
%0 Journal Article
%A Leishman, Michelle R. 
%A Hughes, Miah T. 
%A Gore, Damian B. 
%T Soil phosphorus enhancement below stormwater outlets in urban bushland: spatial and temporal changes and the relationship with invasive plants
%J Soil Research
%D 2004/04/15
%V 42
%N 2
%P 197-202
%K soil nutrients, environmental weeds, disturbance, stormwater runoff.
%R https://doi.org/10.1071/SR03035
%U https://www.publish.csiro.au/paper/SR03035 
%X Invasion by exotic plant species is a significant problem in urban bushland remnants and is often associated with nutrient enrichment of soils. A major source of nutrient enrichment in urban areas is stormwater runoff, which is transferred from impervious surfaces in urban catchments and discharged at outlets on the residential/bushland interface. We measured the spatial extent of soil total phosphorus (P) enhancement below stormwater outlets on Hawkesbury Sandstone-derived soils in northern Sydney and examined whether total P concentration has increased with time since urban development and extended laterally beyond the stormwater flow path. The average area of soil P enhancement below outlets was 0.24 &#177; 0.05 ha and was widest 30&#8211;50 m downslope from the outlet, where it extended an average 40 m across slope. Catchment area was not significantly related to average soil total P concentration. There was a significant decline in total P across slope from the centre of the flow path and a significant positive relationship between soil total P and proportion of exotic plant cover, with soil P accounting for 77.5% of variation. We found evidence for a build-up in soil total P concentration over time within the run-on zone below outlets, with the rate of enhancement being ~68 mg/kg per decade over a 40-year period. Evidence for lateral transfer of soil P out of the run-on area was more equivocal. There was a significant decline in soil total P across slope from the boundary of the run-on zone, with higher concentrations at distances 0.5 m and 1 m from the boundary compared with &#62;1.5 m. However, this could be due to error in locating the boundary between run-on and non run-on areas. There was no significant relationship between soil P in the non run-on zone and age of development, which would be expected if P was being transferred by biological activity beyond the run-on zone over time. It is clear that the primary areas of concern for management must be the run-on areas below outlets. 
