Effects of snow accumulation on survival of beech (Fagus crenata) seed

The escape of beech seeds from seed predators and winter desiccation due to snow accumulation was studied by comparing two sites in Japan: one site that experiences much snow and another site that experiences less snow cover. At the site with greater snow cover, about 70% of the beech seeds escaped seed predation by rodents during winter and about 70% of surviving seeds germinated successfully in spring. At the site with less snow cover, however, all of the beech seeds were eaten by rodents, and all seeds that were protected from feeding were killed by winter desiccation. We confirmed that snow prevents beech seeds from predation by rodents because it conceals their sight and scent. These effects are one of the main reasons why beeches in snowy areas regenerate constantly and those in less snowy areas do not.     

Suppression and release during canopy recruitment in Fagus crenata and Acer mono in two old-growth beech forests in Japan

Beech forests occur widely in the mountains on the main island of Japan. Wind storm is the major regime that causes canopy disturbances in these forests. Fagus crenata Blume is a dominant, and Acer mono Maxim., also a canopy species, co-occurs in these forests. It has been suggested that A. mono is less shade-tolerant than F. crenata. Using dendrochronological data, this study describes suppression and release histories during canopy recruitment for these two species in two old-growth beech forests (at Takahara and Kaname) and provides support for the shade tolerance suggestion given above. In addition, disturbance histories over the past 130 or 160 yr in the two forests have been reconstructed. At Takahara, the forest experienced more frequent wind storms, was about 10–15 m shorter and less dense than that at Kaname. Kaname is in a heavy snow region. On average, F. crenata experienced 1.4 and 2.5 definable episodes of suppression during canopy recruitment at Takahara and Kaname, respectively. At Kaname, the average length of total suppression was 66 yr, and 34 yr at Takahara. On average, at final release, the beech trees had a diameter of 25 cm and an age of about 125 yr old, which were twice as large and twice as old as those at Takahara. In contrast, at the two sites, A. mono experienced similar average numbers of episodes (1.6 episodes at Takahara and 1.8 episodes at Kaname) and similar average length of total suppression (37 yr at Takahara and 30 yr at Kaname) during canopy recruitment. At both sites, at final release, the maple had an average diameter of about 18 cm and an average age of some 70 yr. Our results have revealed that F. crenata is able to be tolerant of a longer shade suppression than A. mono. At Kaname, the canopy disturbances deduced from tree-ring data were more intense or frequent than those at Takahara, This contrasted with occurrences of wind storms at the two sites.     

Gap regeneration of major tree species in different forest types of Japan

Gap regeneration of major tree species was examined, based on the pattern of gap phase replacement, in primary old-growth stands of warm-temperate, cool-temperate and subalpine forests, Japan. Using principal component analysis, the gap-regeneration behavior of major tree species could be divided into three guilds and that of Fagus crenata (monodominant species of cool-temperate forests). The criteria used for this division were total abundance of canopy trees and regenerations and relative abundance of regenerations to canopy trees. The gap-regeneration behavior of species in the first guild was that canopy trees regenerate in gaps from seedlings or saplings recruited before gap formation; they had higher total abundance and more abundant regenerations relative to their canopy trees. The gap-regeneration behavior of F. crenata was same as species in the first guild, but F. crenata had less abundant regenerations relative to its canopy trees. Species in the second guild had lower total abundance and less abundant regenerations to their canopy trees. The guild contained species whose canopy trees regenerate in gaps from seedlings or saplings recruited after gap formation or regenerate following largescale disturbance. The third guild consisted of species with lower total aboundance and more abundant regenerations relative to their canopy trees. The gap-regeneration behavior of some species in this guild was that trees regenerate in gaps from seedlings or saplings recruited before gap formation, and grow, mature, and die without reaching the canopy layer, while the gap-regeneration behavior of other species was same as that of species in the first guild or F. crenata. Major tree species of subalpine forests were not present in the third guild.     

Heterogeneous genetic structure in a Fagus crenata population in an old-growth beech forest revealed by microsatellite markers

The within-population genetic structure of Fagus crenata in a 4-ha plot (200 x 200 m) of an old-growth beech forest was analysed using microsatellite markers. To assess the genetic structure, Moran's I spatial autocorrelation coefficient was calculated. Correlograms of Moran's I showed significant positive values less than 0.100 for short-distance classes, indicating weak genetic structure. The genetic structure within the population is created by limited seed dispersal, and is probably weakened by overlapping seed shadow, secondary seed dispersal, extensive pollen flow and the thinning process. Genetic structure was detected in a western subplot of 50 x 200 m with immature soils and almost no dwarf bamboos (Sasa spp.), where small and intermediate-sized individuals were distributed in aggregations with high density because of successful regeneration. By contrast, genetic structure was not found in an eastern subplot of the same size with mature soils and Sasa cover, where successful regeneration was prevented, and the density of the small and intermediate-sized individuals was low. Moreover, genetic structure of individuals in a small-size class (diameter at breast height < 12 cm) was more obvious than in a large-size class (diameter at breast height >/= 12 cm). The apparent genetic structure detected in the 4-ha plot was therefore probably the result of the structure in the western portion of the plot and in small and intermediate-sized individuals that successfully regenerated under the favourable environment. The heterogeneity in genetic structure presumably reflects variation in the density that should be affected by differences in regeneration dynamics associated with heterogeneity in environmental conditions.     

