Grazing Impacts on Soil Organic Carbon Chemistry and Microbial Community Structure and Functions in a Mixed-Grass Ecosystem
EMSL Project ID
60881
Abstract
Grasslands cover approximately 40% of the Earth's land surface and represent about 70% of the agricultural area. They contain about 10% of terrestrial biomass and contribute about 20–30% of the global soil organic carbon (SOC). Grasslands have some potential to sequester atmospheric CO2 as stable soil carbon (C) and hence could contribute to mitigation of climate change. However, the accumulation and storage of C in grasslands is strongly influenced by livestock grazing. Under dry climate conditions, grazing tended to increase SOC stocks but generally decreased the stocks under moist climate conditions. High grazing intensity increased SOC for C4-dominated grassland compared to C3 dominated and C3-C4 mixed grasslands, and increased total nitrogen and soil bulk density as well. However, the micro- and molecular-scale processes underpinning these changes have not been characterized, limiting our understanding of the grazing impacts on ecosystem processes and services. Thus, the goal of the proposed project is to characterize the molecular composition of soil organic matter (water extractable), the structure and composition of soil microbial communities, and the soil micropore network structure under grazing, in addition to characterizing those basic soil properties.
This study is part of an ongoing field experiment undertaken at the USDA-ARS High Plains Grasslands Research Station near Cheyenne, WY, to investigate the long-term influence of different grazing rates on a northern mixed-grass prairie ecosystem under a cool dry climate. Stocking rate treatments were established in 1982 with two replicate blocks (pastures) for each of the three stocking rates. The three treatments are ungrazed exclosures, and pastures grazed at a light and heavy stocking rates. Two articles have resulted from the 1993 and 2003 soil sampling events (Ingram et al., Soil Sci. Soc. Am. J., 2008; Schuman et al., Ecol. Appl., 1999), and a third from the 2013 sampling is drafted. Grazing increased SOC and N stocks in surface soils due to plant community changes from a C3 to a C4 plant dominated community. The SOC was partially lost due to a drought period (2000 – 2002) occurring prior to the 2003 spring sampling. We propose to collect soils in May 2023, the 40th year since the sites were established. A 50-m permanent transect has been established in each block on nearly level sites. Soils will be sampled at 0, 10, 20, and 40 m along each 50-m transect, generating 24 samples totally.
MONet is a great platform for the proposed project. It houses suitable instruments for the proposed analyses, and its mission is in line with this long-term USDA agroecosystem research.
Project Details
Project type
MONet
Start Date
2023-05-05
End Date
N/A
Status
Active
Released Data Link
Team
Principal Investigator
Team Members