濒危植物疏花水柏枝残存种群数量及群落特征

为揭示濒危植物疏花水柏枝（Myricaria laxiflora (Franch.) P. Y. Zhang et Y. J. Zhang）残存种群的分布格局及群落结构特征,对三峡大坝下游长江流域疏花水柏枝残存种群的分布地（点军胭脂坝、董市江心岛和枝城官洲岛）开展了物种组成、数量、多样性、区系成分和生活型谱等研究。结果显示,疏花水柏枝残存种群分布地共有植物38科73属83种,群落类型为灌丛,灌木层优势种为疏花水柏枝和秋华柳（Salix variegata Franch.）。疏花水柏枝仅在夏季水淹、冬季露出区域呈团块状分布,为增长型种群类型,群落稳定性较差,点军胭脂坝约为222 300株,枝城官洲岛约为774 700株,董市江心岛约为197 400株。3个分布区物种丰富度指数（S）为10.5～11.5,多样性指数（H）为1.21～1.54,均匀度指数（E）为0.74～0.91,优势度指数（D）为0.53～0.69,表明物种多样性指数均较低。研究区植被符合我国亚热带地区植被区系成分,但生活型谱主要为地下芽植物和一年生种子植物,与热带亚热带沙漠气候植被类型相似。     

神农架极小种群植物庙台槭群落特征及种群动态

种群和群落特征分析是揭示物种濒危处境最有效的途径之一。庙台槭(Acermiaotaiense)是极小种群野生植物,被列为国家二级保护植物。然而,由于对神农架地区庙台槭资源状况和群落特征不清楚,严重制约该物种的保护成效。该研究对神农架地区庙台槭种群及其所在的群落开展调查,揭示群落的物种组成和群落结构;通过分析庙台槭种群的径级结构,绘制静态生命表和存活曲线,并分析种群动态变化指数,揭示庙台槭的种群动态。结果表明:(1)群落内共有木本植物33种,隶属于15科20属,群落内优势种为胡桃楸(Juglansmandshurica)、千金榆(Carpinuscordata)、金钱槭(Dipteroniasinensis)和华榛(Coryluschinensis);(2)庙台槭的相对优势度为2.23%,非群落内优势种;(3)神农架庙台槭分布范围十分狭窄(面积约1.7hm2),种群规模小(79株);(4)庙台槭种群内幼龄个体占比较高(79.75%),更新较好;(5)物种存活曲线属Deevey-II型,种群各龄级的死亡率基本相同,但在幼树阶段死亡率增高,在大树阶段(12.5cm≤胸径<17.5cm)...     

湖南八大公山黄杉种群结构和群落特征研究

利用样方法对湖南八大公山黄杉(Pseudotsuga sinensis Dode)群落进行调查,分析黄杉群落的物种组成、区系特征、径级结构和物种多样性。结果显示,群落内共有维管植物132种,隶属于48科89属。群落垂直结构明显,分为乔木层、灌木层和草本层,黄杉是乔木层的优势种,另有檵木(Loropetalum chinense(R.Br.)Oliver)、马尾松(Pinus massoniana Lamb)和油桐(Vernicia fordii(Hemsl.)Airy Shaw)等主要伴生种,檵木为灌木层优势种,两色鳞毛蕨(Dryopteris setosa(Thunb.)Akasawa)为草本层优势种。群落区系组成以泛热带分布和北温带分布为主,具有明显的亚热带向温带过渡的性质。种群年龄结构可分为稳定型向衰退型过渡和衰退型2个类型,样方中幼苗和幼树极度缺失,中龄和老龄个体居多。黄杉、钩栲针阔混交林的物种多样性高于黄杉纯林,其中灌木层的多样性指数最高,乔木层的物种多样性指数最低。群落冠层郁闭度高造成的幼苗缺失可能是影响其濒危的主要原因,建议采取人为干扰创造林窗、加快繁殖技术研究等措施扩大其种群数量。     

