Abundance and distribution of cavity trees in an old-growth subtropical montane evergreen broadleaved forest

We examined the relationship between the density of cavity trees and forest structure characteristics and explored the occurrence of cavity trees among different tree species and diameter breast height (DBH) size in a subtropical evergreen broad-leaved forest in the Ailao Mountains in southwestern China. Cavity trees accounted for 7.9% of living trees and 16.3% of dead trees. Average density of living cavity trees (86.3 trees·ha^-1) was 6.9 times that of dead cavity trees. Density of living cavity trees was positively correlated with the density of living trees. Cavity trees showed a skewed distribution among DBH classes that peaked at DBHs of 20-40cm. Moreover, the probability that a living tree was cavity-bearing was logistically related to DBH. Overall, the likelihood of trees being cavity-bearing differed significantly among species. The proportions of cavity trees among the 23 species having more than 63 trees were positively related to the average DBH and to the largest DBH recorded for each species. We suggest that (1) living tree density is important in determining density of cavity trees and (2) differences in proportion of living cavity trees among species is caused mostly by differences in average DBH of each species.