Litter- and ecosystem-driven decomposition under elevated CO2 and enhanced N deposition in a Sphagnum peatland

Peatlands represent massive global C pools and sinks. Carbon accumulation depends on the ratio between net primary production and decomposition, both of which can change under projected increases of atmospheric CO₂ and N deposition. The decomposition of litter is influenced by 1) the quality of the litter, and 2) the microenvironmental conditions in which the litter decomposes. This study aims at experimentally testing the effects of these two drivers in the context of global change. We studied the in situ litter decomposition from three common peatland species (Eriophorum vaginatum, Polytrichum strictum and Sphagnum fallax) collected after one year of litter production under pre-treatment conditions (elevated CO₂: 560 ppm or enhanced N: 3 g m⁻² y⁻¹ NH₄NO₃) and decomposed the following year under treatment conditions (same as pre-treatment). By considering the cross-effects between pre-treatments and treatments, we distinguished between the effects on mass loss of 1) the pre-treatment-induced litter quality and 2) the treatment conditions under which the litters were decomposing. The combination between CO₂ pre-treatment and CO₂ treatment reduced Polytrichum decomposition by −24% and this can be explained by litter quality-driven decomposition changes brought by the pre-treatment. CO₂ pre-treatment reduced Eriophorum litter quality, although this was not sufficient to predict decomposition. The N addition pre-treatment reduced the decomposition of Eriophorum, due to enhanced lignin and soluble phenols concentrations in the initial litter, and reduced litter-driven losses of starch and enhanced litter-driven losses of soluble phenols. While decomposition indices based on initial litter quality provide a broad explanation of quantitative and qualitative decomposition, they can only be taken as first approximations. Indeed, the microbial ATP activity, the litter N loss and resulting litter quality, were strongly altered irrespective of the compounds' initial concentration and by means of processes that occurred independently of the initial litter-qualitative changes. The experimental design was valuable to assess litter- and ecosystem-driven decomposition pathways simultaneously or independently. The ability to separate these two drivers makes it possible to attest the presence of litter-qualitative changes even without any litter biochemical determinations, and shows the screening potential of this approach for future experiments dealing with multiple plant species.     

2014年-2016年广西地区猪繁殖与呼吸综合征病毒Nsp2和ORF5基因的遗传多样性分析

为了解广西地区猪繁殖与呼吸综合征病毒(PRRSV)流行毒株的遗传进化情况,对2014年-2016年来自广西各地的部分PRRSV阳性病料进行Nsp2和ORF5基因的扩增和测序分析.结果获得34个Nsp2基因序列和45个ORF5基因序列,均属于美洲型毒株.Nsp2基因间核苷酸序列的同源性为91.8％~100％,与PRRSV美洲型毒株VR-2332、CH-1a、JXA1及NADC30株核苷酸序列的同源性分别为81.3％~84.3％、88.9％~92.1％、94.3％~99.3％和73.5％~75.1％,而与PRRSV欧洲型毒株LV株核苷酸序列的同源性为51.5％~53.2％.ORF5基因间核苷酸序列的同源性为82.8％~100％,与PRRSV美洲型毒株VR-2332、CH-1a、JXA1及NADC30株核苷酸序列的同源性分别为83.7％~99.5％、85％~95％、83.8％~99.7％和83.2％~86.4％,而与PRRSV欧洲型毒株LV株核苷酸序列的同源性为62.4％~64.5％.基于Nsp2和ORF5基因推导的氨基酸序列绘制的遗传进化树中,广西地区的毒株主要分布在以JXA1为代表的Ⅳ亚群.表明当前广西PRRSV流行毒株以JXA1株为代表的高致病性美洲型毒株为主,各毒株Nsp2和ORF5基因序列存在一定的差异,尚未发现欧洲型毒株和美洲型NADC30类毒株.     

有益元素对水稻种子萌发的生理效应

将水稻种子浸于从0到10mg·L-1不同浓度梯度的亚硒酸钠溶液中,对其生理指标进行测量可溶性糖含量、呼吸强度及发芽率等.结果表明在低浓度亚硒酸钠溶液浸种的前提下,亚硒酸钠对以上各项生理指标均有促进作用,而高浓度亚硒酸钠溶液浸种,表现出较大抑制作用,同时.由于植物体内复杂多样的同功酶系统的存在,在一定范围内对亚硒酸钠的毒害作用有某种程度的适应与调节能力.     

