Sunlit coponents’ fractions and gap fraction of canopies based on POV-ray
Sunlit coponents’ fractions and gap fraction of canopies based on POV-ray
复制标题
DOI：
10.11834/jrs.20100203
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Ye Lizao
中科院分区：
文献类型：
--
作者：
Ye Lizao
四组分（日照叶、遮荫叶、日照土壤和遮荫土壤）和林隙分数是反映植被冠层结构的特征几何参数，对植被的辐射传输有重要影响。本文采用POV-ray软件，高效、准确地计算了三维冠层的四个组成部分和林隙组成。在同一个三维冠层结构上，利用POV-ray模型和Radiosity-Graphics组合模型（RGM）计算的4个组分的比例和林窗比例具有较好的一致性，利用CLAMP模型生成的更多的三维冠层结构，研究了4个组分的比例和林窗比例的特征。CLAMP模型的关键参数包括播种方式、丛生指数、平均叶角（ALA）和叶面积指数（LAI）。通过分析这些参数对4个组分分数和林隙分数的敏感性，得到了4个组分分数和林隙分数的变化特征，结果表明：丛生指数能有效地控制叶片的空间分布，影响场景中植被和土壤的相对比例。因此，丛生指数对林隙组分和四种组分的分布格局有很大的影响。平均叶角影响结果的各向异性。当平均叶角较大时，各向异性的幅度较大。与其他参数相比，当场景的行结构明显时，行效应对四个分量的分数和间隙分数的影响是主要的。因此，当冠层为行状结构时，四个组分的分数和林隙分数的特征变化比均匀冠层复杂。同时，对3个典型生长阶段的行冠层结果进行了比较，结果表明：在生长初期，土壤对4个组分的贡献率和林窗组分的贡献率均高于植被。随着叶面积指数的增大，植被对结果的影响逐渐增强，日照叶率表现出更明显的各向异性。本文的研究表明，POV-ray是遥感技术定量研究植被的有力工具，具有广阔的应用前景。
The fractions of four components (sunlit leaves, shaded leaves, sunlit soil and shaded soil) and gap fraction are characteristic geometric parameters of canopy’s structure, and have great influence on radiative transfer of the vegetation. In this paper, POV-ray software was introduced to efficiently and accurately calculate the four components’ fractions and gap fraction of three-dimensional (3D) canopies. With the good agreements of computed four components’ fractions and gap fraction be- tween POV-ray and Radiosity-Graphics combined Model (RGM) based on the same 3D canopy structure, more 3D structures generated by the Clumped Architecture Model of Plants (CLAMP) model were used to study the characteristics of four compo- nents’ fractions and gap fraction. The key parameters of CLAMP model include sowing scheme, clumping index, average leaf angle (ALA) and leaf area index (LAI). By analyzing the sensitivity of these parameters to four components’ fractions and gap fraction, the changing features of four components’ fractions and gap fraction were found. The results show that: clumping index can effectively control the spatial distribution of leaves, which affects the relative proportion of vegetation and soil in the scene. Therefore, clumping index has a great impact on the distribution pattern of four components’ fractions and gap fraction. Average leaf angle influences the anisotropy of the results. When the average leaf angle is larger, the magnitude of anisotropy is higher. Compared with other parameters, the impact of row effect on the four components’ fractions and gap fraction is primary when the scene’s row structure is obvious. Therefore, when the canopy is in a row structure, the characteristic change of four components’ fractions and gap fraction is more complex than that of homogeneous canopy. At the same time, the results of row canopy in three typical growing stages were compared, which shows that soil has a higher contribution to the four components’ fractions and gap fraction than that of vegetation at the early stage. With the increase of leaf area index, the influence of vegetation on the result is gradually enhanced and the fraction of sunlit leaves shows more apparent anisotropy. The research of this paper shows that POV-ray is a powerful tool to quantitatively study vegetation by remote sensing technology, and has potential of wider applications.