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Lichen heaths are declining in abundance in alpine and Arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature and soil moisture on an alpine mountain area in southern Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ d−1 during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We predict that the thicker litter layer, the presence of soil shading and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and Arctic areas will lead to atmospheric heating, but it has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.

Lichen heaths are declining in abundance while shrubs are increasing their range in alpine and arctic areas due to climate change. This can have a large impact on the surface albedo of these areas. The aim of this article is to quantify the difference in albedo between lichen heaths and shrub-dominated vegetation and the variability within lichen heaths. Several environmental conditions that can influence the albedo measurements are considered. We measured the albedo of twenty lichen- and shrub-dominated plots on an alpine mountain area in southern Norway in the summer of 2018 with two radiometers using a paired plot design. With this design, we ensured similar weather conditions, aspects, and zenith angles between the paired lichen- and shrub-dominated plots. In addition, we collected patches of Cladonia stellaris and Flavocetraria nivalis to measure their albedo. The average difference in albedo between the lichen- and shrub-dominated plots is 0.124. The albedo of the lichen-dominated plots varies between 0.227 and 0.284, and that of the shrub-dominated plots varies between 0.115 and 0.148. This variation in albedo is explained by differences in aspect and vegetation composition. Further studies should focus on the consequences of this decrease in albedo for the microclimate in alpine and arctic areas.

Lichen heaths are declining in abundance in alpine and arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature, and soil moisture on an alpine mountain area in south Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths, but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ per day during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We hypothesize that the thicker litter layer, the presence of soil shading, and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and arctic areas will lead to atmospheric heating, but has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.

Geographic variations in air and soil temperatures are dependent on several biotic and abiotic factors. Air temperature has mostly been used to characterize thermal conditions for plant life, and studies of bioclimatic gradients. From a biological point of view, it is also essential to know to what extent soil temperature is coupled with air temperature. In this study, we have quantified the deviations between soil and air temperatures along gradients in latitude, altitude, and possible effects of the vegetation. Sixteen different temperature variables were estimated from 49 vegetation plots on 19 mountain summits along the high mountain range in Norway, ranging from 230 to 1780 m a.s.l., and from 59°N to 71°N. Soil and air temperature variables were estimated from the study plots during one year. All air and soil temperature variables were significantly correlated, but the rate of explanation was mostly relatively low (37.0–60.0%), except during the growing season. Start of the growing season, de...

Plant abundance and distribution patterns have mostly been explained in terms of air temperatures, yet a great deal of vascular plant biomass is located below ground. Winter soil temperatures, which are related to both air temperature and snow cover, may therefore be important determinants of species composition in alpine areas. Epigeic lichens, however, have no underground biomass, and they often dominate at sites that are inhospitable to vascular plants, such as those that experience sustained periods of sub-freezing temperatures. In this study, effects of several warm- and cold-season soil-temperature variables on individual plant and lichen species common to oligotrophic alpine heaths was investigated using linear regression and ordination. The differences in growing season length as measured by soil temperatures were compared. Warm season variables were found to have less influence than cold season variables on individual species abundances in these areas. Changes in winter snow cover depth and durat...

This journal is published under the terms of the Creative Commons Attribution 3.0 Unported License Grazing and trampling by the wide-ranging wild tundra reindeer may have major top down landscape effects by causing vegetation changes. Grazing, as the collective effect of eating, trampling, defecation, and urination, has been studied extensively. In contrast, trampling effects per se are rarely studied, and almost never quantified, even though considered very important. The main reason appears to be methodological; effects of trampling imprints are difficult to measure and quantify systematically. In particular, in winter reindeer may largely subsist on slow-growing ground lichens. They grow in habitats with little snow cover and extensive soil frost, and dry lichen may be particularly susceptible to trampling, generating a likely substantial forage loss.

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 d ...

