From late 2009 through 2010, Xishuangbanna in SW China experienced the most severe drought on record since 1959, providing a unique opportunity to directly evaluate how self-organisation indicators (exergy capture and dissipation) change with drought stress in a tropical rainforest. Prof. ZHANG Yiping and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study at a tropical seasonal rainforest site (21°57′ N, 101°12′, 750 m asl) to explore thermodynamic theory to assess the effect of drought stress on self-organisation in the ecosystem.

　   The researchers evaluated the effects of drought stress on the self-organizational properties of Xishuangbanna tropical seasonal rain forest. They measured air temperature, humidity, rainfall, global and infrared incident and reflected radiations on a 72 m meteorological tower. They also collected meteorological data, and calculated vapour pressure deficit. Mathematic analysis of the thermodynamic parameters describing exergy capture ability and exergy dissipation ability of ecosystem was carried out in terms of exergy balance, thermodynamics, physiology and ecology.

The study found that during the 2010 dry season (March–April), the forest was least able to capture exergy. The ecological community was less developed, decreased in the capture exergy and thermal response number in the drought year. Thus, the forest had the lowest level of self-organization in 2010.

 The study entitled “The effect of drought stress on self-organisation in a seasonal tropical rainforest” has been published online in Ecological Modeling.