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Ecological Indicators 127 (2021) 107689
1470-160X/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Assessing the effects of forest gaps on beech (Fagus orientalis L.) trees traits
in the logged temperate broad-leaf forest
Alireza Amolikondori
a
, Kambiz Abrari Vajari
b
,
*
, Mohammad Feizian
c
a
PhD candidate, Faculty of Agriculture and Natural Resource, Lorestan University, Iran
b
Associate Prof, Faculty of Agriculture and Natural Resource, Lorestan University, Iran
c
Associate Prof, Faculty of Agriculture and Natural Resource, Lorestan University, Iran
ARTICLE INFO
Keywords:
Beech
Gap
Single-tree harvesting
Tree traits
ABSTRACT
Silvicultural operations, including single-tree selection create gaps in forest canopies and these gaps impact on
the forests structure. This study examines the inuences of different harvest-created gap sizes on the oriental
beech (Fagus orientalis L.) trees traits in temperate Hyrcanian forest, northern Iran. We selected three gap sizes
(small, medium and large) and the adjacent unlogged closed canopies with ve replications for each and
measured some features of beech trees in overstory at the gaps-edge and closed stands. The results showed that
gap size signicantly inuenced on crown length, crown surface area, crown ratio, bole, height/diameter (H/D)
and minimum radius / maximum radius (CA) ratios of beech trees six years following gap creation (P <0.05).
Many beech tree traits in adjacent closed forest had no signicant difference with gaps, except for crown
asymmetric (P <0.01).Statistically signicant differences were observed in beech trees regarding to the clear
bole, crown ratio, and CA among the four cardinal points of gaps. A signicantly positive correlation was
observed between crown ratio with crown length, crown width, crown area, crown volume, and DBH for trees.
We found that crown ratio increased signicantly with decreasing the bole and total height of beech trees.
Results indicated that H/D ratio and total height, DBH, crown length and bole for beech trees were signicantly
negatively correlated. The CA ratio increased signicantly with increasing the bole of trees. The crown radii of
border beech trees towards gap center were signicantly larger than those of forest-facing side of trees (P <
0.01). This study demonstrates that beech trees in overstory and at the edge of gaps respond differently to
articial gaps after 6 years of formation in oriental beech stand in temperate Hyrcanian forest.
1. Introduction
The forest gap is a major disturbance in many forest ecosystems in
the world which created by death of individual tree or more trees
(Muscolo et al., 2014) and these gaps play an important role in forest
ecology (Schliemann and Bockheim, 2011). In general, disturbances
such as diseases (Miller et al., 2007; Vepakomma et al., 2008), storm
(Collins and Battaglia, 2002; Muller and Wagner, 2003; Kukkenon et al.,
2008), ice damage (Mallik et al., 2014), re (Banal et al., 2007; Zou
et al., 2006) can create gaps in forests. Moreover, harvesting (Miller
et al., 2007; Banal et al., 2007; Toledo-Aceves et al., 2009) cause
removal of trees which nally lead to the creation of a canopy gap. A
number of environmental changes occur soon after gap formation in a
forest (d’Oliveira and Ribas, 2011) and gaps inuence the tree germi-
nation and growth (Sharma et al., 2016; Wang et al., 2017), soil nutrient
cycling (Schliemann and Bockheim, 2014), plant diversity (Richards and
Hart, 2011), understory vegetation (Kermavnar et al., 2018), tree crown
shape (Seidel et al., 2016), and crown expansion (Lu et al., 2015).
Kermavnar et al. (2020) declared that tree logging due to changes in
temperature, humidity in articial gaps cause increasing microclimate
variations in managed r-beech forests in the Dinaric mountains,
Slovenia. Stan and Daniels (2014) mentioned that forest gaps can ex-
ercise a major inuence on forest structure and composition by affecting
the growth of adjacent trees. The reaction of growth processes of any
individual tree to the local environment determines its stature (Lang
et al., 2010). Apparently, when an individual tree dies, neighboring trees
rapidly seize the available growing space and close up the canopy gap
through horizontal crown extension, in that way modifying the size and
architecture of tree and forest stand structure (Richards and Hart, 2011).
Gaps alter the growth conditions for trees in forests whereby increases
* Corresponding author.
E-mail addresses: abrari.k@lu.ac.ir, Kambiz.abrari2003@yahoo.com (K. Abrari Vajari).