Effect of miR-181b on cell proliferation and expression of Bcl-2 and SP1 in HepG2 cells

AIM: To investigate the role of miR-181b in the expression of Bcl-2 and SP1 at mRNA and protein levels in the human hepatoma G2 cells (HepG2), and to explore the effect of miR-181b on the regulation of HepG2 cell proliferation. METHODS: The synthetic double-strand complementary DNA based on the sequence of miR-181b was inserted into the vector of miRNASelect^TM pEGP-miR. The microRNA high-expression plasmid was cloned, and the sequences were identified. The miR-181b plasmid was transfected into HepG2 cells with liposomes. The stable cell line was screened by puromycin. The mRNA and protein levels of Bcl-2 and SP1 were measured by RT-PCR and Western blotting, respectively. Methyl thiazolyl tetrazolium (MTT) method was used to analyze the proliferation of HepG2 cells. RESULTS: The Western blotting results showed that miR-181b inhibited the protein expression of Bcl-2 and SP1. The result of RT-PCR also indicated that the mRNA expression of Bcl-2 and SP1 was suppressed. Compared with the control, the growth rate of HepG2 with high expression of miR-181b was significantly decreased.CONCLUSION: miR-181b inhibits the proliferation of HepG2, which may be related to the down-regulation of Bcl-2 and SP1.     

Negligible contribution from roots to soil-borne phospholipid fatty acid fungal biomarkers 18:2ω6,9 and 18:1ω9

The phospholipid fatty acid biomarkers 18:1ω9, 18:2ω6,9 and 18:3ω3,6,9 are commonly used as fungal biomarkers in soils. They have, however, also been found to occur in plant tissues, such as roots. Thus, the use of these PLFAs as fungal biomarkers in sieved soil, which may still contain small remains of roots, has been questioned. We used data from a recent beech tree girdling experiment to calculate the contribution of roots to these biomarkers and were able to demonstrate that not more than 0.61% of 18:1ω9 and 18:2ω6,9 in sieved soil samples originated from roots (but 4% of 18:3ω3,6,9). Additionally, the abundance of the biomarker 18:2ω6,9 in the soil was found to be highly correlated to ectomycorrhizal root colonization, which further corroborates its fungal origin. PLFA biomarkers were substantially reduced in vital roots from girdled trees compared to roots of control trees (by up to 76%), indicating that the major part of PLFAs measured in roots may actually originate from ectomycorrhizal fungi growing inside the roots. We calculated, that even a near to 50% reduction in fine root biomass - as observed in the girdling treatment - accounted for only 0.8% of the measured decrease of 18:2ω6,9. Our results demonstrate that both 18:1ω9 and 18:2ω6,9 are suitable biomarkers for detecting fungal dynamics in soils and that especially 18:2ω6,9 is a reliable biomarker to study mycorrhizal dynamics in beech forests.     

Greenhouse gas emissions in response to straw incorporation,water management and their interaction in a paddy field in subtropical central China

A field experiment was conducted to study the effects of combination of straw incorporation and water management on fluxes of CH₄, N₂O and soil heterotrophic respiration (Rh) in a paddy field in subtropical central China by using a static opaque chamber/gas chromatography method. Four treatments were set up: two rice straw incorporation rates at 0 (S1) and 6 (S2) t ha^?1 combined with two water managements of intermittent irrigation (W1, with mid-season drainage) and continuous flooding (W2, without mid-season drainage). The cumulative seasonal CH₄ emissions for the treatments of S1W2, S2W1 and S2W2 increased significantly by 1.84, 5.47 and 6.63 times, respectively, while seasonal N₂O emissions decreased by 0.67, 0.29 and 1.21 times, respectively, as compared to S1W1 treatment. The significant increase in the cumulative Rh for the treatments S1W1, S2W1 and S2W2 were 0.54, 1.35 and 0.52 times, respectively, in comparison with S1W2. On a seasonal basis, both the CO₂-equivalents (CO₂e) and yield-scaled CO₂e (GHGI) of CH₄ and N₂O emissions increased with straw incorporation and continuous flooding, following the order: S2W2>S2W1>S1W2>S1W1. Thus, the practices of in season straw incorporation should be discouraged, while mid-season drainage is recommended in paddy rice production from a point view of reducing greenhouse gas emissions.     

牦牛源正呼肠孤病毒2型的检测和分离鉴定

旨在调查川西北牦牛哺乳动物正呼肠孤病毒(MRV)的感染情况并分离病毒.采用RT PCR方法,对采自川西北15个牧场的72份牦牛腹泻粪便样本和其中5个牧场的15份腹泻牦牛血清样本进行MRV检测,阳性样本进一步用分型PCR确定其血清型.结果 显示,粪便样本中MRV检出率为20.83％(15/72),血清2型的比例为60％(...     

