1. Distribution of Earthworms and Other Invertebrates on the Upper and Lower Terraces of Putnam Park
Jenna Barlow, Cory Dick, Brian Johnson, Wil Raasch, Terrance Shaurette and Nathan Sylte
Faculty Mentor: Todd Wellnitz ❖ Biology Department ❖ University of Wisconsin - Eau Claire
Introduction
Results
Discussion
Invasive earthworms can influence forest understory plant composition (Fisichelli et al. 2013), impact soil microbial communities (Brown 1995), and alter invertebrate assemblages (Migge-Kleian et al. 2006). Earthworms are common in UWEC’s Putnam Park, but their impacts there are largely unknown. Data collected by biology classes over the years have shown clear differences in tree composition between the upper and lower terraces of the park, but the composition of invertebrates in general and earthworms in particular has not yet been studied.
There were more worms on the upper terrace than the lower (Figure 1), and worm numbers were positively correlated with % soil moisture (Figure 2), which was greater on the upper terrace. Worm numbers also correlated with % leaf cover (Figure 3).
Our data supports moisture-worm pattern described by Weaver et al. (2001), and we infer that leaf cover had the effect of helping the soil retain water. A positive feedback would result if water availability caused plants to produce more leaves, which would lead to greater leaf cover on the forest floor.
Our pitfall trap data indicate that the distribution of invertebrates was not different between terraces (p > 0.05). We found no correlation between invertebrate and earthworm abundance and conclude they have no effect on each other. There was also no correlation between invertebrate numbers and soil moisture or leaf cover.
Future studies might investigate what impacts invasive earthworms are having on Putnam Park soil communities and leaf decomposition rates.
Figure 1.
A significant difference was found between the number of worms on the upper and lower terraces (p = 0.04). Error bars represent 95% confidence intervals.
Worms per Quadrat
Worms per Quadrat
Figure 2.
There was a positive correlation between worm abundance and % soil moisture (p = 0.007; R2 = 0.43). The upper terrace had significantly higher moisture levels than did the lower terrace (p = 0.026).
The objective of our study was to identify the pattern of the distribution of earthworms and ground-dwelling invertebrates on the upper and the lower terraces of Putnam Park.
Percent Cover of Leaf Litter
Worms per Quadrat
Methods
Figure 3.
A positive correlation was found between worm abundance and % cover leaf cover (p = 0.017; R2 = 0.23).
Study plot locations on the upper and lower terraces of Putnam Park. Points within plots were chosen at random and sampled using quadrats for worms, and pitfall traps for invertebrates.
Thirty-two earthworm samples were collected using 900-cm2 quadrats into which mustard powder solution was poured to extract earthworms. Mustard irritates the worms and makes them come to the surface.
References
Bohlen, P. J., S. Scheu, C. M. Hale, M. A. McLean, S. Migge, P. M. Groffman & D. Parkinson (2004).
Non-native invasive earthworms as agents of change in northern temperate forests. Frontiers in Ecology and the Environment 2(8):
Brown, G. (1995). How do earthworms affect microfloral and faunal community diversity? Plant and
Soil 170(1):
Fisichelli, N. A., L. E. Frelich, P. B. Reich & N. Eisenhauer (2013). Linking direct and indirect
pathways mediating earthworms, deer, and understory composition in Great Lakes forests. Biological Invasions 15:
Migge-Kleian, S., M. A. McLean, J. C. Maerz & L. Heneghan (2006). The influence of invasive
earthworms on indigenous fauna in ecosystems previously uninhabited by earthworms. Biological Invasions 8:
Weaver, L. A., T. J. Lysyk & M. J. Clapperton (2001). The influence of soil moisture and temperature
on the survival, aestivation, growth and development of juvenile Aporrectodea tuberculate (Eisen) (Lumbricidae). Pedobiologia 45(2):
Acknowledgments
We would like to thank Silver Spring Foods, Inc. in Eau Clair for their generous donation of several pounds of mustard powder used for the earthworm extractions in our study.
Forty-eight pitfall traps were buried flush with the ground to collect ground-dwelling invertebrates. These traps were sampled every week for 3 weeks. Soil moisture and percent cover of leaf litter were also measured.
Figure 4.
No significant differences were found among invertebrates caught in pitfall traps on the upper and lower terraces. The pie chart above shows the percent abundance of each invertebrate group across samples. Collembolla (springtails) were the most common, followed by spiders and then beetles. Rare taxa were grouped into the “other” category and included centipedes, millipedes, ants, snails and caterpillars.
Worm and invertebrate data were analyzed using t-tests and linear regression performed using GraphPad Prism software.