Structure and dynamics of Japanese beech (Fagus japonica Maxim.) stools and sprouts in the regeneration of the natural forests

Structure and spatial distribution of stools and root-collar sprouts of Japanese beech (Fagus japonica) were studied to clarify the regeneration processes of the stool and the population, and the ecological importance of this stool formation in five quadrats of the natural forests with different forest floor vegetation on the Pacific side of Japan. F. japonica dominates in the canopy of each quadrat. Most of sprouts formed a circle around the root-collar and lowest parts of the parent stems of the stool with the youngest sprouts at the periphery. The regeneration by seedlings was slight especially on the forest floor vegetation of the dwarf bamboo Sasa. The variety of size structure of stems and the existence of dead traces and/or dead center in each stool, the apparent difference in stool size, and the aggregations of stools in the forests suggest that stool expansion and long persistence of the stool at a given location may contribute to compensate for the scarcity of regeneration by seedlings inhibited by dwarf bamboo, and by the other shrubs and herbs.     

Fluctuation of nut production and seedling appearance of a Japanese beech (Fagus crenata Blume)

The nut productivity, density of fallen nuts, seedling appearance and seedling survival of a Japanese beech (Fagus crenata Blume) were investigated at three localities, Mt Gozaisho, Mt Hodaka and Mt Bandai, Japan, from 1976 to 1992. Two patterns of cycles, a short cycle and a long one, were confirmed in the beech nut productivity. Synchronization in the long cycle was recognized both on Mt Hodaka and Mt Bandai. On Mt Gozaisho, the beech nut productivity was quite low, and the seedlings disappeared within 1 year. The phenomenon on Mt Gozaisho seemed to be caused by the low matter production mainly due to erosion and poor soils. A large number of seedlings appeared in the next spring of heavy mast years on Mt Hodaka and Mt Bandai. The large beech nut productivity contributed to the large seedling supply, and this enhanced the survival probability of beech seedlings. This demonstrates the possibility that beech seedlings survived longer even under dense dwarf bamboos, particularly if the seedling supply was large.     

Structure of primary Japanese beech (Fagus japonica maxim.) forests in the Chichibu Mountains,central Japan,with special reference to regeneration processes

The floristic composition, structure and dynamics of three primaryFagus japonica stands were investigated in the Chichibu Mountains.F. japonica was dominant [RD(%): 64.9–87.0] and showed a slightly inverse J-shaped DBH class distribution in the quadrats [No. of canopy stems (H>20m): 87–138/ha]. The stems ofF. japonica for each size were distributed in the form of colonies, being scattered almost uniformly, and arranged in positive association with each other. Detailed examination of the bases of the stem groups forming colonies revealed that most of them originated from the bases of dead mother stems and that they were from common stools [No. of large stems (H>10 m) per stool: 6–11]. Among six major canopy gaps observed, only one included stems sprouting from the outer part ofF. japonica stools, while all the others were occupied by individuals of species other thanF. japonica. After tree-fall, several undercanopyF. japonica stems remained. Thus canopy gaps in these forest stands recovered through the sprouting of remainingF. japonica stools or by new sprouting ofF. japonica individuals adjacent to the gaps. However, it was considered difficult to fill canopy gaps only with sprouts when the distance between the center of a gap and that of a stool surpasses the crown vector. Such places that are not fully occupied by sprouts will be filled by individuals of other canopy and/or under-canopy species.     

Changes in tree and liana communities along a successional gradient in a tropical dry forest in south-eastern Brazil

We investigated changes in species composition and structure of tree and liana communities along a successional gradient in a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand, liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree–liana interactions.     

