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Transformation toward a sustainable future requires an earth stewardship approach to shift society from its current goal of increasing material wealth to a vision of sustaining built, natural, human, and social capital—equitably distributed across society, within and among nations. Widespread concern about earth's current trajectory and support for actions that would foster more sustainable pathways suggests potential social tipping points in public demand for an earth stewardship vision. Here, we draw on empirical studies and theory to show that movement toward a stewardship vision can be facilitated by changes in either policy incentives or social norms. Our novel contribution is to point out that both norms and incentives must change and can do so interactively. This can be facilitated through leverage points and complementarities across policy areas, based on values, system design, and agency. Potential catalysts include novel democratic institutions and engagement of non-governmental actors, such as businesses, civic leaders, and social movements as agents for redistribution of power. Because no single intervention will transform the world, a key challenge is to align actions to be synergistic, persistent, and scalable. [ABSTRACT FROM AUTHOR]

Stewardship has been increasingly used in the realm of conservation and sustainable land use as an important pathway for action. Ecosystem stewardship, a specific application of this concept, is an approach for natural resource management, but the lack of empirical examples is a shortcoming to its applicability. With this work, we aimed at investigating whether environmental initiatives taking place in a rural watershed in southeast Brazil can be framed as ecosystem stewardship and, if so, whether they address key socialecological feedbacks that influence the quality of critical local ecosystem services (water, food production, soil, forests). Drawing on data from direct and participant observation at community and technical meetings, nine unstructured interviews, and gray literature, we demonstrated that three initiatives encompass all elements of ecosystem stewardship to some extent (dual goals of ecosystem resilience and human well-being, integration of processes across scales and emphasis on actions that shape the future). Only one initiative, a multi-stakeholder network, fully entails all elements of ecosystem stewardship. The initiatives overlap in space and time and entail pressing and non-urgent issues, therefore they promote, as a group, complementary ecosystem stewardship practices at various levels in the territory. They also address the key feedbacks responsible for the degradation of water, food production, and soil. Knowledge, relational values, and care are salient ingredients that combine in different ways, shaping each initiative. Our findings suggest that ecosystem stewardship arises from local social-ecological challenges combined with stakeholders' knowledge and understanding of the system dynamics. Collaboration among initiatives can strengthen their effects on undesired feedbacks and enable the design of joint strategies to tackle the erosion of relational values. Actions focusing on reconnecting local communities and forests may safeguard the flux of ecosystem-service bundles on both the short and long term. [ABSTRACT FROM AUTHOR]

We tested whether post-fire seedling establishment of common boreal tree and expanding shrub species at treeline and in Arctic tundra is facilitated by co-migration of boreal forest mycorrhizal fungi. Wildfires are anticipated to facilitate biome shifts at the forest-tundra ecotone by improving seedbed conditions for recruiting boreal species; at the same time fire alters the composition and availability of mycorrhizal fungi critical to seedling performance. To determine the role of root-associated fungi (RAF) in post-fire seedling recruitment and future biome shifts, we outplanted four dominant boreal tree and shrub species inoculated with one of three treatments at treeline and in tundra: burned boreal forest, unburned boreal forest, or a control treatment of sterilized inoculum. We compared survivorship, growth, and physiological performance of the seedlings in relation to mycorrhizal inoculum treatment and among host species, characterized the RAF communities based on ITS-rDNA sequencing of individual root tips sampled from surviving seedlings, and tested for correlations between RAF composition and the inoculation treatments, host species, and duration of the experiment. We explored correlations between RAF composition and seedling metrics. Both live and sterile autoclaved inoculation treatments had similar effects on seedling survivorship and growth for all species. RAF composition did not vary by treatment, suggesting that most colonization was due to local fungi. However, seedling traits and growth were correlated with RAF species composition, colonization, and the relative abundance of specific RAF taxa. Picea sp. performance in particular showed strong co-variation with RAF metrics. Our results suggest that mycorrhizal co-migration is not a primary limiting factor to boreal seedling recruitment because the experimental provision of inoculum did not affect seedling recruitment; yet, RAF did influence seedling performance, particularly resident RAF at treeline and in tundra, suggesting that mycorrhizal fungi are important to vegetation processes at the treeline-tundra ecotone. [ABSTRACT FROM AUTHOR]

The article presents social and environmental change in the Arctic with emerging opportunities for well-being transformations through stewardship. Topics include stewardship requires respectful conversations among stakeholders to identify synergies and trade-offs; and scientists and other citizens new roles in fostering interventions that support well-being of people and nature in the Arctic.

