Unknown effects of daily-scale solar activity on the plant growth: Data from 6-year growth monitoring of Sphagnum riparium.

The influence of solar activity on plant growth has been studied for over 100 years, however, this phenomenon is still poorly understood on a daily scale. The data from extensive monitoring of the growth of peat moss Sphagnum riparium, which we are conducting in the mires of Karelia (Russia), may shed light on this issue. During the 6 years of observation, 161,190 shoots were measured, and 1075 growth rates were obtained. Considering together the growth rates with the sunspot number and involving data on seasonal temperature, we found previously unknown effects of daily-scale solar activity on plant growth. It was found that the sunspot number weakly but significantly inhibits the growth of Sphagnum. The extreme sunspot number in the 4 days before the growth rate values have a stronger influence. The involvement of temperature data showed that inhibition in growth is observed only in the temperature range from 6.7°C to 15.3°C and disappears beyond these limits. In addition, the data obtained showed that the influence of sunspot number on the growth of Sphagnum is progressively increasing along the gradient from the minimum to the maximum of the 11-year solar cycle. The study provides one of the first results on the effect of solar activity on plant growth on a daily scale. The results expand our knowledge of the biological effects of solar activity. Indirectly, they can also be useful to better our understanding of the ozone layer's involvement in this process.

Variation in symbiotic N2 fixation rates among Sphagnum mosses.

Biological nitrogen (N) fixation is an important process supporting primary production in ecosystems, especially in those where N availability is limiting growth, such as peatlands and boreal forests. In many peatlands, peat mosses (genus Sphagnum) are the prime ecosystem engineers, and like feather mosses in boreal forests, they are associated with a diverse community of diazotrophs (N2-fixing microorganisms) that live in and on their tissue. The large variation in N2 fixation rates reported in literature remains, however, to be explained. To assess the potential roles of habitat (including nutrient concentration) and species traits (in particular litter decomposability and photosynthetic capacity) on the variability in N2 fixation rates, we compared rates associated with various Sphagnum moss species in a bog, the surrounding forest and a fen in Sweden. We found appreciable variation in N2 fixation rates among moss species and habitats, and showed that both species and habitat conditions strongly influenced N2 fixation. We here show that higher decomposition rates, as explained by lower levels of decomposition-inhibiting compounds, and higher phosphorous (P) levels, are related with higher diazotrophic activity. Combining our findings with those of other studies, we propose a conceptual model in which both species-specific traits of mosses (as related to the trade-off between rapid photosynthesis and resistance to decomposition) and P availability, explain N2 fixation rates. This is expected to result in a tight coupling between P and N cycling in peatlands.

Sphagnum growth under N saturation: interactive effects of water level and P or K fertilization.

Sphagnum biomass is a promising material that could be used as a substitute for peat in growing media and can be sustainably produced by converting existing drainage-based peatland agriculture into wet, climate-friendly agriculture (paludiculture). Our study focuses on yield maximization of Sphagnum as a crop. We tested the effects of three water level regimes and of phosphorus or potassium fertilization on the growth of four Sphagnum species (S. papillosum, S. palustre, S. fimbriatum, S. fallax). To simulate field conditions in Central and Western Europe we carried out a glasshouse experiment under nitrogen-saturated conditions. A constant high water table (remaining at 2 cm below capitulum during growth) led to highest productivity for all tested species. Water table fluctuations between 2 and 9 cm below capitulum during growth and a water level 2 cm below capitulum at the start but falling relatively during plant growth led to significantly lower productivity. Fertilization had no effect on Sphagnum growth under conditions with high atmospheric deposition such as in NW Germany (38 kg N, 0.3 kg P, 7.6 kg K·ha-1 ·year-1 ). Large-scale maximization of Sphagnum yields requires precise water management, with water tables just below the capitula and rising with Sphagnum growth. The nutrient load in large areas of Central and Western Europe from atmospheric deposition and irrigation water is high but, with an optimal water supply, does not hamper Sphagnum growth, at least not of regional provenances of Sphagnum.

