Diversity patterns of plants and arthropods in soybean agro-ecosystems in the Grassland Biome of South Africa

Abstract

Abstract. Janse van Rensburg PD, Siebert SJ, Masehela T, Ellis S, Van den Berg J. 2020. Diversity patterns of plants and arthropods in soybean agroecosystems in the grassland biome of South Africa. Biodiversitas 21: 5559-5570. Soybean is widely cultivated in the grassland biome of South Africa (ca. 800 000 ha per annum). Yet the possible effects that large-scale cultivation of soybean has on biodiversity in adjacent habitat are not fully understood. This study aimed to describe the plant and arthropod species assemblages and diversity patterns within these soybean agroecosystems. Surveys were conducted inside soybean fields, field boundaries (transition zones between soybean fields and adjacent habitat), and adjacent pasture. An adapted D-vac was used to sample arthropods in the different zones, while plant surveys were conducted by means of fixed width (2 m) line transect. A total of 320 plant species (4910 specimens) and 373 arthropod morpho-species (9216 specimens) were recorded. Soybean fields had significantly lower plant and arthropod diversity than the adjacent habitats. Plant species diversity was similar in the field boundary and adjacent pasture. Significantly higher species richness and abundance of arthropods were found in the boundary than the pasture. These results show that the cultivation of soybean and the associated agricultural practices had no adverse effects on biodiversity patterns in the adjacent habitats. However, the boundary dominated by alien plant species did contain a significantly different plant species composition from the pasture. This difference was also mirrored by unique assemblages of arthropods. This suggests that disturbance resulting from soybean cultivation contributed to species losses and gains that maintained diversity in the field boundary but changed its plant and arthropod species composition. No effect was found in the pasture beyond the boundary (> 50 m). High diversity, but unique species assemblages of plants and arthropods in the boundary and pasture suggest that these habitats may have important conservation value in soybean agroecosystems by supporting ecosystem functions and services.

Composition and diversity patterns of weeds in herbicide tolerant maize fields and margins in the Eastern Cape, South Africa

“…This could be attributed to herbicide application in the fields which suppresses dominant weeds. This contrasted the findings of Janse van Rensburg et al (2020), who found soybean crop fields to have significantly lower evenness than the boundary. In that instance, the factors that reduced evenness were chemical application and grazing disturbance.…”

“…Agricultural disturbance affects plant diversity in field margins due to grazing but also herbicide drift (Khan et al 2017). The observed lower diversity in margins was also found in other studies, for example, Janse van Rensburg et al (2020) reported lower plant diversity in the field margins adjacent to crop fields that were treated with herbicides. Schmitz et al (2014) observed the same effect due to fertiliser drift from fields into the margin.…”

A new distribution and host record for the rare moth, Callioratis millari (Lepidoptera: Geometridae), and some ecological observations

“…We recorded C. millari for the first time during surveys of arthropod diversity associated with Encephalartos species in AENP in July 2022 ( Janse van Rensburg et al 2022 ). During these initial surveys, we visited approximately 200 E. longifolius , 50 E. lehmannii , and 50 E. caffer plants ( Janse van Rensburg et al 2022 ).…”

“…We recorded C. millari for the first time during surveys of arthropod diversity associated with Encephalartos species in AENP in July 2022 ( Janse van Rensburg et al 2022 ). During these initial surveys, we visited approximately 200 E. longifolius , 50 E. lehmannii , and 50 E. caffer plants ( Janse van Rensburg et al 2022 ). Callioratis millari was not found on E. longifolius or E. lehmannii , although the presence of Z. lepida on these plants was confirmed ( Janse van Rensburg et al 2022 ).…”

Level of urbanization and habitat type, and not patch size, influence predacious arthropod diversity patterns of urban grasslands in South Africa

“…Complex interactions between abiotic and biotic components in ecosystems determine the quantity, quality and reliability of these services (Mace et al 2012). In grassy landscapes, the herbaceous layer provides forage and habitat to arthropods (Botha et al 2017, Janse Van Rensburg et al 2020). These herbaceous layers can be very diverse and thus provide more habitat and foraging opportunities, especially for predacious arthropods.…”