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1.
新疆石河子农耕区不同植被类型昆虫群落结构特征   总被引:3,自引:1,他引:2  
全仁哲  范喜顺 《昆虫知识》2008,45(2):276-281
2006年7~9月,用五点抽样法对新疆石河子农耕区不同植被类型中的昆虫群落结构进行调查,共采集到昆虫68种,隶属10目34科,共计6727头,其中叶蝉和蚜虫是主要害虫,瓢虫和草蛉是主要天敌昆虫。群落结构分析表明:在不同植被类型中昆虫群落多样性显著不同,以苗圃的多样性指数最高(2.5739),玉米的最低(1.0189),果木类的高于农作物的,间作的高于单纯植物的。  相似文献   

2.
干旱指标研究进展   总被引:44,自引:6,他引:38  
李柏贞  周广胜 《生态学报》2014,34(5):1043-1052
干旱作为全球最为常见的自然灾害之一,已经对我国的农业生产造成了严重影响。为更好地预测影响作物的干旱并及时采取应对措施,综述了国内外广泛应用的各类干旱指标,包括气象指标、土壤墒情指标、作物生理生态指标及其它综合监测指标等,评述了各类干旱指标的优缺点以及在农业上的适用性,探讨了未来以作物干旱为核心的干旱指标研究拟重视的方面,以为减缓和预防干旱对农业的不良影响及制订科学的政策提供依据。  相似文献   

3.
AimA systemic review and analysis of evolution journey of indices, such as conformity index (CI), homogeneity index (HI) and gradient index (GI), described in the literature.BackgroundModern radiotherapy techniques like VMAT, SRS and SBRT produce highly conformal plans and provide better critical structure and normal tissue sparing. These treatment techniques can generate a number of competitive plans for the same patients with different dose distributions. Therefore, indices like CI, HI and GI serve as complementary tools in addition to visual slice by slice isodose verification while plan evaluation. Reliability and accuracy of these indices have been tested in the past and found shortcomings and benefits when compared to one another.Material and methodsPotentially relevant studies published after 1993 were identified through a pubmed and web of science search using words “conformity index”, “Homogeneity index”, “Gradient index”,” Stereotactic radiosurgery”,” stereotactic Body radiotherapy” “complexity metrics” and “plan evaluation index”. Combinations of words “plan evaluation index conformity index” were also searched as were bibliographies of downloaded papers.Results and conclusionsMathematical definitions of plan evaluation indices modified with time. CI definitions presented by various authors tested at their own and could not be generalized. Those mathematical definitions of CI which take into account OAR sparing grant more confidence in plan evaluation. Gradient index emerged as a significant plan evaluation index in addition to CI whereas homogeneity index losing its credibility. Biological index base plan evaluation is becoming popular and may replace or alter the role of dosimetrical indices.  相似文献   

4.
Soil mycofloral diversity plays a pivotal role in crop production and is an integral part of any ecosystem. Pigeonpea cropping system provides a congenial environment to soil microbes by fixing nitrogen and solubilizing phosphorus which in turn provides sufficient nutrients for their prolific growth. The present study was undertaken to know the fungal diversity in calcareous soil of Bihar region in India, which are not supportive to growth of many fungi owing to high calcium content. Soil samples were collected from pigeonpea cropping system treated with native and commercial isolates of phosphorus solubilizing bacteria (PSB) and plant growth promoting rhizobacteria (PGPR) along with Rhizobium. Thirty-seven species belonging to seven genera and a group of unidentified species were isolated. Aspergillus and Penicillium were the dominant genera in all the treatments. Absidia and Cunnighmella were distributed only once as rare genera. Though single species of Pythium, Rhizopus, Periconia, Geotrichum and Gliocladium genera were recorded but their occurrence was even in all the treatments. The diversity and equitability index were not varied much in different treatments except one. The deuteromucetous fungi occupied the highest space followed by zygomycetous, mycelia sterilia and mastigomycetous fungi.  相似文献   

