Abstract:
Grazers occupies more than 40 to 50% of earth terrestrial surface and alters soil function, soil microbes’ composition, quantity and quality resources that are produced by plants. The Grassland Biome in South Africa is an important ecosystem for rangeland production. If grazing occurs continuously altering soil function, the soil role will deteriorate, and soil may lose all valuable soil microorganisms and reduce plant productivity. The soil microbes play a significant role in regulating plant productivity as they enhance nutrient uptake, decompose soil organic matter, improve soil fertility, and protect plants from soil pathogens. We selected three Nature Reserves: Abe Bailey (ANR), Suikerbosrand (SNR) and, Roodeplaat Dam (RNR) in Gauteng Province and evaluated the effects of soil microbial diversity on plant productivity in the grassland biome. Shannon- Weiner index was used to determine the plant diversity and Jaccard dissimilarity index was used to determine species composition across all three reserves. Shannon diversity index and Jaccard dissimilarity index showed a constant form in how grazing impacts plant diversity and community structure across all three reserves. Shannon-Weiner index was highest at SNR, followed by ANR, and lowest in RNR. High H’ in SNR shows that it has the greatest plant diversity than ANR and RNR. The Jaccard dissimilarity index showed that the species composition varies sturdily across all three reserves. SNR had the most unique species composition. However, ANR and RNR results showed that they share same species composition, though slightly different. QIIME2 was used to evaluate the effects of soil microbes on plant productivity. QIIME2 converts raw data to statistical results. The soil microbes between grazed and ungrazed sample plots were also identified and analyzed using QIIME 2. Results showed that indeed soil microbes play a vital role in promoting plant productivity. Actinobacteria were the most dominant phyla of bacteria in ANR and Acididobacteriota was dominant in SNR. The pre-dominant bacteria in RNR was Pseudomonadota and there was no differences in the bacteria composition between grazed and ungrazed plots. The dominant fungi was Ascomycota in all three reserves and there was no differences in fungal composition between grazed and ungrazed plots. Furthermore, plant productivity in the grazed and ungrazed plots varied throughout summer, winter and spring across ANR,SNR and RNR. In ANR and RNR, there was no statistical differences between the grazed and ungrazed conditions throughout all late spring (October 2021), summer (2021) and winter (July 2022). In SNR, there was no statistical significance between the grazed and ungrazed conditions in late spring (October 2021) and summer (December 2021). However, there was a statistical significance between the grazed and ungrazed conditions in winter (July 2022).The winter rainfall and grazing played a role in regulating plant productivity. The Poaceae and Astraceae were the most dominant families across all three Nature Reserves. Further research on the effects of soil microbes should be done to understand why soil microbes in ungrazed and grazed plant productivity are the same during late spring (October 2021), summer (December 2021), and winter (July 2022). Also, to determine why there is no differences in bacterial and fungal composition between grazed and ungrazed plots during late spring (October 2021), summer (December 2021), and winter (July 2022). Why plant productivity is low in ungrazed plots when the rainfall is high and why plant productivity is high when the rainfall is low is a question that can be researched.
