新疆艾比湖湿地自然保护区主要植物的种间关系

采用2×2列联表的χ2检验、方差比率(VR)法、Ochiai关联指数、Pearson相关系数和Spearman相关系数,对艾比湖湿地自然保护区典型群落的25个主要植物种进行种间关联和种间相关性分析。结果表明:①胡杨(Populus euphratica)、盐穗木(Halostachys caspica)、甘草(Glycyrrhiza uralensis)分别为该地区乔、灌、草本层的优势种。②艾比湖湿地自然保护区内物种的总体联结性为不显著的负联结,大多数种对间呈不显著关联和无关联,物种趋向于独立分布。③相关性分析表明草本与其他物种的相关对数值高于乔灌木,结合Spearman相关系数、列联表的χ2检验值,可将研究区25种主要植物分为4个生态种组。     

晋西北丘陵风沙区人工植物群落优势种种间关系研究

文中在对晋西北丘陵风沙区人工植物群落进行样方调查的基础上,筛选了16个群落优势种,采用χ~2检验、Pearson相关系数、Spearman秩相关系数和聚类分析相结合的方法,对该16个优势种、共120个种对的种间关系进行了研究。结果表明:1)χ~2检验、Pearson相关分析和Spearman秩相关分析结果基本一致,晋西北丘陵风沙区人工植物群落优势种负关联种对数显著多于正关联的种对数;2)16个优势种种对间关联率较高,且正负关联比均小于1,说明该区大多数人工植物群落比较脆弱,群落结构简单,应加强其科学管护;3)正关联的种对主要体现了种对间生物学特性相近,对生境的生态适应性相似和相互重叠的生态位;而负关联的种对间往往具有不同的生物学特性,对生境条件的适应性相异或存在相互竞争。乔木层中小叶杨与油松,灌木层中乌柳与柠条锦鸡儿,草本层中沙生冰草与披碱草等种对间呈极显著负相关,在植被恢复中不宜混种。而不同层间的小叶杨和沙棘、沙生冰草,油松与达乌里胡枝子、新疆杨与柠条锦鸡儿、鹅观草等种对间呈极显著正相关,在植被恢复中适宜混种;4)根据Spearman秩相关系数聚类分析结果和植物种的生态习性及分布范围,将16个优势种划分为4个生态种组。     

银川平原湿地常见植物种间关系研究

在样方调查的基础上,应用校正χ²检验,结合Jaccard关联指数、Pearson 相关系数和Spearman 秩相关系数,研究了银川平原湿地植物群落的种间关系, 计算测定了33 种常见植物共528个种对的种间关联关系。结果表明: ① 3种检验方法表达的种间关系相似但不完全相同。 χ²检验共有24个种对正关联, 4个种对负关联,其中有12对极显著正关联,1个种对极显著负关联; Pearson 相关系数检验,有30 个种对正相关,其中有19个种对极显著正相关,无负相关种对; Spearman 秩相关系数检验,有50个种对呈正相关,8个种对呈负相关,其中有31个种对极显著正相关,1个种对极显著负相关。② 银川平原湿地33种常见植物可划分为4个生态种组,即水生植物种组、湿生植物种组、中生植物种组和旱生植物种组,组内植物间多为显著正关联,种组植物间多为负关联。③ 银川平原湿地植物群落存在独立分布格局,植物群落不够稳定, 尚处于不断的演替之中。     

滨海盐碱区湿地植被恢复后群落优势种种间关系分析

采用方差比率法(VR),2×2列联表的χ~2和W检验、Ochiai联结指数(OI)、去趋势对应分析(DCA)及Spearman秩相关分析,对天津滨海盐碱区,湿地植被恢复后群落动态变化过程中的物种关联性和相关性进行了分析。结果表明:多物种间整体上表现为显著正关联(VR=2.725>1);χ~2检验正负关联种对比为0.22,总体趋于独立和随机分布(但显著种对中正负关联种对比为1.18,且显著正关联的极显著率达到85%);OI指数多集中于0.2相似文献   

晋西皇姑梁小流域人工植物群落优势种生态位和种间关系研究

在野外102个样方调查数据和双向指示种分析法(TWINSPAN)分类的基础上,采用生态位宽度、生态位重叠、χ2检验和Spearman秩相关系数,对晋西皇姑梁小流域12个群落的12个优势种的生态位和种间关系进行了研究。结果表明:乔灌层Levins生态位宽度较大的种为油松、柠条锦鸡儿、沙棘。12个优势种组成的66个种对中,Pianka重叠指数≥0.4的种对占总对数的45.45%。呈极显著和显著关联的种对数较少,正负关联比均小于1。说明该小流域人工植物群落结构简单,种间资源竞争较激烈,仍处于演替的初、中期阶段。优势种华北落叶松与沙棘,沙棘与鹅观草呈显著正相关,它们均为地带性物种,生态适应性强,可作为皇姑梁小流域人工植被恢复的优选物种进行混种,而油松与小叶杨、小叶杨与沙棘或柠条锦鸡儿等种对间呈极显著负相关,在植被恢复中不宜混种。根据Spearman秩相关系数结果,将12个优势种划分为3个生态种组。     

