典型草原退化群落不同恢复演替阶段羊草种群空间格局的比较

羊草(Leymus chinensis)为典型草原群落的主要建群种之一, 在群落中扮演着重要角色。应用摄影定位法测定处于不同恢复演替阶段的羊草种群空间格局, 通过点格局、种群空斑、种群领地及种群领地密度等方法分析发现, 羊草种群在恢复演替过程中经历了种群增长和种群衰退的过程。在此过程中, 羊草种群数量出现最高点, 此点之前, 种群拓殖大于自疏, 种群整体增长; 此点之后, 种间竞争及种内竞争致使种群衰退, 而种间竞争占主导地位, 种内竞争相对较弱。羊草种群的增衰导致种群空斑发生变化, 从而引起种群格局类型发生相应的变化, 表现为在恢复21 a的群落中, 羊草种群在10 m×10 m的取样范围内表现出两种格局分布类型: 在0~4.85 m之间呈现聚集分布, 当尺度大于4.85 m时, 则表现为随机分布; 在恢复8 a的群落中, 羊草种群在10 m×10 m的取样范围内出现3种格局分布类型: 在0~3.01 m之间呈聚集分布, 在3.01~3.37 m之间为随机分布, 当尺度大于3.37 m时则表现为均匀分布; 在严重退化群落中, 羊草种群在整个10 m×10 m测定尺度上呈现聚集分布。由此可见, 羊草种群格局在恢复演替过程中是变化的, 这种变化主要由群落剩余资源驱动下的种群拓殖及种内种间竞争所致。     

作者更正

王鑫厅等发表于2009年33卷1期63-70页的《典型草原退化群落不同恢复演替阶段羊草种群空间格局的比较》一文中存在一些错误,现更正如下:1.第67页表1中A样地的羊草种群领地密度"159.178"应改为"133.476";2.第68页"结论与讨论"中"这主要是由羊草同其它种群间的竞争引起的,而种内竞争则较弱。在恢复演     

择伐对阔叶红松林主要组成树种种内、种间竞争的影响

以择伐37 年后的阔叶红松林为对象,研究择伐对林内主要树种种内、种间竞争的影响.结果表明：择伐对阔叶红松林主要树种的种群结构、分布格局和竞争指数均产生了极显著影响.各树种的竞争指数变化值与其耐荫性指数存在极显著负相关关系(r=-0.8821).种内竞争强度与聚集强度、个体数呈极显著线性关系,择伐区内枫桦、紫椴等阳性树种的聚集强度最大,种内竞争强度远大于种间竞争,有利于树种之间的共存.择伐降低了红松对其伴生树种的竞争,而阳性树种对其他树种的竞争压力有所上升.择伐37 年后,红松所受的竞争压力变化较小,有利于红松的稳定生长;由于自疏作用,枫桦、紫椴的优势度将有所下降;冷杉所受的竞争压力有所减弱,有利于其种群数量的恢复.     

长喙毛茛泽泻的种群分布格局和群落内种间关联

长喙毛茛泽泻茶陵种群呈斑块分布,格局类型为聚集分布型,每个亚种群也呈聚集分布,但聚集强度不同。长喙毛茛泽泻与其几个主要伴生种的相关性经测定结果是：与莼菜及黄花狸藻之间的相关性不显著;与柳叶箬、双穗雀稗及石龙尾之间正相关显著;与疏勿蓼之间负相关显著,长喙毛茛泽泻种子近距离传播以及无性繁殖特性是造成其聚集分布的主要原因。柳叶箬、双穗雀稗和石龙尾对长喙毛茛泽泻具有极强的竞争作用。     

物种聚集分布与种间关系的多度不对称性

群落内物种的相对多度与其空间分布和种间关系存在内部联系,然而这种联系如何影响物种共存却存在很大的争议.本研究认为,植物群落中的常见种受到更强的种间作用,最终限制了其种群增长;稀有种呈现更强的聚集分布格局,有利于增强种内调节作用,减弱种间作用,从而实现与其他物种的共存.为验证该假设,本研究以长白山25 ha阔叶红松林样地内的主要大树树种(DBH≥10 cm)为研究对象,用空间统计的方法分析各树种间关联和树种聚集分布格局,并探讨其与树种多度之间的联系.结果发现,树种之间以负相关关系(排斥)为主,且呈现明显的多度不对称性,即常见种之间有更明显的排斥作用.在聚集分布格局下,树种的局部优势度在较小范围内(～5 m)没有明显的多度依赖性,这将有利于稀有种和常见种实现局部共存.上述结果表明,在森林群落中种间关系的整体强度主要源于常见种的作用,而物种呈现的聚集分布格局有利于稀有种,进而促进物种的长期共存.该研究揭示了物种空间分布的多度依赖性及其对物种共存的影响,有利于进一步认识温带森林群落的构建过程.     

