Ecology of urban lawns: The impact of establishment and management on plant species composition, soil food webs, and ecosystem functioning

Turfgrass lawns have become a central part of urban and suburban landscapes throughout North America. Although they provide numerous benefits, urban lawns have become chemical input intensive systems with routine and often calendar-based application of water-soluble fertilizers and pesticides. These inputs are expensive and are considered a source of environmental pollution and health risk. However, very little is known about the impacts of chemical inputs on the turfgrass soil ecology and ecosystem functioning. In fact, turfgrass urban lawns are the least studied ecosystems, despite their obvious familiarity to millions of homeowners in North America. Therefore, the environmental impact of chemical inputs associated with manicured urban lawns must be evaluated to provide a sound foundation to build sustainable urban ecosystems.; In this study, we assessed the impact of lawn management practices in Ohio on turfgrass ecosystem using several key ecological indicators, including soil nitrogen pools (NO3-N, NH4-N, and dissolved organic nitrogen), soil organic matter (SOM) content, microbial biomass, and nematode community. We had four specific objectives: (1) to compare turfgrass establishment, nutrient pools, and nematode community in subsoil and topsoil (with or without compost amendment); (2) to determine the effects of nitrogen fertilization on soil nematode community and nutrient pools in lawns established on subsoil and topsoil, with or without compost amendment; (3) to determine long-term effects of management practices on soil nematode community, organic matter, microbial biomass, and nitrogen pools in experimental plots; and (4) to assess the influence of three predominant home lawn management programs on turfgrass quality, weed and insect infestations, disease incidence, and soil food web structure and functions.; We found that topsoil had higher nitrogen pools, microbial biomass, SOM, nematode abundance and genus numbers compared to the subsoil. In addition, compost amendment resulted in higher levels of soil nutrient pools compared to the subsoil, which were maintained during the course of the one-year study period. Nitrogen fertilization had no impacts on soil nematode community during the first year after turfgrass establishment. Our results also showed that topsoil plots had better turfgrass germination but higher weed infestation than subsoil plots after turfgrass establishment. Overall, long-term organic-fertilizer based turf management resulted in higher soil microbial biomass compared to mineral-fertilizer management or the control. But herbicide, insecticide, or fungicide applications had no significant long-term effect on soil microbial biomass, SOM contents, and any aspect of nematode community. Nematode community was significantly affected by long-term nitrogen application (15 years), as Maturity Index (MI) and Combined MI, were generally lower and Enrichment Index was generally higher under high and medium N-input compared to low N-input management. We also found that homeowners relying on typical do-it-yourself (DIY) programs are unable to achieve the desired levels of turf quality (1.5 for DIY lawns but 3 for professionally managed lawns, on a 0 to 3 scale) and weed control, and chemical input intensive management might negatively affect soil microbial biomass and SOM in urban lawns.; In conclusion, topsoil has higher initial soil nutrients and biota and thus higher turfgrass germination compared to the subsoil. However, higher weed infestation in topsoil plots due to weed seed bank suggests that weed control is important during the early stage of turfgrass establishment on topsoil. Also, compost amendment is an effective way to improve soil nutrient pools and biota, and its impact on soil ecosystem remains during the one-year study period. Long-term organic-fertilizer management benefits soil ecosystem in general compared to mineral-fertilizer management. However, herbicide, insecticide, or fungicide app...