Appendix E- Group Selection Feasibility Analysis
APPENDIX E
PILOT AREA GROUP SELECTION
FEASIBILITY ANALYSIS

Introduction

On October 21, 1998, the Herger-Feinstein Quincy Library Group Forest Recovery Act, as included in the Interior and Related Agencies Appropriations Act, became law under Section 401. In Section 401, the law identifies group selection uneven-aged forest management as a resource activity. The law lists yearly accomplishment expectations of 0.57 percent of the pilot project acreage. The reference for acreage is the October 12, 1993 map, "Quincy Library Group Community Stability Proposal," prepared by VESTRA Resources of Redding, California.

Based on the above, the group selection treatment expectation for the pilot area is about 9,300 acres per year. Subsequent GIS analysis and map corrections put the expectation at about 8,700 acres per year. Table E-1 displays expected accomplishment and acres potentially available to meet accomplishment expectations. Of importance, is the frequency of group selection harvests. The most ambitious schedule is a 10-year interval between harvests. Conventional thinking is twenty years. Table E-1 assumes a complete analysis of the pilot project area in 5 years so as to have 20 percent of the land base available for implementation in any given year. Because of logistics (timber sales, service contracts), this is an ambitious schedule. The reader may want to interpret less ambitious schedules into the table presented below.

Table E-1. Expected Acres Accomplishment and Possible Acres Available to Implement On.

 
Year
Cumulative Acreage Expectation (8700 Acres per Year)*
Accumulative Acres Expected to be Made Available for Group Selection Based on Analyzing 20% of the Pilot Area per Year.**
10 Year Cycle.
Accumulative Acres Expected to be Made Available for Group Selection Based on Analyzing 20% of the Pilot Area per Year.***
20 Year Cycle.
1
8,710
17,420
34,840
2
17,420
34,840
69,680
3
26,130
52,260
104,520
4
34,840
69,680
139,360
5
43,550
87,100
174,200
Percent of Land Base 
2.8
5.7
11.4
* This column cccumulates the total acreage expectation of 8,700 Acres per year. At the end off five years, 43,550 acres of accomplishment Is expected.
** Calculated by multiplying the total project area acres (1,528,189) x .20 (assume 20% of the project area is analyzed per year) x 0.57 per (accomplishment yearly expectation rate) x 10 (years of the treatment cycle). Acres are then accumulated. The figure represents the total number of acres potentially available from which to meet accomplishment expectations.
***Same calculation as the 10-year cycle except for using 20 years.


Table E-1 simply shows that there could be plenty of acres available from which to accomplish the expected 8,700 acres per year. Logistics, management objectives and restrictions, and scheduling determine how these acres are accomplished. Keep in mind, this is an arithmetic exercise. Whether there are qualified acres available is a matter of additional analysis. Also key, the intent of the legislation includes all acres into the equation for expected accomplishment. This comprises offbase and deferred lands (PAC's, SOHA's). Old-growth emphasis areas (ALSE's and LSOG's 4 and 5) which could become part of a selected course of action are also included.

Analysis Methods

To analyze qualified available acres, two important criteria drive the analysis. One is current interim spotted owl direction and the other is economic consideration. Available implementation acres then need to be adjusted to reflect offbase/deferred and possible future restrictions.

Spotted Owl Direction

The California Spotted Owl Sierran Province Interim Guidelines Environmental Assessment (1993) Decision Notice selected a course of action which requires adherence to the recommendations as described in General Technical Report PSW-GTR-133 (The California Owl: A Technical Assessment of Its Current Status). This is commonly called CASPO. The legislation requires compliance with current management direction.

Of particular importance is the CASPO direction for harvesting in "select" and "other" strata. Pertaining to select strata (M4G, M4N, M5G, M5N, M6, P4G), standards relevant to the analysis are:

1. Do not harvest live trees 30 inches in diameter or larger.

2. Retain 40 percent of the basal area, consisting of the largest of the healthy trees and culls in each unit.

3. Maintain 40 percent or greater crown cover.

For other strata (P3G, P3N, P4P, M2G, M3P, M3G, M3N, M4P, R3P, R3N, R4G, R4N), standards relevant to the analysis are:
1. Do not harvest live trees 30 inches in diameter or larger.

