Arthropod community patterns and associations along soil environmental gradients in a fine-scale northern grassland habitat

Throughout the Midwestern USA land conversion has removed large amounts of critical grassland habitat, leaving small, fragmented patches. Understanding patterns and associations of arthropods in these fine-scale habitats may help to target conservation efforts to specific arthropod communities. To determine grassland arthropod community patterns and environmental associations I systematically surveyed soil conditions, the plant community, and ground dwelling and foliar arthropods at Oakville Prairie (a 453 ha tract of grassland 19 km west of Grand Forks, ND). Soil conditions were documented through in-lab measurements of soil texture (% sand; silt; clay), pH, and salinity (electrical conductivity) on collected soil cores, and in-field measurements of soil moisture (20 cm depth) throughout the 2014 field season. Plant communities were surveyed for species and functional group richness (S) and percent cover (p_i) from late July through early August. Ground dwelling and foliar arthropods were collected in mid-June and mid-July by pitfall and sweep net sampling, and identified to family and morphospecies. Grouping analysis (a multivariate cluster analysis) shows two major community types in both the ground dwelling and foliar arthropod communities at Oakville Prairie. Mantel tests show that ground dwelling arthropods are most strongly correlated with soil environmental conditions (r_M = 0.4027, p = 0.0001), and foliar arthropods are most strongly correlated with plant species diversity (r_M = 0.3835, p = 0.0006). These results suggest that patterns and associations of different arthropod communities can form separately from one another within the same space, which may inform conservation efforts targeted to specific arthropod communities.