祁连山不同类型草地土壤细菌群落特征研究

祁连山是我国西部重要的生态屏障,拥有大量的草地资源。研究草地土壤细菌群落组成及其与土壤环境因子间的关系,可对维持草地生态及了解祁连山土壤细菌群落组成提供一定的数据基础。采用高通量测序技术检测并分析了祁连山默勒镇3种类型草地 （高寒草甸、人工草地、沼泽化草甸）0~10 cm土壤细菌群落结构及多样性,并对上述土壤细菌群落与土壤理化因子的相关性进行了系统的研究。结果表明：1）沼泽化草甸土壤全氮、全磷、有机质碳、含水量和硝态氮显著高于高寒草甸和人工草地（P<0.05）。2）3地共测得有效序列1022446条,以97%的一致性将序列聚类,高寒草甸、人工草地、沼泽化草甸OTU聚类均值分别是4917、5233、5075条。3）Shannon和Simpson多样性指数3地间差异不显著,Chao1指数表现为人工草地>高寒草甸>沼泽化草甸（P<0.05）。4）在门水平上,3地均以变形菌门、酸杆菌门、放线菌门和浮霉菌门为主要类群;在属水平上,表现出不同类型草地细菌富集类型不同。5）有机质碳、全磷、土壤含水量与土壤细菌群落的组成表现出极显著相关（P<0.01）。综上,祁连山地区小生境内3种草地土壤微生物群落存在差异,有机质碳、全磷、土壤含水量是影响群落的主要驱动因子。     

钾肥对紫花苜蓿根颈丙二醛、可溶性蛋白含量与抗氧化系统的影响

为探究钾肥种类及用量对苜蓿(Medicago sativa)抗寒性的影响,本研究以‘北极熊’为供试紫花苜蓿品种,采用二因素随机区组试验设计,研究了秋季施用不同钾肥(硫酸钾和氯化钾)及不同施用量(0,50,100,150,200 kg·hm^-2 K₂O)对越冬期苜蓿根颈在不同温度(4℃,—20℃)处理下抗氧化酶[过氧化物酶(peroxidase,POD),超氧化物歧化酶(superoxide disimutase,SOD),过氧化氢酶(catalase,CAT)]活性和可溶性蛋白(soluble protein,SP)、丙二醛(malondialdehyde,MDA)含量变化的影响。结果表明:在4℃温度处理下,不同钾肥种类和施肥量处理中,苜蓿越冬根颈中MDA和SP含量及POD,SOD,CAT活性均无显著差异;但经—20℃低温冷冻后,不同钾肥种类和施肥量处理下,苜蓿越冬根颈中MDA含量下降,SP含量增加,POD,SOD,CAT活性增强,适应低温环境能力变强,且硫酸钾效果强于氯化钾;两种钾肥均在150 kg·hm^-2(K₂O)钾肥处理下,MDA含量最低,POD,SOD,CAT活性最强,SP含量最高,表明苜蓿受伤程度最小,抗寒保护能力最强。因此,在科尔沁沙地秋季施用300 kg·hm^-2K₂SO₄有利于苜蓿安全越冬。     

黄河源区建植19年人工草地生物结皮CO2通量与叶绿素荧光参数的变化

为了解黄河源人工草地不同类型生物结皮和植被群落CO₂释放和固定的变化特征,并探讨二者的影响因子,本文通过调查黄河源建植19年人工草地不同类型生物结皮CO₂通量和植被土壤特征变化发现：藻和地衣结皮CO₂通量均显著小于苔藓结皮（10.58 μmol·m^-2·s^-1）（P<0.05）;苔藓结皮对应的植被群落CO₂通量（11.55 μmol·m^-2·s^-1）显著低于藻和地衣结皮（P<0.05）;藻和地衣结皮下的土壤CO₂通量显著大于苔藓结皮（约2倍,P<0.05）。苔藓结皮叶绿素初始荧光参数F₀（Minimal Fluorescence）和最大荧光参数F_m（Maximal Fluorescence）均最大;藻和苔藓结皮的PS Ⅱ最大光化学量子产量F_v/F_m（Optimal/Maximal Quantum Yield of PS Ⅱ）均高于地衣结皮。CO₂通量和叶绿素荧光参数的主要影响因子相似,均与禾本科高度、土壤铵态氮含量正相关,与pH负相关。因此,在研究草地碳平衡过程中应充分考虑生物结皮的贡献,同时需注意不同类型的生物结皮的CO₂通量和叶绿素荧光参数的差异变化。     

藏北燕麦草地持续利用与撂荒对高寒草甸土壤特征的影响

为研究不同利用方式对藏北高寒草甸建植一年生燕麦（Avena sativa Linn.）人工草地的土壤理化性质及土壤细菌群落的影响,本试验于8月份植物生长旺季,在持续利用人工草地（AG）、撂荒人工草地（AC）和对照天然草地（NG）采集土壤样品,分析了土壤理化性质、土壤细菌群落组成和结构特征变化。结果表明,AG样地土壤有机质、全钾含量和pH与NG样地相比无显著性变化,土壤全氮、速效氮和速效钾含量显著降低;AC样地与NG样地相比土壤pH显著升高,土壤有机质、全氮、速效氮和速效钾含量显著降低。AG样地土壤细菌群落Chao1,Shannon和Pielou均匀度指数显著高于NG样地,AC样地酸杆菌门和变形菌门丰度显著升高。土壤理化性质是土壤细菌群落结构组成门、属相对丰度变化主要影响因子。综上所述,高寒草甸一年生燕麦人工草地长期利用应科学补充肥料,保持土壤肥力;草地撂荒需谨慎,应及时采取恢复措施避免草地发生退化。     