不同干扰类型下羊草种群的空间格局

生态系统各层次的空间格局与生态学过程的相互关系一直是生态学的研究热点之一,这一问题的关键是选取合适的观察尺度。羊草(Leymus chinensis)作为呼伦贝尔草原的地带性植被,研究其种群空间格局对理解种群生态过程和草地资源可持续利用具有重要意义。利用Ripley's K函数和Monte Carlo随机模拟方法,对两块样地3种干扰下的羊草种群格局进行定量分析。结果表明:(1)刈割、围封、放牧3种干扰对羊草草甸草原恢复改良样地(LM)和贝加尔针茅试验样地(SM)的羊草种群空间格局具有显著影响,空间格局在不同尺度上存在差异。(2)在较小的空间尺度内,羊草种群倾向于非随机分布,在LM样地、SM样地分别为均匀分布和聚集分布;当空间尺度大于临界值后,羊草种群在围封(30-100cm)、放牧干扰(84-100cm)下倾向于随机分布,刈割干扰下仍为聚集分布。这主要与羊草的繁殖对策、群落地位以及各种干扰下对资源的竞争能力有关。(3)空间结构的规律性表面上取决于观察尺度,但更小尺度的数据对局域空间结构的生物学解释可能更有效。     

羊草草原群落水平格局研究 Ⅰ.二维网函数插值法

本文用二维网函数插值法,对羊草草原群落14种主要植物种群的个体分布格局作了分析。 根据网格法获取的数据资料,应用插值公式计算网点值,全部计算过程由电子计算机实现。计算结果由计算机输出并打印出每个种群的个体分布格局图。 分布格局图提供了以下信息: 1.14种植物种群个体的空间分布类型; 2.聚块的大小; 3.聚块的合计面积。 种群的镶嵌格局图直观的反映了种群之间在空间上的配置关系,并可给出镶嵌体的类型。讨论了研究种群个体分布格局的取样面积以及应用插值法存在的问题。     

羊草草原群落水平格局研究 Ⅱ.二维网函数插值法

本文用二维网函数插值法,对羊草草原群落14种主要植物种群的个体分布格局作了分析。 根据网格法获取的数据资料,应用插值公式计算网点值,全部计算过程由电子计算机实现。计算结果由计算机输出并打印出每个种群的个体分布格局图。 分布格局图提供了以下信息: 1.14种植物种群个体的空间分布类型; 2.聚块的大小; 3.聚块的合计面积。 种群的镶嵌格局图直观的反映了种群之间在空间上的配置关系,并可给出镶嵌体的类型。讨论了研究种群个体分布格局的取样面积以及应用插值法存在的问题。     

不同迁移能力和竞争能力的集合种群竞争模式及其模拟

种群竞争是影响生态系统演化的莺要生态过程之一。本文是在徐彩琳和Tilman研究工作的基础上,将竞争系数引入集合种群动力模式,建立了集合种群之间竞争的数学模型,并对5-集合种群的竞争动态进行了计算机模拟研究。结果表明：种群竞争排除与共存受迁移扩散能力和竞争能力影响很大,排除原理在理论上是存在的,在广域集合种群和实际中物种是竞争共存的．共存的条件是其竞争能力与扩散能力呈非线性负相关关系,竞争的结果使物种的强弱序列发生变化。     

