东祁连山不同退化阶段高寒草甸群落结构与植物多样性特征研究

采用样方法对东祁连山地区不同退化程度高寒草甸植物群落进行了调查,对群落结构、物种组成和群落生产力进行了分析,并运用α多样性、β多样性等指标研究了其物种多样性变化.结果表明,1)研究样地内共有植物种13科27属40多种,从未退化-轻度退化-中度退化-重度退化-极度退化,不同退化演替阶段的优势种分别为线叶嵩草 禾草、线叶嵩草 珠芽蓼、珠芽蓼 线叶嵩草、珠芽蓼 杂类草、平车前 杂类草.2)随退化程度的加剧,草地总盖度降低,优良牧草生物量减少,而毒杂草的比例逐渐上升,草地质量下降;地上、地下生物量均明显降低,地上生物量远低于地下生物量,分布在各层的植物根量越来越少,地下根系具有浅层化特点.3)高寒草甸植物群落α多样性指数基本上与均匀度、丰富度指数呈正相关,与生态优势度指数呈负相关;群落的物种丰富度在中度退化阶段最高,但多样性指数和均匀度指数在重度退化阶段最高,群落多样性更多地受均匀度的影响.4)随退化程度的加剧,样方内微生境或资源异质性减小,样方间异质性增大,从而导致β多样性增加;各草地植物群落物种替代速率由大到小的顺序为重度退化-极度退化>未退化-轻度退化>中度退化-重度退化>轻度退化-中度退化.     

甘肃尕海湿地退化过程中植物生物量及物种多样性变化动态

以尕海湿地区内的典型沼泽泥炭和沼泽化草甸为研究对象,采用空间序列代替时间序列的方法,研究了尕海湿地退化过程中植物生物量及物种多样性的变化特征。结果表明：在尕海湿地退化过程中,湿地的地上、地下生物量均显著降低,但地下生物量降低幅度较大,地下、地上生物量比例系数呈减小趋势;尕海湿地退化过程中植物群落特征发生明显变化,具体表现为,泥炭沼泽退化过程中的优势种从未退化时乌拉苔草（Carex meyeriana）演变为退化时的问荆（Equisetum arvense）。沼泽化草甸退化过程中的优势种从未退化时藏嵩（Kobresia tibetica）演变为轻度和中度退化程度时的青藏苔草（Carex moorcroftii）和密毛白莲蒿（Artemisia sacrorum.var mess-rschmidtiana）;重度退化程度时仅有零星的冷蒿（Artemisia frigida）、珠芽蓼（Polygonum viviparum）;主要伴生种表现为湿生植物逐渐消失,中、旱生毒杂草逐渐增加。泥炭沼泽的植物物种丰富度和多样性指数呈增加趋势,沼泽化草甸为先增加后降低,均匀度指数恰好相反;群落相似性系数逐渐降低。说明尕海湿地原有植物群落物种多样性分布格局向杂草型退化方向演替,建议减少放牧压力,采取人工措施促进尕海湿地生态功能恢复。     

黄河源区不同退化阶段高寒草甸植被特征

研究不同退化阶段高寒草甸植被演替以及草地生产力特征,对进一步探究高寒草甸退化机制,科学评估草地状况和退化草地恢复重建具有重要意义。采用野外植被调查,对黄河源区高寒草甸未退化、轻度退化、中度退化、重度退化和极度("黑土型")退化草地的植被群落结构、物种组成及生物量等植被特征进行了研究。结果表明:黄河源区高寒草甸共有植物48种;随着高寒草地退化程度的加剧,线叶嵩草、垂穗披碱草、高原早熟禾等优势植物种呈下降趋势,黄帚橐吾、青海刺参和臭蒿等则呈上升趋势。随着高寒草地退化程度的加剧,植被群落物种优势度指数、多样性指数和丰富度指数均呈下降趋势,均匀度指数则无明显变化。将高寒草地植被划分为禾本科、莎草科、龙胆科、菊科、杂类草和毒害草六类,随着草地退化程度的加剧,禾本科、莎草科和龙胆科牧草比例显著降低,菊科和毒害草比例则显著升高。高寒草甸不同退化阶段地上生物量呈"V"形变化,轻度退化草地地上生物量最高,显著高于其他阶段。中度退化草地最低,与未退化、轻度退化和重度退化草地之间差异显著。高寒草甸地下生物量80%以上集中于表层土壤,随着高寒草地退化程度的不断加剧,地下生物量显著降低。     

