克隆植物对异质生境的适应对策研究进展

生境异质性是自然生态系统的基本特征,植物生长的必需资源和环境胁迫因子均存在着复杂的时间和空间异质性。克隆植物是指在自然条件下具有克隆特性的植物,即可通过与母株相连的芽、根茎、分蘖或枝条等繁殖体产生无性繁殖的植物,这些繁殖体一旦定居便可成为潜在的独立个体。克隆植物具有独特的生境适应策略(如形态可塑性、克隆整合、克隆分工、觅食行为、风险分摊等),面对异质性的生境条件,它可以通过调整自身的生理和形态结构来适应异质生境。目前,对于克隆植物在异质生境适应行为的研究已有很多报道,然而系统性的归纳和总结尚有欠缺。综述了克隆植物在不同资源异质生境(光照、养分、水分)和不同胁迫生境(盐碱胁迫、风沙胁迫、重金属胁迫)下独特的适应对策。最后,针对克隆植物对异质生境的适应对策,进行了总结并对未来的重点研究方向提出建议：(1)时间异质性尺度上的考量;(2)异质性生境中生物因子的调控作用;(3)克隆植物入侵机制;(4)克隆植物在生态修复中的应用潜力。     

濒危植物峨眉含笑的种内、种间竞争

研究植物种内、种间竞争关系是探究植物濒危原因的重要方式之一, 根据竞争来源和竞争预测模型可以制定具有针对性的保护策略。本文以雅安周公山峨眉含笑(Michelia wilsonii)野生种群为研究对象, 使用逐步扩大范围法确定峨眉含笑的竞争范围半径, 运用Hegyi单木竞争模型计算竞争指数(competition index, CI), 分析其种内、种间竞争关系。结果表明: 峨眉含笑的最适竞争范围半径是10 m, 能较好地反映其种内竞争强度; 峨眉含笑的竞争压力主要来自种内, 种内竞争指数(348.72, 62.52%)远大于种间竞争指数(209.03, 37.48%); 小树、中树阶段个体的竞争强度较大, 平均竞争指数(3.97、3.14)远高于总体平均竞争指数(2.68); 内有21种竞争木, 其中杉木(Cunninghamia lanceolata)、华中樱桃(Prunus conradinae)、细刺枸骨(Ilex hylonoma)是峨眉含笑的主要竞争树种; 胸径与竞争指数间服从指数函数关系(CI = 3.8907e^-0.048x, R² = 0.1087, P < 0.01), 随着对象木胸径的增大, 竞争指数不断降低, 当胸径达到30 cm后, 竞争强度基本稳定。综上, 小树、中树阶段的峨眉含笑个体受到极强的种内竞争, 初入老树阶段的个体受到较强的种间竞争。为更好地保护峨眉含笑的天然种群, 降低竞争对种群更替的影响, 在林分管理中需要促进小树、中树的个体更新, 减轻植株间的竞争消耗, 加速峨眉含笑的生长和维持种群稳定。     

濒危植物宝华玉兰种内与种间竞争

利用Hegyi单木竞争指数模型对江苏镇江宝华山国家森林公园特有濒危植物宝华玉兰种内、种间竞争强度进行定量分析。结果表明:宝华玉兰竞争压力主要来自种间,占总竞争的90.7%。宝华玉兰种内竞争、种间竞争强度大小顺序为:紫楠>野核桃>建始槭>宝华玉兰种内>毛竹>化香>枫香>皂荚>朴树。整个林分竞争木对对象木的竞争强度与对象木的胸径大小近似服从幂函数关系,而伴生树种竞争木对对象木的竞争强度与对象木的胸径大小近似服从对数函数关系。种间竞争强度和对象木的胸径大小呈显著负相关。利用模型预测,当宝华玉兰的胸径达到30cm后,竞争强度几乎没有变化。研究认为,将无性系分株换算为一株与其胸高断面积之和相等的个体更为合理。     

