Sample records for temperate grassland ecosystem

  1. Accounting for variability in soil microbial communities of temperate upland grassland ecosystems

    Microsoft Academic Search

    S. J. Grayston; G. S. Griffith; J. L. Mawdsley; C. D. Campbell; R. D. Bardgett

    2001-01-01

    This study aimed to determine the factors which regulate soil microbial community organisation and function in temperate upland grassland ecosystems. Soil microbial biomass (Cmic), activity (respiration and potential carbon utilisation) and community structure (phospholipid fatty acid (PLFA) analysis, culturing and community level physiological profiles (CLPP) (Biolog®)) were measured across a gradient of three upland grassland types; Festuca–Agrostis–Galium grassland (unimproved grassland,

  2. Net ecosystem productivity of temperate grasslands in northern China: An upscaling study

    USGS Publications Warehouse

    Zhang, Li; Guo, Huadong; Jia, Gensuo; Wylie, Bruce; Gilmanov, Tagir; Howard, Daniel M.; Ji, Lei; Xiao, Jingfeng; Li, Jing; Yuan, Wenping; Zhao, Tianbao; Chen, Shiping; Zhou, Guangsheng; Kato, Tomomichi

    2014-01-01

    Grassland is one of the widespread biome types globally, and plays an important role in the terrestrial carbon cycle. We examined net ecosystem production (NEP) for the temperate grasslands in northern China from 2000 to 2010. We combined flux observations, satellite data, and climate data to develop a piecewise regression model for NEP, and then used the model to map NEP for grasslands in northern China. Over the growing season, the northern China's grassland had a net carbon uptake of 158 ± 25 g C m?2 during 2000–2010 with the mean regional NEP estimate of 126 Tg C. Our results showed generally higher grassland NEP at high latitudes (northeast) than at low latitudes (central and west) because of different grassland types and environmental conditions. In the northeast, which is dominated by meadow steppes, the growing season NEP generally reached 200–300 g C m?2. In the southwest corner of the region, which is partially occupied by alpine meadow systems, the growing season NEP also reached 200–300 g C m?2. In the central part, which is dominated by typical steppe systems, the growing season NEP generally varied in the range of 100–200 g C m?2. The NEP of the northern China's grasslands was highly variable through years, ranging from 129 (2001) to 217 g C m?2 growing season?1 (2010). The large interannual variations of NEP could be attributed to the sensitivity of temperate grasslands to climate changes and extreme climatic events. The droughts in 2000, 2001, and 2006 reduced the carbon uptake over the growing season by 11%, 29%, and 16% relative to the long-term (2000–2010) mean. Over the study period (2000–2010), precipitation was significantly correlated with NEP for the growing season (R2 = 0.35, p-value < 0.1), indicating that water availability is an important stressor for the productivity of the temperate grasslands in semi-arid and arid regions in northern China. We conclude that northern temperate grasslands have the potential to sequester carbon, but the capacity of carbon sequestration depends on grassland types and environmental conditions. Extreme climate events like drought can significantly reduce the net carbon uptake of grasslands.

  3. Components of surface energy balance in a temperate grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.

    1990-01-01

    Eddy correlation measurements of moisture, heat, and momentum fluxes were made at a tall grassland site in Kansas during the First International Satellite Land Surface Climatology Project Field Experiment. The fluxes, stomatal conductance, and leaf water potential of three grass species are reported. The species are big bluestem, indiangrass, and switchgrass. The daily and seasonal variation in the components of the surface energy balance and the aerodynamic and canopy surface conductances for prairie vegetation are examined.

  4. Environmental Controls and Management Effects on Ecosystem Carbon Exchange in Two Grazed Temperate Grasslands

    NASA Astrophysics Data System (ADS)

    Ni Choncubhair, O.; Humphreys, J.; Lanigan, G.

    2013-12-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. Accumulation of carbon (C) in grassland systems predominantly takes place in below-ground repositories, enhanced by the presence of a stable soil environment with low carbon turnover rates, active rhizodeposition and high levels of residue and organic inputs. However, this C sequestration is strongly influenced by soil characteristics and climatic variables. Furthermore, in managed pasture systems, carbon exchange across the soil-atmosphere boundary is additionally affected by management activities, such as biomass removal, grazing events and the deposition or application of organic amendments. These biotic and abiotic factors contribute greatly towards the large uncertainty associated with the carbon balance of grassland ecosystems and demand further analysis. In the present study, the controls and drivers of carbon dynamics in two rotationally-grazed grasslands in Ireland were examined. The sites experience similar temperate climatic regimes but differ in soil texture classification and stocking rate. Eddy covariance measurements of net ecosystem exchange of carbon were complemented by regular assessment of standing biomass, leaf cover, harvest exports and organic amendment inputs. Our study showed that mild weather conditions and an extended growing season sustained net C accumulation at both sites for at least ten months of the year. Despite differing soil drainage characteristics, winter fluxes of net carbon exchange and its component fluxes, gross photosynthesis and ecosystem respiration, were highly comparable between the two sites. Management practices during the active growing season exerted a strong influence on both the direction and the rate of C exchange in the grassland systems, with a strong dependence, however, on the timing and intensity of the management effect. Harvest-induced reductions in productivity and net C uptake were generally greater than grazing-induced shifts, however the effects were at times mediated by environmental conditions. Our research highlighted the complex nature of the investigated grasslands resulting from the heterogeneous footprint induced by rotational grazing, grass harvesting and intensive management practices. Further work will focus on the applicability of different gap-filling methodologies for capturing the temporal and spatial variability observed. The potential of vegetation indices as a means of tracking sward development will also be investigated, with the aim of improving our understanding of the impact of vegetation dynamics on measured ecosystem carbon fluxes.

  5. Uncertainty analysis of a coupled ecosystem response model simulating greenhouse gas fluxes from a temperate grassland

    NASA Astrophysics Data System (ADS)

    Liebermann, Ralf; Kraft, Philipp; Houska, Tobias; Breuer, Lutz; Müller, Christoph; Kraus, David; Haas, Edwin; Klatt, Steffen

    2015-04-01

    Among anthropogenic greenhouse gas emissions, CO2 is the dominant driver of global climate change. Next to its direct impact on the radiation budget, it also affects the climate system by triggering feedback mechanisms in terrestrial ecosystems. Such mechanisms - like stimulated photosynthesis, increased root exudations and reduced stomatal transpiration - influence both the input and the turnover of carbon and nitrogen compounds in the soil. The stabilization and decomposition of these compounds determines how increasing CO2 concentrations change the terrestrial trace gas emissions, especially CO2, N2O and CH4. To assess the potential reaction of terrestrial greenhouse gas emissions to rising tropospheric CO2 concentration, we make use of a comprehensive ecosystem model integrating known processes and fluxes of the carbon-nitrogen cycle in soil, vegetation and water. We apply a state-of-the-art ecosystem model with measurements from a long term field experiment of CO2 enrichment. The model - a grassland realization of LandscapeDNDC - simulates soil chemistry coupled with plant physiology, microclimate and hydrology. The data - comprising biomass, greenhouse gas emissions, management practices and soil properties - has been attained from a FACE (Free Air Carbon dioxide Enrichment) experiment running since 1997 on a temperate grassland in Giessen, Germany. Management and soil data, together with weather records, are used to drive the model, while cut biomass as well as CO2 and N2O emissions are used for calibration and validation. Starting with control data from installations without CO2 enhancement, we begin with a GLUE (General Likelihood Uncertainty Estimation) assessment using Latin Hypercube to reduce the range of the model parameters. This is followed by a detailed sensitivity analysis, the application of DREAM-ZS for model calibration, and an estimation of the effect of input uncertainty on the simulation results. Since first results indicate problems with the correct representation of the seasonal cycle of soil moisture and N2O emissions, our model is soon to be augmented with a more elaborate sub model for hydrology. Subsequent steps include the comparison of simulations and measurements under 20% elevated atmospheric CO2 concentrations, and the integration of a Farquhar-type sub model for photosynthesis.

  6. Impact of inter-annual climatic variability on ecosystem carbon exchange in two grazed temperate grasslands with contrasting drainage regimes

    NASA Astrophysics Data System (ADS)

    Choncubhair, Órlaith Ní; Humphreys, James; Lanigan, Gary

    2014-05-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. Accumulation of carbon (C) in grassland systems predominantly takes place in below-ground repositories, enhanced by the presence of a stable soil environment with low carbon turnover rates, active rhizodeposition and high levels of residue and organic inputs. Predicted future warming is expected to increase productivity in temperate zones, thereby enhancing rates of terrestrial carbon sequestration. However, the susceptibility of many ecosystems, including grasslands, to extreme climatic events and inter-annual variability has been demonstrated previously. Temperature anomalies as well as modifications in the temporal pattern and quantity of precipitation alter the balance between carbon uptake and release processes and a mechanistic understanding of ecosystem response to such changes is still lacking. In the present study, the impact of extreme inter-annual variability in summer rainfall and temperature on carbon dynamics in two rotationally-grazed grasslands in Ireland was examined. The sites experience similar temperate climatic regimes but differ in soil drainage characteristics. Eddy covariance measurements of net ecosystem exchange of carbon were complemented by regular assessment of standing biomass, leaf cover, harvest exports and organic amendment inputs. The summers of 2012 and 2013 showed contrasting climatic conditions, with summer precipitation 93% higher and 25% lower respectively than long-term means. In addition, soil temperatures were 7% lower and 11% higher than expected. Cool, wet conditions in 2012 facilitated net carbon uptake for more than ten months of the year at the poorly-drained site, however the ecosystem switched to a net source of carbon in 2013 during months with significantly reduced rainfall. In contrast, net C accumulation continued at the well-drained site despite the summer drought conditions. Total cumulative annual ecosystem respiration was 20% higher at the poorly-drained site than at the well-drained site in 2013, while a more modest increase in cumulative gross production (9.6%) was observed at the poorly-drained site for the same period. This research highlights the susceptibility of poorly-drained soils to accelerated efflux of carbon during soil drying cycles and points towards potential negative impacts of future warming scenarios, with significant carbon balance implications for grassland ecosystems.

  7. Evapotranspiration flux partitioning using an Iso-SPAC model in a temperate grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Wang, P.

    2014-12-01

    To partition evapotranspiration (ET) into soil evaporation and vegetation transpiration (T), a new numerical Iso-SPAC (coupled heat, water with isotopic tracer in Soil-Plant-Atmosphere-Continuum) model was developed and applied to a temperate-grassland ecosystem in central Japan. Several models of varying complexity have been tested with the aim of obtaining the close to true value for the isotope composition of leaf water and transpiration flux. The agreement between the model predictions and observations demonstrates that the Iso-SPAC model with a steady-state assumption for transpiration flux can reproduce seasonal variations of all the surface energy balance components?leaf and ground surface temperature as well as isotope data (canopy foliage and ET flux). This good performance was confirmed not only at diurnal timescale but also at seasonal timescale. Thus, although the non-steady-state behavior of isotope budget in a leaf and isotopic diffusion between leaf and stem or root is exactly important, the steady-state assumption is practically acceptable for seasonal timescale as a first order approximation. Sensitivity analysis both in physical flux part and isotope part suggested that T/ET is relatively insensitive to uncertainties/errors in assigned model parameters and measured input variables, which illustrated the partitioning validity. Estimated transpiration fractions using isotope composition in ET flux by Iso-SPAC model and Keeling plot are generally in good agreement, further proving validity of the both approaches. However, Keeling plot approach tended to overestimate the fraction during an early stage of glowing season and a period just after clear cutting. This overestimation is probably due to insufficient fetch and influence of transpiration from upwind forest. Consequently, Iso-SPAC model is more reliable than Keeling plot approach in most cases.The T/ET increased with grass growth, and the sharp reduction caused by clear cutting was well reflected. The transpiration fraction ranges from 0.02 to 0.99 during growing seasons, and the mean value was 0.75 with a standard deviation of 0.24.

  8. Evaluating potential indicators of ecosystem processes across local gradients in a temperate grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Science-based information is needed to identify indicators of ecosystem services that may then be used to monitor natural resources and quantify effects of management. Here our aim was to perform a local gradient study to elucidate correlative associations between vegetation and multiple soil prope...

  9. Grazing Management of Temperate Grasslands and Fallows

    E-print Network

    Roder, Walter

    2002-01-01

    44 GRAZING MANAGEMENT OF TEMPERATE GRASSLAND AND FALLOWS Walter Roder* Introduction The paper provides a general overview of fodder resources and their management in temperate Bhutan (altitude range of 1500-3000m). The terms are used... as defined by RC-Jakar (RNR-RC-Jakar, 1996). As per these definitions, temperate pasture can include any kind of land used for grazing. When referring to registered grassland or tsamdro, only the term tsamdrog is used. Where possible, the term pasture...

  10. Declining Birds in Grassland Ecosystems

    NSDL National Science Digital Library

    This United States Geological Survey (USGS) publication discusses the grassland ecosystem with respect to declining bird species. This report is the effort of a number of agencies to develop a strategy for addressing grassland bird information needs. Grasslands are the most imperiled ecosystem worldwide, and birds associated with this ecosystem are on a decline. This report addresses monitoring issues, species in concern, and the effects of habitat and landscape on grassland birds.

  11. American Field Guide: The Formation and Value of Temperate Grasslands

    NSDL National Science Digital Library

    This website integrates video footage and information with lesson plans and activities to teach students about the Temperate Grasslands (Prairie) biome of North America. The activities in this unit are designed to give students an overview of the climate and organisms of this biome in order to better understand this endangered ecosystem. There are lesson plans, instruction sheets, and links for additional information.

  12. Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland: effects of climate and management

    PubMed Central

    Wohlfahrt, Georg; Hammerle, Albin; Haslwanter, Alois; Bahn, Michael; Tappeiner, Ulrike; Cernusca, Alexander

    2013-01-01

    The role and relative importance of climate and cutting for the seasonal and inter-annual variability of the net ecosystem CO2 (NEE) of a temperate mountain grassland was investigated. Eddy covariance CO2 flux data and associated measurements of the green area index and the major environmental driving forces acquired during 2001-2006 at the study site Neustift (Austria) were analyzed. Driven by three cutting events per year which kept the investigated grassland in a stage of vigorous growth, the seasonal variability of NEE was primarily modulated by gross primary productivity (GPP). The role of environmental parameters in modulating the seasonal variability of NEE was obscured by the strong response of GPP to changes in the amount of green area, as well as the cutting-mediated decoupling of phenological development and the seasonal course of climate drivers. None of the climate and management metrics examined was able to explain the inter-annual variability of annual NEE. This is thought to result from (1) a high covariance between GPP and ecosystem respiration (Reco) at the annual time scale which results in a comparatively small inter-annual variation of NEE, (2) compensating effects between carbon exchange during and outside the management period, and (3) changes in the biotic response to rather than the climate variables per se. GPP was more important in modulating inter-annual variations in NEE in spring and before the first and second cut, while Reco explained a larger fraction of the inter-annual variability of NEE during the remaining, in particular the post-cut, periods. PMID:24383047

  13. The measurement of soil fungal:bacterial biomass ratios as an indicator of ecosystem self-regulation in temperate meadow grasslands

    Microsoft Academic Search

    Richard D. Bardgett; Erica McAlister

    1999-01-01

    There is much interest in the development of agricultural land management strategies aimed at enhancing reliance on ecosystem\\u000a self-regulation rather than on artificial inputs such as fertilisers and pesticides. This study tested the usefulness of measures\\u000a of soil microbial biomass and fungal:bacterial biomass ratios as indicators of effective conversion from an intensive grassland\\u000a system, reliant mainly on fertilisers for crop

  14. Efficiency and future potential of urea for temperate grassland

    Microsoft Academic Search

    C. J. Watson; R. J. Stevens; M. K. Garrett; C. H. McMurray

    1990-01-01

    The efficacy of urea as a grassland fertilizer under temperate conditions has been assessed in a wide variety of comparisons with either ammonium nitrate or calcium ammonium nitrate (CAN). Data from the British Isles have been evaluated and compared to results mainly from continental Europe.In general urea is as good as CAN early in the growing season, but less-effective in

  15. Seasonal and inter-annual dynamics in the stable oxygen isotope compositions of water pools in a temperate humid grassland ecosystem: results from MIBA sampling and MuSICA modelling

    NASA Astrophysics Data System (ADS)

    Hirl, Regina; Schnyder, Hans; Auerswald, Karl; Vetter, Sylvia; Ostler, Ulrike; Schleip, Inga; Wingate, Lisa; Ogée, Jérôme

    2015-04-01

    The oxygen isotope composition (?18O) of water in terrestrial ecosystems usually shows strong and dynamic variations within and between the various compartments. These variations originate from changes in the ?18O of water inputs (e.g. rain or water vapour) and from 18O fractionation phenomena in the soil-plant-atmosphere continuum. Investigations of ?18O in ecosystem water pools and of their main drivers can help us understand water relations at plant, canopy or ecosystem scale and interpret ?18O signals in plant and animal tissues as paleo-climate proxies. During the vegetation periods of 2006 to 2012, soil, leaf and stem water as well as atmospheric humidity, rain water and groundwater were sampled at bi-weekly intervals in a temperate humid pasture of the Grünschwaige Grassland Research Station near Munich (Germany). The sampling was performed following standardised MIBA (Moisture Isotopes in the Biosphere and Atmosphere) protocols. Leaf water samples were prepared from a mixture of co-dominant species in the plant community in order to obtain a canopy-scale leaf water ?18O signal. All samples were then analysed for their ?18O compositions. The measured ?18O of leaf, stem and soil water were then compared with the ?18O signatures simulated by the process-based isotope-enabled ecosystem model MuSICA (Multi-layer Simulator of the Interactions between a vegetation Canopy and the Atmosphere). MuSICA integrates current mechanistic understanding of processes in the soil-plant-atmosphere continuum. Hence, the comparison of modelled and measured data allows the identification of gaps in current knowledge and of questions to be tackled in the future. Soil and plant characteristics for model parameterisation were derived from investigations at the experimental site and supplemented by values from the literature. Eddy-covariance measurements of ecosystem CO2 (GPP, NEE) and energy (H, LE) fluxes and soil temperature data were used for model evaluation. The comparison of measured and predicted ecosystem fluxes showed that the model captured the main features of the diurnal cycles of GPP, NEE, LE and H, as well as the soil temperature dynamics. In this presentation I will present the main results of this model-data comparison, as well as results from a model sensitivity analysis performed over a range of soil, plant and meteorological parameters to evaluate the relative importance of each parameter on the ?18O signatures of the various water pools.

  16. Nitrogen relationships in intensively managed temperate grasslands

    Microsoft Academic Search

    P. Roger Ball; J. C. Ryden

    1984-01-01

    Summary Most studies of N relationships in grassland have used cut swards. These have shown that for annual inputs of 200 to 400 kg N\\/ha from fertilizer or fixation, 55 to 80% of the N is recovered in harvested herbage. Generally, no more than 5 to 15% is lost through leaching and denitrification with most of the remaining N incorporated

  17. China's grazed temperate grasslands are a net source of atmospheric methane Zhi-Ping Wang a

    E-print Network

    Yu, Qiang

    China's grazed temperate grasslands are a net source of atmospheric methane Zhi-Ping Wang a , Yang that ruminant production has converted China's grazed temperate grasslands to a net source of atmospheric CH4 warming potential about 25-fold greater than that of CO2 over 100 years (IPCC, 2007). Upland grassland

  18. Quantifying the pedo-ecohydrological structure and function of degraded, grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Brazier, Richard E.

    2015-04-01

    Grassland ecosystems cover significant areas of the terrestrial land mass, across a range of geoclimates, from arctic tundra, through temperate and semi-arid landscapes. In very few locations, such grasslands may be termed 'pristine' in that they remain undamaged by human activities and resilient to changing climates. In far more cases, grasslands are being degraded, often irreversibly so, with significant implications for a number of ecosystem services related to water resources, soil quality, nutrient cycles, and therefore both global food and water security. This paper draws upon empirical research that has been undertaken over the last decade to characterise a range of different grasslands in terms of soil properties, vegetation structure and geomorphology and to understand how these structures or patterns might interact or control how the grassland ecosystems function. Particular emphasis is placed upon quantifying fluxes of water, within and from grasslands, but also fluxes of sediment, via the processes of soil erosion and finally fluxes of the macronutrients Nitrogen, Phosphorus and Carbon from the landscape to surface waters. Data are presented from semi-arid grasslands, which are subject to severe encroachment by woody species, temperate upland grasslands that have been 'improved' via drainage to support grazing, temperate lowland grasslands, that are unimproved (Culm or Rhôs pastures) and finally intensively managed grasslands in temperate regions, that have been significantly modified via land management practices to improve productivity. It is hypothesised that, once degraded, the structure and function of these very diverse grassland ecosystems follows the same negative trajectory, resulting in depleted soil depths, nutrient storage capacities and therefore reduced plant growth and long-term carbon sequestration. Results demonstrate that similar, but highly complex and non-linear responses to perturbation of the ecosystem are observed, regardless of the environmental setting or wider climatic conditions that the grasslands experience. Furthermore, it is demonstrated that the relatively stable ecosystem state that has prevailed in the 'pristine' grasslands studied, is in fact very fragile and may be easily altered, either by anthropogenic forcing, due to land management or by 'semi-natural' processes, related to climate change or changes in the incidence of wildfires (for example). Once structurally altered, it is also shown that positive feedbacks will occur to accelerate the loss of critical resources (topsoil and nutrients) from the ecosystem, in particular in drylands, resulting in widespread land degradation that cannot be reversed. In the temperate grasslands studied, it is shown that anthropogenic intervention may halt or even to some degree reverse the degradation of the soil-vegetation-water continuum. However, such 'landscape restoration' approaches are costly and require long-term management commitment if they are to succeed. degrade these critical ecosystems further. Finally, analysis of water, sediment and nutrient fluxes from this range of grasslands also demonstrates how critical ecosystem services that grasslands can provide; including soil water storage to buffer downstream flooding, soil carbon storage and enhanced biodiversity are reduced, often to the point where restoration of the original (pristine) landscape function is impossible. To conclude, discussion is made of how we can learn across grass landscapes globally, to ensure that those ecosystems that might be restored to build resilient landscapes under future climates are well understood and that future efforts to manage grasslands for increased food production do not degrade these critical ecosystems further.

  19. Quantifying the pedo-ecohydrological structure and function of degraded, grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Brazier, Richard E.

    2015-04-01

    Grassland ecosystems cover significant areas of the terrestrial land mass, across a range of geoclimates, from arctic tundra, through temperate and semi-arid landscapes. In very few locations, such grasslands may be termed 'pristine' in that they remain undamaged by human activities and resilient to changing climates. In far more cases, grasslands are being degraded, often irreversibly so, with significant implications for a number of ecosystem services related to water resources, soil quality, nutrient cycles, and therefore both global food and water security. This paper draws upon empirical research that has been undertaken over the last decade to characterise a range of different grasslands in terms of soil properties, vegetation structure and geomorphology and to understand how these structures or patterns might interact or control how the grassland ecosystems function. Particular emphasis is placed upon quantifying fluxes of water, within and from grasslands, but also fluxes of sediment, via the processes of soil erosion and finally fluxes of the macronutrients Nitrogen, Phosphorus and Carbon from the landscape to surface waters. Data are presented from semi-arid grasslands, which are subject to severe encroachment by woody species, temperate upland grasslands that have been 'improved' via drainage to support grazing, temperate lowland grasslands, that are unimproved (Culm or Rhôs pastures) and finally intensively managed grasslands in temperate regions, that have been significantly modified via land management practices to improve productivity. It is hypothesised that, once degraded, the structure and function of these very diverse grassland ecosystems follows the same negative trajectory, resulting in depleted soil depths, nutrient storage capacities and therefore reduced plant growth and long-term carbon sequestration. Results demonstrate that similar, but highly complex and non-linear responses to perturbation of the ecosystem are observed, regardless of the environmental setting or wider climatic conditions that the grasslands experience. Furthermore, it is demonstrated that the relatively stable ecosystem state that has prevailed in the 'pristine' grasslands studied, is in fact very fragile and may be easily altered, either by anthropogenic forcing, due to land management or by 'semi-natural' processes, related to climate change or changes in the incidence of wildfires (for example). Once structurally altered, it is also shown that positive feedbacks will occur to accelerate the loss of critical resources (topsoil and nutrients) from the ecosystem, in particular in drylands, resulting in widespread land degradation that cannot be reversed. In the temperate grasslands studied, it is shown that anthropogenic intervention may halt or even to some degree reverse the degradation of the soil-vegetation-water continuum. However, such 'landscape restoration' approaches are costly and require long-term management commitment if they are to succeed. Finally, analysis of water, sediment and nutrient fluxes from this range of grasslands also demonstrates how critical ecosystem services that grasslands can provide; including soil water storage to buffer downstream flooding, soil carbon storage and enhanced biodiversity are reduced, often to the point where restoration of the original (pristine) landscape function is impossible. To conclude, discussion is made of how we can learn across grass landscapes globally, to ensure that those ecosystems that might be restored to build resilient landscapes under future climates are well understood and that future efforts to manage grasslands for increased food production do not degrade these critical ecosystems further.

  20. Short sampling intervals reveal very rapid root turnover in a temperate grassland.

    PubMed

    Stewart, Anna M; Frank, Douglas A

    2008-09-01

    Although root growth and mortality play critical regulatory roles in terrestrial ecosystems, little is known about the temporal scale of these dynamics. In temperate grasslands, root dynamics may be particularly rapid because of the high proportion of production allocated to very fine root biomass. In this study, we used minirhizotron tubes to estimate root growth and mortality in an upland grassland in Yellowstone National Park that was grazed by migratory herds of ungulates. Monthly rates of root growth and mortality were estimated from May to September 2005, by measuring the elongation (growth) and disappearance (mortality) of roots at 3-day intervals. Average daily growth (millimeters of root length) was approximately 5 times greater in May and June than in July, August, and September. Average daily mortality (millimeters of root length) did not differ among months. A comparison of the June-September rates of root growth and mortality derived from sampling at short (3-day) and long (1-month) time intervals indicated that the long sampling intervals underestimated both growth and mortality by approximately 60% relative to the short intervals. These results suggest that estimates of grassland root dynamics from minirhizotrons are influenced significantly by sampling interval length, and that rapid root turnover may play a more critical role in regulating energy and nutrient fluxes in temperate grasslands than has previously been recognized. PMID:18566834

  1. Temperate mountain grasslands: a climate-herbivore hypothesis for origins and persistence

    PubMed Central

    Weigl, Peter D; Knowles, Travis W

    2014-01-01

    Temperate montane grasslands and their unique biotas are declining worldwide as they are increasingly being invaded by forests. The origin and persistence of these landscapes have been the focus of such controversy that in many areas their conservation is in doubt. In the USA some biologists have largely dismissed the grass balds of the Southern Appalachians as human artifacts or anomalous and transitory elements of regional geography, worthy of only limited preservation efforts. On the basis of information from biogeography, community ecology, regional history and palaeontology and from consideration of two other montane grassland ecosystems—East Carpathian poloninas and Oregon Coast Range grass balds—we hypothesize that these landscapes are more widespread than was formerly recognized; they are, in many cases, natural and ancient and largely owe their origin and persistence to past climatic extremes and the activities of large mammalian herbivores. PMID:24118866

  2. No evidence of complementary water use along a plant species richness gradient in temperate experimental grasslands.

    PubMed

    Bachmann, Dörte; Gockele, Annette; Ravenek, Janneke M; Roscher, Christiane; Strecker, Tanja; Weigelt, Alexandra; Buchmann, Nina

    2015-01-01

    Niche complementarity in resource use has been proposed as a key mechanism to explain the positive effects of increasing plant species richness on ecosystem processes, in particular on primary productivity. Since hardly any information is available for niche complementarity in water use, we tested the effects of plant diversity on spatial and temporal complementarity in water uptake in experimental grasslands by using stable water isotopes. We hypothesized that water uptake from deeper soil depths increases in more diverse compared to low diverse plant species mixtures. We labeled soil water in 8 cm (with 18O) and 28 cm depth (with ˛H) three times during the 2011 growing season in 40 temperate grassland communities of varying species richness (2, 4, 8 and 16 species) and functional group number and composition (legumes, grasses, tall herbs, small herbs). Stable isotope analyses of xylem and soil water allowed identifying the preferential depth of water uptake. Higher enrichment in 18O of xylem water than in ˛H suggested that the main water uptake was in the upper soil layer. Furthermore, our results revealed no differences in root water uptake among communities with different species richness, different number of functional groups or with time. Thus, our results do not support the hypothesis of increased complementarity in water use in more diverse than in less diverse communities of temperate grassland species. PMID:25587998

  3. The Effects of Warming and Nitrogen Addition on Soil Nitrogen Cycling in a Temperate Grassland, Northeastern China

    PubMed Central

    Ma, Lin-Na; Lü, Xiao-Tao; Liu, Yang; Guo, Ji-Xun; Zhang, Nan-Yi; Yang, Jian-Qin; Wang, Ren-Zhong

    2011-01-01

    Background Both climate warming and atmospheric nitrogen (N) deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood. Methodology/Principal Findings A field manipulation experiment was conducted to examine the effects of warming and N addition on soil N cycling in a temperate grassland of northeastern China from 2007 to 2009. Soil samples were incubated at a constant temperature and moisture, from samples collected in the field. The results showed that both warming and N addition significantly stimulated soil net N mineralization rate and net nitrification rate. Combined warming and N addition caused an interactive effect on N mineralization, which could be explained by the relative shift of soil microbial community structure because of fungal biomass increase and strong plant uptake of added N due to warming. Irrespective of strong intra- and inter-annual variations in soil N mineralization, the responses of N mineralization to warming and N addition did not change during the three growing seasons, suggesting independence of warming and N responses of N mineralization from precipitation variations in the temperate grassland. Conclusions/Significance Interactions between climate warming and N deposition on soil N cycling were significant. These findings will improve our understanding on the response of soil N cycling to the simultaneous climate change drivers in temperate grassland ecosystem. PMID:22096609

  4. Patterns of Plant Biomass Allocation in Temperate Grasslands across a 2500-km Transect in Northern China

    PubMed Central

    Luo, Wentao; Jiang, Yong; Lü, Xiaotao; Wang, Xue; Li, Mai-He; Bai, Edith; Han, Xingguo; Xu, Zhuwen

    2013-01-01

    Plant biomass allocation between below- and above-ground parts can actively adapt to the ambient growth conditions and is a key parameter for estimating terrestrial ecosystem carbon (C) stocks. To investigate how climatic variations affect patterns of plant biomass allocation, we sampled 548 plants belonging to four dominant genera (Stipa spp., Cleistogenes spp., Agropyron spp., and Leymus spp.) along a large-scale (2500 km) climatic gradient across the temperate grasslands from west to east in northern China. Our results showed that Leymus spp. had the lowest root/shoot ratios among the each genus. Root/shoot ratios of each genera were positively correlated with mean annual temperature (MAT), and negatively correlated with mean annual precipitation (MAP) across the transect. Temperature contributed more to the variation of root/shoot ratios than precipitation for Cleistogenes spp. (C4 plants), whereas precipitation exerted a stronger influence than temperature on their variations for the other three genera (C3 plants). From east to west, investment of C into the belowground parts increased as precipitation decreased while temperature increased. Such changes in biomass allocation patterns in response to climatic factors may alter the competition regimes among co-existing plants, resulting in changes in community composition, structure and ecosystem functions. Our results suggested that future climate change would have great impact on C allocation and storage, as well as C turnover in the grassland ecosystems in northern China. PMID:23977135

  5. Potential soil carbon sequestration in overgrazed grassland ecosystems

    Microsoft Academic Search

    Richard T. Conant; Keith Paustian

    2002-01-01

    Excessive grazing pressure is detrimental to plant productivity and may lead to declines in soil organic matter. Soil organic matter is an important source of plant nutrients and can enhance soil aggregation, limit soil erosion, and can also increase cation exchange and water holding capacities, and is, therefore, a key regulator of grassland ecosystem processes. Changes in grassland management which

  6. Belowground grassland herbivores are resistant to elevated atmospheric CO2 concentrations in grassland ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasslands are considered to be one of the most sensitive ecosystems to rising atmospheric CO2 concentrations. Moreover, grasslands support large populations of belowground herbivores that consume a major portion of plant biomass. The direct trophic link between herbivores and plants suggests that...

  7. Controls on winter ecosystem respiration in temperate and boreal ecosystems

    NASA Astrophysics Data System (ADS)

    Wang, T.; Ciais, P.; Piao, S. L.; Ottlé, C.; Brender, P.; Maignan, F.; Arain, A.; Cescatti, A.; Gianelle, D.; Gough, C.; Gu, L.; Lafleur, P.; Laurila, T.; Marcolla, B.; Margolis, H.; Montagnani, L.; Moors, E.; Saigusa, N.; Vesala, T.; Wohlfahrt, G.; Koven, C.; Black, A.; Dellwik, E.; Don, A.; Hollinger, D.; Knohl, A.; Monson, R.; Munger, J.; Suyker, A.; Varlagin, A.; Verma, S.

    2011-07-01

    Winter CO2 fluxes represent an important component of the annual carbon budget in northern ecosystems. Understanding winter respiration processes and their responses to climate change is also central to our ability to assess terrestrial carbon cycle and climate feedbacks in the future. However, the factors influencing the spatial and temporal patterns of winter ecosystem respiration (Reco) of northern ecosystems are poorly understood. For this reason, we analyzed eddy covariance flux data from 57 ecosystem sites ranging from ~35° N to ~70° N. Deciduous forests were characterized by the highest winter Reco rates (0.90 ± 0.39 g C m-2 d-1), when winter is defined as the period during which daily air temperature remains below 0 °C. By contrast, arctic wetlands had the lowest winter Reco rates (0.02 ± 0.02 g C m-2 d-1). Mixed forests, evergreen needle-leaved forests, grasslands, croplands and boreal wetlands were characterized by intermediate winter Reco rates (g C m-2 d-1) of 0.70(±0.33), 0.60(±0.38), 0.62(±0.43), 0.49(±0.22) and 0.27(±0.08), respectively. Our cross site analysis showed that winter air (Tair) and soil (Tsoil) temperature played a dominating role in determining the spatial patterns of winter Reco in both forest and managed ecosystems (grasslands and croplands). Besides temperature, the seasonal amplitude of the leaf area index (LAI), inferred from satellite observation, or growing season gross primary productivity, which we use here as a proxy for the amount of recent carbon available for Reco in the subsequent winter, played a marginal role in winter CO2 emissions from forest ecosystems. We found that winter Reco sensitivity to temperature variation across space (QS) was higher than the one over time (interannual, QT). This can be expected because QS not only accounts for climate gradients across sites but also for (positively correlated) the spatial variability of substrate quantity. Thus, if the models estimate future warming impacts on Reco based on QS rather than QT, this could overestimate the impact of temperature changes.

  8. Optimising stocking rate and grazing management to enhance environmental and production outcomes for native temperate grasslands

    NASA Astrophysics Data System (ADS)

    Badgery, Warwick; Zhang, Yingjun; Huang, Ding; Broadfoot, Kim; Kemp, David; Mitchell, David

    2015-04-01

    Stocking rate and grazing management can be altered to enhance the sustainable production of grasslands but the relative influence of each has not often been determined for native temperate grasslands. Grazing management can range from seasonal rests through to intensive rotational grazing involving >30 paddocks. In large scale grazing, it can be difficult to segregate the influence of grazing pressure from the timing of utilisation. Moreover, relative grazing pressure can change between years as seasonal conditions influence grassland production compared to the relative constant requirements of animals. This paper reports on two studies in temperate native grasslands of northern China and south eastern Australia that examined stocking rate and regionally relevant grazing management strategies. In China, the grazing experiment involved combinations of a rest, moderate or heavy grazing pressure of sheep in spring, then moderate or heavy grazing in summer and autumn. Moderate grazing pressure at 50% of the current district average, resulted in the better balance between maintaining productive and diverse grasslands, a profitable livestock system, and mitigation of greenhouse gases through increased soil carbon, methane uptake by the soil, and efficient methane emissions per unit of weight gain. Spring rests best maintained a desirable grassland composition, but had few other benefits and reduced livestock productivity due to lower feed quality from grazing later in the season. In Australia, the grazing experiment compared continuous grazing to flexible 4- and 20-paddock rotational grazing systems with sheep. Stocking rates were adjusted between systems biannually based on the average herbage mass of the grassland. No treatment degraded the perennial pasture composition, but ground cover was maintained at higher levels in the 20-paddock system even though this treatment had a higher stocking rate. Overall there was little difference in livestock production (e.g. kg lamb/ha), because individual animal performance was greater for continuous grazing than higher intensity grazing systems (4-Paddock and 20-Paddock). Differences in SOC, CO2 flux and erosion were determined by landscape position rather than grazing treatment. To remove the confounding influences of stocking rate and grazing management, the Ausfarm biophysical model, calibrated to the experimental treatments, examined the interaction between grazing management and stocking rates. Ground cover and profitability were similar between grazing systems at lower stocking rates (3 ewes per ha), but continuous grazing had higher profitability and lower ground cover above the optimum stocking rate of 4 ewes per ha. The findings of these two studies suggest that optimising stocking rate is more important than grazing management for a sustainable and profitable grazing system. Grazing management can further enhance environmental outcomes for an optimal stocking rate, but the findings from the Chinese study particularly highlight the need to look at multiple ecosystem services, when optimising systems. The Australian study also suggests the optimum stocking rate is dependent on the intensity of grazing management. Further work is required to understand the influence of landscape on grassland production and how stocking rates and grazing management can be sustainably optimised for different landscape areas to utilise this variation more effectively.

  9. Land surface memory effects on dust emission in a Mongolian temperate grassland

    NASA Astrophysics Data System (ADS)

    Nandintsetseg, Banzragch; Shinoda, Masato

    2015-03-01

    Aeolian processes in temperate grasslands are unique in that the plant growth-decay cycle, soil moisture/snowpack dynamics, and induced grazing interactively affect seasonal and interannual variations of dust emission. This study uses process-based ecosystem model DAYCENT and unique saltation flux measurements to (1) identify primary land surface factors that control dust emission with soil moisture and vegetation components (live grasses, standing dead grasses, and litter) in a Mongolian grassland and (2) test the dead-leaf hypothesis proposed by previous observational studies that correlates plant biomass in summer and dust events the following spring. In general, the DAYCENT model realistically simulates seasonal and interannual variations of the vegetation components and soil moisture that were captured by field observations during 2003-2010. Then, the land surface components are correlated with measured daily saltation flux in the springs of 2008-2009 and the frequency of monthly dusty days during March-June 2002-2010. Results show that dust emission had a similar amplitude of significant correlation with wind speed and a combination of all land surface components, which demonstrates a memory of the preceding year. The memory analysis reveals that vegetation and soil moisture anomalies during spring dust emission are significantly autocorrelated with the preceding year's (autumn) corresponding anomalies, which were controlled by rainfall during a given summer. Most importantly, of the vegetation components, the standing dead grasses had the strongest memory and simultaneous correlation with spring dust emission, suggesting the validity of the dead-leaf hypothesis.

  10. Acetaldehyde exchange above a managed temperate mountain grassland

    PubMed Central

    Hörtnagl, L.; Bamberger, I.; Graus, M.; Ruuskanen, T. M.; Schnitzhofer, R.; Walser, M.; Unterberger, A.; Hansel, A.; Wohlfahrt, G.

    2013-01-01

    An overview of acetaldehyde exchange above a managed temperate mountain grassland in Austria over four growing seasons is presented. The meadow acted as a net source of acetaldehyde in all four years, emitting between 7 and 28 mg C m?2 over the whole growing period. The cutting of the meadow resulted in huge acetaldehyde emission bursts on the day of harvesting or one day later. During undisturbed conditions, both uptake and emission fluxes were recorded. The bidirectional nature of acetaldehyde fluxes was also reflected by clear diurnal cycles during certain time periods, indicating strong deposition processes before the 1st cut and emission towards the end of the growing season. The analysis of acetaldehyde compensation points revealed a complex relationship between ambient acetaldehyde mixing ratios and respective fluxes, significantly influenced by multiple environmental parameters and variable throughout the year. As a major finding of this study, we identified both a positive and negative correlation between concentration and flux on a daily scale, where soil temperature and soil water content were the most significant factors in determining the direction of the slope. In turn, this bidirectional relationship on a daily scale resulted in compensation points between 0.40 ppbv and 0.54 ppbv, which could be well explained by collected ancillary data. We conclude that in order to model acetaldehyde fluxes at the site in Neustift on a daily scale over longer time periods, it is crucial to know the type of relationship, i.e. the direction of the slope, between mixing ratios and fluxes on a given day. PMID:24363666

  11. Acetaldehyde exchange above a managed temperate mountain grassland

    NASA Astrophysics Data System (ADS)

    Hörtnagl, L.; Bamberger, I.; Graus, M.; Ruuskanen, T. M.; Schnitzhofer, R.; Walser, M.; Unterberger, A.; Hansel, A.; Wohlfahrt, G.

    2014-06-01

    An overview of acetaldehyde exchange above a managed temperate mountain grassland in Austria over four growing seasons is presented. The meadow acted as a net source of acetaldehyde in all 4 years, emitting between 7 and 28 mg C m-2 over the whole growing period. The cutting of the meadow resulted in huge acetaldehyde emission bursts of up to 16.5 nmol m-2 s-1 on the day of harvesting or 1 day later. During undisturbed conditions both periods with net uptake and net emissions of acetaldehyde were observed. The bidirectional nature of acetaldehyde fluxes was also reflected by clear diurnal cycles during certain time periods, indicating strong deposition processes before the first cut and emission towards the end of the growing season. The analysis of acetaldehyde compensation points revealed a complex relationship between ambient acetaldehyde mixing ratios and respective fluxes, significantly influenced by multiple environmental parameters and variable throughout the year. As a major finding of this study, we identified both a positive and negative correlation between concentration and flux on a daily scale, where soil temperature and soil water content were the most significant factors in determining the direction of the slope. In turn, this bidirectional relationship on a daily scale resulted in compensation points between 0.40 and 0.54 ppbv, which could be well explained by collected ancillary data. We conclude that in order to model acetaldehyde fluxes at the site in Neustift on a daily scale over longer time periods, it is crucial to know the type of relationship, i.e., the direction of the slope, between mixing ratios and fluxes on a given day.

  12. Biotic, abiotic and management controls on methanol exchange above a temperate mountain grassland

    PubMed Central

    Hörtnagl, Lukas; Bamberger, Ines; Graus, Martin; Ruuskanen, Taina M.; Schnitzhofer, Ralf; Müller, Markus; Hansel, Armin; Wohlfahrt, Georg

    2013-01-01

    Methanol (CH3OH) fluxes were quantified above a managed temperate mountain grassland in the Stubai Valley (Tyrol, Austria) during the growing seasons 2008 and 2009. Half-hourly methanol fluxes were calculated by means of the virtual disjunct eddy covariance (vDEC) method using 3-dimensional wind data from a sonic anemometer and methanol volume mixing ratios measured with a proton-transfer-reaction mass spectrometer (PTR-MS). During (undisturbed) mature and growing phases methanol fluxes exhibited a clear diurnal cycle with close-to-zero fluxes during nighttime and emissions, up to 10 nmol m?2 s?1, which followed the diurnal course of radiation and air temperature. Management events were found to represent the largest perturbations of methanol exchange at the studied grassland ecosystem: Peak emissions of 144.5 nmol m?2 s?1 were found during/after cutting of the meadow reflecting the wounding of the plant material and subsequent depletion of the leaf internal aqueous methanol pools. After the application of organic fertilizer, elevated methanol emissions of up to 26.7 nmol m?2 s?1 were observed, likely reflecting enhanced microbial activity associated with the applied manure. Simple and multiple linear regression analyses revealed air temperature and radiation as the dominant abiotic controls, jointly explaining 47 % and 70 % of the variability in half-hourly and daily methanol fluxes. In contrast to published leaf-level laboratory studies, the surface conductance and the daily change in the amount of green plant area, used as ecosystem-scale proxies for stomatal conductance and growth, respectively, were found to exert only minor biotic controls on methanol exchange. PMID:24349901

  13. Estimating net primary productivity of grasslands from field biomass measurements in temperate northern China

    Microsoft Academic Search

    Jian Ni

    2004-01-01

    Data on field biomass measurements in temperate grasslands of northern China (141 samples from 74 sites) were obtained from\\u000a 23 Chinese journals, reports and books. Net primary productivity (NPP) of grasslands was estimated using three algorithms\\u000a (peak live biomass, peak standing crop and maximum minus minimum live biomass), respectively, based on availability of biomass\\u000a data in sites. 135 samples which

  14. Carbon dioxide and water vapor exchange in a warm temperate grassland

    Microsoft Academic Search

    K. A. Novick; P. C. Stoy; G. G. Katul; D. S. Ellsworth; M. B. S. Siqueira; J. Juang; R. Oren

    2004-01-01

    Grasslands cover about 40% of the ice-free global terrestrial surface, but their contribution to local and regional water and carbon fluxes and sensitivity to climatic perturbations such as drought remains uncertain. Here, we assess the direction and magnitude of net ecosystem carbon exchange (NEE) and its components, ecosystem carbon assimilation ( A c) and ecosystem respiration ( R E), in

  15. REMOTE SENSING GRASSLAND PHENOLOGY IN THE GREATER YELLOWSTONE ECOSYSTEM: BIOPHYSICAL CORRELATES,

    E-print Network

    Hansen, Andrew J.

    REMOTE SENSING GRASSLAND PHENOLOGY IN THE GREATER YELLOWSTONE ECOSYSTEM: BIOPHYSICAL CORRELATES........................................................................................................... 4 2. BIOPHYSICAL CONTROLS ON LAND SURFACE PHENOLOGY OF GRASSLANDS IN THE UPPER YELLOWSTONE RIVER Phenology and Climate in the Greater Yellowstone Ecosystem

  16. Year in Review: Spotlight on 2013 Research by the Grassland, Shrubland and Desert Ecosystems Science Program

    E-print Network

    Year in Review: Spotlight on 2013 Research by the Grassland, Shrubland and Desert Ecosystems of the Grassland, Shrubland and Desert Ecosystems Science Program (GSD) that depict its strengths and focus areas Rocky Mountain Research Station Grassland, Shrubland and Desert Ecosystems Science Program GSDUpdate

  17. Energy exchange and evapotranspiration over two temperate semi-arid grasslands in North America

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The seasonal and interannual variability in surface energy exchange and evapotranspiration (E) of two temperate semi-arid grasslands in southern Arizona, USA were investigated using continuous eddy covariance measurements from 2004 to 2007, including two drought years (2004 and 2005). One of the gra...

  18. ECOSYSTEM EFFECTS OF BIODIVERSITY MANIPULATIONS IN EUROPEAN GRASSLANDS

    Microsoft Academic Search

    E. M. Spehn; A. Hector; J. Joshi; M. Scherer-Lorenzen; B. Schmid; E. Bazeley-White; C. Beierkuhnlein; M. C. Caldeira; M. Diemer; P. G. Dimitrakopoulos; J. A. Finn; H. Freitas; P. S. Giller; J. Good; R. Harris; P. Högberg; K. Huss-Danell; A. Jumpponen; J. Koricheva; P. W. Leadley; M. Loreau; A. Minns; C. P. H. Mulder; G. O'Donovan; S. J. Otway; C. Palmborg; J. S. Pereira; A. B. Pfisterer; A. Prinz; D. J. Read; E.-D. Schulze; A.-S. D. Siamantziouras; A. C. Terry; A. Y. Troumbis; F. I. Woodward; S. Yachi; J. H. Lawton

    2005-01-01

    Abstract. We present a multisite analysis of the relationship between,plant diversity and,ecosystem,functioning,within,the European,BIODEPTH network,of plant-diversity manipulation,experiments.,We report results of the analysis,of 11 variables addressing several aspects of key ecosystem processes like biomass production, resource use (space, light, and nitrogen), and decomposition, measured across three years in plots of varying plant species richness at eight different European,grassland,field sites. Differences among sites

  19. Modeling of nitric oxide emissions from temperate agricultural ecosystems.

    E-print Network

    Paris-Sud XI, Université de

    Modeling of nitric oxide emissions from temperate agricultural ecosystems. M.-N. Rollanda 1 B are a significant source of nitric oxide (NO), most of which is derived from nitrogen2 fertilizers. Precise #12;Introduction1 Nitric oxide (NO) is a chemically active gas and is involved in tropospheric

  20. Ecosystem Respiration in a Cool Temperate Bog Depends on Peat

    E-print Network

    Roulet, Nigel T.

    Ecosystem Respiration in a Cool Temperate Bog Depends on Peat Temperature But Not Water Table P-summer (July-August). As anticipated, there was a strong relationship between ER and peat temperatures (r2 = 0-table depth (r2 = 0.11). A laboratory incubation of peat cores at different moisture contents showed that CO2

  1. Sustainable management of insect herbivores in grassland ecosystems: New perspectives in grasshopper control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasshoppers are insect herbivores commonly found in grassland ecosystems worldwide. They are important components of biodiversity, contribute significantly to grassland function, and periodically exhibit large-scale outbreaks. Under outbreak conditions, they can be important competitors with verteb...

  2. Response of grassland ecosystems to prolonged soil moisture deficit

    NASA Astrophysics Data System (ADS)

    Ross, Morgan A.; Ponce-Campos, Guillermo E.; Barnes, Mallory L.; Hottenstein, John D.; Moran, M. Susan

    2014-05-01

    Soil moisture is commonly used for predictions of plant response and productivity. Climate change is predicted to cause an increase in the frequency and duration of droughts over the next century, which will result in prolonged periods of below-normal soil moisture. This, in turn, is expected to impact regional plant production, erosion and air quality. In fact, the number of consecutive months of soil moisture content below the drought-period mean has recently been linked to regional tree and shrub mortality in the southwest United States. This study investigated the effects of extended periods of below average soil moisture on the response of grassland ANPP to precipitation. Grassland ecosystems were selected for this study because of their ecological sensitivity to precipitation patterns. It has been postulated that the quick ecological response of grasslands to droughts can provide insight to large scale functional responses of regions to predicted climate change. The study sites included 21 grassland biomes throughout arid-to-humid climates in the United States with continuous surface soil moisture records for 2-13 years during the drought period from 2000-2013. Annual net primary production (ANPP) was estimated from the 13-year record of NASA MODIS Enhanced Vegetation Index extracted for each site. Prolonged soil moisture deficit was defined as a period of at least 10 consecutive months during which soil moisture was below the drought-period mean. ANPP was monitored before, during and after prolonged soil moisture deficit to quantify shifts in the functional response of grasslands to precipitation, and in some cases, new species assemblages that included invasive species. Preliminary results indicated that when altered climatic conditions on grasslands led to an increase in the duration of soil water deficit, then the precipitation-to-ANPP relation became non-linear. Non-linearity was associated with extreme grassland dieback and changes in the historic species assemblage. The magnitude of change was related to the precipitation regime, where grasslands in hyper-arid and humid regimes were least likely to be affected by prolonged soil moisture deficit, and semiarid and mesic grasslands were most likely to be impacted, depending on the duration of the deficit. These results were applied to a large grassland region in Australia with soil moisture estimates from the European Space Agency (ESA) Soil Moisture Ocean Salinity (SMOS) sensor to demonstrate the continental-scale potential of this application with satellite measurements. These results are even more relevant for application with the higher-resolution NASA Soil Moisture Active Passive (SMAP) products to be available in 2015.

  3. Resistance of a grassland ecosystem to multiple drought events

    NASA Astrophysics Data System (ADS)

    Smith, Melinda; Hoover, David; Knapp, Alan

    2015-04-01

    Climate extremes, such as severe drought, are forecast to be more frequent and severe with climate change. As a consequence, such events will become increasingly important drivers of future ecosystem dynamics and function. We experimentally imposed an extreme growing season drought over two years in a central US grassland, allowed the ecosystem to recover for two years, and then imposed a second drought of similar magnitude. The first (2-yr) drought reduced aboveground net primary productivity (ANPP) below the lowest level measured in this grassland for almost thirty years. The extreme reduction in ecosystem function with the first drought was a consequence of reduced productivity of the two dominant functional groups in this grassland - C4 grasses and C3 forbs. However, the most abundant (dominant) C3 forb was negatively impacted by the drought more than the dominant C4 grass. This differential sensitivity led to a reordering of species abundances within the plant community. Yet, despite this large shift in plant community composition, which persisted post-drought, ANPP recovered completely the year after drought. This rapid recovery in function was due to the dominant C4 grass compensating for loss of the dominant C3 forb. However, despite the rapid post-drought recovery, the ecosystem was more susceptible to a second drought of similar magnitude, with productivity reduced more in the previously droughted plots than those experiencing drought for the first time. Overall, our results suggest that low resistance of ecosystem function to an extreme climatic event does not preclude rapid ecosystem recovery, but may lead to greater vulnerability to future climate extremes.

  4. Fine-scale belowground species associations in temperate grassland.

    PubMed

    Frank, Douglas A; Pontes, Alyssa W; Maine, Eleanor M; Fridley, Jason D

    2015-06-01

    Evaluating how belowground processes contribute to plant community dynamics is hampered by limited information on the spatial structure of root communities at the scale that plants interact belowground. In this study, roots were mapped to the nearest one mm and molecularly identified by species on vertical (0-15 cm deep) surfaces of soil blocks excavated from dry and mesic grasslands in Yellowstone National Park (YNP) to examine the spatial relationships among species at the scale that roots interact. Our results indicated that average interspecific root - root distances for the majority of species were within a distance (3 mm) that roots have been shown to compete for resources. Most species placed their roots at random, although low root numbers for many species probably led to overestimating the occurrence of random patterns. According to theory, we expected that most of the remaining species would segregate their root systems to avoid competition. Instead we found that more species aggregated than segregated from others. Based on previous investigations, we hypothesize that species aggregate to increase uptake of water, nitrogen and/or phosphorus made available by neighbouring roots, or as a consequence of a reduction in the pathogenicity of soil biota growing in multispecies mixtures. Our results indicate that YNP grassland root communities are organized as closely interdigitating networks of species that potentially can support strong interactions among many species combinations. Future root research should address the prevalence and functional consequences of species aggregation across plant communities. PMID:25951537

  5. Extensive Management Promotes Plant and Microbial Nitrogen Retention in Temperate Grassland

    PubMed Central

    de Vries, Franciska T.; Bloem, Jaap; Quirk, Helen; Stevens, Carly J.; Bol, Roland; Bardgett, Richard D.

    2012-01-01

    Leaching losses of nitrogen (N) from soil and atmospheric N deposition have led to widespread changes in plant community and microbial community composition, but our knowledge of the factors that determine ecosystem N retention is limited. A common feature of extensively managed, species-rich grasslands is that they have fungal-dominated microbial communities, which might reduce soil N losses and increase ecosystem N retention, which is pivotal for pollution mitigation and sustainable food production. However, the mechanisms that underpin improved N retention in extensively managed, species-rich grasslands are unclear. We combined a landscape-scale field study and glasshouse experiment to test how grassland management affects plant and soil N retention. Specifically, we hypothesised that extensively managed, species-rich grasslands of high conservation value would have lower N loss and greater N retention than intensively managed, species-poor grasslands, and that this would be due to a greater immobilisation of N by a more fungal-dominated microbial community. In the field study, we found that extensively managed, species-rich grasslands had lower N leaching losses. Soil inorganic N availability decreased with increasing abundance of fungi relative to bacteria, although the best predictor of soil N leaching was the C/N ratio of aboveground plant biomass. In the associated glasshouse experiment we found that retention of added 15N was greater in extensively than in intensively managed grasslands, which was attributed to a combination of greater root uptake and microbial immobilisation of 15N in the former, and that microbial immobilisation increased with increasing biomass and abundance of fungi. These findings show that grassland management affects mechanisms of N retention in soil through changes in root and microbial uptake of N. Moreover, they support the notion that microbial communities might be the key to improved N retention through tightening linkages between plants and microbes and reducing N availability. PMID:23227252

  6. Monitoring Change in Temperate Coniferous Forest Ecosystems

    NASA Technical Reports Server (NTRS)

    Williams, Darrel (Technical Monitor); Woodcock, Curtis E.

    2004-01-01

    The primary goal of this research was to improve monitoring of temperate forest change using remote sensing. In this context, change includes both clearing of forest due to effects such as fire, logging, or land conversion and forest growth and succession. The Landsat 7 ETM+ proved an extremely valuable research tool in this domain. The Landsat 7 program has generated an extremely valuable transformation in the land remote sensing community by making high quality images available for relatively low cost. In addition, the tremendous improvements in the acquisition strategy greatly improved the overall availability of remote sensing images. I believe that from an historical prespective, the Landsat 7 mission will be considered extremely important as the improved image availability will stimulate the use of multitemporal imagery at resolutions useful for local to regional mapping. Also, Landsat 7 has opened the way to global applications of remote sensing at spatial scales where important surface processes and change can be directly monitored. It has been a wonderful experience to have participated on the Landsat 7 Science Team. The research conducted under this project led to contributions in four general domains: I. Improved understanding of the information content of images as a function of spatial resolution; II. Monitoring Forest Change and Succession; III. Development and Integration of Advanced Analysis Methods; and IV. General support of the remote sensing of forests and environmental change. This report is organized according to these topics. This report does not attempt to provide the complete details of the research conducted with support from this grant. That level of detail is provided in the 16 peer reviewed journal articles, 7 book chapters and 5 conference proceedings papers published as part of this grant. This report attempts to explain how the various publications fit together to improve our understanding of how forests are changing and how to monitor forest change with remote sensing. There were no new inventions that resulted from this grant.

  7. Evidence of Physiological Decoupling from Grassland Ecosystem Drivers by an Encroaching Woody Shrub

    E-print Network

    Nippert, Jesse

    Evidence of Physiological Decoupling from Grassland Ecosystem Drivers by an Encroaching Woody Shrub of America Abstract Shrub encroachment of grasslands is a transformative ecological process by which native assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra

  8. Seasonal variability of CH4 and N2O fluxes over a managed temperate mountain grassland

    NASA Astrophysics Data System (ADS)

    Hoertnagl, Lukas; Wohlfahrt, Georg

    2013-04-01

    The quantification of greenhouse gas (GHG) budgets on a global scale is an important step in assessing the effect of anthropogenic and biogenic controls on a future climate. In the past, measurements of CO2 fluxes were conducted over a wide array of ecosystems, leading to a better understanding of its exchange patterns on different time scales and more sophisticated models. However, only few studies quantified the fluxes of the other two major GHG, methane (CH4) and nitrous oxide (N2O), mainly due to expensive sensors and their time-consuming maintenance. In addition, early CH4 and N2O measurements mainly focused on ecosystems with presumably high emissions of CH4 (e.g. wetlands) or N2O (e.g. heavily fertilized crops). In recent years, devices for CH4 and N2O measurements became widely available and more studies are conducted over sites that exert small and often close-to-zero fluxes. Despite recent advances in sensor sensitivity and stability, the quantification of CH4 and N2O exchange rates remains challenging. Here we present measurements of CH4 and N2O exchange rates of a temperate mountain grassland managed as a hay meadow near the village Neustift in the Stubai Valley, Austria, that started in April 2010 by means of the eddy covariance method. The three wind components and the speed of sound were acquired at a time resolution of 20 Hz, while CH4 and N2O mixing ratios were recorded at 2 Hz by a quantum cascade laser absorption spectrometer (QCL-AS). Fluxes of both compounds were calculated using the virtual disjunct eddy covariance method (vDEC). For better comparability fluxes of N2O and CH4 were also converted to g CO2-equivalents and compared to the CO2 exchange at the same site. In addition to exchange rates, challenges regarding the calculation of GHG fluxes at the investigated grassland site will also be discussed. In 2011, deposition of CH4 was recorded on 9 days with average uptake rates of -0.6 nmol m-2 s-1. Peak emissions of up to 12.9 nmol m-2 s-1 were found in October, about 10 days after the 3rd cutting of the meadow. First results showed cumulative fluxes amounting to a net emission of CH4, corresponding to 58.6 g CO2-equivalents m-2 in 2011. N2O showed net deposition fluxes on 38 days and maximum uptake rates of -0.3 nmol m-2 s-1 during 7 consecutive days with nitrogen uptake in April 2011. Peak emissions of more than 1.2 nmol m-2 s-1 were observed at the end of November, about one month after fertilization. In total, the meadow was a source of N2O (118.9 g CO2-equivalents m-2). In comparison, cumulative fluxes of CO2 in 2011 resulted in a net uptake of -70.4 g CO2 m-2. Distinct diurnal cycles could be observed for N2O, e.g. in April with peak uptake rates of more than -0.7 nmol m-2 s-1 around noon, or in August with peak midday emissions of around 0.8 nmol m-2 s-1. Diurnal cycles of CH4 were less pronounced and more error-prone due to spikes in methane mixing ratios and fluxes, but nevertheless showed a tendency of methane release during the day, around noon up to 10.1 nmol m-2 s-1 in September.

  9. The nonlinearly combined response of the grassland ecosystem to human activity and climate change

    NASA Astrophysics Data System (ADS)

    Sun, G.; Mu, M.

    2012-04-01

    Human activity and climate change are important factors that affect grassland ecosystems. A new optimization approach, the approach of conditional nonlinear optimal perturbation (CNOP) related to initial and parameter perturbations, is employed to explore the nonlinearly combined impacts of human activity and climate change on a grassland ecosystem using a theoretical grassland model. In our study, it is assumed that the initial perturbations and parameter perturbations are regarded as human activities and climate change, respectively. Numerical results indicate that the climate changes causing the maximum effect in the grassland ecosystem are different under disparate intensities of human activities. This implies the pattern of climate change is very critical to the maintenance or degradation of grassland ecosystem in light of high intensity of human activities and that the grassland ecosystem should be rationally managed when the moisture index decreases. The grassland ecosystem influenced by the nonlinear combination of human activities and climate change undergoes abrupt change, while the grassland ecosystem affected by other types of human activities and climate change fails to show the abrupt change under a certain range of perturbations with the theoretical model. The further numerical analyses also indicate that the growth of living biomass and the evaporation from soil surface shaded by the wilted biomass may be crucial factors contributing to the abrupt change of the grassland equilibrium state within the theoretical model.

  10. Carbon dioxide budget in a temperature grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.; Clement, Robert J.

    1992-01-01

    Eddy correlation measurements of CO2 flux made during May-October 1987 and June-August 1989 were employed, in conjunction with simulated data, to examine the net exchange of CO2 in a temperature grassland ecosystem. Simulated estimates of CO2 uptake were used when flux measurements were not available. These estimates were based on daily intercepted photosynthetically active radiation, air temperature, and extractable soil water. Soil CO2 flux and dark respiration of the aerial part of plants were estimated using the relationships developed by Norman et al. (1992) and Polley et al. (1992) at the study site. The results indicate that the CO2 exchange between this ecosystem and the atmosphere is highly variable. The net ecosystem CO2 exchange reached its peak value (12-18 g/sq m d) during the period when the leaf area index was maximum. Drought, a frequent occurrence in this region, can change this ecosystem from a sink to a source for atmospheric CO2. Comparison with data on dry matter indicated that the aboveground biomass accounted for about 45-70 percent of the net carbon uptake, suggesting the importance of the below ground biomass in estimating net primary productivity in this ecosystem.

  11. Effects of Water and Nitrogen Addition on Species Turnover in Temperate Grasslands in Northern China

    PubMed Central

    Xu, Zhuwen; Wan, Shiqiang; Ren, Haiyan; Han, Xingguo; Li, Mai-He; Cheng, Weixin; Jiang, Yong

    2012-01-01

    Global nitrogen (N) deposition and climate change have been identified as two of the most important causes of current plant diversity loss. However, temporal patterns of species turnover underlying diversity changes in response to changing precipitation regimes and atmospheric N deposition have received inadequate attention. We carried out a manipulation experiment in a steppe and an old-field in North China from 2005 to 2009, to test the hypothesis that water addition enhances plant species richness through increase in the rate of species gain and decrease in the rate of species loss, while N addition has opposite effects on species changes. Our results showed that water addition increased the rate of species gain in both the steppe and the old field but decreased the rates of species loss and turnover in the old field. In contrast, N addition increased the rates of species loss and turnover in the steppe but decreased the rate of species gain in the old field. The rate of species change was greater in the old field than in the steppe. Water interacted with N to affect species richness and species turnover, indicating that the impacts of N on semi-arid grasslands were largely mediated by water availability. The temporal stability of communities was negatively correlated with rates of species loss and turnover, suggesting that water addition might enhance, but N addition would reduce the compositional stability of grasslands. Experimental results support our initial hypothesis and demonstrate that water and N availabilities differed in the effects on rate of species change in the temperate grasslands, and these effects also depend on grassland types and/or land-use history. Species gain and loss together contribute to the dynamic change of species richness in semi-arid grasslands under future climate change. PMID:22768119

  12. Biotic, abiotic and management controls on methanol fluxes above a temperate mountain grassland

    NASA Astrophysics Data System (ADS)

    Hörtnagl, Lukas; Bamberger, Ines; Graus, Martin; Ruuskanen, Taina; Schnitzhofer, Ralf; Müller, Markus; Hansel, Armin; Wohlfahrt, Georg

    2010-05-01

    It was previously hypothesised that (i) stomatal conductance and plant growth play a key role in the emission of methanol (Hüve et al. 2007, Niinemets et al. 2004), (ii) methanol fluxes increase with air temperature (Niinemets and Reichstein 2003), and (iii) during cutting (leaf wounding) events and during drying high amounts of methanol are emitted into the atmosphere (Davison et al. 2008). Methanol fluxes were measured above a managed, temperate mountain grassland in Stubai Valley (Tyrol, Austria) during two growing seasons (2008 and 2009). Half-hourly flux values were calculated by means of the disjunct eddy covariance method using 3-dimensional wind-data of a sonic anemometer and mixing ratios of methanol measured with a proton-transfer-reaction-mass-spectrometer (PTR-MS). The surface conductance to water vapour was derived from measured evapotranspiration by inverting the Penman-Monteith combination equation (Wohlfahrt et al., 2009) for dry canopy conditions and used as a proxy for canopyscale stomatal conductance. Methanol fluxes exhibited a clear diurnal cycle with closetozero fluxes during nighttime and emissions, up to 10 nmol m-2 s-1, which followed the diurnal course of radiation and air temperature during daytime. Higher emissions of up to 30 nmol m-2 s-1were observed during cut events and spreading of organic manure. Methanol fluxes showed positive correlations with air temperature, stomatal conductance, and photosynthetically active radiation (PAR), confirming previous studies (e.g. Niinemets and Reichstein 2003). All three previously mentioned factors combined together were able to explain 40% of the observed flux variability. The influence of rapid changes in stomatal conductance on methanol fluxes, pointed out in earlier studies at the leaf-level (e.g. Niinemets and Reichstein 2003), could not be confirmed on ecosystem scale, possibly due to within-canopy gradients in stomatal conductance and the fact that fluxes were determined as half-hourly averages. As methanol is produced in expanding cell walls, the change in the measured green area index (?GAI) was used as a proxy for plant growth. However ?GAI was poorly correlated with methanol fluxes, possible explanations will be discussed. References: Davison, B., Brunner, A., Amman, C., Spirig, C., Jocher, M., Neftel, A. Cut-induced VOC emissions from agricultural grasslands. Plant Biol. 10, 76-85, 2008. Harley, P., Greenberg, J., Niinemets, Ü., and Guenther, A..: Environmental controls over methanol emission from leaves. Biogeosciences, 4, 1083-1099, 2007. Hüve, K., Christ, M., Kleist, E., Uerlings, R., Niinemets, Ü., Walter, A. and Wildt, J.: Simultaneous growth and emission measurements demonstrate an interactive control of methanol release by leaf expansion and stomata. doi:10.1093/jxb/erm038, Journal of Experimental Botany, 2007. Niinemets, Ü. and Reichstein, M.: Controls on the emission of plant volatiles through stomata: A sensitivity analysis. J. Geophys. Res., 108, 4211, doi:10.1029/2002JD002626, 2003. Niinemets, Ü., Loreto, F. and Reichstein, M.: Physiological and physicochemical controls on foliar volatile organic compound emissions. Trends in Plant Science,9, 2004. Wohlfahrt G., Haslwanter A., Hörtnagl L., Jasoni R.L., Fenstermaker L.F., Arnone J.A. III, Hammerle A. (2009) On the consequences of the energy imbalance for calculating surface conductance to water vapour. Agricultural and Forest Meteorology 149, 15561559.

  13. Carbon dioxide exchange in a temperate grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.

    1990-01-01

    Carbon dioxide exchange was measured, using the eddy correlation technique, over a tallgrass prairie in northeastern Kansas, U.S.A., during a six-month period in 1987. The diurnal patterns of daytime and nocturnal CO2 fluxes are presented on eight selected days. These days were distributed throughout most of the growing season and covered a wide range of meteorological and soil water conditions. The midday CO2 flux reached a maximum of 1.3 mg/sq m (ground area)/s during early July and was near zero during the dry period in late July. The dependence of the daytime carbon dioxide exchange on pertinent controlling variables, particularly photosynthetically active radiation, vapor pressure deficit, and soil water content is discussed. The nocturnal CO2 flux (soil plus plant respiration) averaged -0.4 m sq m (ground area)/s during early July and was about -0.2 mg sq/m during the dry period.

  14. Rapid Response of a Grassland Ecosystem to an Experimental Manipulation of a Keystone Rodent and Domestic Livestock

    Microsoft Academic Search

    Ed L. Frederickson; Eduardo Ponce; Dave Lightfoot; Ed Fredrickson; James Brown; Juan Cruzado; Sandra Brantley; Rodrigo Sierra; Rurik List; David Toledo; Gerardo Ceballos

    2010-01-01

    Megaherbivores and small burrowing mammals commonly coexist and play important functional roles in grassland ecosystems worldwide. The interactive effects of these two functional groups of herbivores in shaping the structure and function of grassland ecosystems are poorly understood. In North America's central grasslands, domestic cattle (Bos taurus) have supplanted bison (Bison bison), and now coexist with prairie dogs (Cynomys spp.),

  15. rizona's grassland ecosystems are an integral part of the regional ecology, and they provide important social and economic values

    E-print Network

    A rizona's grassland ecosystems are an integral part of the regional ecology, and they provide European migrants arrived, grasslands covered about one-third of the area that is now Arizona. Significant to understand how valuable native grasslands ecosystems are to society. Resources will be required to conserve

  16. Leaf area controls on energy partitioning of a temperate mountain grassland

    PubMed Central

    Hammerle, A.; Haslwanter, A.; Tappeiner, U.; Cernusca, A.; Wohlfahrt, G.

