Estuarine Total Ecosystem Metabolism

EPA Science Inventory

Total ecosystem metabolism (TEM), both as discrete measurements and as a theoretical concept, has an important history in ecosystem ecology, particularly in estuaries. Some of the earliest ecological studies were developed to determine how energy flowed through an ecosystem and w...

Comprehensive ecosystem model-experiment synthesis using multiple datasets at two temperate forest free-air CO2 enrichment experiments: model performance and compensating biases

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

Walker, Anthony P; Hanson, Paul J; DeKauwe, Martin G

2014-01-01

Free Air CO2 Enrichment (FACE) experiments provide a remarkable wealth of data to test the sensitivities of terrestrial ecosystem models (TEMs). In this study, a broad set of 11 TEMs were compared to 22 years of data from two contrasting FACE experiments in temperate forests of the south eastern US the evergreen Duke Forest and the deciduous Oak Ridge forest. We evaluated the models' ability to reproduce observed net primary productivity (NPP), transpiration and Leaf Area index (LAI) in ambient CO2 treatments. Encouragingly, many models simulated annual NPP and transpiration within observed uncertainty. Daily transpiration model errors were often relatedmore » to errors in leaf area phenology and peak LAI. Our analysis demonstrates that the simulation of LAI often drives the simulation of transpiration and hence there is a need to adopt the most appropriate of hypothesis driven methods to simulate and predict LAI. Of the three competing hypotheses determining peak LAI (1) optimisation to maximise carbon export, (2) increasing SLA with canopy depth and (3) the pipe model the pipe model produced LAI closest to the observations. Modelled phenology was either prescribed or based on broader empirical calibrations to climate. In some cases, simulation accuracy was achieved through compensating biases in component variables. For example, NPP accuracy was sometimes achieved with counter-balancing biases in nitrogen use efficiency and nitrogen uptake. Combined analysis of parallel measurements aides the identification of offsetting biases; without which over-confidence in model abilities to predict ecosystem function may emerge, potentially leading to erroneous predictions of change under future climates.« less

Historical and Possible Future Changes in Permafrost and Active Layer Thickness in Alaska: Implications to Landscape Changes and Permafrost Carbon Pool.

NASA Astrophysics Data System (ADS)

Marchenko, S. S.; Helene, G.; Euskirchen, E. S.; Breen, A. L.; McGuire, D.; Rupp, S. T.; Romanovsky, V. E.; Walsh, J. E.

2017-12-01

The Soil Temperature and Active Layer Thickness (ALT) Gridded Data was developed to quantify the nature and rate of permafrost degradation and its impact on ecosystems, infrastructure, CO2 and CH4 fluxes and net C storage following permafrost thaw across Alaska. To develop this database, we used the process-based permafrost dynamics model GIPL2 developed in the Geophysical Institute Permafrost Lab, UAF and which is the permafrost module of the Integrated Ecosystem Model (IEM) for Alaska and Northwest Canada. The climate forcing data for simulations were developed by the Scenarios Network for Alaska and Arctic Planning (SNAP, http://www.snap.uaf.edu/). These data are based on the historical CRU3.1 data set for the retrospective analysis period (1901-2009) and the five model averaged data were derived from the five CMIP5/AR5 IPCC Global Circulation Models that performed the best in Alaska and other northern regions: NCAR-CCSM4, GFDL-CM3, GISS-E2-R, IPSL-CM5A-LR, MRI-CGCM3. A composite of all five-model outputs for the RCP4.5 and RCP8.5 were used in these particular permafrost dynamics simulations. Data sets were downscaled to a 771 m resolution, using the Parameter-elevation Regressions on Independent Slopes Model (PRISM) climatology. Additional input data (snow characteristics, soil thermal properties, soil water content, organic matter accumulation or its loss due to fire, etc.) came from the Terrestrial Ecosystem Model (TEM) and the ALFRESCO (ALaska FRame-based EcoSystem COde) model simulations. We estimated the dynamics of permafrost temperature, active layer thickness, area occupied by permafrost, and volume of seasonally thawed soils within the 4.75 upper meters (original TEM soil column) across the Alaska domain. Simulations of future changes in permafrost indicate that, by the end of the 21st century, late-Holocene permafrost in Alaska will be actively thawing at all locations and that some Late Pleistocene carbon-rich peatlands underlain by permafrost will start to thaw at some locations. The modeling results also indicate how different types of ecosystems affect the thermal state of permafrost and its stability. The release of carbon and the net effect of this thawing depends on the balance between increased productivity and respiration, which depend, in part, on soil moisture dynamics.

Importance of Past Human and Natural Disturbance in Present-Day Net Ecosystem Productivity

NASA Astrophysics Data System (ADS)

Felzer, B. S.; Phelps, P.

2014-12-01

Gridded datasets of Net Ecosystem Exchange derived from eddy covariance and remote sensing measurements provide a means of validating Net Ecosystem Productivity (NEP, opposite of NEE) from terrestrial ecosystem models. While most forested regions in the U.S. are observed to be moderate to strong carbon sinks, models not including human or natural disturbances will tend to be more carbon neutral, which is expected of mature ecosystems. We have developed the Terrestrial Ecosystems Model Hydro version (TEM-Hydro) to include both human and natural disturbances to compare against gridded NEP datasets. Human disturbances are based on the Hurtt et al. (2006) land use transition dataset and include transient agricultural (crops and pasture) conversion and abandonment and timber harvest. We include natural disturbances of storms and fires based on stochastic return intervals. Tropical storms and hurricane return intervals are based on Zheng et al. (2009) and occur only along the U.S. Atlantic and Gulf coasts. Fire return intervals are based on LANDFIRE Rapid Assessment Vegetation Models and vegetation types from the Hurtt dataset. We are running three experiments with TEM-Hydro from 1700-2011 for the conterminous U.S.: potential vegetation (POT), human disturbance only (agriculture and timber harvest, LULC), and human plus natural disturbance (agriculture, timber harvest, storms, and fire, DISTURB). The goal is to compare our NEP values to those obtained by FLUXNET-MTE (Jung et al. 2009) from 1982-2008 and ECMOD (Xiao et al., 2008) from 2000-2006 for different plant functional types (PFTs) within the conterminous U.S. Preliminary results show that, for the entire U.S., potential vegetation yields an NEP of 10.8 gCm-2yr-1 vs 128.1 gCm-2yr-1 for LULC and 89.8 gCm-2yr-1 for DISTURB from 1982-2008. The effect of regrowth following agricultural and timber harvest disturbance therefore contributes substantially to the present-day carbon sink, while stochastic storms and fires have a negative effect on NEP. Even though the current NEP reflects the carbon uptake from regrowth, a full carbon accounting would also include the carbon released to the atmosphere during disturbance or carbon lost to decomposition of agricultural or timber products

Quantifying the Global Nitrous Oxide Emissions Using a Trait-based Biogeochemistry Model

NASA Astrophysics Data System (ADS)

Zhuang, Q.; Yu, T.

2017-12-01

Nitrogen is an essential element for the global biogeochemical cycle. It is a key nutrient for organisms and N compounds including nitrous oxide significantly influence the global climate. The activities of bacteria and archaea are responsible for the nitrification and denitrification in a wide variety of environments, so microbes play an important role in the nitrogen cycle in soils. To date, most existing process-based models treated nitrification and denitrification as chemical reactions driven by soil physical variables including soil temperature and moisture. In general, the effect of microbes on N cycling has not been modeled in sufficient details. Soil organic carbon also affects the N cycle because it supplies energy to microbes. In my study, a trait-based biogeochemistry model quantifying N2O emissions from the terrestrial ecosystems is developed based on an extant process-based model TEM (Terrestrial Ecosystem Model). Specifically, the improvement to TEM includes: 1) Incorporating the N fixation process to account for the inflow of N from the atmosphere to biosphere; 2) Implementing the effects of microbial dynamics on nitrification process; 3) fully considering the effects of carbon cycling on N nitrogen cycling following the principles of stoichiometry of carbon and nitrogen in soils, plants, and microbes. The difference between simulations with and without the consideration of bacterial activity lies between 5% 25% based on climate conditions and vegetation types. The trait based module allows a more detailed estimation of global N2O emissions.

Understanding the Effect of Land Cover Classification on Model Estimates of Regional Carbon Cycling in the Boreal Forest Biome

NASA Technical Reports Server (NTRS)

Kimball, John; Kang, Sinkyu

2003-01-01

The original objectives of this proposed 3-year project were to: 1) quantify the respective contributions of land cover and disturbance (i.e., wild fire) to uncertainty associated with regional carbon source/sink estimates produced by a variety of boreal ecosystem models; 2) identify the model processes responsible for differences in simulated carbon source/sink patterns for the boreal forest; 3) validate model outputs using tower and field- based estimates of NEP and NPP; and 4) recommend/prioritize improvements to boreal ecosystem carbon models, which will better constrain regional source/sink estimates for atmospheric C02. These original objectives were subsequently distilled to fit within the constraints of a 1 -year study. This revised study involved a regional model intercomparison over the BOREAS study region involving Biome-BGC, and TEM (A.D. McGuire, UAF) ecosystem models. The major focus of these revised activities involved quantifying the sensitivity of regional model predictions associated with land cover classification uncertainties. We also evaluated the individual and combined effects of historical fire activity, historical atmospheric CO2 concentrations, and climate change on carbon and water flux simulations within the BOREAS study region.

Comparative study of modeling the impacts of air pollution on carbon and water cycles in terrestrial ecosystems of China during 1980-2005

NASA Astrophysics Data System (ADS)

Ren, W.; Tian, H.; Liu, M.; Chen, G.; Lu, C.; Xu, X.; Zhang, C.; Pan, S.; Felzer, B. S.; Kicklighter, D. W.; Melillo, J. M.; Mu, Q.; Running, S.; Zhao, M.

2008-12-01

China has experienced one of the most rapid changes in the past three decades, which has resulted in and will raise lots of environment problems as undergoing further rapid development in the coming years. Severe air pollution combined with other changing environment factors such as climate variability, increasing CO2 and nitrogen deposition, land use cover and change including agronomic management, significantly have been the most serious environmental problems that have threatened the sustainability of China's ecosystems as well as its economy. We investigated the potential effects of elevated ozone (O3) along with other multiple stresses on net primary productivity (NPP) and evapotransporatioin (ET) in China's terrestrial ecosystems for the period 1980-2005, by using three process-based models including the Biom-BGC, Dynamic Land Ecosystem Model (DLEM) and Terrestrial Ecosystem Model (TEM) forced by the gridded data of historical tropospheric O3, climate and other environmental factors. The comparative study of the model simulations showed that elevated O3 could result in a reduction of decadal mean NPP up to 390 TgC, and a small temporal change in total ET nationwide from 1980 to 2005. However, changes in annual NPP and ET across China's terrestrial ecosystems show substantial spatial variation and the reduction rate of NPP up to 32% indicate varied sensitivity and vulnerability to elevated ozone pollution among different plant functional types. The comparative study indicates that there is an important need to test the simulated results and models' behavior against field experiments.

Defense Energy Resilience: Lessons from Ecology

DTIC Science & Technology

2010-08-01

ecosystem -based manage- ment of natural resources and sustainability science have yielded theory that is markedly different from theory arising from more...research regarding natural resource management and the provision of ecosystem services reveals how hu- man and “natural” systems are interlinked.18...Ecosys- tems provide the myriad services upon which society depends for survival. Society influences ecosystems through conversion of land cover

A first-order analysis of the potential role of CO2 fertilization to affect the global carbon budget: A comparison of four terrestrial biosphere models

USGS Publications Warehouse

Kicklighter, D.W.; Bruno, M.; Donges, S.; Esser, G.; Heimann, Martin; Helfrich, J.; Ift, F.; Joos, F.; Kaduk, J.; Kohlmaier, G.H.; McGuire, A.D.; Melillo, J.M.; Meyer, R.; Moore, B.; Nadler, A.; Prentice, I.C.; Sauf, W.; Schloss, A.L.; Sitch, S.; Wittenberg, U.; Wurth, G.

1999-01-01

We compared the simulated responses of net primary production, heterotrophic respiration, net ecosystem production and carbon storage in natural terrestrial ecosystems to historical (1765 to 1990) and projected (1990 to 2300) changes of atmospheric CO2 concentration of four terrestrial biosphere models: the Bern model, the Frankfurt Biosphere Model (FBM), the High-Resolution Biosphere Model (HRBM) and the Terrestrial Ecosystem Model (TEM). The results of the model intercomparison suggest that CO2 fertilization of natural terrestrial vegetation has the potential to account for a large fraction of the so-called 'missing carbon sink' of 2.0 Pg C in 1990. Estimates of this potential are reduced when the models incorporate the concept that CO2 fertilization can be limited by nutrient availability. Although the model estimates differ on the potential size (126 to 461 Pg C) of the future terrestrial sink caused by CO2 fertilization, the results of the four models suggest that natural terrestrial ecosystems will have a limited capacity to act as a sink of atmospheric CO2 in the future as a result of physiological constraints and nutrient constraints on NPP. All the spatially explicit models estimate a carbon sink in both tropical and northern temperate regions, but the strength of these sinks varies over time. Differences in the simulated response of terrestrial ecosystems to CO2 fertilization among the models in this intercomparison study reflect the fact that the models have highlighted different aspects of the effect of CO2 fertilization on carbon dynamics of natural terrestrial ecosystems including feedback mechanisms. As interactions with nitrogen fertilization, climate change and forest regrowth may play an important role in simulating the response of terrestrial ecosystems to CO2 fertilization, these factors should be included in future analyses. Improvements in spatially explicit data sets, whole-ecosystems experiments and the availability of net carbon exchange measurements across the globe will also help to improve future evaluations of the role of CO2 fertilization on terrestrial carbon storage.

Constraining terrestrial ecosystem CO2 fluxes by integrating models of biogeochemistry and atmospheric transport and data of surface carbon fluxes and atmospheric CO2 concentrations

NASA Astrophysics Data System (ADS)

Zhu, Q.; Zhuang, Q.; Henze, D.; Bowman, K.; Chen, M.; Liu, Y.; He, Y.; Matsueda, H.; Machida, T.; Sawa, Y.; Oechel, W.

2014-09-01

Regional net carbon fluxes of terrestrial ecosystems could be estimated with either biogeochemistry models by assimilating surface carbon flux measurements or atmospheric CO2 inversions by assimilating observations of atmospheric CO2 concentrations. Here we combine the ecosystem biogeochemistry modeling and atmospheric CO2 inverse modeling to investigate the magnitude and spatial distribution of the terrestrial ecosystem CO2 sources and sinks. First, we constrain a terrestrial ecosystem model (TEM) at site level by assimilating the observed net ecosystem production (NEP) for various plant functional types. We find that the uncertainties of model parameters are reduced up to 90% and model predictability is greatly improved for all the plant functional types (coefficients of determination are enhanced up to 0.73). We then extrapolate the model to a global scale at a 0.5° × 0.5° resolution to estimate the large-scale terrestrial ecosystem CO2 fluxes, which serve as prior for atmospheric CO2 inversion. Second, we constrain the large-scale terrestrial CO2 fluxes by assimilating the GLOBALVIEW-CO2 and mid-tropospheric CO2 retrievals from the Atmospheric Infrared Sounder (AIRS) into an atmospheric transport model (GEOS-Chem). The transport inversion estimates that: (1) the annual terrestrial ecosystem carbon sink in 2003 is -2.47 Pg C yr-1, which agrees reasonably well with the most recent inter-comparison studies of CO2 inversions (-2.82 Pg C yr-1); (2) North America temperate, Europe and Eurasia temperate regions act as major terrestrial carbon sinks; and (3) The posterior transport model is able to reasonably reproduce the atmospheric CO2 concentrations, which are validated against Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) CO2 concentration data. This study indicates that biogeochemistry modeling or atmospheric transport and inverse modeling alone might not be able to well quantify regional terrestrial carbon fluxes. However, combining the two modeling approaches and assimilating data of surface carbon flux as well as atmospheric CO2 mixing ratios might significantly improve the quantification of terrestrial carbon fluxes.

Modeled change in carbon balance between 1970-2100 of a polygonal arctic tundra ecosystem near Barrow, Alaska

NASA Astrophysics Data System (ADS)

Lara, M. J.; McGuire, A. D.; Euskirchen, E. S.; Sloan, V. L.; Iversen, C. M.; Norby, R. J.; Genet, H.; Zhang, Y.; Yuan, F.

2013-12-01

Northern permafrost regions are estimated to cover 16% of the global soil area and account for approximately 50% of the global belowground organic carbon pool. However, there are considerable uncertainties regarding the fate of this soil carbon pool with projected climate warming over the next century. In northern Alaska, nearly 65% of the terrestrial surface is composed of polygonal tundra, where microtopographic position (i.e. high center, low center, trough) varies surface hydrology, plant community composition, and biogeochemical cycling, over small (<5m) spatial scales. Due to large spatial heterogeneity and other non-linear responses of soil carbon to altered thermal regime, it is difficult to accurately estimate the fate of terrestrial carbon balance over decadal time-scales without explicitly considering the dynamically coupled processes driving permafrost dynamics, community structure, and ecosystem function. We use a new version of the terrestrial ecosystem model (TEM), which couples a dynamic vegetation and dynamic organic soil model (DVM-DOS-TEM). This large-scale ecosystem model is designed to study interactions among carbon and nitrogen cycling, vegetation composition, and soil physical properties, including permafrost and active layer dynamics. The model is parameterized and calibrated using data specific to the local climate, vegetation, and soils within various polygon land cover types (i.e. high center & rim, low center, trough) collected from sites (71.28°N 156.60° W) on the arctic coastal plain near Barrow, Alaska to estimate the likely change in carbon balance between 1970 and 2100 in this landscape. Model outputs are scaled across the Barrow Peninsula using the distribution of polygonal tundra land cover types, described by a land cover classification of 26.9 km2, using a 2008 multi-spectral QuickBird satellite image. The polygonal tundra land cover classification found high center & rims to represent 37.5% of the study area, low centers 19.7%, troughs 9.9%, water bodies (i.e. lakes, ponds, rivers) 17.8%, and non-polygonal tundra (i.e. drainage terraces & graminoid meadows) 15.1%, respectively. The overall accuracy of the map was 86%, based on 250 ground control points, and the Kappa coefficient was 0.77. Preliminary model runs for this region indicated variability in response to specific polygonal tundra land cover type through time. Overall, results suggest that it is important to consider discrete polygonal tundra features in regional estimates of carbon balance in northern Alaska.

Estimating Rates of Permafrost Degradation and their Impact on Ecosystems across Alaska and Northwest Canada using the Process-based Permafrost Dynamics Model GIPL as a Component of the Integrated Ecosystem Model (IEM)

NASA Astrophysics Data System (ADS)

Marchenko, S. S.; Genet, H.; Euskirchen, E. S.; Breen, A. L.; McGuire, A. D.; Rupp, S. T.; Romanovsky, V. E.; Bolton, W. R.; Walsh, J. E.

2016-12-01

The impact of climate warming on permafrost and the potential of climate feedbacks resulting from permafrost thawing have recently received a great deal of attention. Permafrost temperature has increased in most locations in the Arctic and Sub-Arctic during the past 30-40 years. The typical increase in permafrost temperature is 1-3°C. The process-based permafrost dynamics model GIPL developed in the Geophysical Institute Permafrost Lab, and which is the permafrost module of the Integrated Ecosystem Model (IEM) has been using to quantify the nature and rate of permafrost degradation and its impact on ecosystems, infrastructure, CO2 and CH4fluxes and net C storage following permafrost thaw across Alaska and Northwest Canada. The IEM project is a multi-institutional and multi-disciplinary effort aimed at understanding potential landscape, habitat and ecosystem change across the IEM domain. The IEM project also aims to tie three scientific models together Terrestrial Ecosystem Model (TEM), the ALFRESCO (ALaska FRame-based EcoSystem Code) and GIPL so that they exchange data at run-time. The models produce forecasts of future fire, vegetation, organic matter, permafrost and hydrology regimes. The climate forcing data are based on the historical CRU3.1 data set for the retrospective analysis period (1901-2009) and the CMIP3 CCCMA-CGCM3.1 and MPI-ECHAM5/MPI-OM climate models for the future period (2009-2100). All data sets were downscaled to a 1 km resolution, using a differencing methodology (i.e., a delta method) and the Parameter-elevation Regressions on Independent Slopes Model (PRISM) climatology. We estimated the dynamics of permafrost temperature, active layer thickness, area occupied by permafrost, and volume of thawed soils across the IEM domain. The modeling results indicate how different types of ecosystems affect the thermal state of permafrost and its stability. Although the rate of soil warming and permafrost degradation in peatland areas are slower than other areas, a considerable volume of peat will be thawed by the end of the current century. The release of carbon and the net effect of this thawing depends on the balance between increased productivity and respiration, which depend, in part, on soil moisture dynamics.

Ecosystem biogeochemistry model parameterization: Do more flux data result in a better model in predicting carbon flux?

DOE PAGES

Zhu, Qing; Zhuang, Qianlai

2015-12-21

Reliability of terrestrial ecosystem models highly depends on the quantity and quality of thedata that have been used to calibrate the models. Nowadays, in situ observations of carbon fluxes areabundant. However, the knowledge of how much data (data length) and which subset of the time seriesdata (data period) should be used to effectively calibrate the model is still lacking. This study uses theAmeriFlux carbon flux data to parameterize the Terrestrial Ecosystem Model (TEM) with an adjoint-baseddata assimilation technique for various ecosystem types. Parameterization experiments are thus conductedto explore the impact of both data length and data period on the uncertaintymore » reduction of the posteriormodel parameters and the quantification of site and regional carbon dynamics. We find that: the modelis better constrained when it uses two-year data comparing to using one-year data. Further, two-year datais sufficient in calibrating TEM’s carbon dynamics, since using three-year data could only marginallyimprove the model performance at our study sites; the model is better constrained with the data thathave a higher‘‘climate variability’’than that having a lower one. The climate variability is used to measurethe overall possibility of the ecosystem to experience all climatic conditions including drought and extremeair temperatures and radiation; the U.S. regional simulations indicate that the effect of calibration datalength on carbon dynamics is amplified at regional and temporal scales, leading to large discrepanciesamong different parameterization experiments, especially in July and August. Our findings areconditioned on the specific model we used and the calibration sites we selected. The optimal calibrationdata length may not be suitable for other models. However, this study demonstrates that there may exist athreshold for calibration data length and simply using more data would not guarantee a better modelparameterization and prediction. More importantly, climate variability might be an effective indicator ofinformation within the data, which could help data selection for model parameterization. As a result, we believe ourfindings will benefit the ecosystem modeling community in using multiple-year data to improve modelpredictability.« less

Ecosystem biogeochemistry model parameterization: Do more flux data result in a better model in predicting carbon flux?

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

Zhu, Qing; Zhuang, Qianlai

Reliability of terrestrial ecosystem models highly depends on the quantity and quality of thedata that have been used to calibrate the models. Nowadays, in situ observations of carbon fluxes areabundant. However, the knowledge of how much data (data length) and which subset of the time seriesdata (data period) should be used to effectively calibrate the model is still lacking. This study uses theAmeriFlux carbon flux data to parameterize the Terrestrial Ecosystem Model (TEM) with an adjoint-baseddata assimilation technique for various ecosystem types. Parameterization experiments are thus conductedto explore the impact of both data length and data period on the uncertaintymore » reduction of the posteriormodel parameters and the quantification of site and regional carbon dynamics. We find that: the modelis better constrained when it uses two-year data comparing to using one-year data. Further, two-year datais sufficient in calibrating TEM’s carbon dynamics, since using three-year data could only marginallyimprove the model performance at our study sites; the model is better constrained with the data thathave a higher‘‘climate variability’’than that having a lower one. The climate variability is used to measurethe overall possibility of the ecosystem to experience all climatic conditions including drought and extremeair temperatures and radiation; the U.S. regional simulations indicate that the effect of calibration datalength on carbon dynamics is amplified at regional and temporal scales, leading to large discrepanciesamong different parameterization experiments, especially in July and August. Our findings areconditioned on the specific model we used and the calibration sites we selected. The optimal calibrationdata length may not be suitable for other models. However, this study demonstrates that there may exist athreshold for calibration data length and simply using more data would not guarantee a better modelparameterization and prediction. More importantly, climate variability might be an effective indicator ofinformation within the data, which could help data selection for model parameterization. As a result, we believe ourfindings will benefit the ecosystem modeling community in using multiple-year data to improve modelpredictability.« less

The sensitivity of terrestrial carbon storage to historical climate variability and atmospheric CO2 in the United States

USGS Publications Warehouse

Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, A.D.; Helfrich, J.

1999-01-01

We use the Terrestrial Ecosystem Model (TEM, Version 4.1) and the land cover data set of the international geosphere-biosphere program to investigate how increasing atmospheric CO2 concentration and climate variability during 1900-1994 affect the carbon storage of terrestrial ecosystems in the conterminous USA, and how carbon storage has been affected by land-use change. The estimates of TEM indicate that over the past 95 years a combination of increasing atmospheric CO2 with historical temperature and precipitation variability causes a 4.2% (4.3 Pg C) decrease in total carbon storage of potential vegetation in the conterminous US, with vegetation carbon decreasing by 7.2% (3.2 Pg C) and soil organic carbon decreasing by 1.9% (1.1 Pg C). Several dry periods including the 1930s and 1950s are responsible for the loss of carbon storage. Our factorial experiments indicate that precipitation variability alone decreases total carbon storage by 9.5%. Temperature variability alone does not significantly affect carbon storage. The effect of CO2 fertilization alone increases total carbon storage by 4.4%. The effects of increasing atmospheric CO2 and climate variability are not additive. Interactions among CO2, temperature and precipitation increase total carbon storage by 1.1%. Our study also shows substantial year-to-year variations in net carbon exchange between the atmosphere and terrestrial ecosystems due to climate variability. Since the 1960s, we estimate these terrestrial ecosystems have acted primarily as a sink of atmospheric CO2 as a result of wetter weather and higher atmospheric CO2 concentrations. For the 1980s, we estimate the natural terrestrial ecosystems, excluding cropland and urban areas, of the conterminous US have accumulated 78.2 Tg C yr-1 because of the combined effect of increasing atmospheric CO2 and climate variability. For the conterminous US, we estimate that the conversion of natural ecosystems to cropland and urban areas has caused a 18.2% (17.7 Pg C) reduction in total carbon storage from that estimated for potential vegetation. The carbon sink capacity of natural terrestrial ecosystems in the conterminous US is about 69% of that estimated for potential vegetation.

Changes in Landscape-level Carbon Balance of an Arctic Coastal Plain Tundra Ecosystem Between 1970-2100, in Response to Projected Climate Change

NASA Astrophysics Data System (ADS)

Lara, M. J.; McGuire, A. D.; Euskirchen, E. S.; Genet, H.; Sloan, V. L.; Iversen, C. M.; Norby, R. J.; Zhang, Y.; Yuan, F.

2014-12-01

Northern permafrost regions are estimated to cover 16% of the global soil area and account for approximately 50% of the global belowground organic carbon pool. However, there are considerable uncertainties regarding the fate of this soil carbon pool with projected climate warming over the next century. In northern Alaska, nearly 65% of the terrestrial surface is composed of polygonal tundra, where geomorphic land cover types such as high-, flat-, and low-center polygons influence local surface hydrology, plant community composition, nutrient and biogeochemical cycling, over small spatial scales. Due to the lack of representation of these fine-scale geomorphic types and ecosystem processes, in large-scale terrestrial ecosystem models, future uncertainties are large for this tundra region. In this study, we use a new version of the terrestrial ecosystem model (TEM), that couples a dynamic vegetation model (in which plant functional types compete for water, nitrogen, and light) with a dynamic soil organic model (in which temperature, moisture, and associated organic/inorganic carbon and nitrogen pools/fluxes vary together in vertically resolved layers) to simulate ecosystem carbon balance. We parameterized and calibrated this model using data specific to the local climate, vegetation, and soil associated with tundra geomorphic types. We extrapolate model results at a 1km2 resolution across the ~1800 km2 Barrow Peninsula using a tundra geomorphology map, describing ten dominant geomorphic tundra types (Lara et al. submitted), to estimate the likely change in landscape-level carbon balance between 1970 and 2100 in response to projected climate change. Preliminary model runs for this region indicated temporal variability in carbon and active layer dynamics, specific to tundra geomorphic type over time. Overall, results suggest that it is important to consider small-scale discrete polygonal tundra geomorphic types that control local structure and function in regional estimates of carbon balance in northern Alaska.

Predicting Changes in Arctic Tundra Vegetation: Towards an Understanding of Plant Trait Uncertainty

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Serbin, S.; Carman, T.; Iversen, C. M.; Salmon, V.; Helene, G.; McGuire, A. D.

2017-12-01

Arctic tundra plant communities are currently undergoing unprecedented changes in both composition and distribution under a warming climate. Predicting how these dynamics may play out in the future is important since these vegetation shifts impact both biogeochemical and biogeophysical processes. More precise estimates of these future vegetation shifts is a key challenge due to both a scarcity of data with which to parameterize vegetation models, particularly in the Arctic, as well as a limited understanding of the importance of each of the model parameters and how they may vary over space and time. Here, we incorporate newly available field data from arctic Alaska into a dynamic vegetation model specifically developed to take into account a particularly wide array of plant species as well as the permafrost soils of the arctic tundra (the Terrestrial Ecosystem Model with Dynamic Vegetation and Dynamic Organic Soil, Terrestrial Ecosystem Model; DVM-DOS-TEM). We integrate the model within the Predicative Ecosystem Analyzer (PEcAn), an open-source integrated ecological bioinformatics toolbox that facilitates the flows of information into and out of process models and model-data integration. We use PEcAn to evaluate the plant functional traits that contribute most to model variability based on a sensitivity analysis. We perform this analysis for the dominant types of tundra in arctic Alaska, including heath, shrub, tussock and wet sedge tundra. The results from this analysis will help inform future data collection in arctic tundra and reduce model uncertainty, thereby improving our ability to simulate Arctic vegetation structure and function in response to global change.

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

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

Kercher, J.R.; Chambers, J.Q.

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 nitrogenmore » 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.« less

Importance of recent shifts in soil thermal dynamics on growing season length, productivity, and carbon sequestration in terrestrial high-latitude ecosystems

USGS Publications Warehouse

Euskirchen, E.S.; McGuire, A.D.; Kicklighter, D.W.; Zhuang, Q.; Clein, Joy S.; Dargaville, R.J.; Dye, D.G.; Kimball, J.S.; McDonald, K.C.; Melillo, J.M.; Romanovsky, V.E.; Smith, N.V.

2006-01-01

In terrestrial high-latitude regions, observations indicate recent changes in snow cover, permafrost, and soil freeze-thaw transitions due to climate change. These modifications may result in temporal shifts in the growing season and the associated rates of terrestrial productivity. Changes in productivity will influence the ability of these ecosystems to sequester atmospheric CO2. We use the terrestrial ecosystem model (TEM), which simulates the soil thermal regime, in addition to terrestrial carbon (C), nitrogen and water dynamics, to explore these issues over the years 1960-2100 in extratropical regions (30-90??N). Our model simulations show decreases in snow cover and permafrost stability from 1960 to 2100. Decreases in snow cover agree well with National Oceanic and Atmospheric Administration satellite observations collected between the years 1972 and 2000, with Pearson rank correlation coefficients between 0.58 and 0.65. Model analyses also indicate a trend towards an earlier thaw date of frozen soils and the onset of the growing season in the spring by approximately 2-4 days from 1988 to 2000. Between 1988 and 2000, satellite records yield a slightly stronger trend in thaw and the onset of the growing season, averaging between 5 and 8 days earlier. In both, the TEM simulations and satellite records, trends in day of freeze in the autumn are weaker, such that overall increases in growing season length are due primarily to earlier thaw. Although regions with the longest snow cover duration displayed the greatest increase in growing season length, these regions maintained smaller increases in productivity and heterotrophic respiration than those regions with shorter duration of snow cover and less of an increase in growing season length. Concurrent with increases in growing season length, we found a reduction in soil C and increases in vegetation C, with greatest losses of soil C occurring in those areas with more vegetation, but simulations also suggest that this trend could reverse in the future. Our results reveal noteworthy changes in snow, permafrost, growing season length, productivity, and net C uptake, indicating that prediction of terrestrial C dynamics from one decade to the next will require that large-scale models adequately take into account the corresponding changes in soil thermal regimes. ?? 2006 Blackwell Publishing Ltd.

Importance of soil thermal dynamics on land carbon sequestration in Northern Eurasia during the 21st century

NASA Astrophysics Data System (ADS)

Kicklighter, David; Monier, Erwan; Sokolov, Andrei; Zhuang, Qianlai; Melillo, Jerry

2015-04-01

Recent modeling studies have suggested that carbon sinks in pan-arctic ecosystems may be weakening partially as a result of warming-induced increases in soil organic matter (SOM) decomposition and the exposure of previously frozen SOM to decomposition. This weakening of carbon sinks is likely to continue in the future as vast amount of carbon in permafrost soils is vulnerable to thaw. Here, we examine the importance of considering soil thermal dynamics when determining the effects of climate change and land-use change on carbon dynamics in Northern Eurasia during the 21st century. This importance is assessed by comparing results for a "business as usual" scenario between a version of the Terrestrial Ecosystem Model that does not consider soil thermal dynamics (TEM 4.4) and a version that does consider these dynamics (TEM 6.0). In this scenario, which is similar to the IPCC Representative Concentration Pathways (RCP) 8.5 scenario, the net area covered by food crops and pastures in Northern Eurasia is assumed to remain relatively constant over the 21st century, but the area covered by secondary forests is projected to double as a result of timber harvest and the abandonment of land associated with displacement of agricultural land. Enhanced decomposition from the newly exposed SOM from permafrost thaw also increases nitrogen availability for plant production so that the loss of carbon from the enhanced decomposition is partially compensated by enhanced uptake and storage of atmospheric carbon dioxide in vegetation. Our results indicate that consideration of soil thermal dynamics have a large influence on how simulated terrestrial carbon dynamics in Northern Eurasia respond to changes in climate, atmospheric chemistry (e.g., carbon dioxide fertilization, ozone pollution, nitrogen deposition) and disturbances.

A multi-model assessment of terrestrial biosphere model data needs

NASA Astrophysics Data System (ADS)

Gardella, A.; Cowdery, E.; De Kauwe, M. G.; Desai, A. R.; Duveneck, M.; Fer, I.; Fisher, R.; Knox, R. G.; Kooper, R.; LeBauer, D.; McCabe, T.; Minunno, F.; Raiho, A.; Serbin, S.; Shiklomanov, A. N.; Thomas, A.; Walker, A.; Dietze, M.

2017-12-01

Terrestrial biosphere models provide us with the means to simulate the impacts of climate change and their uncertainties. Going beyond direct observation and experimentation, models synthesize our current understanding of ecosystem processes and can give us insight on data needed to constrain model parameters. In previous work, we leveraged the Predictive Ecosystem Analyzer (PEcAn) to assess the contribution of different parameters to the uncertainty of the Ecosystem Demography model v2 (ED) model outputs across various North American biomes (Dietze et al., JGR-G, 2014). While this analysis identified key research priorities, the extent to which these priorities were model- and/or biome-specific was unclear. Furthermore, because the analysis only studied one model, we were unable to comment on the effect of variability in model structure to overall predictive uncertainty. Here, we expand this analysis to all biomes globally and a wide sample of models that vary in complexity: BioCro, CABLE, CLM, DALEC, ED2, FATES, G'DAY, JULES, LANDIS, LINKAGES, LPJ-GUESS, MAESPA, PRELES, SDGVM, SIPNET, and TEM. Prior to performing uncertainty analyses, model parameter uncertainties were assessed by assimilating all available trait data from the combination of the BETYdb and TRY trait databases, using an updated multivariate version of PEcAn's Hierarchical Bayesian meta-analysis. Next, sensitivity analyses were performed for all models across a range of sites globally to assess sensitivities for a range of different outputs (GPP, ET, SH, Ra, NPP, Rh, NEE, LAI) at multiple time scales from the sub-annual to the decadal. Finally, parameter uncertainties and model sensitivities were combined to evaluate the fractional contribution of each parameter to the predictive uncertainty for a specific variable at a specific site and timescale. Facilitated by PEcAn's automated workflows, this analysis represents the broadest assessment of the sensitivities and uncertainties in terrestrial models to date, and provides a comprehensive roadmap for constraining model uncertainties through model development and data collection.

Quantifying the visual-sensory landscape qualities that contribute to cultural ecosystem services using social media and LiDAR

USGS Publications Warehouse

Van Berkel, Derek B.; Tabrizian, Payam; Dorning, Monica; Smart, Lindsey S.; Newcomb, Doug; Mehaffey, Megan; Neale, Anne; Meentemeyer, Ross K.

2018-01-01

Landscapes are increasingly recognized for providing valuable cultural ecosystem services with numer- ous non-material benefits by serving as places of rest, relaxation, and inspiration that ultimately improve overall mental health and physical well-being. Maintaining and enhancing these valuable benefits through targeted management and conservation measures requires understanding the spatial and tem- poral determinants of perceived landscape values. Content contributed through mobile technologies and the web are emerging globally, providing a promising data source for localizing and assessing these land- scape benefits. These georeferenced data offer rich in situ qualitative information through photos and comments that capture valued and special locations across large geographic areas. We present a novel method for mapping and modeling landscape values and perceptions that leverages viewshed analysis of georeferenced social media data. Using a high resolution LiDAR (Light Detection and Ranging) derived digital surface model, we are able to evaluate landscape characteristics associated with the visual- sensory qualities of outdoor recreationalists. Our results show the importance of historical monuments and attractions in addition to specific environmental features which are appreciated by the public. Evaluation of photo-image content highlights the opportunity of including temporally and spatially vari- able visual-sensory qualities in cultural ecosystem services (CES) evaluation like the sights, sounds and smells of wildlife and weather phenomena.

Historical and projected carbon balance of mature black spruce ecosystems across north america: The role of carbon-nitrogen interactions

USGS Publications Warehouse

Clein, Joy S.; McGuire, A.D.; Zhang, X.; Kicklighter, D.W.; Melillo, J.M.; Wofsy, S.C.; Jarvis, P.G.; Massheder, J.M.

2002-01-01

The role of carbon (C) and nitrogen (N) interactions on sequestration of atmospheric CO2 in black spruce ecosystems across North America was evaluated with the Terrestrial Ecosystem Model (TEM) by applying parameterizations of the model in which C-N dynamics were either coupled or uncoupled. First, the performance of the parameterizations, which were developed for the dynamics of black spruce ecosystems at the Bonanza Creek Long-Term Ecological Research site in Alaska, were evaluated by simulating C dynamics at eddy correlation tower sites in the Boreal Ecosystem Atmosphere Study (BOREAS) for black spruce ecosystems in the northern study area (northern site) and the southern study area (southern site) with local climate data. We compared simulated monthly growing season (May to September) estimates of gross primary production (GPP), total ecosystem respiration (RESP), and net ecosystem production (NEP) from 1994 to 1997 to available field-based estimates at both sites. At the northern site, monthly growing season estimates of GPP and RESP for the coupled and uncoupled simulations were highly correlated with the field-based estimates (coupled: R2= 0.77, 0.88 for GPP and RESP; uncoupled: R2 = 0.67, 0.92 for GPP and RESP). Although the simulated seasonal pattern of NEP generally matched the field-based data, the correlations between field-based and simulated monthly growing season NEP were lower (R2 = 0.40, 0.00 for coupled and uncoupled simulations, respectively) in comparison to the correlations between field-based and simulated GPP and RESP. The annual NEP simulated by the coupled parameterization fell within the uncertainty of field-based estimates in two of three years. On the other hand, annual NEP simulated by the uncoupled parameterization only fell within the field-based uncertainty in one of three years. At the southern site, simulated NEP generally matched field-based NEP estimates, and the correlation between monthly growing season field-based and simulated NEP (R2 = 0.36, 0.20 for coupled and uncoupled simulations, respectively) was similar to the correlations at the northern site. To evaluate the role of N dynamics in C balance of black spruce ecosystems across North America, we simulated historical and projected C dynamics from 1900 to 2100 with a global-based climatology at 0.5?? resolution (latitude ?? longitude) with both the coupled and uncoupled parameterizations of TEM. From analyses at the northern site, several consistent patterns emerge. There was greater inter-annual variability in net primary production (NPP) simulated by the uncoupled parameterization as compared to the coupled parameterization, which led to substantial differences in inter-annual variability in NEP between the parameterizations. The divergence between NPP and heterotrophic respiration was greater in the uncoupled simulation, resulting in more C sequestration during the projected period. These responses were the result of fundamentally different responses of the coupled and uncoupled parameterizations to changes in CO2 and climate. Across North American black spruce ecosystems, the range of simulated decadal changes in C storage was substantially greater for the uncoupled parameterization than for the coupled parameterization. Analysis of the spatial variability in decadal responses of C dynamics revealed that C fluxes simulated by the coupled and uncoupled parameterizations have different sensitivities to climate and that the climate sensitivities of the fluxes change over the temporal scope of the simulations. The results of this study suggest that uncertainties can be reduced through (1) factorial studies focused on elucidating the role of C and N interactions in the response of mature black spruce ecosystems to manipulations of atmospheric CO2 and climate, (2) establishment of a network of continuous, long-term measurements of C dynamics across the range of mature black spruce ecosystems in North America, and (3) ancillary measureme

Marsh-nekton connectivity - A estuarine food web study in Yaquina Bay, Oregon using dual isotope analysis

EPA Science Inventory

Understanding temporal and spatial variability in community-level interactions of PNW estuaries has implications for ecosystem-based management principles. Here, we are analyzing the contribution of marsh derived food sources to non-commercial resident fish in Yaquina Bay, a tem...

Application of the soil perturbation index to evaluate created and restored wetlands

Treesearch

Rebecca Smith Maul; Marjorie M. Holland

2000-01-01

Biogeochemical properties of wetlands have recently been investigated to assess recovery of wetland ecosys-tems following human alteration. Analyses of soil samples have shown that the natural regeneration of timber-harvested wetlands exhibits predictable trends for soil organic matter, total organic carbon, total Kjeldahl nitrogen, and total phosphorus. Incorporating...

Net emissions of CH4 and CO2 in Alaska: Implications for the region's greenhouse gas budget

USGS Publications Warehouse

Zhuang, Q.; Melillo, J.M.; McGuire, A.D.; Kicklighter, D.W.; Prinn, R.G.; Steudler, P.A.; Felzer, B.S.; Hu, S.

2007-01-01

We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are ???3 Tg CH 4/yr. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicated that CH 4 emissions from wet soils would be enhanced more than consumption by dry soils of tundra and boreal forests. As a consequence, we projected that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide [CO2] and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 69 Tg CO2 equivalents/yr, that is, a balance between net methane emissions of 131 Tg CO2 equivalents/yr and carbon sequestration of 17 Tg C/yr (62 Tg CO2 equivalents/yr). ?? 2007 by the Ecological Society of America.

Greenhouse gas emissions from alternative futures of deforestation and agricultural management in the southern Amazon.

PubMed

Galford, Gillian L; Melillo, Jerry M; Kicklighter, David W; Cronin, Timothy W; Cerri, Carlos E P; Mustard, John F; Cerri, Carlos C

2010-11-16

The Brazilian Amazon is one of the most rapidly developing agricultural areas in the world and represents a potentially large future source of greenhouse gases from land clearing and subsequent agricultural management. In an integrated approach, we estimate the greenhouse gas dynamics of natural ecosystems and agricultural ecosystems after clearing in the context of a future climate. We examine scenarios of deforestation and postclearing land use to estimate the future (2006-2050) impacts on carbon dioxide (CO(2)), methane (CH(4)), and nitrous oxide (N(2)O) emissions from the agricultural frontier state of Mato Grosso, using a process-based biogeochemistry model, the Terrestrial Ecosystems Model (TEM). We estimate a net emission of greenhouse gases from Mato Grosso, ranging from 2.8 to 15.9 Pg CO(2)-equivalents (CO(2)-e) from 2006 to 2050. Deforestation is the largest source of greenhouse gas emissions over this period, but land uses following clearing account for a substantial portion (24-49%) of the net greenhouse gas budget. Due to land-cover and land-use change, there is a small foregone carbon sequestration of 0.2-0.4 Pg CO(2)-e by natural forests and cerrado between 2006 and 2050. Both deforestation and future land-use management play important roles in the net greenhouse gas emissions of this frontier, suggesting that both should be considered in emissions policies. We find that avoided deforestation remains the best strategy for minimizing future greenhouse gas emissions from Mato Grosso.

The role of protected areas in land use/land cover change and the carbon cycle in the conterminous United States

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

Lu, Xiaoliang; Zhou, Yuyu; Liu, Yaling

Protected areas (PAs) cover about 22% of the conterminous United States. Understanding their role on historical land use and land cover change (LULCC) and on the carbon cycle is essential to provide guidance for environmental policies. In this study, we compiled historical LULCC and PAs data to explore these interactions within the terrestrial ecosystem model (TEM). We found that intensive LULCC occurred in the conterminous United States from 1700 to 2005. More than 3 million km2 of forest, grassland and shrublands were converted into agricultural lands, which caused 10,607 Tg C release from land ecosystems to atmosphere. PAs had experiencedmore » little LULCC as they were generally established in the 20th century after most of the agricultural expansion had occurred. PAs initially acted as a carbon source due to land use legacies, but their accumulated carbon budget switched to a carbon sink in the 1960s, sequestering an estimated 1,642 Tg C over 1700–2005, or 13.4% of carbon losses in non-PAs. We also find that PAs maintain larger carbon stocks and continue sequestering carbon in recent years (2001–2005), but at a lower rate due to increased heterotrophic respiration as well as lower productivity associated to aging ecosystems. It is essential to continue efforts to maintain resilient, biodiverse ecosystems and avoid large-scale disturbances that would release large amounts of carbon in PAs.« less

Inference of lithologic distributions in an alluvial aquifer using airborne transient electromagnetic surveys

USGS Publications Warehouse

Dickinson, Jesse; Pool, D.R.; Groom, R.W.; Davis, L.J.

2010-01-01

An airborne transient electromagnetic (TEM) survey was completed in the Upper San Pedro Basin in southeastern Arizona to map resistivity distributions within the alluvial aquifer. This investigation evaluated the utility of 1D vertical resistivity models of the TEM data to infer lithologic distributions in an alluvial aquifer. Comparisons of the resistivity values and layers in the 1D resistivity models of airborne TEM data to 1D resistivity models of ground TEM data, borehole resistivity logs, and lithologic descriptions in drill logs indicated that the airborne TEM identified thick conductive fine-grained sediments that result in semiconfined groundwater conditions. One-dimensional models of ground-based TEM surveys and subsurface lithology at three sites were used to determine starting models and constraints to invert airborne TEM data using a constrained Marquardt-styleunderparameterized method. A maximum structural resolution of six layers underlain by a half-space was determined from the resistivity structure of the 1D models of the ground TEM data. The 1D resistivity models of the airborne TEM data compared well with the control data to depths of approximately 100 m in areas of thick conductive silt and clay and to depths of 200 m in areas of resistive sand and gravel. Comparison of a 3D interpolation of the 1D resistivity models to drill logs indicated resistive (mean of 65 ohm-m ) coarse-grained sediments along basin margins and conductive (mean of 8 ohm-m ) fine-grained sediments at the basin center. Extents of hydrologically significant thick silt and clay were well mapped by the 1D resistivity models of airborne TEM data. Areas of uncertain lithology remain below conductive fine-grained sediments where the 1D resistivity structure is not resolved: in areas where multiple lithologies have similar resistivity values and in areas of high salinity.

How Human and Natural Disturbance Affects the U.S. Carbon Sink

NASA Astrophysics Data System (ADS)

Felzer, B. S.

2015-12-01

Gridded datasets of Net Ecosystem Exchange derived from eddy covariance and remote sensing measurements (EC-MOD and FLUXNET-MTE) provide a means of validating Net Ecosystem Productivity (NEP, opposite of NEE) from terrestrial ecosystem models. While most forested regions in the U.S. are observed to be moderate to strong carbon sinks, models not including human or natural disturbances will tend to be more carbon neutral, which is expected of mature ecosystems. I have developed the Terrestrial Ecosystems Model Hydro version (TEM-Hydro) to include both human and natural disturbances to compare against gridded NEP datasets. Human disturbances are based on the Hurtt et al. land use transition dataset and include transient agricultural (crops and pasture) conversion and abandonment and timber harvest. Natural disturbances include tropical storms and hurricane and fires based on stochastic return intervals. Model results indicate that forests are the largest carbon sink, seconded by croplands and pastures, if not accounting for decomposition of agricultural products and animal respiration. Grasslands and shrublands are both small sinks or carbon neutral. The NEP of forests in EC-MOD from 2001-2006 is 240 gCm2yr-1 and for FLUXNET-MTE from 1982-2007 is 375 gCm-2yr-1. With potential vegetation, the respective forest sinks for those two time periods are 54 and 62 gCm-2yr-1, respectively. Including the effects of human disturbance increases the sinks to 154 and 147 gCm-2yr-1. The effect of stochastic fire and storms is to reduce the NEP to 114 and 108 gCm-2yr-1. While the positive carbon sink today is the result of past land use disturbance, net carbon sequestration, including product decomposition, conversion fluxes, and animal respiration, has not yet returned to predisturbance levels as seen in the potential vegetation. Differences in response to disturbance have to do with the type, frequency, and intensity of disturbance. Fire, in particular, is seen to have a net negative effect on carbon storage in forests due to decomposition of coarse woody debris and the fact that some nitrogen is lost during volatilization. Croplands become a carbon source if assuming product decomposition occurs where the crops are grown, and pasturelands become carbon neutral if accounting for animal respiration.

Greenhouse gas emissions from alternative futures of deforestation and agricultural management in the southern Amazon

PubMed Central

Galford, Gillian L.; Melillo, Jerry M.; Kicklighter, David W.; Cronin, Timothy W.; Cerri, Carlos E. P.; Mustard, John F.; Cerri, Carlos C.

2010-01-01

The Brazilian Amazon is one of the most rapidly developing agricultural areas in the world and represents a potentially large future source of greenhouse gases from land clearing and subsequent agricultural management. In an integrated approach, we estimate the greenhouse gas dynamics of natural ecosystems and agricultural ecosystems after clearing in the context of a future climate. We examine scenarios of deforestation and postclearing land use to estimate the future (2006–2050) impacts on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions from the agricultural frontier state of Mato Grosso, using a process-based biogeochemistry model, the Terrestrial Ecosystems Model (TEM). We estimate a net emission of greenhouse gases from Mato Grosso, ranging from 2.8 to 15.9 Pg CO2-equivalents (CO2-e) from 2006 to 2050. Deforestation is the largest source of greenhouse gas emissions over this period, but land uses following clearing account for a substantial portion (24–49%) of the net greenhouse gas budget. Due to land-cover and land-use change, there is a small foregone carbon sequestration of 0.2–0.4 Pg CO2-e by natural forests and cerrado between 2006 and 2050. Both deforestation and future land-use management play important roles in the net greenhouse gas emissions of this frontier, suggesting that both should be considered in emissions policies. We find that avoided deforestation remains the best strategy for minimizing future greenhouse gas emissions from Mato Grosso. PMID:20651250

Progress in simulating industrial flows using two-equation models: Can more be achieved with further research?

NASA Technical Reports Server (NTRS)

Haroutunian, Vahe

1995-01-01

This viewgraph presentation provides a brief review of two-equation eddy-viscosity models (TEM's) from the perspective of applied CFD. It provides objective assessment of both well-known and newer models, compares model predictions from various TEM's with experiments, identifies sources of modeling error and gives historical perspective of their effects on model performance and assessment, and recommends directions for future research on TEM's.

Abundance of antibiotic resistance genes in environmental bacteriophages.

PubMed

Anand, Taruna; Bera, Bidhan Ch; Vaid, Rajesh K; Barua, Sanjay; Riyesh, Thachamvally; Virmani, Nitin; Hussain, Mubarik; Singh, Raj K; Tripathi, Bhupendra N

2016-12-01

The ecosystem is continuously exposed to a wide variety of antimicrobials through waste effluents, agricultural run-offs and animal-related and anthropogenic activities, which contribute to the spread of antibiotic resistance genes (ARGs). The contamination of ecosystems with ARGs may create increased opportunities for their transfer to naive microbes and eventually lead to entry into the human food chain. Transduction is a significant mechanism of horizontal gene transfer in natural environments, which has traditionally been underestimated as compared to transformation. We explored the presence of ARGs in environmental bacteriophages in order to recognize their contribution in the spread of ARGs in environmental settings. Bacteriophages were isolated against environmental bacterial isolates, purified and bulk cultured. They were characterized, and detection of ARG and intI genes including blaTEM, blaOXA-2, intI1, intI2, intI3, tetA and tetW was carried out by PCR. This study revealed the presence of various genes [tetA (12.7 %), intI1 (10.9 %), intI2 (10.9 %), intI3 (9.1 %), tetW (9.1 %) and blaOXA-2 (3.6 %)] and blaTEM in a significantly higher proportion (30.9 %). blaSHV, blaOXA-1, tetO, tetB, tetG, tetM and tetS were not detected in any of the phages. Soil phages were the most versatile in terms of ARG carriage. Also, the relative abundance of tetA differed significantly vis-à-vis source. The phages from organized farms showed varied ARGs as compared to the unorganized sector, although blaTEM ARG incidences did not differ significantly. The study reflects on the role of phages in dissemination of ARGs in environmental reservoirs, which may provide an early warning system for future clinically relevant resistance mechanisms.

Climatic and biotic controls on annual carbon storage in Amazonian ecosystems

USGS Publications Warehouse

Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, A.D.; Helfrich, J.; Moore, B.; Vorosmarty, C.J.

2000-01-01

1 The role of undisturbed tropical land ecosystems in the global carbon budget is not well understood. It has been suggested that inter-annual climate variability can affect the capacity of these ecosystems to store carbon in the short term. In this paper, we use a transient version of the Terrestrial Ecosystem Model (TEM) to estimate annual carbon storage in undisturbed Amazonian ecosystems during the period 1980-94, and to understand the underlying causes of the year-to-year variations in net carbon storage for this region. 2 We estimate that the total carbon storage in the undisturbed ecosystems of the Amazon Basin in 1980 was 127.6 Pg C, with about 94.3 Pg C in vegetation and 33.3 Pg C in the reactive pool of soil organic carbon. About 83% of the total carbon storage occurred in tropical evergreen forests. Based on our model's results, we estimate that, over the past 15 years, the total carbon storage has increased by 3.1 Pg C (+ 2%), with a 1.9-Pg C (+2%) increase in vegetation carbon and a 1.2-Pg C (+4%) increase in reactive soil organic carbon. The modelled results indicate that the largest relative changes in net carbon storage have occurred in tropical deciduous forests, but that the largest absolute changes in net carbon storage have occurred in the moist and wet forests of the Basin. 3 Our results show that the strength of interannual variations in net carbon storage of undisturbed ecosystems in the Amazon Basin varies from a carbon source of 0.2 Pg C/year to a carbon sink of 0.7 Pg C/year. Precipitation, especially the amount received during the drier months, appears to be a major controller of annual net carbon storage in the Amazon Basin. Our analysis indicates further that changes in precipitation combine with changes in temperature to affect net carbon storage through influencing soil moisture and nutrient availability. 4 On average, our results suggest that the undisturbed Amazonian ecosystems accumulated 0.2 Pg C/year as a result of climate variability and increasing atmospheric CO2 over the study period. This amount is large enough to have compensated for most of the carbon losses associated with tropical deforestation in the Amazon during the same period. 5 Comparisons with empirical data indicate that climate variability and CO2 fertilization explain most of the variation in net carbon storage for the undisturbed ecosystems. Our analyses suggest that assessment of the regional carbon budget in the tropics should be made over at least one cycle of El Nino-Southern Oscillation because of inter-annual climate variability. Our analyses also suggest that proper scaling of the site-specific and sub-annual measurements of carbon fluxes to produce Basin-wide flux estimates must take into account seasonal and spatial variations in net carbon storage.

Reduction of Off-Boresight Fields for a TEM Horn Antenna

DTIC Science & Technology

1994-12-01

model predicts the tapers will reduce the diffraction. Experimental results verify the TPS’s ability to reduce the peak off-hureslht ld& for a. TElL horn...diffractin. Experimental results verify the PS’s ability to reduce the fields foi a T14 horn anitnna xi Reduction of Off-Boresight Fields for a TEM Horn...geometry, has a constant amplitude response. Two simple models repiesent a TEM horn - a high frequency model and a low frequency model [5). At high

Geoelectrical characterization by joint inversion of VES/TEM in Paraná basin, Brazil

NASA Astrophysics Data System (ADS)

Bortolozo, C. A.; Couto, M. A.; Almeida, E. R.; Porsani, J. L.; Santos, F. M.

2012-12-01

For many years electrical (DC) and transient electromagnetic (TEM) soundings have been used in a great number of environmental, hydrological and mining exploration studies. The data of both methods are interpreted usually by individual 1D models resulting in many cases in ambiguous models. This can be explained by how the two different methodologies sample the subsurface. The vertical electrical sounding (VES) is good on marking very resistive structures, while the transient electromagnetic sounding (TEM) is very sensitive to map conductive structures. Another characteristic is that VES is more sensitive to shallow structures, while TEM soundings can reach deeper structures. A Matlab program for joint inversion of VES and TEM soundings, by using CRS algorithm was developed aiming explore the best of the both methods. Initially, the algorithm was tested with synthetic data and after it was used to invert experimental data from Paraná sedimentary basin. We present the results of a re-interpretation of 46 VES/TEM soundings data set acquired in Bebedouro region in São Paulo State - Brazil. The previous interpretation was based in geoelectrical models obtained by single inversion of the VES and TEM soundings. In this work we present the results with single inversion of VES and TEM sounding inverted by the Curupira Program and a new interpretation based in the joint inversion of both methodologies. The goal is increase the accuracy in determining the underground structures. As a result a new geoelectrical model of the region is obtained.

Maximizing Spatial Reuse in Indoor Environments

DTIC Science & Technology

2010-12-01

interference model, which is the key model in our sys - tems to significantly reduce the number of measurements needed to make the coordinated decisions. We...fairness has an agreed-upon definition in wired networks [37, 61, 111] or operating sys - tems [71], there are conflicting notions of fairness in wireless...reasonable. In our systems, we adopt the implicit fairness model in the 802.11 systems. In 802.11 sys - tems, fairness is ensured in the sense that each

2.5D Modeling of TEM Data Applied to Hidrogeological Studies in PARANÁ Basin, Brazil

NASA Astrophysics Data System (ADS)

Bortolozo, C. A.; Porsani, J. L.; Santos, F. M.

2013-12-01

The transient electromagnetic method (TEM) is used all over the world and has shown great potential in hydrological, hazardous waste site characterization, mineral exploration, general geological mapping, and geophysical reconnaissance. However, the behavior of TEM fields are very complex and is not yet fully understood. Forward modeling is one of the most common and effective methods to understand the physical behavior and significance of the electromagnetics responses of a TEM sounding. Until now, there are a limited number of solutions for the 2D forward problem for TEM. More rare are the descriptions of a three-component response of a 3D source over 2D earth, which is the so-called 2.5D. The 2.5D approach is more realistic than the conventional 2D source previous used, once normally the source cannot be realistic represented for a 2D approximation (normally source are square loops). At present the 2.5D model represents the only way of interpreting TEM data in terms of a complex earth, due to the prohibitive amount of computer time and storage required for a full 3D model. In this work we developed a TEM modeling program for understanding the different responses and how the magnetic and electric fields, produced by loop sources at air-earth interface, behave in different geoelectrical distributions. The models used in the examples are proposed focusing hydrogeological studies, once the main objective of this work is for detecting different kinds of aquifers in Paraná sedimentary basin, in São Paulo State - Brazil. The program was developed in MATLAB, a widespread language very common in the scientific community.

VES/TEM 1D joint inversion by using Controlled Random Search (CRS) algorithm

NASA Astrophysics Data System (ADS)

Bortolozo, Cassiano Antonio; Porsani, Jorge Luís; Santos, Fernando Acácio Monteiro dos; Almeida, Emerson Rodrigo

2015-01-01

Electrical (DC) and Transient Electromagnetic (TEM) soundings are used in a great number of environmental, hydrological, and mining exploration studies. Usually, data interpretation is accomplished by individual 1D models resulting often in ambiguous models. This fact can be explained by the way as the two different methodologies sample the medium beneath surface. Vertical Electrical Sounding (VES) is good in marking resistive structures, while Transient Electromagnetic sounding (TEM) is very sensitive to conductive structures. Another difference is VES is better to detect shallow structures, while TEM soundings can reach deeper layers. A Matlab program for 1D joint inversion of VES and TEM soundings was developed aiming at exploring the best of both methods. The program uses CRS - Controlled Random Search - algorithm for both single and 1D joint inversions. Usually inversion programs use Marquadt type algorithms but for electrical and electromagnetic methods, these algorithms may find a local minimum or not converge. Initially, the algorithm was tested with synthetic data, and then it was used to invert experimental data from two places in Paraná sedimentary basin (Bebedouro and Pirassununga cities), both located in São Paulo State, Brazil. Geoelectric model obtained from VES and TEM data 1D joint inversion is similar to the real geological condition, and ambiguities were minimized. Results with synthetic and real data show that 1D VES/TEM joint inversion better recovers simulated models and shows a great potential in geological studies, especially in hydrogeological studies.

Potentials of satellite derived SIF products to constrain GPP simulated by the new ORCHIDEE-FluOR terrestrial model at the global scale

NASA Astrophysics Data System (ADS)

Bacour, C.; Maignan, F.; Porcar-Castell, A.; MacBean, N.; Goulas, Y.; Flexas, J.; Guanter, L.; Joiner, J.; Peylin, P.

2016-12-01

A new era for improving our knowledge of the terrestrial carbon cycle at the global scale has begun with recent studies on the relationships between remotely sensed Sun Induce Fluorescence (SIF) and plant photosynthetic activity (GPP), and the availability of such satellite-derived products now "routinely" produced from GOSAT, GOME-2, or OCO-2 observations. Assimilating SIF data into terrestrial ecosystem models (TEMs) represents a novel opportunity to reduce the uncertainty of their prediction with respect to carbon-climate feedbacks, in particular the uncertainties resulting from inaccurate parameter values. A prerequisite is a correct representation in TEMs of the several drivers of plant fluorescence from the leaf to the canopy scale, and in particular the competing processes of photochemistry and non photochemical quenching (NPQ).In this study, we present the first results of a global scale assimilation of GOME-2 SIF products within a new version of the ORCHIDEE land surface model including a physical module of plant fluorescence. At the leaf level, the regulation of fluorescence yield is simulated both by the photosynthesis module of ORCHIDEE to calculate the photochemical yield and by a parametric model to estimate NPQ. The latter has been calibrated on leaf fluorescence measurements performed for boreal coniferous and Mediterranean vegetation species. A parametric representation of the SCOPE radiative transfer model is used to model the plant fluorescence fluxes for PSI and PSII and the scaling up to the canopy level. The ORCHIDEE-FluOR model is firstly evaluated with respect to in situ measurements of plant fluorescence flux and photochemical yield for scots pine and wheat. The potentials of SIF data to constrain the modelled GPP are evaluated by assimilating one year of GOME-2-SIF products within ORCHIDEE-FluOR. We investigate in particular the changes in the spatial patterns of GPP following the optimization of the photosynthesis and phenology parameters. We analyze the differences obtained using a simpler fluorescence model in ORCHIDEE hypothesizing a linear relationship between SIF and GPP, and an independent simultaneous assimilation of three data-streams (in situ flux measurements, satellite derived NDVI and atmospheric CO2 concentrations).

Optimising electron microscopy experiment through electron optics simulation.

PubMed

Kubo, Y; Gatel, C; Snoeck, E; Houdellier, F

2017-04-01

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling the effects of snowpack on heterotrophic respiration across northern temperate and high latitude regions: Comparison with measurements of atmospheric carbon dioxide in high latitudes

USGS Publications Warehouse

McGuire, A.D.; Melillo, J.M.; Randerson, J.T.; Parton, W.J.; Heimann, Martin; Meier, R.A.; Clein, Joy S.; Kicklighter, D.W.; Sauf, W.

2000-01-01

Simulations by global terrestrial biogeochemical models (TBMs) consistently underestimate the concentration of atmospheric carbon dioxide (CO2) at high latitude monitoring stations during the nongrowing season. We hypothesized that heterotrophic respiration is underestimated during the nongrowing season primarily because TBMs do not generally consider the insulative effects of snowpack on soil temperature. To evaluate this hypothesis, we compared the performance of baseline and modified versions of three TBMs in simulating the seasonal cycle of atmospheric CO2 at high latitude CO2 monitoring stations; the modified version maintained soil temperature at 0 ??C when modeled snowpack was present. The three TBMs include the Carnegie-Ames-Stanford Approach (CASA), Century, and the Terrestrial Ecosystem Model (TEM). In comparison with the baseline simulation of each model, the snowpack simulations caused higher releases of CO2 between November and March and greater uptake of CO2 between June and August for latitudes north of 30??N. We coupled the monthly estimates of CO2 exchange, the seasonal carbon dioxide flux fields generated by the HAMOCC3 seasonal ocean carbon cycle model, and fossil fuel source fields derived from standard sources to the three-dimensional atmospheric transport model TM2 forced by observed winds to simulate the seasonal cycle of atmospheric CO2 at each of seven high latitude monitoring stations, in comparison to the CO2 concentrations simulated with the baseline fluxes of each TBM, concentrations simulated using the snowpack fluxes are generally in better agreement with observed concentrations between August and March at each of the monitoring stations. Thus, representation of the insulative effects of snowpack in TBMs generally improves simulation of atmospheric CO2 concentrations in high latitudes during both the late growing season and nongrowing season. These simulations highlight the global importance of biogeochemical processes during the nongrowing season in estimating carbon balance of ecosystems in northern high and temperate latitudes.

Effects of warming and clipping on ecosystem carbon fluxes across two hydrologically contrasting years in an alpine meadow of the Qinghai-Tibet Plateau.

PubMed

Peng, Fei; You, Quangang; Xu, Manhou; Guo, Jian; Wang, Tao; Xue, Xian

2014-01-01

Responses of ecosystem carbon (C) fluxes to human disturbance and climatic warming will affect terrestrial ecosystem C storage and feedback to climate change. We conducted a manipulative experiment to investigate the effects of warming and clipping on soil respiration (Rs), ecosystem respiration (ER), net ecosystem exchange (NEE) and gross ecosystem production (GEP) in an alpine meadow in a permafrost region during two hydrologically contrasting years (2012, with 29.9% higher precipitation than the long-term mean, and 2013, with 18.9% lower precipitation than the long-tem mean). Our results showed that GEP was higher than ER, leading to a net C sink (measured by NEE) over the two growing seasons. Warming significantly stimulated ecosystem C fluxes in 2012 but did not significantly affect these fluxes in 2013. On average, the warming-induced increase in GEP (1.49 µ mol m(-2) s(-1)) was higher than in ER (0.80 µ mol m(-2) s(-1)), resulting in an increase in NEE (0.70 µ mol m(-2) s(-1)). Clipping and its interaction with warming had no significant effects on C fluxes, whereas clipping significantly reduced aboveground biomass (AGB) by 51.5 g m(-2) in 2013. These results suggest the response of C fluxes to warming and clipping depends on hydrological variations. In the wet year, the warming treatment caused a reduction in water, but increases in soil temperature and AGB contributed to the positive response of ecosystem C fluxes to warming. In the dry year, the reduction in soil moisture, caused by warming, and the reduction in AGB, caused by clipping, were compensated by higher soil temperatures in warmed plots. Our findings highlight the importance of changes in soil moisture in mediating the responses of ecosystem C fluxes to climate warming in an alpine meadow ecosystem.

Effects of Warming and Clipping on Ecosystem Carbon Fluxes across Two Hydrologically Contrasting Years in an Alpine Meadow of the Qinghai-Tibet Plateau

PubMed Central

Peng, Fei; You, Quangang; Xu, Manhou; Guo, Jian; Wang, Tao; Xue, Xian

2014-01-01

Responses of ecosystem carbon (C) fluxes to human disturbance and climatic warming will affect terrestrial ecosystem C storage and feedback to climate change. We conducted a manipulative experiment to investigate the effects of warming and clipping on soil respiration (Rs), ecosystem respiration (ER), net ecosystem exchange (NEE) and gross ecosystem production (GEP) in an alpine meadow in a permafrost region during two hydrologically contrasting years (2012, with 29.9% higher precipitation than the long-term mean, and 2013, with 18.9% lower precipitation than the long-tem mean). Our results showed that GEP was higher than ER, leading to a net C sink (measured by NEE) over the two growing seasons. Warming significantly stimulated ecosystem C fluxes in 2012 but did not significantly affect these fluxes in 2013. On average, the warming-induced increase in GEP (1.49 µ mol m−2s−1) was higher than in ER (0.80 µ mol m−2s−1), resulting in an increase in NEE (0.70 µ mol m−2s−1). Clipping and its interaction with warming had no significant effects on C fluxes, whereas clipping significantly reduced aboveground biomass (AGB) by 51.5 g m−2 in 2013. These results suggest the response of C fluxes to warming and clipping depends on hydrological variations. In the wet year, the warming treatment caused a reduction in water, but increases in soil temperature and AGB contributed to the positive response of ecosystem C fluxes to warming. In the dry year, the reduction in soil moisture, caused by warming, and the reduction in AGB, caused by clipping, were compensated by higher soil temperatures in warmed plots. Our findings highlight the importance of changes in soil moisture in mediating the responses of ecosystem C fluxes to climate warming in an alpine meadow ecosystem. PMID:25291187

Virus-Bacterium Coupling Driven by both Turbidity and Hydrodynamics in an Amazonian Floodplain Lake ▿ † ‡

PubMed Central

Barros, Nathan; Farjalla, Vinicius F.; Soares, Maria C.; Melo, Rossana C. N.; Roland, Fábio

2010-01-01

The importance of viruses in aquatic ecosystem functioning has been widely described. However, few studies have examined tropical aquatic ecosystems. Here, we evaluated for the first time viruses and their relationship with other planktonic communities in an Amazonian freshwater ecosystem. Coupling between viruses and bacteria was studied, focusing both on hydrologic dynamics and anthropogenic forced turbidity in the system (Lake Batata). Samples were taken during four hydrologic seasons at both natural and impacted sites to count virus-like particles (VLP) and bacteria. In parallel, virus-infected bacteria were identified and quantified by transmission electron microscopy (TEM). Viral abundance ranged from 0.5 × 107 ± 0.2 × 107 VLP ml−1 (high-water season, impacted site) to 1.7 × 107 ± 0.4 × 107 VLP ml−1 (low-water season, natural site). These data were strongly correlated with the bacterial abundance (r2 = 0.84; P < 0.05), which ranged from 1.0 × 106 ± 0.5 × 106 cells ml−1 (high water, impacted site) to 3.4 × 106 ± 0.7 × 106 cells ml−1 (low water, natural site). Moreover, the viral abundance was weakly correlated with chlorophyll a, suggesting that most viruses were bacteriophages. TEM quantitative analyses revealed that the frequency of visibly infected cells was 20%, with 10 ± 3 phages per cell section. In general, we found a low virus-bacterium ratio (<7). Both the close coupling between the viral and bacterial abundances and the low virus-bacterium ratio suggest that viral abundance tends to be driven by the reduction of hosts for viral infection. Our results demonstrate that viruses are controlled by biological substrates, whereas in addition to grazing, bacteria are regulated by physical processes caused by turbidity, which affect underwater light distribution and dissolved organic carbon availability. PMID:20833790

Virus-bacterium coupling driven by both turbidity and hydrodynamics in an Amazonian floodplain lake.

PubMed

Barros, Nathan; Farjalla, Vinicius F; Soares, Maria C; Melo, Rossana C N; Roland, Fábio

2010-11-01

The importance of viruses in aquatic ecosystem functioning has been widely described. However, few studies have examined tropical aquatic ecosystems. Here, we evaluated for the first time viruses and their relationship with other planktonic communities in an Amazonian freshwater ecosystem. Coupling between viruses and bacteria was studied, focusing both on hydrologic dynamics and anthropogenic forced turbidity in the system (Lake Batata). Samples were taken during four hydrologic seasons at both natural and impacted sites to count virus-like particles (VLP) and bacteria. In parallel, virus-infected bacteria were identified and quantified by transmission electron microscopy (TEM). Viral abundance ranged from 0.5 × 10⁷ ± 0.2 × 10⁷ VLP ml⁻¹ (high-water season, impacted site) to 1.7 × 10⁷ ± 0.4 × 10⁷ VLP ml⁻¹ (low-water season, natural site). These data were strongly correlated with the bacterial abundance (r² = 0.84; P < 0.05), which ranged from 1.0 × 10⁶ ± 0.5 × 10⁶ cells ml⁻¹ (high water, impacted site) to 3.4 × 10⁶ ± 0.7 × 10⁶ cells ml⁻¹ (low water, natural site). Moreover, the viral abundance was weakly correlated with chlorophyll a, suggesting that most viruses were bacteriophages. TEM quantitative analyses revealed that the frequency of visibly infected cells was 20%, with 10 ± 3 phages per cell section. In general, we found a low virus-bacterium ratio (<7). Both the close coupling between the viral and bacterial abundances and the low virus-bacterium ratio suggest that viral abundance tends to be driven by the reduction of hosts for viral infection. Our results demonstrate that viruses are controlled by biological substrates, whereas in addition to grazing, bacteria are regulated by physical processes caused by turbidity, which affect underwater light distribution and dissolved organic carbon availability.

1D Cole-Cole inversion of TEM transients influenced by induced polarization

NASA Astrophysics Data System (ADS)

Seidel, Marc; Tezkan, Bülent

2017-03-01

Effects of induced polarization (IP) can have an impact on time-domain electromagnetic measurements (TEM) and may lead to sign reversals in the recorded transients. To study these IP effects on TEM data, a new 1D inversion algorithm was developed for both, the central-loop and the separate-loop TEM configurations using the Cole-Cole relaxation model. 1D forward calculations for a homogeneous half-space were conducted with the aim of analyzing the impacts of the Cole-Cole parameters on TEM transients with respect to possible sign reversals. The forward modelings showed that the variation of different parameters have comparable effects on the TEM transients. This leads to an increasing number of equivalent models as a result of inversion calculations. Subsequently, 1D inversions of synthetic data were performed to study the potentials and limitations of the algorithm regarding the resolution of the Cole-Cole parameters. In order to achieve optimal inversion results, it was essential to error-weight the data points in the direct vicinity of sign reversals. The obtained findings were eventually adopted on the inversion of real field data which contained considerable IP signatures such as sign reversals. One field data set was recorded at the Nakyn kimberlite field in Western Yakutiya, Russia, in the central-loop configuration. Another field data set originates from a waste site in Cologne, Germany, and was measured utilizing the separate-loop configuration.

An agent-based model of leukocyte transendothelial migration during atherogenesis.

PubMed

Bhui, Rita; Hayenga, Heather N

2017-05-01

A vast amount of work has been dedicated to the effects of hemodynamics and cytokines on leukocyte adhesion and trans-endothelial migration (TEM) and subsequent accumulation of leukocyte-derived foam cells in the artery wall. However, a comprehensive mechanobiological model to capture these spatiotemporal events and predict the growth and remodeling of an atherosclerotic artery is still lacking. Here, we present a multiscale model of leukocyte TEM and plaque evolution in the left anterior descending (LAD) coronary artery. The approach integrates cellular behaviors via agent-based modeling (ABM) and hemodynamic effects via computational fluid dynamics (CFD). In this computational framework, the ABM implements the diffusion kinetics of key biological proteins, namely Low Density Lipoprotein (LDL), Tissue Necrosis Factor alpha (TNF-α), Interlukin-10 (IL-10) and Interlukin-1 beta (IL-1β), to predict chemotactic driven leukocyte migration into and within the artery wall. The ABM also considers wall shear stress (WSS) dependent leukocyte TEM and compensatory arterial remodeling obeying Glagov's phenomenon. Interestingly, using fully developed steady blood flow does not result in a representative number of leukocyte TEM as compared to pulsatile flow, whereas passing WSS at peak systole of the pulsatile flow waveform does. Moreover, using the model, we have found leukocyte TEM increases monotonically with decreases in luminal volume. At critical plaque shapes the WSS changes rapidly resulting in sudden increases in leukocyte TEM suggesting lumen volumes that will give rise to rapid plaque growth rates if left untreated. Overall this multi-scale and multi-physics approach appropriately captures and integrates the spatiotemporal events occurring at the cellular level in order to predict leukocyte transmigration and plaque evolution.

An agent-based model of leukocyte transendothelial migration during atherogenesis

PubMed Central

Bhui, Rita; Hayenga, Heather N.

2017-01-01

A vast amount of work has been dedicated to the effects of hemodynamics and cytokines on leukocyte adhesion and trans-endothelial migration (TEM) and subsequent accumulation of leukocyte-derived foam cells in the artery wall. However, a comprehensive mechanobiological model to capture these spatiotemporal events and predict the growth and remodeling of an atherosclerotic artery is still lacking. Here, we present a multiscale model of leukocyte TEM and plaque evolution in the left anterior descending (LAD) coronary artery. The approach integrates cellular behaviors via agent-based modeling (ABM) and hemodynamic effects via computational fluid dynamics (CFD). In this computational framework, the ABM implements the diffusion kinetics of key biological proteins, namely Low Density Lipoprotein (LDL), Tissue Necrosis Factor alpha (TNF-α), Interlukin-10 (IL-10) and Interlukin-1 beta (IL-1β), to predict chemotactic driven leukocyte migration into and within the artery wall. The ABM also considers wall shear stress (WSS) dependent leukocyte TEM and compensatory arterial remodeling obeying Glagov’s phenomenon. Interestingly, using fully developed steady blood flow does not result in a representative number of leukocyte TEM as compared to pulsatile flow, whereas passing WSS at peak systole of the pulsatile flow waveform does. Moreover, using the model, we have found leukocyte TEM increases monotonically with decreases in luminal volume. At critical plaque shapes the WSS changes rapidly resulting in sudden increases in leukocyte TEM suggesting lumen volumes that will give rise to rapid plaque growth rates if left untreated. Overall this multi-scale and multi-physics approach appropriately captures and integrates the spatiotemporal events occurring at the cellular level in order to predict leukocyte transmigration and plaque evolution. PMID:28542193

Modeling heat stress effect on Holstein cows under hot and dry conditions: selection tools.

