Urbanization profoundly alters soil through changes in land use and management intensity, affecting both soil functions and microbial communities. These shifts can degrade soil fertility and disrupt ecosystem processes. This study investigates how different public urban land uses -including showcase gardens, parks, tree-covered areas, roadsides, residential zones, sports fields and unused areas-influence nitrogen dynamics and microbial functions. We used a multifaceted approach combining biogeochemical measurements (NH4+, NO3-, total N), functional assays (potential mineralization, potential nitrification, potential denitrification), and molecular techniques (functional gene abundances and bacterial community profiling using Illumina MiSeq). Results showed that land use significantly influenced nitrogen cycle processes. Showcase garden areas were characterized by elevated nitrate levels, driven by fertilization and higher nitrification activity, whereas denitrification and related gene abundances were higher in parks and roadside soils. Structural equation modeling (SEM) revealed that soil organic carbon was a major driver of denitrification in most of the land uses, and pH positively influenced the abundance of ammonia-oxidizing archaea (AOA), whereas soil water retention, often reduced in compacted soils, was negatively correlated with most nitrogen variables. In terms of bacterial communities, this study revealed that bacterial functions linked to the nitrogen cycle varied according to land use. Lightly managed areas harboured more nitrogen-fixing bacteria, while intensely managed areas showed a predominance of bacteria involved in nitrification. Furthermore, the absence of any significant correlation between the multiple stages of the nitrogen cycle (mineralization, nitrification, denitrification) in intensively managed areas suggested a breakdown in nitrogen cycling, probably linked to excessive aeration, tillage and low organic matter accumulation or to differences in organic matter decomposition and stability. These findings highlight the sensitivity of nitrogen cycling to urban land management. Crucially, the role of organic matter dynamics in this context requires deeper investigation.

Snow acts as an insulating layer on soils, preserving microbial function and promoting soil organic matter (SOM) mineralization over winter. Climate change is expected to increase the frequency of winter drought in temperate mountain ecosystems leading to snow-free winter, exposing soils to freezing and drying conditions that can disrupt microbial activity and key biogeochemical processes. However, the consequences of extreme snow drought event on microbial communities and associated C and N dynamics remain poorly understood, particularly from a functional and compositional perspective. This study aimed to investigate the ecological consequences of an extreme snow drought in subalpine grasslands by experimentally excluding all winter snowfall. By isolating the effects of a snow-free winter, without the confounding influences of warming or vegetation change, we were able to trace its impacts on ecosystem functioning from winter through the subsequent spring and summer. We observed a sharp spike in N2O emissions (+700 %) and a significant drop in CO2 fluxes (-70 %) during the snow-free winter, measured through discrete greenhouse gas flux sampling throughout the year, including winter. These changes coincided with immediate soil freezing and were linked to shifts in microbial community composition and function, assessed at three key periods-winter, spring, and peak growing season-using a combination of DNA-based community profiling, biomass quantification, and enzymatic assays. Functional markers showed widespread declines in microbial activity, including respiration, decomposition, and ammonification, along with a compositional shift toward anaerobic taxa and increased denitrification. These functional disruptions were further reflected in SOM mineralization dynamics, characterized via infrared spectroscopy and labile carbon fractions, and in reduced nitrogen cycling, measured through NH4+, NO3- content, and resin bag analyses. Although an extended growing season and compensatory microbial responses partially offset winter impacts, full functional recovery was not achieved by the end of the growing season. These findings highlight how snow-free winters, though extreme, can profoundly disrupt soil functioning, leaving lasting carryover effects that last into subsequent seasons.

