Gunnar Austrheim

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• Professor
• Professor at Norwegian University of Science and Technology

Trophic interactions regulate populations, but anthropogenic processes influence primary productivity and consumption by both herbivore and carnivore species. Trophic ecology studies often focus on natural systems such as protected areas, even though livestock globally comprise the majority of terrestrial vertebrate biomass. Here we explore spatial...

In Norway, cattle (Bos taurus) are released to large areas of boreal forest for summer grazing. To determine to what degree this practice challenges timber production and wildlife management, we need a better understanding of basic cattle ecology. What do cattle, typical grazers, feed on in a habitat typically used by browsers? We determined cattle...

Large parts of the boreal forest ecosystems have been greatly affected by human use, and the current timber-oriented forest management practice that dominates boreal forests is proven to cause biodiversity and ecosystem services declines. These negative effects are mitigated in various ways, including in-situ measures implemented upon harvest. The...

Due to climate change, treelines are moving to higher elevations and latitudes. The estimation of biomass of trees and shrubs advancing into alpine areas is necessary for carbon reporting. Remotely sensed (RS) data have previously been utilised extensively for the estimation of forest variables such as tree height, volume, basal area, and abovegrou...

The moose Alces alces is the largest herbivore in the boreal forest biome, where it can have dramatic impacts on ecosystem structure and dynamics. Despite the importance of the boreal forest biome in global carbon cycling, the impacts of moose have only been studied in disparate regional exclosure experiments, leading to calls for common analyses a...

Moose (Alces alces) is a large herbivore that can mediate boreal forest regeneration after timber harvest through selective browsing of tree species. Despite increasing evidence of moose browsing influence on tree growth in early successional forests, climate effects due to changes in carbon sequestration rates and biophysical factors such as albed...

Land-use and land-cover change strongly affect biodiversity patterns and are assumed to be growing threats in the future. Particularly increasing urbanisation may affect species turnover and functional composition of biological communities. This study aimed to assess the characteristics of land-cover change in a medium-sized urban municipality from...

The panel-based assessment of ecosystem condition (PAEC) is an evidence-based ap-proach to assess the condition of Norwegian ecosystems. The assessment is carried out by an expert panel with broad expertise in the ecosystems to be assessed and is inspired by approaches used in international assessments such as IPCC and IPBES. The assessment follows...

Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperat...

Treelines are expected to expand into alpine ecosystems with global warming, but herbivory may delay this expansion. This study quantifies long-term effects of temporally varying sheep densities on birch recruitment and growth in the treeline ecotone. We examined treeline ecotone successional trajectories and legacy effects in a replicated experime...

Abstract Herbivores shape vegetation by suppressing certain plant species while benefitting others. By thus modifying plant species functional composition, herbivores affect carbon cycling, albedo, vegetation structure and species' interactions. These effects have been suggested to be able to counteract the effects of increasing temperatures on veg...

Large herbivores are often classed as ecosystem engineers, and when they become scarce or overabundant, this can alter ecosystem states and influence climate forcing potentials. This realization has spurred a call to integrate large herbivores in earth system models. However, we lack a good understanding of their net effects on climate forcing, inc...

Urbanisation is expected to function as a filter for plant species by changing the physiochemical environment, causing species turnover along an urbanisation gradient. Analyses of the functional traits of species characteristic of different urbanisation levels allow for comparisons across studies, irrespective of exact species composition. This stu...

1. The availability and quantity of observational species occurrence records have greatly increased due to technological advancements and the rise of online portals, such as the Global Biodiversity Information Facility (GBIF), coalescing occurrence records from multiple datasets. It is well‐established that such records are biased in time, space an...

Large herbivores play a key role in temperate and boreal forest ecosystems. Cervidae (deer) population densities and community structure have undergone drastic changes in many parts of the world over the past decades, often with deer populations increasing. Many studies show impacts of Cervidae on multiple ecosystem properties, including vegetation...

Herbivory has potential to modify vegetation responses to climatic changes. However, climate and herbivory also affect each other, and rarely work in isolation from other ecological factors, such as plant–plant competition. Thus, it is challenging to predict the extent to which herbivory can counteract, amplify, or interact with climate impacts on...

Urbanisation has strong effects on biodiversity patterns, but impacts vary among species groups and across spatial scales. From a local biodiversity management perspective, a more general understanding of species richness across taxonomic groups is required. This study aims to investigate how fine-scale land-cover variables influence species richne...