Public participation is increasingly advocated in natural resource management to meet a spectrum of instrumental to normative goals. However, the success of participation in achieving these goals is highly variable, depending on both societal and institutional contexts. Whether participation realises its benefits or succumbs to its pitfalls is shaped by dynamic interactions operating among three contextual dimensions: participatory rationales (instrumental to normative), institutional fit of different levels (types) of participation (information delivery to partnership to delegation), and social structures (such as cultural context, social capital and power distribution). Some levels of participation may support the existing power hierarchy, others benefit organized stakeholder groups and special interests, and still others foster deliberative democratic outcomes. [ABSTRACT FROM AUTHOR]

Climate change challenges the traditional goals and conservation strategies of protected areas, necessitating adaptation to changing conditions. Denali National Park and Preserve (Denali) in south central Alaska, USA, is a vast landscape that is responding to climate change in ways that will impact both ecological resources and local communities. Local observations help to inform understanding of climate change and adaptation planning, but whose knowledge is most important to consider? For this project we interviewed long-term Denali staff, scientists, subsistence community members, bus drivers, and business owners to assess what types of observations each can contribute, how climate change is impacting each, and what they think the National Park Service should do to adapt. The project shows that each type of long-term observer has different types of observations, but that those who depend more directly on natural resources for their livelihoods have more and different observations than those who do not. These findings suggest that engaging multiple groups of stakeholders who interact with the park in distinct ways adds substantially to the information provided by Denali staff and scientists and offers a broader foundation for adaptation planning. It also suggests that traditional protected area paradigms that fail to learn from and foster appropriate engagement of people may be maladaptive in the context of climate change. [ABSTRACT FROM AUTHOR]

Systems theories of robustness and resilience, which are derived from engineering and ecology, respectively, have been increasingly applied to social-ecological systems (SESs). Social-ecological robustness has been applied primarily to management of physical dimensions of SESs (e.g., water management) and resilience to management of ecological dimensions of SESs (e.g., rangelands). However, cases of highly engineered systems have yet to be adequately evaluated by either approach. We find the robustness framework serves to better explain management options of a highly engineered, ecologically-based SES, the lower Ship Creek fishery in Anchorage, Alaska, USA. Robustness applies well to this system because its dynamics are highly engineered through both structures and institutions. Even the salmon are products of a hatchery fishery that operates independently of many ecological variables and feedbacks within the system. However, robustness theory has yet to develop a prescriptive method for management that can assist practitioners. We conclude by applying Ostrom's design principles to the system dynamics to assess opportunities for increasing the robustness of this urban fishery. [ABSTRACT FROM AUTHOR]

This article presents governance and institutional strategies for climate-induced community relocations. In Alaska, repeated extreme weather events coupled with climate change-induced coastal erosion impact the habitability of entire communities. Community residents and government agencies concur that relocation is the only adaptation strategy that can protect lives and infrastructure. Community relocation stretches the financial and institutional capacity of existing governance institutions. Based on a comparative analysis of three Alaskan communities, Kivalina, Newtok, and Shishmaref, which have chosen to relocate, we examine the institutional constraints to relocation in the United States. We identify policy changes and components of a toolkit that can facilitate community-based adaptation when environmental events threaten people's lives and protection in place is not possible. Policy changes include amendment of the Stafford Act to include gradual geophysical processes, such as erosion, in the statutory definition of disaster and the creation of an adaptive governance framework to allow communities a continuum of responses from protection in place to community relocation. Key components of the toolkit are local leadership and integration of social and ecological well-being into adaptation planning. [ABSTRACT FROM AUTHOR]

Subsistence harvesting and wild food production by Athabascan peoples is part of an integrated social-ecological system of interior Alaska. We describe effects of recent trends and future climate change projections on the boreal ecosystem of interior Alaska and relate changes in ecosystem services to Athabascan subsistence. We focus primarily on moose, a keystone terrestrial subsistence resource of villages in that region. Although recent climate change has affected the boreal forest, moose, and Athabascan moose harvesting, a high dependence by village households on moose persists. An historical account of 20th century socioeconomic changes demonstrates that the vulnerability of Athabascan subsistence systems to climatic change has in some respects increased while at the same time has improved aspects of village resilience. In the face of future climate and socioeconomic changes, communities have limited but potentially effective mitigation and adaptation opportunities. The extent to which residents can realize those opportunities depends on the responsiveness of formal and informal institutions to local needs. For example, increases in Alaska's urban population coupled with climate-induced habitat shifts may increase hunting conflicts in low-moose years. This problem could be mitigated through adaptive co-management strategies that project future moose densities and redirect urban hunters to areas of lower conflict. [ABSTRACT FROM AUTHOR]

In the boreal forests of interior Alaska, feedbacks that link forest soils, fire characteristics, and plant traits have supported stable cycles of forest succession for the past 6000 years. This high resilience of forest stands to fire disturbance is supported by two interrelated feedback cycles: (i) interactions among disturbance regime and plant-soil-microbial feedbacks that regulate soil organic layer thickness and the cycling of energy and materials, and (ii) interactions among soil conditions, plant regeneration traits, and plant effects on the environment that maintain stable cycles of forest community composition. Unusual fire events can disrupt these cycles and trigger a regime shift of forest stands from one stability domain to another (e.g., from conifer to deciduous forest dominance). This may lead to abrupt shifts in forest cover in response to changing climate and fire regime, particularly at sites with intermediate levels of moisture availability where stand-scale feedback cycles are only weakly constrained by environmental conditions. However, the loss of resilience in individual stands may foster resilience at the landscape scale, if changes in the landscape configuration of forest cover types feedback to stabilize regional patterns of fire behavior and climate conditions. [ABSTRACT FROM AUTHOR]

