Download Twenty years of community dynamics in a mixed conifer – broad

1363
Twenty years of community dynamics in a mixed
conifer – broad-leaved forest under a selection
system in northern Japan
Toshiya Yoshida, Mahoko Noguchi, Yukio Akibayashi, Masato Noda,
Masahiko Kadomatsu, and Kaichiro Sasa
Abstract: Single-tree selection has been employed widely in northern Japanese mixed forests, but management-induced
changes in forests are not well understood. This study examined demographic parameters of major tree species during
a 20-year study of a 68 ha stand in which single-tree selection has been conducted since 1971. Results showed that
growth and survival of conifers (mostly Abies sachalinensis (Fr. Schm.) Masters) was the most strongly positively affected by the treatment. Nevertheless, recruitment of conifers was not sufficiently improved, suggesting their decreased
dominance over the longer term. Instead, shade-intolerant broad-leaved species (mainly Betula ermanii Cham.) will
gradually increase because of their higher recruitment rates after the treatment. Shade-tolerant broad-leaved species
(mainly Acer mono Maxim. and Tilia japonica (Miq.) Simonkai) appeared to experience the most distinct negative effects, especially on survival. These trends differed markedly from those reported in previous papers concerning partial
harvesting systems, which predicted an increase in dominance of shade-tolerant species. The results shown here should
be generalized carefully because we have investigated only one stand without repetition of the control area. Nevertheless, trends described in this large-scale, long-term study could provide a basis for simulating stand dynamics. We discussed possible reasons for the observed patterns and provided implications for sustainable management in the region.
Résumé : Le jardinage par pied d’arbre a été largement utilisé dans les forêts mixtes du nord du Japon, mais les changements induits par l’aménagement des forêts ne sont pas encore bien compris. Cette étude se penche sur les paramètres démographiques des principales espèces arborescentes sur une période de 20 ans dans un territoire d’étude de
68 ha à l’intérieur duquel le jardinage par pied d’arbre est appliqué depuis 1971. Les résultats montrent que la croissance et la survie des conifères (surtout Abies sachalinensis (Fr. Schm.) Masters) ont le plus bénéficié du traitement.
Néanmoins, le recrutement des conifères n’a pas été suffisamment amélioré, ce qui suggère une diminution de leur dominance à long terme. En contrepartie, la présence de feuillus intolérants à l’ombre (surtout Betula ermanii Cham.)
augmentera graduellement à cause de leur taux de recrutement plus élevé après le traitement. Les feuillus tolérants à
l’ombre (surtout Acer mono Maxim. et Tilia japonica (Miq.) Simonkai) semblent connaître les effets négatifs les plus
marqués, particulièrement dans le cas du taux de survie. Ces tendances vont clairement à l’encontre de celles qui ont
été publiées précédemment au sujet des systèmes de coupe partielle et qui prévoyaient plutôt une augmentation de la
présence d’espèces tolérantes à l’ombre. Les résultats devraient être généralisés avec précaution parce que les auteurs
n’ont étudié qu’un seul peuplement sans répétition de la zone témoin. Néanmoins, les tendances décrites dans cette
étude à long terme sur un grand territoire pourraient servir de base pour simuler la dynamique des peuplements. Ils
discutent des raisons qui pourraient expliquer les résultats qu’ils ont observés et faitent état des implications pour
l’aménagement durable dans la région.
[Traduit par la Rédaction]
Yoshida et al.
1375
Received 14 August 2005. Accepted 23 January 2006. Published on the NRC Research Press Web site at http://cjfr.nrc.ca on
11 May 2006.
T. Yoshida.1 Uryu Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Moshiri, Horokanai
074-0741, Japan.
M. Noguchi. Faculty of Environmental Earth Science, Hokkaido University, Tokuda 250, Nayoro 096-0071, Japan.
Y. Akibayashi and K. Sasa. Field Science Center for Northern Biosphere, Hokkaido University, Sapporo 060-0809, Japan.
M. Noda. Wakayama Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Hirai, Kozakawa
649-4563, Japan.
M. Kadomatsu. Nakagawa Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Otoineppu
098-2501, Japan.
1
Corresponding author (e-mail: [email protected]).
Can. J. For. Res. 36: 1363–1375 (2006)
doi:10.1139/X06-041
© 2006 NRC Canada
1364
Introduction
Recently, the use of partial harvesting systems is raising
concerns about managing forests both for timber production
and ecosystem functions (Oliver and Larson 1996; Kohm
and Franklin 1997; von Gadow et al. 2002) because it often
engenders stands with complex structure and composition
(O’Hara 1998; Deal 2001; Deal and Tappeiner 2002; Harvey
et al. 2002). In a northern Japanese mixed conifer – broadleaved forest (including Abies, Picea, Acer, Tilia, Quercus,
Betula, etc.), a typical forest type of that region (Tatewaki
1958), a selection system (single-tree selection) has been
widely employed since its exploitation began in the early
20th century as a superior option to manage natural forests.
