Is Net Ecosystem Production Equal to Ecosystem Carbon Accumulation?

Net ecosystem production (NEP), defined as the difference between gross primary production and total ecosystem respiration, represents the total amount of organic carbon in an ecosystem available for storage, export as organic carbon, or nonbiological oxidation to carbon dioxide through fire or ultraviolet oxidation. In some of the recent literature, especially that on terrestrial ecosystems, NEP has been redefined as the rate of organic carbon accumulation in the system. Here we argue that retaining the original definition maintains the conceptual coherence between NEP and net primary production and that it is congruous with the widely accepted definitions of ecosystem autotrophy and heterotrophy. Careful evaluation of NEP highlights the various potential fates of nonrespired carbon in an ecosystem.     

Parasites and Dung Beetles as Ecosystem Engineers in a Forest Ecosystem

Dung beetles serve as the intermediate host for Streptopharagus pigmentatus, a nematode parasite that infects an old world primate, the Japanese Macaque (Macaca fuscata). This study compares the behaviors of infected and uninfected beetles in both transmission dynamics and the ecological role of the parasite. The results suggest that parasitism does not alter the beetle’s use of shelter or choice of substrate on Yakushima Island, Japan. However, infected beetles consume significantly less feces. Dung beetles remove the majority of fecal material in this forest ecosystem, eliminating breeding grounds for many insect pests and burying nutrients that are essential for plant health. Thus, the nematode parasite S. pigmentatus, by altering its host’s behavior, changes the availability of fecal resources to both plant and animal communities and should therefore be classified as an ecosystem engineer.     

Ecosystem growth and development

One of the most important features of biosystems is how they are able to maintain local order (low entropy) within their system boundaries. At the ecosystem scale, this organization can be observed in the thermodynamic parameters that describe it, such that these parameters can be used to track ecosystem growth and development during succession. Thermodynamically, ecosystem growth is the increase of energy throughflow and stored biomass, and ecosystem development is the internal reorganization of these energy mass stores, which affect transfers, transformations, and time lags within the system. Several proposed hypotheses describe thermodynamically the orientation or natural tendency that ecosystems follow during succession, and here, we consider five: minimize specific entropy production, maximize dissipation, maximize exergy storage (includes biomass and information), maximize energy throughflow, and maximize retention time. These thermodynamic orientors were previously all shown to occur to some degree during succession, and here we present a refinement by observing them during different stages of succession. We view ecosystem succession as a series of four growth and development stages: boundary, structural, network, and informational. We demonstrate how each of these ecological thermodynamic orientors behaves during the different growth and development stages, and show that while all apply during some stages only maximizing energy throughflow and maximizing exergy storage are applicable during all four stages. Therefore, we conclude that the movement away from thermodynamic equilibrium, and the subsequent increase in organization during ecosystem growth and development, is a result of system components and configurations that maximize the flux of useful energy and the amount of stored exergy. Empirical data and theoretical models support these conclusions.     

生态系统健康与生物多样性*

生态系统健康学是一门研究人类活动、社会组织、自然系统及人类健康的整合性学科,主要探讨资源环境管理对策,以及生态系统健康与人类健康的关系。生态系统健康是人类健康的基础,是人类可持续发展的重要前提,维护生态系统健康,保护生物多样性,也就是维护人类生存的机会。人类健康依附于健康的生态系统功能和服务日益为人们所认识,关注和理解生物多样性、生态系统健康、人类健康之间的相互联系已成为全球可持续发展的必要条件。本文着重综述了生态系统健康的研究内容及全球环境变化背景下生物多样性的变化对生态系统健康的影响效应。     

Evolution and the Ecosystem

Long-range stability in natural communities is mediated throughavenues of communication. One of the most important pathwaysof communication involves nutrient exchange, although othertypes of communication are suspected as being of considerableimportance. The potential role of special "regulator species"in community stabilization is discussed and illustrated withtwo original examples, one dealing with brackish-water communitiesof the North Carolina coast, and the other dealing with communitiesof the piedmont streams of eastern Mexico. The significanceof multi-species groups in evolution is also considered in thesecond example. It is suggested that the functional ecosystemis the fundamental seleclional unit of evolution and that evolutionproceeds by mutual adjustment of ecological entities into harmonioussystems with some degree ot permanence.     

