Abundance and distribution of cavity trees and the effect of topography on cavity presence in a tropical rainforest, southwestern China

Abstract

Cavity trees play a crucial role in maintaining biodiversity in forest ecosystems as they host numerous birds, mammals, and other cavity-dependent organisms. However, studies on the abundance and distribution of cavity trees in tropical forests are much less common than those in temperate forests. Also, how tree characteristics and topographic variables affect cavity presence is less clear in tropical forests. We surveyed 27 745 living trees from 386 species using ground-based observations in a tropical rainforest in southwestern China. The density of cavity trees was 86.3 trees·ha–1, which dramatically exceeded that in temperate forests. The number of cavity trees showed a left-skewed distribution with a peak at 10–20 cm diameter at breast height (DBH). The probability of cavity presence in a tree increased with DBH, although the patterns varied across species and crown positions. Moreover, cavity presence, which is influenced by topography in this tropical forest, decreased from valleys (concave terrain and low elevation) to ridges (convex terrain and high elevation). The results prove for the first time that topography is a good predictor of cavity presence, in addition to tree DBH. Our results demonstrate that the patterns determined for cavity presence in tropical forests of other regions also apply to Asian tropical forests. This study provides guidance on predicting the occurrence of cavity trees in the tropics.