甘南高寒草甸退化对植物功能群多样性与物种多度分布的影响

为分析甘南高寒草甸植物功能群多样性及其物种多度分布对退化的响应,探讨其多样性的形成与维持机制,采用样地调查法收集数据,并使用物种多度模型对其进行拟合分析。结果表明:随着退化程度的加深,植被优势种以禾草科和莎草科植物为主,逐渐变为杂草功能群植物为主,杂草功能群在群落多样性分布中起着主导作用;全部物种多度分布随着退化程度的加深发生变化,其中,无退化草甸的最优拟合模型是VOLKOV,轻度退化草甸的最优拟合模型是GEO,中度退化草甸和重度退化草甸的最优拟合模型为BRO,资源分配模式由随机分配转向固定分配的分配模式;禾草功能群的最优拟合模型以生态位模型为主,资源分配方式由固定分配和随机分配共同主导,豆科功能群的最优拟合模型是BRO,资源分配方式以固定分配为主,杂草功能群的最优拟合模型从中性模型向生态位模型转变,与全部物种多度分布的最优模型基本一致,且资源分配由随机分配向固定分配转变,可以认为杂草功能群是影响群落物种多度分布的主要原因,但是禾草和豆科功能群的贡献也不可忽视。     

青藏高原高寒草甸植物群落结构和功能对氮、磷、钾添加的短期响应

对中国科学院海北高寒草甸生态系统定位站的矮嵩草草甸水肥样地进行了氮、磷、钾及其组合的施肥处理,研究了施肥对植物群落结构和功能的影响。结果表明:(1)施肥使矮嵩草草甸植物群落物种丰富度减少,不同施肥处理下物种丰富度大小分别为:对照钾磷氮氮磷磷钾氮钾氮磷钾。(2)在氮磷配合施肥处理下,矮嵩草草甸植物群落Shannon-Wiener指数显著高于对照,而其它施肥处理对Shannon-Wiener指数影响不显著。(3)在同一施肥处理下,禾草类和莎草类的重要值明显高于豆科和杂类草功能群,不同施肥处理使禾草、莎草、豆科植物的重要值增加,而杂类草重要值减少。(4)与对照相比,不同施肥(除钾外)处理可不同程度的增加植物群落的高度。(5)除钾、磷钾养分添加对矮嵩草草甸地上生物量的影响与对照差异不显著外,其它养分及其组合添加都极显著增加了群落地上生物量,且大小顺序依次为氮磷氮磷钾磷氮钾氮磷钾钾对照。(6)施用不同种类的肥料后,矮嵩草草甸各功能群地上生物量的比例变化明显,禾草和莎草的比例均增加,杂类草的比例减少,而豆科植物无规律性。(7)熵值法综合评价短期施肥处理对矮嵩草草甸群落的影响表明,氮磷、氮磷钾配合施肥是青藏高原高寒草甸最佳施肥选择。     

围封与放牧管理对高寒草甸植物功能性状和功能多样性的影响

植物功能性状能够响应生存环境的变化并直接决定着生态系统功能。为了揭示围封与放牧管理对物种共存和驱动群落构建的影响机理,该研究以青藏高原东缘高寒草甸为对象,分析了围封与放牧处理对植物功能性状和功能多样性的影响。结果显示:(1)在群落水平,放牧显著降低了比叶面积和植物高度;在物种水平,放牧群落中多数杂类草比叶面积减小,而莎草类和禾草类的比叶面积在处理间无显著差异。(2)叶干物质含量与比叶面积在围封和放牧处理中均呈显著负相关关系,在放牧处理中,叶干物质含量与植物高度呈显著的二次函数关系,即随着叶干物质含量的增大,植物高度先减小后增大;在同等比叶面积的情况下,与围封相比,放牧降低了叶干物质含量;在相同叶干物质含量的情况下,与围封相比,放牧降低了植物高度。(3)放牧在总体上降低了种间性状的平均差异,植物性状表现出趋同响应,具体表现为放牧减小了叶干物质含量和植物高度的种间差异;与围封相比,放牧显著提高了功能均匀度,减小了功能分离度。研究表明,不同植物种对放牧的响应模式存在差异,放牧降低了种间对光资源的竞争,可能增加了对土壤养分的竞争,放牧驱动群落构建的过程中,土壤养分是非常重要的作用因子,说明放牧影响物种共存依赖于对多种资源的竞争。     

