Knut Rydgren

Høgskulen på Vestlandet | HVL

Ecological theory predicts the strongest ecosystem effects of herbivory when dominant and ecologically important species are consumed. Bilberry, Vaccinium myrtillus, is such a key plant species, attractive to many other species in the boreal forests, for example ungulate and invertebrate herbivores. Large herbivores may remove substantial biomass a...

Since alluvial meadows of river valleys of the Cnidion dubii are protected by the EU Habitats Directive, reconciling farmers’ demands for forage quality with the objective of maintaining them in good conservation status is an important issue in grassland research. In a long-term experiment from 2010 to 2018, we investigated the impact of fertilizin...

Wooded hay meadows provide livestock fodder in the form of both foliage from pollarded trees and hay from the understorey, and can be part of an environmentally friendly agroforestry system. However, trees may also have a negative effect on fodder production. Such trade-offs between productivity and sustainability in farming are poorly understood,...

In the last 50–60 years, agricultural intensification and later urban development have threatened the rare and valuable gully landscape formed on marine clay. We studied landscape changes in eastern Akershus county in south-east Norway, which has one of the world’s largest concentrations of marine gullies. Interpretation of aerial photos showed tha...

Functional traits are linked to ecosystem processes and services and therefore relevant in recovery assessment. However, traits of bryophytes and lichens, important components of many ecosystems, have received less attention than those of vascular plants. We explored the use of functional traits of multiple important organism groups in recovery ass...

The globally increasing pace of ecosystem degradation makes it necessary to develop efficient restoration programmes. A reliable tool for estimation of the remaining time to recovery is an important component of such a programme. In this study, we explore the performance of the novel, ordination regression-based approach (ORBA) for prediction of ti...

Plant species of semi-natural grasslands are threatened by several simultaneous global change drivers, most notably land-use and climate change. In this study, we explore spatiotemporal variation and changes in deterministic (λ) and stochastic population growth rates (λs), and the underlying vital rates of eight populations of Arnica montana at the...

1. Restoration of degraded ecosystems may take decades or even centuries. Accordingly, information about the current direction and speed of recovery provided by methods for predicting time to recovery may give important feedback to restoration schemes. While predictions of time to recovery have so far been based mostly upon change in species richne...

Sets of presence records used to model species’ distributions typically consist of observations collected opportunistically rather than systematically. As a result, sampling probability is geographically uneven, which may confound the model's characterization of the species’ distribution. Modelers frequently address sampling bias by manipulating tr...

Hydropower is expanding globally and is regarded a key measure for mitigating climate change, but it also results in major environmental degradation, both at local scale and more widely. We can learn lessons about how restoration can be used to alleviate these problems from failures and successes in countries with a long history of hydropower devel...

The history of restoration ecology in hydropower development context

1.Species composition is a vital attribute of any ecosystem. Accordingly, ecological restoration often has the original, or ‘natural’, species composition as its target. However, we still lack adequate methods for predicting the expected time to compositional recovery in restoration studies. 2.We describe and explore a new, ordination regression‐ba...

Changes in large herbivore distribution and abundance can have effects that potentially cascade throughout the trophic structure of an ecosystem. Little is known about these indirect trophic effects of ungulate herbivory, so the aim of this study was to investigate the role of red deer (Cervus elaphus) in determining the distribution and diversity...

In climate‐change ecology, simplistic research approaches may yield unrealistically simplistic answers to often more complicated problems. In particular, the complexity of vegetation responses to global climate change begs a better understanding of the impacts of concomitant changes in several climatic drivers, how these impacts vary across differe...

Link for Download (valid until 23 November 2017): https://authors.elsevier.com/a/1VqN-cA-ISCFO ______________ In highly productive farmlands, field margins could offer habitats and refuges for many plant and animal species. But species-rich field margins are rapidly declining due to field enlargements and unfavourable management practices. In Euro...

Poster about different rate of recovery of species and functional trait compositions during two decades of succession at four restored alpine spoil heaps

When alpine vegetation is actively restored by seeding, how is vegetation cover influenced by seeding treatments and soil conditions? (2) How does the cover of species differ when they are seeded in a mixture and how is their response influenced by soil conditions? (3) Do individual species perform better or worse in a mixture than when sown separa...

