著者

Hiroo OHMORI Kazutaka IWASAKI Kazuhiko TAKEUCHI

出版者

The Association of Japanese Geographers

雑誌

Geographical Review of Japan (ISSN:00167444)

巻号頁・発行日

vol.56, no.3, pp.131-150, 1983-03-01 (Released:2008-12-24)

参考文献数

26

被引用文献数

3 5

---

For the remobilization of dunes in the southern part of Australia, many causes have been pointed out. The climatological cause, however, has been discussed only insufficiently. In this paper the relationship between the recent dune activities revealed by geologic, geomorphologic, vegetation and hearing surveys, and the rainfall fluctuations induced by the analysis of both instrumental data and drought records was examined. It was confirmed that the patched distribution of presently active dunes with a sharp contrast to the surrounding stable dunes covered with vegetation in the semi-arid and humid zones is not due to the local difference in climate, but due to the patched distribution of thickness of the latest Pleistocene to late Holocene dune sands. Although some of presently active dunes are reported to have been active even before the European settlement, most of them started their sand drifts after the vegetation clearance by them. Therefore, almost all of them can be called “remobilized dunes”. The marked dune activities have been taking place whenever the residual mass curve of rainfall continuously decreased for more than one year resulting in the amount of the sum of the decrease exceeded 500 and/or 600‰ of the mean annual rainfall of each region. It is since the end of the 19 th century that the periods of decreasing in rainfall and severe droughts, when marked sand drifts also occurred, became frequent in the southern part of Australia. It was relatively humid from the end of the 18th century to the end of the 19th century and the dry phase started from the beginning of the 20th century. The remobilized dunes have increased in both number and coverage since the beginning of the 20th century when the dry climate became more frequent. This circumstance continues now at least in the southern part of Australia.

著者

Hiroo OHMORI Jack Hiroki IGUCHI Tsuyoshi OHTA Atsuko TERAZONO Kengo HIKITA

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:13479555)

巻号頁・発行日

vol.77, no.5, pp.301-320, 2004-04-01 (Released:2008-12-25)

参考文献数

32

被引用文献数

1 1

---

In order to investigate the vegetation response to global warming, experimental research was carried out on a high mountain of Japan for three years from 1997 to 1999. The experimental site was in the alpine zone at 2, 780m above sea level, near the peak of Mt. Norikura (3, 026m) in central Japan. Vegetation growing period is about 4 months without snow cover from early June to early October. Five open top chambers with a diameter of 80cm and a height of 30cm were used for temperature enhancement, and another five places were selected as controls outside the chambers. The main objectives were to clarify the differences in vegetation growth, phenology, biomass and coverage of plant between temperature-enhanced chambers and controls. To prove temperature enhancement, air temperature at vegetation height of 5cm high above ground and ground temperature at root layer of 3cm depth were recorded every hour in each chamber and at each control. Vegetation growth and phenology of several alpine species were measured at about four-week intervals, and biomass and coverage were measured on the last experimental day every year. The mean air temperature at vegetation height and mean ground temperature at root layer in chambers were about 0.65°C and 0.25°C higher than in the controls, respectively. Vegetation growth was significantly accelerated, and phenology was surely affected by the extension of growth period due to temperature enhancement for most of the plants observed. Vegetation growth and phenology, however, varied with species, indicating that species vary in response to warming. Differences in biomass between chambers and controls were not significant for all years, suggesting that the total growth of plants in the unit area is controlled by nutrient conditions of the soil. Through three years of experiment, coverage of Loiseleuria procumbens (Ericaceae) recognizably increased, overcoming other species in chambers, while there were no conspicuous changes in controls. It suggests that L. procumbens whose canopy expands horizontally over the other forbs might be more physiologically active than others under warming conditions, although vegetation growth showed positive response to temperature enhancement for most species.

著者

Kayori MAENO Hiroo OHMORI Jun MATSUMOTO Taiichi HAYASHI

出版者

Tokyo Geographical Society

雑誌

Journal of Geography (Chigaku Zasshi) (ISSN:0022135X)

巻号頁・発行日

vol.113, no.4, pp.512-523, 2004-08-25 (Released:2009-11-12)

参考文献数

23

被引用文献数

2 1

---

This paper analyzes the characteristics of daily precipitation during the monsoon season from June to September for 21 years from 1976 to 1996 in Nepal, which is situated in the southern Himalaya. The average monsoon precipitation, and the number of rainy days in Nepal are 1, 410 mm, and 73 days, respectively. On the basis of the total monsoon precipitationand the number of rainy days, 1978, 1984, and 1985 are classified as wet years, and 1977, 1979, and 1992 are classified as dry years. Nepal is divided into six regions on the basis of the statistical characteristics of total monsoon precipitation and number of rainy days.On the other hand, the distribution pattern of 5-year probable rainfall in Nepal, is considerably different from that of average monsoon precipitation. Five-year probable rainfall is small in northern Nepal, and becomes large toward the south. On the basis of 5-year probable rainfall, which is regarded to be the threshold value of heavy rainfall in Nepal, heavy rainfall occurred more frequently in 1981 and 1987. These years did not agree with the wet years based on total precipitation and number of rainy days, indicating that the occurrence of heavy rainfall that causes water hazards in Nepal does not synchronize with wet years.