[[START OF PAGE 1]]
40 75K 21
186153
United States
Department of
Agriculture
Forest Service
Intermountain
Forest and Range
Experiment Station,
Ogden, UT 84401
Research Note
INT-333
July 1983
FOREST SERVICE
UAS
Harvesting
Strategies for
Management of
Mountain Pine USA
Beetle Infestations
in Lodgepole Pine:
USDA
Sunne
-
Preliminary Evaluation, East Long Creek
Demonstration Area, Shoshone National
Forest, Wyoming
ABSTRACT
Diameter-limit and leave-tree cuts were tested as ways to reduce or minimize lodgepole pine losses to the mountain pine beetle. In the first year after treat- ment, loss reductions were proportional to the intensity of cut. According to the Rate of Loss Model, the 100-leave-tree cut was the best deterrent of recurring in- festation, measured as amount of losses and length of time. The 100-leave-tree cut also should provide the best regeneration and has the added benefit of reduc- ing dwarf mistletoe infection.
KEYWORDS: mountain pine beetle, Dendroctonus ponderosae, lodgepole pine, Pinus contor- ta var. latifolia, harvest strategies.
'Principal Entomologist, Population Dynamics of the Mountain Pine Beetle Research Work Unit, Intermountain Forest and Range Experi- ment Station, Ogden, Utah. CANUSA Entomologist, Forest Pest Management, Boise Zone Office, Intermountain Region, USDA Forest Service, Boise, Idaho. Entomologist, Forest Pest Management, Rocky Mountain Region, USDA Forest Service, Lakewood, Colo.
Walter E. Cole, Donn B. Cahill,2 and Gene D. Lessard³
East Long Creek in the Shoshone National Forest is one of a series of demonstration area projects that used management alternatives derived from research (Cole and Cahill 1976) and small-scale tests (Cahill 1978; McGregor and Cole, in press) in an attempt to reduce or minimize lodgepole pine (Pinus contorta var. latifolia Engelm.) losses to the mountain pine beetle (Dendroctonus ponderosae Hopkins).
The objective of this initial large-scale application of management alternatives was to prevent undue losses of lodgepole pine by changing or reducing the food supply of the mountain pine beetle, and also to manipulate the stand to grow at or near optimum site capacity with continued prevention of large losses to the beetle.
Some constraints on the project were to protect or enhance key resource values, remove merchantable material through a commercial timber sale, develop per- manent access roads for general land use and manage- ment, improve forest cover growing conditions through disease control and stocking to attain timber produc- tion potentials on regulated lands, and develop a cost- benefit analysis for each strategy. This report is limited to the reaction of the mountain pine beetle and tree growth response the first year after cutting.
Future efforts to manage stands to prevent losses to the beetle must be made before the beetle epidemic cycle. East Long Creek Demonstration Area provided this opportunity.
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STUDY AREA
The East Long Creek Demonstration Area lies be- tween 7,600 and 8,800 ft (2 317 and 2 683 m) elevation, which is the lower half of the forested zone in the Wind River Drainage. The climate is cool and dry; moisture availability is the most limiting growth factor during the season.
Soils are derived from sedimentary formations and glacial moraines derived from the Wiggins formation. The clay content of the soils and seasonal distribution of precipitation make natural regeneration difficult on southerly and westerly aspects and flats, especially below 8,500 ft (2 591 m).
Cover types change with aspect and elevation; coni- ferous trees grow only on favorable aspects below 7,600 ft (2 317 m), and seldom occur on more adverse aspects at higher elevations.
Reestablishment of conifers following fire is extreme- ly slow on adverse aspects. Recovery from any drastic disturbance on this area can be expected to be slow unless seedlings are planted as the regeneration method. On some of the adverse aspects, the scattered limber pine (P. flexilis James) and lodgepole pine trees appear to be pioneers of a first generation forest.
The lower part of the coniferous cover could be classed as Abies lasiocarpa-Arnica cordifolia habitat type, milk vetch phase. This habitat type on the Wind River District has almost no potential to be dominated by Abies lasiocarpa because the development of the climax community requires more time than is permitted by the natural fire cycle.
Inland Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) predominates in an alternative seral community on this habitat type where soils are basic. At this eleva- tion, the inland Douglas-fir/mountain snowberry habitat is present on soils derived from limestone formations.
Aspen (Populus tremuloides Michx.) is a short-lived seral community replaced by limber pine or lodgepole pine in the first generation. Retention of aspen as a cover type requires a reduction in competition for moisture and cutting the live aspen to break the auxin flow so sprouting can occur.
