DNA hybridization assay for detection of nucleopolyhedrovirus in whitemarked tussock moth (Orgyia leucostigma) larvae

DNA dot‐blot hybridization assays utilizing a horseradish peroxidase‐labelled whole genomic DNA probe and enhanced chemiluminescence were conducted to quantify detection thresholds of nucleopolyhedrovirus (NPV) in whitemarked tussock moth (Orgyia leucostigma) larvae. The minimum detection thresholds for an aqueous suspension of occlusion bodies (OBs), OBs added to macerates of non‐infected larvae and OBs in macerates of diseased larvae were 7.8 × 10³, 7.8 × 10³, and 1.5 × 10³ OBs, respectively. Purified viral DNA was detected at a concentration of 1.6 × 10⁻¹ ng in a 20 µl volume. The presence of pre‐occluded viral nucleocapsids and DNA, inherent to infected larvae, improved the detection threshold five‐fold compared with OBs alone. Larval tissues did not block the detection system utilized, nor did they bind non‐specifically to the probe. Detection thresholds, upon sequential hybridization of the same membrane, on average deteriorated two‐fold between the first and second hybridization and an additional six‐fold between the second and third hybridization. NPV infection was detected two days post‐inoculation (pi) in about one‐third of the larvae examined and in almost all larvae three days pi. Microscopic analysis of stained larval smears missed NPV infection in almost all larvae two days pi and about two‐thirds of the larvae three days pi. Results from the two methods of analysis were not comparable until four days pi. The detection system utilized is a reliable, efficient and simple method for the early detection of NPV infection in large numbers of larvae and may be used for further studies quantifying the role of this baculovirus in the ecology of whitemarked tussock moth populations. © 2001 Society of Chemical Industry     

贵州中部天然暖性草丛草地生产力变化和承载力分析

[目的]探讨放牧与围封对亚热天然暖性草丛草地生产力的影响并分析其草地承载力.[方法]以贵州中部龙里县亚热带天然暖性草丛草地为试验地区,连续调查2010～2012年草地生产力月、季和年动态,并对数据进行分析.[结果]放牧与围封条件下,贵州龙里暖性草丛草地植物现存量、牧草生长量均表现为先增加后减少的趋势,其峰值出现在8～10月份.围封明显提高天然草地的生产力,对天然草地植被组成改变不大.[结论]从草畜平衡的角度分析,贵州中部暖性草地适宜载畜量在3.45～4.66只羊/hm2时,具有良好的生态效益,在经济上可为农牧民所承受.     

大豆叶毒蛾核型多角体病毒(OaNPV)的毒力测定

1987年在哈尔滨从大豆叶毒蛾(Orgyia antiqua L.)感病致死幼虫体中分离出核型多角体病毒OaNPV一株。选1龄和3龄大豆叶毒蛾幼虫作试虫,分别用5个病毒剂量或浓度,采用定量滴叶法进行毒力测定。对应用感染剂量和感染浓度二种计量方法进行分析和比较。1龄幼虫感染剂量或浓度与死亡率回归直线方程分别为y_1=4.94+0.67x_1和Y_1=3.58+0.67X_1致死中量(LD_(50))为1.2PIB/虫,致死中浓度(LC_(50))为1.4×10~2PIB/ml;3龄幼虫感染剂量或浓度与死亡率回归直线方程分别为y_3=3.80+0.49x_3和Y_3=3.01+0.49X_3,致死中量为2.6×10~2PIB/虫,致死中浓度为1.1×10~4PIB/ml。以1.026×10~2、1.026×10~4、1.026×10~5PIB/ml病毒分别处理1龄幼虫所得致死中时(LT_(50))分别为8.9、5.7和4.5天;以1.026×10~2、1.026×10~4和1.026×10~6PIB/ml病毒分别处理3龄幼虫所得致死中时分别为9.4、8.4和4.9天。结果看出OaNPV对大豆叶毒蛾的毒力较高,对用于该虫防治实践具有潜力。     

侧柏毒蛾的发生情况及防治方法初探

侧柏毒蛾是危害侧柏、蜀桧的重要害虫,本文对该虫的发生情况和各虫期的危害特点进行了观察研究,根据其生物学特性提出了业、物理、生物、化学等方面的防治方法。     

A model of arctic tundra vegetation derived from topographic gradients

We present a topographically-derived vegetation model (TVM) that predicts the landscape patterns of arctic vegetation types in the foothills of the Brooks Range in northern Alaska. In the Arctic there is a strong relationship between water and plant structure and function and TVM is based on the relationships between vegetation types and slope (tan ) and discharge (), two independent variables that can be easily derived from digital terrain data. Both slope and discharge relate to hydrological similarity within a landscape: slope determines the gravitational hydrological gradient and hence influences flow velocity, whereas discharge patterns are computed based on upslope area and quantify lateral flow amount. TVM was developed and parameterized based on vegetation data from a small 2.2 km² watershed and its application was tested in a larger 22km² region. For the watershed, TVM performed quite well, having a high spatial resolution and a goodness-of-fit ranging from 71–78%, depending on the functions used. For the larger region, the strength of the vegetation types predictions drops somewhat to between 56–59%. We discuss the various sources of error and limitations of the model for purposes of extrapolation.     

