Toward Measuring and Modeling Regional Variation in Urban Soil CO2 Emissions.

Cities contain extensive greenspaces, which in turn contain potentially high concentrations of soil carbon (C).  However, urban soil C is highly heterogeneous with drivers of soil C change operating at multiple scales.  We have hypothesized these drivers of urban soil C variation tend to increase the amount of soil C in highly managed greenspaces compared to analog native spaces.  Further, management of greenspaces tends to homogenize variation within individual patches but increases variation between patches compared to many native spaces where much larger proportion of the variation of soil C is found at within individual patches.  Based on this landscape perspective of urban soil C, we began a project examining variation in urban soil CO₂ emissions across a dramatic coastal to desert climate gradient in the greater Los Angeles, CA metropolitan region.  Results from landscape surveys and experiments suggest that variation in green space land management and climate influence key environmental drivers of soil CO₂ emissions and to an even greater extent the ecosystem sensitivities to these drivers.   Interestingly, seasonality had a larger influence than management or climate on soil CO2 emissions.  These findings highlight the landscape variation in soil CO₂ fluxes, a key component of soil C dynamics, associated with urbanization across a dominant climate gradient.  These results are leading to an elaboration of more general theory of how urbanization influences soil C content, spatial distribution, and rate of change.