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To investigate the reproductive traits of the dioecious canopy tree Cercidiphyllum japonicum, we performed visual surveys from 2000 to 2007 to assess the flowering and fruiting of 59 individuals in...

Clonal reproduction may contribute to population maintenance in areas where disturbance caused by snow limits tree recruitment. To understand the importance of clonal reproduction in the population dynamics of canopy tree species, it is necessary to determine the frequency of clonal reproduction in the early stages of seedling establishment. We found 106 ramets, including “small-sized” ramets of less than 5 cm in diameter at breast height, aggregated within 4 patches in a 70 × 50 m plot and also identified 20 genets among these ramets with the use of nuclear microsatellite markers. The size structure of the ramets revealed an inverse J-shaped distribution, suggesting that continuous recruitment of new ramets occurs. However, the number of intermediate-sized ramets (around 10 cm DBH) at the present study site was small, suggesting that most new ramets die while they are still small by pressure from heavy snow. Of the 20 genets, 12 included one or more small-sized ramets, which indicated recent recruitment. Of the 12 genets, 3 included only a single small-sized ramet, which suggested seedling recruitment, whereas the other 9 included multiple ramets (39 small-sized ramets in total), which indicated clonal recruitment. The frequency (9/12) and number (39/9) of recent clonal recruits suggest that clonal reproduction effectively maintains the population of Cryptomeria japonica in snowy regions.

Androdioecy is a rare reproductive system.

Rear-edge populations are of significant scientific interest because they can contain allelic variation not found in core-range populations. However, such populations can differ in their level of genetic diversity and divergence reflecting variation in life-history traits, demographic histories and human impacts. Using 13 EST-microsatellites, we investigated the genetic diversity and differentiation of rear-edge populations of the Japanese endemic conifer Thuja standishii (Gordon) Carr. in southwest Japan from the core-range in northeast Japan. Range-wide genetic differentiation was moderate (Fst = 0.087), with northeast populations weakly differentiated (Fst = 0.047), but harboring high genetic diversity (average population-level Ar = 4.76 and Ho = 0.59). In contrast, rear-edge populations were genetically diverged (Fst = 0.168), but contained few unique alleles with lower genetic diversity (Ar = 3.73, Ho = 0.49). The divergence between rear-edge populations exceeding levels observed in the core-range and results from ABC analysis and species distribution modelling suggest that these populations are most likely relicts of the Last Glacial Maximum. However, despite long term persistence, low effective population size, low migration between populations and genetic drift have worked to promote the genetic differentiation of southwest Japan populations of T. standishii without the accumulation of unique alleles.

Sika deer are responsible for diverse effects in the forest vegetation of the Chichibu Mountains. The lowest level of understory plants in the riparian forest of Ooyamazawa in the Chichibu Mountains covered over 90% of the land area in 1983, but the coverage decreased to 3% by 2004. In 2017, the area seemed to have recovered slightly; the coverage was approximately 10%. The decreases in plant populations could be attributed to sudden increases in deer population density, detected post-2000 by cervid research in this area. The plants that remained as of 2017 shared characteristics which could have contributed to their survival in the presence of deer overpopulation. They were either I: toxic plants, II: small herb species which do not increase in plant height, or III: perennial herbs in which the aerial portion withers until the summer and enters yearly dormancy at an early date.

Long-term ecological research (LTER) began at the Ooyamazawa riparian forest research site in 1983. Ooyamazawa comprises a representative cool-temperate zone old-growth riparian forest that is species-rich and contains complex topography. The Ooyamazawa river basin comprises at least 230 species of vascular plants, including 46 woody tree species that are found within the research site. Researchers have used this site to study forest structure and tree life histories over a 35-year period. In particular, research has focused on the life histories of the dominant canopy species Fraxinus platypoda, Pterocarya rhoifolia, and Cercidiphyllum japonicum. After the research site was registered as a Core Site of the Monitoring Sites 1000 Project, research began on avifauna and ground beetles, in addition to ongoing forest research.