Les roselières lacustres sont des habitats structurants des zones riveraines, fournissant abri et lieu de reproduction pour de nombreuses espèces tout en assurant des fonctions biogéochimiques majeures au maintien de la qualité des milieux. Au-delà de la fixation du carbone, elles participent aussi au cycle de l’azote en modulant sa disponibilité via la transformation des nutriments en lien avec l’activité des communautés végétales et microbiennes des sédiments. Les roselières aquatiques ont fortement régressé dans les grands lacs alpins, conséquence principalement de l’aménagement des berges et la régulation des niveaux d’eau. Les travaux du pôle de Recherche et Développement Écosystèmes Lacustres (Pôle ECLA) montrent que la régulation de l’azote dans les zones riveraines dépend étroitement de l’hydrologie et de la présence de roseaux. La nitrification, transformation aérobie de l’ammonium en nitrate par les bactéries, reste très limitée dès que les sédiments sont submergés de façon continue, tandis que l’assimilation de l’ammonium par les roseaux constitue un puits majeur, réduisant fortement sa concentration dans les sédiments jusqu’à 30 cm de profondeur. Ces résultats soulignent que la restauration des roselières ne peut reposer uniquement sur la replantation mais nécessite une approche intégrée combinant génie écologique et gestion hydrologique, pour rétablir les processus biogéochimiques et les services écosystémiques associés. Nos résultats fournissent donc des pistes opérationnelles pour orienter les actions de restauration futures et renforcer la résilience des écosystèmes riverains face au changement global..

Estimating SOC stocks and stability, as well as modeling their response to rising temperatures, is crucial for predicting climate change impacts. This is particularly true in mountainous regions, where low temperatures slow down SOC decomposition, resulting in higher SOC stocks compared to soils at lower elevations. However, these stocks are also more vulnerable to warming, increasing the risk of SOC depletion. Such conditions create the potential for a positive feedback loop in which warming accelerates SOC losses, further amplifying climate change impacts on these sensitive ecosystems. To better understand the factors controlling SOC stocks and stability in mountain soils, we sampled 170 soil profiles along 29 elevation gradients in the western Alps from 280 to 3160 m a.s.l. We assessed SOC stocks and chemical composition using mid-infrared spectroscopy method and SOC stability with Rock-Eval (R) thermal analysis. Our findings, based on an unprecedented dataset, reveal a clear elevational pattern in SOC properties. SOC stocks increase with elevation up to the montane belt (1200-1500 m a.s.l.), remain relatively stable through the subalpine zone, and then decline beyond the subalpine/alpine boundary (2200-2400 m a.s.l.). Notably, this transition is also marked by a significant drop in SOC stability, suggesting a shift in the dominant stabilization processes at higher elevations. Our results also indicate that SOC stocks and stability are influenced by a complex interplay of factors. At higher elevations, climate emerges to be the dominant factor, whereas lithology and weathering play a more significant role at lower elevations. These results suggest that at high-elevations, harsh climatic conditions favor stabilization of SOC, while less developed soils limit organo-mineral interactions. In contrast, at warmer, lower elevations with higher carbon fluxes, more developed soils facilitate organo-mineral interactions, thereby enhancing SOC stability in the long term. Consequently, alpine grasslands, which contain substantial stocks of labile carbon stabilized by climatic conditions, appear to be particularly vulnerable to the effects of climate warming.

If natural and cultivated soils have been widely investigated, urban soils are still poorly understood, especially in terms of the microbial diversity they harbor and its roles in providing soil functions and ecosystem services. This paper presents data collected from urban soils sampled at 135 sites from the medium-sized city of Blois (France), which correspond to different land uses randomly distributed in the city. In total, eight types of land use were identified, undergoing four levels of management intensity and positioned either in or out of the Loire floodplain. This data collection describes the main soil physicochemical characteristics (texture, pH, water status, chemical contents), plant traits (root functional traits) as well as abundances of broad taxonomic groups (bacterial, archaeal, and fungal), and of microbial functional groups involved in soil C, N, and P cycling, microbial diversity (sequencing of Bacteria, Archaea, and Fungi), and different microbial activities (respiration, activities linked to the nitrogen cycle, extracellular enzymatic activities, and potential methanogenesis). The dataset summarized in this article improves our knowledge about physicochemical and (micro)biological characteristics of urban soils and can be used as a reference for future studies of urban soils.

