How Do Light Availability and Soil Characteristics Affect Growth and Reproduction of Platanthera integrilabia (White Fringeless Orchid)?
Platanthera integrilabia (white fringeless orchid) is a candidate for protection under the Endangered Species Act. At present, this species is known from ~50 scattered occurrences located primarily on the Cumberland Plateau. Historically, P. integrilabia occupied a much wider range than at present, and both habitat loss and its exhibited low levels of flower and seed production have been cited as major threats to the species. It has been suggested anecdotally that P. integrilabia requires a critical light intensity to elicit flowering, but that too much light could desiccate its moist habitat via evaporation. To support P. integrilabia conservation and management, we are investigating the influence of light availability and soil conditions on its growth and reproduction. During summer 2013, we collected preliminary data from a forested seep on Starr Mountain in the Cherokee National Forest, TN, which houses the largest known P. integrilabia occurrence. There, we found no correlation between the spatial distribution of reproductive individuals and microsite variability in light availability, soil moisture, or soil pH. However, the distribution of vegetative Plantanthera spp. was correlated significantly and positively with soil pH. These findings contrasted previous assumptions about the importance of light and soil moisture to P. integrilabia. However, it is important to distinguish between the within-site variability that we measured and variability that could occur in these conditions across sites. We will investigate this variability during summer 2014 across four occurrences in KY and TN.
University of Tennessee at Chattanooga
P86 • T. Shearman1, P. Ma1, J. Nankaya1, H. Valdetero1, S. Hart1, H. Yun1, D. Hagan1, E. Mikhailova1, W. Bridges2
The Role of Soil and Landscape Factors in Chinese Privet (Ligustru sinense) Invasion in the Appalachian Piedmont
There is a limited understanding about the ecological mechanisms that enable certain plant species to become successful invaders of natural areas. This study was conducted to determine the soil and landscape characteristics that correlate with invasion of Chinese privet (CHP), and to develop a model to predict the probability of CHP invasion in Piedmont forests. A Landscape Ecosystem Classification (LEC) system - based on the % clay in the B horizon, depth to maximum clay (cm), exposure, terrain shape, and aspect (degrees) - was used to determine the soil moisture characteristics of invaded and uninvaded plots. Additional measurements included the cover classes of CHP and other species, litter depth (cm), slope (degrees), overstory basal area (m² ha⁻¹ ), and soil chemical properties. When CHP cover exceeded 60%, other understory species were largely absent. CHP invasion was negatively correlated with overstory basal area and slope and positively with litter depth and pH. A stepwise logistic regression model containing these four variables was highly sensitive, with an overall accuracy of 78%. Given the accuracy of this model, we propose that it can be used to calculate the probability of invasion in a given area, provided that some basic, readily obtainable site characteristics are known.
1 School of Agricultural, Forest, and Environmental Sciences, Clemson University, SC 29634-0359; 2Mathematical Sciences, Clemson University, SC 29634-0359
P87 • Leslie Russo, Callie Montgomery, Danny Hoover, Jared Odell, Gregory Raymond, Jennifer Boyd
Invasive Plant Species Distribution and Abundance in Tennessee Army National Guard Volunteer Training Sites &Ndash; From Ground Surveys to Geographic Information System Layers
We are conducting extensive ground surveys toward generating Geographic Information System (GIS) maps depicting the distribution and abundance of invasive plant species in Tennessee Army National Guard (TNARNG) Volunteer Training Sites (VTSs). These maps will provide a useful baseline tool for understanding how disturbances associated with military training could influence species invasions and for elucidating the potential impact of invasive species on rare ecological communities and native plant species through habitat overlap. Field surveys of 33 invasive plant species across 1600 ha were completed at the Catoosa County, GA and Milan, TN VTSs during summer 2013. Established methods for rapidly surveying large areas with small minimum units were employed. Preliminary data show that the most common non-woody invasive species include Lonicera japonica (Japanese honeysuckle), which occurs in 75% of all plots surveyed to date; Microstegium vimineum (Japanese stiltgrass), which has a frequency of 70% in Milan plots; and Lespedeza spp. (Chinese and bicolor lespedeza) which have combined 40% frequency in Milan plots. The dominant invasive woody species in all plots surveyed to date was by far Ligustrum spp. (common and Chinese privet) with a combined 40% frequency. Our observations suggest that the frequency of these and other invasive species is negatively correlated with distance from habitat edges.
