Decline in Aboveground Biomass Due to Fragmentation in Subtropical Forests of China

Fragmentation has long been considered the primary cause for ecosystem degradation and biodiversity loss worldwide. Forest fragmentation affects ecosystem functioning and biodiversity in multiple ways. Here, we ask how forest fragmentation influences aboveground biomass storage (AGB) in sub-tropical forests in China. We established 207 20 m x 20 m plots within 69 forest fragments of varying size. Forest fragmentation process simulation was carried out via repeated quadrat sampling using different sized quadrats in two non-fragmented stands. AGB was estimated and compared across forest fragments and quadrats with different sizes within two non-fragmented stands. Our results indicate that AGB is significantly lower in forest fragments than in quadrats within two non-fragmented forests. In addition, species richness and abundance were lower in fragmented stands, respectively. In fragmented forests, the average diameter at breast height (DBH) increased with decreasing patch size, while declined for non-fragmented plots. Species richness, abundance, and mean DBH have strongly positive effects on AGB. This was the case both in forest fragments and quadrats within two non-fragmented forests. Forest fragmentation leads to lower richness, lower abundance, and higher mean DBH in forest fragments than in the two non-fragmented forests. Our results suggest that forest fragmentation increases edge habitats, which drastically decreases forests aboveground biomass storage. These results show that land degradation not only reduces the area of forests, but also reduces the aboveground biomass carbon density of forests.