Alpine and subalpine grasslands experience strong seasonal climatic variations, with snow cover for over six months maintaining steady soil temperature and moisture. This seasonal structure limits plant growth and strongly influences microbial activity, which together control key ecosystem functions like soil organic matter (SOM) inputs, mineralization, and greenhouse gas fluxes, ultimately influencing the composition and quantity of SOM. In our study, we monitored soil pedoclimate (temperature and moisture) and net ecosystem exchange (CO2 flux) at both plot and local footprint scales, using discrete measurements and flux tower, to characterize the seasonal context of alpine and subalpine grasslands. Meanwhile, we investigated the seasonal properties of topsoil organic matter (SOM) at six key times throughout the hydrological year: before snow cover, before snowmelt, after snowmelt, during the growing season, at vegetation peak, and during senescence. SOM properties were analyzed through the combination of methods including DRIFT spectroscopy, RockEval® thermal analysis, water-extractable organic carbon and permanganate-oxidizable carbon (POxC). Finally, soil incubations were conducted to assess microbial respiration sensitivity to temperature and moisture across these six periods, enhancing our understanding of seasonality’s impact on microbial features. Our study integrates in situ and in vitro measurements across multiple scales (soil sample, plot, and landscape), traditionally analyzed separately. This approach bridges microbial mechanisms with SOM quality and links them to ecosystem-scale carbon exchanges. Our findings highlighted a clear seasonality in SOM properties, offering valuable insights into the functioning of these grasslands. We identified a labile seasonal pool of SOM that persists through the winter due to low temperatures and low-carbon outputs, maintaining its availability for mineralization at the onset of the growing season—when primary producers have the highest nutrient demand. This labile pool decreases over the growing season, as microbial activity peaks and organic matter inputs decline. Additionally, seasonal shifts in microbial responses to temperature and humidity indicate functional acclimations: enhanced cold tolerance in winter, waterlogged tolerance during snowmelt, and increased capacity to degrade complex organic molecules during the growing season.

Over the past four decades, seasonal snow cover has declined rapidly in temperate alpine regions. However, the fine-scale dynamics of snowmelt preceding the ongoing warming period remain largely unknown, limiting our understanding of the long-term influence of past snow cover on alpine ecosystems. Here we rely upon the spatial similarities in melt-out patterns and a temperature-based model of fractional snow cover area, to reconstruct fine-scale snow cover changes over the past 250 years in instrumented catchments of the southwestern Alps. We provide evidence that, until the 1980s, prolonged snow cover in many late-lying snowfields delayed ecosystem development and explain why current vegetation cover, soil organic matter content, and mineral weathering are significantly lower in these areas than in surrounding ecosystems. These findings highlight the long-term legacy of snow cover on alpine landscapes and underscore the need to re-evaluate its effects on ecosystem structure, functioning, and responsiveness to ongoing changes.

