葛藤天敌紫茎甲幼虫空间分布研究

本文研究了葛藤天敌紫茎甲Sagrafemorata Lichtenstein的空间水平分布和垂直分布,结果表明:(1)紫茎甲幼虫在水平呈聚集分布,基本成分是个体群,且具聚集度对密度的依赖性,幼虫田间理论抽样公式N=(3.3401/M+0.5147)/D2;(2)紫茎甲幼虫垂直分布符合负二项分布和核心分布.     

西瓜枯萎病病株空间分布格局及其抽样技术

研究了西瓜枯萎病病株田间空间分格局及其抽样技术 ,通过频次分布和聚集度指数的测定以及 m* - m回归和 Taylor幂法则分析 ,结果表明 :西瓜枯萎病病株田间分布趋向于聚集分布。m* - m回归分析表明病株空间分布的基本成分是个体群 ,病株个体间相互吸引 ,病株在大田中存在明显的发病中心 ,个体群在田间呈均匀分布格局 ,即分布的基本成分个体群之间趋于均匀分布 ,而个体群内的个体与核心分布相吻合。Taylor幂法则分析表明 ,西瓜枯萎病病株个体的空间格局随着病株密度的提高越趋均匀分布。用 Iwao最适理论抽样模型 n=t2a/D2 [(α 1) /X β- 1],计算出不同病情指数情况下所需的最适抽样数 ,随着病情指数的增加 ,所需抽样数递减。序贯抽样模型为 T0 ( N) =0 .9871N± 1.2 347N ,调查株数 N株时 ,若累计病情指数超过上界可定为防治对象田 ,若累计病情指数未达到下界时 ,可定为不防治田 ,若累计病情指数在上下界之间 ,则应继续调查 ,直到最大样本数 m0 =0 .9871时 ,也即病情指数 2 5 % ,所需抽样数 130株止。     

角倍蚜干母种群的空间格局及其形成机理研究

对角倍蚜Schlechtendalia chinensis(Bell)干母种群的空间格局及其形成机理的研究表明,角倍蚜干母种群在倍林间呈聚集分布．导致其聚集分布的原因是角倍蚜本身的聚集行为和盐肤木Rhus chinensts Mill复叶生长状况的异质性两个方面：角倍蚜干母种群分布的基本成分是琉松个体群,个体群的大小为3—6株倍树所占的面积(2．3—4．6m^2);当样方大小为1、3、6株时为聚集分布,大于6株时为均匀分布。     

油松毛虫的空间分布型及抽样技术

采用Iwao(1968—1977)的(m)对m的回归方法以测定油松毛虫Dendrolimus tabulaeformis Tsai et Liu越冬幼虫、茧、卵块的空间分布型, 并用不同的抽样方法比较了抽样精确度.油松毛虫越冬幼虫, 茧、卵块在油松人工林内都呈聚集分布.幼虫和茧分布的基本成分是双重个体群.卵块分布的基本成分是卵块个体, 其遵从有一公共K值的负二项分布.抽样方法:当越冬幼虫在低密度情况下以单对角线法最佳, 茧在中密度情况下, 卵块在中低密度条件下均以双对角线法为最佳.     

松林中焦艺夜蛾幼虫的空间格局

应用聚集度指标和回归分析等方法,测定了焦艺夜蛾幼虫的空间格局。结果表明,焦艺夜蛾幼虫在马尾松林内呈聚集型分布,分布的基本成分为个体群,个体之间相互吸引;用马占山重新解释的Taylor幂法则分析表明,焦艺夜蛾幼虫的空间格局归属于“聚集度逆密度制约型”。     

稻纵卷叶螟绒茧蜂空间分布规律研究

研究结果表明稻纵卷叶螟绒茧蜂在稻田呈随机分布,建立了Iwao m*-m回归模型、Tayor幂模型、分别为m*=0.3645+0.8608m、log(s2)=0.069+0.89751og m,通过对模型参数的分析得出稻纵卷叶螟绒茧蜂个体间相互吸引,分布的基本成分是个体群,在所有密度下都是随机分布,且随着密度增大,分布趋于均匀.给出了不同密度、不同准确度要求下的最适理论抽样株数,为该蜂的田间密度调查提供了依据.     

