Ecological Grassland Restoration—A South African Perspective

Effects of landscape edge heterogeneity on biodiversity in grassland restoration context

Habitat loss is a major driver of global biodiversity decline, and grassland ecosystems are critical for habitat conservation. In the Loess Plateau of China, prolonged agricultural practices and overgrazing have led to severe degradation of grasslands, causing biodiversity loss and reduced ecological functionality. This study examined the effects of connectivity and edge heterogeneity in three landscape mosaic types-farmland-grassland, river-grassland, and woodland-grassland-on biodiversity restoration. Using seven experimental units in the Ansai District, we assessed species richness, abundance, and community composition of butterflies, carabid beetles, and vascular plants. Our findings showed that connected habitats, particularly in farmland-grassland and river-grassland mosaics, on average increased species richness by over 38% compared to isolated habitats. Rare species were predominantly distributed in river-grassland mosaics, highlighting the importance of edge connectivity in supporting biodiversity. In contrast, biodiversity was lower in connected woodland-grassland mosaics, suggesting taxon-specific responses to connectivity. Vegetation played a key role in regulating biodiversity by providing food and shelter, emphasizing the need to conserve plant diversity for ecosystem recovery. Grazing intensity negatively affected vascular plants and carabid beetles, highlighting the importance of rational grazing management. Our findings highlight principles of connectivity and heterogeneity that are applicable to grassland restoration in arid and semi-arid ecosystems globally. Future research should explore how climate change and extreme weather events may moderate these effects. The results provide actionable recommendations for designing ecological corridors, optimizing landscape mosaics, and integrating sustainable grazing practices to restore degraded grasslands effectively.

Using grass inflorescence as source material for biomonitoring through environmental DNA metabarcoding

BACKGROUND

Over the last decade, increasing attention has been directed to using different substrates as sources of environmental DNA (eDNA) in ecological research. Reports on the use of environmental DNA located on the surface of plant leaves and flowers have highlighted the utility of this DNA source in studies including, but not limited to, biodiversity, invasive species, and pollination ecology. The current study assesses grass inflorescence as a source of eDNA for detecting invertebrate taxa.

METHODS AND RESULTS

Inflorescences from four common grass species in a central South African grassland were collected for high-throughput sequencing analysis. Universal COI primers were utilised to detect Metazoan diversity. The sequencing results allowed for the detection of three Arthropoda orders, with most OTUs assigned to fungal taxa (Ascomycota and Basidiomycota). Some biases were detected while observing the relative read abundance (RRA) results.

DISCUSSION

The observed biases could be explained by the accidental inclusion of invertebrate specimens during sample collection and DNA extraction. Primer biases towards the amplified taxa could be another reason for the observed RRA results. This study provided insight into the invertebrate community associated with the four sampled grass species. It should be noted that with the lack of negative field controls, it is impossible to rule out the influence of airborne eDNA on the observed diversity associated with each grass species. The lack of the inclusion of PCR and extraction blanks in the sequencing step, as well as the inclusion of negative field controls, including other areas for refinement were highlighted, and suggestions were provided to improve the outcomes of future studies.

Success in restoring native plant communities on kimberlite mining dumps in the Afro-alpine Drakensberg region of Lesotho

Rehabilitation strategies for degraded mine dumps have generally seen limited success due to different complications associated with mining biophysical disturbance. In this study, we tested a combination of two methods to expedite revegetation of kimberlite tailings at Letseng Diamond Mine (i.e., in the Afro-alpine areas of Lesotho). We ran trials on different growth media located on fine and coarse kimberlite tailings (i.e. sites) mixed with different substrate combinations and topsoil and sowing a seed mix comprised of native plant species. Overall, as predicted, fine kimberlite tailings displayed significantly higher plant abundance than coarse kimberlite tailings, and sown seeds performed significantly better than spontaneous colonisation by emerging species. Kimberlite tailings mixed with topsoil (100 mm) showed significantly greater plant abundance, and similarly, when coarse kimberlite tailings were introduced to fine tailings. Physicochemical analyses of growth media components suggested that topsoil provided additional nutrients and that plants could readily access available nutrients in the fine kimberlite tailings. We noted a gradual significant increase in plant abundance over 5 years, enhanced by new plant species emerging from the topsoil seed bank or by natural seed dispersal. Although plant abundance differed significantly, both fine and coarse kimberlite tailings displayed high plant species diversity (H = 3.4 and D = 0.95 and H = 3.5 and D = 0.95, respectively). Out of 36 emerging plant species, 15 species spontaneously colonised both growth media. The significant variation in abundance among plant species between treatments was mostly attributed to dominant forb species, namely Chrysocoma ciliata, Glumicalyx montanus, Oxalis obliquifolia, Senecio inaequidens and Trifolium burchellianum. We have identified suitable growth media for plant community restoration on kimberlite tailings in the Drakensberg alpine area using a seed mix of native plant species in combination with natural seed dispersal from the surrounding pristine environment. We provide evidence for using two complementary approaches to optimise native plant community development during restoration in the Drakensberg alpine area.