昆嵛山天然赤松种群的数量特征及更新动态

1　前　言赤松(ＰｉｎｕｓｄｅｎｓｉｆｌｏｒａＳｉｅｂ.ｅｔＺｕｃｃ.)天然分布于朝鲜、日本和中国,它在我国的天然分布从黑龙江东南部(宁安、东宁)、吉林东部(长白山)、辽东半岛经山东半岛(昆嵛山、崂山、沂山东部)到江苏东北部云台山区,是我国暖温带沿海地区温性针叶林的主要建群种之一[1]。昆嵛山地处山东半岛东端,位于Ｎ37°16′,Ｅ121°43′附近,是赤松在山东半岛的最集中分布地。赤松林在该地区从山麓一直到海拔800ｍ左右都有分布,并与落叶栎林共同组成该地区的地带性天然次生森林植被[2],在调节生态系统结构与功能方面起到重要作用…     

凤阳山白豆杉种群结构及群落特性的研究

对凤阳山自然保护区白豆杉（Pseudotaxus chienii）种群大小级结构、分布格局及群落特性进行了研究.结果表明,白豆杉种群在福建柏 猴头杜鹃林及猴头杜鹃矮林中生长最为良好,其重要值分别可达5%～10%.在猴头杜鹃矮林中,大小级为增长型,存活曲线为Deevy-Ⅰ型,种群将得到长期发展;在福建柏 猴头杜鹃林中,大小级为衰退型,存活曲线为Deevy-Ⅲ型,但由于幼苗储备量较为丰富,在一定时期内还将保持稳定,在这两种群落类型中,种群呈现集群分布.在常绿阔叶林中,白豆杉的重要值只有0.9%,并且种群大小级为衰退型,存活曲线为Deevy-Ⅱ型,分布格局为随机分布,说明常绿阔叶林不适合白豆杉种群的生长.通过对白豆杉和其他种群的相关分析表明,白豆杉种群与猴头杜鹃、福建柏等呈正相关,而与褐叶青冈、木荷等呈负相关.可以认为,如果凤阳山白豆杉种群的生境能够得到切实的保护,该种群就能长期存活和发展.     

濒危植物小黄花茶种群结构和生存群落特征研究

小黄花茶(Camellia luteoflora Li ex H.T.Chang)是分布极狭的贵州特有植物,本文在群落调查的基础上,研究了其生存群落的特征和种群结构。结果表明:小黄花茶主要分布于毛竹林、竹阔混交林、常绿落叶阔叶混交林等3种群落类型中,其中阔叶林分布最多。小黄花茶的生存群落内,高位芽植物占总数的43.24%;地上芽植物占16.22%;地面芽和隐芽植物占16.89%;一年生植物占6.77%。生存群落物种丰富度等5种多样性指数均为草本层灌木层乔木层;小黄花茶种群结构整体属于稳定型,局部区域处于衰退型。近5年来,小黄花茶种群数量减少了约20%,种群生存面临很大威胁。生存群落中竹类植物的快速扩张,加上人为干扰和动物危害等,是小黄花茶种群受威胁的主要因素。     

