Chinese tallow tree, Triadica sebifera, is a highly damaging invasive species of Chinese origin in the U.S., and has become one of the dominant species in coastal ecosystems. In the southeastern U.S., Chinese tallow has naturalized along the Gulf Coast and East Coast from Texas to North Carolina. Within its introduced range, Chinese tallow is believed to be restricted primarily by frigid or arid conditions. However, CLIMEX models indicate that Chinese tallow may have a much larger potential invasive range than it currently occupies and may expand up to 800 km beyond its current range, and into far inland habitats. Survival, stem damage, and time to budbreak of Chinese tallow seedlings after freezing events were measured in both laboratory and field conditions to determine the potential of Chinese tallow to spread beyond its current invasive range. Germination success of Chinese tallow seeds was also measured across coastal, midlands, and piedmont regions of South Carolina. Germination of fall and spring planted seeds were measured at each site to determine whether the harsher winters in inland sites reduced seed viability relative to coastal sites. All experiments included seeds or seedlings from North Carolina, South Carolina, North China, and South China source populations.
Results/Conclusions
Laboratory experiments using a temperature controlled chamber showed that North and South Carolina seedlings were more severely damaged by freezing conditions than seedlings from either population collected from China. A field experiment conducted in the piedmont of South Carolina showed that seedlings from South Carolina populations were more severely damaged by winter conditions than seedlings from North Carolina or China. In addition, significant reductions in germination between spring and fall plantings of South Carolina seeds were observed in inland regions of South Carolina, but not coastal regions where Chinese tallow is currently considered a problematic invasive species. Although not statistically significant, North Carolina seeds showed a similar pattern of reduction in germination between spring and fall plantings in inland regions of South Carolina. Neither China population showed a reduction in seed germination between spring and fall plantings. This likely indicates that populations of Chinese tallow from within its northernmost U.S. range are less tolerant of cold than populations in the native range. It also demonstrates that different populations of Chinese tallow within the U.S. may have different climatic restrictions, and thus may pose differing threats of future range expansion in the United States.