Inducible plant defense is a beneficial strategy for plants, which imply that plants should allocate resources from growth and reproduction to defense when herbivores attack. Plant ecologist has often studied defense responses in wild populations by biomass clipping experiments, whereas laboratory and greenhouse experiments in addition apply chemic...

Selective herbivory can influence both spatial and temporal vegetation heterogeneity. For example, many northern European populations of free-ranging ungulates have reached unprecedented levels, which can influence plant species turnover, long-term maintenance of biodiversity and the subsequent stability of boreal ecosystems. However, the mechanism...

Vegetation conveying culture and history. Documentation of a coastal cultural landscape in Sogn og Fjordane county The small farm, Årdalen, located in Selje municipality, Sogn og Fjordane county, is a farm of the pre-industrial agriculture period before modern technical equipment was taken into use at Western Norwegian farms in the 1950s. Årdalen w...

Wild ungulates are key determinants in shaping boreal plant communities, and may also affect ecosystem function through inducing the plant defence systems of key plant species. We examined whether winter browsing by deer could increase the resistance of bilberry (Vaccinium myrtillus). We used three indicators of induced bilberry defence: reduced gr...

The present loss of species-rich grasslands makes it vital to restore these valuable habitat types, including novel habitat variants such as road verges. Due to the lack of knowledge on long-term outcomes of restoration initiatives, well-designed studies comparing different restoration methods are needed. In this study, we examined fine-scale veget...

The Hoddevik-Liset area is one of 22 selected cultural landscapes in Norway. The valley of Hoddevik is strongly affected by drifting sand. An area of 20 ha with low production is owned by the community in the valley, and was earlier managed by all the farmers for hay making. During the1950s, hay harvest on the common fields came to an end, and ther...

The present loss of species-rich grasslands makes it vital to restore these valuable habitat types, including novel habitat variants such as road verges. Due to the lack of knowledge on long-term outcomes of restoration initiatives, well-designed studies comparing different restoration methods are needed. In this study, we examined fine-scale veget...

QuestionsHow does the understorey plant community in a boreal forest respond to variations in red deer herbivory intensity? Do the conclusions depend on the organizational level (taxon, growth form or functional trait) used for the analyses, and does red deer herbivory create more winners or losers?LocationSvanøy, western Norway.Methods We modelled...

Spoil heaps are the visible footprint of hydropower production, particularly in vulnerable alpine environments. Speeding up vegetation development by seeding commercial grass species has been a common restoration practice for the last 50 years, but we lack information on whether seeded species decline and allow native plant cover to develop. We vis...

The Storegga tsunami, triggered ~8150 yr ago by one of the largest submarine slides on Earth, flooded margins of the North Sea and the Norwegian Sea that were occupied by Mesolithic peoples. Sand deposits of Storegga age overlie the remains of coastal settlements in Norway and Scotland. The resulting casualties, however, depend on the season when t...

QuestionsHow do various grassland restoration methods (hay transfer from local or distant donors, seed sowing or natural regeneration) perform in restoration of species-rich, semi-natural grasslands? Are any of the donors particularly well suited as reference vegetation? Do bare soil treatments give better results than treatments where the soil is...

QuestionsWhat are the most important factors explaining present-day variation in species composition in a glacier foreland? Does the rate of species compositional change in glacier forelands decelerate through primary succession? How do data set properties and analytic methods influence our understanding of glacier foreland successional dynamics?Lo...

Traditional, herb-rich hay meadows are a rare, but a highly-prized, type of semi-natural vegetation. There has been much interest both in preserving such meadows and in attempting to establish similar types in the last 20 years. In this paper we present the results from a three-year experiment of meadow establishment. Our aim was to examine differe...

Disturbance in the form of different management regimes affects established vegetation, but how the same management affects the corresponding seed banks is poorly understood. We used the seedling emergence method to investigate how present and previous management intensity impacts the dynamics of established vegetation and corresponding seed bank i...