Aim In recent decades species ranges have shifted upwards in elevation and northwards in latitude. These shifts are commonly interpreted as a response to recent climate warming. However, several alternative hypotheses have been proposed to explain the elevational shifts, including increased deposition of atmospheric nitrogen, changes in precipitation and dispersal limitation. We evaluate these hypotheses and attempt to identify the dominant drivers for the observed shifts in the upper range limits of alpine plant species. Location European mountains from Svalbard to the southern Alps. Methods We assembled data on observed shifts in the upper range limit of alpine plants over 40 to 100 years on 114 mountains. We related the observed shifts to recent changes in temperature and precipitation and to recent deposition of atmospheric nitrogen. Changes in traits and habitat preferences of species in the summit assemblages were used to evaluate the potential role of different drivers. Results Seventy per cent of the species that showed a detectable change in their upper range limits between surveys shifted their range limits upwards. The same species tend to move up on different mountains. There are, however, large differences between mountains in the proportion of species shifting upwards. This proportion is not found to be statistically related to local changes in temperature. Correspondingly, warmth-demanding species did not move upward more frequently than expected by chance. Snow-bed species have become more common on summits. Main conclusions Our data do not support the idea that climate warming is the dominant factor causing the observed range shifts of alpine plant species on European mountains: first, the amount of change in species assemblages on the summits studied is not related statistically to the amount of climate warming; second, those species that have moved upwards are not particularly warmth demanding. publishedVersion

Background: Theories regarding patterns of species richness often focus on single factors such as stress, productivity and disturbance, but these have recently been challenged. Vascular plant species richness is also frequently used as a surrogate for richness in other species groups, but species richness relationships have rarely been studied in alpine areas.Aims: To establish the relationship between environmental variables and species richness of vascular plants, mosses and liverworts, and to identify common patterns across these different groups.Methods: A stratified random sampling procedure was followed to select sample plots (4 m2) from ecologically different homogeneous alpine vegetation stands. The data were analysed by Pearsson correlation analysis, regression analysis, stepwise regression analysis, principal correlation analysis (PCA), and redundancy analysis (RDA).Results: 210 vascular plants, 152 mosses and 89 liverworts were identified from 304 plots. Humped (quadratic) responses were found ...

Scandinavian alpine vascular plants are red-listed (R-L) according to criteria defined by IUCN. These are based on an evaluation of their risk for extinction in the future, which for most alpine plants have been related to possible effects of climate change. In the present study, ecological characteristics of R-L alpine plants are inferred from their occurrence in previously studied alpine plant communities. In total, data on 231 communities were compiled from studies in Norway and Sweden, and a total of 39 red-listed vascular plants were found in 142 of them. The data were analysed by numerical analyses in order to assess if and how communities with and without R-L species differ in terms of floristic composition and environmental conditions. The analysies show that most of the R-L plants are situated at the ends of the main floristic gradients extracted by Detrended Correspondense Analysis (DCA). These extremes are interpreted to represent high-altitudinal communities with long-lasting snow cover. In productive communities dominated with herbs and ferns, R-L plants are few or missing. A Principal Components Analysis (PCA) indicated that the R-L species form a heterogeneous group both in terms of ecology, abundance, and geographic distribution. Some of the communities were considered to be especially valuable because they included several (up to eight) R-L plants. Such communities are found in the upper part of the middle alpine or high alpine zone (460–675 m above the forest limit) and on calcareous substrate. It may generally be assumed that alpine plants with optima at the edges of the floristic gradients may be especially vulnerable to climate changes.

Coniferous plantations may reduce biodiversity and homogenise environmental conditions but there is a lack of knowledge on the restoration potential of such sites. We assess whether first generation plantation impacts on soil and biodiversity are reversible. The study was carried out in western Norway and we compared species composition, alpha and beta diversity of vascular plants and bryophytes, and soil conditions on five sites of 4-year old wind-felled clearings and adjacent, remnant Norway spruce (Picea abies) plantations. Local native birch (Betula pubescens) forests provided a reference point for assessing the restoration potential of the Norway spruce plantations. We found that species composition in the wind-felled clearings quickly developed similarities to the local birch forests. A rise in humus pH, calcium concentrations and available nitrogen (total N in percentage of loss on ignition), indicates that one rotation of Norway spruce plantations has not imposed long-term impairment of soil conditions. After removal of the plantation tree layer, mean species number per plot (alpha diversity) increased for vascular plants but remained unchanged for bryophytes. Heterogeneity, in terms of beta diversity, and the variance of some soil elements (calcium and magnesium) increased, and beta diversity trends were similar for both vascular plants and bryophytes. During the course of succession, we predict that species composition and vascular plant alpha and beta diversity in wind-felled clearings of Norway spruce plantations may stabilise at levels similar to native birch forests.

