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Ecosystem Resilience (ecosystem + resilience)
Selected AbstractsTradeoffs and thresholds in the effects of nitrogen addition on biodiversity and ecosystem functioning: evidence from inner Mongolia GrasslandsGLOBAL CHANGE BIOLOGY, Issue 1 2010YONGFEI BAI Abstract Nitrogen (N) deposition is widely considered an environmental problem that leads to biodiversity loss and reduced ecosystem resilience; but, N fertilization has also been used as a management tool for enhancing primary production and ground cover, thereby promoting the restoration of degraded lands. However, empirical evaluation of these contrasting impacts is lacking. We tested the dual effects of N enrichment on biodiversity and ecosystem functioning at different organizational levels (i.e., plant species, functional groups, and community) by adding N at 0, 1.75, 5.25, 10.5, 17.5, and 28.0 g N m,2 yr,1 for four years in two contrasting field sites in Inner Mongolia: an undisturbed mature grassland and a nearby degraded grassland of the same type. N addition had both quantitatively and qualitatively different effects on the two communities. In the mature community, N addition led to a large reduction in species richness, accompanied by increased dominance of early successional annuals and loss of perennial grasses and forbs at all N input rates. In the degraded community, however, N addition increased the productivity and dominance of perennial rhizomatous grasses, with only a slight reduction in species richness and no significant change in annual abundance. The mature grassland was much more sensitive to N-induced changes in community structure, likely as a result of higher soil moisture accentuating limitation by N alone. Our findings suggest that the critical threshold for N-induced species loss to mature Eurasian grasslands is below 1.75 g N m,2 yr,1, and that changes in aboveground biomass, species richness, and plant functional group composition to both mature and degraded ecosystems saturate at N addition rates of approximately 10.5 g N m,2 yr,1. This work highlights the tradeoffs that exist in assessing the total impact of N deposition on ecosystem function. [source] Functional roles of remnant plant populations in communities and ecosystemsGLOBAL ECOLOGY, Issue 6 2000Ove Eriksson Abstract A hypothesis is suggested for functional roles of remnant plant populations in communities and ecosystems. A remnant population is capable of persistence during extended time periods, despite a negative population growth rate, due to long-lived life stages and life-cycles, including loops that allow population persistence without completion of the whole life cycle. A list of critera is suggested to help identification of remnant plant populations. Several community and ecosystem features may result from the presence of remnant plant populations. Apart from increasing community and ecosystem resilience just by being present, remnant populations may contribute to resilience through enhancing colonization by other plant species, by providing a persistent habitat for assemblages of animals and microorganisms, and by reducing variation in nutrient cycling. It is suggested that the common ability of plants to develop remnant populations is a contributing factor to ecosystem stability. Remnant populations are important for the capacity of ecosystems to cope with the present-day impact caused by human society, and their occurrence should be recognized in surveys of threatened plant species and communities. [source] The Governance of Rural Land in a Liberalised WorldJOURNAL OF AGRICULTURAL ECONOMICS, Issue 3 2007Ian Hodge Abstract Liberalisation of agricultural policies reduces the influence of policy on land-use decisions, but environmental policy objectives remain. Governance provides an approach that recognises the role of institutions and collective action. The formulation of environmental policy objectives in terms of the provision of public goods raises questions as to the role of economic valuation and as to whether the definition of ,goods' may misdirect policy attention. An alternative approach relates to ecosystem services and sees management issues in terms of ecosystem resilience and the adaptive governance of socio-ecological systems. Governance involves a mix of regulation, markets, government incentives and collective action. Regulation sets the domain within which markets operate and social judgements as to property rights are required as a basis for exchanges. Depending on commodity prices, agri-environment schemes may be required either to reduce agricultural production intensity or to keep land under production. The diffuse nature of the environmental benefits and costs of land uses, the complexity of ecosystems and the need to co-ordinate land management decisions indicate a role for local adaptive co-management of land resources. Governments play a major role in supporting the institutional framework within which this can take place. [source] REVIEW: Mechanisms driving change: altered species interactions and ecosystem function through global warmingJOURNAL OF ANIMAL ECOLOGY, Issue 5 2010Lochran W. Traill Summary 1.,We review the mechanisms behind ecosystem functions, the processes that facilitate energy transfer along food webs, and the major processes that allow the cycling of carbon, oxygen and nitrogen, and use case studies to show how these have already been, and will continue to be, altered by global warming. 2.,Increased temperatures will affect the interactions between heterotrophs and autotrophs (e.g. pollination and seed dispersal), and between heterotrophs (e.g. predators-prey, parasites/pathogens-hosts), with generally negative ramifications for important ecosystem services (functions that provide direct benefit to human society such as pollination) and potential for heightened species co-extinction rates. 3.,Mitigation of likely impacts of warming will require, in particular, the maintenance of species diversity as insurance for the provision of basic ecosystem services. Key to this will be long-term monitoring and focused research that seek to maintain ecosystem resilience in the face of global warming. 