棉花黄萎病株空间格局及抽样技术研究

本文通过聚集度指标(包括:C、C_A、I、I_8、M/X和L/1 X)测定,以及Iwao’sM—X线性回归、Taylor’s幂的法则和格局纹理分析,结果表明棉花黄萎病株空间格局随着病株密度的提高逐步从聚集型向均匀型演变发展。其空间格局的基本成份是疏松的病株个体群,个体群所占面积约为5株棉花,平均约含2.4个病株个体,且个体群内的病株个体呈随机格局。经方差和u检验,结果表明单对角线五点式、双对角线五点式、棋盘式和平行跳跃式等4种取样方法均适用于棉花黄萎病的田间调查,且尤以双对角线五点式为佳。用双对角线五点式取样法调查的最适抽样数:一般病情普查可少至5个样方(每样方系5株棉花),科研调查为30个样方。     

麦红吸浆虫越冬幼虫分布格局与抽样技术再研究

采用研究昆虫种群空间分布格局的经典方法,通过对3块地6个样点各l00个样方连片逐一取样调查、频次分布拟合和5种聚集指标分析表明,麦红吸浆虫越冬幼虫的田间分布格局为聚集分布,最适合奈曼分布型,其次适合负二项分布型.聚集强度因田块和样点而异;聚块面积为10cm×10cm或10cm×20cm,从而从理论上证明了目前小麦吸浆虫调查中所采用的31.85πcm2×20cm或10cm×l0cm×20cm取样单位是合理的.室内模拟"Z”字形、棋盘式、双对角线和平行线4种抽样方法各5、10、15个样方抽样结果比较表明,以双对角线15个样方抽样的代表性最强.     

观赏百合病毒病病株空间分布型及抽样技术研究

对11块田抽样调查结果经聚集指标(Iδ、I、m^*/m、C_A、C、K)和Iwao回归分析法测定,表明观赏百合病毒病病株空间分布以聚集分布为主,分布的基本成分是个体群,个体群之间相互吸引。分析并确定了保证抽样质量的最适抽样数。对平行线、Z字型、W型、五点式、单对角线、双对角线6种抽样方法进行了比较,其中以平行线式抽样方法最好。     

聚块大小对双斑长跗萤叶甲空间分布的影响

为了明确聚块大小对茶园双斑长跗萤叶甲空间分布的影响,为确定最佳样方面积提供科学依据。用聚块样方方差分析方法和聚集强度指数法研究两种茶园两年双斑长跗萤叶甲空间分布的规律性,聚集格局的差异和种群聚集均数变化。不同大小聚块的均方差均出现1～2个峰值,聚块中有1～8个基本样方(K)时,随着K的增大,聚集格局的扩散系数C和种群聚集均数λ都不断增大,其他格局时C和λ不断变小,聚块内基本样方数K为2、4、8时与K为1时的聚集程度|w|值均小于|w|_(0.05)。茶园双斑长跗萤叶甲存在1～2种不同尺度的聚集空间,空间分布具有规律性,个体群占据最小范围为2个基本样方,即4 m~2,为最佳样方的选择提供了科学依据。     

水稻细菌性基腐病株的空间分布及其抽样研究

 经五种聚集度指标测定和Taylor,Iwao法检验,细菌性基腐病株在一切密度下都呈聚集型,属一般负二项分布。病株空间结构以疏松个体群形式存在,个体群间是聚集的,个体群内是随机的。个体群平均大小为0.1~0.2m²。利用分布型参数K、α、β值,分析了病株聚集的原因;探讨了平均密度与k值的关系;确定了理论抽样数。比较几种顺序抽样方法,以平行线法效果最佳。依X=41.5032Pe1·2603关系可由病丛率来估计病株密度。     

水稻二化螟枯鞘株分布型的初步研究

采用聚集指标法测得防治适期二化螟枯鞘株的田间分布型属于聚集分布,经频次分布检验,基本符合核心分却和嵌纹分布。五种抽样方法田间取样对比结果表明:Z字形样行式和分行取样式比五点、单对角线、棋盘式取样误差率小。     

甘蔗条螟卵空间分布型及其抽样技术

应用聚集度指标法、Iwao回归模型法和Taylor幂法等,对甘蔗条螟(Chilo sacchariphagus Bojer)卵块在秋植蔗田的空间分布和抽样技术进行研究.结果表明,甘蔗条螟卵块在田间呈现负二项分布的聚集型分布;在单位样方(5 m行长,1.3m行距)内,个体间相互吸引,分布的基本成分为个体群,其聚集强度随密度升高而增加;条螟卵块聚集原因同卵块密度相关;在田间抽样方式上,以五点取样效果最佳;卵块理论抽样模型为N=t2/D2(1.098/m+0.147).     