2. Retain 30 percent of the basal area, consisting of the largest of the healthy trees and culls in each unit.

In concert with the basal area retention standards described above are upper diameter limit (UDL) calculations. This procedure is described in CASPO. Briefly, the calculated upper diameter limit represents the largest tree (diameter) which can be harvested for a stand or cut unit. In many cases, the UDL is below 30 inches. For more details, refer to General Technical Report PSW-GTR-133, pages 21-22.

If group selection is to be feasible in "select" and "other" strata, enough basal area or trees must be removed to allow for successful establishment of regeneration. For all of the major vegetation types in the project area, an upper limit basal area retention was determined. See attached paper "Upper Limit Basal Area Determination - Group Selection." This represents the upper limit, not the ideal.

The methodology for determining the percent of strata where group selection is biologically feasible follows:

1. For each forest, select and other strata with significant acreages were chosen for analysis.

2. The most recent inventory and the associated cluster plots were identified for each strata.

3. UDL's were calculated for each cluster plot. Hence, each plot was defined as a stand.

4. Residual basal areas (per acre basis) were calculated for each point of each cluster plot using the UDL calculated for the cluster plot. Points where residual basal area was below the upper limit basal area were considered feasible for group selection. All trees up to the UDL were removed. Individual tree vigor, age, and other factors were not a harvest consideration.

5. The percent of the strata feasible for group selection was calculated by dividing the number of feasible group selection points by the total number of points for the strata.

6. To further stratify, the percent of each strata which fell into different residual overstory categories was calculated. This effort gives insight into how much of the strata has ideal group selection opportunity versus more marginal opportunities.

Economic Consideration

Each point of each cluster plot must also meet an economic criteria to be considered feasible. Points must have at least 2.8 MBF of commercial sawlog volume (per acre basis) available for harvest.

Results

CASPO is not feasible for long-range group selection planning. Therefore, the feasibility analysis needs to be limited to the pilot period. Subsequent planning decisions will dictate future (beyond 5 years) feasibility. The analysis below will first address biologic feasibility for the pilot period. Figures generated from this will be adjusted to allow for administrative feasibility.

Biologic Feasibility

Table E-2 and Table E-3 below list percents of the analyzed strata and landbase biologically feasible for group selection. See attachment for a complete spreadsheet listing of calculations. Table E-4 lists acres which could be available to meet yearly accomplishment expectations for the pilot period.

Table E-2. Feasible Strata Acres by Percent

Plumas National Forest
Strata
Total Acres*
Percent GS Feas**
0-5*** TPA Percent
5-10 TPA Percent
10-20 TPA Percent
20+ TPA
Percent
M3G
5,851
40
20
20
0
0
M3N
60,935
56
26
14
13
3
M3P
68,695
51
23
18
10
M4G
16,367
32
7
9
14
2
P3G
21,511
24
11
5
8
0
P3N
22,525
46
26
15
5
0
R3G
6,232
47
12
12
17
6
R3P
8,040
48
19
17
12
0
R3N
12,892
50
24
11
11
4
R4G
3,278
53
19
15
19
0
Ave
47
21
14
11
1
Total Acres
226,326
47,796
31,899
24,271
2,735

Lassen National Forest
Strata
Total Acres*
Percent GS Feas**
0-5*** TPA Percent
5-10 TPA Percent
10-20 TPA Percent
20+ TPA
Percent
M3G
8,756
58
25
4
13
16
M3N
35,740
38
16
9
12
1
M3P
7,279
16
11
0
5
0
M4G
9,094
20
0
0
20
0
M4N
7,496
30
20
0
10
0
R3N
23,205
58
31
10
12
5
R3P
9,285
50
40
0
10
0
R4N
16,228
59
14
14
17
14
Ave
44
20
7
12
5
Total Acres
117,083
23,252
7,988
15,033
5,487

