関東森林研究 73 (2022)

論 文

Understanding urban trees of Setagaya city in correlation with the interests andperceptions of forestry students
Kibalama Marvin Bogere1, Iwao Uehara1
1 Tokyo University of Agriculture

Abstract: Urban forestry involves the art, science and technology of managing trees and forest resources in and around urban
community ecosystems. Also, urban forestry is just as much about people as about trees. This research surveyed 851 urban trees
spread both over 6 km of Setagaya-dori main street and in 4961.49 m2 space of selected green open parks in Setagaya area. Theresearch also collected 29 forestry students’ opinions about urban trees. Tree attributes surveyed included; species scientific name,tree height, trunk diameter (DBH), crown diameter and GPS coordinates. Tree data was collected with the use of Open Foris Collectsoftware. Opinions of 29 students were collected using google form survey. A total of 29 tree species were surveyed, 13 species
discovered in the open green parks only, 8 species discovered on Setagaya Dori only, and 8 species found common in both parksand on Setagaya dori. Street dominant tree species i.e Liquidambar formosana, Ginkgo biloba, etc. have a larger number ofindividuals than park dominant species i.e Camelia japonica, Osmanthus fragrans, etc. Forestry students felt no need to change thecurrent state of the Urban trees in Setagaya.
Keywords: Urban trees, Setagaya ward, forestry students, opinions and interests

林学科の学生の興味・関心と世田谷区の都市樹の相関関係
キバラマ マーヴィン ボゲレ 1 ・上原 巌 1
1 東京農業大学
概要: 都市林業は、都市コミュニティの生態系とその周辺にある樹木や森林資源を管理する芸術、科学、技術に関わっている。
また、都市林業は、樹木と同様に人間にも関与することが特徴である。本研究では、世田谷通り 6 km と世田谷区立緑地公園
4961.49 m2 に分布する 851 本の都市緑化植物を調査した。また、大学林学科の学生 29 名から都市緑化樹木に関する意見を合わせて聴取した。調査対象となった樹木は、樹高、胸高直径、樹冠径、GPS 座標を調べた。樹木のデータは、ソフトウェア
Open Foris Collect を用いて収集し、林学科の学生の意見は、google form アンケートで収集した。調査対象となった樹種は、緑地公園のみで発見された 13 種、世田谷通りのみで発見された 8 種、緑地公園と世田谷通りの両方で見られる 8 種の計 29種である。調査の結果、街路樹の優占種であるタイワンフウ、イチョウなどは、公園の優占種であるヤブツバキ、キンモクセイなどよりも出現数が多く、林学科の学生は、世田谷の都市樹の現状を変える必要性をあまり感じていないことが示された。
キーワード 都市緑化樹木、世田谷区、林学科学生、興味・関心

I. Introduction
Measuring and monitoring urban trees has been conducted forAttitudes towards public trees can vary by neighborhood,over a century (2). Without detailed data on the location,community, region and ethnic background. Being aware ofstructure, and condition of city trees, it is not possible to manage

neighborhood, local, and regional values is extremely importantthem effectively, nor to estimate ecosystem service provision or

in selecting species for city streets (3). A critical step in building

urban forest value, nor to develop informed policy or strategy

public support for urban forestry programs is to determine the(1). An overall street tree management programme consists ofpublic’s knowledge and perception of the urban forest and theestablishing of trees, including species selection, acquisition

importance the public attaches to it (4).

and actual planting (3). However, Urban forestry is just as much

Therefore, this study surveyed urban trees in Setagaya city toabout people as about trees and thus there exists importantunderstand the tree species composition of tree parks andrelationships and interests between people and trees (1).

Setagaya dori street by collecting tree data i.e. (species type,－57－（受理日 2022 年 2 月 28 日）

(27.6%) growing both in parks and on Setagaya street (Table 1).

DBH, crown diameter, tree height and tree health). Additionally,opinions and interests of forestry students were gathered about

The difference in species composition is characteristic of multi-

the city’s trees and this information can inform better species

dimensional urban spaces (6). Street dominant tree species i.e.

selections for the city of Setagaya.

