Promoting Soil Ecosystem Services in Cities: The Role of Green Infrastructure in Reconnecting Urban Ecohydrology.

Urbanization is a dominant form of landscape change that affects the structure and function of ecosystems and alters biogeochemical and hydrologic cycling. Through direct and indirect effects, cities can greatly alter soil properties and desired ecosystem services. Green infrastructure (GI) has been proposed as a solution to urban environmental, and may even help mitigate urban impacts on soils and the ecosystem services of cities. Despite this promise, there has been relatively limited empirical focus to evaluate the efficacy of GI and relationships between design and function. This knowledge gap is especially important for transferring GI BMP approaches designed for temperate environments to cities that are in water-limited settings. Through partnerships with local non-profits that install GI, we have been observing street-scape water harvesting GI features in Tucson, AZ, and more controlled experiments at the Biosphere 2 facility in Oracle, AZ.  These studies assess the ability of GI approaches to storm water harvesting to facilitate ecosystem function and services in an arid context and explore: (1) how GI and water harvesting impacts urban soil quality and ecosystem function, and (2) how design parameters of GI affect their ecological function. Streetscape GI features promote soil C storage, with elevated soil organic matter, labile, and total C pools, while at the same time enhance soil food web structure and microbial populations. We also observe variable sensitivity of microbial activity, soil respiration, and decomposition to different BMPs with respect to GI design properties (soil texture and composition, choice of surface mulches) and antecedent precipitation inputs and soil moisture conditions. These findings indicate that GI can improve urban soil quality. This study highlights the importance of linking ecological principles with performance goals to better inform the design of BMPs to provide soil ecosystem services.