Low naturalness of Swiss broadleaf forests increases their susceptibility to disturbances

The tree species composition of Swiss forests is influenced by both environmental conditions and centuries forest management, resulting in varying degrees naturalness. Here, we estimate the naturalness comparing (i.e., dominance presence/absence species) recorded national inventory with idealised potential natural forests. We aimed to (1) evaluate different types, (2) identify main drivers low (3) investigate influence on susceptibility disturbances. Based our analysis, 45 % had a classified as ‘not natural’ while 42 were ‘natural’ or ‘close natural’. vast majority (65 %) European beech (Fagus sylvatica L.) other broadleaf which are currently dominated conifers. In addition, at higher elevations, often showed proportion larch (Larix decidua Mill.) than expected, based forest. Overall, significantly lower risk being affected stand-level disturbance events. Potential less disturbances, namely insect outbreaks wind throw, when afforested conifers). observed dieback associated loss ecosystem function conifer afforestations (mainly Norway spruce; Picea abies (L.) H. Karst.) plateau likely combination climatic stress pathogen/parasite pressure. These spruce already experience elevated temperature about 2.5 °C compared their optimum primary distribution within Switzerland), representing large-scale, long-term transplantation experiment. discuss question whether similar diebacks problems maladaptation be expected for many species, including beech, due accelerated climate warming during 21st century slow transformation long-lived systems such Consequently, an adaptation current management practices might needed allow faster transition minimizing large-scale diebacks.