节瓜蓟马空间分布图式研究

对节瓜蓟马在节瓜上的空间分布状况进行了调查和分析,结果表明,该虫的空间分布型前期符合奈曼分布,后期符合负二项分布;其空间图式是聚集的,分布的基本成分是个体群;在节瓜不同叶位上分布差异显著。明显向心叶聚集,在瓜栅向光面与背光面虫口比例方面,均以向光面较多。     

长鞘卷叶甲幼虫与成虫的空间格局研究

应用聚集度指标法、回归模型分析法、马占山“重新解释的Taylor幂法则”研究了长鞘卷叶甲幼虫与成虫的空间分布格局.结果表明,长鞘卷叶甲幼虫与成虫在绿竹等丛生类竹林中均呈聚集型分布,分布的基本成分为个体群,个体之间相互吸引;据马占山“重新解释的Taylor幂法则”,长鞘卷叶甲种群类型属于“聚集度逆密度制约型”.     

黑角直缘跳甲幼虫空间分布型及抽样技术的研究

通过运用二种回归方法和六种聚集度指标对黑角直缘跳甲幼虫的空间格局和抽样技术进行了研究。所有的指标表明黑角直缘跳甲幼虫在林间呈聚集分布,分布的基本成分是个体群,且个体间相互吸引。在空间分布型研究的基础上提出了理论抽样数和序贯抽样方案。通过不同抽样方式的精确度比较,表明对角线抽样方式最佳。     

改进的IWAO M—M模型

按照Iwao,倘若?_b/m_b是常数,?=α+βm是线性的。但在自然界,?-m。往往不是线性的,β也不是常数,因此,Iwao的模型有明显的局限性。 我们将β做为m的函数:β=β′+γm。这样,改进模型就是: ,?=α′+β′m+γm~2其中; α′:每个基本成分中个体数的分布的平均拥挤度。 β′:在低密度下基本成分分布的相对聚集度。 γ:基本成分的分布的相对聚集度随种群密度而变化的速率。 本文以温室白粉虱及棉铃虫种群做了例证研究。 结论是: (1)改进的Iwao模型克服了Iwao方法的局限性。既可用于?—m呈线性关系时,也可以应用于?—m呈非线性关系时。因此,改进模型能更准确地描述?和m之间的关系。(2)某种群属随机分布若近似于随机分布时(α′→0,β′→1,γ→0),改进模型可以被原Iwao模型所代替或近似。若在某些种群中,种群密度对基本成分的相对聚集度没有影响(即γ=0),则改进模型就是原Iwao模型。由此可见,Iwao模型是改进模型的一个特例。(3)改进模型的3个参数α′、β′、γ均有其特定的生物学含义,可用于探讨和分析种群的空间格局。此方法不但能提供有关分布的基本成分,基本成分的分布的情况,而且能提供有关基本成分的分布随密度而变化的信息。     

虫草蝠蛾幼虫空间分布型的研究

空间分布型的研究是现代理论生态学的重要基础工作之一,它在实际应用上亦具重要意义。它不仅可揭示出种群的空间结构特征,而且还是确定抽样技术、资料代换和正确估计种群数量的基础。 目前,国内外有关昆虫空间分布型的研究多限于农林业害虫,对其它昆虫的空间分布研究甚少。虫草蝠蛾是我国名贵中药材冬虫夏草的寄主昆虫,主要分布在青海、西藏、四川、云南四省境内的高山草甸。近年来,冬虫夏草产量逐年下降,远远不适应市场的需求,更因自然资源日趋减少,大有枯竭之势。为挽救这一珍贵资源昆虫,急待尽     

The causes of spatial patterning of mounds of a fungus-cultivating termite: results from nearest-neighbour analysis and ecological studies

