Arbuscular mycorrhizal spore composition and diversity associated with different land uses in a tropical savanna landscape, Tanzania

Abstract

Understanding the diversity and community structure of arbuscular mycorrhizal fungi (AMF) is important for potentially optimizing their role in the functioning of terrestrial ecosystems. Land use can have profound effects on AMF abundance, productivity, and species composition, but such effects have been explored less in tropical landscapes where agriculture is often less intensive and wildlife conservation can be predominant. Here, we conducted a landscape-scale investigation to quantify the effects of land uses on the AMF diversity in the Greater Serengeti Ecosystem, Tanzania. Abundance, productivity, and diversity of the spores of AM fungal species were determined from field soils by morphological techniques. A total of 315 AM fungal spores belonging 9 species and four families were recorded. Land use had a significant (P < 0.05) effect on AM fungal spore density and biomass production of AM hyphae in in-growth mesh bags. The AM fungal spore density was statistically significant (P < 0.05) and positively correlated with soil N, organic carbon content and sand contents, but negatively correlated with increasing soil P and pH. After accounting for soil N, Organic carbon, P and pH, wildlife grazed areas had nearly double the spore densities compared to livestock grazed and crop agriculture areas. Likewise, wildlife grazed soils had a higher Shannon-Wiener diversity index (2.13 ± 0.05) than either livestock grazed soils (1.76 ± 0.10) or cultivated soils (1.59 ± 0.09).AM fungal families exhibited significant differences in their abundance among land use types. While Glomeraceae had high abundance under all land uses, Gigasporaceae and Scutellosporaceae exhibited the highest abundance in wildlife grazed sites and Acaulosporaceae had high abundance in livestock-grazed and crop agriculture sites. Species composition within families was mostly similar across land uses, with the exception of Scutellospora sinuosum and Acaulospora denticulata, which exhibited much greater abundance in wildlife grazed sites than in livestock-grazed or crop agriculture sites. These results suggest that protected area grassland sites subject to wildlife grazing held a more abundant, diverse, and compositionally distinct AM fungal community than both livestock-grazed and crop agriculture sites, even after accounting for the influence of land use on soil N, Organic carbon, P and pH that affect AM fungi. From the perspective of sustainable production, it is very important to ascertain tillage practices and moderate grazing that can promote mycorrhizal diversity and, therefore, contribute to the long-term sustainability of agro-pastoral ecosystems under tropical conditions.