Due to their poikilohydric lifestyle and lack of stabilizing tissue, cryptogamic/microbial communities are outcompeted by vascular plants in temperate climates and are thus mainly restricted to extreme habitats where vascular plant growth is limited. They colonize a broad range of niches, including the uppermost millimeters of soil (epi- and endogaeic), tree barks and leaves (epiphytic and epiphyllic), and rock surfaces and interiors (epi- and endolithic), as well as artificial substrates such as concrete, glass, or tar. In temperate regions, such communities thrive in shaded forest understories, dry microsites such as path edges, and nutrient-poor grasslands. In hot and cold drylands, their occurrence is largely confined to the open and not vegetated soil surface, where they form biological soil crusts (biocrusts). Biocrusts are estimated to cover ~30% of warm and hot drylands, while their extent in cold deserts remains less well quantified.
These communities are key components of ecosystems, but the magnitude of their contribution to numerous processes is still uncertain (biogeochemical and water cycling, atmospheric processes, biodiversity, etc.). In this session, we ask for contributions on the biodiversity and functional roles of cryptogams from local to global processes such as nutrient and water cycling, trace gas exchange with the atmosphere, soil erosion, mineral weathering, and vascular plant interactions. Studies of their responses to global change as well as other potential threats are also welcomed.
Around the world, and for the past ~2 billion years, surfaces of many soils have a “living skin” made by tiny plants and microbes called a biological soil crust (biocrust). Biocrusts are crucially important for helping to support the ecosystems they inhabit, for example making soil fertile, storing or redirecting water and stopping erosion. Biocrusts also boost the variety of living things present in an area (biodiversity). The CrustNet project will determine what controls the biodiversity of biocrusts globally for the first time, and its outcomes. CrustNet is a networked, distributed study of biocrust ecology, with participants around the world. Participants conduct the same set of studies and collect the same types of data to be pooled together to create an unprecedented global database about biocrusts. CrustNet addresses: (1) The determinants of the global scale functional biodiversity of biocrusts (2) determinants of the variability and shape of the relationship between biodiversity and ecosystem function across ecosystems, (3) effects of biocrust functional biodiversity on ecosystem resistance and resilience to physical disturbance and climate change, and (4) determinants of plant-biocrust co-occurrence patterns. CrustNet uses a tiered research protocol, including low-cost observational studies and manipulative experiments. Tier 1 includes mandatory detailed surveys of the composition of biocrusts, measurement of ecosystem functions along a biocrust development gradient, and contribution of samples to a trait database. Tier 2 includes low-cost experimentally-applied physical disturbance of the soil and subsequent tracking of the response of biocrusts. Tier 3 includes experimental climate manipulations using reciprocal transplantations and rainfall reduction using passive shelters. These studies will be foundational to our understanding of determinants of biocrust diversity, function and response to disturbance. To date, 14 sites in 5 nations have already been established and sampled, and pledged sites are ever increasing (23 additional sites have been proposed by international sampler-partners). In the process of conducting this research, a world-wide collaboration is being established, leading to greater participation of researchers from diverse backgrounds, and unparalleled training opportunities.
How to cite: Bowker, M., Gugel, S., Ceja-Navarro, J., Antoninka, A., Reed, S., and Darrouzet-Nardi, A.: CrustNet: Global determinants of biodiversity in biocrusts, and outcomes for ecosystem function, resistance and resilience, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14839, https://doi.org/10.5194/egusphere-egu26-14839, 2026.
Biological nitrogen (N) fixation by cyanobacteria on mosses is a critical N source for pristine ecosystems, but studies have largely focused on northern ecosystems, such as boreal and arctic regions. The contribution of moss-associated N fixation in Mediterranean ecosystems remains largely neglected, despite the high abundance of mosses in Mediterranean forests and previous evidence of substantial N fixation activity by their associated cyanobacteria. Here, we combined high-frequency in situ measurements of N fixation in Mediterranean mosses from forest and open sites with a process-based model that incorporates moss-associated N fixation responses to key climatic drivers (light, temperature, humidity). This integrated approach allows us for the first time to simulate diurnal and seasonal dynamics of N fixation and to upscale these dynamics to estimate annual N fixation rates. Our results highlight substantial nocturnal N fixation and indicate that large-scale estimates of N fixation across space and time derived from limited, single-time-point field measurements may be associated with considerable uncertainty. The presented model provides a new framework for simulating N fixation by moss-associated cyanobacteria.
How to cite: Ma, Y. and Rousk, K.: Temporal variation of nitrogen fixation in moss-cyanobacteria associations in the Mediterranean region: integrating experiments and process-based modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5644, https://doi.org/10.5194/egusphere-egu26-5644, 2026.
