富士山北西斜面の森林限界付近における気候環境 Climatic Conditions near the Forest Limit on the Northwestern Slope of Mt.Fuji, Central Japan
This study attempts to quantify the vegetation dynamics of the forest limit and its environment on the northwestern slope ofmt. Fuji. In the study area, meteorological observations were carried out throughout the year. This paper describes climatic conditions near the forest limit based on observations from July 1994 to July 1995 and briefly considers the limits to tree growth.<br> Station A (2, 830m) was at the tree limit; Station B (2, 800m) was in a zone of patchy stunted <i>Larix</i>; and Station C (2, 650m) was at the limit of <i>Larix</i> open forest. Air (100cm) and soil (-10cm and -20cm) temperatures weremeasured at both Stations B and C, while only the soil temperature (-10cm) and solar radiation weremeasured at Station A.<br> The following results were obtained:<br> 1) The respectivemonthlymean air temperatures at Stations B and C were 12.0 and 12.7°C in July, the warmestmonth, and -13.2 and -12.7°C in January, the coldestmonth. The annual ranges of air temperature at Stations B and C were 25.2 and 25.4°C, respectively.<br> 2) At Stations A, B, and C, themaximum soil temperature at a depth of 10cm was recorded in August (13.4, 13.4, and 11.6°C, respectively), while theminimum was recorded in February (-10.8, -11.3, and -3.5°C, respectively). At Station C, the soil temperature at 10cm depth jumped abruptly to near 0°C on 17march 1995 and remained stable near 0°C for 2months. This phenomenon likely results from the infiltration ofmelt water.<br> 3) The diurnal variation in solar radiation varied with the season. At Station A, the peak solar radiation in the summer usually occurred in themorning because of afternoon cloud cover. The days on which the diurnal variation in solar radiation showed such that curre decreased after October. <br>4) The warmth indices at Stations B and C were 19.1°C•month and 22.8°C•month, respectively. Therefore, forest can grow at these stations.<br> 5) The low-temperature period, when the air temperature drops below 0°C, lasted for about 9months at Station B and for about 8months at Station C. 6) At Stations A and B, the frozen period was about 5months, while it was 3months at Station C. The frozen period lasted the longest and ended the latest at Station B.<br> 7) The winter air temperature and solar radiation implied that there was little snow in the study area and that the period of continuous snow cover was short. In this region, strong prevailing winter wind is the reason for the small amount of snow.<br> 8) Itmay be true that soil freezing plays an important role as a controlling factor of the forest limit, judging from themarked difference in the length of freezing period between Stations B and C.
- 地理学評論. Ser. A
地理学評論. Ser. A 73(5), 435-447, 2000-05-01