Woody species diversity is crucial for the resilience of forests under climate change. The early stages of regeneration, particularly after canopy disturbance, shape the composition of future forest. Light availability, browsing pressure and their interactions should be key drivers of woody species diversity, biomass and density, but are not well understood due to limited experimental setups. We used exclosures in a mixed broadleaf forest with high woody diversity to protect seedlings from browsing by roe deer ( Capreolus capreolus ), the predominant ungulate in Central Europe. In a full‐factorial design, we paired 75 exclosure (fenced) and control (unfenced) plots in both closed canopy stands and experimental gaps. We measured woody regeneration 1 and 4 years after the start of the treatments. Rarefaction‐extrapolation curves revealed that diversity of common (Shannon diversity) woody species was highest in sunny and shaded exclosures (7), compared to sunny (4.5) and shaded (3.5) controls, for species that had outgrown the 130 cm browsing‐susceptible height of roe deer. Stage‐structured matrix models showed that saplings ≤20 cm had the highest probability of reaching >130 cm within 3 years in sunny exclosures (1.51%), followed by sunny controls (0.32%), shaded exclosures (0.27%) and shaded controls (0.07%). Browsing resulted in homogenized woody regeneration, particularly in forest gaps. Increasing light availability did not compensate for diversity loss by browsing. Given the densities of roe deer in the study area—typical for many Central European forests—effective population control or fencing appears essential to maintain high diversity of future forest shaping and forestry relevant woody species, especially in open forests. Synthesis and applications . Our results provide strong evidence that in the current context of increasing tree mortality and subsequent light availability, roe deer act as a keystone species. It is crucial to implement browsing protection measures and control roe deer population before or immediately after canopy disturbance. Otherwise, the rapid growth of a few dominant, browsing‐resistant woody species will significantly reduce the woody plant diversity of future forests.

The ephemeral resource patch (ERP) concept provides a framework for understanding how finite, short‐lived resources shape community assembly processes at both patch and landscape scale. Some of these theories and principles can be applied to intermediate‐lived resources, such as deadwood, but this remains largely unexplored. We tested three ecological mechanisms of community assembly ( more‐individuals hypothesis , habitat‐heterogeneity hypothesis and habitat filtering ) to investigate whether beetle assemblages in deadwood fit the ERP concept. We tracked saproxylic beetle communities in experimental logs of Norway spruce ( Picea abies ), European silver fir ( Abies alba ) and beech ( Fagus sylvatica ) in the temperate mountain forest of the Bavarian Forest National Park over a 12‐year decomposition period, from the early decomposition stage until near‐complete resource depletion. Beetle abundance and number of species declined consistently in all tree species until the 4th year but increased again in spruce after ~8 years. Species richness (number of species controlled for abundance) showed inconsistent patterns over time: U‐shaped for spruce, weakly hump‐shaped for fir and no temporal effect for beech. Habitat filtering was more pronounced in the early stage as functional diversity was initially low but increased for all tree species up to 4 years, then plateaued and increased again after ~10 years for both conifers. Conditional inference tree identified two temporally distinct beetle assemblages (years 1–3 and 4–12), and strong differences within the first 4 years. Our findings suggest that the more‐individuals hypothesis and habitat filtering are key mechanisms driving community assembly in saproxylic beetles. Early decomposition stages supported functionally similar assemblages, highlighting this phase as a critical period for decomposer community structuring. Synthesis . The consistency of the early successional trajectories of beetles suggests that the early stages of deadwood decomposition up to the 3rd year in the temperate zone follow ephemerality theories similar to those of short‐lived ERPs, while the advanced stages provide a habitat for a more random combination of beetle species. Furthermore, our findings highlight the need for temporally continuous deadwood input, via natural processes or staggered retention during logging operations, to provide coarse woody debris for wide range of saproxylic beetles.

