Examining how the Presence of Invasive Swallow-wort (Vincetoxicum sp.) Affects the Abundance of Earthworms

Abstract

Swallow-wort (Vincetoxicum sp.), an invasive plant in Western New York, outcompetes native species such as common milkweed (Asclepias syriaca). Swallow-wort may release allelochemicals that change the composition of the soil to benefit its own growth. Earthworms are also an invasive species in our area. In excess, they can till the soil too much, drying it out and making it difficult for any plants to grow. While overturning the soil has its benefits, too many worms can cause the soil horizons to merge, displacing minerals and loosening up the foundation for most plants. Because no one had ever studied the relationship between these organisms, I hypothesized that neither plot type nor season should affect the presence of earthworms. In addition, I had reason to believe that swallow-wort could not only hinder earthworm abundance, but it could also promote it. During the summer and fall, I marked 30 paired forest plots in Mendon Ponds and Oatka Creek Parks where swallow-wort bordered a neighboring patch of non-swallowwort. Within these areas, vegetation was surveyed and worms were collected using the liquid extraction method. The worms were identified, measured and weighed. While non-swallowwort plots tended to have more worms, swallowwort plots had more worm biomass. However, these differences were not statistically significant for either the summer or the fall. The presence of swallow-wort does not appear to affect the presence of earthworms. In addition, the season did not seem to have an effect on the presence of earthworms. These results supported both of my hypotheses.