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.LocationEuropean Alps and Fennoscandia. Methods Of the studied pool of 888 terrestrial vascular plant species occurring in both the Alps and Fennoscandia, we used two complementary approaches to test and quantify climatic-niche shifts for 31 species having strictly disjunct populations and 358 species having either a contiguous or a patchy distribution with distant populations. First, we used species distribution modelling to test for a region effect on each species' climatic niche. Second, we quantified niche overlap and shifts in niche width (i.e. ecological amplitude) and position (i.e. ecological optimum) within a bi-dimensional climatic space. Results Only one species (3%) of the 31 species with strictly disjunct populations and 58 species (16%) of the 358 species with distant populations showed a region effect on their climatic niche. Niche overlap was higher for species with strictly disjunct populations than for species with distant populations and highest for arctic–alpine species. Climatic niches were, on average, wider and located towards warmer and wetter conditions in the Alps. Main conclusion Climatic niches seem to be generally conserved between populations that are separated between the Alps and Fennoscandia and have probably been so for 10,000–15,000 years. Therefore, the basic assumption of species distribution models that a species' climatic niche is constant in space and time – at least on time scales 104 years or less – seems to be largely valid for arctic–alpine plants.

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 that their species composition converges towards that of their undisturbed surroundings. At present we lack knowledge of the rate as well as the direction of these successions. We examined the species composition of five alpine spoil heaps in western Norway at two points in time, after 6–16, and 24–34 years of succession, with regard to vegetation cover, species richness, species composition and soil conditions. We also compared the vegetation of spoil heaps with that of their surroundings. After ca. 30 years, bryophyte and lichen cover and species richness were similar to those of their surroundings, while cover of vascular plants and species richness recovered more slowly. The vegetation development of spoil heaps appears safe-site limited rather than dispersal limited. Topsoil development was slow, but some accumulation of organic matter was observed. The species composition followed a successional trajectory in direction of the vegetation of the surroundings. Estimated linear successional rates indicate that 35–48 years are needed from construction of spoil heaps till a species composition more or less similar to their surroundings has been reached. However, these estimates are likely to be over-optimistic because successional rates tend to decrease with time. Based on our results we propose three changes to the current spoil-heap construction practice that will improve their restoration: (1) to increase surface unevenness, by which the number of safe sites will increase and germination and establishment success will be enhanced; (2) to increase substrate variability, by adding more of fine-grained materials more species will establish in shorter time; and (3) to use seed from local sources or to let the spoil heaps regenerate naturally.

We describe changes in vascular plant richness on 13 high mountain summits based on a historical study performed approximately 40 years ago. A summit is defined as the uppermost 30 m of the mountain tops. The altitudes of the summits range from 1512 to 1814 m. Data from neighboring climatologic stations showed higher mean values for July temperature (+0.7 °C) and January temperature (+1.5 °C), and mean annual precipitation had increased from 714 to 764.7 mm (7.1%) for the period from 1970 until 2009 compared with average data for the normal period (1961–1990). The total “top flora” had during this period increased by 19 taxa. On average, the increase in taxa richness was 18.9 ± 8.4 per summit, representing an average increase of 90.2%. Woody species had an average upward movement of 7.3 m during the study period. The ongoing upward shift of common, ubiquitous alpine species has resulted in a floristic homogenization of the mountain summits, and thus increasing α-diversity was accompanied by decre...

