Vermicompost as an alternative substrate to peat moss for strawberry (Fragaria ananassa) in soilles culture.

BACKGROUND: Consecutive droughts and quantitative and qualitative reduction of surface and underground water resources have caused an increase in greenhouse and hydroponic cultivation for most garden crops, including strawberries, in Iran. On the other hand, most of the inputs of greenhouse crops in Iran are imported. To possibility of replacing vermicompost with peat moss under hydroponic cultivation, an experiment was done in a split plot based on randomized complete blocks design in three replications in Isfahan (Iran) Agricultural and Natural Resources Research Center in 2019. The main treatment was substrate at four levels included different levels of vermicompost (30 and 50%) and peat moss (30 and 50%) in combination with perlite and sub-treatment were Selva and Camarosa cultivars. RESULTS: The results showed that Camarosa cultivar and Selva cultivar in (perlite/ peat moss 50:50) and Selva cultivar in (perlite / vermicompost 70:30) had maximum yield. Leaf number and chlorophyll index were maximum in Camarosa cultivar in peat moss substrates. Strawberry cultivars had the highest root fresh weight, the content of vitamin C and total soluble solids (TSS) in substrates containing vermicompost. Camarosa cultivar in (perlite / peat moss50:50) and Selva cultivar in (perlite /vermicompost 50:50) had maximum root dry weight. Also, the highest number of inflorescences was related to substrates containing peat moss and (perlite /vermicompost 70:30). Maximum amount of fresh and dry weight of shoots were observed in (perlite/ peat moss70:30). Selva cultivar had more inflorescences (16.5%) than Camarosa cultivar and Camarosa cultivar produced more fresh and dry weight of shoots (16.5%, 23.01%) than Selva cultivar. CONCLUSION: Expriment results highlighted the importance of considering both main and sub-treatments in agricultural research, as they interacted to influence various growth and yield parameters. 50% vermicompost treatment combined with perlite had a positive impact on plant growth and in quality index such as vitamin C content and TSS was highest. while the choice of cultivar affected different aspects of plant development. Selva cultivar was known to be more tolerant to salinity caused by vermicompost. Vermicompost is local and more economical, also salt resistant cultivars are recommended in a controlled (30%) amount of vermicompost.

Structure and Functions of Endophytic Bacterial Communities Associated with Sphagnum Mosses and Their Drivers in Two Different Nutrient Types of Peatlands.

Sphagnum mosses are keystone plant species in the peatland ecosystems that play a crucial role in the formation of peat, which shelters a broad diversity of endophytic bacteria with important ecological functions. In particular, methanotrophic and nitrogen-fixing endophytic bacteria benefit Sphagnum moss hosts by providing both carbon and nitrogen. However, the composition and abundance of endophytic bacteria from different species of Sphagnum moss in peatlands of different nutrient statuses and their drivers remain unclear. This study used 16S rRNA gene amplicon sequencing to examine endophytic bacterial communities in Sphagnum mosses and measured the activity of methanotrophic microbial by the 13C-CH4 oxidation rate. According to the results, the endophytic bacterial community structure varied among Sphagnum moss species and Sphagnum capillifolium had the highest endophytic bacterial alpha diversity. Moreover, chlorophyll, phenol oxidase, carbon contents, and water retention capacity strongly shaped the communities of endophytic bacteria. Finally, Sphagnum palustre in Hani (SP) had a higher methane oxidation rate than S. palustre in Taishanmiao. This result is associated with the higher average relative abundance of Methyloferula an obligate methanotroph in SP. In summary, this work highlights the effects of Sphagnum moss characteristics on the endophytic bacteriome. The endophytic bacteriome is important for Sphagnum moss productivity, as well as for carbon and nitrogen cycles in Sphagnum moss peatlands.

A hidden herbivory effect on Sphagnum reproduction.

