ENERGY BALANCE AND EVAPOTRANSPIRATION CHARACTERISTICS OF RUBBER TREE (HEVEA BRASILIENSIS) PLANTATIONS IN XISHUANGBANNA, SOUTHWEST OF CHINA

Rubber tree (Hevea brasiliensis) is important economic agroforestry with high water demand during its growth. Evapotranspiration as the main component of water and energy balance in forest ecosystem which is a vital link between its ecological and hydrological processes. Therefore, it is of extreme significance to study the energy balance and evapotranspiration of rubber plantations for in-depth study of the regional water vapor cycle, scientific and efficient management of water resources. Based on the meteorological and energy data measured by the Bowen ratio system in 2016 at Xishuangbanna, the energy balance and evapotranspiration characteristics of rubber plantations were analyzed by Bowen ratio-energy balance. The result showed that: (1) The daily variations of net radiation (R-n), latent heat flux (LE), sensible heat flux (H) and soil heat flux (G) in rubber plantation were high value in rainy season and low in dry season; (2) The annual ET of the rubber plantation was 1035.91 mm, the average daily ET was 2.83 mm/d in 2016. The ET was about 114%-140% of precipitation in the dry season which indicated that ET of rubber plantation was mainly dependent on the volumetric soil water content (VWC); (3) The dominant environmental factors were R-n, vapour pressure deficit (VPD) and VWC which affect ET of rubber plantation.