    2013-01-01

    Using a six year data set of eddy covariance flux measurements of sensible and latent heat, soil heat flux, net radiation, above-ground phytomass and meteorological driving forces energy partitioning was investigated at a temperate mountain grassland managed as a hay meadow in the Stubai Valley (Austria). The main findings of the study were: (i) Energy partitioning was dominated by latent heat, followed by sensible heat and the soil heat flux; (ii) When compared to standard environmental forcings, the amount of green plant matter, which due to three cuts varied considerably during the vegetation period, explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) There were little, if any, indications of water stress effects on energy partitioning, despite reductions in soil water availability in combination with high evaporative demand, e.g. during the summer drought of 2003. PMID:24348583

  17. Prairie dog decline reduces the supply of ecosystem services and leads to desertification of semiarid grasslands.

    PubMed

    Martínez-Estévez, Lourdes; Balvanera, Patricia; Pacheco, Jesús; Ceballos, Gerardo

    2013-01-01

    Anthropogenic impacts on North American grasslands, a highly endangered ecosystem, have led to declines of prairie dogs, a keystone species, over 98% of their historical range. While impacts of this loss on maintenance of grassland biodiversity have been widely documented, much less is known about the consequences on the supply of ecosystem services. Here we assessed the effect of prairie dogs in the supply of five ecosystem services by comparing grasslands currently occupied by prairie dogs, grasslands devoid of prairie dogs, and areas that used to be occupied by prairie dogs that are currently dominated by mesquite scrub. Groundwater recharge, regulation of soil erosion, regulation of soil productive potential, soil carbon storage and forage availability were consistently quantitatively or qualitatively higher in prairie dog grasslands relative to grasslands or mesquite scrub. Our findings indicate a severe loss of ecosystem services associated to the absence of prairie dogs. These findings suggest that contrary to a much publicize perception, especially in the US, prairie dogs are fundamental in maintaining grasslands and their decline have strong negative impacts in human well - being through the loss of ecosystem services. PMID:24130691

  18. Prairie Dog Decline Reduces the Supply of Ecosystem Services and Leads to Desertification of Semiarid Grasslands

    PubMed Central

    Martínez-Estévez, Lourdes; Balvanera, Patricia; Pacheco, Jesús; Ceballos, Gerardo

    2013-01-01

    Anthropogenic impacts on North American grasslands, a highly endangered ecosystem, have led to declines of prairie dogs, a keystone species, over 98% of their historical range. While impacts of this loss on maintenance of grassland biodiversity have been widely documented, much less is known about the consequences on the supply of ecosystem services. Here we assessed the effect of prairie dogs in the supply of five ecosystem services by comparing grasslands currently occupied by prairie dogs, grasslands devoid of prairie dogs, and areas that used to be occupied by prairie dogs that are currently dominated by mesquite scrub. Groundwater recharge, regulation of soil erosion, regulation of soil productive potential, soil carbon storage and forage availability were consistently quantitatively or qualitatively higher in prairie dog grasslands relative to grasslands or mesquite scrub. Our findings indicate a severe loss of ecosystem services associated to the absence of prairie dogs. These findings suggest that contrary to a much publicize perception, especially in the US, prairie dogs are fundamental in maintaining grasslands and their decline have strong negative impacts in human well – being through the loss of ecosystem services. PMID:24130691

  19. Independent Evolution of Leaf and Root Traits within and among Temperate Grassland Plant Communities

    PubMed Central

    Kembel, Steven W.; Cahill, James F.

    2011-01-01

    In this study, we used data from temperate grassland plant communities in Alberta, Canada to test two longstanding hypotheses in ecology: 1) that there has been correlated evolution of the leaves and roots of plants due to selection for an integrated whole-plant resource uptake strategy, and 2) that trait diversity in ecological communities is generated by adaptations to the conditions in different habitats. We tested the first hypothesis using phylogenetic comparative methods to test for evidence of correlated evolution of suites of leaf and root functional traits in these grasslands. There were consistent evolutionary correlations among traits related to plant resource uptake strategies within leaf tissues, and within root tissues. In contrast, there were inconsistent correlations between the traits of leaves and the traits of roots, suggesting different evolutionary pressures on the above and belowground components of plant morphology. To test the second hypothesis, we evaluated the relative importance of two components of trait diversity: within-community variation (species trait values relative to co-occurring species; ? traits) and among-community variation (the average trait value in communities where species occur; ? traits). Trait diversity was mostly explained by variation among co-occurring species, not among-communities. Additionally, there was a phylogenetic signal in the within-community trait values of species relative to co-occurring taxa, but not in their habitat associations or among-community trait variation. These results suggest that sorting of pre-existing trait variation into local communities can explain the leaf and root trait diversity in these grasslands. PMID:21687704

  20. Effect of Degradation Intensity on Grassland Ecosystem Services in the Alpine Region of Qinghai-Tibetan Plateau, China

    PubMed Central

    Wen, Lu; Dong, Shikui; Li, Yuanyuan; Li, Xiaoyan; Shi, Jianjun; Wang, Yanlong; Liu, Demei; Ma, Yushou

    2013-01-01

    The deterioration of alpine grassland has great impact on ecosystem services in the alpine region of Qinghai-Tibetan Plateau. However, the effect of grassland degradation on ecosystem services and the consequence of grassland deterioration on economic loss still remains a mystery. So, in this study, we assessed four types of ecosystem services following the Millennium Ecosystem Assessment classification, along a degradation gradient. Five sites of alpine grassland at different levels of degradation were investigated in Guoluo Prefecture of Qinghai Province, China. The species composition, aboveground biomass, soil total organic carbon (TOC), and soil total nitrogen (TN) were tested to evaluate major ecological services of the alpine grassland. We estimated the value of primary production, carbon storage, nitrogen recycling, and plant diversity. The results show the ecosystem services of alpine grassland varied along the degradation gradient. The ecosystem services of degraded grassland (moderate, heavy and severe) were all significantly lower than non-degraded grassland. Interestingly, the lightly degraded grassland provided more economic benefit from carbon maintenance and nutrient sequestration compared to non-degraded. Due to the destruction of the alpine grassland, the economic loss associated with decrease of biomass in 2008 was $198/ha. Until 2008, the economic loss caused by carbon emissions and nitrogen loss on severely degraded grassland was up to $8 033/ha and $13 315/ha, respectively. Urgent actions are required to maintain or promote the ecosystem services of alpine grassland in the Qinghai-Tibetan Plateau. PMID:23469278

  1. Grassland ecosystems and climate change: Insights from experiments

    E-print Network

    ;Mesic Grasslands of North America The Flint Hills of Kansas ­ The Konza Prairie · Tallgrass prairie is the most mesic of Great Plains grasslands ­ sufficient precipitation to support forest · Flint Hills

  2. Ecosystem Change in California Grasslands: Impacts of Species Invasion

    NASA Astrophysics Data System (ADS)

    Koteen, L. E.; Harte, J.; Baldocchi, D. D.

    2009-12-01

    Grassland ecosystems of California have undergone dramatic changes, resulting in the almost complete replacement of native perennial grasses by non-native annuals across millions of hectares of grassland habitat. Our research investigates the effects of this community shift on carbon, water and energy cycles at two sites in northern coastal California. Our goal was to understand how changes to California’s grasslands have affected climate through 1. shifting the balance of carbon storage between terrestrial stocks and the atmosphere, and 2. altering the water and energy regimes that heat or cool the earth's surface. To compare the processes that govern material exchange before and after annual grass invasion, we made use of sites where native vegetation is found adjacent to locations that have undergone non-native invasion. In plots of each vegetation type, we monitored whole plant productivity, root and litter decay rates and soil respiration, as well as soil climatic controls on these processes. At one site, we also measured surface albedo and the components of the surface energy balance in each grass community, using the surface renewal method. Although seemingly subtle, the shift in California grassland communities from native perennial to non-native annual grass dominance has had profound consequences for ecosystem biogeochemical, radiative and hydrological cycles. Soil carbon storage was found to be significantly greater in native perennial grass communities. Across both study sites, we found that non-native grass invasion has resulted in the transfer of from 3 to 6 tons of carbon per hectare from the soil to the atmosphere, dependent on site and species. A soil density fractionation and a radiocarbon analysis also revealed the carbon to be more recalcitrant in native grass dominated locations. The primary plant traits that help explain why soil carbon losses follow annual grass invasion are: 1. differences between annual and perennial grasses in above/ belowground allocation, 2. differences in growth plasticity in response to inter-annual precipitation variability, and 3. the effect of differences in rooting depth and aboveground morphology on soil moisture content and soil respiration. Over the years 2004-2006, we found energy partitioning into latent and sensible heat flux to be similar among annual and perennial grass communities during periods of sufficient soil moisture availability. When water becomes scarce in the late spring, however, and annual grasses die, the ratio of latent to sensible heat loss is reduced in annual grass communities relative to perennials. The deep roots of perennial grasses prolong the period over which transpiration occurs. We also found that albedo differs year-round between perennial and annual grasses, tracking differences in grass phenology. Albedo differences are at a maximum during the summer and autumn months. At this time, the lower albedo in non-native annual communities can raise near surface temperatures up to 6 oC midday relative to native perennials.

  3. Understanding of Grassland Ecosystems under Climate Change and Economic Development Pressures in the Mongolia Plateau

    NASA Astrophysics Data System (ADS)

    Qi, J.; Chen, J.; Shan, P.; Pan, X.; Wei, Y.; Wang, M.; Xin, X.

    2011-12-01

    The land use and land cover change, especially in the form of grassland degradation, in the Mongolian Plateau, exhibited a unique spatio-temporal pattern that is a characteristic of a mixed stress from economic development and climate change of the region. The social dimension of the region played a key role in shaping the landscape and land use change, including the cultural clashes with economic development, conflicts between indigenous people and business ventures, and exogenous international influences. Various research projects have been conducted in the region to focus on physical degradation of grasslands and/or on economic development but there is a lack of understanding how the social and economic dimensions interact with grassland ecosystems and changes. In this talk, a synthesis report was made based on the most recent workshop held in Hohhot, Inner Mongolia, of China, that specifically focused on climate change and grassland ecosystems. The report analyzed the degree of grassland degradation, its climate and social drivers, and coupling nature of economic development and conservation of traditional grassland values. The goal is to fully understand the socio-ecological-economic interactions that together shape the trajectory of the grassland ecosystems in the Mongolia Plateau.

  4. Climate impact on net ecosystem productivity of a semi-arid natural grassland: modeling and measurement

    Microsoft Academic Search

    Tao Li; Robert F. Grant; Lawrence B. Flanagan

    2004-01-01

    Models used to estimate net ecosystem productivity (NEP) during climate change should first be shown to simulate the effects on NEP of interannual variability in current climates. Energy and CO2 fluxes simulated by the ecosystem model ecosys were compared with those measured by eddy covariance over a semi-arid ungrazed grassland near Lethbridge, Alberta to improve confidence in model projections of

  5. Soil hydrological properties regulate grassland ecosystem responses to multifactor global change: A modeling analysis

    Microsoft Academic Search

    Ensheng Weng; Yiqi Luo

    2008-01-01

    We conducted a modeling study to evaluate how soil hydrological properties regulate water and carbon dynamics of grassland ecosystems in response to multifactor global change. We first calibrated a process-based terrestrial ecosystem (TECO) model against data from two experiments with warming and clipping or doubled precipitation in Great Plains. The calibrated model was used to simulate responses of soil moisture,

  6. Net ecosystem exchange of grassland in contrasting wet and dry years

    E-print Network

    Katul, Gabriel

    Net ecosystem exchange of grassland in contrasting wet and dry years Vesna Jaksic a , Gerard Kiely. We used an eddy covariance (EC) system to measure the net ecosystem exchange (NEE) at a managed of the components of the farm scale carbon (C) balance we estimated the amount of C fixed to the soil as Ŕ24 Ć 62 g

  7. Mobility and age of black carbon in two temperate grassland soils revealed by differential scanning calorimetry and radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Leifeld, Jens; Feng, Xiaojuan; Eglinton, Timothy; Wacker, Lukas

    2015-04-01

    Black carbon (BC) is a natural component of soil organic matter (SOM) and abundant in many ecosystems. Its stability, due to its relative resistance to microbial decomposition, means it plays an important role in soil C sequestration. A recent review suggests that BC may be mobile in soil; hence, its contribution to a stable SOM pool may change over time due to its lateral or vertical reallocation (Rumpel et al. 2014). However, direct evidence of the mobility of BC, particularly with reference to its vertical mobility, is scarce. We studied the amount of BC in two temperate grassland fields (eutric clayey Camibsol,) that were established in 2001 on former cropland. Volumetric soil samples (0-50 cm, 5 cm increments) were taken at 10 spots in each field in 2001, 2006 and 2011. One of the fields was ploughed in 2007 and the sward was re-sown. BC content was measured by differential scanning calorimetry for a total number of c. 500 samples. The mean BC/OC ratio was 0.10 (±0.05) and reached 0.25 in some samples. Radiocarbon measurements from 24 bulk soil samples revealed relatively small 14C contents in 2001 (92±2.7 pMC) which increased over time (2006: 99.0±1.1 pMC; 2011: 99.1±1.1 pMC). Thermal fractionation of BC by DSC revealed calibrated BC ages of 400 to 1000 years (pMC 87-94), suggesting that BC originates from medieval and post-medieval fire clearings. The change in soil signature may have been caused by a preferential transport of old BC down the soil profile, leading to a selective enrichment of younger soil C over time. In line with this interpretation the DSC measurements suggest that in both fields, BC concentrations significantly decreased for most layers between 2001 and 2006. However, between 2006 and 2011, no further vertical reallocation was observed in the continuous grassland, whereas BC contents of the field ploughed in 2007 significantly increased in the top layers. Together, these data suggest that ploughing in 2001 triggered subsequent downwards movement of BC, a process which ceased after a few years. Repeated ploughing lifted up some of the BC from deeper layers and this material will probably be transported downwards in the future. Rumpel, C. et al. (2014) Movement of biochar in the environment. In: Lehmann, J. (Ed.): Biochar for the Environment, accepted.

  8. Warming and Nitrogen Addition Increase Litter Decomposition in a Temperate Meadow Ecosystem

    PubMed Central

    Gong, Shiwei; Guo, Rui; Zhang, Tao; Guo, Jixun

    2015-01-01

    Background Litter decomposition greatly influences soil structure, nutrient content and carbon sequestration, but how litter decomposition is affected by climate change is still not well understood. Methodology/Principal Findings A field experiment with increased temperature and nitrogen (N) addition was established in April 2007 to examine the effects of experimental warming, N addition and their interaction on litter decomposition in a temperate meadow steppe in northeastern China. Warming, N addition and warming plus N addition reduced the residual mass of L. chinensis litter by 3.78%, 7.51% and 4.53%, respectively, in 2008 and 2009, and by 4.73%, 24.08% and 16.1%, respectively, in 2010. Warming, N addition and warming plus N addition had no effect on the decomposition of P. communis litter in 2008 or 2009, but reduced the residual litter mass by 5.58%, 15.53% and 5.17%, respectively, in 2010. Warming and N addition reduced the cellulose percentage of L. chinensis and P. communis, specifically in 2010. The lignin percentage of L. chinensis and P. communis was reduced by warming but increased by N addition. The C, N and P contents of L. chinensis and P. communis litter increased with time. Warming and N addition reduced the C content and C:N ratios of L. chinensisand P. communis litter, but increased the N and P contents. Significant interactive effects of warming and N addition on litter decomposition were observed (P<0.01). Conclusion/Significance The litter decomposition rate was highly correlated with soil temperature, soil water content and litter quality. Warming and N addition significantly impacted the litter decomposition rate in the Songnen meadow ecosystem, and the effects of warming and N addition on litter decomposition were also influenced by the quality of litter. These results highlight how climate change could alter grassland ecosystem carbon, nitrogen and phosphorus contents in soil by influencing litter decomposition. PMID:25774776

  9. Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem

    E-print Network

    Ickert-Bond, Steffi

    Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems has the potential to substantially improve our understanding of the vulnerability of alpine grassland

  10. China's grazed temperate grasslands are a net source of atmospheric methane

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Ping; Song, Yang; Gulledge, Jay; Yu, Qiang; Liu, Hong-Sheng; Han, Xing-Guo

    A budget for the methane (CH 4) cycle in the Xilin River basin of Inner Mongolia is presented. The annual CH 4 budget in this region depends primarily on the sum of atmospheric CH 4 uptake by upland soils, emission from small wetlands, and emission from grazing ruminants (sheep, goats, and cattle). Flux rates for these processes were averaged over multiple years with differing summer rainfall. Although uplands constitute the vast majority of land area, they consume much less CH 4 per unit area than is emitted by wetlands and ruminants. Atmospheric CH 4 uptake by upland soils was -3.3 and -4.8 kg CH 4 ha -1 y -1 in grazed and ungrazed areas, respectively. Average CH 4 emission was 791.0 kg CH 4 ha -1 y -1 from wetlands and 8.6 kg CH 4 ha -1 y -1 from ruminants. The basin area-weighted average of all three processes was 6.8 kg CH 4 ha -1 y -1, indicating that ruminant production has converted this basin to a net source of atmospheric CH 4. The total CH 4 emission from the Xilin River basin was 7.29 Gg CH 4 y -1. The current grazing intensity is about eightfold higher than that which would result in a net zero CH 4 flux. Since grazing intensity has increased throughout western China, it is likely that ruminant production has converted China's grazed temperate grasslands to a net source of atmospheric CH 4 overall.

  11. Effects of plant pathogens on population dynamics and community composition in grassland ecosystems: two case studies

    Microsoft Academic Search

    Michael J. Jeger; Nabeil K. G. Salama; Michael Shaw; F. van den Berg; Frank Van Den Bosch

    2014-01-01

    Grassland ecosystems comprise a major portion of the earth’s terrestrial surface, ranging from high-input cultivated monocultures or simple species-mixtures to relatively unmanaged but dynamic systems. Plant pathogens are a component of these systems with their impact dependent on many interacting factors, including grassland species population dynamics and community composition, the topics covered in this paper. Plant pathogens are affected by

  12. Nonlinearly combined impacts of initial perturbation from human activities and parameter perturbation from climate change on the grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Sun, G.; Mu, M.

    2011-11-01

    Human activities and climate change are important factors that affect grassland ecosystems. A new optimization approach, the approach of conditional nonlinear optimal perturbation (CNOP) related to initial and parameter perturbations, is employed to explore the nonlinearly combined impacts of human activities and climate change on a grassland ecosystem using a theoretical grassland model. In our study, it is assumed that the initial perturbations and parameter perturbations are regarded as human activities and climate change, respectively. Numerical results indicate that the climate changes causing the maximum effect in the grassland ecosystem are different under disparate intensities of human activities. This implies the pattern of climate change is very critical to the maintenance or degradation of grassland ecosystem in light of high intensity of human activities and that the grassland ecosystem should be rationally managed when the moisture index decreases. The grassland ecosystem influenced by the nonlinear combination of human activities and climate change undergoes abrupt change, while the grassland ecosystem affected by other types of human activities and climate change fails to show the abrupt change under a certain range of perturbations with the theoretical model. The further numerical analyses also indicate that the growth of living biomass and the evaporation from soil surface shaded by the wilted biomass may be crucial factors contributing to the abrupt change of the grassland equilibrium state within the theoretical model.

  13. Alternative states of a semiarid grassland ecosystem: implications for ecosystem services

    USGS Publications Warehouse

    Miller, Mark E.; Belote, R. Travis; Bowker, Matthew A.; Garman, Steven L.

    2011-01-01

    Ecosystems can shift between alternative states characterized by persistent differences in structure, function, and capacity to provide ecosystem services valued by society. We examined empirical evidence for alternative states in a semiarid grassland ecosystem where topographic complexity and contrasting management regimes have led to spatial variations in levels of livestock grazing. Using an inventory data set, we found that plots (n = 72) cluster into three groups corresponding to generalized alternative states identified in an a priori conceptual model. One cluster (biocrust) is notable for high coverage of a biological soil crust functional group in addition to vascular plants. Another (grass-bare) lacks biological crust but retains perennial grasses at levels similar to the biocrust cluster. A third (annualized-bare) is dominated by invasive annual plants. Occurrence of grass-bare and annualized-bare conditions in areas where livestock have been excluded for over 30 years demonstrates the persistence of these states. Significant differences among all three clusters were found for percent bare ground, percent total live cover, and functional group richness. Using data for vegetation structure and soil erodibility, we also found large among-cluster differences in average levels of dust emissions predicted by a wind-erosion model. Predicted emissions were highest for the annualized-bare cluster and lowest for the biocrust cluster, which was characterized by zero or minimal emissions even under conditions of extreme wind. Results illustrate potential trade-offs among ecosystem services including livestock production, soil retention, carbon storage, and biodiversity conservation. Improved understanding of these trade-offs may assist ecosystem managers when evaluating alternative management strategies.

  14. Tropical freshwater ecosystems have lower bacterial growth efficiency than temperate ones

    PubMed Central

    Amado, André M.; Meirelles-Pereira, Frederico; Vidal, Luciana O.; Sarmento, Hugo; Suhett, Albert L.; Farjalla, Vinicius F.; Cotner, James B.; Roland, Fabio

    2013-01-01

    Current models and observations indicate that bacterial respiration should increase and growth efficiency (BGE) should decrease with increasing temperatures. However, these models and observations are mostly derived from data collected in temperate regions, and the tropics are under-represented. The aim of this work was to compare bacterial metabolism, namely bacterial production (BP) and respiration (BR), bacterial growth efficiency (BGE) and bacterial carbon demand (BCD) between tropical and temperate ecosystems via a literature review and using unpublished data. We hypothesized that (1) tropical ecosystems have higher metabolism than temperate ones and, (2) that BGE is lower in tropical relative to temperate ecosystems. We collected a total of 498 coupled BP and BR observations (Ntotal = 498; Ntemperate = 301; Ntropical = 197), calculated BGE (BP/(BP+BR)) and BCD (BP+BR) for each case and examined patterns using a model II regression analysis and compared each parameter between the two regions using non-parametric Mann–Whitney U test. We observed a significant positive linear regression between BR and BP for the whole dataset, and also for tropical and temperate data separately. We found that BP, BR and BCD were higher in the tropics, but BGE was lower compared to temperate regions. Also, BR rates per BP unit were at least two fold higher in the tropics than in temperate ecosystems. We argue that higher temperature, nutrient limitation, and light exposure all contribute to lower BGE in the tropics, mediated through effects on thermodynamics, substrate stoichiometry, nutrient availability and interactions with photochemically produced compounds. More efforts are needed in this study area in the tropics, but our work indicates that bottom-up (nutrient availability and resource stoichiometry) and top-down (grazer pressure) processes, coupled with thermodynamic constraints, might contribute to the lower BGE in the tropics relative to temperate regions. PMID:23801986

  15. Environmental effects of oil and gas lease sites in a grassland ecosystem.

    PubMed

    Nasen, Lawrence C; Noble, Bram F; Johnstone, Jill F

    2011-01-01

    The northern Great Plains of Saskatchewan is one of the most significantly modified landscapes in Canada. While the majority of anthropogenic disturbances to Saskatchewan's grasslands are the result of agricultural practices, development of petroleum and natural gas (PNG) resources is of increasing concern for grassland conservation. Although PNG developments require formal assessment and regulatory approval, follow-up and monitoring of the effects of PNG development on grasslands is not common practice. Consequently, the effects of PNG activity on grasslands and the spatial and temporal extent of such impacts are largely unknown. This paper examines the spatial and temporal extent of PNG development infrastructure from 1955 to 2006 in a grassland ecosystem in southwest Saskatchewan. The effects of PNG development on grassland ecology were assessed from measurements of ground cover characteristics, soil properties, and plant community composition at 31 sites in the study area. PNG lease sites were found to have low cover of herbaceous plants, club moss (Lycopodiaceae), litter, and shallow organic (Ah) horizons. Lease sites were also characterized by low diversity of desirable grassland plants and low range health values compared to off-lease reference sites. These impacts were amplified at active and highly productive lease sites. Impacts of PNG development persisted for more than 50 years following well site construction, and extended outward 20 m-25 m beyond the direct physical footprint of PNG well infrastructure. These results have significant implications with regard to the current state of monitoring and follow-up of PNG development, and the cumulative effective of PNG activity on grassland ecosystems over space and time. PMID:20880628

  16. Effects of increased soil water availability on grassland ecosystem carbon dioxide fluxes

    Microsoft Academic Search

    Anita C. Risch; Douglas A. Frank

    2007-01-01

    There is considerable interest in how ecosystems will respond to changes in precipitation. Alterations in rain and snowfall\\u000a are expected to influence the spatio-temporal patterns of plant and soil processes that are controlled by soil moisture, and\\u000a potentially, the amount of carbon (C) exchanged between the atmosphere and ecosystems. Because grasslands cover over one third\\u000a of the terrestrial landscape, understanding

  17. Ecosystem development in roadside grasslands: Biotic control, plant-soil interactions, and dispersal limitations

    USGS Publications Warehouse

    Garcia-Palacios, P.; Bowker, M.A.; Maestre, F.T.; Soliveres, S.; Valladares, F.; Papadopoulos, J.; Escudero, A.

    2011-01-01

    Roadside grasslands undergoing secondary succession are abundant, and represent ecologically meaningful examples of novel, human-created ecosystems. Interactions between plant and soil communities (hereafter plant-soil interactions) are of major importance in understanding the role of biotic control in ecosystem functioning, but little is known about these links in the context of ecosystem restoration and succession. The assessment of the key biotic communities and interactions driving ecosystem development will help practitioners to better allocate the limited resources devoted to roadside grassland restoration. We surveyed roadside grasslands from three successional stages (0-2, 7-9, and > 20 years) in two Mediterranean regions of Spain. Structural equation modeling was used to evaluate how interactions between plants, biological soil crusts (BSCs), and soil microbial functional diversity (soil microorganisms) affect indicators of ecosystem development and restoration: plant similarity to the reference ecosystem, erosion control, and soil C storage and N accumulation. Changes in plant community composition along the successional gradient exerted the strongest influence on these indicators. High BSC cover was associated with high soil stability, and high soil microbial functional diversity from late-successional stages was associated with high soil fertility. Contrary to our expectations, the indirect effects of plants, mediated by either BSCs or soil microorganisms, were very weak in both regions, suggesting a minor role for plant-soil interactions upon ecosystem development indicators over long periods. Our results suggest that natural vegetation dynamics effectively improved ecosystem development within a time frame of 20 years in the grasslands evaluated. They also indicate that this time could be shortened if management actions focus on: (1) maintaining wellconserved natural areas close to roadsides to enhance plant compositional changes towards late-successional stages, (2) increasing BSC cover in areas under strong erosion risk, to avoid soil loss, and (3) enhancing soil microbial functional diversity in resource-limited areas, to enhance soil C and N accumulation. ?? 2011 by the Ecological Society of America.

  18. Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystem

    E-print Network

    Blair, John

    Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control

  19. Ecosystem response to rainfall variability and warming in a mesic grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grassland ecosystems are strongly responsive to climatic variability, and many fundamental aspects of their structure and function are tied to spatial and temporal variation in precipitation. The pulsed nature of precipitation inputs- short periods of rainfall separated by longer periods during whic...

  20. The impacts of drainage, nutrient status and management practice on the full carbon balance of grasslands on organic soils in a maritime temperate zone

    NASA Astrophysics Data System (ADS)

    Renou-Wilson, F.; Barry, C.; Müller, C.; Wilson, D.

    2014-08-01

    Temperate grasslands on organic soils are diverse due to edaphic properties but also to regional management practices and this heterogeneity is reflected in the wide range of greenhouse gas (GHG) flux values reported in the literature. In Ireland, most grasslands on organic soils were drained several decades ago and are managed as extensive pastures with little or no fertilisation. This study describes a 2-year study of the net ecosystem carbon balance (NECB) of two such sites. We determined GHG fluxes and waterborne carbon (C) emissions in a nutrient-rich grassland and compared it with values measured from two nutrient-poor organic soils: a deep-drained and a shallow-drained site. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes were determined using the chamber technique, and fluvial C fluxes were estimated by combining drainage water concentrations and flows. The nutrient-rich site was an annual source of CO2 (233 g C m-2 yr-1), CH4 neutral, and a small source of N2O (0.16 g N2O-N m-2 yr-1). Net ecosystem exchange (NEE) at the shallow-drained nutrient-poor site was -89 and -99 g C m-2 yr-1 in Years 1 and 2 respectively, and NEE at the deep-drained nutrient-poor site was 85 and -26 g C m-2 yr-1 respectively. Low CH4 emissions (1.3 g C m-2 yr-1) were recorded at the shallow-drained nutrient-poor site. Fluvial exports from the nutrient-rich site totalled 69.8 g C m-2 yr-1 with 54% as dissolved organic C. Waterborne C losses from the nutrient-poor site reflected differences in annual runoff totalling 44 g C m-2 yr-1 in Year 1 and 30.8 g C m-2 yr-1 in Year 2. The NECB of the nutrient-rich grassland was 663 g C m-2 yr-1 with biomass exports being the major component accounting for 53%. The NECB of the nutrient-poor deep-drained site was less than half of the nutrient-rich site (2-year mean 267 g C m-2 yr-1). Although NEE at the nutrient-poor shallow-drained site was negative in both years, high biomass export meant it was a net C source (2-year mean NECB 103 g C m-2 yr-1). While the impacts of the nutrient and drainage status on NEE, biomass exports and fluvial C losses were confirmed, inter-regional differences in management practice and climate were also significant factors which impacted on the overall NECB of these ecosystems. Contrary to expectation, the NECB of nutrient-poor drained organic soils under grasslands is not necessarily a large C source and this has implications for Ireland's choice of national GHG inventory reporting methodologies. This study can also aid the development of strategies to deliver reduced emissions tailored to local grassland types.

  1. Fluxes of CO 2 , N 2 O and CH 4 from a typical temperate grassland in Inner Mongolia and its daily variation

    Microsoft Academic Search

    Yunshe Dong; Shen Zhang; Yuchun Qi; Zuozhong Chen; Yuanbo Geng

    2000-01-01

    Using a dark enclosed chamber technique, the fluxes of CO2, N2O and CH4 from nature and disturbed grassland were measured on the spot in Inner Mongolian Temperate Grassland along the annual rainfall\\u000a gradient section ranging from 450 to 200 mm. The results showed that the measured mean fluxes of CO2, N2O and CH4 were (1 180.4 ± 308.7), (0.010 ±

  2. The biogeochemistry of a north-temperate grassland with native ungulates: Nitrogen dynamics in Yellowstone National Park

    Microsoft Academic Search

    Douglas A. Frank; Richard S. Inouye; Nancy Huntly; G. WAYNE MINSHALL; Jay E. Anderson

    1994-01-01

    Nutrient dynamics of large grassland ecosystems possessing abundant migratory grazers are poorly understood. We examined N cycling on the northern winter range of Yellowstone National Park, home for large herds of free-roaming elk (Cervus elaphus) and bison (Bison bison). Plant and soil N, net N mineralization, and the deposition of ungulate fecal-N were measured at five sites, a ridgetop, mid-slope

  3. Understanding the importance wet, unimproved Culm grasslands have for the provision of multiple ecosystem services

    NASA Astrophysics Data System (ADS)

    Brazier, Richard; Elliot, Mark; Warren, Susan; Puttock, Alan

    2014-05-01

    It is increasingly recognised that catchments must be carefully managed for the provision of multiple, sometimes conflicting ecosystem services. This requires an increased interdisciplinary environmental understanding to inform management policy and practices by government, landowners and stakeholders. The Culm National Character Area (NCA) covers 3,500 square kilometres in South West England with Culm grasslands consisting of wet unimproved, species rich pastures, typically on poorly drained soils. Since the 1960's, policy changes have encouraged the drainage of large areas of land for agricultural improvement and consequently Culm grassland sites have become highly fragmented. There are currently 575 Culm grassland sites in the Culm NCA with a mean area of 7 ha. Traditionally, Culm grasslands have been managed by light grazing and scrub management. Since 2008, Devon Wildlife Trust's Working Wetlands project has been working with farmers and landowners to manage and restore and recreate Culm grasslands. It is part of South West Water's Upstream Thinking initiative and is now augmented by the Northern Devon Nature Improvement Area programme. However, from a hydrological perspective, Culm and similar unimproved grasslands remain poorly understood. In addition to their recognised conservation and biodiversity importance; unimproved grasslands such as Culm are thought to have a high water storage capacity, reducing runoff and therefore flooding during wet periods, whilst slowly releasing and filtering water to help maintain water quality, and base river flows during dry periods. Therefore, if properly understood and managed Culm soils have the potential to play an important role in the management of catchment water resources. Furthermore, Culm grassland soils are thought to have a high potential for the sequestration and storage of carbon, an increasingly valuable ecosystem service. This study aims to increase understanding of the influence Culm grasslands have upon water and soil resources, relative to other land uses and land covers (wet woodland, scrub and intensively managed grassland). Results will be presented demonstrating that relative to intensively managed grassland, Culm soils have a higher water holding capacity, exhibit a more attenuated response to rainfall events and have higher carbon concentrations. Additionally, results show water leaving a Culm dominated sub-catchment is of a higher quality (i.e. exhibiting lower suspended sediment, dissolved organic carbon and phosphate loads) than comparable intensively managed agricultural catchments.

  4. Biocenoses of Collembola in atlantic temperate grass-woodland ecosystems

    Microsoft Academic Search

    J. F. Ponge

    1993-01-01

    Samples (679) from various forest sites in the atlantic temperate region (lowlands in the northern half of France) have been studied. Their Collembolan species composition 145 species, with only 43 rare species) was analysed by Benzecri's correspondence analysis, a multivariate method. Five groups of species, each associated with a given habitat, were determined: above the ground surface a distinction is

  5. Diversity Promotes Temporal Stability across Levels of Ecosystem Organization in Experimental Grasslands

    PubMed Central

    Proulx, Raphaël; Wirth, Christian; Voigt, Winfried; Weigelt, Alexandra; Roscher, Christiane; Attinger, Sabine; Baade, Jussi; Barnard, Romain L.; Buchmann, Nina; Buscot, François; Eisenhauer, Nico; Fischer, Markus; Gleixner, Gerd; Halle, Stefan; Hildebrandt, Anke; Kowalski, Esther; Kuu, Annely; Lange, Markus; Milcu, Alex; Niklaus, Pascal A.; Oelmann, Yvonne; Rosenkranz, Stephan; Sabais, Alexander; Scherber, Christoph; Scherer-Lorenzen, Michael; Scheu, Stefan; Schulze, Ernst-Detlef; Schumacher, Jens; Schwichtenberg, Guido; Soussana, Jean-François; Temperton, Vicky M.; Weisser, Wolfgang W.; Wilcke, Wolfgang; Schmid, Bernhard

    2010-01-01

    The diversity–stability hypothesis states that current losses of biodiversity can impair the ability of an ecosystem to dampen the effect of environmental perturbations on its functioning. Using data from a long-term and comprehensive biodiversity experiment, we quantified the temporal stability of 42 variables characterizing twelve ecological functions in managed grassland plots varying in plant species richness. We demonstrate that diversity increases stability i) across trophic levels (producer, consumer), ii) at both the system (community, ecosystem) and the component levels (population, functional group, phylogenetic clade), and iii) primarily for aboveground rather than belowground processes. Temporal synchronization across studied variables was mostly unaffected with increasing species richness. This study provides the strongest empirical support so far that diversity promotes stability across different ecological functions and levels of ecosystem organization in grasslands. PMID:20967213

  6. Importance of Non-Diffusive Transport for Soil CO2 Efflux in a Temperate Mountain Grassland

    NASA Astrophysics Data System (ADS)

    Roland, Marilyn; Vicca, Sara; Bahn, Michael; Ladreiter-Knauss, Thomas; Schmitt, Michael; Janssens, Ivan A.

    2015-04-01

    A key focus in climate change is on the dynamics and predictions of the soil CO2 efflux (SCE) from terrestrial ecosystems. Limited knowledge of CO2 transport through the soil restricts our understanding of the various biotic and abiotic processes underlying these emissions. Diffusion is often thought to be the main transport mechanism for trace gases in soils, an assumption that is reflected in the increasing popularity of the flux-gradient approach (FGA). Based on Fick's law, the FGA calculates soil CO2 efflux from CO2 concentration profiles, given good estimates of the diffusion coefficient. The latter can be calculated via different commonly used models, and solid-state sensors allow continuous high-frequency measurements of soil CO2 concentrations with minimal disturbance to the soil conditions in a cost-effective way. Fast growing evidence of pressure pumping and advection, makes it impossible to disregard non-diffusive gas transport when evaluating diel and day-to-day dynamics of soil CO2 emissions. We have analyzed combined measurements from solid-state sensors and soil chambers to gain insight in the CO2 transport mechanisms in a grassland site in the Austrian Alps. The FGA-derived efflux underestimated the chamber efflux by 10 to 87% at our site, depending on which model was used for calculation of the diffusion coefficient. We found that the actual transport rates correlated well with irradiation and wind speed, even more when the soil moisture content was below 33%. These findings suggest that bulk soil air transport was enhanced by pressure changes induced by wind shear at the surface and by local heating of the soil surface. Considering the importance of non-diffusive transport processes is a prerequisite when using solid-state CO2 concentration measurements to estimate soil CO2 efflux at any given site.

  7. Leaf and ecosystem response to soil water availability in mountain grasslands

    PubMed Central

    Brilli, Federico; Hörtnagl, Lukas; Hammerle, Albin; Haslwanter, Alois; Hansel, Armin; Loreto, Francesco; Wohlfahrt, Georg

    2014-01-01

    Climate change is expected to affect the Alps by increasing the frequency and intensity of summer drought events with negative impacts on ecosystem water resources. The response of CO2 and H2O exchange of a mountain grassland to natural fluctuations of soil water content was evaluated during 2001-2009. In addition, the physiological performance of individual mountain forb and graminoid plant species under progressive soil water shortage was explored in a laboratory drought experiment. During the 9-year study period the natural occurrence of moderately to extremely dry periods did not lead to substantial reductions in net ecosystem CO2 exchange and evapotranspiration. Laboratory drought experiments confirmed that all the surveyed grassland plant species were insensitive to progressive soil drying until very low soil water contents (<0.01 m3 m?3) were reached after several days of drought. In field conditions, such a low threshold was never reached. Re-watering after a short-term drought event (5±1 days) resulted in a fast and complete recovery of the leaf CO2 and H2O gas exchange of the investigated plant species. We conclude that the present-day frequency and intensity of dry periods does not substantially affect the functioning of the investigated grassland ecosystem. During dry periods the observed “water spending” strategy employed by the investigated mountain grassland species is expected to provide a cooling feedback on climate warming, but may have negative consequences for down-stream water users. PMID:24465071

  8. Amino acids as a nitrogen source in temperate upland grasslands: the use of dual labelled ((13)C, (15)N) glycine to test for direct uptake by dominant grasses.

    PubMed

    Streeter, T C; Bol, R; Bardgett, R D

    2000-01-01

    It is becoming increasingly apparent that soil amino acids are a principal source of nitrogen (N) for certain plants, and especially those of N-limited environments. This study of temperate upland grasslands used glycine-2-(13)C-(15)N and ((15)NH4)(2)SO(4) labelling techniques to test the hypothesis that plant species which dominate 'unimproved' semi-natural grasslands (Festuca-Agrostis-Galium) are able to utilise amino acid N for growth, whereas those plants which dominate 'improved' grasslands (Lolium-Cynosurus), that receive regular applications of inorganic fertiliser, use inorganic N forms as their main N source. Data from field experiments confirmed that 'free' amino acids were more abundant in 'unimproved' than 'improved' grassland and that glycine was the dominant amino acid type (up to 42% of total). Secondly, the injection of representative amounts of glycine-2-(13)C-(15)N (4.76 and 42.86 mM) into intact soil cores from the two grassland types provided evidence of direct uptake of glycine by plants, with both (15)N and (13)C being detected in plant material of both grasslands. Finally, a microcosm experiment demonstrated no preferential uptake of amino acid N by the grasses which dominate the grassland types, namely Holcus lanatus, Festuca rubra, Agrostis capillaris from the 'unimproved' grassland, and Lolium perenne from the 'improved' grassland. Again, both (13)C and (15)N were detected in all grass species suggesting uptake of intact glycine by these plants. PMID:10920354

  9. The impacts of drainage, nutrient status and management practice on the full carbon balance of grasslands on organic soils in a maritime temperate zone

    NASA Astrophysics Data System (ADS)

    Renou-Wilson, F.; Barry, C.; Müller, C.; Wilson, D.

    2014-04-01

    Temperate grasslands on organic soils are diverse due to edaphic properties but also to regional management practices and this heterogeneity is reflected in the wide range of greenhouse gas flux values reported in the literature. In Ireland, most grasslands on organic soils were drained several decades ago and are managed as extensive pastures with little or no fertilisation. This study describes a two-year study of the net ecosystem carbon balance (NECB) of two such sites. We determined greenhouse gas (GHG) fluxes and waterborne carbon emissions in a nutrient rich grassland and compared it with values measured from two nutrient poor organic soils: a deep drained and a shallow drained site. GHG fluxes (CO2, CH4 and N2O) were determined using the chamber technique, and fluvial C fluxes were estimated by combining drainage water concentrations and flows. The nutrient rich site was an annual source of CO2 (NEE 233 g C m-2yr-1), CH4 neutral, and a small source of nitrous oxide (1.6 kg N2O-N ha-1yr-1). NEE at the shallow drained site was -89 and -99 g C m-2yr-1 in Years 1 and 2 respectively, and NEE at the deep drained site was +85 and -26 g C m-2yr-1 respectively. Low CH4 emissions (1.3 g C m-2yr-1) were recorded at the shallow drained nutrient poor site. Fluvial exports from the nutrient rich site totalled 69.8 g C m-2yr-1 with 54% as dissolved organic C (DOC). Waterborne C losses from the nutrient poor site reflected differences in annual runoff totalling 44 g C m-2yr-1 in Year 1 and 30.8 g C m-2yr-1 in Year 2. The NECB of the nutrient rich grassland was 663 g C m-2yr-1 with biomass exports being the major component accounting for 53%. The NECB of the nutrient poor deep drained site was less than half of the nutrient rich site (2 year mean 267 g C m-2yr-1). Although NEE at the nutrient poor shallow drained site was negative in both years, high biomass export meant it was a net C source (2 year mean NECB 103 g C m-2yr-1). While the impacts of the nutrient and drainage status on NEE, biomass exports and fluvial C losses were confirmed, inter-regional differences in management practice and climate are also significant factors which impact on the overall NECB of these ecosystems. Contrary to expectation, the NECB of nutrient poor drained organic soils under grasslands is not necessarily a large C source and this has implications for Ireland's choice of national GHG inventory reporting methodologies. This study can also aid the development of strategies to deliver reduced emissions tailored to local grassland types.

  10. Biocenoses of Collembola in atlantic temperate grass-woodland ecosystems Jean-Francois Ponge

    E-print Network

    Paris-Sud XI, Université de

    Biocenoses of Collembola in atlantic temperate grass-woodland ecosystems Jean-Francois Ponge Museum, it is apparent that vegetation in itself does not directly influence Collembola but may effect them indirectly through humus formation. Key words: Collembola, biocenoses, correspondence analysis, spatial heterogeneity

  11. Land use affects the net ecosystem CO2 exchange and its components in mountain grasslands

    PubMed Central

    Schmitt, M.; Bahn, M.; Wohlfahrt, G.; Tappeiner, U.; Cernusca, A.

    2011-01-01

    Changes in land use and management have been strongly affecting mountain grassland, however, their effects on the net ecosystem exchange of CO2 (NEE) and its components have not yet been well documented. We analysed chamber-based estimates of NEE, gross primary productivity (GPP), ecosystem respiration (R) and light use efficiency (LUE) of six mountain grasslands differing in land use and management, and thus site fertility, for the growing seasons of 2002 to 2008. The main findings of the study are that: (1) land use and management affected seasonal NEE, GPP and R, which all decreased from managed to unmanaged grasslands; (2) these changes were explained by differences in leaf area index (LAI), biomass and leaf-area-independent changes that were likely related to photosynthetic physiology; (3) diurnal variations of NEE were primarily controlled by photosynthetically active photon flux density and soil and air temperature; seasonal variations were associated with changes in LAI; (4) parameters of light response curves were generally closely related to each other, and the ratio of R at a reference temperature/ maximum GPP was nearly constant across the sites; (5) similarly to our study, maximum GPP and R for other grasslands on the globe decreased with decreasing land use intensity, while their ratio remained remarkably constant. We conclude that decreasing intensity of management and, in particular, abandonment of mountain grassland lead to a decrease in NEE and its component processes. While GPP and R are generally closely coupled during most of the growing season, GPP is more immediately and strongly affected by land management (mowing, grazing) and season. This suggests that management and growing season length, as well as their possible future changes, may play an important role for the annual C balance of mountain grassland. PMID:23293657

  12. Effects of management of ecosystem carbon pools and fluxes in grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Ryals, R.; Silver, W. L.

    2010-12-01

    Grasslands represent a large land-use footprint and have considerable potential to sequester carbon (C) in soil. Climate policies and C markets may provide incentives for land managers to pursue strategies that optimize soil C storage, yet we lack robust understanding of C sequestration in grasslands. Previous research has shown that management approaches such as organic amendments or vertical subsoiling can lead to larger soil C pools. These management approaches can both directly and indirectly affect soil C pools. We used well-replicated field experiments to explore the effects of these management strategies on ecosystem C pools and fluxes in two bioclimatic regions of California (Sierra Foothills Research and Extension Center (SFREC) and Nicasio Ranch). Our treatments included an untreated control, compost amendments, plowed (vertical subsoil), and compost + plow. The experiment was conducted over two years allowing us to compare dry (360 mm) and average (632 mm) rainfall conditions. Carbon dioxide (CO2) fluxes were measured weekly using a LI-8100 infrared gas analyzer. Methane (CH4) and nitrous oxide (N2O) fluxes were measured monthly using static flux chambers. Aboveground and belowground biomass were measured at the end of the growing season as an index of net primary productivity (NPP) in the annual plant dominated system. Soil moisture and temperature were measured continuously and averaged on hourly and daily timescales. Soil organic C and N concentrations were measured prior to the application of management treatments and at the ends of each growing season. Soils were collected to a 10 cm depth in year one and at four depth increments (0-10, 10-30, 30-50, and 50-100 cm) in year two. Soil C and N concentrations were converted to content using bulk density values for each plot. During both growing seasons, soil respiration rates were higher in the composted plots and lower in the plowed plots relative to controls at both sites. The effects on C loss via soil respiration were stronger in the first year, with compost soils experiencing a 21 ± 1 % greater cumulative loss at SFREC and 16 ± 3 % more at Nicasio. The second year showed a similar trend, but with a lower magnitude loss. Aboveground NPP responded positively to compost additions and negatively to plowing at both sites. At SFREC, we measured 58 % more ANPP in composted relative to control plots in year one (369 vs 230 g C/m2) and 56 % more in year two (327 vs 209 g C/m2). Aboveground NPP on plowed plots was 129 g C/m2 in year one, and 185 g C/m2 in year two. Plowed soils also showed a significant decline in soil C and N concentrations (C= 2.67 ± 0.13%, N = 0.20 ± 0.01%). Compost additions increased soil C and N concentrations (C= 3.92 ± 0.29%, N = 0.32 ± 0.02%) relative to control soils (C= 3.52 ± 0.20%, N = 0.27 ± 0.07%). Throughout the experiment, we did not detect significant treatment differences in CH4 or N2O fluxes, nor did we detect significant differences at any individual sampling point. These results suggest that compost addition can lead to an increase in ecosystem C storage, with a small offset from elevated soil respiration.

  13. Sustainable Management of Insect Herbivores in Grassland Ecosystems: New Perspectives in Grasshopper Control

    NSDL National Science Digital Library

    DAVID H. BRANSON, ANTHONY JOERN, and GREGORY A. SWORD (; )

    2006-09-01

    This peer reviewed article from Bioscience journal is about the use of grasshoppers in grassland ecosystems. Grasshoppers are insect herbivores common to grassland ecosystems worldwide. They comprise important components of biodiversity, contribute significantly to grassland function, and periodically exhibit both local and large-scale outbreaks. Because of grasshoppers' potential economic importance as competitors with ungulate grazers for rangeland forage, periodic grasshopper outbreaks in western US rangeland often elicit intervention over large areas in the form of chemical control. Available information combined with alternative underlying conceptual frameworks suggests that new approaches for sustainable management of grasshopper outbreaks in US rangeland should be pursued. There are many reasons to believe that approaches to grasshopper management that aim to reduce or prevent outbreaks are possible. These habitat manipulation tactics maintain existing ecological feedbacks responsible for sustaining populations at economically nonthreatening levels. Sustainable strategies to minimize the likelihood and extent of grasshopper outbreaks while limiting the need for chemical intervention are a rational and attainable goal for managing grasslands as renewable resources.

  14. Asymmetric warming significantly affects net primary production, but not ecosystem carbon balances of forest and grassland ecosystems in northern China

    PubMed Central

    Su, Hongxin; Feng, Jinchao; Axmacher, Jan C.; Sang, Weiguo

    2015-01-01

    We combine the process-based ecosystem model (Biome-BGC) with climate change-scenarios based on both RegCM3 model outputs and historic observed trends to quantify differential effects of symmetric and asymmetric warming on ecosystem net primary productivity (NPP), heterotrophic respiration (Rh) and net ecosystem productivity (NEP) of six ecosystem types representing different climatic zones of northern China. Analysis of covariance shows that NPP is significant greater at most ecosystems under the various environmental change scenarios once temperature asymmetries are taken into consideration. However, these differences do not lead to significant differences in NEP, which indicates that asymmetry in climate change does not result in significant alterations of the overall carbon balance in the dominating forest or grassland ecosystems. Overall, NPP, Rh and NEP are regulated by highly interrelated effects of increases in temperature and atmospheric CO2 concentrations and precipitation changes, while the magnitude of these effects strongly varies across the six sites. Further studies underpinned by suitable experiments are nonetheless required to further improve the performance of ecosystem models and confirm the validity of these model predictions. This is crucial for a sound understanding of the mechanisms controlling the variability in asymmetric warming effects on ecosystem structure and functioning. PMID:25766381

  15. Productivity and sustainability influenced by biodiversity in grassland ecosystems

    Microsoft Academic Search

    David Tilman; David Wedin; Johannes Knops

    1996-01-01

    THE functioning and sustainability of ecosystems may depend on their biological diversity1-8. Elton's9 hypothesis that more diverse ecosystems are more stable has received much attention1,3,6,7,10-14, but Darwin's proposal6,15 that more diverse plant communities are more productive, and the related conjectures4,5,16,17 that they have lower nutrient losses and more sustainable soils, are less well studied4-6,8,17,18. Here we use a well-replicated field

  16. Trajectories of grassland ecosystem change in response to experimental manipulations of precipitation

    NASA Astrophysics Data System (ADS)

    Knapp, Alan; Smith, Melinda; Collins, Scott; Blair, John; Briggs, John

    2010-05-01

    Understanding and predicting the dynamics of ecological systems has always been central to Ecology. Today, ecologists recognize that in addition to natural and human-caused disturbances, a fundamentally different type of ecosystem change is being driven by the combined and cumulative effects of anthropogenic activities affecting earth's climate and biogeochemical cycles. This type of change is historically unprecedented in magnitude, and as a consequence, such alterations are leading to trajectories of change in ecological responses that differ radically from those observed in the past. Through both short- and long-term experiments, we have been trying to better understand the mechanisms and consequences of ecological change in grassland ecosystems likely to result from changes in precipitation regimes. We have manipulated a key resource for most grasslands (water) and modulators of water availability (temperature) in field experiments that vary from 1-17 years in duration, and used even longer-term monitoring data from the Konza Prairie LTER program to assess how grassland communities and ecosystems will respond to changes in water availability. Trajectories of change in aboveground net primary production (ANPP) in sites subjected to 17 years of soil water augmentation were strongly non-linear with a marked increase in the stimulation of ANPP after year 8 (from 25% to 65%). Lags in alterations in grassland community composition are posited to be responsible for the form of this trajectory of change. In contrast, responses in ANPP to chronic increases in soil moisture variability appear to have decreased over a 10-yr period of manipulation, although the net effects of more variable precipitation inputs were to reduce ANPP, alter the genetic structure of the dominant grass species, increase soil nitrogen availability and reduce soil respiration. The loss of sensitivity to increased resource variability was not reflected in adjacent plots where precipitation was manipulated for only a single year. And when similar short-term experimental manipulations of precipitation variability were conducted in more arid grasslands, responses in ANPP were opposite those in mesic grassland. This suggests that grassland responses to alterations in precipitation inputs may vary dramatically depending on the long-term hydrologic regime.

  17. Litter Decomposition in Temperate Peatland Ecosystems: The Effect of

    E-print Network

    Moore, Tim

    cases. Within each site, the rate of decomposition at the surface was gener- ally Typha latifolia leaves-quality model initial quality (q0) values ranging from 1.0 (arbitrarily set for Typha leaves) to 0.7 (Sphagnum, com- pared to most well-drained ecosystems. Three litters, roots of sedge and a shrub and Typha leaves

  18. Plant traits as predictor of ecosystem carbon fluxes - a case study across European grasslands

    NASA Astrophysics Data System (ADS)

    Klumpp, Katja; Bahn, Michael; Acosta, Manuel; Altimir, Nuria; Gimeno, Cristina; Jongen, Marjan; Merbold, Lutz; Moors, Eddy; Pinter, Kistina; Darsonville, Olivier

    2015-04-01

    Predicting ecosystem responses to global change has become a major challenge, particularly as terrestrial ecosystems contribute to the mitigation of global climate change through carbon sequestration. Plant traits are major surrogates of ecosystem physiology may thus help to predict carbon (C) fluxes and their consequences for the delivery of ecosystem services (e.g. C sequestration) across climatic gradients and in changing environments. However, linkages between community abundance-weighted means (CWM) of plant functional traits and ecosystem C fluxes have rarely been tested. It is also not known to what degree traits, which are typically measured at a defined point in time, are suitable for predicting annual C fluxes. We analysed the relationships between ecosystem fluxes and community level plant traits for 13 European grasslands under contrasting climate and management regimes, using multiyear eddy covariance data. Plant traits (specific leaf area SLA, leaf dry matter content LDMC, specific root length SLR) were determined at peak biomass. Analyses showed that GPPmax (at maximum radiation) was related to SLA, SRL and LDMC across sites and management, where GPPmax was an excellent indicator for annual GPP. Similar relations were found between for root density (and -diameter) and ecosystem respiration. Ecosystems respiration at GPPmax was also in line with annual respiration, indicating the strong predictive potential of plant community traits. Our study therefore suggests that above- and belowground community level plant traits are well suited surrogates for predicting ecosystem C fluxes at peak biomass and at annual scale.

  19. Comparison of seasonal soil microbial process in snow-covered temperate ecosystems of northern China.

    PubMed

    Zhang, Xinyue; Wang, Wei; Chen, Weile; Zhang, Naili; Zeng, Hui

    2014-01-01

    More than half of the earth's terrestrial surface currently experiences seasonal snow cover and soil frost. Winter compositional and functional investigations in soil microbial community are frequently conducted in alpine tundra and boreal forest ecosystems. However, little information on winter microbial biogeochemistry is known from seasonally snow-covered temperate ecosystems. As decomposer microbes may differ in their ability/strategy to efficiently use soil organic carbon (SOC) within different phases of the year, understanding seasonal microbial process will increase our knowledge of biogeochemical cycling from the aspect of decomposition rates and corresponding nutrient dynamics. In this study, we measured soil microbial biomass, community composition and potential SOC mineralization rates in winter and summer, from six temperate ecosystems in northern China. Our results showed a clear pattern of increased microbial biomass C to nitrogen (N) ratio in most winter soils. Concurrently, a shift in soil microbial community composition occurred with higher fungal to bacterial biomass ratio and gram negative (G-) to gram positive (G+) bacterial biomass ratio in winter than in summer. Furthermore, potential SOC mineralization rate was higher in winter than in summer. Our study demonstrated a distinct transition of microbial community structure and function from winter to summer in temperate snow-covered ecosystems. Microbial N immobilization in winter may not be the major contributor for plant growth in the following spring. PMID:24667929

  20. Comparison of Seasonal Soil Microbial Process in Snow-Covered Temperate Ecosystems of Northern China

    PubMed Central

    Zhang, Xinyue; Wang, Wei; Chen, Weile; Zhang, Naili; Zeng, Hui

    2014-01-01

    More than half of the earth's terrestrial surface currently experiences seasonal snow cover and soil frost. Winter compositional and functional investigations in soil microbial community are frequently conducted in alpine tundra and boreal forest ecosystems. However, little information on winter microbial biogeochemistry is known from seasonally snow-covered temperate ecosystems. As decomposer microbes may differ in their ability/strategy to efficiently use soil organic carbon (SOC) within different phases of the year, understanding seasonal microbial process will increase our knowledge of biogeochemical cycling from the aspect of decomposition rates and corresponding nutrient dynamics. In this study, we measured soil microbial biomass, community composition and potential SOC mineralization rates in winter and summer, from six temperate ecosystems in northern China. Our results showed a clear pattern of increased microbial biomass C to nitrogen (N) ratio in most winter soils. Concurrently, a shift in soil microbial community composition occurred with higher fungal to bacterial biomass ratio and gram negative (G-) to gram positive (G+) bacterial biomass ratio in winter than in summer. Furthermore, potential SOC mineralization rate was higher in winter than in summer. Our study demonstrated a distinct transition of microbial community structure and function from winter to summer in temperate snow-covered ecosystems. Microbial N immobilization in winter may not be the major contributor for plant growth in the following spring. PMID:24667929

  1. A comparison of methods to estimate the height of stable boundary layer over a temperate grassland

    Microsoft Academic Search

    Yu-Kyung Hyun; Kyung-Eak Kim; Kyung-Ja Ha

    2005-01-01

    The development and structure of the nocturnal stable boundary layer (SBL) were analyzed using atmospheric soundings obtained during the field experiment for CASES-99 (Cooperative Atmosphere-Surface Exchange Study-1999) over temperature grassland in Kansas, USA. The present analysis of the nocturnal SBL heights was made using inversion strength in the vertical profiles of potential temperature, which was determined from the residual layer

  2. Influence of sward botanical composition on performance of cool temperate grassland under contrasting nitrogen fertilization regimes

    Microsoft Academic Search

    John S. Bailey

    2000-01-01

    Eight field experiments, which tested the effects of lime, phosphorus (P), and two rates of nitrogen (N) on a range of permanent grassland swards in Northern Ireland (NI), were re?examined to investigate the influence of sward botanical composition on aerial dry matter (DM) productivity under ‘low’ and ‘high’ levels of ? input. The aim of the investigation was to verify

  3. Watershed and ecosystem responses to invasive grass establishment and dominance across a desert grassland watershed

    NASA Astrophysics Data System (ADS)

    Hamerlynck, E.; Scott, R.; Polyakov, V.; Sugg, Z.; Moran, M. S.; Stone, J.; Nearing, M.

    2012-04-01

    Compared to aridland systems that have undergone rapid change in dominant vegetation growth form, the consequences to watershed and ecosystem processes following a shift in dominance between similar growth forms have not been well-studied. Following a five year drought period, strong summer monsoon rains in 2006 across the USDA-ARS Walnut Gulch Experimental Watershed near Tombstone, AZ, were accompanied by widespread native perennial grass mortality, a transient increase in annual forbs, followed by establishment and sustained dominance by the invasive South African bunchgrass, Lehmann lovegrass (Eragrostis lehmanniana) across a semiarid grassland watershed (Kendall grassland, WS#112). This loss of ecological diversity occurred across a watershed already instrumented for quantifying long-term climate, watershed, hill-slope, and ecosystem-level gas exchange. Salient findings from these data sets were: 1) annual watershed sediment discharge rapidly returned to pre-invasion levels following a large spike in 2006 that accounted for 65% of the total sediment yield summed over 35 years, 2) plot-level experimental runoff studies showed hill-slope sediment yields consistently doubled, as did growing season soil evaporation contributions to ET, and 3) the grassland was a carbon sink during dry conditions under lovegrass dominance. These findings show that while some aspects of watershed and ecosystem function rapidly re-established (i.e. sediment yield and net primary productivity), processes acting at lower spatial and temporal scales have been negatively impacted by lovegrass dominance. We believe these lower-order processes underlie the strong ecological effects associated with Lehmann lovegrass invasion, and may also accelerate landform processes and change the basic ecohydrological characteristics of semi-arid grassland watersheds.

  4. Synchronous dynamics of zooplankton competitors prevail in temperate lake ecosystems.

    PubMed

    Vasseur, David A; Fox, Jeremy W; Gonzalez, Andrew; Adrian, Rita; Beisner, Beatrix E; Helmus, Matthew R; Johnson, Catherine; Kratina, Pavel; Kremer, Colin; de Mazancourt, Claire; Miller, Elizabeth; Nelson, William A; Paterson, Michael; Rusak, James A; Shurin, Jonathan B; Steiner, Christopher F

    2014-08-01

    Although competing species are expected to exhibit compensatory dynamics (negative temporal covariation), empirical work has demonstrated that competitive communities often exhibit synchronous dynamics (positive temporal covariation). This has led to the suggestion that environmental forcing dominates species dynamics; however, synchronous and compensatory dynamics may appear at different length scales and/or at different times, making it challenging to identify their relative importance. We compiled 58 long-term datasets of zooplankton abundance in north-temperate and sub-tropical lakes and used wavelet analysis to quantify general patterns in the times and scales at which synchronous/compensatory dynamics dominated zooplankton communities in different regions and across the entire dataset. Synchronous dynamics were far more prevalent at all scales and times and were ubiquitous at the annual scale. Although we found compensatory dynamics in approximately 14% of all combinations of time period/scale/lake, there were no consistent scales or time periods during which compensatory dynamics were apparent across different regions. Our results suggest that the processes driving compensatory dynamics may be local in their extent, while those generating synchronous dynamics operate at much larger scales. This highlights an important gap in our understanding of the interaction between environmental and biotic forces that structure communities. PMID:24966312

  5. Predicting zooplankton response to environmental changes in a temperate estuarine ecosystem

    Microsoft Academic Search

    Sónia Cotrim Marques; Ulisses Miranda Azeiteiro; Sérgio Miguel Leandro; Henrique Queiroga; Ana Lígia Primo; Filipe Martinho; Ivan Viegas; Miguel Ângelo Pardal

    2008-01-01

    A novel strategy that allows to predict the responses of zooplanktonic species to environmental conditions in an estuarine\\u000a temperate ecosystem (Mondego estuary) is presented. It uses 12 indicator species from the zooplanktonic Mondego database (102\\u000a species) that are common members of the different habitats, characterized by their specific hydrological conditions. Indicator-species\\u000a analysis (ISA) was used to define and describe which

  6. Perennial grasslands enhance biodiversity and multiple ecosystem services in bioenergy landscapes.

    PubMed

    Werling, Ben P; Dickson, Timothy L; Isaacs, Rufus; Gaines, Hannah; Gratton, Claudio; Gross, Katherine L; Liere, Heidi; Malmstrom, Carolyn M; Meehan, Timothy D; Ruan, Leilei; Robertson, Bruce A; Robertson, G Philip; Schmidt, Thomas M; Schrotenboer, Abbie C; Teal, Tracy K; Wilson, Julianna K; Landis, Douglas A

    2014-01-28

    Agriculture is being challenged to provide food, and increasingly fuel, for an expanding global population. Producing bioenergy crops on marginal lands--farmland suboptimal for food crops--could help meet energy goals while minimizing competition with food production. However, the ecological costs and benefits of growing bioenergy feedstocks--primarily annual grain crops--on marginal lands have been questioned. Here we show that perennial bioenergy crops provide an alternative to annual grains that increases biodiversity of multiple taxa and sustain a variety of ecosystem functions, promoting the creation of multifunctional agricultural landscapes. We found that switchgrass and prairie plantings harbored significantly greater plant, methanotrophic bacteria, arthropod, and bird diversity than maize. Although biomass production was greater in maize, all other ecosystem services, including methane consumption, pest suppression, pollination, and conservation of grassland birds, were higher in perennial grasslands. Moreover, we found that the linkage between biodiversity and ecosystem services is dependent not only on the choice of bioenergy crop but also on its location relative to other habitats, with local landscape context as important as crop choice in determining provision of some services. Our study suggests that bioenergy policy that supports coordinated land use can diversify agricultural landscapes and sustain multiple critical ecosystem services. PMID:24474791

  7. Potential climate change impacts on temperate forest ecosystem processes

    USGS Publications Warehouse

    Peters, Emily B.; Wythers, Kirk R.; Zhang, Shuxia; Bradford, John B.; Reich, Peter B.

    2013-01-01

    Large changes in atmospheric CO2, temperature and precipitation are predicted by 2100, yet the long-term consequences for carbon, water, and nitrogen cycling in forests are poorly understood. We applied the PnET-CN ecosystem model to compare the long-term effects of changing climate and atmospheric CO2 on productivity, evapotranspiration, runoff, and net nitrogen mineralization in current Great Lakes forest types. We used two statistically downscaled climate projections, PCM B1 (warmer and wetter) and GFDL A1FI (hotter and drier), to represent two potential future climate and atmospheric CO2 scenarios. To separate the effects of climate and CO2, we ran PnET-CN including and excluding the CO2 routine. Our results suggest that, with rising CO2 and without changes in forest type, average regional productivity could increase from 67% to 142%, changes in evapotranspiration could range from –3% to +6%, runoff could increase from 2% to 22%, and net N mineralization could increase 10% to 12%. Ecosystem responses varied geographically and by forest type. Increased productivity was almost entirely driven by CO2 fertilization effects, rather than by temperature or precipitation (model runs holding CO2 constant showed stable or declining productivity). The relative importance of edaphic and climatic spatial drivers of productivity varied over time, suggesting that productivity in Great Lakes forests may switch from being temperature to water limited by the end of the century.

  8. Estimating Daytime Ecosystem Respiration to Improve Estimates of Gross Primary Production of a Temperate Forest

    PubMed Central

    Sun, Jinwei; Wu, Jiabing; Guan, Dexin; Yao, Fuqi; Yuan, Fenghui; Wang, Anzhi; Jin, Changjie

    2014-01-01

    Leaf respiration is an important component of carbon exchange in terrestrial ecosystems, and estimates of leaf respiration directly affect the accuracy of ecosystem carbon budgets. Leaf respiration is inhibited by light; therefore, gross primary production (GPP) will be overestimated if the reduction in leaf respiration by light is ignored. However, few studies have quantified GPP overestimation with respect to the degree of light inhibition in forest ecosystems. To determine the effect of light inhibition of leaf respiration on GPP estimation, we assessed the variation in leaf respiration of seedlings of the dominant tree species in an old mixed temperate forest with different photosynthetically active radiation levels using the Laisk method. Canopy respiration was estimated by combining the effect of light inhibition on leaf respiration of these species with within-canopy radiation. Leaf respiration decreased exponentially with an increase in light intensity. Canopy respiration and GPP were overestimated by approximately 20.4% and 4.6%, respectively, when leaf respiration reduction in light was ignored compared with the values obtained when light inhibition of leaf respiration was considered. This study indicates that accurate estimates of daytime ecosystem respiration are needed for the accurate evaluation of carbon budgets in temperate forests. In addition, this study provides a valuable approach to accurately estimate GPP by considering leaf respiration reduction in light in other ecosystems. PMID:25419844

  9. Characterizing forest fragments in boreal, temperate, and tropical ecosystems.

    PubMed

    Meddens, Arjan J H; Hudak, Andrew T; Evans, Jeffrey S; Gould, William A; González, Grizelle

    2008-12-01

    An increased ability to analyze landscapes in a spatial manner through the use of remote sensing leads to improved capabilities for quantifying human-induced forest fragmentation. Developments of spatially explicit methods in landscape analyses are emerging. In this paper, the image delineation software program eCognition and the spatial pattern analysis program FRAGSTATS were used to quantify patterns of forest fragments on six landscapes across three different climatic regions characterized by different moisture regimes and different influences of human pressure. Our results support the idea that landscapes with higher road and population density are more fragmented; however, there are other, equally influential factors contributing to fragmentation, such as moisture regime, historic land use, and fire dynamics. Our method provided an objective means to characterize landscapes and assess patterns of forest fragments across different forested ecosystems by addressing the limitations of pixel-based classification and incorporating image objects. PMID:19205180

  10. Limitations of net CO 2 uptake in plant species of a temperate dry loess grassland

    Microsoft Academic Search

    Zoltán Nagy; Zoltán Takács; Kálmán Szente; Zsolt Csintalan; Hartmut K. Lichtenthaler; Zoltán Tuba

    1998-01-01

    Possible limitations of net CO2 assimilation (PN) in four drought stressed loess grassland species (Festuca rupicola, Salvia nemorosa, Euphorbia pannonica, all three C3 plants, and Bothriochloa ischaemum, a C4 plant) were characterised using data from measurements of CO2 gas exchange (PN, intercellular CO2 concentration Ci and stomatal conductance Gs) and the slow kinetics of chlorophyll fluorescence (variable Chl fluorescence decrease

  11. The Effects of Warming-Shifted Plant Phenology on Ecosystem Carbon Exchange Are Regulated by Precipitation in a Semi-Arid Grassland

    PubMed Central

    Xia, Jianyang; Wan, Shiqiang

    2012-01-01

    Background The longer growing season under climate warming has served as a crucial mechanism for the enhancement of terrestrial carbon (C) sink over the past decades. A better understanding of this mechanism is critical for projection of changes in C cycling of terrestrial ecosystems. Methodology/Principal Findings A 4-year field experiment with day and night warming was conducted to examine the responses of plant phenology and their influences on plant coverage and ecosystem C cycling in a temperate steppe in northern China. Greater phenological responses were observed under night than day warming. Both day and night warming prolonged the growing season by advancing phenology of early-blooming species but without changing that of late-blooming species. However, no warming response of vegetation coverage was found for any of the eight species. The variances in species-level coverage and ecosystem C fluxes under different treatments were positively dependent upon the accumulated precipitation within phenological duration but not the length of phenological duration. Conclusions/Significance These plants' phenology is more sensitive to night than day warming, and the warming effects on ecosystem C exchange via shifting plant phenology could be mediated by precipitation patterns in semi-arid grasslands. PMID:22359660

  12. Responses of soil respiration to elevated CO[sub 2] in two California grassland ecosystems

    SciTech Connect

    Luo, Y.; Jackson, R.B.; Field, C.B.; Mooney, H.A. (Stanford Univ., CA (United States))

    1994-06-01

    Estimates of soil respiration (SR) in current and elevated CO[sub 2] are critical for predicting future global carbon budgets. We measured SR in two California grassland ecosystems (sandstone and serpentine) growing at ambient and ambient+350 ppm CO[sub 2]. SR was higher in elevated CO[sub 2] for both ecosystems in the field, but differences were not significant. At peak plant growth, SR was approximately 6 [mu]mol m[sup [minus]2]s[sup [minus]1] in elevated CO[sub 2] and 5 [mu]mol m[sup [minus]2] s[sup [minus]1] in ambient CO[sub 2] for both ecosystems. We also examined soil respiration in monocultures of 7 grassland species grown in microecosystems (10-cm diameter by 1-m deep tubes). SR was approximately 2 [mu]mol m[sup [minus]2]s[sup [minus]1] for Plantago, Bromus, Hemizona, and Calycadenia and 7 [minus] 8 [mu]mol m[sup [minus]2]s[sup [minus]2] for Lolium, Avena, and Vulpia. Elevated CO[sub 2] significantly increased soil respiration by 20-30% in Bromus, Hemizonia and Lolium monocultures. SR was significantly correlated with total plant biomass as averaged across all species.

