著者

Yoshimichi YUI

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.79, no.12, pp.629-643, 2006-10-01 (Released:2008-12-25)

参考文献数

13

被引用文献数

3 2 4

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Recently some single women are purchasing their own houses and the number of houses owned by single women is increasing in Tokyo. The article aims to clarify why single women tend to purchase their houses in Tokyo. The author uses the experience reports of housing ownership by single women in the Tokyo metropolitan region. These experience reports contain their economic conditions, their working conditions and their lifestyle. We can understand the housing demands of single women from these reports, because these sources are collected for marketing research. Furthermore the author tries to clarify the background of housing problems for women in the Tokyo metropolitan area. Single women continue to work after they own their house and want to avoid housing problems in their old age. It is important that they can save housing cost by purchasing houses, because housing loan becomes cheaper than rent, which was caused by low rate of interest rent policy. However all women who purchase their houses are not so rich. They want to own their houses because they are not satisfied with the expensive rent price in Tokyo, the costly and cumbersome charge of broker's procedure and anxiety regarding their old age. Furthermore many single women want to enrich their life by ownership of a house. Because of lack of housing policy for them, single women tend to try to reduce their housing problems in future and to change their life.

著者

Hiroo KAMIYA Honami KAGEYAMA Reiko KINOSHITA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.79, no.12, pp.619-628, 2006-10-01 (Released:2008-12-25)

参考文献数

11

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From the Japanese demographic data, it is evident that the category of single women is increasingly constituting a larger segment of the population. Thus far, policies pertaining to housing and social benefits have been targeted at nuclear families based on the “Asian style welfare state, ” and minimum attention has been given to single women. Therefore, in this paper, we attempt to address the factors affecting single women's residential choices by using in-depth interviews. In addition, in order to confirm the research results, triangulation methodologies are applied. Triangulation methods are conducted in two ways. First, my female colleague checks my (male) interpretations against the interview records. Second, my (male) interpretations are compared with the profiles appearing in a non-fiction work by a female writer. As a result, we observe that the residential choices of single women in Tokyo have the following characteristics. 1) Single women are rather myopic in their attitude toward work-and housing-related issues due to their unstable working conditions. 2) They are likely to value easy access to a railway station in their residential choice due to the geographical concentration of job opportunities in the city center and the long working hours. 3) They have limited housing options because most of the available housing stocks cater to nuclear families. Through the triangulation methodologies, other factors affecting their housing choices have been suggested: social contact with their parents and their relationships with their boyfriend. Additionally, the 1996 legislation reform for equal job opportunities and the effects of economic globalization on job opportunities for single women may have affected their working environment.

著者

梶田 真

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.13, pp.913-927, 2005-11-01 (Released:2008-12-25)

参考文献数

23

被引用文献数

4 1

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本稿では経営事項審査データを基に地方圏における土木業者の本店立地の空間パターンを分析した.分析の結果,(1)地方圏に本店を置く業者は完成工事高の規模や支店配置の面で全国ゼネコンとは明らかに区別される,(2)都道府県を超えた営業活動を行っている大規模土木業者の本店がある少数の道県を除いて,地方圏の各県では1位業者の完成工事高規模が62億円から81億円の間に集中し,県内における1位業者の卓越性が低い点で業者構造の類似性が高い,(3)極端に圏域の人口規模が小さい場合などを除き,地方圏の道県の土木関連部署のほとんどの出先機関の管轄域内には平均完成工事高10億円以上の土木業者の本店が立地している,という3点が明らかになった.(3)の知見は発注機関が入札において管轄域内に本店を置く業者を優先的に取り扱っていることによるものであり,発注機関の管轄域の編成が地方圏全域において土木業者の本店立地を強く規定していることが確認された.

