Retrieving forest canopy clumping index using terrestrial laser scanning data

REMOTE SENSING OF ENVIRONMENT

卷:210

Article

Ma, Lixia^1,2  Zheng, Guang¹  Wang, Xiaofei^2,3  Li, Shiming⁴  Lin, Yi⁵  Ju, Weimin¹ 

[1] Nanjing Univ, Int Inst Earth Syst Sci, Nanjing 210023, Jiangsu, Peoples R China

[2] Jiangsu Prov Key Lab Geog Informat Sci & Technol, Nanjing 210023, Jiangsu, Peoples R China

[3] Nanjing Univ, Collaborat Innovat Ctr South China Sea Studies, Nanjing 210023, Jiangsu, Peoples R China

[4] Chinese Acad Forestry, Inst Forest Resource & Informat Tech, Beijing 100091, Peoples R China

[5] Peking Univ, Sch Earth & Space Sci, Beijing 100871, Peoples R China

关键词: Forest clumping index;    Terrestrial laser scanning;    Point cloud slicing;    Gap size;    Leaf area index;   

DOI  :  10.1016/j.rse.2018.03.034

来源: Elsevier

【 摘 要 】

Quantitatively characterizing the non-random spatial distributions of foliage elements including coniferous needles is critical to map the radiation regime and retrieve the biophysical parameters of a given forest canopy from three-dimensional (3-D) perspective. Different experimental setups bring various challenges to the process of retrieving forest canopy clumping index (CI) using terrestrial laser scanning (TLS). In this paper, through developing a voxel-based gap size (VGS) algorithm, we compared the TLS-based forest canopy CIs with the ones obtained using the digital hemispherical photography (DHP)-based and tracing radiation and architecture of canopy (TRAC)-based approaches. Moreover, we investigated the effects of incident directions of solar beams, voxel size, and woody canopy components on the final retrieval accuracy of forest canopy CIs. Our results showed that: (1) TLS -based CIs accounted for 81% (N = 30, p < 0.001) of variations in the DHP-based method. (2) the anisotropic nature of forest canopy CIs suggested that a relatively comprehensive TLS data of a forest canopy was required to investigate the 3-D spatial variations of forest gap size distributions and CIs. (3) The user defined laser sampling spacing was a reliable reference value to determine the voxel size when using the VGS algorithm. (4) It was recommended to separate woody canopy components when computing the forest canopy CI, especially for forest plots with higher proportions of woody material. (5) The effects of the penumbra on TLS based forest canopy CIs were much more limited compared with the traditional optical instruments (i.e., DHP or TRAC). This work provides a solid foundation to dramatically improve the retrieval accuracy of leaf area index (LAI) using TLS.

【 授权许可】

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