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Epiphytic orchids comprise 68% of vascular epiphytes globally; nevertheless, many are endangered. One such epiphytic orchid is Phalaenopsis japonica, which is widely used in the floricultural industry. This study aimed to identify the mycorrhizal fungi of adult P. japonica and their roles in seed germination and seedling development. Root samples were collected from 32 adults across 4 sites in southern Japan, and mycorrhizal fungi were identified using Sanger and high-throughput sequencing (HTS). The results show phylogenetically diverse mycobionts, mainly Ceratobasidiaceae (CE) and Tulasnellaceae (TU), with dominant OTUs designated CE6 and CE22. Sanger sequencing found 9 OTUs, 4 CE, and 5 TU; HTS detected 22 OTUs, 4 CE, 16 TU, and 2 Serendipitaceae. Seeds inoculated with CE6 improved germination and protocorm development compared with other strains. In addition, asymbiotic seedlings inoculated with CE6, CE22, and TU18 displayed varying effects in growth, with CE6 being the most notable. While TU18 did not promote seed germination, it effectively promoted leaf development in seedlings. Overall, Ceratobasidiaceae was predominantly associated with seed germination, seedling growth, and the adult stages, with CE6 and CE22 becoming the primary partners throughout the life history of P. japonica. Our findings illuminate mycorrhizal symbiosis in epiphytic habitats, offering conservation and commercial production insights. [ABSTRACT FROM AUTHOR]

Necrotic lesions were found on the leaves and stems of Japanese white oak (Quercus myrsinifolia) seedlings on a nature trail in Japan. A species of Phytophthora was isolated from the necrotic lesions and adjacent soil. Molecular phylogenetic analysis and morphological examination revealed it to be Phytophthora castaneae, known as a causal pathogen of trunk rot on chestnuts. Pathogenicity testing showed that P. castaneae caused leaf blight on previously healthy Japanese white oak seedlings. In addition, using a soil infestation method, we confirmed that it was also pathogenic to chestnut seedlings, but the roots of Japanese white oak were not infected. This is the first report of P. castaneae causing disease in a natural ecosystem in Japan. [ABSTRACT FROM AUTHOR]

The reproductive characteristics of understory bamboo and the effects of dieback on overstory tree seedlings through temporal changes in the environment at the forest floor have only been examined in a few bamboo species, due to the unpredictable occurrence of flowering events and long intervals between them but provide valuable information on tree regeneration and succession in a forest with dense dwarf bamboo cover.We investigated environmental conditions and assessed seedlings (< 30‐cm tall) of the dwarf bamboo Sasa borealis and overstory tree species at 44–50 measurement points during 2016–2021, which included a S. borealis mass flowering event in 2017. We also conducted seed germination tests to determine germination rates and patterns in S. borealis. Environmental factors affecting seedling recruitment of S. borealis and of overstory trees were analysed using spatiotemporal generalized linear mixed models in the Bayesian framework.We observed gradual temporal changes in the environment, including increasing canopy openness and decreasing maximum height of dead S. borealis culms. The seeds germinated slowly and the emergence of current‐year S. borealis seedlings peaked in spring–summer in 2019. The tree seedling density after 2019 increased significantly compared to that before the dieback. The model results suggest that tree seedling establishment was enhanced by increased light availability.Continuous field observation beginning before S. borealis dieback revealed gradually enhanced tree recruitment in response to slow decay of the remaining dead culms and slow recovery of S. borealis. The seedling regeneration pattern of understory bamboo partly contributes to a prolonged opportunity for overstory tree regeneration. [ABSTRACT FROM AUTHOR]

Rice is the primary source of food for more than half of the global population. Accordingly, improving the cold tolerance of rice is vital for ensuring food security. In this study, a new cold tolerance-related QTL in rice (qPSR7-2) was detected on chromosome 7 following a genome-wide association study involving 173 japonica rice germplasm resources. The fine mapping of this locus identified Os07g0541800 as a candidate gene associated with qPSR7-2. This gene encodes a cysteine-rich receptor-like kinase. The functional verification of Os07g0541800 involving transgenic plants indicated that qPSR7-2 positively regulates rice cold tolerance at the seedling stage. The examination of the cold tolerance of 984 germplasm resources from the 3000 Rice Genomes Project at the seedling stage and their respective haplotypes at qPSR7-2 revealed that the proportion of favorable haplotypes in germplasm resources increased as the latitude increased. More than 90% of the rice varieties cultivated in Europe and Japan appear to carry qPSR7-2, implying that qPSR7-2 may mediate the acclimation of rice to low-temperature stress. The findings of this study will further clarify the molecular networks regulating rice cold tolerance, while also providing researchers and breeders with new genetic resources and information relevant for developing cold-tolerant rice varieties. [ABSTRACT FROM AUTHOR]

Forest trees species are often genetically adapted to local environmental conditions. Therefore, local seeds are recommended for ecological restoration. However, seedlings of broad‐leaved tree species, such as Japanese beech (Fagus crenata), are limited in their commercial seedling production in Japan. Thus, long‐distance transfer of seeds and/or seedlings is common. F. crenata's distinct geographical structure is well known; large‐scale seed transfer may increase the risk of genetic disturbance. Several provenance trials of the species revealed that phenotypic traits such as leaf area and bud flush date differed latitudinally and/or between the Pacific Ocean side and the Japan Sea side. We investigated leaf size and bud flush date and identified the chloroplast DNA haplotype of trees planted in two provenance trials established in Hokkaido, Japan. We then examined whether cpDNA haplotype information is useful as a proxy in ecological restoration when using seedlings with incomplete seed source information. This study indicated that suitable seedlings could be selected based on chloroplast DNA haplotype information in F. crenata in the case of incomplete seed source information. [ABSTRACT FROM AUTHOR]

Since 2002, papaya black rot has been spreading over several islands of Okinawa Prefecture. The pathogen of the disease was identified as Erwinia sp., genetically close to E. mallotivora and E. papayae. In terms of the disease transmission, it is probably carried by the wind or rain. In order to devise a prevention strategy for the disease, in vitro pesticides susceptibility of the pathogen and tests with papaya pot seedlings were conducted. A minimum inhibitory concentration assay demonstrated that copper (II) hydroxide, basic copper sulfate, and captan present in the papaya-registered pesticides inhibited the growth of the pathogen on nutrient agar plates. In addition, mancozeb that is non-papaya-registered pesticide also showed an inhibitory effect on the pathogen. Thus, there is a high possibility that even the existing papaya-registered or non-papaya-registered pesticides can prevent papaya black rot. In the test with papaya pot seedlings, copper (II) hydroxide exerted a relatively lower pesticide effect; however, captan exhibited a pesticide effect, although it is one of the fungicides not registered for use in the treatment of bacterial diseases of plants in Japan till date. Indeed, based on the result of the present study, the official registration of legal expansion for use of captan to control papaya black rot was approved in Japan on December 22, 2021. [ABSTRACT FROM AUTHOR]

