Spatial pattern analysis of hop powdery mildew in the pacific northwest: implications for sampling

ABSTRACT The spatial pattern of hop powdery mildew was characterized using 3 years of disease incidence data collected in commercial hop yards in the Pacific Northwest. Yards were selected randomly from yards with a history of powdery mildew, and two to five rows were selected for sampling within each yard. The proportion of symptomatic leaves out of 10 was determined from each of N sampling units in a row. The binomial and the beta-binomial frequency distributions were fit to the N sampling units observed in each row and to SigmaN sampling units observed in each yard. Distributional analyses indicated that disease incidence was better characterized by the beta-binomial than the binomial distribution in 25 and 47% of the data sets at the row and yard scales, respectively, according to a log-likelihood ratio test. Median values of the beta-binomial parameter theta, a measure of small-scale aggregation, were near 0 at both sampling scales, indicating that disease incidence was close to being randomly distributed. The variability in disease incidence among rows sampled in the same yard generally increased with mean incidence at the yard scale. Spatial autocorrelation analysis, used to measure large-scale patterns of aggregation, indicated that disease incidence was not correlated between sampling units over several lag distances. Results of a covariance analysis showed that heterogeneity of disease incidence was not dependent upon cultivar, region, or time of year when sampling was conducted. A hierarchical analysis showed that disease incidence at the sampling unit scale (proportion of sampling units with one or more diseased leaves) increased as a saturation-type curve with respect to incidence at the leaf level and could be described by a binomial function modified to account for the effects of heterogeneity through an effective sample size. Use of these models permits sampling at the sampling unit scale while allowing inferences to be made at the leaf scale. Taken together, hop powdery mildew was nearly randomly distributed with no discernable foci, suggesting epidemics are initiated from a well-distributed or readily dispersible overwintering population. Implications for sampling are discussed.     

甘肃省河东地区主秋期降水量时空分布特征

利用甘肃省河东地区55个站30a的主秋期降水量资料进行经验正交展开(EOF)和旋转经验正交展开(REOF),分析其空间分布特征和异常类型;以平凉站为例分析了主秋期降水的时间变化规律和周期性;将河东地区主秋期降水量分为8个气候片。分析表明,河东地区主秋期雨量变化规律较为一致,空间分布不均,具有南多北少和东西多中间少的特点;多雨中心和少雨中心的多年平均值相差近200mm;主秋期降水年际变化较大,容易出现不同程度的旱或涝,并有9a左右的周期;20世纪40、60年代为相对多雨期,50、90年代为相对少雨期,70、80年代与平均值持平。     

Temporal development and relationship amongst brown rot blossom blight,fruit blight and fruit rot in integrated and organic sour cherry orchards

The aim of this 4‐year study was to characterize temporal development of brown rot blossom blight and fruit blight (caused by Monilinia spp.) and their sporulating areas in sour cherry orchards; and to determine the relationships amongst incidence and sporulating area of blossom blight, fruit blight and fruit rot. The study was performed in integrated and organic orchard blocks on two cultivars (Újfehértói fürtös and Érdi b?term?). On both cultivars, disease progress on flowers and fruits was 2–10 times slower in the integrated than in the organic management system. The peak incidence values were 9 and 31 days after petal fall for blossom blight and fruit blight, respectively. After these dates, no new blight symptoms on flowers and/or fruits appeared and the disease was levelling off. Final blossom blight incidence ranged from 1 to 5% and from 12 to 34%, and fruit rot incidence from 2 to 6% and from 11 to 26% in the integrated and the organic orchards, respectively. The sum of fruit blight incidence ranged from 9 to 22% for the organic system, but was below 5% for the integrated system, while the final sporulating area was 5–16 mm² and <3 mm², respectively. Among the five highest Pearson's correlation coefficients, relationships between blossom blight and early fruit blight stage (r = 0·845, P = 0·0087 integrated; r = 0·901, P = 0·0015 organic), and between sporulating area and fruit rot (r = 0791, P = 0·0199 integrated; r = 0·874, P = 0·0039 organic) were the most significant relationships from an epidemic standpoint as they indicated a connection between different brown rot symptom types.     

