Plants and Plant Associations as Natural Monuments in Yamaguti Prefecture (1)

Yamaguti Prefecture locates at the southwestern end of the main land (Hondo) , and comprises two Provinces, Nagato and Sud. The Prefecture borders on the sea on three sides, north, west and south. The coast-line is very long and ranks third of all the Prefectures, next to Hokkaid6 and Nagasaki Prefecture. The Tyfigoku mountain range -extends from east to westward forming the highest point (Mt. Zyakuti, 1339m.) on the boundary of Yamaguti, Simane and Hirosima Prefectures. Three hilly distrits Suo, Abu and Nagato develop along it. The plains exist along the coast or rivers, and the basins such as Kuka, Kano, Tokusa or Tabe are found in the mountainous region. The Kuka and Tokusa basins were once in lake condition. Most of the rivers flow into the Inland Sea or Japan Sea. The annual mean temperature of the coastal region is above 15℃., and that of the inner part is about 14TC,< and that of the innermost is about 13℃., Misima or Senzaki has the mean temperature of 16℃. under the influence of Tusima Current. The annual rainfall of the central part is rather high compared with that of the north and south coast. Kano is the highest amounting to 2665mm., while Hohu is the lowest (1924mm.). January and August are the smallest months in rainfall, and June and September are the biggest. The rainfall in June is rather remarkable in Nagato (such as Simososeki, Tasuki, Tyohu ･or Utui) and that in September is conspicuous in the inner part (such as Kano or Tokusa). The coastal region facing to Japan Sea is warmer in winter than the Inland Sea region, though the weather of the former is unfavorable owing to the high humidity and the strong wind throughout the winter season. The evening calm of the Inland Sea region, lasts for several hours and is quite unbearable during the summer. The climate of Mac chia-type (Olivenklima) is barely observed in Oosima, the easternmost island.