Measuring Soil Fauna in Stormwater Green Infrastructure

Stormwater controls in urban environments that use plants are being promoted as green infrastructure. To better understand these controls and their relationship to the environment, soil fauna extraction was performed on a variety of stormwater controls from urban locations including rain gardens and detention basins. Urban wooded areas were also used for background comparisons. Additional metrics including bulk density, loss on ignition (LOI), and soil moisture were also performed on samples. Several ecological indices were calculated and statistically tested. Three groupings were identified for 27 samples collected over a two-year period: background (8), rain gardens (13), and other stormwater controls (6). Statistical testing of these groupings by the Shapiro-Wilk W test indicated several indices were considered parametric. A one-way analysis of variance of the number of taxa and the Shannon diversity index was considered significant (p< 0.05). Comparisons of sample enumerations and indices to the other soil metrics measured were poorly correlated. Specifically, analysis of organic matter to number of fauna or derived indices, while expected to, did not show a linearly increasing correlation; cited literature indicated that maximum organic content may not coincide with maximum fauna observations and further, the fauna extraction method used may have confounded this analysis.