  13. Changes in soil microbial biomass and residual indices as ecological indicators of land use change in temperate permanent grassland.

    PubMed

    Murugan, Rajasekaran; Loges, Ralf; Taube, Friedhelm; Sradnick, André; Joergensen, Rainer Georg

    2014-05-01

    The relationship between microbial biomass, residues and their contribution to microbial turnover is important to understand ecosystem C storage. The effects of permanent grassland (100 % ryegrass--PG), conversion to modified grassland (mixture of grass and clover--MG) or maize monoculture (MM) on the dynamics of soil organic C (SOC), microbial biomass, fungal ergosterol and microbial residues (bacterial muramic acid and fungal glucosamine) were investigated. Cattle slurry was applied to quantify the effects of fertilisation on microbial residues and functional diversity of microbial community across land use types. Slurry application significantly increased the stocks of microbial biomass C and S and especially led to a shift in microbial residues towards bacterial tissue. The MM treatment decreased the stocks of SOC, microbial biomass C, N and S and microbial residues compared with the PG and MG treatments at 0-40 cm depth. The MM treatment led to a greater accumulation of saprotrophic fungi, as indicated by the higher ergosterol-to-microbial biomass C ratio and lower microbial biomass C/S ratio compared with the grassland treatments. The absence of a white clover population in the PG treatment caused a greater accumulation of fungal residues (presumably arbuscular mycorrhizal fungi (AMF), which do not contain ergosterol but glucosamine), as indicated by the significantly higher fungal C-to-bacterial C ratio and lower ergosterol-to-microbial biomass C ratio compared with the MG treatment. In addition to these microbial biomass and residual indices, the community level physiological profiles (CLPP) demonstrated distinct differences between the PG and MG treatments, suggesting the potential of these measurements to act as an integrative indicator of soil functioning. PMID:24549746

  14. Short-term sequestration of slurry-derived carbon into particle size fractions of a temperate grassland soil.

    PubMed

    Bol, Roland; Moering, Judith; Preedy, Neil; Glaser, Bruno

    2004-03-01

    Surface application of animal wastes in intensive grassland systems has caused growing environmental problems during the last decade and, therefore, increasing public and scientific concern. In the present study we examined if the natural abundance 13C stable isotope tracer techniques could be used to investigate a poorly defined aspect of waste application, i.e. incorporation of slurry-derived C and its distribution in soil organic matter (SOM) fractions with different turnover times of a pasture soil. C3 and C4 slurries (delta13C(V-PDB) = -30.7/1000 and -21.3/1000, respectively) from cows fed either on a maize (C4) or perennial ryegrass (C3) diet were applied to a C3 soil with a delta13C value of (-30.0+/-0.2)/1000. The cattle slurry was applied at 50 m3 ha(-1). Coarse sand, fine sand, silt, clay and fine clay were isolated from bulk soil samples (0-2 cm depth), freeze-dried and ground prior to total organic C (TOC) using elemental analysis and 13C natural abundance analysis by isotope-ratio mass spectrometry. The stable isotope tracer technique did allow to quantify the short-term sequestration of slurry-derived C in particle-size fractions of the grassland soil. Slurry-derived carbon was sequestered in various amounts in the five particle-size fractions, but most of it was sequestered in the coarse sand fraction during the two week experiment. The preferential input into the coarse sand fraction suggests that only the larger particulate slurry-derived materials were trapped into the soil during the experimental period. Less than 40% of the applied slurry-derived C was sequestered into the soil, suggesting a potential for large losses into the wider environment. The practice of surface spreading of slurry to temperate grassland soils is clearly not efficient, and improvements in slurry application methods, such as incorporation directly into the soil, should therefore be encouraged. PMID:15085987

  15. Responses of net ecosystem CO 2 exchange to nitrogen fertilization in experimentally manipulated grassland ecosystems

    Microsoft Academic Search

    Xiaoli Cheng; Yiqi Luo; Bo Su; Paul S. J. Verburg; Dafeng Hui; Daniel Obrist; John A. Arnone III; Dale W. Johnson; R. David Evans

    2009-01-01

    Nitrogen (N) addition enhances primary productivity of terrestrial ecosystems. However, the effects of N fertilization and\\/or deposition on net ecosystem CO2 exchange (NEE) are not fully understood. The effects of N on NEE were investigated in two experimental cheatgrass ecosystems in Ecologically Controlled Enclosed Lysimeter Laboratories (EcoCELLs), Reno, Nevada. In this experiment, no N fertilization was added to the two

  16. Plant community responses to precipitation and spatial pattern of nitrogen supply in an experimental grassland ecosystem.

    PubMed

    Xi, Nianxun; Carrčre, Pascal; Bloor, Juliette M G

    2015-06-01

    Recent work suggests that soil nutrient heterogeneity may modulate plant responses to drivers of global change, but interactions between N heterogeneity and changes in rainfall regime remain poorly understood. We used a model grassland system to investigate the interactive effects of N application pattern (homogeneous, heterogeneous) and precipitation-magnitude manipulation during the growing season (control, +50 % rainfall, -50 % rainfall) on aboveground biomass and plant community dominance patterns. Our study resulted in four major findings: patchy N addition increased within-plot variability in plant size structure at the species level, but did not alter total aboveground biomass; patchy N addition increased community dominance and caused a shift in the ranking of subordinate plant species; unlike community-level biomass, plant species differed in their biomass response to the rainfall treatments; and neither aboveground biomass nor community dominance showed significant interactions between N pattern and rainfall manipulation, suggesting that grassland responses to patchy N inputs are insensitive to water addition or rainfall reduction in our temperate study system. Overall, our results indicate that the spatial pattern of N inputs has greater effects on species biomass variability and community dominance than on aboveground production. These short-term changes in plant community structure may have significant implications for longer-term patterns of vegetation dynamics and plant-soil feedbacks. Moreover our results suggest that the magnitude of precipitation during the growing season plays a limited role in grassland responses to heterogeneous organic N inputs, emphasizing the need to consider other components of precipitation change in future heterogeneity studies. PMID:25783490

  17. Transfer of a cyanobacterial neurotoxin within a temperate aquatic ecosystem suggests pathways for human exposure

    PubMed Central

    Jonasson, Sara; Eriksson, Johan; Berntzon, Lotta; Spá?il, Zden?k; Ilag, Leopold L.; Ronnevi, Lars-Olof; Rasmussen, Ulla; Bergman, Birgitta

    2010-01-01

    ?-methylamino-L-alanine (BMAA), a neurotoxic nonprotein amino acid produced by most cyanobacteria, has been proposed to be the causative agent of devastating neurodegenerative diseases on the island of Guam in the Pacific Ocean. Because cyanobacteria are widespread globally, we hypothesized that BMAA might occur and bioaccumulate in other ecosystems. Here we demonstrate, based on a recently developed extraction and HPLC-MS/MS method and long-term monitoring of BMAA in cyanobacterial populations of a temperate aquatic ecosystem (Baltic Sea, 2007–2008), that BMAA is biosynthesized by cyanobacterial genera dominating the massive surface blooms of this water body. BMAA also was found at higher concentrations in organisms of higher trophic levels that directly or indirectly feed on cyanobacteria, such as zooplankton and various vertebrates (fish) and invertebrates (mussels, oysters). Pelagic and benthic fish species used for human consumption were included. The highest BMAA levels were detected in the muscle and brain of bottom-dwelling fishes. The discovery of regular biosynthesis of the neurotoxin BMAA in a large temperate aquatic ecosystem combined with its possible transfer and bioaccumulation within major food webs, some ending in human consumption, is alarming and requires attention. PMID:20439734

  18. Growth response of temperate mountain grasslands to inter-annual variations in snow cover duration

    NASA Astrophysics Data System (ADS)

    Choler, P.

    2015-06-01

    A remote sensing approach is used to examine the direct and indirect effects of snow cover duration and weather conditions on the growth response of mountain grasslands located above the tree line in the French Alps. Time-integrated Normalized Difference Vegetation Index (NDVIint), used as a surrogate for aboveground primary productivity, and snow cover duration were derived from a 13-year long time series of the Moderate-resolution Imaging Spectroradiometer (MODIS). A regional-scale meteorological forcing that accounted for topographical effects was provided by the SAFRAN-CROCUS-MEPRA model chain. A hierarchical path analysis was developed to analyze the multivariate causal relationships between forcing variables and proxies of primary productivity. Inter-annual variations in primary productivity were primarily governed by year-to-year variations in the length of the snow-free period and to a much lesser extent by temperature and precipitation during the growing season. A prolonged snow cover reduces the number and magnitude of frost events during the initial growth period but this has a negligible impact on NDVIint as compared to the strong negative effect of a delayed snow melting. The maximum NDVI slightly responded to increased summer precipitation and temperature but the impact on productivity was weak. The period spanning from peak standing biomass to the first snowfall accounted for two-thirds of NDVIint and this explained the high sensitivity of NDVIint to autumn temperature and autumn rainfall that control the timing of the first snowfall. The ability of mountain plants to maintain green tissues during the whole snow-free period along with the relatively low responsiveness of peak standing biomass to summer meteorological conditions led to the conclusion that the length of the snow-free period is the primary driver of the inter-annual variations in primary productivity of mountain grasslands.

  19. Testing the Link between Functional Diversity and Ecosystem Functioning in a Minnesota Grassland Experiment

    PubMed Central

    Butterfield, Bradley J.; Reich, Peter B.

    2012-01-01

    The functional diversity of a community can influence ecosystem functioning and reflects assembly processes. The large number of disparate metrics used to quantify functional diversity reflects the range of attributes underlying this concept, generally summarized as functional richness, functional evenness, and functional divergence. However, in practice, we know very little about which attributes drive which ecosystem functions, due to a lack of field-based tests. Here we test the association between eight leading functional diversity metrics (Rao’s Q, FD, FDis, FEve, FDiv, convex hull volume, and species and functional group richness) that emphasize different attributes of functional diversity, plus 11 extensions of these existing metrics that incorporate heterogeneous species abundances and trait variation. We assess the relationships among these metrics and compare their performances for predicting three key ecosystem functions (above- and belowground biomass and light capture) within a long-term grassland biodiversity experiment. Many metrics were highly correlated, although unique information was captured in FEve, FDiv, and dendrogram-based measures (FD) that were adjusted by abundance. FD adjusted by abundance outperformed all other metrics in predicting both above- and belowground biomass, although several others also performed well (e.g. Rao’s Q, FDis, FDiv). More generally, trait-based richness metrics and hybrid metrics incorporating multiple diversity attributes outperformed evenness metrics and single-attribute metrics, results that were not changed when combinations of metrics were explored. For light capture, species richness alone was the best predictor, suggesting that traits for canopy architecture would be necessary to improve predictions. Our study provides a comprehensive test linking different attributes of functional diversity with ecosystem function for a grassland system. PMID:23300787

  20. Ground-based grasslands data to support remote sensing and ecosystem modeling of terrestrial primary production

    SciTech Connect

    Olson, R.J.; Turner, R.S. [Oak Ridge National Lab., TN (United States); Scurlock, J.M.O. [King`s College London, (England); Jennings, S.V. [Tennessee Univ., Knoxville, TN (United States)

    1995-12-31

    Estimating terrestrial net primary production (NPP) using remote- sensing tools and ecosystem models requires adequate ground-based measurements for calibration, parameterization, and validation. These data needs were strongly endorsed at a recent meeting of ecosystem modelers organized by the International Geosphere-Biosphere Programme`s (IGBP`s) Data and Information System (DIS) and its Global Analysis, Interpretation, and Modelling (GAIM) Task Force. To meet these needs, a multinational, multiagency project is being coordinated by the IGBP DIS to compile existing NPP data from field sites and to regionalize NPP point estimates to various-sized grid cells. Progress at Oak Ridge National Laboratory (ORNL) on compiling NPP data for grasslands as part of the IGBP DIS data initiative is described. Site data and associated documentation from diverse field studies are being acquired for selected grasslands and are being reviewed for completeness, consistency, and adequacy of documentation, including a description of sampling methods. Data are being compiled in a database with spatial, temporal, and thematic characteristics relevant to remote sensing and global modeling. NPP data are available from the ORNL Distributed Active Archive Center (DAAC) for biogeochemical dynamics. The ORNL DAAC is part of the Earth Observing System Data and Information System, of the US National Aeronautics and Space Administration.

  1. Plant and soil microbial responses to defoliation in temperate semi-natural grassland

    Microsoft Academic Search

    Ramon Guitian; Richard D. Bardgett

    2000-01-01

    There is much interest in understanding the nature of feedback mechanisms between plants and soil organisms in grazed ecosystems.\\u000a In this study, we examine the effects of different intensities of defoliation on the growth of three dominant grass species,\\u000a and observe how these plant responses relate to the biomass and activity of the microbial community in the root zone. Our

  2. Connecting Soil Organic Carbon and Root Biomass with Land-Use and Vegetation in Temperate Grassland

    PubMed Central

    McGranahan, Devan Allen; Daigh, Aaron L.; Veenstra, Jessica J.; Engle, David M.; Miller, James R.; Debinski, Diane M.

    2014-01-01

    Soils contain much of Earth's terrestrial organic carbon but are sensitive to land-use. Rangelands are important to carbon dynamics and are among ecosystems most widely impacted by land-use. While common practices like grazing, fire, and tillage affect soil properties directly related to soil carbon dynamics, their magnitude and direction of change vary among ecosystems and with intensity of disturbance. We describe variability in soil organic carbon (SOC) and root biomass—sampled from 0–170?cm and 0–100?cm, respectively—in terms of soil properties, land-use history, current management, and plant community composition using linear regression and multivariate ordination. Despite consistency in average values of SOC and root biomass between our data and data from rangelands worldwide, broad ranges in root biomass and SOC in our data suggest these variables are affected by other site-specific factors. Pastures with a recent history of severe grazing had reduced root biomass and greater bulk density. Ordination suggests greater exotic species richness is associated with lower root biomass but the relationship was not apparent when an invasive species of management concern was specifically tested. We discuss how unexplained variability in belowground properties can complicate measurement and prediction of ecosystem processes such as carbon sequestration. PMID:25401142

  3. Effects of ploughing on land-atmosphere exchange of greenhouse gases in a managed temperate grassland in central Scotland

    NASA Astrophysics Data System (ADS)

    Helfter, Carole; Drewer, Julia; Anderson, Margaret; Scholtes, Bob; Rees, Bob; Skiba, Ute

    2015-04-01

    Grasslands are important ecosystems covering > 20% and > 30% of EU and Scotland's land area respectively. Management practices such as grazing, fertilisation and ploughing can have significant short- and long-term effects on greenhouse gas exchange. Here we report on two separate ploughing events two years apart in adjacent grasslands under common management. The Easter Bush grassland, located 10 km south of Edinburgh (55° 52'N, 3° 2'W), comprises two fields separated by a fence and is used for grazing by sheep and cattle. The vegetation is predominantly Lolium perenne (> 90%) growing on poorly drained clay loam. The fields receive several applications of mineral fertiliser a year in spring and summer. Net ecosystem exchange (NEE) of carbon dioxide (CO2) has been monitored continuously by eddy-covariance (EC) since 2002 which has demonstrated that the site is a consistent yet variable sink of atmospheric CO2. The EC system comprises a LI-COR 7000 closed-path analyser and a Gill Instruments Windmaster Pro ultrasonic anemometer mounted atop a 2.5 m mast located along the fence line separating the fields. In addition, fluxes of nitrous oxide (N2O), methane (CH4)and CO2were measured with static chambers installed along transects in each field. Gas samples collected from the chambers were analysed by gas chromatography and fluxes calculated for each 60-minute sampling period. The ploughing events in 2012 and 2014 exhibited multiple similarities in terms of NEE. The light response (i.e. relationship between CO2 flux, and photosynthetically active radiation, PAR) of the NF and SF during the month preceding each ploughing event was of comparable magnitude in both years. Following ploughing, CO2 uptake ceased in the ploughed field for approximately one month and full recovery of the photosynthetic potential was observed after ca. 2 months. During the month following the 2014 ploughing event, the ploughed NF released on average 333 ± 17 mg CO2-C m-2 h-1. In contrast, the SF net uptake during the same period was -79 ± 19 mg CO2-C m-2 h-1. Ploughing caused a net release of carbon of 183 g CO2-C m-2 during the month following ploughing, thus turning the grassland into a potent CO2 source. Chamber measurements of CH4 and N2O exhibited high spatial variability in 2012 and no statistical difference could be established between fields and treatments. CH4 fluxes were high in both fields after ploughing which was presumably linked to air temperature. N2O fluxes in the ploughed SF reached on average 100 ?g N2O-N m-2 h-1 29 days after ploughing which corresponded to ca. 20 times the background level recorded at the site. Fluxes of N2O were however considerably larger in 2014, peaking at 2570 ?g N2O-N m-2 h-1 29 days after ploughing. Contrarily to 2012, substantial and statistically significant CH4 emissions were recorded in 2014 in the ploughed field. Whilst spatial variability was high in both years it can nevertheless be concluded that ploughing had substantial adverse short term effects on emissions and that environmental conditions greatly impacted the magnitude of CH4 and N2O fluxes.

  4. Rapid response of a grassland ecosystem to an experimental manipulation of a keystone rodent and domestic livestock.

    PubMed

    Davidson, Ana D; Ponce, Eduardo; Lightfoot, David C; Fredrickson, Ed L; Brown, James H; Cruzado, Juan; Brantley, Sandra L; Sierra-Corona, Rodrigo; List, Rurik; Toledo, David; Ceballos, Gerardo

    2010-11-01

    Megaherbivores and small burrowing mammals commonly coexist and play important functional roles in grassland ecosystems worldwide. The interactive effects of these two functional groups of herbivores in shaping the structure and function of grassland ecosystems are poorly understood. In North America's central grasslands, domestic cattle (Bos taurus) have supplanted bison (Bison bison), and now coexist with prairie dogs (Cynomys spp.), a keystone burrowing rodent. Understanding the ecological relationships between cattle and prairie dogs and their independent and interactive effects is essential to understanding the ecology and important conservation issues affecting North American grassland ecosystems. To address these needs, we established a long-term manipulative experiment that separates the independent and interactive effects of prairie dogs and cattle using a 2 x 2 factorial design. Our study is located in the Janos-Casas Grandes region of northwestern Chihuahua, Mexico, which supports one of the largest remaining complexes of black-tailed prairie dogs (C. ludovicianus). Two years of posttreatment data show nearly twofold increases in prairie dog abundance on plots grazed by cattle compared to plots without cattle. This positive effect of cattle on prairie dogs resulted in synergistic impacts when they occurred together. Vegetation height was significantly lower on the plots where both species co-occurred compared to where either or both species was absent. The treatments also significantly affected abundance and composition of other grassland animal species, including grasshoppers and banner-tailed kangaroo rats (Dipodomys spectabilis). Our results demonstrate that two different functional groups of herbivorous mammals, burrowing mammals and domestic cattle, have distinctive and synergistic impacts in shaping the structure and function of grassland ecosystems. PMID:21141180

  5. Plant species richness drives the density and diversity of Collembola in temperate grassland

    NASA Astrophysics Data System (ADS)

    Sabais, Alexander C. W.; Scheu, Stefan; Eisenhauer, Nico

    2011-05-01

    Declining biodiversity is one of the most important aspects of anthropogenic global change phenomena, but the implications of plant species loss for soil decomposers are little understood. We used the experimental grassland community of the Jena Experiment to assess the response of density and diversity of Collembola to varying plant species richness, plant functional group richness and plant functional group identity. We sampled the experimental plots in spring and autumn four years after establishment of the experimental plant communities. Collembola density and diversity significantly increased with plant species and plant functional group richness highlighting the importance of the singular hypothesis for soil invertebrates. Generally, grasses and legumes beneficially affected Collembola density and diversity, whereas effects of small herbs usually were detrimental. These impacts were largely consistent in spring and autumn. By contrast, in the presence of small herbs the density of hemiedaphic Collembola and the diversity of Isotomidae increased in spring whereas they decreased in autumn. Beneficial impacts of plant diversity as well as those of grasses and legumes were likely due to increased root and microbial biomass, and elevated quantity and quality of plant residues serving as food resources for Collembola. By contrast, beneficial impacts of small herbs in spring probably reflect differences in microclimatic conditions, and detrimental effects in autumn likely were due to low quantity and quality of resources. The results point to an intimate relationship between plants and the diversity of belowground biota, even at small spatial scales, contrasting the findings of previous studies. The pronounced response of soil animals in the present study was presumably due to the fact that plant communities had established over several years. As decomposer invertebrates significantly impact plant performance, changes in soil biota density and diversity are likely to have major feedbacks on plant community productivity and composition.

  6. Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests

    PubMed Central

    Talhelm, Alan F; Pregitzer, Kurt S; Kubiske, Mark E; Zak, Donald R; Campany, Courtney E; Burton, Andrew J; Dickson, Richard E; Hendrey, George R; Isebrands, J G; Lewin, Keith F; Nagy, John; Karnosky, David F

    2014-01-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2) and tropospheric ozone (O3) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3. Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r2 = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m?2) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (?NPP/?N) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2. Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. PMID:24604779

  7. Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests.

    PubMed

    Talhelm, Alan F; Pregitzer, Kurt S; Kubiske, Mark E; Zak, Donald R; Campany, Courtney E; Burton, Andrew J; Dickson, Richard E; Hendrey, George R; Isebrands, J G; Lewin, Keith F; Nagy, John; Karnosky, David F

    2014-08-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2 ) and tropospheric ozone (O3 ) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3 . Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r(2) = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m(-2) ) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (?NPP/?N) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2 . Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. PMID:24604779

  8. How do more extreme rainfall regimes affect ecosystem fluxes in seasonally water-limited Northern Hemisphere temperate shrublands and forests?

    NASA Astrophysics Data System (ADS)

    Ross, I.; Misson, L.; Rambal, S.; Arneth, A.; Scott, R. L.; Carrara, A.; Cescatti, A.; Genesio, L.

    2011-09-01

    As a result of climate change, rainfall regimes became more extreme over the course of the 20th century, characterised by fewer and larger rainfall events. Such changes are expected to continue throughout the current century. The effect of changes in the temporal distribution of rainfall on ecosystem carbon fluxes is poorly understood, with most available information coming from experimental studies of grassland ecosystems. Here, continuous measurements of ecosystem carbon fluxes and precipitation from the worldwide FLUXNET network of eddy-covariance sites are exploited to investigate the effects of differences in rainfall distribution on the carbon balance of seasonally water-limited shrubland and forest sites. Once the strong dependence of ecosystem fluxes on total annual rainfall amount is accounted for, results show that sites with more extreme rainfall distributions have significantly lower gross productivity, slightly lower ecosystem respiration and consequently a smaller net ecosystem productivity.

  9. Prerequisites for application of hyperbolic relaxed eddy accumulation on managed grasslands and alternative net ecosystem exchange flux partitioning

    NASA Astrophysics Data System (ADS)

    Riederer, M.; Hübner, J.; Ruppert, J.; Brand, W. A.; Foken, T.

    2014-12-01

    Relaxed eddy accumulation is still applied in ecosystem sciences for measuring trace gas fluxes. On managed grasslands, the length of time between management events and the application of relaxed eddy accumulation has an essential influence on the determination of the proportionality factor b and thus on the resulting flux. In this study this effect is discussed for the first time. Also, scalar similarity between proxy scalars and scalars of interest is affected until the ecosystem has completely recovered. Against this background, CO2 fluxes were continuously measured and 13CO2 isofluxes were determined with a high measurement precision on two representative days in summer 2010. Moreover, a common method for the partitioning of the net ecosystem exchange into assimilation and respiration based on temperature and light response was compared with an isotopic approach directly based on the isotope discrimination of the biosphere. This approach worked well on the grassland site and could enhance flux partitioning results by better reproducing the environmental conditions.

  10. Water- and Plant-Mediated Responses of Ecosystem Carbon Fluxes to Warming and Nitrogen Addition on the Songnen Grassland in Northeast China

    PubMed Central

    Jiang, Li; Guo, Rui; Zhu, Tingcheng; Niu, Xuedun; Guo, Jixun; Sun, Wei

    2012-01-01

    Background Understanding how grasslands are affected by a long-term increase in temperature is crucial to predict the future impact of global climate change on terrestrial ecosystems. Additionally, it is not clear how the effects of global warming on grassland productivity are going to be altered by increased N deposition and N addition. Methodology/Principal Findings In-situ canopy CO2 exchange rates were measured in a meadow steppe subjected to 4-year warming and nitrogen addition treatments. Warming treatment reduced net ecosystem CO2 exchange (NEE) and increased ecosystem respiration (ER); but had no significant impacts on gross ecosystem productivity (GEP). N addition increased NEE, ER and GEP. However, there were no significant interactions between N addition and warming. The variation of NEE during the four experimental years was correlated with soil water content, particularly during early spring, suggesting that water availability is a primary driver of carbon fluxes in the studied semi-arid grassland. Conclusion/Significance Ecosystem carbon fluxes in grassland ecosystems are sensitive to warming and N addition. In the studied water-limited grassland, both warming and N addition influence ecosystem carbon fluxes by affecting water availability, which is the primary driver in many arid and semiarid ecosystems. It remains unknown to what extent the long-term N addition would affect the turn-over of soil organic matter and the C sink size of this grassland. PMID:23028848

  11. Niche partitioning in arbuscular mycorrhizal communities in temperate grasslands: a lesson from adjacent serpentine and nonserpentine habitats.

    PubMed

    Kohout, Petr; Doubková, Pavla; Bahram, Mohammad; Suda, Jan; Tedersoo, Leho; Vo?íšková, Jana; Sudová, Radka

    2015-04-01

    Arbuscular mycorrhizal fungi (AMF) represent an important soil microbial group playing a fundamental role in many terrestrial ecosystems. We explored the effects of deterministic (soil characteristics, host plant life stage, neighbouring plant communities) and stochastic processes on AMF colonization, richness and community composition in roots of Knautia arvensis (Dipsacaceae) plants from three serpentine grasslands and adjacent nonserpentine sites. Methodically, the study was based on 454-sequencing of the ITS region of rDNA. In total, we detected 81 molecular taxonomical operational units (MOTUs) belonging to the Glomeromycota. Serpentine character of the site negatively influenced AMF root colonization, similarly as higher Fe concentration. AMF MOTUs richness linearly increased along a pH gradient from 3.5 to 5.8. Contrary, K and Cr soil concentration had a negative influence on AMF MOTUs richness. We also detected a strong relation between neighbouring plant community composition and AMF MOTUs richness. Although spatial distance between the sampled sites (c. 0.3-3 km) contributed to structuring AMF communities in K. arvensis roots, environmental parameters were key factors in this respect. In particular, the composition of AMF communities was shaped by the complex of serpentine conditions, pH and available soil Ni concentration. The composition of AMF communities was also dependent on host plant life stage (vegetative vs. generative). Our study supports the dominance of deterministic factors in structuring AMF communities in heterogeneous environment composed of an edaphic mosaic of serpentine and nonserpentine soils. PMID:25753913

  12. Climate change impacts on stream carbon export from coastal temperate rainforest ecosystems in Alaska (Invited)

    NASA Astrophysics Data System (ADS)

    Hood, E. W.

    2013-12-01

    Coastal temperate rainforests (CTR) in Alaska contain about 10% of the total carbon in the forests of the conterminous United States. CTR ecosystems span a large environmental gradient that ranges from icefields mantling the Coast Mountains to carbon-rich conifer forests along the coastal margin and within the islands of the Alexander Archipelago in the Gulf of Alaska. Riverine dissolved organic carbon (DOC) export from Alaskan CTR ecosystems, which can exceed 2 Tg C yr-1, is large relative to other northern ecosystems as a result of high rates of specific discharge (~2.5 m yr-1) and an abundance of organic soils found in peatlands and forested wetlands. Runoff from glaciers, which are rapidly thinning and retreating, has also been shown to an important contributor to land-to-ocean fluxes of DOC in this region. Downscaled regional climate models suggest that CTR ecosystems in Alaska will become warmer and wetter in coming decades, with uncertain effects on riverine organic matter (OM) export. Changes in watershed OM export are likely to be driven by changes in both hydrology and the availability of OM in terrestrial source pools. However, the impacts of these climate driven changes will vary with watershed landcover across the continuum from icefields to coastal temperate forests. Expected hydrological perturbations include changes in the timing and magnitude of streamflow associated with shifts in: 1) the extent and duration of seasonal snowcover and 2) the mass balance of glaciers and icefields in the Coast Mountains. The availability of OM for export along hydrologic flowpaths will likely be altered by increased soil temperatures and shifts in water table elevations during the summer/fall runoff season. This will be particularly true for organic carbon export from peatlands in which changes in temperature and oxygen availability can strongly impact rates of organic matter decomposition. This talk will explore how climate-driven changes in hydrology and terrestrial organic matter stocks are expected to interact and modify riverine organic carbon export from CTR watersheds to near-shore marine ecosystems along the Gulf of Alaska.

  13. Ecosystem properties of semiarid savanna grassland in West Africa and its relationship with environmental variability.

    PubMed

    Tagesson, Torbern; Fensholt, Rasmus; Guiro, Idrissa; Rasmussen, Mads Olander; Huber, Silvia; Mbow, Cheikh; Garcia, Monica; Horion, Stéphanie; Sandholt, Inge; Holm-Rasmussen, Bo; Göttsche, Frank M; Ridler, Marc-Etienne; Olén, Niklas; Lundegard Olsen, Jřrgen; Ehammer, Andrea; Madsen, Mathias; Olesen, Folke S; Ardö, Jonas

    2015-01-01

    The Dahra field site in Senegal, West Africa, was established in 2002 to monitor ecosystem properties of semiarid savanna grassland and their responses to climatic and environmental change. This article describes the environment and the ecosystem properties of the site using a unique set of in situ data. The studied variables include hydroclimatic variables, species composition, albedo, normalized difference vegetation index (NDVI), hyperspectral characteristics (350-1800 nm), surface reflectance anisotropy, brightness temperature, fraction of absorbed photosynthetic active radiation (FAPAR), biomass, vegetation water content, and land-atmosphere exchanges of carbon (NEE) and energy. The Dahra field site experiences a typical Sahelian climate and is covered by coexisting trees (~3% canopy cover) and grass species, characterizing large parts of the Sahel. This makes the site suitable for investigating relationships between ecosystem properties and hydroclimatic variables for semiarid savanna ecosystems of the region. There were strong interannual, seasonal and diurnal dynamics in NEE, with high values of ~-7.5 g C m(-2)  day(-1) during the peak of the growing season. We found neither browning nor greening NDVI trends from 2002 to 2012. Interannual variation in species composition was strongly related to rainfall distribution. NDVI and FAPAR were strongly related to species composition, especially for years dominated by the species Zornia glochidiata. This influence was not observed in interannual variation in biomass and vegetation productivity, thus challenging dryland productivity models based on remote sensing. Surface reflectance anisotropy (350-1800 nm) at the peak of the growing season varied strongly depending on wavelength and viewing angle thereby having implications for the design of remotely sensed spectral vegetation indices covering different wavelength regions. The presented time series of in situ data have great potential for dryland dynamics studies, global climate change related research and evaluation and parameterization of remote sensing products and dynamic vegetation models. PMID:25204271

  14. Relationships between Plant Diversity and the Abundance and ?-Diversity of Predatory Ground Beetles (Coleoptera: Carabidae) in a Mature Asian Temperate Forest Ecosystem

    PubMed Central

    Zou, Yi; Sang, Weiguo; Bai, Fan; Axmacher, Jan Christoph

    2013-01-01

    A positive relationship between plant diversity and both abundance and diversity of predatory arthropods is postulated by the Enemies Hypothesis, a central ecological top-down control hypothesis. It has been supported by experimental studies and investigations of agricultural and grassland ecosystems, while evidence from more complex mature forest ecosystems is limited. Our study was conducted on Changbai Mountain in one of the last remaining large pristine temperate forest environments in China. We used predatory ground beetles (Coleoptera: Carabidae) as target taxon to establish the relationship between phytodiversity and their activity abundance and diversity. Results showed that elevation was the only variable included in both models predicting carabid activity abundance and ?-diversity. Shrub diversity was negatively and herb diversity positively correlated with beetle abundance, while shrub diversity was positively correlated with beetle ?-diversity. Within the different forest types, a negative relationship between plant diversity and carabid activity abundance was observed, which stands in direct contrast to the Enemies Hypothesis. Furthermore, plant species density did not predict carabid ?-diversity. In addition, the density of herbs, which is commonly believed to influence carabid movement, had little impact on the beetle activity abundance recorded on Changbai Mountain. Our study indicates that in a relatively large and heterogeneous mature forest area, relationships between plant and carabid diversity are driven by variations in environmental factors linked with altitudinal change. In addition, traditional top-down control theories that are suitable in explaining diversity patterns in ecosystems of low diversity appear to play a much less pronounced role in highly complex forest ecosystems. PMID:24376582

  15. Effects of Ocean Acidification on Temperate Coastal Marine Ecosystems and Fisheries in the Northeast Pacific

    PubMed Central

    Haigh, Rowan; Ianson, Debby; Holt, Carrie A.; Neate, Holly E.; Edwards, Andrew M.

    2015-01-01

    As the oceans absorb anthropogenic CO2 they become more acidic, a problem termed ocean acidification (OA). Since this increase in CO2 is occurring rapidly, OA may have profound implications for marine ecosystems. In the temperate northeast Pacific, fisheries play key economic and cultural roles and provide significant employment, especially in rural areas. In British Columbia (BC), sport (recreational) fishing generates more income than commercial fishing (including the expanding aquaculture industry). Salmon (fished recreationally and farmed) and Pacific Halibut are responsible for the majority of fishery-related income. This region naturally has relatively acidic (low pH) waters due to ocean circulation, and so may be particularly vulnerable to OA. We have analyzed available data to provide a current description of the marine ecosystem, focusing on vertical distributions of commercially harvested groups in BC in the context of local carbon and pH conditions. We then evaluated the potential impact of OA on this temperate marine system using currently available studies. Our results highlight significant knowledge gaps. Above trophic levels 2–3 (where most local fishery-income is generated), little is known about the direct impact of OA, and more importantly about the combined impact of multi-stressors, like temperature, that are also changing as our climate changes. There is evidence that OA may have indirect negative impacts on finfish through changes at lower trophic levels and in habitats. In particular, OA may lead to increased fish-killing algal blooms that can affect the lucrative salmon aquaculture industry. On the other hand, some species of locally farmed shellfish have been well-studied and exhibit significant negative direct impacts associated with OA, especially at the larval stage. We summarize the direct and indirect impacts of OA on all groups of marine organisms in this region and provide conclusions, ordered by immediacy and certainty. PMID:25671596

  16. [Microbial response mechanism for drying and rewettin g effect on soil respiration in grassland ecosystem: a review].

    PubMed

    He, Yun-Long; Qi, Yu-Chun; Dong, Yun-She; Peng, Qin; Sun, Liang-Jie; Jia, Jun-Qiang; Guo, Shu-Fang; Yan, Zhong-Qing

    2014-11-01

    As one of the most important and wide distribution community type among terrestrial ecosystems, grassland ecosystem plays a critical role in the global carbon cycles and climate regulation. China has extremely rich grassland resources, which have a huge carbon sequestration potential and are an important part of the global carbon cycle. Drying and rewetting is a common natural phenomenon in soil, which might accelerate soil carbon mineralization process, increase soil respiration and exert profound influence on microbial activity and community structure. Under the background of the global change, the changes in rainfall capacity, strength and frequency would inevitably affect soil drying and wetting cycles, and thus change the microbial activity and community structure as well as soil respiration, and then exert important influence on global carbon budget. In this paper, related references in recent ten years were reviewed. The source of soil released, the trend of soil respiration over time and the relationship between soil respiration and microbial biomass, microbial activity and microbial community structure during the processes of dry-rewetting cycle were analyzed and summarized, in order to better understand the microbial response mechanism for drying and rewetting effecting on soil respiration in grassland ecosystem, and provide a certain theoretical basis for more accurate evaluation and prediction of future global carbon balance of terrestrial ecosystems and climate change. PMID:25898639

  17. Carbon fluxes of surfaces vs. ecosystems: advantages of measuring eddy covariance and soil respiration simultaneously in dry grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Nagy, Z.; Pintér, K.; Pavelka, M.; Darenová, E.; Balogh, J.

    2011-09-01

    An automated open system for measurement of soil CO2 efflux (Rsc) was developed and calibrated against known fluxes. The system was tested in the field, while estimating soil respiration simultaneously by the gradient method (Rsg) at a dry, sandy grassland site (Bugac, Hungary). Ecosystem respiration (Rego) was measured using the eddy covariance technique. The small chamber size (5 cm in diameter) made it possible to use the chambers in vegetation gaps, thereby avoiding the necessity of removing shoots and disturbing the spatial structure of vegetation and the upper soil layer. Low air flow rates associated with small chamber volume and chamber design allowed the overpressure range to stabilize between 0.05-0.12 Pa. The correlation between ecosystem and soil CO2 efflux rates as measured by the independent methods was significant, Reco rates were similar or even lower than Rsc in the low flux (up to 2 ?mol CO2 m-2 s-1) range but the differences were within the uncertainty limits for the two fluxes. Rsc from trenched and non-trenched plots amounted to 16 % and 44 % of Reco, respectively. The gradient method showed both up and downward CO2 fluxes originating from the main rooting zone after rains. Diffusive retardation played a smaller role than CO2 production considering the soil air CO2 concentration increase after rains in a given layer. Downward fluxes within the soil profile amounted to 15 % of the simultaneous upward fluxes and to ~7.6 % of the total (upward) effluxes during the 3-month study. The upper 5 cm soil layer contributed to ~50 % of the total soil CO2 efflux. Downward fluxes are expected to seriously affect (1) the Reco vs. temperature response functions and (2) the net ecosystem exchange of CO2 (NEE) vs. photon flux density response functions, therefore potentially affecting the gap filling procedures and to lead to a situation (3) when the measured surface and the real time ecosystem fluxes will necessarily differ in the short term. Simultaneous measurements of Reco and soil CO2 effluxes may reveal the timing and magnitude of the decoupling, thereby contributing to decreasing uncertainty associated with eddy flux measurements over flat terrains. While the correlations between CO2 effluxes measured by independent systems are strong, Rsg was generally larger than Rsc or Reco, mainly due to overestimation of effective diffusivity in the soil.

  18. Effects of grazing on leaf traits and ecosystem functioning in Inner Mongolia grasslands: scaling from species to community

    NASA Astrophysics Data System (ADS)

    Zheng, S. X.; Ren, H. Y.; Lan, Z. C.; Li, W. H.; Bai, Y. F.

    2009-10-01

    More attention has focused on using some easily measured plant functional traits to predict grazing influence on plant growth and ecosystem functioning. However, there has been much controversy on leaf traits response to grazing, thus more research should be conducted at the species level. Here we investigated the leaf area, leaf mass and specific leaf area (SLA) of 263 species in eight grassland communities along a soil moisture gradient in the Xilin River Basin, a semiarid grassland of northern China, to explore the grazing effects on ecosystem functioning. Results demonstrated that grazing decreased the leaf area and leaf mass in more than 56% of species in the Xilin River Basin, however, responses of SLA to grazing varied widely between species. Grazing increased SLA in 38.4% of species, decreased SLA in 31.3% of species and had no effect on 30.3% of species. Annuals and biennials generally developed high SLA as grazing tolerance traits, while perennial graminoids developed low SLA as grazing avoidance traits. Considering the water ecotypes, the SLA-increased and SLA-unchanged species were dominated by hygrophytes and mesophytes, while the SLA-decreased species were dominated by xerophytes. At the community level, grazing decreased the mean leaf area index (LAI) of six communities by 16.9%, leaf biomass by 35.2% and standing aboveground biomass (SAB) by 35.0% in the Xilin River Basin, indicating that overgrazing greatly decreased the ecosystem functioning in the semi-arid grassland of northern China. Soil properties, especially fielding holding capacity and soil organic carbon and total nitrogen could mediate the negative grazing impacts. The results suggest SLA is a better leaf trait to reveal plant adaptability to grazing. Our findings have practical implications for range management and productivity maintenance in the semiarid grassland, and it is feasible to take some measures such as ameliorating soil water and nutrient availabilities to prevent grassland degradation.

  19. Measured and Simulated Nitrous Oxide Emissions from Ryegrass- and Ryegrass/White Clover-Based Grasslands in a Moist Temperate Climate

    PubMed Central

    Li, Dejun; Lanigan, Gary; Humphreys, James

    2011-01-01

    There is uncertainty about the potential reduction of soil nitrous oxide (N2O) emission when fertilizer nitrogen (FN) is partially or completely replaced by biological N fixation (BNF) in temperate grassland. The objectives of this study were to 1) investigate the changes in N2O emissions when BNF is used to replace FN in permanent grassland, and 2) evaluate the applicability of the process-based model DNDC to simulate N2O emissions from Irish grasslands. Three grazing treatments were: (i) ryegrass (Lolium perenne) grasslands receiving 226 kg FN ha?1 yr?1 (GG+FN), (ii) ryegrass/white clover (Trifolium repens) grasslands receiving 58 kg FN ha?1 yr?1 (GWC+FN) applied in spring, and (iii) ryegrass/white clover grasslands receiving no FN (GWC-FN). Two background treatments, un-grazed swards with ryegrass only (G–B) or ryegrass/white clover (WC–B), did not receive slurry or FN and the herbage was harvested by mowing. There was no significant difference in annual N2O emissions between G–B (2.38±0.12 kg N ha?1 yr?1 (mean±SE)) and WC-B (2.45±0.85 kg N ha?1 yr?1), indicating that N2O emission due to BNF itself and clover residual decomposition from permanent ryegrass/clover grassland was negligible. N2O emissions were 7.82±1.67, 6.35±1.14 and 6.54±1.70 kg N ha?1 yr?1, respectively, from GG+FN, GWC+FN and GWC-FN. N2O fluxes simulated by DNDC agreed well with the measured values with significant correlation between simulated and measured daily fluxes for the three grazing treatments, but the simulation did not agree very well for the background treatments. DNDC overestimated annual emission by 61% for GG+FN, and underestimated by 45% for GWC-FN, but simulated very well for GWC+FN. Both the measured and simulated results supported that there was a clear reduction of N2O emissions when FN was replaced by BNF. PMID:22028829

  20. The origin of the indigenous grasslands of southeastern South Island in relation to pre-human woody ecosystems

    Microsoft Academic Search

    M. S. McGlone

    2001-01-01

    Immediately before human settlement, dense tall podocarp-angiosperm forest dominated the moist Southland and southern coastal Otago districts. Open, discontinuous podocarp-angiosperm forest bordered the central Otago dry interior, extending along the north Otago coast. Grassland was mostly patchy within these woody ecosystems, occurring on limited areas of droughty or low-nutrient soils and wetlands, or temporarily after infrequent fire or other disturbance.

  1. FUNCTIONAL AND STRUCTURAL CONVERGENCE OF TEMPERATE GRASSLAND AND SHRUBLAND ECOSYSTEMS. (R824993)

    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...

  2. Integrated mercury monitoring program for temperate estuarine and marine ecosystems on the North American Atlantic coast.

    PubMed

    Evers, David C; Mason, Robert P; Kamman, Neil C; Chen, Celia Y; Bogomolni, Andrea L; Taylor, David L; Hammerschmidt, Chad R; Jones, Stephen H; Burgess, Neil M; Munney, Kenneth; Parsons, Katharine C

    2008-12-01

    During the past century, anthropogenic activities have altered the distribution of mercury (Hg) on the earth's surface. The impacts of such alterations to the natural cycle of Hg can be minimized through coordinated management, policy decisions, and legislative regulations. An ability to quantitatively measure environmental Hg loadings and spatiotemporal trends of their fate in the environment is critical for science-based decision making. Here, we outline a Hg monitoring program for temperate estuarine and marine ecosystems on the Atlantic Coast of North America. This framework follows a similar, previously developed plan for freshwater and terrestrial ecosystems in the U.S. Methylmercury (MeHg) is the toxicologically relevant form of Hg, and its ability to bioaccumulate in organisms and biomagnify in food webs depends on numerous biological and physicochemical factors that affect its production, transport, and fate. Therefore, multiple indicators are needed to fully characterize potential changes of Hg loadings in the environment and MeHg bioaccumulation through the different marine food webs. In addition to a description of how to monitor environmental Hg loads for air, sediment, and water, we outline a species-specific matrix of biotic indicators that include shellfish and other invertebrates, fish, birds and mammals. Such a Hg monitoring template is applicable to coastal areas across the Northern Hemisphere and is transferable to arctic and tropical marine ecosystems. We believe that a comprehensive approach provides an ability to best detect spatiotemporal Hg trends for both human and ecological health, and concurrently identify food webs and species at greatest risk to MeHg toxicity. PMID:19294469

  3. Temporal dynamics of soil aggregates and microbial parameters in permanent and recently established grasslands in the temperate zone

    NASA Astrophysics Data System (ADS)

    Linsler, Deborah; Taube, Friedhelm; Geisseler, Daniel; Joergensen, Rainer Georg; Ludwig, Bernard

    2015-04-01

    While changes over time in soil aggregation or microbial parameters are well studied for arable soils, much less is known about such temporal variations in grassland soils. The objective of the present study was to determine the changes that occur within one year (between October 2010 and October 2011) for water-stable aggregate, microbial biomass carbon (Cmic) and ergosterol (as a proxy for fungal biomass) concentrations of a sandy soil under a permanent and recently established grasslands The analyzed treatments were (i) permanent grassland, (ii) grassland re-established after tillage of previous permanent grassland, and (iii) grassland established on arable land (both in September 2010). Temporal variations were found for the aggregate distribution and ergosterol concentration in the permanent grassland. For instance, the concentration of large macroaggregates (>2000 ?m) in the surface soil (0-10 cm) varied strongly, with the highest concentration (mean ± standard error) in October 2011 (666 ± 12 g kg-1) and a 3.2-fold lower concentration in May 2011. An explanation could be less rainfall and decreasing soil moisture contents in May compared to October, which may have decreased the stability of this fraction. A multiple linear regression analysis showed that the large macroaggregate concentration was well described (R2=0.60) by the gravimetric moisture content, the Cmic concentration and the pH. After the tillage event in the grassland and the subsequent grassland renovation, the concentrations of large macroaggregate, Cmic and ergosterol decreased in the surface soil, while no difference was found in the soil profile (0-40 cm). In the first year after the conversion of arable land into grassland, the concentrations of Cmic and ergosterol increased by a factor of 1.4 and 3.3, respectively, in the surface soil layer, while the macroaggregate concentration was not affected. This study indicates that the aggregate dynamic in grassland is not only affected by management but also by environmental conditions. The fungal biomass seems to be more sensitive to changes in environmental conditions or grassland management than the microbial biomass because the variations for the ergosterol concentrations were stronger than those for the Cmic concentrations.

  4. Analysis of Grassland Ecosystem Physiology at Multiple Scales Using Eddy Covariance, Stable Isotope and Remote Sensing Techniques

    NASA Astrophysics Data System (ADS)

    Flanagan, L. B.; Geske, N.; Emrick, C.; Johnson, B. G.

    2006-12-01

    Grassland ecosystems typically exhibit very large annual fluctuations in above-ground biomass production and net ecosystem productivity (NEP). Eddy covariance flux measurements, plant stable isotope analyses, and canopy spectral reflectance techniques have been applied to study environmental constraints on grassland ecosystem productivity and the acclimation responses of the ecosystem at a site near Lethbridge, Alberta, Canada. We have observed substantial interannual variation in grassland productivity during 1999-2005. In addition, there was a strong correlation between peak above-ground biomass production and NEP calculated from eddy covariance measurements. Interannual variation in NEP was strongly controlled by the total amount of precipitation received during the growing season (April-August). We also observed significant positive correlations between a multivariate ENSO index and total growing season precipitation, and between the ENSO index and annual NEP values. This suggested that a significant fraction of the annual variability in grassland productivity was associated with ENSO during 1999-2005. Grassland productivity varies asymmetrically in response to changes in precipitation with increases in productivity during wet years being much more pronounced than reductions during dry years. Strong increases in plant water-use efficiency, based on carbon and oxygen stable isotope analyses, contribute to the resilience of productivity during times of drought. Within a growing season increased stomatal limitation of photosynthesis, associated with improved water-use efficiency, resulted in apparent shifts in leaf xanthophyll cycle pigments and changes to the Photochemical Reflectance Index (PRI) calculated from hyper-spectral reflectance measurements conducted at the canopy-scale. These shifts in PRI were apparent before seasonal drought caused significant reductions in leaf area index (LAI) and changes to canopy-scale "greenness" based on NDVI values. With further progression of the seasonal drought, LAI and canopy-scale NDVI also declined in strong correlation. In addition, we have observed strong correlation between NDVI calculated from canopy-scale reflectance measurements and NDVI determined by MODIS. Continued reflectance measurements will help to understand and document the response of the grassland to seasonal and annual environmental change.

  5. Satellite-Based Analysis of Evapotranspiration and Water Balance in the Grassland Ecosystems of Dryland East Asia

    PubMed Central

    Xia, Jiangzhou; Liang, Shunlin; Chen, Jiquan; Yuan, Wenping; Liu, Shuguang; Li, Linghao; Cai, Wenwen; Zhang, Li; Fu, Yang; Zhao, Tianbao; Feng, Jinming; Ma, Zhuguo; Ma, Mingguo; Liu, Shaomin; Zhou, Guangsheng; Asanuma, Jun; Chen, Shiping; Du, Mingyuan; Davaa, Gombo; Kato, Tomomichi; Liu, Qiang; Liu, Suhong; Li, Shenggong; Shao, Changliang; Tang, Yanhong; Zhao, Xiang

    2014-01-01

    The regression tree method is used to upscale evapotranspiration (ET) measurements at eddy-covariance (EC) towers to the grassland ecosystems over the Dryland East Asia (DEA). The regression tree model was driven by satellite and meteorology datasets, and explained 82% and 76% of the variations of ET observations in the calibration and validation datasets, respectively. The annual ET estimates ranged from 222.6 to 269.1 mm yr?1 over the DEA region with an average of 245.8 mm yr?1 from 1982 through 2009. Ecosystem ET showed decreased trends over 61% of the DEA region during this period, especially in most regions of Mongolia and eastern Inner Mongolia due to decreased precipitation. The increased ET occurred primarily in the western and southern DEA region. Over the entire study area, water balance (the difference between precipitation and ecosystem ET) decreased substantially during the summer and growing season. Precipitation reduction was an important cause for the severe water deficits. The drying trend occurring in the grassland ecosystems of the DEA region can exert profound impacts on a variety of terrestrial ecosystem processes and functions. PMID:24845063

  6. Separating Drought Effects from Roof Artifacts on Ecosystem Processes in a Grassland Drought Experiment

    PubMed Central

    Vogel, Anja; Fester, Thomas; Eisenhauer, Nico; Scherer-Lorenzen, Michael; Schmid, Bernhard; Weisser, Wolfgang W.; Weigelt, Alexandra

    2013-01-01

    1 Given the predictions of increased drought probabilities under various climate change scenarios, there have been numerous experimental field studies simulating drought using transparent roofs in different ecosystems and regions. Such roofs may, however, have unknown side effects, called artifacts, on the measured variables potentially confounding the experimental results. A roofed control allows the quantification of potential artifacts, which is lacking in most experiments. 2 We conducted a drought experiment in experimental grasslands to study artifacts of transparent roofs and the resulting effects of artifacts on ecosystems relative to drought on three response variables (aboveground biomass, litter decomposition and plant metabolite profiles). We established three drought treatments, using (1) transparent roofs to exclude rainfall, (2) an unroofed control treatment receiving natural rainfall and (3) a roofed control, nested in the drought treatment but with rain water reapplied according to ambient conditions. 3 Roofs had a slight impact on air (+0.14°C during night) and soil temperatures (?0.45°C on warm days, +0.25°C on cold nights), while photosynthetically active radiation was decreased significantly (?16%). Aboveground plant community biomass was reduced in the drought treatment (?41%), but there was no significant difference between the roofed and unroofed control, i.e., there were no measurable roof artifact effects. 4 Compared to the unroofed control, litter decomposition was decreased significantly both in the drought treatment (?26%) and in the roofed control treatment (?18%), suggesting artifact effects of the transparent roofs. Moreover, aboveground metabolite profiles in the model plant species Medicago x varia were different from the unroofed control in both the drought and roofed control treatments, and roof artifact effects were of comparable magnitude as drought effects. 5 Our results stress the need for roofed control treatments when using transparent roofs for studying drought effects, because roofs can cause significant side effects. PMID:23936480

  7. Predicting the response of a temperate forest ecosystem to atmospheric CO{sub 2} increase. Final report, 1984--1995

    SciTech Connect

    Bazzaz, F.A.

    1995-12-31

    This document describes the most recent progress made in several areas of the project. Details of individual experiments in the following areas are provided: (1) the impact of soil volume on the physiological acclimation of temperate deciduous trees in elevated CO{sub 2}; (2) growth under elevated CO{sub 2}: the shape as well as the size of pots is important; (3) a survey of growth responses of temperate deciduous trees to elevated CO{sub 2}; (4) a survey of closely related birch species; (5) the response of temperate deciduous tress to CO{sub 2} in variable light and nutrients conditions; (6) elevated CO{sub 2} differentially alters the response of birch and maple seedlings to a moisture gradient; (7) population dynamics; (8) heat shock in elevated CO{sub 2}: is there a change in temperature sensitivity; (9) response of temperate deciduous trees to CO{sub 2} in variable light and nutrient conditions; (10) changes in tree community composition and their consequences to ecosystem productivity; and (11) species diversity and ecosystem response to carbon dioxide fertilization.

  8. Observations of 14CO2 in ecosystem respiration from a temperate deciduous forest in Northern Wisconsin

    NASA Astrophysics Data System (ADS)

    Phillips, Claire L.; McFarlane, Karis J.; LaFranchi, Brian; Desai, Ankur R.; Miller, John B.; Lehman, Scott J.

    2015-04-01

    The 14CO2 composition of plant and soil respiration can be used to determine the residence time of photosynthetically fixed carbon before it is released back to the atmosphere. To estimate the residence time of actively cycled carbon in a temperate forest, we employed two approaches for estimating the ?14CO2 of ecosystem respiration (?14C-Reco) at the Willow Creek AmeriFlux site in Northern Wisconsin, USA. Our first approach was to construct nighttime Keeling plots from subcanopy profiles of ?14CO2 and CO2, providing estimates of ?14C-Reco of 121.7‰ in June and 42.0‰ in August 2012. These measurements are likely dominated by soil fluxes due to proximity to the ground level. Our second approach utilized samples taken over 20 months within the forest canopy and from 396 m above ground level at the nearby LEF NOAA tall tower site (Park Falls, WI). In this canopy-minus-background approach we employed a mixing model described by Miller and Tans (2003) for estimating isotopic sources by subtracting time-varying background conditions. For the period from May 2011 to December 2012 the estimated ?14C-Reco using the Miller-Tans model was 76.8‰. Together, these ?14C-Reco values represent mean Reco carbon ages of approximately 1-19 years. We also found that heterotrophic soil-respired ? 14C at Willow Creek was 5-38‰ higher (i.e., 1-10 years older) than predicted by the Carnegie-Ames-Stanford Approach global biosphere carbon model for the 1 × 1 pixel nearest to the site. This study provides much needed observational constraints of ecosystem carbon residence times, which are a major source of uncertainty in terrestrial carbon cycle models.

  9. Drivers of long-term variability in CO2 net ecosystem exchange in a temperate peatland

    NASA Astrophysics Data System (ADS)

    Helfter, C.; Campbell, C.; Dinsmore, K. J.; Drewer, J.; Coyle, M.; Anderson, M.; Skiba, U.; Nemitz, E.; Billett, M. F.; Sutton, M. A.

    2014-10-01

    Land-atmosphere exchange of carbon dioxide (CO2) in peatlands exhibits marked seasonal and inter-annual variability, which subsequently affects the carbon sink strength of catchments across multiple temporal scales. Long-term studies are needed to fully capture the natural variability and therefore identify the key hydrometeorological drivers in the net ecosystem exchange (NEE) of CO2. NEE has been measured continuously by eddy-covariance at Auchencorth Moss, a temperate lowland peatland in central Scotland, since 2002. Hence this is one of the longest peatland NEE studies to date. For 11 yr, the site was a consistent, yet variable, atmospheric CO2 sink ranging from -5.2 to -135.9 g CO2-C m-2 yr-1 (mean of -64.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing season. Mean winter air temperature explained 87% of the inter-annual variability in the sink strength of the following summer, indicating a phenological memory-effect. Plant productivity exhibited a marked hysteresis with respect to photosynthetically active radiation (PAR) over the growing season, indicative of two separate growth regimes. Ecosystem respiration (Reco) and gross primary productivity (GPP) were closely correlated (ratio 0.74), suggesting that autotrophic processes were dominant. Whilst the site was wet most of the year (water table depth <5 cm) there were indications that heterotrophic respiration was enhanced by drought, which also depressed GPP. NEE was compared to 5 other peatland sites which have published long-term NEE records. The CO2 uptake rate during the growing season was comparable to 3 other European sites, however the emission rate during the dormant season was significantly higher.

  10. Effects of grazing on ecosystem CO? exchange in a meadow grassland on the Tibetan Plateau during the growing season.

    PubMed

    Chen, Ji; Shi, Weiyu; Cao, Junji

    2015-02-01

    Effects of human activity on ecosystem carbon fluxes (e.g., net ecosystem exchange (NEE), ecosystem respiration (R(eco)), and gross ecosystem exchange (GEE)) are crucial for projecting future uptake of CO2 in terrestrial ecosystems. However, how ecosystem that carbon fluxes respond to grazing exclusion is still under debate. In this study, a field experiment was conducted to study the effects of grazing exclusion on R(eco), NEE, and GEE with three treatments (free-range grazing (FG) and grazing exclusion for 3 and 5 years (GE3 and GE5, respectively)) in a meadow grassland on the Tibetan Plateau. Our results show that grazing exclusion significantly increased NEE by 47.37 and 15.84%, and R eco by 33.14 and 4.29% under GE3 and GE5 plots, respectively, although carbon sinks occurred in all plots during the growing season, with values of 192.11, 283.12, and 222.54 g C m(-2) for FG, GE3, and GE5, respectively. Interestingly, grazing exclusion increased temperature sensitivity (Q10) of R eco with larger increases at the beginning and end of growing season (i.e., May and October, respectively). Soil temperature and soil moisture were key factors on controlling the diurnal and seasonal variations of R(eco), NEE, and GEE, with soil temperature having a stronger influence. Therefore, the combined effects of grazing and temperature suggest that grazing should be taken into consideration in assessing global warming effects on grassland ecosystem CO2 exchange. PMID:25355630

  11. Role of vegetation in modulating rainfall interception and soil water flux in ecosystems under transition from grassland to woodland

    NASA Astrophysics Data System (ADS)

    Zou, Chris; Will, Rodney; Stebler, Elaine; Qiao, Lei

    2014-05-01

    Vegetation exerts strong control on the hydrological budget by shielding the soil from rainfall through interception and modulating water transmission in the soil by altering soil properties and rooting zone water extraction. Therefore, a change in vegetation alters the water cycle by a combination of a passive, rainfall redistribution mechanism controlled by the physical dimensions of vegetation and active, water extracting processes resulting from physiological attributes of different plants. As a result, the role of vegetation on the water cycle is likely to change where vegetation is under transition such as in the southern Great Plains of USA due to woody plant encroachment. However, it remains largely unknown how this physiognomic transformation from herbaceous cover to woody canopy alters rainfall influx, soil water transmission and efflux from the soil profile and consequently alters historic patterns of runoff and groundwater recharge. This knowledge is critical for both water resource and ecosystem management. We conducted a comprehensive, 5-year study involving direct quantification of throughfall and stemflow for grassland and encroached juniper woodland (Juniperus virginiana), water efflux through transpiration using an improved Granier thermal dissipation method (trees) and ET chamber (grassland), soil moisture storage and dynamics (capacitance probe) and streamflow (small catchment). We calibrated a prevailing hydrological model (SWAT) based on observed data to simulate potential change in runoff and recharge for the Cimarron River basin (study site located within this basin) under various phases of grassland to woodland transition. Our results show that juniper encroachment reduces throughfall reaching the soil surface compared with grassland under moderate grazing. The evergreen junipers transpired water year-round including fall and winter when the warm season grasses were senescent. As a result, soil water content and soil water storage on the encroached catchment were generally lower than on the grassland catchment, especially proceeding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events was observed to be substantially reduced in the encroached catchment. Model simulation suggests that conversion of all existing grassland to juniper in the Cimarron River basin will increase overall water efflux through evapotranspiration sufficient to substantially reduce water yield for streamflow. Rapid transformation of mesic grasslands to a woodland state with juniper encroachment, if not confined, has the potential to reduce soil water, streamflow and flow duration of ephemeral streams. Slowing the expansion of woody encroachment into grasslands might be considered as a land-based strategy to sustain or even augment streamflow and groundwater recharge to meet the increase in water demand under increasing climate variability and population growth in the southern Great Plains of USA

  12. Interactions and feedbacks of a temperate lake ecosystem in NE Germany

    NASA Astrophysics Data System (ADS)

    Simard, Sonia; Blume, Theresa; Heidbüchel, Ingo; Heinrich, Ingo; Dreibrodt, Janek; Güntner, Andreas; Helle, Gerhard

    2015-04-01

    Soil water availability is a major driver of plant productivity and a limiting factor in several environments. As much as water has a foremost influence on plant growth, the vegetation itself has an important influence on the landscape hydrology leading to feedbacks between ecological processes and the hydrological cycle. A natural experimental design was set up in NE Germany in a temperate lake ecosystem where major shifts in groundwater and lake levels have been observed in the last decades. The location is characterized by a precipitation regime below 600 mm annually. Soil moisture profiles, matrix potential, piezometers, dendrometers and sapflow sensors, as well as standard climate stations providing high temporal resolution information were installed in sites with different soil water content. Several sites in the surroundings of lake Hinnensee, NE Germany, are currently closely monitored to gain a better understanding of the dynamics of water use of three main European tree species (Pinus sylvestris, Quercus petreae and Fagus sylvatica), its impact on forest productivity and the influence on the landscape hydrology. We discuss how the dynamics varies in time and under different environmental conditions, as well as possible processes that might govern these variations.

  13. A Transmission Model for the Ecology of an Avian Blood Parasite in a Temperate Ecosystem

    PubMed Central

    Murdock, Courtney C.; Foufopoulos, Johannes; Simon, Carl P.

    2013-01-01

    Most of our knowledge about avian haemosporidian parasites comes from the Hawaiian archipelago, where recently introduced Plasmodiumrelictum has contributed to the extinction of many endemic avian species. While the ecology of invasive malaria is reasonably understood, the ecology of endemic haemosporidian infection in mainland systems is poorly understood, even though it is the rule rather than the exception. We develop a mathematical model to explore and identify the ecological factors that most influence transmission of the common avian parasite, Leucocytozoonfringillinarum (Apicomplexa). The model was parameterized from White-crowned Sparrow (Zonotrichialeucophrys) and S. silvestre / craigi black fly populations breeding in an alpine ecosystem. We identify and examine the importance of altricial nestlings, the seasonal relapse of infected birds for parasite persistence across breeding seasons, and potential impacts of seasonal changes in black fly emergence on parasite prevalence in a high elevation temperate system. We also use the model to identify and estimate the parameters most influencing transmission dynamics. Our analysis found that relapse of adult birds and young of the year birds were crucial for parasite persistence across multiple seasons. However, distinguishing between nude nestlings and feathered young of the year was unnecessary. Finally, due to model sensitivity to many black fly parameters, parasite prevalence and sparrow recruitment may be most affected by seasonal changes in environmental temperature driving shifts in black fly emergence and gonotrophic cycles. PMID:24073288

  14. Arsenic concentrations and speciation in a temperateArsenic concentrations and speciation in a temperate mangrove ecosystem, NSW, Australiamangrove ecosystem, NSW, Australia

    E-print Network

    Canberra, University of

    Arsenic concentrations and speciation in a temperateArsenic concentrations and speciation, Australia Received 4 September 2001; Accepted 17 December 2001 Total arsenic concentrations and species were. Mean arsenic concentrations ranged from 0.3 to 55 mg gŔ1 dry mass. Epiphytic algae/fungi associated

  15. Environmental effects of oil and gas lease sites in a grassland ecosystem

    Microsoft Academic Search

    Lawrence C. Nasen; Bram F. Noble; Jill F. Johnstone

    2011-01-01

    The northern Great Plains of Saskatchewan is one of the most significantly modified landscapes in Canada. While the majority of anthropogenic disturbances to Saskatchewan’s grasslands are the result of agricultural practices, development of petroleum and natural gas (PNG) resources is of increasing concern for grassland conservation. Although PNG developments require formal assessment and regulatory approval, follow-up and monitoring of the

  16. The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts.

    PubMed

    Vergés, Adriana; Steinberg, Peter D; Hay, Mark E; Poore, Alistair G B; Campbell, Alexandra H; Ballesteros, Enric; Heck, Kenneth L; Booth, David J; Coleman, Melinda A; Feary, David A; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M; Mizerek, Toni; Mumby, Peter J; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K

    2014-08-22

    Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to 'barrens' when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs. PMID:25009065

  17. The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts

    PubMed Central

    Vergés, Adriana; Steinberg, Peter D.; Hay, Mark E.; Poore, Alistair G. B.; Campbell, Alexandra H.; Ballesteros, Enric; Heck, Kenneth L.; Booth, David J.; Coleman, Melinda A.; Feary, David A.; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M.; Mizerek, Toni; Mumby, Peter J.; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A.; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K.

    2014-01-01

    Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to ‘barrens’ when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs. PMID:25009065

  18. Microbial Enzymatic Response to Reduced Precipitation and Added Nitrogen in a Southern California Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Alster, C. J.; German, D.; Allison, S. D.

    2011-12-01

    Microbial enzymes play a fundamental role in ecosystem processes and nutrient mineralization. Although there have been many studies concluding that global climate change affects plant communities, the effects on microbial communities in leaf litter have been much less studied. We measured extracellular enzyme activities in litter decomposing in plots with either reduced precipitation or increased nitrogen in a grassland ecosystem in Loma Ridge National Landmark in Southern California. We used a reciprocal transplant design to examine the effects of plot treatment, litter origin, and microbial community origin on litter decomposition and extracellular enzyme activity. Our hypothesis was that increased nitrogen would increase activity because nitrogen often limits microbial growth, while decreased precipitation would decrease activity due to lower litter moisture levels. Samples were collected in March 2011 and analyzed for the activities of cellobiohydrolase (CBH), ?-glucosidase (BG), ?-glucosidase (AG), N-acetyl-?-D-glucosaminidase (NAG), ?-xylosidase (BX), acid phosphatase (AP), and leucine aminopeptidase (LAP). None of the factors in the nitrogen manipulation had a significant effect on any of the enzymes, although BG, CBH, and NAG increased marginally significantly in plots with nitrogen addition (p = 0.103, p = 0.082, and p = 0.114, respectively). For the precipitation manipulation, AG, BG, BX, CBH, and NAG significantly increased in plots with reduced precipitation (p = 0.015, p <0.001, p<0.001, and p<0.001, respectively) while LAP significantly decreased (p = 0.002). LAP catalyzes the hydrolysis of polypeptides, so reduced LAP activity could result in lower rates of enzyme turnover in the reduced precipitation treatment. We also observed that AP significantly increased (p = 0.014) in litter originating from reduced precipitation plots, while AG, BX, and LAP significantly decreased (p = 0.011, p = 0.031, and 0.005, respectively). There were no significant correlations found between fungal or bacterial mass and enzymatic activity with either of the treatment types. Our results suggest that increased enzymatic activity due to drought could mitigate negative effects of moisture limitation on decomposition. However, this mitigating effect may be offset by declines in enzyme activity due to changes in plant community composition and associated litter chemistry in response to drought.

  19. Plant and arthropod community sensitivity to rainfall manipulation but not nitrogen enrichment in a successional grassland ecosystem.

    PubMed

    Lee, Mark A; Manning, Pete; Walker, Catherine S; Power, Sally A

    2014-12-01

    Grasslands provide many ecosystem services including carbon storage, biodiversity preservation and livestock forage production. These ecosystem services will change in the future in response to multiple global environmental changes, including climate change and increased nitrogen inputs. We conducted an experimental study over 3 years in a mesotrophic grassland ecosystem in southern England. We aimed to expose plots to rainfall manipulation that simulated IPCC 4th Assessment projections for 2100 (+15% winter rainfall and -30% summer rainfall) or ambient climate, achieving +15% winter rainfall and -39% summer rainfall in rainfall-manipulated plots. Nitrogen (40 kg ha(-1) year(-1)) was also added to half of the experimental plots in factorial combination. Plant species composition and above ground biomass were not affected by rainfall in the first 2 years and the plant community did not respond to nitrogen enrichment throughout the experiment. In the third year, above-ground plant biomass declined in rainfall-manipulated plots, driven by a decline in the abundances of grass species characteristic of moist soils. Declining plant biomass was also associated with changes to arthropod communities, with lower abundances of plant-feeding Auchenorrhyncha and carnivorous Araneae indicating multi-trophic responses to rainfall manipulation. Plant and arthropod community composition and plant biomass responses to rainfall manipulation were not modified by nitrogen enrichment, which was not expected, but may have resulted from prior nitrogen saturation and/or phosphorus limitation. Overall, our study demonstrates that climate change may in future influence plant productivity and induce multi-trophic responses in grasslands. PMID:25224801

  20. Synthesis of Watershed and Ecosystem Responses to Lehmann Lovegrass Invasion in a SE Arizona Desert Grassland Watershed

    NASA Astrophysics Data System (ADS)

    Hamerlynck, E. P.; Scott, R. L.; Polyakov, V.; Sugg, Z.; Moran, S. M.; Stone, J.; Nearing, M.