坡向对东祁连山高寒草甸群落物种功能群及其多样性的影响

为探究祁连山东缘地区不同坡向的高寒草甸群落物种功能群和多样性差异,该研究选择北坡(N坡)、西北坡(NW坡)、西坡(W坡)、东坡(E坡)、东北坡(NE坡)、西南坡(SW坡)和南坡(S坡)7个坡向类型,调查各坡向的植被特征(高度、盖度和频度),测定土壤因子,分析物种均匀度和多样性指数及其相关性等。结果发现：(1)研究区样地共有植物11科18属21种,主要有豆科(4属4种)、菊科(3属3科)、蔷薇科(1属3种)、莎草科(2属2种)、禾本科(2属2种)和蓼科(1属2种);不同坡向的植物科、属数量变化趋势与种相同,均为东北坡、西南坡、北坡(76.19%)>南坡(66.67%)>东坡(61.90%)>西坡、西北坡(19.05%)。(2)不同坡向的草地群落组成不同,其中东坡、南坡和东北坡主要以草本植物为主,西南坡和北坡为草本和灌丛交错区,西坡和西北坡主要以灌丛为主。(3)不同坡向的物种功能群不同,其中东坡、南坡、东北坡、北坡和西南坡的莎草类重要值最高,西坡和西北坡只有豆科和杂类草,且杂类草重要值最高。(4)不同坡向的优势功能群不同,其中：禾本科植物的重要值大小为阴坡(NE坡)>阳坡(S坡和SW坡)>半阳坡(E坡),莎草科植物重要值大小为半阳坡(E坡)>阳坡(S坡)>阴坡(NE坡和N坡),豆科植物重要值大小为阳坡(S坡)>阴坡(N坡、NW坡和NE坡)>半阳坡(E坡)>半阴坡(W坡),杂类草植物重要值大小为半阴坡(W坡)>阴坡(N坡和NE坡)>半阳坡(E坡)>阳坡(SW坡和S坡)。(5)随着坡向梯度变化,物种丰富度和香农 威纳多样性指数变化一致,其大小均表现为：阴坡>阳坡>半阳坡>半阴坡。(6)冗余分析发现,土壤含水量和碳氮比是影响灌丛植物［瑞香(Daphne odora)、金露梅(Potentilla fruticosa)和头花杜鹃(Rhododendron capitatum)］重要值的重要因素。研究表明,不同坡向的土壤水分、养分和光照等的变化显著影响了高寒草甸植物群落物种功能群及其多样性。     

甘南高寒草甸坡向梯度对植物群落功能多样性的影响

植物群落功能多样性对于维持生态系统功能具有十分重要的意义。该研究以青藏高原高寒草甸植物群落为研究对象,运用R软件程序包(FD、Vegan)与单因素方差分析法,分析高寒草甸不同坡向植物群落功能多样性的变化及其与环境因子的关系,以揭示微生境梯度上植物对环境的适应策略以及群落种间功能特征及生态系统内部结构和功能的变化机制。结果显示：(1)青藏高原高寒草甸的北坡和西北坡的物种丰富度、植物株高、比叶面积、叶片有机碳、叶片氮以及叶片磷显著高于其他坡向,且坡向间差异显著(P<0.05)。(2)在北坡到南坡的变化中,功能丰富度差异比较明显(P<0.05),株高、比叶面积、叶片有机碳、叶片氮及叶片磷等功能丰富度均呈递减趋势。(3)北坡的株高功能均匀度、西北坡比叶面积、叶片有机碳、叶片氮及叶片磷等功能均匀度均显著高于南坡,且多元性状功能均匀度在坡向间差异显著(P<0.05)。(4)北坡的比叶面积、叶片氮功能离散度及西北坡的株高、叶片有机碳、叶片磷等功能离散度均高于南坡,且坡向间差异显著(P<0.05)。(5)植物群落功能多样性与土壤含水量、土壤有机碳、土壤全氮、土壤全磷呈显著正相关关系(P<0.05),与坡度、土壤pH、土温、照度呈显著负相关关系(P<0.05)。     