Over the last few decades, population increases of sika deer (Cervus nippon) have become a major issue in various forest ecosystems across temperate regions; however, the influences of deer browsing on riparian forests are less known. In this chapter, we illustrate the herbivore–forest vegetation relationships over a long term from the past when deer was absent to the current when deer became overabundant in an old-growth riparian forests of Ooyamazawa, the Chichibu Mountains of central Japan. We revealed that (1) the browsing activity of deer has a negative influence on riparian forests, (2) the damage of these species is mainly induced by easiness to browsing by deer resulting from small tree size structure, and (3) the resistance to the deer browsing differs among tree species. Thus, small mature trees (i.e., shrub species) with low browsing resistance should be primarily protected for effective management of riparian forests.

Thirteen Acer species were found in Ooyamazawa riparian forest in Japan. Of these, the shrubby species A. carpinifolium and A. argutum and the tall tree species A. shirasawanum and A. mono were the most abundant. Sprouts of shrubby species were common, but not of tall tree species, which implies that individuals of shrubby species are maintained in the understory layer via sprouts, whereas tall tree species extend upward toward the canopy. All four Acer species were found mainly on upstream sediments; moreover, the density of A. shirasawanum was high, implying that A. shirasawanum may eventually become an important species in the sedimentary upstream area. On the other hand, A. carpinifolium was dominant in the unstable downstream V-shaped valley; this species adapts to the disturbed downstream area by producing more sprouts. These differences in life history promote diversity in the forest structure of Ooyamazawa riparian forest.

The canopy tree species Fraxinus platypoda, Pterocarya rhoifolia, and Cercidiphyllum japonicum coexist at the Ooyamazawa riparian forest research site. In this chapter, we clarify the coexistence mechanisms of riparian tree species as they pertain to disturbance regimes, life-history strategies, and responses to environmental factors. Reproductive strategies, e.g., seed production and germination, differ widely among these three species and we observed probable reproductive trade-offs in each species. Canopy-height individuals of F. platypoda are recruited from advanced saplings, and P. rhoifolia and C. japonicum both established following large-scale disturbance events. Basal sprouting, i.e., vegetative reproduction, is likely the mechanism by which C. japonicum survives and attains co-dominance in riparian forests. F. platypoda had greater shade and water tolerance than the other two species. Each of these species is well-adapted to the various disturbances typical of riparian zones. Therefore, the coexistence mechanisms among them are likely a combination of random chance and niche partitioning.

To uncover the population regeneration mechanisms and function of sprouting of the canopy tree species, Pterocarya rhoifolia, in a heavy snowfall region of Sado Island, Japan, we investigated the stool structure and sprouting throughout the life history stages of the tree. We set up a plot, categorized the life history stages, characterized the relationship between individual growth and sprouting, and recorded the age and distribution of sprout stems in stools. We found that established juveniles were often damaged by snow pressure but did produce some sprout stems. Mature individuals had a stool structure with planar expansion by stem layering, experienced stem breakage, and produced sprout stems due to snow pressure. These results suggest that P. rhoifolia occupying heavy snowfall regions can maintain their population by sprouting, which recovers the tree body from snow pressure damage.

Based on organelle DNA phylogeographic analyses and ecological niche modeling (ENM), we investigated the range-shift history of the Japanese wingnut (Pterocarya rhoifolia) during the Quaternary climatic oscillations with particular emphasis on the Last Glacial Maximum (LGM). Phylogeographic patterns of this species were determined using 376 individuals from 53 populations for chloroplast DNA sequencing of three spacers. Spatial analysis of molecular variance revealed that the current phylogeographic structure would be sculptured by multiple range shifts from each glacial refugium, which would have been repeated several times during the Quaternary climatic oscillations. High haplotype diversity and private haplotypes were detected in southwestern Japan, where wingnut is currently infrequent and found mainly in high mountains, whereas in northernmost Japan, haplotype diversity was low though this plant is quite common at present. According to ENM approach, during the LGM, the climatically suitable d...

