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.     

Sprouting traits and population structure of co-occurring Castanopsis species in an evergreen broad-leaved forest in southern China

The role of sprouting in regeneration was compared betweenfour co-occurring Castanopsis species in an evergreen broad-leavedforest in southern China. We considered the largest stem of an individualto be the main stem, while all of the other stems were consideredto be sprouts. To evaluate the degree of dependence on sproutingin the regeneration of each species, we measured the ratio of thenumber of all sprouts to the number of main stems in a population. The ratio was 4.3 in Castanopsis fordii and > 1in Castanopsis fabri and Castanopsis carlesii, althoughit was < 1 in Castanopsis fargesii. The ratioof the number of all sprouts to the number of main stems in a populationwas represented by the product of two factors of sprouting ability:the proportion of sprouting individuals among all individuals andthe number of sprouts per sprouting individual. The proportion ofsprouting individuals among all individuals differed significantlyamong the four species, while the number of sprouts per sproutingindividual did not. Specific variations in sprouting traits werein agreement with the population structure of each species. Specieswith fewer small individuals in the size distribution had a higherratio than species with L-shaped distribution. Furthermore, specieswith a clumped distribution had a larger ratio than species thatwere randomly distributed. These results suggested that specieswhose recruitment by seedlings was temporally and spatially restrictedwere relatively more dependent on sprouting in the regeneration. The specific gradient of sprouting ability and the relative dependencyon sprouts to maintain a population can enhance the coexistenceof these four congeneric species.     

SPATIAL DISTRIBUTION OF GENETIC INDIVIDUALS IN THICKETS OF ALNUS INCANA SSP. RUGOSA,A CLONAL SHRUB

Thickets of speckled alder (Alnus incana ssp. rugosa (Du Roi) Clausen) consist of numerous discrete clumps of stems. Presumably all stems in a single clump are part of a single genetic individual, but a genet could comprise more than one clump. Starch-gel electrophoresis was used to identify genetic individuals in four alder populations in central New York. A single genetic marker, a tetramer with three alleles, could discriminate five genotypes. Nearest neighbor analysis revealed that genotypes were distributed randomly. That is, the pattern of genotypes was statistically indistinguishable from a model where each clump is considered a unique individual and where clump genotypes are randomly distributed. Calculation of Morisita's index of dispersion confirmed that clumps of a single genotype were not aggregated. Although alder is capable of forming root suckers and offsets, lateral expansion of genets is apparently ineffective. Apparently, spatial distribution of genetic individuals within alder thickets is not influenced by clonal growth or by other factors acting to cause patterns in the genetic structure of plant populations.     

EFFECTS OF AVIAN SEED DISPERSAL ON THE GENETIC STRUCTURE OF WHITEBARK PINE POPULATIONS

We used allozyme analysis to examine family structure, the spatial patterning of related individuals, in two populations of whitebark pine (Pinus albicaulis), a subalpine conifer that commonly displays a multistem form. The individual stems within clumps are genetically distinct individuals, having arisen from separate seeds. Individuals within a clump are genetically more similar than individuals in different clumps, but individuals in neighboring clumps do not appear to be more similar than individuals in distant clumps. This family structure appears to be a direct result of the seed-caching behavior of Clark's nutcrackers (Nucifraga columbiana), the primary dispersal agent for whitebark pine seeds.     

Stem turnover strategy of multiple-stemmed woody plants

We have investigated stem turnover strategy for Lindera umbellata, an understory shrub that sprouts from its rootstock under natural conditions to replace constituent stems, on the basis of the hypothesis that the multiple-stemmed form of woody species is an adaptation enabling efficient reproduction in high-stress environments. We tested the hypothesis that the timing of stem replacement maximizes sexual reproduction for the shrub. We developed a model for the time of optimum replacement of a stem by a daughter stem which maximizes the sexual reproduction of a shrub and tested the model using L. umbellata growing in the field. From the model, the optimum time of replacement of a stem with a daughter stem is when cumulative sexual reproduction per unit time for the stem is maximum. In practice, this will be the last age (t _opt) at which annual sexual reproduction in a stem can potentially exceed cumulative sexual reproduction per unit time for the stem. Half of the stems died at almost t _opt and had sexually mature daughter stems at that time. Other stems, however, died at times more remote from t _opt when daughter stems were sexually immature. It is thought that normal replacement of the latter stems was prevented by accidents such as breakage. We conclude that clumps of L. umbellata achieve efficient sexual reproduction by stem replacement at the optimum time, although accidents can, to some extent, determine when the stem actually dies.     

