Differences in beech (Fagus crenata) regeneration between two types of Japanese beech forest and along a snow gradient

Differences in beech (Fagus crenata) regeneration were quantitatively investigated using power function analysis for the size–class (diameter at breast height, DBH) distribution and juvenile-to-canopy tree (J/C) ratio along a snow gradient throughout Japan. In snowy areas, all species combined, as well as F. crenata alone, showed constant regeneration, with parameter b≈−1.6 for the power function y=ax ^b (x=DBH, y=density), which is related to the DBH–class distribution. The good fit of the data to the function suggests that beech regenerates constantly with self-thinning patch dynamics. Parameter a, which indicates the abundance of small trunks, was high. Furthermore, the mean J/C ratio was ≈8, i.e., each parent beech tree produced eight juveniles. These results suggest that beech regenerates constantly with gap dynamics in snowy beech forests on the Japan Sea side of Japan (snowy). However, the fit of F. crenata was lower and nonsignificant in some forests in less snowy areas, despite the high fit of all species combined. In these areas, the mean of a was low, and b was often near zero for F. crenata regressions. These results suggest that the abundance of beech was low, and self-thinning was not evident because of the initial low abundance. Moreover, the mean J/C ratio was <1.0, suggesting that juvenile density was lower than that of canopy trees. Thus, the regeneration of F. crenata on the Pacific Ocean side of Japan (less snowy) is rather sporadic. Less snowy conditions may promote seed desiccation, predation of beechnuts and seedlings, and water stress. Lower F. crenata density may also reduce predator satiation and wind pollination.     

Gap dynamics in climaxFagus crenata forests

Gap characteristics and gap regeneration were studied in several climaxFagus crenata forests in Japan. 278 gaps were observed. Gaps covered 12% of the total land area of 20.05 ha. Gap density was 13.9 gaps per ha and, mean gap size was 92.0 m². Smaller gaps were much more frequent than larger ones. Gaps larger than 400 m² were rare. Most gaps were created by the death of single trees. Canopy trees died more often standing or with broken trunks than by uprooting, although uprooted trees were relatively abundant in the site with poor soil drainage and in the site on upper slope. Differences of gap regeneration behaviour were recognized among tree species.F. crenata regenerates in gaps from saplings recruited before gap creation and can replace not only its own gaps but also gaps of other species. Most species other thanF. crenata andMagnolia obovata could not regenerate in their own gaps. More successful regeneration ofF. crenata may occur in gaps smaller than 200 m², althought it regenerated in a wide range of gap size. However, increased relative density ofF. crenata in the canopy layer seems to prevent its successful regeneration. Gap regeneration of other species did not clearly depend on a species-specific gap size.     

Gnawing damage by rodents to the seedlings ofFagus crenata andQuercus mongolica var.grosseserrata in a temperateSasa grassland-deciduous forest series in southwestern Japan

The effects of dwarf bamboo,Sasa, cover on the initial morrality of hardwood seedlings were investigated by transplanting 1-year-old beech (Fagus crenata) and current-year oak (Quercus mongolica var.grosseserrata) seedling to three different stands; old-growth beech and secondary oak forests withSasa undergrowth, and aSasa grassland in a grassland-forest series near the top of Mt Jippo, southwestern Japan. The most frequent cause of seedling morrality was gnawing of the stems by rodents. In the beech forest, the gnawing was more likely to occur underSasa cover, suggesting that it provides a good habitat for rodents on the beech forest floor. TheSasa under growth may thus play an imporrant role in regeneration of beech forest. In the oak floor, mortality of both species was low and only a little gnawing occurred during a year. However, no natural oak seedling were found in the forest even after a mast year. This may be because most of the acorns disappeated before establishment. The early-stage demography of hardwood seedling as oak may thus play an imporrant role in regeneration of oak forest. In theSasa grassland where the seed supply is small, almost all of the seedlings died fromo gnawing regardless of the presence ofSasa cover. These factors prevent the recruitment of a sizable seedling bank. Rodents may thus play an imporrant role in maintenance of theSasa grassland.     

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.     

