Urban flower field
The Urban Flower Field is a combination of our Stewardship Science research and an urban art project. In 2014, it was used for a phytoremediation project, utilizing plants to remove heavy metals from the soil. The current research is more similar to what we are doing in the Stewardship Garden study plots. Each of the 96 flower circles holds 2 or 3 lysimeters, or groundwater collection devices, from which water samples are taken and analyzed weekly for soluble nitrogen and phosphorus content.
Industrial activity and vehicle emissions can lead to contamination of urban soils by heavy metals, such as lead, arsenic and cadmium. This contamination can adversely affect a variety of ecosystem services and potentially impact the health of urban residents. Due to the high cost of typical soil remediation strategies, areas with heavy metal contamination are largely left untreated. Finding low-cost solutions to heavy metal contamination and engaging citizens in urban revitalization efforts is essential in addressing this issue.
The Urban Flower Field began as a multi-year soil remediation experiment set in an urban public art project. The research component of the project tested whether plant biodiversity increased phytoremediation – the ability of plants to remediate soil, e.g. through uptake of heavy metals. The idea was that biodiversity would increase the collective growth of species planted in mixtures, thereby increasing the total amount of heavy metals removed from the soil. To test this hypothesis, the 2014 team selected 8 wildflower species. Four of the species were known phytoremediators (two variants of Helianthus annuus, Brassica napus, Pelagoium horrtum), two species were native Minnesota legumes (Lupinus perennis, Baptisia australis) and two species were native Minnesota C4 species (Rudbeckia hirta, Phlox drummondii). These wildflowers were planted in plots containing either 1, 2, 4, or 8 species. Soils in plots were periodically sampled with x-ray fluorescence as a way of assessing changes in heavy metal concentrations. At the end of the season researchers assessed root depth and density as well as above ground biomass to quantify the impact of biodiversity on the system.