Water is a critical resource that limits the distribution and abundance of vegetation in the world. Many species-rich tropical forests experience a prolonged dry season during which little or no rainfalls and upper soil layers undergo severe drying. Within the tropical seasonal rainforest of Xishuangbanna, Southwest China, most plants remain evergreen and continue to transpire during dry season months (November –April) when rain is sparse.

Prof. Dr. Liu Wenjie of XTBG and his team assessed patterns of water uptake by two major seasonal rainforest canopy tree species – Pometia tomentosa and Gironniera subaequalis in Xishuangbanna, during two consecutive dry seasons (2005 and 2006). By sampling the stable oxygen isotope ratios of water in soil, fog, rain, groundwater and non-photosynthetic tissue, and measuring gravimetric soil water content and leaf water potential, the researchers determined the proportion of water deriving from shallow soil by mature trees and from fog water by seedlings during the pronounced dry season.

The research results indicated that fog water was an importatn source for seedling growth, especially at the peak of the dry season.

The research observation has been published in Agricultural and Forest Meteorology , 150 (3): 380-388, doi:10.1016/j.agrformet.2009.12.006.