Nitrogen fixation is crucial for the ecology of N-limited drylands. An important, though only recently recognized, plant-independent avenue for N2-fixation takes place in desert topsoils through “C-for-N” mutualisms between specific heterotrophic diazotrophs and the cyanobacterium Microcoleus vaginatus, where partners need to come together into spatially close and partner-specific associations within the background of a diverse soil microbiome. We hypothesized that chemical signaling within the partner microbe’s exometabolome influences the motility behavior of mutualists, enabling them to collocate and stay together. Although well-characterized in the context of trans-kingdom symbiosis, the use of infomolecules to shape microbiomes in exclusively bacterial mutualisms has not yet been described. Using a combination of culture and field research, exometabolomic analyses, and chemotaxis assays, we showed that the M. vaginatus exometabolome can elicit the enrichment of heterodiazotrophs from the soil microbiome. This effect, when the cyanobacterium is N-starved, could be traced to three specific compounds: N-acetylglutamic acid, N-acetyl-L-methionine, and indole-3-acetic acid, which are only significantly produced under this condition. Together with prior reports that M. vaginatus similarly responds to molecular prompts through GABA and glutamate from carbon-starved heterotrophs, our findings unravel a bidirectional chemical dialogue between partners that can sustain symbiotic proximity in space and time. Interestingly, some, though not all of these infomolecules act as such in plant and animal systems. Together with its unique mode of N-transfer through urea, this keystone symbiosis in drylands can maintain its specificity even in an “open system” through the use of infomolecules and specific chemotactic responses, which also allow M. vaginatus to architect a microbiome that is tailored to its nutritional needs.
How to cite: Warsop Thomas, F., Drewes, J., Nelson, C., Bethany, J., Higgins Keppler, E., Kosina, S., Northen, T., Bean, H., and Garcia-Pichel, F.: Interspecies bacterial infomolecules facilitate nutrient exchange in biological soil crusts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19484, https://doi.org/10.5194/egusphere-egu26-19484, 2026.
Primary production by photosynthetic soil microbes can contribute to SOC, and this
contribution can take on additional significance in regions where plant productivity is
restricted, as is the case of arid lands. However, a quantitative rate assessment of these
contributions anywhere is still lacking. We used a combination of direct determinations
and meta-analyses of published literature on a large survey of biological soil crust
communities (biocrusts) dominated by cyanobacteria in US arid regions to obtain
relevant estimates. Directly measured SOC accumulation rates in a single site during a
five-year period yielded an estimate of 3.5 ± 2.2 g C m -2 y -1 in the top 1 cm of soil. Indirect
estimates from a multisite (n= 127) but single time-point survey using Chl a content as a
proxy for biocrust development, which was translated to actual time units using rates of
Chl a accumulation obtained from meta-analyses of the literature, yielded an estimate of
6.2 ± 2.0 g C m -2 y -1 for the same parameter. In order to obtain values integrated
through the soil profile, we used a generalized depth decay relationship in SOC under
biocrusts obtained from a survey of soil cores (n = 93). This resulted in contributions to
the overall SOC pool of 0.0630.039 Kg C m -2 yr -1 (single site) and 0.112 ± 0.036 Kg C
m -2 yr -1 (multi-site). Biocrust sit atop SOC stocks ranging from 1.6 to 5.5 Kg m -2 , not
significantly different from those typical of arid and semiarid pedons. Their average
contribution to these pools through a biocrust’s lifetime (by subtraction of the pools
under crustless soils) is estimated at 1.26 Kg C m -2 Kg m -2 . Not having resisted the
temptation to scale up, and based on published global assessments of biocrust cover,
some 22-33 PgC globally, or some 6-8 % of the global SOC pool in arid lands, may be
attributable to microbial photosynthate.
How to cite: Koger, S. and Garcia-Pichel, F.: Assessing the contribution of microbial primary production to the SOC pools of arid lands., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16360, https://doi.org/10.5194/egusphere-egu26-16360, 2026.
Biological soil crusts (biocrusts) function as a "living skin" at the soil–atmosphere interface, covering approximately 12% of the global terrestrial surface and providing critical ecosystem services. While climate change and anthropogenic pressures are recognized drivers of biocrust degradation, the extensive disturbance induced by rodent communities represents a pervasive yet under-recognized threat. Rodent burrowing activities mechanically destroy biocrusts, creating a distinctive landscape mosaic of high-albedo, excavated soil patches set against the darker, intact biocrust matrix. In this study, we present a hybrid mapping framework that integrates both data- and model-driven approaches to generate the first regional-scale, multi-year (2017–2025) spatiotemporal map of rodent-induced disturbance in the Gurbantunggut Desert, China. Our methodology employs a two-stage strategy: (1) To identify potential disturbance areas, a Swin Transformer segmentation model is trained using semi-automatically generated pseudo-labels leveraging thresholding based on the brightness contrast between burrows and biocrusts. (2) Final boundaries are then optimized through an adaptive Graph Cut algorithm that integrates deep-learning probability maps with morphological priors and spatial gradient information. Validated against 125 field-surveyed sites, the framework achieved an overall accuracy of 0.95, with specific F1-scores for rodent-induced disturbance and background reaching 0.81 and 0.98, respectively. Our analysis revealed that rodent-induced disturbances followed a "rise-and-fall" temporal trend, peaking around 2019. At its peak, the disturbed area accounted for 8% of the entire desert region, representing a striking 23% of the total biocrust coverage. This work offers a reliable methodology and dataset to assess and understand the neglected role of bioturbation in dryland ecology. Our study is highly relevant for dryland conservation, exemplifying how bioturbation shapes desert ecosystem stability and the functional integrity of biocrust-dominated landscapes.
