Biogeochemical and socioeconomic drivers of above- and below-ground carbon stocks in urban residential yards of a small city

Abstract

Research on patterns of below-ground carbon (C) storage in urban lawns has focused on biogeochemical mechanisms, with human activities playing an important but somewhat secondary role. By contrast, studies of above-ground vegetation in urban areas have emphasized socioeconomic factors that influence greenness, abundance, and diversity, without explicitly considering biogeochemical mechanisms. Here we examine how both biogeochemical and socioeconomic factors influence patterns of C storage in urban yards both above- and below-ground. We combined measurements of above- and below-ground C stocks in 36 lawns located in the small city (<200,000 residents) of Manchester, New Hampshire, USA with a suite of indicators such as housing age, population density, median income, home value, and residence duration that we obtained from public assessment databases, the decennial census, and the American Community Survey. We found that for this small city, housing age was the only variable that was significant and positively correlated with soil C stocks. Median income, median resident age, and percent married couples were significant and positively related with above-ground biomass C, with housing age playing a secondary role. The disparity that we observed in how biogeochemical and socioeconomic factors shape the distribution of C stocks in urban yards highlights the need for management approaches tailored to sequestering C in above- versus below-ground pools. Understanding the C dynamics of small cities is critical to ensuring that urban areas of all sizes can enhance urban C storage and minimize urban C loss.