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521.
A dynamic simulation model was constructed using outputs from a balanced Gulf of Maine (GOM) energy budget model as the initial parameter set. The model was structured to provide a recipient control set of dynamics, largely based off of flows to and from different biological groups. The model was used to produce Monte Carlo simulations that were compared (percent change in biomass) with basecase simulations for a variety of scenarios. Changes in primary production, large increases in pelagic and demersal fish biomass, increases in fishing mortality, and large increases in top predators such as baleen whales and pinnepids were simulated. These scenarios roughly simulated the potential impacts of climate change, altered fishing pressure, additional protected species mitigations, and combinations thereof. Results suggest that the GOM system is primarily influenced by bottom-up processes involving phytoplankton, zooplankton, and bacterial biomass. Pelagic and demersal fish were important in determining trends in some of the scenarios. Marine mammals, large pelagic fish, and seabirds have a minor role in the GOM system in terms of biomass flows among the ecosystem components. The system is resilient to large-scale change due, in part to many predator–prey linkages. However, major alterations could occur from sustained climate change, high fishing rates, and by combinations of these types of external forcing mechanisms. 相似文献
522.
This research compares two existing methodologies, mixed trophic impact analysis and utility analysis, which use network analysis to evaluate the direct, pair-wise, and indirect, holistic, ecological relations between ecosystem compartments. The two approaches have many similarities, but differ in some key assumptions which affect both the final results and interpretations. Here, we briefly introduce both methodologies through a series of two simple examples; a 3-compartment competition model and a 3-compartment food chain model, and then apply the methodologies to a 15-compartment ecosystem model of the Chesapeake Bay. This example demonstrates how implementing the various conceptual and methodological assumptions lead to differing results. Notably, the overall number of positive relations is greatly affected by the treatment of the self-interactions and the handling of detritus compartments lead to a distinction between ecological or trophic relations. We recommend slight changes to both methodologies, not necessarily in order to bring them completely together, but because each has some points which are stronger and better defensible. 相似文献
523.
Cycling index is an important ecological indicator used in ecosystem analysis. The higher the cycling in an ecosystem, the higher the utilization of mass and energy within the system before it is lost due to respiration and other factors. For a stock-flow type ecosystem model at steady state, Finn’s cycling index (FCI) can be computed using simple matrix algebra. However, it is difficult to measure how well this index represents the actual cycling occurring in the system. In this paper, we study cycling in ecological networks using an individual based approach (particle tracking algorithm). This new simulation method provides access to the pathway data of individual particles that flow in the system, therefore one can quantify cycling using this pathway data quite literally. We used particle tracking simulations (PTS) to compute a cycling index using Finn’s idea of flux based cycling. Our simulation based results (using no matrix algebra) agree with Finn’s cycling index, verifying the accuracy of both the PTS, and the original linear algebraic formulation of FCI. 相似文献
524.
Urban ecological security assessment and forecasting,based on a cellular automata model: A case study of Guangzhou,China 总被引:2,自引:0,他引:2
Forecasting changes in urban ecological security could be important for the maintenance or improvement of the urban ecological environment. However, there are few references in this field and no landmark research work has been reported, particularly quantitative research. A forecasting model for ecological security based on cellular automata (CA) was developed using preliminary spatial data from an ecological security assessment of Guangzhou conducted previously (1990–2005). The model was constrained using transformation rules based upon proposed planning for 2010–2020. A simulation accuracy of 72.09% was acquired. Using a one-bit assessment grid for 2005 as the starting state for the simulation, the model was used to forecast ecological security for 2020. This revealed that although the ecological security status would be improved relative to current trends, there would still be an overall decline in ecological security over the next 15 years. Even if new urban plans were implemented, landscape pattern analysis suggested a more scattered and homogenous distribution in the urban landscape of Guangzhou and significant variation in landscape characteristics among districts. This suggests that further measures must be adopted to reverse the current trends in Guangzhou's ecological security. The model highlights the need to make ecological protection an integral part of urban planning. This study demonstrates the potential of CA models for forecasting ecological security. Such models could make an important contribution to decision-making for regional governors and to the development of urban planning incorporating assessment and prediction of ecological security. 相似文献
525.
Authors of socioecological models propose that food distribution affects female social relationships in that clumped food
resources, such as fruit, result in strong dominance hierarchies and favor coalition formation with female relatives. A number
of Old World monkey species have been used to test predictions of the socioecological models. However, arboreal forest-living
Old World monkeys have been understudied in this regard, and it is legitimate to ask whether predominantly arboreal primates
living in tropical forests exhibit similar or different patterns of behavior. Therefore, the goal of our study was to investigate
female dominance relationships in relation to food in gray-cheeked mangabeys (Lophocebus albigena). Since gray-cheeked mangabeys are largely frugivorous, we predicted that females would have linear dominance hierarchies
and form coalitions. In addition, recent studies suggest that long food site residence time is another important factor in
eliciting competitive interactions. Therefore, we also predicted that when foods had long site residence times, higher-ranking
females would be able to spend longer at the resource than lower-ranking females. Analyses showed that coalitions were rare
relative to some other Old World primate species, but females had linear dominance hierarchies. We found that, contrary to
expectation, fruit was not associated with more agonism and did not involve long site residence times. However, bark, a food
with a long site residence time and potentially high resource value, was associated with more agonism, and higher-ranking
females were able to spend more time feeding on it than lower-ranking females. These results suggest that higher-ranking females
may benefit from higher food and energy intake rates when food site residence times are long. These findings also add to accumulating
evidence that food site residence time is a behavioral contributor to female dominance hierarchies in group-living species. 相似文献
526.