How to cite: Chen, R., Yin, B., Yang, W., Li, Z., Li, J., Tang, Y., Li, A., Tang, K., Zhang, Y., Weber, B., and Chen, J.: Mapping of Rodent-Induced Disturbance Impact on Biological Soil Crusts via Deep Learning-Informed Adaptive Graph Cut, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7206, https://doi.org/10.5194/egusphere-egu26-7206, 2026.
In global drylands, apparently bare soil between plants is frequently covered by biological soil crusts (biocrusts). Biocrusts are poikilohydric communities that play key ecosystem roles in drylands, as they regulate infiltration, evaporation and water retention, provide soil biodiversity, and control biogeochemical cycling of nutrients. Moreover, biocrusts form a rough, cohesive surface layer that prevents soil particle detachment and nutrient mobilization and lost by wind and water erosion.
Approximately 12% of the Earth surface, corresponding to 40% of the global drylands, are currently covered by biocrusts, and it has been estimated that they prevent approximately 700 Tg of dust per year from being emitted into the atmosphere. However, these estimates are based on very few available measurements and do not represent the large variability in biocrust community composition and underlying soil properties.
Within the framework of the CRUST-R forze project, we have developed a global dataset to quantify the effects of biocrusts on potential dust emission. To this end, we measured the threshold friction velocity (TFV), representing the minimum wind velocity at which the soil starts being blown away, and sediment delivery under controlled wind tunnel conditions. We investigated 177 samples representing a wide range of biocrust communities and reference soils from biocrust-dominated habitats worldwide. In addition to TFV and sediment delivery measurements, our dataset also includes functional traits related to biocrust resistance to wind erosion, such as organic matter content, aggregate stability, surface roughness, and extracellular polymeric substances (EPS) content. This database is relevant to understand the underlying mechanisms of an increase in TFV upon biocrust colonization. Our preliminary results show the high relevance of biocrusts in soil stabilization and dust prevention, supporting the explicit inclusion of biocrusts in dust emission parameterizations of Earth system models.
How to cite: Urueta Urueta, C., Martínez-Sánchez, J. F., Román, R., Chamizo, S., Bowker, M., Chen, N., Chen, R., Giraldo, A., Salazar, A., Couradeau, E., Karnieli, A., Velasco Ayuso, S., Xiao, B., Qi, Y., Cantón, Y., Weber, B., and Rodríguez Caballero, E.: Integrating Biocrusts into Dust Emission Models: A Global Experimental Dataset, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21096, https://doi.org/10.5194/egusphere-egu26-21096, 2026.
Drylands cover ~46%% of Earth's surface and support diverse life forms despite water scarcity. In such a harsh environment, living organisms, including microorganisms, lichens, algae, and mosses, form a few mm-thick structure called biological soil crusts (biocrusts), that prevent soil erosion and play a crucial role in ecosystem stability. Biocrusts host microbial communities that survive desiccation by entering a dormant state, reducing metabolic activity. Upon rehydration, the reactivation of these organisms, followed by energy-generating metabolisms and DNA repair, sustains their survival. Previously, we studied microbial activation after a rain event in the daytime at 27 °C1, while nighttime responses at cooler temperatures remained unexplored. Here, we investigate whether microbial reactivation dynamics vary under contrasting light and temperature regimes, and whether these differences are reflected in resource allocation strategies during early rehydration.
A rehydration experiment was conducted in the dark with biocrusts sampled at the LTER Avdat site in the Negev Desert, Israel. Biocrusts were rehydrated (to 75% water-holding capacity) in a climate-controlled chamber, followed by 12 h of night condition at 19°C and 10 h of day at 27 °C with a 2 h transition. The previously conducted light incubation resulted in desiccation of the biocrusts within 39 hours, whereas nighttime incubation resulted in desiccation within 55 hours. Samples were collected at multiple time points during this experiment for metatranscriptome sequencing. RNA reads were mapped to metagenome-assembled genomes (MAGs) from the same samples for differential gene expression analysis.
Metatranscriptomic analyses revealed a rapid reactivation pattern in both conditions. In the dark, about 70% of MAGs showed significant differential gene expression within 15 minutes of rehydration, increasing to 93% of MAGs between 15 minutes and 3 hours. At daytime, 85% of MAGs reactivated in the first 15 minutes and increased to 95% in three hours. During the early hydration stage, dark-incubated samples exhibited a delayed but increasing transcriptional response, with a higher number of differentially expressed genes per MAG between 30 minutes and 3 hours compared to the light-incubated samples. The light-incubated samples exhibited a stronger initial response within the first 30 minutes, followed by fewer changes at later time points. Consistent with this pattern, a ribosomal-protein-based growth index, calculated as the mean normalized expression of ribosomal protein genes per MAG, remained higher during the first 3 hours under dark-incubated conditions but peaked earlier and declined by 3 hours under light-incubated conditions, despite comparable water availability. Together, these results indicate that hydration at dark and cooler conditions supports a more prolonged and gradual transcriptional adjustment, accompanied by sustained investment in translational capacity, whereas daylight and warmer conditions promote a rapid early response followed by earlier stabilization of core cellular functions.
