筑波大農林技研 第 2 号：  －18，2014

Age Structure and Development Process of a Secondary
Deciduous Broadleaf Forest in Central Japan
Sachiko ISHIHARA1 and Tatsuyuki SEINO2,3＊
1

College of Agro-Biological Resource Sciences, School of Life and Environmental Sciences,
University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan

2

Tsukuba Experimental Forest, Agriculture and Forestry Research Center,
University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8577, Japan

3

Faculty of Life and Environmental Sciences, University of Tsukuba,
Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan

Abstract
Age structure and growth analyses were conducted to reconstruct the disturbance history of asecondary Quercus crispula forest in Nagano Prefecture, central Japan. Two belt plots were placedin the forest (140 m × 4 m each) for measurement of their age. Disks of target trees were collected
at ground level for dendrochronological analysis; 124 disks were used. Quercus crispula and Betula
davurica dominated in both plots. The age peak of Q. crispula and B. davurica is recognized at 60-6
years old. The frequency distribution of tree diameters at ground level was bell-shaped, which reflects
regeneration after strong disturbances. Many of the Q. crispula were multi-stemmed and had sprouts.
Many Q. crispula and B. davurica trees were established during the 140s, indicating a stand-wide
major disturbance in that area. Agricultural cultivation and logging for charcoal and fuel wood in the140s could have initiated the regeneration of many current trees. These trees remain to the presentday, since forest use declined in the following period. This land-use history can also explain why thisstudy site was a relatively young stand, less than 100 years old, while Q. crispula is known as a longliving species.
Key words: Human disturbance; Quercus crispula; Secondary forest; Yatsugatake Mountains

function similarly, as partial logging creates
canopy gaps and land-use change, changing
the forest structure completely (Suzuki andTsukahara 1987; Hannah 1999). The natureof the disturbance, intensity, frequency, andarea impacts the population structure andcourse of succession (Foster et al. 1998). Many
studies have revealed the significant influenceof past land use on present forest vegetation

Introduction
It is widely accepted today that disturbanceplays an important role in forest dynamics
and regeneration, being a major force thatdrives vegetation mosaic structures (White
1979). Disturbances such as forest fires andwindstorms strongly influence forest structure
and composition. Human disturbances*Corresponding Author: Tatsuyuki SEINO Faculty of Life and Environmental Sciences, University of Tsukuba
Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan
E－mail: seino.tatsuyuki.gw@u.tsukuba.ac.jp──

筑波大農林技研 第 2 号 2014of secondary forests (Foster 1992; White andMladenoff 1994) and have confirmed theimportant role of historical human activities indetermining the current distribution of species(Bellemare et al. 2002; Foster 2002; Motzkin etal. 2002).
Secondary forests are generally establishedunder the strong influence of humandisturbances. One type of secondary forest inJapan is characterized as a coppiced forest,
which has been maintained by rotational
logging for fuel wood and charcoal. Frequentand intensive disturbances have promoted
the dominance of Quercus species (Abrams andDowns 1990). As a result, these forests are
dominated by oak species known as Quercus
crispula Blume, Quercus serrata Murray, andQuercus acutissima Carruth (Kimura et al.
1982). However, in the past several decades,
the use of these forests has declined due tolifestyle changes in Japan. Some studies
predict that Q. crispula will decline in density
due to lack of human disturbance by self
thinning (Masaki et al. 1992; Sano and Ohsawa
2008), while similar trends can be seen ineastern parts of the U.S.A. (Abrams and Downs
1990; Abrams 1992; Lorimer et al. 1994). On
the other hand, Quercus species are sometimes
considered to be late successional and an
important component of mature forests (Koike
1988; Kanazawa 1983; Ishikawa and Ito 1989).
To examine successional trends and thedevelopment process, it is important to understand the impact of past disturbance events on
the current forest structure, since the various
types and scales of disturbance influence theforest structure differently. To estimate pasttree growth, dendrochronological techniques
are effective to understand the forest history.
Abrupt increases in radial growth indicate releases due to the mortality of a former canopy
tree (Sugita 1993), and the synchrony of establishment periods correspond with past disturbance events (Svoboda et al. 2012; Suzuki
1979). By combining these methods, it is possible to reconstruct the development process ofthe current forest structure.
In this study, age structure and radial

