Chinese tallow (Triadica sebifera (L.) Small, Sapium sebiferum (L.) Roxb) is an aggressive invader along the Gulf Coastal Plain and has become a major threat to native coastal forest, wetland, and prairie ecosystems in Florida, Louisiana, Mississippi and Texas. Invasion of tallow has been greatly facilitated by flooding and birds (seed dispersers), landscape fragmentation (creation of gaps and edges) caused by both natural and human disturbances, and the resultant demographic characteristics of invasive populations in an invaded landscape. Sampled tallow trees from a wet pine flatwood were mapped using GPS and fell for age structure and stem analysis in the Grand Bay National Wildlife Refuge (GBNWR), Mississippi.
Results/Conclusions
Spatial analysis of the stem map and age data of tallow trees indicated that the density of tallow seedlings changed in a sigmodal relationship with overstory slash pine density, indicating low and moderate canopy openness may promote the invasion of tallow. Tallow seedlings were positively associated with overstory trees at the spatial scale < 8 m (mean crown width). There was an evident edge effect as demonstrated by a negative exponential decrease in tallow seedling density with the distance-to-road. The mean age of tallow seedlings, however, did not change with the distance-to-road. These evidences support that seed-eating birds are the major seed disperser for tallow to spread in the study area. The hurdle model indicated snags, especially those in higher decay classes had a significant, positive effect, while the shrub cover (%) on the ground had a negative effect on the probability and abundance of tallow seedlings. Management activities such as prescribed burn and thinning to restore an open canopy structure and an herbaceous species and/or grass dominated understory and snag retention for wildlife will likely increase the risk of tallow invasion in regions infested by tallow. Resource management and planning should proactively remove tallow seed trees to mitigate its invasion and spread on invaded landscapes.