Invasive plant species are a contemporary threat to biodiversity as they can significantly impact ecosystem processes and ecology. Conservation organizations in the Mid-Atlantic region have begun documenting the naturalization of a non-native tree, Tetradium daniellii (Bee-bee tree). This invasive tree has been planted in arboreta across the region and thus has multiple potential invasion loci. However, there is little known about the ecological impacts of T. daniellii. Recently, this tree was cited as a preferred host for Lycorma delicatula (spotted lantern fly), an invasive insect currently threatening the Mid-Atlantic. This relationship is alarming and shows the need to understand the ecology of T. danielli. During summer 2017, we conducted surveys of two different sites heavily invaded by T. daniellii in Maryland and Virginia. Sites consisted of 20 randomly placed 10 x 10 m plots where plant surveys were conducted. Surveys included understory and shrub diversity and abundance as well as canopy diversity and cover. Diversity was measured using Simpson’s 1 – D index. Abiotic factors were also recorded at each site. Here, we ask the questions: 1.) Does T. daniellii impact understory diversity? 2.) If T. daniellii does impact diversity, what mechanism is driving the difference?
Results/Conclusions
Within the 40 plots, we inventoried 657 trees, with more than half (387) of them being Tetradium daniellii. Densities of adult T. daniellii ranged from 0-82 individuals/10 m2. We identified 69 different woody and herbaceous plant species. Simpson’s 1 – D diversity indices for individual plots ranged from 0.1-0.78. Our results indicate that understory diversity increases with T. daniellii abundance, in contrast to our expectations. We hypothesize this relationship is driven by an increased canopy cover with T. daniellii invasion, which may shade out understory invaders such as Microstegium vimineum (Japanese stiltgrass). Supporting this, we found that M. vimineum relative percent cover is negatively correlated with T. daniellii density. Once T. daniellii naturalize an area, they are able to dominate the canopy and impact the diversity of the understory. Additional analysis will reveal what impacts T. daniellii has on the native floral community, as well as what mechanisms are driving these changes. As this species has quite recently escaped cultivation, understanding its relationship with other more established invaders as well as native plant communities will aid in determining management objectives.