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distinct after about 40 years (Figure 1). Large snags and down logs will begin appearing in two to four decades (Figure 2). There will continue to be little understory, however (Figure 1 ). Dense, single cohort stands not altered by silvicultural treatments or destroyed by disturbances will continue to have similar features for the next 60 years (Figures 6-9). They will have a closed canopy of closely

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366 ASSESSING FOREST ECOSYSTEM HEALTH IN THE INLAND WEST

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FIGURE 3. Projections o f susceptibility o f multiple canopy stands following different silvicultural regimes to destruction by common wind/snow and insect disturbance agents. Susceptibility o f 100 = extreme likelihood of disturbance. Susceptibility values over 200 were assigned a value of 200. Wind and snow susceptibility listed by species. [] = No Activities Regime; + = High Density Regime; * = Low Density Regime. 200

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2000

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2030

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Oliver et al.

368 ASSESSING FOREST ECOSYSTEM HEALTH IN THE INLAND WEST

2000

2010

2020

2030

2040

2050

DATE (YEAR, A.D.)

spaced, small trees and some small snags and down logs (Figure 7). There will continue to be only one canopy layer and a shallow foliage layer with no ground vegetation (Figure 6). The active silvicultural manipulations will dramatically change the old growth structural features in both the multiple canopy and dense, single cohort stands. Some old growth features will immediately increase, while others will initially decrease and later increase. Changes in the various structural features will be as follows: . Canopy Layers-The number of canopy layers will increase with the Mul­ tiple Strata regime in the dense, single cohort stands (Figures 6 and 9); however, the active regimes may reduce the distinctiveriess of different canopy layers in stands already containing muitiple canopy strata (Figure 1). Foliage Depth-Foliage·depth will increase in all regimes as the number ·

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of living trees is reduced (Figures 1 and 6). Crown Closure-Reducing the mirriber of living trees through silvicul­ tural treatments will temporarily decreaSe crown closure (Figures 2 and ·

370 ASSESSING FOREST ECOSYSTEM HEALTH IN THE INLAND WEST

FIGURE 4. Projections of susceptibility of multiple canopy stands (top) and dense, single cohort stands (bottom) to fires with no silvicultural activities ([]) and with various regimes where the thinned trees are left as snags or logs are similar to effects of insects or wind/snow in leaving stands very suscepti­ ble to fires. Susceptibility values are similar to Figure 3. + = High Density Regime;* = Low Density Regime (top) or Multiple Strata Regime (bottom); Black boxes = Thinning regimes where killed trees are removed.

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2000

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DATE (YEAR, A.D.)

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371

Tree Spacing-Tree spacing (Figures 1 and 6) will generally increase with time and with lower density silvicultural regimes, except where the Multiple Canopy regime allows abundant regeneration to develop. Tree Size-Tree sizes will also increase with time, but will increase more rapidly with lower density silvicultural regimes (Figures 2 and 7). Snags and Down Logs-There will be many snags and down logs (Fig­ ures 2 and 7); however, down logs will be very small even under low density silvicultural regimes during thefrrst few decades-until the snags fall over. Active felling of dead trees could create large down logs more rapidly. The down logs will last many decades. Changes in Susceptibilities to Disturbances Without Tree Removal

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374 ASSESSING FOREST ECOSYSTEM HEALTH IN THE INLAND WEST

FIGURE 6. 60-year, stand silhouette projections showing structural features typical of dense, single cohort stands (referred to here as "pole"stands) under different silvicultural regimes. Low.p nsity =Multiple Strata Regime (Scale on left (in feet) represents both horizontal and vertical); Black crown = Doug­ las-fir; White crown =grand fir; Spotted crown =ponderosa pine. 1 so I• 00 •.

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increase in grand firs in the understory, however, stand susceptibility to budworm will increase over time. This trend could be reduced if thinning was heavy enough to favor growth of nonsusceptible species (e.g., ponder­ osa pine). Creating a multiple canopy structure in dense y oung stands will substantially reduce the susceptibility of the stand to wind/snow and in­ sects. After four to five decades, the grand firs will become susceptible to

Oliver et al.

