A study on change of vegetation in sediment deposition areas of check dams and prediction of its succession

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The Rokko Mountains located in the southern part of Hyogo Prefecture was chosen as this study area. Change of vegetation in sediment deposition areas of check dams which were constructed by the Ministry of Land, Infrastructure and Transport from 1928 to 1999 was surveyed by aerial photograph interpretation. Aerial photographs taken in 1969,1979,1989 and 1999 and topographic maps drawn on a scale of one to twenty hundred were used for investigation of vegetation in sediment deposition areas. The years after completion of check dams are smaller, the regeneration are faster. As the size of deposition areas increases, the rate of forestry area tends to decrease. Because if the deposition areas are larger, changes of river bed and water course occur frequently, and the areas suitable for grassland increase.Field investigation was conducted at the 17 check dams in Wachi Town and Ayabe City, Kyoto Prefecture and the Rokko Mountains. At the deposition areas, kinds of plants, micro-topography, types of soil and insolation were surveyed. As the grain size of soil is larger and water holding ability of soil in the deposition areas is weaker than original slope soil, the soil in the deposition areas tends to be dry compared with original slope soil The soil fertility is also lower than original slope, the pace of plant succession is slower. A model of plant succession at the deposition areas was proposed based on this research results.