Contents lists available at ScienceDirect
Ecological Indicators
journal homepage: www.elsevier.com/locate/ecolind
https://doi.org/10.1016/j.ecolind.2021.107689
Received 30 September 2020; Received in revised form 3 March 2021; Accepted 1 April 2021
Ecological Indicators 127 (2021) 107689
2
the heterogeneity of horizontal and vertical structures (Seidel et al.,
2016). Pedersen and Howard (2004) reported higher stem radial growth
rates for overstory trees at gap edges compared to trees which were not
positioned at canopy gap edges in a mature mixed forest. Seidel et al.,
(2016) realized that trees at the border of gaps showed larger crown
surface area and crown volume than other trees growing in a regular
location. The size of a tree is determined to a large extent by its growth
rate (Coonen and Sillett, 2015) and it is recognized that trees demon-
strate exible behavior in response to ecological conditions (Van de Peer
et al., 2017). Thus, it is essential to investigate changes in individual tree
characteristics such as crown dimensions in order to understand canopy
structure within stands. The morphology of tree crown is a major
determining factor of forest function and productivity (Barbeito et al.,
2014). Qualitative and quantitative assessment of tree structure re-
sponses to forest gaps is important for studying forest dynamics and
might offer important insights into forest management. Gap formation
in the canopy bring about signicant effects on the structure and dy-
namics of most temperate and tropical forests (Lima et al., 2013).
Numerous studies have been conducted addressing gaps in the world’s
forest regions, including tropical and temperate forests. However, to the
best of our knowledge, a few studies have investigated the effect of gap
size on the structural features of beech trees in the edge of gap and their
comparison with the structural feature of beech trees in the upper strata
of neighboring closed forest, especially in temperate Hyrcanian forests.
In the Caspian temperate zone of Iran, forest, in particular Oriental
beech stands, have been harvested by selection system which have
created different forest gap sizes. The effect of forest gaps on regenera-
tion (Shabani et al., 2011; Abrari Vajari et al., 2012; Mohammadi et al.,
2015), soil properties (Abrari Vajari et al., 2011; Kooch et al., 2012), and
biodiversity (Shabani et al., 2011; Abrari Vajari et al., 2012; Pourbabaei
et al., 2013) has been extensively studied in oriental beech stands in
Caspian forests. However, little is known about the effects of harvest-
created gaps by single-tree selection system on dominant oriental
beech trees traits in the beech forest stand. In the present study we
investigated the inuence of forest gap size on beech trees characteris-
tics in the edge of gaps in Caspian (Hyrcanian) temperate forest. The
specic objectives of this study were: (i) to determine how oriental
beech crown dimensions differ with forest gap size (ii) to evaluate the
correlation between gap size and trees crown size (iii) to compare crown
properties of beech trees in the cardinal points of edge of gaps (iv) to
assess the relationships between crown ratio, Height/Diameter at breast
height, minimum radius / maximum radius and other parameters of
trees in the border of gaps; and (v) to test the differences between gaps
and adjacent closed canopy stand regarding to beech trees characteris-
tics. This research is helpful to understand mechanisms of the develop-
ment of tree structure inuenced by different gap size in oriental beech
stand.
2. Materials and methods
2.1. Study site
The study site is located in an uneven-aged forest in the Caspian
region, northern Iran (36◦12′N,53◦24′E), comprising an area of about
40.4 ha. It is located at an altitude of 1000–1200 m a.s.l., with a slope of
0–30% and North-oriented. It has a humid climate, with a mean annual
precipitation of 858 mm and a mean annual temperature of 10.5 ◦C
(Forestry plans of Tajan-Talar, 2001). The dominant soil types are
pseudogleyic and gley. Oriental beech trees present in all strata, from
suppressed to dominant ones and form the dominant forest type. Other
tree species including alder (Alnus subcordata C.A.Mey), hornbeam
(Carpinus betulus L.), maple (Acer velutinum Boiss.), Ironwood (Parrotia
persica C.A.Mey) and Oak (Quercus castaneifolia C.A.Mey) observed in
stand (Table 1). Oriental beech as a woody species is one of the main
forest species in the Caspian temperate forests, northern Iran usually
occupying mesic sites and grow in pure and mixed stands. In addition to
its distribution and stand area, it holds great ecological and economical
values. The mean values of number and volume of trees per hectare are
177 and 399.6 m
3
, respectively in the site. Structurally, the examined
beech stand is multi-layered and uneven-aged and developed from
natural regeneration. The stand was managed under single-tree selec-
tion method which has been created different forest gaps in 2011
(Forestry plans of Tajan-Talar, 2001 and eld observations conrmed
the logging within the stand. These gaps occupy a large proportion of the
present forest which makes these forests particularly interesting for
research, especially its effects on tree traits.
