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1.
海三棱Biao草(Scirpus mariqueter Tang et Zhang)是一种典型的先锋植物。它能占据于长江口盐沼的光滩上,生物非常恶劣。为探索该物种在高度环境胁迫下的生活史策略,测定了它在高程梯度上的生物量分配,以及有关形态学参数。结果发现海三棱Biao草在中位高程时密度和单株生物量最高,生长最好。在由低及高的高程梯度上,球茎、根状茎的生物量分配屁例逐渐下降,表明植物体在光滩前沿采取保守策略;而花序的比例则逐渐上升,表明植物在生活史过程中,由无性生殖向有性生殖的转变。这种转变可能有利于种群的扩散和生存。另外,相关分析表明,有性生殖性状与无性生殖、生长性状呈负相关,但无性生殖与生长性状的关系难以确定,可能由于球茎在不同生活史阶段的不同功能引起。  相似文献   

2.
互花米草与海三棱藨草的生长特征和相对竞争能力   总被引:9,自引:0,他引:9  
外来物种互花米草(Spartinaalterniflora)已对我国特有种海三棱藨草 (Scirpusmariqueter)发生了竞争取代。作者通过在长江口崇明东滩湿地取样和盆栽竞争实验,比较了二者的主要生长特征和种间相对竞争能力。结果表明:无论是先锋种群还是成熟种群,互花米草的高度、盖度、地上生物量、地下生物量和平均每花序种子数都显著大于海三棱藨草;海三棱藨草的密度和单位面积结实枝条数显著大于互花米草。两种植物成熟种群的单位面积种子产量和种子的萌发率没有显著差异。种内竞争和种间竞争显著降低了两种植物的平均每株产生的无性小株数、结实株数、地上生物量和地下球茎数(海三棱藨草产生球茎),互花米草的种间竞争能力 (相对邻里效应指数 )显著大于海三棱藨草。互花米草在生长上的优势可能导致其在种间竞争上的优势,从而使互花米草能够在海三棱藨草群落中成功入侵。  相似文献   

3.
互花米草与海三棱蔗草的生长特征和相对竞争能力   总被引:14,自引:0,他引:14  
外来物种互花米草(Spartina alterniflora)已对我国特有种海三棱蔗草(Scirpus mariqueter)发生了竞争取代。作者通过在长江口崇明东滩湿地取样和盆栽竞争实验,比较了二者的主要生长特征和种间相对竞争能力。结果表明:无论是先锋种群还是成熟种群,互花米草的高度、盖度、地上生物量、地下生物量和平均每花序种子数都显著大于海三棱蔗草;海三棱蔗草的密度和单位面积结实枝条数显著大于互花米草。两种植物成熟种群的单位面积种子产量和种子的萌发率没有显著差异。种内竞争和种间竞争显著降低了两种植物的平均每株产生的无性小株数、结实株数、地上生物量和地下球茎数(海三棱蔗草产生球茎),互花米草的种间竞争能力(相对邻里效应指数)显著大于海三棱蔗草。互花米草在生长上的优势可能导致其在种间竞争上的优势,从而使互花米草能够在海三棱蔗草群落中成功入侵。  相似文献   

4.
许宇田  童春富 《生态学报》2018,38(19):7034-7044
海三棱藨草(Scirpus mariqueter)为长江河口盐沼湿地先锋植物。以长江口九段沙湿地为主要研究区域,在江亚南沙、上沙、中下沙等不同区域设置固定站点,进行植被和环境因子的取样调研,分析研究了海三棱藨草的生物量分配特征及其主要影响因子,以期为海三棱藨草的培育与恢复、盐沼湿地生态系统的保护与利用提供科学依据。结果表明:(1)不同站点海三棱藨草的茎基高度、球茎生物量占比、根茎与球茎之比均不存在显著差异(P0.05),而植株密度、植株高度、根茎生物量占比、果实生物量占比、茎叶生物量占比、须根生物量占比、果实与根茎之比、果实与球茎之比在不同站点间存在显著差异(P0.05);(2)不同站点的沉积物电导率、盐度、容积密度(5—10、25—30 cm土层)、总碳含量(10—15、20—25、25—30 cm土层)、总氮含量(5—10 cm土层)存在显著差异(P0.05);(3)海三棱藨草的果实与根茎的生物量之比和沉积物5—10、25—30 cm总碳含量,0—5、5—10 cm总氮含量,0—5 cm容积密度,茎基高度6种因子的组合存在极显著相关(P0.01);而其他生物量分配指标与本文涉及到的环境因子、植物表形参数均不存在显著相关性(P0.05)。海三棱藨草生物量分配特征是其自身生长特征与环境因子综合作用的结果。在今后的研究中需拓展生境因子涵盖范围,深入分析多因子综合作用对海三棱藨草生物量分配特征的影响。  相似文献   

