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1.
  • Bruun, Hans Henrik, et al. (författare)
  • Effects of altitude and topography on species richness of vascular plants, bryophytes and lichens in alpine communities
  • 2006
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 17:1, s. 37-46
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: What is the relationship between species richness of vascular plants, bryophytes and macrolichens, and two important gradients in the alpine environment, altitude and local topography? Location: Northernmost Fennoscandia, 250-152 m a.s.l. corresponding to the range between timberline and mountain top. Methods: The vegetation was sampled in six mountain areas. For each 25 vertical metres, the local topographic gradient from wind-blown ridge to snowbed was sampled in quadrats of 0.8 m x 0.8 m. Patterns in species richness were explored using Poisson regression (Generalized Linear Models). Functional groups of species, i.e. evergreen and deciduous dwarf-shrubs, forbs, graminoids, mosses, hepatics and lichens were investigated separately. Results: Functional groups showed markedly different patterns with respect to both altitude and topography. Species richness of all vascular plants showed a unimodal relationship with altitude. The same was true for graminoids, forbs and lichens analysed separately, but forb richness peaked at Much higher altitudes than total richness. The richness of dwarf-shrubs decreased monotonically with altitude, whereas richness of mosses and liverworts showed an increasing trend. Significant interactions between altitude and local topography were present for several groups. The unimodal pattern for total plant species richness was interpreted in terms of local productivity, physical disturbance, trophic interactions, and in terms of species pool effects. Conclusions: Patterns in local species richness result from the action of two opposing forces: declining species pool and decreasing intensity of competition with altitude.
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2.
  • Reitalu, Triin, et al. (författare)
  • Responses of grassland species richness to local and landscape factors depend on spatial scale and habitat specialization
  • 2012
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1654-1103 .- 1100-9233. ; 23:1, s. 41-51
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions: To what extent is species richness in semi-natural grasslands related to local environmental factors and (present/past) surrounding landscape structure? Do responses of species richness depend on degree of habitat specialization (specialists vs generalists) and/or scale of the study? Location: Öland, Sweden. Methods: Richness of herbaceous vascular plants (subdivided into richness of grassland specialists and generalists) was recorded within 50 9 50 cm plots and 0.1–4.8 ha grassland polygons. Generalized linearmodels and hierarchical partitioning were used to identify local factors (habitat area and heterogeneity, grazing intensity, habitat continuity) and landscape factors (proportion of surrounding grassland in 2004, 1938 and 1800, and landscape diversity in 2004)associated with the richness estimates. Results: At the polygon scale, both specialist and generalist richness was positively associated with local habitat area and heterogeneity and, independently of area and heterogeneity, with grazing intensity, habitat continuity and amount of surrounding grassland in 1800. At the plot scale, specialist species richness was positively associated with habitat heterogeneity, amount of surrounding grassland in 2004 and landscape diversity. Plot-scale generalist richness was negatively associated with surrounding grassland in 1938 and positively associated with local grazing intensity. Conclusions: Because both habitat specialization and study scale influence conclusions about relationships between species richness and local and landscape factors, the study highlights the need to consider species diversity at multiple spatial scales when making decisions about grassland management. Large-scale(polygon) species richness is influenced by immigration processes, with both specialists and generalists accumulating in old grasslands over centuries of grazing management. Habitat heterogeneity increased specialist species richness at both scales, suggesting that management policies should favour maintenance of a heterogeneous mosaic of open areas, trees and shrubs in temperate grazed grasslands. Although grassland specialists are sensitive to grassland isolation, in extensively managed landscapes with high landscape diversity input of grassland species from the landscape matrix may buffer negative effects of habitat fragmentation on grassland communities.
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3.
  • Auffret, Alistair G., et al. (författare)
  • Grazing networks provide useful functional connectivity for plants in fragmented systems
  • 2012
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 23:5, s. 970-977
  • Tidskriftsartikel (refereegranskat)abstract
    • Question To what extent does the movement of animals between fragmented habitat patches provide functional connectivity via endozoochorous seed dispersal? Location The Stockholm archipelago, Sweden. Methods We followed all movements of livestock between islands during one grazing season. After each movement, manure was collected and its seed content assessed through seedling emergence. Seedling data were then compared to vegetation surveys from the grazed islands with regard to functional traits. Results Light- and nitrogen-demanding locally abundant species, and those with relatively small and persistent seeds were more likely to be moved between islands. For quantitative traits, only a subset of the available trait ranges were dispersed, with extreme values left behind. Species apparently specialized to other means of dispersal emerged from the manure samples. Neither dispersed traits nor seed density changed with timing of movement, but seed richness and diversity both increased throughout the season. The subsets of endozoochorously-dispersed species in the established vegetation were more similar than non-dispersed subsets between islands linked by livestock. Conclusions Grazing networks contribute to the connectivity of the core species in the system, and could provide useful tools for grassland management in fragmented landscapes.
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4.
  • Cousins, Sara (författare)
  • Extinction debt in fragmented grasslands: paid or not?
  • 2009
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 20:1, s. 3-7
  • Tidskriftsartikel (refereegranskat)abstract
    • Fragmentation of grasslands and forests is considered amajor threat to biodiversity. In the case of plants, theeffect of fragmentation or landscape context is still unclearand published results are divergent. One explanation forthis divergence is the slow response of long-lived plants,creating an extinction debt. However, this has not beenempirically confirmed. In this study, data were compiledfrom broad-scale studies of grasslands from throughoutthe world that relate plant diversity to fragmentationeffects. Only seven studies from northern Europe, out ofa total 61, gave any information on actual habitat fragmentationin time and space. In landscapes with 410%grassland remaining, present-day species richness wasrelated to past landscape or habitat pattern. In landscapeswith o10% grassland remaining, in contrast, plant speciesrichness was more related to contemporary landscapeor habitat pattern. Studies from landscapes with 410%grassland remaining supported the concept of an extinctiondebt, while studies from more fragmented landscapesdid not provide any evidence of an extinction debt. Inorder to make generalisations about historical legacies onspecies diversity in grasslands it is important to consider arange of highly transformed landscapes, and not onlylandscapes with a high amount of grassland remaining.
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5.
  • Dengler, Jürgen, et al. (författare)
  • Species constancy depends on plot size - a problem for vegetation classification and how it can be solved
  • 2009
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 20:4, s. 754-766
  • Tidskriftsartikel (refereegranskat)abstract
    • Question   While it is well known that species richness depends on plot size, it  is not generally recognised that the same must be true for constancy. Accordingly, many authors use varying plot sizes when classifying   vegetation based on the comparison of constancies between groups of plots. We ask whether the constancy-area relationship follows a general   rule, how strong the effect of plot sizes is on constancies, and if it  is possible to correct constancies for area. Location For empirical evaluation, we use data from plant communities in the   Czech Republic, Sweden and Russia.   Methods   To assess the potential influence of differences in plot size on   constancies, we develop a mathematical model. Then, we use series of   nested plot species richness data from a wide range of community types   (herbaceous and forest) to determine the parameters of the derived   function and to test how much the shape of the constancy-area   relationship depends on taxa or vegetation types.   Results   Generally, the constancy-area relationship can be described by C   (A)=1-(1-C-0)((A/A0)boolean AND d), with C being constancy, A area, C-0   known constancy on a specific area A(0), and d a damping parameter   accounting for spatial autocorrelation. As predicted by this function,   constancies in plant communities always varied from values near 0% to   near 100% if plot sizes were changed sufficiently. For the studied   vegetation types, a two- to fourfold increase in plot size resulted in   a change of conventional constancy classes, i.e. an increase of   constancy by 20% or more.   Conclusions   Vegetation classification, which largely relies on constancy values,   irrespective of whether traditional or modern fidelity definitions are   used, is strongly prone to distorting scale effects when releves of   different plot sizes are combined in studies. The constancy-area   functions presented allow an approximate transformation of constancies   to other plot sizes but are flawed by idiosyncrasies in taxa and   vegetation types. Thus, we conclude that the best solution for future   surveys is to apply uniform plot sizes within a few a priori delimited   formations and to determine diagnostic species only within these   formations. Finally, we suggest that more detailed analyses of constancy-area relationships can contribute to a better understanding of species-area relationships because the latter are the summation of the first for all species.
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6.
  • Eriksson, Ove, et al. (författare)
  • Land-use history and fragmentation of traditionally managed grasslands in Scandinavia
  • 2002
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 13:5, s. 743-748
  • Tidskriftsartikel (refereegranskat)abstract
    • Plants associated with traditional agricultural landscapes in northern Europe and Scandinavia are subjected to drastic habitat fragmentation. In this paper we discuss species response to fragmentation, against a background of vegetation and land-use history. Recent evidence suggests that grassland-forest mosaics have been prevalent long before the onset of human agriculture. We suggest that the creation of infield meadows and outland grazing (during the Iron Age) increased the amount and spatial predictability of grasslands, resulting in plant communities with exceptionally high species densities. Thus, distribution of plant species in the present-day landscape reflects historical land-use. This holds also when traditional management has ceased, due to a slow response by many species to abandonment and fragmentation. The distribution patterns are thus not in equilibrium with the present habitat distribution. Fragmentation influences remaining semi-natural grasslands such that species density is likely to decline as a result of local extinctions and invasion by habitat generalists. However, species that for a long time have been subjected to changing mosaic landscapes may be more resistant to fragmentation than is usually believed. Conservation should focus not only on 'hot-spots' with high species richness, but also consider species dynamics in a landscape context.
