Species richness of vascular plants, bryophytes and lichens in dry grasslands: The effects of environment, landscape structure and competition

We studied the relative importance of local habitat conditions and landscape structure for species richness of vascular plants, bryophytes and lichens in dry grasslands on the Baltic island of Öland (Sweden). In addition, we tested whether relationships between species richness and vegetation cover indicate that competition within and between the studied taxonomic groups is important. We recorded species numbers of vascular plants, bryophytes and lichens in 4 m² plots (n=452), distributed over dry grassland patches differing in size and degree of isolation. Structural and environmental data were collected for each plot. We tested effects of local environmental conditions, landscape structure and vegetation cover on species richness using generalized linear mixed models. Different environmental variables explained species richness of vascular plants, bryophytes and lichens. Environmental effects, particularly soil pH, were more important than landscape structure. Interaction effects of soil pH with other environmental variables were significant in vascular plants. Plot heterogeneity enhanced species richness. Size and degree of isolation of dry grassland patches significantly affected bryophyte and lichen species richness, but not that of vascular plants. We observed negative relationships between bryophyte and lichen species richness and the cover of vascular plants. To conclude, effects of single environmental variables on species richness depend both on the taxonomic group and on the combination of environmental factors on a whole. Dispersal limitation in bryophytes and lichens confined to dry grasslands may be more common than is often assumed. Our study further suggests that competition between vascular plants and cryptogams is rather asymmetric.     

The role of seed rain in determining the assembly of a cliff community

Abstract. Cliff-face communities of the Niagara Escarpment in Ontario, Canada, are dominated by long-lived Thuja occidentalis and a consistent assemblage of other plants. Our objective was to determine whether seed rain plays a role in determining why these species are dominant. Seed rain was collected from the cliff face and from the surrounding plateau-and talus communities at two sites over a 2-yr period in order to compare these three adjacent, but different communities. Multivariate Discriminant Analysis first separated the two sites: primarily due to the importance of Betula papyrifera at one site. The three community types were also separated, although there was still substantial overlap. There was a predictable array of species associated with each community although the seed rain on the cliff faces differed slightly. When characterized by univariate ANOVAs, seed rain in the cliff faces and plateaus had a lower species richness and lower total seed density than the talus sites. Seeds of two of the 11 species analysed individually showed an influence of habitat type on their number. Seed morphology did not influence patterns of seed rain. Finally, there was no correlation between the seed rain and above-ground vegetation in any of the communities. We conclude that the seed rain patterns that exist do not act to filter the plants that form the mature vegetation of cliffs.     

Dynamics of understory vegetation in an old-growth boreal coniferous forest, 1988–1993

Abstract. Understorey vegetation changes in a South Norwegian old-growth coniferous forest were studied between 1988 and 1993 in 200 1-m² vegetation plots. Our aims were to quantify the amount of between-year compositional change, and to elaborate the environmental basis for long-term vegetation change, including the previously identified gradient structure with a major gradient related to topography (and soil nutrient status and soil depth) and a minor gradient reflecting paludification and canopy coverage. Species richness (yearly mean and cumulative species number) and change in species richness differed between vascular plants and cryptogams, and between forest types. The number of vascular plant species decreased in pine forest in dry years; bryophyte species number increased in spruce forest. Statistically significant vegetation change, as tested by constrained ordination (CCA) with time as the constraining variable, is demonstrated for most one-year periods and for the five-year period in most forest types. Vegetation change along identified gradients, measured as plot displacement along DCA ordination axes, also occurred. The magnitude of year-to-year vegetation change was related neither to forest type nor to one-year period; different responses to climatic and environmental change were observed in each forest type. The largest average displacement observed, from medium-rich spruce forest towards poor spruce forest, was interpreted as a long-term trend. Humus-layer pH decreased by ca. 0.25 units from 1988 to 1993, most strongly in medium-rich spruce forest where exchangeable Ca decreased and Al and Mn increased strongly. Our study supports the hypothesis that vascular plants show a long-term and broad-scale response to soil acidification. Change in bryophyte composition is linked to some very long growing-seasons. Detailed analysis of short-term vegetation dynamics enhances the interpretation of long-term changes and stresses the complementarity of univariate and multivariate methods in the analysis of vegetation change.     

