沙地云杉种群调节的研究

 本文运用种群密度调节的-3/2原则研究沙地云杉种群的自疏过程,模拟种群密度变化的动态规律。由于可塑性生长的影响,不同林型中沙地云杉种群的平均胸径、单株平均干重与种群密度关系之间的变化幅度也不相同,但都表现出幂函数的变化特征。运用主成分分析的方法探讨影响沙地云杉种群密度调节的主要因素,表明影响沙地云杉种群自疏过程的主要因子为：坡向、群落类型、坡位、土壤含水量、海拔、土壤平均容重、针叶密度7个因子。分析了沙地云杉种群自疏过程的机制及其在种群密度管理中运用的可能性,对沙地云杉种群的经营管理具有重要的理论与实践意义。     

青冈种群的动态调节初探

本文通过调查统计和实验,对青冈种群动态进行了初步研究,包括种子库动态、种子萌发、无性繁殖以及密度调节等。研究表明,青冈种子量较大,但只有少数能发育成幼苗;有性繁殖和无性的克隆生长相互配合达到种群较高的繁殖效率;种群内个体的自疏定律说明,较成熟(40年左右)的青冈种群的增长速度已减慢。     

浙江省松阳县黄山松种群的密度与生物量动态

 本文研究了浙江省松阳县关山源地区黄山松种群的密度与生物量动态以及它们之间的相互关系。黄山松是该地区森林演替中的先锋种群之一。在演替过程中,黄山松种群的动态可分成三个阶段。大约在黄山松种群入侵次生裸地的最初10年期间,种群的密度和生物量迅速增长(阶段Ⅰ)。此后,种群密度达到饱和,由于自疏作用出现以及其他阔叶树种的入侵,种群密度开始急剧下降,个体平均重量和种群生物量迅速增长(阶段Ⅱ),–3/2自疏定律适用于种群动态的此阶段。随着阔叶树种进入林冠层,虽然个体平均重量仍缓慢增长,黄山松种群的密度和种群生物量逐渐下降直至退出群落(阶段Ⅲ)。但在一些特殊生境中(如裸岩陡坡或山脊),黄山松种群可形成稳定的地形顶极群落,其种群密度、个体平均重量和种群生物量可长期维持相对稳定的状态。     

桤柏混交林种群生物量动态与密度调节

研究了四川省盐亭县桤柏混交林中桤木和柏木种群的生物量动态、密度动态及 种群密度对生物量动态的调节．结果表明,桤木种群生物量在１８ ａ内符合逻辑斯蒂增长, 柏木种群生物量在２０ ａ内呈幂函数增长．而种群密度在 １８ ａ内均呈负幂函数降低在桤 柏混交林中．密度制约是决定种群生物量动态的主要因素,棺木和柏本平均单株生物量较 符合Ｙｏｄａ提出的－３／２自疏定律为快,其自疏系数分别为一２．３３和一３．９７．个体平均生 物量的增长比由密度下降引起的生物量降低快,因此,两种群生物量在密度调节过程中仍 然保持增长状态．其中柏木是生物量增长旺盛的种群．     

缙云山马尾松种群数量动态初步研究

马尾松(Pinus massoniana)种群是我国亚热带森林植被演替的先锋种群之—。研究其数量动态对亚热带森林群落和生态系统的研究有着重要意义。“样地编年序列”的应用为长命多年生植物种群数量动态的研究提供了一条捷径。缙云山马尾松种群,约在7龄前,其密度随时间而增长,其后降低。其间关系可用下式近似表达：(07), 式中,D是种群密度估计值,A是种群年龄。缙云山马尾松种群生物量在灌草从到松阔混交林初期的演替中呈现Logistic增长。符合公式：式中,Bp是种群生物量的估计值,A,e是自然对数的底。在从混交林到常绿阔叶林的演替中,其生物量表现出随时间下降的趋势。在自疏过程中,马尾松种群平均植株生物量与种群密度服从-3/2稀疏定律。符合公式：式中,Bi是平均植株生物量,D是种群密度。导致缙云山马尾松种群数量动态变化的动力,主要是种内光资源竞争引起的自疏和种间光资源竞争引起的他疏。     

