Carl Beierkuhnlein

Paleoclimatic changes during the late Cenozoic led to substantial losses of tree diversity in Western and Central Europe. A modern synthesis linking which taxa were lost, the timing of these losses, and their implications for the adaptation of the region’s forest ecosystems to ongoing climate change is needed. Here, we compile a dataset of fossil occurrences of tree genera from Western and Central Europe to analyze tree diversity changes during the Cenozoic (66 Ma – present). We find that tree genus richness declined 75% after its peak in the Miocene (23 – 5.3 Ma), with most losses already occurring during the Plio-Pleistocene transition (ca. 2 – 3 Ma). We then use genus-level niche models to explore how these changes unfolded within climate space. Our results show how the current regional tree flora was progressively filtered towards the colder and drier margins of climate space. This coincided with the losses of most heat-tolerant lineages, including many temperate genera that could have profited under modern climate warming (e.g., Castanea , Juglans, Aesculus ). We foresee several ways in which our analyses of paleoecological data can inform forest management to increase regional tree diversity and enhance forest resilience under climate change.

Under climate change and shifting fire regimes, a wildfire can trigger forest responses ranging from full recovery to shifts toward non-forest states. Understanding the trajectories of forests after fire and the effectiveness of post-fire management and restoration strategies is essential for designing sustainable forest management. However, our capacity to learn from local field studies is limited as they lack the capacity to extrapolate results to broader scales, and scientific syntheses often suffer from non-standardised data generation. Such limitations can be tacked by conducting coordinated, distributed studies, in which many sampling sites are collaboratively implemented following a common protocol across large geographic regions. This approach allows responding research questions broadly as well as robustly assessing the drivers of heterogeneity.The FireTran project aims to establish an international distributed research network across Mediterranean countries to monitor post-fire forest trajectories and experimentally test the effect of small-scale restoration treatments in modulating these trajectories. The project aims to collaboratively monitor dozens of sites across the region –under small local effort– to quantify regeneration dynamics and assess the drivers of heterogeneity at plot, site, and regional scales. Additionally, voluntary experimental treatments (tree planting, seeding, soil transfer) can be implemented at a subset of participating sites. Remote sensing will help locate field plots and, through integration with field data, it will allow to assess large-scale drivers through spatial upscaling.The FireTran project will soon initiate a local pilot phase in Granada. The study protocol will build on the lessons learned therein and learn from consultation with scientists and stakeholders. It will be published to invite scientists from Mediterranean countries to participate in the distributed study by establishing local sites. The protocol will establish the scientific aims, network structure and governance, field methods, requirements for co-authorship, and the data management approach. The presentation will provide a general overview of the project, invite the audience to provide input for the protocol, and screen their prospective willingness to participate by establishing local field sites.

Biodiversity generally enhances ecosystem productivity, but whether such effects persist or intensify during climate extremes is unclear. Here we synthesized data from 75 biodiversity experiments across grasslands and forests to assess how aridity and soil nutrients modulate plant diversity effects under drought and heat extremes. Biodiversity most strongly enhanced productivity under extreme drought in more arid grasslands but had limited effects in forests under such conditions. More arid grasslands showed enhanced complementarity effects under extreme drought, whereas less arid grasslands favoured selection effects driven by productive species. Heat extremes did not produce comparable context-dependent changes in plant diversity effects across ecosystem types or aridity gradients. Soil nutrients did not have any detectable influence under either drought or heat extremes, suggesting that as climatic stress intensifies, hydric limitations override edaphic constraints. Our synthesis identifies when and where plant diversity most strongly enhances productivity, showing that its effects are the greatest under extreme drought in more arid grasslands.

The distinction between geographical patterns caused by underlying environmental factors and inherent spatial autocorrelation is a general challenge for field research. The quality and validity of phytogeographical studies is strongly dependent on disentangling spatial and ecological proximity. This is also crucial for applied studies in nature conservation. One key assumption for many statistical analyses is the independence of observations. In this study we first identify the range of spatial autocorrelation in managed grasslands based on field data. Along a gradient in a valley bottom, we set up five 60 m x 60 m squares, segmented in 36 10 m x 10 m square grid cells. In 20 of the 10 m x 10 m grid cells, we sampled vegetation along a 10 m line with a buffer of one meter resulting in a 20 m² sampling plot. In a second step, we matched Sentinel-2 images for the same locations and calculated the normalized difference vegetation index NDVI and the normalized difference red edge index NDRE. For both, field data and satellite data, Mantel correlograms for floristic distances and spectral indices were used to analyse the spatial autocorrelation. We found the vegetation in the studied grasslands to be spatially correlated up to 25 m. At none of the studied sites the positive spatial autocorrelation reaches beyond. The spatial autocorrelation of spectral indices correlates well with the correlations observed field data. The correlograms of NDVI resembled the ones of the field data slightly better compared to the correlograms of NDRE and RGB. We conclude that employing remote sensing to assess the role of spatial autocorrelation for grasslands is a valid approach. We show that it reflects similar patterns as the field data. The spatial resolution of freely available satellite data proved sufficient to test for the minimum distance between vegetation samples to avoid spatial autocorrelation.