The effects of windthrow on plant species richness in a Central European beech forest

The effects of soil disturbance caused by the uprooting of a single or a few canopy trees on species richness and composition of vascular plant species and bryophytes were examined in a temperate beech forest (Fagus sylvatica) in northern Germany. We recorded the vegetation in 57 pairs of disturbed and adjacent undisturbed plots and established a chronosequence of mound ages to study the effect of time since microsite formation on plant species richness and composition. We found significant differences in plant species richness and composition between disturbed and adjacent undisturbed plots. Species richness of both vascular plants and bryophytes was higher in the disturbed than in the undisturbed plots, but these differences were more pronounced for bryophytes. We suggest that three main factors are responsible for this differential response. The availability of microsites on the forest floor that are suitable for the recruitment of bryophytes is lower than for vascular plants. Establishment of bryophytes in disturbed microsites is favoured by a greater abundance of propagules in the close vicinity and in the soil of the disturbed microsites, as well as by a greater variety of regeneration strategies in bryophytes than in vascular plants. Time since mound formation was a major factor determining plant species richness and composition. A significant decrease in the mean number of species was found from young mounds to intermediate and old mounds. However, differences were observed between vascular plants and bryophytes in the course of changes through time in species richness and composition. A large number of exclusive and infrequent vascular plant species was observed on young mounds, among them several disturbance specialists. We suggest that the establishment of many vascular plant species was infrequent and short-lived due to unfavourable light conditions and a low abundance of propagules. By contrast, the development of a litter layer was the main reason for the decreased mean number of bryophytes on old mounds. Our study supports the view that groups of species differing in important life history traits exhibit different responses to soil disturbance.     

Bryophyte and vascular plant species richness in boreo-nemoral moist forests and mires

We compare species richness of bryophytes and vascular plants in Estonian moist forests and mires. The material was collected from two wetland nature reserves. Bryophyte and vascular plant species were recorded in 338 homogeneous stands of approximately 1 ha in nine forest and two mire types. Regional species pools for bryophytes and vascular plants were significantly correlated. The correlations between the species richnesses of bryophytes and vascular plants per stand were positive in all community types. The relative richnesses (local richness divided by the regional species pool size) were similar for bryophyte species and for vascular plant species. This shows that on larger scales, conservation of the communities rich in species of one taxonomic plant group, maintains also the species richness of the other. The minimum number of stands needed for the maintenance of the regional species pool of typical species for the every community type was calculated using the species richness accumulation curves. Less stands are needed to maintain the bryophyte species pools (300–5300 for bryophytes and 400–35 000 for vascular plants).     

Species richness,alien species and plant traits in Central Argentine mountain grasslands

Abstract. Pattern of native vegetation, distribution of alien species and variation of environmental parameters were studied in mountain grasslands in a lithologically homogeneous Córdoba mountain range in Central Argentina. CCA showed that altitude was the most important factor determining the compositional variation of the vegetation, with soil nutrient status and stoniness as additional factors. Short‐grass communities, associated with the driest habitats on plateaus, showed higher small‐scale native species richness than wet‐turf communities in valleys and tall‐grass communities on slopes. Species richness was negatively correlated with soil parameters that indicate nutrient status and water availability. Also, there was a negative correlation between soil Ca‐ and Mg‐ content and richness. High native species richness coincided with high alien species richness. When smaller units – community types – were considered, it became evident that within short‐grass vegetation, the three most species‐rich community types contained significant numbers of alien species, while the other two did not. Even within one community type, the same quadrats that contained the highest number of native species, were also characterized by the highest numbers of alien species. Evidently, the same mechanism was responsible for high richness of both native and alien species. Alien species were distinguished by a greater proportion of annuals and prostrate stoloniferous plants, by lower palatability and by smaller proportion of zoochory. DCA ordination of quadrats on the basis of plant traits as attributes resulted in a clear distinction of three main vegetation types. Short‐grass vegetation was distinguished by a predomination of late flowering species, tall‐grass vegetation by the presence of high herbaceous plants and bushes, and wet‐turf vegetation by the presence of plants with storage organs, the lack of hairy leaves, and by a high proportion of cryptophytes. Quadrats with and without alien species were distinguished as well, indicating that the occurrence of aliens may be dependent on plant traits in a particular patch of a community.     

