Background and aims
Invasive plants have been associated with alterations to soil properties, functions, and organisms, with the potential to impact ecosystem processes. An observational study was conducted to determine how the invasive plant Frangula alnus affects soil microbial communities and biogeochemical processes in Wisconsin forests.
Paired invaded/non-invaded sites (n = 10), including high (n = 5) and low (n = 5) density invasions, were sampled in spring, summer, and fall. Soil was analyzed for extractable and total nitrogen (N), N mineralization rate, total carbon, microbial biomass carbon and N, and microbial community structure using terminal restriction fragment length polymorphisms.
Linear regression analysis with robust variance estimation revealed higher N mineralization rates in invaded sites than non-invaded sites in summer, and in high density invaded sites than non-invaded sites overall (p < 0.05). There was not a corresponding increase in extractable N. No differences between invaded and non-invaded sites were observed for other variables.
Nitrogen-rich F. alnus leaf litter (3.2 % of dry mass) may contribute to elevated N mineralization at these sites, though pre-existing conditions may be responsible. Results suggest that F. alnus alters N cycling but has little impact on soil carbon pools and microbial communities.