Matthew Weston Lab Partner: Mackenzie Hoult 09/13/18 Land Use Cover Change 2
Mapping Canopy and Ground Cover
Continuing to look at land use cover change in our community in Portland, we inspected the 90m by 90m site we had set up in the Collins View neighborhood. In order to better understand the change of land we returned to the site of our centroid and inspected canopy and ground cover. Taking 2 paces from the centroid in the NE, SE, NW, and SW, directions we recorded the land cover of the area. Making note of the canopy above us as well as the ground cover below us we recorded the yard. Unfortunately the property was smaller than 8100 square meters so we were not able to record the full space surrounding the centroid. Some of the yard was well taken care of and watered where as other sections were dry from the lack of rain during the summer. There also stood a greenhouse and a garage which affected taking data points. Overall it was an average suburban lawn with some landscaping work done, altering it from its previous more natural cover as shown in the photograph from 1939.
The data above shows the data gathered from the same centroid in the yard. We were able to make 35 total observations in our site despite the boundaries that challenged us. We found our percent canopy cover by taking the number of vertical densiometer canopy observations divided by all observations taken. In total there was 43% canopy cover in the yard, 3% shrub canopy including any shrub between 5 and 50 cm tall. The remaining 40% of our total canopy cover was any tree over 5 cm tall. The canopy cover is also separated by type of tree, evergreen, which is a tree that doesn’t shed its leaves in winter and deciduous trees, which shed seasonally. As seen above in the table, 34% were evergreen trees and 9% were deciduous trees. Ground cover is defined, by GLOBE, as tha touching your feet or lower legs when standing at sample site. For this we found 80% ground cover which is separated into green ground cover, 9%, and 71% brown. The brown cover was due to dead grass as well as landscaping dirt around the bushes. No ground cover was the pavement that made up the driveway which was only 2% of total ground cover. Finally, 9% of the ground cover consisted of shrubs which are considered by GLOBE, woody plants between 50 cm and 5 m tall. Looking at the canopy and ground cover percentages helps us further understand the effect humans have had on the Collins view area and possibly insight to the greater Portland area. Canopy cover can easily be compared to the photos from the 1930’s. For example, the area in the 1939 was mostly agricultural and forest instead the very landscaped and paved area that is there now. Observations like these are very important as we continue to research land use change. We can pair differences in the cover to changes in other impacts on our environment.