东北草地围封恢复过程中物种组成及其多样性比较

为了了解东北草地退化生态系统恢复现状、揭示生态系统恢复过程中的内在机制,试验采用单位面积取样方法,对围栏封育9年的扎龙西甸子草甸草原不同演替系列典型群落的物种组成及其多样性进行了比较研究。结果表明:西甸子草甸草原沿高低梯度分布6种群落类型,群落中物种数量、生活型、所属科均存在一定差异并表现出一致的规律性;物种丰富度指数在杂类草群落中最高,芦苇群落中最低;物种均匀度指数在单优的羊草群落、芦苇群落中较低,在非单优群落中较高;辛普森多样性指数、香农-威纳多样性指数在杂类草群落最高,芦苇群落中最低。物种数量、物种丰富度、辛普森多样性指数、香农-威纳多样性指数在各演替系列间均较好地符合y=abx(a、b为常数;P0.01)指数函数关系。草甸草原围封后存在3条不同的演替途径,羊草+朝鲜碱茅群落、羊草+杂类草群落、羊草+芦苇群落逐渐被以羊草为优势种的群落代替,表现为草原恢复,反之则草原退化。在草原退化或者恢复过程中群落类型及其主要种群都出现了明显的更替现象。     

德令哈-哈拉湖沿线不同生境下群落的物种组成及其多样性

为探讨柴达木盆地的群落物种的多样性和空间分布格局,本文以德令哈-哈拉湖沿线区域为研究对象,测定了5种不同生境下群落的物种组成和多样性指数,并分析了不同生境下群落物种多样性与海拔的关系。结果表明：该区域共记录了79种植物,菊科、禾本科、豆科、十字花科为当地的优势科种。不同生境类型的物种多样性具有相似性,但也存在差异性。从物种组成的群落相似性结果来看,高寒垫状植被与高寒金露梅（Potentilla fruticosa）灌丛草甸的物种组成相似性最高,而与高寒嵩草（Kobresia myosuroides）、杂类草草甸的物种组成相似性最低。随着海拔升高,群落物种丰富度和多样性呈先降低后增加的趋势,但均匀度保持稳定;中海拔区域的群落物种多样性最高,低海拔区域的群落物种多样性略高于高海拔区域,而造成不同生境群落物种组成和多样性差异的主要原因是水热条件和物种竞争力。     

高寒草甸植物群落退化与土壤环境特征的关系研究

为了阐明高寒草甸群落特征和物种多样性的变化特征及其与土壤环境因子的关系,本文研究了未退化、轻度、中度、重度和极度退化程度高寒草甸群落特征和物种多样性,以及各退化等级的土壤温湿度及其化学性质。结果表明,随着退化程度的加剧,高寒草甸群落高度、盖度、生物量和演替度均逐渐降低,而鼠类活动先加剧后减缓;物种多样性指数逐渐降低,丰富度指数和均匀度指数均先升高后降低;土壤温度逐渐升高而湿度逐渐降低;土壤有机碳含量和全氮含量均逐渐降低,而土壤pH值则逐渐升高。群落演替度、土壤湿度、土壤有机碳和全氮含量与物种多样性表现出正相关,而有效鼠洞数、土壤温度和土壤pH值则与物种多样性表现出显著的负相关。     

放牧强度对高寒草甸物种多样性和生产力关系的影响

放牧对草地植物群落结构和功能的影响深远而复杂,为了探讨高寒草甸植物物种多样性和生产力受长期不同放牧强度的影响,在高寒草甸草地群落设置不同放牧强度试验,分析不同放牧强度下植物群落物种多样性和生产力及其关系的变化,以期为高寒草甸生态系统的可持续利用和管理提供理论依据。结果表明,随着放牧强度的增大,草地植物群落的Shannon-Wiener指数和Margalef丰富度指数先增大后减小,高寒草甸植物群落的优势物种由禾本科向莎草科和杂类草转变,其中禾本科植物的优势度从70%降到12%,杂类草植物的优势度由13%增大到82%,植物群落的地上净初级生产力(ANPP)逐渐减小,轻度放牧处理减少了61.56%,中度放牧处理减少了76.75%,重度放牧处理减少了78.72%,重度放牧处理地下净初级生产力(BNPP)比禁牧处理降低了90.06%,轻度放牧、中度放牧处理地下净初级生产力与禁牧处理无明显差异,3个处理下的地下净初级生产力(NPP)总体保持稳定。放牧强度增大会导致植物群落高度下降,中度放牧处理会增加植物群落中莎草科植物的分蘖数。高寒草甸上植物群落的Pielou指数和NPP负相关,Margalef指...     

