Disentangling the effect of tillage, herbicide, pesticide, and temperature change on oribatid mite communities in Georgia.

Abstract

Agricultural practices affect non-target soil fauna either directly or indirectly, e.g. by altering the soil physical structure or by application of chemicals. The effects of tillage, insecticide and herbicide applications on the dominant taxon of soil microarthropods-oribatid mites was studied in two fields over three years (2020, 2021, 2022) at three seasons (spring, summer and autumn). In total 87 species were identified. Herbicide and insecticide application had negative effects on oribatid mite species numbers and abundance; however, tillage mitigated the negative effects of herbicide and insecticide applications, possibly since tillage increases the rate of pesticide degradation and thereby reduces the direct exposure to soil fauna to those chemicals. Insecticides and tillage reduced the number of parthenogenetic individuals, possibly by a decrease of available resources (dead organic matter). Oribatid species richness and density steadily declined from 2020 to 2022 likely due to increased average annual temperature and decreased precipitation associated with global warming. The species richness and density declined from spring to summer and increased again in autumn. The annual decline of the oribatid species richness was expressed by the loss of oribatids with a thin cuticle (Mixonomata, Enarthronota, Oppioidea) and those, who are sensitive towards disturbance (Liacaridae, Ceratozetidae). Dry grassland specific species (Passalozetes africanus, P. perforatus, Scutovertex sculptus) were constantly present in all samples. The study points to the effects of agricultural practices on non-target soil fauna and also on the changes in soil animal communities from meadow to dry steppe species due to global warming.