Bryophyte colonisation in experimental microcosms: the role of nutrients, defoliation and vascular vegetation

A three-year multi-factorial microcosm experiment simulating fertilisation, defoliation and the composition of vascular vegetation in a dry grassland succession was used to test four hypotheses concerning the establishment and survival of bryophytes in grassland vegetation. H₁: bryophyte cover may be used to predict bryophyte species richness. H₂: bryophyte richness is suppressed at high nutrient levels and promoted by defoliation of vascular plants. H₃: species richness of bryophytes is influenced by the species composition of the vascular vegetation. H₄: bryophyte species richness is negatively correlated with vascular plant biomass.
The relationship between bryophyte richness and bryophyte cover was found to follow the classical species-area richness curve. Bryophyte species richness responded positively to defoliation and negatively to fertilisation. The species composition of vascular vegetation had no significant effect on bryophyte richness. Bryophyte species richness was lower at high vascular plant biomass and vascular plant dry weight above 400 g m⁻² appeared fatal to bryophytes. At high nutrient levels, defoliation increased bryophyte richness, but defoliation did not fully compensate for the negative effect of fertilisation. The study reinforces the concern for short lived shuttle bryophytes in the agricultural landscape.     

The role of regional and local scale predictors for plant species richness in Mediterranean forests

Abstract

Both local and regional predictors play a role in determining plant community structure and composition. Climate, soil features as well as different local history and management affect forest understorey and tree species composition, but to date their specific role is relatively unknown. Few studies have addressed the importance of these predictors, especially in the Mediterranean area, where environmental conditions and human impacts have generated heterogeneous forest communities. In this study, the relationships between environmental variables and species richness of different groups of vascular plants (vascular species, woody species and open habitat species) and bryophytes were investigated in Tuscan forests. A total of 37 environmental variables were used by generalised linear model fitting in order to find parsimonious sub-sets of environmental factors (predictors) that are able to explain species diversity patterns at the local scale. Moreover, the role of regional and local variable groups on species richness of the considered plant groups was estimated by using the variance partitioning approach. We found that local variables, such as forest management and structure, explained more variance than regional variables for total species richness, open habitat species richness and bryophyte species richness. On the other hand, regional variables (such as elevation) played a central role for woody species richness.     

Plant communities and landscape diversity along a Canadian Arctic river

Abstract. We analysed the structure and diversity of the vegetation along an Arctic river to determine the relationship between species richness and plant community structure. We examined whether variation in species richness along the corridor is structured as (1) an increase in the number of communities due to increasing landscape heterogeneity, (2) an increase in the floristic distinctiveness (β-diversity) of communities, or (3) an increase in within-community richness (α-diversity) as species-poor communities are replaced by species-rich communities. We described 24 community types and analysed the relationship between site vascular species richness (γ-diversity) and β-diversity, α-diversity, site environmental heterogeneity, and the number of distinct plant communities. We also measured diversity patterns of vascular, bryophyte, and lichen species within communities and examined their relationship to community-level estimates of environmental factors. We found that an increase in site species richness correlated with an increase in the number of communities (r²= 0.323, P= 0.0173) and β-diversity (r²= 0.388, P= 0.0075), rather than an increase in the α-diversity of individual communities. Moisture and pH controlled most of the differences in composition between communities. Measures of species richness and correlations with moisture and pH within communities differed among vascular, bryophyte, and lichen species. Bryophyte richness was positively correlated with moisture (r²= 0.862, P= 0.0010) and lichen richness was negatively correlated with moisture (r²= 0.809, P= 0.0031). Vascular plants had a peak in richness at pH 6.5 (r²= 0.214, P < 0.0001). We conclude that site variation in vascular richness in this region is controlled by landscape heterogeneity, and structured as variation in the number and distinctiveness of recognizable plant communities.     

Productivity–diversity patterns in arctic tundra vegetation

Productivity has long been argued to be a major driver of species richness patterns. In the present study we test alternative productivity–diversity hypotheses using vegetation data from the vast Eurasian tundra. The productivity–species pool hypothesis predicts positive relationships at both fine and coarse grain sizes, whereas the productivity–interaction hypothesis predicts unimodal patterns at fine grain size, and monotonic positive patterns at coarse grain size. We furthermore expect to find flatter positive (productivity–species pool hypothesis) or more strongly negative (productivity–interaction hypothesis) relationships for lichens and bryophytes than for vascular plants, because as a group, lichens and bryophytes are better adapted to extreme arctic conditions and more vulnerable to competition for light than the taller‐growing vascular plants. The normalised difference vegetation index (NDVI) was used as a proxy of productivity. The generally unimodal productivity–diversity patterns were most consistent with the productivity–interaction hypothesis. There was a general trend of decreasing species richness from moderately to maximally productive tundra, in agreement with an increasing importance of competitive interactions. High richness of vascular plants and lichens occurred in moderately low productive tundra areas, whereas that of bryophytes occurred in the least productive tundra habitats covered by this study. The fine and coarse grain richness trends were surprisingly uniform and no variation in beta diversity along the productivity gradient was seen for vascular plants or bryophytes. However, lichen beta diversity varied along the productivity gradient, probably reflecting their sensitivity to habitat conditions and biotic interactions. Overall, the results show evidence that productivity–diversity gradients exist in tundra and that these appear to be largely driven by competitive interactions. Our results also imply that climate warming‐driven increases in productivity will strongly affect arctic plant diversity patterns.     

