Assessing the Climatic Effects on Vegetation Dynamics in the Mekong River Basin

Understanding long-term vegetation dynamics, their responses to climate, and other driving factors is crucial for integrated basin management in the Mekong River Basin (MRB) in a context of global change. In this study, Normalized Difference Vegetation Index (NDVI) and climate data from 1982 to 2013 were collected from Global Inventory Modeling and Mapping Studies (GIMMS) and Climate Research Unit Time Series Version 3.23 (CRU-TS 3.23). The long-term monthly average, Mann-Kendall trend (M-K) test, Sen's slope, the coefficient of variation, correlation analysis, and the Partial Least Square Regression (PLSR) model with the Variable Importance in Projection (VIP) were applied in this study. The results showed an increasing temporal trend in NDVI and climate variables, especially temperature, in all vegetation types. There is a significantly increasing NDVI trend with relatively stable NDVI fluctuation across the majority of the MRB except in part of the Tibetan plateau in China. There is a positive spatial correlation between NDVI and air temperature, precipitation and PET (potential evapotranspiration) in the upper part of the basin. Air temperature is an important explanatory factor for all vegetation types, especially in forest ecosystems and croplands, while the role of precipitation and PET vary depending on vegetation type. In addition to physical aspects of the MRB, such as runoff, we conclude that the vegetation dynamics related to climate variables in the MRB should be considered in policies as the framework for ecological and environmental management plans of the MRB.