Topographic Variation in Forest Expansion Processes across a Mosaic Landscape in Western Canada

Larissa Robinov, Chris Hopkinson and Mark C. Vanderwel
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Larissa Robinov: Department of Biology, University of Regina, Regina, SK S4S 0A2, Canada
Chris Hopkinson: Department of Geography, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada
Mark C. Vanderwel: Department of Biology, University of Regina, Regina, SK S4S 0A2, Canada

Land, 2021, vol. 10, issue 12, 1-18

Abstract: Changes to historic fire and grazing regimes have been associated with the expansion of tree cover at forest–grassland boundaries. We evaluated forest expansion across a mosaic landscape in western Canada using aerial photos, airborne laser scanning, and field transects. The annual rate of forest expansion (0.12%) was on the low end of rates documented across North America and was greater from the 1970s to the 1990s than from the 1990s to 2018. Most forest expansion occurred within 50 m of established forests, and 68% of all tree regeneration in grasslands was within 15 m of the forest edge. The intensity of cattle grazing did not affect the tree regeneration density. Despite the slow pace of land cover change, grassland areas near the forest edge had an average of 20% canopy cover and 9 m canopy height, indicating the presence of tall but sporadic trees. The rate of forest expansion, density of tree regeneration, and tree cover within grasslands were all greater at lower elevations where trembling aspen ( Populus tremuloides ) and white spruce ( Picea glauca ) were the dominant tree species. We conclude that proportions of forest–grassland cover on this landscape are not expected to change dramatically in the absence of major fire over the next several decades.

Keywords: grassland; forest structure; tree regeneration; grazing; remote sensing; aerial photography; airborne laser scanning; lidar (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2021
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