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.     

Linkage between seasonal gas exchange and hydraulic acclimation in the top canopy leaves of Fagus trees in a mesic forest in Japan

We investigated how leaf gas exchange and hydraulic properties acclimate to increasing evaporative demand in mature beech trees, Fagus crenata Blume and Fagus japonica Maxim., growing in their natural habitat. The measurements in the top canopy leaves were conducted using a 16-m-high scaffolding tower over two growing seasons. The daily maxima of net photosynthetic rate for the early growing season were close to the annual maximum value (11.9 mol m^–2 s^–1 in F. crenata and 7.7 mol m^–2 s^–1 in F. japonica). The daily maxima of water vapor stomatal conductance were highest in the summer, approximately 0.3 mol m^–2 s^–1 in F. crenata and 0.15 mol m^–2 s^–1 in F. japonica. From the early growing season to the summer season, the leaf-to-air vapor pressure deficit increased and the daily minima of leaf water potentials decreased. However, there was no loss of leaf turgor in the summer as a result of effective osmotic adjustment. Both the soil-to-leaf hydraulic conductance per unit leaf area and the twig hydraulic conductivity simultaneously increased in the summer, probably as a result of production of new vessels in the xylem. These results suggest that both osmotic adjustment and increased hydraulic conductance resulted in the largest diurnal maximum of stomatal conductance in the summer, resulting in the lowest relative stomatal limitation on net photosynthetic rate, although the leaf-to-air vapor pressure deficit was highest. These results indicate that even in a mesic forest, in which excessive hydraulic stress does not occur, the seasonal acclimation of hydraulic properties at both the single leaf and whole plant levels are important for plant carbon gain.     

Effects of Sika deer on the regeneration of aFagus crenata forest on Kinkazan Island,northern Japan

Kinkazan Island, a sanctuary island that has been conserved for over 100 years, is inhabited by a Sika deer population of high density (60 km⁻²). AFagus crenata forest, a climax forest of this region, was composed of only large sized trees (30–60 cm diameter breast height) and lacked young trees. However, many saplings were found inside a deer proof fence, indicating this forest had a potential to produce seedlings. They were tentatively protected by shrubs ofLeucothoe grayana var.glabra, an upalatable ericaceous shrub, but did not exceed the shrub height. Heavy browsing by the deer suppressed recruitment of saplings ofF. crenata. The forest will be reduced without population control of the deer.     

Relationships between vessel element anatomy and physiological as well as morphological traits of leaves in <Emphasis Type="Italic">Fagus crenata</Emphasis> seedlings originating from different provenances

We attempted to observe differences in vessel element anatomy, and physiological and morphological traits of leaves in Fagus crenata seedlings originated from seven different provenances grown under the uniform environmental conditions. We also investigated the relationships between the anatomical characteristics of the vessel elements and physiological plus morphological traits of leaves in Fagus crenata seedlings. To carry out the experiments, Fagus crenata samples were prepared from Chichibu Research Forest of Tokyo University. For anatomical studies of the vessel elements, vessel number per mm², average vessel area, and the percentage of vessel area from the pith to the bark side were measured. We also measured transpiration rate, stomatal conductance, leaf area, leaf thickness, leaf dry mass per unit leaf area and leaf density for foliar studies. The anatomical characteristics of the vessel elements as well as the physiological and morphological traits of leaves were noticeably different among provenances. In addition, we found significant correlations between the foliar characteristics not only with vessel number per mm², but also with vessel area percentage and sum of the (vessel area)², theoretical hydraulic conductivity, from the pith to the bark side. Therefore, we concluded that variations in physiological and morphological traits of leaves in response to provenance variation were in correspondence with vessel number per mm² as a parameter that determines the total vessel area and consequent water hydraulic conductance in Fagus crenata as a diffuse porous hardwood.     

Didymella fagi sp. nov. and its anamorphAscochyta fagi, causing the yellow leaf spot disease ofFagus crenata andQuercus mongolica var.grosseserrata in Japan

AnAscochyta fungus was obtained during a survey of leaf spot diseases ofFagus crenata in the mountains of Aomori prefecture in 1995. The pathogenicity of the fungus toF. crenata was confirmed by inoculation. Its teleomorph was first found on artificially infected leaves after the leaves were placed in an incubator at 5°C with a 12-h photoperiod (approximately 500lx, daylight strip lamps) for 4 mo. The fungus was found to be the causal agent of yellow leaf spots ofF. crenata andQuercus mongolica var.grosseserrata in the field. Comparison with similar fungi so far described from Fagaceae indicated that the anamorph isAscochyta fagi and the teleomorph is an undescribed species ofDidymella. The nameDidymella fagi is introduced for the teleomorph. Correlation between the two morphs has been proved by cultural, morphological and pathological studies.     