Seedlings of Pinus densiflora and Abies sachalinensis were inoculated with Tuber mycelial strains of the Puberulum clade in vitro to examine the morphological characteristics of their ectomycorrhizas. Axenically germinated seedlings were inoculated with the mycelia of five taxa from the Puberulum clade and grown in glass jars for 4 mo in an illuminated incubator. The seedlings were successfully colonized by the inoculated Tuber strains, as confirmed by the nuclear ribosomal internal transcribed spacer barcoding of the synthesized ectomycorrhizas. The ectomycorrhizas were characterized by a pale yellow to brown color, short needle-shaped cystidia, and net-like hyphal arrangement, and epidermoid cells on the mantle surface; notably, these features are similar to the ectomycorrhizas of various Puberulum clade members. As the ectomycorrhizas of different Tuber species are indistinguishable by morphological characters, molecular techniques are necessary to identify ectomycorrhizas formed by Tuber species within the Puberulum clade. [ABSTRACT FROM AUTHOR]

Failure to sprout due to seed-tuber rot is a serious problem for autumn potato seedling cultivation in Nagasaki Prefecture, Japan. In this study, five strains were isolated from rotten seed tubers sampled in 2015; when tubers were inoculated with these strains, the tubers developed rot and failed to sprout. We identified these strains as Fusarium acuminatum, Fusarium commune, and the known agent of potato dry rot, Fusarium oxysporum based on morphological and DNA sequencing analyses. F. commune and F. acuminatum were identified as causal agents of potato dry for the first time in the world and in Japan, respectively. [ABSTRACT FROM AUTHOR]

The collection of wild oyster seedlings is an integral part of Pacific oyster aquaculture, necessitating efficient methods of seedling collection. Matsushima Bay is a key area for the production of oyster seedlings in Japan. To predict the transport of oyster larvae in the bay during the 2017 seedling collection season, we conducted particle tracking based on the finite volume community ocean model. Larval sampling was conducted early in the seedling collection season to observe the horizontal distribution of hatched larvae, which was then used as the initial distribution for particle tracking. Particle tracking was driven by the predicted tidal elevation, past meteorological forcing variables, and historical river discharges from the period of June–July 2015. This yielded a prediction of larval distribution after one week had elapsed. The location of the predicted daily highest density was predominantly on the eastern side of the bay and did not change considerably over time. The predicted larval distribution differed markedly from the observed distribution of pre‐attachment stage larvae, suggesting that processes other than the circulation in the bay influence actual larval transport. A model that included larval mortality and ontogenetic vertical migration was able to approximate the observed larval distribution, indicating the importance of these processes. Sensitivity analyses for the parameters relating these processes revealed that larvae tend to remain in the bay when they grow quickly. Although there were some differences between predicted and observed outcomes, our study represents notable progress in demonstrating the potential for predicting oyster larval transport. [ABSTRACT FROM AUTHOR]

Understanding variation in root and shoot growth phenology among species is crucial to understanding underlying mechanisms of temporal niche differentiation. However, little is known about the relationship between root and shoot phenology, or how this relationship varies among functional traits. We examined fine root and shoot phenology of 42 seedlings representing a variety of woody species that inhabit the cool temperate forests of northern Japan. Some aspects of phenology were common to the pool of species examined: we found positive relationships between root and shoot phenology for the end of growth, and for the duration of growth, but not for the start of growth. Further, seedlings that started root growth relatively early also ended root growth relatively late. Other aspects of phenology varied predictably with functional traits, i.e. leaf habit and successional status: first, root growth in evergreen species started significantly earlier and ended later than in deciduous species; second, early successional species had the longest duration of shoot growth among all successional types. Our results suggest that niche differentiation may be promoted by differences in phenology between root and shoots, likely contributing to the co‐existence of woody seedlings in temperate forests. [ABSTRACT FROM AUTHOR]

Burkholderia glumae causes bacterial seedling rot (BSR) and bacterial grain rot (BGR) in rice (Oryza sativa), both of which are important diseases in Japan. We previously evaluated major Japanese cultivars for BGR resistance and selected standard cultivars for resistance assessments. Here, we assessed the BSR occurrence rate in cultivars from the World Rice Collection (WRC) and other sources and found wide variation in resistance. Next, we evaluated major Japanese cultivars for BSR resistance and found that two Japanese landraces, 'Kujuu' and 'Aikoku', showed "strong" resistance; most others were categorized as "medium" or "medium to weak". We previously developed a near-isogenic line (RBG1-NIL) by introducing the genomic region containing RBG1, a quantitative trait locus (QTL) for BSR resistance, from 'Nona Bokra' (indica) into 'Koshihikari' (temperate japonica). The resistance level of RBG1-NIL was "strong", indicating the effectiveness of RBG1 against BSR. The correlation between BSR and BGR resistance scores was low, indicating that it is necessary to introduce QTLs for resistance from different sources to develop cultivars resistant to both BSR and BGR. On the basis of the screening results, we selected standard cultivars for BSR resistance to cover a range of resistance levels. [ABSTRACT FROM AUTHOR]

Lianas have a huge influence on forest structure and function. However, it is unclear how the surrounding environment affects the establishment of liana seedlings in temperate forests. We addressed the following questions: (1) Can current-year seedlings persist under a closed canopy? (2) Do current-year seedlings form aggregated distribution and how has their spatial distribution varied over the years? (3) How does the light condition, soil moisture content, forest floor litter, understory vegetation, and the distance from the conspecific adults affect the establishment and survival of seedlings? We examined the distribution pattern and survivorship of current-year seedlings of the temperate liana species, Wisteria floribunda, across a heterogeneous environment for 6 years using 1 m2 sub-quadrats (n = 651) in a 6 ha plot within the Ogawa Forest Reserve, an old-growth, temperate, deciduous forest in central Japan. In total, 908 current-year seedlings were observed during the study period, 87% of which emerged in 2014. Over half (56%) of these seedlings survived until 1 year after germination, which was relatively high compared with other tree species in this forest. The seedlings formed significantly aggregated distribution, but the degree of aggregation decreased over time. The number of emerged seedlings was negatively associated with the presence of dwarf bamboo (Sasa borealis) and the distance from the nearest conspecific adult. However, the survival rate of the seedlings was negatively associated with the presence of dwarf bamboo and soil moisture content and was positively associated with the openness of the canopy and the distance from the nearest conspecific adult. An enhanced survival rate under more intense light conditions and the ability to persist within the shaded understory may be important for the survival of this species in the earlier stage of the life history. [ABSTRACT FROM AUTHOR]

Hondo spruce (Picea jezoensis var. hondoensis (Mayr) Rehder)) is separately distributed among several mountainous regions in central Japan as remnant populations of the last glacial period. To identify factors that affect Hondo spruce seedling regeneration on decaying logs, we investigated the relationships between climatic conditions, log properties, including decay type by fungi, and Hondo spruce seedling density on logs using data from seven subalpine Hondo spruce forests in central Japan. The results showed that the presence of soft rot was associated with higher seedling density, and the effect of brown rot in sapwood and white rot in heartwood on the predicted number of spruce seedlings on logs switched from positive to negative with increasing temperature and precipitation. Because soft rot occurs under humid conditions, the use of forest management techniques that increase the number of logs with soft rot in sapwood (e.g., by keeping the forest floor moist) are recommended for the sustainable regeneration of Hondo spruce. However, the relationships between wood decay type and seedling regeneration can also be affected by climate condition and thus are more complex than previously thought. [ABSTRACT FROM AUTHOR]

