巻号一覧
28 巻 (1967)
- 3-4 号 p. 107-
- 2 号 p. 57-
- 1 号 p. 1-
28 巻, 2 号
選択された号の論文の4件中1～4を表示しています
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小泉 清明, 桜井 善雄, 川島 信二1967 年 28 巻 2 号 p. 57-63
発行日: 1967/07/28
公開日: 2009/06/12
ジャーナル フリーThe following seven species of rooted aquatic plants were listed as dominant for Lake Suwa in 1966:
Emergent—Zizania latifolia (234), Nuphar japonicum (142), Phragmites communis (63); floating—Trapa natans (630); submerged—Hydrilla verticillata (597), Potamogeton malaianus (276), Vallisneria asiatica (16).
Figures in parentheses denote the estimated standing crop of each plant expressed in terms of ton of the wet weight for the total area of the lake.
The hydrophytes densely cover the water along the entire margins of the lake extending to the depths of about 2.3-2.5m, which are shallower than those recorded in 1911 (3.4-4.0m) and 1949 (2.5m) respectively.
The total area occupied by the plants was about 0.92km2 which constitutes 6.3% of the whole area of the lake, 14.53 km2.
The total standing yield of the plants in the lake amounted to about 1, 958 ton in wet weight and to about 220 ton in dry weight in the late summer of the year when the growth reached a maximum. The wet quantity is just twice as large in weight as that reported in 1949 (970 ton).
Ecological succession appeared in the hydrophytes was quite remarkable. It may generally be said that the submerged plants have decreased, and the floating as well as emerged ones have become luxurious, when compared with the conditions in the past. It appears that this phenomenon will have a close relation to the recent trend of eutrophication of the lake.抄録全体を表示PDF形式でダウンロード (257K) -
矢木 博1967 年 28 巻 2 号 p. 64-67
発行日: 1967/07/28
公開日: 2009/06/12
ジャーナル フリー1966年9月10日,最大成長時と考えられる時期に採収した諏訪湖の優占高等値物7種について,化学成分のうち湖水の栄養性に関係する全窒素,全燐酸,全炭素の分析を行つた。
諏訪湖の水生植物の窒素の含量はびわ湖産植物のそれよりかなり高く,水田の水草なみの含量である。
小泉らによる諏訪湖の水生植物現存量から計算すると,全植物の窒素,燐酸,炭素の全量は,それぞれ6,076kg,1,338kg,83,511kgの莫大量に達する。
諏訪湖の沈水および浮葉植物の炭素率(全炭素/全窒素×100)は,レンゲソウより低く,挺水植物のそれはイネやコムギの藁よりかなり低く,ともに湖内での分解が速やかなことを想像させる。
これらの成分は,植物の生育時に湖水,底泥あるいは空気中から体内に吸収保留され,湖外には流亡することはなく,枯死した後再び湖水に返還され,富栄養化に大きな役割りを果たす。
故に水草に関連しての湖水の富栄養化防止には,水草の湖外搬出,草魚その他の方法による除草の対策を講ずる必要がある。抄録全体を表示PDF形式でダウンロード (160K) -
金綱 善恭1967 年 28 巻 2 号 p. 68-91
発行日: 1967/07/28
公開日: 2009/06/12
ジャーナル フリー長野県木曽,伊那地方の乾田についての1956年8月'63年7月の調査結果は次のようである。
1.伊那地方―ケイソウ125種,ツヅミモ35種,木曽地方―ケイソウ78種,ツヅミモ40種,両地方でケイソウ8科,27属,147種,ツヅミモ11属,61種であつた。
2.ケイソウ,ツヅミモともに優占種ならびに亜優占種および比較的広く分布している種はとくに低地の内陸水田ととくにちがう点はみとめられなかつた。
しかし,ケイソウ申,いずれも個体数は少なかつたが,ヨーロッパにおいて北方性高山種と知られているEunotia parallela, Tetracyclus lacustris, Diatoma hiemale var. mesodonなど少数種が伊那にみられたが,ツヅミモでは高山種といわれるものはみられなかつた。
3.伊那地方において著者が採集したツヅミモは1956年8月29種,さらに1963年7月伊那にて7種,木曽40種であつて藤沢の調査に比し少なかつた。"これは藤沢のはとくに豊産した特定の沼田"についてのものであり,著者の今回の調査は"乾田"を対称としたことも原因の一つであると考えられる。抄録全体を表示PDF形式でダウンロード (621K) -
志賀 史光1967 年 28 巻 2 号 p. 92-102
発行日: 1967/07/28
公開日: 2009/06/12
ジャーナル フリーWater samples were obtained at the mouths of the Ono and the Oita rivers and also along the coast of the Beppu Bay, and soluble silica was determined by Iwasaki's method (1960). Soluble silica was defined as the part of the total silica which formed silicomolybdic acid in the part of ammonium molybdate and sulphuric acid.
When a river enters the sea, it would be expected that the high concentration of soluble silica in river water could be reduced by dilution with sea water of a low concentration of soluble silica. The data obtained, however, show that some removal of soluble silica from the river water other than dilution does occur in field samples. Several experiments were performed in the laboratory by mixing river water with Bay water showed similar results.
On the basis of the field data and the laboratory experiments the mechanism of inorganic removal of soluble silica has been proposed as follows.
(1) The removal of soluble silica from the river water is mainly caused by the process that soluble silica is reformed to colloidal silica during the mixing with Bay water. In the river water the initial percentage of soluble silica to total silica is over 95 per cent. This rate slightly drops with increasing chlorinity until 10gm Cl per litre but over this point the dropping rate becomes greater and when it is over 17mg Cl per litre, as in thesurface Bay water, the percentage drops down to 10-14. The difference between the concentrations of soluble and total silica indicates the amount of colloidal silica. Therefore, at a high value of chlorinity nearly all of the soluble silica change to colloidal silica by coagulation of them and are removed from the surface Bay water.
(2) In addition to the mechanism mentioned in (1), the other removal of soluble silica is caused partially by suspensions in river water. In this case increasing removal occurs when the chlorinity is increased and 50-60 per cent of soluble silica removed in maximum by suspended materials.
Other mechanism, i. e., removal of soluble silica due to biological uptake by diatoms and inorganic removal by electrolytes in Bay water are both negligible small.抄録全体を表示PDF形式でダウンロード (344K)
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