Evaluation of the effects of forest management strategies on carbon sequestration in evergreen broad-leaved (Phoebe bournei) plantation forests using FORECAST ecosystem model

In the context of global climate change, it is critical to study how different forest management practices affect forest carbon sequestration. This is especially important for forest managers and policy makers who will have to design and implement appropriate mitigation and adaptation strategies. Previous research has focused on coniferous plantations with rare examination of plantations of evergreen broadleaved species. Phoebe bournei (Hemsley) Yang, as one of the representative species of subtropical evergreen broadleaf forests in Asia, has a unique potential to increase forest carbon sink. In this study, field data were combined with the forest ecosystem management model FORECAST to estimate the impacts of different forest management strategies (combinations of planting densities from 1000 to 4000 trees ha-1, rotation lengths from 20 to 80 years, and different harvesting intensities: stem-only, whole-tree and complete-tree) on carbon sequestration of Phoebe bournei plantations in south-eastern China. Field and previously published data were used to calibrate the model for stand biomass pools accumulation, stand density and mortality, light response curves, photosynthetic efficiency, and data on soil nutrient pools, for three different site conditions. The results showed that the most suitable planting density to maximize carbon sequestration in Phoebe bournei plantations is 2000-3000 trees ha-1. Long rotations (80 years) are better than shorter rotations (20 or 30 years) for the long-term maintenance of site productivity, though the recommended rotation length for maximizing carbon sequestration and maintaining forest productivity is 40-60 years. As for harvesting intensity, stem-only harvesting is the most suitable strategy to manage for carbon sequestration when maintaining long-term site productivity, with whole-tree and complete-tree harvesting constituting less optimal options. Our modelling exercise indicates that Phoebe bournei plantations have great potential for carbon sequestration if they are managed under sustainable and ecologically-based strategies. Given that forests are important in the global carbon cycle, it is recommended that afforestation efforts in relevant sub-tropical regions use appropriate broad-leaved species that can help resolve ecological and socio-economic challenges