紫茎泽兰种子种群动态及萌发特性

在紫茎泽兰的入侵地四川省德昌县, 选择撂荒地、农田和马尾松林3个不同的生境, 从种子雨、种子库角度研究了紫茎泽兰种子种群动态规律,及其种子在不同光照和土壤基质条件下的萌发特性. 结果表明,3个生境下紫茎泽兰种子种群仅存在于当年3～6月,于4月底达到年高峰值. 其年降种子雨量在撂荒地中高达2.4×10⁵粒·m^-2,并均分布于2 cm土层以上, 且在撂荒地生境下紫茎泽兰种子的千粒重和活力均显著高于另外两个生境. 到7月上旬, 3个生境下土壤中均未发现有活力的种子. 在实验的光照条件下, 全光照对紫茎泽兰的种子萌发有抑制作用,而在28%光照条件下萌发率最高;砂壤土较适宜紫茎泽兰种子的萌发,生红土中其萌发速度及萌发率均最低.     

PEG胁迫对紫茎泽兰种子萌发和幼苗生长的影响

目的：开展干旱胁迫对紫茎泽兰种子萌发的影响研究，为其入侵机制的揭示和田间防治提供借鉴。方法：采用聚乙二醇（PEG-6000）梯度溶液模拟干旱胁迫环境，研究紫茎泽兰（Ageratina adenophora）种子萌发和幼苗生长对干旱胁迫的响应。结果：随着PEG-6000浓度的增加，紫茎泽兰种子的发芽率、发芽势、发芽指数和幼苗根长、根冠比均呈先升后降的趋势，而种子活力指数、幼苗胚根长度、胚轴长度、株高相对增长速率和叶片光合色素含量均呈持续下降趋势。结论：轻度干旱胁迫有利于紫茎泽兰种子萌发，而中度和重度干旱胁迫均不利于紫茎泽兰幼苗生长。紫茎泽兰在种子萌发阶段对干旱具有一定的抗逆性。     

不同地理种群紫茎泽兰生长繁殖特征的比较研究

对云南省9个不同地理种群紫茎泽兰的野外生长繁殖特性进行了调查,并采集各种群种子在温室内培植,观测比较它们在同质环境下的种子萌发、幼苗生长发育及植株开花结实情况.研究结果显示,(1)野外不同地理种群紫茎泽兰之间其植株生长和繁殖特征均存在显著差异,从南到北各种群植株的生长发育特征均呈现出先升后降的趋势,符合从高温边缘区到适生区再到低温边缘区的分布格局规律.(2)在温室同质环境下不同地理种群紫茎泽兰之间除植株根冠比和种子发芽指数差异显著外(P＜0.05),植株生长繁殖的其他指标的差异均不显著,说明野外不同地理种群紫茎泽兰的生长繁殖特性差异基本还不具有遗传性,局域适应对紫茎泽兰入侵能力的影响还较小,而较强的表型可塑性对紫茎泽兰入侵能力可能起到主要作用,这可能与其入侵时间较短有关.表明在分布区边缘,紫茎泽兰仍具有较强的繁殖能力,将随着其生理抗性的适应性分化而具有更宽的入侵范围.     

紫茎泽兰土壤种子库特征及其对幼苗的影响

研究紫茎泽兰(Eupatorium adenophorum)土壤种子库特征及其对紫茎泽兰种子的萌发、幼苗命运的影响, 在综合治理紫茎泽兰入侵危害及防止紫茎泽兰的继续扩散等方面有着重要的意义。该文在攀枝花紫茎泽兰入侵严重的地区, 通过采集果园、放牧灌丛以及禁牧灌丛3种不同生境紫茎泽兰土壤种子库的样本, 以说明不同干扰程度下紫茎泽兰种子在土壤中的分布状况。通过野外调查并结合盆栽实验, 初步研究了紫茎泽兰土壤种子库基本特征以及光照和种子在土壤中的埋藏深度等对紫茎泽兰幼苗的影响。结果表明: 1)果园、放牧灌丛和禁牧灌丛等3种干扰程度不同生境的深层种子量占总种子量的比例分别为56.44%、46.96%和24.86% (p=0.006), 这说明土壤深层种子量大小与干扰成正比, 干扰越大, 深层次紫茎泽兰种子量占总种子量的比重越大。2)播种在0、1和5 cm深度的种子萌发率分别为64.67%、22.67%和13.33%, 即种子埋藏越深, 萌发率越低, 不同层次种子萌发率差异极显著(p=0.00); 幼苗死亡率分别为27.95%、0和0, 表层种子萌发的幼苗有较高的死亡率, 而由埋藏在深层的种子萌发的幼苗没有死亡, 土壤表层发芽的幼苗与不同埋藏深度种子萌发的幼苗之间死亡率差异极显著(p=0.00)。3)在无遮蔽、半遮蔽和全遮蔽3种不同情况下, 紫茎泽兰幼苗的死亡率分别为72.15%、30.38%和4.87%, 定居率分别为6.66%、33.99%和46.67%, 即遮蔽程度越高, 死亡率越低, 定居率越高, 不同处理之间死亡率和定居率差异均极显著(p=0.00)。研究结果暗示, 强光可能是导致紫茎泽兰幼苗死亡的重要原因, 人类活动的干扰可能导致更多的紫茎泽兰种子进入土壤深层, 从而改变了紫茎泽兰土壤种子库的结构。由于土壤深层种子比表层种子具有更强的抵抗强光照射等不良环境因子影响的能力, 所萌发的幼苗成活率高, 表明其具有更高的繁殖效率, 因此人类活动干扰是紫茎泽兰入侵后难以根除的原因之一。     

