Estimating forest LAI profiles and structural parameters using a ground-based laser called 'Echidna(R)

Abstract

There are many techniques for measuring leaf area index (LAI) and forest canopy foliage profiles but their accuracy is questionable. This paper briefly reviews current methods of estimating forest LAI and presents a novel, ground-based laser system, Echidna that can make a wide range of measurements of forest structure, including LAI. Here, use of the system to provide field data and derived gap probabilities in the form of a 'hemispherical photograph with range' is demonstrated. The results show consistency and reproducibility and do not depend on special conditions for the natural light field.

Using VEGNET In-Situ Monitoring LiDAR (IML) to Capture Dynamics of Plant Area Index, Structure and Phenology in Aspen Parkland Forests in Alberta, Canada

“…These data are subsequently downloaded and processed to produce an estimate of Plant Area Index following methods by [3] and [15] for PAI retrieval based on LiDAR data. The PAI estimates are typically presented in three forms: (i) a cumulative PAI as a function of canopy height; (ii) the cumulative PAI derivative, termed the Plant Area Volume Density (PAVD); and (iii) the maximum cumulative PAI, which represents the top-of-canopy PAI, incorporating intercepted laser measurements through the full canopy depth.…”

“…The laser beam is directed at a rotating prism that reflects the laser at a fixed angle of 57.5° zenith or the "hinge angle" [15]. As described by [18], the hinge angle is the theoretically optimum sample angle at which estimates of leaf area are least sensitive to assumptions of leaf angle distribution.…”

“…When laser pulses emitted in the visible or near-infrared comes into contact with an object, part of that energy is reflected back toward the instrument and triggers the recording of its distance and intensity [12]. TLS systems typically employ vertical and horizontal scanning about a fixed point of observation, providing a hemispherical representation of biomass distribution in the forest leaves, branches and trunks, which allows exploring foliage angle distributions and clumping [3,[13][14][15].…”

Correction of Erroneous LiDAR Measurements in Artificial Forest Canopy Experimental Setups

“…First, in order to properly process the data, the point clouds were projected to a 2D format. According to [25], the most efficient file structure for extracting data is the projection used by [26] for hemispherical photographs. This format, also known as "plate carrée", is often used for cartographic and GIS data processing.…”

Uso do laser scanner terrestre na estimativa de parâmetros biométricos em povoamentos florestais

“…Dentre as formas de estimativa do volume individual da árvore destaca-se o uso de seções do tronco como variável independente em modelos volumétricos ou funções de afilamento. Estudos tem focado nesta técnica enquanto se mostra eficiente na estimativa dos volumes individuais (GARCÍA et al, 2011;HAUGLIN et al, 2013 Autores têm estudado outras variáveis e parâmetros que possam ser extraídos pelo sistema TLS, alguns desses fatores com maior quantidade de abordagens e outros ainda em estudos iniciais e exploratórios, como biomassa de tronco, galhos e folhas (CALDERS et al, 2015;KANKARE et al, 2013;NEWNHAM et al, 2015;YU et al, 2013), índice de área foliar (JUPP et al, 2009;YANG;DONG, 2013;ZHENG;MOSKAL, 2012), tamanho de clareiras (DANSON et al, 2007;ZHAO et al, 2012), radiação do dossel ( VAN LEEUWEN et al, 2013) Para estimativa do volume total da árvore é executada a soma do volume de sucessivas seções de tronco ao longo do fuste, desde a altura de 0,1m até a altura total. O volume de cada seção é obtido pela aplicação de uma Equação de Cubagem (Equação 3), tendo sido a proposta por Smalian a equação utilizada neste trabalho, dada por:…”