Most forests have experienced at least one instance of harvesting in the past. However, despite basic silvicultural principles (e.g., Smith et al. 1997), actual harvesting practices
were often excessive and showed preferential extraction of
large trees (Nagaike et al. 1999), thereby degrading regional
forests. Most previous studies of harvesting practices in
northern Japan have emphasized sustainable yields (Ohgane
et al. 1988; Nigi et al. 1998); few studies have examined
broader objectives, including maintenance of biodiversity.
Contributing factors for ecosystem integrity (Hunter 1999),
such as changes in stand structure and tree species composition, have not been well understood.
Sustainable forestry attempts to mimic natural disturbances through management practices (Spence 2001; Franklin et al. 2002; Mitchell et al. 2002). The natural disturbance
regime of northern Japanese mixed forests is a combination
of rare large-scale blowdown (>10 000 m2; note that fire is
unimportant in this region) and frequent small-scale tree
death (<1000 m2: Ishikawa and Ito 1989; Kubota 1995;
Nakashizuka and Iida 1995). Although little information is
available regarding the large-scale disturbances in this region, several previous studies have predicted that the establishment of some major component tree species, including
Betula ermanii Cham., Quercus crispula Bl., and Abies
sachalinensis (Fr. Schm.) Masters, is closely related to largescale disturbances (Suzuki et al. 1987; Sano 1988; Ishikawa
and Ito 1989; Osawa 1992; Ishizuka et al. 1998). On the
other hand, as shown in many other regions (Hibbs 1982;
Runkle 1985; Tanaka and Nakashizuka 1998), small-scale
disturbances have been shown to have a fundamental influence on the structure of these natural forests. Natural tree
mortalities in terms of basal area observed in this region
were frequently less than 1% per year (Hiura and Fujiwara
1999; Kubota 2000); some major tree species (Abies
sachalinensis, Acer mono Maxim., and Sorbus commixta
Hedl.) regenerate in the resultant canopy gaps (Ishizuka
1984; Kubota et al. 1994; Hiura et al. 1996; Kubota 2000;
Takahashi et al. 2003).
The objective of this study was to present implications for
sustainable harvesting systems, particularly through evaluating the effects of harvesting on tree species composition.
Single-tree selection superficially resembles a small-scale
disturbance regime (creation of canopy gaps), but it engenders some fundamental differences, such as removal of
stems and the consequent reduction of fallen trees (Noguchi
and Yoshida 2004). In a mixed forest, we can therefore predict that single-tree selection generally enhances the estab-
Can. J. For. Res. Vol. 36, 2006
lishment and growth of particular species that adapt ecologically to small canopy gaps (cf. Runkle 1982; Canham and
Marks 1985; Runkle and Yetter 1987; Abe et al. 1995;
Messier et al. 1999). In fact, some North American studies
have reported that dominance of shade-tolerant species gradually increases after single-tree selection (Leak and Fillip
1977; Jenkins and Parker 1999; Webster and Lorimer 2002;
Shuler 2004). Nevertheless, such a trend in compositional
change may differ among forest types. Constituent species
probably adapt to inherent environmental conditions and
interspecific relationships, both of which can be strongly affected by harvesting treatment. The northern Japanese mixed
forest is characterized by a relatively large gap area in the
canopy layer, which is often more than 20% (Kubota 1995,
2000; Takahashi et al. 2003). This characteristic is conspicuously apparent in heavy-snowfall regions; it is inferred to be
related to slow recruitment rate caused by dense undercover
of dwarf bamboo species (Sasa kurilensis (Rupr.) Makino &
Shibata or Sasa senanensis (Franch. & Savat.) Rehd.)
(Takahashi 1997; Umeki and Kikuzawa 1999). Small trees
may not respond directly to single-tree selection because
dwarf bamboos increasingly dominate the canopy gaps
(Noguchi and Yoshida 2005; cf. Messier et al. 1998).
We addressed the following questions in this study:
(1) Does single-tree selection change tree species composition? (2) If change occurs, does it correspond to the expectations derived from characteristics (e.g., shade-tolerance) of
constituent species? We examined 20 years of community
dynamics of a mixed conifer – broad-leaved forest in northern Japan under a selection system by which single-tree selection at 10-year intervals had been conducted since 1971.
We compared demographic parameters of major component
tree species (and species groups) between treated and untreated areas based on a repeated census of ca. 27 000 individuals in a large (68 ha) plot. We summarized species
recovery for that period and discussed long-term effects of
single-tree selection on stand structure and species composition in the region.
Methods
This study was conducted in the Nakagawa Experimental
Forest of Hokkaido University (44°48′N, 142°14′E, 150 m
elevation; Fig. 1). The forest is located in a cool-temperate
region with heavy snowfall in winter. Typical vegetation in
the Nakagawa forest is mixed conifer – broad-leaved forest,
as described by Tatewaki and Igarashi (1971). This type of
forest is widely distributed in northeastern Asia as representative natural vegetation (Tatewaki 1958) and is responsible
for regional biodiversity. The mean annual temperature is
5.4 °C and the mean precipitation is 1449 mm. Nearly half
of the precipitation falls in the nongrowing season
(November–April). Snow cover usually extends from early
November to early May, with a maximum depth of 200 cm.