3. Field measurements
Data sampling was conducted in summer 2017 on 15 articial forest
gaps within beech stand which were created in 2011. Beech tree in
overstory was the gap maker species accounting for 15 gaps which
selected randomly (Fig. 1). At the time of sampling, age of forest gaps
was 6 years. The area of expanded gaps (hereafter gaps), was calculated
(A=
π
LW
4) by measuring its long (L) and short (W) axes as ellipse shape
(Runkle, 1981). Gap length was divided by gap width to calculate ec-
centricity, where values >1 indicate elliptical gaps (Alexander and
Mack, 2017). The gaps classied into three size classes: small, medium
and large with ve replications for each class (Table 2). Those gaps
which preferably had overstory trees at the edge and the cardinal points
as well as adjacent closed stand were selected. The classication of gap
size was performed based on created space by removal of beech trees. In
the cardinal positions of the edge of gaps also in the adjacent closed
canopy forest at distance of 20 m from gap (Fig. 2), the morphological
variables measured for each beech tree in overstory were: stem diameter
at a height of 1.30 m (DBH), total tree height (m), crown length and
width (m), crown area (m
2
) and volume (m
3
), height-to diameter ratio of
the tree (the slenderness factor, H/D), crown ratio (crown length–tree
height ratio), CA (minimum radius / maximum radius) and the clear
bole (m). Crown radius was calculated as the mean value of radii in four
different directions (N, E, S, and W). The vertical sighting method was
applied to measure crown radius as the distance from the centre of the
trunk of tree to the perimeter of its crown (Pretzsch et al., 2015). The
total height and DBH of all trees were measured using a Suunto
clinometer and diameter tape, respectively. The crown surface area
(CSA) and the crown volume (CV) were calculated (Promis et al., 2009),
supposing that the crown of tree has a parabolic shape:
CSA =
π
×R
6×C2
L
×(R2+4×C2
L)1.5−R3(1)
CV =
π
×R2×CL
2(2)
where CL (m) is the crown length and R is crown radius (m). In addition
to the tree parameters, elevation, slope and aspect for each gap were
recorded.
3.1. Statistical analysis
All data were tested for a normality using Kolmogorov-Smirnov test
and datasets indicated a normal distribution. All structural features of
the border trees were compared to the corresponding features of the
trees in the closed canopy forest using a two-sided independent t-test. A
one- way ANOVA (analyses of variance) was applied for assessing the
Table 1
Descriptive features of different tree species in research site.
Quercus Parrotia Acer Alnus Carpinus Fagus Species
0.6 12.5 2.2 7.5 12.2 65 Number/ha (%)
0.6 3.6 1.5 0.7 8.6 85 Volume/ha (%)
A. Amolikondori et al.
Ecological Indicators 127 (2021) 107689
3
effect of gap sizes on the beech trees morphology in the edge of gaps,
also evaluating trees architecture in the cardinal points of gaps border.
Student-Newman-Keuls (S.N.K) test was used for comparisons of tree
properties following the results of ANOVA. To evaluate the relationship
between gap sizes with some features of trees Pearson’s correlation
coefcient was used. Independent T test was used to compare means of
tree radii in the border of gaps. The comparison between crown radius
toward gap center and forest-facing for beech trees at the edge of gaps
was estimated using independent T test. All data were analyzed with the
SPSS version 20.0 and signicant differences were identied at p <0.05
and p <0.01.
4. Results
Gaps created by single–tree selection system were elliptical in shape
(Table 2) and clearly affected the beech tree traits in the forest stand.