不同放牧强度对西藏邦杰塘高寒草甸土壤种子库的影响

通过研究不同放牧强度下地上植被群落的物种组成、植物生活型、土壤种子库物种种类和种子数量等特征,探讨了地上植被与土壤种子库之间的关系及种子库在地上植被群落构建中的作用,拟为高寒草甸的管理,特别是高寒地区退化生态系统的恢复与重建提供参考。结果表明：土壤种子库物种多样性指数和丰富度指数在围栏样地和中牧样地之间差异不显著。重牧样地土壤种子库物种多样性指数和丰富度指数显著低于中牧样地（P<0.05）;围栏样地、重牧样地、中牧样地土壤种子库密度表现为重牧 >围栏 >中牧,其中重牧样地土壤种子库密度显著高于中牧样地（P<0.05）,达4952.7粒·m^-2;中牧样地和围栏样地的种子库和地上植被之间相似性较低,二者的地上植被与土壤种子库Sorensen相似性指数分别为0.48和0.44。重牧样地上嵩草属（Kobresia）植物严重退化,地上植被群落和土壤种子库均以杂类草物种占优势,地上植被与土壤种子库表现出较高的相似性。因此,对于有退化趋势的嵩草草甸,适当的围栏并考虑利用本地多年生优良牧草种子进行补播将是有利的;嵩草高寒草甸土壤种子库种子主要集中在0~5cm,且各样地中种子数量均随着土壤深度的增加而减少。     

扎龙湿地恢复过程中物种组成及其多样性比较

为了了解扎龙湿地实施长效补水机制后生态系统恢复现状,揭示生态系统恢复过程中的内在机制,试验采用单位面积取样方法,对扎龙湿地干湿交替带不同演替系列过程中典型群落的物种组成及其多样性进行比较。结果表明:扎龙湿地干湿交替带沿高低梯度分布6种群落类型,群落中物种数量、生活型、所属科均存在一定差异并表现出一致的规律性;物种丰富度指数在杂类草群落最高,芦苇群落中最低;物种均匀度指数在单优的羊草群落、芦苇群落中较低,在非单优种群落中较高;辛普森、香农-威纳多样性指数在杂类草群落最高,芦苇群落中最低。物种数量、物种丰富度指数、辛普森和香农-威纳多样性指数在各演替系列间均较好地符合y=a+bx(P0.01)直线关系。说明实施长效人工补水后,湿地缺水现象得到根本缓解,以中旱生植物(羊草)为优势种的群落将逐渐被以水生植物(芦苇)为优势种的群落所代替,群落中物种的组成和多样性具有明显的干湿更替过程。     

不同退化程度高寒草甸草地生物量及土壤养分差异

对三江源区不同退化程度高寒草甸草地植物群落、生物量及土壤养分差异进行了研究,结果表明:随着退化程度的加重,高寒草甸草地的群落组成发生了很大的变化,以莎草科植物为主的植物群落向阔叶型杂类草群落演替;物种多样性、均匀度指数均有下降趋势;地上、地下生物量,土壤养分均呈现明显下降趋势.     

国内生态恢复研究进展

本文介绍了生态恢复的研究进展,从生态恢复的定义、退化生态系统的指标等方面进行阐述,重点对国内在恢复生态学方面的进展做了介绍。对当前的人工草地、草地农业的研究情况做了一些概述。     

国内生态恢复研究进展

本文介绍了生态恢复的研究进展,从生态恢复的定义、退化生态系统的指标等方面进行阐述,重点对国内在恢复生态学方面的进展做了介绍.对当前的人工草地、草地农业的研究情况做了一些概述.     

论宋代对《史记》中管仲形象的接受

宋代,对士大夫来说这一可遇而不可求的特殊历史时期,成就了他们独特的人格结构和精神世界。他们对历史人物的看法尤异于前人,其中对管仲形象的接受就发生了颠覆性的变化。而宋人重新解读管仲的立足点也是宋代《史记》评论中普遍倾向的批评视角。     

Veterinary pathology in Europe in the light of the congresses of the European Society of Veterinary Pathology in the last decade

This paper presents the main trends in the activity of European veterinary pathologists in the context of their oral presentations (plenary lectures and short presentations) and posters provided during annual meetings of the European Society of Veterinary Pathology (ESVP), in the decade 1997-2006. It was found that the issue that was most often brought up in the meetings was organ pathology (566 presentations). Infectious and parasitical diseases were only slightly less frequent (548 presentations). Oncology was another common issue (404 presentations). During this decade, 52 plenary lectures were presented, 765 oral presentations and 1 072 posters. Altogether, 1 889 presentations were made, which is between 127 and 238 per year. Research by Polish scientists accounted for 3.16% of all presentations. Additionally, the subject matter discussed at the annual meetings is analysed, and the trends in the development of veterinary diagnostic pathology and broad pathology education are indicated. It is shown that veterinary pathology enhances knowledge in the field of veterinary medicine by fulfilling a cognitive and diagnostic role.     

