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한국농림기상학회지, 제17권 제1호(2015) (pISSN 1229-5671, eISSN 2288-1859)
Korean Journal of Agricultural and Forest Meteorology, Vol. 17, No. 1, (2015), pp. 58~68
DOI: 10.5532/KJAFM.2015.17.1.58
ⓒ Author(s) 2015. CC Attribution 3.0 License.
단 보
Wind Stability of Commercially Important Tree Species and
Silvicultural Implications, Daegwallyeong Korea
Mani Ram Moktan, Jino Kwon*, Joo-Hoon Lim, Moon-Hyun Shin,
Chan-Woo Park and Sang-Won Bae
Division of Forest Soil and Water Conservation, Department of Forest Conservation,
Korea Forest Research Institute, 57 Hoegiro, Dongdaemun-gu, Seoul 130-712, Korea
(Received August 13, 2014; Revised February 17, 2015; Accepted March 4, 2015)
대관령 지역 경제림에 대한 내풍 안정성 분석 및 임업적 적용
마니 람 목탄·권진오*·임주훈·신문현·박찬우·배상원
국립산림과학원 산림보전부 산림수토보전과
(2014년 8월 13일 접수; 2015년 2월 17일 수정; 2015년 3월 4일 수락)
ABSTRACT
This study compares the wind stability of Larix kaempferi (Lamb.) Carr., Pinus koraiensis Sie. & Zucc. and
Abies holophylla Maxim. to understand and inform wind risk management of these plantation trees at
Daegwallyeong, Korea. Temporary square plots of 20 m × 20 m (400 m2) were laid out, and DBH
(Diameter at Breast Height) and height for trees greater than 10 cm in DBH were measured by species.
A total of 15 plots with 5 plots each in L. kaempferi, P. koraiensis and A. holophylla stands were sampled
at random. Among the species, A. holophylla and P. koraiensis have comparatively lower h/d (Height/DBH)
ratios than L. kaempferi. These results indicate that the former two species are more wind firm than the
latter species. About 9% of the L. kaempferi trees have higher h/d ratios than the critical threshold limit
80. These trees are vulnerable to wind damage and should be removed in the next thinning regime. The
analysis of variance detected a significant difference (p < 0.05) in the h/d ratios and Gini coefficient indicating
species differences and DBH size variation, respectively. Gini coefficient was 16.4% in A. holophylla, 15.9%
in P. koraiensis and 14% in L. kaempferi stands indicating limited DBH size variation. Lower h/d ratios
are attributed to thinning in these stands and tree morphological differences. To increase wind firmness,
low thinning should concentrate to remove trees with the h/d ratio above 80 coinciding at the time of stand
distinction phase. Forest managers and practitioners should measure and maintain h/d ratios of trees
below the critical threshold limit of 80 through stand density management. Variable density thinning
approach should be tested to increase tree DBH sizes of the even-aged stands.
Key words: Wind stability, Silviculture, Height/diameter ratio, Korean white pine, Manchurian fir, Japanese larch
I. INTRODUCTION
Extreme wind such as storms and hurricanes causes
extensive damage to trees in many parts of the world,
but recurrent wind has more subtle effects on tree
* Corresponding Author : Jino Kwon
([email protected])
growth, form and ecology (Peltola et al., 2000). According to Ennos (1997) the effects of extreme wind need to
be considered separately from the recurrent wind. Hurricanes and storms wreck extensive damages to climax
and pioneer tree species and reverse the process of eco-
Mani Ram Moktan et al.: Wind Stability of Commercially Important Tree Species and Silvicultural Implications...
logical succession while recurrent wind of a particular
site has larger effect on forest ecology by causing trees
to undergo acclimatory changes in both short and longterm. Recurrent wind also induces trees of a single species to exhibit genetic differences in their morphological traits, thereby becoming adapted to windy landscapes.
Unlike extreme wind, recurrent wind damages can be
effectively reduced with sound forest management
practices (Stathers et al., 1994). To undertake, longterm wind risk assessment of trees, require the combination of knowledge on climate (including topographic
influences), tree and stand characteristics and their
interactions with features of the site (Peltola et al.,
2000). In this context, models of tree stand stability can
be used to describe the mechanism of damage, because
they can define the causal links between factors affecting the risk. Wind stability of trees is often related to
individual tree characteristics such as species, diameter
at breast height, height, crown size, and root/stem ratio
as well as site characteristics such as rooting depth, soil
moisture, exposure and slope (Cremer et al., 1982;
Ruel, 1995; Becquey and Riou-Nivert, 1987).
