GEO 406 Forest structure and invasive plants

My GEO 406 Field Studies in Geography class (Spring 2016) undertook a project to examine the relationship between forest structure (tree density and dominance) and the abundance of the invasive plant wintercreeper (Euonymus fortunei).  We conducted our work at the UK Arboretum. Shown below is the sampling design from one of the student projects. The circles are the quadrats where they measured tree diameters, wintercreeper ground cover, and the number of wintercreeper vines on a tree. Wintercreeper can form a dense groundcover leading to a depauperate herbaceous ground cover and a decrease in the recruitment of new trees and shrubs. Its vines can climb into the overstory and weaken and bring down small trees. The students had to design and conduct the field sampling, perform calculations for tree density and dominance, and construct histograms for tree size classes. They used online calculators to perform resampling and correlation to statistically assess some the relationships among tree size, stem density, and wintercreeper abundance.  As the density and dominance small trees increased, the height of the wintergreen groundcover increased.