How do environmental conditions affect the deadwood decomposition of European beech (Fagus sylvatica L.)?

Abstract

European beech is one of the most important European trees, not only because of its expected role in the face of climate change, but also as a frequent species in forest reserves, national parks and the NATURA 2000 network. For such areas, naturalness and biodiversity conservation are significant issues, in which the presence of deadwood plays an important role. To manage deadwood in forests, one needs to know how the residence time of coarse woody debris is influenced by the environment. In this study, we analysed a dataset of 4260 logs from beech-dominated primeval and natural forest reserves in three climatically different regions (cold-dry, warm-dry and warm-humid region), working with a time series of more than 40years (1972–2015). With the help of Bayesian Survival Trajectory Analysis, we examined differences between residence times in the three regions and in three DBH classes. In addition, we analysed qualitative characteristics of fallen logs – the mortality mode and the position of logs during decomposition – and calculated their total decomposition time and time to reach an advanced decay stage. The analyses confirmed the significant impact of macroclimate on residence time. In the cold-dry region the diameter classes 10–24cm (small-sized logs) and 25–54cm (medium-sized logs) had the longest residence time (38and48years, respectively). In the warm-dry region with a favourable composition of fungal communities, the diameter class 55+ cm (large-sized logs) logs had the shortest residence time (43years). The rates of decomposition of beech logs in contact with the ground or suspended logs were significantly different in all three regions, with logs lying on the ground decomposing 9–15years sooner. These results can be used in retention forestry. If the continuity of the deadwood environment is to be preserved, it is necessary to ensure a “supply” of dead stems (offering differing habitats) at least once every 24–35years. During this period, 50% of logs decay completely and the other 50% of logs progress to an advanced decay stage.