异质光照环境下克隆整合对南美蟛蜞菊和蟛蜞菊种间关系的影响

很多入侵植物具有克隆性,克隆整合对入侵克隆植物生长和繁殖具有重要的贡献。自然界中,植物生长和繁殖所需的各种资源如光照、水分和矿质养分等在空间上分布通常是异质的,但关于异质环境下克隆整合对入侵植物和本土同属植物种间关系影响的研究相对缺乏。通过温室控制实验,将入侵植物南美蟛蜞菊(Wedelia trilobata)和同属本土植物蟛蜞菊(W.chinensis)的分株对单独种植或者混合种植在异质性光照条件下,同时通过保持或者切断分株之间的连接来控制克隆整合效应的有无,研究异质光照环境下克隆整合对南美蟛蜞菊和蟛蜞菊种间关系的影响。克隆整合对南美蟛蜞菊和蟛蜞菊的生长和繁殖都有促进作用,且南美蟛蜞菊比蟛蜞菊从克隆整合中获益更多。与单独种植相比,两者混种对南美蟛蜞菊的叶生物量有显著影响,而对本地种蟛蜞菊的根生物量有显著影响。克隆整合和种间关系对南美蟛蜞菊的总生物量和叶生物量产生了显著的交互作用,而对蟛蜞菊各指标无显著影响。克隆整合状态显著影响了南美蟛蜞菊和蟛蜞菊的种间关系。这些结果表明,异质环境下克隆整合可以改变入侵植物南美蟛蜞菊和本土植物蟛蜞菊的生长性状及种间关系。     

山西稀有濒危植物脱皮榆种内和种间竞争

通过对山西太岳山一块100 m×100 m样地中128株脱皮榆对象木及1093株竞争木的调查,运用Hegyi的单木竞争指数计算分析了脱皮榆的种内和种间竞争强度。结果表明:(1)脱皮榆种群所受到的竞争强度随着对象木胸径的增大而逐渐减小;(2)调查样地内尽管其他物种种类较多,但数量较少,与脱皮榆种间竞争相对较弱,脱皮榆种内与种间竞争关系的顺序为:脱皮榆-脱皮榆>千金榆-脱皮榆>五角枫-脱皮榆>茶条槭-脱皮榆>其他树种-脱皮榆;(3)竞争强度和对象木胸径的关系服从幂函数关系,当脱皮榆胸径在25 cm以上时,竞争强度变化不大,所得的预测模型能很好地预测脱皮榆种内种间竞争强度。     

麦蚜种间竞争研究初报

麦蚜是小麦的主要害虫之一,不仅直接为害小麦,且传播黄矮病。不同地区,麦蚜发生程度及其优势种不同;同一地区,在小麦不同的生育期麦蚜优势种也会发生变化。有关这方     

濒危植物七子花种内与种间竞争的数量关系

七子花为国家2 级重点保护植物, 现野生资源极少。利用Hegyi 单木竞争指数模型对分布在浙江天台山的七子花种群的种内、种间竞争关系进行定量分析。结果表明:七子花种内竞争强度随着林木径级的增大而逐渐减小, 种内竞争较之与其伴生树种间的竞争剧烈。七子花种内、种间竞争强度大小顺序为:种内 > 苦枥木 > 红脉钓樟 > 青钱柳 > 青榨槭 > 暖木 > 细齿绸李 > 柳杉 > 赤杨叶。竞争强度与对象木的胸径大小服从幂函数关系, 利用模型可预测七子花种内、种间的竞争强度, 从预测结果可知当七子花的胸径达到20 cm 后, 竞争强度变得很小, 且变化幅度不大。     

塔里木荒漠优势植物——胡杨种内、种间竞争研究

采用逐步扩大范围的方法确定影响对象木的邻体最佳竞争范围,利用Hegyi提出的单木竞争指数模型对塔里木荒漠优势植物———胡杨种内、种间竞争强度进行定量分析。结果表明,在胡杨群落中,对象木的最适竞争距离为6 m,胡杨种内、种间竞争强度随着植株径级的增大而逐渐减小,种内竞争较种间竞争剧烈。竞争强度与对象木胸径服从幂函数关系,从模型预测结果可知当胡杨胸径达30 cm以上时,竞争强度变化很小。因此,应在此前采取适当的人工疏伐措施来促进植株生长和增强生态系统的稳定性。     

