黄土高原林草植被建设的地带性特征

 针对黄土高原现有人工林草植被存在的主要问题,依据天然植被地带性分布规律和实测资料,分析了以水分为主的生态条件及林草植被对水分利用的地带性特征,提出了黄土高原林草植被建设的群落学原理和关键技术。即：依据植被地带分布规律指导人工林草植被建设;选择地带性植被优势种作为主要造林种草的植物种;模拟天然植被结构实行乔灌草复层混交是快速建造稳定植被的科学途径。根据一些“适地适树”树种并不能正常成林的现象,提出造林应强调“适地适林”的原则,同时给出适宜黄土高原不同植被地带林草植被建设的主要树草种和伴生种或四旁绿化树种。     

东北珍贵阔叶树适地适树的研究

本文以森林类型为基础,利用数值分析法对东北地区珍贵阔叶树种适地适树进行了研究。白石砬子自然保护区可划分为3个森林类型组和8个森林类型,用逐步回归和立地指数法进行树种立地生产力评价,结果表明A层土厚、坡向、坡度、土壤湿度等是影响人工林生长的主导因子。在阔叶红松混交林,造林树种选择顺序为紫椴、裂叶榆、黄波罗、胡桃楸、水曲柳;而在阔叶杂木林,则是紫椴、胡桃楸、裂叶榆、黄波罗、水曲柳。     

浅析造林中对适地适树栽植技术的应用效果

本文着重分析了适地适树栽植技术在造林中应该遵循的原则:与当地气候环境相适应、选用技术过关人员调研与当地土质相适应和提高树木适应环境能力的原则,并提出进行适地适树栽植技术的有效方法:立地类型划分决策法和模糊决策法,以供广大读者参考。     

辽宁省冰砬山森林立地分类的研究

森林立地的研究是人工林集约经营的基础,正确地选择宜林地,科学造林,真正做到适地适树,必须进行森林立地分类。森林立地分类应是以现代森林生态学和生态系统理论为依据,研究植被(立木、下木、地被物)和地形、植被与土壤以及地形和土壤的关系。在揭     

油茶的分布及其适应性

油茶是重要的木本油料植物。油茶物种繁多,分布广,适应性强,但是不同物种的油茶,其分布范围不同,对环境条件的要求也不同。发展油茶生产,应考虑到种的适应性,做到因地制宜适地适树。     

十个树种生长节律与环境

前言研究主要用材树种生长节律,其目的在于了解树种的生长特点,分析气候条件及其相互关系的规律,为北亚热带气候条件下的主要造林树种的适地适树提供指导性依据;通过对同一树种不同生长阶段的特殊性的了解,为林业生产的抚育管理等措施的实施在时间上的合理性和科学性方面提供理论依据。1982年我们对北亚热带地区的10个主要用     

半干旱区四种针叶林蒸腾作用的研究

樟子松(Pinus sylvestris var. mongolica)等是北方重要的绿化树种,已有离体称重法测定了其蒸腾速率及其与气候因子的关系。但是,由于土壤湿度是影响林木蒸腾的重要因子,因而,我们在查明林下土壤水分动态的同时,直接测试了活体的蒸腾速率的日季变化,并且估算了三种针叶林的蒸腾量,为适地适树造林提供科学依据。     

江西省不同类型退化荒山生态系统植植被恢复与重建措施

对江西省5种不同类型退化荒山生态系统进行综合治理,开展植被恢复与重建技术及理论研究,研究结果表明：优选的植物组合及合理的配置并辅以工程措施是快速启动植被恢复进程,控制水土流失、重建退化荒山生态系统的有效措施。一林多用的树种组合,合理的生物体系设计和针、阔叶树种混交是改良地力、改善环境,促进退化荒山生态系统进行演替的优良途径。先进造林技术的应用和林农牧业结合的复合经营方式是提高综合治疗效益,促进并持续生态恢复过程稳定的先决条件。     

江西植被类型及其历史比较

本文根据江西植被研究的相关文献,梳理了以下问题:(i)建议将两类混交优势树种重要值之差小于或等于这两类优势树种重要值平均值50％的植被类型确定为混交林.(ii)常绿阔叶林、针叶林、落叶阔叶林、针叶阔叶混交林群系名称应采用单一优势树种原则处理并命名,如“南方红豆杉针阔混交林”.(iii)仅当竹林以及针叶林的郁闭度0.1以...     

基于遥感与实地调查对潜在可造林区乔木林和灌草地的比较

气候变化引起祁连山东部地区可适植被类型改变,探究植被类型转换的效果对生态环境可持续发展十分重要,但其转换方式及效果仍有待研究,此外传统植被调查的方法有诸多局限性,不能满足大尺度持续的监测,而遥感监测可以弥补这一劣势。基于遥感和样地调查以祁连山生态交错区甘沟小流域为研究地点,对原有灌草地和植树造林的乔木林进行比较,探究二者土壤理化性质、草本植物多样性及植被归一化指数（NDVI）,增强植被指数（EVI）,植被水分指数（NDMI）,水分胁迫指数（MSI）,叶绿素红外指数（CI）,陆地叶绿素指数（MTCI）的差异。结果表明仅有水分相关指标有显著性差异,其中造林造成浅层土壤水分显著降低（P<0.01）,4-5月份MSI和NDMI造林区植被水分高于灌草地（P<0.01）,7-8月份两种植被类型水分指数以及其余指数无显著性差异,另外造林后的土壤有机质出现了轻微下降（P>0.05）。遥感指数和样地调查指标相关性分析中,土壤有机质和Shannon多样性指数与CI成正相关（P<0.05）,植被覆盖度与NDMI成负相关（P<0.05）,由于覆盖度较低的灌草地EVI和NDVI被高估,覆盖度和EVI与NDVI相关性不显著。综合遥感指数和实地调查分析,短时间造林时间内乔木林牺牲了部分土壤水分,提高了植被盖度,且目前造林并未对当地环境产生胁迫,但对生态环境的改善并不明显。基于遥感和样地调查揭示了潜在植被类型转换区原有灌草地和植树造林区的差异,并探讨遥感在小尺度范围内植被监测上的适用性,为植被建设和遥感监测植被状况提供借鉴。     

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.