Application of the log-linear model in the prediction of the antinuclear antibody test in the dog

To find possible associations between antinuclear antibody (ANA) pattern, ANA titer, and certain clinical changes and clinical laboratory test results in dogs, the veterinary medical records of 111 ANA-positive and 126 ANA-negative dogs were examined. Variables could not be found that had significant associations with ANA pattern (unlike the results in persons), because of the predominance of 2 patterns. A log-linear model for ANA titer adequately fit the observed frequency and included 2-way interactions between titer and polyarthritis, titer and hematologic disorders, and polyarthritis and lymphadenopathy.     

Physiological Changes in the Concentrations of Biotin in the Serum and Milk and in the Physical Properties of the Claw Horn in Holstein Cows

Physiological changes in the concentrations of biotin in the serum and milk and in the physical properties of the claw horn were examined in Holstein cows. A lower concentration of biotin in the serum and a higher concentration of biotin in milk were found during early and late lactation and during the dry period, and a significant (p<0.05) inverse correlation was found between serum and milk biotin concentrations. A high moisture content and a low level of hardness of the claw horn were found during mid-lactation. Our results indicate that change in the serum biotin concentration probably results from the loss of biotin in the milk of cows during each stage of lactation and also confirm that the moisture content and hardness of the claw horn undergo physiological changes.     

Evidence for the non-involvement of the uterus in the lifespan of the corpus luteum in the cyclic dog

Progesterone levels in peripheral blood of dogs were analysed during the cycle in which hysterectomy (n = 5) or sham surgery (n = 3) was performed as well as during the cycle of dogs (n = 5) hysterectomized at least one year prior to this study; the data were compared with the findings in control dogs (n = 3). The averages of the duration of the luteal period observed in the three experimental groups were not significantly different from those of control dogs. Immediately after surgery, the progesterone level decreased from 25 to 50% of the presurgical level, but returned to presurgical level in about four days. Prolactin levels were elevated for about 30 h after surgery. Nevertheless, the averages of the mean prolactin levels for each animal during the luteal period of the experimental groups were not significantly different from those of control dogs. It is concluded that in the dog, the uterus is not involved in the lifespan of the cyclic corpus luteum.     

The role of noradrenaline in the generation of the preovulatory LH surge in the ewe

Increasing plasma estrogen (E) levels during the follicular phase of the estrous cycle trigger the pre-ovulatory surge of gonadotropin-releasing hormone (GnRH)/LH. Noradrenaline (NA)-producing cells of the brain stem are involved in regulating GnRH cells and project to the preoptic area (POA) and bed nucleus of stria terminalis (BnST). Input to GnRH cells may be direct or indirect, via relay neurons in the POA/BnST. To investigate this, we ascertained whether an ₁-adrenergic antagonist would block/delay the LH surge in ovariectomised (OVX), E-treated ewes. E benzoate (EB) (50 μg) was injected (i.m.) and Doxazosin (100 nmol/h) or vehicle was infused into the third ventricle 2–26 h after EB injection. Doxazosin reduced the magnitude of the LH surge, but did not affect timing. To determine if NA is released in the POA/BnST of cyclic ewes, we immunostained dopamine-β-hydroxylase (DBH) in terminal fields. Reduced numbers of varicosities staining for DBH indicates release of NA. The number of varicosities immunostained for DBH was reduced in the dorsal and lateral BnST during the follicular phase and during the preovulatory LH surge compared to the luteal phase. These data suggest that noradrenergic mechanisms are involved in generation of the GnRH/LH surge via projections to the BnST and relay to GnRH cells. Since Doxasozin reduced the magnitude of the LH surge in the E-treated OVX ewe, and release of NA in cyclic ewes occurred during the follicular phase of the estrous cycle, we speculate that NA is a permissive factor in surge generation. Thus, increased noradrenergic activity is not a trigger mechanism for initiation of the surge.