Water use efficiency of China’s terrestrial ecosystems and responses to drought

Abstract

Water use efficiency (WUE) measures the trade-off between carbon gain and water loss of terrestrial ecosystems, and better understanding its dynamics and controlling factors is essential for predicting ecosystem responses to climate change. We assessed the magnitude, spatial patterns, and trends of WUE of China’s terrestrial ecosystems and its responses to drought using a process-based ecosystem model. During the period from 2000 to 2011, the national average annual WUE (net primary productivity (NPP)/evapotranspiration (ET)) of China was 0.79 g C kg−1 H2O. Annual WUE decreased in the southern regions because of the decrease in NPP and the increase in ET and increased in most northern regions mainly because of the increase in NPP. Droughts usually increased annual WUE in Northeast China and central Inner Mongolia but decreased annual WUE in central China. “Turning-points” were observed for southern China where moderate and extreme droughts reduced annual WUE and severe drought slightly increased annual WUE. The cumulative lagged effect of drought on monthly WUE varied by region. Our findings have implications for ecosystem management and climate policy making. WUE is expected to continue to change under future climate change particularly as drought is projected to increase in both frequency and severity.

Projecting water yield and ecosystem productivity across the United States by linking an ecohydrological model to WRF dynamically downscaled climate data

“…Additionally, elevated CO 2 and climate change can also execrate impacts on hydrological and ecosystem productivity through changing water use efficiency (Miller-Rushing et al, 2009;de Kauwe et al, 2013;Zhang, F. et al, 2014;Liu et al, 2015) and vegetation processes (e.g., stomatal conductance and LAI; Sun et al, 2014). However, the WaSSI model did not consider these effects, potentially resulting in errors in estimating ET, GPP, or water yield (Cox et al, 2000;Gedney et al, 2006;Oki and Kanae, 2006;Betts et al, 2007;Piao et al, 2007).…”

Forest Management Challenges for Sustaining Water Resources in the Anthropocene

“…Hence, models and tools need to be dynamic and account for varying land uses, species and structure [69], and disturbances at fine spatial (e.g., tree) and temporal (e.g., storm event) scales. Empirical rainfall-runoff models built from historical data may not be applicable under future climate change conditions when plant growing season length, forest structure and species composition, and plant water use efficiency [70] have changed over time.…”

Monitoring Changes in Water Use Efficiency to Understand Drought Induced Tree Mortality

“…Water use efficiency is recognized as an important characteristic of productivity in various natural scientific disciplines and has been used recently at the ecosystem level [8,16,[47][48][49][50][51]. Ecologists commonly use the ratio of ecosystem fluxes such as NPP [8,16,52], net ecosystem productivity/exchange (NEP/NEE) [49,50], or gross primary productivity (GPP) [48] to water loss (ET or transpiration; [19,48,53] as a measure of WUE.…”

“…Studies have shown that WUE increases with aridity [8,[11][12][13][14][15][16][17] and that water limited ecosystems tend to have higher WUE [11,12,18]. Across all systems, if a drought becomes severe enough, a breakdown in ecosystem resistance can lead to a reduction in WUE [8,14,15,17,19] and ecosystem type conversions [8,17].…”