Defence theories provide predictions about trade-offs in the allocation of resources to defence and growth. However, very little is known about how pressure from herbivores influences the allocation of resources during reproduction. Two common peatland bryophyte species, Sphagnum angustifolium and S. capillifolium, were chosen as study species. Vegetative and reproductive shoots of both Sphagnum species were subjected to treatments with and without herbivores in a lab experiment. After 4 weeks of exposure to herbivores in a growth chamber, we measured biomass production, net photosynthesis rate, defence traits (phenolics in leachate and phenolics in extract), nonstructural carbohydrates (soluble sugar and starch), and reproductive traits (capsule number, weight and diameter, and spore germination) of both Sphagnum species. Reproductive shoots had higher constitutive defence than vegetative shoots in S. angustifolium, and a similar pattern was observed in S. capillifolium. With herbivory, reproductive shoots showed stronger induced defence (released more phenolics) than vegetative shoots in S. capillifolium, but not in S. angustifolium. Herbivory had no effect on capsule number, weight, or diameter, but reduced spore germination percentage by more than half in both species. Our study highlights the hidden effects of herbivory on reproduction of Sphagnum and indicates the presence of maternal effects in bryophytes. Ecologists will benefit from examining both quality- and quantity-based traits when attempting to estimate the herbivory effect on plant fitness.

More is not always better: peat moss mixtures slightly enhance peatland stability.

Terrestrial wetland ecosystems challenge biodiversity-ecosystem function theory, which generally links high species diversity to stable ecosystem functions. An open question in ecosystem ecology is whether assemblages of co-occurring peat mosses contribute to the stability of peatland ecosystem processes. We conducted a two-species (Sphagnum cuspidatum, Sphagnum medium) replacement series mesocosm experiment to evaluate the resistance, resilience, and recovery rates of net ecosystem CO2 exchange (NEE) under mild and deep water table drawdown. Our results show a positive effect of mild water table drawdown on NEE with no apparent role for peat moss mixture. Our study indicates that the carbon uptake capacity by peat moss mixtures is rather resilient to mild water table drawdown, but seriously affected by deeper drought conditions. Co-occurring peat moss species seem to enhance the resilience of the carbon uptake function (i.e. ability of NEE to return to pre-perturbation levels) of peat moss mixtures only slightly. These findings suggest that assemblages of co-occurring Sphagnum mosses do only marginally contribute to the stability of ecosystem functions in peatlands under drought conditions. Above all, our results highlight that predicted severe droughts can gravely affect the sink capacity of peatlands, with only a small extenuating role for peat moss mixtures.

The remediation of marine sediments containing polycyclic aromatic hydrocarbons by peroxymonosulfate activated with Sphagnum moss-derived biochar and its benthic microbial ecology.

This research was to study the efficiency of Sphagnum moss-derived biochar (SMBC) in removing polycyclic aromatic hydrocarbons (PAHs) from marine sediment using a peroxymonosulfate (PMS)-based carbon-advanced oxidation process (PMS-CAOPs). Sphagnum moss-derived biochar (SMBC) was generated via a simple thermochemical process for PMS activation toward enhancing decontamination of sediments. At pH 6, the SMBC/PMS system achieved a PAH removal efficiency exceeding 78% in 12 h reaction time. Moreover, PAHs of 6-, 5-, 4-, 3-, and 2-ring structures exhibited 98%, 74%, 68%, 85%, and 91%, of removal, respectively. The SMBC activation of PMS generated both radicals (SO4•- and HO•) and nonradical (1O2), species responsible for PAHs degradation, attributed primarily to inherent iron and carbon moieties. The significant PAHs degradation efficiency showcased by the SMBC/PMS process holds promise for augmenting the performance of indigenous benthic microbial activity in sediment treatment contexts. The response of sediment microbial communities to PAH-induced stress was particularly associated with the Proteobacteria phylum, specifically the Sulfurovum genus. The findings of the present study highlight the efficacy of environmentally benign reactive radical/nonradical-based PMS-CAOP using pristine carbon materials, offering a sustainable strategy for sediment treatment.

