E. G. Beaubien and M. Hall-Beyer.

Environ.Monit.Assess., Vol. 88, No. 1-3, Oct-Nov 2003. pp, 419-429.

One feature of climate change is the trends to earlier spring onset in many north temperate areas of the world. The timing of spring flowering and leafing of perennial plants is largely controlled by temperature accumulation; both temperature and phenological records illustrate changes in recent decades. Phenology studies date back over a century, with extensive databases existing for western Canada. Earlier spring flowering has been noted for many woody plants, with larger trends seen for species that develop at spring's start. Implications for ecosystems of trends to earlier spring arrival include changes in plant species composition, changes in timing and distribution of pests and disease, and potentially disrupted ecological interactions. While Alberta has extensive phenology databases (for species, years, and geographic coverage) for recent decades, these data cannot provide continuous ground coverage. There is great potential for phenological data to provide ground validation for satellite imagery interpretation, especially as new remote sensors are becoming available. Phenological networks are experiencing a resurgence of interest in Canada (www.plantwatch.ca) and globally, and linking these ground-based observations with the view from space will greatly enhance our capacity to track the biotic response to climate changes.

T. V. Callaghan, L. O. Bjoern and Y. Chernov, et al.

Ambio, Vol. 33, No. 7, Nov 2004. pp, 459-468.

Biological and physical processes in the Arctic system operate at various temporal and spatial scales to impact large-scale feedbacks and interactions with the earth system. There are four main potential feedback mechanisms between the impacts of climate change on the Arctic and the global climate system: albedo, greenhouse gas emissions or uptake by ecosystems, greenhouse gas emissions from methane hydrates, and increased freshwater fluxes that could affect the thermohaline circulation. All these feedbacks are controlled to some extent by changes in ecosystem distribution and character and particularly by large-scale movement of vegetation zones. Indications from a few, full annual measurements of CO sub(2) fluxes are that currently the source areas exceed sink areas in geographical distribution. The little available information on CH sub(4) sources indicates that emissions at the landscape level are of great importance for the total greenhouse balance of the circumpolar North. Energy and water balances of Arctic landscapes are also important feedback mechanisms in a changing climate. Increasing density and spatial expansion of vegetation will cause a lowering of the albedo and more energy to be absorbed on the ground. This effect is likely to exceed the negative feedback of increased C sequestration in greater primary productivity resulting from the displacements of areas of polar desert by tundra, and areas of tundra by forest. The degradation of permafrost has complex consequences for trace gas dynamics. In areas of discontinuous permafrost, warming, will lead to a complete loss of the permafrost. Depending on local hydrological conditions this may in turn lead to a wetting or drying of the environment with subsequent implications for greenhouse gas fluxes. Overall, the complex interactions between processes contributing to feedbacks, variability over time and space in these processes, and insufficient data have generated considerable uncertainties in estimating the net effects of climate change on terrestrial feedbacks to the climate system. This uncertainty applies to magnitude, and even direction of some of the feedbacks.

J. M. Drake and D. M. Lodge.

Proc.R.Soc.Lond., Ser.B: Biol.Sci., Vol. 271, No. 1539, 22 Mar 2004. pp, 575-580.

Biological invasions from ballast water are a severe environmental threat and exceedingly costly to society. We identify global hot spots of invasion based on worldwide patterns of ship traffic. We then estimate the rate of port-to-port invasion using gravity models for spatial interactions, and we identify bottlenecks to the regional exchange of species using the Ford-Fulkerson algorithm for network flows. Finally, using stochastic simulations of different strategies for controlling ballast-water introductions, we find that reducing the per-ship-visit chance of causing invasion is more effective in reducing the rate of biotic homogenization than eliminating key ports that are the epicenters for global spread.

P. A. Fay, J. D. Carlisle, A. K. Knapp, J. M. Blair and S. L. Collins.

Oecologia, Vol. 137, No. 2, Oct 2003. pp, 245-251.

Rainfall variability is a key driver of ecosystem structure and function in grasslands worldwide. Changes in rainfall patterns predicted by global climate models for the central United States are expected to cause lower and increasingly variable soil water availability, which may impact net primary production and plant species composition in native Great Plains grasslands. We experimentally altered the timing and quantity of growing season rainfall inputs by lengthening inter-rainfall dry intervals by 50%, reducing rainfall quantities by 30%, or both, compared to the ambient rainfall regime in a native tallgrass prairie ecosystem in northeastern Kansas. Over three growing seasons, increased rainfall variability caused by altered rainfall timing with no change in total rainfall quantity led to lower and more variable soil water content (0-30 cm depth), a ~10% reduction in aboveground net primary productivity (ANPP), increased root to shoot ratios, and greater canopy photon flux density at 30 cm above the soil surface. Lower total ANPP primarily resulted from reduced growth, biomass and flowering of subdominant warm-season C sub(4) grasses while productivity of the dominant C sub(4) grassAndropogon gerardii was relatively unresponsive. In general, vegetation responses to increased soil water content variability were at least equal to those caused by imposing a 30% reduction in rainfall quantity without altering the timing of rainfall inputs. Reduced ANPP most likely resulted from direct effects of soil moisture deficits on root activity, plant water status, and photosynthesis. Altered rainfall regimes are likely to be an important element of climate change scenarios in this grassland, and the nature of interactions with other climate change elements remains a significant challenge for predicting ecosystem responses to climate change.