金佛山方竹对亮叶水青冈幼树种群数量结构的影响

为探索贵州省宽阔水保护区亮叶水青冈(Fagus lucida)种群的更新维持机制,采用样方法研究金佛山方竹(Chimonobambusa utilis)对亮叶水青冈种群数量结构的影响。结果表明,较高的金佛山方竹密度降低了亮叶水青冈种群数量,亮叶水青冈株数随径级和高度级增加都呈现递减趋势;金佛山方竹密度增加有利于亮叶水青冈小径级向中径级个体的转化,而方竹密度减少则有利于中径级向大径级个体的转化;金佛山方竹密度增大降低了亮叶水青冈种群平均胸径,但增加了平均高度。这表明金佛山方竹能够影响亮叶水青冈个体数量和形态建成,亮叶水青冈通过降低胸径和增加高度来适应竹丛环境。     

辽东栎林内不同小生境下幼树植冠构型分析

以黄土高原黄龙山林区辽东栎林内3个小生境（林下、林隙、林缘）下辽东栎天然更新幼树为研究对象,采用典型抽样法对辽东栎幼树侧枝、叶片和树冠的空间分布状况以及生物量分配状况进行调查分析,探讨微生境与幼树植冠构型特征的关系,明确辽东栎幼树对不同小生境的适应策略,为栎林经营和林分结构优化提供理论依据。结果显示：（1）3种生境下辽东栎幼树构型发生了可塑性变化,林下幼树树冠层次比较单一,林隙与林缘的幼树树冠层次更加丰富。（2）由林下至林缘,幼树的树高、枝下高呈逐渐减小的趋势,而地径变化趋势与之相反;幼树的冠幅、树冠面积、树冠率呈先增加后减小的趋势,并且林下与林隙、林缘的差异显著;幼树的总体分枝率、逐步分枝率、枝径比呈先增加后减小的趋势。（3）3种生境下,幼树的一级枝的枝长、直径与倾角随着树高的增加而呈减小的趋势,但3种生境的差异不显著;林下一级枝主要分布在冠层中上部,而林隙与林缘一级枝主要分布在冠层中下、中上部。（4）由林下至林缘幼树叶长、叶宽、单叶面积和比叶面积逐渐降低,而单株叶数、叶总面积、叶面积指数呈先增大后减小趋势;与其他2种生境相比林下叶片分布趋于冠层上部。（5）幼树地上部分生物量中林下主干生物量占83%,枝和叶生物量只占17%;而林隙与林缘虽然各部位生物量有所差异但比例基本一致,其中主干占66%左右,枝和叶生物量占34%左右。研究表明,林隙生境下幼树的构型优于林缘和林下生境,在今后栎林的经营中,可以通过适当间伐来增加林隙数量,为森林更新和结构的优化提供有利条件。     

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.     

Development and polymorphism of microsatellite markers for Fagus crenata and the closely related species, F. japonica

 We have developed microsatellite markers (SSRs) applicable to Fagus crenata using the RAHM method and investigated their polymorphisms. We also applied the SSRs in an analysis of a closely related species, F. japonica. Here we describe the isolation and characterization of nine polymorphic microsatellite markers, of which eight are applicable to both species. Among 30 individuals of each of F. crenata and F. japonica we detected a total of 79 and 77 alleles, respectively, with an average of 9.9 and 8.6 alleles per locus. The mean expected heterozygosity (He) was 0.615 (range: 0.216–0.925) in F. crenata and 0.660 in F. japonica (range: 0.259–0.827). The He values were considerably higher than those previously found for isozymes. Paternity exclusion probabilities for multiple loci, calculated over all loci, were extremely high (0.999 and 0.998 in F. crenata and F. japonica, respectively): sufficiently high to study pollen flow in both species. Received: 5 December 1998 / Accepted: 28 December 1998     

