Agricultural University of Iceland

Abstract Life can be unstable. This is especially true for seedlings growing on erodible surfaces, such as newly exposed areas after glacier retreat. Here we used a space-for-time approach to study the role of biological soil crust (biocrust) as surface stabilizer and facilitator of ecological succession along a glacier forefield chronosequence at the retreating Conejeras glacier in the Tropical Andes. We used the point-intercept method to estimate surface cover of plants, biocrust, bare ground and rocks, as well as surface roughness; and a field soil aggregate kit to estimate soil stability. As hypothesized, following a bare-ground stage near the edge of the glacier, the successional trajectory involved the development of a biocrust belt, including bryophytes and lichens, followed by an increasing vascular plant cover in more advanced successional stages. The development of biocrust was accompanied by higher roughness and stability, which likely increased seed entrapment and seedling establishment. Our results suggest that the development of cyanobacterial-dominated biocrust at the forefield of the Conejeras glacier may favor the establishment of plants with large seeds, such as graminoids from the Festuca genus. Overall, our findings highlight the key role of biocrusts in the ecological dynamics that follow glacier melt in the Tropical Andes.

Global change affects plant performance, both directly through warming and indirectly through changes in their biotic and abiotic surroundings. Soil microbes can critically influence plant performance, but are vulnerable to warming themselves. Disentangling direct effects of warming on plants from those intermediated by changes in microbial populations is complex under field conditions.To distinguish those effects, we monitored the performance of Agrostis capillaris and Anthoxanthum odoratum grown under uniform and controlled glasshouse conditions in soils inoculated with soil microbiomes conditioned by ambient, medium (14 years; MTW) or long‐term (>55 years; LTW) geothermal warming. This was replicated under normal watering or drought conditions to additionally assess stress resistance. Furthermore, we analysed the microbiome of the inocula through metabarcoding to identify root‐associated fungi and compare their relative abundance under different warming conditions.We found a decreased belowground biomass of both plant species when grown with LTW‐conditioned microbiomes, with an exacerbated effect under drought for Ag. capillaris. We did not observe an associated increase in aboveground biomass, resulting in an increased aboveground biomass:belowground biomass ratio. These changes coincided with concurrent increases in the relative abundance of putative plant pathogens and arbuscular mycorrhizal fungi.We therefore conclude that soil microbes can mediate warming effects on plant performance through reduced belowground biomass.

Abstract The upland soil microbiome is dominated by aerobic bacteria that oxidize atmospheric trace gases, including CO, H 2 , and CH 4 . As a result, soils are the largest biological sink for these climate-active gases. Whether global warming will enhance or suppress these processes remains unclear. Here, we studied the warming responses of soil trace gas oxidizers by profiling natural geothermal gradients in a subarctic grassland with over 60 years of field warming at +6°C. We integrate field flux measurements, ex situ biogeochemical assays, metagenomics, and metatranscriptomics to determine ecosystem and cellular-level responses. Our results show that the oxidation of atmospheric CO and H 2 , but not CH 4 , increased with long-term warming due to higher cell numbers. However, at the cellular level, trace gas oxidizers, especially methanotrophs, tended to reduce gas consumption and transcription of gas-metabolizing enzymes in response to long-term warming. Our findings suggest that soils may remain a robust sink for trace gases despite lower per-cell activity. This work establishes a framework for interpreting the relationships between temperature and microbial trace gas oxidation on timescales relevant to Earth’s climate system.

<strong class="journal-contentHeaderColor">Abstract.</strong> Mineral dust absorbs and scatters solar and infrared radiation, thereby affecting the radiance spectrum at the surface and top-of-atmosphere and the atmospheric heating rate. While half of the outgoing thermal radiation is emitted in the far infrared (FIR, 15&ndash;100 &mu;m), knowledge of the optical properties and thermal radiative effects of dust is currently limited to the mid-infrared region (MIR, 3&ndash;15 &mu;m). In this study we performed pellet spectroscopy measurements to evaluate the MIR and FIR contribution to dust absorbance and explore the variability and spectral diversity of the dust signature within the 2.5&ndash;25 &mu;m range. Thirteen dust samples re-suspended from parent soils with contrasting mineralogy were investigated, including low and mid latitude dust (LMLD) sources in Africa, America, Asia, and Middle East, and high latitude dust (HLD) from Iceland. Results show that the absorbance of dust in the FIR up to 25 &mu;m is comparable in intensity to that in the MIR. Also, spectrally different absorption (position and shape of the peaks) is observed for HLD compared to LMLD, due to differences in mineralogical composition. Corroborated with the few available literature data on absorption properties of natural dust and single minerals up to 100 &mu;m wavelength, these data suggest the relevance of MIR and FIR interactions to the dust radiative effect for low to high latitude sources. Furthermore, the dust spectral signatures in the MIR and FIR could potentially be used to characterise the mineralogy and differentiate the origin of airborne particles based on infrared remote sensing observations.

High-latitude regions store substantial amounts of soil organic matter (SOM). Icelandic volcanic soils have exceptional capabilities for SOM accumulation, but recent changes in land use can significantly impact it. Water-extractable organic matter (WEOM) represents a labile SOM pool and serves as a reliable index of SOM dynamics. We assessed the stable carbon (C), stable nitrogen (N), and WEOC (water-extractable organic carbon), as well as WETN (water-extractable total nitrogen), concentrations in soils under different land uses—semi-natural habitats (tundra and wetland) and human-managed areas (intensively and extensively grazed pasturelands and formerly and presently fertilized meadows)—in southeastern Iceland. The results suggest that human-managed sites contain more total C and N but less WEOM per unit of total C or N than semi-natural habitats, except for wetlands. Wetlands exhibited the highest WEOM content. Extensive pasturelands and fertilized meadows are becoming more common in local ecosystems, highlighting the direction of changes in Icelandic grasslands management.