V. G. Gorshkov, A. M. Makarieva and V. V. Gorshkov.

Ecol.Complex., Vol. 1, No. 1, Mar 2004. pp, 17-36.

The foundations of ecological science were laid down at those times when the problem of a possible loss of local and global environmental sustainability was not as acute as it has become today. To make sure that the proposed scientific solutions to this problem are responsible, it is useful to revise the existing frameworks of environmental thought. In this paper, we present quantitative evidence suggesting that the persistence of an environment suitable for life for any appreciable period of time is only possible as long as a substantial area on the planet's surface is occupied by natural ecosystems undisturbed by anthropogenic activities. Once the natural biotic mechanism of environmental control is destroyed, both local and global environment rapidly (over a time scale of hundreds of years) degrade to a state unfit for life, even if any direct anthropogenic environmental impact like industrial pollution is absent. It is therefore important to quantitatively assess the stabilizing impact of natural ecosystems and to determine the necessary and sufficient global area that must be exempted from anthropogenic activities and let be occupied by natural ecosystems, so that the latter have power enough to sustain the global environment in a stable life-compatible state. This urgent scientific task emerges as the major challenge for modern ecological science. We discuss how the proposed conceptual approach to the biota-environment interaction relates to the important paradigms of biological theory.

S. E. Hartley and T. H. Jones.

Oikos, Vol. 101, No. 1, Apr 2003. pp, 6-17.

There is increasing concern over the potential impact of anthropogenic factors (e.g. increasing nutrient inputs, global climate change) on the rate of loss of diversity in ecosystems. Such losses may affect ecosystem processes. In addition, a change in diversity of one group of organisms may influence the diversity of species of the next trophic level. We examined the extent to which plant species richness influences that of insect herbivores in two systems: a long-term field experiment on heather moorland and a model community in the Ecotron controlled environment facility. We examined the response of these two plant communities to environmental change, specifically increased levels of nutrients, grazing and atmospheric CO sub(2). We measured the indirect effects of changes in these factors on insect herbivores, both above- and below-ground. In the moorland system, grazing was the largest influence on plant community structure. The community was dominated by one species, Calluna vulgaris, and loss of cover under heavy grazing allowed competing species to invade. However, grazing regime was not a major influence on the species richness of the insect herbivore community. Site was more important: there were a greater number of Hemiptera species on sites with more mineral soils than on peat sites, possibly because a greater variety of grass and herb species was present on the former sites. In the Ecotron, below-ground factors were also important drivers of community change: elevated CO sub(2) increased carbon availability in the soil and there were simultaneous changes in the community composition of soil biota. Above-ground, some plant species increased in abundance and others decreased, leading to interaction-specific effects on the insect herbivores. In two very different studies of the effects of environmental change on the interactions between plants and their herbivores, several similar conclusions can be drawn: (1) effects are likely to be site- and interaction-specific; (2) outcomes are likely to be strongly dependent on the initial state and the dominant species of the plant community; and (3) indirect effects, often mediated by below-ground factors, may have a bigger influence on insect-plant interactions than more direct effects of above-ground factors.

Jonathan M. Hoekstra, Timothy M. Boucher, Taylor H. Ricketts and Carter Roberts.

Ecol.Lett., Vol. 8, No. 1, Jan 2005. pp, 23-29.

Human impacts on the natural environment have reached such proportions that in addition to an 'extinction crisis', we now also face a broader 'biome crisis'. Here we identify the world's terrestrial biomes and, at a finer spatial scale, ecoregions in which biodiversity and ecological function are at greatest risk because of extensive habitat conversion and limited habitat protection. Habitat conversion exceeds habitat protection by a ratio of 8 : 1 in temperate grasslands and Mediterranean biomes, and 10 : 1 in more than 140 ecoregions. These regions include some of the most biologically distinctive, species rich ecosystems on Earth, as well as the last home of many threatened and endangered species. Confronting the biome crisis requires a concerted and comprehensive response aimed at protecting not only species, but the variety of landscapes, ecological interactions, and evolutionary pressures that sustain biodiversity, generate ecosystem services, and evolve new species in the future.

D. U. Hooper, F. S. Chapin III and J. J. Ewel, et al.

Ecol.Monogr., Vol. 75, No. 1, Feb 2005. pp, 3-35.

Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the relationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are structured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain. Based on our review of the scientific literature, we are certain of the following conclusions: 1) Species' functional characteristics strongly influence ecosystem properties. Functional characteristics operate in a variety of contexts, including effects of dominant species, keystone species, ecological engineers, and interactions among species (e.g., competition, facilitation, mutualism, disease, and predation). Relative abundance alone is not always a good predictor of the ecosystem-level importance of a species, as even relatively rare species (e.g., a keystone predator) can strongly influence pathways of energy and material flows. 2) Alteration of biota in ecosystems via species invasions and extinctions caused by human activities has altered ecosystem goods and services in many well-documented cases. Many of these changes are difficult, expensive, or impossible to reverse or fix with technological solutions. 3) The effects of species loss or changes in composition, and the mechanisms by which the effects manifest themselves, can differ among ecosystem properties, ecosystem types, and pathways of potential community change. 4) Some ecosystem properties are initially insensitive to species loss because (a) ecosystems may have multiple species that carry out similar functional roles, (b) some species may contribute relatively little to ecosystem properties, or (c) properties may be primarily controlled by abiotic environmental conditions. 5) More species are needed to insure a stable supply of ecosystem goods and services as spatial and temporal variability increases, which typically occurs as longer time periods and larger areas are considered.

