Progress 01/01/05 to 12/31/09
Outputs
Progress Report Objectives (from AD-416) Document carbon dioxide source/sink relationships on grasslands representative of the various North American climatic regimes, the impacts of land use decisions and management practices on major carbon pools and fluxes, and the role of rangelands in the global carbon balance, as influenced by land use decisions and rangeland management practices. Approach (from AD-416) Rate and direction of carbon dioxide fluxes will be continuously monitored above grasslands and shrublands on sites at several ARS locations in the central and western U.S., using pop-on chambers and Bowen ratio/energy balance equipment fitted with infrared gas analyses. Within locations, comparisons will be made on grassland sites with and without shrubs, on grazed and ungrazed sites, or on sites dominated by native or introduced forage species. Carbon dioxide flux measurements will be interpreted in light of concomitant analyses of soil and vegetation carbon dynamics, meteorological monitoring, and changes in the surface energy balance. The overall objective of this project was to determine the net carbon balance of grasslands and other rangelands characteristic of major climatic regions in the western U.S. Net carbon balance was determined by measuring rates of carbon dioxide (CO2) uptake and loss on each rangeland. Rangelands studied include Great Plains grasslands, desert shrubland, desert grasslands, and sagebrush steppe. The rate and direction of CO2 fluxes on these ecosystems was measured continuously during several growing seasons by a consortium of ARS scientists and cooperators from locations in the western U.S. (Burns, OR; Dubois, ID; Ft. Collins, CO; Cheyenne, WY; Las Cruces, NM; Mandan, ND; Miles City, MT; Temple, TX; Tucson, AZ; and El Reno and Woodward, OK). Carbon dioxide fluxes and an array of associated environmental variables were measured for as many as 11 years at each site using Bowen ratio/energy balance equipment fitted with infrared gas analyzers. Cooperators with Texas A&M University in Temple provided quality control of flux data from each site and summarized, shared, and archived quality-controlled data from the network, among other duties. The carbon balance of rangelands varied among years both because environmental factors varied and because the response of carbon balance to a given change in the environment differed among years. Most of the variation in rangeland carbon balance resulted from inter-annual differences in the response of CO2 fluxes to a given change in light, temperature, and other environmental factors. Flux-environment relationships likely differ among years because of inter-annual changes in biological processes that regulate CO2 uptake and release. A simple physiological model was used to calculate photosynthetic and respiratory components of net CO2 exchange. We then determined the contributions of photosynthetic and respiratory components of CO2 fluxes to environmentally caused variation in net CO2 exchange. For most rangelands, relationships between CO2 exchange and the environment differed among years because relationships of photosynthetic parameters to environmental drivers differed among years. Differences in photosynthetic responses were not explained by differences in the amount of leaf area in the plant canopy alone, implying that differences in photosynthesis resulted from variation in leaf-level rates of CO2 uptake. Results indicate that we must account for both environmental variation and shifts in biological processes to determine the carbon balance of rangeland ecosystems. Project participants met monthly to discuss progress.
Impacts
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) Document carbon dioxide source/sink relationships on grasslands representative of the various North American climatic regimes, the impacts of land use decisions and management practices on major carbon pools and fluxes, and the role of rangelands in the global carbon balance, as influenced by land use decisions and rangeland management practices. Approach (from AD-416) Rate and direction of carbon dioxide fluxes will be continuously monitored above grasslands and shrublands on sites at several ARS locations in the central and western U.S., using pop-on chambers and Bowen ratio/energy balance equipment fitted with infrared gas analyses. Within locations, comparisons will be made on grassland sites with and without shrubs, on grazed and ungrazed sites, or on sites dominated by native or introduced forage species. Carbon dioxide flux measurements will be interpreted in light of concomitant analyses of soil and vegetation carbon dynamics, meteorological monitoring, and changes in the surface energy balance. Significant Activities that Support Special Target Populations A consortium of ARS scientists and cooperators from western U.S. sites (Burns, OR; Dubois, ID; Ft. Collins, CO; Cheyenne, WY; Las Cruces, NM; Mandan, ND; Miles City, MT; Temple, TX; Tucson, AZ; and El Reno and Woodward, OK) measured carbon dioxide (CO2) fluxes over a variety of rangeland types using identical instrumentation. During the past year, university cooperators in Temple assisted with statistical analyses of flux data collected at each location. Collaborators and the ARS scientist responsible for this project are co-located at a laboratory in Temple, TX. Project participants meet monthly to discuss progress.
Impacts
(N/A)
Publications
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) Document carbon dioxide source/sink relationships on grasslands representative of the various North American climatic regimes, the impacts of land use decisions and management practices on major carbon pools and fluxes, and the role of rangelands in the global carbon balance, as influenced by land use decisions and rangeland management practices. Approach (from AD-416) Rate and direction of carbon dioxide fluxes will be continuously monitored above grasslands and shrublands on sites at several ARS locations in the central and western U.S., using pop-on chambers and Bowen ratio/energy balance equipment fitted with infrared gas analyses. Within locations, comparisons will be made on grassland sites with and without shrubs, on grazed and ungrazed sites, or on sites dominated by native or introduced forage species. Carbon dioxide flux measurements will be interpreted in light of concomitant analyses of soil and vegetation carbon dynamics, meteorological monitoring, and changes in the surface energy balance. Significant Activities that Support Special Target Populations A consortium of ARS scientists and cooperators from western U.S. sites (Burns, OR; Dubois, ID; Ft. Collins, CO; Cheyenne, WY; Las Cruces, NM; Mandan, ND; Miles City, MT; Temple, TX; Tucson, AZ; and El Reno and Woodward, OK) has for 9 or more years been measuring carbon dioxide (CO2) fluxes over a variety of rangeland types using identical instrumentation. New sites, using eddy covariance (EC) instrumentation, were added at State College, PA, and El Reno, OK, during the last 5 years. During the past year, TAMU-TAES cooperators in Temple conducted quality control of flux data and summarized, shared, and archived quality-controlled data. Cooperators also assisted with statistical analyses of flux data collected at each location. TAMU-TAES collaborators and the ARS scientist responsible for this project are co-located at a laboratory in Temple, TX. Project participants meet monthly to discuss progress.
