Does Grazing Matter for Soil Organic Carbon Sequestration in the Western North American Great Plains?

• Published in: Ecosystems (New York) Vol. 22; no. 5; pp. 1088 - 1094
• Main Authors: Derner, Justin D., Augustine, David J., Frank, Douglas A.
• Format: Journal Article
• Language: English
• Published: New York Springer Science + Business Media 01-08-2019; Springer US; Springer; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Carbon 14; Carbon content; Carbon sequestration; Clay soils; Community composition; Ecological effects; Ecological monitoring; Ecology; Ecosystems; Environmental Management; Geoecology/Natural Processes; Grasslands; Grazing; Herbivores; Hydrology/Water Resources; Life Sciences; Organic carbon; Organic soils; Original Articles; Plant communities; Plant Sciences; Pools; Pretreatment; Silt; Soil properties; Soil texture; Soils; Steppes; Texture; Turnover rate; Zoology; Great Plains; cattle grazing; shortgrass steppe; soil radiocarbon; semiarid rangeland; soil carbon turnover; soil carbon
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-018-0324-3

Considerable uncertainty remains regarding grazing-induced influences on soil organic carbon (SOC) sequestration in semiarid grassland ecosystems due to three important complications associated with studying such effects: (1) Ecologically meaningful shifts in SOC pools attributable to grazing are difficult to detect relative to inherently large grassland SOC pools, (2) a lack of baseline (pre-treatment) data, and (3) frequent lack of or limited replication of long-term grazing manipulations. SOC sequestration rates were determined in 74-year-old grazing exclosures and paired moderately grazed sites, established across a soil texture gradient, in the western North American shortgrass steppe in northeastern Colorado. We sampled soils (0–20 cm) from 12 exclosures and paired grazed sites to measure SOC concentration and soil radiocarbon Δ¹⁴C (&); the latter allowed us to determine turnover of the SOC pool over a 7-decade period in the presence versus the absence of grazing. Removal of grazing for more than 7 decades substantially altered plant community composition but did not affect total soil C, SOC, soil Δ¹⁴C, SOC turnover rate, or total soil N. Grazing effect also did not interact with soil texture to influence any of those soil properties. Soil texture (silt + clay content) did influence total soil C and SOC, and total soil N, but not Δ¹⁴C or SOC turnover. Results provide evidence that long-term removal of grazing from semiarid grassland ecosystems in the western North American Great Plains does not enhance long-term SOC sequestration, despite changes in the relative dominance of C3 versus C4 grasses.