Estimates of changes in forest biomass using lidar in the area of sustainable forest management in the south-western Amazon

Abstract

Estimates of biomass and carbon stocks associated with Reducing Emissions from Deforestation and Forest Degradation (REDD) require information reliability and accuracy. Since obtaining the variables in the field consumes time and resources and, in some cases, is not feasible due to access difficulties, the study of alternative methods has made it possible to extract information from forest areas reliably. The airborne laser systems, based on LiDAR (Light Detection and Ranging) technology, allow obtaining three-dimensional information about the earth’s surface with high precision. The objective of this study was to test the use of LiDAR data to estimate changes in canopy cover and AGB, associated with forest in the Brazilian South-Western Amazon. Overflying occurred in 2013, 2014 and 2015, before and after the exploration, together with field data collection in ten permanent plots where measurement of the diameter of all individuals with DBH ≥ 10 cm at 1.30 m above the ground was carried out. A regression model to estimate changes in AGB was developed from the LiDAR data and field data. A simple differentiation of the canopy covers, before and after the exploration, identified areas where the canopy with more than 10 m of height was removed. The mean reduction in AGB was 21.36 Mg.ha-1 (8.9%). The reduction in canopy cover was estimated at 0.08 ha (8.2%). The model can be considered satisfactory, since it presented good statistical results as Raj 2 of 0.74, RMSE of 21.10 Mg.ha-1 and test of significance F of 27.19. This work demonstrates the potential of LiDAR for quantification of canopy structural changes in tropical forests. These results indicate that LiDAR can be a valuable tool for REDD-related carbon monitoring systems and may provide a means of quantifying changes in above-ground carbon attributable to logging activities. Due to the difficulties associated with field work in remote areas, it is acceptable that the remeasurements be obtained with from LiDAR data, for the purposes of monitoring AGB changes.