Sudden wilt and blight developed on ginseng seedlings (Panax ginseng) in Ibaraki Prefecture, Japan, in June 2017. Rootlets rotted and fell off. Aseptate hyphae were observed in this trace tissue that detached from main roots, which had orange-yellowish tinges. The white mycelium isolated from the diseased main roots was identified as Pythium myriotylum based on morphology and cox1 gene sequences. The isolate reproduced the symptoms on healthy ginseng seedlings and was re-isolated from diseased seedlings. This is the first report of seedling rot (naegusare-byo in Japanese) on ginseng caused by P. myriotylum in Japan. [ABSTRACT FROM AUTHOR]

• We compared two Q-RT-PCR methods for detecting potato spindle tuber viroid. • A RNA sample acquisition method was optimized for PSTVd detection in dahlias. • Q-RT-PCR is a suitable method for identifying PSTVd-infected dahlia bulbs. • Additional dahlia tissues and organs can also be sampled diagnostically. • This article can be used to help prevent widespread dissemination of PSTVd. Potato spindle tuber viroid (PSTVd) belongs to the Pospiviroidae family and is the type species for the genus Pospiviroid. In 2011, PSTVd was first detected in dahlias in Japan. Since that time, unregistered PSTVd isolates have been identified in seven field-grown dahlia cultivars. None of the infected dahlias showed disease symptoms during the early stages of infection, however, growth suppression occasionally occurred during later stages. Therefore, in dahlia, diagnosing PSTVd by the external appearance of plants is difficult, and the threat of new PSTVd isolates spreading to other susceptible hosts still remains. In this study, we developed an efficient inspection method using several dahlia plant tissues and organs including dried bulbs. This developed method will be useful for inspecting seedlings to prevent the invasion of PSTVd at the border. [ABSTRACT FROM AUTHOR]

Plug seedlings are increasingly used in vegetable cultivation in Japan, because they are suitable for machine operations and are disease resistant; however, in cabbage cultivation, variation in seedling growth affects plant growth after transplanting to the field, and eventually, harvesting all the cabbages at the same time is not possible. In this paper, a simulation model used to express the growth variation in cabbage plug seedlings is proposed to reveal their cultivation characteristics and consider a cultivation technique that would produce uniform growth among seedlings. In this simulation model, the mutual shading among neighbouring plug seedlings resulting from high-density planting, which is one of the factors of variation in seedling growth, was modelled. The model parameters were obtained from the results of a cultivation experiment comparing growth against the light quantity that seedlings could receive; however, there were differences between the growth of a single seedling in the cultivation experiment and the growth of the plug seedlings. It is believed that growth rate and mass would be greater for a single seedling than for the plug seedlings. This simulation was able to express the growth variation of the actual plug seedlings by adjusting the model parameters. [ABSTRACT FROM AUTHOR]

Mass mortality of Fagacean tree species caused by Raffaelea quercivora has occurred widely in Japan. Because conidia or other propagules of the pathogen have not been found in infected trees, pathogen spread is assumed to occur primarily by hyphae. To clarify the relationship between hyphal growth of the pathogen within trees and their vessel arrangements, we examined two native Japanese oaks, Quercus crispula and Quercus glauca, and three exotic American oaks, Quercus coccinea, Quercus palustris and Quercus rubra. Quercus glauca is a radial-porous species, whereas the other four species have a ring-porous wood structure. Hyphal growth within inoculated potted living seedlings and in cut, sterilized stem segments of these species was examined microscopically after fungal inoculation. Water conductance in the seedlings was examined using transverse stem sections. The proportion of non-conductive sapwood in Q. crispula, Q. coccinea and Q. palustris differed between inoculation and control treatment, being much higher in inoculated seedlings. The proportions were positively correlated with the extent of the hyphal growth. In sterilized stem segments, the extent of fungal colonization varied among the foreign ring-porous species Q. coccinea, Q. palustris and Q. rubra. It is hypothesized that the extent of colonization by R. quercivora reflects the extent of non-conductive sapwood irrespective of tree species, but is little affected by vessel arrangements. [ABSTRACT FROM AUTHOR]

Seedlessness is a desirable characteristic for both fresh and processed citrus markets and one of the most important breeding objectives. In this paper, progress on studies for seedless breeding of citrus in Japan is reviewed. Among the several types of male sterility, anther abortion is the strictest male sterility in citrus and was shown to be controlled by both nuclear and cytoplasmic genes. Several seedless cultivars with male sterility have been developed. The mechanism and inheritance of the strictest female sterility derived from 'Mukaku Kishu' (Citrus kinokuni hort. ex Tanaka) were clarified and seedless cultivar and parental lines with this female sterility have been released. Some self-incompatible cultivars show seedlessness when coupled with parthenocarpy. S (self-incompatibility) genotypes of several cultivars have been estimated. Tetraploid plants, as parents of triploid offspring, were obtained from nucellar seedlings, and by ploidy mutation, colchicine treatment, and protoplast fusion. Triploid plants were produced from the combination of not only tetraploid and diploid crosses but also diploid and diploid crosses. New triploid seedless cultivars were bred by programmed cross-breeding and protoplast fusion. [ABSTRACT FROM AUTHOR]

International trade is one of the main ways by which a species can expand its geographical range. Since the beginning of the twenty-first century, the worldwide distribution of many pests has increased through the international circulation of crop seeds and seedlings. In this review, viruses and viroids that have invaded Japan since 2000 are described in order of their prevalence. Measures to prevent invasion by such viruses and viroids and protect agricultural production in Japan from alien pests are discussed. [ABSTRACT FROM AUTHOR]

A new disease found on garland chrysanthemum in Osaka, Japan in 2009 and its causal agent were identified and characterized. Light brown spots first appeared on lower leaves of seedlings, and the leaves blighted or rotted. A fungus isolated from diseased plants, described recently as Gibellulopsis chrysanthemi, was demonstrated to reproduce the natural symptoms in inoculation tests. Sufficiently long, moist periods after inoculation promoted the infection even after lengthy dry periods. The pathogen also caused the disease on chrysanthemum and lettuce, but not on seven other vegetables. The fungus caused the disease after 6 months of dry storage. The disease was termed seedling rot ('nae-fuhai-byo' in Japanese). [ABSTRACT FROM AUTHOR]