- Imminger, S. et al. Survival and rapid resuscitation permit limited productivity in desert microbial communities. Nat. Commun. 15, 3056 (2024).
How to cite: Abbaszadeh, J., Imminger, S., Woebken, D., and Meier, D.: Light intensity and temperature drive growth investment strategies during resuscitation in desert biocrust communities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7322, https://doi.org/10.5194/egusphere-egu26-7322, 2026.
The Alps are warming at approximately twice the global mean rate, accompanied by altered precipitation regimes and rapid snow and ice loss. In high-alpine ecosystems, where low temperatures and short growing seasons constrain the establishment of vascular plants, biological soil crusts (biocrusts) form cohesive surface communities that can become a dominant biological component of the landscape. Composed of cyanobacteria, algae, lichens, and bryophytes, along with heterotrophic bacteria, archaea, and fungi, biocrusts play a key role in soil stabilization, water retention, and carbon and nitrogen cycling. Despite their ecological importance, biocrust responses to climate warming in alpine environments remain poorly understood.
To address this, we developed an integrated, field-based experimental framework to investigate alpine biocrust responses to climate change under realistic conditions in the high-alpine region of the Großglockner (Austria). The setup consists of a full-factorial design combining active infrared warming and manual snow-removal treatments. Biocrust responses are monitored using continuous meso- and microclimatic measurements, repeated image-based classification of surface cover using machine-learning methods, and complementary field sampling targeting DNA-based microbial community composition, nutrient availability, and soil aggregate stability.
The project was launched in May 2024. Following installation and optimization, the setup was fully operational throughout the 2025 growing season, providing a first complete field dataset for assessing warming effects on alpine biocrusts.
The experimental warming setup proved to work reliably under high-alpine conditions, with a minor decline in treatment performance towards the end of the growing season. Microclimatic measurements revealed that the warming treatment increased biocrust surface temperatures by approximately 3 °C and soil temperatures at a 5 cm depth by about 2 °C during most of the season, whereas mesoclimatic measurements captured the characteristic seasonal patterns of the high-alpine climate. Mapping of surface cover revealed pronounced seasonal dynamics in coverage, with vascular plants and mosses peaking and cyanobacteria-dominated crusts declining in the middle of the growing season, while lichen cover remained comparatively stable. More in-depth results on microbial composition and effects on nutrient availability are currently being analysed.
This novel experimental field setup improves our understanding of the resilience and functioning of alpine biocrusts under climate warming and their role in high-alpine ecosystem dynamics.
How to cite: Creve, J., Faulhammer, P., Herdy, S., Maier, S., Kim, M., De Melo Silva, L., Avila Clasen, L., Auer, G., Herndl, M., and Weber, B.: Climate change effects on biological soil crusts in high-alpine regions: experimental setup and first insights, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11262, https://doi.org/10.5194/egusphere-egu26-11262, 2026.
Cryptogamic communities (CC) consist of photoautotrophic lichens, bryophytes, algae, and cyanobacteria, as well as heterotrophic fungi, bacteria, and archaea. They colonize soils, rocks, tree stems and leaves across the globe. In the Amazon rainforest, they cover large amounts of tree stem surfaces and potentially play key roles in biogeochemical cycling in these regions. These processes include carbon and nitrogen fixation, as well as water and nutrient cycling. In addition, they emit bioaerosols and are involved in the exchange of volatile organic compounds. Since these processes are driven by the availability of water, light and temperature, knowledge of these parameters is essential in order to quantify these processes at ecosystem scales.
Here we present a novel microclimate sensor system that has been installed on eight trees in two different forest types in the Amazon rainforest. On each tree, sensors measuring temperature, light intensity, and water content of representative bryophytes at 10-minute intervals were installed at three different heights (near ground, at the main stem and in the canopy) in two expositions (north and south). Measurements are sent wirelessly from each tree to a server where data are post-processed, automatically checked for validity and sent to a cloud storage for further analysis. First measurement results of the system provide insights into day and night patterns as well as the hydration status of the investigated bryophyte communities depending on the colonized habitat (height, exposition). Long-term measurements and analyses will improve our understanding of the dynamics of the physiological processes of CC in times of changing climatic conditions, and will serve as a foundation for the upscaling of functional processes.
How to cite: Faulhammer, P., Avila Clasen, L., Herdy, S., Conde, M., Webber, C., Barbosa, C., Frechen, N., Kast, G., Quaresma, C., and Weber, B.: Microclimatic measurement setup to assess the physiological activity patterns of epiphytic cryptogamic communities in the Amazon rainforest, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17334, https://doi.org/10.5194/egusphere-egu26-17334, 2026.