Further, recurrent wind damage at any given site
depends on species and tree size at the stand scale;
topographic, site and stand factors at the landscape
scale (Wood et al., 2008) and; wind speed and precipitation at the regional scale (Xi et al., 2008). Tree species selection is an important criterion in plantation to
minimize wind damages. Species and their stands differ
in their vulnerability to wind damage due to differences
in morphological characteristics, wood properties, rooting strategy and crown shape (Schelhaas, 2008). Early
successional and shade intolerant, fast growing pioneer
species that form over story dominants are more susceptible to wind throw than shade tolerant (Rich et al.,
2007) slow growing species occurring as co-dominant,
intermediate and suppressed canopy trees (Foster,
1988). Diameter and height growth and differentiation
of trees in forest stands affect stability against wind and
snow damages. H/d ratio of a tree is a relative measure
of stand stability under wind and snow loads. Wonn
and O' Hara (2001) pointed out that trees with higher h/
d ratios exceeding a threshold limit of 80 are prone to
wind damage than trees with lower ratios. Trees having
higher h/d ratios require less wind speed to be damaged
(Peltola et al., 1999; Wilson and Oliver, 2000; Cameron, 2002). With increasing height, h/d ratios should
be kept low to maintain the wind risk level (Cremer et
al., 1982; Becquey and Riou-Nivert, 1987; Ruel, 1995).
59
However, forest stands with trees of relatively high h/d
ratios can still be stable, if stand density is adequate,
because of mutual support and sheltering among the
individual trees against wind (Schelhaas et al., 2007).
Variation in h/d ratios results from spacing (Wonn and
O'Hara, 2001) and can be lowered in plantation through
reduced planting densities or early thinning. Thinning
is known to reduce the stand instability for many years
(Cremer et al., 1982; Ruel, 1995; Cameron, 2002)
through lowering the average h/d ratios in the longterm. Stand instability can be addressed by maintaining
reasonably low h/d ratios up to a stand height of 30 m
(Wilson, 1998). Initial stand density can be easily adjusted
by altering planting densities. In highly exposed sites, it
is recommended to use a relatively sparse initial stand
density and not to thin (Quine et al., 1995; Ruel, 1995)
which accentuates the importance of stand density
management for wind stability. Limited tree size variation
in plantation make trees susceptible to developing
higher h/d ratios making them more vulnerable to wind
throw (Wilson, 1998). At the tree and stand scale, silvicultural regimes can be designed to promote tree and
stand acclimation to wind and minimize damages (Mitchell, 2013). The Gini coefficient and coefficient of variation have been identified as the most useful descriptors of
the size variation in forest stands (Weiner and Solbrig,
1984; Benjamin and Hardwick, 1986; Knox et al.,
1989) which, in turn, is a useful predictor of a measure
of stand stability (Wilson, 1998).
Reducing wind damage largely depends on forest
managers and practitioners making appropriate silvicultural decisions. However, managers may not have
the silvicultural knowledge needed to make informed
decisions and understand the long-term implication of
their actions. Little is known about the wind stability of
the commercially important plantation tree species in
the windy landscapes of Daegwallyeong, Korea. This
study compares the wind stability of Larix kaempferi,
Pinus koraiensis and Abies holophylla by measuring
DBH and height and their size variation to understand
and inform decisions on wind risk management of
plantation trees at Daegwallyeong.
II. MATERIALS AND METHODS
2.1. Study area
The study area is located at 37°40' N latitude and
128°42' E longitude Daegwallyeong-myeon in Pyeongchang-gun, Gangwon province in the Republic of
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Korean Journal of Agricultural and Forest Meteorology, Vol. 17, No. 1
2008). The land uses are classified into 4 categories;
plantation and recreation forest, agriculture, pastures
and ecotourism.
2.2. Climate and soil
At Daegwallyeong, the monthly temperature is maximum (22.8°C) in July/August and minimum (-12.6°C)
in January with a total precipitation of 1898 mm/year
(Koh, 2012). Annual precipitation concentrates from the
month of July to September. Daegwallyeong receives
an annual snowfall of 187 cm thickness during the winter months. The area is foggy and cloudy most times of
the year. The average slope of the plantation area varies
from 13-19° with soil pH of more than 5 (Koh, 2012).
