太行山南段森林群落物种多样性研究

分别用多样性指数、丰富度指数、均匀度指数对山西太行山南段森林群落的物种多样性及其与环境的关系进行了分析.结果表明:(1)3个植被型的物种多样性指数的顺序为:落叶阔叶林>温性针阔叶混交林>温性针叶林.(2)落叶阔叶林中各群系的物种多样性指数的顺序为:漆树 青麸杨林>鹅耳枥 青榨槭林>青檀林>辽东栎林>栓皮栎林>白桦林>红桦林>山杨 白桦林.(3)温性针叶林中各群系的物种多样性指数的顺序为南方红豆杉林>油松林>白皮松林>侧柏林.(4)物种丰富度指数在群落梯度上的总体趋势表现为草本层>灌木层>乔木层;多样性指数的趋势则为灌木层>乔木层>草本层;各群落灌木层物种均匀度指数大于乔木层和草本层,乔木层均匀度与草本层相差不明显.(5)各群落多样性指数在海拔梯度上表现出明显的规律,呈单峰曲线变化,即中等海拔高度上的群落物种多样性较高,而高海拔和低海拔多样性较低,这主要是由于在中海拔(大约1 500 m)地段水热条件组合较好、人类活动干扰较少所致.     

华北地区主要灌丛群落物种组成及系统发育结构特征

灌丛在中国北方广泛分布, 研究其物种组成特征及构建机制对植被恢复有重要意义。群落系统发育结构能有效反映群落组成的生态过程, 对揭示群落构建机制具有重要作用。该研究利用华北地区自然植物群落资源综合考察数据库的灌丛数据, 分析了中国华北地区主要灌丛群落的分布情况、物种组成及其系统发育结构特征。同时, 结合WorldClim数据库中的气候因子利用逐步回归和一般线性模型分析了气温和降水对灌丛不同垂直结构层物种系统发育结构特征的影响。经统计, 共调查木本植物75科207属570种; 草本植物99科491属1 221种。按植被型和群系类型分类后, 共有5种植被型, 195个群系, 其中分布最多的群系类型为虎榛子(Ostryopsis davidiana)灌丛、荆条(Vitex negundo var. heterophylla)灌丛、荆条+酸枣(Ziziphus jujuba)灌丛和沙棘(Hippophae rhamnoides)灌丛。整体上, 草本层的物种丰富度高于灌木层。草本层的系统发育结构表现为发散模式, 而灌木层的系统发育结构表现为聚集模式, 且不同植被型灌丛的系统发育结构不同。气候因子的变化对灌木层和草本层系统发育结构都表现出了明显的影响, 但对灌木层的影响要强于对草本层的影响, 且气候因子和植被型、群系类型都有明显的交互作用。分析结果表明, 区域尺度上气温和降水的变化会影响灌丛群落不同结构层的系统发育结构特征, 且对不同的植被型和群系类型的影响不同。     

海拔高度对江油地区杉木人工林群落结构和物种多样性的影响

物种多样性是群落功能复杂性和稳定性的重要量度指标,海拔高度是影响物种多样性的重要因素。该实验采用典型样地法,在800~900m(低海拔)和1 100~1 200m(高海拔)2个海拔高度分别取4个20m×20m的样地,对江油地区的杉木人工林群落结构和物种多样性进行研究,采用物种丰富度指数(D)、Shannon-Wienner多样性指数(H)、Simpson优势度指数(H′)和均匀度指数(Jsw)来综合衡量不同海拔杉木人工林群落的物种多样性。结果表明:(1)组成江油杉木人工林的物种共计205种,分属66科177属;低海拔地区乔木7种,灌木54种,草本47种;高海拔地区乔木10种,灌木60种,草本41种。(2)低海拔和高海拔的木本植物组成无明显差异,草本层的物种组成有明显差异。(3)群落各层次的物种多样性指数在低海拔和高海拔都表现为:灌木层草本层乔木层,乔木层的各项指数最低;物种多样性指数随海拔升高在特定区间内表现出一定规律性,D、H和Jsw值总体上呈高海拔低海拔,H′则相反,表明高海拔杉木人工林物种多样性和物种在群落中分布的均匀度都有增加的趋势,这与高海拔受人为干扰较轻以及环境因子的变化等密切相关。     