著者

Hiroyuki OBANAWA Yuichi ONDA Hiromu MORIWAKI Yukinori MATSUKURA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.859-866, 2005-10-01 (Released:2008-12-25)

参考文献数

12

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To examine running distance of debris flows occurring on the talus slopes, rainfall experiments were carried out. The quantity Vt is defined as the reciprocal of the threshold value of Lc/ Lt, at which debris flows just reach the bottom of the talus slope, where Lc is the horizontal length of the cliff and Lt is the horizontal length of the talus slope. The value of Vt is also a measure of the possibility of sedimentary outflow from the talus slope by debris flow. The value of Vt shows strong correlation with the hydraulic conductivity of talus sediment (K) and the rainfall intensity (Ir). The outflow of debris from the talus slope can be predicted using the values of Lc, Lt, K, and Ir.

著者

Yuichi S. HAYAKAWA Ellen E. WOHL

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.853-858, 2005-10-01 (Released:2008-12-25)

参考文献数

19

被引用文献数

4 4

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The recession rate of Poudre Falls in the Colorado Front Range is examined using an equation by Hayakawa and Matsukura (Earth Surf. Process. Landf., 28, 2003). In spite of stable tectonics and a cold, semi-arid climate in the region, the estimated recession rate of 0.09 m/y for 12, 000 y indicates rapid erosion of the waterfall. This indicates that the waterfall recession is a primary response of fluvial erosion after deglaciation, creating a narrow gorge below the waterfall. Further data collection will be necessary to assess the waterfall recession rates in such glaciated regions.

著者

Yoshihiko KARTYA Shuji IWATA Tetsuya INAMURA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.842-852, 2005-10-01 (Released:2008-12-25)

参考文献数

15

被引用文献数

2 2

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In Cotahuasi and Puica, southern Peru, contrasting landforms of wide plateaus with glacigenic U-shaped valleys (4, 800-5, 000 m ASL) and deep canyons (1, 500-2, 800 m deep from plateaus) are developed. In this area, camelid (alpaca and llama) pastoralism and agriculture have been conducted on the plateaus and in the canyons, respectively, since at least Inca times. This paper describes meso- to micro-scale landforms comprising the plateaus and canyons, and discusses the factors controlling pastoral-agricultural land use of these specific landforms. On the plateaus, flood plains, fluvial terraces, alluvial fans, taluses, and landslide bodies, which are concentrated in the U-shaped valleys, are significant for alpaca pastoralism. These landforms provide relatively gentle slopes, and are covered by wet meadows for livestock if adequate water is supplied by channels or springs. In the canyons, landslide bodies, taluses, alluvial fans, and fluvial terraces are important for agriculture. These landforms also produce gentle places, and are used even if irrigation or channels are absent. The regional/local climate would be the primary factor for the vertical separation between pastoralism and agriculture. Additionally, the physiographical setting, in particular the slope angle, is potentially important for the pastoral-agricultural land use of meso-to micro-scale landforms.

著者

Hiroaki UEDA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.825-841, 2005-10-01 (Released:2008-12-25)

参考文献数

58

被引用文献数

12 18

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Observational evidence is presented to show an atmosphere-ocean coupled system in the maturing process of the Asian summer monsoon (ASM) and the western Pacific monsoon (WPM). The ASM and WPM are characterized by four abrupt seasonal changes that exhibit phase-locking features in the annual cycle. They correspond to the first transition of the ASM (mid May); the Indian monsoon onset (early June); the mature phase of ITCZ (mid June) to the east of Philippines and convection jump around 150°E (late July). The appearance of a warm pool, in excess of 29.0°C, is one of the key elements in understanding the sub-seasonal evolution of the ASM and WPM. Over the Indian Ocean, the seasonal increase of sea surface temperature (SST) follows the solar insolation and reduced evaporative cooling as well. In contrast, increase of SST over the subtropical western Pacific (SWP) lags behind those in the Indian Ocean by about one month. The heat flux analysis at the ocean surface in the SWP reveals that the delayed warming is attributed to reduced evaporative cooling, in relation to the weakening of the tropical easterlies, which is concurrent with the eastward expansion (_??_150°E) of the monsoon westerlies. These processes are also valid for interannual fluctuation; namely, the intensified ASM can induce warm SST anomalies over the SWP. Thus, these physical interpretations suggest further increase of the WPM predictability.

