Juvenile sprouting ability of the endangered maple, <Emphasis Type="Italic">Acer pycnanthum</Emphasis>

Japanese red maple, Acer pycnanthum, is an endangered species having a limited distribution of central Honshu, Japan. Sprouting is an important part of its natural history, and many remnant populations contain high number of multiple-stem clones. However, knowledge of sprout formation and growth is lacking, which has hampered understanding of the reestablishment process after major disturbance. My research objectives were to characterize the formation and growth of basal sprouts in the juvenile stage and determine the effects of light intensity and stump diameter on these characteristics. Twenty sprouting clones were investigated at a natural site in Nagano Prefecture during a four-year period after cutting. Japanese red maple exhibited abundant and vigorous sprouting from the root collar of cut trees. Many sprouts arose immediately after cutting. Average number of sprouts per stump was 12.2. Number of sprouts per stump was negatively correlated with relative light intensity. The two dominant sprouts (sprouts 1 and 2) of each clone were selected to analyze their growth. The average extension growth of sprout 1 (i.e., the tallest and most vigorous) was 173.3 cm at the end of first growing season. At the end of fourth growing season, average height and diameter at breast height (dbh) of sprout 1 were 377 and 2.1 cm, respectively. Relative light intensity and stump diameter significantly and positively affected D²H (diameter at breast height squared × height) of sprout 1. Because the growth rate of sprouts is much faster than that of seedlings, regeneration by sprouting is more significant than seedling regeneration to maintain populations after disturbances.     

木本植物萌生更新研究进展

萌生是植物营养繁殖的方式之一.本文综述了萌生与实生这2种更新方式的差异、植物萌生能力的测定、影响植物萌生能力的因素以及萌生指数在生态系统评估中的意义.与实生相比,萌生具有抗干扰能力强、幼年期生长迅速等优点,因而它在植被演替的前期阶段发挥着明显的促进作用;而当干扰强度较低、种间竞争关系稳定时,物种更倾向于采取实生更新的策略.植物的萌生具有较大的不确定性.影响植物萌生的内在因素主要包括残桩高度、萌枝长出的位置、根的生物量与长度等;环境因素主要包括干扰方式和程度、光照、养分资源的可利用性等.从理论上讲,在一个稳定的、健康的森林生态系统中,其萌生指数应该有一个最佳值范围.     

Sexual reproductive biology of the endangered Japanese red maple (<Emphasis Type="Italic">Acer pycnanthum</Emphasis>)

Japanese red maple, Acer pycnanthum, is an endangered wetland species having dioecious sex expression. Prior studies conclude that land development has caused severe loss of habitat, and seedling regeneration is rare. However, information is lacking on sexual reproduction, which is the first critical stage of regeneration. My research objective was to describe flowering and fruiting characteristics of Japanese red maple, focusing on tree sizes at the onset of flowering, factors affecting flowering regularity and fruit abundance, periodicity of fruit production, and sex ratio. In a study of a young population, Japanese red maple initiated flowering at a small size under 100% light intensity. Initiation of flowering occurred at relatively lower height in males than females, and males flowered more regularly than females. A survey of 1,106 clones from 46 natural populations revealed that male clones were significantly more abundant than female clones. In a 4-year study of mature populations, nearly all clones flowered regularly, and fruit abundance of dominant females was typically high. Fruit abundance at the population level also remained high, although fruit abundance of individual female clones varied year by year. Therefore, sexual reproductive ability is highly vigorous. Sex ratio exhibited a major deviation from a 1:1 ratio in populations with a small number of clones. In conservation planning, we should prioritize avoidance of an unbalanced sex ratio by increasing population sizes. In addition, populations having many clones >40 cm dbh with large, well-lighted crowns have a high potential of regular and abundant seed production.     

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.     

