Tree-Distance and Tree-Species Effects on Soil Biota in a Temperate Agroforestry System

Cropland agroforestry systems are sustainable land-use systems with numerous environmental advantages over monoculture croplands including promotion of soil life. This study aimed to investigate tree-species and tree-distance effects on soil biota in a temperate agroforestry system. Our study was conducted at a paired alley-cropping and monoculture cropland system. The tree rows of the agroforestry system comprised of blocks of poplar Jacometti 78B, poplar Max 1 or black locust. Within the agroforestry system, soil microbial and earthworm communities were collected along transects spanning from the center of the tree rows into the crop rows. Archaea, bacteria, and fungi were quantified using real-time PCR. The community composition of fungi and earthworms was deciphered using amplicon sequencing and morphological identification, respectively. Research domain: Soil Sciences Research question: This study aimed to investigate the impact of three different tree species (two poplar species and black locust) on soil biota (archaea, bacteria, fungi, and earthworms) in a temperate alley-cropping agroforestry system. Furthermore, tree-distance effects on soil biota were tested by sampling multiple locations along transects spanning from the tree row into the crop row of the agroforestry system. We hypothesized that tree rows promote the abundance and alter the community composition of soil biota. We further hypothesized that these changes are dependent on the distance to the trees (tree-distance effect) as well as the tree species (tree-species effect).