著者

Yasushi SAKAKIBARA Emi MATSUI

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.812-824, 2005-10-01 (Released:2008-12-25)

参考文献数

15

被引用文献数

22 31

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This paper demonstrates the relation between the heat island intensity and city size indices/urban canopy characteristics. This is accomplished by analyzing the data at 6 settlements on the Nagano basin, Japan, whose population ranges from 3, 300 to 360, 000. The results show that heat island intensities on fine nights and cloudy nights, ΔTu-r are related to the logarithm of the settlement population P, which has one of the highest correlations to the heat island intensity in a city size index such as city area, DID (Densely Inhabitant District) area, DID population and so on. The gradient of regression between ΔTu-r and P is larger on fine nights than on cloudy nights, and is larger on nights with weak wind than on nights with strong wind. The correlation of population with maximum heat island intensity is remarkably high for Japanese settlements.

著者

Akio TSUCHIYA Akira TANAKA Niro HIGUCHI

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.794-811, 2005-10-01 (Released:2008-12-25)

参考文献数

51

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Soil CO2 concentration and microclimatic parameters were measured at a primary forest and grassland in dry season (August to September 2003) and rainy season (March 2004) in central Amazonia in order to investigate the effects of infiltration of rainfall and evaporation of soil water upon the changes in soil CO2. The CO2 temporarily increased with infiltration, and decreased after soil water descended downward. Then, the increase and decrease moved to deeper soil. This phenomenon was found at both a primary forest and a grassland in the rainy season, and was found in the dry season as well at primary forest. At the grassland in dry season, the soil moisture change was positive during daytime, while the CO2 concentration change was negative. During nighttime, in contrast, the soil moisture change was negative and the concentration change was positive. It was estimated that the fluctuation of radiation between day and night reversed the relative position of soil water and CO2 in the soil. In the rainy season, there was not a large difference in the surface soil concentration (10-30cm: 20, 000-25, 000ppm) between the sites, while in dry season the concentration at the grassland was quite low (2, 500-2, 600ppm). From these findings, it was estimated that the soil CO2 was emitted or the root respiration was quitted due to the withering of herbs on the grassland in the dry season. In either case, it is thought that the decrease in soil CO2 was brought about by the exposure of naked land due to the disappearance of forest canopy.

著者

Haruhisa ASADA Jun MATSUMOTO Rezaur RAHMAN

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.783-793, 2005-10-01 (Released:2008-12-25)

参考文献数

27

被引用文献数

7 14

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The long-term variations of rice production in Bangladesh are examined in the latter half of the 20th century and the impact of recent severe floods is discussed. Unprecedented severe floods, which submerged nearly two thirds of the country, occurred recently in Bangladesh in 1988 and 1998, and the effects of these severe floods to rice cropping are revealed. In these severe flood years, the rainy season crop aman drastically declined in production due to the decrease of the cultivated area and yield. On the other hand, the dry season crop boro, which is planted after the flood withdrawal, increased its production much higher than that of the previous year, mainly because of utilization of the residual flood water. In terms of total annual rice production, it turns out that severe floods have even a positive effect on rice production in Bangladesh. Furthermore, rice production after these severe flood years is higher than that of the previous years, suggesting that severe floods may act as a trigger for increasing rice production level through the change of the hydrological environment and farmers' reaction to it.

著者

Raelyn Lolohea ESAU

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.753-768, 2005-10-01 (Released:2008-12-25)

参考文献数

51

被引用文献数

1

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This study examines the migration experiences of Tongan students and households in Fiji based on two separate surveys. The major findings obtained are summarized as follows. The student survey results elucidate that the decision to migrate for a university education was made on an individual basis, while the role of family and friends in disseminating information about the institution was conspicuous. The destination choice for university was influenced by the availability of scholarships for studying in Fiji. While a majority of students expect to return to Tonga to resume or find employment after completion of their studies, some also anticipated pursuing future graduate studies. The household survey findings confirm the important role of the nuclear family in decisionmaking and reasons for migration while employers funded the migration expenses for most of the individuals. Their highest university degrees were acquired since the 1990s mainly from Fiji and Australian universities. A considerable portion of them are involved in such skilled occupations as education and administrative jobs at major institutions of the South Pacific region, mainly due to their higher educational attainment and work experience prior to migration to Fiji. As a result, they tended to have higher incomes.

