UBC Undergraduate Research

Detecting long term changes in vegetation cover using historic aerial photographs and modern VRI data in the Kennedy Lake watershed Yuan, Qiao Si


Rivers and their associated floodplains produce a wide variety of ecosystem services. However, they are severely altered by human activities such as logging. Riparian vegetation plays an important role in contributing large woody debris to the streams, and the debris directly affects the physical character of the streams. Various vegetation types can have different impacts on the streams. Therefore, it is important to quantify and understand vegetation changes caused by logging. My objective is to assess vegetation changes after logging in Kennedy Lake watershed. Here, I combined historical aerial photography and modern Vegetation Resources Inventory data to quantify vegetation changes over time. Over the 60-year period, conifer abundance decreased by approximately 10% compared to its historical cover. Trees with heights from 30m to 40m experienced the largest decline in percent cover while trees with heights from 10m to 20m increased the most. Site productivity affected change in average tree height. The area with the highest site productivity decreased in average height whereas the average tree heights in areas with all other productivity classes increased. In contrast, average crown closure increased in area with very good site productivity and decreased in areas with lower productivities. Vegetation composition also varied in relation to site productivity classes. Very good site productivity was associated with more decrease in conifers, and increases in deciduous, conifer and deciduous mixed, and shrub and herb covers. My results indicate that historic logging activities had a large impact on vegetation today in the Kennedy Lake watershed, and understanding these patterns can guide potential restoration planning and watershed management.

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