羊草种群无性系生长格局的研究

 本文根据野外实测数据和采用数学分析方法,在研究羊草种群无性系营养扩散和生长过程的基础上,建立了符合描述羊草种群无性系生长格局的相关随机走动模型和简单扩散模型。对模型进行检验,结果表明,所建模型可以定量地描述羊草种群无性系的生长格局。     

羊草(Leymus chinensis)种群无性系种群动态的初步研究

本文根据１９８５－１９９０年在天然羊草种群无性系的观测与统分析,在研究羊草种群性系生活周期的基础上,探讨了其种群动态,建立了用转移概率矩阵表示的种群动态模型。通过用两种营养繁殖系数Ｒｖ１和Ｒｖ２模拟种群密度变化,发现用转移概率矩陈种群动态模型和现存种群营养繁殖系数Ｒｖ２预测羊草种群密度。     

羊草种群生物量分配动态模拟

基于4种密度羊草种群的温室模拟试验,分析了羊草种群地上生物量与地下生物量的动态变化．结果表明：羊草种群的地上生物量与地下生物量随生长期呈增加的趋势,且随密度的增加而增加,但不同密度间羊草地上生物量与地下生物量的相对生长速率没有显著差异;不同密度羊草种群的根冠比随生长进程而增加,但差异不显著,表明环境因子是影响羊草种群根冠比变化的主导因素;单株羊草及羊草种群的地上生物量和地下生物量间存在显著的幂函数关系,但幂函数指数与系数随羊草密度的变化而变化,表明资源竞争引起的微环境差异导致了羊草种群根冠比的动态变化,可为定量研究光合产物分配提供参考．     

不同种群密度关态下羊草地上部生态场、生态势、场梯度及其季节性变化规律研究

本文通过对羊草种群与个体的定位观测与理论分析,给出了描述植物生态属性质的场特征函数──生志势和场梯度的定义,建立了羊草地上部生态场的生态势和场梯度模型。应用实验观测数据进行了模型运算,分析了草草地上部生态场随作用距离改变的生态势与场梯度变化规律。结果表明,羊草地上部场势与场源植物的相对生长速率、资源利用效力以及种群密度相失,场梯度能刻划生态势的空同变化速率,生态势和场梯度均有季节性变化特征。     

羊草种群密度与生长动态研究

 通过人为控制种群密度的栽培实验,从基株和构件水平上观察羊草无性系种群的生长动态,分析不同密度水平上羊草种群通过调节种群的生长、发育、增殖以及死亡过程来适应密度制约的途径。研究结果表明：1)羊草种群密度可在不同的构件水平间得到调节。当基株密度得到适当调节后便可减缓构件密度(无性系枝条、根茎芽等)的变化幅度和影响构件的发育进程。2)无性系枝条是羊草种群的主体,常在生长季后期出现大量增长,都处于生长旺盛的幼苗期,为翌年春季的返青积累能量和物质。3)单位面积总生物量随密度增加而提高,虽然尚未出现产量恒值现象,但存活枝条平均单株重(地上生物量)随密度增加呈下降趋势,这已反映出密度制约的作用。4)不同密度下羊草种群的生殖过程表现为：低密度时以无性繁殖为主,根茎芽的存活力较高;高密度时以有性繁殖为主,生殖分配值较大。     

羊草草地放牧退化演替中种群消长模型的研究

 羊草草地是东北西部及内蒙东部草原区主要的天然放牧场和割草场、具有较高的经济价值,但是由于长期过度放牧,草地已严重退化并盐碱化。本文采用数学手段,以植物种群在群落中的相对优势度为指标,用植被在放牧退化演替系列上的空间分布序列推断其在时间上演替系列的方法,研究羊草等5种植物种群的优势度随放牧退化演替消长的规律及其数学模型。羊草按D＝124.2e-0.35T衰退,寸草苔和糙隐子草分别按D＝2.13T3.3e-0.15T2和 D=1.77T3.7e-0.29T2消长,而角碱蓬和虎尾草分别按D=0.11e1.3T和D=0.38e0.94T增加。     