Effectiveness of preventing flowering of hawthorn in protecting pear orchards from fire blight infection

Since 1984 when a new Ministerial Regulation on fire blight came into force, there have been 20 protected regions in the Netherlands, where nurseries of rosaceous plants, and pear and apple orchards are extra protected against fire blight. This policy is also necessary to meet the requirements of the European Community (EC) on fire blight. Two of the measures in the protected regions are the prohibition of flowering of the native hawthorn (Crataegus monogyna andC. laevigata), and destruction of blighted plants. In the unprotected regions, flowering is allowed, and destruction of blighted plants is limited to a zone of 500 metres around orchards.For three years, the effectiveness of preventing flowering of hawthorn in protecting pear orchards against fire blight infection was studied in the field. Five test areas of about 3 km × 3 km were chosen with hawthorns and pear orchards. Two of these areas were in protected regions and three in unprotected regions. The more than 50 000 hawthorns in the areas were grouped into 1125 sites of hawthorn. The 126 orchards larger than 0.2 ha contained about 180 000 trees.During the three years light to moderate epidemics of fire blight were observed in the regions. Fire blight occurred in 2.3% of the non-flowering sites and 19.8% of the flowering (or fruiting) sites at least once in 1987, 1988 or 1989. The prohibition of flowering for hawthorn in protected areas was rather well implemented, so that in protected areas a smaller proportion of sites of hawthorns had fire blight (4.1%) than in unprotected areas (14%). Moreover, there were fewer sites per square kilometre in the protected areas (13) than in the unprotected areas (26).In protected areas, 53% and in unprotected areas 59% of the pear orchards had fire blight during 1987, 1988 or 1989. The difference was not significant. The first reason for the ineffectiveness of the preventing of flowering prevention in hawthorn to control fire blight in pear orchards was the inadequate hygiene of the pear orchards in both types of region. If it be assumed that a new focus is most probably initiated by the nearest existing focus, the second reason was that fire blight hardly spread from hawthorn to pear in the period of this study. Spread of fire blight within pear orchards and between pear orchards occurred frequently.     

西北地区东部夏季降水日数的变化趋势及其气候特征

以西北地区东部(95°E～112°E,32°N～41°N)104个测站1960～2000历年夏季(6～8月)降水日数资料为基础,通过EOF和REOF等分析方法,研究夏季降水日数时空分布的异常特征。结果表明西北地区东部夏季多年平均降水日数的地区分布特点是西部多、东部少,沿祁连山山脉存在一个降水日数较多中心区域,并且降水量和降水日数均呈增多趋势。降水日数的空间异常主要表现为一致性异常和南北相反异常两种类型。根据REOF方法可将西北区东部分为5个不同降水日数气候区,即甘肃中东部及河套区、渭水流域区、河西走廊区、青海高原北部区、青海南部区和四川北部区。20世纪80年代以来,西北地区东部大部分地区降水日数呈现减少的趋势。冬季(或夏季)青藏高原地面加热场强度偏强,甘肃河西及祁连山地区、宁夏南部等地夏季降水偏多(或少),青海东南部-甘肃南部-渭水流域夏季降水日数偏少(或偏多)。     