    2011-12-01

    Compared to aridland systems that have undergone rapid change in dominant vegetation growth form, the responses of watershed and ecosystem processes to a shift in dominance of similar growth forms have not been well-studied. Following a prolonged drought period (2000-2005) at the Walnut Gulch Experimental Watershed's Kendall grassland site (WS#112), near Tombstone, AZ, strong summer monsoon rains in 2006 were accompanied by widespread mortality most native perennial grasses, a transient increase in annual forbs, followed by establishment and sustained dominance by a single perennial grass, the invasive bunchgrass, Lehmann lovegrass (Eragrostis lehmanniana). This loss of ecological diversity occurred across a watershed already instrumented for quantifying long-term climate, watershed, hill-slope, and ecosystem-level gas exchange processes. Salient findings from these data sets were: 1) annual watershed sediment discharge rapidly returned to pre-invasion levels following a large spike in 2006 that accounted for 65% of the total sediment yield summed over 35 years, 2) plot-level experimental runoff studies showed hill-slope sediment yields consistently doubled, as did growing season soil evaporation contributions to ET, and 3) the grassland was a carbon sink during dry conditions under lovegrass dominance. These findings show that while some aspects of overall watershed and ecosystem function were not strongly affected (i.e. sediment yield and net primary productivity), processes acting at lower spatial and temporal scales have been negatively impacted by lovegrass dominance. We believe these lower-order processes underlie the strong ecological effects associated with Lehmann lovegrass invasion, and will also eventually alter landform processes and change the basic ecohydrological characteristics of desert grassland watersheds.

  1. Exchange of carbonyl sulfide (COS), a potential tracer of gross primary productivity, between grassland ecosystem components and the atmosphere

    NASA Astrophysics Data System (ADS)

    Whelan, M.; Rhew, R. C.

    2013-12-01

    Recently, measurements of carbonyl sulfide (COS) exchange have been used as an independent constraint for estimates of gross primary productivity over terrestrial ecosystems and continents. CO2 is both taken up and released by plants, whereas COS is usually only consumed and at a predictable ratio to CO2. Most of the underlying theoretical assumptions of this method have been verified, however the problem of parsing leaf exchange from other terrestrial sources and sinks of COS is still under investigation. In ecosystems that experience distinct periods of growing and senescence, it is possible to assess COS fluxes in situ when no green plants are present and compare to measurements during the growing season. Taking advantage of this seasonal pattern, we have investigated COS exchange from March 2012 to March 2013 in a Mediterranean grassland outside of Santa Cruz, CA, U.S.A (37.0°N, 122°W). Through lab-based incubation experiments, we found that net COS uptake of grassland soil can be reduced by increased soil moisture. We evaluated this claim in the field with monthly field deployments of static flux chambers over the in-tact soil and plant system. In the dry summer, artificial rain amendments caused COS net uptake to decrease, sometimes leading to overall net production to the atmosphere, in agreement with lab experiments. During the wet growing season, water additions caused over 2x increase in COS uptake from the atmosphere. Contrary to what has been previously claimed, soil exchange of COS is not negligible in grassland ecosystems.

  2. Identifying grasslands suitable for cellulosic feedstock crops in the Greater Platte River Basin: dynamic modeling of ecosystem performance with 250 m eMODIS

    USGS Publications Warehouse

    Gu, Yingxin; Boyte, Stephen P.; Wylie, Bruce K.; Tieszen, Larry L.

    2012-01-01

    This study dynamically monitors ecosystem performance (EP) to identify grasslands potentially suitable for cellulosic feedstock crops (e.g., switchgrass) within the Greater Platte River Basin (GPRB). We computed grassland site potential and EP anomalies using 9-year (2000–2008) time series of 250 m expedited moderate resolution imaging spectroradiometer Normalized Difference Vegetation Index data, geophysical and biophysical data, weather and climate data, and EP models. We hypothesize that areas with fairly consistent high grassland productivity (i.e., high grassland site potential) in fair to good range condition (i.e., persistent ecosystem overperformance or normal performance, indicating a lack of severe ecological disturbance) are potentially suitable for cellulosic feedstock crop development. Unproductive (i.e., low grassland site potential) or degraded grasslands (i.e., persistent ecosystem underperformance with poor range condition) are not appropriate for cellulosic feedstock development. Grassland pixels with high or moderate ecosystem site potential and with more than 7 years ecosystem normal performance or overperformance during 2000–2008 are identified as possible regions for future cellulosic feedstock crop development (ca. 68 000 km2 within the GPRB, mostly in the eastern areas). Long-term climate conditions, elevation, soil organic carbon, and yearly seasonal precipitation and temperature are important performance variables to determine the suitable areas in this study. The final map delineating the suitable areas within the GPRB provides a new monitoring and modeling approach that can contribute to decision support tools to help land managers and decision makers make optimal land use decisions regarding cellulosic feedstock crop development and sustainability.

  3. Reduced diurnal temperature range does not change warming impacts on ecosystem carbon balance of Mediterranean grassland mesocosms

    DOE PAGESBeta

    Phillips, Claire L.; Gregg, Jillian W.; Wilson, John K.

    2011-11-01

    Daily minimum temperature (Tmin) has increased faster than daily maximum temperature (Tmax) in many parts of the world, leading to decreases in diurnal temperature range (DTR). Projections suggest these trends are likely to continue in many regions, particularly northern latitudes and in arid regions. Despite wide speculation that asymmetric warming has different impacts on plant and ecosystem production than equal-night-and-day warming, there has been little direct comparison of these scenarios. Reduced DTR has also been widely misinterpreted as a result of night-only warming, when in fact Tmin occurs near dawn, indicating higher morning as well as night temperatures. We reportmore »on the first experiment to examine ecosystem-scale impacts of faster increases in Tmin than Tmax, using precise temperature controls to create realistic diurnal temperature profiles with gradual day-night temperature transitions and elevated early morning as well as night temperatures. Studying a constructed grassland ecosystem containing species native to Oregon, USA, we found the ecosystem lost more carbon at elevated than ambient temperatures, but was unaffected by the 3şC difference in DTR between symmetric warming (constantly ambient +3.5şC) and asymmetric warming (dawn Tmin=ambient +5şC, afternoon Tmax= ambient +2şC). Reducing DTR had no apparent effect on photosynthesis, likely because temperatures were most different in the morning and late afternoon when light was low. Respiration was also similar in both warming treatments, because respiration temperature sensitivity was not sufficient to respond to the limited temperature differences between asymmetric and symmetric warming. We concluded that changes in daily mean temperatures, rather than changes in Tmin/Tmax, were sufficient for predicting ecosystem carbon fluxes in this reconstructed Mediterranean grassland system.« less

  4. Conversion of temperate forests into heaths: Role of ecosystem disturbance and ericaceous plants

    Microsoft Academic Search

    A. U. Mallik

    1995-01-01

    Fire and logging in nutrient-poor temperate forests with certain ericaceous understory plants may convert the forests into heaths. The process of disturbance-induced heath formation is documented by using examples of Calluna in western Europe, Kalmia in Newfoundland, and Gaultheria (salal) in coastal British Columbia. In a cool, temperate climate, rapid vegetative growth of Calluna, Kalmia, and salal following disturbance results

  5. 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

  6. Bromus tectorum invasion alters nitrogen dynamics in an undisturbed arid grassland ecosystem.

    PubMed

    Sperry, L J; Belnap, J; Evans, R D

    2006-03-01

    The nonnative annual grass Bromus tectorum has successfully replaced native vegetation in many arid and semiarid ecosystems. Initial introductions accompanied grazing and agriculture, making it difficult to separate the effects of invasion from physical disturbance. This study examined N dynamics in two recently invaded, undisturbed vegetation associations (C3 and C4). The response of these communities was compared to an invaded/ disturbed grassland. The invaded/disturbed communities had higher surface NH4+ input in spring, whereas there were no differences for surface input of NO3-. Soil inorganic N was dominated by NH4+, but invaded sites had greater subsurface soil NO3-. Invaded sites had greater total soil N at the surface four years post-invasion in undisturbed communities, but total N was lower in the invaded/disturbed communities. Soil delta15N increased with depth in the noninvaded and recently invaded communities, whereas the invaded/disturbed communities exhibited the opposite pattern. Enriched foliar delta15N values suggest that Bromus assimilated subsurface NO3-, whereas the native grasses were restricted to surface N. A Rayleigh distillation model accurately described decomposition patterns in the noninvaded communities where soil N loss is accompanied by increasing soil delta15N; however, the invaded/ disturbed communities exhibited the opposite pattern, suggesting redistribution of N within the soil profile. This study suggests that invasion has altered the mechanisms driving nitrogen dynamics. Bromus litter decomposition and soil NO3- concentrations were greater in the invaded communities during periods of ample precipitation, and NO3- leached from the surface litter, where it was assimilated by Bromus. The primary source of N input in these communities is a biological soil crust that is removed with disturbance, and the lack of N input by the biological soil crust did not balance N loss, resulting in reduced total N in the invaded/disturbed communities. Bromus produced a positive feedback loop by leaching NO3- from decomposing Bromus litter to subsurface soil layers, accessing that deepsoil N pool with deep roots and returning that N to the surface as biomass and subsequent litter. Lack of new inputs combined with continued loss will result in lower total soil N, evidenced by the lower total soil N in the invaded/disturbed communities. PMID:16602290

  7. Bromus tectorum invasion alters nitrogen dynamics in an undisturbed arid grassland ecosystem

    USGS Publications Warehouse

    Sperry, L.J.; Belnap, J.; Evans, R.D.

    2006-01-01

    The nonnative annual grass Bromus tectorum has successfully replaced native vegetation in many arid and semiarid ecosystems. Initial introductions accompanied grazing and agriculture, making it difficult to separate the effects of invasion from physical disturbance. This study examined N dynamics in two recently invaded, undisturbed vegetation associations (C3 and C4). The response of these communities was compared to an invaded/disturbed grassland. The invaded/disturbed communities had higher surface NH4+ input in spring, whereas there were no differences for surface input of NO3-. Soil inorganic N was dominated by NH4+, but invaded sites had greater subsurface soil NO3-. Invaded sites had greater total soil N at the surface four years post-invasion in undisturbed communities, but total N was lower in the invaded/disturbed communities. Soil ??15N increased with depth in the noninvaded and recently invaded communities, whereas the invaded/disturbed communities exhibited the opposite pattern. Enriched foliar ??15N values suggest that Bromus assimilated subsurface NO3-, whereas the native grasses were restricted to surface N. A Rayleigh distillation model accurately described decomposition patterns in the noninvaded communities where soil N loss is accompanied by increasing soil ??15N; however, the invaded/disturbed communities exhibited the opposite pattern, suggesting redistribution of N within the soil profile. This study suggests that invasion has altered the mechanisms driving nitrogen dynamics. Bromus litter decomposition and soil NO3- concentrations were greater in the invaded communities during periods of ample precipitation, and NO3- leached from the surface litter, where it was assimilated by Bromus. The primary source of N input in these communities is a biological soil crust that is removed with disturbance, and the lack of N input by the biological soil crust did not balance N loss, resulting in reduced total N in the invaded/disturbed communities. Bromus produced a positive feedback loop by leaching NO3- from decomposing Bromus litter to subsurface soil layers, accessing that deep-soil N pool with deep roots and returning that N to the surface as biomass and subsequent litter. Lack of new inputs combined with continued loss will result in lower total soil N, evidenced by the lower total soil N in the invaded/disturbed communities. ?? 2006 by the Ecological Society of America.

  8. On the relationship between ecosystem-scale hyperspectral reflectance and CO2 exchange in European mountain grasslands

    NASA Astrophysics Data System (ADS)

    Balzarolo, M.; Vescovo, L.; Hammerle, A.; Gianelle, D.; Papale, D.; Tomelleri, E.; Wohlfahrt, G.

    2015-05-01

    In this paper we explore the skill of hyperspectral reflectance measurements and vegetation indices (VIs) derived from these in estimating carbon dioxide (CO2) fluxes of grasslands. Hyperspectral reflectance data, CO2 fluxes and biophysical parameters were measured at three grassland sites located in European mountain regions using standardized protocols. The relationships between CO2 fluxes, ecophysiological variables, traditional VIs and VIs derived using all two-band combinations of wavelengths available from the whole hyperspectral data space were analysed. We found that VIs derived from hyperspectral data generally explained a large fraction of the variability in the investigated dependent variables but differed in their ability to estimate midday and daily average CO2 fluxes and various derived ecophysiological parameters. Relationships between VIs and CO2 fluxes and ecophysiological parameters were site-specific, likely due to differences in soils, vegetation parameters and environmental conditions. Chlorophyll and water-content-related VIs explained the largest fraction of variability in most of the dependent variables. Band selection based on a combination of a genetic algorithm with random forests (GA-rF) confirmed that it is difficult to select a universal band region suitable across the investigated ecosystems. Our findings have major implications for upscaling terrestrial CO2 fluxes to larger regions and for remote- and proximal-sensing sampling and analysis strategies and call for more cross-site synthesis studies linking ground-based spectral reflectance with ecosystem-scale CO2 fluxes.

  9. Anatomical and Eco-Physiological Changes in Leaves of Couch-Grass ( Elymus repens L.), a Temperate Loess Grassland Species, after 7 Years Growth Under Elevated CO 2 Concentration

    Microsoft Academic Search

    A. I. Engloner; D. Kovács; J. Balogh; Z. Tuba

    2003-01-01

    Leaf anatomy and eco-physiology of Elymus repens, a temperate loess grassland species, were determined after seven years of exposure to 700 ?mol (CO2) mol?1 (EC). EC treatment resulted in significant reduction of stomatal density on both surfaces of couch-grass leaves. Thickness\\u000a of leaves and that of the sclerenchyma tissues between the vessels and the adaxial surfaces, the area of vascular

  10. Concentrations and ?(2)H values of cuticular n-alkanes vary significantly among plant organs, species and habitats in grasses from an alpine and a temperate European grassland.

    PubMed

    Gamarra, Bruno; Kahmen, Ansgar

    2015-08-01

    n-Alkanes are long-chained hydrocarbons contained in the cuticle of terrestrial plants. Their hydrogen isotope ratios (?(2)H) have been used as a proxy for environmental and plant ecophysiological processes. Calibration studies designed to resolve the mechanisms that determine the ?(2)H values of n-alkanes have exclusively focused on n-alkanes derived from leaves. It is, however, unclear in which quantities n-alkanes are also produced by other plant organs such as roots or inflorescences, or whether different plant organs produce distinct n-alkane ?(2)H values. To resolve these open questions, we sampled leaves, sheaths, stems, inflorescences and roots from a total of 15 species of European C3 grasses in an alpine and a temperate grassland in Switzerland. Our data show slightly increased n-alkane concentrations and n-alkane ?(2)H values in the alpine compared to the temperate grassland. More importantly, inflorescences had typically much higher n-alkane concentrations than other organs while roots had very low n-alkane concentrations. Most interestingly, the ?(2)H values of the carbon autonomous plant organs leaves, sheaths and stems were in general depleted compared to the overall mean ?(2)H value of a species, while non-carbon autonomous organs such as roots and inflorescences show ?(2)H values that are higher compared to the overall mean ?(2)H value of a species. We attribute organ-specific ?(2)H values to differences in the H-NADPH biosynthetic origin in different plant organs as a function of their carbon relationships. Finally, we employed simple mass balance calculations to show that leaves are in fact the main source of n-alkanes in the sediment. As such, studies assessing the environmental and physiological drivers of n-alkanes that focus on leaves produce relationships that can be employed to interpret the ?(2)H values of n-alkanes derived from sediments. This is despite the significant differences that we found among the ?(2)H values in the different plant organs. Our study brings new insights into the natural variability of n-alkane ?(2)H values and has implications for the interpretation of n-alkane ?(2)H values in ecological and paleohydrological research. PMID:25761443

  11. Plant trait-based models identify direct and indirect effects of climate change on bundles of grassland ecosystem services

    PubMed Central

    Lamarque, Pénélope; Lavorel, Sandra; Mouchet, Maud; Quétier, Fabien

    2014-01-01

    Land use and climate change are primary causes of changes in the supply of ecosystem services (ESs). Although the consequences of climate change on ecosystem properties and associated services are well documented, the cascading impacts of climate change on ESs through changes in land use are largely overlooked. We present a trait-based framework based on an empirical model to elucidate how climate change affects tradeoffs among ESs. Using alternative scenarios for mountain grasslands, we predicted how direct effects of climate change on ecosystems and indirect effects through farmers’ adaptations are likely to affect ES bundles through changes in plant functional properties. ES supply was overall more sensitive to climate than to induced management change, and ES bundles remained stable across scenarios. These responses largely reflected the restricted extent of management change in this constrained system, which was incorporated when scaling up plot level climate and management effects on ecosystem properties to the entire landscape. The trait-based approach revealed how the combination of common driving traits and common responses to changed fertility determined interactions and tradeoffs among ESs. PMID:25225382

  12. Comparison of Carbon Sequestration Rates and Energy Balance of Turf in the Denver Urban Ecosystem and an Adjacent Native Grassland

    NASA Astrophysics Data System (ADS)

    Thienelt, T. S.; Anderson, D. E.; Powell, K. M.

    2011-12-01

    Urban ecosystems are currently characterized by rapid growth, are expected to continually expand and, thus, represent an important driver of land use change. A significant component of urban ecosystems is lawns, potentially the single largest irrigated "crop" in the U.S. Beginning in March of 2011 (ahead of the growing season), eddy covariance measurements of net carbon exchange and evapotranspiration along with energy balance fluxes were conducted for a well-watered, fertilized lawn (rye-bluegrass-mix) in metropolitan Denver and for a nearby tallgrass prairie (big bluestem, switchgrass, cheatgrass, blue grama). Due to the semi-arid climate conditions of the Denver region, differences in management (i.e., irrigation and fertilization) are expected to have a discernible impact on ecosystem productivity and thus on carbon sequestration rates, evapotranspiration, and the sensible and latent heat partitioning of the energy balance. By mid-July, preliminary data indicated that cumulative evapotranspiration was approximately 270 mm and 170 mm for urban and native grasslands, respectively, although cumulative carbon sequestration at that time was similar for both (approximately 40 mg/m2). However, the pattern of carbon exchange differed between the grasslands. Both sites showed daily net uptake of carbon starting in late May, but the urban lawn displayed greater diurnal variability as well as greater uptake rates in general, especially following fertilization in mid-June. In contrast, the trend of carbon uptake at the prairie site was occasionally reversed following strong convective precipitation events, resulting in a temporary net release of carbon. The continuing acquisition of data and investigation of these relations will help us assess the potential impact of urban growth on regional carbon sequestration.

  13. Year in Review: Spotlight on 2012 Research by the Grassland, Shrubland and Desert Ecosystems Science Program

    E-print Network

    controls. Five species listed as noxious weeds in Montana were recorded: spotted knapweed (Centaurea stoebe at Tenderfoot Experimental Forest in Montana helps shed some light on the issue. Study partners include Montana Conservation Corps and Montana Department of Agriculture. Rocky Mountain Research Station Grassland, Shrubland

  14. Relationships among soil properties, plant nutrition and arbuscular mycorrhizal fungi-plant symbioses in a temperate grassland along hydrologic, saline and sodic gradients.

    PubMed

    García, Ileana V; Mendoza, Rodolfo E

    2008-03-01

    Temporal variations in the relationships among plant nutrient concentrations, soil properties and arbuscular-mycorrhizal (AM) fungal dynamics were studied along a topographic and saline gradient in a temperate grassland soil. Soil and plant (Lotus tenuis, Paspalum vaginatum, Stenotaphrum secundatum) samples were collected on four seasonally based occasions. The morphology of AM root colonization had a similar pattern in the plants studied. Maximum arbuscular colonization occurred at the beginning of the growing season in late winter and was minimal in late summer, but maximal vesicular colonization occurred in summer and was minimal in winter, suggesting a preferential production of these morphological phases by the fungus with respect to season. The greatest arbuscular colonization was associated with the highest N and P concentrations in plant tissue, suggesting a correspondence with increases in the rate of nutrient transfer between the symbiotic partners. Water content, salinity and sodicity in soil were positively associated with AM root colonization and arbuscule colonization in L. tenuis, but negatively so in the grasses. There were distinct seasonally related effects with respect to both spore density and AM colonization, which were independent of particular combinations of plant species and soil sites. PMID:18205811

  15. Inter-annual variability of carbon fluxes in temperate forest ecosystems: effects of biotic and abiotic factors

    NASA Astrophysics Data System (ADS)

    Chen, M.; Keenan, T. F.; Hufkens, K.; Munger, J. W.; Bohrer, G.; Brzostek, E. R.; Richardson, A. D.

    2014-12-01

    Carbon dynamics in terrestrial ecosystems are influenced by both abiotic and biotic factors. Abiotic factors, such as variation in meteorological conditions, directly drive biophysical and biogeochemical processes; biotic factors, referring to the inherent properties of the ecosystem components, reflect the internal regulating effects including temporal dynamics and memory. The magnitude of the effect of abiotic and biotic factors on forest ecosystem carbon exchange has been suggested to vary at different time scales. In this study, we design and conduct a model-data fusion experiment to investigate the role and relative importance of the biotic and abiotic factors for inter-annual variability of the net ecosystem CO2 exchange (NEE) of temperate deciduous forest ecosystems in the Northeastern US. A process-based model (FöBAAR) is parameterized at four eddy-covariance sites using all available flux and biometric measurements. We conducted a "transplant" modeling experiment, that is, cross- site and parameter simulations with different combinations of site meteorology and parameters. Using wavelet analysis and variance partitioning techniques, analysis of model predictions identifies both spatial variant and spatially invariant parameters. Variability of NEE was primarily modulated by gross primary productivity (GPP), with relative contributions varying from hourly to yearly time scales. The inter-annual variability of GPP and NEE is more regulated by meteorological forcing, but spatial variability in certain model parameters (biotic response) has more substantial effects on the inter-annual variability of ecosystem respiration (Reco) through the effects on carbon pools. Both the biotic and abiotic factors play significant roles in modulating the spatial and temporal variability in terrestrial carbon cycling in the region. Together, our study quantifies the relative importance of both, and calls for better understanding of them to better predict regional CO2 exchanges.

  16. The effects of global climate change on the species composition and ecosystem function in the central grasslands

    SciTech Connect

    Falkner, M.B.; Ojima, D.S.; Parton, W.J. [Colorado State Univ., Fort Collins, CO (United States)

    1995-06-01

    Alterations to the Earth`s environment are projected to be of an amplitude not experienced in the recent biological history. How ecosystems will respond to these changes is a matter of great uncertainty. Using the ecosystem model CENTURY, we evaluated the responses of five grass species, common to the Central Grasslands Region to changing climates. The altered climates used in this simulation, based on CCC GCM outputs, were 2.5 - 4{degrees}C increase in mean annual temperature and a 1% increase in mean annual precipitation with significant variation in seasonal distribution. The species included Agrostis scabra (C{sub 3} grass), Agropyron repens (C{sub 3} grass), Poa pratensis (C{sub 3} grass), Schizachyrium scoparium (C{sub 4} grass), and Andropogon gerardii (C{sub 4} grass). Soil carbon decreased for all five species under the modified climate scenario. Annual production varied among species. Agropyron repens showed a slight increase, A. scabra showed a slight decrease, while the two C{sub 4} species, S. scoparium and A. gerardii, and the C{sub 3} invasive grass Poa pratensis showed larger increases in annual production. The increased annual production of P. pratensis under the modified climate scenario may indicate the potential for this species to further expand its range. What impact a range expansion of P. pratensis will have on ecosystem function and overall species composition is unclear.

  17. The Coastal Temperate Rainforests of Canada: The need for Ecosystem-Based Management

    Microsoft Academic Search

    F. M. Moola; D. Martin; B. Wareham; J. Calof; C. Burda; P. Grames

    2004-01-01

    The Central and North Coast and Haida Gwaii\\/Queen Charlotte Islands regions of British Columbia (B.C.) contain the world's largest remaining areas of intact coastal temperate rainforest. The region has been the focus of intense conflict among environmentalists, forestry companies, First Nations and other interests over the management of these high conservation value old growth forests. Recently completed land use planning

  18. Understanding coupled climatic and ecosystem responses to global climate change in the Central Grasslands

    SciTech Connect

    Falkner, M.B.; Detling, J.; Ojima, D.; Pielke, R.A.; Stohlgren, T.J. (Colorado State Univ., Ft. Collins (United States)); Kittel, T.G.F. (Colorado State Univ., Ft. Collins (United States) UCAR, Boulder, CO (United States)); Lenihan, J.; Neilson, R. (Oregon State Univ., Corvallis (United States)); Reiners, W. (Univ. of Wyoming, Laramie (United States))

    1993-06-01

    A long-term National Park Service research program to assess the potential effect of global climate change on the Central Grasslands Biogeographic Area is underway. The program consists of two integrated projects: Projecting climate and vegetation change at regional to landscape scales; and Predicting the effect of global change on vegetation in park landscapes at the plot to landscape scales. Together, these integrated field and modeling studies establish a means to validate mesoscale and landscape vegetation models, a central goal of the NPS Global Change Research Program. Vegetation life form modeling suggests that under climate change scenarios the distribution of grassland vegetation zones will undergo major shifts. Results indicate that climate change impacts that reduce water availability will more severely depress productivity of C[sub 3] grass communities relative to C[sub 4] grass communities.

  19. Differential effects of elevated ultraviolet-B radiation on plant species of a dune grassland ecosystem

    Microsoft Academic Search

    Marcel Tosserams; Erwin Magendans; Jelte Rozema

    1997-01-01

    In a greenhouse study, plants of three monocotyledonous and five dicotyledonous species, which occur in a Dutch dune grassland, were exposed to four levels of ultraviolet-B (UV-B) radiation. UV-B levels simulated up to 30% reduction of the stratospheric ozone column during summertime in The Netherlands. Six of the plant species studied in the greenhouse were also exposed to enhanced UV-B

  20. Exploring mobilisation and transport of diffuse substances using multiple sediment and colloid tracers applied to a temperate grassland catchment.

    NASA Astrophysics Data System (ADS)

    Granger, S.; Hawkins, J.

    2009-04-01

    The mobilisation and transport of diffuse substances from livestock grassland systems to surface water bodies is known to impact aquatic ecology and human health. Diffuse substances include sediment and colloidal material detached from the soil surface and subsurface and colloidal material solubilised by water travelling across and through the soil matrix. Improving understanding of the dominant processes controlling the mobilisation and transport of sediment and colloid associated materials requires the application of established and novel tracing methods. In this study our objective was to link mobilisation from the plot to head water catchment scales by tracing the movement of slurry material delivered to a first order stream through the application of natural and artificial fluorescence and rare earth oxide (REO) tracing techniques. Slurry treated with fluorescent beads or REO's was applied to a hydrologically isolated field within a ~40 ha catchment. Novel natural fluorescence techniques were used to assess the presence of dissolved slurry material through the distinctive signature of samples in drainage waters. The particulate phase of slurry was traced using artificial fluorescent beads manufactured to represent two particulate phases of slurry: organic and mineral. The bead treated slurry was applied homogeneously across the entire field. REO treated slurry was applied in five 1 ha contour zones across the field, each zone receiving slurry labelled with different REOs. Surface drainage was monitored and sampled at a v-notch weir placed at the hydrological outlet of the field and at a trapezoidal flume at the catchment outlet.

  1. The significance of agricultural vs. natural ecosystem pathways in temperate climates in assessments of long-term radiological impact.

    PubMed

    K?os, Richard; Albrecht, Achim

    2005-01-01

    Recent developments in performance assessment biosphere models have begun to emphasise the importance of natural accumulation pathways. In contrast to the agricultural pathways, the database for natural ecosystem pathways is less well developed, leading to a mismatch in quality of representations of the two types of system. At issue is the lack of reliable soil-plant and animal ingestion transfer factors for key radionuclides in natural ecosystems. The relative importance of the agricultural vs. natural ecosystem pathways is investigated here, in the context of a temperate site in present day, Eastern France. The BIOMASS Candidate Critical Group (CCG) methodology has been applied to map a set of eight candidate critical groups derived from the present-day societal context onto physical locations within a simple model of a river catchment system. The overall assessment model has been implemented using the Aquabios code. Annual individual dose to each of the CCGs has been calculated for each of the key radionuclides (79Se, 94Nb, 99Tc, 129I, 135Cs and 237Np) released to the valley aquifer and river. In addition to the traditional agricultural pathways, lifestyle groups exploiting natural habitats are explicitly addressed. Results show the susceptibility of different candidate critical groups to different radionuclides. A reference database typical of those employed in long-term performance assessment models is employed. Doses from external exposure (94Nb) and dust inhalation (237Np) are shown to dominate agricultural food consumption by factors of more than six, but, with the reference data set, foodstuffs obtained from natural ecosystems do not contribute significantly to critical group dose and, at most, show similar exposures to the agricultural pathways. This may lead to the conclusion that natural food can be ruled out of consideration in performance assessment models. However, systematic parametric sensitivity studies carried out on soil-plant and animal ingestion transfer factors restrict the validity of this observation and demonstrate the limitations of existing databases. Remaining uncertainties can be reduced by improving structural models for performance assessment and by better characterisation of sources of locally obtained foods. Improved characterisation of radionuclide accumulation in natural ecosystems in temperate as well as alternative future climate states should complement the modelling approach. PMID:15960997

  2. Seasonal variation in leaf properties and ecosystem carbon budget in a cool-temperate deciduous broad-leaved forest: simulation analysis at Takayama site, Japan

    Microsoft Academic Search

    Akihiko Ito; Hiroyuki Muraoka; Hiroshi Koizumi; Nobuko Saigusa; Shohei Murayama; Susumu Yamamoto

    2006-01-01

    Seasonal changes in gross primary production (GPP) and net ecosystem production (NEP) in temperate deciduous forests are mostly driven by environmental conditions and the phenology of leaf demography. This study addresses another factor, temporal changes in leaf properties, i.e., leaf aging from emergence to senescence. A process-based model was used to link the ecosystem-scale carbon budget with leaf-level properties on

  3. Flux and turnover of fixed carbon in soil microbial biomass of limed and unlimed plots of an upland grassland ecosystem.

    PubMed

    Rangel-Castro, J Ignacio; Prosser, Jim I; Ostle, Nick; Scrimgeour, Charlie M; Killham, Ken; Meharg, Andy A

    2005-04-01

    The influence of liming on rhizosphere microbial biomass C and incorporation of root exudates was studied in the field by in situ pulse labelling of temperate grassland vegetation with (13)CO(2) for a 3-day period. In plots that had been limed (CaCO(3) amended) annually for 3 years, incorporation into shoots and roots was, respectively, greater and lower than in unlimed plots. Analysis of chloroform-labile C demonstrated lower levels of (13)C incorporation into microbial biomass in limed soils compared to unlimed soils. The turnover of the recently assimilated (13)C compounds was faster in microbial biomass from limed than that from unlimed soils, suggesting that liming increases incorporation by microbial communities of root exudates. An exponential decay model of (13)C in total microbial biomass in limed soils indicated that the half-life of the tracer within this carbon pool was 4.7 days. Results are presented and discussed in relation to the absolute values of (13)C fixed and allocated within the plant-soil system. PMID:15816931

  4. The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO2 efflux in a temperate grassland

    NASA Astrophysics Data System (ADS)

    Burri, S.; Sturm, P.; Prechsl, U. E.; Knohl, A.; Buchmann, N.

    2014-02-01

    Along with predicted climate change, increased risks for summer drought are projected for Central Europe. However, large knowledge gaps exist in terms of how drought events influence the short-term ecosystem carbon cycle. Here, we present results from 13CO2 pulse labeling experiments at an intensively managed lowland grassland in Switzerland. We investigated the effect of extreme summer drought on the short-term coupling of freshly assimilated photosynthates in shoots to roots as well as to soil CO2 efflux. Summer drought was simulated using rainout shelters during two field seasons (2010 and 2011). Soil CO2 efflux and its isotopic composition were measured with custom-built chambers coupled to a quantum cascade laser spectrometer (QCLAS-ISO, Aerodyne Research Inc., MA, USA). During the 90 min pulse labeling experiments, we added 99.9 atom % 13CO2 to the grass sward. In addition to the isotopic analysis of soil CO2 efflux, this label was traced over 31 days into bulk shoots, roots and soil. Drought reduced the incorporation of recently fixed carbon into the shoots, but increased the relative allocation of fresh assimilates below ground compared to the control grasslands. Contrary to our hypothesis, we did not find a change of allocation speed in response to drought. Although drought clearly reduced soil CO2 efflux rates, about 75% of total tracer uptake in control plots was lost via soil CO2 efflux during 19 days after pulse labeling, compared to only about 60% under drought conditions. Thus, the short-term coupling of above- and below-ground processes was reduced in response to summer drought. The occurrence of a natural spring drought in 2011 lead to comparable albeit weaker drought responses increasing the confidence in the generalizability of our findings.

  5. The likely impact of elevated [CO2], nitrogen deposition, increased temperature, and management on carbon sequestration in temperate and boreal forest ecosystems. A literature review

    Microsoft Academic Search

    Norby; Richard J; Sune Linder; Tryggve Persson; M. Francesca Cotrufo; Alf Ekblad; Michael Freeman; Achim Grelle; Ivan A. Janssens; Paul G. Jarvis; Seppo Kellomäki; Anders Lindroth; Denis Loustau; Tomas Lundmark; Richard J. Norby; Ram Oren; Kim Pilegaard; Michael G. Ryan; Bjarni D. Sigurdsson; Monika Strömgren; Marcel Van Oijen; Göran Wallin

    2007-01-01

    Temperate and Boreal forest ecosystems contain a large part of the carbon stored on land, both in the form of biomass and soil organic matter. Increasing atmospheric carbon dioxide concentration, increasing temperatures, elevated nitrogen deposition, and intensified management will change this carbon store. We review current literature and conclude that northern forests will acquire extra carbon as a result of

  6. A comparison of the net ecosystem exchange of carbon dioxide and evapotranspiration for treed and open portions of a temperate peatland

    Microsoft Academic Search

    Stacey L. Strilesky; Elyn R. Humphreys

    Net ecosystem exchange of carbon dioxide (NEE) and evapotranspiration (ET) were measured at open and treed portions of a temperate ombrotrophic bog using the eddy covariance technique to examine the potential influence of plant community characteristics on peatland carbon and water vapour exchange. The sites were located 2.7km from each other within the same peatland complex and thus experienced similar

  7. Conversion of temperate forests into heaths: Role of ecosystem disturbance and ericaceous plants

    NASA Astrophysics Data System (ADS)

    Mallik, A. U.

    1995-09-01

    Fire and logging in nutrient-poor temperate forests with certain ericaceous understory plants may convert the forests into heaths. The process of disturbance-induced heath formation is documented by using examples of Calluna in western Europe, Kalmia in Newfoundland, and Gaultheria (salal) in coastal British Columbia. In a cool, temperate climate, rapid vegetative growth of Calluna, Kalmia, and salal following disturbance results in increasing organic accumulation (paludification), nutrient sequestration, soil acidification, and allelochemicals. These are thought to be the main reasons to conifer regeneration failure in disturbed habitats. If continuation in forest is a land-use objective, then temperate forests with an ericaceous understory should not be logged unless effective silvicultural methods are devised to control the ericaceous plants and restore forest regeneration. Preharvest vegetation control may be considered as an option. Failure to control the understory plants may lead to a long-term vegetation shift, from forest to heathland, particularly in nutrient-poor sites. Successful methods of controlling Kalmia and Gaultheria, however, have yet to be developed. While the Kalmia- and Gaultheria- dominated heathlands are undesirable in Canada and the Pacific Northwest, a wide range of Calluna heathlands of western Europe are being conserved as natural and seminatural vegetation.

  8. Estimating Ecosystem Respiration of Temperate Deciduous Forests in the Eastern USA by Exclusive Use of MODIS Data

    NASA Astrophysics Data System (ADS)

    Rahman, A. F.; Sims, D. A.; Cordova, V. D.

    2006-05-01

    We explored whether remotely sensed data from the MODIS sensor can be exclusively used to track ecosystem respiration (Re) of four sites representing the temperate deciduous forests of eastern USA. Based on our previous observation that 16-day composite values of MODIS enhanced vegetation index (EVI) strongly correlate with gross primary production (GPP) of deciduous forests, and radiometric surface temperature (Tr) correlate well with Re of closed canopy forested sites, we proposed a multiplicative modeling approach to estimate Re from Tr and EVI. Our results show that the modeled output, Remod, was linearly correlated with Re (R2 = 0.82 to 0.96) across a wide range of values (0.4 to 8 g C m-2 d-1). Data scatter increased around the regression lines at Re values higher than 4 g C m-2 d-1, but the overall performance of the model was highly comparable to the exponential Q10 relationships - the conventional method of deriving Re from air temperature (Ta). Using our method and the routinely available MODIS images, it is possible to generate 16-day composite maps of Remod of the temperate deciduous forested areas of eastern USA at 1 km pixel size. This study is the first to demonstrate that the empirical relationships between remotely sensed image data (Tr and EVI) and eddy-covariance data (Re) can be utilized in a multiplicative modeling approach to provide a truly per- pixel method for scaling up flux tower measurements of Re to regional levels.

  9. Effects of climate change on the delivery of soil-mediated ecosystem services within the primary sector in temperate ecosystems: a review and New Zealand case study.

    PubMed

    Orwin, Kate H; Stevenson, Bryan A; Smaill, Simeon J; Kirschbaum, Miko U F; Dickie, Ian A; Clothier, Brent E; Garrett, Loretta G; van der Weerden, Tony J; Beare, Michael H; Curtin, Denis; de Klein, Cecile A M; Dodd, Michael B; Gentile, Roberta; Hedley, Carolyn; Mullan, Brett; Shepherd, Mark; Wakelin, Steven A; Bell, Nigel; Bowatte, Saman; Davis, Murray R; Dominati, Estelle; O'Callaghan, Maureen; Parfitt, Roger L; Thomas, Steve M

    2015-08-01

    Future human well-being under climate change depends on the ongoing delivery of food, fibre and wood from the land-based primary sector. The ability to deliver these provisioning services depends on soil-based ecosystem services (e.g. carbon, nutrient and water cycling and storage), yet we lack an in-depth understanding of the likely response of soil-based ecosystem services to climate change. We review the current knowledge on this topic for temperate ecosystems, focusing on mechanisms that are likely to underpin differences in climate change responses between four primary sector systems: cropping, intensive grazing, extensive grazing and plantation forestry. We then illustrate how our findings can be applied to assess service delivery under climate change in a specific region, using New Zealand as an example system. Differences in the climate change responses of carbon and nutrient-related services between systems will largely be driven by whether they are reliant on externally added or internally cycled nutrients, the extent to which plant communities could influence responses, and variation in vulnerability to erosion. The ability of soils to regulate water under climate change will mostly be driven by changes in rainfall, but can be influenced by different primary sector systems' vulnerability to soil water repellency and differences in evapotranspiration rates. These changes in regulating services resulted in different potentials for increased biomass production across systems, with intensively managed systems being the most likely to benefit from climate change. Quantitative prediction of net effects of climate change on soil ecosystem services remains a challenge, in part due to knowledge gaps, but also due to the complex interactions between different aspects of climate change. Despite this challenge, it is critical to gain the information required to make such predictions as robust as possible given the fundamental role of soils in supporting human well-being. PMID:25891785

  10. Changes in grassland ecosystem function due to extreme rainfall events: implications for responses to climate change

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Climate change driven by increasing atmospheric CO2 concentrations is causing measurable changes in precipitation patterns. Most climate change scenarios forecast continuing increases in extreme precipitation patterns for North American terrestrial ecosystems, manifest as larger precipitation event...

  11. Predicting the response of a temperate forest ecosystem to atmospheric CO[sub 2] increase

    SciTech Connect

    Bazzaz, F.A.

    1993-01-01

    This report summarizes the second year of research progress. Included are progress reports for the following studies: the responses of temperate forest tree to 3 years of exposure to elevated carbon dioxide, and high and low nutrient and light levels; pot-size limitations in carbon dioxide studies, interactive effects of carbon dioxide and soil moisture availability on tree seedling's tissue water relations, growth, and niche characteristics; individual versus population responses to elevated carbon dioxide levels in two species of annual weeds; and the development of gypsy moth larvae raised on gray and yellow birth foliage grown in ambient and elevated carbon dioxide environments.

  12. Timing of climate variability and grassland productivity

    PubMed Central

    Craine, Joseph M.; Nippert, Jesse B.; Elmore, Andrew J.; Skibbe, Adam M.; Hutchinson, Stacy L.; Brunsell, Nathaniel A.

    2012-01-01

    Future climates are forecast to include greater precipitation variability and more frequent heat waves, but the degree to which the timing of climate variability impacts ecosystems is uncertain. In a temperate, humid grassland, we examined the seasonal impacts of climate variability on 27 y of grass productivity. Drought and high-intensity precipitation reduced grass productivity only during a 110-d period, whereas high temperatures reduced productivity only during 25 d in July. The effects of drought and heat waves declined over the season and had no detectable impact on grass productivity in August. If these patterns are general across ecosystems, predictions of ecosystem response to climate change will have to account not only for the magnitude of climate variability but also for its timing. PMID:22331914

  13. Nitrogen controls plant canopy light-use efficiency in temperate and boreal ecosystems

    NASA Astrophysics Data System (ADS)

    Kergoat, Laurent; Lafont, SéBastien; Arneth, Almut; Le Dantec, ValéRie; Saugier, Bernard

    2008-12-01

    Optimum daily light-use efficiency (LUE) and normalized canopy photosynthesis (GEE*) rate, a proxy for LUE, have been derived from eddy covariance CO2 flux measurements obtained at a range of sites located in the mid to high latitudes. These two variables were analyzed with respect to environmental conditions, plant functional types (PFT) and leaf nitrogen concentration, in an attempt to characterize their variability and their potential drivers. LUE averaged 0.0182 mol/mol with a coefficient of variation of 37% (42% for GEE*). Foliar nitrogen N of the dominant plant species was found to explain 71% of LUE (n = 26) and 62% of GEE* (n = 44) variance, across all PFTs and sites. Mean Annual Temperature, MAT, explained 27% of LUE variance, and the two factors (MAT and N) combined in a simple linear model explain 80% of LUE and 76% GEE* variance. These results showed that plant canopies in the temperate, boreal and arctic zones fit into a general scheme closely related to the one, which had been established for plant leaves worldwide. The N-MAT-LUE relationships offer perspectives for LUE-based models of terrestrial photosynthesis based on remote sensing. On a continental scale, the decrease of LUE from the temperate to the arctic zone found in the data derived from flux measurements is not in line with LUE resulting from inversion of atmospheric CO2.

  14. Comparison of ecosystem water-use efficiency among Douglas-fir forest, aspen forest and grassland using eddy covariance and carbon isotope techniques

    Microsoft Academic Search

    STEPHANE P ONTON; BRUCE G. J OHNSON; K AI; T. A NDREW

    Comparisons were made among Douglas-fir forest, aspen (broad leaf deciduous) forest and wheatgrass (C3) grassland for ecosystem-level water-use efficiency (WUE). WUE was defined as the ratio of photosynthetic CO2 assimilation rate and evapotranspiration (ET) rate. The ET data measured by eddy covariance were screened so that they overwhel- mingly represented transpiration. The three sites used in this comparison spanned a

  15. Influence of local air pollution on the deposition of peroxyacetyl nitrate to a nutrient-poor natural grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Moravek, A.; Stella, P.; Foken, T.; Trebs, I.

    2015-01-01

    Dry deposition of peroxyacetyl nitrate (PAN) is known to have a phytotoxic impact on plants under photochemical smog conditions, but it may also lead to higher productivity and threaten species richness of vulnerable ecosystems in remote regions. However, underlying mechanisms or controlling factors for PAN deposition are not well understood and studies on dry deposition of PAN are limited. In this study, we investigate the impact of PAN deposition on a nutrient-poor natural grassland ecosystem situated at the edge of an urban and industrialized region in Germany. PAN mixing ratios were measured within a 3.5 months summer to early autumn period. In addition, PAN fluxes were determined with the modified Bowen ratio technique for a selected period. The evaluation of both stomatal and non-stomatal deposition pathways was used to model PAN deposition over the entire summer-autumn period. We found that air masses at the site were influenced by two contrasting pollution regimes, which led to median diurnal PAN mixing ratios ranging between 50 and 300 ppt during unpolluted and between 200 and 600 ppt during polluted episodes. The measured PAN fluxes showed a clear diurnal cycle with maximal deposition fluxes of ~-0.1 nmol m-2 s-1 (corresponding to a deposition velocity of 0.3 cm s-1) during daytime and a significant non-stomatal contribution was found. The ratio of PAN to ozone deposition velocities was found to be ~0.1, which is much larger than assumed by current deposition models. The modelled PAN flux over the entire period revealed that PAN deposition over an entire day was 333 ?g m-2 d-1 under unpolluted and 518 ?g m-2 d-1 under polluted episodes. Additionally, thermochemical decomposition PAN deposition accounted for 32% under unpolluted episodes and 22% under polluted episodes of the total atmospheric PAN loss. However, the impact of PAN deposition as a nitrogen source to the nutrient-poor grassland was estimated to be only minor, under both unpolluted and polluted episodes.

  16. The role of grasslands in food security and climate change

    PubMed Central

    O'Mara, F. P.

    2012-01-01

    Background Grasslands are a major part of the global ecosystem, covering 37 % of the earth's terrestrial area. For a variety of reasons, mostly related to overgrazing and the resulting problems of soil erosion and weed encroachment, many of the world's natural grasslands are in poor condition and showing signs of degradation. This review examines their contribution to global food supply and to combating climate change. Scope Grasslands make a significant contribution to food security through providing part of the feed requirements of ruminants used for meat and milk production. Globally, this is more important in food energy terms than pig meat and poultry meat. Grasslands are considered to have the potential to play a key role in greenhouse gas mitigation, particularly in terms of global carbon storage and further carbon sequestration. It is estimated that grazing land management and pasture improvement (e.g. through managing grazing intensity, improved productivity, etc) have a global technical mitigation potential of almost 1·5 Gt CO2 equivalent in 2030, with additional mitigation possible from restoration of degraded lands. Milk and meat production from grassland systems in temperate regions has similar emissions of carbon dioxide per kilogram of product as mixed farming systems in temperate regions, and, if carbon sinks in grasslands are taken into account, grassland-based production systems can be as efficient as high-input systems from a greenhouse gas perspective. Conclusions Grasslands are important for global food supply, contributing to ruminant milk and meat production. Extra food will need to come from the world's existing agricultural land base (including grasslands) as the total area of agricultural land has remained static since 1991. Ruminants are efficient converters of grass into humanly edible energy and protein and grassland-based food production can produce food with a comparable carbon footprint as mixed systems. Grasslands are a very important store of carbon, and they are continuing to sequester carbon with considerable potential to increase this further. Grassland adaptation to climate change will be variable, with possible increases or decreases in productivity and increases or decreases in soil carbon stores. PMID:23002270

  17. An Integrated Mercury Monitoring Program for Temperate Estuarine and Marine Ecosystems on the North American Atlantic Coast

    PubMed Central

    Evers, David C.; Mason, Robert P.; Kamman, Neil C.; Chen, Celia Y.; Bogomolni, Andrea L.; Taylor, David L.; Hammerschmidt, Chad R.; Jones, Stephen H.; Burgess, Neil M.; Munney, Kenneth; Parsons, Katharine C.

    2008-01-01

    During the past century, anthropogenic activities have altered the distribution of mercury (Hg) on the earth’s surface. The impacts of such alterations to the natural cycle of Hg can be minimized through coordinated management, policy decisions, and legislative regulations. An ability to quantitatively measure environmental Hg loadings and spatiotemporal trends of their fate in the environment is critical for science-based decision making. Here, we outline a Hg monitoring program for temperate estuarine and marine ecosystems on the Atlantic Coast of North America. This framework follows a similar, previously developed plan for freshwater and terrestrial ecosystems in the United States. Methylmercury (MeHg) is the toxicologically relevant form of Hg, and its ability to bioaccumulate in organisms and biomagnify in food webs depends on numerous biological and physicochemical factors that affect its production, transport, and fate. Therefore, multiple indicators are needed to fully characterize potential changes of Hg loadings in the environment and MeHg bioaccumulation through the different marine food webs. In addition to a description of how to monitor environmental Hg loads for air, sediment, and water, we outline a species-specific matrix of biotic indicators that include shellfish and other invertebrates, fish, birds and mammals. Such a Hg monitoring template is applicable to coastal areas across the Northern Hemisphere and is transferable to arctic and tropical marine ecosystems. We believe that a comprehensive approach provides an ability to best detect spatiotemporal Hg trends for both human and ecological health, and concurrently identify food webs and species at greatest risk to MeHg toxicity. PMID:19294469

  18. Whole-ecosystem labile carbon production in a north temperate deciduous forest

    Microsoft Academic Search

    Christopher M. Gough; Charles E. Flower; Christoph S. Vogel; Danilo Dragoni; Peter S. Curtis

    2009-01-01

    Labile carbon (C), which is principally comprised of non-structural carbohydrates, is an essential intermediary between C assimilation and structural growth in deciduous forests. We developed a new approach that combined meteorological and biometric C cycling data for a mixed deciduous forest in Michigan, USA, to provide novel estimates of whole-ecosystem labile C production and reallocation to structural net primary production

  19. Integrating Climate and Ecosystem-Response Sciences in Temperate Western North American Mountains: The CIRMOUNT Initiative

    NASA Astrophysics Data System (ADS)

    Millar, C. I.; Fagre, D. B.

    2004-12-01

    Mountain regions are uniquely sensitive to changes in climate, vulnerable to climate effects on biotic and physical factors of intense social concern, and serve as critical early-warning systems of climate impacts. Escalating demands on western North American (WNA) mountain ecosystems increasingly stress both natural resources and rural community capacities; changes in mountain systems cascade to issues of national concern. Although WNA has long been a focus for climate- and climate-related environmental research, these efforts remain disciplinary and poorly integrated, hindering interpretation into policy and management. Knowledge is further hampered by lack of standardized climate monitoring stations at high-elevations in WNA. An initiative is emerging as the Consortium for Integrated Climate Research in Western Mountains (CIRMOUNT) whose primary goal is to improve knowledge of high-elevation climate systems and to better integrate physical, ecological, and social sciences relevant to climate change, ecosystem response, and natural-resource policy in WNA. CIRMOUNT seeks to focus research on climate variability and ecosystem response (progress in understanding synoptic scale processes) that improves interpretation of linkages between ecosystem functions and human processing (progress in understanding human-environment integration), which in turn would yield applicable information and understanding on key societal issues such as mountains as water towers, biodiversity, carbon forest sinks, and wildland hazards such as fire and forest dieback (progress in understanding ecosystem services and key thresholds). Achieving such integration depends first on implementing a network of high-elevation climate-monitoring stations, and linking these with integrated ecosystem-response studies. Achievements since 2003 include convening the 2004 Mountain Climate Sciences Symposium (1, 2) and several special sessions at technical conferences; initiating a biennial mountain climate research symposium (MTNCLIM), the first to be held in spring 2005; developing a strategy for climate-monitoring in WNA; installing and networking high-elevation (>3000m) climate-monitoring stations; and completing three target regions (Glacier National Park, MT; Sierra Nevada and White Mountains, CA) of the international GLORIA (Global Observation Research Initiative in Alpine Environments) plant-monitoring project, the first in WNA. CIRMOUNT emphasizes integration at the regional scale in WNA, collaborating with and complementing projects such as the Western Mountain Initiative, whose mandate is more targeted than CIRMOUNT's, and global programs such as GLORIA and the international Mountain Research Initiative. Achievement of continuing success in WNA hinges on the capacity to secure long-term funding and institutional investment. (1) See associated URL for paper and poster pdfs (2) Discussing the future of western U.S. mountains, climate change, and ecosystems. EOS 31 August 2004, 85(35), p. 329

  20. Geographical and interannual variability in biomass partitioning in grassland ecosystems: a synthesis of field data

    Microsoft Academic Search

    Dafeng Hui; Robert B. Jackson

    2006-01-01

    Summary • Biomass partitioning is an important variable in terrestrial ecosystem carbon modeling. However, geographical and interannual variability in f BNPP , defined as the fraction of belowground net primary productivity (BNPP) to total NPP, and its relationship with climatic variables, have not been explored. • Here we addressed these issues by synthesizing 94 site-year field biomass data at 12

  1. Comparison of Ecosystem Water-use Efficiency Among Douglas fir Forest, Aspen Forest and Grassland Using Eddy Covariance and Carbon Isotope Techniques

    NASA Astrophysics Data System (ADS)

    Flanagan, L. B.; Ponton, S.; Alstad, K. P.; Johnson, B. G.; Morgenstern, K.; Kljun, N.; Black, T. A.; Barr, A. G.

    2005-12-01

    Comparisons were made among Douglas fir forest, aspen (broad leaf deciduous) forest and wheatgrass (C3) grassland for ecosystem-level water-use efficiency. Water-use efficiency (WUE) was defined as the ratio of photosynthetic CO2 assimilation rate and evapo-transpiration (ET) rate. The ET data measured by eddy covariance were screened so that they overwhelmingly represented transpiration. The three sites used in this comparison spanned a range of vegetation (plant functional) types and environmental conditions within western Canada. When compared in the relative order Douglas fir (located on Vancouver Island, B.C), aspen (northern Saskatchewan), grassland (southern Alberta), the sites demonstrated a progressive decline in precipitation and a general increase in maximum air temperature and atmospheric saturation deficit (D) during the mid-summer. The average WUE at the grassland site was 2.6 mmol mol-1, which was much lower than the average values observed for the two other sites (aspen: 5.4, Douglas fir: 8.1). The differences in WUE among sites were primarily due to variation in ET. The highest maximum ET rates were approximately 5, 3.2 and 2.7 mm day-1 for the grassland, aspen and Douglas fir sites, respectively. There was a strong negative correlation between WUE and D for all sites. We also made seasonal measurements of the carbon isotope ratio of ecosystem respired CO2 (?R) in order to test for the expected correlation between shifts in environmental conditions and changes to the ecosystem-integrated ratio of leaf intercellular to ambient CO2 concentration (ci/ca). There was a consistent increase in ?R values in the grassland, aspen forest and Douglas fir forest associated with a seasonal reduction in soil moisture. Comparisons were made between WUE measured using eddy covariance with that calculated based on atmospheric saturation deficit and ?R measurements. There was excellent agreement between WUE values calculated using the two techniques. Our ?R measurements indicated that ci/ca values were quite similar among the Douglas fir, aspen and grassland sites, despite large variation in environmental conditions among sites. This implied that the shorter-lived grass species had relatively high ci/ca values for the D of their habitat. By contrast, the longer-lived Douglas fir trees were more conservative in water-use with lower ci/ca values relative to their habitat D. This illustrates the interaction between biological and environmental characteristics influencing ecosystem-level water-use efficiency.

  2. Modelling carbon fluxes of forest and grassland ecosystems in Western Europe using the CARAIB dynamic vegetation model: evaluation against eddy covariance data.

    NASA Astrophysics Data System (ADS)

    Henrot, Alexandra-Jane; François, Louis; Dury, Marie; Hambuckers, Alain; Jacquemin, Ingrid; Minet, Julien; Tychon, Bernard; Heinesch, Bernard; Horemans, Joanna; Deckmyn, Gaby

    2015-04-01

    Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface and vegetation models at regional and global scale. In the framework of the MASC project (« Modelling and Assessing Surface Change impacts on Belgian and Western European climate »), vegetation dynamics and carbon fluxes of forest and grassland ecosystems simulated by the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) are evaluated and validated by comparison of the model predictions with eddy covariance data. Here carbon fluxes (e.g. net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RECO)) and evapotranspiration (ET) simulated with the CARAIB model are compared with the fluxes measured at several eddy covariance flux tower sites in Belgium and Western Europe, chosen from the FLUXNET global network (http://fluxnet.ornl.gov/). CARAIB is forced either with surface atmospheric variables derived from the global CRU climatology, or with in situ meteorological data. Several tree (e.g. Pinus sylvestris, Fagus sylvatica, Picea abies) and grass species (e.g. Poaceae, Asteraceae) are simulated, depending on the species encountered on the studied sites. The aim of our work is to assess the model ability to reproduce the daily, seasonal and interannual variablility of carbon fluxes and the carbon dynamics of forest and grassland ecosystems in Belgium and Western Europe.

  3. The Ecological Significance of the Herbaceous Layer in Temperate Forest Ecosystems

    NSDL National Science Digital Library

    Frank Gilliam (; )

    2007-11-01

    This peer-reviewed article from the November 2007 issue of BioScience examines the importance of the herbaceous layer of the forest ecosystem. Despite a growing awareness that the herbaceous layer serves a special role in maintaining the structure and function of forests, this stratum remains an underappreciated aspect of forest ecosystems. In this article I review and synthesize information concerning the herb layer's structure, composition, and dynamics to emphasize its role as an integral component of forest ecosystems. Because species diversity is highest in the herb layer among all forest strata, forest biodiversity is largely a function of the herb-layer community. Competitive interactions within the herb layer can determine the initial success of plants occupying higher strata, including the regeneration of dominant overstory tree species. Furthermore, the herb layer and the overstory can become linked through parallel responses to similar environmental gradients. These relationships between strata vary both spatially and temporally. Because the herb layer responds sensitively to disturbance across broad spatial and temporal scales, its dynamics can provide important information regarding the site characteristics of forests, including patterns of past land-use practices. Thus, the herb layer has a significance that belies its diminutive stature.

  4. Scale effects on the controls on mountain grassland leaf stomatal and ecosystem surface conductance to water vapour

    NASA Astrophysics Data System (ADS)

    Haslwanter, Alois; Hammerle, Albin; Wohlfahrt, Georg

    2010-05-01

    Stomata are the major pathway by which plants exert control on the exchange of trace gases and water vapour with the aerial environment and thus provide a key link between the functioning of terrestrial ecosystems and the state and composition of the atmosphere. Understanding the nature of this control, i.e. how stomatal conductance differs between plant species and ecosystems and how it varies in response to external and internal forcings, is key to predicting feedbacks plants may be providing to changing climatic conditions. Despite a long history of research on stomatal functioning, a fully mechanistic understanding of how stomata function in response to biotic and abiotic controls is still elusive which has led to the development of a large number of (semi-)empirical models of varying complexity. Two of the most widely used models go back to Jarvis (1976) and Ball, Woodrow and Berry (1987), termed J-model and BWB-model, respectively, in the following. The J-model simulates stomatal conductance as some maximal value attenuated by a series of multiplicative functions which are bound between zero and unity, while the BWB-model predicts stomatal conductance as a linear function of photosynthesis, relative humidity and carbon dioxide concentration in the leaf boundary layer. Both models were developed for the prediction of leaf-scale stomatal conductance to water vapour, but have been applied for simulating ecosystem-scale surface conductance as well. The objective of the present paper is to compare leaf- and ecosystem-scale conductances to water vapour and to assess the respective controls using the two above-mentioned models as analysis frameworks. To this end leaf-level stomatal conductance has been measured by means of leaf-gas exchange methods and ecosystem-scale surface conductance by inverting eddy covariance evapotranspiration estimates at a mountain grassland site in Austria. Our major findings are that the proportionality parameter in the BWB-model is scale-consistent, i.e. does not differ significantly between the leaf- and ecosystem scale, while the residual conductance (at zero light) scales with the amount of above-ground transpiring plant area. Among the environmental forcings, air humidity (either relative humidity or vapour pressure deficit) and carbon dioxide concentration in the boundary layer explained most of the variability of stomatal conductance at the leaf level, while the photosynthetic photon flux density was by far the dominant control at the ecosystem-level. References: Ball J.T., Woodrow I.E., Berry J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: J. Biggens (Editor), Progress in Photosynthesis Research, Vol. IV. Proceedings of the VII International Congress on Photosynthesis. Martinus Nijhoff, Dordrecht, pp. 221-224. Jarvis P.G., 1976. The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field. Philosophical Transactions of the Royal Society London 273(B), 593-610.

  5. Periphyton as a bioindicator of mercury pollution in a temperate torrential river ecosystem.

    PubMed

    Zižek, Suzana; Mila?i?, Radmila; Kova?, Nives; Ja?imovi?, Radojko; Toman, Mihael J; Horvat, Milena

    2011-10-01

    Mercury presents a potential risk to the environment and humans, especially in its methylated form. It is among the highest priority environmental pollutants. River Idrijca (Slovenia) is highly contaminated with mercury due to past mercury mining. The aim of this work was to investigate whether the periphyton community in rivers such as Idrijca is a suitable indicator of Hg pollution and of changes in mercury methylation and could serve as an early warning system of increased input of MeHg in the food chain. Periphyton is the only site of primary production in temperate torrential rivers such as Idrijca and is therefore an important link in the food chain. It is also a potential site of Hg accumulation and its introduction to higher trophic levels. Our aim was to assess the response of the periphyton to seasonal and spatial variations in mercury levels and to evaluate its potential as an early warning system of changes in mercury reactivity and mobilization The results indicate that periphyton in a torrential river is too complex and unpredictable to be used as a sole indicator of mercury concentrations and changes in the river. Nevertheless, it can complement environmental measurements due to its importance in the riverine food web. PMID:21840563

  6. Remote sensing of canopy chemistry and nitrogen cycling in temperate forest ecosystems

    NASA Technical Reports Server (NTRS)

    Wessman, Carol A.; Aber, John D.; Peterson, David L.; Melillo, Jerry M.

    1988-01-01

    The use of images acquired by the Airborne Imaging Spectrometer, an experimental high-spectral resolution imaging sensor developed by NASA, to estimate the lignin concentration of whole forest canopies in Wisconsin is reported. The observed strong relationship between canopy lignin concentration and nitrogen availability in seven undisturbed forest ecosystems on Blackhawk Island, Wisconsin, suggests that canopy lignin may serve as an index for site nitrogen status. This predictive relationship presents the opportunity to estimate nitrogen-cycling rates across forested landscapes through remote sensing.

  7. Reducing Greenhouse Gas Emissions in Grassland Ecosystems of the Central Lithuania: Multi-Criteria Evaluation on a Basis of the ARAS Method

    PubMed Central

    Balezentiene, Ligita; Kusta, Albinas

    2012-01-01

    N2O, CH4, and CO2 are potential greenhouse gas (GHG) contributing to climate change; therefore, solutions have to be sought to reduce their emission from agriculture. This work evaluates GHG emission from grasslands submitted to different mineral fertilizers during vegetation period (June–September) in two experimental sites, namely, seminatural grassland (8 treatments of mineral fertilizers) and cultural pasture (intensively managed) in the Training Farm of the Lithuanian University of Agriculture. Chamber method was applied for evaluation of GHG emissions on the field scale. As a result, soil chemical composition, compactness, temperature, and gravimetric moisture as well as biomass yield of fresh and dry biomass and botanical composition, were assessed during the research. Furthermore, a simulation of multi-criteria assessment of sustainable fertilizers management was carried out on a basis of ARAS method. The multicriteria analysis of different fertilizing regimes was based on a system of environmental and productivity indices. Consequently, agroecosystems of cultural pasture (N180P120K150) and seminatural grassland fertilizing rates N180P120K150 and N60P40K50 were evaluated as the most sustainable alternatives leading to reduction of emissions between biosphere-atmosphere and human-induced biogenic pollution in grassland ecosystems, thus contributing to improvement of countryside environment. PMID:22645463

  8. Diverse responses of phenology to global changes in a grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Cleland, E. E.; Chiariello, N. R.; Loarie, S. R.; Field, C. B.; Mooney, H. A.

    2008-12-01

    Observations of shifting plant phenology in recent decades have demonstrated that species and ecosystems are already responding to global environmental change. Earlier flowering and an extended period of active plant growth across much of the northern hemisphere have been interpreted as responses to warming. However, several kinds of environmental change have the potential to influence the phenology of flowering and primary production. In order to better understand the influences of multiple, interacting environmental changes, we investigated shifts in the phenology of flowering and canopy greenness (Normalized Difference Vegetation Index) in response to four experimentally simulated global changes: warming, elevated CO2, nitrogen (N) deposition, and increased precipitation. Warming accelerated both flowering and greening of the canopy, consistent with previous observations, but phenological responses to the other global change treatments were diverse. Elevated CO2 and N addition delayed flowering in grasses, but slightly accelerated flowering in forbs. The opposing responses of these two important functional groups decreased their phenological complementarity and potentially increased competition for limiting soil resources. At the ecosystem level, elevated CO2 delayed greening, whereas N addition dampened the acceleration of greening caused by warming. Thus the timing of canopy green-up mirrored the flowering phenology of the grasses, which dominated primary production in this system. Increased precipitation had no consistent impacts on phenology. This diversity of phenological changes, between plant functional groups and in response to multiple environmental changes, helps explain the diversity in large-scale observations and highlights the need to understand how multiple drivers, in addition to changing temperature, are reshaping the seasonality of ecosystem processes.

  9. The importance of phenology for the evaluation of impact of climate change on growth of boreal, temperate and Mediterranean forests ecosystems: an overview

    Microsoft Academic Search

    K. Kramer; I. Leinonen; D. Loustau

    2000-01-01

    An overview is presented of the phenological models relevant for boreal coniferous, temperate-zone deciduous and Mediterranean\\u000a coniferous forest ecosystems. The phenology of the boreal forests is mainly driven by temperature, affecting the timing of\\u000a the start of the growing season and thereby its duration, and the level of frost hardiness and thereby the reduction of foliage\\u000a area and photosynthetic capacity

  10. Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem models applied to the Qinghai-Tibetan Plateau

    USGS Publications Warehouse

    Yi, S.; Li, N.; Xiang, B.; Wang, X.; Ye, B.; McGuire, A.D.

    2013-01-01

    Soil surface temperature is a critical boundary condition for the simulation of soil temperature by environmental models. It is influenced by atmospheric and soil conditions and by vegetation cover. In sophisticated land surface models, it is simulated iteratively by solving surface energy budget equations. In ecosystem, permafrost, and hydrology models, the consideration of soil surface temperature is generally simple. In this study, we developed a methodology for representing the effects of vegetation cover and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems on the Qinghai-Tibetan Plateau. Our approach integrated measurements from meteorological stations with simulations from a sophisticated land surface model to develop an equation set for estimating soil surface temperature. After implementing this equation set into an ecosystem model and evaluating the performance of the ecosystem model in simulating soil temperature at different depths in the soil profile, we applied the model to simulate interactions among vegetation cover, freeze-thaw cycles, and soil erosion to demonstrate potential applications made possible through the implementation of the methodology developed in this study. Results showed that (1) to properly estimate daily soil surface temperature, algorithms should use air temperature, downward solar radiation, and vegetation cover as independent variables; (2) the equation set developed in this study performed better than soil surface temperature algorithms used in other models; and (3) the ecosystem model performed well in simulating soil temperature throughout the soil profile using the equation set developed in this study. Our application of the model indicates that the representation in ecosystem models of the effects of vegetation cover on the simulation of soil thermal dynamics has the potential to substantially improve our understanding of the vulnerability of alpine grassland ecosystems to changes in climate and grazing regimes.

  11. Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem models applied to the Qinghai-Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Yi, S.; Li, N.; Xiang, B.; Wang, X.; Ye, B.; McGuire, A. D.

    2013-07-01

    surface temperature is a critical boundary condition for the simulation of soil temperature by environmental models. It is influenced by atmospheric and soil conditions and by vegetation cover. In sophisticated land surface models, it is simulated iteratively by solving surface energy budget equations. In ecosystem, permafrost, and hydrology models, the consideration of soil surface temperature is generally simple. In this study, we developed a methodology for representing the effects of vegetation cover and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems on the Qinghai-Tibetan Plateau. Our approach integrated measurements from meteorological stations with simulations from a sophisticated land surface model to develop an equation set for estimating soil surface temperature. After implementing this equation set into an ecosystem model and evaluating the performance of the ecosystem model in simulating soil temperature at different depths in the soil profile, we applied the model to simulate interactions among vegetation cover, freeze-thaw cycles, and soil erosion to demonstrate potential applications made possible through the implementation of the methodology developed in this study. Results showed that (1) to properly estimate daily soil surface temperature, algorithms should use air temperature, downward solar radiation, and vegetation cover as independent variables; (2) the equation set developed in this study performed better than soil surface temperature algorithms used in other models; and (3) the ecosystem model performed well in simulating soil temperature throughout the soil profile using the equation set developed in this study. Our application of the model indicates that the representation in ecosystem models of the effects of vegetation cover on the simulation of soil thermal dynamics has the potential to substantially improve our understanding of the vulnerability of alpine grassland ecosystems to changes in climate and grazing regimes.

  12. Carbon balance of renovated grasslands: input- or output-driven?

    NASA Astrophysics Data System (ADS)

    Choncubhair, Órlaith Ní; Osborne, Bruce; Lanigan, Gary

    2015-04-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. In permanent temperate grasslands, biomass production and sward quality can deteriorate over time and periodic renovation activities, involving soil tillage and reseeding, are commonly carried out to halt this decline. Long-term cultivation of agricultural land has been associated with soil aggregate degradation and reduced soil carbon storage. However, the impact of these single tillage disturbances on C cycling in grasslands is less clear. This study evaluated gaseous and dissolved organic carbon (DOC) losses following a single tillage event by subjecting grassland lysimeters with contrasting soil drainage characteristics to simulated conventional inversion or minimum tillage. Field-scale CO2 emissions after conventional tillage were also quantified and empirically modelled over short- and medium-term timeframes to delineate the ecosystem response to environmental variables. Soil moisture was the limiting determinant of ecosystem carbon release following conventional tillage. Freshly-tilled soils were associated with reduced water retention and increased sensitivity to soil moisture, which was particularly pronounced following rewetting events. Significantly elevated but ephemeral CO2 effluxes were detected in the hours following inversion ploughing, however tillage disturbance did not generate significantly enhanced C emission rates in the medium term. Equally, DOC losses were not significantly amplified by conventional tillage compared with conservative minimum tillage and were predominantly controlled by soil drainage across tillage regimes. Our results suggest that a net ecosystem source of 120 to 210 g C m-2 over an approximately two-month period was most likely a consequence of reduced productivity and C input rather than enhanced soil CO2 evolution. C emissions from cultivated lands will therefore be minimised by restricting tillage operations and fallow periods to spring or autumn when respiratory losses are reduced and by limiting the length of the fallow period to enhance the compensatory effect of photosynthetic C uptake.

  13. Characterizing Dissolved Organic Matter (DOM) Isolated From Specific Allochthonous and Autochthonous Sources in a North-Temperate Stream Ecosystem

    NASA Astrophysics Data System (ADS)

    Wong, J. C.; Williams, D.

    2009-05-01

    Detrital energy in temperate headwater streams is mainly derived from the annual input of leaf litter from the surrounding landscape. Presumably, its decomposition and other sources of autochthonous organic matter will change dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) quality. To investigate this, DOM was leached from two allochthonous sources: white birch (Betula papyrifera) and white cedar (Thuja occidentalis); and one autochthonous source, streambed biofilm, for a period of 7 days on 3 separate occasions in fall 2007. As a second treatment, microorganisms from the water column were filtered out. Deciduous leaf litter was responsible for high, short-term increases to DOC concentrations whereas the amounts leached from conifer needles were relatively constant in each month. Using UV spectroscopy, changes to DOM characteristics like aromaticity, spectral slopes, and molecular weight were mainly determined by source and indicated a preferential use of the labile DOM pool by the microorganisms. Excitation-emission matrices (EEMs) collected using fluorescence spectroscopy suggested that cedar litter was an important source of protein-like fluorescence and that the nature of the fluorescing DOM components changed in the presence of microorganisms. This study demonstrates that simultaneous examination of DOC concentrations and DOM quality will allow a better understanding of the carbon dynamics that connect terrestrial with aquatic ecosystems.

