Effect of land-use conversion on ecosystem C stock and distribution in subtropical grazing lands

Abstract

Grazing lands worldwide are increasingly subjected to intensification to meet global demand for food; however, management practices intended to increase production can also affect ecosystem carbon (C) stocks. This study evaluated long-term (>22 years) ecosystem C responses to conversion of native grazing lands into more intensively managed silvopasture and sown pastures. Above- and below-ground C pools in each land use type were evaluated. Silvopasture exhibited the greatest total ecosystem C stock (168 Mg ha−1) compared with sown pasture and native rangeland (121 and 94 Mg ha−1, respectively). This response was due to the greater aboveground biomass (59 Mg ha−1 in silvopasture vs. 2.1 and 3.8 Mg ha−1 in sown pasture and native rangeland, respectively), primarily from the tree component. Soil organic C (SOC) accounted for 81 and 90 % of total ecosystem C stocks in native rangeland and sown pasture, respectively, while in silvopasture SOC represented ~ 61 % of total ecosystem C. Soil organic C increased from 76 Mg ha−1 in native rangeland to 110 Mg ha−1 sown pasture. Data indicated that grazing land intensification through the adoption of proper management promoted ecosystem C primarily due to increases in SOC and the associated benefit of a greater above-ground woody biomass.