Plant colonisation in small forest–floor patches: importance of plant group and disturbance traits

It has been proposed that the interaction between life–history attributes of different organisms and distrbance characteristics play an important role in determining the successional pattern following a disturbance event. We compared the responses of vascular plants and bryophytes (mosses and hepatics) to variation in disturbance size and severity in an old-growth boreal forest during a four–year period. The experiment included two patch sizes (0.25 and 2.5 m²) and two levels of severity: humus patches (removal of vegetation) and mineral soil patches (removal of both vegetation and humus layer). Treatments were chosen to reflect some aspects of disturbance by uprooting. Species richness was significantly affected by both disturbance size and severity but the response differed among plant groups. In vascular plants, species numbers were highest in humus patches while mosses were more numerous in mineral soil patches, the most severe disturbance. In contrast, severity had no effect on hepatics. Plant recovery was more rapid in bryophytes than in vascular plants. Species richness of bryophytes had exceeded that of adjacent, undisturbed vegetation after 2-3 yr. We attribute the contrasting response of the plant groups to differences in regeneration strategies. As a group, bryophytes had a greater variety of regeneration methods than vascular plants, with several types of asexual propagules and abundant production of spores in some species. In contrast, clonal ingrowth dominated in vascular plants while seedlings were rare. Thus, our analysis supports the view that plant response to patchy disturbance is strongly dependent on the interplay among disturbance traits and specific attribtites of different plant groups.     

Disturbance effects on diversity of epiphytes and moths in a montane forest in Ecuador

We sampled the diversity of epiphytes (lichens, bryophytes, vascular plants) and moths (Geometridae, Arctiidae) in mature and recovering forest and in open vegetation in the montane belt in Ecuador. No uniform pattern of change in species richness was detected among the different taxonomic groups with increasing disturbance. Species richness of epiphytic bryophytes and vascular plants declined significantly from mature forest towards open vegetation. In contrast, species richness of epiphytic lichens did not change with increasing forest alteration, while that of geometrid moths was significantly higher in recovering forest compared with mature forest and open habitats. Arctiidae were significantly more species-rich in recovering forest and open vegetation than mature forest. Hence, for some organisms, modified habitats may play an important role for biodiversity conservation in the Andes, whereas others suffer from habitat disturbance. However, trends of changes in species composition following deforestation were surprisingly concordant across most studied epiphyte and moth taxa.     

The impact of land abandonment on the plant diversity of olive groves

We investigated the effect of woody species’ encroachment on plant diversity changes with regard to vascular plants and bryophytes in traditional olive groves of the Maremma Regional Park (Tuscany, Italy) and assessed cross-taxon correlation between these two taxa. We classified the olive groves into four land use types, representing different successional stages. To describe the evenness of species distribution within a community, we plotted rank-abundance diagrams for each taxon and each land use type. The relationship between the number and cover of vascular plants, therophytes, bryophytes, colonists and phanerophytes in each plot was examined using linear regression. The effects of land use type on vascular plant and bryophyte richness and assemblages were assessed by permutational uni- and multivariate analysis of variance. The congruence in species composition between the two taxa was evaluated using Procrustes analysis. The number of vascular plants, bryophytes and therophytes decreased linearly with increased phanerophyte species cover. The number of species belonging to Thero-Brachypodietea progressively decreased throughout succession. Rank-abundance diagrams and multivariate analysis showed differences between the land use types, which were statistically significant for vascular plants between the traditional olive groves and the other land use types, and for bryophytes between the traditional olive groves and woodlands. PROTEST analysis and NMDS graphs showed a correlation between vascular plant and bryophyte communities. The results suggested that conservation measures are needed in the study area in order to ensure both the maintenance of traditional olive groves of conservation interest and high levels of environmental heterogeneity.     

