Sweet chestnut (Castanea sativa), formerly cultivated on large areas in southern Switzerland, is increasingly declining due to the combination of drought stress, pathogenic fungi, insects and abandonment. Subsequently, an increase in mortality has been observed, favoring the establishment of invasive tree species such as the tree of heaven (Ailanthus altissima), an early-successional tree species native to China. While recent studies focused on the invasive potential of A. altissima, the decline of C. sativa has not been analyzed at a larger scale. In this study, we use data from the National Forest Inventory (LFI) in Southern Switzerland to examine spatiotemporal patterns and trends of damage and mortality of C. sativa during the last decades. To this end, we develop mortality models for individual trees and quantify tree damage as a promoter of increased light availability. Furthermore, we analyze recruitment patterns of C. sativa and other co-occurring species. The results are expected to provide a representative estimate of the potential of C. sativa in Switzerland and of the sensitivity of its stands to invasive, light-demanding tree species.