摘要
【目的】定量研究欧美杨人工林生态系统净碳交换(NEE)对环境因子响应的时滞现象,为提高生态系统碳源/汇量的估算准确性提供科学依据。【方法】应用涡度相关技术,结合微气象观测系统,对北京市顺义区欧美杨人工林NEE和环境因子进行连续动态观测,获取2014年生长季(4—10月)NEE、空气温度(Ta)、5 cm深处土壤温度(T5)、光合有效辐射(PAR)、饱和水汽压差(VPD)和25 cm深处土壤体积含水量(VWC25)观测数据,采用回归分析与小波互相关分析相结合的方法定量研究NEE与环境因子的时滞关系;以决定系数(R^2)、林氏调和系数(LCCC)和均方根误差(RMSE)作为评价指标,利用偏相关分析和主成分分析方法分析时滞现象对NEE与环境影响因子之间关系的影响。【结果】PAR是影响NEE变化的主导因子;由于该生态系统地下水位高,水分供给充足,VWC25对NEE没有显著影响(P=0.1515);白天NEE与PAR同步变化,比Ta、T5和VPD分别提前2.5、2和2.5 h达到峰值(时滞),夜间NEE与环境因子没有确定的时滞关系;消除时滞现象后,NEE与T5的线性关系由不显著(P=0.2248)变为极显著(P=0.0051);主成分分析表明,对数回归模型可以更准确地描述NEE与环境因子间关系,消除时滞后模型的R^2和LCCC分别提高8.1%和2.0%,RMSE降低0.417μmol·m^-2s^-1。【结论】欧美杨人工林生态系统NEE日动态变化受Ta、T5、PAR和VPD控制,白天时滞现象明显,消除时滞现象可以有效提高NEE模型拟合精度。
【Objective】The objective of this study is to quantify the time-lag responses of net ecosystem exchange of CO2(NEE)to environmental factors in a Populus×euramericana plantation,in order to provid scientific evidence for improving the accuracy of estimating carbon source/sink in the ecosystem.【Method】We used the eddy covariance technique and micrometeorological sensors to continuously measure NEE and environmental elements,such as air temperature(Ta),soil temperature at 5 cm depth(T5),photosynthetically active radiation(PAR),vapor pressure deficiency(VPD)and soil volumetric water content at 25 cm depth(VWC25),during the growing season(April-October)in 2014 in a P.×euramericana plantation adjacent to the Chaobai River in the northern China.We quantified the time-lag responses of NEE to these environmental factors by using regression analysis and wavelet cross-correlation analysis.Besides,partial correlation analysis and principal component analysis were used to evaluate the importance of time lag on the relationship between NEE and the environmental factors based on the determination coefficient(R^2),Lin’s concordance correlation coefficient(LCCC)and root mean square error(RMSE).【Result】Our result showed that PAR was the dominant environmental factor regulating NEE.Additionally,VWC25 had no significant effect on NEE(P=0.1515)due to the high-level groundwater and sufficient water supply in this riparian ecosystem.Although NEE showed the same diurnal variation with PAR,it reached the peak 2.5,2 and 2.5 h earlier than Ta,T5 and VPD,respectively.Interestingly,there were no significant time-lag relationships between NEE and environmental factors at night.After eliminating the time lag,the partial correlation between NEE and T5 was significant(P=0.0051)compared to the insignificant relationship before(P=0.2248).Moreover,the principal component analysis indicated that the relationship between NEE and the climatic elements could be more accurately described by logarithmic regression model.After eliminating the time lag,the model R^2 and LCCC increased by 8.1%and 2.0%,respectively,and RMSE reduced by 0.417μmol·m^-2s^-1.【Conclusion】Therefore,the diurnal dynamics of NEE in this P.×euramericana plantation were controlled by Ta,T5,PAR,and VPD with distinct time-lag phenomenon in the daytime.It is vital for eliminating time lag to evaluate the environmental effects on NEE and improve the model accuracy.
作者
冯鑫炜
张志强
许行
律江
张海泉
孟祥雪
Feng Xinwei;Zhang Zhiqiang;Xu Hang;Lü Jiang;Zhang Haiquan;Meng Xiangxue(School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083;Beijing Gongqing Forest Center ,Beijing 101300)
出处
《林业科学》
EI
CAS
CSCD
北大核心
2020年第2期12-23,共12页
Scientia Silvae Sinicae
基金
国家自然科学基金项目(31872711)
国家科技支撑计划项目(2015BAD07B06-4)
关键词
净生态系统碳交换
环境因子
时滞现象
小波分析
欧美杨人工林
net ecosystem exchange of CO2
environmental factors
time lag
wavelet analysis
Populus×euramericana plantation