Invasive species have had enormous, sometimes irreversible, impacts on biodiversity, human property, and economic activities throughout the world. Invasive plants can compete with native species for resources, disrupt evolutionary processes and hybridize with natives, reduce system productivity, alter disturbance regimes, and threaten native biodiversity. Theoretically, plant communities with high species diversity should be most resistant to invasion. While many empirical studies support this hypothesis, numerous other empirical studies suggest that communities with higher biodiversity tend to be invaded more easily. Hence, we aimed to understand the relationship between abiotic/biotic factors and the coexistence of invasive species. We analyzed an extensive dataset collected as part of the Forest Inventory and Analysis Program of the United States Department of Agriculture (USDA) Forest Service. We associated the data on coexistence of Chinese tallow, Chinese/European privet, and Japanese honeysuckle (SNIPET) with the data on landscape conditions, forest features, disturbance factors, and forest management activities (FIA Data and Tools) using the FIA plot identification numbers. We then checked the relationships. Our results indicated that some abiotic/biotic factors showed significant effects on the coexistence of invasive species.
Among 42,637 forested plots, 147 plots were invaded by all three invaders: Chinese tallow (tree), Chinese and European privets (shrubs), and Japanese honeysuckle (vine). The plots with coexisting invasive species were mainly private lands (93%). They were either loblolly pine (34%), oak/hickory (24%), or oak/gum/cypress (14%) forests. Moreover, those stands were relatively young, with average age of 26.6 years (± 18.4), and highly productive (≥ 50 ft3/acre/year). The average biodiversity measure, Shannon index, was lower in the plots with coexisting invasive species (1.39) than in the non-invaded ones (1.44). Our preliminary results supported the Elton’s hypotheses that higher biodiversity resists plant invasion.