Analysis of Factors Controlling Soil Organic Matter Levels in Great Plains Grasslands

Summary

This modelling study examined the principal controls on soil organic matter in Great Plains grasslands by simulating steady-state C and N levels across 24 locations. The analysis identified climate (temperature and moisture), soil texture, plant lignin content, nitrogen inputs, and grazing intensity as key drivers of organic matter dynamics. Regional trends in soil organic matter can be predicted using these four site-specific variables, though model uncertainty increases where presettlement grazing data are unavailable.

Regional applicability

While this study focuses on the U.S. Great Plains, the mechanistic framework identifying climate, soil texture, plant composition, and grazing as universal controls on grassland soil organic matter has broad applicability. United Kingdom grasslands and upland pastures operate under different climatic regimes and management histories, but the modelling approach and identified control variables are directly transferable to UK grassland research and soil carbon assessment.

Key measures

Soil organic carbon (C) and nitrogen (N) levels; aboveground plant production; steady-state organic matter levels; effects of temperature, moisture, soil texture, plant lignin content, nitrogen inputs, and grazing intensity on SOM

Outcomes reported

The study simulated steady-state soil organic matter (C and N) levels across 24 grassland locations in the Great Plains, examining how climate, soil texture, and grazing intensity control organic matter dynamics. The model predicted aboveground plant production and soil C and N levels across soil textures, though it overestimated values for fine-textured soils by 10–15%.

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