云南红豆杉人工林萌枝特性

萌枝是许多木本植物维持种群稳定和延续的重要机制之一。本文通过对云南红豆杉人工林萌枝情况的调查,分析了云南红豆杉萌枝特征及其对生长的影响。结果表明：（1）云南红豆杉萌枝现象明显,萌枝率达到88.1%,萌枝类型有树基萌枝和树干萌枝两种,其中树基萌枝是最主要的类型,有树基萌枝的个体达到了总株数的80.0%,树干萌枝率仅为39.6%,约为树基萌枝率的一半,两种萌枝都有的比率为31.5%;（2）云南红豆杉的树基萌枝数量与树高呈正相关关系,与地径呈负相关关系,而树干萌枝数量与树高和地径都没有显著的相关关系。总萌枝数量与树高及地径的相关关系与树基萌枝的一样,但相关性略低。（3）树基萌枝和树干萌枝都会影响云南红豆杉枝叶的空间分布格局,但从植株总体上说,它们对云南红豆杉的枝叶生长量没有显著的影响。     

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.     

Discontinuous DBH–height relationship of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> on Yakushima Island: effect of frequent typhoons on the maximum height

The mountain zone of Yakushima Island is covered with a mixed conifer-broadleaved forest dominated by old-growth Cryptomeria japonica (L.f.) D. Don trees. Even though Yakushima Island has been frequently struck by typhoons with wind velocities exceeding 55 m s⁻¹, the Cr. japonica trees in the mountain zone have survived for thousands of years without fatal damage. To evaluate the effect of storms on tree growth, the relationships between the stem diameter at breast height (DBH) and the heights of Cr. japonica and coexistent tree species were investigated. Two models based on an expanded allometric equation and a discontinuous piecewise allometric equation, respectively, to represent DBH–height relationships were evaluated. In all plots, the DBH–height relationship of Cr. japonica was discontinuous between small DBH and large DBH individuals. The tops of the large DBH individuals of Cr. japonica were lost to strong winds. However in each instance, they occupied the highest position in the canopy, even if they had lost their tops. In contrast, the DBH–height relationships of subcanopy broadleaved species were continuous in many plots and the equilibrium heights of the dominant broadleaved species were similar and almost in the same order regardless of the canopy heights of Cr. japonica. These results revealed a constant vertical structure in the Cr. japonica forest on Yakushima Island. Our results demonstrate a vertical niche segregation in the forest under high wind pressures and such vertical structure enables effective use of forest space and increases the basal area density.     

Different biomass-allocation patterns among four tree species in heavily disturbed sites on a volcanic mountain in Hokkaido,northern Japan

We have compared biomass-allocation patterns and frequency of sprouting among saplings of four tree species (Larix kaempferi, Betula platyphylla var. japonica, Populus maximowiczii, and Populus sieboldii) growing on a volcanic mountain in Hokkaido, northern Japan. Growing conditions were very harsh on the mountainside. Leaf mass and fine root mass relative to root mass were larger in L. kaempferi, and L. kaempferi root mass was less than for the other species. Sprouting ratios were high for the broadleaved species. Different allometries and sprouting ratios among species suggest that survival strategies for L. kaempferi were different from those for the broadleaved species. L. kaempferi has greater ability to increase leaf mass under harsh growing conditions; this probably results in large photosynthetic production by L. kaempferi on the volcano. In contrast, the two Populus species and Betula platyphylla seem to maintain populations through their ability to produce sprouts from large root systems.     