Abstract: We examined the effects of ambient ozone, at the somma of Lake Mashu in northern Japan, on the growth and photosynthetic traits of two common birch species in Japan (mountain birch and white birch). Seedlings of the two birch species were grown in open-top chambers and were exposed to charcoal-filtered ambient air (CF) or non-filtered ambient air (NF) at the somma of Lake Mashu during the growing season in 2009. For the mountain birch, ambient ozone significantly increased the ratio of aboveground dry mass to belowground dry mass (T/R ratio), although no difference in the whole-plant biomass was observed between the treatments. For the white birch, in contrast, ozone exposure at ambient level did not decrease in growth and photosynthesis. These results suggest that ambient O3 at the somma of Lake Mashu may shift the allocation of biomass to above-ground rather than below-ground in the mountain birch. [Copyright &y& Elsevier]

Graft unions of nursery stock of grapevine ( Vitis vinifera L.) collected in Japan yielded non-pathogenic strains of Agrobacterium. On the basis of classic diagnostic tests, a sequence analysis and a previously reported multiplex PCR method, the non-pathogenic strains ARK-1, ARK-2 and ARK-3 were identified as Agrobacterium vitis. Stems of grapevine seedlings were inoculated with both a cell suspension of seven mixed strains of A. vitis (Ti) as a pathogen and one of a new strain or A. vitis strain VAR03-1, one of the biological control agents against crown gall previously reported, as competitors to assay the suppression of tumour formation caused by the pathogen. In a test with a 1:1 cell ratio of pathogen/nonpathogen, strains ARK-1, ARK-2 and ARK-3 reduced the tumour incidence.. In particular, strain ARK-1 was strongest at inhibiting tumour formation in this study. Strain ARK-1 established populations on roots of grapevine tree rootstock and persisted on roots for a year. ARK-1, ARK-2 and ARK-3 did not produce a halo of inhibition against A. vitis (Ti) strain on YMA medium. Moreover, strain ARK-1 did not reduce tumour incidence on the stems of grapevine when ARK-1 was dead or only culture filtrate was used. This result indicates the possibility that these new strains inhibit grapevine crown gall in planta by a different mechanism other than VAR03-1. In particular, one of the new strains, named ARK-1, was most effective in inhibiting tumour formation on grapevine and appears to be a promising new agent to control grapevine crown gall. [ABSTRACT FROM AUTHOR]

Low temperatures at the initial stages of rice development prevent fast germination and seedling establishment and may cause significant productivity losses. In order to develop rice cultivars exhibiting cold tolerance, it is necessary to investigate genetic resources, providing basic knowledge to allow the introduction of genes involved in low temperature germination ability from accessions into elite cultivars. Japanese rice accessions were evaluated at the germination under two conditions: 13°C for 28 days (cold stress) and 28°C for seven days (optimal temperature). The traits studied were coleoptile and radicle length under optimal temperature, coleoptile and radicle length under cold and percentage of the reduction in coleptile and radicle length due to low temperature. Among the accessions studied, genetic variation for traits related to germination under low temperatures was observed and accessions exhibiting adequate performance for all investigated traits were identified. The use of multivariate analysis allowed the identification of the genotypes displaying cold tolerance by smaller reductions in coleoptile and radicle lenght in the presence of cold and high vigour, by higher coleoptile and radicle growth under cold. [ABSTRACT FROM AUTHOR]

Abies sachalinensis and Picea glehnii are co-dominant tree species and major components of the forests of Hokkaido, Japan. Recent work suggests that a reversal in potential competitive superiority at different developmental stages could be important to explain their coexistence. Such shifts in competitive advantage can be mechanistically understood by studying the corresponding physiological differences between distinct life stages. Accordingly, our objective was to investigate in the field the photosynthesis of shade-growing juveniles of these species from two different size-classes, seedlings and saplings. Our results show that seedlings of both species had higher concentrations of photoprotective xanthophylls than saplings, especially in spring, and suggest that seedlings have a lower threshold of stress tolerance than saplings. Photosynthetic capacity per needle area and lateral shoot extension rate decreased from the seedling to the sapling stage in A. sachalinensis, while in P. glehnii, both increased from the seedling to the sapling stage. Abies sachalinensis had higher photosynthetic rates at the seedling stage but lower rates at the sapling stage than P. glehnii. Nevertheless, A. sachalinensis had a higher lateral shoot extension rate than P. glehnii at both stages. Our physiological results support previous ecological observations that A. sachalinensis is a superior competitor to P. glehnii in the understory, and show that its competitive advantage is higher at the seedling stage than at the sapling stage. [ABSTRACT FROM AUTHOR]

The alpine timberline on Mt. Fuji (central Japan) is at 2,400-2,500 m above sea level. Over a 21-year period (1978-1999), we tracked changes in this vegetation boundary on a transect at a site impacted by the 1707 volcanic eruption. The timberline advanced rapidly upwards during this time period. Dominant tree species at the timberline ( Alnus maximowiczii, Salix reinii, and Larix kaempferi) colonized sites that were initially largely free of vegetation at higher altitudes. Seedlings of L. kaempferi were particularly abundant at the border of advancing vegetation. According to tree age, we found that this was the first canopy species in the colonized areas. L. kaempferi is drought resistant, and this probably contributes to its establishment capability in the high-altitude climate. Most seedlings of Abies veitchii invaded patches of herbs and shrubs. These vegetation patches in the upper kampfzone provide important shelter for seedlings of invading tree species. We predict that the upward advance of the alpine timberline is a recovery process following the volcanic eruption, and that climate change may accelerate this advance. [ABSTRACT FROM AUTHOR]

Summary To compare the distributions of Raffaelea quercivora hyphae within seedlings of a susceptible species, Quercus crispula, and a resistant species, Q. glauca, we examined water conductance at transverse sections. Raffaelea quercivora was inoculated into the stems of seedlings in July (summer) and October (autumn) and observed by light and fluorescence microscopy at 1 and 2 weeks after inoculation. The hyphal distribution patterns expressed as the Iδ index differed between the species at each occasion. The hyphal growth was wider in Q. crispula than in Q. glauca in July inoculation, but did not differ in October inoculation. Non-conductive sapwood in Q. crispula in transverse section was wider than that in Q. glauca at each occasion. The differences of hyphal growth and hyphal distribution patterns between species as little as 1 week after inoculation reflect differences in host susceptibility to the fungus. [ABSTRACT FROM AUTHOR]

The optimal water temperature in seed germination and the upper critical water temperature in seedling growth were determined for Zostera japonica collected from Ago Bay, Japan. The relationship between the seed germination rates and seed storage period (0, 30, and 60 days) at 0°C was also examined. The optimal water temperature in seed germination was in the range 15–20°C regardless of the storage period, in which germination rates were up to 14%. Seedlings, grown from seeds up to 10 cm in total length, were cultured for 1 week at various water temperatures to measure their relative growth rates. The optimal water temperature in early growth was in the range 20–25°C; relative growth rates ranged from 3.8 to 4.2%. Seedlings could survive up to a water temperature of 29°C, but most seedlings withered at 30 or 35°C. The optimal water temperatures for seed germination and seedling growth were related to the seasonal changes of water temperature in the sampling site. Although seedlings were hardly observed in Ago Bay in summer, Z. japonica might extend its distribution as far as where the summer water temperature is lower than 29°C. [ABSTRACT FROM AUTHOR]

