Impacts of Chinese tallow invasion on ecosystem resilience of pine flatwoods in the coastal area of Gulf of Mexico, USA

Background/Question/Methods: Chinese tallow tree (Sapium sebiferum (L.) Rocb) has become a naturalized and colonized species of pine flatwood and/or wet pine savannah habitats along the Gulf Coast. Understanding the impacts of tallow invasion and establishment on ecosystem resilience of invaded coastal pine flatwood and pine savannah is important to restore this endangered habitat. We investigated the interrelationships between tallow population and native species under varying burn intervals (e.g., no burn, annual burn, periodic burn). Specifically, tallow seed bank, 1-year seedlings and the above- and below- ground biomass, height, and diameter at breast height of individuals (≥ 2 years), over- and under-story vegetative conditions that may affect tallow invasion and establishment had been measured in a number of mapped plots in longleaf-slash pine stands in the Mississippi Sandhill Crane National Wildlife Refuge. These plots were divided into 80 investigation quadrats (10×10 m²) and all the factors mentioned above were measured from these 80 quadrats.

Results/Conclusions: The results indicate that there is significant negative relationship between Chinese tallow seedlings and understory coverage. The spatial regression model indicates that the average number of seedlings is greater in grassy quadrats than in shrubby quadrats. Long fire intervals (> 3 years) tend to greatly increase the below: above biomass ratios of tallow, making the native ecosystem less resilient. In conclusion, high resilient forest ecosystems will have lower probabilities for Chinese tallow to invade. Higher biodiversity and coverage of woody understory will protect native forest stands from Chinese tallow invasion.