In most of the stands in this zone, the lodgepole pine component of the stand is 150 to 200 years old and dy- ing out rapidly. Younger stands are still dominated by lodgepole pine and have a manageable pole and small- size sawtimber component. This zone of the coniferous forest is an Abies lasiocarpa-Vaccinium scoparium habitat type.
Regeneration following disturbance is more rapid in this habitat and will tend to be mixed aged, with some tolerant species seedlings and saplings present in the first 50 years of stand development. The number of spruce and fir trees present during early stand develop- ment probably depends on seed source, once the lodgepole pine component accomplishes the necessary site modification. In some cases, competition by density stocked lodgepole pine may reduce spruce and fir regeneration.
Site index values for lodgepole pine are 30 to 35 ft (9.1 to 10.7 m) in 50 years in the Abies lasiocarpa-Arnica cordifolia-milk vetch phase habitat, increasing to 45 to 50
ft (13.7 to 15.2 m) in 50 years in the Abies lasiocarpa- Vaccinium scoparium habitats.
Throughout this area of the forest, basal area in natural stands follows the site index values, with basal areas as low as 65 ft2/acre (14.4 m²/ha) on the lower site index areas and increasing to 140 ft²/acre (31.1 m²/ha) on the most productive sites. Total live conifer trees over 2 inches (5.08 cm diameter at breast height) (d.b.h.) on the 1,789 acres (724 ha) cruised rarely exceeded 400 per acre (988 per ha).
The demonstration area contained approximately 1,898 acres (768 ha). Before harvesting, the area contained 3,777 board feet (bd.ft.) of gross green volume per acre and 1,664 bd.ft. of dead standing volume per acre. Net volumes were 3,397 bd.ft. of green volume per acre and 1,332 bd.ft. of dead volume per acre, or 4,729 bd.ft. total net volume per acre.
STAND PRESCRIPTIONS
Three general prescriptions were applied: (1) cutting levels based on diameters, (2) leave-tree cuts, and (3) clearcuts. In each case, the primary purpose was to remove the food supply from the beetle; the larger diameter trees generally contain the thicker phloem. However, other criteria were considered in each case. Each prescription required retention of adequate forest cover to promote natural regeneration, wildlife needs, and visual qualities, and was designed to fit the condi- tion of the stand and its ecology to promote future development under natural conditions.
The prescriptions and their applications were:
1. Diameter cuts.
a. Cut all lodgepole pine 7 inches (17.78 cm) d.b.h. and larger and salvage dead trees 8 inches (20.32 cm) d.b.h. and larger. This prescription was applied to three different stand conditions:
(1) Late transitional stands that had converted to the spruce-fir type. The lodgepole pine component was decadent or dying rapidly. In this case, adequate lodgepole pine grow- ing stock was to be retained. Lodgepole pine regeneration could be expected to fill in openings created by logging.
(2) Two-aged lodgepole pine stands that con- tained very few tolerant trees. The understory was primarily lodgepole pine, and the residual stand of seedlings and saplings would be understocked. Trees less than 7 inches (17.78 cm) d.b.h. down to the seedling-sapling understory were not suitable growing stock because of disease-dwarf mistletoe (Arceuthobium americanum) and comandra blister rust (Cronartium comandrae). It was necessary on these sites to retain the undesirable pole timber to protect the site until natural regeneration occurs to bring the seedling- sapling stand up to 300 per acre (121 per ha). Timely removal of mistletoe-infected trees will be required.
2
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In some cases where stocking was inade- quate and residual trees were sparse-less than 100 per acre (40 per ha)-planting would be necessary. Lodgepole pine or in- land Douglas-fir containerized stock should be planted at 200 to 400 trees per acre (81 to 162 per ha) depending on the number and size of residual growing stock trees.
(3) Heavily stocked lodgepole pine pole timber stands where the age and disease condi- tions made regeneration of the stand desirable, and enough trees less than 7 inches (17.78 cm) d.b.h. were present to fur- nish adequate cover to meet forest cover objectives, including site protection. Ade- quate natural regeneration was expected in these stands.
b. Cut all lodgepole pine trees 10 inches (25.40 cm) d.b.h. and larger and salvage all dead or at- tacked trees 8 inches (20.32 cm) d.b.h. and larger. This prescription was applied to isolated stands in the unthinned component where forest cover was not maintained for production of wood products, but primarily where lodge- pole pine was the principal component and cover objectives required retaining forest cover to protect other values. Site potential was low in these stands, eco- systems were exceptionally fragile, and values other than timber were paramount. The prescrip- tion was applied to stands that were sparsely stocked and on adverse aspects. These stands were suspected to be first-generation coni- ferous forests, hence were fragile ecotones, and disruption could reverse ecologic trends. Subse- quent treatments on regulated lands will be overstory removal in one or two steps, depend- ing on disease conditions, regeneration suc- cess, and visual quality needs.
c. Cut all lodgepole pine trees 12 inches (30.48 cm) d.b.h. and larger and salvage all dead or at- tacked trees 8 inches (20.32 cm) and larger. This prescription was applied to stands where lodge- pole pine was the principal component, site potential was extremely low, stands were sparsely stocked, aspects were adverse, and stands contained trees exceeding this diameter limit.
