C. obtusa

The spatial pattern and canopyunderstory association of trees in a
cool temperate, mixed forest in
western Japan
Nobuhiro Akashi
Introduction
• 針広混交林：北半球に広く分布
• 様々なサイズのパッチを形成
• その要因も様々
– 土壌と地形(soil and topography)
– 攪乱履歴(disturbance history)
– 種間競争(competitive interaction)
• Natural mixed forests which consist of evergreen conifers and
deciduous hardwood species are widely dispersed throughout
the northern hemisphere.
• Most species formed patches, although the causes of patch
formation were variable.
Study aims
• 針広混交林の樹種ごとの空間分布パターンの把握
• 分布パターン形成の要因の考察
– 種特性はあるのか、林冠木と下層木で分布パターンは異
なるのか
• To determine the spatial patterns of species over various
spatial scales in a mixed forest.
• To examines the causes of the spatial patterns of conifer and
hardwood species.
Study site
• 紀伊山地の大台ケ原(Ohdaigahara, in the Yoshino Kumano
National Park, Kii Peninsula, western Japan)
• 天然林(人為攪乱履歴なし)(primary forest with no artificial
disturbance)
• 標高(elevation):1400~1500m
• 年平均気温(mean annual temperature):6.4℃
• 年間降水量(annual precipitation):4734mm
• 下層植生(forest floor):スズタケ(Sasamorpha borealis)
Methods
• Line intersect sampling method
– usually applied to herbaceous vegetation
belt transect
line transect
• Eight parallel line transects were established ranging from 100
m to 400 m in length, at 50 m intervals.
Merit: 比較的簡単に広範囲の分布構造を知ることができるTrees in a large
area can be more easily sampled and spatial patterns detected.
Demerit: 小さな個体ほど検出されにくい
Smaller individuals are more difficult to identify than bigger individuals.
• 一本のトランゼクトを分割し、セクションごとに被度を調べる
• 分割する長さを変えることで、様々な空間スケールの分布パ
ターンを把握できる（今回は12.5,25,50,100,200ごとに分割）
• Dividing the line transects into sections of various length, the various scale
of patterns can be analyzed.
• Divided into sections 12.5,25,50,100, and 200 m long in this study.
80 m length transect
10 m
① 10m section section 1-1 section 1-2 section 1-3 section 1-4 secition 1-5 section 1-6 section 1-7 section 1-8
20 m
② 20m section
section 2-1
section 2-2
section 2-3
section 2-4
30 m
③ 30m section
section 3-1
section 3-2
×
•
•
•
•
対象：樹高1.3 m 以上
林冠木(15 m<)と下層木(<15 m)を区別
ギャップ:トランゼクト上に林冠木の樹冠がない部分
Trees taller than 1.3 m and whose crown projection intersected the line
transect were identified and the location of each crown projection over
the transect was recorded.
• Trees more than 15 m tall were defined as canopy trees, less than 15 m as
understory trees.
• Parts of lines without any cover by canopy tree were defined as canopy
gaps.
species
A(赤)
B(青)
C(緑)
被覆率(coverage)(%)
3-1
3-2
0
47
39
0
28
31
Slope inclination
• 地形の指標
• 各トランゼクトを10mのセクションに分割して
それぞれで測定
• indicator of topography
• Each line transect was divided into 10 m
sections, and an average inclination for each
section was obtained .
Results
Species composition
• 27 tree species were observed(4 conifers 23
deciduous broad-leaved)
ブナ
ウラジロモミ
ヒノキ
オオイタヤメイゲツ
コハウチワカエデ
ミズナラ
ミズメ
Spatial distribution of species
Morisita’s index
空間の個体の分布状態を示す指標
通常平面上で用いられるが、ここでは線上に修正
Index to examine the spatial patterns of the different species.
Originally based on the number of individuals in each quadrat.
• Iδ(index of dispersion)
1:ランダム(random)
>1:集中(clumped)
• Cδ(index of inter-specific association)
1:同調(closely associated)
0:ランダム(random)
Iδ
q: the number of sections of a certain size
Pi: relative coverage of a species at section I
p-: the mean coverage of the species
• Iδ(s)/Iδ(2s)=the ratio of the index on length of section s and
2s: a clump size of spatial distribution is detected as s with a
peak of this
Cδ
• pxi,pyi: the relative coverage of species x and y
at section I
• px-,py-: the mean coverage of species x and y
Iδ
F. crenata
canopy: random
understory: slightly clumped
A. homolepis
canopy: clumped
understory: random
C. obtusa
canopy & understory:
clumped in large size
Cδ
ヒノキ:大サイズの排他的な
パッチを形成
ブナ、ウラジロモミ:
同調して分布
C. obtusa: formed large and
exclusive clumps
F. crenata & A. homolepis:
closely associated
relative coverage of understory trees
in canopy gaps
• 51 canopy gaps were counted(15.8% of the line transect in
total)
• F. crenata：ギャップ依存的に更新(gap dependence)
• A. homolepis：耐陰性高い(shade tolerant)
To detect more fine-scale association...
• The contact sampling method
隣り合ってる木を樹種ごとに数えていく
target
contact
neighbor
Lateral canopy tree association
• 同じ樹種が隣り合いやすい
Most of species showed a significantly aggregated distribution.
Vertical association between
understory and canopy layer
• ウラジロモミ下層木:ブナ下に多い、ウラジロモミ下、ギャップ
下に少ない
• ヒノキ：下層木と林冠木が同所的に分布
• Understory A. homolepis : positive association with canopy F. crenata and
negative association with conspecific canopy trees and gaps.
• C. obtusa : positive association between understory and canopy.
Distribution patterns in relation to
topography
As inclination increase…
relative coverage of
• ブナ(F. crena) : decrease
• ヒノキ(C. obtusa) : increase
• gaps : increase
Discussion
C. obtusa
• 大きくて(size:100m~ )排他的パッチを形成
• 急傾斜地に分布
→大規模攪乱後定着？
（付近には地すべり地形がみられた）
• The distribution of C. obtusa was restricted to steep slopes,
and the species was found in larger clumps than other species.
• →Established following landslides or other such large scale
catastrophic events. Several landslide scars of the scale of
several hundreds of m2 were observed in the study area.
F. crenata , A. homolepis
• 同所的に分布(scale : 50~100m)
• ブナがウラジロモミに置き換わっている(contact scale)
• ウラジロモミ：下層でランダム分布→林冠木は集中
→ブナ林のギャップを利用して林冠まで成長する？
• Occurred in the same habitat(scale : 50~100m), where F.
crenata tended to be replaced by A. homolepis(contact scale).
• The distribution of A. homolepis was random in the
understory but clumped in the canopy.
→Occupies canopy gaps in the understory created by broadleaved species.
reciprocal replacement?
相互置換的更新(reciprocal replacement)
針葉樹の次には広葉樹が、広葉樹
の次には針葉樹が更新しやすい
• 北半球の針広混交林で数例報
告
• 複数樹種共存の仕組み？
• 大台ケ原では成り立つのか？
• Conifer species and broad-leaved
species replace each other.
• We can find some reports about
it in the northern hemisphere.
• Hypotheses used to explain the
coexistence of tree species.
broad-leaved
species
under broadleaved canopy
recruit in gaps
conifers recruit
conifer canopy
tree
make gap
frequently?
under conifer
canopy
conifers
don't recruit
Remained question
The effect of
• ササ(dwarf bamboo)
– 一斉枯死(synchronous death)
• シカの増加(increasing Sika deer)

Download Report