首页|Effects of thinning and understory removal on water use efficiency ofPinus massoniana:evidence from photosynthetic capacity and stable carbon isotope analyses
Effects of thinning and understory removal on water use efficiency ofPinus massoniana:evidence from photosynthetic capacity and stable carbon isotope analyses
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Understanding the relationship between forest management and water use efficiency(WUE)is important for evaluating forest adaptability to climate change.How-ever,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 mecha-nisms 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 sub-tropical region of China.Photosynthetic capacity and needle stable carbon isotope composition(δ13C)were measured to assess instantaneous water use efficiency(WUEinst)and long-term water use efficiency(WUEi).Multiple regression models and structural equation modelling(SEM)identified the effects of soil properties and physiological performances on WUEinst and WUEi.The results show that WUEinst val-ues among the four treatments were insignificant.However,compared with the NT stand(35.8 μmol·mol-1),WUEi val-ues significantly increased to 41.7 μmol·mol-1 in the UR,50.1 μmol·mol-1 in the LT and 46.6 μmol·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 pho-tosynthetic capacity).Thinning increased the net photosyn-thetic rate(An)but not stomatal conductance(gs)or predawn needle water potential(Ψpd),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 meas-ure to promote P.massoniana WUE to cope with seasonal droughts under future extreme climates.
Stable carbon isotopeWater use efficiencyThinningUnderstory removalPhotosynthetic capacityNeedle water potential
Ting Wang、Qing Xu、Beibei Zhang、Deqiang Gao、Ying Zhang、Jing Jiang、Haijun Zuo、Yanbo Hu
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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
College of Agronomy and Agricultural Engineering,Liaocheng University,Liaocheng 252000,People's Republic of China
Department of Forest and Conservation Sciences,Faculty of Forestry,University of British Columbia,Vancouver,BC V6T 1Z4,Canada
National Key Research and Development Program of ChinaNational Nonprofit Institute Research Grant of CAFNational Natural Science Foundation of ChinaNational Natural Science Foundation of China
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