In the Baltic Sea region, it is forecasted that climate change will threaten coastal environments through sea level rise and precipitation changes. Salt grassland is a widespread habitat at the German Baltic Sea coast. Its importance with regard to nature conservation and environmental protection arises from peat accumulation, CO₂ sequestration, and biodiversity. However, plants growing in this environment are very sensitive to environmental changes. Due to climate change, plants will be affected by longer flooding periods during winter and drought stress during summer. It is likely that many species are not able to withstand those changes and that therefore the whole ecosystem is endangered. In order to answer the question how plants of coastal salt grasslands are affected by climate changes we investigated five abundant species in climate chambers. We simulated elevated temperature, long flooding and soil water logging (as expected during winter) and soil drought (as expected during summer). In three chambers, we simulated three temperatures (15 °C, 20 °C and 25 °C; during night 5 °C less). In each chamber, we further simulated five different flooding events ranging from nearly constant flooding to only one day flooding. Additional to flooding, plants were grown under low soil moisture conditions to simulate soil drought.

Results/Conclusions

The preliminary results of our study show that enhanced temperature was more important than long flooding or soil drought. All five species were negatively affected by a day-time temperature of 25 °C. At 25 °C, most of the plants with soil water stress died during the 12 weeks experiment. However, also plants with moderate and long flooding times were negatively affected by high temperature and showed significant lower growth rates than at lower temperatures. All five species showed the highest biomass production at 15 °C. Here, drought stress resulted also in a biomass decline, but the effect was not as strong as at the warmer temperatures. Under the same temperature, we found no significant differences between the different flooding times. The results of our study suggest that enhanced temperature will have a much higher effect to plant species of Baltic coastal habitats than so far expected. During summer droughts, many of the typical species are likely to decline. Under higher temperature and long summer drought it is likely that biomass production and peat formation of the whole ecosystem decline and that salt grasslands are not able to grow as fast as the expected sea level rise.