Adaptive plasticity in the life history strategy of a canopy tree species, <Emphasis Type="Italic">Pterocarya rhoifolia</Emphasis>, along a gradient of maximum snow depth

The Japanese wingnut Pterocarya rhoifolia is a riparian canopy tree species that grows under a variety of climate conditions, including heavy snowfall, despite the difficulties posed to canopy trees in such environments. This suggests that P. rhoifolia might adapt its life history strategy to different snowfall conditions. This study compared several life history traits of this tree species in a cool temperate mountainous area in central Japan along a gradient of maximum snow depth. The following trends were observed with increasing maximum snow depth: (1) diameter at breast height decreased, maximum stem length and tree height shortened, and trees tended toward a ‘dwarf shrub’ form; (2) the number of sprout stems increased significantly, and these sprouts contributed to maintaining the population; and (3) seed production decreased. Our results suggest trade-offs between clonal growth (sprouting) and sexual reproduction (seed production), and between sprouting and height growth. We concluded that the life history strategy P. rhoifolia demonstrated adaptive plasticity in response to a gradient of maximum snow depth.     

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。     

Ecological succession following forest decline in a xeric oak forest of south-central United States

Aims The loss of canopy trees associated with forest decline can greatly influence the species composition and structure of a forest and have major impacts on the ecosystem. We studied the changes in forest composition and structure 1 and 5 years following nearly total canopy mortality on several hundreds of hectares of xeric oak forests in south-central United States. Because the forests were within an ecotonal vegetation type composed of a mosaic of forest, savanna and grassland, we sought to learn whether forest decline areas would recover to forest or change to more open savanna and grassland conditions in the landscape pattern of vegetation. Because low intensity fire shaped the vegetation type, we sought to learn whether fire would keep the decline areas open.Methods The study was conducted in a xeric oak forest in east-central Oklahoma, USA. Randomly located vegetation and regeneration surveys were conducted in decline and non-decline stands 1 and 5 years following nearly total canopy mortality. Diameter at breast height (DBH), regeneration and sprout origin were recorded for all woody species.Important findings The major canopy species post oak (Quercus stellata Wangenh.), blackjack oak (Quercus marilandica Muenchh.) and black hickory (Carya texana Buckl.) suffered 85–92% mortality; however, minor canopy components experienced limited mortality. Mortality affected all size classes of canopy trees except those below 5cm breast height diameter. There was abundant regeneration of all species and fire seemed to maintain a high level of sprouting. Decline appeared to decrease the relative importance of stump sprouting and increase other types including root sprouts. Decline areas had abundant true seedlings, with stem origin from a root with the same diameter as the stem, which is very unusual for xeric oak forests. Regeneration height in decline areas was twice that of non-decline forests. Our findings suggest that forest decline may lead to: (i) reduced oak dominance and species change in the canopy, (ii) change in reproduction type to increase success of true seedlings and maintain genetic diversity of oaks.     

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     

鄂东南低山丘陵区枫香种群的天然更新方式与特征

鄂东南低山丘陵区是一个生态脆弱区,枫香（Liquidam bar formasana）林是该地区的重要森林植被类型,对于维持该地区的生态安全和经济发展具有重要意义。为了探明枫香实生和萌芽更新对枫香种群维持的作用,采用样方法研究了该地区枫香林和马尾松（Pinusm assoniana）-枫香混交林枫香种群的天然更新方式,并采用不同年代伐桩构建的时间序列研究了枫香伐桩的萌芽更新规律。结果表明：（1）该地区的枫香种群由实生和萌芽更新植株组成,但二者的比例在马尾松-枫香混交林和枫香林间存在明显差异;（2）萌芽更新可以划分为幼苗萌芽和伐桩萌芽更新2类,其中幼苗萌芽更新是对自然环境的适应,伐桩萌芽更新是对人类砍伐的适应;（3）枫香伐桩萌芽更新存在明显的自疏现象,并最终形成1-2杆的萌代主;与实生幼苗相比,伐桩萌条具有生长迅速的特点。上述结果表明,枫香的实生和萌芽更新共同维持了该地区枫香种群的稳定。     

Analysis of natural Fagus sylvatica L. s.l. regeneration in low elevation stands located in the central part of the Evros region in northeastern Greece: Is sprout origin regeneration significant for species maintenance?