退化土地植被恢复群落物种多样性与生物量分配格局

研究了湘西北女儿寨小流域7种典型植被恢复群落生物量的空间分配格局、物种多样性特征及其相互关系。结果表明:1)润楠次生林乔木层生物量最高,马尾松天然林灌木层生物量最大,油桐人工林草本层生物量最高,乔木层最低,毛竹-杉木林灌木层与草本层生物量最小,群落总生物量以马尾松天然林群落最高,荒草灌丛群落最低。2)乔木层物种以润楠次生林最丰富,多样性指数最高,物种分布最均匀;灌木层物种丰富度以毛竹-杉木混交林最高,油桐人工林多样性与均匀度指数最大,优势度最小,荒草灌丛群落的物种丰富度、多样性及均匀度最低;草本层物种丰富度以油桐人工林最高,马尾松天然林最低,杉木人工林草本层多样性指数与均匀度指数最大,润楠次生林优势度最高;群落总体物种丰富度以油桐人工林最高,润楠次生林群落的多样性指数最高,种群分布最均匀,荒草灌丛群落的多样性、均匀度与优势度都最低。3)女儿寨小流域退化土地物种丰富度与群落生物量之间的关系可用"S"曲线较好地描述,双曲线能较好地描述群落多样性指数、群落均匀度指数与生物量之间的关系,而生态优势度与生物量之间为非性线关系。     

神农架川金丝猴栖息地森林群落的数量分类与排序

在神农架川金丝猴生境典型地段设立样方58块,根据样方资料对神农架川金丝猴栖息地的森林群落用组平均法分类和DCA排序.用组平均法将58块样地分为9个群系,依据《中国植被》的分类原则和系统将研究区植物群落划归为7个植被型.样地的DCA排序较好地揭示了该区森林群落的分布格局与环境梯度的关系;DCA第二轴明显地反映出森林群落的海拔梯度变化,沿DCA第二轴从右到左,海拔逐渐升高;第一轴表现了各植物群落或植物种所在环境的坡度、坡向,即水分和光照因素,沿第一轴从下到上,坡度渐缓、坡向渐向阳.其中海拔梯度是环境因子中对森林群落起决定性作用的因子.研究表明,巴山冷杉+糙皮桦-大齿槭+尾萼蔷薇-高原露珠草+星果草群系发育较好,高大树木占有较大的比例,是神农架川金丝猴最适宜栖息地.7个植被型物种丰富度指数在群落梯度上呈规律性波动.其中针叶林和针叶-阔叶混交林中,物种丰富度指数在群落梯度上的总体趋势表现为灌木层＞草木层＞乔木层;在常绿阔叶林和常绿-落叶阔叶混交林中,该趋势为灌木层＞乔木层＞草本层;在落叶阔叶林中,其丰富度指数的趋势为灌木层＞草本层和乔木层.不同植被类型川金丝猴食源植物种类在群落梯度上的变化趋势与物种丰富度指数相同,但地衣类植物作为川金丝猴冬季的重要食物只在针叶林和针叶-阔叶混交林中生长.本研究为制定栖息地保护计划,更好地保护神农架川金丝猴提供了科学理论依据.     

神农架龙门河地区的植被制图及植被现状分析

依据龙门河地区所处位置的植被地理分布规律性 ,绘制了该地区 1∶50 0 0 0的植被复原图。并在野外调查、资料搜集的基础上 ,辅以全球定位系统 (GPS)、GIS软件及TM影像数据 ,绘制了该地区 1∶50 0 0 0的植被类型图。结果表明 :1 )植被海拔分布由低至高依次为常绿阔叶林 (海拔 90 0m以下 ) ,硬叶常绿阔叶林 (海拔 90 0～ 1 30 0m)、常绿落叶阔叶混交林 (海拔 1 30 0～ 1 60 0m)以及落叶阔叶林 (海拔 1 60 0～ 2 2 0 0m)。 2 )龙门河地区林地面积 441 9.2hm2 ,占该地区总面积的 93 .71 % ,共计 8个植被型 65个群系。其中常绿落叶阔叶混交林面积最大 ,为 1 674.0 9hm2 ,占林地面积的 37.88%。另外 ,果园 (3种类型 )和农田两种农业用地面积 2 2 8.1 2hm2 ,占总面积的 4 .84%。 3)由植被复原图与现状植被类型图叠加分析可知 ,干扰后增加了针叶林、针阔混交林、灌丛、草地 4种植被类型 ,占龙门河地区总面积的 34 .6 %。其中针阔混交林所占面积最大 ,996 .79hm2 。     

