Limestone ecosystem is one of the principal vegetation types in tropical Yunnan of southwest China. It is extremely diverse in community types and very rich in endemic taxa. Within the seasonal tropical rainforest (locally termed as limestone tropical seasonal moist forest), most plants remain evergreen and continue to transpire during the 4–6 month dry season when rain is sparse. Although it is reasonable to expect that plants in this seasonal tropical rainforest might rely on water stored in the bedrock and water from radiational fog, no work had been done to test if this was true.

  Prof. LIU Wenjie and his colleagues of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study at a seasonal tropical rainforest site located on a small karst hill in Xishuangbanna, Southwest China (21°55′39″N, 101°15′55″E, 700ma.s.l.). The objective of the study was to determine the dry season water utilization for three important evergreen tree species, Cleistanthus sumatranus, Lasiococca comberi var.pseudoverticillata and Celtis wightii, by sampling the stable isotope ratios (δD and δ¹⁸O) of water in soil/bedrock, fog and non-photosynthetic tissue. Gravimetric soil water content (SWC) and stem water content were also measured during dry seasons. Specifically, they tested the use of fog water by adult trees and seedlings.

 The large decreases in stem water content between November and April indicated that both adult trees and seedlings encountered a considerable water stress during the dry season. Adult trees of the three species were quite dependent on water stored within the weathered bedrock at the peak of the dry season. Their study also showed that seedlings experienced more severe water stress than adult trees. Fog water was an important source for seedling growth during the pronounced dry season.