Abstract

The aim of this study was (a) to analyse natural Fagus sylvatica L. s.l. regeneration in low elevation stands located in the central part of Evros region in northeastern Greece in relation to factors such as site productivity, type of silvicultural treatment and regeneration origin and (b) to determine whether or not sprout origin regeneration is significant for the maintenance of beech stands. One hundred and twenty plots (3 m × 3 m) were established in areas where thinnings and regeneration fellings had taken place, and in two site productivity regimes. In each plot, the number of beech seedlings, saplings, and stump or root sprouts (regeneration plants) with a height of up to 3 m was counted, and their height measured. Our findings indicate that even though reproduction by seed is the predominant regeneration mechanism in our stands, in the medium productivity sites sprouts represent a significant percentage of the total number of plants. Moreover, sprouting functions as a mechanism of maintenance of beech stands in medium productivity sites. During the regeneration fellings practised in this area, it is advisable to cut the seedlings and saplings of the advanced regeneration in order to supplement the seed-derived plants with seedling sprouts.     

鄂东南低山丘陵区枫香种群的天然更新方式与特征

鄂东南低山丘陵区是一个生态脆弱区, 枫香(Liquidamb ar formasana)林是该地区的重要森林植被类型, 对于维持该地区的生态安全和经济发展具有重要意义。为了探明枫香实生和萌芽更新对枫香种群维持的作用, 采用样方法研究了该地区枫香林和马尾松(Pinus massoniana)-枫香混交林枫香种群的天然更新方式, 并采用不同年代伐桩构建的时间序列研究了枫香伐桩的萌芽更新规律。结果表明: (1) 该地区的枫香种群由实生和萌芽更新植株组成, 但二者的比例在马尾松-枫香混交林和枫香林间存在明显差异; (2) 萌芽更新可以划分为幼苗萌芽和伐桩萌芽更新2类, 其中幼苗萌芽更新是对自然环境的适应, 伐桩萌芽更新是对人类砍伐的适应; (3) 枫香伐桩萌芽更新存在明显的自疏现象, 并最终形成1-2杆的萌代主; 与实生幼苗相比,伐桩萌条具有生长迅速的特点。上述结果表明, 枫香的实生和萌芽更新共同维持了该地区枫香种群的稳定。     

Intrinsic units of growth for teak trees

Attempts were made to evaluate intrinsic biological units of growth of teak trees, which were identified as age and size at inflection point of diameter at breast height. The observations were further utilized in estimating fractal dimension of the tree crown, which is an important eco-physiological characteristic of the species. A total of 38 teak plantations belonging to different age groups and site quality classes were selected for estimating the intrinsic units. Altogether, 57 stumps were identified for gathering information on age and size at inflection point at stump level (10 cm above ground) from the selected plantations. Photographs of the upper surface of the selected stumps were taken using a digital camera. Counting of annual rings/ring age and recording the radial distance from pith to each of the annual rings were done directly (visually) by using Photoshop and CorelDRAW software in a computer. Thus the age and size at inflection point at stump level were estimated. The values of intrinsic units at breast height level were estimated using allometric relations. The present study revealed that these units viz., (namely) age and size (diameter) at inflection point were 6 years and 6 cm at stump level, respectively. The corresponding values at breast-height level were estimated as 8 years and 10.6 cm including the bark. Fractal dimension was calculated based on the growth parameters, which were estimated through stump analysis. The fractal dimension worked out to 2.13 for the species. The value of fractal dimension obtained was biologically justifiable considering the light demanding nature of the species.     

