The impacts of different nitrogen supply on root traits, root exudates, and soil enzyme activities of exotic and native plant communities

The effects of nitrogen (N) deposition on root traits, root exudates, and soil extracellular enzyme activities (EEAs) of exotic and native plant communities are not well understood.

We established two experimental plant communities comprising exotic (Alternanthera philoxeroides) and native plants (Eleocharis dulcis, Juncus alatus, and Persicaria hydropiper) under varying controlled nitrogen regimes, respectively.

Our findings indicated that both the exotic and native plant communities did not exhibit a short-term (60 days with experiment) preference for nitrogen sources. Compared to the control, nitrogen application narrowed the difference in total biomass between the two plant communities. Exotic plant community exhibit significantly higher root biomass and specific root length (except control treatment) and a smaller root diameter compared to native community. The specific root surface area and the root tissue density of exotic plant community demonstrate a heightened sensitivity to nitrogen application. Furthermore, exotic plant community secrete a significantly higher total content of allelochemicals from their root systems than native plant community. The application of nitrogen is notably improving the investment in phenols compounds by exotic plants, unlike in the native community. The enzyme activities of the rhizosphere soil within the two plant communities demonstrate species-specific responses to varying nitrogen treatments. There were slight differences in the effects of two nitrogen forms on the root traits of two plant communities, but the effects on root exudates and soil enzyme activity were relatively small.

These findings imply that atmospheric nitrogen deposition could potentially accelerate the invasion of exotic plants.