Soil type is brown forest soils classified into dry,
slightly dry and moderately moist brown forest soils
with distinct A and B horizons (Korea Forest Research
Institute, 2005). The aspect is south west. According to
KMA (2012), the average wind velocity is 4.3 m/s with
a highest velocity in the month of December (5.8 m/s)
and January (5.6 m/s) and lowest (2.7 m/s) in September (Fig. 2(a)). The wind flows in west and south west
direction mostly (Fig. 2(b)).
Fig. 1. Map of the study area (A = A. holophylla, P = P.
koraiensis, L = L. kaempferi).
Korea (Fig. 1).
The total area is 221.63 km2 with a population of
6,085 persons in 2008 and; elevation ranged from 8001,000 m above sea level (Pyeongchang County Office,
Fig. 2. Wind speed (m/s) by month (a) and direction (b).
2.3. Plantation history
Daegwallyeong is one of the high flat lands in the
Baekdu - Daegan mountain landscapes that experiences
recurrent wind. History revealed that in the past, residents used the area for agricultural crop cultivation.
After mass population migration in 1968, the area was
left in a state of devastation aggravated by recurrent
wind and poor soil condition. In order to bring the area
Mani Ram Moktan et al.: Wind Stability of Commercially Important Tree Species and Silvicultural Implications...
under managed land use and restore the degraded forest, wooden wind barriers of 3 m height, 20 m length at
50 m interval were installed prior to start of the plantation. Planting techniques such as windbreak net and
weirs, wooden tripods and soil dressings were done to
minimize wind and snow damages to trees and improve
site condition (Koh, 2012). Protective wire mesh of 50
cm diameter and 70 cm height with its base at 30 cm
soil depth were installed around seedlings. In the first
year, seedling survival was reportedly poor due to desiccation from recurrent winds. From second year onwards,
intensive measures were put in place to protect seedlings from wind desiccation. When seedlings attained
saplings and pole size trees, wooden tripods buttressed
individual trees to prevent lodging and allow rooting
firmly in the soil. In between plantation stands, nitrogen fixing trees and shrubs were planted to fertilize and
enrich soil and maintain understory cover, respectively.
With an overarching objective of ecosystem restoration
of Baekdu - Daegan Mountain System, 4 years-long special plantation program was implemented from 19992002. The main species planted were; A. holophylla, P.
koraiensis and L. kaempferi. The management plan
prescribes to carry out forest tending for improving
stand productivity, developing appropriate silvicultural
regimes and create a wind firm plantation for eventually developing into an ecologically sound forest for
environmental conservation. Accordingly, thinning, weeding, replenishment planting, and fertilization were done.
This study forms part of the current research project on
‘topography based knowledge for forest landscape restoration in the Baekdu - Daegan Mountain System’
(Kwon, 2014).
In this study, P. koraiensis (Korean white pine), A.
holophylla (Manchurian fir) and L. kaempferi (Japanese larch) were selected due to their increasing commercial importance as domestic timber (Seo et al.,
2014). In the Republic of Korea, plantation forest species composition have gradually changed from an
exotic single species to mixed species with natives in
response to the policy of sustainable forest management and enhancing the recreational value of forest to
public (Korea Forest Service, 2013). P. koraiensis is a
native conifer species of northeast Asia. In the Republic of Korea, P. koraiensis is planted mostly and occupies an area of 230,000 ha (Korea Forest Service,
2009). It also occurs as scattered natural stands in the
mountains (Korea Forest Research Institute, 2010). It
grows to a height of 20-30 m and attains 1 m diameter;
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bark is dark brown colour; leaves are 5 needles; and
flowers are monoecious (Korea Forest Research Institute, 2011). A. holophylla is an evergreen tree that
grows about 40 m height and 1.5 m diameter; grayish
dark brown bark and twigs; linear leaves with sharp
apex at the tip and; flowers are monoecious (Korea
Forest Research Institute, 2011). L. kaempferi is native
to Japan. It is a medium to large-size deciduous conifer
tree reaching 20-40 m height and 1 m diameter. Leaves
are needle-like, light glaucous green in colour, which
turns bright yellow to orange before they fall in the
autumn. In the Republic of Korea, it is planted in many
places and occupies an area of 460, 000 ha (Korea Forest Research Institute, 2010).