内蒙古锡林河流域不同生境中羊草的克隆构型和分株种群特征

 克隆植物的形态可塑性在基株和种群水平上分别表现为克隆构型和分株种群特征的变化。研究对象为内蒙古锡林河流域草地、林地、沙地3种生境下的羊草(Leymus chinensis)种群,通过对羊草根茎节间长度、间隔子长度、分枝强度、分枝角度、株高和分株密度等指标的测定和分析,对这3种不同生境中羊草的克隆构型及分株种群特征进行了研究。结果表明羊草克隆构型相关特征,如,根茎节间长度,根茎节间长度频次分布格局、间隔子长度、间隔子长度频次分布格局,在不同生境差异较大。同时,羊草的分枝角度在不同生境间差异显著。而每间隔子所     

西辽河平原不同利用条件下羊草无性系种群结构的研究

1　引　　言羊草 (Ｌｅｙｍｕｓｃｈｉｎｅｎｓｉｓ(Ｔｒｉｎ .)Ｔｚｖｅｌ.)是典型的无性系根茎禾草 ,营养繁殖力强 ,在我国内蒙古东部和东北西部以及黄土高原地区的天然草地有广泛分布 .羊草具有很高的营养价值 ,是我国优良的牧草之一 ,多年来一直是草地学和生态学工作者研究的热点 ,并已开展到生物学的各个层次水平[1～ 3 ,8] .但对羊草无性系种群的研究较少 ,主要集中在年龄结构及营养繁殖特性等方面[4～ 7] .本文以天然草地灰绿型和黄绿型羊草种群为研究对象 ,对种群在不同干扰地段的变化进行了现实种群与潜在种群年龄结构的分析 ,为羊…     

不同种群密度羊草生态场梯度及其变化特征

通过对植物个体与种群生态场定位实验研究,提出了生态场梯度的概念,并给出了植物与羊草个体生态场梯度的模型,植物生态场的场梯度是,生态场中生态势沿任意方向的变化率。羊草个体生态场梯度同羊草种群密度相关。     

羊草与其主要伴生种竞争与共存的格局分析

在羊草种群与其它植物种群的交错区,应用频度、格避形式,格局强度指数对羊草及其主要伴生种之间的共存格局进行了分析。结果表明,羊草及其主要伴生种的格局呈多样化,集聚格局形式是羊草抵御外来物种入侵,或者是自身扩散的一种对策,羊草与其主要伴生种之间存在竞争与共存作用,羊草与芦苇之间通过拮抗作用实现竞争与共存,羊草与鸡儿肠通过竞争而实现共存,光稃茅香,碱茅以营养繁殖策略实现与羊草竞争,指子茅的生长受羊草竞争的抑制。     

Root foraging traits and competitive ability in heterogeneous soils

The responses of plant roots to nutrient patches in soil may be an important component of competitive ability. In particular, the scale, precision, and rate of foraging for patchy soil resources may influence competitive ability in heterogeneous soils. In a target–neighbor experiment in the field, per-individual and per-gram competitive effects were measured for six old-field species with known root foraging scale, precision, and rate. The presence and number of nutrient patches were also manipulated in a full factorial design. Number and presence of patches did not influence the outcome of competition. Competitive ability was not related to total plant size, growth rate, or root:shoot allocation, or to root foraging precision. Per-individual competitive effects were marginally correlated with root foraging scale (biomass of roots) and root foraging rate (time required to reach a patch). Therefore, competitive ability was more closely related to ability to quickly fill a soil volume with roots than to ability to preempt resource-rich patches.     

