Scale invariance in food web properties

The robustness of five common food web properties is examined by varying the resolution of the data through aggregation of trophic groupings. A surprising constancy in each of these properties is revealed as webs are collapsed down to approximately half their original size. This analysis of 60 invertebrate-dominated community food webs confirms the existence of all but one of these properties in such webs and addresses a common concern held by critics of food web theory that observed food web properties may be sensitive to trophic aggregation. The food web statistics (chain length; predator/prey ratio; fraction of top, intermediate, and bottom species; and rigid circuits) are scaling in the sense that they remain roughly invariant over a wide range of data resolution. As such, within present standards of reporting food web data, these statistics may be used to compare systems whose trophic data are resolved differently within a factor of 2.     

Early warnings of regime shifts: a whole-ecosystem experiment

Catastrophic ecological regime shifts may be announced in advance by statistical early warning signals such as slowing return rates from perturbation and rising variance. The theoretical background for these indicators is rich, but real-world tests are rare, especially for whole ecosystems. We tested the hypothesis that these statistics would be early warning signals for an experimentally induced regime shift in an aquatic food web. We gradually added top predators to a lake over 3 years to destabilize its food web. An adjacent lake was monitored simultaneously as a reference ecosystem. Warning signals of a regime shift were evident in the manipulated lake during reorganization of the food web more than a year before the food web transition was complete, corroborating theory for leading indicators of ecological regime shifts.     

Direct and indirect effects of resource quality on food web structure

The diversity and complexity of food webs (the networks of feeding relationships within an ecological community) are considered to be important factors determining ecosystem function and stability. However, the biological processes driving these factors are poorly understood. Resource quality affects species interactions by limiting energy transfer to consumers and their predators, affecting life history and morphological traits. We show that differences in plant traits affect the structure of an entire food web through a series of direct and indirect effects. Three trophic levels of consumers were influenced by plant quality, as shown by quantitative herbivore-parasitoid-secondary parasitoid food webs. We conclude, on the basis of our data, that changes in the food web are dependent on both trait- and density-mediated interactions among species.     

食物网研究进展

食物网是群落中各种生物有机体通过营养关系连接成的集合体。关于食物网的基本结构、HSS与MS观点的争论、食物链长度、与食物网大小相关的特性、食物网连接中的问题以及小瀑布模型等等,都是食物网生态学研究的主题。这些问题的深入研究将为认识食物网中种群调控机制,营养级之间的关系、各种食物链的存在及其能量转化机制、生物群落的行为机制以及自然保护设计等等作出贡献。同时,对于食物网理论的进一步完善与发展,生态学理论与应用都具有重要的意义。     

A major food web component in the orinoco river channel: evidence from planktivorous electric fishes

Deep-water sampling of the Orinoco River main channel resulted in the collection of an unexpectedly high abundance and diversity of specialized fishes. Twenty-eight of the more than 60 species collected belong to the Gymnotiformes(New World electric or knife fishes). One of the more numerous of these, a recently described species of the genus Rhabdolichops, consumes large numbers of very small planktonic Crustacea and insect larvae. These items are captured in the very swift, turbid, and deep waters of the Orinoco. Although the strong dependence of the river food web on terrestrial and floodplain food sources is well known, the specialized capabilities of Rhabdolichops and of other fishes that occur with it indicate a significant extension of the river food web into the main channel.     

Stalking the wily multinational: Power and control in the US food system

The ten largest food and beveragecorporations control over half of the food sales inthe United States and their share may be increasing.Using data from a range of secondary sources, weexamine these corporations and their boards ofdirectors. Social and demographic characteristics ofboard members gleaned from corporate reports, thebusiness press, and elsewhere are presented.Information on interlocking corporate directorates andother common ties among members of the boards ofdirectors show that US based food and beveragecorporations are tied together through a web ofindirect interlocks.     

