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

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

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

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

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

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

Alternative Equilibrium Age Class Distributions

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

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

Annual Area Burned

Annual Area Burned (log scale)

CDF for Burn Rate  

Monte Carlo Simulations

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

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

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

Four Age Class Outcomes

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

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

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

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

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 Potential conflicts between timber supply and habitat protection... For. Ecol. Manage. (68)

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

Pine Marten Habitat Preferences

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

Simulated Habitat Projections

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

Harvest With Percentile Constraints

Trade-off Analysis

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

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

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

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

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