Development of Carbon Pools and Enzyme Activities in Constructed Urban Soils

Constructed soils (CSs) are important for rehabilitation of degraded lands, carbon (C) sequestration, and urban agriculture, but little is known about the development and dynamics of organic matter pools in these soils. In this study, we tracked these pools over 21 months in CSs (1/3 compost and 2/3 fine glacio-fluvial sediments) planted with eight different vegetation treatments with densimetric and enzymatic approaches. Time was the main driver influencing soil parameters, followed by vegetation. A high diversity “All” treatment had a significant impact on soil development, notably enriching mineral/sand-associated organic carbon (MSOC) and nitrogen (MSON) by 15% and 12%, respectively, compared to a non-vegetated “Bare” treatment. The presence of sunflower (Helianthus annuus L.) in the vegetation treatment was associated with low values of nitrate-N, particulate organic N (PON), hot-water extractable carbon (HWEC), and β-glucosidase. These CSs appear to be undergoing rapid soil development driven by organic matter accumulation processes that facilitate nutrient cycling and accumulation of stable MSOC.