  14. Applicability of the flood-pulse concept in a temperate floodplain river ecosystem: Thermal and temporal components

    USGS Publications Warehouse

    Schramm, H.L., Jr.; Eggleton, M.A.

    2006-01-01

    Annual growth increments were calculated for blue catfish (Ictalurus furcatus) and flathead catfish (Pylodictis olivaris) from the lower Mississippi River (LMR) to assess hypothesized relationships between fish growth and floodplain inundation as predicted by the Flood-Pulse Concept. Variation in catfish growth increment was high for all age classes of both species, and growth increments were not consistently related to various measures of floodplain inundation. However, relationships became stronger, and usually direct, when water temperature was integrated with area and duration of floodplain inundation. Relationships were significant for four of six age classes for blue catfish, a species known to utilize floodplain habitats. Though similar in direction, relationships were weaker for flathead catfish, which is considered a more riverine species. Our results indicate the Flood-Pulse Concept applies more strongly to temperate floodplain-river ecosystems when thermal aspects of flood pulses are considered. We recommend that future management of the LMR should consider ways to 'recouple' the annual flood and thermal cycles. An adaptive management approach will allow further determination of important processes affecting fisheries production in the LMR. Copyright ?? John Wiley & Sons, Ltd.

  15. Forest and grassland ecosystem studies using the advanced solid-state array spectroradiometer

    NASA Technical Reports Server (NTRS)

    Irons, James R.; Ranson, K. Jon; Williams, Darrel L.; Irish, Richard R.

    1989-01-01

    The advanced solid-state array spectroradiometer (ASAS) is an airborne, off-nadir pointing imaging spectroradiometer used to acquire bidirectional radiance data for terrestrial targets. As its platform aircraft flies over a target the sensor can image the target through a sequence of at least seven fore-to-aft view directions ranging up to 45 deg on either side of nadir. ASAS acquires data for 29 spectral bands in the visible and near-infrared portions of the spectrum with a resolution of 15 nm. ASAS data were recently acquired for a prairie ecosystem and a northern forest ecosystem. The data demonstrate the combined effects of reflectance anisotropy and increased atmospheric path length on off-nadir observations. One result of these effects is a variation in vegetation indices as a function of view direction. Normalized-difference-vegetation-indices for prairie grass, coniferous, and deciduous canopies varied up to 14 percent, 23 percent, and 6 percent, respectively, relative to nadir as a function of view zenith angle along the solar principal plane.

  16. Impact of climate change on GHG emissions of (pre-) alpine grassland ecosystems under intensive and extensive management - a climate sequence lysimeter study

    NASA Astrophysics Data System (ADS)

    Kiese, Ralf; Lu, Haiyan; Fu, Jin; Diaz-Pines, Eugenio; Gasche, Rainer; Dannenmann, Michael; Butterbach-Bahl, Klaus

    2015-04-01

    Due to cool and moist climatic conditions alpine grassland soils of moderate elevation are rich in soil organic carbon and associated nitrogen. In the framework of an in-situ climate change experiment we test the hypothesis that soil organic carbon and nitrogen are either volatilized (GHG emissions) or leached with seepage water due to increase in temperature. Field investigations are carried out in the (Pre-) Alpine TERENO Observatory covering several research sites (including ICOS sites) in South-Bavaria, Germany. IMK-IFU has installed 36 weighable lysimeters with undisturbed intact grassland soil cores (diameter 1m, depth 1.4m) and is operating them at three sites differing in altitude and thus climatic conditions (850m, 750m, 600m) since 2011. Lysimeters were partly translocated from higher elevation to sites at lower elevation and other soil cores still staying at the sites as controls. In addition to the space for time in-situ climate change approach the total of 36 lysimeters are split into treatments of intensive and extensive grassland management. GHG exchange was measured by manual (850m site) but also with two novel automatic robot chamber systems (750m, 600m) connected to QCLs for simultaneous detection of CO2, N2O, and CH4 concentration changes in chamber headspace. GHG flux monitoring was supplemented by NEE measurements with transparent chambers since 2014. Climate change, generally stimulated plant growth (according to biomass sampling after cutting events) and soil C and N turnover leading to increased soil CO2 emissions and an increased uptake of atmospheric CH4. N2O emission were generally low and slightly increased in spring, summer and autumn but significantly decreased during the winter period under global change conditions, the latter due to lower intensity and frequency of frost-thaw events. The main gaseous nitrogen component emitted from the grassland ecosystems was N2 which also showed a much stronger increase with climate change than N2O. Furthermore, climate change lead to a significant increase in nitrate leaching, whereas leaching of ammonium and DON as well as DOC were hardly affected. Climate induced changes in the GHG balance of (pre-) alpine grassland ecosystems are mainly triggered by alteration of ecosystem CO2 exchange since magnitude of CH4 (mainly uptake) and N2O exchange, even regarding their much higher global warming potential are of lower importance. Overall, impacts of climate change on ecosystem C and N losses seem to be more severe under extensive management.

  17. Grassland/atmosphere response to changing climate: Coupling regional and local scales. Final report

    SciTech Connect

    Coughenour, M.B.; Kittel, T.G.F.; Pielke, R.A.; Eastman, J.

    1993-10-01

    The objectives of the study were: to evaluate the response of grassland ecosystems to atmospheric change at regional and site scales, and to develop multiscaled modeling systems to relate ecological and atmospheric models with different spatial and temporal resolutions. A menu-driven shell was developed to facilitate use of models at different temporal scales and to facilitate exchange information between models at different temporal scales. A detailed ecosystem model predicted that C{sub 3} temperate grasslands wig respond more strongly to elevated CO{sub 2} than temperate C{sub 4} grasslands in the short-term while a large positive N-PP response was predicted for a C{sub 4} Kenyan grassland. Long-term climate change scenarios produced either decreases or increases in Colorado plant productivity (NPP) depending on rainfall, but uniform increases in N-PP were predicted in Kenya. Elevated CO{sub 2} is likely to have little effect on ecosystem carbon storage in Colorado while it will increase carbon storage in Kenya. A synoptic climate classification processor (SCP) was developed to evaluate results of GCM climate sensitivity experiments. Roughly 80% agreement was achieved with manual classifications. Comparison of lx and 2xCO{sub 2} GCM Simulations revealed relatively small differences.

  18. Carbon-Nitrogen Cycle Model of Terrestrial Ecosystem for Plot Scale: Application to Cool Temperate Deciduous Broad-leaved Forest and Cool Temperate Evergreen Coniferous Forest in Central Japan

    NASA Astrophysics Data System (ADS)

    Ito, A.; Inatomi, M.

    2007-12-01

    By developing a biogeochemical model that fully includes carbon cycle and nitrogen cycle in a single framework, we can consider nitrogen nutrition as a limiting elements in the model and evaluate atmosphere-ecosystem exchange of trace greenhouse gases in addition to carbon dioxide (i.e. methane and nitrous oxide). In this study, a process-based model simulating carbon-nitrogen cycle was developed and applied to a cool-temperate deciduous broad-leaved forest in Takayama (36N, 137E, 1420m ASL) and a cool-temperate evergreen coniferous forest in Fujiyoshida (35N, 138E, 1030m ASL), central Japan. Models of nitrogen cycle were introduced into a revised terrestrial ecosystem model Sim-CYCLE, which is a simple box-type carbon cycle model simulating net ecosystem CO2 exchange on the basis of ecophysiological relationships. Using the model, photosynthetic and respiratory CO2 fluxes were simulated during the periods from 1948 to 2004 at daily step using time-series climate data. On average during the last 10 years, the model estimated that the temperate forest absorbed net CO2 and CH4 at rates of 804.53 g CO2 m-2 yr-1 and 0.34 g CH4 m-2 yr-1, and net released N2O at a rate of 0.02 g N2O m-2 yr-1, respectively. Based on the 100-year GWP of greenhouse gases in IPCC (2001), the forest was estimated to have a negative (i.e. ameliorating) effect of GWP by 807.74 g CO2 (equivalent) m-2 yr-1. Because the results seem reasonable, we are working on scaling-up of the model to regional scale, in our forthcoming studies.

  19. The North Wyke Farm Platform, a UK national capability for research into sustainability of temperate agricultural grassland management: progress and developments

    NASA Astrophysics Data System (ADS)

    Harris, Paul; Dungait, Jennifer; Griffith, Bruce; Shepherd, Anita; Sint, Hadewij; Blackwell, Martin; Cardenas, Laura; Collins, Adrian; Goulding, Keith; Lee, Michael; Orr, Robert

    2015-04-01

    The North Wyke Farm Platform (NWFP) at Rothamsted Research in the South-West of England, is a large, farm-scale experiment for collaborative research, training and knowledge exchange in agro-environmental sciences; with the aim of addressing agricultural productivity and ecosystem responses to different management practices. The 63 ha NWFP site, captures the spatial and/or temporal data necessary to develop a better understanding of the dynamic processes and underlying mechanisms that can be used to model how agricultural grassland systems respond to different management inputs. Here, via beef and sheep production, the underlying principle is to manage each of three farmlets (each consisting of five man-made, hydrologically-isolated sub-catchments) in three contrasting ways: (i) improvement through use of mineral fertilizers; (ii) improvement through use of legumes; and (iii) improvement through innovation. The connectivity between the timing and intensity of the different management operations, together with the transport of nutrients and potential pollutants from the NWFP is evaluated using various data collection and data modelling exercises. The primary data collection strategy involves the use of a ground-based, wireless sensor network, where in each of the fifteen sub-catchments, water characteristics such as flow, turbidity and chemistry are measured at a flume laboratory that captures the sub-catchment's water drainage (via a system of directed French drains). This sensor network also captures: precipitation, soil moisture and soil temperature data for each sub-catchment; greenhouse gas data across key subsets of the fifteen sub-catchments; and meteorological data (other than precipitation) at a single site only (representative of the NWFP site, as a whole). Such high temporal resolution data sets (but with limited spatial resolution) are coupled with a secondary data collection strategy, for high spatial resolution data sets (but with limited temporal resolution). These latter data sets include (multi-spectral and hyper-spectral) remote sensing data, together with more traditional field studies that provide information on soils nutrients and biodiversity. Both the primary and secondary data collection strategies are complemented by a dedicated geodatabase for the geographical layout of the NWFP site that includes soil class and LiDAR data. All described data collections are relatable to farm field event and farm animal data sets, so that key research objectives can be met. We describe all such NWFP data sets and introduce some of the data modelling opportunities that are possible. All data sets will at some point be freely available to download from a dedicated web-site.

  20. Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?

    PubMed

    Seabloom, Eric W; Borer, Elizabeth T; Buckley, Yvonne; Cleland, Elsa E; Davies, Kendi; Firn, Jennifer; Harpole, W Stanley; Hautier, Yann; Lind, Eric; MacDougall, Andrew; Orrock, John L; Prober, Suzanne M; Adler, Peter; Alberti, Juan; Anderson, T Michael; Bakker, Jonathan D; Biederman, Lori A; Blumenthal, Dana; Brown, Cynthia S; Brudvig, Lars A; Caldeira, Maria; Chu, Chengjin; Crawley, Michael J; Daleo, Pedro; Damschen, Ellen I; D'Antonio, Carla M; DeCrappeo, Nicole M; Dickman, Chris R; Du, Guozhen; Fay, Philip A; Frater, Paul; Gruner, Daniel S; Hagenah, Nicole; Hector, Andrew; Helm, Aveliina; Hillebrand, Helmut; Hofmockel, Kirsten S; Humphries, Hope C; Iribarne, Oscar; Jin, Virginia L; Kay, Adam; Kirkman, Kevin P; Klein, Julia A; Knops, Johannes M H; La Pierre, Kimberly J; Ladwig, Laura M; Lambrinos, John G; Leakey, Andrew D B; Li, Qi; Li, Wei; McCulley, Rebecca; Melbourne, Brett; Mitchell, Charles E; Moore, Joslin L; Morgan, John; Mortensen, Brent; O'Halloran, Lydia R; Pärtel, Meelis; Pascual, Jesús; Pyke, David A; Risch, Anita C; Salguero-Gómez, Roberto; Sankaran, Mahesh; Schuetz, Martin; Simonsen, Anna; Smith, Melinda; Stevens, Carly; Sullivan, Lauren; Wardle, Glenda M; Wolkovich, Elizabeth M; Wragg, Peter D; Wright, Justin; Yang, Louie

    2013-12-01

    Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions. PMID:24038796

  1. Communities of Endophytic Sebacinales Associated with Roots of Herbaceous Plants in Agricultural and Grassland Ecosystems Are Dominated by Serendipita herbamans sp. nov

    PubMed Central

    Riess, Kai; Oberwinkler, Franz; Bauer, Robert; Garnica, Sigisfredo

    2014-01-01

    Endophytic fungi are known to be commonly associated with herbaceous plants, however, there are few studies focusing on their occurrence and distribution in plant roots from ecosystems with different land uses. To explore the phylogenetic diversity and community structure of Sebacinales endophytes from agricultural and grassland habitats under different land uses, we analysed the roots of herbaceous plants using strain isolation, polymerase chain reaction (PCR), transmission electron microscopy (TEM) and co-cultivation experiments. A new sebacinoid strain named Serendipita herbamans belonging to Sebacinales group B was isolated from the roots of Bistorta vivipara, which is characterized by colourless monilioid cells (chlamydospores) that become yellow with age. This species was very common and widely distributed in association with a broad spectrum of herbaceous plant families in diverse habitats, independent of land use type. Ultrastructurally, the presence of S. herbamans was detected in the cortical cells of Plantago media, Potentilla anserina and Triticum aestivum. In addition, 13 few frequent molecular operational taxonomic units (MOTUs) or species were found across agricultural and grassland habitats, which did not exhibit a distinctive phylogenetic structure. Laboratory-based assays indicate that S. herbamans has the ability to colonize fine roots and stimulate plant growth. Although endophytic Sebacinales are widely distributed across agricultural and grassland habitats, TEM and nested PCR analyses reinforce the observation that these microorganisms are present in low quantity in plant roots, with no evidence of host specificity. PMID:24743185

  2. Decomposition of Organic Carbon in Fine Soil Particles Is Likely More Sensitive to Warming than in Coarse Particles: An Incubation Study with Temperate Grassland and Forest Soils in Northern China

    PubMed Central

    Ding, Fan; Huang, Yao; Sun, Wenjuan; Jiang, Guangfu; Chen, Yue

    2014-01-01

    It is widely recognized that global warming promotes soil organic carbon (SOC) decomposition, and soils thus emit more CO2 into the atmosphere because of the warming; however, the response of SOC decomposition to this warming in different soil textures is unclear. This lack of knowledge limits our projection of SOC turnover and CO2 emission from soils after future warming. To investigate the CO2 emission from soils with different textures, we conducted a 107-day incubation experiment. The soils were sampled from temperate forest and grassland in northern China. The incubation was conducted over three short-term cycles of changing temperature from 5°C to 30°C, with an interval of 5°C. Our results indicated that CO2 emissions from sand (>50 µm), silt (2–50 µm), and clay (<2 µm) particles increased exponentially with increasing temperature. The sand fractions emitted more CO2 (CO2-C per unit fraction-C) than the silt and clay fractions in both forest and grassland soils. The temperature sensitivity of the CO2 emission from soil particles, which is expressed as Q10, decreased in the order clay>silt>sand. Our study also found that nitrogen availability in the soil facilitated the temperature dependence of SOC decomposition. A further analysis of the incubation data indicated a power-law decrease of Q10 with increasing temperature. Our results suggested that the decomposition of organic carbon in fine-textured soils that are rich in clay or silt could be more sensitive to warming than those in coarse sandy soils and that SOC might be more vulnerable in boreal and temperate regions than in subtropical and tropical regions under future warming. PMID:24736659

  3. Plant diversity predicts beta but not alpha diversity of soil microbes across grasslands worldwide

    USGS Publications Warehouse

    Prober, Suzanne M.; Leff, Jonathan W.; Bates, Scott T.; Borer, Elizabeth T.; Firn, Jennifer; Harpole, W. Stanley; Lind, Eric M.; Seabloom, Eric W.; Adler, Peter B.; Bakker, Jonathan D.; Cleland, Elsa E.; DeCrappeo, Nicole; DeLorenze, Elizabeth; Hagenah, Nicole; Hautier, Yann; Hofmockel, Kirsten S.; Kirkman, Kevin P.; Knops, Johannes M. H.; La Pierre, Kimberly J.; MacDougall, Andrew S.; McCulley, Rebecca L.; Mitchell, Charles E.; Risch, Anita C.; Schuetz, Martin; Stevens, Carly J.; Williams, Ryan J.; Fierer, Noah

    2015-01-01

    Aboveground–belowground interactions exert critical controls on the composition and function of terrestrial ecosystems, yet the fundamental relationships between plant diversity and soil microbial diversity remain elusive. Theory predicts predominantly positive associations but tests within single sites have shown variable relationships, and associations between plant and microbial diversity across broad spatial scales remain largely unexplored. We compared the diversity of plant, bacterial, archaeal and fungal communities in one hundred and forty-five 1 m2 plots across 25 temperate grassland sites from four continents. Across sites, the plant alpha diversity patterns were poorly related to those observed for any soil microbial group. However, plant beta diversity (compositional dissimilarity between sites) was significantly correlated with the beta diversity of bacterial and fungal communities, even after controlling for environmental factors. Thus, across a global range of temperate grasslands, plant diversity can predict patterns in the composition of soil microbial communities, but not patterns in alpha diversity.

  4. Grasslands and Grassland Sciences in

    E-print Network

    Wu, Jianguo "Jingle"

    Grasslands and Grassland Sciences in Northern China A Report of the Committee on Scholarly,andsometypographicerrorsmayhavebeenaccidentallyinserted.Pleaseusetheprintversionofthispublicationastheauthoritativeversionforattribution. Copyright © National Academy of Sciences. All rights reserved. Grasslands and Grassland Sciences in Northern steppe (Map 1-3) is one of the few well-preserved areas of the Inner Mongolia grassland region. Although

  5. Testing mechanisms of N-enrichment-induced species loss in a semiarid Inner Mongolia grassland: critical thresholds and implications for long-term ecosystem responses

    PubMed Central

    Lan, Zhichun; Bai, Yongfei

    2012-01-01

    The increase in nutrient availability as a consequence of elevated nitrogen (N) deposition is an important component of global environmental change. This is likely to substantially affect the functioning and provisioning of ecosystem services by drylands, where water and N are often limited. We tested mechanisms of chronic N-enrichment-induced plant species loss in a 10-year field experiment with six levels of N addition rate. Our findings on a semi-arid grassland in Inner Mongolia demonstrated that: (i) species richness (SR) declined by 16 per cent even at low levels of additional N (1.75 g N m–2 yr?1), and 50–70% species were excluded from plots which received high N input (10.5–28 g N m?2 yr?1); (ii) the responses of SR and above-ground biomass (AGB) to N were greater in wet years than dry years; (iii) N addition increased the inter-annual variations in AGB, reduced the drought resistance of production and hence diminished ecosystem stability; (iv) the critical threshold for chronic N-enrichment-induced reduction in SR differed between common and rare species, and increased over the time of the experiment owing to the loss of the more sensitive species. These results clearly indicate that both abundance and functional trait-based mechanisms operate simultaneously on N-induced species loss. The low initial abundance and low above-ground competitive ability may be attributable to the loss of rare species. However, shift from below-ground competition to above-ground competition and recruitment limitation are likely to be the key mechanisms for the loss of abundant species, with soil acidification being less important. Our results have important implications for understanding the impacts of N deposition and global climatic change (e.g. change in precipitation regimes) on biodiversity and ecosystem services of the Inner Mongolian grassland and beyond. PMID:23045710

  6. Testing mechanisms of N-enrichment-induced species loss in a semiarid Inner Mongolia grassland: critical thresholds and implications for long-term ecosystem responses.

    PubMed

    Lan, Zhichun; Bai, Yongfei

    2012-11-19

    The increase in nutrient availability as a consequence of elevated nitrogen (N) deposition is an important component of global environmental change. This is likely to substantially affect the functioning and provisioning of ecosystem services by drylands, where water and N are often limited. We tested mechanisms of chronic N-enrichment-induced plant species loss in a 10-year field experiment with six levels of N addition rate. Our findings on a semi-arid grassland in Inner Mongolia demonstrated that: (i) species richness (SR) declined by 16 per cent even at low levels of additional N (1.75 g N m(-2) yr(-1)), and 50-70% species were excluded from plots which received high N input (10.5-28 g N m(-2) yr(-1)); (ii) the responses of SR and above-ground biomass (AGB) to N were greater in wet years than dry years; (iii) N addition increased the inter-annual variations in AGB, reduced the drought resistance of production and hence diminished ecosystem stability; (iv) the critical threshold for chronic N-enrichment-induced reduction in SR differed between common and rare species, and increased over the time of the experiment owing to the loss of the more sensitive species. These results clearly indicate that both abundance and functional trait-based mechanisms operate simultaneously on N-induced species loss. The low initial abundance and low above-ground competitive ability may be attributable to the loss of rare species. However, shift from below-ground competition to above-ground competition and recruitment limitation are likely to be the key mechanisms for the loss of abundant species, with soil acidification being less important. Our results have important implications for understanding the impacts of N deposition and global climatic change (e.g. change in precipitation regimes) on biodiversity and ecosystem services of the Inner Mongolian grassland and beyond. PMID:23045710

  7. Population size and conservation of the last eastern remnants of the regal fritillary, Speyeria idalia (Drury) [Lepidoptera, Nymphalidae]; implications for temperate grassland restoration

    Microsoft Academic Search

    Betty Ferster; Kevina Vulinec

    2010-01-01

    We monitored the last remaining Pennsylvania population of the regal fritillary butterfly (Speyeria idalia) for 8 years (1997–2005) at Fort Indiantown Gap, a National Guard training facility located in south-central Pennsylvania,\\u000a USA. We observed demes of this population in five grassland areas, four of which received limited protection from anthropogenic\\u000a military activities (i.e., motorized vehicles were prohibited). The Pollard walk technique

  8. Effect of rainfall patterns on soil surface CO2 efflux, soil moisture, soil temperature and plant growth in a grassland ecosystem of northern Ontario, Canada: implications for climate change

    Microsoft Academic Search

    Michael F Laporte; LC Duchesne; S Wetzel

    2002-01-01

    BACKGROUND: The effect of rainfall patterns on soil surface CO2 efflux, soil moisture, soil temperature and plant growth was investigated in a grassland ecosystem of northern Ontario, Canada, where climatic change is predicted to introduce new precipitation regimes. Rain shelters were established in a fallow field consisting mainly of Trifolium hybridum L., Trifolium pratense L., and Phleum pratense L. Daytime

  9. Community diversity and invasion resistance: An experimental test in a grassland ecosystem and a review of comparable studies

    Microsoft Academic Search

    Andy Hector; Kim Dobson; Asher Minns; Ellen Bazeley-White; John Hartley Lawton

    2001-01-01

    The relationship between community diversity and invasion resistance in a grassland was examined using experimental plant assemblages that varied in species richness and composition. The assemblages were weeded for three seasons to remove unsown species and we used the number of weeded seedlings, their total biomass and the number of species removed as indicators of community resistance and susceptibility to

  10. ECOLOGICAL RESPONSES TO PRECIPITATION QUANTITY AND FREQUENCY IN GRASSLANDS: PATTERN AND PROCESS FROM THE GENE TO THE ECOSYSTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasslands account for 40% of the U.S. land mass and are highly responsive to temperature and precipitation variability. Climate models and observations indicate warming and increased temporal variability in continental rainfall patterns resulting from increasing greenhouse gas concentrations. Gro...

  11. GRASSLAND MANAGEMENT AND CONVERSION INTO GRASSLAND: EFFECTS ON SOIL CARBON

    Microsoft Academic Search

    RICHARD T. C ONANT; K EITH PAUSTIAN; EDWARD T. E LLIOTT

    2001-01-01

    Grasslands are heavily relied upon for food and forage production. A key component for sustaining production in grassland ecosystems is the maintenance of soil organic matter (SOM), which can be strongly influenced by management. Many management techniques intended to increase forage production may potentially increase SOM, thus sequestering atmospheric carbon (C). Further, conversion from either cultivation or native vegetation into

  12. The effects of climatic and CO[sub 2] changes on grassland storage of soil carbon

    SciTech Connect

    Ojima, D.S.; Parton, W.J. (Colorado State Univ., Fort Collins (United States)); Schimel, D.S. (National Centerfor Atmospheric Research, Boulder, CO (United States)); Scurlock, J.M.O. (Kings College London (United Kingdom))

    1993-06-01

    We present results from analysis of the sensitivity of global grassland ecosystems to modified climate. We assess over 30 grassland sites from around the world under two different GCM double CO[sub 2] climates. The results indicate that soil C losses occur in Ar grassland regions (losses range from 1.6 to 8.8% of current soil C levels for the surface 20 cm). The Eurasian grasslands lost the greatest amount of soil C ([approximately]700 g C/m[sub 2]) and the other temperate grasslands lost approximately half this amount. The tropical grasslands and savannas lost the least amount of soil C per unit area (ranging from no change to 130 g C/m[sub 2] losses). Plant production varies according to modifications in rainfall amounts under the altered climate and to altered nitrogen mineralization rates. The two GCM's differed in predictions of rainfall with a doubling of CO[sub 2], and this difference is reflected in plant production. Soil decomposition rates responded most predictably to changes in temperature. CO[sub 2] fertilization effects on soil C loss and plant production tended to reduce the net impact of climate alterations.

  13. Characterizing Dissolved Organic Matter (DOM) Isolated From Specific Allochthonous and Autochthonous Sources in a North-Temperate Stream Ecosystem

    Microsoft Academic Search

    J. C. Wong; D. Williams

    2009-01-01

    Detrital energy in temperate headwater streams is mainly derived from the annual input of leaf litter from the surrounding landscape. Presumably, its decomposition and other sources of autochthonous organic matter will change dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) quality. To investigate this, DOM was leached from two allochthonous sources: white birch (Betula papyrifera) and white cedar

  14. Assimilating LANDSAT data in an ecosystem model for multi-year simulation of grassland carbon, water and energy budget

    Microsoft Academic Search

    Y. Nouvellon; M. S. Moran; A. Chehbouniz; D. Lo Seen; R. Bryant; M. Nichols; L. Prevot; S. Rambal; W. Ni; A. Begue; P. Heilman; T. O. Keefer

    2000-01-01

    In this study, a spatially explicit hydro-ecological model (SEHEM) has been developed and validated over a semi-arid grassland sub-watershed in Arizona. The model combines a plant growth sub-model to simulate the seasonal dynamics of root and aboveground biomass, and a hydrological sub-model to simulate soil moisture and temperature dynamics, energy and water budgets for the soil and the vegetation. In

  15. Effects of grazing on leaf traits and ecosystem functioning in Inner Mongolia grasslands: scaling from species to community

    Microsoft Academic Search

    S. X. Zheng; H. Y. Ren; Z. C. Lan; W. H. Li; K. B. Wang; Y. F. Bai

    2010-01-01

    Understanding the mechanistic links between environmental drivers, human disturbance, plant functional traits, and ecosystem properties is a fundamental aspect of biodiversity-ecosystem functioning research. Recent studies have focused mostly on leaf-level traits or community-level weighted traits to predict species responses to grazing and the consequent change in ecosystem functioning. However, studies of leaf-level traits or community-level weighted traits seldom identify the

  16. The origin of grasslands in the temperate forest zone of east-central Europe: long-term legacy of climate and human impact

    NASA Astrophysics Data System (ADS)

    Kuneš, Petr; Svobodová-Svitavská, Helena; Kolá?, Jan; Hajnalová, Mária; Abraham, Vojt?ch; Macek, Martin; Tká?, Peter; Szabó, Péter

    2015-05-01

    The post-glacial fate of central European grasslands has stimulated palaeoecological debates for a century. Some argued for the continuous survival of open land, while others claimed that closed forest had developed during the Middle Holocene. The reasons behind stability or changes in the proportion of open land are also unclear. We aim to reconstruct regional vegetation openness and test the effects of climate and human impact on vegetation change throughout the Holocene. We present a newly dated pollen record from north-western fringes of the Pannonian Plain, east-central Europe, and reconstruct Holocene regional vegetation development by the REVEALS model for 27 pollen-equivalent taxa. Estimated vegetation is correlated in the same area with a human activity model based on all available archaeological information and a macrophysical climate model. The palaeovegetation record indicates the continuous presence of open land throughout the Holocene. Grasslands and open woodlands were probably maintained by local arid climatic conditions during the early Holocene delaying the spread of deciduous (oak) forests. Significantly detectable human-made landscape transformation started only after 2000 BC. Our analyses suggest that Neolithic people spread into a landscape that was already open. Humans probably contributed to the spread of oak, and influenced the dynamics of hazel and hornbeam.

  17. The CROSTVOC project - an integrated approach to study the effect of stress on BVOC exchange between agricultural crops and grassland ecosystems and the atmosphere

    NASA Astrophysics Data System (ADS)

    Amelynck, Crist; Heinesch, Bernard; Aubinet, Marc; Bachy, Aurélie; Delaplace, Pierre; Digrado, Anthony; du Jardin, Patrick; Fauconnier, Marie-Laure; Mozaffar, Ahsan; Schoon, Niels

    2015-04-01

    Global changes in atmospheric composition and climate are expected to affect BVOC exchange between terrestrial vegetation and the atmosphere through changes in the drivers of constitutive BVOC emissions and by increases in frequency and intensity of biotic or abiotic stress episodes. Indeed, several studies indicate changes in the emission patterns of constitutive BVOCs and emission of stress-induced BVOCs following heat, drought and oxidative stress, amongst others. Relating changes in BVOC emissions to the occurrence of one or multiple stressors in natural environmental conditions is not straightforward and only few field studies have dealt with it, especially for agricultural crop and grassland ecosystems. The CROSTVOC project aims to contribute in filling this knowledge gap in three ways. Firstly, it aims at performing long-term BVOC emission field measurements from maize (Zea mays L.) and wheat (Triticum aestivum L.), two important crop species on the global scale, and from grassland. This should lead to a better characterization of (mainly oxygenated) BVOC emissions from these understudied ecosystems, allowing a better representation of those emissions in air quality and atmospheric chemistry and transport models. BVOC fluxes are obtained by the Disjunct Eddy Covariance by mass scanning (DEC-MS) technique, using a hs-PTR-MS instrument for BVOC analysis. Secondly, the eddy covariance BVOC flux measurements (especially at the grassland site) will be accompanied by ozone flux, chlorophyll fluorescence, photosynthesis and soil moisture measurements, amongst others, to allow linking alterations in BVOC emissions to stress episodes. Simultaneously, automated dynamic enclosures will be deployed in order to detect specific abiotic and biotic stress markers by PTR-MS and identify them unambiguously by GC-MS. Thirdly, the field measurements will be accompanied by laboratory BVOC flux measurements in an environmental chamber in order to better disentangle the responses of the BVOC emissions to driving factors that co-occur in field conditions and to determine the influence of single abiotic stressors on BVOC emissions. Next to a general presentation, some preliminary results of the project will be shown.

  18. Some Insights on Grassland Health Assessment Based on Remote Sensing

    PubMed Central

    Xu, Dandan; Guo, Xulin

    2015-01-01

    Grassland ecosystem is one of the largest ecosystems, which naturally occurs on all continents excluding Antarctica and provides both ecological and economic functions. The deterioration of natural grassland has been attracting many grassland researchers to monitor the grassland condition and dynamics for decades. Remote sensing techniques, which are advanced in dealing with the scale constraints of ecological research and provide temporal information, become a powerful approach of grassland ecosystem monitoring. So far, grassland health monitoring studies have mostly focused on different areas, for example, productivity evaluation, classification, vegetation dynamics, livestock carrying capacity, grazing intensity, natural disaster detecting, fire, climate change, coverage assessment and soil erosion. However, the grassland ecosystem is a complex system which is formed by soil, vegetation, wildlife and atmosphere. Thus, it is time to consider the grassland ecosystem as an entity synthetically and establish an integrated grassland health monitoring system to combine different aspects of the complex grassland ecosystem. In this review, current grassland health monitoring methods, including rangeland health assessment, ecosystem health assessment and grassland monitoring by remote sensing from different aspects, are discussed along with the future directions of grassland health assessment. PMID:25643060

  19. Elevated carbon dioxide alters impacts of precipitation pulses on ecosystem photosynthesis and respiration in a semi-arid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Predicting net carbon (C) balance under future global change scenarios requires a comprehensive understanding of photosynthetic (GPP) and ecosystem respiration (Re) responses to atmospheric CO2 concentration and water availability. We measured net ecosystem exchange of CO2 (NEE), GPP and Re prior to...

  20. HYDRO-MICROMETEOROLOGICAL RELATIONSHIPS ACROSS MOUNTAIN ISLAND FOREST, GRASSLAND AND RIPARIAN ECOSYSTEMS OF A SEMI-ARID BASIN 1760

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Observations from a sky Island forested ecosystem in the semi-arid southwestern U.S.established that the type of ecosystems represented by the Mt Bigelow site in the Santa Catalina Mountain Ranges, NE of Tucson Arizona, respond to an annual wet-dry cycle instead of a hot-cold (summer-winter) cycle t...

  1. Scale effects on the controls on mountain grassland leaf stomatal and ecosystem surface conductance to water vapour

    Microsoft Academic Search

    Alois Haslwanter; Albin Hammerle; Georg Wohlfahrt

    2010-01-01

    Stomata are the major pathway by which plants exert control on the exchange of trace gases and water vapour with the aerial environment and thus provide a key link between the functioning of terrestrial ecosystems and the state and composition of the atmosphere. Understanding the nature of this control, i.e. how stomatal conductance differs between plant species and ecosystems and

  2. Gross primary production and net ecosystem exchange of a cool-temperate deciduous forest estimated by the eddy covariance method

    Microsoft Academic Search

    Nobuko Saigusa; Susumu Yamamoto; Shohei Murayama; Hiroaki Kondo; Noboru Nishimura

    2002-01-01

    An eddy covariance measurement system was installed to measure long-term turbulent fluxes of heat, water vapor, and CO2 over a cool-temperate deciduous forest in the central part of Japan. Previous to a long-term measurement, a comparison of flux measurements using open- and closed-path type infrared gas analyzers was conducted for CO2 and water vapor. The closure of the energy budget

  3. Community structure, trophic position and reproductive mode of soil and bark-living oribatid mites in an alpine grassland ecosystem

    PubMed Central

    Schatz, Heinrich; Maraun, Mark

    2010-01-01

    The community structure, stable isotope ratios (15N/14N, 13C/12C) and reproductive mode of oribatid mites (Acari, Oribatida) were investigated in four habitats (upper tree bark, lower tree bark, dry grassland soil, forest soil) at two sites in the Central Alps (Tyrol, Austria). We hypothesized that community structure and trophic position of oribatid mites of dry grassland soils and bark of trees are similar since these habitats have similar abiotic characteristics (open, dry) compared with forest soil. Further, we hypothesized that derived taxa of oribatid mites reproducing sexually dominate on the bark of trees since species in this habitat consume living resources such as lichens. In contrast to our hypothesis, the community structure of oribatid mites differed among grassland, forest and bark indicating the existence of niche differentiation in the respective oribatid mite species. In agreement with our hypothesis, sexually reproducing taxa of oribatid mites dominated on the bark of trees whereas parthenogenetic species were more frequent in soil. Several species of bark-living oribatid mites had stable isotope signatures that were similar to lichens indicating that they feed on lichens. However, nine species that frequently occurred on tree bark did not feed on lichens according to their stable isotope signatures. No oribatid mite species could be ascribed to moss feeding. We conclude that sexual reproduction served as preadaptation for oribatid mites allowing them to exploit new habitats and new resources on the bark of trees. Abiotic factors likely are of limited importance for bark-living oribatid mites since harsh abiotic conditions are assumed to favor parthenogenesis. PMID:20490626

  4. Spatial and temporal variability of bacterial 16S rDNA-based T-RFLP patterns derived from soil of two Wyoming grassland ecosystems.

    PubMed

    Mummey, Daniel L; Stahl, Peter D

    2003-10-01

    Abstract Spatial and temporal variability of soil bacterial 16S rDNA terminal restriction fragment (TRF) size variation was evaluated in a homogeneous grassland (HG) dominated by the turf-forming grass Bouteloua gracilis and in a shrubland (SL) dominated by Artemisia tridentata (Wyoming big sagebrush). Temporal variability was also evaluated on the HG site over a growing season. No trends toward dissimilarity were detected with temporal (180 days) or spatial (up to 100 m) distance in the HG system. Terminal-restriction fragment length polymorphism (T-RFLP) profiles of the SL site exhibited pronounced small-scale spatial variability (<70 cm), although spatial analysis indicated weak spatial autocorrelation to distances greater than 36 cm. While shrub-induced nutrient localization was shown to significantly influence T-RFLP profiles, very little of the variability could be accounted for on the basis of spatial characteristics, suggesting that soil bacterial 16S rDNA composition of this site is predominantly controlled at scales other than those measured. Average dissimilarity values differed greatly between the two sites (0.27 and 0.59 for HG and SL sites, respectively). These results suggest that plant community structure strongly influences bacterial community composition in these semiarid ecosystems, highlighting the importance of considering spatial variability when designing field studies related to bacterial diversity in ecosystems having patchy or heterogeneous plant cover. PMID:19719588

  5. Dew water isotopic ratios and their relationships to ecosystem water pools and fluxes in a cropland and a grassland in China.

    PubMed

    Wen, Xue-Fa; Lee, Xuhui; Sun, Xiao-Min; Wang, Jian-Lin; Hu, Zhong-Min; Li, Sheng-Gong; Yu, Gui-Rui

    2012-02-01

    Dew formation has the potential to modulate the spatial and temporal variations of isotopic contents of atmospheric water vapor, oxygen and carbon dioxide. The goal of this paper is to improve our understanding of the isotopic interactions between dew water and ecosystem water pools and fluxes through two field experiments in a wheat/maize cropland and in a short steppe grassland in China. Measurements were made during 94 dew events of the D and (18)O compositions of dew, atmospheric vapor, leaf, xylem and soil water, and the whole ecosystem water flux. Our results demonstrate that the equilibrium fractionation played a dominant role over the kinetic fractionation in controlling the dew water isotopic compositions. A significant correlation between the isotopic compositions of leaf water and dew water suggests a large role of top-down exchange with atmospheric vapor controlling the leaf water turnover at night. According to the isotopic labeling, dew water consisted of a downward flux of water vapor from above the canopy (98%) and upward fluxes originated from soil evaporation and transpiration of the leaves in the lower canopy (2%). PMID:21822725

  6. Fire effects on ecosystem nitrogen cycling in a Californian bishop pine forest

    Microsoft Academic Search

    P. Grogan; T. D. Burns; F. S. Chapin III

    2000-01-01

    Fire can cause severe nitrogen (N) losses from grassland, chaparral, and temperate and boreal forest ecosystems. Paradoxically,\\u000a soil ammonium levels are markedly increased by fire, resulting in high rates of primary production in re-establishing plant\\u000a communities. In a manipulative experiment, we examined the influence of wild-fire ash residues on soil, microbial and plant\\u000a N pools in a recently burned Californian

  7. Climate warming increases biodiversity of small rodents by favoring rare or less abundant species in a grassland ecosystem.

    PubMed

    Jiang, Guangshun; Liu, Jun; Xu, Lei; Yu, Guirui; He, Honglin; Zhang, Zhibin

    2013-06-01

    Our Earth is facing the challenge of accelerating climate change, which imposes a great threat to biodiversity. Many published studies suggest that climate warming may cause a dramatic decline in biodiversity, especially in colder and drier regions. In this study, we investigated the effects of temperature, precipitation and a normalized difference vegetation index on biodiversity indices of rodent communities in the current or previous year for both detrended and nondetrended data in semi-arid grassland of Inner Mongolia during 1982-2006. Our results demonstrate that temperature showed predominantly positive effects on the biodiversity of small rodents; precipitation showed both positive and negative effects; a normalized difference vegetation index showed positive effects; and cross-correlation function values between rodent abundance and temperature were negatively correlated with rodent abundance. Our results suggest that recent climate warming increased the biodiversity of small rodents by providing more benefits to population growth of rare or less abundant species than that of more abundant species in Inner Mongolia grassland, which does not support the popular view that global warming would decrease biodiversity in colder and drier regions. We hypothesized that higher temperatures might benefit rare or less abundant species (with smaller populations and more folivorous diets) by reducing the probability of local extinction and/or by increasing herbaceous food resources. PMID:23731812

  8. Effects of Seasonality and Species Diversity on Nitrogen Uptake in Grassland Johanna Jensen

    E-print Network

    Vallino, Joseph J.

    1 Effects of Seasonality and Species Diversity on Nitrogen Uptake in Grassland Ecosystems Johanna controls on nitrogen cycling in grassland ecosystems than species diversity in fall months. Three grassland growing season and affinity for nitrate, while a senescing, diverse grassland had the least. In addition

  9. Predicting the response of a temperate forest ecosystem to atmospheric CO{sub 2} increase. Annual report, 1992--1993

    SciTech Connect

    Bazzaz, F.A.

    1993-03-01

    This report summarizes the second year of research progress. Included are progress reports for the following studies: the responses of temperate forest tree to 3 years of exposure to elevated carbon dioxide, and high and low nutrient and light levels; pot-size limitations in carbon dioxide studies, interactive effects of carbon dioxide and soil moisture availability on tree seedling`s tissue water relations, growth, and niche characteristics; individual versus population responses to elevated carbon dioxide levels in two species of annual weeds; and the development of gypsy moth larvae raised on gray and yellow birth foliage grown in ambient and elevated carbon dioxide environments.

  10. Representing agro-pastoral sahelian ecosystems in the global land surface model ORCHIDEE: in situ validation and comparison between croplands and grasslands.

    NASA Astrophysics Data System (ADS)

    Berg, Alexis; Brender, Pierre; Boulain, Nicolas; Ramier, David; Sultan, Benjamin; de Noblet, Nathalie; Ciais, Philippe; Ottlé, Catherine; Cappelaere, Bernard; Demarty, Jerome

    2010-05-01

    In a effort to improve the representation of tropical agro-ecosystems in the global terrestrial biosphere model ORCHIDEE, recent model developments have been made in order to better account for tropical croplands and savannahs. Here we compare the simulations performed with these new versions with in situ data from the AMMA-Niger Wankama "local site". Indeed, since 2005, soil moisture, vegetation (biomass, LAI) and eddy-covariance flux tower measurements have been conducted at Wankama over both a millet and a fallow site, resulting in a unique dataset of carbon and energy fluxes over two different agricultural land-cover types and for several climatically-contrasted years in the sahelian zone. Thus, we performed on-site simulations with ORCHIDEE forced with local meteorological data over 2005-2007: we assess the ability of the two land-use specific versions of the model (croplands and grasslands) to capture the respective observed characteristics of vegetation, water balance and energy fluxes over time scales ranging from diurnal to inter-annual. We also discuss the ability of the model to account for the relative differences between crops and fallow in terms of land/atmosphere interactions - for on a large scale these differences may feed back on the atmosphere as grasslands are gradually converted to croplands. We finally attempt to discriminate between the validated features and deficiencies that are most likely to be site-specific and the ones that may impair the representation of the contrast between these two land cover types at larger scale.

  11. The impacts of land-use change from grassland to bioenergy Short Rotation Coppice (SRC) Willow on the crop and ecosystem greenhouse gas balance

    NASA Astrophysics Data System (ADS)

    Harris, Zoe M.; Alberti, Giorgio; Dondini, Marta; Smith, Pete; Taylor, Gail

    2014-05-01

    The aim of this research is to better understand the greenhouse gas balance of land-use transition to bioenergy cropping systems in a UK context. Given limited land availability, addressing the food-energy-water nexus remains a challenge, and it is imperative that bioenergy crops are sited appropriately and that competition with food crops is minimized. Here we present the results of a years' worth of soil and GHG data for a conversion from ex-set aside grassland to short rotation coppice (SRC) willow for bioenergy on a commercial scale. Initial results indicate that willow was a net sink for CO2 in comparison to grassland which was a net source of CO2. This provides evidence that the GHG balance of transitions to SRC bioenergy crops will potentially result in increased soil carbon. The empirical findings from this study have been combined with modelled estimates for the site to both test and validate the ECOSSE model. Initial comparisons show that the model is able to accurately predict the respiration occurring at the field site, suggesting that it is a valuable approach for up-scaling from point sites such as this to wider geographical areas and for considering future climate scenarios. The modelling output will also provide a user-friendly tool for land owners which will determine the GHG and soil carbon effects of changing land to bioenergy for UK. This work is based on the Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project, which was commissioned and funded by the Energy Technologies Institute (ETI). This work was also jointly funded by the Carbo Biocrop Project.

  12. Effects of an increase in summer precipitation on leaf, soil, and ecosystem fluxes of CO 2 and H 2 O in a sotol grassland in Big Bend National Park, Texas

    Microsoft Academic Search

    Lisa Patrick; Jessica Cable; Daniel Potts; Danielle Ignace; Greg Barron-Gafford; Alden Griffith; Holly Alpert; Natasja Van Gestel; Traesha Robertson; Travis E. Huxman; John Zak; Michael E. Loik; David Tissue

    2007-01-01

    Global climate models predict that in the next century precipitation in desert regions of the USA will increase, which is\\u000a anticipated to affect biosphere\\/atmosphere exchanges of both CO2 and H2O. In a sotol grassland ecosystem in the Chihuahuan Desert at Big Bend National Park, we measured the response of leaf-level\\u000a fluxes of CO2 and H2O 1 day before and up to

  13. Increasing diurnal and seasonal amplitudes in carbon and water fluxes after conversion from arable to grassland

    NASA Astrophysics Data System (ADS)

    Vetter, S. H.; Auerswald, K.; Bernhofer, C.

    2012-04-01

    Land-use change is a topical scientific and political issue due to its potential to affect atmospheric greenhouse gas concentrations. Conversion of arable land to permanent grassland has been proposed as a strategy to sequester atmospheric CO2 into soil organic matter. In this context, eddy covariance measurements were recorded over grazed grassland at a site in the temperate region of southern Germany (annual precipitation 775 mm, annual temperature 9°C) from 2002 to 2008. The site had been arable farm land for decades but from 2000 it became grassland grazed by cattle (Bos taurus). Over the study period the total ecosystem respiration (TER), gross primary production (GPP) and evapotranspiration (ET) increased during the growing season and, therefore, in annual totals (by about 80%, 85%, and 33%, respectively, during seven-year period). A similar trend could not be found for net ecosystem exchange (NEE) of carbon in the daily to annual sums, but was evident in the separated day and night fluxes of NEE. There was no trend in the meteorological conditions (temperature, precipitation) causing the trends. The main effect of the land use change was not a change in C sequestration but an increase in temperature sensitivity; in grassland the C distribution within the soil is closer to the surface than in arable systems, which causes the daily and yearly variations in C balance to increase.

  14. Response of grassland soil respiration to drought: Results from an ecosystem manipulation experiment including 19 sites differing in productivity and diversity

    NASA Astrophysics Data System (ADS)

    Burri, Susanne; Niklaus, Pascal; Buchmann, Nina; Kahmen, Ansgar

    2015-04-01

    Soil respiration returns around 80-100 Pg carbon (C) per year from ecosystems globally to the atmosphere and thus is the main component of the natural respiratory carbon dioxide (CO2) release to the atmosphere. Despite its crucial role in global C cycling, its potential response to climate change, in particular extreme events such as drought, is subject to large uncertainty. One reason for this knowledge gap is the uncertain role of above-ground drivers, such as productivity and diversity, in the response of soil respiration to drought. We had the unique chance to investigate this aspect within an ecosystem manipulation experiment at 19 grassland sites differing in productivity and diversity levels in central Germany (Thüringer Schiefergebirge/Frankenwald). Drought was simulated by rainout shelters in early summer 2002 and 2003. Soil respiration was measured every 2-3 weeks during the growing seasons and annual courses of soil respiration were estimated separately for control and drought conditions. Soil respiration was significantly reduced in response to drought in both years, the reduction outlasted the actual drought treatment for several weeks and was not overcompensated on the annual basis. The mean reduction in mean daily C release by soil respiration was 9.9 ± 11.8% in 2002 and 12.8 ± 12.1% in 2003 (mean ± SD). The overall mean daily C release was correlated with annual above-ground productivity in both years and the drought-induced change was fully explainable by the change in annual above-ground productivity in 2003 (but not in 2002). The relative extent of the drought response of soil respiration, however, was dependent on the level of below-ground standing biomass and soil C at the respective site, with higher reductions at sites with soils characterized by low levels of standing below-ground biomass and soil C. Our results clearly call for the integration of above-and below-ground productivity as well as soil C concentrations, when it comes to quantifying the effect of future drought events on grassland soil respiration.

  15. Dom Export from Coastal Temperate Bog Forest Watersheds to Marine Ecosystems: Improving Understanding of Watershed Processes and Terrestrial-Marine Linkages on the Central Coast of British Columbia

    NASA Astrophysics Data System (ADS)

    Oliver, A. A.; Giesbrecht, I.; Tank, S. E.; Hunt, B. P.; Lertzman, K. P.

    2014-12-01

    The coastal temperate bog forests of British Columbia, Canada, export high amounts of dissolved organic matter (DOM) relative to the global average. Little is known about the factors influencing the quantity and quality of DOM exported from these forests or the role of this terrestrially-derived DOM in near-shore marine ecosystems. The objectives of this study are to better understand patterns and controls of DOM being exported from bog forest watersheds and its potential role in near-shore marine ecosystems. In 2013, the Kwakshua Watershed Ecosystems Study at Hakai Beach Institute (Calvert Island, BC) began year-round routine collection and analysis of DOM, nutrients, and environmental variables (e.g. conductivity, pH, temperature, dissolved oxygen) of freshwater grab samples from the outlets of seven watersheds draining directly to the ocean, as well as near-shore marine samples adjacent to freshwater outflows. Dissolved organic carbon (DOC) varied across watersheds (mean= 11.45 mg L-1, sd± 4.22) and fluctuated synchronously with seasons and storm events. In general, higher DOC was associated with lower specific UV absorbance (SUVA254; mean= 4.59 L mg-1 m-1, sd± 0.55). The relationship between DOC and SUVA254 differed between watersheds, suggesting exports in DOM are regulated by individual watershed attributes (e.g. landscape classification, flow paths) as well as precipitation. We are using LiDAR and other remote sensing data to examine watershed controls on DOC export. At near-shore marine sites, coupled CTD (Conductivity Temperature Depth) and optical measures (e.g. spectral slopes, slope ratios (SR), EEMs), showed a clear freshwater DOM signature within the system following rainfall events. Ongoing work will explore the relationship between bog forest watershed attributes and DOM flux and composition, with implications for further studies on biogeochemical cycling, carbon budgets, marine food webs, and climate change.

  16. Algal biomass and primary production within a temperate zone sandstone

    SciTech Connect

    Bell, R.A.; Sommerfeld, M.R. (Arizona State Univ., Tempe (USA))

    1987-02-01

    The use of dimethyl sulfoxide (DMSO) to extract chlorophyll a and {sup 14}C-labelled photosynthate from endolithic algae of sparsely vegetated, cold temperate grasslands on the Colorado Plateau in Arizona has yielded the first estimates of biomass and photosynthesis for this unusual community. These subsurface microorganisms are found widespread in exposed Coconino Sandstone, a predominant formation in this cold temperate region. The endolithic community in Coconino Sandstone, composed primarily of coccoid blue-green and coccoid/sarcinoid green algae, yielded a biomass value (as chlorophyll a content) of 87 mg m{sup {minus}2} rock surface area and a photosynthetic rate of 0.37 mg CO{sub 2} dm{sup {minus}2} hr{sup {minus}1} or 0.48 mg CO{sub 2} mg{sup {minus}1} chl a hr{sup {minus}1}. The endolithic algal community contributes moderate biomass (5-10%) and substantial photosynthesis (20-80%) to the sparse grassland ecosystem.

  17. Soil-specific C and N responses to changing atmospheric CO2 concentrations in a mesic grassland ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long-term increases in ecosystem productivity under elevated atmospheric CO2 can be expected only when the increased assimilation of carbon (C) is not limited by soil nutrients, namely nitrogen (N). We examined how changes in atmospheric CO2 concentrations affect C and N dynamics in a mesic grasslan...

  18. Summer rain pulse size and rainwater uptake by three dominant desert plants in a desertified grassland ecosystem in northwestern China

    E-print Network

    Chen, Jiquan

    chosen for the experiment. The perennial grass Stipa bungeana, the shrub Artemisia ordosia, and the herb will facilitate development of C. komarovii, and large events will advance A. ordosia in this community ecosystem processes (e.g., carbon fixation, plant growth, respiration) and function (e.g., net pri- mary

  19. Effects of grazing on leaf traits and ecosystem functioning in Inner Mongolia grasslands: scaling from species to community

    Microsoft Academic Search

    S. X. Zheng; H. Y. Ren; Z. C. Lan; W. H. Li; Y. F. Bai

    2009-01-01

    More attention has focused on using some easily measured plant functional traits to predict grazing influence on plant growth and ecosystem functioning. However, there has been much controversy on leaf traits response to grazing, thus more research should be conducted at the species level. Here we investigated the leaf area, leaf mass and specific leaf area (SLA) of 263 species

  20. Methane fluxes in wetland and forest soils, beaver ponds, and low-order streams of a temperate forest ecosystem

    NASA Technical Reports Server (NTRS)

    Yavitt, J. B.; Lang, G. E.; Sexstone, A. J.

    1990-01-01

    This study was conducted to determine whether temperate wetlands and forests play important roles in the global balances of atmospheric methane. Flux measurements for methane in several different wetland, forest, and open-water (e.g., beaver pond and low-order stream) sites were determined using collection chambers placed over the soil- or water-air interface. All of the sites were located in the Appalachian Mountain region of West Virginia and western Maryland. Between June 1987 and April 1989 the wetland sites acted as small sources of atmospheric methane, with emission rates for methane usually lower than 200 mg CH4/sq m per day; consumption of atmospheric methane in the wetland soils was observed frequently.

  1. Spatial and temporal dynamics of biotic and abiotic features of temperate coastal ecosystems as revealed by a combination of ecological indicators

    NASA Astrophysics Data System (ADS)

    Grangeré, K.; Lefebvre, S.; Blin, J.-L.

    2012-08-01

    Coastal ecosystems exhibit complex spatio-temporal patterns due to their position at the interface between land and sea. This is particularly the case of temperate ecosystems where exploitation of coastal resources (fisheries and aquaculture) and intensive agricultural use of watersheds further complicate our understanding of their dynamics. The aim of the present study was to unravel the spatio-temporal dynamics of contrasted megatidal coastal ecosystems located at the same regional scale (i.e. under the same regional climate), but under different kinds of human pressure. Two kinds of ecological indicators were assessed over a period of four years at 11 locations along the coast of the Cotentin peninsula (Normandy, France). A first set of hydrobiological variables (dissolved nutrients, Chl a, temperature, salinity, etc.) was measured fortnightly in the water column. These data were analysed by principal components analysis (PCA). A second set of variables were the carbon and nitrogen stable isotope ratios of the adductor muscles of cultured Crassostrea gigas introduced every year to typify the bentho-pelagic coupling at each location. Food sources were also investigated using a mixing model with data on the isotopic composition of the food sources obtained previously. To identify which environmental variables played a significant role in determining the oyster diet, the contributions of oyster food sources were combined with environmental variables in a canonical correspondence analysis (CCA). Isotopic values of adductor muscles varied significantly between -20.12‰ and -16.79‰ for ?13C and between 8.28‰ and 11.87‰ for ?15N. The PCA distinguished two groups of coastal ecosystems that differed in their coastal hydrology, nutrient inputs, and the size of their respective watershed, irrespective of the year. In each zone, different spatial patterns in the measured variables were observed depending on the year showing that local impacts differed temporally. As revealed by CCA, food sources used by the oysters were mainly explained by salinity suggesting regional differences between ecosystems. On the west coast of the peninsula, climatic factors act in synergy with anthropogenic factors (i.e. nutrient enrichment) whereas on the east coast, climatic factors appear to be dampened by anthropogenic factors.

  2. Net ecosystem productivity of temperate and boreal forests after clearcutting - a Fluxnet-Canada measurement and modelling synthesis

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Barr, A.; Black, T. A.; Margolis, H. A.; McCaughey, J. H.; Trofymow, J. A.

    2010-05-01

    Clearcutting strongly affects subsequent forest net ecosystem productivity (NEP). Hypotheses for ecological controls on NEP in the ecosystem model ecosys were tested with CO2 fluxes measured by eddy covariance (EC) in three post-clearcut conifer chronosequences. An algorithm for microbial colonization of fine and woody debris allowed the model to reproduce sigmoidal declines in debris observed after clearcutting. In the model, Rh drove debris decomposition that drove microbial growth, N mineralization and asymbiotic N2 fixation. These processes controlled root N uptake, and thereby CO2 fixation in regrowing vegetation. Interactions among soil and plant processes allowed the model to simulate hourly CO2 fluxes and annual NEP within the uncertainty of EC measurements from 2003 through 2007 over forest stands from 1 to 80 years of age in all three chronosequences without site- or species-specific parameterization. The model was then used to study the impacts of increasing harvest removals on subsequent C stocks at one of the chronosequence sites. Model results indicated that increasing harvest removals would hasten recovery of NEP during the first 30 years after clearcutting, but would reduce ecosystem C stocks by about 15% of the increased removals at the end of an 80 year harvest cycle.

  3. Net ecosystem productivity of temperate and boreal forests after clearcutting-a Fluxnet-Canada measurement and modelling synthesis

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Barr, A. G.; Black, T. A.; Margolis, H. A.; McCaughey, J. H.; Trofymow, J. A.

    2010-11-01

    ABSTRACT Clearcutting strongly affects subsequent forest net ecosystem productivity (NEP). Hypotheses for ecological controls on NEP in the ecosystem model ecosys were tested with CO2 fluxes measured by eddy covariance (EC) in three post-clearcut conifer chronosequences in different ecological zones across Canada. In the model, microbial colonization of postharvest fine and woody debris drove heterotrophic respiration (Rh), and hence decomposition, microbial growth, N mineralization and asymbiotic N2 fixation. These processes controlled root N uptake, and thereby CO2 fixation in regrowing vegetation. Interactions among soil and plant processes allowed the model to simulate hourly CO2 fluxes and annual NEP within the uncertainty of EC measurements from 2003 to 2007 over forest stands from 1 to 80 yr of age in all three chronosequences without site- or species-specific parameterization. The model was then used to study the impacts of increasing harvest removals on subsequent C stocks at one of the chronosequence sites. Model results indicated that increasing harvest removals would hasten recovery of NEP during the first 30 yr after clearcutting, but would reduce ecosystem C stocks by about 15% of the increased removals at the end of an 80-yr harvest cycle.

  4. Net Ecosystem Productivity of Temperate and Boreal Forests after Clearcutting - a Fluxnet-Canada Measurement and Modelling Synthesis

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Barr, A. G.; Black, T. A.; Margolis, H. A.; McCaughey, J. H.; Trofymow, J. A.

    2010-12-01

    Clearcutting strongly affects subsequent forest net ecosystem productivity (NEP). Hypotheses for ecological controls on NEP in the ecosystem model ecosys were tested with CO2 fluxes measured by eddy covariance (EC) in three post-clearcut conifer chronosequences in different ecological zones across Canada. In the model, microbial growth drove colonization of postharvest fine and woody debris and hence determined the time course of heterotrophic respiration (Rh), and hence decomposition, microbial growth, N mineralization and asymbiotic N2 fixation. These processes controlled the time course of root N uptake, and thereby CO2 fixation in regrowing vegetation. Interactions among soil and plant processes allowed the model to simulate hourly CO2 fluxes and annual NEP within the uncertainty of EC measurements from 2003 through 2007 over forest stands from 1 to 80 years of age in all three chronosequences without site- or species-specific parameterization. The model was then used to study the impacts of increasing harvest removals on subsequent C stocks at one of the chronosequence sites. Model results indicated that increasing harvest removals would hasten recovery of NEP during the first 30 years after clearcutting, but would reduce ecosystem C stocks by about 15% of the increased removals at the end of an 80 year harvest cycle.

  5. Grassland responses to grazing: effects of grazing intensity and management system in an Inner Mongolian steppe ecosystem

    Microsoft Academic Search

    Philipp Schönbach; Hongwei Wan; Martin Gierus; Yongfei Bai; Katrin Müller; Lijun Lin; Andreas Susenbeth; Friedhelm Taube

    2011-01-01

    The major aims of this study were, firstly, to analyse the grazing-induced steppe degradation process and, secondly, to identify\\u000a an efficient and sustainable grazing management system for the widely degraded Inner Mongolian typical steppe ecosystem. From\\u000a 2005–2008 a grazing experiment was conducted to compare two grazing management systems, the Mixed System (MS) and the Traditional\\u000a System (TS), along a gradient

  6. Herbivore influence on soil microbial biomass and nitrogen mineralization in a northern grassland ecosystem: Yellowstone National Park

    Microsoft Academic Search

    Benjamin F. Tracy; Douglas A. Frank

    1998-01-01

    Microorganisms are largely responsible for soil nutrient cycling and energy flow in terrestrial ecosystems. Although soil\\u000a microorganisms are affected by topography and grazing, little is known about how these two variables may interact to influence\\u000a microbial processes. Even less is known about how these variables influence microorganisms in systems that contain large populations\\u000a of free-roaming ungulates. In this study, we

  7. Recovery of coastal ecosystems after large tsunamis in various climatic zones - review of cases from tropical, temperate and polar zones (Invited)

    NASA Astrophysics Data System (ADS)

    Szczucinski, W.

    2013-12-01

    Large tsunamis cause significant changes in coastal ecosystems. They include modifications in shoreline position, sediment erosion and deposition, new initial soil formation, salination of soils and waters, removal of vegetation, as well as direct impact on humans and infrastructure. The processes and rate of coastal zone recovery from large tsunamis has been little studied but during the last decade a noteworthy progress has been made. This study focus on comparison of recovery processes in various climatic zones, namely in monsoonal-tropical, temperate and polar zone. It is based on own observation and monitoring in areas affected by 2004 Indian Ocean Tsunami in Thailand, 2011 Tohoku-oki tsunami in Japan and 2000 Paatuut landslide-generated tsunami in Vaigat Strait (west Greenland), as well as on review of published studies from those areas. The particular focus is on physical and biological recoveries of beaches, recovery of coastal vegetation, new soil formation in eroded areas and those covered by tsunami deposits, marine salt removal from soils, surface- and groundwater, as well as landscape adjustment after the tsunamis. The beach zone - typically the most tsunami-eroded zone, has been recovered already within weeks to months and has been observed to be in the pre-tsunami equilibrium stage within one year in all the climate zones, except for sediment-starved environments. The existing data on beach ecosystems point also to relatively fast recovery of meio- and macrofauna (within weeks to several months). The recovery of coastal vegetation depends on the rate of salt removal from soils or on the rate of soil formation in case of its erosion or burial by tsunami deposits. The salt removal have been observed to depend mainly on precipitation and effective water drainage. In tropical climate with seasonal rainfall of more 3000 mm the salt removal was fast, however, in temperate climate with lower precipitation and flat topography the salinities still exceeded the recommended concentrations for freshwater plants after one year. The new soil formation and vegetation recovery depends mainly on the rate of biological production. In tropical climate the vegetation largely recovered already after the first rainy season and supported the new soil formation. In temperate climate this process was much slower, in particular in flat lying areas and on coastal dunes with poor sandy soils. In polar climate only limited vegetation recovery (mainly of Salix species) has been observed after 12 years and vegetation withered due to salt stress still marked the tsunami inundation limit and the new soil formation was very slow and focused on low lying, wet areas buried with thin tsunami deposits cover. The post-tsunami recovery processes may be grouped into climate-related (vegetation recovery, removal of salts from soils) and non climate-related (e.g. beach recovery) or modified by climatic and local factors (for instance, the rate of tsunami deposits reworking and thus new soil formation). The rate of recovery varies from days / weeks as in case of beach recovery to several decades as in case of new soil formation on tsunami deposits. The study was partly funded by Polish National Science Centre grant No. 2011/01/B/ST10/01553. The review results from studies in collaboration with number of researchers from Australia, Japan, Poland, Thailand, United Kingdom and United States to whom I express sincere thanks.

  8. Effects of elevated CO?, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status.

    PubMed

    Albert, K R; Ro-Poulsen, H; Mikkelsen, T N; Michelsen, A; Van Der Linden, L; Beier, C

    2011-07-01

    The impact of elevated CO?, periodic drought and warming on photosynthesis and leaf characteristics of the evergreen dwarf shrub Calluna vulgaris in a temperate heath ecosystem was investigated. Photosynthesis was reduced by drought in midsummer and increased by elevated CO? throughout the growing season, whereas warming only stimulated photosynthesis early in the year. At the beginning and end of the growing season, a T × CO? interaction synergistically stimulated plant carbon uptake in the combination of warming and elevated CO?. At peak drought, the D × CO? interaction antagonistically down-regulated photosynthesis, suggesting a limited ability of elevated CO? to counteract the negative effect of drought. The response of photosynthesis in the full factorial combination (TDCO?) could be explained by the main effect of experimental treatments (T, D, CO?) and the two-factor interactions (D × CO?, T × CO?). The interactive responses in the experimental treatments including elevated CO? seemed to be linked to the realized range of treatment variability, for example with negative effects following experimental drought or positive effects following the relatively higher impact of night-time warming during cold periods early and late in the year. Longer-term experiments are needed to evaluate whether photosynthetic down-regulation will dampen the stimulation of photosynthesis under prolonged exposure to elevated CO?. PMID:21410715

  9. Precipitation patterns alter growth of temperate vegetation Jingyun Fang,1

    E-print Network

    Myneni, Ranga B.

    major temperate biomes in China: grassland, deciduous broadleaf forest, and deciduous coniferous forest. With increased precipitation, NDVI of grassland and deciduous broadleaf forest increased, but that of deciduous and deciduous broadleaf forest, but did not alter that of deciduous coniferous forest at low precipitation

  10. STATUS AND CONSERVATION OF THE PALOUSE GRASSLAND IN IDAHO

    Microsoft Academic Search

    Juanita Lichthardt; Robert K. Moseley

    ABSTRACT The Palouse Grassland is recognized as an ecologically distinct element of the Pacific Northwest Bunchgrass biome. The area once occupied by Palouse Grassland has seen nearly 100% conversion to cultivated agriculture, making it an imperiled ecosystem. Remnants of Palouse Grassland vegetation are now restricted to small areas on the edge of cultivated fields, or rocky slopes along the margin

  11. Grazing effects on carbon fluxes in a northern China grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grazing is a widespread use of grasslands in northern China, but if stocking rate exceeds grassland carrying capacity, degradation and desertification can occur. As a result, grazing management is critical and can play a significant role in driving C sink and source activity in grassland ecosystems...

  12. Soil microbial biomass response to woody plant invasion of grassland

    Microsoft Academic Search

    J. D. Liao; T. W. Boutton

    2008-01-01

    Woody plant proliferation in grasslands and savannas has been documented worldwide in recent history. To better understand the consequences of this vegetation change for the C-cycle, we measured soil microbial biomass carbon (Cmic) in remnant grasslands (time 0) and woody plant stands ranging in age from 10 to 130 years in a subtropical ecosystem undergoing succession from grassland to woodlands

  13. MANAGING GRASSLAND AS A CO2 SINK

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although net ecosystem CO2 exchange (NEE) rates tend to be low in most grasslands, especially native grasslands, these regions occupy a large portion of Earth’s terrestrial surface and thus represent a potentially large and significant sink or source for C. Herein we report on findings from several ...

  14. Biological soil crusts are the main contributor to winter soil respiration in a temperate desert ecosystem of China

    NASA Astrophysics Data System (ADS)

    He, M. Z.

    2012-04-01

    Aims Biological soil crusts (BSCs) are a key biotic component of desert ecosystems worldwide. However, most studies carried out to date on carbon (fluxes) in these ecosystems, such as soil respiration (RS), have neglected them. Also, winter RS is reported to be a significant component of annual carbon budget in other ecosystems, however, we have less knowledge about winter RS of BSCs in winter and its contribution to carbon cycle in desert regions. Therefore, the specific objectives of this study were to: (i) quantify the effects of different BSCs types (moss crust, algae crust, physical crust) on the winter RS; (ii) explore relationships of RS against soil temperature and water content for different BSCs, and (iii) assess the relative contribution of BSCs to the annual amount of C released by RS at desert ecosystem level. Methods Site Description The study sites are located at the southeast fringe of the Tengger Desert in the Shapotou region of the Ningxia Hui Autonomous Region [37°32'N and 105°02'E, at 1340 m above mean sea level (a.m.s.l.)], western China. The mean daily temperature in January is -6.9°C , while it is 24.3°C in July. The mean annual precipitation is 186 mm, approximately 80% of which falls between May and September. The annual potential evaporation is 2800 mm. The landscape of the Shapotou region is characterized by large and dense reticulate barchans chains of sand dunes that migrate south-eastward at a velocity of 3-6 m per year. The soil is loose, infertile and mobile and can thus be classified as orthic sierozem and Aeolian sandy soil. Additionally, the soil has a consistent gravimetric water content that ranges from 3 to 4%. The groundwater in the study area is too deep (>60 m) to support large areas of the native vegetation cover; therefore, precipitation is usually the only source of freshwater. The predominant native plants are Hedysarum scoparium Fisch. and Agriophyllum squarrosum Moq., Psammochloa cillosa Bor, which scattered distribute with cover about 1% of the entire study area. Prior to revegetation, straw-checkerboards approximately 1×1 m2 in area were constructed using wheat or rice straw to stabilize the dune surface and allow time for the planted xerophytic shrubs to adapt to the new environment. In 1956, the following 2-year-old xerophytic shrub seedlings were planted within the checkerboard at a density of 16 individuals per 100 m2 and grown without irrigation: Artemisia ordosica Krasch, H. scoparium Fisch, Calligonum mongolicum Turc'z, Caragana microphylla Lam., Caragana korshinskii Kom, Salix gordejevii and Atraphaxis bracteata A.Los. The stabilized area was then expanded to parallel areas in 1964 and 1982 using the same method and species. As a result, the initial stages of change that have occurred at these sites were similar. After more than fifties years succession, the predominant plants are semi-shrubs, shrubs, forbs, and grasses at present and BSCs formed. The common BSCs in the region may be dominated by cyanobacteria, algae, lichens and mosses, or any combination of these organisms. Cyanobacteria species include Microcolous vaginatus Gom., Hydrocoleus violacens Gom., Lyngbya crytoraginatus Schk., Phormidium amblgum Gom., P. autumnale (Ag.) Gom., P. foveolarum (Mont.) Gom. and Phormidium luridum (Kutz) Gom. etc; algal species mainly include Anabaena azotica Ley, Euglena sp., Hantzschia amphioxys var capitata Grum, Oscillatoria obscura Gom., O. pseudogeminate G. Schm. And Scytonema javanicum (Kutz) Bornet Flash etc; lichen species include Collema tenax (Sw.) Ach., Endocarpon pusillum Hedw.; and moss species are dominated by Bryum argenteum Hedw., Didymodon constrictus (Mitt.) Saito., Tortula bidentata Bai Xue Liang and T. desertorum Broth.. Experimental Design and Rs measurements On October 2010, We selected the moss-dominated BSCs at four revegetation sites and natural vegetation sites, in which 3 replicated plots were selected randomly. In each plot, olyvinyl chloride (PVC) collar (lenth 10 cm, internal diameter 10cm ) were inserted 7 cm into the soil. During the

  15. Observed and modeled ecosystem isoprene fluxes from an oak-dominated temperate forest and the influence of drought stress

    SciTech Connect

    Potosnak, M.; LeStourgeon, Lauren; Pallardy, Stephen G.; Hosman, Kevin P.; Gu, Lianghong; Karl, Thomas; Geron, Chris; Guenther, Alex B.