PubMed

Carabaño, M J; Bachagha, K; Ramón, M; Díaz, C

2014-12-01

Data from milk recording of Holstein-Friesian cows together with weather information from 2 regions in Southern Spain were used to define the models that can better describe heat stress response for production traits and somatic cell score (SCS). Two sets of analyses were performed, one aimed at defining the population phenotypic response and the other at studying the genetic components. The first involved 2,514,762 test-day records from up to 5 lactations of 128,112 cows. Two models, one fitting a comfort threshold for temperature and a slope of decay after the threshold, and the other a cubic Legendre polynomial (LP) model were tested. Average (TAVE) and maximum daily temperatures were alternatively considered as covariates. The LP model using TAVE as covariate showed the best goodness of fit for all traits. Estimated rates of decay from this model for production at 25 and 34°C were 36 and 170, 3.8 and 3.0, and 3.9 and 8.2g/d per degree Celsius for milk, fat, and protein yield, respectively. In the second set of analyses, a sample of 280,958 test-day records from first lactations of 29,114 cows was used. Random regression models including quadratic or cubic LP regressions (TEM_) on TAVE or a fixed threshold and an unknown slope (DUMMY), including or not cubic regressions on days in milk (DIM3_), were tested. For milk and SCS, the best models were the DIM3_ models. In contrast, for fat and protein yield, the best model was TEM3. The DIM3DUMMY models showed similar performance to DIM3TEM3. The estimated genetic correlations between the same trait under cold and hot temperatures (ρ) indicated the existence of a large genotype by environment interaction for fat (ρ=0.53 for model TEM3) and protein yield (ρ around 0.6 for DIM3TEM3) and for SCS (ρ=0.64 for model DIM3TEM3), and a small genotype by environment interaction for milk (ρ over 0.8). The eigendecomposition of the additive genetic covariance matrix from model TEM3 showed the existence of a dominant component, a constant term that is not affected by temperature, representing from 64% of the variation for SCS to 91% of the variation for milk. The second component, showing a flat pattern at intermediate temperatures and increasing or decreasing slopes for the extremes, gathered 15, 11, and 24% of the variation for fat and protein yield and SCS, respectively. This component could be further evaluated as a selection criterion for heat tolerance independently of the production level. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

GISAXS modelling of helium-induced nano-bubble formation in tungsten and comparison with TEM

NASA Astrophysics Data System (ADS)

Thompson, Matt; Sakamoto, Ryuichi; Bernard, Elodie; Kirby, Nigel; Kluth, Patrick; Riley, Daniel; Corr, Cormac

2016-05-01

Grazing-incidence small angle x-ray scattering (GISAXS) is a powerful non-destructive technique for the measurement of nano-bubble formation in tungsten under helium plasma exposure. Here, we present a comparative study between transmission electron microscopy (TEM) and GISAXS measurements of nano-bubble formation in tungsten exposed to helium plasma in the Large Helical Device (LHD) fusion experiment. Both techniques are in excellent agreement, suggesting that nano-bubbles range from spheroidal to ellipsoidal, displaying exponential diameter distributions with mean diameters μ=0.68 ± 0.04 nm and μ=0.6 ± 0.1 nm measured by TEM and GISAXS respectively. Depth distributions were also computed, with calculated exponential depth distributions with mean depths of 8.4 ± 0.5 nm and 9.1 ± 0.4 nm for TEM and GISAXS. In GISAXS modelling, spheroidal particles were fitted with an aspect ratio ε=0.7 ± 0.1. The GISAXS model used is described in detail.

Climate change, species distribution models, and physiological performance metrics: predicting when biogeographic models are likely to fail.

PubMed

Woodin, Sarah A; Hilbish, Thomas J; Helmuth, Brian; Jones, Sierra J; Wethey, David S

2013-09-01

Modeling the biogeographic consequences of climate change requires confidence in model predictions under novel conditions. However, models often fail when extended to new locales, and such instances have been used as evidence of a change in physiological tolerance, that is, a fundamental niche shift. We explore an alternative explanation and propose a method for predicting the likelihood of failure based on physiological performance curves and environmental variance in the original and new environments. We define the transient event margin (TEM) as the gap between energetic performance failure, defined as CTmax, and the upper lethal limit, defined as LTmax. If TEM is large relative to environmental fluctuations, models will likely fail in new locales. If TEM is small relative to environmental fluctuations, models are likely to be robust for new locales, even when mechanism is unknown. Using temperature, we predict when biogeographic models are likely to fail and illustrate this with a case study. We suggest that failure is predictable from an understanding of how climate drives nonlethal physiological responses, but for many species such data have not been collected. Successful biogeographic forecasting thus depends on understanding when the mechanisms limiting distribution of a species will differ among geographic regions, or at different times, resulting in realized niche shifts. TEM allows prediction of the likelihood of such model failure.

Survival study of natural orifice translumenal endoscopic surgery for rectosigmoid resection using transanal endoscopic microsurgery with or without transgastric endoscopic assistance in a swine model.

PubMed

Sylla, Patricia; Sohn, Dae Kyung; Cizginer, Sevdenur; Konuk, Yusuf; Turner, Brian G; Gee, Denise W; Willingham, Field F; Hsu, Maylee; Mino-Kenudson, Mari; Brugge, William R; Rattner, David W

2010-08-01

The feasibility of transanal rectosigmoid resection with transanal endoscopic microsurgery (TEM) was previously demonstrated in a swine nonsurvival model in which transgastric endoscopic assistance also was shown to extend the length of colon mobilized transanally. A 2-week survival study evaluating transanal endoscopic rectosigmoid resection with stapled colorectal anastomosis was conducted with swine using the transanal approach alone (TEM group, n = 10) or a transanal approach combined with transgastric endoscopic assistance (TEM + TG group, n = 10). Gastrotomies were created using a needleknife and balloon dilation, then closed using prototype T-tags. Outcomes were evaluated and compared between the groups using Student's t-test and Fisher's exact test. Relative to the TEM group, the average length of rectosigmoid mobilized in the TEM + TG group was 15.6 versus 10.5 cm (p < 0.0005), the length of the resected specimen was 9 versus 6.2 cm (p < 0.0005), and the mean operative time was 254.5 versus 97.5 min (p < 0.0005). Intraoperatively, no organ injury or major bleeding was noted. Two T-tag misfires occurred during gastrotomy closure and four small staple line defects requiring transanal repair including one in the TEM group and three in the TEM + TG group (p = 0.2). Postoperatively, there was no mortality, and the animals gained an average of 3.4 lb. Two major complications (10%) were identified at necropsy in the TEM + TG group including an intraabdominal abscess and an abdominal wall hematoma related to T-tag misfire. Gastrotomy closure sites and colorectal anastomoses were all grossly healed, with adhesions noted in 60 and 70% and microabscesses in 50 and 20% of the gastrotomy sites and colorectal anastomoses, respectively. Natural orifice translumenal endoscopic surgery (NOTES) for rectosigmoid resection using TEM with or without transgastric endoscopic assistance is feasible and associated with low morbidity in a porcine survival model. Transgastric assistance significantly prolongs the operative time but extends the length of the rectosigmoid mobilized transanally, with a nonsignificant increase in complication rates related to gastrotomy creation.

Microscopic evaluation of trace metals in cloud droplets in an acid precipitation region.

PubMed

Li, Weijun; Wang, Yan; Collett, Jeffrey L; Chen, Jianmin; Zhang, Xiaoye; Wang, Zifa; Wang, Wenxing

2013-05-07

Mass concentrations of soluble trace metals and size, number, and mixing properties of nanometal particles in clouds determine their toxicity to ecosystems. Cloud water was found to be acidic, with a pH of 3.52, at Mt. Lu (elevation 1,165 m) in an acid precipitation region in South China. A combination of Inductively Coupled Plasma Mass Spectrometry (ICPMS) and Transmission Electron Microscopy (TEM) for the first time demonstrates that the soluble metal concentrations and solid metal particle number are surprisingly high in acid clouds at Mt. Lu, where daily concentrations of SO2, NO2, and PM10 are 18 μg m(-3), 7 μg m(-3), and 22 μg m(-3). The soluble metals in cloudwater with the highest concentrations were zinc (Zn, 200 μg L(-1)), iron (Fe, 88 μg L(-1)), and lead (Pb, 77 μg L(-1)). TEM reveals that 76% of cloud residues include metal particles that range from 50 nm to 1 μm diameter with a median diameter of 250 nm. Four major metal-associated particle types are Pb-rich (35%), fly ash (27%), Fe-rich (23%), and Zn-rich (15%). Elemental mapping shows that minor soluble metals are distributed within sulfates of cloud residues. Emissions of fine metal particles from large, nonferrous industries and coal-fired power plants with tall stacks were transported upward to this high elevation. Our results suggest that the abundant trace metals in clouds aggravate the impacts of acid clouds or associated precipitation on the ecosystem and human health.

Results of time-domain electromagnetic soundings in Miami-Dade and southern Broward Counties, Florida

USGS Publications Warehouse

Fitterman, David V.; Prinos, Scott T.

2011-01-01

Time-domain electromagnetic (TEM) soundings were made in Miami-Dade and southern Broward Counties to aid in mapping the landward extent of saltwater in the Biscayne aquifer. A total of 79 soundings were collected in settings ranging from urban to undeveloped land, with some of the former posing problems of land access and interference from anthropogenic features. TEM soundings combined with monitoring-well data were used to determine if the saltwater front had moved since the last time it was mapped, to provide additional spatial coverage where existing monitoring wells were insufficient, and to help interpret a previously collected helicopter electromagnetic (HEM) survey flown in the southernmost portion of the study area. TEM soundings were interpreted as layered resistivity-depth models. Using information from well logs and water-quality data, the resistivity of the freshwater saturated Biscayne aquifer is expected to be above 30 ohm-meters, and the saltwater-saturated aquifer will have resistivities of less than 10 ohm-meters allowing determination of water quality from the TEM interpretations. TEM models from 29 soundings were compared to electromagnetic induction logs collected in nearby monitoring wells. In general, the agreement of these results was very good, giving confidence in the use of the TEM data for mapping saltwater encroachment.

Time-domain electromagnetic surveys at Fort Irwin, San Bernardino County, California, 2010-12: Chapter F in Geology and geophysics applied to groundwater hydrology at Fort Irwin, California

USGS Publications Warehouse

Burgess, Matthew K.; Bedrosian, Paul A.; Buesch, David C.

2014-01-01

Between 2010 and 2012, a total of 79 time-domain electromagnetic (TEM) soundings were collected in 12 groundwater basins in the U.S. Army Fort Irwin National Training Center (NTC) study area to help improve the understanding of the hydrogeology of the NTC. The TEM data are discussed in this chapter in the context of geologic observations of the study area, the details of which are provided in the other chapters of this volume. Selection of locations for TEM soundings in unexplored basins was guided by gravity data that estimated depth to pre-Tertiary basement complex of crystalline rock and alluvial thickness. Some TEM data were collected near boreholes with geophysical logs. The TEM response at locations near boreholes was used to evaluate sounding data for areas without boreholes. TEM models also were used to guide site selection of subsequent boreholes drilled as part of this study. Following borehole completion, geophysical logs were used to ground-truth and reinterpret previously collected TEM data. This iterative process was used to site subsequent TEM soundings and borehole locations as the study progressed. Although each groundwater subbasin within the NTC boundaries was explored using the TEM method, collection of TEM data was focused in those basins identified as best suited for development of water resources. At the NTC, TEM estimates of some lithologic thicknesses and electrical properties in the unsaturated zone are in good accordance with borehole data; however, water-table elevations were not easily identifiable from TEM data.

Transient Electromagnetic Soundings Near Great Sand Dunes National Park and Preserve, San Luis Valley, Colorado (2006 Field Season)

USGS Publications Warehouse

Fitterman, David V.; de Sozua Filho, Oderson A.

2009-01-01

Time-domain electromagnetic (TEM) soundings were made near Great Sand Dunes National Park and Preserve in the San Luis Valley of southern Colorado to obtain subsurface information of use to hydrologic modeling. Seventeen soundings were made to the east and north of the sand dunes. Using a small loop TEM system, maximum exploration depths of about 75 to 150 m were obtained. In general, layered earth interpretations of the data found that resistivity decreases with depth. Comparison of soundings with geologic logs from nearby wells found that zones logged as having increased clay content usually corresponded with a significant resistivity decrease in the TEM determined model. This result supports the use of TEM soundings to map the location of the top of the clay unit deposited at the bottom of the ancient Lake Alamosa that filled the San Luis Valley from Pliocene to middle Pleistocene time.

Implications of Ozone on Carbon Sequestration and Climate Policy in the U.S. Using the MIT Integrated Global Systems Model

NASA Astrophysics Data System (ADS)

Felzer, B. S.; Reilly, J. M.; Melillo, J. M.; Kicklighter, D. W.; Wang, C.; Prinn, R.; Sarofim, M. C.; Zhuang, Q.

2003-12-01

Exposure of plants to ozone inhibits photosynthesis and therefore reduces vegetation production and carbon sequestration. The damaging effects of tropospheric ozone vary spatially because human activities responsible for the emissions of ozone precursors are highly concentrated in urban and industrial centers. We developed scenarios of ozone-precursor emissions and the resultant ozone concentrations using the MIT Integrated Global Systems Model (IGSM) through the year 2100 and explored the consequent effects on terrestrial ecosystems using the Terrestrial Ecosystem Model (TEM). We then used the Emissions Prediction and Policy Analysis (EPPA) model, a component of the IGSM, to evaluate the cost of increased mitigation efforts required to offset lost carbon sequestration. We considered both a global climate policy that limits future greenhouse gas (GHG) emissions and an air quality policy that limits pollutant emissions to their 1995 levels in the developed countries. We also considered agricultural management that includes optimal irrigation and fertilization and no irrigation and fertilization for croplands. We found that the loss of carbon sequestration in the U.S. at the end of the 21st century due to ozone pollution ranged from negligible to as much as 0.3 PgC yr-1 depending upon the policy options pursued. We valued these reductions in terms of the change in the net present value of the cost to the U.S. through 2100 of a global carbon policy designed to approximately stabilize atmospheric CO2 levels at 550 ppm. For the U.S., failure to consider ozone damages to vegetation would by itself raise the costs over the next century of stabilizing atmospheric concentrations of CO2 by 11 to 19% (\\0.3 to \\0.6 trillion) because emissions from fossil fuels will need to be reduced more to compensate for the reduced carbon sequestration by terrestrial ecosystems. With a pollution cap, damages are reduced to 6 to 12% (\\0.2 to \\0.3 trillion) of the total cost. However, climate policy that reduces fossil fuel use and methane emissions would also reduce the emissions of the ozone precursors and therefore, ozone concentrations and ozone damages. The savings in reduced carbon emissions reductions costs are estimated to be between 1 and 17% (\\0.09 to \\0.3 trillion) of the cost of the climate policy. The cost estimates are sensitive to the assumed 5% discount rate and the details of the climate policy and how the burden is allocated among countries. Tropospheric ozone effects on terrestrial ecosystems produce a surprisingly large feedback in estimating climate policy costs that, heretofore, has not been included in cost estimates.

Modelling proteins' hidden conformations to predict antibiotic resistance

NASA Astrophysics Data System (ADS)

Hart, Kathryn M.; Ho, Chris M. W.; Dutta, Supratik; Gross, Michael L.; Bowman, Gregory R.

2016-10-01

TEM β-lactamase confers bacteria with resistance to many antibiotics and rapidly evolves activity against new drugs. However, functional changes are not easily explained by differences in crystal structures. We employ Markov state models to identify hidden conformations and explore their role in determining TEM's specificity. We integrate these models with existing drug-design tools to create a new technique, called Boltzmann docking, which better predicts TEM specificity by accounting for conformational heterogeneity. Using our MSMs, we identify hidden states whose populations correlate with activity against cefotaxime. To experimentally detect our predicted hidden states, we use rapid mass spectrometric footprinting and confirm our models' prediction that increased cefotaxime activity correlates with reduced Ω-loop flexibility. Finally, we design novel variants to stabilize the hidden cefotaximase states, and find their populations predict activity against cefotaxime in vitro and in vivo. Therefore, we expect this framework to have numerous applications in drug and protein design.

Changes in vegetation in northern Alaska under scenarios of climate change, 2003-2100: implications for climate feedbacks

USGS Publications Warehouse

Euskirchen, Eugénie S.; McGuire, Anthony David; Chapin, F. Stuart; Yi, S.; Thompson, Catharine Copass

2009-01-01

Assessing potential future changes in arctic and boreal plant species productivity, ecosystem composition, and canopy complexity is essential for understanding environmental responses under expected altered climate forcing. We examined potential changes in the dominant plant functional types (PFTs) of the sedge tundra, shrub tundra, and boreal forest ecosystems in ecotonal northern Alaska, USA, for the years 2003–2100. We compared energy feedbacks associated with increases in biomass to energy feedbacks associated with changes in the duration of the snow-free season. We based our simulations on nine input climate scenarios from the Intergovernmental Panel on Climate Change (IPCC) and a new version of the Terrestrial Ecosystem Model (TEM) that incorporates biogeochemistry, vegetation dynamics for multiple PFTs (e.g., trees, shrubs, grasses, sedges, mosses), multiple vegetation pools, and soil thermal regimes. We found mean increases in net primary productivity (NPP) in all PFTs. Most notably, birch (Betula spp.) in the shrub tundra showed increases that were at least three times larger than any other PFT. Increases in NPP were positively related to increases in growing-season length in the sedge tundra, but PFTs in boreal forest and shrub tundra showed a significant response to changes in light availability as well as growing-season length. Significant NPP responses to changes in vegetation uptake of nitrogen by PFT indicated that some PFTs were better competitors for nitrogen than other PFTs. While NPP increased, heterotrophic respiration (RH) also increased, resulting in decreases or no change in net ecosystem carbon uptake. Greater aboveground biomass from increased NPP produced a decrease in summer albedo, greater regional heat absorption (0.34 ± 0.23 W·m−2·10 yr−1 [mean ± SD]), and a positive feedback to climate warming. However, the decrease in albedo due to a shorter snow season (−5.1 ± 1.6 d/10 yr) resulted in much greater regional heat absorption (3.3 ± 1.24 W·m−2·10 yr−1) than that associated with increases in vegetation. Through quantifying feedbacks associated with changes in vegetation and those associated with changes in the snow season length, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the climate system.

The EBM-DPSER Conceptual Model: Integrating Ecosystem Services into the DPSIR Framework

PubMed Central

Kelble, Christopher R.; Loomis, Dave K.; Lovelace, Susan; Nuttle, William K.; Ortner, Peter B.; Fletcher, Pamela; Cook, Geoffrey S.; Lorenz, Jerry J.; Boyer, Joseph N.

2013-01-01

There is a pressing need to integrate biophysical and human dimensions science to better inform holistic ecosystem management supporting the transition from single species or single-sector management to multi-sector ecosystem-based management. Ecosystem-based management should focus upon ecosystem services, since they reflect societal goals, values, desires, and benefits. The inclusion of ecosystem services into holistic management strategies improves management by better capturing the diversity of positive and negative human-natural interactions and making explicit the benefits to society. To facilitate this inclusion, we propose a conceptual model that merges the broadly applied Driver, Pressure, State, Impact, and Response (DPSIR) conceptual model with ecosystem services yielding a Driver, Pressure, State, Ecosystem service, and Response (EBM-DPSER) conceptual model. The impact module in traditional DPSIR models focuses attention upon negative anthropomorphic impacts on the ecosystem; by replacing impacts with ecosystem services the EBM-DPSER model incorporates not only negative, but also positive changes in the ecosystem. Responses occur as a result of changes in ecosystem services and include inter alia management actions directed at proactively altering human population or individual behavior and infrastructure to meet societal goals. The EBM-DPSER conceptual model was applied to the Florida Keys and Dry Tortugas marine ecosystem as a case study to illustrate how it can inform management decisions. This case study captures our system-level understanding and results in a more holistic representation of ecosystem and human society interactions, thus improving our ability to identify trade-offs. The EBM-DPSER model should be a useful operational tool for implementing EBM, in that it fully integrates our knowledge of all ecosystem components while focusing management attention upon those aspects of the ecosystem most important to human society and does so within a framework already familiar to resource managers. PMID:23951002

The EBM-DPSER conceptual model: integrating ecosystem services into the DPSIR framework.

PubMed

Kelble, Christopher R; Loomis, Dave K; Lovelace, Susan; Nuttle, William K; Ortner, Peter B; Fletcher, Pamela; Cook, Geoffrey S; Lorenz, Jerry J; Boyer, Joseph N

2013-01-01

There is a pressing need to integrate biophysical and human dimensions science to better inform holistic ecosystem management supporting the transition from single species or single-sector management to multi-sector ecosystem-based management. Ecosystem-based management should focus upon ecosystem services, since they reflect societal goals, values, desires, and benefits. The inclusion of ecosystem services into holistic management strategies improves management by better capturing the diversity of positive and negative human-natural interactions and making explicit the benefits to society. To facilitate this inclusion, we propose a conceptual model that merges the broadly applied Driver, Pressure, State, Impact, and Response (DPSIR) conceptual model with ecosystem services yielding a Driver, Pressure, State, Ecosystem service, and Response (EBM-DPSER) conceptual model. The impact module in traditional DPSIR models focuses attention upon negative anthropomorphic impacts on the ecosystem; by replacing impacts with ecosystem services the EBM-DPSER model incorporates not only negative, but also positive changes in the ecosystem. Responses occur as a result of changes in ecosystem services and include inter alia management actions directed at proactively altering human population or individual behavior and infrastructure to meet societal goals. The EBM-DPSER conceptual model was applied to the Florida Keys and Dry Tortugas marine ecosystem as a case study to illustrate how it can inform management decisions. This case study captures our system-level understanding and results in a more holistic representation of ecosystem and human society interactions, thus improving our ability to identify trade-offs. The EBM-DPSER model should be a useful operational tool for implementing EBM, in that it fully integrates our knowledge of all ecosystem components while focusing management attention upon those aspects of the ecosystem most important to human society and does so within a framework already familiar to resource managers.

Direct observation of a stacking fault in Si(1 - x)Ge(x) semiconductors by spherical aberration-corrected TEM and conventional ADF-STEM.

PubMed

Yamasaki, Jun; Kawai, Tomoyuki; Tanaka, Nobuo

2004-01-01

Spherical aberration (C(S))-corrected transmission electron microscopy (TEM) and annular dark-field scanning TEM (ADF-STEM) are applied to high-resolution observation of stacking faults in Si(1 - x)Ge(x) alloy films prepared on a Si(100) buffer layer by the chemical vapor deposition method. Both of the images clarify the individual nature of stacking faults from their directly interpretable image contrast and also by using image simulation in the case of the C(S)-corrected TEM. Positions of the atomic columns obtained in the ADF-STEM images almost agree with a projection of the theoretical model studied by Chou et al. (Phys. Rev. B 32(1985): 7979). Comparison between the C(S)-corrected TEM and ADF-STEM images shows that their resolution is at a similar level, but directly interpretable image contrast is obtained in ultrathin samples for C(S)-corrected TEM and in slightly thicker samples for ADF-STEM.

Benchmarking Terrestrial Ecosystem Models in the South Central US

NASA Astrophysics Data System (ADS)

Kc, M.; Winton, K.; Langston, M. A.; Luo, Y.

2016-12-01

Ecosystem services and products are the foundation of sustainability for regional and global economy since we are directly or indirectly dependent on the ecosystem services like food, livestock, water, air, wildlife etc. It has been increasingly recognized that for sustainability concerns, the conservation problems need to be addressed in the context of entire ecosystems. This approach is even more vital in the 21st century with formidable increasing human population and rapid changes in global environment. This study was conducted to find the state of the science of ecosystem models in the South-Central region of US. The ecosystem models were benchmarked using ILAMB diagnostic package developed as a result of International Land Model Benchmarking (ILAMB) project on four main categories; viz, Ecosystem and Carbon Cycle, Hydrology Cycle, Radiation and Energy Cycle and Climate forcings. A cumulative assessment was generated with weighted seven different skill assessment metrics for the ecosystem models. This synthesis on the current state of the science of ecosystem modeling in the South-Central region of US will be highly useful towards coupling these models with climate, agronomic, hydrologic, economic or management models to better represent ecosystem dynamics as affected by climate change and human activities; and hence gain more reliable predictions of future ecosystem functions and service in the region. Better understandings of such processes will increase our ability to predict the ecosystem responses and feedbacks to environmental and human induced change in the region so that decision makers can make an informed management decisions of the ecosystem.

Assessing Ecosystem Model Performance in Semiarid Systems

NASA Astrophysics Data System (ADS)

Thomas, A.; Dietze, M.; Scott, R. L.; Biederman, J. A.

2017-12-01

In ecosystem process modelling, comparing outputs to benchmark datasets observed in the field is an important way to validate models, allowing the modelling community to track model performance over time and compare models at specific sites. Multi-model comparison projects as well as models themselves have largely been focused on temperate forests and similar biomes. Semiarid regions, on the other hand, are underrepresented in land surface and ecosystem modelling efforts, and yet will be disproportionately impacted by disturbances such as climate change due to their sensitivity to changes in the water balance. Benchmarking models at semiarid sites is an important step in assessing and improving models' suitability for predicting the impact of disturbance on semiarid ecosystems. In this study, several ecosystem models were compared at a semiarid grassland in southwestern Arizona using PEcAn, or the Predictive Ecosystem Analyzer, an open-source eco-informatics toolbox ideal for creating the repeatable model workflows necessary for benchmarking. Models included SIPNET, DALEC, JULES, ED2, GDAY, LPJ-GUESS, MAESPA, CLM, CABLE, and FATES. Comparison between model output and benchmarks such as net ecosystem exchange (NEE) tended to produce high root mean square error and low correlation coefficients, reflecting poor simulation of seasonality and the tendency for models to create much higher carbon sources than observed. These results indicate that ecosystem models do not currently adequately represent semiarid ecosystem processes.

Enhancement of structure images of interstellar diamond microcrystals by image processing

NASA Technical Reports Server (NTRS)

O'Keefe, Michael A.; Hetherington, Crispin; Turner, John; Blake, David; Freund, Friedemann

1988-01-01

Image processed high resolution TEM images of diamond crystals found in oxidized acid residues of carbonaceous chondrites are presented. Two models of the origin of the diamonds are discussed. The model proposed by Lewis et al. (1987) supposes that the diamonds formed under low pressure conditions, whereas that of Blake et al (1988) suggests that the diamonds formed due to particle-particle collisions behind supernova shock waves. The TEM images of the diamond presented support the high pressure model.

The Eating Motivation Survey: results from the USA, India and Germany.

PubMed

Sproesser, Gudrun; Ruby, Matthew B; Arbit, Naomi; Rozin, Paul; Schupp, Harald T; Renner, Britta

2018-02-01

Research has shown that there is a large variety of different motives underlying why people eat what they eat, which can be assessed with The Eating Motivation Survey (TEMS). The present study investigates the consistency and measurement invariance of the fifteen basic motives included in TEMS in countries with greatly differing eating environments. The fifteen-factor structure of TEMS (brief version: forty-six items) was tested in confirmatory factor analyses. An online survey was conducted. US-American, Indian and German adults (total N 749) took part. Despite the complexity of the model, fit indices indicated a reasonable model fit (for the total sample: χ 2/df=4·03; standardized root-mean-squared residual (SRMR)=0·063; root-mean-square error of approximation (RMSEA)=0·064 (95 % CI 0·062, 0·066)). Only the comparative fit index (CFI) was below the recommended threshold (for the total sample: CFI=0·84). Altogether, 181 out of 184 item loadings were above the recommended threshold of 0·30. Furthermore, the factorial structure of TEMS was invariant across countries with respect to factor configuration and factor loadings (configural v. metric invariance model: ΔCFI=0·009; ΔRMSEA=0·001; ΔSRMR=0·001). Moreover, forty-three out of forty-six items showed invariant intercepts across countries. The fifteen-factor structure of TEMS was, in general, confirmed across countries despite marked differences in eating environments. Moreover, latent means of fourteen out of fifteen motive factors can be compared across countries in future studies. This is a first step towards determining generalizability of the fifteen basic eating motives of TEMS across eating environments.

Ecosystem Model Skill Assessment. Yes We Can!

PubMed Central

Olsen, Erik; Fay, Gavin; Gaichas, Sarah; Gamble, Robert; Lucey, Sean; Link, Jason S.

2016-01-01

Need to Assess the Skill of Ecosystem Models Accelerated changes to global ecosystems call for holistic and integrated analyses of past, present and future states under various pressures to adequately understand current and projected future system states. Ecosystem models can inform management of human activities in a complex and changing environment, but are these models reliable? Ensuring that models are reliable for addressing management questions requires evaluating their skill in representing real-world processes and dynamics. Skill has been evaluated for just a limited set of some biophysical models. A range of skill assessment methods have been reviewed but skill assessment of full marine ecosystem models has not yet been attempted. Northeast US Atlantis Marine Ecosystem Model We assessed the skill of the Northeast U.S. (NEUS) Atlantis marine ecosystem model by comparing 10-year model forecasts with observed data. Model forecast performance was compared to that obtained from a 40-year hindcast. Multiple metrics (average absolute error, root mean squared error, modeling efficiency, and Spearman rank correlation), and a suite of time-series (species biomass, fisheries landings, and ecosystem indicators) were used to adequately measure model skill. Overall, the NEUS model performed above average and thus better than expected for the key species that had been the focus of the model tuning. Model forecast skill was comparable to the hindcast skill, showing that model performance does not degenerate in a 10-year forecast mode, an important characteristic for an end-to-end ecosystem model to be useful for strategic management purposes. Skill Assessment Is Both Possible and Advisable We identify best-practice approaches for end-to-end ecosystem model skill assessment that would improve both operational use of other ecosystem models and future model development. We show that it is possible to not only assess the skill of a complicated marine ecosystem model, but that it is necessary do so to instill confidence in model results and encourage their use for strategic management. Our methods are applicable to any type of predictive model, and should be considered for use in fields outside ecology (e.g. economics, climate change, and risk assessment). PMID:26731540

Consequences of changes in vegetation and snow cover for climate feedbacks in Alaska and northwest Canada

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Bennett, A. P.; Breen, A. L.; Genet, H.; Lindgren, M. A.; Kurkowski, T. A.; McGuire, A. D.; Rupp, T. S.

2016-10-01

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m-2 decade-1 regionally) compared to the CCCMA (+1.3 W m-2 decade-1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (-0.2 to -0.3 W m-2 decade-1). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m-2 decade regionally in the ECHAM scenario compared to +0.76 W m-2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Consequences of Changes in Vegetation and Snow Cover for Climate Feedbacks in Alaska and Northwest Canada

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Breen, A. L.; Bennett, A.; Genet, H.; Lindgren, M.; Kurkowski, T. A.; McGuire, A. D.; Rupp, S. T.

2016-12-01

A continuing challenge in global change studies is to determine how land surface changes may impact atmospheric heating. Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90-year period from 2010- 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We consider a more comprehensive suite of possible feedbacks to climate due to shifts in vegetation than previous studies, including both boreal and tundra fire, an advance of treeline, reduction in forest cover due to drought, and increases in the distribution of shrub tundra. However, changes in snow cover still provided the dominant positive land surface feedback to atmospheric heating. This positive feedback was partially moderated by an increase in area burned in spruce forests and shrub tundra. Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks, we can reach a more integrated understanding of the vulnerability of this region to changes in climate.

Fluorescent TEM-1 β-lactamase with wild-type activity as a rapid drug sensor for in vitro drug screening

PubMed Central

Cheong, Wing-Lam; Tsang, Ming-San; So, Pui-Kin; Chung, Wai-Hong; Leung, Yun-Chung; Chan, Pak-Ho

2014-01-01

We report the development of a novel fluorescent drug sensor from the bacterial drug target TEM-1 β-lactamase through the combined strategy of Val216→Cys216 mutation and fluorophore labelling for in vitro drug screening. The Val216 residue in TEM-1 is replaced with a cysteine residue, and the environment-sensitive fluorophore fluorescein-5-maleimide is specifically attached to the Cys216 residue in the V216C mutant for sensing drug binding at the active site. The labelled V216C mutant has wild-type catalytic activity and gives stronger fluorescence when β-lactam antibiotics bind to the active site. The labelled V216C mutant can differentiate between potent and impotent β-lactam antibiotics and can distinguish active-site binders from non-binders (including aggregates formed by small molecules in aqueous solution) by giving characteristic time-course fluorescence profiles. Mass spectrometric, molecular modelling and trypsin digestion results indicate that drug binding at the active site is likely to cause the fluorescein label to stay away from the active site and experience weaker fluorescence quenching by the residues around the active site, thus making the labelled V216C mutant to give stronger fluorescence in the drug-bound state. Given the ancestor's role of TEM-1 in the TEM family, the fluorescent TEM-1 drug sensor represents a good model to demonstrate the general combined strategy of Val216→Cys216 mutation and fluorophore labelling for fabricating tailor-made fluorescent drug sensors from other clinically significant TEM-type β-lactamase variants for in vitro drug screening. PMID:25074398

Processing grounded-wire TEM signal in time-frequency-pseudo-seismic domain: A new paradigm

NASA Astrophysics Data System (ADS)

Khan, M. Y.; Xue, G. Q.; Chen, W.; Huasen, Z.

2017-12-01

Grounded-wire TEM has received great attention in mineral, hydrocarbon and hydrogeological investigations for the last several years. Conventionally, TEM soundings have been presented as apparent resistivity curves as function of time. With development of sophisticated computational algorithms, it became possible to extract more realistic geoelectric information by applying inversion programs to 1-D & 3-D problems. Here, we analyze grounded-wire TEM data by carrying out analysis in time, frequency and pseudo-seismic domain supported by borehole information. At first, H, K, A & Q type geoelectric models are processed using a proven inversion program (1-D Occam inversion). Second, time-to-frequency transformation is conducted from TEM ρa(t) curves to magneto telluric MT ρa(f) curves for the same models based on all-time apparent resistivity curves. Third, 1-D Bostick's algorithm was applied to the transformed resistivity. Finally, EM diffusion field is transformed into propagating wave field obeying the standard wave equation using wavelet transformation technique and constructed pseudo-seismic section. The transformed seismic-like wave indicates that some reflection and refraction phenomena appear when the EM wave field interacts with geoelectric interface at different depth intervals due to contrast in resistivity. The resolution of the transformed TEM data is significantly improved in comparison to apparent resistivity plots. A case study illustrates the successful hydrogeophysical application of proposed approach in recovering water-filled mined-out area in a coal field located in Ye county, Henan province, China. The results support the introduction of pseudo-seismic imaging technology in short-offset version of TEM which can also be an useful aid if integrated with seismic reflection technique to explore possibilities for high resolution EM imaging in future.

Current experience and future directions of completely NOTES colorectal resection.

PubMed

Sylla, Patricia

2010-06-27

Clinical implementation and widespread application of natural orifice translumenal surgery (NOTES) has been limited by the lack of specialized endoscopic equipment, which has prevented the ability to perform complex procedures including colorectal resections. Relative to other types of translumenal access, transanal NOTES using transanal endoscopic microsurgery (TEM) provides a stable platform for endolumenal and direct translumenal access to the peritoneal cavity, and specifically to the colon and rectum. Completely NOTES transanal rectosigmoid resection using TEM, with or without transgastric endoscopic assistance, was demonstrated to be feasible and safe in a swine survival model. The same technique was successfully replicated in human cadavers using commercially available TEM, with endoscopic and laparoscopic instrumentation. This approach also permitted complete rectal mobilization with total mesorectal excision to be performed completely transanally. As in the swine model, transgastric and/or transanal endoscopic assistance extended the length of proximal colon mobilized and overcame some of the difficulties with TEM dissection including limited endoscopic visualization and maladapted instrumentation. This extensive laboratory experience with NOTES transanal rectosigmoid resection served as the basis for the first human NOTES transanal rectal cancer excision using TEM and laparoscopic assistance. Based on this early clinical experience, NOTES transanal approach using TEM holds significant promise as a safe and substantially less morbid alternative to conventional colorectal resection in the management of benign and malignant colorectal diseases. Careful patient selection and substantial improvement in NOTES instrumentation are critical to optimize this approach prior to widespread clinical application, and may ultimately permit completely NOTES transanal colorectal resection.

Linking biophysical models and public preferences for ecosystem service assessments: a case study for the Southern Rocky Mountains

USGS Publications Warehouse

Bagstad, Kenneth J.; Reed, James; Semmens, Darius J.; Sherrouse, Ben C.; Troy, Austin

2016-01-01

Through extensive research, ecosystem services have been mapped using both survey-based and biophysical approaches, but comparative mapping of public values and those quantified using models has been lacking. In this paper, we mapped hot and cold spots for perceived and modeled ecosystem services by synthesizing results from a social-values mapping study of residents living near the Pike–San Isabel National Forest (PSI), located in the Southern Rocky Mountains, with corresponding biophysically modeled ecosystem services. Social-value maps for the PSI were developed using the Social Values for Ecosystem Services tool, providing statistically modeled continuous value surfaces for 12 value types, including aesthetic, biodiversity, and life-sustaining values. Biophysically modeled maps of carbon sequestration and storage, scenic viewsheds, sediment regulation, and water yield were generated using the Artificial Intelligence for Ecosystem Services tool. Hotspots for both perceived and modeled services were disproportionately located within the PSI’s wilderness areas. Additionally, we used regression analysis to evaluate spatial relationships between perceived biodiversity and cultural ecosystem services and corresponding biophysical model outputs. Our goal was to determine whether publicly valued locations for aesthetic, biodiversity, and life-sustaining values relate meaningfully to results from corresponding biophysical ecosystem service models. We found weak relationships between perceived and biophysically modeled services, indicating that public perception of ecosystem service provisioning regions is limited. We believe that biophysical and social approaches to ecosystem service mapping can serve as methodological complements that can advance ecosystem services-based resource management, benefitting resource managers by showing potential locations of synergy or conflict between areas supplying ecosystem services and those valued by the public.

Assimilation of satellite color observations in a coupled ocean GCM-ecosystem model

NASA Technical Reports Server (NTRS)

Sarmiento, Jorge L.

1992-01-01

Monthly average coastal zone color scanner (CZCS) estimates of chlorophyll concentration were assimilated into an ocean global circulation model(GCM) containing a simple model of the pelagic ecosystem. The assimilation was performed in the simplest possible manner, to allow the assessment of whether there were major problems with the ecosystem model or with the assimilation procedure. The current ecosystem model performed well in some regions, but failed in others to assimilate chlorophyll estimates without disrupting important ecosystem properties. This experiment gave insight into those properties of the ecosystem model that must be changed to allow data assimilation to be generally successful, while raising other important issues about the assimilation procedure.

Development of thermal model to analyze thermal flux distribution in thermally enhanced machining of high chrome white cast iron

NASA Astrophysics Data System (ADS)

Ravi, A. M.; Murigendrappa, S. M.

2018-04-01

In recent times, thermally enhanced machining (TEM) slowly gearing up to cut hard metals like high chrome white cast iron (HCWCI) which were impossible in conventional procedures. Also setting up of suitable cutting parameters and positioning of the heat source against the work appears to be critical in order to enhance the machinability characteristics of the work material. In this research work, the Oxy - LPG flame was used as the heat source and HCWCI as the workpiece. ANSYS-CFD-Flow software was used to develop the transient thermal model to analyze the thermal flux distribution on the work surface during TEM of HCWCI using Cubic boron nitride (CBN) tools. Non-contact type Infrared thermo sensor was used to measure the surface temperature continuously at different positions, and is validated with the thermal model results. The result confirms thermal model is a better predictive tool for thermal flux distribution analysis in TEM process.

Ecosystem Model Skill Assessment. Yes We Can!

PubMed

Olsen, Erik; Fay, Gavin; Gaichas, Sarah; Gamble, Robert; Lucey, Sean; Link, Jason S

2016-01-01

Accelerated changes to global ecosystems call for holistic and integrated analyses of past, present and future states under various pressures to adequately understand current and projected future system states. Ecosystem models can inform management of human activities in a complex and changing environment, but are these models reliable? Ensuring that models are reliable for addressing management questions requires evaluating their skill in representing real-world processes and dynamics. Skill has been evaluated for just a limited set of some biophysical models. A range of skill assessment methods have been reviewed but skill assessment of full marine ecosystem models has not yet been attempted. We assessed the skill of the Northeast U.S. (NEUS) Atlantis marine ecosystem model by comparing 10-year model forecasts with observed data. Model forecast performance was compared to that obtained from a 40-year hindcast. Multiple metrics (average absolute error, root mean squared error, modeling efficiency, and Spearman rank correlation), and a suite of time-series (species biomass, fisheries landings, and ecosystem indicators) were used to adequately measure model skill. Overall, the NEUS model performed above average and thus better than expected for the key species that had been the focus of the model tuning. Model forecast skill was comparable to the hindcast skill, showing that model performance does not degenerate in a 10-year forecast mode, an important characteristic for an end-to-end ecosystem model to be useful for strategic management purposes. We identify best-practice approaches for end-to-end ecosystem model skill assessment that would improve both operational use of other ecosystem models and future model development. We show that it is possible to not only assess the skill of a complicated marine ecosystem model, but that it is necessary do so to instill confidence in model results and encourage their use for strategic management. Our methods are applicable to any type of predictive model, and should be considered for use in fields outside ecology (e.g. economics, climate change, and risk assessment).

Bacterial diversity in faeces from polar bear (Ursus maritimus) in Arctic Svalbard.

PubMed

Glad, Trine; Bernhardsen, Pål; Nielsen, Kaare M; Brusetti, Lorenzo; Andersen, Magnus; Aars, Jon; Sundset, Monica A

2010-01-14

Polar bears (Ursus maritimus) are major predators in the Arctic marine ecosystem, feeding mainly on seals, and living closely associated with sea ice. Little is known of their gut microbial ecology and the main purpose of this study was to investigate the microbial diversity in faeces of polar bears in Svalbard, Norway (74-81 degrees N, 10-33 degrees E). In addition the level of blaTEM alleles, encoding ampicillin resistance (ampr) were determined. In total, ten samples were collected from ten individual bears, rectum swabs from five individuals in 2004 and faeces samples from five individuals in 2006. A 16S rRNA gene clone library was constructed, and all sequences obtained from 161 clones showed affiliation with the phylum Firmicutes, with 160 sequences identified as Clostridiales and one sequence identified as unclassified Firmicutes. The majority of the sequences (70%) were affiliated with the genus Clostridium. Aerobic heterotrophic cell counts on chocolate agar ranged between 5.0 x 10(4) to 1.6 x 10(6) colony forming units (cfu)/ml for the rectum swabs and 4.0 x 10(3) to 1.0 x 10(5) cfu/g for the faeces samples. The proportion of ampr bacteria ranged from 0% to 44%. All of 144 randomly selected ampr isolates tested positive for enzymatic beta-lactamase activity. Three % of the ampr isolates from the rectal samples yielded positive results when screened for the presence of blaTEM genes by PCR. BlaTEM alleles were also detected by PCR in two out of three total faecal DNA samples from polar bears. The bacterial diversity in faeces from polar bears in their natural environment in Svalbard is low compared to other animal species, with all obtained clones affiliating to Firmicutes. Furthermore, only low levels of blaTEM alleles were detected in contrast to their increasing prevalence in some clinical and commensal bacterial populations.

Bacterial diversity in faeces from polar bear (Ursus maritimus) in Arctic Svalbard

PubMed Central

2010-01-01

Background Polar bears (Ursus maritimus) are major predators in the Arctic marine ecosystem, feeding mainly on seals, and living closely associated with sea ice. Little is known of their gut microbial ecology and the main purpose of this study was to investigate the microbial diversity in faeces of polar bears in Svalbard, Norway (74-81°N, 10-33°E). In addition the level of blaTEM alleles, encoding ampicillin resistance (ampr) were determined. In total, ten samples were collected from ten individual bears, rectum swabs from five individuals in 2004 and faeces samples from five individuals in 2006. Results A 16S rRNA gene clone library was constructed, and all sequences obtained from 161 clones showed affiliation with the phylum Firmicutes, with 160 sequences identified as Clostridiales and one sequence identified as unclassified Firmicutes. The majority of the sequences (70%) were affiliated with the genus Clostridium. Aerobic heterotrophic cell counts on chocolate agar ranged between 5.0 × 104 to 1.6 × 106 colony forming units (cfu)/ml for the rectum swabs and 4.0 × 103 to 1.0 × 105 cfu/g for the faeces samples. The proportion of ampr bacteria ranged from 0% to 44%. All of 144 randomly selected ampr isolates tested positive for enzymatic β-lactamase activity. Three % of the ampr isolates from the rectal samples yielded positive results when screened for the presence of blaTEM genes by PCR. BlaTEM alleles were also detected by PCR in two out of three total faecal DNA samples from polar bears. Conclusion The bacterial diversity in faeces from polar bears in their natural environment in Svalbard is low compared to other animal species, with all obtained clones affiliating to Firmicutes. Furthermore, only low levels of blaTEM alleles were detected in contrast to their increasing prevalence in some clinical and commensal bacterial populations. PMID:20074323

Predicting neutron damage using TEM with in situ ion irradiation and computer modeling

NASA Astrophysics Data System (ADS)

Kirk, Marquis A.; Li, Meimei; Xu, Donghua; Wirth, Brian D.

2018-01-01

We have constructed a computer model of irradiation defect production closely coordinated with TEM and in situ ion irradiation of Molybdenum at 80 °C over a range of dose, dose rate and foil thickness. We have reexamined our previous ion irradiation data to assign appropriate error and uncertainty based on more recent work. The spatially dependent cascade cluster dynamics model is updated with recent Molecular Dynamics results for cascades in Mo. After a careful assignment of both ion and neutron irradiation dose values in dpa, TEM data are compared for both ion and neutron irradiated Mo from the same source material. Using the computer model of defect formation and evolution based on the in situ ion irradiation of thin foils, the defect microstructure, consisting of densities and sizes of dislocation loops, is predicted for neutron irradiation of bulk material at 80 °C and compared with experiment. Reasonable agreement between model prediction and experimental data demonstrates a promising direction in understanding and predicting neutron damage using a closely coordinated program of in situ ion irradiation experiment and computer simulation.

2D Inversion of Transient Electromagnetic Method (TEM)

NASA Astrophysics Data System (ADS)

Bortolozo, Cassiano Antonio; Luís Porsani, Jorge; Acácio Monteiro dos Santos, Fernando

2017-04-01

A new methodology was developed for 2D inversion of Transient Electromagnetic Method (TEM). The methodology consists in the elaboration of a set of routines in Matlab code for modeling and inversion of TEM data and the determination of the most efficient field array for the problem. In this research, the 2D TEM modeling uses the finite differences discretization. To solve the inversion problem, were applied an algorithm based on Marquardt technique, also known as Ridge Regression. The algorithm is stable and efficient and it is widely used in geoelectrical inversion problems. The main advantage of 1D survey is the rapid data acquisition in a large area, but in regions with two-dimensional structures or that need more details, is essential to use two-dimensional interpretation methodologies. For an efficient field acquisition we used in an innovative form the fixed-loop array, with a square transmitter loop (200m x 200m) and 25m spacing between the sounding points. The TEM surveys were conducted only inside the transmitter loop, in order to not deal with negative apparent resistivity values. Although it is possible to model the negative values, it makes the inversion convergence more difficult. Therefore the methodology described above has been developed in order to achieve maximum optimization of data acquisition. Since it is necessary only one transmitter loop disposition in the surface for each series of soundings inside the loop. The algorithms were tested with synthetic data and the results were essential to the interpretation of the results with real data and will be useful in future situations. With the inversion of the real data acquired over the Paraná Sedimentary Basin (PSB) was successful realized a 2D TEM inversion. The results indicate a robust geoelectrical characterization for the sedimentary and crystalline aquifers in the PSB. Therefore, using a new and relevant approach for 2D TEM inversion, this research effectively contributed to map the most promising regions for groundwater exploration. In addition, there was the development of new geophysical software that can be applied as an important tool for many geological/hydrogeological applications and educational purposes.

Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology

NASA Astrophysics Data System (ADS)

Schimel, David S.; Kittel, Timothy G. F.; Parton, William J.

1991-08-01

Ecosystem scientists have developed a body of theory to predict the behaviour of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behaviour of ecosystems coupled by transport is limited by our ability (1) to extrapolate biotic function to large spatial scales and (2) to measure and model transport. We review developments in ecosystem theory, remote sensing, and geographical information systems (GIS) that support new efforts in spatial modeling. A paradigm has emerged to predict behaviour of ecosystems based on understanding responses to multiple resources (e.g., water, nutrients, light). Several ecosystem models couple primary production to decomposition and nutrient availability using the above paradigm. These models require a fairly small set of environmental variables to simulate spatial and temporal variation in rates of biogeochemical cycling. Simultaneously, techniques for inferring ecosystem behaviour from remotely measured canopy light interception are improving our ability to infer plant activity from satellite observations. Efforts have begun to couple models of transport in air and water to models of ecosystem function. Preliminary work indicates that coupling of transport and ecosystem processes alters the behaviour of earth system components (hydrology, terrestrial ecosystems, and the atmosphere) from that of an uncoupled mode.

USGS River Ecosystem Modeling: Where Are We, How Did We Get Here, and Where Are We Going?

USGS Publications Warehouse

Hanson, Leanne; Schrock, Robin; Waddle, Terry; Duda, Jeffrey J.; Lellis, Bill

2009-01-01

This report developed as an outcome of the USGS River Ecosystem Modeling Work Group, convened on February 11, 2008 as a preconference session to the second USGS Modeling Conference in Orange Beach, Ala. Work Group participants gained an understanding of the types of models currently being applied to river ecosystem studies within the USGS, learned how model outputs are being used by a Federal land management agency, and developed recommendations for advancing the state of the art in river ecosystem modeling within the USGS. During a break-out session, participants restated many of the recommendations developed at the first USGS Modeling Conference in 2006 and in previous USGS needs assessments. All Work Group recommendations require organization and coordination across USGS disciplines and regions, and include (1) enhancing communications, (2) increasing efficiency through better use of current human and technologic resources, and (3) providing a national infrastructure for river ecosystem modeling resources, making it easier to integrate modeling efforts. By implementing these recommendations, the USGS will benefit from enhanced multi-disciplinary, integrated models for river ecosystems that provide valuable risk assessment and decision support tools for adaptive management of natural and managed riverine ecosystems. These tools generate key information that resource managers need and can use in making decisions about river ecosystem resources.

Towards a Stochastic Predictive Understanding of Ecosystem Functioning and Resilience to Environmental Changes

NASA Astrophysics Data System (ADS)

Pappas, C.

2017-12-01

Terrestrial ecosystem processes respond differently to hydrometeorological variability across timescales, and so does our scientific understanding of the underlying mechanisms. Process-based modeling of ecosystem functioning is therefore challenging, especially when long-term predictions are envisioned. Here we analyze the statistical properties of hydrometeorological and ecosystem variability, i.e., the variability of ecosystem process related to vegetation carbon dynamics, from hourly to decadal timescales. 23 extra-tropical forest sites, covering different climatic zones and vegetation characteristics, are examined. Micrometeorological and reanalysis data of precipitation, air temperature, shortwave radiation and vapor pressure deficit are used to describe hydrometeorological variability. Ecosystem variability is quantified using long-term eddy covariance flux data of hourly net ecosystem exchange of CO2 between land surface and atmosphere, monthly remote sensing vegetation indices, annual tree-ring widths and above-ground biomass increment estimates. We find that across sites and timescales ecosystem variability is confined within a hydrometeorological envelope that describes the range of variability of the available resources, i.e., water and energy. Furthermore, ecosystem variability demonstrates long-term persistence, highlighting ecological memory and slow ecosystem recovery rates after disturbances. We derive an analytical model, combining deterministic harmonics and stochastic processes, that represents major mechanisms and uncertainties and mimics the observed pattern of hydrometeorological and ecosystem variability. This stochastic framework offers a parsimonious and mathematically tractable approach for modelling ecosystem functioning and for understanding its response and resilience to environmental changes. Furthermore, this framework reflects well the observed ecological memory, an inherent property of ecosystem functioning that is currently not captured by simulation results with process-based models. Our analysis offers a perspective for terrestrial ecosystem modelling, combining current process understanding with stochastic methods, and paves the way for new model-data integration opportunities in Earth system sciences.

Current experience and future directions of completely NOTES colorectal resection

PubMed Central

Sylla, Patricia

2010-01-01

Clinical implementation and widespread application of natural orifice translumenal surgery (NOTES) has been limited by the lack of specialized endoscopic equipment, which has prevented the ability to perform complex procedures including colorectal resections. Relative to other types of translumenal access, transanal NOTES using transanal endoscopic microsurgery (TEM) provides a stable platform for endolumenal and direct translumenal access to the peritoneal cavity, and specifically to the colon and rectum. Completely NOTES transanal rectosigmoid resection using TEM, with or without transgastric endoscopic assistance, was demonstrated to be feasible and safe in a swine survival model. The same technique was successfully replicated in human cadavers using commercially available TEM, with endoscopic and laparoscopic instrumentation. This approach also permitted complete rectal mobilization with total mesorectal excision to be performed completely transanally. As in the swine model, transgastric and/or transanal endoscopic assistance extended the length of proximal colon mobilized and overcame some of the difficulties with TEM dissection including limited endoscopic visualization and maladapted instrumentation. This extensive laboratory experience with NOTES transanal rectosigmoid resection served as the basis for the first human NOTES transanal rectal cancer excision using TEM and laparoscopic assistance. Based on this early clinical experience, NOTES transanal approach using TEM holds significant promise as a safe and substantially less morbid alternative to conventional colorectal resection in the management of benign and malignant colorectal diseases. Careful patient selection and substantial improvement in NOTES instrumentation are critical to optimize this approach prior to widespread clinical application, and may ultimately permit completely NOTES transanal colorectal resection. PMID:21160873

POEM: PESTICIDE ORCHARD ECOSYSTEM MODEL

EPA Science Inventory

The Pesticide Orchard Ecosystem Model (POEM) is a mathematical model of organophosphate pesticide movement in an apple orchard ecosystem. In addition submodels on invertebrate population dynamics are included. The fate model allows the user to select the pesticide, its applicatio...

Comparing approaches to spatially explicit ecosystem service modeling: a case study from the San Pedro River, Arizona

USGS Publications Warehouse

Bagstad, Kenneth J.; Semmens, Darius J.; Winthrop, Robert

2013-01-01

Although the number of ecosystem service modeling tools has grown in recent years, quantitative comparative studies of these tools have been lacking. In this study, we applied two leading open-source, spatially explicit ecosystem services modeling tools – Artificial Intelligence for Ecosystem Services (ARIES) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) – to the San Pedro River watershed in southeast Arizona, USA, and northern Sonora, Mexico. We modeled locally important services that both modeling systems could address – carbon, water, and scenic viewsheds. We then applied managerially relevant scenarios for urban growth and mesquite management to quantify ecosystem service changes. InVEST and ARIES use different modeling approaches and ecosystem services metrics; for carbon, metrics were more similar and results were more easily comparable than for viewsheds or water. However, findings demonstrate similar gains and losses of ecosystem services and conclusions when comparing effects across our scenarios. Results were more closely aligned for landscape-scale urban-growth scenarios and more divergent for a site-scale mesquite-management scenario. Follow-up studies, including testing in different geographic contexts, can improve our understanding of the strengths and weaknesses of these and other ecosystem services modeling tools as they move closer to readiness for supporting day-to-day resource management.

Strains on the nano- and microscale in nickel-titanium: An advanced TEM study

NASA Astrophysics Data System (ADS)

Tirry, Wim

2007-12-01

A general introduction to shape memory behavior and the martensitic transformation is given in chapter 1, with speck information concerning the NiTi material. The technique used to study the material is transmission electron microscopy (TEM) of which the basics are explained in chapter 2 as well as information concerning the NiTi material. The main goal was to apply more advanced TEM techniques in order to measure some aspects in a quantitative way rather than qualitative, which is mostly the case in conventional TEM. (1) Quantitative electron diffraction was used to refine the structure of Ni4Ti3 precipitates, this was done by using the MSLS method in combination with density functional theory (DFT) calculations. (2) These Ni4Ti3 precipitates are (semi-)coherent which results in a strain field in the matrix close to the precipitate. High resolution TEM (HRTEM) in combination with image processing techniques was used to measure these strain fields. The obtained results are compared to the Eshelby model for elliptical inclusions, and major difference is an underestimation of the strain magnitude by the model. One of the algorithms used to extract strain information from HRTEM images is the geometric phase method. (3) The Ni4Ti3-Ni4Ti3 and Ni4Ti3-precipitate interface was investigated with HRTEM showing that the Ni4Ti3-precipitate interface might be diffuse over a range of 3nm. (4) In-situ straining experiments were performed on single crystalline and superelastic polycrystalline NiTi samples. It seems that the strain induced martensite planes in the polycrystalline sample show no sign of twinning. This is in contradiction to what is expected and is discussed in the view of the crystallographic theory of martensite, in addition a first model explaining this behavior is proposed. In this dissertation the main attention is divided over the material aspects of NiTi and on how to apply these more advanced TEM techniques.

Modelling carbon responses of tundra ecosystems to historical and projected climate: Sensitivity of pan-Arctic carbon storage to temporal and spatial variation in climate

USGS Publications Warehouse

McGuire, A.D.; Clein, Joy S.; Melillo, J.M.; Kicklighter, D.W.; Meier, R.A.; Vorosmarty, C.J.; Serreze, Mark C.

2000-01-01

Historical and projected climate trends for high latitudes show substantial temporal and spatial variability. To identify uncertainties in simulating carbon (C) dynamics for pan-Arctic tundra, we compare the historical and projected responses of tundra C storage from 1921 to 2100 between simulations by the Terrestrial Ecosystem Model (TEM) for the pan-Arctic and the Kuparuk River Basin, which was the focus of an integrated study of C dynamics from 1994 to 1996. In the historical period from 1921 to 1994, the responses of net primary production (NPP) and heterotrophic respiration (RH) simulated for the Kuparuk River Basin and the pan-Arctic are correlated with the same factors; NPP is positively correlated with net nitrogen mineralization (NMIN) and RH is negatively correlated with mean annual soil moisture. In comparison to the historical period, the spatially aggregated responses of NPP and RH for the Kuparuk River Basin and the pan-Arctic in our simulations for the projected period have different sensitivities to temperature, soil moisture and NMIN. In addition to being sensitive to soil moisture during the projected period, RH is also sensitive to temperature and there is a significant correlation between RH and NMIN. We interpret the increases in NPP during the projected period as being driven primarily by increases in NMIN, and that the correlation between NPP and temperature in the projected period is a result primarily of the causal linkage between temperature, RH, and NMIN. Although similar factors appear to be controlling simulated regional-and biome-scale C dynamics, simulated C dynamics at the two scales differ in magnitude with higher increases in C storage simulated for the Kuparuk River Basin than for the pan-Arctic at the end of the historical period and throughout the projected period. Also, the results of the simulations indicate that responses of C storage show different climate sensitivities at regional and pan-Arctic spatial scales and that these sensitivities change across the temporal scope of the simulations. The results of the TEM simulations indicate that the scaling of C dynamics to a region of arctic tundra may not represent C dynamics of pan-Arctic tundra because of the limited spatial variation in climate and vegetation within a region relative to the pan-Arctic. For reducing uncertainties, our analyses highlight the importance of incorporating the understanding gained from process-level studies of C dynamics in a region of arctic tundra into process-based models that simulate C dynamics in a spatially explicit fashion across the spatial domain of pan-Arctic tundra. Also, efforts to improve gridded datasets of historical climate for the pan-Arctic would advance the ability to assess the responses of C dynamics for pan-Arctic tundra in a more realistic fashion. A major challenge will be to incorporate topographic controls over soil moisture in assessing the response of C storage for pan-Arctic tundra.

Modelling impacts of second generation bioenergy production on Ecosystem Services in Europe

NASA Astrophysics Data System (ADS)

Henner, Dagmar N.; Smith, Pete; Davies, Christian; McNamara, Niall P.

2015-04-01

Bioenergy crops are an important source of renewable energy and are a possible mechanism to mitigate global climate warming, by replacing fossil fuel energy with higher greenhouse gas emissions. There is, however, uncertainty about the impacts of the growth of bioenergy crops on ecosystem services. This uncertainty is further enhanced by the unpredictable climate change currently going on. The goal of this project is to develop a comprehensive model that covers as many ecosystem services as possible at a Continental level including biodiversity, water, GHG emissions, soil, and cultural services. The distribution and production of second generation energy crops, such as Miscanthus, Short Rotation Coppice (SRC) and Short Rotation Forestry (SRF), is currently being modelled, and ecosystem models will be used to examine the impacts of these crops on ecosystem services. The project builds on models of energy crop production, biodiversity, soil impacts, greenhouse gas emissions and other ecosystem services, and on work undertaken in the UK on the ETI-funded ELUM project (www.elum.ac.uk). In addition, methods like water footprint tools, tourism value maps and ecosystem valuation tools and models (e.g. InVest, TEEB database, GREET LCA Model, World Business Council for Sustainable Development corporate ecosystem valuation, Millennium Ecosystem Assessment and the Ecosystem Services Framework) will be utilised. Research will focus on optimisation of land use change feedbacks on ecosystem services and biodiversity, and weighting of the importance of the individual ecosystem services. Energy crops will be modelled using low, medium and high climate change scenarios for the years between 2015 and 2050. We will present first results for GHG emissions and soil organic carbon change after different land use change scenarios (e.g. arable to Miscanthus, forest to SRF), and with different climate warming scenarios. All this will be complemented by the presentation of a matrix including all the factors and ecosystem services influenced by land use change to bioenergy crop production under different climate change scenarios.

Population-reaction model and microbial experimental ecosystems for understanding hierarchical dynamics of ecosystems.

PubMed

Hosoda, Kazufumi; Tsuda, Soichiro; Kadowaki, Kohmei; Nakamura, Yutaka; Nakano, Tadashi; Ishii, Kojiro

2016-02-01

Understanding ecosystem dynamics is crucial as contemporary human societies face ecosystem degradation. One of the challenges that needs to be recognized is the complex hierarchical dynamics. Conventional dynamic models in ecology often represent only the population level and have yet to include the dynamics of the sub-organism level, which makes an ecosystem a complex adaptive system that shows characteristic behaviors such as resilience and regime shifts. The neglect of the sub-organism level in the conventional dynamic models would be because integrating multiple hierarchical levels makes the models unnecessarily complex unless supporting experimental data are present. Now that large amounts of molecular and ecological data are increasingly accessible in microbial experimental ecosystems, it is worthwhile to tackle the questions of their complex hierarchical dynamics. Here, we propose an approach that combines microbial experimental ecosystems and a hierarchical dynamic model named population-reaction model. We present a simple microbial experimental ecosystem as an example and show how the system can be analyzed by a population-reaction model. We also show that population-reaction models can be applied to various ecological concepts, such as predator-prey interactions, climate change, evolution, and stability of diversity. Our approach will reveal a path to the general understanding of various ecosystems and organisms. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

A multi-objective constraint-based approach for modeling genome-scale microbial ecosystems.

PubMed

Budinich, Marko; Bourdon, Jérémie; Larhlimi, Abdelhalim; Eveillard, Damien

2017-01-01

Interplay within microbial communities impacts ecosystems on several scales, and elucidation of the consequent effects is a difficult task in ecology. In particular, the integration of genome-scale data within quantitative models of microbial ecosystems remains elusive. This study advocates the use of constraint-based modeling to build predictive models from recent high-resolution -omics datasets. Following recent studies that have demonstrated the accuracy of constraint-based models (CBMs) for simulating single-strain metabolic networks, we sought to study microbial ecosystems as a combination of single-strain metabolic networks that exchange nutrients. This study presents two multi-objective extensions of CBMs for modeling communities: multi-objective flux balance analysis (MO-FBA) and multi-objective flux variability analysis (MO-FVA). Both methods were applied to a hot spring mat model ecosystem. As a result, multiple trade-offs between nutrients and growth rates, as well as thermodynamically favorable relative abundances at community level, were emphasized. We expect this approach to be used for integrating genomic information in microbial ecosystems. Following models will provide insights about behaviors (including diversity) that take place at the ecosystem scale.

The evolution of ecosystem ascendency in a complex systems based model.

PubMed

Brinck, Katharina; Jensen, Henrik Jeldtoft

2017-09-07

General patterns in ecosystem development can shed light on driving forces behind ecosystem formation and recovery and have been of long interest. In recent years, the need for integrative and process oriented approaches to capture ecosystem growth, development and organisation, as well as the scope of information theory as a descriptive tool has been addressed from various sides. However data collection of ecological network flows is difficult and tedious and comprehensive models are lacking. We use a hierarchical version of the Tangled Nature Model of evolutionary ecology to study the relationship between structure, flow and organisation in model ecosystems, their development over evolutionary time scales and their relation to ecosystem stability. Our findings support the validity of ecosystem ascendency as a meaningful measure of ecosystem organisation, which increases over evolutionary time scales and significantly drops during periods of disturbance. The results suggest a general trend towards both higher integrity and increased stability driven by functional and structural ecosystem coadaptation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ecological Assimilation of Land and Climate Observations - the EALCO model

NASA Astrophysics Data System (ADS)

Wang, S.; Zhang, Y.; Trishchenko, A.

2004-05-01

Ecosystems are intrinsically dynamic and interact with climate at a highly integrated level. Climate variables are the main driving factors in controlling the ecosystem physical, physiological, and biogeochemical processes including energy balance, water balance, photosynthesis, respiration, and nutrient cycling. On the other hand, ecosystems function as an integrity and feedback on the climate system through their control on surface radiation balance, energy partitioning, and greenhouse gases exchange. To improve our capability in climate change impact assessment, a comprehensive ecosystem model is required to address the many interactions between climate change and ecosystems. In addition, different ecosystems can have very different responses to the climate change and its variation. To provide more scientific support for ecosystem impact assessment at national scale, it is imperative that ecosystem models have the capability of assimilating the large scale geospatial information including satellite observations, GIS datasets, and climate model outputs or reanalysis. The EALCO model (Ecological Assimilation of Land and Climate Observations) is developed for such purposes. EALCO includes the comprehensive interactions among ecosystem processes and climate, and assimilates a variety of remote sensing products and GIS database. It provides both national and local scale model outputs for ecosystem responses to climate change including radiation and energy balances, water conditions and hydrological cycles, carbon sequestration and greenhouse gas exchange, and nutrient (N) cycling. These results form the foundation for the assessment of climate change impact on ecosystems, their services, and adaptation options. In this poster, the main algorithms for the radiation, energy, water, carbon, and nitrogen simulations were diagrammed. Sample input data layers at Canada national scale were illustrated. Model outputs including the Canada wide spatial distributions of net radiation, evapotranspiration, gross primary production, net primary production, and net ecosystem production were discussed.

Mid-depth temperature maximum in an estuarine lake

NASA Astrophysics Data System (ADS)

Stepanenko, V. M.; Repina, I. A.; Artamonov, A. Yu; Gorin, S. L.; Lykossov, V. N.; Kulyamin, D. V.

2018-03-01

The mid-depth temperature maximum (TeM) was measured in an estuarine Bol’shoi Vilyui Lake (Kamchatka peninsula, Russia) in summer 2015. We applied 1D k-ɛ model LAKE to the case, and found it successfully simulating the phenomenon. We argue that the main prerequisite for mid-depth TeM development is a salinity increase below the freshwater mixed layer, sharp enough in order to increase the temperature with depth not to cause convective mixing and double diffusion there. Given that this condition is satisfied, the TeM magnitude is controlled by physical factors which we identified as: radiation absorption below the mixed layer, mixed-layer temperature dynamics, vertical heat conduction and water-sediments heat exchange. In addition to these, we formulate the mechanism of temperature maximum ‘pumping’, resulting from the phase shift between diurnal cycles of mixed-layer depth and temperature maximum magnitude. Based on the LAKE model results we quantify the contribution of the above listed mechanisms and find their individual significance highly sensitive to water turbidity. Relying on physical mechanisms identified we define environmental conditions favouring the summertime TeM development in salinity-stratified lakes as: small-mixed layer depth (roughly, ~< 2 m), transparent water, daytime maximum of wind and cloudless weather. We exemplify the effect of mixed-layer depth on TeM by a set of selected lakes.

Homology modeling and virtual screening of inhibitors against TEM- and SHV-type-resistant mutants: A multilayer filtering approach.

PubMed

Baig, Mohammad H; Balaramnavar, Vishal M; Wadhwa, Gulshan; Khan, Asad U

2015-01-01

TEM and SHV are class-A-type β-lactamases commonly found in Escherichia coli and Klebsiella pneumoniae. Previous studies reported S130G and K234R mutations in SHVs to be 41- and 10-fold more resistant toward clavulanic acid than SHV-1, respectively, whereas TEM S130G and R244S also showed the same level of resistance. These selected mutants confer higher level of resistance against clavulanic acid. They also show little susceptibility against other commercially available β-lactamase inhibitors. In this study, we have used docking-based virtual screening approach in order to screen potential inhibitors against some of the major resistant mutants of SHV and TEM types β-lactamase. Two different inhibitor-resistant mutants from SHV and TEM were selected. Moreover, we have retained the active site water molecules within each enzyme. Active site water molecules were placed within modeled structure of the mutant whose structure was unavailable with protein databank. The novelty of this work lies in the use of multilayer virtual screening approach for the prediction of best and accurate results. We are reporting five inhibitors on the basis of their efficacy against all the selected resistant mutants. These inhibitors were selected on the basis of their binding efficacies and pharmacophore features. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

Minimum depth of investigation for grounded-wire TEM due to self-transients

NASA Astrophysics Data System (ADS)

Zhou, Nannan; Xue, Guoqiang

2018-05-01

The grounded-wire transient electromagnetic method (TEM) has been widely used for near-surface metalliferous prospecting, oil and gas exploration, and hydrogeological surveying in the subsurface. However, it is commonly observed that such TEM signal is contaminated by the self-transient process occurred at the early stage of data acquisition. Correspondingly, there exists a minimum depth of investigation, above which the observed signal is not applicable for reliable data processing and interpretation. Therefore, for achieving a more comprehensive understanding of the TEM method, it is necessary to perform research on the self-transient process and moreover develop an approach for quantifying the minimum detection depth. In this paper, we first analyze the temporal procedure of the equivalent circuit of the TEM method and present a theoretical equation for estimating the self-induction voltage based on the inductor of the transmitting wire. Then, numerical modeling is applied for building the relationship between the minimum depth of investigation and various properties, including resistivity of the earth, offset, and source length. It is guide for the design of survey parameters when the grounded-wire TEM is applied to the shallow detection. Finally, it is verified through applications to a coal field in China.

Comparing two tools for ecosystem service assessments regarding water resources decisions.

PubMed

Dennedy-Frank, P James; Muenich, Rebecca Logsdon; Chaubey, Indrajeet; Ziv, Guy

2016-07-15

We present a comparison of two ecohydrologic models commonly used for planning land management to assess the production of hydrologic ecosystem services: the Soil and Water Assessment Tool (SWAT) and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) annual water yield model. We compare these two models at two distinct sites in the US: the Wildcat Creek Watershed in Indiana and the Upper Upatoi Creek Watershed in Georgia. The InVEST and SWAT models provide similar estimates of the spatial distribution of water yield in Wildcat Creek, but very different estimates of the spatial distribution of water yield in Upper Upatoi Creek. The InVEST model may do a poor job estimating the spatial distribution of water yield in the Upper Upatoi Creek Watershed because baseflow provides a significant portion of the site's total water yield, which means that storage dynamics which are not modeled by InVEST may be important. We also compare the ability of these two models, as well as one newly developed set of ecosystem service indices, to deliver useful guidance for land management decisions focused on providing hydrologic ecosystem services in three particular decision contexts: environmental flow ecosystem services, ecosystem services for potable water supply, and ecosystem services for rainfed irrigation. We present a simple framework for selecting models or indices to evaluate hydrologic ecosystem services as a way to formalize where models deliver useful guidance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Examining Ecological and Ecosystem Level Impacts of Aquatic Invasive Species in Lake Michigan Using An Ecosystem Productivity Model, LM-Eco

EPA Science Inventory

Ecological and ecosystem-level impacts of aquatic invasive species in Lake Michigan were examined using the Lake Michigan Ecosystem Model (LM-Eco). The LM-Eco model includes a detailed description of trophic levels and their interactions within the lower food web of Lake Michiga...

Strategy for modeling putative multilevel ecosystems on Europa.

PubMed

Irwin, Louis N; Schulze-Makuch, Dirk

2003-01-01

A general strategy for modeling ecosystems on other worlds is described. Two alternative biospheres beneath the ice surface of Europa are modeled, based on analogous ecosystems on Earth in potentially comparable habitats, with reallocation of biomass quantities consistent with different sources of energy and chemical constituents. The first ecosystem models a benthic biosphere supported by chemoautotrophic producers. The second models two concentrations of biota at the top and bottom of the subsurface water column supported by energy harvested from transmembrane ionic gradients. Calculations indicate the plausibility of both ecosystems, including small macroorganisms at the highest trophic levels, with ionotrophy supporting a larger biomass than chemoautotrophy.

Remote sensing and modeling to fill the “gap” in missing natural capital

USGS Publications Warehouse

Bagstad, Kenneth J.; Willcock, Simon; Lange, Glenn-Marie

2018-01-01

This chapter reviews recent advances in remote sensing and environmental modeling that address the first step in ecosystem accounting: biophysical quantification of ecosystem services. The chapter focuses on those ecosystem services in which the most rapid advances are likely, including crop pollination, sediment regulation, carbon sequestration and storage, and coastal flood regulation. The discussion highlights data sources and modeling approaches that can support wealth accounting, next steps for mapping and biophysical modeling of ecosystem services, and considerations for integrating biophysical modeling and monetary valuation. These approaches could make the inclusion of some ecosystem services increasingly feasible in future versions of wealth accounts.

Integrating ecosystem sampling, gradient modeling, remote sensing, and ecosystem simulation to create spatially explicit landscape inventories

Treesearch

Robert E. Keane; Matthew G. Rollins; Cecilia H. McNicoll; Russell A. Parsons

2002-01-01

Presented is a prototype of the Landscape Ecosystem Inventory System (LEIS), a system for creating maps of important landscape characteristics for natural resource planning. This system uses gradient-based field inventories coupled with gradient modeling remote sensing, ecosystem simulation, and statistical analyses to derive spatial data layers required for ecosystem...

Modeling of the nearshore marine ecosystem with the AQUATOX model

EPA Science Inventory

Process-based models can be used to forecast the responses of coastal ecosystems to changes under future scenarios. However, most models applied to coastal systems do not include higher trophic levels, which are important providers of ecosystem services. AQUATOX is a mechanistic...

Terrestrial biogeochemical cycles - Global interactions with the atmosphere and hydrology

NASA Technical Reports Server (NTRS)

Schimel, David S.; Parton, William J.; Kittel, Timothy G. F.

1991-01-01

A review is presented of developments in ecosystem theory, remote sensing, and geographic information systems that support new endeavors in spatial modeling. A paradigm has emerged to predict ecosystem behavior based on understanding responses to multiple resources. Ecosystem models couple primary production to decomposition and nutrient availability utilizing this paradigm. It is indicated that coupling of transport and ecosystem processes alters the behavior of earth system components (terrestrial ecosystems, hydrology, and the atmosphere) from that of an uncoupled model.

Upscaling key ecosystem functions across the conterminous United States by a water‐centric ecosystem model

Treesearch

Ge Sun; Peter Caldwell; Asko Noormets; Steven G. McNulty; Erika Cohen; al. et.

2011-01-01

We developed a water‐centric monthly scale simulation model (WaSSI‐C) by integrating empirical water and carbon flux measurements from the FLUXNET network and an existing water supply and demand accounting model (WaSSI). The WaSSI‐C model was evaluated with basin‐scale evapotranspiration (ET), gross ecosystem productivity (GEP), and net ecosystem exchange (NEE)...

Development of simplified ecosystem models for applications in Earth system studies: The Century experience

NASA Technical Reports Server (NTRS)

Parton, William J.; Ojima, Dennis S.; Schimel, David S.; Kittel, Timothy G. F.

1992-01-01

During the past decade, a growing need to conduct regional assessments of long-term trends of ecosystem behavior and the technology to meet this need have converged. The Century model is the product of research efforts initially intended to develop a general model of plant-soil ecosystem dynamics for the North American central grasslands. This model is now being used to simulate plant production, nutrient cycling, and soil organic matter dynamics for grassland, crop, forest, and shrub ecosystems in various regions of the world, including temperate and tropical ecosystems. This paper will focus on the philosophical approach used to develop the structure of Century. The steps included were model simplification, parameterization, and testing. In addition, the importance of acquiring regional data bases for model testing and the present regional application of Century in the Great Plains, which focus on regional ecosystem dynamics and the effect of altering environmental conditions, are discussed.

Using landscape limnology to classify freshwater ecosystems for multi-ecosystem management and conservation

USGS Publications Warehouse

Soranno, Patricia A.; Cheruvelil, Kendra Spence; Webster, Katherine E.; Bremigan, Mary T.; Wagner, Tyler; Stow, Craig A.

2010-01-01

Governmental entities are responsible for managing and conserving large numbers of lake, river, and wetland ecosystems that can be addressed only rarely on a case-by-case basis. We present a system for predictive classification modeling, grounded in the theoretical foundation of landscape limnology, that creates a tractable number of ecosystem classes to which management actions may be tailored. We demonstrate our system by applying two types of predictive classification modeling approaches to develop nutrient criteria for eutrophication management in 1998 north temperate lakes. Our predictive classification system promotes the effective management of multiple ecosystems across broad geographic scales by explicitly connecting management and conservation goals to the classification modeling approach, considering multiple spatial scales as drivers of ecosystem dynamics, and acknowledging the hierarchical structure of freshwater ecosystems. Such a system is critical for adaptive management of complex mosaics of freshwater ecosystems and for balancing competing needs for ecosystem services in a changing world.

