Invasive woody plants are often strong competitors that can have large effects on ecosystem function. While there is evidence that Northeastern invasive species can increase nitrogen cycling in monocultures, little is known about how invasive plants alter biogeochemistry in the field. We hypothesized that invaders’ high quality leaf and root litter would enhance the quality of soil organic matter, leading to greater belowground microbial activity and thus faster rates of nitrogen mineralization. In the summer of 2017, we conducted a field survey of invasive and native understory shrubs to see how woody plants influenced microbial activity in central New York temperate forests. We collected paired soil samples from the rhizosphere of each shrub and 0.5 m away from the shrub canopy. Short-term soil incubations were used to measure mineralizable carbon (C) and nitrogen (N) in vitro, and a hierarchical model was used to determine if these mineralization rates were driven by plant traits (e.g., leaf N, specific leaf area, and root N concentration).
Results/Conclusions
Soil underneath natives had significantly faster potential C mineralization rates than soil underneath invaders. This greater microbial activity resulted in more inorganic N, as natives had significantly higher rates of potential N mineralization than invaders. C and N mineralization rates were not correlated with leaf N, SLA, and root N, which indicates that factors other than quality of leaf and root litter are driving soil microbial activity in our incubations. These results do not support our hypothesis and suggest that invasive species do not facilitate in situ rates of rhizospheric C and N processes more than their native counterparts.