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  software.

Results/Conclusions

Initial results suggested 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). Over the last year, further statistical analyses and examination of specimens with expert entomologists led us to adjust our results. Current data indicate that species richness is 65 overall sites, and community diversity (Shannon entropy) is greatest (H’= 1.36) at the CSU prairie during summer (p=0.05). The next highest diversity (H’=0.75) was found at the GM prairie in summer.  Fall turf and CSU prairie indices were lowest (H’= 0.49 and 0.40, respectively. The high abundance of Collembola species in the fall CSU prairie samples depressed biodiversity.  Sorenson’s Quantitative Index of Similarity revealed less difference in species composition occurred between summer and fall at the GM prairie (C_N=0.58) than the CSU prairie (C_N=0.26). The composition of arthropods was least similar in fall samples of GM prairie and CSU turf (C_N=0.40). The new findings suggest the young CSU prairie is developing a high level of biodiversity, but unlike the GM prairie, pronounced seasonal differences occur.