Vegetation Database of the Okavango Basin
Revermann, Rasmus; Gomes, Amândio Luis; Gonçalves, Francisco Maiato; Wallenfang, Johannes; Hoche, Torsten; Jürgens, Norbert; Finckh, Manfred
The Okavango river basin, located in southern Africa and shared by the countries Angola, Namibia and Botswana, harbours large extents of natural and semi-natural ecosystems. At the same time, it is a hot spot of accelerating land use change causing transformation of vegetation in many regions of the basin. However, knowledge on vegetation composition and plant diversity is very limited, especially of the upper reaches of the river in Angola. The Future Okavango (TFO) project aimed at closing this gap and initiated a plot-based vegetation survey in 2011. Here we present the resulting Vegetation Database of the Okavango Basin (GIVD ID: AF-00-009; http://www. givd. info/ID/AF-00-009). We used unsupervised classification of MODIS land surface phenology metrics to identify existing major vegetation units forming the basis of a random, stratified sampling design. However, sampling was largely constrained by limited access and the hazard of land mines, a legacy of the civil war in Angola. Furthermore, detailed sampling on four local study sites of 100 km2 representing the different macro-ecosystems of the basin was carried out. Vegetation plots followed a nested design of a 100-m2 plot resting in the centre of a 1,000-m2 plot. In every plot, we recorded all vascular plant species with their estimated, projected cover, vegetation height, cover of vegetation strata, topography, and intensity of land use activities. Furthermore, soil samples were taken, and diameters of trees measured. Currently, the database has a focus on terrestrial vegetation, including Miombo woodlands and forests, geoxylic grasslands, Baikiaea-Burkea woodlands, and Colophospermum mopane woodlands. However, the database also includes plots of the tropical wetlands and peat bogs of the Angolan Central Plateau. The specific vegetation of the Okavango Delta is not yet included. The collected vegetation data will feed into a phytosociological classification and ecological modelling applications. Another objective is the identification of successional pathways after disturbance through land use. Ultimately, it will provide the basis for a vegetation map of the Okavango region.