Monitoring vegetation dynamics with open earth observation tools: the case of fire-modulated savanna to forest transitions in Central Africa

• Published in: ISPRS journal of photogrammetry and remote sensing 2022-06, Vol.188, p.142-156
• Main Authors: Sagang, Le Bienfaiteur Takougoum, Ploton, Pierre, Viennois, Gaëlle, Féret, Jean-Baptiste, Sonké, Bonaventure, Couteron, Pierre, Barbier, Nicolas
• Format: Article
• Language: English
• Subjects: Aboveground biomass; Biodiversity; Biodiversity and Ecology; Botanics; Ecology, environment; Ecosystems; Environmental Sciences; Fire; Forest-savanna transition; Google Earth Engine; Life Sciences; Species assemblage; Systematics, Phylogenetics and taxonomy; UAV-LiDAR; Vegetal Biology
• ISSN: 0924-2716; 1872-8235
• DOI: 10.1016/j.isprsjprs.2022.04.008

Woody encroachment and forest progression are widespread in forest-savanna transitional areas in Central Africa. Quantifying these dynamics and understanding their drivers at relevant spatial scales has long been a challenge. Recent progress in open access imagery sources with improved spatial, spectral and temporal resolution combined with cloud computing resources, and the advent of relatively cheap solutions to deploy laser sensors in the field, have transformed this domain of study. We present a study case in the Mpem & Djim National Park (MDNP), a 1,000 km2 protected area in the Centre region of Cameroon. Using open source algorithms in Google Earth Engine (GEE), we characterized vegetation dynamics and the fire regime based on Landsat multispectral imagery archive (1975–2020). Current species assemblages were estimated from Sentinel 2 imagery and the open source biodivMapR package, using spectral dissimilarity. Vegetation structure (aboveground biomass; AGB) was characterized using Unmanned Aerial vehicle (UAV) LiDAR scanning data sampled over the study area. Savanna vegetation, which was initially dominant in the MDNP, lost about 50% of its initial cover in