Interpolated maps of pollen percentages in Europe over the last 15,000 years

Aim Palaeoecological reconstructions document past vegetation change with estimates of rapid rates of changing species distribution limits that are often not matched by model simulations of climate-driven vegetation dynamics. Genetic surveys of extant plant populations have yielded new insight into continental vegetation histories, challenging traditional interpretations that had been based on pollen data. Our aim is to examine an updated continental pollen data set from Europe in the light of the new ideas about vegetation dynamics emerging from genetic research and vegetation modelling studies. Location Europe Methods: We use pollen data from the European Pollen Database (EPD) to construct interpolated maps of pollen percentages documenting change in distribution and abundance of major plant genera and the grass family in Europe over the last 15,000 years. Results: Our analyses confirm high rates of postglacial spread with at least 1000 metres per year for Corylus, Ulmus and Alnus and average rates of 400 metres per year for Tilia, Quercus, Fagus and Carpinus. The late Holocene expansions of Picea and Fagus populations in many European regions cannot be explained by migrational lag. Both taxa shift their population centres towards the Atlantic coast suggesting that climate may have played a role in the timing of their expansions. The slowest rates of spread were reconstructed for Abies. Main conclusions: The calculated rates of postglacial plant spread are higher in Europe than those from North America, which may be due to more rapid shifts in climate mediated by the Gulf Stream and westerly winds. Late Holocene anthropogenic land use practices in Europe had major effects on individual taxa, which in combination with climate change contributed to shifts in areas of abundance and dominance. The high rates of spread calculated from the European pollen data are consistent with the common tree species rapidly tracking early Holocene climate change and contribute to the debate on the consequences of global warming for plant distributions.

Mesocosm experiment on warming and acidification effects in 2012: Microzooplankton data

Global warming and ocean acidification are among the most important stressors for aquatic ecosystems in the future. To investigate their direct and indirect effects on a near-natural plankton community, a multiple-stressor approach is needed. Hence, we set up mesocosms in a full-factorial design to study the effects of both warming and high CO2 on a Baltic Sea autumn plankton community, concentrating on the impacts on microzooplankton (MZP). MZP abundance, biomass, and species composition were analysed over the course of the experiment. We observed that warming led to a reduced time-lag between the phytoplankton bloom and an MZP biomass maximum. MZP showed a significantly higher growth rate and an earlier biomass peak in the warm treatments while the biomass maximum was not affected. Increased pCO2 did not result in any significant effects on MZP biomass, growth rate, or species composition irrespective of the temperature, nor did we observe any significant interactions between CO2 and temperature. We attribute this to the high tolerance of this estuarine plankton community to fluctuations in pCO2, often resulting in CO2 concentrations higher than the predicted end-of-century concentration for open oceans. In contrast, warming can be expected to directly affect MZP and strengthen its coupling with phytoplankton by enhancing its grazing pressure.

Mesocosm experiment on warming and acidification effects in 2012: Microzooplankton abundance

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2015) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2016-10-12.