三江源区高寒草地退化与恢复过程中二氧化碳净交换特征

采用同化箱法测定了青海省南部果洛藏族自治州玛沁县不同退化程度天然草地及不同建植年限人工草地植物群落光合作用、暗呼吸及CO2净交换量。结果表明,天然草地植物群落光合作用过程CO2吸收量与暗呼吸作用CO2释放量的变化趋势为:中度退化草地重度退化极度退化未退化草地;未退化、中度及重度退化高寒草地植物群落净吸收CO2,而极度退化高寒草地植物群落净释放CO2。对"黑土滩"型极度退化草地进行人工恢复后,植物群落通过光合作用吸收CO2量增加;2000和2004年建植的垂穗披碱草(Ely-musnutans)单播人工草地植物群落净吸收CO2量分别为1.33和2.3μmolCO2.m-2.s-1,大于2002和2005年混播人工草地;对单播或混播人工草地而言,随着建植年限增加,草地出现一定程度的退化现象,CO2净吸收量也逐渐下降。从青藏高原碳管理的角度,中、重度退化草地要防止退化为"黑土滩"型极度退化草地,使其恢复到未退化程度;极度退化草地要及时进行人工恢复,有效增加碳的吸收量。     

封育对高寒草甸植物群落构成及生态位特征的影响

封育是天然草地管理的一种有效措施,利于草地生产力提高和退化草地恢复。该研究通过对青藏高原高寒草甸放牧和封育草地物种多样性、植被构成、植物种生态位特征、草地演替度等分析,解析高寒草甸植物种间关系及草地演替方向。结果表明:(1)封育显著降低了草地群落植物物种数以及α和β多样性指数,显著增加了草地1年生植物种数、地面芽植物种数和地上生物量。(2)放牧草地地上生物量以莎草科(59.7%)和禾本科(23.9%)为主,封育草地地上生物量以禾本科(85.0%)为主;放牧草地优势种为矮嵩草(Kobresia humilis)和线叶嵩草(K.capillifolia),封育草地优势种为垂穗披碱草(Elymus nutans)和早熟禾(Poasp.)。(3)放牧和封育草地的群落植物种重要值均与各自的生态位宽度变化规律一致。(4)草地植物种间竞争主要发生在不同科属植物种之间,封育增加了群落植物种整体生态位重叠值和植物种间竞争。(5)草地群落演替度为封育地放牧地,封育群落处于较稳定状态。研究认为,封育促进了高寒草甸由莎草+杂类草群落向禾草+杂类草群落演替。     

江河源区人工草地及"黑土滩"退化草地群落演替与物种多样性动态

研究了“黑土滩”退化草地以及在“黑土滩”上建植的垂穗披碱草人工草地在第2～6年间植物群落演替及物种多样性动态。结果表明：随着演替的发生．两种不同类型草地群落的α多样性指数均呈现单峰变化趋势。人工草地群落的α多样性指数比“黑土滩”退化草地群落的低,建植第4年的人工草地群落和封育4年的“黑土滩”退化草地群落的各指数最高。两种不同类型草地草场质量指数也呈现先降后升的趋势,人工草地群落的草场质量和生物量比“黑土滩”退化草地群落高。从植物的生活型看．一年生植物被多年生植物替代。β多样性的时间动态反映出演替过程中,两种类型的草地群落2龄与5龄、6龄群落间的β多样性低,物种周转率高;2龄与3龄,5龄与6龄群落间的β多样性高．物种周转率低,4龄群落是过渡群落。在时间序列上可分为两个阶段．2～4龄主要是一年生草本的入侵．4～6龄主要是多年生草本的定居。     