苦瓜棕榈蓟马空间格局及抽样技术研究

应用５种聚集度指数和２种回归方法对苦瓜榈蓟马的空间格局和抽样技术进行了研究,所在的指标表明瓜棕榈蓟马在田间聚集分布,分布的基本成分是个体群,且个体间相互吸引。聚集的原因可以由昆虫本身的聚集行为,或由此行为与环境异质性共同所致。田间调查以５点式抽样方式最佳。     

一种省工高效小麦吸浆虫淘土取样调查方法

现行小麦吸浆虫淘土调查方法按统一的测报办法要求,田间取回土样全部用80目铜纱或尼龙纱筛淘土,费工费时,劳动强度大,由于人力所限,很难较准确地掌握大面积虫口密度分布情况。为寻找一种省工高效的淘土取样方法,我们经实地调查及分析对比,确定采用下列方法取样淘士,收到了较好效果,现介绍如下。1、调查方法:1988年春在14块麦田取样140个,每块田对角线五点取样,每点同时取2个样方(10×10×20cm/方)并编号分装,一块田共取样10个,取其中5个样方的土样,将其     

大丽轮枝菌在茄田土壤中的分布及抽样方法

对茄子黄萎病在田间的空间分布及取样方法进行了研究,并探讨了田间土壤带菌量的准确测定方法。研究结果表明:用分布型指数法测定茄田土壤中微菌核的空间分布型,当菌核数量在8-63 ～39-93 个/g 干土范围内,为聚集分布。当茄田发病率小于75 % 时,病株在田间均属聚集分布;发病率大于75 % 时呈均匀分布。土壤中微菌核的调查方法以棋盘式为最适宜。     

不同寄主作物烟粉虱种群数量的研究

采用等距机械抽样法对棉花、茄子、豇豆等不同作物上烟粉虱成虫、蛹、卵的种群数量进行调查,并对其空间分布进行分析。结果表明,在茄子叶片上烟粉虱成虫和蛹的数量最多,豇豆叶片上卵的数量最多。棉花上烟粉虱成虫种群的空间分布呈聚集型,蛹、卵的种群为均匀分布,茄子上烟粉虱成虫和蛹为均匀分布,卵呈聚集分布;豇豆上烟粉虱成虫为均匀分布,蛹和卵为聚集分布。     

模糊聚类分析在稻纹枯病流行动态研究中的应用

 本文引入模糊(Fuzzy)集论中基于模糊等价关系的模糊聚类分析方法,将发病数量(病害强度)、空间和时间动态的相互关系联系起来作为统一整体,研究了稻纹枯病田间流行动态。以平均发病株数(X)、聚集度指标(Ṁ/M)和发病丛率(P)作为群体动态的特征测度。从整体水平上,将对病害流行系统的考察,化成对若干亚系统(若干阶段)来研究,使复杂的系统得以简化,为深入定量研究和刻划纹枯病流行动态进行了初步尝试。作为一种新的研究方法,文中给出了具体的应用过程。     

Use of SADIE statistics to study spatial dynamics of plant disease epidemics

Using a previously developed stochastic simulation model for plant disease epidemics, the relationship of the SADIE aggregation statistic I _a with initial epidemic conditions, spore dispersal distance, sampling quadrat size and other spatial statistics was investigated. Most variation in I _a was attributable to the initial spatial pattern of infected plants and sampling quadrat size. The importance of initial spatial pattern on SADIE clustering indices (for patches and gaps) was also demonstrated using a number of selected data sets. Correlation of I _a with clustering indices was close to 1·0. Epidemics arising from the regular and random initial patterns resulted in the smallest and greatest I _a values, respectively, at sampling times after disease spread had occurred. Furthermore, the variability in I _a between simulation runs also varied greatly with initial patterns, being lowest and greatest for the clumped and random initial patterns, respectively. I _a increased initially and then decreased with increasing incidence, especially for the clumped and random initial patterns. Overall, the effect of median spore dispersal distance on I _a was very small, especially for the random initial pattern. The correlation between I _a and intraclass correlation was generally small and varied greatly between initial patterns. However, there was a high positive correlation between I _a and a parameter describing the rate of decline of autocorrelation over spatial lags, indicating that I _a, clustering indices and autocorrelations measure some common properties of patterns.     

大丽轮枝菌在茄田土壤中的分布及抽样方法

对茄子黄萎病在田间的空间分布及取样方法进行了研究,并探讨了田间土壤带菌量的准确测定方法。研究结果表明:用分布型指数法测定茄田土壤中微菌核的空间分布型,当菌核数量在8-63 ～39-93 个/g 干土范围内,为聚集分布。当茄田发病率小于75 % 时,病株在田间均属聚集分布;发病率大于75 % 时呈均匀分布。土壤中微菌核的调查方法以棋盘式为最适宜。     

Spatial Patterns of Microsclerotia of Verticillium dahliae in Soil and Verticillium Wilt of Cauliflower

