1. Bailey, J.D. and J.C. Tappeiner.
1998. Effects of thinning on structural development in 40- to 100-year-old
Douglas-fir stands in western Oregon. Forest-Ecology-and-Management 108(1/2): 99-113.
Keywords: thinning
commercial thinning
regeneration
tree morphology
Abstract: The
composition and structure of the understorey was
studied in thinned and unthinned Douglas fir/western
hemlock (Pseudotsuga menziesii/Tsuga
heterophylla) stands on 32 sites in western Oregon. These stands had regenerated naturally after timber was
harvested between 1880 and 1940; they were thinned between 1969 and 1984.
Commercially thinned stands had 8-60% of their volume removed 10-24 yr before
the study (in 1993-95). Undisturbed old-growth Douglas fir stands were present
for comparison on 20 of these paired sites. Conifer regeneration density and
frequency were consistently greater in thinned than unthinned
stands. For example, average seedling density in thinned stands (1433/ha) was
significantly greater than in unthinned stands
(233/ha), but very similar to that in old-growth stands (1010/ha). Seedling
density and frequency were strongly related to the volume removed and to stand
density index (and other measures of overstorey
density) just after thinning. In thinned stands, the density of small trees
(intermediate crown class overstorey trees and
advanced regeneration) was 159/ha, significantly greater than in unthinned stands (90/ha), but not significantly different
from that of old-growth (204/ha). The live crown ratio of these trees in
thinned stands (66%) was greater than in unthinned
(44%) and old-growth (48%) stands. Cover and stem density of shrubs was
variable in all 3 stand types. There was significantly less tall shrub cover in
unthinned stands than in either thinned or old-growth
stands, which did not differ. Thinned stands had the most low shrub cover. Salal (Gaultheria shallon) and
bracken fern (Pteridium aquilinum)
cover was greater in thinned stands than in the other stand types, but there
was no difference in sword fern (Polystichum munitum) and Oregongrape [Berberis nervosa] cover. Leaf area index in thinned stands
(6.6) was not significantly different from that in unthinned
(6.8) and old-growth stands (7.1); however, there was more leaf area in shrubs
in the thinned stands. Thinning young Douglas-fir stands will hasten the
development of multistorey stands by recruitment of
conifer regeneration in the understorey as well as by
enabling the survival of small overstorey trees and
growth of advanced understorey regeneration. Thinning
will also help develop the shrub layer by increasing tall shrub stem density
and cover of some low shrubs.
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2. Barbour, R.J. and D.L. Parry.
2001. Log and lumber grades as indicators of wood quality in 20- to
100-year-old Douglas-fir trees from thinned and unthinned
stands. Pacific-Northwest-Research-Station,-USDA-Forest-Service General-Technical-Report
PNW-GTR-510. 22 p.
Keywords: thinning
commercial thinning
wood quality
Abstract: This
report examines the differences in wood characteristics found in coastal Pacific Northwest Douglas-fir (Pseudotsuga mensziesii) trees harvested at the age of 70 to 100 years
old or at the age of 40 to 60 years from a trial involving multiple thinnings in Seattle, Washington, USA. Comparisons of differences in domestic log grades suggest
that the proportion of log volume in the higher grades (Special Mill and No. 2
Sawmill) increased with both stand age and tree size. Simulation of lumber
grade yields based on log characteristics suggests that yields of higher grades
of lumber increased until about age 60 to 70, and then levelled
off over the rest of the age range examined in this analysis. We included
structural lumber products in the analysis but not higher value appearance
grade products, and some evidence suggests that yields of these products might
have begun to increase in the oldest trees. The analysis also showed that the
younger trees had larger branches and more juvenile wood, possibly because they
had been grown in stands that received a higher level of early stand management
than the older trees. If these young trees were grown to the ages of 70 to 100,
they likely would not produce the same log and lumber grade yields found in the
older trees we examined.
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3. Bettinger, P., K.A. Bettinger and K.
Boston. 1998. Correlation among spatial and non-spatial variables describing a
cut-to-length thinning site in the Pacific Northwest, USA. Forest-Ecology-and-Management 104(1/3): 139-149.
Keywords: thinning
commercial thinning
tree/stand health
Abstract: Variables
describing the pre- and post-logging conditions of a thinning site in 47-yr-old
naturally regenerated stand of second-growth Douglas fir (Pseudotsuga
menziesii) and western hemlock (Tsuga
heterophylla) in western Oregon, were examined for
correlation, and subsequently used to develop models to estimate residual stand
damage levels. A cut-to-length harvesting system was utilized to perform the
thinning operation, which used a single-grip harvester and a forwarder, and
marked logging trails. Several of the variables were measured in an intensive
field survey; other variables were developed using geographic information system (GIS) processes. An analysis of
correlations among the site variables showed several obvious, and a few
interesting, results that describe the operation. Most of the variables
provided negative, or inconclusive, assistance in describing the variation in
stand damage levels. Only one variable, the number of original trees/hectare,
was significantly correlated with residual stand damage levels, and was
represented in the models that were developed to estimate residual stand damage
levels. The resulting models are of limited practical value, however, since
they explain little of the variability in damage levels. Most of the variation
in residual stand damage levels may well be explained by random chance,
operator error, other unmeasured operational variables
associated with this harvesting system, or interactions among variables. The
main conclusion from the study is that although both spatial and non-spatial
data were utilized in describing the logging operation and in developing models
to estimate stand damage levels, the importance of using spatial data was
inconclusive.