We investigated the seedling survival of five evergreen tree species over 3 years inside and outside deer-exclusion fences in a warm temperate evergreen broad-leaved forest on Yakushima Island, Japan. Seedling survival was examined in relation to topography, herbivory by sika deer, and the soil surface environment (i.e., soil surface wetness, light conditions, slope inclination, and soil disturbance). The study species included Myrsine seguinii Lév., Syzygium buxifolium Hook. et Arn. (Group A: species distributed on the upper slope of the study site), Litsea accuminata (Bl.) Kurata, Schefflera octophylla (Lour.) Harms (Group B: species distributed on the lower slope), and Cleyera japonica Thunb. p.p. emend. Sieb. et Zucc. (Group C: species distributed on both slopes). The soil surface environment on the upper slope was drier, lighter, and more easily disturbed than the lower slope. Generalized linear model analyses indicated that seedling survival in fenced and unfenced quadrats was greater on the upper slope than on the lower slope for Group A and B species but not for Group C species. A micro-spatial scale analysis revealed that seedling survival was correlated with soil wetness, ground light conditions, and soil disturbance but not slope inclination. These results indicate that seedling survival was correlated with topography, sika deer herbivory, and the micro-spatial scale environment. Topography-related differences in seedling survival appear to adequately reflect the observed adult plant distributions for Group A and C species but not for Group B species. [ABSTRACT FROM AUTHOR]

Photosynthetic activities of seedlings of Zostera marina were successively measured using a gas volumeter for 6 days at seven light (0–400 μmol photons/m2 per s) and 11 water temperature conditions (5–35°C). The seedlings were collected from mature plants (Ise Bay, central Japan), and stored and cultured in incubators accurately controlled at each test temperature. The maximum gross photosynthesis ( Pmaxg) was recorded at an optimal water temperature of 29°C after 0 days. After 6 days, Pmaxg appeared at 25°C and most plants cultured at 29–30°C bleached and withered after the drastic increase of light compensation point ( Ic). On the contrary, at 5–28°C, the photosynthetic activities either changed little (5–25°C) or recovered after a temporal reduction (26–28°C); seedlings survived and looked healthy after being cultured for 6 days. The recovery was thought to be an acclimation to tolerate higher water temperature. As a result, the critical upper water temperature for Z. marina seedlings was proposed as 28°C. The temperature was consistent with the previously reported maximum water temperature in habitats around the southern boundary of Z. marina in the northern hemisphere. [ABSTRACT FROM AUTHOR]

To examine whether the Janzen–Connell hypothesis is valid in temperate forests, we investigated the density, growth, mortality, and agents of mortality of seedlings and the density, size, and age of saplings of Prunus grayana Maxim. at three distances (0–3, 6–10, and 16–26 m) from conspecific adults in a temperate forest in Japan. An inoculation experiment was also conducted to test the host range of a leaf pathogen. The probability of mortality was highest at 0–3 m during the first 2 years of growth. Mortality mainly resulted from distance-dependent attack by two types of pathogen that caused damping-off epidemics and spot symptoms on leaves. The leaf pathogen was identified as Phaeoisariopsis pruni-grayanae Sawada, which infected many more seedlings of Prunus grayana than of the two other tree species tested in an inoculation experiment. The vertical and diameter growth was lowest at 0–3 m and highest at 16–26 m in both seedlings and saplings. As a result, the greatest number of large and older saplings was observed at 16–26 m. Our results demonstrate that the Janzen–Connell mechanism operates in a beech-dominated forest in the temperate region of Japan. [ABSTRACT FROM AUTHOR]

. Question: Are the seed banks of an isolated subtropical oceanic island capable of naturally regenerating vegetation either with species of the historical forest community or with the existing grassland community after severe damage to the vegetation by goats? Location: Nakoudojima Island, Bonin Archipelago (Ogasawara Shoto), Japan. Methods: Soil samples were collected at 0-5 cm and 5-10 cm depths from seven plots in forests, grasslands, artificially matted areas and bare land. Soil seed banks were assessed using the seedling emergence method followed by the hand-sorting of ungerminated seeds. We determined the size and composition of the seed banks in upper soil layers of plots and compared the seed banks to the standing vegetation. Results: A total of 12 220 seedlings belonging to 42 species from 20 families germinated. Total mean seed density (0-5 cm depth) was low in all plots within forest, grassland, and heavily degraded vegetation types (34.7 ± 8.6 to 693.5 ± 123.6, 58.6 ± 7.8 to 107.1 ± 10.0, and 1.1 ± 0.5 to 7.2 ± 2.3 seeds/m2, respectively). Forbs and graminoids dominated the seed banks of grassland and forest plots including Cyperus brevifolius, Gnaphalium pensylvanicum, Oxalis corniculata and Solanum nigrum, and these alien species comprised 90% of the density of the seed bank. There was little correlation between seed banks and standing vegetation of the island (Sørensen similarity coefficient values 0.26 to 0.45). Conclusions: If natural regeneration occurs from the seed bank of the island, future vegetation will not move toward the original forest community, because the seed bank is dominated by non-native herbaceous grassland species. Though isolated, a few forest remnants with low species richness could be an important source for the natural re-establishment of forest on the island; however, seed availability may be limited by either poor dispersal or pollination so that woody species will probably recover very slowly on this goat-impacted island. [ABSTRACT FROM AUTHOR]

The optimal water temperature in seed germination and the upper critical water temperature in seedling growth were determined for Zostera marina collected from Ise Bay, Japan. The relationship between the seed germination rates and seed storage period (0, 30 and 60 days at 0°C) was also examined. The optimal water temperature for seed germination was in the range from 10 to 15°C regardless of the storage periods, in which germination rates ranged from 35 to 57%. Seedlings grown from seed up to 10 cm in total length were cultured for 1 week under various water temperatures to measure their relative growth rates. The optimal water temperature in growth was in the range from 20 to 25°C; relative growth rates ranged from 2.0 to 2.6%. Seedlings could survive up to a water temperature of 28°C, but most seedlings withered at 29 or 30°C. The optimal water temperatures for seed germination and seedling growth were related to the seasonal changes of water temperature at the sampling site. Although seedlings were rarely observed in the field in summer, they can grow at temperatures as high as 28°C. Therefore, Z. marina may extend its distribution as far as where the summer water temperature is lower than 28°C. [ABSTRACT FROM AUTHOR]

The short-lived monocarpic perennial Aster kantoensis Kitamura inhabits gravelly floodplains in the Kanto district of Honshu, Japan. Seedlings of this species are often found in unembedded-gravel habitats where gravels shade the sand surface, and are rare in embedded-gravel habitats where the sand surface is exposed to sunlight. To examine whether gravel conditions at the ground surface directly affect the seedling emergence of A. kantoensis, seeds were experimentally sown around unembedded gravels in the unembedded-gravel habitat and around embedded and artificially unembedded gravels in the embedded-gravel habitat on a floodplain of the Tama River. The cumulative numbers of seedlings that emerged around the unembedded and artificially unembedded gravels were approximately fourfold and sixfold of that around the embedded gravel. Results of this study indicate that gravel conditions at the ground surface directly affect the seedling emergence of A. kantoensis and that unembedded gravel conditions created by flooding provide microhabitats suitable for seedling emergence. [ABSTRACT FROM AUTHOR]

