Search

Woody encroachment can lead to a switch from open savannas to dense woodlands or forests. This has implications for both the composition of ecological communities and the provision of ecosystem services such as nutrient cycling and grazing capacity. The patterns and underlying drivers responsible for woody encroachment are not fully understood. Here, we investigate the underlying determinants of bush clump formation (a form of encroachment) in a South African savanna and explore whether bush clump succession is driven by deterministic (i.e., predictable changes in species composition) or stochastic (i.e., random) processes. Specifically, we test (1) whether the similarity in species composition of saplings and trees differs among small and large clumps, (2) which environmental factors are driving succession, and (3) whether forest specialization of tree and sapling species within bush clumps increases with the successional gradient. Similarity in species composition between saplings in small clumps and trees in large clumps was higher than similarity between trees in small clumps and trees in large clumps. Furthermore, temperature, soil moisture, relative humidity, and light intensity were related to changes in species composition along the successional gradient. As expected, forest specialization of trees increased with increasing clump area indicating that late‐successional bush clumps have more forest‐type species. The directional changes of species found along the successional gradient suggest a deterministic process of succession driven by changes in local environmental conditions during clump formation. [ABSTRACT FROM AUTHOR]

The large-scale cultivation of crops may lead to biodiversity decreases as a result of habitat loss and degradation of natural habitats. A popular strategy for enhancing insect diversity in intensively cultivated habitats involves maintaining plant diversity in field margins by means of sown grass and wildflower strips., Despite extensive cultivation of maize/corn (approximately 3.1 million ha) in the grassy biomes of South Africa, little effort has been made to understand whether plant groups maintain insect biodiversity within these agro-ecosystems., The diversity relationships between three prominent guilds of arthropods (herbivores, parasitoids and predators) and three large plant families ( Asteraceae, Fabaceae and Poaceae) are described at regional scale across the Grassland and Savanna Biomes of South Africa., The results obtained indicate general positive relationships between plant and arthropod diversity of the lower vegetation layers (≤2 m)., An increased abundance of members of the grass family ( Poaceae) led to significantly higher invertebrate numbers in maize fields and adjacent vegetation. This suggests that grasses play a significant role in supporting arthropod diversity within these agro-ecosystems., When considering farm design in maize-agro-ecosystems, our results indicate that maintaining grassy natural vegetation patches adjacent to actively cultivated maize fields may be sufficient to maintain and conserve arthropod diversity within agricultural landscapes. [ABSTRACT FROM AUTHOR]