Dry tropical forests and woodlands of the Cubango Basin in southern Africa - First classification and assessment of their woody species diversity

Aim: The social-ecological systems of south east Angola currently undergo rapid transformations and at the same time the region is highly understudied. We aim to provide a first comprehensive analysis of vegetation types, their environmental drivers and woody species diversity of the region. Study area: Cubango River Basin in south-east Angola and northern Namibia. Methods: We conducted a plot-based vegetation survey covering all major terrestrial vegetation types. 190 releves of 1000 m(2) were classified based on a numerical classification approach. We used NMDS ordination and data on soils from field sampling, topography, climate and remotely sensed land surface phenology to investigate vegetation-environment relationships. The number of woody species was estimated using four non-parametric species richness estimators and rarefaction curves. Results: We provided a detailed description of the resulting twelve woody plant communities, in terms of species composition, structure, and habitat characteristics. At the scale of the Cubango Basin, differences in the regional climate were the most important drivers of plant species composition. Topsoil properties did not vary much throughout the study area, but higher contents of silt and clay in the lower soil horizons appeared to drive species composition in the miombo woodlands. Furthermore, we demonstrated how the usage of land surface phenology metrics add value to the interpretation of ecological properties of plant communities in providing insights on the timing of the growing season and on different aspects of above-ground biomass. The number of woody species in the entire Cubango Basin was estimated to be 471 (SD=29) species, for the miombo woodlands 302 (SD=11) species, and for the Baikiaea woodlands 262 (SD=20) species. Conclusion: The presented classification scheme and the analysis of environmental drivers of vegetation types provide a solid basis for future investigations of the vegetation of southeast Angola, and will provide important baseline data for conservation planning and sustainable natural resource management.