白龙江上游地区森林植物群落物种多样性的研究

 白龙江上游地区属长江防护林工程重点地区之一。根据36个样地的调查资料,分析了该地区森林植物群落物种多样性的特征：群落内各层物种丰富度指数的大小顺序为“灌木层>草本层>乔木层”;均匀度指数变化比较复杂,在杜鹃巴山冷杉（Rhododendron fastigiatum-Abies fargesii）林中为“草本层>灌木层>乔木层”,在苔藓巴山冷杉林中为“乔木层>灌木层>草本层”,其余群落中为“灌木层>草本层>乔木层”;多样性指数的大小顺序为“乔木层<灌木层和草本层”,而灌木层与草本层的多样性指数随林分郁闭度变化而变化,在郁闭度30%的杜鹃巴山冷杉林中,草本层大于灌木层,在郁闭度47%的箭竹巴山冷杉林中,草本层和灌木层相当,在郁闭度55%以上的各个群落内,灌木层大于草本层。同一海拔不同坡向群落的物种多样性表现为分布于阳坡的油松（Pinus tabulaeformis）林大于分布于阴坡的草类云杉（Picea asperata）林。物种多样性沿海拔梯度的变化表现为随海拔升高先降低后增加,从海拔2 400 m的栎类阔叶林,2 600 m的草类云杉林,2 800 m的箭竹(Sinarundinaria nitida)巴山冷杉林,到3 000 m的苔藓巴山冷杉林和3 200 m的杜鹃巴山冷杉林,物种多样性依次下降,到海拔3 400 m的高山杜鹃（Rhododendron fastigiatum）灌丛,物种多样性增加。物种多样性在紫果云杉(Picea purpurea)林的演替系列中表现为随群落演替发展而增加,后降低,在针阔混交林阶段达到最大。     

贺兰山木本植物群落物种多样性的海拔格局

 贺兰山位于中国温带草原和温带荒漠的过渡带,是研究干旱区山地物种多样性海拔格局的理想区域。该文通过样方法调查研究区的森林和灌丛群落,并运用广义可加模型分析物种多样性的海拔分布格局。结果表明：1）海拔是物种丰富度的重要影响因子,一般能解释原始数据30%～40%的变差。2）对于森林和灌丛群落,草本植物都是群落中比例最高的物种, 而且决定了群落总物种丰富度的海拔分布格局。3）森林群落的乔木层物种丰富度在中海拔区域最高,反映了中海拔区域相对优越的水热条件。灌木层和草本层的物种丰富度明显受到乔木层郁闭度的影响,有随海拔升高而降低的趋势。4）灌丛群落的灌木层和草本层物种丰富度均呈单峰格局,皆因低海拔的干旱和高海拔的寒冷抑制了多数物种的生存,仅气候条件适宜的中海拔区域能够生存丰富的物种。     

太行山南段油松群落物种多样性研究

油松是太行山区重要的植树造林树种。本文以太行山南段为研究区域,采用随机取样法对武乡、黎城、襄垣、平顺、壶关、屯留6个地区油松的物种多样性与群落多样性进行了分析比较。结果表明:(1)6个地区油松群落中共有种子植物34科70属81种,包含乔木4科4属5种、灌木7科12属15种、草本23科54属61种;(2)太行山南段油松群落种子植物属的区系成分类型多样,以温带成分占绝对优势;(3)武乡、黎城、襄垣、平顺、壶关5个地区油松群落的物种多样性表现出较为一致的变化趋势,即草本层灌木层乔木层,而屯留的不同功能群物种多样性表现为草本层=灌木层乔木层;(4)6个地区油松群落多样性从高到低依次为平顺黎城襄垣武乡屯留壶关;(5)油松群落多样性和物种多样性水平受群落演替进程、地理环境、人为干扰等诸多因子的协同作用。     

祁连山北坡中段植物群落多样性的垂直分布格局

利用DCCA排序和海拔高程排序相结合的方法 ,对祁连山北坡中段植物群落物种多样性垂直分布格局进行了初步研究。结果表明 :1)植物群落草本层和灌木层物种丰富度和多样性在环境梯度上呈单峰曲线变化趋势 ,乔木层的物种丰富度和多样性在环境梯度上无变化。物种丰富度和多样性对环境梯度变化敏感程度的次序是草本层 >灌木层 >乔木层 ;2 )植物群落各层次均匀度在环境梯度上没有表现出一定的变化规律 ,均匀度可能更多地受制于群落自身动态的影响 ,而独立于生境的资源水平 ;3)草地群落物种多样性在DCCA环境梯度上曲线的拟合效果优于按海拔高程排序效果 ,灌木群落则相反 ;4)低海拔、中低海拔和中海拔地带的草本层物种丰富度和Shannon Wiener多样性指数 (H′)显著高于灌木层 (p <0 .0 1) ;高海拔地带草本层仅丰富度指数显著高于灌木层 (p <0 .0 5 )。在整个海拔范围内 ,草本层和灌木层的均匀度无显著差异。就资源的可利用性而言 ,研究区域植物群落物种多样性在垂直环境梯度上的变化规律表达了物种多样性与资源生产力的单调关系内涵。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.