The magnitude and causes of edge effects on soil organic carbon stocks within and across urban to rural forest patches

Landscape fragmentation has created large areas of forest edge. Understanding how soil organic carbon (SOC) stocks within forest edges respond to fragmentation is essential to assess carbon budgets; however, the causes and magnitude of edge effects on SOC stocks have been poorly characterized. Here, we quantify the edge effects on SOC stocks within and across urban to rural forest patches from three fragmented urban forests to a large patch of rural forest. The SOC stocks within 20 m of the rural forest edge (1.86 kgC m −2 ) is on average 80% lower than the interiors of rural forest (10.47 kgC m −2 ). We found that biotic factors, including annual litterfall mass ( R 2 > 0.94), peak leaf area index ( R 2 > 0.92), and fine-root mass density ( R 2 > 0.77), explained the spatial variation in SOC stocks within the rural forest. In urban forests, human activities at forest edges led to contra…