Y. Itoh, K. -i Tainaka, T. Sakata, T. Tao and N. Nakagiri.

Ecol.Model., Vol. 174, No. 1-2, May 2004. pp, 191-201.

Ecosystem dynamics can be studied using model populations. Perturbation experiments have often been applied to simulated populations in order to study the uncertainty in ecosystem dynamics. Most of these studies have predicted a stationary state. We report on the uncertainty in the dynamics near extinction. In particular, we explore fluctuation enhancements, i.e. enhanced variability in dynamics of paths to extinction. We examine two dynamic models on a two-dimensional lattice of finite size: (1) the contact process (CP) in which interactions are restricted to occur between adjacent lattice points, and (2) mean-field simulation (MFS), where interactions occur globally, between any pair of lattice points. Computer simulation reveals that, for both CP and MFS, the random drift of density about a stationary state increases with the decrease of steady-state density. Drift is much more pronounced in the vicinity of the critical mortality rate, at the transition to extinction. Simulation demonstrates that MFS shows greater variability when relative mortality rate is low whereas CP shows much more pronounced variability when mortality is near the critical threshold. The CP process shows wider fluctuations while the MFS process shows minimal increases following perturbations that lead to extinction. Because interactions are local for CP, there are a variety of different paths to extinction.

Valentina Krysanova, Fred Hattermann and Frank Wechsung.

Hydrol.Process., Vol. 19, No. 3, 2005. pp, 763-783.

In this paper the ecohydrological model SWIM developed for regional impact assessment is presented, and examples of approaches to climate and land use change impact studies are described. SWIM is a continuous-time semi-distributed ecohydrological model, integrating hydrological processes, vegetation, nutrients (nitrogen and phosphorus) and sediment transport at the river basin scale. Its spatial disaggregation scheme has three levels: (1) basin, (2) sub-basins and (3) hydrotopes within sub-basins. The model was extensively tested and validated for hydrological processes, nitrogen dynamics, crop yield and erosion (mainly in mesoscale sub-basins of the German part of the Elbe River basin). After appropriate validation in representative sub-basins, the model can be applied at the regional scale for impact studies. Particular interest in the global change impact studies is given to effects of expected changes in climate and land use on hydrological processes and agro-ecosystems, including water balance components, water quality and crop yield. This paper (a) introduces the reader to the class of process-based ecohydrological catchment scale models, (b) introduces SWIM as one such model, and [copyright] presents two examples of impact studies performed with SWIM for the federal state of Brandenburg (Germany), which overlaps with the lowland part of the Elbe drainage area. The impact studies provide a better understanding of the complex interactions between climate, hydrological processes and vegetation, and improve our potential adaptation to the expected changes.

Hongyu Liu, Shikui Zhang, Zhaofu Li, Xianguo Lu and Qing Yang.

Ambio, Vol. 33, No. 6, 2004. pp, 306-310.

The Small Sanjiang Plain (SSP), was formerly the largest wetland complex in China, located in the North-eastern part of Heilongjiang Province, China. Home to vast numbers of waterfowl, fish, and plants, the SSP is globally significant for biodiversity conservation. The loss and fragmentation of wetlands as a result agricultural development over 50 years has impacted wetland communities and their biodiversity. We used GIS to inventory large-scale land-use changes from 1950 to 2000, together with other statistical data. We found that 73.6% of the wetlands were lost due to agricultural development. Consequences of these land-use changes included: i) a rapid decline in waterfowl and plant species with the loss and fragmentation of natural wetlands and wetland ecosystem degradation; ii) greater variation in wetland water levels as the result of land-use changes over the years; iii) disruption of the dynamic river-floodplain connection by construction of drainage ditches and levees; and iv) a decrease in floodplain area that caused increased flooding peak flows and runoff. Here we show how these changes affect wetland biodiversity and impact important wetland species.

M. Loreau, N. Mouquet and R. D. Holt.

Ecol.Lett., Vol. 6, No. 8, Aug 2003. pp, 673-679.

This contribution proposes the meta-ecosystem concept as a natural extension of the metapopulation and metacommunity concepts. A meta-ecosystem is defined as a set of ecosystems connected by spatial flows of energy, materials and organisms across ecosystem boundaries. This concept provides a powerful theoretical tool to understand the emergent properties that arise from spatial coupling of local ecosystems, such as global source-sink constraints, diversity-productivity patterns, stabilization of ecosystem processes and indirect interactions at landscape or regional scales. The meta-ecosystem perspective thereby has the potential to integrate the perspectives of community and landscape ecology, to provide novel fundamental insights into the dynamics and functioning of ecosystems from local to global scales, and to increase our ability to predict the consequences of land-use changes on biodiversity and the provision of ecosystem services to human societies.