Modelling multi-species interactions in the Barents Sea ecosystem with special emphasis on minke whales and their interactions with cod, herring and capelin

NASA Astrophysics Data System (ADS)

Lindstrøm, Ulf; Smout, Sophie; Howell, Daniel; Bogstad, Bjarte

2009-10-01

The Barents Sea ecosystem, one of the most productive and commercially important ecosystems in the world, has experienced major fluctuations in species abundance the past five decades. Likely causes are natural variability, climate change, overfishing and predator-prey interactions. In this study, we use an age-length structured multi-species model (Gadget, Globally applicable Area-Disaggregated General Ecosystem Toolbox) to analyse the historic population dynamics of major fish and marine mammal species in the Barents Sea. The model was used to examine possible effects of a number of plausible biological and fisheries scenarios. The results suggest that changes in cod mortality from fishing or cod cannibalism levels have the largest effect on the ecosystem, while changes to the capelin fishery have had only minor effects. Alternate whale migration scenarios had only a moderate impact on the modelled ecosystem. Indirect effects are seen to be important, with cod fishing pressure, cod cannibalism and whale predation on cod having an indirect impact on capelin, emphasising the importance of multi-species modelling in understanding and managing ecosystems. Models such as the one presented here provide one step towards an ecosystem-based approach to fisheries management.

Simulation and analysis of the effect of ungrounded rectangular loop distributed parameters on TEM response

NASA Astrophysics Data System (ADS)

Shi, Zongyang; Liu, Lihua; Xiao, Pan; Geng, Zhi; Liu, Fubo; Fang, Guangyou

2018-02-01

An ungrounded loop in the shallow subsurface transient electromagnetic surveys has been studied as the transmission line model for early turn-off stage, which can accurately explicate the early turn-off current waveform inconsistency along the loop. In this paper, the Gauss-Legendre numerical integration method is proposed for the first time to simulate and analyze the transient electromagnetic (TEM) response considering the different early turn-off current waveforms along the loop. During the simulation, these integral node positions along the loop are firstly determined by solving these zero points of Legendre polynomial, then the turn-off current of each node position is simulated by using the transfer function of the transmission line. Finally, the total TEM response is calculated by using the Gauss-Legendre integral formula. In addition, the comparison and analysis between the results affected by the distributed parameters and that generated by lumped parameters are presented. It is found that the TEM responses agree well with each other after current is thoroughly switched off, while the transient responses in turn-off stage are completely different. It means that the position dependence of the early turn-off current should be introduced into the forward model during the early response data interpretation of the shallow TEM detection of the ungrounded loop. Furthermore, the TEM response simulations at four geometric symmetry points are made. It shows that early responses of different geometric symmetry points are also inconsistent. The research on the influence of turn-off current position dependence on the early response of geometric symmetry point is of great significance to guide the layout of the survey lines and the transmitter location.

Direct observation of morphological evolution of a catalyst during carbon nanotube forest growth: new insights into growth and growth termination

NASA Astrophysics Data System (ADS)

Jeong, Seojeong; Lee, Jaegeun; Kim, Hwan-Chul; Hwang, Jun Yeon; Ku, Bon-Cheol; Zakharov, Dmitri N.; Maruyama, Benji; Stach, Eric A.; Kim, Seung Min

2016-01-01

In this study, we develop a new methodology for transmission electron microscopy (TEM) analysis that enables us to directly investigate the interface between carbon nanotube (CNT) arrays and the catalyst and support layers for CNT forest growth without any damage induced by a post-growth TEM sample preparation. Using this methodology, we perform in situ and ex situ TEM investigations on the evolution of the morphology of the catalyst particles and observe the catalyst particles to climb up through CNT arrays during CNT forest growth. We speculate that the lifted catalysts significantly affect the growth and growth termination of CNT forests along with Ostwald ripening and sub-surface diffusion. Thus, we propose a modified growth termination model which better explains various phenomena related to the growth and growth termination of CNT forests.In this study, we develop a new methodology for transmission electron microscopy (TEM) analysis that enables us to directly investigate the interface between carbon nanotube (CNT) arrays and the catalyst and support layers for CNT forest growth without any damage induced by a post-growth TEM sample preparation. Using this methodology, we perform in situ and ex situ TEM investigations on the evolution of the morphology of the catalyst particles and observe the catalyst particles to climb up through CNT arrays during CNT forest growth. We speculate that the lifted catalysts significantly affect the growth and growth termination of CNT forests along with Ostwald ripening and sub-surface diffusion. Thus, we propose a modified growth termination model which better explains various phenomena related to the growth and growth termination of CNT forests. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05547d

Mathematical modeling of tumor-associated macrophage interactions with the cancer microenvironment.

PubMed

Mahlbacher, Grace; Curtis, Louis T; Lowengrub, John; Frieboes, Hermann B

2018-01-30

Immuno-oncotherapy has emerged as a promising means to target cancer. In particular, therapeutic manipulation of tumor-associated macrophages holds promise due to their various and sometimes opposing roles in tumor progression. It is established that M1-type macrophages suppress tumor progression while M2-types support it. Recently, Tie2-expressing macrophages (TEM) have been identified as a distinct sub-population influencing tumor angiogenesis and vascular remodeling as well as monocyte differentiation. This study develops a modeling framework to evaluate macrophage interactions with the tumor microenvironment, enabling assessment of how these interactions may affect tumor progression. M1, M2, and Tie2 expressing variants are integrated into a model of tumor growth representing a metastatic lesion in a highly vascularized organ, such as the liver. Behaviors simulated include M1 release of nitric oxide (NO), M2 release of growth-promoting factors, and TEM facilitation of angiogenesis via Angiopoietin-2 and promotion of monocyte differentiation into M2 via IL-10. The results show that M2 presence leads to larger tumor growth regardless of TEM effects, implying that immunotherapeutic strategies that lead to TEM ablation may fail to restrain growth when the M2 represents a sizeable population. As TEM pro-tumor effects are less pronounced and on a longer time scale than M1-driven tumor inhibition, a more nuanced approach to influence monocyte differentiation taking into account the tumor state (e.g., under chemotherapy) may be desirable. The results highlight the dynamic interaction of macrophages within a growing tumor, and, further, establish the initial feasibility of a mathematical framework that could longer term help to optimize cancer immunotherapy.

Using multiple lines of evidence to assess the risk of ecosystem collapse

PubMed Central

Regan, Tracey J.; Dinh, Minh Ngoc; Ferrari, Renata; Keith, David A.; Lester, Rebecca; Mouillot, David; Murray, Nicholas J.; Nguyen, Hoang Anh; Nicholson, Emily

2017-01-01

Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment. PMID:28931744

Using multiple lines of evidence to assess the risk of ecosystem collapse.

PubMed

Bland, Lucie M; Regan, Tracey J; Dinh, Minh Ngoc; Ferrari, Renata; Keith, David A; Lester, Rebecca; Mouillot, David; Murray, Nicholas J; Nguyen, Hoang Anh; Nicholson, Emily

2017-09-27

Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment. © 2017 The Authors.

Ecosystem performance monitoring of rangelands by integrating modeling and remote sensing

USGS Publications Warehouse

Wylie, Bruce K.; Boyte, Stephen P.; Major, Donald J.

2012-01-01

Monitoring rangeland ecosystem dynamics, production, and performance is valuable for researchers and land managers. However, ecosystem monitoring studies can be difficult to interpret and apply appropriately if management decisions and disturbances are inseparable from the ecosystem's climate signal. This study separates seasonal weather influences from influences caused by disturbances and management decisions, making interannual time-series analysis more consistent and interpretable. We compared the actual ecosystem performance (AEP) of five rangeland vegetation types in the Owyhee Uplands for 9 yr to their expected ecosystem performance (EEP). Integrated growing season Normalized Difference Vegetation Index data for each of the nine growing seasons served as a proxy for annual AEP. Regression-tree models used long-term site potential, seasonal weather, and land cover data sets to generate annual EEP, an estimate of ecosystem performance incorporating annual weather variations. The difference between AEP and EEP provided a performance measure for each pixel in the study area. Ecosystem performance anomalies occurred when the ecosystem performed significantly better or worse than the model predicted. About 14% of the Owyhee Uplands showed a trend of significant underperformance or overperformance (P<0.10). Land managers can use results from weather-based rangeland ecosystem performance models to help support adaptive management strategies.

The Dependencies of Ecosystem Pattern, Structure, and Dynamics on Climate, Climate Variability, and Climate Change

NASA Astrophysics Data System (ADS)

Flanagan, S.; Hurtt, G. C.; Fisk, J. P.; Rourke, O.

2012-12-01

A robust understanding of the sensitivity of the pattern, structure, and dynamics of ecosystems to climate, climate variability, and climate change is needed to predict ecosystem responses to current and projected climate change. We present results of a study designed to first quantify the sensitivity of ecosystems to climate through the use of climate and ecosystem data, and then use the results to test the sensitivity of the climate data in a state-of the art ecosystem model. A database of available ecosystem characteristics such as mean canopy height, above ground biomass, and basal area was constructed from sources like the National Biomass and Carbon Dataset (NBCD). The ecosystem characteristics were then paired by latitude and longitude with the corresponding climate characteristics temperature, precipitation, photosynthetically active radiation (PAR) and dew point that were retrieved from the North American Regional Reanalysis (NARR). The average yearly and seasonal means of the climate data, and their associated maximum and minimum values, over the 1979-2010 time frame provided by NARR were constructed and paired with the ecosystem data. The compiled results provide natural patterns of vegetation structure and distribution with regard to climate data. An advanced ecosystem model, the Ecosystem Demography model (ED), was then modified to allow yearly alterations to its mechanistic climate lookup table and used to predict the sensitivities of ecosystem pattern, structure, and dynamics to climate data. The combined ecosystem structure and climate data results were compared to ED's output to check the validity of the model. After verification, climate change scenarios such as those used in the last IPCC were run and future forest structure changes due to climate sensitivities were identified. The results of this study can be used to both quantify and test key relationships for next generation models. The sensitivity of ecosystem characteristics to climate data shown in the database construction and by the model reinforces the need for high-resolution datasets and stresses the importance of understanding and incorporating climate change scenarios into earth system models.

The Importance of Uncertainty and Sensitivity Analysis in Process-based Models of Carbon and Nitrogen Cycling in Terrestrial Ecosystems with Particular Emphasis on Forest Ecosystems — Selected Papers from a Workshop Organized by the International Society for Ecological Modelling (ISEM) at the Third Biennal Meeting of the International Environmental Modelling and Software Society (IEMSS) in Burlington, Vermont, USA, August 9-13, 2006

USGS Publications Warehouse

Larocque, Guy R.; Bhatti, Jagtar S.; Liu, Jinxun; Ascough, James C.; Gordon, Andrew M.

2008-01-01

Many process-based models of carbon (C) and nitrogen (N) cycles have been developed for terrestrial ecosystems, including forest ecosystems. They address many basic issues of ecosystems structure and functioning, such as the role of internal feedback in ecosystem dynamics. The critical factor in these phenomena is scale, as these processes operate at scales from the minute (e.g. particulate pollution impacts on trees and other organisms) to the global (e.g. climate change). Research efforts remain important to improve the capability of such models to better represent the dynamics of terrestrial ecosystems, including the C, nutrient, (e.g. N) and water cycles. Existing models are sufficiently well advanced to help decision makers develop sustainable management policies and planning of terrestrial ecosystems, as they make realistic predictions when used appropriately. However, decision makers must be aware of their limitations by having the opportunity to evaluate the uncertainty associated with process-based models (Smith and Heath, 2001 and Allen et al., 2004). The variation in scale of issues currently being addressed by modelling efforts makes the evaluation of uncertainty a daunting task.

A protocol for the intercomparison of marine fishery and ecosystem models: Fish-MIP v1.0

NASA Astrophysics Data System (ADS)

Tittensor, Derek P.; Eddy, Tyler D.; Lotze, Heike K.; Galbraith, Eric D.; Cheung, William; Barange, Manuel; Blanchard, Julia L.; Bopp, Laurent; Bryndum-Buchholz, Andrea; Büchner, Matthias; Bulman, Catherine; Carozza, David A.; Christensen, Villy; Coll, Marta; Dunne, John P.; Fernandes, Jose A.; Fulton, Elizabeth A.; Hobday, Alistair J.; Huber, Veronika; Jennings, Simon; Jones, Miranda; Lehodey, Patrick; Link, Jason S.; Mackinson, Steve; Maury, Olivier; Niiranen, Susa; Oliveros-Ramos, Ricardo; Roy, Tilla; Schewe, Jacob; Shin, Yunne-Jai; Silva, Tiago; Stock, Charles A.; Steenbeek, Jeroen; Underwood, Philip J.; Volkholz, Jan; Watson, James R.; Walker, Nicola D.

2018-04-01

Model intercomparison studies in the climate and Earth sciences communities have been crucial to building credibility and coherence for future projections. They have quantified variability among models, spurred model development, contrasted within- and among-model uncertainty, assessed model fits to historical data, and provided ensemble projections of future change under specified scenarios. Given the speed and magnitude of anthropogenic change in the marine environment and the consequent effects on food security, biodiversity, marine industries, and society, the time is ripe for similar comparisons among models of fisheries and marine ecosystems. Here, we describe the Fisheries and Marine Ecosystem Model Intercomparison Project protocol version 1.0 (Fish-MIP v1.0), part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), which is a cross-sectoral network of climate impact modellers. Given the complexity of the marine ecosystem, this class of models has substantial heterogeneity of purpose, scope, theoretical underpinning, processes considered, parameterizations, resolution (grain size), and spatial extent. This heterogeneity reflects the lack of a unified understanding of the marine ecosystem and implies that the assemblage of all models is more likely to include a greater number of relevant processes than any single model. The current Fish-MIP protocol is designed to allow these heterogeneous models to be forced with common Earth System Model (ESM) Coupled Model Intercomparison Project Phase 5 (CMIP5) outputs under prescribed scenarios for historic (from the 1950s) and future (to 2100) time periods; it will be adapted to CMIP phase 6 (CMIP6) in future iterations. It also describes a standardized set of outputs for each participating Fish-MIP model to produce. This enables the broad characterization of differences between and uncertainties within models and projections when assessing climate and fisheries impacts on marine ecosystems and the services they provide. The systematic generation, collation, and comparison of results from Fish-MIP will inform an understanding of the range of plausible changes in marine ecosystems and improve our capacity to define and convey the strengths and weaknesses of model-based advice on future states of marine ecosystems and fisheries. Ultimately, Fish-MIP represents a step towards bringing together the marine ecosystem modelling community to produce consistent ensemble medium- and long-term projections of marine ecosystems.

More than Anecdotes: Fishers' Ecological Knowledge Can Fill Gaps for Ecosystem Modeling.

PubMed

Bevilacqua, Ana Helena V; Carvalho, Adriana R; Angelini, Ronaldo; Christensen, Villy

2016-01-01

Ecosystem modeling applied to fisheries remains hampered by a lack of local information. Fishers' knowledge could fill this gap, improving participation in and the management of fisheries. The same fishing area was modeled using two approaches: based on fishers' knowledge and based on scientific information. For the former, the data was collected by interviews through the Delphi methodology, and for the latter, the data was gathered from the literature. Agreement between the attributes generated by the fishers' knowledge model and scientific model is discussed and explored, aiming to improve data availability, the ecosystem model, and fisheries management. The ecosystem attributes produced from the fishers' knowledge model were consistent with the ecosystem attributes produced by the scientific model, and elaborated using only the scientific data from literature. This study provides evidence that fishers' knowledge may suitably complement scientific data, and may improve the modeling tools for the research and management of fisheries.

Ecosystem behavior at Bermuda Station [open quotes]S[close quotes] and ocean weather station [open quotes]India[close quotes]: A general circulation model and observational analysis

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

Fasham, M.J.R.; Sarmiento, J.L.; Slater, R.D.

1993-06-01

One important theme of modern biological oceanography has been the attempt to develop models of how the marine ecosystem responds to variations in the physical forcing functions such as solar radiation and the wind field. The authors have addressed the problem by embedding simple ecosystem models into a seasonally forced three-dimensional general circulation model of the North Atlantic ocean. In this paper first, some of the underlying biological assumptions of the ecosystem model are presented, followed by an analysis of how well the model predicts the seasonal cycle of the biological variables at Bermuda Station s' and Ocean Weather Stationmore » India. The model gives a good overall fit to the observations but does not faithfully model the whole seasonal ecosystem model. 57 refs., 25 figs., 5 tabs.« less

Modelling the excitation field of an optical resonator

NASA Astrophysics Data System (ADS)

Romanini, Daniele

2014-06-01

Assuming the paraxial approximation, we derive efficient recursive expressions for the projection coefficients of a Gaussian beam over the Gauss--Hermite transverse electro-magnetic (TEM) modes of an optical cavity. While previous studies considered cavities with cylindrical symmetry, our derivation accounts for "simple" astigmatism and ellipticity, which allows to deal with more realistic optical systems. The resulting expansion of the Gaussian beam over the cavity TEM modes provides accurate simulation of the excitation field distribution inside the cavity, in transmission, and in reflection. In particular, this requires including counter-propagating TEM modes, usually neglected in textbooks. As an illustrative application to a complex case, we simulate reentrant cavity configurations where Herriott spots are obtained at cavity output. We show that the case of an astigmatic cavity is also easily modelled. To our knowledge, such relevant applications are usually treated under the simplified geometrical optics approximation, or using heavier numerical methods.

Quantification of transendothelial migration using three-dimensional confocal microscopy.

PubMed

Cain, Robert J; d'Água, Bárbara Borda; Ridley, Anne J

2011-01-01

Migration of cells across endothelial barriers, termed transendothelial migration (TEM), is an important cellular process that underpins the pathology of many disease states including chronic inflammation and cancer metastasis. While this process can be modeled in vitro using cultured cells, many model systems are unable to provide detailed visual information of cell morphologies and distribution of proteins such as junctional markers, as well as quantitative data on the rate of TEM. Improvements in imaging techniques have made microscopy-based assays an invaluable tool for studying this type of detailed cell movement in physiological processes. In this chapter, we describe a confocal microscopy-based method that can be used to assess TEM of both leukocytes and cancer cells across endothelial barriers in response to a chemotactic gradient, as well as providing information on their migration into a subendothelial extracellular matrix, designed to mimic that found in vivo.

3D contour fluorescence spectroscopy with Brus model: Determination of size and band gap of double stranded DNA templated silver nanoclusters

NASA Astrophysics Data System (ADS)

Kamalraj, Devaraj; Yuvaraj, Selvaraj; Yoganand, Coimbatore Paramasivam; Jaffer, Syed S.

2018-01-01

Here, we propose a new synthetic methodology for silver nanocluster preparation by using a double stranded-DNA (ds-DNA) template which no one has reported yet. A new calculative method was formulated to determine the size of the nanocluster and their band gaps by using steady state 3D contour fluorescence technique with Brus model. Generally, the structure and size of the nanoclusters determine by using High Resolution Transmission Electron Microscopy (HR-TEM). Before imaging the samples by using HR-TEM, they are introduced to drying process which causes aggregation and forms bigger polycrystalline particles. It takes long time duration and expensive methodology. In this current methodology, we found out the size and band gap of the nanocluster in the liquid form without any polycrystalline aggregation for which 3D contour fluorescence technique was used as an alternative approach to the HR-TEM method.

Theoretical analysis and modeling of Thickness-Expansion Mode (TEM) sensors for fluid characterization.

PubMed

Elvira, Luis; Resa, Pablo; Castro, Pedro

2013-03-01

In this paper, the principles of Thickness-Expansion Mode (TEM) resonators for the characterization of fluids are described. From the measurement of the resonance parameters of a TEM piezoelectric transducer, the compressional acoustic impedance of gases and liquids can be determined. Since the propagation of mechanical waves into the fluid is not necessary, information in a wide range of frequencies can be obtained. Alternatively, these sensors can be driven in combination with other ultrasonic techniques to simultaneously determine the density, speed of sound and viscosity of samples. Some potential applications include the probe monitoring of processes and the characterization of fluids under harsh conditions. The main experimental criteria for the design and construction of high-resolution impedance meters (such as piezoelectric material, protective coating or thermal response) have been studied using equivalent electrical circuit modeling and finite element analysis. Copyright © 2012 Elsevier B.V. All rights reserved.

Consequences of changes in vegetation and snow cover for climate feedbacks in Alaska and northwest Canada

USGS Publications Warehouse

Euskirchen, Eugénie S.; Bennett, A. P.; Breen, Amy L.; Genet, Helene; Lindgren, Michael A.; Kurkowski, Tom; McGuire, A. David; Rupp, T. Scott

2016-01-01

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m−2 decade−1regionally) compared to the CCCMA (+1.3 W m−2 decade−1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (−0.2 to −0.3 W m−2 decade−1). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m−2decade regionally in the ECHAM scenario compared to +0.76 W m−2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Flux frequency analysis of seasonally dry ecosystem fluxes in two unique biomes of Sonora Mexico

NASA Astrophysics Data System (ADS)

Verduzco, V. S.; Yepez, E. A.; Robles-Morua, A.; Garatuza, J.; Rodriguez, J. C.; Watts, C.

2013-05-01

Complex dynamics from the interactions of ecosystems processes makes difficult to model the behavior of ecosystems fluxes of carbon and water in response to the variation of environmental and biological drivers. Although process oriented ecosystem models are critical tools for studying land-atmosphere fluxes, its validity depends on the appropriate parameterization of equations describing temporal and spatial changes of model state variables and their interactions. This constraint often leads to discrepancies between model simulations and observed data that reduce models reliability especially in arid and semiarid ecosystems. In the semiarid north western Mexico, ecosystem processes are fundamentally controlled by the seasonality of water and the intermittence of rain pulses which are conditions that require calibration of specific fitting functions to describe the response of ecosystem variables (i.e. NEE, GPP, ET, respiration) to these wetting and drying periods. The goal is to find functions that describe the magnitude of ecosystem fluxes during individual rain pulses and the seasonality of the ecosystem. Relaying on five years of eddy covariance flux data of a tropical dry forest and a subtropical shrubland we present a flux frequency analysis that describe the variation of net ecosystem exchange (NEE) of CO2 to highlight the relevance of pulse driven dynamics controlling this flux. Preliminary results of flux frequency analysis of NEE indicate that these ecosystems are strongly controlled by the frequency distribution of rain. Also, the output of fitting functions for NEE, GPP, ET and respiration using semi-empirical functions applied at specific rain pulses compared with season-long statistically generated simulations do not agree. Seasonality and the intrinsic nature of individual pulses have different effects on ecosystem flux responses. This suggests that relationships between the nature of seasonality and individual pulses can help improve the parameterization of process oriented ecosystem models.

Management Strategy Evaluation Applied to Coral Reef Ecosystems in Support of Ecosystem-Based Management.

PubMed

Weijerman, Mariska; Fulton, Elizabeth A; Brainard, Russell E

2016-01-01

Ecosystem modelling is increasingly used to explore ecosystem-level effects of changing environmental conditions and management actions. For coral reefs there has been increasing interest in recent decades in the use of ecosystem models for evaluating the effects of fishing and the efficacy of marine protected areas. However, ecosystem models that integrate physical forcings, biogeochemical and ecological dynamics, and human induced perturbations are still underdeveloped. We applied an ecosystem model (Atlantis) to the coral reef ecosystem of Guam using a suite of management scenarios prioritized in consultation with local resource managers to review the effects of each scenario on performance measures related to the ecosystem, the reef-fish fishery (e.g., fish landings) and coral habitat. Comparing tradeoffs across the selected scenarios showed that each scenario performed best for at least one of the selected performance indicators. The integrated 'full regulation' scenario outperformed other scenarios with four out of the six performance metrics at the cost of reef-fish landings. This model application quantifies the socio-ecological costs and benefits of alternative management scenarios. When the effects of climate change were taken into account, several scenarios performed equally well, but none prevented a collapse in coral biomass over the next few decades assuming a business-as-usual greenhouse gas emissions scenario.

Management Strategy Evaluation Applied to Coral Reef Ecosystems in Support of Ecosystem-Based Management

PubMed Central

Weijerman, Mariska; Fulton, Elizabeth A.; Brainard, Russell E.

2016-01-01

Ecosystem modelling is increasingly used to explore ecosystem-level effects of changing environmental conditions and management actions. For coral reefs there has been increasing interest in recent decades in the use of ecosystem models for evaluating the effects of fishing and the efficacy of marine protected areas. However, ecosystem models that integrate physical forcings, biogeochemical and ecological dynamics, and human induced perturbations are still underdeveloped. We applied an ecosystem model (Atlantis) to the coral reef ecosystem of Guam using a suite of management scenarios prioritized in consultation with local resource managers to review the effects of each scenario on performance measures related to the ecosystem, the reef-fish fishery (e.g., fish landings) and coral habitat. Comparing tradeoffs across the selected scenarios showed that each scenario performed best for at least one of the selected performance indicators. The integrated ‘full regulation’ scenario outperformed other scenarios with four out of the six performance metrics at the cost of reef-fish landings. This model application quantifies the socio-ecological costs and benefits of alternative management scenarios. When the effects of climate change were taken into account, several scenarios performed equally well, but none prevented a collapse in coral biomass over the next few decades assuming a business-as-usual greenhouse gas emissions scenario. PMID:27023183

Objective function analysis for electric soundings (VES), transient electromagnetic soundings (TEM) and joint inversion VES/TEM

NASA Astrophysics Data System (ADS)

Bortolozo, Cassiano Antonio; Bokhonok, Oleg; Porsani, Jorge Luís; Monteiro dos Santos, Fernando Acácio; Diogo, Liliana Alcazar; Slob, Evert

2017-11-01

Ambiguities in geophysical inversion results are always present. How these ambiguities appear in most cases open to interpretation. It is interesting to investigate ambiguities with regard to the parameters of the models under study. Residual Function Dispersion Map (RFDM) can be used to differentiate between global ambiguities and local minima in the objective function. We apply RFDM to Vertical Electrical Sounding (VES) and TEM Sounding inversion results. Through topographic analysis of the objective function we evaluate the advantages and limitations of electrical sounding data compared with TEM sounding data, and the benefits of joint inversion in comparison with the individual methods. The RFDM analysis proved to be a very interesting tool for understanding the joint inversion method of VES/TEM. Also the advantage of the applicability of the RFDM analyses in real data is explored in this paper to demonstrate not only how the objective function of real data behaves but the applicability of the RFDM approach in real cases. With the analysis of the results, it is possible to understand how the joint inversion can reduce the ambiguity of the methods.

Structure and Dynamics of Domains in Ferroelectric Nanostructures. In-situ TEM Studies

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

Pan, Xiaoqing

2015-06-30

The goal of this project was to explore the structure and dynamic behaviors of ferroelectric domains in ferroelectric thin films and nanostructures by advanced transmission electron microscopy (TEM) techniques in close collaboration with phase field modeling. The experimental techniques used include aberration-corrected sub-Å resolution TEM and in-situ TEM using a novel scanning tunneling microscopy (STM) - TEM holder that allows the direct observation of nucleation and dynamic evolution of ferroelectric domains under applied electric field. Specifically, this project was aimed to (1) to study the roles of static electrical boundary conditions and electrical charge in controlling the equilibrium domain structuresmore » of BiFeO 3 thin films with controlled substrate constraints, (2) to explore the fundamental mechanisms of ferroelectric domain nucleation, growth, and switching under an applied electric field in both uniform thin films and nanostructures, and to understand the roles of crystal defects such as dislocations and interfaces in these processes, (3) to understand the physics of ferroelectric domain walls and the influence of defects on the electrical switching of ferroelectric domains.« less

A bottom-up evolution of terrestrial ecosystem modeling theory, and ideas toward global vegetation modeling

NASA Technical Reports Server (NTRS)

Running, Steven W.

1992-01-01

A primary purpose of this review is to convey lessons learned in the development of a forest ecosystem modeling approach, from it origins in 1973 as a single-tree water balance model to the current regional applications. The second intent is to use this accumulated experience to offer ideas of how terrestrial ecosystem modeling can be taken to the global scale: earth systems modeling. A logic is suggested where mechanistic ecosystem models are not themselves operated globally, but rather are used to 'calibrate' much simplified models, primarily driven by remote sensing, that could be implemented in a semiautomated way globally, and in principle could interface with atmospheric general circulation models (GCM's).

Increased production of outer membrane vesicles by cultured freshwater bacteria in response to ultraviolet radiation.

PubMed

Gamalier, Juliana P; Silva, Thiago P; Zarantonello, Victor; Dias, Felipe F; Melo, Rossana C N

2017-01-01

Secretion of membrane vesicles is an important biological process of both eukaryotic and prokaryotic cells. This process has been characterized in pathogenic bacteria, but is less clear in non-pathogenic bacteria from aquatic ecosystems. Here, we investigated, for the first time, the process of formation of outer membranes vesicles (OMVs), nanoscale vesicles extruded from the outer membrane (OM) of gram-negative bacteria, in cultures of freshwater bacteria after exposure or not to ultraviolet radiation (UVR) as an environmental stressor. Non-axenic cultures of freshwater bacteria isolated from a Brazilian aquatic ecosystem (Funil reservoir) were exposed or not to UVR (UVA+UVB) over a 3h period, during which cell density, viability and ultrastructure were analyzed. First, we showed that UVR induce bacterial death. UVR triggered significant negative effect on cell density after 3h of UVR treatment. This decrease was directly associated with cell death as revealed by a cell viability fluorescent probe that enables the distinction of live/dead bacteria. Transmission electron microscopy (TEM) revealed changes indicative of cell death after 3h of UVR exposure, with significant increase of damaged cells compared to the control group. Second, we demonstrated that gram-negative bacteria release OMVs during normal growth and after UVR exposure. OMVs were clearly identified as round, membrane-bound vesicles budding off from the bacterial OM as isolated or clustered vesicles or free in the extracellular medium. Remarkably, quantitative TEM analyses showed that bacteria respond to UVR with increased formation of OMVs. Moreover, while OMVs numbers per intact or damaged cell did not differ in the untreated group, UVR led to a higher vesiculation by bacteria in process of death. This means that degenerating bacteria release OMVs before lysis and that this secretion might be an adaptive/protective response to rapid changes in environmental conditions such as UV radiation. Copyright © 2016 Elsevier GmbH. All rights reserved.

Thermoelectric Generators for Automotive Waste Heat Recovery Systems Part I: Numerical Modeling and Baseline Model Analysis

NASA Astrophysics Data System (ADS)

Kumar, Sumeet; Heister, Stephen D.; Xu, Xianfan; Salvador, James R.; Meisner, Gregory P.

2013-04-01

A numerical model has been developed to simulate coupled thermal and electrical energy transfer processes in a thermoelectric generator (TEG) designed for automotive waste heat recovery systems. This model is capable of computing the overall heat transferred, the electrical power output, and the associated pressure drop for given inlet conditions of the exhaust gas and the available TEG volume. Multiple-filled skutterudites and conventional bismuth telluride are considered for thermoelectric modules (TEMs) for conversion of waste heat from exhaust into usable electrical power. Heat transfer between the hot exhaust gas and the hot side of the TEMs is enhanced with the use of a plate-fin heat exchanger integrated within the TEG and using liquid coolant on the cold side. The TEG is discretized along the exhaust flow direction using a finite-volume method. Each control volume is modeled as a thermal resistance network which consists of integrated submodels including a heat exchanger and a thermoelectric device. The pressure drop along the TEG is calculated using standard pressure loss correlations and viscous drag models. The model is validated to preserve global energy balances and is applied to analyze a prototype TEG with data provided by General Motors. Detailed results are provided for local and global heat transfer and electric power generation. In the companion paper, the model is then applied to consider various TEG topologies using skutterudite and bismuth telluride TEMs.

Evaluating carbon fluxes of global forest ecosystems by using an individual tree-based model FORCCHN.

PubMed

Ma, Jianyong; Shugart, Herman H; Yan, Xiaodong; Cao, Cougui; Wu, Shuang; Fang, Jing

2017-05-15

The carbon budget of forest ecosystems, an important component of the terrestrial carbon cycle, needs to be accurately quantified and predicted by ecological models. As a preamble to apply the model to estimate global carbon uptake by forest ecosystems, we used the CO 2 flux measurements from 37 forest eddy-covariance sites to examine the individual tree-based FORCCHN model's performance globally. In these initial tests, the FORCCHN model simulated gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) with correlations of 0.72, 0.70 and 0.53, respectively, across all forest biomes. The model underestimated GPP and slightly overestimated ER across most of the eddy-covariance sites. An underestimation of NEP arose primarily from the lower GPP estimates. Model performance was better in capturing both the temporal changes and magnitude of carbon fluxes in deciduous broadleaf forest than in evergreen broadleaf forest, and it performed less well for sites in Mediterranean climate. We then applied the model to estimate the carbon fluxes of forest ecosystems on global scale over 1982-2011. This application of FORCCHN gave a total GPP of 59.41±5.67 and an ER of 57.21±5.32PgCyr -1 for global forest ecosystems during 1982-2011. The forest ecosystems over this same period contributed a large carbon storage, with total NEP being 2.20±0.64PgCyr -1 . These values are comparable to and reinforce estimates reported in other studies. This analysis highlights individual tree-based model FORCCHN could be used to evaluate carbon fluxes of forest ecosystems on global scale. Copyright © 2017 Elsevier B.V. All rights reserved.

Application of a Lower Food Web Ecosystem Productivity Model to Investigate Population Dynamics of Invasive Species in Lake Michigan

EPA Science Inventory

A Lake Michigan Ecosystem Model (LM-Eco) that includes a detailed description of trophic levels and their interactions was developed for Lake Michigan. The LM-Eco model constitutes a first step toward a comprehensive Lake Michigan ecosystem productivity model to investigate ecosy...

Description of the General Equilibrium Model of Ecosystem Services (GEMES)

Treesearch

Travis Warziniack; David Finnoff; Jenny Apriesnig

2017-01-01

This paper serves as documentation for the General Equilibrium Model of Ecosystem Services (GEMES). GEMES is a regional computable general equilibrium model that is composed of values derived from natural capital and ecosystem services. It models households, producing sectors, and governments, linked to one another through commodity and factor markets. GEMES was...

Application of a Lower Food Web Ecosystem Productivity Model for Investigating Dynamics of the Invasive Species Bythortrephes longimanus in Lake Michigan

EPA Science Inventory

A Lake Michigan Ecosystem Model (LM-Eco) that includes a detailed description of trophic levels and their interactions was developed for Lake Michigan. The LM-Eco model constitutes a first step toward a comprehensive Lake Michigan ecosystem productivity model to investigate ecos...

TEM measurement in a low resistivity overburden performed by using low temperature SQUID

NASA Astrophysics Data System (ADS)

Ji, Yanju; Du, Shangyu; Xie, Lijun; Chang, Kai; Liu, Yang; Zhang, Yi; Xie, Xiaoming; Wang, Yuan; Lin, Jun; Rong, Liangliang

2016-12-01

Exploration of areas with thick low resistivity overburden is still a challenge for time domain transient electromagnetic method (TEM). We report modeling of a sandwich-layered earth by simulating the B field response with different conductive target layer thicknesses, thus obtaining a relationship between the resolution of the B field and the exploration depth. A low temperature Superconducting Quantum Interference Device (SQUID) is an ideal sensor for measuring the secondary magnetic field B in TEM measurements, because its sensitivity of several fT/√Hz is independent of frequency. In our TEM experiments, we utilized two different coils as receivers, a simple SQUID system, and a large transmitter loop of 200 × 200 m2 to compare the detected decay curves. At some measurement points, a decay signal of more than 300 ms duration was obtained by using the SQUID. Apparent resistivity profiles of about 9 km length are presented.

High-Resolution Characterization of UMo Alloy Microstructure

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

Devaraj, Arun; Kovarik, Libor; Joshi, Vineet V.

2016-11-30

This report highlights the capabilities and procedure for high-resolution characterization of UMo fuels in PNNL. Uranium-molybdenum (UMo) fuel processing steps, from casting to forming final fuel, directly affect the microstructure of the fuel, which in turn dictates the in-reactor performance of the fuel under irradiation. In order to understand the influence of processing on UMo microstructure, microstructure characterization techniques are necessary. Higher-resolution characterization techniques like transmission electron microscopy (TEM) and atom probe tomography (APT) are needed to interrogate the details of the microstructure. The findings from TEM and APT are also directly beneficial for developing predictive multiscale modeling tools thatmore » can predict the microstructure as a function of process parameters. This report provides background on focused-ion-beam–based TEM and APT sample preparation, TEM and APT analysis procedures, and the unique information achievable through such advanced characterization capabilities for UMo fuels, from a fuel fabrication capability viewpoint.« less

Two takes on the ecosystem impacts of climate change and fishing: Comparing a size-based and a species-based ecosystem model in the central North Pacific

NASA Astrophysics Data System (ADS)

Woodworth-Jefcoats, Phoebe A.; Polovina, Jeffrey J.; Howell, Evan A.; Blanchard, Julia L.

2015-11-01

We compare two ecosystem model projections of 21st century climate change and fishing impacts in the central North Pacific. Both a species-based and a size-based ecosystem modeling approach are examined. While both models project a decline in biomass across all sizes in response to climate change and a decline in large fish biomass in response to increased fishing mortality, the models vary significantly in their handling of climate and fishing scenarios. For example, based on the same climate forcing the species-based model projects a 15% decline in catch by the end of the century while the size-based model projects a 30% decline. Disparities in the models' output highlight the limitations of each approach by showing the influence model structure can have on model output. The aspects of bottom-up change to which each model is most sensitive appear linked to model structure, as does the propagation of interannual variability through the food web and the relative impact of combined top-down and bottom-up change. Incorporating integrated size- and species-based ecosystem modeling approaches into future ensemble studies may help separate the influence of model structure from robust projections of ecosystem change.

Placing biodiversity in ecosystem models without getting lost in translation

NASA Astrophysics Data System (ADS)

Queirós, Ana M.; Bruggeman, Jorn; Stephens, Nicholas; Artioli, Yuri; Butenschön, Momme; Blackford, Jeremy C.; Widdicombe, Stephen; Allen, J. Icarus; Somerfield, Paul J.

2015-04-01

A key challenge to progressing our understanding of biodiversity's role in the sustenance of ecosystem function is the extrapolation of the results of two decades of dedicated empirical research to regional, global and future landscapes. Ecosystem models provide a platform for this progression, potentially offering a holistic view of ecosystems where, guided by the mechanistic understanding of processes and their connection to the environment and biota, large-scale questions can be investigated. While the benefits of depicting biodiversity in such models are widely recognized, its application is limited by difficulties in the transfer of knowledge from small process oriented ecology into macro-scale modelling. Here, we build on previous work, breaking down key challenges of that knowledge transfer into a tangible framework, highlighting successful strategies that both modelling and ecology communities have developed to better interact with one another. We use a benthic and a pelagic case-study to illustrate how aspects of the links between biodiversity and ecosystem process have been depicted in marine ecosystem models (ERSEM and MIRO), from data, to conceptualisation and model development. We hope that this framework may help future interactions between biodiversity researchers and model developers by highlighting concrete solutions to common problems, and in this way contribute to the advance of the mechanistic understanding of the role of biodiversity in marine (and terrestrial) ecosystems.

Ecosystem functioning is enveloped by hydrometeorological variability.

PubMed

Pappas, Christoforos; Mahecha, Miguel D; Frank, David C; Babst, Flurin; Koutsoyiannis, Demetris

2017-09-01

Terrestrial ecosystem processes, and the associated vegetation carbon dynamics, respond differently to hydrometeorological variability across timescales, and so does our scientific understanding of the underlying mechanisms. Long-term variability of the terrestrial carbon cycle is not yet well constrained and the resulting climate-biosphere feedbacks are highly uncertain. Here we present a comprehensive overview of hydrometeorological and ecosystem variability from hourly to decadal timescales integrating multiple in situ and remote-sensing datasets characterizing extra-tropical forest sites. We find that ecosystem variability at all sites is confined within a hydrometeorological envelope across sites and timescales. Furthermore, ecosystem variability demonstrates long-term persistence, highlighting ecological memory and slow ecosystem recovery rates after disturbances. However, simulation results with state-of-the-art process-based models do not reflect this long-term persistent behaviour in ecosystem functioning. Accordingly, we develop a cross-time-scale stochastic framework that captures hydrometeorological and ecosystem variability. Our analysis offers a perspective for terrestrial ecosystem modelling and paves the way for new model-data integration opportunities in Earth system sciences.

Linking an ecosystem model and a landscape model to study forest species response to climate warming

Treesearch

Hong S. He; David J. Mladenoff; Thomas R. Crow

1999-01-01

No single model can address forest change from single tree to regional scales. We discuss a framework linking an ecosystem process model {LINKAGES) with a spatial landscape model (LANDIS) to examine forest species responses to climate warming for a large, heterogeneous landscape in northern Wisconsin, USA. Individual species response at the ecosystem scale was...

Modelling Southern Ocean ecosystems: krill, the food-web, and the impacts of harvesting.

PubMed

Hill, S L; Murphy, E J; Reid, K; Trathan, P N; Constable, A J

2006-11-01

The ecosystem approach to fisheries recognises the interdependence between harvested species and other ecosystem components. It aims to account for the propagation of the effects of harvesting through the food-web. The formulation and evaluation of ecosystem-based management strategies requires reliable models of ecosystem dynamics to predict these effects. The krill-based system in the Southern Ocean was the focus of some of the earliest models exploring such effects. It is also a suitable example for the development of models to support the ecosystem approach to fisheries because it has a relatively simple food-web structure and progress has been made in developing models of the key species and interactions, some of which has been motivated by the need to develop ecosystem-based management. Antarctic krill, Euphausia superba, is the main target species for the fishery and the main prey of many top predators. It is therefore critical to capture the processes affecting the dynamics and distribution of krill in ecosystem dynamics models. These processes include environmental influences on recruitment and the spatially variable influence of advection. Models must also capture the interactions between krill and its consumers, which are mediated by the spatial structure of the environment. Various models have explored predator-prey population dynamics with simplistic representations of these interactions, while others have focused on specific details of the interactions. There is now a pressing need to develop plausible and practical models of ecosystem dynamics that link processes occurring at these different scales. Many studies have highlighted uncertainties in our understanding of the system, which indicates future priorities in terms of both data collection and developing methods to evaluate the effects of these uncertainties on model predictions. We propose a modelling approach that focuses on harvested species and their monitored consumers and that evaluates model uncertainty by using alternative structures and functional forms in a Monte Carlo framework.

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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.

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

PubMed

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

2015-03-13

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.

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

Spatial dynamics of ecosystem service flows: a comprehensive approach to quantifying actual services

USGS Publications Warehouse

Bagstad, Kenneth J.; Johnson, Gary W.; Voigt, Brian; Villa, Ferdinando

2013-01-01

Recent ecosystem services research has highlighted the importance of spatial connectivity between ecosystems and their beneficiaries. Despite this need, a systematic approach to ecosystem service flow quantification has not yet emerged. In this article, we present such an approach, which we formalize as a class of agent-based models termed “Service Path Attribution Networks” (SPANs). These models, developed as part of the Artificial Intelligence for Ecosystem Services (ARIES) project, expand on ecosystem services classification terminology introduced by other authors. Conceptual elements needed to support flow modeling include a service's rivalness, its flow routing type (e.g., through hydrologic or transportation networks, lines of sight, or other approaches), and whether the benefit is supplied by an ecosystem's provision of a beneficial flow to people or by absorption of a detrimental flow before it reaches them. We describe our implementation of the SPAN framework for five ecosystem services and discuss how to generalize the approach to additional services. SPAN model outputs include maps of ecosystem service provision, use, depletion, and flows under theoretical, possible, actual, inaccessible, and blocked conditions. We highlight how these different ecosystem service flow maps could be used to support various types of decision making for conservation and resource management planning.

Ecosystem oceanography for global change in fisheries.

PubMed

Cury, Philippe Maurice; Shin, Yunne-Jai; Planque, Benjamin; Durant, Joël Marcel; Fromentin, Jean-Marc; Kramer-Schadt, Stephanie; Stenseth, Nils Christian; Travers, Morgane; Grimm, Volker

2008-06-01

Overexploitation and climate change are increasingly causing unanticipated changes in marine ecosystems, such as higher variability in fish recruitment and shifts in species dominance. An ecosystem-based approach to fisheries attempts to address these effects by integrating populations, food webs and fish habitats at different scales. Ecosystem models represent indispensable tools to achieve this objective. However, a balanced research strategy is needed to avoid overly complex models. Ecosystem oceanography represents such a balanced strategy that relates ecosystem components and their interactions to climate change and exploitation. It aims at developing realistic and robust models at different levels of organisation and addressing specific questions in a global change context while systematically exploring the ever-increasing amount of biological and environmental data.

Toward a Mexican eddy covariance network for carbon cycle science

NASA Astrophysics Data System (ADS)

Vargas, Rodrigo; Yépez, Enrico A.

2011-09-01

First Annual MexFlux Principal Investigators Meeting; Hermosillo, Sonora, Mexico, 4-8 May 2011; The carbon cycle science community has organized a global network, called FLUXNET, to measure the exchange of energy, water, and carbon dioxide (CO2) between the ecosystems and the atmosphere using the eddy covariance technique. This network has provided unprecedented information for carbon cycle science and global climate change but is mostly represented by study sites in the United States and Europe. Thus, there is an important gap in measurements and understanding of ecosystem dynamics in other regions of the world that are seeing a rapid change in land use. Researchers met under the sponsorship of Red Temática de Ecosistemas and Consejo Nacional de Ciencia y Tecnologia (CONACYT) to discuss strategies to establish a Mexican eddy covariance network (MexFlux) by identifying researchers, study sites, and scientific goals. During the meeting, attendees noted that 10 study sites have been established in Mexico with more than 30 combined years of information. Study sites span from new sites installed during 2011 to others with 9 to 6 years of measurements. Sites with the longest span measurements are located in Baja California Sur (established by Walter Oechel in 2002) and Sonora (established by Christopher Watts in 2005); both are semiarid ecosystems. MexFlux sites represent a variety of ecosystem types, including Mediterranean and sarcocaulescent shrublands in Baja California; oak woodland, subtropical shrubland, tropical dry forest, and a grassland in Sonora; tropical dry forests in Jalisco and Yucatan; a managed grassland in San Luis Potosi; and a managed pine forest in Hidalgo. Sites are maintained with an individual researcher's funds from Mexican government agencies (e.g., CONACYT) and international collaborations, but no coordinated funding exists for a long-term program.

Predictors of Drought Recovery across Forest Ecosystems

NASA Astrophysics Data System (ADS)

Anderegg, W.

2016-12-01

The impacts of climate extremes on terrestrial ecosystems are poorly understood but central for predicting carbon cycle feedbacks to climate change. Coupled climate-carbon cycle models typically assume that vegetation recovery from extreme drought is immediate and complete, which conflicts with basic plant physiological understanding. Here, we discuss what we have learned about forest ecosystem recovery from extreme drought across spatial and temporal scales, drawing on inference from tree rings, eddy covariance data, large scale gross primary productivity products, and ecosystem models. In tree rings, we find pervasive and substantial "legacy effects" of reduced growth and incomplete recovery for 1-4 years after severe drought, and that legacy effects are most prevalent in dry ecosystems, Pinaceae, and species with low hydraulic safety margins. At larger scales, we see relatively rapid recovery of ecosystem fluxes, with strong influences of ecosystem productivity and diversity and longer recovery periods in high latidue forests. In contrast, no or limited legacy effects are simulated in current climate-vegetation models after drought, and we highlight some of the key missing mechanisms in dynamic vegetation models. Our results reveal hysteresis in forest ecosystem carbon cycling and delayed recovery from climate extremes and help advance a predictive understanding of ecosystem recovery.

How models can support ecosystem-based management of coral reefs

NASA Astrophysics Data System (ADS)

Weijerman, Mariska; Fulton, Elizabeth A.; Janssen, Annette B. G.; Kuiper, Jan J.; Leemans, Rik; Robson, Barbara J.; van de Leemput, Ingrid A.; Mooij, Wolf M.

2015-11-01

Despite the importance of coral reef ecosystems to the social and economic welfare of coastal communities, the condition of these marine ecosystems have generally degraded over the past decades. With an increased knowledge of coral reef ecosystem processes and a rise in computer power, dynamic models are useful tools in assessing the synergistic effects of local and global stressors on ecosystem functions. We review representative approaches for dynamically modeling coral reef ecosystems and categorize them as minimal, intermediate and complex models. The categorization was based on the leading principle for model development and their level of realism and process detail. This review aims to improve the knowledge of concurrent approaches in coral reef ecosystem modeling and highlights the importance of choosing an appropriate approach based on the type of question(s) to be answered. We contend that minimal and intermediate models are generally valuable tools to assess the response of key states to main stressors and, hence, contribute to understanding ecological surprises. As has been shown in freshwater resources management, insight into these conceptual relations profoundly influences how natural resource managers perceive their systems and how they manage ecosystem recovery. We argue that adaptive resource management requires integrated thinking and decision support, which demands a diversity of modeling approaches. Integration can be achieved through complimentary use of models or through integrated models that systemically combine all relevant aspects in one model. Such whole-of-system models can be useful tools for quantitatively evaluating scenarios. These models allow an assessment of the interactive effects of multiple stressors on various, potentially conflicting, management objectives. All models simplify reality and, as such, have their weaknesses. While minimal models lack multidimensionality, system models are likely difficult to interpret as they require many efforts to decipher the numerous interactions and feedback loops. Given the breadth of questions to be tackled when dealing with coral reefs, the best practice approach uses multiple model types and thus benefits from the strength of different models types.

In praise of mechanistically-rich models

USGS Publications Warehouse

DeAngelis, Donald L.; Mooij, Wolf M.; Canham, Charles D.; Cole, Jonathan J.; Lauenroth, William K.

2003-01-01

The book opens with an overview of the status and role of modeling in ecosystem science, including perspectives on the long-running debate over the appropriate level of complexity in models. This is followed by eight chapters that address the critical issue of evaluating ecosystem models, including methods of addressing uncertainty. Next come several case studies of the role of models in environmental policy and management. A section on the future of modeling in ecosystem science focuses on increasing the use of modeling in undergraduate education and the modeling skills of professionals within the field. The benefits and limitations of predictive (versus observational) models are also considered in detail. Written by stellar contributors, this book grants access to the state of the art and science of ecosystem modeling.

Available fuel dynamics in nine contrasting forest ecosystems in North America

Treesearch

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

2004-01-01

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

Design Automation for Streaming Systems

DTIC Science & Technology

2005-12-16

which are FIFO buffered channels. We develop a process network model for streaming sys - tems (TDFPN) and a hardware description language with built in...and may include an automatic address generator. A complete synthesis sys - tem would provide separate segment operator implementations for every...Acoustics, Speech, and Signal Processing (ICASSP ’89), pages 988– 991, 1989. [Luk et al., 1997] Wayne Luk, Nabeel Shirazi, and Peter Y. K. Cheung

Modeling an aquatic ecosystem: application of an evolutionary algorithm with genetic doping to reduce prediction uncertainty

NASA Astrophysics Data System (ADS)

Friedel, Michael; Buscema, Massimo

2016-04-01

Aquatic ecosystem models can potentially be used to understand the influence of stresses on catchment resource quality. Given that catchment responses are functions of natural and anthropogenic stresses reflected in sparse and spatiotemporal biological, physical, and chemical measurements, an ecosystem is difficult to model using statistical or numerical methods. We propose an artificial adaptive systems approach to model ecosystems. First, an unsupervised machine-learning (ML) network is trained using the set of available sparse and disparate data variables. Second, an evolutionary algorithm with genetic doping is applied to reduce the number of ecosystem variables to an optimal set. Third, the optimal set of ecosystem variables is used to retrain the ML network. Fourth, a stochastic cross-validation approach is applied to quantify and compare the nonlinear uncertainty in selected predictions of the original and reduced models. Results are presented for aquatic ecosystems (tens of thousands of square kilometers) undergoing landscape change in the USA: Upper Illinois River Basin and Central Colorado Assessment Project Area, and Southland region, NZ.

Dynamical implications of bi-directional resource exchange within a meta-ecosystem.

PubMed

Messan, Marisabel Rodriguez; Kopp, Darin; Allen, Daniel C; Kang, Yun

2018-05-05

The exchange of resources across ecosystem boundaries can have large impacts on ecosystem structures and functions at local and regional scales. In this article, we develop a simple model to investigate dynamical implications of bi-directional resource exchanges between two local ecosystems in a meta-ecosystem framework. In our model, we assume that (1) Each local ecosystem acts as both a resource donor and recipient, such that one ecosystem donating resources to another results in a cost to the donating system and a benefit to the recipient; and (2) The costs and benefits of the bi-directional resource exchange between two ecosystems are correlated in a nonlinear fashion. Our model could apply to the resource interactions between terrestrial and aquatic ecosystems that are supported by the literature. Our theoretical results show that bi-directional resource exchange between two ecosystems can indeed generate complicated dynamical outcomes, including the coupled ecosystems having amensalistic, antagonistic, competitive, or mutualistic interactions, with multiple alternative stable states depending on the relative costs and benefits. In addition, if the relative cost for resource exchange for an ecosystem is decreased or the relative benefit for resource exchange for an ecosystem is increased, the production of that ecosystem would increase; however, depending on the local environment, the production of the other ecosystem may increase or decrease. We expect that our work, by evaluating the potential outcomes of resource exchange theoretically, can facilitate empirical evaluations and advance the understanding of spatial ecosystem ecology where resource exchanges occur in varied ecosystems through a complicated network. Copyright © 2018 Elsevier Inc. All rights reserved.

Prototyping an online wetland ecosystem services model using open model sharing standards

USGS Publications Warehouse

Feng, M.; Liu, S.; Euliss, N.H.; Young, Caitlin; Mushet, D.M.

2011-01-01

Great interest currently exists for developing ecosystem models to forecast how ecosystem services may change under alternative land use and climate futures. Ecosystem services are diverse and include supporting services or functions (e.g., primary production, nutrient cycling), provisioning services (e.g., wildlife, groundwater), regulating services (e.g., water purification, floodwater retention), and even cultural services (e.g., ecotourism, cultural heritage). Hence, the knowledge base necessary to quantify ecosystem services is broad and derived from many diverse scientific disciplines. Building the required interdisciplinary models is especially challenging as modelers from different locations and times may develop the disciplinary models needed for ecosystem simulations, and these models must be identified and made accessible to the interdisciplinary simulation. Additional difficulties include inconsistent data structures, formats, and metadata required by geospatial models as well as limitations on computing, storage, and connectivity. Traditional standalone and closed network systems cannot fully support sharing and integrating interdisciplinary geospatial models from variant sources. To address this need, we developed an approach to openly share and access geospatial computational models using distributed Geographic Information System (GIS) techniques and open geospatial standards. We included a means to share computational models compliant with Open Geospatial Consortium (OGC) Web Processing Services (WPS) standard to ensure modelers have an efficient and simplified means to publish new models. To demonstrate our approach, we developed five disciplinary models that can be integrated and shared to simulate a few of the ecosystem services (e.g., water storage, waterfowl breeding) that are provided by wetlands in the Prairie Pothole Region (PPR) of North America.

Northern Forest Ecosystem Dynamics Using Coupled Models and Remote Sensing

NASA Technical Reports Server (NTRS)

Ranson, K. J.; Sun, G.; Knox, R. G.; Levine, E. R.; Weishampel, J. F.; Fifer, S. T.

1999-01-01

Forest ecosystem dynamics modeling, remote sensing data analysis, and a geographical information system (GIS) were used together to determine the possible growth and development of a northern forest in Maine, USA. Field measurements and airborne synthetic aperture radar (SAR) data were used to produce maps of forest cover type and above ground biomass. These forest attribute maps, along with a conventional soils map, were used to identify the initial conditions for forest ecosystem model simulations. Using this information along with ecosystem model results enabled the development of predictive maps of forest development. The results obtained were consistent with observed forest conditions and expected successional trajectories. The study demonstrated that ecosystem models might be used in a spatial context when parameterized and used with georeferenced data sets.

A Generic 1D Forward Modeling and Inversion Algorithm for TEM Sounding with an Arbitrary Horizontal Loop

NASA Astrophysics Data System (ADS)

Li, Zhanhui; Huang, Qinghua; Xie, Xingbing; Tang, Xingong; Chang, Liao

2016-08-01

We present a generic 1D forward modeling and inversion algorithm for transient electromagnetic (TEM) data with an arbitrary horizontal transmitting loop and receivers at any depth in a layered earth. Both the Hankel and sine transforms required in the forward algorithm are calculated using the filter method. The adjoint-equation method is used to derive the formulation of data sensitivity at any depth in non-permeable media. The inversion algorithm based on this forward modeling algorithm and sensitivity formulation is developed using the Gauss-Newton iteration method combined with the Tikhonov regularization. We propose a new data-weighting method to minimize the initial model dependence that enhances the convergence stability. On a laptop with a CPU of i7-5700HQ@3.5 GHz, the inversion iteration of a 200 layered input model with a single receiver takes only 0.34 s, while it increases to only 0.53 s for the data from four receivers at a same depth. For the case of four receivers at different depths, the inversion iteration runtime increases to 1.3 s. Modeling the data with an irregular loop and an equal-area square loop indicates that the effect of the loop geometry is significant at early times and vanishes gradually along the diffusion of TEM field. For a stratified earth, inversion of data from more than one receiver is useful in noise reducing to get a more credible layered earth. However, for a resistive layer shielded below a conductive layer, increasing the number of receivers on the ground does not have significant improvement in recovering the resistive layer. Even with a down-hole TEM sounding, the shielded resistive layer cannot be recovered if all receivers are above the shielded resistive layer. However, our modeling demonstrates remarkable improvement in detecting the resistive layer with receivers in or under this layer.

Modelling impacts of second generation bioenergy production on Ecosystem Services in Europe

NASA Astrophysics Data System (ADS)

Henner, Dagmar; Smith, Pete; Davies, Christian; McNamara, Niall

2016-04-01

Bioenergy crops are an important source of renewable energy and are a possible mechanism to mitigate global climate warming, by replacing fossil fuel energy with higher greenhouse gas emissions. There is, however, uncertainty about the impacts of the growth of bioenergy crops on ecosystem services. This uncertainty is further enhanced by the unpredictable climate change currently going on. The goal of this project is to develop a comprehensive model that covers high impact, policy relevant ecosystem services at a Continental scale including biodiversity and pollination, water and air security, erosion control and soil security, GHG emissions, soil C and cultural services like tourism value. The technical distribution potential and likely yield of second generation energy crops, such as Miscanthus, Short Rotation Coppice (SRC) with willow, poplar, eucalyptus and other broadleaf species and Short Rotation Forestry (SRF), is currently being modelled using ECOSSE, DayCent, SalixFor and MiscanFor, and ecosystem models will be used to examine the impacts of these crops on ecosystem services. The project builds on models of energy crop production, biodiversity, soil impacts, greenhouse gas emissions and other ecosystem services, and on work undertaken in the UK on the ETI-funded ELUM project (www.elum.ac.uk). In addition, methods like water footprint tools, tourism value maps and ecosystem valuation tools and models (e.g. InVest, TEEB database, GREET LCA Model, World Business Council for Sustainable Development corporate ecosystem valuation, Millennium Ecosystem Assessment and the Ecosystem Services Framework) will be utilised. Research will focus on optimisation of land use change feedbacks on above named ecosystem services, impact on food security, land management practices and impacts from climate change. We will present results for GHG emissions and soil organic carbon change after different land use change scenarios (e.g. arable to Miscanthus, forest to SRF), and with different climate warming scenarios. Further, we will show modelled yield maps for Miscanthus, Salix and Poplar in Europe and will present constraint/opportunity maps for Europe based on yield modelled and other factors e.g. total economic value, technical potential, current land use, trade off and synergies, and so on. All this will be complemented by the presentation of a matrix including the factors and ecosystem services influenced by land use change to bioenergy crop production under different climate change scenarios.

More than Anecdotes: Fishers’ Ecological Knowledge Can Fill Gaps for Ecosystem Modeling

PubMed Central

Bevilacqua, Ana Helena V.; Carvalho, Adriana R.; Angelini, Ronaldo; Christensen, Villy

2016-01-01

Background Ecosystem modeling applied to fisheries remains hampered by a lack of local information. Fishers’ knowledge could fill this gap, improving participation in and the management of fisheries. Methodology The same fishing area was modeled using two approaches: based on fishers’ knowledge and based on scientific information. For the former, the data was collected by interviews through the Delphi methodology, and for the latter, the data was gathered from the literature. Agreement between the attributes generated by the fishers’ knowledge model and scientific model is discussed and explored, aiming to improve data availability, the ecosystem model, and fisheries management. Principal Findings The ecosystem attributes produced from the fishers’ knowledge model were consistent with the ecosystem attributes produced by the scientific model, and elaborated using only the scientific data from literature. Conclusions/Significance This study provides evidence that fishers’ knowledge may suitably complement scientific data, and may improve the modeling tools for the research and management of fisheries. PMID:27196131

Biogenic synthesized nanoparticles and their applications

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

Singh, Abhijeet, E-mail: abhijeet.singh@jaipur.manipal.edu; Sharma, Madan Mohan

In the present scenario, there are growing concerns over the potential impacts of bioengineered nanoparticles in the health sector. However, our understanding of how bioengineered nanoparticles may affect organisms within natural ecosystems, lags far behind our rapidly increasing ability to engineer novel nanoparticles. To date, research on the biological impacts of bioengineered nanoparticles has primarily consisted of controlled lab studies of model organisms with single species in culture media. Here, we described a cost effective and environment friendly technique for green synthesis of silver nanoparticles. Silver nanoparticles were successfully synthesized from 1 mM AgNO{sub 3} via a green synthesis processmore » using leaf extract as reducing as well as capping agent. Nanoparticles were characterized with the help of UV–vis absorption spectroscopy, X-ray diffraction and TEM analysis which revealed the size of nanoparticles of 30-40 nm size. Further the nanoparticles synthesized by green route are found highly toxic against pathogenic bacteria and plant pathogenic fungi viz. Escherichia coli, Pseudomonas syringae and Sclerotiniasclerotiorum. The most important outcome of this work will be the development of value-added products and protection of human health from pathogens viz., bacteria, virus, fungi etc.« less

Transport and fate of radionuclides in aquatic environments--the use of ecosystem modelling for exposure assessments of nuclear facilities.

PubMed

Kumblad, L; Kautsky, U; Naeslund, B

2006-01-01

In safety assessments of nuclear facilities, a wide range of radioactive isotopes and their potential hazard to a large assortment of organisms and ecosystem types over long time scales need to be considered. Models used for these purposes have typically employed approaches based on generic reference organisms, stylised environments and transfer functions for biological uptake exclusively based on bioconcentration factors (BCFs). These models are of non-mechanistic nature and involve no understanding of uptake and transport processes in the environment, which is a severe limitation when assessing real ecosystems. In this paper, ecosystem models are suggested as a method to include site-specific data and to facilitate the modelling of dynamic systems. An aquatic ecosystem model for the environmental transport of radionuclides is presented and discussed. With this model, driven and constrained by site-specific carbon dynamics and three radionuclide specific mechanisms: (i) radionuclide uptake by plants, (ii) excretion by animals, and (iii) adsorption to organic surfaces, it was possible to estimate the radionuclide concentrations in all components of the modelled ecosystem with only two radionuclide specific input parameters (BCF for plants and Kd). The importance of radionuclide specific mechanisms for the exposure to organisms was examined, and probabilistic and sensitivity analyses to assess the uncertainties related to ecosystem input parameters were performed. Verification of the model suggests that this model produces analogous results to empirically derived data for more than 20 different radionuclides.

Effect of interparticle interactions on size determination of zirconia and silica based systems – A comparison of SAXS, DLS, BET, XRD and TEM

PubMed Central

Pabisch, Silvia; Feichtenschlager, Bernhard; Kickelbick, Guido; Peterlik, Herwig

2012-01-01

The aim of this work is a systematic comparison of size characterisation methods for two completely different model systems of oxide nanoparticles, i.e. amorphous spherical silica and anisotropic facet-shaped crystalline zirconia. Size and/or size distribution were determined in a wide range from 5 to 70 nm using small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), nitrogen sorption (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM). A nearly perfect coincidence was observed only for SAXS and TEM for both types of particles. For zirconia nanoparticles considerable differences between different measurement methods were observed. PMID:22347721

Nanoparticle formation of deposited Agn-clusters on free-standing graphene

NASA Astrophysics Data System (ADS)

Al-Hada, M.; Peters, S.; Gregoratti, L.; Amati, M.; Sezen, H.; Parisse, P.; Selve, S.; Niermann, T.; Berger, D.; Neeb, M.; Eberhardt, W.

2017-11-01

Size-selected Agn-clusters on unsupported graphene of a commercial Quantifoil sample have been investigated by surface and element-specific techniques such as transmission electron microscopy (TEM), spatially-resolved inner-shell X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). An agglomeration of the highly mobile clusters into nm-sized Ag-nanodots of 2-3 nm is observed. Moreover, crystalline as well as non-periodic fivefold symmetric structures of the Ag-nanoparticles are evident by high-resolution TEM. Using a lognormal size-distribution as revealed by TEM, the measured positive binding energy shift of the air-exposed Ag-nanodots can be explained by the size-dependent dynamical liquid-drop model.

Linking biodiversity to ecosystem function: Implications for conservation ecology

USGS Publications Warehouse

Schwartz, M.W.; Brigham, C.A.; Hoeksema, J.D.; Lyons, K.G.; Mills, M.H.; van Mantgem, P.

2000-01-01

We evaluate the empirical and theoretical support for the hypothesis that a large proportion of native species richness is required to maximize ecosystem stability and sustain function. This assessment is important for conservation strategies because sustenance of ecosystem functions has been used as an argument for the conservation of species. If ecosystem functions are sustained at relatively low species richness, then arguing for the conservation of ecosystem function, no matter how important in its own right, does not strongly argue for the conservation of species. Additionally, for this to be a strong conservation argument the link between species diversity and ecosystem functions of value to the human community must be clear. We review the empirical literature to quantify the support for two hypotheses: (1) species richness is positively correlated with ecosystem function, and (2) ecosystem functions do not saturate at low species richness relative to the observed or experimental diversity. Few empirical studies demonstrate improved function at high levels of species richness. Second, we analyze recent theoretical models in order to estimate the level of species richness required to maintain ecosystem function. Again we find that, within a single trophic level, most mathematical models predict saturation of ecosystem function at a low proportion of local species richness. We also analyze a theoretical model linking species number to ecosystem stability. This model predicts that species richness beyond the first few species does not typically increase ecosystem stability. One reason that high species richness may not contribute significantly to function or stability is that most communities are characterized by strong dominance such that a few species provide the vast majority of the community biomass. Rapid turnover of species may rescue the concept that diversity leads to maximum function and stability. The role of turnover in ecosystem function and stability has not been investigated. Despite the recent rush to embrace the linkage between biodiversity and ecosystem function, we find little support for the hypothesis that there is a strong dependence of ecosystem function on the full complement of diversity within sites. Given this observation, the conservation community should take a cautious view of endorsing this linkage as a model to promote conservation goals.

Modeling the impact of watershed management policies on marine ecosystem services with application to Hood Canal, WA, USA

NASA Astrophysics Data System (ADS)

Sutherland, D. A.; Kim, C.; Marsik, M.; Spiridonov, G.; Toft, J.; Ruckelshaus, M.; Guerry, A.; Plummer, M.

2011-12-01

Humans obtain numerous benefits from marine ecosystems, including fish to eat; mitigation of storm damage; nutrient and water cycling and primary production; and cultural, aesthetic and recreational values. However, managing these benefits, or ecosystem services, in the marine world relies on an integrated approach that accounts for both marine and watershed activities. Here we present the results of a set of simple, physically-based, and spatially-explicit models that quantify the effects of terrestrial activities on marine ecosystem services. Specifically, we model the circulation and water quality of Hood Canal, WA, USA, a fjord system in Puget Sound where multiple human uses of the nearshore ecosystem (e.g., shellfish aquaculture, recreational Dungeness crab and shellfish harvest) can be compromised when water quality is poor (e.g., hypoxia, excessive non-point source pollution). Linked to the estuarine water quality model is a terrestrial hydrology model that simulates streamflow and nutrient loading, so land cover and climate changes in watersheds can be reflected in the marine environment. In addition, a shellfish aquaculture model is linked to the water quality model to test the sensitivity of the ecosystem service and its value to both terrestrial and marine activities. The modeling framework is general and will be publicly available, allowing easy comparisons of watershed impacts on marine ecosystem services across multiple scales and regions.

Diversity, Stability, and Reproducibility in Stochastically Assembled Microbial Ecosystems

NASA Astrophysics Data System (ADS)

Goyal, Akshit; Maslov, Sergei

2018-04-01

Microbial ecosystems are remarkably diverse, stable, and usually consist of a mixture of core and peripheral species. Here we propose a conceptual model exhibiting all these emergent properties in quantitative agreement with real ecosystem data, specifically species abundance and prevalence distributions. Resource competition and metabolic commensalism drive the stochastic ecosystem assembly in our model. We demonstrate that even when supplied with just one resource, ecosystems can exhibit high diversity, increasing stability, and partial reproducibility between samples.

Emergent Global Patterns of Ecosystem Structure and Function from a Mechanistic General Ecosystem Model

PubMed Central

Emmott, Stephen; Hutton, Jon; Lyutsarev, Vassily; Smith, Matthew J.; Scharlemann, Jörn P. W.; Purves, Drew W.

2014-01-01

Anthropogenic activities are causing widespread degradation of ecosystems worldwide, threatening the ecosystem services upon which all human life depends. Improved understanding of this degradation is urgently needed to improve avoidance and mitigation measures. One tool to assist these efforts is predictive models of ecosystem structure and function that are mechanistic: based on fundamental ecological principles. Here we present the first mechanistic General Ecosystem Model (GEM) of ecosystem structure and function that is both global and applies in all terrestrial and marine environments. Functional forms and parameter values were derived from the theoretical and empirical literature where possible. Simulations of the fate of all organisms with body masses between 10 µg and 150,000 kg (a range of 14 orders of magnitude) across the globe led to emergent properties at individual (e.g., growth rate), community (e.g., biomass turnover rates), ecosystem (e.g., trophic pyramids), and macroecological scales (e.g., global patterns of trophic structure) that are in general agreement with current data and theory. These properties emerged from our encoding of the biology of, and interactions among, individual organisms without any direct constraints on the properties themselves. Our results indicate that ecologists have gathered sufficient information to begin to build realistic, global, and mechanistic models of ecosystems, capable of predicting a diverse range of ecosystem properties and their response to human pressures. PMID:24756001

Emergent global patterns of ecosystem structure and function from a mechanistic general ecosystem model.

PubMed

Harfoot, Michael B J; Newbold, Tim; Tittensor, Derek P; Emmott, Stephen; Hutton, Jon; Lyutsarev, Vassily; Smith, Matthew J; Scharlemann, Jörn P W; Purves, Drew W

2014-04-01

Anthropogenic activities are causing widespread degradation of ecosystems worldwide, threatening the ecosystem services upon which all human life depends. Improved understanding of this degradation is urgently needed to improve avoidance and mitigation measures. One tool to assist these efforts is predictive models of ecosystem structure and function that are mechanistic: based on fundamental ecological principles. Here we present the first mechanistic General Ecosystem Model (GEM) of ecosystem structure and function that is both global and applies in all terrestrial and marine environments. Functional forms and parameter values were derived from the theoretical and empirical literature where possible. Simulations of the fate of all organisms with body masses between 10 µg and 150,000 kg (a range of 14 orders of magnitude) across the globe led to emergent properties at individual (e.g., growth rate), community (e.g., biomass turnover rates), ecosystem (e.g., trophic pyramids), and macroecological scales (e.g., global patterns of trophic structure) that are in general agreement with current data and theory. These properties emerged from our encoding of the biology of, and interactions among, individual organisms without any direct constraints on the properties themselves. Our results indicate that ecologists have gathered sufficient information to begin to build realistic, global, and mechanistic models of ecosystems, capable of predicting a diverse range of ecosystem properties and their response to human pressures.

Adventures in holistic ecosystem modelling: the cumberland basin ecosystem model

NASA Astrophysics Data System (ADS)

Gordon, D. C.; Keizer, P. D.; Daborn, G. R.; Schwinghamer, P.; Silvert, W. L.

A holistic ecosystem model has been developed for the Cumberland Basin, a turbid macrotidal estuary at the head of Canada's Bay of Fundy. The model was constructed as a group exercise involving several dozen scientists. Philosophy of approach and methods were patterned after the BOEDE Ems-Dollard modelling project. The model is one-dimensional, has 3 compartments and 3 boundaries, and is composed of 3 separate submodels (physical, pelagic and benthic). The 28 biological state variables cover the complete estuarine ecosystem and represent broad functional groups of organisms based on trophic relationships. Although still under development and not yet validated, the model has been verified and has reached the stage where most state variables provide reasonable output. The modelling process has stimulated interdisciplinary discussion, identified important data gaps and produced a quantitative tool which can be used to examine ecological hypotheses and determine critical environmental processes. As a result, Canadian scientists have a much better understanding of the Cumberland Basin ecosystem and are better able to provide competent advice on environmental management.

Geophysical Evidence to Link Terrestrial Insect Diversity and Groundwater Availability in Non-Riparian Ecosystems

NASA Astrophysics Data System (ADS)

Pehringer, M.; Carr, G.; Long, H.; Parsekian, A.

2015-12-01

Wyoming, the third driest state in the United States, is home to a high level of biodiversity. In many cases, ecosystems are dependent on the vast systems of water resting just below the surface. This groundwater supports a variety of organisms that live far from surface water and its surrounding riparian zone, where more than 70% of species reside. In order to observe the correlation of groundwater presence and biodiversity in non-riparian ecosystems, a study was conducted to look specifically at terrestrial insect species linked to groundwater in Bighorn National Forest, WY. It was hypothesized that the more groundwater present, the greater the diversity of insects would be. Sample areas were randomly selected in non-riparian zones and groundwater was evaluated using a transient electromagnetic (TEM) geophysical instrument. Electrical pulses were transmitted through a 40m by 40m square of wire to measure levels of resistivity from near the surface to several hundred meters below ground. Pulses are echoed back to the surface and received by a smaller 10m by 10m square of wire, and an even smaller 1m by 1m square of wire set inside the larger transmitting wire. An insect population and species count was then conducted within the perimeter set by the outer transmitting wire. The results were not as hypothesized. More inferred groundwater below the surface resulted in a smaller diversity of species. Inversely, the areas with a smaller diversity held a larger total population of terrestrial insects.

Appraisal of an Array TEM Method in Detecting a Mined-Out Area Beneath a Conductive Layer

NASA Astrophysics Data System (ADS)

Li, Hai; Xue, Guo-qiang; Zhou, Nan-nan; Chen, Wei-ying

2015-10-01

The transient electromagnetic method has been extensively used for the detection of mined-out area in China for the past few years. In the cases that the mined-out area is overlain by a conductive layer, the detection of the target layer is difficult with a traditional loop source TEM method. In order to detect the target layer in this condition, this paper presents a newly developed array TEM method, which uses a grounded wire source. The underground current density distribution and the responses of the grounded wire source TEM configuration are modeled to demonstrate that the target layer is detectable in this condition. The 1D OCCAM inversion routine is applied to the synthetic single station data and common middle point gather. The result reveals that the electric source TEM method is capable of recovering the resistive target layer beneath the conductive overburden. By contrast, the conductive target layer cannot be recovered unless the distance between the target layer and the conductive overburden is large. Compared with inversion result of the single station data, the inversion of common middle point gather can better recover the resistivity of the target layer. Finally, a case study illustrates that the array TEM method is successfully applied in recovering a water-filled mined-out area beneath a conductive overburden.

From Bacteria to Whales: Using Functional Size Spectra to Model Marine Ecosystems.

PubMed

Blanchard, Julia L; Heneghan, Ryan F; Everett, Jason D; Trebilco, Rowan; Richardson, Anthony J

2017-03-01

Size-based ecosystem modeling is emerging as a powerful way to assess ecosystem-level impacts of human- and environment-driven changes from individual-level processes. These models have evolved as mechanistic explanations for observed regular patterns of abundance across the marine size spectrum hypothesized to hold from bacteria to whales. Fifty years since the first size spectrum measurements, we ask how far have we come? Although recent modeling studies capture an impressive range of sizes, complexity, and real-world applications, ecosystem coverage is still only partial. We describe how this can be overcome by unifying functional traits with size spectra (which we call functional size spectra) and highlight the key knowledge gaps that need to be filled to model ecosystems from bacteria to whales. Copyright © 2017 Elsevier Ltd. All rights reserved.

Linking water quality and quantity in environmental flow assessment in deteriorated ecosystems: a food web view.

PubMed

Chen, He; Ma, Lekuan; Guo, Wei; Yang, Ying; Guo, Tong; Feng, Cheng

2013-01-01

Most rivers worldwide are highly regulated by anthropogenic activities through flow regulation and water pollution. Environmental flow regulation is used to reduce the effects of anthropogenic activities on aquatic ecosystems. Formulating flow alteration-ecological response relationships is a key factor in environmental flow assessment. Traditional environmental flow models are characterized by natural relationships between flow regimes and ecosystem factors. However, food webs are often altered from natural states, which disturb environmental flow assessment in such ecosystems. In ecosystems deteriorated by heavy anthropogenic activities, the effects of environmental flow regulation on species are difficult to assess with current modeling approaches. Environmental flow management compels the development of tools that link flow regimes and food webs in an ecosystem. Food web approaches are more suitable for the task because they are more adaptive for disordered multiple species in a food web deteriorated by anthropogenic activities. This paper presents a global method of environmental flow assessment in deteriorated aquatic ecosystems. Linkages between flow regimes and food web dynamics are modeled by incorporating multiple species into an ecosystem to explore ecosystem-based environmental flow management. The approach allows scientists and water resources managers to analyze environmental flows in deteriorated ecosystems in an ecosystem-based way.

[Structure and function of Fenshuijiang Reservoir ecosystem based on the analysis with Ecopath model].

PubMed

Wu, Zhen; Jia, Pei-Qiao; Hu, Zhong-Jun; Chen, Li-Qiao; Gu, Zhi-Min; Liu, Qi-Gen

2012-03-01

Based on the 2008-2009 survey data of fishery resources and eco-environment of Fenshuijiang Reservoir, a mass balance model for the Reservoir ecosystem was constructed by Ecopath with Ecosim software. The model was composed of 14 functional groups, including silver carp, bighead carp, Hemibarbus maculates, Cutler alburnus, Microlepis and other fishes, Oligochaeta, aquatic insect, zooplankton, phytoplankton, and organic detritus, etc. , being able to better simulate Fenshuijiang Reservoir ecosystem. In this ecosystem, there were five trophic levels (TLs), and the nutrient flow mainly occurred in the first three TLs. Grazing and detritus food chains were the main energy flows in the ecosystem, but the food web was simpler and susceptible to be disturbed by outer environment. The transfer efficiency at lower TLs was relatively low, indicating that the ecosystem had a lower capability in energy utilization, and the excessive stock of nutrients in the ecosystem could lead to eutrophication. The lower connectance index, system omnivory index, Finn' s cycled index, and Finn's mean path length demonstrated that the ecosystem was unstable, while the high ecosystem property indices such as Pp/R and Pp/B showed that the ecosystem was immature and highly productive. It was suggested that Fenshuijiang Reservoir was still a developing new reservoir ecosystem, with a very short history and comparatively high primary productivity.