2. Leave-tree cuts.
The leave-tree prescription was applied to two stands and required leaving 100 trees per acre (40 trees per ha), while removing the balance of the lodgepole pine component of the stand. All selected leave trees were the largest, most desirable lodgepole pine, growing stock, and suffi- cient desirable growing stock trees of other
species were retained to result in an average stock- ing of 100 trees per acre (40 per ha) over 7 inches (17.78 cm) d.b.h..
Because of small islands of old lodgepole pine that escaped the fire that regenerated these two stands, and because these stands contained mistletoe in- fection centers, small clearcuts also were required. Natural regeneration could be expected in 5 years if these clearcuts did not exceed 5 acres (2 ha).
3. Clearcuts. Six areas, averaging 14 acres (5.7 ha) each, were clearcut. These were in fire-regenerated pole timber stands. There were small islands of old-aged, larger diameter lodgepole pine trees that were diseased and decadent. Some of these islands had lodge- pole pine and/or spruce-fir understories. Because of the heavy fuel accumulations in the pockets of old growth, bulldozer piling and slash burning were desirable to meet fuel management objectives.
METHODS
A total of 37 cutting units and one check block unit were laid out in the demonstration area:
- 10 units in the 7-inch (17.78-cm) cutting block
- 17 units in the 10-inch (25.40-cm) cutting
block
- 2 units in the 12-inch (30.48-cm) cutting
block
- 2 units in the 100-leave-tree cutting block
- 6 units in the clearcut block
- 1 check block unit
Harvesting began in January 1979 and was completed in February 1981, well before the 1981 beetle flight. A summary of the pretreatment stand structure and pro- posed cuts is shown in table 1.
A survey of the demonstration area was made in the spring of 1982 to determine tree loss to the mountain pine beetle. A 20-percent survey was conducted in 22 of the 38 units:
- 6 of 10 units in the 7-inch (17.78-cm) cutting block
- 11 of 27 units in the 10-inch (25.40-cm) cutting block
- 2 of 2 units in the 12-inch (30.48-cm) cutting block
- 2 of 2 units in the 100-leave-tree block
- 1 check block unit
The 20-percent survey used a 1-chain-wide strip (20 m) every 5 chains (100 m) and recorded beetle-killed trees in 1979, 1980, and 1981, other causes of death, and diameter.
Tree growth data were collected during the loss surveys. Basal area and radial growth measurements were taken at 5-chain (100 m) intervals along the cruise strip, using a 10 BAF gage. Unfortunately, similar data were not taken before the harvest for comparison.
3
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Table 1.-Summary of stand data and proposed cuts for East Long Creek Demonstration Area
| Stand structure and volumes | Treatment | Treatment | Treatment | Treatment | Treatment |
|-|-|-|-|-|-|
| Stand structure and volumes | 7-inch | 10-inch | 12-inch | 100-leave-tree | Clearcut |
| Acres | | | | | |
| Total | 1,132.0 | 581.0 | 60.0 | 39.0 | 86.0 |
| Mean | 113.2 | 34.2 | 30.0 | 19.5 | 14.3 |
| Live lodgepole/acre | | | | | |
| Total | 1,633.0 | 3,668.0 | 686.0 | 428.0 | 1,475.0 |
| Mean | 163.3 | 215.7 | 343.0 | 214.0 | 245.8 |
| <7-inch | 864.0 | 1,925.0 | 458.0 | 242.0 | 769.0 |
| Mean | 86.4 | 113.2 | 229.0 | 121.0 | 128.2 |
| > 7-inch | 769.0 | 1,743.0 | 228.0 | 186.0 | 706.0 |
