Analysis of the multi-stem clump structure ofLitsea japonica Juss. growing in a coastal dwarf forest

The multi-stem clump structure of a coastal dwarf forest dominated byLitsea japonica Juss. was investigated in order to clarify the sprouting characteristics and self-maintenance of clumps by stem alternation. The size and age distribution of multi-stem clumps were analyzed using cumulative relative frequency curves.L. japonica had a large number of stems and an even height distribution or young age-biased distribution of stems within a clump. These results indicated the sequential flushing of sprouts at high frequency. Height distribution within a clump ofL. japonica was relatively even compared to other species. This clump structure suggested the stable self-maintenance of individuals in all ranges of size and age without disturbances. It originated specific sprouting characteristics as a response to the severe stress of salty wind.Ardisia sieboldii Miq. had few stems within a clump. Although the stem height distribution of large individuals tended to be even, most clumps had a large size-biased distribution of stem height which indicated simultaneous sprouting. From this structure, sprouts of this species were thought to be of less significance in the stable self-maintenance of individuals thanL. Japonica.     

残存银杏群落的结构及种群更新特征

银杏是现存裸子植物中最古老的孑遗植物,也是银杏纲植物现存的唯一种,但其自然群落和种群生态学特征至今尚未明晰。对分布于贵州省和重庆市交界的大娄山区7个地点的残存银杏群落的物种组成、垂直结构、主要组成种的种群大小级结构等群落结构特征以及银杏种群更新特征进行了研究。林木层共记录到82个种,其中常绿针叶树3种,常绿阔叶树和落叶阔叶树分别为37种和42种;各群落中相对优势度均以落叶阔叶树为高,银杏在7个样方中为顶极优势种,其中在6个样方中为单优势种。银杏群落林木层在垂直结构上一般可分为3层,银杏为乔木层的主要成分。各个群落中银杏种群的大小级结构均为逆-J型或多峰型,更新连续,而其余种类多为单峰型。不同微地形单元上银杏具有不同的萌枝特性,沟谷生境中银杏的萌枝率显著高于下部边坡和崖锥,有萌个体率的差异是主要的贡献因子,而银杏的萌枝能力与主干的胸径无显著关联。残存银杏群落为典型的发育在不稳定立地上的落叶阔叶林地形顶级群落,银杏通过萌枝维系种群的长期存留和群落的相对稳定。群落中银杏、红豆杉(Taxus chinensis)、红椿(Toona ciliata)和川黄檗(Phellodendron chinense)等多种珍稀濒危植物共存,有必要从群落层次上加强对残存银杏群落的保护。     

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。     

The Role of Sprouts in the Restoration of Atlantic Rainforest in Southern Brazil

The relative importance of sexual reproduction (seed) and sprouting as sources for regeneration in Brazilian Atlantic Forest was evaluated in three different successional forest stages: young forest, immature forest, and late‐successional forest. Young plants (10–100 cm tall) of tree species were classified into the following categories: (1) seedlings that are nonsprouting—plants that originated through sexual reproduction as seeds; (2) stem base sprouting—plants that sprouted at the base of an existing plant; and (3) underground stem sprouting—plants that sprouted from subterranean stems of an existing plant. A total of 1,030 individuals of 48 species were collected. Underground stem sprouting is the rarest form of propagation, with stem base sprouting somewhat more common and possibly associated with recovery of damaged parts. The greatest contribution to regeneration was due to seeds: 92% of the individuals counted in 67% of the plant species. However, 13 species were “facultative” sprouters as seedlings and sprouters were observed in this group. The three forest ages differed in the proportion of regeneration strategies; in immature forest, sprouting was more common (15%) than in young (7%) and late‐successional (3%; p < 0.05) forest. In these three forest stages, germinating seeds are the major source of new plants; although sprouting as a reproductive strategy is rare, it is related to recovery after damage of an already existing plant and may be due to previous land use history (agriculture) and low soil fertility. Restoration using natural regeneration should consider these factors to understand seed arrival as seed is the main source of regeneration.     

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.     

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.     

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.     

