GA-2010_Invasive_Plants_(for_Tech_Edit).docx

Invasive Plants Found in Georgia’s Forests, 2010 S. Oswalt & C. Oswalt Invasive Plants Found in Georgia’s Forests, 2010—FIA Factsheet

Sonja N. Oswalt Christopher M. Oswalt Authors Statement Sonja N. Oswalt is a Forester and Christopher M. Oswalt is a Research Forester, Southern Research Station Forest Inventory and Analysis, 4700 Old Kingston Pike, Knoxville, TN 37919.

Introduction This publication provides an overview of invasive plants found in forests of the State of Georgia based on an annual inventory conducted by the Forest Inventory and Analysis (FIA) Program at the Southern Research Station (SRS) of the U.S. Department of Agriculture Forest Service in cooperation with the Georgia Forestry Commission. These estimates and coverage maps will be updated on a periodic basis. For more information regarding past inventory reports for this State, inventory program information, field sampling methodology, and estimation procedures, please refer to the citations at the end of this report.

Foresters and ecologists have noted the spread of invasive species onto U.S. forest land for decades. Despite the soaring costs of management and control, and inestimable negative environmental impacts, invasive species continue to spread across managed and natural forests. This update describes current results from data collected in Georgia between 2005 and 2010 and provides graphic illustrations of where invasive plants are being observed in forests across the State of Georgia. Observations of invasive plants include only those plants on the southern FIA invasive plants “watch list” which in this case contains 33 plant species regionally recognized as problematic invasive plants.

Findings Invasive plants were detected on 2,584 plots across the State, or 56 percent of all forested plots measured (fig. 1). The maximum number of the surveyed invasive plant species detected on an individual plot was 12, which occurred on <1 percent (1 plot) of forested plots (table 1). Approximately 40 percent of invaded plots contained only one invasive plant from the SRS FIA “watch list,” while 76 percent of invaded plots contained only one or two invasive plants (table 1). Forests in the North Central unit exhibited the highest frequency of invasion with 89 percent of sampled plots containing at least one invasive plant. Forested plots in the Southeast unit were less likely to contain invasive plants with only 26 percent of plots containing at least one invasive plant.

The distribution of invasive plants in the extreme northeastern and southeastern forests is considerably lower than observed in the central and southwestern parts of the State (fig. 1). Invasive vines such as Japanese honeysuckle (Lonicera japonica) and shrubs such as privets (Ligustrum spp.) are primarily culpable for this dichotomy as the most frequently observed plant invaders, many of the invasive plants monitored by FIA exhibit a similar pattern. These differences may be due to land use, differences in overall species richness, site productivity, length of growing season, forest type characteristics or other environmental differences (for example, soil, moisture, temperature, precipitation, elevation, aspect). One driving factor in this case may be the Atlanta metropolitan area’s influence within the Central and North Central Units compared against relatively low populations and large swaths of national forest land in the northeast, and managed timberlands in the southeast.

Japanese honeysuckle was the most frequently detected invasive plant species in Georgia (table 2). The seemingly ubiquitous invasive vine was found on 47 percent of all forested plots surveyed, and 83 percent of all plots containing an invasive species. On average, Japanese honeysuckle foliage covered 12 percent of the subplots on which it was found. The Chinese/European privet (Ligustrum sinense/L. vulgare), as a group, was the second most frequently detected species, and was noted on 32 percent of measured plots, with an average percent cover of approximately 11 percent on subplots where it was detected. Chinese lespedeza (Lespedeza cuneata) was the third most frequently detected species, and was noted on only 5 percent of measured plots, with an average percent cover of approximately 3 percent on subplots where it was detected. Chinaberry (Melia azedarach) was the fourth most frequently observed invasive plant species in forests of Georgia. The above mentioned species along with Japanese climbing fern (Lygodium japonicum), Nepalese browntop (Microstegium vimineum), mimosa (Albizia julibrissin), nonnative roses (Rosa spp.), autumn olive (Elaeagnus umbellata), and shrubby lespedeza (Lespedeza bicolor) comprise the top 10 most frequently detected invasive plants surveyed for on forested plots in Georgia (table 2).

Invasive vines, primarily Japanese honeysuckle, was the most frequently detected invasive plant life form (table 3) and was found on nearly half (49 percent) of all forested plots. Invasive shrubs were found on 37 percent of all forested plots, while trees (8 percent), forbs (7 percent), grasses (4 percent), and ferns (4 percent) were observed on far fewer forested plots.

