Above Ground Biomass
Intimately known as the lungs of the earth, forests sequester carbon dioxide from the atmosphere for stem growth and mass gains thus are a major source of terrestrial carbon. Forests provide many environmental services which are critical such as carbon storage, the hydrological cycle, the atmospheric composition, sediment transport, albedo, global temperatures and wildlife habitat for 80% of the world’s terrestrial biodiversity, however, with average global CO2 concentrations reaching 412.5ppm due to increases in carbon dioxide emissions from fossil fuels and other large-scale industrial emissions, managing and accounting for carbon stocks in forests is paramount. New Zealand’s Emissions Trading Scheme (NZ ETS) is a tool that promotes a change in behaviour of producers to limit their emissions. Built using years of growth modelling techniques for tree stem growth, volume, height and wood density, it provides a simple default look-up table for accounting carbon stocks in a forested area. This study endeavours to identify the spatial variations in above ground biomass within forest plantations using airborne LiDAR derived point clouds and to compare that with the NZ ETS look-up tables. The area of study was the Bottle Lake Forest using LiDAR point clouds obtained from the 2018-2019 Ashley River and Christchurch survey and relationships made between AGB from plot data with LiDAR metrics. Whilst not violating the regression assumptions in the predictors, AGB estimation from the predictive performance of the model yielded an R2 value of 0.83 given that there were few forest sampling plots in total to cover the Bottle Lake Forest. Its critical p-value from the F-Statistic test assessed the predictors in the model and found that the predictors did contribute significantly to the model performance under a significance level of 0.05 and therefore supporting the alternate hypothesis that carbon stockings from LiDAR derived AGB estimates were more accurate than using the NZ ETS look-up tables.