Aim The treeline is an obvious ecotone between forest and tundra ecosystems. Climatic warming is expected to lead to the treeline advancing, although in many cases this has not been observed. This is most likely because other factors can also influence treeline dynamics, notably land use and herbivory in European treelines. In this study, the roles...

Large vertebrate herbivores are ubiquitous and increasingly numerous in boreal forests where they are known to influence ecosystems in many ways. However, separating the direct effects of herbivores from their indirect effects on plant communities via forest structural changes and microclimate remains unexplored, limiting the predictability of herb...

Social and economic development need to be within safe environmental boundaries, but the thresholds for human impact and resource use are difficult to define which often results in degraded nature. In Norway, grassland and forest ecosystems are vulnerable, and scenario studies predict that biodiversity will be traded off against increased harvest o...

Aim Biodiversity databases are valuable resources for understanding plant species distributions and dynamics, but they may insufficiently represent the actual geographic distribution and climatic niches of species. Here we propose and test a method to assess sampling coverage of species distribution in biodiversity databases in geographic and clima...

Herbivores have important impacts on ecological and ecosystem dynamics. Population density and species composition are both important determinants of these impacts. Large herbivore communities are shifting in many parts of the world driven by changes in livestock management and exploitation of wild populations. In this study, we analyse changes in...

Large herbivores can shape young forest stands and determine the successional trajectory of forested ecosystems by selectively browsing palatable species at the sapling stage. Moose (Alces alces) is the dominant vertebrate herbivore in Fennoscandian boreal forests, and high population densities have raised concerns about potential negative effects...

Large herbivores are capable of modifying entire ecosystems with a combination of direct (for example browsing/grazing, trampling, defecation) and indirect (for example affecting plant species composition that then alters soil properties) effects. With many ungulate populations increasing across the northern hemisphere it is important to develop a...

Priorities for future sustainable development within Europe and Central Asia are formulated in visions by governments and societal actors. Integrated scenario and modelling studies enable the assessment of impacts on nature, nature’s contributions to people, and a good quality of life resulting from these priorities, and help to co-design and co-de...

Herbivores are often drivers of ecosystem states and dynamics and in many situations are managed either as livestock or through controlled or exploitative hunting of wild populations. Changes in herbivore density can affect the composition of plant communities. Management of herbivore densities could therefore be regulated to benefit plant species...

Domestic livestock drives ecosystem changes in many of the world's mountain regions, and can be the dominant influence on soil, habitat and wildlife dynamics. Grazing impacts on ecosystem services (ES) vary according to densities of sheep, but an ES framework accounting for these is lacking. We devised an experiment to evaluate synergies and trade-...

Sheep grazing is an important part of agriculture in the North Atlantic region, defined here as the Faroe Islands, Greenland, Iceland, Norway and Scotland. This process has played a key role in shaping the landscape and biodiversity of the region, sometimes with major environmental consequences, and has also been instrumental in the development of...

Large herbivore consumption of forage is known to affect vegetation composition and thereby ecosystem functions. It is thus important to understand how diet composition arises as a mixture of individual variation in preferences and environmental drivers of availability, but few studies have quantified both. Based on 10 years of data on diet composi...

Data used to model sheep diet. (PDF)

Abstract Aim Previous research on how climatic niches vary across species ranges has focused on a limited number of species, mostly invasive, and has not, to date, been very conclusive. Here we assess the degree of niche conservatism between distant populations of native alpine plant species that have been separated for thousands of years. Locatio...

Vegetation data constitute an important knowledge base for research and management, but the sharing of data has been difficult to realize for various reasons. This report reviews important legal principles for data sharing and collaboration, as well as possible scientific and technical standards and solutions to facilitate data exchange. In order t...

Treelines differentiate vastly contrasting ecosystems: open tundra from closed forest. Treeline advance has implications for the climate system due to the impact of the transition from tundra to forest ecosystem on carbon (C) storage and albedo. Treeline advance has been seen to increase above-ground C stocks as low vegetation is replaced with tree...

Recent debate on whether the climatic niche of species is conserved or not in a context of climate change has generally focused either solely on invasive species or on a relatively limited number of native species. However, invasive species may not be optimal for assessing the likelihood of niche conservatism because the time since geographical sep...

Treelines differentiate vastly contrasting ecosystems: open tundra from closed forest. Treeline advance has implications for the climate system due to the impact of the transition from tundra to forest ecosystem on carbon (C) storage and albedo. Treeline advance has been seen to increase above-ground C stocks as low vegetation is replaced with tree...

