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Lichen heaths are decreasing in abundance in alpine and Arctic areas because of an increased competition with shrubs. This shift in vegetation might have important consequences for the soil temperature. The aim of this study is to find the drivers of the variation in soil temperature below lichen heaths and shrubs. Moreover, we want to gain more insight in the variability of the soil temperature below lichen heaths. We measured the soil temperature in thirty lichen plots and fifteen shrub plots in an alpine area in southern Norway during July and August 2019. We applied several treatments to study the drivers behind the variation in soil temperature between lichen heaths and shrub vegetation. We found that the average soil temperature was 1.45°C higher below lichen heaths than below shrub vegetation. Moreover, we measured a difference in soil temperature of 1.66°C between north- and south-facing lichen heaths, which contributes to the small-scale spatial variability in soil temperature below lichen heaths. Based on our experiments, we conclude that the buffering capacity of the litter layer below shrubs and shading of the soil by the shrub canopy lead to a lower soil temperature below shrubs compared to lichen heaths during the summer.

Abstract Optimal foraging models predict that individual animals will optimize net energy gain by intensifying forage activity and/or reducing forage energy cost. Then, the free distribution model predicts an animal's distribution in a patchy landscape will match the distribution of the resources. If not modified by other factors, such patterns may be expected to be particularly explicit in variable and extreme, forage‐limited, and patchy environments, notably alpine and Arctic environments during winter. The large ungulate wild mountain reindeer (Rangifer tarandus tarandus) surviving in such environments is used as a model during the forage‐limited winter season. The largest wild reindeer area in Western Europe (Hardangervidda, 8130 km2) is actively managed to sustain 10,000–12,000 wild reindeer. Since 2001, 104 different individuals have been GPS‐tracked at 3‐hr intervals. In winter, mountain reindeer may either choose to seek out and forage in patchy snow‐free habitats, typically on top of wind‐blown ridges, or use energy‐demanding digging through the snow to reach ground forage (cratering). We use late April satellite data from Landsat 5 and 8 (30 × 30 m), airborne laser scanning subsampling (processed to 1 × 1 m grid), and topographic information (1 m resolution) derived from digital aerial photographs (0.25 × 0.25 m resolution) to delineate snow‐free patches, constituting less than 694 km2. By overlaying recorded wild reindeer GPS positions winters 2001–2017 (188,942 positions), we document a strong positive selection for snow‐free patches, which were used about four times more frequently than expected from a “random walk” model. On a daily basis, the preference for snow‐free areas was slightly stronger in the evenings. In the sustainable management of wild mountain reindeer, the area of snow‐free patches is an important predictor of winter forage availability and important winter source areas. It may be derived from remote sensing data.

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.

The boundary between the boreal and arctic biomes in northwest Europe has been a matter of debate for many years. Some authors consider that the boundary is marked by the northern limit of tree growth in the northernmost Norwegian mainland. In this study we have collected air and soil temperature data from 37 heath stands from northern Finnmark (71°N), the northernmost part of the Norwegian mainland, through Bear Island (74°N) in the Barents sea, to Adventsdalen (78)°N (in Spitsbergen) in Svalbard archipelago. In Finnmark, plots both south and north of the treeline were investigated. Vegetation and soil chemistry analyses were performed on the plots in Finnmark and Svalbard. Significant decreasing south-north trends in air and soil temperatures were observed from Finnmark to Spitsbergen. Soils in Finnmark were acidic and rich in organic matter, while those on Adventsdalen were basic and poor in organic matter. Vegetational analysis identified five communities: three in Finnmark and two on Adventsdalen. The communities in Finnmark had marked mutual similarities but were very different from those on Adventsdalen. No significant ecological differences between heaths south and north of the treeline in Finnmark were observed. Air and soil temperature variables in Finnmark were outside the recognized range for the arctic biome and inconsistent with the presence of permafrost both south and north of the treeline. A major difference between Finnmark and Spitsbergen was amount of soil frost and length of the growing season. Our results suggest that the boreal biome extends all the way to the north coast of mainland Norway; and previously used division of heaths in Finnmark into boreal, alpine and arctic biomes is not justified.

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.

Previously published isoline maps of Fennoscandian timberlines show that their highest elevations lie in the high mountain areas in central south Norway and from there the limits decrease in all directions. These maps are assumed to show differences in “climatic forest limits”, but the isoline patterns indicate that factors other than climate may be decisive in most of the area. Possibly the effects of ‘massenerhebung’ and the “summit syndrome” may locally have major effects on the timberline elevation. The main aim of the present study is to quantify the effect of latitude and mountain height on the regional variation of mountain birch timberline elevation. The study is a statistical analysis of previous published data on the timberline elevation and nearby mountain height. Selection of the study sites has been stratified to the Scandinavian mountain range (the Scandes) from 58 to 71o N where the timberlines reach their highest elevations. The data indicates that only the high mountain massifs in S Norway and N Sweden are sufficiently high to allow birch forests to reach their potential elevations. Stepwise regression shows that latitude explains 70.9% while both latitude and mountain explain together 89.0% of the timberline variation. Where the mountains are low (approximately 1000 m higher than the measured local timberlines) effects of the summit syndrome will lower the timberline elevation substantially and climatically determined timberlines will probably not have been reached. This indicates that models of future timberlines and thereby the alpine area extent in a warmer world may result in unrealistic conclusions without taking account of local mountain heights.

The main aim of the present paper was to study regional differences in the altitudinal distribution limits of vascular plants in relation to mountain height and latitudinal position. Altitudinal limits from previously studied areas were compared with the altitudinal distribution limits given by Lid and Lid (2005) as a reference. Based on these comparisons, different trend lines were used to evaluate the effects of mountain height and thereby estimate how high a mountain must be for vascular plants to reach their potential altitudinal limits. Study areas were Hardangervidda and Aurland in southern Norway, Jämtland in central Sweden, Lule Lappmark in northern Sweden, Troms in northern Norway and Graubünden in Switzerland. A regression analysis of the altitudinal limits for 177 vascular plants in Scandinavia compared with the same species in Switzerland gave a highly significant (p < 0.001) linear equation with a slope coefficient of 0.95 and a Y-intercept of 1057. Species limits in Hardangervidda, Aurland and Jämtland, however, showed non-linear altitudinal trends for the whole mountain ranges when they were compared with the highest recorded limits for the same species in Scandinavia. Differences between the recorded altitudinal limits from Scandinavia (mostly from the Jotunheimen mountains) and the same species from Switzerland were in average the same for lowland, boreal and high altitudinal species (p > 0.422). Comparisons within Scandinavia show that lowland/boreal and high altitudinal species showed different altitudinal distribution patterns. The position of the forest limit increased on average with 72.4 m per degree increase in latitude from Switzerland to northern Scandinavia. The altitudinal span of the alpine zone was approximately 1100 m in Switzerland and in Jotunheimen but considerably lower in the southern Scandinavian study areas. Studies of altitudinal distribution limits of vascular plants may give an indication of to what extent the height of a particular mountain influence plant distribution and thereby its vegetation zonation.

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.