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4. Bettinger,
P. and L.D. Kellogg. 1993. Residual stand damage from cut-to-length thinning of
second-growth timber in the Cascade Range of western Oregon. Forest-Products-Journal 43(11/12): 59-64.
Keywords: thinning
commercial thinning
tree/stand health
Abstract: Residual
stand damage was measured on 25% of an area that had been thinned with a
cut-to-length logging system. Total damage (scar area) per acre was less than
in any similar study in the Pacific Northwest, although 39.8% of the residual trees sustained some
damage. Only 0.8% of the trees, however, sustained significant damage. Western
hemlock (Tsuga heterophylla)
was more susceptible to damage than Douglas fir (Pseudotsuga
menziesii). Most of the damage occurred within 15
feet of a trail centreline and originated within 3
feet of the groundline. Early summer logging may have
resulted in more damaged trees than might occur during other seasons. Future
volume loss due to decay is likely to be minimal because a low percentage of
scars were considered vulnerable to wood-decaying fungi.
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5. Brandeis, T.J., M. Newton and E.C.
Cole. 2001. Underplanted conifer seedling survival
and growth in thinned Douglas-fir stands. Canadian-Journal-of-Forest-Research
31(2): 302-312.
Keywords: planting operations
thinning
commercial thinning
site preparation
chemical preparation
release treatments
chemical release
growth
tree/stand health
regeneration
Abstract: In a
multilevel study conducted at the Oregon State University's McDonald-Dunn
Research Forest, Oregon, USA, to determine limits to underplanted
conifer seedling growth, Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis), western redcedar (Thuja plicata) and western
hemlock (Tsuga heterophylla)
seedlings were planted in January 1993 beneath second-growth Douglas-fir stands
that had been thinned in 1992 to basal areas ranging from 16 to 31 m2/ha. Understorey vegetation was treated with a broadcast
herbicide (glyphosate + imazapyr)
application prior to thinning, a directed release herbicide (glyphosate, plus triclopyr for
tolerant woody stems) application 2 years later, or no treatment beyond harvest
disturbance. Residual overstorey density was
negatively correlated with percent survival for all four species. Broadcast
herbicide application improved survival of grand fir and western hemlock.
Western redcedar, grand fir and western hemlock stem
volumes were inversely related to overstorey tree
density and this effect increased over time. There was a strong indication that
this was also the case for Douglas-fir. Reduction of competing understorey vegetation resulted in larger fourth-year stem
volumes in grand fir and western hemlock.
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6. Curtis, R.O. 1987.
Levels-of-growing-stock cooperative study in Douglas-fir: Report No. 9 - some
comparisons of DFSIM estimates with growth in the levels-of-growing stock
study. Pacific-Northwest-Research-Station,-USDA-Forest-Service Research-Paper PNW-RP-376. 34 p.
Keywords: thinning
commercial thinning
growth
tree/stand
health
computer modeling
Abstract: Initial
stand statistics for the 9 levels-of-growing-stock (LOGS) study installations
in Oregon and Washington, USA, and Vancouver Island, British Columbia, Canada, were projected by the Douglas fir (Pseudotsuga
menziesii) stand simulation program (DFSIM) over the
available periods of observation. Thinnings were simulated
by use of observed top height trends, actual residual basal areas, and actual
ratios of cut tree diameters to stand diameter before cutting (d/D). Estimates
were compared with observed gross and net volumes and basal area growth, net
change in quadratic mean diameter, and change in number of trees. Although the
LOGS installations included regimes quite different from those in most of the
data used to construct DFSIM, overall agreement was reasonably good. Results
indicated some density-related bias in the thinned stands and a need for
revision in the method used to control the maximum density in the DFSIM program
and in the associated mortality estimates.
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7. Curtis, R.O., G.W. Clendenen and D.J. DeMars. 1981.
A new stand simulator for coast Douglas-fir: DFSIM user's guide. Pacific-Northwest-Forest-and-Range-Experiment-Station,-USDA-Forest-Service General-Technical-Report
PNW-GTR-128. ii
+ 79 p.
Keywords: planting operations
thinning
precommercial thinning
commercial thinning
fertilization
yield
computer modeling
Abstract: A description
of a computer program, written in FORTRAN IV, for simulating managed stands.
The program has been developed from remeasured plot
data contributed by many organizations in the Pacific Northwest USA. It can
produce yield tables which include estimates of effects of initial spacing, precommercial and commercial thinning and addition of N
fertilizer. Topics discussed include program limitation and potential for
further development. Appendices include operating instructions and notes on
testing. The program is available from the authors on request.
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8. Curtis, R.O. and D.D. Marshall.
1986. Levels-of-growing-stock cooperative study in Douglas-fir. Report no. 8 -
The LOGS study: twenty-year results. Pacific Northwest Research Station, USDA Forest Service Research-Paper PNW-RP-356. v + 113 p.
Keywords: thinning
commercial thinning
growth
Abstract: A
further report in a series on 9 study areas in Oregon, Washington and British Columbia. The programme aimed to
determine relations between growing stock and vol., b.a. and diam. growth for 8
thinning regimes. Results presented are mainly from 5 site class II
installations. Growth was strongly related to growing stock. Thinning
treatments produced marked differences in volume distribution by tree sizes.
There were considerable unexplained differences in productivity between
installations, beyond those attributable to site quality. During the 4th
treatment period (32-42 yr old in site class II sites) c.a.i.
was approx. twice m.a.i. An evaluation is given of
the LOGS study design.
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9. Curtis, R.O. and D.D. Marshall.
2002. Levels-of-growing-stock cooperative study in Douglas-fir: report no. 14 -
Stampede Creek: 30-year results. Pacific-Northwest-Research-Station,-USDA-Forest-Service Research-Paper PNW-RP-543. xi + 77 p.
