Project Number: 3098-11220-008-00-D
Project Type: In-House Appropriated
Start Date: Jan 4, 2016
End Date: Aug 1, 2018
Objective 1: Evaluate the long-term effects of atmospheric CO2 enrichment from pre-industrial to mid-21st century concentrations on carbon cycling, soil nutrient pools, and soil microbial communities in native grassland and switchgrass. Objective 2: Determine the contributions of abiotic, and biotic factors including precipitation variability, frequency/magnitude of water limitation, and exotic species on plant productivity and community composition, biogeochemical cycling, and soil microbial communities of native grassland and switchgrass, and incorporate process-level understanding into the ALMANAC simulation model. Objective 3: Evaluate economic and environmental consequences of alternative cropping and grazing systems management practices.
Expose vegetated monoliths of three soil types to a continuous gradient in atmospheric carbon dioxide ranging from low levels of the pre-industrial period to elevated concentrations predicted within the century. We will measure plant production, and changes in the relative abundances of tallgrass prairie vegetation growing on each soil type. Changes in soil organic carbon content, soil nutrient pools, and soil microbial community composition will be measured in each soil as a function of carbon dioxide treatment. We also will compare responses of aboveground net primary productivity and the relative abundances of tallgrass prairie vegetation in field-scale plantings of switchgrass monocultures and mixtures of tallgrass prairie species to inter-annual variability in precipitation on upland and lowland soils. The Agricultural Land Management Alternative with Numerical Assessment Criteria model will be validated with data from the carbon dioxide experiment and field-scale plots of switchgrass and prairie species to simulate effects of changes in both atmospheric carbon dioxide concentration and precipitation patterns on grassland carbon cycling. To evaluate short-term carbon mineralization and water extractable organic C and N as a predictor of potential nitrogen mineralization, soil samples collected from across the country, including samples from the NAPT soil database, will be analyzed using the ARS-developed Solvita respiration method and other currently used mineralization tests. Compare soil health and water quality differences in fields managed with traditional techniques versus enhanced techniques focused on optimal fertilizer rates and cover crop rotations.