The Japanese wingnut Pterocarya rhoifolia is a riparian canopy tree species that grows under a variety of climate conditions, including heavy snowfall, despite the difficulties posed to canopy trees in such environments. This suggests that P. rhoifolia might adapt its life history strategy to different snowfall conditions. This study compared several life history traits of this tree species in a cool temperate mountainous area in central Japan along a gradient of maximum snow depth. The following trends were observed with increasing maximum snow depth: (1) diameter at breast height decreased, maximum stem length and tree height shortened, and trees tended toward a ‘dwarf shrub’ form; (2) the number of sprout stems increased significantly, and these sprouts contributed to maintaining the population; and (3) seed production decreased. Our results suggest trade-offs between clonal growth (sprouting) and sexual reproduction (seed production), and between sprouting and height growth. We concluded that the life history strategy P. rhoifolia demonstrated adaptive plasticity in response to a gradient of maximum snow depth.

How phenotypic or genetic diversity is maintained in a natural habitat is a fundamental question in evolutionary biology. Flower color polymorphism in plants is a common polymorphism. Hepatica nobilis var. japonica on the Sea of Japan (SJ) side of the Japanese mainland exhibits within population flower color polymorphism (e.g., white, pink, and purple), while only white flowers are observed on the Pacific Ocean (PO) side. To determine the relationships between flower color polymorphism, within and among populations, and the genetic structure of H. nobilis var. japonica, we estimated the genetic variation using simple sequence repeat (SSR) markers. First, we examined whether cryptic lineages corresponding to distinct flower colors contribute to the flower color polymorphisms in H. nobilis var. japonica. In our field observations, no bias in color frequency was observed among populations on Sado Island, a region with high variation in flower color. Simple sequence repeat (SSR) analyses revealed that 18% of the genetic variance was explained by differences among populations, whereas no genetic variation was explained by flower color hue or intensity (0% for both components). These results indicate that the flower color polymorphism is likely not explained by cryptic lineages that have different flower colors. In contrast, populations in the SJ and PO regions were genetically distinguishable. As with the other plant species in these regions, refugial isolation and subsequent migration history may have caused the genetic structure as well as the spatially heterogeneous patterns of flower color polymorphisms in H. nobilis var. japonica.

East Asia's temperate deciduous forests served as sanctuary for Tertiary relict trees, but their ages and response to past climate change remain largely unknown. To address this issue, we elucidated the evolutionary and population demographic history of Cercdiphyllum, comprising species in China/Japan (Cercdiphyllum japonicum) and central Japan (Cercdiphyllum magnificum). Fifty-three populations were genotyped using chloroplast and ribosomal DNA sequences and microsatellite loci to assess molecular structure and diversity in relation to past (Last Glacial Maximum) and present distributions based on ecological niche modelling. Late Tertiary climate cooling was reflected in a relatively recent speciation event, dated at the Mio-/Pliocene boundary. During glacials, the warm-temperate C. japonicum experienced massive habitat losses in some areas (north-central China/north Japan) but increases in others (southwest/-east China, East China Sea landbridge, south Japan). In China, the Sichuan Basin and/or the middle-Yangtze were source areas of postglacial northward recolonization; in Japan, this may have been facilitated through introgressive hybridization with the cool-temperate C. magnificum. Our findings challenge the notion of relative evolutionary and demographic stability of Tertiary relict trees, and may serve as a guideline for assessing the impact of Neogene climate change on the evolution and distribution of East Asian temperate plants.

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.

Cercidiphyllum japonicum and C. magnificum are deciduous tree species that produce large numbers of sprouts. They are found mainly in riparian and/or disturbed areas. C. japonicum is distributed in the montane zone in Japan, whereas C. magnificum is distributed mostly in the subalpine zone of central Japan. However, the two species sometimes coexist, e.g., on the talus slope at the valley head of the Chichibu Mountains. We investigated differences in sprouting traits in these two species by comparing class distributions of sprout diameter at breast height (DBH) and heights of individuals on the talus slope. Sprout DBH and individual height were smaller in C. magnificum as compared to C. japonicum. Moreover, the analysis of the DBH-class distribution of each species indicated that C. magnificum had numerous small sprouts and experienced high mortality, whereas C. japonicum had fewer small sprouts and low mortality. It is likely that the sprouting traits of C. magnificum make it more adapted to severe conditions in the subalpine zone than those of C. japonicum.