The soils are classified as Inceptisol (acidic brown forest
soil), and the predominant bedrock is Cretaceous sedimentary rock (Tatewaki and Igarashi 1971).
Since 1967, a long-term study has been conducted at a
110 ha study site (Fig. 1, Table 1). Few large-scale disturbances or outbreaks were recorded during the study period,
enabling us to clearly evaluate the effects of selection har© 2006 NRC Canada
Yoshida et al.
1365
Fig. 1. Location and topography of the study area. Compartments 5–10 (62.1 ha) and the control (5.9 ha) were studied.
Table 1. Description of the study forest.
Basal area (m2/ha)
Compartment*
Area (ha)
Initial
First period
Second period
Census year†
5
6
7
8
9
10
Control
11.1
5.6
8.2
6.7
12.9
17.6
5.9
27.8
34.0
22.6
27.9
25.3
31.4
26.6
6.8
4.4
3.2
2.9
5.3
6.8
0.0
3.2
5.7
4.2
3.8
3.4
4,2
0.0
1970,
1971,
1972,
1974,
1976,
1977,
1979,
1980,
1981,
1982,
1983,
1984,
1985,
1990
1990
1991
1992
1993
1994
1995
*Compartments 1–4 were not analysed in this study, because their trees were censused without individual
identification.
†
The census years were in the year before harvesting.
vesting. The primary objective of the original study was to
develop a relevant management system to extract sustainable
yield (Ohgane et al. 1988; Nigi et al. 1998). The “check
method” presented by Knuchel (1953), which was intended
to maintain timber volume and quality in the stand, was applied (see later paragraph for detailed practices).
The original stand had a multiaged structure that was similar to that of other mixed forests in the region (Suzuki et al.
1987; Takahashi et al. 2003). Before plot establishment, the
stand had been partially harvested at very low intensity for
domestic fuel materials. The sum of the basal area at the
first census (i.e., preharvest basal area) was 29.9 m2·ha–1,
which was typical of the region. There were 27 tall-tree species in all (4 evergreen conifers and 23 deciduous broadleaved species), of which Abies sachalinensis shared nearly
half of the total basal area, with lesser areas occupied, in
descending order, by Acer mono, Tilia japonica (Miq.)
Simonkai, Quercus crispula, Betula ermanii, and others (see
Table 2 for a complete list).
The forest was divided into 11 compartments (areas ranging from 5.6 to 17.6 ha) including a control compartment
(5.9 ha). The dominant species showed no strong preferences in their spatial distributions (T. Yoshida, unpublished
data), and tree species compositions before the treatments
were similar among the compartments. A selection system
was employed in which single-tree selections were conducted at 10-year intervals (one compartment per year). This
study analyzed 20 years of data (i.e., two rounds of harvesting) from six compartments and the control (68 ha in all),
within which 27 300 trees were censused individually and
identified with numbered tags. Compartments 1–4 were not
included in this study, because their censuses were conducted without individual identifications. The area, the sum
of the basal area, and the harvested level of the compart© 2006 NRC Canada
1366
Can. J. For. Res. Vol. 36, 2006
Table 2. Preharvest composition of trees with DBH ≥12.5 cm in the study forest.
Basal area
Species
Abbreviation
Group*
m2/ha
Abies sachalinensis
Acer mono
Tiljajaponica
Quercus crispula
Betula ermanii
Α1nus hirsuta
Magnolia obovata
Ulmus davidiana
Ulmus laciniata
Kalopanax pictus
Sorbus alnifolia
Sorbus commixta
Prunus sargentii
Phellodendron amurense
Prunus ssiori
Betula maximowicxiana
Picea jezoensis,
Taxus cuspidata
Fraxinus mandshurica
Salix hultenii
Swida controversa
Picea glehnii
Betula platyphylla
Acanthopanax sciadophylloides
Juglans mandshurica
Total
Conifer
Shade-tolerant broad-leaved
Shade-intolerant broad-leaved
AS
AM
TJ
QC
BE
AH
MO
UD
UL
KΡ
SA
SC
PS
PA
PR
BM
PJ
TC
FM
SH
SW
PG
BP
AC
JM
CF
BT
BT
BI
BI
BΙ
BI
BT
BT
BI
BT
BT
BT
BI
BT
BI
CF
CF
BT
BI
BI
CF
BI
BT
BT
14.68
3.10
3.06
3.06
2.17
0.64
0.56
0.49
0.44
0.28
0.23
0.23
0.21
0.18
0.12
0.10
0.08
0.07
0.05
0.04
0.04
0.03
0.02
0.01
0.01
29.9
14.9
8.0
7.1
%
49.1
10.4
10.2
10.2
7.2
2.1
1.9
1.6
1.5
0.9
0.8
0.8
0.7
0.6
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0.1
0.1
0.04
0.02
100.0
49.7
26.6
23.7
Density (stems/ha)
Max. DBH (cm)
80
70
75
150
95
75
45
80
65
100
50
45
45
50
50
75
55
60
65
40
45
55
50
40
25
150
80
80
150
212.9
78.9
50.4
33.1
27.1
12.3
16.2
6.8
6.0
3.5
6.1
7.3
6.4
4.8
3.2
1.0
1.0
1.4
0.9
1.6
1.2
0.3
0.5
0.4
0.3
484
216
167
101
*CF, conifer; BI, shade-intolerant broad-leaved species; BT, shade-tolerant broad-leaved species. The classification was based on Koike (1988) and
Masaki (2002).
