散射辐射对杨树人工林生态系统总初级生产力的影响  

Effects of Diffuse Radiation on the Gross Primary Productivity of a Poplar Plantation

作　　者：万家鸣 律江 石云 许行 张志强[1,2] Wan Jiaming;Lü Jiang;Shi Yun;Xu Hang;Zhang Zhiqiang(School of Soil and Water Conservation,Beijing Forestry University,Beijing 100083;Jixian National Forest Ecosystem Observation and Research Station,Jixian 042299;Beijing Gongqing Forest Farm,Beijing 101300)

机构地区：[1]北京林业大学水土保持学院,北京100083 [2]山西吉县森林生态系统国家野外科学观测研究站,吉县042299 [3]北京市共青林场,北京101300

出　　处：《林业科学》2023年第5期1-10,共10页Scientia Silvae Sinicae

基　　金：中央高校基本科研业务费专项资金(BLX202108);中国博士后科学基金面上项目(2022M710407);国家自然科学基金面上项目“大气气溶胶对森林生态系统碳水耦合过程的影响机理”(31872711)。

摘　　要：【目的】在量化生态系统阳冠层和阴冠层光合参数的基础上,通过探究其季节动态变化和主要生物物理调控因子,揭示散射辐射变化对杨树人工林生态系统总初级生产力(GPP)的影响,为人工林生态系统服务功能和碳汇能力的准确评估提供参考。【方法】以北京顺义区共青林场的杨树人工林生态系统为研究对象,利用涡度相关技术和微气象观测系统,对生态系统碳循环过程和生物物理因素进行了连续4年(2015—2018年)的定位观测;采用非线性拟合方法将生态系统最大光合速率(A_(max))和表观量子效率(α)拆分为受直接辐射(A_(max),dir、αdir)和散射辐射(A_(max,dif)、α_(dif))影响的两部分。由于直角双曲线模型(Michaelis-Menten model)在模拟GPP时会出现不饱和现象,本研究采用PAR为2000μmol·m^(–2)s^(–1)时的GPP作为最大光合速率(A_(2000))。【结果】采用晴空指数和太阳高度角模拟的散射辐射与实测值接近(斜率为0.82,R^(2)=0.87,RMSE=51.67 W·m^(–2),P<0.01)。2015—2018年生长季杨树人工林的α_(dif)、A_(2000,dir)和A_(2000,dif)呈先增加后减小的变化趋势,α_(dif)和A_(2000,dif)显著高于αdir和A_(2000,dir)(pα=0.02;p A_(2000)=0.03),α_(dif)/αdir和A_(2000,dif)/A_(2000,dir)分别为5.6和6.1,二者的比例在夏季表现出明显差异。生长季GPP呈单峰变化模式,且GPP与A_(2000,dif)显著相关(P<0.01),随着PAR_(dif)/PAR_(dir)的增加,GPP显著增加(P<0.01)。在夏季,A_(2000,dif)主要受Ta的影响,随着Ta的增加而增加(偏相关系数为0.74,R^(2)=0.49,P<0.05);在春季和秋季,LAI主导着A_(2000,dif)的变化(偏相关系数为0.69,R^(2)=0.53,P<0.01),而PrestleyTaylor系数(η)和晴空指数(CI)无论是在春秋还是夏季,对A_(2000,dif)都无显著影响。【结论】α和A_(2000)会随季节发生变化,散射辐射对A_(2000)和α的影响要显著高于直接辐射的影响,且在生长季中期更加明显,A_(2000,dif)在春秋季和夏季的变化�【Objective】Intensive human activities have resulted in significant changes in aerosols and particulate matter content in the atmosphere,thereby posing an important impact on the total amount and proportion of global diffuse radiation.In this study,based on the clarification of the canopy photosynthetic parameters corresponding to the radiation components,the seasonal dynamics and the main biophysical regulators were explored to gain insight into the effects of diffuse radiation on the gross primary productivity(GPP)of a poplar plantation,providing a reference for the accurate assessment of ecosystem functions and carbon sink of plantations in the future.【Method】The carbon cycling processes and biophysical factors of a poplar(Populus×euramericana cv.'74/76')plantation in Gongqing Farmland,Shunyi District,Beijing,were observed for the consecutive four years(2015—2018).A nonlinear fitting method was used to split the ecosystem maximum photosynthetic rate(A_(max))and apparent quantum efficiency(α)into two components influenced by direct radiation(A_(max),dir,αdir)and diffuse radiation(A_(max,dif),α_(dif)),respectively.Since the rectangle hyperbola light response model(Michaelis-Menten model)would appear unsaturated phenomenon when simulating GPP,GPP at PAR of 2000μmol·m^(–2)s^(–1) was used as the maximum photosynthetic rate(A_(2000))in this study.【Result】In this study,simulated diffuse radiation based on clearness index and solar altitude angle was found to be consistent with the measured values(slope 0.82,R^(2)=0.87,RMSE=51.67 W·m^(–2),P<0.01).Theα_(dif),A_(2000,dir) and A_(2000,dif) of this poplar plantation during the growing season showed an increasing trend and then a decreasing trend.Theα_(dif) and A_(2000,dif) were significantly higher thanαdir and A_(2000,dir)(Pα=0.02;PA_(2000)=0.03).Theα_(dif)/αdir and A_(2000,dif)/A_(2000,dir) were 5.6 and 6.1,respectively,and the two ratios showed significant differences in summer.The growing season GPP showed a single-peaked variation patt

关 键 词：散射辐射 表观量子效率 最大光合速率 总初级生产力 杨树人工林 

分 类 号：S718.43[农业科学—林学]