ABSTRACTMountains are particularly vulnerable to climate change, as they are warming at a rate that exceeds the global average, significantly impacting cold‐adapted ecosystems. In these environments, soil organic matter (SOM) stocks are often considerably larger than at lower elevations. These stocks are therefore highly susceptible to global warming and the associated risk of greenhouse gas (GHG) (CO₂, CH₄, N₂O) emissions driven by temperature‐induced increases in SOM mineralisation. In order to quantify these emissions and the change of mineralisation rates under warming, it is necessary to gain an understanding of the annual mineralisation balance. We investigated how warming impacts the duration and intensity of mineralisation in different seasons. The main aim of this study is to quantify alpine SOM mineralisation rates and GHG production under a range of seasonal conditions, including those associated with warming. An in vitro approach was employed to expose alpine topsoils (0–10 cm) to the conditions of key seasonal periods: snow cover, growing season and rainfall/snowmelt. This was achieved by experimentally varying temperature and inflow of precipitation water. Additionally, the soil samples were subjected to a temperature increase of 4°C. The short‐term responses of carbon (C), nitrogen (N) and phosphorus (P) mineralisation and GHG production were monitored. The results demonstrated that alpine soil respiration rates exhibited a twofold increase with a 4°C warming, while the relative proportion of labile SOM demonstrated a decline with rising temperatures. Water saturation from simulated rain and snowmelt played a crucial role in organic matter mineralisation and increased the mineralisation of carbon (+12% to +53%), nitrogen (+20% to +80% of net ammonification) and phosphorus (+50% of net phosphate production). This suggests that nutrients present in the snowpack or the rain were added to the soil. In contrast, soil–water saturation decreased net nitrate production by between 10% and 90%. The results of this study highlight the potential for alpine soil warming to release labile SOM and demonstrate the influence of the snow regime on nutrient and carbon fluxes.

Alpine ecosystems, shaped by cold temperatures and prolonged snow cover, are warming twice as fast as lowlands, making them particularly vulnerable to climate change. This rapid warming alters ecosystem functioning by increasing soil temperatures and shifting snow regimes, leading to shorter snow cover periods and longer growing seasons. Such changes impact soil organic matter (SOM), which regulates carbon storage and soil fertility through microbial mineralization. We investigated long-term SOM changes following experimental warming in alpine grasslands. By transplanting soil plots downslope (2470 m a.s.l. to 1920 m a.s.l.), we increased mean annual temperature by 3 degrees C and extended the growing season by 77 days. Seven years later, we analyzed soil nutrients content, SOM characteristics (chemistry, labile pools, and thermal stability) and conducted discrete flux measurements to determine net ecosystem exchange (NEE). Soil incubations assessed microbial traits and their acclimation to warming. Our results indicate that, even after seven years, alpine soil microbial activities showed limited acclimation to warming, contributing to SOM destabilization and soil nutrients enrichment by boosting mineralization. Indeed, warmed plots acted as carbon sources, with an 18 % decrease in SOC stocks and increased NEE. Carbon losses exceeded C gains from plant productivity, primarily depleting labile pools. This may create a positive feedback loop between carbon cycling and climate warming. These findings highlight the long-term consequences of temperature increases and snow regime shifts on alpine ecosystem functioning and suggest that soil carbon losses in warming mountain environments may continue over time.

Increasing climate warming and summer droughts are known to affect mountain plant communities, their functional traits and life strategies. However, little is known about how strongly and efficiently communities respond to climate change, and how tightly plant responses are linked to responses of ecosystem functions. To test this, we transplanted alpine plant communities to subalpine conditions, exposing them to warming and drying. We compared these transplanted communities to alpine and subalpine control communities to assess their responses. Five years after transplantation, we found slower growth (e.g. lower leaf nitrogen) and more outsourcing strategies (e.g. lower specific root length) in the warmer and drier subalpine control communities compared to the alpine controls, probably due to drought. Traits of warmed alpine communities shifted toward subalpine controls. However, neither below- nor aboveground traits nor productivity of plants fully acclimated to subalpine conditions. Nevertheless, standard litter decomposition rates, arbuscular colonization and bacterial biomass showed no acclimation lag to the subalpine controls. Significant but insufficient acclimation of plant functional traits and strategies is prone to result in maladapted plant productivity, impairing competitiveness with better adapted subalpine species and leading to the temporally delayed loss of ecosystem features specific to alpine environments.

