Robert L. Smith II SUNY College of Environmental Science and Forestry Final Report To
Effects and interactions of multiple variables on the species richness and diversity within northern white-cedar (Thujaoccidentalis)swamps in north central New York
Robert L. Smith II SUNY College of Environmental Science and Forestry Final Report to the Edna Bailey Sussman Foundation, 2015
Introduction
Many studies have been conducted concerning the factors that most affect plant species diversity. Factors proposed have included light intensity, nutrient levels, microtopography, soil moisture, and both natural and anthropogenic disturbance. The “humpbacked” model proposed by J. Philip Grime suggests that stress and disturbance are the key factors in determining plant species richness. This model contends that those communities with intermediate stress or disturbance levels should lead to the greatest species richness (Keddy 2005). The centrifugal organization model proposes that areas with large numbers of extreme environmentswill likely lead to an overall greater species diversity (Keddy 2005).
An ecosystem where these factors and hypotheses have not been thoroughly explored and could benefit from such an analysis is northern white-cedar swamps. These swamps are known for both their large degree of microtopography in the form of hummocks and hollows and their high plant diversity and rare species like ram's-head ladyslipper (Cypripedium arietinum) and showy ladyslipper(Cypripedium reginae). This appears to be no coincidence since greater microtopography creates an abundance of microhabitats with different levels of light, pH, moisture, and nutrients as well as level of natural disturbance suitable to a variety of plant species (Vivian-Smith 1997).
My research involves a two summer investigation into 10 cedar swamps on Fort Drum in north-central New York. No prior research has been conducted in these swamps concerning the cause of their plant diversity. These10 swamps vary in their amount of microtopography as well as other landscape level factors such as canopy cover, depth to water table, soil nutrients, and levels of anthropogenic and natural disturbance. A specific disturbance that is being investigated in this research is the effects of deer density on the plant diversity within these swamps. A 1992 report on 98 rare species concluded that a high proportion of rare lilies (40%), orchids (39%), and dicots (56%) were adversely affected by deer herbivory (WallerAlverson, 1997). This makes the understory of northern white-cedar swamps particularly vulnerable since it contains many such rare species.
The main goal of this research is to determine which attributes contribute the most to the plant diversity in these swamps and at what levels. An additional goal is to determine the effects of deer herbivory on the plant diversity in these swamps. The results of this study will allow Fort Drum and other organizations to better manage these valuable natural communities and ensure their preservation.
Methods
Plots were set up in each of the 10 northern-white cedar swamps along transects 80 m apart at 40 m increments from the nearest road. Two main plots will be constructed from plot center (figure 1). Vegetation plots will be 5 by 5 m quadrats with 4 small microplots and 1 medium sized microplot. Deer plots will be 2 by 10 m in size and will start 2.5 m from vegetation plot center. In addition, the deer plots will be used for microtopographymeasurements.
Figure 1: Vegetation and Deer Plots including four small understory plant microplots and one medium sized sub-canopy microplot.
Within each of the four microplots, an inventory of understory plant species composition, cover, stem count, and deer browse will be conducted. Within the medium sized microsite, an inventory of sub-canopy plant species composition, cover, stem count will be conducted in the same manner as with the understory.
Soil specific conductivity and pH at each plot will be measured by digging a hole and immersing the sensor ofa YSI Model 63 Handheld pH and Conductivity Meter. Depth to water table will be measured by digging a hole and using a meter stick to measure the distance from the top of the water table to thetop of the hole. In order to measure microtopography, a meter stick will be used to measure the distancebetween the ground and a string suspended for 10 m from two wooden stakes 1 m in height. Estimation of deer density will take place during two summers since deer pellets in swamps are known to take several years to decompose (H. B. Underwood, personal communication). In the first year, each deer plot will be cleared of any deer pellets present. During the second summer, deer pellet groups will be recorded at each deer plot along with their position within the plot.
Preliminary Results
Mean Soil pH of these swamps were slightly acidic and ranged from 5.56 in stand 1660B to 6.2 in stand 1900F (figure 2). The mean soil specific conductivity was lowest in stand 1660B at 87.9 μS/cm and highest in stand 1344 at 248.75μS/cm (figure 3). The mean water table also varied among the swamps from 25.5 cm below the surface in stand 2689 to 7.9 cm below the surface in stand 4009B (figure 4). The degree of microtopography was compared using the mean variance and resulted in stand 2689 having the lowest microtopography of 71.8 cm2 and stand 4009B having the highest microtopography of 167.9 cm2 (figure 5). A total of 94 plant species were found in stands 1660B and 2033B (Table 1).
Future Work
During the second summer, a deer pellet group count will be conducted in all deer plots that were cleared of deer pellets during the previous summer. The water table levels of all swamp plots will be measured at the beginning and the end of the summer to determine how much these tables fluctuate during this time period. Light availability at each cedar swamp will be measured through the use of hemispherical photography. Lastly, plant composition, cover, and stem count will be determined in the remaining 8 cedar swamps.
Acknowledgements
I would like to thank my major professor Dr. Donald J. Leopold for his guidance throughout this research. I would also like to thank Jason Wagner, the chief of Natural Resources Branch on Fort Drum, and his staff for allowing me to conduct this research and providing datasets concerning these swamps. I am especially grateful to the Edna Bailey Sussman Foundation for the financial support that made this research possible.
Literature Cited
Keddy, P. (2005). Putting the Plants Back into Plant Ecology: Six Pragmatic Models for Understanding and Conserving Plant Diversity. Annals of Botany, 96, 177-189.
Vivian-Smith, G. (1997). Microtopographic Heterogeneity and Floristic Diversity in Experimental Wetland Communities. Journal of Ecology, 85, 71-82.
Waller, D. M., & Alverson, W.S. (1997). The White-Tailed Deer: A Keystone Herbivore.
Wildlife Society Bulletin 1997, 25(2), 217-226.
Figures and Tables
Figure 2. Mean Soil pH of 10 Northern White-Cedar Swamps on Fort Drum, New York.
Figure 3. Mean Specific Conductivity of 10 Northern White-Cedar Swamps on Fort Drum, New York.
Figure 4. Mean Water Table Depth of 10 Northern White-Cedar Swamps on Fort Drum, New York.
Figure 5.Topography (Mean Variance) of 10 Northern White-Cedar Swamps on Fort Drum, New York.
Table 1.Plant Composition of Cedar Stands 1660B and 2033B on Fort Drum, New York.
