Background: Evapotranspiration (ET) is an essential component of the water cycle and is composed of a connecting process, i.e., evaporation of water from the surface of plant and soil and transpiration consists of an exchange of water vapors between the plant and atmosphere through plant stomata. Relationships between vegetation type and annual evapotranspiration was primarily assessed on regional-scale studies during the 20th century. However, the magnitude of this annual evapotranspiration in different climate zones and forest types on a global scale study is largely lacking. The control of climatic factors, i.e., annual precipitation and temperature on annual evapotranspiration of forest ecosystem, is the need of current time to better understand the complexity of future climatic change issues.
Objective: To determine the global patterns of variability in the forest ecosystem evapotranspiration, and their underlying controls.
Methods: Data on annual evapotranspiration was synthesize from 206 (456 sites) published literature.
Results/Conclusions
Results: The results of global synthesis showed that median ET is significantly higher in Tropical, followed by Subtropical, temperate, and lowest in the boreal forest zone (p<0.0001). Similarly, in the sub climate zone, the Mediterranean showing considerably higher ET than continental (p<0.0001). Whereas, broadleaved forest with more top ET >mixed>needle leaved forest stand is lowest (p<0.0001). Overall, annual temperature and precipitation are considered as primary factors of influencing ET. The control of annual temperature showed an increasing trend in ET of temperate, boreal, and tropical (p<0.05) while non-significant in the subtropical region. Whereas, annual precipitation only influences ET of temperate and boreal forests (p<0.05). The regression analysis of annual temperature and ET in both the Mediterranean and the continental regions is significant with an increasing trend (p<0.05). In contrast, this trend is non-significant between annual precipitation and ET of the Mediterranean region. The control of annual temperature and precipitation is positive and linear in all forest types (p<0.05).
Conclusion: The higher Evapotranspiration losses due to an increase in annual temperature of broadleaved and tropical regions, indicating the climate extreme may influences in these regions in near future. Therefore, planning for large-scale afforestation schemes for carbon sequestration requires careful consideration of the gain in biomass production and the tradeoff for other regulatory services.