Sphagnum mosses, the impact of disturbances and anthropogenic management actions on their ecological role in CO2 fluxes generated in peatland ecosystems.

Mosses of the genus Sphagnum are the dominant vegetation in most pristine peatlands in temperate and high-latitude regions. They play a crucial role in carbon sequestration, being responsible for ca. 50% of carbon accumulation through their active participation in peat formation. They have a significant influence on the dynamics of CO2 emissions due to an efficient maximum potential photosynthetic rate, lower respiration rates, and the production of a recalcitrant litter whose decomposition is gradual. However, various anthropogenic disturbances and land use management actions that favor its reestablishment have the potential to modify the dynamics of these CO2 emissions. Therefore, the objective of this review is to discuss the role of Sphagnum in CO2 emissions generated in peatland ecosystems, and to understand the impacts of anthropogenic practices favorable and detrimental to Sphagnum on these emissions. Based on our review, increased Sphagnum cover reduces CO2 emissions and fosters C sequestration, but drainage transforms peatlands dominated by Sphagnum into a persistent source of CO2 due to lower gross primary productivity of the moss and increased respiration rates. Sites with moss removal used as donor material for peatland restoration emit twice as much CO2 as adjacent undisturbed natural sites, and those with commercial Sphagnum extraction generate almost neutral CO2 emissions, yet both can recover their sink status in the short term. The reintroduction of fragments and natural recolonization of Sphagnum in transitional peatlands, can reduce emissions, recover, or increase the CO2 sink function in the short and medium term. Furthermore, Sphagnum paludiculture is seen as a sustainable alternative for the use of transitional peatlands, allowing moss production strips to become CO2 sink, however, it is necessary to quantify the emissions of all the components of the field of production (ditches, causeway), and the biomass harvested from the moss to establish a final closing balance of C.

Sulfur speciation in Sphagnum peat moss modified by mutualistic interactions with cyanobacteria.

Peat moss (Sphagnum spp.) develops mutualistic interactions with cyanobacteria by providing carbohydrates and S compounds in exchange for N-rich compounds, potentially facilitating N inputs into peatlands. Here, we evaluate how colonization of Sphagnum angustifolium hyaline cells by Nostoc muscorum modifies S abundance and speciation at the scales of individual cells and across whole leaves. For the first time, S K-edge X-ray Absorption Spectroscopy was used to identify bulk and micron-scale S speciation across isolated cyanobacteria colonies, and in colonized and uncolonized leaves. Uncolonized leaves contained primarily reduced organic S and oxidized sulfonate- and sulfate-containing compounds. Increasing Nostoc colonization resulted in an enrichment of S and changes in speciation, with increases in sulfate relative to reduced S and sulfonate. At the scale of individual hyaline cells, colonized cells exhibited localized enrichment of reduced S surrounded by diffuse sulfonate, similar to observations of cyanobacteria colonies cultured in the absence of leaves. We infer that colonization stimulates plant S uptake and the production of sulfate-containing metabolites that are concentrated in stem tissues. Sulfate compounds that are produced in response to colonization become depleted in colonized cells where they may be converted into reduced S metabolites by cyanobacteria.

Carbon emissions from Australian Sphagnum peatlands increase with feral horse (Equus caballus) presence.