ments are shown in Table 1. The mean harvested level in
terms of basal area was 19% (range 10%–28%) for the first
treatment and 16% (range 12%–18%) for the second treatment. These intensities were determined carefully in consideration of the census data, to maintain a harvested volume
equivalent to the growth (i.e., volume increment) of the
compartments. In these harvests, trees with a lower timber
value (i.e., with injury, crack, etc.) were selected mainly to
improve the future economic quality of the stand. Nevertheless, the harvested trees were selected from a broad range of
size classes and showed no bias for any particular tree species; the total amounts of harvested conifers and harvested
broad-leaved species were roughly equal.
Harvests were conducted in the winter. Trees were felled
and their major branches cut immediately using a chainsaw.
Then the logs were extracted using a tractor (a sled was used
only in a few early years). Snow, normally 100–200 cm
deep, covered the forest floor. Consequently, soil disturbances
that typically accompany treatments were minor. Although
supplemental plantings were conducted for some large
nonwooded openings (e.g., canopy gaps larger than 400 m2),
we did not consider them in this study because planted trees
did not reach the lower limit size set for the census (see later
paragraph). More detailed descriptions of the practices are
available in Ohgane et al. (1988).
In the 68 ha area, we identified 27 300 trees with a diameter at breast height (DBH) ≥12.5 cm. The DBH classes (5 cm
intervals) of all living trees were determined by measurement in the year before treatment. Checks of survival or
death, repeated measures of the DBH class, and records of
newly recruited trees were carried out in the second and
third censuses. The basal area of individuals was calculated
using the median of the DBH class. We calculated the following demographic parameters.
[1]
Tree DBH class promotion rate
⎡(N + N p) ⎤
= ⎢
⎥
⎦
⎣ N
0.1
−1
01
.
[2]
⎡(N − N d ) ⎤
Tree mortality = 1 − ⎢
⎥
⎦
⎣ N
[3]
⎡(N + N r ) ⎤
Tree recruitment rate = ⎢
⎥
⎦
⎣ N
0.1
−1
where N represents the initial tree number (except for harvested trees); Np is the number of trees that are promoted to
the next DBH class; Nd is the number of naturally dead
© 2006 NRC Canada
Yoshida et al.
1367
Fig. 2. The DBH class promotion rates in the treated area (first and second periods) and the control.
0.05
0.05
DBH class promotion rates (year-1)
All
0.04
0.04
0.03
0.03
0.02
0.02
First period
Second period
Control
0.01
0.01
Conifer
0
0
0.05
0.05
Shade-tolerant
broad-leaved
0.04
0.04
0.03
0.03
0.02
0.02
0.01
0.01
0
0
12.5-22.4
22.5-32.4
32.5-42.4 42.5-52.4
Shade-intolerant
broad-leaved
12.5-22.4
22.5-32.4
32.5-42.4 42.5-52.4
DBH class (cm)
trees; and Nr is the number of trees recruited during the
10-year period. Compartments with exceptional intervals
(8 or 9 years) in the first period were calculated separately;
then the weighted averages by area were used as a representative value. We calculated these indices for four DBH
classes (12.5–22.4, 22.5–32.4, 32.5–42.4, and over 42.4 cm
(in the case of the DBH promotion rate, 42.5–52.4 cm)) by
species. In addition, species were grouped into conifer,
shade-tolerant broad-leaved species, and shade-intolerant
broad-leaved species to summarize the results. The conifer
group consists of four shade-tolerant species, represented
mostly by Abies sachalinensis. The broad-leaved species
were classified with reference to previous studies of physiological traits (Koike 1988) or regeneration mode in an oldgrowth stand (i.e., species with abundant smaller trees are
assumed to be shade tolerant: Masaki 2002) (Table 2). Conifers shared nearly half of the total basal area: shade-tolerant
(dominated by Acer mono and Tilia japonica) and shadeintolerant broad-leaved species (dominated by Quercus
crispula and Betula ermanii) respectively shared a quarter.
