Spread pattern of Chinese tallow (Triadica sebifera) in the northern Gulf coastal forests
Nana Tian, Graduate Research Assistant , Zhaofei Fan, Associate Professor,
Department of Forestry, Mississippi State University
Abstract: Chinese tallow tree (Triadica sebifera (L.)) as an invasive species threating the southern United States’ forestlands with its rapid spread rate. To better understand the dispersal and
spread processes of tallow at both the regional and stand scales in the southern forestlands, site-specific data and USDA Forest Service’s Forest Inventory and Analysis (FIA) data were
integrated using ArcGIS. An analysis of FIA data at the regional level shows the number of tallow infested plots is increasing and extending into more inland areas as well as more eastern
coastal areas. To explore the potential contributing factors attributed to this spread, a sample plot (300 * 200 feet) was designed at the Grand Bay National Estuarine Research Reserve
(GBNERR) in coastal Mississippi. Spatial statistics including kernel smoothing and Poisson point process models were used to analyze the data collected from the sample plot. The results
indicated that the density of slash pine positively affects the density of tallow while distance to a road negatively affected the spread of tallow. Consequently, areas which are easily accessible
and vulnerable to disturbances are potential invasion regions of tallow.
Objectives
Knowing the spread pattern of tallow and finding the potential contribution factors is quite important to design mitigation protocols; hence there are two objectives:
1. At regional level, map distribution of tallow in southern forestlands including seven southern states.
2. At stand level, explore the spatial spread pattern of tallow using a sample plot collected from a slash pine wetland at the Grand Bay National Estuarine Research Reserve (GBNERR).
Methods
1. Study area:
 At regional level, tallow presence plots were mainly collected from FIA data covering seven states(Texas,
Louisiana, Mississippi, Alabama, Georgia, Florida, and South Carolina) between 2000 and 2012.
 At stand level, a rectangle sample plot (300 by 200 feet) in a slash pine wetland at the Grand Bay NERR
was collected.
2. Statistical methods:
 Mapping the distribution of tallow was finished in ArcGIS.
 Kernel smoothing and Inhomogeneous Poisson point process model (IPPM) was used to explore the spatial
spread of tallow using sample plot.
Sample plot (left) and stem map of slash pine and tallow in it
Results
1. At regional level, the map for the presence plots of tallow between 2000 and 2012 (Map 1) showed:
 The total number of plots being invaded by tallow is increasing.
 The distribution area of tallow is extending from coastal area into more inland area and also expand
from eastern coastal area to western coastal area.
2. At stand level, spatial statistical analyze results:
 kernel smoothing demonstrated that most of tallow were gathering in the area close to the road and
with the increase of distance to the road, the density of tallow decreases; while for slash pine there
was no obvious trend (Figure 3and 4).
 IPPM model indicated that distance to road negatively affected the density of tallow while density of
slash pine positively affect it (Figure 5).
Figure 5 Distance and density of slash pine versus tallow
Map 1 Presence of tallow
Figure 3 Kernel smoothing for tallow tree
Figure 4 Kernel smoothing for slash pine
Discussion and Conclusions
At regional level all data was collected mainly based on the FIA data and in order to get more accurate information about the spread of tallow, more intensive plot need to be investigated.
In addition, future research also need to focus on the growth of tallow on the basis of plots collected from FIA because it can provide the information about how fast tallow grow in different
stand conditions and forest type groups. According to the results at regional level, we draw the conclusion that the total number of plots being infested by tallow is increasing and also
expanding into further northern inland and eastern coastal area.
At stand level the sample plot collected from Grand Bay NERR showed that most of tallow was distributed in the area close to the road; and the density of tallow was decreasing with the
increase of distance to the road. And Poisson point process model result indicated that: the density of slash pine positively affect the density of tallow while distance to road negatively affected
it. However, factors including soil (texture, moisture), vegetation condition/structure (e.g., canopy openness), and historical disturbance needs to be further collected and study how they
influence the spread of tallow.
References
Fan, Z., Y.Tan, and M. K. Crosby. 2012. Factors associated with the spread of Chinese Tallow in East Texas forestlands. Open Journal of Ecology. 2(3): 121-130.
Zou, J., W. E. Rogers, E. Siemann. 2008. Increased competitive ability and herbivory tolerance in the invasive plant Sapium sebiferum. Biological Invasions. 10: 291–302.
Acknowledge
I would like to thank my advisor Zhaofei, Fan for his support and help in this project; moreover, thanks for Allison Stoklosa and Zhen Sui for their help in collecting data.