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  • 1. Acharya, Kamal Prasad
    et al.
    De Frenne, Pieter
    Brunet, Jörg
    Chabrerie, Olivier
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Diekmann, Martin
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Verheyen, Kris
    Graae, Bente Jessen
    Latitudinal variation of life-history traits of an exotic and a native impatiens species in Europe2017In: Acta Oecologica, ISSN 1146-609X, E-ISSN 1873-6238, Vol. 81, p. 40-47Article in journal (Refereed)
    Abstract [en]

    Understanding the responses of invasive and native populations to environmental change is crucial for reliable predictions of invasions in the face of global change. While comparisons of responses across invasive species with different life histories have been performed before, comparing functional traits of congeneric native and invasive species may help to reveal driving factors associated with invasion. Here we compared morphological functional trait patterns of an invasive species (Impatiens parviflora) with its congeneric native species (I. noli-tangere) along an approximately 1600 km European latitudinal gradient from France (49 degrees 34'N) to Norway (63 degrees 40'N). Soil nitrogen was recorded during six weeks of the growing season, and light, soil moisture, and nutrient availability were estimated for each sampled population using community weighted means of indicator values for co-occurring species. Temperature data were gathered from nearby weather stations. Both the native and invasive species are taller at higher latitudes and this response is strongest in the invasive species. Seed mass and number of seeds per capsule increase in I. noli-tangere but decrease in I. parviflora towards higher latitudes. Surprisingly, plant height in the invasive I. parviflora decreases with increasing soil nitrogen availability. The latitudinal pattern in seed mass is positively related to temperature in I. noli-tangere and negatively in I. parviflora. Leaf area of both species decreases with increasing Ellenberg indicator values for nitrogen and light but increases with increasing soil moisture. Soil nitrogen concentrations and Ellenberg indicator values for nitrogen have significant positive (I. nolitangere) and negative (I. parviflora) effects on the number of seeds per capsule. Our results show that the native I. noli-tangere has efficient reproduction at its range edge while the invasive I. parviflora shows a marked decrease in seed size and seed number per capsule. These patterns are unrelated to the growth and obtained size of the plants: even low soil nitrogen availability in the north seemed not to limit plant growth and size. Our results suggest that the invasive I. parviflora tends to become more invasive at lower latitudes by producing heavier seeds and more seeds per capsule.

  • 2. Albert, Aurélie
    et al.
    Auffret, Alistair G.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cosyns, Eric
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    D'hondt, Bram
    Eichberg, Carsten
    Eycott, Amy E.
    Heinken, Thilo
    Hoffmann, Maurice
    Jaroszewicz, Bogdan
    Malo, Juan E.
    Mårell, Anders
    Mouissie, Maarten
    Pakeman, Robin J.
    Picard, Mélanie
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Poschlod, Peter
    Provoost, Sam
    Schulze, Kiowa Alraune
    Baltzinger, Christophe
    Seed dispersal by ungulates as an ecological filter: a trait-based meta-analysis2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 9, p. 1109-1120Article in journal (Refereed)
    Abstract [en]

    Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filter - which differentially affects individuals according to their characteristics and shapes species assemblages - and that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and non-dispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales.

  • 3.
    Auffret, Alistair G.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Aggemyr, Elsa
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Spatial scale and specialization affect how biogeography and functional traits predict long-term patterns of community turnover2017In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 31, no 2, p. 436-443Article in journal (Refereed)
    Abstract [en]

    1. Immigration, extirpation and persistence of individual populations of species are key processes determining community responses to environmental change. However, they are difficult to study over long time periods without corresponding historical and modern-day species occurrences.

    2. We used historical and present-day plant species occurrence data from two different spatial scales (resolutions) to investigate the plant community turnover during the 20th century in a Baltic Sea archipelago. Patterns of turnover were analysed in relation to plant functional traits relating to dispersal and competition/persistence, as well as biogeographical variables.

    3. Turnover was largely driven by interactions between functional traits and measures of area, connectivity and distance to mainland. However, the combinations of traits and biogeographical variables that were most important for predicting immigration and extirpation differed between data sets, and between species associated with grassland management and the entire species pool.

    4. Taller plants were more likely to persist regardless of scale and biogeography, reflecting the grazing abandonment that occurred in the study area. Interactions between dispersal traits and biogeography were related to immigrations when the entire species pool was considered. However, increased dispersal potential, a smaller island size and increasing distance to mainland combined to promote extirpations in management-associated species. A perennial life span and seed banking contributed to species persistence. At the larger spatial scale, trait-driven turnover was not mediated by the biogeographical context.

    5. We showed that it is important to consider functional traits, biogeographical variables and their interactions when analysing community turnover over time. Furthermore, we found that the understanding of how combinations of traits and biogeography predict turnover depends on the source and spatial scale of the available data, and the species pool analysed.

  • 4.
    Auffret, Alistair G.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of York, UK.
    Kimberley, Adam
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Skånes, Helle
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jakobsson, Simon
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Waldén, Emelie
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wennbom, Marika
    Wood, Heather
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bullock, James M.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gartz, Mira
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hooftman, Danny A. P.
    Tränk, Louise
    Stockholm University, Faculty of Science, Department of Physical Geography.
    HistMapR: Rapid digitization of historical land-use maps in R2017In: Methods in Ecology and Evolution, ISSN 2041-210X, E-ISSN 2041-210X, Vol. 8, no 11, p. 1453-1457Article in journal (Refereed)
    Abstract [en]

    Habitat destruction and degradation represent serious threats to biodiversity, and quantification of land-use change over time is important for understanding the consequences of these changes to organisms and ecosystem service provision. Comparing land use between maps from different time periods allows estimation of the magnitude of habitat change in an area. However, digitizing historical maps manually is time-consuming and analyses of change are usually carried out at small spatial extents or at low resolutions. HistMapR contains a number of functions that can be used to semi-automatically digitize historical land use according to a map's colours, as defined by the RGB bands of the raster image. We test the method on different historical land-use map series and compare results to manual digitizations. Digitization is fast, and agreement with manually digitized maps of around 80-90% meets common targets for image classification. We hope that the ability to quickly classify large areas of historical land use will promote the inclusion of land-use change into analyses of biodiversity, species distributions and ecosystem services.

  • 5.
    Auffret, Alistair G.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Swedish University of Agricultural Sciences, Sweden; University of York, UK.
    Kimberley, Adam
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Sweden.
    Waldén, Emelie
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Super-regional land-use change and effects on the grassland specialist flora2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3464Article in journal (Refereed)
    Abstract [en]

    Habitat loss through land-use change is the most pressing threat to biodiversity worldwide. European semi-natural grasslands have suffered an ongoing decline since the early twentieth century, but we have limited knowledge of how grassland loss has affected biodiversity across large spatial scales. We quantify land-use change over 50-70 years across a 175,000 km(2) super-region in southern Sweden, identifying a widespread loss of open cover and a homogenisation of landscape structure, although these patterns vary considerably depending on the historical composition of the landscape. Analysing species inventories from 46,796 semi-natural grasslands, our results indicate that habitat loss and degradation have resulted in a decline in grassland specialist plant species. Local factors are the best predictors of specialist richness, but the historical landscape predicts present-day richness better than the contemporary landscape. This supports the widespread existence of time-lagged biodiversity responses, indicating that further species losses could occur in the future.

  • 6.
    Auffret, Alistair G.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Scale-dependent diversity effects of seed dispersal by a wild herbivore in fragmented grasslands2014In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 175, no 1, p. 305-313Article in journal (Refereed)
    Abstract [en]

    Dispersal limitation between habitat fragments is a known driver of landscape-scale biodiversity loss. In Europe, agricultural intensification during the twentieth century resulted in losses of both grassland habitat and traditional grassland seed dispersal vectors such as livestock. During the same period, populations of large wild herbivores have increased in the landscape. Usually studied in woodland ecosystems, these animals are found to disperse seeds from grasslands and other open habitats. We studied endozoochorous seed dispersal by roe deer (Capreolus capreolus) in fragmented grasslands and grassland remnants, comparing dispersed subcommunities of plant species to those in the established vegetation and the seed bank. A total of 652 seedlings of 67 species emerged from 219 samples of roe deer dung. This included many grassland species, and several local grassland specialists. Dispersal had potentially different effects on diversity at different spatial scales. Almost all sites received seeds of species not observed in the vegetation or seed bank at that site, suggesting that local diversity might not be dispersal limited. This pattern was less evident at the landscape scale, where fewer new species were introduced. Nonetheless, long-distance dispersal by large wild herbivores might still provide connectivity between fragmented habitats within a landscape in the areas in which they are active. Finally, as only a subset of the available species were found to disperse in space as well as time, the danger of future biodiversity loss might still exist in many isolated grassland habitats.