Results
Growth
The DBH class promotion rates of the treated area were
lower than those in the control (about 0.8 times) in the first
period, but became higher (about 1.5 times) in the second
period in all the DBH classes (Fig. 2). Improvement in the
second period was particularly apparent for conifers, but not
so distinct for broad-leaved species. A markedly high promotion rate was observed in the largest DBH class (42.5–
52.4 cm) of shade-intolerant broad-leaved species in the
control, but it was not followed by that in the treated area,
even in the second period. In the first period, nearly half the
species had lower DBH promotion rates in the treated area
than in the control (Fig. 3). In the smallest DBH class (12.5–
22.4 cm), shade-tolerant broad-leaved species tended to
show higher promotion rates, whereas shade-intolerant
broad-leaved species tended to show lower rates. Nevertheless, in the larger DBH classes (≥32.5 cm), a shade-intolerant
broad-leaved species, Quercus crispula, which generally
showed the highest promotion rate among species in the
control, showed a considerably lower rate. In the second period, although the apparent decrease in the treated area was
observed only for Quercus crispula in the largest DBH class
(42.5–52.4 cm), most species showed an improved promotion rate. A shade-tolerant conifer, Abies sachalinensis,
showed the highest promotion rates among species in the
treated area in all the DBH classes in the second period.
Natural mortality
In the second period, natural mortality for the larger DBH
classes (≥32.5 cm) in the treated area was considerably lower
than in the control when considering all species (Fig. 4).
This trend was largely reflected by conifers, and the respective mortalities of broad-leaved (both shade-tolerant and
shade-intolerant) species in the treated area were rather
higher than of those in the control. Among shade-tolerant
broad-leaved species, the increase in mortality in the smallest DBH class (12.5–22.4 cm) was significantly large.
The species’ trends (Fig. 5) demonstrated that the range of
natural mortality among species was generally smaller in the
treated area than in the control: species with higher mortality
in the control tended to show a lower mortality rate, and vice
© 2006 NRC Canada
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Can. J. For. Res. Vol. 36, 2006
Fig. 3. DBH class promotion rates for major tree species in the treated area (first and second periods) plotted against those in the control. Species abbreviations are defined in Table 2.
0.1
0.1
(a) First period
12.5 ⱕ DBH < 22.5
AS
QC
AH
UD
KP
SA
QC
AS
TJ
BE SB
SB
SC
MO
SA
0.0
TJ
AM
PR
MO
PR
(b) Second period
12.5 ⱕ DBH < 22.5
PA
0.0
0.1
0.1
DBH class promotion rates (year–1) in the treated area
SC
UD
AM
PA
KP
AH
BE
AS
(c) First period
22.5 ⱕ DBH < 32.5
UD
QC
AS
QC
AH
TJ
AH
AM
UD
MO
TJ
(d) Second period
22.5 ⱕ DBH < 32.5
MO
AM
0.0
0.0
0.1
0.1
(e) First period
32..5 ⱕ DBH < 42.5
AS
QC
AS
UD
TJ
QC
UD
AM
TJ
(f) Second period
32.5 ⱕ DBH < 42.5
AM
0.0
0.0
0.1
0.1
(g) First period
42..5 ⱕ DBH < 52.5
AS
QC
AS
TJ
QC
TJ
0.0
0.0
0.1
0.0
(h) Second period
42.5 ⱕ DBH < 52.5
0.0
0.1
–1
DBH class promotion rates (year ) in control
conifer
shade-tolerant broad-leaved
versa. Trees in the larger DBH classes (≥ 32.5 cm) exhibited
generally lower mortality in the second period. In contrast,
for trees in the smaller DBH classes (<32.5 cm), the change
between the periods was small; it showed no general trend
among species.
Recruitment
For the three species groups, recruitment rates in the
shade-intolerant broad-leaved
treated area in the first period were similar to that in the
control and double that in the second period (Fig. 6). The recruitment rate of shade-intolerant broad-leaved species was
highest: in the second period, recruitment was roughly two
and three times higher than that of shade-tolerant broadleaved species and conifers, respectively. Although shadetolerant broad-leaved species had the lowest recruitment
rates among the groups in the control, they showed the
© 2006 NRC Canada
Yoshida et al.
1369
Fig. 4. Tree mortality in the treated area (first and second periods) and the control.
0.010
0.010
First period
All
Conifer
Second period
Tree mortality (year-1)
Control
0.005
0.005
0.000
0.000
0.010
0.010
Shade-tolerant
broad-leaved
Shade-intolerant
broad-leaved
0.005
0.005
0.000
0.000
12.5-22.4
22.5-32.4
32.5-42.4
42.5-
12.5-22.4
22.5-32.4
32.5-42.4
42.5-
DBH class (cm)
greatest improvement. In contrast, the improvement was
smallest for conifers.
Five species (four shade-intolerant broad-leaved and one
conifer) had lower recruitment rates in the treated area
(Fig. 7). However, in the second period, almost all the subjected species were over the equivalence line (i.e., the
treated area showed higher rates than the control), with considerable improvement of shade-intolerant broad-leaved species (such as Betula ermanii and Salix sp.). In contrast to the
control, Abies sachalinensis showed the lowest rate among
all species in the treated area. Shade-tolerant broad-leaved
species did not show a clear trend among species.
Change in basal area
Table 3 summarizes changes in basal area of species (and
species groups) during the 20-year study period. In total,
87% of the harvested basal area was recovered in that period; conifers showed considerably higher recovery (112%).
