Impacts of fire on Chinese tallow (Triadica sebifera) invasion in slash-longleaf pine flatwoods and savannas in the Gulf of Mexico coastal region, United States

Abstract

The coastal area of the southeastern United States is historically wet pine savannas, prairie, and hardwoods. Many exotic species have invaded this area and become a serious threat to native forest ecosystems. Among those exotic species, Chinese tallow (Triadica sebifera) has become one of the most serious invasive tree species in the southern coastal states, including Alabama, Mississippi, Louisiana, and Texas. How landscape/stand features affect Chinese tallow invasion under fire disturbances is an important consideration for the control and management of Chinese tallow invasion and restoration of native ecosystems. In this research, study plots were established in the Mississippi Sandhill Crane National Wildlife Refuge (MSCNWR) to evaluate Chinese tallow invasion at the landscape level, and plots were established in Grand Bay National Wildlife Refuge (GBNWR) to analyze Chinese tallow invasion at the stand level. At the landscape scale, under frequent and low-intensity fire pine flatwoods are more susceptible to tallow invasion than pine savannas. There was higher invasion probability and greater prevalence of seedlings and saplings encroaching in understory. Sites closer to roads and seed trees had a higher invasion probability and a greater number of Chinese tallow, suggesting that landscape fragmentation could facilitate the spread of Chinese tallow across the entire landscape. At the stand scale, invasion probability of Chinese tallow was related to distance to road and microtopography, with a higher abundance of large tallow in quadrats that were closer to a road and seed trees and at lower elevation. The abundance of tallow saplings and seedlings was highest in quadrats with greater coverage of grass. Tallow sapling and seedling abundance increased significantly after a prescribed burn. There were more tallow seedlings in pine- dominated quadrats than that in hardwood-dominated quadrats after prescribed fire, and this may suggest that overstory pine can facilitate tallow invasion after burn while other risk factors are held unchanged or the same. suggest that overstory pine can facilitate tallow invasion after burn while other risk factors are held unchanged or the same.