亚热带针阔混交林光化学植被指数与光能利用效率关系研究

Investigating the relationship between photochemical reflectance index(PRI) and light-use efficiency(LUE) during different seasons in a subtropical needle-leaf and broadleaf mixed forest

利用光化学植被指数(PRI)反演区域尺度植被光能利用效率(LUE)的动态变化特征是当前生态系统生产力遥感研究的一个重要方向。基于2014年4月-2015年3月在广东省肇庆市鼎湖山森林生态试验站开展了植被冠层光谱和涡度相关通量同步观测,探讨亚热带常绿针阔混交林LUE与PRI的相关性及其调控因素。研究表明:(1)亚热带常绿针阔混交林LUE-PRI存在显著相关关系,但其相关性存在较大的季节性差异,冬季的相关性(R^2=0.40,P<0.01)明显优于夏季(R^2=0.04,P<0.01);(2)削弱植被自身的色素含量以及观测区内部的冠层结构、土壤背景、观测和光照条件影响后的?PRI难以有效表征亚热带常绿针阔混交林的LUE动态变化(表征程度为10%左右);(3)植被吸收的光合有效辐射(PAR)对LUE-PRI关系影响较大,饱和水汽压差(VPD)和日均温(Ta)对LUE-PRI相关性的影响较弱。需要进一步分析森林冠层结构、物候变化等因素对两者关系的影响,提高PRI作为亚热带森林LUE动态变化指示器的精度。

Light use efficiency（LUE） is a critical parameter for remote sensing estimation of ecosystem productivity. Therefore, accurate estimates of spatio-temporal variation of LUE is essentially required. Photochemical reflectance index（PRI） has been widely accepted to hold the potential to track the LUE variations. Here we combined spectral and eddy covariance observations in a subtropical mixed forest to investigate the ability of PRI to estimate LUE at a half-hourly time-scale in different seasons. The forest is located at Dinghu mountain forest ecological experiment station in Zhaoqing of Guangdong province and the observations ranged from April 2014 to March 2015. The results showed that：（1） LUE was significantly correlated with PRI but the correlation strength was different in different seasons; The correlation was the strongest in winter（R^2=0.40, P〈0.01） and the weakest in summer（R^2=0.04, P〈0.01）.（2） The standardized PRI（？PRI）, which removes noises from canopy and soil background, did not well capture the dynamics of LUE.（3） Photosynthetic active radiation（PAR） had the largest influence on the relationship between LUE and PRI among various climatic variables. Our analysis featured the temporal limitation of PRI in estimating LUE in subtropical forests and similar efforts are needed to quantify PRI ability to estimate LUE in other ecosystem types.