1. Most current climate–carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR, i.e. primarily decomposition). 2. Under conditions near steady state, geographic patterns of decomposition closely match those of NPP, and net C emissions are adequately described as a simple balance of NPP and HR (the Woodwell-Whittaker model). This close coupling between NPP and HR occurs largely because of tight coupling between C and N (nitrogen) cycles and because NPP constrains the food available to heterotrophs. 3. Processes in addition to NPP and HR become important to understanding net C emissions from ecosystems under conditions of rapid changes in climate, hydrology, atmospheric CO2, land cover, species composition and/or N deposition. Inclusion of these processes in climate–C cycle models would improve their capacity to simulate recent and future climatic change. 4. Processes that appear critical to soil C dynamics but warrant further research before incorporation into ecosystem models include below-ground C flux and its partitioning among roots, mycorrhizas and exudates; microbial community effects on C sequestration; and the effects of temperature and labile C on decomposition. The controls over and consequences of these processes are still unclear at the ecosystem scale. 5. Carbon fluxes in addition to NPP and HR exert strong influences over the climate system under conditions of rapid change. These fluxes include methane release, wildfire, and lateral transfers of food and fibre among ecosystems. 6. Water and energy exchanges are important complements to C cycle feedbacks to the climate system, particularly under non-steady-state conditions. An integrated understanding of multiple ecosystem–climate feedbacks provides a strong foundation for policies to mitigate climate change. 7. Synthesis. Current climate systems models that include only NPP and HR are inadequate under conditions of rapid change. Many of the recent advances in biogeochemical understanding are sufficiently mature to substantially improve representation of ecosystem C dynamics in these models. [ABSTRACT FROM AUTHOR]

The article discusses a feasibility research on switching power generation from fossil fuels to wood energy in 33 rural Alaska communities in forested regions of interior Alaska. Findings suggested that the costs of installing biomass systems would be compensated within 12 years for the 32 communities in the region. It was revealed that fire suppression around inhabited areas may decline to average annual area burned, which over time increases average forest stand age, reduces variability, and intensifies the risk of future fires. The cited social factors that can affect the feasibility of fuel substitution are existing social infrastructure related to village electrical utility, fire prevention, and biomass harvest, institutional barriers, and potential positive and negative feedback.

Recent global environmental and social changes have created a set of "wicked problems" for which there are no optimal solutions. In this article, we illustrate the wicked nature of such problems by describing the effects of global warming on the wildfire regime and indigenous communities in Alaska, and we suggest an approach for minimizing negative impacts and maximizing positive outcomes. Warming has led to an increase in the areal extent of wildfire in Alaska, which increases fire risk to rural indigenous communities and reduces short-term subsistence opportunities. Continuing the current fire suppression policy would minimize these negative impacts, but it would also create secondary problems near communities associated with fuel buildup and contribute to a continuing decline in subsistence opportunities. Collaborations between communities and agencies to harvest flammable fuels for heating and electrical power generation near communities, and to use wildland fire for habitat enhancement in surrounding forests, could reduce community vulnerability to both the direct and the indirect effects of global climate change. [ABSTRACT FROM AUTHOR]

Computational thinking (CT) is a way to solve problems and understand complex systems that draws on concepts fundamental to computer science and is well suited to the challenges that face researchers of complex, linked social-ecological systems. This paper explores CT’s usefulness to sustainability science through the application of the services-oriented architecture (SOA). The SOA is a popular organizational framework in information technology that enables businesses to describe the services they offer, including how, where, to whom, and under what terms these services are available to consumers. It provides a straightforward, scalable, and portable way to describe and organize complex business systems, with an emphasis on system controls and component interactions rather than on the system components themselves. Here, we present the SOA as a path to a more mature ecosystem services concept, in support of integrated assessment frameworks such as the Millennium Ecosystem Assessment (MA). With the SOA we capture important interrelationships among ecosystems, ecosystem service consumers, and ecosystem service governance authorities, particularly the effects of their interactions on the viability of ecosystem services. By standardizing the description and relationships involving ecosystem services, the SOA supports a diagnostic approach for evaluating stability and change in ecosystem service use across both space and time, when influenced by drivers of social, political, and/or ecological change, whether directional or stochastic, planned or otherwise. We present here a prototype of the SOA and illustrate its utility with an example from rural Alaskan communities. [ABSTRACT FROM AUTHOR]

Projected warming in Sweden and other Fennoscandian countries will probably increase growth rates of forest trees near their northern limits, increase the probability of new pest outbreaks, and foster northerly migration of both native and exotic species. The greatest challenges for sustainable forestry are to restore and enhance the ecological and socioeconomic diversity of intensively managed forested landscapes. With appropriate management, climate warming may facilitate the regeneration of this diversity. Experimental transplant gardens along latitudinal or altitudinal gradients and high-resolution maps of expected future climate could provide a scientific basis for predicting the climate response of potential migrant species. Management of corridors and assisted migration could speed the movement of appropriate species. [ABSTRACT FROM AUTHOR]