濒危植物大花黄牡丹(Paeonia ludlowii)种群数量动态

运用种群静态生命表、存活曲线、生殖力表和Leslie矩阵模型,研究了西藏特有的濒危植物大花黄牡丹种群数量动态过程。静态生命表和种群存活曲线反映出大花黄牡丹在树龄10a之前和20~25a之间分别经历了强烈的环境筛和竞争自疏,20a左右为其生理寿命,35a左右为极限寿命;大花黄牡丹种群的净增长率、内禀增长率和周限增长率较低,表现为衰退型种群;Leslie矩阵模型的模拟结果表明,在20a内种群幼苗数量和总数量呈现出下降趋势,下降了大约30%;大花黄牡丹种群存活表现为Deevey-Ⅰ型,早期个体死亡极高,幼龄苗木严重不足;现行种群数量主要是靠自身的萌蘖繁殖来维持。导致大花黄牡丹濒危的可能原因是大花黄牡丹的生物学特性以及人为干扰。     

濒危植物大花黄牡丹（Paeonia ludlowii）种群数量动态

运用种群静态生命表、存活曲线、生殖力表和Leslie矩阵模型,研究了西藏特有的濒危植物大花黄牡丹种群数量动态过程。静态生命表和种群存活曲线反映出大花黄牡丹在树龄10a之前和20～25a之间分别经历了强烈的环境筛和竞争自疏,20a左右为其生理寿命,35a左右为极限寿命;大花黄牡丹种群的净增长率、内禀增长率和周限增长率较低,表现为衰退型种群;Leslie矩阵模型的模拟结果表明,在20a内种群幼苗数量和总数量呈现出下降趋势,下降了大约30%;大花黄牡丹种群存活表现为Deevey-Ⅰ型,早期个体死亡极高,幼龄苗木严重不足;现行种群数量主要是靠自身的萌蘖繁殖来维持。导致大花黄牡丹濒危的可能原因是大花黄牡丹的生物学特性以及人为干扰。     

长白山岳桦种群格局的地统计学分析

应用地统计学的原理和方法研究了长白山岳桦种群空间分布格局及其空间相关关系,首先通过样方调查数据计算岳桦材积的半变异函数,拟合半变异函数模型,然后根据拟合的最优半变异函数模型,进行空间数据插值、绘制岳桦材积的克立拉图,最后对所得到的不同海拔质海拔岳桦材积的半变异函数图和克立格图进行分析。结果表明,在海拔1650－1700m岳桦材积的半变异函数曲线为球形,其空间分布格局为聚集型,种群呈衰退趋势;海拔1750－2000m岳桦材积的半变异函数曲线为直线形,其空间分布格局为随机型,种群较稳定;在海拔2000－2150m岳桦材积的半变异函数曲线为球形,其空间分布格局为聚集型,种群呈增长趋势,这说明长白山桦整体上有一种向上迁移的趋势,尤其是过渡带中的岳桦表现则为更为明显。     

油松植物种群自疏规律模型的研究

根据植物生长的密度理论和有关生物学假设,推导出一种新的植物各自疏规律模型,即Ｎ＝ｅｘｐ（ａｌｎ＾２Ｂ＋ｂｌｎＢ＋ｃ）,这里Ｎ和Ｂ分别为种群密度和植物种群平均重量或平均胸高断面积,ａ,ｂ,ｃ为参数。将该模型应用于油松种群密度变化规律研究中,证明该模型能很好地拟合实际的观测资料,并且具有表达式简单等特点,因而,该模型是油松植物种群自疏规律的有效描述。     

红花尔基沙地樟子松种群优势度增长动态及自疏规律的研究

用逻辑斯谛模型分析了红花尔基沙地不同类型樟子松种群胸高断面积增长规律,发现从坡底到坡顶,环境容纳量逐渐减小,种群内禀增长率降低,种群胸高断面积最大增长速度逐渐减小,种媾和的特征返回时间逐渐增大。樟子松种群自疏规律为：平均胸径与密度的关系符合负幂函数模型。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.