Gap size signicantly inuenced crown length, crown surface area,
crown ratio, bole, H/D and CA ratios of beech trees for 6-years following
gap creation (P <0.05, Table 3). Tree crown asymmetric (CA) high-
lighted differences between gaps and adjacent closed stands but most
tree measurements were not signicantly different between gaps and the
adjacent closed forest (P <0.01, Table 4). Statistically signicant
differences were observed among the four cardinal points for the bole,
crown ratio and CA only, but no signicant differences were observed
for other beech tree morphology at edge of canopy gaps (Table 5). The
coefcients of correlation between morphology and CR, H/D and CA
ratios of trees are presented in Table 6. A signicantly positive corre-
lation was observed between crown ratio with crown length, crown
width, crown area, crown volume and DBH. We found that crown ratio
increased signicantly with decreasing the bole and total height of
beech trees. Regression analysis showed that H/D ratio and total height,
Fig. 1. Beech (Fagus orientalis L.) trees at the edge of canopy gaps (A) and adjacent closed stand (B) in site.
Table 2
Descriptive statistics for the articial gaps in oriental beech stand.
Class No.
of
gap
Size(m
2
) Mean
area of
gap(m
2
)
SD No. of
bordering
tree
Eccentricity
(mean ±SD)
1 5 84–130 106.91 19.18 20 1.9 ±0.48
2 5 131–175 151.91 15.32 20 2 ±0.68
3 5 175–300 252.41 75.60 20 1.7 ±0.31
Fig. 2. Layout of sampling points in gaps and closed stand (N, S, E and W:
Cardinal positions).
Table 3
Comparison of beech trees characteristics for six years following gap creation, by
different tree gap size.
Gap
Parameter Small(n =20) Medium(n =
20)
Large(n =20) P-
value
Total height(m) 29.05 ±2.06
a
29.89 ±1.95
a
32.47 ±1.53
a
0.219
DBH(cm) 54.75 ±5.49
a
53.88 ±5.05
a
32.47 ±1.53
a
0.195
Crown length(m) 11.30 ±
0.77
ab
9.25 ±0.71
b
12.22 ±0.92
a
0.036*
Crown width(m) 9.8 ±0.72
a
9.9 ±0.88
a
10.96 ±0.96
a
0.584
Crown surface
area(m
2
)
105.95 ±
11.26
ab
77.95 ±
10.05
b
125.23 ±
16.01
a
0.036*
Crown volume
(m
3
)
581.83 ±
117.90
a
520.24 ±
112.61
a
516.57 ±
103.42
a
0.898
Bole(m) 18.5 ±1.22
b
18.3 ±1.21
b
22.25 ±1.04
a
0.024*
Crown ratio 0.38 ±0.02
a
0.30 ±0.02
b
0.36 ±0.02
a
0.013*
H/D 60.45 ±
4.75
ab
66.77 ±3.51
a
51.85 ±3.24
b
0.035*
CA 0.37 ±0.02
a
0.31 ±0.01
b
0.35 ±0.02
ab
0.035*
DBH (diameter at breast height), H/D (height/diameter ratio), CA (minimum
radius/maximum radius); Signicantly different means are indicated by
different letters. (SNK test, * P <0.05, mean ±SE); n: number of beech tree.
Table 4
Comparison of mean (±SE) morphology of beech trees between gaps and adja-
cent closed stands.
Parameter Gaps Gap (n =60) Adjacent stand(n =60) P-value
Total height(m) 30.12 ±1.53 31.78 ±1.07 0.293
DBH(cm) 10.9 ±1.51 11.1 ±0.52 0.782
Crown length(m) 11.28 ±0.48 11.14 ±0.43 0.831
Crown width(m) 11.13 ±0.52 10.82 ±0.47 0.658
Crown surface area(m
2
) 102.73 ±7.56 120.44 ±12.79 0.228
Crown volume(m
3
) 614.26 ±73.08 699.89 ±81.67 0.435
Bole(m) 19.82 ±0.88 20.92 ±0.85 0.357
Crown ratio 0.34 ±0.01 0.36 ±0.01 0.306
H/D 59.25 ±2.38 57.18 ±2.24 0.503
CA 1/82 ±0.06 1.54 ±0.05 0.001
**
DBH (diameter at breast height), H/D (height/diameter ratio), CA (minimum
radius/maximum radius);
**
P <0.01; n: number of beech tree.
A. Amolikondori et al.
Ecological Indicators 127 (2021) 107689
4
DBH, crown length and bole for beech trees were signicantly nega-
tively correlated. The CA ratio increased signicantly with increasing
the bole of trees in research site. The crown radii of border trees towards
gap center were signicantly larger than those of forest-facing side of
trees (Fig. 3, t = − 2.94, df =116, Sig. =0.004). Beech tree traits
highlighted slight differences among the cardinal points of each gap size
(Table 7).