科尔沁沙地流动沙丘-丘间低地过渡带植被分布特征及种间关联

运用Pearson相关检验、Spearman秩相关检验、CA群落多元统计分析等,系统研究科尔沁沙地流动沙丘与丘间低地过渡带物种的空间分布特征和种间关联性。结果表明：物种间表现出有选择性的种间积聚,但偏流动沙丘一侧沙蓬(Agriophyllum squarrosum)和乌丹蒿(Artemisia wudanica)的分布相对独立,说明沙蓬和乌丹蒿占有相对独立的生态位。丘间低地一侧黄柳[WTBX](Salix gordejevii)和小红柳(Salix microstachya[WTBZ] var. bordensis)主要分布于丘间低地北部,占有相似的生态位,而山竹岩黄蓍(Hedysarum fruticosum)主要分布于丘间低地南部,与前两个物种生态位相分离。Pearson相关性检验与Spearman秩相关检验的结果基本一致,负相关种对数高于正相关种对数,存在生态位分化,群落处于不稳定的演替阶段。     

塔里木河下游植物群落组成及主要种间关系研究

对塔里木河下游38个植物样地野外采集的数据进行分析,结果表明:代表性的植物有胡杨、多枝柽柳、刚毛柽柳、黑果枸杞、花花柴、骆驼刺等14种,物种较为贫乏。通过重要值分析,确定各物种在群落中的地位和作用。通过2×2联列表,应用方差比率(VR)、X2统计和r检验等方法对上述14个优势种群间的总体相关性、各种对间联结显著性进行了测定,结果表明:塔河下游各物种的总体关联性为不显著的正联结,种间绝大多数不存在显著、极显著的正联结或负联结,无相关的较多,总体上趋于独立分布。显示出该群落的年轻性和不稳定性,与先锋林地的特点相吻合。另据分析结果可将塔河下游物种分为3个生态种组。     

塔里木河下游植被种间关系与稳定性分析

在样方调查的基础上,对塔里木河下游的英苏、喀尔达依、阿拉干和依干不及麻4个监测断面的样地植被状况进行调查,在2×2列联表基础上,采用方差比率法(VR),应用联结系数(AC)、χ2检验与M. Godron稳定性测度方法对植被群落进行了种间联结分析与稳定性研究,得到如下结论:①总体相关性检验结果表明,4个断面中没有出现显著正联结的植物群落,塔里木河下游植物群落演替目前尚未达到稳定水平,且阿拉干与依干不及麻断面的植物群落正处于发育初期。②植物群落种间关系不显著,分布松散,更倾向于独立分布。群落的结构不稳定,存在于同一个样地内种对之间的依赖性不强,个别区域植物群落物种之间存在一定的竞争关系与排它作用。③根据已有的种间关系,可将塔里木河下游的植物群落划分为3个生态种组。     

塔里木河下游植被种间关系与稳定性分析

在样方调查的基础上,对塔里木河下游的英苏、喀尔达依、阿拉干和依干不及麻4个监测断面的样地植被状况进行调查,在2×2列联表基础上,采用方差比率法(VR),应用联结系数(AC)、c²检验与M.Godron稳定性测度方法对植被群落进行了种间联结分析与稳定性研究,得到如下结论：① 总体相关性检验结果表明,4个断面中没有出现显著正联结的植物群落,塔里木河下游植物群落演替目前尚未达到稳定水平,且阿拉干与依干不及麻断面的植物群落正处于发育初期。② 植物群落种间关系不显著,分布松散,更倾向于独立分布。群落的结构不稳定,存在于同一个样地内种对之间的依赖性不强,个别区域植物群落物种之间存在一定的竞争关系与排它作用。③ 根据已有的种间关系,可将塔里木河下游的植物群落划分为3个生态种组。     

相关分析及其在农作物病虫测报中的应用

介绍了农业病虫害预测预报中常用的Pearson相关分析,多序列相关系数和Spearman秩相关3种相关分析方法的原理、参数估计以及统计检验的方法。结合两个实际例子介绍了多序列相关系数和Spearman秩相关的具体应用。     

Analysis of the association among three viruses infecting hop in Australia

Associations among Hop latent virus (HpLV), Hop mosaic virus (HpMV), and Apple mosaic virus (ApMV) were assessed in five hop cultivars at four commercial hop-growing regions in Victoria and Tasmania, Australia. The presence or absence of each virus was confirmed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Spatial patterns of virus-infected plants were characterized using the Spatial Analysis by Distance IndicEs ( sadie ) system of pattern analysis. The association among viruses (occurrence and covariation) was assessed using the Jaccard similarity index, Spearman's rank correlation coefficient, and sadie . The spatial pattern of plants infected by HpLV and HpMV ranged from random to highly aggregated depending upon the cultivar infected and the mean disease incidence. The spatial pattern of plants infected by ApMV was aggregated in six of the seven plots where ApMV was present. A strong positive association between HpLV and HpMV was found in all cultivars at all locations. This association may be the result of the viruses sharing a common aphid vector species, the presence of one virus enhancing the ability of the aphid vector to acquire the other virus either through transencapsidation or influences on virus titre, or mixed infections within source plants. Significant associations, positive or negative, were found less frequently between HpLV and ApMV, and HpMV and ApMV.     

