The mixed severity disturbance regime of primary beech-dominated forests and its trends of 200 years development

Abstract

Primary beech-dominated forests are rare in Central Europe, while the knowledge of natural processes of these ecosystems is crucial for understanding the forest dynamics providing complex of ecosystem services. In order to understand these ecosystems better, which were one of the most widespread in this region, we decided to study their disturbance regimes and their long-term and recent trends driven mostly by natural disturbances. The study was conducted within the region of Carpathian Mountains including 14 stands and 210 permanent study plots. All living and dead trees were inventoried on these plots, while selected trees were cored. Disturbances were reconstructed by examining individual tree growth patterns: (1) rapid juvenile growth rate (open canopy recruitment), and (2) abrupt, sustained increases in radial growth (release). From these disturbance patterns we reconstructed other disturbance parameters as disturbance severities, patch sizes and plot proportions of disturbed plots on the stand scale characterizing disturbance regime. Further, generalized linear mixed effect models were used to asses long-term and recent trends in these disturbance parameters. Studied ecosystems were driven by mixed severity disturbance regime. The disturbance events revealed continuous gradient from low-severity, small-scale events to higher-severity, larger-scale events, and this gradient was progressively increasing with the rotation period. The low severity class was the most frequent, but it had similar canopy area disturbed (23.9 %) as moderate and high severity class (34.4 %, 27.1 %), respectively. The very high severity class had the longest rotation period and it affected only 14.7 % of overall canopy area disturbed. Long-term and recent trends in disturbance severities and patch areas were not detected. Plot proportions of disturbed plots on the stand scale had slightly declining trend in time over last two centuries, but the recent trend was not detected. Analysis of the recent trends in disturbance characteristics have not shown increasing trend, as it was reversely observed in Europe proving the value and stability of these ecosystems under pressure of climate changes. Based on our findings we highly recommend to localize and protect primary and old-growth forests for their high conservation values, high and stable carbon stock, and provision of other ecosystem services. For enhancement of the managed forests´ stability we could recommend to support natural species composition and nature-based forest management mimicking natural disturbance regimes as retention silvicultural system combining irregular shelterwood and selection systems with occasional clear cuts. The study and its authors were supported by the Czech Science Foundation (project No. 21‐27454S). We thank all staff involved in the data collection and their processing.