We aimed to accumulate the useful information of Calystegia soldanella and Lathyrus japonicus for the conservation of them and as the landscape material in coastal sand dune. The germination ecology of them was investigated. Seeds of both species, which collected in the Hokkaido Ishikari beach, were treated with sulfuric acid to release the hard seed dormancy. Seeds were sown in sand dune with various burial depths in the autumn and next summer. In the sowing in autumn, seedling of C. soldanella emerged at the highest 89% from the burial depth 5 cm, and the emergence rate was decreased with the burial depth and even at 1 cm of depth. In the sowing in summer, highest emergence rate was shown from the burial depth 5 cm as well as the sowing in autumn, though emergence rates decreased less than sowing in autumn at the each burial depth. In the sowing in autumn, L. japonicus showed good emergence rate of 60-76% from 1 cm to 15 cm of burial depth, and it was the lowest at burial depth 1 cm. The highest emergence rate in the sowing in summer was 11%. The dry sand layer, which became extreme high temperature and dry, was considered as the cause of decreasing in emergence rates of both species in summer or at the burial depth of 1 cm. The influence of the burial depth of 5 cm or more on the emergence was different in both species. It seemed that this reason was a difference of the soil penetration power of both seedling.

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In coastal dunes, the destruction of vegetation by vehicles is of great concern. The purpose of this study was to investigate the running impact of vehicles on vegetation and soil, by comparing disturbed and undisturbed areas. The study area was enclosed by a fence and vehicles were prohibited from entering from 1992. At that time the disturbed areas were bare ground. This study was carried out in 2001, in the Ishikari coastal dune in Hokkaido. In the zone dominated by Elymus mollis near the shoreline, vegetation in disturbed areas had almost recovered. The spread of the species, reproduced by rhizomes, was thought to be the reason for the fast recovery. However, in this zone, except for the areas nearest the shoreline, soil was hardened and running impact remained. The reason the impact on soil did not remain only nearest the shoreline is thought to be that the impacted soil had been buried by accumulated sand carried from the sea along with wind. In the zone dominated by Rosa rugosa farther from the shoreline, the species, which is a naturalized and not present in the undisturbed areas, invaded the disturbed areas. Thus, vehicle running destroyed the zonation of vegetation. The soil hardness was still observed from the surface to a depth of 50 cm. Since sand hardly accumulates in this zone, the impact on soil is considered to remain over the long term, and there is also thought to be the possibility of not recovering to original vegetation.

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An effect of application of silk waste to planting of Pinus thunbergii in devastated land was investigated. Silk waste is a byproduct of silk reeling and mainly consists of silk proteins. Although the silk waste have high N content (about 13%), net N mineralization in soil was very slow. When the planting ground of broken granite was prepared on 13 November 1998, silk waste was applied into the planting ground at a rate of about 65 g N tree^-1. On March 1999, young trees of Pinus thunbergii about 30 cm in height were planted at intervals of 0.8 m. At 26 months after planting, the thickening growth at the plot with the silk waste was 32% higher than that with the compound fertilizer, which was commonly applied at revegetation sites. The concentration of inorganic N (NO₃^--N and NH₄⁺-N) at the plot with compound fertilizer was less than 3.5 mg kg^-1 throughout the experimental period, while that with the silk waste was more than 8.7 mg kg^-1 except in winter. The undecomposed residue of the silk waste remained in the ground at 30 months after application. The roots of Pinus thunbergii elongated into the silk residue. These results suggested that a large amount of N can be applied at the one time without the salt damage by the application of silk waste before planting.

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[in Japanese]

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[in Japanese]

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