  • 7.
    Auffret, Alistair G.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    The spatial and temporal components of functional connectivity in fragmented landscapes2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, p. s51-S59Article in journal (Refereed)
    Abstract [en]

    Connectivity is key for understanding how ecological systems respond to the challenges of land-use change and habitat fragmentation. Structural and functional connectivity are both established concepts in ecology, but the temporal component of connectivity deserves more attention. Whereas functional connectivity is often associated with spatial patterns (spatial functional connectivity), temporal functional connectivity relates to the persistence of organisms in time, in the same place. Both temporal and spatial processes determine biodiversity responses to changes in landscape structure, and it is therefore necessary that all aspects of connectivity are considered together. In this perspective, we use a case study to outline why we believe that both the spatial and temporal components of functional connectivity are important for understanding biodiversity patterns in the present-day landscape, and how they can also help us to make better-informed decisions about conserving and restoring landscapes and improving resilience to future change.

  • 8. Bagger-Sjöbäck, Dan
    et al.
    Strömbäck, Karin
    Hakizimana, Pierre
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Larsson, Christina
    Hultcrantz, Malou
    Papatziamos, Georgios
    Smeds, Henrik
    Danckwardt-Lillieström, Niklas
    Hellström, Sten
    Johansson, Ann
    Tideholm, Bo
    Fridberger, Anders
    A Randomised, Double Blind Trial of N-Acetylcysteine for Hearing Protection during Stapes Surgery2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 3, article id e0115657Article in journal (Refereed)
    Abstract [en]

    Background Otosclerosis is a disorder that impairs middle ear function, leading to conductive hearing loss. Surgical treatment results in large improvement of hearing at low sound frequencies, but high-frequency hearing often suffers. A likely reason for this is that inner ear sensory cells are damaged by surgical trauma and loud sounds generated during the operation. Animal studies have shown that antioxidants such as N-Acetylcysteine can protect the inner ear from noise, surgical trauma, and some ototoxic substances, but it is not known if this works in humans. This trial was performed to determine whether antioxidants improve surgical results at high frequencies. Methods We performed a randomized, double-blind and placebo-controlled parallel group clinical trial at three Swedish university clinics. Using block-stratified randomization, 156 adult patients undergoing stapedotomy were assigned to intravenous N-Acetylcysteine (150 mg/kg body weight) or matching placebo (1:1 ratio), starting one hour before surgery. The primary outcome was the hearing threshold at 6 and 8 kHz; secondary outcomes included the severity of tinnitus and vertigo. Findings One year after surgery, high-frequency hearing had improved 2.7 +/- 3.8 dB in the placebo group (67 patients analysed) and 2.4 +/- 3.7 dB in the treated group (72 patients; means +/- 95% confidence interval, p = 0.54; linear mixed model). Surgery improved tinnitus, but there was no significant intergroup difference. Post-operative balance disturbance was common but improved during the first year, without significant difference between groups. Four patients receiving N-Acetylcysteine experienced mild side effects such as nausea and vomiting. Conclusions N-Acetylcysteine has no effect on hearing thresholds, tinnitus, or balance disturbance after stapedotomy.

  • 9. Caron, M. M.
    et al.
    De Frenne, P.
    Brunet, J.
    Chabrerie, O.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    De Backer, L.
    Decocq, G.
    Diekmann, M.
    Heinken, T.
    Kolb, A.
    Naaf, T.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Selvi, F.
    Strimbeck, G. R.
    Wulf, M.
    Verheyen, K.
    Interacting effects of warming and drought on regeneration and early growth of Acer pseudoplatanus and A. platanoides2015In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 17, no 1, p. 52-62Article in journal (Refereed)
    Abstract [en]

    Climate change is acting on several aspects of plant life cycles, including the sexual reproductive stage, which is considered amongst the most sensitive life-cycle phases. In temperate forests, it is expected that climate change will lead to a compositional change in community structure due to changes in the dominance of currently more abundant forest tree species. Increasing our understanding of the effects of climate change on currently secondary tree species recruitment is therefore important to better understand and forecast population and community dynamics in forests. Here, we analyse the interactive effects of rising temperatures and soil moisture reduction on germination, seedling survival and early growth of two important secondary European tree species, Acer pseudoplatanus and A.platanoides. Additionally, we analyse the effect of the temperature experienced by the mother tree during seed production by collecting seeds of both species along a 2200-km long latitudinal gradient. For most of the responses, A.platanoides showed higher sensitivity to the treatments applied, and especially to its joint manipulation, which for some variables resulted in additive effects while for others only partial compensation. In both species, germination and survival decreased with rising temperatures and/or soil moisture reduction while early growth decreased with declining soil moisture content. We conclude that although A.platanoides germination and survival were more affected after the applied treatments, its initial higher germination and larger seedlings might allow this species to be relatively more successful than A.pseudoplatanus in the face of climate change.

  • 10. Caron, M. M.
    et al.
    De Frenne, P.
    Brunet, J.
    Chabrerie, O.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    De Backer, L.
    Diekmann, M.
    Graae, B. J.
    Heinken, T.
    Kolb, A.
    Naaf, T.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Selvi, F.
    Strimbeck, G. R.
    Wulf, M.
    Verheyen, K.
    Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus2014In: Plant Ecology, ISSN 1385-0237, E-ISSN 1573-5052, Vol. 215, no 8, p. 911-925Article in journal (Refereed)
    Abstract [en]

    Climate change will likely affect population dynamics of numerous plant species by modifying several aspects of the life cycle. Because plant regeneration from seeds may be particularly vulnerable, here we assess the possible effects of climate change on seed characteristics and present an integrated analysis of seven seed traits (nutrient concentrations, samara mass, seed mass, wing length, seed viability, germination percentage, and seedling biomass) of Acer platanoides and A. pseudoplatanus seeds collected along a wide latitudinal gradient from Italy to Norway. Seed traits were analyzed in relation to the environmental conditions experienced by the mother trees along the latitudinal gradient. We found that seed traits of A. platanoides were more influenced by the climatic conditions than those of A. pseudoplatanus. Additionally, seed viability, germination percentage, and seedling biomass of A. platanoides were strongly related to the seed mass and nutrient concentration. While A. platanoides seeds were more influenced by the environmental conditions (generally negatively affected by rising temperatures), compared to A. pseudoplatanus, A. platanoides still showed higher germination percentage and seedling biomass than A. pseudoplatanus. Thus, further research on subsequent life-history stages of both species is needed. The variation in seed quality observed along the climatic gradient highlights the importance of studying the possible impact of climate change on seed production and species demography.

  • 11. Caron, M. M.
    et al.
    De Frenne, P.
    Brunet, J.
    Chabrerie, O.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Decocq, G.
    Diekmann, M.
    Graae, B. J.
    Heinken, T.
    Kolb, A.
    Lenoir, J.
    Naaf, T.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Selvi, F.
    Wulf, M.
    Verheyen, K.
    Divergent regeneration responses of two closely related tree species to direct abiotic and indirect biotic effects of climate change2015In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 342, p. 21-29Article in journal (Refereed)
    Abstract [en]

    Changing temperature and precipitation can strongly influence plant reproduction. However, also biotic interactions might indirectly affect the reproduction and recruitment success of plants in the context of climate change. Information about the interactive effects of changes in abiotic and biotic factors is essential, but still largely lacking, to better understand the potential effects of a changing climate on plant populations. Here we analyze the regeneration from seeds of Acer platanoides and Acer pseudoplatanus, two currently secondary forest tree species from seven regions along a 2200 km-wide latitudinal gradient in Europe. We assessed the germination, seedling survival and growth during two years in a common garden experiment where temperature, precipitation and competition with the understory vegetation were manipulated. A. platanoides was more sensitive to changes in biotic conditions while A. pseudoplatanus was affected by both abiotic and biotic changes. In general, competition reduced (in A. platanoides) and warming enhanced (in A. pseudoplatanus) germination and survival, respectively. Reduced competition strongly increased the growth of A. platanoides seedlings. Seedling responses were independent of the conditions experienced by the mother tree during seed production and maturation. Our results indicate that, due to the negative effects of competition on the regeneration of A. platanoides, it is likely that under stronger competition (projected under future climatic conditions) this species will be negatively affected in terms of germination, survival and seedling biomass. Climate-change experiments including both abiotic and biotic factors constitute a key step forward to better understand the response of tree species' regeneration to climate change.

