Modelling the eco-cultural niche of giant chestnut trees: new insights into land use history in southern Switzerland through distribution analysis of a living heritage

During the Middle Ages and the early modern period the cultivation of the chestnut tree became dominant in various mountain regions in Western Europe. Large numbers of giant chestnut trees have been reported throughout the continent that may be considered the living heritage of this period. In this paper we used a systematic inventory of giant chestnut trees in southern Switzerland for reconstructing the eco-cultural niche related to the long-term cultivation and conservation of such remarkable trees. To this purpose we implemented a retrospective logistic modelling approach with the presence of giant chestnuts as response variable compared with 65 environmental and cultural predictors. We performed different logistic regression analyses using untransformed and transformed variables. Out of the 42 models produced, we finally selected two models, on the basis of their parsimony and accuracy. Many of the selected predictors, such as distance from the lake, abundance of small livestock or number of secondary settlements, reveal that former local and regional socio-economic conditions and environmental constraints have considerable explanatory power. The approach allows us to detect several aspects of the targeted eco-cultural niche that may have acted in the distant past to support the development of the traditional fruit chestnut culture, as well as more recently, to preserve the giant chestnut tree population during the disruption phase of this culture. Most results are in line with the historical documentation, while others go beyond the dictates of written history and reveal interesting traits of the past economic and cultural systems.