高寒草甸不同海拔梯度下多年生黄帚橐吾的克隆生长特征

通过对多年生植物黄帚橐吾(Ligularia virgaurea)在四个不同海拔梯度下的克隆生长行为进行研究,结果表明：(1)资源水平(土壤养分)、干扰和群落性质影响间隔物(spacer)长度的变化。在第一和第四海拔梯度中(土壤养分较丰富)间隔物长度较短,而在第二和第三海拔梯度中(土壤养分较贫乏)间隔物长度较长,说明其能对资源水平和生境优劣作出反应。(2)分枝强度(branching intensity)随资源水平的增加而上升。(3)在高海拔、寒冷和资源较丰富的生境中,其生物量的投资偏向于地下部分生物量,说明黄帚橐吾的资源分配方式受到环境资源条件和群落性质的影响。     

Effects of the spreading of Ligularia virgaurea on soil physicochemical property and microbial functional diversity

黄帚橐吾(Ligularia virgaurea)是高寒草甸退化的指示物种, 其种群扩张已严重影响了草地生态系统的经济服务功能, 但目前仍不明确土壤微生物是否参与了黄帚橐吾的种群扩张。该研究依托兰州大学高寒草甸试验站, 选择了4个不同密度的黄帚橐吾斑块, 分析了黄帚橐吾种群扩张对该草甸土壤微生物功能多样性的影响。结果显示: 黄帚橐吾种群扩张虽然提高了土壤微生物活性, 但降低了土壤速效氮浓度。各斑块间土壤微生物Shannon指数、碳源利用种类、均一度指数均无显著差异, 但高密度斑块的土壤微生物碳源利用结构与对照斑块有显著差异。表明黄帚橐吾分布地土壤微生物功能多样性的改变所引起的土壤氮素限制是黄帚橐吾种群数量急剧增加的机制之一。     

密度制约下尕海湿地黄帚橐吾叶绿素与叶面积、叶厚度间的关系

密度制约下植物叶性状间的关系,对于认识植物叶片的物理构建与生理代谢的关系具有重要的意义。本研究采用标准化主轴估计分析方法,按黄帚橐吾(Liguaria virgaurea)种群数设置I(171～240株·m~(-2))、II(101～170株·m~(-2))和III(30～100株·m~(-2))3个密度,分析了尕海湿地不同种群密度黄帚橐吾叶绿素含量与叶面积、叶厚度的关系。结果表明:随着黄帚橐吾种群密度的降低,湿地群落的密度呈先减小后增大的U型趋势、盖度逐渐降低、高度和土壤水分逐渐增加,黄帚橐吾的叶面积和叶绿素含量逐渐增加、叶厚度和群落内部光合有效辐射逐渐减小、净光合速率和蒸腾速率呈先减小后增大的U型趋势;叶绿素含量与叶面积呈显著负相关(P0.05)、与叶厚度呈显著正相关(P0.05)。生长在高密度湿地的黄帚橐吾选择增加叶绿素含量且构建小而厚的叶片,在低密度湿地选择减少叶绿素含量且构建大而薄的叶片,反映了植物适应光照条件等异质性环境因子的资源利用策略和光合产物积累模式。     

内蒙古锡林河流域不同生境中羊草的克隆构型和分株种群特征

 克隆植物的形态可塑性在基株和种群水平上分别表现为克隆构型和分株种群特征的变化。研究对象为内蒙古锡林河流域草地、林地、沙地3种生境下的羊草(Leymus chinensis)种群,通过对羊草根茎节间长度、间隔子长度、分枝强度、分枝角度、株高和分株密度等指标的测定和分析,对这3种不同生境中羊草的克隆构型及分株种群特征进行了研究。结果表明羊草克隆构型相关特征,如,根茎节间长度,根茎节间长度频次分布格局、间隔子长度、间隔子长度频次分布格局,在不同生境差异较大。同时,羊草的分枝角度在不同生境间差异显著。而每间隔子所     

