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Browsing Publications by Subject "alpine tundra"

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    ItemOpen Access
    Treeline monitoring in the San Juan Basin tundra: a pilot project, 2012
    (Colorado State University. Libraries, 2012) Kummel, Miroslav, author; Rodda, Gordon, author; Fink, Michelle, author; Rondeau, Renée Jane, author; Colorado Natural Heritage Program, publisher
    In order to monitor the effects of climate change in the San Juan alpine, the Colorado Natural Heritage Program (CNHP) set up permanent monitoring plots near treeline, the most likely area to notice tree and shrub recruitment. We field checked three sites (Lizard Head Pass, Kendall Mountain, and Deer Creek Park) prior to choosing the Deer Creek Park area near Kendall Mountain and Silverton. In addition to the field work, we conducted a GIS analysis to detect changes in treeline and tree density between the years 1951 and 2011. This report discusses the methods and results of the field monitoring and GIS analysis and describes a scenario to expand this project to more sites within the San Juan Mountains.
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    ItemOpen Access
    Treeline monitoring in the San Juan Mountains
    (Colorado State University. Libraries, 2014-12) Decker, Karin, author; Rondeau, Renée Jane, author; Fink, Michelle, author; Colorado Natural Heritage Program, publisher
    Temperatures in the San Juan Mountain region have risen approximately 1.8°F over the last 30 years, primarily after 1990, and are projected to continue warming. As temperatures rise we expect increased rates of tree growth and tree establishment at the subalpine/alpine ecotone (treeline). We wanted to discern if upper treeline changes could already be detected through remote sensing. We compared aerial photographs from 1951 and 2011 for 8 San Juan mountain peaks. The images were georeferenced and virtual transects were created to help establish position of treeline in each sample year. We found that the treeline has not moved, but that tree density has increased. Therefore, the difference between 1951 and 2011 treeline was calculated by determining differences in tree density within the area delimited as treeline. Differences in shadows between images were corrected for by examining shadows of immutable objects and calculating a correction factor. Detected differences varied widely, from 2 - 27% increase in tree density (mean 12%) over the last 60 years. We conclude that treeline changes can be detected, although the rate of change is slow and variable. The high variability may be due to aspect, with the wetter aspects increasing faster. We also suggest that this cost-effective remote sensing technique could be a useful monitoring tool for determining landscape changes in areas that are hard to access.