种间竞争对香蒲与芦苇生长的影响

为了探究种间竞争对香蒲（Typha domingensis）与芦苇（Phragmites australis）生长的影响,利用根系分隔盆栽试验研究了3种不同分隔方式条件下香蒲与芦苇的种间竞争特性,包括塑料膜分隔（根系完全分隔,无相互作用,无物质交换）、尼龙网分隔（根系部分分隔,无相互作用,有物质交换）和不分隔（根系完全相互作用,有物质交换）,分析了香蒲与芦苇根系形态和地上部生长的变化,探究香蒲与芦苇种间竞争的差异。结果发现（1）在尼龙网分隔和不分隔处理中芦苇具有明显的劣势。与塑料膜分隔处理相比,芦苇的总生物量、植株密度在尼龙网分隔和不分隔处理中分别减少了39.14%、49.41%和82.08%、79.22%,总根长、总根表面积、总根体积分别减少了40.53%、44.84%、62.52%和85.7%、82.45%、89.67%,且均具有极显著差异（P<0.01）;根系分隔方式也影响芦苇的株高、茎粗和叶片数,表现为不分隔 > 塑料膜分隔 > 尼龙网分隔。（2）与塑料膜分隔处理相比,香蒲总生物量在尼龙网分隔和不分隔中虽有增加,但差异不显著,植株密度和株高在尼龙网分隔和不分隔处理中都有增加且具有显著差异（P<0.05）,其总根长、总根表面积、总根体积在尼龙网分隔中分别增加了57.93%、26.5%、8.04%,但在不分隔处理中分别减少了11.57%、14.92%、11.39%（P<0.05）,虽然根系的相互作用对香蒲根系的生长具有促进作用,但植物种间根系相互作用越强,对两者的生长越不利。（3）在不同的分隔方式中,芦苇与香蒲间也存在明显变化。在不分隔处理中,香蒲的生物量和植株密度是芦苇的1.7倍和6.74倍,与塑料膜分隔处理相比增加了6倍,表明芦苇与香蒲根系的完全相互作用,显著削减了芦苇的繁殖生长,增加了香蒲的根系分蘖。（4）通过种间相互作用强度（RII值）分析也表明,尼龙网分隔和不分隔处理下芦苇表现为抑制作用（RII值为负值）,香蒲表现为促进作用（RII值为正值）。香蒲与芦苇互作对芦苇具有抑制作用,说明种间相互作用是能改变植物的适应性和植物群落的繁殖,同时也表明植物根系不仅在吸收土壤中的水和养分中起着关键作用,在种间关系中也起着重要作用。因此利用种间竞争控制植物生长,可以为保护生物多样性和生态系统的功能提供有效的技术支撑。     

沙地云杉种内、种间竞争的研究

根据调查资料,采用Ｈｅｇｙｉ提出的单木竞争指数模型ＣＩ＝∑Ｎｊ＝１（Ｄｊ／Ｄｉ）１Ｌｉｊ对内蒙古白音敖包自然保护区的沙地云杉种内、种间的竞争强度进行定量分析。结果表明：沙地云杉种内竞争强度随着林木径级的增大而逐渐减小;种内竞争和种间竞争的强度顺序为：山杨＞沙地云杉种内＞白桦＞家榆。竞争强度与对象木的胸高直径服从幂函数关系ＣＩ＝ＡＤ－Ｂ,当沙地云杉胸高直径达到４０ｃｍ以上时,竞争强度变化很小。利用模型预测了沙地云杉种内、种间的竞争强度。说明Ｈｅｇｙｉ的单木竞争模型可为种内、种间竞争指数的研究提供可适用的数量指标。     