growth analyses were conducted to reconstruct
the disturbance history of a secondary Quercus
crispula forest in Nagano Prefecture, central
Japan. The forests in this area are known
to have had frequent contact with humanactivities. However, whether the developmentof the current forest structure was influenced
by human or natural disturbance is still
unknown. To clarify the above subjects, thespecific objectives were to (1) examine thecurrent stand structure, (2) estimate theimpact of past disturbances by analysis of age
structure and radial growth patterns, and (3)reveal the development history in a secondary
forest in central Japan.
Methods
The study site
The study was conducted in the Yatsugatake
Forest, University of Tsukuba, Minami-Maki,
Nagano Prefecture, Japan (35°57’N, 138°28’
E). The study area is located in a secondary
broadleaf forest on a foothill at an elevationof approx. 1350-1450 m. Mean annual
precipitation is approx. 1450 mm, and meanannual temperature from 2000 to 2010 isapprox. 7°C (Inami et al. 2012).
Field methods
Two belt plots were placed (140-m ×4-m each)in the forest. Tree species and their location
were recorded for all trees larger than 10 cm
in girth at ground level. Basal area at groundlevel (BA0, m2 ha-1) was calculated as sum of
diameter at ground height (D0). The disk of thetarget trees were collected at ground level in2009 for dendrochronological analyses. Disks
were oven dried more than 48 hours at thelaboratory.
Dendrochronological analysis
Tree rings were counted at four cardinal
directions (NSEW), and the average of the four
directions was used as the age to avoid missing
rings. A total of 124 disks (55 from Belt-1 and
69 from Belt-2) were used. Five samples eachof Q. crispula and Betula davurica Pall. were used

─ 10 ─

Age Structure and Development Process of a Secondary Deciduous Broadleaf Forest in Central Japanfor radial growth analysis. To avoid climate
influences, ring width was measured at each 5
years at four cardinal directions (NSEW), andthe average of the four directions was used.
Results
Stand structure
Quercus crispula and Betula davurica dominatedin both Belt-1 and Belt-2. In relative,BA00, Q.
crispula shared 17.8% in Belt-1 and 59.7% in
Belt-2, and B. davurica shared 44.9% in Belt-1
and 13.4% in Belt-2 (Table 1). Malus toringo(Siebold) Siebold ex de Vriese shared 14.6%
in Belt-1, and Castanea crenata Siebold et Zucc.
Table 1

Fig.1

shared 9.6% in Belt-2.
Spatial distribution of stems with stem age
is shown in Fig. 1. There were no apparent
patches or relationships between age andlocation in either plot. In the two plots,
53.7% of Q. crispula stems and 50.0% of the B.
davurica stems were multi-stemmed by sprout
regeneration.
Fig 2 shows the frequency distribution of D0
for Belt-1 and Belt-2. Q. crispula, B. davurica, andC. crenata show a bell-shaped distribution witha mode of 20-24 cm, 25-30 cm, and 15-20 cm.
In comparison, M. toringo in Belt-1 and Symploco
sawafutagi Nagam. show an inverted J-shaped
distribution.

Relative basal area (BAO), number of trees per plot and basal area of species in each belt plot.

Spatial distribution of individual stems and age of Q. crispula (circle), B. davurica (triangle) and otherspecies (diamond) in Belt-1 and Belt-2 (140 ×4 m plot). Open and colored shapes indicate single-stemand multiple-stem, respectively.
─ 11 ─

筑波大農林技研 第 2 号 2014

Number of trees

Q. crispula
M. toringo

B. davurica

C. maximowiczii

S. sawafutagi

C.crenataS. udensis

Diameter at ground height (cm)Fig.2

Distribution of diameter at ground height of tree species in Belt-1 and Belt-2 (tree species were excluded
when number of trees were under two). Colored bars show Belt-1 and open bars show Belt-2.

