Beaver Herbivory at the Vassar Farm Ecological Preserve

By Annie Greene (Biology ’19), Dylan Finley (Urban Studies ’17)

This semester in Lynn Christenson’s ecology class (BIOL-241), we mapped the locations of trees affected by beavers near the beaver dam at the Vassar Farm and Ecological Preserve. Our studies revealed preferences in beaver foraging in regards to species, tree size, and distance from water.  We used Vassar’s “Maps & Apps” ArcGIS Online implementation and the ArcGIS Collector App on a GPS-enabled Apple iPad to map the location of the trees based on their geographic coordinates.

Back at the lab, we analyzed our data by creating a series of maps demonstrating relationships between species, tree size, and distance to water. We found that the size of trees affected by beavers decreases with increasing distance to water. We also found a significant relationship between the diameter of the trees (indicated by the proportional size of the point symbols in the map above) and the type of impact on the tree (indicated by the color of the point symbol). Click the >> button in the upper left corner of the map to view the legend, or click the points themselves to view the tree diameter and type of impact; i.e. “Trunk Status”. Only trees with a diameter between 5-10 cm were removed completely, whereas trees with diameters greater than 10 cm were either girdled or showed signs of mastication.

This project may lead to future research that will also utilize GIS technology. One important area of investigation would be modeling the effects of rising water levels as the dam height increases, specifically in relation to the location of the sewer line running adjacent to the Casperkill Creek. If the pond were to come in contact with the sewer line, it might become a water quality issue for the Town of Poughkeepsie. GIS modeling would help Vassar to manage the height of the beaver dam.

If you would like help creating a web map, print map, or using GPS for your class project or research project, please contact GIS Academic Computing Consultant Neil Curri for assistance.

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