5.
A collection of 368 advanced lines and cultivars of spring wheat(Triticum aestivum L.) from Chile, Uruguay, and CIMMYT(Centro Internacional de Mejoramiento de Maíz y Trigo), with good agronomic characteristics were evaluated under the Mediterranean conditions of central Chile. Three different water regimes were assayed: severe water stress(SWS, rain fed), mild water stress(MWS; one irrigation around booting), and full irrigation(FI; four irrigations: at tillering,flag leaf appearance, heading, and middle grain filling). Traits evaluated were grain yield(GY), agronomical yield components,days from sowing to heading, carbon isotope discrimination(△^13C) in kernels, and canopy spectral reflectance. Correlation analyses were performed for 70 spectral reflectance indices(SRI) and the other traits evaluated in the three trials. GY and △^13C were the traits best correlated with SRI, particularly when these indices were measured during grain filling. However,only GY could be predicted using a single regression, with ResearchNormalized Difference Moisture Index(NDMI2: 2,200; 1,100)having the best fit to the data for the three trials. For △^13C, only individual regressions could be forecast under FI(r^2: 0.25–0.37)and MWS(r^2: 0.45–0.59) but not under SWS(r^2: 0.03–0.09).NIR‐based SRI proved to be better predictors than those that combine visible and NIR wavelengths.  相似文献   

6.
At birth, the index weight/height is the highest correlated with weight, height and cephalic perimeter, for the index of Quételet (BMI) the correlations are also significant although lower. In both cases, the variation with age is significant. For the Rohrer index, the situation is different, the changes with age being almost absent. In front of these results, can we decide which index would be adequate to establish the nutritional status at birth? For Cole (1986), for such a ponderal index the correlation with height would have to be absent. Rolland-Cachera (1982) proposed also that the correlations with height would be absent but would be high with weight. In the case of the newborns of our study the only index being not correlated to height is the Rohrer index with low correlation also with the cephalic perimeter and high correlation with weight (although here the correlation is even higher with BMI and W/H). During the utero-placentary disfunction the foetal weight is affected but not height and cephalic perimeter: in this case, the advantage is also to an index correlated with weight but not with height.  相似文献   

7.
A multi-trait index for ranking different genetic groups/populations with homogeneous covariance structure is developed and illustrated with live data.  相似文献   

8.
甲真菌病患者分离真菌多样性分析   总被引:2,自引:0,他引:2  
为了探寻甲真菌病患者病甲部位的真菌多样性,以期对临床治疗提供参考,结合菌种培养的形态学研究和rDNA ITS序列分析的方法,对临床拟诊为甲真菌病患者的病甲分离培养菌株进行物种鉴定,并以丰富性指数(Ma)、多样性指数(H′)、均匀度指数(J)等指标分析指甲和趾甲分离真菌的多样性。2010年2月至9月在北京大学第三医院皮肤科的1 568例拟诊甲真菌病患者中,641例培养阳性,包括趾甲561例和指甲80例。检测到的皮肤癣菌占59.13%(其中红色毛癣菌为96.04%),酵母菌17.00%,其他真菌23.87%。分离自趾甲的Candida galli、Lewia infectoria和Paraconiothyrium hawaiiense,以及分离自指甲的Cyberlindnera jadinii确定为中国新记录种。趾甲分离菌的物种多样性指数H′、丰富度指数Ma和均匀度指数J均高于指甲分离菌。研究结果表明,该医院就诊甲真菌病患者可分离培养的真菌以皮肤癣菌的红色毛癣菌为主要物种,且趾甲分离菌的菌种多样性较指甲的更为明显。  相似文献   