Spatial heterogeneity of belowground microbial communities linked to peatland microhabitats with different plant dominants.

Peatland vegetation is composed mostly of mosses, graminoids and ericoid shrubs, and these have a distinct impact on peat biogeochemistry. We studied variation in soil microbial communities related to natural peatland microhabitats dominated by Sphagnum, cotton-grass and blueberry. We hypothesized that such microhabitats will be occupied by structurally and functionally different microbial communities, which will vary further during the vegetation season due to changes in temperature and photosynthetic activity of plant dominants. This was addressed using amplicon-based sequencing of prokaryotic and fungal rDNA and qPCR with respect to methane-cycling communities. Fungal communities were highly microhabitat-specific, while prokaryotic communities were additionally directed by soil pH and total N content. Seasonal alternations in microbial community composition were less important; however, they influenced the abundance of methane-cycling communities. Cotton-grass and blueberry bacterial communities contained relatively more α-Proteobacteria but less Chloroflexi, Fibrobacteres, Firmicutes, NC10, OD1 and Spirochaetes than in Sphagnum. Methanogens, syntrophic and anaerobic bacteria (i.e. Clostridiales, Bacteroidales, Opitutae, Chloroflexi and Syntrophorhabdaceae) were suppressed in blueberry indicating greater aeration that enhanced abundance of fungi (mainly Archaeorhizomycetes) and resulted in the highest fungi-to-bacteria ratio. Thus, microhabitats dominated by different vascular plants are inhabited by unique microbial communities, contributing greatly to spatial functional diversity within peatlands.

Dispersal limitations and historical factors determine the biogeography of specialized terrestrial protists.

Recent studies show that soil eukaryotic diversity is immense and dominated by micro-organisms. However, it is unclear to what extent the processes that shape the distribution of diversity in plants and animals also apply to micro-organisms. Major diversification events in multicellular organisms have often been attributed to long-term climatic and geological processes, but the impact of such processes on protist diversity has received much less attention as their distribution has often been believed to be largely cosmopolitan. Here, we quantified phylogeographical patterns in Hyalosphenia papilio, a large testate amoeba restricted to Holarctic Sphagnum-dominated peatlands, to test if the current distribution of its genetic diversity can be explained by historical factors or by the current distribution of suitable habitats. Phylogenetic diversity was higher in Western North America, corresponding to the inferred geographical origin of the H. papilio complex, and was lower in Eurasia despite extensive suitable habitats. These results suggest that patterns of phylogenetic diversity and distribution can be explained by the history of Holarctic Sphagnum peatland range expansions and contractions in response to Quaternary glaciations that promoted cladogenetic range evolution, rather than the contemporary distribution of suitable habitats. Species distributions were positively correlated with climatic niche breadth, suggesting that climatic tolerance is key to dispersal ability in H. papilio. This implies that, at least for large and specialized terrestrial micro-organisms, propagule dispersal is slow enough that historical processes may contribute to their diversification and phylogeographical patterns and may partly explain their very high overall diversity.

Deposition of mullite in peatlands of southern Poland: Implications for recording large-scale industrial processes.

Mullite, a pure aluminosilicate (Al6Si2O13), is a rare natural rock component, known for centuries as a very resistant ceramic material. It is also a common waste product of high-temperature coal combustion that is emitted in quantity from coal-based power stations. The occurrence of mullite in two Sphagnum-dominated peatlands located near the Upper Silesia industrial region in southern Poland is described. For the first time, a complete record of mullite deposition in the peat profiles has been obtained by XRD analyses of ashed peat samples. The mullite distribution is compared with records of Hg, Pb and Cu. While mullite is supplied during high temperature processes only, Cu, Pb and Hg show more complex pattern of distribution. Both peat profiles contain elevated amounts of mullite in the time span between ca 1950-1990 with a maximum content in ca 1980. The first appearance (∼1900) of mullite is indicative of the beginning of energy production in coal-based power plants in the region. Mullite is proposed here as an indicator of industrialization in geological records. It is resistant to post-depositional processes, emitted globally, and restricted to large-scale industry.