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7.
  • Gallegos Torell, Åsa, et al. (författare)
  • Computer-aided calibration for visual estimation of vegetation cover
  • 2009
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 20, s. 973-983
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionWhat precision and accuracy of visual cover estimations can be achieved after repeated calibration with images of vegetation in which the true cover is known, and what factors influence the results?MethodsDigital images were created, in which the true cover of vegetation was digitally calculated. Fifteen observers made repeated estimates with immediate feedback on the true cover. The effects on precision and accuracy through time were evaluated with repeated proficiency tests. In a field trial, cover estimates, before and after calibration, were compared with point frequency data.ResultsEven a short time of calibration greatly improves precision and accuracy of the estimates, and can also reduce the influence of different backgrounds, aggregation patterns and experience. Experienced observers had a stronger tendency to underestimate the cover of narrow-leaved grasses before calibration. The field trial showed positive effects of computer-based calibration on precision, in that it led to considerably less between-observer variation for one of the two species groups.ConclusionsComputer-aided calibration of vegetation cover estimation is simple, self-explanatory and time-efficient, and might possibly reduce biases and drifts in estimate levels over time. Such calibration can also reduce between-observer variation in field estimates, at least for some species. However, the effects of calibration on estimations in the field must be further evaluated, especially for multilayered vegetation.
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8.
  • Hedenås, H, et al. (författare)
  • Spatial distribution of epiphytes on Populus tremula in relation to dispersal mode
  • 2003
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 14:2, s. 233-242
  • Tidskriftsartikel (refereegranskat)abstract
    • We examined if the spatial distribution of epiphytes in a forest stand differs between two sexually and three asexually dispersed species. As study species we have chosen two sexually dispersed species, the lichen Collema curtisporum and the bryophyte Orthotrichum speciosum, and three asexually dispersed species, the lichens C. furfuraceum and Leptogium saturninum and the bryophyte O. obtusifolium. All of these species grow on Populus tremula. In P. tremula stands, individual trees may be regarded as distinct patches for the studied species, while the stand represents a 'landscape" of discrete patches. The study was performed in two relatively homogeneous forest stands. The study revealed that the asexually dispersed species were more common than the sexually dispersed. It was also shown that the sexually dispersed species were more aggregated than P. tremula in both stands. In contrast, the distribution of the asexually dispersed species mirrors, more or less, the distribution of their host, i.e. the spatial pattern shown by P. tremula. It is unlikely that the measured environmental variables strongly influenced the observed spatial distribution. Thus, we suggest that the different dispersal and establishment strategies were important in shaping the local distribution of the species.
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9.
  • Hedwall, Per-Ola, et al. (författare)
  • Changes in the abundance of keystone forest floor species in response to changes of forest structure
  • 2013
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 24, s. 296-306
  • Tidskriftsartikel (refereegranskat)abstract
    • Question Does the abundance of keystone forest floor species change in response to changes in the forest structure? Location Sweden Methods We used data from the Swedish National Forest Inventory to investigate changes in the abundance of three common species, as well as the total abundance of all understorey vascular plants (the field layer) in forests in the boreal and temperate parts of Sweden. GLMs and GAMs were used to relate species abundance and temporal changes in abundances to forest structure and forest structural change. Results Productivity, measured as the site index, was the most important determinant of individual species' abundance. The volume of Picea abies, the density of tree stems and forest age were among the most important forest structural variables. We found that the dwarf shrub Vaccinium myrtillus, the narrow-leaved grasses (mainly Avenella flexuosa) and the total field layer cover decreased in boreal Sweden from 1994 through 2010 and that these changes coincided with an increase in forest density and with a reduction in forest age. Conclusions Changes in Swedish forests to higher tree layer density and younger age appear to contribute significantly to current changes in forest floor vegetation. The use of more intensive thinning practices to reduce the total density of the forest and to increase the proportion of broad-leaved tree species and Pinus sylvestris would favour the forest floor species in this study. Moreover, increasing forest age (i.e. the length of rotation periods) might favour V. myrtillus in particular, for which the time since disturbance is important for the recovery of pre-disturbance abundance. However, increased thinning intensity and forest age will reduce the potential for wood production, implying a trade-off between production of wood and maintenance of well-developed forest floor vegetation.
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10.
  • Hofgaard, Annika, et al. (författare)
  • Tree recruitment above the treeline and potential for climate-driven treeline change
  • 2009
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 20:6, s. 1133-1144
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions   How do population structure and recruitment characteristics of Betula   saplings beyond the treeline vary among climatic regions, and what is   the potential for development into tree-sized individuals with   interacting grazing pressure?   Location   Scandes Mountains.   Methods   Sapling characteristics of Betula pubescens subsp. tortuosa, their   topographic position above the treeline, growth habitat and evidence of   recent grazing was investigated in three areas with a long continuous   grazing history, along a latitudinal gradient (62-69 degrees N).   Results   Saplings were common up to 100 m above the treeline in all areas. The   northern areas were characterised by small (< 30 cm) and young (mean 14   years old) saplings in exposed micro-topographic locations unfavourable   to long-term survival. In the southern area, broad height (2-183 cm)   and age (4-95 years; mean 32 years) distributions were found in   sheltered locations. Age declined with altitude in all areas. Sapling   growth rate varied within and between areas, and the age x height   interaction was significant only in the southern area. Growth rates   decreased from south to north and indicated a considerable time   required to reach tree size under prevailing conditions.   Conclusions   Regional differences can be attributed to climatic differences,   however, interacting biotic and abiotic factors such as   micro-topography, climate and herbivory, mutually affect the   characteristics of birch saplings. In view of the long time needed to   reach tree size, the generally expected evident and fast treeline   advance in response to climate warming may not be a likely short-term   scenario. The sapling pool in the southern region possesses strongest   potential for treeline advance.
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11.
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12.
  • Hylander, Kristoffer, et al. (författare)
  • In situ survival of forest bryophytes in small-scale refugia after an intense forest fire
  • 2010
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 21:6, s. 1099-1109
  • Tidskriftsartikel (refereegranskat)abstract
    • Question Species can persist in landscapes with recurring disturbances either by migrating to places suitable for the moment or by enduring the threatening conditions. We investigated to what extent boreal forest bryophytes survived an intense forest fire in situ and whether bryophytes had started to recolonize the area 7-8 years later. Location Tyresta National Park, eastern Sweden. Methods We recorded bryophytes in 14 burnt and 12 forest reference plots (50 x 50 m). In each plot we investigated 15 random 1-m2 micro-plots. In plots in the burnt area we also examined micro-plots at locations of all fire refugia, and in case of the forest references, of 10 potential refugia. Results We found on average three small refugia per 50 x 50-m plot; each containing on average 4.8 forest bryophytes, a level similar to that of micro-plots in the references, but significantly higher than in random micro-plots in the burnt plots (1.5 species). Many refugia were located in rocky areas, but few were in wet sites. The burnt area remained dominated by a few fire-favoured species, even if recolonization of forest bryophytes had begun. There was, however, no significant correlation between number of refugia and number of forest species in random micro-plots, leaving open the question of the importance of refugia as regulators of early succession. Conclusion We conclude that small-scale refugia can also occur for sensitive species such as forest bryophytes, and that the refugia in our case were frequently found on rocky or mesic rather than wet sites. The role of such refugia in recolonization, however, warrants further investigation.
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13.
  • Johansson, Victor, et al. (författare)
  • Detection probability and abundance estimation of epiphytic lichens based on height-limited surveys
  • 2010
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 21, s. 332-341
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionsWhat are the detection probabilities of epiphytic crustose lichens on oak (Quercus robur) when only the lowest 2 m of the trunk are surveyed? How does the abundance of lichen species change with height above the ground, and is the change related to tree age? How well can total abundance (0-6 m) be predicted based on data from the lowest 2 m? Which tree characteristics explain the vertical distribution of the study species?LocationSoutheast Sweden.MethodsThe occurrence and abundance of eight crustose lichen species were recorded on 35 oaks, 0-6 m from the ground.ResultsThe detection probability was high (> 96%) for seven out of the eight species. The abundance of six species declined significantly with increasing height. For five species, > 69% of the total abundance (0-6 m) was recorded on the lowest 2 m. The proportion of the total abundance present above 2 m increased significantly with age for three species. Models predicting total abundance based on data from the lowest 2 m and diameter explained > 80% of the deviance for all except one species. The vertical distribution of the study species was explained by bark fissure depth, area and cover of macrolichens.ConclusionsFor crustose lichens associated with old oaks, surveying only the lowest 2 m of the trunk yields reliable occurrence data and fairly good estimates of total abundance. However, before interpreting data from the lowest 2 m, knowledge of species vertical distribution, and how the distribution changes with tree age is essential.
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14.
