青藏高原草地产量与草畜平衡变化

深入了解青藏高原草地生产力与草畜平衡状态的变化,是青藏高原生态屏障建设和生态环境保护的基础。利用遥感植被指数和叶面积指数产品,基于VIP生态水文过程模型,模拟分析了青藏高原2000—2018年间草地生产力的时空格局,并结合同期农牧业统计资料,分析了青藏高原县域尺度草畜平衡状态的变化。结果表明:青藏高原草地多年平均净初级生产力(NPP)为158.4 g C·m^-2·a^-1;近20年来草地生产力上升趋势明显,显著上升面积的比例为44.7%。气候变暖、降水量增加、草本植物生长期延长和大气CO₂浓度升高是青藏高原草地生产力提高的主要驱动因素。基于草场产量估算的青藏高原平均理论载畜量为1.17 SU·hm^-2,年增长率为0.011 SU·hm^-2。2000年以来青藏高原草地超载情况总体趋于好转,严重超载县的面积比例已降至20%以下,其中超载程度较严重的地区,畜牧业的维持和发展主要依靠作物秸秆补饲。研究结果可为区域农牧业结构调整和生态环境保护提供科学依据。     

盐池县草地沙漠化过程中植物群落的动态变化

对盐池县潜在沙漠化草地、轻度沙漠化草地、中度沙漠化草地、重度沙漠化草地和极度沙漠化草地5种不同沙化类型草地植被物种组成及多样性进行研究,以探讨沙漠化对地上植被的影响。结果表明:随着沙化程度的加重,多年生草本植物逐渐减少,优势度由潜在沙漠化草地的88.73%降至极度沙漠化草地的19.97%;一年生草本植物及沙生灌木、半灌木逐渐增加,优势度由潜在沙漠化草地的12.67%增至极度沙漠化草地的80.03%。多样性指数由轻度沙漠化草地的2.21下降至极度沙漠化草地的1.52。     

川西北不同沙化程度草地植物功能性状及其驱动因子

以川西北不同沙化程度草地典型群落为研究对象,分析了不同沙化程度草地(未沙化草地、轻度沙化草地、中度沙化草地、重度沙化草地)植物功能性状之间的关系及其与地形和土壤因子的相关性,并对不同沙化程度草地植物功能性状进行了比较。结果发现:(1)从未沙化草地到重度沙化草地变化过程中,植物群落呈现出"湿生-中生-旱生"的演替格局,植物群落高度、盖度和物种丰富度随着沙化程度加剧而逐渐降低。(2)叶厚度(LT)、比叶面积(SLA)、叶组织密度(LD)、比根长(SRL)、根组织密度(RD)、叶氮含量(LN)、叶磷含量(LP)、根氮含量(RN)、根磷含量(RP)随着草地沙化程度的增加而降低。(3)未沙化地草本植物的植物功能性状最大,对资源的利用效率很高,其中SLA极差值最大(250.53),LT极差值最小(9.56),RD、SLA、RN、RP和LD具有较高的变异性,LT具有较低的变异系数,其保守性最高。(4)RN与所有的叶性状均有不同程度的相关性;SLA与LD呈极显著负相关关系,与RN呈显著正相关关系;SRL与LN呈极显著负相关关系,与RN呈显著负相关关系;LN与RN呈显著正相关关系。(5)逐步回归分析表明,功能性状与土壤因子间具有一定明显的相关性,可以通过土壤因子的定量分析来确定地上植物功能性状的变化趋势及可变范围。(6)灰色关联度分析发现,SLA、SRL、RD、LN、RP受海拔的影响较大,LT、LD、RN受坡向的影响最大,坡位对LP影响最大。研究表明,地形因子中海拔对植物功能性状影响较大,土壤因子中pH值对植物功能性状影响较大。     

