现场采购的利弊分析及解决对策探讨

从现场采购与其他采购方式的比较出发,对现场采购的优势、弊端进行深入的分析,提出做好现场采购工作的一些对策。     

Advanced Agriculture of lsrael Roots in its Decision Making Mechanism

ln the past 70 years, lsrael has not only realized the self-sufficiency of agri-cultural products, but also make its way to becoming one of leading exporters of agri-cultural products in the world rapi...     

不同林型天然红松混交林林隙大小和枯叶分解对土壤微生物碳的影响

[目的]分析凉水国家级自然保护区不同林型天然红松混交林林隙大小、凋落物放置位置和采样时间对土壤微生物碳(SMBC)的影响,揭示影响本地区SMBC变化的因素,为天然红松混交林生态系统碳循环的研究提供基础数据。[方法]在天然红松混交林3种林型的大、中、小林隙内不同位置的土壤表层放置装有红松、椴树、枫桦枯叶的分解袋,并以各自的郁闭林分为对照,在2012年植物生长季的6—9月,每月采集枯叶分解袋下0 10 cm土层土样,采用氯仿熏蒸-K2SO4浸提法测定SMBC。[结果]在椴树红松混交林(TP)内,林隙大小对SMBC的影响依次为小林隙大林隙中林隙;在云冷杉红松混交林(PAP)内,依次为中林隙大林隙小林隙;在枫桦红松混交林(BP)内,依次为大林隙中林隙小林隙。3种林型下,采样时间(月份)对SMBC均有显著的影响(P0.05);林隙大小对其影响均不显著(P0.05);枯叶分解袋放置位置对大、中、小林隙内SMBC的影响均不显著(P0.05)。[结论]不同林型下林隙大小对SMBC的影响排列顺序不同;枯叶分解袋放置位置对天然红松混交林3种林型大、中和小林隙内SMBC的影响均未达到显著水平。     

Effect of 1α, 25-dihydroxyvitamin D3 on T helper cell 17 and expression of related cytokines in penetrating keratoplasty in mice

AIM: To evaluate the effects of 1α, 25-dihydroxyvitamin D3 on T helper cell 17 (Th17 cells) and its related cytokines in a mouse model of corneal allograft transplantation. METHODS: C57BL/6 mice were transplanted with corneal grafts from BALB/c mice and treated intraperitoneally with 1.0 μg 1α, 25-dihydroxyvitamin D3 or soybean oil every other day after operation. The transparency of the corneal grafts was evaluated for potential rejection signs by slit lamp biomicroscopy and histopathology. The expression levels of IL-17, RORγt and IFN-γ in the spleen were measured by real-time PCR. Moreover, the protein expression of RORγt and IL-17 in the peripheral blood was analyzed by Western blotting. IL-17 and IFN-γ in peripheral blood were measured by flow cytometry. RESULTS: 1α, 25-dihydroxyvitamin D3 significantly inhibited the rejection of the corneal allograft and reduced the numbers of inflammatory infiltrates in the corneal graft. In the spleen, 1α, 25-dihydroxyvitamin D3 treatment reduced the expression levels of IL-17, RORγt and IFN-γ. In the peripheral blood, 1α, 25-dihydroxyvitamin D3 treatment downregulated the expression levels of RORγt, IL-17 and IFN-γ. CONCLUSION: The effects of 1α, 25-dihydroxyvitamin D3 on suppressing corneal transplantation-induced allograft rejection in mice are closely associated with its modulation on IL-17 and related cytokine RORγt.     

饲养方式和卢氏绿壳蛋鸡经济效益的相关性

讨论不同饲养方式对卢氏绿壳蛋鸡体重、屠宰性能、消化器官、肠道组织的影响。本试验选取卢氏绿壳蛋鸡200只,其中放养组和笼养组各100只,且每组公鸡、母鸡各50只,对其相关指标进行测定分析。结果表明:放养鸡的各项指标都优于笼养鸡,产出效益较高,同时放养鸡具有较强的自由觅食能力,能起到降低成本的效果。通过经济性比较,养殖企业选择科学的管理方式有助于提高经济效益,增强市场竞争力,促进企业生存和发展。     

Site variability effect on field measurement of symbiotic nitrogen fixation using the 15N isotope dilution method

The sensitivity of the isotope dilution method involving the application of ¹⁵N-enriched fertilizers to estimate symbiotic N₂ fixation in legumes under field conditions is analysed with respect to the variability of atom% ¹⁵N excess in the fixing and non-fixing (reference) crops. Field data collected along a 96 m transect with 63 plots split into two strips, one sown with ryegrass and the other with alfalfa, showed that the sensitivity of the methodology increased with the level of fixation. The results further showed that the sensitivity of the ¹⁵N isotope dilution method for estimating N₂ fixed can be greatly improved by selecting fairly homogeneous sites, although use of a heterogenous site is quite practicable if the non-fixing reference crop is sited reasonably close to the test plots. Errors associated with mismatch between reference and fixing crops or heterogeneity of site become smaller as the amount of fixation increases. The data also revealed that relative comparisons of N₂ fixing abilities of legume treatments based on their ¹⁵N enrichments may not be valid for soils with highly variable N content. Under such circumstances, the use of a reference crop sited close to each legume treatment is necessary.     

利用无瓣海桑控制入侵种互花米草的初步研究

禾本科草本植物互花米草(Spartina alterniflora Loisel.),原产北美洲中纬度海岸潮间带)由于对潮间带生境的适应性特征而具有较宽的生态幅,现已严重入侵了世界许多河口和海湾,包括我国整个大陆沿海的潮间带[1-3],尤其对我国南方沿海红树林的更新繁殖、潮间带物种多样性、河道畅通以及滩涂养殖业等带来严重的负面影响[4-5],单在经济上,每年给广东、福建沿海养殖业带来的损失可达数亿至数十亿元人民币[6].互花米草已被公认为危害最严重的全球性入侵杂草之一[2].     

配合饲料中不同蛋白含量对方斑东风螺稚螺生长和体组成的影响

为探讨人工配合饲料中不同蛋白水平对方斑东风螺稚螺生长和体组成的影响。采用蛋白质含量分别是18.58%,24.30%,30.08%,36.44%,42.64%和48.86%的配合饲料进行了试验。试验水温(28.5±1.5)℃,海水盐度1.0178±0.0008,pH值7.9±0.5,试验期6周。结果表明:配合饲料各组中,当蛋白水平高于36.44%(IV组)时,方斑东风螺稚螺壳高和壳宽增长率以及增重率均显著高于18.58%～30.08%组;各组间成活率差异不显著(P0.05)。配合饲料中不同蛋白水平对方斑东风螺肉中水分、灰分和磷的含量均有显著的影响(P0.05),肉中蛋白含量各组间差异不显著(P0.05)。采用折线回归模型分析配合饲料中蛋白水平与增重率的变化关系,通过折线回归方程y1=5.573X-1.84(R2=0.922);y2=2.367X+135.33(R2=0.823)。可见,0.34～1.18 g方斑东风螺稚螺配合饲料中,适宜的蛋白质添加水平为42.78%。     

珠海市城区林地管理与集体林权制度改革

介绍珠海市城区林地管理和收入情况,以及林业生态建设现状.阐述城区森林资源林权制度历史沿革和管理情况.分析城区集体林地不适宜进行集体林权制度改革的原因,包括城区农业人口已全部转为城镇居民;林地主要为生态公益林地;历次林改不彻底,林地纠纷多等,并提出了将其转变为国有林地经营和管理的途径.