The seasonal occurrence of endophytic fungus, <Emphasis Type="Italic">Mycosphaerella buna</Emphasis>, in Japanese beech, <Emphasis Type="Italic">Fagus crenata</Emphasis>

The seasonal occurrence of Mycosphaerella buna in leaves and contiguous organs of Fagus crenata was studied in a Japanese beech forest, Ibaraki, Japan, in 1998 and 1999. Mycosphaerella buna was not isolated from newly developed leaves in May, but it was isolated from asymptomatic leaves after June. The frequency of its occurrence gradually increased until leaffall. In contrast, M. buna was not isolated from overwintered buds, leaf petioles, or contiguous current-year twigs. The spermogonia and pseudothecia were observed in dead leaves after leaffall. The mature pseudothecia were found on dead leaves from May to July. The ascospores produced in the pseudothecia were suggested to infect newly developed leaves.Contribution no. 173, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan     

Distribution pattern and age structure ofAbies firma saplings in a mature mixed forest ofA. firma andFagus japonica

Age and spatial distribution ofAbies firma saplings were analyzed in a mature mixed forest ofA. firma andFagus japonica. There were two major peaks in the age structure ofAbies saplings at around 10 and 75 years of age. Distribution of these age classes of saplings was contagious, while that of all saplings was approximately random. These facts showed that most of the establishment ofA. firma occurs just after a gap is formed, and the frequency at which such establishment occurs is about once every 60 years in a 1600 m² area.     

Mycorrhizae ofMonotropastrum globosum growing in aFagus crenata forest

The achlorophyllousMonotropastrum globosum was found growing in aFagus crenata forest. Samples ofM. globosum and their interpenetrating root systems ofF. crenata were collected to investigate the mycorrhizal association.Monotropastrum globosum mycorrhizae showed thick sheaths, invasion of the epidermal cells by fungal pegs, and Hartig nets, which reached only the first layer of cortical cells. TheF. crenata mycorrhizae also showed thick sheaths, but Hartig nets penetrated deep into the cortex and intracellular hypha were seen in the outer cortical cells. The similarities observerd in the mantle inner plan view and emanating hypha suggest that both mycorrhizae are formed by the same fungus.     

Shoot structure and dynamics of saplings and canopies of three deciduous broad-leaved trees of a coppice forest in central Japan

Three deciduous broad-leaved trees, Quercus serrata, Castanea crenata and Carpinus laxiflora, were the main constituents of a coppice forest in central Japan. The shoot elongation and leaf emergence modes of both saplings and the canopy of the three species were investigated. The shoot elongation modes of Q. serrata and C. crenata were the same in saplings and the upper layer of the canopy. The second shoots of these two species were formed after the first shoots were elongated. C. laxiflora was different between saplings and the upper layer of the canopy. In saplings, only the first shoots took a long time to elongate. In the upper canopy layer, higher order shoots were formed in the same way as in the other two species. In the lower layer of the canopy, all three species showed the same shoot elongation mode, in which only the first shoot and its duration of elongation was short. Leaf longevity, individual leaf area, leaf mass per unit leaf area and the stem mass per unit stem length of C. laxiflora were significantly shorter or significantly smaller than those of Q. serrata and C. crenata. The length of the stem per unit leaf area of C. laxiflora was three times that of Q. serrata and five times that of C. crenata. The elongation growth of C. laxiflora was highly efficient as it occurred with a small leaf area. The shoot dynamics and the shoot structure of C. laxiflora are more suitable for elongation growth than in Q. serrata and C. crenata. Furthermore, the shoot structures of the three species were compared and ecological characteristics of the three species are discussed. Received: 29 September 1998 / Accepted: 17 September 1999     

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.     

Mycosphaerella buna sp. nov. with aPseudocercospora anamorph isolated from the leaves of Japanese beech

A species ofMycosphaerella with aPseudocercospora anamorph was collected on overwintered fallen leaves of Japanese beech,Fagus crenata. Based on comparison of morphology withMycosphaerella species on Fagaceae, the fungus was newly described asMycosphaerella buna. ThePseudocercospora anamorph derived from a single ascospore of the fungus was morphologically identical to an endophytic anamorph isolated from asymptomatic living leaves of Japanese beech. Contribution No. 150, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba     

Shoot dynamics and architecture of saplings in Fagus crenata across its geographical range