Increasing droughts threaten soil microbial communities and the multiple functions they control in agricultural soils. These soils are often fertilized with mineral nutrients, but it remains unclear how this fertilization may alter the capacity of soil multifunctionality (SMF) to be maintained under drought, and how plant-soil interactions shape these effects. In this study, we used a mountain grassland soil to test the interactive effect of mineral nutrient (Nitrogen and Phosphorous) addition and drought on SMF with and without plants (Lolium perenne) in a mesocosm experiment. We calculated SMF based on 8 microbial properties associated with the capacity of soil microbes to store carbon (C), nitrogen (N) and phosphorous (P) in their biomass, and to process these elements through organic matter depolymerization, mineralization, nitrification and denitrification processes. To investigate mechanisms underlying the SMF response we characterized the associated changes in soil stoichiometry and microbial community composition using 16S and 18S rRNA amplicon sequencing. Our results showed that fertilization decreased the SMF drought resistance when plants were present, but the opposite was observed in the unplanted mountain grassland soil. Our analysis suggested this was due to the interaction of plants, fertilization and drought in influencing four coupled properties related to high SMF: high soil moisture, low microbial C limitation, high bacterial diversity and low bacteria gram positive:gram negative ratio. Altogether, our results suggested that reducing the use of mineral fertilizer for plant production in mountain grassland could improve the ability of their soils to maintain their multifunctionality during drought period. Finally, our study clearly further demonstrated the importance of plant in the complex responses of SMF to global changes and showed that combining stoichiometric and microbial diversity assessment represents a powerful approach to disentangle the underlying mechanisms.

Worldwide wetland loss has made the conservation of these ecosystems a policy priority and led to the multiplication of restoration programmes. However, the lack of long‐term monitoring limits our understanding of the processes influencing the vegetation composition of restored wetlands and our ability to predict outcomes over multiple decades. Here, we assessed the extent to which hydrological regime and planting density of target species, two critical factors driving wetland vegetation and restoration success, can predict restoration outcomes. Using correlation analyses and generalised models, we assessed the role of target species planting density and analogous hydrological conditions (e.g. level, variation, seasonality) to reference wetlands for achieving and predicting restored vegetation similarity to reference plant communities in 12 sedge and/or willow‐dominated wetlands in Mountain Village, Colorado over 25 years post‐restoration. We found a significant positive correlation between hydrological similarity and vegetation similarity, peaking at 15 years post‐restoration (rho = 0.61). Similarly, planting density was positively correlated with vegetation similarity, peaking 5 years after restoration (rho = 0.75). For both variables, communities with the shallowest water table exhibited the strongest correlations. The similarity of restored vegetation to the reference community can be predicted using hydrological similarity and planting density. The models that combined these two variables outperformed single‐variable models. However, the model accuracy decreased 25 years after restoration, making predictions over two decades inaccurate for most communities. Synthesis and applications . Hydrological similarity to a reference, combined with appropriate planting densities, reliably predicts restored wetland vegetation convergence towards reference communities over two decades. Such models could provide managers with tools to assess failure risks across potential restoration sites, allowing them to select the most suitable locations and tailor planting efforts to maximise wetland restoration success.

