数学分析方法在水稻螟虫测报上的应用研究

本利用福建省将乐县1963-1994年测报积累的观察赍料和气象资料,建立了越冬代二化螟、三化螟蛾高峰逐步回归顶测模型．Fuzzy分析预报模型,四代三化螟发生期发生量璜测模型。     

合理搭配品种 减轻三化螟害

从品种搭配、栽培技术等方面寻找减轻三化螟为害的措施,是经济有效而又切实可行的。现将我们几年来的观察叙述如下: 一、三化螟发生期与水稻 生育期的关系 我县三化螟一般发生四代。第一、三代为害早、晚稻,造成枯心;第二、四代为害早、晚稻,造成白穗。发生期大致是:第一代为4月上中旬至5月中下旬;第     

田秧和坡秧三化螟生长发育的比较

我县水稻三化螟,一年发生六代,以第三代发生量最多,为害最严重。但到第四代,发生量锐减。原因是什么?我县晚季稻秧苗,因播种地理环境不同,有田秧和坡秧两种,其中以播种旱地坡秧为主。此时正是三化螟第三代发生为害时期,调查并了解上述两种秧苗对第三代螟虫幼虫生长发育的影响,对稻田三化螟的种群数量消长规律及其测报与防治工作有一定的意     

第二代三化螟滞育的发现及其与预测预报的关系

<正> 重庆市三化螟Tryporyza incertulas (Walker)每年发生四代,以第三代的发生量最大,危害最严重。 1976年我们在对第二代三化螟发育进度进行调查中,发现第三代三化螟的主要虫源田——中稻在收割完毕时(8月18日),田间幼虫化蛹率才27.3％,而此时诱蛾已有367头,占当年灯下第三代总蛾量378头的97.1％。当时晚稻田治螟工作已结束,可见这两代螟虫发育进度出现了极尖锐的矛眉,因此,我们对第二代三化螟发生滞育提出了怀疑。 1979年我市一些测报站重复作了这一工作,所得结果列表1。     

人工神经网络在三化螟预测中的应用

本应用神经网络对闽北四代三化螟的发生情况进行了预测,三化螟的预报可视作高维空间的非线性分类问题。利用BP网络的反向传播算法．我们对三化螟种群发生趋势进行预测,并获得了满意的结果。     

三化螟第3—4世代数量变动因素初步分析

三化螟的数量变动是个异常复杂的问题,必须通过长期的、艰苦的研究才有希望彻底解决。笔者于1964年在总结历年资料的基础上,试图对部分世代发生数量变动因素的有关问题提出一些看法。由于水平所限,错漏之处请读者指正。 一、三化螟年度消长概况 1957年-1964年新兴县三化螟发生消长规律为:1-3代显著上升,4-5代显著下降。属第3代多发型。历年事实表明,第3-4代之间的数量变动是年中消减的     

稻螟预测预报中螟卵寄生率的检查法

天敌对稻螟的抑制,在某些地区个别年度,起到决定性的作用,甚至是毁灭性的打击。例如四川南充第三代三化螟卵盛期的卵寄生率,一般都在40％左右,晚期高达82.87％。湖南长沙1954年第三代二化螟卵寄生率63.54％,1962年双峰第四代三化螟寄生率77.86％(等腹黑卵蜂达71.88％);1963年长沙三化螟卵寄生率第一代28.35％(稻螟赤眼蜂达20.25％),第二代47.78％(稻螟赤眼蜂达42.49％),第三代28.27—53.45％(稻螟赤眼蜂21.37—33.94％),第四代45.99—54.70％(等腹黑卵蜂达38.93—41.61％)。湘中邵东第四代卵寄生率高达83.46％(螟卵啮小蜂达71.17％)。浙江余姚第二代二化螟卵寄生率为80.82％,第三代最高达87.70％;浙江加兴二化螟卵寄生率最高达90.74％(1956年5月)。 稻螟幼虫天敌种类为数更多,作用也不小,例如1962年长沙越冬幼虫被三化螟虫霉(Erctomophothorasp.)寄生致死平均达48.65％,1963年长沙西数大队     