著者

Haruhiro DOI

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.12, pp.727-752, 2005-10-01 (Released:2008-12-25)

参考文献数

40

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The author examines China's urban developments such as housing developments for the purpose of understanding land use changes and their driving forces in urban areas of China. Economic growth and the increase of the urban population in China have influenced urban development, especially in terms of housing; urban developed areas have rapidly increased in the latter half of the 1990s. Private real estate development enterprises have had an important role in such urban development. Such enterprises are functioning actively in metropolises such as Beijing and Shanghai, which are economically advanced areas, and in provinces along the coast. Residential developments promote the land-use change in the built-up area and also promote the spatial expansion of the built-up area in Changchun City.

著者

中辻 享

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.11, pp.688-709, 2005-10-01 (Released:2008-12-25)

参考文献数

29

被引用文献数

3 3

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ラオス北部の山岳地域では現在も焼畑による自給向けの陸稲栽培が盛んに営まれているが,その一方で焼畑民による現金収入を目的とした仕事も活発化している.その結果,世帯間で異なる生計活動がみられる.本稿はこの生計活動の世帯差とそれが生ずる要因を,集落移転政策によって成立した一行政村,10番村を事例として,各世帯の稲作規模やコメ収支,現金収入の分析を通じ考察した.その結果,10番村では市場経済の浸透後,経済格差を生む新たな要因が生じ,貧富の差とそれに伴う生計活動の世帯差が明瞭にみられること,10番村における貧富の差は民族間の経済格差の問題を含んでおり,焼畑民の貧困問題をこの問題抜きに論じられないこと,幹線道路沿いの領域では土地に対する人口圧が高まり,焼畑の継続が困難になり始めているのに対し,山間僻地領域では人口圧が低く,焼畑が今なお継続しやすくなっていることを明らかにした.

著者

劉 農 王 勤学 一ノ瀬 俊明 大坪 国順

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.9, pp.586-600, 2005-08-01 (Released:2008-12-25)

参考文献数

33

被引用文献数

5 2

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人ロセンサスなどの統計資料を用い,中国国内における1990年と2000年の流動人口(戸籍を移さない転居人口)の空間分布,およびその変化を県レベルの精度で調べた.その結果,以下の事実が明らかとなった.流動人口の空間分布は主に都市部に集中し,北京市,天津市,珠江デルタ,長江デルタ,各省の省都が巨大な流動人口の受皿となっている.1990~2000年の10年間に流動人ロの規模と範囲は急激に増加し,1990年には到着地が大都市に集中した点状分布となっていたのが,2000年には大都市を中心とした経済発展の著しい地域に面状に分布するように変化し,沿海,長江沿い,交通要路沿い(たとえば,北京-広州問京広鉄道沿線),国境沿いの四つの増加帯を形成した.省間移動は1990~2000年の10年間に急増し,省内移動を上回るようになった.また,流入の多い約100都市について,経済格差,投資,都市化,雇用,産業構成,交通の便利さを代表する10変数を独立変数として流動人口に対して重回帰分析を行い,移動要因を解析するとともに流入大都市における流動人口を推測する重回帰式を提案した.その結果,2000年においては,都市GDP,1万人当たり旅客運送量,1人当たりGDP,海外からの投資額の4変数で流入現象の83.7%を説明できた。都市GDPが流動人口と最大の偏相関を持ち,移動先の経済力が人々を引き付ける最も重要な要因ということが裏付けられた.さらに,全国県(都市を含む2327箇所)に対して県内GDPと流動人口の回帰分析を行い,中国全県に対する流動人口を推測する式を提案した.

