globalchange  > 影响、适应和脆弱性
DOI: 10.1016/j.foreco.2015.09.030
Scopus记录号: 2-s2.0-84942585285
论文题名:
An improved theoretical model of canopy gap probability for Leaf Area Index estimation in woody ecosystems
作者: Woodgate W.; Disney M.; Armston J.D.; Jones S.D.; Suarez L.; Hill M.J.; Wilkes P.; Soto-Berelov M.; Haywood A.; Mellor A.
刊名: Forest Ecology and Management
ISSN:  0378-1127
出版年: 2015
卷: 358
起始页码: 303
结束页码: 320
语种: 英语
英文关键词: Clumping ; Eucalypt ; Gap fraction ; Leaf area index ; Projection function ; Woody area index
Scopus关键词: Ecology ; Ecosystems ; Forestry ; Area index ; Clumping ; Eucalypt ; Gap fraction ; Leaf Area Index ; Projection function ; Three dimensional computer graphics ; accuracy assessment ; canopy gap ; dicotyledon ; experimental study ; forest ecosystem ; leaf area index ; model validation ; sensor ; stand dynamics ; theoretical study ; three-dimensional modeling
英文摘要: This study presents an improved theoretical formulation of the gap probability (Pgap) model, typically applied to indirectly estimate LAI in woody ecosystems. Specifically, we present the woody element projection function (GW), which characterises the angular contribution of non-leaf facets in woody ecosystems, and explain how it may be used to improve the accuracy of indirect LAI retrieval via the application of the Pgap model. GW enables separate treatment of the leaf and wood projection functions in the theoretical model, important in the typical case when Pgap includes the influence of both leaf and wood canopy elements. This study then validates the improved theoretical model using experimental data. Here, Pgap was calculated from a 3D scattering model, parameterised with highly-detailed 3D explicit tree models reconstructed from empirical data of a sampled forest stand. The experimental data was then used to quantify additional effects of view zenith angle (VZA), leaf angle distribution (LAD), and the influence of woody components on the indirect estimation of LAI and within-crown clumping via application of the Pgap model. Additionally, we quantify within-crown clumping of reconstructed tree models for leaf and woody elements both together and separately for the first time. LAI errors up to 25% at zenith were found when ignoring GW and were shown to be a function of VZA. Conversely, at the approximate 57.3° (1 radian) VZA, results show that there was no effect of GW due to the wood projection function converging with leaf projection functions. Within-crown clumping factors for the modelled dataset were as low as 0.35. Consequently, making a common assumption of a random distribution of canopy elements at the crown scale would lead to an LAI error of up to 65% for the 3D forest stand. We also conclude that when estimating LAI via the Pgap model, separate treatment of canopy material projection '. G' functions are required at VZA's other than 1 radian. The findings of this study and the extended physical formulation presented here impact upon indirect Pgap LAI retrieval methods from sensors of all platforms in clumped canopy environments or canopies with woody (non-leaf) elements contributing to the extinction of light. © 2015 Elsevier B.V.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/65255
Appears in Collections:影响、适应和脆弱性

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作者单位: School of Mathematical and Geospatial Sciences, RMIT University, GPO Box 2476V, Melbourne, VIC, Australia; Cooperative Research Centre for Spatial Information, Carlton, VIC, Australia; Department of Geography and NERC National Centre for Earth Observation, University College London, Gower Street, London, United Kingdom; Remote Sensing Centre, Science Delivery, Department of Science, Information Technology, and Innovation, 41 Boggo RoadQLD, Australia; Joint Remote Sensing Research Program, School of Geography, Planning and Environmental Management, University of Queensland, St Lucia, QLD, Australia; Department of Earth System Science and Policy, University of North Dakota, Clifford Hall, 4149 University Drive, Grand Forks, ND, United States; ITC, University of Twente, PO Box 217, AE Enschede, Netherlands; Department of Environment, Land, Water and Planning, East Melbourne, VIC, Australia

Recommended Citation:
Woodgate W.,Disney M.,Armston J.D.,et al. An improved theoretical model of canopy gap probability for Leaf Area Index estimation in woody ecosystems[J]. Forest Ecology and Management,2015-01-01,358
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