In order to establish more secured stabilized slope by introducing vegetation onto bare steep cutslopes of the Siwalik region resulting from road construction, we, surveyed the root morphology of the vegetation that was introduced by seeding and investigated the combination of plants from slope stabilization point of view. The root survey of the introduced plants, of Nepalese, Japanese and naturally invaded species onto the steep slopes of the Siwalik region was carried out. As a result, the root morphology of trees on slopes could be broadly divided in two types namely, Main root type and Lateral root type. Furthermore, each of the two types could be furtherdivided into two. Hence, the root types were divided into four types; Intensive main root type, Main root divergence type, Lateral root dispersion type and Lateral root concentration type. Observing the relationship between the root type and soil conservation on the slopes, we were able to approve that the Intensive root type was effective for stabilizing weathered slope and the Lateral root concentration type for surface erosion protection. Under root morphological aspect, the combination of plants from the slope stability perspective is discussed.

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Transference intact surface soil is the new method which transfer forest surface soil without disturbance as much as possible for preparation of artificial urban open space. We investigated physical and chemical characteristics of soils in coppice forest which was made using transference intact surface soil on Higashi Imperial Gardens (T) about 10 years ago and natural coppice forest (N) which established near the collecting area of surface soil for the transference and compared these characteristics between T and N to examine the changes in T soil for about 10 years. Thickness of transferred soil on T soil was approximatery 10 cm. The soil acidities of T soils transferred were higher than N soils. The carbon and nitrogen concentrations of T soils were considerably lower than N soils. The exchangeable bases concentrations of T soils shows tendency to exceed them of N soils. It seemed that soil organic matter in T were decreased. It seemed that the transferred soil on T were affected by deposition and so on. Because it is expected that those changes in the characteristics of T soil affect vegetations and soil organisms, further investigations concerning them are needed.

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As a field of recreation and scenic beauty for people or habitat for animal community, hydrophytes such as Phragmites australisTrin., Scirpus tabernaemontaniGmel., Zizania latifoliaTurcz. and Typha latifoliaL. have frequently been planted in waterfront. The purpose of this study is to propose a consideration for planting of foregoing plants based on the allelopathic potential of interspecies. The allelopathic potential was examined using root chambers in which each young shoot independently lived. That is to say, it was examined from the elongation rate of young shoot root which changed by the contact of each root chamber. On the other hand, the experiment which divided each root chamber at the time of contact by filter was also carried out. The filter adsorbs and removes chemical compound of several. Results were as follows. Phragmites australis; Elongation rate of the root significantly lowered in contact with the root chamber in which Zizania latifoliaor Typha latifolialived. Scirpus tabernaemontani; Elongation rate of the root significantly lowered in contact with the root chamber in which Phragmites australis or Typha latifolia lived. Zizania latifolia; Elongation rate of the root significantly lowered in contact with the root chamber in which Scirpus tabernaemontani or Typha latifolia lived. Typha latifolia; Elongation rate of the root significantly did not lower in contact with the root chamber in which either species lived. As a result of dividing root chambers by the filter, combinations of species which elongation rate of the root significantly did not lower increased in comparison with the experiment which did not divide the root chamber. From the above results, it was guessed that the allelopathy which inhibited elongation of the root by secreting some kind of chemical compound existed in foregoing interspecies. Therefore, a consideration of ensuring the sufficient planting interval was required for elongation of foregoing roots.

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The fertilizer efficiency of silk waste for planting of bulbous plants in construction byproduct as a planting ground were examined and compared with two commercial controlled release fertilizers, isobutylidene diurea (IBDU) and polyolefin-coated fertilizer. Silk waste mainly consists of silk proteins, which has high N content and is decomposed slowly in soil. Five species of bulbous plant, Narcissus tazetta var. chinensis, Lycoris albiflora, Allium chinense, Muscari armeniacum and Oxalis variabilis, were planted with each of the three fertilizers. No maintenance was carried out, except for weeding once during the experimental period. The silk waste was decomposed continuously for about 400 days, which indicated that the silk waste had fertilizer efficiency for not less than 400 days under the conditions used in this study. In the second growing season after planting, all plants grown with the silk waste or IBDU were larger than those grown without any fertilizers, except for 0. variabilis, which was hardly viable until the second season. In the case of A. chinense and M. armeniacum, no or little effects of fertilizer were seen on growth with polyolefin-coated fertilizer. Regardless of the type of fertilizer or the degree of plant growth, the ratios of green coverage, determined by image analysis, were equally increased relative to those without fertilizer, except for A. chinense and M. armeniacum with polyolefin-coated fertilizer. N. tazetta var. chinensis with IBDU had many thin leaves of daughter bulbs, which indicated that the division of bulbs occurred during the first growing season due to the excess N released from IBDU. The weight of M. armeniacum with IBDU was smaller than that with the silk waste, which suggested that salt damage occurred in the first growing season resulting in the depression of fertilizer efficiency or that the fertilizer efficiency of the silk waste was higher than that of IBDU in the second growing season. These results suggested that silk waste was an efficacious fertilizer in planting under these conditions.

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We investigated the characteristics of nutrition concentrations, decomposition and carbon (C) mineralization of plant waste originated from tree (i.e. wood chip, stems or leaves and branches of Prunus×yedoensis, Cinnamomum camphora and Pinus thunbergii), and discussed the relationships among those factors. Futhermore, we examined the effects of addition of mineral nitrogen (N) or manganese (Mn) to the wood chips on the characteristics of C mineralization. The nutrition concentrations of leaves and branches were higher than those in stems, and showed the highest value in Cinnamomum. The amounts of C mineralization of wood chips mixedinto soil had negative correlations with the C: N or C: P ratios of the wood chips. The amounts of C mineralizations of wood chips for 50 days after mixing wood chips and soil were accelerated by mineral N addition, and weren't affected by mineral Mn addition. The accelerations of C mineralization by mineral N addition were enhanced with the increases in C: N ratio of wood chips. The weights of wood chips from leaves and branches on surface soil were decreased with increases in accumutlated temperature from immidiately after the placement. On the other hand, the weight of wood chips from stems were decreased after decreasing in those C: N ratio by immobilization of N. The chemical characteristics of wood chips as C: N ratio or C: P ratio influenced strongly on weight losses of wood chips.

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