一类捕食—被捕食系统的恢复率

为了研究捕食者的捕获率受到被捕食者最大容量影响条件下的一类捕食模型对应的生态系统的恢复率与被捕食者最大容量之间的关系,采用"系统的稳定均衡点处的Jacobian矩阵的主特征值的实部的绝对值"作为"恢复率",并通过理论与图像进行了分析,结果表明:此系统的预警长度较短,模型有较好的实际意义。     

关于一类捕食-食饵模型恢复率的研究

研究食饵具有常数投放率及受食饵最大容量影响下捕食者的捕获率,引用参考文献所提到的"恢复率"和"预警长度"这两个概念,通过理论计算,绘制图像及算例,得出:本模型的预警长度较长,生态工作者可以有足够的时间采取措施应对转移,有较好的预警效果.     

基于捕食-被捕食理论的“以虫治虫”模型研究

建立了一类被捕食者具有幼虫阶段的率依赖捕食-被捕食模型,通过对其平衡点稳定性的研究,得到其平衡点稳定的条件,为以虫治虫策略提供理论参考.并通过与无捕食模型稳态解进行比较,论证了"以虫治虫"策略的合理性.     

具有多时滞影响的阶段结构捕食-被捕食模型研究

研究一个捕食者与被捕食者均有时滞影响的且捕食者只捕食幼年食饵的捕食-被捕食模型,通过构造适当的Lyapunov泛函,讨论了该模型的正平衡点与非负边界平衡点的渐进稳定性,从而得到了该生态模型的永久持续生存与灭绝的充分性条件。     

具有阶段结构的时滞捕食与被捕食系统的持久性

研究一类捕食者和被捕食者都具有阶段结构,功能响应是非单调函数的时滞捕食与被捕食系统的持久性。利用比较定理得到了系统持久性的条件。     

一类捕食者有病的捕食-被捕食的SIS模型

建立了一类捕食者有病的捕食-被捕食的SIS模型,并讨论了系统平衡点的稳定性,得到了无病平衡点和地方病平衡点稳定的条件.     

具有多时滞影响的阶段结构捕食—被捕食模型研究

研究一个捕食者与被捕食者均有时滞影响的且捕食者只捕食幼年食饵的捕食—被捕食模型,通过构造适当的Lyapunov泛函,讨论了该模型的正平衡点与非负边界平衡点的渐进稳定性,从而得到了该生态模型的永久持续生存与灭绝的充分性条件。     

具有父母照顾的捕食者捕食模型分析

分析了一个描述生态系统的反应扩散方程组.在此系统中,捕食者被分成不成熟和成熟两部分,不成熟的捕食者不能捕获猎物而是靠父母喂养;假设不成熟的捕食者的成熟率是食物的函数,研究了该系统的耗散性以及常数稳态解的局部稳定性.     

具有功能性反应的捕食模型的持久性和灭绝性

讨论了一类具有第Ⅱ类功能性反应函数的捕食-被捕食模型。分别给出了捕食者和被捕食者种群均灭绝;捕食者种群灭绝,而被捕食者种群幸存;以及两种群长期共存的条件。最后通过实例说明所得结论的可实现性。     

依赖比率的捕食被捕食系统的全局分析:捕食与被捕食者均有密度制约的情况

近年来依赖比率的捕食与被捕食模型已引起了生态学者和生物数学研究者的密切注意，这是因为它们比传统的模型更加接近实际情形．本文研究了依赖比率的捕食与被捕食系统的全局定性性态，这里捕食与被捕食者均为密度制约的．     

具有非线性密度制约的一类微分生态系统的定性分析

本文利用定性分析方法，研究了一类食饵具有非线性密度制约及常数存放率的微分生态系统，讨论了系统平衡点的相对位置和性态，可行平衡点的全局稳定性，给出了一组解的有界性，系统无环性以及极限环的存在唯一性的条件。     

