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With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed. [ABSTRACT FROM AUTHOR]

Climate change will alter forest ecosystems and their provisioning of services. Forests in the Carpathian Mountains store high amounts of carbon and provide livelihoods to local people; however, no study has yet assessed their future long-term dynamics under climate change. Therefore, we selected a representative area of 1340 km2 to investigate the effects of changing climate and disturbance regimes on (i) the spatial dynamics of the dominant tree species and forest types and (ii) the trajectories of the associated aboveground live carbon (ALC). We simulated 500 years of change under four Representative Concentration Pathway (RCP) scenarios, incorporating wind and bark beetle disturbances using the LANDIS-II forest change model. Our simulations revealed a lagged adaptation of the forest landscape to climate change. While Picea abies dominance declined in all scenarios, Carpinus betulus expanded at low elevations and Acer pseudoplatanus at mid-elevations. We also found a slow but continuous expansion of Quercus petraea and Q. robur at low elevations and of Fagus sylvatica at mid and high elevations. This change in species composition was accompanied by a significant reduction of ALC: on average over the simulation period, unmitigated climate change reduced ALC between − 2.1% (RCP2.6) and − 14.0% (RCP8.5), while disturbances caused an additional reduction of ALC between − 4.5% (RCP2.6) and − 6.6% (RCP8.5). Therefore, foresighted management strategies are needed to facilitate vegetation adaptation to climate change, with the goal of stabilizing carbon storage and maintaining economic value of future Carpathian forests. [ABSTRACT FROM AUTHOR]