The utility of LiDAR for landscape biodiversity assessment
Creators: name: Miura, Naoko
Publisher: name: RMIT University
Year: 2024

description: The potential of LiDAR to inform landscape biodiversity assessments is investigated. The objectives of this research are to examine how LiDAR discrete return and full waveform systems can be used to recover forest structure information, how LiDAR intensity can be used for biodiversity assessment and whether the utility of LiDAR can compliment traditional survey methods. Experiments using LiDAR discrete return and full waveform systems were conducted. An eight category forest characterisation scheme (FCS) derived from a LiDAR full waveform system was proposed and validated using field derived variables. Intensity variables derived from LiDAR full waveform were explored to determine its utility. The applicability of the proposed scheme was also examined by comparing two independent LiDAR full waveform datasets of the same area and by comparing to commonly used field-based biodiversity metrics. From these surveys, it was concluded that conventional discrete return systems can be used to recover forest structure information for forests with an ecologically simple structure. Vertically stratified LiDAR intensity, using range information, has potential to recover canopy cover, grass cover and the amount of fallen trees. The combination of LiDAR intensity mean and standard deviation can be used to differentiate forest types; sparse canopy with few fallen trees or dense canopy with many fallen trees. The LiDAR full waveform system experiment demonstrated that the FCS allows for quantification of gaps (above bare ground, low vegetation and medium vegetation), canopy cover and its vertical density as well as the presence of various canopy strata (low, medium and high). Regression analysis showed LiDAR derived variables were good predictors of field recorded variables. The FCS clearly showed the potential of full waveform LiDAR to provide information on the complexity of habitat structure. The exploratory analysis of intensity derived from LiDAR full waveform system displayed the potential of intensity variables to recover forest structure variables, however further study is required to account for the utility of intensity variables. In terms of the applicability of the FCS, a multiple dataset comparison showed that the FCS was resilient when recovering canopy cover, openings above the ground and medium vegetation, and presence of mid-storey vegetation and high trees, however it was less so when recovering openings above low vegetation, the presence of understorey vegetation and vertical canopy density of high trees. These last categories were considered to be affected by the difference in the pulse repetition frequency. Obtaining sufficient multiple returns by setting an appropriate pulse repetition frequency is the key to maintaining good performance of the scheme. The FCS was also found to be incompatible with commonly used field-based biodiversity metrics due to the qualitative and subjective measurements used in field-based metrics. Refinement in field methodology would be necessary for measuring structural variables to maximise the utility of FCS in their metrics. This study demonstrated how LiDAR technology can be used to derive forest structure information for landscape biodiversity assessment. The method proposed in this study is versatile, repeatable and quantitative, which can provide useful information to inform decisions and conservation strategies.