Soil Carbon Stability Responds to Land‐Use and Groundcover Management in Southern Appalachian Agroecosystems

Abstract

Soil C storage can be altered by land‐use conversion and by agroforestry management techniques such as weed management and fertilization. The Southern Appalachian Mountains have a mosaic of land uses, including Christmas tree [Abies fraseri (Pursh) Poir] farms, pastures, and unmanaged forests. We contrasted Christmas tree farm soil C pools with those of adjacent pastures and forests to estimate C storage differences due to land use. We partitioned soil C into fractions delineated by stability, an important determinant of long‐term C sequestration potential. Soil C pools were quantified across a chronosequence of tree farms that varied in cultivation duration (3–51 yr) and interspace groundcover. We found that the duration of tree cultivation did not alter tree farm soil C pools; however, recalcitrant C pools were twice as high when interspace groundcover increased from 35 to 70%. Total, active, slow, and recalcitrant soil C pools were highest in forests compared with pastures and tree farms. Tree farm soils had about 25% lower C concentration than the adjacent forest soils, but because there was no downward trend with duration of cultivation, the reduction probably occurred rapidly following initial clearing. Tree farms and forests had longer mean residence times for active and slow C than pastures, potentially indicating an influence of woody root production. Our findings suggest that maintaining tree farm interspace vegetation, possibly through reduced herbicide use, can enhance soil C sequestration.