Biological soil crusts or biocrusts, are complex communities composed of photoautotrophic organisms (cyanobacteria, algae, lichens, and bryophytes) and heterotrophs living in intimate association with soil surface particles covering most open areas of drylands. These poikilohydric communities play a crucial role in the functioning of dryland ecosystems by regulating water, carbon, and nitrogen cycles, stabilizing soil and preventing erosion. In addition, biocrusts accumulate protective and photosynthetic pigments such as scytonemin, carotenoids, and chlorophyll, which, together with their surface roughness, exert a strong control on surface spectral response.
In this study, we aimed at exploring the influence of different biocrust types on surface spectral signal and to explore the relationship between the observed biocrusts spectral traits and related key functional attributes at different spectral and spatial resolutions.
As expected, biocrusts showed higher pigment concentration, carbon and nitrogen content, and surface roughness than bare soil, and this effect increases from low-developed cyanobacteria to well-developed lichen- and moss-dominated biocrusts. These functional differences are reflected in their spectral signal, and more developed biocrusts exhibited more pronounced pigment and water absorption peaks and higher values of broadband spectral indices compared to early cyanobacteria or bare soil. Moreover, this effect is accentuated under wet conditions. Finally, we found a clear relationship between spectral signal and functional traits that facilitates the quantification of key functional attributes using the biocrust spectral signal from both field spectra and UAV This linkage facilitates the identification and estimation of functional traits of biocrusts at the ecosystem scale and improves the interpretation of high-resolution remote sensing data in dryland landscapes.
How to cite: Martinez Sanchez, J. F., Urueta Urueta, C. A., Pagli, C., Martinez Sanchez, E. M., Fernandez Galera, J., Ramon, R., Chamizo de la Piedra, S., Canton, Y., and Rodriguez Caballero, E.: Linking functional traits and spectral responses of biocrust at different scales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20686, https://doi.org/10.5194/egusphere-egu26-20686, 2026.
Climate projections predict that warming, drought frequency and severity, and water stress will increase in drylands at rates faster than the global means. Notably, drylands, which cover more than 41% of Earth’s terrestrial surface, support various desert ecosystems. An increasing amount of solid evidence indicates that considering biocrusts is of paramount importance when assessing the direct and indirect impacts of climate change on global desert functioning and highlights the significance of biocrusts as modulators of these impacts. Changes in the precipitation regime have stronger negative impacts than warming on the biocrust component and structure, as well as on the linked ecosystem functioning; however, the impacts of warming coupled with precipitation alterations are more prominent. Climate change induces inconsistent responses to warming and precipitation alteration in the biocrust cryptogams, such as mosses and lichens. Warming coupled with precipitation alterations contributes to reducing the wet period and biocrust water availability for lichens and mosses to fix atmospheric CO2 and N2, leading to drought stress and a potential biocrust backslide from the late successional stage to the early stage, which in turn results in global decreases in dryland carbon and nitrogen due to deficits in biocrust carbon sequestration and nitrogen fixation. Alterations of the water balance can also occur when warming influences infiltration, runoff, non-rainfall water entrapment, evaporation and soil water reallocation. These changes in the biocrust ecosystem functioning are unlikely to be conducive to both passive and artificially facilitated eco-restoration of drylands. Conversely, to a large extent, the presence of well-developed biocrusts regulates and alleviates the negative impacts of climate change on dryland ecosystems.
How to cite: Li, X. and Dou, W.: Warming decreases the desert ecosystem functioning of global drylands by altering biocrust cryptogams, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8463, https://doi.org/10.5194/egusphere-egu26-8463, 2026.
Global climate change is projected to cause a dramatic increase in precipitation uncertainty (increased or decreased precipitation) in the future, particularly in semiarid ecosystems. Biocrusts are a critical surface cover in semiarid regions, occupying 12% of the global land surface. They perform various ecological functions by influencing soil properties, such as regulating soil water and nutrient cycles, carbon and nitrogen sequestration, biodiversity, and vegetation recovery—effectively impacting nearly all surface ecological processes. Notably, they influence soil carbon emissions through respiration, thereby regulating the carbon balance in drylands. However, the patterns and mechanisms by which biocrust soil respiration responds to precipitation changes under semiarid climates remain unclear. Our precipitation manipulation experiment (–50%, –30%, –10%, +10%, +30%, and +50% of CK) conducted on the Chinese Loess Plateau revealed that increased precipitation (+10% to +50%) suppressed biocrust formation, while moderate precipitation (–10% and –30%) reduction promoted biocrust development. Compared to natural precipitation, increased precipitation (+10% to +50%) reduced biocrust respiration rates by 8.9%–22.1%. Conversely, moderate precipitation reductions (–10% and –30%) enhanced biocrust respiration rates, whereas extreme drought stress (–50%) suppressed these rates. Therefore, the response of biocrust soil respiration to precipitation changes exhibits a negative asymmetry effect. Our structural equation model further indicates that soil temperature and biocrust traits are the primary factors influencing the response of biocrust soil respiration to precipitation variations. These findings suggest that intensified precipitation variability driven by future global climate change may positively impact the stability of soil carbon stocks contributed by biocrusts in semiarid regions, thereby reducing dryland soil carbon emissions.