Peatlands are globally significant carbon sinks, but when disturbed, have the potential to release carbon back to the atmosphere as greenhouse gases. Feral horse populations in the Australian Alps degrade Sphagnum peatlands, which are highly sensitive to disturbance. However, the link between this degradation and peatland carbon cycling is not understood. Here, we compared the autumn daytime carbon dioxide (CO2) and methane (CH4) fluxes of 12 alpine and subalpine Sphagnum peatlands in Kosciuszko National Park, Australia. The presence of feral horses at these sites was correlated with higher carbon loss: sites with horses were losing carbon to the atmosphere (4.83 and 8.18 g CO2-e m-2 d-1 in areas of Sphagnum moss and bare soil, respectively), whereas sites without horses were removing carbon from the atmosphere (-6.39 g CO2-e m-2 d-1). Sites with feral horses also had higher soil bulk density, temperature, and electrical conductivity (EC), and higher water pH, EC, and turbidity, than sites without horses. Our findings suggest that excluding feral horses from peatland areas could reduce rates of carbon loss to the atmosphere, in addition to improving overall site condition, peat soil condition, and water quality. We discuss potential management applications, further research, and restoration opportunities arising from these results.

Climate-induced hydrological fluctuations shape Arctic Alaskan peatland plant communities.

Rapidly increasing temperatures in high-latitude regions are causing major changes in wetland ecosystems. To assess the impact of concomitant hydroclimatic fluctuations, mineral deposition, and autogenous succession on the rate and direction of changing arctic plant communities in Arctic Alaska, we conducted detailed palaeoecological analyses using plant macrofossil, pollen, testate amoebae, elemental analyses, and radiocarbon and lead (210Pb) dating on two replicate monoliths from a peatland that developed in a river valley on the northern foothills of the Books Range. We observed an expansion of Sphagnum populations and vascular plants preferring dry habitats, such as Sphagnum warnstorfii, Sphagnum teres/squarrosum, Polytrichum strictum, Aulacomnium palustre and Salix sp., in recent decades between 2000 and 2015 CE, triggered by an increase in temperature and deepening water tables. Deepening peatland water tables became accentuated over the last two decades, when it reached its lowest point in the last 700 years. Conversely, a higher water-table between ca. 1500 and 1950 CE led to a recession of Sphagnum communities and an expansion of sedges. The almost continuous supply of mineral matter during this time led to a dominance of minerotrophic plant communities, although with varying species composition throughout the study period. The replicate cores show similar patterns, but nuanced differences are also visible, depicting fine spatial scale differences particularly in peat-forming plant distribution and the different timings of their presence. In conclusion, our study provides valuable insights into the impact of hydroclimatic fluctuations on peatland vegetation in Arctic Alaska, highlighting their tendency to dry out in recent decades. It also highlights the importance of river valley peatlands in paleoenvironmental reconstructions.

Sphagnum increases soil's sequestration capacity of mineral-associated organic carbon via activating metal oxides.

Sphagnum wetlands are global hotspots for carbon storage, conventionally attributed to the accumulation of decay-resistant litter. However, the buildup of mineral-associated organic carbon (MAOC) with relatively slow turnover has rarely been examined therein. Here, employing both large-scale comparisons across major terrestrial ecosystems and soil survey along Sphagnum gradients in distinct wetlands, we show that Sphagnum fosters a notable accumulation of metal-bound organic carbon (OC) via activating iron and aluminum (hydr)oxides in the soil. The unique phenolic and acidic metabolites of Sphagnum further strengthen metal-organic associations, leading to the dominance of metal-bound OC in soil MAOC. Importantly, in contrast with limited MAOC sequestration potentials elsewhere, MAOC increases linearly with soil OC accrual without signs of saturation in Sphagnum wetlands. These findings collectively demonstrate that Sphagnum acts as an efficient 'rust engineer' that largely boosts the rusty carbon sink in wetlands, potentially increasing long-term soil carbon sequestration.

Comparison of carbon and nitrogen accumulation rate between bog and fen phases in a pristine peatland with the fen-bog transition.