  • Jönsson, Mari, et al. (författare)
  • Forest history and the development of old-growth characteristics in fragmented boreal forests
  • 2009
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 20:1, s. 91-106
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions: Can small and isolated high-conservation value forests (e.g. designated woodland key habitats) maintain old-growth forest characteristics and functionality in fragmented landscapes? To what extent have past disturbances (natural and anthropogenic) influenced the development of old-growth characteristics of these forests? How long does it take for selectively cut stands to attain conditions resembling old-growth forests? Location: Southern boreal zone of central Sweden. Methods: We linked multiple lines of evidence from historical records, biological archives, and analyses of current forest structure to reconstruct the forest history of a boreal landscape, with special emphasis on six remaining core localities of high-conservation value forest stands. Results: Our reconstructions revealed that several of these stands experienced wildfires up to the 1890s; all had been selectively harvested in the late 1800s; and all underwent substantial structural and compositional reorganization over the following 100-150 years. This time interval was sufficient to recover considerable amounts of standing and downed dead wood (mean 60.3 m3 ha−1), a range of tree ages and sizes (mean basal area 32.6 m2 ha−1), and dominance of shade-tolerant spruce. It was insufficient to obtain clearly uneven tree age structures and large (>45 cm diameter) living and dead trees. Thus, these forests contain some, but not all, important compositional and structural attributes of old-growth forests, their abundance being dependent on the timing and magnitude of past natural and anthropogenic disturbances. Our landscape-level analysis showed marked compositional and structural differences between the historical forest landscape and the present landscape, with the latter having a greater proportion of young forests, introduction of non-native species, and lack of large trees and dead wood. Conclusions: The remnant high-conservation value stands were not true representatives of the pre-industrial forests, but represent the last vestige of forests that have regenerated naturally and maintained a continuous tree cover. These traits, coupled with their capacity for old-growth recovery, make them valuable focal areas for conservation. 
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15.
  • Marteinsdottir, Bryndis, et al. (författare)
  • Development of vegetation patterns in early primary succession
  • 2010
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 21:3, s. 531-540
  • Tidskriftsartikel (refereegranskat)abstract
    • Question We investigated colonisation filters in early plant community development on a glacial outwash plain. We asked if these were related to seed limitation or to a lack of safe sites, if topographical heterogeneity affected species patchiness and how species life cycles influence successional trajectories. Location An outwash plain (Skeithararsandur) in southeast Iceland. Methods We identified surface heterogeneity at two different scales, ca. 10-15 cm (larger stones and established plants) and ca. 50 m (shallow depressions representing dry river beds) at two study sites. We quantified species cover, flowering plant density, seed production, seed rain, seed bank density, seedling emergence and seedling survival from June 2005 to June 2007 for the whole plant community, and measured seed production for five species. Results Mean vegetation cover was < 2.5% at the sites. Low emergence rates and high seedling mortality were the two main recruitment filters. Only 1.4% of seedlings emerging in 2005 survived into the 2007 growing season. Topographical heterogeneity had little effect on plant colonisation. High annual variation was recorded, and the two study sites (ca. 2 km apart) differed in their colonisation success. Of the five species, establishment of Cerastium alpinum and Silene uniflora was most limited by lack of seeds, whereas establishment of Luzula spicata, Poa glauca and Rumex acetosella was most limited by safe sites. Conclusions We conclude that colonisation processes and patterns in early primary succession on Skeithararsandur were largely influenced by stochastic factors.
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16.
  • Mathisen, Karen Marie, et al. (författare)
  • Moose density and habitat productivity affects reproduction, growth and species composition in field layer vegetation
  • 2010
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 21, s. 705-716
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionWhat is the effect of a gradient in moose density on reproduction, growth and functional composition of the field layer vegetation in a boreal forest, and how is this effect modified by habitat productivity?LocationNorthwest of Umea, Vasterbotten, northern Sweden.MethodsField layer vegetation was surveyed in an experimental setup with simulation of three different moose densities and a control in eight study sites along a gradient of habitat productivity.ResultsWe found that increased moose density led to decreased cover and reproductive effort of a browsed dwarf shrub (bilberry, Vaccinium myrtillus L.) and increased cover and reproductive effort of a non-browsed graminoid (wavy hair-grass, Avenella flexuosa (L.) Drejer). Increased moose density led to increased light availability and probably reduced competition from V. myrtillus. Total reproductive effort in the field layer vegetation increased, height decreased and cover of light-demanding species and graminoids increased with increasing moose density. The effects of moose density were modified by the productivity gradient, leading to a higher relative increase in light availability and reproductive effort in highly productive areas than in low productive areas.ConclusionsIncreased light availability was an important indirect effect of moose density, leading to less competition for light and a shift towards early successional species. The effect of moose density on light availability was modified by habitat productivity, leading to stronger relative effects in highly productive areas than in low productive areas.
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17.
  • Moen, Jon, et al. (författare)
  • Variations in mountain vegetation use by reindeer (Rangifer tarandus) affects dry heath but not grass heath
  • 2009
  • Ingår i: Journal of Vegetation Science. - : John Wiley & Sons. - 1100-9233 .- 1654-1103. ; 20, s. 805-813
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: Are differences in landscape use of semi-domesticated reindeer reflected in the vegetation of summer grazing grounds?Location: Alpine heaths, central east Sweden.Methods: Dry heath and grass heath vegetation plots with inferred grazing intensities (high, intermediate and low) were selected a priori from an interpolated pellet count map compiled in 2002. In each plot, faecal pellets were counted, environmental variables measured and vegetation sampled by listing presence and absence. Species composition was compared with a detrended correspondence analysis, and a canonical correspondence analysis was used to infer relations between species composition and environmental variables. Plots were also clustered to provide groupings for an indicator species analysis.Results: Significant differences in faecal pellet count were present between the highest and lowest grazing intensities for both vegetation types, showing that the pattern in the interpolated pellet maps was robust. Differences in species composition between grazing intensities were found for the dry heath only. Here, there was an apparent grazing gradient, with lichens and mosses in the low-use plots and grasses and herbs in the high-use plots. No such gradient was found for the grass heath.Conclusions: Within the dry heath vegetation type, grazing levels had a subtle effect on the vegetation, while no effects were seen in the grass heath, probably as a result of the dominance of more grazing-tolerant graminoids. Even in the dry heath, species richness did not differ between grazing levels, but the relative abundances of species differed.
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18.
  • Pajunen, A.M., et al. (författare)
  • Compositional differentiation, vegetation-environment relationships and classification of willow-characterised vegetation in the western Eurasian Arctic
  • 2010
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 21:1, s. 107-119
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: How does willow-characterised tundra vegetation of western Eurasia vary, and what are the main vegetation types? What are the ecological gradients and climatic regimes underlying vegetation differentiation?Location: The dataset was collected across a wide spectrum of tundra habitats at 12 sites in subarctic and arctic areas spanning from NW Fennoscandia to West Siberia.Methods: The dataset, including 758 vegetation sample plots (relevés), was analysed using a TWINSPAN classification and NMDS ordination that also included analyses of vegetation-environment correlations.Results: Based on the TWINSPAN classification, eight vegetation types characterised by willow (cover of upright willows >10%) were discerned: (1) Salix glauca-Carex aquatilis type, (2) Aulacomnium-Tomentypnum type, (3) Salix-Betula-Hylocomium type, (4) Salix lanata-Brachythecium mildeanum type, (5) Salix-Pachypleurum type, (6) S. lanata-Myosotis nemorosa type, (7) Salix-Trollius-Geranium type and (8) Salix-Comarum palustre-Filipendula ulmaria type. Willow-characterised vegetation types were compositionally differentiated from other tundra vegetation and were confined to relatively moist valley and sloping tundra sites, from mire to mineral soils. These vegetation types were encountered across a broad latitudinal zone in which July mean temperature ranged from 6 to 10°C.Conclusions: Willow-characterised tundra vegetation forms a broad category of ecologically and geographically differentiated vegetation types that are linked to dwarf shrub tundra, shrub tundra or mire. Because of complex ecological gradients underlying compositional differentiation, predicting the responses of willow-characterised tundra vegetation to a warming climate may be complicated.
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19.
  • Plue, Jan, et al. (författare)
  • Consistent seed bank spatial structure across semi natural habitats determines plot sampling
  • 2012
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 23:3, s. 505-516
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: Seed bank sampling remains a critical bottleneck to the quality of studies investigating community patterns in the seed bank. The main cause is a large knowledge gap in two aspects critical to sampling, i. e. spatial autocorrelation and species-area relations. The central question of this study is howthe seed bank of a single plot should be sampled, in order to obtain more precise estimates on plot seed bank characteristics, without resorting to a disproportionate investment of available resources. Similar seed bank samples may then enable better plot-based statistical inference of ecological patterns in the seed bank in community ecology studies. Location: Semi-natural habitats in Flanders (Belgium) and northern France. Methods: We investigated the fine-scale spatial structure of individual seed banking species across 12 2.1 m 9 2.1 m plots in three widespread habitats: temperate forest, grassland and heathland. Soil core samples (128) were collected in each plot, using a combined systematic (64) and random design (64). This enabled both geostatistical analyses of the fine-scale spatial structure of individual species-plot combinations as well as the calculation of sampled-based species rarefaction curves. Results: Fine-scale (i. e. within plot) spatial seed bank structure was detected in all plots in each habitat, in at least one or usually more plant species. Over half of the species records displayed significant spatial structure -visible as a random distribution of seed clusters -with medium to strong spatial dependence between point observations of a species of ca. 30 cm. Species rarefaction curves did not attain an asymptote at the actual sampling intensity of 128 samples. Seven out of 12 extrapolated species rarefaction curves did reach an asymptote in less than 384 samples. Conclusions: Using these consistent results in spatial structure and species-area relations across habitats, we present a method of how researchers can develop a tailor-made seed bank design to accommodate their individual needs, abiding by simple predefined boundaries. When the tailored design samples ca. 3% of a plot surface area along a systematic grid with a mesh width of at least 30 cm, these studies will potentially significantly increase the comparability among future seed bank community studies in semi-natural habitats.