An interactive effect of simultaneous death of dwarf bamboo, canopy gap, and predatory rodents on beech regeneration

To clarify the interactive effect of the simultaneous death of dwarf bamboo (Sasa kurilensis), forest canopy gap formation, and seed predators on beech (Fagus crenata) regeneration, we analyzed beech demography from seed fall until the end of the first growing season of seedlings in an old-growth forest near Lake Towada, northern Japan. The simultaneous death of S. kurilensis took place in 1995. We established four types of sampling site differing in forest canopy conditions (closed or gap) and Sasa status (dead or alive). Beech seed survival and emergence ratio were both highest in gaps with dead Sasa (gap-dead), because rate of predation was lowest. Seedling survival during the first growing season was also highest in the gap-dead treatment, because of less predation and less damping off. As a result, even though density of seed fall was lowest in the gap-dead treatment, the living seedling density there was highest at the end of the first growing season. Predation, which caused the greatest mortality during the seed and seedling stages, was significantly lower at both sites in gaps and sites with dead Sasa. This was probably due to changes in the behavior of rodents in response to the structure of the forest canopy and undergrowth. Both the death of Sasa and canopy gap formation allowed seedlings to avoid damping off because of the high light availability. The indirect effect of the simultaneous death of Sasa and canopy gap formation in reducing predation contributed more to beech regeneration than their direct effect in increasing light for the seedlings.     

The spatial pattern and canopy-understory association of trees in a cool temperate,mixed forest in western Japan

The spatial distribution pattern of trees and the association between canopy and understory individuals were examined with reference to the distribution of tree crowns in a cool temperate, mixed forest in Ohdaigahara, western Japan. Line transect and contact sampling methods were used to examine the pattern over various spatial scales. These methods are useful to detect patterns over a large study area. The dominance ofChamaecyparis obtusa on steep slopes forming large patches suggested that the distribution of this species is a consequence of landslides. UnderstoryFagus crenata showed a clumped distribution, and the relative coverage of this species was larger in canopy gaps than under a closed canopy. Understory individuals ofAbies homolepis showed a positive association with canopy trees ofF. crenata but a negative association with conspecific canopy individuals. These patterns suggested thatF. crenata regenerates in canopy gaps and is replaced byA. homolepis. The dynamics of these two species are consistent with the process of gap dynamics. The effects of both small- and large-scale disturbance must be evaluated to understand the mechanisms of patch formation and the coexistence of forest tree species.     

Two types of matter economy for the wintering of evergreen shrubs in regions of heavy snowfall

Plant adaptation to an environment subject to heavy snowfalls was investigated in four species of evergreen shrubs growing in a Fagus crenata forest in an area of Honshu on the Sea of Japan. These shrubs stored carbohydrates in some organs before the snowy season and were covered with snow for 4–5 months. Aucuba japonica var. borealis, Camellia rusticana, and Ilex crenata var. paludosa maintained a reserve of carbohydrates during the snowy season. In Daphniphyllum macropodum var. humile, the reserve of carbohydrates decreased during winter. The respiration rates in the first three species decreased from autumn to winter, whereas the decrease in D. macropodum was slight. It was found that the first three species could use reserve carbohydrates for the growth of new shoots after the thaw, whereas in the last species the growth of new shoots depends on high photosynthetic activity in late spring. Our findings suggest some types of matter economy in evergreen shrubs for wintering in an environment of heavy snow.     

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.     

Regeneration of beech (Fagus crenata) after the simultaneous death of undergrowing dwarf bamboo (Sasa kurilensis)

Seedling recruitment and survivorship of beech (Fagus crenata) were studied with special reference to the simultaneous death of undergrowing bamboo (Sasa kurilensis). The survival rate of beech seedlings on the floor whereSasa had withered was much higher than that on the floor whereSasa survived. Damping off caused the largest mortality among beech seedlings. However, the allocation pattern of matter to different parts of the seedlings indicated that their survival was greatly affected by production economy. The dense cover of dwarf bamboo prevented the establishment of beech seedling banks on the forest floor. The interval between the times when simultaneous death ofSasa occur and the length of its recovery period are thus important factors controlling the dynamics of beech forests in Japan.     