Long-term carbon and nitrogen dynamics in peatlands are affected by both vegetation production and decomposition processes. Here, we examined the carbon accumulation rate (CAR), nitrogen accumulation rate (NAR) and δ13 C, δ15 N of plant residuals in a peat core dated back to ~8500 cal year BP in a temperate peatland in Northeast China. Impacted by the tephra during 1160 and 789 cal year BP and climate change, the peatland changed from a fen dominated by vascular plants to a bog dominated by Sphagnum mosses. We used the Clymo model to quantify peat addition rate and decay constant for acrotelm and catotelm layers during both bog and fen phases. Our studied peatland was dominated by Sphagnum fuscum during the bog phase (789 to -59 cal year BP) and lower accumulation rates in the acrotelm layer was found during this phase, suggesting the dominant role of volcanic eruption in the CAR of the peat core. Both mean CAR and NAR were higher during the bog phase than during the fen phase in our study, consistent with the results of the only one similar study in the literature. Because the input rate of organic matter was considered to be lower during the bog phase, the decomposition process must have been much lower during the bog phase than during the fen phase and potentially controlled CAR and NAR. During the fen phase, CAR was also lower under higher temperature and summer insolation, conditions beneficial for decomposition. δ15 N of Sphagnum hinted that nitrogen fixation had a positive effect on nitrogen accumulation, particular in recent decades. Our study suggested that decomposition is more important for carbon and nitrogen sequestration than production in peatlands in most conditions and if future climate changes or human disturbance increase decomposition rate, carbon sequestration in peatlands will be jeopardized.

Recovery of Smelter-Impacted Peat and Sphagnum Moss: a Microbial Perspective.

Peatlands store approximately one-half of terrestrial soil carbon and one-tenth of non-glacial freshwater. Some of these important ecosystems are located near heavy metal emitting smelters. To improve the understanding of smelter impacts and potential recovery after initial pollution controls in the 1970s (roughly 50 years of potential recovery), we sampled peatlands along a distance gradient of 134 km from a smelter in Sudbury, Ontario, Canada, an area with over a century of nickel (Ni) and copper (Cu) mining activity. This work is aimed at evaluating potential shifts in bacterial and archaeal community structures in Sphagnum moss and its underlying peat within smelter-impacted poor fens. In peat, total Ni and Cu concentrations were higher (0.062-0.067 and 0.110-0.208 mg/g, respectively) at sites close to the smelter and exponentially dropped with distance from the smelter. This exponential decrease in Ni concentrations was also observed in Sphagnum. 16S rDNA amplicon sequencing showed that peat and Sphagnum moss host distinct microbiomes with peat accommodating a more diverse community structure. The microbiomes of Sphagnum were dominated by Proteobacteria (62.5%), followed by Acidobacteria (11.9%), with no observable trends with distance from the smelter. Dominance of Acidobacteria (32.4%) and Proteobacteria (29.6%) in peat was reported across all sites. No drift in taxonomy was seen across the distance gradient or from the reference sites, suggesting a potential microbiome recovery toward that of the reference peatlands microbiomes after decades of pollution controls. These results advance the understanding of peat and Sphagnum moss microbiomes, as well as depict the sensitivities and the resilience of peatland ecosystems.

Predicted structural proteome of Sphagnum divinum and proteome-scale annotation.

MOTIVATION: Sphagnum-dominated peatlands store a substantial amount of terrestrial carbon. The genus is undersampled and under-studied. No experimental crystal structure from any Sphagnum species exists in the Protein Data Bank and fewer than 200 Sphagnum-related genes have structural models available in the AlphaFold Protein Structure Database. Tools and resources are needed to help bridge these gaps, and to enable the analysis of other structural proteomes now made possible by accurate structure prediction. RESULTS: We present the predicted structural proteome (25 134 primary transcripts) of Sphagnum divinum computed using AlphaFold, structural alignment results of all high-confidence models against an annotated nonredundant crystallographic database of over 90,000 structures, a structure-based classification of putative Enzyme Commission (EC) numbers across this proteome, and the computational method to perform this proteome-scale structure-based annotation. AVAILABILITY AND IMPLEMENTATION: All data and code are available in public repositories, detailed at https://github.com/BSDExabio/SAFA. The structural models of the S. divinum proteome have been deposited in the ModelArchive repository at https://modelarchive.org/doi/10.5452/ma-ornl-sphdiv.