Investigating the community consequences of competition among clonal plants

Although clonal plants comprise most of the biomass of several widespread ecosystems, including many grasslands, wetlands, and tundra, our understanding of the effects of clonal attributes on community patterns and processes is weak. Here we present the conceptual basis for experiments focused on manipulating clonal attributes in a community context to determine how clonal characteristics affect interactions among plants at both the individual and community levels. All treatments are replicated at low and high density in a community density series to compare plant responses in environments of different competitive intensity. We examine clonal integration, the sharing of resources among ramets, by severing ramets from one another and comparing their response to ramets with intact connections. Ramet aggregation, the spacing of ramets relative to each other, is investigated by comparing species that differ in their natural aggregation (either clumped growth forms, with ramets tightly packed together, or runner growth forms, with ramets loosely spread) and by planting individual ramets of all species evenly spaced throughout a mesocosm. We illustrate how to test predictions to examine the influence of these two clonal traits on competitive interactions at the individual and community levels. To evaluate the effect of clonal integration on competition, we test two predictions: at the individual level, species with greater clonal integration will be better individual-level competitors, and at the community level, competition will cause a greater change in community composition when ramets are integrated (connected) than when they are not. For aggregation we test at the individual level: clumped growth forms are better competitors than runner growth forms because of their ability to resist invasion, and at the community level: competition will have a greater effect on community structure when ramets are evenly planted. An additional prediction connects the individual- and community-level effects of competition: resistance ability better predicts the effects of competition on relative abundance in a community than does invasion ability. We discuss additional experimental design considerations as revealed by our ongoing studies. Examining how clonal attributes affect both the individual- and community-level effects of competition requires new methods and metrics such as those presented here, and is vital to understanding the role of clonality in community structure of many ecosystems.     

Thoughts on clonal integration: Facing the evolutionary context

Summary In this essay, I have pointed out that the appropriate evolutionary context for plant clonality dictates a focus on the impact of the derived trait of potential independence of subunits on the evolutionarily primitive trait of obligate interdependence of plant subunits, i.e. the advantages of independence. This fact prescribes a major shift in approach from previous lines of investigation which have assumed that clonal plants should fall apart and sought to determine the advantages of interdependence. The delineated reorientation calls for a significant change in the investigation of the ecology of clonality in higher plants, emphasizing factors that select for physical and physiological disintegration of the genet and de-emphasizing the need to derive ecological explanations for properties a plant will possess entirely by reason of its phylogenetic and developmental heritage. I suggest that (1) patterns of ramet independence may result from selective pressures on the cost of interconnections (2) programmed ramet independendence may be a response to the selective pressure of a high possibility of traumatic breakage and (3) programmed ramet independence may allow escape of the genet from mortality due to pathogen infestation.     

Asexual and sexual reproductive strategies in clonal plants

Most plants can reproduce both sexually and asexually (or vegetatively),and the balance between the two reproductive modes may vary widely between and within species.Extensive clonal growth may affect the evolution of life history traits in many ways.First,in some clonal species,sexual reproduction and sex ratio vary largely among populations.Variation in sexual reproduction may strongly affect plant's adaptation to local environments and the evolution of the geographic range.Second,clonal growth can increase floral display,and thus pollinator attraction,while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal.Geitonogamous pollination can bring a cost to plant fitness through both female and male functions.Some co-evolutionary interactions,therefore,may exist between the spatial structure and the mating behavior of clonal plants.Finally,a trade-off may exist between sexual reproduction and clonal growth.Resource allocation to the two reproductive modes may depend on environmental conditions,competitive dominance,life span,and genetic factors.If different reproductive modes represent adaptive strategies for plants in different environments,we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition,while clonal growth should be dominant in stable habitats.Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes.Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives.     

Asexual and sexual reproductive strategies in clonal plants

Most plants can reproduce both sexually and asexually (or vegetatively), and the balance between the two reproductive modes may vary widely between and within species. Extensive clonal growth may affect the evolution of life history traits in many ways. First, in some clonal species, sexual reproduction and sex ratio vary largely among populations. Variation in sexual reproduction may strongly affect plant’s adaptation to local environments and the evolution of the geographic range. Second, clonal growth can increase floral display, and thus pollinator attraction, while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal. Geitonogamous pollination can bring a cost to plant fitness through both female and male functions. Some co-evolutionary interactions, therefore, may exist between the spatial structure and the mating behavior of clonal plants. Finally, a trade-off may exist between sexual reproduction and clonal growth. Resource allocation to the two reproductive modes may depend on environmental conditions, competitive dominance, life span, and genetic factors. If different reproductive modes represent adaptive strategies for plants in different environments, we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition, while clonal growth should be dominant in stable habitats. Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes. Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives. Translated from Acta Phytoecologica Sinica, 2006, 20(1): 174–183 [译自: 植物生态学报]     

