@article{deFrenneKolbVerheyenetal.2009, author = {de Frenne, Pieter and Kolb, Annette and Verheyen, Kris and Brunet, Johanne and Chabrerie, Olivier and Decocq, Guillaume and Diekmann, Martin and Eriksson, Ove and Heinken, Thilo and Hermy, Martin and J{\~o}gar, {\"U}lle and Stanton, Sara and Quataert, Paul and Zindel, Renate and Zobel, Martin and Graae, Bente Jessen}, title = {Unravelling the effects of temperature, latitude and local environment on the reproduction of forest herbs}, issn = {1466-822X}, doi = {10.1111/j.1466-8238.2009.00487.x}, year = {2009}, abstract = {Aim To investigate the effect of temperature, latitude and local environment on the reproductive traits of widespread perennial forest herbs to better understand the potential impacts of rising temperatures on their population dynamics and colonization capacities. Location Six regions along a latitudinal gradient from France to Sweden. Methods Within each region, we collected data from three to five populations of up to six species. For each species, several variables were recorded in each region (temperature, latitude) and population (local abiotic and biotic environmental variables), and seed production and germination were estimated. Resource investment in reproduction (RIR) was quantified as seed number ¥ seed mass, while germinable seed output (GSO) was expressed as seed number ¥ germination percentage.We performed linear regression and mixed effect models to investigate the effects of temperature (growing degree hours), latitude and local abiotic and biotic environment on RIR and GSO. Results Temperature and latitude explained most of the variation in RIR and GSO for early flowering species with a northerly distribution range edge (Anemone nemorosa, Paris quadrifolia and Oxalis acetosella). Reproduction of the more southerly distributed species (Brachypodium sylvaticum, Circaea lutetiana and Primula elatior), in contrast, was independent of temperature/latitude. In the late summer species, B. sylvaticum and C. lutetiana, variation in RIR and GSO was best explained by local environmental variables, while none of the investigated variables appeared to be related to reproduction in P. elatior. Main conclusions We showed that reproduction of only two early flowering, northerly distributed species was related to temperature. This suggests that the potential reproductive response of forest herbs to climate warming partly depends on their phenology and distribution, but also that the response is to some extent species dependent. These findings should be taken into account when predictions about future shifts in distribution range are made.}, language = {en} } @article{GraaeVerheyenKolbetal.2009, author = {Graae, Bente Jessen and Verheyen, Kris and Kolb, Annette and van der Veken, Sebastian and Heinken, Thilo and Chabrerie, Olivier and Diekmann, Martin and Valtinat, Karin and Zindel, Renate and Karlsson, Elisabeth and Str{\"o}m, Lotta and Decocq, Guillaume and Hermy, Martin and Baskin, Carol C.}, title = {Germination requirements and seed mass of slow- and fast-colonizing temperate forest herbs along a latitudinal gradient}, issn = {1195-6860}, doi = {10.2980/16-2-3234}, year = {2009}, abstract = {Predictions on displacement of suitable habitats due to climate change suggest that plant species with poor colonization ability may be unable to move fast enough to match forecasted climate-induced changes in habitat distribution. However, studies on early Holocene plant migration show fast migration of many plant species that are poor colonizers today. We hypothesize that warmer temperatures during the early Holocene yielded higher seed quality, contributing to explaining the fast migration. We studied how the 3 seed quality variables, seed mass, germinability, and requirements for break of seed dormancy, vary for seeds of 11 forest herb species with varying colonization capacity collected along a 1400-km latitudinal gradient. Within species, seed mass showed a positive correlation with latitude, whereas germinability was more positively correlated with temperature (growing degree hours obtained at time of seed collection). Only slow-colonizing species increased germinability with temperature, whereas only fast-colonizing species increased germinability with latitude. These interactions were only detectable when analyzing germinability of the seeds, even though this trait and seed mass were correlated. The requirement for dormancy break did not correlate with latitude or temperature. The results indicate that seed development of slow colonizers may be favoured by a warmer climate, which in turn may be important for their migration capacity.}, language = {en} } @article{WinklerHeinken2007, author = {Winkler, Eckart and Heinken, Thilo}, title = {Spread of an ant-dispersed annual herb : an individual-based simulation study on population development of Melampyrum pratense L.