In this article we extend the theory of community prediction by presenting seven hypotheses for predicting community structure in a directionally changing world. The first three address well-studied community responses to environmental and ecological change: ecological communities are most likely to exhibit threshold changes in structure when perturbations cause large changes in limiting soil or sediment resources, dominant or keystone species, or attributes of disturbance regime that influence community recruitment. Four additional hypotheses address social-ecological interactions and apply to both ecological communities and social-ecological systems. Human responsiveness to short-term and local costs and benefits often leads to human actions with unintended long-term impacts, particularly those that are far from the site of decision making or are geographically dispersed. Policies are usually based on past conditions of ecosystem services rather than expected future trends. Finally, institutions that strengthen negative feedbacks between human actions and social-ecological consequences can reduce human impacts through more responsive (and thus more effective) management of public ecosystem services. Because of the large role that humans play in modifying ecosystems and ecosystem services, it is particularly important to test and improve social-ecological hypotheses as a basis for shaping appropriate policies for long-term ecosystem resilience. [ABSTRACT FROM AUTHOR]

Human activities are altering many factors that determine the fundamental properties of ecological and social systems. Is sustainability a realistic goal in a world in which many key process controls are directionally changing? To address this issue, we integrate several disparate sources of theory to address sustainability in directionally changing social-ecological systems, apply this framework to climate-warming impacts in Interior Alaska, and describe a suite of policy strategies that emerge from these analyses. Climate warming in Interior Alaska has profoundly affected factors that influence landscape processes (climate regulation and disturbance spread) and natural hazards, but has only indirectly influenced ecosystem goods such as food, water, and wood that receive most management attention. Warming has reduced cultural services provided by ecosystems, leading to some of the few institutional responses that directly address the causes of climate warming, e.g., indigenous initiatives to the Arctic Council. Four broad policy strategies emerge: (i) enhancing human adaptability through learning and innovation in the context of changes occurring at multiple scales; (ii) increasing resilience by strengthening negative (stabilizing) feedbacks that buffer the system from change and increasing options for adaptation through biological, cultural, and economic diversity; (iii) reducing vulnerability by strengthening institutions that link the high-latitude impacts of climate warming to their low-latitude causes; and (iv) facilitating transformation to new, potentially more beneficial states by taking advantage of opportunities created by crisis. Each strategy provides societal benefits, and we suggest that all of them be pursued simultaneously. [ABSTRACT FROM AUTHOR]

Unprecedented global changes caused by human actions challenge society's ability to sustain the desirable features of our planet. This requires proactive management of change to foster both resilience (sustaining those attributes that are important to society in the face of change) and adaptation (developing new socioecological configurations that function effectively under new conditions). The Arctic may be one of the last remaining opportunities to plan for change in a spatially extensive region where many of the ancestral ecological and social processes and feedbacks are still intact. If the feasibility of this strategy can be demonstrated in the Arctic, our improved understanding of the dynamics of change can be applied to regions with greater human modification. Conditions may now be ideal to implement policies to manage Arctic change because recent studies provide the essential scientific understanding, appropriate international institutions are in place, and Arctic nations have the wealth to institute necessary changes, if they choose to do so. [ABSTRACT FROM AUTHOR]

Ceanothus is a widely speciated genus with two sections that differ markedly in size, patterns of biomass allocation and reproductive strategies. On greenhouse-grown seedlings we tested whether divergence occurred in single traits or in suites of traits, and whether taxonomic affinity or the ability to fix nitrogen (N) influenced the relationships among functional traits. Species of the subgenus Cerastes differed from species in the subgenus Ceanothus in the following characteristics: reproduction by seed rather than primarily resprouting, high rates of photosynthesis and high stomatal conductance, thick leaves, low root allocation, and high leaf allocation. Correlations of traits across the entire genus showed positive correlations among traits that maximize photosynthesis and tradeoffs between root allocation and carbon gain patterns frequently observed in other broad taxonomic comparisons. Trait correlations differed between the two subgenera (divergence in allocation-photosynthesis tradeoffs in Ceanothus and divergence of growth-related traits in Cerastes). Similarly, N-fixers, which were distributed broadly between the two subgenera, differed in trait correlations (primarily among traits related to photosynthesis) from non-fixers (primarily among traits related to growth and allocation). These results indicate that 1) divergence in genus Ceanothus was associated with changes in entire suite of traits, rather than independent changes in individual traits and 2) evolution occurring under different environmental or nutritional circumstances alters the suites of traits exhibited by plants. [ABSTRACT FROM AUTHOR]

Plant species effects on ecosystem processes are mediated by traits such as litter quality and exudation. These same traits also influence the activity and distribution of animals that play key roles in regulating ecosystem dynamics. We planted monocultures of eight plant species commonly found in California grasslands to investigate the relative importance of plant species direct effects on nitrogen cycling, versus their indirect effects mediated by plant interactions with gophers. Plant species differed in their litter C:N ratio, which closely related to species effects on rates of net mineralization and nitrification in undisturbed soil. However, the effect of selective gopher disturbance on N cycling greatly altered these species effects.Plant species differed in their effects on the type and timing of gopher disturbance. Small feeding holes were formed in late spring in plots containing species with high tissue quality. These feeding holes minimally disturbed the soil and did not alter N cycling rates over the short term. Large gopher mounds were formed in the winter and early spring, primarily in plots containing the grass,Aegilops triuncialis, and to a lesser extent in plots containingAvena barbata. These large mounds significantly disturbed the soil and greatly increased net nitrification rates, but had no consistent effects on net N mineralization. In undisturbed soil,Aegilopshad the highest litter C:N ratio and one of the lowest rates of net nitrification. However, gophers preferentially built large mounds inAegilopsplots. Once the effects of gopher burrowing were considered,Aegilopshad one of the highest rates of net nitrification, indicating that the indirect effects of plant species on N cycling can be more important than the direct effects alone. This experiment indicates that it is vital to consider interactions between plants and other organisms in order to predict the ecosystem effects of plant communities. [ABSTRACT FROM AUTHOR]