A high-throughput glasshouse bioassay to detect crown rot resistance in wheat germplasm

A high-throughput and reliable seedling bioassay to screen wheat germplasm for crown rot resistance was developed. Single wheat seedlings were grown in square seedling punnets in a glasshouse and inoculated with a monoconidial Fusarium pseudograminearum isolate 10 days after emergence. The punnets were laid horizontally on their side and a 10- µ L inoculum droplet placed on the stem base. Seedlings were incubated at near-saturated relative humidity, and crown rot severity was assessed 35 days after inoculation. Studies on the duration of incubation period, inoculum concentration and temperature were carried out to optimize these parameters. Seedling growth at 25/15(±5)°C in a glasshouse and 48-h incubation at near-saturated RH in darkness gave the best results. When crown rot resistance rankings of 16 Australian cultivars from the bioassay were compared with their field performance, Spearman's rank correlation coefficient was highly significant. This indicated that the seedling bioassay mimicked field resistance to crown rot in adult plants. A bootstrap resampling analysis showed little or no improvement in the coefficient of variation with an increasing number of replications, indicating a high level of precision and reproducibility. By detecting small but consistent differences in crown rot severity, the bioassay proved effective in large-scale screening for partial resistance: already over 1400 wheat genotypes have been screened. The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialization and parasitic fitness.     

Evaluation of carrot resistance to alternaria leaf blight in controlled environments

The objective of this study was to find a technique for plant resistance screening to alternaria leaf blight (ALB), caused by the fungus Alternaria dauci , in controlled environments. Glasshouse and laboratory screening methods were compared using three cultivars and F₂ genotypes segregating for ALB resistance evaluated against self-pollinated F₃ field-grown plants. Plant disease was assessed through a disease index obtained from the size and number of symptoms on carrot leaves. The results indicated the value of glasshouse evaluation and the inadequacy of detached leaf and hypocotyl assays for carrot screening for ALB resistance. Spearman's rank correlation, applied to results obtained with both F₂ plants and their progeny, indicated that the optimal evaluation stage for ALB resistance in carrot is 20 days after inoculation. This test was powerful enough to be used as a prescreening test in breeding programmes.     

Analysis of the temporal and spatial disease progress of Bemisia tabaci-transmitted Cucurbit yellow stunting disorder virus and Cucumber vein yellowing virus in cucumber

Cucurbit yellow stunting disorder virus (CYSDV) has been present in greenhouse-grown cucumber in Spain since 1992. However, in the autumn of 2000 Cucumber vein yellowing virus (CVYV) was introduced, leading to mixed infections of both Bemisia tabaci -transmitted viruses. The temporal and spatial spread of disease symptoms were monitored in experimental plastic-covered greenhouses during six consecutive cucumber plantings from 2000 to 2002. Using linear regression analysis of 46 disease-progress curves, the Gompertz model best described the CYSDV epidemics in 2000, whereas the logistic model best described the development of CYSDV and CVYV epidemics in 2001 and 2002. The fitted models were used to calculate the amount of degree Celsius-days at half-maximum infection in the greenhouses (° D _0·5). After multiple regression analysis, 56% of the variation in ° D _0·5 of CYSDV was related to the numbers of whiteflies infesting the cucumber crops, and was independent of the mean temperatures in the greenhouses. In contrast, 76% of the variation in ° D _0·5 of CVYV was related to both the numbers of vectors present and maximum temperature. Symptom expression in cucumbers mechanically inoculated with CVYV was most prevalent when plants were grown at regimes of at least 28°C day temperature. According to analysis of spread using Taylor's power law, beta-binomial distribution fitting, and the ordinary runs test, the prevalence of CVYV showed significant overdispersion, whereas that of CYSDV did not. The χ² test of independence and Spearman's rank correlation coefficient were used to measure co-occurrence and covariation, respectively, during the first half of the cultivation period. These results showed that the two diseases were not associated.     

泽漆对小麦的为害损失及经济阈值研究

为明确泽漆的发生对小麦产量及其构成因素的影响,人工接种结合田间自然出草进行泽漆不同密度对小麦为害损失试验。１９９５－１９９６年研究结果表明,泽漆发生密度和小麦产量及穗数损失率的最佳数学模型均直线函数关系,方程分别为：Ｙ＝－０．３９１８＋１．５１９Ｘ,Ｙ１＝２．２３２＋１．５５３Ｘ。泽漆的发生为害对小麦穗粒数、千粒重的影响不显著。经济阈值计算结果表明,用使它隆进行防除,泽漆发生密度达３．０株／ｍ＾３