利用气象因素预测三化螟蛾各世代发生期

<正> 三化螟在南宁地区一年发生5代(包括越冬代)。笔者根据南宁地区历年诱蛾灯资料和气象资料结合三化螟的特性,找出影响本地区三化螟各世代发生期迟、早的主要因素(5厘米深的土壤温度和雨日)用数理统计的方法进行探索,建立了各世代发生期的预报方程。并经过1979年实际预报应用,收到了较好的效果。同时对广西荔浦、贵县、钦州三县的三化螟各世代发生期资料以同样的因素建立了各世代螟蛾发生期预报方程。现将初步研究结果报道如下:     

江淮稻区三化螟发生、防治的几个问题及防治对策的重新思考

20 0 0年江淮稻区 3代三化螟Ｔｒｙｐｏｒｙｚａｉｎ ｃｅｒｔｕｌａｓ(Ｗａｌｋｅｒ)发生危害严重 ,部分县、乡 (镇 )特大发生 ,发生危害实属历史罕见。相当一部分田块危害 (白穗 )程度可称为触目惊心。以邗江新坝为例 ,3代三化螟白穗率最高达 6 5 7% ;白穗率 3 0 %以上的田块占 1 0 %左右 ;白穗率5%～ 1 0 %的田块占 40 %～ 50 % ;5%左右的田块占 3 0 %～ 40 %。相当一部分严重危害的田块看上去象秋天的芦苇滩 ,健穗反而难以见到。本文就 2 0 0 0年三化螟的发生、防治的调查结果 ,结合过去对三化螟的一些研究阐述三化螟的几个问题 ,并提出…     

稻螟赤眼蜂(Trichogramma japonica Asbm.)观察简报

稻螟赤眼蜂是三化螟卵的一种寄生蜂。根据前人研究,它对三化螟卵的寄生率,各世代间的变化缺乏规律,常呈波浪式的消长现象,在应用时就很难掌握。故此,未能引起人们的足够重视。我所1963年进行水稻螟虫预测预报时,对该蜂进行了观察。现将有关资料整理如下。 从左表可以看出,赤眼蜂的寄生率是逐代上升的,尤其是第三代到第四代,寄生效果的变化幅度颇大,卵块寄生率由71.7％上升到100％,卵粒寄生率由17.3％上升到64.5％,第四代三化螟卵平均每块孵出蚁螟数仅7.8条,由于寄生率高,对减轻当年晚稻螟害起了很大作用。     

从文献看种群、种群生态及种群行为研究

通过维普中文期刊网和英文ScienceDirect数据库有关种群、种群生态和种群行为文献的查询,发现文献的发表量很不平衡,种群研究文献的年增长率远大于种群生态和种群行为。英文文献中关于种群行为研究的文献增长率高于种群生态,而中文文献正好相反。     

Modelling the effectiveness of contraception for controlling introduced populations of elephant in South Africa

Re‐introduced African elephant (Loxodonta africana Blumenbach) populations are growing at very high rates in many of southern Africa’s reserves, have attained densities higher than previously thought possible and may be exhibiting irruptive growth. Active management of such populations is necessary to prevent the potentially negative effects on habitat and biodiversity that are associated with elephant overpopulation. One potentially feasible method of elephant management is immunocontraception, but very little is known about the long‐term effectiveness of this method. Using demographic data from three South African elephant populations, we made model projections of the effects of contraception on population growth rates to determine whether contraception may be a feasible management tool for elephant. In comparison with noncontracepted populations, realistic reductions in population growth rate after 20 years of contraception were projected to be up to c. 64%, with 50% being a very feasible target. Through its ability to reduce population growth rates, immunocontraception should be an effective tool for preventing or minimizing irruption in elephants and, perhaps, other introduced ungulate species.     