著者

山田 晴通

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.9, pp.545-559, 2005-08-01 (Released:2008-12-25)

参考文献数

10

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コミュニティ放送は,既存放送制度に対抗する,「コミュニティ」のための放送として,各国で制度化されてきた.コミュニティ放送局が対象とする「コミュニティ」概念の実態的な有効性を,オーストラリアの地方都市アーミデールの事例で検討した.アーミデールでは,大学に基盤を持つ「ラジオ」局としてRUNEが1970年から存在し,その後の制度変更によってHPON(大出力ナローキャスティング)のTUNE! FMとなり,現在に至っている.1970年代半ばに「公共放送」(コミュニティ放送の前身)が注目されると, RUNEを母体に,新たに2ARMが組織され,放送が始まった.やがて, RUNEから独立した2ARMは,安定的に運営された時期を経て,近年では補助金の削減などから経営困難に直面している. 2ARMは,本来,地域社会と同義の「地理的コミュニティ」に根ざすラジオ局として想定されながら, RUNE~TUNE! FMとの競合関係の中で,十分な地域的存立基盤を確保できなかった.一方, RUNE~TUNE! FMは,通常は商業的に利用されるHPONを,非営利目的に活用している.アーミデールの小規模ラジオ局は,地域事情を反映し,役割の棲み分けを行っており,その実態は,「コミュニティ」をめぐるオーストラリアの放送制度の想定に忠実に沿ったかたちとはなっていない.

著者

Keiji KIMURA Tatsuto AOKI Shigeki SANO Yasuhiro SUZUKI

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.5, pp.276-288, 2005-04-01 (Released:2008-12-25)

参考文献数

30

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The relationships between successional vegetation change and geomorphic conditions were analyzed by using a high-resolution digital terrain model (DTM) and a time series of converted digital vegetation maps combined within a geographical information system (GIS). The results of the analysis confirmed that the pattern of vegetation change is a function of geomorphic conditions (measured in terms of spatio-statistical values of various parameters and time series of those values). Current geoecological studies are usually carried out by means of detailed field observations with high spatial resolution, and the results of our study suggest that a GIS can easily deal with such data over a large area and long time period. In the study area, unforested sites were reforested using Japanese red pine (Pinus densiflora) as part of the forest rehabilitation work that occurred in the early 1950s. After that, two main patterns of vegetation change from pine forest to deciduous broadleaved forest occurred. In one type, the deciduous broadleaved forest reappeared quickly. In the other, the pine forests remained for a long time. Stands that underwent relatively rapid succession were found on north-facing gentle slopes close to large bodies of water. Stands that did not undergo rapid succession were found on steeper, warmer, and drier slopes (often south-facing slopes farther from bodies of water). The rate of forest succession towards deciduous broadleaved forest is a function of these geomorphic conditions. This suggests that forest succession is influenced by intermediate factors controlling by geomorphic conditions of site, such as soil moisture and soil thickness.

著者

Yuichi HAYAKAWA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.5, pp.265-275, 2005-04-01 (Released:2008-12-25)

参考文献数

39

被引用文献数

4 4

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Relationships between recession rates of waterfalls and their controlling factors are examined for waterfalls in the Boso district using an equation proposed by Hayakawa and Matsukura (Earth Surf. Process. Landforms, 28, 2003). The long-term mean recession rates of waterfalls are obtained by estimating the original location and age of waterfalls, while the factors affecting the rate are determined with measurable physical parameters including: drainage area and mean annual precipitation of catchments above a waterfall; height and width of waterfall face; and unconfined compressive strength of bedrock. In the present study, measurements are undertaken for eight waterfalls in the middle to southern Boso Peninsula. Together with nine existing data, seventeen data are contributed to the examination of the equation, revealing the equation to be basically applicable to the waterfalls in the studied area. However, derivation of recession rates for some waterfalls remains improved. Similar analyses for other regions should also be continuously undertaken.

著者

Masafumi MIKI

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.5, pp.247-264, 2005-04-01 (Released:2008-12-25)

参考文献数

60

被引用文献数

1

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This study attempts to clarify the formation of commutation by focusing on transportation, labor, and education in modern Japan. “Commutation” in this study refers to the everyday habit of commuting by public transportation between a home and a workplace in separate areas. Since previous studies analyzed commutation quantitatively on the basis of National Census Reports, they failed to show the prototype and formation of commutation in geography and its cognate disciplines. Some historical studies on metropolitan areas point out that an important factor in the formation of commutation was the growth of residential suburbs, but they do not clarify the causal relationships between the development of commutation and the growth of residential suburbs in modern Japan. The present study therefore clarifies the prototype and formation of commutation from a social historical viewpoint. It shows that increasing commutation by workers and students between urban and suburban areas after the 1920s was closely related to the development of railways, an increase in “white-collar” workers, and an increase in graduates from higher schools. In particular, commutation by workers and by students accounted for the popularization of commutation, and the two were closely related and created a regenerative structure.