Ericoid shrub encroachment shifts aboveground-belowground linkages in three peatlands across Europe and Western Siberia.

In northern peatlands, reduction of Sphagnum dominance in favour of vascular vegetation is likely to influence biogeochemical processes. Such vegetation changes occur as the water table lowers and temperatures rise. To test which of these factors has a significant influence on peatland vegetation, we conducted a 3-year manipulative field experiment in Linje mire (northern Poland). We manipulated the peatland water table level (wet, intermediate and dry; on average the depth of the water table was 17.4, 21.2 and 25.3 cm respectively), and we used open-top chambers (OTCs) to create warmer conditions (on average increase of 1.2°C in OTC plots compared to control plots). Peat drying through water table lowering at this local scale had a larger effect than OTC warming treatment per see on Sphagnum mosses and vascular plants. In particular, ericoid shrubs increased with a lower water table level, while Sphagnum decreased. Microclimatic measurements at the plot scale indicated that both water-level and temperature, represented by heating degree days (HDDs), can have significant effects on the vegetation. In a large-scale complementary vegetation gradient survey replicated in three peatlands positioned along a transitional oceanic-continental and temperate-boreal (subarctic) gradient (France-Poland-Western Siberia), an increase in ericoid shrubs was marked by an increase in phenols in peat pore water, resulting from higher phenol concentrations in vascular plant biomass. Our results suggest a shift in functioning from a mineral-N-driven to a fungi-mediated organic-N nutrient acquisition with shrub encroachment. Both ericoid shrub encroachment and higher mean annual temperature in the three sites triggered greater vascular plant biomass and consequently the dominance of decomposers (especially fungi), which led to a feeding community dominated by nematodes. This contributed to lower enzymatic multifunctionality. Our findings illustrate mechanisms by which plants influence ecosystem responses to climate change, through their effect on microbial trophic interactions.

Characteristic Photoprotective Molecules from the Sphagnum World: A Solution-Phase Ultrafast Study of Sphagnic Acid.

A natural UV-absorbing chromophore extracted from sphagnum mosses, sphagnic acid, is proposed as a new natural support to chemical UV filters for use in cosmetic applications. Sphagnic acid is structurally related to the cinnamate family of molecules, known for their strong UV absorption, efficient non-radiative decay, and antioxidant properties. In this study, transient electronic absorption spectroscopy is used, in conjunction with steady-state techniques, to model the photodynamics following photoexcitation of sphagnic acid in different solvent systems. Sphagnic acid was found in each system to relax with lifetimes of ~200 fs and ~1.5 ps before generating a cis-isomer photoproduct. This study helps to elucidate the photoprotective mechanism of a new potential natural support to sunscreens, from a unique plant source.

Clonality, local population structure and gametophyte sex ratios in cryptic species of the Sphagnum magellanicum complex.