Original Articles: Differential Influence of Plant Species on Soil Nitrogen Transformations Within Moist Meadow Alpine Tundra

Plant species can influence nitrogen (N) cycling indirectly through the feedbacks of litter quality and quantity on soil N transformation rates. The goal of this research was to focus on small-scale (within-community) variation in soil N cycling associated with two community dominants of the moist meadow alpine tundra. Within this community, the small-scale patchiness of the two most abundant species (Acomastylis rossii and Deschampsia caespitosa) provides natural variation in species cover within a relatively similar microclimate, thus enabling estimation of the effects of plant species on soil N transformation rates. Monthly rates of soil N transformations were dependent on small-scale variation in both soil microclimate and species cover. The relative importance of species cover compared with soil microclimate increased for months 2 and 3 of the 3-month growing season. Growing-season net N mineralization rates were over ten times greater and nitrification rates were four times greater in Deschampsia patches than in Acomastylis patches. Variability in litter quality [carbon:nitrogen (C:N) and phenolic:N], litter quantity (aboveground and fine-root production), and soil quality (C:N) was associated with three principal components. Variability between the species in litter quality and fine-root production explained 31% of the variation in net N mineralization rates and 36% of net nitrification rates. Site variability across the landscape in aboveground production and soil C:N explained 33% of the variation in net N mineralization rates and 21% of net nitrification rates. Within the moist meadow community, the high spatial variability in soil N transformation rates was associated with differences in the dominant species' litter quality and fine-root production. Deschampsia-dominated patches consistently had greater soil N transformation rates than did Acomastylis-dominated patches across the landscape, despite site variability in soil moisture, soil C:N, and aboveground production. Plant species appear to be an important control of soil N transformation in the alpine tundra, and consequently may influence plant community structure and ecosystem function.     

高寒草甸植物群落中相似性、物种多样性与地上生物量的年际变异性

相似性似说通过物种构成的相似性来解释物种丧失是如何影响生物量的变异性的,但还没有得到检验。本研究通过设置在青藏高原东部地区的高寒草甸植物群落中的74个永久样方．采集3年(1999～2001)植物生长高峰期的群落数据,试图检验物种构成的相似性是如何解释物种多样性对地上生物量年际变异性的影响。结果表明：随着物种丰富度增加,生物量变异性降低;而随着均匀度的增加,生物量的变异性尽管在均匀度中等程度时似乎保持在同一水平,但总体上呈下降趋势;物种构成上的相似性解释了地上生物量变异性的大部分,而且随着物种构成上的相似性的增加,生物量的变异性降低;物种丰富度和均匀度均与物种构成上的相似性没有显著相关关系。这些结果表明：尽管生物多样性的丧失可能不必导致物种丰富群落中物种构成上的相似性,但相似性与地上生物量的变异性的因果联系可能是稳健的．由于本研究是在自然群落中进行的,对物种构成的相似性没有进行直接控制,因此,要深入理解相似性是如何影响生物多样性对生态系统功能变异性的效应的机制,可能还需要直接对物种构成的相似性进行控制的实验研究。     

Effects of Warming and Nitrogen Addition on Plant Photosynthate Partitioning in an Alpine Meadow on the Tibetan Plateau