4.,We provide guidelines for pursuing research that quantifies the nexus between ecosystem function and global warming. These include documentation of key functional species groups within systems, and understanding the principal outcomes arising from direct and indirect effects of a rapidly warming environment. Localized and targeted research and monitoring, complemented with laboratory work, will determine outcomes for resilience and guide adaptive conservation responses and long-term planning. [source] Contrasting responses of arable spiders to the landscape matrix at different spatial scalesJOURNAL OF BIOGEOGRAPHY, Issue 1 2008Martin H. Schmidt Abstract Aim, Animal communities can be influenced by the composition of the surrounding landscape through immigration. Depending on habitat preferences, however, the effect of the landscape matrix can be positive or negative and can vary with scale. We tested this idea with arable spiders and tried to infer dispersal distances from relationships between local density and landscape composition at different spatial scales. Location, Thirty-eight landscapes around the cities of Göttingen and Giessen, Germany. Methods, Spiders were captured with pitfall traps in one field of winter wheat in each landscape. Landscape composition around the fields was characterized at 11 scales from 95 m to 3 km radius by land-use mapping and subsequent GIS analysis. Correlation tests were performed between landscape composition and local densities or species richness. Results, In both study regions, local species richness was enhanced by non-crop habitats on a landscape scale. The overall densities of wolf spiders (Lycosidae), long-jawed spiders (Tetragnathidae), crab spiders (Thomisidae), and dwarf sheet spiders (Hahniidae) increased significantly in landscapes with high percentages of non-crop habitats. Out of the 40 species tested, 19 responded positively to the percentage of non-crop habitats in the surrounding landscape, and five responded negatively. Depending on the species, the spatial scales with the highest explanatory power ranged from 95 m to 3 km radius around the study fields, potentially reflecting dispersal distances. Main conclusions, Arable spider species showed contrasting responses to the landscape context with respect both to the direction and to the spatial scale of the relationship. The variation in landscape requirements among species ensures high spider densities in a wide range of situations, which contributes to ecosystem resilience. However, species richness of arable spiders depends on heterogeneous landscapes with high percentages of non-crop habitats. [source] Junk-food in marine ecosystemsOIKOS, Issue 7 2008Henrik Österblom The abundance and availability of food are critical determininants of reproductive success and population dynamics of marine top predators. However, recent work has indicated that the quality of the food may also be critically important for some marine predators. The ,junkfood hypothesis' was originally suggested as a potential explanation for a dramatic population decline of Stellers sea lions Eumetopias jubatus in the Gulf of Alaska. According to the hypothesis, a dietary switch to prey of low energy content led to detrimental effects on the population of sea lions. A number of observations indicate that the hypothesis is relevant for several population parameters. Recent work on piscivorous seabirds has provided substantial evidence indicating the relevance of this hypothesis in food webs in e.g. the North Pacific, the North Sea and the Baltic Sea. The emergence of ,junk-food' in these systems may be coupled to large scale changes in climatological and oceanographic forcing, although predation, fishing and competition provide additional plausible hypotheses. It may be possible to predict which kinds of animals will be particularly sensitive to food quality; these seem to be species with limited ability to carry food loads, with energetically-expensive foraging behaviour, and with digestive anatomy evolved to minimize mass at the cost of digestive efficiency. This review suggests that the junk-food hypothesis is a highly relevant factor in relation to sustaining ecosystem resilience, and is an important consideration in ecosystem management. Sustaining healthy populations of marine top-predators requires an understanding of the role of food quality, in addition to food abundance and availability. [source] Stability of ecosystem properties in response to above-ground functional group richness and compositionOIKOS, Issue 1 2000David A. Wardle While there has been a rapidly increasing research effort focused on understanding whether and how composition and richness of species and functional groups may determine ecosystem properties, much remains unknown about how these community attributes affect the dynamic properties of ecosystems. We conducted an experiment in 540 mini-ecosystems in glasshouse conditions, using an experimental design previously shown to be appropriate for testing for functional group richness and composition effects in ecosystems. Artificial communities representing 12 different above-ground community structures were assembled. These included treatments consisting of monoculture and two- and four-species mixtures from a pool of four plant species; each plant species represented a different functional group. Additional treatments included two herbivore species, either singly or in mixture, and with or without top predators. These experimental units were then either subjected to an experimentally imposed disturbance (drought) for 40 d or left undisturbed. Community composition and drought both had important effects on plant productivity and biomass, and on several below-ground chemical and biological properties, including those linked to the functioning of the decomposer subsystem. Many of these compositional effects were due to effects both of plant and of herbivore species. Plant functional group richness also exerted positive effects on plant biomass and productivity, but not on any of the below-ground properties. Above-ground composition also had important effects on the response of below-ground properties to drought