5. Discussion
Results from this study provide insight into how harvested-created
gaps impact beech tree structure in the temperate forest. The results
conrmed that gaps created by single-tree selection system inuenced
beech tree traits at the edge of gaps (Table 3). Forest gaps (n =15)
formed by selection system occupied 0.63% of the forest stand and thus
the gaps in this site might contribute in beech forest structure. Large
gaps signicantly increased the crown width, crown surface area, and
bole of gap-edge trees while the effects of small and medium gap were
weak. The increase in abovementioned parameters in larger gaps can be
attributed to the increase in light and temperature in these gaps as
mentioned by Zhao et al., (2015). Trees demonstrate notable plasticity
in reaction to the environmental conditions (Van de Peer et al., 2017).
The structure of shade-tolerant plant is devised to absorb light and
morphological characteristics like crown size are generally determined
by light competition; Therefore, tree growth to a large extent is
dependent on light capture (Fichtner et al., 2013). Signicant morpho-
logical differences in our study show that beech trees at the edge of gaps
are able to change their architecture. In this study, trees H/D ratio varied
signicantly with regard to gap size. According to Juchheim et al.,
(2017), trees with higher H/D ratio show more susceptibility to wind
injury within forest; therefore, it can be stated that the beech trees at the
edge of medium gaps are exposed to wind damages within beech stand.
Studies on pure stands conrmed that wood quality of trees is identied
by its crown and stem structure (Pretzsch, 2014). The higher values for
some features of beech trees such as CA, H/D, height, and the bole at the
gap edge and in the north-facing can be attributed to light conditions in
this direction (Table 3). Pedersen and Howard (2004) asserted that in
northern latitudes, overstory trees situated in the north-facing edge of a
gap will receive more light and may display a stronger growth reaction
to the gap-edge environment. Many studies have stated that the highest
amount of light was observed in the northern side of gaps and the lowest
amount was found in the southern side (Hu et al., 2010). The distribu-
tion of light availability among vertical layers may determine spatial
arrangement of tree architecture in a forest (yang et al., 2015). Over-
story trees in the study area have little below ground competition from
understory trees in the gaps. Light availability in the gaps is signicantly
different from that in the adjacent closed forest (Muth and Bazzaz,
2002). The articial gaps were 6 years old at the time we measured tree
morphology so it sounds impossible that this duration have essentially
caused high growth in tree attributes at edge of gaps. The greater H/D
ratio of oriental beech trees at the edge of gaps could be a sign of
increased competition for light for beech in gaps. A higher H/D ratio is
an indication of greater light competition (Thurm and Pretzsch, 2016).
We did not nd any signicant differences in beech trees structure in
gaps and closed adjacent canopy (Table 4). This nding conrm that
there are relatively similar environmental conditions between gaps and
closed stand after applying single-tree selection harvesting in site. The
variations in length of the clear bole, crown ratio and CA in beech trees
at different positions and at edge of gaps might be attributed to light,
humidity conditions, tree growth (Table 5), so it may positively affect
tree value although gap formation may negatively affect economic value
of the trees in the border, particularly for long periods of time (Seidel
et al., 2016). The different size of beech tree crown radii at the edge of
Table 5
Beech tree traits (mean ±SE) at the four cardinal points of gaps in the research site.