光和不同打破种子休眠方法对紫茎泽兰种子萌发及幼苗状态的影响

紫茎泽兰是著名的外来入侵植物,作为入侵的第一步,发芽及其幼苗生长应该与其强入侵能力有关.基于此,通过不同光照强度处理和不同打破休眠方法的双因素实验,旨在探讨紫茎泽兰种子是否具有需光萌发特性以及低温、水杨酸、聚乙二醇,硝酸钾等常规打破休眠方法和光照如何共同影响其萌发、幼苗生长等问题.结果表明:在全光照条件下,不同处理的紫茎泽兰种子的萌发率均大于63％,铝箔纸覆盖的遮光条件(0.23％光照)萌发率均大于60％,而在完全黑暗条件下,其萌发率较低(均小于30％),这表明紫茎泽兰种子具有需光萌发的特性.有别于以往对其它植物种子的报道,低温处理、水杨酸处理、聚乙二醇处理和硝酸钾处理不能代替光照打破种子休眠,显示紫茎泽兰种子可能处于一种强迫休眠状态(种子静态).全光照与水杨酸处理、PEG处理对幼苗生长具有交互影响:黑暗下水杨酸处理浓度与幼苗生物量成正相关(P＜0.05),但全光照和加铝箔下不相关(P＞0.05);全光照下PEG处理浓度与根长显著正相关(P＜0.05),而加铝箔和黑暗下不相关(P＞0.05).紫茎泽兰种子需光萌发特征及其幼苗生长特点是人为破坏表土壤、深层土壤种子库地表化导致快速入侵的基础.结果也为通过引入适宜树种造林来控制光照因子对紫茎泽兰进行生态控制提供了理论依据.     

紫茎泽兰种子形态特征和萌发特性与其入侵性的关系

利用纸皿法在不同条件下比较研究了紫茎泽兰(Ageratina adenophora)和3种同亚族本地植物种子萌发特性,同时比较了种子大小等形态特性,探讨了种子形态特征和萌发特性与紫茎泽兰成功入侵的关系。紫茎泽兰种子重量、长度、宽度以及冠毛长度均小于3种本地植物;在不同的释放高度下,紫茎泽兰种子的沉降速度低于本地植物。紫茎泽兰种子萌发温度范围广,在亚适宜的低温下,萌发率和萌发指数均高于本地植物白头婆和水泽兰。紫茎泽兰种子萌发对水和盐胁迫响应更强烈,但在适宜条件下,紫茎泽兰种子的萌发率和萌发速度均显著高于3种本地植物。这些特性可能与紫茎泽兰的入侵性有关。     

不同生境条件下紫茎泽兰实生幼苗的生存特性比较

外来植物紫茎泽兰(Eupatorium adenophorum)入侵我国西南地区并造成了严重的生态灾难, 了解其幼苗的生存特性, 有助于预防和治理其危害。本研究于2005年8月到2006年8月通过盆栽实验和样方调查, 研究了不同光照和水分条件下紫茎泽兰幼苗的生长、生存状况和开花比例。结果表明: (1) 紫茎泽兰从种子萌发到1年后形成幼苗并开花结果的概率为1.16×10^–13–2.43×10^–11; (2) 湿润偏阴生境利于紫茎泽兰的种子萌发和幼苗存活, 其萌发出现率和存活率都达到最高, 分别为13.93%和79.50%; (3) 在水分充足的情况下, 增加光照有利于紫茎泽兰生长; (4) 出土1年后的紫茎泽兰有3.92–5.05%的植株开花结果, 产生的种子密度为23,000–52,000 inds./m²。虽然紫茎泽兰种子个体成功生存的概率很小, 但种子产量大增加了该物种成功定居的机会, 特别是湿润偏阴环境能够促进幼苗的定居。     

