Impact of drought on carbon and water fluxes and their coupling in a Quercus variabilis plantation
Aims Water use efficiency(WUE)is an important indicator for understanding the carbon and water cycles and coupling mechanisms in terrestrial ecosystems.Inherent water use efficiency(IWUE)is a more suitable indicator than WUE for analyzing the carbon-water coupling mechanism of ecosystems on a daily scale.Here,we aimed to investigate the mechanism of water and carbon fluxes and their responses to drought in a planted forest ecosystem.Methods We carried out an in-situ observation on the water and carbon fluxes and environmental factors in a Quercus variabilis plantation using eddy covariance techniques and the micrometeorological observation system.The effects of biophysical factors on the gross primary productivity(GPP),evapotranspiration(ET),and IWUE during 2021-2022 were analyzed.Important findings GPP,ET,and IWUE showed obvious seasonal variations.GPP and ET in the wet year were 7.9％and 21.0％higher than those in the normal year,respectively,whereas IWUE in the wet year was 21.4％lower than that in the normal year.Vapor pressure deficit(VPD)was the main factor affecting GPP in the normal year,and net radiation(Rn)was the primarily factor limiting GPP in the wet year.ET was mainly determined by Rn in both normal and wet years.Relative extractable soil water(REW)was the main factor regulating IWUE in the normal year,whereas leaf area index(LAI)was the main factor controlling IWUE in the wet year.Environmental factors regulated carbon and water fluxes by affecting canopy conductance,and consequently impacting IWUE.The occurrence of soil drought significantly increased IWUE.The response of GPP and ET to REW showed a time lag of 1 month,while the response of IWUE to REW had no lag.
water use efficiencydroughtcarbon-water couplinggross primary productionevapotranspiration
万方数据
维普