Three minor conifers (Picea jezoensis (Sieb. & Zucc.) Carr.),
Picea glehnii (Fr. Schm.) Masters, and Taxus cuspidate Sieb.
et Zucc.) showed a similar trend to that of Abies sachalinensis.
These high recoveries were mainly attributable to high
growth, and less so to recruitment.
In contrast, the recovery of shade-tolerant broad-leaved
species remained at only 48%, reflecting both low growth
and high mortality. In particular, species with high dead
basal area (Acer mono, Sorbus alnifolia (Sieb. & Zucc.) C.
Koch, and Prunus sargentii Rehd.) exhibited the lowest recovery. Shade-intolerant broad-leaved species showed intermediate recovery (85%), with high a contribution of
recruitment. The species with lowest recoveries (Magnolia
obovata Thunb., Alnus hirsuta Turcz., and Betula maximo-
wicziana Regel) in this group also showed high dead basal
area.
Discussion
Demographic parameters of tree species and species
groups differ widely between the treated area and the control; the response to single-tree selection changed considerably between the first and second harvests. Such a temporal
change in the response may be attributable to a delay in the
response of trees (e.g., Oliver and Larson 1996; Youngblood
and Ferguson 2003) and a cumulative effect of repetitive
harvests. General expectations of selection harvesting are increased growth, recruitment, and survival of trees, all positive effects, to compensate the loss of harvested trees.
Actually, opposite and negative effects were dominant in the
first period.
Many previous studies have suggested that partial harvesting systems can maintain structural complexities of the stand
(Deal 2001; Deal and Tappeiner 2002). We can expect that
the multiaged structure of this stand was generally maintained, because harvested trees were selected from a broad
range of size classes. Nevertheless, our results showed
clearly that selection harvesting changes tree species composition, even if basal area levels are nearly maintained. Although longer term trends do not necessarily follow the
observed characteristics of demography, we could applied
those results for predicting stand dynamics. In the short term
(i.e., several decades), Abies sachalinensis will become more
dominant relative to broad-leaved species because its growth
and survival were the most strongly positively affected by
selection harvesting. Such a positive response to small-scale
canopy disturbances has already been reported in natural for© 2006 NRC Canada
1370
Can. J. For. Res. Vol. 36, 2006
Fig. 5. Tree mortality for major tree species in the treated area (first and second periods) plotted against those in the control. Species
abbreviations are defined in Table 2.
0.02
0.02
(a) First period
12.5 ⱕ DBH < 22.5
(b) Second period
12.5 ⱕ DBH < 22.5
PS
SH
AH
AM
AM
UD
BE
TJ
TJ
SA
UD
MO
PA
PA
SC
AS
SA
SC
BE
QC
KP
0.00
PS
AH
AS
SH
QC
KP
MO
0.00
0.02
0.02
(d) Second period
22.5 ⱕ DBH < 32.5
(c) First period
22.5 ⱕ DBH < 32.5
AH
Mortality (year-1) in the treated area
AH
AM
MO
TJ
UD
QC
AS
QC
AM
TJ
0.00
0.00
0.02
0.01
UD
MO
AS
0.00
0.00
0.02
0.01
(f) Second period
32.5 ⱕ DBH < 42.5
(e) First period
32.5 ⱕ DBH < 42.5
AM
AM
UD
UD
AS
TJ
QC
AS
QC
0.00
TJ
0.00
0.01
0.01
(g) First period
42.5 ⱕ DBH
(h) Second period
42.5 ⱕ DBH
TJ
AS
QC
TJ
QC
AS
0.00
0.00
0.01
0.00
0.00
0.01
Mortality (year-1) in the control
conifer
shade-tolerant broad-leaved
ests (Hiura et al. 1996; cf. Veblen 1986), probably because
of the physiological ability of Abies spp. to rapidly respond
to increased light availability (Noguchi et al. 2003; cf.
Kneeshaw et al. 1998; Youngblood and Ferguson 2003).
Nevertheless, we found that recruitment of this species was
not sufficiently improved after the treatment: it was the lowest among major tree species. This trend should engender a
shade-intolerant broad-leaved
lack of small-sized trees and decreased dominance of this
species over the long term (i.e., more than 100 years).
Past studies have shown two different regeneration modes
of Abies sachalinensis: continuous age distribution, suggesting dependence of its regeneration on small-scale disturbances (Ishizuka 1984; Takahashi et al. 2003), and
discontinuous distribution, suggesting importance of large© 2006 NRC Canada
Yoshida et al.
1371
Fig. 6. Tree recruitment rate in the treated area (first and second periods) and the control.
Tree recruitment rate (year–1)
0.03
First period
Second period
Control
0.02
0.01
0
All
Shade-tolerant
broad-leaved
Conifer
Shade-intolerant
broad-leaved
Fig. 7. Tree recruitment rate for major tree species in the treated area (first and second periods) plotted against those in the control.
Species abbreviations are defined in Table 2.
