摘要:
估算并消除冠层非光合组分(non-photosynthetic vegetation,NPV)吸收的光合有效辐射,对准确估算生态系统总初级生产力(gross primary productivity,GPP)具有重要意义.以落叶阔叶林为例,通过设置不同情景,应用任意倾斜叶片散射(scattering by arbitrary inclined leaves,SAIL)模型进行冠层光合有效辐射吸收分量(fraction of absorbed photosynthetically active radiation,FPAR)的分层模拟,分析冠层NPV的FPAR的变动及其对冠层FPAR的贡献,并初步探讨落叶阔叶林NPV的FPAR的估算方法.结果表明,冠层NPV的FPAR的大小与冠层结构相关,在高覆盖度植被区NPV对冠层FPAR的贡献通常较小,但在低植被覆盖区的贡献会较高;NPV降低了冠层在近红外波段的反射;增强型植被指数(enhanced vegetation index,EVI)与NPV的FPAR存在显著的线性负相关关系,可用来描述NPV的变化.
Abstract:
Fraction of absorbed photosynthetically active radiation(FPAR) of the canopy is an important biophysical variable widely used in satellite-based production efficiency models to estimate the gross primary productivity(GPP).Vegetation canopy is composed primarily of photosynthetically active vegetation(PAV)and non-photosynthetic vegetation(NPV).Only the PAR absorbed by PAV is used for photosynthesis.Therefore, the photosynthetically active radiation absorbed by NPV in the canopy should be estimated and removed from canopy PAR so as to estimate GPP more accurately.Scattering by arbitrary inclined leaves(SAIL)model assumes canopy as a turbid medium with a number of layers, each treated as an infinite, horizontal, homogeneous medium.This assumption and configuration of model makes it possible to calculate PAR absorbed of each layers.In this study, SAIL model was used to calculate spectral reflectance and the PAR absorbed by PAV and NPV of deciduous broadleaved forest, and at last FPAR of NPV (FPARNPV) was calculated and analyzed.The results show that FPARNPV is dominated by canopy architecture.The contribution of NPV to canopy FPAR is low in high-cover regions, and the result is opposite in low-cover regions.NPV in the canopy can reduce reflectance in near infrared band.A significant and negative correlation is found between enhanced vegetation index(EVI)and FPARNPV.Though the simulation condition is ideal, the study is a good attempt which provides a means for acquiring deciduous broadleaf forests FPARNPV.
下载: