不同频次刈割对羊草草原主要植物种群能量现存量的影响

对内蒙古羊草草原主要植物种群能量现存量对刈割频次响应的研究表明,在17年不同频次刈割干扰影响下,植物种群能量现存量随刈割频次的变化表现出不同的变化趋势,据此可以划分出3个不同的刈割响应类群:受抑种、耐刈种和受益种.受抑种包括羊草、羽茅、黄囊苔草、葱属植物和直根型杂类草;耐刈种包括大针茅和冰草;受益种包括洽草和糙隐子草.对于种群相对能量现存量而言,除羊草随刈割频次的增加呈显著下降趋势外,其他受抑种均随刈割频次的增加保持相对稳定,而受益种和耐刈种的相对值则随刈割频次的增加而呈增加趋势.同时,刈割对植物能量现存量的影响还表现在植物热值变化上,但变化幅度小于10%.     

刈割干扰下内蒙古草原两种丛生禾草繁殖策略的适应性调节

刈割是内蒙古草原的主要利用方式之一。当植物面对刈割干扰时, 可以通过繁殖策略的调节适应变化的环境。研究刈割干扰下植物繁殖策略的调节对于揭示植物的适应与进化机制具有重要意义。为此, 选择内蒙古典型草原的大针茅(Stipa grandis)和糙隐子草(Cleistogenes squarrosa), 在1979年围封的羊草(Leymus chinensis)样地(对照)和毗邻的长期刈割区对其繁殖策略进行了研究。结果显示: 1)长期刈割干扰下, 大针茅的种群生物量与对照区无显著差异, 由于其株丛生物量显著降低, 大针茅种群生物量的维持得益于种群密度的显著增加。糙隐子草的种群生物量比对照区显著提高, 由于其株丛生物量与对照区无显著差异, 糙隐子草种群生物量的增加也是因为密度的显著提高。因此, 密度调节是两种植物应对长期刈割干扰的重要的调节机制。2)长期刈割干扰下, 两种植物在无性繁殖和有性繁殖过程所采取的密度调节策略并不相同。大针茅种群生殖株丛的密度无显著变化, 非生殖株丛的密度显著提高, 导致其非生殖株丛的相对密度显著增加, 而生殖株丛的相对密度显著降低。因此刈割干扰下大针茅种群在密度调节上采取了保持有性繁殖株丛密度, 增加无性繁殖株丛密度的策略。糙隐子草种群非生殖株丛的密度显著增加, 但生殖株丛的密度增加幅度更大, 导致其非生殖株丛的相对密度显著降低, 而生殖株丛的相对密度显著提高。因此刈割干扰下糙隐子草种群在密度调节上采取了增加无性繁殖株丛密度的同时, 更大幅度地增加有性繁殖株丛密度的策略。3)长期刈割干扰下, 两种植物对生物量生殖分配的调节采取了不同的策略。大针茅株丛生物量向生殖枝分配的比例无显著变化, 通过降低生殖枝向穗的生物量分配比例, 降低了对有性生殖过程的生物量分配的投入; 而糙隐子草则通过增加株丛生物量向生殖枝分配的比例, 维持生殖枝向穗的生物量分配比例, 从而增加了对有性繁殖过程生物量分配的投入。4)长期刈割干扰下, 大针茅的株丛面积和株丛分蘖数与对照区无显著差异。糙隐子草株丛面积降低, 但是株丛分蘖数无显著变化。本实验说明, 植物种群有性繁殖和无性繁殖之间的密度调节和资源分配调节是草原植物应对刈割干扰下的重要调节机制, 不同的响应策略影响着植物种群的消长动态。     

