INTRODUCTION

The second phase of treatment in the Fort Valley 10K unit will include two 100-acre demonstrations of "uneven-aged" management, in areas with and without major dwarf mistletoe infestation. Uneven-aged management is better termed "multi-aged" or "multi-sized" for southwestern ponderosa pine given regeneration and survival patterns in this forest type. Multi-aged management, particularly when using group selection marking, creates vertical and horizontal structure associated with pre-settlement forest conditions, interrupts crown continuity to reduce the risk of catastrophic fire, and provides for long-term sustainability of forest structure. Stand conditions following treatment are based on 'BDq', the desired residual basal area (B), maximum tree diameter (D), and a q-ratio - a ratio of the number of trees in one diameter class to that of the next, which controls of the 'shape' of a diameter distribution.

Basal area: Cooper (1960) describes two unmanaged stands with basal areas of 66 and 86 ft2/ac that are representative of conditions before Euro-American settlement, including logging and grazing, and fire control. Basal area in the Gus Pearson Natural Area averaged 62 ft2/ac in 1920 for trees > 4-inches DBH (Avery et al. 1976). To account for growth at 1 ft2/ac/year and a 20-year entry cycle into the area, we will mark to a basal area of 55 ft2/ac and the stand will grow to 75 ft2/ac before the next treatment. Given a historical tendency by foresters to mark insufficient numbers of stems for removal and a potential for excess trees in large diameter classes (that will not be cut) in some areas, the treatment will more likely result in 60+ ft2/ac growing to 80+ ft2/ac. These values are similar to density standards for past management in this area of the Coconino National Forest.

Maximum diameter: Under timber management circumstances, maximum diameter would reflect a desired product size above which all trees are harvested. For this demonstration, maximum diameter reflects the existing distribution of trees >16 inches DBH, since such trees will not be harvested in the Fort Valley 10K area. That distribution in 4-inch diameter classes is shown in Table 1; maximum diameter recorded was 21 inches. Note that the desired residual distribution requires 15.3 trees/ac > 16 inches DBH (the 18- and 22-inch diameter classes), which equals 33.1 of the desired 55 ft2/ac (more than half). In contrast, the stand currently has <4 trees/ac, or 5.7 ft2/ac of basal area, in trees > 16 inches DBH.

Q-ratio: Residual diameter distributions in classical uneven-aged management require details on 'shape', described by the negative exponential frequency distribution that specifies the ratio between numbers of trees in successive diameter classes (called a "q-ratio"). Again referring to previous studies of unmanaged stands of ponderosa pine, Cooper (1960) and Avery et al. (1976) determined natural stands to have q-ratios for 2-inch diameter classes of 1.22 to 1.34. Bailey and Covington (in review) fit a q-ratio of 1.24 to presettlement restoration plots using 4-inch diameter classes, as did Edminster in 1990 with the Gus Pearson restoration (attached). Lower q-ratios produce flatter distributions, which favor greater numbers of larger trees; higher q-ratios produce steeper distributions that favor greater numbers of smaller trees. Large numbers of small trees are not appropriate for a species such as southwestern ponderosa pine, whose regeneration success is often marginal. Therefore, we have selected a q-ratio of 1.24 (4-inch classes) to provide for a reasonable range of diameters in the Fort Valley area.

As shown in Figure 1, the Fort Valley area is severely overstocked in 10-inch and smaller diameter classes and understocked in the 18- and 22-inch diameter classes. Attaining a balanced diameter distribution therefore will not be possible with a single group-selection cut planned for the near future. After the initial treatment, residual structure will give some appearance of multi-sized stand structure. Saving all trees > 16 inches DBH and compensating for missing larger trees with 10- and 14-inch diameter class trees (there are an insufficient number extra 14-inch class trees) will ensure sufficient current basal area and adequate future stocking in the larger size classes.

Dwarf mistletoe infestations are present in many areas of the stands. Our intent is to locate "removal groups" (i.e., gaps) in areas of highest mistletoe occurrence. In tree groups between these gaps, excess trees in diameter classes are also thinned; again, mistletoe will be selected against to 'improve' stand condition. Pearson and Schubert have shown improvement selection cutting to be effective in limiting the occurrence and rate of spread of mistletoe in the nearby S9 and S10 study plots.

We will be using a leave tree mark (orange) given that most trees are removed from the site; marking leave trees is more efficient and uses less paint. We will mark leave trees in the 2- inch diameter class as well to afford some protection to them during the harvesting. Generally, markers in the field need to distinguish between viable groups of trees that contain the desired growing stock and removal groups (or "gaps") - groups of similar diameter trees not needed to meet the desired diameter distribution or to fill basal area deficits. Most removal groups will be in the 2- and 6-inch diameter classes and can be left unmarked. Gap size is usually in the 0.25 to 1-acre range (60 to 120-feet radius, respectively), though gap size may be as small as 0.1 acre (37-feet radius). Large diameter trees (> 12 inches) are retained in and/or around these future openings to serve as a seed source and some shelter for the opening; the opening will serve as a firebreak around such valuable trees. Snags are also preserved, preferably with some distance to other fuels for fire protection.