Herbivores may increase or decrease aboveground plant productivity depending on factors such as herbivore density and habitat productivity. The grazing optimization hypothesis predicts a peak in plant production at intermediate herbivore densities, but has rarely been tested experimentally in an alpine field setting. In an experimental design with...

Background/Question/Methods Climate warming has been linked to elevational advance of treelines, species and communities and an increase in species richness in mountain vegetation. However, grazing can also have substantial impacts on mountain vegetation, and alpine areas of Norway have a long history of livestock grazing. Here we use a long-term...

Ecosystem stores of carbon are a key component in the global carbon cycle. Many studies have examined the impact of climate change on ecosystem carbon storage, but few have investigated the impact of land-use change and herbivory. However, land-use change is a major aspect of environmental change, and livestock grazing is the most extensive land us...

Understanding the responses of ecological communities to perturbation is a key challenge within contemporary ecology research. In this study we seek to separate specific community responses from general community responses of plant communities to exclusion of large cervid herbivores. Cervid herbivory and forestry are the main drivers of vegetation...

Habitat selection is a density-dependent process, but little is known regarding how this relationship may vary across different temporal scales. Over long time scales, grazing shapes the structure, diversity and functioning of terrestrial ecosystems, and grazing-induced changes in forage production over time are likely to affect the level of densit...

Large herbivores are important drivers in eco-systems worldwide. Changes in herbivore densities are predicted to especially affect herbs that are strongly preferred by herbivores. The persistence of herbs could be challenged by enhanced grazing, but also grazing cessation may affect persistence, especially for prostrate herbs, which might be out-co...

Quantification of vegetation cover based on fossil pollen assemblages is valuable for proper assessment of past landscape dynamics. In the present investigation, the past vegetation cover around a pre-historic iron production site in the Budalen valley in central Norway was quantified using direction of vegetation change models. A set of fixed rule...

Browsing by cervids plays a key role in structuring forest ecosystems and dynamics. Many boreal forest systems are managed for timber resources, and at the same time the wild cervid populations are also harvested. Thus, the determination of sustainable densities of cervids for the purpose of forest and game management is challenging. In this study...

The widespread expansion of shrubs into arctic and alpine regions has frequently been linked to climatic warming, but herbivory can play a role in addition to, or in interaction with, climate. Willow (Salix spp.) shrubs are important constituents of alpine ecosystems, influencing community structure and providing habitat and forage for many species...

One of the clearest predictions from the IPCC is that we can expect much less snow cover due to global warming in the 21st century, especially in the lower alpine areas. In alpine ecosystems, snow accumulation in depressions gives rise to distinct snow‐bed vegetation types, assumed to play a key role in ecosystem function. A delayed plant phenology...

Alpine ecosystems, representing a large proportion of the land area in Europe, are under pressure from changes in climate and land-use. This may also impact the quality of drainage waters. Here, we assess effects of plant communities (snowbed, dwarf shrub heath, and tall herb meadow) on concentrations of dissolved organic carbon and nitrogen (DOC a...

1. Species richness of plants generally decreases along elevational gradients or peaks at intermediate elevations. Land use including grazing by wild and domestic herbivores also affects plant communities and diversity, but how grazing affects plant diversity along elevational gradients is less clear. 2. Using a field experiment along an elevationa...

Recent studies from mountainous areas of small spatial extent (<2,500 km2) suggest that fine-grained thermal variability over tens or hundreds of metres exceeds much of the climate warming expected for the coming decades. Such variability in temperature provides buffering to mitigate climate-change impacts. Is this local spatial buffering restricte...

Sallow (Salix caprea L.) and rowan (Sorbus aucuparia L.) constitute small proportions of the deciduous tree volume in Scandinavia, but are highly preferred winter forage for moose and red deer, which occur at historically high densities. Thus, a possible decline of these tree species has been indicated. Against this background, we have reviewed the...

Temporal variation both due to density dependent and density independent processes affect performance and vital rates in large herbivores. Annual fluctuations in climate affect foraging conditions and thus body growth of large herbivores during the short growing season in alpine habitats. Also, high animal densities on summer ranges may increase co...

Forests are often managed for the timber resources they contain, but they also provide habitat for large and commonly increasing populations of cervids. Interactions between forest management and cervid browsing are thus of importance, but are rarely investigated except within isolated exclosure studies. In this study we use a regional network of e...

Mountain areas of Europe have been managed by humans for a long time, leading to a prevalence of semi-natural habitats in mountain landscapes today. These landscapes contain both natural and cultural heritage; however, natural and cultural heritage are rarely considered together when valuing landscapes and developing management plans in protected a...

