. The sown species richness can be considered the equivalent of a local species pool in natural communities. However, in addition to species richness, realized diversity is also an important community diversity component. Realized diversity is affected by environmental filtering and biotic interactions operating within a community. As both sown species richness and the realized diversity in BEF studies (as well as local species pool vs observed realized richness in natural communities) can differ markedly, so can their effects on the community functioning. We tested this assumption using two data sets: data from a short-term pot experiment and data from the long-term Jena biodiversity plot experiment. We considered three possible predictors of community functioning (aboveground biomass production): sown species richness, realized diversity (defined as inverse of Simpson dominance index), and survivor species richness. Sown species richness affected biomass production positively in all cases. Realized diversity as well as survivor species richness had positive effects on biomass in approximately half of cases. When realized diversity or survivor species richness was tested together with sown species richness, their partial effects were none or negative. Our results suggest that we can expect positive diversity-productivity relationship when the local species pool size is the decisive factor determining realized observed diversity; in other cases, the shape of the diversity-functioning relationship may be quite opposite.

Establishment of the Geoglam Rangelands Acivity and Progress

NASA Astrophysics Data System (ADS)

Youngentob, K. N.; Held, A. A.; Grundy, M.; Donohue, R. J.

2014-12-01

With global population predicted to reach around 9 billion by 2050 and the area of arable land per person declining, there is increased focus on the need to increase food production. As part of a systematic response to that need, improved monitoring of global food production has been identified by the G20 as a priority. The Global Agricultural Monitoring initiative has been established under the Group on Earth Observations (known as GEOGLAM) as a response to this need, with initial focus on the four main food crops of the world and the major exporting regions. However, it is not only the world's croplands that will come under pressure to further increase their productivity and production. Global rangelands, scrublands and pasturelands must become more productive in producing grassland plant biomass and increased animal protein production, to supply an ever-growing global demand for essential animal protein. An essential complementary focus is needed on the sustainability of these systems to both ensure sustained productivity and to maintain the broader range of ecosystem services providing out of these large global lands. Termed "GEOGLAM Rangelands and Pasture Productivity (RAPP)", this new GEO initiative will provide the global community with the means to monitor the world's rangelands and pasture lands on a routine basis, and the capacity to produce animal protein in real-time, at global, regional and national levels. The primary scope of RAPP will be to monitor aboveground biomass and the condition of land cover for those lands and ecosystems that are integral to producing animal protein on a 'free-range', open-field basis, and their sustainable management. Using available national animal herd statistics, aims to include global and regional population information on beef cattle, goats, sheep, camels, pork, dairy cattle, wild and managed buffalo and deer. This paper will provide a broad overview of the status of implementation of the RAPP monitoring system, and some highlights of the Australian pilot and partnerships that are contributing to this GEO task.

NORTH ELEVATION WITH GRADUATED MEASURING POLE. ABOVEGROUND PORTION IS ON ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

NORTH ELEVATION WITH GRADUATED MEASURING POLE. ABOVE-GROUND PORTION IS ON THE LEFT. VIEW FACING SOUTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

Elicitors aboveground: an alternative for control of a belowground pest

USDA-ARS?s Scientific Manuscript database

Plant defense pathways mediate multitrophic interactions above and belowground. Understanding the effects of these pathways on pests and natural enemies above and belowground holds great potential for designing effective control strategies. Here we investigate the effects of aboveground stimulation ...

Interactions between aboveground herbivores and the mycorrhizal mutualists of plants.

PubMed

Gehring, C A; Whitham, T G

1994-07-01

Plant growth, reproduction and survival can be affected both by mycorrhizal fungi and aboveground herbivores, but few studies have examined the interactive effects of these factors on plants. Most of the available data suggest that severe herbivory reduces root colonization by vesicular-arbuscular and ectomycorrhizal fungi. However, the reverse interaction has also been documented - mycorrhizal fungi deter herbivores and interact with fungal endophytes to influence herbivory. Although consistent patterns and mechanistic explanations are yet to emerge, it is likely that aboveground herbivore-mycorrhiza interactions have important implications for plant populations and communities. Copyright © 1994. Published by Elsevier Ltd.