An ecosystem model of an exploited southern Mediterranean shelf region (Gulf of Gabes, Tunisia) and a comparison with other Mediterranean ecosystem model properties

NASA Astrophysics Data System (ADS)

Hattab, Tarek; Ben Rais Lasram, Frida; Albouy, Camille; Romdhane, Mohamed Salah; Jarboui, Othman; Halouani, Ghassen; Cury, Philippe; Le Loc'h, François

2013-12-01

In this paper, we describe an exploited continental shelf ecosystem (Gulf of Gabes) in the southern Mediterranean Sea using an Ecopath mass-balance model. This allowed us to determine the structure and functioning of this ecosystem and assess the impacts of fishing upon it. The model represents the average state of the ecosystem between 2000 and 2005. It includes 41 functional groups, which encompass the entire trophic spectrum from phytoplankton to higher trophic levels (e.g., fishes, birds, and mammals), and also considers the fishing activities in the area (five fleets). Model results highlight an important bentho-pelagic coupling in the system due to the links between plankton and benthic invertebrates through detritus. A comparison of this model with those developed for other continental shelf regions in the Mediterranean (i.e., the southern Catalan, the northern-central Adriatic, and the northern Aegean Seas) emphasizes similar patterns in their trophic functioning. Low and medium trophic levels (i.e., zooplankton, benthic molluscs, and polychaetes) and sharks were identified as playing key ecosystem roles and were classified as keystone groups. An analysis of ecosystem attributes indicated that the Gulf of Gabes is the least mature (i.e., in the earliest stages of ecosystem development) of the four ecosystems that were compared and it is suggested that this is due, at least in part, to the impacts of fishing. Bottom trawling was identified as having the widest-ranging impacts across the different functional groups and the largest impacts on some commercially-targeted demersal fish species. Several exploitation indices highlighted that the Gulf of Gabes ecosystem is highly exploited, a finding which is supported by stock assessment outcomes. This suggests that it is unlikely that the gulf can be fished at sustainable levels, a situation which is similar to other marine ecosystems in the Mediterranean Sea.

Testing a land model in ecosystem functional space via a comparison of observed and modeled ecosystem flux responses to precipitation regimes and associated stresses in a Central U.S. forest: Test Model in Ecosystem Functional Space

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

Gu, Lianhong; Pallardy, Stephen G.; Yang, Bai

Testing complex land surface models has often proceeded by asking the question: does the model prediction agree with the observation? This approach has yet led to high-performance terrestrial models that meet the challenges of climate and ecological studies. Here we test the Community Land Model (CLM) by asking the question: does the model behave like an ecosystem? We pursue its answer by testing CLM in the ecosystem functional space (EFS) at the Missouri Ozark AmeriFlux (MOFLUX) forest site in the Central U.S., focusing on carbon and water flux responses to precipitation regimes and associated stresses. In the observed EFS, precipitationmore » regimes and associated water and heat stresses controlled seasonal and interannual variations of net ecosystem exchange (NEE) of CO 2 and evapotranspiration in this deciduous forest ecosystem. Such controls were exerted more strongly by precipitation variability than by the total precipitation amount per se. A few simply constructed climate variability indices captured these controls, suggesting a high degree of potential predictability. While the interannual fluctuation in NEE was large, a net carbon sink was maintained even during an extreme drought year. Although CLM predicted seasonal and interanual variations in evapotranspiration reasonably well, its predictions of net carbon uptake were too small across the observed range of climate variability. Also, the model systematically underestimated the sensitivities of NEE and evapotranspiration to climate variability and overestimated the coupling strength between carbon and water fluxes. Its suspected that the modeled and observed trajectories of ecosystem fluxes did not overlap in the EFS and the model did not behave like the ecosystem it attempted to simulate. A definitive conclusion will require comprehensive parameter and structural sensitivity tests in a rigorous mathematical framework. We also suggest that future model improvements should focus on better representation and parameterization of process responses to environmental stresses and on more complete and robust representations of carbon-specific processes so that adequate responses to climate variability and a proper degree of coupling between carbon and water exchanges are captured.« less

Testing a land model in ecosystem functional space via a comparison of observed and modeled ecosystem flux responses to precipitation regimes and associated stresses in a Central U.S. forest: Test Model in Ecosystem Functional Space

DOE PAGES

Gu, Lianhong; Pallardy, Stephen G.; Yang, Bai; ...

2016-07-14

Testing complex land surface models has often proceeded by asking the question: does the model prediction agree with the observation? This approach has yet led to high-performance terrestrial models that meet the challenges of climate and ecological studies. Here we test the Community Land Model (CLM) by asking the question: does the model behave like an ecosystem? We pursue its answer by testing CLM in the ecosystem functional space (EFS) at the Missouri Ozark AmeriFlux (MOFLUX) forest site in the Central U.S., focusing on carbon and water flux responses to precipitation regimes and associated stresses. In the observed EFS, precipitationmore » regimes and associated water and heat stresses controlled seasonal and interannual variations of net ecosystem exchange (NEE) of CO 2 and evapotranspiration in this deciduous forest ecosystem. Such controls were exerted more strongly by precipitation variability than by the total precipitation amount per se. A few simply constructed climate variability indices captured these controls, suggesting a high degree of potential predictability. While the interannual fluctuation in NEE was large, a net carbon sink was maintained even during an extreme drought year. Although CLM predicted seasonal and interanual variations in evapotranspiration reasonably well, its predictions of net carbon uptake were too small across the observed range of climate variability. Also, the model systematically underestimated the sensitivities of NEE and evapotranspiration to climate variability and overestimated the coupling strength between carbon and water fluxes. Its suspected that the modeled and observed trajectories of ecosystem fluxes did not overlap in the EFS and the model did not behave like the ecosystem it attempted to simulate. A definitive conclusion will require comprehensive parameter and structural sensitivity tests in a rigorous mathematical framework. We also suggest that future model improvements should focus on better representation and parameterization of process responses to environmental stresses and on more complete and robust representations of carbon-specific processes so that adequate responses to climate variability and a proper degree of coupling between carbon and water exchanges are captured.« less

Land-use planning for nearshore ecosystem services—the Puget Sound Ecosystem Portfolio Model

USGS Publications Warehouse

Byrd, Kristin

2011-01-01

The 2,500 miles of shoreline and nearshore areas of Puget Sound, Washington, provide multiple benefits to people—"ecosystem services"—including important fishing, shellfishing, and recreation industries. To help resource managers plan for expected growth in coming decades, the U.S. Geological Survey Western Geographic Science Center has developed the Puget Sound Ecosystem Portfolio Model (PSEPM). Scenarios of urban growth and shoreline modifications serve as model inputs to develop alternative futures of important nearshore features such as water quality and beach habitats. Model results will support regional long-term planning decisions for the Puget Sound region.

Testing the sensitivity of terrestrial carbon models using remotely sensed biomass estimates

NASA Astrophysics Data System (ADS)

Hashimoto, H.; Saatchi, S. S.; Meyer, V.; Milesi, C.; Wang, W.; Ganguly, S.; Zhang, G.; Nemani, R. R.

2010-12-01

There is a large uncertainty in carbon allocation and biomass accumulation in forest ecosystems. With the recent availability of remotely sensed biomass estimates, we now can test some of the hypotheses commonly implemented in various ecosystem models. We used biomass estimates derived by integrating MODIS, GLAS and PALSAR data to verify above-ground biomass estimates simulated by a number of ecosystem models (CASA, BIOME-BGC, BEAMS, LPJ). This study extends the hierarchical framework (Wang et al., 2010) for diagnosing ecosystem models by incorporating independent estimates of biomass for testing and calibrating respiration, carbon allocation, turn-over algorithms or parameters.

Development and Application of Operando TEM to a Ruthenium Catalyst for CO Oxidation

NASA Astrophysics Data System (ADS)

Miller, Benjamin Kyle

Operando transmission electron microscopy (TEM) is an extension of in-situ TEM in which the performance of the material being observed is measured simultaneously. This is of great value, since structure-performance relationships lie at the heart of materials science. For catalyst materials, like the SiO2-supported Ru nanoparticles studied, the important performance metric, catalyst activity, is measured inside the microscope by determining the gas composition during imaging. This is accomplished by acquisition of electron energy loss spectra (EELS) of the gas in the environmental TEM while catalysis is taking place. In this work, automated methods for rapidly quantifying low-loss and core-loss EELS of gases were developed. A new sample preparation method was also established to increase catalytic conversion inside a differentially-pumped environmental TEM, and the maximum CO conversion observed was about 80%. A system for mixing gases and delivering them to the environmental TEM was designed and built, and a method for locating and imaging nanoparticles in zone axis orientations while minimizing electron dose rate was determined. After atomic resolution images of Ru nanoparticles observed during CO oxidation were obtained, the shape and surface structures of these particles was investigated. A Wulff model structure for Ru particles was compared to experimental images both by manually rotating the model, and by automatically determining a matching orientation using cross-correlation of shape signatures. From this analysis, it was determined that most Ru particles are close to Wulff-shaped during CO oxidation. While thick oxide layers were not observed to form on Ru during CO oxidation, thin RuO2 layers on the surface of Ru nanoparticles were imaged with atomic resolution for the first time. The activity of these layers is discussed in the context of the literature on the subject, which has thus far been inconclusive. We conclude that disordered oxidized ruthenium, rather than crystalline RuO2 is the most active species.

TEM PSHA2015 Reliability Assessment

NASA Astrophysics Data System (ADS)

Lee, Y.; Wang, Y. J.; Chan, C. H.; Ma, K. F.

2016-12-01

The Taiwan Earthquake Model (TEM) developed a new probabilistic seismic hazard analysis (PSHA) for determining the probability of exceedance (PoE) of ground motion over a specified period in Taiwan. To investigate the adequacy of the seismic source parameters adopted in the 2015 PSHA of the TEM (TEM PSHA2015), we conducted several tests of the seismic source models. The observed maximal peak ground acceleration (PGA) of the ML > 4.0 mainshocks in the 23-year data period of 1993-2015 were used to test the predicted PGA of PSHA from the areal and subduction zone sources with the time-independent Poisson assumption. This comparison excluded the observations from 1999 Chi-Chi earthquake, as this was the only earthquake associated with the identified active fault in this past 23 years. We used tornado diagrams to analyze the sensitivities of these source parameters to the ground motion values of the PSHA. This study showed that the predicted PGA for a 63% PoE in the 23-year period corresponded to the empirical PGA and the predicted numbers of PGA exceedances to a threshold value 0.1g close to the observed numbers, confirming the parameter applicability for the areal and subduction zone sources. We adopted the disaggregation analysis from a hazard map to determine the contribution of the individual seismic sources to hazard for six metropolitan cities in Taiwan. The sensitivity tests of the seismogenic structure parameters indicated that the slip rate and maximum magnitude are dominant factors for the TEM PSHA2015. For densely populated faults in SW Taiwan, maximum magnitude is more sensitive than the slip rate, giving the concern on the possible multiple fault segments rupture with larger magnitude in this area, which was not yet considered in TEM PSHA2015. The source category disaggregation also suggested that special attention is necessary for subduction zone earthquakes for long-period shaking seismic hazards in Northern Taiwan.

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.

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.

The Integrated Landscape Modeling partnership - Current status and future directions

USGS Publications Warehouse

Mushet, David M.; Scherff, Eric J.

2016-01-28

The Integrated Landscape Modeling (ILM) partnership is an effort by the U.S. Geological Survey (USGS) and U.S. Department of Agriculture (USDA) to identify, evaluate, and develop models to quantify services derived from ecosystems, with a focus on wetland ecosystems and conservation effects. The ILM partnership uses the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) modeling platform to facilitate regional quantifications of ecosystem services under various scenarios of land-cover change that are representative of differing conservation program and practice implementation scenarios. To date, the ILM InVEST partnership has resulted in capabilities to quantify carbon stores, amphibian habitat, plant-community diversity, and pollination services. Work to include waterfowl and grassland bird habitat quality is in progress. Initial InVEST modeling has been focused on the Prairie Pothole Region (PPR) of the United States; future efforts might encompass other regions as data availability and knowledge increase as to how functions affecting ecosystem services differ among regions.The ILM partnership is also developing the capability for field-scale process-based modeling of depressional wetland ecosystems using the Agricultural Policy/Environmental Extender (APEX) model. Progress was made towards the development of techniques to use the APEX model for closed-basin depressional wetlands of the PPR, in addition to the open systems that the model was originally designed to simulate. The ILM partnership has matured to the stage where effects of conservation programs and practices on multiple ecosystem services can now be simulated in selected areas. Future work might include the continued development of modeling capabilities, as well as development and evaluation of differing conservation program and practice scenarios of interest to partner agencies including the USDA’s Farm Service Agency (FSA) and Natural Resources Conservation Service (NRCS). When combined, the ecosystem services modeling capabilities of InVEST and the process-based abilities of the APEX model should provide complementary information needed to meet USDA and the Department of the Interior information needs.

Watershed sustainability, modeling, and model uncertainty

USDA-ARS?s Scientific Manuscript database

The Millennium Ecosystem Assessment (MEA) was the first major integrated global assessment examining degradation of ecosystems and the impacts on humans (Millennium Ecosystem Assessment, 2005). It concluded that unprecedented ecological change has occurred in the last 50 years. Although many of thes...

Integrated geophysical application to investigate groundwater potentiality of the shallow Nubian aquifer at northern Kharga, West

NASA Astrophysics Data System (ADS)

Younis, Abdellatif; Soliman, Mamdouh; Moussa, Salah; Massoud, Usama; ElNabi, Sami Abd; Attia, Magdy

2016-06-01

Continuous evaluation of groundwater aquifers in the basin of Kharga Oasis is very important. Groundwater in Kharga Oasis represents the major factor for the development plans of this area as it is the sole source for water supplies required for drinking and irrigation purposes. This study is concerned by analyzing the groundwater potentiality of the shallow aquifer at the northern part of Kharga basin by integrated application of Vertical Electrical Sounding (VES) and Time domain Electromagnetic (TEM) techniques. The VES data were measured at 28 points arranged along a north-south trending line by applying Schlumberger array with a maximum current-electrode spacing (AB) of 1000 m. The TEM data were measured at 167 points arranged along 11 east-west trending lines by using a single square loop with 50 m loop-side length. The VES and TEM data have been individually inverted, where the VES models were used as initial models for TEM data inversion. The final models were used for construction of 17 geoelectrical sections and 5 contour maps describing subsurface water-bearing layers at the investigated area. Correlation of the obtained models with geologic, hydrogeologic and borehole information indicates that the shallow aquifer comprises two zones (A-up) and (B-down) separated by a highly conductive shale layer. The upper zone (A) is composed of fine to medium sand with thin clay intercalations. It exhibits low to moderate resistivities. This zone was detected at depth values ranging from 10 to 70 m below ground surface (bgs) and shows a thickness of 25-90 m. The lower zone (B) exhibits moderate to high resistivity values with expected good water quality. The upper surface of zone B was detected at 60-165 m depth.

3D Airborne Electromagnetic Inversion: A case study from the Musgrave Region, South Australia

NASA Astrophysics Data System (ADS)

Cox, L. H.; Wilson, G. A.; Zhdanov, M. S.; Sunwall, D. A.

2012-12-01

Geophysicists know and accept that geology is inherently 3D, and is resultant from complex, overlapping processes related to genesis, metamorphism, deformation, alteration, weathering, and/or hydrogeology. Yet, the geophysics community has long relied on qualitative analysis, conductivity depth imaging (CDIs), 1D inversion, and/or plate modeling. There are many reasons for this deficiency, not the least of which has been the lack of capacity for historic 3D AEM inversion algorithms to invert entire surveys so as to practically affect exploration decisions. Our recent introduction of a moving sensitivity domain (footprint) methodology has been a paradigm shift in AEM interpretation. The basis of this method is that one needs only to calculate the responses and sensitivities for that part of the 3D earth model that is within the AEM system's sensitivity domain (footprint), and then superimpose all sensitivity domains into a single, sparse sensitivity matrix for the entire 3D earth model which is then updated in a regularized inversion scheme. This has made it practical to rigorously invert entire surveys with thousands of line kilometers of AEM data to mega-cell 3D models in hours using multi-processor workstations. Since 2010, over eighty individual projects have been completed for Aerodat, AEROTEM, DIGHEM, GEOTEM, HELITEM, HoisTEM, MEGATEM, RepTEM, RESOLVE, SkyTEM, SPECTREM, TEMPEST, and VTEM data from Australia, Brazil, Canada, Finland, Ghana, Peru, Tanzania, the US, and Zambia. Examples of 3D AEM inversion have been published for a variety of applications, including mineral exploration, oil sands exploration, salinity, permafrost, and bathymetry mapping. In this paper, we present a comparison of 3D inversions for SkyTEM, SPECTREM, TEMPET and VTEM data acquired over the same area in the Musgrave region of South Australia for exploration under cover.

Bayesian resolution of TEM, CSEM and MT soundings: a comparative study

NASA Astrophysics Data System (ADS)

Blatter, D. B.; Ray, A.; Key, K.

2017-12-01

We examine the resolution of three electromagnetic exploration methods commonly used to map the electrical conductivity of the shallow crust - the magnetotelluric (MT) method, the controlled-source electromagnetic (CSEM) method and the transient electromagnetic (TEM) method. TEM and CSEM utilize an artificial source of EM energy, while MT makes use of natural variations in the Earth's electromagnetic field. For a given geological setting and acquisition parameters, each of these methods will have a different resolution due to differences in the source field polarization and the frequency range of the measurements. For example, the MT and TEM methods primarily rely on induced horizontal currents and are most sensitive to conductive layers while the CSEM method generates vertical loops of current and is more sensitive to resistive features. Our study seeks to provide a robust resolution comparison that can help inform exploration geophysicists about which technique is best suited for a particular target. While it is possible to understand and describe a difference in resolution qualitatively, it remains challenging to fully describe it quantitatively using optimization based approaches. Part of the difficulty here stems from the standard electromagnetic inversion toolkit, which makes heavy use of regularization (often in the form of smoothing) to constrain the non-uniqueness inherent in the inverse problem. This regularization makes it difficult to accurately estimate the uncertainty in estimated model parameters - and therefore obscures their true resolution. To overcome this difficulty, we compare the resolution of CSEM, airborne TEM, and MT data quantitatively using a Bayesian trans-dimensional Markov chain Monte Carlo (McMC) inversion scheme. Noisy synthetic data for this study are computed from various representative 1D test models: a conductive anomaly under a conductive/resistive overburden; and a resistive anomaly under a conductive/resistive overburden. In addition to obtaining the full posterior probability density function of the model parameters, we develop a metric to more directly compare the resolution of each method as a function of depth.

Modeling coupled interactions of carbon, water, and ozone exchange between terrestrial ecosystems and the atmosphere

Treesearch

Ned Nikolova; Karl F. Zeller

2003-01-01

A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology....

One carbon cycle: Impacts of model integration, ecosystem process detail, model resolution, and initialization data, on projections of future climate mitigation strategies

NASA Astrophysics Data System (ADS)

Fisk, J.; Hurtt, G. C.; le page, Y.; Patel, P. L.; Chini, L. P.; Sahajpal, R.; Dubayah, R.; Thomson, A. M.; Edmonds, J.; Janetos, A. C.

2013-12-01

Integrated assessment models (IAMs) simulate the interactions between human and natural systems at a global scale, representing a broad suite of phenomena across the global economy, energy system, land-use, and carbon cycling. Most proposed climate mitigation strategies rely on maintaining or enhancing the terrestrial carbon sink as a substantial contribution to restrain the concentration of greenhouse gases in the atmosphere, however most IAMs rely on simplified regional representations of terrestrial carbon dynamics. Our research aims to reduce uncertainties associated with forest modeling within integrated assessments, and to quantify the impacts of climate change on forest growth and productivity for integrated assessments of terrestrial carbon management. We developed the new Integrated Ecosystem Demography (iED) to increase terrestrial ecosystem process detail, resolution, and the utilization of remote sensing in integrated assessments. iED brings together state-of-the-art models of human society (GCAM), spatial land-use patterns (GLM) and terrestrial ecosystems (ED) in a fully coupled framework. The major innovative feature of iED is a consistent, process-based representation of ecosystem dynamics and carbon cycle throughout the human, terrestrial, land-use, and atmospheric components. One of the most challenging aspects of ecosystem modeling is to provide accurate initialization of land surface conditions to reflect non-equilibrium conditions, i.e., the actual successional state of the forest. As all plants in ED have an explicit height, it is one of the few ecosystem models that can be initialized directly with vegetation height data. Previous work has demonstrated that ecosystem model resolution and initialization data quality have a large effect on flux predictions at continental scales. Here we use a factorial modeling experiment to quantify the impacts of model integration, process detail, model resolution, and initialization data on projections of future climate mitigation strategies. We find substantial effects on key integrated assessment projections including the magnitude of emissions to mitigate, the economic value of ecosystem carbon storage, future land-use patterns, food prices and energy technology.

An original model of the northern Gulf of Mexico using Ecopath with Ecosim and its implications for the effects of fishing on ecosystem structure and maturity

NASA Astrophysics Data System (ADS)

Geers, T. M.; Pikitch, E. K.; Frisk, M. G.

2016-07-01

The Gulf of Mexico (GoM) is a valuable ecosystem both socially and economically, and fisheries contribute substantially to this value. Gulf menhaden, Brevoortia patronus, support the largest fishery in the Gulf (by weight) and provide forage for marine mammals, seabirds and commercially and recreationally important fish species. Understanding the complex interactions among multiple fisheries and myriad unfished species requires tools different from those used in traditional single-species management. One such tool, Ecopath with Ecosim (EwE) is increasingly being used to construct food web models of aquatic ecosystems and to evaluate fisheries management options within a broader, ecosystem context. Here, an EwE model was developed to examine the impact of Gulf fisheries on ecosystem structure and maturity. This model builds on previously published EwE models of the GoM, and is tailored to the range and habitat of Gulf menhaden. The model presented here consists of 47 functional groups, including 4 seabird groups, 1 marine mammal group, 3 elasmobranch groups, 26 bony fish groups, 9 invertebrate groups, 3 primary producer groups and 1 detritus group. A number of different management scenarios for Gulf fisheries were modeled and the results were evaluated in terms of impacts on ecosystem maturity and development. The results of the model simulations indicated that the northern Gulf of Mexico is in an immature state (sensuOdum, 1969). Management scenarios that increased fishing pressure over time consistently resulted in a decrease in the maturity indices. In particular, we found that Gulf menhaden, as a key forage fish in the ecosystem, plays a substantial role in the structure and functioning of the ecosystem.

Modelling hydrological processes and analysing water-related ecosystem services of Western Siberian lowland basins

NASA Astrophysics Data System (ADS)

Schmalz, Britta; Kiesel, Jens; Kruse, Marion; Pfannerstill, Matthias; Sheludkov, Artyom; Khoroshavin, Vitaliy; Veshkurseva, Tatyana; Müller, Felix; Fohrer, Nicola

2015-04-01

For discussing and planning sustainable land management of river basins, stakeholders need suitable information on spatio-temporal patterns of hydrological components and ecosystem services. The ecosystem services concept, i.e., services provided by ecosystems that contribute to human welfare benefits, contributes comprehensive information for sustainable river management. This study shows an approach to use ecohydrological modelling results for quantifying and assessing water-related ecosystem services in three lowland river basins in Western Siberia, a region which is of global significance in terms of carbon sequestration, agricultural production and biodiversity preservation. Using the ecohydrological model SWAT, the three basins Pyschma (16762 km²), Vagai (3348 km²) and Loktinka (373 km²) were modelled following a gradient from the landscape units taiga, pre-taiga to forest steppe. For a correct representation of the Siberian lowland hydrology, the consideration of snow melt and retention of surface runoff as well as the implementation of a second groundwater aquifer was of great importance. Good to satisfying model performances were obtained for the extreme hydrological conditions. The simulated SWAT output variables of different hydrological processes were used as indicators for the two regulating services water flow and erosion regulation. The model results were translated into a relative ecosystem service valuation scale. The resulting ecosystem service maps show different spatial and seasonal patterns. Although the high resolution modelling results are averaged out within the aggregated relative valuation scale, seasonal differences can be depicted: during snowmelt, low relevant regulation can be determined, especially for water flow regulation, but a very high relevant regulation was calculated for the vegetation period during summer and for the winter period. The SWAT model serves as a suitable quantification method for the assessment of water-related ecosystem services on different spatial scales and ecoregions of the Western Siberian lowlands.

Electron microscopy of the amphibian model systems Xenopus laevis and Ambystoma mexicanum.

PubMed

Kurth, Thomas; Berger, Jürgen; Wilsch-Bräuninger, Michaela; Kretschmar, Susanne; Cerny, Robert; Schwarz, Heinz; Löfberg, Jan; Piendl, Thomas; Epperlein, Hans H

2010-01-01

In this chapter we provide a set of different protocols for the ultrastructural analysis of amphibian (Xenopus, axolotl) tissues, mostly of embryonic origin. For Xenopus these methods include: (1) embedding gastrulae and tailbud embryos into Spurr's resin for TEM, (2) post-embedding labeling of methacrylate (K4M) and cryosections through adult and embryonic epithelia for correlative LM and TEM, and (3) pre-embedding labeling of embryonic tissues with silver-enhanced nanogold. For the axolotl (Ambystoma mexicanum) we present the following methods: (1) SEM of migrating neural crest (NC) cells; (2) SEM and TEM of extracellular matrix (ECM) material; (3) Cryo-SEM of extracellular matrix (ECM) material after cryoimmobilization; and (4) TEM analysis of hyaluronan using high-pressure freezing and HABP labeling. These methods provide exemplary approaches for a variety of questions in the field of amphibian development and regeneration, and focus on cell biological issues that can only be answered with fine structural imaging methods, such as electron microscopy. Copyright © 2010 Elsevier Inc. All rights reserved.

Targeted nanodiamonds for identification of subcellular protein assemblies in mammalian cells

PubMed Central

Lake, Michael P.; Bouchard, Louis-S.

2017-01-01

Transmission electron microscopy (TEM) can be used to successfully determine the structures of proteins. However, such studies are typically done ex situ after extraction of the protein from the cellular environment. Here we describe an application for nanodiamonds as targeted intensity contrast labels in biological TEM, using the nuclear pore complex (NPC) as a model macroassembly. We demonstrate that delivery of antibody-conjugated nanodiamonds to live mammalian cells using maltotriose-conjugated polypropylenimine dendrimers results in efficient localization of nanodiamonds to the intended cellular target. We further identify signatures of nanodiamonds under TEM that allow for unambiguous identification of individual nanodiamonds from a resin-embedded, OsO4-stained environment. This is the first demonstration of nanodiamonds as labels for nanoscale TEM-based identification of subcellular protein assemblies. These results, combined with the unique fluorescence properties and biocompatibility of nanodiamonds, represent an important step toward the use of nanodiamonds as markers for correlated optical/electron bioimaging. PMID:28636640

TEM in situ micropillar compression tests of ion irradiated oxide dispersion strengthened alloy

NASA Astrophysics Data System (ADS)

Yano, K. H.; Swenson, M. J.; Wu, Y.; Wharry, J. P.

2017-01-01

The growing role of charged particle irradiation in the evaluation of nuclear reactor candidate materials requires the development of novel methods to assess mechanical properties in near-surface irradiation damage layers just a few micrometers thick. In situ transmission electron microscopic (TEM) mechanical testing is one such promising method. In this work, microcompression pillars are fabricated from a Fe2+ ion irradiated bulk specimen of a model Fe-9%Cr oxide dispersion strengthened (ODS) alloy. Yield strengths measured directly from TEM in situ compression tests are within expected values, and are consistent with predictions based on the irradiated microstructure. Measured elastic modulus values, once adjusted for the amount of deformation and deflection in the base material, are also within the expected range. A pillar size effect is only observed in samples with minimum dimension ≤100 nm due to the low inter-obstacle spacing in the as received and irradiated material. TEM in situ micropillar compression tests hold great promise for quantitatively determining mechanical properties of shallow ion-irradiated layers.

A facile and cost-effective TEM grid approach to design gold nano-structured substrates for high throughput plasmonic sensitive detection of biomolecules.

PubMed

Jia, Kun; Bijeon, Jean Louis; Adam, Pierre Michel; Ionescu, Rodica Elena

2013-02-21

A commercial TEM grid was used as a mask for the creation of extremely well-organized gold micro-/nano-structures on a glass substrate via a high temperature annealing process at 500 °C. The structured substrate was (bio)functionalized and used for the high throughput LSPR immunosensing of different concentrations of a model protein named bovine serum albumin.

Cladding for transverse-pumped solid-state laser

NASA Technical Reports Server (NTRS)

Byer, Robert L. (Inventor); Fan, Tso Y. (Inventor)

1989-01-01

In a transverse pumped, solid state laser, a nonabsorptive cladding surrounds a gain medium. A single tranverse mode, namely the Transverse Electromagnetic (TEM) sub 00 mode, is provided. The TEM sub 00 model has a cross sectional diameter greater than a transverse dimension of the gain medium but less than a transverse dimension of the cladding. The required size of the gain medium is minimized while a threshold for laser output is lowered.

Alternative ways of using field-based estimates to calibrate ecosystem models and their implications for ecosystem carbon cycle studies

Treesearch

Y. He; Q. Zhuang; A.D. McGuire; Y. Liu; M. Chen

2013-01-01

Model-data fusion is a process in which field observations are used to constrain model parameters. How observations are used to constrain parameters has a direct impact on the carbon cycle dynamics simulated by ecosystem models. In this study, we present an evaluation of several options for the use of observations inmodeling regional carbon dynamics and explore the...

How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola

DOE PAGES

Maloubier, Melody; Shuh, David K.; Minasian, Stefan G.; ...

2016-09-15

In the ocean, complex interactions between natural and anthropogenic radionuclides, seawater, and diverse marine biota provide a unique window through which to examine ecosystem and trophic transfer mechanisms in cases of accidental dissemination. The nature of interaction between radionuclides, the marine environment, and marine species is therefore essential for better understanding transfer mechanisms from the hydrosphere to the biosphere. Although data pertaining to the rate of global transfer are often available, little is known regarding the mechanism of environmental transport and uptake of heavy radionuclides by marine species. Among marine species, sponges are immobile active filter feeders and have beenmore » identified as hyperaccumulators of several heavy metals. We have selected the Mediterranean sponge Aplysina cavernicola as a model species for this study. Actinide elements are not the only source of radioactive release in cases of civilian nuclear events; however, their physicochemical transfer mechanisms to marine species remain largely unknown. We have targeted europium(III) as a representative of the trivalent actinides such as americium or curium. To unravel biological uptake mechanisms of europium in A. cavernicola, we have combined radiometric (γ) measurements with spectroscopic (time-resolved laser-induced fluorescence spectroscopy, TRLIFS, and X-ray absorption near-edge structure, XANES) and imaging (transmission electron microscopy, TEM, and scanning transmission X-ray microscopy, STXM) techniques. Here, we have observed that the colloids of NaEu(CO 3) 2 ·nH 2O formed in seawater are taken up by A. cavernicola with no evidence that lethal dose has been reached in our working conditions. Spectroscopic results suggest that there is no change of speciation during uptake. Finally, TEM and STXM images recorded at different locations across a sponge cross section, together with differential cell separation, indicate the presence of europium particles (around 200 nm) mainly located in the skeleton and toward the outer surface of the sponge.« less

How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola

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

Maloubier, Melody; Shuh, David K.; Minasian, Stefan G.

In the ocean, complex interactions between natural and anthropogenic radionuclides, seawater, and diverse marine biota provide a unique window through which to examine ecosystem and trophic transfer mechanisms in cases of accidental dissemination. The nature of interaction between radionuclides, the marine environment, and marine species is therefore essential for better understanding transfer mechanisms from the hydrosphere to the biosphere. Although data pertaining to the rate of global transfer are often available, little is known regarding the mechanism of environmental transport and uptake of heavy radionuclides by marine species. Among marine species, sponges are immobile active filter feeders and have beenmore » identified as hyperaccumulators of several heavy metals. We have selected the Mediterranean sponge Aplysina cavernicola as a model species for this study. Actinide elements are not the only source of radioactive release in cases of civilian nuclear events; however, their physicochemical transfer mechanisms to marine species remain largely unknown. We have targeted europium(III) as a representative of the trivalent actinides such as americium or curium. To unravel biological uptake mechanisms of europium in A. cavernicola, we have combined radiometric (γ) measurements with spectroscopic (time-resolved laser-induced fluorescence spectroscopy, TRLIFS, and X-ray absorption near-edge structure, XANES) and imaging (transmission electron microscopy, TEM, and scanning transmission X-ray microscopy, STXM) techniques. Here, we have observed that the colloids of NaEu(CO 3) 2 ·nH 2O formed in seawater are taken up by A. cavernicola with no evidence that lethal dose has been reached in our working conditions. Spectroscopic results suggest that there is no change of speciation during uptake. Finally, TEM and STXM images recorded at different locations across a sponge cross section, together with differential cell separation, indicate the presence of europium particles (around 200 nm) mainly located in the skeleton and toward the outer surface of the sponge.« less

Adressing optimality principles in DGVMs: Dynamics of Carbon allocation changes

NASA Astrophysics Data System (ADS)

Pietsch, Stephan

2017-04-01

DGVMs are designed to reproduce and quantify ecosystem processes. Based on plant functions or species specific parameter sets, the energy, carbon, nitrogen and water cycles of different ecosystems are assessed. These models have been proven to be important tools to investigate ecosystem fluxes as they are derived by plant, site and environmental factors. The general model approach assumes steady state conditions and constant model parameters. Both assumptions, however, are wrong, since: (i) No given ecosystem ever is at steady state! (ii) Ecosystems have the capability to adapt to changes in growth conditions, e.g. via changes in allocation patterns! This presentation will give examples how these general failures within current DGVMs may be addressed.

Adressing optimality principles in DGVMs: Dynamics of Carbon allocation changes.

NASA Astrophysics Data System (ADS)

Pietsch, S.

2016-12-01

DGVMs are designed to reproduce and quantify ecosystem processes. Based on plant functions or species specific parameter sets, the energy, carbon, nitrogen and water cycles of different ecosystems are assessed. These models have been proven to be important tools to investigate ecosystem fluxes as they are derived by plant, site and environmental factors. The general model approach assumes steady state conditions and constant model parameters. Both assumptions, however, are wrong. Any given ecosystem never is at steady state! Ecosystems have the capability to adapt to changes in growth conditions, e.g. via changes in allocation patterns! This presentation will give examples how these general failures within current DGVMs may be addressed.

Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems?

NASA Astrophysics Data System (ADS)

Moullec, Fabien; Gascuel, Didier; Bentorcha, Karim; Guénette, Sylvie; Robert, Marianne

2017-08-01

Trophic models are key tools to go beyond the single-species approaches used in stock assessments to adopt a more holistic view and implement the Ecosystem Approach to Fisheries Management (EAFM). This study aims to: (i) analyse the trophic functioning of the Celtic Sea and the Bay of Biscay, (ii) investigate ecosystem changes over the 1980-2013 period and, (iii) explore the response to management measures at the food web scale. Ecopath models were built for each ecosystem for years 1980 and 2013, and Ecosim models were fitted to time series data of biomass and catches. EcoTroph diagnosis showed that in both ecosystems, fishing pressure focuses on high trophic levels (TLs) and, to a lesser extent, on intermediate TLs. However, the interplay between local environmental conditions, species composition and ecosystem functioning could explain the different responses to fisheries management observed between these two contiguous ecosystems. Indeed, over the study period, the ecosystem's exploitation status has improved in the Bay of Biscay but not in the Celtic Sea. This improvement does not seem to be sufficient to achieve the objectives of an EAFM, as high trophic levels were still overexploited in 2013 and simulations conducted with Ecosim in the Bay of Biscay indicate that at current fishing effort the biomass will not be rebuilt by 2030. The ecosystem's response to a reduction in fishing mortality depends on which trophic levels receive protection. Reducing fishing mortality on pelagic fish, instead of on demersal fish, appears more efficient at maximising catch and total biomass and at conserving both top-predator and intermediate TLs. Such advice-oriented trophic models should be used on a regular basis to monitor the health status of marine food webs and analyse the trade-offs between multiple objectives in an ecosystem-based fisheries management context.

Competition favors elk over beaver in a riparian willow ecosystem

USGS Publications Warehouse

Baker, B.W.; Peinetti, H.R.; Coughenour, M.C.; Johnson, T.L.

2012-01-01

Beaver (Castor spp.) conservation requires an understanding of their complex interactions with competing herbivores. Simulation modeling offers a controlled environment to examine long-term dynamics in ecosystems driven by uncontrollable variables. We used a new version of the SAVANNA ecosystem model to investigate beaver (C. Canadensis) and elk (Cervus elapses) competition for willow (Salix spp.). We initialized the model with field data from Rocky Mountain National Park, Colorado, USA, to simulate a 4-ha riparian ecosystem containing beaver, elk, and willow. We found beaver persisted indefinitely when elk density was or = 30 elk km_2. The loss of tall willow preceded rapid beaver declines, thus willow condition may predict beaver population trajectory in natural environments. Beaver were able to persist with slightly higher elk densities if beaver alternated their use of foraging sites in a rest-rotation pattern rather than maintained continuous use. Thus, we found asymmetrical competition for willow strongly favored elk over beaver in a simulated montane ecosystem. Finally, we discuss application of the SAVANNA model and mechanisms of competition relative to beaver persistence as metapopulations, ecological resistance and alternative state models, and ecosystem regulation.

Indicators of ecosystem function identify alternate states in the sagebrush steppe.

PubMed

Kachergis, Emily; Rocca, Monique E; Fernandez-Gimenez, Maria E

2011-10-01

Models of ecosystem change that incorporate nonlinear dynamics and thresholds, such as state-and-transition models (STMs), are increasingly popular tools for land management decision-making. However, few models are based on systematic collection and documentation of ecological data, and of these, most rely solely on structural indicators (species composition) to identify states and transitions. As STMs are adopted as an assessment framework throughout the United States, finding effective and efficient ways to create data-driven models that integrate ecosystem function and structure is vital. This study aims to (1) evaluate the utility of functional indicators (indicators of rangeland health, IRH) as proxies for more difficult ecosystem function measurements and (2) create a data-driven STM for the sagebrush steppe of Colorado, USA, that incorporates both ecosystem structure and function. We sampled soils, plant communities, and IRH at 41 plots with similar clayey soils but different site histories to identify potential states and infer the effects of management practices and disturbances on transitions. We found that many IRH were correlated with quantitative measures of functional indicators, suggesting that the IRH can be used to approximate ecosystem function. In addition to a reference state that functions as expected for this soil type, we identified four biotically and functionally distinct potential states, consistent with the theoretical concept of alternate states. Three potential states were related to management practices (chemical and mechanical shrub treatments and seeding history) while one was related only to ecosystem processes (erosion). IRH and potential states were also related to environmental variation (slope, soil texture), suggesting that there are environmental factors within areas with similar soils that affect ecosystem dynamics and should be noted within STMs. Our approach generated an objective, data-driven model of ecosystem dynamics for rangeland management. Our findings suggest that the IRH approximate ecosystem processes and can distinguish between alternate states and communities and identify transitions when building data-driven STMs. Functional indicators are a simple, efficient way to create data-driven models that are consistent with alternate state theory. Managers can use them to improve current model-building methods and thus apply state-and-transition models more broadly for land management decision-making.

Dynamical entropy via entropy of non-random matrices: application to stability and complexity in modelling ecosystems.

PubMed

Chakrabarti, C G; Ghosh, Koyel

2013-10-01

In the present paper we have first introduced a measure of dynamical entropy of an ecosystem on the basis of the dynamical model of the system. The dynamical entropy which depends on the eigenvalues of the community matrix of the system leads to a consistent measure of complexity of the ecosystem to characterize the dynamical behaviours such as the stability, instability and periodicity around the stationary states of the system. We have illustrated the theory with some model ecosystems. Copyright © 2013 Elsevier Inc. All rights reserved.

Can we reliably estimate managed forest carbon dynamics using remotely sensed data?

NASA Astrophysics Data System (ADS)

Smallman, Thomas Luke; Exbrayat, Jean-Francois; Bloom, A. Anthony; Williams, Mathew

2015-04-01

Forests are an important part of the global carbon cycle, serving as both a large store of carbon and currently as a net sink of CO2. Forest biomass varies significantly in time and space, linked to climate, soils, natural disturbance and human impacts. This variation means that the global distribution of forest biomass and their dynamics are poorly quantified. Terrestrial ecosystem models (TEMs) are rarely evaluated for their predictions of forest carbon stocks and dynamics, due to a lack of knowledge on site specific factors such as disturbance dates and / or managed interventions. In this regard, managed forests present a valuable opportunity for model calibration and improvement. Spatially explicit datasets of planting dates, species and yield classification, in combination with remote sensing data and an appropriate data assimilation (DA) framework can reduce prediction uncertainty and error. We use a Baysian approach to calibrate the data assimilation linked ecosystem carbon (DALEC) model using a Metropolis Hastings-Markov Chain Monte Carlo (MH-MCMC) framework. Forest management information is incorporated into the data assimilation framework as part of ecological and dynamic constraints (EDCs). The key advantage here is that DALEC simulates a full carbon balance, not just the living biomass, and that both parameter and prediction uncertainties are estimated as part of the DA analysis. DALEC has been calibrated at two managed forests, in the USA (Pinus taeda; Duke Forest) and UK (Picea sitchensis; Griffin Forest). At each site DALEC is calibrated twice (exp1 & exp2). Both calibrations (exp1 & exp2) assimilated MODIS LAI and HWSD estimates of soil carbon stored in soil organic matter, in addition to common management information and prior knowledge included in parameter priors and the EDCs. Calibration exp1 also utilises multiple site level estimates of carbon storage in multiple pools. By comparing simulations we determine the impact of site-level observations on uncertainty and error on predictions, and which observations are key to constraining ecosystem processes. Preliminary simulations indicate that DALEC calibration exp1 accurately simulated the assimilated observations for forest and soil carbon stock estimates including, critically for forestry, standing wood stocks (R2 = 0.92, bias = -4.46 MgC ha-1, RMSE = 5.80 MgC ha-1). The results from exp1 indicate the model is able to find parameters that are both consistent with EDC and observations. In the absence of site-level stock observations (exp2) DALEC accurately estimates foliage and fine root pools, while the median estimate of above ground litter and wood stocks (R2 = 0.92, bias = -48.30 MgC ha-1, RMSE = 50.30 MgC ha-1) are over- and underestimated respectively, site-level observations are within model uncertainty. These results indicate that we can estimate managed forests dynamics using remotely sensed data, particularly as remotely sensed above ground biomass maps become available to provide constraint to correct biases in woody accumulation.

Priming effect and microbial diversity in ecosystem functioning and response to global change: a modeling approach using the SYMPHONY model.

PubMed

Perveen, Nazia; Barot, Sébastien; Alvarez, Gaël; Klumpp, Katja; Martin, Raphael; Rapaport, Alain; Herfurth, Damien; Louault, Frédérique; Fontaine, Sébastien

2014-04-01

Integration of the priming effect (PE) in ecosystem models is crucial to better predict the consequences of global change on ecosystem carbon (C) dynamics and its feedbacks on climate. Over the last decade, many attempts have been made to model PE in soil. However, PE has not yet been incorporated into any ecosystem models. Here, we build plant/soil models to explore how PE and microbial diversity influence soil/plant interactions and ecosystem C and nitrogen (N) dynamics in response to global change (elevated CO2 and atmospheric N depositions). Our results show that plant persistence, soil organic matter (SOM) accumulation, and low N leaching in undisturbed ecosystems relies on a fine adjustment of microbial N mineralization to plant N uptake. This adjustment can be modeled in the SYMPHONY model by considering the destruction of SOM through PE, and the interactions between two microbial functional groups: SOM decomposers and SOM builders. After estimation of parameters, SYMPHONY provided realistic predictions on forage production, soil C storage and N leaching for a permanent grassland. Consistent with recent observations, SYMPHONY predicted a CO2 -induced modification of soil microbial communities leading to an intensification of SOM mineralization and a decrease in the soil C stock. SYMPHONY also indicated that atmospheric N deposition may promote SOM accumulation via changes in the structure and metabolic activities of microbial communities. Collectively, these results suggest that the PE and functional role of microbial diversity may be incorporated in ecosystem models with a few additional parameters, improving accuracy of predictions. © 2013 John Wiley & Sons Ltd.

An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems

Treesearch

Yu Zhang; Changsheng Li; Carl C. Trettin; Harbin Li; Ge Sun

2002-01-01

Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global clinlate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model...

Conceptual ecological models to guide integrated landscape monitoring of the Great Basin

USGS Publications Warehouse

Miller, D.M.; Finn, S.P.; Woodward, Andrea; Torregrosa, Alicia; Miller, M.E.; Bedford, D.R.; Brasher, A.M.

2010-01-01

The Great Basin Integrated Landscape Monitoring Pilot Project was developed in response to the need for a monitoring and predictive capability that addresses changes in broad landscapes and waterscapes. Human communities and needs are nested within landscapes formed by interactions among the hydrosphere, geosphere, and biosphere. Understanding the complex processes that shape landscapes and deriving ways to manage them sustainably while meeting human needs require sophisticated modeling and monitoring. This document summarizes current understanding of ecosystem structure and function for many of the ecosystems within the Great Basin using conceptual models. The conceptual ecosystem models identify key ecological components and processes, identify external drivers, develop a hierarchical set of models that address both site and landscape attributes, inform regional monitoring strategy, and identify critical gaps in our knowledge of ecosystem function. The report also illustrates an approach for temporal and spatial scaling from site-specific models to landscape models and for understanding cumulative effects. Eventually, conceptual models can provide a structure for designing monitoring programs, interpreting monitoring and other data, and assessing the accuracy of our understanding of ecosystem functions and processes.

Use of hydrologic and hydrodynamic modeling for ecosystem restoration

USGS Publications Warehouse

Obeysekera, J.; Kuebler, L.; Ahmed, S.; Chang, M.-L.; Engel, V.; Langevin, C.; Swain, E.; Wan, Y.

2011-01-01

Planning and implementation of unprecedented projects for restoring the greater Everglades ecosystem are underway and the hydrologic and hydrodynamic modeling of restoration alternatives has become essential for success of restoration efforts. In view of the complex nature of the South Florida water resources system, regional-scale (system-wide) hydrologic models have been developed and used extensively for the development of the Comprehensive Everglades Restoration Plan. In addition, numerous subregional-scale hydrologic and hydrodynamic models have been developed and are being used for evaluating project-scale water management plans associated with urban, agricultural, and inland costal ecosystems. The authors provide a comprehensive summary of models of all scales, as well as the next generation models under development to meet the future needs of ecosystem restoration efforts in South Florida. The multiagency efforts to develop and apply models have allowed the agencies to understand the complex hydrologic interactions, quantify appropriate performance measures, and use new technologies in simulation algorithms, software development, and GIS/database techniques to meet the future modeling needs of the ecosystem restoration programs. Copyright ?? 2011 Taylor & Francis Group, LLC.

Modeling Net Ecosystem Carbon Exchange of Alpine Grasslands with a Satellite-Driven Model

PubMed Central

Zhao, Yuping; Zhang, Xianzhou; Fan, Yuzhi; Shi, Peili; He, Yongtao; Yu, Guirui; Li, Yingnian

2015-01-01

Estimate of net ecosystem carbon exchange (NEE) between the atmosphere and terrestrial ecosystems, the balance of gross primary productivity (GPP) and ecosystem respiration (Reco) has significant importance for studying the regional and global carbon cycles. Using models driven by satellite data and climatic data is a promising approach to estimate NEE at regional scales. For this purpose, we proposed a semi-empirical model to estimate NEE in this study. In our model, the component GPP was estimated with a light response curve of a rectangular hyperbola. The component Reco was estimated with an exponential function of soil temperature. To test the feasibility of applying our model at regional scales, the temporal variations in the model parameters derived from NEE observations in an alpine grassland ecosystem on Tibetan Plateau were investigated. The results indicated that all the inverted parameters exhibit apparent seasonality, which is in accordance with air temperature and canopy phenology. In addition, all the parameters have significant correlations with the remote sensed vegetation indexes or environment temperature. With parameters estimated with these correlations, the model illustrated fair accuracy both in the validation years and at another alpine grassland ecosystem on Tibetan Plateau. Our results also indicated that the model prediction was less accurate in drought years, implying that soil moisture is an important factor affecting the model performance. Incorporating soil water content into the model would be a critical step for the improvement of the model. PMID:25849325

Modeling net ecosystem carbon exchange of alpine grasslands with a satellite-driven model.

PubMed

Yan, Wei; Hu, Zhongmin; Zhao, Yuping; Zhang, Xianzhou; Fan, Yuzhi; Shi, Peili; He, Yongtao; Yu, Guirui; Li, Yingnian

2015-01-01

Estimate of net ecosystem carbon exchange (NEE) between the atmosphere and terrestrial ecosystems, the balance of gross primary productivity (GPP) and ecosystem respiration (Reco) has significant importance for studying the regional and global carbon cycles. Using models driven by satellite data and climatic data is a promising approach to estimate NEE at regional scales. For this purpose, we proposed a semi-empirical model to estimate NEE in this study. In our model, the component GPP was estimated with a light response curve of a rectangular hyperbola. The component Reco was estimated with an exponential function of soil temperature. To test the feasibility of applying our model at regional scales, the temporal variations in the model parameters derived from NEE observations in an alpine grassland ecosystem on Tibetan Plateau were investigated. The results indicated that all the inverted parameters exhibit apparent seasonality, which is in accordance with air temperature and canopy phenology. In addition, all the parameters have significant correlations with the remote sensed vegetation indexes or environment temperature. With parameters estimated with these correlations, the model illustrated fair accuracy both in the validation years and at another alpine grassland ecosystem on Tibetan Plateau. Our results also indicated that the model prediction was less accurate in drought years, implying that soil moisture is an important factor affecting the model performance. Incorporating soil water content into the model would be a critical step for the improvement of the model.

Soil process modelling in CZO research: gains in data harmonisation and model validation

NASA Astrophysics Data System (ADS)

van Gaans, Pauline; Andrianaki, Maria; Kobierska, Florian; Kram, Pavel; Lamacova, Anna; Lair, Georg; Nikolaidis, Nikos; Duffy, Chris; Regelink, Inge; van Leeuwen, Jeroen P.; de Ruiter, Peter

2014-05-01

Various soil process models were applied to four European Critical Zone observatories (CZOs), the core research sites of the FP7 project SoilTrEC: the Damma glacier forefield (CH), a set of three forested catchments on geochemically contrasing bedrocks in the Slavkov Forest (CZ), a chronosequence of soils in the former floodplain of the Danube of Fuchsenbigl/Marchfeld (AT), and the Koiliaris catchments in the north-western part of Crete, (GR). The aim of the modelling exercises was to apply and test soil process models with data from the CZOs for calibration/validation, identify potential limits to the application scope of the models, interpret soil state and soil functions at key stages of the soil life cycle, represented by the four SoilTrEC CZOs, contribute towards harmonisation of data and data acquisition. The models identified as specifically relevant were: The Penn State Integrated Hydrologic Model (PIHM), a fully coupled, multiprocess, multi-scale hydrologic model, to get a better understanding of water flow and pathways, The Soil and Water Assessment Tool (SWAT), a deterministic, continuous time (daily time step) basin scale model, to evaluate the impact of soil management practices, The Rothamsted Carbon model (Roth-C) to simulate organic carbon turnover and the Carbon, Aggregation, and Structure Turnover (CAST) model to include the role of soil aggregates in carbon dynamics, The Ligand Charge Distribution (LCD) model, to understand the interaction between organic matter and oxide surfaces in soil aggregate formation, and The Terrestrial Ecology Model (TEM) to obtain insight into the link between foodweb structure and carbon and nutrient turnover. With some exceptions all models were applied to all four CZOs. The need for specific model input contributed largely to data harmonisation. The comparisons between the CZOs turned out to be of great value for understanding the strength and limitations of the models, as well as the differences in soil conditions between the CZOs. The CZO modelling led to further developments of the PIHM, with incorporation of functionality for karstic fracture flow (Koiliaris) and fracture flow anisotropy (Damma). The Damma case also provided experience on how to use results from geophysical investigations in model refinement. The SWAT modelling showed variability among the CZOs in hydraulic conductivity, the curve number that determines how fast rainfall results in runoff, and soil moisture capacity. Roth-C and CAST showed carbon sequestration fluxes to be low for old cultivated soils (Koiliaris) and high for new soils (Damma), where the latter site also had very high turnover rates. The LCD modelling, so far limited to the calcareous floodplain soils in Austria, explains differences in C-sequestration capacity between forest and agricultural soils from competition between phosphate and soil organic matter for adsorption sites on Fe-(hydr)oxides. The wide variety of soil (eco)system conditions challenged the TEM model and showed important directions for refinement: 1) differentiating between various fractions of organic matter and concomitant microbial decomposition pathways, and 2) the need to better define the physiological traits of the organisms in relation to local environmental conditions.

Controlling species richness in spin-glass model ecosystems

NASA Astrophysics Data System (ADS)

Poderoso, Fábio C.; Fontanari, José F.

2006-11-01

Within the framework of the random replicator model of ecosystems, we use equilibrium statistical mechanics tools to study the effect of manipulating the ecosystem so as to guarantee that a fixed fraction of the surviving species at equilibrium display a predefined set of characters (e.g., characters of economic value). Provided that the intraspecies competition is not too weak, we find that the consequence of such intervention on the ecosystem composition is a significant increase on the number of species that become extinct, and so the impoverishment of the ecosystem.

An underwater light attenuation scheme for marine ecosystem models.

PubMed

Penta, Bradley; Lee, Zhongping; Kudela, Raphael M; Palacios, Sherry L; Gray, Deric J; Jolliff, Jason K; Shulman, Igor G

2008-10-13

Simulation of underwater light is essential for modeling marine ecosystems. A new model of underwater light attenuation is presented and compared with previous models. In situ data collected in Monterey Bay, CA. during September 2006 are used for validation. It is demonstrated that while the new light model is computationally simple and efficient it maintains accuracy and flexibility. When this light model is incorporated into an ecosystem model, the correlation between modeled and observed coastal chlorophyll is improved over an eight-year time period. While the simulation of a deep chlorophyll maximum demonstrates the effect of the new model at depth.

AQUATOX coupled foodweb model for ecosystem risk assessment of Polybrominated diphenyl ethers (PBDEs) in lake ecosystems.

PubMed

Zhang, Lulu; Liu, Jingling

2014-08-01

The AQUATOX model considers the direct toxic effects of chemicals and their indirect effects through foodwebs. For this study, the AQUATOX model was applied to evaluating the ecological risk of Polybrominated diphenyl ethers (PBDEs) in a highly anthropogenically disturbed lake-Baiyangdian Lake. Calibration and validation results indicated that the model can adequately describe the dynamics of 18 biological populations. Sensitivity analysis results suggested that the model is highly sensitive to temperature limitation. PBDEs risk estimate results demonstrate that estimated risk for natural ecosystems cannot be fully explained by single species toxicity data alone. The AQUATOX model could provide a good basis in ascertaining ecological protection levels of "chemicals of concern" for aquatic ecosystems. Therefore, AQUATOX can potentially be used to provide necessary information corresponding to early warning and rapid forecasting of pollutant transport and fate in the management of chemicals that put aquatic ecosystems at risk. Copyright © 2014 Elsevier Ltd. All rights reserved.

A novel CFS-PML boundary condition for transient electromagnetic simulation using a fictitious wave domain method

NASA Astrophysics Data System (ADS)

Hu, Yanpu; Egbert, Gary; Ji, Yanju; Fang, Guangyou

2017-01-01

In this study, we apply fictitious wave domain (FWD) methods, based on the correspondence principle for the wave and diffusion fields, to finite difference (FD) modeling of transient electromagnetic (TEM) diffusion problems for geophysical applications. A novel complex frequency shifted perfectly matched layer (PML) boundary condition is adapted to the FWD to truncate the computational domain, with the maximum electromagnetic wave propagation velocity in the FWD used to set the absorbing parameters for the boundary layers. Using domains of varying spatial extent we demonstrate that these boundary conditions offer significant improvements over simpler PML approaches, which can result in spurious reflections and large errors in the FWD solutions, especially for low frequencies and late times. In our development, resistive air layers are directly included in the FWD, allowing simulation of TEM responses in the presence of topography, as is commonly encountered in geophysical applications. We compare responses obtained by our new FD-FWD approach and with the spectral Lanczos decomposition method on 3-D resistivity models of varying complexity. The comparisons demonstrate that our absorbing boundary condition in FWD for the TEM diffusion problems works well even in complex high-contrast conductivity models.

Direct Visualization of Aggregate Morphology and Dynamics in a Model Soil Organic–Mineral System

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

Hufschmid, Ryan; Newcomb, Christina J.; Grate, Jay W.

Interactions between mineral surfaces and organic matter are ubiquitous in soils and the environment. Through both physical and chemical mechanisms, organic-mineral assemblages prevent decomposition of soil organic matter by limiting accessibility or reducing efficacy of enzymes and microbes. To understand the mechanisms underlying organic-mineral interactions, researchers have begun to interrogate these systems at smaller length scales. Current techniques that maintain a hydrated state and allow researchers to characterize nanometer length scales are limited. Here we chose a model organic-mineral system and performed complementary imaging techniques that enable direct nanoscale observations in environmentally relevant conditions: cryogenic TEM and in-situ liquid cellmore » TEM. We observed a three-fold increase in aggregate size of goethite nanoparticles upon addition of a model organic phosphate ligand and quantification of nanoparticle orientation reveals a preference for side-to-side interactions independent of the addition of an organic ligand. Additionally, in-situ liquid cell TEM experiments provides a dynamic view of the interactions allowing us to report velocities of mineral assemblages during aggregation and disaggregation, which could potentially provide binding energetics and kinetic parameters about organic-mineral and mineral-mineral systems.« less

Marine ecosystem modeling beyond the box: using GIS to study carbon fluxes in a coastal ecosystem.

PubMed

Wijnbladh, Erik; Jönsson, Bror Fredrik; Kumblad, Linda

2006-12-01

Studies of carbon fluxes in marine ecosystems are often done by using box model approaches with basin size boxes, or highly resolved 3D models, and an emphasis on the pelagic component of the ecosystem. Those approaches work well in the ocean proper, but can give rise to considerable problems when applied to coastal systems, because of the scale of certain ecological niches and the fact that benthic organisms are the dominant functional group of the ecosystem. In addition, 3D models require an extensive modeling effort. In this project, an intermediate approach based on a high resolution (20x20 m) GIS data-grid has been developed for the coastal ecosystem in the Laxemar area (Baltic Sea, Sweden) based on a number of different site investigations. The model has been developed in the context of a safety assessment project for a proposed nuclear waste repository, in which the fate of hypothetically released radionuclides from the planned repository is estimated. The assessment project requires not only a good understanding of the ecosystem dynamics at the site, but also quantification of stocks and flows of matter in the system. The data-grid was then used to set up a carbon budget describing the spatial distribution of biomass, primary production, net ecosystem production and thus where carbon sinks and sources are located in the area. From these results, it was clear that there was a large variation in ecosystem characteristics within the basins and, on a larger scale, that the inner areas are net producing and the outer areas net respiring, even in shallow phytobenthic communities. Benthic processes had a similar or larger influence on carbon fluxes as advective processes in inner areas, whereas the opposite appears to be true in the outer basins. As many radionuclides are expected to follow the pathways of organic matter in the environment, these findings enhance our abilities to realistically describe and predict their fate in the ecosystem.

Multiple resource use efficiency (mRUE): A new concept for ecosystem production

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

Han, Juanjuan; Chen, Jiquan; Miao, Yuan

The resource-driven concept, which is an important school for investigating ecosystem production, has been applied for decades. However, the regulatory mechanisms of production by multiple resources remain unclear. We formulated a new algorithm model that integrates multiple resource uses to study ecosystem production and tested its applications on a water-availability gradient in semi-arid grassland. The result of our experiment showed that changes in water availability significantly affected the resources of light and nitrogen, and altered the relationships among multiple resource absorption rate (ε), multiple resource use efficiency (mRUE), and available resource (R avail). The increased water availability suppressed ecosystem mRUEmore » (i.e., “declining marginal returns”); The changes in mRUE had a negative effect on ε (i.e., “inverse feedback”). These two processes jointly regulated that the stimulated single resource availability would promote ecosystem production rather than suppress it, even when mRUE was reduced. This study illustrated the use of the mRUE model in exploring the coherent relationships among the key parameters on regulating the ecosystem production for future modeling, and evaluated the sensitivity of this conceptual model under different dataset properties. Furthermore, this model needs extensive validation by the ecological community before it can extrapolate this method to other ecosystems in the future.« less

Multiple resource use efficiency (mRUE): A new concept for ecosystem production

DOE PAGES

Han, Juanjuan; Chen, Jiquan; Miao, Yuan; ...

2016-11-21

The resource-driven concept, which is an important school for investigating ecosystem production, has been applied for decades. However, the regulatory mechanisms of production by multiple resources remain unclear. We formulated a new algorithm model that integrates multiple resource uses to study ecosystem production and tested its applications on a water-availability gradient in semi-arid grassland. The result of our experiment showed that changes in water availability significantly affected the resources of light and nitrogen, and altered the relationships among multiple resource absorption rate (ε), multiple resource use efficiency (mRUE), and available resource (R avail). The increased water availability suppressed ecosystem mRUEmore » (i.e., “declining marginal returns”); The changes in mRUE had a negative effect on ε (i.e., “inverse feedback”). These two processes jointly regulated that the stimulated single resource availability would promote ecosystem production rather than suppress it, even when mRUE was reduced. This study illustrated the use of the mRUE model in exploring the coherent relationships among the key parameters on regulating the ecosystem production for future modeling, and evaluated the sensitivity of this conceptual model under different dataset properties. Furthermore, this model needs extensive validation by the ecological community before it can extrapolate this method to other ecosystems in the future.« less

Multiple Resource Use Efficiency (mRUE): A New Concept for Ecosystem Production.

PubMed

Han, Juanjuan; Chen, Jiquan; Miao, Yuan; Wan, Shiqiang

2016-11-21

The resource-driven concept, which is an important school for investigating ecosystem production, has been applied for decades. However, the regulatory mechanisms of production by multiple resources remain unclear. We formulated a new algorithm model that integrates multiple resource uses to study ecosystem production and tested its applications on a water-availability gradient in semi-arid grassland. The result of our experiment showed that changes in water availability significantly affected the resources of light and nitrogen, and altered the relationships among multiple resource absorption rate (ε), multiple resource use efficiency (mRUE), and available resource (R avail ). The increased water availability suppressed ecosystem mRUE (i.e., "declining marginal returns"); The changes in mRUE had a negative effect on ε (i.e., "inverse feedback"). These two processes jointly regulated that the stimulated single resource availability would promote ecosystem production rather than suppress it, even when mRUE was reduced. This study illustrated the use of the mRUE model in exploring the coherent relationships among the key parameters on regulating the ecosystem production for future modeling, and evaluated the sensitivity of this conceptual model under different dataset properties. However, this model needs extensive validation by the ecological community before it can extrapolate this method to other ecosystems in the future.

Combined MTOR and autophagy inhibition

PubMed Central

Rangwala, Reshma; Chang, Yunyoung C; Hu, Janice; Algazy, Kenneth M; Evans, Tracey L; Fecher, Leslie A; Schuchter, Lynn M; Torigian, Drew A; Panosian, Jeffrey T; Troxel, Andrea B; Tan, Kay-See; Heitjan, Daniel F; DeMichele, Angela M; Vaughn, David J; Redlinger, Maryann; Alavi, Abass; Kaiser, Jonathon; Pontiggia, Laura; Davis, Lisa E; O’Dwyer, Peter J; Amaravadi, Ravi K

2014-01-01

The combination of temsirolimus (TEM), an MTOR inhibitor, and hydroxychloroquine (HCQ), an autophagy inhibitor, augments cell death in preclinical models. This phase 1 dose-escalation study evaluated the maximum tolerated dose (MTD), safety, preliminary activity, pharmacokinetics, and pharmacodynamics of HCQ in combination with TEM in cancer patients. In the dose escalation portion, 27 patients with advanced solid malignancies were enrolled, followed by a cohort expansion at the top dose level in 12 patients with metastatic melanoma. The combination of HCQ and TEM was well tolerated, and grade 3 or 4 toxicity was limited to anorexia (7%), fatigue (7%), and nausea (7%). An MTD was not reached for HCQ, and the recommended phase II dose was HCQ 600 mg twice daily in combination with TEM 25 mg weekly. Other common grade 1 or 2 toxicities included fatigue, anorexia, nausea, stomatitis, rash, and weight loss. No responses were observed; however, 14/21 (67%) patients in the dose escalation and 14/19 (74%) patients with melanoma achieved stable disease. The median progression-free survival in 13 melanoma patients treated with HCQ 1200mg/d in combination with TEM was 3.5 mo. Novel 18-fluorodeoxyglucose positron emission tomography (FDG-PET) measurements predicted clinical outcome and provided further evidence that the addition of HCQ to TEM produced metabolic stress on tumors in patients that experienced clinical benefit. Pharmacodynamic evidence of autophagy inhibition was evident in serial PBMC and tumor biopsies only in patients treated with 1200 mg daily HCQ. This study indicates that TEM and HCQ is safe and tolerable, modulates autophagy in patients, and has significant antitumor activity. Further studies combining MTOR and autophagy inhibitors in cancer patients are warranted. PMID:24991838

Combined MTOR and autophagy inhibition: phase I trial of hydroxychloroquine and temsirolimus in patients with advanced solid tumors and melanoma.

PubMed

Rangwala, Reshma; Chang, Yunyoung C; Hu, Janice; Algazy, Kenneth M; Evans, Tracey L; Fecher, Leslie A; Schuchter, Lynn M; Torigian, Drew A; Panosian, Jeffrey T; Troxel, Andrea B; Tan, Kay-See; Heitjan, Daniel F; DeMichele, Angela M; Vaughn, David J; Redlinger, Maryann; Alavi, Abass; Kaiser, Jonathon; Pontiggia, Laura; Davis, Lisa E; O'Dwyer, Peter J; Amaravadi, Ravi K

2014-08-01

The combination of temsirolimus (TEM), an MTOR inhibitor, and hydroxychloroquine (HCQ), an autophagy inhibitor, augments cell death in preclinical models. This phase 1 dose-escalation study evaluated the maximum tolerated dose (MTD), safety, preliminary activity, pharmacokinetics, and pharmacodynamics of HCQ in combination with TEM in cancer patients. In the dose escalation portion, 27 patients with advanced solid malignancies were enrolled, followed by a cohort expansion at the top dose level in 12 patients with metastatic melanoma. The combination of HCQ and TEM was well tolerated, and grade 3 or 4 toxicity was limited to anorexia (7%), fatigue (7%), and nausea (7%). An MTD was not reached for HCQ, and the recommended phase II dose was HCQ 600 mg twice daily in combination with TEM 25 mg weekly. Other common grade 1 or 2 toxicities included fatigue, anorexia, nausea, stomatitis, rash, and weight loss. No responses were observed; however, 14/21 (67%) patients in the dose escalation and 14/19 (74%) patients with melanoma achieved stable disease. The median progression-free survival in 13 melanoma patients treated with HCQ 1200mg/d in combination with TEM was 3.5 mo. Novel 18-fluorodeoxyglucose positron emission tomography (FDG-PET) measurements predicted clinical outcome and provided further evidence that the addition of HCQ to TEM produced metabolic stress on tumors in patients that experienced clinical benefit. Pharmacodynamic evidence of autophagy inhibition was evident in serial PBMC and tumor biopsies only in patients treated with 1200 mg daily HCQ. This study indicates that TEM and HCQ is safe and tolerable, modulates autophagy in patients, and has significant antitumor activity. Further studies combining MTOR and autophagy inhibitors in cancer patients are warranted.

A Simulation Model for Studying Effects of Pollution and Freshwater Inflow on Secondary Productivity in an Ecosystem. Ph.D. Thesis - North Carolina State Univ.

NASA Technical Reports Server (NTRS)

Johnson, R. W.

1974-01-01

A mathematical model of an ecosystem is developed. Secondary productivity is evaluated in terms of man related and controllable factors. Information from an existing physical parameters model is used as well as pertinent biological measurements. Predictive information of value to estuarine management is presented. Biological, chemical, and physical parameters measured in order to develop models of ecosystems are identified.

The response of soil organic carbon of a rich fen peatland in interior Alaska to projected climate change

USGS Publications Warehouse

Fan, Zhaosheng; McGuire, Anthony David; Turetsky, Merritt R.; Harden, Jennifer W.; Waddington, James Michael; Kane, Evan S.

2013-01-01

It is important to understand the fate of carbon in boreal peatland soils in response to climate change because a substantial change in release of this carbon as CO2 and CH4 could influence the climate system. The goal of this research was to synthesize the results of a field water table manipulation experiment conducted in a boreal rich fen into a process-based model to understand how soil organic carbon (SOC) of the rich fen might respond to projected climate change. This model, the peatland version of the dynamic organic soil Terrestrial Ecosystem Model (peatland DOS-TEM), was calibrated with data collected during 2005–2011 from the control treatment of a boreal rich fen in the Alaska Peatland Experiment (APEX). The performance of the model was validated with the experimental data measured from the raised and lowered water-table treatments of APEX during the same period. The model was then applied to simulate future SOC dynamics of the rich fen control site under various CO2 emission scenarios. The results across these emissions scenarios suggest that the rate of SOC sequestration in the rich fen will increase between year 2012 and 2061 because the effects of warming increase heterotrophic respiration less than they increase carbon inputs via production. However, after 2061, the rate of SOC sequestration will be weakened and, as a result, the rich fen will likely become a carbon source to the atmosphere between 2062 and 2099. During this period, the effects of projected warming increase respiration so that it is greater than carbon inputs via production. Although changes in precipitation alone had relatively little effect on the dynamics of SOC, changes in precipitation did interact with warming to influence SOC dynamics for some climate scenarios.

Modelling Mediterranean agro-ecosystems by including agricultural trees in the LPJmL model

NASA Astrophysics Data System (ADS)

Fader, M.; von Bloh, W.; Shi, S.; Bondeau, A.; Cramer, W.

2015-11-01

In the Mediterranean region, climate and land use change are expected to impact on natural and agricultural ecosystems by warming, reduced rainfall, direct degradation of ecosystems and biodiversity loss. Human population growth and socioeconomic changes, notably on the eastern and southern shores, will require increases in food production and put additional pressure on agro-ecosystems and water resources. Coping with these challenges requires informed decisions that, in turn, require assessments by means of a comprehensive agro-ecosystem and hydrological model. This study presents the inclusion of 10 Mediterranean agricultural plants, mainly perennial crops, in an agro-ecosystem model (Lund-Potsdam-Jena managed Land - LPJmL): nut trees, date palms, citrus trees, orchards, olive trees, grapes, cotton, potatoes, vegetables and fodder grasses. The model was successfully tested in three model outputs: agricultural yields, irrigation requirements and soil carbon density. With the development presented in this study, LPJmL is now able to simulate in good detail and mechanistically the functioning of Mediterranean agriculture with a comprehensive representation of ecophysiological processes for all vegetation types (natural and agricultural) and in a consistent framework that produces estimates of carbon, agricultural and hydrological variables for the entire Mediterranean basin. This development paves the way for further model extensions aiming at the representation of alternative agro-ecosystems (e.g. agroforestry), and opens the door for a large number of applications in the Mediterranean region, for example assessments of the consequences of land use transitions, the influence of management practices and climate change impacts.

Southwest Ecosystem Services Project (SwESP): Identifying Ecosystems Services Based on Tribal Values

EPA Science Inventory

USEPA Office of Research Development (ORD) new strategic focus is the measurement of benefits and services of ecosystem. The primary objective of the Ecosystem Services Research Program (ESRP) is to identify, measure, monitor, model and map ecosystem services and to enable their ...

An integrated eco-hydrologic modeling framework for assessing the effects of interacting stressors on forest ecosystem services

EPA Science Inventory

The U.S. Environmental Protection Agency recently established the Ecosystem Services Research Program to help formulate methods and models for conducting comprehensive risk assessments that quantify how multiple ecosystem services interact and respond in concert to environmental ...

An integrated eco-hydrologic modeling framework for assessing the effects of interacting stressors on multiple ecosystem services

EPA Science Inventory

The U.S. Environmental Protection Agency recently established the Ecosystem Services Research Program to help formulate methods and models for conducting comprehensive risk assessments that quantify how multiple ecosystem services interact and respond in concert to environmental ...

SIMULATION MODEL FOR WATERSHED MANAGEMENT PLANNING. VOLUME 1. MODEL THEORY AND FORMULATION

EPA Science Inventory

Evaluation of nonpoint source pollution problems requires an understanding of the behavioral response to an ecosystem to the impacts of land use activities on individual components of that ecosystem. By analyzing basic ecosystem processes and impacts of land use activities on spe...

Development of an integrated generic model for multi-scale assessment of the impacts of agro-ecosystems on major ecosystem services in West Africa.

PubMed

Belem, Mahamadou; Saqalli, Mehdi

2017-11-01

This paper presents an integrated model assessing the impacts of climate change, agro-ecosystem and demographic transition patterns on major ecosystem services in West-Africa along a partial overview of economic aspects (poverty reduction, food self-sufficiency and income generation). The model is based on an agent-based model associated with a soil model and multi-scale spatial model. The resulting Model for West-Africa Agro-Ecosystem Integrated Assessment (MOWASIA) is ecologically generic, meaning it is designed for all sudano-sahelian environments but may then be used as an experimentation facility for testing different scenarios combining ecological and socioeconomic dimensions. A case study in Burkina Faso is examined to assess the environmental and economic performances of semi-continuous and continuous farming systems. Results show that the semi-continuous system using organic fertilizer and fallowing practices contribute better to environment preservation and food security than the more economically performant continuous system. In addition, this study showed that farmers heterogeneity could play an important role in agricultural policies planning and assessment. In addition, the results showed that MOWASIA is an effective tool for designing, analysing the impacts of agro-ecosystems. Copyright © 2017. Published by Elsevier Ltd.

Sensitivity of productivity and respiration to water availability determines the net ecosystem exchange of carbon terrestrial ecosystems of the United States

NASA Astrophysics Data System (ADS)

Liu, Z.; Ballantyne, A.; Poulter, B.; Anderegg, W.; Jacobson, A. R.; Miller, J. B.

2017-12-01

Interannual variability (IAV) of atmospheric CO2 is primarily driven by fluctuations in net carbon exchange (NEE) by terrestrial ecosystems. Recent analyses suggested that global terrestrial carbon uptake is dominated by the sensitivity of productivity to precipitation in semi-arid ecosystems, or sensitivity of respiration to temperature in tropical ecosystems. There is a need to better understand factors that control the carbon balance of land ecosystems across spatial and temporal scales. Here we used multiple observational dataset to assess: (1) What are the dominant processes controlling the IAV of NEE in terrestrial ecosystem? What are the climatic controls on the variability gross primary productivity (GPP) and total ecosystem respiration (TER) in the contiguous United States (CONUS). Our analysis revealed that there is a strong positive correlation between IAV of GPP and IAV of NEE in drier (mean annual precipitation: MAP < 750mm) western ecosystem, while there is no correlation between IAV of GPP and IAV of NEE in moist (MAP > 750mm) eastern ecosystem using observational dataset. Both βspatial and βtemporal of GPP and TER to precipitation exhibit an emergent threshold where GPP is more sensitive than TER to precipitation in semi-arid western ecosystems and TER is more sensitive than GPP to precipitation in more humid eastern ecosystems. This emergent ecosystem threshold was evident in several independent observations. However, analyses from 10 TRENDY models indicate current Dynamic Global Vegetation Models (DGVMs) tend to overestimate the sensitivity of NEE to GPP and underestimate the sensitivity of NEE to TER to precipitation across CONUS ecosystems. TER experiments showed that commonly used TER models failed to capture the IAV of TER in the moist region in CONUS. This is because heterotrophic respiration (Rh) was relatively independent of GPP in moist regions of CONUS, but was too tightly coupled to GPP in the DGVMs. The emergent thresholds at the ecosystem and continental scale may help reconcile model simulations and observations of terrestrial carbon processes.

Invasive species: an increasing threat to marine ecosystems under climate change?

NASA Astrophysics Data System (ADS)

Artioli, Yuri; Galienne, Chris; Holt, Jason; Wakelin, Sarah; Butenschön, Momme; Schrum, Corinna; Daewel, Ute; Pushpadas, Dhania; Cannaby, Heather; Salihoglu, Baris; Zavatarelli, Marco; Clementi, Emanuela; Olenin, Sergej; Allen, Icarus

2013-04-01

Planktonic Non-Indigenous Species (NIS) are a potential threat to marine ecosystems: a successful invasion of such organisms can alter significantly the ecosystem structure with shift in species composition that can affect different levels of the trophic network and also with local extinction of native species in the more extreme cases. Such changes will also impact some ecosystem functions like primary and secondary production or nutrient cycling, and services, like fishery, aquaculture or carbon sequestration. Understanding how climate change influences the susceptibility of a marine ecosystem to invasion is challenging as the success and the impact of an invasion depend on many different factors all tightly interconnected (e.g. time of the invasion, location, state of the ecosystem…). Here we present DivERSEM, a new version of the biogeochemical model ERSEM modified in order to account for phytoplankton diversity. With such a model, we are able to simulate invasion from phytoplankton NIS, to assess the likelihood of success of such an invasion and to estimate the potential impact on ecosystem structure, using indicator like the Biopollution index. In the MEECE project (www.meece.eu), the model has been coupled to a 1D water column model (GOTM) in two different climate scenarios (present day and the IPCC SRES A1B scenario for 2100) in 4 different European shelf seas (North Sea, Baltic Sea, Black Sea and Adriatic Sea). The model has been forced with atmospheric data coming from the IPSL climate model, and nutrient concentration extracted from a set of 3D biogeochemical models running under the same climate scenario. The response of the ecosystem susceptibility to invasion to climate change has been analysed comparing the successfulness of invasions in the two time slices and its impact on community structure and ecosystem functions. At the same time, the comparison among the different basins allowed to highlight some of the characteristics that make the ecosystems more vulnerable to NIS.