A Test for the Resource Remobilization Hypothesis: Tree Sprouting using Carbohydrates from Above-ground Parts

To test the resource remobilization hypothesis, i.e. the hypothesisthat some trees sprout from root-collars or from the lower partof trunks using resources obtained from above-ground parts ratherthan from resources reserved in their roots, we conducted cuttingexperiments forEuptelea polyandra, a frequently sprouting treespecies with little carbohydrate reserves in its roots,Quercusserrata,a frequently sprouting tree species with large reservesin the roots, andMallotus japonicus, a rarely sprouting treespecies. Trees of each species were cut down in winter leavingtwo kinds of stumps, those approx. 1.5 m in height and thosecut off near the ground. The number and total dry weight ofnewly sprouted shoots per stump were compared between the twotreatments and among the three species at the end of the followinggrowing season. InE. polyandra,both the number and total dryweight of sprouts per stump were very small for both treatmentsand were similar to, or less than, those ofM. japonicus. Onthe other hand,Q. serratasprouted abundantly in both treatments.These results indicate thatE. polyandracannot sprout sufficientlywithout a considerably large volume of above-ground parts orthat additional structures such as foliage and branches maybe necessary for sprouting. We conclude that the resource remobilizationhypothesis is supported for this species.Copyright 1998 Annalsof Botany Company Euptelea polyandraSieb. et Zacc,Quercus serrataThunb,Mallotus japonicus(Thunb.) Muell. Arg., tree sprouting, cutting experiment, resprouter, resource movement, carbohydrate allocation, ground-surface disturbance, root stock, resource remobilization hypothesis.     

川滇高山栎灌丛萌生过程中的营养元素供应动态

萌生更新是森林更新的重要方式, 是硬叶栎林受到干扰后植被恢复的主要机制。以位于青藏高原东南缘的川西折多山东坡川滇高山栎(Quercus aquifoliodes)灌丛为研究对象, 调查分析了砍伐后灌丛萌生过程中基株根系和萌株生物量动态、营养元素含量, 以及基株根系和土壤对萌株生长过程中的营养元素供应动态。结果表明, 川滇高山栎灌丛平均地上和地下生物量分别为(11.25 ± 0.92) t·hm^-2和(34.85 ± 2.02) t·hm^-2, 具有较大的根冠比(3.10:1); 萌生过程中, 萌株生物量呈线性增加趋势, 以灌丛活细根生物量变化为最大, 其次是活中根和活粗根, 树桩和根蔸生物量变化最小; 萌生过程中, 灌丛细根和中根N、P含量表现为先增加、后降低的变化趋势, 萌生初期树桩、粗根和根蔸中N和K的含量明显下降, 根蔸中Ca含量略有下降, 而P没有明显下降, 根系Mg含量变化幅度较大, 灌丛地下根系储存了较多的营养元素; 土壤、树桩、粗根和根蔸是川滇高山栎灌丛砍伐后0-120天萌生生长的主要营养来源, 砍伐后60天, 萌株生长所需的营养除K元素主要来源于根系外, 其余营养元素主要来源于土壤; 在砍伐后60-120天, 基株根系对萌株生长所需的N、K和Ca贡献较大, 而对P和Mg的贡献较小; 在砍伐后120-180天, 根系除K元素对萌生生长还保持较大的贡献外, 对其余营养元素的贡献均较小。高山栎林管理要注重加强地下根系的保护。     

平茬高度对四合木生长及生理特性的影响

为改善珍稀濒危植物四合木种群衰退现状,促进其更新复壮及可持续发展,对四合木老龄化植株进行了0 cm、5 cm、10 cm、15 cm（文中定义为A、B、C、D）四种平茬高度处理,以未平茬老龄植株为对照（CK）,跟踪测定各处理的生长指标和生理指标变化规律,结果表明：（1）平茬能够促进四合木老龄化植株更新复壮,平茬后第一生长季各处理组株高生长量极显著大于CK（p<0.01）,处理B、C、D冠幅年生长量极显著大于CK（p<0.01）,各处理组新生萌条数量大于CK、萌条基径和萌条枝长极显著大于CK（p<0.01）,其中处理B株高和冠幅生长量分别较对照组增加241.43 %和417.21 %,平均萌条数量为324枝分别大于处理A、C、D和CK的293枝、229枝、221枝159枝;（2）对照植株净光合速率及蒸腾速率日变化均为双峰曲线,四种平茬处理植株平茬后第一个生长季7月份净光合速率和蒸腾速率为单峰曲线,而平茬后第二个生长季7月份变为双峰曲线;（3）平茬后前两个生长季7月份净光合速率日均值排序均为：处理B>D>C>A>CK,其中,处理B日均值分别为CK的2.07倍和1.94倍;（4）平茬处理改善了四合木植株水分状况,提高了四合木抵御干旱胁迫的能力,处理组蒸腾速率和水势均高于对照组;（5）平茬处理提高了四合木水分利用效率,其中,处理B提高程度最为明显,前两个生长季的水分利用效率分别是CK的1.38倍和1.42倍;（6）在平茬后前两个生长季内,5 cm平茬较其他高度平茬在生长和生理特性均有明显优势,但随平茬年限的增加其状况如何尚需进一步研究。     