Glacial forelands are expanding worldwide due to glacier shrinkage1, exposing new areas prone to the development of post-glacial ecosystems2,3. Nitrogen (N) is generally considered as a (co-)limiting nutrient in alpine regions, and deposition of atmospheric N, mainly emitted due to fossil fuel combustion, has for long been admitted as the main source of N4. However, other N sources such as glacial meltwaters5, long-range transport of fertilizers6 or bedrock erosion7 have recently been suspected of playing a more significant role than previously thought and could drive the establishment of pioneer microbial and plant communities in glacial forelands.Here, we show the isotopic composition and concentration of nitrate (δ15N, δ18O, Δ17O) and ammonium (δ15N) in glacial meltwaters, soils and plants from three glacial forelands in the French Alps. Samples were collected along transects expanding from the glacier front to areas deglaciated around 60 years ago. We find that the contribution of atmospheric deposition to the nitrate pool in soils decreases as time since deglaciation increases, but never exceeds 40%, not even at the glacier front where soils are entirely mineral with no detectable nitrification enzymatic activity. This pattern suggests that bedrock nitrogen and glacial meltwaters are the main N sources in post-glacial ecosystems and calls for a better quantification of those inputs. (1) Hugonnet, R.; McNabb, R.; Berthier, E.; Menounos, B.; Nuth, C.; Girod, L.; Farinotti, D.; Huss, M.; Dussaillant, I.; Brun, F.; Kääb, A. Accelerated Global Glacier Mass Loss in the Early Twenty-First Century. Nature 2021, 592 (7856), 726–731. https://doi.org/10.1038/s41586-021-03436-z.(2) Bosson, J. B.; Huss, M.; Cauvy-Fraunié, S.; Clément, J. C.; Costes, G.; Fischer, M.; Poulenard, J.; Arthaud, F. Future Emergence of New Ecosystems Caused by Glacial Retreat. Nature 2023, 620 (7974), 562–569. https://doi.org/10.1038/s41586-023-06302-2.(3) Ficetola, G. F.; Marta, S.; Guerrieri, A.; Gobbi, M.; Ambrosini, R.; Fontaneto, D.; Zerboni, A.; Poulenard, J.; Caccianiga, M.; Thuiller, W. Dynamics of Ecological Communities Following Current Retreat of Glaciers. Annu. Rev. Ecol. Evol. Syst. 2021, 52(1), 405–426. https://doi.org/10.1146/annurev-ecolsys-010521-040017.(4) Holtgrieve, G. W.; Schindler, D. E.; Hobbs, W. O.; Leavitt, P. R.; Ward, E. J.; Bunting, L.; Chen, G.; Finney, B. P.; Gregory-Eaves, I.; Holmgren, S.; Lisac, M. J.; Lisi, P. J.; Nydick, K.; Rogers, L. A.; Saros, J. E.; Selbie, D. T.; Shapley, M. D.; Walsh, P. B.; Wolfe, A. P. A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere. Science 2011, 334 (6062), 1545–1548. https://doi.org/10.1126/science.1212267.(5) Saros, J. E.; Rose, K. C.; Clow, D. W.; Stephens, V. C.; Nurse, A. B.; Arnett, H. A.; Stone, J. R.; Williamson, C. E.; Wolfe, A. P. Melting Alpine Glaciers Enrich High-Elevation Lakes with Reactive Nitrogen. Environ. Sci. Technol. 2010, 44 (13), 4891–4896. https://doi.org/10.1021/es100147j.(6) Hundey, E. J.; Russell, S. D.; Longstaffe, F. J.; Moser, K. A. Agriculture Causes Nitrate Fertilization of Remote Alpine Lakes. Nat. Commun. 2016, 7 (1), 10571. https://doi.org/10.1038/ncomms10571.(7) Houlton, B. Z.; Morford, S. L.; Dahlgren, R. A. Convergent Evidence for Widespread Rock Nitrogen Sources in Earth’s Surface Environment. Science 2018, 360 (6384), 58–62. https://doi.org/10.1126/science.aan4399.

Soil organic carbon (SOC) is crucial for ecosystem function and carbon storage, especially in mountain regions where cooler temperatures limit microbial activity, leading to higher SOC stocks compared to lowlands. However, the available data are insufficient to fully understand the distribution of SOC properties along elevation and snow cover duration gradients. Given that climate change models predict a reduction in snow cover duration, it is essential to better characterize these properties at a finer, mesotopographic scale (e.g., ridges and slopes), corresponding to the distribution of mountain plant communities. This study investigates the impact of microclimate on SOC content and stability in European mountain grasslands. We focused on two types of grasslands on acidic soils to maintain homogeneity in key parameters such as soil properties and plant communities. These grasslands, located across temperate European mountain ranges (Alps, Pyrenees, Vosges, Balkans, Carpathians, Black Forest, Bohemian Forest, and Sudetes), span a gradient of snow cover duration, ranging from frost-exposed ridges dominated by Carex curvula, to intermediate grasslands, without frost, dominated by Nardus stricta. SOC content and stability were assessed using Rock-Eval (R) thermal analysis across all sites. The results indicate that microclimate significantly influences SOC properties. Cooler temperatures, driven by elevation and reduced snow cover duration, were associated with increased SOC content but decreased stability. On windy ridges, extended growing seasons combined with intense winter freezing led to higher SOC lability, as freezing slows down mineralization processes. In contrast, intermediate grasslands, with longer growing seasons, showed enhanced SOC stability due to higher decomposition activity. These findings provide valuable insights into how SOC properties may evolve under climate change, particularly in relation to rising temperatures and shifting snow cover dynamics.