Soil Moisture Limitations on Monitoring Boreal Forest Regrowth Using Spaceborne L-Band SAR Data

NASA Technical Reports Server (NTRS)

Kasischke, Eric S.; Tanase, Mihai A.; Bourgeau-Chavez, Laura L.; Borr, Matthew

2011-01-01

A study was carried out to investigate the utility of L-band SAR data for estimating aboveground biomass in sites with low levels of vegetation regrowth. Data to estimate biomass were collected from 59 sites located in fire-disturbed black spruce forests in interior Alaska. PALSAR L-band data (HH and HV polarizations) collected on two dates in the summer/fall of 2007 and one date in the summer of 2009 were used. Significant linear correlations were found between the log of aboveground biomass (range of 0.02 to 22.2 t ha-1) and (L-HH) and (L-HV) for the data collected on each of the three dates, with the highest correlation found using the LHV data collected when soil moisture was highest. Soil moisture, however, did change the correlations between L-band and aboveground biomass, and the analyses suggest that the influence of soil moisture is biomass dependent. The results indicate that to use L-band SAR data for mapping aboveground biomass and monitoring forest regrowth will require development of approaches to account for the influence that variations in soil moisture have on L-band microwave backscatter, which can be particularly strong when low levels of aboveground biomass occur

Impact of logging on aboveground biomass stocks in lowland rain forest, Papua New Guinea.

PubMed

Bryan, Jane; Shearman, Phil; Ash, Julian; Kirkpatrick, J B

2010-12-01

Greenhouse-gas emissions resulting from logging are poorly quantified across the tropics. There is a need for robust measurement of rain forest biomass and the impacts of logging from which carbon losses can be reliably estimated at regional and global scales. We used a modified Bitterlich plotless technique to measure aboveground live biomass at six unlogged and six logged rain forest areas (coupes) across two approximately 3000-ha regions at the Makapa concession in lowland Papua New Guinea. "Reduced-impact logging" is practiced at Makapa. We found the mean unlogged aboveground biomass in the two regions to be 192.96 +/- 4.44 Mg/ha and 252.92 +/- 7.00 Mg/ha (mean +/- SE), which was reduced by logging to 146.92 +/- 4.58 Mg/ha and 158.84 +/- 4.16, respectively. Killed biomass was not a fixed proportion, but varied with unlogged biomass, with 24% killed in the lower-biomass region, and 37% in the higher-biomass region. Across the two regions logging resulted in a mean aboveground carbon loss of 35 +/- 2.8 Mg/ha. The plotless technique proved efficient at estimating mean aboveground biomass and logging damage. We conclude that substantial bias is likely to occur within biomass estimates derived from single unreplicated plots.

Leaf mass per area, not total leaf area, drives differences in above-ground biomass distribution among woody plant functional types.

PubMed

Duursma, Remko A; Falster, Daniel S

2016-10-01

Here, we aim to understand differences in biomass distribution between major woody plant functional types (PFTs) (deciduous vs evergreen and gymnosperm vs angiosperm) in terms of underlying traits, in particular the leaf mass per area (LMA) and leaf area per unit stem basal area. We used a large compilation of plant biomass and size observations, including observations of 21 084 individuals on 656 species. We used a combination of semiparametric methods and variance partitioning to test the influence of PFT, plant height, LMA, total leaf area, stem basal area and climate on above-ground biomass distribution. The ratio of leaf mass to above-ground woody mass (MF /MS ) varied strongly among PFTs. We found that MF /MS at a given plant height was proportional to LMA across PFTs. As a result, the PFTs did not differ in the amount of leaf area supported per unit above-ground biomass or per unit stem basal area. Climate consistently explained very little additional variation in biomass distribution at a given plant size. Combined, these results demonstrate consistent patterns in above-ground biomass distribution and leaf area relationships among major woody PFTs, which can be used to further constrain global vegetation models. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Contrasting Strategies of Alfalfa Stem Elongation in Response to Fall Dormancy in Early Growth Stage: The Tradeoff between Internode Length and Internode Number