A total of 24 isolates of Pythium spinosum from cucumber obtained from five regions in Oman were characterized for genetic diversity using amplified fragment length polymorphism (AFLP) fingerprinting and three isolates from the Netherlands, South Africa and Japan were included for comparison. Isolates from Oman were also characterized for aggressiveness on cucumber seedlings and sensitivity to metalaxyl. Identity of all isolates was confirmed using sequences of the internal transcribed spacer (ITS) region of the ribosomal DNA (rDNA), which showed more than 99% nucleotide similarity among all isolates. Using six primer-pair combinations, AFLP fingerprinting resolved 295 AFLP markers of which 193 were polymorphic among isolates from other countries and only six were polymorphic among isolates of P. spinosum from Oman. Seven different AFLP phenotypes of P. spinosum were recovered in Oman; two of them were found to contain over 79% of isolates and one was recovered from all regions in Oman. Phenotypes from Oman showed very high (≥99%) levels of genetic similarity to each other compared to moderate (mean =53%) levels of genetic similarity with phenotypes from other countries. In addition, all isolates from Oman were found to be highly sensitive to metalaxyl and all were aggressive on cucumber seedlings at 25°C. The high genetic similarity among phenotypes of P. spinosum in Oman as well as recovering two major clones across regions may suggest that P. spinosum has been recently introduced in Oman via a common source. [ABSTRACT FROM AUTHOR]

We analyzed effects of seed-hoarding by rodents on the variation in seed mass and seed success for a perennial forest undergrowth plant — Symplocarpus renifolius Schott ex Miquel — in Hokkaido, northern Japan. Although density of rodents differed greatly between seasons, more rodents were always captured in mesic Sasa sp. patches with dense foliage than in wet Lysichiton sp. patches. In the season with fewer rodents, they cached seeds close to the original places irrespective of vegetation, while in the season with abundant rodents, they transported seeds further and cached seeds disproportionately in Lysichiton patches. Seeds missed by rodents were larger than seeds that were eaten or that survived. Sasa patches are more suitable for seedlings to establish and a size advantage was observed there, but even small seeds could establish in Lysichiton patches, although seedling success was lower. We concluded that maternal plants of Symplocarpus renifolius increase their reproductive success by having small to middle-sized seeds transported to suitable sites while offering larger seeds as rewards to the transporters. Since the variation in seed mass was not correlated with the biomass per seed of the maternal plant, the large variation in seed mass is considered to have evolved through the density-dependent hoarding by rodents. [ABSTRACT FROM AUTHOR]

To investigate the seedling growth of a biologically invasive larch Larix kaempferi (Lamb.) Carr. on Mount Koma, Japan, seedlings were excavated from three microhabitats (bareground = BA, Salix reinii patch = SP, and Larix understory = LU) in three elevational zones. Seedlings showed the highest ectomycorrhizal (ECM) colonization percentage in the most shaded microhabitat, LU. ECM colonization percentages in BA and SP were found to decrease with decreasing elevation. These results inferred that the ECM colonization percentages were related to seedling growth, particularly in BA and SP. However, the annual seedling growth was not synchronized with the increases in either elevational gradients. Although ECM colonization was most evident in LU, the seedling growth was the lowest. We concluded that the effects of ECM colonization on seedling growth were reduced mostly by microhabitat characteristics. [ABSTRACT FROM AUTHOR]

Seed dispersal determines a plant’s reproductive success, range expansion, and population genetic structures. Camellia japonica, a common evergreen tree in Japan, has been the subject of recent genetic studies of population structure, but its mode of seed dispersal has been assumed, without detailed study, to be barochory. The morphological and physiological features of C. japonica seeds, which are large and nutritious, suggest zoochorous dispersal, however. We compared actual distances between mother trees and seedlings with distances attributable to gravity dispersion only, to test the zoochory hypothesis of C. japonica. The animals that transport the seeds for caching were identified experimentally. We also examined the extent to which seed dispersal is affected by the behavior of animal vectors. Seed dispersal by Apodemus speciosus was confirmed by taking photographs of animals that were consuming seeds experimentally deposited on the ground. Camellia seeds hoarded by the rodents under the litter or soil were protected from drying. On the basis of microsatellite analysis of maternal tissue from the seed coat, the mother trees of 28 seedlings were identified. Maternity analysis revealed the average seed-dispersal distance from mother trees was 5.8 m±6.0 SD, a distance greater than initial dispersal by gravity alone. These results indicate that C. japonica is a zoochorous species dispersed by A. speciosus. Fifty percent of the seed dispersal occurred from mature evergreen forests to dwarf bamboo thickets. This directional seed dispersal would contribute to range expansion of C. japonica. Home range sizes of A. speciosus were 0.85 ha at most and covered with different types of vegetation, from evergreen forests to grassland. This low specificity of their microhabitat use might enhance seed dispersal to different types of vegetation. [ABSTRACT FROM AUTHOR]

1 The spatial genetic structure of soil seed banks establishes the initial template for development of spatial genetic structure in above-ground plants, but is rarely evaluated. 2 We used kinship coefficients to analyse the fine-scale spatial genetic autocorrelation of plants and of seed banks from different soil depths for Primula modesta at a subalpine fen site on Mt Asama, central Japan. 3 The spatial genetic structure of surface seeds (0–1 cm depth) was significant, while deeper seeds (1–5 cm depth) had no significant genetic structure. We also detected a more pronounced spatial genetic association between the surface seeds and flowering genets than between the deeper seeds and flowering genets. 4 These results suggest that the surface seed bank accounts for a large proportion of the previous season's seed dispersal and therefore represents the transient seed bank, whereas the deeper (persistent) seed bank pools the reproductive output of multiple generations. 5 Directional analysis indicated that secondary dispersal by running water modifies the spatial genetic structure and extends dispersal distances. Over time, this may impact on the spatial pattern of soil seeds, possibly accounting for the absence of spatial genetic structure in deeper seeds. 6 Emerging seedlings and flowering ramets were strongly clustered together at distances up to 20 cm. Surviving seedlings were aggregated at short distances because of the patchy spatial distribution of safe sites for establishment, allowing development and strengthening of the marked fine-scale spatial genetic structure. [ABSTRACT FROM AUTHOR]