Comparison of two contrasting Leymus chinensis accessions reveals the roles of the cell wall and auxin in rhizome development

Leymus chinensis, a perennial native forage grass, is widely distributed in the steppes of Inner Mongolia as the dominant species. The main reproductive strategy of this grass is clonal propagation, which occurs via the proliferation of subterranean horizontal stems known as rhizomes. To elucidate the mechanism underlying rhizome development in this grass, we collected 60 accessions of L. chinensis and evaluated their rhizome development. One accession, which we named SR-74 (Strong Rhizomes), had significantly better rhizome development capacity than the accession WR-16 (Weak Rhizomes) in terms of rhizome number, total and primary rhizome length, and number of rhizome seedlings. Rhizome elongation was positively correlated with the number of internodes in the rhizome, which affected plant biomass. Compared to WR-16, SR-74 had higher rhizome tip hardness, higher abundance of transcripts participating in the biosynthesis of cell wall components, and higher levels of the metabolites L-phenylalanine, trans-cinnamic acid, 3-coumaric acid, ferulic acid, and coniferin. These metabolites in the phenylpropanoid biosynthesis pathway are precursors of lignin. In addition, SR-74 rhizomes contained higher amounts of auxin and auxin metabolites, including L-Trp, IPA, IBA, IAA and IAA-Asp, as well as upregulated expression of the auxin biosynthesis and signaling genes YUCCA6, YUCCA8, YUCCA10, YUCCA11, PIN1, PIN2, UGT1, UGT2, UGT4, UGT10, GH3, IAA7, IAA23, and IAA30. We propose a network between auxin signaling and the cell wall underlying rhizome development in L. chinensis.

Determining the critical recruitment needs for the declining population of Olea europaea subsp. africana (Mill.) P.S. Green in Free State, South Africa

Olea europaea subsp. africana (Mill.) P.S. Green (medium-sized tree species known as "African wild olive"), provides important ecological goods and services for sustaining frugivores in the grassland biome in South Africa. We speculate that O. europaea subsp. africana's population has been declining due to habitat loss and exploitation for domestic benefits suggesting an unrecognized conservation threat. Therefore, the study aimed to investigate the anthropogenic conservation threats for O. europaea subsp. africana in the Free State, South Africa and to determine the potential importance of seed dispersal effectiveness in the restoration of the species in the study area. Overall, the results showed that 39% of the natural habitat range has been transformed by human-mediated activities. Agricultural activities accounted for 27%, while mining activities and human settlement accounted for 12%, of natural habitat loss. In support of the study predictions, seeds of O. europaea subsp. africana had significantly higher germination and germinated faster after passing through the mammal gut (i.e., 28% and 1.49 per week), compared to other seed treatments (i.e., over 39 weeks). However, there were no statistically significant differences between seed germination of the bird-ingested seeds, with intact fruits as the experimental control, although both were significantly greater than the de-pulped seeds. Potential seed dispersal distances by birds were relatively larger, ranging from 9.4 km to 53 km, than those of mammals (1.5 km-4.5 km). We propose that the O. europaea subsp. africana's habitat range may have been declining, and since it is a keystone plant species, we recommend that the complementary seed dispersal services by birds and mammals could be important for its recruitment and restoration in the degraded habitat.

Grassland cover declined in Southern Africa but increased in other African subcontinents in early twenty-first century

The African continent has the most extensive grassland cover in the world, providing valuable ecosystem services. African grasslands, like other continental grasslands, are prone to various anthropogenic disturbances and climate, and require data-driven monitoring for efficient functioning and service delivery. Yet, knowledge of how the African grassland cover has changed in the past years is lacking, especially at the subcontinent level, due to lack of relevant long-term, Africa-wide observations and experiments. In this study, we used Moderate Resolution Imaging Spectroradiometer (MODIS) Land Cover Type (MCD12Q1) data spanning 2001 to 2017 to conduct land use land cover (LULC) change analyses and map grassland distribution in Africa. Specifically, we assessed the changes in grassland cover across and within African subcontinents over three periods (2001-2013, 2013-2017, and 2001-2017). We found that the African grassland cover was 16,777,765.5 km², 16,999,468.25 km², and 16,968,304.25 km² in 2001, 2013, and 2017, respectively. There were net gain (1.32%) and net loss (- 0.19%) during 2001-2013 and 2013-2017 periods, respectively, and the annual rate of change during these periods were 0.11% and - 0.05%, respectively. Generally, the African grassland cover increased by 1.14% (0.07% per annum) over the entire study period (2001-2017) at the expense of forestland, cropland, and built-up areas. The East and West African grassland cover reduced by 0.07% (- 0.02% per annum) and 1.35% (- 0.34% per annum), respectively from 2013 to 2017 but increased in other periods. On the other hand, the grassland cover in North and Central Africa increased throughout the three periods while that of Southern Africa decreased over the three periods. Overall, the net gains in the grassland cover of other African subcontinents offset the loss in Southern Africa and promoted the overall gain across Africa. This study underscores the need for continuous monitoring of African grasslands and the causes of their changes for efficient delivery of ecosystem services.