Standing crop of higher aquatic plants in Lake Suwa (Materials for the limnology of Lake Suwa I)

概要

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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.
日本陸水学会の論文