S. A. Lourie and A. C. Vincent.

Conserv.Biol., Vol. 18, No. 4, Aug 2004. pp, 1004-1020.

Biogeographic information has great potential to enhance systematic conservation planning, although it has yet to be routinely incorporated in marine situations. Fundamental differences between marine and terrestrial environments (physical, biological, and sociopolitical) mean that biogeographic data are harder to obtain for marine systems, biogeographic boundaries more difficult to define, and the outcomes of similar conservation approaches may differ. Despite these challenges, an understanding of spatial context, connections, and scales of processes is needed to set conservation priorities that ensure the representation and continued persistence of species and habitats within functioning ecosystems. As we discovered in our review, scientific knowledge of marine systems is increasing rapidly thanks to recent advances in genetics, remote sensing, and geographical information systems. Such knowledge and tools have important implications for marine planning. We also reviewed the degree to which biogeography is incorporated into current marine conservation projects at spatial scales ranging from global to local. Overall, initiatives are becoming more regional in scope and incorporating biogeographic data in an increasingly rigorous manner. However, initiatives that use few or no data are also on the rise and need to be treated with due caution. We recommend undertaking global and regional reviews within biogeographic frameworks; combining analytical approaches to determine biogeographic classifications and to define a range of potential conservation areas with stakeholder involvement to set priorities; understanding contemporary processes that maintain species distributions; and acquiring knowledge of historical distributions to provide appropriate baselines for current conservation. The urgent need for marine conservation, however, means that planning should proceed with the best currently available biogeographic information even while biogeographic research continues.

Original Abstract: La informacion biogeografica tiene gran potencial para mejorar la planeacion de la conservacion sistematica, aunque aun debe ser incluida rutinariamente a situaciones marinas. Las diferencias (fisicas, biologicas y sociopoliticas) fundamentales entre ambientes marinos y terrestres significan que los datos biogeograficos son mas dificiles de obtener para sistemas marinos, es mas dificil definir los limites biogeograficos y los resultados de metodos de conservacion similares pueden diferir. A pesar de estos retos, se requiere entendimiento del contexto espacial, conexiones y escalas de procesos para definir prioridades de conservacion que garanticen la representacion y persistencia continuada de especies y habitat dentro de ecosistemas funcionales. En nuestras revisiones descubrimos que nuestro conocimiento de los sistemas marinos esta aumentado rapidamente gracias a los avances recientes en genetica, percepcion remota y sistemas de informacion geografica. Estas herramientas han tenido importantes implicaciones en la planeacion marina. Tambien revisamos el grado en que la biogeografia es incorporada a los proyectos actuales de conservacion en escalas espaciales que varian de globales a locales. En general, las iniciativas se estan volviendo mas regionales en alcance y estan incorporando datos biogeograficos de manera cada vez mas rigurosa. Las iniciativas que utilizan pocos o ningun dato tambien estan incrementando y deben ser tratados con la debida precaucion. Recomendamos abordar revisiones globales y regionales en contextos biogeograficos, mediante la combinacion de metodos analiticos para determinar clasificaciones biogeograficas y definir un rango de areas de conservacion potenciales y la participacion del publico para fijar prioridades; el entendimiento de los procesos contemporaneos que mantienen la distribucion de especies; y la adquisicion de conocimiento de las distribuciones historicas para proporcionar bases apropiadas para la conservacion actual. Sin embargo, la urgente necesidad de la conservacion marina significa que la planeacion debe proceder con la mejor informacion biogeografica disponible actualmente aun mientras la investigacion biogeografica continua.

Y. -Q Luo, B. Su and W. S. Currie, et al.

Bioscience, Vol. 54, No. 8, Aug 2004. pp, 731-739.

A highly controversial issue in global biogeochemistry is the regulation of terrestrial carbon (C) sequestration by soil nitrogen (N) availability. This controversy translates into great uncertainty in predicting future global terrestrial C sequestration. We propose a new framework that centers on the concept of progressive N limitation (PNL) for studying the interactions between C and N in terrestrial ecosystems. In PNL, available soil N becomes increasingly limiting as C and N are sequestered in long-lived plant biomass and soil organic matter. Our analysis focuses on the role of PNL in regulating ecosystem responses to rising atmospheric carbon dioxide concentration, but the concept applies to any perturbation that initially causes C and N to accumulate in organic forms. This article examines conditions under which PNL may or may not constrain net primary production and C sequestration in terrestrial ecosystems. While the PNL-centered framework has the potential to explain diverse experimental results and to help researchers integrate models and data, direct tests of the PNL hypothesis remain a great challenge to the research community.

P. R. Moorcroft.

Proc.R.Soc.Lond., Ser.B: Biol.Sci., Vol. 270, No. 1521, 22 Jun 2003. pp, 1215-1227.