2.4. Selection of forest stands and plots
Initial site and stand reconnaissance were done after
consulting the Pyeongchang county forest office in January 2014. Our study focuses on the species and trees
at stand scale. Temporary square plots of 20 m × 20
m (400 m2) were laid out. From the center of the plot,
starting from the north and moving in a clockwise
direction, DBH (diameter at breast height measured
at 1.30 m above ground) and height (from the base to
the top of the green crown using a digital hypsometer) of all trees for greater than 10 cm in DBH were
measured by species. A total of 15 plots (0.6 ha) with
5 plots each in L. kaempferi, P. koraiensis and A. holophylla stands were sampled at random. In these
sampled stands, low thinning was already done. Further details are not available from the Pyeongchang
county forest office.
2.5. Data analysis
We used Statistical Package for Social Sciences
(SPSS 16.0), 2004) for data analysis. H/d ratio was calculated from height divided by DBH (both in same
unit) by species. The coefficient of variation and Gini
coefficient measures tree size variation, which are useful indicators of stand stability against wind (Wilson,
1998). The coefficient of variation is a dimensionless
ratio that allows comparison of variability in populations, where standard deviation changes with the mean
(Benjamin and Hardwick, 1986). We used Gini coefficient (Weiner and Solbrig, 1984) to characterize DBH
size inequality. Lorenz curve is the curve below the 45º
line gained by plotting the cumulative frequency of tree
population and cumulative frequency of basal area
(Knox et al., 1989; Nilsson, 1994; Stöcker, 2002). In
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Korean Journal of Agricultural and Forest Meteorology, Vol. 17, No. 1
order to draw the curve, trees in the stands were sorted
by increasing dbh order, then the cumulative tree number and basal area were calculated. If all trees have
equal DBH, the Lorenz curve aligns with 45° line
and thus, the area under the Lorenz curve has largest
value of 0.5. The more the size of trees varies, the
smaller is the area under Lorenz curve. Thus, Gini
coefficient is defined as the proportion of the area
between the 45° line and the Lorenz curve in percent
of 0.5 as measure of variability of tree sizes in the
stand. Data were tested for normality and homogeneity of variance before subjecting to parametric and
non-parametric tests. Unless otherwise stated, all
tests are two-tailed.
III. RESULTS
3.1. Height/diameter ratio
The h/d ratios of L. kaempferi, P. koraiensis and A.
holophylla in relation to their DBH and height are
given in the Fig. 3. The h/d ratio decreases as DBH
increases. The mean h/d ratio of L. kaempferi was 69.3
and ranged from 53.4 to 95.2 (Fig. 3(a) and (b)). The
pooled DBH of the trees was 25.5±3.6 cm and height
17.5±1.6 m and ranged from 16.1 to 36.5 cm and 11.4
to 21.6 m, respectively (Table 1). In proportionate
terms, about 9% of the larch trees, had h/d ratios of
85.1 and ranged from 80.3 to 95.2, above the critical
threshold limit of 80. These trees have an average DBH
Fig. 3. Height/diameter ratio versus DBH and height of L. kaempferi (a and b), P. koraiensis (c and d) and A. holophylla (e and f).
Mani Ram Moktan et al.: Wind Stability of Commercially Important Tree Species and Silvicultural Implications...
63
nificant mean difference in the h/d ratio between L.
kaempferi and A. holophylla, (p < 0.01)
of 20.7±1.4 cm and height of 17.6±1.2 m and ranged
from 18.7 to 23.1 cm and 15.6 to 20 m, respectively.
The height of these trees were little more than the
pooled height of all the trees. A large proportion (91%)
of the trees has average h/d ratio of 67.7 and ranged
from 53.4 to 79.1 falling below the threshold limit of
80. These trees have an average DBH of 26±3.4 cm
and ranged from 16.1 to 36.5 cm and height was 17.5±
1.6 m and ranged from 11.4 to 21.6 m.
The average h/d ratio of P. koraiensis was 55.7
ranging from 42.3 to 78.8 (Fig. 3(c) and (d)). The
pooled DBH of the trees was 23.2±3.8 cm and ranged
from 13.2 to 34.3 cm while the height was 12.7±1.5 m
and ranged from 8.1 to 16 m (Table 1). Most of trees
have h/d ratios below the threshold limit of 80. Similar
to P. koraiensis, A. holophylla has an average h/d ratio
of 51.7 and ranged from 39.7 to 69.4 (Fig. 3(e) and (f)).
