面向21世纪的美国农业工程教育

由传统的农业工程专业向生物工程专业发展已经成为美国的发展趋势，进而怎样建立生物工程专业也已成为研究的热点。该文介绍了这种发展的起因与可能性，生物工程专业建设的框架原则，它与农业工程专业的关系以及工程师与生物学家间的界接面。     

GFILANguardN．S．S在网络漏洞扫描中的应用

漏洞扫描技术从一个新的角度解决了网络安全fq题。GFI LANguard Network Security Scanner作为一个网络漏洞扫描系统,能够扫描、检测、评估和修复网络中的任何安全漏洞,使用GFILANguard N．S．S可以更有效地解决漏洞管理的主要问题。     

Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations

More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems provide a carbon sink, the size, distribution, and interannual variability of this sink remain uncertain. Here we report a terrestrial carbon sink in the conterminous U.S. at 0.63 pg C yr⁻¹ with the majority of the sink in regions dominated by evergreen and deciduous forests and savannas. This estimate is based on our continuous estimates of net ecosystem carbon exchange (NEE) with high spatial (1 km) and temporal (8-day) resolutions derived from NEE measurements from eddy covariance flux towers and wall-to-wall satellite observations from Moderate Resolution Imaging Spectroradiometer (MODIS). We find that the U.S. terrestrial ecosystems could offset a maximum of 40% of the fossil-fuel carbon emissions. Our results show that the U.S. terrestrial carbon sink varied between 0.51 and 0.70  pg C yr⁻¹ over the period 2001-2006. The dominant sources of interannual variation of the carbon sink included extreme climate events and disturbances. Droughts in 2002 and 2006 reduced the U.S. carbon sink by ∼20% relative to a normal year. Disturbances including wildfires and hurricanes reduced carbon uptake or resulted in carbon release at regional scales. Our results provide an alternative, independent, and novel constraint to the U.S. terrestrial carbon sink.     

B／S架构的高校教学管理系统研究与开发

研究开发了基于ASP．NET技术、B／S模式的高校教学管理系统,并对该系统的体系结构、功能模块以及实现系统的数据集等关键技术进行了深入探讨,指出系统的实现极大地提高了教学管理效率。     

短序十大功劳基因组总DNA提取方法研究

以短序大功劳嫩叶为材料,采用CTAB法、CTAB改良法1、CTAB改良法2、SDS法和试剂盒法五种方法提取短序十大功劳基因组总DNA,用分光光度计和琼脂糖凝胶电泳方法检测所得总DNA的纯度和得率,用ISSR-PCR扩增的方法检测所得总DNA的质量。结果表明,五种方法均能从短序大功劳叶片中提取到基因组DNA,但不同方法提取得的基因组DNA的纯度、浓度和得率存在明显的差异。CTAB改良法2和试剂盒法提取的DNA纯度高,可直接用于下游分子生物学实验,CTAB法、CTAB改良法1和SDS法提取的总DNA质量较差,不利于下游的分子生物学实验;五种方法提取的总DNA的得率在10．836-451．709μg/g之间,呈CTAB法〉SDS法〉CTAB改良法1〉CTAB改良法2〉试剂盒法的现象。此实验获得的结果可以为短序十大功劳分子生物学研究提供基础。     

中国景天科植物一新种——伴矿景天

本文描述了景天属(景天科)一新种,即伴矿景天(SedumplumbizincicolaX.H.GuoetS.B.Zhousp.nov.)。     

基于B/S模式的通用教学资源库系统的设计与实现

介绍了一个基于B/S模式的通用教学资源库系统的设计思想,并详细阐述其在可视化环境下基于SQLServer2005数据库和ASP.net、ADO.net、ODBC等技术的实现方法。该系统在结构上被划分为数据、功能和应用三个层次,实现了数据库建立,资源录入、查询和管理,对使用记录的处理,资源自动上传、下载,在线线阅读、打印和管理等功能。该系统的实现技术使其具备良好的开放性、安全性、稳定性及通用性,目前已经投入使用且运行良好。     

土壤因子对链霉菌S506定殖和促生功能的影响

链霉菌S506是从植物根际分离获得的具有促生、防病和降解根系毒素功能的根际微生物,为了解土壤环境条件对其在根际定殖和功能表达的影响,以链霉菌S506为试材,研究了土壤质地、环境温度和土壤湿度对S506在番茄根际土壤定殖及番茄植株生长的影响.结果表明,适宜链霉菌S506在番茄根际定殖和促生作用发挥的土壤质地为壤土,其次为砂土和黏土;试验所设温度梯度中,利于S506在根际定殖的环境温度为30℃,其次为22.5℃和15℃,而利于目的菌株促生功能表达的环境温度则依次为22.5℃、30℃和15℃;适宜于目的菌株在根际定殖和促生功能发挥的土壤相对湿度为20%、25%,其次为15%和30%.     