The atmosphere and terrestrial ecosystems are fundamentally coupled on a variety of time-scales. On short time-scales, this bi-directional interaction is dominated by the rapid exchange of CO sub(2), water and energy between the atmosphere and the land surface; on long time-scales, the interaction involves changes in ecosystem structure and composition in response to changes in climate that feed back through biophysical and biogeochemical mechanisms to influence climate over decades and centuries. After briefly describing some early pioneering work, I focus this review on recent advances in understanding long-term ecosystem-atmosphere interactions through a discussion of three case studies. I then examine how efforts to assess the stability and resilience of ecosystem-atmosphere interactions over these long time-scales using Dynamic Global Vegetation Models are hampered by the presence of important functional diversity and heterogeneity within plant communities. Recent work illustrates how this issue can be addressed through the use of Structured Ecosystem Models that more accurately scale between the short-term physiological responses of individual plants and the long-term, large-scale dynamics of heterogeneous, functionally diverse ecosystems.

S. J. Ormerod.

J.Appl.Ecol., Vol. 40, No. 2, Apr 2003. pp, 204-213.

1. By any measure, fishes are among the world's most important natural resources. Annual exploitation from wild populations exceeds 90 million tonnes, and fish supply over 15% of global protein needs as part of total annual trade exceeding $US 55 billion. Additionally, with over 25 000 known species, the biodiversity and ecological roles of fishes are being increasingly recognised in aquatic conservation, ecosystem management, restoration and aquatic environmental regulation. 2. At the same time, substantial management problems now affect the production, exploitable stocks, global diversity, trophic structure, habitat quality and local composition of fish communities. 3. In marine systems, key issues include the direct effects of exploitation on fish, habitats and other organisms, while habitat or water quality problems arise also from the atmospheric, terrestrial and coastal environments to which marine systems are linked. In freshwaters, flow regulation and obstruction by dams, fragmentation, catchment management, pollution, habitat alterations, exotic fish introductions and nursery-reared fish are widespread issues. 4. Management responses to the problems of fish and fisheries include aquatic reserves in both marine and freshwater habitats, and their effectiveness is now being evaluated. Policies on marine exploitation increasingly emphasise fishes as integral components of aquatic ecosystems rather than individually exploitable stocks, but the rationalisation of fishing pressures presents many challenges. In Europe, North America and elsewhere, policies on freshwaters encourage habitat protection, integrated watershed management and restoration, but pressures on water resources will cause continued change. All these management approaches require development and evaluation, and will benefit from a perspective of ecological understanding with ecologists fully involved. 5. Synthesis and applications. Although making a small contribution to the Journal of Applied Ecology in the past, leading work on aquatic problems and fish-related themes appear increasingly in this and other mainstream ecology journals. As this special profile of five papers shows, significant contributions arise on diverse issues that here include the benefit of aquatic reserves, river restoration for fish, the accumulation of contaminants, interactions with predators, and the fitness of salmonids from nurseries. This overview outlines the current context in which papers on the applied ecology of fish and fisheries are emerging, and it identifies scope for further contributions.

C. M. P. Ozanne, D. Anhuf and S. L. Boulter, et al.

Science (Wash.), Vol. 301, No. 5630, 11 Jul 2003. pp, 183-186.

The forest canopy is the functional interface between 90% of Earth's terrestrial biomass and the atmosphere. Multidisciplinary research in the canopy has expanded concepts of global species richness, physiological processes, and the provision of ecosystem services. Trees respond in a species-specific manner to elevated carbon dioxide levels, while climate change threatens plant-animal interactions in the canopy and will likely alter the production of biogenic aerosols that affect cloud formation and atmospheric chemistry.

G. K. Phoenix and J. A. Lee.

Ecol.Res., Vol. 19, No. 1, Jan 2004. pp, 65-74.

General circulation models predict increases in temperature and precipitation in the Arctic as the result of increases in atmospheric carbon dioxide concentrations. Arctic ecosystems are strongly constrained by temperature, and may be expected to be markedly influenced by climate change. Perturbation experiments have been used to predict how Arctic ecosystems will respond to global climatic change, but these have often simulated individual perturbations (e.g. temperature alone) and have largely been confined to the short Arctic summer. The importance of interactions between global change variables (e.g. CO sub(2), temperature, precipitation) has rarely been examined, and much experimentation has been short-term. Similarly, very little experimentation has occurred in the winter when General circulation models predict the largest changes in climate will take place. Recent studies have clearly demonstrated that Arctic ecosystems are not dormant during the winter and thus much greater emphasis on experimentation during this period is essential to improve our understanding of how these ecosystems will respond to global change. This, combined with more long-term experimentation, direct observation of natural vegetation change (e.g. at the tundra/taiga boundary) and improvements in model predictions is necessary if we are to understand the future nature and extent of Arctic ecosystems in a changing climate.

R. M. Roman-Cuesta, M. Gracia and J. Retana.

Ecol.Appl., Vol. 13, No. 4, Aug 2003. pp, 1177-1192.