  • 12. Caron, M. M.
    et al.
    De Frenne, P.
    Chabrerie, O.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    De Backer, L.
    Decocq, G.
    Diekmann, M.
    Heinken, T.
    Kolb, A.
    Naaf, T.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Selvi, F.
    Strimbeck, G. R.
    Wulf, M.
    Verheyen, K.
    Impacts of warming and changes in precipitation frequency on the regeneration of two Acer species2015In: Flora: Morphologie, Geobotanik, Oekophysiologie, ISSN 0367-2530, E-ISSN 1618-0585, Vol. 214, p. 24-33Article in journal (Refereed)
    Abstract [en]

    Climate projections indicate that temperatures will increase by up to 4.5 degrees C in Europe by the end of this century, and that more extreme rainfall events and longer intervening dry periods will take place. Climate change will likely affect all phases of the life cycle of plants, but plant reproduction has been suggested to be especially sensitive. Here, using a combination of approaches (soil heaters and different provenances along a latitudinal gradient), we analyzed the regeneration from seeds of Acer platanoides and A. pseudoplatanus, two tree species considered, from a management point of view, of secondary relevance. We studied germination, seedling survival and growth in a full-factorial experiment including warming and changes in watering frequency. Both species responded to warming, watering frequency and seed provenance, with stronger (negative) effects of warming and provenance than of watering frequency. In general, the central provenances performed better than the northernmost and southern-most provenances. We also detected interactive effects between warming, watering frequency and/or seed provenance. Based on these results, both species are expected to show dissimilar responses to the changes in the studied climatic factors, but also the impacts of climate change on the different phases of plant regeneration may differ in direction and magnitude. In general increases in the precipitation, frequency will stimulate germination while warming will reduce survival and growth. Moreover, the frequent divergent responses of seedlings along the latitudinal gradient suggest that climate change will likely have heterogeneous impacts across Europe, with stronger impacts in the northern and southern parts of the species' distribution ranges.

  • 13. Ceulemans, Tobias
    et al.
    Van Geel, Maarten
    Jacquemyn, Hans
    Boeraeve, Margaux
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Saar, Liina
    Kasari, Liis
    Peeters, Gerrit
    van Acker, Kasper
    Crauwels, Sam
    Lievens, Bart
    Honnay, Olivier
    Arbuscular mycorrhizal fungi in European grasslands under nutrient pollution2019In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 28, no 12, p. 1796-1805Article in journal (Refereed)
    Abstract [en]

    Aim: Our aim was to quantify the extent to which nutrient pollution explains arbuscular mycorrhizal fungal community richness and composition.

    Location: Europe.

    Time period: 2014-2016.

    Major taxa studied: Arbuscular mycorrhizal fungi.

    Methods: We sampled soils of calcareous and acidic grasslands and roots of 34 host plant species across a large geographical gradient of atmospheric nitrogen deposition and soil phosphorus availability. Furthermore, we performed an independent pairwise comparison between fertilized and unfertilized grasslands in Belgium and Iceland to compare results.

    Results: We found that nitrogen deposition had a significant negative relationship to arbuscular mycorrhizal fungal richness, with a negative community threshold of 7.7 kg N/ha/year corresponding to the greatest reduction in operational taxonomic units. Additionally, we found that soil phosphorus had a significant negative relationship to mycorrhizal fungal richness.

    Main conclusions: Our results highlight the necessity to revisit the critical loads of atmospheric nitrogen deposition used in European environmental policy, currently set at 10-15 kg N/ha/year. Importantly, our observed threshold of 7.7 kg N/ha/year does not correspond to a critical load below which there is no environmental harm, because the least negative changes in arbuscular mycorrhizal fungal communities were observed at < 5 kg N/ha/year. Therefore, to avoid compromising the policy tenet of no environmental harm with respect to grassland mycorrhizal fungi, areas of zero tolerance to nitrogen pollution should be delimited. Our results also indicate that environmental policy biased towards reducing nitrogen pollution alone will fail to preserve mycorrhizal biodiversity in European grasslands. We advocate increased policy attention to avoid phosphorus enrichment, particularly through agricultural fertilization. Here too, areas of zero phosphorus input, ideally set in the currently unpolluted (or least polluted) areas, seem key for effective environmental policy, because elevated levels of soil phosphorus after phosphorus fertilization are known to be extremely persistent.

  • 14. De Frenne, Pieter
    et al.
    Brunet, Jörg
    Cougnon, Mathias
    Decocq, Guillaume
    Graae, Bente J.
    Hagenblad, Jenny
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard H.
    Ma, Shiyu
    Orczewska, Anna
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Vranckx, Guy
    Wulf, Monika
    Verheyen, Kris
    Biological Flora of the British Isles: Milium effusum2017In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 105, no 3, p. 839-858Article in journal (Refereed)
    Abstract [en]

    1. This account presents information on all aspects of the biology of Milium effusum L. (Wood Millet) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation.

    2. The grass Milium effusum is a common species of mature woodland in central and southern England, but is less common in the wetter parts of northern England, Wales, Scotland and Ireland. Worldwide, the species is native to many temperate, boreal, subarctic and subalpine parts of the northern hemisphere: from eastern North America across most of Europe (excluding Mediterranean climates) to the Ural Mountains and Black Sea, extending eastwards to the Himalaya, Korea and Japan.

    3. Wood Millet is a shade-tolerant, relatively tall grass (up to 1.8 m) producing up to 700 caryopses per individual. It is characteristic of temperate deciduous woodland, but can also occur in other woodland and forest types and even in scrub, alpine meadows, along railways and roads, and on rocks. In woods, it is one of the most conspicuous plants of the herb layer in the early summer after the disappearance of spring flowering species. While the species is generally considered an ancient woodland indicator in England and western Europe, it is also known to colonize secondary, post-agricultural forests relatively rapidly in other areas such as Denmark, southern Sweden and Poland.

    4. The species has a wide amplitude in terms of soil acidity and nutrient availability, but predominantly grows on soils of intermediate soil fertility and soil pH and with high organic matter concentration. However, M. effusum can tolerate large quantities of tree-leaf litter on the forest floor and is able to grow on very acidic soils.

    5. Changes in land use, climate, densities of large herbivores and atmospheric deposition of nitrogen are having effects on populations of Wood Millet. Significant responses of the life-history traits and population characteristics have been detected in response to environmental variation and to experimental treatments of temperature, nutrients, light and acidity. In many of its habitats across its range, M. effusum is currently becoming more frequent. During the last century, its mean elevation of occurrence in upland areas of Europe has also increased by several hundreds of metres. Typically, management actions are directed towards the conservation of its main habitat type (e.g. ancient woodlands of the Milio-Fagetum association) rather than to the species specifically.

  • 15. De Frenne, Pieter
    et al.
    Coomes, David A.
    De Schrijver, An
    Staelens, Jeroen
    Alexander, Jake M.
    Bernhardt-Roemermann, Markus
    Brunet, Jorg
    Chabrerie, Olivier
    Chiarucci, Alessandro
    den Ouden, Jan
    Eckstein, R. Lutz
    Graae, Bente J.
    Gruwez, Robert
    Hedl, Radim
    Hermy, Martin
    Kolb, Annette
    Marell, Anders
    Mullender, Samantha M.
    Olsen, Siri L.
    Orczewska, Anna
    Peterken, George
    Petrik, Petr
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Simonson, William D.
    Tomescu, Cezar V.
    Vangansbeke, Pieter
    Verstraeten, Gorik
    Vesterdal, Lars
    Wulf, Monika
    Verheyen, Kris
    Plant movements and climate warming: intraspecific variation in growth responses to nonlocal soils2014In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 202, no 2, p. 431-441Article in journal (Refereed)
    Abstract [en]

    <list list-type=bulleted id=nph12672-list-0001> Most range shift predictions focus on the dispersal phase of the colonization process. Because moving populations experience increasingly dissimilar nonclimatic environmental conditions as they track climate warming, it is also critical to test how individuals originating from contrasting thermal environments can establish in nonlocal sites. We assess the intraspecific variation in growth responses to nonlocal soils by planting a widespread grass of deciduous forests (Milium effusum) into an experimental common garden using combinations of seeds and soil sampled in 22 sites across its distributional range, and reflecting movement scenarios of up to 1600km. Furthermore, to determine temperature and forest-structural effects, the plants and soils were experimentally warmed and shaded. We found significantly positive effects of the difference between the temperature of the sites of seed and soil collection on growth and seedling emergence rates. Migrant plants might thus encounter increasingly favourable soil conditions while tracking the isotherms towards currently colder' soils. These effects persisted under experimental warming. Rising temperatures and light availability generally enhanced plant performance. Our results suggest that abiotic and biotic soil characteristics can shape climate change-driven plant movements by affecting growth of nonlocal migrants, a mechanism which should be integrated into predictions of future range shifts.

