Decomposition of tree leaf litter on pavement: implications for urban water quality

Abstract

Leaf litter may be an important source of nutrients to stormwater and ultimately contribute to eutrophication of surface waters associated with urbanization. Thus, understanding decomposition and nutrient release from leaf litter that falls on impervious surfaces is important for stormwater management. However, few studies have examined leaf litter decomposition in the unique urban environment of the street gutter. We compared decomposition of leaf litter of five street tree species in a parking lot gutter in St. Paul, Minnesota, USA. In contrast to our expectations, comparisons with past studies revealed that litter decomposed more rapidly in the gutter than in nearby natural areas. And decomposition rates were as rapid as those measured in other urban settings (forests and streams), with most species losing 80 % of their initial mass after 1 year. Litter of most species had retained more than half of its initial N and P after 1 year. However, in contrast to N, litter P dynamics largely were uncoupled from litter mass dynamics, with litter P increasing and decreasing unpredictably over the year. Shortterm (24 h) laboratory studies revealed that litter had the potential to lose a high fraction of its initial P, with high variation among species (from 27 to 88 %), and a smaller fraction of its initial N (<10 %) via leaching. Thus, street tree species may differ in their potential contributions to nutrients that are released during decomposition. Our results suggest that careful selection of street tree species and timely removal of litterfall have significant potential to reduce nutrient fluxes from streets to storm drains, particularly for P.

Leaf litter decomposition in urban forests: test of the home-field advantage hypothesis

“…The abundance and richness of soil microbes in broadleaf forests were generally higher than those of coniferous forests (Wang and Wang 2007;Liu et al 2012). The decomposing rates for four sets of litter were much faster in rainy season, which is consistent with the finding from a previous study on decomposition of tree leaf litter on pavement (Hobbie et al 2014). The varied decomposition rates can be partially attributed to the microclimate conditions such as temperature and relative humidity (Fig.…”

Composition of nitrogen in urban residential stormwater runoff: Concentrations, loads, and source characterization of nitrate and organic nitrogen

“…When the wet season begins in June, these partly decomposed materials (acorns and oak leaves) are carried by the stormwater runoff into the gutter and then contribute PON in runoff [69]. This hypothesis is supported by several studies that demonstrated the decomposition of leaf litter as a contributor to dissolved N in stormwater [11,28,29,70]. These studies suggested particulates were decomposed by vehicle activity on the road surface, movement during storm events, and further decomposition in road gutters, thus contributing PON while DON was gained from leaching of freshly fallen litter.…”

Evaluation of Stormwater Treatment Vault with Coanda-Effect Screen for Removal of Solids and Phosphorus in Urban Runoff

“…Although a 21% reduction in TP was achieved across all high-intensity events, this was balanced by the 7% reduction in TP during low-intensity events. Low TP reductions could be due to leaching and conversion of phosphorus to the dissolved phase in an aquatic reducing environment (sump) (Hobbie et al 2014;Selbig 2016;Olsen 2017), or simply to the fact that most phosphorus is associated with particles smaller than the screen size, as seen by Balakrishnan et al (2015). Although nearly 60% of annual TP in an urban environment can come from fall leaf litter (Selbig 2016), this study was unable to test the removal efficiency of the modified treatment system during that period due to rising lake levels inundating the effluent pipe.…”