}, issn = {0304-3800}, year = {2007}, abstract = {The paper presents a simulation and parameter-estimation approach for evaluating stochastic patterns of population growth and spread of an annual forest herb, Melampyrum pratense (Orobanchaceae). The survival of a species during large-scale changes in land use and climate will depend, to a considerable extent, on its dispersal and colonisation abilities. Predictions on species migration need a combination of field studies and modelling efforts. Our study on the ability of M. pratense to disperse into so far unoccupied areas is based on experiments in secondary woodland in NE Germany. Experiments started in 1997 at three sites where the species was not yet present, with 300 seeds sown within 1m2. Population development was then recorded until 2001 by mapping of individuals with a resolution of 5 cm. Additional observations considered density dependence of seed production. We designed a spatially explicit individual-based computer simulation model to explain the spatial patterns of population development and to predict future population spread. Besides primary drop of seeds (barochory) it assumed secondary seed transport by ants (myrmecochory) with an exponentially decreasing dispersal tail. An important feature of population-pattern explanation was the simultaneous estimation of both population-growth and dispersal parameters from consistent spatio-temporal data sets. As the simulation model produced stochastic time series and random spatially discrete distributions of individuals we estimated parameters by minimising the expectation of weighted sum of squares. These sums of squares criteria considered population sizes, radial population distributions around the area of origin and distributions of individuals within squares of 25cm×25 cm, the range of density action. Optimal parameter values, together with the precision of the estimates, were obtained from calculating sum of squares in regular grids of parameter values. Our modelling results showed that transport of fractions of seeds by ants over distances of 1-2m was indispensable for explaining the observed population spread that led to distances of at most 8mfrom population origin within 3 years. Projections of population development over four additional years gave a diffusion-like increase of population area without any "outposts". This prediction generated by the simulation model gave a hypothesis which should be revised by additional field observations. Some structural deviations between observations and model output already indicated that for full understanding of population spread the set of dispersal mechanisms assumed in the model may have to be extended by additional features of plant-animal mutualism.}, language = {en} } @article{LiangHeinrichSimardetal.2013, author = {Liang, Wei and Heinrich, Ingo and Simard, Sonia and Helle, Gerhard and Linan, Isabel Dorado and Heinken, Thilo}, title = {Climate signals derived from cell anatomy of Scots pine in NE Germany}, series = {Tree physiology}, volume = {33}, journal = {Tree physiology}, number = {8}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0829-318X}, doi = {10.1093/treephys/tpt059}, pages = {833 -- 844}, year = {2013}, abstract = {Tree-ring chronologies of Pinus sylvestris L. from latitudinal and altitudinal limits of the species distribution have been widely used for climate reconstructions, but there are many sites within the temperate climate zone, as is the case in northeastern Germany, at which there is little evidence of a clear climate signal in the chronologies. In this study, we developed long chronologies of several cell structure variables (e. g., average lumen area and cell wall thickness) from P. sylvestris growing in northeastern Germany and investigated the influence of climate on ring widths and cell structure variables. We found significant correlations between cell structure variables and temperature, and between tree-ring width and relative humidity and vapor pressure, respectively, enabling the development of robust reconstructions from temperate sites that have not yet been realized. Moreover, it has been shown that it may not be necessary to detrend chronologies of cell structure variables and thus low-frequency climate signals may be retrieved from longer cell structure chronologies. The relatively extensive resource of archaeological material of P. sylvestris covering approximately the last millennium may now be useful for climate reconstructions in northeastern Germany and other sites in the temperate climate zone.}, language = {en} } @article{VerheyenBaetenDeFrenneetal.2012, author = {Verheyen, Kris and Baeten, Lander and De Frenne, Pieter and Bernhardt-R{\"o}mermann, Markus and Brunet, Jorg and Cornelis, Johnny and Decocq, Guillaume and Dierschke, Hartmut and Eriksson, Ove and Hedl, Radim and Heinken, Thilo and Hermy, Martin and Hommel, Patrick and Kirby, Keith J. and Naaf, Tobias and Peterken, George and Petrik, Petr and Pfadenhauer, Joerg and Van Calster, Hans and Walther, Gian-Reto and Wulf, Monika and Verstraeten, Gorik}, title = {Driving factors behind the eutrophication signal in understorey plant communities of deciduous temperate forests}, series = {The journal of ecology}, volume = {100}, journal = {The journal of ecology}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0022-0477}, doi = {10.1111/j.1365-2745.2011.01928.x}, pages = {352 -- 365}, year = {2012}, abstract = {1. Atmospheric nitrogen (N) deposition is expected to change forest understorey plant community composition and diversity, but results of experimental addition studies and observational studies are not yet conclusive. A shortcoming of observational studies, which are generally based on resurveys or sampling along large deposition gradients, is the occurrence of temporal or spatial confounding factors. 