北京东灵山海拔梯度上辽东栎种群结构和空间分布

种群年龄结构和空间分布格局是种群生态学的核心研究内容.为了阐明辽东栎种群海拔梯度分布特点,在北京东灵山地区辽东栎海拔分布范围(1000～1800m)内调查10条样带,研究种群大小级结构和空间分布的变异.种群的平均胸径在海拔梯度上表现出两段式的分布特征,海拔1480m为两段分布的分界点,在每一段内随海拔增加平均胸径也增加, 这反映了海拔梯度上种群的不同发育历史.种群密度、种群的聚集程度、种群的结构在海拔梯度上的分布特征都与平均胸径分布相似,种群密度和聚集程度与平均胸径为负相关系,其分布趋势与平均胸径相反.总体上,东灵山海拔梯度上辽东栎种群还是比较稳定的.辽东栎种群结构和空间分布在海拔梯度上的分布特征是种群发育历史、物种特性、环境、干扰等因素在海拔梯度上综合作用的结果.     

Why are population growth rate estimates of past and present hunter–gatherers so different?

Hunter–gatherer population growth rate estimates extracted from archaeological proxies and ethnographic data show remarkable differences, as archaeological estimates are orders of magnitude smaller than ethnographic and historical estimates. This could imply that prehistoric hunter–gatherers were demographically different from recent hunter–gatherers. However, we show that the resolution of archaeological human population proxies is not sufficiently high to detect actual population dynamics and growth rates that can be observed in the historical and ethnographic data. We argue that archaeological and ethnographic population growth rates measure different things; therefore, they are not directly comparable. While ethnographic growth rate estimates of hunter–gatherer populations are directly linked to underlying demographic parameters, archaeological estimates track changes in the long-term mean population size, which reflects changes in the environmental productivity that provide the ultimate constraint for forager population growth. We further argue that because of this constraining effect, hunter–gatherer populations cannot exhibit long-term growth independently of increasing environmental productivity.This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.     

A conceptual model of the dynamics of the Syamozero Lake community

We present a conceptual mathematical model of the dynamics of a spatially heterogeneous population system whose prototype is the fish community of Lake Syamozero. Analysis of the solutions of this model is used to demonstrate that interactions between the predator and prey populations in two neighboring biotopes (the pelagic and coastal zones) may result in either undamped oscillations or steady states of the population sizes. The model population densities are of the same order of magnitude as the values obtained in long-term observations of the Syamozero biota. It is also demonstrated that the transition to steady states may be accompanied by long-term (dozens or hundreds of years) damped oscillations of the prey and predator population densities. Under natural conditions, long transitional periods may prevent fish communities from reaching stationary modes.     

The macroecology of population dynamics: taxonomic and biogeographic patterns in population cycles

Regular cycles in population abundance are fascinating phenomena, but are they common in natural populations? How are they distributed among taxa? Are there differences between different regions of the world, or along latitudinal gradients? Using the new Global Population Dynamics Database we analysed nearly 700 long (25 + years) time series of animal field populations, looking for large-scale patterns in cycles. Nearly 30% of the time series were cyclic. Cycle incidence varied among taxonomic classes, being most common in mammal and fish populations, but only in fish did cycle incidence vary among orders. Cycles were equally common in European and North American populations, but were more common in Atlantic fish than Pacific fish. The incidence of cycles increased with latitude in mammals only. There was no latitudinal gradient in cycle period, but cycle amplitude declined with latitude in some groups of fish. Even after considering the biases in the data source and expected type I error, population cycles seem common enough to warrant ecological attention.     

Catastrophic events and recovery from low densities in populations of otariids: implications for risk of extinction

Two key factors in a population's risk of extinction are major population declines induced by natural or anthropogenic events (catastrophes) and whether the population's rate of growth increases or decreases at very low abundance levels. These two elements should be included in any population viability analysis (PVA), but estimates of the frequency and intensity of catastrophic events and data on the dynamics of low population densities are difficult to obtain. We examined the literature on population dynamics of otariids (fur seals and sea lions), to determine how frequently populations are subjected to major population declines, and to what extent depleted populations recover from low population size. We present frequency distributions for percentage declines for otariid life‐stages (pup, juvenile, adult female and male), and describe eight examples of events leading to a population decline of 50% or greater among otariids. We found that numerous otariid populations have been reduced to very low densities by exploitation (low enough to be thought extinct) and have recovered to levels where they are no longer at risk of extinction. This suggests that the reduction in population rate of increase at low densities in otariid populations may not be strong.     