5.
滨海湿地生态修复已成为阻止海岸带生态系统退化、保护生物多样性以及提供生态服务的关键措施。以长江口原生盐沼植物海三棱藨草(Scirpus mariqueter)为研究对象,选取崇明东滩新生滩涂湿地为研究区域,通过沿潮滩高程梯度的海三棱藨草植株斑块的移植实验,探究胁迫梯度假说和互惠理论(即种内的正相互作用)对长江口海三棱藨草种群恢复的指导意义。研究结果显示:(1)在一定的胁迫梯度范围内(潮滩高程2.0 m以上),增大种植斑块可以促进海三棱藨草的种内正相互作用,显著提高种植斑块的存活率和植株密度(P0.05);(2)潮滩水文动力沉积条件与潮滩高程梯度密切相关(P0.05),水文动力沉积作用对海三棱藨草定居和生长的胁迫随高程梯度下降而增强。潮滩高程2.0 m以下处强烈的水文动力条件干扰限制了生物-物理因素的正反馈作用。滨海湿地盐沼植被修复工作的成功率可以通过改进种植方式,增强种内的正相互作用得到极大的提高。研究可为开展大规模滨海湿地盐沼植被修复工程和提高生态修复效率提供科学依据和技术支持。  相似文献   

6.
崇明东滩湿地高等植被演替特征   总被引:11,自引:0,他引:11  
研究了崇明东滩湿地植被演替过程中生态特征以及重要值、地上部分生物量、植被地上部分氮含量以及氮容量的季节性变化.结果表明:随着高程的升高,演替早期的代表物种海三棱藨草(Scirpus mariqueter)的重要值逐渐减小,互花米草(Spartina alterniflora)和芦苇(Phragmites australis)的重要值增大.演替过程中植物的生物多样性逐渐增加.3种植物地上部分生物量在生长季节内(3—10月)均呈单峰变化,一般在夏季(7、8月)生物量最大.3种植物地上部分氮含量在生长季节内均呈降低趋势,氮容量在生长季节内呈单峰变化.估算每年崇明东滩保护区内芦苇地上部分蓄积的氮为383.4 t,互花米草为39.3 t,海三棱藨草为50.5 t.  相似文献   

7.
海三棱藨草及互花米草对模拟盐胁迫的响应及其耐盐阈值   总被引:1,自引:0,他引:1  
盐度作为滨海湿地的关键环境因子之一,影响盐沼植物的存活、生长及分布。未来海平面上升引起的盐水入侵,将导致滨海湿地的盐沼植物面临高盐胁迫的挑战,进而影响滨海湿地生态系统的结构和功能。本研究选择长江口中低潮滩的主要先锋植物海三棱藨草(Scirpus mariqueter)和互花米草(Spartina alterniflora)为对象,通过人工控制实验,比较不同盐度处理下两种盐沼植物存活、营养生长及繁殖的响应,并确定两种盐沼植物存活的耐盐阈值,从而比较未来盐水入侵背景下,本地物种海三棱藨草及外来物种互花米草对盐胁迫的响应和适应性。结果表明:(1)海三棱藨草和互花米草的存活率随着盐度的增加均呈下降趋势,相同盐度处理下互花米草的存活率显著高于海三棱藨草的存活率(P0.05);(2)盐胁迫明显影响了海三棱藨草和互花米草的生长,随着盐度的增加,海三棱藨草株高、地上生物量及地下生物量均呈逐渐下降的趋势,而互花米草株高、地上生物量及地下生物量呈先增加后下降的趋势,均在盐度为10‰时最高;(3)海三棱藨草和互花米草的分蘖数及结穗率均随着盐度增加呈下降趋势,盐胁迫在一定程度上抑制了两种植物的繁殖能力;(4)互花米草存活的耐盐阈值为43‰,高于海三棱藨草存活的耐盐阈值(21‰);(5)外来物种互花米草比本地物种海三棱藨草具有更强的耐盐性,未来海平面上升引起的盐水入侵将对本地物种海三棱藨草产生更加严重的影响。  相似文献   