浙江九龙山国家级自然保护区伯乐树群落特征及种群结构分析

采用实地踏查及样方法,对浙江九龙山国家级自然保护区6块样地内伯乐树(Bretschneidera sinensis Hemsl.)的分布和群落特征及种群结构进行了初步研究.调查结果表明:伯乐树分布于该保护区内海拔438 ～1 134 m的低山区域,大多呈零星分布,数量少(仅23株)且分布范围狭窄,分布总面积约15 hm2.根据群落外貌和乔木层优势种,可将6个样地分为3种群落类型:落叶阔叶林,主要包括香椿-枫香树群落(Toona sinensis-Liquidambar formosana community)和赤杨叶群落(Alniphyllum fortunei community);针阔叶混交林,主要包括杉木-甜槠群落(Cunninghamia lanceolata-Castanopsis eyrei community)、杉木-木荷群落(Cunninghamia lanceolata-Schima superba community)和马尾松-木荷群落(Pinus massoniana-Schima superba community);杉木-毛竹林,即杉木-毛竹群落(Cunninghamia lanceolata-Phyllostachys heterocycla‘Pubescens' community).在针阔叶混交林中伯乐树生长最好、分布数量最多,在落叶阔叶林中生长较差.根据胸径和株高可将种群结构分为6个径级,其中Ⅰ级幼苗和Ⅱ级幼树数量为0;Ⅲ级和Ⅳ级成年株数量分别占总株数的17.39％和4.35％;而V级成熟株数量最多,占总株数的60.87％;Ⅵ级衰老株数量也占总株数的17.39％.研究结果表明:该伯乐树种群为衰退型种群,幼苗和幼树数量明显不足,因而,应加强人工繁育研究、有效扩大种群规模.     

小陇山国家级自然保护区华山松种群更新动态分析

以种群生命表及生存分析理论为基础,将林木依胸径大小分级,以林木径级结构代替年龄结构,采用分段匀滑技术编制小陇山国家级自然保护区华山松种群静态生命表,对其种群年龄结构、死亡率曲线、损失度曲线、存活曲线、生存函数曲线及其幼苗的更新动态、死亡率和原因进行分析。结果表明:该种群属于增长型,表现出前期增长,中期稳定,后期衰退的特点;该种群的整个生命过程,显示了三次死亡高峰,其中幼苗死亡率较高,以后的死亡率低而平缓,符合种群的自然动态规律,也指出"天保工程"实施的意义和效果;该研究指示了华山松的动态以及种群的变化趋势,对保护区已经实施的生态监测和森林保护有着十分重要的意义。     

辽河源自然保护区油松群落特征及优势种群结构

通过实地踏查,选取辽河源自然保护区内成片的不同年龄的油松天然次生林群落,采用样方法进行群落学特征信息调查,分析研究区的群落区系特征、外貌特征和优势种群结构特征,为油松天然林的保护和抚育管理提供理论依据。结果表明：（1）辽河源自然保护区油松天然次生林群落中共有种子植物41科90属144种,植物种类丰富,具有明显的温带针叶林特征,以地面芽植物为主（60.27%）,中叶植物占优势（82.19%）;区系组成与温带的成分关系最为密切。（2）优势种油松在研究区构成成片的不同林龄的纯林,幼龄林的群落中小径级（Ⅰ~Ⅲ）个体所占比例较高（75%）,随着年龄增加,大径级个体所占比例逐渐增加,成熟林径级呈正态分布,各龄组高度级和冠幅的变化趋势与径级相似。（3）4个龄组幼苗储备都很丰富,均占更新层的58%以上,成熟林中幼苗所占比例达90%,但幼树比例较少,群落的更新状况不佳,但潜在更新能力较强。     

植物种群与群落结构动态量化分析方法研究

植物种群与群落结构动态量化分析方法研究＊陈晓德（西南师范大学亚热带生物地理研究所重庆４００７１５）＊国家“八五”科技攻关计划（８５－１９－０１－１１－０２）,国家自然科学基金重点（３９３３００４０）资助项目。收稿日期：１９９５－１０－１６,修改稿收到...     

