崇明东滩湿地不同盐沼植物群落土壤碳储量分布

海岸带盐沼植被的高生产力对湿地土壤碳库的形成具有重要意义.本文研究了长江口崇明东滩湿地3种主要盐沼植物(芦苇、互花米草和海三棱藨草)群落生物量差异、土壤碳储量时空动态和垂向分布特征.结果表明： 湿地盐沼植被总生物量表现为互花米草群落(5750.7 g·m^-2)>芦苇群落(4655.1 g·m^-2)>海三棱藨草群落(812.7 g·m^-2),且地上生物量在夏、秋季最高,地下生物量在冬季最高.湿地土壤碳储量(0～50 cm)在春季最低,随后逐渐增加,至冬季达到最大值.土壤碳储量年增量从高潮滩向低潮滩递减,表现为芦苇群落(711.8 g·m^-2)>互花米草群落(646.2 g·m^-2)>海三棱藨草群落(185.3 g·m^-2)>光滩(65.6 g·m^-2).光滩土壤碳储量在25～30 cm处最高,海三棱藨草、互花米草和芦苇群落土壤碳储量分别在10～15、30～35和30～40 cm处达到最大值,且不同群落土壤碳储量与植被地下生物量具有显著的线性关系.     

崇明东滩湿地自然植被演替过程中储碳及固碳功能变化

采用实地调查与实验室测定相结合的方法,研究了崇明东滩湿地植被演替过程中储碳、固碳功能的变化.结果表明：不同演替阶段的湿地植被的现存碳储量及其分配格局特征存在较大差异.先锋物种海三棱藨草的现存碳储量仅占芦苇现存碳储量的13%;地下根茎为芦苇现存碳储量的主要场所,而地上部分是海三棱藨草碳储量的主要场所.处于潮滩湿地演替中后期的芦苇群落比处在生态演替早期的海三棱藨草群落具有更强的固碳能力,芦苇群落和海三棱藨草群落的年固碳能力分别为(1.63±0.39) kg·m^-2和(0.63±0.28) kg·m^-2,说明随着海三棱藨草群落向芦苇群落演替,其固碳能力不断增强.     

九段沙湿地植被群落演替与格局变化趋势

长江口新生湿地九段沙由上沙、中沙和下沙三部分组成。2004年对湿地植被群落的演替与格局变化进行了研究。结果表明,九段沙湿地植被群落由芦苇(Phragmites austra-lis)、互花米草(Spartina alterniflora)、海三棱藨草(Scirpus mariqueter)和藨草(S.triqueter)构成。芦苇和互花米草生长于潮滩高程,海三棱藨草和藨草生长于低潮位。1998—2004年,上沙植被覆盖面积年平均约增长17%,中沙22%,下沙38%~39%,植被群落处于快速增长演替状态,这可能与沙洲发育速度有关。由于在中沙、下沙人为种植过外来物种互花米草,其增长速度最快,覆盖面积占九段沙植被总面积的比例从1998年不足1%上升到2004年的22%,地上部分总生物量的年平均增长率为79.79%,互花米草对藨草-海三棱藨草的竞争压力较大。鉴于互花米草对九段沙的影响尚无定论,本文提出了初步的植被管理措施。     

5种湿地植物对生活污水净化效果研究

选择芦苇、水葱、千屈菜、扁秆藨草、长苞香蒲5种常见湿地植物分别构建人工湿地小试系统,测试它们对生活污水的净化作用,分析污水净化过程中氮磷元素在植物体内和土壤中的动态分布,以明确各湿地植物对污水的综合净化能力。结果表明:（1）5种湿地植物对生活污水中的CODcr、铵态氮、总氮和总磷的去除效果显著高于无植物对照;随处理时间延续,污水中CODcr、铵态氮、总氮和总磷浓度均呈下降趋势,定植土壤中的总氮和总磷含量呈先上升后下降的变化趋势。（2）5种植物能够吸收污水中89.7%～97.9%的磷元素,污水中剩余的磷元素量较少（2.1%～10.3%）;污水中氮元素在植物体、污水和土壤中分布因植物种类不同有很大差别,芦苇、水葱和长苞香蒲可吸收污水中76.1%～83.4%的大部分氮元素,而千屈菜和扁秆藨草对氮元素吸收量较少（分别为45.0%和46.8%）,在污水和土壤中滞留的氮元素较多（21.7%～31.6%）。（3）5种植物对氮元素的积累能力显著大于对磷元素的积累能力;5种湿地植物对生活污水的综合净化能力差异较大,从强到弱依次为芦苇＞长苞香蒲＞水葱＞扁秆藨草＞千屈菜。     

