Transpiration of Moso bamboo in southern China is influenced by ramet age, phenology, and drought

Forest transpiration is coupled with environmental variables and has a profound effect on regional water cycle and water balance. Understanding how the biotic and abiotic environments influence transpiration is vital in understanding forest water use strategies, and for evaluating forest feedback to climate change. Moso bamboo (Phyllostachys edulis), a woody bamboo species, is rapidly spreading in the southern parts of China and must have a significant influence on ecosystem processes here. This study examined cuhn sap flow in P. edulis in southern China to identify key factors that determine its transpiration at individual and stand scale. Sap flux density was higher in the 1-2 years old ramets than those > 3 years old, during the entire growing season. Daily accumulated sap flux density and its sensitivity to the physical environment (air vapor pressure deficit-VPD and solar radiation) during the non-shooting period were approximately 2 and 3 times higher than during the shooting-leafing period for 1-2 and > 3 years old culms, respectively. During the non-shooting period, daily maximum and accumulated sap flux density of the 1-2 years old ramets had no correlation with soil water content, while that of > 3 years old ramets declined linearly with decreasing soil water content (SWC). Stand transpiration remained low, and was not affected by changes in SWC during the shooting-leafing period, while that of nonshooting period was linearly correlated with SWC. The results showed that transpiration of Moso bamboo was interactively influenced by culm age, phenological stages and soil drought. We demonstrate the role of ramet age and phenology on bamboo stand transpiration and how it responds to soil drought. Our study reveals the special water use strategies in Moso bamboo forests.