MICROSTEGIUM VIMINEUM INVASION IN CENTRAL PENNSYLVANIAN SLOPE, SEEP WETLANDS: SITE COMPARISONS, SEED BANK INVESTIGATION AND WATER AS A VECTOR FOR DISPERSAL
Open Access
- Author:
- Romanello, Genevieve Allen
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Andrew Cole, Thesis Advisor/Co-Advisor
Charles Andrew Cole, Thesis Advisor/Co-Advisor - Keywords:
- Microstegium vimineum
slope wetlands
habitat suitability
seed banks
seed dispersal - Abstract:
- The invasive grass, Microstegium vimineum, was only recently documented in slope, seep wetlands of the Centre County region of Central Pennsylvania. M. vimineum can replace other vegetation within three to five years of arrival and increased dominance of M. vimineum has been associated with decreased plant diversity. Currently, there are no studies that address M. vimineum in slope, seep wetlands yet it is rapidly and extensively invading these wetlands. Slope, seep wetlands within the forests of the Ridge and Valley Province of Central Pennsylvania are considered to have an exceptional variety of native flora and fauna. Therefore, the abundance of M. vimineum in these habitats is alarming. Since M. vimineum it is able to germinate, grow and reproduce in a wide range of environmental conditions it is vital that we understand more about what site characteristics in slope, seep wetlands support M. vimineum growth, describe aboveground and seed bank floral diversity in wetlands with and without M. vimineum, and examine how seed could be transported into these wetlands. For this research study slope, seep wetlands with and without M. vimineum were compared from June 2008 to September 2008 from two different locales, called ‘AgRidge’ and ‘I99’ within the Centre County region of Central Pennsylvania. Each locale contained 3 sites with M. vimineum and 3 sites without M. vimineum. Results of a principle components analysis using environmental data of sites from the ‘AgRidge’ locale only revealed significant positive correlations between photosynthetically active radiation (tau=0.600) and the presence of M. vimineum, which supports the findings of others. M. vimineum can grow extensively in high light environments, including wetland habitats. There were no significant correlations between measured environmental variables and the presence of M. vimineum at the I99 locale, thus provoking questions related to propagule pressure. Future habitat studies like this one require an additional examination of propagule pressures, like site proximity to source populations of M. vimineum, in order to fully determine what suite of characteristics are correlated with the presence of M. vimineum. The aboveground plant community in sites without M. vimineum was dominated by forbs whereas the sites with M. vimineum were not dominated by a single plant functional group. Results of the seed bank study from sites with and without M. vimineum indicated that greater percentages of M. vimineum seed germinated from seed banks of sites where the species was present aboveground, particularly from soil samples taken at a depth of 0-10 cm when compared to 10-20 cm soil depths. The 0-10 cm and 10-20 cm seed bank plant composition were very similar to each other but different from the aboveground composition as confirmed by the multiple-response permutation procedures (p=0.0001). Analysis of the seed bank compositions indicated that M. vimineum sites were dominated by sedges at the AgRidge locale and grasses at the I99 locale. Non- M. vimineum sites were dominated by forbs at the AgRidge and a combination of forbs and grasses at I99. It is very possible that different sampling times and the germination method used in the greenhouse were responsible for differences between the aboveground and seed bank compositions. Therefore, further studies of plant diversity in slope, seep wetland sites with and without M. vimineum should include a more detailed analysis of flora sampled several times over one growing season in order to compare aboveground and seed bank compositions. Additional studies are also needed to determine if sites with M. vimineum actually contain lower percentages of native flora and if an abundance of forbs renders some sites more inhabitable for invasive species. The results of a seed dispersal study determined that M. vimineum seed travels via water and highlights the need for future landscape-scale dispersal studies closely examining propagule pressure and water conduits. In order to address control of M. vimineum in this region the mechanisms behind range expansion must be better understood. Therefore, source populations of M. vimineum, landscape contours, and water conduits need to be mapped to assist with the identification of currently unknown populations. By considering these variables in addition to environmental variables present on site which promote growth, it may be possible to locate sites at risk for invasion. Then, these areas can be monitored and populations eradicated earlier. Overall, this research provides foundational descriptions of M. vimineum in slope, seep wetlands of the Centre County region of Central Pennsylvania and sets the stage to address further questions about habitat suitability, seed dispersal, and control of M. vimineum.