Maintaining functional connectivity in grassland corridors between plantation forests promotes high-quality habitat and conserves range restricted grasshoppers

Context Grassland corridors are set aside for biodiversity conservation within the commercial timber plantation landscape of South Africa, potentially connecting high value conservation areas together. However, the impact of the production landscape on functional connectivity within these corridors has not been investigated. Objectives We combine stacked species distribution modelling, functional connectivity analysis, species turnover calculations, and community analysis, to improve our understanding of how grassland corridors contribute to functional connectivity and biodiversity conservation within plantation landscapes. Methods Grasshoppers, which are reliable indicators of grassland quality, were used as model organisms and sampled within grassland corridors. Remote sensing and machine learning was used to predict functional connectivity and its influence on grasshoppers. Results Wide corridors along an elevation gradient with different aspects support different grasshopper assemblages and promote species turnover. Sensitive species occur at high elevations with a north-west facing slope in wide corridors that are functionally connected to large high-quality remnant patches. Maintenance of functional connectivity is dependent on the availability of high-quality habitat, which is shaped by prescribed burning, and has a significant effect on range restricted species. Not all high-quality habitat is functionally connected, attributed to exclusion of fire and/or invasive plants, requiring conservation intervention. Conclusions Prescribed burning should be used to maintain functional connectivity. We recommend less frequent fires, burning every 2-3 years, guided by NDVI. Large corridors at high elevation are priority. In estates with narrow corridors and low functional connectivity, stepping-stone habitats and grassland buffers next to roads should be considered for improved functional connectivity.

Automated summary

Grassland corridors within commercial timber plantations in South Africa have the potential to connect conservation areas, but the impact of the production landscape on functional connectivity has not been investigated. This study used grasshoppers as indicators and combined species distribution modelling, functional connectivity analysis, and community analysis to understand how these corridors contribute to biodiversity conservation. The results show that wide corridors with different elevations and slopes support different grasshopper assemblages and promote species turnover. Functional connectivity depends on the availability of high-quality habitat shaped by prescribed burning, with implications for range restricted species. Not all high-quality habitat is functionally connected, suggesting the need for conservation intervention.