著者

野上 道男

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.3, pp.133-146, 2005-03-01 (Released:2008-12-25)

参考文献数

53

被引用文献数

1 1

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地図は現実世界のモデルである.したがって地図上で行われるすべての営為は広義のシミュレーションと呼ばれてしかるべきである.このような地理的シミュレーションは地図のデジタル化,GISによって改新された.私の以前の研究から,日本列島における植生の帯状分布に関する地理的シミュレーションを事例として取り上げた.1km解像度の植生と気候のグリッドマップを用いて,常緑広葉,落葉広葉,常緑針葉,高山低木などの天然森林帯を分ける熱的閾値を求めた.これらの値を使い,人間活動によって本来の植生が失われた場所の潜在植生を推定し,また気温が7°C低下した気候,2°C上昇した気候下における潜在植生を推定した.現在の地理的分布とそれを決めている制約要因の空間的相関は,過去の鍵であると同時に未来の鍵でもある.さらに他の分野と共通する意味の,すなわち狭義のシミュレーションを私の以前の研究から事例として二つ取り上げた.一つは小流域の地形発達に関するものである.流域は斜面と河川プロセスの領域に2分割され,異なる発展方程式(時間を含む偏微分方程式)をモデルに採用した.このスキームを採用したことで,二次元モデルに,岩石制約と気候的影響をセットにして拡散係数として,また海面変化を境界条件として組み込むことができた.これからの10万年はこれまでの10万年と同じ気候変化や海面変化があるという仮定の下で,正六角形DEM上でシミュレーションを行った.もう一つの事例は排水網の確率的モデルに関するものである.排水網ネットワークシステムは基本的に二分木である.シミュレーションモデルは再帰関数群から成り,一つは乱数によって新しい分岐を発生させて(モンテカルロ法)水路網を作り出す.もう一つは水路網の特性(流域面積,ホートン・ストレーラの次数,分岐比など)を計算する.シミュレーションという用語によって,地理学は何であるか,地理学とはどのようなものであるかを語ることが,地理学を広く知ってもらう最良の方策であると思っている.なぜなら科学はその予知能力によって評価されるからである.

著者

山中 勤 三谷 克之輔 小野寺 真一 開發 一郎

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.78, no.2, pp.113-125, 2005-02-01 (Released:2008-12-25)

参考文献数

12

被引用文献数

3 4

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遊休農林地の放牧地への転換が,瀬戸内海や流域圏地下水の水質環境に及ぼす影響を予測するための基礎資料として,風化花崗岩を母材とした貧栄養土壌から成る牧草地において,年間の水・熱・物質収支を実測値に基づいて評価した.年降水量1,262mmに対して,地下水涵養量はおよそ4割の523mmであったが,その半分近くは1999年9月の豪雨時に生じていた.水の下方移動速度は年平均で約7mm/day,豪雨期を除くとおよそ3mm/dayであった.蒸発散量は年降水量のおよそ6割を占め,それによる消費エネルギーは年間正味放射量(2,712MJ/m2)の約3分の2に相当した.蒸発散量は日射量の季節変化や植生の状態に強く規定されていた.元素ごとにみた溶脱フラックスは,大気降下フラックスのおよそ2倍から9倍程度であり,施肥およびそれに付随する土壌中のイオン交換反応に依存していたが,窒素の溶脱率は7%未満とかなり小さかった.すなわち,硝酸性窒素汚染や水域の富栄養化といった観点からは,牧草地における適度な施肥は大きな問題とならないことが確認された.ただし,植生状態の管理や施肥のスケジューリングなどによって溶脱率が変化する可能性があることには注意を要する.