9.
近50年京津冀气候舒适度的区域时空特征分析   总被引:1,自引:0,他引:1  
曹云  孙应龙  吴门新 《生态学报》2019,39(20):7567-7582
受气候变化影响,区域气候舒适期势必会发生不同程度的变化。从气候舒适性的视角出发,利用京津冀地区1966—2015年的170个观测站点50年逐日气象资料,以温湿指数、风效指数、着衣指数及其综合指数为气候舒适性的评价指标,统计分析区域气候舒适期的起止日期、天数及其年际间变化规律,揭示京津冀区域气候舒适度的时空变化特征,为区域人口合理分布和气候资源评价提供科学依据。此外,以日为时间尺度进行气候舒适期分析,有利于气候变化背景下区域间横向和区域内纵向的比较研究。结果显示:(1)京津冀气候舒适度指数近50年来的变化趋势基本相同,综合指数呈显著增加趋势;但各地间变幅存在一定差异,其中天津气候舒适度指数变化幅度最为明显,北京变化相对平稳。(2)从气候舒适度综合指数来看,京津冀地区气候舒适期年内分布呈"M"型,舒适期相对集中在4—5月、9—10月,舒适和较舒适等级的月累计日数均达到28 d以上,其中5月气候最为舒适,舒适等级日数最多,达到24—26 d;北京年平均舒适天数最多(100 d),天津最少(91 d)。(3)从单一气候舒适度指数来看,京津冀舒适和较舒适等级的初始日期大多呈显著的提前趋势;终止日期和天数大多略有增加,但变化趋势不显著。而综合指数显示,1966—2015年较舒适等级的初始日期变化最为显著,大约每10年提前3—4 d;天津和河北终止日期变化也达到显著水平,大约每10年推迟1—2 d,北京增加趋势不明显。(4)京津冀气候舒适期的空间分布显示,舒适等级的日数从西北向东南地区呈减少特征,河北北部舒适等级的年平均日数最多达115—120 d,东南部最少,不足90 d。  相似文献   

10.
Composite indicators (CIs) are increasingly used to measure and track environmental systems. However, they have faced criticism for not accounting for uncertainties and their often arbitrary nature. This review highlights methodological challenges and uncertainties involved in creating CIs and provides advice on how to improve future CI development in practice. Linguistic and epistemic uncertainties enter CIs at different stages of development and may be amplified or reduced based on subjective decisions during construction. Lack of transparency about why decisions were made can risk impeding proper review and iterative development. Research on uncertainty in CIs currently focuses on how different construction decisions affect the overall results and is explored using sensitivity and uncertainty analysis. Much less attention is given to uncertainties arising from the theoretical framework underpinning the CI, and the sub-indicator selection process. This often lacks systematic rigour, repeatability and clarity. We recommend use of systems modelling as well as systematic elicitation and engagement during CI development in order to address these issues. Composite indicators make trends in complex environmental systems accessible to wider stakeholder groups, including policy makers. Without proper discussion and exposure of uncertainty, however, they risk misleading their users through false certainty or misleading interpretations. This review offers guidance for future environmental CI construction and users of existing CIs, hence supporting their iterative development and effective use in policy-making.  相似文献   

11.
线虫区系分析指示土壤食物网结构和功能研究进展   总被引:10,自引:0,他引:10  
陈云峰  韩雪梅  李钰飞  胡诚 《生态学报》2014,34(5):1072-1084
土壤食物网结构复杂,功能众多,直接测定土壤食物网各功能群生物量并结合数学模型来推断土壤食物网结构和功能,工作量大且分析过程繁琐。线虫生态学的发展为土壤食物网的研究开辟了一条新的思路,即利用线虫区系分析来定性推断食物网的结构和功能。线虫作为土壤中数量最丰富的后生动物,占据着土壤食物网的中心位置,其物种多样性、食性多样性、生活史策略多样性、功能团多样性奠定了其作为土壤食物网结构和功能指示生物的生态学基础。线虫区系分析根据发展历史可以分为个体分类、生活史策略分类、功能团分类和代谢足迹分类四个时期,其中后两个时期主要用于推断土壤食物网结构和功能。基于功能团的线虫区系分析将线虫的食性和生活史策略结合起来,发展出一系列指数来判断土壤食物网的连通性、食物网链长度、外界养分投入情况、分解途径及对外界干扰的响应等。基于代谢足迹的线虫区系分析在功能团分析基础上,加入线虫能流分析,从而定性反映了土壤食物网功能的大小。两者在指示土壤食物网自下而上调节及对植物线虫控制等方面起着重要的作用。  相似文献   