海洋食物网结构稳定性及干扰响应研究综述

针对当前全球环境急剧变化的背景,本文归纳了海洋食物网结构复杂性常用的量化指标,梳理了食物网稳定性不同维度的概念并深入探究其与复杂性之间的内在联系。根据海洋生态系统的不同干扰类型,分析了各种类型干扰的发生方式以及食物网在应对干扰时的适应机理,最后总结了海洋生态系统数据获取分析以及食物网构建时有待解决的问题,并指出开展初级生产者与消费者之间的相互作用研究能更利于解析全球变化对海洋食物网结构和功能的影响。     

食物链的一种计数法

群落食物网常用的向图直观表示,食物网链映射矩阵的引入给出了食物网的一种代数表示,本文通过食物网映射矩阵的乘法运算给出了食物网中,物种ｉ到物种ｊ的ｋ级食物链个数的简单计数法,它尤其适合复杂食物网中食物链的计数,是用矩阵方法进行食物链研究的一个先例,具有重要的方法论意义。     

Challenges of modeling ocean basin ecosystems

With increasing pressure for a more ecological approach to marine fisheries and environmental management, there is a growing need to understand and predict changes in marine ecosystems. Biogeochemical and physical oceanographic models are well developed, but extending these further up the food web to include zooplankton and fish is a major challenge. The difficulty arises because organisms at higher trophic levels are longer lived, with important variability in abundance and distribution at basin and decadal scales. Those organisms at higher trophic levels also have complex life histories compared to microbes, further complicating their coupling to lower trophic levels and the physical system. We discuss a strategy that builds on recent advances in modeling and observations and suggest a way forward that includes approaches to coupling across trophic levels and the inclusion of uncertainty.     

Cadmium pollution from phosphate fertilizers in arable soils and crops: an overview

The application of mineral and organic phosphorus fertilizers to arable land has greatly increased crop yield to meet the world food demand. On the other hand, impurities in these fertilizers, such as heavy metals, are being added to agricultural soils, resulting both from the raw materials themselves and the processes used to obtain the final product. Cadmium, a non-essential and toxic heavy metal, has been found in relatively high amounts in common P fertilizers obtained from sediments. This metal poses a high risk for soil fertility, crop cultivation, and plants in general. Furthermore, human health might be compromised by the cadmium concentrations in agricultural and livestock products, due to the bioaccumulation effect in the food web. The accumulation in the different matrixes is the result of the high mobility and flexible availability of this harmful metal. This review summarizes risks to human health, the factors influencing cadmium movement in soils and crop uptake, as well as common plant responses to its toxicity. In addition, it summarizes cadmium balances in soils, trends, long-term experiments, and further studies. Cadmium inputs and outputs in arable soil, together with their calculated concentrations, are compared between two different regions: the European countries (in particular Germany) and China. The comparison appears useful because of the different proportions in the inputs and outputs of cadmium, and the diverse geographical, environmental and social factors. Moreover, these variables and their influences on cadmium contamination improve the understanding of the pollution from phosphate fertilizers and will help to establish future mitigation policies.     

土壤动物对土壤食物网抑病功能研究进展

从土壤中常见的土传病害、土壤动物在土壤食物网中的地位和功能、土壤动物的抑病功能、调控食物网的抑病功能、土壤动物对土壤食物网抑病功能的价值和展望5个方面阐述了近年来土壤动物对土壤食物网抑病功能研究进展.     