Quantifying plant carbon (C) allocation among different pools is critical for understanding and predicting how C turnover responds to global climate change in terrestrial ecosystems. A field experiment with increasing warming and nitrogen (N) was established to investigate interactive effects on plant C allocation in alpine meadows. Open-top chambers (OTCs) were used to simulate warming. In OTCs, daytime air and soil temperature at 5 cm depth increased by 2.0 and 1.6 °C, respectively, compared with ambient conditions, but soil moisture at 5 cm depth decreased by 4.95% (v/v) from 2012 to 2014. Warming reduced aboveground biomass by 38, 36, and 43% in 2012, 2013, and 2014, respectively, and increased belowground biomass by 64% and 29% in 2013 and 2014, respectively, and the root-to-shoot ratio was significantly increased. Specifically, warming increased the proportion of plant roots in the deep layers (10–20 cm). Both N addition and its combination with warming substantially enhanced belowground biomass. Pulse-labeling experiments for ¹³C revealed that warming reduced the translocation of assimilated C to shoots by 8.8% (38.7% in warming, and 47.5% in the control [CK]), and increased the allocation to root by 12.2% (55.5% in warming, and 43.3% in CK) after 28 days labeling. However, N addition increased the proportion of assimilated C allocated to shoots by 6.5% (54.0% in N addition, and 47.5% in CK), whereas warming combined with N addition reduced this proportion by 10.9%. A decline in soil water content in the surface layer may be the main cause of plants allocating more newly fixed photosynthate to roots. Therefore, plants promoted root growth to draw water from deeper soil layers (10–20 cm). We concluded that climate warming will change the allocation patterns of plant photosynthates by affecting soil water availability, whereas N addition will increase plant photosynthates aboveground in alpine meadows and thus will significantly affect C turnover under future climate change scenarios.

     

Plant Functional Diversity and Species Diversity in the Mongolian Steppe

Background

The Mongolian steppe is one of the most important grasslands in the world but suffers from aridization and damage from anthropogenic activities. Understanding structure and function of this community is important for the ecological conservation, but has seldom been investigated.

Methodology/Principal Findings

In this study, a total of 324 quadrats located on the three main types of Mongolian steppes were surveyed. Early-season perennial forbs (37% of total importance value), late-season annual forbs (33%) and late-season perennial forbs (44%) were dominant in meadow, typical and desert steppes, respectively. Species richness, diversity and plant functional type (PFT) richness decreased from the meadow, via typical to desert steppes, but evenness increased; PFT diversity in the desert and meadow steppes was higher than that in typical steppe. However, above-ground net primary productivity (ANPP) was far lower in desert steppe than in the other two steppes. In addition, the slope of the relationship between species richness and PFT richness increased from the meadow, via typical to desert steppes. Similarly, with an increase in species diversity, PFT diversity increased more quickly in both the desert and typical steppes than that in meadow steppe. Random resampling suggested that this coordination was partly due to a sampling effect of diversity.

Conclusions/Significance

These results indicate that desert steppe should be strictly protected because of its limited functional redundancy, which its ecological functioning is sensitive to species loss. In contrast, despite high potential forage production shared by the meadow and typical steppes, management of these two types of steppes should be different: meadow steppe should be preserved due to its higher conservation value characterized by more species redundancy and higher spatial heterogeneity, while typical steppe could be utilized moderately because its dominant grass genus Stipa is resistant to herbivory and drought.     

