林冠截留与大气降水关系的数学模型

本文依据实测数据及有关资料,对林冠截留进行了深入细致的分析,并以物理化学中溶液吸附理论引伸出的上升-饱和函数关系曲线为类比,提出了一组关于林内雨量率、截留率、截留量与大气降水关系的新的数学模型。模型中的3个参数μm、P_o、k水文学意义明确,拟合效果较好,对深入研究林冠截留具有一定现实意义。 林内雨量率公式: 林冠截留率公式: 林冠截留量公式:     

辽宁东部山区落叶松人工林林冠降雨截留观测及模拟

利用2005-2008年辽东山区落叶松人工林林冠降雨截留观测数据,并选取Gash解析模型模拟林冠截留过程.结果表明：落叶松人工林林内穿透雨量与林外降雨量呈显著正相关关系(R²=0.98),年均穿透雨量占总降雨量的77.64%;林冠截留量与降雨量和降雨强度之间呈正相关关系;除2007年由于降雨间隔时间短导致模拟截留量大于实测截留量外,模型模拟的林冠截留量均小于实测林冠截留量;模型模拟的绝对误差与林外降水量呈负指数相关,为1.26%～68.96%,平均值为29.09%;模拟值与实测值之间的相关系数为0.91,模型模拟结果与实测结果相吻合.     

林冠截持降雨模型的初步研究

通过对林冠截持过程的研究,将单场降雨划分成很多个小的时段,顺序计算各小时段内降雨在林冠内的分配,建立了一个林冠降雨截持模型.模型考虑了冠层和树干干燥度对冠层雨期蒸发的影响,并在计算雨期蒸发时引入冠层叶面积指数、单位林地面积上树干表面积.运用模型对华北落叶松林的降雨截持进行模拟,结果表明,模拟穿透雨与实测穿透雨基本吻合,误差在±1 mm范围内,但在小降雨(＜6 mm)时模拟值偏低;树干茎流量模拟值偏低,茎流模拟相对误差随着降雨量增大而减小.同时模拟了穿透降雨的过程,结果与林内自动气象站实测穿透降雨的过程基本吻合,模拟效果较好.     

华北石质山区油松林对降水再分配过程的影响

森林通过降水再分配过程影响着流域的水量平衡和物质循环。根据2005-2008年汛期华北石质山区主要造林树种油松林的林外降雨、穿透降雨、树干径流定位观测数据,探讨了人工油松林对降雨再分配过程的影响。结果表明,测定期间32场次降雨过程中油松林穿透雨量、树干径流量和林冠截留量平均值分别为8.67,0.11,1.07mm;透过率,树干径流率和林冠截留率分别为82.18%(57.74%-87.55%),1.07%(0.22%-2.07%),16.75%(11.01%-42.07%)。油松林冠层穿透降雨量、树干径流量和林冠截留量均与林外降雨量呈明显的线性关系(R2=0.995,R2=0.907,R2=0.855),根据回归方程,当林外降雨量大于0.3mm时,可发生穿透降雨,当林外降雨量大于3.51mm时,可发生树干径流;林冠截留率与林外降雨呈双曲线衰减趋势,回归方程为y=12.091+55.537/(x+0.426)(N=32,R2=0.685)。典型次降雨再分配过程表明,林冠不仅在量上对降雨进行再分配,还在时程上进行了再分配。     

祁连山青海云杉林冠生态水文效应及其影响因素

以位于祁连山中段大野口关滩森林站的青海云杉林为研究对象,利用2008年观测期间(6月12日至10月8日)34场降雨的大气降雨量、穿透雨量和树干茎流量观测资料,对青海云杉林的降雨再分配特征及其影响因素进行综合分析。结果表明:青海云杉林的总穿透雨量、截留量和干流量分别为212.6、64.5 mm和3.4 mm,分别占大气降雨量的75.8%、23.0%和1.2%;穿透雨在林内具有较大的空间变异性,其变异程度随降雨量的增大而减小,叶面积指数和冠层郁闭度在一定程度上也影响穿透雨的空间分布,且降雨量越小其影响效果越明显;青海云杉林的总干流量为3.4 mm,平均干流率为0.58%,雨前林冠的湿润程度对树干流的产生有很大影响,导致当降雨量为5.6 mm时就开始产生树干茎流;青海云杉林冠截留率的大小主要取决于降雨量,且随着降雨量的增大先减小并逐渐趋于稳定,林冠截留量总体上随冠层郁闭度和叶面积指数的增大而增大,但当观测点位于树冠边缘或多个树冠重叠处时出现负截留现象。所以,就特定林分而言,冠层结构特征对于其林冠生态水文效应起着重要的作用。     

