Consequences of Long-Term Agriculture and Grassland Restoration in the Tallgrass Prairie Region of North America

Tallgrass prairie soils are thought to have historically contained some of the largest soil carbon stocks in North America. In part because of these high fertility soils, more than 99% of this region has been converted to row-crop agriculture over the past 150 years. Traditional agricultural techniques are thought to reduce soil C pools by 30-50%, leading to the hypothesis that significant soil C sequestration will occur if agricultural practices are stopped and grassland communities are restored. We tested this hypothesis at 5 locations (Texas, Kansas, 2 sites in Iowa, and Minnesota). We also assessed the effects of long-term agriculture and grassland restoration on soil microbial communities. At all locations, native, uncultivated tallgrass prairie had significantly more soil C than all other land use types; however, we found that neither soil C nor microbial communities responded to grassland restoration in a consistent manner. Some sites gained soil C over time with grassland restoration, and the microbial communities converged to those of adjacent native prairie, consistent with the goals of restoration. However, others had no appreciable increase or clearly identifiable change in the microbial community. Understanding the effects of land use change in this region may be more difficult than has been previously realized.

Metagenomic microbial work illustrates that Verrucomicrobia are important in native tallgrass prairie soils, perhaps due to high amounts of relatively recalcitrant carbon.  Understanding the effects of land use change and restoration on soil microbes and ecosystem function in this region may be more difficult than has been previously realized.

 

Collaborators:  Noah Fierer (Univ. of Colorado – Boulder); Rob Jackson (Stanford University)
 
Associated Manuscripts:
Sanderman, J., T. Hangl, and G.J. Fiske. 2017. Soil carbon debt of 12,000 years of human land use. PNAS 114: 9575-9580.

This paper used the soil C data collected in this project to validate its model projections.

Fierer, N., J. Ladau, J.C. Clemente, J.W. Leff, S.M. Owens, K.S. Pollard, R. Knight, J.A. Gilbert, and R.L. McCulley.  2013. Reconstructing the microbial diversity and function of pre-agricultural tallgrass prairie soils in the United States. Science 342:621-624.
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