Tahoe National Forest
Strata
Total Acres*
Percent GS Feas**
0-5 TPA %***
5-10 TPA Percent
10-20 TPA Percent
20+ 
TPA
Percent
R3P
11,206
34
15
10
6
3
R4G
14,813
42
13
15
13
1
Ave
38
14
12
10
2
Total Acres
26,019
3,624
3,389
2,536
448
* Total acres for the strata. Includes offbase and deferred acres as defined by QLG.
** Calculated by dividing the total number of feasible group selection cluster plot points by the total number of cluster plot points.
*** Calculated by dividing the total number of feasible points with less than 5 trees per acre of residual overstory trees (remaining after harvest) by the total number of points.
If group selections that result in less than 10 trees per acre are considered good opportunities, the Plumas, Lassen, and Tahoe have 35, 27, and 26 percent respectively of the suitable owl habitat available for group selection. For groups which have 10 to 20 trees per acre remaining after treatment, the Plumas, Lassen, and Tahoe have 47, 44, and 38 percent respectively available for group selection.

Table E-2 also indicates the three forests have ample acreage available to implement group selection across the pilot area. A ten-year treatment cycle requires 5.7 percent of the landbase be placed in groups and a 20-year treatment cycle requires 11.4 percent. This needs to be balanced against the fact that only 20 percent of the landbase is available for treatment at any given year. Table E-3 lists percentage of both suitable habitat and non suitable habitat landbase that is available to meet both the accomplishment expectations (assuming 20 percent of pilot area is analyzed each year).

Table E-3. Percent of Suitable and Non-Suitable Habitat Available for Group Selection.
Forest
Total Suitable Habitat Available* Planning Suitable Habitat Available** Non-Suitable Habitat Available*** Planning Non-Suitable Habitat Available
Plumas
35
7.0
80
16
Lassen
27
5.4
80
16
Tahoe
26
5.2
80
16
* For 0-10 trees per acre. These percentages would raise to 47, 44, 38 percent respectively for the Plumas, Lassen, and Tahoe for less than 20 trees per acre.
** Only 20 percent of the available acres will be analyzed each year.
*** This includes the following strata: F3G,F3N,F4G,F4N,J3G, J3N,J4G,J4P,E3N, W3G,W3N,W4N.
Table E-4 below converts Table E-3 to actual acres.

Table E-4. Available Group Selection Acres for a 5-Year Planning Cycle.

 
Forest
Planning Acres of Group Selection Available. Suitable Habitat* Planning Acres of Group Selection Available. Non-Suitable Habitat** Grand Total. Acres Available for Group Selection in Planning.
Plumas
7,469
25,040
Lassen
2,794
76,555
Tahoe
520
5,682
Total
10,783
107,277
118,062
* Total suitable acres (103,703 P, 51,758 L, 9,996 T) x percent group selection suitable habitat available. See Table E-3, Column 3. Assumes that 20 percent of the Project Area landbase is environmentally analyzed per year.
** Total unsuitable habitat (156,501 P, 477,555 L, 35,513 T) x percent group selection non-suitable available. See Table E-3, Column 5.
The amount of the project area analyzed per year will exceed the rate needed to meet 10-year or 20-year treatment cycles and the 0.57 percent treatment rate. Hence, there appears to be plenty of flexibility to find the needed acres for each year of the pilot period. For example, the pilot area has 369,428 acres of suitable habitat in the strata analyzed. The area of 369.428 M acres times 0.0057 treatment rate equals 2,106 acres. Long-range feasibility analysis is problematic.

Administrative Feasibility

The Herger-Feinstein Quincy Library Group Forest Recovery Act list spotted owl habitat areas (SOHA) and protected activity centers (PAC) as deferred from resource activity. However, these acres are used to compute group selection accomplishment expectations. The rationale for the 5-year pilot is that the over-accomplishment can be easily adjusted for in later years. The legislation also requires the riparian standards and guidelines as described in Viability Assessments and Management Considerations for Species Associated with Late-Successional and Old-Growth Forests of the Pacific Northwest, A Report of the Scientific Analysis Team, 1993, be followed. This is commonly referred to as SAT. The stated guidelines prohibit establishment of group selection in defined riparian areas. These acres are also included in the landbase for determining accomplishment expectation.