六盘山华北落叶松林下穿透雨空间变异特征

受林冠截持影响后形成的林下穿透雨的数量和空间分布会影响林地的入渗、产流、蒸发等水文过程和林木生长及枯落物分解等生态过程,因而精细的森林水文功能评价和森林生态系统经营都需要准确描述林下穿透雨的空间变异规律。在宁夏六盘山香水河小流域设立了面积为30 m×30 m的华北落叶松人工林样地,均匀布设了40个截面面积230.58 cm2的雨量收集器,测定了2015年生长季(5—10月)34次降雨事件的穿透雨量。结果表明,研究期间林外总降雨量567.0 mm,林下总穿透雨量483.5 mm,占同期雨量的85.3%。随着次降雨量增加,林内次穿透雨率呈现先快速增加后趋于稳定的变化。穿透雨量在林内存在较大空间变异,其变异程度随次降雨量增加先快速下降后趋于稳定。林下穿透雨空间分布受树木特征(穿透雨收集器上方的林冠叶面积指数和冠层厚度、穿透雨测点离最近树干的距离)的影响,且其影响随次降雨量大小而变,当次降雨量10 mm时,穿透雨量与叶面积指数显著负相关;当次降雨量在10—20 mm时,穿透雨量与距最近树干距离显著正相关,与冠层厚度显著负相关;当次降雨量20 mm时,穿透雨量与3个树木特征均不显著相关。考虑到研究区次降雨量集中在0—10 mm,在95%或90%的置信区间下,若将测定的次穿透雨数值误差控制在10%以内时,在30 m×30 m样地内至少需布设13或9个本研究所用大小的收集器;满足次穿透雨数值误差在5%以内时,至少需布设26或23个这样的收集器。     

西藏原始林芝云杉林雨季林冠降水分配特征

利用2006-2007年对西藏米林县南伊沟原始林芝云杉(Picea likiangensis var.linzhiensis)林林外降水、穿透水和树干茎流定位观测数据,对林芝云杉林的林冠降水再分配特征进行研究。结果表明:西藏南伊沟的年降水量为716.4mm,主要集中在4-9月份,占全年降雨量的86.95%。在林芝云杉的生长季节(4-10月份),林冠截留量为338.6mm,占同期林外降水量的51.60%;林内穿透水量为316.3mm,占同期林外降水量的48.21%;树干茎流量仅为1mm,仅占0.19%。林内穿透水(Tp)、树干茎流(Sf)、林冠截留量(Ip)及林冠截留率(PIp)与林外降水量(p)之间的关系分别为:Tp=0.8622p-3.5229,r=0.9964;Sf=0.0004p1.4586,r=0.9458;Ip=1.2222p0.6341,r=0.874;PIp=253.6p-0.7008,r=0.9732。林芝云杉林雨季林冠降水的分配规律与该森林结构复杂、林分年龄高、胸高断面积大密切相关,说明该森林在涵养水源和保持水土等方面发挥着重要的作用。     

马尾松林分结构对冠层水文效应的影响

了解不同林分结构森林的水文效应及其主要影响因素,可为林分抚育经营管理提供科学依据。本研究在三峡库区九领头林场设置14块20 m×30 m马尾松林样地,观测其林冠截留量、树干茎流量和穿透雨量,调查马尾松林分结构因子,利用Pearson相关分析、主成分分析、冗余分析等方法分析林分结构(叶面积指数、混交度、大小比数、竞争指数等)对水文效应(冠层截留率、穿透雨率、树干茎流率)的影响。研究期间(6—10月)林外降雨总量1008.4 mm,林冠截留量、穿透雨量和树干茎流量分别占总降雨的16.3%、82.3%和1.4%。Pearson相关分析结果表明:叶面积指数、胸高断面积、冠幅面积与冠层截留率呈显著正相关(P0.05),与穿透雨率呈显著负相关(P0.05),树干茎流率与树高、冠层厚度呈显著负相关(P0.05),与叶面积指数、林分密度呈显著正相关(P0.05);冗余分析结果表明:水文效应的再分配特征能被结构变量组合解释59.6%,蒙特卡罗置换检验结果表明:冠层截留率和穿透雨率主要受蓄积量这类结构组合变量的影响,蓄积量越大,冠层截留率越高,穿透雨率越低,树干茎流率主要受林分竞争状况及水平结构(R~2=0.46,P0.05)和蓄积量(R~2=0.51,P0.05)的影响。林分结构与冠层水文效应密切相关,林分生长状况越好,蓄积量越大,马尾松林涵养水源效果越好。     

两种不同林分截留能力的比较研究

根据林冠对大气降雨截留的实测资料,采取同雨量下取最大值的方法近似确定了两种不同林分的截留能力与雨量的关系并进行了比较。结果表明,林冠枝叶空间分布均匀的人工林分,截留能力随雨量增加较快,不仅对〈３０ｍｍ的中小雨量表现出了较强的截留作用,而且容易满足林冠的饱和截留容量,尽管天然林对〈３０ｍｍ的雨量截留能力相对较弱,但对超过３０ｍｍ的降雨其截留能力大于人工林。林冠饱和截留容量与冠层枝叶量有关,天然林大于     

岷江上游亚高山川滇高山栎林的降雨再分配

基于2007年6-9月岷江上游地区的气象数据,采用定位研究方法对该区川滇高山栎林的降雨再分配进行了研究.结果表明：研究期间,林外总降雨量486.7 mm,林内穿透雨量、树干茎流量和林冠截留量分别占总降雨量的82.6%、0.9%和16.5%;穿透雨量和树干茎流量与降雨量均呈极显著的线性关系(P<0.01,n=49),穿透雨率和树干茎流率与降雨量的关系可用非线性曲线表示;当林外降雨量>3.2 mm时开始出现树干茎流,且树干茎流量(L)与树干基面积(cm²)呈明显的指数关系(R²=0.623).林冠截留率随降雨量(mm)的增加呈双曲线递减;林冠截留率与降雨量、降雨持续时间、降雨强度、降雨时空气相对湿度均呈极显著负相关(P<0.01,n=49),而与风速呈极显著正相关(P<0.01,n=49).     

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.