Bjune, A. E., Birks, H. J. B., Peglar, S. M. & Odland, A. 2010: Developing a modern pollen–climate calibration data set for Norway. Boreas, Vol. 39, pp. 674–688. 10.1111/j.1502-3885.2010.00158.x. ISSN 0300-9483. Modern pollen–climate data sets consisting of modern pollen assemblages and modern climate data (mean July temperature and mean annual precipitation) have been developed for Norway based on 191 lakes and 321 lakes. The original 191-lake data set was designed to optimize the distribution of the lakes sampled along the mean July temperature gradient, thereby fulfilling one of the most critical assumptions of weighted-averaging regression and calibration and its relative, weighted-averaging partial least-squares regression. A further 130 surface samples of comparable taphonomy, taxonomic detail and analyst became available as a result of other projects. These 130 samples, all from new lakes, were added to the 191-lake data set to create the 321-lake data set. The collection and construction of these data sets are outlined. Numerical analyses involving generalized linear modelling, constrained ordination techniques, weighted-averaging partial least-squares regression, and two different cross-validation procedures are used to asses the effects of increasing the size of the calibration data set from 191 to 321 lakes. The two data sets are used to reconstruct mean July temperature and mean annual precipitation for a Holocene site in northwest Norway and a Lateglacial site in west-central Norway. Overall, little is to be gained by increasing the modern data set beyond about 200 lakes in terms of modern model performance statistics, but the down-core reconstructions show less between-sample variability and are thus potentially more plausible and realistic when based on the 321-lake data set.

The main aim of this study is to quantify environmental differences along altitudinal gradients on the basis of different sets of plant indicator systems and recorded vascular plants within 100-m altitudinal bands. Two areas are included in the study, and in total they include an altitudinal span from sea-level up to 2400 m a.s.l. The applied indicator systems are the six values defined by Ellenberg et al. [Ellenberg, H., Weber, H.E., Dull, R., Wirth, V., Werner, W., Paulissen, D., 1991. Zeigerwerte von Pflanzen in Mitteleuropa. Scripta Geobotanica 18, 1–248], eight Raunkiaer life forms, the respiration values of Dahl [Dahl, E., 1998. The phytography of Northern Europe. Cambridge University Press], and the snow indicator values of Odland and Munkejord [Odland, A., Munkejord, H.K., 2008. Plants as indicators of snow layer duration in southern Norwegian mountains. Ecological Indicators 8, 57–68]. Mean indicator values are calculated for each altitudinal band, and they show significant linear increasing or decreasing trends, significant unimodal (quadratic) trends or no significant altitudinal trend. The altitudinal variation in mean indicator values is discussed in relation to general environmental conditions such as bedrock, soil characteristics, topography, summer temperature, light, snow and distribution of major vegetation types. The main differences between the altitudinal bands as shown by a PCA analysis indicate that the highest bands, representing the high alpine zone (more than 1800 m a.s.l.) strongly differ from the others. The altitudinal gradient is mainly associated with variation in temperature, nitrogen indicators and some of the Raunkiaer life forms (primarily the Phanerophytes, Nanophanerophytes, Geophytes and Therophytes). The two tested temperature indicator systems tested were highly linearly correlated, but the altitudinal variation in respiration value followed the general temperature lapse rate better than the Ellenberg temperature indicator value. Indicators of high soil moisture have their optima at intermediate altitudes. The uppermost bands in Aurland show lower mean temperature indicator values and a higher snow indicator value compared to bands at the same altitude in Jotunheimen. This may partly be explained as a result of the Massenerhebung effect. Relationships between altitudinal distribution patterns of some vascular plants in Aurland and their Ellenberg temperature indicator value indicate that the values should be revised to better suit Norwegian conditions.