and thus influenced ecosystem stability (resistance); effects of composition on drought resistance of above-ground plant response variables and soil chemical properties were weaker and less consistent. Despite the positive effects of plant functional group richness on some ecosystem properties, there was no effect of richness on the resistance of any of the ecosystem properties we considered. Although herbivores had detectable effects on the resistance of some ecosystem properties, there were no effects of the mixed herbivore species treatment on resistance relative to the single species herbivore treatments. Increasing above-ground food chain length from zero to three trophic levels did not have any consistent effect on the stability of ecosystem properties. There was no evidence of either above-ground composition or functional group richness affecting the recovery rate of ecosystem properties from drought and hence ecosystem resilience. Our data collectively point to the role of composition (identity of functional group), but not functional group richness, in determining the stability (resistance to disturbance) of ecosystem properties, and indicates that the nature of the above-ground community can be an important determinant of the consistency of delivery of ecosystem services. [source] Applying forest restoration principles to coral reef rehabilitationAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2003N. Epstein Abstract 1.Forest restoration through silviculture (gardening) programs revives productivity, biodiversity, and stability. As in silviculture approaches, the coral ,gardening' strategy is based on a two-step protocol. 2.The first step deals with the establishment of in situ and/or ex situ coral nurseries in which corals are farmed (originating from two types of source material: asexual [ramets, nubbins], and sexual [planula larvae, spat] recruits). 3.The second is the reef rehabilitation step, where maricultured colonies are transplanted into degraded sites. 4.We compare here the rationale of forest restoration to coral reef ecosystem restoration by evaluating major key criteria. As in silviculture programs, a sustainable mariculture operation that focuses on the prime structural component of the reef (,gardening' with corals) may promote the persistence of threatened coral populations, as well as that of other reef taxa, thus maintaining genetic diversity. In chronically degrading reef sites this may facilitate a halt in biodiversity depletion. 5.Within the current theoretical framework of ecosystem restoration, the recovery of biodiversity indices is considered a core element since a rich species diversity provides higher ecosystem resilience to disturbances. 6.The gardening measure may also be implemented worldwide, eliminating the need to extract existing colonies for transplantation operations. At degraded reef sites, the coral gardening strategy can assist in managing human and non-human stakeholders' requirements as is done in forest management. Copyright © 2003 John Wiley & Sons, Ltd. [source] Trophic-dynamic considerations in relating species diversity to ecosystem resilienceBIOLOGICAL REVIEWS, Issue 3 2000KRIS H. JOHNSON ABSTRACT Complexity in the networks of interactions among and between the living and abiotic components forming ecosystems confounds the ability of ecologists to predict the economic consequences of perturbations such as species deletions in nature. Such uncertainty hampers prudent decision making about where and when to invest most intensively in species conservation programmes. Demystifying ecosystem responses to biodiversity alterations may be best achieved through the study of the interactions allowing biotic communities to compensate internally for population changes in terms of contributing to ecosystem function, or their intrinsic functional redundancy. Because individual organisms are the biologically discrete working components of ecosystems and because environmental changes are perceived at the scale of the individual, a mechanistic understanding of functional redundancy will hinge upon understanding how individuals' behaviours influence population dynamics in the complex community setting. Here, I use analytical and graphical modelling to construct a conceptual framework for predicting the conditions under which varying degrees of interspecific functional redundancy can be found in dynamic ecosystems. The framework is founded on principles related to food web successional theory, which provides some evolutionary insights for mechanistically linking functional roles of discrete, interacting organisms with the dynamics of ecosystems because energy is the currency both for ecological fitness and for food web commerce. Net productivity is considered the most contextually relevant ecosystem process variable because of its socioeconomic significance and because it ultimately subsumes all biological processes and interactions. Redundancy relative to productivity is suggested to manifest most directly as compensatory niche shifts among adaptive foragers in exploitation ecosystems, facilitating coexistence and enhancing ecosystem recovery after disturbances which alter species' relative abundances, such as extinctions. The framework further explicates how resource scarcity and environmental stochasticity may constitute ,ecosystem legacies' influencing the emergence of redundancy by shaping the background conditions for foraging behaviour evolution and, consequently, the prevalence of compensatory interactions. Because it generates experimentally testable predictions for a priori hypothesis testing about when and where varying degrees of functional redundancy are likely to be found in food webs, the framework may be useful for advancing toward the reliable knowledge of biodiversity and ecosystem function relations necessary for prudent prioritization of conservation programmes. The theory presented here introduces explanation of how increasing diversity can have a negative influence on ecosystem sustainability by altering the environment for biotic interactions - and there by changing functional compensability among biota - under particular conditions. [source] | ||||||||||