Japanese horse chestnut (Aesculus turbinata: Hippocastanaceae) is one of the typical woody plants that grow in temperate riparian forests in the Japanese Archipelago. To analyze the phylogeography of this plant in the Japanese Archipelago, we determined cpDNA haplotypes for 337 samples from 55 populations covering the entire distribution range. Based on 1,313 bp of two spacers, we determined ten haplotypes that are distinguished from adjacent haplotypes by one or two steps. Most of the populations had a single haplotype, suggesting low diversity. Spatial analysis of molecular variance suggested three obvious phylogeographic structures in western Japan, where Japanese horse chestnut is scattered and isolated in mountainous areas. Conversely, no clear phylogeographic structure was observed from the northern to the southern limit of this species, including eastern Japan, where this plant is more common. Rare and private haplotypes were also found in southwestern Japan, where Japanese horse chestnuts are distributed sparsely. These findings imply that western Japan might have maintained a relatively large habitat for A. turbinata during the Quaternary climatic oscillations, while northerly regions could not.

The objective of this study is to clarify the effect of the surface under tree crown to the remote sensing imagery.Using the airborne hyperspectral sensor imagery, the second differential absorbance in row of trees of Prunus × yedoensis in Rissho University was calculated.In reflectance of the road and grass under crown, the values in the infrared region was different each other.But the reflectance spectrum was similar.The influence of the different surface under crown was not able to be judged from the difference of the value of reflectance.On the other hand, the second differential absorbance showed the difference of the surface under crown.The difference appeared at a point of the peak and trough in the distribution of the second differential absorbance.The classification error in the crown part was about 20% in reflectance, and about 2% in the second differential absorbance.About 70% of the edge of the crown where was above the road was recognized as the result of the influence of the road from the first principal component score.This study showed that the difference of the surface under the crown could be detected by the second differential absorbance of the forest structure calculated by the hyperspectral imagery.

The effects of flooding on growth of seedlings were compared over a 7-month period (April–November) among six different woody species: Aesculus turbinata, Cercidiphyllum japonicum, Fraxinus platypoda, Pterocarya rhoifolia, Pterostyrax hispida, and Quercus mongolica var. grosseserrata. Flooding reduced the shoot length of F. platypoda, P. rhoifolia, C. japonicum, P. hispida, and Q. mongolica var. grosseserrata seedlings but did not affect that of A. turbinata seedlings. Among control seedlings, shoot elongation occurred once in A. turbinata and twice in F. platypoda and Q. mongolica var. grosseserrata; the other species continued to grow from April to August. Among the flooded plants of all species, shoot elongation occurred only once at the beginning of the growing season. On August 25, flooding significantly reduced the number of developed leaves as compared with control plants except for A. turbinata. In the flooded plants except for F. platypoda, leaf fall began on June 30; in controls, by contrast, the number of developed leaves increased until August 25. Flooding reduced the total dry weight increment in all species. The survival ratio of flooded plants after the experiment differed with species. All of the F. platypoda and A. turbinata seedlings survived the flooding treatment, while only 20% of P. hispida and 30% of Q. mongolica var. grosseserrata survived. Flooding seriously affected the growth of riparian pioneer species including P. rhoifolia, C. japonicum, P. hispida, and Q. mongolica var. grosseserrata. The effects of flooding on growth of the seedlings differed with the tree species because of differences in leaf-emergence pattern and physiological flood tolerance. The responses of tree seedlings to flooding reflected species habitats and growth patterns.