Spatial and temporal patterns of drought in Zambia

Drought acutely affects economic sectors, natural habitats and communities. Understanding the past spatial and temporal patterns of drought is crucial because it facilitates the forecasting of future drought occurrences and informs decision-making processes for possible adaptive measures. This is especially important in view of a changing climate. This study employed the World Meteorological Organization(WMO)-recommended standardized precipitation index(SPI) to investigate the spatial and temporal patterns of drought in Zambia from 1960 to 2016. The relationship between the occurrence of consecutive dry days(CDD; consecutive days with less than 1 mm of precipitation) and SPI was also investigated. Horizontal wind vectors at 850 hPa during the core of the rainy season(December–February)were examined to ascertain the patterns of flow during years of extreme and severe drought; and these were contrasted with the patterns of flow in 2007, which was a generally wet year. Pressure vertical velocity was also investigated. Based on the gamma distribution, SPI successfully categorized extremely dry(with a SPI value less than or equal to –2.0) years over Zambia as 1992 and 2015, a severely dry(–1.9 to –1.5) year as 1995, moderately dry(–1.4 to –1.0) years as 1972, 1980, 1987, 1999 and 2005, and 26 near normal years(–0.9 to 0.9). The occurrence of CDD was found to be strongly negatively correlated with SPI with a coefficient of –0.6. Further results suggest that, during wet years, Zambia is influenced by a clockwise circulating low-pressure zone over the south-eastern Angola, a second such zone over the northern and eastern parts, and a third over the Indian Ocean. In stark contrast, years of drought were characterized by an anti-clockwise circulating high-pressure zone over the south-western parts of Zambia,constraining precipitation activities over the country. Further, wet years were characterized by negative pressure vertical velocity anomalies, signifying ascending motion; while drought years were dominated by positive anomalies, signifying descending motion, which suppresses precipitation. These patterns can be used to forecast drought over Zambia and aid in strategic planning to limit the potential damage of drought.     

西北旱区主要气候资源的空间变异性研究

西北旱区地处生态脆弱区,为充分利用其气候资源、协调区域生态环境与社会经济发展,开展主要气候资源的空间变异性研究极为重要。文中利用西北旱区191个气象站点的7个主要气象因子,运用经典统计学和地统计学分析方法来研究各气象因子空间变异性特征。结果表明:(1)干燥度的变异系数>1,其余因子变异系数皆∈(0.157,0.712),表明各气象因子在空间上呈现中等或强烈的空间变异特征;(2)各因子的基底效应值均>0.75,说明气象因子主要受到结构性因子的影响,不会轻易改变或在短时期内难以改变;(3)降水量和相对湿度自西北向东南呈现出递增趋势;蒸发量和干燥度则反之。年均温于新疆和陕西南部出现峰值;日照时数和风速整体上自北向南呈递减趋势。文中通过研究西北旱区气候变化的空间变异特征,有利于把握西北旱区的气候变化规律,为西北旱区农牧业发展提供科学依据。     

干旱季节渭北果园土壤水分时空变化特征

针对渭北旱塬干旱季节主要发生在春季到夏初,制约苹果早期生长发育的客观实际,对渭北旱塬苹果园和农田从3月初到5月底,0～100 cm土壤含水量时空变化进行了研究。结果表明:冬春季渭北果园土壤含水量明显高于农田,进入春季随着果树萌发并进入生长旺盛季节,果园土壤水分消耗较小麦农田更为明显,在0～100cm果园土壤耗水量显著,其中5月份0～60 cm土壤水分消耗更加明显。而农田土壤水分消耗层主要在0～30 cm。相对于农田而言,冬春季渭北果园土壤表现出极为明显的保墒性,有助于缓解春旱的威胁;而春季到夏初则表现为极为显著的土壤耗水性,土壤干燥化趋势明显,5月初为果园土壤水分管理的关键时期。     

滴灌和覆盖条件下山地苹果园土壤蒸发的空间分布

减少土壤蒸发是提高果园水分利用效率的重要途径,覆盖是减少土壤蒸发的有效方式。在黄土高原山地苹果园4个土壤干湿循环周期中,设置3个灌水水平,即高水(85%θ_f)、中水(70%θ_f)和不灌水;2种覆盖方式,即园艺地布覆盖和不覆盖。各处理中根据与果树种植行的间距在水平方向设置3个空间点位(点位A,120 cm;点位B,60 cm;点位C,0 cm),研究滴灌与覆盖下果园土壤蒸发的空间分布并分析点位、气象因素和土壤水分情况对土壤蒸发的影响。研究表明：高水和中水处理下,土壤蒸发在空间上呈“单峰型”曲线分布,不灌水处理下水平方向上3个点位的土壤蒸发差异不显著。园艺地布覆盖可有效抑制土壤蒸发。在中水水平下,园艺地布覆盖显著增大了距果树行60 cm点位的土壤水分,土壤蒸发量减少5.26%～27.75%。偏相关分析表明,园艺地布覆盖减弱了点位和环境因素对土壤蒸发的影响,增大了土壤水分对土壤蒸发的影响。本研究推荐处理组合为园艺地布覆盖+中水。     