沙化草地恢复过程中土壤有机碳物理组分和全氮含量的变化

以宁夏中北部盐池县不同恢复阶段的沙化草地(流动沙地、半固定沙地、固定沙地和荒漠草地)土壤为研究对象,分析土壤粗砂粒有机碳、细砂粒有机碳、粘粉粒有机碳、重组有机碳、轻组有机碳和土壤全氮的变异特征,探讨沙化草地恢复过程中土壤有机碳变化机制。结果显示:(1)荒漠草地、固定沙地、半固定沙地0~30cm土层土壤,粗砂粒有机碳、细砂粒有机碳和粘粉粒有机碳含量分别比流动沙地增加了67.7%、69.8%、212.1%和48.8%、35.3%、99.9%以及33.6%、23.0%、48.9%。(2)随着沙化草地不同程度的恢复,轻组有机碳含量、分配比例和重组有机碳含量均表现为流动沙地半固定沙地固定沙地荒漠草地;重组有机碳分配比例随沙化草地恢复程度的升高呈降低趋势。(3)土壤细砂粒、粘粉粒、重组有机碳、轻组有机碳、粗砂粒有机碳、细砂粒有机碳、粘粉粒有机碳含量与土壤有机碳、土壤全氮含量均呈显著正相关关系,与粗砂粒含量均呈显著负相关关系。研究表明,轻组有机碳和粘粉粒有机碳含量对土壤有机碳的影响最大,轻组有机碳、重组有机碳、粗砂粒有机碳和粘粉粒有机碳对土壤全氮的影响最大,表明沙化草地的恢复有利于减小土壤侵蚀,改善土壤结构与质量。     

沙化和退化状态对甘南草地生态系统固碳的影响

陆地生态系统作为全球第二大碳库,其碳收支应对气候变化一直是研究的热点领域.多数研究主要探讨温/湿度、CO2浓度等对陆地生态系统碳循环的影响,而针对草地的沙化、退化对植被整个固碳过程所产生影响的研究相对不足.本研究以30 m×30 m空间分辨率的遥感数据做支撑,参考国家标准GB/T 24255-2009解译草地沙化和退化...     

若尔盖沙化草地恢复过程中土壤特性及水源涵养功能

1995年以来,政府大力开展对若尔盖沙化草地生态系统的恢复重建工作,其生态恢复效益受到广泛关注。而水源涵养功能作为衡量草地生态系统恢复程度的重要生态指标,其变化对水分循环及全球气候变化有一定的影响和响应。以若尔盖县不同治理年限的沙化草地治理区为研究对象(包括1995年、2007年、2009年、2010年、2011年的治理区,2012年的正常放牧区和2012年的无治理区),采用野外采样和室内分析相结合的方法,将土壤含水量作为研究指标,结合土壤的理化性质,分析沙化草地在恢复重建过程中水源涵养功能的变化及其影响因素,结果表明:若尔盖草地在恢复重建过程中,(1)土壤质地发生变化,由紧砂土逐渐恢复成砂壤土,保水能力及保肥性都得到显著提高;土壤容重随着治理时间的增加而降低,由无治理区的1.7 g/cm~3下降到正常放牧区的1.3 g/cm~3;(2)土壤p H值随着治理时间的增加而逐渐降低,由7.6逐渐下降到6.7,土壤总体上为中性土,适宜植被生长;土壤有机质的变化相对不明显,但治理区的有机质远低于正常放牧区的土壤有机质,总体呈缓慢上升趋势;(3)土壤含水量呈"V"型变化趋势,在治理初期,土壤含水量先减小,2009年治理区的含水量最低,仅为6.8%,但到了治理后期,土壤的含水量开始增加,1995年的沙化治理区含水量达到了12.1%,说明水源涵养能力得到相应的提升;(4)经过相关分析,土壤含水量和有机质、土壤质地、土壤p H值、生物量以及土壤碳含量呈显著相关关系,其中,含水量与有机质、土壤质地以及土壤碳含量呈极显著正相关,而与p H值呈显著负相关;(5)随着治理时间的增加,土壤退化指数逐渐减小,土壤状况得到不断的改善。     