云南哀牢山中山湿性常绿阔叶林树种萌生特征研究

在云南省哀牢山徐家坝地区选择保存完好的原生林与20多年前受到砍伐的森林两种类型的样地。通过调查其中各树种的更新方式和萌生状况,探讨该地区砍伐林的主要恢复途径、树种的萌生特征。结果表明,在种子萌发、地面萌生和地上萌生三种更新方式中,地上萌生所占的比例最大,尤其是变色锥、木果柯、蒙自连蕊茶等树种。在砍伐林中,<0.5m残桩上的萌枝数量显著高于1～2m以及≥2m高的残桩;萌生位置距地面高度与全株高度之比(以下简称萌高比)<0.1处所具有的萌枝数量显著高于其它位置;而在原生林中,残桩高度对萌枝数量无影响,萌高比<0.1处所具有的萌枝数量显著高于萌高比为0.5～0.9处的。     

金佛山方竹经营对扁刺栲群落物种多样性和优势种种群结构的影响

为探讨金佛山方竹经营对扁刺栲群落物种多样性和优势种种群结构的影响,该研究以金佛山的扁刺栲自然群落和金佛山方竹经营群落为对象,分析了两类群落的物种组成特征、物种多样性及优势种种群结构。结果表明：(1)两种群落内共记录维管束植物84种,隶属于40科63属,以樟科、蔷薇科、壳斗科、山茶科物种为主;扁刺栲为群落优势种,中华木荷和灰柯为次优势种,金佛山方竹为灌木层优势种,扁刺栲群落组成与亚热带其他地区的扁刺栲群落组成相似。(2)金佛山方竹经营群落的灌木层物种丰富度显著低于自然群落,草本层Shannon-Wiener指数和Pielou指数均显著低于自然群落。(3)扁刺栲和灰柯在自然群落中为稳定型种群,而在金佛山方竹经营群落中为衰退型种群,中华木荷在两类群落中均为衰退型种群。(4)自然群落中扁刺栲、中华木荷、灰柯种群的萌枝率、有萌个体率和幼苗相对优势度均高于金佛山方竹经营群落。综上认为,金佛山方竹经营对金佛山扁刺栲群落灌木层和草本层物种多样性产生了负面影响,并显著影响扁刺栲群落优势种种群更新和维持。     

Structure and dynamics of a <Emphasis Type="Italic">Castanopsis cuspidata</Emphasis> var. <Emphasis Type="Italic">sieboldii</Emphasis> population in an old-growth,evergreen, broad-leaved forest: The importance of sprout regeneration

The population structure and dynamics of Castanopsis cuspidata var. sieboldii were studied to evaluate vegetative and sapling regeneration in an old-growth, evergreen broad-leaved forest exposed to low-severity typhoon disturbances by annual typhoons on the Tsushima Islands in Japan. The density of individuals 5cm d.b.h. was 38.0ha^–1 in 1990; 7.9% were multiple-stemmed individuals. Over the 7-year study period (1990–1997), the number of individuals decreased, although the number of stems increased. Over 30% of apparently dead individuals were reconstituted by sprouting stems. Compared with sprout regeneration, sapling regeneration rarely occurred and was only observed in canopy gaps. Most individuals had at least one sprout shoot (H 30cm, d.b.h. <5cm), and the number and size of sprout shoots increased as the size of the individuals increased. During the study period, larger individuals with stem breakage tended to produce sprout stems. The density of saplings was 1074ha^–1 and they were more abundant in canopy gaps than under closed canopies, but large saplings were very rare even in canopy gaps. The population of C.cuspidata var. sieboldii consisted primarily of single-stemmed individuals with a few multiple-stemmed individuals providing a sprout bank. Larger individuals responded to the low severity typhoon disturbances and formed sprout stems. Although many saplings were observed, regeneration occurred more often by sprout formation than by growth of saplings. Thus, sprout regeneration is an important mode of regeneration, which allows this pioneer-like species to maintain its population in this forest.     

Seedling and Sprout Response to Slash-and-Burn Agriculture in a Tropical Deciduous Forest1

Survival and growth of seedlings and sprouts were assessed in three plots for 16 mo following the slashing and burning of a tropical deciduous forest in Jalisco, Mexico. We encountered a total of 47 species: 21 seedling species and 35 sprout species. Calliandra formosa and Piptadenia flava were the most common seedling species; Bursera arborea, Cordia alliodora, and Piptadenia constricta were the most common sprouts. Colubrina triflora, Diphysa occidentalis, and Cnidoscolus spinosus had limited sprouting ability. Twenty-six species were represented by one seedling or one sprout. Thirty-eight percent of the seedlings were tree species, 59 percent were shrub species, and 2 percent were vines species. In contrast, 86 percent of the sprouts were from trees and 13 percent from shrubs. One year after the initial measurements, 29 percent of the seedlings and 13 percent of the sprouts were dead. Each of the seedling means (number of stems/individual, height and diameter of the tallest stem, and elliptical crown area) was significantly smaller (P < 0.05) than that of sprouts at all three measurement periods, but relative growth rates were similar. Total canopy area of seedlings had a larger relative increase than did the canopy area of sprouts. The presence of seedlings increased species diversity compared to calculated diversity excluding seedlings. Timing of fruit dispersal in relation to the date of burning and the high number of Leguminosae species in the forest appeared to favor seedling establishment for some species.     