崇明东滩南部盐沼植被空间分布及影响因素分析

崇明东滩南部滩面高程、土壤盐度在空间上呈明显的梯度变化规律。高程整体西高东低、北高南低, 盐度东北高、西南低, 两者共同限制着盐沼植物在空间上的分布。该文围绕崇明东滩南部主要植被类群及其空间分布, 探讨了土壤盐度、潮滩高程两大环境因子与植物种群分布的对应关系。基于2013年夏、秋季植被空间网格采样和空间插值, 分析了东滩南部植物的空间分布现状, 发现不同植物类群在高程和土壤盐度上存在极显著的差异(p < 0.01)。高程差异: 莎草科类群主要分布于高程区间2.93-4.07 m的低潮滩, 禾本科主要集中分布在高程3.13-4.31 m的中、高潮滩; 盐度差异: 海三棱藨草(Scirpus mariqueter)和互花米草(Spartina alterniflora)优势种群植被覆盖区表层30 cm的平均土壤盐度为(3.2 ± 0.6) g·kg^-1, 显著高于其他类群植物分布区的平均土壤盐度(2.0 ± 0.3) g·kg^-1 (p < 0.01)。崇明东滩湿地生态系统的关键种兼先锋种——海三棱藨草, 分布高程介于2.53-3.97 m, 而互花米草能适应海三棱藨草80%的高程区间, 两者在高程上存在竞争关系。统计数据显示, 研究区域中近90%的海三棱藨草分布在研究区东北部, 土壤盐度范围为1.6-4.5 g·kg^-1, 海三棱藨草、互花米草能较好地适应该空间内的盐度胁迫, 两种植物在此交替出现。但是在高程和土壤盐度的综合作用下, 互花米草的生长状况更好, 因此该区的海三棱藨草很可能会被互花米草逐步取代。对各类群植被分布和优势面积的研究发现, 海三棱藨草总分布面积为294 hm², 优势群落面积120 hm², 海三棱藨草仅占莎草科植物总优势面积的15.7%, 占研究区总面积的6.9%, 在6种主要植物(芦苇(Phragmites australis)、白茅(Imperata cylindrica)、互花米草、糙叶薹草(Carex scabrifolia)、藨草(Scirpus triqueter)、海三棱藨草)中比重最小, 这给保护区内海三棱藨草种群的恢复和保护带来极大的挑战。     

洞庭湖湿地土壤碳、氮、磷及其与土壤物理性状的关系

以洞庭湖3类典型湿地的8个土壤剖面为代表,研究了土壤碳、氮、磷,微生物量碳、氮、磷和土壤物理性状的分布特征.结果表明,土壤表层有机碳含量为19.63～50.20 g·kg^-1,微生物量碳为424.63～1 597.36 mg·kg^-1,微生物量碳占有机碳的比例为3.17%～4.82%;土壤表层全氮1.85～4.45 g·kg^-1,微生物量氮5.90～259.47 mg·kg^-1,微生物量氮占全氮的比例3.13%～6.42%;土壤表层微生物量磷含量顺序为:湖草洲滩地(200.99 mg·kg^-1)＞垦殖水田(163.27 mg·kg^-1)＞芦苇洲滩地(24.16 mg·kg^-1),微生物量磷占全磷的比例为1.09%～11.20%;土壤表层容重0.65～1.04 g·cm^-3;土壤表层粘粒(＜0.001mm)26.24%～39.48%.土壤表层有机碳、全氮、微生物量氮、微生物量磷的含量,湖草洲滩地＞垦殖水田＞芦苇洲滩地.土壤表层微生物量碳,垦殖水田和湖草洲滩地接近,而大于芦苇湿地;土壤表层容重,芦苇洲滩地＞垦殖水田＞湖草洲滩地;土壤表层＜0.01 mm、＜0.001 mm粘粒,湖草洲滩地、芦苇洲滩地＞垦殖水田.湿地土壤剖面中有机碳、微生物量碳、全氮、微生物量氮、微生物量磷、容重以及微生物量碳占有机碳的比例、微生物量氮占全氮的比例、微生物量磷占全磷的比例均随深度的增加而降低,至一定深度稳定,而土壤全磷在剖面上下的差异很小.湿地土壤微生物量碳、氮、磷之间呈极显著的正相关关系;土壤容重与有机碳、全氮、微生物量碳、氮、磷之间呈极显著指数负相关关系.湿地土壤＜0.001 mm粘粒与有机碳、全氮、微生物量碳、氮、磷含量呈极显著对数正相关关系.     

