Varied effects of the forest on aquatic resources in a coastal mountain stream, in southern Hokkaido, northern Japan, 2: Autumn leaf processing of nine deciduous trees along the stream.
1995
Yanai S. | Terasawa K.
The leaf decomposition processes of nine deciduous trees wee studied by a mountain stream in southern Hokkaido, northern Japan. Fallen autumn leaves were collected, selected, dried, weighted, and packed into nylon net bags with 5 mm mesh openings. These bags were placed in a shallow pool of third-order stream. To evaluate the effects of invertebrates, two types of litter bags, one covered with fine net (0.2 mm mesh; control treatment) and the other without the net (open treatment), were used for each tree species. Five bags of each treatment of each tree species were removed randomly at monthly or bimonthly intervals until early summer. Significant differences in leaf decomposition rates were observed among the nine species. The processing rates were classified into three groups by the decaying co-efficient k: fast-Alnus hirsuta (k=0.0129), intermediate-Betula platyphylla var. japonica, Carpinus cordata, Acer mono and Salix sp. (0.002<k<0.005) and slow Quercus mongolica var. grosseserrata, Magnolia obovata, Fagus crenata and Aesculus turbinata (k<0.002). By comparing the two treatments, the decaying rates by aquatic invertebrates ranged from 5 to 49%, and the decomposition rates by other factors, including leaching and bacterial activity, were estimated to be from 5 to 30%. A number of aquatic invertebrates colonized in the bags during winter. A case bearing cadissfly, (Goerodes satoi, Lepidostomatidae) was very dominant and very important in decaying leaves. The analysis of the carbon and nitrogen contents of the leaves implied that the food preferences by aquatic invertebrates were related to the C-N ratio of each tree species.
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