The Effect of Callery Pear (Pyrus calleryana) on Soil Macrofauna (Diplopoda and Oligochaeta)
Abstract
Callery pear (Pyrus calleryana) is a relatively recent invader of North America. Its ecological effects are still being explored, including those affecting soil macrofauna such as millipedes (Diplopoda) and earthworms (Clitellata: Oligochaeta). These animals play important roles in many soil processes so understanding how they respond to invasive species is vital to soil health. A previous study exploring potential herbicide control was completed in 2019, however as of 2022 there are still treatment zones with little to no Callery pear alongside fully invaded plots, providing an optimal habitat mosaic for comparison. This allowed us to pursue two research goals: To determine the medium-term (3–4 years) effects of chemical control and to determine how soil macrofauna biodiversity is affected by the local plant community in the presence of invasive Callery pear. Soil fauna were sampled using four methods for thorough investigation. 1) Leaf litter was processed in Berlese funnels to draw out small millipedes. 2) Large millipedes were collected on sight by hand. 3) Earthworms were collected by digging soil monoliths and sorting through the soil by hand. 4) Additional earthworm collections were done via the octet method, using an electroshock machine to drive fauna out of the ground. Surveying the plant communities and collecting soil for texture, pH, and C:N ratios also helped achieve the goals of this study. We found that Shannon plant diversity indices were lower in the Callery pear plots but statistically similar between the herbicide and reference plots, suggesting the effectiveness of chemical control. Additionally, millipede diversity (Shannon index) was positively correlated with basal area of live Callery pear but was not statistically different between treatments. Nonnative earthworm abundance had no correlation with Callery pear. These findings will help land managers make informed decisions when creating management plans for invasive pear.