On May 1, 1998, the Regional Forester issued instructions to the Forests of the Sierra Nevada. He urged Forest Supervisors to not conduct any harvesting in Late Seral-Old Growth (LSOG) ranked 4 and 5 polygons. For reference, see Sierra Nevada Ecosystem Project - Final Report to Congress (SNEP), Volume II, Chapter 21, Appendix 21.1. In several of the DEIS alternatives, LSOG 4 and 5's are analyzed as no-harvest. These acres also are included in calculating the accomplishment expectation.

In two of the alternatives in the DEIS, Areas of Late Successional Emphasis (ALSE) will be established and analyzed as no harvest. SNEP, Addendum to the Final Report , pages 54-62 describes a likely scenario for the Sierra Nevada as well as the pilot area. Again, these acres are included in calculating the accomplishment expectation.

For Table E-5, the following assumptions and adjustments to Table E-4 apply:

1. PAC's and SOHA's.

a. Number of acres in pilot area not in withdrawn lands - 138,521.
b. Estimated percent in suitable/non-suitable habitat (>size 3) - 90/10.
c. Percent acreage reduction adjustment for suitable/non-suitable habitat (>size 3) - 34/2.
2. SAT Guidelines.
a. Estimated percentage of pilot area (outside of PAC's and SOHA's) - 10.
b. Estimated percent in suitable/non-suitable habitat (>size 3) - 75/25.
c. Percent acreage reduction adjustment for suitable/non-suitable habitat - 7/2.
3. LSOG 4 and 5.
a. Number of acres in pilot area not in withdrawn, deferred, PAC's, SOHA's - 45,370.
b. Estimated percent in suitable/non-suitable habitat (>size3) - 90/10.
c. Percent reduction adjustment for suitable/non-suitable habitat (>size 3) - 11/1.
4. ALSE's.
a. Number of acres not in withdrawn/SAT/PAC's and SOHA's/LSOG - 98,320.
b. Estimated percent in suitable/non-suitable habitat (>size 3) - 70/30.
c. Percent reduction adjustment for suitable/non-suitable habitat (>size 3) - 18/3


Table E-5. Available Group Selection Acres for a 5 Year Planning Cycle, Adjusted. *

 
Suitable Habitat less PAC/SOHA
Less SAT
Less LSOG
Less ALSE
Non-suitable habitat less PAC/SOHA
Less SAT
Less LSOG
Less ALSE
7,117
6,362
5,175
3,235
105,131
102,986
101,913
98,694
* For suitable and non-suitable habitat, acre deductions accumulate from left to right. For example, less LSOG includes PAC, SOHA, SAT , and LSOG acre deductions.
All DEIS alternatives allow no harvest in PAC's, SOHA's, and SAT. In addition, three DEIS alternatives allow no harvest in LSOG. Two alternatives establish and restrict harvest in ALSE. Table E-5 illustrates non-suitable habitat availability is not affected significantly. Flexibility in suitable habitat can be reduced significantly, according to the alternative selected. Under the most restrictive scenario for suitable habitat, it is unlikely 2,106 acres can logically be found and treated. In all cases, expected accomplishment can be achieved by relying more on non-suitable habit

Concluding Remarks

The above is mostly arithmetic. The analysis shows acres are available to meet accomplishment expectation for the pilot period. Except for the most restrictive scenarios, "select" and "other" strata are available for five years of treatment.

One important point warrants mention. To implement the above, spotted owl interim guidelines requires a "blind obedience" mentality. Silvicultural dilemmas are evident. Historically, silviculturists have used group selection as a tool to restock understocked areas, treat disease centers, regenerate pockets of old trees. Group selection is an uneven-aged tool and is usually associated with a rotation age. Under full regulation, a portion of the land is regenerated (harvested) each year and this progresses through time with each age class representing a portion of the land base. Group selection management can not continue indefinitely without the harvest of larger trees.