高寒草场优势杂草黄帚橐吾水浸液对牧草的化感作用

研究了高寒草场中主要毒杂草——黄帚橐吾水浸液对同域分布的5种牧草的化感作用.将反应指数(RI)相加平均后分为一、二、三级敏感指数,分别评价不同测定指标、不同发育期和物种水平对化感作用的敏感性;从供体角度对相应RI值做同样处理,以综合评价不同水浸液及其不同浓度的化感效应.结果表明,5种牧草对黄帚橐吾化感作用的敏感性从强到弱依次为早熟禾>大雀麦>中华羊茅>羊茅>垂穗披碱草;牧草种子萌发期的敏感性强于幼苗生长期,尤以萌发指数受化感作用的影响明显.黄帚橐吾根、叶水浸液对牧草生物测定结果大多达到显著差异水平,物种水平的化感效应均表现为抑制作用,说明雨水淋溶是黄帚橐吾向环境中释放化感物质的途径之一.黄帚橐吾根部化感效应强于叶片,可能与其地下种间激烈的资源竞争有关.化感作用在增强黄帚橐吾生存竞争力、扩大种群和入侵草场中起着不容忽视的作用,可能是黄帚橐吾单优势种群落形成和草场退化的原因之一.     

不同生境中淫羊藿克隆构型和分株种群特征

为探求淫羊藿资源的保护策略,通过野外样地调杏、审内测定和统计分析等方法,对林缘旷地、林缘和林下三种不同生境中淫羊藿（Epimedium brevicornum）克隆构型及其分株种群特征进行了研究,并初步分析环境因子对淫羊藿克隆构型和分株种群特征的影响。结果表明：分枝强度、间隔子长度、分枝高度、根状茎长度及分株种群密度在3种生境中差异显著,且与生境相对光强和土壤含水量有较强的回归关系。群落相对光强、土壤含水量在淫羊藿的克隆生长过程中起着重要作用。淫羊藿以地下根茎为克隆器官进行克隆生长,有着较强的克隆构型可塑性。结合克隆植物对资源的利用策略,讨论不同生境中淫羊藿克隆构型和分株种群特征可塑性的生态适应意义及淫羊藿保护机制。     

不同生境下黄帚橐吾（Ligularia Virgaurea）个体大小依赖的繁殖分配

 研究了不同生境和密度下黄帚橐吾(Ligularia virgaurea)个体大小依赖的繁殖分配。结果表明无论在种群水平还是在个体水平上,黄帚橐吾都表现出：1) 在不同的生境和种群密度中,个体大小与繁殖体大小均不相同,其排列顺序依次为沙地＞坡地＞滩地、裸地＞非裸地、低密度＞高密度;2) 繁殖分配和单株种子均重在不同生境和种群密度中,其差异程度均从不显著(p>0.05)到极显著(p<0.01)不等;3) 繁殖体大小与个体大小在不同生境和种群密度中均呈极显著的正相关关系(p<0.01);4) 单株种子均重与个体     

黄帚橐吾对高寒草甸凋落物分解及氮释放的影响

受过度放牧等干扰因素的影响,黄帚橐吾(Ligularia virgaurea)在高寒草甸逐渐扩张成为优势种而被称为“退化指示种”,从而威胁生态系统功能和养分循环。然而,黄帚橐吾扩张引起的凋落物比例增多,对分解及养分释放的影响尚不清晰。凋落物分解连结着生态系统碳、氮循环,对于系统功能维持具有重要意义。本试验在三江源区黄帚橐吾为优势种的高寒草甸中,设置黄帚橐吾和其他物种凋落物的多梯度混合分解试验,测定黄帚橐吾和其他物种凋落物的重量损失和氮释放,分析黄帚橐吾生物量增多对凋落物分解的影响。结果表明：(1)分解1年后,黄帚橐吾重量损失及氮素释放较其他物种更缓慢;(2)随着黄帚橐吾生物量比例的增加,凋落物整体重量损失及氮素释放显著降低;(3)混合凋落物中黄帚橐吾能限制其他物种的分解,这种拮抗效应进一步延缓了混合凋落物的分解。综上,高寒草甸黄帚橐吾扩张引起的凋落物生物量增多通过延缓凋落物分解及氮释放,阻碍土壤养分输入,进而对草地碳氮循环过程产生不利影响。     