Keywords: thinning
commercial thinning
growth
yield
tree morphology
tree/stand health
Abstract: Results
of the Stampede Creek installation of the levels-of-growing-stock (LOGS) study
in Douglas-fir (Pseudotsuga menziesii)
are summarized. To age 63 (planned completion of 60 feet of height growth), volume growth on the site III natural stand has been
strongly related to level of growing stock, but basal area growth-growing stock
relations were considerably weaker. Marked differences in tree size
distributions have resulted from thinning. Periodic annual volume increments at
age 63 are two to three times greater than mean annual increment; this stand is
still far from culmination. Results for this southwest Oregon installation are generally similar to those reported from
other LOGS installations, although development has been slower than on the site
II installations that make up the majority of the series.
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10. Curtis, R.O., D.D. Marshall and
J.F. Bell. 1997. LOGS: a pioneering example of silvicultural
research in coast Douglas-fir. Journal-of-Forestry 95(7): 19-25.
Keywords: thinning
commercial thinning
growth
yield
Abstract: A
regional levels-of-growing-stock (LOGS) study of young Douglas fir (Pseudotsuga menziesii) stands in
western Oregon and western Washington, USA and Vancouver Island, British Columbia, Canada, was conducted between 1961 and 1970. The objective was to
determine how the amount of growing stock retained in repeatedly thinned stands
of P. menziesii affects cumulative wood production,
tree size and growth:growing
stock ratios. Nine LOGS installations were established during the study period,
each consisting of 27 one-fifth acre plots, with 8 thinning treatments (and
controls). All plots received initial calibration thinning. After the first 10
feet of height growth and at intervals of 10 feet thereafter, 5 subsequent
thinning treatments were made. As of 1994, all installations on site class II,
and most installations on site classes III and IV had completed the planned
thinning sequence over 60 ft of height growth. Periodic annual increment of
both basal area and volume was clearly related to basal area of growing stock
and several measures of density. Thinning accelerated diameter growth, and
diameter and volume distributions differed greatly among treatments. Mean
annual increment and periodic annual increment showed no sign of approach to
culmination in either total or merchantable cubic volume. Cumulative volume
production (live stand plus thinning) of the controls exceeded all thinning
treatments to date when measured in total cubic volume of all trees, although
when volume was measured in merchantable cubic feet several thinning treatments
exceeded net volume production of the controls. A discussion of the results
includes: a comparison with other thinning studies; an analysis of application
of the Langsaeter hypothesis (that the same cubic
volume production could be obtained over a wide range of stand densities);
growth trends and rotations; thinning gains; non-timber values; and critical
analysis of the study design. The continuing value of the demonstration stands
is discussed.
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11. Curtis, R.O., D.D. Marshall and
D.S. DeBell. 2004. Silvicultural
options for young-growth Douglas-fir forests: the Capitol Forest study - establishment and first results. Pacific Northwest-Research-Station,-USDA-Forest-Service General-Technical-Report
PNW-GTR-598. xi
+ 110 p.
Keywords: thinning
commercial thinning
economics
soil properties
Abstract: This
report describes the origin, design, establishment and measurement procedures
and first results of a large long term cooperative study comparing a number of
widely different silvicultural regimes applied to
young-growth Douglas-fir (Pseudotsuga menziesii) stands managed for multiple objectives. Regimes
consist of (1) conventional clear felling followed by intermediate thinning;
(2) retention of reserve trees to create a two-aged stand; (3) small patch cuts
dispersed within a thinned matrix, repeated at approximately 15-year intervals
to create a mosaic of age classes; (4) group selection within a thinned matrix
on an approximate 15-year cycle; (5) continued thinning on an extended
rotation; and (6) an untreated control. Each of these regimes is on
operation-size units (approximately 30 to 70 acres each). A LIDAR system was
used to scan the surface of the 2 miles2 that encompass the Blue Ridge study site on the Capitol State Forest, near Olympia, Washington, USA. This measurement technology emits laser pulses that are
reflected by vegetation, buildings, or the ground surface. Output variables
from the study to be evaluated include conventional timber growth and yield
statistics, harvest costs, sale layout and administration costs, aesthetic
effects and public acceptance, soil disturbance, bird populations, and economic
aspects. Descriptive statistics and some initial results are presented for the
first replicate, established in 1997-98.
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12. El Kassaby,
Y.A. and A. Benowicz. 2000. Effects of
commercial thinning on genetic, plant species and structural diversity in
second growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands.
Forest-Genetics 7(3): 193-203.
Keywords: thinning
commercial thinning
genetic relationships
Abstract: The
impact of commercial thinning on biodiversity was studied in two Douglas-fir (Pseudotsuga menziesii)
plantations, Weeks Lake (WL) and Fairservice Creek
(FC) located on southern Vancouver Island, British Columbia, Canada. The age of the stands at thinning was 53 and 70 years for
FC and WL, respectively. Other tree species were also present in both sites due
to natural regeneration. Biodiversity was evaluated before and after commercial
thinning with respect to tree species composition/abundance, tree species
genetic diversity assessed by allozyme analysis and
stand structural diversity represented by the diameter class (5-cm)
distribution. In addition, understorey plant species
diversity was monitored in WL and FC for 4 and 5 years following thinning,
respectively. Tree species composition changed in both plantations in a similar
fashion as the proportion of Douglas-fir increased at the expense of all other
tree species. Stand structural diversity was simplified due to the decreased
number of trees in small diameter classes. These results were expected since
the commercial thinning was conducted to promote the growth of Douglas-fir.
