Growth of floating hook-moss (Warnstorfia fluitans) differs with nutrient and water flow adjustments in greenhouse and cold room conditions.

Floating hook-moss (Warnstorfia fluitans) is a bryophyte growing in northern aquatic and peatland ecosystems. W. fluitans uptakes metals and excessive amounts of nitrogen from wastewater, which suggests that it may have commercial potential for use in phytoremediation. Optimization of growth conditions would allow artificial cultivation of floating hook moss in large quantities for phytoremediation applications. We tested how application of combined nutrient (NPK 7-2-2 ranging from 0.1 to 1 ml per liter of water) and water flow (ranging from 0.15 to 1.9 ml/min) treatments affect growth of W. fluitans in greenhouse conditions. At the end of the experiment, all treatment combinations were subjected to an additional cold room condition at low temperature (0-2 °C) without constant water flow. The moss generally produced biomass in the various treatment combinations. However, contrary to our expectations, we found that increase of nutrients and water flow had a negative effect on the growth of W. fluitans. The highest growth rates in the experiment were detected in the control unit that had no nutrient addition or applied water flow. Our results suggest that cold temperatures are beneficial for W. fluitans growth. Our results show that the commercial production of W. fluitans may not require nutrient or water flow manipulation, at least in the tested scale. Instead, the growth conditions should mimic the natural cold climate conditions of W. fluitans habitats in northern peatlands and/or spring ecosystems.

Reindeer grazing history determines the responses of subarctic soil fungal communities to warming and fertilization.

Composition and functioning of arctic soil fungal communities may alter rapidly due to the ongoing trends of warmer temperatures, shifts in nutrient availability, and shrub encroachment. In addition, the communities may also be intrinsically shaped by heavy grazing, which may locally induce an ecosystem change that couples with increased soil temperature and nutrients and where shrub encroachment is less likely to occur than in lightly grazed conditions. We tested how 4 yr of experimental warming and fertilization affected organic soil fungal communities in sites with decadal history of either heavy or light reindeer grazing using high-throughput sequencing of the internal transcribed spacer 2 ribosomal DNA region. Grazing history largely overrode the impacts of short-term warming and fertilization in determining the composition of fungal communities. The less diverse fungal communities under light grazing showed more pronounced responses to experimental treatments when compared with the communities under heavy grazing. Yet, ordination approaches revealed distinct treatment responses under both grazing intensities. If grazing shifts the fungal communities in Arctic ecosystems to a different and more diverse state, this shift may dictate ecosystem responses to further abiotic changes. This indicates that the intensity of grazing cannot be left out when predicting future changes in fungi-driven processes in the tundra.

Association of prevalent vaginal microbiome of mother with occurrence of type I diabetes in child.

Type I diabetes (T1D) is a rapidly increasing autoimmune disease especially in the Western countries and poses a serious global health problem. Incidence of T1D cannot be fully explained by genetic background, and environmental factors have been assumed to play a role. Environmental conditions and composition of human microbiome have been found to correlate with the incidence of T1D. We asked whether mothers' prevalent vaginal microbiome could correlate with the incidence of T1D in child. To test this hypothesis, we collected samples of vaginal microbiomes from eight mothers that had at least one child with T1D (child age maximum of 11 years at the time of sampling), born with a vaginal delivery. Eight control mothers had child/children with vaginal delivery and no diabetic child/children. The microbiomes were studied by using 16S rRNA Ion Torrent high throughput sequencing. We found that composition of total and Lactobacillus microbiome was altered, and saw an indication that diversity of vaginal microbiomes of the mothers with a diabetic child could be higher. Based on these pilot observations, we strongly encourage a larger population study to verify whether mother vaginal microbiome diversity and composition are linked to the prevalence of T1D in children.

Moth outbreaks alter root-associated fungal communities in subarctic mountain birch forests.

Climate change has important implications on the abundance and range of insect pests in forest ecosystems. We studied responses of root-associated fungal communities to defoliation of mountain birch hosts by a massive geometrid moth outbreak through 454 pyrosequencing of tagged amplicons of the ITS2 rDNA region. We compared fungal diversity and community composition at three levels of moth defoliation (intact control, full defoliation in one season, full defoliation in two or more seasons), replicated in three localities. Defoliation caused dramatic shifts in functional and taxonomic community composition of root-associated fungi. Differentially defoliated mountain birch roots harbored distinct fungal communities, which correlated with increasing soil nutrients and decreasing amount of host trees with green foliar mass. Ectomycorrhizal fungi (EMF) abundance and richness declined by 70-80 % with increasing defoliation intensity, while saprotrophic and endophytic fungi seemed to benefit from defoliation. Moth herbivory also reduced dominance of Basidiomycota in the roots due to loss of basidiomycete EMF and increases in functionally unknown Ascomycota. Our results demonstrate the top-down control of belowground fungal communities by aboveground herbivory and suggest a marked reduction in the carbon flow from plants to soil fungi following defoliation. These results are among the first to provide evidence on cascading effects of natural herbivory on tree root-associated fungi at an ecosystem scale.