Soil nitrogen determines greenhouse gas emissions from northern peatlands under concurrent warming and vegetation shifting.

Boreal peatlands store an enormous pool of soil carbon that is dependent upon - and vulnerable to changes in - climate, as well as plant community composition. However, how nutrient availability affects the effects of climate and vegetation change on ecosystem processes in these nutrient-poor ecosystems remains unclear. Here we show that although warming promoted higher CH4 emissions, the concurrent addition of N counteracted most (79%) of this effect. The regulation effects of the vegetation functional group, associated with the substrate quality, suggest that CH4 emissions from peatlands under future warming will be less than expected with predicted shrub expansion. In contrast, N2O flux will be enhanced under future warming with predicted shrub expansion. Our study suggests that changes in greenhouse gas emissions in response to future warming and shifts in plant community composition depend on N availability, which reveals the complex interactions that occur when N is not a limiting nutrient.

Quantitative analysis of self-organized patterns in ombrotrophic peatlands.

We numerically investigate a diffusion-reaction model of an ombrotrophic peatland implementing a Turing instability relying on nutrient accumulation. We propose a systematic and quantitative sorting of the vegetation patterns, based on the statistical analysis of the numbers and filling factor of clusters of both Sphagnum mosses and vascular plants. In particular, we define the transition from Sphagnum-percolating to vascular plant-percolating patterns as the nutrient availability is increased. Our pattern sorting allows us to characterize the peatland pattern stability under climate stress, including strong drought.

Hydrology-driven environmental variability determines abiotic characteristics and Oribatida diversity patterns in a Sphagnum peatland system.

We investigated oribatid mite communities in a Sphagnum-dominated boreal peatland system characterised by a mosaic of oligotrophic and meso-eutrophic areas. We aimed to determine the relative importance of environmental factors (pH, Sphagnum nutrient content, water table level, diversity of vascular plants and bryophytes in the surrounding plant community) and spatial variation in influencing abundance, diversity and community composition of aquatic and terrestrial oribatid mites. Among environmental variables, water table level (micro-topography), pH, and K in Sphagnum tissues were the main predictors of Oribatida community structure. Aquatic species were associated with pools; two terrestrial species-Hoplophthiracarus illinoisensis and Nothrus pratensis-were associated with oligotrophic hummocks; the rest of terrestrial species were associated with dryer mesotrophic and eutrophic habitats. Low water table depth (hummocks), high local plant diversity, and high P in Sphagnum tissues were predictors of high abundance of terrestrial Oribatida. Species richness of terrestrial Oribatida was linked with low water table and high plant diversity. For aquatic Oribatida abundance, water table depth was the single most important predictor variable. Plot trophic class (its status on the peatland poor-rich gradient assigned based on plant indicator species) was also a significant predictor of terrestrial Oribatida abundance, richness, and community structure. Spatial structuring was important for terrestrial Oribatida community composition, weak (P < 0.10) for terrestrial Oribatida abundance and richness, and not significant for aquatic Oribatida.

Development of a method for protonema proliferation of peat moss (Sphagnum squarrosum) through regeneration analysis.

The moss Sphagnum (peat moss) is ecologically and economically important. There is a paucity of physiological and developmental studies on Sphagnum because of the lack of an axenic culture system for its whole life cycle. A culture system has been established for the Sphagnum gametophore, but not the protonema (juvenile vegetative stage after spore germination). Therefore, the aim of this study was to develop a protonema culture system for Sphagnum. Sphagnum squarrosum gametophore tissue was disrupted and then cultured in liquid Knop medium. The regeneration of protonemata from the gametophore fragments was analyzed in detail by microscopy. We observed a developmental balance between filamentous and thalloid protonemata, and growth competition between the thalloid protonema and the gametophore. On the basis of these findings, we established a relatively stable peat moss protonema proliferation method. Using this method, all the developmental stages of peat moss vegetative growth could be obtained through differentiation or regeneration. The method can provide abundant homogeneous Sphagnum materials at desired stages for physiological and developmental studies, and will be useful for large-scale Sphagnum vegetative proliferation. The regeneration analysis method will be useful for establishing protonema proliferation systems for other mosses.