Questions: How do biological invasion patterns of Larix kaempferi seedlings change with different microhabitats along an elevational gradient on a volcano? How are seedling attributes such as establishment, competitive ability and morphological plasticity, advantageous to the invasion of stressful disturbed areas? Location: Mount Koma, Hokkaido, Japan. Methods: Seed sowing experiments and natural seedling censuses were conducted with L. kaempferi and the dominant native tree Betulaermanii. Seed germination, seedling survival and allocation were investigated on three microhabitats (bare ground, Salix reinii patch and Larix understorey) in three elevational zones for three years. Results: Seed germination was higher in Larix understorey than in bare ground and Salix patches, but did not differ between elevations. Survival rates were not different between elevations and microhabitats. Larix had a higher survival rate than Betala. Larix showed the highest natural seedling density in Sa/ix patches, independent of elevational differences, while Betu/a density was nearly zero. Larix seedlings changed allocations between microhabitats, while the ratio of leaf to total biomass was constant. In bare ground Larix was more stunted and branched and increased its allocation to the roots. This form is adaptive to windy, nutrient-poor environments. Larix seedlings were taller and more slender in Salix patches, indicating that the priority was light acquisition in shaded habitats. Little change in Betula allocation was detected. Conclusion: Invasive species establish themselves more efficiently than native species in every microhabitat investigated, especially at higher elevations, by having higher survival and growth rates derived from superior seedling performance. Plant communities on and above the tree line are modified by the biological invasion. [ABSTRACT FROM AUTHOR]

The life-history characteristics of Allium victorialis ssp. platyphyllum (Alliaceae), a representative circumboreal element, are described here. This plant is a typical polycarpic perennial of lowland deciduous forests, extending its range to lower subalpine forests. It flashes in early to late April (and in May to early June at higher elevations) on the deciduous forest floor in the lowlands to lower montane zone in Hokkaido and Honshu (north of Nara Prefecture). Flowering individuals bear a single head with numerous whitish or pale purplish flowers on the top of the scape. This plant is a typical insect-pollinated outbreeder, and representative pollinators include small flies (Diptera) and horse flies (Hymenoptera). The number of pollen grains per flower is 4.8–6 × 104, and in the 3-locular ovary only a single ovule is produced for each locule. Pollen/ovule ratios are 1.8–2 × 104. Black ovoid seeds, measuring approximately 3 mm, are dispersed onto the soil layer in late summer. Seed germination occurs in late autumn and germinated seeds overwinter as a radicle. Seedlings with a narrow lanceolate leaf 4–5 cm long begin to appear above ground in early March of the succeeding season. In general, individuals take several years to become sexually mature, but mature individuals with two to three radical leaves will flower continuously and produce seeds. [ABSTRACT FROM AUTHOR]

The population of the endangered plant species Nymphoides peltata in Lake Kasumigaura, Japan, has been declining drastically recently, and seedlings that emerge from the remaining soil seed bank have entirely failed to establish. The decline has followed artificial control of the water level in the lake. To examine the environmental requirements at the seedling establishment stage, we investigated the survival and growth of emerged seedlings at various microsites on the lakeshore by manipulating environmental conditions such as exposure to waves, inundation, and light availability so as to include the conditions of the presumed safe sites. Seedling survival at the early stage was affected most by environmental variables relating to the susceptibility to inundation. Survival until seedling establishment was profoundly affected by light availability as well as by susceptibility to inundation. In all, 136 genets were established in quadrats less prone to inundation and with sufficient light availability, which is consistent with the presumed safe-site characteristics of the original water regime: bare ground exposed during the spring water-level drawdown. Recovering the original water regime with seasonal drawdown will be indispensable for recovering a self-sustainable population. However, as first-aid measures, active restoration efforts through adaptive management using the remnant soil seed bank are urgently needed before the soil seed bank becomes exhausted. [ABSTRACT FROM AUTHOR]

We examined microsites for the seedling establishment of Tsuga diversifolia, Abies veitchii and Abies mariesii in a subalpine coniferous forest with moss-type undergrowth dominated by Hylocomium splendens and Pleurozium schreberi on Mt. Fuji, a less-snowy mountain located on the Pacific Ocean side of the central part of Honshu Island, Japan, and compared these microsites with cases in other regions of Japan with different undergrowth vegetation (herb type, dwarf-bamboo type) under snowier conditions. L-shaped size structures with abundant seedlings and small trees were identified for all three species. Established seedlings of T. diversifolia showed remarkable preference for elevated microsites such as fallen logs and convex ground (i.e. ground raised around trunk bases), while A. veitchii and A. mariesii indicated no significant bias toward such elevated microsites in the large seedling stage. However, the relative frequency of T. diversifolia seedlings established on flat ground reached high values of 54–77%, since the relative occupation area of the flat ground was large (85–89%). Such a large share suggests that flat ground should be regarded as the most important microsite for the seedling establishment of T. diversifolia in forests with moss-type undergrowth. This preference trait for T. diversifolia observed with moss-type undergrowth has not been reported in previous studies examining forests with herb- and dwarf bamboo-type undergrowth, where T. diversifolia seedlings are scarce on the ground and restricted to elevated microsites. We conclude that the major microsite for T. diversifolia seedling establishment changes according to the undergrowth vegetation type: a large ground share for moss-type undergrowth and a small ground share for herb- and dwarf bamboo-type undergrowth. [ABSTRACT FROM AUTHOR]

Investigates the growth inhibition and acetolactate synthase activity of soybean seedlings and suspension-cultured cells treated with bensulfuron-methyl in Japan. Inhibition of growth by bensulfuron-methyl; Plant materials used; Inhibition of acetolactate synthase activity by bensulfuron-methyl; Susceptibility of cultured cells of soybean to bensulfuron-methyl.

The spatial genetic substructuring of five local populations of Siebold's beech ( Fagus crenata Blume) in the western Tanzawa Mountains were analyzed using allozyme polymorphisms for 13 loci (11 enzyme systems). The beech forests in Tanzawa have been rapidly deteriorating in recent years. The two main causes for this are heavy damage or death of mature trees caused by air pollution, and feeding pressure on seedlings and juveniles by sika deer. The distributions of genotypes showed localization of particular genetic diversities. Spatial autocorrelation analyses revealed slightly positive significant values within small distance classes and negative values in further distance classes, but those values more or less fluctuated in the distrograms. In addition, an analysis was conducted using a stepping-stone model to estimate the migration rate and to quantify the gene flow among neighboring patch populations to detect the population differentiation. Twelve patch populations were discriminated as localized assemblages of Siebold's beech individuals in one of the local populations according to the assemblage of individuals along the topography of an established site. The migration rate for each generation was estimated to be m = 0.09 between neighboring patch populations. The population migration rate ( Nm = 2.7) was revealed to be larger than one migrant for every other generation, which indicates that the population differentiation is not significant in the present state. Although the model analysis demonstrated sufficient gene flow between neighboring patch populations, severe damage to local beech populations in Tanzawa may cause the extinction of one or more of the patch populations. Further fragmentation and isolation of local populations were also discussed in terms of loss and retreat of genetic diversity. [ABSTRACT FROM AUTHOR]