12.
The relative toxicity of pesticides to Phyllocnistis citrella and its parasitoid Ageniaspis citricola was compared by several bioassay methods. A clip-cage bioassay measured survival of adults exposed to fresh residues at 0.25-times (0.25×), 0.5×, 1×, and 2× the lowest recommended rate of each pesticide, a water control (0×), and 24- and 48-h aged residues of oil at 1.5% (1×) rate. A one-species cylinder bioassay determined the effects of pesticides on immature stages of the citrus leafminer after treating young citrus trees with the same rates of pesticides (except for avermectin, tested at 0×, 0.01×, 0.025×, 0.05×, 0.1×, and 0.25× rates). A sublethal rate of petroleum oil (0.4%) was added as an adjuvant in some treatments. The effect of pesticides on immature stages of A. citricola was determined with a two-species cylinder bioassay after treating young citrus trees with the same rates as above. An index of IPM compatibility was developed based on the efficacy of the pesticide as a control agent of the leafminer (or other pests) and its selectivity to the parasitoid at the lowest recommended field rate (0.25× the field rate for avermectin). Azadirachtin (Neemix) + oil, diflubenzuron (Micromite) + oil, fenoxycarb (Eclipse) + oil, and oil alone (FC 435-66) were classified as IPM-compatible insecticides. Sprays of azadirachtin (Align) + oil, neem oil (Neemgard), and drenched imidacloprid (Admire) were ranked as a semi-compatible insecticides. The fungicide copper hydroxide (Kocide 101) and a fish oil-based foliar fertilizer (Zapata HFE) were considered compatible. Avermectin (Agri-Mek) + oil, ethion (Ethion), and imidacloprid (Provado) applied as a spray were IPM-incompatible insecticides. These products should be tested under field conditions to confirm these ratings.  相似文献   

13.
高光谱植被指数与水稻叶面积指数的定量关系   总被引:14,自引:0,他引:14  
基于不同水稻品种、施氮水平和不同生育期下的大田试验,确立了水稻叶面积指数(LAI)与冠层光谱特征参数的定量关系.结果表明:水稻叶面积指数与部分高光谱植被指数存在良好的相关性,其中原始光谱组成的2波段差值指数(DI)形式相关性最好,其次为比值(RI)和归一化(NI)植被指数.相关最好的原始光谱植被指数是由近红外波段组成的差值指数DI(854,760),相关最好的一阶导数光谱植被指数是红光和近红外光组成的导数差值指数DI(D676, D778),但总体上导数光谱指数不如原始光谱指数与LAI关系密切.独立试验数据检验结果表明,以差值指数DI(854,760)为变量建立的水稻LAI监测模型具有较好的表现,可用于水稻LAI的估测.  相似文献   

14.
恒定磁场对小鼠免疫功能的影响   总被引:6,自引:0,他引:6  
目的:从免疫学方面探讨不同照射时间的恒定磁场对小鼠免疫功能的影响。方法:用同一强度不同照射时间的恒定磁场(2小时恒定磁场照射组、3小时恒定磁场照射组、4小时恒定磁场照射组和无磁场照射的正常对照组)对小鼠进行照射,连续20天。每天一次,末次12小时后称其体重,取出胸腺、脾脏、肝脏,称重,计算各器官指数。结果:与正常对照组比较,三组同一强度不同照射时间的恒定磁场组对小鼠的胸腺指数有显著的降低(p〈0.05);2小时组与3小时组的肝脏指数也有显著的降低(p〈0.06);对脾脏指数无显著影响(p〉0.05)。结论:一定照射时间的恒定磁场对小鼠的免疫功能具有抑制作用。  相似文献   

