Alexandra Wehnert

Forest regeneration is crucial for forest adaptability to environmental changes and the maintenance of ecosystem services. However, assessing regeneration across different spatial scales remains a challenge. While modern remote sensing methods improve data collection, they still face technical challenges such as image interpretation, sensor calibration, and data processing. Detailed spatial recording of forest regeneration thus remains time-consuming and costly. This study introduces an innovative method based on point pattern reconstruction, which predicts the spatial distribution of regenerating trees cost-effectively over large areas. The method was tested in two 1-hectare forest areas: one in the Billenhagener Forest near Rostock and one in the Dippoldiswalder Heathland near Malter. In each area, a 0.09-hectare reference plot containing both the overstory and regeneration was analysed using terrestrial laser scanning. A reconstruction method was developed using spatial tree data and correlations between tree attributes to extrapolate the regeneration patterns to the entire area. Spatial analyses showed that the structural properties of regeneration were successfully scaled from the small reference plot to the full study site. The bimodal diameter distribution of regenerated tree species observed in the reference plot was also well reproduced throughout the area. The results confirm that the method presented enables an adequate reconstruction of regeneration based on overstory structure from a small sample plot. It provides an efficient, time- and labour-saving approach for assessing forest regeneration capacity. It has the potential to support sustainable forest management by offering scalable, data-driven insights into regeneration dynamics.

The impact of extreme weather events such as droughts, heatwaves, storms and the associated intensifcation of bark beetle outbreaks in Norway spruce forests in recent years, has led to a large-scale forest loss in Central Europe. There are various options for post-disturbance management, from complete clearing to no intervention, but their pros and cons - in the context of multifunctional forest management - are not resolved. The ResEt-Fi project ('Pioneering reforestation: Regional management for establishing multifunctional forests on post-disturbed Norway spruce areas') consortium implemented a cross-regional field trial to test how specific practices of deadwood retention affect the ecological conditions and subsequent reforestation dynamics of natural regeneration and planted trees. It aims at generating climate-stable mixed forests within an ecological valuable transition, balancing ecosystem functioning and socio-economic benefits. As an outcome for stakeholders and forest practitioners, guidelines and showcase scenarios for facilitating the selection of management procedures will be created. In this article, we provide insight into (i) the applied post-disturbance deadwood management practices and the rationale for their selection, (ii) the experimental setup of our cross-regional field trial, (iii) the initial post-disturbance status and perspective with respect to regional site conditions and deadwood treatment. While the setup and site conditions will primarily serve as a reference for subsequent studies in our joint project, this is the first systematic, cross-regional study on the effects of the management options standing deadwood, high stumps and clearing on microclimate, biodiversity, and tree regeneration in the critical early stages of forest regeneration after disturbance.

Current management strategies for European Scots pine (Pinus sylvestris L.) forests are oriented towards the use of natural regeneration processes. They aim to maintain continuity of stand structure by preserving seed-producing and shelter trees at varying densities. Soil scarification techniques may be employed to support the natural regeneration of pine. Our study is based on data from seven study sites in the German lowlands, where the basal areas of the overstorey pine trees varied between 4 and 21 m²/ha. The soil scarification methods ranged from full surface ploughing by tractor or horse through small-scale scarification by cultivators to sites without soil scarification. Differences in the densities, spatial distributions, age structures, and above-ground development of pine seedlings were evaluated. We analysed the spatial interactions between overstorey pine trees and the densities of naturally regenerated pine seedlings as a function of the microsite types using the multitype Strauss hard-core process (MSH) method. The results show a significant decrease in height growth with increasing stand density after a period of 5 years, with seedling density and spatial patterns strongly influenced by soil scarification. The MSH pairwise interaction analyses revealed significant negative effects on seedling densities based on combinations of microsites and overstorey trees.

The multiple-use approach to forestry applied in Germany aims to combine timber production and habitat management by preserving specific stand structures. We selected four forest stand types comprising (i) pure oak, (ii) equal oak–pine mixtures, (iii) single tree admixtures of oak in pine forest and (iv) pure pine. We analysed the effects of stand composition parameters on species representative of the larger carabid beetles (Carabus arvensis, C. coriaceus, C. hortensis, C. violaceus, Calosoma inquisitor). The main statistical methods used were correlation analyses and generalised linear mixed models. Cal. inquisitor was observed in pure oak forests exclusively. C. coriaceus and C. hortensis were absent from pure pine stands. High activity densities of C. arvensis and C. violaceus were observed in all four forest types. When assessed at the smaller scales of species crown cover proportions and spatial tree species effect zones, C. hortensis was found to be positively related to oak trees with a regular spatial distribution, whereas C. coriaceus preferred lower and more aggregated oak tree proportions. C. violaceus showed strong sex-specific tree species affinities. Information about preferences of carabid beetles is necessary for management activities targeting the adaptation of forest structures to habitat requirements.

In a region with poor soil fertility, low annual precipitation and large areas of homogenous Pinus sylvestris L. forests, conservation of old sessile oak (Quercus petraea (Matt.) Liebl.) trees is one option to enrich structure and species richness. We studied the affinities of Carabus coriaceus, C. violaceus, C. hortensis and C. arvensis for specific tree species and the resultant intra- and interspecific interactions. We focused on their temporal and spatial distributions. Pitfall traps were used as a surface-related capture method on a grid over an area of three hectares. Generalised linear models and generalised linear geostatistical models were used to analyse carabid activity densities related to distance-dependent spatial effects corresponding to tree zones (oak, oak–pine, pine). The results demonstrated significant spatial affinities among these carabids, especially for females and during the period of highest activity. Individuals of C. coriaceus showed a tendency to the oak zone and C. hortensis exhibited a significant affinity to the oak–pine mixture. Imagines of C. arvensis and C. violaceus were more closely related to pine. The observed temporal and spatial coexistence of the different Carabus species reveals that single admixed old oak trees can support greater diversity within pine-dominated forests.

The importance of tree mixtures to the faunal and floral biodiversity of forests has been documented on many occasions, but little is known about the relationships between single‐tree effects, such as litter distribution and carabid beetles. The aim of the study was to investigate the relationship between the occurrence of carabid beetles and the locations of admixed oak trees within a Scots pine ( Pinus sylvestris L.) stand. Individuals of four Carabus species were collected in dry pitfall traps in a pine forest with single admixed sessile oaks [ Quercus petraea (Matt.) Liebl.]. The capture–mark–recapture technique was used to differentiate carabid beetles by species, gender (female, male), and development stage (imagines, larvae). Three zones of influence were defined according to the distribution of oak leaf litter. The beetle counts from trap data were transformed to a point pattern by means of a random‐field approach where it is assumed that the beetle count per trap is representative of a specified number of single points in the square surrounding the trap. Spatial patterns specific to species, gender, and development stage were observed relative to the oak tree locations. Females and larvae of C. coriaceus and C. hortensis had a high affinity to the oaks, whereas C. violaceus revealed a negative association to the oak trees. No clear trend could be observed for C. arvensis . It was concluded that single‐tree admixtures of oaks affect the spatial patterns of mobile organisms (e.g. Coleoptera) serving as ecological niches in pine forests.