紫茎泽兰入侵地区土壤种子库特征

土壤种子库是植物潜在的种群,其时空分布格局对植物群落的动态与稳定性有着举足轻重的影响,尤其是在受外来种入侵危害地区,土壤种子库的特征对生态系统的恢复和未来植被的结构、功能、组成与动态等更为重要。本文通过野外调查与萌发实验相结合的方法研究了四川攀枝花市紫茎泽兰（Eupatorium adenophorum）入侵地区的植被组成和紫茎泽兰种子雨前后土壤种子库的变化,初步探讨了受入侵地区种子库中包括紫茎泽兰在内的物种的种类与储量情况。结果表明：（1）在紫茎泽兰危害严重的地带,群落组成比较简单,草本层以紫茎泽兰最为丰富,种群构成为1–4年生植株及其荫庇下大量的实生幼苗,Drude多度极大,频度达100%;（2）在土壤种子库中有13种高等植物出现,与植被组成的相似度为0.31;土壤种子库总储量为3,180粒/m^2,其中紫茎泽兰1,950粒/m^2,占总储量的61.3%。种子库各层种子储量不同,上层种子少于中下层,差异不显著（P〉0.05）,在土壤下层（5–10cm层）的紫茎泽兰种子仍然可以萌发;（3）种子雨后,表层土中（0–2cm）紫茎泽兰种子总储量为4,733粒/m^2;紫茎泽兰种子雨后种子萌发出现2个峰值,分别为第9天与第17天,表明土壤中的紫茎泽兰种子会阶段性打破休眠。紫茎泽兰在当地植被和土壤种子库中都占绝对优势,其他物种从种子阶段就开始亏缺,是紫茎泽兰不断更新和难以彻底控制的重要原因。     

持久性土壤种子库种子萌发的个体竞争能力会衰减吗?——以紫茎泽兰为例

持久性土壤种子库(PSSB)是一种重要的植物生活史对策, 很多学者就这种对策对物种适应和进化的影响进行过推理。但种子在土壤中的长时间存留是一种风险行为, 所有的PSSB影响的推理都取决于一个假设, 即PSSB种子萌发的个体的竞争能力没有因为存留损耗而显著降低。为验证这一假设, 该文以紫茎泽兰(Eupatorium adenophorum)为研究材料, 比较了埋藏1年和3年的PSSB种子萌发的个体与同母体的当年新种子萌发的个体之间在无竞争和4种密度制约竞争条件下的株高和生物量的差异。结果显示, 无论株高还是生物量, PSSB种子萌发的个体较同母体的新种子萌发的个体均有所降低, 但在多数检测时间内的降低程度未达到显著水平, 表明紫茎泽兰PSSB种子萌发的个体相对于同母体的新种子萌发的个体的竞争能力无显著下降。     

紫茎泽兰不同入侵程度的土壤及其提取物对旱稻生长的影响

在室内人工气候箱条件下,研究了紫茎泽兰不同入侵程度下的土壤及其提取物对旱稻种子萌发和幼苗生长的影响。结果表明：紫茎泽兰入侵地土壤及土壤提取物对旱稻种子萌发和幼苗生长存在不同程度的抑制作用,且随着紫茎泽兰入侵程度越重,土壤的抑制作用越明显;抑制作用强度大小依次为重度入侵地土>中度入侵地土>轻度入侵地土>当地植物土,紫茎泽兰入侵地的土壤提取物也呈现类似的规律。推测紫茎泽兰产生的化感物质随着入侵程度加深,而在土壤中逐步积累,对本地植物生长产生了不利作用。     

Fine-scale spatial heterogeneity and seed size determine early seedling survival in a desert perennial shrub (<Emphasis Type="Italic">Ericameria nauseosa:</Emphasis> Asteraceae)

