Combining long-term field data and remote sensing to test how tree diversity influences aboveground biomass recovery in logged tropical forests

There is a worldwide loss in tropical forests with the remaining areas being more degraded secondary forest than undisturbed old growth. This degradation occurs largely through selective logging which has negative effects on the functioning of the forest as well as on its biodiversity. Research outside of the tropics in ecosystems like temperate grasslands has demonstrated a positive relationship between biodiversity and a range of ecosystem functions, including primary productivity. However, the challenges of scientific research in the tropics mean there is much less evidence of whether there is a positive relationship between levels of tree diversity and above ground biomass production in tropical forest ecosystems.

The project, the Sabah Biodiversity Experiment, is one of the world’s largest ecological experiments, making it of particular relevance to real-world efforts to restore and sustainably manage tropical forests. The over-arching goal of the project is to test the unanswered question of whether the functioning of tropical forest ecosystems, such as how much biomass they produce, how diverse they are and therefore whether replanting degraded forests with diverse mixtures of species can accelerate their recovery and help fund replanting costs through carbon credits. The project has adopted the existing forest restoration activity of ‘enrichment planting’ to plant more than 100,000 seedlings of native tree species across an area of 500 hectares of logged forest, allowing the recovery rates of naturally regenerating control plots to be robustly compared with those planted with different diversities (1, 4 or 16 species) and mixtures of tree species. Comparing the newly-planted seedlings to nearby old growth forest, the project will assess the restoration process.

In the final phase, the project working with local partners, including the Sabah Forestry Department, will produce a cost-benefit analysis of forest restoration and communicate these results so that local and regional management policies for the conservation and restoration of forests and the stored carbon can be informed.