Recruitment rate (year–1)
in the treated area
0.06
0.06
(b) Second period
(a) First period
KP
PA
SH
PA
BE
KP
SC
SH
UD
UD
SC
BE
MO
SA
PR
PS
QC
TJ
AM
MO
AH
SA
PR
AM
0.00
AS
0.00
0.06
PS
TJ
AH
QC
AS
0.00
0.00
0.06
Recruitment rate (year –1) in the control
conifer
shade-tolerant broad-leaved
scale disturbances (Suzuki et al. 1987; Ishikawa and Ito
1989). The present results are, at least, not consistent with
the former. We presume that the limited recruitment can be
explained as follows: (1) contrary to growth improvement
(see previous paragraph), photosynthesis of Abies sachalinensis was found to decrease in response to severe increased
light availability, especially in the dry summer (Noguchi et
al. 2003; cf. Kneeshaw et al. 2002; Bourgeois et al. 2004);
(2) because seedlings and saplings of this species are frequently distributed around the stems of overstory trees
(Suzuki et al. 1987; Takahashi 1997), they may be affected
greatly by physical damage accompanying the treatments
(Harvey and Bergeron 1989). In general, conifers are predicted to be more vulnerable to such physical damage than
are broad-leaved species because of the general inability of
conifers to sprout (Greene et al. 1999). Furthermore, because
conifers base their establishment largely on fallen logs as a
preferable substrate (Hiura et al. 1996), the possible decrease in fallen logs resulting from repetitive selection harvestings (Noguchi and Yoshida 2004) may accelerate that
decreasing trend over a longer term. This tendency should
be more apparent in minor conifer species in this forest (but
shade-intolerant broad-leaved
common in the region), Picea jezoensis and Picea glehnii,
which show a particular dependency upon fallen logs
(Kubota et al. 1994; Takahashi 1997).
Despite increased light availability after the selection harvesting, growth improvement of shade-intolerant broadleaved species was less than that of Abies sachalinensis.
Even in the second period, large-sized trees in the treated
area had considerably lower growth than those in the control. These facts seem to greatly reflect the trend observed
for Quercus crispula, but its small-sized trees showed an improved response (also see Yoshida and Kamitani 1998). A
great difference might exist in response to canopy opening
between size classes. Quercus crispula had discontinuous
age distribution in natural mixed stands (Sano 1988;
Takahashi et al. 2003), suggesting the lower contribution of
small-scale disturbances. Our results are consistent with this
hypothesis. Regarding other shade-intolerant broad-leaved
species, we found improved growth in small-sized Betula
ermanii and Alnus firma and decreased mortality in midsized Magnolia obovata and Kalopanax pictus (Thunb.)
Nakai. These are expected results in consideration of responses to high light availability (Ishikawa and Ito 1989).
© 2006 NRC Canada
1372
Can. J. For. Res. Vol. 36, 2006
Table 3. Changes in basal area during the 20-year study period.
Basal area (m2/ha)
Species
Abbreviation
Group*
Abies sachalinensis
Acer mono
Tilia japonica
Quercus crispula
Betula ermanii
Alnus hirsuta
Magnolia obovata
Ulmus davidiana
Ulmus laciniata
Kalopanax pictus
Sorbus alnifolia
Sorbus commixta
Prunus sargentii
Phellodendron amurense
Prunus ssiori
Betula maximowicziana
Picea jezoensis
Taxus cuspidata
Fraxinus mandshurica
Salix hultenii
Swida controversa
Picea glehnii
Betula platyphylla
Acanthopanax sciadophylloides
Juglans mandshurica
Total
Conifer
Shade-tolerant broad-leaved
Shade-intolerant broad-leaved
AS
AM
TJ
QC
BE
AH
MO
UD
UL
KP
SA
SC
PS
PA
PR
BM
PJ
TC
FM
SH
SW
PG
BP
AC
JM
CF
BT
BT
BI
BI
BI
BI
BT
BT
BI
BT
BT
BT
BI
BT
BI
CF
CF
BT
BI
BI
CF
BI
BT
BT
Harvested
(H)
Grown
(G)
Recruited
(R)
Naturally
dead (D)
4.454
1.299
0.842
0.689
0.803
0.245
0.248
0.204
0.017
0.049
0.094
0.117
0.097
0.043
0.024
0.035
0.004
0.013
0.004
0.010
0.014
0.001
0.002
0.005
0.002
9.315
4.471
2.705
2.139
5.189
0.521
0.546
0.738
0.365
0.157
0.083
0.143
0.103
0.102
0.037
0.044
0.026
0.062
0.026
0.014
0.039
0.010
0.024
0.021
0.010
0.012
0.017
0.003
0.005
8.296
5.250
1.477
1.569
0.286
0.136
0.114
0.101
0.137
0.056
0.046
0.036
0.009
0.069
0.012
0.032
0.013
0.093
0.009
0.013
0.003
0.003
0.016
0.022
0.024
0.001
0.010
0.002
0.002
1.245
0.292
0.381
0.571
0.526
0.277
0.127
0.118
0.052
0.071
0.034
0.006
0.085
0.006
0.012
0.009
0.016
0.010
0.012
0.012
0.003
0.002
0.005
0.005
0.001
0.000
0.004
0.002
0.001
1.396
0.532
0.552
0.313
Recovered
(G+R+D)/H
1.11
0.29
0.63
1.05
0.56
0.58
0.38
0.85
1.59
3.34
0.39
0.57
0.24
3.32
1.00
0.44
9.79
0.87
9.37
3.70
2.36
11.92
10.43
0.40
3.69
0.87
1.12
0.48
0.85
*CF, conifer; BI, shade-intolerant broad-leaved species; BT, shade-tolerant broad-leaved species. The classification was based on Koike (1988) and
Masaki (2002).