Impacts of prescribed burning on Sphagnum mosses in a long-term peatland field experiment.

Understanding fire impacts on peatland vegetation can inform management to support function and prevent degradation of these important ecosystems. However, time since burn, interval between burns and number of past burns all have the potential to modify impacts. Grazing regime may also affect vegetation directly or via an interaction with burning. We used new, comprehensive survey data from a hillslope-scale field experiment initiated in 1954 to investigate the effects of burning and grazing treatments on Sphagnum. Historical data were consulted to aid interpretation of the results. The unburned reference and the most frequently burned (10-year rotation) treatments had greater Sphagnum abundance and hummock height than intermediate treatments (20-year rotation and no-burn since 1954). Abundance of the most common individual species (S. capillifolium, S. subnitens and S. papillosum) followed similar patterns. Light grazing had no impact on Sphagnum-related variables, nor did it interact with the burning treatments.These results suggest that in some cases fire has a negative impact on Sphagnum, and this can persist for several decades. However, fire return interval and other factors such as atmospheric pollution may alter effects, and in some cases Sphagnum abundance may recover. Fire severity and site specific conditions may also influence effects, so we advise consideration of these factors, and caution when using fire as a management tool on peatlands where Sphagnum is considered desirable.

Diversity of Active Viral Infections within the Sphagnum Microbiome.

Sphagnum-dominated peatlands play an important role in global carbon storage and represent significant sources of economic and ecological value. While recent efforts to describe microbial diversity and metabolic potential of the Sphagnum microbiome have demonstrated the importance of its microbial community, little is known about the viral constituents. We used metatranscriptomics to describe the diversity and activity of viruses infecting microbes within the Sphagnum peat bog. The vegetative portions of six Sphagnum plants were obtained from a peatland in northern Minnesota, and the total RNA was extracted and sequenced. Metatranscriptomes were assembled and contigs were screened for the presence of conserved virus marker genes. Using bacteriophage capsid protein gp23 as a marker for phage diversity, we identified 33 contigs representing undocumented phages that were active in the community at the time of sampling. Similarly, RNA-dependent RNA polymerase and the nucleocytoplasmic large DNA virus (NCLDV) major capsid protein were used as markers for single-stranded RNA (ssRNA) viruses and NCLDV, respectively. In total, 114 contigs were identified as originating from undescribed ssRNA viruses, 22 of which represent nearly complete genomes. An additional 64 contigs were identified as being from NCLDVs. Finally, 7 contigs were identified as putative virophage or polinton-like viruses. We developed co-occurrence networks with these markers in relation to the expression of potential-host housekeeping gene rpb1 to predict virus-host relationships, identifying 13 groups. Together, our approach offers new tools for the identification of virus diversity and interactions in understudied clades and suggests that viruses may play a considerable role in the ecology of the Sphagnum microbiome.IMPORTANCESphagnum-dominated peatlands play an important role in maintaining atmospheric carbon dioxide levels by modifying conditions in the surrounding soil to favor the growth of Sphagnum over that of other plant species. This lowers the rate of decomposition and facilitates the accumulation of fixed carbon in the form of partially decomposed biomass. The unique environment produced by Sphagnum enriches for the growth of a diverse microbial consortia that benefit from and support the moss's growth, while also maintaining the hostile soil conditions. While a growing body of research has begun to characterize the microbial groups that colonize Sphagnum, little is currently known about the ecological factors that constrain community structure and define ecosystem function. Top-down population control by viruses is almost completely undescribed. This study provides insight into the significant viral influence on the Sphagnum microbiome and identifies new potential model systems to study virus-host interactions in the peatland ecosystem.

Peat moss Sphagnum riparium follows a circatrigintan growth rhythm in situ: A case report.