Changes in boreal climate of the magnitude projected for the 21st century have always caused vegetation changes large enough to be societally important. However, the rates and patterns of vegetation change are difficult to predict. We review evidence suggesting that these vegetation changes may be gradual at the northern forest limit or where seed dispersal limits species distribution. However forest composition may be quite resilient to climate change in the central portions of a species range until some threshold is surpassed. At this point, changes can be rapid and unexpected, often causing a switch to very different ecosystem types. Many of these triggers for change are amenable to management, suggesting that our choice of policies in the coming decades will substantially influence the ecological and societal consequences of current climatic change. [ABSTRACT FROM AUTHOR]

Plant species differ in how they influence many aspects of ecosystem structure and function, including soil characteristics, geomorphology, biogeochemistry, regional climate, and the activity and distribution of other organisms. Attempts to generalize plant species effects on ecosystems have focused on single traits or suites of traits that strongly covary (functional groups). However, plant effects on any ecosystem process are mediated by multiple traits, and many of these traits vary independently from one another. Thus, most species have unique combinations of traits that influence ecosystems, and there is no single trait or functional-group classification that can capture the effects of these multiple traits, or can predict the multiple functions performed by different plant species. We present a new theoretical framework, the functional matrix, which builds upon the functional group and single trait approaches to account for the ecosystem effects of multiple traits that vary independently among species. The functional matrix describes the relationship between ecosystem processes and multiple traits, treating traits as continuous variables, and determining if the effects of these multiple traits are additive or interactive. The power of this approach is that the ecosystem effects of multiple traits are the underlying mechanisms determining species effects, how the effects of an individual species change across seasons and under varying environmental conditions, the nonadditive effects of plant species mixtures, and the effects of species diversity. [ABSTRACT FROM AUTHOR]

Many attempts have been made to link invasions of exotic plants to specific plant traits and key attributes of invaded ecosystems. While these factors play a role in determining the potential for invasion, they are often inadequate in predicting the success of a specific invasion. We show that interactions of an invasive grass with other members of the community determine the local pattern of invasion. A fungus, Ulocladium atrum, aids the establishment of barbed goatgrass (Aegilops triuncialis) by weakening the grass's tough seed head, thereby accelerating germination and seedling establishment. In contrast, gophers, Thoraomys bottae, decrease establishment of this invader by selectively burying patches of goatgrass seedlings under mounds. Plants that survive these gopher disturbances produce seeds that are uninfected by Ulocladium atrum, which may further decrease the establishment of the next generation of goatgrass. A field survey indicated that goatgrass achieves dominance in areas with minimal gopher disturbance, but has limited establishment in pastures with high gopher activity, indicating that the landscape pattern of gopher activity influences patterns of goatgrass invasion by manipulating gopher-plant-fungal interactions. [ABSTRACT FROM AUTHOR]

In a growing body of literature from a variety of ecosystems is strong evidence that various components of biodiversity have significant impacts on ecosystem functioning. However, much of this evidence comes from short-term, small-scale experiments in which communities are synthesized from relatively small species pools and conditions are highly controlled. Extrapolation of the results of such experiments to longer time scales and larger spatial scales--those of whole ecosystems--is difficult because the experiments do not incorporate natural processes such as recruitment limitation and colonization of new species. We show how long-term study of planned and accidental changes in species richness and composition suggests that the effects of biodiversity on ecosystem functioning will vary over time and space. More important, we also highlight areas of uncertainty that need to be addressed through coordinated cross-scale and cross-site research. [ABSTRACT FROM AUTHOR]

Grouping organisms into categories based on common traits has been a tool of ecological scientists for some time now. Defining groups of species, examples being life forms and functional types, is an operational procedure, conducted to answer a particular question. This becomes rather practical when performing analyses at coarse spatial scales, given data limitations and the potential for species redundancy. However, the implications of aggregating organisms for modeling purposes are still unclear. Does averaging the traits of several species into a functional type sufficiently represent the dynamics of the individual components? How much variability is lost when we aggregate species into groups? In an attempt to address these questions, we examined how the level of vegetation aggregation affected a variety of ecosystem properties using a regional-scale model of arctic tundra ecosystems (ArcVeg). We used four levels of aggregation: species (15 dominant ones), functional types (7), life forms (4) and vegetation type (1), in addition to two methods of aggregation (simple vs weighted means of plant parameter values). We found that the level of aggregation consistently affected community composition, total community biomass and ecosystem net primary production (NPP). Neither simple means nor weighted means of aggregated parameter values adequately captured the ecosystem properties simulated at lower levels of aggregation. Aggregation of vegetation (i.e. reduced parameter variability) using simple means underestimated total biomass, whereas aggregation using weighted means overestimated total biomass. Aggregation led to increases in NPP with both methods. These findings suggest that aggregating vegetation, particularly to levels less detailed than plant functional types, will have important implications for regional-scale modeling of vegetation dynamics and carbon cycling. [ABSTRACT FROM AUTHOR]

