著者
斎藤 功 矢ヶ崎 典隆
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.110, no.3, pp.293-313, 2001
被引用文献数
2

Covered with short grass and bushes and called llano estacado by Spanish explorers, the Texas Panhandle constitutes the southern part of the American High Plains. Following the decline of the open range cattle industry in the late nineteenth century, large-scale cattle ranches appeared, such as LIT, LS, and XIT. Irrigation has rapidly expanded in the region during the past fifty years. It supports production of corn and grain sorghum (milo) in the flat plains of the northern Panhandle and wheat and cotton in the southern Panhandle. Cattle ranches still dominate in the undulating and sloping country of the Canadian River valley. This paper examines the nature of cattle ranching in the Texas Panhandle during the age of irrigation that promoted differentiation of land use.<BR>Hartley and Oldham counties are chosen for our intensive field study. Large-scale ranches are identified on the map using farm plats, topographic maps, and aerial photographs. They vary in size, from family-operated ranches of 2, 000 hectares to corporate ranches exceeding 40, 000 hectares. Historic ranch names such as LIT and LS are still maintained by contemporary owners. The cow-calf operation is still the basic method in this region, while some beef cattle ranches, not owning cows, depend on purchased yearlings. Others combine cow-calf operations with raising yearlings. As a single animal is given 12 hectares of pasture, 150 to 200 head are grazed on a 4, 000 hectares ranch. Calves born on the ranch during the spring are sold at livestock auctions in Dalhart and Amarillo to farmers, who graze them in wheat fields during the winter. In March, farmers sell their yearlings weighing around 200 kilograms at livestock auctions to ranchers. After being grazed on pasture and reaching 300 kilograms in the fall, they are finally sold to the neighboring feedlots for finishing. Therefore, cattle transactions at the Dalhart livestock auction have peak periods in March and October.<BR>The Texas Panhandle has a concentration of feedlots. They fatten two-year old cattle weighing 300 kilograms for four months until they reach 570 kilograms. They are large-scale commercial feeders, with the largest raising 85, 000 head. Agribusiness companies such as Continental Grain and Cargill operate large feedlots. Some local feedlot owners operate large ranches in order to secure a supply of cattle. Large beef packing plants are also concentrated in the Texas Panhandle for processing locally finished beef cattle.<BR>Beef packers, feedlots, ranches and wheat growers of the Texas Panhandle are interrelated, taking advantage of the groundwater resources of Ogallala Aquifer. Cattle ranches are the basis of the feedlot and beef-packing industries, while they depend on local wheat growers for winter grazing. Unlike the cattle industry in the late nineteenth century and first half of the twentieth century, contemporary cattle-ranching industry in the Texas Panhandle represents a regional change that took place in the American High Plains in response to the opportunities offered by groundwater exploitation.
著者
青山 高義
出版者
学術雑誌目次速報データベース由来
雑誌
季刊地理学 (ISSN:09167889)
巻号頁・発行日
vol.47, pp.91-102, 1995
被引用文献数
1

後氷期に異なった植生変遷をたどったと考えられている。ヒノキアスナロとスギの寒冷環境に対する性質を, 現在の天然分布と気候環境を比較することによって検討した。東北地方において, ヒノキアスナロとスギは, 同じ地域に成育することもあるが, ヒノキアスナロは北上山地などのより乾燥した太平洋側に, スギは日本海側のより湿潤な地域に分布している。特にヒノキアスナロの高度限界は, このような水文環境に関連して, 乾燥側で上昇し, 匍匐形で森林限界を越えるという性質を持っている。すなわち, ヒノキアスナロは年水過剰量700mm, 冬3ヶ月の降水量200~300mmで, 暖かさの指数25℃・month の気候環境で成育することができる。<br>最終氷期の温度低下を7℃程度とすると, スギは東北地方が北限地域となって北海道では成育不可能であるが, ヒノキアスナロは降水量が減少した条件下で, 渡島半島で標高約200m, 東北地方で標高約500mまで成育可能で, レフユジアを形成し得たと考えられる。
著者
田近 栄治 林 文子
出版者
学術雑誌目次速報データベース由来
雑誌
經濟研究 (ISSN:00229733)
巻号頁・発行日
vol.47, no.3, pp.217-228,286, 1996
被引用文献数
1
著者
宇都 浩三 風早 康平 斎藤 元治 伊藤 順一 高田 亮 川辺 禎久 星住 英夫 山元 孝広 宮城 磯治 東宮 昭彦 佐藤 久夫 濱崎 聡志 篠原 宏志
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.110, no.2, pp.257-270, 2001
被引用文献数
7 13

To understand the eruptive mechanism of the 2000 Miyakejima volcanic activity, we conducted intensive geological, petrographic, and mineralogical studies on the pyroclastics of the August 18 eruption. Volcanic ashes, which were rich in accretionary lapilli, covered most of the islands. Cauliflower-shaped bombs and lapilli were ejected along with accidental lava blocks. Black-colored angular scoriaceous particles with abundant vesicles 10 -100 μm in diameter are found among ashes, comprising about 40 wt. % of total constituents. These bombs, lapilli, and black ashes have identical bulk chemical compositions and constituent mineral compositions, suggesting a common origin. Existence of oxidized ashes and accretionary lapilli attached to a large flattened bomb and chemicallyreacted anhydrite particles trapped in the voids of bombs suggest that bombs were still hot and ductile when they were emplaced on the ground. We, therefore, conclude that the August 18 eruption was a phreatomagmatic eruption and cauliflower-shaped bombs and black ashes were essential magmatic materials. Significant SO<SUB>2</SUB> emissions from the volcano after August 18 also suggest convective upwelling of magmas to a shallower level beneath the volcanic edifice. We propose a magma-ascending model in which vesiculating magmas continuously ascend through the wall of subsided piston-like blocks.