| Mean | 76.9 | 102.5 | 114.0 | 93.0 | 117.7 |
| > 10-inch | 352.0 | 656.0 | 88.0 | 62.0 | 271.0 |
| Mean | 35.2 | 38.6 | 44.0 | 31.0 | 45.2 |
| >12-inch | 166.0 | 282.0 | 14.0 | 24.0 | 156.0 |
| Mean | 16.6 | 16.6 | 7.0 | 12.0 | 26.0 |
| Live species/acre | | | | | |
| Subalpine fir and other | 768.0 | 699.0 | 66.0 | 30.0 | 1,006.0 |
| Mean | 76.8 | 41.1 | 33.0 830000 | 15.0 | 167.7 |
| Engelmann spruce | 194.0 | 47.2 | | 2.4 | 248.0 |
| Mean | 19.4 | 2.8 | | 1.2 | 41.3 |
| Aspen | 1,683.0 | 232.0 | | 64.0 | 34.0 |
| Mean | 168.3 | 13.6 | | 32.0 | 5.7 |
| Proposed cut | | | | | |
| T/A | 769.0 | 656.0 | 14.0 | 228.0 | 1,475.0 |
| Mean | 76.9 | 38.6 | 7.0 | 114.0 | 245.8 |
| Gross volume/acre | | | | | |
| Live cut | 4,468.0 | 3,518.0 | 3,683.0 | 3,205.0 | 4,093.0 |
| Mean | 4,468.0 | 3,518.0 | 3,683.0 | 3,205.0 | 4,093.0 |
| Salvage cut | 2,290.0 | 1,480.0 | 1,583.0 | 1,231.0 | 2,337.0 |
| Mean | 2,290.0 | 1,480.0 | 1,583.0 | 1,231.0 | 2,337.0 |
| Gross volume (M) | | | | | |
| Green | 5,058.0 | 2,044.0 | 221.0 | 125.0 | 352.0 |
| Mean | 505.8 | 120.2 | 110.5 | 62.5 | 58.7 |
| Dead (≥8") | 2,592.0 | 860.0 | 95.0 | 48.0 | 201.0 |
| Mean | 259.2 | 50.6 | 47.5 | 24.0 | 33.5 |
| Uncut per acre | | | | | |
| Lodgepole pine (≥2") | 891.0 | 2,916.0 | 558.0 | 39.0 | 877.0 |
| Mean | 89.1 | 171.5 | 279.0 | 19.5 | 146.2 |
| Total trees (≥2") | 1,602.0 | 3,661.0 | 624.0 | 43.0 | 2,132.0 |
| Mean | 160.2 | 215.4 | 312.0 | 21.5 | 355.3 |
| Average gross volume
per acre (M) | Average gross volume
per acre (M) | Average gross volume
per acre (M) | Average gross volume
per acre (M) | Average gross volume
per acre (M) | Average gross volume
per acre (M) |
| Green | 4.468 | 3.518 | 3.683 | 3.205 | 4.093 |
| Dead | 2.290 | 1.480 | 1.583 | 1.231 | 2.337 |
| Average net volume
per acre (M) | | | | | |
| Green | 4.023 | 3.166 | 3.315 | 2.885 | 3.684 |
| Dead | 1.832 | 1.184 | 1.267 | .985 | 1.870 |
| Total adjusted net volume | | | | | |
| Volume per acre | 5.855 | 4.350 | 4.582 | 3.870 | 5.554 |
| Net volume | 6.628 | 2.528 | .275 | .151 | .478 |
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RESULTS
The stand structure changed proportionally to the in- tensity of harvest cut used in each block (table 2). Stand average diameter (d.b.h.) changes were:
| Treatment | Original
diameter | Original
diameter | Diameter
after harvest | Diameter
after harvest |
|-|-|-|-|-|
| Treatment | Inches | cm | Inches | cm |
| 7-inch (17.78-cm) cut | 7.8 | 19.81 | 7.0 | 17.78 |
| 10-inch (25.40-cm) cut | 7.7 | 19.56 | 7.0 | 17.78 |
| 12-inch (30.48-cm) cut | 7.4 | 18.80 | 7.3 | 18.54 |
| 100-leave-tree cut | 7.5 | 19.05 | 8.0 | 20.32 |
Considering only the kill by the mountain pine beetle, the trend for the 3 years (2 years before the cut was com- pleted and 1 year after completed cuts) is rather dramatic (table 3 and fig. 1). In all cutting blocks, the number of trees infested dropped considerably after harvesting; the check block continued to lose trees to the beetle at about the same rate.
It is evident that tree loss to secondary insects, such as Ips, Pityophthorus, Pityogenes, and Pityokteines, and comandra rust lessened after treatment (table 4). How- ever, this apparent reduction of loss may be an artificial effect of sampling, because the check areas also showed no loss due to these factors in 1981 (the year after cutting was completed).