In situ growth of Sphagnum riparium Ångstr. shoots were monitored during the 2015 and 2016 growing seasons in Karelia, Russia. It was established that shoot growth rates fluctuated with a period of around 30 days, that is, showed a circatrigintan rhythm. Such rhythms from mosses have not been previously reported. Correlation of growth rates with the percentage of the illuminated portion of the Moon was statistically significant (p<0.01) in both years. Shoot growth rates were reliably higher around the new Moon compared to the full Moon. This phenomenon may be due either to causality or to a pure coincidence of processes with similar rhythms.

Sphagnum establishment in alkaline fens: Importance of weather and water chemistry.

Sphagnum expansion to alkaline fens has accelerated during the last decades in Europe, leading to changes in diversity, habitat distributions and carbon storage. The causes are still not clearly understood and involve an interplay between climate change, hydrology, nutrient supply and Sphagnum physiology. We conducted a 4-year field experiment in eight fens in Central European highlands and assessed survival and establishment of individual apical shoot fragments of S. flexuosum, S. warnstorfii and S. squarrosum transplanted along the microtopographical gradient. In a laboratory experiment, we tested combined effects of desiccation and high calcium bicarbonate concentration on Sphagnum survival. We found that in unflooded positions, living shoots of Sphagnum and brown mosses lowered [Ca2+] and pH in their capillary water, in contrast to dead fragments; yet without differences between species. Survival and expansion of Sphagnum fragments, which did not die of acute calcium toxicity during first weeks/months, was negatively affected by dry weather and alkaline water chemistry, reflecting Sphagnum intolerance to desiccation and to combined high [Ca2+] and pH. Shoot fragments expanded to patches only when precipitation was high. Interestingly, non-toxic concentration of calcium bicarbonate reduced desiccation damage in Sphagnum, probably through protection of membranes or other cell components. This mechanism would facilitate Sphagnum survival in elevated, frequently desiccated microhabitats of calcareous fens such as brown-moss hummocks. However, since water-retaining capacity of few Sphagnum shoots is insufficient to change water chemistry in its surroundings, surface acidification may occur only once the environment (e.g. sufficient humidity) enabled expansion to larger mats. Then, the retained rainwater together with hardly decomposable Sphagnum litter would separate mire surface from groundwater, speeding up successional shift towards poor fens. Sphagnum expansion to alkaline fens is therefore more likely in humid regions.

Enhanced winter soil frost reduces methane emission during the subsequent growing season in a boreal peatland.

Winter climate change may result in reduced snow cover and could, consequently, alter the soil frost regime and biogeochemical processes underlying the exchange of methane (CH4 ) in boreal peatlands. In this study, we investigated the short-term (1-3 years) vs. long-term (11 years) effects of intensified winter soil frost (induced by experimental snow exclusion) on CH4 exchange during the following growing season in a boreal peatland. In the first 3 years (2004-2006), lower CH4 emissions in the treatment plots relative to the control coincided with delayed soil temperature increase in the treatment plots at the beginning of the growing season (May). After 11 treatment years (in 2014), CH4 emissions were lower in the treatment plots relative to the control over the entire growing season, resulting in a reduction in total growing season CH4 emission by 27%. From May to July 2014, reduced sedge leaf area coincided with lower CH4 emissions in the treatment plots compared to the control. From July to August, lower dissolved organic carbon concentrations in the pore water of the treatment plots explained 72% of the differences in CH4 emission between control and treatment. In addition, greater Sphagnum moss growth in the treatment plots resulted in a larger distance between the moss surface and the water table (i.e., increasing the oxic layer) which may have enhanced the CH4 oxidation potential in the treatment plots relative to the control in 2014. The differences in vegetation might also explain the lower temperature sensitivity of CH4 emission observed in the treatment plots relative to the control. Overall, this study suggests that greater soil frost, associated with future winter climate change, might substantially reduce the growing season CH4 emission in boreal peatlands through altering vegetation dynamics and subsequently causing vegetation-mediated effects on CH4 exchange.

Factors affecting re-vegetation dynamics of experimentally restored extracted peatland in Estonia.