中亚地区气温变化的时空特征分析

基于中亚地区63个气象站点1960~2012年月平均气温时间序列,利用Mann-Kendall非参数检验法、R/S分析法和Kriging空间插值,对中亚地区近50多年来气温变化的时空特征进行了分析。结果表明:1)1960~2012年,中亚地区年平均气温变化速率为0.273℃/10a,四季中尤以秋季增温最快,速率高达0.39℃/10a,且R/S指数表明该区气温变暖趋势在未来一段时间内仍会持续;2)中亚地区年平均气温在1989年发生由低温到高温的跃变,跃变前后均值相差0.84℃,其中夏季和冬季跃变时间为1980年左右,而春季则在1999年;3)中亚地区增暖趋势具有明显的时空差异性,年均增幅大体上由东北至西南趋小,各地区在不同季节的气温增幅也不尽相同。     

Spatial pattern analysis of strawberry leaf blight in perennial production systems

ABSTRACT Spatial pattern of the incidence of strawberry leaf blight, caused by Phomopsis obscurans, was quantified in commercial strawberry fields in Ohio using statistics for heterogeneity and spatial correlation. For each strawberry planting, two transects were randomly chosen and the proportion of leaflets (out of 15) and leaves (out of five) with leaf blight symptoms was determined from N = 49 to 106 (typically 75) evenly spaced sampling units, thus establishing a natural spatial hierarchy to compare patterns of disease. The beta-binomial distribution fitted the data better than the binomial in 92 and 26% of the 121 data sets over 2 years at the leaflet and leaf levels, respectively, based on a likelihood ratio test. Heterogeneity in individual data sets was measured with the index of dispersion (variance ratio), C(alpha) test, a standard normal-based test statistic, and estimated theta parameter of the beta-binomial. Using these indices, overdispersion was detected in approximately 94 and 36% of the data sets at the leaflet and leaf levels, respectively. Estimates of the slope from the binary power law were significantly (P < 0.01) greater than 1 and estimates of the intercept were significantly greater than 0 (P < 0.01) at both the leaflet and leaf levels for both years, indicating that degree of heterogeneity was a function of incidence. A covariance analysis indicated that cultivar, time, and commercial farm location of sampling had little influence on the degree of heterogeneity. The measures of heterogeneity indicated that there was a positive correlation of disease status of leaflets (or leaves) within sampling units. Measures of spatial association in disease incidence among sampling units were determined based on autocorrelation coefficients, runs analysis, and a new class of tests known as spatial analysis by distance indices (SADIE). In general, from 9 to 22% of the data sets had a significant nonrandom spatial arrangement of disease incidence among sampling units, depending on which test was used. When significant associations existed, the magnitude of the association was small but was about the same for leaflets and leaves. Comparing test results, SADIE analysis was found to be a viable alternative to spatial autocorrelation analysis and has the advantage of being an extension of heterogeneity analysis rather than a separate approach. Collectively, results showed that incidence of Phomopsis leaf blight was primarily characterized by small, loosely aggregated clusters of diseased leaflets, typically confined within the borders of the sampling units.     

