Response of Ecosystem Water Use Efficiency to Drought over China during 1982–2015: Spatiotemporal Variability and Resilience

Hong Wang,Hongquan Wang,Limai Guo,Benxu Du,Jie Zhang,Yongguang Zhang,Huijuan Cui,Fubao Sun,Wenbin Liu

doi:10.3390/f10070598

Abstract

Ecosystem water use efficiency (WUE describes carbon-water flux coupling in terrestrial ecosystems. Understanding response and resilience of WUE to drought are essential for sustainable water resource and ecosystem management under increasing drought risks over China due to climate warming. Here we analyzed the response of ecosystem WUE to drought (spatiotemporal variability and resilience) over China during 1982–2015 based on an evapotranspiration (ET) dataset based on the model tree ensemble (MTE) algorithm using flux-tower ET measurements and satellite-retrieved GPP data. The results showed that the multiyear average WUE was 1.55 g C kg−1 H2O over China. WUE increased in 77.1% of Chinese territory during the past 34 years. During drought periods, the ecosystem WUE increased mainly in the northeast of Inner Mongolia, Northeast China and some regions in southern China with abundant forests but decreased in northwestern and central China. An apparent lagging effect of drought on ecosystem WUE was observed in the east of Inner Mongolia and Northeast China, the west and east regions of North China and the central part of Tibetan Plateau. Some ecosystems (e.g., deciduous needle-leaf forests, deciduous broadleaf forests, evergreen broadleaf forests and evergreen needle-leaf forests) in Central China, Northeast and Southwest China exhibited relatively greater resilience to drought than others by improving their WUE. Our findings would provide useful information for Chinese government to adopt a reasonable approach for maintaining the structure and functions of ecosystems under drought disturbance in future.

Highlights

Drought is an intermittent disturbance when water supply does not satisfy the demand for a long time [1,2], which can bring profound effects on carbon-water fluxes in terrestrial ecosystems at global and regional scales [3,4]
The annual mean Water use efficiency (WUE) were similar in croplands
WUE increased in approximately 77.1% of Chinese territory during the past 34 years, which was mostly distributed in the west parts in Inner Mongolia and Northeast China, the north parts in Southeast China, south parts in Southwest China and most regions in North China, South China and Tibetan Plateau

Summary

Introduction

Drought is an intermittent disturbance when water supply does not satisfy the demand for a long time [1,2], which can bring profound effects on carbon-water fluxes in terrestrial ecosystems at global and regional scales [3,4]. Water use efficiency (WUE) is a widely accepted parameter in describing carbon-water flux coupling between terrestrial ecosystems and the atmosphere and linking biological (e.g., vegetation transpiration and photosynthesis) and physical (e.g., soil evaporation) processes [12,13]. It reflects how much water is consumed by an ecosystem while it obtains carbon unit, which can be quantified as the ratio of carbon uptake (measured by GPP—gross primary productivity, NPP—net primary productivity or NEP—net ecosystem productivity) and water consumption (measured by ET—evapotranspiration or precipitation) [14,15,16]. Many previous studies have investigated the spatiotemporal changes of WUE

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Conclusion