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.     

米槠-木荷林优势种群的年龄结构及其更新策略

通过年轮分析,构建了浙江天童米槠-木荷林优势种木荷、米槠、石栎的年龄结构,分析了高生长和径向生长及萌枝策略随年龄的变化规律,探讨了干扰对群落动态的影响。研究结果表明:(1)3个物种的胸径、高度与年龄的关系均可用logistic曲线和线性模型拟合,但随年龄增加胸径、高度与年龄的关系显著下降。(2)随年龄增加3树种的DBH/H逐渐增加,米槠、石栎幼龄个体(1-20a)的有萌个体率和有萌个体萌枝数逐渐下降;米槠和石栎幼苗的主干较木荷细长、多萌枝,木荷和石栎成树主干较米槠细长;体现了米槠的更新策略具开拓性,木荷的具保守性,石栎在幼龄期具开拓性,成年期转为保守性。(3)米槠和石栎的年龄结构呈逆J型,幼龄个体充足,但中龄段(21-40a)存在更新断层,这与其高消耗的开拓性策略有关;木荷的年龄结构呈间歇型,各龄级均存有个体,这与其保守性策略有关;(4)3物种在大龄级上(52-60a)均存在更新高峰,与该地区的择伐干扰时间一致,高强度的干扰促生了次生演替,形成了以木荷为第一优势种的群落。(5)米槠、木荷、石栎的年龄结构是更新策略和干扰的综合表现,它不仅与径级结构一样可展现种群更新特征、预测种群发展动态,更能精确地反映群落动态事件的发生频次和发生时间。     

Effect of laurel wilt invasion on redbay populations in a maritime forest community

Invasive insects and fungal pathogens have triggered numerous declines in ecologically important tree species in the forests of eastern North America. Although now functionally extinct in many ecosystems, these tree species have been able to persist through sprouting or the presence of a low density of resistant individuals. In this study, we document widespread mortality of another dominant North American hardwood species, redbay (Persea borbonia, Lauraceae), from an exotic disease, laurel wilt. This disease is caused by a nonnative Asian ambrosia beetle, Xyleborus glabratus, and its pathogenic fungal symbiont, Raffaelea lauricola, which were introduced to Georgia, USA in 2003. We conducted tree surveys on an island near the center of introduction from 2004 to 2009 and assessed the trajectory of tree mortality caused by laurel wilt. Additionally, we examined sprouting as a mechanism for persistence and whether changes in community structure occurred after laurel wilt introduction. We observed 98 % death of main stems and widespread mortality of genets (79 %) independent of main stem size. All remaining individuals were symptomatic of laurel wilt. Sprouting does not appear to give redbay the ability to maintain genets and recruit new stems into the forest canopy. We identified a negative interaction between laurel wilt and deer browse on stems and new sprouts, which may accelerate death rates of infected populations. If our results are applicable across redbay’s geographic range, a once abundant tree species may become ecologically extinct from coastal forest ecosystems in the southeastern United States.     

不同生境下景宁玉兰灌丛萌株形态及其生殖特征

景宁玉兰是萌生能力很强的灌木树种,为了解不同生境下景宁玉兰萌枝形态及其生殖特征,选择了灌丛(SH)、黄山松林(PTF)、落叶阔叶林(DBF)、杉木林(CLF)和林缘(FE)等5种坡向一致的生境类型,通过典型样地调查,比较分析了5种不同生境下景宁玉兰萌枝数量、大小、高度、枝系、开花及结实等性状。结果表明:(1)景宁玉兰在黄山松林下的分布密度最高,但5种生境下景宁玉兰每丛的萌枝数量没有差异,每丛最大萌枝基径对每丛萌枝数有一定影响,但最大萌枝高度与每丛萌枝数没有关系。在所有调查的景宁玉兰居群中,大于2根以上萌枝的灌丛达82.5%,说明萌生更新在种群繁衍中发挥着重要作用。(2)在落叶阔叶林下的萌枝基径显著小于其他生境(P0.05),黄山松林下一级枝粗度和长度显著小于其他生境(P0.05);灌丛中的总分枝率和逐步分枝率最高,灌丛和林缘生境的逐步分枝率(SBR2:3)高于其他生境。(3)生殖萌枝基径(r=0.320,P0.05)和高度(r=0.349,P0.05)与花量均呈显著正相关关系。杉木林下景宁玉兰生殖萌枝的花量显著高于黄山松林、落叶阔叶林和林缘生境(P0.05)。虽然黄山松林下景宁玉兰萌枝开花率及开花萌枝比例最低,但其果实大小、单果种子粒数及每丛结实率却较高(P0.05),(4)景宁玉兰对环境变化极为敏感,生境类型和海拔对萌枝形态和生殖性状均有一定影响。研究表明,景宁玉兰萌生特征主要受其内在生物学特性所控制,而萌枝形态及生殖特征则与其所处环境条件更为密切。     

