Evaluating the effects of canine urine on urban soil microbial communities

Abstract

Due to extensive areas of impermeable surfaces, combined sewer overflow (CSO) is currently a major problem in urban areas across the United States. In CSO systems, sewage can travel through underground pipes to be decontaminated in treatment facilities, or it can combine with stormwater after a precipitation event and discharge into local waterways. Many cities are implementing green infrastructure installations, which use vegetation and bioactive soil microbial communities to enhance soil water-holding capacity, thereby minimizing CSO events. Understanding the factors that structure soil microbial communities in green infrastructure will facilitate more effective management of these engineered ecosystems; however, few studies to date have evaluated ecological patterns and processes of microbes in the urban environment. Nitrogen loading is known to be a major factor structuring fungi and bacteria in non-urban soils, and since cities also contain large populations of canines, N-rich urine deposition is a potential factor that could be important for structuring soil microbes in ground-level green infrastructure installations. Our study investigated the effects of canine urine on the urban soil microbial communities in a greenhouse experiment by treating Liriope muscari, a common plant found in New York City green infrastructure, with different concentrations of canine urine for 4 weeks in an experimental setting. We found that urine application significantly decreased total soil microbial biomass and microbial richness, and increased water runoff volume. These findings indicate that canine urine may have negative consequences for soil water-holding capacity and nutrient cycling in urban green infrastructure installations by directly decreasing the abundance and richness of soil microbial communities.