8.
崇明东滩南部滩面高程、土壤盐度在空间上呈明显的梯度变化规律。高程整体西高东低、北高南低,盐度东北高、西南低,两者共同限制着盐沼植物在空间上的分布。该文围绕崇明东滩南部主要植被类群及其空间分布,探讨了土壤盐度、潮滩高程两大环境因子与植物种群分布的对应关系。基于2013年夏、秋季植被空间网格采样和空间插值,分析了东滩南部植物的空间分布现状,发现不同植物类群在高程和土壤盐度上存在极显著的差异(p0.01)。高程差异:莎草科类群主要分布于高程区间2.93–4.07 m的低潮滩,禾本科主要集中分布在高程3.13–4.31 m的中、高潮滩;盐度差异:海三棱藨草(Scirpus mariqueter)和互花米草(Spartina alterniflora)优势种群植被覆盖区表层30 cm的平均土壤盐度为(3.2±0.6)g·kg–1,显著高于其他类群植物分布区的平均土壤盐度(2.0±0.3)g·kg–1(p0.01)。崇明东滩湿地生态系统的关键种兼先锋种——海三棱藨草,分布高程介于2.53–3.97 m,而互花米草能适应海三棱藨草80%的高程区间,两者在高程上存在竞争关系。统计数据显示,研究区域中近90%的海三棱藨草分布在研究区东北部,土壤盐度范围为1.6–4.5 g·kg–1,海三棱藨草、互花米草能较好地适应该空间内的盐度胁迫,两种植物在此交替出现。但是在高程和土壤盐度的综合作用下,互花米草的生长状况更好,因此该区的海三棱藨草很可能会被互花米草逐步取代。对各类群植被分布和优势面积的研究发现,海三棱藨草总分布面积为294 hm2,优势群落面积120 hm2,海三棱藨草仅占莎草科植物总优势面积的15.7%,占研究区总面积的6.9%,在6种主要植物(芦苇(Phragmites australis)、白茅(Imperata cylindrica)、互花米草、糙叶薹草(Carex scabrifolia)、藨草(Scirpus triqueter)、海三棱藨草)中比重最小,这给保护区内海三棱藨草种群的恢复和保护带来极大的挑战。  相似文献   

9.
以三种莎草科克隆植物藨草(Scirpus triqueter),海三棱藨草(Scirpus mariqueter)和糙叶苔草(Carex scabrifolia)为研究对象,通过盆栽受控实验,探讨三种初始种植密度处理(1株/盆、4株/盆和16株/盆)对个体表现与种群增长的影响。结果表明,三种植物种群经过一个月左右的适应后均开始加速增长,生长季后期增长率逐渐降低,而海三棱藨草种群甚至出现了一定程度的衰退。生长季中前期藨草在中低密度处理下密度增长率高于高密度和整簇种植处理,而海三棱蔗草、糙叶苔草种群的整体密度增长与初始种植密度成反比。最终收获时,藨草和海三棱蔗草不同处理下的密度、冠层高度、最高高度、地上生物量和地下生物量均没有显著差异,糙叶苔草在低种植密度下的密度最低,中等种植密度下冠层高度最高。薦草、海三棱藨草的单株平均生物量与密度呈显著负相关,而藨草、糙叶苔草的总生物量与密度呈显著正相关,三种莎草科植物的根冠比都没有随密度发生显著变化。三种莎草科植物在高密度下的种内竞争效应均强于中密度。  相似文献   