Article, FOREST ECOLOGY AND MANAGEMENT. 213(1-3): 253-260 (2005)

This data paper reports census data of ground-dwelling beetle and other fauna of the forest floor environment; collections were made from a network of 22 forest sites in Japan. To our knowledge, this represents the largest dataset for long-term monitoring of a ground-dwelling beetle community and other taxa in a ground environment in forests, which covers a broad climatic range in the temperate zone and is freely available. The network forms part of the Monitoring Sites 1000 Project launched by the Ministry of the Environment, Japan. It covers subalpine, cool- and warm-temperate and subtropical climatic zones and the four major forest types of Japan. Thirty-three permanent plots usually 1 ha in size were established in old-growth, secondary natural and a few plantation forests. Censuses of the ground-dwelling beetle community were conducted using pitfall trapping and forest floor environment monitoring every year from 2004 to the present. During the initial 9 years of the census (2004–2012), 59,762 beetle individuals (including 3182 larvae) of more than 314 species were recorded. This dataset includes taxonomy and biomass of each beetle individual and each taxonomic group of other invertebrates coincidently captured in pitfall trapping. The dataset also includes data related to ground coverage by forest floor vegetation, dry mass of the accumulated organic litter layer, and carbon and nitrogen contents and cellulose decomposition rate in organic layer and surface mineral soil. The data could be used to investigate geographical patterns and intra- and inter-annual dynamics of individual body mass, populations and community structures of ground-dwelling beetles, and their relationships with the forest floor environment. Furthermore, the data could be analyzed with other open datasets related to tree community dynamics and litter fall continuously measured in the same study plots. This dataset also provides information related to the distribution and average body mass of each beetle species.

Three canopy tree species (Fraxinus platypoda, Pterocarya rhoifolia, andCercidiphyllum japonicum) coexist in riparian forests in the Chichibu Mountains of central Japan. We compared the forest structure and the reproductive characteristics of these species.F. platypoda was the dominant canopy species. It produced many saplings and grew in abandoned channels and floodplains, and was able to invade both large and small disturbance sites.P. rhoifolia was a subdominant species that occurred on the deposits of large-scale landslides and grew in patches containing even-aged trees.C. japonicum was the other subdominant species that produced few saplings and invaded large disturbance sites together withP. rhoifolia. Establishment sites ofC. japonicum were restricted to fine mineral soils and fallen logs. We found tradeoffs in reproductive characteristics (seed size, seed number, irregular seed production, and sprouting) among the three canopy species.F. platypoda andP. rhoifolia had large seeds and produced fruits irregularly.C. japonicum produced many small seeds every year and sprouted prolifically around the main stem. The causes of the coexistence mechanism of the three riparian canopy tree species may be both niche- and chance-determined to varying degrees. In riparian areas, the three canopy species were well-adapted to disturbances throughout their life-history.

PREMISE OF THE STUDY: Microsatellite markers were developed and characterized in a typically coastal, widespread, and dominant tree species of the evergreen broadleaf forests, Machilus thunbergii, for comparison of the genetic diversity and structure of inland populations surrounding the ancient Lake Biwa and coastal populations in Japan. METHODS AND RESULTS: Eighteen polymorphic microsatellites of this species were isolated using an improved technique for isolating codominant compound microsatellite markers. These isolated loci provided compound simple sequence repeat (SSR) markers with polymorphisms of three to 19 alleles per locus, with an average of 10.9. The expected and observed within-population heterozygosities ranged from 0.16 to 0.86 and from 0.13 to 0.72, respectively. CONCLUSIONS: These markers may be useful tools for further investigation of the population genetic structure and biogeographic history of M. thunbergii in the warm-temperate zone of East Asia.

To compare the nutrient economy of woody plants at timberline of Mt. Fuji, seasonal changes in nitrogen content in leaves were examined. There was remarkable difference in seasonal changes in leaf nitrogen content betweenAlnus maximowiczii and other deciduous trees at same habitat.A. maximowiczii scarcely withdrew the leaf nitrogen to woody part during the shedding period, while the other species withdrew about half of the leaf nitrogen to woody part.

Forest vegetation in the upper basin was strongly dependent upon the topography. More specifically, landforms vary in the riparian zone, and the valley floors are mosaics that include active channels, abandoned channels, floodplains, terraces, and alluvial fans Gregory et al. 1991; Sakio 1997. These complex mosaic structures of landforms result from various disturbance regimes in the riparian zone, and the high diversity of microsites and disturbance regimes may promote the coexistence of canopy trees in riparian zones.