15.
目的:从免疫学方面探讨不同照射时间的恒定磁场对小鼠免疫功能的影响。方法:用同一强度不同照射时间的恒定磁场(2小时恒定磁场照射组、3小时恒定磁场照射组、4小时恒定磁场照射组和无磁场照射的正常对照组)对小鼠进行照射,连续20天,每天一次,末次12小时后称其体重,取出胸腺、脾脏、肝脏,称重,计算各器官指数。结果:与正常对照组比较,三组同一强度不同照射时间的恒定磁场组对小鼠的胸腺指数有显著的降低(p<0.05);2小时组与3小时组的肝脏指数也有显著的降低(p<0.05);对脾脏指数无显著影响(p>0.05)。结论:一定照射时间的恒定磁场对小鼠的免疫功能具有抑制作用。  相似文献   

16.
Urban lakes belong to various groups, for example from “young” to “old” with regard to development, and from “natural” to “anthropogenic” with respect to transformations due to human activity. The majority of these lakes are eutrophic and polytrophic, but special attention should be paid to mesotrophic ones, with relatively unchanged vegetation, with species of the class Charetea, e.g. Lake Redykajny (43.3% of the phytolittoral) or Lake Tyrsko (44.0% of the phytolittoral).  相似文献   

17.
18.
The objective of this study was to determine if low secondary selection differentials, caused by selecting within full-sib families, may have accounted for the failure of an intended restricted selection index to reduce epididymal fat pad weight (EF) without changing body weight (BW) in mice. Replicate lines that had been selected within full-sib families for high (HE) or low (LE) EF, while holding BW constant, were crossed. After two generations of random mating, two replicates were sampled and selection initiated for the same restricted index criteria except that mass selection was used to increase the selection differentials. In both phases of selection the HE restricted index selection, designed to increase EF without altering BW, was in agreement with expectation. In contrast, the LE index, designed to decrease EF without changing BW, did not agree with theory since BW increased while EF decreased only slightly. Therefore, reduced selection differentials could not explain the deviation from theory. A possible explanation may reside in the restricted selection index being more sensitive to changes in genetic parameters due to shifts in gene frequency as a consequence of the selection applied. However, linkage disequilibrium and genetic drift can not be ruled out as contributing factors to the asymmetry of response.The research reported in this publication was funded by the North Carolina Agricultural Research Service (NCARS), Raleigh, NC 27695-7643. Use of trade names in this publication does not imply endorsement by the NCARS of the products named, nor criticism of similar ones not mentioned  相似文献   

19.
研究了如何提取基因图谱信息的方法问题,提出一种新的基因"标签"提取方法.该方法采用秩和检验法选取基因"标签",得到不同显著性水平下基因"标签"的数目,然后将秩和检验法和分类信息指数相结合,在与基于SVM建立的分类模型比较后,提取最合适的基因"标签",再结合分类信息指数重复数次对这些基因"标签"选取主基因,最后用SVM检验主基因选取及分类的准确率,发现准确率有所提高,说明该方法的有效性.  相似文献   

20.
中国东北主要植被类型的分布与气候的关系   总被引:38,自引:0,他引:38       下载免费PDF全文
本文根据吉良的热量指标和作者提出的湿度指数,研究了我国东北主要植被类型的分布与气候之间的关系:1.确定了东北地区10个水平地带性植被类型的热量分布范围和水热指标的平均值。2.研究了东北山地垂直地带性植被类型的水热指标分布特点,并用定量指标讨论了东北东部山地岳桦林带的分布、大兴安岭存在山地冻原和东北植被区域的分界线问题。  相似文献   

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