不同栖息地状态下物种竞争模式及模拟研究与应用

物种竞争是影响生态系统演化的重要生态过程之一.而物种在受人类影响出现不同程度毁坏的栖息地上的演化又是非常复杂的,因此研究物种演化对栖息地毁坏的响应是非常必要的.在Tilman研究工作的基础上,将竞争系数引入集合种群动力模式,建立了多物种集合种群竞争共存的数学模型,并对5-物种集合种群在不同栖息地状态下的竞争动态进行了计算机模拟研究.结果表明：（1）不同结构的群落（q值不同）,物种之间的竞争排斥作用强度不同,优势物种明显的群落,物种之间的排斥强度大;（2）随着栖息地毁坏程度的增加,对优势物种的负面影响逐渐减小,而对弱势物种的负面影响逐渐增加;（3）随着栖息地恢复幅度的增加,优势物种和弱势物种之间的竞争越强烈,优势物种受到的竞争排斥加大,而弱势物种逐渐变强,出现了强者变弱、弱者变强的格局;（4）物种竞争排斥与共存受迁移扩散能力和竞争能力影响很大,竞争共存的条件是其竞争能力与扩散能力呈非线性负相关关系;（5）竞争共存的物种的强弱序列发生了变化.     

Resource use patterns predict long-term outcomes of plant competition for nutrients and light

An 11-year competition experiment among combinations of six prairie perennial plant species showed that resource competition theory generally predicted the long-term outcome of competition. We grew each species in replicated monocultures to determine its requirements for soil nitrate (R*) and light (I*). In six pairwise combinations, the species with the lower R* and I* excluded its competitor, as predicted by theory. In the remaining two pairwise combinations, one species had a lower R*, and the second had a lower I*; these species pairs coexisted, although it is unclear whether resource competition alone was responsible for their coexistence. Smaller differences in R* or I* between competing species led to slower rates of competitive exclusion, and the influence of R* differences on the rate of competitive exclusion was more pronounced on low-nitrogen soils, while the influence of I* differences was more pronounced on high-nitrogen (low-light) soils. These results were not explained by differences in initial species abundances or neutrality. However, only a few of our paired species coexisted under our experimentally imposed conditions (homogeneous soils, high seeding densities, minimal disturbance, regular water, and low herbivory levels), suggesting that other coexistence mechanisms help generate the diversity observed in natural communities.     

五爪金龙对其草本伴生种部分生理指标的影响

采用电导率法和分光光度法,测定了5个不同的自然生境中入侵杂草五爪金龙(Ipomoea cairica)的4种草本伴生植物火炭母(Polygonum chinense)、三叶鬼针草(Bidens pilosa)、红花酢浆草(Oxalis corymbosa)、鸡矢藤(Pae-deria scandens)的相对电导率和叶绿素含量等生理指标,并设相同生境中不与五爪金龙伴生的这4种草本植物为空白对照。结果表明:4种伴生草本植物的叶绿素含量与对照相比差异达显著或极显著水平;三叶鬼针草相对电导率差异显著,另外3种伴生植物的相对电导率变化不明显,说明五爪金龙对火炭母、红花酢浆草、鸡矢藤3种草本伴生植物的叶绿素含量影响显著,而对三叶鬼针草的叶绿素含量和质膜透性均有显著影响。     

Plant coexistence alters terpene emission and content of Mediterranean species

There is evidence that secondary metabolism may modulate plant interactions and is modified by different biotic stress agents, such as herbivores or pathogens. However, it is poorly understood whether secondary metabolism is altered during competition among plants. The intraspecific and interspecific coexistence of some Mediterranean potted seedlings, namely Rosmarinus officinalis, Pinus halepensis, Cistus albidus and Quercus coccifera was investigated through their terpene accumulation within leaves (except for Q. coccifera, a non-storing species) and terpene emissions (for all species). Competition had both positive and negative effects for both terpene emissions and content, depending on the species a seedling coexisted with. For R. officinalis, terpene concentrations (1.8-cineole and camphor) and terpene emissions (camphene, camphor and overall monoterpenes) were lower when the neighbour species was P. halepensis. For C. albidus, no changes were observed in its content, while the overall sesquiterpene emissions (70% of total emissions) were reduced in all competition conditions, except in intraspecific competition. In the case of P. halepensis, the highest terpene content occurred when it grew with C. albidus, and in intraspecific competition, while its emissions were reduced under these conditions. Only emissions of Q. coccifera showed no significant changes in the different competition treatments.     

