Using Political Ecology to Contextualize Alterations to Soil Biogeochemistry of Alternative Yard Types in Six U.S. Cities

Background/Question/Methods

The biogeochemistry of carbon (C) and nitrogen (N) soil cycling are increasingly of concern in relation to the preservation of biodiversity and as regulators of ecosystem response to climate change. With an increasing proportion of U.S. cities taking the form of suburban development, considerable focus is placed on the future of yards. Soil samples were analyzed from six U.S. cities (Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, and Phoenix) to contrast different yard types including low and high fertilizer turfgrass yards, hydrologically oriented yards (xeriscaping/rain gardens), wildlife certified yards, as well as native reference sites for each city. Topsoils (0-10 cm depth) were tested for soil microbial biomass C and N content, respiration rates, nitrite/nitrate and ammonium content, potential net N mineralization and nitrification, denitrification potential, and total N. A key challenge in analyses of residential yards relates to understanding the sociohistorical context for these soils. To address this challenge, a political economy related to suburbanization was developed for the six cities with particular focus on transportation and race. This approach aims to yield an integrated sociobiogeochemistry, providing a perspective of anthropogenic landscape regimes as a basis for interpreting results.

Results/Conclusions

We observed significant variation in soil C and N cycle parameters in residential yards with different management regimes. Nitrite/nitrate content and total N were higher in high intensity fertilizer turfgrass yards, suggesting that alternative management regimes can result in improved environmental performance. There were no differences in microbial biomass C or respiration either across cities or when averaging cities by treatment, suggesting that all yard types had an active C cycle that can be managed to improve environmental performance and carbon sequestration. Patterns of U.S. suburbanization that accelerated in the early twentieth century were quite similar across cities, driven by a variety of factors associated with transportation and race. Federal initiatives such as the Federal Housing Association and the Home Owners' Loan Corporation encouraged such patterns of development. The homogenization, or commonality of drivers, may be a key for facilitating widespread adoption of alternative yard management strategies. A sociobiogeochemical approach may allow us to shift discourse towards larger scales of landscape alteration that have recently occurred, allowing for broader visions towards the possibilities of ecologically healthier futures.