A major empirical approach in community ecology is to describe the dynamics of a community by examining small subsets of species. Unfortunately, interaction modifications, which cause pair-wise interaction coefficients to depend on the presence or absence of additional species, can make it difficult to predict the overall dynamics of species within a community from experiments with pairs of species. In a similar fashion, one of the major approaches in evolutionary ecology has been to describe the likely evolutionary dynamics of a single species by focusing on the selection imposed by a limited number of other species within the community. However, recent work on diffuse coevolution indicates that selection pressures due to one species can change in the presence of other species. The magnitude of the difficulty that interaction modifications and diffuse coevolution present for predicting ecological and evolutionary dynamics is an unresolved question. Here we outline the similarities and differences between the two topics, discuss experimental and statistical approaches to studying them, and make predictions about when ecological interaction modifications are likely to cause diffuse coevolution. Since the currencies for interaction modifications are usually fitness components such as growth, fecundity, or survival, is it likely that these will translate into corresponding differences in the relative fitness of individuals or genotypes, and thus in general these two phenomena will occur together. We argue that community ecologists and evolutionary ecologists will both benefit from experiments that test for the effects of interaction modifications, and that studies of the mechanisms driving interaction modifications and diffuse coevolution (e.g., changes in behavior, nonlinear effects on shared resources, genetic covariances) will aid our progress in understanding the ecological and evolutionary dynamics of communities. [ABSTRACT FROM AUTHOR]

Focuses on the interpolation of data related to geographic patterns and dynamics obtained from a sparse network of climate stations in Alaska to provide maps of mean monthly temperature and precipitation. Basis of the model on thin-plate smoothing splines; Range of information included in the maps provided in the model; Indications about the eastward movement of low-pressure centers.

Biome differences in surface energy balance strongly affect climate. However, arctic vegetation is considered sufficiently uniform that only a single arctic land surface type is generally used in climate models. Field measurements in northern Alaska show large differences among arctic ecosystem types in summer energy absorption and partitioning. Simulations with the Arctic Regional Climate System Model demonstrate that these variations in land surface parameters and ecological processes cause variation in surface fluxes that is sufficiently large to affect the regional climate. Plausible changes in arctic vegetation in response to high-latitude warming would feed back positively to local summer warming. This local warming could extend into the boreal zone. Climate feedbacks that operate during the growing season are particularly likely to impact vegetation and ecosystem properties. These field and model results suggest that vegetation changes within a biome could be climatically important and warrant consideration in regional climate modeling. [ABSTRACT FROM AUTHOR]

Discusses changing biodiversity as a result of human alteration, and examines the consequences of these changes on the resilience of ecosystems to environmental change. Global number of species threatened with extinction; How species interactions determine ecosystem characteristics; Social consequences of biodiversity and ecosystem properties; Need for regulation of factors causing altered biodiversity.

Investigates competition and microenvironmental modification in an Alaskan postfire boreal forest. Establishment of seedlings by white spruce and paper birch in patches dominated by horsetail and bluestem; Reduction of survivorship, growth and nitrogen accumulation in the presence of aboveground vegetation.

Deals with a study which identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes and the major sources of uncertainties. Global scenarios of biodiversity change in terrestrial biomes and in freshwater ecosystems for the year 2100; Factors which contributed to biodiversity changes; Differences among biomes in the causes of future change in biodiversity.

Examines the mechanisms of primary succession following deglaciation at Glacier Bay, Alaska. Effect of initial nitrogen-fixing colonizers; Background on Glacier Bay; Change of environment through the first 200 years of succession; Seeds of early-successional species; Growth of naturally occurring spruce seedlings.

Barleygrass (Hordeum leporinum) from Australian low-P (phosphorus) soils and commercial barley (H. vulgare) with high fertilizer requirements were grown in solution culture at 3 levels of P supply. The high-P-adapted barley produced more biomass at all levels of P supply and was more responsive to added P in terms of rate of tillering, rate of leaf production, final leaf size, and therefore total shoot weight compared to barleygrass. In both species root: shoot ratio decreased in response to improved tissue P status, even at P levels where total biomass did not respond to P supply. Removal of endosperm reserves of barley reduced total biomass to a greater extent than it altered phosphate absorption rate, thus increasing tissue P status and making plants less responsive to added P. Similarly, barleygrass had a slower growth rate but a comparable P absorption rate to that of barley. Thus barleygrass also accumulated tissue P and was unresponsive to added P. All phosphorus chemical fractions increased in response to improved tissue P status, but to differing extents (inorganic-P > nucleic acid-P > lipid-F > ester-P), suggesting that all P fractions (particularly inorganic P) serve, in part, a storage function. Both barleygrass and barley without endosperm had higher concentrations of all P fractions (particularly inorganic P) than did unaltered barley, but this was due entirely to their higher P status (due to slow growth) rather than to any major difference in P metabolism between species. We conclude that slow growth is more important than interspecific differences in P metabolism, P absorption, or efficiency of P utilization in explaining the success of barleygrass and other low-P-adapted species on infertile soils. [ABSTRACT FROM AUTHOR]