封育和放牧对高寒草甸植被群落特征和土壤特性的影响

为探究封育和放牧对高寒草甸植被群落和土壤特性的影响,本研究以封育13年和连续放牧高寒草甸为研究对象,采用野外群落调查和室内土壤分析相结合的方法,探究封育和放牧对植被群落状况和土壤特性的影响。结果表明：封育显著提高了群落的盖度和地上生物量（P<0.01）;封育显著提高了0~30 cm土壤总氮（Total nitrogen,TN）、速效氮（Available nitrogen,AN）、速效磷（Available phosphorus,AP）和速效钾（Available potassium,AK）（P<0.01）;封育显著降低了群落密度、物种丰富度指数、香农-维纳多样性指数和均匀度指数（P<0.01）。总之,封育虽增加了高寒草甸植物群落生物量和土壤养分,但在一定程度上导致草地植物群落多样性的下降,研究建议针对封育13年的高寒草甸进行适当的放牧以增加群落物种多样性和丰富度。     

稻谷籽粒的压缩特性与含水率关系的实验研究

通过Brookfield质构仪测定了不同含水率的稻谷籽粒(含水率为10.63%、12.25%、13.71%、15.18%、16.53%w.b.)在Z轴(短轴)方向上的压缩特性(破坏力、破坏能、表观接触弹性模量、最大接触应力、破坏应变),得出含水率对稻谷压缩特性的影响规律。实验结果表明:随着压缩形变的增加,稻谷籽粒受到的压力逐渐增加,当到达破裂点时达到最大值,随之急剧减小。随着含水率的增加,稻谷籽粒的压缩破坏力、破坏能、表观接触弹性模量、破坏应力逐渐减小,压缩破坏应变逐渐增加。     

Flowering phenology of a herbaceous species (Poa annua) is regulated by soil Collembola

The role of soil organisms as possible driver of flowering has never been investigated. We hypothesized that Collembola (microarthropods) will change plant allocation to reproductive modes by changing soil nutrient availability. Individual seedlings of Poa annua were planted in microcosms, in the presence or absence of Collembola. Collembola affected biotic (fungal biomass) and abiotic ($\text{N}-{{\text{NO}}_3}^{-}$, P₂O₅) soil properties and some morphological (number of leaves, root biomass) and chemical (C:N, K, Mg, N) traits of P. annua. As a result, flowering of P. annua was promoted by the presence of Collembola. This provides experimental evidence that soil microarthropods can affect the reproduction strategy and phenology of a plant.     

基于视景仿真技术的联合收割机牵引及加载性能研究

随着农业机械化的不断发展,联合收割机的应用越来越普遍,大大地提高了农业生产效率。然而,在联合收割机使用中还存在一些驾驶员视域不开阔、可视环境差等不安全因素。针对这些问题,本文引入了视景仿真技术概念,通过构建基于视景仿真技术的联合收割机牵引及加载性能模型,对联合收割机的牵引及加载性能进行仿真分析。结果显示,将视景仿真技术应用与联合收割机,方便了驾驶员及时掌握实地信息,提高了牵引性能和加载性能,降低了驾驶危险系数。     

Immunogenic properties of Landrace pigs selected for resistance to mycoplasma pneumonia of swine

Mycoplasma pneumonia of swine (MPS) lung lesions and immunogenic properties were compared between a Landrace line that was genetically selected for reduced incidence of pulmonary MPS lesions, and a non‐selected Landrace line. The MPS‐selected Landrace line showed significantly lower degrees of pulmonary MPS lesions compared with the non‐selected Landrace line. When changes in immunity before and after vaccination were compared, the percentage of B cells in the peripheral blood of the MPS‐selected Landrace line was significantly lower than that of the non‐selected line. Furthermore, the concentration of growth hormone and the mitogen activity of peripheral blood mononuclear cells in the MPS‐selected Landrace line showed significantly (P < 0.05) lower increases after vaccination than the non‐selected line. Conversely, the concentration of peripheral blood interferon (IFN)‐γ and salivary immunoglobulin A (IgA) after Mycoplasma hyopneumoniae vaccination was significantly higher in the MPS‐selected Landrace line than in the non‐selected line. Gene expression of toll‐like receptor (TLR)2 and TLR4 was significantly higher in the MPS‐selected Landrace line in immune tissues, with the exception of the hilar lymph nodes. The present results suggest that peripheral blood IFN‐γ, salivary IgA TLR2, and TLR4 are important immunological factors influencing the development of MPS lesions.     

Nutritional properties of dried salmon silage for broiler feeding

The aim of this study was to evaluate the chemical composition, energy and amino acid profile of dried salmon silage (DSS) for broilers. The DSS was obtained by acid digestion of salmon mortalities and subsequently co‐dried with wheat bran in a 70:30 ratio (70 parts silage and 30 parts wheat bran). Samples of DSS were evaluated for chemical composition, gross energy, nitrogen‐corrected true metabolizable energy (TME_n), mineral content, total and digestible amino acids for broilers, and amino acid score. The chemical composition of DSS was (mean ± SD): moisture (12.3 ± 0.8%), crude protein (44.0 ± 1.1%), ether extract (5.0 ± 2.4%), crude fiber (3.3 ± 0.4%) and ash (9.4 ± 0.6%). The gross energy and TME_n for broilers were 4 069 kcal/kg and 2 613 kcal/kg, respectively. The DSS mineral composition showed a high content of calcium (1.01%) and phosphorus (1.08%). The DSS had high levels of digestible methionine (0.74%), lysine (2.27%), and threonine (1.16%), and did not present limiting amino acids for broilers. Nutritional composition of DSS showed high protein content with an amino acid profile considered to be suitable as a protein source for broiler feeding.