To reveal the effects of artificial alteration of water level regime on the regeneration of lakeshore plants from seeds, we examined the factors causing regeneration failure in Lake Kasumigaura, Japan. A survey of microtopography within and around a remnant fragment of lakeshore vegetation revealed that, over a large range, the habitat is frequently inundated in spring under the current water regime, although it was rarely inundated under past water regimes. Analysis of the patterns of seedling emergence and establishment at microsites at various elevations revealed a significant negative correlation between number of inundation days and abundance or species-richness of seedlings that emerged in the spring. Most seedling deaths occurred when the study site was inundated. We suggest that regeneration failure caused by the artificial raising of the lake's water level is one of the principal mechanisms of the recent vegetational decline in the lake. [ABSTRACT FROM AUTHOR]

Cercidiphyllum japonicum SIEB. et ZUCC. is found in riparian forests in Japan, but the seedlings rarely regenerate more than coexisting tree species. We investigated C. japonicum emergence and seedling survival in a nursery for 21 months. Bare soil, soil-with-litter, and gravel treatments and 3.0%, 10.9%, 22.7%, 60.1%, and 100% relative photosynthetic photon flux density (RPPFD) light conditions were tested. Seedling emergence depended on soil type and light conditions. Owing to C. japonicum's small seed size, germinated seedlings could not penetrate the litter layer and became desiccated in gravel, but most seedlings emerged and survived in bare soil. These surviving seedlings needed quite bright light to germinate but not extreme light conditions. Initial mortality was high, but most of the seedlings that survived the first three months survived for the duration of the study, even under quite dark 10% RPPFD conditions. Current-year seedlings grew poorly under bright light conditions and rarely survived under the brightest light condition, when survival was probably negatively affected by desiccation. After one year, seedlings were able to use the higher light conditions more efficiently for growth. Such seedlings probably have a high chance of survival. Under low light conditions, both current- and second-year seedlings grew poorly. However, even small seedlings are likely to survive under low light conditions in a nursery, because the seedbed is level and nursery seedlings do not face all of the threats that are present in an actual forest. [ABSTRACT FROM AUTHOR]

In the subalpine mixed forest of Mt. Ôdaigahara, mid-western Japan, the understory is dominated by dwarf bamboo ( Sasa nipponica), which is the major forage of overly populous sika deer ( Cervus nippon). In the present study, we monitored the survival and growth of Abies homolepis seedlings over 5 years to determine how they responded to the experimental removal of dwarf bamboo and to the exclusion of sika deer and mice ( Apodemus argenteus and A. speciosus). Deer and dwarf bamboo reduced the survival of seedlings but had different effects on growth. The stems of seedlings were shorter in the presence of deer, indicating that taller seedlings were apt to be browsed by deer, whereas the diameters of seedlings were smaller in the presence of dwarf bamboo, mainly owing to its shading effect. The presence of mice decreased the number of seedlings germinating in a particular site, but had no effect on seedling survival after germination. There was no significant indirect effect whereby the survival of seedlings was predicted to be facilitated by the decreased biomass of bamboo because of grazing by deer. We supposed that this might be because the direct negative effect of deer was so large as to conceal the positive indirect effect. [ABSTRACT FROM AUTHOR]

Fallen logs on the forest floor play an important role in tree seedling establishment in boreal and subalpine old-growth forests. We examined the abundance and state (degree of decay, moss coverage on their surfaces) of fallen logs on the forest floor and compared the occurrence of conifer seedlings and saplings on soil and fallen logs in old-growth evergreen boreal (Taisetsu) and subalpine (Yatsugatake) coniferous forest stands in Japan. The forest floors of both stands were covered mostly by soil, and fallen logs covered only a small proportion (4.5% in Taisetsu and 2.5% in Yatsugatake) of the forest floor. In both stands, no seedlings were found on freshly fallen logs. Both moss coverage and the occurrence of seedlings or saplings on fallen logs increased with decay in both stands. In Taisetsu, the occurrence of all conifer seedlings and saplings was, in general, restricted to fallen logs. In contrast, in Yatsugatake, Picea and Tsuga seedlings occurred much more frequently on fallen logs than on soil, whereas Abies seedlings and saplings became established on both soil and fallen logs. Seedlings were taller on decayed fallen logs, but taller saplings were rare on fallen logs in Yatsugatake. Results indicate that species’ characteristics, the condition of the fallen logs and environmental factors determine the preponderance of seedling and sapling establishment on fallen logs. The condition of fallen logs varies with the degree of decay, and fallen logs that function as seedling establishment sites on the forest floor are thought to be limited by time and space. [ABSTRACT FROM AUTHOR]

• In a coinoculation test of seed-epiphytic Penicillium species and pathogenic Pythium vexans to Picea glehnii seedlings, the number of surviving seedlings which were inoculated with P. vexans 5 d after preinoculation with Penicillium damascenum PGS-O7 increased compared with those inoculated with P. vexans alone. • The phytotoxicity of antifungal compounds to P. glehnii seeds and seedlings was assessed in growth experiments. Production of these compounds was quantitatively analysed in the rhizosphere of the host seedlings using chromatography techniques. • Dense mycelial growth of P. damascenum was observed microscopically around the roots of the inoculated seedlings. Furthermore, the antifungal and phytotoxic compound citrinin produced by P. damascenum was detected as a component released around the roots of the normally growing fungus-inoculated seedlings. • We propose two possible mechanisms for the protection of P. glehnii seedlings by P. damascenum from P. vexans; first, chemical protection by an antibiotic agent, citrinin produced by P. damascenum, and second, the occupation of the space around the P. glehnii roots by the P. damascenum mycelia. [ABSTRACT FROM AUTHOR]

Seedling and tree-establishment microhabitats of Tsuga diversifolia and Abies mariesii were examined on the herb- and dwarf bamboo-dominated forest floor on Mount Hayachine, a mountain under intermediate snow conditions in northern Honshu, Japan. The four microsite types were fallen logs, buttresses, rocks and ground. The ground substratum was further divided into four subtypes by dominant undergrowth species: Lycopodium, Pteridophyllum, Carex and dwarf bamboo. The establishment of T. diversifolia seedlings on the ground was scarce, and depended mostly on non-ground microsites (i.e. fallen logs, buttresses and rocks). The seedling establishment of A. mariesii was not dependent on specific substrata, although on the ground, establishment sites were limited to the Lycopodium subtype situated on convex sites. Among the microhabitats for seedling establishment, larger trees of A. mariesii rarely occurred on higher portions of the non-ground microsites. In contrast, T. diversifolia could grow up to the height of canopy-layer trees in such microsites. Thus, non-ground microsites seem to be unsuitable for tree establishment in A. mariesii, and are probably useful microhabitats for regenerating T. diversifolia to avoid competition with A. mariesii. We also compared seedling-establishment microhabitats for the two conifers between Mount Hayachine and two other mountain regions under different undergrowth conditions (moss-dominated and dense dwarf bamboo-dominated). Our findings suggested that seedling recruitment in non-ground microsites was primarily determined by undergrowth conditions; T. diversifolia preferred such microsites where the moss-covered area was low, and A. mariesii preferred where dwarf bamboo-covered area was high. [ABSTRACT FROM AUTHOR]