Transpiration in the global water cycle

A compilation of 81 studies that have partitioned evapotranspiration (ET) into its components transpiration (T) and evaporation (E) at the ecosystem scale indicates that T accounts for 61% (+/- 15% s.d.) of ET and returns approximately 39 +/- 10% of incident precipitation (P) to the atmosphere, creating a dominant force in the global water cycle. T as a proportion of ET is highest in tropical rainforests (70 +/- 14%) and lowest in steppes, shrublands and deserts (51 15%), but there is no relationship of If El versus P across all available data (R-2 = 0.01). Changes to transpiration due to increasing CO2 concentrations, land use changes, shifting ecozones and climate warming are expected to have significant impacts upon runoff and groundwater recharge. (C) 2014 Elsevier B.V. All rights reserved.