2. We were able to assess the contribution of N deposition versus other ecological drivers on forest understorey plant communities by combining a temporal and spatial approach. Data from 1205 (semi-)permanent vegetation plots taken from 23 rigorously selected understorey resurvey studies along a large deposition gradient across deciduous temperate forest in Europe were compiled and related to various local and regional driving factors, including the rate of atmospheric N deposition, the change in large herbivore densities and the change in canopy cover and composition. 3. Although no directional change in species richness occurred, there was considerable floristic turnover in the understorey plant community and a shift in species composition towards more shade-tolerant and nutrient-demanding species. However, atmospheric N deposition was not important in explaining the observed eutrophication signal. This signal seemed mainly related to a shift towards a denser canopy cover and a changed canopy species composition with a higher share of species with more easily decomposed litter. 4. Synthesis. Our multi-site approach clearly demonstrates that one should be cautious when drawing conclusions about the impact of atmospheric N deposition based on the interpretation of plant community shifts in single sites or regions due to other, concurrent, ecological changes. Even though the effects of chronically increased N deposition on the forest plant communities are apparently obscured by the effects of canopy changes, the accumulated N might still have a significant impact. However, more research is needed to assess whether this N time bomb will indeed explode when canopies will open up again.}, language = {en} } @article{SchulzeBuchwaldHeinken2014, author = {Schulze, Kiowa Alraune and Buchwald, Rainer and Heinken, Thilo}, title = {Epizoochory via the hooves - the European bison (Bison bonasus L.) as a dispersal agent of seeds in an open-forest-mosaic}, series = {Tuexenia : Mitteilungen der Floristisch-Soziologischen Arbeitsgemeinschaft}, journal = {Tuexenia : Mitteilungen der Floristisch-Soziologischen Arbeitsgemeinschaft}, number = {34}, publisher = {Floristisch-Soziologische Arbeitsgemeinschaft}, address = {G{\"o}ttingen}, issn = {0722-494X}, pages = {131 -- 144}, year = {2014}, abstract = {Large herbivores are significant vectors for the long-distance dispersal of seeds in various habitats, both attached to animals (epizoochory) and via gut passage (endozoochory). The majority of studies on epizoochory have examined dispersal in the fur of domesticated ungulates. Studies on wild ungulates are important to understand dispersal processes in many habitats, but rare due to methodological constraints. We studied epizoochory of seeds by European bison in an open-forest-mosaic (nutrient-poor grassland and heathland, mixed forest) in NW Germany, where bison had been introduced for the purpose of nature conservation. At the study site it was possible to apply a method by which hoof material of free-ranging bison was non-invasively collected. We identified a total of 1082 seeds from 32 plant species in the hoof material. The three most abundant species were Polygonum aviculare, Agrostis capillaris and Betula spp. Seed species originated from various habitat types of the study area, while the majority of seeds derived from trampled areas. Compared to the non-dispersed plant species of the study area, dispersed plant species had a higher seed longevity index, suggesting that many seeds were picked up from the soil seed bank. Epizoochory ranking indices of dispersed seed species, classifying the importance of epizoochory, revealed that transport in the fur may be of minor importance for many species, i.e. epizoochory by the hooves turned out to be negatively correlated to epizoochory in the fur. We conclude that European bison disperses a considerable number of seed species through trampling. Further research should consider epizoochory via the hooves and include integrative approaches to understand the different dispersal mechanisms by ungulates and their long-term synergetic effect on plant communities.}, language = {en} } @article{CaronDeFrenneBrunetetal.2015, author = {Caron, Maria Mercedes and De Frenne, Pieter and Brunet, J{\"o}rg and Chabrerie, Olivier and Cousins, Sara A. O. and Decocq, Guillaume and Diekmann, Martin and Graae, Bente Jessen and Heinken, Thilo and Kolb, Annette and Lenoir, Jonathan and Naaf, Tobias and Plue, Jan and Selvi, Federico and Wulf, Monika and Verheyen, Kris}, title = {Divergent regeneration responses of two closely related tree species to direct abiotic and indirect biotic effects of climate change}, series = {Forest ecology and management}, volume = {342}, journal = {Forest ecology and management}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0378-1127}, doi = {10.1016/j.foreco.2015.01.003}, pages = {21 -- 29}, year = {2015}, abstract = {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. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{DeFrenneGraaeBrunetetal.2012, author = {De Frenne, Pieter and Graae, Bente J. and Brunet, J{\"o}rg and Shevtsova, Anna and De Schrijver, An and Chabrerie, Olivier and Cousins, Sara A. O. and Decocq, Guillaume and Diekmann, Martin and Hermy, Martin and Heinken, Thilo and Kolb, Annette and Nilsson, Christer and Stanton, Sharon and Verheyen, Kris}, title = {The response of forest plant regeneration to temperature variation along a latitudinal gradient}, series = {Annals of botany}, volume = {109}, journal = {Annals of botany}, number = {5}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0305-7364}, doi = {10.1093/aob/mcs015}, pages = {1037 -- 1046}, year = {2012}, abstract = {The response of forest herb regeneration from seed to temperature variations across latitudes was experimentally assessed in order to forecast the likely response of understorey community dynamics to climate warming. Seeds of two characteristic forest plants (Anemone nemorosa and Milium effusum) were collected in natural populations along a latitudinal gradient from northern France to northern Sweden and exposed to three temperature regimes in growth chambers (first experiment). To test the importance of local adaptation, reciprocal transplants were also made of adult individuals that originated from the same populations in three common gardens located in southern, central and northern sites along the same gradient, and the resulting seeds were germinated (second experiment). Seedling establishment was quantified by measuring the timing and percentage of seedling emergence, and seedling biomass in both experiments. Spring warming increased emergence rates and seedling growth in the early-flowering forb A. nemorosa. Seedlings of the summer-flowering grass M. effusum originating from northern populations responded more strongly in terms of biomass growth to temperature than southern populations. The above-ground biomass of the seedlings of both species decreased with increasing latitude of origin, irrespective of whether seeds were collected from natural populations or from the common gardens. The emergence percentage decreased with increasing home-away distance in seeds from the transplant experiment, suggesting that the maternal plants were locally adapted. Decreasing seedling emergence and growth were found from the centre to the northern edge of the distribution range for both species. Stronger responses to temperature variation in seedling growth of the grass M. effusum in the north may offer a way to cope with environmental change. The results further suggest that climate warming might differentially affect seedling establishment of understorey plants across their distribution range and thus alter future understorey plant dynamics.}, language = {en} } @article{BaetenWartonVanCalsteretal.2014, author = {Baeten, Lander and Warton, David I. and Van Calster, Hans and De Frenne, Pieter and Verstraeten, Gorik and Bonte, Dries and Bernhardt-R{\"o}mermann, Markus and Cornelis, Johnny and Decocq, Guillaume and Eriksson, Ove and Hedl, Radim and Heinken, Thilo and Hermy, Martin and Hommel, Patrick and Kirby, Keith J. and Naaf, Tobias and Petrik, Petr and Walther, Gian-Reto and Wulf, Monica and Verheyen, Kris}, title = {A model-based approach to studying changes in compositional heterogeneity}, series = {Methods in ecology and evolution : an official journal of the British Ecological Society}, volume = {5}, journal = {Methods in ecology and evolution : an official journal of the British Ecological Society}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {2041-210X}, pages = {156 -- 164}, year = {2014}, language = {en} } @article{DeFrenneKolbGraaeetal.2011, author = {De Frenne, P. and Kolb, Annette and Graae, Benete Jessen and Decocq, Guillaume and Baltora, S. and De Schrijver, A. and Brunet, J. and Chabrerie, Olivier and Cousins, Sara A. O. and Dhondt, Rob and Diekmann, Martin and Gruwez, R. and Heinken, Thilo and Hermy, Martin and Liira, J. and Saguez, R. and Shevtsova, Anna and Baskin, Carol C. and Verheyen, Kris}, title = {A latitudinal gradient in seed nutrients of the forest herb Anemone nemorosa}, series = {Plant biology}, volume = {13}, journal = {Plant biology}, number = {3}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1435-8603}, doi = {10.1111/j.1438-8677.2010.00404.x}, pages = {493 -- 501}, year = {2011}, abstract = {The nutrient concentration in seeds determines many aspects of potential success of the sexual reproductive phase of plants, including the seed predation probability, efficiency of seed dispersal and seedling performance. Despite considerable research interest in latitudinal gradients of