 Relationships between leaf or shoot size, number, and arrangement in response to light were investigated to test the hypothesis that these characteristics are linked. In order to test this hypothesis, the divergence in allometry and shoot dynamics in saplings of Japanese beech (Fagus crenata) obtained from four populations and having different leaf sizes were examined in a nursery under both full sun and shade conditions. Trees with different leaf sizes also showed large differences in canopy structure, particularly when shade-grown saplings were compared. The final leaf mass distributions of the large-leaf populations were conical or “bottom - heavy”, while those of the small-leaf populations were planar or “top - heavy”. The slope of the allometric relations between leaf mass and shoot and branch mass in small-leaved populations were steeper than those in large-leaf populations. The four populations were classified into two growth types: populations producing a few large leaf and shoot modules corresponded to “stem growth type”, and those producing many small leaf and shoot modules corresponded to “leaf growth type”. These kinds of intra-specific variation in architecture and growth of F. crenata trees may influence the structure and dynamics of forests in accordance with differences in competitive ability or sensitivity to disturbances such as windstorm. Received: 18 March 1997 / Accepted: 21 October 1997     

Influence of canopy tree phenology on understorey populations of Fagus crenata

Question: Is light available for subcanopy individuals of Fagus crenata spatiotemporally heterogeneous across patches with closed canopies of different foliage phenologies and gaps? Is local abundance of Sasa influenced by the composition of the canopy layer? If so, does the Sasa layer also affect the amount of light available to small F. crenata saplings? Is variation in F. crenata population structure consistent with the hypothesis that light is important? Location: Mt. Kurikoma, Japan 780 m a.s.l. Methods: Population structure of subcanopy individuals of Fagus crenata and importance of Sasa were examined in five patch types. The patch‐types were Fc (F. crenata only in the crown), Qm (Quercus mongolica var. grosseserrata only in the crown), Mo (Magnolia obovata only in the crown), Fc’ (periphery of F. crenata) and Gap. Seasonal changes in light availability above and below the Sasa layer was examined by using hemispherical photographs and quantum sensors. Results: Subcanopy individuals of F. crenata began unfolding their leaves approximately one month earlier than canopy trees of Q. mongolica var. grosseserrata and M. obovata, but a few days later than those of adult F. crenata. Accumulated photosynthetic photon flux density above the Sasa layer was greatest in Qm and Mo, and lowest in Fc. Importance of Sasa was highest in Gap. Maximum height and the number of subcanopy individuals of F. crenata were greatest in Qm, followed by Mo, and lowest in Fc. Conclusions: Differences in canopy layer composition probably influence the regeneration of F. crenata both directly through their foliage phenologies, and also indirectly by determining the importance of Sasa.     

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.     

Photosynthetic acclimation and photoinhibition on exposure to high light in shade-developed leaves of Fagus crenata seedlings

The physiological response of leaves developed in low light (L) on Fagus crenata seedlings exposed to different levels of high light (H: high light, M: medium light) was studied. Measurements were conducted on potted seedlings in the F. crenata forest understory. The seedlings with leaves developed in L were transferred to H (L–H) and M (L–M) in summer. On exposure to high light, the photochemical efficiency of dark-adapted PSII (F_v/F_m) immediately decreased and was followed by a subsequent recovery in both L–H and L–M leaves. The mean value of F_v/F_m in L–H leaves was lower than that in L–M leaves through experiments, indicating that the degree of photoinhibition in L–H leaves was greater than that in L–M leaves. About 1 month after transfer, 37% and 5% of leaves had fallen in L–H and L–M seedlings, respectively. This result also indicated the greater photoinhibition in L–H leaves. Moreover, the photosynthetic capacity (P_Nmax) of L–H leaves decreased. In contrast, the P_Nmax of L–M leaves increased, although the P_Nmax was lower than that of M control leaves. An increase in the xanthophyll cycle pool (VAZ), indicating an increase of the photoprotective function, was found in both L–H and L–M leaves. Especially, the VAZ pool in L–M leaves was higher than that in M leaves by the end of experiments. L–M leaves may avoid photoinhibition effectively by the decrease in excess light with the increase of the P_Nmax or VAZ pool, compared to L–H leaves. Thus, the physiological acclimation on exposure to high light depended on the degree of high light. To achieve successful photosynthetic acclimation with slight photoinhibition, the variation of light intensity before and after exposure to high light would be an important factor because of the difference in excess light.