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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 broad-leaved 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.

In Japan, land readjustment projects have standardized and expanded the design and size ofrice paddy fields. These projects have simultaneously promoted the conversion of levee slopes into stableinclines by expanding the difference in levels between paddy fields, which has expanded levee slopes, i.e. theweeding area. Continuous weeding work is required to prevent erosion and the collapse of steep levee slopes,and serious accidents sometimes occur in the weeding work using brush cutters on such slopes. Brush cuttershave been popular for weeding work, but mowing machines are increasingly popular for reasons of safetyand work efficiency. However, the levee form was designed based on the assumption of using brush cutters,which recommends small horizontal standing places both at the middle and the bottom of the slope.Therefore, it is necessary to examine whether the form of the levee slope is suitable for mowing machines.We conducted weeding work experiments in two types of levee slopes (with and without standing places)using two types of weeding equipment (mowing machines and brush cutters), and the flora of the leveeslopes and the working stress on operators were investigated. Our conclusions are that (1) mowing machinesare safer and more efficient than brush cutters and (2) the conventional levee form with standing places willalso be effective for mowing machines.

Dense bamboo grasses have delayed the growth of tree seedlings after the wind damage in a natural coniferous forest in deep mountains of Kiso District, Central Japan. After suppression treatment of the bamboo grass, a native sedge Carex oxyandra replaced them and made the growth of tree seedlings worse. The technique to suppress colonized Carex oxyandra is unknown, since this sedge has not ever been a harmful weed to be controlled. Thus, we established first experimental plots for suppressing Carex oxyandraby a herbicide, glyphosate potassium salt solution (Roundup Max load) by normal levels of dilution (control without herbicide, diluted to ×25, ×50 and ×100 volume with water) in May 2010. Next experimental plots with above-normal levels (diluted to ×100, ×200, ×400, ×800, ×1,600 and ×3,200) were established in June 2011. Coverage percentage, plant height of Carex oxyandra and tree seedlings were measured in each plot in autumn up to 2015. As a result, coverage and plant height of Carex oxyandra decreased obviously after a half year in all dilution levels, and the suppressing effect continued during 2 years in the lower dilution from ×25 to ×400. However, withered leaves formed a carpet-like thick mat, which remained several years and was suspected to restrict the germination and growth of tree seedlings. Consequently, the herbicide proved out effective to the sedge for 2 years, but some additional treatment is needed to secure the foundation space for tree seedlings within the mat of withered leaves.

Alien species in the family Poaceae play an important role as cover plants for erosion control on slopes, particularly in Japan. However, concerns have arisen regarding the adverse effects of these species on the local ecosystem and biodiversity. This study therefore examined the succession and seed propagation of alien Poaceae that are used for erosion control on the cut slopes of Sakurajima volcano in southwesternJapan. The results were as follows: Although the alien species used as cover plants were dominant for the first couple of years following their introduction to the slopes, they were displaced entirely by native species after the sixth year, which is considerably faster than ordinary succession. In addition, heading (flowering) of alien species was also rarely observed in this period. It is considered that the observed results were caused by the oligotrophic conditions of the slopes on Sakurajima volcano.

Many old trees were blown down by typhoons in 1959 and 1961 in a natural coniferous forestdeep in the mountains of Kiso District, Central Japan, and dense dwarf bamboo subsequently delayed thegrowth of tree seedlings. Forest engineers have tried to suppress dwarf bamboo to promote the regenerationof arboreal vegetation. However, after suppression of dwarf bamboo, an unknown grass unexpectedlycolonized the area and replaced them. Afterward, almost no tree seedlings could be observed in the newlyformed community, which seemed to worsen the extent of regeneration. It has been identified that the grassas Carex oxyandra, a native sedge species indigenous to Kiso District. Commonly, Carex oxyandra grows asshort as about 10 cm like lawn grass, but it seems to have exceedingly enlarged the size in the community.Thus, investigation on the morphological variation of this sedge in Miure Experimental Forest within theKiso National Forest was carried out. Leaf blade length, basal tiller length, and number of leaves per tillerwere measured in upper and lower stands on three slopes in 2009. Results revealed that leaf blade length andbasal tiller length in lower stands were approximately twice as large as those in upper stands on each slope,whereas the number of leaves per tiller was almost the same (8.8-9.4 leaves). Consequently, tussocks of thissedge became large in lower stands on a slope, which made the community overcrowded and damp,restricting tree regeneration.