Genetic diversity parameters (average number of alleles per locus, percent
polymorphic loci and expected heterozygosities) did
not differ significantly before and after thinning; however, thinning resulted
in a loss of 8 and 7 alleles across species for FC and WL, respectively. Most
of the allelic loss occurred in the naturally regenerated species (93%). This
allelic loss represents 7 and 6% of the total alleles present in FC and WL,
respectively. Thus, only one allele was lost from the crop tree in the FC
plantation. Understorey vegetation species richness
decreased the year following commercial thinning and then consistently
increased over time in both plantations. A total of 17 and 9 new species
colonized FC and WL, respectively. One species was replaced in each plantation.
In FC, diversity of the understorey plant community
based on the Shannon diversity index (H) changed in an increasing linear trend
that corresponded to the increase in species richness. On the other hand, H in
WL remained stable. Species evenness (H/Hmax) did not
change in WL and FC over the course of study except for seasonal fluctuations.
Rare species diversity increased over time in both plantations.
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13. Emmingham,
W.L., P. Oester, M. Bennett, F. Kukulka,
K. Conrad and A. Michel. 2002. Comparing short-term financial aspects of four
management options in Oregon: implications for uneven-aged management. Forestry-Oxford
75(4): 489-494.
Keywords: thinning
commercial thinning
economics
yield
Abstract: Private
family forest owners are often more interested in comparing short-term
financial outcomes of management options, as opposed to longer time horizons
and classical economic analyses including net present value. Therefore, we
compared projected 10-year value of timber and land for four theoretical
management scenarios starting with stands ripe for thinning. The options were
(1) hold for 10 years (i.e. no thinning), (2) thin for even-age, or (3) partial
cut for uneven-age and (4) clearcut now. To simulate
the outcomes of these scenarios, we marked and measured 2-ha plots
in 10 stands typical of private forest ownerships across Oregon and projected timber yields and revenues. The financial
analysis included current market values for logs, payment of taxes and typical
reforestation costs and computation of net asset values (NAV) at a 7 per cent
interest rate. The hold option consistently gave the highest NAV for timber and
land after 10 years, and the thin option was within 2 per cent. For the eight
western Oregon stands, the partial-cut option averaged about 3 per cent
less, and the clearcut option ranged from 8 to 17 per
cent less than holding. Pine stands of eastern Oregon showed similar trends; however, all options were within
about 6 per cent of the hold option. Thus, using financial criteria typical of
those used by private forest owners, we found that
there was little short-term financial loss in choosing to thin toward even-age,
partial cut toward uneven-age, or the hold approach in well-stocked stands.
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14. Garman, S.L., J.H. Cissel and J.H. Mayo. 2003. Accelerating development of
late-successional conditions in young managed
Douglas-fir stands: a simulation study. Pacific-Northwest-Research-Station,-USDA-Forest-Service
General-Technical-Report PNW-GTR-557. ii + 57
p.
Keywords: thinning
commercial thinning
yield
Abstract: The
goal of this simulation study was to provide information for defining thinning
regimes for young Douglas-fir (Pseudotsuga menziesii) stands in the Central Cascades Adaptive
Management Area, located in west-central Oregon, USA. Specifically, this study used the ZELIG.PNW (3.0) gap
model to evaluate effects of experimental thinning treatments on the
development of late-successional attributes and on
extracted merchantable volume. Sixty-four thinning treatments were simulated
for four rotation intervals (260, 180, 100, and 80 years) starting with a
40-year-old managed Douglas-fir stand. The amount of time for five late successional attributes to reach defined threshold levels,
long-term developmental trends of these attributes, and amount of extracted
merchantable volume were recorded for each treatment. Stand conditions of
selected treatments were used in a subsequent harvest rotation in which 64
additional experimental thinning treatments were applied and evaluated. A total
of 1744 thinning treatments was evaluated in this
study. Results of this study confirm previous recommendations for accelerating
development of late-successional attributes in young
managed stands. Additionally, results show the potential for a range of
thinning treatments to attain late-successional
conditions in about the same amount of time, but with different trade-offs in
terms of merchantable volume and long-term stand conditions. In general, heavy
thinning of existing stands at ages 40 and 60 years promoted rapid development
of large boles, vertical diversity, and tree-species diversity, but provided
the least amount of extracted volume and required artificial creation of dead
wood. Treatments that retained more than 40% of the original overstorey and thinned to 99 trees per hectare at age 60
delayed attainment of late-successional conditions by
10 to 30 years but provided 12 to 20% more extracted volume, resulted in higher
levels of most late-successional attributes at the
end of a rotation, and required less artificial creation of dead wood.
Treatments providing the fastest development of late-successional
conditions in subsequent rotations varied with the amount of canopy cover
retained at the end of the first rotation. For stands starting with <more or
=>30% canopy cover, delaying the first commercial thin for 40 years promoted
the most rapid development of vertical structure and shade-tolerant stems.
Lower canopy-retention levels required heavy or light thins in subsequent
entries, depending on the rotation interval, for rapid development of late-successional attributes.
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15. Greene, S.E. and W.H. Emmingham. 1986. Early lessons from commercial thinning in
a 30-year-old Sitka spruce-western hemlock forest. Pacific-Northwest-Research-Station,-USDA-Forest-Service Research-Note PNW-RN-448. 14 p.