    2014-02-19

    Ecosystem fluxes of isoprene emission were measured during the majority of the 2011 growing season at the University of Missouri's Baskett Wildlife Research and Education Area in centralMissouri, USA (38.7° N, 92.2° W). This broadleaf deciduous forest is typical of forests common in theOzarks region of the central United States. The goal of the isoprene flux measurements was to test ourunderstanding of the controls on isoprene emission from the hourly to the seasonal timescale using a state-of-the-art emission model, MEGAN (Model of Emissions of Gases and Aerosols from Nature). Isoprene emission rates were very high from the forest with a maximum of 50.9 mg m-2 hr-1 (208 nmol m-2 s-1), which to our knowledge exceeds all other reports of canopy-scale isoprene emission. The fluxes showed a clear dependence on the previous temperature and light regimes which was successfully captured by the existing algorithms in MEGAN. During a period of drought, MEGAN was unable to reproduce the time-dependent response of isoprene emission to water stress. Overall, the performance of MEGAN was robust and could explain 87% of the observed variance in the measured fluxes, but the response of isoprene emission to drought stress is a major source of uncertainty.

  16. Impacts of Diffuse Radiation on Light Use Efficiency across Terrestrial Ecosystems Based on Eddy Covariance Observation in China

    PubMed Central

    Huang, Kun; Wang, Shaoqiang; Zhou, Lei; Wang, Huimin; Zhang, Junhui; Yan, Junhua; Zhao, Liang; Wang, Yanfen; Shi, Peili

    2014-01-01

    Ecosystem light use efficiency (LUE) is a key factor of production models for gross primary production (GPP) predictions. Previous studies revealed that ecosystem LUE could be significantly enhanced by an increase on diffuse radiation. Under large spatial heterogeneity and increasing annual diffuse radiation in China, eddy covariance flux data at 6 sites across different ecosystems from 2003 to 2007 were used to investigate the impacts of diffuse radiation indicated by the cloudiness index (CI) on ecosystem LUE in grassland and forest ecosystems. Our results showed that the ecosystem LUE at the six sites was significantly correlated with the cloudiness variation (0.24?R2?0.85), especially at the Changbaishan temperate forest ecosystem (R2?=?0.85). Meanwhile, the CI values appeared more frequently between 0.8 and 1.0 in two subtropical forest ecosystems (Qianyanzhou and Dinghushan) and were much larger than those in temperate ecosystems. Besides, cloudiness thresholds which were favorable for enhancing ecosystem carbon sequestration existed at the three forest sites, respectively. Our research confirmed that the ecosystem LUE at the six sites in China was positively responsive to the diffuse radiation, and the cloudiness index could be used as an environmental regulator for LUE modeling in regional GPP prediction. PMID:25393629

  17. Net Ecosystem Exchange of Carbon Dioxide in a Temperate Poor Fen: A Comparison of Automated and Manual Chamber Techniques

    NASA Astrophysics Data System (ADS)

    Burrows, E. H.; Bubier, J. L.; Mosedale, A.; Cobb, G. W.; Crill, P. M.

    2004-05-01

    We used five techniques to compare Net Ecosystem Exchange (NEE) of carbon dioxide (CO2) in a poor fen using automated and manual static chambers, and found the methods comparable. Once per week we sampled manually from ten collars with a closed chamber system using a LiCor 6200 portable photosynthesis system, and simulated four photosynthetically active radiation (PAR) levels using shrouds. Ten automated chambers sampled CO2 flux every three hours with a LiCor 6252 infrared gas analyzer. Results of the five comparisons showed (1) NEE measurements made from May - August, 2001 by the manual and automated chambers had similar ranges: -10.8 to 12.7 ? mol CO2 m-2 s-1 and -17.2 to 13.1 ? mol CO2 m-2 s-1 respectively. (2) When sorted into four PAR regimes and adjusted for temperature (respiration was measured under different temperature regimes), mean NEE did not differ significantly between the chambers (p<0.05). (3) Chambers were not significantly different in regression of ln(-respiration) on temperature. (4) But differences were found in the PAR vs. NEE relationship with manual chambers providing higher maximum gross photosynthesis estimates (GPmax), and slower uptake of CO2 at low PAR (? ) even after temperature adjustment. (5) Due to the high variability in chamber characteristics, we developed an equation to include foliar biomass and water table as well as temperature and PAR, to provide a more direct comparison between automated and manual NEE. Comparing fitted parameters did not identify new differences between the chambers. These complementary chamber techniques offer a unique opportunity to assess the variability and uncertainty in CO2 flux measurements.

  18. Phytoplankton Diversity and Community Composition along the Estuarine Gradient of a Temperate Macrotidal Ecosystem: Combined Morphological and Molecular Approaches

    PubMed Central

    Bazin, Pauline; Jouenne, Fabien; Friedl, Thomas; Deton-Cabanillas, Anne-Flore; Le Roy, Bertrand; Véron, Benoît

    2014-01-01

    Microscopical and molecular analyses were used to investigate the diversity and spatial community structure of spring phytoplankton all along the estuarine gradient in a macrotidal ecosystem, the Baie des Veys (eastern English Channel). Taxa distribution at high tide in the water column appeared to be mainly driven by the tidal force which superimposed on the natural salinity gradient, resulting in a two-layer flow within the channel. Lowest taxa richness and abundance were found in the bay where Teleaulax-like cryptophytes dominated. A shift in species composition occurred towards the mouth of the river, with the diatom Asterionellopsis glacialis dramatically accumulating in the bottom waters of the upstream brackish reach. Small thalassiosiroid diatoms dominated the upper layer river community, where taxa richness was higher. Through the construction of partial 18S rDNA clone libraries, the microeukaryotic diversity was further explored for three samples selected along the surface salinity gradient (freshwater - brackish - marine). Clone libraries revealed a high diversity among heterotrophic and/or small-sized protists which were undetected by microscopy. Among them, a rich variety of Chrysophyceae and other lineages (e.g. novel marine stramenopiles) are reported here for the first time in this transition area. However, conventional microscopy remains more efficient in revealing the high diversity of phototrophic taxa, low in abundances but morphologically distinct, that is overlooked by the molecular approach. The differences between microscopical and molecular analyses and their limitations are discussed here, pointing out the complementarities of both approaches, for a thorough phytoplankton community description. PMID:24718653

  19. 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.

  20. Assessing the Effects of Land-use Change on Plant Traits, Communities and Ecosystem Functioning in Grasslands: A Standardized Methodology and Lessons

    E-print Network

    Kleyer, Michael

    in Grasslands: A Standardized Methodology and Lessons from an Application to 11 European Sites ERIC GARNIER1 that some traits (vegetative plant height, stem dry matter content) should be omitted in studies invol- ving

  1. The effect of enhanced ultraviolet-B radiation on germination and seedling development of plant species occurring in a dune grassland ecosystem

    Microsoft Academic Search

    Marcel Tosserams; Esther Bolink; Jelte Rozema

    1997-01-01

    The germination of seeds of seven plant species occurring in a dune grassland vegetation of the Netherlands, was studied at four levels of UV-B radiation simulating unto 45% stratospheric ozone reduction during April. With the exception of seeds of Senecio jacobaea, germination of the dune grassland species was not affected by enhanced UV-B irradiance. Although a clear UV-B fluence-response relationship

  2. Ecosystems

    NSDL National Science Digital Library

    Houghton Mifflin Science

    This self-contained module on ecosystems includes a range of fun activities that students can perform in the classroom and at home with family members. They impart important concepts such as observation, identification, measurement, and differentiation.

  3. Biologic cycling of silica across a grassland bioclimosequence

    Microsoft Academic Search

    S. W. Blecker; R. L. McCulley; O. A. Chadwick; E. F. Kelly

    2006-01-01

    The dynamics of biologic Si cycling in grassland ecosystems are largely unknown and likely to impact mineral weathering rates regionally and diatom productivity globally; key regulatory processes in the global Si cycle are closely tied to the global carbon cycle. Across a bioclimatic sequence spanning major grassland ecosystems in the Great Plains, soil biogenic silica depth distributions are similar to

  4. Short communication Land use change patterns in the Rio de la Plata grasslands: The influence of

    E-print Network

    Nacional de San Luis, Universidad

    Short communication Land use change patterns in the Ri´o de la Plata grasslands: The influence) hold one of the largest area of temperate grasslands of the world, the Ri´o de la Plata grasslands (RPG­387) (Fig. 1). Ri´o de la Plata grasslands have an area of 3.4 Â 106 km2 at the center-east of Argentina

  5. Spatial and temporal CO2 exchanges measured by Eddy Correlation over a temperate intertidal flat and their relationships to net ecosystem production

    NASA Astrophysics Data System (ADS)

    Polsenaere, P.; Lamaud, E.; Lafon, V.; Bonnefond, J.-M.; Bretel, P.; Delille, B.; Deborde, J.; Loustau, D.; Abril, G.

    2011-06-01

    Measurements of carbon dioxide fluxes were performed over a temperate intertidal mudflat in southwestern France using the micrometeorological Eddy Correlation (EC) technique. EC measurements were carried out in two contrasting sites of the Arcachon lagoon during four periods and in three different seasons (autumn 2007, summer 2008, autumn 2008 and spring 2009). In this paper, spatial and temporal variations in vertical CO2 exchanges at the diurnal, tidal and seasonal scales are presented and discussed. In addition, satellite images of the tidal flat at low tide were used to link the net ecosystem exchange (NEE) with the occupation of the mudflat by primary producers, particularly by Zostera noltii meadows. CO2 fluxes during the four deployments showed important spatial and temporal variations, with the lagoon rapidly shifting from a sink to a source of CO2. CO2 fluxes showed generally low negative (influx) and positive (efflux) values and ranged from -13 to 19 ?mol m-2 s-1 at maximum. Low tide and daytime conditions were always characterised by an uptake of atmospheric CO2. In contrast, during immersion and during low tide at night, CO2 fluxes where positive, negative or close to zero, depending on the season and the site. During the autumn of 2007, at the innermost station with a patchy Zostera noltii bed (cover of 22 ± 14 % in the wind direction of measurements), CO2 influx was -1.7 ± 1.7 ?mol m-2 s-1 at low tide during the day, and the efflux was 2.7 ± 3.7 ?mol m-2 s-1 at low tide during the night. A gross primary production (GPP) of 4.4 ?mol m-2 s-1 during emersion could be attributed mostly to microphytobenthic communities. During immersion, the water was a source of CO2 to the atmosphere, suggesting strong heterotrophy or resuspension of microphytobenthic cells. During the summer and autumn of 2008, at the central station with a dense eelgrass bed (92 ± 10 %), CO2 uptakes at low tide during the day were -1.5 ± 1.2 and -0.9 ± 1.7 ?mol m-2 s-1, respectively. Nighttime effluxes of CO2 were 1.0 ± 0.9 and 0.2 ± 1.1 ?mol m-2 s-1 in summer and autumn, respectively, resulting in a GPP during emersion of 2.5 and 1.1 ?mol m-2 s-1, respectively, attributed primarily to the seagrass community. At the same station in April 2009, before Zostera noltii started to grow, the CO2 uptake at low tide during the day was the highest (-2.7 ± 2.0 ?mol m-2 s-1) and could be attributed to microphytobenthos dominance on NEP in this case. NEE versus PAR relationships for data ranked by wind directions were generally negative where and when Zostera noltii was dominant and positive when this community was minor. The latter relationship suggests important processes of photo-acclimatisation by the microphytobenthos, such as migration through the sediment. Influxes of CO2 were also observed during immersion at the central station in spring and early autumn and were apparently related to phytoplankton blooms occurring at the mouth of the lagoon, followed by the advection of CO2-depleted water with the tide. Although winter data would be necessary to determine a precise CO2 budget for the lagoon, our results suggest that tidal flat ecosystems are a modest contributor to the CO2 budget of the coastal ocean.

  6. Spatial and temporal CO2 exchanges measured by Eddy Covariance over a temperate intertidal flat and their relationships to net ecosystem production

    NASA Astrophysics Data System (ADS)

    Polsenaere, P.; Lamaud, E.; Lafon, V.; Bonnefond, J.-M.; Bretel, P.; Delille, B.; Deborde, J.; Loustau, D.; Abril, G.

    2012-01-01

    Measurements of carbon dioxide fluxes were performed over a temperate intertidal mudflat in southwestern France using the micrometeorological Eddy Covariance (EC) technique. EC measurements were carried out in two contrasting sites of the Arcachon flat during four periods and in three different seasons (autumn 2007, summer 2008, autumn 2008 and spring 2009). In addition, satellite images of the tidal flat at low tide were used to link the net ecosystem CO2 exchange (NEE) with the occupation of the mudflat by primary producers, particularly by Zostera noltii meadows. CO2 fluxes during the four deployments showed important spatial and temporal variations, with the flat rapidly shifting from sink to source with the tide. Absolute CO2 fluxes showed generally small negative (influx) and positive (efflux) values, with larger values up to -13 ?mol m-2 s-1 for influxes and 19 ?mol m-2 s-1 for effluxes. Low tide during the day was mostly associated with a net uptake of atmospheric CO2. In contrast, during immersion and during low tide at night, CO2 fluxes where positive, negative or close to zero, depending on the season and the site. During the autumn of 2007, at the innermost station with a patchy Zostera noltii bed (cover of 22 ± 14% in the wind direction of measurements), CO2 influx was -1.7 ± 1.7 ?mol m-2 s-1 at low tide during the day, and the efflux was 2.7 ± 3.7 ?mol m-2 s-1 at low tide during the night. A gross primary production (GPP) of 4.4 ± 4.1 ?mol m-2 s-1 during emersion could be attributed to microphytobenthic communities. During the summer and autumn of 2008, at the central station with a dense eelgrass bed (92 ± 10%), CO2 uptakes at low tide during the day were -1.5 ± 1.2 and -0.9 ± 1.7 ?mol m-2 s-1, respectively. Night time effluxes of CO2 were 1.0 ± 0.9 and 0.2 ± 1.1 ?mol m-2 s-1 in summer and autumn, respectively, resulting in a GPP during emersion of 2.5 ± 1.5 and 1.1 ± 2.0 ?mol m-2 s-1, respectively, attributed primarily to the seagrass community. At the same station in April 2009, before Zostera noltii started to grow, the CO2 uptake at low tide during the day was the highest (-2.7 ± 2.0 ?mol m-2 s-1). Influxes of CO2 were also observed during immersion at the central station in spring and early autumn and were apparently related to phytoplankton blooms occurring at the mouth of the flat, followed by the advection of CO2-depleted water with the flooding tide. Although winter data as well as water carbon measurements would be necessary to determine a precise CO2 budget for the flat, our results suggest that tidal flat ecosystems are a modest contributor to the CO2 budget of the coastal ocean.

  7. Temper Tantrums

    MedlinePLUS

    Your toddler's second temper tantrum of the day shows no signs of stopping, and supersonic, ear-shattering, teeth-jarring ... when language skills are starting to develop. Because toddlers can't yet say what they want, feel, ...

  8. Tempered glass

    SciTech Connect

    Bunnell, L.R.

    1991-11-01

    This document describes a demonstration for making tempered glass using minimal equipment. The demonstration is intended for a typical student of materials science, at the high school level or above. (JL)

  9. March 2005 / Vol. 55 No. 3 BioScience 243 Grasslands and savannas occupy more than 40%

    E-print Network

    Blair, John

    March 2005 / Vol. 55 No. 3 · BioScience 243 Articles Grasslands and savannas occupy more than 40 and climate can have dramatic ecological and social consequences (Lauenroth et al.1999).Temperate grasslands are important from both agronomic and ecological perspectives. These grasslands are the basis of an extensive

  10. Gross primary production variability associated with meteorology, physiology, leaf area, and water supply in contrasting woodland and grassland semiarid riparian ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding ecosystem-atmosphere carbon exchanges in dryland environments has been more challenging than in mesic environments, likely due to more pronounced nonlinear responses of ecosystem processes to environmental variation. To better understand diurnal to interannual variation in gross primar...

  11. Our current understanding of lake ecosystem response to climate change: What have we really learned from the north temperate deep lakes?

    Microsoft Academic Search

    Yuko Shimoda; M. Ekram Azim; Gurbir Perhar; Maryam Ramin; Melissa A. Kenney; Somayeh Sadraddini; Alex Gudimov; George B. Arhonditsis

    2011-01-01

    Climatic change is recognized as an important factor capable of influencing the structural properties of aquatic ecosystems. Lake ecosystems are particularly sensitive to climate change. Several long time-series studies have shown close coupling between climate, lake thermal properties and individual organism physiology, population abundance, community structure, and food-web structure. Understanding the complex interplay between climate, hydrological variability, and ecosystem structure

  12. Ecosystems

    NSDL National Science Digital Library

    R. Herzog

    This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on biodiversity within ecosystems and within species. Students visit a local area and collect leaves to demonstrate how diverse life can exist within a small area. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

  13. Preliminary Research on Grassland Fine-classification Based on MODIS

    NASA Astrophysics Data System (ADS)

    Hu, Z. W.; Zhang, S.; Yu, X. Y.; Wang, X. S.

    2014-03-01

    Grassland ecosystem is important for climatic regulation, maintaining the soil and water. Research on the grassland monitoring method could provide effective reference for grassland resource investigation. In this study, we used the vegetation index method for grassland classification. There are several types of climate in China. Therefore, we need to use China's Main Climate Zone Maps and divide the study region into four climate zones. Based on grassland classification system of the first nation-wide grass resource survey in China, we established a new grassland classification system which is only suitable for this research. We used MODIS images as the basic data resources, and use the expert classifier method to perform grassland classification. Based on the 1:1,000,000 Grassland Resource Map of China, we obtained the basic distribution of all the grassland types and selected 20 samples evenly distributed in each type, then used NDVI/EVI product to summarize different spectral features of different grassland types. Finally, we introduced other classification auxiliary data, such as elevation, accumulate temperature (AT), humidity index (HI) and rainfall. China's nation-wide grassland classification map is resulted by merging the grassland in different climate zone. The overall classification accuracy is 60.4%. The result indicated that expert classifier is proper for national wide grassland classification, but the classification accuracy need to be improved.

  14. Regional variability of grassland CO2 fluxes in Tyrol/Austria

    NASA Astrophysics Data System (ADS)

    Irschick, Christoph; Hammerle, Albin; Haslwanter, Alois; Wohlfahrt, Georg

    2010-05-01

    The FLUXNET project [1] aims at quantifying the magnitude and controls on the CO2, H2O and energy exchange of terrestrial ecosystems. Ideally, the various biomes of the Earth would be sampled in proportion to their spatial extent - in reality, however, study site selection is usually based on other (more practical) criteria so that a bias exists towards certain biomes and ecosystem types. This may be problematic because FLUXNET data are used to calibrate/parameterize models at various scales - if certain ecosystems are poorly replicated this may bias model predictions. Here we present data from a project in Tyrol/Austria where we have been investigating the CO2, H2O and energy exchange of five grassland sites during 2005-2007. The five permanent grassland sites were exposed to similar climate, but differed slightly in management. In a FLUXNET style approach, any of these sites might have been selected for making long-term flux measurements - the aim of this project was to examine the representativeness of these sites and, if evident, elucidate the causes for and controls on differences between sites. To this end we conducted continuous eddy covariance flux measurements at one (anchor) site [2, 3], and episodic, month long flux measurements at the four additional sites using a roving eddy covariance tower. These data were complemented by measurements of environmental drivers, the amount of above ground phytomass and basic data on vegetation and soil type, as well as management. Data are subject to a rigorous statistical analysis in order to quantify significant differences in the CO2, H2O and energy exchange between the sites and to identify the factors which are responsible for these differences. In the present contribution we report results on CO2 fluxes. Our major findings are that (i) site-identity of the surveyed grassland ecosystems was a significant factor for the net ecosystem CO2 exchange (NEE), somewhat less for gross primary production (GPP) and not for ecosystem respiration (RECO), (ii) GPP depended mainly on the amount of incident photosynthetically active radiation and the amount of green plant matter, the scale of influence of these two factors varying fourfold between the sites, and not so much on the available water, (iii) RECO was mainly affected by the soil temperature, but some evidence for priming effects was also found, (iv) the NEE was mainly influenced by GPP and to a lower extent by RECO. Taken together our results indicate that even within the same ecosystem type exposed to similar climate and land use, site selection may strongly affect the resulting NEE estimates. References: [1] D.D. Baldocchi, "Breathing of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurement systems", Australian Journal of Botany vol.56 (2008) pp. 1-26. [2] A. Hammerle, A. Haslwanter, U. Tappeiner, A. Cernusca, G. Wohlfahrt, "Leaf area controls on energy partitioning of a temperate mountain grassland", Biogeosciences vol.5 (2008) pp. 421 431. [3] G. Wohlfahrt, A. Hammerle, A. Haslwanter, M. Bahn, U. Tappeiner, A. Cernusca, "Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland: effects of weather and management", Journal of Geophysical Research 113 (2008) D08110, doi:10.1029/2007JD009286.

  15. Carbon and Nitrogen Dynamics of Temperate and Subarctic Heath

    E-print Network

    Carbon and Nitrogen Dynamics of Temperate and Subarctic Heath Ecosystems with Emphasis on Cold-season cycling of carbon and nitrogen in temperate and subarctic heath ecosystems. Over the last three years, I of the carbon flux studies............................................................ 14 3. The nitrogen cycle

  16. Spatial and temporal variability of bacterial 16S rDNA-based T-RFLP patterns derived from soil of two Wyoming grassland ecosystems

    Microsoft Academic Search

    Daniel L Mummey; Peter D Stahl

    2003-01-01

    Spatial and temporal variability of soil bacterial 16S rDNA terminal restriction fragment (TRF) size variation was evaluated in a homogeneous grassland (HG) dominated by the turf-forming grass Bouteloua gracilis and in a shrubland (SL) dominated by Artemisia tridentata (Wyoming big sagebrush). Temporal variability was also evaluated on the HG site over a growing season. No trends toward dissimilarity were detected

  17. Effects of plant diversity on invertebrate herbivory in experimental grassland.

    PubMed

    Scherber, Christoph; Mwangi, Peter N; Temperton, Vicky M; Roscher, Christiane; Schumacher, Jens; Schmid, Bernhard; Weisser, Wolfgang W

    2006-03-01

    The rate at which a plant species is attacked by invertebrate herbivores has been hypothesized to depend on plant species richness, yet empirical evidence is scarce. Current theory predicts higher herbivore damage in monocultures than in species-rich mixtures. We quantified herbivore damage by insects and molluscs to plants in experimental plots established in 2002 from a species pool of 60 species of Central European Arrhenatherum grasslands. Plots differed in plant species richness (1, 2, 4, 8, 16, 60 species), number of functional groups (1, 2, 3, 4), functional group and species composition. We estimated herbivore damage by insects and molluscs at the level of transplanted plant individuals ("phytometer" species Plantago lanceolata, Trifolium pratense, Rumex acetosa) and of the entire plant community during 2003 and 2004. In contrast to previous studies, our design allows specific predictions about the relative contributions of functional diversity, plant functional identity, and species richness in relation to herbivory. Additionally, the phytometer approach is new to biodiversity-herbivory studies, allowing estimates of species-specific herbivory rates within the larger biodiversity-ecosystem functioning context. Herbivory in phytometers and experimental communities tended to increase with plant species richness and the number of plant functional groups, but the effects were rarely significant. Herbivory in phytometers was in some cases positively correlated with community biomass or leaf area index. The most important factor influencing invertebrate herbivory was the presence of particular plant functional groups. Legume (grass) presence strongly increased (decreased) herbivory at the community level. The opposite pattern was found for herbivory in T. pratense phytometers. We conclude that (1) plant species richness is much less important than previously thought and (2) plant functional identity is a much better predictor of invertebrate herbivory in temperate grassland ecosystems. PMID:16231192

  18. Biodiversity and stability in grasslands

    Microsoft Academic Search

    David Tilman; John A. Downing

    1994-01-01

    ONE of the ecological tenets justifying conservation of biodiversity is that diversity begets stability. Impacts of biodiversity on population dynamics and ecosystem functioning have long been debated1-7, however, with many theoretical explorations2-6,8-11 but few field studies12-15. Here we describe a long-term study of grasslands16,17 which shows that primary productivity in more diverse plant communities is more resistant to, and recovers

  19. GRASSLAND INVADER RESPONSES TO REALISTIC CHANGES IN NATIVE SPECIES RICHNESS

    Microsoft Academic Search

    Matthew J. Rinella; Monica L. Pokorny; Romdhane Rekaya

    2007-01-01

    The importance of species richness for repelling exotic plant invasions varies from ecosystem to ecosystem. Thus, in order to prioritize conservation objectives, it is critical to identify those ecosystems where decreasing richness will most greatly magnify invasion risks. Our goal was to determine if invasion risks greatly increase in response to common reductions in grassland species richness. We imposed treatments

  20. EFFECTS OF LAND-USE HISTORY ON SOIL QUALITY: IMPLICATIONS FOR SANDPLAIN GRASSLAND RESTORATION

    E-print Network

    Vallino, Joseph J.

    EFFECTS OF LAND-USE HISTORY ON SOIL QUALITY: IMPLICATIONS FOR SANDPLAIN GRASSLAND RESTORATION, The Ecosystems Center, Woods Hole Marine Biological Lab, Woods Hole, MA Abstract Coastal sandplain grasslands few sandplain grasslands remaining, and consequently many restoration efforts are focused on creating

  1. Impacts of seasonality and surface heterogeneity on water-use efficiency in mesic grasslands

    E-print Network

    Nippert, Jesse

    Impacts of seasonality and surface heterogeneity on water-use efficiency in mesic grasslands N. A encroachment is occurring in grasslands worldwide, with largely unknown effects on local carbon and water evapotranspiration. Here, a was compared among three different grassland ecosystems in eastern KS, USA, by using

  2. Observations and modeling of biomass and soil organic matter dynamics for the grassland biome worldwide

    Microsoft Academic Search

    W. J. Parton; J. M. O. Scurlock; D. S. Ojima; T. G. Gilmanov; R. J. Scholes; D. S. Schimel; T. Kirchner; J.-C. Menaut; T. Seastedt; E. Garcia Moya; Apinan Kamnalrut; J. I. Kinyamario

    1993-01-01

    Century is a model of terrestrial biogeochemistry based on relationships between climate, human management (fire, grazing), soil properties, plant productivity, and decomposition. The grassland version of the Century model was tested using observed data from 11 temperate and tropical grasslands around the world. The results show that soil C and N levels can be simulated to within +\\/-25% of the

  3. SPATIAL PATTERNS OF LIGHT GAPS IN MESIC GRASSLANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasions by non-resident species into grasslands are a global phenomenon that can affect ecosystem structure and function, and dramatically alter vegetation composition. Predictive capacity for assessing invasibility of grasslands, however, has been hindered by the complex interaction of several fa...

  4. Variation in the carbon and oxygen isotope composition of plant biomass and its relationship to water-use efficiency at the leaf- and ecosystem-scales in a northern Great Plains grassland.

    PubMed

    Flanagan, Lawrence B; Farquhar, Graham D

    2014-02-01

    Measurements of the carbon (?(13) Cm ) and oxygen (?(18) Om ) isotope composition of C3 plant tissue provide important insights into controls on water-use efficiency. We investigated the causes of seasonal and inter-annual variability in water-use efficiency in a grassland near Lethbridge, Canada using stable isotope (leaf-scale) and eddy covariance measurements (ecosystem-scale). The positive relationship between ?(13) Cm and ?(18) Om values for samples collected during 1998-2001 indicated that variation in stomatal conductance and water stress-induced changes in the degree of stomatal limitation of net photosynthesis were the major controls on variation in ?(13) Cm and biomass production during this time. By comparison, the lack of a significant relationship between ?(13) Cm and ?(18) Om values during 2002, 2003 and 2006 demonstrated that water stress was not a significant limitation on photosynthesis and biomass production in these years. Water-use efficiency was higher in 2000 than 1999, consistent with expectations because of greater stomatal limitation of photosynthesis and lower leaf ci /ca during the drier conditions of 2000. Calculated values of leaf-scale water-use efficiency were 2-3 times higher than ecosystem-scale water-use efficiency, a difference that was likely due to carbon lost in root respiration and water lost during soil evaporation that was not accounted for by the stable isotope measurements. PMID:23862667

  5. From fronds to fish: the use of indicators for ecological monitoring in marine benthic ecosystems, with case studies from temperate Western Australia

    Microsoft Academic Search

    Dan A. Smale; Timothy J. Langlois; Gary A. Kendrick; Jessica J. Meeuwig; Euan S. Harvey

    Ecological indicators are used for monitoring in marine habitats the world over. With the advent of Ecosystem Based Fisheries\\u000a Management (EBFM), the need for cost effective indicators of environmental impacts and ecosystem condition has intensified.\\u000a Here, we review the development, utilisation and analysis of indicators for monitoring in marine benthic habitats, and outline\\u000a important advances made in recent years. We

  6. BVOC fluxes above mountain grassland

    PubMed Central

    Bamberger, I.; Hortnagl, L.; Schnitzhofer, R.; Graus, M.; Ruuskanen, T. M.; Muller, M.; Dunkl, J.; Wohlfahrt, G.; Hansel, A.

    2013-01-01

    Grasslands comprise natural tropical savannah over managed temperate fields to tundra and cover one quarter of the Earth’s land surface. Plant growth, maintenance and decay result in volatile organic compound (VOCs) emissions to the atmosphere. Furthermore, biogenic VOCs (BVOCs) are emitted as a consequence of various environmental stresses including cutting and drying during harvesting. Fluxes of BVOCs were measured with a proton-transfer-reaction-mass-spectrometer (PTR-MS) over temperate mountain grassland in Stubai Valley (Tyrol, Austria) over one growing season (2008). VOC fluxes were calculated from the disjunct PTR-MS data using the virtual disjunct eddy covariance method and the gap filling method. Methanol fluxes obtained with the two independent flux calculation methods were highly correlated (y = 0.95×?0.12, R2 = 0.92). Methanol showed strong daytime emissions throughout the growing season – with maximal values of 9.7 nmol m?2 s?1, methanol fluxes from the growing grassland were considerably higher at the beginning of the growing season in June compared to those measured during October (2.5 nmol m?2 s?1). Methanol was the only component that exhibited consistent fluxes during the entire growing periods of the grass. The cutting and drying of the grass increased the emissions of methanol to up to 78.4 nmol m?2 s?1. In addition, emissions of acetaldehyde (up to 11.0 nmol m?2 s?1), and hexenal (leaf aldehyde, up to 8.6 nmol m?2 s?1) were detected during/after harvesting. PMID:24339833

  7. Estimation of nitrous oxide emissions from US grasslands

    SciTech Connect

    Mummey, D.L.; Smith, J.L.; Bluhm, G.

    2000-02-01

    Nitrous oxide (N{sub 2}O) emissions from temperate grasslands are poorly quantified and may be an important part of the atmospheric N{sub 2}O budget. In this study N{sub 2}O emissions were simulated for 1,052 grassland sites in the US using the NGAS model of Parton and others (1996) coupled with an organic matter decomposition model. N{sub 2}O flux was calculated for each site using soil and land use data obtained from the National Resource Inventory (NRI) database and weather data obtained from NASA. The estimates were regionalized based upon temperature and moisture isotherms. Annual N{sub 2}O emissions for each region were based on the grassland area of each region and the mean estimated annual N{sub 2}O flux from NRI grassland sites in the region. The regional fluxes ranged from 0.18 to 1.02 kg N{sub 2}O N/ha/yr with the mean flux for all regions being 0.29 kg N{sub 2}O N/ha/yr. Even though fluxes from the western regions were relatively low, these regions made the largest contribution to total emissions due to their large grassland area. Total US grassland N{sub 2}O emissions were estimated to be about 67 Gg N{sub 2}O N/yr. Emissions from the Great Plains states, which contain the largest expanse of natural grassland in the US, were estimated to average 0.24 kg N{sub 2}O N/ha/yr. Using the annual flux estimate for the temperate Great Plains, the authors estimate that temperate grasslands worldwide may potentially produce 0.27 Tg N{sub 2}O N/yr. Even though the estimate for global temperate grassland N{sub 2}O emissions is less than published estimates for other major temperate grasslands are a significant part of both United States and global atmospheric N{sub 2}O budgets. This study demonstrates the utility of models for regional N{sub 2}O budgets. This study demonstrates the utility of models for regional N{sub 2}O flux estimation although additional data from carefully designed field studies is needed to further validate model results.

  8. Tempered fractional calculus

    NASA Astrophysics Data System (ADS)

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  9. Scaling-up knowledge of growing-season net ecosystem exchange for long-term assessment of North Dakota grasslands under the Conservation Reserve Program

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Scaling-up knowledge of land-atmosphere net ecosystem exchange (NEE) from a single experimental site to numerous perennial grass fields in the Northern Great Plains (NGP) requires appropriate scaling protocols. We addressed this problem using synoptic data available from the Landsat sensor for ten ...

  10. Effect of rainfall patterns on soil surface CO2 efflux, soil moisture, soil temperature and plant growth in a grassland ecosystem of northern Ontario, Canada: implications for climate change

    PubMed Central

    Laporte, Michael F; Duchesne, LC; Wetzel, S

    2002-01-01

    Background The effect of rainfall patterns on soil surface CO2 efflux, soil moisture, soil temperature and plant growth was investigated in a grassland ecosystem of northern Ontario, Canada, where climatic change is predicted to introduce new precipitation regimes. Rain shelters were established in a fallow field consisting mainly of Trifolium hybridum L., Trifolium pratense L., and Phleum pratense L. Daytime ambient air temperatures within the shelters increased by an average of 1.9°C similar to predicted future increases in air temperatures for this region. To simulate six precipitation regimes which cover the maximum range to be expected under climate change, a portable irrigation system was designed to modify the frequency of monthly rainfall events with a constant delivery rate of water, while maintaining contemporary average precipitation volumes. Controls consisted of blocks irrigated with frequencies and total monthly precipitation consistent with the 25 year average rainfall for this location. Results Seasonal soil moisture correlated with soil surface CO2 efflux (R = 0.756, P < 0.001) and above ground plant biomass (R = 0.447, P = 0.029). By reducing irrigation frequency, soil surface CO2 efflux decreased by 80%, P < 0.001, while soil moisture content decreased by 42%, P < 0.001. Conclusions Manipulating the number of precipitation events and inter-rainfall intervals, while maintaining monthly rainfall averages impacted CO2 efflux and plant growth. Even with monthly rainfall averages that are similar to contemporary monthly precipitation averages, decreasing the number of monthly rainfall events reduced soil surface CO2 efflux and plant growth through soil moisture deficits. Although many have speculated that climate change will increase ecosystem productivity, our results show that a reduction in the number of monthly rainfall events while maintaining monthly averages will limit carbon dynamics. PMID:12445327

  11. Carbon Sequestration Rates and the Energy Balance of Turf in the Denver Urban Ecosystem and in an Adjacent Native Grassland Under Contrasting Management Practices

    NASA Astrophysics Data System (ADS)

    Anderson, D. E.; Powell, K.; Szanko, G.; Mladinich, C.; Curry, S.; Griebel, A.

    2010-12-01

    Although urban areas occupy just a few percent of US land area, they are expanding rapidly and are expected to maintain this trend for the foreseeable future. Within these domains is the largest irrigated crop in the US - lawns. Utilizing eddy covariance instruments, surface chambers, and destructive leaf sampling, well watered, fertilized lawns in metropolitan Denver were found to sequester substantially more carbon (1.3 T C ha-1 yr-1) than adjacent native grassland (0.6 T C ha-1 yr-1) over a growing season. Due to the semi-arid environment, contrasts in lawn management (irrigation and fertilization) led to wide variation in carbon sequestration rates, evapotranspiration, and the sensible and latent heat partitioning of the energy balance. Measured leaf area was correlated with remotely sensed vegetation indices obtained from aircraft and satellite hyperspectral instruments to quantify spatial variability in leaf area over contrasting land surfaces and lawn management practices. These relations applied to continuing acquisition of remotely sensed data provide us with a means to assess potential variability in carbon sequestration in space and time domains.

  12. The greenhouse gas balance of European grasslands

    NASA Astrophysics Data System (ADS)

    Ciais, P.; Soussana, J. F.; Vuichard, N.; Luyssaert, S.; Don, A.; Janssens, I. A.; Piao, S. L.; Dechow, R.; Lathičre, J.; Maignan, F.; Wattenbach, M.; Smith, P.; Ammann, C.; Freibauer, A.; Schulze, E. D.; Carboeurope Synthesis Team

    2010-08-01

    The long-term carbon balance (NBP) of grasslands is estimated by combining scarce multi-year eddy-covariance observations at ecosystem observation sites where information on carbon inputs and harvesting removals is available. Following accounting for carbon leached to rivers, we estimated grasslands to be net carbon sinks of 74±10 g C m-2 yr-1. Uncertainties arise from the small number of sites and the short measurement period. Only 11 sites, out of a total of 20 grassland sites in Europe where eddy covariance systems are installed, were set-up for estimating NBP. These 11 selected sites are representative of intensive management practice and we lack information on disturbance history, such as plowing. This suggests that the grassland NBP estimate is likely biased towards overestimating the sink, compared to the European average. Direct measurements of Net Primary Productivity (NPP) are not possible in grasslands given permanent biomass removal by grazing and mowing, uncertainties in rhizodeposition and production of volatile organic carbon compounds lost to the atmosphere. Therefore, the grassland process-based ecosystem model PASIM was used to estimate the spatial-temporal distribution of NPP, providing a European average value of 750±150 g C across extensively grazed, intensively grazed pastures, and forage production systems. In Europe the NPP of grasslands seems higher than that of croplands and forests. The carbon sequestration efficiency of grasslands, defined as the ratio of NBP to NPP, amounts to 0.09±0.10. Therefore, per unit of carbon input, grasslands sequester 3-4 times more carbon in the soil than forests do, making them a good candidate for managing onsite carbon sinks. When using the 100 yr greenhouse warming potential for CH4 and N2O, their emissions due to management of grasslands together offset roughly 70-80% of the carbon sink. Uncertainties on the European grassland greenhouse gas balance, including CO2, CH4 and N2O fluxes are likely to be reduced in the near future, with data being collected from more sites, and improved up-scaling methods.

  13. Grassland carbon and nitrogen dynamics: effects of seasonal fire and clipping in a mixed-grass prairie of the southern great plains

    E-print Network

    Harris, Wylie Neal

    2006-08-16

    Plant production and soil microbial biomass (SMB) in grassland ecosystems are linked by flows of carbon (C) and nitrogen (N) between the two groups of organisms. In native mixed grasslands of the southern Great Plains, these cycles are strongly...

  14. Grassland carbon and nitrogen dynamics: effects of seasonal fire and clipping in a mixed-grass prairie of the southern great plains 

    E-print Network

    Harris, Wylie Neal

    2006-08-16

    Plant production and soil microbial biomass (SMB) in grassland ecosystems are linked by flows of carbon (C) and nitrogen (N) between the two groups of organisms. In native mixed grasslands of the southern Great Plains, these cycles are strongly...

  15. Effects of Nitrogen Addition and Fire on Plant Nitrogen Use in a Temperate Steppe

    PubMed Central

    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. PMID:24594654

  16. Long-term resistance to simulated climate change in an infertile grassland

    PubMed Central

    Grime, J. Philip; Fridley, Jason D.; Askew, Andrew P.; Thompson, Ken; Hodgson, John G.; Bennett, Chris R.

    2008-01-01

    Climate shifts over this century are widely expected to alter the structure and functioning of temperate plant communities. However, long-term climate experiments in natural vegetation are rare and largely confined to systems with the capacity for rapid compositional change. In unproductive, grazed grassland at Buxton in northern England (U.K.), one of the longest running experimental manipulations of temperature and rainfall reveals vegetation highly resistant to climate shifts maintained over 13 yr. Here we document this resistance in the form of: (i) constancy in the relative abundance of growth forms and maintained dominance by long-lived, slow-growing grasses, sedges, and small forbs; (ii) immediate but minor shifts in the abundance of several species that have remained stable over the course of the experiment; (iii) no change in productivity in response to climate treatments with the exception of reduction from chronic summer drought; and (iv) only minor species losses in response to drought and winter heating. Overall, compositional changes induced by 13-yr exposure to climate regime change were less than short-term fluctuations in species abundances driven by interannual climate fluctuations. The lack of progressive compositional change, coupled with the long-term historical persistence of unproductive grasslands in northern England, suggests the community at Buxton possesses a stabilizing capacity that leads to long-term persistence of dominant species. Unproductive ecosystems provide a refuge for many threatened plants and animals and perform a diversity of ecosystem services. Our results support the view that changing land use and overexploitation rather than climate change per se constitute the primary threats to these fragile ecosystems. PMID:18606995

  17. The recovery of ant communities in regenerating temperate conifer forests

    Microsoft Academic Search

    Jennifer D. Palladini; Maureen G. Jones; Nathan J. Sanders; Erik S. Jules

    2007-01-01

    Although ants perform many critical functions in forested ecosystems, little is known about how they respond to timber harvesting, especially in temperate systems. We examined ground-foraging ant communities and 11 forest characteristics in temperate conifer forests of southwestern Oregon, USA that ranged in age from 5 to 427 years. Seven forest characteristics were related to stand age and were summarized

  18. A comparative study of arbuscular mycorrhizal fungi in forest, grassland and cropland in the Tibetan Plateau, China

    Microsoft Academic Search

    Qing-Ming Gao; Liang-Dong Guo

    2010-01-01

    Arbuscular mycorrhizal (AM) fungus community composition and diversity among the forest, grassland, and cropland ecosystems in the Tibetan Plateau were carried out in this study. A total of 44 AM fungi belonging to six genera were isolated from 144 soil samples collected from forest, grassland, and cropland. Of these AM fungi, 40 taxa were found in forest, 19 in grassland,

  19. QWhat are grassland landowners' knowledge and perceptions about the use of prescribed fire and grazing as management

    E-print Network

    Debinski, Diane M.

    QWhat are grassland landowners' knowledge and perceptions about the use of prescribed fire grassland ecosystems. However, private landowners have been slow to learn about and adopt these practices and knowledge, information exchanges, and practices on grazing native grasslands and potential impacts to water

  20. Changes in soil organic matter driven by shifts in co-dominant plant species in a grassland

    E-print Network

    Paris-Sud XI, Université de

    1 Changes in soil organic matter driven by shifts in co-dominant plant species in a grassland R.geoderma.2013.07.027 #12;2 Abstract Globally, grassland soils, if managed properly, are important for the sake. Rangeland ecosystems are very diverse (i.e. grassland, shrubland

  1. Biotransference and biomagnification of selenium copper, cadmium, zinc, arsenic and lead in a temperate seagrass ecosystem from Lake Macquarie Estuary, NSW, Australia.

    PubMed

    Barwick, M; Maher, W

    2003-10-01

    In this study the biotransference of selenium copper, cadmium, zinc, arsenic and lead was measured in a contaminated seagrass ecosystem in Lake Macquarie, NSW, Australia, to determine if biomagnification of these trace metals is occurring and if they reach concentrations that pose a threat to the resident organisms or human consumers. Selenium was found to biomagnify, exceeding maximum permitted concentrations for human consumption within carnivorous fish tissue, the highest trophic level examined. Selenium concentrations measured within carnivorous fish were also above those shown to elicit sub-lethal effects in freshwater fish. As comparisons are made to selenium concentrations known to effect freshwater fish, inferences must be made with caution. There was no evidence of copper, cadmium, zinc or lead biomagnification within the food web examined. Copper, cadmium, zinc and lead concentrations were below concentrations shown to elicit adverse responses in biota. Copper concentrations within crustaceans M. bennettae and P. palagicus were found to exceed maximum permitted concentrations for human consumption. It is likely that copper concentrations within these species were accumulated due to the essential nature of this trace metal for many species of molluscs and crustaceans. Arsenic showed some evidence of biomagnification. Total arsenic concentrations are similar to those found in other uncontaminated marine ecosystems, thus arsenic concentrations are unlikely to cause adverse effects to aquatic organisms. Inorganic arsenic concentrations are below maximum permitted concentrations for human consumption. PMID:12860434

  2. Stimulation of Symbiotic N2 Fixation in Trifolium repens L. under Elevated Atmospheric pCO2 in a Grassland Ecosystem.

    PubMed

    Zanetti, S.; Hartwig, U. A.; Luscher, A.; Hebeisen, T.; Frehner, M.; Fischer, B. U.; Hendrey, G. R.; Blum, H.; Nosberger, J.

    1996-10-01

    Symbiotic N2 fixation is one of the main processes that introduces N into terrestrial ecosystems. As such, it may be crucial for the sequestration of the extra C available in a world of continuously increasing atmospheric CO2 partial pressure (pCO2). The effect of elevated pCO2 (60 Pa) on symbiotic N2 fixation (15N-isotope dilution method) was investigated using Free-Air-CO2-Enrichment technology over a period of 3 years. Trifolium repens was cultivated either alone or together with Lolium perenne (a nonfixing reference crop) in mixed swards. Two different N fertilization levels and defoliation frequencies were applied. The total N yield increased consistently and the percentage of plant N derived from symbiotic N2 fixation increased significantly in T. repens under elevated pCO2. All additionally assimilated N was derived from symbiotic N2 fixation, not from the soil. In the mixtures exposed to elevated pCO2, an increased amount of symbiotically fixed N (+7.8, 8.2, and 6.2 g m-2 a-1 in 1993, 1994, and 1995, respectively) was introduced into the system. Increased N2 fixation is a competitive advantage for T. repens in mixed swards with pasture grasses and may be a crucial factor in maintaining the C:N ratio in the ecosystem as a whole. PMID:12226411

  3. Stimulation of Symbiotic N2 Fixation in Trifolium repens L. under Elevated Atmospheric pCO2 in a Grassland Ecosystem.

    PubMed Central

    Zanetti, S.; Hartwig, U. A.; Luscher, A.; Hebeisen, T.; Frehner, M.; Fischer, B. U.; Hendrey, G. R.; Blum, H.; Nosberger, J.

    1996-01-01

    Symbiotic N2 fixation is one of the main processes that introduces N into terrestrial ecosystems. As such, it may be crucial for the sequestration of the extra C available in a world of continuously increasing atmospheric CO2 partial pressure (pCO2). The effect of elevated pCO2 (60 Pa) on symbiotic N2 fixation (15N-isotope dilution method) was investigated using Free-Air-CO2-Enrichment technology over a period of 3 years. Trifolium repens was cultivated either alone or together with Lolium perenne (a nonfixing reference crop) in mixed swards. Two different N fertilization levels and defoliation frequencies were applied. The total N yield increased consistently and the percentage of plant N derived from symbiotic N2 fixation increased significantly in T. repens under elevated pCO2. All additionally assimilated N was derived from symbiotic N2 fixation, not from the soil. In the mixtures exposed to elevated pCO2, an increased amount of symbiotically fixed N (+7.8, 8.2, and 6.2 g m-2 a-1 in 1993, 1994, and 1995, respectively) was introduced into the system. Increased N2 fixation is a competitive advantage for T. repens in mixed swards with pasture grasses and may be a crucial factor in maintaining the C:N ratio in the ecosystem as a whole. PMID:12226411

  4. Impact of N-input by wet deposition on N-trace gas fluxes and CH 4-oxidation in spruce forest ecosystems of the temperate zone in Europe

    NASA Astrophysics Data System (ADS)

    Butterbach-Bahl, K.; Gasche, R.; Huber, Ch; Kreutzer, K.; Papen, H.

    In an effort to elucidate the impact of N-deposition from the atmosphere on trace gas fluxes (N 2O, NO, CH 4) from soils of temperate coniferous forests, two spruce forest sites in Germany and Ireland with comparable edaphic and climatic conditions, but with pronounced differences in the amounts of N-input from the atmosphere were compared at different seasons. At the site in Germany trace gas fluxes as well as wet deposition of NH +4 and NO -3 were recorded continuously over the entire year 1994. Correlation analysis between fluxes and N-input data were performed, in order to elucidate if a direct effect between flux and N-deposition could be demonstrated. At all sampling dates N 2O fluxes at the site receiving high atmospheric N-input (Höglwald, Germany) were significantly 1.5-5 fold higher than N 2O emission rates at the site receiving low N-input by wet deposition from the atmosphere (Ballyhooly, Ireland). In contrast to the Höglwald site, at which only emission of N 2O to the atmosphere was observed, at certain periods the Ballyhooly soil functioned as a sink for atmospheric N 2O. Methane oxidation rates were significantly lower at the Höglwald site compared to the Ballyhooly site. At the Höglwald site it could be demonstrated by correlation analysis that the input of NH +4 and NO -3 by wet deposition significantly altered emissions of N 2O and NO (stimulation) and of CH 4 oxidation (reduction). The coefficient of determination was better for NH +4 than for NO -3 for all trace gases studied and was best for the relation between NO emission rates and NH +4-input.

  5. Interannual variation in root production in grasslands affected by artificially modified amount of rainfall.

    PubMed

    Fiala, Karel; T?ma, Ivan; Holub, Petr

    2012-01-01

    The effect of different amounts of rainfall on the below-ground plant biomass was studied in three grassland ecosystems. Responses of the lowland (dry Festuca grassland), highland (wet Cirsium grassland), and mountain (Nardus grassland) grasslands were studied during five years (2006-2010). A field experiment based on rainout shelters and gravity irrigation simulated three climate scenarios: rainfall reduced by 50% (dry), rainfall increased by 50% (wet), and the natural rainfall of the current growing season (ambient). The interannual variation in root increment and total below-ground biomass reflected the experimentally manipulated amount of precipitation and also the amount of current rainfall of individual years. The effect of year on these below-ground parameters was found significant in all studied grasslands. In comparison with dry Festuca grassland, better adapted to drought, submontane wet Cirsium grassland was more sensitive to the different water inputs forming rather lower amount of below-ground plant matter at reduced precipitation. PMID:22629201

  6. Water, temperature, and defoliation effects on perennial grassland respiration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in respiration can have a profound effect on ecosystem C balance. This talk will present results from eddy covariance studies describing environment and management effects on ecosystem C flux from cool- and warm-season perennial grasslands. In addition, stable C isotope studies that partitio...

  7. Landscape cultivation alters ?ł?Si signature in terrestrial ecosystems.

    PubMed

    Vandevenne, Floor I; Delvaux, Claire; Hughes, Harold J; André, Luc; Ronchi, Benedicta; Clymans, Wim; Barăo, Lúcia; Govers, Gerard; Meire, Patrick; Struyf, Eric; Cornelis, Jean-Thomas

    2015-01-01

    Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (?(30)Si) signatures in soil water samples across a temperate land use gradient. We show that - independent of geological and climatological variation - there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in ?(30)Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on ?(30)Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate). PMID:25583031

  8. Landscape cultivation alters ?30Si signature in terrestrial ecosystems

    PubMed Central

    Vandevenne, Floor I.; Delvaux, Claire; Hughes, Harold J.; André, Luc; Ronchi, Benedicta; Clymans, Wim; Barăo, Lúcia; Govers, Gerard; Meire, Patrick; Struyf, Eric

    2015-01-01

    Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (?30Si) signatures in soil water samples across a temperate land use gradient. We show that – independent of geological and climatological variation – there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in ?30Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on ?30Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate). PMID:25583031

  9. Evaluating Eddy Covariance Flux Filtering Methods For Producing Ecosystem-Representative Carbon Exchange Estimates For A Fetch-Limited Temperate Forest

    NASA Astrophysics Data System (ADS)

    Bowling, D. R.; Bird, J. A.; Schmidt, S. K.

    2011-12-01

    Producing time-integrated (daily to annual) estimates of ecosystem-atmosphere carbon exchanges from eddy covariance (EC) measurements requires the careful exclusion of non-representative fluxes prior to gap-filling model application. Half-hourly fluxes are typically excluded when atmospheric turbulence is below an acceptable level (friction velocity threshold, u*Th), or when the relative contribution from non-target surfaces is greater than a tolerable amount (footprint threshold, fpTh). In this study, we compare and evaluate a variety of commonly-used footprint- and friction velocity-filtering methods applied to six years (2006-2011) of carbon flux estimates for a fetch-limited, 74-year old planted Eastern white pine (Pinus Strobus L.) forest in southern Ontario, Canada. A data-driven approach was used, where factorial combinations of footprint models, fpTh values and u*Th determination methods were applied prior to gap-filling. Filtering applications were compared in terms of the quantity and distribution of data removed, while ANOVA and multiple comparison tests were used to quantify the influence of these applications on annual estimates of Net Ecosystem Productivity (NEP), Ecosystem Respiration (RE) and Gross Ecosystem Productivity (GEP). Finally, preferred filtering applications were selected using an objective evaluation of gap-filling model performance metrics to provide information on the internal consistency of the filtered data. Results showed that the choice of footprint model and fpTh exerted a greater influence on NEP, RE and GEP estimates than the u*Th estimation method used. Variation in u*Th estimates were partly explained by footprint filtering specifications, indicating significant u*Th differences between the target forest and the surrounding forested and agricultural land. Applying the footprint model of Kljun (2004. Bound. Layer Met. 112[3]) at fpTh = 0.8 resulted in greatest improvement in model performance; increasing fpTh above this value diminished performance markedly, as insufficient input data quantity and temporal coverage caused poor parameterization. Thus, footprint filter application at this site (and likely other sites), must balance competing needs: accepting only the most representative flux data, while retaining a sufficient amount for successful gap-filling model operation. Compared to the no-footprint (control) case, applying these optimal filtering methods increased annual NEP estimates between 75 and 250 g C m-2 y-1, implying that this forest sequesters substantially more carbon annually than the surrounding landscape. NEP changes were solely attributed to decreased annual RE estimates, as GEP varied only minimally between different footprint and friction velocity applications. This result, caused by a significant day/night flux footprint discrepancy, suggests the need for half-hourly footprint filter application and analyses at all EC flux tower sites that experience measurement fetch limitations.

  10. Evaluating Eddy Covariance Flux Filtering Methods For Producing Ecosystem-Representative Carbon Exchange Estimates For A Fetch-Limited Temperate Forest

    NASA Astrophysics Data System (ADS)

    Brodeur, J. J.; Peichl, M.; Arain, M.

    2013-12-01

    Producing time-integrated (daily to annual) estimates of ecosystem-atmosphere carbon exchanges from eddy covariance (EC) measurements requires the careful exclusion of non-representative fluxes prior to gap-filling model application. Half-hourly fluxes are typically excluded when atmospheric turbulence is below an acceptable level (friction velocity threshold, u*Th), or when the relative contribution from non-target surfaces is greater than a tolerable amount (footprint threshold, fpTh). In this study, we compare and evaluate a variety of commonly-used footprint- and friction velocity-filtering methods applied to six years (2006-2011) of carbon flux estimates for a fetch-limited, 74-year old planted Eastern white pine (Pinus Strobus L.) forest in southern Ontario, Canada. A data-driven approach was used, where factorial combinations of footprint models, fpTh values and u*Th determination methods were applied prior to gap-filling. Filtering applications were compared in terms of the quantity and distribution of data removed, while ANOVA and multiple comparison tests were used to quantify the influence of these applications on annual estimates of Net Ecosystem Productivity (NEP), Ecosystem Respiration (RE) and Gross Ecosystem Productivity (GEP). Finally, preferred filtering applications were selected using an objective evaluation of gap-filling model performance metrics to provide information on the internal consistency of the filtered data. Results showed that the choice of footprint model and fpTh exerted a greater influence on NEP, RE and GEP estimates than the u*Th estimation method used. Variation in u*Th estimates were partly explained by footprint filtering specifications, indicating significant u*Th differences between the target forest and the surrounding forested and agricultural land. Applying the footprint model of Kljun (2004. Bound. Layer Met. 112[3]) at fpTh = 0.8 resulted in greatest improvement in model performance; increasing fpTh above this value diminished performance markedly, as insufficient input data quantity and temporal coverage caused poor parameterization. Thus, footprint filter application at this site (and likely other sites), must balance competing needs: accepting only the most representative flux data, while retaining a sufficient amount for successful gap-filling model operation. Compared to the no-footprint (control) case, applying these optimal filtering methods increased annual NEP estimates between 75 and 250 g C m-2 y-1, implying that this forest sequesters substantially more carbon annually than the surrounding landscape. NEP changes were solely attributed to decreased annual RE estimates, as GEP varied only minimally between different footprint and friction velocity applications. This result, caused by a significant day/night flux footprint discrepancy, suggests the need for half-hourly footprint filter application and analyses at all EC flux tower sites that experience measurement fetch limitations.

  11. Enhancement of Carbon Sequestration in Soil in the Temperature Grasslands of Northern China by Addition of Nitrogen and Phosphorus

    PubMed Central

    He, Nianpeng; Yu, Qiang; Wang, Ruomeng; Zhang, Yunhai; Gao, Yang; Yu, Guirui

    2013-01-01

    Increased nitrogen (N) deposition is common worldwide. Questions of where, how, and if reactive N-input influences soil carbon (C) sequestration in terrestrial ecosystems are of great concern. To explore the potential for soil C sequestration in steppe region under N and phosphorus (P) addition, we conducted a field experiment between 2006 and 2012 in the temperate grasslands of northern China. The experiment examined 6 levels of N (0–56 g N m-2 yr-1), 6 levels of P (0–12.4 g P m-2 yr-1), and a control scenario. Our results showed that addition of both N and P enhanced soil total C storage in grasslands due to significant increases of C input from litter and roots. Compared with control plots, soil organic carbon (SOC) in the 0–100 cm soil layer varied quadratically, from 156.8 to 1352.9 g C m-2 with N addition gradient (R2 = 0.99, P < 0.001); and logarithmically, from 293.6 to 788.6 g C m-2 with P addition gradient (R2 = 0.56, P = 0.087). Soil inorganic carbon (SIC) decreased quadratically with N addition. The net C sequestration on grassland (including plant, roots, SIC, and SOC) increased linearly from -128.6 to 729.0 g C m-2 under N addition (R2 = 0.72, P = 0.023); and increased logarithmically, from 248.5 to 698 g C m-2under P addition (R2 = 0.82, P = 0.014). Our study implies that N addition has complex effects on soil carbon dynamics, and future studies of soil C sequestration on grasslands should include evaluations of both SOC and SIC under various scenarios. PMID:24130863

  12. Comparing the carbon budgets of boreal and temperate deciduous forest stands

    E-print Network

    Lee, Xuhui

    Comparing the carbon budgets of boreal and temperate deciduous forest stands A.G. Barr, T and temperate deciduous forests at northern mid-latitudes play an important role in the global carbon cycle. We deciduous forest ecosystems in the boreal and temperate regions of central Canada. The two forest stands

  13. Associations of grassland bird communities with black-tailed praire dogs in the North American Great Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Colonial, burrowing herbivores can serve as ecosystem engineers in grassland and shrubland ecosystems by creating belowground refugia, modifying vegetation structure and composition, serving as prey, and generating landscape heterogeneity. They can also serve a keystone species role by affecting the...

  14. Earthworm-Mycorrhiza Interactions Can Affect the Diversity, Structure and Functioning of Establishing Model Grassland Communities

    PubMed Central

    Zaller, Johann G.; Heigl, Florian; Grabmaier, Andrea; Lichtenegger, Claudia; Piller, Katja; Allabashi, Roza; Frank, Thomas; Drapela, Thomas

    2011-01-01

    Both earthworms and arbuscular mycorrhizal fungi (AMF) are important ecosystem engineers co-occurring in temperate grasslands. However, their combined impacts during grassland establishment are poorly understood and have never been studied. We used large mesocosms to study the effects of different functional groups of earthworms (i.e., vertically burrowing anecics vs. horizontally burrowing endogeics) and a mix of four AMF taxa on the establishment, diversity and productivity of plant communities after a simulated seed rain of 18 grassland species comprising grasses, non-leguminous forbs and legumes. Moreover, effects of earthworms and/or AMF on water infiltration and leaching of ammonium, nitrate and phosphate were determined after a simulated extreme rainfall event (40 l m?2). AMF colonisation of all three plant functional groups was altered by earthworms. Seedling emergence and diversity was reduced by anecic earthworms, however only when AMF were present. Plant density was decreased in AMF-free mesocosms when both anecic and endogeic earthworms were active; with AMF also anecics reduced plant density. Plant shoot and root biomass was only affected by earthworms in AMF-free mesocosms: shoot biomass increased due to the activity of either anecics or endogeics; root biomass increased only when anecics were active. Water infiltration increased when earthworms were present in the mesocosms but remained unaffected by AMF. Ammonium leaching was increased only when anecics or a mixed earthworm community was active but was unaffected by AMF; nitrate and phosphate leaching was neither affected by earthworms nor AMF. Ammonium leaching decreased with increasing plant density, nitrate leaching decreased with increasing plant diversity and density. In order to understand the underlying processes of these interactions further investigations possibly under field conditions using more diverse belowground communities are required. Nevertheless, this study demonstrates that belowground-aboveground linkages involving earthworms and AMF are important mediators of the diversity, structure and functioning of plant communities. PMID:22216236

  15. Different response of bulk and n-alkane ?13C signatures to seasonal shifts in environmental conditions in a temperate coastal ecosystem

    NASA Astrophysics Data System (ADS)

    Eley, Yvette; Pedentchouk, Nikolai; Dawson, Lorna

    2014-05-01

    The carbon isotope signal recorded in land plants represents an important reservoir of information for reconstructing climatically driven shifts in plant ecophysiology and biochemistry. Analytical advances have led to widespread usage of compound-specific (CS) carbon isotope analysis of leaf wax biomarkers, such as n-alkanes, in addition to traditional bulk isotope methods, to identify shifts in the relative percentage of C3 and C4 vegetation contributing to the sedimentary record. Recent studies, however, have extended the application of leaf wax biomarkers, using bulk and n-alkane ?13C values interchangeably to derive information about plant-environment relations, both in modern ecosystems and throughout the geological past. Even though previous work on C3 plants has shown a clear link between climatically influenced plant physiology and bulk ?13C values, further research is needed to establish whether the same link can be seen in leaf wax biomarkers. To address this question, we collected bulk and n-alkane ?13C data from plants growing at Stiffkey marsh on the north Norfolk coast, UK over a period of 15 months. Maximum interspecies variation in weighted average (WA) n-alkane ?13C among C3 species was typically 2-3o greater than in bulk. We observed a close correlation in the bulk and WA n-alkane ?13C seasonal trends from C3 grasses and reeds (R2=0.9, P

  16. The source of dissolved silicon in soil surface solutions of a temperate forest ecosystem: Ge/Si and Si isotope ratios as biogeochemical tracers

    NASA Astrophysics Data System (ADS)

    Cornelis, J.; Delvaux, B.; Cardinal, D.; André, L.; Ranger, J.; Opfergelt, S.

    2010-12-01

    Understand the biogeochemical cycle of silicon (Si) in the Earth’s critical zone and the dissolved Si transfer from the litho-pedosphere into the hydrosphere is of great interest for the global balance of biogeochemical processes, including the global C cycle. Indeed, the interaction between Si and C cycles regulates the atmospheric CO2 through the chemical weathering of silicate minerals, the C sequestration in stable organo-mineral compounds and the Si nutrition of phytoplankton CO2-consumers in oceans. H4SiO4 released by mineral dissolution contributes to the critical zone evolution through neoformation of secondary minerals, adsorption onto hydroxyl-bearing phases and recycling by vegetation and return of phytoliths on topsoil. The neoformation of secondary precipitates (clay minerals and phytoliths polymerized in plants) and adsorption of Si onto Fe and Al (hydr)oxides are processes favoring the light Si isotope incorporation, generating rivers enriched in heavy Si isotopes. On the other hand, clay minerals and phytoliths display contrasting Ge/Si ratios since clay-sized weathering products are enriched in Ge and phytoliths are depleted in Ge. Thus stable Si isotope and Ge/Si ratios constitute very interesting proxies to trace transfer of Si in the critical zone. Here we report Si isotopic and Ge/Si ratios of the different Si pools in a temperate soil-tree system (Breuil experimental forest, France) involving various tree species grown on Alumnic Cambisol derived from granitic bedrock. Relative to granitic bedrock (?30Si = -0.07 ‰; Ge/Si = 2.5 µmol/mol), clay-sized minerals are enriched in 28Si (-1.07 ‰) and Ge (6.2 µmol/mol) while phytoliths are enriched in 28Si (-0.28 to -0.64 ‰) and depleted in Ge (0.1 to 0.3 µmol/mol). This contrast allows us to infer the relative contribution of litho/pedogenic and biogenic mineral dissolution on the release of H4SiO4 in soil surface solutions. The Si-isotope signatures and Ge/Si ratios of forest floor solutions evolve towards lighter values (-1.38 and -2.05 ‰) and higher Ge/Si ratios (2.7 µmol/mol) relative to granite bedrock. This suggests a partial dissolution of 28Si and Ge-enriched secondary clays minerals incorporated by bioturbation in organic-rich horizons, with a fractionation releasing preferentially light Si isotopes. Without considering that organic acids promote dissolution of minerals, clay minerals detected in the organic layer (vermiculite, chlorite, illite and Ca-montmorillonite) are not stable and could have been partially dissolved and transformed in the chemical environment of forest floor. Sources of H4SiO4 in forest floor solutions are influenced by tree species which control the extent of clay-sized minerals mixed in organic horizons by bioturbation and, to a lesser extent, the Si recycling by forest vegetation.

  17. Convergent responses of nitrogen and phosphorus resorption to nitrogen inputs in a semiarid grassland

    USGS Publications Warehouse

    Lü, Xiao-Tao; Reed, Sasha; Yu, Qiang; He, Nian-Peng; Wang, Zheng-Wen; Han, Xing-Guo

    2013-01-01

    Human activities have significantly altered nitrogen (N) availability in most terrestrial ecosystems, with consequences for community composition and ecosystem functioning. Although studies of how changes in N availability affect biodiversity and community composition are relatively common, much less remains known about the effects of N inputs on the coupled biogeochemical cycling of N and phosphorus (P), and still fewer data exist regarding how increased N inputs affect the internal cycling of these two elements in plants. Nutrient resorption is an important driver of plant nutrient economies and of the quality of litter plants produce. Accordingly, resorption patterns have marked ecological implications for plant population and community fitness, as well as for ecosystem nutrient cycling. In a semiarid grassland in northern China, we studied the effects of a wide range of N inputs on foliar nutrient resorption of two dominant grasses, Leymus chinensis and Stipa grandis. After 4 years of treatments, N and P availability in soil and N and P concentrations in green and senesced grass leaves increased with increasing rates of N addition. Foliar N and P resorption significantly decreased along the N addition gradient, implying a resorption-mediated, positive plant–soil feedback induced by N inputs. Furthermore, N : P resorption ratios were negatively correlated with the rates of N addition, indicating the sensitivity of plant N and P stoichiometry to N inputs. Taken together, the results demonstrate that N additions accelerate ecosystem uptake and turnover of both N and P in the temperate steppe and that N and P cycles are coupled in dynamic ways. The convergence of N and P resorption in response to N inputs emphasizes the importance of nutrient resorption as a pathway by which plants and ecosystems adjust in the face of increasing N availability.

  18. Exploring the Sensitivity of Terrestrial Ecosystems and Atmospheric Exchange

    E-print Network

    Jain, Atul K.

    with ISAM. #12;Global Terrestrial C-N ISAM · 18 Biome types · 0.5 x 0.5 degree resolution · Carbon cycle · Nitrogen cycle · Feedbacks: Climate-C-N-LUC... Biome Types Yang et al. (2009, GBC) Temperate Deciduous Temperate Evergreen Tropical Evergreen Tropical Deciduous Boreal Forest Savanna Grassland Shrubland Tundra

  19. Temperate Evergreen Forest, Temperate Deciduous Forest, Boreal Forest

    E-print Network

    Richerson, Peter J.

    Temperate Evergreen Forest, Temperate Deciduous Forest, Boreal Forest Lectures 11 & 12 #12;Distribution of Temperate Evergreen Forest (5), Temperate Deciduous Forest (6), and Boreal Forest (8) #12;A. Lines on maps! #12;In the Temperate Evergreen Forest and in the warmer parts of the Temperate Deciduous

  20. Restoring biopedturbation in grasslands with anthropogenic focal disturbance

    Microsoft Academic Search

    Ryan F. Limb; David M. Engle; Terrence G. Bidwell; Donald P. Althoff; Alan B. Anderson; Philip S. Gipson; Heidi R. Howard

    2010-01-01

    Grassland ecosystems evolved with natural disturbance events on multiple spatial scales in which focal, fine-scale soil disturbance\\u000a by animals often was imbedded within large-scale grazing disturbance. The resulting plant communities adapted to both broad-scale\\u000a and fine-scale disturbance that resulted in species-rich plant communities. These natural disturbance regimes have been largely\\u000a replaced by anthropogenic disturbance. While we generally understand grassland response

  1. A new tower-based hyperspectral system for the estimation of CO2 fluxes and biophysical parameters in a subalpine grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Vescovo, L.; Gianelle, D.; Marcolla, B.; Zaldei, A.; Sakowska, K.

