Margarete Eggli

Institute of Botany

Supervisor:Dr. Alexander Land and Prof.Dr.Manfred Küppers

The annual ring archive of the Institute of Botany at the University of Hohenheim is a world-renowned  archive for research into past environmental and climatic conditions. The tree ring archive contains  precisely dated wood samples spanning the last 12,500 years.  Spruce, fir and oak store tree species climatic  information in their annual rings and thus enable the climate of past centuries to be  reconstructed without gaps and with yearly accuracy.

In the project presented here, a unique data set of over 60,000 tree ring series can be accessed to achieve the following scientific goals:

• Development of regional climate growth models for spruce, fir, oak using  tree ring series and high-resolution climate data (1870 - today)
• Reconstruction of climate variability between AD 1300 to 1800 using precisely dated spruce, fir and oak series from the southeast (SE) and southwest (SW) of Germany
• Comparison of the climate reconstructions (AD 1300-1800) from SE and SW with regard to regional differences / similarities
• Verification of the developed climate reconstructions by means of historical, written sources
• Dating and analysis of extreme climate events (e.g. drought or prolonged drought)  between AD 1300 to 1800 in terms of duration and intensity.

Within the calibration period (AD 1870 - present), climate growth analyses are carried out with the above-mentioned tree species for the southeast (SE) and southwest (SW) of Germany and climate growth models are developed. This is achieved by statistically analysing tree ring growth (tree ring chronology) with daily weather data from southern German climate stations during the calibration period (correlation analyses).
The tree species-specific climate growth models generated from this provide the basis for reconstructing climate variability between AD 1300 - 1800 using precisely dated tree ring series from historical buildings. This unique data set makes it possible to calculate an independent reconstruction of the climate over 500 years for each of the SE and SW regions. The errors that such climate archives always carry can be minimised by independently examining and combining several tree species from one region.This combination allows a critical evaluation of e.g. 'mega-droughts' to the extent that a misinterpretation by the multi-species application is almost impossible. In addition, historical written sources are evaluated in close cooperation with historians and used to verify individual extreme climate events between AD 1600 and 1800.

The results of this project will provide detailed insights into the past variability of the southern German climate and important findings for climate impact assessment. In addition, the created climate reconstructions with high spatial and temporal resolution will be made available to scientists from other disciplines and thus lay the foundation for future interdisciplinary projects.