Air temperature and soil phosphorus availability correlate with trait differences between two types of tropical cloud forests

Tropical cloud forests are characterized by lower air temperature and high frequency of fog condensation at canopy level, as compared with forests at lower altitudes. Few studies have been conducted to understand differences of plant functional traits in relation to the environment in this kind of forest. In this paper, we explored the community-level differences of specific leaf area (SLA) and height of plants in relation to major environmental conditions between two adjacent tropical cloud forests on Hainan Island, South China. We measured the two functional traits for all individual plants within twenty-nine and thirty-two 10 m x 10 m plots located in a low altitude tropical montane evergreen forest (TMEF) and a high altitude tropical dwarf forest (TDF), respectively. The results showed that both mean SLA and height decreased from TMEF to TDF, while phenotypic plasticity for the two functional traits increased from TMEF to TDF. Correlation analysis and multiple regression analysis showed that the mean SLA and its plasticity were significantly correlated with both air temperature and soil phosphorus. The mean height was only significantly correlated with air temperature, but its plasticity was significantly correlated with both air temperature and soil phosphorus. Our results suggest that plants in dwarf tropical cloud forests have decreased SLA and height, correlated with less favorable soil and atmospheric conditions, with a higher plasticity of these traits, as compared with the tropical montane evergreen forest. Community-level differences in SLA and plant height thus can be taken as indicators characterizing plant distribution to different types of tropical cloud forests. (C) 2011 Elsevier GmbH. All rights reserved.