The main aim of this paper was to study the responses of mountain plants in relation to the time of snowmelt. Three mountain areas situated along an oceanic–continental gradient were selected as study sites, and the sample plots ranged from 182 m below to 473 m above the climatic forest limit. In total, 185 quadrats (2 m × 2 m), stratified to include only oligotrophic and mesotrophic mountain vegetation types, were selected to represent a topographic range along altitudinal gradients. In each quadrat, the percentage groundcover of the species was recorded. From the beginning of April until July 2004, snow thickness was monitored, and the Julian day when the snow had completely melted was determined for all plots. The relationship between species abundances and Julian day of snowmelt were analysed by two different numerical methods: (1) relative values for species optimum and tolerance were given by Detrended Canonical Correspondence Analysis (DCCA) with Julian day of snowmelt as the constraining variable. (2) Species responses were modelled by Generalized Linear Models (GLM). For species with significant unimodal responses, optimum and tolerance were calculated. For species with significant linear models, different species response models were identified by the regression intercepts. One hundred and twenty six species (taxa) were tested, and 103 evidenced statistically significant ( p

The main aim of this study was to quantify differences in the structure of dense Matteuccia struthiopteris (L) Todaro among geographically separated populations in Norway, and to relate these differences to variation in environmental variables. A stratified random sampling procedure was applied to select 4 m2 quadrats restricted to populations dominated (>75% cover) by the fern. This dimorphic fern can produce three types of leaves (fronds): fertile (sporophyll) and sterile (trophophyll), and in addition also intermediate fronds. In all, 178 populations from different parts of the country were analysed, and in total 9,346 rootstocks were measured. Fifteen percent of the rootstocks were fertile, each producing from one to eight sporophylls, and 2.0% had developed intermediate fronds. Rootstocks with five or more sporophylls were mainly found in Southern Norway. Within the plots, there were major variations in density (10–112), number of small (new) ramets (0–58), total number of sporophylls (0–94) and estimated total fern wet-weight (0.33–22.8 kg). All new additions to the populations were connected to a mother plant (ramets), and none were of sexual origin (genets). The main environmental variables associated with the variation in population structure were mean July temperature (highly correlated with altitude and latitude), mean precipitation and density of the canopy cover. The density of small ramets and number of intermediate fronds increased from south to north. The latitudinal variation in sporophyll development and maximum trophophyll height was best explained by a unimodal model. There were statistically significant differences in the population structure between the eight studied geographic areas in Norway.

The main aim of our study was to investigate seasonal variation in the frequency of abnormal anaphases and mitotic index values in wild populations of herb-Paris (Paris quadrifolia L., Trilliaceae). Plant material was collected in the year 2000 in Norway and in the year 2001 in Lithuania. There was statistically significant variation in the mitotic index values (chi(2)=1087.9, d.f.=16, P

The Myrkdalen Lake, western Norway, was subjected to a ca. 1.4 m permanent drawdown in June 1987. This left the original wetland vegetation belts “hanging” over the new water level. One year after the drawdown, a permanent transect with contiguous 1.0m × 0.5 m quadrats was established through a Carex vesicariawetland belt, and was analysed annually through 2001. The transect was 17 m long and included the lower part of a Phalaris arundinaceavegetation and the upper part of an Equisetum fluviatile vegetation. All quadrats were located on the same type of substrate and extended through a 65-cm difference in elevation. During the study period, the transect was completely inundated for only 6 days. A secondary succession was initiated immediately after the drawdown. The main trend was a gradual decreased cover of C. vesicaria and an increase particularly in the cover of P. arundinaceaand Calamagrostis purpurea. Regression analyses indicated that variation in the cover of the different species could be expressed as linear, quadratic, or exponential functions of the number of years since drawdown. Parallel with the decreased abundance of C. vesicaria, there was a linear decrease in the number of its fertile shoots. Very low numbers of flowering shoots were found after the mean cover of P. arundinaceaexceeded the cover of C. vesicaria. The study indicates that the drawdown resulted in a hydrological regime that was not optimal for C. vesicaria. Despite this, a clonal wetland sedge may obviously survive a major drawdown for more than 14 years. © 2002 Elsevier Science B.V. All rights reserved.

