Northern Watershed Project (Report 4). Simulation of Four Riparian Guidelines on Seral Stage and Canopy Type Distributions on Forests in Northwestern Alberta.
Author(s)
Philip Lee and Tim Barker
Summary
This report examines the impact of riparian buffer guidelines on the seral stage and canopy type distribution in northwestern Alberta. Four different sets of riparian guidelines were applied through computer simulation over two forest management units for a 200-year time horizon. Scenarios included; 1) Strict adherence to Alberta’s 1994 guidelines, 2) Planning and operational interpretations of the 1994 guidelines, 3) Special management of fish-bearing streams, and 4) Two-zone, partial harvest buffers. All scenarios met wood supply and other economic targets. Across all scenarios, the amount of old seral forest initially accrues but greatly decreases after 40 years. At this point, the seral stage distribution is largely converted to the initiation to mature stages. For both the conifer and deciduous canopy types, there are relatively constant percentages after 100 years. In contrast, initiation to mature mixedwood forests exhibit cyclic patterns of dominance and recession driven large by succession to other forest types. Old seral mixedwood forests virtually disappear from the landscape. The location of most old seral stages shifts from the operational, i.e. harvest, to riparian landbases between 100 and 140 years. Then it shifts back to the operational landbase for deciduous changes and under some management conditions for conifer canopies.
Differences amongst guideline criteria are relatively small. Of the three formulations examined, fish-bearing guidelines retain more riparian area with “few-sizes-fits-all” and two-zone buffers retaining about the same amount of riparian area and overall amounts of old growth. Two-zone buffers also exhibit much less temporal variability than the other guidelines. Fish-bearing guidelines retain more conifer old growth than either “few-sizes-fits-all” and two-zone buffers which retain more deciduous and mixedwood old growth.
The application of operational and field factors demonstrates the importance of management philosophy when dealing with uncertainty in riparian management. The initial riparian area was approximately 3 times greater when operational and field components were also considered. The amount of old growth for the last 50 years of simulations was 3 to 7 times greater when operational and field considerations were included. In this case, the application of a precautionary principle by personnel at Peace River Pulp, Peace River, Alberta, overrode the specifics of different criteria for riparian management. Increases in the amount of buffer area had significant “ripple effects” throughout harvest planning including: 1) Decreased rotation age, 2). Greater rate of expansion over an unharvested landbase in the first pass, and 3). Harvest of more marginal (in terms of stand volume) forest types.
The management implications of this study are: 1). The need for improvements in the resolution and accuracy of both the hydrological and digital elevation map layers, 2). The application of a precautionary principle for the management of riparian areas, 3). If buffers are to serve in the dual roles of riparian protection and old seral forest, then the application of buffers based on fish-bearing guidelines provides the greatest efficacy for maintenance of both values, and 4). The need for a strategy that ensures the maintenance of mature and old seral mixedwoods on the operational and riparian landbases.