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20.
  • Snäll, Tord (författare)
  • Forest fire history, aspen and goat willow in a Fennoscandian old-growth landscape: are current population structures a legacy of historical fires?
  • 2012
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 23, s. 1159-1169
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions Is the current aspen or goat willow populations in boreal old-growth forest a legacy of the historical fires? Location A middle-boreal, old-growth forest landscape with a large proportion of wetlands in eastern Finland. Method Forest fire history of a 2100-ha area was reconstructed using fire scars, forest age estimates and the presence or absence of charred stumps and charcoal particles in the soil in 63 systematically located plots. Age and size structures of aspen and goat willow were studied in a subsample of 12 plots. Results During the past 400yr, forest fires have been seven times more numerous in the study area than could be expected based on modern lightning fire statistics. The ages of mature aspens (average 177 and maximum 213yr) and mature goat willows (average 111 and maximum 173yr) were higher than earlier reported, strikingly so in goat willow. Aspen age structure clearly reflected the past fires. Most aspens originated from the beginning of the 19th century, during a period of frequent forest fires. The regeneration of aspen leading to mature trees has been very low since the cessation of forest fires in the late 19th century. In turn, goat willow has also regenerated in spite of the absence of fires. Conclusions The majority of the mature aspen trees were recruited at the time of the last fires, and there was a notable lack of middle-aged trees. This relationship to fires was not valid for goat willow. The main reason for the lack of young aspen cohorts in aspen populations in Fennoscandian old-growth stands is most likely the lack of forest fires. Small-scale gap dynamics cannot offset the lack of large-scale disturbances, such as forest fires, for the regeneration of aspen, possibly because of the prevailing herbivory and competitive effects. Hence, the population decline of aspen is likely to continue and to threaten a wealth of species specialized on aspen in boreal forests.
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21.
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22.
  • Voss, Nicole, et al. (författare)
  • Vegetation databases as a tool to analyse factors affecting the range expansion of the forest understory herb Ceratocapnos claviculata
  • 2011
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 22:4, s. 726-740
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: The eu-atlantic forest herb Ceratocapnos claviculata showed a recent increase in frequency within its native range and an eastward and northward range expansion in Central Europe. To gain deeper understanding of factors affecting the range expansion of the species, we analyzed vegetation releves at three different scales and asked the following questions: As the species occurs in a wide range of vegetation types, is variation in community composition across the entire range related to climatic environmental zones and tree cover? Are there differences in species composition and habitat characteristics between the native range and the two invaded regions (S Sweden and NE Germany)? Did community composition and habitat characteristics within the native range (The Netherlands) change between 'before 1970' and '1990 to 2006'? Location: W, C and N Europe. Methods: We analysed vegetation-plot data with C. claviculata from various databases and own surveys using partial CCA, partial DCA, Indicator Species Analysis, MANCOVA and multiple regression. Results: Using vegetation plots from the entire distribution range, climatic environmental zones explained 68.9% of the total canonical Eigenvalue. Differences in floristic composition and habitat characteristics between the two invaded regions were as large as between native and invaded range sites. However, releves from the invaded range were generally characterized by anthropogenic disturbance. Accordingly, abundance of C. claviculata was positively linked to silvicultural intensity. New releves from 1990 to 2006 were characterized by higher Ellenberg nutrient indicator values, lower species diversity, higher proportions of neophytic and hemerobic species and showed a lower cover of the study species than old releves from before 1970. Conclusions: Across the range of C. claviculata, climatic environmental zones determine vegetation composition. Accordingly, the species is characterized by a broad macroclimatic amplitude. Vegetation composition and structure differ significantly between the two regions of the new range. Thus, the species has successfully established under various biotic and abiotic environmental conditions. Beyond potential positive effects of soil eutrophication and mild winters, anthropogenic impact may directly facilitate seed dispersal and provide sites and resource conditions suitable for germination and establishment of C. claviculata, whereas a decrease of forest management may constrain the species.
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23.
  • Öster, Mathias, et al. (författare)
  • Size and heterogeneity rather than landscape context determine plant species richness in semi-natural grasslands
  • 2007
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 18:6, s. 859-868
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: Is plant diversity in fragmented semi-natural grasslands related to present and historical landscape context?Location: Southern Sweden.Methods: Plant diversity was described at 30 semi-natural grassland sites in terms of total and specialist plant species richness at the site and species density at different scales (0.5–10 m2). These measures are commonly used to assess conservation value of semi-natural grasslands. Landscape context was measured as contemporary connectivity to other semi-natural grasslands, historical connectivity 50 years ago, amount of linear elements potentially suitable for dispersal (road verges, power line clearings), and amount of forest (inverse of the openness of the landscape).Results: The diversity measures were generally correlated with each other, implying that species richness in a subset of the grassland can predict the total richness. Plant species density at three scales (0.5 m2, 10 m2 and total) was related to the landscape context using an information theoretic approach. Results showed that total species richness increased with increased size of grasslands, contrary to earlier diversity studies in semi-natural grasslands. Larger grasslands were more heterogeneous than smaller grasslands, and this is a likely reason for the species-area relationship. Heterogeneity was also of high importance at the smaller scales (0.5 m2, 10 m2). With increased amount of forest, total species richness increased but species density on 10 m2 decreased. There was no influence of connectivity in either the contemporary or the historical landscape, contrary to previous studies.Conclusions: Grassland size and heterogeneity are of greater importance for plant diversity in semi-natural grassland, than grassland connectivity in the landscape.
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24.
  • Alessi, Nicola, et al. (författare)
  • Ancient refugia and present-day habitat suitability of native laurophylls in Italy
  • 2019
  • Ingår i: Journal of Vegetation Science. - : WILEY. - 1100-9233 .- 1654-1103. ; 30:3, s. 564-574
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions European native laurophyllous species are interesting for their biogeography and evolutionary history, as well as for their responses to global changes. We identified Italian native laurophylls on the basis of morphology, biogeographical history and ecological niche to study whether these species are in equilibrium with the present-day climate. Furthermore, we localized Quaternary refugia and areas of potential spread of native laurophylls using distribution patterns of realized and potential aggregations of native laurophylls, respectively. Location Italy. Methods We extracted data for 17 087 forest plots from a phytosociological database. Detrended Correspondence Analysis of these plots with overlay of climatic and environmental variables was performed to identify native laurophylls, i.e., evergreen broad-leaved species of late Tertiary radiation, occupying a warm and humid niche. Potential ranges of laurophylls were calculated using Beals' index of sociological favourability. The realized/potential range-size ratio was calculated for each single laurophyll to understand whether it is in equilibrium with the present-day climate. Distribution patterns of realized and potential aggregations of laurophylls were mapped. Results Ordination analysis provided a selection of 11 species as Italian native laurophylls. Most of them occupied less than half of their estimated potential range. Realized aggregations richest in native laurophylls were localized in the central Apennines. However, the Italian forests showed high potential for native laurophylls with the richest potential aggregations in the whole Apennines and in the southern Alps. Conclusions Most of the Italian native laurophylls showed non-equilibrium with the current climate, suggesting that late-Quaternary events could better explain their present-day distribution than on-going climate change. Furthermore, their refugia in central Italy suggest the persistence in sites with temperate climate during Quaternary environmental changes. The high suitability of Italian forests for laurophylls, along with global changes, suggests possible future spreading of these species.
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25.
  • Arellano, Gabriel, et al. (författare)
  • Tree death and damage: A standardized protocol for frequent surveys in tropical forests
  • 2021
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 32
  • Tidskriftsartikel (refereegranskat)abstract
    • Tree mortality drives changes in forest structure and dynamics, community composition, and carbon and nutrient cycles. Since tropical forests store a large fraction of terrestrial biomass and tree diversity, improved understanding of changing tree mortality and biomass loss rates is critical. Tropical tree mortality rates have been challenging to estimate due to low background rates of tree death, and high spatial and temporal heterogeneity. Furthermore, the causes of mortality remain unclear because many factors may be involved in individual tree death, and the rapid decomposition of wood in the tropics obscures evidence of possible causes of tree mortality. We present a field protocol to assess tree mortality in tropical forests. The protocol focuses on the rapid, repeatable and inexpensive assessment of individual tree death and damage. The protocol has been successfully tested with annual assessments of >62,000 stems in total in several ForestGEO plots in Asia and the Neotropics. Standardized methods for the assessment of tree death and biomass loss will advance understanding of the underlying causes and consequences of tree mortality.
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26.