Tropical and subtropical areas present the vast majority of contemporary global fires. Despite the human origin of most of these fires, little is known of how environmental and socioeconomic variables contribute to the spatial patterns of fire incidence and burned areas. The tropical Mexican State of Chiapas represents a good case study to analyze these interactions, due to the availability of official data, and its similarities to other tropical countries, in terms of environmental and socioeconomic characteristics. This study evaluates the relative importance of human-related and environmental variables in determining the distribution of the number of fires and area burned in the tropical State of Chiapas in years of normal and extreme climatic conditions (non-El Nino vs. El Nino). We have searched for causal relationships among fire, environmental, and socioeconomic variables in Chiapas using path analysis. Results of this study show a major importance of environmental variables in non-El Nino years, suggesting that the status of the vegetation was the main cause determining fire ignition and fire spread in these years. Contrarily, the observed trends in the El Nino period indicate that fire trends were mainly determined by the presence of ignition agents. In these El Nino years, vegetation is so severely water stressed that, when fire starts, all vegetation types burn, regardless of their flammability properties. The main vegetation types affected by fire in non-El Nino years were the most flammable ones, such as pine-oak communities, while rainforests burned the most in El Nino years. Altitude, pine-oak communities, and poverty levels played major roles in the arboreal fire incidence in non-El Nino years, whereas the distribution of pastures appeared as an important variable determining arboreal fire incidence in El Nino years. When all fires were considered (affecting any vegetation layer), almost identical trends were observed, with the incorporation of a new variable influencing the area burned: density of infrastructure. The results of this study strengthen the importance of El Nino years in the conservation of rainforest ecosystems and suggest the existence of synergistic effects involving fires, fragmentation, and certain elements of the landscape, such as cattle pastures, in tropical areas.

O. J. Schmitz, E. Post, C. E. Burns and K. M. Johnston.

Bioscience, Vol. 53, No. 12, Dec 2003. pp, 1199-1205.

Current assessments of climate-change effects on ecosystems use two key approaches: (1) empirical synthesis and modeling of species range shifts and life-cycle processes that coincide with recent evidence of climate warming, from which scenarios of ecosystem change are inferred; and (2) experiments examining plant-soil interactions under simulated climate warming. Both kinds of assessment offer indisputable evidence that climate change and its effects on ecosystems are ongoing. However, both approaches often provide conservative estimates of the effects of climate change on ecosystems, because they do not consider the interplay and feedback among higher trophic levels in ecosystems, which may have a large effect on plant species composition and on ecosystem services such as productivity. Understanding the impacts of these top-down processes on ecosystems is critical for determining large-scale ecosystem response to climate change. Using examples of links between climate forcing, trophic interactions, and changes in ecosystem state in selected terrestrial, freshwater, and marine systems, we show that the ability to understand and accurately forecast future effects of climate change requires an integrated perspective, linking climate and the biotic components of the ecosystem as a whole.

D. Schroter, L. Brussaard and G. De Deyn, et al.

Basic Appl.Ecol., Vol. 5, No. 6, Dec 2004. pp, 515-528.

The rate and scale of human-driven changes can exert profound impacts on ecosystems, the species that make them up and the services they provide that sustain humanity. Given the speed at which these changes are occurring, one of society's major challenges is to coexist within ecosystems and to manage ecosystem services in a sustainable way. The effect of possible scenarios of global change on ecosystem services can be explored using ecosystem models. Such models should adequately represent ecosystem processes above and below the soil surface (aboveground and belowground) and the interactions between them. We explore possibilities to include such interactions into ecosystem models at scales that range from global to local. At the regional to global scale we suggest to expand the plant functional type concept (aggregating plants into groups according to their physiological attributes) to include functional types of aboveground-belowground interactions. At the scale of discrete plant communities, process-based and organism-oriented models could be combined into "hybrid approaches" that include organism-oriented mechanistic representation of a limited number of trophic interactions in an otherwise process-oriented approach. Under global change the density and activity of organisms determining the processes may change non-linearly and therefore explicit knowledge of the organisms and their responses should ideally be included. At the individual plant scale a common organism-based conceptual model of aboveground-belowground interactions has emerged. This conceptual model facilitates the formulation of research questions to guide experiments aiming to identify patterns that are common within, but differ between, ecosystem types and biomes. Such experiments inform modelling approaches at larger scales. Future ecosystem models should better include this evolving knowledge of common patterns of aboveground-belowground interactions. Improved ecosystem models are necessary tools to reduce the uncertainty in the information that assists us in the sustainable management of our environment in a changing world.