Environmental controls of raised-bog vegetation in the Baltic boreo-nemoral zone

Raised peat bogs harbor unique vegetation types in specific hydrological conditions. Environmental controls of peat bog vegetation are relatively well known for the boreal zone, while in the European boreo-nemoral zone healthy raised bogs are nowadays very rare. By contrast, Latvia, located in the transition zone between the nemoral and the boreal biomes, still has a large number of active raised bogs. The aim of the present study was to characterize the environmental controls on raised bog vegetation structure, species composition and ecology in Latvia. The study includes 17 raised bogs, where vascular plants, bryophytes and lichens were recorded in 480 sample plots and related to environmental variables (microtopography, litter cover, electric conductivity, pH, and macroelements Na, K, Ca, Mg and P in bog surface waters). The factor best explaining total species richness and composition was microtopography, which also affected most other explanatory factors. Thereby total species richness and cover were highest on hummocks. However, the importance and direction of the effects of microtopography and the other factors differed between vegetation groups. When disregarding microtopography, species composition was most strongly correlated with alkaline ions and litter cover and for bryophytes also with vascular plant cover. The present study is the first wide-scale study in Latvia relating raised bog vegetation to environmental conditions.     

Is vascular plant species diversity a predictor of bryophyte species diversity in Mediterranean forests?

This study aimed to (i) investigate the congruence among the species composition and diversity of bryophytes and vascular plants in forests; (ii) test if site prioritization for conservation aims by the maximization of the pooled number of vascular plant species is effective to maximize the pooled number of bryophyte species. The study was performed in six forests in Tuscany, Italy. Four-hundred and twenty vascular plant species (61 of which were woody) and 128 bryophyte species were recorded in 109 plots. Despite the good predictive value of the compositional patterns of both woody plants and total vascular with respect to the compositional pattern of bryophytes, the species richness of the latter was only marginally related to the species richness of the former two. Bryophyte rare species were not spatially related to rare plant species and neither coincided with the sites of highest plant species richness. The species accumulation curves of bryophytes behaved differently with respect to those of woody plants or total vascular plants. Reserve selection analysis based on the maximization of the pooled species richness of either woody plants or total vascular plants were not effective in maximizing the pooled species richness of bryophytes. This study indicates that species diversity of vascular plants is not likely to be a good indicator of the bryophyte species diversity in Mediterranean forests.     

Do vascular plants and bryophytes respond differently to coniferous invasion of coastal heathlands?

Invasion by non-native conifers may pose a threat to local biodiversity, but knowledge about introduced conifer effects on Northern Hemisphere ecosystems is scarce. The coastal heathlands of north-west Europe are threatened by invasion of native and introduced tree species. We assess how spread of the introduced conifer Sitka spruce (Picea sitchensis (Bong.) Carr.) into European coastal heathlands affect two major functional groups; vascular plants and bryophytes, and how these effects relate to the environmental changes imposed by the developing tree canopies. We compared the impact of introduced Sitka spruce and native Scots pine (Pinus sylvestris L.) by analysing effects on species richness and turnover of vascular plants and bryophytes along fine-scale transects from individual tree stems into open heathland vegetation. Environmental impacts were assessed by measured environmental variables, and the responses of the two species groups were assessed by calculating changes in their respective mean Ellenberg indicator values. Species richness decreased beneath both conifers, related to decreased light and increased nitrogen and pH. Whereas vascular plants responded negatively to poor light conditions beneath dense and low Sitka spruce canopies, bryophytes were more negatively affected by the warmer and drier microclimates beneath Scots pine. Introduced Sitka spruce impacts the sub-canopy environment differently from the native Scots pine, and the two functional plant groups responded differently to these impacts. This suggests that future forests are likely to differ in species richness and composition, depending on whether succession is based on native or introduced coniferous trees.     

Biodiversity surrogate effectiveness in two habitat types of contrasting gradient complexity

Enormous and increasing loss of biodiversity requires evaluation of surrogate taxa as a tool for conservation biology and new reserve selection, in spite of the fact that this approach has become questionable. The aim of this study was to assess the effect of gradient complexity on species richness and community composition among three taxonomic groups. We compared efficiency of vascular plants to indicate diversity of cryptogams (bryophytes, lichens) and snails in two contrasting habitat types (treeless fens and forests) within the same geographic region. We examined correlation of their species richness (Spearman rank correlation), community composition (Bray–Curtis similarity, Mantel test) and their responses to environmental variables (detrended and canonical correspondence analysis). We also focused on Red List species. We found that spatial congruence among studied taxa was affected by habitat type, however vascular plants were good indicator of snail biodiversity in both habitats. Nevertheless, all significant positive correlations of species richness were associated with the congruence in main environmental gradients. Although there was a consistency in significantly positive cross-taxon correlation in community similarity, the congruence was insufficient for conservation purposes. Furthermore we confirmed the necessity of integration of at-risk species in conservation planning as Red List species were poor indicators for total species richness and vice versa. We suggest the complementation of existing reserve network with small-scale protected areas focused on conservation of at-risk ecosystems, communities or species. In this study vascular plants were not found as a sufficient indicator for fine-filter conservation of other taxa.     