三江源区“黑土滩”型退化草地人工恢复植物群落的演替动态

选取青藏高原三江源区"黑土滩"型退化草地上建植的人工草地为研究对象,对不同建植年限人工草地植物群落及其各功能群的物种组成、平均高度、盖度和地上生物量及植物多样性等进行实地调查和对比分析,探讨"黑土滩型"退化草地在人工恢复过程中植物群落组成和多样性变化,以期回答人工恢复的草地植物群落何时才能接近天然草地、人工恢复的时间阈值应为多长等问题,从而为三江源区"黑土滩"型退化草地的恢复重建提供科学的理论指导。研究结果表明:草地恢复前5年内,禾本科植物的数量大量增加,植物群落的高度增加了847.6%,植物群落盖度增加了134.5%;不同恢复年限的草地植物群落的多样性指数都有相似的变化趋势,恢复8年后植物群落组成达到阶段性的稳定状态,在恢复时间达16—18年后,逐渐向更稳定的状态转化;恢复18年的草地与天然草地植物群落的Jaccard及Sorensen相似度指数分别为0.596、0.747,Cody差异度指数为9.5。由此可见,建植人工草地的方式恢复退化草地,可在建植8年后达较好的恢复效果;恢复时间达16年以上的人工草地采取适度的调控措施,有利于其向天然草地恢复演替;建植18年的人工草地物种组成情况与天然草地最接近,但仍有差异。因此,"黑土滩"型退化草地的人工促进恢复,到未退化的状态至少需要18年以上。     

蚁丘干扰下高寒草甸植物群落特征和生态位

蚁丘作为高寒草甸上一种重要的生态干扰因子,对高寒草甸植物群落特征和生态位产生重要影响。2012年9月在四川红原县对蚁丘干扰后的高寒草甸植物群落进行了研究。结果表明:蚁丘干扰后高寒草甸植物群落的物种丰富度和多样性降低,但禾本科和莎草科的盖度、重要值和生态位宽度增加,尤其是禾本科的草地早熟禾(Poa pratensis)与垂穗披碱草(Elymus nutans)的生态位宽度明显高于对照,成为优势种群。蚁丘干扰后高寒草甸植物种群生态位重叠程度普遍偏小,以保证占据较大生态位宽度的禾本科和莎草科优势种群与其他物种间在生态学上的长期共存适应,有利于受干扰的高寒草甸朝着增加优良牧草比例、增强可牧能力的方向发展。     

植物生长季节不同栖息地高原鼠兔的食物选择

本文采用胃内容物镜检分析法,对栖息于青藏高原矮嵩草草甸、垂穗披碱草草甸和杂类草草甸中的高原鼠兔的主要食物组成进行了比较分析,旨在探讨栖息地变化对高原鼠兔食物组成的影响,揭示高原鼠兔对栖息地变化的生存对策和适应性.研究结果表明:在矮嵩草草甸,高原鼠兔主要取食垂穗披碱草、早熟禾、蓝花棘豆和甘肃棘豆;在垂穗披碱草草甸,主要选择垂穗披碱草、甘肃棘豆、蓝花棘豆、矮嵩草和二柱头蔗草;在杂类草草甸,喜食植物种类为垂穗披碱草、蓝花棘豆、甘肃棘豆、早熟禾、弱小火绒草、长茎藁本、兰石草和红花岩生忍冬.在整个植物生长季节,高原鼠兔在3种栖息地共取食27种植物,其中垂穗披碱草、甘肃棘豆和蓝花棘豆在不同栖息地中选择指数较高,为高原鼠兔优先选择的食物;在不同栖息地,高原鼠兔取食植物有差别,垂穗披碱草草甸为16种、矮嵩草草甸为22种,杂类草草甸为24种;喜食食物比例也存在着明显差别,在垂穗披碱草草甸,垂穗披碱草比例高达40.5%,在矮嵩草草甸,甘肃棘豆比例也达到23.7%,而在杂类草草甸,选食比例最高的兰石草仅为14.6%,说明在该草甸高原鼠兔食物选择呈现泛化趋势.相似性指数分析结果也表明,杂类草草甸中高原鼠兔主要食物组成与其它两种栖息地有较大的区别.从而说明当栖息地植物群落种类组成发生变化后,高原鼠兔可以通过改变其食物组成而适应新的栖息地.     