375

wind/snow breakage; however, these trees will be very small and will have little impact on stand structure. Where silvicultural activities kill trees but do not remove any of them (to create more snags and logs for "old growth" habitat), both multiple canopy and dense single cohort stands will become extremely susceptible to fires. This extreme susceptibility would also occur where trees were killed by the common wind/snow and insect disturbances (Figure 3). Re­ moving most or all of the killed trees during the silvicultural operations or performing other silvicultural treatments to remove fuels can dramatically reduce the stand's susceptibility to fires (Figure 4).

Effects of Timber Removal D u ring Silvicultural Treatments Stand Structures-If all merchantable trees are removed in thinnings, the absence of snags and downed logs will be the most noticeably changed structural features. If twigs, foliage, and buds are not removed, the nutrient losses will be minimal. Only y oung, small snags and very old snags will then be present, since most large trees will be removed before they die. Old down logs will eventually disappear, and few new down logs will be recruited. To provide these features in the future, some trees would need to be designated and left for snag and down log recruitment. It is highly unlikely that all trees killed in the silvicultural treatments will need to remain in the forest for snags and for down logs. For example, some treatments will create nearly 1,000 snags per acre. At the end of 60 years, there will be over 10,000 linear feet of down logs per acre with some regimes. Evenly distributed, these forests would contain a down log every 4 feet across the forest floor. Since most of a tree's timber value is in the lower one third of the bole, removing this portion and leaving the top as a down log may be a cost-effective way of producing down logs, provided the top is large enough to serve structural purposes. Removing some of the trees during thinnings and lopping the tree tops and branches to ensure contact with the soil and rapid decomposition will markedly reduce fire susceptibility. Costs-If no silvicultural activities are done in the stands, the primary direct costs will be fighting and recovering from the catastrophic fires which will occur with or without preceding wind or snow breakages and insect disturbances. If active silvicultural treatments are imposed and no timber is removed to offset their costs, the different regimes will require between $742.00 and $1,515.00 per acre (not discounted) over the next 60 years to implement (Table 3). Where thousands of acres are to be sustained for old growth and no timber is removed, millions of dollars will be neces­

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FIGURE 7. Projections of species diameters, and percent crown closure, hard snag numbers, and down log lengths for dense, single cohort stands (Figure 6). (Diameters show largest tree of each species and stand. Snags and logs are in 3 diameter classes. N No Activity Regime; C Multiple Strata Regime; T High Density Regime. Snag & down log scales are logarithmic. 50 =

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378 ASSESSING FOREST ECOSYSTEM HEALTH IN THE INLAND WEST

FIGURE 8. Projections of susceptibility of dense, single cohort stands fol­ lowing different silvicultural regimes to destruction by common wind/snow and insect disturbance agents. Susceptibility of 100 extreme likelihood of disturbance. Susceptibility values over 200 were assigned a value of 200. Wind and snow susceptibility listed by species. [] No activities re­ gime; + High Density Regime; M ltiple_ Strata Regime.

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sary to create and maintain suitable habitat. These costs do not include the 2000

2010

2020

2030

2040

2050

direct costs of fighting and recovering from catastrophic f'rres and the indirect costs of losses of habitat and water quality following f'rres. If all merchantable timber is removed in the silvicultural treatments, the different regimes will yield a return of between

$1,215 and $14,042 per 3 and Figure 10). This

acre (not discounted) over the next 60 years (Table

GRAND FIR WIND/SNOW

return does not include the direct and indirect savings created by avoiding catastrophic wildf'rres and unemployment. ----

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Removing trees as forest products can reduce costs of implementing the various systems-or create a monetary gain-as well as reducing the stand's susceptibility to f'rres (Figure 4). Removing some trees for forest products and leaving others for wildlife habitat could bring enough revenue to cover the costs of creating habitat while reducing f'rre danger. Wildlife and ecological expertise will be necessary to determine the appropriate num­

2000

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. 2030

DATE (YEAR, A.D.)

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bers of snags and down logs to leave.

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382 ASSESSING FOREST ECOSYSTEM . HEALTH IN THE INLAND WEST .

: FIGURE 10. Living (line) and dead volume (block) by time for multiple ' canopy stands and den se stands, single cohort and silvicultural regimes in eastern Washington. Removing some volume would reduce risk of fire and provide a montary returo or offset the costs of silvicultural activities to create old growth structures. ·

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