水分胁迫下墨西哥羽毛草耐旱生理

本研究以一年生墨西哥羽毛草(Nassella tenuissima)为试验材料,采用盆栽控水法对墨西哥羽毛草进行水分胁迫,测定其各项指标,以期为墨西哥羽毛草的养护管理与在园林中的合理应用提供理论基础。结果表明,土壤水分为田间最大持水量的20%、40%、60%处理(D20、D40、D60)的植株株高生长速度和叶片相对含水量随干旱胁迫时间的延长而大幅度地降低,复水后D₂₀、D₄₀、D₆₀各处理的叶片含水量与对照(土壤水分为田间最大持水量的80%)相差7.11%、2.68%、0.80%,只有D₂₀处理与对照差异显著(P<0.05)未恢复到对照水平;相对电导率和丙二醛(MDA)含量随各处理水分胁迫时间的延长而呈逐步增加的趋势,复水后,D₂₀、D₄₀、D₆₀各处理相对电导率分别比对照高12.1%、5.92%、2.42%,D₂₀、D₄₀、D₆₀处理MDA含量分别为对照的152.18%、151.92%、133.97%,与对照差异显著(P<0.05);在水分胁迫下的超氧化物歧化酶(SOD)和过氧化酶(POD)活性均呈先上升后下降的变化趋势,复水后,D₂₀、D₄₀、D₆₀各处理SOD活性恢复到对照的82.65%、90.68%、97.13%,只有D₂₀处理与对照差异显著(P<0.05),其余处理均恢复到对照水平,D₂₀、D₄₀、D₆₀处理POD活性与对照相差7.54%、5.55%、11.73%,D₂₀、D₄₀处理与对照差异显著(P<0.05)。通过本研究可以得出,墨西哥羽毛草具有较强的抗旱性,能够适应40%田间持水量的土壤水分条件,是干旱地区优良的园林地被植物。     

双线盗毒蛾的初步研究

双线盗毒蛾是黑荆树的重要害虫之一,在福建一年发生7代,以幼虫越冬。卵成块产于小枝条上,3—11天孵化。幼虫五龄,少数四龄,以取食嫩叶为主,也取食叶柄、花序等。幼虫老熟时下树,多在草丛里,枯枝落叶中结茧化蛹,预蛹期1—4天。成虫羽化后当天即可交配,第2日开始产卵,每雌平均产卵量214粒。成虫寿命3—10天。 室内试验表明:90％敌百虫晶体800—1000倍液,80％敌敌畏乳剂1000—2000倍液,50％辛硫磷乳油1000—2000倍液对4—5龄幼虫均有良好效果。化学农药防治应抓住越冬代或第一代幼虫盛发期。     

Assessing regional scale weed distributions, with an Australian example using Nassella trichotoma

Knowledge of the spatial distribution of weed infestations over regional scales is essential for effective management of source populations and to assess future threats. To this end, the distributions of Nassella trichotoma across a study area in south‐east New South Wales, Australia, were analysed using the geographically local Getis–Ord G_i* spatial hotspot clustering statistic. The clustering of N. trichotoma observations was analysed at three infestation levels: presence (at any density), patch level and the occasional plant level. The results indicate that there are c. 578 km² of cells containing N. trichotoma in strongly clustered infestations, 11.2 km² within weakly clustered infestations distinct from the main clusters, and 55 km² that are not clustered. There are 117 km² of strongly clustered patch level cells, 3 km² in distinct but weak clusters, and none outside of a cluster area. Of the occasional plant level cells, 329 km² are strongly clustered, 6.2 km² are in distinct but weak clusters, and 19 km² are not clustered. These results provide a mechanism by which control efforts can be prioritized. The analysis approach described in this paper provides a consistent, quantitative and repeatable approach to assess weed infestations across regional scales and can be applied to any weed species for which spatial distribution data are available.     

Comparison of management strategies for controlling Nassella trichotoma in modified tussock grasslands in New Zealand: a spatial and economic analysis

The weedy grass Nassella trichotoma (nassella tussock), historically an economically damaging invader of modified tussock grasslands in New Zealand, currently causes little if any reduction in farm production. This is a result of successful historical regional management programmes in which plants have been removed manually (by grubbing) each year before they seed. To inform a debate about the need for ongoing regional management, we developed a stage‐structured spatially explicit integrodifference equation population model and linked this to a cost analysis. We used the model to compare the weed's future population trajectories and related regional control costs over 50 years under three alternative management scenarios. The total discounted (3% p.a.) costs of no management, three‐yearly grubbing and continued annual grubbing were NZ $417 million, $736 million and $131 million respectively. These analyses indicate that annual grubbing of N. trichotoma returns a net benefit of $286 million ($417 – $131 million) compared with doing nothing and a net benefit of $605 million ($736 – $131 million) compared with a 3‐yearly grubbing programme. These results support the continuation of annual grubbing as the long‐term economically optimal management strategy for N. trichotoma on pastoral farms infested by the weed in New Zealand.     

山西主要草地类型土壤有机碳储量及其垂直分配特征

对山西暖性灌草丛、暖性草丛、温性草原和温性山地草甸4种主要类型草地土壤0~5cm、5~10cm、10~20cm、20~30cm、30~50cm、50~70cm和70~100cm不同垂直剖面有机碳密度及碳储量的分配特征进行研究,结果表明:山西4种主要草地土壤有机碳含量在107.98~145.62g/kg之间,平均为131.42g/kg。土壤有机碳密度平均为6.78kg/m^2,暖性草丛类最高,为7.25kg/m^2,其次为暖性灌草丛类和温性草原类,温性山地草甸类最小,为6.32kg/m^2。4种主要类型草地土壤有机碳表聚性明显,表层土壤有机碳占总有机碳的比例分别为52.85%、49.12%、46.79%和50.36%。随土层深度的增加,土壤有机碳含量逐渐降低,但不同类型草地减少的程度不同。草地土壤有机碳密度随土层深度的增加逐渐增大,暖性类草地0~100cm土层平均土壤碳密度均高于温性类草地。4种主要草地土壤总碳储量为257.39Tg。