高寒草甸不同演替阶段植物叶片功能性状研究

以甘南高寒草甸演替过程中5个阶段的典型群落为研究对象,对围封样地内不同演替阶段群落叶片功能性状进行比较,分析了围封地内各演替阶段群落水平上主要物种叶性状与环境因子的关系。结果显示:(1)此围封地形成了一个从草本到灌木的演替过程。随着演替的进行,Margalef指数显著增加,Shannon-Wiener指数呈先增加后降低的趋势。(2)从演替前期到演替后期,土壤有机碳(SOC)、土壤全氮(STN)、土壤含水量(SWC)逐渐升高,光照度(LI)、土壤温度(ST)逐渐降低,土壤全磷(STP)呈先降低后增加趋势;叶片有机碳(LCC)、全氮(LNC)、含水量(LWC)逐渐升高;比叶面积(SLA)、磷利用效率(PUPE)、稳定碳同位素(δ13C)逐渐下降,叶片全磷(LPC)先降低后升高,而氮利用效率(PUNE)先升高后降低。(3)RDA冗余分析表明,在此围封样地内,演替前期植物群落叶性状主要受到LI和ST的限制作用。而在演替的中后期SWC[WTBZ]是主要影响因子。此研究有助于我们认识高寒草甸生态系统的退化过程所导致的生态环境问题,进而寻求更好的草地恢复和重建方法。     

单户与联户经营对高寒草甸土壤理化性质与植物多样性的影响

在甘南高寒草甸单户经营草场与联户经营草场进行野外群落学调查,分析其物种多样性和功能多样性的变化,以揭示不同经营方式下土壤理化性质对植物多样性的影响机制。结果显示：（1）联户草场内植物群落的Margalef指数、Simpson指数、Shannon-Winener指数较大,而Pielou指数在不同放牧经营方式下的差异并不显著。（2）不同经营方式下,土壤含水量、土壤全氮、土壤全磷和土壤有机碳质量分数表现为联户大于单户的趋势且差异显著（P<0.05）;单户草场土壤电导率与土壤pH大于联户草场;随着土层的加深土壤含水量、土壤全氮质量分数、土壤全磷质量分数、土壤有机碳质量分数和土壤电导率增加,而土壤pH在土层之间的差异并不显著。（3）联户经营方式下的功能丰富度、功能均匀度与功能离散度显著大于单户草场（P<0.05）。（4）相关性分析表明,植物群落物种多样性和功能多样性与土壤含水量、土壤全氮质量分数和土壤全磷质量分数存在正相关关系,土壤电导率和土壤pH与植物群落物种多样性和功能多样性存在负相关关系。冗余分析表明,联户经营方式下土壤理化性质对植物多样性的影响更显著,且0相似文献   

Genetic Diversity and the Reintroduction of Meadow Species

Abstract: Restoration of formerly nutrient‐poor and species‐rich grasslands generally leads to an increase in species diversity. However, species without a persistent seed bank and with poor dispersal ability often do not re‐establish spontaneously. Here, reintroduction is an option. If existing populations are comparable in their genetic composition, any population will do. This is not the case if populations have local adaptations. Unfortunately, whether populations are adapted locally is not easily determined, in contrast to assessing differentiation using neutral genetic markers. We used AFLP to study genetic diversity of Cirsium dissectum and Succisa pratensis within and among several Junco‐Molinion plant communities in the Netherlands (up to 200 km apart) that were potential source populations, and followed the reintroduction using seeds from these populations. Also, vegetative growth phase characteristics of three populations of C. dissectum were analyzed under controlled conditions. Most of the genetic variation in these cross‐fertilizing species was found within populations. Small but significant genetic differences in band frequencies were found among populations (F_st 0.100 ‐ 0.135). The first generation of reintroduced plants contained less polymorphic bands than the source populations. The genetic differences caused by reintroduction using a limited number of seeds (founder effects) were significant in all except one case (F_st 0.012 ‐ 0.101 between source and corresponding reintroduced population), but the magnitude was smaller than the source population differentiation. In assignment tests, reintroduced populations resembled their source population more than any other population, but all populations contained sizeable proportions of plants that were assigned to most similar plants from other populations, indicating that the populations are only marginally distinct. Calculations show that reintroduction from more than one source population introduces significantly more polymorphic bands into the new population, capitalizing on the existence of band frequency differences among populations.     

