Transpiration in the Global Water Cycle

Abstract:

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 T/ET versus P across all available data (R² = 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, reflecting human impacts on the global biogeochemical cycle of water.