Worldwide wetland loss over the past 50 years has made wetland conservation a public policy priority, leading to an increase in wetland restoration programs. However, predicting long‐term restoration outcomes remains difficult. The monitoring of these programs rarely exceeds 5–10 years, forcing wetland managers to rely on short‐term success criteria that may be criticized by the scientific community. Our objective was to assess the significance of four short‐term success criteria (Carex ssp. shoot density, Salix ssp. survival, invasive species cover, and hydrologic dissimilarity to reference sites) used in a restoration program of 12 wetlands monitored for 5 years post‐restoration in predicting restoration outcomes 15 years post‐restoration. We defined the success of restoration efforts after 15 years using a cluster analysis‐based approach, and the clusters were described using principal coordinate analysis and Tukey's post hoc honest significant difference test. Finally, we assessed the pertinence of each short‐term success criteria in predicting long‐term restoration outcomes using Pearson correlation tests and spatial regressive models. Our results demonstrate that stress‐based short‐term success criteria can be reliable predictors of longer‐term success for communities with shallow water tables, whereas target‐species‐based short‐term success criteria are not. Hydrologic dissimilarity to the reference site was appropriate for willow‐sedge community outcome predictions, while invasive species cover was best for sedge community outcome predictions. For communities in drier habitats, such as the willow‐herb community, none of the tested short‐term success criteria were significant predictors of long‐term restoration outcomes, and further research is required to identify suitable short‐term success criteria.

Global change affects soil microbial communities and the multiple functions they control in soil. However, our understanding of the combined effects of multiple global change factors on soil multifunctionality (SMF), and how plant-soil interactions shape these effects remain limited. In this study, we used a mountain grassland soil to test the interactive effect of mineral nutrient (Nitrogen and Phosphorous) addition and drought on SMF with and without plant in a mesocosm experiment. We calculated SMF based on 8 microbial properties associated with the capacity of soil microbes to store carbon (C), nitrogen (N) and phosphorous (P) in their biomass, and to process these elements through organic matter depolymerization, mineralization, nitrification and denitrification processes. To investigate mechanisms underlying the SMF response we characterized the associated changes in soil nutrients stoichiometry and microbial community composition using 16S and 18S rRNA amplicon sequencing. Our results showed that nutrient addition decreased the SMF drought resistance when plants were present, but the opposite was observed in unplanted soil. We suggest this was due to the interaction of plant, fertilization and drought in influencing four coupled properties related to high SMF: high soil moisture, low microbial C limitation, high bacterial diversity and low bacteria gram positive:gram negative ratio. Our study revealed that plant presence can reverse the response of SMF to interacting global change factors, and further showed that combining stoichiometric and biodiversity assessment represents a powerful approach to disentangle the underlying mechanisms. ### Competing Interest Statement The authors have declared no competing interest.