基于遥感的九段沙湿地植被群落动态变化分析

九段沙是长江口重要的新生湿地.作为主要地物类型之一的植被群落,是反映潮滩湿地生态环境变化重要而又敏感的指标因子.本文通过1987～2008年六景Landsat卫星遥感数据对九段沙植被群落进行了分类提取,并利用ArcGIS软件分析了长江口九段沙植被群落20年来的时空动态变化.结果显示1987～1997年间,九段沙湿地植被以先锋植被海三棱藨草为主,植被面积随潮滩不断淤涨而增长;1997年人工促淤种植了芦苇和互花米草,至2008年,芦苇、互花米草和海三棱藨草三种植被群落所占植被总面积百分比分别为31.47%、39.35%和29.17%,其中外来物种互花米草优势明显,当地植被海三棱藨草所占面积比例显著下降.     

九段沙不同演替阶段湿地土壤微生物呼吸的差异性及其影响因素

通过分析九段沙不同演替阶段湿地土壤微生物呼吸及其土壤微环境因子,研究了不同类型湿地土壤微生物呼吸的差异性及其影响因素。结果表明,处于不同植被演替阶段的湿地土壤微生物呼吸具有显著差异(P0.05),海三棱藨草区高于芦苇区,互花米草区最高(0.367 mg.g-1.(24h)-1),互花米草的引种及蔓延增强了入侵区域土壤微生物呼吸。综合考虑不同植被类型湿地土壤微生物呼吸及植被生物量,芦苇区呼吸微弱、植被生物量最高,在理论上具有更高的有机碳碳汇聚能力。通径分析结果显示,影响土壤微生物呼吸强度的主要生物因素有:原核微生物多样性(Shannon指数)和土壤微生物生物量;土壤有机质、硝态氮及土壤含水量对上述微生物活性指标有显著影响,因此也属于土壤微生物呼吸的主要影响因素。     

闽江口潮滩湿地不同植被带土壤及间隙水中硅的分布特征

以闽江口潮滩湿地为研究对象,由岸及海方向对芦苇、短叶茳芏、互花米草(潮沟内)和互花米草(潮沟外)4种湿地土壤生物硅和土壤间隙水氮硅营养盐含量及其随深度变化的特征进行为期1a的季度观测。结果显示:互花米草(外)、短叶茳芏、芦苇和互花米草(内)带湿地土壤生物硅的年均含量依次降低,分别为14.33、10.40、9.98、7.50 mg/g;互花米草(外)、互花米草(内)、短叶茳芏和芦苇带湿地土壤间隙水活性硅酸盐年均含量依次降低,分别为407、359、344、323μmol/L;湿地各植被带土壤及间隙水含硅量均呈现夏秋季节高于冬春季节的趋势。统计分析表明:间隙水活性硅酸盐与土壤生物硅含量、距潮沟的距离之间的正相关性均比较显著(P0.05),温度对土壤中硅含量的影响也有一定的正相关性,说明湿地植被、温度和潮汐作用是影响闽江口湿地硅分布的重要因素。与土著种对比,互花米草入侵在一定程度上改变了闽江口潮滩湿地土壤硅分布的格局。     

莫莫格扁秆藨草恢复湿地土壤种子库对长芒稗入侵的响应

湿地恢复过程中,时常有外来种或本地杂草入侵。土壤种子库作为未来植被的潜在种源,对湿地恢复效果具有重要的指示意义。在莫莫格国家级自然保护区,以恢复白鹤栖息地(扁秆藨草(Scirpus planiculmis)沼泽)为目的,进行了退化湿地的水文恢复;但退化湿地恢复2a后,一年生杂草长芒稗(Echinochloa caudata)在大部分区域成为建群种。以长芒稗入侵湿地和扁秆藨草自然湿地为研究对象,对比分析了长芒稗和扁秆藨草的土壤种子库及生长结实特征。结果表明,在自然湿地扁秆藨草种子库规模是长芒稗的18.42倍,而在恢复湿地长芒稗种子库大小是扁秆藨草的5.04倍。与自然湿地相比,扁秆藨草种子库密度在入侵湿地明显减少,但仍保留了一定量具有活力的种子(664.32±105.98)粒/m~2,这与研究区扁秆藨草较高的种子生产力(9210.4±1513.4)粒/m~2及种子较强的浮力(FP50=39.7d)有关,说明扁秆藨草具备通过种子库或水传播恢复的潜力。长芒稗土壤种子库密度在入侵湿地高达(3345.9±520.3)粒/m~2,明显高于自然湿地种子库规模(P0.01),说明恢复湿地受长芒稗入侵影响严重,这与长芒稗较高的种子生产力(7621.4±376.25)粒/m~2及较弱的种子浮力(FP0=5d)有关,同时也表明长芒稗通过水传播扩散的能力较弱。另外,研究区长芒稗平均高度超过1m,且盖度较大,不仅阻碍扁秆藨草种子的水播,也降低了到达地表的光照水平,从而抑制扁秆藨草更新。因此,在莫莫格受长芒稗入侵湿地,于开花结实前收获长芒稗地上植物体及凋落物应是限制长芒稗扩展、同时促进扁秆藨草恢复的有效措施。     

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.