影响黄帚橐吾种子生产的因素I．生境和花序结构

通过对黄帚橐吾(Ligularia virgaurea)自然种群在不同生境和种群密度下的种子生产的研究,结果显示:1)黄帚橐吾的种子生产无论是在种群水平,还是在总花序上同一部位头状花序水平,均受到生境条件的影响,其种子数量、种子均重和种子总重量等特征在不同生境问表现出沙地>滩地>坡地,在同一生境内则为高密度种群>低密度种群和植被盖度较低>植被盖度较高的趋势(滩地例外);2)种子生产中的种子数量和种子总重与总花序大小、头状花序数量以及无性系株大小多呈显著正相关,与个体密度无关,但种子均重与上述因素(除无性系株大小外)的关系不显著;3)在总花序内不同部位头状花序问表现出的种子生产变化趋势(顶部>基部)不受生境条件、种群密度等因素的影响;4)种子生产在总花序上所表现出的这种部位依赖性可能是由于不同部位头状花序间开花时序上的差异引起种子从母体获取资源上的不同所致。     

不同光照处理下青藏高原克隆植物黄帚橐吾(Ligulariavirgaurea)种子大小对其幼苗生长的影响

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明:(1)在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。(2)黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量(TB)大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比(R/S)大于小种子幼苗。(3)黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率(RGR)较大于大种子幼苗,但叶面积比率(LAR)、叶面积干质量比(SLA)、叶干质量(LWR)差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。     

Effects of resource level and habitat type on behavioral and morphological plasticity in Eurasian perch

Spatial and temporal heterogeneity in the environment is a common feature affecting many natural populations. For example, both the resource levels and optimal habitat choices of individuals likely change over time. One way for organisms to cope with environmental variation is to display adaptive plasticity in traits such as behavior and morphology. Since trait plasticity is hypothesized to be a prerequisite for character divergence, studies of mechanisms behind such plasticity are warranted. In this study, we looked at the interaction of two potentially important environmental variables on behavioral and morphological plasticity in Eurasian perch (Perca fluviatilis L.). More specifically, the plastic responses in activity and morphology of perch exposed to different resource levels and simulated habitat types were studied in an aquarium experiment. The resource level experienced had a large influence on plasticity in both activity and morphology. Behavioral adaptations have been thought to mediate morphological transitions, and we suggest that the morphological response to the resource level was mediated by differences in activity and growth rates. The habitat type also affected morphological plasticity but to a lesser extent, and there was no effect on activity from habitat type. Based on these results, we suggest that it is essential to include several environmental factors acting in concert when studying mechanisms behind trait plasticity. We also propose that variation in resource levels might play a key role in fostering trait plasticity in at least fish populations, while other environmental variables such as divergent habitat complexities and prey types might be less influential. Dynamics in resource levels and optimal habitat choices might thus be important factors influencing character divergence in natural populations.     

竹类植物对异质生境的适应——表型可塑性

竹类植物是一类以木本为主的克隆植物,凭借表型可塑性的优势,对异质生境具有很强适应能力。然而,目前对竹类植物表型可塑性的实现方式及其异质生境适应对策未见系统总结,从而在一定程度上限制了竹类生态学的发展。从形态可塑性、选择性放置、克隆整合和克隆分工等4个方面对竹类植物的表型可塑性研究进行分析和梳理,结果表明:竹类植物在异质生境中具有明显的表型可塑反应,主要采用形态可塑性、选择性放置和克隆整合来适应异质生境,而克隆分工的普遍性仍有待验证;目前侧重于研究构件形态和生物量分配格局,而很少深入探讨形态、生理和行为等可塑性机理。今后竹类植物表型可塑性研究重点在于:1)克隆整合的格局与机理;2)克隆整合对生态系统的影响;3)克隆分工的形成及其与环境关系;4)表型可塑性的等级性及环境影响;5)不同克隆构型的表型可塑性特征及其内在机制。     

林冠环境对亚高山针叶林下缺苞箭竹生物量分配和克隆形态的影响

通过对亚高山针叶林的林下、小林窗(130 m²)、中林窗(300 m²)和大林窗(500 m²) 4种林冠环境中缺苞箭竹(Fargesia denudata)分株种群特征进行调查, 研究其生物量分配格局和克隆形态可塑性。研究结果表明: (1)分株生物量、基径、高度以及分株各构件生物量随林冠郁闭度减小均表现为先增加后减小的趋势, 在小林窗中达到最大值; (2)大林窗中, 根生物量分配和数量显著高于其他林冠环境, 随林冠郁闭度增大, 分株不断增大叶生物量分配、比叶面积和分枝百分比等地上部分投资, 以适应低光环境; (3)比茎长和比地下茎长随林冠郁闭度增大表现为先减小后增加的趋势, 在小林窗值最低, 分枝强度在小林窗和中林窗中显著高于林下和大林窗环境。结果显示, 缺苞箭竹在不同林冠环境中具有生物量分配和克隆形态的可塑性, 以利于种群对光资源的有效利用。小林窗环境是缺苞箭竹较适宜的生境, 生物量积累最多, 长势最好。     