Table 2.-Stand structure before and after cutting
Live lodgepole pine per acre by diameter class.
| Treatment | Before cut | Before cut | Before cut | Before cut | Before cut | Trees
cut per
acre | After cut | After cut | After cut | After cut | After cut |
|-|-|-|-|-|-|-|-|-|-|-|-|
| Treatment | Total | <7
inches | 7-9
inches | 10-11
inches | >12
inches | Trees
cut per
acre | Total | <7
inches | 7-9
inches | 10-11
inches | >12
inches |
| 7-inch cut | 163.3 | 86.4 | 41.7 | 18.6 | 16.6 | 76.9 | 86.4 | 86.4 | 0 | 0 | |
| 10-inch cut | 215.7 | 113.2 | 63.9 | 22.0 | 16.6 | 38.6 | 177.1 | 113.2 | 63.9 | 0 | 000102 |
| 12-inch cut | 343.0 | 229.0 | 70.0 | 37.0 | 7.0 | 7.0 | 336.0 | 229.0 | 70.0 | 37.0 | |
| 100-leave-tree cut | 214.0 | 121.0 | 62.0 | 19.0 | 12.0 | 114.0 | 100.0 | | | | |
| Clearcut | 245.8 | 128.2 | 72.5 | 19.2 | 26.0 | 245.0 | 0 | 0 | 9 | 0 | |
| Check area | 251.0 | 255.0 | 196.0 | 91.0 | 42.0 | 0 | 251.0 | 255.0 | 196.0 | 91.0 | 42 |
'Data not available on distribution. Include only 4- to 6-inch trees.
Table 3.-Tree mortality due to the mountain pine beetle
| Treatment | Number of trees killed per acre | Number of trees killed per acre | Number of trees killed per acre |
|-|-|-|-|
| Treatment | 1979 | 1980 | 1981 |
| 7-inch cut | 0.72 | 0.51 | g0 0.09
.07
completed 1.15
0
4.23
cut |
| 10-inch cut | .35 | .66 | g0 0.09
.07
completed 1.15
0
4.23
cut |
| 12-inch cut | .19 | 5.00 | g0 0.09
.07
completed 1.15
0
4.23
cut |
| 100-leave-tree cut | .20 | .10 | g0 0.09
.07
completed 1.15
0
4.23
cut |
| Check area | 2.53 | 5.77 | g0 0.09
.07
completed 1.15
0
4.23
cut |
5
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Grouped bar chart of mountain-beetle tree mortality in demonstration areas from 1979 to 1981, measured in trees per acre. Patterned bars represent 7-inch, 10-inch, and 12-inch cuts and a 100-leave-tree cut; solid bars represent the check area. A dashed line marks “CUT COMPLETED” after 1980. The check area is highest in every year, rising from about 2.5 in 1979 to 5.8 in 1980 and 4.2 in 1981. The 12-inch cut peaks at about 5.0 in 1980, while the other cut treatments remain below about 0.7 per acre.
Figure 1.-Tree loss due to the mountain beetle within the demonstration areas.
6
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Table 4.-Trees killed per acre by cutting block, year, cause, and diameter
| Treat-
ment | Year
of
kill | Cause
of
death | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Diameter of tree killed (inches) | Total
trees
killed | Trees
སྦྱོརྞྞ༔ killed
per acre |
|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|
| Treat-
ment | Year
of
kill | Cause
of
death | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | >17 | Total
trees
killed | Trees
སྦྱོརྞྞ༔ killed
per acre |
| 7-inch
cut | 1979 | MPB
Pity's² | 2
1 | 3 | 3
1 | 3
1 | 7 | 4 | 1 | 1 | | | | | 24
3 | 0.72
.09 |
| 7-inch
cut | | Total | | 3 | 3 | 4 | 4 | 7 | 4 | 1 | 1 | | | | 27 | .81 |
| 7-inch
cut | 1980 | MPB | | 2 | 3 | 5 | 1 | 2 | 3 | 1 | | | | | 17 | .51 |
| 7-inch
cut | | Pity's | | | 1 | 1 | | | | | | | | | 2 | .06 |
| 7-inch
cut | | Comandra | 1 | | | | | | | | | | | | 1 | .03 |
