Abstract: [Objective] Buttress is a type of lateral root and a typical feature of tropical rain forests, with its own ecological significance. There were only some descriptive analysis on buttress in studies on ecological characteristics of rain forest in China. In this paper, characteristics of buttresses of Diaoluoshan mountain rain forests in Hainan Island were studied, and the objective is to understand the ecology of the buttress trees and the buttresses. [Method] Buttress tree was analyzed with the data from field investigation. Buttress tree density, and buttress density and size were tested for normality with Kolmogorov-Smirnov method or distribution patterns of those measurements that were fitted. The diffusion coefficients (C) was calculated to decide buttress trees' distribution pattern. [Result] There were 52 in total buttress tree species belonging to 33 genera of 25 families. There were 18 species could be found only in primary forests (PFs), and 23 in degraded primary forests (DPFs). And there were 11 species could be found both in PFs and DPFs. Buttress trees were distributed in clumped patterns both in PFs and DPFs. Density of buttress trees were in a range from 0.0 to 133.3 stem·hm^-2. Average density of buttress trees of the two stands was 38.9 stem·hm^-2; average density in PFs was 48.9 stem·hm^-2 and DPFs was 34.1 stem·hm^-2. As to the buttress, density was in a range from 0.0 to 666.7 root·hm^-2, and the total average was 160.0 root·hm^-2, average in PFs was 197.9 root·hm^-2, average in DPFs was 142.2 root·hm^-2. Height of buttresses were in a range of 0.30 to 5.00 m, and the average was 1.19 m. There was a positive relationship between buttresses' length and height which could be fitted in simple linear regression equation. Distribution of density of buttress trees and buttresses, and height of buttresses could be described well by negative exponential function. Counts of buttresses in each buttress tree satisfied Poisson distribution and average buttresses were 4.1 in each buttress tree. [Conclusion] There were abundant buttress tree species in mountain rain forest of Diaoluoshan National Forest Park. The analysis of quantitative indicators of buttress tree species and their buttress provides a basis for study of their ecological characteristics in future. And it also has some practical value for the investigation and evaluation of that special tourism resources.

Key words: mountain rain forest, buttress tree species, buttress, distribute pattern, density, size of buttress