Spatial Pattern of Plant Transpiration Over China Constrained by Observations

Abstract

Plant transpiration is a key flux of surface water loss to the atmosphere, determining the available surface water for ecosystem and human use. However, over China, the magnitude of transpiration and its spatial pattern remain poorly understood due to a lack of constraints from in situ observations. Here we compile 34 plot-scale annual transpiration measurements across China to evaluate the performance of four transpiration products, and then produce a new constrained transpiration map for China. The transpiration map reveals an annual value of 209.0 mm yr−1, while the four transpiration products have a large spread of values (173.4–307.9 mm yr−1), especially in the wet southeastern regions. Land surface models exhibit large biases in modeled transpiration (−62.8% to 49.1%) compared to our constrained transpiration, and tend to underestimate transpiration in wet regions while overestimating it in dry regions. This behavior introduces bias in runoff projections which has ramifications for regional water resource management policies.