Danielle Seeley
Dr. Andrea Worthington
Siena College
Loudonville, NY 12211
Introduction
Every fall on a drive around the Northeast, especially near wetlands or ponds, one can see masses brilliant mauve-purple flowers belonging to Purple Loosestrife. This plant is not a native; it escaped from garden plantings, invaded wetlands and dominated the native plants. The loss of native wetland plants has had impacts on wildlife and hydrology of these wetlands. The most prominent change has been in the population of the Phragmites population. The combination of the introduction of the Galerucella beetles and changes in water flow seems to have aided the great population growth of Phragmites.
In the spring of 2000, NYSDEC and Cornell University gave Siena College 1000 2 mm beetles (Galerucella) to release into the wetlands on the campus (to the north of Cushing Village townhouses). The hope was that the beetles would mate that spring and lay eggs on the purple Loosestrife and the larvae would feed on the stems, bud and leaf tissue. The larvae overwinter in the soil as pupae next to their host plant. The population of beetles would increase in time and eventually reduce the population of Purple Loosestrife so that native wetland plants could become dominant again in the wetlands. There has been a significant reduction in Purple Loosestrife and it looked like up to 2007 that the native plants were returning. Siena College, at the request of the Town of Colonie, built a weir at the outlet of the marsh where it becomes the Kromma Kill at the crossroads that connect Cushing Village to the MAC and the main campus. At that point the water level of the marsh appeared to rise and the flow of the small stream changed. This is when the invasive plant, Phragmites or Bull rush, began to dominate and the hypothesis is that changes in the water depth and flow promoted the population growth of Phragmites.
Developing a GIS model of the Siena College marsh will aid in identifying the relationships between the changes in populations of Phragmites and Galerucella. By including hydrology data that starts at the walking bridge that connects the two townhouse complexes to the north of the campus and going to the weir, documentation of the changes in water depth in the marsh and meander of this stream can be made. We need to understand more about the hydrology of this marsh to understand if it is impacting the plant populations and the biological control agent, the Galerucella beetles.
Objectives
This project will ascertain whether a GIS model based on hydrology variables of the Siena College marsh can be used to predict the behavior of Phragmites and Galerucella. Specific objectives include:
- Correlating known Phragmites occurrence to hydrological parameters, such as flow rate and stream depth
- Correlating declining Galerucella occurrence to hydrological parameters, such as flow rate and stream depth
- Developing a model to predict if the current Phragmites behavior will continue
- Developing a model to predict if the current Galerucella behavior will continue
- Testing the model predictions using additional field surveys
The GIS analysis will use standard multivariate regression techniques to identify potential correlations between the abundance of Galerucella beetles, the abundance of Phragmites, and the hydrological patterns of the Siena College stream. Parameters tested will include water depth, shore line, abundance of Phragmites, abundance of Galerucella, at collected GPS locations over time. The final product will include a map showing the densities of Phragmites and Galerucella over the course of a few spring months and the change in hydrological patterns.
After the start of the growing season for these flora, and prior to extensive expansion of the stream’s shoreline, the map will be field checked to develop an accuracy estimate for the regression model. Systematic sampling sites along the stream transect will be located using the BADL Trimble GPS unit, and the water depth and stream width will be measured and compared to past data collected.
Data Sources
Dr. Worthington, of Siena College in Loudonville, New York, possesses the past distribution and abundance data for Galerucella and for Phragmites, as well as all of the equipment needed to collect further data and conduct analysis. USGS possesses the base maps to be used.
2009 Siena College topographic map (shapefile)
1:24,000 vegetation communities map (coverage)
1:24,000 USGS Geologic Map (coverages)
1:24,000 USGS Digital Line Graph stream and water bodies (coverages)
2010 Spring Data of Phragmites and Galerucella collected map
Work Plan
March
- Compile Data from Dr. Worthington
- Merge quads into single layers
- Clip layers to study only the area in Siena College
- Begin collecting data from stream
- Continue and finish collecting data from Siena stream
- Convert data collected from Excel data into ArcGIS data
- Layer the data correctly
- Analyze results and write final report for Dr. Worthington