When eggs hatch asynchronously, offspring arising from last-hatched eggs often exhibit a competitive disadvantage compared
with their older, larger nestmates. Strong sibling competition might result in a pattern of resource allocation favoring larger
nestlings, but active food allocation towards smaller offspring may compensate for the negative effects of asynchronous hatching.
We examined patterns of resource allocation by green-rumped parrotlet parents to small and large broods under control and
food-supplemented conditions. There was no difference between parents and among brood sizes in visit rate or number of feeds
delivered, although females spent marginally more time in the nest than males. Both male and female parents preferentially
fed offspring that had a higher begging effort than the remainder of the brood. Mean begging levels did not differ between
small and large broods, but smaller offspring begged more than their older nestmates in large broods. Male parents fed small
offspring less often in both brood sizes. Female parents fed offspring evenly in small broods, while in large broods they
fed smaller offspring more frequently, with the exception of the very last hatched individual. These data suggest male parrotlets
exhibit a feeding preference for larger offspring—possibly arising from the outcome of sibling competition—but that females
practice active food allocation, particularly in larger brood sizes. These differential patterns of resource allocation between
the sexes are consistent with other studies of parrots and may reflect some level of female compensation for the limitations
imposed on smaller offspring by hatching asynchrony. 相似文献
527.
Ting Chen Yingying Zhao Xiaopeng Qiu Xiaoyan Zhu Xiaojie Liu Jun Yin Dongsheng Shen Huajun Feng 《Frontiers of Environmental Science & Engineering》2021,15(2):33
528.
西藏粮食安全状况及主要粮食供需关系研究 总被引:6,自引:2,他引:4
西藏粮食安全事关当地的长治久安以及社会经济的可持续发展。论文基于2010年农户层面的食物消费调研数据,并且结合粮食市场调研、粮食加工企业调研以及政府部门调研数据等,在研究西藏粮食生产和消费基础之上,重点分析了西藏主要粮食(青稞、小麦和水稻)供应和需求之间的关系。结果显示,全区粮食供应数量较高,特别是外地调入粮食供给能力不断增强,提高了西藏粮食安全保障程度。2010年全区主要粮食生产为85.09万t,而家庭层面主要粮食消费为88.81万t,粮食生产和消费基本持平;但是考虑到本地粮食消费比重为60.8%,2010年本地粮食消费只有54.0万t。从整个西藏地区来看,虽然西藏地区粮食供应已经大于其需求(西藏地区三大粮食作物总供应146.3万t,而总需求超过95.9万t,供应为需求的1.5倍),但是从不同地区来看,区域之间的粮食供需差别非常大,尤其是藏北牧区(主要是那曲地区),粮食缺口比较大,未来需要加强藏北地区粮食的供给力度,提升其粮食安全的保障能力。随着内地粮食进藏数量和种类不断增加,未来需要进一步转变粮食购销体制系统,把粮食生产者(即农民)考虑在粮食流通市场之内,进一步加强和重视西藏粮食生产者在粮食流通中所发挥的作用,从而增加西藏农村地区家庭中余粮流通,增加青稞特色产业发展,提高农民收入。 相似文献
529.
Chi Zhang Wenhui Kuang Jianguo Wu Jiyuan Liu Hanqin Tian 《Frontiers of Environmental Science & Engineering》2021,15(2):29
530.
广州市城市生态用地空间冲突与生态安全隐患情景分析 总被引:7,自引:0,他引:7
生态安全隐患区域的空间检测和获取对城市生态安全保护起到重要的作用。论文利用智能计算模型和空间分析技术,对广州市城市生态用地空间冲突与生态安全隐患进行了多情景模拟和分析。研究表明:① 空间冲突区域主要分布在城市边缘区。在城市生态用地占广州市总面积的15%、30%和50%情景下,分别占空间冲突总面积的95.40%、86.28%和77.45%,白云、花都、天河和番禺是空间冲突发生的主要区域。与之相反,城市核心区冲突区域面积所占比例逐渐增加。在50%情景时,空间冲突区域面积急剧增加,广州市城市生态用地控制指标面临着巨大的空间冲突压力。② 城市生态安全隐患区域主要分布在城市边缘区,在50%情景时,城市边缘区的隐患区域面积占隐患区域总面积的74.13%,白云区和花都区是生态安全隐患区域分布最集中的区域。而位于城市核心区的隐患区域,面临着更大的生态安全压力。研究结果可为城市生态安全的监控和预警提供参考,为城市生态保护提供可借鉴的方法和分析工具。 相似文献