Spoil heaps of surplus rock from hydropower tunnel construction negatively impact alpine landscapes unless restored. Such spoil heaps have been created for more than 100 years, but we still lack knowledge about the relative importance of compensatory mitigation (seeding and fertilization), spoil‐heap construction method, local environmental factors...

Premise of the study: The perennial feather moss Hylocomium splendens is one of the most widely distributed and common bryophytes in the Northern Hemisphere and has, because of its capacity to grow under a wide range of environmental conditions, been used as a biomonitor for atmospheric metal deposition in Europe. Methods and results: We present...

Whether road verge vegetation can be manipulated to resemble traditionally managed grassland has been much debated. This short-term study compared management effects on road verge and pasture vegetation in western Norway. We quantified vegetation change and explored whether it occurred along underlying environmental gradients. We found management-r...

The liverwort Trichocolea tomentella is known from 65 localities in southern Norway. Almost half of these are in Hordaland county in Western Norway. T. tomentella has been observed at many localities (42%) in the last decade. On the other hand it has not been observed at 23% of the previously known localities after 1950, although a complete re-surv...

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,...

The species composition and the depth distribution of the soil propagule banks of bryophytes and vascular plants from three different soil layers in a boreal old-growth spruce forest in SE Norway were studied using the emergence method. A total of 34 taxa germinated with a predominance of ferns and mosses. The frequency of the different species exh...

Human disturbances in the alpine region can have long-lasting ecosystem effects because biological recovery in harsh environments proceeds slowly. As a by-product of the exploitation of hydroelectricity, surplus masses from tunnel excavations are deposited as spoil heaps in the alpine landscape. The typical management goal for such spoil heaps is t...

Alien species can have a considerable impact on native species and ecosystems. Garden-centres generally import and sell many different alien plant species. We studied the species assortment from ten garden centres distributed from southern to northern Norway, and categorized the species into three groups: native, 'imported' and 'not in Lids flora'...

This study focused on a suite of vascular plant species (six herbs and two grasses) common to traditionally managed, species-rich grasslands in Western Norway. We assessed the suitability of two species transfer methods (seed sowing and soil seed bank) for restoration of species-rich grassland on a newly established road verge. We compared the spec...

Semi-natural grasslands and their species and populations are declining rapidly throughout Europe, bringing about a need for successful vegetation recreation methods. To maintain biodiversity and ecological services of semi-natural grasslands, we need more knowledge on the relative performance of different recreation methods. In a replicated experi...

Abandonment and fragmentation are the primary causes of decline for many light-demanding grassland species in the modern agricultural landscape. In order to maintain a flora rich in such species, design of management practices based upon knowledge of life-history consequences following management shifts is essential. In this study, we investigated...

1. Sex ratios in unisexual bryophytes are most often female biased, whereas male-biased sex ratios predominate in unisexual seed plants. This ‘bryophyte paradox’, i.e. that sex ratios are biased in favour of the sex associated with the highest reproductive costs, has remained unexplained. 2. Analysis of sex-ratio patterns via the influence of sex d...

In this study the variation in species richness, species composition and habitat specificity is examined among all land patches in a 43-ha landscape in W Norway, created by traditional agricultural management practices, with particular focus on the distribution of semi-natural grassland species, i.e. species known to be typical of species-rich semi...

Habitat specificity analysis provides a tool for partitioning landscape species diversity on landscape elements by separating patches with many rare specialist species from patches with the same number of species, all of which are common generalists and thus provide information of relevance to conservation goals at regional and national levels. Our...

Plants of low stature may benefit from the presence of large herbivores through removal of tall competitive neighbours and increased light availability. Accordingly, removal of grazers has been predicted to disfavour small species. In addition to this indirect beneficial effect, the population dynamics of plants is strongly influenced by variation...

Dense ungulate populations in forest accompanied by high grazing intensities have the potential to affect plant population dynamics, and such herbivory effects on populations are hypothesised to differ along environmental gradients. We investigated red deer grazing and resource interaction effects on the performance and dynamics of the functionally...