Diversity and persistence of arbuscular mycorrhizas in a low-Arctic meadow habitat

Little is known about the ecology and diversity of arbuscular mycorrhizal (AM) fungi in Arctic ecosystems. Here, the diversity and composition of the AM fungal community and its response to host plant community composition were studied in a low-Arctic meadow habitat. The natural vegetation in two low-Arctic meadow sites was manipulated. Plots with natural vegetation, monoculture and no vegetation were established. Seeds of Solidago virgaurea were sown into the plots and the AM fungal community in the seedling roots was analysed using the terminal restriction fragment length polymorphism (T-RFLP) method. The vegetation manipulation treatments affected the community composition but not the diversity of AM fungi found in S. virgaurea roots. The diversity of AM fungi was higher in S. virgaurea roots in the site with naturally higher plant species diversity. These results show that AM fungi in low-Arctic meadows are able to survive for a period of 2 yr without a host plant. This ability buffers the AM fungal community against short-term changes in host plant community composition and diversity.     

Response of clonal plasticity of Fargesia nitida to different canopy conditions of subalpine coniferous forest

The aim of this study is to explore the effects of canopy conditions on clump and culm numbers, and the morphological plasticity and biomass distribution patterns of the dwarf bamboo species Fargesia nitida. Specifically, we investigated the effects of canopy condi-tions on the growth and morphological characteristics of F. nitida, and the adaptive responses of F. nitida to dif-ferent canopy conditions and its ecological senses. The results indicate that forest canopy had a significant effect on the genet density and culm number per clump, while it did not affect the ramet density. Clumps tended to be few and large in gaps and forest edge plots, and small under forest understory plots. The ramets showed an even distribution under the closed canopy, and clus-ter distribution under gaps and forest edge plots. The forest canopy had a significant effect on both the ramets'biomass and biomass allocation. Favourable light conditions promoted ramet growth and biomass accumulation. Greater amounts of biomass in gaps and forest edge plots were shown by the higher number of culms per clump and the diameter of these culms. Under closed canopy, the bamboos increased their branching angle, leaf biomass allocation, specific leaf area and leaf area ratio to exploit more favourable light conditions in these locations. The spacer length, specific spacer length and spacer branching angles all showed significant differences between gaps and closed canopy conditions. The larger specific spacer length and spacer branching angle were beneficial for bamboo growth, scattering the ramets and exploiting more favourable light conditions. In summary, this study shows that to varying degrees, F nitida exhibits both a wide ecological amplitude and high degree of morphological plasticity in response to differing forest canopy conditions. More-over, the changes in plasticity enable the plants to optimize their light usage efficiency to promote growth and increase access to resources available in heteerogeneous light environoments.     

Effects of light on the growth and clonal reproduction of Ligularia virgaurea

Ligularia virgaurea is a perennial herb that is widely distributed in the alpine meadow on the eastern Qinghai-Tibet plateau.We investigated the patterns of growth and reproduction of L.virgaurea under two contrasting levels of light conditions for two continuous growing seasons.Our results showed that the light affects on the maximum relative growth rate,the shoot weight ratio and the root weight ratio differed between the two growing seasons.L.virgaurea reproduced initially through rhizome in the second growing season,rather than sexual reproduction.The proportion of genets with clonal reproduction decreased under shaded conditions.A minimum genet size should be attained for clonal reproduction to begin under the shaded conditions.There was a positive linear relationship between clonal reproduction and genet size.Light level affected the allocation of total biomass to clonal structures,with less allocation under the full natural irradiance than under the shaded conditions.There seemed to be a trade-off between vegetative growth and clonal reproduction under the full natural irradiance,in terms of smaller relative growth rates of genets with clonal reproduction than those without clonal reproduction.L.virgaurea emphasized clonal reproduction under the full natural irradiance,while the plant emphasized vegetative growth under the shaded conditions.     

