塔里木河流域上游天然胡杨叶片叶绿素与可见光-近红外光谱反射率的相关性研究

Study on the Correlation between Leaf Chlorophyll Content of Populus euphratica and the Hyperspectral Remote Sensing Data in Upstream of Tarim River

采用ISI921VF-512野外地物光谱辐射计实地测量了塔里木河上游天然胡杨5月至10月叶片可见光-近红外波段光谱反射率以及叶绿素含量,比较了不同月份间叶绿素含量的差异,并对叶绿素含量与光谱反射率进行了相关分析。研究结果表明:不同月份之间胡杨叶片叶绿素a、叶绿素b、叶绿素a+b含量差异极显著(p<0.01),叶绿素含量最高的月份是8月,最低的月份是10月;胡杨叶片的可见光-近红外波段反射光谱与绿色植物的反射光谱曲线是一致的,不同波长位置的光谱反射率与叶绿素含量的相关性因波长不同而存在明显差异。在510～710 nm,胡杨光谱反射率与叶绿素含量之间呈极显著负相关,其中645 nm处的相关系数最低(r在-0.45～-0.35之间);在415～510 nm和710～920 nm,胡杨光谱反射率与叶绿素含量之间呈极显著正相关,其中769 nm处相关系数最高(r在0.34～0.41之间)。645 nm和769 nm是两个具有特殊意义的波长位置,用于指示胡杨叶片叶绿素与反射率的相关性。

In Tarim River Basin, Populus euphratica has important biological and ecological protection values. Remote sensing tech- niques provide quickly and timely information, which is beneficial to protecting and utilization the Populus euphratica woodland resources. In this study, field spectral radiometer ISI921VF - 512 was used to monthly measure the reflectance of leaves of Populus euphratica in the visible - near infrared band from May to October 2011. At the same time the chlorophyU a, chlorophyll b and chlorophyll a ＋ b content （mg/g Fw, mg/g Dw and rag/m2） of leaves ofPopulus euphratica were determined. Analysis of variance （ANO-VA） and correlation analysis were performed to test the significant effects of the chlorophyll content on different months and the relationships between reflectance and the chlorophyll content, respectively. The results were as follows： There were significant differences （p 〈 0. 01 ） of chlorophyll a, chlorophyll b, chlorophyll a ＋ b content among months. The reflectance spectrum of leaves of Populus euphratica was consistent with the green plant reflectance spectrum. The significances of correlation coefficients between chlorophyll contents and reflectance differed from different band wavelengths. During 510 -710 nm, there was a significant negative correlation be- tween chlorophyll and reflectance, and the lowest correlation coefficients were found at the 645 nm （r = - 0. 45 - - 0. 35 ）. On the other hand, between 415 - 510 nm and 710 -920 nm, there was a significant positive correlation between chlorophyll and reflectance, and the highest correlation coefficients were found at the 769 nm （ r = 0. 34 - 0. 41 ）. The wavelength positions of 645nm and 769nm have a particular significance for indicating the correlations between chlorophyll and reflectance of leaves of Populus euphratica.