Influence of fertilization and organic amendments on organic‐carbon fractions in Heilu soil on the loess plateau of China

The influence of fertilization on organic‐carbon fractions separated by density and particle size in Heilu soil (Calcic Kastanozems, FAO) was investigated in a 20‐year (1979–1999) long‐term experiment on the Loess Plateau of China. Compared to an unfertilized treatment, N application alone did not increase total organic carbon (TOC) and its fractions of density and particle size. However, the treatment of N + P fertilization significantly increased salty‐solution–soluble organic carbon (SSOC), microbial biomass C (MB‐C), and organic C associated with fine silt. When manure was applied alone and in combination with N and P fertilizer, the light fraction of organic C (LFOC), SSOC, and MB‐C were increased significantly, and the TOC was as high as that of a native Heilu soil. Organic C associated with different particle‐size fractions was also increased significantly, and the allocation of C among the fractions was altered: the proportions of C in sand (>50 μm), coarse‐silt (20–50 μm), and fine‐clay (<0.2 μm) fractions were increased whereas fine‐silt (2–20 μm) and coarse‐clay (0.2–2 μm) fractions were decreased. It is concluded that N fertilizer alone is not capable of restoring organic‐matter content in the Heilu soils of the Loess Plateau and that C‐containing material like manure and straw is necessary to produce significant increase in soil organic carbon in these soils.     

黔中喀斯特山区坡耕地产流产沙对无籽刺梨种植的响应

产流产沙是坡耕地土壤侵蚀的主要形式,为探讨无籽刺梨对黔中喀斯特山区坡耕地土壤侵蚀治理效应,采用径流小区野外定位观测法和相关性分析法,分析了坡度15°和25°坡耕地共6个自然坡面径流小区2016年6—9月15次野外实测侵蚀性降雨产流产沙数据。结果表明:(1)在同坡度同降雨量同I₃₀下,无籽刺梨地较自然恢复地有显著保水保沙能力,无籽刺梨+自然荒草地模式优于无籽刺梨单种模式。(2)无籽刺梨种植模式减流减沙效果坡度25°优于15°,减沙效果优于减流效果。其中无籽刺梨+自然荒草地减流减沙效果最优,在小雨、中雨、大雨、暴雨4种雨型下,坡度15°度时较自然恢复地分别平均减流59.08%,65.23%,56.96%,54.87%,分别平均减沙87.32%,71.64%,51.10%,74.69%;坡度25°度时分别平均减流53.11%,76.09%,76.72%,46.12%,分别平均减沙85.40%,86.87%,71.55%,73.99%。(3)研究区产流产沙量与降雨参数(P、I₃₀)高度相关且在0.01水平上显著,在不同雨型下无籽刺梨减流减沙均有明显效果,小雨、中雨时减流减沙效果最佳。研究证实了研究区无籽刺梨种植能抵御不同雨型的降雨侵蚀,可作为贵州省喀斯特山区生态修复的极优经济选种。     