Length of the Spacer Rather than its Plasticity Relates to Species Distribution in Various Natural Habitats

Much evidence from laboratory experiments and theoretical studies show that plasticity of clonal growth traits like lateral spread provides advantage in heterogeneous conditions. However, few tests of whether species with plastic clonal growth have an advantage over non-plastic species in natural conditions exist. I analyzed whether spacer length (i.e., length of a stolon or a rhizome branch between two ramets) and the variation of it (as a surrogate to its plasticity) relate to species presence and abundance in open meadow, wooded meadow and forest habitats with varying environmental conditions at Laelatu wooded meadow, Estonia. In fertilized, compared to unfertilized conditions, a weak and non-conclusive advantage of both long spacers and high variability of spacer length was detected. Abandonment in open meadows lead to a prevalence of species with shorter spacers, while on abandoned wooded meadows the species with longer spacers dominated. There was no difference in variability of spacer length between managed and abandoned meadows. In more heterogeneous forest habitats high variability of spacer length was more common, but the effect of lengthy spacers was more pronounced. The results suggest that while the variability of spacer length indeed corresponds with larger abundance in some conditions, the actual length of spacers has a more pronounced relationship with abundance of plants in natural vegetation.     

根茎型植物扁秆荆三棱对光照强度和养分水平的生长响应及资源分配策略

自然界中光照和养分因子常存在时空变化,对植物造成选择压力。克隆植物可通过克隆生长和生物量分配的可塑性来适应环境变化。尽管一些研究关注了克隆植物对光照和养分因子的生长响应,但尚未深入全面了解克隆植物对光照和养分资源投资的分配策略。以根茎型草本克隆植物扁秆荆三棱(Bolboschoenus planiculmis)为研究对象,在温室实验中,将其独立分株种植于由2种光照强度(光照和遮阴)和4种养分水平(对照、低养分、中养分和高养分)交叉组成的8种处理组合中,研究了光照和养分对其生长繁殖及资源贮存策略的影响。结果表明,扁秆荆三棱的生长、无性繁殖及资源贮存性状均受到光照强度的显著影响,在遮阴条件下各生长繁殖性状指标被抑制。且构件的数目、长度等特征对养分差异的可塑性响应先于其生物量积累特征。在光照条件下,高养分处理的总生物量、叶片数、总根茎分株数、长根茎分株数、总根茎长、芽长度、芽数量等指标大于其他养分处理,而在遮阴条件下,其在不同养分处理间无显著差异,表明光照条件可影响养分对扁秆荆三棱可塑性的作用,且高营养水平不能补偿由于光照不足而导致的生长能力下降。光照强度显著影响了总根茎、总球茎及大、中、小球茎的生物量分配,遮阴条件下,总生物量减少了对地下部分根茎和球茎的分配,并将有限的生物量优先分配给小球茎。总根茎的生物量分配未对养分发生可塑性反应,而随着养分增加,总球茎分配下降,说明在养分受限的环境中球茎的贮存功能可缓冲资源缺乏对植物生长的影响。在相同条件下,根茎生物量对长根茎的分配显著大于短根茎,以保持较高的繁殖能力;而总球茎对有分株球茎的生物量分配小于无分株球茎,表明扁秆荆三棱总球茎对贮存功能的分配优先于繁殖功能。研究为进一步理解根茎型克隆植物对光强及基质养分环境变化的生态适应提供了依据。     

入侵植物银胶菊在不同生境下表型可塑性和构件生物量

研究了入侵植物银胶菊在4种不同小生境间花果期形态特征变化和构件生物量特征。结果显示:在植株密度小但土壤肥沃的小生境中,植株各形态指标如茎长、茎直径和花序直径等都明显高于其它小生境,在生物量结构特征上则表现为总生物量和花果生物量所占比例的升高。随着植株密度的增加以及土壤肥力下降,上述各形态指标都发生了较明显的变化,生物量投资也进行了优化配置,银胶菊表现出了较高的形态可塑性。银胶菊与觅光和竞争相关的几个指标如叶和根的比例都增加,但用于生殖构件的比例却减少了。相关分析显示,银胶菊花果期各构件生物量与高度成正相关,与密度为负相关,并受环境因素的制约。表明,较高的形态可塑性和较强的生殖配置策略可能是银胶菊成功入侵我国的重要特征。