Behavioral and energetic costs of group membership in a coral reef fish

Animals in social aggregations often spend more time foraging than solitary conspecifics. This may be a product of the relative safety afforded by aggregations: group members can devote more time to foraging and less time to antipredator behaviors than solitary animals (the “risk reduction” effect). All else being equal, risk reduction should result in higher food intake for grouped animals. However, intragroup competition may force group members to spend more time foraging in order to obtain the same food ration as solitary individuals (the “resource competition” effect). We compared these opposing explanations of foraging time allocation in a coral reef fish, bluehead wrasse (Thalassoma bifasciatum). Aggregations of juvenile bluehead wrasse experience safety-in-numbers, and preliminary observations suggested that juveniles in aggregations spent more time foraging for copepods in the water column than solitary juveniles. However, the risk reduction and resource competition hypotheses are indistinguishable on the basis of behavioral observations alone. Therefore, we collected behavioral, dietary, and growth data (using otolith growth rings) for bluehead wrasse at multiple reefs around a Caribbean island. Despite spending more time foraging in the water column, grouped fish did not capture more prey items and had slower growth rates than solitary fish. Thus, the increased foraging time of grouped fish appears to reflect resource competition, not risk reduction. This competition may limit the size and frequency of aggregations among juvenile bluehead wrasse, which have been shown to experience reduced mortality rates in larger groups. Bluehead wrasse recruits also spent less time foraging but grew faster at sites where planktonic copepod prey were more abundant. This suggests the possibility that large-scale spatiotemporal variability in the abundance of planktonic copepods over coral reefs may produce corresponding variability in the dynamics of reef fish populations. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ultimate and proximate factors affecting the breeding performance of a marine top-predator

Variability in ecosystems affects the life history of organisms. In marine ecosystems where interannual variability is high, relationships between fluctuations in oceanographic parameters and top-predator breeding performance are increasingly documented but it is less clear why such relationships exist. In this study, we examined the connections between marine environment fluctuations and breeding performance of a long-lived top-predator, the black-browed albatross Diomedea melanophris at Kerguelen, through study of resource acquisition and allocation processes. Our results show that this population used the same foraging zones and spent similar time foraging year after year, but adult body condition varied between years. Foraging trips are regulated mainly by changes in body condition. During years of low resource availability, birds return to their nest with lower body condition and adults in low body condition were more frequent and therefore were more likely to stop breeding. Poor breeding success was related to the presence of colder waters in the foraging zones of breeding albatrosses as measured by the positive correlation between sea surface temperatures and breeding success measured over 18 years. Lower breeding success was mainly due to failure by inexperienced birds. The results of this study demonstrate how oceanographic conditions affect breeding performance through allocation processes. We compared these results to those at South Georgia where the breeding success is lower and more variable. This population relies mainly on krill, a resource that shows a very variable year-to-year availability compared to fish prey consumed by Kerguelen birds. This study shows that, in the same species, differences in resource variability and availability affect the demographic strategies probably through differences in allocation strategies.     

People's study time allocation and its relation to animal foraging

In this article we suggest a relation between people's metacognitively guided study time allocation strategies and animal foraging. These two domains are similar insofar as people use specific metacognitive cues to assist their study time allocation just as other species use cues, such as scent marking. People decline to study items that they know they already know, just as other species use a win-shift strategy - avoiding already visited and depleted patches - in foraging. People selectively study the easiest as-yet-unlearned items first, before turning to more difficult items just as other species take the ‘just right’ size and challenge of prey—the so-called Goldilocks principle. People use a stop rule by which they give up on one item and turn to another when the returns diminish just as others species use a stop rule that guides shifting from one patch to another. The value that each item is assigned on the criterion test, if known during study, influences which items people choose to study and how long they study them just as knowledge of the nutritional or energy value of the food influences choices and perseverance in foraging. Finally, study time allocation strategies can differ in their effectiveness depending upon the expertise of the student just as some species forage close to optimally while others do not.     

