Suburban development and resultant changes in the phosphorus status of soils in the area of Ku-ring-gai Sydney Australia

Total phosphorus of urban bushland soils from the Ku-ring-gai area in the northern suburbs of Sydney was measured. Sampling sites were located on hillslopes, undeveloped ridgetops, adjacent to creeks and roads, downslope of suburban boundaries and stormwater outlets, and along sewerage lines. All sites were located on soils derived from Hawkesbury Sandstone. Within urban bush valleys, sites adjacent to nutrient sources had significantly higher phosphorus levels than sites remote from nutrient sources. Sites downslope of suburban boundaries were the least affected (average 90 ppm) while sites receiving urban runoff directly had the highest levels of phosphorus (e.g. downslope of stormwater outlets 438 ppm). The area of phosphorus enhancement around nutrient sources was largest for sites located downslope of any source. These results have important implications for the management of urban bushland and the control of exotic plant species.