Keywords: thinning
commercial thinning
growth
tree/stand health
tree morphology
Abstract: Three
commercial thinning treatments were applied to a 30-yr-old stand of Picea sitchensis and Tsuga heterophylla with Pseudotsuga menziesii that had
been precommercially thinned at 15 yr old on the Oregon coast. Data were collected to determine the effects of
thinning on diam. and ht. growth, the amount of
damage and subsequent decay in remaining trees and relations between leaf area
and volume production.
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16. Haight,
R.G. 1993a. The economics of Douglas-fir and red alder
management with stochastic price trends.
Canadian-Journal-of-Forest-Research 23(8): 1695-1703.
Keywords: planting operations
site preparation
prescribed fire
release treatments
chemical release
thinning
precommercial thinning
commercial thinning
tree/stand protection
economics
Abstract: A
financial analysis of Douglas fir (Pseudotsuga menziesii) and red alder (Alnus rubra) management was conducted using yield projections
from the Stand Projection Simulator for the Pacific Northwest region of the United Sates. The analysis included
uncertainty in the price trends and stocking levels of both species following
reforestation. Results from a case study in which Douglas fir price is likely
to increase faster than red alder price show that (i)
on more productive sites, greater regeneration investment is justified to
increase the likelihood of Douglas fir establishment, (ii) on less productive
sites, low-cost regeneration options that produce mixed-species stands have
expected present values close to or greater than a high-cost Douglas fir
regeneration effort, (iii) optimal precommercial
removal of red alder depends on mid-rotation prices and regeneration success,
and in many cases growing a mixed-species stand to maturity produces the
highest economic return, and (iv) commercial thinning of Douglas fir increases
the expected present value of the most intensive regeneration option by up to
10%. The low-cost regeneration options have relatively high expected returns
because of low initial investments and the presence of two species that may
have high values in the future. The sensitivity of these results to changes in
the probability distributions of regeneration success and price trends is
discussed.
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17. Haight,
R.G. 1993b. Technology change and the economics of silvicultural investment.
Rocky-Mountain-Forest-and-Range-Experiment-Station,-USDA-Forest-Service General-Technical-Report RM-GTR-232. ii + 18 p.
Keywords: planting operations
site preparation
prescribed fire
release treatments
chemical release
tree/stand protection
thinning
commercial thinning
precommercial thinning
yield
economics
Abstract: Financial
analyses of intensive and low-cost reforestation options are conducted for
loblolly pine (Pinus contorta)
stands with broadleaved competition in the Southern USA, and Douglas fir with
red alder (Pseudotsuga menziesii
with Alnus rubra) in the
Pacific Northwest. Results show that the expected present values (EPVs) of low-cost options that result in mixtures of
conifers and broadleaves are superior in some situations to the EPVs of the intensive options.
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18. Hunt, J.A. 1995. Commercial thinning a coastal second-growth forest with a Timberjack cut-to-length system. Forest-Engineering-Research-Institute-of-Canada
FERIC TN-235. 14.
Keywords: thinning
commercial
thinning
economics
tree/stand
health
Abstract: In the summer of 1994, after 2 years operation, FERIC
monitored a thinning operation of second-growth forest dominated by Douglas fir
[Pseudotsuga menziesii]
near Cowichan Lake, Vancouver Island, to determine productivities, costs and impacts to sites
and residual stands. The thinning treatment was carried out with a Timberjack 1270 harvester and a Timberjack
910 forwarder.
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19. Kellogg, L.D., G.V. Milota and M. Miller, Jr. 1996. A
comparison of skyline harvesting costs for alternative commercial thinning
prescriptions. Journal-of-Forest-Engineering 7(3): 7-23.
Keywords: thinning
commercial thinning
economics
Abstract: Harvesting
production and costs were examined for three alternative silvicultural
prescriptions at two sites in the Coast Range of Oregon, USA.
Thirty-three-year-old Douglas fir (Pseudotsuga menziesii) stands were commercially thinned to residual
densities of 247, 148, and 74 trees per hectare (tph).
Detailed time studies were conducted on manual felling and uphill skyline yarding with small yarders.
Separate regression equations were developed to predict delay-free felling
cycle time and delay-free yarding cycle time. The 74 tph treatment had the highest production rate and was the
least costly to harvest. Total harvesting costs of the other two treatments
averaged from 6.0% (148 tph) to 12.3% (247 tph) more than the 74 tph
treatment.
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20. Kellogg, L.D., G.V. Milota and B. Stringham. 1998.
Logging planning and layout costs for thinning: experience from the Willamette young stand project. Forest-Research-Laboratory
Research Contribution 20, Oregon-State-University, Corvaliis, OR.
Keywords: thinning
commercial thinning
economics
Abstract: Logging
planning and layout costs were examined for commercial thinning of 40- to
50-yr-old stands of Douglas-fir (Pseudotsuga menziesii) on the Willamette National Forest in the Cascade Mountains of Oregon. The study consisted of
four replications of three silvicultural treatments.
Thinning involved three types of logging systems: mechanized cut-to-length (a
combination of single-grip harvester and forwarder), tractor, and skyline. Data
for the study came from two sources: activities completed by the Forest Service
in preparing sales for bid, and the layout completed by the logging contractor
after a contract was awarded. Planning and layout costs showed no consistent
relationship to type of silvicultural treatment.
Logging contractor layout costs showed a relationship to type of logging
system: the mechanized system had the lowest layout cost, followed by the
tractor systems, with the skyline systems having the highest costs.
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21. King, J.E., D.D. Marshall and
J.F. Bell. 2002. Levels-of-growing-stock cooperative study in Douglas-fir:
report no. 17 - the Skykomish study, 1961-93; the
Clemons study, 1963-94. Pacific-Northwest-Research-Station,
USDA-Forest-Service Research-Paper PNW-RP-548. vii
+ 120 p.