10.
我国滨海湿地外来物种入侵威胁较为严重。以长江口湿地为例,快速蔓延的互花米草(Spatina alterniflora)逐渐替代了中国特有的原生种—海三棱藨草(Scirpus mariqueter Ts.TangF.T.Wang)。基于正在实施的外来入侵种生态控制工程,开展了海三棱藨草在新生湿地的种群恢复实验。实验采用两种恢复策略,即建立种子库和植物球茎(地下繁殖体)种植,并实施了低、中、高密度种植处理以比较其成本效益。研究结果表明,海三棱藨草种子在实验室条件下有较高的出苗率,且5 cm的种植深度最佳。但由于潮滩湿地泥沙淤积的掩埋胁迫,在5 cm的种植深度下,即使采用高密度种植处理也仅有极少数种子能萌发生成植株,且不同种植密度处理间的幼苗存活率和植株密度没有显著差异。而将海三棱藨草球茎作为植被恢复的种植材料时,其出苗率和植株密度远优于种子种植策略,多数球茎能实现出苗和定居,并通过地下分蘖和地下根茎发育迅速形成密集的种群。密度处理结果表明,中密度和高密度种植处理下的生长季后期的植株密度没有显著差异,说明在滨海湿地原生植物种群重建时宜选择经济高效的中密度种植策略。据此可为大规模的长江口原生植被恢复工程提供参考。  相似文献   

11.
The sexual and asexual reproductive features of the graminoid species Arundinella hirta growing at riversides of the Jialing River were analyzed.It was found that the total seed mass,seed number per plant,and sexual reproductive allocation of A.hirta decreased with decreasing bank elevation,and plants growing at the lowest elevations of banks subjected to intense flooding did not show sexual reproduction.The total plant biomass and the number of ramifications per plant increased with flooding intensity,which implies that,contrary to sexual reproduction,asexual reproduction of A.hirta was enhanced by flooding.  相似文献   

12.
In order to assess the importance of sexual and asexual reproduction during the life history of Scirpus mariqueter, its reproductive and growth characters were concurrently examined along an elevational gradient (from low elevation to high elevation). The proportions of flowering shoot and inflorescence mass, seed : flower ratio and seed weight were used to quantify the investment in sexual reproduction. The proportions of current-year shoot and rhizome mass were used to quantify the investment in asexual reproduction, and the proportion of corm mass was used for growth, respectively. It was found that vegetative propagation predominated at low elevation, whereas sexual reproduction predominated at high elevation; and that sexual reproduction increased with declining asexual reproduction along the gradient. The results suggest that asexual reproduction is relatively favored in the early life stage, whereas sexual reproduction is favored when the population becomes mature and aged, probably because of the functional differentiation between the two reproductive types. Sexual productive characters (i.e. the proportions of flowering shoot and inflorescence mass) were negatively correlated to both growth and asexual reproductive characters along the gradient, indicating there might exist some trade-offs among growth, sexual and asexual reproduction during the life history. However, no obvious pattern was found between asexual reproductive characters and growth characters along the elevational gradient, possibly because of the varied relationships between them at different life stages. The variations in sexual and asexual reproduction in the species and the relationship between them are thought to be of great significance for local population growth, species persistence and evolution.  相似文献   

13.
The sexual and asexual reproductive features of the graminoid species Arundinella hirta growing at riversides of the Jialing River were analyzed. It was found that the total seed mass, seed number per plant, and sexual reproductive allocation of A. hirta decreased with decreasing bank elevation, and plants growing at the lowest elevations of banks subjected to intense flooding did not show sexual reproduction. The total plant biomass and the number of ramifications per plant increased with flooding intensity, which implies that, contrary to sexual reproduction, asexual reproduction of A. hirtawas enhanced by flooding. Translated from the Journal of Southwest China Normal University (Natural Science), 2005, 30(2) (in Chinese)  相似文献   