    2013-12-01

    Linking optical remote sensing with carbon fluxes and biophysical parameters is critical to exploit spatial and temporal extensive information useful for validating model simulations at different scales. Proximal sensing is fundamental to quantify and understand the seasonal dynamics of ecosystems and to upscale the observations carried out at the ground level. In this study, we present the results from an ongoing research project at the FLUXNET eddy covariance site of Monte Bondone (Italy). The site is located at 1550 m a.s.l. on a mountain plateau in the Italian Alps (Viote del Monte Bondone). The area is managed as an extensively-managed meadow, cut once a year, and dominated by Nardus stricta and Festuca nigrescens. The climate of this area is sub-continental (warm and wet summer), with precipitation peaks in spring and autumn. A new hyperspectral system (WhiteRef Box, developed by Fondazione Edmund Mach in collaboration with the Institute of Biometeorology, CNR, Italy) based on the ASD FieldSpec spectrometer (spectral range 350-2500 nm, resolution ~3 nm at 700 nm) was designed to acquire continuous radiometric measurements. The system was installed on the eddy covariance tower at a height of 6 m, with a field of view of 25°. To obtain reflectance values, white panel radiance spectra and canopy radiance spectra were collected every 5 minutes between 10:00 a.m. and 1:00 p.m. (solar time) during the growing season of 2013. In addition, measurements of biophysical parameters such as above-ground biomass, fraction of Absorbed Photosynthetically Active Radiation (fAPAR), Plant Area Index, Canopy Chlorophyll Content, Canopy Water Content and Green Herbage Ratio were performed at weekly intervals within the spectrometer footprint (~5 m2). In this work, we present some preliminary results regarding the potential of spectral vegetation indices - based on VNIR and SWIR spectral bands- for capturing seasonal trends of CO2 fluxes as well as vegetation biophysical parameters dynamics. Spectral vegetation indices sensitive to chlorophyll content (such as Meris Terrestrial ChIorophyll Index, Vogelmann Indices) showed a good linear correlation with fAPAR, daily Gross Primary Production and chlorophyll content (R2> 0.8 for all the three variables). The SWIR-based Vegetation Indices (e.g. Normalised Difference Infrared Index, Moisture Stress Index) confirmed their ability to estimate Canopy Water Content. Most of the analyzed indices showed to be linearly related with Green Herbage Ratio (explaining more than 80% of variance). The Near Infrared Difference Index (Vescovo et al., 2012) confirmed his potential in predicting canopy structural parameters such as Plant Area Index and biomass (R2> 0.90).

  2. A minimal model of fire-vegetation feedbacks and disturbance stochasticity generates alternative stable states in grassland–shrubland–woodland systems

    NASA Astrophysics Data System (ADS)

    Batllori, Enric; Ackerly, David D.; Moritz, Max A.

    2015-03-01

    Altered disturbance regimes in the context of global change are likely to have profound consequences for ecosystems. Interactions between fire and vegetation are of particular interest, as fire is a major driver of vegetation change, and vegetation properties (e.g., amount, flammability) alter fire regimes. Mediterranean-type ecosystems (MTEs) constitute a paradigmatic example of temperate fire-prone vegetation. Although these ecosystems may be heavily impacted by global change, disturbance regime shifts and the implications of fire-vegetation feedbacks in the dynamics of such biomes are still poorly characterized. We developed a minimal modeling framework incorporating key aspects of fire ecology and successional processes to evaluate the relative influence of extrinsic and intrinsic factors on disturbance and vegetation dynamics in systems composed of grassland, shrubland, and woodland mosaics, which characterize many MTEs. In this theoretical investigation, we performed extensive simulations representing different background rates of vegetation succession and disturbance regime (fire frequency and severity) processes that reflect a broad range of MTE environmental conditions. Varying fire-vegetation feedbacks can lead to different critical points in underlying processes of disturbance and sudden shifts in the vegetation state of grassland–shrubland–woodland systems, despite gradual changes in ecosystem drivers as defined by the environment. Vegetation flammability and disturbance stochasticity effectively modify system behavior, determining its heterogeneity and the existence of alternative stable states in MTEs. Small variations in system flammability and fire recurrence induced by climate or vegetation changes may trigger sudden shifts in the state of such ecosystems. The existence of threshold dynamics, alternative stable states, and contrasting system responses to environmental change has broad implications for MTE management.

  3. Investigations on the potential of woodlice as bioindicators of grassland habitat quality

    Microsoft Academic Search

    C. Souty-Grosset; I. Badenhausser; J. D. Reynolds; A. Morel

    2005-01-01

    As intensive land-use practices may reduce available leaf litter, woodlice—important decomposers of leaf litter—may show a loss of biomass and a decrease in number of species. Their diversity as grassland detritivores could thus be a potential guide to ecosystem activity in natural and cultivated grasslands. Woodlice diversity was studied in different grassland types at three sites in Western France: Avon,

  4. Prescribed fire, soil nitrogen dynamics, and plant responses in a semiarid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fire is a key driver of the structure and function of grassland ecosystems. In arid and semiarid ecosystems, where moisture limits plant production more than light, fire can potentially affect ecosystem dynamics through changes in soil moisture, temperature, and nitrogen cycling, as well as through ...

  5. Ceballos, G., List, R., Davidson, A., Fredrickson, E.L., Sierra Corona, R., Martinez, L., Herrick, J.E., Pacheco, J. 2009. Grassland in the Borderlands. Understanding coupled

    E-print Network

    ., Herrick, J.E., Pacheco, J. 2009. Grassland in the Borderlands. Understanding coupled natural-human systems of Arizona Press. p. 188-203. Chapter 12 Grasslands in the borderlands: understanding coupled human, Rodrigo Sierra, Lourdes Martínez, Jeff E. Herrick and Jesús Pacheco In a Nutshell Grassland ecosystems

  6. The effect of sulfur and nitrogen additions on nutrient cycling and vegetative cover composition in sandplain grassland restoration plots in Edgartown, MA

    E-print Network

    Vallino, Joseph J.

    in sandplain grassland restoration plots in Edgartown, MA Fiona Jevon Harvard University Mentor: Chris Neill Ecosystems Center, Marine Biological Laboratories December 19th , 2011 #12;Abstract Sandplain grasslands to be dominated by non-native vegetation. One theory for restoring these systems to native sandplain grassland

  7. CONTINGENCY OF GRASSLAND RESTORATION ON YEAR, SITE, AND COMPETITION FROM INTRODUCED GRASSES

    Microsoft Academic Search

    Jonathan D. Bakker; Scott D. Wilson; Janice M. Christian; Xingdong Li; Laura G. Ambrose; John Waddington

    2003-01-01

    Semiarid ecosystems such as grasslands are characterized by high temporal variability in abiotic factors, which has led to suggestions that management actions may be more effective in some years than others. Here we examine this hypothesis in the context of grassland restoration, which faces two major obstacles: the contingency of native grass establishment on unpredictable precipitation, and competition from introduced

  8. Shrub expansion in northern Chihuahuan Desert grasslands: Spatial patterns and biophysical constraints

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Conserving and restoring grasslands and shrub-steppe has important ecological and socioeconomic implications in arid rangelands of the world. Among the greatest contemporary threats to the structure, function and biological diversity of desert grassland and shrub savanna ecosystems of the southweste...

  9. REPRODUCTIVE SUCCESS OF CHESTNUT-COLLARED LONGSPURS IN NATIVE AND EXOTIC GRASSLAND

    Microsoft Academic Search

    John D. Lloyd; Thomas E. Martin

    2005-01-01

    Habitat loss and fragmentation have been identified as important factors in the decline of grassland bird populations. However, population declines are apparent even in prairie ecosystems that remain relatively intact suggesting that additional factors are involved. The degradation of breeding habitat may be one such factor, but few studies have examined habitat- specific demography of grassland birds, and thus little

  10. Spatial patterns of grasses and shrubs in an arid grassland environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the Chihuahuan Desert of Mexico and New Mexico, shrub invasion is a common problem, and once-abundant grassland ecosystems are being replaced by shrub-dominated habitat. The spatial arrangement of grasses and shrubs in these arid grasslands can provide better insight into community dynamics and c...

  11. Ungulate vs. landscape control of soil C and N processes in grasslands of Yellowstone National Park

    Microsoft Academic Search

    Douglas A. Frank; Peter M. Groffman

    1998-01-01

    Within large grassland ecosystems, climatic and topographic gradients are considered the primary controls of soil processes. Ungulates also can influence soil dynamics; however the relative contribution of large herbivores to controlling grassland soil processes remains largely unknown. In this study, the authors compared the effects of native migratory ungulates and variable site (landscape) conditions, caused by combined climatic and topographic

  12. Effects of Grassland Restoration on Avian Assemblage Characteristics and Dickcissel Nesting Success in Texas 

    E-print Network

    Lituma, Christopher M.

    2010-07-14

    , including: grazing, row-crop farming, depressed fire regimes, and exotic grass species introduction. In Texas, 35% of the historic grassland ecosystems have been either altered or converted. Introduced in the 1940's, exotic grass species such as Bermuda...

  13. N 2O emission from the semi-arid ecosystem under mineral fertilizer (urea and superphosphate) and increased precipitation in northern China

    NASA Astrophysics Data System (ADS)

    Zhang, Jinfeng; Han, Xingguo

    Soil management and climate change affect N 2O emission significantly. The semi-arid grassland in northern China is under strong anthropogenic disturbance (fertilization and land use) and toward a 30% increase in precipitation in future. To investigate their impacts on N 2O emission, N 2O fluxes were measured monthly in the grassland and abandoned cropland under mineral fertilizer (urea and superphosphate) and increased precipitation during the growing season. During the measured period, WFPS (water filled pore space) from all the treatments never exceeded 70%, suggesting that nitrification was the predominant source of N 2O for all the treatments. Increased precipitation induced an additional growing season emission of 0.28-0.30 kg N 2O-N ha -1 y -1. N 2O emission increased linearly with nitrogen application rate and emission factors (EFs) for grassland and abandoned cropland averaged 0.35% and 0.52%, respectively. Superphosphate addition induced N 2O emission from abandoned cropland ( P<0.05), but had no significant effect in the grassland ( P>0.05). Despite of substantial differences in soil properties, N 2O emissions were not significantly different between the grassland and abandoned cropland ( P>0.05). Increased precipitation and nitrogen application at 15 g N m -2 y -1 across the grassland and abandoned cropland of northern China will increase the growing season emissions of 71.4-76.5 and 139.23 Gg N 2O-N into atmosphere annually. These increased emissions are about 40% and 75% of the annual emission of 186.15 Gg N 2O-N from untreated soils, respectively. Therefore, in the temperate semi-arid ecosystem, abandoned cropland does not constitute a potent source for increasing N 2O while the effect of nitrogen fertilization and increased precipitation cannot be neglected from the regional or national emission.

  14. Trophic diversity in two grassland ecosystems

    Microsoft Academic Search

    Clark V. Pearson; Lee A. Dyer

    2006-01-01

    The roles of consumers (top-down forces) versus resources (bottom-up forces) as determinants of alpha diversity in a community are not well studied. Numerous community ecology models and empirical studies have provided a framework for understanding how density at various trophic levels responds to variation in the relative strength of top-down and bottom-up forces. The resulting trophic theory can be applied

  15. Residual Characteristics of Picloram In Grassland Ecosystems

    E-print Network

    Bovey, R. W.; Scifres, C. J.

    1971-01-01

    : 1 ratio of picloram f ?,4,5-T for control of honey mesquite Prosopis l*r(iflora (S~vartz) DC. var. gtandulosa (Tom.) Cockrell) tn wlmiarid areas (54) and for control of other species in mbhumitl regions (9) has been established. PicIe I 'Pmnd... AND THEIR RESPONSE TO SINGLE SPRAY APPLICA- TIONS OF PICLORAM, 2, 4, 5-T, OR MIXTURES OF PIC- LORAM PLUS 2,4,5-T1 Controlled by- Species Picloram Picloram 2,4,5-T + 2,4,5-T Honey mesquite (Prosopis juli- flora (Swartz) DC. var. glan- d ulosa (Torr...

  16. Monitoring Rehabilitation in Temperate North American Estuaries

    SciTech Connect

    Rice, Casimir A.; Hood, W Gregory; Tear, Lucinda M.; Simenstad, Charles; Williams, Gregory D.; Johnson, L. L.; Feist, B. E.; Roni, P.

    2005-02-01

    In this chapter, we propose that monitoring rehabilitation in estuarine ecosystems by necessity requires quantifying relationships between dynamic estuarine processes and sensitive indicators of ecosystem function. While we do discuss temperate systems in general, emphasis is placed on anadromous salmon habitats in the Pacific Northwest because anadromous fishes are such a major focus of rehabilitation efforts, and present some of the greater challenges in linking function of one segment of their life history to conditions in a specific habitat. We begin with a basic overview of the ecological and socioeconomic significance of, as well as anthropogenic effects on, estuaries. Next, we briefly summarize the various kinds of estuarine rehabilitation historically practiced in temperate regions, and review estuarine rehabilitation monitoring design and methods, highlighting the unique challenges involved in monitoring estuarine systems. We then close with a summary and conclusions.

  17. Deriving Vegetation Dynamics of Natural Terrestrial Ecosystems from MODIS NDVI/EVI Data over Turkey

    PubMed Central

    Evrendilek, Fatih; Gulbeyaz, Onder

    2008-01-01

    The 16-day composite MODIS vegetation indices (VIs) at 500-m resolution for the period between 2000 to 2007 were seasonally averaged on the basis of the estimated distribution of 16 potential natural terrestrial ecosystems (NTEs) across Turkey. Graphical and statistical analyses of the time-series VIs for the NTEs spatially disaggregated in terms of biogeoclimate zones and land cover types included descriptive statistics, correlations, discrete Fourier transform (DFT), time-series decomposition, and simple linear regression (SLR) models. Our spatio-temporal analyses revealed that both MODIS VIs, on average, depicted similar seasonal variations for the NTEs, with the NDVI values having higher mean and SD values. The seasonal VIs were most correlated in decreasing order for: barren/sparsely vegetated land > grassland > shrubland/woodland > forest; (sub)nival > warm temperate > alpine > cool temperate > boreal = Mediterranean; and summer > spring > autumn > winter. Most pronounced differences between the MODIS VI responses over Turkey occurred in boreal and Mediterranean climate zones and forests, and in winter (the senescence phase of the growing season). Our results showed the potential of the time-series MODIS VI datasets in the estimation and monitoring of seasonal and interannual ecosystem dynamics over Turkey that needs to be further improved and refined through systematic and extensive field measurements and validations across various biomes.

  18. Restoring Native Grasslands

    E-print Network

    Hays, K. Brian; Wagner, Matthew; Smeins, Fred; Wilkins, Neal

    2005-03-23

    Much of Texas' native grasslands has been converted to improved pastures and cropland, neither of which is suitable for wildlife habitat. Now, many landowners are interested in restoring native grasses because they are cheaper to produce for forage...

  19. Restoring Native Grasslands 

    E-print Network

    Hays, K. Brian; Wagner, Matthew; Smeins, Fred; Wilkins, Neal

    2005-03-23

    Much of Texas' native grasslands has been converted to improved pastures and cropland, neither of which is suitable for wildlife habitat. Now, many landowners are interested in restoring native grasses because they are cheaper to produce for forage...

  20. Multisensor analysis of NDVI, surface temperature and biophysical variables at a mixed grassland site

    Microsoft Academic Search

    S. J. GOETZ

    1997-01-01

    A unique remotely sensed data set derived for a temperate mixed grassland in the central United States was used to test the comparability of a suite of satellite and aircraft sensors, and to characterize temporal variability in the normalized diÄ erence vegetation index (NDVI), retrieved surface radiant temperature (Ts), and surface biophysical variables. The temporal evolution of atmospherically corrected NDVI

  1. Disentangling root responses to climate change in a semiarid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Future ecosystem properties of grasslands will be driven largely by belowground plant biomass responses to climate change, whose understanding has been limited by experimental and technical constraints. We use a multi-faceted approach and a factorial field experiment to explore impacts of elevated C...

  2. Stream acidification and base cation losses with grassland afforestation

    Microsoft Academic Search

    Kathleen A. Farley; Gervasio Pińeiro; Sheila M. Palmer; Esteban G. Jobbágy; Robert B. Jackson

    2008-01-01

    Afforestation of natural grasslands with fast-growing pine and eucalyptus species is increasing globally, but little is known about its effect on ecosystems and watersheds and, ultimately, the quality of water resources. To investigate the biogeochemical and hydrological consequences of this land use change, we sampled stream water in paired watersheds in Uruguay and Argentina. In watersheds planted with pine, we

  3. Interactions Among Grassland Plant Species, Microbial Communities, and Soil Processes

    Microsoft Academic Search

    V. Eviner; M. Waldrop; E. Schwartz; J. Pett-Ridge; M. Firestone

    2002-01-01

    Plant-microbial interactions are thought to be an important determinant of ecosystem processes, yet we do not know whether impacts of plant species on soil microbial community composition translate to impacts on function. We established field plots in a California annual grassland of five plant monocultures for two years to determine the effects of different plant species on the composition of

  4. I.B.P. Studies on Montane Grassland and Moorlands

    Microsoft Academic Search

    O. W. Heal; D. F. Perkins

    1976-01-01

    The aim of the grassland and moorland studies was to measure primary and secondary production and to describe the main pathways of dry matter and nutrients within these ecosystems. The strategy was to make detailed studies on two main sites (Snowdonia and Moor House N.N.R. in the northern Pennines) with a limited number of supporting studies. The examination of the

  5. Altering Rainfall Timing and Quantity in a Mesic Grassland

    E-print Network

    Blair, John

    Altering Rainfall Timing and Quantity in a Mesic Grassland Ecosystem: Design and Performance of Rainfall Manipulation Shelters Philip A. Fay,1 * Jonathan D. Carlisle,1 Alan K. Knapp,1 John M. Blair,1 ABSTRACT Global climate change is predicted to alter growing season rainfall patterns, potentially reducing

  6. Seasonal not annual rainfall determines grassland biomass response to carbon dioxide

    NASA Astrophysics Data System (ADS)

    Hovenden, Mark J.; Newton, Paul C. D.; Wills, Karen E.

    2014-07-01

    The rising atmospheric concentration of carbon dioxide (CO2) should stimulate ecosystem productivity, but to what extent is highly uncertain, particularly when combined with changing temperature and precipitation. Ecosystem response to CO2 is complicated by biogeochemical feedbacks but must be understood if carbon storage and associated dampening of climate warming are to be predicted. Feedbacks through the hydrological cycle are particularly important and the physiology is well known; elevated CO2 reduces stomatal conductance and increases plant water use efficiency (the amount of water required to produce a unit of plant dry matter). The CO2 response should consequently be strongest when water is limiting; although this has been shown in some experiments, it is absent from many. Here we show that large annual variation in the stimulation of above-ground biomass by elevated CO2 in a mixed C3/C4 temperate grassland can be predicted accurately using seasonal rainfall totals; summer rainfall had a positive effect but autumn and spring rainfall had negative effects on the CO2 response. Thus, the elevated CO2 effect mainly depended upon the balance between summer and autumn/spring rainfall. This is partly because high rainfall during cool, moist seasons leads to nitrogen limitation, reducing or even preventing biomass stimulation by elevated CO2. Importantly, the prediction held whether plots were warmed by 2 °C or left unwarmed, and was similar for C3 plants and total biomass, allowing us to make a powerful generalization about ecosystem responses to elevated CO2. This new insight is particularly valuable because climate projections predict large changes in the timing of rainfall, even where annual totals remain static. Our findings will help resolve apparent differences in the outcomes of CO2 experiments and improve the formulation and interpretation of models that are insensitive to differences in the seasonal effects of rainfall on the CO2 response.

  7. Grassland to shrubland state transitions enhance carbon sequestration in the northern Chihuahuan Desert.

    PubMed

    Petrie, M D; Collins, S L; Swann, A M; Ford, P L; Litvak, M E

    2015-03-01

    The replacement of native C4 -dominated grassland by C3 -dominated shrubland is considered an ecological state transition where different ecological communities can exist under similar environmental conditions. These state transitions are occurring globally, and may be exacerbated by climate change. One consequence of the global increase in woody vegetation may be enhanced ecosystem carbon sequestration, although the responses of arid and semiarid ecosystems may be highly variable. During a drier than average period from 2007 to 2011 in the northern Chihuahuan Desert, we found established shrubland to sequester 49 g C m(-2) yr(-1) on average, while nearby native C4 grassland was a net source of 31 g C m(-2) yr(-1) over this same period. Differences in C exchange between these ecosystems were pronounced--grassland had similar productivity compared to shrubland but experienced higher C efflux via ecosystem respiration, while shrubland was a consistent C sink because of a longer growing season and lower ecosystem respiration. At daily timescales, rates of carbon exchange were more sensitive to soil moisture variation in grassland than shrubland, such that grassland had a net uptake of C when wet but lost C when dry. Thus, even under unfavorable, drier than average climate conditions, the state transition from grassland to shrubland resulted in a substantial increase in terrestrial C sequestration. These results illustrate the inherent tradeoffs in quantifying ecosystem services that result from ecological state transitions, such as shrub encroachment. In this case, the deleterious changes to ecosystem services often linked to grassland to shrubland state transitions may at least be partially offset by increased ecosystem carbon sequestration. PMID:25266205

  8. Tempered fractional Brownian motion

    NASA Astrophysics Data System (ADS)

    Sabzikar, Farzad

    Tempered fractional Brownian motion (TFBM) modifies the power law kernel in the moving average representation of a fractional Brownian motion (FBM), adding an exponential tempering. It also has a harmonizable representation. The increments of TFBM are stationary, and the autocovariance of the resulting tempered fractional Gaussian noise (TFGN) has semi-long range dependence, in which the autocorrelations decay like a power law over a moderate length scale, but eventually fall off more rapidly. TFBM can be represented as the linear combination of tempered fractional derivative (or tempered fractional integral) of the indicator functions. This representation and the classical Ito isometry provides to characterize the class of all deterministic functions for which the stochastic integral with respect to TFBM is well defined. Replacing the Gaussian random measure (Brownian motion) in the moving average or harmonizable representation of TFBM by a stable random measure, a linear tempered fractional stable motion (LTFSM), or a real harmonizable tempered fractional stable motion (HTFSM), respectively. Unlike the Gaussian case, LTFSM and HTFSM are two completely different processes. Existence, basic properties, sample path behavior, and dependence structure of both processes will be described.

  9. Behavior of multitemporal and multisensor passive microwave indices in Southern Hemisphere ecosystems

    NASA Astrophysics Data System (ADS)

    Barraza, Veronica; Grings, Francisco; Ferrazzoli, Paolo; Huete, Alfredo; Restrepo-Coupe, Natalia; Beringer, Jason; Van Gorsel, Eva; Karszenbaum, Haydee

    2014-12-01

    This study focused on the time series analysis of passive microwave and optical satellite data collected from six Southern Hemisphere ecosystems in Australia and Argentina. The selected ecosystems represent a wide range of land cover types, including deciduous open forest, temperate forest, tropical and semiarid savannas, and grasslands. We used two microwave indices, the frequency index (FI) and polarization index (PI), to assess the relative contributions of soil and vegetation properties (moisture and structure) to the observations. Optical-based satellite vegetation products from the Moderate Resolution Imaging Spectroradiometer were also included to aid in the analysis. We studied the X and Ka bands of the Advanced Microwave Scanning Radiometer-EOS and Wind Satellite, resulting in up to four observations per day (1:30, 6:00, 13:30, and 18:00 h). Both the seasonal and hourly variations of each of the indices were examined. Environmental drivers (precipitation and temperature) and eddy covariance measurements (gross ecosystem productivity and latent energy) were also analyzed. It was found that in moderately dense forests, FI was dependent on canopy properties (leaf area index and vegetation moisture). In tropical woody savannas, a significant regression (R2) was found between FI and PI with precipitation (R2 > 0.5) and soil moisture (R2 > 0.6). In the areas of semiarid savanna and grassland ecosystems, FI variations found to be significantly related to soil moisture (R2 > 0.7) and evapotranspiration (R2 > 0.5), while PI varied with vegetation phenology. Significant differences (p < 0.01) were found among FI values calculated at the four local times.

  10. Growth and nutrient content of perennial grasslands following burning in semi-arid, sub-tropical Australia

    Microsoft Academic Search

    L. T. Bennett; T. S. Judd; M. A. Adams

    2003-01-01

    Fire often increases the productivity of perennial tussock grasslands inmesic environments but can reduce growth for one or more growing seasons inaridand semi-arid environments. We examined effects of single-burns on growth andnutrient content of grasslands in sub-tropical, northwestern Australia. Thesegrasslands were dominated by Themeda triandra, a speciesoften managed by regular burning in wetter temperate and tropical zones. Burnswere in the

  11. Multiple constraints on grassland evapotranspiration: implications for closing the energy balance

    PubMed Central

    Wohlfahrt, Georg; Irschick, Christoph; Thalinger, Bettina; Hörtnagl, Lukas; Obojes, Nikolaus; Hammerle, Albin

    2013-01-01

    When using the eddy covariance (EC) method for measuring the ecosystem-atmosphere exchange of sensible and latent heat, it is not uncommon to find that these two energy fluxes fall short of available energy by 20-30 %. As the causes for the energy imbalance are still under discussion, it is currently not clear how the energy balance should be closed. The objective of the present paper is to use independent measurements of evapotranspiration (ET) for empirically devising on how to best close the energy balance. To this end ET of a temperate mountain grassland was quantified during two measurement campaigns using both an open- and a closed-path EC system, lysimeters and an approach scaling up leaf-level stomatal conductance to canopy level transpiration. Our study showed that both EC systems underestimated ET measured independently by lysimeters and the up-scaling approach. Best correspondence to independently measured ET was achieved by assigning the entire energy imbalance to ET and by adjusting ET according to the average energy balance ratio during the first and second measurement campaign, respectively. Due to a large spatial variability in ET during the first measurement campaign and given large differences in spatial scale between the EC and the independent methods, we are more confident with the comparison of approaches during the second measurement campaign and thus recommend forcing energy balance closure by adjusting for the average energy balance ratio. PMID:24339743

  12. The amplifying effects of humans on fire regimes in temperate rainforests in western Patagonia

    Microsoft Academic Search

    Andrés Holz; Thomas T. Veblen

    2011-01-01

    During European colonization and settlement of southern hemisphere temperate ecosystems, historical fire regimes were often dramatically altered by either burning vast areas to create farmland, or reducing fire frequencies by suppressing fires or by eliminating aboriginal populations that formerly set fires. To determine the historical range of variability of wildfire and the potential human influences on wildfire activity in temperate

  13. A common framework for greenhouse gas assessment protocols in temperate agroforestry systems: Connecting via GRACEnet

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agroforestry systems offer many ecosystem benefits, but such systems have previously been marginalized in temperate environments due to overriding economic goals and perceived management complexity. In view of adaptation to a changing climate, agroforestry systems offer advantages that require quan...

  14. Soil Litter: Temperate Zones

    NSDL National Science Digital Library

    Pulse of the Planet

    2006-06-23

    This two-minute radio program focuses on why temperate soils harbor more biodiversity than do tropical soils. The guest on the program, a soil biologist, explains that cooler temperatures and large-scale disturbances have promoted the evolution of more soil-dwelling species in temperate areas. The program, part of the Pulse of the Planet radio show, is available here in text and audio formats. Copyright 2005 Eisenhower National Clearinghouse

  15. ECOSYSTEM ECOLOGY -ORIGINAL PAPER Rapid topdown regulation of plant C:N:P stoichiometry

    E-print Network

    Elser, Jim

    by grasshoppers in an Inner Mongolia grassland ecosystem Guangming Zhang · Xingguo Han · James J. Elser Received. An experiment manipulating densities of the grasshopper Oedaleus asiaticus was per- formed to assess top­down effects of grasshoppers on C:N:P stoichiometry of plants and soil in a grassland ecosystem in Inner

  16. 4, 36073638, 2007 Grassland energy

    E-print Network

    Boyer, Edmond

    BGD 4, 3607­3638, 2007 Grassland energy partitioning A. Hammerle et al. Title Page Abstract partitioning of a mountain grassland A. Hammerle, A. Haslwanter, U. Tappeiner, A. Cernusca, and G. Wohlfahrt.hammerle@uibk.ac.at) 3607 #12;BGD 4, 3607­3638, 2007 Grassland energy partitioning A. Hammerle et al. Title Page Abstract

  17. Preferential uptake of soil nitrogen forms by grassland plant species.

    PubMed

    Weigelt, Alexandra; Bol, Roland; Bardgett, Richard D

    2005-02-01

    In this study, we assessed whether a range of temperate grassland species showed preferential uptake for different chemical forms of N, including inorganic N and a range of amino acids that commonly occur in temperate grassland soil. Preferential uptake of dual-labelled (13C and 15N) glycine, serine, arginine and phenylalanine, as compared to inorganic N, was tested using plants growing in pots with natural field soil. We selected five grass species representing a gradient from fertilised, productive pastures to extensive, low productivity pastures (Lolium perenne, Holcus lanatus, Anthoxanthum odoratum, Deschampsia flexuosa, and Nardus stricta). Our data show that all grass species were able to take up directly a diversity of soil amino acids of varying complexity. Moreover, we present evidence of marked inter-species differences in preferential use of chemical forms of N of varying complexity. L. perenne was relatively more effective at using inorganic N and glycine compared to the most complex amino acid phenylalanine, whereas N. stricta showed a significant preference for serine over inorganic N. Total plant N acquisition, measured as root and shoot concentration of labelled compounds, also revealed pronounced inter-species differences which were related to plant growth rate: plants with higher biomass production were found to take up more inorganic N. Our findings indicate that species-specific differences in direct uptake of different N forms combined with total N acquisition could explain changes in competitive dominance of grass species in grasslands of differing fertility. PMID:15549402

  18. Additive effects of simulated climate changes, elevated CO2, and nitrogen deposition on grassland diversity

    Microsoft Academic Search

    Erika S. Zavaleta; M. Rebecca Shaw; Nona R. Chiariello; Harold A. Mooney; Christopher B. Field

    2003-01-01

    Biodiversity responses to ongoing climate and atmospheric changes will affect both ecosystem processes and the delivery of ecosystem goods and services. Combined effects of co-occurring global changes on diversity, however, are poorly understood. We examined plant diversity responses in a California annual grassland to manipulations of four global environmental changes, singly and in combination: elevated CO2, warming, precipitation, and nitrogen

  19. Carbon dioxide exchange in a semidesert grassland through drought-induced vegetation change

    Microsoft Academic Search

    Russell L. Scott; Erik P. Hamerlynck; G. Darrel Jenerette; M. Susan Moran; Greg A. Barron-Gafford

    2010-01-01

    Global warming may intensify the hydrological cycle and lead to increased drought severity and duration, which could alter plant community structure and subsequent ecosystem water and carbon dioxide cycling. We report on the net ecosystem exchange of carbon dioxide (NEE) of a semidesert grassland through a severe drought which drove succession from native bunchgrasses to forbs and to eventual dominance

  20. Nitrogen deposition in endemic-rich California serpentine grasslands Project details

    E-print Network

    Zavaleta, Erika

    Nitrogen deposition in endemic-rich California serpentine grasslands Project details 1. Historical reconstruction of anthropogenic N inputs into a Bay Area serpentine ecosystem using tree ring 15 N analysis High serpentine ecosystem with above-surface ammonium and nitrate collectors. We seek to quantify whether and how

  1. Response of net ecosystem gas exchange to a simulated precipitation pulse in a semi-arid grassland: the role of native versus non-native grasses and soil texture

    Microsoft Academic Search

    Travis E. Huxman; Jessica M. Cable; Danielle D. Ignace; J. Alex Eilts; Nathan B. English; Jake Weltzin; David G. Williams

    2004-01-01

    Physiological activity and structural dynamics in arid and semi-arid ecosystems are driven by discrete inputs or “pulses” of growing season precipitation. Here we describe the short-term dynamics of ecosystem physiology in experimental stands of native ( Heteropogon contortus) and invasive ( Eragrostis lehmanniana) grasses to an irrigation pulse across two geomorphic surfaces with distinctly different soils: a Pleistocene-aged surface with

  2. Incorporating grassland management in a global vegetation model

    NASA Astrophysics Data System (ADS)

    Chang, Jinfeng; Viovy, Nicolas; Vuichard, Nicolas; Ciais, Philippe; Wang, Tao; Cozic, Anne; Lardy, Romain; Graux, Anne-Isabelle; Klumpp, Katja; Martin, Raphael; Soussana, Jean-François

    2013-04-01

    Grassland is a widespread vegetation type, covering nearly one-fifth of the world's land surface (24 million km2), and playing a significant role in the global carbon (C) cycle. Most of grasslands in Europe are cultivated to feed animals, either directly by grazing or indirectly by grass harvest (cutting). A better understanding of the C fluxes from grassland ecosystems in response to climate and management requires not only field experiments but also the aid of simulation models. ORCHIDEE process-based ecosystem model designed for large-scale applications treats grasslands as being unmanaged, where C / water fluxes are only subject to atmospheric CO2 and climate changes. Our study describes how management of grasslands is included in the ORCHIDEE, and how management affects modeled grassland-atmosphere CO2 fluxes. The new model, ORCHIDEE-GM (Grassland Management) is capable with a management module inspired from a grassland model (PaSim, version 5.0), of accounting for two grassland management practices (cutting and grazing). The evaluation of the results of ORCHIDEE-GM compared with those of ORCHIDEE at 11 European sites equipped with eddy covariance and biometric measurements, show that ORCHIDEE-GM can capture realistically the cut-induced seasonal variation in biometric variables (LAI: Leaf Area Index; AGB: Aboveground Biomass) and in CO2 fluxes (GPP: Gross Primary Productivity; TER: Total Ecosystem Respiration; and NEE: Net Ecosystem Exchange). But improvements at grazing sites are only marginal in ORCHIDEE-GM, which relates to the difficulty in accounting for continuous grazing disturbance and its induced complex animal-vegetation interactions. Both NEE and GPP on monthly to annual timescales can be better simulated in ORCHIDEE-GM than in ORCHIDEE without management. At some sites, the model-observation misfit in ORCHIDEE-GM is found to be more related to ill-constrained parameter values than to model structure. Additionally, ORCHIDEE-GM is able to simulate forage yield, herbage consumption, animal products (e.g. milk), animal respiration and animal CH4 emissions. These new variables combined with organic C fertilizer applied on the field could provide a more complete view of grasslands C fluxes for applications of the model on a grid. The 11 site simulations of this study show that European grasslands generally are C sinks (positive NBP). At grazed grasslands, both C export in the form of milk production and CH4 emissions by animals only consist a minor part of net primary production (NPP), and this means that NBP mainly depends on NPP. On the contrary, the cut sites accumulate less C in soils because a large part of NPP has been exported as forage production. Furthermore, theoretically potential of productivity and livestock density in European grassland can be predicted by ORCHIDEE-GM, based on the strategy modeling of the optimal livestock density and management change.

  3. Earth on Edge: Ecosystems

    NSDL National Science Digital Library

    Janet Overton

    This site provides information about the six ecosystems on which life on Earth most heavily depends: agricultural, forest, freshwater, grassland, coastal, and urban. It is part of a Public Broadcasting System (PBS) project, which includes a discussion guide. Ecosystems are described as communities of interacting organisms and the physical environment in which they live. The goods and services that ecosystems provide are said to form the foundation of human economies. Ecosystems purify air and water, help to control climate, and produce valuable soil-services. Site users may access a discussion guide to accompany the broadcast of the video/television program, which can be used in colleges, secondary schools, and in community groups. Case studies are taken from the companion book, World Resources 2000-2001: Ecosystems and People: The Fraying Web of Life, and from Pilot Analysis of Global Ecosystems: Agroecosystems (World Resources Institute). This online text includes profiles, case studies, and ecosystem assessments with references to ecosystems around the world. A list of additional resources includes links to environmental organizations, books, and periodicals.

  4. Economics of Grassland Conversion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this paper we provide an overview of economic factors that contribute to changes in grassland area including the relative profitability of crop and livestock production, effects of land productivity, and effects of conversion costs. We also identify other potential socio-economic influences on gr...

  5. Impacts of tree rows on grassland birds and potential nest predators: a removal experiment.

    PubMed

    Ellison, Kevin S; Ribic, Christine A; Sample, David W; Fawcett, Megan J; Dadisman, John D

    2013-01-01

    Globally, grasslands and the wildlife that inhabit them are widely imperiled. Encroachment by shrubs and trees has widely impacted grasslands in the past 150 years. In North America, most grassland birds avoid nesting near woody vegetation. Because woody vegetation fragments grasslands and potential nest predator diversity and abundance is often greater along wooded edge and grassland transitions, we measured the impacts of removing rows of trees and shrubs that intersected grasslands on potential nest predators and the three most abundant grassland bird species (Henslow's sparrow [Ammodramus henslowii], Eastern meadowlark [Sturnella magna], and bobolink [Dolichonyx oryzivorus]) at sites in Wisconsin, U.S.A. We monitored 3 control and 3 treatment sites, for 1 yr prior to and 3 yr after tree row removal at the treatment sites. Grassland bird densities increased (2-4 times for bobolink and Henslow's sparrow) and nesting densities increased (all 3 species) in the removal areas compared to control areas. After removals, Henslow's sparrows nested within ?50 m of the treatment area, where they did not occur when tree rows were present. Most dramatically, activity by woodland-associated predators nearly ceased (nine-fold decrease for raccoon [Procyon lotor]) at the removals and grassland predators increased (up to 27 times activity for thirteen-lined ground squirrel [Ictidomys tridecemlineatus]). Nest success did not increase, likely reflecting the increase in grassland predators. However, more nests were attempted by all 3 species (175 versus 116) and the number of successful nests for bobolinks and Henslow's sparrows increased. Because of gains in habitat, increased use by birds, greater production of young, and the effective removal of woodland-associated predators, tree row removal, where appropriate based on the predator community, can be a beneficial management action for conserving grassland birds and improving fragmented and degraded grassland ecosystems. PMID:23565144

  6. Long term effects of fen restoration: Parameterization of net ecosystem exchange models along a land use-degradation gradient

    NASA Astrophysics Data System (ADS)

    Bergmann, L.; Drösler, M.; Schultz, R.; Freibauer, A.; Jungkunst, H.; Höll, B.

    2010-05-01

    In combination with fluctuating water regimes and extreme variations in weather conditions expected through climate change, continual disturbance to the soils through peat use poses a risk to the carbon storage capacities and sequestration potentials of peatlands. Restoration and/ or extensive use of peatlands are strategies to optimize vegetation and hydrological balance within these sensitive ecosystems. Our goal was to determine the long term effects of fen restoration on CO2 fluxes and to identify the driving parameters causing differential fluxes along a disturbance gradient. This study aimed specifically to provide a CO2-C flux dataset to determine net ecosystem exchange (NEE) in restored temperate fens ecosystems. A climate controlled chamber system was used for measuring instantaneous NEE over the entire year in the Donauried in 2005 and in the Loisach-Kochelsee fens in 2006, both in southern Germany. The sites were chosen to represent both a management gradient (from intensive grasslands and crops to long-term restored Carex lawns) and a water table gradient (-78 cm below surface to -1 cm below surface). NEE was measured using the closed chamber technique, allowing for separation of NEE into gross ecosystem production (GEP) and ecosystem respiration (Reco). In both study areas, management strongly influenced ecosystem respiration and GPP and thus NEE, where Reco remained a strong determinant of NEE balances. Whereas the managed-degraded sites are acting as sources of CO2, a positive effect of restoration is seen in terms of NEE exchange. The restored sites are either acting as significant sinks for CO2 (Donauried old restored sites) or are have significantly lower emissions as the managed-degraded sites. NEE values ranged from 1041 g CO2-C m2 a1source to the atmosphere in a two cut grassland to a -130 g CO2-C m2 a1sinkin the long-term restored unmanaged Carex paniculata site. Reco was highest in grassland sites and lowest in the restored Carex sites. A micro-water table gradient in the restored sites offered additional insight to the differential fluxes. An indication of a time effect of restoration on NEE was seen in comparing short-term and long-term restored sites. Our results indicate that shifting management intensities from intensive to extensive, as well as raising the water table to near surface levels are viable options for climate friendly peatland management.

  7. Carbon sink activity and GHG budget of managed European grasslands

    NASA Astrophysics Data System (ADS)

    Klumpp, Katja; Herfurth, Damien; Soussana, Jean-Francois; Fluxnet Grassland Pi's, European

    2013-04-01

    In agriculture, a large proportion (89%) of greenhouse gas (GHG) emission saving potential may be achieved by means of soil C sequestration. Recent demonstrations of carbon sink activities of European ecosystemes, however, often questioned the existence of C storing grasslands, as though a net sink of C was observed, uncertainty surrounding this estimate was larger than the sink itself (Janssens et al., 2003, Schulze et al., 2009. Then again, some of these estimates were based on a small number of measurements, and on models. Not surprising, there is still, a paucity of studies demonstrating the existence of grassland systems, where C sequestration would exceed (in CO2 equivalents) methane emissions from the enteric fermentation of ruminants and nitrous oxide emissions from managed soils. Grasslands are heavily relied upon for food and forage production. A key component of the carbon sink activity in grasslands is thus the impact of changes in management practices or effects of past and recent management, such as intensification as well as climate (and -variation). We analysed data (i.e. flux, ecological, management and soil organic carbon) from a network of European grassland flux observation sites (36). These sites covered different types and intensities of management, and offered the opportunity to understand grassland carbon cycling and trade-offs between C sinks and CH4 and N2O emissions. For some sites, the assessment of carbon sink activities were compared using two methods; repeated soil inventory and determination of the ecosystem C budget by continuous measurement of CO2 exchange in combination with quantification of other C imports and exports (net C storage, NCS). In general grassland, were a potential sink of C with 60±12 g C /m2.yr (median; min -456; max 645). Grazed sites had a higher NCS compared to cut sites (median 99 vs 67 g C /m2.yr), while permanent grassland sites tended to have a lower NCS compared to temporary sown grasslands (median 64 vs 125 g C /m2.yr). Including CH4 and N2O emission in the budget , revealed that for most sites, GHG emissions were compensated by NCS. The role of management impact,soil organic C and fluxes driven by interannual climate variation will be dicussed in the presentation.

  8. Carbon-Negative Biofuels from Low-Input High-Diversity Grassland Biomass

    Microsoft Academic Search

    David Tilman; Jason Hill; Clarence Lehman

    2006-01-01

    Biofuels derived from low-input high-diversity (LIHD) mixtures of native grassland perennials can provide more usable energy, greater greenhouse gas reductions, and less agrichemical pollution per hectare than can corn grain ethanol or soybean biodiesel. High-diversity grasslands had increasingly higher bioenergy yields that were 238% greater than monoculture yields after a decade. LIHD biofuels are carbon negative because net ecosystem carbon

  9. Influence of tree canopies on grassland productivity and nitrogen dynamics in deciduous oak savanna

    Microsoft Academic Search

    L. E. Jackson; R. B. Strauss; M. K. Firestone; J. W. Bartolome

    1990-01-01

    Jackson, L.E., Strauss, R.B., Firestone, M.K. and Bartolome, J.W., 1990. Influence of tree canopies on grassland productivity and nitrogen dynamics in deciduous oak savanna. Agric. Ecosystems En- viron., 32: 89-105. In oak and annual grassland savanna in the foothills of the Sierra Nevada, CA, soils under deci- duous blue oak (Quercus douglasii) canopies have higher nitrogen (N) turnover and inorganic

  10. Elevated CO2 and Leaf Longevity in the C4 Grassland?Dominant Andropogon gerardii

    Microsoft Academic Search

    Alan K. Knapp; Naomi Bargmann; Laura A. Maragni; Christine A. McAllister; Dale J. Bremer; Jay M. Ham; Clenton E. Owensby

    1999-01-01

    In central U.S. grasslands, plant and ecosystem responses to elevated CO2 are most pronounced when water availability is limited. In a northeast Kansas grassland, responses to elevated CO2 in leaf area, number, development, and longevity were quantified for the tallgrass prairie dominant, Andropogon gerardii. Plants were grown in open?top chambers (OTCs) modified to limit water availability and to maximize responses

  11. Current and Future Impacts of Atmospheric Nitrogen Deposition on Grassland GHG Balance

    NASA Astrophysics Data System (ADS)

    Hudiburg, T. W.; Gomez-Casanovas, N.; Bernacchi, C.; DeLucia, E. H.

    2014-12-01

    Nitrogen deposition (Ndep), a consequence of human activities, affects the greenhouse gas (GHG; CO2, N2O and CH4) sink capacity of terrestrial ecosystems. Grasslands play an important role in determining the concentration of GHGs in the atmosphere. While they store greater than 10% of terrestrial net primary productivity and sustain up to 30% of the world's organic C in their soils, grasslands also may be responsible for significant CH4 and N2O emissions. Many fertilization experiments have examined the response of grasslands to N loads of 50 to 100 kg N ha-1 yr-1. However, few studies have been designed to examine ecosystem responses to low N loads (< 20 kg N ha-1 yr-1) which they are likely to experience in the future according to the new IPCC representative concentration pathway (RCP) scenarios. This is consistent with the notion that the N saturation threshold at which Net Ecosystem Productivity (NEP) levels off, or the dose-response relationships between N2O, N-trace gases, CH4, and Ndep in grasslands have not being well characterized. We combined data from grassland ecosystems in major climate zones and biogeochemical modeling (DayCent v. 4.5) to characterize the dose-response relationship between increased Ndep and GHG, and other N-trace gases fluxes and N leaching of these grasslands. We used the synthesized data to evaluate the modeling for above- and belowground NPP, N2O, CH4, and response to N fertilization and climate. We found that in most cases increased Ndep will continue to increase the non-CO2 GHG source strength of grasslands, whereas NEP will saturate at N levels ranging from 10 - 70 kg N ha-1 yr-1depending on the precipitation, fire regime, and/or species composition of the grassland. Given these thresholds, we modeled the potential net GHG sink capacity for the world's major grassland biomes using several of the IPCC RCP scenarios which include a range of climate and Ndep trajectories. Our results suggest that although global grassland C storage can increase by up to 30% with increased Ndep, the increased non-CO2 emissions significantly reduce the net GHG sink capacity of grasslands. Improved understanding on how grasslands respond to Ndep loads that agree with future scenarios is essential to predicting the role of pastures on the global C and N cycles.

  12. Estimation of rainfall interception in grassland using eddy flux measurements

    NASA Astrophysics Data System (ADS)

    Maruyama, A.; Miyazawa, Y.; Inoue, A.

    2014-12-01

    Rainfall interception plays an important role in the water cycle in natural ecosystems. Interception by the forest canopies have been widely observed or estimated over various ecosystems, such as tropical rainforest, evergreen forest and deciduous forest. However interception by the short canopies, e.g. shrubby plant, grassland and crop, has been rarely observed since it has been difficult to obtain reliable precipitation measurements under the canopy. In this study, we estimated monthly and annual rainfall interception in grassland using evapotranspiration data of eddy flux measurements. Experiments were conducted in grassland (Italian ryegrass) from 2010 to 2012 growing season in Kumamoto, Japan. Evapotranspiration (latent heat flux) were observed throughout the year based on the eddy covariance technique. A three dimensional sonic anemometer and an open path CO2/H2O analyzer were used to calculate 30 min flux. Other meteorological factors, such as air temperature, humidity and solar radiation, were also observed. Rainfall interception was estimated as follows. 1) Using evapotranspiration data during dry period, environmental response of surface conductance (gc) was inversely calculated based on the big-leaf model. 2) Evapotranspiration without interception during precipitation period was estimated using above model and environmental response of gc. 3) Assuming that evaporation of intercepted rainfall is equal to the difference in evapotranspiration between above estimation and actual measurements, rainfall interception was estimated over experimental period. The account of rainfall interception in grassland using this technique will be presented at the meeting.

  13. The relative importance of the evaporation components for modeling the land surface-atmosphere interactions in temperate European forests

    NASA Astrophysics Data System (ADS)

    Van den Hoof, C.; Vidale, P. L.; Verhoef, A.; Vincke, C.

    2012-04-01

    The increasing demand for ecosystem services, in conjunction with climate change, are expected to significantly alter the terrestrial ecosystems and, by consequence, the energy, water, and carbon fluxes between land and atmosphere. In order to evaluate the severity of the sustainability issues, in particular water availability, that we might face in the future, there is a need for a better understanding of the relationships between the land surface characteristics, and the energy and water cycles. Simulating the various processes that interact to form the water cycle is a challenging task for climate models. Successful simulation of these interactions by the land surface component of a climate model requires detailed representation of processes such as interception, throughfall, snow accumulation, infiltration, runoff, soil moisture recharge and uptake, as well as the partitioning of evapotranspiration between canopy evaporation, transpiration, and soil evaporation (Oleson et al., 2008). An important factor affecting this partitioning is the forest structure and tree species composition. In this study, JULES (Best, 2011), which is the land surface model used in the climate model of the UK Met Office, has been evaluated for temperate forests in Europe. Europe accounts for one-quarter of the total forest area in the world and most of these forests are classified as temperate. According to Bonan (2008), the future of temperate forests and their climate services is highly uncertain as well as the net climate forcing of these forests. Change in the balance between deciduous and evergreen trees within these forests is likely in the future (Bonan, 2008). The response of European forests to climate variability and change, in particular during heat waves, has also been discussed in Teuling et al. (2010) from the point of use of water use strategy, and contrasted with that of grasslands. Particular attention has been paid to the different components of the evaporative flux and to the role of the forest composition on the partitioning of these components. JULES has mainly been evaluated against the European Eddy Fluxes database (formerly FLUXNET), which provided spatio-temporal information of the energy and water balance fluxes and related variables above deciduous, evergreen and mixed forests. Despite the lack of detailed measurements, limited data on flux partitioning are now available and an attempt was made to understand the model shortcomings and to improve the process descriptions underlying the evaporative flux and its components. This helped to increase the performance of the model to simulate the spatial and temporal variability of the fluxes over temperate forests. Best, M. J. et al. (2011). The Joint UK Land Environment Simulator (JULES), model description - Part 1: Energy and water fluxes. Geosci. Model Dev., 4, 677-699. Bonan, G. B. (2008). Forests and climate change: forcings, feedbacks, and the climate benefits of forests. Science 320, 1444-1449. Oleson, K. et al. (2008). Improvements to the community land model and their impact on the hydrological cycle. J. Geophys. Res. 113, 1-26. Teuling. A.J. et al. (2010). Contrasting response of European forest and grassland energy exchange to heatwaves, Nature Geoscience 3, 722-727.

  14. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 false National Grasslands. 222.52 Section 222.52 Parks...MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will be established under concepts and...

  15. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false National Grasslands. 222.52 Section 222.52 Parks...MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will be established under concepts and...

  16. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false National Grasslands. 222.52 Section 222.52 Parks...MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will be established under concepts and...

  17. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 false National Grasslands. 222.52 Section 222.52 Parks...MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will be established under concepts and...

  18. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false National Grasslands. 222.52 Section 222.52 Parks...MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will be established under concepts and...

  19. GRAZING ANNUAL GRASSLANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the Intermountain-Colorado Plateau area, we commonly think of cheatgrass (Bromus tectorum L.) as being the dominant exotic, highly invasive annual grass on rangelands in the temperate deserts and the similar species red brome (Bromus rubens L.) on rangelands of the warm deserts. There is no clear...

  20. Greenhouse gas budgets of managed European grasslands

    NASA Astrophysics Data System (ADS)

    Ammann, C.; Horváth, L.; Jones, S. K.

    2012-04-01

    Greenhouse gas exchange of grasslands are directly and indirectly related to the respective carbon (C) and nitrogen (N) budget. Within the framework of the NitroEurope project we investigated the greenhouse gas, carbon, and nitrogen budgets of four European grassland systems over several years: Easter Bush (UK), Oensingen intensive and extensive (CH), and Bugac (HU). They span contrasting climatic conditions, management types (grazing, cutting) and intensity. While Easter Bush (pasture) and Oensingen int. (meadow) were intensively managed and received a considerable amount of fertiliser, the unfertilised sites Bugac (pasture) and Oensingen ext. (meadow) depended on atmospheric N input (wet and dry deposition) and biological N fixation. The experimental results of the four sites were also compared to published GHG fluxes of other European grasslands. While the ecosystem CO2 exchange was measured on the field scale with the eddy covariance method, the soil fluxes of the other greenhouse gases CH4 and N2O have been detected generally by means of static chambers (only occasional application of eddy covariance). The emission of CH4 by grazing ruminant resulting from enteric fermentation was estimated by animal type specific emission factors. For characterizing the total GHG effect of the grassland sites, the contributions of the different GHGs were normalised to CO2-equivalents. Except for Oensingen ext., all sites showed positive C budgets (sequestration). The observed positive correlation between C and N sequestration (with a ratio between 10 and 20) agrees with studies reported in the literature. The magnitude of N2O emission depended mainly on management intensity (fertiliser input) and on the soil moisture conditions. Whereas for the Oensingen and the Bugac sites, the total GHG budget was dominated by the carbon budget, for Easter Bush the combined effect of N2O and CH4 emission (including animal enteric fermentation) was in the same order of magnitude as the carbon sequestration leading to a strong compensation of the GHG effects. However, if digestion of harvested biomass is also attributed to the GHG budget of the non-grazed meadows, they become dominated by CH4 emission from enteric fermentation. The results show that the comparison of GHG budgets of grazed and non-grazed grasslands is difficult and needs clearly defined system boundaries.

  1. Empirically Modeling Carbon Fluxes over the Northern Great Plains Grasslands

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Wylie, B. K.; Ji, L.; Gilmanov, T.; Tieszen, L. L.

    2007-12-01

    Grasslands cover nearly one-fifth of the global terrestrial surface and store most of their carbon below ground. The grassland ecosystem in the Great Plains occupies over 1.5 million km2 of land area and is the primary resource for livestock production in North America. However, the contributions of grasslands to local and regional carbon budgets remain uncertain due to the lack of carbon flux data for the expansive grassland ecosystems under various managements, land uses, and climate variability. A quantitative understanding of carbon fluxes across these systems is essential for developing regional, national, and global carbon budgets and providing guidance to policy makers and managers when substantial conversion to biofuels are implemented. Additionally, these estimates will provide insights into how the grassland ecosystem will respond to future climate and what systems are sustainable and offer net carbon sinks. This knowledge base and decisions support tools are needed for developing land management strategies for the region under a variety of environmental conditions and land use options. In the past, we used a remote sensing-based piecewise regression (PWR) model to estimate the grassland carbon fluxes in the northern Great Plains using the 1-km SPOT VEGETATION normalized difference vegetation index (NDVI) data. We estimated the carbon fluxes through integrated spatial databases and remotely sensed extrapolations of flux tower data to regional scales. The PWR model was applied to derive an empirical relationship between environmental variables and tower-based measurements. The PWR equations were then applied through time and space to estimate carbon fluxes across the study area at 1-km resolution. We now improve this modeling approach by 1) using Moderate Resolution Imaging Spectroradiometer (MODIS) data with higher temporal, spatial, and spectral resolutions (8-day, 500-m, and 7-band) as input; 2) incorporating the actual vegetation evapotranspiration data derived from the VegET model, which takes into account soil moisture and land surface phenology; 3) adding an additional flux tower from Brookings, SD, and additional years at other flux towers to the training data sets; and 4) considering the lag response of vegetation production to precipitation. We modeled and mapped 8-day and 500-m carbon fluxes for the years 2000-2006 in the northern Great Plains grasslands. These maps were then used to assess the regional and temporal trends of carbon fluxes in this region, identify carbon sink and source areas, and determine important transitions and environmental drivers of carbon sinks/sources. Cross-validation at sites showed that the improved model increases the estimation accuracies and reflects the variations in water stress that may not be monitored by vegetation indices alone because of the lag-response of vegetation indices to water deficits.

  2. 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

  3. Non-Linear Responses to Precipitation and Shrub Encroachment in Semi-Arid Grassland: Isotopes and CO2 Fluxes Reveal Soil Microsite Alteration as Explanation 1875

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Responses of net ecosystem production (NEP) to growing season rainfall amount is non-linear over a gradient of woody-plant encroachment in semi-arid riparian grassland. NEP is positively correlated with growing season precipitation amount in the grassland, but is negatively correlated with precipita...

  4. EVAPOTRANSPIRATION FROM NORTHERN SEMIARID GRASSLANDS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of forage production for livestock grazing on semiarid grasslands depends on water availability. Evapotranspiration (ET) was measured using the Bowen ratio/energy balance (BREB) method on three grasslands at Mandan, North Dakota: a nongrazed mixed-grass prairie (prairie), a grazed mixed-...

  5. Prescribed fire as an alternative measure in European grassland conservation

    NASA Astrophysics Data System (ADS)

    Valkó, Orsolya; Deák, Balázs; Török, Péter; Tóthmérész, Béla

    2015-04-01

    There are contrasting opinions on the perspectives of prescribed burning management in European grasslands. One hand, prescribed burning can be effectively used with relatively low implementation costs for the management of open landscapes, the reduction of accumulated litter or for decreasing the chance of wildfires. On the other hand burning can also have serious detrimental impacts on grassland ecosystems by promoting the dominance of some problem species (e.g. some competitors or invasive species) and by threatening endangered plant and animal species, especially invertebrates, thus, inappropriate burning can result in a loss of biodiversity in the long run. Our goal was to review the publications on the application of prescribed burning in European grasslands considering general (e.g. timing, frequency and duration) and specific (e.g. types of grasslands, effects on endangered species) circumstances. Even prescribed burning forms an integral part of the North-American grassland management practice, it is rarely applied in Europe, despite the fact that uncontrolled burning occurs frequently in some regions. According to the North-American experiences prescribed burning can be a viable solution for biodiversity conservation and can be a feasible solution for several nature conservation problems. We reviewed prescribed burning studies from Europe and North-America to identify findings which might be adapted to the European grassland conservation strategy. We found that not only the application of fire management is scarce in Europe but there is also a lack of published studies on this topic. European studies - contrary to the North-American practice - usually used yearly dormant-season burning, and concluded that this burning type solely is not feasible to preserve and maintain species-rich grasslands. In North-American grasslands, application of burning has a stronger historical, practical and scientific background; it is fine-tuned in terms of timing, frequency and generally combined with other measures, such as grazing, seed sowing or herbicide application. By this complex approach several nature conservation goals can be fulfilled like increasing landscape-scale heterogeneity and invasion control. We emphasize that for establishing a fine-tuned prescribed burning management plan for the European grasslands the general findings of carefully designed case studies should be combined with the practical knowledge of conservation managers concerning the local application circumstances to reach specific management objectives.

  6. Separation of grassland litter and ecosite influences on seasonal soil moisture and plant growth dynamics

    Microsoft Academic Search

    Eliza S. Deutsch; Edward W. Bork; Walter D. Willms

    2010-01-01

    While plant litter is known to regulate soil moisture, little is known about the extent to which litter impacts moisture over\\u000a and above the physical environment (i.e., ecosite) throughout the growing season, particularly in cool-temperate grasslands\\u000a where moisture is considered less limiting for plant growth. In this study, we examined the relative impact of litter and\\u000a ecosite on growing season

  7. [Application of near-infrared spectroscopy to management of vegetation for natural grassland].

    PubMed

    Xu, Dong-mei; Wang, Kun

    2007-10-01

    Vegetation is a major index for monitoring the grassland condition and productivity. The change in vegetation directly reflects degradation and restoration of grassland ecosystem. It is important to monitoring the information of vegetation changes to prevent degradation and realize sustainable development of grassland. Predication of vegetation was often completed by field investigation and laboratory analysis in the past, and could not satisfy the needs for inspecting of grassland degradation and restoration. Near-infrared spectroscopy (NIRS) is a rapid, convenient, high-efficiency, non-destructive and low-cost analytical technique, and has been widely used in various fields for quantitative and qualitative analysis. It has been one of the most important techniques for monitoring the succession of grassland ecosystem, and has great potential for applying in natural grassland management. Botanical composition is a major index of the vegetation community structure. The change in botanical composition indicates the developing stage of the plant community. Determining the botanical composition during vegetation succession can provide sound basis for establishing feasible measure of grassland management. NIRS can be successfully used as a rapid method to predict the grass, legume and other plant proportion in natural or semi-natural grasslands. The legume content in multi-species mixtures and the species composition in root mixtures can accurately be estimated by means of NIRS. Leaf/stem ratio of grass stands is an important factor affecting forage quality, diet selection, intake, and the intensity of photosynthesis. Estimates of leaf/stem ratios commonly are based on a labor intensive process of hand separating leaf and stem fractions. NIRS can be used successfully to predict leaf/stem ratios and mineral contents. The results of NIRS technique were well correlated with labor separating method. The decomposition of litter in grasslands is an important aspect of material cycle in grassland ecosystem. To study material cycling, especially mineral cycling in grassland ecosystems, it is essential to know the decomposition rate of the litter. NIRS technique can accurately predict the decomposition status of litter and the change of lignin, cellulose, nitrogen, ash and other nutrient contents during the decomposition of litter. NIRS has potential to provide rapid and effective estimates of material cycling in grassland ecosystems to assist managers in establishing application rates of grasslands that fall within productive and environmentally safe levels. The chemical composition of the plants in grassland is an important factor affecting herbivorous intake and material cycle, and is an important parameter in determining the status of degradation and restoration of grassland ecosystems. NIRS has been confirmed as a technique for reliably and accurately determining the dry matter, crude protein, acid detergent fibre, neutral detergent fibre, and certain microelement contents. With the development of spectral technique, the NIRS method will be more widely used in vegetation management. PMID:18306785

  8. Introduction to Grassland Management. Instructor Guide, Student Reference [and] Crop and Grassland Plant Identification Manual.

    ERIC Educational Resources Information Center

    Suits, Susie

    This packet contains an Instructor guide and student reference for a course in introduction to grassland management, as well as a crop and grassland plant identification manual. The three-unit curriculum contains the following 11 lessons: (unit I, grasslands and grassland plants): (1) an introduction to grasslands; (2) plant classification; (3)…

  9. Saprotrophic Basidiomycetes in Grasslands: Distribution and Function

    E-print Network

    Griffith, Gareth

    Basidiomycetes in Grasslands: Distribution and Function Gareth W. Griffith and Kevin Roderick Contents 1. Introduction 276 2. What is Grassland? 276 3. Functional Groups of Grassland Fungi 279 3.1 Litter Decomposers Endophytes/Pathogens 284 4. Detection of Grassland Fungi 285 5. Contribution of Saprotrophic Basidiomycetes

  10. Diversity and abundance of photosynthetic sponges in temperate Western Australia

    PubMed Central

    Lemloh, Marie-Louise; Fromont, Jane; Brümmer, Franz; Usher, Kayley M

    2009-01-01

    Background Photosynthetic sponges are important components of reef ecosystems around the world, but are poorly understood. It is often assumed that temperate regions have low diversity and abundance of photosynthetic sponges, but to date no studies have investigated this question. The aim of this study was to compare the percentages of photosynthetic sponges in temperate Western Australia (WA) with previously published data on tropical regions, and to determine the abundance and diversity of these associations in a range of temperate environments. Results We sampled sponges on 5 m belt transects to determine the percentage of photosynthetic sponges and identified at least one representative of each group of symbionts using 16S rDNA sequencing together with microscopy techniques. Our results demonstrate that photosynthetic sponges are abundant in temperate WA, with an average of 63% of sponge individuals hosting high levels of photosynthetic symbionts and 11% with low to medium levels. These percentages of photosynthetic sponges are comparable to those found on tropical reefs and may have important implications for ecosystem function on temperate reefs in other areas of the world. A diverse range of symbionts sometimes occurred within a small geographic area, including the three "big" cyanobacterial clades, Oscillatoria spongeliae, "Candidatus Synechococcus spongiarum" and Synechocystis species, and it appears that these clades all occur in a wide range of sponges. Additionally, spongin-permeating red algae occurred in at least 7 sponge species. This study provides the first investigation of the molecular phylogeny of rhodophyte symbionts in sponges. Conclusion Photosynthetic sponges are abundant and diverse in temperate WA, with comparable percentages of photosynthetic to non-photosynthetic sponges to tropical zones. It appears that there are three common generalist clades of cyanobacterial symbionts of sponges which occur in a wide range of sponges in a wide range of environmental conditions. PMID:19196460

  11. Soil carbon and nitrogen storage in response to fire in a temperate mixed-grass savanna.

    PubMed

    Dai, X; Boutton, T W; Hailemichael, M; Ansley, R J; Jessup, K E

    2006-01-01

    Vegetation fires may alter the quantity and quality of organic matter inputs to soil, rates of organic matter decay, and environmental factors that influence those processes. However, few studies have evaluated the impacts of this land management technique on soil organic carbon (SOC) and total N in grasslands and savannas. We evaluated the impact of repeated fires and their season of occurrence on SOC and total N storage in a temperate mixed-grass-mesquite savanna where fire is used to control woody plant encroachment. Four fire treatments varying in season of occurrence were examined: summer only (SF), winter only (WF), alternate summer and winter fires (SWF), and unburned controls. In each treatment, soils were sampled to 1 m under three vegetation types: C3 grasses, C4 grasses, and mesquite trees. The SOC storage at 0 to 20 cm was significantly greater in SF (2693 g C m(-2)) and SWF (2708 g C m(-2)) compared to WF (2446 g C m(-2)) and controls (2445 g C m(-2)). The SWF treatment also increased soil total N (271 g N m(-2)) relative to all other treatments (228-244 g N m(-2)) at 0 to 20 cm. Fire had no effect on SOC or total N at depths of > 20 cm. Vegetation type had no significant influence on SOC or total N stocks. The delta13C value of SOC was not affected by fire, but increased from -21 per thousand at 0 to 10 cm to -15 per thousand at depths of > 20 cm indicating that all treatments were once dominated by C4 grasses before woody plant encroachment during the past century. These results have implications for scientists, land managers, and policymakers who are now evaluating the potential for land uses to alter ecosystem C storage and influence atmospheric CO2 concentrations and global climate. PMID:16825482

  12. Winter climate change effects on soil C and N cycles in urban grasslands.

    PubMed

    Durán, Jorge; Rodríguez, Alexandra; Morse, Jennifer L; Groffman, Peter M

    2013-09-01

    Despite growing recognition of the role that cities have in global biogeochemical cycles, urban systems are among the least understood of all ecosystems. Urban grasslands are expanding rapidly along with urbanization, which is expected to increase at unprecedented rates in upcoming decades. The large and increasing area of urban grasslands and their impact on water and air quality justify the need for a better understanding of their biogeochemical cycles. There is also great uncertainty about the effect that climate change, especially changes in winter snow cover, will have on nutrient cycles in urban grasslands. We aimed to evaluate how reduced snow accumulation directly affects winter soil frost dynamics, and indirectly greenhouse gas fluxes and the processing of carbon (C) and nitrogen (N) during the subsequent growing season in northern urban grasslands. Both artificial and natural snow reduction increased winter soil frost, affecting winter microbial C and N processing, accelerating C and N cycles and increasing soil : atmosphere greenhouse gas exchange during the subsequent growing season. With lower snow accumulations that are predicted with climate change, we found decreases in N retention in these ecosystems, and increases in N2 O and CO2 flux to the atmosphere, significantly increasing the global warming potential of urban grasslands. Our results suggest that the environmental impacts of these rapidly expanding ecosystems are likely to increase as climate change brings milder winters and more extensive soil frost. PMID:23630015

  13. Contrasting response of grassland versus forest carbon and water fluxes to spring drought in Switzerland

    NASA Astrophysics Data System (ADS)

    Wolf, Sebastian; Eugster, Werner; Ammann, Christof; Häni, Matthias; Zielis, Sebastian; Hiller, Rebecca; Stieger, Jacqueline; Imer, Dennis; Merbold, Lutz; Buchmann, Nina

    2013-09-01

    Since the European summer heat wave of 2003, considerable attention has been paid to the impacts of exceptional weather events on terrestrial ecosystems. While our understanding of the effects of summer drought on ecosystem carbon and water vapour fluxes has recently advanced, the effects of spring drought remain unclear. In Switzerland, spring 2011 (March-May) was the warmest and among the driest since the beginning of meteorological measurements. This study synthesizes Swiss FluxNet data from three grassland and two forest ecosystems to investigate the effects of this spring drought. Across all sites, spring phenological development was 11 days earlier in 2011 compared to the mean of 2000-2011. Soil moisture related reductions of gross primary productivity (GPP) were found at the lowland grassland sites, where productivity did not recover following grass cuts. In contrast, spring GPP was enhanced at the montane grassland and both forests (mixed deciduous and evergreen). Evapotranspiration (ET) was reduced in forests, which also substantially increased their water-use efficiency (WUE) during spring drought, but not in grasslands. These contrasting responses to spring drought of grasslands compared to forests reflect different adaptive strategies between vegetation types, highly relevant to biosphere-atmosphere feedbacks in the climate system.

  14. [Spatiotemporal differentiation of land cover change and grassland degradation pattern in Yangtze River headwaters area].

    PubMed

    Guo, Luo; Du, Shi-Hong; Xue, Da-Yuan; Cai, Liang

    2012-05-01

    Based on field survey data, remote sensing images and statistical data, this paper analyzed the spatiotemporal differentiation of land use and grassland degradation patterns in Yangtze River headwaters area in 1987-2007, and discussed the main natural factors (elevation, position and slope) leading to the changes of this area's grassland ecological environment. In 1987-2007, the fragmentation of this area' s landscape patterns had an increasing trend, and natural environment and climate change were the main driving forces of land use pattern change. There existed significant differences in the areas of grassland degradation at different altitudes. Grassland degradation mainly occurred at altitudes 4800-5100 m. The grassland degradation area tended to increase with increasing elevation, and the proportions of the degradation area varied greatly over different slopes and aspects. The climate in the study area became warm and dry, and the spatial structure of regional land cover changed obviously. The distribution patterns of grassland degradation at different elevation, position and slope coincided with alpine environment and human disturbances, suggesting that alpine environment and climatic change were the decisive factors to the grassland ecosystem pattern in Yangtze River headwaters area. PMID:22919830

  15. Comparing the carbon budgets of boreal and temperate deciduous forest stands

    Microsoft Academic Search

    A. G. Barr; T. J. Griffis; T. A. Black; X. Lee; R. M. Staebler; J. D. Fuentes; Z. Chen; K. Morgenstern

    2002-01-01

    Boreal and temperate deciduous forests at northern mid-latitudes play an important role in the global carbon cycle. We analyze 3 years (1996-1998) of eddy-covariance carbon dioxide flux measurements from two contrasting deciduous forest ecosystems in the boreal and temperate regions of central Canada. The two forest stands have similar ages, heights, and leaf area indices but differ in species composition

  16. Pedogenesis and soil moisture, but not soil temperature best explain large-scale patterns of soil carbon and soil nitrogen contents in the permafrost ecosystems of Tibetan alpine grasslands

    NASA Astrophysics Data System (ADS)

    Baumann, F.; He, J.-S.; Kühn, P.; Scholten, T.