Keywords: thinning
commercial thinning
growth
yield
tree/stand health
Abstract: A study
was conducted at the Skykomish Tree Farm, and at the
Clemons Tree Farm, Washington, USA, to determine how the amount of growing stock in
repeatedly thinned stands of Douglas Fir (Pseudotsuga menziesii) affects
cumulative wood production, tree size and growth-growing stock ratios. Initial
stands were thinned to the same level of growing stock so that all plots would
have virtually the same growth potential except the unthinned
controls. The Skykomish and Clemons stands were 24
and 19 years old, respectively, when the studies were started. Stand treatments
were completed at ages 42 and 36, and measurements were continued to ages 56
and 50. After 32 years at Skykomish and 31 years at
Clemons, the basal area per acre in the eight regimes ranged from 119-244 ft2
at Skykomish and 101-195 at Clemons. The
corresponding gross yields in cubic feet per acre were 8709-13 579 at Skykomish and 6329-9072 at Clemons. Volume
in thinnings were 18-53% of the gross yield.
Stand treatments included four regimes with different combinations of heavy and
light thinning and four regimes with constant intensities of thinning. Variable
regimes were found to have consistent advantage over constant regimes. Within a
given level of growing stock, the constant regimes are recommended for
applications where wood production is the primary objective. A substantial
increase in the yield was produced in all regimes during the post thinning
holding period. Based on standing volume after the last thinning, the holding
period of 4 years produced approximately 30% more volume in all regimes.
Extending the period to 9 years produced approximately 70% more volume, and at
14 years, the standing volume was more than double the volume remaining after
the last thinning. This extra yield enhanced by the high quality of the stands
makes the length of the holding period an important factor in the scheduling of
final harvest.
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22. Latham, P. and J. Tappeiner. 2002. Response of old-growth conifers to
reduction in stand density in western Oregon forests. Tree-Physiology 22(2/3): 137-146.
Keywords: thinning
commercial thinning
growth
Abstract: The
positive growth response of healthy young trees to density reduction is well
known. In contrast, large old trees are usually thought to be intrinsically
limited in their ability to respond to increased growing space; therefore,
density reduction is seldom used in stands of old-growth trees. We tested the
null hypothesis that old-growth trees are incapable of responding with
increased growth following density reduction. The diameter growth response of
271 Douglas-fir (Pseudotsuga menziesii),
ponderosa pine (Pinus ponderosa) and sugar pine (Pinus lambertiana) trees in Oregon, USA, ranging in age from 158 to 650 years was examined 20 to
50 years after density reduction. Density reduction involved either light
thinning with removal of less vigorous trees, or shelterwood
treatments in which overstorey trees were not
removed. Ratios of basal area growth after treatment to basal area growth
before treatment, and several other measures of growth, all indicated that the
old trees sometimes benefited and were not harmed by density reduction. Growth
increased by 10% or more for 68% of the trees in treated stands, and nearly 30%
of trees increased growth by over 50%. This growth response persisted for at
least 20 years. During this 20-year period, only three trees in treated stands
(1.5%) exhibited a rapid decrease in growth, whereas growth decreased in 64% of
trees in untreated stands. The length of time before a growth response to
density reduction occurred varied from 5 to 25 years, with the greatest growth response often
occurring 20 to 25 years after treatment. These results have important
implications both for the basic biology of aging in woody plants as well as for
silvicultural practices in forests with old-growth
trees.
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23. LeDoux,
C.B., R.D. Fight and T.L. Ortman. 1986.
Stump-to-truck cable logging cost equations for young-growth Douglas-fir.
Western-Journal-of-Applied-Forestry 1(1): 19-22.
Keywords: thinning
commercial thinning
economics
Abstract: Data on
log sizes were generated to simulate young (age 40-120 yr) Douglas fir site III
and IV in the Pacific
Northwest. The data
were used to develop equations for estimating the delay-free costs of: (1)
felling, limbing and cross-cutting; (2) yarding; (3) loading; (4) road changing; and (5) moving in
and out and initial rigging up and down. An additional equation estimates the
number of logs per 1000 ftsuperscript 3 for logs of d.b.h. 6-24 inch. The equations were developed for 2 small
and 1 medium sized yarders and are applicable on
slopes of 10-50%. The equations can be used to provide detailed estimates for
thinning, partial or shelterwood felling and clearfelling. A BASIC computer program is available from
the authors.
OSU
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24. Maguire, D.A., J.A. Kershaw, Jr.
and D.W. Hann. 1991. Predicting the effects of silvicultural regime on branch size and crown wood core in
Douglas-fir. Forest-Science 37(5): 1409-1428.
Keywords: thinning
precommercial thinning
commercial thinning
wood quality
Abstract: Three
major determinants of wood quality (whorl frequency, branch size and crown wood
core) in Douglas fir (Pseudotsuga menziesii)
were estimated from the dynamics of crown structure in ORGANON, an
individual-tree, distance-independent growth model. Data for the model were
collected from Douglas fir plots in SW Oregon. Branch whorl locations were estimated directly from the
height growth predictions assuming formation of one whorl per year. Mean
maximum branch diameter was predicted as crown base receded past each whorl;
branch diameter estimates were based on current depth of the whorl into crown,
tree diameter, stand relative density, and site index. Diameter of crown wood
core was established as diameter inside bark, also as crown base receded past
each branch whorl. This approach facilitated description of harvested log
distribution (40-ft butt logs) by various branch size, whorl frequency and
crown wood core indices. Based on projections of a 9-yr-old Douglas fir stand
to final harvest at 65 years, thinning precommercially
to 121 trees/acre at 9 yr old resulted in a BD4 (mean of four largest branch
diameters per log) of 2.5 inches, vs. 1.5 inches for the unthinned
stand (484 trees/acre). When thinned to 121 trees/acre,
approximately 55% of the volume/acre in 40-ft butt logs consisted of crown
wood, as opposed to 30% at 484 trees/acre. Responses to subsequent thinnings were less pronounced, but included larger
branches in the largest 80 trees/acre, and larger total crown wood percentages
for a given initial stand density. Thinning from below resulted in larger
average BD4 values and slightly greater crown wood percentages than
proportional thinning. Individual-tree growth models that contain a crown
recession component can easily be modified to predict crown wood core and
indices of branch size.