Many stands do not lend themselves to group selection. Much of the mixed conifer belt in the pilot area is comprised of uneven-aged stands which are best managed using an individual tree selection uneven-aged technique. Blind obedience will require younger thriftier age groups be harvested to meet accomplishment expectation. Refer to the attached "Group Selection Priorities" white paper for more insight.

This analysis has some limitations. Groups harvests will probably average one acre in size across the landscape. Cluster plot points, which were central to the group selection feasibility determination decisions, sampled less than an acre. This may have caused some overstatement of the available group selection acreage. It is recognized that the analysis is probably not statistically correct. The intent is to provide useful insight.

In summary, accomplishment expectations for the 5-year pilot can be met given adequate budget and staffing. Large areas will have to be analyzed each year to meet accomplishment. If group selection is expected to be a significant management tool after the pilot period, new direction will need to be in place to relieve some of the silviculture dilemmas described above as well as to address long range planning.

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ATTACHMENTS

GROUP SELECTION PRIORITIES
Herger-Feinstein Quincy Library Group Forest Recovery Act

Introduction

The Herger-Feinstein Quincy Library Group Forest Recovery Act (Act) describes group selection occurring "on an average of .57 percent of the pilot project area land each year of the pilot project." The land base to implement on is identified as "available for group selection" on the Quincy Library Group Community Stability Proposal map, October 12, 1993. According to this landbase (1.63 million acres), the annual group selection acreage expectations for the pilot area is 9,300 acres. Because of some inaccuracies associated with this map, these expectations may be revised downward slightly. At the time of this writing, the available landbase GIS analysis shows is 1.528 million acres or approximately 8,710 acres of yearly group selection accomplishment.

How does this compare to current accomplishment rates? The seven Ranger Districts of the Act pilot area are currently implementing very little group selection prescriptions. The yearly accomplishments are at a rate of less than 300 acres.

Implementing the group selection system as described in the Act presents logic and strategy dilemmas. These can be categorized by biologic and economic concerns. With these in mind, the Forest Service needs to develop treatment priorities which will allow the best chance for success.

Biologic Concerns.

The Decision Notice and Finding of No Significant Impact for California Spotted Owl Sierran Province Interim Guidelines, January 1993 selected Alternative 2 as described in the Environmental Assessment (EA). Alternative 2 requires implementation of the recommendations of the Technical Team. These recommendations are developed in the Pacific Southwest Experiment Station General Technical Report PSW-GTR-133, The California Owl: A Technical Assessment of Its Current Status, July 1992. Of particular importance to implementing group selection are the guidelines listed on pages III-3 to 4 of the EA. Act requires compliance with existing direction.

Both "select" and "other" suitable habitats (See page III-3 of EA) refer to retaining 40 and 30 percent respectively of the existing basal area, consisting of the largest of the healthy trees and culls in each unit proposed for harvest. Pages 21-23 of the Technical Report give very specific guidelines for determining the largest tree size which can be harvested as it relates to meeting basal area guidelines. This process is often referred to as calculating the upper diameter limit. Meeting the basal area retention guidelines can result in restricting harvesting of trees which have diameters less than 30 inches.

Conventional group selection thinking allows for area control where each age class is represented. When a land base is fully managed and regulated, the older "groups" are regenerated upon reaching rotation age. During the transition period prior to full regulation, decisions of how and when to implement group selection is based on: 1) current age structure of the land base; 2) pathogen conditions and risks; 3) age structure of individual stands; and 4) economic considerations.

Dilemmas.

1. The upper diameter limits (UDL) for select and other strata restrict flexibility. For many stands, UDL will be considerably less than the no-harvest 30-inch diameter guideline. The Act requires implementation at a full regulation rate. Obedience to Act may require removing groups of thrifty younger aged trees. The Act assumes an average 175-year rotation.