Characterization and antioxidant activity of Ginkgo biloba exocarp polysaccharides

Ginkgo biloba exocarp polysaccharide (GBEP) was obtained by hot water extraction, the crude polysaccharide was deproteinized by Sevag method and fractionized by a DEAE Sepharose fast flow anion-exchange column. Five fragments were obtained, including neutral polysaccharide (GBEP-N) and four acidic polysaccharides (GBEP-A1, GBEP-A2, GBEP-A3 and GBEP-A4). GBEP-N and GBEP-A3 were further purified by Superdex 200 gel column chromatography. The resulted two fractions GBEP-NN, and GBEP-AA were characterized by FT-IR, and HPGFC (high pressure gel filtration chromatography). Monosaccharide composition was determined by RP-HPLC method of precolumn derivatization with 1-phenyl-3-5-pyrazolone. GBEP-NN was mainly composed of rhamnose, arabinose, mannose, glucose and galactose, while GBEP-AA was mainly made up of mannose, rhamnose, glucuronic acid, galacturonic acid, galactosamine, glucose, galactose, xylose, arabinose, and fucose. The crude GBEP exhibited certain antioxidant activity. At the concentration of 5 mg/mL, the hydroxyl radical scavenging effect of GBEP was 90.52%, greater than 77.37% for the positive control ascorbic acid.     

A novel substance with allelopathic activity in Ginkgo biloba

Ginkgo (Ginkgo biloba) is one of the oldest living tree species and has been widely used in traditional medicine. Leaf extracts of ginkgo, such as the standardized extract EGb761, have become one of the best-selling herbal products. However, no bioactive compound directed at plants has been reported in this species. Therefore, we investigated possible allelopathic activity and searched for allelopathically active substances in ginkgo leaves. An aqueous methanol leaf extract inhibited the growth of roots and shoots of garden cress (Lepidium sativum), lettuce (Lactuca sativa), timothy (Phleum pratense) and ryegrass (Lolium multiflorum) seedlings. The extract was purified by several chromatographic runs and an allelopathically active substance was isolated and identified by spectral analysis to be the novel compound 2-hydroxy-6-(10-hydroxypentadec-11-enyl)benzoic acid. The compound inhibited root and shoot growth of garden cress and timothy at concentrations greater than 3 μM. The activity of the compound was 10- to 52-fold that of nonanoic acid. These results suggest that 2-hydroxy-6-(10-hydroxypentadec-11-enyl)benzoic acid may contribute to the allelopathic effect caused by ginkgo leaf extract. The compound may also have potential as a template for the development of new plant control substances.     

Community characteristics and population structure of dominant species of Abies fargesii forests in Shennongjia National Nature Reserve

In this paper, the community composition of Abies fargesii and the population structure of dominant species in this community were studied using a sampling plot method. The research plot was located in Shennongjia National Nature Reserve, China. Results showed that the appearance of the community was characterized by evergreen phanerophytes with microphyllous (or mesophyllous), coriaceous and single leaves. The vertical structure of the community can be clearly divided into 4 layers: arbor layer, shrub layer, herb layer and developed moss layer. Abies fargesii population was a developing population as there were more seedlings and young trees than old trees. Saplings were found more frequently in gaps than under the close canopy, which indicated a pattern of gap regeneration. The height structure of Abies fargesii population presented a reversed pyramid shape. Crown size structure of the population showed a typical reversed J shape. The relation between crown size and DBH (diameter at breast height) was closer than that between crown size and height.     

The effects of disturbance on the population structure and regeneration potential of five dominant woody species – in Hugumburda‐Gratkhassu National Forest Priority Area,North‐eastern Ethiopia

Vast areas of forests in North‐eastern Ethiopia have been replaced by cropland, shrub land or grazing areas. Thus, information about how vegetation composition and structure varies with disturbance is fundamental to conservation of such areas. This study aimed to investigate the effects of disturbance on the population structure and regeneration potential of five dominant woody species within forest where local communities harvest wood and graze livestock. Vegetation structure and environmental variables were assessed in 50 quadrats (20 m × 20 m). In most of both disturbed and undisturbed treatments, Juniperus procera was the highest contributor to the basal area of the forest, while that of Olinia rochetiana was the lowest. Analysis of population structure showed high density at lower Diameter at Breast Height (DBH) and low density at higher DBH classes. Undisturbed forest treatments had 84% canopy cover, 22 m mean vegetation height and a density of 1320 trees of dominant species and 1024 seedlings/saplings ha^?1. In disturbed habitats, canopy cover (73%), mean vegetation height (18 m) and density of dominant trees and saplings were significantly lower than in undisturbed habitats. Thus, to ensure species, survival and maintain species diversity managed use of the protected area is essential.     

