Variation of soil microbial and earthworm communities along an agricultural transect with tree windbreak

Abstract

Windbreaks are among the most widespread agroforestry systems in the temperate biome. Tree windbreaks are expected to have unique soil properties and biotic communities, compared to adjacent agricultural fields. We compared key soil properties and communities of earthworms, bacteria and fungi along an agricultural transect through a tree windbreak into a cropped field. Soil properties, earthworm abundance and diversity, and bacterial and fungal alpha-diversity (16S-rRNA and ITS gene sequencing) were assessed along transects at distances of 0 (directly under the tree canopy), 8 (ecotone in the cropped field) and 50 m from the tree row in six mature (20- to 70-years-old) tree windbreaks located in southeastern Quebec, Canada. Soil organic C, total N and C:N ratio were higher, while soil pH was lower in the tree row than in the adjacent cropped fields at distances of 8 m and 50 m from the windbreak. Each group of biota had a distinct pattern along the agricultural transect. Earthworm abundance and biomass were greater at 50 m than 8 m from the windbreak. Epigeic, endogeic, and anecic earthworms varied similarly along the agricultural transect. Fungal diversity was higher at 8 m than at 0 m from the windbreak. Bacterial diversity was higher at 50 m than at 0 m from the windbreak. Tree windbreaks made the soil environment in the ecotone more favorable for fungal communities, but less favorable for earthworm communities. Greater bacterial diversity was associated with agricultural activities than windbreaks.