The U-shaped pattern of size-dependent mortality and its driving factors in a subtropical monsoon evergreen forest

1. Tree mortality is an important ecological process influencing multiple functions of forest ecosystems. Previous studies have shown two basic size-mortality patterns, including a competition-driven declining and a disturbance-driven increasing mortality rate with tree size. Subtropical forests, which have a high species diversity and subject to frequent monsoon disturbances, are widely distributed in eastern Asia. However, the tree size-mortality pattern in the mature subtropical forests remains unclear.

2. Here we analyzed patterns of size-dependent mortality from tree species to forest community using a 5-year inventory data from 117 species and 163,612 individuals in a 20-ha forest dynamic plot in a mature subtropical monsoon evergreen forest in eastern China. To explain the spatial variability in mortality patterns, two major biotic drivers (competition and tree size) and multiple local-scale environmental factors were further analyzed.

3. Our results showed that tree size w...