Forest characteristics and population structure of a threatened palm tree Caryota obtusa in the karst forest ecosystem of Yunnan,China

中国云南石灰岩山地森林系统中受到威胁的董棕的森林特征和种群结构 别具魅力的董棕(Caryota obtusa)属于棕榈科(Arecaceae)的树种,在中国西南地区、印度、缅甸、泰国、老挝和越南有自然分布。董棕是一个具有重要经济价值且受到人为活动威胁的物种,其在云南的一些石灰岩山地乔木层占据优势。本研究的目的是阐明在云南石灰岩山地森林生态系统中董棕的群落结构、物种多样性、种群现状及其更新动态。为了全面深入的调查董棕群落,我们在云南南部10个县设置56个样方。根据样方数据,我们分析了群落的垂直结构、物种组成和种群结构,并对当地村民进行问卷采访记录了长期以来人为活动对董棕林的干扰情况。研究结果表明,董棕棕榈林分布在石灰岩山坡和沟谷,有7个群落类型。每个群落的垂直结构明显,分为乔木层、灌木层和林床。群落物种组成丰富,各群落类型的木本物种和草本物种的香农-维纳多样性指数均在2.1–3.8。董棕在胸径级上的分布为多峰型,属间歇性更新,且依赖于一定的自然干扰,董棕小树主要在无人为干扰或人为干扰小的群落中出现,重度人为干扰严重地阻碍了董棕的更新,其次的中度人为干扰也给董棕的更新带来了一定的困难。     

城市地表硬化对银杏生境及生理生态特征的影响

城市大规模的地表硬化改变了城市环境,影响了城市中植物的正常生长。利用土壤水分温度仪ECH2O测定了不同硬化地表下土壤含水率(WCS)和土壤温度(Ts),利用LI-6400光合仪,并配备荧光叶室,测定了银杏生长的环境因子和银杏生理生态参数。研究结果表明,城市地表硬化对银杏生长环境的影响主要表现为空气温度(Ta)和土壤温度(Ts)升高,空气相对湿度(RH)和土壤含水率(WCS)下降,银杏对地表硬化的生理生态响应表现为净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)降低,叶面饱和水汽压亏缺(VPDL)增大,叶片含水率(LWC)下降;最大光化学效率(Fv/Fm)和PSⅡ实际光合电子传递量子效率(ΦPSⅡ)下降,硬化程度越高,银杏受到的胁迫越重;受城市地表硬化的影响,银杏吸收的光能用于光化学反应的比例减少,而用于热耗散和荧光耗散的比例增加,城市硬化地表上银杏的水分利用效率(WUE)、光能利用效率(LUE)和CO2利用效率(CUE)明显下降。     

Maintenance and natural regeneration of Castanopsis sclerophylla populations on islands of Qiandao Lake Region, China

Qiandao Lake was formed in 1959 when the Xin'anjiang Hydroelectric Plant was built. There are 1078 islands with areas larger than 2500 m² and many smaller islands. The population structure of C. sclerophylla was investigated to reveal whether it can sustain on islands so as to provide suggestions for ecological restoration. C. sclerophylla can be found on islands with a water level higher than 105.4 m, whereas the highest water level of Qiandao Lake was 108.2 m. Number of individuals on islands, with a range from 4 to more than 4000, was significantly related to the areas or altitudes of the islands. Population structure indicated that, at genet level, C. sclerophylla on large and most medium-size islands could be self-sustainable, whereas on small and some medium-size islands C. sclerophylla could not be self-sustainable and would decline. However, at the ramet level, almost all the C. sclerophylla populations, no matter on large, medium or small islands, seem to be self-sustainable. Further analysis indicated that re-sprouting contributed to more than 81.6% of the genets and 94.8% of the shoots formed after the creation of the Lake. The results above indicated that although small size of populations exist on some islands, these populations might be sustained via vegetative reproduction, especially re-sprouting, for a long period under the present situation without human disturbance and dramatic environmental changes. Conditions of most islands meet the standards necessary for the survival and growth of C. sclerophylla. Therefore, lack of seed or seedling is the main limitation for the ecological restoration of evergreen broad-leaved forests on islands of Qiandao Lake. However, that no individual was reproduced from sexual reproduction on some medium and small islands indicates that environmental condition might be another limiting factor for restoration.     

