Urban agriculture is increasingly important to sustainably feed the world’s growing population. Although communities of soil-associated arthropods are influential in crop success, there has been little research on the differences in these communities along the urban to rural gradient. Urbanization favors the influx and establishment of non-native and invasive species, while habitats are fragmented and homogenized, all of which are deleterious to species diversity. The urban atmospheric environment is warmer than the rural environment, which could favor greater abundance of particular arthropods. We examined arthropod abundance, and morpho-type diversity at urban, peri-urban, and rural field sites around Salt Lake City, Utah. Specimens were collected bi-weekly from six sites, containing multiple crop species from July to October 2016. Using pitfall traps, we surveyed arthropods in eight pots with a uniform soil mixture planted with beans (Phaseolus vulgaris). Abundance was predicted to be greater at urban sites than at rural sites as a result of larger numbers of a few morpho-species. Diversity was predicted to be higher in rural sites than the others due to diversity of niches and source populations nearby.
Results/Conclusions
Our study suggests that there are important differences in the arthropod communities in urban agroecosystems compared to their rural counterparts. Total abundance was highest at both urban sites, lowest in the two rural sites, and intermediate at the peri-urban sites. Total abundance of all arthropods collected ranged widely from 562 individuals at a rural site, to 8,449 individuals at an urban site. The most numerous arthropods at all sites, but most notably at the urban sites, were isopods and springtails. The large abundance of a select few species proportional to total abundance contributed to the lower species diversity measured at the urban sites compared to the rural sites. Mean species diversity of arthropods ranged from 1.03 at an urban site to 2.01 at a rural site. The results of our study suggest that, despite uniform soil and crop conditions, the soil arthropod communities are not the same across an urban to rural gradient. These findings have potential consequences for nutrient cycling, pest management, and crop productivity, and may influence successful farming practices. Future studies could examine the implications of these findings, with an aim to more fully understand causal relationships that may exist between agroecosystems along the urban rural gradient and the character of arthropod communities therein.