Substantially Enhanced Landscape Carbon Sink Due To Reduced Terrestrial-Aquatic Carbon Transfer Through Soil Conservation in the Chinese Loess Plateau

Soil conservation is of global importance, as accelerated soil erosion by human activity is a primary threat to ecosystem viability. However, the significance and role of soil conservation in reshaping landscape carbon (C) accounting has not been comprehensively integrated in the terrestrial C sink. Here, we present the first integrated assessment of the modified terrestrial C sink and aquatic C transport due to soil conservation for the semiarid Chinese Loess Plateau (CLP), the world's most vulnerable region to soil erosion. We show a surprisingly low terrestrial-aquatic C transfer that offset the terrestrial net ecosystem productivity by only 7.5%, which we attribute to the effective implementation of soil conservation practices. Despite the highest soil erosion, the semiarid CLP acts as effective C sink at 43.2 +/- 22.6 g C m(-2) year(-1), which is comparable to temperate forest in absorbing atmospheric CO2. Moreover, C burial in reservoirs has created an additional anthropogenic C sink of 2.9 +/- 1.1 g C m(-2) year(-1). Our findings indicate that effective soil conservation can significantly increase landscape C sequestration capacity. The co-benefits of soil conservation in erosion control and C sequestration have important implications for policy makers in other regions undergoing increasing erosion intensity to pursue environmental sustainability. Plain Language Summary Aquatic export of terrestrial carbon (C) plays a significant role in modulating the magnitude of terrestrial C sink. Previous estimates of terrestrial C sink may be overestimated because not all C losses across heterogeneous landscapes are accurately determined and properly accounted for. This is particularly possible for catchments with high erosion and terrestrial-aquatic C transfer potential. Meanwhile, soil conservation can greatly modify landscape C sequestration capacity. Thus, a more comprehensive assessment of net landscape C budget is needed that integrates aquatic export of terrestrial C while considering the role and significance of soil conservation. For the Chinese Loess Plateau in semiarid climates that once characterized the world's high soil erosion rate, we show a surprisingly low aquatic C transfer that offset the terrestrial C sink by only 7.5%, due largely to successful soil conservation in the past decades. Our findings suggest that effective implementation of soil conservation practices can substantially reduce terrestrial-aquatic C transfer and enhance the landscape C sequestration capacity.