Coexistence via resource partitioning fails to generate an increase in community function

Classic ecological theory suggests that resource partitioning facilitates the coexistence of species by reducing inter-specific competition. A byproduct of this process is an increase in overall community function, because a greater spectrum of resources can be used. In contrast, coexistence facilitated by neutral mechanisms is not expected to increase function. We studied coexistence in laboratory microcosms of the bactivorous ciliates Paramecium aurelia and Colpidium striatum to understand the relationship between function and coexistence mechanism. We quantified population and community-level function (biomass and oxygen consumption), competitive interactions, and resource partitioning. The two ciliates partitioned their bacterial resource along a size axis, with the larger ciliate consuming larger bacteria than the smaller ciliate. Despite this, there was no gain in function at the community level for either biomass or oxygen consumption, and competitive effects were symmetrical within and between species. Because other potential coexistence mechanisms can be ruled out, it is likely that inter-specific interference competition diminished the expected gain in function generated by resource partitioning, leading to a system that appeared competitively neutral even when structured by niche partitioning. We also analyzed several previous studies where two species of protists coexisted and found that the two-species communities showed a broad range of biomass levels relative to the single-species states.     

Coexistence of S. cerevisiae and E. coli in chemostat under substrate competition and product inhibition

A mixed culture of Saccharomyces cerevisiae and Escherichia coli was established in a stable coexistence steady state in a chemostat under constant operating conditions. The species competed for glucose, the growth-limiting resource, and produced acetate and ethanol. The acetic acid was shown to be very inhibitory to E. coli in pure culture at pH 5 while ethanol inhibition was only marginal. No significant inhibition of S. cerevisiae growth was observed by either acetate or ethanol. Pure culture parameters were measured and used in the analysis. Linearized stability analysis for the case when both organisms produce the inhibitor showed that a transition through three stable outcomes was possible as the feed concentration is lowered. Experimental studies verified these predictions, and successive transitions from a yeast growth steady state, to a coexistence steady state, and to an E. coli growth steady state were obtained by lowering the glucose concentration in the feed from 10 to 5 to 2.5 g/L, respectively. This dynamic behavior is distinct from the outcomes of other competition-inhibition combinations and experimentally demonstrates for the first time that coexistence is possible due to substrate competition and product inhibition.     

三峡库区不同消落带下中华蚊母树群落特征及其与土壤环境因子的关系

中华蚊母树(Distylium chinense)是华中地区特有种, 在三峡库区局部地段占优势形成群落。对三峡库区不同生境下中华蚊母树群落特征及其与土壤环境因子的关系进行研究可为其保护及消落带植被恢复提供科学依据。运用数据分类和排序等方法, 对中华蚊母树群落物种组成、植物区系、物种多样性及其与土壤环境因子的关系进行研究。结果表明, 共发现维管植物56种, 隶属于36科54属, 植物区系以世界分布、泛热带分布和北温带分布为主, 生活型以草本和灌木为主。自然消落带灌木层重要值最大的是中华蚊母树, 草本层重要值最大的是藤本植物地果(Ficus tikoua), 主要伴生种为具有一定水淹耐受性的灌木和多年生草本, 如小梾木(Swida paucinervis)、白茅(Imperata cylindrica)等; 反季节消落带灌木层仅中华蚊母树一种, 草本层重要值最大的物种是狗牙根(Cynodon dactylon), 主要伴生种为苍耳(Xanthium sibiricum)、苘麻(Abutilon theophrastic)等一年生草本。双向聚类分析将调查的6个样地分为四大类群: 中华蚊母树+小梾木群落、中华蚊母树+地果群落、中华蚊母树+细叶水团花(Adina rubella)群落、中华蚊母树+狗牙根群落。典范对应分析表明, 海拔高度和土壤pH是影响中华蚊母树群落物种分布的主要环境因子, 土壤有机质、全氮、全磷和速效钾含量是次要因素, 但它们是影响群落物种多样性指数的主要因子, 其中土壤氮是群落的限制因子。因此, 在反季节消落带植被重建中, 对中华蚊母树群落进行构建时, 除考虑细叶水团花、小梾木等作为高海拔消落带伴生物种外, 还应增加土壤氮和钾的供给, 使中华蚊母树群落保持较高的物种多样性, 维持消落带生态系统稳定。     