Question: Tephra deposition is one of the most critical sudden alterations caused by volcanic eruptions in ecosystems. Tephra accumulation on the ground decreases with distance from the crater. The effect of ash deposition on the seed bank and its subsequent germination success has previously been studied by removing the tephra from the soil. However, conducting controlled experiments on the effect of tephra thickness on the seed bank and its seedling emergence capacity is a new approach to tackle and quantify recruitment mechanisms. Here, we present the first experimental study of the impact of tephra layer thickness on the seed bank combined with field surveys on seedling emergence. Location: Tajogaite volcano, Cumbre Vieja Ridge, La Palma, Canary Islands. Methods: The study includes a controlled experiment and a field survey along a gradient from the volcano crater to the perimeter within the Canary Island's pine forest. In the experiment, six tephra thickness categories were used to bury seeds (1, 5, 10, 45, 75 and 150 cm) based on observatory evidence corresponding to the distance away from the crater (7, 4, 2, 1.5, 0.75 and 0.15 km, respectively). Seeds were collected from the four most characteristic endemic pine forest species, representing different seed sizes and growth forms: Pinus canariensis (Pinaceae, tree), Chamaecytisus proliferus (Fabaceae, shrub), Lotus campylocladus (Fabaceae, forb) and Cistus symphytifolius (Cystaceae, shrub). One hundred seeds of each species were used per treatment (2800 seeds). In the field survey, we randomly established six quadrats (30 × 30 m) at the same distance from the crater as indicated above. Seedlings (< 5 cm in height) from natural regeneration were counted every three months. Results: After 18 months under ash, germination in the experiment was only detected in the treatments of control (germination rate of P. canariensis = 71%, Ch. proliferus = 13%, L. campylocladus = 24%, C. symphytifolius = 1%), and at 1 cm (51%, 18%, 11%, 1%) and 5 cm (5%, 4%, 0%, 0%) of ash depth. Conclusions: The massive ashfall during this eruption completely and suddenly dysfunctionalized the seed bank as a reservoir of recruitment in areas within a radius of approximately 5 km from the crater (still buried under a 5 cm thick ash layer to date). Therefore, we provide evidence for the hypothesis that the recent volcanic eruption will profoundly change plant community dynamics and composition within large areas of the Canary Island's pine forest.

Wildfire risk increases following non-fire disturbance events, but this relationship is not always linear or cumulative, and previous studies are not consistent in differentiating between disturbance loops versus cascades. Previous research on disturbance interactions and their influence on forest fires has primarily focused on fire-prone regions, such as North America, Australia, and Southern Europe. In contrast, less is known about these dynamics in Central Europe, where wildfire risk and hazard are increasing. In recent years, forest disturbances, particularly windthrow, insect outbreaks, and drought, have become more frequent in Central Europe. At the same time, climate change is influencing fire weather conditions that further intensify forest fire dynamics. Here, we synthesize findings from the recent literature on disturbance interactions in Central Europe with the aim to identify disturbance-driven processes that influence the regional fire regime. We propose a conceptual framework of interacting disturbances that can be used in wildfire risk assessments and beyond. In addition, we identify knowledge gaps and make suggestions for future research regarding disturbance interactions and their implications for wildfire activity. Our findings indicate that fire risk in the temperate forests of Central Europe is increasing and that non-fire disturbances and their interactions modify fuel properties that subsequently influence wildfire dynamics in multiple ways.

This study examines the vulnerability of Madagascar’s protected areas (PAs) to climate change, focusing on climate change velocity, and its impact on biodiversity. We analyzed current and near future climate data using principal component analysis (PCA) and climate change velocity metrics to predict shifts in climatic conditions from the present to the near future, while under the mild and extreme emission scenarios (SSP 126, SSP 585). Forward velocities, which are characterized by the minimum distances that must be overcome by species to keep in track with their appropriate comparative climate, are most pronounced in western and southern Madagascar. In contrast, the backward velocity, which uses future climatic conditions in grid cells in comparison to current conditions, is more common in the eastern regions of the island, and hints at the minimum distance that organisms would have to overcome in colonizing a new habitat. Even though the correlations between PA size and climate change velocity are weak, there is a tendency for larger PAs to exhibit more stable climatic conditions. Conservation strategies must prioritize enhancing the resilience of PAs through adaptive management to mitigate climate impacts. Our findings provide crucial insights for policymakers and conservation planners to develop climate-smart strategies that ensure the long-term efficacy of Madagascar’s PA network.

Over the course of industrialization in the 20th century, vast emissions of air pollutants have occurred. The exhaust gasses contain sulfur and nitrogen oxides, which are converted to sulfuric acid and nitric acid in the atmosphere. This causes acid rain to enter aquatic and terrestrial ecosystems, the most serious consequence of which is large-scale forest dieback across Europe and North America. However, through various political measures, the exhaust gasses have been reduced and, thus, acid rain and forest dieback were stopped. Nevertheless, the lingering effects of this pollution are still present today and are reflected in hydrochemistry. More recently, fluctuating precipitation regimes are causing additional stress to ecosystems in Central Europe. Climatic extremes are becoming more pronounced with climate change. Substantial differences between drought years and years with regular precipitation are directly altering the discharge of springs. Now, two overlapping and interacting syndromes of environmental pressures can be studied in these small catchments at a landscape scale: (1) acidification and (2) climate change. In this long-term study, the waters of 102 forest springs, located in two neighboring forest landscapes in north-eastern Bavaria, Germany (Frankenwald and Fichtelgebirge), were investigated over 24 years (1996 to 2020). By linking changes in pH values with changes in precipitation and spring discharge, we found that pH increases with decreasing discharge and decreasing precipitation. This effect was strongest in the Frankenwald compared to the Fichtelgebirge. We hypothesize that this temporal pattern reflects the longer residence time and, in consequence, the increased buffering of acidic interflow in small catchments during periods of drought. However, this should not be misinterpreted as rapid recovery from acidification because this effect fades in times of enhanced precipitation. We recommend that fluctuations in weather regimes be considered when investigating biogeochemical patterns throughout forest landscapes.