Historical grassland fire events in southern Germany investigated by soil charcoal content

In Central Europe, burning has been widely practiced as part of the slash-and-burn cultivation since the Neolithic Age and was an essential component in forming the recent landscape. To improve our knowledge on historical fire events, we evaluated charcoals in the soil of 44 semi-dry and 38 wet grasslands in Southern Germany. With 92%, most locations contained charcoal, proving fire as a common tool applied in both grassland types. Charcoals of 57 locations were identified. The tree composition was then used to classify the locations at the time burning took place into open conditions, early succession and late succession. Around two-thirds of the sites showed open conditions or early succession and had been already part of the agricultural landscape at the time of fire. Correlations of additional parameters to the charcoal content were rather subtle. Semi-dry grasslands with high charcoal contents tended to be steeper and exhibited more endangered plants. Wet meadows with high amounts of charcoal had low levels of nitrogen since a lot becomes airborne by fire and is not available in the long term. Radiocarbon dating showed that the history of burning was continuous for semi-dry grasslands from Modern times to the early Iron Age and for wet meadows almost continuous until the Bronze Age. These results revealed a frequent occurrence of fires and a long history of fire application in Southern Germanys agricultural landscape. Burning was an important tool regardless of the grassland type and period to ensure good harvests.