  • 16. De Frenne, Pieter
    et al.
    Graae, Bente J.
    Rodriguez-Sanchez, Francisco
    Kolb, Annette
    Chabrerie, Olivier
    Decocq, Guillaume
    De Kort, Hanne
    De Schrijver, An
    Diekmann, Martin
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gruwez, Robert
    Hermy, Martin
    Lenoir, Jonathan
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Coomes, David A.
    Verheyen, Kris
    Latitudinal gradients as natural laboratories to infer species' responses to temperature2013In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 101, no 3, p. 784-795Article, review/survey (Refereed)
    Abstract [en]

    Macroclimatic variation along latitudinal gradients provides an excellent natural laboratory to investigate the role of temperature and the potential impacts of climate warming on terrestrial organisms. Here, we review the use of latitudinal gradients for ecological climate change research, in comparison with altitudinal gradients and experimental warming, and illustrate their use and caveats with a meta-analysis of latitudinal intraspecific variation in important life-history traits of vascular plants. We first provide an overview of latitudinal patterns in temperature and other abiotic and biotic environmental variables in terrestrial ecosystems. We then assess the latitudinal intraspecific variation present in five key life-history traits [plant height, specific leaf area (SLA), foliar nitrogen:phosphorus (N:P) stoichiometry, seed mass and root:shoot (R:S) ratio] in natural populations or common garden experiments across a total of 98 plant species. Intraspecific leaf N:P ratio and seed mass significantly decreased with latitude in natural populations. Conversely, the plant height decreased and SLA increased significantly with latitude of population origin in common garden experiments. However, less than a third of the investigated latitudinal transect studies also formally disentangled the effects of temperature from other environmental drivers which potentially hampers the translation from latitudinal effects into a temperature signal. Synthesis. Latitudinal gradients provide a methodological set-up to overcome the drawbacks of other observational and experimental warming methods. Our synthesis indicates that many life-history traits of plants vary with latitude but the translation of latitudinal clines into responses to temperature is a crucial step. Therefore, especially adaptive differentiation of populations and confounding environmental factors other than temperature need to be considered. More generally, integrated approaches of observational studies along temperature gradients, experimental methods and common garden experiments increasingly emerge as the way forward to further our understanding of species and community responses to climate warming.

  • 17.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Borgström, Sara
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Boyd, Emily
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Reading, England.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dalen, Love
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ermold, Matti
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hedlund, Johanna
    Stockholm University, Faculty of Science, Department of Zoology.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lagerholm, Vendela K.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Moor, Helen
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Nykvist, Björn
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Stockholm Environment Institute.
    Pasanen-Mortensen, Marianne
    Stockholm University, Faculty of Science, Department of Zoology.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    van der Velde, Ype
    Stockholm University, Faculty of Science, Department of Physical Geography. Wageningen University & Research Center, Netherlands.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services2015In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 20, no 1, article id UNSP 23Article in journal (Refereed)
    Abstract [en]

    Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6 degrees C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts.

  • 18. Hagenblad, Jenny
    et al.
    Hülskötter, Jennifer
    Acharya, Kamal Prasad
    Brunet, Jörg
    Chabrerie, Olivier
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dar, Pervaiz A.
    Diekmann, Martin
    De Frenne, Pieter
    Hermy, Martin
    Jamoneau, Aurélien
    Kolb, Annette
    Lemke, Isgard
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Reshi, Zafar A.
    Graae, Bente Jessen
    Low genetic diversity despite multiple introductions of the invasive plant species Impatiens glandulifera in Europe2015In: BMC Genetics, ISSN 1471-2156, E-ISSN 1471-2156, Vol. 16, article id 103Article in journal (Refereed)
    Abstract [en]

    Background: Invasive species can be a major threat to native biodiversity and the number of invasive plant species is increasing across the globe. Population genetic studies of invasive species can provide key insights into their invasion history and ensuing evolution, but also for their control. Here we genetically characterise populations of Impatiens glandulifera, an invasive plant in Europe that can have a major impact on native plant communities. We compared populations from the species' native range in Kashmir, India, to those in its invaded range, along a latitudinal gradient in Europe. For comparison, the results from 39 other studies of genetic diversity in invasive species were collated. Results: Our results suggest that I. glandulifera was established in the wild in Europe at least twice, from an area outside of our Kashmir study area. Our results further revealed that the genetic diversity in invasive populations of I. glandulifera is unusually low compared to native populations, in particular when compared to other invasive species. Genetic drift rather than mutation seems to have played a role in differentiating populations in Europe. We find evidence of limitations to local gene flow after introduction to Europe, but somewhat less restrictions in the native range. I. glandulifera populations with significant inbreeding were only found in the species' native range and invasive species in general showed no increase in inbreeding upon leaving their native ranges. In Europe we detect cases of migration between distantly located populations. Human activities therefore seem to, at least partially, have facilitated not only introductions, but also further spread of I. glandulifera across Europe. Conclusions: Although multiple introductions will facilitate the retention of genetic diversity in invasive ranges, widespread invasive species can remain genetically relatively invariant also after multiple introductions. Phenotypic plasticity may therefore be an important component of the successful spread of Impatiens glandulifera across Europe.

  • 19. Helsen, Kenny
    et al.
    Acharya, Kamal P.
    Brunet, Jörg
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Decocq, Guillaume
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard H.
    Lenoir, Jonathan
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Verheyen, Kris
    De Frenne, Pieter
    Graae, Bente J.
    Biotic and abiotic drivers of intraspecific trait variation within plant populations of three herbaceous plant species along a latitudinal gradient2017In: BMC Ecology, ISSN 1472-6785, E-ISSN 1472-6785, Vol. 17, article id 38Article in journal (Refereed)
    Abstract [en]

    Background: The importance of intraspecific trait variation (ITV) is increasingly acknowledged among plant ecologists. However, our understanding of what drives ITV between individual plants (ITVBI) at the population level is still limited. Contrasting theoretical hypotheses state that ITVBI can be either suppressed (stress-reduced plasticity hypothesis) or enhanced (stress-induced variability hypothesis) under high abiotic stress. Similarly, other hypotheses predict either suppressed (niche packing hypothesis) or enhanced ITVBI (individual variation hypothesis) under high niche packing in species rich communities. In this study we assess the relative effects of both abiotic and biotic niche effects on ITVBI of four functional traits (leaf area, specific leaf area, plant height and seed mass), for three herbaceous plant species across a 2300 km long gradient in Europe. The study species were the slow colonizing Anemone nemorosa, a species with intermediate colonization rates, Milium effusum, and the fast colonizing, non-native Impatiens glandulifera.

    Results: Climatic stress consistently increased ITVBI across species and traits. Soil nutrient stress, on the other hand, reduced ITVBI for A. nemorosa and I. glandulifera, but had a reversed effect for M. effusum. We furthermore observed a reversed effect of high niche packing on ITVBI for the fast colonizing non-native I. glandulifera (increased ITVBI), as compared to the slow colonizing native A. nemorosa and M. effusum (reduced ITVBI). Additionally, ITVBI in the fast colonizing species tended to be highest for the vegetative traits plant height and leaf area, but lowest for the measured generative trait seed mass.

    Conclusions: This study shows that stress can both reduce and increase ITVBI, seemingly supporting both the stress-reduced plasticity and stress-induced variability hypotheses. Similarly, niche packing effects on ITVBI supported both the niche packing hypothesis and the individual variation hypothesis. These results clearly illustrates the importance of simultaneously evaluating both abiotic and biotic factors on ITVBI. This study adds to the growing realization that within-population trait variation should not be ignored and can provide valuable ecological insights.