PubMed Central

Wang, Zongli; Sun, Qizhong

2015-01-01

Fall dormancy (FD) in alfalfa (Medicago sativa L.) can be described using 11 FD ratings, is widely used as an important indicator of stress resistance, productive performance and spring growth. However, the contrasting growth strategies in internode length and internode number in alfalfa cultivars with different FD rating are poorly understood. Here, a growth chamber study was conducted to investigate the effect of FD on plant height, aboveground biomass, internode length, and internode number in alfalfa individuals in the early growth stages. In order to simulate the alfalfa growth environment in the early stage, 11 alfalfa cultivars with FD ratings from one to 11 were chosen and seeded at the greenhouse, and then were transplanted into an artificial growth chamber. The experimental design was a randomized complete block in a split-plot arrangement with three replicates. Plant height, above-ground biomass, internode length, and internode number were measured in early growth stage in all individuals. Our findings showed that plant height and the aboveground biomass of alfalfa did not significantly differ among 11 different FD rated cultivars. Also, internode length and internode number positively affected plant height and the aboveground biomass of alfalfa individuals and the average internode length significantly increased with increasing FD rating. However, internode number tended to sharply decline when the FD rating increased. Moreover, there were no correlations, slightly negative correlations, and strongly negative correlations between internode length and internode number in alfalfa individuals among the three scales, including within-FD ratings, within-FD categories and inter-FD ratings, respectively. Therefore, our results highlighted that contrasting growth strategies in stem elongation were adopted by alfalfa with different FD ratings in the early growth stage. Alfalfa cultivars with a high FD rating have longer internodes, whereas more dormant alfalfa cultivars have a larger number of internodes. There were tradeoffs between internode length and internode number in response to FD in alfalfa, which reflected certain scale-dependence. PMID:26281014

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.

Effects of biochar, compost and biochar-compost on growth and nutrient status of maize in two Mediterranean soils

NASA Astrophysics Data System (ADS)

Manolikaki, Ioanna; Diamadopoulos, Evan

2017-04-01

During the past years, studies have shown that biochar alone or combined with compost, has the potential to improve soil fertility and maize yield mostly on tropical soils whereas experiments on Mediterranean soils are rare. Therefore, the influence of biochar, compost and mixtures of the two, on maize (Zea mays L.) growth and nutrient status were investigated, in this study. Biochars were produced from 2 feedstocks: grape pomace (GP) and rice husks (RH) pyrolyzed at 300°C. Maize was grown for 30 days in a greenhouse pot trial on two Mediterranean soils amended with biochar or/with compost at application rates of 0% and 2% (w/w) (equivalent to 0 and 16 t ha-1) and N fertilization. Total aboveground dry matter yield of maize was significantly improved relative to the control for all organic amendments, with increases in yield 43-60.8%, in sandy loam soil, while, in loam soil a statistically significant increase of 70.6-81.3% was recorded for all the amendments apart from compost. Some morphological traits, such as aboveground height of plants, shoot diameter and belowground dry matter yield were significantly increased by the organic treatments. Aboveground concentration of P was significantly increased from 1.46 mg g-1 at control to 1.69 mg g-1 at 2% GP biochar in sandy loam soil, whereas GP biochar combined with compost gave an increase of 2.03 mg g-1 compared to control 1.23 mg g-1. K and Mn concentrations of above ground tissues were significantly increased only in sandy loam soil, while Fe in both soils. N concentration of aboveground tissues declined for all the amendments in loam soil and in sandy loam soil apart from compost amendment. Significant positive impacts of amended soils on nutrients uptake were observed in both soils as compared to the control related to the improved dry matter yield of plant. The current study demonstrated that maize production could be greatly improved by biochar and compost because of the nutrients they supply and their conditioning effect.