Myrkdalen Lake in Western Norway was subjected to a 1.4 m drawdown in June 1987. Plant establishment and vegetation succession on the exposed sediments of a fluvial delta plain was monitored through 2000. The investigated area extended from the original Equisetum fluviatile zone to the new lake edge. The substrate was homogeneous and consisted mainly of minerogenous fluvial sediments. Vegetation data were sampled within continuous quadrats along transects perpendicular to the shore, and they dropped 93 cm in elevation. Detrended Correspondence Analysis and Canonical Correspondence Analysis confirmed that “time since drawdown” and “elevation of the quadrats” appeared to be of nearly equal importance in explaining succession. Plant establishment was rapid on the exposed sediments due to a seed bank and to rapid invasion of plants. The succession includes both floristic change as a function of time and a spatial separation in relation to the water level. The species succession was marked by a growth form progression: mosses and annuals → non-clonal perennials → clonal perennials. After one month, the annual Subularia aquatica and small acrocarpous mosses dominated the site. Dominance then shifted to Deschampsia cespitosa, Juncus filiformis, Blasia pusilla and Polytrichum commune. Subsequently there was an increase of Carex vesicaria in the lower zone and Calamagrostis purpurea in the upper zone, while Phalaris arundinacea was common over most of the elevational gradient. Equisetum declined where it had dominated before drawdown, but it expanded gradually towards the new shoreline. The vegetation remained dynamic after 13 years and it is not considered to be in equilibrium with the new environmental gradient yet. However, annual changes measured by DCA scores have slowed and two vegetation zones have developed. The major vegetational differences along the elevational gradient can be explained by the height of the mean June water limit. This example of species turnover in space and time may be a model for other successions that occur along a strong gradient.

Quantification of lichen abundance is important for management of reindeer populations. We measured dry lichen biomass in 876 micro plots (16.5 cm × 16.5 cm) systematically sampled within 219 vegetation plots (2 m × 2 m) from 7 different areas in S Norway. Lichen biomass was quantified as: (a) dry weight in g m-2, (b) lichen height in cm, (c) lichen cover, and (d) lichen volume (lichen height × lichen cover). Lichen biomass decreased with increasing precipitation and increasing altitude. On local scale, the variation in lichen biomass varied strongly with snow conditions. The grazed parts of Hardangervidda had in general a low average lichen biomass (an average mostly lower than 150 g m-2). Lichen biomass was much higher in area where reindeer migration was interfered by human activity. Lichen height and lichen volume were strongly linearly correlated with dry lichen biomass. These proxy methods may therefore be used to predict lichen biomass, but deviations from exact measurements should be expected.

The Myrkdalen lake, western Norway was subjected to a permanent 1.4 m drawdown in June 1987. After the drawdown, channels and artificial islands were constructed within the exposed floodplain system. Two permanent transects were established within this man-made environment, and these have been analyzed annually until 1995. The quadrats lie all on the same type of substrate, are at different elevations in relation to the water-level. This paper describes vegetation development on these newly created islands. The investigation shows major vegetational changes during the eight year period. Two main processes have taken place, vegetation zonation and primary succession. The first year after the construction, most of the created sites had a similar floristic composition, regardless of elevation. Major dominants during the first three years (e.g., Subularia aquatica, Marchantia polymorpha, Blasia pusilla, and numerous acrocarpous mosses) disappeared or were greatly reduced, and they were gradually replaced by species which were climax species in the wetland communities before the drawdown (e.g., Carex rostrata, C. vesicaria, Phalaris arundinacea, Salix nigricans). The main vegetational change occurred between the third and the fourth year. After three years characteristic vegetation zones were differentiated, with aquatic plants and helophytes in the lowermost parts, and willow shrubs in the uppermost parts of the islands