Differences in sapling architecture betweenFagus crenata andFagus japonica

The ecological significance of architectural patterns for saplings ofFagus crenata andFagus japonica co-occurring in a secondary oak forest were evaluated by comparing the size and shape of leaves, trunks and crowns.Fagus japonica saplings were different fromF. crenata saplings in some architectural properties: (i) the leaf area and specific leaf area were larger; (ii) the ratio of sapling height to trunk length was lower, indicating greater leaning of the trunk; and (iii) the projection area of the crown was larger and the leaf area index lower indicating less mutual shading of leaves. These architectural features indicated thatF. japonica saplings were more shade tolerant thanF. crenata andF. crenata saplings were superior toF. japonica for growth in height and could, therefore, utilize sunlight in the upper layer. An erect trunk inF. crenata and a leaning trunk inF. japonica may be important characteristics associated with the regenerations patterns of each species; regeneration from seedlings under canopy gaps in the former and vegetative regeneration by sprouting in the latter.     

Mitochondrial DNA Variation Follows a Geographic Pattern in Japanese Beech Species

The amount and distribution of mitochondrial (mt) DNA restriction fragment length polymorphism was determined among individual tree samples of two Japanese beech species, Fagus crenata and F.japonica. Individual plants were collected from 16 F. crenata populations throughout the range of the species, and from three F. japonica populations. We detected enough variation to characterize eleven and three chondriome types in F. crenata and F.japonica, respectively. The grouping of beech chondriome types based upon the cladistic analysis of mtDNA polymorphism allowed us to recognize the apparent geographical patterns of mtDIMA diversity: the resulting three main groups occupied distinct geographic areas. This geographic differentiation is likely to reflect the history of the Japanese beech forests after the last glacial period of the Pleistocene. In addition, the mtDNA polymorphism encountered within F. crenata encompassed all the variation observed in F.japonica. Our result suggests the need for re-evaluation of their phylogenetic relationships.     

Initial establishment and regeneration processes of an outlying isolated <Emphasis Type="Italic">Fagus crenata</Emphasis> Blume forest stand in the northernmost boundary of its range in Hokkaido,northern Japan

We investigated initial establishment and regeneration of an outlying isolated Fagus crenata forest stand at the northernmost boundary of its range in Hokkaido, northern Japan. The study site was located in the Sannosuke beech forest (42°46′48″N, 140°23′43″E), a representative outlying beech stand beyond its continuous range. A rectangular 0.75 ha plot was established on a southwest-facing slope and divided into 300 square sub-plots of 25 m². Within each sub-plot, stems over 5 cm in diameter at breast height (DBH) were identified and measured. Furthermore, the location of stems over 10 cm in DBH (canopy stem) was recorded within each sub-plot, and their increment core samples were extracted. Wood from fallen logs was sampled to estimate the species composition of the coarse woody debris. Micro-relief of the plot was investigated by leveling with compasses for a 2.5 m × 2.5 m grid system. In the plot, the population of F. crenata was divided into three sub-populations by their frequency distribution of age. The oldest sub-population, over 121 years old, had been established in small-localized gap in the plot. The sub-population between 81 and 120 years old and the sub-population less than 80 years old were regenerated after a landslide and windthrow in a 1954 typhoon, respectively. Furthermore, dominant species in the plot shifted from Quercus mongolica var. grosseserrata to F. crenata. Consequently, regeneration of F. crenata, i.e., expansion of forest stands, at the northernmost boundary of its range was primarily dependent on episodic natural disturbance, which may be responsible for the reduction of their migration rate in Hokkaido, northern Japan.     

Ecological geography of the range of theAbies mariesii forest in northeast Honshu,Japan, with special reference to the physiographic conditions

In the subalpine areas of the snowy regions of Japan (the Japan Sea side), there are some mountains with no or very small stands ofAbies mariesii, although this species dominates the subalpine coniferous forests of the region. In order to discuss the cause and process of this phenomenon, present horizontal and vertical ranges, as well as physiographic conditions, of theA. mariesii forest were examined in detail on the mountains in the Tohoku District. Sites in the subalpine zone were classified into two types: ‘azonal sites’ which should be excluded from the habitat ofA. mariesii because of their edaphic or small-scale climatic properties, and ‘zonal sites’. Mountains with vast less-inclined zonal sites generally had well developed stands ofA. mariesii forest. On the mountains with only small, solitary stands ofA. mariesii, the distribution was limited to flats or slightly inclined slopes at relatively low altitudes. These less-inclined zonal sites were regarded as an important habitat for theA. mariesii forest in the Hypsithermal period and the extent of these sites controls the extent of the stands in that period and the success of the subsequent range expansion of the forest.     