Moth herbivory enhances resource turnover in subarctic mountain birch forests?

Massive moth outbreaks cause large-scale damage in subarctic mountain birch forests with a concomitant decrease in carbon flux to mycorrhizal fungi and an increased deposition of dissolved carbon and nutrients as moth frass into soil. We investigated impacts of moth herbivory along three replicated gradients with three levels of moth herbivory (undamaged, once damaged, repeatedly damaged) on soil nutrient levels and biological parameters. We found an increase in soil nutrients and in the biomass of enchytraeid worms, which are key faunal decomposers. Fungi bacteria ratio and C:N ratio decreased in humus with increasing severity of herbivory. Our findings suggest enhanced resource turnover in mountain birch forests due to massive moth herbivory. This may provide a shortcut for carbon and nutrient input to subarctic soils, which largely bypasses the main routes of carbon from plants to soil via mycorrhizal and litter-decomposing fungi. Moreover, a temporal shift occurs in carbon allocation to soil, providing decomposers an opportunity to use an early-season peak in resource availability. Our results suggest a hitherto unappreciated role of massive insect herbivore attacks on resource dynamics in subarctic ecosystems.

Neighboring Deschampsia flexuosa and Trientalis europaea harbor contrasting root fungal endophytic communities.

Fungal endophytic communities and potential host preference of root-inhabiting fungi of boreal forest understory plants are poorly known. The objective of this study was to find out whether two neighboring plant species, Deschampsia flexuosa (Poaceae) and Trientalis europaea (Primulaceae), share similar root fungal endophytic communities and whether the communities differ between two sites. The study was carried out by analysis of pure culture isolates and root fungal colonization percentages. A total of 84 isolates from D. flexuosa and 27 isolates from T. europaea were obtained. The roots of D. flexuosa harbored 16 different isolate types based on macromorphological characteristics, whereas only 4 isolate types were found in T. europaea. The root colonization by dark septate and hyaline septate hyphae correlated with isolate numbers being higher in D. flexuosa compared to T. europaea. The different isolate types were further identified on the basis of internal transcribed spacer sequence and phylogenetic analysis. An isolate type identified as dark septate endophyte Phialocephala fortinii colonized 50 % of the T. europaea and 21 % of the D. flexuosa specimens. In addition, Meliniomyces variabilis, Phialocephala sphaeroides, and Umbelopsis isabellina were found colonizing the grass, D. flexuosa, for the first time and Mycena sp. was confirmed as an endophyte of D. flexuosa. Site-specific differences were observed in the abundance and diversity of endophytic fungi in the roots of both study plants, but the differences were not as predominant as those between plant species. It is concluded that D. flexuosa harbors both higher amount and more diverse community of endophytic fungi in its roots compared to T. europaea.

Mycorrhizal benefit in two low arctic herbs increases with increasing temperature.

Climate change may influence the relationship between arctic plants and their symbiotic mycorrhizal fungi. The benefit of the symbiosis for the host plant affects vegetation succession and may be a key parameter in predicting vegetation responses to warming. We investigated the mycorrhizal benefit in the low arctic perennial herbs Potentilla crantzii and Ranunculus acris in symbiosis with the arbuscular mycorrhizal fungus Glomus claroideum. Temperature response in the mycorrhiza-mediated acquisition of nitrogen (N) and phosphorus (P), growth, and photosynthetic nutrient-use efficiency were determined. Near the average natural soil temperature (12°C), mycorrhiza did not improve plant nutrient capture but significantly enhanced plant P capture at 17°C. Photosynthetic nitrogen-use efficiency was higher at 17°C than at 12°C and was further increased by mycorrhiza at 17°C. Photosynthetic phosphorus-use efficiency was not affected by temperature or mycorrhiza. Increasing the growing temperature by 5°C increased the relative shoot growth rate by 15%. Mycorrhizal symbiosis did not enhance plant growth rate, but the plants gained between 20% and 90% more mycorrhiza-mediated P when grown at higher temperature. The results suggest that these low arctic species have good potential to respond positively to increasing temperatures.