Allometric Scaling and Resource Limitations Model of Total Aboveground Biomass in Forest Stands: Site-scale Test of Model

NASA Astrophysics Data System (ADS)

CHOI, S.; Shi, Y.; Ni, X.; Simard, M.; Myneni, R. B.

2013-12-01

Sparseness in in-situ observations has precluded the spatially explicit and accurate mapping of forest biomass. The need for large-scale maps has raised various approaches implementing conjugations between forest biomass and geospatial predictors such as climate, forest type, soil property, and topography. Despite the improved modeling techniques (e.g., machine learning and spatial statistics), a common limitation is that biophysical mechanisms governing tree growth are neglected in these black-box type models. The absence of a priori knowledge may lead to false interpretation of modeled results or unexplainable shifts in outputs due to the inconsistent training samples or study sites. Here, we present a gray-box approach combining known biophysical processes and geospatial predictors through parametric optimizations (inversion of reference measures). Total aboveground biomass in forest stands is estimated by incorporating the Forest Inventory and Analysis (FIA) and Parameter-elevation Regressions on Independent Slopes Model (PRISM). Two main premises of this research are: (a) The Allometric Scaling and Resource Limitations (ASRL) theory can provide a relationship between tree geometry and local resource availability constrained by environmental conditions; and (b) The zeroth order theory (size-frequency distribution) can expand individual tree allometry into total aboveground biomass at the forest stand level. In addition to the FIA estimates, two reference maps from the National Biomass and Carbon Dataset (NBCD) and U.S. Forest Service (USFS) were produced to evaluate the model. This research focuses on a site-scale test of the biomass model to explore the robustness of predictors, and to potentially improve models using additional geospatial predictors such as climatic variables, vegetation indices, soil properties, and lidar-/radar-derived altimetry products (or existing forest canopy height maps). As results, the optimized ASRL estimates satisfactorily resemble the FIA aboveground biomass in terms of data distribution, overall agreement, and spatial similarity across scales. Uncertainties are quantified (ranged from 0.2 to 0.4) by taking into account the spatial mismatch (FIA plot vs. PRISM grid), heterogeneity (species composition), and an example bias scenario (= 0.2) in the root system extents.

Field Variability of Invading Populations of Spartina densiflora Brong. in Different Habitats of the Odiel Marshes (SW Spain)

NASA Astrophysics Data System (ADS)

Nieva, F. J. J.; Díaz-Espejo, A.; Castellanos, E. M.; Figueroa, M. E.

2001-04-01

Spartina densiflora is a species of South American origin that has invaded the marshes of the Gulf of Cádiz, in many of which it has become the most abundant plant. This work studies six populations of S. densiflora representative of the physiographic positions most commonly occupied by the species. The aspects considered are redox potential, conductivity and pH of the sediment, below- and above-ground biomass, stem density, rates of flowering and production of vegetative propagules. Eh and conductivity values vary greatly, responding to differences in tidal effect. The below-ground biomass (in particular, live rhizomes) is accumulated mostly in the first centimetres of the soil; mean values of total below-ground biomass are between 6961 and 30 696 g DW m -2. Above-ground biomass levels for the populations ranges between 419 and 15 251 g DW m -2. The stem density within the tussocks is high, between 3985 and 10 513 stems m -2, with higher percentages of live stems on low and brackish marshes compared with those on higher topographic levels. This accumulation of dead and live intratussock biomass is important for the ability to exclude competitors. The flowering rates vary depending on topographic position, with maximum values being recorded in the low marsh (37·6%) and minima in the high marsh (0·1 to 0·3%). Besides the production of ramets from below-ground rhizomes (common to all species of the genus), S. densiflora presents another mode of asexual reproduction, in which extravaginal tillers are originated from the nodes of senescent ramets; populations on the higher levels of the marshes present higher densities of these propagules, with a negative correlation between rate of flowering and rate of propagule production. Nevertheless, the contribution of these propagules to the total stem population is very small. Our results show a high tolerance of S. densiflora to different environmental factors, an intense occupation of the available below-ground and above-ground space, and the capacity of sexual reproduction and of producing stems that sprout directly from the upper part of the canopy of S. densiflora, aspects that help to explain the ecological success of this species in the marshes of the Gulf of Cádiz.