  • 20. Helsen, Kenny
    et al.
    Hagenblad, Jenny
    Acharya, Kamal P.
    Brunet, Jörg
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Decocq, Guillaume
    De Frenne, Pieter
    Kimberley, Adam
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kolb, Annette
    Michaelis, Jana
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Verheyen, Kris
    Speed, James D. M.
    Graae, Bente J.
    No genetic erosion after five generations for Impatiens glandulifera populations across the invaded range in Europe2019In: BMC Genetics, ISSN 1471-2156, E-ISSN 1471-2156, Vol. 20, article id 20Article in journal (Refereed)
    Abstract [en]

    Background

    The observation that many alien species become invasive despite low genetic diversity has long been considered the ‘genetic paradox’ in invasion biology. This paradox is often resolved through the temporal buildup genetic diversity through multiple introduction events. These temporal dynamics in genetic diversity are especially important for annual invasive plants that lack a persistent seed bank, for which population persistence is strongly dependent on consecutive seed ‘re-establishment’ in each growing season. Theory predicts that the number of seeds during re-establishment, and the levels of among-population gene flow can strongly affect recolonization dynamics, resulting in either an erosion or build-up of population genetic diversity through time. This study focuses on temporal changes in the population genetic structure of the annual invasive plant Impatiens glandulifera across Europe. We resampled 13 populations in 6 regions along a 1600 km long latitudinal gradient from northern France to central Norway after 5 years, and assessed population genetic diversity with 9 microsatellite markers.

    Results

    Our study suggests sufficiently high numbers of genetically diverse founders during population re-establishment, which prevent the erosion of local genetic diversity. We furthermore observe that I. glandulifera experiences significant among-population gene flow, gradually resulting in higher genetic diversity and lower overall genetic differentiation through time. Nonetheless, moderate founder effects concerning population genetic composition (allele frequencies) were evident, especially for smaller populations.

    Despite the initially low genetic diversity, this species seems to be successful at persisting across its invaded range, and will likely continue to build up higher genetic diversity at the local scale.

  • 21. Helsen, Kenny
    et al.
    Smith, Stuart W.
    Brunet, Jörg
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    De Frenne, Pieter
    Kimberley, Adam
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kolb, Annette
    Lenoir, Jonathan
    Ma, Shiyu
    Michaelis, Jana
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Verheyen, Kris
    Speed, James D. M.
    Graae, Bente J.
    Impact of an invasive alien plant on litter decomposition along a latitudinal gradient2018In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 9, no 1, article id e02097Article in journal (Refereed)
    Abstract [en]

    Invasive alien plant effects on ecosystem functions are often difficult to predict across environmental gradients due to the context-dependent interactions between the invader and the recipient communities. Adopting a functional trait-based framework could provide more mechanistic predictions for invasive species' impacts. In this study, we contrast litter decomposition rates among communities with and without the invasive plant Impatiens glandulifera in five regions along a 1600 km long latitudinal gradient in Europe. Across this gradient, four functional traits, namely leaf dry matter content (LDMC), specific leaf area (SLA), stem-specific density (SSD), and plant height, are correlated to rates of litter decomposition of standardized rooibos (labile), green tea (recalcitrant), and I. glandulifera litter. Our results show that both invaded and non-invaded plant communities had a higher expression of acquisitive traits (low LDMC and SSD, high SLA) with increasing temperature along the latitudinal gradient, partly explaining the variation in decomposition rates along the gradient. At the same time, invasion shifted community trait composition toward more acquisitive traits across the latitudinal gradient. These trait changes partly explained the increased litter decomposition rates of the labile litter fraction of rooibos and I. glandulifera litter in invaded communities, a shift that was most evident in the warmer study regions. Plant available nitrogen was lower in invaded communities, likely due to high nutrient uptake by I. glandulifera. Meanwhile, the coldest study region was characterized by a reversed effect of invasion on decomposition rates. Here, community traits related to low litter quality and potential allelopathic effects of the invader resulted in reduced litter decomposition rates, suggesting a threshold temperature at which invader effects on litter decomposition turn positive. This study therefore illustrates how functional trait changes toward acquisitive traits can help explain invader-induced changes in ecosystem functions such as increased litter decomposition.

  • 22.
    Jakobsson, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Exploring the effects of pasture trees on plant community patternsManuscript (preprint) (Other academic)
  • 23.
    Jakobsson, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Norwegian Institute for Nature Research, Norway.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Exploring the effects of pasture trees on plant community patterns2019In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 30, no 5, p. 809-820Article in journal (Refereed)
    Abstract [en]

    Questions

    We aim to answer three questions: (a) what are the effects of canopy shading of different tree species on seed germination of eight understorey grassland species? (b) how is plant species’ occurrence in understorey communities affected by differences in canopy cover and does that depend on tree species composition? and (c) are there mechanistic links between the effects of trees on species’ germination and their occurrence in the understorey plant community?

    Location

    Semi‐natural wooded pastures in the biosphere reserve Östra Vätterbranterna, southern Sweden.

    Methods

    In this study, we examined the germination of eight grassland plant species in a seed sowing experiment under natural conditions in the field. Seeds were sown beneath and outside the canopy of two tree species within 48 plots split up by four wooded pasture sites. We combined observed germination responses with a plant community survey to assess the effects of canopy cover in relation to tree species composition on plant community responses. We analysed these data in relation to species’ seed mass and vegetative shade tolerance.

    Results

    Shade‐tolerant species germinated better beneath compared to outside tree canopies, without any clear advantage of large‐seeded over small‐seeded species. As expected, species’ shade tolerance was also positively related to canopy cover within the understorey plant community. Importantly, we found strong tree species‐specific effects of canopy shading on the species’ germination response, but not on their presence within the plant community. However, optimal canopy cover conditions for germination and for the mature plants differed across grassland species and depended on tree species.

    Conclusions

    Our results show that different tree species play key ecosystem engineering roles in shaping wooded grassland plant community composition at the germination stage. Management practices favouring specific tree species may therefore be highly relevant for targeted biodiversity conservation of wooded semi‐natural grasslands.

  • 24.
    Lindborg, Regina
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Andersson, K.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Function of small habitat elements for enhancing plant diversity in different agricultural landscapes2014In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 169, p. 206-213Article in journal (Refereed)
    Abstract [en]

    The extensive transformation of agricultural landscapes worldwide has led to a decrease in grassland species related to traditional low-intensive farming. To properly manage and protect species, habitats and ecosystems in any of these landscapes requires a better understanding of direct and indirect effects of the processes driving biodiversity decline. In this study, we investigated how small habitat elements, represented by mid-field islets and road verges, in different types of agricultural landscapes can sustain a regional species pool for plant diversity otherwise associated to semi-natural grasslands. Although semi-natural grasslands had higher total and specialist richness, we found that small habitat elements harboured relatively high plant species richness, especially in a landscape with many semi-natural grasslands left. In the most intensively managed landscape, total richness declined as distance to the nearest semi-natural grassland increased. In contrast, beta-diversity was highest in these landscapes indicating that small habitats are also negatively affected by distance to grassland. We found that species trait composition varied depending on habitat and landscape. The results confirm that fragmentation shape trait composition within plant communities, e.g. plant size, clonality, longevity, and dispersal traits. We conclude that small habitat elements increase the total area available to grassland species present in the landscape, boosting the spatio-temporal dynamics of grassland communities. Small habitat elements may hence function as refugia or stepping stone habitats, especially in intensively utilized agricultural landscapes, and should be regarded as a functional part of a semi-natural grassland network, analogous to a meta-population.

  • 25. Ma, S.
    et al.
    De Frenne, P.
    Wasof, S.
    Brunet, J.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Decocq, G.
    Kolb, A.
    Lemke, I
    Liira, J.
    Naaf, T.
    Orczewska, A.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Sweden.
    Wulf, M.
    Verheyen, K.
    Plant-soil feedbacks of forest understorey plants transplanted in nonlocal soils along a latitudinal gradient2019In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 21, no 4, p. 677-687Article in journal (Refereed)
    Abstract [en]

    Climate change is driving movements of many plants beyond, as well as within, their current distributional ranges. Even migrant plants moving within their current range may experience different plant-soil feedbacks (PSF) because of divergent nonlocal biotic soil conditions. Yet, our understanding to what extent soil biotic conditions can affect the performance of within-range migrant plants is still very limited. We assessed the emergence and growth of migrant forest herbs (Milium effusum and Stachys sylvatica) using soils and seeds collected along a 1,700 km latitudinal gradient across Europe. Soil biota were manipulated through four soil treatments, i.e. unsterilized control soil (PSFUS), sterilized soil (PSFS), sterilized soil inoculated with unsterilized home soil (PSFS+HI) and sterilized soil inoculated with unsterilized foreign soil (PSFS+FI, expected to occur when both plants and soil biota track climate change). Compared to PSFS, PSFUS had negative effects on the growth but not emergence of both species, while PSFS+FI only affected S. sylvatica across all seed provenances. When considering seed origin, seedling emergence and growth responses to nonlocal soils depended on soil biotic conditions. Specifically, the home-away distance effect on seedling emergence differed between the four treatments, and significant responses to chemistry either disappeared (M. effusum) or changed (S. sylvatica) from PSFUS to PSFS. Soil biota emerge as an important driver of the estimated plant migration success. Our results of the effects of soil microorganisms on plant establishment provide relevant information for predictions of the distribution and dynamics of plant species in a changing climate.