In heterogenous landscapes, seeds settle in some microsites more readily than others, independently of whether those microsites are suitable for germination and subsequent growth, and survival of seedlings. Wild seeds and seedlings of Ericameria nauseosa var. oreophila in the sand-dune ecosystem near Mono Lake, California show both concordance and conflict in where seeds are retained and where seedlings flourish. Using a field experiment, we followed performance of seeds and seedlings (i.e., the rate of germination and successful emergence, initial seedling size, seedling growth and survival over first growing season), by planting seeds of known sizes in pre-identified microsites (windward and lee aspects of interspaces between shrubs, under shrub canopies, and under snag canopies, respectively). Heavier seeds were more likely to germinate and emerge successfully and resulted in initially larger seedlings than lighter seeds. These initially larger seedlings subsequently remained larger over the growing season and lived longer than initially smaller seedlings. Independent of seed and initial seedling size, seedlings that germinated under the canopy of adult shrubs grew larger and survived longer than seedlings that germinated in interspaces (open space with little or no vegetation) or under snags (dead adult shrubs). Seedlings grown under the canopy of adult shrubs experienced significantly less solar radiation and wind-deposited sand than seedlings grown in interspace or snag microsites. Sand burial more than 1 cm was lethal for seedlings. The two variables of seed size and microsite type had by far greater impact on eventual growth and survival of seedlings than did aspect, and the effects of the former two variables were independent of each other. This study amplifies the body of work on E. nauseosa at this site demonstrating that the earliest events in the life history of this long-lived perennial shrub appear to persist through time despite the harsh and variable environment.     

Study on the Dynamics and Rhythms of Midmontane Wet Evergreen Broad-Leaved Forest at Xujiaba,Ailao Mountains,Yunnan

According to data of long-term observation, the dynamics and the rhythms of the wet evergreen broad-leaved forest in respect of seed germination, seedling growth, growth laws, and phenological rhythms of the mature trees of constituent species were analyzed. The species numbers of the seeds, germinable seeds and germinated seeds of the forest in rainy season were larger than those in dry season. The growth rate of the seedlings was faster in rainy season as well indicating a season most favourable for the growth of seedlings. The growth of trees was a process of inter-specific competition, self-regulation and self-thinning. The long and indistinctive phenologieal phases of the mature trees differed from those short and distinctive phenological phases of the broad-leaved forests in the temperate. Its continuous flowering, fruiting and fruit-falling were similar to the phenological rhythms of seasonal rain forests in Xishuangbanna. However, leaf-shedding of the seasonal rain forests in Xishuangbanna, the evergreen broad-leaved forests and the temperate broad-leaved forests was in spring (February ～March), in Winter (November ～ December) and in autumn (September～October) respectively. Based on the characteristics in the phenological rhythms of the species and their responses to the climates, the three eeo-phenological types were divided as: 1. The warm temperate eeo-phenological type, whieh accounts for 82 % of the total species number (50); 2. The temperate ecophenological type, 12%; 3. The cool temperate eco-phenological type, 0. 6 %.     

原始老龄林内兴安落叶松种子命运的试验研究

兴安落叶松土壤种子库的支出主要有３个方面：种子萌发、动物取食和生活力丧失。兴安落叶松种子在６月份迅速萌发,占全年总萌发量的９０％。７月中下旬,土壤已经不存在有生活力的种子。在生长季初期,鼠类对种子取食率仅１％,到生长季中后期接近２０％。然而,此时幼苗发生基本结束,被食种子大部分为生活力很弱或丧失生活力者。红背Ｐｉｎｇ是主要的食种子者。落叶松在时间上逃避了鼠类取食种子。一般,鼠类仅就地取食１０％的落     

Patterns of Seed Size,Germination and Seed Viability of Tropical Tree Species in Southern India1

Seed weight, days to germination and seed viability were observed for 99 species growing in the Western Ghats of Karnataka, India. Seed size was strongly correlated with days to germination; smaller seeds germinated faster than larger seeds. Species which flowered during the rainy season had lighter seeds than species which flowered during the dry season. It was also found that seed size and viability of seeds were related to the season of fruiting. Species which fruit during the rainy season had heavier seeds and shorter viability than species which fruit during the dry season. These flowering and fruiting patterns and varying seed sizes are argued to be adaptations to the time of dispersal, time of moisture availability in the habitat and seedling survival.     

地涌金莲种子形态生理休眠及激素的动态变化

珍稀植物地涌金莲在野外能产生大量的种子,但成熟的种子散布后不能顺利地转化为幼苗。在暖层积（25℃）过程中,蘑菇形的小胚逐渐分化与生长,6个月后,胚已形态成熟且能很好地萌发;同时,胚内激素ABA含量不断下降,GA4含量显著增加,且与胚的形态成熟和萌发力的增强密切相关。这些结果充分证实地涌金莲种子具有形态生理休眠——在很大程度上限制了野外种子萌发。此外,种子不萌发可能与生境长时间干旱胁迫有关。     

Interference effects of Cassia uniflora Mill on Parthenium hysterophorus L.