Age structure
The age structure is shown of the two plots in
Fig. 3. Annual rings of 15 samples could not becounted completely due to stem decay at thecenter. The peak of Q. crispula and B. davurica isrecognized at 60-69 years old, and M. toringo in
Belt-2 showed a slight peak at 50-59 years old,slightly delayed from the former two species.
The oldest stem of Q. crispula was 74 years old
in Belt-2, and the oldest stem of B. davurica wasmore than 93 years old in Belt-1 (unknown
due to decay). The oldest stem of the researchplots was M. toringo at 103 years old. Figure 4
shows the relationships between tree age anddiameter at ground level for each belt plot.
There was no remarkable relationship between
age and D0.
Growth curve of diameter at ground level
The growth curve of diameter at ground levelfor five samples each from both belt plots ofQ. crispula and B. davurica are shown in Fig.
5. Remarkable growth change that indicatesrelease from suppression by canopy trees could
not be observed.

─ 12 ─

Age Structure and Development Process of a Secondary Deciduous Broadleaf Forest in Central JapanQ. crispula‫غ‬belt2

B. davurica

Number of trees

M. toringo

C. maximowiczii

S. sawafutagi

C.crenataS. udensis

Age (years)
Fig.3

Age frequency distributions of tree species in
Belt1 and 2 (tree species were excluded when
number of trees were under two.)

Discussion
Quercus crispula and Betula davurica dominatedin both belt plots. The distribution of tree
diameter at ground level of Q. crispula and B.
davurica was bell-shaped. In general, shadetolerant species that can regenerate undera closed canopy tend to show an inverted
J-shaped distribution, and shade-intolerant
sun trees that can only develop in open
environments show a bell-shaped distribution(Lorimer and Krug 2011). It is known that Q.
crispula in post-disturbance forest stands andBetula species show a bell-shaped distribution(Higo and Teramoto 1989), which reflects
regeneration after strong disturbances (Higo1990). Species that showed an inverted
J-shaped distribution, Malus toringo andSymploco sawafutagi, were likely to regeneratecontinuously independent of disturbances,in contrast to the other species that seem tohave a disturbance-dependent regeneration
pattern. From the age structure of this study,
M. toringo showed a wide range of ages, from
20 to100 years old, which supports continuous
regeneration. On the other hand, S. sawafutagi
also showed an inverted J-shaped distribution,
while the age structure showed a regeneration
pattern that was characterized as disturbancedependent. Individuals that regenerated andestablished at a similar period tend to show awide range in growth (Suzuki 1981), and thiscan be due to competition among individuals(Higo and Teramoto 1989).
Many Q. crispula at our study site were
multi-stemmed. Single-stem trees can beconsidered to have originated from seedlings
and multi-stemmed trees from stumps (Fujita
and Sano 2000). Kanazawa (1983) discusses
that continued existence and dominance of Q.
crispula may attest to its longevity and vigorous
sprouting ability. Since Q. crispula was foundrelatively young at this study site, we could
not find evidence of advantages of longevity inthis case. Meanwhile, some studies documentthat frequent and intense logging enhances
the dominance of Q. crispula (Fujita and Sano
2000). Thus, historical use as a coppice forest
benefited the sprouting ability of Q. crispulaand could have promoted the dominance of Q.
crispula through rotational logging.
In general, regeneration of Betulaceae isstrongly affected by large-scale disturbances.
For example, studies on mountainsides showthat surface disturbances such as landslides

─ 13 ─

筑波大農林技研 第 2 号 2014

Belt-160
Q. crispula50

B. davurica
M. toringo

D (cm)

40

others

30

20

10

0
0

10

20

30

40

50

60

70

80

90

100

60

70

80

90

100

Age (years old)

Belt-260
Q. crispula50

B. davurica
M. toringo

D (cm)

40

others

30
20
10
0
0

10

20

30

40

50
Age (years old)

Fig. 4

Relationship between age and D0 in Belt1 and Belt2.

are necessary for regeneration (Ogawa andOkitsu 2010), while B. davurica only exist
as individual trees in canopy gaps in areas
with a thick litter and humus layer and few
surface disturbances (Ogawa and Okitsu 2011).
Potential causes of surface disturbance that
initiated the regeneration of B. davurica at
this study site can include activities related tologging, such as dragging the logged trees orcreating temporary paths for logging operation.
Similar to Q. crispula, many of the B. davurica
trees at our study site were multi-stemmed andtherefore are assumed to have originated fromstumps. Thus, the ages of seed establishmentof these individuals stretch back to earlier
ages than the observed stem ages. Charcoal

─ 14 ─

Age Structure and Development Process of a Secondary Deciduous Broadleaf Forest in Central Japan

