Impacts of intensive wetting, stagnation and drying cycles on carbon pools and allocation within stormwater processing system substrates designed for multifunctionality

Greening of our urban ecosystems provides a multiplicity of benefits, from the mood-lifting impact of nature-based aesthetics to the increased available habitat broadening the range of species within our densely packed cities. In recent years, greening efforts have largely been centered around the introduction of street trees, as their strong evapotranspiration effect mitigates increasing urban temperatures. However, the health and vitality of trees requires a significant amount of roadside space and are highly sensitive to stormwater dynamics as well as pollution, making implementation ill-suited in some urban spaces. Infiltration swales offer a practical, low-cost opportunity to counter-act the climatic increase in severe stormevents by purposely constructing substrates capable of processing polluted stormwaters and providing a habit for native plants to thrive. In testing high carbon organic amendments for their capabilities to adsorb road-side heavy metals and biocides as well as for their role in enhancing soil physical, chemical, and biological functioning - a mixture combining urban green waste compost with a high temperature biochar showed superior multidimensional functionality. In this follow-up experiment, informed substrate combinations are compared in their ability to support native plant diversity under cyclic flooded conditions across one growing season. An assessment is made on the potentials of carbon allocation to different pools between the plant, rhizosphere and bulk soil within this system. Results of this study hope not only to inform the scientific community but emphasize to city planners and officials the broadly interdisciplinary nature of soil systems, particularly the importance in pinpointing synergistic services as well as identifying those functions that may stand in opposition to one another.