平茬高度对中国沙棘萌枝能力及非结构性碳水化合物积累与分配的影响

为探讨中国沙棘(Hippophae rhamnoides ssp.sinensis)伐桩萌枝的养分投资与分配机制,以陕西省定边县15a中国沙棘人工林为研究对象,设置不平茬(对照)和平茬高度0、10、20 cm处理,分析伐桩萌枝能力、非结构性碳水化合物(NSC)对平茬高度的响应规律及其因果关系.结果显示:(1)随平茬高度...     

香果树根萌苗生长特性及影响因子分析

香果树(Emmenopterys henryi)为我国Ⅱ级野生保护植物,由于生境遭到破坏、过度开发利用以及种群自然更新能力差等原因,导致自然环境下香果树种群数量迅速衰减。运用方差分析、多重比较、主成分分析等方法,对自然环境下香果树种群的根萌苗生长状况及其主要影响因子进行了研究。结果表明:香果树根萌苗的数量随着苗龄的增长逐渐减少,1a根萌苗的死亡率最高;苗高和基径均随苗龄的增大呈指数增长;香果树根萌苗主要生长在母树东南方120°~150°(以正北方为0°按顺时针方向旋转,下同)位置、距母树树干2 m以内及直径2 cm、长度30 cm的露根上;根萌苗苗高受母树方位影响较小,受露根直径、露根长度以及与母树间距离的影响稍大;母树南向(168.75°)根萌苗的基径显著大于其它方向的根萌苗基径;与北向和南向相比,母树东向和西向根萌苗的冠幅较大;根萌苗苗高、基径和冠幅等形态指标均随着与母树树干间距离的增加而降低,但随着露根直径的增加各形态指标均呈先升高后降低的趋势(露根直径6.5 cm时苗高和基径达到最大值),随着露根长度的增加各形态指标呈先降低后升高的趋势;与树冠内根萌苗相比,香果树母树树冠外根萌苗的死亡率较高。主成分分析结果表明,随着林内光照条件的改善、土壤中有机质含量的增加、砾石覆盖率的增加以及适度的人为干扰均有利于香果树根萌苗的生长。因此,减小林冠郁闭度、增加人工抚育措施对维持香果树的种群发展、实现其种群自然更新具有重要作用。     

Breeding Increases the Efficacy of Chondrostereum purpureum in the Sprout Control of Birch

We tested whether the pairing of selected isolates could be used to increase the efficiency of a decay fungus Chondrostereum purpureum (Pers. Ex Fr.) Pouzar to control hardwood sprouting in Finland. We paired C. purpureum strains efficient in sprout control or highly active in laccase production, and tested the efficacy of their progeny in spout control experiments. This procedure resulted in a strain with an efficacy superior to that of the parental strains. The mortality of birch (Betula pendula Roth. and B. pubescens Ehrh.) 1 cm in stump diameter was 78%, 56% and 9% for the best progeny, the best parental strain and the control, respectively. Mortality was only slightly higher for B. pendula than for B. pubescens but no significant differences were found between the number or maximum height of stump sprouts. Our results showed that cross breeding of this decay fungus is a good alternative in attempts to produce efficient biocontrol agents against hardwood sprouting.