Land use change associated with urbanization modifies soil nitrogen cycling and increases N<sub>2</sub>O emissions
Abstract. Urbanization is becoming increasingly important in terms of climate change and ecosystem functionality worldwide. We are only beginning to understand how the processes of urbanization influence ecosystem dynamics, making peri-urban environments more vulnerable to nutrient losses. Brisbane in South East Queensland has the most extensive urban sprawl of all Australian cities. This research estimates the environmental impact of land use change associated with urbanisation by examining soil nitrogen (N) turnover and subsequent nitrous oxide (N2O) emissions with a fully automated system that measured emissions on a sub-daily basis. There was no significant difference in soil N2O emissions between a native dry sclerophyll eucalypt forest and an extensively grazed pasture, wherefrom only low annual emissions were observed amounting to 0.1 and. 0.2 kg N2O ha−1 y−1, respectively. The establishment of a fertilised turf grass lawn increased soil N2O emissions by 18 fold (1.8 kg N2O ha−1 y−1) with highest emission occurring in the first 2 month after establishment. Once established, the turf grass lawn presented relatively low N2O emissions after fertilization and rain events for the rest of the year. Soil moisture was significantly higher and mineralised N accumulated in fallow land, resulting in highest N2O emissions (2.8 kg N2O ha−1 y−1) and significant nitrate (NO3−) losses of up to 63 kg N ha−1 from a single rain event due to plant cover removal. The study concludes that urbanization processes into peri-urban ecosystems can greatly modify N cycling and increase the potential for losses in form of N2O and NO3−.