Urbanization effects on leaf litter decomposition, foliar nutrient dynamics and aboveground net primary productivity in the subtropics

Abstract

Urbanization can alter nutrient cycling. This research evaluated how urbanization affected nutrient dynamics in the subtropics. We established 17–0.04 ha plots in five different land cover types—slash pine (Pinus elliottii) plantations (n = 3), rural natural pine forests (n = 3), rural natural oak forests (n = 4), urban pine forests (n = 3) and urban oak forests (n = 4) in the Florida panhandle, a subtropical region that has experienced rapid urbanization. On each plot, we measured the decomposition of mixed species foliar litter, the nutrient release patterns in decomposing litter, foliar litter quality, and forest floor temperatures. Aboveground net primary productivity and soil carbon and nitrogen contents were also measured to characterize the carbon and nitrogen stocks and fluxes in the urban and rural sites. Litter decay rates, liter quality indices and nutrient release patterns in decomposing litter did not differ among urban and rural forests despite differences in forest floor temperatures between urban and rural sites. Urban forest floor temperatures are on average warmer by 0.63 °C in the winter (p = 0.005) and tend to have a more narrow temperature range than those of the rural forested sites. Foliar mass was measured over an 82 week period that was characterized by drought, which may have masked an urbanization effect. Urban forest land covers had higher aboveground net primary productivity and foliar productivity compared to rural land covers. This increased input of foliar carbon is not reflected in statistically different forest floor or surface soil (0–7.5 cm) carbon contents between urban and rural sites. Understanding how drought interacts with other drivers of change in urban systems may be a necessary component of city specific ecological knowledge.