施氮对空心莲子草(Alternanthera philoxeroides)和莲子草(Alternanthera sessilis)种间关系的影响

自然界的氮素释放总是呈现出空间和时间上的异质性,但关于异质性氮释放对于入侵植物和本地植物种间关系影响的研究相对较少。将入侵植物空心莲子草(Alternanthera philoxeroides)和同属本地植物莲子草(Alternanthera sessilis)分别进行单种种植(12株,无种间竞争)和混种种植(每种6株,有种间竞争),模拟大气氮湿沉降设置由两种不同施氮总量(15g N m~(-2)a~(-1)和30g N m~(-2)a~(-1))和两种不同施氮频率(每5天1次和每15天1次)交叉组成的4种施氮处理,并以不施氮为对照。施氮总量的增加显著促进了两种植物的生长,但对两种植物的种间竞争关系没有显著影响。施氮频率对两种植物的生长以及种间竞争关系都没有显著影响。两种植物在面对竞争时表现出不同的生物量分配策略,空心莲子草将更多的生物量分配到茎,而莲子草将更多的生物量分配到根。在全球变化的背景下,大气氮湿沉降可能会改变两种植物的种群结构和动态,但可能对这两种植物的种间关系影响较小。     

Two types of division of labour in clonal plants: benefits, costs and constraints

Clonal plants spread vegetatively within their habitats by forming rooted ramets on stolons or rhizomes. Each of these ramets is capable of an independent existence after establishment. Nevertheless, ramets remain physically connected by stolon or rhizome internodes for variable periods of time, thereby allowing for resource movement and signal transduction within clones.Interconnected ramets of clonal plants, though potentially independent and totipotent, can specialize functionally in the performance of limited numbers of tasks such as the uptake of resources from above- vs below-ground sources, carbohydrate storage, vegetative spread and sexual reproduction. Such specialization and cooperation is comparable to a division of labour in economic systems or in colonies of social animals. The ecological significance of division of labour in clonal plants may be found in the increased efficiency of entire clones in exploiting their environments.Two different types of division of labour in clonal plants will be discussed in this review. The first type is an environmentally-induced specialization of ramets in the uptake of locally abundant resources (plastic division of labour), which can be found in several stoloniferous species. Evidence exists that this response increases resource uptake in spatially heterogeneous environments. The second type of division of labour, which occurs mainly in rhizomatous species, relates to a developmentally-programmed specialization and cooperation between interconnected ramets. This response pattern is thought to enhance plant performance by restricting the number of tasks for individual ramets and thereby significantly increasing the efficiency of task performance. In some plants, such an inherent division of labour is likely to contribute to nutrient extraction from poor and unpredictably variable sources.In this article not only benefits but also potential costs and constraints on division of labour in clonal plants are shown. The aim is to provide a review of existing knowledge and to develop concepts and hypotheses for future research.     

长苞铁杉天然林群落种内及种间竞争关系研究

通过各种竞争指数的比较筛选,得到较能客观反映长苞铁杉种内、种间竞争关系的竞争指数,定量地分析了长苞铁杉种内和种间竞争强度。结果表明:长苞铁杉种内竞争随胸径的增大而逐渐减少;种间与种内竞争关系顺序为:长苞铁杉-长苞铁杉>猴头杜鹃-长苞铁杉>青冈栎-长苞铁杉>其它树种-长苞铁杉。竞争强度与对象木的胸高直径服从双曲线回归关系,利用模型预测了长苞铁杉种内、种间的竞争强度。     

沙区植物种的一类种间竞争模型及应用

以沙坡头人工固沙植物油蒿和柠条为研究对象,针对水分是沙坡头植物生r长的限制因子的现实,研究了在水分条件限制下两种植物的种间关系,建立了混播油蒿、柠条种间竞争模型,验证了油蒿、柠条既竞争又稳定共存的关系,其目的为充分有效利用水资源、稳定人工生态系统提供科学依据。