European beech, silver fir, and Norway spruce differ in establishment, height growth, and mortality rates on coarse woody debris and forest floor-a study from a mixed beech forest in the Western Carpathians

Key message In mixed forests, coarse woody debris promotes the successful establishment and growth of conifers and beech. In contrast to beech and fir, older spruce seedlings were only present on coarse woody debris and not on the forest floor. Context Coarse woody debris (CWD) is considered a suitable seedbed for small-seeded and light-demanding species. Its role in enhancing tree regeneration is well reported in boreal or subalpine spruce forests. Less is known about its role in the establishment, growth, and survival of other species, particularly in mixed forests. Aims We analyzed the role of CWD in seedling establishment, growth, and survival for European beech, silver fir, and Norway spruce. Methods We tracked the growth and survival of all germinants and seedlings over 5 years. Results Conifers were relatively more successful than beech at colonizing on CWD. The density of seedlings was variable in all CWD decay classes but was the highest on well-decomposed CWD. CWD supported the growth of all species. Beech cohorts and older seedlings had similar mortality rates on both microsites. Spruce germinants did not survive on the forest floor for more than a year, and older seedlings were only observed on CWD. Fir cohorts had similar mortality rates on both microsites, but older seedlings survived better on the forest floor. Conclusion Although the three species differed in their preferred microsite for establishment, CWD can be considered a suitable regeneration microsite for all three species by enhancing their growth and, in the case of spruce, both short- and long-term survival.