Abstract
Urban landscapes are not homogeneous, and small-scale variations in plant community or management inputs can give rise to a large range of environmental conditions. In this paper, we investigated the small-scale variability of soil nitrogen (N) properties in a single urban landscape that has distinctly different patches or types of cover. We specifically measured soil net N mineralization, nitrification, and exchangeable forms of inorganic N for patches with traditional turfgrass versus patches with common turfgrass alternatives such as ornamental grasses, groundcovers, and mulches. All soil N properties were variable among landscape patches, showing that soil N processing can vary on scales of a few meters. Notably, both mineralization and nitrification were the highest in a patch covered with perennial peanut, but exchangeable nitrate (NO3−) was low for the same soil, indicating that soils under perennial peanut may be producing high levels of inorganic N but that the produced N does not stay in the soil, possibly leaching to underlying groundwater. We recommend future studies on the mechanisms that drive the variable N properties seen under distinct urban landscape patches, with special emphasis on potential patterns in N losses for mixed-vegetation landscapes.
Highlights
A well-managed, aesthetically pleasing landscape is associated with wellbeing in many residential landscapes, and the area of turfgrass in the United States is larger than that for any irrigated crop [1]
While numerous studies have indicated that nutrient losses via leaching and runoff are minimal from healthy, properly maintained turfgrass and that turfgrass lawns are sinks of nitrogen (N) in urban watersheds [6–8], turfgrass fertilizers are increasingly targeted by management practices and policies aimed at reducing anthropogenic nutrient inputs to aquatic ecosystems [9]
The premise behind these bans is that summer rains may lead to increased leaching and runoff losses of N and P applied as fertilizer to lawns, in turn leading to increased anthropogenic nutrient loading to nearby waterbodies
Summary
A well-managed, aesthetically pleasing landscape is associated with wellbeing in many residential landscapes, and the area of turfgrass in the United States is larger than that for any irrigated crop [1]. Flowers, managed turfgrass, and ornamental deciduous and evergreen trees represented a lower risk of NO3 − loss from the soil than unplanted mulched areas, which the authors recommended should be used sparingly in urban landscapes because of the potential for NO3 − leaching to groundwater. Variation in habitat structure gives rise to differences in soil pH, moisture content, microbial populations, temperature, and vegetation cover, which in turn may all cause variations in the N cycling processes within an urban landscape [15,20–22] This means that distinct patches may emerge, creating a landscape mosaic where ecological variables can vary at scales of just a few meters or less. We selected a mixed-species urban landscape with this type of small-scale patchiness in vegetative cover and investigated the spatial variability of inorganic N production in soils. In this we show how how cycling processes in a single urban landscape can be highly variable, aaa that efforts to constrain the of urban urbanlandscape nutrient sources can bevariable, improved how incan a fate single can beargue highly that efforts to constrain the fate of urban nutrient sources can be improved cycling processes in that a single urban landscape be highly variable, and we that efforts constrain the of urban nutrient attention to to mixed-vegetation landscape scenarios assources well as can databe at improved finer spa that to constrain the fate fate of be urban nutrient sources can efforts to constrain the fateefforts of urban nutrient sources can improved byasgreater attention to mixed-vegetation mixed-vegetation landscape scenarios well as asattention databe at improved finer spa attention to landscape scenarios as well data at attention toscenarios mixed-vegetation scenarios as well as data at finer finer spa spa to mixed-vegetation landscape as well as landscape data at finer spatial scales
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