foliar nutrients, a similar gradient for seeds remains unexplored. We investigated a potential latitudinal gradient in seed nutrient concentrations within the widespread European understorey forest herb Anemone nemorosa L. We sampled seeds of A. nemorosa in 15 populations along a 1900-km long latitudinal gradient at three to seven seed collection dates post-anthesis and investigated the relative effects of growing degree-hours > 5 degrees C, soil characteristics and latitude on seed nutrient concentrations. Seed nitrogen, nitrogen:phosphorus ratio and calcium concentration decreased towards northern latitudes, while carbon:nitrogen ratios increased. When taking differences in growing degree-hours and measured soil characteristics into account and only considering the most mature seeds, the latitudinal decline remained particularly significant for seed nitrogen concentration. We argue that the decline in seed nitrogen concentration can be attributed to northward decreasing seed provisioning due to lower soil nitrogen availability or greater investment in clonal reproduction. This pattern may have large implications for the reproductive performance of this forest herb as the degree of seed provisioning ultimately co-determines seedling survival and reproductive success.}, language = {en} } @article{AlbertAuffretCosynsetal.2015, author = {Albert, Aurelie and Auffret, Alistair G. and Cosyns, Eric and Cousins, Sara A. O. and Eichberg, Carsten and Eycott, Amy E. and Heinken, Thilo and Hoffmann, Maurice and Jaroszewicz, Bogdan and Malo, Juan E. and Marell, Anders and Mouissie, Maarten and Pakeman, Robin J. and Picard, Melanie and Plue, Jan and Poschlod, Peter and Provoost, Sam and Schulze, Kiowa Alraune and Baltzinger, Christophe}, title = {Seed dispersal by ungulates as an ecological filter: a trait-based meta-analysis}, series = {Oikos}, volume = {124}, journal = {Oikos}, number = {9}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0030-1299}, doi = {10.1111/oik.02512}, pages = {1109 -- 1120}, year = {2015}, abstract = {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.}, language = {en} } @article{DeFrenneGraaeKolbetal.2011, author = {De Frenne, Pieter and Graae, Bente J. and Kolb, Annette and Shevtsova, Anna and Baeten, Lander and Brunet, J{\"o}rg and Chabrerie, Olivier and Cousins, Sara A. O. and Decocq, Guillaume and Dhondt, Rob and Diekmann, Martin and Gruwez, Robert and Heinken, Thilo and Hermy, Martin and Oster, Mathias and Saguez, Robert and Stanton, Sharon and Tack, Wesley and Vanhellemont, Margot and Verheyen, Kris}, title = {An intraspecific application of the leaf-height-seed ecology strategy scheme to forest herbs along a latitudinal gradient}, series = {Ecography : pattern and diversity in ecology ; research papers forum}, volume = {34}, journal = {Ecography : pattern and diversity in ecology ; research papers forum}, number = {1}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0906-7590}, doi = {10.1111/j.1600-0587.2010.06399.x}, pages = {132 -- 140}, year = {2011}, abstract = {We measured LHS traits in 41 Anemone nemorosa and 44 Milium effusum populations along a 1900-2300 km latitudinal gradient from N France to N Sweden. We then applied multilevel models to identify the effects of regional (temperature, latitude) and local (soil fertility and acidity, overstorey canopy cover) environmental factors on LHS traits. Both species displayed a significant 4\% increase in plant height with every degree northward shift (almost a two-fold plant height difference between the southernmost and northernmost populations). Neither seed mass nor SLA showed a significant latitudinal cline. Temperature had a large effect on the three LHS traits of Anemone. Latitude, canopy cover and soil nutrients were related to the SLA and plant height of Milium. None of the investigated variables appeared to be related to the seed mass of Milium. The variation in LHS traits indicates that the ecological strategy determined by the position of each population in this three-factor triangle is not constant along the latitudinal gradient. The significant increase in plant height suggests greater competitive abilities for both species in the northernmost populations. We also found that the studied environmental factors affected the LHS traits of the two species on various scales: spring-flowering Anemone was affected more by temperature, whereas early-summer flowering Milium was affected more by local and other latitude-related factors. Finally, previously reported cross-species correlations between LHS traits and latitude were generally unsupported by our within-species approach.