| 7-inch
cut | | Total | 1 | 2 | 4 | 6 | 1 | 2 | 3 | 1 | | | | | 20 | .60 |
| 7-inch
cut | 1981 | MPB
Total | | | | | | | | 1
1 | | | 1
1 | 1
1 | 3
3 | .09
.09 |
| 7-inch
cut | All years | | 4 | ch 5 | 8 | 10 | 82 | 16 | 4 | 3 | | | 1 | 1 | 50 | 1.51 |
| 10-inch
cut | 1979 | MPB
Ips spp. | 1
1 | 238-563NT | 2231 | 10 | | 2 | | | | | | | 21
6 | སྦྱིནངྐཧ8ཨཽཞཐཅཧྲ་ནིཐཱསྐ ཿརྗཇRཎྜན
.35
.10 |
| 10-inch
cut | | Pity's | 6 | | | 5 | | | | | | | | | 22 | .36 |
| 10-inch
cut | | Comandra
Total | | 1
15 | 9 | | 24 | 2 | | | | | | | 2
51 | .03
.84 |
| 10-inch
cut | 1980 | MPB | 818 | | 12 | 9 | | 3 | 2 | 1 | 1 | | | 1 | 40 | .66 |
| 10-inch
cut | | Pity's
Comandra | 4 | | 24288 | 52111N | | | | | | | | | 12
5 | .20
.08 |
| 10-inch
cut | | Total | 5 | 11 | 18 | | 4 | 3 | 2 | 1 | 1 | | | 1 | 57 | .94 |
| 10-inch
cut | 1981 | MPB | | | 1 | | 1 | | | | | | | | 4 | .07 |
| 10-inch
cut | | Total | | | 1 | | 1 | | | | | | | | 4 | .07 |
| 10-inch
cut | All years | | 13 | 26 26 | | 27 | 7 | 5 | 2 | 1 | 1 | | 1 | 1 | 112 | བིརྟ་ 1.78 |
| 12-inch
cut | 1979 | MPB | | | | | | | | | | | 1 | | 1 | .19 |
| 12-inch
cut | | Comandra | 22 | | 1 | | | | | | | | 1 | | 4 | .77 |
| 12-inch
cut | | Total | | | 1 | | 1151 | | | | | | 1 | | 5 | .96 |
| 12-inch
cut | 1980 | MPB | 1 | 1 | 4 | 5 | | 7 | 3 | | | | | | 26 | 5.00 |
| 12-inch
cut | | Pity's | | | | | | | | | | | | | 1 | .19 |
| 12-inch
cut | | Comandra | | 1 | | | | | | | | | 1 | | 1 | .19 |
| 12-inch
cut | | Total | 1 | 2 | 422 | 5 | 6 | 7 | 3 | | | | | | 28 | ཤཱཎནི་བྷཱགྷརྒྱུུཤྲྰི་ྲ་ྲ8 5.38 |
| 12-inch
cut | 1981 | MPB | | 1 | | | | | | | | | | | 6 | 1.15 |
| 12-inch
cut | | Total | | 1 | | | | 330 | | | | | | | 6 | 1.15 |
| 12-inch
cut | All years | | 3 | 3 | 7 | 5 | 7 | 10 | 3 | | | | 1 | | 39 | 7.50 |
| 100-leave
tree cut | 1979 | MPB | 1 | | 1 | | | | | | | | | | 2 | .20 |
| 100-leave
tree cut | | Ips spp. | 1 | | | 1 | | 1 | | | | | | | 3 | .30 |
| 100-leave
tree cut | | Total | 2 | | 1 | 1 | | 1 | | | | | | | 5 | .50 |
| 100-leave
tree cut | 1980 | MPB | | 1 | | | | | | | | | | | 1 | .10 |
| 100-leave
tree cut | | Ips spp.
Total | 1
1 | 1
2 | | | | | | | | | | | 2
3 | ཞགཽRཨཽཋཱ8 .20
.30 |
| 100-leave
tree cut | 1981 | MPB | 1 | | | | | | | | | | | | 1 | .10 |
| 100-leave
tree cut | | Total | 1 | | | | | | | | | | | | 1 | .10 |
| 100-leave
tree cut | All years | | 4 | | 1 | 1 | | | | | | | | | 9 | .90 |
| Check | 1979 | MPB | | | | 9 | 5 | 9 | 1 | 5 | 1 | 1 | | | 36 | 2.53 |
| area | | Pity's | | 434 | | | | | | | | | | | 3 | ཤྲྰིསཧྰུྃ .21 |
| | | Total | | | 34 | 9 | 54 | 86 | 10 | | 16 | 1 | | | 39 | 2.74 |
| | 1980 | MPB | 1 | 1 | | 11 | 14 | | 10 | 58 | | 1 | 2 | 6 | 82 | ཏཱིཤི 5.77 |
| | | Pity's | | | | 1 | | | | | | | | | 1 | .07 |
| | | Comandra | | | | | | | | | | | | | 1 | ཧི .07 |
| | | Total | 1 | 1 | | 12 | 15002 | 18 | 10 | | | 1 | | | 84 | ཧུ 5.91 |
| | 1981 | MPB | | | 4965 | 2558 | 9 | 11 | 13 | 8998 6 | 6552 | | 2446 | 6119 | 60 | ཤྲཱ 4.23 |
| | | Total | | | | | 9 | 11 | 13 | 6 | | | | | 60 | ཤྲཱ 4.23 |
| | All years | | 1 | 5 | 13 | 26 | 29 | 38 | 24 | 19 | | 2 | | | 183 | བྷཱ |
'MPB Mountain pine beetle.
