[in Japanese]

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We wish to demonstrate the effectiveness of biodegradable resin-coated rhombic wire nets (BRC-nets) in preventing the encroachment that gradually eats into the roots and bases of introduced woody plants when galvanized rhombic wire nets (GRW-nets) are used in seeding work. The superior effectiveness of BRC-nets was established on the basis of the results of an investigation conducted over a period of 7 years and 2 months after the completion of seeding work on an engineered bank slope in Tochigi prefecture. The following results were obtained: 1) Although it was not considered statistically significant, the average height growth in the GRW-nets was 93.5% and 89.4% of that in BRC-nets with mesh sizes of 50 mm and 75 mm. 2) The biomass in the basal area of the GRW-net was 71.4% and 65.0% that of BRC-nets with mesh sizes of 50 mm and 75 mm. Furthermore, the D²H values when D used as the base diameter of the GRW-net were 64.5% and 55.6% that of the corresponding BRC-nets with mesh sizes of 50 and 75 mm, respectively. 3) The encroachment rate in the case of GRW-nets was 68.8%, whereas those in the case of BRC-nets with mesh sizes of 50 mm and 75 mm were 15.1% and 15.8%, respectively. 4) If the base diameter of the introduced woody plant that was greater than 50 mm, the encroachment rate in the case of the GRW-nets was 100%, whereas in the case of the BRC-nets the rates were 35.0% and 36.8%, respectively. 5) The GRW-nets remained completely uncorroded; however, the BRC-net corroded and broke to a large degree, or disappeared. 6) The initial breaking load of the BRC-nets was 921.2 N, and they showed a tendency to decline sharply after 3 years and 5 months (35.0 N). Part of the wire net corroded severely during the 7 years and 2 months following the completion of the seeding work. However, the breaking load of the GRW-nets did not change from its initial value of 1,195.6 N. These results clearly show that encroachment can affect growth negatively, and that BRC-nets are superior and highly effective in preventing encroachment after the completion of seeding work and installation of wire-netting that affects the introduced woody plants.

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[in Japanese]

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