Biogeochemical cycling in terrestrial ecosystems - Modeling, measurement, and remote sensing

NASA Technical Reports Server (NTRS)

Peterson, D. L.; Matson, P. A.; Lawless, J. G.; Aber, J. D.; Vitousek, P. M.

1985-01-01

The use of modeling, remote sensing, and measurements to characterize the pathways and to measure the rate of biogeochemical cycling in forest ecosystems is described. The application of the process-level model to predict processes in intact forests and ecosystems response to disturbance is examined. The selection of research areas from contrasting climate regimes and sites having a fertility gradient in that regime is discussed, and the sites studied are listed. The use of remote sensing in determining leaf area index and canopy biochemistry is analyzed. Nitrous oxide emission is investigated by using a gas measurement instrument. Future research projects, which include studying the influence of changes on nutrient cycling in ecosystems and the effect of pollutants on the ecosystems, are discussed.

Transient traceability analysis of land carbon storage dynamics: procedures and its application to two forest ecosystems

NASA Astrophysics Data System (ADS)

Jiang, L.; Shi, Z.; Xia, J.; Liang, J.; Lu, X.; Wang, Y.; Luo, Y.

2017-12-01

Uptake of anthropogenically emitted carbon (C) dioxide by terrestrial ecosystem is critical for determining future climate. However, Earth system models project large uncertainties in future C storage. To help identify sources of uncertainties in model predictions, this study develops a transient traceability framework to trace components of C storage dynamics. Transient C storage (X) can be decomposed into two components, C storage capacity (Xc) and C storage potential (Xp). Xc is the maximum C amount that an ecosystem can potentially store and Xp represents the internal capacity of an ecosystem to equilibrate C input and output for a network of pools. Xc is co-determined by net primary production (NPP) and residence time (𝜏N), with the latter being determined by allocation coefficients, transfer coefficients, environmental scalar, and exit rate. Xp is the product of redistribution matrix (𝜏ch) and net ecosystem exchange. We applied this framework to two contrasting ecosystems, Duke Forest and Harvard Forest with an ecosystem model. This framework helps identify the mechanisms underlying the responses of carbon cycling in the two forests to climate change. The temporal trajectories of X are similar between the two ecosystems. Using this framework, we found that two different mechanisms leading to the similar trajectory. This framework has potential to reveal mechanisms behind transient C storage in response to various global change factors. It can also identify sources of uncertainties in predicted transient C storage across models and can therefore be useful for model intercomparison.

Characterizing the performance of ecosystem models across time scales: A spectral analysis of the North American Carbon Program site-level synthesis

Treesearch

Michael C. Dietze; Rodrigo Vargas; Andrew D. Richardson; Paul C. Stoy; Alan G. Barr; Ryan S. Anderson; M. Altaf Arain; Ian T. Baker; T. Andrew Black; Jing M. Chen; Philippe Ciais; Lawrence B. Flanagan; Christopher M. Gough; Robert F. Grant; David Hollinger; R. Cesar Izaurralde; Christopher J. Kucharik; Peter Lafleur; Shugang Liu; Erandathie Lokupitiya; Yiqi Luo; J. William Munger; Changhui Peng; Benjamin Poulter; David T. Price; Daniel M. Ricciuto; William J. Riley; Alok Kumar Sahoo; Kevin Schaefer; Andrew E. Suyker; Hanqin Tian; Christina Tonitto; Hans Verbeeck; Shashi B. Verma; Weifeng Wang; Ensheng Weng

2011-01-01

Ecosystem models are important tools for diagnosing the carbon cycle and projecting its behavior across space and time. Despite the fact that ecosystems respond to drivers at multiple time scales, most assessments of model performance do not discriminate different time scales. Spectral methods, such as wavelet analyses, present an alternative approach that enables the...

A methodology for evaluation of parent-mutant competition using a generalized non-linear ecosystem model

Treesearch

Raymond L. Czaplewski

1973-01-01

A generalized, non-linear population dynamics model of an ecosystem is used to investigate the direction of selective pressures upon a mutant by studying the competition between parent and mutant populations. The model has the advantages of considering selection as operating on the phenotype, of retaining the interaction of the mutant population with the ecosystem as a...

Modeling Population and Ecosystem Response to Sublethal Toxicant Exposure

DTIC Science & Technology

2000-09-30

Modeling Population and Ecosystem Response to Sublethal Toxicant Exposure Principal Investigator: Roger M. Nisbet Department of Ecology, Evolution...DATES COVERED 00-00-2000 to 00-00-2000 4. TITLE AND SUBTITLE Modeling Population and Ecosystem Response to Sublethal Toxicant Exposure 5a...those of real populations. We have also investigated how toxicants may affect the stability of the system. If the toxicant effect is primarily an

Modeling Population and Ecosystem Response to Sublethal Toxicant Exposure

DTIC Science & Technology

2001-09-30

mutualism utilized modified Lotka - Volterra (L-V) competition equations in which the sign of the interspecific interaction term was changed from...within complex communities and ecosystems. Prior to the current award, the PIs formulated and tested general dynamic energy budget models...Nisbet, 1998; chapter 7) make a convincing case that ecosystems do truly have dynamics that can be described by relatively simple, general , models

Incorporating historical ecosystem diversity into conservation planning efforts in grass and shrub ecosystems

Treesearch

Amy C. Ganguli; Johathan B. Haufler; Carolyn A. Mehl; Jimmie D. Chew

2011-01-01

Understanding historical ecosystem diversity and wildlife habitat quality can provide a useful reference for managing and restoring rangeland ecosystems. We characterized historical ecosystem diversity using available empirical data, expert opinion, and the spatially explicit vegetation dynamics model SIMPPLLE (SIMulating Vegetative Patterns and Processes at Landscape...

Predicting Trophic Interactions and Habitat Utilization in the California Current Ecosystem

DTIC Science & Technology

2013-09-30

in the California Current Ecosystem Jerome Fiechter UC Santa Cruz Institute of Marine Sciences 1156 High Street Santa Cruz, CA 95064 phone... Ecosystem (CCLME), the long-term goal of our modeling approach is to better understand and characterize biological “hotspots” (i.e., the aggregation of...multiple marine organisms over multiple trophic levels) off the U.S. west coast and in other regions where similar fully-coupled ecosystem models may

Invited OSU class lecture: An integrated eco-hydrologic modeling framework for assessing the effects of interacting stressors on multiple ecosystem services

EPA Science Inventory

The U.S. Environmental Protection Agency recently established the Ecosystem Services Research Program to help formulate methods and models for conducting comprehensive risk assessments that quantify how multiple ecosystem services interact and respond in concert to environmental ...

An integrated eco-hydrologic modeling framework for assessing the effects of interacting stressors on forest ecosystem services - ESRP mtg

EPA Science Inventory

The U.S. Environmental Protection Agency recently established the Ecosystem Services Research Program to help formulate methods and models for conducting comprehensive risk assessments that quantify how multiple ecosystem services interact and respond in concert to environmental ...

An integrated eco-hydrologic modeling framework for assessing the effects of interacting stressors on multiple ecosystem services - 4/27/10

EPA Science Inventory

The U.S. Environmental Protection Agency recently established the Ecosystem Services Research Program to help formulate methods and models for conducting comprehensive risk assessments that quantify how multiple ecosystem services interact and respond in concert to environmental ...

MODELING MINERAL NITROGEN EXPORT FROM A FOREST TERRESTRIAL ECOSYSTEM TO STREAMS

EPA Science Inventory

Terrestrial ecosystems are major sources of N pollution to aquatic ecosystems. Predicting N export to streams is a critical goal of non-point source modeling. This study was conducted to assess the effect of terrestrial N cycling on stream N export using long-term monitoring da...

Study on the ecosystem construction of using ecopath model in inland waterway

NASA Astrophysics Data System (ADS)

Zhao, Junjie; Bai, Jing; Zhang, Lu; Wang, Ning; Shou, Youping

2018-04-01

In this paper, Ecopath with Ecosim 5.1 software is used to simulate the constructed water ecosystem of inland waterway. According to the characteristics of feeding relationship, the ecopath model of water ecosystem is divided into seven functional groups: phytoplankton, hydrophyte, zooplankton, herbivorous, omnivorous, polychaetes and detritus. By analyzing the important ecological parameters of the ecosystem, such as biomass, biomass / biomass, consumption / biomass, trophic level and ecological nutrient conversion efficiency, the software integrates the energy flow process of the ecosystem, the ratio of the total net primary production and the sum of all respiratory flows is 1.314, it’s indicating that the ecosystem is equilibrium. The research method of this paper can be widely used to evaluate the stability of the ecosystem of the domestic river.

Ecosystem Model Performance at Wetlands: Results from the North American Carbon Program Site Synthesis

NASA Astrophysics Data System (ADS)

Sulman, B. N.; Desai, A. R.; Schroeder, N. M.; NACP Site Synthesis Participants

2011-12-01

Northern peatlands contain a significant fraction of the global carbon pool, and their responses to hydrological change are likely to be important factors in future carbon cycle-climate feedbacks. Global-scale carbon cycle modeling studies typically use general ecosystem models with coarse spatial resolution, often without peatland-specific processes. Here, seven ecosystem models were used to simulate CO2 fluxes at three field sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor, sphagnum-dominated bog, from 2002-2006. Flux residuals (simulated - observed) were positively correlated with measured water table for both gross ecosystem productivity (GEP) and ecosystem respiration (ER) at the two fen sites for all models, and were positively correlated with water table at the bog site for the majority of models. Modeled diurnal cycles at fen sites agreed well with eddy covariance measurements overall. Eddy covariance GEP and ER were higher during dry periods than during wet periods, while model results predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP had no significant dependence on water table, while models predicted higher GEP during wet periods. All models significantly over-estimated GEP at the bog site, and all but one over-estimated ER at the bog site. Carbon cycle models in peatland-rich regions could be improved by incorporating better models or measurements of hydrology and by inhibiting GEP and ER rates under saturated conditions. Bogs and fens likely require distinct treatments in ecosystem models due to differences in nutrients, peat properties, and plant communities.

Modelling ecosystem service flows under uncertainty with stochiastic SPAN

USGS Publications Warehouse

Johnson, Gary W.; Snapp, Robert R.; Villa, Ferdinando; Bagstad, Kenneth J.

2012-01-01

Ecosystem service models are increasingly in demand for decision making. However, the data required to run these models are often patchy, missing, outdated, or untrustworthy. Further, communication of data and model uncertainty to decision makers is often either absent or unintuitive. In this work, we introduce a systematic approach to addressing both the data gap and the difficulty in communicating uncertainty through a stochastic adaptation of the Service Path Attribution Networks (SPAN) framework. The SPAN formalism assesses ecosystem services through a set of up to 16 maps, which characterize the services in a study area in terms of flow pathways between ecosystems and human beneficiaries. Although the SPAN algorithms were originally defined deterministically, we present them here in a stochastic framework which combines probabilistic input data with a stochastic transport model in order to generate probabilistic spatial outputs. This enables a novel feature among ecosystem service models: the ability to spatially visualize uncertainty in the model results. The stochastic SPAN model can analyze areas where data limitations are prohibitive for deterministic models. Greater uncertainty in the model inputs (including missing data) should lead to greater uncertainty expressed in the model’s output distributions. By using Bayesian belief networks to fill data gaps and expert-provided trust assignments to augment untrustworthy or outdated information, we can account for uncertainty in input data, producing a model that is still able to run and provide information where strictly deterministic models could not. Taken together, these attributes enable more robust and intuitive modelling of ecosystem services under uncertainty.

TEM Derivative-Producing Enterobacter aerogenes Strains: Dissemination of a Prevalent Clone

PubMed Central

Dumarche, P.; De Champs, C.; Sirot, D.; Chanal, C.; Bonnet, R.; Sirot, J.

2002-01-01

TEM-24 (CAZ-6) extended-spectrum β-lactamase (ESBL) was detected in 1988 in Clermont-Ferrand, France, in Klebsiella pneumoniae (blaTEM-24) and Enterobacter aerogenes (blaTEM-24b), and since 1994, a TEM-24-producing E. aerogenes clonal strain has been observed elsewhere in the country. To determine if the spread of this clonal strain was restricted to TEM-24-producing E. aerogenes strains, 84 E. aerogenes strains (non-TEM/SHV-producing strains, TEM-1- or -2-producing strains, and different ESBL-producing strains), isolated from 1988 to 1999 in Clermont-Ferrand (n = 59) and in 11 other French hospitals in 1998 (n = 25), were studied. A clonal strain was found for TEM-24- but also for TEM-3- and TEM-1- or 2-producing isolates. This study shows that there is a clonal strain dependent on acquisition of the TEM-type enzyme (TEM-24 and other TEM types). PMID:11897606

Extraction and Use of Noise Models from Production-Mode Transient Electromagnetic Data

NASA Astrophysics Data System (ADS)

Rasmussen, S.; Nyboe, N. S.; Larsen, J. J.

2016-12-01

In the interpretation of data acquired using the Transient Electromagnetic Method (TEM), noise in the measurements from external sources, such as the power grid, spherics and radio transmitters and from internal sources in the TEM system itself is unavoidable. This noise lowers the data quality, and it is therefore desirable to know the noise conditions.Typically, the noise spectrum is measured one or more times during a survey with the transmitter turned off, i.e. with no TEM signal present.In production-mode, when the pulses of alternating signs are continually transmitted, the TEM signal contributes powerful, narrow spikes to the spectrum at the odd harmonics of the waveform repetition rate.In between these TEM-spikes, the noise spectrum is preserved. Using a simple interpolation method and an appropriate spectral estimation method, we show how to recover an estimate of the clean noise spectrum from short intervals of production-mode data.The resulting estimate can be used for in-field tailoring the data acquisition strategy to the present conditions, specifically gating scheme, stacking scheme and repetition rate, such that less noise enters the measurements.Another application is in the interpretation phase, where the noise level for each gate can be computed and used as input to the inversion code.

Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch

NASA Astrophysics Data System (ADS)

Williams, Z. R.; Pueschel, M. J.; Terry, P. W.; Hauff, T.

2017-12-01

The robustness and the effect of zonal flows in trapped electron mode (TEM) turbulence and Ion Temperature Gradient (ITG) turbulence in the reversed-field pinch (RFP) are investigated from numerical solutions of the gyrokinetic equations with and without magnetic external perturbations introduced to model tearing modes. For simulations without external magnetic field perturbations, zonal flows produce a much larger reduction of transport for the density-gradient-driven TEM turbulence than they do for the ITG turbulence. Zonal flows are studied in detail to understand the nature of their strong excitation in the RFP and to gain insight into the key differences between the TEM- and ITG-driven regimes. The zonal flow residuals are significantly larger in the RFP than in tokamak geometry due to the low safety factor. Collisionality is seen to play a significant role in the TEM zonal flow regulation through the different responses of the linear growth rate and the size of the Dimits shift to collisionality, while affecting the ITG only minimally. A secondary instability analysis reveals that the TEM turbulence drives zonal flows at a rate that is twice that of the ITG turbulence. In addition to interfering with zonal flows, the magnetic perturbations are found to obviate an energy scaling relation for fast particles.

A framework for the resilience of seagrass ecosystems.

PubMed

Unsworth, Richard K F; Collier, Catherine J; Waycott, Michelle; Mckenzie, Len J; Cullen-Unsworth, Leanne C

2015-11-15

Seagrass ecosystems represent a global marine resource that is declining across its range. To halt degradation and promote recovery over large scales, management requires a radical change in emphasis and application that seeks to enhance seagrass ecosystem resilience. In this review we examine how the resilience of seagrass ecosystems is becoming compromised by a range of local to global stressors, resulting in ecological regime shifts that undermine the long-term viability of these productive ecosystems. To examine regime shifts and the management actions that can influence this phenomenon we present a conceptual model of resilience in seagrass ecosystems. The model is founded on a series of features and modifiers that act as interacting influences upon seagrass ecosystem resilience. Improved understanding and appreciation of the factors and modifiers that govern resilience in seagrass ecosystems can be utilised to support much needed evidence based management of a vital natural resource. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optimal advanced credit releases in ecosystem service markets.

PubMed

BenDor, Todd K; Guo, Tianshu; Yates, Andrew J

2014-03-01

Ecosystem service markets are popular policy tools for ecosystem protection. Advanced credit releases are an important factor affecting the supply side of ecosystem markets. Under an advanced credit release policy, regulators give ecosystem suppliers a fraction of the total ecosystem credits generated by a restoration project before it is verified that the project actually achieves the required ecological thresholds. In spite of their prominent role in ecosystem markets, there is virtually no regulatory or research literature on the proper design of advanced credit release policies. Using U.S. aquatic ecosystem markets as an example, we develop a principal-agent model of the behavior of regulators and wetland/stream mitigation bankers to determine and explore the optimal degree of advance credit release. The model highlights the tension between regulators' desire to induce market participation, while at the same time ensuring that bankers successfully complete ecological restoration. Our findings suggest several simple guidelines for strengthening advanced credit release policy.

Optimal Advanced Credit Releases in Ecosystem Service Markets

NASA Astrophysics Data System (ADS)

BenDor, Todd K.; Guo, Tianshu; Yates, Andrew J.

2014-03-01

Ecosystem service markets are popular policy tools for ecosystem protection. Advanced credit releases are an important factor affecting the supply side of ecosystem markets. Under an advanced credit release policy, regulators give ecosystem suppliers a fraction of the total ecosystem credits generated by a restoration project before it is verified that the project actually achieves the required ecological thresholds. In spite of their prominent role in ecosystem markets, there is virtually no regulatory or research literature on the proper design of advanced credit release policies. Using U.S. aquatic ecosystem markets as an example, we develop a principal-agent model of the behavior of regulators and wetland/stream mitigation bankers to determine and explore the optimal degree of advance credit release. The model highlights the tension between regulators' desire to induce market participation, while at the same time ensuring that bankers successfully complete ecological restoration. Our findings suggest several simple guidelines for strengthening advanced credit release policy.

Modeling Hawaiian ecosystem degradation due to invasive plants under current and future climates

USGS Publications Warehouse

Vorsino, Adam E.; Fortini, Lucas B.; Amidon, Fred A.; Miller, Stephen E.; Jacobi, James D.; Price, Jonathan P.; `Ohukani`ohi`a Gon, Sam; Koob, Gregory A.

2014-01-01

Occupation of native ecosystems by invasive plant species alters their structure and/or function. In Hawaii, a subset of introduced plants is regarded as extremely harmful due to competitive ability, ecosystem modification, and biogeochemical habitat degradation. By controlling this subset of highly invasive ecosystem modifiers, conservation managers could significantly reduce native ecosystem degradation. To assess the invasibility of vulnerable native ecosystems, we selected a proxy subset of these invasive plants and developed robust ensemble species distribution models to define their respective potential distributions. The combinations of all species models using both binary and continuous habitat suitability projections resulted in estimates of species richness and diversity that were subsequently used to define an invasibility metric. The invasibility metric was defined from species distribution models with 0.8; True Skill Statistic >0.75) as evaluated per species. Invasibility was further projected onto a 2100 Hawaii regional climate change scenario to assess the change in potential habitat degradation. The distribution defined by the invasibility metric delineates areas of known and potential invasibility under current climate conditions and, when projected into the future, estimates potential reductions in native ecosystem extent due to climate-driven invasive incursion. We have provided the code used to develop these metrics to facilitate their wider use (Code S1). This work will help determine the vulnerability of native-dominated ecosystems to the combined threats of climate change and invasive species, and thus help prioritize ecosystem and species management actions.

Divergent patterns of experimental and model derived variables of tundra ecosystem carbon exchange in response to arctic warming

NASA Astrophysics Data System (ADS)

Schaedel, C.; Koven, C.; Celis, G.; Hutchings, J.; Lawrence, D. M.; Mauritz, M.; Pegoraro, E.; Salmon, V. G.; Taylor, M.; Wieder, W. R.; Schuur, E.

2017-12-01

Warming over the Arctic in the last decades has been twice as high as for the rest of the globe and has exposed large amounts of organic carbon to microbial decomposition in permafrost ecosystems. Continued warming and associated changes in soil moisture conditions not only lead to enhanced microbial decomposition from permafrost soil but also enhanced plant carbon uptake. Both processes impact the overall contribution of permafrost carbon dynamics to the global carbon cycle, yet field and modeling studies show large uncertainties in regard to both uptake and release mechanisms. Here, we compare variables associated with ecosystem carbon exchange (GPP: gross primary production; Reco: ecosystem respiration; and NEE: net ecosystem exchange) from eight years of experimental soil warming in moist acidic tundra with the same variables derived from an experimental model (Community Land Model version 4.5: CLM4.5) that simulates the same degree of arctic warming. While soil temperatures and thaw depths exhibited comparable increases with warming between field and model variables, carbon exchange related parameters showed divergent patterns. In the field non-linear responses to experimentally induced permafrost thaw were observed in GPP, Reco, and NEE. Indirect effects of continued soil warming and thaw created changes in soil moisture conditions causing ground surface subsidence and suppressing ecosystem carbon exchange over time. In contrast, the model predicted linear increases in GPP, Reco, and NEE with every year of warming turning the ecosystem into a net annual carbon sink. The field experiment revealed the importance of hydrology in carbon flux responses to permafrost thaw, a complexity that the model may fail to predict. Further parameterization of variables that drive GPP, Reco, and NEE in the model will help to inform and refine future model development.

When 1+1 can be >2: Uncertainties compound when simulating climate, fisheries and marine ecosystems

NASA Astrophysics Data System (ADS)

Evans, Karen; Brown, Jaclyn N.; Sen Gupta, Alex; Nicol, Simon J.; Hoyle, Simon; Matear, Richard; Arrizabalaga, Haritz

2015-03-01

Multi-disciplinary approaches that combine oceanographic, biogeochemical, ecosystem, fisheries population and socio-economic models are vital tools for modelling whole ecosystems. Interpreting the outputs from such complex models requires an appreciation of the many different types of modelling frameworks being used and their associated limitations and uncertainties. Both users and developers of particular model components will often have little involvement or understanding of other components within such modelling frameworks. Failure to recognise limitations and uncertainties associated with components and how these uncertainties might propagate throughout modelling frameworks can potentially result in poor advice for resource management. Unfortunately, many of the current integrative frameworks do not propagate the uncertainties of their constituent parts. In this review, we outline the major components of a generic whole of ecosystem modelling framework incorporating the external pressures of climate and fishing. We discuss the limitations and uncertainties associated with each component of such a modelling system, along with key research gaps. Major uncertainties in modelling frameworks are broadly categorised into those associated with (i) deficient knowledge in the interactions of climate and ocean dynamics with marine organisms and ecosystems; (ii) lack of observations to assess and advance modelling efforts and (iii) an inability to predict with confidence natural ecosystem variability and longer term changes as a result of external drivers (e.g. greenhouse gases, fishing effort) and the consequences for marine ecosystems. As a result of these uncertainties and intrinsic differences in the structure and parameterisation of models, users are faced with considerable challenges associated with making appropriate choices on which models to use. We suggest research directions required to address these uncertainties, and caution against overconfident predictions. Understanding the full impact of uncertainty makes it clear that full comprehension and robust certainty about the systems themselves are not feasible. A key research direction is the development of management systems that are robust to this unavoidable uncertainty.

Monitoring and modeling for investigating driver/pressure-state/impact relationships in coastal ecosystems: Examples from the Lagoon of Venice

NASA Astrophysics Data System (ADS)

Pastres, Roberto; Solidoro, Cosimo

2012-01-01

In this paper, we show how the integration of monitoring data and mathematical model can generate valuable information by using a few examples taken from a well studied but complex ecosystem, namely the Lagoon of Venice. We will focus on three key issues, which are of concern also for many other coastal ecosystems, namely: (1) Nitrogen and Phosphorus annual budgets; (2) estimation of Net Ecosystem Metabolism and early warnings for anoxic events; (3) assessment of ecosystem status. The results highlight the importance of framing monitoring activities within the "DPSIR" conceptual model, thus going far beyond the monitoring of major biogeochemical variables and including: (1) the estimation of the fluxes of the main constituents at the boundaries; (2) the use of appropriate mathematical models. These tools can provide quantitative links among Pressures and State/Impacts, thus enabling decision makers and stakeholders to evaluate the effects of alternative management scenarios.

Revisiting the choice of the driving temperature for eddy covariance CO2 flux partitioning

PubMed Central

Wohlfahrt, Georg; Galvagno, Marta

2017-01-01

So-called CO2 flux partitioning algorithms are widely used to partition the net ecosystem CO2 exchange into the two component fluxes, gross primary productivity and ecosystem respiration. Common CO2 flux partitioning algorithms conceptualize ecosystem respiration to originate from a single source, requiring the choice of a corresponding driving temperature. Using a conceptual dual-source respiration model, consisting of an above- and a below-ground respiration source each driven by a corresponding temperature, we demonstrate that the typical phase shift between air and soil temperature gives rise to a hysteresis relationship between ecosystem respiration and temperature. The hysteresis proceeds in a clockwise fashion if soil temperature is used to drive ecosystem respiration, while a counter-clockwise response is observed when ecosystem respiration is related to air temperature. As a consequence, nighttime ecosystem respiration is smaller than daytime ecosystem respiration when referenced to soil temperature, while the reverse is true for air temperature. We confirm these qualitative modelling results using measurements of day and night ecosystem respiration made with opaque chambers in a short-statured mountain grassland. Inferring daytime from nighttime ecosystem respiration or vice versa, as attempted by CO2 flux partitioning algorithms, using a single-source respiration model is thus an oversimplification resulting in biased estimates of ecosystem respiration. We discuss the likely magnitude of the bias, options for minimizing it and conclude by emphasizing that the systematic uncertainty of gross primary productivity and ecosystem respiration inferred through CO2 flux partitioning needs to be better quantified and reported. PMID:28439145

Linkages between terrestrial ecosystems and the atmosphere

NASA Technical Reports Server (NTRS)

Bretherton, Francis; Dickinson, Robert E.; Fung, Inez; Moore, Berrien, III; Prather, Michael; Running, Steven W.; Tiessen, Holm

1992-01-01

The primary research issue in understanding the role of terrestrial ecosystems in global change is analyzing the coupling between processes with vastly differing rates of change, from photosynthesis to community change. Representing this coupling in models is the central challenge to modeling the terrestrial biosphere as part of the earth system. Terrestrial ecosystems participate in climate and in the biogeochemical cycles on several temporal scales. Some of the carbon fixed by photosynthesis is incorporated into plant tissue and is delayed from returning to the atmosphere until it is oxidized by decomposition or fire. This slower (i.e., days to months) carbon loop through the terrestrial component of the carbon cycle, which is matched by cycles of nutrients required by plants and decomposers, affects the increasing trend in atmospheric CO2 concentration and imposes a seasonal cycle on that trend. Moreover, this cycle includes key controls over biogenic trace gas production. The structure of terrestrial ecosystems, which responds on even longer time scales (annual to century), is the integrated response to the biogeochemical and environmental constraints that develop over the intermediate time scale. The loop is closed back to the climate system since it is the structure of ecosystems, including species composition, that sets the terrestrial boundary condition in the climate system through modification of surface roughness, albedo, and, to a great extent, latent heat exchange. These separate temporal scales contain explicit feedback loops which may modify ecosystem dynamics and linkages between ecosystems and the atmosphere. The long-term change in climate, resulting from increased atmospheric concentrations of greenhouse gases (e.g., CO2, CH4, and nitrous oxide (N2O)) will further modify the global environment and potentially induce further ecosystem change. Modeling these interactions requires coupling successional models to biogeochemical models to physiological models that describe the exchange of water, energy, and biogenic trace gases between the vegetation and the atmosphere at fine time scales. There does not appear to be any obvious way to allow direct reciprocal coupling of atmospheric general circulation models (GCM's), which inherently run with fine time steps, to ecosystem or successional models, which have coarse temporal resolution, without the interposition of physiological canopy models. This is equally true for biogeochemical models of the exchange of carbon dioxide and trace gases. This coupling across time scales is nontrivial and sets the focus for the modeling strategy.

Evaluating Energy Flows Through Jellyfish and Forage Fish and the Effects of Fishing on the Northern Humboldt Current Ecosystem

NASA Astrophysics Data System (ADS)

Chiaverano, L.; Robinson, K. L.; Ruzicka, J.; Quiñones, J.; Tam, J.; Acha, M.; Graham, W. M.; Brodeur, R.; Decker, M. B.; Hernandez, F., Jr.; Leaf, R.; Mianzan, H.; Uye, S. I.

2016-02-01

Increases in the frequency of jellyfish mass occurrences in a number of coastal areas around the globe have intensified concerns that some ecosystems are becoming "jellyfish-dominated". Gelatinous planktivores not only compete with forage fish for food, but also feed on fish eggs and larvae. When jellyfish abundance is high, the fraction of the energy and the efficiency at which it is transferred upwards in the food web are reduced compared with times when fish are dominant. Hence, ecosystems supporting major forage fish fisheries are the most likely to experience fish-to-jellyfish shifts due to the harvest pressure on mid-trophic planktivores. Although forage fish-jellyfish replacement cycles have been detected in recent decades in some productive, coastal ecosystems (e.g. Gulf of Mexico, Northern California Current), jellyfish are typically not included in ecosystem-based fisheries management (EBFM) production models. Here we explored the roles of jellyfish and forage fish as trophic energy transfer pathways to higher trophic levels in the Northern Humboldt Current (NHC) ecosystem, one of the most productive ecosystems in the world. A trophic network model with 33 functional groups was developed using ECOPATH and transformed to an end-to-end model using ECOTRAN techniques to map food web energy flows. Predicted, relative changes in functional group productivity were analyzed in simulations with varying forage fish consumption rates, jellyfish consumption rates, and forage fish harvest rates in a suite of static, alternative-energy-demand scenarios. Our modeling efforts will not only improve EBFM of forage fish and their predators in the NHC ecosystem, but also increase our understanding of trophic interactions between forage fish and large jellyfish, an important, but overlooked component in most ecosystem models to date.

Model ecosystem evaluation of the environmental impacts of the veterinary drugs phenothiazine, sulfamethazine, clopidol, and diethylstilbestrol.

PubMed Central

Coats, J R; Metcalf, R L; Lu, P Y; Brown, D D; Williams, J F; Hansen, L G

1976-01-01

Four veterinary drugs of dissimilar chemical structures were evaluated for environmental stability and penchant for bioaccumulation. The techniques used were (1) a model aquatic ecosystem (3 days) and (2) a model feedlot ecosystem (33 days) in which the drugs were introduced via the excreta of chicks or mice. The model feedlot ecosystem was supported by metabolism cage studies to determine the amount and the form of the drug excreted by the chicks or mice. Considerable quantities of all the drugs were excreted intact or as environmentally short-lived conjugates. Diethylstilbestrol (DES) and Clopidol were the most persistent molecules, but only DES bioaccumulated to any appreciable degree. Phenothiazine was very biodegradable; sulfamethazine was relatively biodegradable and only accumulated in the organisms to very low levels. Data from the aquatic model ecosystem demonstrated a good correlation between the partition coefficients of the drugs and their accumulation in the fish. Images FIGURE 1. PMID:1037611

A framework for predicting impacts on ecosystem services from (sub)organismal responses to chemicals.

PubMed

Forbes, Valery E; Salice, Chris J; Birnir, Bjorn; Bruins, Randy J F; Calow, Peter; Ducrot, Virginie; Galic, Nika; Garber, Kristina; Harvey, Bret C; Jager, Henriette; Kanarek, Andrew; Pastorok, Robert; Railsback, Steve F; Rebarber, Richard; Thorbek, Pernille

2017-04-01

Protection of ecosystem services is increasingly emphasized as a risk-assessment goal, but there are wide gaps between current ecological risk-assessment endpoints and potential effects on services provided by ecosystems. The authors present a framework that links common ecotoxicological endpoints to chemical impacts on populations and communities and the ecosystem services that they provide. This framework builds on considerable advances in mechanistic effects models designed to span multiple levels of biological organization and account for various types of biological interactions and feedbacks. For illustration, the authors introduce 2 case studies that employ well-developed and validated mechanistic effects models: the inSTREAM individual-based model for fish populations and the AQUATOX ecosystem model. They also show how dynamic energy budget theory can provide a common currency for interpreting organism-level toxicity. They suggest that a framework based on mechanistic models that predict impacts on ecosystem services resulting from chemical exposure, combined with economic valuation, can provide a useful approach for informing environmental management. The authors highlight the potential benefits of using this framework as well as the challenges that will need to be addressed in future work. Environ Toxicol Chem 2017;36:845-859. © 2017 SETAC. © 2017 SETAC.

Nucleation and Growth of Crystalline Grains in RF-Sputtered TiO 2 Films

DOE PAGES

Johnson, J. C.; Ahrenkiel, S. P.; Dutta, P.; ...

2009-01-01

Amore » morphous TiO 2 thin films were radio frequency sputtered onto siliconmonoxide and carbon support films on molybdenum transmission electron microscope (TEM) grids and observed during in situ annealing in a TEM heating stage at 250 ∘ C. The evolution of crystallization is consistent with a classical model of homogeneous nucleation and isotropic grain growth. The two-dimensional grain morphology of the TEM foil allowed straightforward recognition of amorphous and crystallized regions of the films, for measurement of crystalline volume fraction and grain number density. By assuming that the kinetic parameters remain constant beyond the onset of crystallization, the final average grain size was computed, using an analytical extrapolation to the fully crystallized state. Electron diffraction reveals a predominance of the anatase crystallographic phase.« less

Structural properties of GaAsN grown on (001) GaAs by metalorganic molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ok, Young-Woo; Choi, Chel-Jong; Seong, Tae-Yeon; Uesugi, K.; Suemune, I.

2001-07-01

Detailed transmission electron microscopy (TEM) and transmission electron diffraction (TED) examination has been made of metalorganic molecular beam epitaxial GaAsN layers grown on (001) GaAs substrates. TEM results show that lateral composition modulation occurs in the GaAs1-xNx layer (x 6.75%). It is shown that increasing N composition and Se (dopant) concentration leads to poor crystallinity. It is also shown that the addition of Se increases N composition. Atomic force microscopy (AFM) results show that the surfaces of the samples experience a morphological change from faceting to islanding, as the N composition and Se concentration increase. Based on the TEM and AFM results, a simple model is given to explain the formation of the lateral composition modulation.

An online database for informing ecological network models: http://kelpforest.ucsc.edu.

PubMed

Beas-Luna, Rodrigo; Novak, Mark; Carr, Mark H; Tinker, Martin T; Black, August; Caselle, Jennifer E; Hoban, Michael; Malone, Dan; Iles, Alison

2014-01-01

Ecological network models and analyses are recognized as valuable tools for understanding the dynamics and resiliency of ecosystems, and for informing ecosystem-based approaches to management. However, few databases exist that can provide the life history, demographic and species interaction information necessary to parameterize ecological network models. Faced with the difficulty of synthesizing the information required to construct models for kelp forest ecosystems along the West Coast of North America, we developed an online database (http://kelpforest.ucsc.edu/) to facilitate the collation and dissemination of such information. Many of the database's attributes are novel yet the structure is applicable and adaptable to other ecosystem modeling efforts. Information for each taxonomic unit includes stage-specific life history, demography, and body-size allometries. Species interactions include trophic, competitive, facilitative, and parasitic forms. Each data entry is temporally and spatially explicit. The online data entry interface allows researchers anywhere to contribute and access information. Quality control is facilitated by attributing each entry to unique contributor identities and source citations. The database has proven useful as an archive of species and ecosystem-specific information in the development of several ecological network models, for informing management actions, and for education purposes (e.g., undergraduate and graduate training). To facilitate adaptation of the database by other researches for other ecosystems, the code and technical details on how to customize this database and apply it to other ecosystems are freely available and located at the following link (https://github.com/kelpforest-cameo/databaseui).

An Online Database for Informing Ecological Network Models: http://kelpforest.ucsc.edu

PubMed Central

Beas-Luna, Rodrigo; Novak, Mark; Carr, Mark H.; Tinker, Martin T.; Black, August; Caselle, Jennifer E.; Hoban, Michael; Malone, Dan; Iles, Alison

2014-01-01

Ecological network models and analyses are recognized as valuable tools for understanding the dynamics and resiliency of ecosystems, and for informing ecosystem-based approaches to management. However, few databases exist that can provide the life history, demographic and species interaction information necessary to parameterize ecological network models. Faced with the difficulty of synthesizing the information required to construct models for kelp forest ecosystems along the West Coast of North America, we developed an online database (http://kelpforest.ucsc.edu/) to facilitate the collation and dissemination of such information. Many of the database's attributes are novel yet the structure is applicable and adaptable to other ecosystem modeling efforts. Information for each taxonomic unit includes stage-specific life history, demography, and body-size allometries. Species interactions include trophic, competitive, facilitative, and parasitic forms. Each data entry is temporally and spatially explicit. The online data entry interface allows researchers anywhere to contribute and access information. Quality control is facilitated by attributing each entry to unique contributor identities and source citations. The database has proven useful as an archive of species and ecosystem-specific information in the development of several ecological network models, for informing management actions, and for education purposes (e.g., undergraduate and graduate training). To facilitate adaptation of the database by other researches for other ecosystems, the code and technical details on how to customize this database and apply it to other ecosystems are freely available and located at the following link (https://github.com/kelpforest-cameo/databaseui). PMID:25343723

Development of the BIOME-BGC model for the simulation of managed Moso bamboo forest ecosystems.

PubMed

Mao, Fangjie; Li, Pingheng; Zhou, Guomo; Du, Huaqiang; Xu, Xiaojun; Shi, Yongjun; Mo, Lufeng; Zhou, Yufeng; Tu, Guoqing

2016-05-01

Numerical models are the most appropriate instrument for the analysis of the carbon balance of terrestrial ecosystems and their interactions with changing environmental conditions. The process-based model BIOME-BGC is widely used in simulation of carbon balance within vegetation, litter and soil of unmanaged ecosystems. For Moso bamboo forests, however, simulations with BIOME-BGC are inaccurate in terms of the growing season and the carbon allocation, due to the oversimplified representation of phenology. Our aim was to improve the applicability of BIOME-BGC for managed Moso bamboo forest ecosystem by implementing several new modules, including phenology, carbon allocation, and management. Instead of the simple phenology and carbon allocation representations in the original version, a periodic Moso bamboo phenology and carbon allocation module was implemented, which can handle the processes of Moso bamboo shooting and high growth during "on-year" and "off-year". Four management modules (digging bamboo shoots, selective cutting, obtruncation, fertilization) were integrated in order to quantify the functioning of managed ecosystems. The improved model was calibrated and validated using eddy covariance measurement data collected at a managed Moso bamboo forest site (Anji) during 2011-2013 years. As a result of these developments and calibrations, the performance of the model was substantially improved. Regarding the measured and modeled fluxes (gross primary production, total ecosystem respiration, net ecosystem exchange), relative errors were decreased by 42.23%, 103.02% and 18.67%, respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

An online database for informing ecological network models: http://kelpforest.ucsc.edu

USGS Publications Warehouse

Beas-Luna, Rodrigo; Tinker, M. Tim; Novak, Mark; Carr, Mark H.; Black, August; Caselle, Jennifer E.; Hoban, Michael; Malone, Dan; Iles, Alison C.

2014-01-01

Ecological network models and analyses are recognized as valuable tools for understanding the dynamics and resiliency of ecosystems, and for informing ecosystem-based approaches to management. However, few databases exist that can provide the life history, demographic and species interaction information necessary to parameterize ecological network models. Faced with the difficulty of synthesizing the information required to construct models for kelp forest ecosystems along the West Coast of North America, we developed an online database (http://kelpforest.ucsc.edu/) to facilitate the collation and dissemination of such information. Many of the database's attributes are novel yet the structure is applicable and adaptable to other ecosystem modeling efforts. Information for each taxonomic unit includes stage-specific life history, demography, and body-size allometries. Species interactions include trophic, competitive, facilitative, and parasitic forms. Each data entry is temporally and spatially explicit. The online data entry interface allows researchers anywhere to contribute and access information. Quality control is facilitated by attributing each entry to unique contributor identities and source citations. The database has proven useful as an archive of species and ecosystem-specific information in the development of several ecological network models, for informing management actions, and for education purposes (e.g., undergraduate and graduate training). To facilitate adaptation of the database by other researches for other ecosystems, the code and technical details on how to customize this database and apply it to other ecosystems are freely available and located at the following link (https://github.com/kelpforest-cameo/data​baseui).

A quantitative assessment of a terrestrial biosphere model's data needs across North American biomes

NASA Astrophysics Data System (ADS)

Dietze, Michael C.; Serbin, Shawn P.; Davidson, Carl; Desai, Ankur R.; Feng, Xiaohui; Kelly, Ryan; Kooper, Rob; LeBauer, David; Mantooth, Joshua; McHenry, Kenton; Wang, Dan

2014-03-01

Terrestrial biosphere models are designed to synthesize our current understanding of how ecosystems function, test competing hypotheses of ecosystem function against observations, and predict responses to novel conditions such as those expected under climate change. Reducing uncertainties in such models can improve both basic scientific understanding and our predictive capacity, but rarely are ecosystem models employed in the design of field campaigns. We provide a synthesis of carbon cycle uncertainty analyses conducted using the Predictive Ecosystem Analyzer ecoinformatics workflow with the Ecosystem Demography model v2. This work is a synthesis of multiple projects, using Bayesian data assimilation techniques to incorporate field data and trait databases across temperate forests, grasslands, agriculture, short rotation forestry, boreal forests, and tundra. We report on a number of data needs that span a wide array of diverse biomes, such as the need for better constraint on growth respiration, mortality, stomatal conductance, and water uptake. We also identify data needs that are biome specific, such as photosynthetic quantum efficiency at high latitudes. We recommend that future data collection efforts balance the bias of past measurements toward aboveground processes in temperate biomes with the sensitivities of different processes as represented by ecosystem models. ©2014. American Geophysical Union. All Rights Reserved.

Biological data assimilation for parameter estimation of a phytoplankton functional type model for the western North Pacific

NASA Astrophysics Data System (ADS)

Hoshiba, Yasuhiro; Hirata, Takafumi; Shigemitsu, Masahito; Nakano, Hideyuki; Hashioka, Taketo; Masuda, Yoshio; Yamanaka, Yasuhiro

2018-06-01

Ecosystem models are used to understand ecosystem dynamics and ocean biogeochemical cycles and require optimum physiological parameters to best represent biological behaviours. These physiological parameters are often tuned up empirically, while ecosystem models have evolved to increase the number of physiological parameters. We developed a three-dimensional (3-D) lower-trophic-level marine ecosystem model known as the Nitrogen, Silicon and Iron regulated Marine Ecosystem Model (NSI-MEM) and employed biological data assimilation using a micro-genetic algorithm to estimate 23 physiological parameters for two phytoplankton functional types in the western North Pacific. The estimation of the parameters was based on a one-dimensional simulation that referenced satellite data for constraining the physiological parameters. The 3-D NSI-MEM optimized by the data assimilation improved the timing of a modelled plankton bloom in the subarctic and subtropical regions compared to the model without data assimilation. Furthermore, the model was able to improve not only surface concentrations of phytoplankton but also their subsurface maximum concentrations. Our results showed that surface data assimilation of physiological parameters from two contrasting observatory stations benefits the representation of vertical plankton distribution in the western North Pacific.

Abundance of antibiotic resistance genes and bacterial community composition in wild freshwater fish species.

PubMed

Marti, Elisabet; Huerta, Belinda; Rodríguez-Mozaz, Sara; Barceló, Damià; Marcé, Rafael; Balcázar, Jose Luis

2018-04-01

This study was aimed to determine the abundance of four antibiotic resistance genes (bla TEM , ermB, qnrS and sulI), as well as bacterial community composition associated with the intestinal mucus of wild freshwater fish species collected from the Foix and La Llosa del Cavall reservoirs, which represent ecosystems with high and low anthropogenic disturbance, respectively. Water and sediments from these reservoirs were also collected and analyzed to determine the pollution level by antibiotics. The bla TEM gene was only detected in brown trout and Ebro barbel, which were collected from La Llosa del Cavall reservoir. In contrast, the sulI and qnrS genes were only detected in common carp, which were collected from the Foix reservoir. Although the ermB gene was also detected in common carp, the values were below the limit of quantification. Likewise, water and sediment samples from the Foix reservoir had higher concentrations and more classes of antibiotics than those from La Llosa del Cavall. Pyrosequencing analysis of 16S rRNA genes revealed significant differences in bacterial communities associated with the intestinal mucus of fish species. Therefore, these findings suggest that anthropogenic activities are not only increasing the pollution of aquatic environments, but also contributing to the emergence and spread of antibiotic resistance in organisms that inhabit such environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

EcoPAD, an interactive platform for near real-time ecological forecasting by assimilating data into model

NASA Astrophysics Data System (ADS)

MA, S.; Huang, Y.; Stacy, M.; Jiang, J.; Sundi, N.; Ricciuto, D. M.; Hanson, P. J.; Luo, Y.; Saruta, V.

2017-12-01

Ecological forecasting is critical in various aspects of our coupled human-nature systems, such as disaster risk reduction, natural resource management and climate change mitigation. Novel advancements are in urgent need to deepen our understandings of ecosystem dynamics, boost the predictive capacity of ecology, and provide timely and effective information for decision-makers in a rapidly changing world. Our study presents a smart system - Ecological Platform for Assimilation of Data (EcoPAD) - which streamlines web request-response, data management, model execution, result storage and visualization. EcoPAD allows users to (i) estimate model parameters or state variables, (ii) quantify uncertainty of estimated parameters and projected states of ecosystems, (iii) evaluate model structures, (iv) assess sampling strategies, (v) conduct ecological forecasting, and (vi) detect ecosystem acclimation to climate change. One of the key innovations of the web-based EcoPAD is the automated near- or real-time forecasting of ecosystem dynamics with uncertainty fully quantified. The user friendly webpage enables non-modelers to explore their data for simulation and data assimilation. As a case study, we applied EcoPAD to the Spruce and Peatland Responses Under Climatic and Environmental Change Experiment (SPRUCE), a whole ecosystem warming and CO2 enrichment treatment project in the northern peatland, assimilated multiple data streams into a process based ecosystem model, enhanced timely feedback between modelers and experimenters, ultimately improved ecosystem forecasting and made better use of current knowledge. Built in a framework with flexible API, EcoPAD is easily portable and will benefit scientific communities, policy makers as well as the general public.

Linking land use change to recreational fishery valuation with a spatially explicit behavior model: A case study from Tampa Bay, FL USA

EPA Science Inventory

Drawing a link between habitat change and production and delivery of ecosystem services is a priority in coastal estuarine ecosystems. This link is needed to fully understand how human communities can influence ecosystem sustainability. Mechanistic modeling tools are highly fun...

Mechanistic models as a transferable framework for projecting effects of habitat change on production and delivery of ecosystem services

EPA Science Inventory

Drawing a link between habitat change and the production and delivery of ecosystem services is a priority in coastal estuarine ecosystems. Mechanistic modeling tools are highly functional for exploring this link because they allow for the synthesis of multiple ecological and beh...

Knowledge Management in Preserving Ecosystems: The Case of Seoul

ERIC Educational Resources Information Center

Lee, Jeongseok

2009-01-01

This study explores the utility of employing knowledge management as a framework for understanding how public managers perform ecosystem management. It applies the grounded theory method to build a model. The model is generated by applying the concept of knowledge process to an investigation of how the urban ecosystem is publicly managed by civil…

A general predictive model for estimating monthly ecosystem evapotranspiration

Treesearch

Ge Sun; Karrin Alstad; Jiquan Chen; Shiping Chen; Chelcy R. Ford; al. et.

2011-01-01

Accurately quantifying evapotranspiration (ET) is essential for modelling regional-scale ecosystem water balances. This study assembled an ET data set estimated from eddy flux and sapflow measurements for 13 ecosystems across a large climatic and management gradient from the United States, China, and Australia. Our objectives were to determine the relationships among...

Using Ecosystem Experiments to Improve Vegetation Models

DOE PAGES

Medlyn, Belinda; Zaehle, S; DeKauwe, Martin G.; ...

2015-05-21

Ecosystem responses to rising CO2 concentrations are a major source of uncertainty in climate change projections. Data from ecosystem-scale Free-Air CO2 Enrichment (FACE) experiments provide a unique opportunity to reduce this uncertainty. The recent FACE Model–Data Synthesis project aimed to use the information gathered in two forest FACE experiments to assess and improve land ecosystem models. A new 'assumption-centred' model intercomparison approach was used, in which participating models were evaluated against experimental data based on the ways in which they represent key ecological processes. Identifying and evaluating the main assumptions caused differences among models, and the assumption-centered approach produced amore » clear roadmap for reducing model uncertainty. We explain this approach and summarize the resulting research agenda. We encourage the application of this approach in other model intercomparison projects to fundamentally improve predictive understanding of the Earth system.« less

Using an ecosystem service decision support tool to support ridge to reef management: An example of sediment reduction in west Maui, Hawaii

NASA Astrophysics Data System (ADS)

Falinski, K. A.; Oleson, K.; Htun, H.; Kappel, C.; Lecky, J.; Rowe, C.; Selkoe, K.; White, C.

2016-12-01

Faced with anthropogenic stressors and declining coral reef states, managers concerned with restoration and resilience of coral reefs are increasingly recognizing the need to take a ridge-to-reef, ecosystem-based approach. An ecosystem services framing can help managers move towards these goals, helping to illustrate trade-offs and opportunities of management actions in terms of their impacts on society. We describe a research program building a spatial ecosystem services-based decision-support tool, and being applied to guide ridge-to-reef management in a NOAA priority site in West Maui. We use multiple modeling methods to link biophysical processes to ecosystem services and their spatial flows and social values in an integrating platform. Modeled services include water availability, sediment retention, nutrient retention and carbon sequestration on land. A coral reef ecosystem service model is under development to capture the linkages between terrestrial and coastal ecosystem services. Valuation studies are underway to quantify the implications for human well-being. The tool integrates techniques from decision science to facilitate decision making. We use the sediment retention model to illustrate the types of analyses the tool can support. The case study explores the tradeoffs between road rehabilitation costs and sediment export avoided. We couple the sediment and cost models with trade-off analysis to identify optimal distributed solutions that are most cost-effective in reducing erosion, and then use those models to estimate sediment exposure to coral reefs. We find that cooperation between land owners reveals opportunities for maximizing the benefits of fixing roads and minimizes costs. This research forms the building blocks of an ecosystem service decision support tool that we intend to continue to test and apply in other Pacific Island settings.

Diversity of Cultivable Methane-Oxidizing Bacteria in Microsites of a Rice Paddy Field: Investigation by Cultivation Method and Fluorescence in situ Hybridization (FISH)

PubMed Central

Dianou, Dayéri; Ueno, Chihoko; Ogiso, Takuya; Kimura, Makoto; Asakawa, Susumu

2012-01-01

The diversity of cultivable methane-oxidizing bacteria (MOB) in the rice paddy field ecosystem was investigated by combined culture-dependent and fluorescence in situ hybridization (FISH) techniques. Seven microsites of a Japanese rice paddy field were the focus of the study: floodwater, surface soil, bulk soil, rhizosphere soil, root, basal stem of rice plant, and rice stumps of previous harvest. Based on pmoA gene analysis and transmission electron microscopy (TEM), four type I, and nine type II MOB isolates were obtained from the highest dilution series of enrichment cultures. The type I MOB isolates included a novel species in the genus Methylomonas from floodwater and this is the first type I MOB strain isolated from floodwater of a rice paddy field. In the type I MOB, two isolates from stumps were closely related to Methylomonas spp.; one isolate obtained from rhizosphere soil was most related to Methyloccocus-Methylocaldum-Methylogaea clade. Almost all the type II MOB isolates were related to Methylocystis methanotrophs. FISH confirmed the presence of both types I and II MOB in all the microsites and in the related enrichment cultures. The study reported, for the first time, the diversity of cultivable methanotrophs including a novel species of type I MOB in rice paddy field compartments. Refining growth media and culture conditions, in combination with molecular approaches, will allow us to broaden our knowledge on the MOB community in the rice paddy field ecosystem and consequently to implement strategies for mitigating CH4 emission from this ecosystem. PMID:22446309

Modeling Global Biogenic Emission of Isoprene: Exploration of Model Drivers

NASA Technical Reports Server (NTRS)

Alexander, Susan E.; Potter, Christopher S.; Coughlan, Joseph C.; Klooster, Steven A.; Lerdau, Manuel T.; Chatfield, Robert B.; Peterson, David L. (Technical Monitor)

1996-01-01

Vegetation provides the major source of isoprene emission to the atmosphere. We present a modeling approach to estimate global biogenic isoprene emission. The isoprene flux model is linked to a process-based computer simulation model of biogenic trace-gas fluxes that operates on scales that link regional and global data sets and ecosystem nutrient transformations Isoprene emission estimates are determined from estimates of ecosystem specific biomass, emission factors, and algorithms based on light and temperature. Our approach differs from an existing modeling framework by including the process-based global model for terrestrial ecosystem production, satellite derived ecosystem classification, and isoprene emission measurements from a tropical deciduous forest. We explore the sensitivity of model estimates to input parameters. The resulting emission products from the global 1 degree x 1 degree coverage provided by the satellite datasets and the process model allow flux estimations across large spatial scales and enable direct linkage to atmospheric models of trace-gas transport and transformation.

PICUS v1.6 - enhancing the water cycle within a hybrid ecosystem model to assess the provision of drinking water in a changing climate

NASA Astrophysics Data System (ADS)

Schimmel, A.; Rammer, W.; Lexer, M. J.

2012-04-01

The PICUS model is a hybrid ecosystem model which is based on a 3D patch model and a physiological stand level production model. The model includes, among others, a submodel of bark beetle disturbances in Norway spruce and a management module allowing any silvicultural treatment to be mimicked realistically. It has been tested intensively for its ability to realistically reproduce tree growth and stand dynamics in complex structured mixed and mono-species temperate forest ecosystems. In several applications the models capacity to generate relevant forest related attributes which were subsequently fed into indicator systems to assess sustainable forest management under current and future climatic conditions has been proven. However, the relatively coarse monthly temporal resolution of the driving climate data as well as the process resolution of the major water relations within the simulated ecosystem hampered the inclusion of more detailed physiologically based assessments of drought conditions and water provisioning ecosystem services. In this contribution we present the improved model version PICUS v1.6 focusing on the newly implemented logic for the water cycle calculations. Transpiration, evaporation from leave surfaces and the forest floor, snow cover and snow melt as well as soil water dynamics in several soil horizons are covered. In enhancing the model overarching goal was to retain the large-scale applicability by keeping the input requirements to a minimum while improving the physiological foundation of water related ecosystem processes. The new model version is tested against empirical time series data. Future model applications are outlined.

Assimilation of Leaf and Canopy Spectroscopic Data to Improve the Representation of Vegetation Dynamics in Terrestrial Ecosystem Models

NASA Astrophysics Data System (ADS)

Serbin, S. P.; Dietze, M.; Desai, A. R.; LeBauer, D.; Viskari, T.; Kooper, R.; McHenry, K. G.; Townsend, P. A.

2013-12-01

The ability to seamlessly integrate information on vegetation structure and function across a continuum of scales, from field to satellite observations, greatly enhances our ability to understand how terrestrial vegetation-atmosphere interactions change over time and in response to disturbances. In particular, terrestrial ecosystem models require detailed information on ecosystem states and canopy properties in order to properly simulate the fluxes of carbon (C), water and energy from the land to the atmosphere as well as address the vulnerability of ecosystems to environmental and other perturbations. Over the last several decades the amount of available data to constrain ecological predictions has increased substantially, resulting in a progressively data-rich era for global change research. In particular remote sensing data, specifically optical data (leaf and canopy), offers the potential for an important and direct data constraint on ecosystem model projections of C and energy fluxes. Here we highlight the utility of coupling information provided through the Ecosystem Spectral Information System (EcoSIS) with complex process models through the Predictive Ecosystem Analyzer (PEcAn; http://www.pecanproject.org/) eco-informatics framework as a means to improve the description of canopy optical properties, vegetation composition, and modeled radiation balance. We also present this an efficient approach for understanding and correcting implicit assumptions and model structural deficiencies. We first illustrate the challenges and issues in adequately characterizing ecosystem fluxes with the Ecosystem Demography model (ED2, Medvigy et al., 2009) due to improper parameterization of leaf and canopy properties, as well as assumptions describing radiative transfer within the canopy. ED2 is especially relevant to these efforts because it contains a sophisticated structure for scaling ecological processes across a range of spatial scales: from the tree-level (demography, physiology) to the distribution of stands across a landscape, which allows for the direct use of remotely sensed data at the appropriate spatial scale. A sensitivity analysis is employed within PEcAn to illustrate the influence of ED2 parameterizations on modeled C and energy fluxes for a northern temperate forest ecosystem as an example of the need for more detailed information on leaf and canopy optical properties. We then demonstrate a data assimilation approach to synthesize spectral data contained within EcoSIS in order to update model parameterizations across key vegetation plant functional types, as well as a means to update vegetation state information (i.e. composition, LAI) and improve the description of radiation transfer through model structural updates. A better understanding of the radiation balance of ecosystems will improve regional and global scale C and energy balance projections.

Response to comments by Adam Smiarowski and Shane Mulè on: Christensen, N., and Lawrie, K., 2012. Resolution analyses for selecting an appropriate airborne electromagnetic (AEM) system, Exploration Geophysics, 43, 213-227

NASA Astrophysics Data System (ADS)

Christensen, Niels B.; Lawrie, Ken

2015-06-01

We analyse and compare the resolution improvement that can be obtained from including x-component data in the inversion of AEM data from the SkyTEM and TEMPEST systems. Except for the resistivity of the bottom layer, the SkyTEM system, even without including x-component data, has the better resolution of the parameters of the analysed models.

Tampa Bay Ecosystem Services Demonstration Project Website: Phase II

EPA Science Inventory

The Tampa Bay Ecosystem Services Demonstration Project models the impact of human development and natural stressors on the economic, aesthetic and cultural value of local ecosystems. By linking ecological structures, functions, and condition to the ecosystem services valued by h...

HUMAN-ECOSYSTEM INTERACTIONS: THE CASE OF MERCURY

EPA Science Inventory

Human and ecosystem exposure studies evaluate exposure of sensitive and vulnerable populations. We will discuss how ecosystem exposure modeling studies completed for input into the US Clean Air Mercury Rule (CAMR) to evaluate the response of aquatic ecosystems to changes in mercu...

Human - Ecosystem Interactions: The Case of Mercury

EPA Science Inventory

Human and ecosystem exposure studies evaluate exposure of sensitive and vulnerable populations. We will discuss how ecosystem exposure modeling studies completed for input into the US Clean Air Mercury Rule (CAMR) to evaluate the response of aquatic ecosystems to changes in mercu...

Disentangling the effects of climate variability and functional change on ecosystem carbon dynamics using semi-empirical modelling

NASA Astrophysics Data System (ADS)

Wu, J.; van der Linden, L.; Lasslop, G.; Carvalhais, N.; Pilegaard, K.; Beier, C.; Ibrom, A.

2012-04-01

The ecosystem carbon balance is affected by both external climatic forcing (e.g. solar radiation, air temperature and humidity) and internal dynamics in the ecosystem functional properties (e.g. canopy structure, leaf photosynthetic capacity and carbohydrate reserve). In order to understand to what extent and at which temporal scale, climatic variability and functional changes regulated the interannual variation (IAV) in the net ecosystem exchange of CO2 (NEE), data-driven analysis and semi-empirical modelling (Lasslop et al. 2010) were performed based on a 13 year NEE record in a temperate deciduous forest (Pilegaard et al 2011, Wu et al. 2012). We found that the sensitivity of carbon fluxes to climatic variability was significantly higher at shorter than at longer time scales and changed seasonally. This implied that the changing distribution of climate anomalies during the vegetation period could have stronger impacts on future ecosystem carbon balances than changes in average climate. At the annual time scale, approximately 80% of the interannual variability in NEE was attributed to the variation in the model parameters, indicating the observed IAV in the carbon dynamics at the investigated site was dominated by changes in ecosystem functioning. In general this study showed the need for understanding the mechanisms of ecosystem functional change. The method can be applied at other sites to explore ecosystem behavior across different plant functional types and climate gradients. Incorporating ecosystem functional change into process based models will reduce the uncertainties in long-term predictions of ecosystem carbon balances in global climate change projections. Acknowledgements. This work was supported by the EU FP7 project CARBO-Extreme, the DTU Climate Centre and the Danish national project ECOCLIM (Danish Council for Strategic Research).

Using the CARDAMOM framework to retrieve global terrestrial ecosystem functioning properties

NASA Astrophysics Data System (ADS)

Exbrayat, Jean-François; Bloom, A. Anthony; Smallman, T. Luke; van der Velde, Ivar R.; Feng, Liang; Williams, Mathew

2016-04-01

Terrestrial ecosystems act as a sink for anthropogenic emissions of fossil-fuel and thereby partially offset the ongoing global warming. However, recent model benchmarking and intercomparison studies have highlighted the non-trivial uncertainties that exist in our understanding of key ecosystem properties like plant carbon allocation and residence times. It leads to worrisome differences in terrestrial carbon stocks simulated by Earth system models, and their evolution in a warming future. In this presentation we attempt to provide global insights on these properties by merging an ecosystem model with remotely-sensed global observations of leaf area and biomass through a data-assimilation system: the CARbon Data MOdel fraMework (CARDAMOM). CARDAMOM relies on a Markov Chain Monte Carlo algorithm to retrieve confidence intervals of model parameters that regulate ecosystem properties independently of any prior land-cover information. The MCMC method thereby enables an explicit representation of the uncertainty in land-atmosphere fluxes and the evolution of terrestrial carbon stocks through time. Global experiments are performed for the first decade of the 21st century using a 1°×1° spatial resolution. Relationships emerge globally between key ecosystem properties. For example, our analyses indicate that leaf lifespan and leaf mass per area are highly correlated. Furthermore, there exists a latitudinal gradient in allocation patterns: high latitude ecosystems allocate more carbon to photosynthetic carbon (leaves) while plants invest more carbon in their structural parts (wood and root) in the wet tropics. Overall, the spatial distribution of these ecosystem properties does not correspond to usual land-cover maps and are also partially correlated with disturbance regimes. For example, fire-prone ecosystems present statistically significant higher values of carbon use efficiency than less disturbed ecosystems experiencing similar climatic conditions. These results raise concerns on the suitability of the plant functional type paradigm for terrestrial carbon cycling.

Ecosystem services sustainability in the Mediterranean Sea: assessment of status and trends using multiple modelling approaches

NASA Astrophysics Data System (ADS)

Liquete, Camino; Piroddi, Chiara; Macías, Diego; Druon, Jean-Noël; Zulian, Grazia

2016-09-01

Mediterranean ecosystems support important processes and functions that bring direct benefits to human society. Yet, marine ecosystem services are usually overlooked due to the challenges in identifying and quantifying them. This paper proposes the application of several biophysical and ecosystem modelling approaches to assess spatially and temporally the sustainable use and supply of selected marine ecosystem services. Such services include food provision, water purification, coastal protection, lifecycle maintenance and recreation, focusing on the Mediterranean region. Overall, our study found a higher number of decreasing than increasing trends in the natural capacity of the ecosystems to provide marine and coastal services, while in contrast the opposite was observed to be true for the realised flow of services to humans. Such a study paves the way towards an effective support for Blue Growth and the European maritime policies, although little attention is paid to the quantification of marine ecosystem services in this context. We identify a key challenge of integrating biophysical and socio-economic models as a necessary step to further this research.

Ecosystem services sustainability in the Mediterranean Sea: assessment of status and trends using multiple modelling approaches

PubMed Central

Liquete, Camino; Piroddi, Chiara; Macías, Diego; Druon, Jean-Noël; Zulian, Grazia

2016-01-01

Mediterranean ecosystems support important processes and functions that bring direct benefits to human society. Yet, marine ecosystem services are usually overlooked due to the challenges in identifying and quantifying them. This paper proposes the application of several biophysical and ecosystem modelling approaches to assess spatially and temporally the sustainable use and supply of selected marine ecosystem services. Such services include food provision, water purification, coastal protection, lifecycle maintenance and recreation, focusing on the Mediterranean region. Overall, our study found a higher number of decreasing than increasing trends in the natural capacity of the ecosystems to provide marine and coastal services, while in contrast the opposite was observed to be true for the realised flow of services to humans. Such a study paves the way towards an effective support for Blue Growth and the European maritime policies, although little attention is paid to the quantification of marine ecosystem services in this context. We identify a key challenge of integrating biophysical and socio-economic models as a necessary step to further this research. PMID:27686533

Reducing the uncertainty in the projection of the terrestrial carbon cycle by fusing models with remote sensing data

NASA Astrophysics Data System (ADS)

Serbin, S.; Shiklomanov, A. N.; Viskari, T.; Desai, A. R.; Townsend, P. A.; Dietze, M.

2015-12-01

Modeling global change requires accurate representation of terrestrial carbon (C), energy and water fluxes. In particular, capturing the properties of vegetation canopies that describe the radiation regime are a key focus for global change research because the properties related to radiation utilization and penetration within plant canopies provide an important constraint on terrestrial ecosystem productivity, as well as the fluxes of water and energy from vegetation to the atmosphere. As such, optical remote sensing observations present an important, and as yet relatively untapped, source of observations that can be used to inform modeling activities. In particular, high-spectral resolution optical data at the leaf and canopy scales offers the potential for an important and direct data constraint on the parameterization and structure of the radiative transfer model (RTM) scheme within ecosystem models across diverse vegetation types, disturbance and management histories. In this presentation we highlight ongoing work to integrate optical remote sensing observations, specifically leaf and imaging spectroscopy (IS) data across a range of forest ecosystems, into complex ecosystem process models within an efficient computational assimilation framework as a means to improve the description of canopy optical properties, vegetation composition, and modeled radiation balance. Our work leverages the Predictive Ecosystem Analyzer (PEcAn; http://www.pecanproject.org/) ecoinformatics toolbox together with a RTM module designed for efficient assimilation of leaf and IS observations to inform vegetation optical properties as well as associated plant traits. Ultimately, an improved understanding of the radiation balance of ecosystems will provide a better constraint on model projections of energy balance, vegetation composition, and carbon pools and fluxes thus allowing for a better diagnosis of the vulnerability of terrestrial ecosystems in response to global change.

Linking ecosystem services with state-and-transition models to evaluate rangeland management decisions

NASA Astrophysics Data System (ADS)

Lohani, S.; Heilman, P.; deSteiguer, J. E.; Guertin, D. P.; Wissler, C.; McClaran, M. P.

2014-12-01

Quantifying ecosystem services is a crucial topic for land management decision making. However, market prices are usually not able to capture all the ecosystem services and disservices. Ecosystem services from rangelands, that cover 70% of the world's land area, are even less well-understood since knowledge of rangelands is limited. This study generated a management framework for rangelands that uses remote sensing to generate state and transition models (STMs) for a large area and a linear programming (LP) model that uses ecosystem services to evaluate natural and/or management induced transitions as described in the STM. The LP optimization model determines the best management plan for a plot of semi-arid land in the Empire Ranch in southeastern Arizona. The model allocated land among management activities (do nothing, grazing, fire, and brush removal) to optimize net benefits and determined the impact of monetizing environmental services and disservices on net benefits, acreage allocation and production output. The ecosystem services under study were forage production (AUM/ac/yr), sediment (lbs/ac/yr), water runoff (inches/yr), soil loss (lbs/ac/yr) and recreation (thousands of number of visitors/ac/yr). The optimization model was run for three different scenarios - private rancher, public rancher including environmental services and excluding disservices, and public rancher including both services and disservices. The net benefit was the highest for the public rancher excluding the disservices. A result from the study is a constrained optimization model that incorporates ecosystem services to analyze investments on conservation and management activities. Rangeland managers can use this model to understand and explain, not prescribe, the tradeoffs of management investments.

Meta-ecosystem dynamics and functioning on finite spatial networks

PubMed Central

Marleau, Justin N.; Guichard, Frédéric; Loreau, Michel

2014-01-01

The addition of spatial structure to ecological concepts and theories has spurred integration between sub-disciplines within ecology, including community and ecosystem ecology. However, the complexity of spatial models limits their implementation to idealized, regular landscapes. We present a model meta-ecosystem with finite and irregular spatial structure consisting of local nutrient–autotrophs–herbivores ecosystems connected through spatial flows of materials and organisms. We study the effect of spatial flows on stability and ecosystem functions, and provide simple metrics of connectivity that can predict these effects. Our results show that high rates of nutrient and herbivore movement can destabilize local ecosystem dynamics, leading to spatially heterogeneous equilibria or oscillations across the meta-ecosystem, with generally increased meta-ecosystem primary and secondary production. However, the onset and the spatial scale of these emergent dynamics depend heavily on the spatial structure of the meta-ecosystem and on the relative movement rate of the autotrophs. We show how this strong dependence on finite spatial structure eludes commonly used metrics of connectivity, but can be predicted by the eigenvalues and eigenvectors of the connectivity matrix that describe the spatial structure and scale. Our study indicates the need to consider finite-size ecosystems in meta-ecosystem theory. PMID:24403323

Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model

USGS Publications Warehouse

Euskirchen, E.S.; Carman, T.B.; McGuire, Anthony David

2013-01-01

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970 -2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared to simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions.

Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model.

PubMed

Euskirchen, Eugénie S; Carman, Tobey B; McGuire, A David

2014-03-01

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970-2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared with simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions. © 2013 John Wiley & Sons Ltd.

Partitioning sources of uncertainty in projecting the impact of future climate extremes on site to regional ecosystem carbon cycling

NASA Astrophysics Data System (ADS)

Simkins, J.; Desai, A. R.; Cowdery, E.; Dietze, M.; Rollinson, C.

2016-12-01

The terrestrial biosphere assimilates nearly one fourth of anthropogenic carbon dioxide emissions, providing a significant ecosystem service. Anthropogenic climate changes that influence the distribution and frequency of weather extremes and can have a momentous impact on this useful function that ecosystems provide. However, most analyses of the impact of extreme events on ecosystem carbon uptake do not integrate across the wide range of structural, parametric, and driver uncertainty that needs to be taken into account to estimate probability of changes to ecosystem function under shifts in climate patterns. In order to improve ecosystem model forecasts, we integrated and estimated these sources of uncertainty using an open-sourced informatics workflow, the Predictive ECosystem Analyzer (PEcAn, http://pecanproject.org). PEcAn allows any researcher to parameterize and run multiple ecosystem models and automate extraction of meteorological forcing and estimation of its uncertainty. Trait databases and a uniform protocol for parameterizing and driving models were used to test parametric and structural uncertainty. In order to sample the uncertainty in future projected meteorological drivers, we developed automated extraction routines to acquire site-level three-hourly Coupled Model Intercomparison Project 5 (CMIP5) forcing data from the Geophysical Fluid Dynamics Laboratory general circulation models (CM3, ESM2M, and ESM2G) across the r1i1p1, r3i1p1 and r5i1p1 ensembles and AR5 emission scenarios. We also implemented a site-level high temporal resolution downscaling technique for these forcings calibrated against half-hourly eddy covariance flux tower observations. Our hypothesis claims that parametric and driver uncertainty dominate over the model structural uncertainty. In order to test this, we partition the uncertainty budget on the ChEAS regional network of towers in Northern Wisconsin, USA where each tower is located in forest and wetland ecosystems.

Assessing the vulnerability of human and biological communities to changing ecosystem services using a GIS-based multi-criteria decision support tool

USGS Publications Warehouse

Villarreal, Miguel; Norman, Laura M.; Labiosa, William B.

2012-01-01

In this paper we describe an application of a GIS-based multi-criteria decision support web tool that models and evaluates relative changes in ecosystem services to policy and land management decisions. The Santa Cruz Watershed Ecosystem Portfolio (SCWEPM) was designed to provide credible forecasts of responses to ecosystem drivers and stressors and to illustrate the role of land use decisions on spatial and temporal distributions of ecosystem services within a binational (U.S. and Mexico) watershed. We present two SCWEPM sub-models that when analyzed together address bidirectional relationships between social and ecological vulnerability and ecosystem services. The first model employs the Modified Socio-Environmental Vulnerability Index (M-SEVI), which assesses community vulnerability using information from U.S. and Mexico censuses on education, access to resources, migratory status, housing situation, and number of dependents. The second, relating land cover change to biodiversity (provisioning services), models changes in the distribution of terrestrial vertebrate habitat based on multitemporal vegetation and land cover maps, wildlife habitat relationships, and changes in land use/land cover patterns. When assessed concurrently, the models exposed some unexpected relationships between vulnerable communities and ecosystem services provisioning. For instance, the most species-rich habitat type in the watershed, Desert Riparian Forest, increased over time in areas occupied by the most vulnerable populations and declined in areas with less vulnerable populations. This type of information can be used to identify ecological conservation and restoration targets that enhance the livelihoods of people in vulnerable communities and promote biodiversity and ecosystem health.

Carbon and energy fluxes in cropland ecosystems: a model-data comparison

USGS Publications Warehouse

Lokupitiya, E.; Denning, A. Scott; Schaefer, K.; Ricciuto, D.; Anderson, R.; Arain, M. A.; Baker, I.; Barr, A. G.; Chen, G.; Chen, J.M.; Ciais, P.; Cook, D.R.; Dietze, M.C.; El Maayar, M.; Fischer, M.; Grant, R.; Hollinger, D.; Izaurralde, C.; Jain, A.; Kucharik, C.J.; Li, Z.; Liu, S.; Li, L.; Matamala, R.; Peylin, P.; Price, D.; Running, S. W.; Sahoo, A.; Sprintsin, M.; Suyker, A.E.; Tian, H.; Tonitto, Christina; Torn, M.S.; Verbeeck, Hans; Verma, S.B.; Xue, Y.

2016-01-01

Croplands are highly productive ecosystems that contribute to land–atmosphere exchange of carbon, energy, and water during their short growing seasons. We evaluated and compared net ecosystem exchange (NEE), latent heat flux (LE), and sensible heat flux (H) simulated by a suite of ecosystem models at five agricultural eddy covariance flux tower sites in the central United States as part of the North American Carbon Program Site Synthesis project. Most of the models overestimated H and underestimated LE during the growing season, leading to overall higher Bowen ratios compared to the observations. Most models systematically under predicted NEE, especially at rain-fed sites. Certain crop-specific models that were developed considering the high productivity and associated physiological changes in specific crops better predicted the NEE and LE at both rain-fed and irrigated sites. Models with specific parameterization for different crops better simulated the inter-annual variability of NEE for maize-soybean rotation compared to those models with a single generic crop type. Stratification according to basic model formulation and phenological methodology did not explain significant variation in model performance across these sites and crops. The under prediction of NEE and LE and over prediction of H by most of the models suggests that models developed and parameterized for natural ecosystems cannot accurately predict the more robust physiology of highly bred and intensively managed crop ecosystems. When coupled in Earth System Models, it is likely that the excessive physiological stress simulated in many land surface component models leads to overestimation of temperature and atmospheric boundary layer depth, and underestimation of humidity and CO2 seasonal uptake over agricultural regions.

Carbon and energy fluxes in cropland ecosystems: a model-data comparison

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

Lokupitiya, E.; Denning, A. S.; Schaefer, K.

2016-06-03

Croplands are highly productive ecosystems that contribute to land–atmosphere exchange of carbon, energy, and water during their short growing seasons. We evaluated and compared net ecosystem exchange (NEE), latent heat flux (LE), and sensible heat flux (H) simulated by a suite of ecosystem models at five agricultural eddy covariance flux tower sites in the central United States as part of the North American Carbon Program Site Synthesis project. Most of the models overestimated H and underestimated LE during the growing season, leading to overall higher Bowen ratios compared to the observations. Most models systematically under predicted NEE, especially at rain-fedmore » sites. Certain crop-specific models that were developed considering the high productivity and associated physiological changes in specific crops better predicted the NEE and LE at both rain-fed and irrigated sites. Models with specific parameterization for different crops better simulated the inter-annual variability of NEE for maize-soybean rotation compared to those models with a single generic crop type. Stratification according to basic model formulation and phenological methodology did not explain significant variation in model performance across these sites and crops. The under prediction of NEE and LE and over prediction of H by most of the models suggests that models developed and parameterized for natural ecosystems cannot accurately predict the more robust physiology of highly bred and intensively managed crop ecosystems. When coupled in Earth System Models, it is likely that the excessive physiological stress simulated in many land surface component models leads to overestimation of temperature and atmospheric boundary layer depth, and underestimation of humidity and CO 2 seasonal uptake over agricultural regions.« less

Electric shielding films for biased TEM samples and their application to in situ electron holography.

PubMed

Nomura, Yuki; Yamamoto, Kazuo; Hirayama, Tsukasa; Saitoh, Koh

2018-06-01

We developed a novel sample preparation method for transmission electron microscopy (TEM) to suppress superfluous electric fields leaked from biased TEM samples. In this method, a thin TEM sample is first coated with an insulating amorphous aluminum oxide (AlOx) film with a thickness of about 20 nm. Then, the sample is coated with a conductive amorphous carbon film with a thickness of about 10 nm, and the film is grounded. This technique was applied to a model sample of a metal electrode/Li-ion-conductive-solid-electrolyte/metal electrode for biasing electron holography. We found that AlOx film with a thickness of 10 nm has a large withstand voltage of about 8 V and that double layers of AlOx and carbon act as a 'nano-shield' to suppress 99% of the electric fields outside of the sample. We also found an asymmetry potential distribution between high and low potential electrodes in biased solid-electrolyte, indicating different accumulation behaviors of lithium-ions (Li+) and lithium-ion vacancies (VLi-) in the biased solid-electrolyte.

Growth, characterization and estimation of lattice strain and size in CdS nanoparticles: X-ray peak profile analysis

NASA Astrophysics Data System (ADS)

Solanki, Rekha Garg; Rajaram, Poolla; Bajpai, P. K.

2018-05-01

This work is based on the growth, characterization and estimation of lattice strain and crystallite size in CdS nanoparticles by X-ray peak profile analysis. The CdS nanoparticles were synthesized by a non-aqueous solvothermal method and were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and UV-visible spectroscopy. XRD confirms that the CdS nanoparticles have the hexagonal structure. The Williamson-Hall (W-H) method was used to study the X-ray peak profile analysis. The strain-size plot (SSP) was used to study the individual contributions of crystallite size and lattice strain from the X-rays peaks. The physical parameters such as strain, stress and energy density values were calculated using various models namely, isotropic strain model, anisotropic strain model and uniform deformation energy density model. The particle size was estimated from the TEM images to be in the range of 20-40 nm. The Raman spectrum shows the characteristic optical 1LO and 2LO vibrational modes of CdS. UV-visible absorption studies show that the band gap of the CdS nanoparticles is 2.48 eV. The results show that the crystallite size estimated from Scherrer's formula, W-H plots, SSP and the particle size calculated by TEM images are approximately similar.