Response of Japanese beech (Fagus japonica Maxim.) sprouts to canopy gaps

The response of Japanese beech (Fagus japonica Maxim.) sprouts to canopy gaps in natural beech forest in central Japan was studied using two contrasted gaps in which tree-ring chronologies of regenerating stems were analyzed. The gaps were created by uprooting of a single Quercus mongolica var. grosseserrata stem (diameter: 50 cm; gap size: 40 m²; 23 years old) and by concurrent uprootings of four F. japonica stools (gap size: 180 m²; 30 years old). Japanese beech sprouts emerged before and after the gap formation and dominated stem populations in both gaps. In gaps, growth of F. japonica sprouts was equal or lower than growth of stems of seed origin, but most sprouts (F. japonica, Acer mono var. marmoratum) appeared a few years before emergence of seedlings. The small gap created by single stem fall was dominated by some beech sprouts from stools adjacent to the gap. The multiple gap was not closed by beech sprouts from stools surrounding the gap, but some dominant beech stems were resprouts from the uprooted beech stools. The existence of a sprout bank under the canopy may play an important role in the closing process of gaps in natural Japanese beech forest.     

Sexual dimorphism in clonal growth forms and ramet distribution patterns in <Emphasis Type="Italic">Rumex acetosella</Emphasis> (Polygonaceae)

We investigated clonal traits in the dioecious herb Rumex acetosella to characterize sexual dimorphism in clonal forms and to correlate below-ground clonal patterns and above-ground ramet distributions. We recorded creeping root length, branching patterns, ramet and clump (caespitose ramets from the same position on the root) sprouting patterns, and biomass allocations in three females and males. We also estimated the patch size of flowering ramets within a quadrat. No sexual dimorphism was detected in the frequencies of branches and flowering ramets per root length. Male plants allocated proportionally more biomass to below-ground organs. Total root length did not differ between the sexes. Females sprouted more clumps with fewer flowering ramets per root length than males, which sprouted fewer clumps with more flowering ramets, which meant that clump sprouting patterns were phalanx-like in females and guerrilla-like in males. Flowering ramets were aggregately distributed in both females and males and patch sizes were similar between sexes, indicating that the spreader propagations were not found in the guerrilla-like males. We assumed that sexual dimorphism occurred in response to physiological integration for higher reproductive effort in females.     

On the benefits of living in clumps: a case study on Polytrichastrum formosum

• The study concerns the mechanics and water relationships of clumps of a species of endohydric moss, Polytrichastrum formosum.
• Anatomical and morphological studies were done using optical and scanning electron microscopy. Experiments on waterdrop capture and their distribution to adjacent shoots within a moss clump were performed with the experimental set‐up for the droplet collision phenomena and ultra‐high speed camera. The mechanical strength of the moss clump was tested on an electromechanical testing machine.
• During the process of moss clump wetting, the falling water drops were captured by the apical stem part or leaves, then flowed down while adhering to the gametophore and never lost their surface continuity. In places of contact with another leaf, the water drop stops there and joins the leaves, enabling their hydration. Mathematical analysis of anatomical images showed that moss stems have different zones with varying cell lumen and cell wall/cell radius ratios, suggesting the occurrence of a periodic component structure. Our study provides evidence that the reaction of mosses to mechanical forces depends on the size of the clump, and that small groups are clearly stronger than larger groups.
• The clump structure of mosses acts as a net for falling rain droplets. Clumps of Polytrichastrum having overlapping leaves, at the time of loading formed a structure similar to a lattice. The observed reaction of mosses to mechanical forces indicates that this phenomenon appears to be analogous to the ‘size effect on structural strength’ that is of great importance for various fields of engineering.

     

Codominance of <Emphasis Type="Italic">Acer saccharum</Emphasis> and <Emphasis Type="Italic">Fagus grandifolia</Emphasis>: the role of <Emphasis Type="Italic">Fagus</Emphasis> root sprouts along a slope gradient in an old-growth forest