}, language = {en} } @article{BernhardtRoemermannBaetenCravenetal.2015, author = {Bernhardt-R{\"o}mermann, Markus and Baeten, Lander and Craven, Dylan and De Frenne, Pieter and Hedl, Radim and Lenoir, Jonathan and Bert, Didier and Brunet, Jorg and Chudomelova, Marketa and Decocq, Guillaume and Dierschke, Hartmut and Dirnboeck, Thomas and D{\"o}rfler, Inken and Heinken, Thilo and Hermy, Martin and Hommel, Patrick and Jaroszewicz, Bogdan and Keczynski, Andrzej and Kelly, Daniel L. and Kirby, Keith J. and Kopecky, Martin and Macek, Martin and Malis, Frantisek and Mirtl, Michael and Mitchell, Fraser J. G. and Naaf, Tobias and Newman, Miles and Peterken, George and Petrik, Petr and Schmidt, Wolfgang and Standovar, Tibor and Toth, Zoltan and Van Calster, Hans and Verstraeten, Gorik and Vladovic, Jozef and Vild, Ondrej and Wulf, Monika and Verheyen, Kris}, title = {Drivers of temporal changes in temperate forest plant diversity vary across spatial scales}, series = {Global change biology}, volume = {21}, journal = {Global change biology}, number = {10}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/gcb.12993}, pages = {3726 -- 3737}, year = {2015}, abstract = {Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta-analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17-75years between the two surveys) by assessing the importance of (i) coarse-resolution (i.e., among sites) vs. fine-resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local-scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among-site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse-resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine-resolution environmental conditions.}, language = {en} } @article{LiangHeinrichHelleetal.2013, author = {Liang, Wei and Heinrich, Ingo and Helle, Gerhard and Linan, Isabel Dorado and Heinken, Thilo}, title = {Applying CLSM to increment core surfaces for histometric analyses a novel advance in quantitative wood anatomy}, series = {Dendrochronologia : an interdisciplinary journal of tree-ring science}, volume = {31}, journal = {Dendrochronologia : an interdisciplinary journal of tree-ring science}, number = {2}, publisher = {Elsevier}, address = {Jena}, issn = {1125-7865}, doi = {10.1016/j.dendro.2012.09.002}, pages = {140 -- 145}, year = {2013}, abstract = {A novel procedure has been developed to conduct cell structure measurements on increment core samples of conifers. The procedure combines readily available hardware and software equipment. The essential part of the procedure is the application of a confocal laser scanning microscope (CLSM) which captures images directly from increment cores surfaced with the advanced WSL core-microtome. Cell wall and lumen are displayed with a strong contrast due to the monochrome black and green nature of the images. Consecutive images are merged into long images representing entire increment cores which are then analysed for cell structures in suitable software.}, language = {en} } @article{DeFrenneBrunetShevtsovaetal.2011, author = {De Frenne, Pieter and Brunet, Jorg and Shevtsova, Anna and Kolb, Annette and Graae, Bente J. and Chabrerie, Olivier and Cousins, Sara Ao and Decocq, Guillaume and De Schrijver, An and Diekmann, Martin and Gruwez, Robert and Heinken, Thilo and Hermy, Martin and Nilsson, Christer and Stanton, Sharon and Tack, Wesley and Willaert, Justin and Verheyen, Kris}, title = {Temperature effects on forest herbs assessed by warming and transplant experiments along a latitudinal gradient}, series = {Global change biology}, volume = {17}, journal = {Global change biology}, number = {10}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/j.1365-2486.2011.02449.x}, pages = {3240 -- 3253}, year = {2011}, abstract = {Slow-colonizing forest understorey plants are probably not able to rapidly adjust their distribution range following large-scale climate change. Therefore, the acclimation potential to climate change within their actual occupied habitats will likely be key for their short-and long-term persistence. We combined transplant experiments along a latitudinal gradient with open-top chambers to assess the effects of temperature on phenology, growth and reproductive performance of multiple populations of slow-colonizing understorey plants, using the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum as study species. In both species, emergence time and start of flowering clearly advanced with increasing temperatures. Vegetative growth (plant height, aboveground biomass) and reproductive success (seed mass, seed germination and germinable seed output) of A. nemorosa benefited from higher temperatures. Climate warming may thus increase future competitive ability and colonization rates of this species. Apart from the effects on phenology, growth and reproductive performance of M. effusum generally decreased when transplanted southwards (e. g., plant size and number of individuals decreased towards the south) and was probably more limited by light availability in the south. Specific leaf area of both species increased when transplanted southwards, but decreased with open-top chamber installation in A. nemorosa. In general, individuals of both species transplanted at the home site performed best, suggesting local adaptation. We conclude that contrasting understorey plants may display divergent plasticity in response to changing temperatures which may alter future understorey community dynamics.