  • 26. Ma, Shiyu
    et al.
    De Frenne, Pieter
    Boone, Nico
    Brunet, Jörg
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Decocq, Guillaume
    Kolb, Annette
    Lemke, Isa
    Liira, Jaan
    Naaf, Tobias
    Orczewska, Anna
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Sweden.
    Wulf, Monika
    Verheyen, Kris
    Plant species identity and soil characteristics determine rhizosphere soil bacteria community composition in European temperate forests2019In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 95, no 6, article id fiz063Article in journal (Refereed)
    Abstract [en]

    Soil bacteria and understorey plants interact and drive forest ecosystem functioning. Yet, knowledge about biotic and abiotic factors that affect the composition of the bacterial community in the rhizosphere of understorey plants is largely lacking. Here, we assessed the effects of plant species identity (Milium effusum vs. Stachys sylvatica), rhizospheric soil characteristics, large-scale environmental conditions (temperature, precipitation and nitrogen (N) deposition), and land-use history (ancient vs. recent forests) on bacterial community composition in rhizosphere soil in temperate forests along a 1700 km latitudinal gradient in Europe. The dominant bacterial phyla in the rhizosphere soil of both plant species were Acidobacteria, Actinobacteria and Proteobacteria. Bacterial community composition differed significantly between the two plant species. Within plant species, soil chemistry was the most important factor determining soil bacterial community composition. More precisely, soil acidity correlated with the presence of multiple phyla, e.g. Acidobacteria (negatively), Chlamydiae (negatively) and Nitrospirae (positively), in both plant species. Large-scale environmental conditions were only important in S. sylvatica and land-use history was not important in either of the plant species. The observed role of understorey plant species identity and rhizosphere soil characteristics in determining soil bacterial community composition extends our understanding of plant-soil bacteria interactions in forest ecosystem functioning.

  • 27. Ma, Shiyu
    et al.
    De Frenne, Pieter
    Vanhellemont, Margot
    Wasof, Safaa
    Boeckx, Pascal
    Brunet, Jörg
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Decocq, Guillaume
    Kolb, Annette
    Lemke, Isa
    Liira, Jaan
    Naaf, Tobias
    Orczewska, Anna
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wulf, Monika
    Verheyen, Kris
    Local soil characteristics determine the microbial communities under forest understorey plants along a latitudinal gradient2019In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 36, p. 34-44Article in journal (Refereed)
    Abstract [en]

    The soil microbial community is essential for maintaining ecosystem functioning and is intimately linked with the plant community. Yet, little is known on how soil microbial communities in the root zone vary at continental scales within plant species. Here we assess the effects of soil chemistry, large-scale environmental conditions (i.e. temperature, precipitation and nitrogen deposition) and forest land-use history on the soil microbial communities (measured by phospholipid fatty acids) in the root zone of four plant species (Geum urbanum, Milium effusum, Poa nemoralis and Stachys sylvatica) in forests along a 1700 km latitudinal gradient in Europe. Soil microbial communities differed significantly among plant species, and soil chemistry was the main determinant of the microbial community composition within each plant species. Influential soil chemical variables for microbial communities were plant species-specific; soil acidity, however, was often an important factor. Large-scale environmental conditions, together with soil chemistry, only explained the microbial community composition in M. effusum and P. nemoralis. Forest land-use history did not affect the soil microbial community composition. Our results underpin the dominant role of soil chemistry in shaping microbial community composition variation within plant species at the continental scale, and provide insights into the composition and functionality of soil microbial communities in forest ecosystems.

  • 28.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Sweden; University of Leuven, Belgium.
    Aavik, Tsipe
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Grazing networks promote plant functional connectivity among isolated grassland communities2019In: Diversity & distributions: A journal of biological invasions and biodiversity, ISSN 1366-9516, E-ISSN 1472-4642, Vol. 25, no 1, p. 102-115Article in journal (Refereed)
    Abstract [en]

    Aim Habitat loss threatens plant diversity globally. Lack of plant functional connectivity between isolated populations is often pinpointed as one of the major underlying mechanisms driving subsequent species extinctions. Therefore, landscape-scale conservation management promoting functional connectivity needs to be implemented urgently. Supporting the movement of seed dispersal vectors such as grazing animals may help safeguard local and regional plant diversity in fragmented landscapes. However, the efficacy of such management remains to be thoroughly assessed. Location Stockholm archipelago, Sweden. Methods We test how grazing animals may serve as mobile corridors within rotational grazing networks promoting plant functional connectivity via directed seed dispersal. Using landscape genetics, we compare isolated populations of the grassland perennial Campanula rotundifolia located in either active or abandoned grazing networks, to test if spatial patterns in their genetic diversity, differentiation and allele frequencies relate to the presence or absence of connectivity via rotational grazing management. Results Grazing networks imprinted strong landscape-scale spatial patterning in pairwise population genetic differentiation and within-population genetic diversity. Isolated C. rotundifolia populations functionally connected by grazing animals held higher genetic diversity compared to populations no longer connected by grazing livestock. Gene flow linked to the directed seed dispersal was higher between populations within grazing networks, confirmed by their increased allele richness. We found a predictable, nested loss of genetic diversity among C. rotundifolia populations in abandoned grazing networks. Main conclusions Grazing animals were important seed dispersal vectors, functionally connecting isolated grassland communities, so being vital to the successful long-term persistence and conservation of not only species but also genetic diversity. Crucially, the study underlines the possibilities of using domestic livestock as mobile corridors within rotational grazing networks as an effective tool to manage, conserve and restore both genetic and species diversity among isolated plant communities in fragmented landscapes.

  • 29.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Bremen, Germany.
    Colas, F.
    Auffret, Alistair G.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Methodological bias in the seed bank flora holds significant implications for understanding seed bank community functions2017In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 19, no 2, p. 201-210Article in journal (Refereed)
    Abstract [en]

    Persistent seed banks are a key plant regeneration strategy, buffering environmental variation to allow population and species persistence. Understanding seed bank functioning within herb layer dynamics is therefore important. However, rather than assessing emergence from the seed bank in herb layer gaps, most studies evaluate the seed bank functioning via a greenhouse census. We hypothesise that greenhouse data may not reflect seed bank-driven emergence in disturbance gaps due to methodological differences. Failure in detecting (specialist) species may then introduce methodological bias into the ecological interpretation of seed bank functions using greenhouse data. The persistent seed bank was surveyed in 40 semi-natural grassland plots across a fragmented landscape, quantifying seedling emergence in both the greenhouse and in disturbance gaps. Given the suspected interpretational bias, we tested whether each census uncovers similar seed bank responses to fragmentation. Seed bank characteristics were similar between censuses. Census type affected seed bank composition, with >25% of species retrieved better by either census type, dependent on functional traits including seed longevity, production and size. Habitat specialists emerged more in disturbance gaps than in the greenhouse, while the opposite was true for ruderal species. Both censuses uncovered fragmentation-induced seed bank patterns. Low surface area sampling, larger depth of sampling and germination conditions cause underrepresentation of the habitat-specialised part of the persistent seed bank flora during greenhouse censuses. Methodological bias introduced in the recorded seed bank data may consequently have significant implications for the ecological interpretation of seed bank community functions based on greenhouse data.

