Heterogeneity of soil CO2 efflux from local parks across an urban landscape

Context The soil-atmosphere carbon exchange is an important component of the carbon cycle; however, dynamics of CO2 fluxes from urban landscapes are particular complicated and poorly understood due their heterogeneity. Objectives The objectives of this study were to examine the total and temporal variation in CO2 flux from wooded and turfgrass areas of local parks in different part of town and identify the biophysical characteristics and landscape level factors that contribute to CO2 flux spatiotemporal variance in urban greenspaces. Methods We characterized the soil CO2 fluxes, temporal variation, and response to soil temperature from five parks under uniform management of a medium-sized town in southwestern Virginia, USA. We measured site scale characteristics (soil properties, tree cover) as well as the urbanicity of the surrounding land (land cover composition, population). Results Soil total nitrogen, soil temperature, and bulk density explained approximately 70% variation in the annual CO2 flux across the five parks. Diurnal, weekly, and seasonal CO2 fluxes were primarily related to changing soil temperature and differed between the turfgrass and wooded areas. Contrary to predictions that increased urbanicity around parks would increase soil temperature and CO2 fluxes, both CO2 and soil temperature of turfgrass were higher at parks located on town edges compared to parks in the center. Conclusions In sum, this study indicates that soil nitrogen and compaction, urbanicity, and the resulting site-scale structure of vegetation have a strong influence on temperature dependent biogeochemical processes like CO2 efflux.