Recent studies from mountainous areas of small spatial extent (2500 km(2) ) 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 restricted to topographically complex terrains? To answer this, we here study fine-grained thermal variability across a 2500-km wide latitudinal gradient in Northern Europe encompassing a large array of topographic complexities. We first combined plant community data, Ellenberg temperature indicator values, locally measured temperatures (LmT) and globally interpolated temperatures (GiT) in a modelling framework to infer biologically relevant temperature conditions from plant assemblages within1000-m(2) units (community-inferred temperatures: CiT). We then assessed: (1) CiT range (thermal variability) within 1-km(2) units; (2) the relationship between CiT range and topographically and geographically derived predictors at 1-km resolution; and (3) whether spatial turnover in CiT is greater than spatial turnover in GiT within 100-km(2) units. Ellenberg temperature indicator values in combination with plant assemblages explained 46-72% of variation in LmT and 92-96% of variation in GiT during the growing season (June, July, August). Growing-season CiT range within 1-km(2) units peaked at 60-65°N and increased with terrain roughness, averaging 1.97 °C (SD = 0.84 °C) and 2.68 °C (SD = 1.26 °C) within the flattest and roughest units respectively. Complex interactions between topography-related variables and latitude explained 35% of variation in growing-season CiT range when accounting for sampling effort and residual spatial autocorrelation. Spatial turnover in growing-season CiT within 100-km(2) units was, on average, 1.8 times greater (0.32 °C km(-1) ) than spatial turnover in growing-season GiT (0.18 °C km(-1) ). We conclude that thermal variability within 1-km(2) units strongly increases local spatial buffering of future climate warming across Northern Europe, even in the flattest terrains.

The increased spread of insect outbreaks is among the most severe impacts of climate warming predicted for northern boreal forest ecosystems. Compound disturbances by insect herbivores can cause sharp transitions between vegetation states with implications for ecosystem productivity and climate feedbacks. By analysing vegetation plots prior to and immediately after a severe and widespread outbreak by geometrid moths in the birch forest-tundra ecotone, we document a shift in forest understorey community composition in response to the moth outbreak. Prior to the moth outbreak, the plots divided into two oligotrophic and one eutrophic plant community. The moth outbreak caused a vegetation state shift in the two oligotrophic communities, but only minor changes in the eutrophic community. In the spatially most widespread communities, oligotrophic dwarf shrub birch forest, dominance by the allelopathic dwarf shrub Empetrum nigrum ssp. hermaphroditum, was effectively broken and replaced by a community dominated by the graminoid Avenella flexuosa, in a manner qualitatively similar to the effect of wild fires in E. nigrum communities in coniferous boreal forest further south. As dominance by E. nigrum is associated with retrogressive succession the observed vegetation state shift has widespread implications for ecosystem productivity on a regional scale. Our findings reveal that the impact of moth outbreaks on the northern boreal birch forest system is highly initial-state dependent, and that the widespread oligotrophic communities have a low resistance to such disturbances. This provides a case for the notion that climate impacts on arctic and northern boreal vegetation may take place most abruptly when conveyed by changed dynamics of irruptive herbivores. Electronic supplementary material The online version of this article (doi:10.1007/s00442-013-2648-1) contains supplementary material, which is available to authorized users.

Odland, A. 1995. Frond development and phenology of Thelypteris limbosperma, Athyrium distentifolium, and Matteuccia struthiopteris in Western Norway. — Nord. J. Bot. 15: 225–236. Copenhagen. ISSN 0107–055X. The pattern of growth and phenology of Thelypteris limbosperma, Athyrium distentifolium, and Matteuccia struthiopteris fronds has been investigated, with particular emphasis on height increments of the sporophytes and the development of fertile fronds. In order to study both interspecific and intraspecific differences, fern stands along altitudinal gradients have been monitored. To investigate the initiation of fertility, fronds representing different developmental stages have been sampled. Climatic data have been collected with a data-logger during the study periods. The ferns show significant differences in growth pattern and phenology. Matteuccia struthiopteris has a growth curve that is best described as monomolecular, characterised by high growth rates during the early developmental stage, while the development of Thelypteris limbosperma and Athyrium distentifolium follow a logistic growth curve. The species need different periods of time to develop their fronds. The main frond elongation does not start before soil temperature has reached 7 C. After that, the growth is mainly controlled by air temperature. Within the interval when mean maximum temperatures are 8–20 C, all three ferns showed increased growth rates with increasing air temperatures, but the increase was greatest in M. struthiopteris. At higher temperatures, the growth rate of M. struthiopteris and T. limbosperma decreased. Athyrium distentifolium is characterised by producing sori at an early developmental stage. Fertile Matteuccia strurhiopteris fronds are developed at a much later developmental stage. Thelypteris limbosperma needs a longer period of time to produce mature fronds than the other species. The investigation indicates that plant growth and development are determined by both internal and external factors. It is concluded that growth rate, phenology, and the ability of ferns to produce mature fronds reveal close similarities with their response to environmental variables, and hence with their broad-scale geographical distributional patterns.