Pityophthorus, Pityogenes, and Pityokteines.
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Adding the loss due to the mountain pine beetle, secondary insects, and comandra rust to the trees cut per acre gives the gross number of trees removed and thus the residual trees per acre (table 5). All cutting blocks now contain almost the same number of trees per acre, which is about one-half the number per acre now in the check area, although the average stand diameter is different.
Residual basal area followed the level of cut as would be expected (fig. 2). Using the check blocks as a base, then 66 percent of the basal area was removed in the 7-inch (17.78-cm) blocks; 55 percent in the 10-inch (25.40-cm) blocks; 45 percent in the 12-inch (30.48-cm) blocks; and 63 percent in the 100-leave-tree blocks.
There was an apparent and slightly greater radial growth, of those residual trees measured, in the 12-inch (30.48-cm), 100-leave-tree, and check blocks as compared to the 7-inch (17.78-cm) and 10-inch (25.40-cm) blocks (fig. 3). This does not necessarily reflect release by cut- ting, because only 1 to 2 years of growth occurred since cutting was started.
Table 5.-Net effects to the stands from cutting levels and mortality factors
| Treatment | Trees per acre | Trees per acre | Trees per acre | Trees per acre | Trees per acre | Trees per acre | Residual |
|-|-|-|-|-|-|-|-|
| Treatment | Before Number | Before Number | Trees Killed by | Trees Killed by | Trees Killed by | Trees Killed by | Residual |
| Treatment | cut | cut | MPB | Ips spp. | Pity's | Comandra | Residual |
| 7-inch cut | 163.3 | 76.9 | 1.32 | 0 | 0.15 | 0.03 | 84.90 |
| 10-inch cut | 215.7 | 113.2 | 11.08 | 0.10 | .56 | .11 | 90.76 |
| 12-inch cut | 343.0 | 229.0 | 6.34 | 0 | .19 | .96 | 88.66 |
| 100-leave- | | | | | | | |
| tree cut | 214.0 | 114.0 | .30 | .60 | 50 | 0 | 99.70 |
| Check area | 196.0 | 0 | 12.53 | 0 | 28 | .07 | 183.12 |
'MPB Mountain pine beetle.
Pityophthorus, Pityogenes, and Pityokteines.
Bar chart of residual basal area per cutting block after harvest, comparing 7-inch, 10-inch, 12-inch, 100-leave-tree, and check blocks. The check block has the highest residual basal area, while the 7-inch and 100-leave-tree blocks are lowest.
Figure 2.-Residual basal area of cutting
blocks.
Line chart of average annual radial growth (inches) for five cutting-block treatments from 1972 to 1981. The 100-leave-tree and 10-inch series show sharp peaks of about 0.06 in 1977 and 1978, while the 7-inch series remains lowest and ends near 0.028. By 1981, the 100-leave-tree and 10-inch treatments rise to roughly 0.047 and 0.043 inches, above the 12-inch, check-area, and 7-inch treatments.
Figure 3.-Average radial growth of stand per year for last 10 years by cutting block.
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DISCUSSION
Having seen the immediate results of the cutting levels, the question now is of the future of these stands, with respect to the activity of the beetle and stand development. The harvest levels reduced the current level of loss somewhat proportionally, but will the beetle resume killing trees at the same ratio as before treat- ment or has a change been induced in the course of the infestation? To project an answer to this question, these mortality trend data were used in the Rate of Loss Model (Cole and McGregor, in press) to predict the rate of future tree loss and number of years of such an infesta- tion (fig. 4).
Line chart of predicted mountain pine beetle tree mortality after harvest, comparing a check area with 7-, 10-, and 12-inch cutting levels and a 100-leave-tree treatment. The x-axis is year of kill from about 1980 to 2010, and the y-axis is predicted trees per acre killed from 0 to 50. The check area has the largest spike, peaking near 47 trees per acre around 1980; the 12-inch treatment peaks lower, around 22, while the 7-inch, 10-inch, and 100-leave-tree treatments show smaller peaks and decline toward near zero by the late 1980s to early 1990s.
Figure 4.-Predicted trees per acre killed by mountain pine beetle, postharvest by cutting levels.
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This projection showed that the infestation within the check area should peak in 1981, with 46.9 trees killed per acre (19 per ha), and subside to 1.1 trees per acre (0.44 per ha) by 1989, tailing to 0.02 tree per acre (0.008 per ha) by 1993. The diameter-limit cuts reduced the peak loss rather proportionally to the extent of cutting; for exam- ple, peak kill was greater in the 12-inch (30.48-cm) cuts than in the 7-inch (17.78-cm) cuts. The expected length of infestation changed accordingly, with the longest period of outbreak expected for the 7-inch (17.78-cm) cut. The exception was the 100-leave-tree cut. This cut extended the predicted life of the infestation to the year 2012, with peak tree loss of only 1.5 trees per acre (0.61 per ha) in the year 1993 (table 6).
