The objective of this research is to evaluate the importance of vegetation of retaining walls made of natural stones (i.e., masonry revetment) in plant biodiversity. In this paper, plant compositions and the characteristics of masonry revetments were surveyed in terraced fields in Toho Village, southern Japan. In total, 43 families and 88 species were recorded in the spaces of the masonry revetments. Of these 88 species, 68 (77.3%) were herbaceous, excluding 13 (14.8%) ferns, and 7 (8.0%) species were woody plants. Native species accounted for 69 (78.4%) of the 88 species. Furthermore, numerous species not found in the horizontal environments around the terraced fields were also seen in the spaces of the masonry revetments. From these results, the authors consider that masonry revetments provide a habitat for plants and therefore contribute toward the conservation of plant biodiversity on a local scale.

Street trees are one of the important components of green infrastructure in urban area. This study surveyed the relationship between introduction trends of street trees in Japan and factors such as latitude and climatic conditions. The results showed that Japanese street trees tended to be mainly broadleaved rather than coniferous, and many of these were native species. In addition, we found that street trees not only fulfill the roles of disaster prevention and disaster reduction, but also contribute to citizen welfare and recreation because a relatively large number were flowering trees (generally planted to enjoy flowers). Also, it was suggested that Cerasus sp. are the street trees that represent Japan, because could be confirmed in all 47 prefectures. Meanwhile, Japan is categorized into four groups with characteristic street trees introduced under the influence of the latitude and temperature in each group. Particularly, while the introduction of street trees is conducted by the individual municipalities (prefectures, cities, towns, villages, and areas), similarities in the response in terms of latitude and temperature regarding the street trees in Japan are being observed beyond the administrative borders. Incidentally, weeds which invade at the base of street trees were managed by periodic weeding, instead of any special treatment, is the most common weed management strategy in Japan. In addition, installation of shrubs, artificial inorganic cover such as concrete, and equipment, etc. has also been observed and may lead to a reduction in the weeding previously mentioned.

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