Community assembly of soil fauna functional groups in differently managed agroecosystems

Background/Question/Methods

Agricultural ecosystems are driven by the need to increase yield margins, due to the increased food demands. Some practices are not sustainable as they disrupt the biodiversity in the soil which performs an assembly of ecosystem functions that sustain productivity and soil resilience. Conservation agriculture has been centralised as the most sustainable and biodiversity conserving agriculture, functioning under the principles of reduced intensification of inputs such as chemical fertilisers, pesticides and tillage. In South Africa knowledge regarding the influence of conservation agriculture on faunal biodiversity remains limited. In this study, we focus on soil macrofauna and mesofauna community groups, we establish knowledge on their response to different intensities of agricultural management, understanding such responses is important for sustainability planning and conservation of ecosystem services. Data was collected from four different land-use types; these included conventional, integrated, conservation and, natural ecosystems. Each land-use was replicated ten times, totalling 40 spatially heterogeneous sites. Sampling occurred across two seasons following the methodology of the Tropical Soil Biology and Fertility. Generalized Linear Models were used to examine differences between the management practices in terms of species richness, abundance, and functional guilds. Non-parametric species estimators Chao 2 and Jacknife 2 were also calculated.

Results/Conclusions

From the recorded results, soil macro-and mesofauna displayed sensitivity towards conventional management compared to other land-uses. With regards to species groups, beetles, spiders, and earthworms contributed the most abundance and richness. The dark pigmented earthworms, in particular, were found in relatively large numbers within integrated systems and absent in the conventional systems; these are epigeic and anecic species known to be deep burrowers and litter feeders thereby contributing to organic matter decomposition and soil structure formation. The low record of soil fauna species diversity within conventional management can be attributed to unfavourable environmental conditions. Soil macro-and mesofauna are known to be sensitive to habitat fragmentations, therefore, periodic soil destruction during tillage reduces their diversity and functions, which subsequently leads to the loss of resilience and ecosystem service provision. The study highlights that no-till plantings coupled with diversified crop rotations and cover crop mixtures under conservation and integrated agricultural management stimulates soil macro-and mesofauna diversity and supports the establishment of functional groups, which are crucial for pest control, nutrient cycling, and decomposition.