GIS mapping

The second week of our conservation biology course focused on the use of GIS (geographic information system) software for making maps of a nearby island. We went over to Shaw Island, WA to conduct tree surveys in a forest on Cedar Rock Preserve. A hundred years ago the preserve was managed by allowing controlled fires to clear the undergrowth. The management method has changed since then, due to the inhabitants on the island not wanted to risk fires destroying their homes, and mowing is now used to control the undergrowth.

Our class gathering to start the transect in Cedar Rock Preserve.

Our plan was to lay out 200 meter transect parallel to each other to form four bands that were 30 meters in width and record the trees inside of the bands. We were especially interested in marking the oldest trees with GPS and took measurements of circumference and counted the neighboring trees in a five meter radius around the tree. The smaller trees were divided into classes based on circumference size, class one trees were <0.5 m, class two trees were 0.5 - 1.0 m, class three trees were 1.0- 1.5 m, and class four trees were >1.5 m. We went into the field on two separate days to conduct the surveys, and were able to cover quite a large area. On the second day we were lucky enough to see the bald eagles flying around their nest at the edge of the forest.

The rest of the week was spent learning how to input the data into the GIS program and generate maps. This is not as simple as it sounds, and I have a greater respect for all map makers. Our project for the week was to create two different maps, one looking at the date collected from the tree surveys, and another map looking at the data for the polygon areas that the entire survey area was divided into. This morning we presented to the class all of our maps, and every map helped to explain the patterns we observed in the field.

Below are the two maps that Monika and I made.

This graduated symbol dot density map was created to distinguish the differences between the four different size classes of trees and their relative abundances in each polygon. The size of each dot corresponds to the size of tree. This map also contains a visual of terrain differences (forest or meadow) of each polygon. This map is easily interpreted by any audience. They could conclude that meadows polygons are less dense than forest polygons, and that specific forest areas such as the northeastern corner are more tree dense than others.

The forest of Cedar Rock Preserve on Shaw Island, Washington was surveyed using three different class sizes of nearest growing neighbors of old growth trees. This map shows the numbers of nearest neighbors with circumferences between 0.0 and 0.5 meters (class one) in a 5 meter radius of the old growth trees, where sizes of circles correspond to number of trees; a larger circle means more trees. Purple circles represent burned trees, and green circles represent non-burned trees. This map displays the effectiveness of the two different management types, moving and burning.