Road verges have been proposed as refuges for vulnerable grassland species in the modern, changing landscape, but little comparative knowledge exists on how management regimes affect population dynamics of such species. We compared the effects of various management regimes on the population dynamics of Pimpinella saxifraga in road verges and pastur...

Vegetation science has relied on untested paradigms relating to the shape of species response curves along environmental gradients. To advance in this field, we used the HOF approach to model response curves for 112 plant species along six environmental gradients and three ecoclines (as represented by DCA ordination axes) in SE Norwegian swamp fore...

We studied revegetation patterns after experimental fine-scale disturbance (e.g. uprooting) in an old-growth Picea abies forest in southeastern Norway. An experimental severity gradient was established by manipulation of the depth of soil disturbance; two types of disturbed areas were used. Species recovery was recorded in the disturbed patches in...

Question: What is the relative importance of environmental gradients and surface microtopography (variation in vertical level within sampling units) for fine-scale plant species richness in Picea abies swamp forests?Location: 11 swamp forests in SE Norway.Methods: We recorded species richness (number of species of vascular plants, mosses, Sphagnum...

Bryophytes may be more appropriate than vascular plants for testing hypotheses relating to plant reproductive biology due to their relatively simple structure. Nevertheless, they have rarely been used for this purpose, and remain poorly known with respect to reproductive biology. It is, for instance, still not known if bryophytes generally exhibit...

The vegetation of herb-rich spruce forests in three localities in Brønnøy municipality, W Nordland, N Norway, has been analysed using 120 sample plots, each 25 m2, distributed by a restricted random method. In connection with every sample plot a set of ecological variables have been measured. The most important gradients for the differentiation of...

Two inshore and four shore localitites of Ligusticum scoticum in C Norway were studied regarding the growth and reproductive characteristics of the L. scoticum individuals, and the vegetation and ecology of the sites. L. scoticum showed a similar growth and reproductive characteristics at the inshore and the shore localities. The inshore localities...

The relationship between vegetation and environmental variables has been studied in 100 sample plots, each 0.25 m2, in old-growth spruce forest at Høgkollen, ØOstmarka Nature Reserve, SE Norway. Each sample plot was supplied with measurements of 13 environmental and 5 biotic variables. Parallel application of three ordination techniques, PCA, DCA a...

Questions: Which environmental and management factors determine plant species composition in semi-natural grasslands within a local study area? Are vegetation and explanatory factors scale-dependent?Location: Semi-natural grasslands in Lærdal, Sognog Fjordane County, western Norway.Methods: We recorded plant species composition and explanatory vari...

Many studies of land-cover and structural changes in cultural landscapes have used historical maps as a source for information about past land-cover. All transformations of historical maps onto modern coordinate systems are however burdened with difficulties when it comes to accuracy. We show that a detailed land survey of the present landscape may...

Bryophytes have increased in abundance in northern regions, and climate changes have been proposed to account for this change. However, changes in the population dynamics of microtine rodents may also contribute to changes in bryophyte abundance. New evidence indicates a tendency for microtine rodent population oscillations to change from periodici...

Summary 1. Plant ecologists have long since realized that the persistence of many facultative biennial plants depends upon disturbance. However, we still have a limited knowledge of the population-level effects of disturbance, and the connection between adult and seed bank dynamics. 2. Using data from a 3-year demographic study combined with experi...

Female reproductive success in the unisexual perennial clonal moss Hylocomium splendens was examined by recording, if the segment was reproductive [produced sporophyte(s)] or not, together with several distance-to-male and male density variables, and segment size. This was done for every female segment in a population over a 5 year study period. A...

The allozyme haplotype was determined for 157 ramets of the unisexual, perennial, clonal moss Hylocomium splendens within five 10×10 cm plots, which had been the subject of demographic studies over a 5-yr period. In addition, 25 shoots were analyzed from outside the plots and from four neighbouring patches. Only four haplotypes were encountered wit...

The impact on the performance of dwarf shrub Vaccinium myrtillus L. (bilberry) subjected to differing natural intensities of grazing by Cervus elaphus L. (red deer) was examined in a mature Scandinavian pine forest, on Svanoy, an island on the western coast of Norway. All the study sites were in forest where bilberry dominated the forest floor and...