  • Asplund, Johan, et al. (författare)
  • The influence of tree-scale and ecosystem-scale factors on epiphytic lichen communities across a long-term retrogressive chronosequence
  • 2014
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 25, s. 1100-1111
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions: We tested the relationship between total cover, species richness and composition of epiphytic lichens on trunks of Betula pubescens and ecosystem retrogression (i.e. prolonged absence of major disturbance). We then investigated how the relationships changed when also accounting for tree-scale factors (aspect, height and bark characteristics) and ecosystem-scale factors (e. g. light transmission, tree species diversity and soil fertility).Location: Thirty forested islands in northern Sweden differing in fire history, which collectively represent a retrogressive chronosequence spanning ca. 5000 yr.Results: Total lichen cover responded negatively to long-term absence of major disturbance, but only at exposed positions on the tree trunk, indicating that lichen cover on substrates with more favourable microclimates is less susceptible to environmental change at the ecosystem scale. Further, although there was no overall effect of island size on lichen species richness, we did find a significant interactive effect between island size and height on trunk on species richness. This emerged because species richness decreased with retrogression for lichen communities at breast height, but showed a hump-shaped response to retrogression at the trunk base. Shifts in ecosystem properties with retrogression explained some of the variation in lichen community composition, but most of the variation could be explained by tree-scale factors, notably height on the trunk.Conclusions: While it has frequently been shown that lichens increase in abundance and richness during the first two or three centuries of succession, our results highlight that over a much longer time scale, encompassing soil aging and declining soil fertility, the lichen flora can be negatively affected. However, these effects are heavily mediated by tree-scale factors. These changes in the lichen community may be of potential importance for ecosystem processes and higher trophic level interactions driven by lichen communities.
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27.
  • Backéus, Ingvar (författare)
  • Distribution and vegetation dynamics of humid savannas in Africa and Asia
  • 1992
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 3, s. 345-356
  • Tidskriftsartikel (refereegranskat)abstract
    • A review is presented on the literature about the distribution of savannas in humid climates in Africa and Asia and their vegetation dynamics. Sections are devoted to African lowland and montane savannas (the latter divided into southern, eastern, western and northern African), Madagascar, Indian subcontinent, SE Asia and New Guinea. It is concluded that the extension of savannas under humid climatic conditions and the relation to the distribution of forests is a function of cultivation, grazing by domestic and wild animals, present and previous climate, geomorphology and soil characteristics. Once established, savannas are often maintained by fires, both natural and man-made.Montane savannas are generally brought about by man's clearing, cultivation and burning. Fire is a stochastic variable; it creates an ecotone sensu stricto (an environmentally stochastic stress zone) at the forest/savanna border. On the other hand, if geomorphology and soil are the determinants, the transition between forest and savanna would have the character of an ecocline (a gradient zone) with fundamentally different conditions.In humid African lowland climates forests expand into savannas if the latter are not maintained by man. Whether forests also expand in less humid climates is disputed. In montane areas forest expansion may be delayed on degraded soils and when diaspores are lacking
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28.
  • Backéus, Ingvar, et al. (författare)
  • Vegetation changes on formerly overgrazed hill slopes in semi-arid central Tanzania
  • 1994
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 5, s. 327-336
  • Tidskriftsartikel (refereegranskat)abstract
    • Composition of hill slope vegetation was studied in a semi-arid part of upland Tanzania where all grazing had been banned for 12 yr. The hills had been severely overgrazed previously and suffered from heavy gully and sheet erosion. Eight vegetation types are described. Floristic gradients revealed by numerical ordination techniques were found to be related mainly to degree of erosion, soil type and succession. The more or less bare soil that prevailed after grazing had ceased is now covered by grassland, woodland and immature secondary forest. The grasslands are still characterized by early successional species and they will probably remain open grassland as long as frequent burning continues. Brachystegia woodlands may have developed during earlier periods when the field layer was sparse due to grazing. The grazing had reduced the frequency of fire which in turn promoted the establishment of Brachystegia spp. Secondary forests are believed to have developed mainly where fires were not frequent, particularly at higher altitudes.
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29.
  • Berglund, Håkan, et al. (författare)
  • Predictability of plant and fungal species richness of old-growth boreal forest islands
  • 2001
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 12:6, s. 857-866
  • Tidskriftsartikel (refereegranskat)abstract
    • The fragmentation and deterioration of old-growth forest habitat by modern forestry have become a major threat to species diversity in Fennoscandia. In order to develop a conservation strategy for the remaining diversity it is essential to identify the existing diversity and to develop appropriate conservation and monitoring programs. For these purposes indicators of conservation value for administrative prioritization are required. This study examines the predictability of plant and fungal species richness on two spatial scales on 46 isolated old-growth forest islands (0.17-12 ha) in a forest-wetland mosaic. We explore (1) to what extent area, isolation and stand structure variables can explain the variation in species richness and (2) if richness patterns of individual species groups correlate. Isolation showed no relation to species richness. Area explained 50-70% of the variation in total species richness and was positively related to the density of crustose lichens and Red-list species in island interiors. Stand structure variables explained 28-66% of the residual variation in total species richness after controlling for island size, and 15-73% of the variation in density of species in island interiors. The highest predictability of species richness was found among substrate-specific fungi and Red-list species. Different stand structure variables were found to explain richness in the different species groups, and only among a few species groups species richness correlated. Thus, species richness of one single species group is unlikely to be a good indicator for total biodiversity. The results show that measurements of stand size and stand structure variables may be a strong complementary tool. and sometimes a substitute to extensive species inventories when one aims to estimate and monitor plant and fungal species diversity in old-growth Picea abies forests.
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30.
  • Biurrun, Idoia, et al. (författare)
  • Benchmarking plant diversity of Palaearctic grasslands and other open habitats
  • 2021
  • Ingår i: Journal of Vegetation Science. - Oxford : John Wiley & Sons. - 1100-9233 .- 1654-1103. ; 32:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Journal of Vegetation Science published by John Wiley & Sons Ltd on behalf of International Association for Vegetation Science.Aims: Understanding fine-grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine-grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups). Location: Palaearctic biogeographic realm. Methods: We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m2 and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class. Results: Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi-natural) grasslands and natural grasslands are the richest vegetation type. The open-access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/databases/GrasslandDiversityExplorer) and provide more insights into species richness patterns in the Palaearctic open habitats. Conclusions: The GrassPlot Diversity Benchmarks provide high-quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation-plot databases, species recordings in GrassPlot are on average more complete, making it a valuable complementary data source in macroecology. © 2021 The Authors.
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31.
  • Blume-Werry, Gesche, et al. (författare)
  • Proportion of fine roots, but not plant biomass allocation below ground, increases with elevation in arctic tundra
  • 2018
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 29:2, s. 226-235
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions: Roots represent a considerable proportion of biomass, primary production and litter input in arctic tundra, and plant allocation of biomass to above- or below-ground tissue in response to climate change is a key factor in the future C balance of these ecosystems. According to optimality theory plants allocate C to the above- or below-ground structure that captures the most limiting resource. We used an elevational gradient to test this theory and as a space-for-time substitution to inform on tundra carbon allocation patterns under a shifting climate, by exploring if increasing elevation was positively related to the root:shoot ratio, as well as a larger plant allocation to adsorptive over storage roots.Location: Arctic tundra heath dominated by Empetrum hermaphroditum close to Abisko, Sweden.Methods: We measured root:shoot and fine:coarse root ratios of the plant communities along an elevational gradient by sampling above- and below-ground biomass, further separating root biomass into fine (<1 mm) and coarse roots.Results: Plant biomass was higher at the lower elevations, but the root:shoot ratio did not vary with elevation. Resource allocation to fine relative to coarse roots increased with elevation, resulting in a fine:coarse root ratio that more than doubled with increasing elevation.Conclusions: Contrary to previous works, the root:shoot ratio along this elevational gradient remained stable. However, communities along our study system were dominated by the same species at each elevation, which suggests that when changes in the root:shoot ratio occur with elevation these changes may be driven by differences in allocation patterns among species and thus turnover in plant community structure. Our results further reveal that the allocation of biomass to fine relative to coarse roots can differ between locations along an elevational gradient, even when overall above- vs below-ground biomass allocation does not. Given the functionally different roles of fine vs coarse roots this could have large implications for below-ground C cycling. Our results highlight the importance of direct effects vs indirect effects (such as changes in plant community composition and nutrient availability) of climate change for future C allocation above and below ground.
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32.
  • Bognounou, Fidele, et al. (författare)
  • Role of climate and herbivory on native and alien conifer seedling recruitment at and above the Fennoscandian tree line
  • 2018
  • Ingår i: Journal of Vegetation Science. - : Wiley-Blackwell. - 1100-9233 .- 1654-1103. ; 29:4, s. 573-584
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions: We investigated the importance of climate and herbivory on native and alien conifer colonization of the birch-dominated Fennoscandian tree line by addressing the following questions: (a) are tree line and tundra habitats similarly suitable for conifer seedling recruitment; (b) do ungulate and rodent herbivores differentially impact seedling recruitment; and (c) how does the role of habitat and herbivory on seedling recruitment vary across a marked climate gradient?Location: Northern Fennoscandia, Sweden (Vassijaure and Paddus), and Norway (Joatka and Seiland).Methods: We conducted an experiment to assess the emergence rate, survival probability and height development of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and Siberian larch (Larix sibirica) seedlings. Three experimental plots (i.e., open control, reindeer exclosure and complete vertebrate exclosure) were established in both tree line and tundra habitats at each of the four locations. Seeds of the three conifer species were sown in each plot in June 1999 during three consecutive years. The surviving seedlings were counted in August to September 1999, 2000, 2001, 2002 and 2007. The height of all seedlings was measured in 2007.Results: Our study reveals that Norway spruce, Scots pine and Siberian larch can regenerate from seed at and above the current tree line in northern Fennoscandia. Their performance was generally higher above tree line in tundra than at tree line, but depended on species identity, climate aridity and mammal herbivory, particularly by rodents. These results suggest that the species composition and latitudinal limit of the tree line in the future might depend not only on direct effects of the future climate on the current tree line species, but also on the intensity of alien and native conifer introductions, as well as changes in herbivore populations.Conclusion: If sufficient seeds of Norway spruce, Scots pine and Siberian larch should reach the current tree line, their performances will increase with a warmer and wetter climate, and this effect will be markedly modulated by herbivores (particularly rodents). Further work is required to extend these results to determine the ability of these conifers to become tree line-forming species in the future.
