Soil CO2, CH4 and N2O fluxes in open lawns, treed lawns and urban woodlands in Angers, France

Urban green spaces (UGSs) are mostly represented by lawns and wooded areas. These UGSs can store carbon in soil and above-ground biomass, potentially modulated by management intensity and vegetation cover. Trees in lawns can create a local microclimate modifying soil biogeochemical cycles affecting in turn greenhouse gas (GHG) emissions. The objective of this study was to assess the effects of trees on microclimate (temperature and moisture) and soil properties influencing GHG fluxes in contrasted UGS types. We monthly monitored (from March to November 2021) and compared soil CO2, CH4 and N2O fluxes simultaneously with surface temperature and moisture in treed lawns, open lawns and urban woodlands. Lawns included 4 different management intensities including mowing, irrigation and fertilization practices. Temperature was the best predictor of soil respiration in all UGS types studied and was the highest in open lawns. We showed that moisture reflected by the water filled pore space (WFPS) significantly added on variation explanation. The shading of trees decreased soil respiration by 34% in treed lawns while soil properties were similar, indicating a straightforward effect of lowering temperature. On the contrary, in woodland soils the lower rates of soil respiration were attributed to both soil properties and temperature decreasing. Urban woodlands were a sink for CH4 throughout the year (- 0.19 mg m over bar (2) h over bar (1)). Methane consumption in lawns was small and even a CH4 source in irrigated parks when WFPS overpassed 75%. N2O fluxes were small (0.014 mg m over bar (2) h over bar (1)) probably reflecting the transition already made from mineral to controlled-release fertilization limiting N availability.