高寒地区白苞筋骨草对几种禾草的化感作用

采用青藏高原“黑土滩”次生毒杂草群落的优势植物——白苞筋骨草（Aerba lupulin）地上部分和地下部分水浸液,对青藏高原高寒地区4种禾草种子萌发、幼苗生长的抑制作用进行了分析。结果表明：白苞筋骨草地上部分水浸液对4种禾草种子萌发和幼苗生长具有显著抑制作用（P<0.05）,地下部分水浸液的化感抑制作用不显著（P>0.05）;4种牧草种子萌发对白苞筋骨草水浸提物敏感性强弱顺序为：垂穗披碱草（Elymus nutans）＞老芒麦（E. sibiricus）＞冷地早熟禾（Poa crymophila）＞中华羊茅 （Festuca sinensis）,禾草幼苗生长对白苞筋骨草水浸液的敏感性强弱顺序为：垂穗披碱草＞中华羊茅＞老芒麦＞冷地早熟禾;整体上,4种牧草对白苞筋骨草化感作用的敏感性强弱顺序为：垂穗披碱草＞老芒麦＞冷地早熟禾＞中华羊茅;4种牧草幼苗生长对白苞筋骨草的水浸液敏感性弱于种子萌发。白苞筋骨草的化感抑制作用是高寒地区毒杂草在退化草地蔓延,并最终形成"黑土滩"次生毒杂草群落的一个因素。     

甘南山地草原人工草场的演替

 在同一地点选择了1985年和1979年播种的两块垂穗披碱草(Elymus nutans)人工草地,于1986年和1988年进行两次观测。所得结果如下：(1)人工草场建立后就开始逐渐向天然植被恢复;(2)在初期演替速度大于在后期的演替速度;(3)多样性和均匀性随着演替而增大,而群落优势度则随着演替而减小;(4)草场质量随着演替趋于下降,到天然群落阶段又开始恢复。     

不同处理对藏北地区退化人工草地垂穗披碱草种群克隆表型的影响

以不同退化程度和采用不同恢复措施的垂穗披碱草人工草地为对象,通过野外调查和室内分析相结合的方法研究了各类草地垂穗披碱草克隆种群相关表型特征的差异,结果表明,随着人工草地建植年限的延长,草地退化渐趋严重,垂穗披碱草克隆种群相关表型参数显著降低.相比较而言,封育可以提高种群的有性繁殖能力,但施肥和补播措施可以显著提高垂穗披碱草种群的克隆生长,其株高、分株数以及株丛数显著增加,而有性繁殖能力相对降低.因此,针对藏北高原以垂穗披碱草为最主要建群种或单优种群的退化草地恢复,施肥和补播应为最有效措施.     

高寒草甸植被退化过程中生物土壤结皮演变特征

对生物土壤结皮(BSCs)在青藏高原的分布和作用还知之甚少,为了解其在高寒草甸退化过程中的演变特征,以高寒草甸为对象,研究其退化和人工重建对BSCs生长和分布影响。结果表明:随草甸退化,植被盖度不断降低,苔藓类结皮在禾草嵩草草甸和6年人工草地出现频度最高,随植被退化出现频度降低,"黑土滩"阶段最低(43.6%);黑斑、菌斑和地衣都是在矮嵩草阶段形成,在小嵩草草甸裂缝期或者剥蚀期出现频度最高,在禾草嵩草群落、6年人工草地及黑土滩均未出现;相关分析表明,苔藓类结皮出现频率与植被盖度呈极显著相关(P0.01),而与黑斑和地衣出现频率呈负相关,菌斑与地衣出现频度呈显著相关(P0.05)。BSCs在高寒草甸广泛分布,不同演替阶段,其分布和物种组成存在较大差别。植被生长和表土稳定性状况导致了BSCs的异质性分布格局。     

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.