Little is known about processes regulating population dynamics in termites. We investigated the distribution of mound-colonies of the fungus-cultivating termite Macrotermes bellicosus (Smeathman) in two habitats in the Comoé National Park (Côte d'Ivoire) with nearest-neighbour analysis differentiating between different age classes. These results were compared with ecological data on processes influencing population dynamics. High mound densities were recorded in shrub savannah while only a few mounds were found in gallery forest. Mounds were distributed randomly in both habitats when all mounds were considered together, and when inhabited and uninhabited mounds were treated separately. However, distinctive non-random patterns were revealed in the savannah when we distinguished between different age classes. Small, young colonies were aggregated when they coexisted with larger, older colonies, which were more regularly distributed. This indicates that the distribution of older colonies is influenced by intraspecific competition whereas that of younger colonies is influenced by opposing factors that lead to aggregation. This is in accordance with ecological data. Food is a limiting resource for large colonies, while patchily distributed appropriate microclimatic conditions seem to be more important for young colonies. Colonies that had formerly coexisted (i.e. living colonies and recently dead colonies) showed aggregated, random and regular distribution patterns, suggesting several causes of mortality. Colonies that had never had contact with each other were randomly distributed and no specific regulation mechanism was implicated. These results show that different age classes seem to be regulated by different processes and that separation between age classes is necessary to reveal indicative spatial patterns in nearest-neighbour analysis.     

Spatial distribution and sampling plans for Mesoplatys ochroptera (Coleoptera: Chrysomelidae) on sesbania

With the widespread introduction of the nitrogen-fixing legume sesbania, Sesbania sesban (L.) Merril, in agroforestry systems, the defoliating beetle Mesoplatys ochroptera St?l has become a serious pest of the trees in Africa. To determine within-field and within-plant spatial distribution of M. ochroptera on both seedlings and trees of sesbania, distribution statistics were computed using Iwao's mean crowding regression model. In 1- to 3-mo-old seedlings, the model accounted for 29.8, 32.2, and 61.0% of the variation observed in mean crowding to mean relationships in egg masses, larvae and adults, respectively. The model slopes of the regression were greater than unity for all stages indicating aggregated spatial distribution. Values of the intercept were greater than zero for egg masses, larvae and adults indicating that the basic components of the population are groups of individuals. The highest density (>80%) of mating and feeding adults was found in the upper third of 1- to 2-mo-old seedlings, while most of the egg masses were found in the lower half of seedlings. In trees, >60% of the individuals of all stages were found in the lower third of the foliage canopy, while <10% were found in the upper third. Sampling adults was found to be easier and gave better density estimates of M. ochroptera population than egg masses and larvae. Therefore, sampling plans useful for population studies and decision-making in pest management were developed for adults.     

兴安落叶松原始林林木空间格局的研究

本文采用格局分析,相关分析的方法,结合样地立木定位图研究了不同年龄结构类型的兴安落叶松种群的空间格局。结果表明,该种群具有明显的聚集分布特点,在格局分析图上,中年世代有２－３个均方峰,峰值多位于区组大小为８ｍ＾２和３２ｍ＾２处,成年世代仅具具一个均方峰,峰值多位于区组大小为１６ｍ＾２和３２ｍ＾２处;老年世代均方峰不明显或仅在区组大小为１２８ｍ＾２处有一个均方峰。不同世代在空间上也呈现明显的镶嵌特点     

玉米螟赤眼蜂的寄生卵块在玉米上的田间分布型

玉米螟赤眼蜂是松辽平原玉米带寄生亚洲玉米螟卵的优势种。通过几年来的田间释放结果,取得优异的成效。通过对它在玉米田间的分布型研究,揭示了它在玉米田间第一代螟卵发生期间的分布规律,为以疏松的寄生卵块集团形式呈聚集分布;集团内寄生卵块的分布是随机的,无论在高密度时,还是在一般密度条件下,均为聚集分布型;它不受风向的影响。这一研究结果为它的田间释放和应用技术提供重要的科学依据。     

Spatio-temporal dynamics of willow beetle (Phratora vulgatissima) in short-rotation coppice willows grown as monocultures or a genetically diverse mixture

1 Phratora vulgatissima (Chrysomelidae) is the major pest of short-rotation coppice willows in the U.K., capable of causing severe defoliation in monoculture plantations. As this beetle shows feeding preferences between willow clones, knowledge of the spatio-temporal dynamics of P. vulgatissima is needed in order to assess the effects of mixed clonal plantings on the management of this pest. 2 Distribution patterns of adult P. vulgatissima were monitored over a season at a spatial scale of every tree or every other tree in single clone plantings (monocultures) of three willow clones and in a regular row mixture of these clones. 3 Distribution indices (deviation from Complete Spatial Randomness) demonstrated that P. vulgatissima adults were spatially aggregated on favourable clones in the monocultures and the mixture. The degree of aggregation (measured by the k-parameter of the negative binomial) differed between willow clones. Beetles were highly aggregated at the start of the season, but less so later. 4 Dispersal studies of P. vulgatissima adults over time showed a pattern of beetle infestation along rows of the preferred clones in a regularly structured mixture. In the monocultures, movement was less directional. 5 Plantation design offers some potential for more effective non-chemical pest management for P. vulgatissima. Monitoring of the pest must take account of our findings that adults occur in mobile aggregations.     

