関東森林研究 73 (2022)

論 文

Distribution and characteristic tree shapes of Larix kaempferi seedlings in Okutama
Practice Forest of Tokyo University of Agriculture
Iwao UEHARA1
1 Faculty of Regional Environment Science, Tokyo University of Agriculture
Abstract: Larix kaempferi is a woody plant of the genus Larix Pinaceae. It is only one native deciduous coniferous trees in Japan.
Larix kaempferi is a strong intolerant tree and grows fast. It is also a pioneer species and invades bare areas such as ground coveredby volcanic ash and gravel. The soil demand of Larix kaempferi is low, therefore, a colony of them is sometimes formed at sites
with poor soil. However, it is rare to see the seedlings in the Okutama Practice Forest of Tokyo University of Agriculture (TUA).
The distribution and characteristic tree shapes have yet to be clearly identified. Thus, this study focused on the seedlings of Larix
kaempferi at 900 m above sea level around a forest road and surveyed the seedlings’ distribution and characteristic tree shape. Results
showed that 1 to 5-year-old seedlings of Larix kaempferi were distributed at bright sites (relative illuminance was 70 %) in the radiusof 10 m from the Larix kaempferi stand. Seedlings were distributed on the soft ground (soil hardness: 0.5 kg / cm2) among the gravelsoil. The tree shape was mainly dwarf or creeping types, the leaves are 3 to 4 cm long, and T/R ratio was 1.5 on average.
Key-word: seedlings, soil hardness, Yamanaka soil hardness meter, tree shape, T/R ratio

東京農業大学奥多摩演習林におけるカラマツ実生の分布と特性
上原 巌 1
１ 東京農業大学地域環境科学部
要旨：カラマツ（Larix kaempferi)は，マツ科カラマツ属の樹木であり，日本に唯一自生する落葉針葉樹である。極陽樹で成長が早く，パイオニア樹木であり，裸地への初期侵入をする樹種の１つである。カラマツは土地の養分に対する要求度も低いため，他の樹木が成立できない立地条件において，群落が成立することがある。しかしながら，東京農業大学・奥多摩演習林内でその実生および群落を見ることは稀であり，その分布や樹形の変化などについてはあまり調べられていない。そこで本研究では，同演習林の標高 900 ｍ 前後の作業道周辺に見られる，カラマツ実生の分布状況と樹形の特徴を調べた。調査の結果，相対照度 70％程度の明るい裸地の，石礫土壌の中でも土壌硬度の低い部分（0.5 kg/cm2 前後）に多く分布し，矮性または匍匐型に近い樹形で葉長は 3～4 cm，T/R 率が低いことなどが明らかになった。
キーワード：実生，土壌硬度，山中式土壌硬度計，樹形，T/R 率

shape.

Ⅰ Introduction
Larix kaempferi is a woody plant of the genus Larix, Pinaceae

Ⅱ Materials and Methods

and it is only one native deciduous coniferous trees in Japan.
Larix kaempferi is a strong intolerant tree and grows fast and is

The survey plots were set at 900 m above sea level around aalso one of the pioneer tree species and invades bare areas suchforest road in the Okutama Practice Forest of Tokyo University

as ground covered by volcanic ash and gravel (1, 3, 4). The soilof Agriculture. The Okutama Practice Forest is located 650 todemand of Larix kaempferi is low, therefore a colony of them1450 m above sea level in Okutama Town of Tokyo. The forest

can sometimes be formed at poor soil sites (1, 3, 4). However,road was constructed in 2017. Forest tree species are mainly

it is rare to see seedlings in the Okutama Practice Forest ofLarix kaempferi and the species Quercus serrata and Quercus

Tokyo University of Agriculture (TUA). The distribution andmongolia. The average tree height was 17.8 (± 4.8) m, averagecharacteristic tree shapes have yet to be clearly identified.

branch height was 6.0 (± 1.2) m, average tree crown diameters

Therefore, this study focused on the seedlings of Larix

were 4.4 (± 1.4) m, and the average DBH (diameter at breast

kaempferi at 900 m above sea level around a forest road andheight) was 26.6 (± 6.1) cm. The stand density of Larix

surveyed the seedlings’ distribution and characteristic tree

kaempferi was 450 / ha. The survey plot was 50 m long and 25－37－（受理日 2022 年 2 月 18 日）

m wide (1,250 m2) with 50 meshes (each mesh was 5 m×5ｍ:
25 m2) in the plot (Fig.1 ). The slope of the stand wasapproximately 17 degrees.

%100

A Tokyo Koden illuminometer measured the relative

9080

illuminance (ANA-F11), hardness of the soil was measured by70

a Yamanaka soil hardness meter, and soil pH was measured by

60

a TOA-DKK pH meter (IM-32P). The soil and stones were50

separated by a 2mm mesh sieve. The distribution condition of40

the Larix seedlings was also surveyed, along with the stand3020conditions, other present vegetation seedlings, and thecharacteristics of the seedlings’ shape, which includes

10

the0Larix seedlings
distributed

length of the needles and the T/R ratio. Analysis of variance wasused for relative illuminance of the seedling distribution andLarix seedlings
undistributed

Center of forestroad

hardness of the sites. Correlation analysis and regression wereFig. 2. Relative illuminance of the distributed and undistributed

also used to identify the relationship between the number ofsites (%)

Larix seedlings and the soil hardness.
2 Site condition All Larix kaempferi seedlings were found on
Ⅲ Results and Discussion

bare sites with gravel. Soil colors were bright (Mansell’sWithin the 5 meshes, 85 Larix kaempferi seedlings were foundpigment table:10 YR 5/6 - 6/6). The hardness of the soil was(Fig.1).

measured by a Yamanaka soil hardness meter; Fig. 3 shows thehardness of the sites. The average hardness of the sites whereseedlings were found was 0.5 (± 0.4), sites with no foundseedlings had a hardness of 3.8 (± 1.7), and the middle of theroad was reported to be 11.5 (± 6.4). These results showed that
the Larix kaempferi seedlings were distributed on softer ground,even when the site was composed of gravel. This shows that thesoil hardness was statistically lower than the un-distributed sites
by analysis of variance (p< 0.01). Fig. 4 also shows the numberof Larix kaempferi seedlings and soil hardness. The relationshipfound between them was (r= 0.7023, p< 0.01).