Original Abstract: of our environment in a changing world. Rate und Ausmaß menschen-gemachter Veranderungen wirken sich auf Okosysteme, die Arten die diese zusammensetzen und Okosystemfunktionen von denen die Menschheit abhangt aus. Angesichts der Geschwindigkeit dieser Veranderungen ist es eine der großen Herausforderungen der Gesellschaft miteinander und in Okosystemen zu leben und deren Okosystemfunktionen nachhaltig zu nutzen. Die Auswirkungen plausibler Szenarien des Globalen Wandels auf Okosystemfunktionen konnen mit Hilfe von Okosystemmodellen untersucht werden. Solche Modelle sollten die Okosystemprozesse oberhalb und unterhalb der Erdoberflache („ oberirdisch und unterirdisch") und die Interaktionen zwischen diesen Prozessen angemessen abbilden. Auf Skalenebenen, die von global bis lokal reichen, erkunden wir in diesem Artikel Moglichkeiten solche Interaktionen in Modelle einzubauen. Auf der regionalen bis globalen Ebene schlagen wir vor dasKonzept der funktionellen Pflanzentypen (Pflanzenarten, die aufgrund von physiologischen Ä hnlichkeiten in Gruppen zusammengefasst sind) auszudehnen, so dass Typen von oberirdisch-unterirdischen Interaktionen mitenthalten sind. Auf der Skalenebene eigenstandiger Pflanzengesellschaften konnten prozessbasierte und organsimen-orientierte Modelle zu „ Hybridmodellen"verschmolzen werden, die organismen-orientierte, mechanistische Abbildungen einiger trophischer Interaktionen enthalten, aber ansonsten prozess-basiert sind. Der Einfluss des Globalen Wandels auf die Haufigkeit und Aktivitat von Organismen und die Okosystemprozesse, die sie bestimmen, ist sehr wahrscheinlich haufig nicht- linear, so dass im Idealfall explizites Wissen uber die Organismen und ihre Reaktionen in Modellen enthalten sein sollte. Auf der Skalenebene der einzelnen Pflanze hat sich ein gebrauchliches, organismen-basiertes Konzeptmodell der oberirdisch-unterirdisch Interaktionen herausgebildet. Dies erleichtert die Formulierung von Hypothesen und Fragestellungen in Experimenten, die nach gemeinsamen Mustern innerhalb von Okosystemen und Unterschieden zwischen Okosystemtypen und Biomen suchen. Dies ist die Basis fur Modellierungsansatze auf großeren Skalenebenen. Zukunftige Okosystemmodelle sollten die gemeinsamen Muster oberirdisch-unterirdischer Interaktionen besser berucksichtigen, die sich neuerdings abzuzeichnen beginnen. Verbesserte Okosystemmodelle sind notwendige Werkzeuge um die Unsicherheit in der Information zu vermindern, auf der nachhaltiges Umweltmanagement in einer sichwandelnden Welt beruht.

P. Shepson, P. Matrai, L. Barrie and J. Bottenheim.

EOS Trans.Am.Geophys.Union, Vol. 84, No. 36, 9 Sep 2003. pp, 349-355.

The discovery of the nature of Arctic haze in the late 1970s and early 1980s [Barrie, 1986] showed that the Arctic is not a pristine environment isolated from human activity, but rather, a region well connected to natural and anthropogenic sources of chemicals by winds, ice movement, and marine currents. Copious pollution is carried on the winds to the Arctic during winter and spring from Europe and northern Asia. The study of this phenomenon led serendipitously to the discovery of ozone depletion chemistry in the Arctic marine boundary layer (MBL) at polar sunrise [Oltmans, 1981; Bottenheim et al., 1986]. In turn, research to understand surface ozone depletion chemistry led to the discovery that it is perturbing the biogeochemical cycle of many elements such as mercury; and that ozone depletion chemistry is likely to have a significant impact on radiative transfer in the atmospheric layer near the surface, with important consequences on the air-sea exchange of biologically-mediated compounds. Surface layer ozone depletion has now been observed all around the Arctic. It frequently extends from the surface up to 1-1.5 km altitude, with ozone concentrations depleting from background concentrations of similar to 40 ppb to as low as similar to 0.050 ppb [Bottenheim et al., 2002]. The discovery of the phenomenon of surface ozone depletion in the Arctic has opened a window on a significant deficiency in our understanding of chemistry involving gas-surface interactions. In particular, the global sinks for ozone, an important "greenhouse" gas, a respiratory irritant, and a phytotoxic species--yet an essential atmospheric oxidant at the same time--generally do not include halogen atom chemistry or halogen biogeochemistry.

J. E. Smith.

J.Phycol., Vol. 39, No. S1, Jun 2003. pp, 53.

The introduction of non-indigenous species is currently viewed as one of the largest threats to global biodiversity. Non-indigenous marine algae (NIMA) in temperate seas around the world have caused significant losses to ecosystem structure and function. However, the introduction of invasive species in tropical marine ecosystems has not typically been viewed as a significant threat despite the number of species that have been transported to reef regions around the world for open-reef aquaculture. The research presented here represents some of the first quantified evidence of significant negative impacts of NIMA in tropical waters. This study characterized several ecological and physiological aspects of one the most successful and potentially threatening NIMA on Hawaii's coral reefs, K. alvarezii. Results of large-scale surveys and a number of permanently established invader removal plots suggest that K. alvarezii is having negative impacts on native species diversity. Interactions between K. alvarezii and coral abundance were examined using photoquadrats and results indicate that the invader is causing coral death as a result of overgrowth and shading. Possible mechanisms influencing invader success including responses to nutrient enrichment, grazer consumption rates and reproductive characteristics were examined. Results from a number of experiments suggest that without mitigation K. alvarezii will continue to spread. In an effort to minimize negative impacts and prevent spread several management strategies were examined including manual removal, use of chemical and temperature treatments and enhancement of native sea urchins. While some of these tools are promising control options, rapid implementation is needed to prevent further damage.

H. L. Throop and M. T. Lerdau.

Ecosystems, Vol. 7, No. 5, Aug 2004. pp, 109-133.

