Canadian Forest Service Publications
Forest closure and encroachment at the grassland interface: a century‐scale analysis using oblique repeat photography. Stockdale, C., Macdonald, S. E., & Higgs, E.S. (2019). Ecosphere, 10(6), e02774.
Issued by: Northern Forestry Centre
Catalog ID: 40422
Availability: PDF (download)
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We used repeat oblique photography to quantify and determine the drivers of vegetation change, particularly forest closure and encroachment, in the Rocky Mountains of southern Alberta, Canada, from the beginning of the twentieth century to the present. We classified the landscape into seven distinct vegetation types (closed-canopy conifer forest, broadleaf deciduous forest, mixedwood forest, open-canopy woodlands, shrublands, grasslands and meadows, non-vegetated) and assessed vegetation change between the two time periods. We found that closed-canopy coniferous forest, broadleaf deciduous forest, and mixedwood forest increased on an area basis by 35%, 45%, and 80%, respectively, over this time period; concomitantly, grasslands and open-canopy woodlands declined by 25% and 39%, respectively. Overall, 28% of the landscape was in a more advanced successional state in 2008 as compared to the early twentieth century. The Montane and Subalpine Natural Subregions (NSR) experienced the most change (42% and 26%, respectively, in a more advanced successional state). The loss of open-canopy woodlands was observed across the entire landscape, while grassland and meadow losses were most acute in the Subalpine and Alpine NSRs. The probability of vegetation change to a more advanced successional condition was greater at higher elevations and in areas receiving lower amounts of solar insolation. The changes observed are consistent with what we would expect to see due to lengthening of fire return intervals. Understanding the magnitude of change in vegetation types and the drivers of this change is important for the development of effective contemporary ecosystem management and restoration practices.
Plain Language Summary
We used a type of photography to determine the factors influencing vegetation change, particularly forest closure in the Rocky Mountains of southern Alberta, Canada. We assessed these factors from the beginning of the twentieth century to the present. We classified the landscape into seven vegetation types and assessed vegetation change between the two time periods. The probability of vegetation change to a more advanced condition was greater at higher elevations and in cooler and moister areas. The changes observed are consistent with the expected predictions. Understanding the changes in vegetation types and the reasons for change are important for effective ecosystem management and restoration practices.