Alessandro Petraglia

Shrubification (i.e., increasing shrub abundance) and thermophilisation (i.e., increasing dominance of warmth-demanding species) are among the most widely documented imprints of climate change on mountain ecosystems. Still, it remains insufficiently quantified how increasing shrub cover alters the near-ground microclimate and snow duration, and in turn, how this interacts with the climate-change responses of alpine plant communities. To this end, we leveraged 21 years of vegetation resampling data and soil temperature time-series from 576 permanent plots positioned on European mountaintops and covering the treeline ecotone up to the middle alpine belt. Snow duration decreased faster in plots with stronger macroclimate warming, which in turn led to a rise in minimum soil temperatures of 0.28°C per decade across all plots. Overall thermophilisation rates were higher in sheltered habitats with snow accumulation, while habitats with higher shrub cover showed faster loss of cold-adapted species. Further research is needed to disentangle the joint effects of shrubs, snow and microclimates, yielding more accurate projections of climate-induced plant community reshuffling in alpine habitats.

Aim: The European alpine life zone is a recognized biodiversity hotspot, currently impacted by warming temperatures. Here, we investigated temporal plant diversity changes and thermophilization processes on multiple summits' flora. Location: Italy: six mountain regions across the Alps and the Apennines. Methods: We evaluated two decades (2001–2024) of plant species presence and abundance across 23 summits, covering an elevation gradient from the treeline ecotone to the nival belt, monitored through permanent sampling areas. We investigated temporal trends of species gain and disappearance, species richness, alpha and beta diversity indices, species‐specific abundance changes, and the thermic indicator of plant assemblages. Results: Three summits in the Central and Northern Apennines experienced net species loss, involving endemic taxa, although species richness significantly increased in all other summits. At summit level, 7% of species significantly declined in abundance (’losers’), and with the same rate across the upper alpine and subnival belts (7%). About 5% of the species significantly increased (’winners’), and colonization rates were highest in the uppermost vegetation belts. The thermic indicator significantly increased in all mountain regions but the Central Apennines, with increasingly higher rates from the lowermost to uppermost vegetation belts, and accelerated during 2015–2024 in the Texel Group. Main Conclusions: We provide evidence of recent increasing thermophilization trends across the Alps and the Northern Apennines. The local plant species loss, including endemic taxa, and the widespread trend of loser species (not yet disappeared) may signal future local extinctions across both the Alps and Apennines also at the high‐elevated belts. The colonization rate observed in the uppermost vegetation belts further suggests a shift towards warmer thermic conditions at high elevations.

Plant litter decomposition governs how much carbon soils store and emit, yet the microbial traits that shape ecosystem-scale decay remain unresolved. Metagenomes can quantify genes encoding plant cell-wall-degrading enzymes, but it is unclear whether ecosystem differences in decay reflect distinct enzymatic repertoires, and whether these data improve prediction beyond climate and soil properties. We paired standardized green and rooibos tea-bag decomposition assays across 3–24 months with 295 soil metagenomes from 264 global sites. Using 196 European plots for primary inference, we built a stage-resolved catalogue of 17.6 million carbohydrate-active enzyme (CAZyme) genes. Forest microbiomes decomposed tea faster than grasslands, but this was not explained by greater CAZyme family richness. Instead, ecosystems differed in CAZyme abundance, subfamily and protein-sequence variation, and allocation across biochemical stages of plant cell-wall decay, with evidence of ecosystem-specific selection. CAZyme profiles added explanatory power for 24-month mass loss and improved within-ecosystem prediction but generalized poorly across ecosystems and continents. By showing that ecosystem differences in decomposition arise from the stage-specific distribution of shared enzymatic functions rather than their presence alone, this work shifts microbial trait inference beyond gene inventories and provides a mechanistic genomic framework for carbon-cycle modelling within defined environmental limits.

Springs are biodiversity hotspots and climate refugia, yet they remain among the most overlooked and threatened freshwater ecosystems, largely absent from regional monitoring programs. In the Emilia-Romagna Region (Northern Apennines, Italy), where more than 8400 springs are documented but most persist as unmonitored “ghost springs”, we developed and tested an ecohydrogeological framework to support their long-term monitoring and conservation. Twenty-five springs were selected as representatives of five strategic zones, which we identify, defined by aquifer type (Ophiolites, Turbiditic Sandstones, Shallow Marine Sandstones, Triassic Gypsum, and lowland Fontanili) and characterized through integrated hydrogeological, hydrochemical, and biological sampling. Benthic diatoms (393 species in 69 genera) growing on three different substrates (epibryon, epilithon and epipelon) per spring, vegetation, and physical and chemical parameters were analyzed. Diatom assemblage composition differed significantly among zones (PERMANOVA, p < 0.001), structured primarily by electrical conductivity between sites (community level) and by discharge regime between substrates (microhabitat level); the proportion of aerial diatoms (88 species) proved a useful indicator of discharge fluctuations, inferable from a single biological sample. Threatened taxa (41% of evaluated species) concentrated in the ridge zones. Although calibrated in the Northern Apennines, the five-zone framework offers a biologically validated and transferable tool to other regions for spring conservation as sentinel ecosystems under climate change and anthropogenic exploitation.