OSU
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25. Marshall, D.D. and R.O. Curtis.
2002. Levels-of-growing-stock cooperative study in Douglas-fir: report no. 15 -
Hoskins: 1963-1998. Pacific-Northwest-Research-Station,-USDA-Forest-Service Research-Paper PNW-RP-537. 80 p.
Keywords: thinning
commercial thinning
growth
yield
tree/stand health
tree morphology
Abstract: The
cooperative levels-of-growing-stock (LOGS) study in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was begun to study the relations between
growing stock, growth, cumulative wood production, and tree size in repeatedly
thinned stands. This report summarizes results from the Hoskins installation
through age 55. Growing stock has been allowed to accumulate for 19 years since
the last treatment thinning was applied in this high site class II natural
stand. Volume and diameter growth were strongly related to growing stock. Basal
area growth-growing stock relations were considerably weaker. Differences in
tree size and volume distribution were considerable. Culmination of mean annual
increment has not occurred for any of the treatments, although the control has
culminated for total stem cubic volume and is near culmination for merchantable
cubic volume. Only small differences are seen in growth percentages between
thinning treatments. Results demonstrate potential flexibility in managing
Douglas-fir to reach a range of objectives.
OSU
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26. Miller, M. and B. Emmingham. 2001. Can selection thinning convert even-age
Douglas-fir stands to uneven-age structures?
Western-Journal-of-Applied-Forestry 16(1): 35-43.
Keywords: thinning
commercial thinning
growth
yield
tree/stand health
regeneration
Abstract:
Uneven-age management of Douglas-fir (Pseudotsuga menziesii) stands can be used to address aesthetic,
wildlife habitat, biodiversity and sustainability concerns, but there has been
little long-term experience with this type of management. To develop timely
information on converting even-age stands to uneven-age forests, we used
retrospective stand reconstruction methods to document harvest frequency, intensity
and stand structural development at four sites in western Oregon,
USA.
We studied stands managed by selection thinning and identified strategies for
creating and managing uneven-age forests. Selection thinning
benefited mid- and understorey trees and stimulated
natural regeneration. Although stand growth was less than expected from
low thinning, growth per unit of growing stock was similar to that in unmanaged
stands. Douglas-fir often dominated natural regeneration and had satisfactory vigour at stocking levels about half that considered full
stocking for even-age management, but good growth of regeneration may require
even lower overstorey stocking. Shade-tolerant grand
fir (Abies grandis) and
western hemlock (Tsuga heterophylla),
however, were more abundant at higher stocking levels. Selection thinning of
young Douglas-fir (Pseudotsuga menziesii)
stands can sometimes be effective in promoting viable regeneration while
providing regular income and biodiversity. Because this was a retrospective
study only, further, long-term testing is necessary.
OSU
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27. O'-Hara, K.L. 1988. Stand
structure and growing space efficiency following thinning in an even-aged
Douglas-fir stand. Canadian-Journal-of-Forest-Research 18(7): 859-866.
Keywords: thinning
commercial thinning
growth
tree morphology
carbon allocation
Abstract: The
growth of individual trees from four thinning treatments in a 64-yr-old Pseudotsuga menziesii stand in
western Washington was analysed to determine
desirable residual stand structures after thinning. Dominant and codominant trees had the highest individual tree stem vol.
growth rates over the previous 5 yr and accounted for most stand vol. growth in
thinned and unthinned stands. Two measures of growing
space, crown projection area and sapwood b.a. (a surrogate for leaf area), were used to
measure how efficiently individual trees used their growing space. Crown
classes were useful in characterizing growing space efficiency (vol. growth per
unit of growing space) only in the unthinned
treatment. In thinned treatments, tall trees with medium-sized crowns were most
efficient, while in the unthinned treatment tall
trees with relatively large crowns were most efficient. A large crown in an unthinned stand was comparable in size to a medium-sized
crown in a thinned stand. Results suggest growing space is not limiting
individual tree growth in thinned stands and that thinning to a particular
stand structure is more appropriate than thinning to a particular stand
density.
OSU
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28. O'-Hara, K.L. 1989. Stand growth
efficiency in a Douglas fir thinning trial. Forestry-Oxford 62(4): 409-418.
Keywords: thinning
commercial thinning
growth
carbon allocation
tree morphology
Abstract: Stand growth
efficiency (ratio of periodic stand volume growth to sapwood basal area) was
measured over 5 yr (1980-84) in a long term Douglas fir (Pseudotsuga
menziesii) thinning trial (established in 1957 at
36-yr-old, with 5 thinnings over 23 yr) in coastal Washington, USA. Sapwood basal area - as a surrogate for leaf area - and
volume growth were estimated in two fifth-hectare plots from each of three
thinning treatments, and from a single fifth-hectare control plot. Stand growth
increased with increasing sapwood basal area. No distinct pattern of stand
growth efficiency with sapwood basal area was evident. Large differences in
efficiency between plots of the same treatment were found and were attributed
to differences in stand structure, or the arrangement of tree sizes.