The pooled DBH of trees was 26.2±4.2 cm and ranged
from 16 to 37 cm and height was 13.4±1.7 m and
ranged from 8.2 to 17.2 m (Table 1). Again, all trees
have h/d ratios below the threshold limit of 80.
One –way analysis of variance result of h/d ratio and
Gini coefficient of DBH sizes between species is given
in the Table 2. There was significant difference in the
h/d ratio between the species (p < 0.01). The Bonferroni’s post-hoc multiple comparison test detected sig-
3.2. DBH/height variation and stand density
The Gini coefficient and coefficient of variation of
DBH was significantly correlated in L. kaempferi (r2adj
= 0.95, p < 0.01), P. koraiensis (r2adj = 0.97, p < 0.01
and A. holophylla (r2adj = 0.95, p < 0.01) indicating size
variation (Fig. 4(a)). The coefficient of variation of height
of trees was larger in A. holophylla (11%) compared to
L. kaempferi (8%) and P. koraiensis (7%) but statistically not significant (Fig. 4(b)). There was no significant difference in the number of trees per hectare by
species (χ2(2) = 3.248, p = 0.197 Kruskal-Wallis test).
However, P. koraiensis has higher tree densities (800
trees/ha) than L. kaempferi (730 trees/ha) and A. holophylla (640 trees/ha) (Fig. 4(c)). There was also no significant difference in the basal area between species
(χ2(2) = 0.980, p = 0.613). L. kaempferi has higher basal
area (38.12 m2/ha) than A. holophylla (35.28 m2/ha)
and P. koraiensis (34.68 m2/ha).
There was significant difference in Gini coefficient of
DBH sizes between stands (F2,14 = 4.95, p < 0.05) (Table
2). The Lorenz curve and Gini coefficient of DBH sizes of
stands by species are given in the Figure 5. DBH variation
was little in A. holophylla (16.4%) (Fig. 5(c)) closely fol-
Table 1. DBH and height variation of the sampled species and stands
DBH (cm)
Height (m)
Species
Plot
N
Mean ± SD
Max.
Min.
Range
Mean ± SD
Maxi.
Min.
L. kaempferi
1
2
3
4
5
36
27
23
30
30
24.6 ± 3.64
24.2 ± 3.25
27.4 ± 3.26
27.2 ± 3.74
24.7 ± 3.33
31.6
30.9
36.5
34.4
31.0
16.1
17.0
21.0
20.7
18.7
15.5
13.9
15.5
13.7
12.3
16.6 ± 1.42
16.5 ± 1.42
18.6 ± 1.14
18.3 ± 1.44
17.7 ± 1.48
19.0
19.2
20.1
21.6
20.0
11.4
13.3
16.3
15.7
13.0
7.6
5.9
3.8
5.9
7.0
Pooled mean
25.5 ± 3.67
36.5
16.1
20.4
17.5 ± 1.60
21.6
11.4
10.2
35
25
26
27
47
23.9 ± 2.82
25.3 ± 3.35
24.1 ± 2.75
25.6 ± 3.37
19.5 ± 2.93
31.4
34.3
29.3
34.3
26.0
18.6
19.8
17.8
20.1
13.2
12.8
14.5
11.5
14.2
12.8
13.4 ± 0.85
13.4 ± 0.91
13.8 ± 0.84
13.7 ± 1.06
10.8 ± 0.88
15.0
15.7
15.5
16.0
12.6
11.7
11.5
12.1
11.7
8.1
3.3
4.2
3.4
4.3
4.5
Pooled mean
23.2 ± 3.84
34.3
13.2
21.1
12.7 ± 1.53
16.0
8.1
7.9
26
25
25
26
26
25.3 ± 3.23
26.3 ± 4.33
25.0 ± 3.83
27.3 ± 4.95
26.7 ± 4.58
31.0
34.0
33.0
34.0
37.0
19.0
19.0
20.0
16.0
17.0
13.0
14.0
13.0
18.0
20.0
12.2 ± 0.94
13.0 ± 1.03
12.7 ± 1.51
14.4 ± 2.05
14.5 ± 1.72
14.2
15.0
16.2
17.2
16.7
10.1
11.1
8.6
8.2
11.0
4.1
3.9
7.6
9.0
5.7
Pooled mean
26.2 ± 4.25
37.0
16.0
21.0
13.4 ± 1.75
17.2
8.2
9.0
P. koraiensis
A. holophylla
1
2
3
4
5
1
2
3
4
5
Range
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Korean Journal of Agricultural and Forest Meteorology, Vol. 17, No. 1
Fig. 4. Comparison of coefficient of variation versus Gini
coefficient, (a) average height versus coefficient of variation,
(b) and trees per hectare versus height, (c) between species.
lowed by P. koraiensis (15.9%) (Fig. 5(b)) and L.
kaempferi (14%) (Fig. 5(a)) stands. The Lorenz curves
of the three species lie near the 45 line of equality.