高原鼠兔刈割行为与栖息地植物群落的关系

采用观察法和样条法对不同栖息地高原鼠兔刈割植物的行为、相对频次、生物量百分比以及刈割植物与鼠兔冬季食物组成之间的关系进行了分析,并阐述了高原鼠兔刈割植物的生物学意义。结果表明:高原鼠兔刈割植物始于每年的6 月下旬,早于其它草原小型哺乳动物贮草时间。不同栖息地鼠兔对植物的刈割频次和生物量比例并非完全一致。在矮嵩草草甸,鼠兔刈割频次较高的为垂穗披碱草、二柱头藨草、甘肃棘豆、短穗兔耳草、铺散亚菊和鹅绒萎陵菜;这些植物生物量所占比例亦较高,仅短穗兔耳草比例较低;在垂穗披碱草草甸,鼠兔刈割频次较高的为垂穗披碱草和早熟禾;垂穗披碱草生物量较高;而在杂类草草甸,鼠兔主要刈割植物为铺散亚菊、大籽蒿、黄帚橐吾、长茎藁本和圆齿狗娃花,生物量比例较高的主要为铺散亚菊。相似性分析结果表明,不同栖息地间鼠兔刈割植物频次和生物量比例差异较大,相似性系数最大分别为0. 7862 和0. 6100, 最小仅为0.1422 和0. 1035,而同一栖息地间鼠兔刈割植物频次和生物量差异相对较小,相似性系数最高达0. 9203 和0. 8490,最小亦达到0. 6662 和0. 4440,表明栖息地变化对鼠兔刈割植物频次和比例有明显的影响作用。鼠兔刈割主要植物频次和生物量比例与冬季主要食物组成的相关分析结果表明,生物量比例与主要食物组成呈显著的正相关(r =0.8412,df = 6, P <0. 05),而刈割植物频次与主要食物相关不显著。     

割一年休一年割草制度下羊草群落植物多样性动态变化

利用1982—2002年样方观测资料,对典型草原区羊草草原群落割一年休一年刈割处理过程中的植物多样性变化规律及引起这些变化的主要植物种群进行了研究。结果表明:建群种羊草的个体数量先下降然后略有上升,但总体呈下降趋势;偶见种和伴生种增加,但组成有所不同。就群落多样性而言,多样性指数和均匀性指数均呈现一个明显高峰值的单峰曲线,物种分布的均匀度是影响多样性指数变化的主要因子。群落主要植物种群密度、生物量与多样性指数存在显著的相关关系,这与它们在群落中的作用有关。     

刈割频次对白三叶能量分配及构型的影响

4～ 10月 ,在亚热带高山人工草地 ,通过生长季割 2、4和 7次的刈割试验后发现 ,不同刈割频次对翌年白三叶能量分配、构件密度、分枝数量及分枝角度影响显著 .随刈割频次的增加 ,白三叶匍匐茎的能量分配递增 ,分别为 42 .8%、44 .9%、47.7% ,而单位长度茎所含能量递减 ,分别为 13 .0、12 .2和 11.1kJ·m-1;叶密度、茎密度、分枝数量及节间长度出现低→高→低的变化趋势 .提高刈割频次后 ,白三叶的分枝强度由 15分枝·m-1递增到 2 3 .7分枝·m-1;分枝角度由 49.5°递增到 60 .2° ,从而提高了白三叶种群在刈割干扰下对土壤微生境资源的利用率     

香港山坡地草本、灌木群落的植物能量生产

利用收获法和植物热值分析,在研究香港桃金娘灌木群落、芒萁群落和鸭嘴草+野古草+金茅草地植物的生物量和净生产量的基础上,探讨群落各组分的干重热值以及植物能量现存量、净固定量和现存净增量.结果表明,芒萁具有较高的热值,而禾草植物的干重热值较低.草地、芒萁、灌木群落植物的能量现存量分别为18683、38436和65632kJ·m^-2;能量净固定量为13286、20354和18784kJ·m^-2·a^-1;能量现存净增量为3437、9626和6695kJ·m^-2·a^-1.与地带性植被南亚热带常绿阔叶林相比,草地、芒萁、灌木群落的能量现存量、能量净固定量和能量现存净增量都较低.刈割实验也表明,随着人类干扰活动强度加大,植物能量净固定量明显下降.     

水分梯度上放牧对内蒙古主要草原群落功能群多样性与生产力关系的影响

应用样线法对放牧对内蒙古草原沿水分梯度分布的主要植物群落:小针茅(Stipaklemenzii)群落、大针茅(Stipagrandis)群落、羊草(Leymuschinensis)群落和羊草杂类草群落多样性、生产力以及两者关系的影响进行了研究,结果表明,除羊草杂类草群落外,物种多样性、生活型多样性和水分生态类型多样性随放牧强度的加大而降低,但适度放牧增加了羊草杂类草群落的上述多样性指标。群落地上现存量一般随放牧强度的增大而下降,但小针茅群落反之,主要与1年生植物猪毛菜(Salsolacollina)的生物量迅速增加有关。除羊草群落外,其他群落0～10cm地下生物量随放牧强度的变化不显著;放牧显著降低羊草群落和羊草杂类草群落0～30cm地下生物量。多样性和生产力间的关系在群落水平上的趋势是不同的,但放牧影响下内蒙古草原4种群落多样性与生产力总体而言呈线性增加关系;同时两者之间的关系还和采用哪种多样性指标和生产力指标有关,用水分生态类型多样性比物种多样性更能反映与地上地下总生产力间的关系,得到放牧影响下内蒙古草原植物群落地上地下总生物量与水分生态类型多样性的回归方程。     

