Mapping old growth communities using time series aerial photo analysis in a Minnesota oak savanna

Authors: Madison Sherwood*, University of Minnesota - Twin Cities, Tanner Johnson, University of Minnesota - Twin Cities, Daniel Griffin, University of Minnesota - Twin Cities
Topics: Physical Geography, Remote Sensing, Land Use and Land Cover Change
Keywords: disturbance detection, natural areas, remote sensing, ecology
Session Type: Poster
Day: 4/11/2018
Start / End Time: 8:00 AM / 9:40 AM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

Old growth trees contribute immense ecological value and reflect the environmental and climate histories of their landscapes. Due to urban and agricultural development, few of these natural sites remain in Minnesota. In response to the Minnesota Department of Natural Resources concern over the state’s disappearing old-growth forests, it is imperative to locate these old growth stands to preserve the ecological record they hold, and in some cases prompt a restoration project. The Cedar Creek Ecosystem Science Reserve, located in the central Minnesota oak savanna, is the center of this study. This site provides the perfect environment for bur oak (Quercus macrocarpa) to thrive. Bur oak is an adaptable and resilient species generally tolerant to natural disturbances, such as wildfire or drought, making it a suitable old growth candidate that would have survived centuries in their natural landscapes. In order to find old growth trees, this project qualitatively analyzed a time series of historical aerial photographs taken between 1938 and the present to detect disturbances in the savanna. After the historical aerial photos were obtained, they were orthorectified using ESRI ArcGIS software. From here, polygons were created over forest cover for each time step. Ultimately, these polygons were overlaid to determine which areas have had forest cover present for the entirety of the study period. To confirm the validity of this method as a way to locate old growth, bur oak core samples were taken from within these demarcated polygons to confirm the trees are of old growth age.

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