Interannual variation in stand transpiration estimated by sap flow measurement in a semi‐arid black locust plantation, Loess Plateau, China

Abstract

AbstractThe semi‐arid region of the Loess Plateau in China is characterized by its fragile ecosystems. Soil erosion and water shortage are major factors influencing the ecology and hydrology of vegetation in this area. For proper management of watershed ecosystems, quantification of water use by major vegetation types is needed. We used Granier‐type thermal dissipation probes in a black locust (Robinia pseudoacacia) plantation and upscaled stand transpiration from individual measurements of stem sap flow. Stand transpiration water use during the growing seasons of 2008–2010 was estimated on the basis of measured sap flux densities and sapwood areas. Seasonal and interannual variations were observed in stand‐scale transpiration. Within a monthly timescale, water use by daily transpiration was correlated with daily solar radiation and daytime average vapour pressure deficit. The monthly changes in stand transpiration were mainly correlated with changes in leaf area index and with mean daytime vapour pressure deficit, solar radiation and potential evapotranspiration at lower significance. A positive relationship between stand transpiration and soil moisture conditions was detected at an annual scale, but not at a monthly scale. Precipitation did not show a clear correlation with stand transpiration at either seasonal or annual timescale. The results suggest that although the stand transpiration is controlled by multiple factors, those contributing to a significant difference vary with timescales. Some factors (e.g. soil moisture) may only be detected upon long‐term observations. Copyright © 2014 John Wiley & Sons, Ltd.