2. Group selection is a regeneration harvest. UDL will in many cases result in residual stocking within the groups. Residual stocking must be low enough to allow for seedling survival and adequate growth. The silviculturist must determine how much residual stocking he/she can tolerate for stands and vegetation types. Much of the project area will simply not be conducive for group selection because of this residual stocking.

3. The stands which lend themselves best to group selection are even-aged in structure or have a definite patch mosaic appearance. Uneven-aged structure which is not "patchy" will be a hard fit for group selection strategy.

4. Current interim owl direction does not allow for long-range implementation of fully regulated group selection as expected in Act. The stands will simply grow themselves out of group selection options.

Economic Concerns

The Act's purpose is in response to the Quincy Library Group - Community Stability Proposal, November 1993. The Proposal has forest health and community stability as drivers. It is expected that harvesting associated with group selection will contribute to community stability.

Dilemmas

1. Group selection by conventional implementation is expensive to plan and execute. Interim owl direction will, in many cases, force harvest of smaller less valuable trees, thus aggravating the economics more.

2. The Act allows for some individual tree selection on "matrix." UDL will limit flexibility somewhat. Stand structures, in many cases, will not be conducive to individual tree selection. Many even-aged stands will be a hard fit for individual tree selection.

3. The Act does not allow for thinning of large acreages. Aggressive thinning of matrix land could be a positive economic action. Conventional appropriated funding is scarce. This will continue for the foreseeable future. Funding outside of the Act for matrix land thinning is not expected.

4. Within many stands, there are understocked or non-stocked areas. There are obvious reasons for regenerating these. Expending money and resources toward these areas would be another economic drain.

Priorities

The dilemmas outlined above present challenges. The Act is a five-year pilot. Forest Plan revisions and other management directions will drive actions after the pilot period. The expectations of the Act basically will require that the entire pilot project area will be analyzed for treatment in the near future. Trying to define where to begin analysis and implementation may not be that critical. Within the pilot area there should be a program balance between eastside and transition zone/westside conditions.

What can be prioritized is the stand structure types which best address the dilemmas mentioned above and also allow for accomplishment success. Some vegetation and stand structures will provide more flexibility and may have to be treated over the 0.57 percent rate (assume a ten-year treatment cycle). Others vegetation types and structures will have to assume lower rates. In any case, no more that twice the 0.57 rate (assume a ten-year treatment cycle) should be realized by any vegetation type for the pilot period.

One caution here. Within each item listed below, pest management and economics are important considerations. To the extent that economics allow, treating pest problems (such as root disease and dwarf-mistletoe) will be incorporated into project design. The priority should be for treatments to move forward which allow for positive net forest health gain, yet provide for real timber sale value and meaningful commodity outputs.

Priorities

1. Mature even-aged stand structure. The assumption here is for small to medium-sized sawtimber which has substantial stocking under 30 inches diameter. Under most strata labeling, this would be size 3 or 4. Eastside pine would have the most management flexibility. White fir (W) and red fir (R) vegetation types would be high priority. Residual overstory stocking would allow for seedling establishment and growth. Most flexibility exists in the size 3 (other strata) type.

2. Uneven-aged patchy stand structure. As observed for much of the mixed conifer and eastside pine vegetation types, stands exist in mosaics of small even-aged patches. Patch sizes range from one-fourth acre to several acres. To the extent that UDL allows, regenerate the largest tree size groups as possible. Residual overstory stocking would allow for seedling establishment and growth.

3. Uneven-aged stand structure. Patches for regeneration may be more difficult to find. UDL's will be lower then "2" above. These would be good candidates for individual tree selection. To the extent that UDL allows, regenerate the largest tree size groups as possible. Residual overstory stocking would allow for seedling establishment and growth.

Conclusion

Implementing the group selection expectation of the Act will be a challenge. Obedience to the accomplishment expectations will involve some compromising of conventional growth and yield thinking. There is room for good decision making and prescription development.

