Towards More Accurate Tree Biomass Estimation and Projections: Tree Growth, Hardwood Competition, Prescribed Fire and Environmental Factors

Abstract

Estimating tree biomass is a common task in forest management, and generalized allometric equations are popular tools used for this estimation. However, the most accurate estimates come from site- and species-specific models, which are often unavailable due to their high cost and destructive nature. In this study, we provided new site- and species-specific biomass allometric models for two slash pine stands located in the coastal regions of Mississippi, USA. One stand grows in a high-salinity environment under a long fire return interval (~7–10 years), while the other is in a low-salinity environment with a frequent fire return interval (~2–3 years). We explored the benefits of including an additional wood density variable in developing these models. Our results demonstrated that where environmental variations are high, including a wood density variable may improve the biomass allometric model.

Additionally, using four longleaf pine (LLP) stands, we evaluated the effects of inter- and intra-specific competition on pine tree growth under different fire regimes. Our results showed significant relationships between competition and tree growth. We saw that while LLP trees face lower competition from their hardwood neighbors, this hardwood competition had a larger effect on basal area growth than intra-specific competition. We also found that the tree competition model had greater variance explanation under burning conditions. Finally, we recommended the inclusion of a neighborhood competition variable in forest growth models, which we suggest may improve forest biomass and carbon sequestration projections.