The aim of our research was to understand the dynamics and coexistence mechanisms of riparian forests with respect to natural disturbance and the life-history strategies of plant species and to contribute to the conservation and restoration of riparian ecosystems (see Chapter 1). There are many types of riparian vegetation in Japan (see Chapter 4). We have studied the vegetation of more than 20 riparian forests across Japan, from Hokkaido to Kyushu, and from headwater streams to lowland rivers. The studies were relatively broad, and included geography, vegetation science, population ecology, landscape ecology, and ecophysiology. In this chapter, I describe (1) the natural disturbance regime in riparian areas, (2) the life-history strategies of riparian trees, (3) the coexistence mechanisms of riparian trees, and (4) the conservation and management of riparian forests.

Two functional groups occur in the forest herbaceous layer: resident species and transient species (Gilliam & Roberts 2003). Resident species have life-history characteristics that confine them to aboveground strata of the herb layer. In contrast, transient species occur temporarily in the herb layer because they have the potential to grow taller, into higher strata. Thus, resident species include annuals, perennials, and small shrubs, whereas transient species include large shrubs and trees. Tree species’ distributions are generally limited by various combinations of disturbances (Loehle 2000), but trees have the potential for rapid migration (Clark 1998). In contrast, the distributions of herbaceous plants are determined by the availability of suitable habitats, the likelihood of seed dispersal to these habitats, and successful germination of seeds and subsequent growth (Ehrlen & Eriksson 2000; Gilliam & Roberts 2003). In this chapter, we discuss the species diversity of herbaceous species as a community composed of resident species.

The landscapes of riparian ecosystems are so beautiful that they are often the subject of photographs, picture postcards, or paintings. These prints illustrate the harmony between forests and water. Riparian forests are of great importance because of their range of ecological functions, diversity, and services.

This data paper reports litter fall data collected in a network of 21 forest sites in Japan. This is the largest litter fall data set freely available in Japan to date. The network is a part of the Monitoring Sites 1000 Project launched by the Ministry of the Environment, Japan. It covers subarctic to subtropical climate zones and the four major forest types in Japan. Twenty-three permanent plots in which usually 25 litter traps were installed were established in old-growth or secondary natural forests. Litter falls were collected monthly from 2004, and sorted into leaves, branches, reproductive structures and miscellaneous. The data provide seasonal patterns and inter-annual dynamics of litter falls, and their geographical patterns, and offer good opportunities for meta-analyses and comparative studies among forests.

This data paper reports tree census data collected in a network of 34 forest sites in Japan. This is the largest forest data set freely available in Japan to date. The network is a part of the Monitoring Sites 1000 Project launched by the Ministry of the Environment, Japan. It covers subarctic to subtropical climate zones and the four major forest types in Japan. Forty-two permanent plots, usually 1 ha in size, were established in old-growth or secondary natural forests. Censuses of woody species ≥15 cm girth at breast height were conducted every year or once during 2004 to 2009. The data provide species abundance, survivorship and stem girth growth of 52,534 individuals of 334 tree and liana species. The censuses adopted common census protocol, which provide good opportunities for meta-analyses and comparative studies among forests. The data have been used for ecological studies as well as for the biodiversity reports published by the Ministry of the Environment.

シオジ，サワグルミ，カツラが林冠を構成する奥秩父大山沢渓畔林の埋土種子の種構成を発芽試験法により調べた。本渓畔林の表層土壌（深さ5 cm）からは，現存植生にあるヤマアジサイ，フサザクラやミズメなどの他に，現存植生にはないフジウツギの実生が多く発芽した。本渓畔林の埋土種子組成の特徴として，優占種のシオジがほとんど含まれなかったこと，エビガライチゴやサルナシのような動物被食散布種子が少ないこと，現存植生との共通種が多いことがあげられた。渓畔林では出水を伴う撹乱によって，古い埋土種子集団が流亡するため，動物被食散布種子が蓄積されにくく，その代わりに現存植生に由来する風散布種子や重力散布種子が多いものと考えられる。