Using ground- and satellite-based measurements and models to quantify response to multiple disturbances and climate change in South African semi-arid ecosystems

NASA Astrophysics Data System (ADS)

Falge, Eva; Brümmer, Christian; Schmullius, Christiane; Scholes, Robert; Twine, Wayne; Mudau, Azwitamisi; Midgley, Guy; Hickler, Thomas; Bradshaw, Karen; Lück, Wolfgang; Thiel-Clemen, Thomas; du Toit, Justin; Sankaran, Vaith; Kutsch, Werner

2016-04-01

Sub-Saharan Africa currently experiences significant changes in shrubland, savanna and mixed woodland ecosystems driving degradation, affecting fire frequency and water availability, and eventually fueling climate change. The project 'Adaptive Resilience of Southern African Ecosystems' (ARS AfricaE) conducts research and develops scenarios of ecosystem development under climate change, for management support in conservation or for planning rural area development. For a network of research clusters along an aridity gradient in South Africa, we measure greenhouse gas exchange, ecosystem structure and eco-physiological properties as affected by land use change at paired sites with natural and altered vegetation. We set up dynamic vegetation models and individual-based models to predict ecosystem dynamics under (post) disturbance managements. We monitor vegetation amount and heterogeneity using remotely sensed images and aerial photography over several decades to examine time series of land cover change. Finally, we investigate livelihood strategies with focus on carbon balance components to develop sustainable management strategies for disturbed ecosystems and land use change. Emphasis is given on validation of estimates obtained from eddy covariance, model approaches and satellite derivations. We envision our methodological approach on a network of research clusters a valuable means to investigate potential linkages to concepts of adaptive resilience.

Using the Soil and Water Assessment Tool (SWAT) to model ecosystem services: A systematic review

NASA Astrophysics Data System (ADS)

Francesconi, Wendy; Srinivasan, Raghavan; Pérez-Miñana, Elena; Willcock, Simon P.; Quintero, Marcela

2016-04-01

SWAT, a watershed modeling tool has been proposed to help quantify ecosystem services. The concept of ecosystem services incorporates the collective benefits natural systems provide primarily to human beings. It is becoming increasingly important to track the impact that human activities have on the environment in order to determine its resilience and sustainability. The objectives of this paper are to provide an overview of efforts using SWAT to quantify ecosystem services, to determine the model's capability examining various types of services, and to describe the approach used by various researchers. A literature review was conducted to identify studies in which SWAT was explicitly used for quantifying ecosystem services in terms of provisioning, regulating, supporting, and cultural aspects. A total of 44 peer reviewed publications were identified. Most of these used SWAT to quantify provisioning services (34%), regulating services (27%), or a combination of both (25%). While studies using SWAT for evaluating ecosystem services are limited (approximately 1% of SWAT's peered review publications), and usage (vs. potential) of services by beneficiaries is a current model limitation, the available literature sets the stage for the continuous development and potential of SWAT as a methodological framework for quantifying ecosystem services to assist in decision-making.

Constructing a Conceptual Model Linking Drivers and Ecosystem Services in Piedmont Streams

DTIC Science & Technology

2011-04-01

to the Virginia-Maryland border and is bound by the Appalachian Mountains and Blue Ridge to the northwest and the Atlantic Coastal Plain to the south...demand on freshwater ecosystem services, and a growing appreciation for the value of functioning ecosystems, the Appalachian Piedmont has developed a...the model and how it can be adapted and ap - plied for specific projects. A FRAMEWORK FOR CONCEPTUAL MODELING The general approach to conceptual

Modeling Hawaiian Ecosystem Degradation due to Invasive Plants under Current and Future Climates

PubMed Central

Vorsino, Adam E.; Fortini, Lucas B.; Amidon, Fred A.; Miller, Stephen E.; Jacobi, James D.; Price, Jonathan P.; Gon, Sam 'Ohukani'ohi'a; Koob, Gregory A.

2014-01-01

Occupation of native ecosystems by invasive plant species alters their structure and/or function. In Hawaii, a subset of introduced plants is regarded as extremely harmful due to competitive ability, ecosystem modification, and biogeochemical habitat degradation. By controlling this subset of highly invasive ecosystem modifiers, conservation managers could significantly reduce native ecosystem degradation. To assess the invasibility of vulnerable native ecosystems, we selected a proxy subset of these invasive plants and developed robust ensemble species distribution models to define their respective potential distributions. The combinations of all species models using both binary and continuous habitat suitability projections resulted in estimates of species richness and diversity that were subsequently used to define an invasibility metric. The invasibility metric was defined from species distribution models with <0.7 niche overlap (Warrens I) and relatively discriminative distributions (Area Under the Curve >0.8; True Skill Statistic >0.75) as evaluated per species. Invasibility was further projected onto a 2100 Hawaii regional climate change scenario to assess the change in potential habitat degradation. The distribution defined by the invasibility metric delineates areas of known and potential invasibility under current climate conditions and, when projected into the future, estimates potential reductions in native ecosystem extent due to climate-driven invasive incursion. We have provided the code used to develop these metrics to facilitate their wider use (Code S1). This work will help determine the vulnerability of native-dominated ecosystems to the combined threats of climate change and invasive species, and thus help prioritize ecosystem and species management actions. PMID:24805254

Modeling Hawaiian ecosystem degradation due to invasive plants under current and future climates.

PubMed

Vorsino, Adam E; Fortini, Lucas B; Amidon, Fred A; Miller, Stephen E; Jacobi, James D; Price, Jonathan P; Gon, Sam 'ohukani'ohi'a; Koob, Gregory A

2014-01-01

Occupation of native ecosystems by invasive plant species alters their structure and/or function. In Hawaii, a subset of introduced plants is regarded as extremely harmful due to competitive ability, ecosystem modification, and biogeochemical habitat degradation. By controlling this subset of highly invasive ecosystem modifiers, conservation managers could significantly reduce native ecosystem degradation. To assess the invasibility of vulnerable native ecosystems, we selected a proxy subset of these invasive plants and developed robust ensemble species distribution models to define their respective potential distributions. The combinations of all species models using both binary and continuous habitat suitability projections resulted in estimates of species richness and diversity that were subsequently used to define an invasibility metric. The invasibility metric was defined from species distribution models with <0.7 niche overlap (Warrens I) and relatively discriminative distributions (Area Under the Curve >0.8; True Skill Statistic >0.75) as evaluated per species. Invasibility was further projected onto a 2100 Hawaii regional climate change scenario to assess the change in potential habitat degradation. The distribution defined by the invasibility metric delineates areas of known and potential invasibility under current climate conditions and, when projected into the future, estimates potential reductions in native ecosystem extent due to climate-driven invasive incursion. We have provided the code used to develop these metrics to facilitate their wider use (Code S1). This work will help determine the vulnerability of native-dominated ecosystems to the combined threats of climate change and invasive species, and thus help prioritize ecosystem and species management actions.

Towards end-to-end models for investigating the effects of climate and fishing in marine ecosystems

NASA Astrophysics Data System (ADS)

Travers, M.; Shin, Y.-J.; Jennings, S.; Cury, P.

2007-12-01

End-to-end models that represent ecosystem components from primary producers to top predators, linked through trophic interactions and affected by the abiotic environment, are expected to provide valuable tools for assessing the effects of climate change and fishing on ecosystem dynamics. Here, we review the main process-based approaches used for marine ecosystem modelling, focusing on the extent of the food web modelled, the forcing factors considered, the trophic processes represented, as well as the potential use and further development of the models. We consider models of a subset of the food web, models which represent the first attempts to couple low and high trophic levels, integrated models of the whole ecosystem, and size spectrum models. Comparisons within and among these groups of models highlight the preferential use of functional groups at low trophic levels and species at higher trophic levels and the different ways in which the models account for abiotic processes. The model comparisons also highlight the importance of choosing an appropriate spatial dimension for representing organism dynamics. Many of the reviewed models could be extended by adding components and by ensuring that the full life cycles of species components are represented, but end-to-end models should provide full coverage of ecosystem components, the integration of physical and biological processes at different scales and two-way interactions between ecosystem components. We suggest that this is best achieved by coupling models, but there are very few existing cases where the coupling supports true two-way interaction. The advantages of coupling models are that the extent of discretization and representation can be targeted to the part of the food web being considered, making their development time- and cost-effective. Processes such as predation can be coupled to allow the propagation of forcing factors effects up and down the food web. However, there needs to be a stronger focus on enabling two-way interaction, carefully selecting the key functional groups and species, reconciling different time and space scales and the methods of converting between energy, nutrients and mass.

Understanding variation in ecosystem pulse responses to wetting: Benefits of data-model coupling

NASA Astrophysics Data System (ADS)

Jenerette, D.

2011-12-01

Metabolic pulses of activity are a common ecological response to intermittently available resources and in water-limited ecosystems these pulses often occur in response to wetting. Net ecosystem CO2 exchange (NEE) in response to episodic wetting events is hypothesized to have a complex trajectory reflecting the distinct responses, or "pulses", of respiration and photosynthesis. To help direct research activities a physiological-based model of whole ecosystem metabolic activity up- and down-regulation was developed to investigate ecosystem energy balance and gas exchange pulse responses following precipitation events. This model was to investigate pulse dynamics from a local network of sites in southern Arizona, a global network of eddy-covariance ecosystem monitoring sites, laboratory incubation studies, and field manipulations. Pulse responses were found to be ubiquitous across ecosystem types. These pulses had a highly variable influence on NEE following wetting, ranging from large net sinks to sources of CO2 to the atmosphere. Much of the variability in pulse responses of NEE could be described through a coupled up- and down-regulation pulse response model. Respiration pulses were hypothesized to occur through a reduction in whole ecosystem activation energy; this model was both useful and corroborated through laboratory incubation studies of soil respiration. Using the Fluxnet eddy-covariance measurement database event specific responses were combined with the pulse model into an event specific twenty-five day net flux calculation. Across all events observed a general net accumulation of CO2 following a precipitation event, with the largest net uptake within deciduous broadleaf forests and smallest within grasslands. NEE pulses favored greater uptake when pre-event ecosystem respiration rates and total precipitation were higher. While the latter was expected, the former adds to previous theory by suggesting a larger net uptake of CO2 when pre-event metabolic activity is higher. Scenario analyses of precipitation regimes suggested increased uptake with increasing total precipitation while more complex NEE responses to increasing number of events and interval between events. Pulse dynamics provides a general framework for understanding ecosystem responses to intermittent wetting projected to occur more frequently in future climates. Pulse dynamics also provides an opportunity to evaluate processes spanning cellular upregulation to global change.

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

Impacts of diffuse radiation on light use efficiency across terrestrial ecosystems based on Eddy covariance observation in China.

PubMed

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 ≤ R(2) ≤ 0.85), especially at the Changbaishan temperate forest ecosystem (R(2) = 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.

TEM Systems Design: Using Full Maxwell FDTD Modelling to Study the Transient Response of Custom-madeTx and Rx Coils.

NASA Astrophysics Data System (ADS)

Chevalier, A.; Rejiba, F.; Schamper, C.; Thiesson, J.; Hovhannissian, G.

2016-12-01

From airborne applications to field scale measurements of Transient Electromagnetic Methods(TEM), an accurate knowledge of the sensitivity of the inductive coil sensors (system response) is aprerequisite to interpret the measured transient magnetic flux density into a subsurface distributionof conductivity. The system response is a term that refers to the cumulative effect of inductive andcapacitive couplings (cross-talks) between each component constituting a TEM apparatus and thenearby conductive structures. As a result, the frequency sensitivity of the voltage coil sensor (Rx)along with the emitted current waveform in the current emitting coil (Tx) are controlled by thegeometry and electronic characteristic of the set-up as well as the near surface electromagneticproperties. During the early development of an innovative airborne TEM solutions (French nationalTEMas project), determining the coil geometries and the impedance matching between all parts ofthe transmission link (electronic parts and coils) for various environmental set-ups, has been a majorissue. In this study, we review the required theoretical framework and propose a versatile numericalmethodology to ease the coil design and impedance matching process while extending ourunderstanding of short-time transient that operates from DC to moderately high frequencies (0 to 20Mhz). We used a full Maxwell equations FDTD model along with a semi-analytical 1D modeler to infercoils emitting and receiving properties, for various coil geometries and site-dependent conditions.Results highlight the influence of the environment on the emitting and sensing properties. Theincreasing effects of cross-talks between the Tx and the Rx coils depending on their size is shown.Strategies regarding the impedance adaptation between the electronical components and the coilsensors are then discussed for different geophysical specifications.

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.

NDVI indicated long-term interannual changes in vegetation activities and their responses to climatic and anthropogenic factors in the Three Gorges Reservoir Region, China.

PubMed

Wen, Zhaofei; Wu, Shengjun; Chen, Jilong; Lü, Mingquan

2017-01-01

Natural and social environmental changes in the China's Three Gorges Reservoir Region (TGRR) have received worldwide attention. Identifying interannual changes in vegetation activities in the TGRR is an important task for assessing the impact these changes have on the local ecosystem. We used long-term (1982-2011) satellite-derived Normalized Difference Vegetation Index (NDVI) datasets and climatic and anthropogenic factors to analyze the spatiotemporal patterns of vegetation activities in the TGRR, as well as their links to changes in temperature (TEM), precipitation (PRE), downward radiation (RAD), and anthropogenic activities. At the whole TGRR regional scale, a statistically significant overall uptrend in NDVI variations was observed in 1982-2011. More specifically, there were two distinct periods with different trends split by a breakpoint in 1991: NDVI first sharply increased prior to 1991, and then showed a relatively weak rate of increase after 1991. At the pixel scale, most parts of the TGRR experienced increasing NDVI before the 1990s but different trend change types after the 1990s: trends were positive in forests in the northeastern parts, but negative in farmland in southwest parts of the TGRR. The TEM warming trend was the main climate-related driver of uptrending NDVI variations pre-1990s, and decreasing PRE was the main climate factor (42%) influencing the mid-western farmland areas' NDVI variations post-1990s. We also found that anthropogenic factors such as population density, man-made ecological restoration, and urbanization have notable impacts on the TGRR's NDVI variations. For example, large overall trend slopes in NDVI were more likely to appear in TGRR regions with large fractions of ecological restoration within the last two decades. The findings of this study may help to build a better understanding of the mechanics of NDVI variations in the periods before and during TGDP construction for ongoing ecosystem monitoring and assessment in the post-TGDP period. Copyright © 2016 Elsevier B.V. All rights reserved.

Freshwater Ecosystem Service Flow Model To Evaluate Regional Water Security: A Case Study In Beijing-Tianjin-Hebei Region, China

NASA Astrophysics Data System (ADS)

Li, D.; Li, S.

2016-12-01

Freshwater service, as the most important support ecosystem service, is essential to human survival and development. Many studies have evidenced the spatial differences in the supply and demand of ecosystem services and raised the concept of ecosystem service flow. However, rather few studies quantitatively characterize the freshwater service flow. This paper aims to quantify the effect of freshwater ecosystem service flow on downstream areas in Beijing-Tianjin-Hebei (BTH) region, China over 2000, 2005 and 2010. We computed the freshwater ecosystem service provision with InVEST model. We calculated freshwater ecosystem service consumption with water quota method. We simulated the freshwater ecosystem service flow using our simplified flow model and assessed the regional water security with the improved freshwater security index. The freshwater provision service mainly depends on climatic factors that cannot be influenced by management, while the freshwater consumption service is constrained by human activities. Furthermore, the decrease of water quota for agricultural, domestic and industrial water counteracts the impact of increasing freshwater demand. The analysis of freshwater ecosystem service flow reveals that the majority area of the BTH (69.2%) is affected by upstream freshwater. If freshwater ecosystem service flow is considered, the water safety areas of the whole BTH account for 66.9%, 66.1%, 71.3%, which increase 6.4%, 6.8% and 5.7% in 2000, 2005 and 2010, respectively. These results highlight the need to understand the teleconnections between distant freshwater ecosystem service provision and local freshwater ecosystem service use. This approach therefore helps managers choose specific management and investment strategies for critical upstream freshwater provisions across different regions.

Trapping force and optical lifting under focused evanescent wave illumination.

PubMed

Ganic, Djenan; Gan, Xiaosong; Gu, Min

2004-11-01

A physical model is presented to understand and calculate trapping force exerted on a dielectric micro-particle under focused evanescent wave illumination. This model is based on our recent vectorial diffraction model by a high numerical aperture objective operating under the total internal condition. As a result, trapping force in a focused evanescent spot generated by both plane wave (TEM00) and doughnut beam (TEM*01) illumination is calculated, showing an agreement with the measured results. It is also revealed by this model that unlike optical trapping in the far-field region, optical axial trapping force in an evanescent focal spot increases linearly with the size of a trapped particle. This prediction shows that it is possible to overcome the force of gravity to lift a polystyrene particle of up to 800 nm in radius with a laser beam of power 10 microW.

Individual and binary toxicity of anatase and rutile nanoparticles towards Ceriodaphnia dubia.

PubMed

Iswarya, V; Bhuvaneshwari, M; Chandrasekaran, N; Mukherjee, Amitava

2016-09-01

Increasing usage of engineered nanoparticles, especially Titanium dioxide (TiO2) in various commercial products has necessitated their toxicity evaluation and risk assessment, especially in the aquatic ecosystem. In the present study, a comprehensive toxicity assessment of anatase and rutile NPs (individual as well as a binary mixture) has been carried out in a freshwater matrix on Ceriodaphnia dubia under different irradiation conditions viz., visible and UV-A. Anatase and rutile NPs produced an LC50 of about 37.04 and 48mg/L, respectively, under visible irradiation. However, lesser LC50 values of about 22.56 (anatase) and 23.76 (rutile) mg/L were noted under UV-A irradiation. A toxic unit (TU) approach was followed to determine the concentrations of binary mixtures of anatase and rutile. The binary mixture resulted in an antagonistic and additive effect under visible and UV-A irradiation, respectively. Among the two different modeling approaches used in the study, Marking-Dawson model was noted to be a more appropriate model than Abbott model for the toxicity evaluation of binary mixtures. The agglomeration of NPs played a significant role in the induction of antagonistic and additive effects by the mixture based on the irradiation applied. TEM and zeta potential analysis confirmed the surface interactions between anatase and rutile NPs in the mixture. Maximum uptake was noticed at 0.25 total TU of the binary mixture under visible irradiation and 1 TU of anatase NPs for UV-A irradiation. Individual NPs showed highest uptake under UV-A than visible irradiation. In contrast, binary mixture showed a difference in the uptake pattern based on the type of irradiation exposed. Copyright © 2016 Elsevier B.V. All rights reserved.

Projecting supply and demand of hydrologic ecosystem services under future climate conditions

NASA Astrophysics Data System (ADS)

Chiang, Li-Chi; Huang, Tao; Lee, Tsung-Yu

2014-05-01

Ecosystems provide essential goods and services, such as food, clean water, water purification, soil conservation and cultural services for human being. In a watershed, these water-related ecosystem goods and services can directly or indirectly benefit both local people and downstream beneficiaries through a reservoir. Water quality and quantity in a reservoir are of importance for agricultural, industrial and domestic uses. Under the impacts of climate and land use changes, both ecosystem service supply and demand will be affected by changes in precipitation patterns, temperature, urbanization and agricultural activities. However, the linkage between ecosystem service provisioning (ESP) and ecosystem service beneficiary (ESB), and scales of supply and demand of ecosystem services are not clear yet. Therefore, to investigate water-related ecosystem service supply under climate and land use change, we took the Xindian river watershed (303 km2) as a case study, where the Feitsui Reservoir provides hydro-power and daily domestic water use of 3,450,000 m3 for 3.46 million people in Taipei, Taiwan. We integrated a hydrological model (Soil and Water Assessment Tool, SWAT) and a land use change model (Conversion of Land Use and its Effects, CLUE-s) with future climate change scenarios derived from General Circulation Models (GCMs), to assess the changes in ecosystem service supply and demand at different hydrologic scales. The results will provide useful information for decision-making on future land use management and climate change adaptation strategies in the watersheds. Keywords: climate change, land use change, ecosystem service, watershed, scale

An ecosystem model for tropical forest disturbance and selective logging

Treesearch

Maoyi Huang; Gregory P. Asner; Michael Keller; Joseph A. Berry

2008-01-01

[1] A new three-dimensional version of the Carnegie-Ames-Stanford Approach (CASA) ecosystem model (CASA-3D) was developed to simulate regional carbon cycling in tropical forest ecosystems after disturbances such as logging. CASA-3D has the following new features: (1) an alternative approach for calculating absorbed photosynthetically active radiation (APAR) using new...

Modelled effects of precipitation on ecosystem carbon and water dynamics in different climatic zones

Treesearch

Dieter Gerten; Yiqi Luo; Guerric Le Maire; William J. Parton; Cindy Keough; Ensheng Weng; Claus Beier; Philippe Ciais; Wolfgang Cramer; Jeffrey S. Dukes; Paul J. Hanson; Alan A. K. Knapp; Sune Linder; Dan Nepstad; Lindsey Rustad; Alwyn. Sowerby

2008-01-01

The ongoing changes in the global climate expose the world’s ecosystems not only to increasing CO2 concentrations and temperatures but also to altered precipitation (P) regimes. Using four well-established process-based ecosystem models (LPJ, DayCent, ORCHIDEE, TECO), we explored effects of potential P...

A non-linear induced polarization effect on transient electromagnetic soundings

NASA Astrophysics Data System (ADS)

Hallbauer-Zadorozhnaya, Valeriya Yu.; Santarato, Giovanni; Abu Zeid, Nasser; Bignardi, Samuel

2016-10-01

In a TEM survey conducted for characterizing the subsurface for geothermal purposes, a strong induced polarization effect was recorded in all collected data. Surprisingly, anomalous decay curves were obtained in part of the sites, whose shape depended on the repetition frequency of the exciting square waveform, i.e. on current pulse length. The Cole-Cole model, besides being not directly related to physical parameters of rocks, was found inappropriate to model the observed distortion, due to induced polarization, because this model is linear, i.e. it cannot fit any dependence on current pulse. This phenomenon was investigated and explained as due to the presence of membrane polarization linked to constrictivity of (fresh) water-saturated pores. An algorithm for mathematical modeling of TEM data was then developed to fit this behavior. The case history is then discussed: 1D inversion, which accommodates non-linear effects, produced models that agree quite satisfactorily with resistivity and chargeability models obtained by an electrical resistivity tomography carried out for comparison.

An analytical framework to assist decision makers in the use of forest ecosystem model predictions

USDA-ARS?s Scientific Manuscript database

The predictions of most terrestrial ecosystem models originate from deterministic simulations. Relatively few uncertainty evaluation exercises in model outputs are performed by either model developers or users. This issue has important consequences for decision makers who rely on models to develop n...

Benefits from bremsstrahlung distribution evaluation to get unknown information from specimen in SEM and TEM

NASA Astrophysics Data System (ADS)

Eggert, F.; Camus, P. P.; Schleifer, M.; Reinauer, F.

2018-01-01

The energy-dispersive X-ray spectrometer (EDS or EDX) is a commonly used device to characterise the composition of investigated material in scanning and transmission electron microscopes (SEM and TEM). One major benefit compared to wavelength-dispersive X-ray spectrometers (WDS) is that EDS systems collect the entire spectrum simultaneously. Therefore, not only are all emitted characteristic X-ray lines in the spectrum, but also the complete bremsstrahlung distribution is included. It is possible to get information about the specimen even from this radiation, which is usually perceived more as a disturbing background. This is possible by using theoretical model knowledge about bremsstrahlung excitation and absorption in the specimen in comparison to the actual measured spectrum. The core aim of this investigation is to present a method for better bremsstrahlung fitting in unknown geometry cases by variation of the geometry parameters and to utilise this knowledge also for characteristic radiation evaluation. A method is described, which allows the parameterisation of the true X-ray absorption conditions during spectrum acquisition. An ‘effective tilt’ angle parameter is determined by evaluation of the bremsstrahlung shape of the measured SEM spectra. It is useful for bremsstrahlung background approximation, with exact calculations of the absorption edges below the characteristic peaks, required for P/B-ZAF model based quantification methods. It can even be used for ZAF based quantification models as a variable input parameter. The analytical results are then much more reliable for the different absorption effects from irregular specimen surfaces because the unknown absorption dependency is considered. Finally, the method is also applied for evaluation of TEM spectra. In this case, the real physical parameter optimisation is with sample thickness (mass thickness), which is influencing the emitted and measured spectrum due to different absorption with TEM measurements. The effects are in the very low energy part of the spectrum, and are much more visible with most recent windowless TEM detectors. The thickness of the sample can be determined in this way from the measured bremsstrahlung spectrum shape.

Comparative structural and computational analysis supports eighteen cellulose synthases in the plant cellulose synthesis complex

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

Nixon, B. Tracy; Mansouri, Katayoun; Singh, Abhishek

A six-lobed membrane spanning cellulose synthesis complex (CSC) containing multiple cellulose synthase (CESA) glycosyltransferases mediates cellulose microfibril formation. The number of CESAs in the CSC has been debated for decades in light of changing estimates of the diameter of the smallest microfibril formed from the β-1,4 glucan chains synthesized by one CSC. We obtained more direct evidence through generating improved transmission electron microscopy (TEM) images and image averages of the rosette-type CSC, revealing the frequent triangularity and average cross-sectional area in the plasma membrane of its individual lobes. Trimeric oligomers of two alternative CESA computational models corresponded well with individualmore » lobe geometry. A six-fold assembly of the trimeric computational oligomer had the lowest potential energy per monomer and was consistent with rosette CSC morphology. Negative stain TEM and image averaging showed the triangularity of a recombinant CESA cytosolic domain, consistent with previous modeling of its trimeric nature from small angle scattering (SAXS) data. Six trimeric SAXS models nearly filled the space below an average FF-TEM image of the rosette CSC. In conclusion, the multifaceted data support a rosette CSC with 18 CESAs that mediates the synthesis of a fundamental microfibril composed of 18 glucan chains.« less

Comparative structural and computational analysis supports eighteen cellulose synthases in the plant cellulose synthesis complex

DOE PAGES

Nixon, B. Tracy; Mansouri, Katayoun; Singh, Abhishek; ...

2016-06-27

A six-lobed membrane spanning cellulose synthesis complex (CSC) containing multiple cellulose synthase (CESA) glycosyltransferases mediates cellulose microfibril formation. The number of CESAs in the CSC has been debated for decades in light of changing estimates of the diameter of the smallest microfibril formed from the β-1,4 glucan chains synthesized by one CSC. We obtained more direct evidence through generating improved transmission electron microscopy (TEM) images and image averages of the rosette-type CSC, revealing the frequent triangularity and average cross-sectional area in the plasma membrane of its individual lobes. Trimeric oligomers of two alternative CESA computational models corresponded well with individualmore » lobe geometry. A six-fold assembly of the trimeric computational oligomer had the lowest potential energy per monomer and was consistent with rosette CSC morphology. Negative stain TEM and image averaging showed the triangularity of a recombinant CESA cytosolic domain, consistent with previous modeling of its trimeric nature from small angle scattering (SAXS) data. Six trimeric SAXS models nearly filled the space below an average FF-TEM image of the rosette CSC. In conclusion, the multifaceted data support a rosette CSC with 18 CESAs that mediates the synthesis of a fundamental microfibril composed of 18 glucan chains.« less

Comparative Structural and Computational Analysis Supports Eighteen Cellulose Synthases in the Plant Cellulose Synthesis Complex

PubMed Central

Nixon, B. Tracy; Mansouri, Katayoun; Singh, Abhishek; Du, Juan; Davis, Jonathan K.; Lee, Jung-Goo; Slabaugh, Erin; Vandavasi, Venu Gopal; O’Neill, Hugh; Roberts, Eric M.; Roberts, Alison W.; Yingling, Yaroslava G.; Haigler, Candace H.

2016-01-01

A six-lobed membrane spanning cellulose synthesis complex (CSC) containing multiple cellulose synthase (CESA) glycosyltransferases mediates cellulose microfibril formation. The number of CESAs in the CSC has been debated for decades in light of changing estimates of the diameter of the smallest microfibril formed from the β-1,4 glucan chains synthesized by one CSC. We obtained more direct evidence through generating improved transmission electron microscopy (TEM) images and image averages of the rosette-type CSC, revealing the frequent triangularity and average cross-sectional area in the plasma membrane of its individual lobes. Trimeric oligomers of two alternative CESA computational models corresponded well with individual lobe geometry. A six-fold assembly of the trimeric computational oligomer had the lowest potential energy per monomer and was consistent with rosette CSC morphology. Negative stain TEM and image averaging showed the triangularity of a recombinant CESA cytosolic domain, consistent with previous modeling of its trimeric nature from small angle scattering (SAXS) data. Six trimeric SAXS models nearly filled the space below an average FF-TEM image of the rosette CSC. In summary, the multifaceted data support a rosette CSC with 18 CESAs that mediates the synthesis of a fundamental microfibril composed of 18 glucan chains. PMID:27345599

Methodology to assess and map the potential development of forest ecosystems exposed to climate change and atmospheric nitrogen deposition: A pilot study in Germany.

PubMed

Schröder, Winfried; Nickel, Stefan; Jenssen, Martin; Riediger, Jan

2015-07-15

A methodology for mapping ecosystems and their potential development under climate change and atmospheric nitrogen deposition was developed using examples from Germany. The methodology integrated data on vegetation, soil, climate change and atmospheric nitrogen deposition. These data were used to classify ecosystem types regarding six ecological functions and interrelated structures. Respective data covering 1961-1990 were used for reference. The assessment of functional and structural integrity relies on comparing a current or future state with an ecosystem type-specific reference. While current functions and structures of ecosystems were quantified by measurements, potential future developments were projected by geochemical soil modelling and data from a regional climate change model. The ecosystem types referenced the potential natural vegetation and were mapped using data on current tree species coverage and land use. In this manner, current ecosystem types were derived, which were related to data on elevation, soil texture, and climate for the years 1961-1990. These relations were quantified by Classification and Regression Trees, which were used to map the spatial patterns of ecosystem type clusters for 1961-1990. The climate data for these years were subsequently replaced by the results of a regional climate model for 1991-2010, 2011-2040, and 2041-2070. For each of these periods, one map of ecosystem type clusters was produced and evaluated with regard to the development of areal coverage of ecosystem type clusters over time. This evaluation of the structural aspects of ecological integrity at the national level was added by projecting potential future values of indicators for ecological functions at the site level by using the Very Simple Dynamic soil modelling technique based on climate data and two scenarios of nitrogen deposition as input. The results were compared to the reference and enabled an evaluation of site-specific ecosystem changes over time which proved to be both, positive and negative. Copyright © 2015 Elsevier B.V. All rights reserved.

APPROACHES TO ECOSYSTEM AND HUMAN EXPOSURE TO MERCURY FOR SENSITIVE POPULATIONS

EPA Science Inventory

Both human and ecosystem exposure studies evaluate exposure of sensitive and vulnerable populations. We will discuss how ecosystem exposure modeling studies completed for input into the US Clean Air Mercury Rule (CAMR) to evaluate the response of aquatic ecosystems to changes in ...

Linking Ecosystem Services Benefit Transfer Databases and Ecosystem Services Production Function Libraries

EPA Science Inventory

The quantification or estimation of the economic and non-economic values of ecosystem services can be done from a number of distinct approaches. For example, practitioners may use ecosystem services production function models (ESPFMs) for a particular location, or alternatively, ...

Multiple ecosystem services in a working landscape

PubMed Central

Eastburn, Danny J.; O’Geen, Anthony T.; Tate, Kenneth W.; Roche, Leslie M.

2017-01-01

Policy makers and practitioners are in need of useful tools and models for assessing ecosystem service outcomes and the potential risks and opportunities of ecosystem management options. We utilize a state-and-transition model framework integrating dynamic soil and vegetation properties to examine multiple ecosystem services—specifically agricultural production, biodiversity and habitat, and soil health—across human created vegetation states in a managed oak woodland landscape in a Mediterranean climate. We found clear tradeoffs and synergies in management outcomes. Grassland states maximized agricultural productivity at a loss of soil health, biodiversity, and other ecosystem services. Synergies existed among multiple ecosystem services in savanna and woodland states with significantly larger nutrient pools, more diversity and native plant richness, and less invasive species. This integrative approach can be adapted to a diversity of working landscapes to provide useful information for science-based ecosystem service valuations, conservation decision making, and management effectiveness assessments. PMID:28301475

Multiple ecosystem services in a working landscape.

PubMed

Eastburn, Danny J; O'Geen, Anthony T; Tate, Kenneth W; Roche, Leslie M

2017-01-01

Policy makers and practitioners are in need of useful tools and models for assessing ecosystem service outcomes and the potential risks and opportunities of ecosystem management options. We utilize a state-and-transition model framework integrating dynamic soil and vegetation properties to examine multiple ecosystem services-specifically agricultural production, biodiversity and habitat, and soil health-across human created vegetation states in a managed oak woodland landscape in a Mediterranean climate. We found clear tradeoffs and synergies in management outcomes. Grassland states maximized agricultural productivity at a loss of soil health, biodiversity, and other ecosystem services. Synergies existed among multiple ecosystem services in savanna and woodland states with significantly larger nutrient pools, more diversity and native plant richness, and less invasive species. This integrative approach can be adapted to a diversity of working landscapes to provide useful information for science-based ecosystem service valuations, conservation decision making, and management effectiveness assessments.

Biodiversity and ecosystem stability across scales in metacommunities

PubMed Central

Wang, Shaopeng; Loreau, Michel

2016-01-01

Although diversity-stability relationships have been extensively studied in local ecosystems, the global biodiversity crisis calls for an improved understanding of these relationships in a spatial context. Here we use a dynamical model of competitive metacommunities to study the relationships between species diversity and ecosystem variability across scales. We derive analytic relationships under a limiting case; these results are extended to more general cases with numerical simulations. Our model shows that, while alpha diversity decreases local ecosystem variability, beta diversity generally contributes to increasing spatial asynchrony among local ecosystems. Consequently, both alpha and beta diversity provide stabilizing effects for regional ecosystems, through local and spatial insurance effects, respectively. We further show that at the regional scale, the stabilizing effect of biodiversity increases as spatial environmental correlation increases. Our findings have important implications for understanding the interactive effects of global environmental changes (e.g. environmental homogenization) and biodiversity loss on ecosystem sustainability at large scales. PMID:26918536

Spatially-explicit modeling of multi-scale drivers of aboveground forest biomass and water yield in watersheds of the Southeastern United States.

PubMed

Ajaz Ahmed, Mukhtar Ahmed; Abd-Elrahman, Amr; Escobedo, Francisco J; Cropper, Wendell P; Martin, Timothy A; Timilsina, Nilesh

2017-09-01

Understanding ecosystem processes and the influence of regional scale drivers can provide useful information for managing forest ecosystems. Examining more local scale drivers of forest biomass and water yield can also provide insights for identifying and better understanding the effects of climate change and management on forests. We used diverse multi-scale datasets, functional models and Geographically Weighted Regression (GWR) to model ecosystem processes at the watershed scale and to interpret the influence of ecological drivers across the Southeastern United States (SE US). Aboveground forest biomass (AGB) was determined from available geospatial datasets and water yield was estimated using the Water Supply and Stress Index (WaSSI) model at the watershed level. Our geostatistical model examined the spatial variation in these relationships between ecosystem processes, climate, biophysical, and forest management variables at the watershed level across the SE US. Ecological and management drivers at the watershed level were analyzed locally to identify whether drivers contribute positively or negatively to aboveground forest biomass and water yield ecosystem processes and thus identifying potential synergies and tradeoffs across the SE US region. Although AGB and water yield drivers varied geographically across the study area, they were generally significantly influenced by climate (rainfall and temperature), land-cover factor1 (Water and barren), land-cover factor2 (wetland and forest), organic matter content high, rock depth, available water content, stand age, elevation, and LAI drivers. These drivers were positively or negatively associated with biomass or water yield which significantly contributes to ecosystem interactions or tradeoff/synergies. Our study introduced a spatially-explicit modelling framework to analyze the effect of ecosystem drivers on forest ecosystem structure, function and provision of services. This integrated model approach facilitates multi-scale analyses of drivers and interactions at the local to regional scale. Copyright © 2017 Elsevier Ltd. All rights reserved.

Linking remote-sensing and ecosystem services modeling to support and assess management for regenerative grazing in the South Gobi, Mongolia

NASA Astrophysics Data System (ADS)

Chaplin-Kramer, R.; Kowal, V. A.; Sharp, R.

2017-12-01

Managing and monitoring supply chain sustainability is a major challenge and opportunity for business, especially in rangelands, heavily managed and often degraded natural systems that provide significant resources and raw materials for production. One of the largest and most threatened rangeland systems in the world is in Mongolia, which has seen a rapid rise in grazing pressure due to increasing global demand for cashmere along with privatization of a formerly government-run livestock industry. A new opportunity is emerging for remote-sensing to improve the management decisions of the producers and their incentive-setters, leading to a more sustainable rangeland system and better outcomes for biodiversity and people in this unique and imperiled landscape. Oyu Tolgoi (OT), the Mongolian subsidiary of the mining company Rio Tinto, in cooperation with Kering, an apparel conglomerate that sources cashmere from the region, are providing financial incentives to improve grazing patterns through a Sustainable Cashmere program, in order to restore the degraded rangeland ecosystem in the Gobi desert region. We present a framework and approach for predicting the effect of changing grazing practices on biodiversity and ecosystem services, which we are developing into decision-support tools for OT, Kering, and their local partner Wildlife Conservation Society to quantify the impacts of their programs and where these interventions will have greatest benefit. Our approach integrates remote-sensing and ecosystem modeling to scale up field monitoring data and forecast future impacts. Our rangeland production model, based on the soil-vegetation model CENTURY and the livestock model GRAZPLAN, predicts biomass production and plant species composition changes, and can feed into ecosystem services models such as soil retention and water regulation in the InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) software suite. This presents a significant advance in ecosystem services modeling, moving toward continuous functions related to remotely-sensed ecosystem condition or quality rather than categorical land cover class. Preliminary findings suggest that categorical approaches may underestimate ecosystem services loss from degradation or gain from restoration by a factor of 2-5.

Analysis of Seasonal Signal in GPS Short-Baseline Time Series

NASA Astrophysics Data System (ADS)

Wang, Kaihua; Jiang, Weiping; Chen, Hua; An, Xiangdong; Zhou, Xiaohui; Yuan, Peng; Chen, Qusen

2018-04-01

Proper modeling of seasonal signals and their quantitative analysis are of interest in geoscience applications, which are based on position time series of permanent GPS stations. Seasonal signals in GPS short-baseline (< 2 km) time series, if they exist, are mainly related to site-specific effects, such as thermal expansion of the monument (TEM). However, only part of the seasonal signal can be explained by known factors due to the limited data span, the GPS processing strategy and/or the adoption of an imperfect TEM model. In this paper, to better understand the seasonal signal in GPS short-baseline time series, we adopted and processed six different short-baselines with data span that varies from 2 to 14 years and baseline length that varies from 6 to 1100 m. To avoid seasonal signals that are overwhelmed by noise, each of the station pairs is chosen with significant differences in their height (> 5 m) or type of the monument. For comparison, we also processed an approximately zero baseline with a distance of < 1 m and identical monuments. The daily solutions show that there are apparent annual signals with annual amplitude of 1 mm (maximum amplitude of 1.86 ± 0.17 mm) on almost all of the components, which are consistent with the results from previous studies. Semi-annual signal with a maximum amplitude of 0.97 ± 0.25 mm is also present. The analysis of time-correlated noise indicates that instead of flicker (FL) or random walk (RW) noise, band-pass-filtered (BP) noise is valid for approximately 40% of the baseline components, and another 20% of the components can be best modeled by a combination of the first-order Gauss-Markov (FOGM) process plus white noise (WN). The TEM displacements are then modeled by considering the monument height of the building structure beneath the GPS antenna. The median contributions of TEM to the annual amplitude in the vertical direction are 84% and 46% with and without additional parts of the monument, respectively. Obvious annual signals with amplitude > 0.4 mm in the horizontal direction are observed in five short-baselines, and the amplitudes exceed 1 mm in four of them. These horizontal seasonal signals are likely related to the propagation of daily/sub-daily TEM displacement or other signals related to the site environment. Mismodeling of the tropospheric delay may also introduce spurious seasonal signals with annual amplitudes of 5 and 2 mm, respectively, for two short-baselines with elevation differences greater than 100 m. The results suggest that the monument height of the additional part of a typical GPS station should be considered when estimating the TEM displacement and that the tropospheric delay should be modeled cautiously, especially with station pairs with apparent elevation differences. The scheme adopted in this paper is expected to explicate more seasonal signals in GPS coordinate time series, particularly in the vertical direction.

A multitrophic model to quantify the effects of marine viruses on microbial food webs and ecosystem processes

PubMed Central

Weitz, Joshua S; Stock, Charles A; Wilhelm, Steven W; Bourouiba, Lydia; Coleman, Maureen L; Buchan, Alison; Follows, Michael J; Fuhrman, Jed A; Jover, Luis F; Lennon, Jay T; Middelboe, Mathias; Sonderegger, Derek L; Suttle, Curtis A; Taylor, Bradford P; Frede Thingstad, T; Wilson, William H; Eric Wommack, K

2015-01-01

Viral lysis of microbial hosts releases organic matter that can then be assimilated by nontargeted microorganisms. Quantitative estimates of virus-mediated recycling of carbon in marine waters, first established in the late 1990s, were originally extrapolated from marine host and virus densities, host carbon content and inferred viral lysis rates. Yet, these estimates did not explicitly incorporate the cascade of complex feedbacks associated with virus-mediated lysis. To evaluate the role of viruses in shaping community structure and ecosystem functioning, we extend dynamic multitrophic ecosystem models to include a virus component, specifically parameterized for processes taking place in the ocean euphotic zone. Crucially, we are able to solve this model analytically, facilitating evaluation of model behavior under many alternative parameterizations. Analyses reveal that the addition of a virus component promotes the emergence of complex communities. In addition, biomass partitioning of the emergent multitrophic community is consistent with well-established empirical norms in the surface oceans. At steady state, ecosystem fluxes can be probed to characterize the effects that viruses have when compared with putative marine surface ecosystems without viruses. The model suggests that ecosystems with viruses will have (1) increased organic matter recycling, (2) reduced transfer to higher trophic levels and (3) increased net primary productivity. These model findings support hypotheses that viruses can have significant stimulatory effects across whole-ecosystem scales. We suggest that existing efforts to predict carbon and nutrient cycling without considering virus effects are likely to miss essential features of marine food webs that regulate global biogeochemical cycles. PMID:25635642

A multitrophic model to quantify the effects of marine viruses on microbial food webs and ecosystem processes.

PubMed

Weitz, Joshua S; Stock, Charles A; Wilhelm, Steven W; Bourouiba, Lydia; Coleman, Maureen L; Buchan, Alison; Follows, Michael J; Fuhrman, Jed A; Jover, Luis F; Lennon, Jay T; Middelboe, Mathias; Sonderegger, Derek L; Suttle, Curtis A; Taylor, Bradford P; Frede Thingstad, T; Wilson, William H; Eric Wommack, K

2015-06-01

Viral lysis of microbial hosts releases organic matter that can then be assimilated by nontargeted microorganisms. Quantitative estimates of virus-mediated recycling of carbon in marine waters, first established in the late 1990s, were originally extrapolated from marine host and virus densities, host carbon content and inferred viral lysis rates. Yet, these estimates did not explicitly incorporate the cascade of complex feedbacks associated with virus-mediated lysis. To evaluate the role of viruses in shaping community structure and ecosystem functioning, we extend dynamic multitrophic ecosystem models to include a virus component, specifically parameterized for processes taking place in the ocean euphotic zone. Crucially, we are able to solve this model analytically, facilitating evaluation of model behavior under many alternative parameterizations. Analyses reveal that the addition of a virus component promotes the emergence of complex communities. In addition, biomass partitioning of the emergent multitrophic community is consistent with well-established empirical norms in the surface oceans. At steady state, ecosystem fluxes can be probed to characterize the effects that viruses have when compared with putative marine surface ecosystems without viruses. The model suggests that ecosystems with viruses will have (1) increased organic matter recycling, (2) reduced transfer to higher trophic levels and (3) increased net primary productivity. These model findings support hypotheses that viruses can have significant stimulatory effects across whole-ecosystem scales. We suggest that existing efforts to predict carbon and nutrient cycling without considering virus effects are likely to miss essential features of marine food webs that regulate global biogeochemical cycles.

An operational model for mainstreaming ecosystem services for implementation

PubMed Central

Cowling, Richard M.; Egoh, Benis; Knight, Andrew T.; O'Farrell, Patrick J.; Reyers, Belinda; Rouget, Mathieu; Roux, Dirk J.; Welz, Adam; Wilhelm-Rechman, Angelika

2008-01-01

Research on ecosystem services has grown markedly in recent years. However, few studies are embedded in a social process designed to ensure effective management of ecosystem services. Most research has focused only on biophysical and valuation assessments of putative services. As a mission-oriented discipline, ecosystem service research should be user-inspired and user-useful, which will require that researchers respond to stakeholder needs from the outset and collaborate with them in strategy development and implementation. Here we provide a pragmatic operational model for achieving the safeguarding of ecosystem services. The model comprises three phases: assessment, planning, and management. Outcomes of social, biophysical, and valuation assessments are used to identify opportunities and constraints for implementation. The latter then are transformed into user-friendly products to identify, with stakeholders, strategic objectives for implementation (the planning phase). The management phase undertakes and coordinates actions that achieve the protection of ecosystem services and ensure the flow of these services to beneficiaries. This outcome is achieved via mainstreaming, or incorporating the safeguarding of ecosystem services into the policies and practices of sectors that deal with land- and water-use planning. Management needs to be adaptive and should be institutionalized in a suite of learning organizations that are representative of the sectors that are concerned with decision-making and planning. By following the phases of our operational model, projects for safeguarding ecosystem services are likely to empower stakeholders to implement effective on-the-ground management that will achieve resilience of the corresponding social-ecological systems. PMID:18621695

Model development of a participatory Bayesian network for coupling ecosystem services into integrated water resources management

NASA Astrophysics Data System (ADS)

Xue, Jie; Gui, Dongwei; Lei, Jiaqiang; Zeng, Fanjiang; Mao, Donglei; Zhang, Zhiwei

2017-11-01

There is an increasing consensus on the importance of coupling ecosystem services (ES) into integrated water resource management (IWRM), due to a wide range of benefits to human from the ES. This paper proposes an ES-based IWRM framework within which a participatory Bayesian network (BN) model is developed to assist with the coupling between ES and IWRM. The framework includes three steps: identifying water-related services of ecosystems; analysis of the tradeoff and synergy among users of water; and ES-based IWRM implementation using the participatory BN model. We present the development, evaluation and application of the participatory BN model with the involvement of four participant groups (stakeholders, water manager, water management experts, and research team) in Qira oasis area, Northwest China. As a typical catchment-scale region, the Qira oasis area is facing severe water competition between the demands of human activities and natural ecosystems. Results demonstrate that the BN model developed provides effective integration of ES into a quantitative IWMR framework via public negotiation and feedback. The network results, sensitivity evaluation, and management scenarios are broadly accepted by the participant groups. The intervention scenarios from the model conclude that any water management measure remains unable to sustain the ecosystem health in water-related ES. Greater cooperation among the stakeholders is highly necessary for dealing with such water conflicts. In particular, a proportion of the agricultural water saved through improving water-use efficiency should be transferred to natural ecosystems via water trade. The BN model developed is appropriate for areas throughout the world in which there is intense competition for water between human activities and ecosystems.

Simulating carbon and water fluxes at Arctic and boreal ecosystems in Alaska by optimizing the modified BIOME-BGC with eddy covariance data

NASA Astrophysics Data System (ADS)

Ueyama, M.; Kondo, M.; Ichii, K.; Iwata, H.; Euskirchen, E. S.; Zona, D.; Rocha, A. V.; Harazono, Y.; Nakai, T.; Oechel, W. C.

2013-12-01

To better predict carbon and water cycles in Arctic ecosystems, we modified a process-based ecosystem model, BIOME-BGC, by introducing new processes: change in active layer depth on permafrost and phenology of tundra vegetation. The modified BIOME-BGC was optimized using an optimization method. The model was constrained using gross primary productivity (GPP) and net ecosystem exchange (NEE) at 23 eddy covariance sites in Alaska, and vegetation/soil carbon from a literature survey. The model was used to simulate regional carbon and water fluxes of Alaska from 1900 to 2011. Simulated regional fluxes were validated with upscaled GPP, ecosystem respiration (RE), and NEE based on two methods: (1) a machine learning technique and (2) a top-down model. Our initial simulation suggests that the original BIOME-BGC with default ecophysiological parameters substantially underestimated GPP and RE for tundra and overestimated those fluxes for boreal forests. We will discuss how optimization using the eddy covariance data impacts the historical simulation by comparing the new version of the model with simulated results from the original BIOME-BGC with default ecophysiological parameters. This suggests that the incorporation of the active layer depth and plant phenology processes is important to include when simulating carbon and water fluxes in Arctic ecosystems.

A framework for predicting impacts on ecosystem services ...

EPA Pesticide Factsheets

Protection of ecosystem services is increasingly emphasized as a risk-assessment goal, but there are wide gaps between current ecological risk-assessment endpoints and potential effects on services provided by ecosystems. The authors present a framework that links common ecotoxicological endpoints to chemical impacts on populations and communities and the ecosystem services that they provide. This framework builds on considerable advances in mechanistic effects models designed to span multiple levels of biological organization and account for various types of biological interactions and feedbacks. For illustration, the authors introduce 2 case studies that employ well-developed and validated mechanistic effects models: the inSTREAM individual-based model for fish populations and the AQUATOX ecosystem model. They also show how dynamic energy budget theory can provide a common currency for interpreting organism-level toxicity. They suggest that a framework based on mechanistic models that predict impacts on ecosystem services resulting from chemical exposure, combined with economic valuation, can provide a useful approach for informing environmental management. The authors highlight the potential benefits of using this framework as well as the challenges that will need to be addressed in future work. The framework introduced here represents an ongoing initiative supported by the National Institute of Mathematical and Biological Synthesis (NIMBioS; http://www.nimbi

LAI is the major cause of divergence in CO2 fertilization effect in land surface models

NASA Astrophysics Data System (ADS)

Li, Q.; Luo, Y.; Lu, X.; Wang, Y.; Huang, X.; Lin, G., Sr.

2017-12-01

Concentration-carbon feedback (β), also called CO2 fertilization effect, is an important feedback between terrestrial ecosystems and atmosphere to alleviate global climate change. However, models participating in C4MIP and CMIP5 predicted diverse CO2 fertilization effects under future CO2 inceasing scenarios. Hence identifing the key processes dominating the divergence of β in land surface models is of significance. We calculated CO2 fertilization effects from leaf level, canopy gross productivity level, net ecosystem productivity level and ecosystem carbon stock level in Community Atmosphere Biosphere Land Exchange (CABLE) model. Our results identified LAI is the key factor dominating the divergence of β among C3 plants in CABLE model. Saturation of the ecosystem productivity to increasing CO2 is not only regulated by leaf-level response, but also the response of LAI to increasing CO2. The greatest variation among C3 plants at ecosystem level suggests that other processes such as different allocation patterns and soil carbon dynamics of various vegetation types are also responsible for the divergence. Our results indicate that processes regarding to LAI need to be better calibrated according to experiments and observations in order to better represent the response of ecosystem productivity to increasing CO2.

Comparative Model Evaluation Studies of Biogenic Trace Gas Fluxes in Tropical Forests

NASA Technical Reports Server (NTRS)

Potter, C. S.; Peterson, David L. (Technical Monitor)

1997-01-01

Simulation modeling can play a number of important roles in large-scale ecosystem studies, including synthesis of patterns and changes in carbon and nutrient cycling dynamics, scaling up to regional estimates, and formulation of testable hypotheses for process studies. Recent comparative studies have shown that ecosystem models of soil trace gas exchange with the atmosphere are evolving into several distinct simulation approaches. Different levels of detail exist among process models in the treatment of physical controls on ecosystem nutrient fluxes and organic substrate transformations leading to gas emissions. These differences are is in part from distinct objectives of scaling and extrapolation. Parameter requirements for initialization scalings, boundary conditions, and time-series driven therefore vary among ecosystem simulation models, such that the design of field experiments for integration with modeling should consider a consolidated series of measurements that will satisfy most of the various model requirements. For example, variables that provide information on soil moisture holding capacity, moisture retention characteristics, potential evapotranspiration and drainage rates, and rooting depth appear to be of the first order in model evaluation trials for tropical moist forest ecosystems. The amount and nutrient content of labile organic matter in the soil, based on accurate plant production estimates, are also key parameters that determine emission model response. Based on comparative model results, it is possible to construct a preliminary evaluation matrix along categories of key diagnostic parameters and temporal domains. Nevertheless, as large-scale studied are planned, it is notable that few existing models age designed to simulate transient states of ecosystem change, a feature which will be essential for assessment of anthropogenic disturbance on regional gas budgets, and effects of long-term climate variability on biosphere-atmosphere exchange.

[Measuring water ecological carrying capacity with the ecosystem-service-based ecological footprint (ESEF) method: Theory, models and application].

PubMed

Jiao, Wen-jun; Min, Qing-wen; Li, Wen-hua; Fuller, Anthony M

2015-04-01

Integrated watershed management based on aquatic ecosystems has been increasingly acknowledged. Such a change in the philosophy of water environment management requires recognizing the carrying capacity of aquatic ecosystems for human society from a more general perspective. The concept of the water ecological carrying capacity is therefore put forward, which considers both water resources and water environment, connects socio-economic development to aquatic ecosystems and provides strong support for integrated watershed management. In this paper, the authors proposed an ESEF-based measure of water ecological carrying capacity and constructed ESEF-based models of water ecological footprint and capacity, aiming to evaluate water ecological carrying capacity with footprint methods. A regional model of Taihu Lake Basin was constructed and applied to evaluate the water ecological carrying capacity in Changzhou City which located in the upper reaches of the basin. Results showed that human demand for water ecosystem services in this city had exceeded the supply capacity of local aquatic ecosystems and the significant gap between demand and supply had jeopardized the sustainability of local aquatic ecosystems. Considering aqua-product provision, water supply and pollutant absorption in an integrated way, the scale of population and economy aquatic ecosystems in Changzhou could bear only 54% of the current status.

Interferon-γ converts human microvascular pericytes into negative regulators of alloimmunity through induction of indoleamine 2,3-dioxygenase 1

PubMed Central

Liu, Rebecca; Manes, Thomas D.; Qin, Lingfeng; Tietjen, Gregory T.; Broecker, Verena; Fang, Caodi; Xie, Catherine; Chen, Ping-Min; Kirkiles-Smith, Nancy C.; Jane-Wit, Dan; Pober, Jordan S.

2018-01-01

Early acute rejection of human allografts is mediated by circulating alloreactive host effector memory T cells (TEM). TEM infiltration typically occurs across graft postcapillary venules and involves sequential interactions with graft-derived endothelial cells (ECs) and pericytes (PCs). While the role of ECs in allograft rejection has been extensively studied, contributions of PCs to this process are largely unknown. This study aimed to characterize the effects and mechanisms of interactions between human PCs and allogeneic TEM. We report that unstimulated PCs, like ECs, can directly present alloantigen to TEM, but while IFN-γ–activated ECs (γ-ECs) show increased ability to stimulate alloreactive T cells, IFN-γ–activated PCs (γ-PCs) instead suppress TEM proliferation but not cytokine production or signaling. RNA sequencing analysis of PCs, γ-PCs, ECs, and γ-ECs reveal induction of indoleamine 2,3-dioxygenase 1 (IDO1) in γ-PCs to significantly higher levels than in γ-ECs that correlates with tryptophan depletion in vitro. Consistently, shRNA knockdown of IDO1 markedly reduces γ-PC–mediated immunoregulatory effects. Furthermore, human PCs express IDO1 in a skin allograft rejection humanized mouse model and in human renal allografts with acute T cell–mediated rejection. We conclude that immunosuppressive properties of human PCs are not intrinsic but instead result from IFN-γ–induced IDO1-mediated tryptophan depletion. PMID:29515027

ECOSYSTEM SERVICES AND BEYOND: INTEGRATION OF ECOSYSTEM SCIENCE AND MULTIMEDIA EXPOSURE MODELING FOR ENVIRONMENTAL PROTECTION

EPA Science Inventory

Decision-making for ecosystem protection and resource management requires an integrative science and technology applied with a sufficiently comprehensive systems approach. Single media (e.g., air, soil and water) approaches that evaluate aspects of an ecosystem in a stressor-by-...

Ecosystem development of Haizhou Bay Ecological Restoration Area from 2003 to 2013

NASA Astrophysics Data System (ADS)

Wang, Teng; Li, Yunkai; Xie, Bin; Zhang, Hu; Zhang, Shuo

2017-12-01

Two Ecopath mass-balance models were implemented for evaluating the structure and function of Haizhou Bay Ecological Restoration Area ecosystem using 14 ecological indicators in two distinctive years (2003 and 2013). The results showed that the size of HZERA ecosystem became larger as total biomass was increased in last decade, especially in primary producer and zooplankton groups. Total system throughput increased from 7496.00 t km-2 yr-1 to 9547.54 t km-2 yr-1. The P/R (production/respiration) ratio decreased over the decade. Finn's cycling index and Finn's mean path length increased over the decade. No keystone species (KS) occurred during ten years; however, evidences of top-down control in 2003 and 2013 models were demonstrated by high KS value belonging to Lophius litulon group in food web. Drawing upon Odum's theory of ecosystem maturity, the structured, web-like ecosystem of 2013 model had developed into a highly mature system compared with that of 2003 model.

Tailored expectant management in couples with unexplained infertility does not influence their experiences with the quality of fertility care.

PubMed

Kersten, F A M; Hermens, R P G M; Braat, D D M; Tepe, E; Sluijmer, A; Kuchenbecker, W K; Van den Boogaard, N; Mol, B W J; Goddijn, M; Nelen, W L D M

2016-01-01

Do couples who were eligible for tailored expectant management (TEM) and did not start treatment within 6 months after the fertility work-up, have different experiences with the quality of care than couples that were also eligible for TEM but started treatment right after the fertility work-up? Tailored expectant management of at least 6 months in couples with unexplained infertility is not associated with the experiences with quality of care or trust in their physician. In couples with unexplained infertility and a good prognosis of natural conception within 1 year, expectant management for 6-12 months does not compromise ongoing birth rates and is equally as effective as starting medically assisted reproduction immediately. Therefore, TEM is recommended by various international clinical guidelines. Implementation of TEM is still not optimal because of existing barriers on both patient and professional level. An important barrier is the hesitance of professionals to counsel their patients for TEM because they fear that patients will be dissatisfied with care. However, if and how adherence to TEM actually affects the couples' experience with care is unknown. Experiences with the quality care can be measured by evaluating the patient-centredness of care and the patients' trust in their physician. This is a retrospective cross-sectional study. A survey with written questionnaires was performed among all couples who participated in the retrospective audit of guideline adherence on TEM in 25 Dutch clinics. Couples were eligible to participate if they were diagnosed with unexplained infertility and had a good prognosis (>30%) of natural conception within 1 year based on the Hunault prediction model. We used patient's questionnaires to collect data on the couples' experience with the quality of care and possible confounders for their experiences other than having undergone TEM or not. Multilevel regression analyses were performed to investigate case-mix adjusted association of TEM with the patient-centredness of care (PCQ-Infertility) and the patients' trust in their physician (Wake Forest Trust Scale). Couples who adhered to TEM experienced the quality of care on the same level as couples who were exposed to early treatment, i.e. started fertility treatment within 6 months after fertility work-up. There were no associations between adherence to TEM and the patient-centredness of care or the patients' trust in their physician. Because this study is retrospective, recall bias might occur. Furthermore, we were unable to measure the difference in experience with care over time. Therefore, our results have to be interpreted carefully. Prospective research on couples undergoing TEM have to be performed to provide more detailed insight in the patients' experiences with the decision making process and subsequently the expectant period. Tackling the barriers surrounding TEM, i.e. better counselling and more patient information material, could further improve patient experiences with the quality of care for couples who are advised TEM. Supported by Netherlands Organisation for Health Research and Development (ZonMW). ZonMW had no role in designing the study, data collection, analysis and interpretation of data or writing of the report. Competing interests: none. www.trialregister.nl NTR3405. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Merging a mechanistic enzymatic model of soil heterotrophic respiration into an ecosystem model in two AmeriFlux sites of northeastern USA

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

Sihi, Debjani; Davidson, Eric A.; Chen, Min

Heterotrophic respiration (Rh), microbial processing of soil organic matter to carbon dioxide (CO 2), is a major, yet highly uncertain, carbon (C) flux from terrestrial systems to the atmosphere. Temperature sensitivity of Rh is often represented with a simple Q 10 function in ecosystem models and earth system models (ESMs), sometimes accompanied by an empirical soil moisture modifier. More explicit representation of the effects of soil moisture, substrate supply, and their interactions with temperature has been proposed as a way to disentangle the confounding factors of apparent temperature sensitivity of Rh and improve the performance of ecosystem models and ESMs.more » The objective of this work was to insert into an ecosystem model a more mechanistic, but still parsimonious, model of environmental factors controlling Rh and evaluate the model performance in terms of soil and ecosystem respiration. The Dual Arrhenius and Michaelis-Menten (DAMM) model simulates Rh using Michaelis-Menten, Arrhenius, and diffusion functions. Soil moisture affects Rh and its apparent temperature sensitivity in DAMM by regulating the diffusion of oxygen, soluble C substrates, and extracellular enzymes to the enzymatic reaction site. Here, we merged the DAMM soil flux model with a parsimonious ecosystem flux model, FöBAAR (Forest Biomass, Assimilation, Allocation and Respiration). We used high-frequency soil flux data from automated soil chambers and landscape-scale ecosystem fluxes from eddy covariance towers at two AmeriFlux sites (Harvard Forest, MA and Howland Forest, ME) in the northeastern USA to estimate parameters, validate the merged model, and to quantify the uncertainties in a multiple constraints approach. The optimized DAMM-FöBAAR model better captured the seasonal and inter-annual dynamics of soil respiration (Soil R) compared to the FöBAAR-only model for the Harvard Forest, where higher frequency and duration of drying events significantly regulate substrate supply to heterotrophs. However, DAMM-FöBAAR showed improvement over FöBAAR-only at the boreal transition Howland Forest only in unusually dry years. The frequency of synoptic-scale dry periods is lower at Howland, resulting in only brief water limitation of Rh in some years. At both sites, the declining trend of soil R during drying events was captured by the DAMM-FöBAAR model; however, model performance was also contingent on site conditions, climate, and the temporal scale of interest. While the DAMM functions require a few more parameters than a simple Q10 function, we have demonstrated that they can be included in an ecosystem model and reduce the model-data mismatch. Moreover, the mechanistic structure of the soil moisture effects using DAMM functions should be more generalizable than the wide variety of empirical functions that are commonly used, and these DAMM functions could be readily incorporated into other ecosystem models and ESMs.« less

The distribution of persistent organic pollutants in a trophically complex Antarctic ecosystem model

NASA Astrophysics Data System (ADS)

Bates, Michael L.; Bengtson Nash, Susan M.; Hawker, Darryl W.; Shaw, Emily C.; Cropp, Roger A.

2017-06-01

Despite Antarctica's isolation from human population centres, persistent organic pollutants (POPs) are transported there via long range atmospheric transport and subsequently cold-trapped. The challenging nature of working in the Antarctic environment greatly limits our ability to monitor POP concentrations and understand the processes that govern the distribution of POPs in Antarctic ecosystems. Here we couple a dynamic, trophically complex biological model with a fugacity model to investigate the distribution of hexachlorobenzene (HCB) in a near-shore Antarctic ecosystem. Using this model we examine the steady-state, and annual cycle of HCB concentration in the atmosphere, ocean, sediment, detritus, and 21 classes of biota that span from primary producers to apex predators. The scope and trophic resolution of our model allows us to examine POP pathways through the ecosystem. In our model the main pathway of HCB to upper trophic species is via pelagic communities, with relatively little via benthic communities. Using a dynamic ecosystem model also allows us to examine the seasonal and potential climate change induced changes in POP distribution. We show that there is a large annual cycle in concentration in the planktonic communities, which may have implications for biomagnification factors calculated from observations. We also examine the direct effects of increasing temperature on the redistribution of HCB in a changing climate and find that it is likely minor compared to other indirect effects, such as changes in atmospheric circulation, sea ice dynamics, and changes to the ecosystem itself.

Climate-based models for pulsed resources improve predictability of consumer population dynamics: outbreaks of house mice in forest ecosystems.

PubMed

Holland, E Penelope; James, Alex; Ruscoe, Wendy A; Pech, Roger P; Byrom, Andrea E

2015-01-01

Accurate predictions of the timing and magnitude of consumer responses to episodic seeding events (masts) are important for understanding ecosystem dynamics and for managing outbreaks of invasive species generated by masts. While models relating consumer populations to resource fluctuations have been developed successfully for a range of natural and modified ecosystems, a critical gap that needs addressing is better prediction of resource pulses. A recent model used change in summer temperature from one year to the next (ΔT) for predicting masts for forest and grassland plants in New Zealand. We extend this climate-based method in the framework of a model for consumer-resource dynamics to predict invasive house mouse (Mus musculus) outbreaks in forest ecosystems. Compared with previous mast models based on absolute temperature, the ΔT method for predicting masts resulted in an improved model for mouse population dynamics. There was also a threshold effect of ΔT on the likelihood of an outbreak occurring. The improved climate-based method for predicting resource pulses and consumer responses provides a straightforward rule of thumb for determining, with one year's advance warning, whether management intervention might be required in invaded ecosystems. The approach could be applied to consumer-resource systems worldwide where climatic variables are used to model the size and duration of resource pulses, and may have particular relevance for ecosystems where global change scenarios predict increased variability in climatic events.

Modelling Mediterranean agro-ecosystems by including agricultural trees in the LPJmL model

NASA Astrophysics Data System (ADS)

Fader, M.; von Bloh, W.; Shi, S.; Bondeau, A.; Cramer, W.

2015-06-01

Climate and land use change in the Mediterranean region is expected to affect natural and agricultural ecosystems by decreases in precipitation, increases in temperature as well as biodiversity loss and anthropogenic degradation of natural resources. Demographic growth in the Eastern and Southern shores will require increases in food production and put additional pressure on agro-ecosystems and water resources. Coping with these challenges requires informed decisions that, in turn, require assessments by means of a comprehensive agro-ecosystem and hydrological model. This study presents the inclusion of 10 Mediterranean agricultural plants, mainly perennial crops, in an agro-ecosystem model (LPJmL): nut trees, date palms, citrus trees, orchards, olive trees, grapes, cotton, potatoes, vegetables and fodder grasses. The model was successfully tested in three model outputs: agricultural yields, irrigation requirements and soil carbon density. With the development presented in this study, LPJmL is now able to simulate in good detail and mechanistically the functioning of Mediterranean agriculture with a comprehensive representation of ecophysiological processes for all vegetation types (natural and agricultural) and in a consistent framework that produces estimates of carbon, agricultural and hydrological variables for the entire Mediterranean basin. This development pave the way for further model extensions aiming at the representation of alternative agro-ecosystems (e.g. agroforestry), and opens the door for a large number of applications in the Mediterranean region, for example assessments on the consequences of land use transitions, the influence of management practices and climate change impacts.

Current and future carbon budget at Takayama site, Japan, evaluated by a regional climate model and a process-based terrestrial ecosystem model.

PubMed

Kuribayashi, Masatoshi; Noh, Nam-Jin; Saitoh, Taku M; Ito, Akihiko; Wakazuki, Yasutaka; Muraoka, Hiroyuki

2017-06-01

Accurate projection of carbon budget in forest ecosystems under future climate and atmospheric carbon dioxide (CO 2 ) concentration is important to evaluate the function of terrestrial ecosystems, which serve as a major sink of atmospheric CO 2 . In this study, we examined the effects of spatial resolution of meteorological data on the accuracies of ecosystem model simulation for canopy phenology and carbon budget such as gross primary production (GPP), ecosystem respiration (ER), and net ecosystem production (NEP) of a deciduous forest in Japan. Then, we simulated the future (around 2085) changes in canopy phenology and carbon budget of the forest by incorporating high-resolution meteorological data downscaled by a regional climate model. The ecosystem model overestimated GPP and ER when we inputted low-resolution data, which have warming biases over mountainous landscape. But, it reproduced canopy phenology and carbon budget well, when we inputted high-resolution data. Under the future climate, earlier leaf expansion and delayed leaf fall by about 10 days compared with the present state was simulated, and also, GPP, ER and NEP were estimated to increase by 25.2%, 23.7% and 35.4%, respectively. Sensitivity analysis showed that the increase of NEP in June and October would be mainly caused by rising temperature, whereas that in July and August would be largely attributable to CO 2 fertilization. This study suggests that the downscaling of future climate data enable us to project more reliable carbon budget of forest ecosystem in mountainous landscape than the low-resolution simulation due to the better predictions of leaf expansion and shedding.

Ensemble ecosystem modeling for predicting ecosystem response to predator reintroduction.

PubMed

Baker, Christopher M; Gordon, Ascelin; Bode, Michael

2017-04-01

Introducing a new or extirpated species to an ecosystem is risky, and managers need quantitative methods that can predict the consequences for the recipient ecosystem. Proponents of keystone predator reintroductions commonly argue that the presence of the predator will restore ecosystem function, but this has not always been the case, and mathematical modeling has an important role to play in predicting how reintroductions will likely play out. We devised an ensemble modeling method that integrates species interaction networks and dynamic community simulations and used it to describe the range of plausible consequences of 2 keystone-predator reintroductions: wolves (Canis lupus) to Yellowstone National Park and dingoes (Canis dingo) to a national park in Australia. Although previous methods for predicting ecosystem responses to such interventions focused on predicting changes around a given equilibrium, we used Lotka-Volterra equations to predict changing abundances through time. We applied our method to interaction networks for wolves in Yellowstone National Park and for dingoes in Australia. Our model replicated the observed dynamics in Yellowstone National Park and produced a larger range of potential outcomes for the dingo network. However, we also found that changes in small vertebrates or invertebrates gave a good indication about the potential future state of the system. Our method allowed us to predict when the systems were far from equilibrium. Our results showed that the method can also be used to predict which species may increase or decrease following a reintroduction and can identify species that are important to monitor (i.e., species whose changes in abundance give extra insight into broad changes in the system). Ensemble ecosystem modeling can also be applied to assess the ecosystem-wide implications of other types of interventions including assisted migration, biocontrol, and invasive species eradication. © 2016 Society for Conservation Biology.

Satellite-based modeling of gross primary production in an evergreen needleleaf forest

Treesearch

Xiangming Xiao; David Hollinger; John Aber; Mike Goltz; Eric A. Davidson; Qingyuan Zhang; Berrien Moore III

2004-01-01

The eddy covariance technique provides valuable information on net ecosystem exchange (NEE) of CO2, between the atmosphere and terrestrial ecosystems, ecosystem respiration, and gross primary production (GPP) at a variety of C02 eddy flux tower sites. In this paper, we develop a new, satellite-based Vegetation Photosynthesis Model (VPM) to estimate the seasonal dynamcs...

Modeled effect of warming on ecosystem carbon and water dynamics within grassland/old-field ecosystems along a moisture gradient

USDA-ARS?s Scientific Manuscript database

As a consequence of steadily increasing concentrations of greenhouse gases in Earth’s atmosphere, average world-wide surface temperature is expected to increase 1.5-6.4°C by the end of the 21st Century. Results from manipulative field experiments and ecosystem modeling indicate that plants and soil...

Inverse estimation of Vcmax, leaf area index, and the Ball-Berry parameter from carbon and energy fluxes

Treesearch

Adam Wolf; Kanat Akshalov; Nicanor Saliendra; Douglas A. Johnson; Emilio A. Laca

2006-01-01

Canopy fluxes of CO2 and energy can be modeled with high fidelity using a small number of environmental variables and ecosystem parameters. Although these ecosystem parameters are critically important for modeling canopy fluxes, they typically are not measured with the same intensity as ecosystem fluxes. We developed an algorithm to estimate leaf...

A comparison of tools for modeling freshwater ecosystem services.

PubMed

Vigerstol, Kari L; Aukema, Juliann E

2011-10-01

Interest in ecosystem services has grown tremendously among a wide range of sectors, including government agencies, NGO's and the business community. Ecosystem services entailing freshwater (e.g. flood control, the provision of hydropower, and water supply), as well as carbon storage and sequestration, have received the greatest attention in both scientific and on-the-ground applications. Given the newness of the field and the variety of tools for predicting water-based services, it is difficult to know which tools to use for different questions. There are two types of freshwater-related tools--traditional hydrologic tools and newer ecosystem services tools. Here we review two of the most prominent tools of each type and their possible applications. In particular, we compare the data requirements, ease of use, questions addressed, and interpretability of results among the models. We discuss the strengths, challenges and most appropriate applications of the different models. Traditional hydrological tools provide more detail whereas ecosystem services tools tend to be more accessible to non-experts and can provide a good general picture of these ecosystem services. We also suggest gaps in the modeling toolbox that would provide the greatest advances by improving existing tools. Copyright © 2011 Elsevier Ltd. All rights reserved.

Modeling forest C and N allocation responses to free-air CO2 enrichment

NASA Astrophysics Data System (ADS)

Luus, Kristina; De Kauwe, Martin; Walker, Anthony; Werner, Christian; Iversen, Colleen; McCarthy, Heather; Medlyn, Belinda; Norby, Richard; Oren, Ram; Zak, Donald; Zaehle, Sönke

2015-04-01

Vegetation allocation patterns and soil-vegetation partitioning of C and N are predicted to change in response to rising atmospheric concentrations of CO2. These allocation responses to rising CO2 have been examined at the ecosystem level through through free-air CO2 enrichment (FACE) experiments, and their global implications for the timing of progressive N limitation (PNL) and C sequestration have been predicted for ~100 years using a variety of ecosystem models. However, recent FACE model-data syntheses studies [1,2,3] have indicated that ecosystem models do not capture the 5-10 year site-level ecosystem allocation responses to elevated CO2. This may be due in part to the missing representation of the rhizosphere interactions between plants and soil biota in models. Ecosystem allocation of C and N is altered by interactions between soil and vegetation through the priming effect: as plant N availability diminishes, plants respond physiologically by altering their tissue allocation strategies so as to increase rates of root growth and rhizodeposition. In response, either soil organic material begins to accumulate, which hastens the onset of PNL, or soil microbes start to decompose C more rapidly, resulting in increased N availability for plant uptake, which delays PNL. In this study, a straightforward approach for representing rhizosphere interactions in ecosystem models was developed through which C and N allocation to roots and rhizodeposition responds dynamically to elevated CO2 conditions, modifying soil decomposition rates without pre-specification of the direction in which soil C and N accumulation should shift in response to elevated CO2. This approach was implemented in a variety of ecosystem models ranging from stand (G'DAY), to land surface (CLM 4.5, O-CN), to dynamic global vegetation (LPJ-GUESS) models. Comparisons against data from three forest FACE sites (Duke, Oak Ridge & Rhinelander) indicated that representing rhizosphere interactions allowed models to more reliably capture responses of ecosystem C and N allocation to free-air CO2 enrichment because they were able to simulate the priming effect. Insights were therefore gained into between-site differences observed in forest FACE experiments, and the underlying physiological and biogeochemical mechanisms determining ecosystem C and N allocation responses to elevated CO2. References 1. De Kauwe, M. G., et al. (2014), Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites, New Phytologist, 203, 883-899. 2. Walker, A. P., et al. (2014), Comprehensive ecosystem model-data synthesis using multiple data sets at two temperate forest free-air CO2 enrichment experiments: Model performance at ambient CO2 concentration, Journal of Geophysical Research: Biogeosciences, 119, 937-964. 3. Zaehle, S., et al. (2014), Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies, New Phytologist, 202 (3), 803-822.

Activation of the marine ecosystem model 3D CEMBS for the Baltic Sea in operational mode

NASA Astrophysics Data System (ADS)

Dzierzbicka-Glowacka, Lidia; Jakacki, Jaromir; Janecki, Maciej; Nowicki, Artur

2013-04-01

The paper presents a new marine ecosystem model 3D CEMBS designed for the Baltic Sea. The ecosystem model is incorporated into the 3D POPCICE ocean-ice model. The Current Baltic Sea model is based on the Community Earth System Model (CESM from the National Center for Atmospheric Research) which was adapted for the Baltic Sea as a coupled sea-ice model. It consists of the Community Ice Code (CICE model, version 4.0) and the Parallel Ocean Program (version 2.1). The ecosystem model is a biological submodel of the 3D CEMBS. It consists of eleven mass conservation equations. There are eleven partial second-order differential equations of the diffusion type with the advective term for phytoplankton, zooplankton, nutrients, dissolved oxygen, and dissolved and particulate organic matter. This model is an effective tool for solving the problem of ecosystem bioproductivity. The model is forced by 48-hour atmospheric forecasts provided by the UM model from the Interdisciplinary Centre for Mathematical and Computational Modelling of Warsaw University (ICM). The study was financially supported by the Polish State Committee of Scientific Research (grants: No N N305 111636, N N306 353239). The partial support for this study was also provided by the project Satellite Monitoring of the Baltic Sea Environment - SatBaltyk founded by European Union through European Regional Development Fund contract no. POIG 01.01.02-22-011/09. Calculations were carried out at the Academy Computer Centre in Gdańsk.

Investigation of C3 S hydration mechanism by transmission electron microscope (TEM) with integrated Super-XTM EDS system.