}, language = {en} } @article{LemkeKolbGraaeetal.2015, author = {Lemke, Isgard H. and Kolb, Annette and Graae, Bente J. and De Frenne, Pieter and Acharya, Kamal P. and Blandino, Cristina and Brunet, Jorg and Chabrerie, Olivier and Cousins, Sara A. O. and Decocq, Guillaume and Heinken, Thilo and Hermy, Martin and Liira, Jaan and Schmucki, Reto and Shevtsova, Anna and Verheyen, Kris and Diekmann, Martin}, title = {Patterns of phenotypic trait variation in two temperate forest herbs along a broad climatic gradient}, series = {Plant ecology : an international journal}, volume = {216}, journal = {Plant ecology : an international journal}, number = {11}, publisher = {Springer}, address = {Dordrecht}, issn = {1385-0237}, doi = {10.1007/s11258-015-0534-0}, pages = {1523 -- 1536}, year = {2015}, abstract = {Phenotypic trait variation plays a major role in the response of plants to global environmental change, particularly in species with low migration capabilities and recruitment success. However, little is known about the variation of functional traits within populations and about differences in this variation on larger spatial scales. In a first approach, we therefore related trait expression to climate and local environmental conditions, studying two temperate forest herbs, Milium effusum and Stachys sylvatica, along a similar to 1800-2500 km latitudinal gradient. Within each of 9-10 regions in six European countries, we collected data from six populations of each species and recorded several variables in each region (temperature, precipitation) and population (light availability, soil parameters). For each plant, we measured height, leaf area, specific leaf area, seed mass and the number of seeds and examined environmental effects on within-population trait variation as well as on trait means. Most importantly, trait variation differed both between and within populations. Species, however, differed in their response. Intrapopulation variation in Milium was consistently positively affected by higher mean temperatures and precipitation as well as by more fertile local soil conditions, suggesting that more productive conditions may select for larger phenotypic variation. In Stachys, particularly light availability positively influenced trait variation, whereas local soil conditions had no consistent effects. Generally, our study emphasises that intra-population variation may differ considerably across larger scales-due to phenotypic plasticity and/or underlying genetic diversity-possibly affecting species response to global environmental change.}, language = {en} } @article{GraaeDeFrenneKolbetal.2012, author = {Graae, Bente J. and De Frenne, Pieter and Kolb, Annette and Brunet, Jorg and Chabrerie, Olivier and Verheyen, Kris and Pepin, Nick and Heinken, Thilo and Zobel, Martin and Shevtsova, Anna and Nijs, Ivan and Milbau, Ann}, title = {On the use of weather data in ecological studies along altitudinal and latitudinal gradients}, series = {Oikos}, volume = {121}, journal = {Oikos}, number = {1}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0030-1299}, doi = {10.1111/j.1600-0706.2011.19694.x}, pages = {3 -- 19}, year = {2012}, abstract = {Global warming has created a need for studies along climatic gradients to assess the effects of temperature on ecological processes. Altitudinal and latitudinal gradients are often used as such, usually in combination with air temperature data from the closest weather station recorded at 1.52 m above the ground. However, many ecological processes occur in, at, or right above the soil surface. To evaluate how representative the commonly used weather station data are for the microclimate relevant for soil surface biota, we compared weather station temperatures for an altitudinal (500900 m a.s.l.) and a latitudinal gradient (4968 degrees N) with data obtained by temperature sensors placed right below the soil surface at five sites along these gradients. The mean annual temperatures obtained from weather stations and adjusted using a lapse rate of -5.5 degrees C km-1 were between 3.8 degrees C lower and 1.6 degrees C higher than those recorded by the temperature sensors at the soil surface, depending on the position along the gradients. The monthly mean temperatures were up to 10 degrees C warmer or 5 degrees C colder at the soil surface. The within-site variation in accumulated temperature was as high as would be expected from a 300 m change in altitude or from a 4 degrees change in latitude or a climate change scenario corresponding to warming of 1.63.8 degrees C. Thus, these differences introduced by the decoupling are significant from a climate change perspective, and the results demonstrate the need for incorporating microclimatic variation when conducting studies along altitudinal or latitudinal gradients. We emphasize the need for using relevant temperature data in climate impact studies and further call for more studies describing the soil surface microclimate, which is crucial for much of the biota.