Effects of Sand Dune Stabilization on the Spatial Pattern of Artemisia ordosica Population in Mu Us Desert,Northwest China

Vegetation patterns are strongly influenced by sand mobility in desert ecosystems. However, little is known about the spatial patterns of Artemisia ordosica, a dominant shrub in the Mu Us desert of Northwest China, in relation to sand fixation. The aim of this study was to investigate and contrast the effects of sand dune stabilization on the population and spatial distribution of this desert shrub. Spatial autocorrelation, semi-variance analysis, and point-pattern analysis were used jointly in this study to investigate the spatial patterns of A. ordosica populations on dunes in Yanchi County of Ningxia, China. The results showed that the spatial autocorrelation and spatial heterogeneity declined gradually, and the distance between the clustered individuals shortened following sand dune fixation. Seedlings were more aggregated than adults in all stage of dune stabilization, and both were more aggregated on shifting sand dunes separately. Spatial associations of the seedlings with the adults were mostly positive at distances of 0–5 m in shifting sand dunes, and the spatial association changed from positive to neutral in semi-fixed sand dunes. The seedlings were spaced in an almost random pattern around the adults, and their distances from the adults did not seem to affect their locations in semi-fixed sand dunes. Furthermore, spatial associations of the seedlings with the adults were negative in the fixed sand dune. These findings demonstrate that sand stabilization is an important factor affecting the spatial patterns of A. ordosica populations in the Mu Us desert. These findings suggest that, strong association between individuals may be the mechanism to explain the spatial pattern formation at preliminary stage of dune fixation. Sand dune stabilization can change the spatial pattern of shrub population by weakening the spatial association between native shrub individuals, which may affect the development direction of desert shrubs.     

Physical structure of an ant community in semi-arid Australia

A study was carried out on the physical structure of an ant community in a semi-arid habitat of southern New South Wales. Thirty-seven species were collected from the area, and the relative abundance and spatial distribution of colonies of these species were determined in two plots, one in an area dominated by saltbush (Atriplex vesicaria), the other in an area where saltbush had been removed by overgrazing, leaving a simple grassland. The composition and community structure of the populations were found to be little affected by vegetation, and there were no marked differences between the ant faunas of the two areas. Analyses of spatial distribution of the ant colonies showed a variety of patterns, ranging from aggregated to overdispersed, both within and between species. It is suggested that the contemporary structure of an ant community results in the main from processes involving aggressive interactions, determined by the intrinsic properties of the constituent species.     

Analysis of the spatio-temporal distribution of Eurygaster integriceps (Hemiptera: Scutelleridae) by using spatial analysis by distance indices and geostatistics

Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is the most serious insect pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in Iran. In this study, spatio-temporal distribution of this pest was determined in wheat by using spatial analysis by distance indices (SADIE) and geostatistics. Global positioning and geographic information systems were used for spatial sampling and mapping the distribution of this insect. The study was conducted for three growing seasons in Gharamalek, an agricultural region to the west of Tabriz, Iran. Weekly sampling began when E. integriceps adults migrated to wheat fields from overwintering sites and ended when the new generation adults appeared at the end of season. The adults were sampled using 1- by 1-m quadrat and distance-walk methods. A sweep net was used for sampling the nymphs, and five 180° sweeps were considered as the sampling unit. The results of spatial analyses by using geostatistics and SADIE indicated that E. integriceps adults were clumped after migration to fields and had significant spatial dependency. The second- and third-instar nymphs showed aggregated spatial structure in the middle of growing season. At the end of the season, population distribution changed toward random or regular patterns; and fourth and fifth instars had weaker spatial structure compared with younger nymphs. In Iran, management measures for E. integriceps in wheat fields are mainly applied against overwintering adults, as well as second and third instars. Because of the aggregated distribution of these life stages, site-specific spraying of chemicals is feasible in managing E. integriceps.