In the Solomon Islands, a large earthquake of magnitude 8.1 occurred on April 2, 2007, and the coastal area was badly damaged by the tsunami. We carried out a field survey in the southern coastal area of Gizo Island in August, 2007 in order to verify the effect of coastal forest in tsunami damage reduction. Most houses in the villages we surveyed had been washed away. We identified the position of the houses using satellite images before the tsunami disaster, and we obtained information on the structure, material and degree of damage of all houses by observation and interviews with the residents. Complete enumeration of coastal forest was carried out, while the representative landform was clarified by surveying the traverse baseline. As a result, factors which reduced damage to houses by the tsunami were considered to be the height of the house floor, ground height and the forest stand of the coastal area. Although the relationship between these factors could not be clarified due to heavy damage to the houses, it became clear that the coastal forest reduced the tsunami damage

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We investigated blown sand and the revegetation process following severe damage to Japanese black pines caused by pine wilt disease in the Fukiage sand dune. We found that blown sand following severe damage tended to increase with increasing damage to Japanese black pine from pine wilt disease. Moreover, numbers of trees, tree species, total volume of tree trunks, Fisher-Williams'index of diversity and the void ratio of surface soil tended to decrease with increasing amounts of blown sand. Thus the difference of the revegetation condition affects greatly on the spatial distribution of the volume of blown sand.

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The management conditions of Pinus thunbergii windbreak forest around Goosipo Beach, Sangha-Myon, Gochang-Gun, Jeollabuk-Do have been investigated, and the results are summarized as follows. The topography of Goosipo Beach district was by front sand dune-breakwater-P. thunbergii forests-cropland, while that of Myongsasipri district was structured typically by front sand dune-sand dune-P. thunbergii forests-cropland. It was assumed that forests of Goosipo Beach and Myongsasipri district had been planted around 1962～1964 and 1977～1978, respectively. The planting density survey showed that there were 10,000 trees/ha (7,000 trees/ha of P. thunbergii and 3,000 trees/ha of Robinia pseudoacacia). Some management projects were completed in these sites such as complementary planning in 1991, thinning and natural forest cultivation in 1994, and trunk injection treatment against Pinus orientals and dead tree cutting in 2000. Since most of these forests are private lands, forests were severely damaged by development and cultivation. The private lands within the forest need to be communized as possible as soon in order to preserve as coastal windbreak forest. More trees need to be planted in the denuded parts, and some thinning need at high tree density areas.

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We aimed to clarify the present vertical distribution of vegetation and the impact of volcanic activity on this distribution. In 2007, we conducted a vegetation survey ranging from 220 m to 500 m above sea level in the Amida river basin that is located on the northern flank of Mount Sakurajima. Tree age, numbers and species of trees, and the Fisher-Williams'index of diversity tended to decrease with increasing of elevation. Moreover, these items also tended to decrease with increasing thickness of the volcanic ash layer deposited since the Taisho eruption in 1914, the median diameter of solid particles in the volcanic ash layer, and the dry density of the volcanic ash layer. However, comparing 2007, when vegetation suffered a severe impact from volcanic activity, with 1963, when vegetation was only slightly impacted by volcanic activity, the vegetation in 2007 was found to be destroyed down to around 220 m above sea level. Thus vegetation succession in 2007 was much poorer than that in 1963.

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The suitable habitat for establishing of seedlings derived from old and large-sized Japanese black pine trees on the coastal pine forest was estimated. Germination rate of seeds of old and large-sized pine tree was high. It was considered that preserving seeds of old and large-sized pine trees and planting these seedlings would be effective in order to maintain pine forests which consisted of old and large-sized pine trees. Open habitat which were covered with sand was suitable for establishing low and thick pine seedlings, although the number of seedlings was low.

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In 2007, we investigated the impact of volcanic activity on growth of vegetation, and deposition and physical nature of volcanic ash at the same altitude on the flank of Mount Sakurajima. The constituent tree species, the tree age, the breast high cross-sectional area and the Shannon-Wiener's index of diversity tended to increase with decreasing volcanic activity effects. Moreover, thickness of the volcanic ash layer deposited since the Taisho eruption in 1914, the median diameter of solid particles in the volcanic ash layer, and the dry density of the volcanic ash layer tended to decrease with decreasing volcanic activity effects. The decrease of volcanic activity effects caused the decrease of volcanic ash deposition, and it brought the recovery of the vegetation. However, comparing 2007, when vegetation suffered a severe impact from volcanic activity, with 1963, when vegetation was only slightly impacted by volcanic activity, the vegetation in 2007 was much poorer than that in 1963.

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The role of coastal forests in reducing the damage caused by the recent Indian Ocean tsunami is drawing attention. In the coastal regions of southern Sri Lanka, which was one of the affected areas, the current state of the coastal forests was ascertained through classification based on satellite photo readings with field surveys and by calculating the area ratio for each type of coastal forests. The coastal forests were divided into six types, the distribution of which differs greatly from coasts facing the open sea to the shores around lagoons. On a coast facing the open sea, natural forests characteristic of coastal areas were not found, but approximately 83 ha of casuarina plantations have been established on sand dunes. Mangrove forests are characteristic of lagoon shores and do not exist on coasts facing the open sea. They occupy approximately 10 % of the area within a range of 100m from the lagoon shores in this region. If coastal forests are to be used as protection against disasters, it is necessary to consider differences caused by these site conditions.

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