生态系统与耗散结构

1977年,比利时著名科学家伊·普里高津成功地提出耗散结构理论,荣获了诺贝尔奖。普里高津的理论告诉我们:“一个远离平衡态的复杂系统,各元素的作用具有非线性特点,正是这种非线性的相关机制,导致了大量离子的协同动作,突变而产生有序结构。”普里高津的耗散结构理论,研究系统怎样从混沌无序的动态向稳定有序的结构组织演化及其规律,故也称为非平衡系统自组织理论。这一系统理论的奇葩,对于生态系统的深入研究将起到不可估量的作用。同时,这一理论使我们对生态     

Ecosystem thresholds with hypoxia

Hypoxia is one of the common effects of eutrophication in coastal marine ecosystems and is becoming an increasingly prevalent problem worldwide. The causes of hypoxia are associated with excess nutrient inputs from both point and non-point sources, although the response of coastal marine ecosystems is strongly modulated by physical processes such as stratification and mixing. Changes in climate, particularly temperature, may also affect the susceptibility of coastal marine ecosystems to hypoxia. Hypoxia is a particularly severe disturbance because it causes death of biota and catastrophic changes in the ecosystem. Bottom water oxygen deficiency not only influences the habitat of living resources but also the biogeochemical processes that control nutrient concentrations in the water column. Increased phosphorus fluxes from sediments into overlying waters occur with hypoxia. In addition, reductions in the ability of ecosystems to remove nitrogen through denitrification and anaerobic ammonium oxidation may be related to hypoxia and could lead to acceleration in the rate of eutrophication. Three large coastal marine ecosystems (Chesapeake Bay, Northern Gulf of Mexico, and Danish Straits) all demonstrate thresholds whereby repeated hypoxic events have led to an increase in susceptibility of further hypoxia and accelerated eutrophication. Once hypoxia occurs, reoccurrence is likely and may be difficult to reverse. Therefore, elucidating ecosystem thresholds of hypoxia and linking them to nutrient inputs are necessary for the management of coastal marine ecosystems. Finally, projected increases in warming show an increase in the susceptibility of coastal marine ecosystems to hypoxia such that hypoxia will expand. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

Mobile Link Organisms and Ecosystem Functioning: Implications for Ecosystem Resilience and Management

Current natural resource management seldom takes the ecosystem functions performed by organisms that move between systems into consideration. Organisms that actively move in the landscape and connect habitats in space and time are here termed “mobile links.” They are essential components in the dynamics of ecosystem development and ecosystem resilience (that is, buffer capacity and opportunity for reorganization) that provide ecological memory (that is, sources for reorganization after disturbance). We investigated the effects of such mobile links on ecosystem functions in aquatic as well as terrestrial environments. We identify three main functional categories: resource, genetic, and process linkers and suggest that the diversity within functional groups of mobile links is a central component of ecosystem resilience. As the planet becomes increasingly dominated by humans, the magnitude, frequency, timing, spatial extent, rate, and quality of such organism-mediated linkages are being altered. We argue that global environmental change can lead to (a) the decline of essential links in functional groups providing pollination, seed dispersal, and pest control; (b) the linking of previously disconnected areas, for example, the spread of vector-borne diseases and invasive species; and (c) the potential for existing links to become carriers of toxic substances, such as persistent organic compounds. We conclude that knowledge of interspatial exchange via mobile links needs to be incorporated into management and policy-making decisions in order to maintain ecosystem resilience and hence secure the capacity of ecosystems to supply the goods and services essential to society. Received 23 April 2001; accepted 17 June 2002.     

