Abstract
This research examines the role of canopy cover in influencing above ground biomass (AGB) dynamics of an open canopied forest and evaluates the efficacy of individual-based and plot-scale height metrics in predicting AGB variation in the tropical forests of Angkor Thom, Cambodia. The AGB was modeled by including canopy cover from aerial imagery alongside with the two different canopy vertical height metrics derived from LiDAR; the plot average of maximum tree height (Max_CH) of individual trees, and the top of the canopy height (TCH). Two different statistical approaches, log-log ordinary least squares (OLS) and support vector regression (SVR), were used to model AGB variation in the study area. Ten different AGB models were developed using different combinations of airborne predictor variables. It was discovered that the inclusion of canopy cover estimates considerably improved the performance of AGB models for our study area. The most robust model was log-log OLS model comprising of canopy cover only (r = 0.87; RMSE = 42.8 Mg/ha). Other models that approximated field AGB closely included both Max_CH and canopy cover (r = 0.86, RMSE = 44.2 Mg/ha for SVR; and, r = 0.84, RMSE = 47.7 Mg/ha for log-log OLS). Hence, canopy cover should be included when modeling the AGB of open-canopied tropical forests.
Highlights
Tropical forests sequestered 2.4 ± 0.4 pentagrams of carbon annually from 1990–2007, making them an important terrestrial carbon sink [1]
The mean height of trees delineated within the Light detection and ranging (LiDAR) imagery (i.e. maximum canopy height (Max_CH)) and average field tree heights had a mean difference of 60 cm
Comparison of five least-square-regression models and five support vector regression (SVR) models indicated that the best-supported model used log-log regression and had canopy cover as the only explanatory variable, closely followed by the SVR model that included both Max_CH and canopy cover (Table 1, Fig 3)
Summary
Tropical forests sequestered 2.4 ± 0.4 pentagrams of carbon annually from 1990–2007, making them an important terrestrial carbon sink [1]. Tropical land use changes, especially those leading to deforestation can contribute to carbon emissions from these carbon stocks [1]. From 2001–14, at 14.4%, Cambodia had the fastest acceleration in the annual forest rate per annum [2]. This potentially leaves behind a largely degraded landscape containing fragments. Canopy Cover Is an Important Determinant of AGB in Open Canopied Forests study design, data collection and analysis, decision to publish, or preparation of the manuscript
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