In some parts of Karnataka and Maharashtra states (India), a leguminous undershrub, Cassia uniflora has effectively replaced the problematic weed Parthenium hysterophorus (parthenium). The studies revealed that the phenolic leachates from different parts of C. uniflora, specially from germinating seeds significantly inhibited the germination of parthenium seeds and retarded the growth of seedlings from the successfully germinated parthenium seeds. At field level, seedlings of C. uniflora outcompeted the seedlings of summer generation of parthenium causing reduction in height, dry weight and number of inflorescences of the latter which ultimately resulted in reduction of their seed output. Because of its longer life span, C. uniflora effectively prevented the establishment of parthenium plants of the winter generation in its area of growth. Results indicate that C. uniflora replaces parthenium through interference.     

泽兰实蝇寄生状况及其对紫茎泽兰生长与生殖的影响

泽兰实蝇(Procecidochares utilis)作为天敌控制紫茎泽兰(Eupatorium adenophorum)已经在国内外得到广泛的应用,但关于它对紫茎泽兰控制的有效性和防治现状的研究尚不深入。该文通过对攀西地区紫茎泽兰入侵危害严重的路域生态系统中泽兰实蝇寄生状况的抽样调查,初步研究了泽兰实蝇对紫茎泽兰生长,特别是生殖能力的影响。寄生率的调查采用随机取样法,分别从植株寄生率和枝条寄生率两方面进行,并比较不同生境下及不同年龄植株枝条寄生率的差异;选取相同数量、相同部位的各年龄植株寄生和非寄生枝条(对照),分别调查其花枝量、头状花序数及结实量,进行分析比较。研究结果表明:1)植株寄生率与枝条寄生率有显著差异(p<0.05),分别为71.67%和17.30%,前者显著高于后者;样方调查结果,成熟群落中枝条寄生率为17.48枝·m^-2;1虫瘿·枝条^-1的枝条占所有寄生枝条的92.30%;2)湿润生境下紫茎泽兰的枝条寄生率为20.27%,显著高于干旱生境下的枝条寄生率(9.33%)(p<0.05);3)不同年龄植株枝条寄生率有差异,0~1年生植株枝条寄生率分别为36.36%和21.56%,显著高于2~4年生的植株枝条寄生率,分别为13.50%、8.82%和12.16%(p<0.05);4)在目前的寄生强度下,泽兰实蝇对紫茎泽兰枝条的直径、花枝量、头状花序数及结实量均无显著影响(p>0.05)。     

The ecology of germination and reproduction of less frequent and vanishing species of Czechoslovak flora

The ripened seeds show no marked dormancy and germinate within wide limits of temperature, where the temperatures of 6–10/25°C represent the optimum. 18 months old seeds germinated at the temperature of 10/25°C by 69% 13 year old seeds did not germinate. This annual winter species reproduces only in the generative way, the seeds sown in the middle of October 1987 and 1988 sprouted at the end of October, and the seedlings with 1–2 pairs of true leaves survived successfully the winter.     

Population biology of Senecio integrifolius (Compositae), a rare plant in Sweden

In a study of natural populations of Senecio integrifolius in southern Sweden (1979–1983) seeds were found to disperse from mid-June to late July and most of them germinated in autumn. No soil seed bank was observed. On a heavily grazed site few seeds were produced but the percentage of estimated germination was high (c. 75%). In two moderately grazed habitats 8–10% of the estimated number of seeds produced in permanent plots germinated. In a lightly grazed habitat many seeds were produced but only a small percentage germinated (1.4%). In field experiments the average germination was 50–53% when newly harvested seeds were sown where the vegetation had been removed, and 20–33% when sown in undisturbed vegetation at a moderately grazed site. Germination was much lower in a lightly grazed habitat (3–12%). Survival of seedlings was much higher in heavily and moderately grazed habitats than in lightly grazed habitats. Mortality tended to be higher during the growing season (mid-April to early November) than during the winter, and increased markedly during a drought period in the summer of 1982. The half-life of plants established in 1980 varied from 39.3 years at the most intensively grazed site to 7.2 at the lightly grazed site. The number of flowering stems varied between years mainly according to weather. Few plants in the permanent plots flowered every year, the flowering being most frequent at heavily grazed sites. It is concluded that heavy grazing by cattle after seed dispersal is the appropriate management for maintaining S. integrifolius in Sweden.