松嫩平原羊草草甸草原主要植物种群能量积累和分配

在松嫩平原羊草草甸草原,羊草、拂子茅、碱茅和虎尾草各器官热值的季节变化呈波动型,但总的规律是穗＞叶＞茎＞立枯体．4种植物种群地上部能量现存量的季节变化均呈单峰曲线,能量积累量为羊草＞拂子茅＞虎尾草＞碱茅．能量增长率一般呈双峰曲线,第一次峰值出现在抽穗期,第二次在种子成熟期,生长末期出现负值．地上部能量的水平分布规律,不同生育期在各器官中的分配比率不同．4种植物种群能量的垂直分布规律相似,即地上部能量的垂直空间分配格局基本上呈塔形,最大值出现在10-30cm空间内．地下部能量垂直结构由地表至土壤深层呈典型的倒塔形,最大值在0-10cm层．地下部的能量现存量约为地上部的3-4倍。     

刈割留茬高度对大针茅草原群落结构及稳定性的影响

2014—2018年8月在内蒙古锡林郭勒盟毛登牧场大针茅典型草原,以围封为对照,设置2、5和8 cm 3个刈割留茬高度,研究刈割留茬高度对群落结构及稳定性的影响。结果表明: 群落中共出现15科23属27种植物;优势种为大针茅、知母、羊草及糙隐子草,累计相对重要值为76.1%。多年生杂类草15种,一、二年生植物5种,多年生丛生禾草和灌木半灌木植物各有3种,多年生根茎禾草有1种。大针茅等处于群落上层;知母、羊草等植物处于群落中层;糙隐子草、刺穗藜、猪毛菜等植物处于群落底层。刈割造成大针茅及多年生丛生禾草相对重要值降低,使得糙隐子草、刺穗藜、猪毛菜及一、二年生植物相对重要值增加。留茬2 cm降低羊草相对重要值,而留茬5、8 cm使其增加;留茬5 cm增加知母相对重要值,而留茬2、8 cm使其降低;留茬8 cm降低杂类草相对重要值,而留茬2、5 cm使其增加。物种及功能群多样性年度间差异显著。总体上,刈割对物种丰富度无显著影响,对其物种多样性影响较小,但对功能群多样性存在一定影响。表明在刈割过程中,群落各功能群存在一定的补偿作用,使得群落保持相对稳定。刈割使群落稳定性增加,留茬5和8 cm时群落稳定性较大;留茬5 cm时群落变异性较大,而留茬8 cm时最小。留茬8 cm时群落稳定性高且变异性小,能促进群落长期稳定。     

羊草种群生物量分配动态模拟

基于4种密度羊草种群的温室模拟试验,分析了羊草种群地上生物量与地下生物量的动态变化．结果表明：羊草种群的地上生物量与地下生物量随生长期呈增加的趋势,且随密度的增加而增加,但不同密度间羊草地上生物量与地下生物量的相对生长速率没有显著差异;不同密度羊草种群的根冠比随生长进程而增加,但差异不显著,表明环境因子是影响羊草种群根冠比变化的主导因素;单株羊草及羊草种群的地上生物量和地下生物量间存在显著的幂函数关系,但幂函数指数与系数随羊草密度的变化而变化,表明资源竞争引起的微环境差异导致了羊草种群根冠比的动态变化,可为定量研究光合产物分配提供参考．     

Molecular diagnosis for a Tamarix species from two reclaimed lands along the Yellow Sea in Korea inferred from genome wide SNP markers

The taxonomy and phylogenetic relationships of related taxa are important for understanding the biology of a species. Also, spatial distribution of genetic variation may offer insights into history of range shifts and demographic changes. The genus Tamarix L. from the Old World is a taxonomically challenging group that has widely expanded its range in the recent past. We examined genomic diversity patterns and the taxonomic identities of Korean Tamarix species whose taxonomy has remained unresolved. We used a total of 1773 SNP data from genotyping by sequencing for 37 Tamarix plants representing two species; T. chinensis and T. ramosissima to infer species delimitation and the geographic distribution of genomic diversity. Clustering (STRUCTURE; PCA, neighbor joining) and phylogenetic tree results indicated that the two morphologically similar species T. chinensis and T. ramosissima are genetically distinct and the two Korean populations (Sihwa & Songdo) are clustered closely with T. chinensis. Approximate Bayesian Computation based hypothesis testing results suggested that one of the two Korean populations, Songdo might have primarily been derived from the native area, China, followed by range expansion to Sihwa with a secondary admixture event between an established population, Songdo, and a native population, Beijing.     

