Plant diversity and vegetation patterns in the north of the Kaokoland endemic centre, Iona national park

Abstract

Angola has high biodiversity, representing the second-largest ecoregional diversity in Africa, with 7 biomes, 15 ecoregions, 22 vegetation types, and 4 regional centres of endemism. The first studies on the distribution, composition and classification of vegetation in Angola at a national level were part of the floristic exploration and scientific missions during the colonial time. The Kaokoveld Desert and Namib Escarpment Woodlands are ecoregions represented in Iona National Park. Few vegetation or ethnobotanical studies were done in the south of Namibe province, where the oldest park of Angola is located: Iona National Park. Himba community are semi-nomadic herders, they move with their herds both on a daily and seasonal basis, according to fodder availability. This is reflected in a long deep traditional ecological knowledge, cultural heritage developed. Information on plant species and the distribution of vegetation types is an essential baseline for conservation management and planning of the natural resources for any country. This research aims to study the spatial patterns of the vegetation, as well as the use of the plants by the communities in Iona National Park, in Namibe province, southern Angola, as well as the potential that plants present for the economy and tourism. Vegetation data were obtained using sample plots and all the species that were seen in the field during the trips were recorded. The field sampling was randomly stratified. Multi-Response Permutation Procedures and Indicator Species Analysis results were used to determine the number of vegetation communities. Environmental variables were selected as predictors for the vegetation analysis based on the correlation with the ordination axes and contribution to Random forest model. Random forest was used to investigate the vegetation patterns and create a vegetation map. In total 157 different plants species were recorded, of which 120 species were identified that belong to 49 genera. Of the 120 species, 89 are listed in the Checklist of Angola plants, 31 are new species for the Checklist of Angola plants, with 4 are listed as endemic. The vegetation in the area was divided into eight communities, 1- Acacia mellífera, 2- Terminalia prunioides -Colophospermum mopane, 3- Calicorema capitata, 4- Commiphora multijuga - Rhigozum virgatum, 5- Salvadora persica - Combretum imberbe, 6- Grasses, 7- Euphorbia virosa - Commiphora wildii, 8- Welwitschia mirabilis. Normalized Difference Vegetation Index, slope, bedrock and annual precipitation were the most important variables in the model aiming to map the vegetation. The analysis demonstrated that the quantity of the plots used and the choices of environmental variables for the model are the main factors to cause the high OOB error for Random Forest modelling. xiv The interviews made with the local people that are familiar with plants, resulted in the description of 45 native plant uses by communities living in Iona National Park. Future studies may consider collecting more vegetation data and environmental variables for the model. Comparing the Kaokoveld vegetation between Angola and Namibia, makes more sense to consider plants as endemics to the Kaokoveld region rather than to each country.