Empirical in-situ measurements of ecosystem carbon dioxide respiration ( R _eco ) in high-latitude ecosystems remain limited, yet they are essential for understanding how tundra carbon cycling responds to climate warming across different environmental contexts and for reducing uncertainties in upscaled carbon budgets and carbon–climate feedbacks. Here, we present the TundraFlux Database, which to date is the most comprehensive synthesis of tundra R _eco responses to experimental warming. The database compiles over 24 000 daily-aggregated in-situ R _eco measurements from control and warmed plots with open-top chambers at 64 Arctic and alpine tundra sites across 12 countries. By coupling R _eco measurements with extensive metadata on climate, vegetation, and soil characteristics, the TundraFlux Database enables the integration of field-scale ecological processes into large-scale models, offering new opportunities to refine global carbon budgets and test predictions of tundra ecosystem responses to warming. Open access to the TundraFlux Database will empower the research community to better quantify and predict how warming alters carbon cycling in Arctic and alpine tundra ecosystems. The data can be accessed on Zenodo (https://doi.org/10.5281/zenodo.17976235, Schwieger, 2026a).

Understanding the drivers of plant community stability is crucial for predicting ecosystem responses to extreme drought events. In grasslands, drought resistance supports the maintenance of key functions such as above‐ground primary productivity, making the identification of resistance drivers essential to guide management under climate change. Proposed factors contributing to grassland stability include multiple diversity facets, functional traits and long‐term climate, but most assessments focus on temporal invariability under historical disturbance regimes, leaving mechanisms of extreme drought resistance and their variation across climatic contexts relatively underexplored. Here, we analysed data from 54 grassland sites of the International Drought Experiment to examine the resistance of above‐ground net primary productivity to a short‐term (i.e. 1 year) extreme drought. We investigated the relative importance and joint influence of functional composition (i.e. community‐weighted means of leaf and root traits), plant diversity facets (taxonomic, functional and phylogenetic) and climate (aridity and rainfall variability) on drought resistance. We used structural equation models to disentangle direct, indirect, and moderating pathways linking these drivers to drought resistance. Long‐term aridity appeared as one of the most important drivers of grassland resistance to drought, with more arid sites showing lower resistance. Moreover, aridity impacted resistance through indirect effects by shaping functional composition and plant diversity, and by moderating the influence of plant diversity and functional composition. Functional composition related to dehydration avoidance and dehydration tolerance was also positively associated with resistance, while diversity had a weaker relationship with resistance, mostly through functional and phylogenetic facets. Interannual rainfall variability also influenced resistance, with different effects in more arid versus humid and less arid sites. Synthesis . Widely studied stability drivers such as plant diversity and functional composition have only partial explanatory power for short‐term drought resistance of above‐ground productivity in grasslands at a global scale. The abiotic context, particularly long‐term aridity, is crucial for understanding ecosystem responses to rainfall variation and can improve predictive models for advancing the study of ecosystem resistance to drought. Along with management practices that target high species diversity or specific traits, restoration and conservation practices should support vulnerable sites experiencing high aridity

Aims: Warming and drought are predicted to affect litter decomposition, although the magnitude of their effects in cold ecosystems remains uncertain. Since influences of litter alteration during the winter may be more important than impacts during the short summer, this study aims to assess how early-decomposition is driven by climatic seasonality. Methods: We tested the effects of simulated summer warming and/or drought on litter decomposition in an alpine grassland using high- and low-quality standard material (i.e. green and rooibos tea) incubated on the soil surface and belowground. Local litter decomposition was also assessed and linked to that of teabags after one year, considering winter and summer separately. To disentangle the effects of litter alteration and microclimate, a further set of teabags was incubated during the summer. Results: Summer warming and drought did not affect teabag decomposition. Decomposition was instead driven by litter quality, incubation depth, and their interaction. The majority of local litter types experienced higher decomposition during winter compared to summer, with decomposability of standard litter being similar to that of leaf litter of graminoids and shrubs. Finally, although summer conditions were more favourable for decomposition than winter ones, this advantage was cancelled out by litter alteration during winter. Conclusions: It appears that, at present, early decomposition phases occurring during the long winters characterizing snow-dominated ecosystems buffer subsequent decay against the effects of warmer and/or drier summers. However, climate-induced changes in the quality, quantity, and temporal dynamics of snow, litter, and decomposers will probably alter decomposition processes in the future.