How to cite: Dou, W. and Li, X.: Asymmetric negative effects of precipitation changes on soil respiration of cryptogamic biocrusts in semiarid ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8612, https://doi.org/10.5194/egusphere-egu26-8612, 2026.
Drylands are characterized by a high spatiotemporal heterogeneity, which complicates the development of remote sensing applications for these regions. Biological soil crusts are among the key phenomena driving this heterogeneity. Biocrusts are living communities composed of photoautotrophic organisms (cyanobacteria, algae, lichens, and bryophytes) in intimate association with heterotrophic microorganisms and covering the soil surface across global drylands. Biocrusts modify surface reflectance through specific absorption features arising from insulation-protective and photosynthetic pigments. These features have been used to develop local applications for biocrust mapping and monitoring, but their extrapolation, especially to the global scale, remains difficult because the biocrust reflectance interacts with the underlying soil signal. Moreover, the currently available biocrust spectral datasets do not capture the great variety of biocrust communities and their diverse spectral signals. Furthermore, these data are often collected without standardized protocols, which hampers data comparison, transferability and the development of standard procedures for mapping and monitoring.
To overcome this limitation, we developed a standard protocol to build the first consistent biocrust spectral library, which aims to support new biocrust mapping and monitoring efforts. that aims at supporting new biocrust mapping and monitoring actions. Spectra of 354 samples representing different biocrust communities from around the world were recorded in the laboratory under dry and wet conditions under controlled illumination intensity in the lab. The library includes a reflectance spectrum, a continuum removal spectrum, albedo, and a set of narrow- and broad-band spectral indices commonly applied for vegetation, soil, and characterization. We also used associated metadata, including general descriptors of habitats, location and sampling time information, and physicochemical variables related to biocrusts development and functioning. The latter facilitates the quantification of some key functional traits for comparison with remote sensing products (e.g., photosynthetic pigments, organic matter, stability, surface roughness, EPS concentration). Spectra and physicochemical features of the underlying soil are also included, as they are known to significantly influence the response of biocrust organisms. Overall, this spectral library encompasses a wide range of biocrust functional types from global drylands but further input from currently not well-covered geographic regions is still welcome.
Awknoledgment:CRUST R-Forze (PID2021-127631NA-I00) project funded by MICIU/AEI /10.13039/501100011033 and FEDER, UE; Support for Encouraging Research Consolidation (CNS2024-154916) funded by MICIU/AEI /10.13039/501100011033 and UE NextGenerationEU/PRTR. ERC was supported by the Ramon y Cajal Fellowship (RYC2020-030762-I) founded by MICIU/AEI/10.13039/501100011033 and El FSE invierte en tu future.
How to cite: Rodriguez-Caballero, E., Martinez-Sanchez, J. F., Urueta-Urueta, C., Roman, J. R., Chamizo, S., Bowker, M., Chen, N., Qi, Y., Chen, R., Giraldo, A., Salazar, A., Couradeau, E., Karnieli, A., Velasco-Ayuso, S., Xiao, B., Weber, B., Cantón, Y., and Martin, M. P.: Development of a spectral library of biocrusts and related functional traits, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21191, https://doi.org/10.5194/egusphere-egu26-21191, 2026.
Cryptogams (mosses, lichens and liverworts) are widespread and can influence nitrogen cycling and biosphere–atmosphere exchange of volatile organic compounds (VOCs), especially in high-latitude ecosystems. However, the contributions of their symbiotic microbiota (e.g. cyanobacteria and other diazotrophs) to both N fixation and VOC emissions remain relatively underexplored. Here, we conducted controlled incubations of multiple subarctic cryptogam species before and after the removal of their symbiotic microbiota on the surface. We quantified N fixation activity using acetylene reduction assays and characterised VOC emissions using complementary GC–MS and PTR–TOF–MS measurements. Preliminary results showed that N fixation rates decreased significantly in several moss species after the removal of the symbiotic microbiota, whereas responses in lichens and liverwort were weaker or non-significant. Both total VOC emission rates and composition were altered for most species. A random forest model identified several sesquiterpenes (SQTs) as key discriminant compounds; their emission rates were increased after the removal of surface-associated symbionts from the cryptogams. Partial least squares analysis further revealed coupling between selected VOC fingerprints and N fixation rates. Overall, these results demonstrate that removable surface symbionts can concurrently regulate cryptogam N fixation and VOC emissions in subarctic systems, with potential implications for ecosystem N inputs and VOC-mediated atmospheric chemistry.
How to cite: Zhang, W., Engroff, A., Jiao, Y., Roslund, K., Alvarenga, D., Rousk, K., and Rinnan, R.: Symbiotic microbiota of cryptogams regulate VOC emissions and nitrogen fixation in subarctic tundra, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19547, https://doi.org/10.5194/egusphere-egu26-19547, 2026.