PubMed

Sakalli, Y; Trettin, R

2017-07-01

Tricalciumsilicate (C 3 S, Alite) is the major component of the Portland cement clinker. Hydration of Alite is decisive in influencing the properties of the resulting material. This is due to its high content in cement. The mechanism of the hydration of C 3 S is very complicated and not yet fully understood. There are different models describing the hydration of C 3 S in various ways. In this work for a better understanding of hydration mechanism, the hydrated C 3 S was investigated by using the transmission electron microscope (TEM) and for the first time, the samples for the investigations were prepared by using of focused ion beam from sintered pellets of C 3 S. Also, an FEI Talos F200x with an integrated Super-X EDS system was used for the investigations. FEI Talos F200X combines outstanding high-resolution S/TEM and TEM imaging with energy dispersive X-ray spectroscopy signal detection, and 3D chemical characterization with compositional mapping. TEM is a very powerful tool for material science. A high energy beam of electrons passes through a very thin sample, and the interactions between the electrons and the atoms can be used to observe the structure of the material and other features in the structure. TEM can be used to study the growth of layers and their composition. TEM produces high-resolution, two-dimensional images and will be used for a wide range of educational, science and industry applications. Chemical analysis can also be performed. The purpose of these investigations was to get the information about the composition of the C-S-H phases and some details of the nanostructure of the C-S-H phases. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Complete Tem-Tomography: 3D Structure of Gems Cluster

NASA Technical Reports Server (NTRS)

Matsuno, J.; Miyake, A.; Tsuchiyama, A.; Messenger, S.; Nakamura-Messenger, K.

2015-01-01

GEMS (glass with embedded metal and sulfide) grains in interplanetary dust particles (IDPs) are considered to be one of the ubiquitous and fundamental building blocks of solids in the Solar System. They have been considered to be interstellar silicate dust that survived various metamorphism or alteration processes in the protoplanetary disk but the elemental and isotopic composition measurements suggest that most of them have been formed in the protoplanetary disk as condensates from high temperature gas. This formation model is also supported by the formation of GEMS-like grains with respect to the size, mineral assemblage, texture and infrared spectrum by condensation experiments from mean GEMS composition materials. Previous GEMS studies were performed only with 2D observation by transmission electron microscopy (TEM) or scanning TEM (STEM). However, the 3D shape and structure of GEMS grains and the spatial distribution of Fe/FeS's has critical information about their formation and origin. Recently, the 3D structure of GEMS grains in ultrathin sections of cluster IDPs was revealed by electron tomography using a TEM/STEM (JEM-2100F, JEOL). However, CT images of thin sections mounted on Cu grids acquired by conventional TEM-tomography are limited to low tilt angles (e. g., less than absolute value of 75 deg. In fact, previous 3D TEM observations of GEMS were affected by some artifacts related to the limited tilt range in the TEM used. Complete tomographic images should be acquired by rotating the sample tilt angle over a range of more than absolute value of 80 deg otherwise the CT images lose their correct structures. In order to constrain the origin and formation process of GEMS grains more clearly, we performed complete electron tomography for GEMS grains. Here we report the sample preparation method we have developed for this study, and the preliminary results.

Simulation of hydrologic influences on wetland ecosystem succession. Master's thesis

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

Pompilio, R.A.

1994-09-01

This research focuses on the development of a simulation model to determine the affects of hydrological influences on a wetland ecosystem. The model allows perturbations to the inputs of various wetland data which in turn, influences the successional development of the ecosystem. This research consisted of converting a grassland ecosystem model to one which simulates wetland conditions. The critical factor in determining the success of wetland creation is the hydrology of the system. There are four of the areas of the original model which are affected by the hydrology. The model measures the health or success of the ecosystem throughmore » the measurement of the systems gross plant production, the respiration and the net primary production of biomass. Altering the auxiliary variables of water level and the rate of flow through the system explicitly details the affects hydrologic influences on those production rates. Ten case tests depicting exogenous perturbations of the hydrology were run to identify these affects. Although the tests dealt with the fluctuation of water through the system, any one of the auxiliary variables in the model could be changed to reflect site specific data. Productivity, Hazardous material management, Hazardous material pharmacy.« less

The Functionally-Assembled Terrestrial Ecosystem Simulator Version 1

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

Xu, Chonggang; Christoffersen, Bradley

The Functionally-Assembled Terrestrial Ecosystem Simulator (FATES) is a vegetation model for use in Earth system models (ESMs). The model includes a size- and age-structured representation of tree dynamics, competition between functionally diverse plant functional types, and the biophysics underpinning plant growth, competition, mortality, as well as the carbon, water, and energy exchange with the atmosphere. The FATES model is designed as a modular vegetation model that can be integrated within a host land model for inclusion in ESMs. The model is designed for use in global change studies to understand and project the responses and feedbacks between terrestrial ecosystems andmore » the Earth system under changing climate and other forcings.« less

Strong and nonlinear effects of fragmentation on ecosystem service provision at multiple scales

NASA Astrophysics Data System (ADS)

Mitchell, Matthew G. E.; Bennett, Elena M.; Gonzalez, Andrew

2015-09-01

Human actions, such as converting natural land cover to agricultural or urban land, result in the loss and fragmentation of natural habitat, with important consequences for the provision of ecosystem services. Such habitat loss is especially important for services that are supplied by fragments of natural land cover and that depend on flows of organisms, matter, or people across the landscape to produce benefits, such as pollination, pest regulation, recreation and cultural services. However, our quantitative knowledge about precisely how different patterns of landscape fragmentation might affect the provision of these types of services is limited. We used a simple, spatially explicit model to evaluate the potential impact of natural land cover loss and fragmentation on the provision of hypothetical ecosystem services. Based on current literature, we assumed that fragments of natural land cover provide ecosystem services to the area surrounding them in a distance-dependent manner such that ecosystem service flow depended on proximity to fragments. We modeled seven different patterns of natural land cover loss across landscapes that varied in the overall level of landscape fragmentation. Our model predicts that natural land cover loss will have strong and unimodal effects on ecosystem service provision, with clear thresholds indicating rapid loss of service provision beyond critical levels of natural land cover loss. It also predicts the presence of a tradeoff between maximizing ecosystem service provision and conserving natural land cover, and a mismatch between ecosystem service provision at landscape versus finer spatial scales. Importantly, the pattern of landscape fragmentation mitigated or intensified these tradeoffs and mismatches. Our model suggests that managing patterns of natural land cover loss and fragmentation could help influence the provision of multiple ecosystem services and manage tradeoffs and synergies between services across different human-dominated landscapes.

A comparative assessment of tools for ecosystem services quantification and valuation

USGS Publications Warehouse

Bagstad, Kenneth J.; Semmens, Darius; Waage, Sissel; Winthrop, Robert

2013-01-01

To enter widespread use, ecosystem service assessments need to be quantifiable, replicable, credible, flexible, and affordable. With recent growth in the field of ecosystem services, a variety of decision-support tools has emerged to support more systematic ecosystem services assessment. Despite the growing complexity of the tool landscape, thorough reviews of tools for identifying, assessing, modeling and in some cases monetarily valuing ecosystem services have generally been lacking. In this study, we describe 17 ecosystem services tools and rate their performance against eight evaluative criteria that gauge their readiness for widespread application in public- and private-sector decision making. We describe each of the tools′ intended uses, services modeled, analytical approaches, data requirements, and outputs, as well time requirements to run seven tools in a first comparative concurrent application of multiple tools to a common location – the San Pedro River watershed in southeast Arizona, USA, and northern Sonora, Mexico. Based on this work, we offer conclusions about these tools′ current ‘readiness’ for widespread application within both public- and private-sector decision making processes. Finally, we describe potential pathways forward to reduce the resource requirements for running ecosystem services models, which are essential to facilitate their more widespread use in environmental decision making.

Biological interactions and cooperative management of multiple species.

PubMed

Jiang, Jinwei; Min, Yong; Chang, Jie; Ge, Ying

2017-01-01

Coordinated decision making and actions have become the primary solution for the overexploitation of interacting resources within ecosystems. However, the success of coordinated management is highly sensitive to biological, economic, and social conditions. Here, using a game theoretic framework and a 2-species model that considers various biological relationships (competition, predation, and mutualism), we compute cooperative (or joint) and non-cooperative (or separate) management equilibrium outcomes of the model and investigate the effects of the type and strength of the relationships. We find that cooperation does not always show superiority to non-cooperation in all biological interactions: (1) if and only if resources are involved in high-intensity predation relationships, cooperation can achieve a win-win scenario for ecosystem services and resource diversity; (2) for competitive resources, cooperation realizes higher ecosystem services by sacrificing resource diversity; and (3) for mutual resources, cooperation has no obvious advantage for either ecosystem services or resource evenness but can slightly improve resource abundance. Furthermore, by using a fishery model of the North California Current Marine Ecosystem with 63 species and seven fleets, we demonstrate that the theoretical results can be reproduced in real ecosystems. Therefore, effective ecosystem management should consider the interconnection between stakeholders' social relationship and resources' biological relationships.

THE AQUATOX MODEL

EPA Science Inventory

This lecture will present AQUATOX, an aquatic ecosystem simulation model developed by Dr. Dick Park and supported by the U.S. EPA. The AQUATOX model predicts the fate of various pollutants, such as nutrients and organic chemicals, and their effects on the ecosystem, including fi...

Global carbon assimilation system using a local ensemble Kalman filter with multiple ecosystem models

NASA Astrophysics Data System (ADS)

Zhang, Shupeng; Yi, Xue; Zheng, Xiaogu; Chen, Zhuoqi; Dan, Bo; Zhang, Xuanze

2014-11-01

In this paper, a global carbon assimilation system (GCAS) is developed for optimizing the global land surface carbon flux at 1° resolution using multiple ecosystem models. In GCAS, three ecosystem models, Boreal Ecosystem Productivity Simulator, Carnegie-Ames-Stanford Approach, and Community Atmosphere Biosphere Land Exchange, produce the prior fluxes, and an atmospheric transport model, Model for OZone And Related chemical Tracers, is used to calculate atmospheric CO2 concentrations resulting from these prior fluxes. A local ensemble Kalman filter is developed to assimilate atmospheric CO2 data observed at 92 stations to optimize the carbon flux for six land regions, and the Bayesian model averaging method is implemented in GCAS to calculate the weighted average of the optimized fluxes based on individual ecosystem models. The weights for the models are found according to the closeness of their forecasted CO2 concentration to observation. Results of this study show that the model weights vary in time and space, allowing for an optimum utilization of different strengths of different ecosystem models. It is also demonstrated that spatial localization is an effective technique to avoid spurious optimization results for regions that are not well constrained by the atmospheric data. Based on the multimodel optimized flux from GCAS, we found that the average global terrestrial carbon sink over the 2002-2008 period is 2.97 ± 1.1 PgC yr-1, and the sinks are 0.88 ± 0.52, 0.27 ± 0.33, 0.67 ± 0.39, 0.90 ± 0.68, 0.21 ± 0.31, and 0.04 ± 0.08 PgC yr-1 for the North America, South America, Africa, Eurasia, Tropical Asia, and Australia, respectively. This multimodel GCAS can be used to improve global carbon cycle estimation.

Mechanisms controlling primary and new production in a global ecosystem model - Part I: Validation of the biological simulation

NASA Astrophysics Data System (ADS)

Popova, E. E.; Coward, A. C.; Nurser, G. A.; de Cuevas, B.; Fasham, M. J. R.; Anderson, T. R.

2006-12-01

A global general circulation model coupled to a simple six-compartment ecosystem model is used to study the extent to which global variability in primary and export production can be realistically predicted on the basis of advanced parameterizations of upper mixed layer physics, without recourse to introducing extra complexity in model biology. The "K profile parameterization" (KPP) scheme employed, combined with 6-hourly external forcing, is able to capture short-term periodic and episodic events such as diurnal cycling and storm-induced deepening. The model realistically reproduces various features of global ecosystem dynamics that have been problematic in previous global modelling studies, using a single generic parameter set. The realistic simulation of deep convection in the North Atlantic, and lack of it in the North Pacific and Southern Oceans, leads to good predictions of chlorophyll and primary production in these contrasting areas. Realistic levels of primary production are predicted in the oligotrophic gyres due to high frequency external forcing of the upper mixed layer (accompanying paper Popova et al., 2006) and novel parameterizations of zooplankton excretion. Good agreement is shown between model and observations at various JGOFS time series sites: BATS, KERFIX, Papa and HOT. One exception is the northern North Atlantic where lower grazing rates are needed, perhaps related to the dominance of mesozooplankton there. The model is therefore not globally robust in the sense that additional parameterizations are needed to realistically simulate ecosystem dynamics in the North Atlantic. Nevertheless, the work emphasises the need to pay particular attention to the parameterization of mixed layer physics in global ocean ecosystem modelling as a prerequisite to increasing the complexity of ecosystem models.

Prevalence of bla TEM-220 gene in Penicillinase-producing Neisseria gonorrhoeae strains carrying Toronto/Rio plasmid in Argentina, 2002 - 2011.

PubMed

Gianecini, Ricardo; Oviedo, Claudia; Guantay, Cristina; Piccoli, Laura; Stafforini, Graciela; Galarza, Patricia

2015-12-16

Penicillinase-producing Neisseria gonorroheae (PPNG) was first isolated in 1976. PPNG strains carrying bla TEM-1 and bla TEM-135 gene have been described in different countries. Recently, a novel bla TEM-220 allele was detected in PPNG isolates carrying Toronto/Rio plasmid. The prevalence and characteristics of TEM-220 strains worldwide are unknown, and therefore, it needs to be studied. The purpose of this study was to detect bla TEM-220 gene in PPNG strains possessing Toronto/Rio plasmid over a period of ten years in Argentina, and to evaluate the proportion of isolates producing non-TEM-220 containing the T539C substitution in the bla TEM allele. One hundred and fifty one PPNG isolates carrying Toronto/Rio plasmid were studied between 2002 and 2011. A mismatch amplification mutation assay (MAMA) PCR was used to identify the T539C substitution in the bla TEM allele and a MAMA-PCR protocol was developed to detect the G547A substitution in the bla TEM-220. The reference agar dilution method of the Clinical and Laboratory Standard Institute (CLSI) was used for susceptibility testing to five β-lactams antibiotics, ciprofloxacin, tetracycline and azithromycin. In all TEM-220-producing isolates, the whole bla TEM gene was sequenced and the isolates were typed using N. gonorroheae multiantigen sequence typing (NG-MAST). MAMA PCR successfully identified the G547A substitution in the bla TEM-220 allele. The proportion of isolates that possessed the bla TEM-220 allele was 2.6 %, and 93.2 % MAMA TEM-220 PCR-negative isolates showed the T539C substitution in the bla TEM gene. No differences in the susceptibility to five beta-lactam antibiotics tested were observed in PPNG isolates TEM-220-producing and PPNG isolates carrying the T539C substitution in the bla TEM gene. All TEM-220 isolates were indistinguishable by NG-MAST. This is the first study which shows the prevalence of bla TEM-220 in N. gonorrhoeae isolates carrying Toronto/Rio plasmid in Argentina. Although the bla TEM-220 allele does not appear to be associated with an extended spectrum beta-lactamase (ESBL) phenotype of resistance, a single nucleotide polymorphism added to the bla TEM-220 or bla TEM containing the T539C substitution could lead to the emergence of ESBL. Thus, it is imperative to investigate in surveillance programs, not only the plasmid type in PPNG isolates and the bla TEM allele associated, but phenotypical characteristics and geographical distribution of isolates.

Modeling Ecosystem Services in an Arid Landscape Using the InVEST Tool

EPA Science Inventory

In this paper we describe the US Environmental Protection Agency’s Southwest Ecosystem Services Program (SwESP) initial efforts to use the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) tool to quantify and map the values of multiple ecosystem services in the S...

The Interior Columbia Basin Ecosystem Management Project: scientific assessment.

Treesearch

1999-01-01

This CD-ROM contains digital versions (PDF) of the major scientific documents prepared for the Interior Columbia Basin Ecosystem Management Project (ICBEMP). "A Framework for Ecosystem Management in the Interior Columbia Basin and Portions of the Klamath and Great Basins" describes a general planning model for ecosystem management. The "Highlighted...

Ecosystem Jenga!

ERIC Educational Resources Information Center

Umphlett, Natalie; Brosius, Tierney; Laungani, Ramesh; Rousseau, Joe; Leslie-Pelecky, Diandra L.

2009-01-01

To give students a tangible model of an ecosystem and have them experience what could happen if a component of that ecosystem were removed; the authors developed a hands-on, inquiry-based activity that visually demonstrates the concept of a delicately balanced ecosystem through a modification of the popular game Jenga. This activity can be…

Quantitative Models Describing Past and Current Nutrient Fluxes and Associated Ecosystem Level Responses in the Narragansett Bay Ecosystem

EPA Science Inventory

Multiple drivers, including nutrient loading and climate change, affect the Narragansett Bay ecosystem in Rhode Island/Massachusetts, USA. Managers are interested in understanding the timing and magnitude of these effects, and ecosystem responses to restoration actions. To provid...

Ceftazidime-Resistant Enterobacteriaceae Isolates from Three Polish Hospitals: Identification of Three Novel TEM- and SHV-5-Type Extended-Spectrum β-Lactamases

PubMed Central

Gniadkowski, Marek; Schneider, Ines; Jungwirth, Renate; Hryniewicz, Waleria; Bauernfeind, Adolf

1998-01-01

Twelve ceftazidime-resistant isolates of the family Enterobacteriaceae (11 Klebsiella pneumoniae isolates and 1 Escherichia coli isolate) were collected in 1995 from three Polish hospitals located in different cities. All were identified as producers of extended-spectrum β-lactamases (ESBLs). Detailed analysis of their β-lactamase contents revealed that six of them expressed SHV-5-like ESBLs. The remaining six were found to produce three different TEM enzymes, each characterized by a pI value of 6.0 and specified by new combinations of amino acid substitutions. The amino acid substitutions compared to the TEM-1 β-lactamase sequence were Gly238Ser, Glu240Lys, and Thr265Met for TEM-47; Leu21Phe, Gly238Ser, Glu240Lys, and Thr265Met for TEM-48; and Leu21Phe, Gly238Ser, Glu240Lys, Thr265Met, and Ser268Gly for TEM-49. The new TEM β-lactamases, TEM-47, TEM-48, and TEM-49, belong to a subfamily of TEM-2-related enzymes. Genes coding for TEM-47 and TEM-49 could have originated from the TEM-48-encoding sequence by various single genetic events. The new TEM derivatives probably document the already advanced microevolution of ESBLs ongoing in Polish hospitals, in a majority of which no monitoring of ESBL producers was performed before 1996. PMID:9517925

Scientific Foundations for an IUCN Red List of Ecosystems

PubMed Central

Keith, David A.; Rodríguez, Jon Paul; Rodríguez-Clark, Kathryn M.; Nicholson, Emily; Aapala, Kaisu; Alonso, Alfonso; Asmussen, Marianne; Bachman, Steven; Basset, Alberto; Barrow, Edmund G.; Benson, John S.; Bishop, Melanie J.; Bonifacio, Ronald; Brooks, Thomas M.; Burgman, Mark A.; Comer, Patrick; Comín, Francisco A.; Essl, Franz; Faber-Langendoen, Don; Fairweather, Peter G.; Holdaway, Robert J.; Jennings, Michael; Kingsford, Richard T.; Lester, Rebecca E.; Nally, Ralph Mac; McCarthy, Michael A.; Moat, Justin; Oliveira-Miranda, María A.; Pisanu, Phil; Poulin, Brigitte; Regan, Tracey J.; Riecken, Uwe; Spalding, Mark D.; Zambrano-Martínez, Sergio

2013-01-01

An understanding of risks to biodiversity is needed for planning action to slow current rates of decline and secure ecosystem services for future human use. Although the IUCN Red List criteria provide an effective assessment protocol for species, a standard global assessment of risks to higher levels of biodiversity is currently limited. In 2008, IUCN initiated development of risk assessment criteria to support a global Red List of ecosystems. We present a new conceptual model for ecosystem risk assessment founded on a synthesis of relevant ecological theories. To support the model, we review key elements of ecosystem definition and introduce the concept of ecosystem collapse, an analogue of species extinction. The model identifies four distributional and functional symptoms of ecosystem risk as a basis for assessment criteria: A) rates of decline in ecosystem distribution; B) restricted distributions with continuing declines or threats; C) rates of environmental (abiotic) degradation; and D) rates of disruption to biotic processes. A fifth criterion, E) quantitative estimates of the risk of ecosystem collapse, enables integrated assessment of multiple processes and provides a conceptual anchor for the other criteria. We present the theoretical rationale for the construction and interpretation of each criterion. The assessment protocol and threat categories mirror those of the IUCN Red List of species. A trial of the protocol on terrestrial, subterranean, freshwater and marine ecosystems from around the world shows that its concepts are workable and its outcomes are robust, that required data are available, and that results are consistent with assessments carried out by local experts and authorities. The new protocol provides a consistent, practical and theoretically grounded framework for establishing a systematic Red List of the world’s ecosystems. This will complement the Red List of species and strengthen global capacity to report on and monitor the status of biodiversity PMID:23667454

Scientific foundations for an IUCN Red List of ecosystems.

PubMed

Keith, David A; Rodríguez, Jon Paul; Rodríguez-Clark, Kathryn M; Nicholson, Emily; Aapala, Kaisu; Alonso, Alfonso; Asmussen, Marianne; Bachman, Steven; Basset, Alberto; Barrow, Edmund G; Benson, John S; Bishop, Melanie J; Bonifacio, Ronald; Brooks, Thomas M; Burgman, Mark A; Comer, Patrick; Comín, Francisco A; Essl, Franz; Faber-Langendoen, Don; Fairweather, Peter G; Holdaway, Robert J; Jennings, Michael; Kingsford, Richard T; Lester, Rebecca E; Mac Nally, Ralph; McCarthy, Michael A; Moat, Justin; Oliveira-Miranda, María A; Pisanu, Phil; Poulin, Brigitte; Regan, Tracey J; Riecken, Uwe; Spalding, Mark D; Zambrano-Martínez, Sergio

2013-01-01

An understanding of risks to biodiversity is needed for planning action to slow current rates of decline and secure ecosystem services for future human use. Although the IUCN Red List criteria provide an effective assessment protocol for species, a standard global assessment of risks to higher levels of biodiversity is currently limited. In 2008, IUCN initiated development of risk assessment criteria to support a global Red List of ecosystems. We present a new conceptual model for ecosystem risk assessment founded on a synthesis of relevant ecological theories. To support the model, we review key elements of ecosystem definition and introduce the concept of ecosystem collapse, an analogue of species extinction. The model identifies four distributional and functional symptoms of ecosystem risk as a basis for assessment criteria: A) rates of decline in ecosystem distribution; B) restricted distributions with continuing declines or threats; C) rates of environmental (abiotic) degradation; and D) rates of disruption to biotic processes. A fifth criterion, E) quantitative estimates of the risk of ecosystem collapse, enables integrated assessment of multiple processes and provides a conceptual anchor for the other criteria. We present the theoretical rationale for the construction and interpretation of each criterion. The assessment protocol and threat categories mirror those of the IUCN Red List of species. A trial of the protocol on terrestrial, subterranean, freshwater and marine ecosystems from around the world shows that its concepts are workable and its outcomes are robust, that required data are available, and that results are consistent with assessments carried out by local experts and authorities. The new protocol provides a consistent, practical and theoretically grounded framework for establishing a systematic Red List of the world's ecosystems. This will complement the Red List of species and strengthen global capacity to report on and monitor the status of biodiversity.

Linking hydrology, ecosystem function, and livelihood sustainability in African papyrus wetlands using a Bayesian Network Model

NASA Astrophysics Data System (ADS)

van Dam, A.; Gettel, G. M.; Kipkemboi, J.; Rahman, M. M.

2011-12-01

Papyrus wetlands in East Africa provide ecosystem services supporting the livelihoods of millions but are rapidly degrading due to economic development. For ecosystem conservation, an integrated understanding of the natural and social processes driving ecosystem change is needed. This research focuses on integrating the causal relationships between hydrology, ecosystem function, and livelihood sustainability in Nyando wetland, western Kenya. Livelihood sustainability is based on ecosystem services that include plant and animal harvest for building material and food, conversion of wetlands to crop and grazing land, water supply, and water quality regulation. Specific objectives were: to integrate studies of hydrology, ecology, and livelihood activities using a Bayesian Network (BN) model and include stakeholder involvement in model development. The BN model (Netica 4.16) had 35 nodes with seven decision nodes describing demography, economy, papyrus market, and rainfall, and two target nodes describing ecosystem function (defined by groundwater recharge, nutrient and sediment retention, and biodiversity) and livelihood sustainability (drinking water supply, crop production, livestock production, and papyrus yield). The conditional probability tables were populated using results of ecohydrological and socio-economic field work and consultations with stakeholders. The model was evaluated for an average year with decision node probabilities set according to data from research, expert opinion, and stakeholders' views. Then, scenarios for dry and wet seasons and for economic development (low population growth and unemployment) and policy development (more awareness of wetland value) were evaluated. In an average year, the probability for maintaining a "good" level of sediment and nutrient retention functions, groundwater recharge, and biodiversity was about 60%. ("Good" is defined by expert opinion based on ongoing field research.) In the dry season, the probability was reduced to about 40% and in the wet season increased to about 85%. Both ecosystem functions and livelihood sustainability were most sensitive to flooding and the human pressure, notably the area of crop conversion, grazing pressure, and papyrus harvest. Flooded conditions limit cropping, livestock herding and vegetation harvesting but have a strong positive effect on ecosystem function. Preliminary results suggest that the effects of economic and policy development on ecosystem function and livelihood sustainability were negligible, but more data on these aspects will be included in further model development. The advantage of this modeling approach, which integrates data from hydrological, ecological, and socio-economic studies, is that it highlights the relative effect of hydrologic conditions and socio-economic pressures on ecosystem function. This model is static, however, with long-term changes in climate and exploitation levels superimposed on seasonal hydrology dynamics. Further work should address this issue as well as further constrain probabilities at each node as field research continues.

Global Patterns in Ecological Indicators of Marine Food Webs: A Modelling Approach

PubMed Central

Heymans, Johanna Jacomina; Coll, Marta; Libralato, Simone; Morissette, Lyne; Christensen, Villy

2014-01-01

Background Ecological attributes estimated from food web models have the potential to be indicators of good environmental status given their capabilities to describe redundancy, food web changes, and sensitivity to fishing. They can be used as a baseline to show how they might be modified in the future with human impacts such as climate change, acidification, eutrophication, or overfishing. Methodology In this study ecological network analysis indicators of 105 marine food web models were tested for variation with traits such as ecosystem type, latitude, ocean basin, depth, size, time period, and exploitation state, whilst also considering structural properties of the models such as number of linkages, number of living functional groups or total number of functional groups as covariate factors. Principal findings Eight indicators were robust to model construction: relative ascendency; relative overhead; redundancy; total systems throughput (TST); primary production/TST; consumption/TST; export/TST; and total biomass of the community. Large-scale differences were seen in the ecosystems of the Atlantic and Pacific Oceans, with the Western Atlantic being more complex with an increased ability to mitigate impacts, while the Eastern Atlantic showed lower internal complexity. In addition, the Eastern Pacific was less organised than the Eastern Atlantic although both of these systems had increased primary production as eastern boundary current systems. Differences by ecosystem type highlighted coral reefs as having the largest energy flow and total biomass per unit of surface, while lagoons, estuaries, and bays had lower transfer efficiencies and higher recycling. These differences prevailed over time, although some traits changed with fishing intensity. Keystone groups were mainly higher trophic level species with mostly top-down effects, while structural/dominant groups were mainly lower trophic level groups (benthic primary producers such as seagrass and macroalgae, and invertebrates). Keystone groups were prevalent in estuarine or small/shallow systems, and in systems with reduced fishing pressure. Changes to the abundance of key functional groups might have significant implications for the functioning of ecosystems and should be avoided through management. Conclusion/significance Our results provide additional understanding of patterns of structural and functional indicators in different ecosystems. Ecosystem traits such as type, size, depth, and location need to be accounted for when setting reference levels as these affect absolute values of ecological indicators. Therefore, establishing absolute reference values for ecosystem indicators may not be suitable to the ecosystem-based, precautionary approach. Reference levels for ecosystem indicators should be developed for individual ecosystems or ecosystems with the same typologies (similar location, ecosystem type, etc.) and not benchmarked against all other ecosystems. PMID:24763610

Global patterns in ecological indicators of marine food webs: a modelling approach.

PubMed

Heymans, Johanna Jacomina; Coll, Marta; Libralato, Simone; Morissette, Lyne; Christensen, Villy

2014-01-01

Ecological attributes estimated from food web models have the potential to be indicators of good environmental status given their capabilities to describe redundancy, food web changes, and sensitivity to fishing. They can be used as a baseline to show how they might be modified in the future with human impacts such as climate change, acidification, eutrophication, or overfishing. In this study ecological network analysis indicators of 105 marine food web models were tested for variation with traits such as ecosystem type, latitude, ocean basin, depth, size, time period, and exploitation state, whilst also considering structural properties of the models such as number of linkages, number of living functional groups or total number of functional groups as covariate factors. Eight indicators were robust to model construction: relative ascendency; relative overhead; redundancy; total systems throughput (TST); primary production/TST; consumption/TST; export/TST; and total biomass of the community. Large-scale differences were seen in the ecosystems of the Atlantic and Pacific Oceans, with the Western Atlantic being more complex with an increased ability to mitigate impacts, while the Eastern Atlantic showed lower internal complexity. In addition, the Eastern Pacific was less organised than the Eastern Atlantic although both of these systems had increased primary production as eastern boundary current systems. Differences by ecosystem type highlighted coral reefs as having the largest energy flow and total biomass per unit of surface, while lagoons, estuaries, and bays had lower transfer efficiencies and higher recycling. These differences prevailed over time, although some traits changed with fishing intensity. Keystone groups were mainly higher trophic level species with mostly top-down effects, while structural/dominant groups were mainly lower trophic level groups (benthic primary producers such as seagrass and macroalgae, and invertebrates). Keystone groups were prevalent in estuarine or small/shallow systems, and in systems with reduced fishing pressure. Changes to the abundance of key functional groups might have significant implications for the functioning of ecosystems and should be avoided through management. Our results provide additional understanding of patterns of structural and functional indicators in different ecosystems. Ecosystem traits such as type, size, depth, and location need to be accounted for when setting reference levels as these affect absolute values of ecological indicators. Therefore, establishing absolute reference values for ecosystem indicators may not be suitable to the ecosystem-based, precautionary approach. Reference levels for ecosystem indicators should be developed for individual ecosystems or ecosystems with the same typologies (similar location, ecosystem type, etc.) and not benchmarked against all other ecosystems.

Improving the precision of lake ecosystem metabolism estimates by identifying predictors of model uncertainty

USGS Publications Warehouse

Rose, Kevin C.; Winslow, Luke A.; Read, Jordan S.; Read, Emily K.; Solomon, Christopher T.; Adrian, Rita; Hanson, Paul C.

2014-01-01

Diel changes in dissolved oxygen are often used to estimate gross primary production (GPP) and ecosystem respiration (ER) in aquatic ecosystems. Despite the widespread use of this approach to understand ecosystem metabolism, we are only beginning to understand the degree and underlying causes of uncertainty for metabolism model parameter estimates. Here, we present a novel approach to improve the precision and accuracy of ecosystem metabolism estimates by identifying physical metrics that indicate when metabolism estimates are highly uncertain. Using datasets from seventeen instrumented GLEON (Global Lake Ecological Observatory Network) lakes, we discovered that many physical characteristics correlated with uncertainty, including PAR (photosynthetically active radiation, 400-700 nm), daily variance in Schmidt stability, and wind speed. Low PAR was a consistent predictor of high variance in GPP model parameters, but also corresponded with low ER model parameter variance. We identified a threshold (30% of clear sky PAR) below which GPP parameter variance increased rapidly and was significantly greater in nearly all lakes compared with variance on days with PAR levels above this threshold. The relationship between daily variance in Schmidt stability and GPP model parameter variance depended on trophic status, whereas daily variance in Schmidt stability was consistently positively related to ER model parameter variance. Wind speeds in the range of ~0.8-3 m s–1 were consistent predictors of high variance for both GPP and ER model parameters, with greater uncertainty in eutrophic lakes. Our findings can be used to reduce ecosystem metabolism model parameter uncertainty and identify potential sources of that uncertainty.

Sense of place: An elusive concept that is finding a home in ecosystem management

Treesearch

Daniel R. Williams; Susan I. Stewart

1998-01-01

One of the great and largely unmet challenges associated with ecosystem management is treating people as a rightful part of ecosystems. In many ecosystem models, despite occasional rhetoric to the contrary, there is still a tendency to treat people as autonomous individual agents outside the ecosystem, at best a source of values to be incorporated into decisions, at...

Measuring and Mapping the Topography of the Florida Everglades for Ecosystem Restoration

USGS Publications Warehouse

Desmond, Gregory B.

2003-01-01

One of the major issues facing ecosystem restoration and management of the Greater Everglades is the availability and distribution of clean, fresh water. The South Florida ecosystem encompasses an area of approximately 28,000 square kilometers and supports a human population that exceeds 5 million and is continuing to grow. The natural systems of the Kissimmee-Okeechobee-Everglades watershed compete for water resources primarily with the region's human population and urbanization, and with the agricultural and tourism industries. Surface water flow modeling and ecological modeling studies are important means of providing scientific information needed for ecosystem restoration planning and modeling. Hydrologic and ecological models provide much-needed predictive capabilities for evaluating management options for parks, refuges, and land acquisition and for understanding the impacts of land management practices in surrounding areas. These models require various input data, including elevation data that very accurately define the topography of the Florida Everglades.

Disturbance Distance: Using a process based ecosystem model to estimate and map potential thresholds in disturbance rates that would give rise to fundamentally altered ecosystems

NASA Astrophysics Data System (ADS)

Dolan, K. A.; Hurtt, G. C.; Fisk, J.; Flanagan, S.; LePage, Y.; Sahajpal, R.

2014-12-01

Disturbance plays a critical role in shaping the structure and function of forested ecosystems as well as the ecosystem services they provide, including but not limited to: carbon storage, biodiversity habitat, water quality and flow, and land atmosphere exchanges of energy and water. As recent studies highlight novel disturbance regimes resulting from pollution, invasive pests and climate change, there is a need to include these alterations in predictions of future forest function and structure. The Ecosystem Demography (ED) model is a mechanistic model of forest ecosystem dynamics in which individual-based forest dynamics can be efficiently implemented over regional to global scales due to advanced scaling methods. We utilize ED to characterize the sensitivity of potential vegetation structure and function to changes in rates of density independent mortality. Disturbance rate within ED can either be altered directly or through the development of sub-models. Disturbance sub-models in ED currently include fire, land use and hurricanes. We use a tiered approach to understand the sensitivity of North American ecosystems to changes in background density independent mortality. Our first analyses were conducted at half-degree spatial resolution with a constant rate of disturbance in space and time, which was altered between runs. Annual climate was held constant at the site level and the land use and fire sub-models were turned off. Results showed an ~ 30% increase in non-forest area across the US when disturbance rates were changed from 0.6% a year to 1.2% a year and a more than 3.5 fold increase in non-forest area when disturbance rates doubled again from 1.2% to 2.4%. Continued runs altered natural background disturbance rates with the existing fire and hurricane sub models turned on as well as historic and future land use. By quantify differences between model outputs that characterize ecosystem structure and function related to the carbon cycle across the US, we are identifying areas and characteristics that display higher sensitivities to change in disturbance rates.

The experimental electron mean-free-path in Si under typical (S)TEM conditions.

PubMed

Potapov, P L

2014-12-01

The electron mean-free-path in Si was measured by EELS using the test structure with the certified dimensions as a calibration standard. In a good agreement with the previous CBED measurements, the mean-free-path is 150nm for 200keV and 179nm for 300keV energy of primary electrons at large collection angles. These values are accurately predicted by the model of Iakoubovskii et al. while the model of Malis et al. incorporated in common microscopy software underestimates the mean-free-path by 15% at least. Correspondingly, the thickness of TEM samples reported in many studies of the Si-based materials last decades might be noticeably underestimated. Copyright © 2014 Elsevier B.V. All rights reserved.

An Evaluation of a Testing Model for Listening Comprehension.

ERIC Educational Resources Information Center

Kangli, Ji

A model for testing listening comprehension in English as a Second Language is discussed and compared with the Test for English Majors (TEM). The model in question incorporates listening for: (1) understanding factual information; (2) comprehension and interpretation; (3) detailed and selective information; (4) global ideas; (5) on-line tasks…

INTEGRATED PROBABILISTIC AND DETERMINISTIC MODELING TECHNIQUES IN ESTIMATING EXPOSURE TO WATER-BORNE CONTAMINANTS: PART 2 PHARMACOKINETIC MODELING

EPA Science Inventory

The Total Exposure Model (TEM) uses deterministic and stochastic methods to estimate the exposure of a person performing daily activities of eating, drinking, showering, and bathing. There were 250 time histories generated, by subject with activities, for the three exposure ro...

Bayesian calibration of terrestrial ecosystem models: a study of advanced Markov chain Monte Carlo methods

NASA Astrophysics Data System (ADS)

Lu, Dan; Ricciuto, Daniel; Walker, Anthony; Safta, Cosmin; Munger, William

2017-09-01

Calibration of terrestrial ecosystem models is important but challenging. Bayesian inference implemented by Markov chain Monte Carlo (MCMC) sampling provides a comprehensive framework to estimate model parameters and associated uncertainties using their posterior distributions. The effectiveness and efficiency of the method strongly depend on the MCMC algorithm used. In this work, a differential evolution adaptive Metropolis (DREAM) algorithm is used to estimate posterior distributions of 21 parameters for the data assimilation linked ecosystem carbon (DALEC) model using 14 years of daily net ecosystem exchange data collected at the Harvard Forest Environmental Measurement Site eddy-flux tower. The calibration of DREAM results in a better model fit and predictive performance compared to the popular adaptive Metropolis (AM) scheme. Moreover, DREAM indicates that two parameters controlling autumn phenology have multiple modes in their posterior distributions while AM only identifies one mode. The application suggests that DREAM is very suitable to calibrate complex terrestrial ecosystem models, where the uncertain parameter size is usually large and existence of local optima is always a concern. In addition, this effort justifies the assumptions of the error model used in Bayesian calibration according to the residual analysis. The result indicates that a heteroscedastic, correlated, Gaussian error model is appropriate for the problem, and the consequent constructed likelihood function can alleviate the underestimation of parameter uncertainty that is usually caused by using uncorrelated error models.

Biogeochemical modelling vs. tree-ring data - comparison of forest ecosystem productivity estimates

NASA Astrophysics Data System (ADS)

Zorana Ostrogović Sever, Maša; Barcza, Zoltán; Hidy, Dóra; Paladinić, Elvis; Kern, Anikó; Marjanović, Hrvoje

2017-04-01

Forest ecosystems are sensitive to environmental changes as well as human-induce disturbances, therefore process-based models with integrated management modules represent valuable tool for estimating and forecasting forest ecosystem productivity under changing conditions. Biogeochemical model Biome-BGC simulates carbon, nitrogen and water fluxes, and it is widely used for different terrestrial ecosystems. It was modified and parameterised by many researchers in the past to meet the specific local conditions. In this research, we used recently published improved version of the model Biome-BGCMuSo (BBGCMuSo), with multilayer soil module and integrated management module. The aim of our research is to validate modelling results of forest ecosystem productivity (NPP) from BBGCMuSo model with observed productivity estimated from an extensive dataset of tree-rings. The research was conducted in two distinct forest complexes of managed Pedunculate oak in SE Europe (Croatia), namely Pokupsko basin and Spačva basin. First, we parameterized BBGCMuSo model at a local level using eddy-covariance (EC) data from Jastrebarsko EC site. Parameterized model was used for the assessment of productivity on a larger scale. Results of NPP assessment with BBGCMuSo are compared with NPP estimated from tree ring data taken from trees on over 100 plots in both forest complexes. Keywords: Biome-BGCMuSo, forest productivity, model parameterization, NPP, Pedunculate oak

Improved global simulation of groundwater-ecosystem interactions via tight coupling of a dynamic global ecosystem model and a global hydrological model

NASA Astrophysics Data System (ADS)

Braakhekke, Maarten; Rebel, Karin; Dekker, Stefan; Smith, Benjamin; Sutanudjaja, Edwin; van Beek, Rens; van Kampenhout, Leo; Wassen, Martin

2017-04-01

In up to 30% of the global land surface ecosystems are potentially influenced by the presence of a shallow groundwater table. In these regions upward water flux by capillary rise increases soil moisture availability in the root zone, which has a strong effect on evapotranspiration, vegetation dynamics, and fluxes of carbon and nitrogen. Most global hydrological models and several land surface models simulate groundwater table dynamics and their effects on land surface processes. However, these models typically have relatively simplistic representation of vegetation and do not consider changes in vegetation type and structure. Dynamic global vegetation models (DGVMs), describe land surface from an ecological perspective, combining detailed description of vegetation dynamics and structure, and biogeochemical processes and are thus more appropriate to simulate the ecological and biogeochemical effects of groundwater interactions. However, currently virtually all DGVMs ignore these effects, assuming that water tables are too deep to affect soil moisture in the root zone. We have implemented a tight coupling between the dynamic global ecosystem model LPJ-GUESS and the global hydrological model PCR-GLOBWB, which explicitly simulates groundwater dynamics. This coupled model allows us to explicitly account for groundwater effects on terrestrial ecosystem processes at global scale. Results of global simulations indicate that groundwater strongly influences fluxes of water, carbon and nitrogen, in many regions, adding up to a considerable effect at the global scale.

Perturbations and gradients as fundamental tests for modeling the soil carbon cycle

NASA Astrophysics Data System (ADS)

Bond-Lamberty, B. P.; Bailey, V. L.; Becker, K.; Fansler, S.; Hinkle, C.; Liu, C.

2013-12-01

An important step in matching process-level knowledge to larger-scale measurements and model results is to challenge those models with site-specific perturbations and/or changing environmental conditions. Here we subject modified versions of an ecosystem process model to two stringent tests: replicating a long-term climate change dryland experiment (Rattlesnake Mountain) and partitioning the carbon fluxes of a soil drainage gradient in the northern Everglades (Disney Wilderness Preserve). For both sites, on-site measurements were supplemented by laboratory incubations of soil columns. We used a parameter-space search algorithm to optimize, within observational limits, the model's influential inputs, so that the spun-up carbon stocks and fluxes matched observed values. Modeled carbon fluxes (net primary production and net ecosystem exchange) agreed with measured values, within observational error limits, but the model's partitioning of soil fluxes (autotrophic versus heterotrophic), did not match laboratory measurements from either site. Accounting for site heterogeneity at DWP, modeled carbon exchange was reasonably consistent with values from eddy covariance. We discuss the implications of this work for ecosystem- to global scale modeling of ecosystems in a changing climate.

Regional and climate forcing on forage fish and apex predators in the California Current: new insights from a fully coupled ecosystem model.

NASA Astrophysics Data System (ADS)

Fiechter, J.; Rose, K.; Curchitser, E. N.; Huckstadt, L. A.; Costa, D. P.; Hedstrom, K.

2016-12-01

A fully coupled ecosystem model is used to describe the impact of regional and climate variability on changes in abundance and distribution of forage fish and apex predators in the California Current Large Marine Ecosystem. The ecosystem model consists of a biogeochemical submodel (NEMURO) embedded in a regional ocean circulation submodel (ROMS), and both coupled with a multi-species individual-based submodel for two forage fish species (sardine and anchovy) and one apex predator (California sea lion). Sardine and anchovy are specifically included in the model as they exhibit significant interannual and decadal variability in population abundances, and are commonly found in the diet of California sea lions. Output from the model demonstrates how regional-scale (i.e., upwelling intensity) and basin-scale (i.e., PDO and ENSO signals) physical processes control species distributions and predator-prey interactions on interannual time scales. The results also illustrate how variability in environmental conditions leads to the formation of seasonal hotspots where prey and predator spatially overlap. While specifically focused on sardine, anchovy and sea lions, the modeling framework presented here can provide new insights into the physical and biological mechanisms controlling trophic interactions in the California Current, or other regions where similar end-to-end ecosystem models may be implemented.

The exploration of trophic structure modeling using mass balance Ecopath model of Tangerang coastal waters

NASA Astrophysics Data System (ADS)

Dewi, N. N.; Kamal, M.; Wardiatno, Y.; Rozi

2018-04-01

Ecopath model approach was used to describe trophic interaction, energy flows and ecosystem condition of Tangerang coastal waters. This model consists of 42 ecological groups, of which 41 are living groups and one is a detritus group. Trophic levels of these groups vary between 1.0 (for primary producers and detritus) to 4.03 (for tetraodontidae). Groups with trophic levels 2≤TL<3 and 3≤TL<4 have a range of ecotropic efficiency from 0 to 0.9719 and 0 to 0.7520 respectively.The Mean transfer efficiency is 9.43% for phytoplankton and 3.39% for detritus. The Mixed trophic impact analysis indicates that phytoplankton havea positive impact on the majority of pelagic fish, while detritus has a positive impact on the majority of demersal fish. Leiognathidae havea negative impact on phytoplankton, zooplankton and several other groups. System omnivory index for this ecosystem is 0.151. System primary production/respiration (P/R) ratio of Tangerang coastal waters is 1.505. This coastal ecosystem is an immatureecosystem because it hasdegraded. Pedigree index for this model is 0.57. This model describes ecosystem condition affected by overfishing and antropogenic activities. Therefore, through Ecopath model we provide some suggestions about the ecosystem-based fisheries management.

Challenges and opportunities for integrating lake ecosystem modelling approaches

USGS Publications Warehouse

Mooij, Wolf M.; Trolle, Dennis; Jeppesen, Erik; Arhonditsis, George; Belolipetsky, Pavel V.; Chitamwebwa, Deonatus B.R.; Degermendzhy, Andrey G.; DeAngelis, Donald L.; Domis, Lisette N. De Senerpont; Downing, Andrea S.; Elliott, J. Alex; Ruberto, Carlos Ruberto; Gaedke, Ursula; Genova, Svetlana N.; Gulati, Ramesh D.; Hakanson, Lars; Hamilton, David P.; Hipsey, Matthew R.; Hoen, Jochem 't; Hulsmann, Stephan; Los, F. Hans; Makler-Pick, Vardit; Petzoldt, Thomas; Prokopkin, Igor G.; Rinke, Karsten; Schep, Sebastiaan A.; Tominaga, Koji; Van Dam, Anne A.; Van Nes, Egbert H.; Wells, Scott A.; Janse, Jan H.

2010-01-01

A large number and wide variety of lake ecosystem models have been developed and published during the past four decades. We identify two challenges for making further progress in this field. One such challenge is to avoid developing more models largely following the concept of others ('reinventing the wheel'). The other challenge is to avoid focusing on only one type of model, while ignoring new and diverse approaches that have become available ('having tunnel vision'). In this paper, we aim at improving the awareness of existing models and knowledge of concurrent approaches in lake ecosystem modelling, without covering all possible model tools and avenues. First, we present a broad variety of modelling approaches. To illustrate these approaches, we give brief descriptions of rather arbitrarily selected sets of specific models. We deal with static models (steady state and regression models), complex dynamic models (CAEDYM, CE-QUAL-W2, Delft 3D-ECO, LakeMab, LakeWeb, MyLake, PCLake, PROTECH, SALMO), structurally dynamic models and minimal dynamic models. We also discuss a group of approaches that could all be classified as individual based: super-individual models (Piscator, Charisma), physiologically structured models, stage-structured models and trait-based models. We briefly mention genetic algorithms, neural networks, Kalman filters and fuzzy logic. Thereafter, we zoom in, as an in-depth example, on the multi-decadal development and application of the lake ecosystem model PCLake and related models (PCLake Metamodel, Lake Shira Model, IPH-TRIM3D-PCLake). In the discussion, we argue that while the historical development of each approach and model is understandable given its 'leading principle', there are many opportunities for combining approaches. We take the point of view that a single 'right' approach does not exist and should not be strived for. Instead, multiple modelling approaches, applied concurrently to a given problem, can help develop an integrative view on the functioning of lake ecosystems. We end with a set of specific recommendations that may be of help in the further development of lake ecosystem models.

Assessing ecosystem response to multiple disturbances and climate change in South Africa using ground- and satellite-based measurements and model

NASA Astrophysics Data System (ADS)

Kutsch, W. L.; Falge, E. M.; Brümmer, C.; Mukwashi, K.; Schmullius, C.; Hüttich, C.; Odipo, V.; Scholes, R. J.; Mudau, A.; Midgley, G.; Stevens, N.; Hickler, T.; Scheiter, S.; Martens, C.; Twine, W.; Iiyambo, T.; Bradshaw, K.; Lück, W.; Lenfers, U.; Thiel-Clemen, T.; du Toit, J.

2015-12-01

Sub-Saharan Africa currently experiences rapidly growing human population, intrinsically tied to substantial changes in land use on shrubland, savanna and mixed woodland ecosystems due to over-exploitation. Significant conversions driving degradation, affecting fire frequency and water availability, and fueling climate change are expected to increase in the immediate future. However, measured data of greenhouse gas emissions as affected by land use change are scarce to entirely lacking from this region. The project 'Adaptive Resilience of Southern African Ecosystems' (ARS AfricaE) conducts research and develops scenarios of ecosystem development under climate change, for management support in conservation or for planning rural area development. This will be achieved by (1) creation of a network of research clusters (paired sites with natural and altered vegetation) along an aridity gradient in South Africa for ground-based micrometeorological in-situ measurements of energy and matter fluxes, (2) linking biogeochemical functions with ecosystem structure, and eco-physiological properties, (3) description of ecosystem disturbance (and recovery) in terms of ecosystem function such as carbon balance components and water use efficiency, (4) set-up of individual-based models to predict ecosystem dynamics under (post) disturbance managements, (5) combination with long-term landscape dynamic information derived from remote sensing and aerial photography, and (6) development of sustainable management strategies for disturbed ecosystems and land use change. Emphasis is given on validation (by a suite of field measurements) of estimates obtained from eddy covariance, model approaches and satellite derivations.

Joint TEM and MT aquifer study in the Atacama Desert, North Chile

NASA Astrophysics Data System (ADS)

Ruthsatz, Alexander D.; Sarmiento Flores, Alvaro; Diaz, Daniel; Reinoso, Pablo Salazar; Herrera, Cristian; Brasse, Heinrich

2018-06-01

The Atacama Desert represents one of the driest regions on earth, and despite the absence of sustainable clean water reserves the demand has increased drastically since 1970 as a result of growing population and expanding mining activities. Magnetotelluric (MT) and Transient Electromagnetic (TEM) measurements were carried out for groundwater exploration in late 2015 in the area of the Profeta Basin at the western margin of the Chilean Precordillera. Both methods complement each other: While MT in general attains larger penetration depths, TEM allows better resolution of near surface layers; furthermore TEM is free from galvanic distortion. Data were collected along three profiles, enabling a continuous resistivity image from the surface to at least several hundred meters depth. TEM data were inverted in a 1-D manner, consistently yielding a poorly conductive near-surface layer with a thickness of approximately 30 m and below a well-conducting layer which we interpret as the aquifer with resistivities around 10 Ωm. At marginal sites of the main SW-NE-profile the resistive basement was found in 150 m. These depths are confirmed by interpretation of the MT soundings. Those were firstly inverted with a 2-D approach and then by 3-D inversion as clear indications of three-dimensionality exist. Several modeling runs were performed with different combinations of transfer functions and smoothing parameters. Generally, MT and TEM results agree reasonably well and an overall image of the resistivity structures in the Profeta Basin could be achieved. The aquifer reaches depths of more than 500 m in parts and, by applying Archie's law, resistivities of 1 Ωm can be assumed, indicating highly saline fluids from the source region of the surrounding high Andes under persisting arid conditions.

Constitutive Lck Activity Drives Sensitivity Differences between CD8+ Memory T Cell Subsets.

PubMed

Moogk, Duane; Zhong, Shi; Yu, Zhiya; Liadi, Ivan; Rittase, William; Fang, Victoria; Dougherty, Janna; Perez-Garcia, Arianne; Osman, Iman; Zhu, Cheng; Varadarajan, Navin; Restifo, Nicholas P; Frey, Alan B; Krogsgaard, Michelle

2016-07-15

CD8(+) T cells develop increased sensitivity following Ag experience, and differences in sensitivity exist between T cell memory subsets. How differential TCR signaling between memory subsets contributes to sensitivity differences is unclear. We show in mouse effector memory T cells (TEM) that >50% of lymphocyte-specific protein tyrosine kinase (Lck) exists in a constitutively active conformation, compared with <20% in central memory T cells (TCM). Immediately proximal to Lck signaling, we observed enhanced Zap-70 phosphorylation in TEM following TCR ligation compared with TCM Furthermore, we observed superior cytotoxic effector function in TEM compared with TCM, and we provide evidence that this results from a lower probability of TCM reaching threshold signaling owing to the decreased magnitude of TCR-proximal signaling. We provide evidence that the differences in Lck constitutive activity between CD8(+) TCM and TEM are due to differential regulation by SH2 domain-containing phosphatase-1 (Shp-1) and C-terminal Src kinase, and we use modeling of early TCR signaling to reveal the significance of these differences. We show that inhibition of Shp-1 results in increased constitutive Lck activity in TCM to levels similar to TEM, as well as increased cytotoxic effector function in TCM Collectively, this work demonstrates a role for constitutive Lck activity in controlling Ag sensitivity, and it suggests that differential activities of TCR-proximal signaling components may contribute to establishing the divergent effector properties of TCM and TEM. This work also identifies Shp-1 as a potential target to improve the cytotoxic effector functions of TCM for adoptive cell therapy applications. Copyright © 2016 by The American Association of Immunologists, Inc.

Ecosystem shifts under climate change - a multi-model analysis from ISI-MIP

NASA Astrophysics Data System (ADS)

Warszawski, Lila; Beerling, David; Clark, Douglas; Friend, Andrew; Ito, Akihito; Kahana, Ron; Keribin, Rozenn; Kleidon, Axel; Lomas, Mark; Lucht, Wolfgang; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Tito Rademacher, Tim; Schaphoff, Sibyll

2013-04-01

Dramatic ecosystem shifts, relating to vegetation composition and water and carbon stocks and fluxes, are potential consequences of climate change in the twenty-first century. Shifting climatic conditions, resulting in changes in biogeochemical properties of the ecosystem, will render it difficult for endemic plant and animal species to continue to survive in their current habitat. The potential for major shifts in biomes globally will also have severe consequences for the humans who rely on vital ecosystem services. Here we employ a novel metric of ecosystem shift to quantify the magnitude and uncertainty in these shifts at different levels of global warming, based on the response of seven biogeochemical Earth models to different future climate scenarios, in the context of the Intersectoral Impact Model Intercomparison Project (ISI-MIP). Based on this ensemble, 15% of the Earth's land surface will experience severe ecosystem shifts at 2°C degrees of global warming above 1980-2010 levels. This figure rises monotonically with global mean temperature for all models included in this study, reaching a median value of 60% of the land surface in a 4°C warmer world. At both 2°C and 4°C of warming, the most pronounced shifts occur in south-eastern India and south-western China, large swathes of the northern lattitudes above 60°N, the Amazon region and sub-Saharan Africa. Where dynamic vegetation composition is modelled, these shifts correspond to significant reductions in the land surface of vunerable vegetation types. We show that global mean temperature is a robust predictor of ecosystem shifts, whilst the spread across impact models is the greatest contributor to uncertainty.

Exploring eco-hydrological consequences of the Amazonian ecosystems under climate and land-use changes in the 21st century

NASA Astrophysics Data System (ADS)

Zhang, K.; Castanho, A. D.; Moghim, S.; Bras, R. L.; Coe, M. T.; Costa, M. H.; Levine, N. M.; Longo, M.; McKnight, S.; Wang, J.; Moorcroft, P. R.

2012-12-01

Deforestation and drought have imposed regional-scale perturbations onto Amazonian ecosystems and are predicted to cause larger negative impacts on the Amazonian ecosystems and associated regional carbon dynamics in the 21st century. However, global climate models (GCMs) vary greatly in their projections of future climate change in Amazonia, giving rise to uncertainty in the expected fate of the Amazon over the coming century. In this study, we explore the possible eco-hydrological consequences of the Amazonian ecosystems under projected climate and land-use changes in the 21st century using two state-of-the-art terrestrial ecosystem models—Ecosystem Demography Model 2.1(ED2.1) and Integrated Biosphere Simulator model (IBIS)—driven by three representative, bias-corrected climate projections from three IPCC GCMs (NCARPCM1, NCARCCSM3 and HadCM3), coupled with two land-use change scenarios (a business-as-usual and a strict governance scenario). We also analyze the relative roles of climate change, CO2 fertilization, land-use change and fire in driving the projected composition and structure of the Amazonian ecosystems. Our results show that CO2 fertilization enhances vegetation productivity and above-ground biomass (AGB) in the region, while land-use change and fire cause AGB loss and the replacement of forests by the savanna-like vegetation. The impacts of climate change depend strongly on the direction and severity of projected precipitation changes in the region. In particular, when intensified water stress is superimposed on unregulated deforestation, both ecosystem models predict large-scale dieback of Amazonian rainforests.

Estimating the impacts of conservation on ecosystem services and poverty by integrating modeling and evaluation.

PubMed

Ferraro, Paul J; Hanauer, Merlin M; Miteva, Daniela A; Nelson, Joanna L; Pattanayak, Subhrendu K; Nolte, Christoph; Sims, Katharine R E

2015-06-16

Scholars have made great advances in modeling and mapping ecosystem services, and in assigning economic values to these services. This modeling and valuation scholarship is often disconnected from evidence about how actual conservation programs have affected ecosystem services, however. Without a stronger evidence base, decision makers find it difficult to use the insights from modeling and valuation to design effective policies and programs. To strengthen the evidence base, scholars have advanced our understanding of the causal pathways between conservation actions and environmental outcomes, but their studies measure impacts on imperfect proxies for ecosystem services (e.g., avoidance of deforestation). To be useful to decision makers, these impacts must be translated into changes in ecosystem services and values. To illustrate how this translation can be done, we estimated the impacts of protected areas in Brazil, Costa Rica, Indonesia, and Thailand on carbon storage in forests. We found that protected areas in these conservation hotspots have stored at least an additional 1,000 Mt of CO2 in forests and have delivered ecosystem services worth at least $5 billion. This aggregate impact masks important spatial heterogeneity, however. Moreover, the spatial variability of impacts on carbon storage is the not the same as the spatial variability of impacts on avoided deforestation. These findings lead us to describe a research program that extends our framework to study other ecosystem services, to uncover the mechanisms by which ecosystem protection benefits humans, and to tie cost-benefit analyses to conservation planning so that we can obtain the greatest return on scarce conservation funds.

Estimating the impacts of conservation on ecosystem services and poverty by integrating modeling and evaluation

PubMed Central

Ferraro, Paul J.; Hanauer, Merlin M.; Miteva, Daniela A.; Nelson, Joanna L.; Pattanayak, Subhrendu K.; Nolte, Christoph; Sims, Katharine R. E.

2015-01-01

Scholars have made great advances in modeling and mapping ecosystem services, and in assigning economic values to these services. This modeling and valuation scholarship is often disconnected from evidence about how actual conservation programs have affected ecosystem services, however. Without a stronger evidence base, decision makers find it difficult to use the insights from modeling and valuation to design effective policies and programs. To strengthen the evidence base, scholars have advanced our understanding of the causal pathways between conservation actions and environmental outcomes, but their studies measure impacts on imperfect proxies for ecosystem services (e.g., avoidance of deforestation). To be useful to decision makers, these impacts must be translated into changes in ecosystem services and values. To illustrate how this translation can be done, we estimated the impacts of protected areas in Brazil, Costa Rica, Indonesia, and Thailand on carbon storage in forests. We found that protected areas in these conservation hotspots have stored at least an additional 1,000 Mt of CO2 in forests and have delivered ecosystem services worth at least $5 billion. This aggregate impact masks important spatial heterogeneity, however. Moreover, the spatial variability of impacts on carbon storage is the not the same as the spatial variability of impacts on avoided deforestation. These findings lead us to describe a research program that extends our framework to study other ecosystem services, to uncover the mechanisms by which ecosystem protection benefits humans, and to tie cost-benefit analyses to conservation planning so that we can obtain the greatest return on scarce conservation funds. PMID:26082549

Ecosystem Services Flows: Why Stakeholders' Power Relationships Matter.

PubMed

Felipe-Lucia, María R; Martín-López, Berta; Lavorel, Sandra; Berraquero-Díaz, Luis; Escalera-Reyes, Javier; Comín, Francisco A

2015-01-01

The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the "cascade" framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders' interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders' ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services.

Ecosystem Services Flows: Why Stakeholders’ Power Relationships Matter

PubMed Central

Felipe-Lucia, María R.; Martín-López, Berta; Lavorel, Sandra; Berraquero-Díaz, Luis; Escalera-Reyes, Javier; Comín, Francisco A.

2015-01-01

The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the “cascade” framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders’ interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders’ ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services. PMID:26201000

Evolution of TEM-type enzymes: biochemical and genetic characterization of two new complex mutant TEM enzymes, TEM-151 and TEM-152, from a single patient.

PubMed

Robin, Frédéric; Delmas, Julien; Schweitzer, Cédric; Tournilhac, Olivier; Lesens, Olivier; Chanal, Catherine; Bonnet, Richard

2007-04-01

Two clinical isolates of Escherichia coli, CF1179 and CF1295, were isolated from a patient hospitalized in the hematology unit of the University Hospital of Clermont-Ferrand, Clermont-Ferrand, France. They were resistant to penicillin-clavulanate combinations and to ceftazidime. The double-disk synergy test was positive only for isolate CF1179. Molecular comparison of the isolates showed that they were clonally related. E. coli recombinant strains exhibiting the resistance phenotype of the clinical strains were obtained by cloning. The clones corresponding to strains CF1179 and CF1295 produced TEM-type beta-lactamases with pI values of 5.7 and 5.3, respectively. Sequencing analysis revealed two novel blaTEM genes encoding closely related complex mutant TEM enzymes, designated TEM-151 (pI 5.3) and TEM-152 (pI 5.7). These two genes also harbored a new promoter region which presented a 9-bp deletion. The two novel beta-lactamases differed from the parental enzyme, TEM-1, by the substitution Arg164His, previously observed in extended-spectrum beta-lactamases (ESBLs), and by the substitutions Met69Val and Asn276Asp, previously observed in the inhibitor-resistant penicillinase TEM-36/IRT-7. They differed by two amino acid substitutions: TEM-152 harbored a Glu240Lys ESBL-type substitution and TEM-151 had an Ala284Gly substitution. Functional analysis of TEM-151 and TEM-152 showed that both enzymes had hydrolytic activity against ceftazidime (kcat, 5 and 16 s-1, respectively). TEM-152 was more resistant than TEM-151 to the inhibitor clavulanic acid (50% inhibitory concentrations, 1 versus 0.17 microM). These results confirm the evolution of TEM-type enzymes toward complex enzymes harboring the two kinds of substitutions which confer an extended spectrum of action against beta-lactam antibiotics and resistance to inhibitors.

Intelligent Model Management in a Forest Ecosystem Management Decision Support System

Treesearch

Donald Nute; Walter D. Potter; Frederick Maier; Jin Wang; Mark Twery; H. Michael Rauscher; Peter Knopp; Scott Thomasma; Mayukh Dass; Hajime Uchiyama

2002-01-01

Decision making for forest ecosystem management can include the use of a wide variety of modeling tools. These tools include vegetation growth models, wildlife models, silvicultural models, GIS, and visualization tools. NED-2 is a robust, intelligent, goal-driven decision support system that integrates tools in each of these categories. NED-2 uses a blackboard...

Hybrid modeling approach for the northern Adriatic watershed management.

PubMed

Volf, Goran; Atanasova, Nataša; Škerjanec, Mateja; Ožanić, Nevenka

2018-04-23

Northern Adriatic (NA) is one of the most productive parts of the Mediterranean Sea due to vast nutrient discharges from the contributing watershed. To understand better the excess of nutrients as stressors to the state of the marine ecosystem, a hybrid modeling approach following the DPSIR framework and terminology was developed, linking: 1) the AVGWLF model for modeling the pressures, i.e. nutrients originating from the watershed caused by two major drivers (urbanization and agriculture), 2) the ML tool MTSMOTI for inducing a model tree connecting the pressures with the marine ecosystem state, and 3) the water quality index, TRIX, equation to evaluate the trophic state of the marine ecosystem. Data used for the modeling purpose comprised GIS layers (i.e., digital terrain model, land use/cover data, soil map, locations of hydro-meteorological stations and WWTPs), time series data (i.e., hydro-meteorological data and nutrient concentrations), and statistical data (i.e., number of inhabitants, connections to wastewater treatment, livestock statistics, etc.) as well as physical, chemical and biological parameters, measured at six marine water monitoring stations, located between the Po River delta (Italy) and the city of Rovinj (west Istrian coast, Croatia). Using the model, seven watershed management scenarios related to wastewater treatment and agricultural activities were evaluated for their influence on the state of the NA marine ecosystem. According to the results, the gradual implementation of the UWWTD in the last 10years contributed significantly to the preservation and improvement of the NA marine ecosystem state. However, despite the full implementation of the UWWTD, the state of the NA marine ecosystem could deteriorate in case of increased nutrient loads from agriculture. Since the UWWTD is already close to its full implementation, NA watershed management should focus on controlling agricultural activities in order to maintain 'high' state of the NA marine ecosystem. Copyright © 2018 Elsevier B.V. All rights reserved.

Decadal trends in the seasonal-cycle amplitude of terrestrial CO 2 exchange resulting from the ensemble of terrestrial biosphere models

DOE PAGES

Ito, Akihiko; Inatomi, Motoko; Huntzinger, Deborah N.; ...

2016-05-12

The seasonal-cycle amplitude (SCA) of the atmosphere–ecosystem carbon dioxide (CO 2) exchange rate is a useful metric of the responsiveness of the terrestrial biosphere to environmental variations. It is unclear, however, what underlying mechanisms are responsible for the observed increasing trend of SCA in atmospheric CO 2 concentration. Using output data from the Multi-scale Terrestrial Model Intercomparison Project (MsTMIP), we investigated how well the SCA of atmosphere–ecosystem CO 2 exchange was simulated with 15 contemporary terrestrial ecosystem models during the period 1901–2010. Also, we made attempt to evaluate the contributions of potential mechanisms such as atmospheric CO 2, climate, land-use,more » and nitrogen deposition, through factorial experiments using different combinations of forcing data. Under contemporary conditions, the simulated global-scale SCA of the cumulative net ecosystem carbon flux of most models was comparable in magnitude with the SCA of atmospheric CO 2 concentrations. Results from factorial simulation experiments showed that elevated atmospheric CO 2 exerted a strong influence on the seasonality amplification. When the model considered not only climate change but also land-use and atmospheric CO 2 changes, the majority of the models showed amplification trends of the SCAs of photosynthesis, respiration, and net ecosystem production (+0.19 % to +0.50 % yr –1). In the case of land-use change, it was difficult to separate the contribution of agricultural management to SCA because of inadequacies in both the data and models. The simulated amplification of SCA was approximately consistent with the observational evidence of the SCA in atmospheric CO 2 concentrations. Large inter-model differences remained, however, in the simulated global tendencies and spatial patterns of CO 2 exchanges. Further studies are required to identify a consistent explanation for the simulated and observed amplification trends, including their underlying mechanisms. Furthermore, this study implied that monitoring of ecosystem seasonality would provide useful insights concerning ecosystem dynamics.« less

Are more complex physiological models of forest ecosystems better choices for plot and regional predictions?

Treesearch

Wenchi Jin; Hong S. He; Frank R. Thompson

2016-01-01

Process-based forest ecosystem models vary from simple physiological, complex physiological, to hybrid empirical-physiological models. Previous studies indicate that complex models provide the best prediction at plot scale with a temporal extent of less than 10 years, however, it is largely untested as to whether complex models outperform the other two types of models...

Secondary Students' Dynamic Modeling Processes: Analyzing, Reasoning About, Synthesizing, and Testing Models of Stream Ecosystems.

ERIC Educational Resources Information Center

Stratford, Steven J.; Krajeik, Joseph; Soloway, Elliot

This paper presents the results of a study of the cognitive strategies in which ninth-grade science students engaged as they used a learner-centered dynamic modeling tool (called Model-It) to make original models based upon stream ecosystem scenarios. The research questions were: (1) In what Cognitive Strategies for Modeling (analyzing, reasoning,…

In vitro effects of 6 % hydroxyethyl starch 130/0.42 solution on feline whole blood coagulation measured by rotational thromboelastometry.

PubMed

Albrecht, Nathalie A; Howard, Judith; Kovacevic, Alan; Adamik, Katja N

2016-07-26

The artificial colloid, hydroxyethyl starch (HES), is recommended for intravascular volume expansion and colloid-osmotic pressure enhancement in dogs and cats. A well-known side effect of HES solutions in humans and dogs is coagulopathy. However, HES-associated coagulopathy has thus far not been investigated in cats. The goal of this study was to assess the in vitro effects of 6 % HES 130/0.42 on feline whole blood samples using rotational thromboelastometry (ROTEM). A further goal was to develop feline reference intervals for ROTEM at our institution. In this in vitro experimental study, blood samples of 24 adult healthy cats were collected by atraumatic jugular phlebotomy following intramuscular sedation. Baseline ROTEM analyses (using ex-tem, in-tem and fib-tem assays) were performed in duplicate. Additionally, ROTEM analyses were performed on blood samples after dilution with either Ringer's acetate (RA) or 6 % HES 130/0.42 (HES) in a 1:6 dilution (i.e. 1 part solution and 6 parts blood). Coefficients of variation of duplicate measures were below 12 % in all ex-tem assays, 3 of 4 in-tem assays but only 1 of 3 fib-tem assays. Reference intervals were similar albeit somewhat narrower than those previously published. Dilution with both solutions lead to significantly prolonged CT (in-tem), CFT (ex-tem and in-tem), and reduced MCF (ex-tem, in-tem, and fib-tem) and alpha (ex-tem and in-tem). Compared to RA, dilution with HES caused a significant prolongation of CT in fib-tem (P = 0.016), CFT in ex-tem (P = 0.017) and in-tem (P = 0.019), as well as a reduction in MCF in in-tem (P = 0.032) and fib-tem (P = 0.020), and alpha in ex-tem (P = 0.014). However, only a single parameter (CFT in ex-tem) was outside of the established reference interval after dilution with HES. In vitro hemodilution of feline blood with RA and HES causes a small but significant impairment of whole blood coagulation, with HES leading to a significantly greater effect on coagulation than RA. Further studies are necessary to evaluate the in vivo effects and the clinical significance of these findings.

Same pattern, different mechanism: Locking onto the role of key species in seafloor ecosystem process

PubMed Central

Woodin, Sarah Ann; Volkenborn, Nils; Pilditch, Conrad A.; Lohrer, Andrew M.; Wethey, David S.; Hewitt, Judi E.; Thrush, Simon F.

2016-01-01

Seafloor biodiversity is a key mediator of ecosystem functioning, but its role is often excluded from global budgets or simplified to black boxes in models. New techniques allow quantification of the behavior of animals living below the sediment surface and assessment of the ecosystem consequences of complex interactions, yielding a better understanding of the role of seafloor animals in affecting key processes like primary productivity. Combining predictions based on natural history, behavior of key benthic species and environmental context allow assessment of differences in functioning and process, even when the measured ecosystem property in different systems is similar. Data from three sedimentary systems in New Zealand illustrate this. Analysis of the behaviors of the infaunal ecosystem engineers in each system revealed three very different mechanisms driving ecosystem function: density and excretion, sediment turnover and surface rugosity, and hydraulic activities and porewater bioadvection. Integrative metrics of ecosystem function in some cases differentiate among the systems (gross primary production) and in others do not (photosynthetic efficiency). Analyses based on behaviors and activities revealed important ecosystem functional differences and can dramatically improve our ability to model the impact of stressors on ecosystem and global processes. PMID:27230562

Same pattern, different mechanism: Locking onto the role of key species in seafloor ecosystem process.

PubMed

Woodin, Sarah Ann; Volkenborn, Nils; Pilditch, Conrad A; Lohrer, Andrew M; Wethey, David S; Hewitt, Judi E; Thrush, Simon F

2016-05-27

Seafloor biodiversity is a key mediator of ecosystem functioning, but its role is often excluded from global budgets or simplified to black boxes in models. New techniques allow quantification of the behavior of animals living below the sediment surface and assessment of the ecosystem consequences of complex interactions, yielding a better understanding of the role of seafloor animals in affecting key processes like primary productivity. Combining predictions based on natural history, behavior of key benthic species and environmental context allow assessment of differences in functioning and process, even when the measured ecosystem property in different systems is similar. Data from three sedimentary systems in New Zealand illustrate this. Analysis of the behaviors of the infaunal ecosystem engineers in each system revealed three very different mechanisms driving ecosystem function: density and excretion, sediment turnover and surface rugosity, and hydraulic activities and porewater bioadvection. Integrative metrics of ecosystem function in some cases differentiate among the systems (gross primary production) and in others do not (photosynthetic efficiency). Analyses based on behaviors and activities revealed important ecosystem functional differences and can dramatically improve our ability to model the impact of stressors on ecosystem and global processes.

Top 10 principles for designing healthy coastal ecosystems

USGS Publications Warehouse

Gaydos, Joseph K.; Dierauf, Leslie; Kirby, Grant; Brosnan, Deborah; Gilardi, Kirsten; Davis, Gary E.

2008-01-01

Like other coastal zones around the world, the inland sea ecosystem of Washington (USA) and British Columbia (Canada), an area known as the Salish Sea, is changing under pressure from a growing human population, conversion of native forest and shoreline habitat to urban development, toxic contamination of sediments and species, and overharvest of resources. While billions of dollars have been spent trying to restore other coastal ecosystems around the world, there still is no successful model for restoring estuarine or marine ecosystems like the Salish Sea. Despite the lack of a guiding model, major ecological principles do exist that should be applied as people work to design the Salish Sea and other large marine ecosystems for the future. We suggest that the following 10 ecological principles serve as a foundation for educating the public and for designing a healthy Salish Sea and other coastal ecosystems for future generations: (1) Think ecosystem: political boundaries are arbitrary; (2) Account for ecosystem connectivity; (3) Understand the food web; (4) Avoid fragmentation; (5) Respect ecosystem integrity; (6) Support nature's resilience; (7) Value nature: it's money in your pocket; (8) Watch wildlife health; (9) Plan for extremes; and (10) Share the knowledge.

Degradation and damages from utilizing ecosystem services in a river basin

Treesearch

Travis W. Warziniack

2012-01-01

We examine the tradeoffs between utilizing multiple ecosystem services in an economic model of the Lower Mississippi-Atchafalaya River Basin. We show how economic development in the basin degraded the ecosystem, but diversified the economy. A degraded ecosystem and more employment opportunities elsewhere reduced the region's reliance on agriculture and other...

Using Landscape Hierarchies To Guide Restoration Of Disturbed Ecosystems

Treesearch

Brian J. Palik; Charles P. Goebel; Katherine L. Kirkman; Larry West

2000-01-01

Reestablishing native plant communities is an important focus of ecosystem restoration. In complex landscapes containing a diversity of ecosystem types, restoration requires a set of reference vegetation conditions for the ecosystems of concern, and a predictive model to relate plant community composition to physical variables. Restoration also requires an approach for...

Ecosystem services and emergent vulnerability in managed ecosystems: A geospatial decision-support tool

Treesearch

Colin M. Beier; Trista M. Patterson; F. Stuart Chapin III

2008-01-01

Managed ecosystems experience vulnerabilities when ecological resilience declines and key flows of ecosystem services become depleted or lost. Drivers of vulnerability often include local management actions in conjunction with other external, larger scale factors. To translate these concepts to management applications, we developed a conceptual model of feedbacks...

Recent drought effects on ecosystem carbon uptake in California ecosystems

NASA Astrophysics Data System (ADS)

Chen, M.; Guan, K.; Brodrick, P. G.; Berry, J. A.; Asner, G. P.

2016-12-01

California is one of the Earth's most biodiverse places and most of California has experienced an extreme (millennium scale) drought in the period of 2012-2015. Although the effect of the drought on the water resources have been well studied, the responses of ecosystems has not been explored in this detail. This study used advanced remotely sensed data (e.g., remotely sensed vegetation indices and solar-induced fluorescence), an ecosystem model, and model-data fusion techniques to study the impacts of the severe drought on ecosystem carbon uptakes in California. We have found that: (1) the drought has significantly suppressed carbon uptake and light use efficiency in California ecosystems - except in the semi-deserts, and the moist forests in the northern coast; (2) effects on the photosynthetic capacity of the ecosystems extends after the drought is relieved; and (3) the drought has shifted both the timing and magnitude of the seasonality of the carbon uptake in non-forested regions. These findings provide a better understanding of the impacts of droughts, and provide an improved basis for prediction of ecosystem responses under a more extreme climate in the future.

Genetic information and ecosystem health: arguments for the application of chaos theory to identify boundary conditions for ecosystem management.

PubMed Central

Stomp, A M

1994-01-01

To meet the demands for goods and services of an exponentially growing human population, global ecosystems will come under increasing human management. The hallmark of successful ecosystem management will be long-term ecosystem stability. Ecosystems and the genetic information and processes which underlie interactions of organisms with the environment in populations and communities exhibit behaviors which have nonlinear characteristics. Nonlinear mathematical formulations describing deterministic chaos have been used successfully to model such systems in physics, chemistry, economics, physiology, and epidemiology. This approach can be extended to ecotoxicology and can be used to investigate how changes in genetic information determine the behavior of populations and communities. This article seeks to provide the arguments for such an approach and to give initial direction to the search for the boundary conditions within which lies ecosystem stability. The identification of a theoretical framework for ecotoxicology and the parameters which drive the underlying model is a critical component in the formulation of a prioritized research agenda and appropriate ecosystem management policy and regulation. PMID:7713038

Mathematical modeling relevant to closed artificial ecosystems

USGS Publications Warehouse

DeAngelis, D.L.

2003-01-01

The mathematical modeling of ecosystems has contributed much to the understanding of the dynamics of such systems. Ecosystems can include not only the natural variety, but also artificial systems designed and controlled by humans. These can range from agricultural systems and activated sludge plants, down to mesocosms, microcosms, and aquaria, which may have practical or research applications. Some purposes may require the design of systems that are completely closed, as far as material cycling is concerned. In all cases, mathematical modeling can help not only to understand the dynamics of the system, but also to design methods of control to keep the system operating in desired ranges. This paper reviews mathematical modeling relevant to the simulation and control of closed or semi-closed artificial ecosystems designed for biological production and recycling in applications in space. Published by Elsevier Science Ltd on behalf of COSPAR.

Use of an ecosystem model for testing ecosystem response to inaccuracies of root and microflora productivity estimates

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

Petersen, H.; O'Neill, R.V.; Gardner, R.H.

