Abstract
Precise vegetation descriptions and maps are essential tools for the management of natural areas, as well as for understanding animal habitat use. The Chobe Enclave (CE), adjacent to the Chobe National Park and the Chobe Forest Reserve, forms a critical dry season range for many large herbivores. As a tool for future management and studies about wildlife habitat use and migration, this study proposed to describe the plant communities in the CE and to study their relationships with microtopography and soils. Plant species were inventoried in 82 sampling plots (40 x 20 m), covering the vegetation diversity recognised by an unsupervised classification (Landsat images, 30-m resolution). A hierarchical clustering classified the inventories in eight plant communities, mapped with a supervised classification. This study was conducted in parallel with a soil study. Soil variations and degree of flooding largely determine community composition. Floodplains along the Linyanti River and dambos (concentrating local run off from rainfall) provide reliable green forage for wildlife during the dry season. Adjacent to floodplains, riverine forests also maintain green browse and grazing well into the dry season. In drylands, vegetation is largely determined by soil texture. Forests dominated by Baikiaea plurijuga occupy the acidic, red sands in the east, while sandveld vegetation grows on deep sands in paleo-river channels. These habitats support dominant grasses, which provide important forage for grazers during the wet season. Finally, woodlands dominated by Colophospermum mopane, characterised by sodium-rich and alkaline soils, enable herbivores to meet their mineral requirements during reproduction. Conservation implications: Our soil and vegetation studies provide important insights into factors determining plant communities. Their diversity and close vicinity play a critical role in enabling herbivores to adapt to seasonal variations in forage quantity and quality. Results will enable researchers to gain insights into animal habitat seasonal use in the Chobe Enclave.
Highlights
Biodiversity is threatened worldwide by human activities, directly by its land-use change and introduced species, as well as indirectly by pollution and climate change (Sala et al 2000)
The very high sand proportion (~98%) of the substrate is related to the lowest content of organic matter (< 0.1%), both explaining the low cation exchange capacity (CEC; < 0.4 cmol+ kg−1; Table 2)
With a mean of 21.9 ± 4.8 species, plots belonging to this unit were amongst the species poorest (Figure 3). This is probably related to three stressing factors: a seasonally high water table, alternating with dry conditions, and very low nutrient availability because of the low CEC
Summary
Biodiversity is threatened worldwide by human activities, directly by its land-use change and introduced species, as well as indirectly by pollution and climate change (Sala et al 2000). Exhaustive species inventories are directly beneficial to study their distribution in the landscape and to understand how biodiversity is related to environmental factors. Such exhaustive plant surveys provide information on the dominant species, their co-occurrence with other species and are the basis for the classification of plant communities (Ewald 2003). The classification of plant communities remains an important tool for improved management and conservation of species and ecosystems and provides the basis for vegetation maps (De Cáceres et al 2015)
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