Impacts
(N/A)
Publications
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) Document carbon dioxide source/sink relationships on grasslands representative of the various North American climatic regimes, the impacts of land use decisions and management practices on major carbon pools and fluxes, and the role of rangelands in the global carbon balance, as influenced by land use decisions and rangeland management practices. Approach (from AD-416) Rate and direction of carbon dioxide fluxes will be continuously monitored above grasslands and shrublands on sites at several ARS locations in the central and western U.S., using pop-on chambers and Bowen ratio/energy balance equipment fitted with infrared gas analyses. Within locations, comparisons will be made on grassland sites with and without shrubs, on grazed and ungrazed sites, or on sites dominated by native or introduced forage species. Carbon dioxide flux measurements will be interpreted in light of concomitant analyses of soil and vegetation carbon dynamics, meteorological monitoring, and changes in the surface energy balance. Significant Activities that Support Special Target Populations This report serves to document research conducted under a specific cooperative agreement between ARS and the Texas A&M University/Agricultural Experiment Station (TAES) at Temple, TX. Additional details of research can be found in the report from the parent project 6206-11220-004-00D Global Change and the Carbon Balance on Western Rangelands. A consortium of ARS scientists and cooperators from western U.S. sites (Burns, OR; Dubois, ID; Ft. Collins, CO; Cheyenne, WY; Las Cruces, NM; Mandan, ND; Miles City, MT; Temple, TX; Tucson, AZ; and El Reno and Woodward, OK) has for 8 or more years been measuring carbon dioxide (CO2) fluxes over a variety of rangeland types using identical instrumentation. New sites, using eddy covariance (EC) instrumentation, were added at State College, PA, and El Reno, OK, during the last 5 years. During the past year, TAES cooperators in Temple conducted quality control of flux data and summarized, shared, and archived quality- controlled data. Cooperators also assisted with statistical analyses of flux data collected at each location. TAES collaborators and the ARS scientist responsible for this project are co-located at a laboratory in Temple, TX. Project participants meet weekly to discuss progress.
Impacts
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Publications
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 4d Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and the Texas A&M University, Texas Agricultural Experiment Station (TAES) at Temple, TX, that was initiated during the last year. Additional details of research can be found in the report from the parent project 6206-11220-004-00D Global Change and the Carbon Balance on Western Rangelands. A consortium of ARS scientists and cooperators from western U.S. sites (Burns, OR; Dubois, ID; Ft. Collins, CO; Cheyenne, WY; Las Cruces, NM; Mandan, ND; Miles City, MT; Temple, TX; Tucson, AZ; and El Reno and Woodward, OK) has for 8 or more years been measuring carbon dioxide (CO2) fluxes over a variety of rangeland types using identical instrumentation. New sites, using eddy covariance (EC) instrumentation, were added at State College, PA, and El Reno, OK, during the last 4 years. During the last year, TAMU/TAES cooperators in Temple
continued to conduct quality control of flux data; summarize, share, and archive quality-controlled network data; troubleshoot (via email and telephone) problems with the operation of instrumentation for measuring fluxes and environmental data; loan instrumentation to other locations; and coordinate yearly calibration of net radiometers. Cooperators also were responsible for analyzing and providing continuous, real time quality control of flux data collected in Las Cruces, NM.
Impacts
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Progress 10/01/04 to 09/30/05
Outputs
4d Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and Texas A&M University, Texas Agricultural Experiment Station (TAES) at Temple, TX, that was initiated during the last year. Additional details of research can be found in the report from the parent project 6206-11220-004-00D Global Change and the Carbon Balance on Western Rangelands. A consortium of ARS scientists and cooperators from western U.S. sites (Burns, OR; Dubois, ID; Ft. Collins, CO; Cheyenne, WY; Las Cruces, NM; Mandan, ND; Miles City, MT; Temple, TX; Tucson, AZ; and El Reno and Woodward, OK) has for 7 or more years been measuring carbon dioxide (CO2) fluxes over a variety of rangeland types using identical instrumentation. New sites, using eddy covariance (EC) instrumentation, were added at State College, Pennsylvania, and El Reno, Oklahoma, during the last 3 years. During the last year, TAES cooperators in Temple continued to
conduct quality control of flux data; summarize, share, and archive quality-controlled network data; troubleshoot (via email and telephone) problems with the operation of instrumentation for measuring fluxes and environmental data; loan instrumentation to other locations; coordinate yearly calibration of net radiometers; and assist in operation of eddy covariance instrumentation at El Reno, Oklahoma, and University Park, Pennsylvania. Cooperators also were responsible for analyzing and providing continuous, real time quality control of flux data collected in Las Cruces, NM.
Impacts
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