Determining woody-to-total area ratio using terrestrial laser scanning (TLS)

Abstract

Accurately determining woody-to-total area ratio (WTA) is a key step to indirectly retrieve leaf area index (LAI) from terrestrial laser scanning (TLS) data. In this work, we first collected both individual tree and forest plot point cloud data (PCD) from broadleaf-and coniferous tree species and leaf characteristics using both side-lateral and full field-of-view TLS field setups with scan distances between 2.5 to 28 meters. Using a local geometrical feature-based algorithm, the generated PCD were automatically classified into three different categories including photosynthetic canopy components, non-photosynthetic canopy components, and bare earth. To convert each classified point into a surface area, we then developed and validated a novel approach that considers sampling space, laser incidence angle, and leaf orientation information. The estimated surface areas from this approach showed strong agreements with validation datasets for single leaf (91.44 %), photosynthetic (95.64 %), and non-photosynthetic canopy components (89.60 %) of an artificial tree and stems of an old-growth coniferous tree (93.53 %), two individual broadleaf trees (98.31 % and 97.46 %) and a broadleaf forest plot (90.26 %). By doing this, we computed the parameter WTA for an individual artificial tree (10.90 %), an old-growth coniferous tree (29.97 %), two individual broadleaf tree (14.83 % and 4.27 %) and four natural forest stands ranging from 7.74 % − 15.57 %, respectively. The proposed method can effectively improve the accuracy of retrieving true LAI by removing the effects of woody components and converting each point into a surface area.

An Overview of Global Leaf Area Index (LAI): Methods, Products, Validation, and Applications

“…The range of typical values of woody‐to‐total‐plant‐area ratio ( α , equation ) for different vegetation types. (1) Sonnentag et al (); (2) Asner, Wessman, et al (); (3) Deblonde et al () and Z. Li et al (); (4) J. M. Chen () and Weiskittel and Maguire (); (5) Gower et al (), Z. Liu et al (), and Ma et al (); (6) Kalácska et al (); and (7) Olivas et al ().…”

Retrieval of the Fraction of Radiation Absorbed by Photosynthetic Components (FAPARgreen) for Forest using a Triple-Source Leaf-Wood-Soil Layer Approach

“…In this study, we used a constant value of the woody-to-total area ratio for each forest type and derived the WAI from the PAI value for the peak growth stage. We obtained woody-to-total area ratios for different forest types (ENF, EBF, DBF, and DNF) from an extensive literature review [58,[64][65][66][67]-the statistical metrics, including the mean, standard deviation, and coefficient of variation, are shown in Table 4. These results show that the woody-to-total area ratios for different forest types vary from 0.158 to 0.3.…”

Light interception modelling using unstructured LiDAR data in avocado orchards

“…These parameters were the transmission coefficient β and the absorption coefficient α, which estimate the proportion 1. Future work will consider automated approaches such as those presented by Lalonde et al (2006), Olofsson et al (2014) and Ma et al (2016a) Fig. 8: A point cloud model of a target tree with points manually labelled as woody matter and foliage.…”