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     

北京山区辽东栎林的径级结构、种群起源及生态学意义

 北京山区的辽东栎(Quercus wutaishanica)林径级结构的调查分析结果表明,辽东栎林是稳定性的群落类型,其更新主要通过萌生来完成。能够与辽东栎长期共存的伴生种有色木(Acer mono)、大果榆(Ulmus macrocarpa)、大叶白蜡(Fraxinus rhynchophylla)等。萌生在辽东栎种群中十分普遍,除辽东栎伐桩、枯木和大树根际有较多的萌生茎干外,多年生实生苗也有萌生现象发生。辽东栎林的更新在辽东栎总体种群的幼树阶段(径级2)存在着明显的瓶颈现象,但萌生特性使辽东栎林在更新时或受到干扰后形成较大的萌生种群,使辽东栎的大幼树能够得到迅速的补充,顺利地通过瓶颈进行更新,保持群落的相对稳定。一定数量的辽东栎实生种群的存在对于维持辽东栎的遗传多样性、种群整体活力和群落的稳定,提高辽东栎种群对环境变化的反应能力等方面有着十分重要的生态学意义。     

钱江源国家公园古田山常绿阔叶林木本植物的萌生更新特征

萌生更新是木本植物在原位进行更新的有效手段,使群落具有较强的恢复力。但以往研究侧重于实生更新,森林中木本植物的萌生更新特征及其在森林群落中的地位仍未得到足够理解。基于钱江源国家公园古田山国家级自然保护区内5 hm2亚热带常绿阔叶林样地的群落数据,分析木本植物萌生更新的数量特征,同时对不同分类单元、不同功能类群的萌生能力等进行比较。结果表明:(1)样地内64%的物种、20%的实生个体已经发生萌生更新现象,且萌生茎的数量占样地总个体数量的24%;(2)物种水平与科水平上,萌生能力均表现为显著差异(F=13.11,P0.001;F=27.45,P0.001)。腺蜡瓣花、柳叶蜡梅、宜昌荚蒾、窄基红褐柃、美丽马醉木等物种的萌生能力较强,蜡梅科、忍冬科、木兰科、壳斗科等类群的萌生能力较强;(3)不同垂直结构层次(林冠层、亚乔木层、灌木层)的萌生能力差异显著(F=117.5,P0.001),灌木层物种的萌生能力是林冠层与亚乔木层的1倍左右。不同生活型(常绿组分与落叶组分)的萌生能力差异显著,常绿类群的萌生能力显著高于落叶类群(P0.001)。萌生更新在亚热带常绿阔叶林中具有重要地位,可能是物种多样性维持、群落更新与演替的机制之一。灌木物种与常绿物种有着较强的萌生能力,暗示着萌生可能是植物适应荫蔽环境的生态策略之一。     

Plant diversity in managed sal (Shorea robusta Gaertn.) forests of Gorakhpur, India: species composition, regeneration and conservation

The sal (Shorea robusta) forest vegetation of Sohagibarawa Wildlife Sanctuary, Gorakhpur, India was analysed to assess plant diversity, regeneration pattern and the status of species conservation. A total of 208 plant species representing 165 genera and 72 families were recorded. Species richness, mean density and basal area of individuals in the observed forest were compared with those of other sal-dominated forests of India. The sal forest was rich in Papilionaceae (23 species), which contributed maximally to the total number of individuals of <30 cm girth. After sal, density was maximal for a leguminous shrub, Moghania chappar. In addition to the usual recruitment by seed, a number of species also showed non-seed regeneration through storage roots, sprouts or ramet proliferation. The individuals regenerating as sprouts from underground stem or storage organs contributed significantly to the sum total of individuals/ha. As much as 45.5% of the total individuals were of ramet origin and shared 10.6% of the total species richness of the forest. In stands facing moderate to low disturbance, thickets of dense entangled mass of vegetation, predominantly composed of thorny lianas, were identified that usually contained less common and rare species like Rauwolfia serpentina, Desmodium latifolium, Crotalaria alata and Gloriosa superba in addition to the frequent ones. These thickets help to conserve the special habitat conditions and provide protection for natural regeneration of several infrequent and rare plant species and thus contribute towards the maintenance and in situ conservation of overall diversity of recurrently disturbed forest vegetation.     

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.