RESIDUAL BASAL AREA DETERMINATION - GROUP SELECTION

Introduction

CASPO interim guidelines require basal area retention for "select" and "other" strata. The Herger-Feinstein Quincy Library Group Forest Recovery Act requires an aggressive group selection strategy. Group selections function as a mechanism for regeneration.

With the above in mind, decisions on the amount of overstory (interpret residual basal area) that can exist in a group and still allow for meaningful regeneration, are in order. Conceptually, this would equate to a shelterwood system with maximum allowed overstory. The point of meaningful regeneration establishment and growth should be near this overstory level. Adjustments for edge effects from the surrounding stand also need to be considered. Described below are a literature review plus recommendations.

Literature Review.

Fiske, John. 1992. Major Silvicultural Systems and Their Application. Lassen National Forest Land and Resource Management Plan Environmental Impact Statement. USDA Forest Service Appendix O.

Page O-3 states: "The shelterwood system (shown in Figure O-3) requires leaving sufficient trees per acre (typically 10-20), during the regeneration cutting, to provide an environment that protects (shelters) the seedlings of a new even-aged stand."

Seidel, K. W. 1979. Regeneration in Mixed Conifer Shelterwood Cuttings in the Cascade Range of Eastern Oregon. Pacific Northwest Forest and Range Experiment Station. PNW-264. 1979.

This study surveyed mixed conifer shelterwood cuttings. On page 8, the author states: "My observations suggest that if at least 40-percent stocking of milacre plots is desired, then a basal area of about 60 square feet per acre should result in adequate stocking on most units."

Williamson, Richard L. 1973. Results of Shelterwood Harvesting of Douglas-fir in the Cascades of Western Oregon. Pacific Northwest Range and Experiment Station. PNW-161. 1973.

A survey of 21 shelterwoods was conduction. The author states the following:

a. Page 8. "There are indications that overstory densities above about 50 percent of normal basal area are too dense for satisfactory regeneration."

b. Page 9. "If, in anticipation of some future mortality, one assume that 70-percent stocking is desirable objective, then figure 4 indicates, for example, about 75 square feet of basal area as being desirable overstory density for the average seed bed condition in this study..."

Gordon, Donald T. 1970. Natural Regeneration of White and Red Fir...Influence of Several Factors. PSW-58.

This study looked at regeneration results from different cutting treatments on the Swain Mountain Experimental Forest. Swain Mountain is located within the administrative boundaries of the Lassen National Forest. In addressing the shelterwood system, the author concludes that more than 10 trees per acre should be left.

Fiske, John et al. Effects of a Group Selection Strategy for the Sierra Nevada Mixed Conifer: A Report of a Regional Ad Hoc Team. U.S. Forest Service, R5. 1993.

The authors reported that suppression from large edge trees probably extend out at least 20 feet, 40 feet, and 50 feet for Dunning I, II, and III sites, respectively.

Recommendations

There were other studies showing regeneration in shelterwoods and groups. These did not provide any insight as to what might be maximum residual basal area and the effect of matrix stand edge effect. Ideal reserve stockings for shelterwoods as stated in the literature range from 10-20 trees per acre or 60 to 80 square feet per acre. The problem is to define reserve basal area that would allow for reasonable regeneration performance in a group selection situation where most of the groups will be around one acre in size. Listed below are some basic assumptions used to make this determination.

1. On the average, 60 percent of normal is considered fully stocked and not capable of reasonable understory regeneration. Use the Basal Area at 150-year stand age and use most common site index for the vegetation type.

2. Edge effect will affect 60 percent of the group opening (use one acre as the average and 40 feet of edge effect).

3. A good approximation of the maximum amount of stocking that can allow for regeneration establishment would be 50 percent of full stocking reduced by 10 percent to adjust for edge effect.

Table. E-6. Upper Residual BA for Regional Vegetation Type

 
Regional Vegetation Type
Basal Area
A
100
E
50
F
50
J
60
L
85
M
85
P
60
R
100
W
90

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