贵州无籽刺梨基地土壤及树体特征对种植年限的响应

基于贵州喀斯特山区典型无籽刺梨种植基地的根系土壤的化学指标、物理指标和生物学指标和树体特征,采用空间替换时间的方法,对喀斯特山区无籽刺梨种植基地的土壤质量现状进行全面分析与评价,研究不同种植年限的基地的土壤质量及其树体特征对植被恢复的响应与机制。结果显示:不同林龄的无籽刺梨种植基地的土壤化学、物理和生物学指标差异明显,兴仁县(1~2a)土壤的整体变异程度大于乌当区(3~4a)和西秀区(8~9a),并随着种植年限的增加,土壤质量有所提高;无籽刺梨的冠幅、树高、叶绿素和地径呈现逐渐增加趋势,而分枝数则呈现先增加后下降趋势;兴仁县的pH(0.25)、乌当区的有机质(0.44)和西秀区的全磷(0.46)的隶属度均值最小,分别为三地土壤质量限制性因子;而有效磷(0.19)、有效钾(0.17)和容重(0.25)分别为三地的最大权重系数,是提高各自土壤质量的最重要因子;土壤质量综合指数分别为1.17、1.40和1.90,分别较兴仁县增加了19.69%和61.69%,增加趋势明显。研究表明,无籽刺梨的种植有利于贵州喀斯特山区土壤质量的改善,可作为中度、轻度和潜在石漠化地区生态重建的经济树种。     

基于R/S和Morlet小波分析的北洛河上游径流变化特征

为了深入探究北洛河上游长时间序列年径流量变化规律及周期特征,加强对流域水资源规划管理和可持续开发利用,基于北洛河上游吴旗水文站1971—2014年实测径流量数据,采用M-K(Mann-Kendall)趋势检验法和R/S法(rescaled range analysis)分析了全年及汛期径流量的变化趋势和持续性; 并采用Morlet小波变换对径流时间序列进行了多尺度周期特征分析。结果表明:(1)从径流量年内分配来看,1971—2014年,北洛河上游径流年内集中分布在6—9月,月最大径流量一般出现在8月,分配曲线呈“双峰型”。随着时间推移,径流量年内分配不均匀性逐渐减弱;(2)汛期径流量占年径流量的比例降低,全年和汛期的径流量变化均呈显著减少趋势(p<0.05),且未来变化趋势与过去一致的可能性很大,即减少趋势具有一定的持续性(全年和汛期径流量序列Hurst值分别为0.53,0.69);(3)北洛河上游径流量呈现出多尺度性、主周期性和同步性变化的特点。汛期和全年径流量具有相似且显著的变化周期,主要受到3,11,19 a左右3个主周期的影响。总之,北洛河上游径流量呈显著减少趋势且变化周期比较明显。     

Effects of Precipitation on Nonpoint Sources of Nitrogen Contamination to Surface Waters in the U.S. Great Plains

Declining surface water quality is of great concern across the Great Plains. Recent trends in the earth’s climate can create abrupt changes in precipitation, which can alter the impact of nonpoint sources on water quality. A 2-year study [dry (2009) and wet (2010) year] was initiated to assess the impact of nitrate nitrogen (N) loss from the Roca watershed on water quality in Salt Creek. The water flow and nitrate N concentration was determined weekly in Salt Creek. The predicted average nitrate N concentration in runoff during the dry year (38.3 mg L^?1) was almost five times greater than that (7.9 mg L^?1) for the wet year. However, the predicted amount of nitrate N in runoff was similar for both years because the runoff for the wet year (51.8 million m³) was about five times greater than that for the dry year (10.7 million m³). The total amount of nitrate N found in Salt Creek was 18 and 127 metric tons for the dry and wet years, respectively. These data implied that 95% (dry year) and 69% (wet year) of the nitrate N has been removed from streams water in Salt Creek. Factors responsible for removing nitrate N from water include heavy growth of algae, weeds, and aquatic plants as well as denitrification and volatilization reactions. The predicted amount of nitrate N lost from soils by leaching was almost seven times greater for the wet (1,037 metric tons) than the dry year (156 metric tons). It was concluded that high precipitation for the wet year raised both the amount of nitrate N in runoff and loading into Salt Creek and could increase the negative impact on water quality.     

Crop management and phenology trends in the U.S. Corn Belt: Impacts on yields, evapotranspiration and energy balance