14.
Asexuality is an important mode of reproduction in eukaryotic taxa and has a theoretical advantage over sexual reproduction because of the increased ability to propagate genes. Despite this advantage, hidden signs of cryptic sex have been discovered in the genomes of asexual organisms. This has provided an interesting way to address the evolutionary impact of sex in plant and animal populations. However, the identification of rare sexual reproduction events in mainly asexual species has remained a challenging task. We examined the reproductive history in populations of the plant parasitic nematode Xiphinema index by genotyping individuals collected from six grapevine fields using seven microsatellite markers. A high level of linkage disequilibrium and heterozygous excess suggested a clonality rate of 95–100%. However, we also detected rare sexual reproduction events within these highly clonal populations. By combining highly polymorphic markers with an appropriate hierarchical sampling, and using both Bayesian and multivariate analysis with phylogenetic reconstructions, we were able to identify a small number of sexually produced individuals at the overlapping zones between different genetic clusters. This suggested that sexual reproduction was favoured when and where two nematode patches came into contact. Among fields, a high degree of genetic differentiation indicated a low level of gene flow between populations. Rare genotypes that were shared by several populations suggested passive dispersal by human activities, possibly through the introduction of infected plants from nurseries. We conclude that our method can be used to detect and locate sexual events in various predominantly asexual species.  相似文献   

15.
不同生境下珠芽蓼(蓼科)的繁殖策略比较   总被引:3,自引:0,他引:3  
在青藏高原横断山区以海拔相同的高山流石滩和高寒草甸中的珠芽蓼(Polygonum viviparum)居群为研究对象,探讨该物种在不同生境条件下的繁殖策略以及无性繁殖和有性繁殖间的关系。结果发现,流石滩居群的珠芽蓼植株高度和珠芽数量显著低于高寒草甸居群,而珠芽和花总数量、花数量和每个花序上的花比例却显著高于高寒草甸居群。研究结果表明珠芽蓼在环境更为恶劣的高山流石滩生境中增加了对繁殖器官和花资源的投资,说明在高山植物中繁殖优先于营养生长,且有性繁殖比无性繁殖具有更为重要的作用。而对每个植株上花数量和珠芽数量的统计结果表明,两者呈显著的负相关关系,进一步证明了同一植株内无性繁殖和有性繁殖的权衡关系。  相似文献   

16.
  1. Terrestrial plant populations located at the margins of species’ distributions often display reduced sexual reproduction and an increased reliance on asexual reproduction. One hypothesis to explain this phenomenon is that the decline is associated with environmental effects on the energetic costs to produce reproductive organs.
  2. In order to clarify the changing processes of sexual reproduction along an elevational gradient, we investigated the sexual reproductive parameters, such as the number of sporophytes and gametangia, in Racomitrium lanuginosum, a dioicous moss found on Mt. Fuji.
  3. Matured sporophytes were present only below 3,000 m, and the number of sporophytes per shoot tended to be lower at higher elevation habitats. The numbers of male inflorescences per shoot and antheridia per inflorescence and shoot significantly decreased with increasing elevation. In contrast, the numbers of female inflorescences per shoot and archegonia per inflorescence and shoot varied little across elevations.
  4. Synthesis. Our results suggest that the reasons for this limitation are assumed to be limitations in sporophyte development that result in abortion, and the spatial segregation between males and females. Possible reasons for the abortion of sporophytes are the inhibitory effects of low air temperature, a shortened growth period, and winter environmental conditions at higher elevations. Remarkable differences between male and female on various reproductive parameters found in this study are thought to affect the mode of sexual reproduction under the harsh environment. These differences between males and females may be caused by differences in the costs of production and development of gametangia, sensitivity to environmental stressors, and phenological patterns.
  相似文献   

