(1) Due to global warming, distribution ranges of temperate tree species are shifting northwards and upslope to cooler areas. Shifts in distribution first become visible through changes in regeneration dynamics. However, the future distribution of tree species in the face of rapid climate change depends not only on the climatic suitability of the tree species, but also on its ability to disperse into new habitats. The aim of the study was therefore to examine how the distribution of European beech and European oak shifts and how species can spread from fragmented seed trees. (2) In order to investigate the shift in distribution of beech and oak, the bioclimatic envelopes of the old trees and different size classes of the natural regeneration were compared. Subsequently, a simulation of the potential distribution for the present climate, as well as for the climate for the reference period 2091–2100, for three different representative concentration pathways (RCP) scenarios was determined. In order to determine which of these areas can actually be colonised, a dispersal potential for the species was determined using a quantile regression, taking habitat fragmentation into account. (3) The results of the present study demonstrate range shifts of the tree species regeneration distribution (B0, B1 and B2) compared to the overstorey distribution (OST). While oak regeneration shows an expansion of its distribution in the cold-wet range, beech regeneration shows a reduction of its distribution in the dry-warm range. As the dispersal potential of oak exceeds that of beech, it is expected that oak will be better able to spread from fragmented seed trees. However, the results also indicate that many areas, despite climatic suitability, cannot be colonised due to too large dispersal distances. (4) For the forest management, this results in an important planning tool for future tree species composition, as climatic suitability, habitat connectivity and dispersal ability are taken into account.

The potential utilisation of natural regeneration of European beech (Fagus sylvatica L.) for forest conversion has received little attention to date. Ecological knowledge is necessary to understand and predict successful natural regeneration of beech. The objective of this study was to improve understanding of what drives the occurrence of beech regeneration and, once regeneration is present, what drives its density. In the study, we utilised a forest inventory dataset provided by Sachsenforst, the state forestry service of Saxony, Germany. The dataset was derived from 8725 permanent plots. Zero-altered negative binomial models (ZANB) with spatial random effects were used to analyse factors influencing occurrence and density simultaneously. The results provided by the spatial ZANB models revealed that the probability of the occurrence of beech regeneration is highly dependent on seed availability, i.e. dependent on source trees in close proximity to a plot. The probability of beech regeneration rises with the increasing diameter of a potential seed tree and decreases with increasing distance to the nearest potential seed source. The occurrence of regeneration is affected by overstorey composition and competition exerted by spruce regeneration. Where sites are affected by groundwater or temporary waterlogging, the impact on the occurrence of regeneration is negative. Although distance to the nearest potential seed source has an influence on occurrence, this variable exerts no influence on density. A high regeneration density arises in conjunction with a high beech basal area in the overstorey. Beech regeneration density, but not occurrence, is negatively affected by browsing intensity. These variables can be used to predict the occurrence and density of beech regeneration in space to a high level of precision. The established statistical tool can be used for decision-making when planning forest conversion using natural regeneration.

About 100 years ago, groups of European beech were reintroduced into Norway spruce stands in some parts of Germany as a restoration approach. The aim of this approach was to maintain or rehabilitate the ecological function of soil fertility and the regeneration option of beech for the next generation. The effect of beech groups on surrounding spruce stands was studied in the Ore Mountains by recording natural regeneration of beech and humus layer thickness and form. Point pattern statistics were used to analyse the spread of beech regeneration and to determine factors influencing its establishment. It was found that the density of regeneration decreases with increasing distance from the beech group. However, beech regeneration was found up to distances of 69 m. Furthermore, it becomes evident that PAR radiation (maximum regeneration densities at PAR values of 35 W/m²) and fencing (3.41 times higher regeneration density compared to unfenced areas) against deer have a positive influence on beech regeneration density. Ordered categorical models were used to model humus form and non-linear models were used to model humus layer thickness. It could be proven that the most bioactive humus forms and lowest humus layer thicknesses were found within the beech group. With increasing distance to the beech group, the total humus layer thickness and the proportion of mormoder in the spruce stand increased. The positive influence of the beech group on the humus composition extends to about 40 m from the centre of the beech group. Due to the former arrangement of the beech groups in the terrain, the effects can also extend to the spruce stands in between. The hypotheses on the restoration approach of reintroducing groups of beech into spruce stands formulated by foresters 100 years ago can thus be confirmed. For future restoration approaches of spruce stands, groupwise mixtures of beech should be established with a distance of 40–50 m.

Scots pine is of greatest importance in northern Germany regarding its cultivation area and expected capability to perform in climate change. However, pine predominantly occurs in monocultures. Therefore, future pine forestry depends on an adaptation to climate change while improving ecological and economic forest functions. Yet future development of pine remains uncertain due to leeway in silvicultural guidelines and future climate. This study questions: (i) what is the range of future pine shares under climate change and different silvicultural management in northern Germany, (ii) how will the current stands develop and (iii) what is the range of uncertainty arising from climate models and silvicultural options? To answer these issues we (i) selected forest development types site- and climate-sensitively to either minimize or to maximize pine shares, (ii) simulated four, now practiced forest management scenarios for 50 years based on the German National Forest Inventory and (iii) analyzed the differences, to be interpreted as uncertainty. Novel to our approach is the site- and climate-sensitive selection of forest development types on large scales which emphasizes the contrasts of the different management guidelines. The results show that growing stock and cultivation area will decrease even if pine is promoted in forestry. The predicted restoration rate ranges from 50 to 72% depending on scenario and previous thinning regime. In conclusion, under the given management concepts and considering today’s high proportion of old pine, restoration is alarmingly slow. Amid the rapidly changing climate, we recommend to further adjust the management guidelines to accelerate forest restoration.

Recent mortality pulses indicate pathways to restore maladapted forests towards more natural, mixed, resilient ecosystems. Under climate change, carbon sequestering forests serve as forces for mitigation but face threats from disturbances. The uncertain development of this duality complicates stakeholder-relevant predictions of timber yield or tree species compositions. We analyzed uncertainty in forest development over 50 years, focusing primarily– but not exclusively– on Scots pine, the most important tree species in northern Germany,. Thereunto, i. future survival was examined on a site- and climate-specific basis. The novelty of the simulations lies in ii. quantifying the influence of irregular die-off on forests under stand-wise (discrete) or tree-wise (diffuse) mortality patterns to iii. investigate yield and harvest potentials. By spanning a scenario funnel from two management and two climate projections on 17,551 National Forest Inventory plots in northern Germany, we assess prospective uncertainties. The transition of forest composition through space and time with conditional hazard rates resembles a Markov process via Monte Carlo sampling. Prospectively, i. mortality doubles depending on the species. Compared to undisturbed development, ii. forest restoration outcomes are uncertain; stand-losses can accelerate restoration by up to 10%, while tree-losses might slow it down. Under disturbances, iii. volume increment and stand age decrease as harvests rise in the medium-term with large dimensioned timber increasing fivefold. Driven by climate change and forest demographics, the decline in yield and the remaining 40% monocultures are critical. Forest development is inert, therefore we suggest more differentiated silvicultural concepts for actively adapting forests to alarming changes.