Multiple treatment meta-analysis of products evaluated for control of fire blight in the eastern United States

The aim of this analysis was to estimate the effect sizes and consistency of products evaluated for fire blight control in the eastern United States over the last decade. Because only 3% of the 69 studies published from 2000 to 2008 explicitly presented a measure of within-study variability, a method for estimating the least significant difference (LSD) and, hence the sampling variance, for studies with at least two significant mean separations in the presented mean multiple comparisons was developed. Lin's concordance analysis indicated that the estimated LSD was an accurate predictor of the actual LSD based on 35 studies in a calibration evaluation (ρ(c) = 0.997). Separate multi-treatment random-effects meta-analyses were performed for three control categories: antibiotics, biological control, and plant defense-activating products and mean log response ratios relative to the nontreated controls ([Formula: see text]) were computed for each treatment and then back-transformed to obtain the mean percent disease control. None of the products evaluated performed as well as streptomycin, the standard product for fire blight control, for which the mean disease control was 68.6%. As a group, experimental antibiotics provided the best fire blight control with mean effect sizes ranging from 59.7 to 61.7%. Among the biological controls, the best control was noted for treatments combining the antibiotic streptomycin with a product based on Pantoea agglomerans (55.0% mean disease reduction) or Bacillus subtilis (53.9%). Mean disease control was 31.9, 25.7, and 22.6%, respectively, for products based on B. subtilis, Pantoea agglomerans, and Pseudomonas fluorescens without an antibiotic, suggesting that the higher efficacy of the combination treatments was due to the antibiotic. Among the plant defense-activating products, prohexadione calcium had the highest and most consistent effect size (50.7% control), while other products provided modest mean disease control of between 6.1 and 25.8%. Percent control values were significantly moderated by study location and cultivar used in the study, and were smaller, but more variable, when products were tested under high disease intensity compared with low disease intensity. Results indicate that wide-scale use of biological control and plant defense-activating products in the eastern United States is likely to remain low.     

Spatial variability of fusarium head blight pathogens and associated mycotoxins in wheat crops

The spatial pattern of Fusarium‐infected kernels and their mycotoxin contamination was studied in four wheat fields in Germany using geo‐referenced sampling grids (12–15 × 20–30 m, 28–30 samples per field) at harvest. For each sample, frequency of Fusarium‐infected kernels and spectrum of species were assessed microbiologically; mycotoxin contents were determined by HPLC‐MS/MS analysis. Spatial variability of pathogens and mycotoxins was analysed using various parameters including Spatial Analysis by Distance IndicEs (sadie^® ). Microdochium majus, the most frequent head blight pathogen in 1998, was less frequent in 1999 and could not be detected in kernels from two fields in 2004. Fusarium avenaceum, F. graminearum and F. poae were the most frequent Fusarium species, with 7–8 species per field. The frequency of Fusarium‐infected kernels was 3–15% and the incidence of species showed considerable within‐field variability. Spatial patterns varied among Fusarium species as well as from field to field. Although pathogens and mycotoxin were often distributed randomly in the field, F. avenaceum, F. graminearum, F. poae, F. sporotrichioides, F. tricinctum and the mycotoxin moniliformin had an aggregated pattern in at least one field. Patterns are discussed in relation to spread of Fusarium species depending on inoculum sources, spore type, kind of dispersal, availability of susceptible host tissue and micro‐climate. Sampling of wheat fields for representative assessment of mycotoxins is complicated by random patterns of Fusarium‐infected kernels, especially where the frequency of infection is small.     

河南小麦叶枯类病害春季流行的时间动态规律研究

1997～1998年的研究结果表明:小麦叶枯病害在河南麦田春季的流行曲线基本呈S型曲线。始发期一般在3月20日～4月10日,指数增长期大约10～20d,该期流行速率最高;4月10～20日以后该病进入逻辑斯蒂增长期,可持续30～40d,流行速率比指数增长期稍低,没有明显的衰退期;影响小麦叶枯类病害始发期的气象因子为3月份的日照、降水量和气温,4月份的气温、日照、降水日数、相对湿度与发生程度关系密切。河南主栽小麦品种中没有对叶枯类病害免疫的品种,70%以上的主栽小麦品种为感叶枯病品种。     

Simultaneous temporal progress of sorghum anthracnose and leaf blight in crop mixtures with disparate patterns

