Critical effects on the photosynthetic efficiency and stem sap flow of poplar in the Yellow River Delta in response to soil water  

作　　者：Changxi Wang Huanyong Liu Jiangbao Xia Xianshuang Xing Shuyong Zhang 

机构地区：[1]State Forestry and Grassland Administration Key Laboratory of Silviculture in Downstream Areas of the Yellow River,Shandong Agricultural University,Taian 271018,People’s Republic of China [2]Shandong Key Laboratory of Eco-Environmental Science for the Yellow River Delta,Binzhou University,Binzhou 256603,People’s Republic of China [3]Hydrographic Office of Shandong Province,Jinan 250002,People’s Republic of China

出　　处：《Journal of Forestry Research》2021年第6期2485-2498,共14页林业研究（英文版）

基　　金：This study was supported by the National Natural Science Foundation of China(No.31770761,No.31870379);the Forestry Science and Technology Innovation Project of Shandong Province(No.2019LY006);the Science and Technology Projects of Shandong Province(No.2017CXGC0316);the Taishan Scholars Program of Shandong Province,P.R.China(No.TSQN201909152).

摘　　要：To explore the critical relationships of photosynthetic efficiency and stem sap flow to soil moisture,two-year-old poplar saplings were selected and a packaged stem sap flow gauge,based on the stem-heat balance method,and a CIRAS-2 portable photosynthesis system were used.The results show that photosynthetic rates(P_(n)),transpiration rates(T_(r)),instantaneous water use efficiency(WUE)and the stem sap flow increased initially and then decreased with decreasing soil water,but their critical values were different.The turning point of relative soil water content(W_(r))from stomatal limitation to nonstomatal limitation of P_(n)was 42%,and the water compensation point of P_(n)was 13%.Water saturation points of P_(n)and T_(r)were 64%and 56%,respectively,and the WUE was 71%.With increasing soil water,the apparent quantum yield(AQY),light saturation point(LSP)and maximum net photosynthetic rate(P_(n)max)increased first and then decreased,while the light compensation point(LCP)decreased first and then increased.When W_(r)was 64%,LCP reached a lower value of 30.7µmol m^(-2)s^(-1),and AQY a higher value of 0.044,indicating that poplar had a strong ability to utilize weak light.When W_(r)was 74%,LSP reached its highest point at 1138.3µmol·m^(-2)s^(-1),indicating that poplar had the widest light ecological amplitude and the highest light utilization efficiency.Stem sap flow and daily sap flow reached the highest value(1679.7 g d^(-1))at W_(r)values of 56%and 64%,respectively,and then declined with increasing or decreasing W_(r),indicating that soil moisture significantly affected the transpiration water-consumption of poplar.Soil water was divided into six threshold grades by critical values to maintain photosynthetic efficiency at different levels,and a W_(r)of 64-71%was classified to be at the level of high productivity and high efficiency.In this range,poplar had high photosynthetic capacity and efficient physiological characteristics for water consumption.The saplings had characteristics of water tolerance and were no

关 键 词：Gas exchange parameters Sap flow Soil moisture Water use efficiency Yellow River Delta 

分 类 号：S792.11[农业科学—林木遗传育种]