青藏高原生态屏障区近10 年生态系统结构变化研究

以2000, 2005和2010年3期生态系统类型数据为基础, 采用生态系统转移矩阵、动态度等统计分析方法, 研究青藏高原生态屏障区近10年的生态系统结构变化及驱动因素分析。研究结果表明: 1) 近10年屏障区内生态系统结构较为稳定, 以草地生态系统为主, 约占研究区总面积的69%; 2) 生态用地与非生态用地均有增加或减少, 其中湿地增加2660.9 km², 草地减少1377.5 km², 城镇面积增加224.6 km², 农田面积减少163.4 km², 荒漠减少1388.5 km²; 3) 受人类活动影响较大的城镇、农田类型变化速率明显高于湿地等生态用地, 2000-2010年城镇面积以2.88% 的年平均增长率迅速增加, 农田面积以0.64%的年均速率持续减少, 而湿地年均增长率仅为0.44%; 4) 生态系统类型整体转移量较小, 仅为整个研究区的0.5%, 其中草地→湿地、荒漠→湿地的转移量最大, 两个转移方向的总转移比例达到69%; 5) 自然因素和人为因素是生态系统结构变化的共同驱动因素, 其中气候变化是引起湿地面积增加的主要自然因素, 人口与GDP的急速增长导致城镇不断扩张, 其深层次原因是工矿业的发展, 载畜量增加是引起草地退化的主要原因, 但生态保护工程对草地生态系统恢复具有积极作用。     

Group formation stabilizes predator-prey dynamics

Theoretical ecology is largely founded on the principle of mass action, in which uncoordinated populations of predators and prey move in a random and well-mixed fashion across a featureless landscape. The conceptual core of this body of theory is the functional response, predicting the rate of prey consumption by individual predators as a function of predator and/or prey densities. This assumption is seriously violated in many ecosystems in which predators and/or prey form social groups. Here we develop a new set of group-dependent functional responses to consider the ecological implications of sociality and apply the model to the Serengeti ecosystem. All of the prey species typically captured by Serengeti lions (Panthera leo) are gregarious, exhibiting nonlinear relationships between prey-group density and population density. The observed patterns of group formation profoundly reduce food intake rates below the levels expected under random mixing, having as strong an impact on intake rates as the seasonal migratory behaviour of the herbivores. A dynamical system model parameterized for the Serengeti ecosystem (using wildebeest (Connochaetes taurinus) as a well-studied example) shows that grouping strongly stabilizes interactions between lions and wildebeest. Our results suggest that social groups rather than individuals are the basic building blocks around which predator-prey interactions should be modelled and that group formation may provide the underlying stability of many ecosystems.     

贵阳市生态承载力评价及其障碍因素诊断

根据城市生态承载力内涵,从压力系统和支持力系统2个方面选取30个指标,构建了城市生态承载力评价指标体系,借助生态承载负荷度模型、生态承载力综合评价模型、障碍因素诊断模型,对贵阳市生态承载力进行评价并对其障碍因素进行诊断,结果显示:研究期内,贵阳市生态系统压力呈波动减小趋势,支持力则呈上升趋势;2003—2007年,生态承载高负荷,2008—2014年,生态承载低负荷;生态承载力不断提高,生态系统正在向良性方向发展;生态系统支持力对贵阳市生态承载力的影响具有主导作用;城市化率、人均公共绿地面积等16个因子是影响贵阳市生态承载力变化的主导因子;万元GDP烟尘排放量、万元GDP能耗、万元GDP废水排放量、万元GDP二氧化硫排放量、万元GDP工业固体废物产生量5个因子是目前制约贵阳市生态承载力提升的关键障碍因子.根据上述结论,提出相应的建议,以促进贵阳市生态承载力进一步提高.     

具有阶段性结构一捕食者两食饵模型的持久性

研究了具有阶段性结构的一捕食者两食饵模型的持久性,运用比较原理对模型进行分析,得到系统永久持续生存和捕食者灭绝的充分条件.     

非自治一食饵-两竞争捕食者模型的动力学行为

研究了非自治的食饵-捕食模型,该系统是一食饵种群被两个具有竞争关系的捕食者种群捕食.其动力学行为包括:持久性、全局渐近稳定性、正周期解和正概周期解的存在唯一性.     