Selection for performance in horse breeding benefits from precise genetic insights at a molecular level, but knowledge remains limited. This study used whole-genome sequences of 39 elite and non-elite Icelandic horses to identify candidate causal variants linked to previously identified haplotypes in the STAU2 and RELN genes affecting pace and other gaits. A frameshift variant in linkage disequilibrium with the previously identified haplotypes in the STAU2 gene (r2 = 0.85) was identified within a predicted STAU2 transcript. This variant alters the amino acid sequence and introduces a premature stop codon but does not appear harmful or disease-causing and is potentially unique to equine biology. A large portion of the RELN haplotype overlapped with an H3K27me3 modification mark, suggesting a regulatory role of this region. Despite the small sample size, the RELN haplotype’s effects were validated for tölt, trot, and canter/gallop. Additionally, the RELN haplotype significantly influenced the age at which horses were presented for breeding field tests, indicating a potential role of the region in precocity and trainability. Functional experiments are needed to further investigate the regions’ influences on biological processes and their potential impact on horse performance.

<strong class="journal-contentHeaderColor">Abstract.</strong> Iceland is a major high-latitude dust source area. Airborne Icelandic dust influences the climate system via interacting with radiation, clouds, and biogeochemical systems, impacts the snow/ice albedo, and air quality. These impacts are sensitive to its mineralogical, chemical, and physical composition. However, comprehensive particle measurement and analysis of Icelandic dust is still limited. This study examines dust samples collected during a field campaign in the Dyngjusandur desert (August&ndash;September 2021) using active and passive aerosol sampling. Over 190,000 individual particles, ranging from 0.1 to 120 &micro;m, were analyzed for their chemical and physical properties using scanning electron microscopy/energy dispersive X-ray spectroscopy (ccSEM/EDX). Results show heterogeneity in particle size, shape, and composition. The most abundant particle type was Medium-Al mixed particles, likely glass-like, comprising 35&ndash;93 % of the aerosol volume. Sulfate particles, suggesting volcanic contributions, were detected in some samples. Iron (Fe) and titanium (Ti)-rich particles made up 3.5 % and 1.8 % of the aerosol volume, respectively, mainly in the fine fraction. The median aspect ratio ranged from 1.37 to 1.53, increasing with particle size. Our findings highlight key differences in Icelandic dust compared to Moroccan dust, including higher iron and titanium content and a lack of potassium in Icelandic dust. Additionally, Icelandic dust shows a size-dependent increase in aspect ratio, unlike Moroccan dust, which remains constant. These observations can improve model simulations of high-latitude dust&rsquo;s role in the Earth system.

Abstract BackgroundIn breeding the aim is to identify and accumulate beneficial variants. However, detection of these variants may be challenging in the presence of extensive genotype x environment interactions (GxE), as variant effects will be conditional on environment.MethodsThe study assesses the performance of264diploid perennial ryegrass accessions in a multi-environment field trial. We investigate the extent of GxE, for yield (total dry matter) and persistence traits, i.e. winter kill and spring cover, under environmental conditions experienced in Nordic and Baltic regions at the limit of the species distribution. Two different approaches to modelling GxE were tested: reaction norm and envirotyping, and the models were validated under three different breeding scenarios.ResultsOur analysis documented the presence of significant GxE interaction for all traits investigated in the study. Validation showed improvements in prediction accuracy when accounting for GxE: up to 4% for yield when predicting in unobserved environments, and up to 22% and 9% for spring cover and winter kill, respectively when predicting unobserved germplasm. Genome-wide-association-studies (GWAS) were utilized to detect genetic variants with marginal effects (environment-independent effect) and conditional effects (environment-dependent effects). Results showed the presence of large-effect genetic variants with marginal effects, in addition to few QTL whose effects were adaptive under specific environmental conditions while neutral or deleterious under different environmental conditions.ConclusionThis study demonstrates the usefulness and limitations of genomic prediction models for predicting GxE in highly diverse samples, and describes the extent of GxE interactions at the limit of species distribution for perennial ryegrass. Finally, our study points toward adaptive variation, which may enhance persistence of perennial ryegrass populations in Nordic and Baltic growing conditions.

Soils at high latitudes are experiencing significant warming due to climate change, raising concerns about potential disruptions in nitrogen (N) and carbon (C) cycling. This study investigates the decadal effects of soil warming on microbial N transformations in an Icelandic grassland. To this purpose, a geothermal gradient was utilized, where soil temperatures varied naturally from +0&amp;#186;C to&amp;#160;+12.3&amp;#176;C, simulating enhanced warming effects. Seasonal sampling of N pools and rates of gross N transformations&amp;#8212;including amino acid, ammonia, and nitrate consumption and production&amp;#8212;provided insights into microbial responses to prolonged warming.&amp;#160;Warming accelerated the turnover of amino acids, driven by increased rates of microbial production and consumption, but did not affect net protein depolymerization. Ammonia consumption rates increased with temperature, although production rates remained constant. Additionally, total soil N content decreased substantially after five years of warming but remained stable between 5 and 10 years of warming. These findings suggest that N losses induced by warming occurred primarily within the first five years, stabilizing in a new equilibrium without further N losses. The enhanced microbial C limitation in warmed soils likely compelled microorganisms to rely more on the turnover of organic N pools as a dual source of both C and N to meet their heightened metabolic demands, thus preventing further N losses. &amp;#160;Overall, these findings challenge the assumption of progressive N depletion under warming conditions and highlight the role of microbial physiological adaptations in maintaining soil N availability despite increased metabolic demands.&amp;#160;