Active dispersal is differentially affected by inter‐ and intraspecific competition in closely related nematode species

Competition is one of the main drivers of dispersal, which can be an important mechanism to achieve permanent or temporal coexistence of multiple species. This coexistence can be achieved by a dispersal‐competition tradeoff, spatial store effects or neutral dynamics. Here we test the effect of inter‐ and intraspecific competition on dispersal of four species of the marine nematode species complex Litoditis marina. A previous study in closed microcosms without a possibility for dispersal had demonstrated pronounced interspecific competition, leading to the exclusion of one species. We now investigated whether 1) the dispersal is affected by interspecific interactions, by intraspecific competition (density) or by food availability, 2) the dispersal dynamics influence assemblage composition and can lead to co‐occurrence of the species, and 3) the abiotic environment (here salinity) can affect these dynamics. We show that density is the main driver for dispersal in two of the four species. Dispersal of a third species always started at the same time irrespective of density, whereas in the fourth species interspecific interactions accelerated dispersal. Remarkably, this fourth species was not a strong competitor, suggesting that a dispersal–competition tradeoff does not explain the observed coexistence. Salinity did not alter the timing of dispersal when interspecific interactions were present but did affect assemblage composition. Consequently, spatial store effects may influence coexistence. All four species co‐occurred in fairly stable abundances throughout the present experiment indicating the importance of species specific dispersal strategies for coexistence. Co‐occurrence can be facilitated because competition is postponed or avoided by dispersal. Neutral dynamics also played a role as intra‐ and interspecific competition were of similar importance in three of the four species. We conclude that dispersal is a driver of the coexistence of closely related nematode species, and that population density and interspecific interactions shape these dynamics.     

福建琅岐岛台湾相思群落灌木层主要物种生态位与种间联结

为探究福建琅岐岛台湾相思(Acacia confusa)群落种间关系和群落演替动态,对其灌木层主要物种的生态位和种间联结特征进行了分析。结果表明,重要值和生态位宽度最大的物种为雀梅藤(Sageretia thea),其竞争优势、环境适应能力最强;灌木层主要物种的生态位相似性和生态位重叠较小,表明种间对环境资源的利用和要求存在较大差异,表现为较稳定的种间关系;灌木层主要物种的总体联结性为显著正联结,种对间正负联结比为1.72,检验显著率为7.35%,表明种对间联结程度较弱,独立性相对较强,物种竞争不激烈,群落处于相对后期且稳定的演替阶段;红锥(Castanopsis hystrix)与许多物种间存在垂直方向上对生境要求的互补性,生态位重叠较小,种间呈正联结关系;外来物种马缨丹(Lantanacamara)与福建胡颓子(Elaeagnus oldhamii)存在一定的竞争,与灌木层其他主要植物之间的资源竞争不激烈,其对该群落的影响相对较小。琅岐岛台湾相思群落目前已发展为地带性的顶级群落,物种竞争不激烈,种间关系较稳定;而海岛上恶劣的环境和外来物种的扩散会导致植物生境资源短缺,迫使物种聚集在...     

Competition and soil fungi affect the physiological and growth traits of an alien and a native tree species

Competition plays an important role in the replacement of native species by alien plants. A greenhouse experiment was conducted to investigate whether the competition pattern of alien Robinia pseudoacacia L. and native Quercus acutissima Carr. is affected by soil sterilization. Physiological traits, such as gas-exchange parameters and chlorophyll (Chl) content, and growth traits, such as the biomass accumulation of the two species, were examined in natural soil or in soil sterilized with benomyl. The results show that native Q. acutissima inhibits the growth of R. pseudoacacia in natural soil. When the two plants coexisted and competed under sterilization treatment, R. pseudoacacia was less inhibited by Q. acutissima and the competition of R. pseudoacacia decreased the growth of Q. acutissima in terms of biomass, Chl a, Chl b, total Chl, and Chl a/b. These results suggest that soil sterilization benefits the growth of R. pseudoacacia and changes the competition pattern by the changed soil biota. Soil sterilization increased the biomass of root nodules, which ultimately benefits the growth of R. pseudoacacia and root nodule bacteria may be important in the dispersal and invasion process of nitrogen-fixing alien plants such as R. pseudoacacia.