（kg/c㎡）
20

Fig.1 Surveying plots and number of seedlings

1816

The seedlings were 1 to 5-years-old, suggesting these14

seedlings appeared after the forest road construction. The site

12conditions are described below.
1.

10

Average relative illuminance Fig. 2 shows the average

8

relative illuminance of the seedlings in the distributed sites.

6Larix kaempferi seedlings were found in bright places with4

more than 70 % relative illuminance. Tree crowns did not2cover the sites. This shows that the relative illuminance was0
Larix seedlings Larix seedlings Middle of forest
distributed sites undistributed sites
roadstatistically higher than undistributed sites by analysis ofvariance (p< 0.05). However, the the number of seedlings andFig. 3 Hardness of the sites (kg/cm2)

relative illuminance had no relation.

－38－関東森林研究 73 (2022)

16Alnus
Carpinus sieboldian
Carpinus japonica
a3%tschonoskii
2%4%
Others4%
Alnus
hirsuta5%
Rubus
crataegifollus
5%
Carpinus
Clethralaxiflorabarbinervis
6%55%（number of seedlings）

14
12108
y = -7.5349x + 10.269
R = 0.7023

64

Acerrufinerve
16%

20-2

00.5

1

1.52（kg/c㎡）

Fig. 6. The appearance rate of woody plants except for Larix

Fig. 4 Relation between the number of Larix seedlings and thesoil hardness (kg / cm2,kaempferi (n= 761)

n= 85)

The average pH condition of the sites was 6.46 (± 0.3). The
reason for this weak acidic soil condition might be affected bya B soil layer of clay soil coming to the surface by logging andthe construction of the forest road. It has been reported thatLarix kaempferi can survive on acidic soil, this result confirmedthat Larix could survive on weak acidic soil. Average soil
moisture was approximately 14%. This showed again that Larix
kaempferi could survive in dry conditions. In addition, theweight ratio of soil and stones was 3 : 7.（Fig. 5）.
Fig.7 Symbiosis of Clethra barvinervis, with Larix’s root

Carpinus
laxiflora
17%

Acerrufinerve
26%

Fig.5 Site(left) and soil (right: soil and stone)

Clethrabarbinervis
57%

3.Vegetation In total, 20 woody plant species and 761
seedlings were found in the meshes where Larix kaempferi wasfound. Fig. 6 shows the appearance rate of other species. SomeFig. 8 The rate of species symbiosis with Larix’s root

species had exogenous root bacteria or necose veins, such as(n= 23)

Acer, Carpinus, and Alnus. Especially, Clethra barvinervis,
Acer rufinerve, and Carpinus laxiflora were often found with

4. Tree shape Most of the seedlings’ shape was dwarf orLarix’s roots (Fig.7). Fig. 8 shows the rate of symbiosis withcreeping types The average tree height was 12.8 (± 5.4) cm, andLarix’s root, and the symbiosis percentage of Larix seedlingthe average root diameter was 2.5 (± 0.7) cm. The average

was found to be 27 %.

needle length was 3.1(± 0.8) cm (Fig. 9), with the needles
growing in multiple directions.

－39－Fig.11 Advanced root system of the seedlings
Fig. 9 The leaves of Larix seedlings
There were two types of seedlings, one with long needles (4 to5 cm-long) and one with short needles (2 to 3 cm-long). It isreported that the growth of pines varies significantly by theaffection of mycorrhizal fungi (2). These differences in needle
leaf length between individuals might be affected bymycorrhizal fungi (Fig.10).

Fig. 12 Seedling inflective in a right angle
Ⅳ Conclusion
This research showed the distribution of Larix kaempferi
seedlings in the Okutama Practice Forest. They grow on the soft
sites among gravel stands, and the root system was able toprogress on the weak acid stand. The next step for this researchis how to promote the growth and cultivation of Larix kaempferiby thinning.

Fig. 10. 2 to 3cm-long leaves type (left) and 4 to 5 cm-longleaves type (right) of the Larix seedlings

References
Larix kaempferi has been regarded to have a shallow root

(1) Hayashi Y (1969) Diagram of useful trees (有用樹木system (1). However, the seedlings’ root system was observed

図説). pp. 255. Seikodoshinkosha. Tokyo. (in Japanese)to be advanced with the average T/R ratio at 1.6 (± 0.5), and(2) Taniguchi T (2011) Interactions between plants andeven the ordinary Larix kaempferi stocks’ was 3 to 4 (Fig.11).

mycorrhizal fungi associated with plant diversity in forests.

More than 60 % of the seedlings were inflective in a right angle

Japanese Journal of Ecology 61：311 – 318.
(3) Uehara I (2018) Silviculture Field Note (造林学フィ

position, showing the ability to adapt to specific geographicalールドノート). 165p. Corona-sha. Tokyo. (in Japanese)features, like the slope of the terrain (Fig.12).

(4) Uehara

I (2021) Introduction to Silvicultural Trees（造林樹木学ノート） . 116p. Corona-sha. Tokyo.
(in Japanese)－40－