Complex Effects of Ecosystem Engineer Loss on Benthic Ecosystem Response to Detrital Macroalgae

Ecosystem engineers change abiotic conditions, community assembly and ecosystem functioning. Consequently, their loss may modify thresholds of ecosystem response to disturbance and undermine ecosystem stability. This study investigates how loss of the bioturbating lugworm Arenicola marina modifies the response to macroalgal detrital enrichment of sediment biogeochemical properties, microphytobenthos and macrofauna assemblages. A field manipulative experiment was done on an intertidal sandflat (Oosterschelde estuary, The Netherlands). Lugworms were deliberately excluded from 1× m sediment plots and different amounts of detrital Ulva (0, 200 or 600 g Wet Weight) were added twice. Sediment biogeochemistry changes were evaluated through benthic respiration, sediment organic carbon content and porewater inorganic carbon as well as detrital macroalgae remaining in the sediment one month after enrichment. Microalgal biomass and macrofauna composition were measured at the same time. Macroalgal carbon mineralization and transfer to the benthic consumers were also investigated during decomposition at low enrichment level (200 g WW). The interaction between lugworm exclusion and detrital enrichment did not modify sediment organic carbon or benthic respiration. Weak but significant changes were instead found for porewater inorganic carbon and microalgal biomass. Lugworm exclusion caused an increase of porewater carbon and a decrease of microalgal biomass, while detrital enrichment drove these values back to values typical of lugworm-dominated sediments. Lugworm exclusion also decreased the amount of macroalgae remaining into the sediment and accelerated detrital carbon mineralization and CO₂ release to the water column. Eventually, the interaction between lugworm exclusion and detrital enrichment affected macrofauna abundance and diversity, which collapsed at high level of enrichment only when the lugworms were present. This study reveals that in nature the role of this ecosystem engineer may be variable and sometimes have no or even negative effects on stability, conversely to what it should be expected based on current research knowledge.     

Emergent Global Patterns of Ecosystem Structure and Function from a Mechanistic General Ecosystem Model

Anthropogenic activities are causing widespread degradation of ecosystems worldwide, threatening the ecosystem services upon which all human life depends. Improved understanding of this degradation is urgently needed to improve avoidance and mitigation measures. One tool to assist these efforts is predictive models of ecosystem structure and function that are mechanistic: based on fundamental ecological principles. Here we present the first mechanistic General Ecosystem Model (GEM) of ecosystem structure and function that is both global and applies in all terrestrial and marine environments. Functional forms and parameter values were derived from the theoretical and empirical literature where possible. Simulations of the fate of all organisms with body masses between 10 µg and 150,000 kg (a range of 14 orders of magnitude) across the globe led to emergent properties at individual (e.g., growth rate), community (e.g., biomass turnover rates), ecosystem (e.g., trophic pyramids), and macroecological scales (e.g., global patterns of trophic structure) that are in general agreement with current data and theory. These properties emerged from our encoding of the biology of, and interactions among, individual organisms without any direct constraints on the properties themselves. Our results indicate that ecologists have gathered sufficient information to begin to build realistic, global, and mechanistic models of ecosystems, capable of predicting a diverse range of ecosystem properties and their response to human pressures.     

Ecosystem services provided by waterbirds

Ecosystem services are ecosystem processes that directly or indirectly benefit human well‐being. There has been much recent literature identifying different services and the communities and species that provide them. This is a vital first step towards management and maintenance of these services. In this review, we specifically address the waterbirds, which play key functional roles in many aquatic ecosystems, including as predators, herbivores and vectors of seeds, invertebrates and nutrients, although these roles have often been overlooked. Waterbirds can maintain the diversity of other organisms, control pests, be effective bioindicators of ecological conditions, and act as sentinels of potential disease outbreaks. They also provide important provisioning (meat, feathers, eggs, etc.) and cultural services to both indigenous and westernized societies. We identify key gaps in the understanding of ecosystem services provided by waterbirds and areas for future research required to clarify their functional role in ecosystems and the services they provide. We consider how the economic value of these services could be calculated, giving some examples. Such valuation will provide powerful arguments for waterbird conservation.     

一类生态系统的脉冲控制

利用脉冲系统的线性近似判定的方法对一个具有脉冲控制的生物模型进行研究,得到了使其渐近稳定到原先不稳定的平衡点的充要条件并给出了生态解释。