Forest microclimates, their dependence on forest structure, and their impact on biodiversity are crucial for future forest management under climate change. However, standard approaches for measuring forest microclimates do not capture within-plot heterogeneity, which, according to the habitat heterogeneity hypothesis, is a key driver of local biodiversity. We quantified horizontal and vertical microclimatic heterogeneity within 30 broad-leaved forest plots in Central Europe using a three-dimensional design with high spatial resolution. Moreover, we examined whether microclimatic heterogeneity differs among silvicultural treatments and whether it can be predicted using forest structure indices derived from laser scanning. Additionally, we explored the relationship between microclimatic heterogeneity and biodiversity. In the understory of canopy gaps, warm and cold habitats co-existed in close proximity, leading to a high horizontal microclimatic heterogeneity. In closed stands with high structural complexity, we found steep gradients of increasing temperature and vapor pressure deficit from the ground to the canopy during mid-day. Canopy cover and forest structural complexity were strong indicators of microclimatic heterogeneity. We found positive relationships between herb layer temperature heterogeneity and the diversity of plants, Hymenoptera, and Diptera. Our results demonstrate that single-point measurements fail to capture the substantial microclimatic heterogeneity within plots, potentially misrepresenting the conditions experienced by forest species. However, laser scanning provides reliable indicators for within- plot microclimatic heterogeneity. With canopy gaps featuring high horizontal microclimatic heterogeneity and promoting the biodiversity of several taxonomic groups, we argue that managing forests for maximized temperature buffering should not be the only strategy to conserve forest biodiversity. Highlights: High small-scale horizontal microclimatic heterogeneity in canopy gaps Steep vertical microclimatic gradients in closed-canopy forests Canopy cover and structural complexity: indicators for microclimatic heterogeneity Positive relationship between herb layer temperature heterogeneity and biodiversity

Humans are significantly impacting ecosystems worldwide. Scientists of the IPBES Global Assessment are therefore calling for a transformative change that includes all aspects of society in order to address drivers of biodiversity loss. However, these calls are rather abstract, and thus it remains unclear how this goal can be achieved. With this conceptual contribution, we present an analytical framework for evaluating existing processes of societal change which are enhancing biodiversity, and we illustrate its application using three case studies in Germany. We argue that an empirical analysis provides insights into the causal mechanisms that initiate or promote change processes. In doing so, we can draw recommendations for future transformative change processes with regard to biodiversity conservation. In our analysis, we are dealing with questions concerning the following three areas: the drivers and context of societal change processes, the change processes themselves and finally their impacts. Subsequently, we generate recommendations on how to enhance and support the process of future societal transformation that aims at biodiversity conservation: (a) Retaining co‐benefits for biodiversity with goals that are primarily focussing on other objectives; (b) harmonising biodiversity use and conservation by turning conflicts into drivers of transformation; (c) prioritising biodiversity conservation by taking advantage of windows of opportunity. With our conceptual framework, we provide an analytical tool to learn from existing processes of societal change how to support future transformative change. This is an important step that contributes to the generation of relevant knowledge of promoting transformative change for nature and people. Read the free Plain Language Summary for this article on the Journal blog.

Centuries of timber production have homogenized many forests by reducing variation in canopy density and deadwood availability, with far‐reaching consequences for biodiversity and trophic interactions. Recent studies indicate that increasing structural heterogeneity through canopy gap creation and deadwood enrichment can promote biodiversity and support tree regeneration. These management practices may also influence tree performance, among others assessed by folivory and leaf fluctuating asymmetry, which indicate how well trees resist leaf damage and maintain developmental stability under environmental stress. However, it remains unknown whether such management enables trees to mitigate folivory and developmental instability, especially across macroclimatic gradients such as elevation. We conducted a large‐scale experiment in Germany across 11 pairs of forests: one structurally homogeneous control forest and one experimentally heterogenized forest, where canopy gaps and deadwood were created to increase between‐patch structural heterogeneity. The forests spanned an elevation gradient from 38 to 1143 m. Across all forest pairs, we sampled 19,656 leaves from 1404 European beech ( Fagus sylvatica L.) trees. We quantified folivory, leaf fluctuating asymmetry, microclimatic conditions (temperature, vapour pressure deficit) and biotic pressures (predation, parasitism, competition). Experimental enhancement of structural heterogeneity reduced folivory overall but increased leaf fluctuating asymmetry. Folivory increased with elevation, while leaf fluctuating asymmetry declined, producing an inverse relationship: At low elevations, structural enhancement reduced folivory but increased asymmetry, whereas at high elevations it increased folivory but reduced asymmetry. Microclimatic variables explained variation in both folivory and leaf asymmetry more consistently than biotic pressures. These findings extend the stress‐gradient framework by showing that identical management interventions can yield opposite outcomes depending on the macroclimatic gradient associated with elevation. Thus, integrating elevation and climate context into forest management seems to be crucial for maintaining the resilience of temperate forests under global change. Read the free Plain Language Summary for this article on the Journal blog.