Increasing human activity continues to threaten peatlands, and as the area of natural mires declines, our obligation is to restore their ecosystem functions. Several restoration strategies have been developed for restoration of extracted peatlands, including "The moss layer transfer method", which was initiated on the Tässi extracted peatland in central Estonia in May 2012. Three-year study shows that despite the fluctuating water table, rainfall events can compensate for the insufficient moisture for mosses. Total plant cover on the restoration area attained 70 %, of which ~60 % is comprised of target species-Sphagnum mosses. From restoration treatments, spreading of plant fragments had a significant positive effect on the cover of bryophyte and vascular plants. Higher water table combined with higher plant fragments spreading density and stripping of oxidised peat layer affected positively the cover of targeted Sphagnum species. The species composition in the restoration area became similar to that in the donor site in a natural bog. Based on results, it was concluded that the method approved for restoration in North America gives good results also in the restoration of extracted peatland towards re-establishment of bog vegetation under northern European conditions.

[Effect of fires on phytomass and primary production dynamics of the mesotrophic undershrub-sphagnum bog in the Amur region].

Data are presented on the dynamics of phytomass and primary production of the undershrub-sphagnum bog. Comparison of productivity parameters in sites with unimpaired and bumt-out vegetation is used as a method of analysis of the phytocenosis functioning during its 6-year recovery after a fire. Net primary production varied from 4.9 to 9.6 tons/ha • yr in the unimpaired bog site and from 5.3 to 15.1 tons/ha • yr in the burnt-out one. By the end of the fifth year of recovery, the phytocenosis fully compensated the loss of carbon due to the fire, mainly at the expense of roots production. Recurrent fires have a result of more profound changes in phytomass structure and reduction of primary production.

Short-Term Summer Inundation as a Measure to Counteract Acidification in Rich Fens.

In regions with intensive agriculture, water level fluctuation in wetlands has generally become constricted within narrow limits. Water authorities are, however, considering the re-establishment of fluctuating water levels as a management tool in biodiverse, base-rich fens ('rich fens'). This includes temporary inundation with surface water from ditches, which may play an important role in counteracting acidification in order to conserve and restore biodiversity. Inundation may result in an increased acid neutralizing capacity (ANC) for two reasons: infiltration of base-rich inundation water into peat soils, and microbial alkalinity generation under anaerobic conditions. The main objectives of this study were to test whether short-term (2 weeks) summer inundation is more effective than short-term winter inundation to restore the ANC in the upper 10 cm of non-floating peat soils, and to explain potential differences. Large-scale field experiments were conducted for five years in base-rich fens and Sphagnum-dominated poor fens. Winter inundation did not result in increased porewater ANC, because infiltration was inhibited in the waterlogged peat and evapotranspiration rates were relatively low. Also, low temperatures limit microbial alkalinity generation. In summer, however, when temperature and evapotranspiration rates are higher, inundation resulted in increased porewater Ca and HCO3- concentrations, but only in areas with characteristic rich fen bryophytes. This increase was not only due to stronger infiltration into the soil, but also to higher microbial alkalinity generation under anaerobic conditions. In contrast, porewater ANC did not increase in Sphagnum-plots as a result of the ability of Sphagnum spp. to acidify their environment. In both rich and poor fens, flooding-induced P-mobilization remained sufficiently low to safeguard P-limited vegetation. NO3(-) and NH4(+) dynamics showed no considerable changes either. In conclusion, short-term summer inundation with base-rich and nutrient-poor surface water is considered beneficial in the management of non-floating rich fens, and much more effective than winter inundation.

Testing the Effect of Refrigerated Storage on Testate Amoeba Samples.

Samples for analysis of testate amoebae and other protists frequently need to be stored for many months before microscopy. This storage commonly involves refrigeration, but we know that testate amoebae can live and reproduce in these conditions. This raises the question: do communities change during storage and how might this effect the data produced? We analysed Sphagnum samples over a 16-week period to address this question. Our results show no evidence for detectable change. This is a reassuring result supporting much current practice although we suggest that frozen storage or the addition of a fixative may be worthwhile precautions where feasible.