}, language = {en} } @article{PauliukMuellerHeinken2011, author = {Pauliuk, Franziska and M{\"u}ller, J{\"o}rg and Heinken, Thilo}, title = {Bryophyte dispersal by sheep on dry grassland}, series = {Nova Hedwigia : Zeitschrift f{\"u}r Kryptogamenkunde}, volume = {92}, journal = {Nova Hedwigia : Zeitschrift f{\"u}r Kryptogamenkunde}, number = {3-4}, publisher = {Cramer}, address = {Stuttgart}, issn = {0029-5035}, doi = {10.1127/0029-5035/2011/0092-0327}, pages = {327 -- 341}, year = {2011}, abstract = {Many bryophytes may depend on epizoochorous dispersal by large mammals for maintaining their populations and colonizing new habitats. On dry grassland we investigated the transport of bryophyte diaspores by sheep, which are known to be effective epizoochorous dispersal vectors of seed plants. Twelve sheep of two breeds were examined by collecting gametophyte fragments from their fleece and hooves. Furthermore, microscopic diaspores from the soil adhering to the hooves were grown in a greenhouse. Species frequency and composition were compared to bryophyte vegetation on the pasture. Considerable amounts of unspecialized gametophyte fragments from 16 moss species, 40\% of the species growing on the pasture, were transported by sheep, especially on the belly and the tail. Additionally, we provide first evidence of epizoochorous dispersal of thallus fragments from fruticose lichens. Sheep breeds differed in species spectrum and frequency, i.e. sheep with dense, curly fleece carried more fragments and larger species than those with smooth and fine hair. Among the dispersed bryophytes pleurocarps, certain taxa, sizes (small species) and life forms (mats) were overrepresented compared to the vegetation of the pasture, while large species, acrocarps, wefts and turfs were underrepresented, reflecting fragmentation and adhesion features of the species. In the hooves mostly acrocarpous colonist species were transported. We conclude that sheep are important dispersal vectors with the potential of long-range dispersal for bryophytes, especially for species without sexual reproduction, and that epizoochorous dispersal of microscopic diaspores might be underestimated in its importance so far.}, language = {en} } @article{CaronDeFrenneBrunetetal.2014, author = {Caron, Maria Mercedes and De Frenne, P. and Brunet, J. and Chabrerie, Olivier and Cousins, S. A. O. and De Backer, L. and Diekmann, M. and Graae, B. J. and Heinken, Thilo and Kolb, A. and Naaf, T. and Plue, J. and Selvi, F. and Strimbeck, G. R. and Wulf, Monika and Verheyen, Kris}, title = {Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus}, series = {Plant ecology : an international journal}, volume = {215}, journal = {Plant ecology : an international journal}, number = {8}, publisher = {Springer}, address = {Dordrecht}, issn = {1385-0237}, doi = {10.1007/s11258-014-0343-x}, pages = {911 -- 925}, year = {2014}, abstract = {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.}, language = {en} } @article{ReineckeKlemmHeinken2014, author = {Reinecke, Jennifer and Klemm, Gunther and Heinken, Thilo}, title = {Vegetation change and homogenization of species composition in temperate nutrient deficient scots pine forests after 45 yr}, series = {Journal of vegetation science}, volume = {25}, journal = {Journal of vegetation science}, number = {1}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1100-9233}, doi = {10.1111/jvs.12069}, pages = {113 -- 121}, year = {2014}, abstract = {QuestionDoes eutrophication drive vegetation change in pine forests on nutrient deficient sites and thus lead to the homogenization of understorey species composition? LocationForest area (1600ha) in the Lower Spreewald, Brandenburg, Germany. MethodsResurvey of 77 semi-permanent plots after 45yr, including vascular plants, bryophytes and ground lichens. We applied multidimensional ordination of species composition, dissimilarity indices, mean Ellenberg indicator values and the concept of winner/loser species to identify vegetation change between years. Differential responses along a gradient of nutrient availability were analysed on the basis of initial vegetation type, reflecting topsoil N availability of plots. ResultsSpecies composition changed strongly and overall shifted towards higher N and slightly lower light availability. Differences in vegetation change were related to initial vegetation type, with strongest compositional changes in the oligotrophic forest type, but strongest increase of nitrophilous species in the mesotrophic forest type. Despite an overall increase in species number, species composition was homogenized between study years due to the loss of species (mainly ground lichens) on the most oligotrophic sites. ConclusionsThe response to N enrichment is confounded by canopy closure on the N-richest sites and probably by water limitation on N-poorest sites. The relative importance of atmospheric N deposition in the eutrophication effect is difficult to disentangle from natural humus accumulation after historical litter raking. However, the profound differences in species composition between study years across all forest types suggest that atmospheric N deposition contributes to the eutrophication, which drives understorey vegetation change and biotic homogenization in Central European Scots pine forests on nutrient deficient sites.}, language = {en} }