Parameter North(n =15) South(n =15) East(n =15) West(n =15) P-value
Total height(m) 31.7 ±1.61
a
32.9 ±1.27
a
30.8 ±2.95
a
26.3 ±2.51
a
0.174
DBH(cm) 50.7 ±5.56
a
58.9 ±1.27
a
61.3 ±7.79
a
51.51.6 ±7.69
a
0.610
Crown length(m) 10.9 ±0.74
a
11.0 ±0.52
a
11.4 ±1.12
a
10.4 ±1.26
a
0.905
Crown width(m) 11.6 ±1.15
a
11.3 ±0.86
a
10.42 ±1.12
a
10.2 ±0.97
a
0.704
Crown surface area(m
2
) 90.55 ±9.82
a
108.21 ±8.36
a
87.71 ±13.41
a
91.29 ±15.48
a
0.704
Crown volume(m
3
) 357.04 ±84.01
a
645.82 ±114.62
a
632.28 ±159.74
a
466.95 ±104.89
a
0.294
Bole(m) 20.94 ±1.03
a
21.44 ±0.98
a
21.94 ±2.34
a
14.84 ±1.71
b
0.009
**
Crown ratio 0.36 ±0.01
ab
0.34 ±0.01
ab
0.31 ±0.02
a
0.39 ±0.02
a
0.047*
H/D 64.9 ±5.3
a
58.7 ±5.04
a
56.4 ±4.1
a
60.4 ±5.5
a
0.680
CA 1.9 ±0.16
a
1.7 ±0.11
ab
1.8 ±0.08
ab
1.5 ±0.04
b
0.042*
DBH (diameter at breast height), H/D (height/diameter ratio), CA (minimum radius / maximum radius); * P <0.05;
**
P <0.01; Different letters indicate signicant
differences between treatments; n: number of beech tree.
Table 6
Pearson’s correlation (r) and p values for the correlation between the CR, HD, CA ratios and morphological attributes for beech trees at edge of gaps.
Parameter CR H/D CA
Total height(m) r = − 0.287* p =0.026 r = − 0.419
**
p =0.000 r =0.245 p =0.060
DBH(cm) r =0.264* p =0.045 r = − 0.836
**
p =0.000 r =0.193 p =0.140
Crown length(m) r =0.526
**
p =0.000 r = − 0.416
**
p =0.001 r =0.123 p =0.349
Crown width(m) r =0.302* p =0.019 r = − 0.193 p =0.139 r =0.180 p =0.168
Crown surface area(m
2)
r =0.132 p =0.315 r = − 0.046 p =0.735 r =0.026 p =0.843
Crown volume(m
3
) r =0.281* p =0.030 r =0.021 p =0.873 r =0.054 p =0.680
Bole(m) r = − 0.619
**
p =0.000 r = − 0.260* p =0.045 r =0.332* p =0.013
DBH (diameter at breast height), CR (crown ratio), H/D (slenderness factor), CA (minimum radius/maximum radius); * P <0.05;
**
P <0.01.
5.57
4.31
0
1
2
3
4
5
6
gnicaf-tserofpagdrawot
radii(m)
Fig. 3. Comparison of mean values of beech trees radii (m) between toward
gap center and forest-facing side.
A. Amolikondori et al.
Ecological Indicators 127 (2021) 107689
5
gap and forest-facing side can be associated to high level of light and
decreased competition in gaps (Fig. 3). Lu et al., (2015) found that the
lateral growth of trees at edge of gaps was enhanced after forest gap
creation. Muth and Bazzaz (2002) reported that canopy depth of toward
gaps in trees was larger than on forest-facing directions in a mature
mixed hardwood stand. Forest gap generate varied light condition and
competition identify the tree crowns position (Schr¨
oter et al., 2012).
Seidel et al., (2016) asserted that increased light in forest gap cause
crown asymmetry of the bordering trees in the direction of gap center.
The horizontal extension in the overstory trees of the gap edge play an
important role in gap closure and these conditions can be expected in the
harvest-created gaps in oriental beech stand. In general, crown of trees
grows to gap-facing sides for absorbing light (Olivier et al., 2016) and
Pretzch and Schutze (2016) believed that crown position of trees reveals
the light conditions. The correlation among some features of beech trees
at the edge of gaps (Table 6) can be attributed to tree species architec-
tural model and genotype and competition based on Schr¨
oter et al.,
(2012). In the cardinal points of each gap in the site, there was a slight
difference among some features of the beech trees at the edge of gap
(Table 7) and these differences actually reect the effect of gap size on
beech tree morphology after six years. All trees at the border of gaps
positioned in overstory and it can be play important role in tree struc-
ture. It is clear that tree structure could be impacted by vertical crown
position of it in a forest stand (Yang et al., 2015), especially at the edge
of gaps.
6. Conclusions
Dynamic changes in beech tree traits indicate beech tree develop-
ment is signicantly affected by canopy position at the gap edge and the
vertical and lateral crown expansion is related to environmental con-
ditions in different gap sizes created by single-tree selection harvesting.