  • 30.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Stockholm.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Seed dispersal in both space and time is necessary for plant diversity maintenance in fragmented landscapes2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 6, p. 780-791Article in journal (Refereed)
    Abstract [en]

    Metacommunity theory emphasizes that seed dispersal not only limits but equally maintains plant diversity, though the latter receives little empirical attention. Discerning the temporal and spatial components of seed dispersal and understanding how their interaction shapes fragmented communities and maintains their diversity may be pivotal to further our ecological understanding of spatial and temporal seed dispersal and its implications for landscape-scale conservation management. To investigate the relative importance of spatial and temporal seed dispersal and their roles in maintaining plant diversity, the herb layer and seed bank of grassland communities were inventoried in 77 sites across abandoned and intact rotational grazing networks in a 100 km(2) fragmented grassland landscape in the Stockholm archipelago (Baltic Sea, Sweden). Besides analysing alpha- and beta-diversity patterns, nestedness analyses connect deterministic community changes and diversity losses with dispersal-related life-history traits and habitat specialization to identify the mechanism driving community changes and maintaining local diversity. The loss of rotational grazing networks caused community diversity declines via non-random extinctions of spatially and temporally poor dispersers, particularly among grassland specialists. Temporal seed dispersal halted further community disassembly, maintaining diversity in the abandoned grazing networks. Spatial dispersal within the intact grazing networks was found to be an overriding, homogenizing agent conserving diversity in both the herb layer and seed bank. This empirical evidence establishes how spatial and temporal seed dispersal interact to maintain diversity in fragmented landscapes. Poorly connected grasslands appear limited by spatial dispersal, yet are maintained by temporal seed dispersal. In fragmented landscapes where grazing networks are rarely present, temporal rather than spatial seed dispersal may be more important in maintaining species diversity, since effective spatial dispersal may be significantly diminished. The grazing network's efficacy at boosting spatial dispersal and upholding community diversity presents a powerful management tool to conserve local and regional species diversity.

  • 31.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Temporal dispersal in fragmented landscapes2013In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 160, p. 250-262Article in journal (Refereed)
    Abstract [en]

    Despite a good understanding on how dispersal in space structures plant communities in fragmented landscapes, we know little about dispersal in time. Empirical evidence on temporal dispersal - the soil seed bank - is lacking, with only trait-based evidence on the seed banks' importance for species persistence in fragmented landscapes. Therefore, seed banks of remnant grassland fragments were analyzed in how they changed compared to semi-natural grasslands following fragmentation. We studied the historical trajectories in time since fragmentation, fragment size and habitat quality of 134 grassland plots, linking these to their seed bank and plant community to understand how seed banks temporally connect grassland fragments, potentially conserving the flora of historically large semi-natural grasslands. Seed-banking grassland species were present in similar proportions in all remnant grassland fragments. The seed bank composition changed with time since fragmentation started, triggered by the deterministic loss of grassland species, generating nested subsets of the seed banks of semi-natural grasslands. The spatial heterogeneity in seed bank composition among grassland fragments limited the loss of grassland species at the landscape scale. The seed bank became an increasingly important constituent of total plant diversity with time since fragmentation started, as grassland species stored an increasingly larger proportion of their local diversity in the seed bank. Temporal dispersal enables the prolonged presence and persistence of numerous typical grassland species in fragmented landscapes. The seed banks' storage effect of plant diversity is of considerable significance to efforts aimed at conserving and restoring plant diversity in fragmented landscapes.

  • 32.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    De Frenne, Pieter
    Acharya, Kamal
    Brunet, Jorg
    Chabrerie, Olivier
    Decocq, Guillaume
    Diekmann, Martin
    Graae, Bente J.
    Heinken, Thilo
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard
    Liira, Jaan
    Naaf, Tobias
    Shevtsova, Anna
    Verheyen, Kris
    Wulf, Monika
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Climatic control of forest herb seed banks along a latitudinal gradient2013In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 22, no 10, p. 1106-1117Article in journal (Refereed)
    Abstract [en]

    Aim Seed banks are central to the regeneration strategy of many plant species. Any factor altering seed bank density thus affects plant regeneration and population dynamics. Although seed banks are dynamic entities controlled by multiple environmental drivers, climatic factors are the most comprehensive, but still poorly understood. This study investigates how climatic variation structures seed production and resulting seed bank patterns. Location Temperate forests along a 1900km latitudinal gradient in north-western (NW) Europe. Methods Seed production and seed bank density were quantified in 153 plots along the gradient for four forest herbs with different seed longevity: Geum urbanum, Milium effusum, Poa nemoralis and Stachys sylvatica. We tested the importance of climatic and local environmental factors in shaping seed production and seed bank density. Results Seed production was determined by population size, and not by climatic factors. G.urbanum and M.effusum seed bank density declined with decreasing temperature (growing degree days) and/or increasing temperature range (maximum-minimum temperature). P.nemoralis and S.sylvatica seed bank density were limited by population size and not by climatic variables. Seed bank density was also influenced by other, local environmental factors such as soil pH or light availability. Different seed bank patterns emerged due to differential seed longevities. Species with long-lived seeds maintained constant seed bank densities by counteracting the reduced chance of regular years with high seed production at colder northern latitudes. Main conclusions Seed bank patterns show clear interspecific variation in response to climate across the distribution range. Not all seed banking species may be as well equipped to buffer climate change via their seed bank, notably in short-term persistent species. Since the buffering capacity of seed banks is key to species persistence, these results provide crucial information to advance climatic change predictions on range shifts, community and biodiversity responses.

  • 33.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Sweden; University of Bremen, Germany.
    De Frenne, Pieter
    Acharya, Kamal
    Brunet, Jörg
    Chabrerie, Olivier
    Decocq, Guillaume
    Diekmann, Martin
    Graae, Bente J.
    Heinken, Thilo
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard
    Liira, Jaan
    Naaf, Tobias
    Verheyen, Kris
    Wulf, Monika
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Where does the community start, and where does it end? Including the seed bank to reassess forest herb layer responses to the environment2017In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 28, no 2, p. 424-435Article in journal (Refereed)
    Abstract [en]

    QuestionBelow-ground processes are key determinants of above-ground plant population and community dynamics. Still, our understanding of how environmental drivers shape plant communities is mostly based on above-ground diversity patterns, bypassing below-ground plant diversity stored in seed banks. As seed banks may shape above-ground plant communities, we question whether concurrently analysing the above- and below-ground species assemblages may potentially enhance our understanding of community responses to environmental variation. LocationTemperate deciduous forests along a 2000km latitudinal gradient in NW Europe. MethodsHerb layer, seed bank and local environmental data including soil pH, canopy cover, forest cover continuity and time since last canopy disturbance were collected in 129 temperate deciduous forest plots. We quantified herb layer and seed bank diversity per plot and evaluated how environmental variation structured community diversity in the herb layer, seed bank and the combined herb layer-seed bank community. ResultsSeed banks consistently held more plant species than the herb layer. How local plot diversity was partitioned across the herb layer and seed bank was mediated by environmental variation in drivers serving as proxies of light availability. The herb layer and seed bank contained an ever smaller and ever larger share of local diversity, respectively, as both canopy cover and time since last canopy disturbance decreased. Species richness and -diversity of the combined herb layer-seed bank community responded distinctly differently compared to the separate assemblages in response to environmental variation in, e.g. forest cover continuity and canopy cover. ConclusionsThe seed bank is a below-ground diversity reservoir of the herbaceous forest community, which interacts with the herb layer, although constrained by environmental variation in e.g. light availability. The herb layer and seed bank co-exist as a single community by means of the so-called storage effect, resulting in distinct responses to environmental variation not necessarily recorded in the individual herb layer or seed bank assemblages. Thus, concurrently analysing above- and below-ground diversity will improve our ecological understanding of how understorey plant communities respond to environmental variation.

  • 34.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hermy, Martin
    Consistent seed bank spatial structure across semi natural habitats determines plot sampling2012In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 23, no 3, p. 505-516Article in journal (Refereed)
    Abstract [en]

    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.

  • 35.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Sweden.
    Kimberley, Adam
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Slotte, Tanja
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Interspecific variation in ploidy as a key plant trait outlining local extinction risks and community patterns in fragmented landscapes2018In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 32, no 8, p. 2095-2106Article in journal (Refereed)
    Abstract [en]

    1. Polyploidy is associated with a plethora of phenotypic and genetic changes yielding transformative effects on species' life-history and ecology. These biological attributes can contribute to the success of species on ecological timescales, as observed in the invasion success or rapid environmental and climatic adaptation of polyploids. However, to date there has been a distinct lack of empirical evidence linking species' local extinction risk, species distributions and community structure in fragmented landscapes with interspecific variation in ploidy. 2. We aimed to investigate the relationship between levels of habitat fragmentation and patterns in both diversity and the frequency of species with different ploidy levels. We included additional persistence-and dispersal related life-history traits, to establish the relative importance of ploidy in determining species richness and frequencies following habitat fragmentation. We therefore collected plant community presence-absence data and landscape data from grassland fragments from south-central Sweden. 3. Community-level analysis uncovered that interspecific variation in ploidy proved the strongest predictor of plant community species richness and turn-over across grassland fragments. Local extinction risk decreased as ploidy increased, with diploids most prone to local extinction. 4. In the species-level analysis, ploidy outweighed the combined explanatory power of commonly used life-history traits such as clonality, dispersal mechanism and mating system; key predictors of plant species distributions across fragmented landscapes. 5. Ploidy appears to capture parallel variation in a series of advantageous genetic and life-history mechanisms which operate on ecological timescales, emerging as the strongest predictor of local extinction risk even after accounting for variation in other crucial life-history traits. Our results therefore highlight the importance of genomic traits such as ploidy and total chromosome number as valuable factors explaining and predicting local extinction risk in fragmented landscapes.