This paper synthesizes the main results of botanical investigations carried out within the Aurland river catchment. The data include floristic records from the area prior to regulation, data sampling in connection with the hydropower development (1966–1979), and own investigations during 1988–1992. The investigation includes both general data on plant distribution within the whole catchment, and more detailed analyses from selected localities. Special emphasis is given to a floristic comparison of the Aurland catchment in relation to other catchments in W. Norway, and thereby giving an evaluation of the botanical value of the area. The floristic composition of the whole catchment is compared with that of 60 other catchments in W. Norway using numerical methods. Botanical consequences as a result of the regulation are investigated on both a general scale and a detailed scale related to the river regulation.

A 25 m long transect was positioned along the spray gradient of a waterfall (880 m a.s.l.) in the Aurland River, western Norway. The vegetational composition in contiguous 1 m × 1 m quadrats was recorded in 1968 before regulation of the river, and again 20 years later. Spray precipitation, temperature, and humidity were also measured. The 92 per cent reduction in mean annual discharge of the river has resulted in a 98-100 per cent reduction in spray precipitation along the transect. In general, there has been a great decrease in hygrophilous bryophytes and alpine vascular plants, and an increase in lichens and drought-tolerant bryophytes. At the end of the transect furthest from the waterfall, which previously received less than 1200 mm of spray precipitation per year, there has only been minor floristic change. Similarly, in the nearest 5 quadrats, where spray precipitation is still substantial, there has been little change in the vegetation. The greatest change occurred in the middle of the transect which formerly received substantial amounts of spray, but is now almost dry.

The investigation is based on phytosociological and ecological analyses of T. limbosperma-dominated stands from different parts of W Norway. The distribution and floristical composition of the stands are related to different environmental parameters, such as climate, soil and topography. The data are analysed by numerical methods, of which two-way indicator species analysis (TWINSPAN), canonical correspondence analysis (CCA), and simple discriminant functions (DISCRIM) are the most useful. The broad-scale distribution of T. limbosperma stands is determined by climatic factors. Within its distribution area soil factors and human influence govern the floristic composition and development of different types of such stands. Based on the TWINSPAN classification 9 different stand types are distinguished. The first major division of the TWINSPAN classification is mainly correlated with soil factors. Most of the stands growing on the richest soils are interpreted as representing regeneration stages after intensive human influence. Divisions at lower levels are well correlated with altitude and temperature conditions. The stands are all characterized by low pH and base saturation. Some types are concentrated to certain geographical regions, indicating that both altitudinal and west-east-gradients are important in influencing the floristic composition of the different types. The investigations indicate that T. limbosperma has a rather narrow realised phytosociological niche. It is mainly concentrated to stands that are floristically most related to the poorest part of Vaccinio-Piceion communities. Occasionally it is also dominant in Alno-Padion and Lactucion alpinae communities.

Six tall herb and fern vegetation types in Roldal have been investigated. They are referred to the alliances Lactucion alpinae and Alno–Ulmion. Lactucion alpinae is divided into two suballiances, one oligotrophic to mesotrophic (Dryoptero–Calamagrostenion purpureae) to which are referred Athyrium distentifolium– Salix scrub, and Athyrium distentifolium meadow, and one eutrophic (Lactucenion alpinae) to which belongs Geranium sylvatkum meadow and Lactuca alpina meadow. Alnus incana forest, herb/fern and Matteuccia struthiopteris types belong to Alno–Ulmion. Lactucion alpinae is considered subalpine, whilst Alno Uimion is prealpine. The pre– and subalpine zones are considered oceanic sections of middle– and upper oroboreal vegetation zones.