Crop yields are affected by many factors, related to breeding, management and climate. Understanding these factors, and their relative contributions to historical yield increases, is important to help ensure that these yield increases can continue in the future. Two important factors that can affect yields are planting dates and the crop's growing degree day (GDD) requirements. We analyzed 25 years of data collected by the USDA in order to document trends in planting dates, lengths of the vegetative and reproductive growth periods, and the length of time between maturity and harvest for corn and soybeans across the United States. We then drove the Agro-IBIS agroecosystem model with these observations to investigate the effects of changing planting dates and crop GDD requirements on crop yields and fluxes of water and energy. Averaged across the U.S., corn planting dates advanced about 10 days from 1981 to 2005, and soybean planting dates about 12 days. For both crops, but especially for corn, this was accompanied by a lengthening of the growth period. The period from corn planting to maturity was about 12 days longer around 2005 than it was around 1981. A large driver of this change was a 14% increase in the number of GDD needed for corn to progress through the reproductive period, probably reflecting an adoption of longer season cultivars. If these changes in cultivars had not occurred, yields around 2005 would have been 12.6 bu ac⁻¹ lower across the U.S. Corn Belt, erasing 26% of the yield increase from 1981 to 2005. These changes in crop phenology, together with a shortening of the time from maturity to harvest, have also modified the surface water and energy balance. Earlier planting has led to an increase in the latent heat flux and a decrease in the sensible heat flux in June, while a shorter time from maturity to harvest has meant an increase in net radiation in October.     

A phylogenetic microarray targeting 16S rRNA genes from the bacterial division Acidobacteria reveals a lineage-specific distribution in a soil clay fraction

We designed an oligonucleotide microarray using probe sequences based upon a phylogenetic analysis of 16S rRNA genes recovered from members of the bacterial division Acidobacteria. A total of 42,194 oligonucleotide probes targeting members of the Acidobacteria division at multiple phylogenetic levels were included on a high-density microarray. Positive control hybridizations revealed a linear relationship between hybridization signal and template concentration, and a substantial decrease in non-specific hybridization was achieved through the addition of 2.5 M betaine to the hybridization buffer. A mean hybridization signal value was calculated for each Acidobacteria lineage, with the resultant lineage-specific hybridization data revealing strong predictive value for the positive control hybridizations. The Acidobacteria phylochip was then used to evaluate Acidobacteria rRNA genes from a Wisconsin soil and within a soil clay fraction. The Acidobacteria hybridization profile revealed the predominance of Acidobacteria subdivisions four and six, and also suggested a decrease in the abundance of subdivision six relative to subdivision four in the soil clay fraction. The change in relative abundance of these subdivisions in a soil clay fraction was supported by data from quantitative PCR. These results support the utility of a phylogenetic microarray in revealing changes in microbial population-level distributions in a complex soil microbial assemblage.     

A comparison of mineral-magnetic and distributed RUSLE modeling in the assessment of soil loss on a southeastern U.S. cropland

As geospatial technologies increasingly figure into resource management activities, there is a corresponding need to provide commensurately detailed high resolution spatial data. This study addresses the capacity of rapidly and cheaply acquired mineral-magnetic data to provide detailed spatially distributed assessments of long-term cumulative soil loss from agricultural fields. Model output from a simple distributed implementation of the Revised Universal Soil Loss Equation (RUSLE) and from a field-data-oriented soil magnetism-based erosion model are compared for a small Alabama (USA) farm lot. An undisturbed reference soil toposequence is used as input to the magnetism model, in contrast with earlier studies that relied on a single reference soil profile. Results from this procedure, while likely to be more dependable, proved primarily to further emphasize spatial patterns noted in prior studies. In addition, the use of a toposequence decreased the area over which RUSLE and magnetism models were in agreement. RUSLE underpredicted denudation relative to magnetism-model results over upper slopes, and overpredicted it on lower slopes. The locations of former access roads may explain underprediction on the upper slopes. The differences between the two method outcomes are discussed with regard to the potential for spatial variability in parent materials, the efficacies of non-fluvial soil redistribution processes, and the availability of detailed land use records for the 100+ years of agricultural activities at the site.     

Partitioning soil respiration and assessing the carbon balance in a Setaria italica (L.) Beauv. Cropland on the Loess Plateau, Northern China