    2009-04-01

    The Tibetan Plateau is an essential area to study potential feedback effects of soils to climate change due to the rapid rise of air temperature in the past several decades as well as the large amounts of organic carbon (Corg) stored in soils, particularly in permafrost-affected areas. In order to predict the impact of environmental change on ecosystem functioning, it is of great importance to understand how Corg and soil nitrogen (N) stocks are controlled under changing climate conditions in extreme environments. We therefore investigated the main parameters influencing Corg and N at 47 sites along a 1,200 km transect across the high-altitude and low-latitude permafrost region of the central-eastern Tibetan Plateau. Sites with continuous or discontinuous permafrost as well as areas without or heavily degraded permafrost were studied for comparison of soil dynamics under various environmental settings. Due to the high number of samples and the large-scale transect concept, sophisticated statistical analyses showing significant relationships between pedological parameters as well as Corg and N contents were carried out. The aim of the presented research was to evaluate consequences of permafrost degradation for C and N stocks and hence nutrient supply for plants. The landscape along the investigated transect is a patchwork of geochemically very diverse micro-ecosystems showing variations in organic matter, nutrient stocks, plant communities and productivity. These differences are closely related to topographic position, hydrological regimes and consequently permafrost distribution. The main controlling mechanisms of this heterogeneity on the Tibetan Plateau are related to different soil drainage classes. Ecosystem ecology has traditionally focused on temperature and modeled soils mostly as an ecosystem feature whose attributes vary strongly by thermodynamic principles. However, the general linear regression model (GLM) suggests soil moisture as the most important parameter explaining 64% of Corg and 60% of N variation. The explanatory power of the GLM for C and N concentrations is significantly improved by adding two parameters for pedogenesis to the model, i.e. CaCO3 and soil texture. The extent of the effect of soil moisture is determined by permafrost, current aeolian sedimentation occurring mostly on sites with permafrost degradation, and pedogenesis. We conclude that degradation of permafrost and corresponding changes in soil hydrology combined with a shift from mature stages of pedogenesis to initial stages, have severe impact on soil carbon and importantly on plant available N. Our study shows that other factors than temperature are more important between years and sites at regional and continental scales. Temperature dependence may rather be relevant for ecosystems when soil moisture or other factors are not limiting or altering the relationship between temperature and soil processes. Soil respiration data demonstrate that biomass and particularly belowground biomass as well as soil water content are determinant of spatial variation of soil respiration across the plateau. In summary, both stocks (Corg and N) are coupled with complex feedback mechanisms between permafrost, aeolian processes and the stage of pedogenesis. The latter can be described by acidity, carbonate content and grain size distribution.

  17. Rapid Decline of a Grassland System and Its Ecological and Conservation Implications

    PubMed Central

    Ceballos, Gerardo; Davidson, Ana; List, Rurik; Pacheco, Jesús; Manzano-Fischer, Patricia; Santos-Barrera, Georgina; Cruzado, Juan

    2010-01-01

    One of the most important conservation issues in ecology is the imperiled state of grassland ecosystems worldwide due to land conversion, desertification, and the loss of native populations and species. The Janos region of northwestern Mexico maintains one of the largest remaining black-tailed prairie dog (Cynomys ludovicianus) colony complexes in North America and supports a high diversity of threatened and endangered species. Yet, cattle grazing, agriculture, and drought have greatly impacted the region. We evaluated the impact of human activities on the Janos grasslands, comparing changes in the vertebrate community over the last two decades. Our results reveal profound, rapid changes in the Janos grassland community, demonstrating large declines in vertebrate abundance across all taxonomic groups. We also found that the 55,000 ha prairie dog colony complex has declined by 73% since 1988. The prairie dog complex has become increasingly fragmented, and their densities have shown a precipitous decline over the years, from an average density of 25 per ha in 1988 to 2 per ha in 2004. We demonstrated that prairie dogs strongly suppressed woody plant encroachment as well as created open grassland habitat by clearing woody vegetation, and found rapid invasion of shrubland once the prairie dogs disappeared from the grasslands. Comparison of grasslands and shrublands showed markedly different species compositions, with species richness being greatest when both habitats were considered together. Our data demonstrate the rapid decline of a grassland ecosystem, and documents the dramatic loss in biodiversity over a very short time period concomitant with anthropogenic grassland degradation and the decline of a keystone species. PMID:20066035

  18. Rapid decline of a grassland system and its ecological and conservation implications.

    PubMed

    Ceballos, Gerardo; Davidson, Ana; List, Rurik; Pacheco, Jesús; Manzano-Fischer, Patricia; Santos-Barrera, Georgina; Cruzado, Juan

    2010-01-01

    One of the most important conservation issues in ecology is the imperiled state of grassland ecosystems worldwide due to land conversion, desertification, and the loss of native populations and species. The Janos region of northwestern Mexico maintains one of the largest remaining black-tailed prairie dog (Cynomys ludovicianus) colony complexes in North America and supports a high diversity of threatened and endangered species. Yet, cattle grazing, agriculture, and drought have greatly impacted the region. We evaluated the impact of human activities on the Janos grasslands, comparing changes in the vertebrate community over the last two decades. Our results reveal profound, rapid changes in the Janos grassland community, demonstrating large declines in vertebrate abundance across all taxonomic groups. We also found that the 55,000 ha prairie dog colony complex has declined by 73% since 1988. The prairie dog complex has become increasingly fragmented, and their densities have shown a precipitous decline over the years, from an average density of 25 per ha in 1988 to 2 per ha in 2004. We demonstrated that prairie dogs strongly suppressed woody plant encroachment as well as created open grassland habitat by clearing woody vegetation, and found rapid invasion of shrubland once the prairie dogs disappeared from the grasslands. Comparison of grasslands and shrublands showed markedly different species compositions, with species richness being greatest when both habitats were considered together. Our data demonstrate the rapid decline of a grassland ecosystem, and documents the dramatic loss in biodiversity over a very short time period concomitant with anthropogenic grassland degradation and the decline of a keystone species. PMID:20066035

  19. Changes in the temperature sensitivity of SOM decomposition with grassland succession: implications for soil C sequestration

    PubMed Central

    Nianpeng, He; Ruomeng, Wang; Yang, Gao; Jingzhong, Dai; Xuefa, Wen; Guirui, Yu

    2013-01-01

    Understanding the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is important for predicting soil carbon (C) sequestration in terrestrial ecosystems under warming scenarios. Whether Q10 varies predictably with ecosystem succession and the ways in which the stoichiometry of input SOM influences Q10 remain largely unknown. We investigate these issues using a grassland succession series from free-grazing to 31-year grazing-exclusion grasslands in Inner Mongolia, and an incubation experiment performed at six temperatures (0, 5, 10, 15, 20, and 25°C) and with four substrates: control (CK), glucose (GLU), mixed grass leaf (GRA), and Medicago falcata leaf (MED). The results showed that basal soil respiration (20°C) and microbial biomass C (MBC) logarithmically decreased with grassland succession. Q10 decreased logarithmically from 1.43 in free-grazing grasslands to 1.22 in 31-year grazing-exclusion grasslands. Q10 increased significantly with the addition of substrates, and the Q10 levels increased with increase in N:C ratios of substrate. Moreover, accumulated C mineralization was controlled by the N:C ratio of newly input SOM and by incubation temperature. Changes in Q10 with grassland ecosystem succession are controlled by the stoichiometry of newly input SOM, MBC, and SOM quality, and the combined effects of which could partially explain the mechanisms underlying soil C sequestration in the long-term grazing-exclusion grasslands in Inner Mongolia, China. The findings highlight the effect of substrate stoichiometry on Q10 which requires further study. PMID:24455135

  20. Changes in the temperature sensitivity of SOM decomposition with grassland succession: implications for soil C sequestration.

    PubMed

    Nianpeng, He; Ruomeng, Wang; Yang, Gao; Jingzhong, Dai; Xuefa, Wen; Guirui, Yu

    2013-12-01

    Understanding the temperature sensitivity (Q 10) of soil organic matter (SOM) decomposition is important for predicting soil carbon (C) sequestration in terrestrial ecosystems under warming scenarios. Whether Q 10 varies predictably with ecosystem succession and the ways in which the stoichiometry of input SOM influences Q 10 remain largely unknown. We investigate these issues using a grassland succession series from free-grazing to 31-year grazing-exclusion grasslands in Inner Mongolia, and an incubation experiment performed at six temperatures (0, 5, 10, 15, 20, and 25°C) and with four substrates: control (CK), glucose (GLU), mixed grass leaf (GRA), and Medicago falcata leaf (MED). The results showed that basal soil respiration (20°C) and microbial biomass C (MBC) logarithmically decreased with grassland succession. Q 10 decreased logarithmically from 1.43 in free-grazing grasslands to 1.22 in 31-year grazing-exclusion grasslands. Q 10 increased significantly with the addition of substrates, and the Q 10 levels increased with increase in N:C ratios of substrate. Moreover, accumulated C mineralization was controlled by the N:C ratio of newly input SOM and by incubation temperature. Changes in Q 10 with grassland ecosystem succession are controlled by the stoichiometry of newly input SOM, MBC, and SOM quality, and the combined effects of which could partially explain the mechanisms underlying soil C sequestration in the long-term grazing-exclusion grasslands in Inner Mongolia, China. The findings highlight the effect of substrate stoichiometry on Q 10 which requires further study. PMID:24455135

  1. Alcohol, Temperance & Prohibition

    NSDL National Science Digital Library

    That legendary man of letters, Samuel Johnson, once opined that â??Abstinence is as easy to me as temperance would be difficultâ?ť. Over the centuries, many have shared at least part of Johnsonâ??s sentiment as regards the temptations offered by spirits, and just as many have concerned themselves with the cause of cautioning others about alcohol and its potentially pernicious effects. The good people at Brown University have created this digital collection which includes a host of primary documents from the past several centuries, including broadsides, sheet music, and government publications. These items will be of great interest to anyone interested in the history of alcoholism, and how various forms of media were used to disseminate ideas and information about this phenomenon and the prohibition movement. Visitors can browse the collection by document creator, publisher, and general title. Another item of note here is the online essay â??Temperance and Prohibition Era Propaganda: A Study in Rhetoricâ?ť by Leah Rae Berk.

  2. How soil moisture, rain pulses, and growth alter the response of ecosystem respiration to temperature

    Microsoft Academic Search

    Liukang Xu; Dennis D. Baldocchi; Jianwu Tang

    2004-01-01

    In this paper, we analyzed 3 years of carbon flux data from continuous eddy covariance measurements to investigate how soil moisture, rain pulses, and growth alter the response of ecosystem respiration to temperature. The data were acquired over an annual grassland and from the grass understory of an oak\\/grass savanna ecosystem in California. We observed that ecosystem respiration was an

  3. North Temperate Lakes Long-Term Ecological Research (NTL-LTER)

    NSDL National Science Digital Library

    The University of Wisconsin's world-renown Center for Limnology operates the North Temperate Lakes Long-Term Ecological Research program, emphasizing long-term ecological phenomena in urban, agricultural, and forested watersheds. This information-rich site offers general and detailed information on the North Temperate Lakes LTER's impressive array of projects. Research projects encompass several themes, including long-term trends in physical, chemical, and biological properties of lake ecosystems; the dynamics of internal and external processes affecting lake ecosystems; the temporal responses of lake ecosystems to disturbance and stress; the interaction between spatial heterogeneity and temporal variability of lake ecosystems; and lake-ecosystem properties in a broad regional context. Also of interest are descriptions of lake properties, a searchable bibliography, biodiversity and species lists, and more than a dozen online datasets ranging from Aquatic Macrophytes through Zooplankton. A query-able climate data section and Links to Other Sites of Interest round out the site.

  4. Preliminary results on nitric oxide emission from a southern African savanna ecosystem

    Microsoft Academic Search

    F. X. Meixner; Th. Fickinger; L. Marufu; D. Serça; F. J. Nathaus; E. Makina; L. Mukurumbira; M. O. Andreae

    1997-01-01

    During October to December 1994, we measured diel and seasonal variability in nitric oxide (NO) exchange by a southern African savanna ecosystem (Grasslands Research Station, Marondera, Zimbabwe). A set of automated dynamic chambers was installed in three sub-sites: Miombo forest, natural grassland, and cropped soils (maize, sorghum, groundnut). The latter received a single application of commercialy available in-organic or cowdung

  5. Post-fire resource redistribution and fertility island dynamics in shrub encroached desert grasslands: a modeling approach

    Microsoft Academic Search

    Sujith Ravi; Paolo D’Odorico

    2009-01-01

    A common form of land degradation in desert grasslands is associated with the relatively rapid encroachment of woody plants,\\u000a a process that has important implications on ecosystem structure and function, as well as on the soil hydrological and biogeochemical\\u000a properties. Until recently this grassland to shrubland transition was thought to be highly irreversible. However recent studies\\u000a have shown that at

  6. Comparison of single-year and multiyear NDVI time series principal components in cold temperate biomes

    Microsoft Academic Search

    Mryka Hall-Beyer

    2003-01-01

    Standardized principal components analysis (SPCA) is performed on normalized difference vegetation index (NDVI) time series of a 10° latitude by 10° longitude area of western Canada including grassland, parkland, and forest ecosystems. When used with input from a single growing season (April-October), early components correspond closely to ecoregional mapping based on long-term vegetation composition. Later components isolate areas showing agricultural

  7. A comparison of the diversity and structure of butterfly communities in semi-natural and human-modified grassland habitats at the foot of Mt. Fuji, central Japan

    Microsoft Academic Search

    Masahiko Kitahara; Kunihiko Sei

    2001-01-01

    To examine the effects of human land use and disturbance on butterfly communities we compared the diversity and structure of communities in relatively undisturbed, semi-natural grassland habitats and highly disturbed, human-modified ones. Comparisons were based on transect counts conducted at 6 study sites at the foot of Mt. Fuji in the cool temperate zone of central Japan during 1995. Out

  8. Aerial photo classification for monitoring the spread of Eragrostis lehmanniana in a semiarid Arizona grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasion by exotic grasses is a common threat to biodiversity in grassland ecosystems. Phenological variation can be a key consideration in efforts to characterize and monitor the spread of invasive grasses. This study investigated a transition from a vegetation assemblage historically dominated by ...

  9. Functional traits, productivity and effects on nitrogen cycling of 33 grassland species

    Microsoft Academic Search

    J. M. Craine; D. Tilman; D. Wedin; P. Reich; M. TJOELKERand; J. Knops

    2002-01-01

    Summary 1. Our goal was to determine the relationships among ecophysiological, whole-plant and ecosystem traits of a wide variety of grassland species grown under field conditions in the long term. We measured 87 traits for 33 species (32 perennial, one annual) grown in monoculture for 5 years on sandy soils, and determined the relationship among traits and their correspondence with

  10. Soil fungal communities respond to grassland plant community richness and soil edaphics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fungal communities in soil have significant influences on terrestrial ecosystem dynamics, yet our understanding of the drivers of fungal diversity and community structure in soil is limited. Fungal communities associated with the rhizosphere of four native perennial grassland plant species grown in ...

  11. Investigating Grazing Intensity and Range Condition of Grasslands in Northeastern Kansas Using Landsat Thematic Mapper Data

    Microsoft Academic Search

    Dana L. Peterson; Kevin P. Price; Edward A. Martinko

    2002-01-01

    Grazing changes plant species composition of grassland ecosystems by selective removal and trampling. Grazing also alters soil physical and biogeochemical properties and can dramatically change hydrologic processes that can impact water budgets and quality. For these reasons, practical means are needed to assess grazing management practices and its impacts upon the land. This study examines whether a grazing intensity and

  12. Differential Sensitivity to Drought in Six Central U.S. Grasslands

    NASA Astrophysics Data System (ADS)

    Knapp, A.; Carroll, C. J. W.; Denton, E. M.; La Pierre, K. J.; Wilcox, K. R.; Collins, S. L.; Smith, M.

    2014-12-01

    Terrestrial ecosystems often vary dramatically in their responses to drought, but the reasons why are unclear. With climate change forecasts for more frequent and extensive drought in the future, a more complete understanding of the mechanisms that determine differential ecosystem sensitivity to drought is needed. In 2012, the Central U.S. experienced the 4th largest drought in a century, with a regional-scale 40% reduction in growing season precipitation affecting ecosystems ranging from desert grassland to mesic tallgrass prairie. This provided an opportunity to assess ecosystem sensitivity to a drought of common magnitude in six native grasslands. We tested the prediction that drought sensitivity is inversely related to mean annual precipitation (MAP) by quantifying reductions in aboveground net primary production (ANPP). Long-term ANPP data available for each site (mean length = 16 yrs) were used as a baseline for calculating reductions in ANPP, and drought sensitivity was estimated as the reduction in ANPP per mm reduction in precipitation. Arid grasslands were the most sensitive to drought, but drought responses and sensitivity varied by more than 2-fold among the six grasslands, despite all sites experiencing 40% reductions in growing season precipitation. Although drought sensitivity generally decreased with increasing MAP as predicted, there was evidence that the identity and traits of the dominant species, as well as plant functional diversity, influenced sensitivity.

  13. Long-term measurements of CO2 flux and evapotranspiration in a Chihuahuan desert grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We measured CO2 and evapotranspiration (ET) fluxes above a Chihuahuan desert grassland from 1996 through 2001. Averaged across six years, this ecosystem was a source (positive flux)of CO2 in every month. Over that period, sustained periods of carbon uptake (negative flux)were rare. Averaged across a...

  14. Distribution and Nodulation of Spontaneous Legume Species in Grasslands and Shrublands in Mediterranean Lebanon

    Microsoft Academic Search

    Thérčse Atallah; Hélčne Rizk; Abdallah Cherfane; Firas Bou Daher; Rouba El-Alia; Phillipe De Lajuide; Samih Hajj

    2008-01-01

    In Lebanon, a country known for its biodiversity and plant richness, many threats including quarries endanger its natural habitats and ecosystems. With the objective of finding the most suitable legume-rhizobia associations for revegetation trials, we surveyed grasslands and shrublands in an altitudinal transect up to 1302 m in Mediterranean subhumid and humid regions. For comparison, two abandoned quarries on hard limestone

  15. Municipal biosolid applications: Improving ecosystem services across urban, agricultural, and wildlife interfaces in Austin, Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our project encompasses emerging contaminants, ecosystem services, and urban-agriculture-wildlife interfaces. This seminal research collaboration between USDA-ARS Grassland, Soil, and Water Research Laboratory, The City of Austin Water Utility, and Texas Parks and Wildlife Environmental Contaminant...

  16. Biomass-dependent susceptibility to drought in experimental grassland communities.

    PubMed

    Wang, Yongfan; Yu, Shixiao; Wang, Jiang

    2007-05-01

    Earlier studies indicated that plant diversity influences community resistance in biomass when ecosystems are exposed to perturbations. This relationship remains controversial, however. Here we constructed grassland communities to test the relationships between species diversity and productivity under control and experimental drought conditions. Species richness was not correlated with biomass either under constant conditions or under drought conditions. However, communities with lower biomass production were more resistant to drought stress than those that were more productive. Our results also showed that ecosystem resistance to drought is a decreasing but nonlinear function of biomass. In contrast, species diversity had little and an equivocal effect on ecosystem resistance. From the results reported here, and the results of several previous studies, we suggest that high biomass systems exhibited a greater biomass reduction in response to drought than low biomass systems did, regardless of the relationship between plant diversity and community biomass production. PMID:17498139

  17. Estimating Critical Nitrogen Loads for a California Grassland

    NASA Astrophysics Data System (ADS)

    Weiss, S. B.

    2007-12-01

    Rigorously established critical nitrogen loads to protect biodiversity can be effective policy tools for addressing the insidious impacts of atmospheric N-deposition on ecosystems. This presentation describes methods for determining critical N-loads to a California grassland ecosystem by careful examination of the continuum from emissions, transport, atmospheric chemistry, deposition, ecosystem response, and impacts on biodiversity. Nutrient-poor soils derived from serpentinite bedrock support diverse native grasslands with dazzling wildflower displays and numerous threatened and endangered species, including the Bay checkerspot butterfly. Under moderate atmospheric N-deposition, these sites are rapidly invaded by introduced nitrophilous annual grasses in the absence of appropriate grazing or other management. Critical loads to this ecosystem have been approached by measurements of atmospheric concentrations of reactive N gases using Ogawa passive samplers and seasonally averaged deposition velocities. A regional-scale pollution gradient was complemented by a very local-scale pollution gradient extending a few hundred meters downwind of a heavily traveled road in a relatively unpolluted area. The local gradient suggests a critical load of 5 kg-N ha-1 a-1 or less. The passive monitor calculations largely agree with deposition calculated with the CMAQ model at 4 km scale. Emissions of NH3 from catalytic converters are the dominant N-source at the roadway site, and are a function of traffic volume and speed. Plant tissue N-content and 15N gradients support the existence of N-deposition gradients. The complexities of more detailed calculations and measurements specific to this ecosystem include seasonal changes in LAI, temporal coincidence of traffic emissions and stomatal conductance, surface moisture, changes in oxidized versus reduced N sources, and annual weather variation. The concept of a "critical cumulative load" may be appropriate over decadal time scales in this ecosystem and other semi-arid systems where N-export is minimal.

  18. Stabilizing effects of diversity on aboveground wood production in forest ecosystems: linking patterns and processes

    E-print Network

    Jucker, Tommaso; Bouriaud, Olivier; Avacaritei, Daniel; Coomes, David A.

    2014-10-13

    of the stabilizing influence of 46 diversity on ecosystem-level processes comes from grasslands, where numerous studies have 47 shown that interannual fluctuations in primary productivity are consistently lower in diverse 48 herbaceous communities compared... , as underlying drivers may vary among ecosystems 60 (Jiang & Pu 2009; Loreau & de Mazancourt 2013; Gross et al. 2014). Although forests share 61 5 certain basic features with model systems such as grasslands, they also differ from them in a 62 number...

  19. Humans influence every ecosystem on Earth, lead-ing to impairment of natural ecosystem structure and

    E-print Network

    into grasslands (Wali et al.2002),inevitably leading to changes in ecosystem function. Conserving native land for modern land manage- ment and conservation (Hobbs and Harris 2001). Setting achievable goals University in Fort Collins. Harmony J. Dalgleish is a postdoctoral researcher in the Department of Wildland

  20. Remaining large grasslands may not be sufficient to prevent grassland bird declines

    Microsoft Academic Search

    Anthony W. King; William E. Jensen

    2008-01-01

    Grassland birds are in steep decline throughout many regions of the world. In North America, even some common species have declined by >50% over the last few decades. Declines in grassland bird populations have generally been attributed to widespread agricultural conversion of grasslands; more than 80% of North American grasslands have been converted to agriculture and other land uses, for

  1. 75 FR 73911 - Grassland Reserve Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-29

    ...authorized under the Soil and Water Resources...basic to effective soil, water, and related...negative impacts to health, human safety...emphasizes support for grazing operations, enhancement...procedure, agriculture, soil conservation, grassland...grassland protection, grazing land...

  2. Ecosystem Explorations

    NSDL National Science Digital Library

    Kristen L. Gunckel

    1999-09-01

    The Ecosystem Explorations curriculum includes eleven classroom lessons. The lessons are divided into two sections--Understanding Ecosystems and Human Connections to Ecosystems. The curriculum incorporates scientific inquiry skills, cooperative l

  3. Parallel ecological networks in ecosystems

    PubMed Central

    Olff, Han; Alonso, David; Berg, Matty P.; Eriksson, B. Klemens; Loreau, Michel; Piersma, Theunis; Rooney, Neil

    2009-01-01

    In ecosystems, species interact with other species directly and through abiotic factors in multiple ways, often forming complex networks of various types of ecological interaction. Out of this suite of interactions, predator–prey interactions have received most attention. The resulting food webs, however, will always operate simultaneously with networks based on other types of ecological interaction, such as through the activities of ecosystem engineers or mutualistic interactions. Little is known about how to classify, organize and quantify these other ecological networks and their mutual interplay. The aim of this paper is to provide new and testable ideas on how to understand and model ecosystems in which many different types of ecological interaction operate simultaneously. We approach this problem by first identifying six main types of interaction that operate within ecosystems, of which food web interactions are one. Then, we propose that food webs are structured among two main axes of organization: a vertical (classic) axis representing trophic position and a new horizontal ‘ecological stoichiometry’ axis representing decreasing palatability of plant parts and detritus for herbivores and detrivores and slower turnover times. The usefulness of these new ideas is then explored with three very different ecosystems as test cases: temperate intertidal mudflats; temperate short grass prairie; and tropical savannah. PMID:19451126

  4. Description, calibration and sensitivity analysis of the local ecosystem submodel of a global model of carbon and nitrogen cycling and the water balance in the terrestrial biosphere

    SciTech Connect

    Kercher, J.R. [Lawrence Livermore National Lab., CA (United States); Chambers, J.Q. [Lawrence Livermore National Lab., CA (United States); [California Univ., Santa Barbara, CA (United States). Dept. of Biological Sciences

    1995-10-01

    We have developed a geographically-distributed ecosystem model for the carbon, nitrogen, and water dynamics of the terrestrial biosphere TERRA. The local ecosystem model of TERRA consists of coupled, modified versions of TEM and DAYTRANS. The ecosystem model in each grid cell calculates water fluxes of evaporation, transpiration, and runoff; carbon fluxes of gross primary productivity, litterfall, and plant and soil respiration; and nitrogen fluxes of vegetation uptake, litterfall, mineralization, immobilization, and system loss. The state variables are soil water content; carbon in live vegetation; carbon in soil; nitrogen in live vegetation; organic nitrogen in soil and fitter; available inorganic nitrogen aggregating nitrites, nitrates, and ammonia; and a variable for allocation. Carbon and nitrogen dynamics are calibrated to specific sites in 17 vegetation types. Eight parameters are determined during calibration for each of the 17 vegetation types. At calibration, the annual average values of carbon in vegetation C, show site differences that derive from the vegetation-type specific parameters and intersite variation in climate and soils. From calibration, we recover the average C{sub v} of forests, woodlands, savannas, grasslands, shrublands, and tundra that were used to develop the model initially. The timing of the phases of the annual variation is driven by temperature and light in the high latitude and moist temperate zones. The dry temperate zones are driven by temperature, precipitation, and light. In the tropics, precipitation is the key variable in annual variation. The seasonal responses are even more clearly demonstrated in net primary production and show the same controlling factors.

  5. Greenhouse gas emissions from a managed grassland

    Microsoft Academic Search

    S. K. Jones; R. M. Rees; U. M. Skiba; B. C. Ball

    2005-01-01

    Managed grasslands contribute to global warming by the exchange of the greenhouse gases carbon dioxide, nitrous oxide and methane. To reduce uncertainties of the global warming potential of European grasslands and to assess potential mitigation options, an integrated approach quantifying fluxes from all three gases is needed. Greenhouse gas emissions from a grassland site in the SE of Scotland were

  6. Disturbance-induced bird diversity in early successional habitats in the humid temperate region of northern Japan

    Microsoft Academic Search

    Reiko Kurosawa

    2009-01-01

    The positive role of moderate natural disturbance is less known for a mobile organism such as birds, compared to sessile organisms.\\u000a In the face of recent declines of grassland birds, it is necessary to identify the mechanism to maintain avian diversity in\\u000a early successional open habitats in different regions. In the humid temperate region, the predominant habitat type is woody

  7. Intermediate Coupling between Aboveground and Belowground Biomass Maximises the Persistence of Grasslands

    PubMed Central

    Scheiter, Simon; Higgins, Steven I.

    2013-01-01

    Aboveground and belowground biomass compartments of vegetation fulfil different functions and they are coupled by complex interactions. These compartments exchange water, carbon and nutrients and the belowground biomass compartment has the capacity to buffer vegetation dynamics when aboveground biomass is removed by disturbances such as herbivory or fire. However, despite their importance, root-shoot interactions are often ignored in more heuristic vegetation models. Here, we present a simple two-compartment grassland model that couples aboveground and belowground biomass. In this model, the growth of belowground biomass is influenced by aboveground biomass and the growth of aboveground biomass is influenced by belowground biomass. We used the model to explore how the dynamics of a grassland ecosystem are influenced by fire and grazing. We show that the grassland system is most persistent at intermediate levels of aboveground-belowground coupling. In this situation, the system can sustain more extreme fire or grazing regimes than in the case of strong coupling. In contrast, the productivity of the system is maximised at high levels of coupling. Our analysis suggests that the yield of a grassland ecosystem is maximised when coupling is strong, however, the intensity of disturbance that can be sustained increases dramatically when coupling is intermediate. Hence, the model predicts that intermediate coupling should be selected for as it maximises the chances of persistence in disturbance driven ecosystems. PMID:23637792

  8. Intermediate coupling between aboveground and belowground biomass maximises the persistence of grasslands.

    PubMed

    Scheiter, Simon; Higgins, Steven I

    2013-01-01

    Aboveground and belowground biomass compartments of vegetation fulfil different functions and they are coupled by complex interactions. These compartments exchange water, carbon and nutrients and the belowground biomass compartment has the capacity to buffer vegetation dynamics when aboveground biomass is removed by disturbances such as herbivory or fire. However, despite their importance, root-shoot interactions are often ignored in more heuristic vegetation models. Here, we present a simple two-compartment grassland model that couples aboveground and belowground biomass. In this model, the growth of belowground biomass is influenced by aboveground biomass and the growth of aboveground biomass is influenced by belowground biomass. We used the model to explore how the dynamics of a grassland ecosystem are influenced by fire and grazing. We show that the grassland system is most persistent at intermediate levels of aboveground-belowground coupling. In this situation, the system can sustain more extreme fire or grazing regimes than in the case of strong coupling. In contrast, the productivity of the system is maximised at high levels of coupling. Our analysis suggests that the yield of a grassland ecosystem is maximised when coupling is strong, however, the intensity of disturbance that can be sustained increases dramatically when coupling is intermediate. Hence, the model predicts that intermediate coupling should be selected for as it maximises the chances of persistence in disturbance driven ecosystems. PMID:23637792

  9. Monitoring for change: Using generalised least squares, non-metric multidimensional scaling, and the Mantel test on western Montana grasslands

    Microsoft Academic Search

    P. Sikkink; A. Zuur; E. Ieno; G. Smith

    Monitoring programs are vital to assess how plant community succession is affected by environmental change. Each plant community\\u000a has many biologic, climatic, and abiotic interactions that affect its species differently over time. In temperate grasslands,\\u000a plant community composition and species dominance can change rapidly in response to changes in the timing and amount of precipitation\\u000a (Fay et al. 2002; Knapp

  10. Parts of Amazon on the verge of forest-to-grassland shift

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-10-01

    The stability of the Amazon rainforest and the ecosystem's resilience to widespread deforestation may be much lower than previously thought. The replacement of stands of trees with grassland changes evapotranspiration rates and atmospheric moisture convergence, which, in turn, reduce regional rainfall. This feedback effect could drive further deforestation. Previous research indicated that a dramatic shift from forest to grassland could overtake the Amazon when the total deforested area hits 40% to 50% of the forest's current size. New research by Pires and Costa, however, found that the deforestation needed to trigger this equilibrium shift is much lower, closer to just 10%.

  11. Land use affects the resistance and resilience of carbon dynamics of mountain grassland to extreme drought

    NASA Astrophysics Data System (ADS)

    Ingrisch, Johannes; Karlowsky, Stefan; Hasibeder, Roland; Anadon-Rosell, Alba; Augusti, Angela; Scheld, Sarah; König, Alexander; Gleixner, Gerd; Bahn, Michael

    2015-04-01

    Climatic extremes like droughts are expected to occur more frequently and to be more severe in a future climate and have been shown to strongly affect the carbon (C) cycle. Few studies have so far explored how the management intensity of ecosystems and land-use changes alter C cycle responses to extreme climatic events. In many mountain areas land-use changes have been taking place at a rapid pace and have altered plant species composition and biogeochemical cycles. It is still unknown whether and how abandonment of mountain grasslands affects the resistance and the resilience of carbon dynamics to extreme drought. We carried out an in situ experiment to test the hypothesis that abandonment increases the resistance of grassland C dynamics to extreme drought, but decreases its resilience (i.e. post-drought recovery). In a common garden experiment at a mountain meadow in the Austrian Central Alps we exposed large intact monoliths from the meadow and a nearby abandoned grassland to extreme drought conditions during the main growth period in late spring. We measured above- and belowground productivity and net ecosystem exchange and its components over the course of the drought and during the recovery to assess and quantify their resistance and resilience. Furthermore, we analysed the coupling of the two major ecosystem CO2 fluxes, photosynthesis and soil respiration, as based on 13CO2 pulse labelling campaigns at peak drought and during post-drought recovery using isotope laser spectroscopy. Four weeks of early season drought induced a strong decrease of aboveground biomass at the mountain meadow, whereas no effect was observed for the abandoned grassland. At peak drought gross primary productivity was reduced at both grasslands compared to the respective controls, but with a stronger decrease at the meadow (80%) compared to the abandoned grassland (60%). The same pattern was observed for ecosystem respiration. However, the effect was less pronounced compared to carbon uptake (meadow 60%, abandoned grassland 25%). After the drought gross primary productivity reached values of control plots within 9 days and 17 days at the meadow and the abandoned site, respectively, resulting in distinctly higher recovery rates at the meadow. From our study we conclude that the managed meadow had a smaller resistance but a higher resilience to extreme drought compared to the abandoned grassland.

  12. Avian assemblages on altered grasslands

    USGS Publications Warehouse

    Knopf, Fritz L.

    1994-01-01

    Grasslands comprise 17% of the North American landscape but provide primary habitat for only 5% of native bird species. On the Great Plains, grasslands include an eastern component of tall grasses and a western component of short grasses, both of which have been regionally altered by removing native grazers, plowing sod, draining wetlands, and encouraging woody vegetation. As a group, populations of endemic bird species of the grasslands have declined more than others (including neotropical migrants) in the last quarter century. Individually, populations of the Upland Sandpiper and McCown’s Longspur have increased; the wetlands-associated Marbled Godwit and Wilson’s Phalarope appear stable; breeding ranges are shifting for the Ferruginous Hawk, Mississippi Kite, Short-eared Owl, Upland Sandpiper, Horned Lark, Vesper, Savannah, and Henslow’s sparrows, and Western Meadowlark; breeding habitats are disappearing locally for Franklin’s Gull, Dickcissel, Henslow’s and Grasshopper sparrows. Lark Bunting, and Eastern Meadowlark; and populations are declining throughout the breeding ranges for Mountain Plover, and Cassin’s and Clay-colored sparrows. Declines of these latter three species, and also the Franklin’s Gull, presumably are due to ecological phenomena on their respective wintering areas. Unlike forest species that winter in the neotropics, most birds that breed in the North American grasslands also winter on the continent and problems driving declines in grassland species are associated almost entirely with North American processes. Contemporary programs and initiatives hold promise for the conservation of breeding habitats for these birds. Ecological ignorance of wintering habits and habitats clouds the future of the endemic birds of grasslands, especially those currently experiencing widespread declines across breeding locales.

  13. Improved grazing management may increase soil carbon sequestration in temperate steppe

    PubMed Central

    Chen, Wenqing; Huang, Ding; Liu, Nan; Zhang, Yingjun; Badgery, Warwick B.; Wang, Xiaoya; Shen, Yue

    2015-01-01

    Different grazing strategies impact grassland plant production and may also regulate the soil carbon formation. For a site in semiarid temperate steppe, we studied the effect of combinations of rest, high and moderate grazing pressure over three stages of the growing season, on the process involved in soil carbon sequestration. Results show that constant moderate grazing (MMM) exhibited the highest root production and turnover accumulating the most soil carbon. While deferred grazing (RHM and RMH) sequestered less soil carbon compared to MMM, they showed higher standing root mass, maintained a more desirable pasture composition, and had better ability to retain soil N. Constant high grazing pressure (HHH) caused diminished above- and belowground plant production, more soil N losses and an unfavorable microbial environment and had reduced carbon input. Reducing grazing pressure in the last grazing stage (HHM) still had a negative impact on soil carbon. Regression analyses show that adjusting stocking rate to ~5SE/ha with ~40% vegetation utilization rate can get the most carbon accrual. Overall, the soil carbon sequestration in the temperate grassland is affected by the grazing regime that is applied, and grazing can be altered to improve soil carbon sequestration in the temperate steppe. PMID:26137980

  14. Improved grazing management may increase soil carbon sequestration in temperate steppe.

    PubMed

    Chen, Wenqing; Huang, Ding; Liu, Nan; Zhang, Yingjun; Badgery, Warwick B; Wang, Xiaoya; Shen, Yue

    2015-01-01

    Different grazing strategies impact grassland plant production and may also regulate the soil carbon formation. For a site in semiarid temperate steppe, we studied the effect of combinations of rest, high and moderate grazing pressure over three stages of the growing season, on the process involved in soil carbon sequestration. Results show that constant moderate grazing (MMM) exhibited the highest root production and turnover accumulating the most soil carbon. While deferred grazing (RHM and RMH) sequestered less soil carbon compared to MMM, they showed higher standing root mass, maintained a more desirable pasture composition, and had better ability to retain soil N. Constant high grazing pressure (HHH) caused diminished above- and belowground plant production, more soil N losses and an unfavorable microbial environment and had reduced carbon input. Reducing grazing pressure in the last grazing stage (HHM) still had a negative impact on soil carbon. Regression analyses show that adjusting stocking rate to ~5SE/ha with ~40% vegetation utilization rate can get the most carbon accrual. Overall, the soil carbon sequestration in the temperate grassland is affected by the grazing regime that is applied, and grazing can be altered to improve soil carbon sequestration in the temperate steppe. PMID:26137980

  15. Does complementary resource use enhance ecosystem functioning? A model of light competition in plant communities

    Microsoft Academic Search

    Shigeo Yachi; Michel Loreau

    2007-01-01

    Abstract Recent experiments,on grassland ecosystems,have shown,that biodiversity can enhance ecosystem,processes such as plant biomass production. Functional complementarity,is generally regarded,as the main,class of mechanisms,generating these effects of biodiversity on ecosystem,functioning. Although intuitively appealing and supported by some data, the complementarity hypothesis has been little explored theoretically using mechanistic approaches. Here, we present a simple dynamical model for a light-limited terrestrial ecosystem,to

  16. New spectral vegetation indices based on the near-infrared shoulder wavelengths for remote detection of grassland phytomass

    PubMed Central

    VESCOVO, LORIS; WOHLFAHRT, GEORG; BALZAROLO, MANUELA; PILLONI, SEBASTIAN; SOTTOCORNOLA, MATTEO; RODEGHIERO, MIRCO; GIANELLE, DAMIANO

    2013-01-01

    This article examines the possibility of exploiting ground reflectance in the near-infrared (NIR) for monitoring grassland phytomass on a temporal basis. Three new spectral vegetation indices (infrared slope index, ISI; normalized infrared difference index, NIDI; and normalized difference structural index, NDSI), which are based on the reflectance values in the H25 (863–881 nm) and the H18 (745–751 nm) Chris Proba (mode 5) bands, are proposed. Ground measurements of hyperspectral reflectance and phytomass were made at six grassland sites in the Italian and Austrian mountains using a hand-held spectroradiometer. At full canopy cover, strong saturation was observed for many traditional vegetation indices (normalized difference vegetation index (NDVI), modified simple ratio (MSR), enhanced vegetation index (EVI), enhanced vegetation index 2 (EVI 2), renormalized difference vegetation index (RDVI), wide dynamic range vegetation index (WDRVI)). Conversely, ISI and NDSI were linearly related to grassland phytomass with negligible inter-annual variability. The relationships between both ISI and NDSI and phytomass were however site specific. The WinSail model indicated that this was mostly due to grassland species composition and background reflectance. Further studies are needed to confirm the usefulness of these indices (e.g. using multispectral specific sensors) for monitoring vegetation structural biophysical variables in other ecosystem types and to test these relationships with aircraft and satellite sensors data. For grassland ecosystems, we conclude that ISI and NDSI hold great promise for non-destructively monitoring the temporal variability of grassland phytomass. PMID:24347746

  17. Functional patterns in an annual grassland during an AVIRIS overflight

    NASA Technical Reports Server (NTRS)

    Gamon, John A.; Field, Christopher B.; Roberts, Dar A.; Ustin, Susan L.; Valentini, Riccardo

    1993-01-01

    This study relates Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imagery to ground measurements of vegetation distribution, physiology, and productivity at Stanford University's Jasper Ridge Biological Preserve. Primary efforts focused on a 9-ha region of annual grassland where we completed a detailed ground-based study in conjunction with a 15 May 1991 AVIRIS overflight. Spectral mixture analysis and the normalized difference vegetation index (NDVI) calculated from AVIRIS data were used to evaluate spatial patterns of vegetation type, productivity, and potential physiological activity. Concurrent ground sampling revealed a high degree of correlation between NDVI and estimates of canopy chemistry, structure, productivity, and CO2 flux, supporting the use of imaging spectrometry to estimate spatial and temporal trends in vegetation physiology and productivity in this relatively simple grassland ecosystem. Geostatistical analyses of both ground and AVIRIS data supported the conclusion that the AVIRIS pixel size was suitable for describing the influence of major landscape features in this grassland and that spatial detail would be lost at slightly larger pixel sizes typical of other imaging spectrometers.

  18. Canopy reflectance modeling in a tropical wooded grassland

    NASA Technical Reports Server (NTRS)

    Simonett, David; Franklin, Janet

    1986-01-01

    Geometric/optical canopy reflectance modeling and spatial/spectral pattern recognition is used to study the form and structure of savanna in West Africa. An invertible plant canopy reflectance model is tested for its ability to estimate the amount of woody vegetation from remotely sensed data in areas of sparsely wooded grassland. Dry woodlands and wooded grasslands, commonly referred to as savannas, are important ecologically and economically in Africa, and cover approximately forty percent of the continent by some estimates. The Sahel and Sudan savannas make up the important and sensitive transition zone between the tropical forests and the arid Sahara region. The depletion of woody cover, used for fodder and fuel in these regions, has become a very severe problem for the people living there. LANDSAT Thematic Mapper (TM) data is used to stratify woodland and wooded grassland into areas of relatively homogeneous canopy cover, and then an invertible forest canopy reflectance model is applied to estimate directly the height and spacing of the trees in the stands. Because height and spacing are proportional to biomass in some cases, a successful application of the segmentation/modeling techniques will allow direct estimation of tree biomass, as well as cover density, over significant areas of these valuable and sensitive ecosystems. The model being tested in sites in two different bioclimatic zones in Mali, West Africa, will be used for testing the canopy model. Sudanian zone crop/woodland test sites were located in the Region of Segou, Mali.

  19. Earthworm invasion into previously earthworm-free temperate and boreal forests

    Microsoft Academic Search

    Lee E. Frelich; Cindy M. Hale; Stefan Scheu; Andrew R. Holdsworth; Liam Heneghan; Patrick J. Bohlen; Peter B. Reich

    2006-01-01

    Earthworms are keystone detritivores that can influence primary producers by changing seedbed conditions, soil characteristics, flow of water, nutrients and carbon, and plant–herbivore interactions. The invasion of European earthworms into previously earthworm-free temperate and boreal forests of North America dominated by Acer, Quercus, Betula, Pinus and Populus has provided ample opportunity to observe how earthworms engineer ecosystems. Impacts vary with

  20. Influence of atmospheric CO2 enrichment on methane consumption in a temperate forest soil

    Microsoft Academic Search

    REBECCA L. P HILLIPS; STEPHEN C. W HALEN; WILLIAM H. S CHLESINGER

    2001-01-01

    Rates of atmospheric CH4 consumption of soils in temperate forest were com- pared in plots continuously enriched with CO2 at 200 m LL -1 above ambient and in control plots exposed to the ambient atmosphere of 360 m LC O 2 L -1 . The pur- pose was to determine if ecosystem atmospheric CO2 enrichment would alter soil microbial CH4

  1. Detrimental Influence of Invasive Earthworms on North American Cold-Temperate Forest Soils

    ERIC Educational Resources Information Center

    Enerson, Isabel

    2012-01-01

    The topic of invasive earthworms is a timely concern that goes against many preconceived notions regarding the positive benefits of all worms. In the cold-temperate forests of North America invasive worms are threatening forest ecosystems, due to the changes they create in the soil, including decreases in C:N ratios and leaf litter, disruption of…

  2. Disparate distribution patterns between canopy and subcanopy life-forms in two temperate North American forests

    Microsoft Academic Search

    R. D. Rheinhardt

    1992-01-01

    Quantitative vegetational data of canopy and woody subcanopy species (two life-forms adapted to occupy different strata at maturity) were compared with data collected in two temperate forest ecosystems to determine whether they exhibit a similar pattern of distribution. Tidal freshwater swamps (21 stands) and southern Appalachian forests (19 stands) were examined from data obtained using identical sampling methods. Separate structural

  3. THE NORTHERN FLYING SQUIRREL AS AN INDICATOR SPECIES OF TEMPERATE RAIN FOREST: TEST OF AN HYPOTHESIS

    Microsoft Academic Search

    WINSTON P. S MITH; SCOTT M. GENDE; JEFFREY V. N ICHOLS

    2005-01-01

    Management indicator species (MIS) often are selected because their life history and demographics are thought to reflect a suite of ecosystem conditions that are too difficult or costly to measure directly. The northern flying squirrel ( Glaucomys sabrinus) has been proposed as an MIS of temperate rain forest of southeastern Alaska based on previous studies in the Pacific Northwest that

  4. Intensive management in grasslands causes diffuse water pollution at the farm scale.

    PubMed

    Peukert, Sabine; Griffith, Bruce A; Murray, Phillip J; Macleod, Christopher J A; Brazier, Richard E

    2014-11-01

    Arable land use is generally assumed to be the largest contributor to agricultural diffuse pollution. This study adds to the growing evidence that conventional temperate intensively managed lowland grasslands contribute significantly to soil erosion and diffuse pollution rates. This is the first grassland study to monitor hydrological characteristics and multiple pollutant fluxes (suspended sediment [SS] and the macronutrients: total oxidized nitrogen-N [TON], total phosphorus [TP], and total carbon [TC]) at high temporal resolution (monitoring up to every 15 min) over 1 yr. Monitoring was conducted across three fields (6.5-7.5 ha) on the North Wyke Farm Platform, UK. The estimated annual erosion rates (up to 527.4 kg ha), TP losses (up to 0.9 kg ha), and TC losses (up to 179 kg ha) were similar to or exceeded the losses reported for other grassland, mixed land-use, and arable sites. Annual yields of TON (up to 3 kg ha) were less than arable land-use fluxes and earlier grassland N studies, an important result as the study site is situated within a Nitrate Vulnerable Zone. The high-resolution monitoring allowed detailed "system's functioning" understanding of hydrological processes, mobilization- transport pathways of individual pollutants, and the changes of the relative importance of diffuse pollutants through flow conditions and time. Suspended sediment and TP concentrations frequently exceeded water quality guidelines recommended by the European Freshwater Fisheries Directive (25 mg L) and the European Water Framework Directive (0.04 mg soluble reactive P L), suggesting that intensively managed grasslands pose a significant threat to receiving surface waters. Such sediment and nutrient losses from intensively managed grasslands should be acknowledged in land management guidelines and advice for future compliance with surface water quality standards. PMID:25602218

  5. Impact of grazing on carbon balance of a Belgian grassland

    NASA Astrophysics Data System (ADS)

    Jérôme, Elisabeth; Beckers, Yves; Bodson, Bernard; Moureaux, Christine; Dumortier, Pierre; Beekkerk van Ruth, Joran; Aubinet, Marc

    2013-04-01

    This work analyzes the impact of grazing on the carbon balance of a grassland grazed by the Belgian Blue breed of cattle. The research was run at the Dorinne terrestrial observatory (DTO). The experimental site is a permanent grassland of ca. 4.2 ha located in the Belgian Condroz (50° 18' 44" N; 4° 58' 07" E; 248 m asl.). Other studies are conducted at the DTO including measurements of methane (CH4) and nitrous oxide fluxes (Dumortier et al., Geophysical Research Abstracts, Vol. 15, EGU2013-2083-1, 2013; Beekkerk van Ruth et al., Geophysical Research Abstracts, Vol. 15, EGU2013-3211, 2013, respectively). Grassland carbon budget (Net Biome Productivity, NBP) was calculated from Net Ecosystem Exchange (NEE) measured by eddy covariance by taking imports and exports of organic C and losses of carbon as CH4 into account. After 2 years of measurements (May 2010 - May 2012), the grassland behaved on average as a CO2 source (NEE = 73 ±31 g C m-2 y-1). After inclusion of all the C inputs and outputs the site was closed to equilibrium (NBP = 23 ±34 g C m-2 y-1). To analyze the impact of grazing on CO2 fluxes, we studied the temporal evolution of gross maximal photosynthetic capacity GPPmax and dark respiration Rd (deduced from the response of daytime fluxes to radiation over 5-day windows). We calculated GPPmax and Rd variation between the end and the beginning of grazing or non-grazing periods (?GPPmax and ?Rd, respectively). We observed a significant decrease of GPPmax during grazing periods and measured a ?GPPmax dependence on the average stocking rate. This allows us to quantify the assimilation reduction due to grass consumption by cattle. On the contrary, no Rd decrease was observed during grazing periods. Moreover, we found that cumulated monthly NEE increased significantly with the average stocking rate. In addition, a confinement experiment was carried out in order to analyze livestock contribution to Total Ecosystem Respiration. Each experiment extended over two days: the first day, cattle was confined in the footprint of the eddy covariance set-up (1.76 ha, 27 LU ha-1) and the second day, it was removed from it. We compared filtered half-hourly data made at 24h intervals, in the presence or absence of cattle, considering that environmental conditions were equivalent (air temperature, wind speed, radiation and wind direction). Results showed that CO2 fluxes were significantly higher when cattle were on the plot. Livestock contribution estimation to CO2 fluxes was on average 6.6 ?mol m-2 s-1. Key words: grassland, carbon budget, carbon dioxide exchange, impact of grazing.

  6. Meltwater migration in temperate ice

    NASA Astrophysics Data System (ADS)

    Schoof, C.; Hewitt, I.

    2014-12-01

    Frictional heating in the fast deforming ice of an ice stream potentially warms the ice to the melting point and there is evidence that a substantial region of temperate ice may exist near the base of the ice-stream margins. The production of meltwater in such a region alters the heat balance and the usual temperature equation solved in ice-sheet models must be modified to take account of this. In some cases, simply capping the temperature at the melting point and assuming excess heating produces meltwater can give the correct dynamics. But in general this is too simplistic an approach. Meltwater drains under gravity and dynamic pressure gradients, and the resulting transport of heat must be accounted for in order to correctly locate the boundaries between temperate and subtemperate ice. In this study, we look in detail at the dynamics of the temperate ice, focussing on the movement of meltwater in a compacting, viscous matrix of ice and the way in which meltwater transport influences the subtemperate-temperate transition. Four canonical cases can be considered: when the ice flows into or out of the temperate region, and when the meltwater flows towards or away from the interface. We examine the possible formation of boundary layers near these regions, and discuss how these may be responsible for channeling meltwater to the ice bed. We also discuss the use of numerical enthalpy and enthalpy-gradient methods, and the conditions under which these can correctly describe the dynamics.

  7. MANAGEMENT OF ALFALFA IN GRASSLANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alfalfa can enhance the quality and quantity of forages on range and grasslands and new cultivars of alfalfa are being developed with improved grazing tolerance; however, little is known regarding defoliation management. A hay-type (Vernal) and 2 grazing-type (Anik and SCMF 3713) alfalfas were spac...

  8. PHOSPHORUS EXPORT FROM AERATED GRASSLANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface-applied manures are of particular concern in the Southern Piedmont (USA) because of a high concentration of broiler production. As these manures can contribute to P in runoff, a study was conducted to examine the water conservation potential of mechanical aeration of grasslands which has po...

  9. Emissions from Miombo Woodland and Dambo Grassland Savanna Fires

    NASA Technical Reports Server (NTRS)

    Sinha, Parikhit; Hobbs, Peter V.; Yokelson, Robert J.; Blake, Donald R.; Gao, Song; Kirchstetter, Thomas W.

    2004-01-01

    Airborne measurements of trace gases and particles over and downwind of two prescribed savanna fires in Zambia are described. The measurements include profiles through the smoke plumes of condensation nucleus concentrations and normalized excess mixing ratios of particles and gases, emission factors for 42 trace gases and seven particulate species, and vertical profiles of ambient conditions. The fires were ignited in plots of miombo woodland savanna, the most prevalent savanna type in southern Africa, and dambo grassland savanna, an important enclave of miombo woodland ecosystems. Emission factors for the two fires are combined with measurements of fuel loading, combustion factors, and burned area (derived from satellite burn scar retrievals) to estimate the emissions of trace gases and particles from woodland and grassland savanna fires in Zambia and southern Africa during the dry season (May-October) of 2000. It is estimated that the emissions of CO2, CO, total hydrocarbons, nitrogen oxides (NOx as NO), sulfur dioxide (SO2), formaldehyde, methyl bromide, total particulate matter, and black carbon from woodland and grassland savanna fires during the dry season of 2000 in southern Africa contributed 12.3%, 12.6%, 5.9%, 10.3%, 7.5%, 24.2%, 2.8%, 17.5%, and 11.1%, respectively, of the average annual emissions from all types of savanna fires worldwide. In 2000 the average annual emissions of methane, ethane, ethene, acetylene, propene, formaldehyde, methanol, and acetic acid from the use of biofuels in Zambia were comparable to or exceeded dry season emissions of these species from woodland and grassland savanna fires in Zambia.

  10. COMPARISON OF THREE METHODS TO PROJECT FUTURE BASELINE CARBON EMISSIONS IN TEMPERATE RAINFOREST, CURINANCO, CHILE

    SciTech Connect

    Patrick Gonzalez; Antonio Lara; Jorge Gayoso; Eduardo Neira; Patricio Romero; Leonardo Sotomayor

    2005-07-14

    Deforestation of temperate rainforests in Chile has decreased the provision of ecosystem services, including watershed protection, biodiversity conservation, and carbon sequestration. Forest conservation can restore those ecosystem services. Greenhouse gas policies that offer financing for the carbon emissions avoided by preventing deforestation require a projection of future baseline carbon emissions for an area if no forest conservation occurs. For a proposed 570 km{sup 2} conservation area in temperate rainforest around the rural community of Curinanco, Chile, we compared three methods to project future baseline carbon emissions: extrapolation from Landsat observations, Geomod, and Forest Restoration Carbon Analysis (FRCA). Analyses of forest inventory and Landsat remote sensing data show 1986-1999 net deforestation of 1900 ha in the analysis area, proceeding at a rate of 0.0003 y{sup -1}. The gross rate of loss of closed natural forest was 0.042 y{sup -1}. In the period 1986-1999, closed natural forest decreased from 20,000 ha to 11,000 ha, with timber companies clearing natural forest to establish plantations of non-native species. Analyses of previous field measurements of species-specific forest biomass, tree allometry, and the carbon content of vegetation show that the dominant native forest type, broadleaf evergreen (bosque siempreverde), contains 370 {+-} 170 t ha{sup -1} carbon, compared to the carbon density of non-native Pinus radiata plantations of 240 {+-} 60 t ha{sup -1}. The 1986-1999 conversion of closed broadleaf evergreen forest to open broadleaf evergreen forest, Pinus radiata plantations, shrublands, grasslands, urban areas, and bare ground decreased the carbon density from 370 {+-} 170 t ha{sup -1} carbon to an average of 100 t ha{sup -1} (maximum 160 t ha{sup -1}, minimum 50 t ha{sup -1}). Consequently, the conversion released 1.1 million t carbon. These analyses of forest inventory and Landsat remote sensing data provided the data to evaluate the three methods to project future baseline carbon emissions. Extrapolation from Landsat change detection uses the observed rate of change to estimate change in the near future. Geomod is a software program that models the geographic distribution of change using a defined rate of change. FRCA is an integrated spatial analysis of forest inventory, biodiversity, and remote sensing that produces estimates of forest biodiversity and forest carbon density, spatial data layers of future probabilities of reforestation and deforestation, and a projection of future baseline forest carbon sequestration and emissions for an ecologically-defined area of analysis. For the period 1999-2012, extrapolation from Landsat change detection estimated a loss of 5000 ha and 520,000 t carbon from closed natural forest; Geomod modeled a loss of 2500 ha and 250 000 t; FRCA projected a loss of 4700 {+-} 100 ha and 480,000 t (maximum 760,000 t, minimum 220,000 t). Concerning labor time, extrapolation for Landsat required 90 actual days or 120 days normalized to Bachelor degree level wages; Geomod required 240 actual days or 310 normalized days; FRCA required 110 actual days or 170 normalized days. Users experienced difficulties with an MS-DOS version of Geomod before turning to the Idrisi version. For organizations with limited time and financing, extrapolation from Landsat change provides a cost-effective method. Organizations with more time and financing could use FRCA, the only method where that calculates the deforestation rate as a dependent variable rather than assuming a deforestation rate as an independent variable. This research indicates that best practices for the projection of baseline carbon emissions include integration of forest inventory and remote sensing tasks from the beginning of the analysis, definition of an analysis area using ecological characteristics, use of standard and widely used geographic information systems (GIS) software applications, and the use of species-specific allometric equations and wood densities developed for local species.

  11. Measuring dry plant residues in grasslands: A case study using AVIRIS

    NASA Technical Reports Server (NTRS)

    Fitzgerald, Michael; Ustin, Susan L.

    1992-01-01

    Grasslands, savannah, and hardwood rangelands are critical ecosystems and sensitive to disturbance. Approximately 20 percent of the Earth's surface are grasslands and represent 3 million ha. in California alone. Developing a methodology for estimating disturbance and the effects of cumulative impacts on grasslands and rangelands is needed to effectively monitor these ecosystems. Estimating the dry biomass residue remaining on rangelands at the end of the growing season provides a basis for evaluating the effectiveness of land management practices. The residual biomass is indicative of the grazing pressure and provides a measure of the system capacity for nutrient cycling since it represents the maximum organic matter available for decomposition, and finally, provides a measure of the erosion potential for the ecosystem. Remote sensing presents a possible method for measuring dry residue. However, current satellites have had limited application due to the coarse spatial scales (relative to the patch dynamics) and insensitivity of the spectral coverage to resolve dry plant material. Several hypotheses for measuring the biochemical constituents of dry plant material, particularly cellulose and lignin, using high spectral resolution sensors were proposed. The use of Airborne Visible/Infrared Imaging Spectrometers (AVIRIS) to measure dry plant residues over an oak savannah on the eastern slopes of the Coast Range in central California was investigated and it was asked what spatial and spectral resolutions are needed to quantitatively measure dry plant biomass in this ecosystem.

  12. Water and Productivity of Floodplain Grasslands: Exploring Linkages through Experimentations and Models in the Tana River Delta, Kenya

    NASA Astrophysics Data System (ADS)

    Leauthaud, C.; Musila, W.; Kergoat, L.; Hiernaux, P.; Manuela, G.; Duvail, S.

    2014-12-01

    Floodplain grasslands have one of the highest productivities of non-cultivated ecosystems on Earth. They procure a wide variety of benefits to human beings. In Eastern Africa, grasslands of Echinochloa stagnina are primordial for pastoralists as highly productive dry-season grazing zones. Regular flooding is a critical property in maintaining their productivity and resulting services. Yet, construction of hydrologic infrastructure modifies the flooding regime of rivers and the consequences on downstream floodplain grasslands need to be assessed. This presentation focuses on quantifying the productivity of the floodplain grasslands in the Tana River Delta, Kenya, in order to assess potential changes under varying flooding regimes. The interactions between growth and floods are explored firstly at an experimental site, then through the construction of a process-based plant growth model adapted to floodplain grasslands. The 15-month experiment consisted in quantifying daily growth rates under various rainfall, irrigation, cutting and flooding regimes . Floods increased growth rates three-folds, and high productivities were maintained after the floods. The cutting regime and contribution of non-flood water also influenced productivity. Modelling allowed exploring the underlying processes explaining such behaviour. In an exploratory endeavour, the productivity of the grassland at the ecosystem scale was assessed with the model for a variety of flood and non-flooded scenarios. Decreasing floods led to a drop in annual productivity that could have serious consequences for the livestock keeping activities of the zone. This research highlights the importance of floods in the maintenance of high productivities for a floodplain grassland typical of East Africa, and maybe of the Sahelian band. The model, once further validated, could be used on other floodplain grasslands, such as those of the Niger delta. Results for the Tana River Delta would need to be discussed with the stakeholders so that proper action can be taken.

  13. Effect of microtopography and species composition on small-scale variability of CO2 fluxes in a subalpine grassland

    NASA Astrophysics Data System (ADS)

    Galvagno, Marta; Filippa, Gianluca; Cremonese, Edoardo; Morra di Cella, Umberto; Isabellon, Michel

    2015-04-01

    Grassland ecosystems cover around 30% of the Earth's land surface and consequently play an important role in the terrestrial carbon balance. Climate and land use changes have a significant effect on the sink/source strength of grasslands, especially in mountain regions. For these reasons the carbon cycle of high-altitude grasslands has recently received higher attention, however little is know on the within-ecosystem variability in CO2 fluxes. In fact, alpine and subalpine grasslands are often characterized by complex topography which generates differences in snowmelt dynamics at site level and related different microhabitats. The deriving patchy distribution of vegetation leads to the coexistence of different plant functional traits and developmental strategies within the same ecosystem. In this study we evaluated the effect of microtopography and associated vegetation types on the CO2 flux components of an unamanaged subalpine grassland located at 2160 m asl, by means of automated clear and opaque chambers. In order to disentangle the contribution of different growth forms to the whole ecosystem carbon sequestration we compare chambers with eddy covariance CO2 flux data. Results show that: i) different growth forms are associated with concave o convex shapes of the terrain and, in detail, grass species dominate in convex areas while forbs are especially found in concave ones ii) two distinct CO2 flux trajectories associated to these shapes can be distinguished in this ecosystem: graminoids show a later beginning of the carbon uptake period but higher CO2 net uptake (NEE), while forbs develop just after snowmelt but show lower NEE. The observed small-scale patterns of carbon sequestration may reflect the distinct vegetation type responses to snowmelt and different adaptations to resource use efficiency (light, temperature, nutrients) specific of their own microhabitat. Further investigations will be carried on to better evaluate the role of microhabitat-related environmental factors, such as temperature, soil water content and nutrients on small-scale variability in species distribution and heterogeneity in ecosystem processes.

  14. Plague bacterium as a transformer species in prairie dogs and the grasslands of western North America.

    PubMed

    Eads, David A; Biggins, Dean E

    2015-08-01

    Invasive transformer species change the character, condition, form, or nature of ecosystems and deserve considerable attention from conservation scientists. We applied the transformer species concept to the plague bacterium Yersinia pestis in western North America, where the pathogen was introduced around 1900. Y. pestis transforms grassland ecosystems by severely depleting the abundance of prairie dogs (Cynomys spp.) and thereby causing declines in native species abundance and diversity, including threatened and endangered species; altering food web connections; altering the import and export of nutrients; causing a loss of ecosystem resilience to encroaching invasive plants; and modifying prairie dog burrows. Y. pestis poses an important challenge to conservation biologists because it causes trophic-level perturbations that affect the stability of ecosystems. Unfortunately, understanding of the effects of Y. pestis on ecosystems is rudimentary, highlighting an acute need for continued research. PMID:25817984

  15. Assessing long-term land-use legacies in subalpine grasslands by using a plant trait-based generic modelling framework

    Microsoft Academic Search

    Fabien Quétier; Sandra Lavorel; Pierre Liancourt; Aurélie Thébault; Ian D. Davies

    2011-01-01

    Background: In European mountains, where semi-natural grasslands have high cultural and nature conservation value, land-use legacies from past ploughing are associated with distinct floristic compositions and ecosystem properties. It remains unknown if these differences are stable or if post-arable grasslands are only transient states that eventually follow a predictable successional pathway.Aims: We use a generic vegetation dynamics model based on

  16. Assessing long-term land-use legacies in subalpine grasslands by using a plant trait-based generic modelling framework

    Microsoft Academic Search

    Fabien Quétier; Sandra Lavorel; Pierre Liancourt; Aurélie Thébault; Ian D. Davies

    2012-01-01

    Background: In European mountains, where semi-natural grasslands have high cultural and nature conservation value, land-use legacies from past ploughing are associated with distinct floristic compositions and ecosystem properties. It remains unknown if these differences are stable or if post-arable grasslands are only transient states that eventually follow a predictable successional pathway.Aims: We use a generic vegetation dynamics model based on

  17. Seasonally Flooded Grasslands -Grand CaymanSeasonally Flooded Grasslands -Grand Cayman 0 1 2 3 4 50.5

    E-print Network

    Exeter, University of

    Seasonally Flooded Grasslands - Grand CaymanSeasonally Flooded Grasslands - Grand Cayman 0 1 2 3 4 Protected Areas Seasonally Flooded Grasslands V.A.1.N.g. #12;Seasonally Flooded Grasslands - Little CaymanSeasonally Flooded Grasslands - Little Cayman 0 0.5 1 1.5 2 2.50.25 Kilometers Cayman Islands National Biodiversity

  18. The difference between temperate and tropical saltwater species' acute sensitivity to chemicals is relatively small.

    PubMed

    Wang, Zhen; Kwok, Kevin W H; Lui, Gilbert C S; Zhou, Guang-Jie; Lee, Jae-Seong; Lam, Michael H W; Leung, Kenneth M Y

    2014-06-01

    Due to a lack of saltwater toxicity data in tropical regions, toxicity data generated from temperate or cold water species endemic to North America and Europe are often adopted to derive water quality guidelines (WQG) for protecting tropical saltwater species. If chemical toxicity to most saltwater organisms increases with water temperature, the use of temperate species data and associated WQG may result in under-protection to tropical species. Given the differences in species composition and environmental attributes between tropical and temperate saltwater ecosystems, there are conceivable uncertainties in such 'temperate-to-tropic' extrapolations. This study aims to compare temperate and tropical saltwater species' acute sensitivity to 11 chemicals through a comprehensive meta-analysis, by comparing species sensitivity distributions (SSDs) between the two groups. A 10 percentile hazardous concentration (HC10) is derived from each SSD, and then a temperate-to-tropic HC10 ratio is computed for each chemical. Our results demonstrate that temperate and tropical saltwater species display significantly different sensitivity towards all test chemicals except cadmium, although such differences are small with the HC10 ratios ranging from 0.094 (un-ionised ammonia) to 2.190 (pentachlorophenol) only. Temperate species are more sensitive to un-ionised ammonia, chromium, lead, nickel and tributyltin, whereas tropical species are more sensitive to copper, mercury, zinc, phenol and pentachlorophenol. Through comparison of a limited number of taxon-specific SSDs, we observe that there is a general decline in chemical sensitivity from algae to crustaceans, molluscs and then fishes. Following a statistical analysis of the results, we recommend an extrapolation factor of two for deriving tropical WQG from temperate information. PMID:24289976

  19. The effect of fire-induced soil hydrophobicity on wind erosion in a semiarid grassland: Experimental observations and theoretical framework

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aridland ecosystems are often susceptible to degradation resulting from disturbances like fires and grazing. By exposing the soil surface to the erosive action of winds, these disturbances contribute to the redistribution of soil nutrients associated with grassland-to-shrubland conversions, and to t...

  20. Temporal Changes in Native and Exotic Vegetation and Soil Characteristics following Disturbances by Feral Pigs in a California Grassland

    Microsoft Academic Search

    Trisha A. Tierney; J. Hall. Cushman

    2006-01-01

    Invasive species that increase prevailing disturbance regimes can profoundly alter the composition and structure of ecosystems they invade. Using both comparative and manipulative approaches, we investigated how native and exotic vegetation and soil characteristics at a coastal grassland site in northern California changed through time following disturbances by feral pigs (Sus scrofa). We quantified these successional changes by comparing pig

  1. Nine years of enriched CO 2 changes the function and structural diversity of soil microorganisms in a grassland

    Microsoft Academic Search

    D. Drissner; H. Blum; D. Tscherko; E. Kandeler

    2007-01-01

    Summary To gain insight into microbial function following increased atmospheric CO2 concentration, we investi- gated the influence of 9 years of enriched CO2 (600 ml litre ? 1 ) on the function and structural diversity of soil microorganisms in a grassland ecosystem under free air carbon dioxide enrichment (FACE), as affected by plant species (Trifolium repens L. and Lolium perenne

  2. Soil organic carbon beneath croplands and re-established grasslands in the North Dakota prairie pothole region

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grassland ecosystems established under the conservation reserve program (CRP) in the Prairie Pothole Region (PPR) currently provide soil conservation and wildlife habitat services. We aimed to determine if these lands also sequester soil organic carbon (SOC), as compared with neighboring croplands a...

  3. Plant composition and the effects of temperature, soil moisture, and aboveground biomass on soil respiration in grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Future changes in climate are likely to cause shifts in plant species composition. In grasslands, the growth form composition (i.e., grass/forb) and species diversity of vegetation are important controls on ecosystem carbon cycling because species and growth forms vary in their capacities for carbon...

  4. Spatial patterns of grassland-shrubland state transitions: a 74-year record on grazed and protected areas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tree and shrub abundance has increased in many grasslands, causing changes in ecosystem carbon and nitrogen pools that are related to patterns of woody plant distribution. However, with regard to spatial patterns, little is known about (i) how they develop; (ii) how they are influenced by grazing; o...

  5. Artificial climate warming positively affects arbuscular mycorrhizae but decreases soil aggregate water stability in an annual grassland

    Microsoft Academic Search

    Matthias C. Rillig; Sara F. Wright; M. Rebecca Shaw; Christopher B. Field

    2002-01-01

    Despite the importance of arbuscular mycorrhizae to the functioning of terrestrial ecosystems (e.g. nutrient uptake, soil aggregation), and the increasing evidence of global warming, responses of arbuscular mycorrhizal fungi (AMF) to climate warm- ing are poorly understood. In a field experiment using infrared heaters, we found effects of warming on AMF after one growing season in an annual grassland, in

  6. Stimulation of soil nitrification and denitrification by grazing in grasslands: do changes in plant species composition matter?

    Microsoft Academic Search

    X. Le Roux; M. Bardy; P. Loiseau; F. Louault

    2003-01-01

    Stimulation of nitrification and denitrification by long term (from years to decades) grazing has commonly been reported in different grassland ecosystems. However, grazing generally induces important changes in plant species composition, and whether changes in nitrification and denitrification are primarily due to changes in vegetation composition has never been tested. We compared soil nitrification- and denitrification-enzyme activities (NEA and DEA,

  7. Response of native short grass prairie and Conservation Reserve Program grassland soil microbial communities to feedyard cattle manure applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study documents the effect of annual (both fall and spring) applications of three rates of N (50, 125, and 200 kg/ha) in the form of feedyard cattle manure on grassland ecosystems and on soil microbial composition. Replicate treatments (n=4) of feedyard cattle manure N applications plus check...

  8. Effects of invasion by the indigenous shrub Acacia sophorae on plant composition of coastal grasslands in south-eastern Australia

    Microsoft Academic Search

    David A Costello; Ian D Lunt; Jann E Williams

    2000-01-01

    Invasion of natural ecosystems by weeds is often associated with increasing levels of disturbance. However, there is substantial evidence that cessation of disturbance can also lead to plant invasions, especially of woody species. In some coastal grasslands in south-eastern Australia, removal of grazing and burning appears to have triggered invasion by the indigenous shrub, Acacia sophorae. To quantify the impacts

  9. FIRE AS A MANAGEMENT TOOL TO FACILITATE EXPANSION OF REINTRODUCED BLACK-TAILED PRAIRIE DOG COLONIES IN CHIHUAHUAN DESERT GRASSLANDS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Within the last hundred years, pu