Using terrestrial laser scanning and empirical allometries to develop error estimates for tree biomass in mangroves

Given the value of ecosystem services provided by mangrove forests, land managers and conservationists are increasingly interested in quantifying their structure and biomass at multiple scales. Due to numerous challenges with traditional forest mensuration methods in these forests, scientists are increasingly exploring remote sensing-based approaches. Here we report on efforts to quantify mangrove volume and biomass in monospecific Avicennia germinans stands. Using high density terrestrial laser scanning (TLS), we measured 176 trees in three plots in Cedar Key, Florida, USA. Following merging, cleaning and segmentation of the collected point clouds, we fit quantitative structure models (QSM) to estimate the volume and mass (volume times density) of the main trunk and lower branches of 176 individual trees. Comparing the QSM mass estimates to mass predicted from empirical allometric relationships, we show that TLS captures approximately 65% of the trees volume (and thus mass) on average. We also show that the mean estimate does not change as a function of tree size. Our work highlights the potential of TLS to aid scientists and land managers in their efforts to measure trees, provides error estimates to aid similar research efforts, and identifies areas in need of methodological improvements for future work.