Impact of ecological and socioeconomic determinants on the spread of tallow tree in southern forest lands
Based on USDA Forest Service Forest Inventory and Analysis (FIA) database, relationships between the presence of tallow tree and related driving variables including forest landscape metrics, stand and site conditions, as well as natural and anthropogenic disturbances were analyzed for the southern states infested by tallow trees. Of the 9,966 re-measured FIA plots in eastern Texas, Alabama, Georgia and South Carolina, 190 plots (1.9%) were found to be infested by tallow trees during the new measurement cycle (between 2004 and 2008). Logistic regression showed that the probability for a plot to be infested by tallow trees is significantly related to ecoregion, forest type, stand size class, slope and distance to other infested plots and highways. Tallow trees are mainly distributed in the western Gulf section of coastal plains and flatwoods (16.4%), the western section of mid-coastal plains (5.2%) and the Atlantic coastal flatwoods section (4.2%), where oak-gum-cypress, elm-ash-cottonwood, oak-pine and pine (loblolly pine/shortleaf pine) forests dominate. Younger stands or stands near to infested sites are more prone to be infested. Regionally, southeast Texas and southern Louisiana were the most vulnerable areas with the highest abundance of tallow trees.