Table 6.-Predicted peak loss, length of infestation, and annual drain from the mountain pine beetle by cutting level (trees per acre)
| Treatment | Peak
loss | Peak
year | Years of
infestation | Total
loss | Annual
drain |
|-|-|-|-|-|-|
| Check area | 46.9 | 1981 | 14 | 180.5 | 12.9 |
| 12-inch cut | 22.1 | 1981 | 18 | 80.1 | 4.4 |
| 10-inch cut | 10.3 | 1982 | 26 | 62.5 | 2.4 |
| 7-inch cut | 12.3 | 1982 | 13 | 32.8 | 2.5 |
| 100-leave-
tree cut | 1.5 | 1993 | 33 | 23.6 | .7 |
The 100-leave-tree cut, according to these predictions, would reduce tree loss from the mountain pine beetle to a low amount. This cut would also be advantageous in reducing or minimizing dwarf mistletoe occurrence (Wicker 1967; Wicker and Shaw 1967). Once the area is reseeded and the regeneration height exceeds snow depth, the leave trees should be removed. The small target area of the regeneration, the washing action of the snow in removing dwarf mistletoe seeds, and the young stand being immune to the mountain pine beetle may well be the keys to producing a healthy new stand of lodgepole pine.
SUMMARY
The demonstration area on which diameter-limit and leave-tree cuts were applied to reduce or minimize lodgepole pine losses to the mountain pine beetle was evaluated the first year after cutting. First-year losses were reduced proportionally to the intensity of cut. Pro- jected losses and continuation of the mountain pine beetle infestation were derived from the predictive Rate of Loss Model. The best deterrent of recurring infesta- tion-amount of losses and length of time-was the 100-leave-tree cut. The 100-leave-tree cut also was the best in encouraging regeneration and reducing dwarf mistletoe infection.
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PUBLICATIONS CITED
Cahill, Donn B. Cutting strategies as control measures of the mountain pine beetle in lodgepole pine in Colo- rado. In: Berryman, Alan A.; Amman, Gene D.; Stark, Ronald W., tech. eds. Theory and practice of mountain pine beetle management in lodgepole pine forests: symposium proceedings; 1978 April 25-27; Pullman, WA. Moscow, ID: University of Idaho, Forest, Wildlife and Range Experiment Station; 1978: 188-191.
Cole, Walter E.; Cahill, Donn B. Cutting strategies can reduce probabilities of mountain pine beetle epidemics in lodgepole pine. J. For. 74: 294-297; 1976.
Cole, Walter E.; McGregor, Mark D. Estimating the rate and amount of tree loss from a mountain pine beetle infestation. In press.
McGregor, Mark D.; Cole, Walter E. Harvesting strat- egies for management of mountain pine beetle infesta- tions in lodgepole pine. In press.
Wicker, Ed F. Seed destiny as a klendusic factor of in- fection and its impact upon propagation of Arceuthobium spp. Phytopathology. 57(11): 1164-1168; 1967.
Wicker, Ed F.; Shaw, C. Gardner. Target area as a klendusic factor in dwarf mistletoe infections. Phytopathology. 57(11): 1161-1163; 1967.
11
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The Intermountain Station, headquartered in Ogden, Utah, is one of eight regional experiment stations charged with providing scien- tific knowledge to help resource managers meet human needs and protect forest and range ecosystems.
The Intermountain Station includes the States of Montana, Idaho, Utah, Nevada, and western Wyoming. About 231 million acres, or 85 percent, of the land area in the Station territory are classified as forest and rangeland. These lands include grass- lands, deserts, shrublands, alpine areas, and well-stocked forests. They supply fiber for forest industries; minerals for energy and in- dustrial development; and water for domestic and industrial con- sumption. They also provide recreation opportunities for millions of visitors each year.
Field programs and research work units of the Station are main- tained in:
Boise, Idaho
Bozeman, Montana (in cooperation with Montana State
University)
Logan, Utah (in cooperation with Utah State University)
Missoula, Montana (in cooperation with the University
of Montana)
Moscow, Idaho (in cooperation with the University of
Idaho)
Provo, Utah (in cooperation with Brigham Young Univer-
sity)
Reno, Nevada (in cooperation with the University of
Nevada)
FOREST SERVICE
UAS
TMENT OF AGRICU
*
U.S. GOVERNMENT PRINTING OFFICE: 1983-676-032/1021 REGION NO.8
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