We studied the resilience of southeastern Norwegian old-growth Picea abies forest floor vegetation to experimental disturbance. Five treatments, differing in depth of removal of vegetation and soil layers and making up a gradient in disturbance severity, and three controls, were replicated 10 times. The experiment was analyzed with respect to the f...

1We studied demography and population dynamics of the sympatric perennial herbs Drosera anglica and D. rotundifolia on a boreal bog in SE Norway. Dry mass of 2872 D. anglica plants and 2467 D. rotundifolia plants (estimated from field morphological measurements) was used to classify plants into five species-specific size classes. Demographic change...

Previous studies point to biogeographic (i:e., evolutionary and demographic) and ecological (i.e., habitat differentiation and disturbance) processes as the most important causes of spatial variation in species richness and species composition (occurrence and abundance). We examined patterns of variation in vascular plant and bryophyte species comp...

Bryophytes may be more appropriate than vascular plants for testing hypotheses relating to plant reproductive biology due to their relatively simple structure. Nevertheless, they have rarely been used for this purpose, and remain poorly known with respect to reproductive biology. It is, for instance, still not known if bryophytes generally exhibit...

We studied four south-facing and three north-facing boreal spruce forest stands (ca. 0.1 ha each) in SE Norway with the aim of testing the hypothesis that former logging has long-term effects on boreal forest-floor vegetation. The stand series comprised unlogged natural forests and forests that were selectively or clear cut 60–70 years prior to our...

Production in the field layer of a wooded hay meadow in Sogn, Western Norway, was studied by comparing two sites, one in active use and the other abandoned since 1975. We also studied how production in the field layer varied with the composition of the vegetation and the influence of trees, and the extent to which production from the trees (foliage...

The sex ratio and factors that affect sporophyte production were studied by following one population of the clonal moss Hylocomium splendens growing on top of a boulder in a S.E. Norwegian boreal spruce forest valley for 5 years. Sex of ca 75% of all segments recorded during the study period could be determined from records of occurrence of sporoph...

Matrix population models have, for more than 20 years, been popular analytical tools in studies of vascular plants, but have until recently not been applied to bryophytes. In this review we explain the rationale behind the simplest matrix modelling approaches, and show how to proceed when using such models in studies of bryophytes. Focussing on the...

A richly sporophyte-producing population of the dioecious perennial clonal moss Hylocomium splendens was followed for five years in order to investigate the long-term costs of sporophyte production. Female mature segments were divided into two subpopulations: sporophyte producing and reference without sporophytes. Ultimate (long-term) population gr...

1. The boreal forest is subject to disturbance but the effects on population dynamics are poorly understood. We investigated how a prominent species of the forest floor, the clonal moss Hylocomium splendens, responded to different types of fine-scale disturbance. 2. Canopy gap formation was simulated in H. splendens populations by removing 50␘f the...

The importance of light intensity and shoot density for sporophyte production in the dioecious moss Hylocomium splendens was addressed by following populations subjected to two types of fins-scale disturbance treatments and an unmanipulated reference ("REF") for 3 years. The two treatments were: reduction of the bryophyte layer to approximately 50%...

Swamp forests dominated by Picea abies contribute strongly to the total plant species richness in boreal forests. The variation in species composition and environmental conditions in swamp forests and the relationships of swamp forests to mires and upland forest, have, however, remained insufficiently known. From a preliminary survey of 57 spruce s...

A model for tree influence on understorey vegetation in boreal spruce forests is developed according to the principles of ecological field theory. Single-tree influence at a point in space was modelled as the product of two factors: (1) the size (diameter at breast height) of the tree relative to that of the largest tree encountered in the area; a...

We studied demographic effects of density reduction by fine-scale disturbance on the perennial clonal moss species Hylocomium splendens in a field experiment in an SE Norwegian boreal forest. Half the bryophyte cover was removed from 10 plots in a fine-scaled pattern. Size of ca 800 mature segments (estimated from morphological field measurements)...