Field studies were conducted at Alupe in western Kenya in 1995 and 1996 to evaluate the efficacy of crop and species mixtures for the management of sorghum anthracnose (caused by Colletotrichum sublineolum) and leaf blight (caused by Exserohilum turcicum). The progress of these diseases developing simultaneously on a susceptible sorghum cultivar planted in inter- or intra-row mixtures of varying proportions with either maize or resistant sorghum was monitored. The effects of host type and mixture patterns on disease progress were compared by parameter estimates derived from fitted Lotka-Volterra competition equations and nonlinear logistic models. Competition coefficients were not significant and their confidence intervals included zero in most cases, suggesting that interactions between C. sublineolum and E. turcicum did not occur. Mixtures of the susceptible sorghum with either the nonhost maize or the resistant sorghum delayed the time when disease is first observed and reduced the rate of disease progress and carrying capacity for both anthracnose and leaf blight, with a more pronounced effect on the latter disease. The lower efficacy of mixtures in reducing anthracnose was attributed to an aggregated spatial pattern, coupled with higher rates of progress for this disease. Intra-row mixtures were more efficient than inter-row mixtures in reducing disease development in all years. The implications of these observations for the management of sorghum diseases under small-scale farming systems are discussed.     

塔吉克斯坦百年降水量时空变化特征

利用塔吉克斯坦百年逐月降水资料,以线性趋势分析、Mann-Kendall法、小波分析法以及ArcGIS地统计模块普通Kriging插值法对降水量的时空变化进行了分析.结果表明:过去百年,塔吉克斯坦年总降水量和四季降水量都呈增加趋势并有明显的变化周期;除夏季以外,春季、秋季、冬季平均降水量以及年降水都发生显著性的突变;空间变化上,在1901-2011年,塔吉克斯坦年平均降水总体上呈从西南和东部向中部递增的特征,其中1901-1930年处于少雨期;1931-1960年和1991-2011年处于多雨期.     

基于大样地的乌拉山油松天然林种群空间结构

2010年5-8月于乌拉山自然保护区内建立油松天然林固定监测样地10hm2,应用Ripley’k点格局法对油松种群空间格局和不同生长阶段油松空间关联性进行分析。结果表明:乌拉山油松在研究尺度上呈聚集分布,聚集强度随研究尺度增大持续上升,在尺度达到55m后开始下降,并且在油松的幼树、小树、大树三个生长阶段均呈聚集分布。油松幼树与小树在研究尺度内始终是正关联,幼树与大树在尺度小于48m时呈正相关,小树与大树在研究尺度内呈正相关。     

西北旱区农业水土资源空间变异特征研究

农业水土资源是人类赖以生存的物质基础。为合理利用和开发西北旱区农业水土资源,利用经典统计学和地统计学方法研究了其水资源指数和耕地资源指数的空间变异特征。结果表明:西北旱区水资源指数和耕地资源指数均具有中等变异性特征,其半方差最优拟合模型分别是高斯模型和指数模型,且均呈现空间不均衡分布,分别具有较强和中等空间相关性,其空间变异主要受结构性因子的影响。研究结果不仅可为西北旱区农业水土资源的配置、高效利用和优化提供依据,也为在较大研究范围内开展空间因子变异特征研究提供了方法参考。     

我国城市整体交通运输流发展的时空演化及其空间关联性分析

运用标准差椭圆和空间自相关分析方法,对我国交通运输流在2005-2013年间发展的时空演化及城市间空间关联性进行了相关测度。结果表明:2005-2013年间,交通运输流发展重心向东移动后持续西移,发展空间收缩后扩张,发展轴线顺时针偏转后逆时针偏转,南北方向收缩,东西方向扩张,表明国际市场的萧条影响了交通运输业的发展,国内市场作用开始显现;从发展密集性变化看,2008年密集性增速迅猛,2012年后明显降低,说明靠投资带动的交通运输业的发展不可持续,这种"假性"提升必定会转入中低速度;我国交通运输流的发展存在一定的空间正相关性,但是相关性较低,同时各类集聚区规模随着国家投资及地区战略的实施发生着动态变化。