Abstract: Transpiration rate of rubber tree (Hevea brasiliensis) was measured continuously from February to November in 2013, using the Granier’s thermal dissipation probe method. The main environmental factors (including air temperature, relative humidity, photosynthetically active radiation (PAR) and soil moisture) were also measured simultaneously. The results showed that the transpiration rate of rubber tree exhibited a unimodal pattern, with the value being higher during the daytime and lower at night. The average transpiration rate and daily transpiration of sunny day were 4 times more than those of rainy day. The transpiration started 0.5-1.0 h earlier and the peak time was 2.0-4.5 h earlier during the rainy season than during the dry season. During the study period, the average daily transpiration was 27.84 kg·d^-1. The largest amount of stand transpiration (54.3 mm) occurred in April and minimum (29.6 mm) in November. Environmental factors in terms of their effects on the transpiration rate were ranked as air temperature effects > air relative humidity > PAR > soil moisture in the dry season, and PAR > air relative humidity > air temperature > soil moisture in the rainy season. Despite water deficit during the dry season, the rubber tree can get deep soil water due to its welldeveloped root system, and is not affected by severe water stress.

Key words: interactive effects, warming, changing precipitation, elevated CO₂ concentration, crops