国际30年来土壤食物网的研究历程与热点分析

利用文献计量学方法,研究1989—2018年来土壤食物网研究领域的热点内容,概括土壤食物网的研究脉络及国际土壤食物网未来的研究方向。结果显示:土壤生物多样性、食物网的碳氮循环功能及管理方式对土壤食物网结构的干扰是现在研究热点,而土壤食物网功能多样性、系统稳定性、及土壤食物网对全球变化的响应则是新兴的研究方向。     

Top predators in the Southern ocean: a major leak in the biological carbon pump

Primary productivity in the Southern Ocean is approximately 3.5 gigatons of carbon per year, which accounts for nearly 15 percent of the global total. The presence of high concentrations of nitrate in Antarctic waters suggests that it might be possible to increase primary production significantly and thereby alleviate the net accumulation of atmospheric carbon dioxide. An analysis of the food web for these waters implies that the Southern Ocean may be remarkably inefficient as a carbon sink. This inefficiency is caused by the large flux of carbon respired to the atmosphere by air-breathing birds and mammals, dominant predators in the unusually simple food web of Antarctic waters. These top predators may transfer into the atmosphere as much as 20 to 25 percent of photosynthetically fixed carbon.     

食物链长度远因与近因研究进展综述

食物链长度是生态系统的基本属性,其变化决定着群落结构和生态系统功能。稳定同位素分析技术的进步推进了生态系统中食物链长度决定因子相关研究的开展。尽管近期的研究证明了食物链长度与资源可利用性、生态系统大小、干扰等远因之间的关系,但是对于食物网内部结构变化这一近因对食物链长度的影响作用关注较少。综述了边界明确和开放类型淡水生态系统中食物链长度的相关研究进展;探讨了远因和近因机制在决定食物链长度中的作用;给出了判断不同层次和尺度上决定食物链长度机制的概念框架;为今后更好的开展不同生态系统间食物链长度的比较研究提出了建议。     

Effects of long-term straw incorporation on nematode community composition and metabolic footprint in a rice–wheat cropping system

Soil nematode communities can provide valuable information about the structure and functions of soil food webs, and are sensitive to agricultural practices, including short-term straw incorporation. However, currently, such effects under longterm straw incorporation conditions at different fertility levels are largely unknown. Thus, we conducted a 13-year ongoing experiment to evaluate the effects of long-term straw incorporation on the structure and functions of the soil food web in low and high fertility soils through analyzing its effects on nematode communities, food web indices and metabolic footprints. Four treatments were included: straw removal(–S) under non-fertilized(–NPK) or fertilized(+NPK) conditions; and straw incorporation(+S) under –NPK or +NPK conditions. Soil samples from a 0–20 cm depth layer were collected when wheat and rice were harvested. Compared with straw removal, straw incorporation increased the abundances of total nematodes, bacterivores, plant-parasites and omnivores-predators, as well the relative abundances of omnivores-predators with increases of 73.06, 89.29, 95.31, 238.98, and 114.61% in –NPK soils and 16.23, 2.23, 19.01, 141.38, and 90.23% in +NPK soils, respectively. Regardless of sampling times and fertilization effects, straw incorporation increased the diversity and community stability of nematodes, as indicated by the Shannon-Weaver diversity index and maturity index. Enrichment and structure index did not show significant responses to straw incorporation, but a slight increase was observed in the structure index. The analysis of nematode metabolic footprints showed that straw incorporation increased the plant-parasite footprint and structure footprint by 97.27 and 305.39% in –NPK soils and by 11.29 and 149.56% in +NPK soils, but did not significantly influence enrichment, bacterivore and fungivore footprints. In conclusion, long-term straw incorporation, particularly under a low fertility level, favored the soil nematodes and regulated the soil food web mainly via a top-down effect.     

Sustaining production and strengthening the agritourism product: Linkages among Michigan agritourism destinations

Agricultural restructuring has disproportionately impacted smaller US farms, such as those in Michigan where the average farm size is 215 acres. To keep agricultural land in production, entrepreneurial Michigan farmers are utilizing agritourism as a value-added way to capitalize on their comparative advantages, their diverse agricultural products, and their locations near large, urban, tourist-generating areas. Using focus groups, this paper illustrates how entrepreneurial farmers have strengthened Michigan agritourism by fostering producer networks through brochures and web linkages, information sharing in refining the agritourism product, referrals to other agritourism businesses that serve different markets or offer different products, purchase linkages, and a regional approach to establishing agritourism destinations and increase visitation. Successful entrepreneurial, agritourism developers thus work cooperatively, rather than individualistically and competitively. Agritourism destinations facing stiff competition from alternative venues for leisure time and food purchases benefit from supportive linkages that help sustain a critical mass of producers who offer diverse goods, maintain land in agriculture, and thus, reinforce Michigans image for agritourism.     