The persistence of soil organic carbon (SOC) in forest ecosystems depicts not only the quantity of organic matter (OM) inputs but also how carbon (C) is distributed among functionally distinct soil pools with different roles. In forest ecosystems, mosses significantly influence SOC dynamics not merely by increasing surface C stocks, but by altering its partitioning into more persistent, mineral associated fractions. However, the influence of mosses on C stability in occluded and mineral-associated SOM fractions based on contrasting temperate forest types has rarely been quantified.
To address this knowledge gap, our study aims to characterize and quantify soil particulate organic matter (POM) fractions to assess C sequestration potential under moss cover and forest types. A total of 42 soil samples were collected from coniferous mixed (Baden-Württemberg) and pine forests (Brandenburg) from the top soil layer (0-2 cm) with and without mosses. Physical density fractionation was done to quantify SOC distribution among free POM (FPOM), occluded POM (OPOM), and mineral-associated POM (MAPOM) which represent soil pools with varying turnover times.
The moss cover across coniferous mixed forest significantly increased the C concentration in MAPOM by up to 75% which indicate a long- term C stabilization via stable MAPOM. But the scenario was different for pine forest, where mosses significantly increased the C:N ratio of labile fractions which denote different decomposition dynamics. The results also indicate that the long-term SOC sequestration was highest in the moss-covered coniferous forests which stored about six- fold more C in MAPOM than pine forests. Further results will be presented at EGU 2026.
How to cite: Parajuli, M., Adhikari, R., Yang, X., Scholten, T., Seitz, S., and Gall, C.: From Moss to Mineral: Soil Organic Carbon Fractionation under Bryophytes in Temperate Forests, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2865, https://doi.org/10.5194/egusphere-egu26-2865, 2026.
Being uniquely adapted to extreme environmental conditions, rock-dwelling lecideoid lichens are a diverse and major component of terrestrial vegetation in Antarctica. Climate change is reshaping Antarctic ecosystems, potentially forcing cold-adapted species to shift their distributions to maintain their climatic niche. Here, we provide a circum-Antarctic assessment of lecideoid lichen diversity and project future distributional changes under contrasting climate change scenarios.
Fungal (mycobiont) and algal (photobiont) symbionts of lecideoid lichen species from a circum-Antarctic sampling were classified using DNA barcoding. The climatic niches of nine common mycobiont species and four photobiont OTUs were predicted, and spatial range shifts were projected across four Antarctic bioregions under three Shared Socioeconomic Pathways: (1) SSP1-2.6: sustainable development, (2) SSP3-7.0: medium–high reference scenario with high methane emissions and (3) SSP5-8.5: continued dependence on fossil fuels.
DNA-barcoding revealed 34 species of lecideoid lichens associated with nine photobiont OTUs for the Antarctic continent, including three previously undescribed species of the genus Lecidella.
Model projections indicate that future warming is likely to promote a range expansion rather than climate-induced habitat loss for both mycobionts and photobionts. Patterns of climate-induced range expansion differ markedly between maritime Antarctica and continental Antarctica. In the maritime Antarctic, Lecidea atrobrunnea and its main photobiont Tr_I01 are predicted to substantially increase their potential distribution, whereas the other species remain restricted to climatically distinct south-eastern regions of maritime Antarctica. In continental Antarctica, species show broadly similar expansion patterns, with the Transantarctic Mountains representing the region with the greatest projected gain in climatically suitable habitat. Although the greatest range expansion generally occurs under SSP5-8.5, some photobiont OTUs in the Prince Charles Mountains are projected to gain more climatically suitable habitat under the high-methane scenario SSP3-7.0. Notably, areas of high climatic suitability are predicted to shift towards inland regions under future warming scenarios. Consequently, ice-free areas may function as potential refugia for cold-adapted lichen species under ongoing climate warming.
Overall, our results indicate that Antarctic lecideoid lichens are likely to undergo widespread range expansion under future warming, particularly into currently uncolonized ice-free inland areas of continental Antarctica. Projected shifts in climatically suitable areas suggest the emergence of new habitats, with potential consequences for future biodiversity patterns across Antarctica.
How to cite: Götz, A., Andreev, M., Junker, R. R., Maislinger, L., Sancho, L. G., Trutschnig, W., and Ruprecht, U.: Future Range Shifts and Diversity Patterns of Antarctic Lecideoid Lichens Under Climate Change Scenarios, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7122, https://doi.org/10.5194/egusphere-egu26-7122, 2026.
Biopatina refers to cryptogamic organisms that naturally thrive on urban architectural surfaces, such as buildings, stone walls, and monuments, often influencing the surface coloration and structure. Similar to other cryptogams that thrive in natural environments, biopatinas represent photosynthetic communities composed of various organisms that serve numerous ecosystem functions. Here, we hypothesize that biopatinas can provide a microclimatic cooling effect, serve as a valuable carbon sink, and function as natural biofilters by trapping particulate matter and dust. Additionally, we suggest that they may act as a bioremediation system for breaking down polycyclic aromatic hydrocarbons (PAHs). Our hypothesis will be investigated on representative biopatinas on building surfaces in the city of Vienna in the framework of our project “Biopatinas on buildings in urban environments” funded by WWTF (Wiener Wissenschafts-, Forschungs- und Technologiefonds). We will collect biopatina as well as uncolonized samples from randomly selected buildings during two different seasons (e.g., summer and winter). On these samples, we will conduct CO₂ gas exchange measurements to assess the carbon fixation and measure the dust entrapment properties of wet and dry biopatina. Furthermore, the role of biopatina in regulating surface temperature of building walls will be examined under varying hydration conditions. Since the function of biopatina is related to its microbial composition, we will characterize its composition by means of metagenomics. We will map the biopatina coverage in a representative part of Vienna to be used for upscaling in order to develop predictive models.
