Effects of overwinter conditions on Chinese Tallow germination along a coastal-inland gradient in South Carolina

Chinese Tallow tree, Triadica sebifera, is an invasive species of Chinese origin in the U.S. and has become one of the dominant plants in coastal ecosystems. In the U.S., Chinese Tallow has naturalized along the Coastal Plain 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 larger potential invasive range than it currently occupies, including possible expansion 800 km northward and much farther inland. To determine its inland invasive potential, germination rates of Chinese Tallow seeds are being measured in coastal, midlands, and piedmont regions of South Carolina. Germination rates of seeds planted in fall and those planted the following spring will be compared to determine whether cold winter temperatures at inland sites reduce seed germination relative to coastal sites. Germination rates among seeds from North Carolina, South Carolina, North China, and South China populations will also be compared to test for ecotypic differences in cold tolerance. Germination rates of seeds planted in spring 2006 showed that germination was similar across regions of South Carolina and that seeds from China had lower germination rates than U.S. seeds. Comparison of fall and spring planted seed germination will determine whether overwintering of seeds in inland regions limits inland expansion and whether T. sebifera is capable of extending its range inland.