Nutrient pulses are a commonly cited means by which species are able to enter new habitats. Biological differences between native and invasive species can shift the community’s competitive balance, especially when one group more effectively utilizes a nutrient pulse. These differences may play a role in invasions into a variety of habitats including deciduous forest understories. Alliaria petiolata (Garlic mustard, Brassicaceae) is an important invader of deciduous forests throughout much of North America. This invaded community consists mainly of spring ephemeral species which perform the majority of growth and reproduction before canopy closure. As a wintergreen biennial species, A. petiolata may be active in these habitats during autumn and winter, allowing it to utilize nutrient release from decaying leaf-litter before its spring-ephemeral competitors. We manipulated the timing of leaf-litter addition (fall or spring) and also simulated the nutrient pulse from decaying leaves with artificial fertilizer addition.
Results/Conclusions
We found that autumn nutrient-amended plots had greater adult biomass than plots receiving spring nutrient additions. In addition, silique production per plant and bolting stem was highest in fall litter-amended plots compared to all other treatments. These results suggest that the wintergreen habit may provide a unique opportunity for A. petiolata to spread through otherwise undisturbed deciduous forest understories.