A Comparison of soil arthropod biodiversity in two urban prairies and turfgrass

Background/Question/Methods

Prairies improve environmental health through building and reclaiming soil, capturing storm water runoff, sequestering carbon, and enhancing biodiversity. These qualities are especially important in urban areas where prairies also contribute benefits associated with green spaces. Few studies have examined arthropod communities in prairies as potential bioindicators of ecosystem health and diversity. In this study, soil arthropod communities were compared at the 1 ha Chicago State University (CSU) prairie established 10 years ago, the adjacent turfgrass landscape, and a nearby 24 ha Gensburg-Markham (GM) prairie remnant. Our objectives were to A) compare soil arthropod communities within a relatively young, urban prairie restoration (CSU) and a decades old, high quality prairie remnant (GM); B) quantify potential differences in arthropod taxa and diversity between the CSU prairie and adjacent turfgrass. Both prairies were sampled in June and October, 2012 using 25 pitfall traps per site. The turfgrass was sampled in October using 10 pitfall traps. All traps were left in the field for three days, after which arthropods were collected, sorted, and stored in vials containing 70% ethanol. Individual specimens were examined microscopically and identified to genus and species when possible. ANOVA and means separations tests were done using JMP â software.

Results/Conclusions

A total of 1186 arthropods were collected, encompassing 16 orders, 7 genera and 69 species. The CSU prairie had the greatest species richness during summer (31 taxa), a value twice as high as the GM site. Richness was lowest in the turfgrass (8 taxa). The  Shannon-Weaver pooled diversity indices for each site showed the summer season at both prairies were most diverse. An ANOVA and means separation test (Tukey-Kramer) revealed that CSU prairie had significantly higher (p=0.05) mean arthropod biodiversity in summer (H’= 1.36) compared to all other locations and seasons. The GM prairie’s summer biodiversity was next highest (H’=0.75) and the fall turf and CSU prairie indices  were lowest (H’= 0.49 and 0.40, respectively). An extremely high abundance of Collembola species (springtails) in the CSU prairie samples in fall resulted in low biodiversity. Sorenson’s Quantitative Index of Similarity revealed there is greater similarity in species between seasons in the GM prairie (C_N=0.30) than in the CSU prairie (C_N=0.017). The CSU prairie species composition in fall was similar to the low diversity turf (C_N=0.78). These findings indicate pronounced seasonal differences occur in soil arthropod communities and striking differences in species composition between the high quality GM prairie and the CSU site.