Natural disturbance and tree species coexistence in an old-growth beech - dwarf bamboo forest,southwestern Japan

Abstract. The structure and composition of a cool-temperate old-growth beech (Fagus crenata) - dwarf bamboo (Sasa spp.) forest, partially affected by landslide disturbance, in the Daisen Forest Reserve of southwestern Japan, were investigated in relation to forest floor and canopy conditions. All stems ≥ 4 cm DBH were mapped on a 4-ha plot and analyses were made of population structure, spatial distribution and spatial association of major tree species. The dominant species, F. crenata, which had the maximum DBH among the species present, had the highest stem density. However, for other species, larger-sized species had lower stem density with few smaller stems or saplings, while smaller-sized species had higher stem density with many smaller stems or saplings. Canopy trees of F. crenata were distributed randomly in the plot, while its stems in the other layers and all other species were distributed patchily. Small patches represent gap-phase regeneration. Larger patches correlate with landslide disturbance, difference in soil age, or the presence/absence of Sasa. Cluster analysis for spatial associations among species and stems in the different layers revealed that the forest community consists of several groups. One main group was formed on sites not covered with Sasa. This group contained a successional subgroup (from Betula grossa to Acer mono and/or F. crenata) initiated by landslide disturbance and a subgroup of tree species that avoid Sasa. Another group was formed on sites with mature soils covered largely with Sasa. This contained associations of canopy trees of F. crenata and smaller-sized tree species such as Acanthopanax sciadophylloides and Acer japonicum. It is found that the community of this old-growth beech forest is largely organized by natural disturbance and heterogeneous conditions of the forest floor (difference in soil age and presence/absence of Sasa). The existence of these different factors and the different responses of species to them largely contribute to the maintenance of tree species diversity in this forest.; Keywords: Cluster analysis; Fagus crenata; Forest dynamics; Gap; Landslide; Spatial pattern.     

Effects of snow pressure on growth form and life history of tree species in Japanese beech forest

Abstract. In the cool temperate zone in Japan Fagus crenata (beech) is a highly dominating climax species, especially in the snow-rich regions at higher altitudes. The explanation for this dominance was studied with special reference to the tolerance of tree trunks to snow pressure. Traits of six tree species: trunk bend, trunk height decrease, trunk damage and basal sprouting rate were measured in Fagus forest in the Echigo Mountains, central Japan along a snow pressure gradient. The following general trends were recognized: (1) trunk bend and trunk height decrease; (2) snow pressure caused trunk injury; (3) when the trunk bend exceeded a critical angle, the number of sprouts increased remarkably. Although the tolerances were different among the six species, most of them were seriously damaged by snow pressure, and many trunks were reduced in size. On the other hand, many sprouts emerged from deformed trunks and contributed to the maintenance of the population under heavy snow pressure. F. crenata was the only species whose trunk form and maximum size were hardly influenced by snow pressure.     

Impact of a strong typhoon on the structure and dynamics of an old-growth beech (<Emphasis Type="Italic">Fagus crenata</Emphasis>) forest,southwestern Japan

Typhoon no. 19 of 1991 (T9119) caused multiple treefalls and created large openings in an old-growth beech (Fagus crenata) forest at Mt. Daisen, in the Daisen Forest Reserve, southwestern Japan. The area of the largest opening was about 1.7 ha (300 m by 70 m). To predict the dynamics of the beech stand after the disturbance of T9119, we investigated the damage to the stand and the density and growth rate of trees with DBH=5–10 cm in a 1-ha plot covering a large part of the largest opening and the adjacent closed canopy. The beech did not regenerate immediately. The regeneration and growth rate of trees with DBH=5–10 cm were related to the frequency of the typhoon attack for at least the past century. In beech forests, small gap formation is the prevailing mode of disturbance. Our results indicate that typhoons affect the structure and dynamics of this beech stand. We suggest that both small gap formation and large-scale disturbance are important for the maintenance of beech forest in some areas.     

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.     