Liquidambar formosana, Ginkgo biloba, Acer buergerianum,etc. have a larger number of individuals than park dominantII. Materials and methods

species i.e. Prunus yedoensis, Camelia japonica, Osmanthus

1. Site: The site of survey is Setagaya ward. Tree data from afragrans, Ilex rotunda etc. (Fig.1)
2. Average tree height, Dbh and crown diameter

6 km length of Setagaya-dori street and eight selected open
public parks with a total space of 4961.49 m2 was collected. TheFig. 2 shows the average height of individual tree species

selection of this survey area was based on its proximity tosurveyed. The street dominant tree species i.e Ginkgo bilobaTokyo University of Agriculture (NODAI). 851 trees wereand Zelkova serrata have higher average heights than park

surveyed in total. 29 forestry students were interviewed using

dominant tree species. This is because road side trees are

the online google forms for their opinions and interests of trees

planted close to one another and thus compete for height otheron roads and in parks of Setagaya city. These are (NODAI)

than investing in outward expansion.

students who study / live in Setagaya. The tree attributes

Figs. 3-4 show the average DBH and crown width ofsurveyed include; species type, tree height, crown diameter,individual tree species surveyed respectively. With exception ofDBH, tree GPS coordinates and tree health.

Pinus thunbergii, park dominant tree species i.e Prunus

2. Tree species type and dominance; This research surveyed

yedoensis and Zelkova serrata have largest DBH and crown

the type of tree species on Setagaya dori street and in eight open

widths than street dominant species because they have a lot ofgreen parks. The proportion of individuals in the different

space to invest in outward growth i.e tree crown and tree stem

species was used as a measure to classify the dominant and non-diameter growth are very sensitive to competition (9).

dominant tree species.

3. Health and age estimation of trees

3. Tree height; This research also measured tree heights forFig. 5 shows the health of trees surveyed. About 843 trees

all individual trees surveyed using the Blume Leiss hypsometer.

(99.9%) of surveyed trees are in healthy condition, 5 trees

4. Crown diameter; This research also gathered data on tree

(0.0035%) are in declining health condition and 3 trees

crown diameter for every tree surveyed, using a method of(0.0059%) are diseased. The street tree health condition waspacing and checking with a measuring tape.

highly influenced by the prevailing urban stresses, including

5. Diameter at breast height (DBH); This research also

confined

growthspace,

conflictwithabove-groundcollected data on trunk diameter for every tree surveyed, using

infrastructures, and frequent pruning (7). About 77% of alla diameter tape.

street trees were estimated to be over 30 years of age while only

6. GPS coordinates; This research also gathered data on

26% of all park trees were estimated to be over 30 years of age.

individual tree position, using the android tablet fitted withThis is largely because parks almost always have available

Open Foris Collect software. The software package gathers

planting spots to accommodate new and younger trees.

digital tree data for field-based forestry inventories.
7. Tree health and age estimation; Tree health was assessed

Table 1 A distribution of species surveyed

for every individual tree by use of the criteria as provided by theParks onlySetagaya

SharedDori only

species

1388

44.8%

27.6%

27.6%

International Society of Arboriculture (ISA) i.e. Accurate
identification of the tree, careful examination of the landscape,Species

and assessment of tree roots, trunk and leaf situation (5). Treeabundance

age was estimated by visual assessment of the size of tree

Species %parameters i.e. trunk size, height and crown size etc.
III. Results and Discussion
1. Species distribution and abundanceThis research surveyed a total count of 29 tree species, ofwhich 13 species (44.8%) of the total are growing in green parks,8 species (27.6%) growing on Setagaya street and 8 species－58－関東森林研究 73 (2022)

Fig. 1 Number of individuals in eachFig. 3 Average DBH of each species

species surveyed

surveyed

Fig. 2 Average heights of each species surveyed

Fig. 4 Average Crown width of species
surveyed－59－

Fig. 7 Opinions of students about changing theFig. 5 Health of trees surveyed

standing tree types available in Setagaya
4. Perceptions of forestry students about trees of Setagaya
Setagaya research area. This research also found thatcity

Liquidambar formosana (Fuu) is very unknown to the forestry

Fig. 6 shows the commonest tree species often seen by forestry

students. This research also found a larger number of young

students on Setagaya street and in eight parks of Setagaya city.

trees in parks than on Setagaya street, this represents more

Ginkgo biloba, Prunus yedoensis and Zelkova serrata are theplanting opportunities in parks than on Setagaya street. This

trees most identified by the forestry students. This suggests that

research also showed that more forestry students (72%) do notthese are the trees that they associate with the most.

support a change of tree species currently growing in Setagaya

Fig. 7 shows opinions of forestry students about changing thecity thus the standing trees should be maintained as it is.

tree species types planted in Setagaya city. The majority ofstudents (72%) do not support a change of tree species inReferences

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