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33.
  • Brunet, Jörg (författare)
  • Hedging against biodiversity loss: Forest herbs' performance in hedgerows across temperate Europe
  • 2020
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 31, s. 817-829
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions How do contrasting environmental conditions among forests and hedgerows affect the vegetative and reproductive performance of understorey forest herbs in both habitats? Can hedgerows support reproductive source populations of forest herbs, thus potentially allowing progressive dispersal of successive generations along these linear habitats? Location Hedgerows and deciduous forest patches in agricultural landscapes across the European temperate biome. Methods First, we assessed differences in environmental conditions among forests and hedgerows. Next, we quantified plant performance based on a set of functional life-history traits for four forest herbs (Anemone nemorosa,Ficaria verna,Geum urbanum, Poa nemoralis) with contrasting flowering phenology and colonisation capacity in paired combinations of forests and hedgerows, and compared these traits among both habitats. Finally, we assessed relationships between plant performance and environmental conditions in both habitats. Results All study species showed a higher above-ground biomass in hedgerows than in forests. ForPoa nemoralisandGeum urbanum, we also found a higher reproductive output in hedgerows, which was mainly correlated to the higher sub-canopy temperatures therein. The "ancient forest herb"Anemone nemorosa, however, appeared to have a lower reproductive output in hedgerows than in forests, while forFicaria vernano reproductive differences were found between the two habitats. Conclusions This is the first study on such a broad geographical scale to provide evidence of reproductive source populations of forest herbs in hedgerows. Our findings provide key information on strategies by which forest plants grow, reproduce and disperse in hedgerow environments, which is imperative to better understand the dispersal corridor function of these wooded linear structures. Finally, we highlight the urgent need to develop guidelines for preserving, managing and establishing hedgerows in intensive agricultural landscapes, given their potential to contribute to the long-term conservation and migration of forest herbs in the face of global environmental change.
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34.
  • Brunet, Jörg (författare)
  • Interactive effects of past land use and recent forest management on the understorey community in temperate oak forests in South Sweden
  • 2019
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 30, s. 917-928
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions Past agricultural land use and forest management have shaped and influenced the understorey composition in European forests for centuries. We investigated whether understorey vegetation assemblages are affected by (a) legacies from a historical infield/outland agricultural system (i.e., a system with nutrient-enriched vs nutrient-depleted areas), (b) recent management intensity (i.e., thinning/felling activities), and (c) the interaction of recent management and potential legacies. Location Oak forests in Skane, south Sweden. Methods We use three vegetation surveys (1983, 1993/94 and 2014) and notes on management and land-use history, available for 62 permanent 500 m(2) plots. We conducted linear mixed effect modelling to detect both main and interactive effects of past land use and recent management on understorey diversity measures and vegetation indicator values for light and fertility. We combined nonmetric multidimensional scaling with permutational multivariate analysis of variance and indicator species analysis to detect compositional differences caused by past land use and/or recent management. Results Understorey diversity was mainly affected by management activities, but the former infield/outland agricultural system was an important determinant of understorey composition. Understorey composition of former infields reflected higher nutrient availability and lower light availability compared to former outland. Past land use and recent management had interactive effects on light-related understorey variables: for the less intensively managed plots, the outland plots contained more light-demanding species than the infield plots, while for the more intensively managed plots, the light-demanding signature of the understorey was similar for infield and outland plots. Conclusions Different intensities of past land use as well as recent forest management influenced the composition of the forest understorey, and interactions were present. Therefore, careful consideration of both the long-term land-use history and the more recent disturbances due to forest management are necessary when making future predictions of understorey composition and diversity.
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35.
  • Brunet, Jörg (författare)
  • Plant taxonomic and phylogenetic turnover increases toward climatic extremes and depends on historical factors in European beech forests
  • 2021
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 32
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims The effect of biogeographical processes on the spatial turnover component of beta-diversity over large spatial extents remains scarcely understood. Here, we aim at disentangling the roles of environmental and historical factors on plant taxonomic and phylogenetic turnover, while controlling for the effects of species richness and rarity.Location European beech (Fagus sylvatica) forests in Europe.Methods We aggregated plant species occurrences from vegetation plots in spatial grid cells of 0.25o x 0.25o to calculate the spatial turnover component of taxonomic (TBDturn) and phylogenetic (PBDturn) beta-diversity for each cell. We also calculated the deviation of PBDturn given TBDturn (PBDdev-turn), which measures the importance of phylogenetic turnover after factoring out taxonomic turnover. Beta-diversity was calculated for each grid cell as the mean pairwise dissimilarity between the focal cell and all other cells. We used structural equation modeling (SEM) to examine the relationships between environmental (climate, soil pH, and distance from the geographical distribution limit of beech) and historical (distance from beech glacial refugia) predictors and beta-diversity metrics.Results We found a geographically consistent variation in taxonomic and phylogenetic turnover. Overall, TBDturn and PBDturn increased significantly toward more extreme climatic conditions, on more acidic soils, and toward the margins of beech distribution. The effects of environmental variables and the distance from glacial refugia on beta-diversity metrics were mediated by species richness and rarity. Phylogenetic turnover was low in relation to taxonomic turnover (i.e., high PBDdev-turn) in areas closer to glacial refugia.Conclusions Continental-scale patterns of beta-diversity in European beech forests are the result of complementary ecological and evolutionary processes. In general, beech forests are taxonomically and phylogenetically more distinct in climatically marginal areas of their European range. However, the spatial variation of beta-diversity in European beech forest flora is still strongly characterized by the distribution of groups of closely related species that evolved or survived in glacial refugia.
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36.
  • Brunet, Jörg (författare)
  • ReSurveyEurope: A database of resurveyed vegetation plots in Europe
  • 2024
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 35
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: We introduce ReSurveyEurope - a new data source of resurveyed vegetation plots in Europe, compiled by a collaborative network of vegetation scientists. We describe the scope of this initiative, provide an overview of currently available data, governance, data contribution rules, and accessibility. In addition, we outline further steps, including potential research questions. Results: ReSurveyEurope includes resurveyed vegetation plots from all habitats. Version 1.0 of ReSurveyEurope contains 283,135 observations (i.e., individual surveys of each plot) from 79,190 plots sampled in 449 independent resurvey projects. Of these, 62,139 (78%) are permanent plots, that is, marked in situ, or located with GPS, which allow for high spatial accuracy in resurvey. The remaining 17,051 (22%) plots are from studies in which plots from the initial survey could not be exactly relocated. Four data sets, which together account for 28,470 (36%) plots, provide only presence/absence information on plant species, while the remaining 50,720 (64%) plots contain abundance information (e.g., percentage cover or cover-abundance classes such as variants of the Braun-Blanquet scale). The oldest plots were sampled in 1911 in the Swiss Alps, while most plots were sampled between 1950 and 2020. Conclusions: ReSurveyEurope is a new resource to address a wide range of research questions on fine-scale changes in European vegetation. The initiative is devoted to an inclusive and transparent governance and data usage approach, based on slightly adapted rules of the well-established European Vegetation Archive (EVA). ReSurvey:Europe data are ready for use, and proposals for analyses of the data set can be submitted at any time to the coordinators. Still, further data contributions are highly welcome.
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37.
  • Christiansen, Ditte Marie, 1990-, et al. (författare)
  • Effects of past and present microclimates on northern and southern plant species in a managed forest landscape
  • 2023
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 34:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions: Near-ground temperatures can vary substantially over relatively short distances, enabling species with different temperature preferences and geographical distributions to co-exist within a small area. In a forest landscape, the near-ground temperatures may change due to management activities that alter forest density. As a result of such management activities, current species distributions and performances might not only be affected by current microclimates, but also by past conditions due to time-lagged responses.Location: Sweden.Methods: We examined the effects of past and current microclimates on the distributions and performances of two northern, cold-favoured, and two southern, warm-favoured, plant species in 53 managed forest sites. Each pair was represented by one vascular plant and one bryophyte species. We used temperature logger data and predictions from microclimate models based on changes in basal area to relate patterns of occurrence, abundance, and reproduction to current and past microclimate.Results: The two northern species were generally favoured by microclimates that were currently cold, characterised by later snowmelt and low accumulated heat over the growing season. In contrast, the two southern species were generally favoured by currently warm microclimates, characterised by high accumulated heat over the growing season. Species generally had higher abundance in sites with a preferred microclimate both in the past and present, and lower abundance than expected from current conditions, if the past microclimate had changed from warm to cold or vice versa, indicating time-lags in abundance patterns of the species.Conclusions: Our results show a potential importance of past and present microclimate heterogeneity for the co-existence of species with different temperature preferences in the same landscape and highlight the possibility to manage microclimates to mitigate climate change impacts on forest biodiversity.
