Ecological Knowledge and Environmental Problem-Solving Concepts and Case Studies (1986) / Chapter Skim
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19. Optimizing Timber Yields in New Brunswick Forests
19. Optimizing Timber Yields in New Brunswick Forests
Pages 275-300
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From page 275... ...
This case study illustrates an attempt to link local decisions with regional ones where the valued ecosystem component (wood) is readily identified and the processes producing wood are well known.
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From page 276... ...
Their implementation initiates a biological response that alters forest development and production of wood, and the response must be forecast to permit the design of useful intervention strategies. This is all made difficult by disparities of scale, in both time and space, between the stand level at which the actions are taken and the forest level at which the response must be assessed.
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From page 277... ...
How can the time and scale differences between the stand level at which actions are taken and the forest level at which management is planned and evaluated be bridged to permit the formulation of local intervention tactics that address the forest management problem in the most appropriate, biologically realistic manner? The case described here, involving a 300,000ha forest management license in New Brunswick, is an attempt to construct a part of that local-global bridge.
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From page 278... ...
But they concentrate on stand-level responses and ignore the interplay of stand dynamics, governed by the interactions among trees in a stand, and forest dynamics, governed by the collective development of stands in the forest. Failure to place stand development in the context of forest development has separated the elegant silvicultural solutions from the forest management problem and has impeded evaluation and selection of efficient means to address overall wood-supply concerns.
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From page 279... ...
that displays relationships between stand-level decision variables and forest-level performance indicators. USES OF KNOWLEDGE AND UNDERSTANDING Valued Ecosystem Component Within the six-step framework described above, the valued ecosystem component is the wood supply, as described by the performance indicators at the stand and forest levels.
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From page 280... ...
Consequently, the 80-year horizon was divided into 2-year steps for forecasting forest development and for tracking performance indicators. For purposes of this chapter, it was decided not to consider the impact of spruce budworm on the forest and not to consider the numerous other issues that pervade real forest management.
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From page 281... ...
for various initial stand densities. The results of density-dependent tree competition in plantation development can be captured in two stand variables and their change over time: salable volume per hectare (m3/-ha)
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From page 282... ...
Broken horizontal lines represent operability constraints of 100 m3/ha (above) and 9 stems/m3 (below)
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From page 283... ...
\\ ~"\~ \i Initial Trees /ha 4000 - 2000 500 75 100 1 1 1 1 \ 500 Initial Trees/ ha ~ 4000 2000 25 50 75 100 Stand age (years ) 283 FIGURE 3 Effect of initial stand density on timing of stand availability for harvest.
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From page 284... ...
ultimately, stand growth. It must be density affects tree growth and comprehensive enough to address such a question as: What will be the pattern of volume per hectare and average tree size over the life of a black spruce (Picea mariana (Mill.)
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From page 285... ...
. Cumulative Effects To evaluate the cumulative effects of stand-level tactics on forest-level performance, the hypotheses with respect to stand development, operability limits, and forest development were systematically knitted together.
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From page 286... ...
The forest structure and natural stand growth are more adequately described by data sets available in the New Brunswick forest inventory and the records of the industrial land owner in this case. The forest-level characterization is presented in simplified form in Figure 4, which shows the present forest to comprise three types of stands: softwood stands dominated by fir (Abies balsamea (L.)
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From page 287... ...
The present forest structure is a product of history and is obviously nonuniform, with a preponderance of mature stands, a moderate presence of newly regenerating stands, and a dearth of stands at stages of development between the extremes. This age structure bears the ecological imprint of the two main historical forces behind the forest's developmentharvesting by man and harvesting by spruce budworm (Choristoneura fumiferana (Clem.~.
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From page 288... ...
Specific Models Two models were used to make the required forecasts of stand and forest dynamics. At the stand level, a simulation model was constructed by giving quantitative form to the principles stated above and using available field data to define the maximal potential growth rates for black spruce in the region.
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From page 289... ...
At 2-year intervals, the model advances the age-class structures for each stand type along their yield curves, performs the harvest and planting activities, and calculates forest-level indicators, such as total available growing stock, volume loss in mortality, and the evolving forest age structure. The two models are linked, in that the stand model is an input source
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From page 290... ...
The results are presented as a set of response surfaces, or nomograms, in Figure 6. This format is particularly useful when two decision variables are to be assessed via their control over the valued ecosystem components through several indicator variables (Peterman, 19751.
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From page 291... ...
Essentially, the biological limitation on wood supply switches from scarcity of young stands at low planting rates to scarcity of mature stands at high planting rates. The time to stand operability associated with each plantation density regulates the planting rate at which this switch occurs.
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From page 292... ...
Figure 6C contains information relevant to possible future increases in harvest, showing the growing stock available 60 years from now. Appreciable gains in growing stock occur at planting rates higher than those needed to achieve the maximal immediate harvest.
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From page 293... ...
In Figure 7B, for example, under the stringent requirement of 6 stems/m3, plantation densities of 1,000-1,500 stems/ha provide the maximal harvest. However, as the treesize constraint is relaxed, both the maximal sustainable harvest and the plantation density at which the maximal harvest is realized increase.
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From page 294... ...
at 205 m3/ha volume constraint 10/ - Ad/ / 1 ~/420/ / //~ 6 8 10 12 14 Required stems /m3 FIGURE 7 Impact on wood supply of plantation density (Y axis) and minimal acceptable tree size (X axis)
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From page 295... ...
The purpose is to make the decision-maker aware of the importance of linking the two levels of consideration. No recommendations of optimal planting densities or planting rates are presented, because such decisions are strongly influenced by specific industrial strategies and objectives and by the degree of risk aversion of decision-makers.
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From page 296... ...
1978. Toward a Framework for Forest Management Decision-Making in New Brunswick.
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From page 297... ...
Management actions can alter those trajectories. Although wood is considered the only valued ecosystem component in this model, additional components, such as control of spruce budworm and maintenance of an aesthetically pleasing mosaic of forest patches, have been considered in other analyses of the system (Baskerville, 1976; Clark et at., 19791.
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From page 298... ...
But there is no reason to believe that these more elegant models would have appreciably improved the results obtained by Erdle and Baskerville. An additional aspect of ecological knowledge central to the success of the Erdle and Baskerville analysis was the existence of an accurate description of the present age distribution of provincial forests.
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From page 299... ...
They use nomograms to illustrate the trade-offs in valued ecosystem components that are likely to result from alternative management actions or other development interventions. In this forest-management case, as in many other environmental problems, interpretations of what is important vary considerably within and among government agencies, private interest groups, and the ecological profession.
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From page 300... ...
1976. Report of the Task Force for Evaluation of Spruce Budworm Control Alternatives.
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