Mountains are particularly affected by climate change because they are warming faster than the global average and the warming is affecting cold-adapted ecosystems. In these ecosystems, soil organic matter (SOM) and carbon (SOC) stocks tend to be much higher than at lower elevation, but their stability has been shown to be weaker, suggesting a high vulnerability to global warming and a potential release of greenhouse gases into the atmosphere (CO2, CH4, N2O). To quantify these emissions and the change of mineralisation rates under warming, it is necessary to understand the annual mineralisation balance, and how warming impacts duration and intensity of mineralization at different seasons. Using an in vitro approach, we exposed alpine soils to the conditions of three key seasons, snow-cover, snowmelt and growing season, by experimentally varying temperature and snowmelt water inflow. We also warmed the soils by 4°C and monitored the short-term responses of carbon (C), nitrogen (N) and phosphorus (P) mineralisation and greenhouse gas production. Alpine soil respiration rates doubled with a 4°C warming during the snowmelt and growing seasons, and the relative proportion of labile SOM decreased as the temperature increased. We found that snowmelt played a crucial role in organic matter mineralization. This season was characterized by an over-mineralisation of carbon, nitrogen and phosphorus, suggesting that the nutrients contained in the snow pack were released into the soil during the melting process (priming effect). Contrastingly, soil saturation during snowmelt decreased net nitrate production. Our results highlight how alpine soil warming can release labile SOM and how nutrient and carbon fluxes depend on snow regimes. In order to improve model predictions of SOM dynamics in alpine regions, these warming effects on alpine soils should be better considered.

Subalpine grasslands support biodiversity, agriculture, and tourism but their resilience to extreme climatic events is challenged accelerating their vulnerability to tipping points. Microbial communities, central in ecosystem functioning, are usually considered more resistant and highly resilient to extreme events albeit their functional redundancy and strong selection by local harsh climatic conditions. This study explored the soil microbial responses upon recurrent spring‐summer droughts associated with early snowmelt in subalpine grasslands mesocosms set‐up at the Lautaret Pass (French Alps). Potential soil microbial respiration, nitrification and denitrification activities were monitored over a period of two growing seasons along with quantification of related gene abundances. Impacts of simulated spring‐summer drought and early snowmelt were quantified to assess their resistance and recovery. Results revealed that droughts had a low and short‐term adverse impact on bacterial total respiration supporting their hypothesized high resilience, i.e. resistance and ability to recover. Nitrification and abundances of the corresponding functional guilds showed relatively strong resistance to summer droughts but declined in response to early snowmelt. This resistance of nitrification was paralleled by the recovery of denitrification and abundances of denitrifying communities from all climatic extremes, except from the summer droughts where nitrifiers were collapsed. Denitrification and respective functional groups faced high impact of applied stresses with strong reduction in abundance and activity. Although, consequently lower denitrifiers' competition for nitrate may be positive for plant biomass production, warnings exist when considering the potential nitrate leaching as well as risks of greenhouses gases emission such as N2O from these ecosystems.

Glacier shrinkage and the development of post-glacial ecosystems related to anthropogenic climate change are some of the fastest ongoing ecosystem shifts, with marked ecological and societal cascading consequences 1 – 6 . Yet, no complete spatial analysis exists, to our knowledge, to quantify or anticipate this important changeover 7 , 8 . Here we show that by 2100, the decline of all glaciers outside the Antarctic and Greenland ice sheets may produce new terrestrial, marine and freshwater ecosystems over an area ranging from the size of Nepal (149,000 ± 55,000 km 2 ) to that of Finland (339,000 ± 99,000 km 2 ). Our analysis shows that the loss of glacier area will range from 22 ± 8% to 51 ± 15%, depending on the climate scenario. In deglaciated areas, the emerging ecosystems will be characterized by extreme to mild ecological conditions, offering refuge for cold-adapted species or favouring primary productivity and generalist species. Exploring the future of glacierized areas highlights the importance of glaciers and emerging post-glacial ecosystems in the face of climate change, biodiversity loss and freshwater scarcity. We find that less than half of glacial areas are located in protected areas. Echoing the recent United Nations resolution declaring 2025 as the International Year of Glaciers’ Preservation 9 and the Global Biodiversity Framework 10 , we emphasize the need to urgently and simultaneously enhance climate-change mitigation and the in situ protection of these ecosystems to secure their existence, functioning and values.