Abstract
This paper presents an open-source canopy height profile (CHP) toolkit designed for processing small-footprint full-waveform LiDAR data to obtain the estimates of effective leaf area index (LAIe) and CHPs. The use of the toolkit is presented with a case study of LAIe estimation in discontinuous-canopy fruit plantations. The experiments are carried out in two study areas, namely, orange and almond plantations, with different percentages of canopy cover (48% and 40%, respectively). For comparison, two commonly used discrete-point LAIe estimation methods are also tested. The LiDAR LAIe values are first computed for each of the sites and each method as a whole, providing “apparent” site-level LAIe, which disregards the discontinuity of the plantations' canopies. Since the toolkit allows for the calculation of the study area LAIe at different spatial scales, between-tree-level clumping can be easily accounted for and is then used to illustrate the impact of the discontinuity of canopy cover on LAIe retrieval. The LiDAR LAIe estimates are therefore computed at smaller scales as a mean of LAIe in various grid-cell sizes, providing estimates of “actual” site-level LAIe. Subsequently, the LiDAR LAIe results are compared with theoretical models of “apparent” LAIe versus “actual” LAIe, based on known percent canopy cover in each site. The comparison of those models to LiDAR LAIe derived from the smallest grid-cell sizes against the estimates of LAIe for the whole site has shown that the LAIe estimates obtained from the CHP toolkit provided values that are closest to those of theoretical models.
Highlights
K NOWLEDGE of 3-D vegetation structure and foliage amount is important for many ecological applications [1]
The main aim of this study is to present an open-source canopy height profile (CHP) toolkit as a tool to examine the influence of the discontinuity of canopy cover on leaf area index (LAIe) retrieval from small-footprint full-waveform airborne LiDAR data
This study has presented the use of an open-source CHP toolkit for the estimation of LAIe in a discontinuous-canopy environment of fruit plantations
Summary
K NOWLEDGE of 3-D vegetation structure and foliage amount is important for many ecological applications [1]. The estimation of LAI still remains problematic [9], [10], as the only way of retrieving the true value of LAI is by harvesting. This is, a destructive method that is not really feasible at larger scales [9] or for long-term monitoring [11]
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