@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{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{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} }