Genetic population structure, fitness variation and the importance of population history in remnant populations of the endangered plant Silene chlorantha (Willd.) Ehrh. (Caryophyllaceae)

Habitat fragmentation can lead to a decline of genetic diversity, a potential risk for the survival of natural populations. Fragmented populations can become highly differentiated due to reduced gene flow and genetic drift. A decline in number of individuals can result in lower reproductive fitness due to inbreeding effects. We investigated genetic variation within and between 11 populations of the rare and endangered plant Silene chlorantha in northeastern Germany to support conservation strategies. Genetic diversity was evaluated using AFLP techniques and the results were correlated to fitness traits. Fitness evaluation in nature and in a common garden approach was conducted. Our analysis revealed population differentiation was high and within population genetic diversity was intermediate. A clear population structure was supported by a Bayesian approach, AMOVA and neighbour-joining analysis. No correlation between genetic and geographic distance was found. Our results indicate that patterns of population differentiation were mainly caused by temporal and/or spatial isolation and genetic drift. The fitness evaluation revealed that pollinator limitation and habitat quality seem, at present, to be more important to reproductive fitness than genetic diversity by itself. Populations of S. chlorantha with low genetic diversity have the potential to increase in individual number if habitat conditions improve. This was detected in a single large population in the investigation area, which was formerly affected by bottleneck effects.     

Ginkgo biloba extract suppresses endotoxin-mediated monocyte activation by inhibiting nitric oxide- and tristetraprolin-mediated toll-like receptor 4 expression

Monocytes expressing toll-like receptor 4 (TLR4) play a major role in regulating the innate immune response and are involved in systemic inflammation. Previous studies have shown that Ginkgo biloba extract (GBE) may act as a therapeutic agent for some cardiovascular and neurological disorders. The objective of this study was to determine whether GBE could modulate immunity in human cells. The monocytic cell line THP-1 was used. Enzyme-linked immunosorbent assay results showed that lipopolysaccharide (LPS) induces the expression of monocyte chemotactic protein-1 (MIP-1), tumor necrosis factor-α, stromal cell-derived factor-1, and MIP-1α, and this induction may be repressed by GBE treatment due to TLR4 blockade. The Griess reagent assay and western blot analysis showed that GBE-mediated inhibition of TLR4 expression was associated with the activation of mitogen-activated protein kinase and production of nitric oxide (NO). Actinomycin D chase experiments demonstrated that GBE decreased the TLR4 mRNA stability in cells. Confocal microscopy and real-time polymerase chain reaction showed that GBE induced the expression of intracellular tristetraprolin (TTP). Transfection with TTP siRNA reversed the effects of GBE in naïve or TLR4-overexpressing cells. Treatment with SNAP (an NO donor) may increase intracellular TTP expression in cells. Immunoprecipitation analysis showed that GBE mediates TTP activation and increases the interaction of TTP with the 3′ untranslated region (UTR) of TLR4 mRNA by regulating NO production. Our findings indicate that GBE could decrease the sensitivity of monocytes to LPS. Utilizing TTP to control TLR4 expression may be a promising approach for controlling systemic inflammation, and GBE may have potential applications in the clinical treatment of immune diseases.