青藏高原高寒草甸3种植物对模拟增温的生理生化响应

采用国际冻原计划(ITEX)模拟增温对植物影响的研究方法,将开项式生长室(OTC)按不同直径设置5个增温梯度,并按其直径从小到大的顺序依次标记为A、B、C、D、E 5个处理,研究了增温效应对青藏高原高寒草甸3种植物生理生化特性的影响。研究表明:（1） A~E 5个增温处理使OTC内部气温依次比对照升高了2.68 ℃、1.57 ℃、1.20 ℃、1.07 ℃ 和0.69 ℃,土壤温度依次比对照升高了1.74 ℃、1.06 ℃、0.80 ℃、0.60 ℃和0.30 ℃。（2）增温对3种植物的叶绿素含量、可溶性糖含量、可溶性蛋白含量、SOD活性、谷胱甘肽等生理生化特性产生了一系列的影响,3种植物对增温效应的响应也不尽相同。（3）增温对青藏高原3种植物生理生化特性的影响明显且复杂,适度增温0.69 ℃~1.07 ℃（D、E处理）对3种植物生理生化特性在总体上表现为正效应。     

高寒草甸放牧扰动与两种植物的反应研究

对不同放牧强度下矮嵩草草甸植物垂穗披碱草和鹅绒委陵菜的生长和繁殖特性进行了5年研究。结果表明,垂穗披碱草株高、分蘖数、地上物量、地下生物量、有性繁殖效力在不放牧或轻度放牧下最大,营养生长效力在重度放牧中最大,而贮藏效力在重度放牧中最小。鹅绒委陵菜叶数、匍匐茎长度、地上生物量、匍匐茎生物量、开花数、生殖生物量、有性繁殖效力及营养繁殖效力在放牧区显著高于不放牧的对照区。说明适当的放牧干扰有利于垂穗披碱草营养生长,但放牧过重会抑制其有性繁殖;由于放牧采食减少了种间竞争影响,从而提高了鹅绒委陵菜营养,生长效力和有性繁殖效力。两物种地下贮藏物的比例随着放牧强度增加显著减少。放牧强度对高寒草甸的群落演替方向有显著影响。     

牦牛放牧率对小嵩草高寒草甸暖季草场植物群落组成和植物多样性的影响

两年的牦牛放牧试验结果表明:在暖季草场,随着放牧率的提高,禾草和莎草类功能群的盖度、生物量及其组成与高度减小,它们与放牧率呈显著的负相关 P<0.05 可食杂草和毒杂草类功能群的盖度、生物量及其组成与高度增加,它们与放牧率呈显著的正相关 P<0.05 各功能群的盖度与生物量之间是显著的正相关关系 P<0.05 .对照草地由于没有牦牛的采食,群落由少数优势种植物所统治,群落结构趋于简单,物种组成贫乏,物种多样性和均匀度指数最小;轻度放牧牦牛选择采食对植物群落的影响较小,群落的物种丰富度指数、均匀度指数和多样性指数均不高;中度放牧提高了资源的利用效率,增加了群落结构的复杂性,草地的物种丰富度指数、均匀度指数和多样性指数均最高,该结果支持 中度干扰理论 ;重度放牧由于牦牛采食过于频繁,改变了植物的竞争能力,导致植物种的均匀度下降,多样性减少.不同放牧率草地群落的物种数 S 、丰富度指数 Ma 、多样性指数 Shan-non-Wiener指数H′和Simpson指数D 、均匀度指数 Pielow指数J′ 的排序为:对照<轻度放牧<重度放牧<中度放牧,优势度指数 Berger-Parke指数 的变化趋势则与之相反.     

