Lunch Seminar "Environmental Services of Urban and Rural Soils: Retention, Release and Reactive Soil Pools of DOC and DON"

Retention and release of dissolved organic carbon (DOC) and nitrogen (DON) in urban soils had not been investigated. Construction and management of urban soils may compromise their ability to perform the environmental service of DOC and DON retention and release.  Twenty-four soils were collected along an urban to rural gradient under land use classifications ranging from highly developed urban areas to forests and analyzed using an initial mass isotherm experiment.  Mean partition coefficients for DOC ranged from 0.13±0.03 in pasture to 0.34±0.10 in urban open area soils and from 0.16± 0.06 in pasture soils to 0.51 ±0.21 in wetland soils for DON.  Release of DOC was significantly higher from soils under urban open areas (608±247 mg kg^-1) relative to all other land uses, with the exception of urban high density areas.  Reactive soil pools of DOC were significantly higher in urban open area soils (965 mg kg^-1) than all other soils (range 108 – 386 mg kg^-1). Water extractable soil sodium explained the high variance in DOC reactive soil pools (Adj. R² = 0.95; p < 0.001) and release (Adj. R² = 0.94; p<0.001).  Soil pH explained the high variance in DON reactive soil pools (Adj. R² = 0.85; p < 0.001) and release (Adj. R² = 0.91; p < 0.001).  Our data suggest that soils in urban environments are compromised in their capacity to retain DOC and DON relative to the soils under shrub scrub land use, which was the land cover prior to urbanization.