Integral projection models perform better for small demographic data sets than matrix population models: a case study of two perennial herbs

1. Matrix population models are widely used to describe population dynamics, conduct population viability analyses and derive management recommendations for plant populations. For endangered or invasive species, management decisions are often based on small demographic data sets. Hence, there is a need for population models which accurately assess population performance from such small data sets.
2. We used demographic data on two perennial herbs with different life histories to compare the accuracy and precision of the traditional matrix population model and the recently developed integral projection model (IPM) in relation to the amount of data.
3. For large data sets both matrix models and IPMs produced identical estimates of population growth rate (λ). However, for small data sets containing fewer than 300 individuals, IPMs often produced smaller bias and variance for λ than matrix models despite different matrix structures and sampling techniques used to construct the matrix population models.
4. Synthesis and applications . Our results suggest that the smaller bias and variance of λ estimates make IPMs preferable to matrix population models for small demographic data sets with a few hundred individuals. These results are likely to be applicable to a wide range of herbaceous, perennial plant species where demographic fate can be modelled as a function of a continuous state variable such as size. We recommend the use of IPMs to assess population performance and management strategies particularly for endangered or invasive perennial herbs where little demographic data are available.     

内蒙古贺兰山冬春季岩羊种群现状及保护

为调查内蒙古贺兰山国家级自然保护区内岩羊（Pseudois nayaur alashanicus）的种群现状,通过样线法在2017、2018年冬季,2018、2019年春季进行了调查,利用R 4.0.3中的Distance 1.0.2对样线观测数据进行分析,估测保护区内岩羊的种群数量及密度,分析其种群结构。结果显示,调查共观测到岩羊6299只,其中,2018年冬季种群数量最高,约为2654（2230-3161）只（括号内为95%数量置信区间）,种群密度为3.921（3.293-4.668）只/km²。与2003年同季节的调查数据对比发现,保护区内岩羊的种群数量在15年间增长迅速,岩羊的种群密度累计增长了约53.17%,年平均增长3.54%。岩羊集群形式：混合群（88.03%,80.95%）为岩羊冬、春最主要的集群形式,且混合群的数量冬季多于春季,独羊出现的次数最低（1.99%,2.86%）,不同的集群类型在不同的季节的差异极显著（P<0.001）;岩羊平均群大小：春季为（13.439±12.085）只,冬季为（9.011±8.610）只,调查季节中集群大小多为1-10只,岩羊的不同季节的群大小差异极显著（P<0.001）。种群成体与幼体比在不同季节的变化范围为1.411-2.673,雌雄比在不同季节的变化范围为0.934-1.469,种群结构的季节性差异极显著（P<0.001）。集群类型、群大小及群组成的调查表明,不同季节间岩羊种群结构差异明显。     

The relevance of time series in molecular ecology and conservation biology

The genetic structure of a species is shaped by the interaction of contemporary and historical factors. Analyses of individuals from the same population sampled at different points in time can help to disentangle the effects of current and historical forces and facilitate the understanding of the forces driving the differentiation of populations. The use of such time series allows for the exploration of changes at the population and intraspecific levels over time. Material from museum collections plays a key role in understanding and evaluating observed population structures, especially if large numbers of individuals have been sampled from the same locations at multiple time points. In these cases, changes in population structure can be assessed empirically. The development of new molecular markers relying on short DNA fragments (such as microsatellites or single nucleotide polymorphisms) allows for the analysis of long‐preserved and partially degraded samples. Recently developed techniques to construct genome libraries with a reduced complexity and next generation sequencing and their associated analysis pipelines have the potential to facilitate marker development and genotyping in non‐model species. In this review, we discuss the problems with sampling and available marker systems for historical specimens and demonstrate that temporal comparative studies are crucial for the estimation of important population genetic parameters and to measure empirically the effects of recent habitat alteration. While many of these analyses can be performed with samples taken at a single point in time, the measurements are more robust if multiple points in time are studied. Furthermore, examining the effects of habitat alteration, population declines, and population bottlenecks is only possible if samples before and after the respective events are included.