OSU
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29. O'-Hara, K.L. 1990. Twenty-eight years
of thinning at several intensities in a high-site Douglas-fir stand in western Washington. Western-Journal-of-Applied-Forestry 5(2): 37-40.
Keywords: thinning
commercial thinning
growth
yield
Abstract: Results
are presented of a 28-year thinning study of a dense (182-452 tree/acre)
natural, second growth Douglas fir (Pseudotsuga menziesii) stand at Delezenne,
which compared 3 thinning treatments with an unthinned
control. Treatments were: an increasing basal area treatment; a constant basal
area treatment (of approximately 140 ftsuperscript
2/acre); a decreasing/increasing reserve basal area treatment; and control
plots, which were 35 to 37-years-old with basal area 80-203 ftsuperscript
2/acre in 1957 when the tests were started. Gross, net, and total recoverable
periodic cubic volume increments of the control treatment (10 396, 9108 and 16
092 ftsuperscript 3/acre, respectively) were not
significantly different from the highest yielding treatment, which was the
increasing reserve basal area thinning treatment (8896, 8594 and 16 636 ftsuperscript 3/acre, respectively). These results, and
options for thinning schedules, are discussed; it is suggested that commercial thinnings of dense or fully stocked plantations of Douglas
fir may produce similar results, that is, vigorous stands with rapid growth
potential.
OSU
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30. Oliver, C.D. and M.D. Murray.
1984. Stand structure, thinning prescriptions, and density indexes in a
Douglas-fir thinning study, Western
Washington, U.S.A.
Canadian-Journal-of-Forest-Research 13(1): 126-136.
Keywords: thinning
commercial thinning
growth
stand conditions
Abstract: In a
stand regenerated after logging in 1930, thinnings to
set b.a. values were carried
out in 1959, 1962, 1966, and 1970. On each plot both large and small trees were
removed since av. b.a. per
tree was kept constant before and after thinning. Volume growth varied greatly
between plots of the same age, initial b.a.,
and site because of differences in stand structure. Large trees on a plot grew
more per tree and per b.a. than
small trees. Stand b.a.,
stand vol., number of stems, or number of dominant and codominant
trees were not closely related to vol. growth/ha, although density indexes
giving weight to larger trees showed the closest relationship. The lack of a
close relationship between stand desnsity indexes and
growth probably means the indexes do not uniquely define structures; it does
not necessarily mean that thinning will not increase volume growth/ha. Volume
growth/ha after thinning to a given b.a. will be
greater and probably more consistent if larger trees are left and enough time
is allowed for the stand to recover following thinning.
OSU
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31. Omule, S.A.Y. 1988. Growth and yield 35 years
after commercially thinning 50-year-old Douglas-fir. B.C.
Ministry of Forests FRDA-Report 021. vi + 15 p.
Keywords: thinning
commercial thinning
growth
yield
tree/stand health
Abstract: Remeasurement data
over a period of 35 years from fourteen 0.2023-ha permanent plots were analysed to determine the growth and yield effects of
commercially thinning 50-year-old Douglas fir (Pseudotsuga
menziesii) stands on a good site on Vancouver Island,
British Columbia. Compared to unthinned stands, the
commercially thinned stands had: virtually the same total volume gross annual
increment, top height and top height increment; 12% more potentially usable
total volume yield (including thinnings); 18% less
total volume at final harvest age 86 yr; virtually the same crop tree (193
largest diameter trees per hectare) average diameter, but 24% larger entire
stand quadratic mean diameter; and 11% less total volume production lost to
mortality. These results show that commercial thinning slightly increased total
stand yield (including thinnings) and produced larger
stand diameter at rotation age 86 yr, but that it also reduced usable total
volume at final harvest and had virtually no effect on size of the crop trees.
Data from this study are useful for validating growth models, and for
constructing and comparing managed stand yield tables for various commercial
thinning regimes.
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32. Ralston, R., J. Buongiorno and J.S. Fried. 2004. Potential yield, return,
and tree diversity of managed, uneven-aged Douglas-fir stands. Silva-Fennica 38(1): 55-70.
Keywords: thinning
commercial thinning
economics
yield
Abstract: The
effects of different management regimes on uneven-aged Douglas-fir stands in
the Pacific
Northwest of the United States were predicted with a simulation model. Management
alternatives were defined by residual stand structure and cutting cycle. The
residual stand structure was set by basal area-diameter-q-ratio (BDq) distributions, diameter-limit cuts (assuming
concurrent stand improvement), or the current diameter distribution. Cutting
cycles of 10 or 20 years were applied for 200 years. The current diameter
distribution was defined as the average of the uneven-aged Douglas-fir stands
sampled in the most recent Forest Inventory and Analysis conducted in Oregon and Washington. Simulation results were compared in terms of financial
returns, timber productivity, species group diversity (hardwoods vs softwoods), size class diversity, and stand structure.
Other things being equal, there was little difference between 10- and 20-year
cutting cycles. The highest financial returns were obtained with either a 58.4
cm diameter-limit cut, or a BDq distribution with 8.4
m2 of residual basal area, a 71.1 cm maximum diameter, and a q-ratio of 1.2.
Using the current stand state as the residual distribution was the best way to
obtain high tree size diversity, and high species group diversity. Several uneven-aged
regimes gave net present values comparable to that obtained by converting the
initial, uneven-aged stand to an even-aged, commercially thinned, plantation.
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