17.
Masting is defined as the intermittent highly variable production of seed in a plant population. According to reproductive modes, that is, sexual and asexual reproduction, masting species can be separated into three groups, that is, (1) species, for example, bamboo, flower only once before they die; (2) species, for example, Fagus, reproduce sexually; and (3) species, for example, Stipa tenacissima, reproduce both sexually and asexually. Several theories have been proposed to explore the underlying mechanisms of masting. However, to our knowledge, no theory has been found to explain the mechanism of masting species that reproduce both sexually and asexually. Here we refine the Resource Budget Model by considering a trade‐off between sexual and asexual reproduction. Besides the depletion efficient (i.e., the ratio of the cost of seed setting and the cost of flowering), other factors, such as the annual remaining resource (i.e., the rest of the resource from the photosynthetic activity after allocating to growth and maintenance), the trade‐off between sexual and asexual reproduction, and the reproductive thresholds, also affect masting. Moreover, two potential reproductive strategies are found to explain the mechanisms: (1) When the annual remaining resource is relatively low, plants reproduce asexually and a part of the resource is accumulated as the cost of asexual reproduction is less than the annual remaining resource. Plants flower and set fruits once the accumulated resource exceeds the threshold of sexual reproduction; (2) when the annual remaining resource is relatively high, and the accumulated resource surpasses the threshold of sexual reproduction, masting occurs. Remarkably, under certain depletion efficient, more investigation in sexual reproduction will lead plants to reproduce periodically. Additionally, plants investigate less resource to reproduce periodically when depletion efficient keeps increasing as plants can reproduce efficiently. Overall, our study provides new insights into the interpretation of masting, especially for species that reproduce both sexually and asexually.  相似文献   

18.
通过原产地调查,引种试验,扦插及种子萌发等实验,研究了太行花的繁殖及扩散方式。结果表明,太行花有两条生殖途径:一条是有性生殖;另一条是无性生殖。在原产地因生境条件特殊,有性生殖能力弱,主要靠无性生殖扩大种群。在北京人工栽培条件下,两种生殖方式都能正常进行。  相似文献   

19.
Many aquatic and riparian plant species are characterized by the ability to reproduce both sexually and asexually. Yet, little is known about how spatial variation in sexual and asexual reproduction affects the genotypic diversity within populations of aquatic and riparian plants. We used six polymorphic microsatellites to examine the genetic diversity within and differentiation among 17 populations (606 individuals) of Sparganium emersum, in two Dutch-German rivers. Our study revealed a striking difference between rivers in the mode of reproduction (sexual vs. asexual) within S. emersum populations. The mode of reproduction was strongly related to locally reigning hydrodynamic conditions. Sexually reproducing populations exhibited a greater number of multilocus genotypes compared to asexual populations. The regional population structure suggested higher levels of gene flow among sexually reproducing populations compared to clonal populations. Gene flow was mainly mediated via hydrochoric dispersal of generative propagules (seeds), impeding genetic differentiation among populations even over river distances up to 50 km. Although evidence for hydrochoric dispersal of vegetative propagules (clonal plant fragments) was found, this mechanism appeared to be relatively less important. Bayesian-based assignment procedures revealed a number of immigrants, originating from outside our study area, suggesting intercatchment plant dispersal, possibly the result of waterfowl-mediated seed dispersal. This study demonstrates how variation in local environmental conditions in river systems, resulting in shifting balances of sexual vs. asexual reproduction within populations, will affect the genotypic diversity within populations. This study furthermore cautions against generalizations about dispersal of riparian plant species in river systems.  相似文献   

20.
The maintenance of sexual reproduction is discussed using a model based on the familiar Lotka-Volterra competition equations. Both the equilibrium and the stability conditions that allow a sexual population to resist invasion by a single asexual clone are considered. The equilibrium conditions give results similar to previous models: When the cost of sex, within phenotype niche width, and environmental variance are low, the sexual population coexists with the asexual clone and remains at a high density. However, the asexual clone is never completely excluded. Analysis of the stability conditions shows a different picture: The introduction of an asexual clone considerably reduces the stability of the community. However, owing to its larger total niche width, the sexual population exists partly in a “competitor-free space” where the asexual clone has almost no influence on the outcome of the interactions. Therefore the asexual clone is less stable than the sexual population and has a higher probability of extinction. In contrast, the sexual population does not become extinct, since the extreme phenotypes remain at a stable, though low, density, and the central phenotypes, where stability is low, are recreated every generation through recombination. I therefore conclude that the ecological conditions under which sexual reproduction is favored over asexual reproduction are fairly easily attained and are more general than previous analyses had suggested.  相似文献   

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