Are nematodes effective bioindicators of soil conditions and processes along distance from roads and age of development in urban areas?
SUN-JEONG PARK1,2, ZHIQIANG CHENG2, BRIAN B. McSPADDEN GARDENER1,3 and PARWINDER S. GREWAL1,2
1Environmental Science Graduate Program, Urban Landscape Ecology Program, Ohio State University-OARDC, Wooster, OH 44691
2Department of Entomology, Ohio State University-OARDC, Wooster, OH 44691
3Department of Plant Pathology, Ohio State University-OARDC, Wooster, OH 44691
In a previous study, we found that soil chemical properties vary with distance from roads and development age in urban areas. As nematodes are considered as potential bioindicators for soil conditions and processes, we tested whether nematodes can serve as effective bioindicators of the observed differences in urban soil chemistry along the two factors. Urban boundaries dating from the 1920’s (old), 1960’s (middle) and 2000’s (new) were identified in three cities in northeast Ohio; Canton, Massillon, and Wooster. Soil samples were collected from two road-side and two interior lawns in one public school site within each urban age ring in each city. Nematodes were extracted from the soil samples, counted, identified to genus-level and assigned to functional guilds. Most soil nematode variables varied with urban age and season, but not with the distance from the road. Abundance and genus-level richness of nematodes were greater in old urban sites (50 and 100 years) than those in newly established sites (~10 years). This pattern was particularly significant with the colonizer-persister 2 class nematodes. On the other hand, nematode maturity, enrichment and structure indices did not differ with urban age. In October, overall nematode abundance increased, but the structure of nematode food web degraded as indicated by decrease in maturity and structure index values. Correlation analyses revealed that soil nematode abundance variables were positively correlated with soil chemical properties along urban age, but not along the distance from road. The lack of correlation between soil nematode and chemical variables in the road-side soils suggests suppression of soil processes such as decomposition and nutrient cycling in urban road-side soils. In conclusion, abundance and diversity indices of soil nematodes were particularly useful for detecting differences in soil chemistry and assessing potential suppression of soil processes in urban areas.
Key words: urban soils, urban development age, distance from roads, nematodes