云南哀牢山徐家坝常绿阔叶林的鸟类取食集团

2006年3-4月,采用无距离估计样线法对云南哀牢山徐家坝中山湿性常绿阔叶林中的鸟类群落做了直接观察,观察到鸟类取食行为14 345次只.运片j聚类分析,依据鸟类的栖息取食行为格局将62种鸟划分为11个取食集团:(G1)地面拾取集团、(G2)地面扒取集团、(G3)树冠层飞取/拾取集团、(G4)树冠层飞取集团、(G5)树干层探取集团、(G6)灌层竹秆探取集团、(G7)树干粗枝搜寻集团、(G8)树冠层粗枝搜寻集团、(G9)树冠层拾取集团、(G10)灌丛下层叶层/树干/地面拾取集团、(G11)灌层拾取集团.结果表明,由于各个集团在栖息基层、取食基层及取食方式上的分离,使各集团分割了该地区的取食空间和食物资源;而集团内部的各个种间主要通过对取食高度的划分,使得集团内部的取食空『白j和食物资源得到了更深层次的利用,使种间竞争减至最小.其结果还表明,鸟类取食集团的数量和结构因不同的植被类型而异,顶级群落中包含的鸟类种类更多,各个种间的生态位分化也更为细致.     

Influence of intertree distance on foraging behaviour of Rhagoletis pomonella in the field

Abstract. 1. We tested a prediction from contemporary foraging theory that animals should decrease their allocation of energy to the searching of individual patches when interpatch travel costs decrease.
2. We used individual Rhagoletis pomonella Walsh (Diptera: Tephritidae) females foraging for oviposition sites (= Crataegus fruit) in a host tree which was surrounded by four other trees at varying distances.
3. We found that flies generally invested less search, measured as time spent searching a tree or number of leaves visited on a tree, when neighbouring trees were nearby than when farther away.
4. Under our test conditions, flies appeared to have difficulty locating neighbouring trees at a distance of more than 1.6 m.
5. Our study calls into question the interpretation of search effort by insects within resource patches in the absence of information on interpatch distances.     

Optimizing foraging behaviour through learning

Manifestation of life-history strategy is through the allocation of resources acquired by foraging. Foraging efficiency can be improved by learning, as fishes adjust their behaviour to changing circumstances. We briefly review the influence of learning on the foraging behaviour of fishes and make recommendations for further research. We stress the importance of quantifying learning and memory in relation to ontogeny and life history.     

Forager success increases with experience inPolybia occidentalis (Hymenoptera: Vespidae)

Summary Foragers of the neotropical swarm-founding waspPolybia occidentalis showed improved task performance, as indicated by foraging success rate, with foraging age. Foragers also spent significantly more time in the field on foraging trips as they aged, while foraging rate did not change with age. These patterns were not explained by directional changes in resource availability or colony need over time. We compare these results to earlier findings on changes in task performance with experience in social insect foragers, and suggest that increases in forager persistence in the field explain improved foraging success with experience.     

Distance effects on resource profitability and recruitment in the giant tropical ant,Paraponera clavata

Summary We examine how cost and benefit components of resource profitability affect recruitment in the giant tropical ant, Paraponera clavata. To vary resource profitability, we changed the quantity of artificial nectar baits presented to foragers and the distance of nectar baits from the nest. Both distance to and amount of resource affected quantitative aspects of recruitment. At increased distances foragers were less likely to recruit, and fewer workers were recruited to the resource area. The amount of nectar affected the tendency of foragers to recruit, but had no effect on the number of ants recruited. Variation in resource distance was also associated with qualitative changes in recruitment strategy. Foragers at distant sites recruited from the canopy rather than from the nest, and often transferred nectar to other workers for transport to the nest. Nectar transfer and extra-nidal recruitment significantly reduced the time required for resource collection. It may also have increased the ability of workers to specialize in specific foraging tasks. A portion of the colony's foraging force specialized spatially by remaining in distant foraging areas without returning to the nest. The flexible recruitment system of P. clavata increases colonial net energetic gain rates by concentrating foraging effort on resources yielding the highest net energetic rewards, and increases the competitive abilities of individual colonies at resource sites by decreasing collection times.