A size-distribution-based model of forest dynamics along a latitudinal environmental gradient

A geographically extended model of the dynamics of tree size structure of forests is proposed to simulate the change of forest zonation along latitude in response to global environmental change. To predict the response of forests to global change, it is necessary to construct functional models of forest tree populations. The size-structure-based model requires far less memory and steps of calculation compared with individual-based models, and it is easy to incorporate the dimension of geographic locations into the model to describe large-scale dynamics of forest-type distributions. The effect of increasing size growth rate, expected from increasing atmospheric carbon dioxide, was diminished at the stand-level basal area density, because of regulation by one-sided competition. Model simulations of a century-long global warming at around 3 °C predicted that (1) biomass changed in resident forests rather simultaneously in response to warming, and that (2) there was a considerable time lag in movement at the boundaries of different forest types, particularly under the existence of resident forest types that would be finally replaced. It required several thousand years after a century-long warming spell for forest types to attain new steady-state distributions after shifting. As a consequence, global warming created a zigzag pattern of biomass distribution along a latitudinal gradient, i.e., an increase in the cooler-side boundary of forest types and a decrease in the warmer-side boundary.     

Seasonal dynamics of wood formation in Oriental beech (Fagus orientalis Lipsky) along an altitudinal gradient in the Hyrcanian forest, Iran

The cambium dynamics and wood formation of Oriental beech (Fagus orientalis Lipsky) was investigated during the 2008 growing season in the Nowshahr Hyrcanian forest, Iran (36°N, 51°E). Three study sites were selected along an altitudinal gradient (650, 1,100 and 1,600 m a.s.l.), and cambial activity rates of cell formation and cell maturation were studied on micro-cores collected in intervals of 10–20 days. The cambium reactivation of the low-altitude (L) and mid-altitude (M) trees occurred contemporaneously in late March, and also the consecutive phases of cell differentiation took place almost at the same time; however, the entry into cambial dormancy varied considerably from late August to mid-November. Due to lower temperature, the upper-altitude (U) trees showed a 10-day delay in their cambium reactivation, an earlier entry into cambium dormancy (mid-September) and a slower growth rate resulting in narrower tree rings. Despite these differences, the daily increment rates of the trees at all sites reached maximum values coincidently in the early June. Since the photoperiod is the only common external factor among different sites, it is concluded that the timing of the highest growth rate is controlled by the photoperiod.     

Quantitative food webs of lepidopteran leafminers and their parasitoids in a Japanese deciduous forest

Quantitative food webs were constructed to explore the community structure of leaf-mining moths in the family Gracillariidae and their parasitoid wasps in a deciduous forest in Hokkaido, Japan. A whole food web was constructed from data collected from June to October 2001. In the web, 16 leafminer species on seven tree species were attacked by 58 species of hymenopteran parasitoid; 376 links between leafminers and parasitoids were observed. Leafminers were specialist herbivores, but most parasitoids were generalists. Five webs were constructed for the seasonal prevalence of leafminers over the one-year period to reveal the temporal dynamics in community structure. Among the seasonal webs, the first web in June was distinctive because two tree species, Japanese umbrella tree Magnolia obovata and Japanese magnolia M. kobus, supported the community. Second to fourth webs from July to September were dominated by the leafminer species on Japanese oak Quercus crispula, and the fifth web was marked by that on Carpinus cordata. The extent of potential apparent competition among leafminers was evaluated using quantitative parasitoid overlap diagrams. These diagrams suggested that abundant host species are likely to have large indirect effects on less abundant species. Moreover, the potential for apparent competition between leafminer species inhabiting different host tree species can occur, although leafminers sharing the same tree species are prone to interact via shared parasitoids. In this system, particular leafminer species, acting as potential sources of apparent competition, can affect other species as sinks, and control whole-community dynamics. Directed apparent competition may potentially occur around oak trees.     

神农架天然针阔混交林乔木更新的空间格局

为深入了解神农架天然针阔混交林群落乔木树种的更新特征,于神农架国家公园设置1 hm²森林动态监测样地对树种更新进行调查,利用Ripley的L函数分析优势更新树种的空间分布格局、种间空间关联性以及与大树的空间分布关系。结果显示：（1）更新个体共有35 752株,隶属于19科29属45种。更新优势种基本是乔木层优势树种,物种更新数量表现为：巴山冷杉（Abies fargesii Franch.） > 华山松（Pinus armandii Franch.） > 四蕊槭（Acer stachyophyllum subsp.tetramerum（Pax）A.E.） > 华中山楂（Crataegus wilsonii Sarg.）,混交林群落更新良好。（2）随着尺度增加,巴山冷杉、华山松更新空间格局由聚集分布向随机分布和均匀分布发展;华中山楂、四蕊槭更新的空间格局在整个尺度上均为聚集分布,表明针叶、阔叶树种更新在空间生态利用策略上出现分化。（3）巴山冷杉与其余3个优势更新树种、华山松与华中山楂更新呈显著正相关,表现出对微生境的共同喜好;四蕊槭分别与华山松、华中山楂更新的空间关系表现为显著负相关,种间竞争激烈。（4）巴山冷杉、华中山楂、四蕊槭的更新个体与大树的空间分布总体为显著正相关,这可能与种子传播限制相关;华山松幼苗、幼树与大树的空间分布在小尺度上呈负相关,存在资源不对称竞争。     

