Iwao M~*-M模型随机分析偏离度检验方法的研究

Iwao M~~*-M模型中其参数α、β揭示了种群分布的特性,当α■0,β■1,种群分布呈随机型。在实际应用中α,β值不会恰好为0和1,存在一定偏离。本文提出一种偏离度检验方法(F检验),解决了种群空间分布型判断为随机型时,允许存在多大偏离,即偏离度的检验问题。式中:n为供建立Iwao M~*-M模型的样地数,α、β为Iwao M~*-M模型中常数项和回归系数,M~*为平均拥挤度,M为平均密度。应用该检验方法对两个实例进行判断,收到满意效果。     

菜粉蝶绒茧蜂种群空间分布型及其应用

本文应用频次分布x~2检验法,Iwao法,Taylor幂法则以及其它聚集指标等方法,分析研究了菜粉蝶绒茧蜂种群(茧块)的空间分布型。结果表明:菜粉蝶绒茧蜂茧块在甘蓝上呈聚集分布,分布的基本成分是以个体群形式存在,个体群之间是随机的,茧块的聚集是由寄主等环境因素引起的。此外,利用分布型参数确定了理论抽样数及序贯抽样。     

呼和浩特市大气环境质量与局地环流关系的探讨

本文通过对呼和浩特地区地面气象观测资料统计，分析了污染物的时空分布规律，从气象条件的角度说明了呼市大气污染往往是由局地环流形成的，并根据分析结果对呼市今后的污染治理提出了相应的建议。     

荔枝龟背天牛幼虫空间分布型研究

对荔龟背天牛幼虫于荔枝园中的空间分状况调查和分析，表明该虫的空间分布为负二项分布；空间图式是聚集型；分布的基本成分为疏松的个体群。聚集行为受环境因素（主要是荔枝品种）的影响，此外，利用分布型参数确定了龟背天牛的理论抽样数并建立了序贯抽样检定表。     

家鸡(Gallus domesticus)和鹌鹑(Coturnix coturnix)染色体核型及G带比较分析

采用外周血淋巴细胞培养法和胰酶处理法，对家鸡和鹌鹑染色体的核型和G带进行了研究。结果表明，家鸡和鹌鹑染色体数目均为2n=78，但染色体的形态存在明显差异，主要表现在NO．1、NO．4、NO．6、NO．8和Z染色体上。NO．1染色体，家鸡为m型，而鹌鹑为sm型；NO．4、NO．6、NO．8和Z染色体，家鸡分别为sm、sm、m、m型，而鹌鹑全为t型。G带分析结果显示，家鸡和鹌鹑的G带差异主要反映在NO．1、NO．2染色体上，这可能是由于臂间倒位所致。     

Quantifying patch distribution at multiple spatial scales: Applications to wildlife-habitat models

Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns.     

阿拉善荒漠特有珍稀濒危植物绵刺克隆生长构型研究

绵刺是阿拉善荒漠特有珍稀濒危植物 ,其具有独特的克隆生长构型 :由枝条下垂形成长间隔物的典型的游击型克隆生长构型和由根茎处形成的典型的密集型克隆生长构型。本文以环境塑造与克隆生长构型的可塑性关系研究绵刺的克隆生长构型 ,揭示其对环境表现出生态对策的高度适应性和可塑性     

Fire-induced changes in northern Patagonian landscapes

In northern Patagonia, Argentina we quantify changes in fire frequency along a gradient from mesic Nothofagus dombeyi forest to xeric woodlands of Austrocedrus chilensis at the steppe ecotone, and we examine patterns of vegetation change coincident with the changes in fire regimes across a range of spatial scales. At a regional scale changes in land cover types are documented by comparing 1:250000 scale cover type maps from 1913 and 1985. Changes in landscape structure are analyzed by comparing vegetation patterns on 1:24000 scale aerial photographs taken in 1940 and 1970. Fire frequency peaked in the late nineteenth-century due to widespread burning and clearing of forests by European settlers late in the century. Subsequently, fire frequency declined dramatically about 1910 due to the cessation of intentional fires and has remained low due to increasingly effective fire exclusion. At a regional scale there has been a dramatic increase during the twentieth century in the proportion of forest cover relative to areas mapped as recent burns or shrublands in 1913. Remnant forest patches that survived the widespread late-nineteenth century burning have coalesced to form more continuous forest covers, and formerly continuous areas of shrublands have become dissected by forest. Under reduced fire frequency there has been a shift in dominance from short-lived resprouting species (mostly shrubs) towards longer-lived species and obligate seed-dispersers such as Austrocedrus chilensis and Nothofagus dombeyi. Due to limited seed dispersal of these tree species, the spatial configuration of remnant forest patches plays a key role in subsequent changes in landscape pattern.     

新疆畜牧业持续快速发展探讨

发展畜牧业是新疆农业生产的重要内容,根据物业生产和市场供求的实际情况,调整畜牧业生产布局,牧区建立育肥商品畜源基地,农区发展育肥,建立着牛肉生产基地;同时,建立各级粗精饲料生产供应网络,保证畜牧业低成本运转,促进新疆畜牧业持续快速发展。     

The 1997-1998 classical swine fever epidemic in The Netherlands--a survival analysis

The aim of this analysis was to characterise the temporal pattern of infection during the 1997/98 classical swine fever (CSF) epidemic in The Netherlands and hence identify and quantify risk factors for infection in different enterprise types and areas. Survival analysis and Cox proportional hazards regression were used to describe the epidemic. Substantial differences in temporal survival patterns (herd breakdown rate) were found between areas where different control policies operated. Factors with a significant influence on the infection hazard of individual herds included: sow numbers as a percentage of total sows and fatteners (HR = 3.38 for mixed herds (0.1–60% sows) vs. fattening herds (0% sows) and HR = 2.74 for breeding herds (60–100% sows) vs. fattening herds), the number of ‘transport contacts per month’ (>0.3 vs. <0.3; HR = 4.11), pig density (pigs/km²) in the area (HR_{1000 pigs} 1.48) and herd size (HR_{100 pigs} = 1.01).

Pre-emptive slaughter in an area appeared to be associated with lower subsequent disease levels. Higher frequency of transport contacts for welfare slaughter during the epidemic, however, well regulated and controlled, was associated with a substantially higher risk of becoming infected. The positive association of a higher pig density with CSF indicates the potential importance of local spread as a factor in disease transmission and emphasizes that dilution of the pig population can contribute to reduction in CSF occurrence. This analysis suggests however, that if pre-emptive slaughter can promptly be applied effectively in an area after initial diagnosis, pig density is then not a significant factor. Mixed and breeding herds had a higher probability of becoming infected than fattening herds, possibly due to different types and frequencies of inter-herd contacts. These contacts continue to some extent during the epidemic, despite the standstill of animal movements.