In addition to creating group openings, small- and intermediate-sized trees in areas between removal group openings are marked for thinning to approximate the target diameter distribution and basal area for that size class (Table 1). These thinnings follow general marking guides for even-aged stands with two exceptions: a grouped or clumped spatial pattern should be emphasized in the marking, and trees should not be marked strictly 'from below' but should attempt to retain the desired numbers of trees in a diameter class. Trees in the 2- and 6-inch diameter classes or flagged for leave trees; trees in the 10-inch diameter class are painted for cut trees per above.

Generally, the most desirable groups and/or trees in each diameter class will be retained - trees with vigorous-looking crowns and little forking or other evidence of past damage. It may, however, be necessary to retain marginal quality trees due to original stand composition and structure. As much as possible, trees infected with dwarf mistletoe should be marked for removal. At the very least, trees retained should appear to be able to survive until the next treatment tentatively scheduled in 20 years. Hopefully it will be possible to remove these less-than-desirable trees during the next cultural operation.

Trees will be marked using tree-marking paint from the USFS. Marking follows local practice of a mark across each of at least two sides of the tree at approximately breast height, with a mark below stump height on the lower side of the tree.

Field procedures: Our recommended field approach is to select (within view of the marker's location - about an acre) preliminary residual groups in each of the 2-, 6- and 10-inch diameter classes, individually. These should be areas where trees have good form and vigorous crowns. Within each of these selected groups, it may be necessary to mark some trees for removal as part of improvement thinning and to create space around larger (>12-inch) trees within the group. Next, estimate the residual number of trees in these groups, and compare to the residual diameter distribution goals in Table 1. In balancing the mark to the target, it may be necessary to select more residual groups and/or to enlarge the groups to achieve the required density and basal area. Conversely, if the preliminary selection of groups results in leaving too many trees, it may be necessary to leave fewer groups and/or reduce the size of some of the groups.

Within these featured tree groups, trees of smaller size classes should be removed to more closely simulate conditions before fire suppression. We anticipate that nearly every existing group with < 2-inch diameter trees that are of desirable form (e.g., lower H:D ratio and 40% LCR) will need to be maintained, and as large as it currently exists, with minimal improvement thinning within the group. Most trees in the 2-inch diameter class, however, are 2- to 3.9-inch diameter, very slender and suppressed - these should be removed.

LANDINGS AND ROADS WITHIN THE DEMONSTRATION

There should be little need for major road construction to implement the treatments discussed above. Terrain over the study area is fairly flat and access is excellent. There is a network of old roads and trails throughout much of the area; as much as possible these old routes should be improved as needed for access. Landings and roads should be located away from residual groups, especially those with larger trees. Landings and roads should avoid damage to the site that may affect future stand response (e.g., soil compaction). A preferred location for landings will be in gaps near major roads. Landings should be as small as possible to avoid soil compaction within group openings which could adversely impact future regeneration response.

LOGGING PRACTICES

Logging operations should be implemented in such a manner as to minimize damage to the residual stand and site. Trees should be felled into group openings and existing natural openings, and away from residual trees. Care should be exercised in skidding operations to avoid damage to residual trees and the limited amount of advanced regeneration in seedling and sapling size classes. These small trees are the future growing stock. Relatively small numbers of logs should be skidded at one time. The ideal goal is no damage to residual trees due to logging operations.

Acceptable damage would include minor damage to lateral branches on one side of a tree crown, which will not adversely affect future growth and survival, and/or minor debarking at tree base during skidding. Unacceptable damage includes debarking of more than 40 percent of the circumference of a stem during skidding, top breakage during felling operations (which seriously damages or destroys future merchantability of a tree), and/or destruction of a major portion of a tree crown. When trees are unacceptably damaged, every effort should be made to locate a nearby tree that was marked for removal but has characteristics similar to the damaged tree (before it was damaged). This tree should now be retained as a substitute for the severely damaged tree, which should be removed.

Slash should be scattered on the site to minimize concentrations of fuels. Particular attention should be given to avoiding fuel accumulations near groups of small diameter trees (seedlings and saplings in the 2-inch diameter class) and large trees (> 16-inch diameter).

FUEL TREATMENTS

Fuel treatments, to reduce logging residue and other accumulated fuels and to prepare seedbeds, will be carried out in conjunction with other planned understory burning in the Fort Valley 10K block. This demonstration provides an excellent opportunity to show the effects of prescribed burning as a silvicultural tool for site preparation in group openings and other openings where tree regeneration is a goal. Where possible, prescribed burning of an area should be paired with an unburned area for comparison purposes.

LITERATURE CITED

Avery, C.C., F.R. Larson, and G.H. Schubert. 1976. Fifty-year record of virgin stand development in southwestern ponderosa pine. USDA Forest Service General Technical Report RM-22. Rocky Mountain Forest and Range Experiment Station. Fort Collins, CO. 71 p.

Bailey, J.D. and W.W. Covington. (in review) Regeneration goals for southwestern ponderosa pine ecosystem restoration. Forest Ecology and Management.

Cooper, C.F. 1960. Changes in vegetation, structure, and growth of southwestern pine forests since white settlement. Ecological Monographs 30:129-164.

Myers, C.A., and E.C. Martin. 1963. Fifty year's progress in converting virgin southwestern ponderosa pine to managed stands. Journal of Forestry 61(8):583-586.

Schubert, G.H. 1974. Silviculture of southwestern ponderosa pine: the status of our knowledge. USDA Forest Service Research Paper RM-123. Rocky Mountain Forest and Range Experiment Station. Fort Collins, CO. 71 p.

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