Community composition and tree population structure in a sub-tropical broad-leaved forest along a disturbance gradient

Floristic composition, diversity, dominance and distribution pattern of species and tree population structure were studied in three stands of a sub-tropical wet hill broad-leaved forest of Meghalaya, India, along a disturbance gradient. Tree species diversity declined with increasing disturbance. Disturbed stands showed low equitability or high dominance and the undisturbed stand exhibited high equitability or low dominance. Contagious distribution among the tree species increased with increasing intensity of disturbance. Species showing regular distribution were restricted only to the undisturbed stand. Effect of disturbance on tree population structure was analysed using density-diameter curves. In the disturbed stands tree species showed reverse J-shaped and/or negative exponential curves, while those in the undisturbed stand exhibited sigmoid to bimodal mound shaped curves.     

Occurrence of tannins in leaves of beech trees (Fagus sylvatica) along an ecological gradient, detected by histochemical and ultrastructural analyses

Sclerophylly and synthesis of phenolic compounds are active responses of plants subjected to environmental stress (drought, low nutrient supply, u.v.-B radiation, ozone). Here we describe the morphological and histochemical alterations occurring in field-grown leaves of Fagus sylvatica L. from three sites located along an ecological gradient: from a site in cool and protected conditions to one located on a mountain ridge, where the trees grow on a thin layer of soil and are exposed to the wind and to intense solar radiation in summer. The morphological data show that, as the ecological conditions of the stand worsen, individual leaf surface decreases, while the thickness of the leaves and their specific d. wt (i.e. d. wt per unit leaf area) increases. Histochemical and ultrastructural tests show a marked increase of phenolics during the course of the year. These substances, present primarily in the leaves of trees growing in stress conditions, have been identified mainly as tannins. They accumulate in the vacuoles, especially those of the upper epidermal layer and the palisade mesophyll; at a later stage they appear to be solubilized in the cytoplasm and retranslocated, eventually impregnating the outer wall of the epidermal cells amidst the cellulose fibrils, where they cluster together and form an electron-opaque layer between the wall and the cuticle. Observation of the epidermal cells also reveals that the outer cell wall is thicker. The paper discusses the roles of secondary metabolites in protection and detoxification processes; the possible ecological significance of these alterations in the ecophysiology of beech trees.     

A 15-year study on the relationship between beech (Fagus crenata) reproductive-organ production and the numbers of nuisance Japanese black bears (Ursus thibetanus japonicus) killed in a snowy rural region in central Japan

Landscape and Ecological Engineering - The relationship between beech (Fagus crenata) reproductive-organ (female flowers: FFs, male inflorescences: MIs, and filled masts: FMs) production and the...     

Field testing a global positioning system (GPS) collar on a Japanese monkey: reliability of automatic GPS positioning in a Japanese forest

A global positioning system (GPS) collar recorded the locations of an adult female Japanese macaque over a 9-day period in a habitat with mixed suburban and rural land-uses in Chiba Prefecture, Japan. The GPS device acquired positions even in forested areas. The GPS data located the female mostly in forested areas, although the female had ranged through a habitat with inter-mingled fields, orchards, quarries, and residential areas. However, the GPS position acquisition rate was low compared to studies carried out on North American mammals. The GPS fixed a position in 20% of positioning attempts. When the collared female was tracked by radio-telemetry, almost all failures of the GPS to fix a position occurred in forest.     

Population dynamics of coniferous and broad-leaved trees in a Japanese temperate mixed forest

The growth and survival of coniferous and broad-leaved trees were followed over a 5-yr period in a temperate old-growth mixed forest in Japan, and dynamic features of the forest were studied in relation to the life history of the dominants, the coniferous Abies homolepis and the broad-leaved Fagus crenata. During this period, the gap formation rate was 31m² ha^?1yr^?1, the mortality of trees > 2m high was 1.7%/yr, and the rate of loss in basal area 1.4%/yr. These values were much higher than the recruitment, 0.3%/yr, and the total growth of surviving and new trees, 0.6%/yr, owing to the inhibition of regeneration by understorey dwarf bamboo (Sasa borealis). A transition matrix model based on DBH size classes predicts that the basal area of the forest will decrease by 14% in 50 yr, but that the DBH distribution of trees > 10 cm diameter will change little. Equilibrium DBH distributions assuming recruitment being equal to mortality, were quite different between broad-leaved and coniferous trees, reflecting different survivorship curves of the two dominants. The composition and structure of the forest may change depending on the pattern and frequency of disturbances, or episodic events, notably the synchronous death of Sasa borealis.