Vegetation history since the last glacial period in the Mikata lowland,the Sea of Japan area,western Japan

Local and regional vegetation since the last glacial period was reconstructed on the basis of a palynological study of sediment at Iwaya, in the Sea of Japan area, western Japan. During the interstade (before about 30 000 years BP), forests were composed predominantly ofCryptomeria japonica withTsuga sieboldii and cool-temperate deciduous broad-leaved trees. In the pre-full-glacial, the full-glacial and the early late-glacial (30 000-12 000 years BP), forests were dominated by temperate (montane) and boreal (subalpine) Pinaceae andBetula. During the early full-glacial, the pinaceous forests were mixed with cool-temperate trees such asFagus crenata. In the late full-glacial (18 000-16 000 years BP), the maximum development of pinaceous conifer forests was recognized. Cool-temperate broad-leaved forests composed mainly ofF. crenata andQuercus (Lepidobalanus) replaced the pinaceous forests at about 12 000 years BP and were maintained to the early postglacial.Cryptomeria japonica was distributed around the Mikata lowland during the last glacial.Cryptomeria japonica, which began to increase at 16 000 years BP, increased abruptly in the early postglacial and spread throughout the postglacial in the lowlands. After 6300 years BP, lucidophyllous forests composed mainly ofQuercus (Cyclobalanopsis) andCastanopsis were established in the Mikata district; this was later than in the inland and the Pacific Ocean areas in the Kinki region, western Japan. In historic times (afterca 2000 years BP), secondary forest ofPinus densiflora, which can grow as a pioneer in disturbed habitats, spread.     

Analysis of topography and vegetation distribution using a digital elevation model: case study of a snowy mountain basin in northeastern Japan

This study examines the relations between the local variations in vegetation and topography using logistic regression (LR) and GIS in a snowy basin in the Ohu Mountains of northeastern Japan. The spatial distribution of seven vegetation classes interpreted from aerial photographs—(a) large-sparse crown beech forest, (b) middle-dense crown beech forest, (c) dwarf beech scrub, (d) dwarf bamboo thicket, (e) Japanese white pine forest, (f) snow-avalanche scrub or meadow, and (g) riparian forest—was analyzed with terrain parameters derived from a 10 m digital elevation model (10 m DEM) and parameters of landslide distribution and surface geology. While large-sparse crown beech forests dominate the slopes, smaller crown beech forests or scrubs are often found on the west-facing (i.e., windward side) upper parts of slopes and crests. On the contrary, snow-avalanche scrubs or meadows are found on the leeward side of steep slopes and concave plan curvatures. Dwarf bamboo thickets are often found on east-facing (i.e., leeward side) gently sloping crests, where the snow remains until summer. Japanese white pine forests respond positively to sharp ridges, whereas riparian forests show a positive response to the gently sloping lower parts of slopes and bottomlands at low elevation. The heterogeneous vegetation distribution in the basin indicates differences in site conditions (e.g., soil–water conditions), and the existence of various disturbance regimes induced by the strong winter monsoon with heavy snowfall, snow movements (e.g., avalanches), and temporal differences in snowmelt on different topographies. The estimated vegetation maps could be used for forest management and restoration.

     

Architecture and development in Fagus japónica - Fagus crenata forest near Mount Takahara,Japan

Abstract. The architecture and development of forest eco-units in a mixed Japanese beech forest were studied by means of aerial photographs and belt-transects. Fagus japónica dominates in this forest because it has the ability to reproduce through root-collar sprouts. Each individual has a number of stems that reach the canopy. Two eco-unit types are recognized. Most abundant is the type dominated by multiple-stem F. japónica individuals (type A). The other type is dominated by other tall tree species, mostly Fagus crenata (type B). The most common cycle of development for type A is mature / stem-breakage / growing / mature. After stem-breakage, suppressed sprouts of the same individual replace the broken stem by growing quickly into the canopy. This accounts for the low coverage of patches in the early growing phases and the high coverage in mature phases in the aerial photographs. After uprooting off. japónica or after death of other canopy tree species, a seedling phase will be necessary, during which canopy species establish themselves from seed and F. japónica may establish itself from sprouts. Dwarf bamboo appeared to inhibit the establishment of seedlings but it does not affect the establishment of F. japónica sprouts. It is concluded that the dominance of F. japónica over other tall tree species is the result of F. japónica reproducing by sprouts.