The deposition of anthropogenically fixed nitrogen (N) from the atmosphere onto land and plant surfaces has strong influences on terrestrial ecosystem processes. Although recent research has expanded our understanding of how N deposition affects ecosystems directly, less attention has been directed toward the investigation of how N deposition may affect ecosystems indirectly by modifying interactions among organisms. Empirical evidence suggests that there are several mechanisms by which N deposition may affect interactions between plants and insect herbivores. The most likely mechanisms are deposition-induced shifts in the quality and availability of host plant tissues. We discuss the effects of N deposition on host plant chemistry, production, and phenology, and we review the evidence for the effects of N deposition on insect herbivores at the individual, population, and community levels. In general, N deposition has positive effects on individual insect performance, probably due to deposition-induced improvements in host plant chemistry. These improvements include increased N and decreased carbon-based defensive compound concentrations. The evidence to date suggests that N deposition may also have a positive effect on insect populations. These effects may have considerable ecological, as well as economic consequences if the rates of herbivory on economically important timber species continue to increase. Deposition-induced changes in plant-herbivore relationships may affect community and ecosystem processes. However, we predict that the larger-scale consequences of interactions between N deposition and herbivory will vary based on site-specific factors. In addition, interactions between N deposition and other global-scale changes may lead to nonadditive effects on patterns of herbivory.

L. Weissflog, N. Elansky and E. Putz, et al.

Atmos.Environ., Vol. 38, No. 25, Aug 2004. pp, 4197-4204.

One of the issues provided for by the 1993 existing substances regulation (793/93/EEC) is the assessment of the environmental risk emanating from waste materials. One such material is the highly volatile substance perchloroethene (PER; TECE). PER is produced in large quantities all over the world by the chemical industry. There are many industrial processes in which PER escapes into the environment, especially the atmosphere. It has since been proven that after entering plants via the air/leaf pathway, airborne PER can be metabolised into the phytotoxic substance trichloroacetic acid. However our own studies detected relatively high levels of TCA in environmental compartments in regions far away from industry which cannot be explained by the anthropogenic input of airborne substances into the relevant ecosystems. This indicates that natural PER emittents also exist and must be identified, in order to find out more about the global spread of PER. This paper reports on the findings of related fieldwork in the Kalmykian Steppe. This area of steppe in southern Russia spans an area extending west-to-east from the Black Sea and the Caspian Sea and north-to-south between the Greater Caucasus and Volgograd. The main aim of the experiments in the Kalmykian Steppe was to study water from lakes, rivers and springs with differing levels of salinity. The concentrations of the chlorinated hydrocarbons (VCHCs) chloroform (CHCl sub(3)), tetrachloromethane (CCl sub(4)), 1, 1, 1- trichloroethane (1, 1, 1-C sub(2)H sub(3)Cl sub(3)), trichloroethene (TRI; C sub(2)HCl sub(3)), tetrachloroethene (PER; C sub(2)Cl sub(4)) and TCA in these waters were measured, along with the levels of cations and anions and the pH-value of the waters. The measurements indicate that in particular water from salt lakes located in semiarid/arid areas of the study region must be considered as new types of natural emittents of PER and other chlorinated hydrocarbons as well as trichloroacetic acid. Furthermore, attention is drawn to ecological impacts resulting from the occurrence of these substances in connection with the desertification observed in this area since the mid-20th century. Possible global associations between TCA phytotoxicity, the consumption of water by contaminated plants and the resulting impact on the regional water cycle are discussed.

J. F. Weltzin, M. E. Loik and S. Schwinning, et al.

Bioscience, Vol. 53, No. 10, Oct 2003. pp, 941-952.

Changes in Earth's surface temperatures caused by anthropogenic emissions of greenhouse gases are expected to affect global and regional precipitation regimes. Interactions between changing precipitation regimes and other aspects of global change are likely to affect natural and managed terrestrial ecosystems as well as human society. Although much recent research has focused on assessing the responses of terrestrial ecosystems to rising carbon dioxide or temperature, relatively little research has focused on understanding how ecosystems respond to changes in precipitation regimes. Here we review predicted changes in global and regional precipitation regimes, outline the consequences of precipitation change for natural ecosystems and human activities, and discuss approaches to improving understanding of ecosystem responses to changing precipitation. Further, we introduce the Precipitation and Ecosystem Change Research Network (PrecipNet), a new interdisciplinary research network assembled to encourage and foster communication and collaboration across research groups with common interests in the impacts of global change on precipitation regimes, ecosystem structure and function, and the human enterprise.

B. Worm and J. E. Duffy.

Trends Ecol.Evol., Vol. 18, No. 12, Dec 2003. pp, 628-632.

The global biodiversity crisis has motivated new theory and experiments that explore relationships between biodiversity (species richness and composition in particular), productivity and stability. Here we emphasize that these relationships are often bi-directional, such that changes in biodiversity can be both a cause and a consequence of changes in productivity and stability. We hypothesize that this bi-directionality creates feedback loops, as well as indirect effects, that influence the complex responses of communities to biodiversity losses. Important, but often neglected, mediators of this complexity are trophic interactions. Recent work shows that consumers can modify, dampen or even reverse the directionality of biodiversity-productivity-stability linkages inferred from the plant level alone. Such consumer mediation is likely to be common in many ecosystems. We suggest that merging biodiversity research and food-web theory is an exciting and pressing frontier for ecology, with implications for biodiversity conservation.