A study was conducted in a Setaria italica (L.) Beauv. cropland on the Loess Plateau in order to partition total soil respiration (Rt) into microbial respiration (Rm) and root respiration (Rr) and to determine the carbon balance of the cropland ecosystem. A trenching method with micro-pore mesh was used to create root-free soil cores. Differences between mesh and non-mesh treatments were used to determine root respiration. Similar pattern was found in the diurnal variation of Rt and Rm with the minimum values at 3:00-6:00 h and the maximum at 13:00-15:00 h. The diurnal pattern of Rr was completely different, the minimum values appeared at 11:00-13:00 h and the maximum at 0:00-3:00 h. Soil temperature exerted predominant control over the diurnal variations of Rt and Rm. The daily mean values of Rt, Rm and Rr were close to the measurements taken at 9:00 h. On the seasonal scale, Rm was strongly dependent on soil temperature, with higher correlation with 2-cm-depth temperature (r² = 0.79, P < 0.001) than with 5-cm-depth temperature. When the effects of both soil temperature and moisture were considered, a linear model provided more accurate prediction of Rm (r² = 0.83, P < 0.0001). Root respiration (Rr) exhibited pronounced daily variation corresponding to changes in photosynthesis and seasonal variation related to crop phenological development. The seasonal variation in Rr was strongly correlated with leaf area index (LAI) (r² = 0.85, P < 0.05), and also positively, but marginally correlated with root biomass (RB, P = 0.073). Contribution of root respiration to total soil respiration (Rr/Rt ratio) showed pronounced diurnal and seasonal variations. The daily mean values of Rr/Rt ratios were close to the values obtained at 9:00 h. In different phenological stages, Rr/Rt ratios ranged from 22.3% to 86.6%; over the entire growing season, the mean Rr/Rt ratio was 67.3%.Total annual loss of C due to Rm in 2007 was estimated to be 121.3 g C m⁻² at the study site, while the annual NPP (net primary production) was 262.1 g C m⁻². The cropland system thus showed net carbon input of 140.8 g C m⁻².     

不同土壤盐分条件下新疆杨可溶性盐离子含量变化的研究

对2种含盐量土壤条件下新疆杨可溶性盐离子含量的研究结果表明,退水渠土壤各盐离子含量均高于灌渠土壤,且二者除HCO3-和K 外,其余盐离子含量差异显著;但2种含盐量土壤同龄新疆杨地上部可溶性盐离子含量差异不显著,仅根内Cl-、Mg2 、Na 和K 含量差异显著,说明新疆杨对土壤中较高浓度盐离子有一定排斥作用,并将对树木产生毒害的Cl-、Na 控制在根系中,限制其向地上部输送;新疆杨根系对SO24-和Ca2 有较强的选择吸收性,并将过多的SO2-和Ca2 排除其体外,而对Cl-、Mg2 和Na 的选择吸收性较小。     

连作对再植枸杞根际细菌群落多样性和群落结构的影响研究

受枸杞道地产区土地资源等因素限制,连作障碍已成为影响枸杞产业发展的重要原因之一,导致严重的经济损失.研究连作条件下枸杞农田土壤生态系统微生物群落的演替规律对枸杞产业的可持续发展具有重要的理论意义.以宁夏银川市南梁农场连作多年的枸杞地为研究对象,利用Illumina MiSeq测序技术分析了连作对再植枸杞根际/非根际细菌群落的影响.结果表明,连作地显著抑制再植枸杞苗地径的增加,且其土壤pH较对照样地显著降低(p<0.05).测序结果证实,与对照样地相比,连作地再植枸杞根际土壤细菌物种数显著降低(p<0.05),细菌群落α多样性下降(p>0.05).主坐标分析表明,连作和对照样地间枸杞非根际细菌群落结构无明显差异,但连作显著改变再植枸杞根际细菌的群落结构.对细菌群落丰度的统计分析发现,连作地枸杞根际浮霉菌门、非根际假单胞菌门的相对丰度较对照样地显著降低(p<0.05).此外,冗余分析结果表明:枸杞园土壤pH和有效磷含量是影响枸杞非根际土壤细菌群落结构变化的主要因素,分别解释了41.8%和35.4%的群落结构变化(p<0.05),其他土壤因子无统计学意义,但土壤理化因子对再植枸杞根际细菌群落结构变化的影响均未达显著水平.这些结果证实连作能够显著抑制再植枸杞生长、影响再植枸杞根际细菌群落结构和多样性,干扰枸杞与土壤细菌群落间的互作关系.这些研究结果将为解析枸杞连作障碍机制提供理论基础.     

南方红豆杉扦插繁殖技术研究——V.温室扦插苗病虫害综合防治技术

研究建立了温室南方红豆杉扦插苗病虫害综合防治技术体系,主要包括生态防治技术、物理防治技术、栽培防治技术、消毒技术以及化学防治技术,应用该防治技术体系可减少化学农药使用量50%以上,病虫害防治效果达95%。