基于植物冠层分析仪单线多角度测量的叶面积指数与叶倾角分布关系

Relationship between leaf area index and leaf angle distribution based on single line,multi-angle measurement by TRAC

叶面积指数(LAI)和叶倾角分布(LAD)作为研究植被冠层结构的重要参数,二者间存在一定的定量关系。以白桦(Betula platyphylla)纯林为研究对象,基于单线多角度观测结果、Norman和Campbell线性最小二乘反演技术(NC技术)以及Compbell模型三者结合,分析LAI和LAD间的定量关系。NC技术能很好地反演叶倾角分布,对实测的叶倾角分布的解释能力达90%以上;根据NC技术计算得到的叶倾角概率密度较实际偏大,Campbell模型模拟结果则偏小,尤其在[0°,10°]区间内;2种技术存在一种互补关系,而2种技术计算得到的结果取平均时,对实测叶倾角分布的解释能力得到一定提高,达96%以上;此外,多角度测量中利用NC技术反演时,叶倾角分布区间个数一般以取观测太阳天顶角个数的1/2为最佳。本研究为LAI和LAD的间接测量提供了方法,同时为大范围的LAI测量提供了验证手段,也为定量遥感模型参数优化提供了理论依据。

A quantitative relationship exists between leaf area index（ LAI） and leaf inclination angle distribution（ LAD）,two important parameters in study of vegetation canopy structure. In this study,the quantitative relationship between LAI and LAD of Betula platyphylla pure forest was analyzed based on the data of single line,multi-angle measurement by TRAC,with Norman and Campbell’s linear least-square inversion technique（ NC technique） and Campbell model.The NC technique received a very good inversion result of leaf inclination angle distribution,and its interpretation capacity to the measured leaf angle distribution was up to 90%. The leaf inclination probability density calculated by the NC technique was slightly higher than the real density,while the fitting result of Campbell model was relatively lower,especially in the interval of[0°,10°]. Considering the complementary relationship between the results of the two techniques,the correlation between the mean values of the results of the two techniques and the measured results was up to 96%. Besides,when using the NC technique,it is best that the number of the leaf angle interval is half of the number of the solar zenith angle during multi-angle measurements. Our study provides an algorithm for LAI and LAD and a theoretical basis for parameter optimization of quantitative remote sensing. Meanwhile,the quantitative inversion of LAI can provide strong authentication in a wide range of LAI measurements.