Reinstatement of traditional mowing regimes counteracts population senescence in the rare perennial Primula vulgaris

Question: Traditional management of grassland verges or ditch banks included mowing as a way to provide additional harvesting of hay. Nowadays, such sites are often left unmanaged, as mowing verges is no longer profitable in modern agricultural systems. Are vulnerable plant species able to withstand competition with the surrounding vegetation and maintain viable populations under these circumstances? How do they respond to reinstatement of traditional mowing regimes? Location: Oedelem, northwestern Belgium. Methods: To investigate the effect of reinstatement of the rare perennial Primula vulgaris, demography and adult plant performance were monitored in a grassland verge between 1999 and 2003 under different mowing regimes. Year transitions between life stages were analysed with matrix population models. To disentangle the contributions of the deviations in different life stage transitions to the variation in overall population growth rate, life table response experiments were used. Results: Both management and year had a strong impact on demographic traits of P. vulgaris. If plots were left unmanaged, lower plant performance and declining population growth rates were observed. While population growth rates differed significantly between mowing regimes, mowing of plots only in July did not differ from mowing in July and October in terms of vegetative and reproductive output of adults. Mowing twice a year appeared to be most efficient in increasing population growth rate both by raising recruitment and growth of individuals into large reproductive adults. Conclusions: Large P. vulgaris populations show a good ability to recover from recent abandonment of traditional management regimes. By mowing twice a year, managers are able to target vital rates that are most influential: growth and flowering of adult individuals.     

太白山太白红杉种群空间分布格局研究

针对研究区太白红杉种群分布特点,设置了15个20 m×20 m样地,采用离散分布理论拟合和聚集强度测定方法,对太白红杉种群空间分布格局进行了比较分析.太白红杉种群空间分布格局属于聚集型,在25m²和100m²面积上聚集强度较大.随海拔上升,聚集强度降低;在分布下限地区,聚集最强的尺度较小,中下部地区较大;阴坡的种群分布聚集强度大于阳坡.随着年龄增加,种群分布由聚集型向随机型过渡,强度减弱;聚集性最强的格局尺度在幼、老龄期为150m²,中龄期则为100m².分布格局受生物学特性、年龄阶段、群落组成、环境因素等影响.在未来保护与利用中,低海拔和阴坡应该适度间伐乔木层非目的树种;在高海拔和阳坡地区,适度间伐灌木,促进群落内团块状更新;育林作业面积应该与聚集性最强的面积相适应.     

The adaptive potential of plant populations in response to extreme climate events

The frequency and magnitude of extreme climate events are increasing with global change, yet we lack predictions and empirical evidence for the ability of wild populations to persist and adapt in response to these events. Here, we used Fisher's Fundamental Theorem of Natural Selection to evaluate the adaptive potential of Lasthenia fremontii, a herbaceous winter annual that is endemic to seasonally flooded wetlands in California, to alternative flooding regimes that occur during El Niño Southern Oscillation (ENSO) events. The results indicate that populations may exhibit greater adaptive potential in response to dry years than wet years, and that the relative performance of populations will change across climate scenarios. More generally, our findings show that extreme climate events can substantially change the potential for populations to adapt to climate change by modulating the expression of standing genetic variation and mean fitness.     

Phylogeography and genetic structure of the orchid Himantoglossum hircinum (L.) Spreng. across its European central–marginal gradient

