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Kathryn MartellPatterns of Riparian Disturbance in Alberta's Boreal
Mixedwood Forest: Beavers, Roads, and Buffers

In the past several decades, northern Alberta's boreal mixedwood forests have been changing dramatically. Rapidly expanding industrial activity - mainly forestry and petroleum product extraction - has brought extensive road networks, pipelines, well sites, seismic lines, and people to a region previously relatively undisturbed by human activity.

In 1951, almost no dams were present and the creeks were very narrow and almost indistinguishable from the surrounding forest. n the 1970's, beaver dams start to appear and by the late 1990's, the streams have long chains of dams.
A beaver pond and lodge
A beaver pond and lodge

At the same time, populations of beaver (Castor canadensis) have been recovering from past near-extirpation. Wetlands cover more than 20% of the area in boreal Alberta and provide critical habitat for a variety of wetland-dependent wildlife such as moose, muskrat, waterfowl, and other birds. Beavers build many of these wetlands but their impacts have never been studied in northern mixedwood forests.

A sequence of beaver dams in northeastern Alberta
A sequence of beaver dams in northeastern Alberta

Where roads cross streams, they sometimes block flow and create upstream ponds or raised water tables, and lower water tables downstream. This effect might be similar to what happens naturally at a beaver dam. Unlike beaver dams, however, roads are essentially permanent features of the landscape - they may be changing riparian areas in ways that differ from the impacts of beaver activities.

This study addressed these questions:

  • How does beaver flooding and feeding alter riparian areas in northeastern Alberta?
  • What are the implications of beaver activity for forest management and riparian buffer strips?
  • Do road crossings alter riparian habitats in similar ways to beaver dams?

I conducted detailed vegetation surveys on six streams with a paired road crossing and beaver dam.

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