长白山常见树种新叶与老叶的光谱特征差异分析

Hyperspectral Differences Between New and Old Leaves of Dominant Tree Species in Changbai Mountain

揭示新叶与老叶叶片的叶属性及其光谱特征的差异,不仅对于植被生理生态参数的无损监测有重要意义,而且可为林业定量遥感提供更多理论支撑。对长白山8个树种的新叶和老叶叶片进行采样和光谱测量,获取新老叶片的反射率光谱曲线,并进行一阶微分变换和光谱指数计算,同时实验测定比叶面积(SLA)、叶含水率、叶氮含量及叶碳含量等叶属性参数。利用方差分析与相关性分析方法,研究不同树种新老叶片在理化性质、光谱特征上的差异,并分析两者的相关性在新老叶之间的差异。结果表明:(1)多个树种的叶属性在新老叶的表现出显著差异。除叶碳含量之外,其他3个叶属性均在多个树种新老叶间表现出显著的差异性,叶碳含量在新老叶间均不存在显著差异。(2)不同树种叶片光谱特征在新老叶间的差异不一致,仅枫桦、裂叶榆、三角槭和红松的新老叶具有较明显的光谱曲线特征差异,枫桦新老叶在光谱三边特征表现出显著差异,尤其是红边。(3)叶属性与光谱信号的相关性在新老叶间表现出显著差异,说明光谱对新老叶叶属性的指示能力不同。近红外光谱反射率对老叶叶氮含量的指示能力强于新叶,而多个光谱指数对新叶含水率和叶碳含量的指示能力强于老叶。研究表明新老叶间不仅叶属性和光谱特征存在差异,而且二者之间的相关性也不同,这对于森林叶属性的无损观测过程中选择代表性叶片具有指导意义。

Revealing the differences in foliar traits and leaf spectral characteristics between new and old leaves is important for the non-destructive monitoring of vegetation physiological and ecological parameters and can provide more theoretical support for quantitative remote sensing in forestry.This study sampled new and old leaves of 8 tree species in Changbai Mountain,and their reflectance spectra were measured.Then,the first-order derivative transformations and spectral indices were calculated.Foliar traits such as specific leaf area(SLA),leaf water content,leaf nitrogen content,and leaf carbon content were measured in our laboratory.Using variance analysis and correlation analysis,the differences in physicochemical properties and spectral characteristics between the old and new leaves of different tree species were investigated,and the differences in related coefficients were also analyzed between the old and new leaves.The results show that:(1)Multiple foliar traitsof thetree species showed significant differences between old and new leaves.Except for leaf carbon content,which did not differ significantly between old and new leaves,the other three traits showed significant variability between old and new leaves.(2)The differences in the spectral characteristics of different tree species were inconsistent between the old and new leaves.Only the old and new leaves of Betula costata,Ulmus laciniata,Acer buergerianum,and Pinus koraiensis showed more obvious differences in spectral curve characteristics.Betula costata showed significant differences in the spectral trilateral characteristics.(3)The correlation between leaf traits and spectra showed significant differences between old and new leaves,and the spectra have different abilities to indicate leaf traits.Near-infrared spectrum spectral reflectance is a better indicator of leaf nitrogen content for old leaves than for new leaves.In contrast,many spectral indices indicate better water and leaf carbon content in newer and older leaves.This study shows that there are not only differences in leaf properties and spectral characteristics but also differences in their correlations between old and new leaves.This study has a guiding significance for selecting representative leaves in the non-destructive observation of forest leaf properties.