宁夏东部风沙区沙化草地土壤水分和植被的空间特征

土壤水分作为土壤-植被-大气连续体的关键因子,对沙化草地的演化过程具有重要作用。为探讨宁夏东部风沙区沙化草地土壤水分、物种丰富度指数及植被盖度的空间变异及其相互关系,以哈巴湖自然保护区沙化草地为对象,采用样线法自潜在沙化草地至重度沙化草地进行植被调查和土壤取样,通过经典统计学和地统计学分析,得出以下结果：0—100 m各土层土壤水分含量、植被盖度和物种丰富度指数的分布范围分别为0.82%—28.22%、41.00%—93.00%和0.82—2.80,变异系数范围为0.20—0.48,均属于中等变异。各土层土壤水分和物种丰富度指数表现为中等的空间自相关性,植被盖度则表现为强烈的空间自相关性。Kriging插值结果表明,0—100 cm各土层土壤水分和植被盖度的空间插值图呈条带状和斑块状的梯度变化,物种丰富度呈斑块分布,自潜在沙化草地至重度沙化草地,表现为逐渐降低的趋势。相关分析表明,植被盖度与0—40 cm各土层土壤水分呈显著正相关,与40—100 cm各土层土壤水分呈极显著正相关。宁夏东部风沙区沙化草地土壤水分含量总体较低,由于结构因素和随机因素的共同作用,随草地沙化程度的加重,表现为...     

吉林省西部与内蒙古东部农牧交错区草地退化现状及管理对策

吉林西部和内蒙古东部的农牧交错区是半湿润与半干旱气候的过渡地带,草地退化严重,主要表现为盐碱化和沙化。人为因素是导致草地退化的主要因素,人口压力和不合理利用是加速草地退化的主导因素。提出了要对现有草地开展健康诊断,对健康草地实施保护,对已受损的草地实施恢复与重建,建立科学管理制度等解决对策。     

若尔盖高寒草地退化沙化过程中土壤养分与团聚体结构的变化特征

若尔盖地处青藏高原东缘, 是黄河上游重要的水源涵养地。近来受过度放牧、鼠虫害等影响, 若尔盖高寒草地出现严重退化, 部分草地已完全沙化。草地沙化已成为若尔盖高寒草地生态安全所面临的重大问题。研究以若尔盖典型的沙化地区麦溪乡为研究对象, 以植被覆盖率为沙化梯度划分标准, 分别划分未退化、轻度退化、中度退化、重度退化和极度退化5种不同退化阶段草地, 探究退化沙化过程中草地土壤养分与团聚体结构变化特征。结果表明: (1)退化沙化过程中, 土壤养分含量总体随着草地沙化程度的加剧而显著下降(P<0.05)。(2)退化沙化过程中土壤团聚体结构发生明显变化, 团聚体平均重量直径(MWD)、几何平均直径(GWD)随着沙化程度的加剧而显著降低(P<0.05); 各粒级团聚体百分比仅5—2 mm粒级团聚体在重度退化阶段发生显著降低变化(P<0.05), 其他粒级并未表现出明显的变化趋势。(3)团聚体MWD与微生物生物量、有机质、全氮、硝态氮、有机碳均呈显著或极显著正相关, 与pH呈极显著负相关(P<0.01)。在整个草地退化沙化过程中, 土壤养分含量显著下降, 土壤结构受到严重破坏, 二者之间变化关系紧密。草地沙化治理与防护过程中, 要兼顾土壤结构修复与养分输入, 处理好土壤团聚体结构稳定与养分转化间的交互关系。     

开展高寒退化生态系统恢复与重建技术研究,助力西藏生态安全屏障保护与建设

西藏是青藏高原的核心,是我国重要的生态安全屏障。由于高、寒、旱的特点,西藏高寒生态系统极为脆弱,在自然和人为因素影响下极易发生退化,治理难度大。草地退化和土地沙化治理一直是西藏生态安全屏障保护与建设的重中之重。为此,国家在"典型脆弱生态修复与保护研究"重点专项里启动了"西藏退化高寒生态系统恢复与重建技术及示范(2016YFC0502000)"项目,旨在研究生态系统演变规律和影响机理的基础上,针对西藏高原不同的退化区域,重点研发高寒退化草地恢复、沙化土地治理、生态产业及生态畜牧业发展等技术与模式,开展县域水平的集成示范,实现高寒生态系统功能的提升与适应性优化管理的目标,为西藏生态安全屏障保护与建设提供技术支撑。     

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.