The diversity index of various layers can be calculated using the formulae listed earlier. According to the characteristic of community vertical structure, when measuring the total index of community, the indices of different growth types are weighted. The weight is the average of the relative coverage and the thickness of the leaf layer (Fan et al., 2006). We applied the following formula (Gao et al., 1997):Wi ¼ Ci C
þ hi
h
=2