Root fungal colonisation in Deschampsia flexuosa: effects of pollution and neighbouring trees.

In industrial barrens adjacent to a nickel-copper smelter at Monchegorsk, the Kola Peninsula, root colonisation in Deschampsia flexuosa by arbuscular mycorrhizal (AM)-type of hyphae was lower than in unpolluted forests (60.9 vs. 80.4%), while Olpidium-colonisation showed a marginally significant decline, and dark septate endophytic (DSE) hyphal colonisation was not affected. We detected an interactive effect of pollution and a neighbouring tree on DSE hyphal colonisation: at the highly polluted sites, colonisation was lower in D. flexuosa growing near trees, whereas at sites with low pollution the presence of the neighbouring tree had no effect on colonisation. High numbers of intracellular DSE sclerotia in the industrial barrens (13.3 vs. 3.4%) may indicate a survial strategy in an unfavourable environment and a dispersal strategy into a more favourable environment. While lower root colonisation by AM fungi has been also earlier reported in graminoids for heavy metal contamination, the results on other ubiquitous fungi colonising D. flexuosa roots are more novel.

Mycorrhiza does not alter low temperature impact on Gnaphalium norvegicum.

Extreme arctic-alpine vegetation has relatively low affinity to form mycorrhizal symbiosis. We asked whether the mycorrhizal growth benefit for the host plant is lower at low temperatures. We investigated the role of two root-associated fungi and temperature in growth, carbon-nitrogen relations and germination of an arctic-alpine herb. Seeds of Gnaphalium norvegicum were germinated at 8 degrees or 15 degrees C with or without arbuscular mycorrhizal (AM, Glomus claroideum) and dark septate endophytic (DSE, Phialocephala fortinii) inocula in a climate chamber. We found that germination percentage, shoot and root biomass, shoot N% and root AM colonization were lower at 8 degrees C than at 15 degrees C. P. fortinii inoculation had a positive impact on germination at both temperatures, whereas G. claroideum produced no effect. N% was lower in AM plants at both temperatures. Plant biomass and shoot N content were higher in AM plants than in control plants at 15 degrees C, but not at 8 degrees C. DSE inoculation tended also to have positive effects on plant biomass and N content at 15 degrees C. At 15 degrees C, rate of photosynthesis, photosynthetic nutrient use efficiency and specific leaf area were positively affected by G. claroideum, which suggests that G. claroideum formed a carbon sink and possibly enhanced the seedling water economy. The positive effects of P. fortinii were probably due to its saprotrophic function in the substrate because it did not colonize the roots. These results suggest that the effects of AM and DSE on plant growth are affected by temperature and that the mycorrhizal benefit for the host plant was lower at the lower temperature. Low saprotrophic activity and decreased mycorrhiza-mediated nutrient acquisition may thus constrain plant nutrient acquisition in cold environments. Decreased mycorrhizal benefit may be related to the comparatively low mycotrophy of cold environment vegetation.

The modelled growth of mycorrhizal and non-mycorrhizal plants under constant versus variable soil nutrient concentration.

We studied the response of mycorrhizal and non-mycorrhizal plants to variation in soil nutrient concentration. A model for the relative growth rate (RGR) of plant biomass was constructed with soil nutrients as an explanatory variable. A literature survey was carried out to find the relative magnitudes of parameter values for mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants had higher RGR at low nutrient concentrations and non-mycorrhizal plants at high nutrient concentrations. The RGR of mycorrhizal and non-mycorrhizal plants at constant versus log-normally distributed soil nutrient concentration were compared to see the effect of mycorrhizal status on responses to variation. Variation in nutrient concentration generally reduced RGR, especially in mycorrhizal plants. The RGR of a non-mycorrhizal plant may increase with variation where a growth function threshold exists, i.e. a soil nutrient concentration that must be exceeded to allow growth. Mycorrhizal plants appeared more sensitive to variation in nutrient concentration than non-mycorrhizal plants due to the higher affinity of mycorrhizal roots at low nutrient levels. However, this prediction may be reversed if mycorrhizal symbiosis considerably stabilises flow of nutrients to plant physiological processes, such that mycorrhizal plants experience less variation in soil nutrient concentration than non-mycorrhizal plants. Our results also attain broader significance by suggesting a general trade-off between competitive ability in a constant versus variable resource availability.