How EAB facilitates a secondary spread of invasive plant species: Impacts of EAB eradication and tree mortality

Background/Question/Methods

Since the discovery of the Emerald Ash Borer in 2002, eradication efforts have been implemented in an attempt to eliminate or contain the spread of this beetle. At the time, the eradication protocol called for the removal of every ash tree within a half mile radius around an infested tree. In 2005 this study was established to identify environmental changes attributed to the eradication program and measure subsequent shifts in forest community composition and structure. This project compares areas that received the eradication treatment (all ash trees cut down), to areas that were left uncut, (control, ash still standing). Fourteen 20mx25m plots (8 uncut and 6 cut) were established within Pearson Metropark Lucas County, Ohio. The goal of this project is to identify how the plant community is responding in these two areas. Specifically it is designed to describe the successional stages of plant colonization after a disturbance event, such as the eradication protocol, and to determine the potential for a secondary spread of invasive plant species. 

Results/Conclusions

The eradication protocol accelerated the formation and size of gaps within the forest and thus increased the duration and intensity of light penetrating through to the forest floor. In addition, the vehicles used during the eradication efforts caused significant soil compaction. The degree of soil compaction in 2006 was greater in cut versus uncut plots, with those results detectable at each depth of the soil profile (P<0.0001). These environmental changes impacted the composition of the herbaceous community. Shannon’s Diversity Index (H′) was assessed for the plant understory. Higher diversity was detected in cut plots (H′=0.56) where there is greater disturbance compared to uncut plots (H′=0.43)(P=0.005). Species composition differences were also detected between treatments. Out of 73 species surveyed, 13 were non-native, all of which were present within cut plots including 10 that were found exclusively within cut plots.

The spread of EAB is going to increase the light environment. However, do eradication efforts cause a further compounding negative effect by providing a physical disturbance? In 2007, another treatment was added to isolate the impact of an increased light environment without the effects of soil compaction. Six new plots, designated as cut without compaction, had all ash removed within them but without using vehicles. By adding the cut without compaction treatment, we will be able to determine if the eradication protocol has greater detrimental effects on the integrity of the forest habitats.