The spread of earthworm cocoons by vehicular traffic on unpaved roads

Abstract

The introduction and spread of non-native species have been heavily influenced by human activities, resulting in the distribution and accelerated spread of species worldwide. Earthworms are largely non-native in Canada and their presence, particularly in forested ecosystems, can cause substantial consequences as they are able to substantially alter the soil conditions. Earthworms and earthworm cocoons are easily distributed unknowingly along with soil, and earthworm populations have been found to be more concentrated in areas of frequent human use. Not much is known about how exactly human movements are able to distribute earthworms and earthworm cocoons, so more knowledge in this area would be useful. This study aimed to find out how earthworm cocoons are spread by vehicle traffic on unpaved roads, as well as some of the factors which influence this spread. I looked at how differences in cocoon size, represented by different sizes of plastic beads, wet and dry weather conditions, and two different vehicle types, a car and an all-terrain vehicle, affected the distance the beads were able to spread. Five replicate trials were completed for each unique combination, resulting in eighty trials in total. It was hypothesized that smaller beads and wet weather conditions would cause the beads to travel farthest, and that distance travelled would be unaffected by vehicle type. The results did not support my hypothesis and showed that larger beads were more likely to be moved and moved farther than the smallest bead size and this was most likely to happen under dry conditions. Vehicle type as predicted did not have a significant effect. These results suggest that earthworm cocoons can easily travel along roads as vehicles drive on them, which is important in predicting their rates of spread, although more research would be valuable in this area to obtain more accurate results.