In this highly interdisciplinary project, the scientific approach will be supported by the use of participatory art-based practices to achieve greater public awareness and acceptance of biopatina on monuments and architecture in the city. The results of our study will help to embrace the functional complexity of biopatina, which will be essential for protecting cultural heritage, increasing urban environmental quality, and developing biologically informed solutions for sustainable cities.
How to cite: Fathinejad, A., Rabbachin, L., Kim, M., Weber, B., and Sterflinger, K.: Biopatinas: Cryptogams in urban environment as potential biofilters, CO2 sinks, and bioremediation systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12260, https://doi.org/10.5194/egusphere-egu26-12260, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 2
EGU26-15468 | ECS | Posters virtual | VPS5
Biocrusts mediate seasonal warming effects of soil N transformation in drylandsTue, 05 May, 14:42–14:45 (CEST) vPoster spot 2
Drylands are mostly covered by biocrusts and are sensitive to climate change, which will likely affect nitrogen (N) transformation. However, it remains unclear the response of N transformation-related variables (N transformation rates, microbial biomass, and enzyme activity) to warming in biocrust-dominated dryland ecosystems. Here, we examined three soil cover types (bare soil, cyanobacteria- and moss-dominated soil) over a full year as we conducted a warming treatment (open top chambers) in the Tengger Desert. In order to quantify the response of N transformation-related variables to warming, we defined the warming effects (WEs) as the increment of N transformation-related variable per-unit variation of temperature. Our results showed that the presence of biocrusts can significantly increase the WEs of soil N mineralization rates (Rmin), nitrification rates (Rnit), the content of microbial biomass carbon (MBC) and nitrogen (MBN), and the activities of soil nitrate reductase (S-NR) and urease (S-UE). Microbial biomass under biocrusts was more sensitive to warming followed by enzyme activity. Meanwhile, the WEs in spring and fall were higher than those in winter and summer. The cumulative rainfall was the driving factor affecting the seasonal change of WEs. Therefore, the defining and studying warming effects expand our understanding of seasonal dynamics of N transformation, microbial biomass and enzyme activity, and emphasize the important roles of biocrusts as modulators of N cycling under climate change in dryland ecosystems.
How to cite: Hu, R. and Zhang, Z.: Biocrusts mediate seasonal warming effects of soil N transformation in drylands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15468, https://doi.org/10.5194/egusphere-egu26-15468, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 2
EGU26-22143 | Posters virtual | VPS6
Alleviating Biocrust Blindness: An Easy Guide to Morphogroups of BiocrustsThu, 07 May, 14:54–14:57 (CEST) vPoster spot 2
Biological soil crusts (biocrusts) are increasingly recognized as important components of ecosystems. Biocrusts are instrumental in maintaining functions such as soil stability and reduced abundance of invasive annual grasses. Impacts of fire are likely to be less severe where invasive plants are reduced and biocrusts are abundant. These organisms can thrive under drought conditions and help intact ecosystems be more resilient to drought. However, expertise on these organisms remains limited. Practitioners are often interested in the topic but might feel they would benefit from additional resources on how to identify these organisms. We have developed a single-page, front and back guide that enables anyone, regardless of previous experience, to recognize biocrusts in the field and categorize them into ecologically meaningful groups, with known functional roles. The guide has been tested both in the field and by examining biocrust samples in hand. Data associated with testing the guide was used to improve it. The resulting guide describes higher-level groups of algae, mosses, and lichens. Light algal crusts are described as their own group. Dark algal crusts are presented with gelatinous lichens due to similar ecologies and increased accuracy of identification when these groups are combined. The determination of algal crusts was accepted as correct, regardless of the light or dark designation, due to the quality of our samples. Mosses are split into short and tall. In addition to the gelatinous lichens / dark algal crust group, lichens were classified into five additional categories: crustose, cup, foliose, fruticose, and scale. This tool has been created from the ground up, driven largely by the accuracy with which non-experts can correctly classify presented groups. In addition to reporting on the accuracy of each group, we explain how sample type (resin, dried and in petri dishes, or enlarged photographs) played a role in the accuracy of identification. We describe the ecology and functional roles of the presented groups, giving further justification for their classification. We anticipate that adoption of the guide is likely to have far-reaching implications, such as an increase in the number of studies on biocrusts at the level of functional roles.
How to cite: Condon, L., Barker, C., and Coates, P.: Alleviating Biocrust Blindness: An Easy Guide to Morphogroups of Biocrusts , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22143, https://doi.org/10.5194/egusphere-egu26-22143, 2026.