Comparison of changes of typical river segment ecosystem service value in LRGR

Land use changes of river segment ecosystems from the Lancang River and Yuanjiang River were studied from 1985 to 2000 in order to compare their changes of service values and analyze the driving mechanisms based on eco-economic and GIS methods. Results showed that forest areas in both the river segment ecosystems were reduced. The reduced forest in the Lancang River (LR) segment ecosystem was mostly transformed into glebe with the conversion rate of 56.0%, while the reduced forest in the Yuanjiang River (YR) segment ecosystem was mostly transformed into residence land with the conversion rate of 42.5%. Both change amount and change rate of areas of each land use type in the LR segment ecosystem were much larger than those in the YR segment ecosystem. The total service value of the LR segment ecosystem was decreased with the change rate of 15.3%, while that of YR segment ecosystem was increased with the change rate of 0.6%. Manwan Hydropower development was the major anthropogenic driving factor which led to the change of service value of the LR segment ecosystem with the contribution rate of 93%. Agricultural activities were the most important driving factors in the YR segment ecosystem with the contribution rate of 59%. The loss of value of Sediment transportation service resulting from Manwan Hydropower Project construction should take responsibility for the significant decrease of service value of waters, even for the whole LR segment ecosystem. The ecosystem service coefficients of forest and grassland in the study area were much higher than the average level in China, so were the ratios of indirect value to direct value of both the river segment ecosystems. Under the impacts of human activities, the capacity of river ecosystem for providing products was enhanced, while it was weakened to maintain natural ecosystem health.

     

Tracking apex marine predator movements in a dynamic ocean

Pelagic marine predators face unprecedented challenges and uncertain futures. Overexploitation and climate variability impact the abundance and distribution of top predators in ocean ecosystems. Improved understanding of ecological patterns, evolutionary constraints and ecosystem function is critical for preventing extinctions, loss of biodiversity and disruption of ecosystem services. Recent advances in electronic tagging techniques have provided the capacity to observe the movements and long-distance migrations of animals in relation to ocean processes across a range of ecological scales. Tagging of Pacific Predators, a field programme of the Census of Marine Life, deployed 4,306 tags on 23 species in the North Pacific Ocean, resulting in a tracking data set of unprecedented scale and species diversity that covers 265,386 tracking days from 2000 to 2009. Here we report migration pathways, link ocean features to multispecies hotspots and illustrate niche partitioning within and among congener guilds. Our results indicate that the California Current large marine ecosystem and the North Pacific transition zone attract and retain a diverse assemblage of marine vertebrates. Within the California Current large marine ecosystem, several predator guilds seasonally undertake north-south migrations that may be driven by oceanic processes, species-specific thermal tolerances and shifts in prey distributions. We identify critical habitats across multinational boundaries and show that top predators exploit their environment in predictable ways, providing the foundation for spatial management of large marine ecosystems.     

具有一类Holling功能性反应的捕食—被捕食系统的极限环

本文研究一类随着食物量的增加捕食者捕食速度的变化率起变化的种群模型。得到它在R{(x,y):x≥0,y≥0}内存在唯一正平衡点的充要条件和该系统在R内全局渐近稳定的条件,指出其可以出现至少一个(或两个单侧环)或至少两个极限环线的情形以及所存在的极限环的大致位置,从而得出两种群在相互竞争中一种群趋于灭绝或两者互惠共存而达到“生态平衡”的条件。     

低盐度水驱提高采收率实验研究

为了研究低盐度水驱时不同盐度条件下注水速度对开发的影响，通过室内岩芯驱替实验开展了注水速度对低盐度水驱提高采收率的影响研究。研究结果表明：当注水速度小于0.4 mL/min时，在相同注入体积情况下，与较高盐度水驱相比，低盐度水驱的采出程度更高，达到最大采出程度所需要的时间也更长；而在注水速度大于0.4 mL/min时，在相同注入体积情况下，低盐度水驱时的采出程度相对更低，达到最大采出程度所需的时间也更短；就提高采收率而言，高盐度水驱与低盐度水驱均存在最佳注水速度，且低盐度水驱的最佳注水速度要小于高盐度水驱的最佳注水速度。