IV. DISCUSSION
The h/d ratios were found to be higher in L. kaempferi
Fig. 5. Dbh distribution of L. kaempferi, (a) P. koraiensis,
(b) and A. holophylla (c).
compared to P. koraiensis and A. holophylla. The analysis of variance detected significant difference in the h/d
ratios between the species. These results indicate that
L. kaempferi is relatively vulnerable to wind damage
than P. koraiensis and A. holophylla. The latter two
species have comparatively lower h/d ratios falling
below the critical threshold limit of 80 and considered
stable. In our study, about 9% of the L. kaempferi trees,
have h/d ratios above the critical threshold limit. These
Table 2. Height/diameter ratios and Gini coefficient of DBH sizes between species
Species
Between species
Within species
Total
df
2
431
433
h / d ratio
Gini coefficient
SS
MS
F
p
df
SS
23968.15
19283.33
43251.48
11984.07
44.74
267.86
0.000**
2
12
14
0.0009
0.001
0.002
** and * denotes significant difference at 1% and 5% levels, respectively
MS
F
0.000478 4.95
0.0000965
p
0.027*
Mani Ram Moktan et al.: Wind Stability of Commercially Important Tree Species and Silvicultural Implications...
trees are vulnerable to wind damage and should be targeted for cutting in the next thinning regime. Wonn and
O' Hara (2001)found out that damaged western larch
had extremely high h/d ratios due to its deciduous nature
than ponderosa pine, lodgepole pine and Douglas fir in
response to wind and snow damage. High h/d ratios of
the 9% L. kaempferi trees may be attributed to increased
height increment plausibly due to good site quality. In
the European managed forest dominated by even-aged
stands, storm damage typically increased with stand
height and age (Mitchell, 2013). Our study results
revealed that L. kaempferi trees were taller than P.
koraiensis and A. holophylla. Generally, shade-intolerant tree species allocate more resources to height increment instead of overall structural strength (Givnish,
1995) making them less wind firm (Rich et al., 2007).
Our results are consistent with the findings from longterm growth monitoring research, which pointed out
that L. kaempferi height increment was higher than P.
koraiensis but diameter increment was vice-versa (Seo
et al., 2014). The lower h/d ratios in P. koraiensis and
A. holophylla are attributed to thinning of the stands.
The variation in h/d ratios can be largely attributed to
thinning and spacing (Wonn and O' Hara, 2001; Cremer et al., 1982).
Lower tree densities but higher height increment of
L. kaempferi trees makes them vulnerable to wind
damage due to little mutual support and sheltering
among the individual trees (Schelhaas et al., 2007). A.
holophylla in particular has relatively lower tree densities and lower height increment. Lower tree densities,
however, result from wider spacing created by thinning, reducing tree densities as in the case of A. holophylla. Wonn and O' Hara (2001) pointed out that
heavy thinning lowers h/d ratios indicating the potential of thinning to spacing and consequently improving
stand stability. Post thinning damages from snow and
wind were minimum (1-20%) of the basal area compared to unthinned stands (Valinger and Pettersson,
1996; Valinger et al., 1994). The lower h/d ratios in A.
holophylla and P. koraiensis could also be attributed to
morphological differences between species. A. holophylla and P. koraiensis are shade tolerant native species (Park and Jeon, 2010) with lower stand height and
dense canopies similar to wind resistant black pine (P.
thunbergii) (Bitog et al., 2011; Kwon et al., 2004; Kim,
2010) than shade intolerant exotic larch. Everham and
Brokaw (1996) concluded that differences in tree morphology, wood properties and disease resistance result
65
differences in species vulnerability within and between
stands, however, these differences can be obscured by
differences in site, stand and silvicultural characters.
Studies in the European forests revealed that Douglas
fir has better stem form and anchorage particularly in
permeable soil condition than larch and pines (Schütz
et al., 2006; Bosshard, 1967). However, we observed a
few A. holophylla and P. koraiensis trees top snapped,
which may be due to stem structural weakness (Stathers et
al., 1994).
