Monsoonal climate and asymmetric heating facilitate the slope-aspect to influence landscape-scale tree structure in the Western Ghats, India

The regional variation of rainfall and length of the rainy season are identified to control the vegetation distribution in the Western Ghats (WG) of India, one of the important biodiversity hotspots. Here we demonstrate the existence of two new modes related to monsoonal climate and asymmetric solar heating that influence the vegetation structure at the landscape-scale in the WG: (i) the north-facing slopes have a higher tree cover (TC) and canopy height (CH) than the south-facing slopes and (ii) higher TC and CH on the west-facing slopes than the east-facing slopes. The asymmetry associated with these modes increases with the slope angle. The interaction of these modes often leads northwest and southeast aspects to have the highest and lowest TC (and CH), respectively. We thus demonstrate that even in low-latitude regions, the slope-aspect plays an important role in determining the TC and CH if the relief is higher. This fundamental driver of vegetation structure needs to be considered while formulating and executing programs aimed at increasing tree cover and conserving biodiversity, especially in the high relief areas in the tropics having seasonal rainfall, such as in the WG.