FACE对三系杂交籼稻汕优63根系活性影响的研究

2005、2006年利用我国惟一的农田开放式空气CO2浓度增高（FACE）研究平台,设计施N量为125kg·hm^-2（LN）、250kg·hm^-2（NN）处理,研究大气CO2浓度比对照高200umol·mol^-1的FACE处理对三系杂交籼稻汕优63根系活性的影响。结果表明：（1）FACE处理使汕优63不同生育时期单位干质量根系的总吸收面积、活跃吸收面积、α-萘胺氧化量等根系活性指标均极显著小于对照。由于FACE处理促进汕优63根系发生量的大幅度增加,因此分蘖期、拔节期其单穴根系活性与对照多无明显差异,到抽穗期FACE处理单穴根系活性显著大于对照;（2）拔节期、抽穗期汕优63每穴的不定根数、不定根总长度、根系体积、根干质量与单位干质量根系活性的关系密切,根量越大单位于质量根系活性越低;（3）不同生育时期汕优63植株含氮率与单位干质量的根系活性多呈正相关,植株碳氮比与单位干质量的根系活性多呈负相关;（4）FACE处理汕优63根系生长量大、植株含氮率低、碳氮比高等可能是造成其单位干质量根系活性低于对照的重要原因。     

80%赖氨酸硫酸盐与98%赖氨酸盐酸盐对生长中期草鱼生长性能、消化吸收能力和消化器官生长发育影响的比较研究

本试验通过比较80%赖氨酸硫酸盐[80%L-Lys·H2SO4,简称80赖氨酸(80-Lys)]与98%赖氨酸盐酸盐[98%L-Lys·HCl,简称98赖氨酸(98-Lys)]对生长中期草鱼生长性能、消化吸收能力和消化器官生长发育的影响,探讨80-Lys和98-Lys在草鱼上的生物效价并确定以80-Lys为赖氨酸(Lys)添加形式时饲料中Lys的适宜含量。选择初始体重为275.80 g左右的健康草鱼540尾,随机分成6组(每组3个重复,每个重复30尾鱼),分别饲喂Lys含量为0.8%(基础饲料)、1.0%、1.2%、1.4%和1.6%的添加80-Lys的饲料及Lys含量为1.2%的添加98-Lys的饲料60 d。结果表明:与基础饲料相比,饲料中添加适宜水平的80-Lys使饲料Lys含量达到1.2%时可显著提高生长中期草鱼的增重率(W GR),特定生长率(SGR),采食量(FI),全肠脂肪酶、淀粉酶活力,肝胰脏谷草转氨酶(GOT)和谷丙转氨酶(GPT)活力,前、中、后肠碱性磷酸酶(AKP)、肌酸激酶(CK)活力,肝体指数与肠体指数以及前、后肠皱襞高度(P0.05),显著降低血清GOT和GPT活力(P0.05),且80-Lys对上述指标的作用效果显著优于98-Lys(P0.05);此外,还可显著提高生长中期草鱼的饲料效率(FE),全肠胰蛋白酶活力,前、中、后肠Na+,K+-ATP酶(Na+,K+-ATPase)和γ-谷胺酰转肽酶(γ-GT)活力,肠长与肠长指数以及中肠皱襞高度(P0.05),但80-Lys对上述指标的作用效果与98-Lys差异不显著(P0.05)。由此得出,与98-Lys相比,80-Lys能更有效地提高生长中期草鱼的消化吸收能力,进而促进其生长。以80-Lys为Lys添加形式,以SGR和FE为标识,生长中期草鱼(276~667 g)饲料中Lys的最适含量分别为1.31%(占饲料蛋白质的4.68%)和1.27%(占饲料蛋白质的4.54%)。     

河流地貌单元研究综述

在河流生态系统嵌套层级结构中,地貌单元作为水流和泥沙输移过程的物理表现,是表征河流形态的重要斑块。多样的河流地貌单元特征决定了栖息地的多样性特征,为生态过程提供了物理基础。为更好地理解地貌单元的结构与功能,通过辨析河流地貌单元内涵,对其分类体系与识别方法、地貌单元的生态响应进行了归纳梳理,并总结了河流地貌单元在栖息地调查评估、河流地貌单元制图及河流分类等方面的应用,从而为认识自然河流、修复受损河流提供技术支持。