In general, there was less DBH variation of trees
between species and stands. Among the species, A. holophylla and P. koraiensis has relatively large DBH
variation than L. kaempferi stands. Less tree size variation of L. kaempferi stands may have developed high
h/d ratios. Wilson and Oliver (2000) pointed out that
limited tree size variation in coastal Douglas fir plantation make them susceptible to developing high h/d
ratios in dominant trees. Relatively large DBH sizes of
A. holophylla and P. koraiensis stands may be attributed to acclimatory responses developed over longterm due to recurrent wind effects. Ennos (1997) pointed
out that trees reduces height increment but increases
diameter increment particularly at the base of the trunk
and branches, acting to reduce the peak mechanical
wind stress and overturning moment in trees. Diameter
increment relative to height increment in P. koraiensis
trees have been reported after thinning (Bae et al.,
2010) and similar aged A. holophylla trees had diverse
DBH values (Park and Jeon, 2010). Further thinning, in
these species and stands, should aim to increase diameter sizes to improve wind stability.
V. CONCLUSIONS AND
RECOMMENDATION
It can be concluded that A. holophylla and P. koraiensis have relatively lower h/d ratios and large DBH variation than L. kaempferi. This result clearly indicates
that the former two species are more wind firm than the
latter species. Generally, there was limited DBH size
variation between the stands. To increase wind firmness, low thinning or thinning from below should concentrate to remove trees with high h/d ratios above 80
coinciding with the early or at the time of stand distinction phase. This will benefit remaining trees to quickly
utilize growing space and increase diameter increment
relative to height increment (Schmidt and Seidel, 1988;
Cameron, 2002). Thinning done after the stand distinc-
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Korean Journal of Agricultural and Forest Meteorology, Vol. 17, No. 1
tion phase may result in stand instability (Cameron,
2002; Wilson and Oliver, 2000). Forest managers and
practitioners should measure, calculate and maintain h/d
ratios of trees below the critical threshold limit of 80
through stand density management. Trees with higher
h/d ratios than 80 should be cut in the successive thinning regimes. Variable density thinning approach that
deliberately leaves trees on variable spacing, so that
some residual trees are nearly in open-grown conditions, whereas others are in heavy competition (OHara
and Waring, 2005) resulting in a variety of tree sizes in
an even-aged stands (Thornburgh et al., 2000) should
be experimented.
적 요
본 연구는 대관령 특수조림지에 식재된 주요 경제수
종인 잣나무, 전나무, 일본잎갈나무의 내풍 안정성을
비교 분석하여 조림지의 풍해관리에 대한 이해와 인식
을 높이고자 수행되었다. 각 수종별로 5개씩 총 15개
의 임시 방형구(20m × 20 m)를 설치하였으며, 흉고
직경 10cm 이상의 수목에 대하여 수고 및 흉고직경
을 측정하였다. 수종별 수고/흉고직경 비율(h/d 비율)을
분석한 결과 잣나무와 전나무가 일본잎갈나무에 비해
비교적 낮은 h/d 비율을 나타내어 내풍성이 상대적으
로 높은 것으로 보인다. 약 9%의 일본잎갈나무가 내
풍 임계치(80) 이상의 h/d 비율을 나타낸 것으로 조사
되었으며 이들 수목들은 풍해에 매우 취약하여 다음
간벌 기간 동안 제거되어야 할 것으로 판단된다. 분산
분석 결과 수종별 h/d 비율과 흉고직경의 지니계수에
서 각각 유의한 차이가 나타났다. 수종별 흉고직경의
지니계수는 전나무 16.4%, 잣나무 14%, 일본잎갈나무
14%로 나타났다. 낮은 h/d 비율은 수종별 형태학적
차이와 간벌 시업에 기인한 것으로 판단된다. 수목의
내풍성을 향상시키기 위해서는 h/d 비율이 80 이상인
수목에 대한 하층간벌이 초기 혹은 임분 분화기(stand
distinction phase)에 집중되어야 한다. 산림관리자와
시업자는 수목의 h/d 비율을 측정하고 임분 밀도를 관
리하여 비율을 내풍 임계치인 80 이하 수준으로 유지
하여야 한다. 따라서 동령림에서 수목의 흉고직경을 증
가시키기 위해서는 h/d 비율이 높은 수목에 대한 택벌
이 수행되어야 할 것으로 판단된다.
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