Diversity and Abundance of Dung Beetles Across Different Land Use Types and Their Role in Soil Fertility Improvement in Kenya

Abstract

Dung beetles are crucial in livestock systems due to their contribution to dung removal, nutrients cycling and sustainable pasture production. There are limited studies to elucidate biodiversity and species-specific contribution of dung beetles to ecosystem services in Kenya. This study aimed at evaluating abundance of soil macrofauna and soil chemical properties across selected land-use types (LUTs), effect of LUTs and seasons on abundance and diversity of dung beetles and finally assessing effect of dung beetle species and dung type on dung removal and chemical quality of relocated dung balls. This information would be critical for conservation and utilization of dung beetles in the study sites. A survey on soil macrofauna was done using eight monoliths per each of the selected LUTs in Kabete and Chepkoilel sites located in Kiambu and Uasin Gishu Counties, respectively. Sampling of dung beetles was done using 10 cattle-dung baited pitfall traps per each LUT. Role of dung beetles on soil fertility was conducted through a terrarium experiment comprising of six treatments arranged in completely randomized design (CRD). Redundancy analysis (RDA) was carried out to correlate soil chemical properties with abundance of macrofauna. Analysis of variance (ANOVA) was undertaken to determine the effect of LUTs and season on the abundance and diversity of dung beetles. Abundance of termites, earthworms, ants, beetles and millipedes differed significantly across LUTs (p < 0.05) in both sites. Termites, beetles, spiders and centipedes were positively correlated with total N, organic C, pH, available P and exchangeable K along axis 2 in Kabete soils. All macrofauna groups were positively correlated with organic C, total N and pH, but negatively with exchangeable K and available P along axis 2 in Chepkoilel soils. Land use type and Season significantly affected the abundance and diversity of coprophagous beetles (p < 0.001). They were significantly higher during the wet season and in LUTs under frequent gazing influence. Grazed pasturelands in Kabete and Chepkoilel had significantly highest abundance of dung beetles of 27.3 and 18.5, respectively (p < 0.001). In Kabete, grazed and non-grazed pasturelands had the highest species richness of 6.2 and 6.5, respectively (p < 0.001) while in Chepkoilel, it was significantly highest in grazed pasturelands, wattle plantation and mixed woodland (4.9, 4.4 and 4.3, respectively) at p < 0.001. Type of animal fecal material and species of coprophagous beetle significantly influenced the amount and rate of dung removal (p < 0.001). Euoniticellus triangulatus removed cattle dung at significantly faster rate of 13.04 g g-1 day-1 compared to Milichus picticollis which buried dung at the rate of 1.4 g g-1 day-1(p < 0.001). Relocated dung balls contained significantly lesser amounts of N, C, K and P than the original dung at p ≤ 0.001. E. triangulatus is more efficient in relocating animal dung with significantly higher contents of N, P and K than M. picticollis (p < 0.001). In conclusion, E. triangulatus should be introduced into grazed pasturelands to enhance pasture production and dung removal.