This study conrmed that single-tree selection system has signicant
impacts on beech tree morphology within forest stand. The lack of sig-
nicant differences between gaps and closed canopies in terms of tree
structure indicate that gap creation could be considered as a manage-
ment approach to foresters. By examining gap formation mechanisms,
gap features, and tree response to forest gaps, we can achieve a better
understanding of the role of gap dynamics in the development of broad-
leaved forests.
Author contributions
AAK conducted the eld work, AAK, KAV and MF performed the
statistical analysis and wrote the draft and contribute to the nal
manuscript.
Declaration of Competing Interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
the work reported in this paper.
Acknowledgements
I would like to extend our gratitude to Lorestan University, Lorestan,
Iran to provide us with nancial supports.
Funding
This work was supported by the Lorestan Unversity, Iran.
Table 7
Comparison of means (SE) of beech tree morphology in cardinal directions for each gap size.
Small gap(n =
5)
Medium gap(n
=5)
Large gap(n =
5)
Variable North South East West North South East West North South East West
CL(m) 10.91 (2.58) 10.81 (1.01) 12.20 (1.54) 13.25 (2.43) 10.32 (0.81) 10.66 (1.00) 9.58 (2.30) 8.23 (2.15) 10.91 (2.58) 10.81 (1.01) 12.20 (1.85) 13.25 (2.43)
CA 1.61 (0.13) 1.68 (0.24) 1.73 (0.13) 1.45 (0.05) 2.29 (0.35) 1.90 (0.14) 1.98 (0.15) 1.82 (0.27) 2.57 (0.65) 1.58 (0.18) 2.14 (0.26) 1.65 (0.14)
CR 0.37 (0.03) 0.38 (7.68) 0.34 (0.05) 0.39 (0.03) 0.33 (0.02) 0.32 (0.02) 0.40 (0.14) 0.41 (0.15) 0.34 (0.03) 0.34 (0.03) 0.32 (0.03) 0.43 (0.04)
H(m) 31.20 (2.78) 34.40 (2.80) 27.0 (6.30) 23.60 (2.99) 29.00 (1.94) 32.80 (2.61) 28.60 (5.51) 25.40 (5.88) 30.80 (5.58) 31.60 (1.12) 37.00 (2.70) 30.00 (4.13)
DBH
(cm)
52.00 (9.02) 65.0 (6.51) 55.0 (13.78) 47.0 (14.71) 46.00 (4.84) 53.00 (10.67) 53.00 (13.83) 48.00 (13.74) 64.00 (15.76) 69.00 (13.17) 76.00 (13.26) 60.00 (13.78)
CW(m) 9.74 (1.94) 11.98 (1.93) 9.42 (1.87) 9.25 (1.22) 9.92 (1.28) 10.48 (1.63) 10.58 (2.33) 9.56 (2.21) 15.31 (1.83) 11.40 (1.10) 11.28 (1.96) 11.36 (1.75)
Bole(m) 19.54 (1.75) 21.40 (1.75) 17.79 (4.41) 13.99 (1.66) 20.68 (1.79) 22.14 (2.26) 19.02 (6.31) 17.17 (5.49) 19.89 (93.43) 20.79 (1.28) 24.80 (2.05) 16.75 (2.37)
CSA(m
2
) 158.32
(54.42)
112.17
(11.39)
97.49 (22.86) 132.89
(27.07)
88.96 (17.67) 88.70 (25.22) 90.26 (19.71) 48.10 (17.31) 158.32
(54.42)
112.17
(11.39)
97.50 (22.86) 132.89
(27.07)
CV(m
3
) 720.70
(405.85)
564.26
(111.10)
784.14
(308.62)
881.92
(401.73)
421.90 (118.42) 525.28
(215.27)
637.03
(328.43)
496.72
(258.37)
720.70
(405.85)
564.26
(111.10)
784.14
(308.62)
881.92
(401.73)
H/D 65.41 (8.92) 55.13 (7.64) 54.31 (7.76) 65.95 (14.24) 69.64 (6.28) 68.68 (9.56) 62.13 (8.17) 59.85 (7.10) 59.59 (12.72) 52.23 (8.83) 52.84 (6.70) 54.38 (6.82)
CL (crown length), CA (minimum radius/maximum radius), CR (crown ratio), H (height), DBH (diameter at breast height), CW (crown width), CSA (crown surface area), CV (crown volume), H/D (height/diameter ratio).
A. Amolikondori et al.
Ecological Indicators 127 (2021) 107689
6
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