We studied how the unusual capacity of mature Fagus grandifolia to form clumps of clonal stems from root sprouts can contribute to its frequent codominance with Acer saccharum in southern Quebec, Canada. In an old-growth forest, the degree of dominance by the two species shifted along topographic gradients spanning a few hundreds of meters, with Fagus more frequent on lower slopes and Acer on upper slopes. The frequency distribution of Fagus stem diameter had an inverse J distribution at all slope positions, which is indicative of continuous recruitment. Acer stem diameter also had an inverse J pattern, except at lower slope positions where size structure was discontinuous. For stems <2 m tall, Fagus regenerated mainly by sprouts at the upper and mid-slopes, while regeneration from seed was more pronounced on the lower slope. This change of regeneration mode affected the spatial pattern of Fagus stems. Understory trees of Fagus were positively correlated with conspecific canopy trees on upper and mid-slopes, but not on lower slopes where Fagus regenerated mainly by seedlings. Understory trees of Acer were positively correlated with conspecific canopy trees only on the mid-slope. There were many Fagus seedlings around Acer canopy trees at the lower slope, suggesting the potential replacement of Acer canopy trees by Fagus. This study suggests that the regeneration traits of the two species changed with slope position and that Fagus patches originating from root sprouts can contribute to the maintenance of Acer–Fagus codominance at the scale of local landscapes.     

Continuous basal sprouting from a lignotuber:Arbutus unedo L. andErica arborea L., as woody Mediterranean examples

Summary The two dominant species of the Corsican mattoral,Arbutus unedo L. andErica arborea L., can produce abundant sprouts from the lignotuber not only immediately after fire but also more or less continuously in the absence of major disturbance. The lignotuber appears to be more important during the early stages of development; the result is an increase in the number of sprouts during the 25 years following the establishment of the individuals. Later the lignotuber seems to lose the ability to ensure the development of new basal sprouts. A hypothesis is that the presence of a lignotuber is related to the growth form.Arbutus unedo andErica arborea show behaviour intermediate between acrotony and basitony, as the shoots show acrotony, and continuous sprouting is characteristic of basitonic species. The fact that sprouting from the lignotuber is not necessarily a result of fire suggests that the relation between fire and vegetation in the Mediterranean region should be reconsidered.     

The regeneration mechanisms of a <Emphasis Type="Italic">Pterocarya rhoifolia</Emphasis> population in a heavy snowfall region of Japan

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.     

Sprout initiation and growth for three years after cutting in an abandoned secondary forest in Kyoto,Japan

Secondary forests in Japan have been abandoned and the ecosystem has degraded since the high economic growth period. We carried out cutting in January in three small areas of a long-abandoned secondary forest and investigated the sprout initiation and growth of woody plants for three years in order to reveal the early stage of sprout regeneration and to understand the sprouting ability and characteristics of each species for effective management. The percentage of sprouted stumps and the number of sprouting shoots was substantially maximized in autumn in the first year. These results suggest that autumn monitoring in the first year after cutting shows the maximum percentage of sprouted stumps and the maximum sprout number when cutting was conducted in the dormant season. With regards to species characteristics, Eurya japonica showed a low percentage of sprouted stumps in the lower plot, where the mean diameter at breast height for this species was smaller than in the other plots. The sprouting ability of E. japonica was deemed to be influenced by parent tree size. Ilex pedunculosa and Lyonia ovalifolia var. elliptica had high percentages of sprouted stumps and many sprouts. These species are useful for obtaining sprouting shoots (e.g., for firewood), but it is difficult to control their sprouting.     

Marked Point Process: Using Correlation Functions to Explore a Spatial Data Set

The relationship between the locations of the clumps of sprouts, some morphological characteristics of the clumps and the local soil environment in an old sweet chestnut coppice are studied. The theory of marked point process, which has not yet been used extensively in forestry studies, is shown to be adequate for the analysis of this type of spatial data. The marks correspond to morphological characteristics of the clumps: “diameter”, “number of sprouts”, “height at one year”, and “height at three years”. Several covariance functions are described which give a method for exploring the spatial relationships within the stand. Some of these functions are introduced for the first time in an actual statistical analysis. By using these functions, it is shown that the clumps are regularly distributed. The variables “diameter” and “number of sprouts” are strongly spatially negatively correlated, whereas the heights are slightly or not correlated. By categorising the individuals according to the mark values, it is shown that the small clumps tended to be aggregated in the gaps between medium and large clumps. Values of heights in the ties of the distribution are related as well as their spatial correlation to the local soil environment.     