Typhoon 9512 hit the island of Mikura-jima in 1995, causing many landslides and destruction of forest vegetation. For long-term observation of vegetation change, a research plot was established on a landslide slope in 2003. A simple terrace was built on this slope, which was planted with native species (Alnus sieboldiana and Miscanthus condensatus) in 2000 to accelerate vegetation recovery. From 2003 to 2012, a vegetation survey of the plot was conducted to elucidate the vegetation recovery process at an early stage. A. sieboldiana grew steadily and its density of individuals decreased. The number of species gradually increased due to invasion of new seedlings from adjacent forests, i.e. Castanopsis cuspidata, Persea thunbergii. We found some differences in vegetation recovery from another research site, which is a landslide slope seeded with exotic pasture grasses by helicopter in 2002. Seeding of exotic pasture gasses prevented the establishment of trees and reduces successional velocity.

In order to clarify the factors affecting the species diversity of plant communities around an irrigation pond, we surveyed Obaste-oike Irrigation Pond in Nagano Prefecture, Japan. The pond is comprised of three subdivided ponds, Kami-ike, Naka-ike, and Shimo-ike. Despite being adjacent to each other and connected by streams, the water levels in the three ponds differ. Five plant communities were studied, and one or two survey plots were selected in each community along each subdivided pond. A 32-m 2 quadrat was established in each plot of grassland, and a 400-m 2 quadrat was established in each plot of forest. The results of the distribution of species revealed that approximately 40% of the species were endemic to each subdivided pond in the terrestrial communities, whereas over 60% were endemic in the hydrophytic communities. To increase species diversity in irrigation ponds, especially in hyrdophytic communities, we suggest that dividing the ponds into several zones with distinct water levels and managing them in a sustainable manner is important.

Typhoon 9512 hit Mikura-jima Island, Izu Islands, Japan in 1995, producing many landslide slopes. Torino-o No.3 landslide slope was fascined with fallen trees and planted with seedlings of native species (Alnus sieboldiana tree and Miscanthus condensatus grass) as part of vegetation recovery efforts, and was subsequently seeded by helicopter in 2002 with exotic pasture grasses. To elucidate the influence of fertilization on the growth of transplanted seedlings of native species, exotic pasture grasses and newly invading trees and herbs, we designated seven plots in 2004, and surveyed vegetation every summer until 2013: four fertilized plots (fowl manure applied at 0.2 g/m 2 ) and three non-fertilized plots. The native species seedlings grew steadily irrespective of fertilization, but with self-thinning in A. sieboldiana. Exotic pasture grasses decreased gradually and almost disappeared in 2013. Fertilizing temporarily enhanced the growth of some species, but seemed to induce species competition, judging from the delay of invading of native trees and the increase of climbing plants in herbaceous layer in fertilized plots.

The objective of this study is to collect basic information on vegetation in road crack, especially in curbside crack of road, for evaluating plant biodiversity in urban landscape. A curbside crack in this study was defined as a linear space (under 20 mm in width) between the asphalt pavement and curbstone. The species composition of plants invading curbside cracks was surveyed in 38 plots along the serial National Route, over a total length of 36.5 km, in Fukuoka City in southern Japan. In total, 113 species including native plants (83 species, 73.5%), perennial herbs (57 species, 50.4%) and woody plants (13 species, 11.5%) were recorded in curbside cracks. Buried seeds were also obtained from soil in curbside cracks, which means the cracks would possess a potential as seed bank. Incidentally, no significant differences were found in the vegetation characteristics of curbside cracks among land-use types (Kolmogorov-Smirnov Test, P > 0.05). From these results, curbside cracks would be likely to play an important role in offering habitat for plants in urban area.