ABSTRACT The spatial patterns of microsclerotia of Verticillium dahliae in soil and wilt symptoms on cauliflower were determined at three sites in each of two fields in 1994 and 1995. Each site was an 8 x 8 grid divided into 64 contiguous quadrats (2 by 2 m each). Soil samples were collected to a depth of 15 cm with a probe (2.5 cm in diameter), and samples from four sites in each quadrat were bulked. Plants in each quadrat were cut transversely, and the number of plants with vascular discoloration and the number without discoloration were recorded. The soil was assayed for microsclerotia by the modified Anderson sampler technique. Lloyd's index of patchiness (LIP) was used as an indicator to evaluate the aggregation of microsclerotia in the field. Spatial autocorrelation and geostatistical analyses were also used to assess the autocorrelation of microsclerotia among quadrats. The LIP for microsclerotia was greater than 1, indicating aggregation of propagules; however, the degree of aggregation at most sites was not high. Significant autocorrelation within or across rows was detected in some spatial autocorrelograms of propagules, and anisotropic patterns were also detected in some oriented semivariograms from geostatistical analyses for microsclerotia, indicating the influence of bed preparation in the fields on pathogen distribution. The parameter estimates p and theta in the beta-binomial distribution and the index of dispersion (D) associated with the distribution were used to assess the aggregation of diseased plants at each site. A random pattern of wilt incidence was detected at 7 of 12 sites, and an aggregated pattern was detected at 5 of 12 sites. The degree of aggregation was not high. A regular pattern of wilt severity was detected at all sites. The high disease incidence (77 to 98%) observed at 11 of the 12 sites could be explained by high inoculum density.     

The influence of verticillium wilt epidemics on cotton yield in southern Spain

Experiments were conducted in the Guadalquivir Valley of Andalucía, southern Spain, in 1986 and 1987, using field plots naturally infested with different inoculum densities of the defoliating and nondefoliating pathotypes of Verticillium dahliae to determine the influence of verticillium wilt epidemics on yield of cotton cultivar Coker 310. The total number of bolls, the number of open bolls, and seed cotton yield were related to the growth stage of plants at first appearance of foliar symptoms, and to inoculum density and virulence of the V. dahliae pathotype prevailing in the soil. For the three yield components, the greatest reduction was observed in plants showing symptoms before opening of first flowers (about 650 degree-days after sowing). Yield increased with delay in the development of foliar symptoms during the crop season, and the effect of the wilt epidemics on yield was small or nil for plants that developed symptoms after opening of the first bolls (1400–1500 degree-days after sowing). A multiple regression equation was derived that related yield reduction to the physiological time accumulated from the time of sowing until the appearance of foliar symptoms and to the rate of disease intensity increase over physiological time. This multiple point model explained about 70% of the variation in cotton yield loss due to verticillium wilt.     

Effects of microtopography on spatial point pattern of forest stands on the semi-arid Loess Plateau,China

Microtopography may affect the distribution of forests through its effect on rain redistribution and soil water distribution on the semi-arid Loess Plateau,China.In this study,we investigated the characteristics of microtopography on two shady slopes(slope A,5 hm2,uniform slope;slope B,5 hm2,microtopography slope) and surveyed the height,the diameter at breast height and the location(x,y coordinates) of all selected individual trees(Robinia pseudoacacia Linn.,Pyrus betulifolia Bunge,Populus hopeiensis Hu & Chow,Armeniaca sibirica Lam.,Populus simonii Carr.and Ulmus pumila Linn.) on slope A and slope B in the watersheds of Wuqi county,Shaanxi province.Subsequently,the effects of microtopography on the spatial pattern of forest stands were analyzed using Ripley’s K(r) function.The results showed that:(1) The maximal aggregation radiuses of the tree species on the uniform slope(slope A) were larger than 40 m,whereas those of the tree species on the microtopography slope(slope B) were smaller than 30 m.(2) On slope B,the spatial association of R.pseudoacacia with P.betulifolia,A.sibirica,P.simonii and U.pumila varied from being strongly negative to positive at microtopography scales.The spatial association of Populus hopeiensis Hu & Chow with U.pumila also varied from being strongly negative to positive at microtopography scales.However,there was no spatial association between P.betulifolia and P.hopeiensis,P.betulifolia and A.sibirica,P.betulifolia and P.simonii,P.betulifolia and U.pumila,P.hopeiensis and A.sibirica,P.hopeiensis and P.simonii,A.sibirica and P.simonii,A.sibirica and U.pumila,and P.simonii and U.pumila.On slope A,the spatial association between tree species were strongly negative.The results suggest that microtopography may shape tree distribution patterns on the semi-arid Loess Plateau.     

纹枯病株在杂交稻田的空间分布型的研究及其应用

 本文引入聚集度指数(I;C;Iδ和M^*等)及平均拥挤度~平均密度系数的测定方法研究了纹枯病(Pellicularia sasakii)株在杂交稻田的空间分布型。研究表明,纹枯病株和丛的分布是:分布的基本成份是聚集的(α>0),即有明显的成团性。而集群内的分布是均匀的(β<1)。