1984-01-01

A seventy-compartment model for a Danish beech forest ecosystem is described in outline. The unmodified model predicts considerable accumulation of wood litter and decreasing accumulation through secondary to final decomposition products. Increment rates are similar for all components of the detritus based food chain. Modification of fine root production rate produces strong, positive response for root litter, and less, but still significant, response for detritus, humus and the components of the decomposer food chain. Increase of microbial biomass with adjustments of metabolism and production causes reduced accumulation of detritus and humus. The soil organisms respond according to food source. Themore » use of the model for testing the sensitivity of the ecosystem to inaccuracies of rroot- and microflora estimates is discussed. 21 references, 3 figures, 1 table.« less

Ecological Footprint and Ecosystem Services Models: A Comparative Analysis of Environmental Carrying Capacity Calculation Approach in Indonesia

NASA Astrophysics Data System (ADS)

Subekti, R. M.; Suroso, D. S. A.

2018-05-01

Calculation of environmental carrying capacity can be done by various approaches. The selection of an appropriate approach determines the success of determining and applying environmental carrying capacity. This study aimed to compare the ecological footprint approach and the ecosystem services approach for calculating environmental carrying capacity. It attempts to describe two relatively new models that require further explanation if they are used to calculate environmental carrying capacity. In their application, attention needs to be paid to their respective advantages and weaknesses. Conceptually, the ecological footprint model is more complete than the ecosystem services model, because it describes the supply and demand of resources, including supportive and assimilative capacity of the environment, and measurable output through a resource consumption threshold. However, this model also has weaknesses, such as not considering technological change and resources beneath the earth’s surface, as well as the requirement to provide trade data between regions for calculating at provincial and district level. The ecosystem services model also has advantages, such as being in line with strategic environmental assessment (SEA) of ecosystem services, using spatial analysis based on ecoregions, and a draft regulation on calculation guidelines formulated by the government. Meanwhile, weaknesses are that it only describes the supply of resources, that the assessment of the different types of ecosystem services by experts tends to be subjective, and that the output of the calculation lacks a resource consumption threshold.

State-and-transition model archetypes: a global taxonomy of rangeland change

USDA-ARS?s Scientific Manuscript database

State and transition models (STMs) synthesize science-based and local knowledge to formally represent the dynamics of rangeland and other ecosystems. Mental models or concepts of ecosystem dynamics implicitly underlie all management decisions in rangelands and thus how people influence rangeland sus...

A probabilistic process model for pelagic marine ecosystems informed by Bayesian inverse analysis

EPA Science Inventory

Marine ecosystems are complex systems with multiple pathways that produce feedback cycles, which may lead to unanticipated effects. Models abstract this complexity and allow us to predict, understand, and hypothesize. In ecological models, however, the paucity of empirical data...

PESTICIDE ORCHARD ECOSYSTEM MODEL (POEM): A USER'S GUIDE

EPA Science Inventory

A mathematical model was developed to predict the transport and effects of a pesticide in an orchard ecosystem. The environmental behavior of azinphosmethyl was studied over a two-year period in a Michigan apple orchard. Data were gathered for the model on initial distribution wi...

Biodiversity and ecosystem stability across scales in metacommunities.

PubMed

Wang, Shaopeng; Loreau, Michel

2016-05-01

Although diversity-stability relationships have been extensively studied in local ecosystems, the global biodiversity crisis calls for an improved understanding of these relationships in a spatial context. Here, we use a dynamical model of competitive metacommunities to study the relationships between species diversity and ecosystem variability across scales. We derive analytic relationships under a limiting case; these results are extended to more general cases with numerical simulations. Our model shows that, while alpha diversity decreases local ecosystem variability, beta diversity generally contributes to increasing spatial asynchrony among local ecosystems. Consequently, both alpha and beta diversity provide stabilising effects for regional ecosystems, through local and spatial insurance effects respectively. We further show that at the regional scale, the stabilising effect of biodiversity increases as spatial environmental correlation increases. Our findings have important implications for understanding the interactive effects of global environmental changes (e.g. environmental homogenisation) and biodiversity loss on ecosystem sustainability at large scales. © 2016 John Wiley & Sons Ltd/CNRS.

Global sensitivity analysis of DRAINMOD-FOREST, an integrated forest ecosystem model

Treesearch

Shiying Tian; Mohamed A. Youssef; Devendra M. Amatya; Eric D. Vance

2014-01-01

Global sensitivity analysis is a useful tool to understand process-based ecosystem models by identifying key parameters and processes controlling model predictions. This study reported a comprehensive global sensitivity analysis for DRAINMOD-FOREST, an integrated model for simulating water, carbon (C), and nitrogen (N) cycles and plant growth in lowland forests. The...

Nitrous oxide emissions from cropland: A procedure for calibrating the DayCent biogeochemical model using inverse modelling

USDA-ARS?s Scientific Manuscript database

DayCent is a biogeochemical model of intermediate complexity widely used to simulate greenhouse gases (GHG), soil organic carbon (SOC) and nutrients in crop, grassland, forest and savannah ecosystems. Although this model has been applied to a wide range of ecosystems, it is still typically parameter...

Equilibrium responses of global net primary production and carbon storage to doubled atmospheric carbon dioxide: Sensitivity to changes in vegetation nitrogen concentration

USGS Publications Warehouse

McGuire, David A.; Melillo, J.M.; Kicklighter, D.W.; Pan, Y.; Xiao, X.; Helfrich, J.; Moore, B.; Vorosmarty, C.J.; Schloss, A.L.

1997-01-01

We ran the terrestrial ecosystem model (TEM) for the globe at 0.5?? resolution for atmospheric CO2 concentrations of 340 and 680 parts per million by volume (ppmv) to evaluate global and regional responses of net primary production (NPP) and carbon storage to elevated CO2 for their sensitivity to changes in vegetation nitrogen concentration. At 340 ppmv, TEM estimated global NPP of 49.0 1015 g (Pg) C yr-1 and global total carbon storage of 1701.8 Pg C; the estimate of total carbon storage does not include the carbon content of inert soil organic matter. For the reference simulation in which doubled atmospheric CO2 was accompanied with no change in vegetation nitrogen concentration, global NPP increased 4.1 Pg C yr-1 (8.3%), and global total carbon storage increased 114.2 Pg C. To examine sensitivity in the global responses of NPP and carbon storage to decreases in the nitrogen concentration of vegetation, we compared doubled CO2 responses of the reference TEM to simulations in which the vegetation nitrogen concentration was reduced without influencing decomposition dynamics ("lower N" simulations) and to simulations in which reductions in vegetation nitrogen concentration influence decomposition dynamics ("lower N+D" simulations). We conducted three lower N simulations and three lower N+D simulations in which we reduced the nitrogen concentration of vegetation by 7,5, 15.0, and 22.5%. In the lower N simulations, the response of global NPP to doubled atmospheric CO2 increased approximately 2 Pg C yr-1 for each incremental 7.5% reduction in vegetation nitrogen concentration, and vegetation carbon increased approximately an additional 40 Pg C, and soil carbon increased an additional 30 Pg C, for a total carbon storage increase of approximately 70 Pg C. In the lower N+D simulations, the responses of NPP and vegetation carbon storage were relatively insensitive to differences in the reduction of nitrogen concentration, but soil carbon storage showed a large change. The insensitivity of NPP in the N+D simulations occurred because potential enhancements in NPP associated with reduced vegetation nitrogen concentration were approximately offset by lower nitrogen availability associated with the decomposition dynamics of reduced litter nitrogen concentration. For each 7.5% reduction in vegetation nitrogen concentration, soil carbon increased approximately an additional 60 Pg C, while vegetation carbon storage increased by only approximately 5 Pg C. As the reduction in vegetation nitrogen concentration gets greater in the lower N+D simulations, more of the additional carbon storage tends to become concentrated in the north temperateboreal region in comparison to the tropics. Other studies with TEM show that elevated CO2 more than offsets the effects of climate change to cause increased carbon storage. The results of this study indicate that carbon storage would be enhanced by the influence of changes in plant nitrogen concentration on carbon assimilation and decomposition rates. Thus changes in vegetation nitrogen concentration may have important implications for the ability of the terrestrial biosphere to mitigate increases in the atmospheric concentration of CO2 and climate changes associated with the increases.

Deactivation of TEM-1 β-Lactamase Investigated by Isothermal Batch and Non-Isothermal Continuous Enzyme Membrane Reactor Methods

PubMed Central

Rogers, Thomas A.

2011-01-01

The thermal deactivation of TEM-1 β-lactamase was examined using two experimental techniques: a series of isothermal batch assays and a single, continuous, non-isothermal assay in an enzyme membrane reactor (EMR). The isothermal batch-mode technique was coupled with the three-state “Equilibrium Model” of enzyme deactivation, while the results of the EMR experiment were fitted to a four-state “molten globule model”. The two methods both led to the conclusions that the thermal deactivation of TEM-1 β-lactamase does not follow the Lumry-Eyring model and that the Teq of the enzyme (the point at which active and inactive states are present in equal amounts due to thermodynamic equilibrium) is at least 10 °C from the Tm (melting temperature), contrary to the idea that the true temperature optimum of a biocatalyst is necessarily close to the melting temperature. PMID:22039393

Theory of the spatial resolution of (scanning) transmission electron microscopy in liquid water or ice layers.

PubMed

de Jonge, Niels

2018-04-01

The sample dependent spatial resolution was calculated for transmission electron microscopy (TEM) and scanning TEM (STEM) of objects (e.g., nanoparticles, proteins) embedded in a layer of liquid water or amorphous ice. The theoretical model includes elastic- and inelastic scattering, beam broadening, and chromatic aberration. Different contrast mechanisms were evaluated as function of the electron dose, the detection angle, and the sample configuration. It was found that the spatial resolution scales with the electron dose to the -1/4th power. Gold- and carbon nanoparticles were examined in the middle of water layers ranging from 0.01--10 µm thickness representing relevant classes of experiments in both materials science and biology. The optimal microscope settings differ between experimental configurations. STEM performs the best for gold nanoparticles for all layer thicknesses, while carbon is best imaged with phase-contrast TEM for thin layers but bright field STEM is preferred for thicker layers. The resolution was also calculated for a water layer enclosed between thin membranes. The influence of chromatic aberration correction for TEM was examined as well. The theory is broadly applicable to other types of materials and sample configurations. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of ice storm on forest ecosystem of southern China in 2008 Shaoqiang Wang1, Lei Zhou1, Weimin Ju2, Kun Huang1 1Key Lab of Ecosystem Network Observation and Modeling, Institute of Geographical Sciences and Natural Resources Research, Beijing, 10010

NASA Astrophysics Data System (ADS)

Wang, Shaoqiang

2014-05-01

Evidence is mounting that an increase in extreme climate events has begun to occur worldwide during the recent decades, which affect biosphere function and biodiversity. Ecosystems returned to its original structures and functions to maintain its sustainability, which was closely dependent on ecosystem resilience. Understanding the resilience and recovery capacity of ecosystem to extreme climate events is essential to predicting future ecosystem responses to climate change. Given the overwhelming importance of this region in the overall carbon cycle of forest ecosystems in China, south China suffered a destructive ice storm in 2008. In this study, we used the number of freezing day and a process-based model (Boreal Ecosystem Productivity Simulator, BEPS) to characterize the spatial distribution of ice storm region in southeastern China and explore the impacts on carbon cycle of forest ecosystem over the past decade. The ecosystem variables, i.e. Net primary productivity (NPP), Evapotranspiration (ET), and Water use efficiency (WUE, the ratio of NPP to ET) from the outputs of BEPS models were used to detect the resistance and resilience of forest ecosystem in southern China. The pattern of ice storm-induced forest productivity widespread decline was closely related to the number of freezing day during the ice storm period. The NPP of forest area suffered heavy ice storm returned to normal status after five months with high temperature and ample moisture, indicated a high resilience of subtropical forest in China. The long-term changes of forest WUE remain stable, behaving an inherent sensitivity of ecosystem to extreme climate events. In addition, ground visits suggested that the recovery of forest productivity was attributed to rapid growth of understory. Understanding the variability and recovery threshold of ecosystem following extreme climate events help us to better simulate and predict the variability of ecosystem structure and function under current and future climate change.

On the Locality of Transient Electromagnetic Soundings with a Single-Loop Configuration

NASA Astrophysics Data System (ADS)

Barsukov, P. O.; Fainberg, E. B.

2018-03-01

The possibilities of reconstructing two-dimensional (2D) cross sections based on the data of the profile soundings by the transient electromagnetic method (TEM) with a single ungrounded loop are illustrated on three-dimensional (3D) models. The process of reconstruction includes three main steps: transformation of the responses in the depth dependence of resistivity ρ(h) measured along the profile, with their subsequent stitching into the 2D pseudo section; point-by-point one-dimensional (1D) inversion of the responses with the starting model constructed based on the transformations; and correction of the 2D cross section with the use of 2.5-dimensional (2.5D) block inversion. It is shown that single-loop TEM soundings allow studying the geological media within a local domain the lateral dimensions of which are commensurate with the depth of the investigation. The structure of the medium beyond this domain insignificantly affects the sounding results. This locality enables the TEM to reconstruct the geoelectrical structure of the medium from the 2D cross sections with the minimal distortions caused by the lack of information beyond the profile of the transient response measurements.

Evaluation of model predictions of the ecological effects of 4-nonylphenol -- before and after model refinement

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

Hanratty, M.P.; Liber, K.

1994-12-31

The Littoral Ecosystem Risk Assessment Model (LERAM) is a bioenergetic ecosystem effects model. It links single species toxicity data to a bioenergetic model of the trophic structure of an ecosystem in order to simulate community and ecosystem level effects of chemical stressors. LERAM was used in 1992 to simulate the ecological effects of diflubenzuron. When compared to the results from a littoral enclosure study, the model exaggerated the cascading of effects through the trophic levels of the littoral ecosystem. It was hypothesized that this could be corrected by making minor changes in the representation of the littoral food web. Twomore » refinements of the model were therefore performed: (1) the plankton and macroinvertebrate model populations [eg., predatory Copepoda, herbivorous Insecta, green phytoplankton, etc.] were changed to better represent the habitat and feeding preferences of the endemic taxa; and (2) the method for modeling the microbial degradation of detritus (and the resulting nutrient remineralization) was changed from simulating bacterial populations to simulating bacterial function. Model predictions of the ecological effects of 4-nonylphenol were made before and after these refinements. Both sets of predictions were then compared to the results from a littoral enclosure study of the ecological effects of 4-nonylphenol. The changes in the LERAM predictions were then used to determine the success of the refinements, to guide. future research, and to further define LERAM`s domain of application.« less

Processes influencing model-data mismatch in drought-stressed, fire-disturbed eddy flux sites

NASA Astrophysics Data System (ADS)

Mitchell, Stephen; Beven, Keith; Freer, Jim; Law, Beverly

2011-06-01

Semiarid forests are very sensitive to climatic change and among the most difficult ecosystems to accurately model. We tested the performance of the Biome-BGC model against eddy flux data taken from young (years 2004-2008), mature (years 2002-2008), and old-growth (year 2000) ponderosa pine stands at Metolius, Oregon, and subsequently examined several potential causes for model-data mismatch. We used the Generalized Likelihood Uncertainty Estimation methodology, which involved 500,000 model runs for each stand (1,500,000 total). Each simulation was run with randomly generated parameter values from a uniform distribution based on published parameter ranges, resulting in modeled estimates of net ecosystem CO2 exchange (NEE) that were compared to measured eddy flux data. Simulations for the young stand exhibited the highest level of performance, though they overestimated ecosystem C accumulation (-NEE) 99% of the time. Among the simulations for the mature and old-growth stands, 100% and 99% of the simulations underestimated ecosystem C accumulation. One obvious area of model-data mismatch is soil moisture, which was overestimated by the model in the young and old-growth stands yet underestimated in the mature stand. However, modeled estimates of soil water content and associated water deficits did not appear to be the primary cause of model-data mismatch; our analysis indicated that gross primary production can be accurately modeled even if soil moisture content is not. Instead, difficulties in adequately modeling ecosystem respiration, mainly autotrophic respiration, appeared to be the fundamental cause of model-data mismatch.

Processes influencing model-data mismatch in drought-stressed, fire-disturbed eddy flux sites

NASA Astrophysics Data System (ADS)

Mitchell, S. R.; Beven, K.; Freer, J. E.; Law, B. E.

2010-12-01

Semi-arid forests are very sensitive to climatic change and among the most difficult ecosystems to accurately model. We tested the performance of the Biome-BGC model against eddy flux data taken from young (years 2004-2008), mature (years 2002-2008), and old-growth (year 2000) Ponderosa pine stands at Metolius, Oregon, and subsequently examined several potential causes for model-data mismatch. We used the generalized likelihood uncertainty estimation (GLUE) methodology, which involved 500,000 model runs for each stand (1,500,000 total). Each simulation was run with randomly generated parameter values from a uniform distribution based on published parameter ranges, resulting in modeled estimates of net ecosystem CO2 exchange (NEE) that were compared to measured eddy flux data. Simulations for the young stand exhibited the highest level of performance, though they over-estimated ecosystem C accumulation (-NEE) 99% of the time. Among the simulations for the mature and old-growth stands, 100% and 99% of the simulations under-estimated ecosystem C accumulation. One obvious area of model-data mismatch is soil moisture, which was overestimated by the model in the young and old-growth stands yet underestimated in the mature stand. However, modeled estimates of soil water content and associated water deficits did not appear to be the primary cause of model-data mismatch; our analysis indicated that gross primary production can be accurately modeled even if soil moisture content is not. Instead, difficulties in adequately modeling ecosystem respiration, both autotrophic and heterotrophic, appeared to be fundamental causes of model-data mismatch.

A new theoretical approach to terrestrial ecosystem science based on multiscale observations and eco-evolutionary optimality principles

NASA Astrophysics Data System (ADS)

Prentice, Iain Colin; Wang, Han; Cornwell, William; Davis, Tyler; Dong, Ning; Evans, Bradley; Keenan, Trevor; Peng, Changhui; Stocker, Benjamin; Togashi, Henrique; Wright, Ian

2016-04-01

Ecosystem science focuses on biophysical interactions of organisms and their abiotic environment, and comprises vital aspects of Earth system function such as the controls of carbon, water and energy exchanges between ecosystems and the atmosphere. Global numerical models of these processes have proliferated, and have been incorporated as standard components of Earth system models whose ambitious goal is to predict the coupled behaviour of the oceans, atmosphere and land on time scales from minutes to millennia. Unfortunately, however, the performance of most current terrestrial ecosystem models is highly unsatisfactory. Models typically fail the most basic observational benchmarks, and diverge greatly from one another when called upon to predict the response of ecosystem function and composition to environmental changes beyond the narrow range for which they were developed. This situation seems to have arisen for two inter-related reasons. First, general principles underlying many basic terrestrial biogeochemical processes have been neither clearly formulated nor adequately tested. Second, extensive observational data sets that could be used to test process formulations have become available only quite recently, long postdating the emergence of the current modelling paradigm. But the situation has changed now and ecosystem science needs to change too, to reflect both recent theoretical advances and the vast increase in the availability of relevant data sets at scales from the leaf to the globe. This presentation will outline an emerging mathematical theory that links biophysical plant and ecosystem processes through testable hypotheses derived from the principle of optimization by natural selection. The development and testing of this theory has depended on the availability of extensive data sets on climate, leaf traits (including δ13C measurements), and ecosystem properties including green vegetation cover and land-atmosphere CO2 fluxes. Achievements to date include unified explanations for observed climate and elevation effects on leaf CO2 drawdown (ci:c¬a¬ ratio) and photosynthetic capacity (Vcmax), growth temperature effects on the Jmax:Vcmax ratio, the adaptive nature of acclimation to enhanced CO2 concentration, the controls of leaf versus sapwood respiration, the controls of leaf N content (Narea), the relative constancy of the light use efficiency of gross primary production, and the relative conservatism of leaf dark respiration with climate. These findings call into question many assumptions in supposed "state-of-the-art" terrestrial ecosystem models, and provide a foundation for next-generation global ecosystem models that will rest on a greatly strengthened theoretical and empirical basis.

Biofuels on the landscape: Is "land sharing" preferable to "land sparing"?

NASA Astrophysics Data System (ADS)

DeLucia, E. H.; Anderson-Teixeira, K. J.; Duval, B. D.; Long, S. P.

2012-12-01

Widespread land use changes—and ensuing effects on biodiversity and ecosystem services—are expected as a result of expanding bioenergy production. Although almost all US production of ethanol today is from corn, it is envisaged that future ethanol production will also draw from cellulosic sources such as perennial grasses. In selecting optimal bioenergy crops, there is debate as to whether it is preferable from an environmental standpoint to cultivate bioenergy crops with high ecosystem services (a "land sharing" strategy) or to grow crops with lower ecosystem services but higher yield, thereby requiring less land to meet bioenergy demand (a "land sparing" strategy). Here, we develop a simple model to address this question. Assuming that bioenergy crops are competing with uncultivated land, our model calculates land requirements to meet a given bioenergy demand intensity based upon the yields of bioenergy crops and combines fractional land cover of each ecosystem type with its associated ecosystem services to determine whether land sharing or land sparing strategies maximize ecosystem services at the landscape level. We apply this model to a case in which climate protection through GHG regulation—an ecosystem's greenhouse gas value (GHGV)—is the ecosystem service of interest. We consider five bioenergy crops competing for land area with five unfarmed ecosystem types in the central and eastern US. Our results show that the relative advantages of land sparing and land sharing depend upon the type of ecosystem with which the bioenergy crop is competing for land; as the GHGV value of the unfarmed land increases, the preferable strategy shifts from land sharing to land sparing. This implies that, while it may be preferable to replace ecologically degraded land with high-GHGV, lower yielding bioenergy crops, average landscape GHGV will most often be maximized through high yielding bioenergy crops that leave more land for uncultivated, high-GHGV ecosystems. While our case study focuses on GHGV, the same principles will be generally applicable to any ecosystem service whose value does not depend upon the spatial configuration of the landscape. Whenever bioenergy crops have substantially lower ecosystem services than the ecosystems with which they are competing for land, the most effective strategy for meeting bioenergy demand while maximizing ecosystem services on a landscape level is one of land sparing—that is, focusing simultaneously on maximizing the yield of bioenergy crops while preserving or restoring natural ecosystems.

DayCent-Chem Simulations of Ecological and Biogeochemical Processes of Eight Mountain Ecosystems in the United States

USGS Publications Warehouse

Hartman, Melannie D.; Baron, Jill S.; Clow, David W.; Creed, Irena F.; Driscoll, Charles T.; Ewing, Holly A.; Haines, Bruce D.; Knoepp, Jennifer; Lajtha, Kate; Ojima, Dennis S.; Parton, William J.; Renfro, Jim; Robinson, R. Bruce; Van Miegroet, Helga; Weathers, Kathleen C.; Williams, Mark W.

2009-01-01

Atmospheric deposition of nitrogen (N) and sulfur (S) cause complex responses in ecosystems, from fertilization to forest ecosystem decline, freshwater eutrophication to acidification, loss of soil base cations, and alterations of disturbance regimes. DayCent-Chem, an ecosystem simulation model that combines ecosystem nutrient cycling and plant dynamics with aqueous geochemical equilibrium calculations, was developed to address ecosystem responses to combined atmospheric N and S deposition. It is unique among geochemically-based models in its dynamic biological cycling of N and its daily timestep for investigating ecosystem and surface water chemical response to episodic events. The model was applied to eight mountainous watersheds in the United States. The sites represent a gradient of N deposition across locales, from relatively pristine to N-saturated, and a variety of ecosystem types and climates. Overall, the model performed best in predicting stream chemistry for snowmelt-dominated sites. It was more difficult to predict daily stream chemistry for watersheds with deep soils, high amounts of atmospheric deposition, and a large degree of spatial heterogeneity. DayCent-Chem did well in representing plant and soil carbon and nitrogen pools and fluxes. Modeled stream nitrate (NO3-) and ammonium (NH4+) concentrations compared well with measurements at all sites, with few exceptions. Simulated daily stream sulfate (SO42-) concentrations compared well to measured values for sites where SO42- deposition has been low and where SO42- adsorption/desorption reactions did not seem to be important. The concentrations of base cations and silica in streams are highly dependent on the geochemistry and weathering rates of minerals in each catchment, yet these were rarely, if ever, known. Thus, DayCent-Chem could not accurately predict weathering products for some catchments. Additionally, few data were available for exchangeable soil cations or the magnitude of base cation deposition as a result of dry and fog inputs. The uncertainties related to weathering reactions, deposition, soil cation exchange capacity, and groundwater contributions influenced how well the simulated acid neutralizing capacity (ANC) and pH estimates compared to observed values. Daily discharge was well represented by the model for most sites. The chapters of this report describe the parameterization for each site and summarize model results for ecosystem variables, stream discharge, and stream chemistry. This intersite comparison exercise provided insight about important and possibly not well understood processes.

Terrestrial ecosystems - Isobioclimates of the conterminous United States

USGS Publications Warehouse

Cress, Jill J.; Sayre, Roger G.; Comer, Patrick; Warner, Harumi

2009-01-01

However, the biophysical stratification approach used for the ecosystems modeling effort required a single climate layer that accurately reflected regional variation in wet/dry gradients and hot/cold gradients, with a manageable number of classes. Therefore, the data layers for thermotypes and ombrotypes were combined, yielding 127 unique thermotype-ombrotype combinations.The isobioclimates image shows ombrotypic regions (dry/wet gradients) for each thermotypic (warm/cold) region. Additional information about this map and any of the data developed for the ecosystems modeling of the conterminous United States is available online at http://rmgsc.cr.usgs.gov/ecosystems/.

Improving Marine Ecosystem Models with Biochemical Tracers

NASA Astrophysics Data System (ADS)

Pethybridge, Heidi R.; Choy, C. Anela; Polovina, Jeffrey J.; Fulton, Elizabeth A.

2018-01-01

Empirical data on food web dynamics and predator-prey interactions underpin ecosystem models, which are increasingly used to support strategic management of marine resources. These data have traditionally derived from stomach content analysis, but new and complementary forms of ecological data are increasingly available from biochemical tracer techniques. Extensive opportunities exist to improve the empirical robustness of ecosystem models through the incorporation of biochemical tracer data and derived indices, an area that is rapidly expanding because of advances in analytical developments and sophisticated statistical techniques. Here, we explore the trophic information required by ecosystem model frameworks (species, individual, and size based) and match them to the most commonly used biochemical tracers (bulk tissue and compound-specific stable isotopes, fatty acids, and trace elements). Key quantitative parameters derived from biochemical tracers include estimates of diet composition, niche width, and trophic position. Biochemical tracers also provide powerful insight into the spatial and temporal variability of food web structure and the characterization of dominant basal and microbial food web groups. A major challenge in incorporating biochemical tracer data into ecosystem models is scale and data type mismatches, which can be overcome with greater knowledge exchange and numerical approaches that transform, integrate, and visualize data.

Phytoplankton competition and coexistence: Intrinsic ecosystem dynamics and impact of vertical mixing

NASA Astrophysics Data System (ADS)

Perruche, Coralie; Rivière, Pascal; Pondaven, Philippe; Carton, Xavier

2010-04-01

This paper aims at studying analytically the functioning of a very simple ecosystem model with two phytoplankton species. First, using the dynamical system theory, we determine its nonlinear equilibria, their stability and characteristic timescales with a focus on phytoplankton competition. Particular attention is paid to the model sensitivity to parameter change. Then, the influence of vertical mixing and sinking of detritus on the vertically-distributed ecosystem model is investigated. The analytical results reveal a high diversity of ecosystem structures with fixed points and limit cycles that are mainly sensitive to variations of light intensity and total amount of nitrogen matter. The sensitivity to other parameters such as re-mineralisation, growth and grazing rates is also specified. Besides, the equilibrium analysis shows a complete segregation of the two phytoplankton species in the whole parameter space. The embedding of our ecosystem model into a one-dimensional numerical model with diffusion turns out to allow coexistence between phytoplankton species, providing a possible solution to the 'paradox of plankton' in the sense that it prevents the competitive exclusion of one phytoplankton species. These results improve our knowledge of the factors that control the structure and functioning of plankton communities.

An exactly solvable coarse-grained model for species diversity

NASA Astrophysics Data System (ADS)

Suweis, Samir; Rinaldo, Andrea; Maritan, Amos

2012-07-01

We present novel analytical results concerning ecosystem species diversity that stem from a proposed coarse-grained neutral model based on birth-death processes. The relevance of the problem lies in the urgency for understanding and synthesizing both theoretical results from ecological neutral theory and empirical evidence on species diversity preservation. The neutral model of biodiversity deals with ecosystems at the same trophic level, where per capita vital rates are assumed to be species independent. Closed-form analytical solutions for the neutral theory are obtained within a coarse-grained model, where the only input is the species persistence time distribution. Our results pertain to: the probability distribution function of the number of species in the ecosystem, both in transient and in stationary states; the n-point connected time correlation function; and the survival probability, defined as the distribution of time spans to local extinction for a species randomly sampled from the community. Analytical predictions are also tested on empirical data from an estuarine fish ecosystem. We find that emerging properties of the ecosystem are very robust and do not depend on specific details of the model, with implications for biodiversity and conservation biology.

Modeling leaf phenology variation by groupings of species within and across ecosystems in northern Alaska

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Carman, T. B.; McGuire, A. D.

2012-12-01

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst and in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over a regional to global scale typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observational data of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and ecotonal boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest. This implementation improves the timing of the onset of carbon uptake in the spring, permitting a more accurate assessment of the contribution of each grouping of species to ecosystem performance. Furthermore, this implementation provides a more nuanced perspective on light competition among species and across ecosystems. For example, in the shrub tundra, the sedges and grasses leaf-out before the shade-inducing willow and dwarf birch, thereby providing the sedges and grasses time to accumulate biomass before shading effects arise. Also in the shrub tundra, the forbs leaf-out last, and are therefore, more prone to shading impacts by the taller willow and dwarf birch shrubs. However, in the wet sedge and heath tundra ecosystems, the forbs leaf-out before the shrubs, and are therefore less prone to shading impacts early in the growing season. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape. These findings also demonstrate that high-latitude dynamic vegetation models should consider variation in leaf-out by groupings of species within and across ecosystems in order to provide more accurate projections of future plant distributions in Arctic regions.

From Metaphors to Formalism: A Heuristic Approach to Holistic Assessments of Ecosystem Health.

PubMed

Fock, Heino O; Kraus, Gerd

2016-01-01

Environmental policies employ metaphoric objectives such as ecosystem health, resilience and sustainable provision of ecosystem services, which influence corresponding sustainability assessments by means of normative settings such as assumptions on system description, indicator selection, aggregation of information and target setting. A heuristic approach is developed for sustainability assessments to avoid ambiguity and applications to the EU Marine Strategy Framework Directive (MSFD) and OSPAR assessments are presented. For MSFD, nineteen different assessment procedures have been proposed, but at present no agreed assessment procedure is available. The heuristic assessment framework is a functional-holistic approach comprising an ex-ante/ex-post assessment framework with specifically defined normative and systemic dimensions (EAEPNS). The outer normative dimension defines the ex-ante/ex-post framework, of which the latter branch delivers one measure of ecosystem health based on indicators and the former allows to account for the multi-dimensional nature of sustainability (social, economic, ecological) in terms of modeling approaches. For MSFD, the ex-ante/ex-post framework replaces the current distinction between assessments based on pressure and state descriptors. The ex-ante and the ex-post branch each comprise an inner normative and a systemic dimension. The inner normative dimension in the ex-post branch considers additive utility models and likelihood functions to standardize variables normalized with Bayesian modeling. Likelihood functions allow precautionary target setting. The ex-post systemic dimension considers a posteriori indicator selection by means of analysis of indicator space to avoid redundant indicator information as opposed to a priori indicator selection in deconstructive-structural approaches. Indicator information is expressed in terms of ecosystem variability by means of multivariate analysis procedures. The application to the OSPAR assessment for the southern North Sea showed, that with the selected 36 indicators 48% of ecosystem variability could be explained. Tools for the ex-ante branch are risk and ecosystem models with the capability to analyze trade-offs, generating model output for each of the pressure chains to allow for a phasing-out of human pressures. The Bayesian measure of ecosystem health is sensitive to trends in environmental features, but robust to ecosystem variability in line with state space models. The combination of the ex-ante and ex-post branch is essential to evaluate ecosystem resilience and to adopt adaptive management. Based on requirements of the heuristic approach, three possible developments of this concept can be envisioned, i.e. a governance driven approach built upon participatory processes, a science driven functional-holistic approach requiring extensive monitoring to analyze complete ecosystem variability, and an approach with emphasis on ex-ante modeling and ex-post assessment of well-studied subsystems.

From Metaphors to Formalism: A Heuristic Approach to Holistic Assessments of Ecosystem Health

PubMed Central

Kraus, Gerd

2016-01-01

Environmental policies employ metaphoric objectives such as ecosystem health, resilience and sustainable provision of ecosystem services, which influence corresponding sustainability assessments by means of normative settings such as assumptions on system description, indicator selection, aggregation of information and target setting. A heuristic approach is developed for sustainability assessments to avoid ambiguity and applications to the EU Marine Strategy Framework Directive (MSFD) and OSPAR assessments are presented. For MSFD, nineteen different assessment procedures have been proposed, but at present no agreed assessment procedure is available. The heuristic assessment framework is a functional-holistic approach comprising an ex-ante/ex-post assessment framework with specifically defined normative and systemic dimensions (EAEPNS). The outer normative dimension defines the ex-ante/ex-post framework, of which the latter branch delivers one measure of ecosystem health based on indicators and the former allows to account for the multi-dimensional nature of sustainability (social, economic, ecological) in terms of modeling approaches. For MSFD, the ex-ante/ex-post framework replaces the current distinction between assessments based on pressure and state descriptors. The ex-ante and the ex-post branch each comprise an inner normative and a systemic dimension. The inner normative dimension in the ex-post branch considers additive utility models and likelihood functions to standardize variables normalized with Bayesian modeling. Likelihood functions allow precautionary target setting. The ex-post systemic dimension considers a posteriori indicator selection by means of analysis of indicator space to avoid redundant indicator information as opposed to a priori indicator selection in deconstructive-structural approaches. Indicator information is expressed in terms of ecosystem variability by means of multivariate analysis procedures. The application to the OSPAR assessment for the southern North Sea showed, that with the selected 36 indicators 48% of ecosystem variability could be explained. Tools for the ex-ante branch are risk and ecosystem models with the capability to analyze trade-offs, generating model output for each of the pressure chains to allow for a phasing-out of human pressures. The Bayesian measure of ecosystem health is sensitive to trends in environmental features, but robust to ecosystem variability in line with state space models. The combination of the ex-ante and ex-post branch is essential to evaluate ecosystem resilience and to adopt adaptive management. Based on requirements of the heuristic approach, three possible developments of this concept can be envisioned, i.e. a governance driven approach built upon participatory processes, a science driven functional-holistic approach requiring extensive monitoring to analyze complete ecosystem variability, and an approach with emphasis on ex-ante modeling and ex-post assessment of well-studied subsystems. PMID:27509185

Global and regional ecosystem modeling: comparison of model outputs and field measurements

NASA Astrophysics Data System (ADS)

Olson, R. J.; Hibbard, K.

2003-04-01

The Ecosystem Model-Data Intercomparison (EMDI) Workshops provide a venue for global ecosystem modeling groups to compare model outputs against measurements of net primary productivity (NPP). The objective of EMDI Workshops is to evaluate model performance relative to observations in order to improve confidence in global model projections terrestrial carbon cycling. The questions addressed by EMDI include: How does the simulated NPP compare with the field data across biome and environmental gradients? How sensitive are models to site-specific climate? Does additional mechanistic detail in models result in a better match with field measurements? How useful are the measures of NPP for evaluating model predictions? How well do models represent regional patterns of NPP? Initial EMDI results showed general agreement between model predictions and field measurements but with obvious differences that indicated areas for potential data and model improvement. The effort was built on the development and compilation of complete and consistent databases for model initialization and comparison. Database development improves the data as well as models; however, there is a need to incorporate additional observations and model outputs (LAI, hydrology, etc.) for comprehensive analyses of biogeochemical processes and their relationships to ecosystem structure and function. EMDI initialization and NPP data sets are available from the Oak Ridge National Laboratory Distributed Active Archive Center http://www.daac.ornl.gov/. Acknowledgements: This work was partially supported by the International Geosphere-Biosphere Programme - Data and Information System (IGBP-DIS); the IGBP-Global Analysis, Interpretation and Modelling Task Force (GAIM); the National Center for Ecological Analysis and Synthesis (NCEAS); and the National Aeronautics and Space Administration (NASA) Terrestrial Ecosystem Program. Oak Ridge National Laboratory is managed by UT-Battelle LLC for the U.S. Department of Energy under contract DE-AC05-00OR22725

Conceptualizing and Communicating River Restoration

NASA Astrophysics Data System (ADS)

Jacobosn, R. B.

2007-12-01

River restoration increasingly involves collaboration with stakeholders having diverse values and varying technical understanding. In cases where river restoration proceeds through collaborative processes, scientists are required to communicate complex understanding about riverine ecosystem processes to broad audiences. Of particular importance is communication of uncertainties in predictions of ecosystem responses to restoration actions, and how those uncertainties affect monitoring and evaluation strategies. I present a relatively simple conceptual model of how riverine ecosystems operate. The model, which has been used to conceptualize and communicate various river-restoration and management processes in the Lower Missouri River, emphasizes a) the interdependencies of driving regimes (for example, flow, sediment, and water quality), b) the filtering effect of management history, c) the typical hierarchical nature of information about how ecosystems operate, and d) how scientific understanding interacts with decision making. I provide an example of how the conceptual model has been used to illustrate the effects of extensive channel re-engineering of the Lower Missouri River which is intended to mitigate the effects of channelization and flow regulation on aquatic and flood-plain ecosystems. The conceptual model illustrates the logic for prioritizing investments in monitoring and evaluation, interactions among ecosystem components, tradeoffs between ecological and social-commercial benefits, and the feedback loop necessary for successful adaptive management.

Impacts of insect disturbance on the structure, composition, and functioning of oak-pine forests

NASA Astrophysics Data System (ADS)

Medvigy, D.; Schafer, K. V.; Clark, K. L.

2011-12-01

Episodic disturbance is an essential feature of terrestrial ecosystems, and strongly modulates their structure, composition, and functioning. However, dynamic global vegetation models that are commonly used to make ecosystem and terrestrial carbon budget predictions rarely have an explicit representation of disturbance. One reason why disturbance is seldom included is that disturbance tends to operate on spatial scales that are much smaller than typical model resolutions. In response to this problem, the Ecosystem Demography model 2 (ED2) was developed as a way of tracking the fine-scale heterogeneity arising from disturbances. In this study, we used ED2 to simulate an oak-pine forest that experiences episodic defoliation by gypsy moth (Lymantria dispar L). The model was carefully calibrated against site-level data, and then used to simulate changes in ecosystem composition, structure, and functioning on century time scales. Compared to simulations that include gypsy moth defoliation, we show that simulations that ignore defoliation events lead to much larger ecosystem carbon stores and a larger fraction of deciduous trees relative to evergreen trees. Furthermore, we find that it is essential to preserve the fine-scale nature of the disturbance. Attempts to "smooth out" the defoliation event over an entire grid cells led to large biases in ecosystem structure and functioning.

An Integrated Coral Reef Ecosystem Model to Support Resource Management under a Changing Climate

PubMed Central

Weijerman, Mariska; Fulton, Elizabeth A.; Kaplan, Isaac C.; Gorton, Rebecca; Leemans, Rik; Mooij, Wolf M.; Brainard, Russell E.

2015-01-01

Millions of people rely on the ecosystem services provided by coral reefs, but sustaining these benefits requires an understanding of how reefs and their biotic communities are affected by local human-induced disturbances and global climate change. Ecosystem-based management that explicitly considers the indirect and cumulative effects of multiple disturbances has been recommended and adopted in policies in many places around the globe. Ecosystem models give insight into complex reef dynamics and their responses to multiple disturbances and are useful tools to support planning and implementation of ecosystem-based management. We adapted the Atlantis Ecosystem Model to incorporate key dynamics for a coral reef ecosystem around Guam in the tropical western Pacific. We used this model to quantify the effects of predicted climate and ocean changes and current levels of current land-based sources of pollution (LBSP) and fishing. We used the following six ecosystem metrics as indicators of ecosystem state, resilience and harvest potential: 1) ratio of calcifying to non-calcifying benthic groups, 2) trophic level of the community, 3) biomass of apex predators, 4) biomass of herbivorous fishes, 5) total biomass of living groups and 6) the end-to-start ratio of exploited fish groups. Simulation tests of the effects of each of the three drivers separately suggest that by mid-century climate change will have the largest overall effect on this suite of ecosystem metrics due to substantial negative effects on coral cover. The effects of fishing were also important, negatively influencing five out of the six metrics. Moreover, LBSP exacerbates this effect for all metrics but not quite as badly as would be expected under additive assumptions, although the magnitude of the effects of LBSP are sensitive to uncertainty associated with primary productivity. Over longer time spans (i.e., 65 year simulations), climate change impacts have a slight positive interaction with other drivers, generally meaning that declines in ecosystem metrics are not as steep as the sum of individual effects of the drivers. These analyses offer one way to quantify impacts and interactions of particular stressors in an ecosystem context and so provide guidance to managers. For example, the model showed that improving water quality, rather than prohibiting fishing, extended the timescales over which corals can maintain high abundance by at least 5–8 years. This result, in turn, provides more scope for corals to adapt or for resilient species to become established and for local and global management efforts to reduce or reverse stressors. PMID:26672983

An Integrated Coral Reef Ecosystem Model to Support Resource Management under a Changing Climate.

PubMed

Weijerman, Mariska; Fulton, Elizabeth A; Kaplan, Isaac C; Gorton, Rebecca; Leemans, Rik; Mooij, Wolf M; Brainard, Russell E

2015-01-01

Millions of people rely on the ecosystem services provided by coral reefs, but sustaining these benefits requires an understanding of how reefs and their biotic communities are affected by local human-induced disturbances and global climate change. Ecosystem-based management that explicitly considers the indirect and cumulative effects of multiple disturbances has been recommended and adopted in policies in many places around the globe. Ecosystem models give insight into complex reef dynamics and their responses to multiple disturbances and are useful tools to support planning and implementation of ecosystem-based management. We adapted the Atlantis Ecosystem Model to incorporate key dynamics for a coral reef ecosystem around Guam in the tropical western Pacific. We used this model to quantify the effects of predicted climate and ocean changes and current levels of current land-based sources of pollution (LBSP) and fishing. We used the following six ecosystem metrics as indicators of ecosystem state, resilience and harvest potential: 1) ratio of calcifying to non-calcifying benthic groups, 2) trophic level of the community, 3) biomass of apex predators, 4) biomass of herbivorous fishes, 5) total biomass of living groups and 6) the end-to-start ratio of exploited fish groups. Simulation tests of the effects of each of the three drivers separately suggest that by mid-century climate change will have the largest overall effect on this suite of ecosystem metrics due to substantial negative effects on coral cover. The effects of fishing were also important, negatively influencing five out of the six metrics. Moreover, LBSP exacerbates this effect for all metrics but not quite as badly as would be expected under additive assumptions, although the magnitude of the effects of LBSP are sensitive to uncertainty associated with primary productivity. Over longer time spans (i.e., 65 year simulations), climate change impacts have a slight positive interaction with other drivers, generally meaning that declines in ecosystem metrics are not as steep as the sum of individual effects of the drivers. These analyses offer one way to quantify impacts and interactions of particular stressors in an ecosystem context and so provide guidance to managers. For example, the model showed that improving water quality, rather than prohibiting fishing, extended the timescales over which corals can maintain high abundance by at least 5-8 years. This result, in turn, provides more scope for corals to adapt or for resilient species to become established and for local and global management efforts to reduce or reverse stressors.

CONCEPTUAL MODELS AND METHODS TO GUIDE DIAGNOSTIC RESEARCH INTO CAUSES OF IMPAIRMENT TO AQUATIC ECOSYSTEMS

EPA Science Inventory

Methods and conceptual models to guide the development of tools for diagnosing the causes of biological impairment within aquatic ecosystems of the United States are described in this report. The conceptual models developed here address nutrients, suspended and bedded sediments (...

Models for predicting fuel consumption in sagebrush-dominated ecosystems

Treesearch

Clinton S. Wright

2013-01-01

Fuel consumption predictions are necessary to accurately estimate or model fire effects, including pollutant emissions during wildland fires. Fuel and environmental measurements on a series of operational prescribed fires were used to develop empirical models for predicting fuel consumption in big sagebrush (Artemisia tridentate Nutt.) ecosystems....

Driving terrestrial ecosystem models from space

NASA Technical Reports Server (NTRS)

Waring, R. H.

1993-01-01

Regional air pollution, land-use conversion, and projected climate change all affect ecosystem processes at large scales. Changes in vegetation cover and growth dynamics can impact the functioning of ecosystems, carbon fluxes, and climate. As a result, there is a need to assess and monitor vegetation structure and function comprehensively at regional to global scales. To provide a test of our present understanding of how ecosystems operate at large scales we can compare model predictions of CO2, O2, and methane exchange with the atmosphere against regional measurements of interannual variation in the atmospheric concentration of these gases. Recent advances in remote sensing of the Earth's surface are beginning to provide methods for estimating important ecosystem variables at large scales. Ecologists attempting to generalize across landscapes have made extensive use of models and remote sensing technology. The success of such ventures is dependent on merging insights and expertise from two distinct fields. Ecologists must provide the understanding of how well models emulate important biological variables and their interactions; experts in remote sensing must provide the biophysical interpretation of complex optical reflectance and radar backscatter data.

Model-experiment synthesis at two FACE sites in the southeastern US. Forest ecosystem responses to elevated CO[2]. (Invited)

NASA Astrophysics Data System (ADS)

Walker, A. P.; Zaehle, S.; De Kauwe, M. G.; Medlyn, B. E.; Dietze, M.; Hickler, T.; Iversen, C. M.; Jain, A. K.; Luo, Y.; McCarthy, H. R.; Parton, W. J.; Prentice, C.; Thornton, P. E.; Wang, S.; Wang, Y.; Warlind, D.; Warren, J.; Weng, E.; Hanson, P. J.; Oren, R.; Norby, R. J.

2013-12-01

Ecosystem observations from two long-term Free-Air CO[2] Enrichment (FACE) experiments (Duke forest and Oak Ridge forest) were used to evaluate the assumptions of 11 terrestrial ecosystem models and the consequences of those assumptions for the responses of ecosystem water, carbon (C) and nitrogen (N) fluxes to elevated CO[2] (eCO[2]). Nitrogen dynamics were the main constraint on simulated productivity responses to eCO[2]. At Oak Ridge some models reproduced the declining response of C and N fluxes, while at Duke none of the models were able to maintain the observed sustained responses. C and N cycles are coupled through a number of complex interactions, which causes uncertainty in model simulations in multiple ways. Nonetheless, the major difference between models and experiments was a larger than observed increase in N-use efficiency and lower than observed response of N uptake. The results indicate that at Duke there were mechanisms by which trees accessed additional N in response to eCO[2] that were not represented in the ecosystem models, and which did not operate with the same efficiency at Oak Ridge. Sequestration of the additional productivity under eCO[2] into forest biomass depended largely on C allocation. Allocation assumptions were classified into three main categories--fixed partitioning coefficients, functional relationships and a partial (leaf allocation only) optimisation. The assumption which best constrained model results was a functional relationship between leaf area and sapwood area (pipe-model) and increased root allocation when nitrogen or water were limiting. Both, productivity and allocation responses to eCO[2] determined the ecosystem-level response of LAI, which together with the response of stomatal conductance (and hence water-use efficiency; WUE) determined the ecosystem response of transpiration. Differences in the WUE response across models were related to the representation of the relationship of stomatal conductance to CO[2] and the relative importance of the combined boundary and aerodynamic resistances in the total resistance to leaf-atmosphere water transport.

Hydraulic redistribution affects modeled carbon cycling via soil microbial activity and suppressed fire.

PubMed

Fu, Congsheng; Wang, Guiling; Bible, Kenneth; Goulden, Michael L; Saleska, Scott R; Scott, Russell L; Cardon, Zoe G

2018-04-13

Hydraulic redistribution (HR) of water from moist to drier soils, through plant roots, occurs world-wide in seasonally dry ecosystems. Although the influence of HR on landscape hydrology and plant water use has been amply demonstrated, HR's effects on microbe-controlled processes sensitive to soil moisture, including carbon and nutrient cycling at ecosystem scales, remain difficult to observe in the field and have not been integrated into a predictive framework. We incorporated a representation of HR into the Community Land Model (CLM4.5) and found the new model improved predictions of water, energy, and system-scale carbon fluxes observed by eddy covariance at four seasonally dry yet ecologically diverse temperate and tropical AmeriFlux sites. Modeled plant productivity and microbial activities were differentially stimulated by upward HR, resulting at times in increased plant demand outstripping increased nutrient supply. Modeled plant productivity and microbial activities were diminished by downward HR. Overall, inclusion of HR tended to increase modeled annual ecosystem uptake of CO 2 (or reduce annual CO 2 release to the atmosphere). Moreover, engagement of CLM4.5's ground-truthed fire module indicated that though HR increased modeled fuel load at all four sites, upward HR also moistened surface soil and hydrated vegetation sufficiently to limit the modeled spread of dry season fire and concomitant very large CO 2 emissions to the atmosphere. Historically, fire has been a dominant ecological force in many seasonally dry ecosystems, and intensification of soil drought and altered precipitation regimes are expected for seasonally dry ecosystems in the future. HR may play an increasingly important role mitigating development of extreme soil water potential gradients and associated limitations on plant and soil microbial activities, and may inhibit the spread of fire in seasonally dry ecosystems. © 2018 John Wiley & Sons Ltd.

Integrating ecophysiology and forest landscape models to improve projections of drought effects under climate change.

PubMed

Gustafson, Eric J; De Bruijn, Arjan M G; Pangle, Robert E; Limousin, Jean-Marc; McDowell, Nate G; Pockman, William T; Sturtevant, Brian R; Muss, Jordan D; Kubiske, Mark E

2015-02-01

Fundamental drivers of ecosystem processes such as temperature and precipitation are rapidly changing and creating novel environmental conditions. Forest landscape models (FLM) are used by managers and policy-makers to make projections of future ecosystem dynamics under alternative management or policy options, but the links between the fundamental drivers and projected responses are weak and indirect, limiting their reliability for projecting the impacts of climate change. We developed and tested a relatively mechanistic method to simulate the effects of changing precipitation on species competition within the LANDIS-II FLM. Using data from a field precipitation manipulation experiment in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) ecosystem in New Mexico (USA), we calibrated our model to measurements from ambient control plots and tested predictions under the drought and irrigation treatments against empirical measurements. The model successfully predicted behavior of physiological variables under the treatments. Discrepancies between model output and empirical data occurred when the monthly time step of the model failed to capture the short-term dynamics of the ecosystem as recorded by instantaneous field measurements. We applied the model to heuristically assess the effect of alternative climate scenarios on the piñon-juniper ecosystem and found that warmer and drier climate reduced productivity and increased the risk of drought-induced mortality, especially for piñon. We concluded that the direct links between fundamental drivers and growth rates in our model hold great promise to improve our understanding of ecosystem processes under climate change and improve management decisions because of its greater reliance on first principles. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Full Waveform Modeling of Transient Electromagnetic Response Based on Temporal Interpolation and Convolution Method

NASA Astrophysics Data System (ADS)

Qi, Youzheng; Huang, Ling; Wu, Xin; Zhu, Wanhua; Fang, Guangyou; Yu, Gang

2017-07-01

Quantitative modeling of the transient electromagnetic (TEM) response requires consideration of the full transmitter waveform, i.e., not only the specific current waveform in a half cycle but also the bipolar repetition. In this paper, we present a novel temporal interpolation and convolution (TIC) method to facilitate the accurate TEM modeling. We first calculate the temporal basis response on a logarithmic scale using the fast digital-filter-based methods. Then, we introduce a function named hamlogsinc in the framework of discrete signal processing theory to reconstruct the basis function and to make the convolution with the positive half of the waveform. Finally, a superposition procedure is used to take account of the effect of previous bipolar waveforms. Comparisons with the established fast Fourier transform method demonstrate that our TIC method can get the same accuracy with a shorter computing time.

Modelling proteins’ hidden conformations to predict antibiotic resistance

PubMed Central

Hart, Kathryn M.; Ho, Chris M. W.; Dutta, Supratik; Gross, Michael L.; Bowman, Gregory R.

2016-01-01

TEM β-lactamase confers bacteria with resistance to many antibiotics and rapidly evolves activity against new drugs. However, functional changes are not easily explained by differences in crystal structures. We employ Markov state models to identify hidden conformations and explore their role in determining TEM’s specificity. We integrate these models with existing drug-design tools to create a new technique, called Boltzmann docking, which better predicts TEM specificity by accounting for conformational heterogeneity. Using our MSMs, we identify hidden states whose populations correlate with activity against cefotaxime. To experimentally detect our predicted hidden states, we use rapid mass spectrometric footprinting and confirm our models’ prediction that increased cefotaxime activity correlates with reduced Ω-loop flexibility. Finally, we design novel variants to stabilize the hidden cefotaximase states, and find their populations predict activity against cefotaxime in vitro and in vivo. Therefore, we expect this framework to have numerous applications in drug and protein design. PMID:27708258

Thermoelectric technique to precisely control hyperthermic exposures of human whole blood.

PubMed

DuBose, D A; Langevin, R C; Morehouse, D H

1996-12-01

The need in military research to avoid exposing humans to harsh environments and reduce animal use requires the development of in vitro models for the study of hyperthermic injury. A thermoelectric module (TEM) system was employed to heat human whole blood (HWB) in a manner similar to that experienced by heat-stroked rats. This system precisely and accurately replicated mild, moderate, and extreme heat-stress exposures. Temperature changes could be monitored without the introduction of a test sample thermistor, which reduced contamination problems. HWB with hematocrits of 45 or 50% had similar heating curves, indicating that the system compensated for differences in sample character. The unit's size permitted its containment within a standard carbon dioxide incubator to further control sample environment. These results indicate that the TEM system can precisely control temperature change in this heat stress in vitro model employing HWB. Information obtained from such a model could contribute to military preparedness.

Use of Combined Biogeochemical Model Approaches and Empirical Data to Assess Critical Loads of Nitrogen

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

Fenn, Mark E.; Driscoll, Charles; Zhou, Qingtao

2015-01-01

Empirical and dynamic biogeochemical modelling are complementary approaches for determining the critical load (CL) of atmospheric nitrogen (N) or other constituent deposition that an ecosystem can tolerate without causing ecological harm. The greatest benefits are obtained when these approaches are used in combination. Confounding environmental factors can complicate the determination of empirical CLs across depositional gradients, while the experimental application of N amendments for estimating the CL does not realistically mimic the effects of chronic atmospheric N deposition. Biogeochemical and vegetation simulation models can provide CL estimates and valuable ecosystem response information, allowing for past and future scenario testing withmore » various combinations of environmental factors, pollutants, pollutant control options, land management, and ecosystem response parameters. Even so, models are fundamentally gross simplifications of the real ecosystems they attempt to simulate. Empirical approaches are vital as a check on simulations and CL estimates, to parameterize models, and to elucidate mechanisms and responses under real world conditions. In this chapter, we provide examples of empirical and modelled N CL approaches in ecosystems from three regions of the United States: mixed conifer forest, desert scrub and pinyon- juniper woodland in California; alpine catchments in the Rocky Mountains; and lakes in the Adirondack region of New York state.« less

Natural variability of marine ecosystems inferred from a coupled climate to ecosystem simulation

NASA Astrophysics Data System (ADS)

Le Mézo, Priscilla; Lefort, Stelly; Séférian, Roland; Aumont, Olivier; Maury, Olivier; Murtugudde, Raghu; Bopp, Laurent

2016-01-01

This modeling study analyzes the simulated natural variability of pelagic ecosystems in the North Atlantic and North Pacific. Our model system includes a global Earth System Model (IPSL-CM5A-LR), the biogeochemical model PISCES and the ecosystem model APECOSM that simulates upper trophic level organisms using a size-based approach and three interactive pelagic communities (epipelagic, migratory and mesopelagic). Analyzing an idealized (e.g., no anthropogenic forcing) 300-yr long pre-industrial simulation, we find that low and high frequency variability is dominant for the large and small organisms, respectively. Our model shows that the size-range exhibiting the largest variability at a given frequency, defined as the resonant range, also depends on the community. At a given frequency, the resonant range of the epipelagic community includes larger organisms than that of the migratory community and similarly, the latter includes larger organisms than the resonant range of the mesopelagic community. This study shows that the simulated temporal variability of marine pelagic organisms' abundance is not only influenced by natural climate fluctuations but also by the structure of the pelagic community. As a consequence, the size- and community-dependent response of marine ecosystems to climate variability could impact the sustainability of fisheries in a warming world.

Machine-Thermal Coupling Stresses Analysis of the Fin-Type Structural Thermoelectric Generator

NASA Astrophysics Data System (ADS)

Zhang, Zheng; Yue, Hao; Chen, Dongbo; Qin, Delei; Chen, Zijian

2017-05-01

The design structure and heat-transfer mechanism of a thermoelectric generator (TEG) determine its body temperature state. Thermal stress and thermal deformation generated by the temperature variation directly affect the stress state of thermoelectric modules (TEMs). Therefore, the rated temperature and pressing force of TEMs are important parameters in TEG design. Here, the relationships between structural of a fin-type TEG (FTEG) and these parameters are studied by modeling and "machine-thermal" coupling simulation. An indirect calculation method is adopted in the coupling simulation. First, numerical heat transfer calculations of a three-dimensional FTEG model are conducted according to an orthogonal simulation table. The influences of structural parameters for heat transfer in the channel and outer fin temperature distribution are analyzed. The optimal structural parameters are obtained and used to simulate temperature field of the outer fins. Second, taking the thermal calculation results as the initial condition, the thermal-solid coupling calculation is adopted. The thermal stresses of outer fin, mechanical force of spring-angle pressing mechanism, and clamping force on a TEM are analyzed. The simulation results show that the heat transfer area of the inner fin and the physical parameters of the metal materials are the keys to determining the FTEG temperature field. The pressing mechanism's mechanical force can be reduced by reducing the outer fin angle. In addition, a corrugated cooling water pipe, which has cooling and spring functionality, is conducive to establishing an adaptable clamping force to avoid the TEMs being crushed by the thermal stresses in the body.

Insights into resource consumption, cross-feeding, system collapse, stability and biodiversity from an artificial ecosystem

PubMed Central

Sumpter, David

2017-01-01

Community ecosystems at very different levels of biological organization often have similar properties. Coexistence of multiple species, cross-feeding, biodiversity and fluctuating population dynamics are just a few of the properties that arise in a range of ecological settings. Here we develop a bottom-up model of consumer–resource interactions, in the form of an artificial ecosystem ‘number soup’, which reflects basic properties of many bacterial and other community ecologies. We demonstrate four key properties of the number soup model: (i) communities self-organize so that all available resources are fully consumed; (ii) reciprocal cross-feeding is a common evolutionary outcome, which evolves in a number of stages, and many transitional species are involved; (iii) the evolved ecosystems are often ‘robust yet fragile’, with keystone species required to prevent the whole system from collapsing; (iv) non-equilibrium dynamics and chaotic patterns are general properties, readily generating rich biodiversity. These properties have been observed in empirical ecosystems, ranging from bacteria to rainforests. Establishing similar properties in an evolutionary model as simple as the number soup suggests that these four properties are ubiquitous features of all community ecosystems, and raises questions about how we interpret ecosystem structure in the context of natural selection. PMID:28100827

Atmospheric redistribution of reactive nitrogen and phosphorus by wildfires and implications for global carbon cycling

NASA Astrophysics Data System (ADS)

Randerson, J. T.; Xu, L.; Wiggins, E. B.; Chen, Y.; Riley, W. J.; Mekonnen, Z. A.; Pellegrini, A.; Mahowald, N. M.

2017-12-01

Fires are an important process regulating the redistribution of nutrients within terrestrial ecosystems. Frequently burning ecosystems such as savannas are a net source of N and P to the atmosphere each year, with atmospheric transport and dry and wet deposition increasing nutrient availability in downwind ecosystems and over the open ocean. Transport of N and P aerosols from savanna fires within the Hadley circulation contributes to nutrient deposition over tropical forests, yielding an important cross-biome nutrient transfer. Pyrodenitrification of reactive N increases with fire temperature and modified combustion efficiency, generating a global net biospheric loss of approximately 14 Tg N per year. Here we analyze atmospheric N and P redistribution using the Global Fire Emissions Database version 4s and the Accelerated Climate Modeling for Energy earth system model. We synthesize literature estimates of N and P concentrations in fire-emitted aerosols and ecosystem mass balance measurements to help constrain model estimates of these biosphere-atmosphere fluxes. In our analysis, we estimate the fraction of terrestrial net primary production (NPP) that is sustained by fire-emitted P and reactive N from upwind ecosystems. We then evaluate how recent global declines in burned area in savanna and grassland ecosystems may be changing nutrient availability in downwind ecosystems.

Modeling dynamic interactions and coherence between marine zooplankton and fishes linked to environmental variability

NASA Astrophysics Data System (ADS)

Liu, Hui; Fogarty, Michael J.; Hare, Jonathan A.; Hsieh, Chih-hao; Glaser, Sarah M.; Ye, Hao; Deyle, Ethan; Sugihara, George

2014-03-01

The dynamics of marine fishes are closely related to lower trophic levels and the environment. Quantitatively understanding ecosystem dynamics linking environmental variability and prey resources to exploited fishes is crucial for ecosystem-based management of marine living resources. However, standard statistical models typically grounded in the concept of linear system may fail to capture the complexity of ecological processes. We have attempted to model ecosystem dynamics using a flexible, nonparametric class of nonlinear forecasting models. We analyzed annual time series of four environmental indices, 22 marine copepod taxa, and four ecologically and commercially important fish species during 1977 to 2009 on Georges Bank, a highly productive and intensively studied area of the northeast U.S. continental shelf ecosystem. We examined the underlying dynamic features of environmental indices and copepods, quantified the dynamic interactions and coherence with fishes, and explored the potential control mechanisms of ecosystem dynamics from a nonlinear perspective. We found: (1) the dynamics of marine copepods and environmental indices exhibiting clear nonlinearity; (2) little evidence of complex dynamics across taxonomic levels of copepods; (3) strong dynamic interactions and coherence between copepods and fishes; and (4) the bottom-up forcing of fishes and top-down control of copepods coexisting as target trophic levels vary. These findings highlight the nonlinear interactions among ecosystem components and the importance of marine zooplankton to fish populations which point to two forcing mechanisms likely interactively regulating the ecosystem dynamics on Georges Bank under a changing environment.

Carbon Cycle Model Linkage Project (CCMLP): Evaluating Biogeochemical Process Models with Atmospheric Measurements and Field Experiments

NASA Astrophysics Data System (ADS)

Heimann, M.; Prentice, I. C.; Foley, J.; Hickler, T.; Kicklighter, D. W.; McGuire, A. D.; Melillo, J. M.; Ramankutty, N.; Sitch, S.

2001-12-01

Models of biophysical and biogeochemical proceses are being used -either offline or in coupled climate-carbon cycle (C4) models-to assess climate- and CO2-induced feedbacks on atmospheric CO2. Observations of atmospheric CO2 concentration, and supplementary tracers including O2 concentrations and isotopes, offer unique opportunities to evaluate the large-scale behaviour of models. Global patterns, temporal trends, and interannual variability of the atmospheric CO2 concentration and its seasonal cycle provide crucial benchmarks for simulations of regionally-integrated net ecosystem exchange; flux measurements by eddy correlation allow a far more demanding model test at the ecosystem scale than conventional indicators, such as measurements of annual net primary production; and large-scale manipulations, such as the Duke Forest Free Air Carbon Enrichment (FACE) experiment, give a standard to evaluate modelled phenomena such as ecosystem-level CO2 fertilization. Model runs including historical changes of CO2, climate and land use allow comparison with regional-scale monthly CO2 balances as inferred from atmospheric measurements. Such comparisons are providing grounds for some confidence in current models, while pointing to processes that may still be inadequately treated. Current plans focus on (1) continued benchmarking of land process models against flux measurements across ecosystems and experimental findings on the ecosystem-level effects of enhanced CO2, reactive N inputs and temperature; (2) improved representation of land use, forest management and crop metabolism in models; and (3) a strategy for the evaluation of C4 models in a historical observational context.

Global morphological analysis of marine viruses shows minimal regional variation and dominance of non-tailed viruses.

PubMed

Brum, Jennifer R; Schenck, Ryan O; Sullivan, Matthew B

2013-09-01

Viruses influence oceanic ecosystems by causing mortality of microorganisms, altering nutrient and organic matter flux via lysis and auxiliary metabolic gene expression and changing the trajectory of microbial evolution through horizontal gene transfer. Limited host range and differing genetic potential of individual virus types mean that investigations into the types of viruses that exist in the ocean and their spatial distribution throughout the world's oceans are critical to understanding the global impacts of marine viruses. Here we evaluate viral morphological characteristics (morphotype, capsid diameter and tail length) using a quantitative transmission electron microscopy (qTEM) method across six of the world's oceans and seas sampled through the Tara Oceans Expedition. Extensive experimental validation of the qTEM method shows that neither sample preservation nor preparation significantly alters natural viral morphological characteristics. The global sampling analysis demonstrated that morphological characteristics did not vary consistently with depth (surface versus deep chlorophyll maximum waters) or oceanic region. Instead, temperature, salinity and oxygen concentration, but not chlorophyll a concentration, were more explanatory in evaluating differences in viral assemblage morphological characteristics. Surprisingly, given that the majority of cultivated bacterial viruses are tailed, non-tailed viruses appear to numerically dominate the upper oceans as they comprised 51-92% of the viral particles observed. Together, these results document global marine viral morphological characteristics, show that their minimal variability is more explained by environmental conditions than geography and suggest that non-tailed viruses might represent the most ecologically important targets for future research.

A conceptual framework for the study of human ecosystems in urban areas

Treesearch

Steward T.A. Pickett; William R. Burch; Shawn E. Dalton; Timothy W. Foresman; J. Morgan Grove; Rowan Rowntree

1997-01-01

The need for integrated concepts, capable of satisfying natural and social scientists and supporting integrated research, motivates a conceptual framework for understanding the role of humans in ecosystems. The question is how to add humans to the ecological models used to understand urban ecosystems. The ecosystem concept can serve as the basis, but specific social...

Joint Inversion of Multi-type and Time-lapse Airborne Electromagnetic Data Sets for Tempo-spatial Variation of Groundwater Salinity

NASA Astrophysics Data System (ADS)

Yang, D.; Oldenburg, D.

2016-12-01

The salinization of the floodplains of Lower Murray River in South Australia has caused negative consequences to the local ecosystem. As part of the Living Murray Initiative, the Clark's Floodplain at Bookpurnong was chosen to examine the effectiveness of different intervention methods from 2005 to 2008. Because of the link between groundwater salinity and electric conductivity, electromagnetic (EM) methods have been an integrated part of the project to test it as a cost-effective tool for monitoring. In this paper, we analyze two airborne EM surveys that assess the salinization at the regional scale: the SkyTEM in 2006 and the RESOLVE in 2008. Conventional interpretation often inverts those data sets separately using the 1D layered earth modeling, which often produces inconsistent images if different surveys are carried out at different times. Here we propose a new approach that considers the coherence in time and across systems. We allow each data set to iteratively construct its own model with guidance from a common reference model that is updated in a democratic voting procedure after every iteration. There are two possible outcomes. If the data sets are intrinsically compatible, the individual models will converge to essentially the same model, like in the regular unimodal joint inversion. If there are survey-specific errors or a change of ground truth, the inversion can still fit the data but leaves discrepancy in the models. By applying this approach to the two data sets at Bookpurnong, we identify an area of increased conductivity at the midstream section of the river that can only be explained by a temporal variation of salinity, a plausible evidence of escalated saline water intrusion due to irrigation on the nearby riverbank. This study illustrates that multi-type time-lapse EM, in conjunction with advanced inversion techniques, can achieve superior temporal resolution for the purpose of groundwater evaluation and management.

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

Ito, Akihiko; Inatomi, Motoko; Huntzinger, Deborah N.

The seasonal-cycle amplitude (SCA) of the atmosphere–ecosystem carbon dioxide (CO 2) exchange rate is a useful metric of the responsiveness of the terrestrial biosphere to environmental variations. It is unclear, however, what underlying mechanisms are responsible for the observed increasing trend of SCA in atmospheric CO 2 concentration. Using output data from the Multi-scale Terrestrial Model Intercomparison Project (MsTMIP), we investigated how well the SCA of atmosphere–ecosystem CO 2 exchange was simulated with 15 contemporary terrestrial ecosystem models during the period 1901–2010. Also, we made attempt to evaluate the contributions of potential mechanisms such as atmospheric CO 2, climate, land-use,more » and nitrogen deposition, through factorial experiments using different combinations of forcing data. Under contemporary conditions, the simulated global-scale SCA of the cumulative net ecosystem carbon flux of most models was comparable in magnitude with the SCA of atmospheric CO 2 concentrations. Results from factorial simulation experiments showed that elevated atmospheric CO 2 exerted a strong influence on the seasonality amplification. When the model considered not only climate change but also land-use and atmospheric CO 2 changes, the majority of the models showed amplification trends of the SCAs of photosynthesis, respiration, and net ecosystem production (+0.19 % to +0.50 % yr -1). In the case of land-use change, it was difficult to separate the contribution of agricultural management to SCA because of inadequacies in both the data and models. The simulated amplification of SCA was approximately consistent with the observational evidence of the SCA in atmospheric CO 2 concentrations. Large inter-model differences remained, however, in the simulated global tendencies and spatial patterns of CO 2 exchanges. Further studies are required to identify a consistent explanation for the simulated and observed amplification trends, including their underlying mechanisms. Nevertheless, this study implied that monitoring of ecosystem seasonality would provide useful insights concerning ecosystem dynamics.« less

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

Ito, Akihiko; Inatomi, Motoko; Huntzinger, Deborah N.

The seasonal-cycle amplitude (SCA) of the atmosphere–ecosystem carbon dioxide (CO 2) exchange rate is a useful metric of the responsiveness of the terrestrial biosphere to environmental variations. It is unclear, however, what underlying mechanisms are responsible for the observed increasing trend of SCA in atmospheric CO 2 concentration. Using output data from the Multi-scale Terrestrial Model Intercomparison Project (MsTMIP), we investigated how well the SCA of atmosphere–ecosystem CO 2 exchange was simulated with 15 contemporary terrestrial ecosystem models during the period 1901–2010. Also, we made attempt to evaluate the contributions of potential mechanisms such as atmospheric CO 2, climate, land-use,more » and nitrogen deposition, through factorial experiments using different combinations of forcing data. Under contemporary conditions, the simulated global-scale SCA of the cumulative net ecosystem carbon flux of most models was comparable in magnitude with the SCA of atmospheric CO 2 concentrations. Results from factorial simulation experiments showed that elevated atmospheric CO 2 exerted a strong influence on the seasonality amplification. When the model considered not only climate change but also land-use and atmospheric CO 2 changes, the majority of the models showed amplification trends of the SCAs of photosynthesis, respiration, and net ecosystem production (+0.19 % to +0.50 % yr –1). In the case of land-use change, it was difficult to separate the contribution of agricultural management to SCA because of inadequacies in both the data and models. The simulated amplification of SCA was approximately consistent with the observational evidence of the SCA in atmospheric CO 2 concentrations. Large inter-model differences remained, however, in the simulated global tendencies and spatial patterns of CO 2 exchanges. Further studies are required to identify a consistent explanation for the simulated and observed amplification trends, including their underlying mechanisms. Furthermore, this study implied that monitoring of ecosystem seasonality would provide useful insights concerning ecosystem dynamics.« less

Nutrient supply and mercury dynamics in marine ecosystems: A conceptual model

PubMed Central

Chen, Celia Y.; Hammerschmidt, Chad R.; Mason, Robert P.; Gilmour, Cynthia C.; Sunderland, Elsie M.; Greenfield, Ben K.; Buckman, Kate L.; Lamborg, Carl H.

2013-01-01

There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine ecosystems. One of the challenges in assessing these effects is that the cycling and trophic transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change the transport, transformations and fate of Hg, including increases in fixation of organic carbon and deposition to sediments, decreases in the redox status of sediments and changes in fish habitat. In this paper we present a conceptual model which suggests that increases in loading of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and trophic transfer. This conceptual model is most applicable to coastal waters, but may also be relevant to the pelagic ocean. We present information from case studies that both support and challenge this conceptual model, including marine observations across a nutrient gradient; results of a nutrient-trophic transfer Hg model for pelagic and coastal ecosystems; observations of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. Unfortunately none of the case studies is comprehensive; each only addresses a portion of the conceptual model and has limitations. Nevertheless, our conceptual model has important management implications. Many estuaries near developed areas are impaired due to elevated nutrient inputs. Widespread efforts are underway to control N loading and restore coastal ecosystem function. An unintended consequence of nutrient control measures could be to exacerbate problems associated with Hg contamination. Additional focused research and monitoring are needed to critically examine the link between nutrient supply and Hg contamination of marine waters. PMID:22749872

Modeling soil moisture memory in savanna ecosystems

NASA Astrophysics Data System (ADS)

Gou, S.; Miller, G. R.

2011-12-01

Antecedent soil conditions create an ecosystem's "memory" of past rainfall events. Such soil moisture memory effects may be observed over a range of timescales, from daily to yearly, and lead to feedbacks between hydrological and ecosystem processes. In this study, we modeled the soil moisture memory effect on savanna ecosystems in California, Arizona, and Africa, using a system dynamics model created to simulate the ecohydrological processes at the plot-scale. The model was carefully calibrated using soil moisture and evapotranspiration data collected at three study sites. The model was then used to simulate scenarios with various initial soil moisture conditions and antecedent precipitation regimes, in order to study the soil moisture memory effects on the evapotranspiration of understory and overstory species. Based on the model results, soil texture and antecedent precipitation regime impact the redistribution of water within soil layers, potentially causing deeper soil layers to influence the ecosystem for a longer time. Of all the study areas modeled, soil moisture memory of California savanna ecosystem site is replenished and dries out most rapidly. Thus soil moisture memory could not maintain the high rate evapotranspiration for more than a few days without incoming rainfall event. On the contrary, soil moisture memory of Arizona savanna ecosystem site lasts the longest time. The plants with different root depths respond to different memory effects; shallow-rooted species mainly respond to the soil moisture memory in the shallow soil. The growing season of grass is largely depended on the soil moisture memory of the top 25cm soil layer. Grass transpiration is sensitive to the antecedent precipitation events within daily to weekly timescale. Deep-rooted plants have different responses since these species can access to the deeper soil moisture memory with longer time duration Soil moisture memory does not have obvious impacts on the phenology of woody plants, as these can maintain transpiration for a longer time even through the top soil layer dries out.

Trophic flow structure of a neotropical estuary in northeastern Brazil and the comparison of ecosystem model indicators of estuaries

NASA Astrophysics Data System (ADS)

Lira, Alex; Angelini, Ronaldo; Le Loc'h, François; Ménard, Frédéric; Lacerda, Carlos; Frédou, Thierry; Lucena Frédou, Flávia

2018-06-01

We developed an Ecopath model for the Estuary of Sirinhaém River (SIR), a small-sized system surrounded by mangroves, subject to high impact, mainly by the sugar cane and other farming industries in order to describe the food web structure and trophic interactions. In addition, we compared our findings with those of 20 available Ecopath estuarine models for tropical, subtropical and temperate regions, aiming to synthesize the knowledge on trophic dynamics and provide a comprehensive analysis of the structures and functioning of estuaries. Our model consisted of 25 compartments and its indicators were within the expected range for estuarine areas around the world. The average trophic transfer efficiency for the entire system was 11.8%, similar to the theoretical value of 10%. The Keystone Index and MTI (Mixed Trophic Impact) analysis indicated that the snook (Centropomus undecimalis and Centropomus parallelus) and jack (Caranx latus and Caranx hippos) are considered as key resources in the system, revealing their high impact in the food web. Both groups have a high ecological and commercial relevance, despite the unregulated fisheries. As result of the comparison of ecosystem model indicators in estuaries, differences in the ecosystem structure from the low latitude zones (tropical estuaries) to the high latitude zones (temperate system) were noticed. The structure of temperate and sub-tropical estuaries is based on high flows of detritus and export, while tropical systems have high biomass, respiration and consumption rates. Higher values of System Omnivory Index (SOI) and Overhead (SO) were observed in the tropical and subtropical estuaries, denoting a more complex food chain. Globally, none of the estuarine models were classified as fully mature ecosystems, although the tropical ecosystems were considered more mature than the subtropical and temperate ecosystems. This study is an important contribution to the trophic modeling of estuaries, which may also help the knowledge of the role of key ecosystem processes in SIR.

Assessing The Ecosystem Service Freshwater Production From An Integrated Water Resources Management Perspective. Case Study: The Tormes Water Resources System (Spain)

NASA Astrophysics Data System (ADS)

Momblanch, Andrea; Paredes-Arquiola, Javier; Andreu, Joaquín; Solera, Abel

2014-05-01

The Ecosystem Services are defined as the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfil human life. A strongly related concept is the Integrated Water Resources Management. It is a process which promotes the coordinated development and management of water, land and related resources in order to maximise the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems. From these definitions, it is clear that in order to cover so many water management and ecosystems related aspects the use of integrative models is increasingly necessary. In this study, we propose to link a hydrologic model and a water allocation model in order to assess the Freshwater Production as an Ecosystem Service in anthropised river basins. First, the hydrological model allows determining the volume of water generated by each sub-catchment; that is, the biophysical quantification of the service. This result shows the relevance of each sub-catchment as a source of freshwater and how this could change if the land uses are modified. On the other hand, the water management model allocates the available water resources among the different water uses. Then, it is possible to provide an economic value to the water resources through the use of demand curves, or other economic concepts. With this second model, we are able to obtain the economical quantification of the Ecosystem Service. Besides, the influence of water management and infrastructures on the service provision can be analysed. The methodology is applied to the Tormes Water Resources System, in Spain. The software used are EVALHID and SIMGES, for hydrological and management aspects, respectively. Both models are included in the Decision Support System Shell AQUATOOL for water resources planning and management. A scenario approach is presented to illustrate the potential of the methodology, including the current state and some intervention scenarios.