Microenvironmental air quality impact of a commercial-scale biomass heating system.

PubMed

Tong, Zheming; Yang, Bo; Hopke, Philip K; Zhang, K Max

2017-01-01

Initiatives to displace petroleum and climate change mitigation have driven a recent increase in space heating with biomass combustion. However, there is ample evidence that biomass combustion emits significant quantities of health damaging pollutants. We investigated the near-source micro-environmental air quality impact of a biomass-fueled combined heat and power system equipped with an electrostatic precipitator (ESP) in Syracuse, NY. Two rooftop sampling stations with PM 2.5 and CO 2 analyzers were established in such that one could capture the plume while the other one served as the background for comparison depending on the wind direction. Four sonic anemometers were deployed around the stack to quantify spatially and temporally resolved local wind patterns. Fuel-based emission factors were derived based on near-source measurement. The Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model was then applied to simulate the spatial variations of primary PM 2.5 without ESP. Our analysis shows that the absence of ESP could lead to an almost 7 times increase in near-source primary PM 2.5 concentrations with a maximum concentration above 100 μg m -3 at the building rooftop. The above-ground "hotspots" would pose potential health risks to building occupants since particles could penetrate indoors via infiltration, natural ventilation, and fresh air intakes on the rooftop of multiple buildings. Our results demonstrated the importance of emission control for biomass combustion systems in urban area, and the need to take above-ground pollutant "hotspots" into account when permitting distributed generation. The effects of ambient wind speed and stack temperature, the suitability of airport meteorological data on micro-environmental air quality were explored, and the implications on mitigating near-source air pollution were discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dynamics and controls of CO2 and CH4 emissions in the wetland of a montane permafrost region, northeast China

NASA Astrophysics Data System (ADS)

Liu, Xia; Guo, Yuedong; Hu, Haiqing; Sun, Chengkun; Zhao, Xikuan; Wei, Changlei

2015-12-01

To quantify the fluxes and examine the controls on greenhouse gas emissions from the permafrost marshes where the fate of the large quantity of soil organic carbon remains poorly understood, we measured carbon dioxide (CO2) and methane (CH4) emissions in the northern region of the Great Xing'an Mountains, northeast China, in the thawing seasons of 2011 and 2012. The mean CO2 and CH4 fluxes from the marshes were estimated at 403.47 and 0.14 mg m-2 h-1 on average during the two years. Soil temperature was determined as the primary control on the seasonal greenhouse gas emissions during the growing period. The Q10 values, calculated from the exponential regression between soil temperature and CO2 emissions, suggest that the sensitivity of CO2 flux to climate warming has a high spatially variability in the study area. Absorption of atmospheric CH4 was seasonally detected at the sites with lower water table, which confirms the potential of the natural marshes as CH4 sink when water table goes down due to climate change. When viewed from the ecosystem scale, the mean annual water table level and aboveground primary production were deemed as the dominant influencing factors for the mean annual fluxes, which suggests that there were different controls on the gas emissions at different spatial scales. Therefore, the primary controls of the CO2 and CH4 emissions at different spatial scales need to be surveyed in more detail when focusing on the future alteration of greenhouse gas emissions from permafrost marshes due to climate warming.