Sprouting success of shrubs after fire: height-dependent relationships for different strategies

The sprouting success of co-occurring populations of shrub species in a temperate woodland of semi-arid Australia was investigated and related to population survival strategies. Straw was added to 21 × 15 m plots in the woodland, burnt and the pre-fire characteristics of shrubs were used to determine the basis for sprouting success. Species differed widely (4–94%) in sprouting success; a high percentage of established seedlings of all species were killed by fire but survival increased with height reaching a maximum at 25–60 cm (depending on the species). Thickness of bark at stem bases increased with height growth but sprouting success was not related to bark thickness; sprouting success of shrubs at similar thickness varied greatly between species. All species were able to initiate sprouts after cutting through their basal stems, so lack of active meristems was not a limitation. Species differed in the height at which shrubs began flowering but this was always after maximum sprouting success was reached. It is proposed that differences between individual shrubs in supply of nutrients, carbohydrates, and/or water to activated meristems would account for patterns of in ter- and intra-specific sprouting success. The data are consistent with recognised fire survival strategies. `Sprouters', the species relying more on sprouting than recruitment for population persistence, maintained maximum sprouting success with height growth and gained sprouting ability along stems once they reached 1 m in height. In contrast, `non-sprouters', the species largely relying on recruitment from seed to maintain populations, were either not able to sprout after seedling establishment or steadily lost the ability to maintain sprouts with growth beyond 60 cm and did not develop axillary buds along stems at any height. Received: 19 July 1997 / Accepted: 8 February 1998     

Growth strategy of the stoloniferous rattan Calamus javensis in Mt. Halimun, Java

Calamus javensis is a widespread understorey rattan in Southeast Asia and is one of the dominant rattan species in Mt. Halimun National Park, West Java. This species can establish clumps either sexually with seeds or clonality with stolons. To analyze the role of sexual reproduction and clonality for clump establishment in C. javensis, we studied the vegetative and genetic structures of the population. Totals of 2,777 ramets comprising 1,321 clumps were found in three 0.16 ha plots. The number of ramets per clump showed reverse J-shaped distribution with a maximum of 15. Clustering and stoloniferous ramets accounted for 62 and 20% of all ramets, respectively. This indicates that C. javensis is actively engaged in clustering clonal growth. The longest stem was 14 m although 75% of all stems were shorter than 1 m long. The stolon ranged from 6 to 538 cm in length, which decreased the local density of ramets. Using randomly amplified polymorphic DNA (RAPD) analysis, we obtained 56 polymorphic bands for 118 clumps sampled from one of the plots. All samples showed different RAPD banding patterns, except one pair at a distance of 225 cm from each other. The genetic similarity among samples closer than 10 m was significantly higher than the expected value from a purely random distribution. These results suggest that most separate clumps are established by recruitment from seeds, and most seeds dispersed near mother plants. Hence, in C. javensis, clonality is more a growth strategy to increase the size of the genet than a dispersion-propagation strategy to expand the habitat.     

米心水青冈种群萌条更新与高度生长

萌条是许多木本植物更新的重要方式,尤其是在干扰生境中.有种观点认为萌条需要消耗大量资源,导致其他方面投入减少,据此提出萌条数-高度的权衡假说.对该假说的检验多比较萌条和非萌条同属植物的高度,然而由于生活史以及其他生物学习性的差异,可能使这一比较的基础不成立.在米心水青冈中比较萌条现象不同的个体间高度来检验该假说,结果表明米心水青冈萌条和非萌条个体间的高度不存在显著差异(p=0.873),多茎干和少茎干成体间的高度也没有显著差异(p=0.559),并且个体的高度与茎干数存在显著的正相关,表明在米心水青冈中不存在茎干数-高度的权衡关系,其原因是由于萌条的叶片也具有光合能力,向萌条的资源运输随着萌条的长大而逐渐减少,直至中止.在调查的米心水青冈种群中,多干指数达到96.4%,几乎所有的幼苗、幼树和小树都是通过萌条形成的,表明萌条在种群的更新中起着关键作用.