DOC and DON Release and Reactive Soil Pools in Urban and Remnant Soils

Abstract

Release of dissolved organic carbon (DOC) and nitrogen (DON) from subtropical urban soils has had little investigation, even though the growth of metropolitan areas is unprecedented in southern states. The time of initial disturbance from native or agricultural to urban land use and irrigation with sodic water may compromise urban soils' ability to retain DOC and DON. We examined 21 soils from beneath remnant native land use and urban land use in south-central Texas. Soils were collected from five classes of urban land use and four classes of remnant native land use and analyzed using initial mass isotherms. We found that release of DOC was significantly higher from soils under urban parks (range, 433–782 mg kg−1) relative to soils from residential lawns (range, 89–228 mg kg−1) and remnant native soils (range, 43–264 mg kg−1). Release of DON and DON reactive soil pools were also significantly increased in soils under urban relative to remnant land use (P < 0.05). Older urban soils with minimal irrigation tended to have DOC and DON reactive soil pools similar to remnant soils, perhaps illustrating that equilibrium is reached over time.