Selected lipid properties were compared between populations of Carex aquatilis occupying adjacent hot spring and permafrost‐dominated sites in interior Alaska. Analyses were carried out on a variety of plant parts and results correlated with prevailing ambient temperature. Phospholipid concentrations were higher in plants from permafrost than from hot spring areas, even though there was no consistent interpopulation difference in total lipid content. The population differences in phospholipid content were greatest in those plant parts that experienced the greatest interpopulation temperature difference. Despite lower soil phosphorus availability, permafrost plants had higher total phosphorus concentrations, and a larger proportion of their phosphorus was contained in phospholipid than in hot spring plants. There was no consistent relationship between the proportion of various classes of phospholipids present and prevailing ambient temperature. Fatty acid chain length and degree of unsaturation of the phospholipid fraction were inversely correlated with temperature both between populations and among plant parts. No such relationship was found in the fraction containing neutral lipids. We suggest that the high tissue phosphorus content that characterizes northern plants may be necessary in part to maintain large quantities of phospholipid‐containing membrane. Increased amounts of membrane in turn may be a prerequisite for the high rates of membrane‐associated processes characteristic of plants in the cold subarctic environment. [ABSTRACT FROM AUTHOR]

Evaluates whether tundra sedges could take up amino acid nitrogen (N) in situ. Amino acids; N cycling; Wet meadow; Coring method; Injection methods; Nitrogen partitioning; Plant uptake.

Looks at an experiment to determine Physiological and growth responses of artic plants. Description of methods used in specific categories; Information on results; Discussions on findings in selected categories.

Determines the effects of climatic changes on the community and the ecosystem processes in moist tussock tundra near Toolik Lake, Alaska. Comparison between the long-term and short-term responses of the community to the climatic changes; Nutrient availability; Growth-form composition; Net primary production; Species richness.

Presents a study that examines the relative importance of phenotypic and genotypic factors in controlling nutrient resorption by sampling several mediterranean trees and shrubs growing in serpentine and nonserpentine soils in northern California. Tissue analysis; Decline in concentrations of nitrogen in mature leaves in spring; No significant differences among species adapted to poor versus rich soils.

Seasonal measurements of phosphorus (P) pools in the tussock-forming sedge Eriophorum vaginatum L. indicated low annual P uptake, but pronounced fluxes of P to growing biomass from below-ground stores in spring, and a return in autumn. Additions of 32P to tussocks in early spring and mid summer confirmed this deduction. Addition of 32P caused a rapid incorporation of about 10% of the labelled P in the tillers within a few days. Subsequent uptake was negligible, presumably because the 32P not immediately absorbed was fixed in the soil and unavailable to plants. This demonstrates that nutrient pulses were more important than steady-state mineralization in supporting P uptake by Eriophorum vaginatum. After the 32P additions, roots initially retained 60% of the total 32P taken up. During the following weeks, part of the 32P was transported slowly to stem bases and leaf sheaths, the principal storage organs. A lower proportion was transported to the leaf blades. We suggest that storage and recirculation of nutrients are the main sources of the annual nutrient supply to growth of E. vaginatum under normal field conditions, where P fixation in the soil and low rate of P diffusion towards the roots limit P uptake from soil except during periods of pulsed release. [ABSTRACT FROM AUTHOR]

Focuses on the responses of terrestrial ecosystems to the changing atmosphere. Discussion on environmental forcing factors; Assessment of organism responses to environmental factors; Consideration on the ecosystem processes.

The article focuses on storage which is a characteristic feature of most plants, particularly perennials. Storage is a major plant function, along with acquisition, transport, growth, defense, and reproduction. The author suggests criteria for defining storage in ecological and economic contexts in order to examine the costs and benefits of storage. He evaluates the evidence for, and ecological importance of, different types of storage. Storage in relation to vegetative growth and reproduction is discussed.

Studies the relationship between plant growth and resource balance in an economic perspective. Outline of the economic theory; Major complication in extrapolating from economics to ecology; Characteristics of higher plants that facilitate the evaluation of economic parameters; Presentation of the four economic theorems on profit maximization and optimal resource allocation.

Presents a study on the mineral nutrition of wild plants. Comparison of crop responses to nutrient stress to those of species that have evolved under more natural conditions; Elements that most commonly limit plant growth; Dependence of the rate of nutrient absorption by a root on nutrient supply to the root surface.