  • 36.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Thompson, Ken
    Verheyen, Kris
    Hermy, Martin
    Seed banking in ancient forest species: why total sampled area really matters2012In: Seed Science Research, ISSN 0960-2585, E-ISSN 1475-2735, Vol. 22, no 2, p. 123-133Article in journal (Refereed)
    Abstract [en]

    This study investigates how methodological aspects of seed-bank sampling affect seed-bank records in temperate deciduous forests. We focused explicitly on seed-bank records of ancient forest species, which are assumed to lack a persistent seed bank; a hypothesis suspected to be partly due to methodological shortcomings. Through a quantitative review of 31 seed-bank studies in temperate deciduous forests of central and north-west Europe, we quantified the role of sampling methodology in constraining total seed-bank records and seed-bank records of ancient forest species (gamma-diversity, average species' retrieval frequency and average seed density). A major methodological trade-off was established between sampled plot area and the number of plots: at an increased number of plots, the area sampled per plot decreased significantly. The total surface area sampled in a study was the primary determinant of gamma-diversity, both for overall species richness and for ancient forest species richness. A high retrieval frequency of ancient forest species indicated that few plots were intensively sampled. The parallel increase in total species richness and ancient forest species richness and the non-significance of their ratio in relation to methodological variables suggests that ancient forest species are not particularly rare in the seed bank compared to other species. These results imply that sampling methodology has a far-reaching impact on seed-bank records such as gamma-diversity, the detection of ancient forest species and ultimately seed-bank composition. We formulate a set of guidelines to improve the quality of seed-bank studies in temperate deciduous forests.

  • 37.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Stockholm, Sweden.
    Vandepitte, Katrien
    Honnay, Olivier
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Does the seed bank contribute to the build-up of a genetic extinction debt in the grassland perennial Campanula rotundifolia?2017In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 120, no 3, p. 373-385Article in journal (Refereed)
    Abstract [en]

    Background and Aims

    Habitat fragmentation threatens global biodiversity. Many plant species persist in habitat fragments via persistent life cycle stages such as seed banks, generating a species extinction debt. Here, seed banks are hypothesized to cause a temporal delay in the expected loss of genetic variation, which can be referred to as a genetic extinction debt, as a possible mechanism behind species extinction debts.

    Methods

    Fragmented grassland populations of Campanula rotundifolia were examined for evidence of a genetic extinction debt, investigating if the seed bank contributed to the extinction debt build-up. The genetic make-up of 15 above- and below-ground populations was analysed in relation to historical and current levels of habitat fragmentation, both separately and combined.

    Key Results

    Genetic diversity was highest in above-ground populations, though below-ground populations contained 8 % of unique alleles that were absent above-ground. Above-ground genetic diversity and composition were related to historical patch size and connectivity, but not current patch characteristics, suggesting the presence of a genetic extinction debt in the above-ground populations. No such relationships were found for the below-ground populations. Genetic diversity measures still showed a response to historical but not present landscape characteristics when combining genetic diversity of the above- and below-ground populations.

    Conclusions

    The fragmented C. rotundifolia populations exhibited a genetic extinction debt. However, the role of the seed banks in the build-up of this extinction debt is probably small, since the limited, unique genetic diversity of the seed bank alone seems unable to counter the detrimental effects of habitat fragmentation on the population genetic structure of C. rotundifolia.

  • 38.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Vandepitte, Katrien
    Honnay, Olivier
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Isolation by 454-sequencing and characterization of polymorphic microsatellite markers in the tetraploid perennial herb Campanula rotundifolia2015In: Conservation Genetics Resources, ISSN 1877-7252, E-ISSN 1877-7260, Vol. 7, no 3, p. 721-722Article in journal (Refereed)
    Abstract [en]

    Campanula rotundifolia is a perennial polyploid herb with a wide circumpolar distribution growing in a range of grassland, heathland and dune communities. The species is showing signs of strong decline in most parts of its range due to habitat degradation. Eight polymorphic microsatellites were developed using a 454-sequencing approach and subsequently characterized in 323 tetraploid individuals from 15 populations in a fragmented landscape in central Sweden. Between 7 and 26 alleles were observed per locus with observed and expected heterozygosity ranging between 0.71-0.98 and 0.71-0.93, respectively. C. rotundifolia may serve as a model species for studying the relative importance of life-history traits in genetic diversity responses to environmental changes.

  • 39. Reinecke, J.
    et al.
    Wulf, M.
    Baeten, L.
    Brunet, J.
    Decocq, G.
    De Frenne, G.
    Diekmann, M.
    Graae, B. J.
    Heinken, T.
    Hermy, M.
    Jamoneau, A.
    Lenoir, J.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Orczewska, A.
    Van Calster, H.
    Verheyen, K.
    Naaf, T.
    Acido- and neutrophilic temperate forest plants display distinct shifts in ecological pH niche across north-western Europe2016In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 39, no 12, p. 1164-1175Article in journal (Refereed)
    Abstract [en]

    Ecological niches of organisms vary across geographical space, but niche shift patterns between regions and the underlying mechanisms remain largely unexplored. We studied shifts in the pH niche of 42 temperate forest plant species across a latitudinal gradient from northern France to boreo-nemoral Sweden. We asked 1) whether species restrict their niches with increasing latitude as they reach their northern range margin (environmental constraints); 2) whether species expand their niches with increasing latitude as regional plant species richness decreases (competitive release); and 3) whether species shift their niche position toward more acidic sites with increasing latitude as the relative proportion of acidic soils increases (local adaptation). Based on 1458 vegetation plots and corresponding soil pH values, we modelled species response curves using Huisman-Olff-Fresco models. Four niche measures (width, position, left and right border) were compared among regions by randomization tests. We found that with increasing latitude, neutrophilic species tended to retreat from acidic sites, indicating that these species retreat to more favorable sites when approaching their range margin. Alternatively, these species might benefit from enhanced nitrogen deposition on formerly nutrient-poor, acidic sites in southern regions or lag behind in post-glacial recolonization of potential habitats in northern regions. Most acidophilic species extended their niche toward more base-rich sites with increasing latitude, indicating competitive release from neutrophilic species. Alternatively, acidophilic species might benefit from optimal climatic conditions in the north where some have their core distribution area. Shifts in the niche position suggested that local adaptation is of minor importance. We conclude that shifts in the pH niche of temperate forest plants are the rule, but the directions of the niche shifts and possible explanations vary. Our study demonstrates that differentiating between acidophilic and neutrophilic species is crucial to identify general patterns and underlying mechanisms.

  • 40. Van Geel, Maarten
    et al.
    Jacquemyn, Hans
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Saar, Liina
    Kasari, Liis
    Peeters, Gerrit
    van Acker, Kasper
    Honnay, Olivier
    Ceulemans, Tobias
    Abiotic rather than biotic filtering shapes the arbuscular mycorrhizal fungal communities of European seminatural grasslands2018In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 220, no 4, p. 1262-1272Article in journal (Refereed)
    Abstract [en]

    Although it is well known that arbuscular mycorrhizal fungi (AMF) play a key role in the functioning of natural ecosystems, the underlying drivers determining the composition of AMF communities remain unclear. In this study, we established 138 sampling plots at 46 grassland sites, consisting of 26 acidic grasslands and 20 calcareous grasslands spread across eight European countries, to assess the relative importance of abiotic and biotic filtering in driving AMF community composition and structure in both the grassland soils and in the roots of 13 grassland plant species. Soil AMF communities differed significantly between acidic and calcareous grasslands. In root AMF communities, most variance was attributable to soil variables while very little variation was explained by host plant identity. Root AMF communities in host plant species occurring in only one grassland type closely resembled the soil AMF communities of that grassland type and the root AMF communities of other host plant species occurring in the same grassland type. The observed AMF-host plants networks were not modular but nested. Our results indicate that abiotic conditions, rather than biotic filtering through host plant specificity, are the most important drivers in shaping AMF communities in European seminatural grasslands.

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