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38.
  • Cousins, Sara A. O. (författare)
  • Moving towards the edge : matrix matters!
  • 2013
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 24:1, s. 7-8
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • In this issue of the Journal of Vegetation Science, Chabrerie et al. use plant inventories and geographical data to investigate effects on species richness and turnover caused by management intensity in the surrounding matrix in new and old forest fragments. Although forest edge age was important, more intensive management of the matrix clearly sharpened the edgeinterior gradient.
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39.
  • Dai, Xiaobing (författare)
  • Impact of cattle dung deposition on the distribution pattern of plant species in an alvar limestone grassland
  • 2000
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 11:5, s. 715-724
  • Tidskriftsartikel (refereegranskat)abstract
    • Seed banks in cattle dung, soil under cattle dung and soil under vegetation and growth response of plant species to the changes in soil nitrogen availability were studied in an alvar limestone grassland on Öland, Sweden, in order to analyse the impact of dung deposition and decomposition on the formation of patches of plant species. Results suggest that patches of four plant species could result from cattle dung deposition and decomposition. Impact of dung could proceed in three ways: (1) by changing the relative abundance of species in the soil seed bank under dung, and/or (2) by influencing the deposition of seeds in the dung, and/or (3) by intensifying the growth of some species through nutrient release. Species patches could result from one or more of these aspects. For instance, patches of Arenaria serpyllifolia may be induced by dung deposition because of the dominance of its seeds in dung, while the pattern of Cerastium semidecandrum and Festuca ovina may be due to the abundance of their seeds in the soil seed bank under dung and their positive growth response to increased nitrogen availability.
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40.
  • De Pauw, Karen, et al. (författare)
  • Nutrient-demanding and thermophilous plants dominate urban forest-edge vegetation across temperate Europe
  • 2024
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 35:1
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionsForests are highly fragmented across the globe. For urban forests in particular, fragmentation increases the exposure to local warming caused by the urban heat island (UHI) effect. We here aim to quantify edge effects on herbaceous understorey vegetation in urban forests, and test whether these effects interact with forest structural complexity.LocationWe set up a pan-European study at the continental scale including six urban forests in Zurich, Paris, Katowice, Brussels, Bremen, and Stockholm.MethodsWe recorded understorey plant communities from the edge towards the interior of urban forests. Within each urban forest, we studied edge-to-interior gradients in paired stands with differing forest structural complexity. Community composition was analysed based on species specialism, life form, light, nutrient, acidity and disturbance indicator values and species' thermal niches.ResultsWe found that herbaceous communities at urban forest edges supported more generalists and forbs but fewer ferns than in forests' interiors. A buffered summer microclimate proved crucial for the presence of fern species. The edge communities contained more thermophilous, disturbance-tolerant, nutrient-demanding and basiphilous plant species, a pattern strongly confirmed by corresponding edge-to-interior gradients in microclimate, soil and light conditions in the understorey. Additionally, plots with a lower canopy cover and higher light availability supported higher numbers of both generalists and forest specialists. Even though no significant interactions were found between the edge distance and forest structural complexity, opposing additive effects indicated that a dense canopy can be used to buffer negative edge effects.ConclusionThe urban environment poses a multifaceted filter on understorey plant communities which contributes to significant differences in community composition between urban forest edges and interiors. For urban biodiversity conservation and the buffering of edge effects, it will be key to maintain dense canopies near urban forest edges. The urban environment poses a multifaceted filter on understorey plant communities which contributes to significant differences in community composition between urban forest edges and interiors. For urban biodiversity conservation and the buffering of edge effects, it will be key to maintain dense canopies near urban forest edges.image
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41.
  • Derroire, Geraldine (författare)
  • Isolated trees as nuclei of regeneration in tropical pastures: testing the importance of niche-based and landscape factors
  • 2016
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 27, s. 679-691
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionsOur study tests the relative importance of different attributes of isolated trees in explaining the properties of the regeneration assemblage beneath their crowns to evaluate their effect on the composition of early successional stages and understand the processes underlying this effect. We asked: (1) does the regeneration assemblage contain a high proportion of individuals conspecific with the isolated tree; (2) how does the landscape surrounding an isolated tree influence the properties of the regeneration assemblage; and (3) what is the respective importance of structural variables and functional traits of isolated trees for their influence on the properties of the regeneration assemblage?LocationThree pasture sites in Guanacaste Province, a tropical seasonally dry area, Costa Rica.MethodsNinety isolated trees were characterized by their position in the landscape relative to patches of trees, individual structural variables related to tree and crown size, and species functional traits. The assemblage of woody plants regenerating under their crowns was characterized by number of individuals and species, and taxonomic and functional composition. To understand the mechanisms underlying the facilitative effect of isolated trees on regeneration, correlations between their attributes and properties of the regeneration assemblage were assessed.ResultsWe found that a low proportion of regenerating individuals were conspecific with the isolated trees beneath which they have established. Landscape factors influenced the regeneration but their effects were site-dependent. The attributes of isolated trees correlated well with the functional composition of the regeneration assemblage: their structure and phenological habits with traits associated with drought tolerance, and their dispersal syndrome with the dispersal syndrome of the regeneration assemblage. However, isolated tree attributes correlated poorly with the regeneration assemblage's taxonomic composition.ConclusionsOur study shows that an approach based on functional composition can provide a better understanding of community assembly mechanisms than does a taxonomic approach. Two main mechanisms are suggested to explain the influence of isolated trees on the regeneration assemblage: modification of micro-scale environmental conditions (shade and moisture) and influence on dispersal agents. The effect of attributes of isolated trees on the properties of the regeneration assemblage predicts a long-term legacy of the early stages of succession.
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42.
  • Edman, Mattias, et al. (författare)
  • Spatial pattern of downed logs and wood-living fungi in an old-growth spruce forest
  • 2001
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 12:5, s. 609-620
  • Tidskriftsartikel (refereegranskat)abstract
    • Since many wood-living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood-decaying fungi in an old-growth boreal Picea abies forest in northwestern Sweden that is governed by gap-phase dynamics. The spatial pattern of wood-decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter 10 cm were mapped and analysed with Ripley's K-function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10-29 cm were aggregated up to 25 m, whereas logs ≥30 cm diameter were randomly distributed. The result suggests that gap-dynamics do have an impact on the spatial pattern of the CWD, creating fine-scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n 20) of wood-decaying fungi were analysed with Ripley's K-function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations.
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43.
  • Egelkraut, Dagmar, 1989-, et al. (författare)
  • Reindeer trampling promotes vegetation changes in tundra heathlands : Results from a simulation experiment
  • 2020
  • Ingår i: Journal of Vegetation Science. - : John Wiley & Sons. - 1100-9233 .- 1654-1103. ; 31:3, s. 476-486
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: Herbivores exert strong influences on vegetation through activities such as trampling, defoliation, and fertilization. The combined effect of these activities on plant performance may cause dramatic vegetation shifts. Because herbivore pressures and the relative importance of their different activities are not equally distributed across the landscape, it is important to understand their isolated effect. One example of an herbivore‐induced vegetation shift is the reindeer‐driven transition from a subarctic tundra vegetation dominated by dwarf shrubs into a more productive, graminoid‐dominated state. Here, we asked how each of the grazing activities by reindeer separately and combined shape vegetation composition.Location: Nordreisa, Norway.Methods: We used a field experiment over six summers to study the separate and interacting effects of reindeer trampling, defoliation, addition of faeces and removal of moss on tundra heath vegetation, and to identify which of these factors were most important in driving the plant community towards a graminoid‐dominated state.Results: The combination of all treatments resulted in the strongest changes in vegetation, but trampling was the single most important factor altering the vegetation composition by reducing the abundance of both evergreen and deciduous dwarf shrubs. In contrast to what was expected, none of our treatments, separate or combined, resulted in an increased abundance of graminoids in 5 years, although such rapid vegetation changes have been observed in the field in similar environmental conditions.Conclusions: Trampling is the key process by which reindeer influence the abundance of functional groups, but only many processes combined result in strong changes in community composition. Moreover, additional factors not included in this experiment, such as urine, may be important in causing a state shift to a graminoid‐dominated community.
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44.
  • Elumeeva, Tatiana G., et al. (författare)
  • Is intensity of plant root mycorrhizal colonization a good proxy for plant growth rate, dominance and decomposition in nutrient poor conditions?