These species also showed higher recruitment rates after the
treatment, which may contribute considerably to their recovery. They may gain a relative advantage because their potential high growth rate occasionally enables them to escape
faster from the understory to a lighter environment. We can
expect these species to gradually increase in density after
several decades.
In contrast, shade-tolerant broad-leaved species appeared
to incur the most distinct negative effects from the treatment.
Recovery of the basal area (percentage of the increment to
that lost) in the 20-year period was only 48%; in particular,
recovery rates of Acer mono, Sorbus alnifolia, and Prunus
sargentii were less than 40%. These low recoveries were
mainly attributable to high mortality, presumably resulting
from increased risks of wind or frost damage through canopy exposure (Peltola et al. 1999). In addition, we found no
distinct positive effects of the treatment on growth of these
species. Despite some exceptions (e.g., small-sized Ulmus
davidiana Planch. var. japonica (Rehd.) Nakai and Sorbus
alnifolia), growth rates of dominant species (Acer mono and
Tilia japonica) were unchanged or decreased in the treated
area. This trend is consistent with a previous finding that
these species showed low plasticity of growth against high
light availability (Umeki 2001). In contrast, recruitment of
this species group increased in the second period, showing
the greatest improvement, compared with the control, among
the three species groups. However, the absolute amount of
recruitment was still half that of shade-intolerant species.
Our study demonstrated complicated responses of the
mixed-species community under the selection system. The
observed trends of change in species composition differ
markedly from those reported in North America (Leak and
Fillip 1977; Jenkins and Parker 1999; Webster and Lorimer
2002; Shuler 2004). We suspect that this difference is attributable to large canopy gap areas in the overstory and dominance of dwarf bamboo species in this forest’s understory.
Selection harvesting, and its consequent creation of canopy
gaps, increases dwarf bamboos (Noguchi and Yoshida 2005),
which thereby suppresses tree regeneration (Nagaike 1999;
Umeki and Kikuzawa 1999). Those two distinct characteristics are closely correlated. We presume that the results are
informative, even for management of stands with rich understory vegetation (e.g., Harvey and Bergeron 1989; Messier et al.
1998; Beckage et al. 2000; Bourgeois et al. 2004), where
© 2006 NRC Canada
Yoshida et al.
such an indirect negative effect of harvesting on light availability seems to occur.
The present results should be generalized carefully because we have investigated only one 68 ha stand without
repetition of the control area. Nevertheless, trends described
in this large-scale, long-term study present implications for
improving current harvesting practices. Attention should be
devoted to the possible change in species composition toward shade-intolerant broad-leaved species, which might alter the ecosystem integrity of these mixed forests.
Management plans must mitigate the negative effects of selection harvesting on growth, survival, and recruitment of
particular species. For conifer species, supplemental planting
or site preparation for natural regeneration (Wurtz and
Zasada 2001; Yoshida et al. 2005) should be included to enhance their recruitment. At the same time, while considering
the distinct negative effects, harvesting level of shadetolerant broad-leaved species should be limited to preserve
their relative dominance. We need more detailed mechanisms by which observed patterns and processes are produced. In particular, we note that the amount of recruitment
in this study might depend largely on preharvesting accumulation of a seedling bank because most of the recruited trees
seemed to be older than 20 years (H. Miya, unpublished
data). Longer term studies or those examining dynamics of
seedlings and saplings (M. Noguchi and T. Yoshida, in preparation) are needed. In addition, we should consider site
variations in the stand. Further studies that include responses
of individual trees with spatial consideration (M. Noguchi
and T. Yoshida, in preparation) are expected to yield additional important information. Together with the results of the
current study, these extension studies can form an appropriate basis for adaptive management in this region.
Acknowledgements
We would like to thank anonymous reviewers for their
helpful comments and suggestions. We gratefully acknowledge S. Taniguchi, E. Ohgane, T. Nigi, Y. Hishinuma, K.
Fujiwara, K. Koshika, and K. Kanuma for their combined efforts in maintaining this long-term study. We thank the staff
of the Nakagawa Experimental Forest for their proper management of fieldwork, harvesting practices, and the data collection. Thanks are also extended to the members of the
laboratory of forest management, Hokkaido University, for
their assistance in the fieldwork.
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