Impacts of land use change on biomass and diversity in the forest landscape of the Yangambi Biosphere Reserve in the Democratic Republic of Congo

Abstract

The tropical forests of the Democratic Republic of Congo are threatened by deforestation and forest degradation, which affect tree structure and diversity. This study aims to quantify biomass and diversity losses resulting from deforestation and degradation, with a focus on the Yangambi Biosphere Reserve. Invento-ries were conducted in four 50 m x 50 m plots in each of the eight land-use types identified: mixed mature forest, mature forest with Gilbertiodendron dewevrei, subsistence crop fields, fallows (5 to 10 years), secondary forests (20 to 40 years), and cacao, coffee and oil palm plantations. Biomass stocks in mature forests amounted to ~ 400 and 380 Mg/ha for G. dewevrei and mixed forest respec-tively. Our results show that mature forests lose 50, 70 and 90%, respectively, of their above-ground biomass when converted to cocoa, coffee and palm plantations, and almost all (99%) when converted to food crops. However, when a crop field is abandoned, above-ground biomass gradually recovers to 7.5% after 5-10 years and to 38.8% after 20-40 years. Conversion also has an impact on diversity, and although species rich-ness appears to recover faster than bio-mass, its composition is fundamentally altered. Although the approach needs to be scaled up, these results provide essential information for quantifying the impacts of “natural” solutions to climate change, i.e. protection of mature forests, improved forest management and refor-estation.