Aim This study aims to link demographic traits and post‐glacial recolonization processes with genetic traits in Himantoglossum hircinum (L.) Spreng (Orchidaceae), and to test the implications of the central–marginal concept (CMC) in Europe. Location Twenty sites covering the entire European distribution range of this species. Methods We employed amplified fragment length polymorphism (AFLP) markers and performed a plastid microsatellite survey to assess genetic variation in 20 populations of H. hircinum located along central–marginal gradients. We measured demographic traits to assess population fitness along geographical gradients and to test for correlations between demographic traits and genetic diversity. We used genetic diversity indices and analyses of molecular variance (AMOVA) to test hypotheses of reduced genetic diversity and increased genetic differentiation and isolation from central to peripheral sites. We used Bayesian simulations to analyse genetic relationships among populations. Results Genetic diversity decreased significantly with increasing latitudinal and longitudinal distance from the distribution centre when excluding outlying populations. The AMOVA revealed significant genetic differentiation among populations (F_ST = 0.146) and an increase in genetic differentiation from the centre of the geographical range to the margins (except for the Atlantic group). Population fitness, expressed as the ratio N_R/N, decreased significantly with increasing latitudinal distance from the distribution centre. Flower production was lower in most eastern peripheral sites. The geographical distribution of microsatellite haplotypes suggests post‐glacial range expansion along three major migratory pathways, as also supported by individual membership fractions in six ancestral genetic clusters (C1–C6). No correlations between genetic diversity (e.g. diversity indices, haplotype frequency) and population demographic traits were detected. Main conclusions Reduced genetic diversity and haplotype frequency in H. hircinum at marginal sites reflect historical range expansions. Spatial variation in demographic traits could not explain genetic diversity patterns. For those sites that did not fit into the CMC, the genetic pattern is probably masked by other factors directly affecting either demography or population genetic structure. These include post‐glacial recolonization patterns and changes in habitat suitability due to climate change at the northern periphery. Our findings emphasize the importance of distinguishing historical effects from those caused by geographical variation in population demography of species when studying evolutionary and ecological processes at the range margins under global change.     

内蒙古草原退化群落恢复演替的研究I. 退化草原的基本特征与恢复演替动力

 本项研究自1983年起在锡林河中游对放牧退化的冷蒿(Artemisia frigida)占优势的草原群落变型进行封育恢复实验与长期监测。每年在植物生长季以15天为间隔进行取样测定,即每年测定9期,每期做10或20个1m×1m的样方。测定项目包括：群落中各植物种群的地上现存生物量、密度、高度、花(果)枝数等。还采用改进的样方方差法监测植物种群空间分布格局的动态。并同时在保护良好的羊草+大针茅(Leymus chinensis+Stipa grandis)群落中进行测定取得完全对应的数据,作为对照系列。以上两种群落的土壤水分与养分动态的长期监测由本站土壤组承担。根据连续十二年监测数据的分析,对退化草原群落的性质与特征提出以下的认识,并对退化草原恢复演替的驱动因素进行厂探讨。1．草原退化演替阶段是与一定强度的放牧压力保持平衡而相对稳定的群落变形,退化阶段取决于牧压强度与持续的年代。2．当群落退化到冷蒿为主要优势种的阶段时,与原生群落的种类组成相比,只发生一定的数量消长变化,对群落的物种丰富度影响不大。3．退化群落植物种群空间格局的均匀性较高,随着恢复演替的进展,因一些种群斑块增大而使空间不均匀性增强。4．退化群落与其原生群落的种—生物量关系呈对数正态模式,其演替过渡阶段成为分割线段模式,也反映出群落资源分配格局与群落空间格局的关系。5．退化草原的显著特征是植被生产力下降,冷蒿群落的生物量下降到原生群落的30％～40％,家畜嗜食的植物种减少50％～70％总生产力不足原生群落的30％。6．退化群落在自然封育条件下能够迅速恢复的原因,可归结为植物在削除放牧干扰后的种群拓殖能力与群落资源(水分,矿质养分等)的剩余。群落资源条件是种群拓殖的物质基础,从而成为恢复演替的动力。     

Characterisation of Adaptive Genetic Diversity in Environmentally Contrasted Populations of Eucalyptus camaldulensis Dehnh. (River Red Gum)

As an increasing number of ecosystems face departures from long standing environmental conditions under climate change, our understanding of the capacity of species to adapt will become important for directing conservation and management of biodiversity. Insights into the potential for genetic adaptation might be gained by assessing genomic signatures of adaptation to historic or prevailing environmental conditions. The river red gum (Eucalyptus camaldulensis Dehnh.) is a widespread Australian eucalypt inhabiting riverine and floodplain habitats which spans strong environmental gradients. We investigated the effects of adaptation to environment on population level genetic diversity of E. camaldulensis, examining SNP variation in candidate gene loci sampled across 20 climatically diverse populations approximating the species natural distribution. Genetic differentiation among populations was high (F_ST = 17%), exceeding previous estimates based on neutral markers. Complementary statistical approaches identified 6 SNP loci in four genes (COMT, Dehydrin, ERECTA and PIP2) which, after accounting for demographic effects, exhibited higher than expected levels of genetic differentiation among populations and whose allelic variation was associated with local environment. While this study employs but a small proportion of available diversity in the eucalyptus genome, it draws our attention to the potential for application of wide spread eucalypt species to test adaptive hypotheses.     

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