BACKGROUND AND AIMS: Sphagnum (peatmoss) comprises a moss (Bryophyta) clade with ~300-500 species. The genus has unparalleled ecological importance because Sphagnum-dominated peatlands store almost a third of the terrestrial carbon pool and peatmosses engineer the formation and microtopography of peatlands. Genomic resources for Sphagnum are being actively expanded, but many aspects of their biology are still poorly known. Among these are the degree to which Sphagnum species reproduce asexually, and the relative frequencies of male and female gametophytes in these haploid-dominant plants. We assess clonality and gametophyte sex ratios and test hypotheses about the local-scale distribution of clones and sexes in four North American species of the S. magellanicum complex. These four species are difficult to distinguish morphologically and are very closely related. We also assess microbial communities associated with Sphagnum host plant clones and sexes at two sites. METHODS: Four hundred and five samples of the four species, representing 57 populations, were subjected to restriction site-associated DNA sequencing (RADseq). Analyses of population structure and clonality based on the molecular data utilized both phylogenetic and phenetic approaches. Multi-locus genotypes (genets) were identified using the RADseq data. Sexes of sampled ramets were determined using a molecular approach that utilized coverage of loci on the sex chromosomes after the method was validated using a sample of plants that expressed sex phenotypically. Sex ratios were estimated for each species, and populations within species. Difference in fitness between genets was estimated as the numbers of ramets each genet comprised. Degrees of clonality [numbers of genets/numbers of ramets (samples)] within species, among sites, and between gametophyte sexes were estimated. Sex ratios were estimated for each species, and populations within species. Sphagnum-associated microbial communities were assessed at two sites in relation to Sphagnum clonality and sex. KEY RESULTS: All four species appear to engage in a mixture of sexual and asexual (clonal) reproduction. A single ramet represents most genets but two to eight ramets were dsumbers ansd text etected for some genets. Only one genet is represented by ramets in multiple populations; all other genets are restricted to a single population. Within populations ramets of individual genets are spatially clustered, suggesting limited dispersal even within peatlands. Sex ratios are male-biased in S. diabolicum but female-biased in the other three species, although significantly so only in S. divinum. Neither species nor males/females differ in levels of clonal propagation. At St Regis Lake (NY) and Franklin Bog (VT), microbial community composition is strongly differentiated between the sites, but differences between species, genets and sexes were not detected. Within S. divinum, however, female gametophytes harboured two to three times the number of microbial taxa as males. CONCLUSIONS: These four Sphagnum species all exhibit similar reproductive patterns that result from a mixture of sexual and asexual reproduction. The spatial patterns of clonally replicated ramets of genets suggest that these species fall between the so-called phalanx patterns, where genets abut one another but do not extensively mix because of limited ramet fragmentation, and the guerrilla patterns, where extensive genet fragmentation and dispersal result in greater mixing of different genets. Although sex ratios in bryophytes are most often female-biased, both male and female biases occur in this complex of closely related species. The association of far greater microbial diversity for female gametophytes in S. divinum, which has a female-biased sex ratio, suggests additional research to determine if levels of microbial diversity are consistently correlated with differing patterns of sex ratio biases.

Divergent selection and climate adaptation fuel genomic differentiation between sister species of Sphagnum (peat moss).

BACKGROUND AND AIMS: New plant species can evolve through the reinforcement of reproductive isolation via local adaptation along habitat gradients. Peat mosses (Sphagnaceae) are an emerging model system for the study of evolutionary genomics and have well-documented niche differentiation among species. Recent molecular studies have demonstrated that the globally distributed species Sphagnum magellanicum is a complex of morphologically cryptic lineages that are phylogenetically and ecologically distinct. Here, we describe the architecture of genomic differentiation between two sister species in this complex known from eastern North America: the northern S. diabolicum and the largely southern S. magniae. METHODS: We sampled plant populations from across a latitudinal gradient in eastern North America and performed whole genome and restriction-site associated DNA sequencing. These sequencing data were then analyzed computationally. KEY RESULTS: Using sliding-window population genetic analyses we find that differentiation is concentrated within 'islands' of the genome spanning up to 400 kb that are characterized by elevated genetic divergence, suppressed recombination, reduced nucleotide diversity and increased rates of non-synonymous substitution. Sequence variants that are significantly associated with genetic structure and bioclimatic variables occur within genes that have functional enrichment for biological processes including abiotic stress response, photoperiodism and hormone-mediated signalling. Demographic modelling demonstrates that these two species diverged no more than 225 000 generations ago with secondary contact occurring where their ranges overlap. CONCLUSIONS: We suggest that this heterogeneity of genomic differentiation is a result of linked selection and reflects the role of local adaptation to contrasting climatic zones in driving speciation. This research provides insight into the process of speciation in a group of ecologically important plants and strengthens our predictive understanding of how plant populations will respond as Earth's climate rapidly changes.