Humans have used resources in mountain landscapes for thousands of years, but the intensity and continuity of different land uses and the corresponding landscape changes are not well understood. This study examined long-term interactions between land use and landscapes in Budalen, central Norway, by using a multidisciplinary approach. Palaeoecologi...

Density dependent processes affecting foraging strategies may in turn influence vital rates and population regulation in large herbivores. Increased competition may lower both forage availability and quality, but whether the main activity constraint at high density is increased searching time or increased digestion time is poorly investigated. In a...

QuestionResources quality and quantity are both important determinants of habitat use for large herbivores. We aim to understand how these two variables vary throughout the growing season in sub-alpine grasslands. How do productivity and phenology (quality) of different plant communities within a landscape vary over time? Do productivity and phenol...

Understanding diet selection is important since diet determines energy intake and therefore growth of ungulate populations. Yet very few studies have reported annual variation in diet. Density-dependent diet choice by large herbivores has been reported several times, but these studies are typically either short-term or they lack replication of the...

QuestionA warming climate has been linked to changes in the distribution of many species, yet the interactions between climate and other environmental drivers are relatively poorly understood. Mountain regions are expected to be particularly at risk in a warming climate, and in many upland regions land use has also changed dramatically over the pas...

Alpine ecosystems are generally nitrogen (N) limited with low rates of N mineralization. Herbivory may affect N cycling and N losses and thus long-term productivity of ecosystems. Using a controlled grazing experiment in a low-alpine region at Hol, southern Norway, with three density levels of sheep, we determined effects of grazing on in situ avai...

Question: A warming climate has been linked to changes in the distribution of many species, yet the interactions between climate and other environmental drivers are relatively poorly understood. Mountain regions are expected to be particularly at risk in a warming climate, and in many upland regions land use has also changed dramatically over the p...

Grazing in outlying fields has a long history and is important in local communities worldwide. During the last few decades, grazing pressure has both decreased and increased in alpine ecosystems, but little is known about the effects on soil carbon storage. As part of a sheep grazing experiment with three sheep stocking rates of no sheep (control),...

1. A warming climate has been linked to shifts in plant distribution and growth. The relationship between climate and growth is used to infer past climate conditions within dendrochronological studies. However, browsing may interact with climate to determine growth, yet the impact of large herbivores on tree-ring growth series is largely unknown....

Many rangelands around the world are degraded by severe overgrazing with resulting loss of nutrients and reduced productivity. However, grazing may also increase nutrient cycling and enhance ecosystem productivity. The aim of this study was to determine effects of grazing on availability of nitrogen (N), sources of N utilized by plants and cycling...

During recent decades, rough livestock grazing has decreased markedly on unimproved land (i.e. natural and semi-natural habitats) across most of Europe, whilst the number of wild cervids has increased. However, we still know little about the overall changes in the herbivore pressure and how herbivore regimes vary between biogeographic regions. We h...

An improved understanding of population-level consequences of grazing on plants can be facilitated by an assessment of grazing effects on all stages in the life-cycle. In this study, 6years of demographic data for three populations of the perennial herb Geranium sylvaticum were analysed. We examined the effects of sheep grazing (high sheep density,...

Many rangelands around the world are degraded by severe overgrazing with resulting loss of nutrients and reduced productivity. However, grazing may also increase nutrient cycling and enhance ecosystem productivity. The aim of this study was to determine effects of grazing on availability of nitrogen (N), sources of N utilized by plants and cycling...

Large herbivores are affecting a suite of plant traits in many ecosystems, including plant quality. At northern latitudes, the phenological development of plants over the growing season is also regarded crucial for plant quality. The relative role of grazing and seasonality for quality of different plant functional groups has not been quantified in...

Treelines are advancing on a global scale and encroaching upon alpine ecosystems. Browsing by vertebrate herbivores could affect treeline dynamics and forest expansion by limiting growth of trees. However, this has not been experimentally investigated, and due to a combination of herbivore behaviour and plant responses to herbivory, is unlikely to...

Aspen (Populus tremula L.) is associated with high biodiversity and provides high-quality forage for wild browsing herbivores in boreal and temperate ecosystems. The long-term persistence of aspen in many regions in Scandinavia has been questioned due to the historically high browsing levels. We here review the basic ecology, genetics and life hist...

Recruitment is critical for the maintenance of plant populations and community diversity, but sexual regeneration is considered to be infrequent in climatically harsh habitats such as subalpine grasslands. This study examines the importance of regeneration through seed for 16 sparse herb species, and we asked whether their populations are limited b...