Spider community shift in response to farming practices in a sub-humid agroecosystem of southern Africa

Abstract

Most spiders are generalist predators and important biological control agents of various insect pests of agricultural crops. A study was conducted to determine the impact of cultural practices on the abundnace and diversity of soil surface-dwelling spiders (Araneae). Two experiments were conducted at the Chinhoyi University of Technology experimental farm, Zimbabwe, over the 2013/2014 and 2014/2015 cropping seasons. The two experiments were conducted using a split-split-plot design arranged in randomized complete blocks using tillage, mulching, fertilizer and weeding management as factors, with spider diversity being a response variable. Tillage and mulching had strong effects on spider composition. In the first experiment that involved tillage system as the main plot factor, conventional tillage had a negative effect on ground dwelling taxa as evidenced by high negative taxon weights of Lycosidae, Gnaphosidae and Salticidae. In the second experiment, mulching had strong positive effects on ground dwelling spiders with the strongest being Lycosidae followed Gnaphosidae and Thomisidae. The no-tillage option increased richness by 14.5% compared to conventional tillage. The effective number of species was higher in the no-tillage option (exp^Hʹ = 2.2) than in conventional tillage (exp^Hʹ = 1.8). Our results suggest that no-tillage and retention of plant residue on the soil surface facilitate the abundance of ground and plant wandering spiders. More research is required to assess the specific benefits associated with this increased abundance, such as biological pest control.