川西北高寒草甸蚁丘植物群落演替：种类组成与物种多样性

蚂蚁通过构建蚁丘,提高了群落生境异质性,影响群落物种组成,甚至生态系统结构和功能。我们在川西北典型高寒草甸调查了平地（非蚁丘,即距离蚁丘4～5m的草地）和不同大小广布弓背蚁（Cam-ponotus herculeanus）蚁丘（小蚁丘、中蚁丘和大蚁丘3种,平均面积大小分别为309．45cm^2、948．45cm^2、2124．90cm^2）上的植物种类组成、物种多样性,以及每个物种的高度,盖度和多度,在此基础上分析了蚁丘植物群落演替进程中的优势种变迁及其机制。调查发现,与平地相比,天气晴朗条件下蚁丘的土壤温度在白天较高,而在夜晚较低,日变化的波动性较大;蚁丘中心的相对湿度低于边缘,更低于平地。群落结构分析表明,不同大小蚁丘之间植物物种丰富度和多样性差异不显著,但是优势种变化明显。随蚁丘增大,钩状嵩草（Kobresia uncinoides）的群落地位（重要值）逐渐上升,小、中、大蚁丘上的次优种分别为拉拉藤（Galium aparine）、羊茅（Festuca ovina）、垂穗披碱草（Elymus nutans）。蚁丘上禾草类优势度显著高于平地,而杂草类优势度则显著低于平地。平地上菊科（Compositae）和毛莨科（Ranunculaceae）植物占优势,蚁丘上莎草科（Cyperaceae）和禾本科（Gramineae）植物占优势。文中还讨论了蚁丘植物群落演替的可能机制,以及蚁丘对整个草甸群落组成和动态的潜在意义。     

Plant Community Succession on Ant-hills of a Sub-alpine Meadow in Northwestern Sichuan,China: Species Composition and Diversity

Ants may increase habitat heterogeneity by means of building ant-hills, thereby changing community species composition and ecosystem structure and functioning. We investigated plant height, coverage and abundance for each species and calculated species richness and diversity for ant-hills of Camponotus herculeanus differing in size (309.45cm2, 948.45cm2, 2124.90cm2 for the small, intermediate and large ant-hills, respectively). The dominant species was subsequently identified for the three size-classes of ant-hills and the mechanism underlying anthill community succession was derived. Our results showed that diurnal temperature fluctuation was greater in ant-hills than the surrounding flat soil, where the temperature of the ant-hills was higher in daytime but lower at night relative to the counterpart. The soil moisture was lower in center than in edge of ant-hills whose moisture was lower than the flat soil. Plant species diversity and richness were not significantly different among the three classes of ant-hills while the dominant species conspicuously changed. The importance value of the most dominant species, Kobresia uncinoides, increased significantly with increasing ant-hill size; the subdominant species was Galium aparine, Festuca ovina, Elymus nutans for the small, intermediate and large ant-hills, respectively. The dominance of grasses was significantly higher, but that of forbs was lower on ant-hills than in surrounding communities. The ant-hills were dominated by species from Cyperaceae and Gramineae while Compositae and Ranunculaceae dominated the surrounding communities. In addition, we discussed the possible mechanisms driving ant-hill community succession and the potential significance of ant-hills to the whole community composition and dynamics in the alpine meadow.     