Bryophyte and Lichen Diversity Under Simulated Environmental Change Compared with Observed Variation in Unmanipulated Alpine Tundra

Effects of simulated environmental change on bryophyte and lichen species richness and diversity in alpine tundra were investigated in a 5-year experiment at Latnjajaure, northern Sweden. The experiment had a factorial design including fertilisation and temperature enhancement in one meadow and one heath plant community. Responses in species richness, biodiversity, and species composition of bryophytes and lichens to experimental treatments were compared to the observed variation in six naturally occurring plant communities. The combination of fertilisation and enhanced temperature resulted in a species impoverishment, for bryophytes in the bryophyte-dominated community, and for lichens in the lichen-dominated communities, but the species composition stayed within the observed natural variation. During the course of the study, no species new to the investigated mid-alpine landscape were recorded, but that scenario is realistic within a decade when comparing with the processes seen in vascular plants.     

Microtopographic control of vascular plant, bryophyte and lichen communities on cliff faces

Cliff faces worldwide have recently been recognized as sites that harbour ancient forests, endangered biota and high levels of biodiversity, but knowledge is limited of the physical factors organizing cliff-face vegetation communities. Two large scale (geographic), five local, and eight fine scale (microtopographic) physical factors were examined using regression and Canonical Correspondence Analysis (CCA) to determine what scale of physical factors best explains variation in cliff-face vegetation on the 785 km long Niagara Escarpment in southern Ontario, Canada. The richness, frequency and community composition of vascular plants, bryophytes and lichens were determined for 72 cliff-face quadrats to discern whether these vegetation groups followed different patterns in their responses to the measured physical factors. A total of 124 different taxa (consisting of 50 vascular plant species, 21 bryophyte species, and 53 lichen taxa) were found on the cliff faces sampled in this study, though only 28 of these taxa were present in more than 10% of the sampled quadrats. Vascular plant and bryophyte species richness and frequency, and lichen frequency were only significantly correlated with microtopographic factors, while lichen species richness was correlated with a variety of fine and local scale physical factors. The fine scale factor ‘volume of soil’, in particular, was highly correlated with variation in richness or frequency for all vegetation groups, with increasing volume of soil correlated with increasing vascular plant richness and frequency and decreasing bryophyte richness and lichen frequency. A suite of local and fine scale physical factors also explained large proportions of variation in cliff-face vegetation community composition. A large scale gradient in the vegetation community was detected, though it resulted from fine scale physical differences between sites rather than from a latitudinal gradient. These results suggest that distinct subcommunities of vegetation exist on cliff faces and correlate with fine scale differences in microtopography.     

Impact of climate change on alpine vegetation of mountain summits in Norway

Climate change is affecting the composition and functioning of ecosystems across the globe. Mountain ecosystems are particularly sensitive to climate warming since their biota is generally limited by low temperatures. Cryptogams such as lichens and bryophytes are important for the biodiversity and functioning of these ecosystems, but have not often been incorporated in vegetation resurvey studies. Hence, we lack a good understanding of how vascular plants, lichens and bryophytes respond interactively to climate warming in alpine communities. Here we quantified long-term changes in species richness, cover, composition and thermophilization (i.e. the increasing dominance of warm-adapted species) of vascular plants, lichens and bryophytes on four summits at Dovrefjell, Norway. These summits are situated along an elevational gradient from the low alpine to high alpine zone and were surveyed for all species in 2001, 2008 and 2015. During the 15-year period, a decline in lichen richness and increase in bryophyte richness was detected, whereas no change in vascular plant richness was found. Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects. Lichens showed less thermophilization and, for the bryophytes, no significant thermophilization was found. Although recent climate change may have primarily caused the observed changes in vegetation, combined effects with non-climatic factors (e.g. grazing and trampling) are likely important as well. At a larger scale, alpine vegetation shifts could have a profound impact on biosphere functioning with feedbacks to the global climate.