Invasive trees were noted throughout the State (fig. 2). However 42 percent of the plots with observations of invasive trees were located in the Central unit (table 3). Chinaberry was the most frequently detected invasive tree across the State and found on a significantly higher number of plots than any other invasive tree monitored (Chinaberry found on 209 plots, mimosa found on 94 plots, and tallowtree found on 41 plots). Although tallowtree was only observed on slightly <1 percent of all forested plots sampled, the species is known to be aggressively invading new areas resulting in a rapidly expanding distribution in the southern United States. Japanese honeysuckle was the most commonly detected vine (fig. 3) and was recorded on 19, 34, 63, 83, and 42 percent of forested plots in the Southeast, Southwest, Central, North Central, and North units, respectively. Observations of Japanese honeysuckle were considerably lower in the Southeast unit of Georgia. No other invasive vine was detected on >2 percent of plots in any region with the sole exception of Kudzu (Pueraria Montana var. lobata) in the North Central unit which was found on approximately 4 percent of forested plots. Chinese and European privet, as a group, were clearly the most frequently detected shrubs (fig. 4) on Georgia forest land and were detected on 32 percent of all forested plots across the State. Chinese and European privet occupied more plots in each region than any other invasive shrub on the “watch list.”

While invasive grasses were not observed on forest lands within the State with the same frequency as other life forms, Nepalese browntop was observed in the three most northern units of the State with enough frequency to warrant attention. Nepalese browntop was most frequently noted in the North Central unit being found on 11 percent of forested plots within the unit.

Japanese climbing fern represented one invasive plant species from the watch list that departed from the geographical distribution trends of most all other invasive plants monitored by the program. Instead of observing large portions of the Japanese climbing fern population in the northern units within the State, it was observed primarily in the southern units. Japanese climbing fern was only found in the Southeast (2 percent of forested plots), Southwest (22 percent of forested plots), and Central (2 percent of forested plots) units.

Conclusions Invasive species are common on forested plots across the State of Georgia. The prevalence of invasive plants on Georgia forest land illustrates the need for public education regarding the ecological and economic costs of invasive plants, and the need for concentrated control and management efforts for invasive plants.

Tables Table 1—Invasive species on Georgia forest land by number of species detections and the number and percent of plots on which they occur, 2010.

Table 2—Invasive species detected on Georgia forest land with frequency of plot detections and mean percent subplot cover, 2010.

Table 3—Invasive species detected on Georgia forest land by FIA unit and invasive plant life form, 2010.

Figures Figure 1—Presence/absence of invasive plant species on forest land, statewide, Georgia, 2010.

Figure 2—Number of invasive trees on plots, Georgia 2010.

Figure 3—Number of invasive vines on plots, Georgia 2010.

Figure 4—Number of invasive shrubs on plots, Georgia 2010.

How to Cite this Publication Oswalt, Sonja N.; Oswalt, Christopher M. 2011. Invasive plants found in Georgia’s forests, 2010—Forest Inventory and Analysis factsheet. e-Science Update SRS–XXX. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. x p.

FIA Program Information Bechtold, W.A.; Patterson, P.L., eds. 2005. The enhanced forest inventory and analysis program: national sampling design and estimation procedures. Gen. Tech. Rep. SRS–80. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 85 p.

Smith, W.B. 2002. Forest inventory and analysis: a national inventory and monitoring program. Environmental Pollution. 116: 233–242.

U.S. Department of Agriculture Forest Service. 2005. Forest inventory and analysis national core field guide. Field data collection procedures for phase 2 plots. Version 3.0. Vol. 1. Arlington, VA: U.S. Department of Agriculture Forest Service, Forest Inventory and Analysis Program. http://www.fia.fs.fed.us/library/field-guides-methods-proc/. [Date accessed unknown].

Additional Information Harper, R.A.; McClure, N.D.; Johnson, T.G. [and others]. 2009. Georgia's forests, 2004. Resour. Bull. SRS–149. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 78 p.

Harper, R.A. 2012. Georgia, 2011—forest inventory and analysis factsheet. e-Science Update SRS–053. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 5 p.

Miller, J.H.; Chambliss, E.B.; Loewenstein, N.J. 2010. A field guide for the identification of invasive plants in southern forests. Gen. Tech. Rep. SRS–119. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 126 p. http://www.srs.fs.usda.gov/pubs/35292 and http://wiki.bugwood.org/Archive:IPSF.

Miller, J.H.: Manning, S.; Enloe, S.F. 2010. A management guide for invasive plants in southern forests. Gen. Tech. Rep. SRS–131. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 120 p. http://www.srs.fs.usda.gov/pubs/36915 and http://wiki.bugwood.org/Invplantmgmt.