200
150

Belt 1
Belt 2100

Q. crispula
50

Radius (mm)0-80 -75 -70 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10

-5

200
150

B. davurica

100
50
0
-80 -75 -70 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10-5Years from present
Fig. 5 Some examples of the growth curve of diameter at ground level, measured at each 5 years for Q. crispulaand B. davurica in Belt-1 and Belt-2.

production has historically been an important
local industry around this study site (Village
History Publishing Association 1986). Hence,
operations related to these logging activities
may have caused surface disturbance andenhanced the establishment of B. davurica at
this study site.
For both Q. crispula and B. davurica, age
peaks were recognized at 60-69 years old,
meaning that many trees were establishedduring the 1940s. Therefore, a major
disturbance is likely to have occurred
around 1940. The slightly delayed peak of
M. toringo can be a delayed response to thesame disturbance event only due to species
characteristics. No apparent growth change
could be observed from individual growth
curves (Fig. 5), thus it is most likely that there

was no major disturbance within the past
60-70 years in this forest stand. From the latter
half of the 19th century to the period prior toWorld War II, charcoal production was one of
the major industries in this region (Kawakami
Village History Publish Association 1986;
Minamimaki-sonshi Editing Committee 1986).
During the war, while trees in the forest were
logged for fuel wood, the land was later set
as one of the exercise areas of the JapaneseArmy (Sunasaka 2006). After the WWII, theforest recovered from the exercise areas.
Gradually, the amount of logging declined
due to the replacement of wood with gas andelectricity for fuel and due to lifestyle changes
that decreased the demand for charcoal andfuel wood. The forest was established as
the University Forest in 1956 and has been─ 15 ─

筑波大農林技研 第 2 号 2014

managed by the staff of the University ofTsukuba since then. In conclusion, logging
activities for charcoal and fuel wood andagricultural cultivation in the 1940s could
be the major disturbance that initiated theregeneration of many trees constituting thecurrent forest structure. The trees establishedduring this period survive to the presentday, since forest use declined in the following
period. This land-use history can also explain
why this study site was a relatively young
stand, less than 100 years old, while Q. crispula
is known as a long-living species (Higo andTeramoto 1989).
Acknowledgments
We are grateful to Drs. Toru Nakamura, Takashi Kamijo, and Kiyokazu Kawada for theiradvice and encouragement throughout thisstudy. We also thank Akihiro Inami, Masanori
Sugiyama, and Kenta Nasu for kind field assistance; and staff members of the Yatsugatake
Forest, Agricultural and Forestry ResearchCenter, University of Tsukuba, for kind support during our stay.
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筑波大農林技研 第 2 号 2014

中部日本の落葉広葉樹二次林における樹齢構造と林分の発達過程

石原祥子1・清野達之2,3＊
1

筑波大学生命環境学群生物資源学類

305－85722茨城県つくば市天王台1－1－1

筑波大学農林技術センター筑波実験林

305－85773

305－8572

茨城県つくば市天王台1－1－1
筑波大学生命環境系
茨城県つくば市天王台1－1－1

要旨

長野県に位置する筑波大学農林技術センター八ヶ岳演習林のミズナラ二次林において、樹齢構造と成長解析から過去の撹乱履歴の再構成を行なった。八ヶ岳演習林内のミズナラ二次林に140m×4mのベルトプ
ロットを二箇所設置し、プロット内の樹木から124個の円板を採取し、樹齢を測定した。その結果、ミズナラとヤエガワカンバが両プロットで優占し、両種とも樹齢60－6にピークをもつ分布となった。胸高直径階分布も両種とも鐘形の分布となり、強い撹乱の影響を受けたことを反映していた。ミズナラの多くは萌芽由来の幹から構成されていた。このことから、ミズナラとヤエガワカンバの多くは、140年代に八ヶ岳演習林付近であった薪炭利用や造林による大規模な撹乱後に成立したと推測した。その後、薪炭利用や造林が行われなくなり、現在の林分はこの後に再生したものであろう。
キーワード：人為撹乱、二次林、ミズナラ、八ヶ岳連峰＊

連絡者：清野達之 筑波大学生命環境系
305－8572 茨城県つくば市天王台1－1－1
E－mail：seino.tatsuyuki.gw@u.tsukuba.ac.jp

─ 18 ─