Effects of thinning and understory removal on water use efficiency of Pinus massoniana:evidence from photosynthetic capacity and stable carbon isotope analyses  

作　　者：Ting Wang Qing Xu Beibei Zhang Deqiang Gao Ying Zhang Jing Jiang Haijun Zuo 

机构地区：[1]Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration,Ecology and Nature Conservation Institute,Chinese Academy of Forestry,Beijing 100091,People’s Republic of China [2]College of Agronomy and Agricultural Engineering,Liaocheng University,Liaocheng 252000,People’s Republic of China [3]Department of Forest and Conservation Sciences,Faculty of Forestry,University of British Columbia,Vancouver,BC V6T 1Z4,Canada

出　　处：《Journal of Forestry Research》2024年第2期42-53,共12页林业研究（英文版）

基　　金：supported by the National Key Research and Development Program of China(2016YFD0600201);the National Nonprofit Institute Research Grant of CAF(CAFYBB2017ZB003);the National Natural Science Foundation of China(31870716;31670720)。

摘　　要：Understanding the relationship between forest management and water use efficiency(WUE)is important for evaluating forest adaptability to climate change.However,the effects of thinning and understory removal on WUE and its key controlling processes are not well understood,which limits our comprehension of the physiological mechanisms of various management practices.In this study,four forest management measures(no thinning:NT;understory removal:UR;light thinning:LT;and heavy thinning:HT)were carried out in Pinus massoniana plantations in a subtropical region of China.Photosynthetic capacity and needle stable carbon isotope composition(δ^(13)C)were measured to assess instantaneous water use efficiency(WUE_(inst))and long-term water use efficiency(WUE_(i)).Multiple regression models and structural equation modelling(SEM)identified the effects of soil properties and physiological performances on WUE_(inst)and WUE_(i).The results show that WUE_(inst)values among the four treatments were insignificant.However,compared with the NT stand(35.8μmol·mol^(-1)),WUE_(i)values significantly increased to 41.7μmol·mol^(-1)in the UR,50.1μmol·mol^(-1)in the LT and 46.6μmol·mol^(-1)in HT treatments,largely explained by photosynthetic capacity and soil water content.Understory removal did not change physiological performance(needle water potential and photosynthetic capacity).Thinning increased the net photosynthetic rate(A_n)but not stomatal conductance(g_s)or predawn needle water potential(ψ_(pd)),implying that the improvement in water use efficiency for thinned stands was largely driven by radiation interception than by soil water availability.In general,thinning may be an appropriate management measure to promote P.massoniana WUE to cope with seasonal droughts under future extreme climates.

关 键 词：Stable carbon isotope Water use efficiency THINNING Understory removal Photosynthetic capacity Needle water potential 

分 类 号：S791.248[农业科学—林木遗传育种]