1. The Natural Disturbance Regime: Implications for Forest Management Glen W. Armstrong University of Alberta CIFFC Science Forum 4 November 1999

2. Presentation Outline Context Two studies –A characterization of the natural disturbance regime –Planning for timber and wildlife under uncertainty Concluding comments

3. Context Sustainable forest management –Biodiversity Coarse filter –Manage for a natural (natural-appearing) forest structure: this may accommodate the majority of species Extractive uses are important

4. Context (cont’d) Malcolm Hunter. 1993. Natural fire regimes as spatial models for managing boreal forests. –Frequency of harvest –Size and distribution of openings –Residual organic matter

5. Characterization of the Natural Disturbance Rate of Alberta’s Boreal Mixedwood Forest Glen Armstrong

6. Natural Disturbance Regimes Murphy –Based on analysis of age class data –2%/year –Independent of stand characteristics Cumming –Based on analysis of fire history –~0.5%/year –Dependent on softwood content

7. Alternative Equilibrium Age Class Distributions

8. Outline Statistical characterization of the natural disturbance rate Monte Carlo simulations –Confidence intervals –Age classes Conclusions and implications

9. Study Area and Parameters 8.6 million ha Fire history data 1961-1995 Annual area of lightning caused fires that started in the study area

10. Annual Area Burned

11. Annual Area Burned (log scale)

12. CDF for Burn Rate  

13. Monte Carlo Simulations

14. Mean Rate Confidence Limits 95% confidence limits for estimates mean disturbance rates 10 000 sets of draws for each sample period of interest Calculate the mean for each set Determine the 2.5 and 97.5 percentiles

15. Confidence Interval Results The 2 % and 1/2 % rates are within both confidence intervals

16. Age Class Distributions Starting age class distribution 1000 years of disturbance –Random draw of annual burn rate –Area burned in each age class proportional to area 100 replications

17. Four Age Class Outcomes

18. Conclusions The annual burn rate for the study area can be characterized by a simple two-parameter distribution The burn rate is highly variable: the mean rate of disturbance cannot be determined precisely There is no equilibrium age-class structure

19. Implications No “ecologically correct” disturbance rate or age class distribution exists for my study area Determination of burn rates based on age class distributions is highly questionable

20. Planning for Timber and Wildlife Habitat Under Uncertainty Glen Armstrong, Jim Beck, Vic Adamowicz, Fiona Schmiegelow, and Steve Cumming

21. Modeling Strategy Describe the existing forest using state variables Relate this description to habitat Use Monte Carlo simulation to project the range of natural variability in habitat area Use simulation results to guide constraint selection for optimization model Quantify trade-offs between timber and habitat in the context of RNV

22. Forest State Descriptors Cover type 1) pine 2) white spruce 3) aspen 4) mixed 5) black spruce Habitat stage 1) establishment 2) max density 3) max crown closure 4) max basal area 5) mature 6) overmature See... Cumming, S.G. et al. 1994. Potential conflicts between timber supply and habitat protection... For. Ecol. Manage. (68) 281- 302.

23. Selected Wildlife Species Pine marten Meadow vole Broad-winged hawk Three-toed woodpecker Black-throated green warbler (BTGW)

24. Pine Marten Habitat Preferences

25. Starting Forest Inventory A portion of the DMI FMA 888 000 ha of the net merchantable land base Large spike at the 60 year age class

26. Simulated Habitat Projections

27. Optimization Runs Maximize net present value of timber harvest s.t. non-declining yield constraints s.t. habitat constraint levels –None (business as usual) –Habitat area for all species at different percentiles

28. Harvest With Percentile Constraints

29. Trade-off Analysis

30. What Have We Done? Developed a system that –Projects probability distributions of wildlife habitat and/or forest structure through time –Incorporates natural disturbance –Allows for comparisons between managed outcomes and the range of natural variability –Explicitly quantifies trade-offs between financial values and wildlife habitat

31. What Should We Do? Incorporate succession Refine the disturbance model Refine the timber cost model Stochastic optimization Explore the use of the system in a public consultation context

32. Final Summary Natural Disturbance Management is likely to have a large impact on timber supply The “natural” rate of disturbance and age class structure do not exist Optimization approaches that consider variablity may be useful tools

33. Acknowledgements Sustainable Forest Management Network Alberta-Pacific Forest Industries Inc. Daishowa-Marubeni International Ltd.

34. Acknowledgements (cont’d) Vic Adamowicz, Jim Beck, Steve Cumming, Rick Pelletier, and Fiona Schmiegelow Stan Boutin, Darrell Errico, Daryll Hebert, Ellen Macdonald, Peter Murphy, Bill Reed, and Brad Stelfox