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Fig. 2 Reconstructed seasonal precipitation for 3250 BC to 2250 BC. a Raw TRW (black) and 11-
year moving average (red) of the HOC for the millennium between 3250 BC and 2250 BC of theMR.
Brown bars indicate a coincidence of
flood occurrence derived from WAA and high precipitation
events (>1 sample standard deviation [
σ
]). b Number of subfossil oak trees used for TRW index
development for the MR (grey
filled area). The values for RBar (grey) and EPS (black) display high
common signal strength except for a short period at 2700 BC. c Seasonal reconstruction of summer
precipitation variability. Severe wet (>2
σ
) years are marked with [+] and severe dry (<
−
2
σ
) years are
marked with [
−
]. Flood events based on WAA are marked with colored bars
conditions. The precipitation reconstruction for the period from 2785 BC to 2747
BC as well as an accumulation of
flood events dated from WAA prior to 2747 BC
would con
rm the thesis of unfavorable wet growth conditions for seedlings.
However during the period of increasing raw TRW three
ood events (2703 BC,
2693 BC and 2650 BC) can also be observed. Even though the precipitation
reconstruction shows a series of severe dry years, the floods indicate a possible
more complex relation which might also involve human interaction (Spurk et al.
2002
). Though it is known from historical records from Main and other central
European rivers for the period of the Little Ice Age that increased
ood occurrence
is a likely effect of a changing climate (Glaser
2008
).
Our study shows evidence for a shift in climate and hydrological conditions on
regional scale around the year 2750 BC.
References
Astrade L, Begin Y (1997) Tree-ring response of Populus tremula L. and Quercus robur L. to
recent spring floods of the Saone River, France. Ecoscience 4(2):232
239
Buentgen U, Tegel W, Nicolussi K, McCormick M, Frank D, Trouet V, Kaplan JO, Herzig F,
Heussner KU, Wanner H, Luterbacher J, Esper J (2011) 2500 Years of European climate
variability and human susceptibility. Science 331(6017):578
-
582. doi:
10.1126/science.1197175
-
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