高寒沙化草地中先锋灌木根系水浸提液对4种高原牧草的化感效应分析

以川西北沙化地生态修复治理过程中2种先锋灌木植物高山红柳(Salix cupularis)和沙棘(Hippophae rhamnoides)为供体植物,中华羊茅(Festuca sinensis)、燕麦(Avena sativa)、垂穗披碱草(Elymus nutans)和老芒麦(E.sibiricus)等4种高原优质牧草为受体植物,比较2种先锋灌木的根系水浸提液,对受体植物种子发芽率、幼苗生长以及抗氧化保护酶活性的化感效应的差异,为先锋灌木选择适宜伴生的经济牧草植物提供理论依据。结果显示:2种灌木根系水浸提液对受试植物生长均具有显著的化感效应,且基本表现出低促高抑的规律。(1)燕麦、中华羊茅、垂穗披碱草和老芒麦种子发芽率在沙棘和高山红柳根系浸提液为10和20g·L~(-1)时均得到显著提高,当浸提液浓度达80g·L~(-1)后基本表现出抑制作用,但只有沙棘浸提液处理下燕麦和中华羊茅达到显著水平。(2)2种根系水浸提液处理下燕麦和中华羊茅幼苗根系生长被完全抑制,但垂穗披碱草只在浓度为80g·L~(-1)时才出现抑制现象;当沙棘根系浸提液为20g·L~(-1)时对燕麦和垂穗披碱草的叶长和鲜重均有显著的促进作用,而高山红柳仅对中华羊茅具有显著促进效应。(3)沙棘根系浸提液为20g·L~(-1)时,对4种受体幼苗体内过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均有显著或极显著的促进效应;浓度为20和40g·L~(-1)的高山红柳根系浸提液,能极显著提高燕麦和老芒麦的CAT活性以及中华羊茅的SOD活性,但浓度为40g·L~(-1)时对燕麦和垂穗披碱草SOD活性有显著的抑制作用;4种受体植物幼苗MDA含量变化趋势均基本与酶活性吻合,能较好地反映酶活性变化下其受到的氧化胁迫程度。(4)综合化感效应指数(SE)显示,垂穗披碱草对2种灌木根系水浸提液适应性最好,其抑制浓度均为80g·L~(-1);各浓度根系浸提液处理中,高山红柳对燕麦和中华羊茅的促进效应均高于沙棘,但沙棘对垂穗披碱草和老芒麦则表现出更强的促进优势。     

青藏高原高寒草甸罂粟科植物种子萌发特性研究

对9种罂粟科植物种子在5个温度(5℃、10℃、15℃、20℃、25℃)下的萌发特性进行了研究.结果显示:(1)采自低海拔的小果博落回、秃疮花和白屈菜在15～25℃的萌发率高于5～10℃;采自高海拔的全缘叶绿绒蒿和多刺绿绒蒿达到最大萌发率的温度分别为5℃和10℃;而采自高海拔的红花绿绒蒿和五脉绿绒蒿只有通过5℃冷处理后才能萌发,表明种子的最佳萌发温度与采集地海拔相关.(2)萌发速率随温度升高增大,秃疮花和苣叶秃疮花在25℃萌发速率最大,其余种25℃的萌发速率略小于20℃的萌发速率.(3)萌发时滞表现出随温度升高而缩短的趋势,秃疮花、白屈菜和苣叶秃疮花在25℃萌发时滞最短,其余种25℃萌发时滞又长于20℃萌发时滞.(4)一年生植物多刺绿绒蒿在所有温度下的萌发率和萌发速率均最高,而萌发时滞最短,这可能是一年生植物适应特殊环境的一种对策.     

封育对高寒草甸植物群落构成及生态位特征的影响

封育是天然草地管理的一种有效措施,利于草地生产力提高和退化草地恢复。该研究通过对青藏高原高寒草甸放牧和封育草地物种多样性、植被构成、植物种生态位特征、草地演替度等分析,解析高寒草甸植物种间关系及草地演替方向。结果表明:(1)封育显著降低了草地群落植物物种数以及α和β多样性指数,显著增加了草地1年生植物种数、地面芽植物种数和地上生物量。(2)放牧草地地上生物量以莎草科(59.7%)和禾本科(23.9%)为主,封育草地地上生物量以禾本科(85.0%)为主;放牧草地优势种为矮嵩草(Kobresia humilis)和线叶嵩草(K.capillifolia),封育草地优势种为垂穗披碱草(Elymus nutans)和早熟禾(Poasp.)。(3)放牧和封育草地的群落植物种重要值均与各自的生态位宽度变化规律一致。(4)草地植物种间竞争主要发生在不同科属植物种之间,封育增加了群落植物种整体生态位重叠值和植物种间竞争。(5)草地群落演替度为封育地放牧地,封育群落处于较稳定状态。研究认为,封育促进了高寒草甸由莎草+杂类草群落向禾草+杂类草群落演替。