Porewater constituents inhibit microbially mediated greenhouse gas production (GHG) and regulate the response of soil organic matter decomposition to warming in anoxic peat from a Sphagnum-dominated bog.

Northern peatlands store approximately one-third of terrestrial soil carbon. Climate warming is expected to stimulate the microbially mediated degradation of peat soil organic matter (SOM), leading to increasing greenhouse gas (GHG; carbon dioxide, CO2; methane, CH4) production and emission. Porewater dissolved organic matter (DOM) plays a key role in SOM decomposition; however, the mechanisms controlling SOM decomposition and its response to warming remain unclear. The temperature dependence of GHG production and microbial community dynamics were investigated in anoxic peat from a Sphagnum-dominated peatland. In this study, peat decomposition, which was quantified by GHG production and carbon substrate utilization is limited by terminal electron acceptors (TEA) and DOM, and these controls of microbially mediated SOM degradation are temperature-dependent. Elevated temperature led to a slight decrease in microbial diversity, and stimulated the growth of specific methanotrophic and syntrophic taxa. These results confirm that DOM is a major driver of decomposition in peatland soils contains inhibitory compounds, but the inhibitory effect is alleviated by warming.

Nutrient dynamics of 12 Sphagnum species during establishment on a rewetted bog.

Peatland degradation through drainage and peat extraction have detrimental environmental and societal consequences. Rewetting is an option to restore lost ecosystem functions, such as carbon storage, biodiversity and nutrient sequestration. Peat mosses (Sphagnum) are the most important peat-forming species in bogs. Most Sphagnum species occur in nutrient-poor habitats; however, high growth rates have been reported in artificial nutrient-rich conditions with optimal water supply. Here, we demonstrate the differences in nutrient dynamics of 12 Sphagnum species during their establishment in a 1-year field experiment at a Sphagnum paludiculture area in Germany. The 12 species are categorized into three groups (slower-, medium- and fast-growing). Establishment of peat mosses is facilitated by constant supply of nutrient-rich, low pH, and low alkalinity surface water. Our study shows that slower-growing species (S. papillosum, S. magellancium, S. fuscum, S. rubellum, S. austinii; often forming hummocks) displayed signs of nutrient imbalance. These species accumulated higher amounts of N, P, K and Ca in their capitula, and had an elevated stem N:K quotient (>3). Additionally, this group sequestered less C and K per m2 than the fast and medium-growing species (S. denticulatum, S. fallax, S. riparium, S. fimbriatum, S. squarrosum, S. palustre, S. centrale). Lower lawn thickness may have amplified negative effects of flooding in the slower-growing species. We conclude that nutrient dynamics and carbon/nutrient sequestration rates are species-specific. For bog restoration, generating ecosystem services or choosing suitable donor material for Sphagnum paludiculture, it is crucial to consider their compatibility with prevailing environmental conditions.

A multi-analytical approach to studying the chemical composition of typical carbon sink samples.

Peatlands in southern South America (Tierra del Fuego region, TdF) play a key role in the ecological dynamics of Patagonia. It is, therefore, necessary to increase our knowledge and awareness of their scientific and ecological value to ensure their conservation. This study aimed to assess the differences in the distribution and accumulation of elements in peat deposits and Sphagnum moss from the TdF. Chemical and morphological characterization of the samples was carried out using various analytical techniques, and total levels of 53 elements were determined. Furthermore, a chemometric differentiation based on the elemental content of peat and moss samples was performed. Some elements (Cs, Hf, K, Li, Mn, Na, Pb, Rb, Si, Sn, Ti and Zn) showed significantly higher contents in moss samples than in peat samples. In contrast, only Mo, S and Zr were significantly higher in peat samples than in moss samples. The results obtained highlight the ability of moss to accumulate elements and to act as a means to facilitate the entry of elements into peat samples. The valuable data obtained in this multi-methodological baseline survey can be used for more effective conservation of biodiversity and preservation of the ecosystem services of the TdF.