RESEARCH

Impacts of Biological Invasions

Importance of native plants to urban forests and natural areas

Most plants in our urban ecosystems (e.g. home landscaping and street trees) are non-native. How do these non-native plants differ from native plants in their influence on communities at higher trophic levels? Can restoring native plants to these systems provide improved ecosystem services?

Ailanthus wilt and restoration of sites invaded by Tree-of-Heaven

The use of the fungus Verticillium non-alfalfae has recently been demonstrated to induce dramatic and species-specific mortality of Tree-of-Heaven (Ailanthus altissima) stems and clones. But how effective are fungal treatments in restoring healthy native plant communities? Are there legacy effects of Tree-of-Heaven allelochemistry or Verticillium-infection on soil microbial communities?

Allochthonous Inputs to Stream Ecosystems

Hemlock headwater ecosystems
​and Hemlock Wooly Adelgid

With non-native Hemlock Wooly Adelgid (Adelges tsugae) causing major declines of eastern hemlock (Tsuga canadensis), how will stream ecosystems in these forests be impacted? Will the loss of these evergreen canopies result in altered abiotic (e.g. higher stream temperatures, lower pH) or biotic (e.g. reduced diversity of macroinvertebrate or fish communities) conditions?

Ecosystem  impacts of ​stocked trout

Fish stocking represents a significant, yet under-studied input of nutrients into stream ecosystems. In a typical year, as many as 5 million hatchery-raised trout are stocked in streams across Pennsylvania, a significant nutrient load to these ecosystems. ​How many fish are subsequently caught and removed from streams (return-to-creel)? To what degree are the remaining fish taken up into local food webs or left to degrade further downstream?