Detritus-Based Food Webs: Exploitation by Juvenile Chum Salmon (Oncorhynchus keta)

Harpacticoid copepods are the principal food of chum salmon during the first critical weeks of estuarine life. Heterotrophic food sources are preferentially ingested by harpacticoids. A commercially valuable fisheries resource, usually considered to be planktivorous, is related to a detritus-based, benthically derived food web.     

气孔对环境因子的感知及趋适应答

作为气体(主要为CO2和水蒸气)进出植物体的门户,气孔分布于植物茎、叶、果实和种子等器官的表皮上。气孔感知外界环境的时限可以短至几分钟,也可以长达上百万年,可以适应局部或全球的气候变化。近年来,对气孔在形态、解剖、生理、遗传进化、分子调控机制及全球生态等众多领域的研究取得了重大进展。气孔的形态、分布及其行为是对小到胞内信号、大到全球气候变化一系列信号系统的响应结果。以上一系列适应策略的调控系统是一张无尺度的网络,将现有的有关气孔的各个层面的研究整合起来可以更好地了解这个网络。文章从气孔对光合作用及蒸腾作用的影响、气孔的进化、气孔发育的环境调控、气孔孔径对环境信号的趋适响应等方面阐述气孔的研究进展。     

Eating disorders among women: An historical review of the literature from a women's history perspective

Within a relatively brief period of time, there has been a veritable outpouring of research on anorexia nervosa and bulimia nervosa. This article presents a concise overview of some of the major works on these eating disorders from a variety of disciplines including biomedicine, psychology, sociology, and history. The article establishes a general context of Americans' preoccupation with food and diet. However, since the majority of those suffering from anorexia nervosa and bulimia nervosa are female, this article places these eating disorders in the specific historical context of American women's history. In earlier times, some women reacted to their role expectations with physical responses. While linking modern phenomena to these earlier physical reactions of American women, the article also highlights the various twentieth-century social and cultural factors that push some modern girls and women to respond to their situations either by refusing food or consuming and regurgitating large quantities of food. In addition to the historical perspective, which points to the relevance of social and cultural factors as well as biomedical and psychological ones, the article offers an overview of the various theories currently suggested to explain the meaning of food to those who suffer from these disorders. These theories range from the addiction model to food as a metaphor for control and self-definition. Whatever the meaning of food, it is important to note that both anorexia nervosa and bulimia nervosa are determined by an interaction of many factors both personal and biological and social and cultural.     

Supermarkets and private standards: unintended consequences of the audit ritual

Recent scholarship has considered the implications of the rise of voluntary private standards in food and the role of private actors in a rapidly evolving, de-facto ‘mandatory’ sphere of governance. Standards are an important element of this globalising private sphere, but are an element that has been relatively peripheral in analyses of power in agri-food systems. Sociological thought has countered orthodox views of standards as simple tools of measurement, instead understanding their function as a governance mechanism that transforms many things, and people, during processes of standardisation. In a case study of the Australian retail supermarket duopoly and the proprietary standards required for market access this paper foregrounds retailers as standard owners and their role in third-party auditing and certification. Interview data from primary research into Australia’s food standards captures the multifaceted role supermarkets play as standard-owners, who are found to impinge on the independence of third-party certification while enforcing rigorous audit practices. We show how standard owners, in attempting to standardize the audit process, generate tensions within certification practices in a unique example of ritualism around audit. In examining standards to understand power in contemporary food governance, it is shown that retailers are drawn beyond standard-setting into certification and enforcement, that is characterized by a web of institutions and actors whose power to influence outcomes is uneven.