  • 2018
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 29:4, s. 715-725
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionsMycorrhizae may be a key element of plant nutritional strategies and of carbon and nutrient cycling. Recent research suggests that in natural conditions, intensity of mycorrhizal colonization should be considered an important plant feature. How are inter-specific variations in mycorrhizal colonization rate, plant relative growth rate (RGR) and leaf litter decomposability related? Is (arbuscular) mycorrhizal colonization linked to the dominance of plant species in nutrient-stressed ecosystems? LocationTeberda State Biosphere Reserve, northwest Caucasus, Russia. MethodsWe measured plant RGR under mycorrhizal limitation and under natural nutrition conditions, together with leaf litter decomposability and field intensity of mycorrhizal colonization across a wide range of plant species, typical for alpine communities of European mountains. We applied regression analysis to test whether the intensity of mycorrhizal colonization is a good predictor of RGR and decomposition rate, and tested how these traits predict plant dominance in communities. ResultsForb species with a high level of field mycorrhizal colonization had lower RGR under nutritional and mycorrhizal limitation, while grasses were unaffected. Litter decomposition rate was not related to the intensity of mycorrhizal colonization. Dominant species mostly had a higher level of mycorrhizal colonization and lower RGR without mycorrhizal colonization than subordinate species, implying that they were more dependent on mycorrhizal symbionts. There were no differences in litter decomposability. ConclusionsIn alpine herbaceous plant communities dominated by arbuscular mycorrhizae, nutrient dynamics are to a large extent controlled by mycorrhizal symbiosis. Intensity of mycorrhizal colonization is a negative predictor for whole plant RGR. Our study highlights the importance of mycorrhizal colonization as a key trait underpinning the role of plant species in carbon and nutrient dynamics in nutrient-limited herbaceous plant communities.
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45.
  • Eriksson, Ove (författare)
  • A closer look at the species behind abundance-occupancy relationships
  • 2013
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 24:4, s. 589-590
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Guedo & Lamb (), in this issue of the Journal of Vegetation Science, used a 35-yr data series from two prairie communities to show that abundance-occupancy relationships change over time. Scrutinizing the details behind this finding, they show that species groups follow different trajectories during succession after disturbance. These results will inspire further species-level studies unraveling mechanisms behind abundance-occupancy relationships.
  •  
46.
  • Eriksson, Ove (författare)
  • Vegetation change and eco-evolutionary dynamics
  • 2014
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 25:5, s. 1141-1147
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: Eco-evolutionary dynamics is a concept encapsulating a feedback between ecology and evolution, acting on short ecological time-scales. Recent studies suggest that such dynamics have been generally over-looked. The objective of this paper is to examine how eco-evolutionary dynamics may contribute to vegetation science. Location: Global. Methods: In this paper I discuss eco-evolutionary dynamics in the context of vegetation science, with a focus on effects derived from human-mediated niche construction, manifested as new habitats, non-native species, and changing connectivity and spatial configuration of habitats. Results and Conclusions: I suggest that eco-evolutionary dynamics have the potential to influence plant community composition and assembly, and thus that eco-evolutionary dynamics should become focus of studies in vegetation science.
  •  
47.
  • Esseen, Per-Anders, et al. (författare)
  • Factors driving structure of natural and anthropogenic forest edges from temperate to boreal ecosystems
  • 2016
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 27:3, s. 482-492
  • Tidskriftsartikel (refereegranskat)abstract
    • Questions What factors control broad-scale variation in edge length and three-dimensional boundary structure for a large region extending across two biomes? What is the difference in structure between natural and anthropogenic edges? Location Temperate and boreal forests across all of Sweden, spanning latitudes 55-69 degrees N. MethodsWe sampled more than 2000 forest edges using line intersect sampling in a monitoring programme (National Inventory of Landscapes in Sweden). We compared edge length, ecosystem attributes (width of adjacent ecosystem, canopy cover, canopy height, patch contrast in canopy height, forest type) and boundary attributes (profile, abruptness, shape) of natural edges (lakeshore, wetland) with anthropogenic edges (clear-cut, agricultural, linear disturbance) in five regions. Results Anthropogenic edges were nearly twice as abundant as natural edges. Length of anthropogenic edges was largest in southern regions, while the abundance of natural edges increased towards the north. Edge types displayed unique spectrums of boundary structures, but abrupt edges dominated, constituting 72% of edge length. Anthropogenic edges were more abrupt than natural edges; wetland edges had the most gradual and sinuous boundaries. Canopy cover, canopy height, patch contrast and forest type depended on region, whereas overall boundary abruptness and shape showed no regional pattern. Patch contrast was related to temperature sum (degree days5 degrees C), suggesting that regional variability can be predicted from climate-controlled forest productivity. Boundary abruptness was coupled with the underlying environmental gradient, land use and forest type, with higher variability in deciduous than in conifer forest. Conclusions Edge origin, land use, climate and tree species are main drivers of broad-scale variability in forest edge structure. Our findings have important implications for developing ecological theory that can explain and predict how different factors affect forest edge structure, and help to understand how land use and climate change affect biodiversity at forest edges.
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48.
  • Fraver, Shawn, et al. (författare)
  • Demographics and disturbance history of a boreal old-growth Picea abies forest
  • 2008
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 19:6, s. 789-798
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: To what extent do tree growth, mortality, and long-term disturbance patterns affect stand structure and composition of an old-growth Picea abies forest?Location: Boreal Sweden.Methods: We linked data from three 50 m × 50 m permanent plots established in 1986 with dendrochronology data to evaluate tree growth and mortality over an 18-year period and to describe a several-hundred-year disturbance history for this forest type.Results: Averaged over all diameters, P. abies trees had an annual mortality rate of 0.60%; however, diameter had a striking effect on both growth and mortality, with trees of intermediate diameters (ca. 20–30 cm) showing faster growth and lower mortality. Their increased vigor gave rise to a diameter distribution resembling the ‘rotated sigmoid’ (not reverse-J) proposed for such conditions, and it led to a deficit of snags of intermediate diameters. Slow-growing trees had an increased likelihood of dying. Although recruitment occurred in most decades over the past 400 years, two prominent recruitment peaks occurred (mid 1700s and 1800s), neither of which appeared to cause a shift in tree species composition. The lack of fire evidence suggests that fire was not responsible for these recruitment peaks.Conclusions: Taken together, these results depict a rather impassive system, where canopy trees die slowly over decades. Field observations suggest that fungal infections, mediated by wind, account for much of the mortality during these periods of relative quiescence. However, these periods are at times punctuated by moderate-severity disturbances that foster abundant recruitment. 
  •  
49.
  • Fraver, Shawn (författare)
  • Disturbance dynamics of old-growth Picea rubens forests of northern Maine
  • 2005
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 16:5, s. 597-610
  • Tidskriftsartikel (refereegranskat)abstract
    • Question: How have the spatial and temporal aspects of past disturbance shaped the current structure and composition of old-growth Picea rubens forests?Location: Northern Maine, USA.Methods: We established three 50 m x 50 m plots in old-growth Picea rubens forests and mapped the location of trees and saplings. We extracted increment cores from canopy trees, and recorded growth releases indicating past disturbance. By linking spatial data (tree positions) and temporal data (dated growth releases), we reconstructed the location and size of former canopy gaps back to 1920, and determined a more general disturbance chronology extending as far back as 1740.Results: We found no evidence of stand-replacing disturbances. The disturbance dynamic includes pulses of moderate-severity disturbances caused by wind storms and hostspecific disturbance agents (spruce budworm, spruce bark beetle) interposed upon a background of scattered smaller canopy gaps. Consequently, rates of disturbance fluctuated considerably overtime. Reconstructed canopy gaps were temporally and spatially scattered; during disturbance peaks, they were both larger and more numerous.Conclusions: Despite peaks in disturbance, several of which created relatively large gaps, this system has experienced no significant change in species composition. Instead, the shade-tolerant Picea rubens has maintained canopy dominance. The patch dynamics described here consist of dramatic structural, not compositional, changes to the forest. The persistence of Picea rubens is attributed to a combination of traits: (1) abundance of advance regeneration; (2) ability to endure suppression and respond favourably to release; and (3) longevity relative to ecologically similar species.
  •  
50.
  • Fraver, Shawn, et al. (författare)
  • Tree growth and competition in an old-growth Picea abies forest of boreal Sweden : influence of tree spatial patterning
  • 2014
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 25:2, s. 374-385
  • Tidskriftsartikel (refereegranskat)abstract
    • Question What factors best characterize tree competitive environments in this structurally diverse old-growth forest, and do these factors vary spatially within and among stands? Location Old-growth Picea abies forest of boreal Sweden. Methods Using long-term, mapped permanent plot data augmented with dendrochronological analyses, we evaluated the effect of neighbourhood competition on focal tree growth by means of standard competition indices, each modified to include various metrics of trees size, neighbour mortality weighting (for neighbours that died during the inventory period), and within-neighbourhood tree clustering. Candidate models were evaluated using mixed-model linear regression analyses, with mean basal area increment as the response variable. We then analysed stand-level spatial patterns of competition indices and growth rates (via kriging) to determine if the relationship between these patterns could further elucidate factors influencing tree growth. Results Inter-tree competition clearly affected growth rates, with crown volume being the size metric most strongly influencing the neighbourhood competitive environment. Including neighbour tree mortality weightings in models only slightly improved descriptions of competitive interactions. Although the within-neighbourhood clustering index did not improve model predictions, competition intensity was influenced by the underlying stand-level tree spatial arrangement: stand-level clustering locally intensified competition and reduced tree growth, whereas in the absence of such clustering, inter-tree competition played a lesser role in constraining tree growth. Conclusions Our findings demonstrate that competition continues to influence forest processes and structures in an old-growth system that has not experienced major disturbances for at least two centuries. The finding that the underlying tree spatial pattern influenced the competitive environment suggests caution in interpreting traditional tree competition studies, in which tree spatial patterning is typically not taken into account. Our findings highlight the importance of forest structure - particularly the spatial arrangement of trees - in regulating inter-tree competition and growth in structurally diverse forests, and they provide insight into the causes and consequences of heterogeneity in this old-growth system.
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