(1) Eight years after abandonment, mean total cover of native vascular plants on gravel pads in arctic Alaska was 2.7%, and mean number of species per site was 4.6. (2) Five of the nine most important colonizing species were legumes; all nine were species commonly associated with riparian. gravel bars. (3) Distance from riparian seed sources explained 25% of the variance in cover of native species and 35% of the variance in species richness. Legumes were more restricted to sites near seed sources than were non-legumes. (4) The low cover and diversity of native plants on abandoned gravel pads were attributed to a combination of dispersal limitation, lack of water for germination, and slow growth due to limited availability of mineral nutrients. [ABSTRACT FROM AUTHOR]

(1) The effects of water and nutrient availability on germination, survival and growth of Salix alaxensis on an abandoned gravel pad (construction site) in arctic Alaska were examined. (2) Germination of S. alaxensis was strongly limited by moisture availability. Watering or surface addition of stones in the field enhanced germination. The addition of fertilizer in pots reduced germination. Seeds failed to germinate at water potentials below - 0.2 MPa. (3) The availability of water and nutrients in the gravel pad soil did not limit the survival of established seedlings of S. alaxensis. (4) The addition of NPK fertilizer increased growth of transplanted seedlings to the end of the second growing season. (5) Transplanting seedlings of S. alaxensis onto abandoned gravel pads would be a practical method of site restoration when a specific need warranted the expanse. [ABSTRACT FROM AUTHOR]

(I) Presence or absence of buried seed was the major factor governing natural revegetation of a bulldozed disturbance in Alaskan tusseck tundra. The viable buried seed pool contained 97% Eriophorum vaginatum and Carex bigelowii seed and was restricted io organic soil horizons. Consequently. disturbed organic soils reached a final seedling density of 250 seedlings m&sup-2; (primarily Carex and Eriophorum)4 years after disturbance. whereas mineral soils which were colonized by current seed deposition had only 30 seedlings m&sup-2; including many grasses. (2) Fertilization enhanced the growth of grass and 2-4-year-old Corex seedlings four- to ten-fold but had no significant effect upon Eriophorum seedling growth. Growth was not significantly affected by presencc of aircady established seedlings and did not differ between substrates. except ror grasses which grew more rapidly on mineral than organic soils. (3) Seedling mortality during the first 2 years after germination was low (43% in triophorum. 27% in grass. and 13% in Carex) and did not differ between organic and mineral substrates. Mortality of 1- and 2-year-old seedlings was concentrated during the growing season, but mortality of larger seedlings was primarily a consequence of winter grazing. Mortality was increased by lertilization. (4) The greater vascular plant biomass and cover on organic than mineral soils was due primarily to recruitment from the buried seed pool. The increase in hiomass and cover with fertiiiiation was a consequence of a stimulation of growth by grass and Carex. (5) We recommend stockpiling and re-utilizing soil organic matter, supplemented under certain conditions by Fertilization and sowing of seeds, as a mechanism of enhancing natural community restoration or arctic tussock tundra following man-made disturbances. [ABSTRACT FROM AUTHOR]

(1) Soil characteristics and vegetation were studied in vehicle tracks and adjacent undisturbed tundra along local moisture gradients at four tundra sites in northern Alaska. Vehicle tracks generally had 2 °C higher soil temperatures, deeper thaw, and higher concentrations of available soil phosphate than adjacent undisturbed tundra, but did not differ consistently from controls in soil bulk density, volumetric moisture content, pH, or soil organic content. (2) Vegetation in vehicle tracks had fewer species than controls, reflecting decreased abundance of shrubs, particularly evergreens, and increased dominance by a few species of graminoids. (3) Wet and mesic tracks exhibited a 2- to 15-fold increase in above-ground standing crop of nitrogen and phosphorus as a result of increased leaf nutrient concentrations and increased leaf biomass of graminoids, a consequence of increases in both shoot density and shoot weight. (4) We reject our original hypothesis that the known temperature effects upon root growth, nutrient absorption, and organic matter mineralization account for the increased standing crop of biomass and nutrients in vehicle trails. We conclude that other factors, perhaps related to soil water and nutrient movement, are in large part responsible for the increased nutrient status and production of vehicle tracks and exert an important control over growth in undisturbed tundra. [ABSTRACT FROM AUTHOR]

(1} Succession on an organic tundra soil in interior Alaska was monitored for ten growing seasons following removal of vegetation. (2) Exotic grasses sown following disturbance became established in the first growing season, decreased in density after 3 yr. and were virtually eliminated after 5 yr. Fertilization did not affect initial density or long-term survival of exotic species, but did increase shoot density of native species 3 yr following disturbance. (3) Native sedges established on the disturbed site in 5–10 yr, producing an above-ground biomass equal to that in undisturbed tundra. (4) A procedure is outlined whereby the growth and reproduction of Eriophorum vaginatum can he manipulated by fertilization to revegetate disturbances using plains in adjacent undisturbed tundra (rather than harvested seed) as the seed Source. [ABSTRACT FROM AUTHOR]

Reports that field-collected roots of Eriophorum vaginatum, an arctic sedge, rapidly absorb free amino acids, accounting for at least 60 percent of the nitrogen absorbed by this species in the field. Seasonal average concentration of ammonium and free amino acids in tussock tundra and kinetics of uptake; Final biomass, nitrogen accumulation during the experiment; Bacterial density and pH of nutrient solutions 24h after replenishment; More.