Earth’s systems are in a constant state of change. This is a fundamental principle that students will approach from a variety of perspectives this year in AP Environmental Science. In order to understand change we must have a good understanding of our reference point, a baseline from which to measure all other data.
This week in science class, CS17 made the first step towards building a long term monitoring plan of white tail deer population on campus. Our fieldwork took us to the east side of Little Donahue Lake into the old growth hemlock forest. Hemlock forests are dominated by hemlock (Tsuga canadensis), yellow birch (Betula alleghaniensis), and sugar maple (Acer saccharum). All of these trees are unique in their ability to tolerate the low light conditions that are found in the hemlock forests. This late successional climax community provided a pristine setting for our task, counting deer pellet groupings.
The most accurate method of measuring a wildlife population would be to count every single individual in that population, however that is most always impractical. Limited time, a mobile population, and the lack of a barrier to immigration and emigration in our study area all compounded to limit our ability to conduct a census survey. To overcome this challenge we engaged in the process of ecological modelling, or using mathematical representations of ecological processes in nature. At the core of our model was the counting of deer pellet groupings along a transect. A deer pellet grouping is the group of individual pellets deposited by one deer from one defecation. A transect is a straight line overlaid on a map to facilitate a random sampling; our transect was 50 meters long by 2 meters wide, at a bearing of 104°. For our model to work, we also needed to make several assumptions. The first assumption is that the average deer deposits 25 pellet groups each day as observed by researchers at Penn State University. The second assumption is that the pellet groups we observed in our transects were deposited after the snow melted last spring. We referred to our community phenology book from CS16 and determined that the snow melted 19 weeks ago in early May.
We determined the deer density in hemlock forests at Conserve School campus in the fall of 2018 is between .43 Deer/Km2 and 2.58. Deer/Km2. This survey supported our study of population ecology while reinforcing critical skills in natural resource management including random sampling using a transect, taking and following a bearing using a compass, and building a long term data set.
Photos contributed by Rob Houle, Technology and Media Specialist.
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