Responses to rapid warming at Termination 1a at Gerzensee (Central Europe): Primary succession, albedo, soils, lake development, and ecological interactions

The transition from the Oldest Dryas to the Bølling around 14,685 cal yr BP was a period of extremely rapid climatic warming. From a single core of lake marl taken at Gerzensee (Switzerland) we studied the transition in stable isotopes of oxygen and carbon on bulk sediment and charophyte remains, as well as on monospecific samples of ostracods, after Pisidium a; in addition pollen, chironomids, and Cladocera were analyzed. The δ18O record serves as an estimate of mean air temperature, and by correlation to the one from NGRIP in Greenland it provides a timescale.

The timing of responses: The statistically significant zone boundaries of the biostratigraphies are telescoped at the rapid increase of about 3‰ in δ18O at the onset of Bølling. Biotic responses may have occurred within sampling resolution (8 to 16 years), although younger zone boundaries are less synchronous. Gradual and longer-lasting responses include complex processes such as primary or secular succession. During the late-glacial interstadial of Bølling and Allerød, two stronger and two weaker cool phases were found.

Biological processes involved in the responses occurred on levels of individuals (e.g. pollen productivity), of populations (increases or decreases, immigration, or extinction), and on the ecosystem level (species interactions such as facilitation or competition).

Abiotic and biotic interactions include pedogenesis, nitrogen-fixation, nutrient cycling, catchment hydrology, water chemistry of the lake and albedo (controlled by the transition from tundra to forest).

For the Swiss Plateau this major change in vegetation induced a change in the mammal fauna, which in turn led to changes in the tool-making by Paleolithic people.