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1. Arctic ecosystems are experiencing rapid climate change, which could result in positive feedbacks on climate warming if ecosystem carbon (C) loss exceeds C uptake through plant growth. Bryophytes (mosses, liverworts and hornworts) are important components of Arctic vegetation, but are currently not well represented in terrestrial C models; in particular, seasonal patterns in bryophyte C metabolism compared to vascular plant vegetation are poorly understood. 2. Our objective was to quantify land-surface CO fluxes for common sub-Arctic bryophyte patches (dominated by Polytrichum piliferum and Sphagnum fuscum) in spring (March-May) and during the summer growing season (June-August) and to develop a simple model of bryophyte gross primary productivity fluxes (P B ). We use the model to explore the key environmental controls over P B for P. piliferum and S. fuscum and compare seasonal patterns of productivity with those of typical vascular plant communities at the same site. 3. The modelled total gross primary productivity (∑P B ) over 1 Year (March November) for P. piliferum was c. 360 g C m² ground and for S. fuscum c. 112 g C m ² ground, c. 90% and 30% of total gross primary productivity for typical vascular plant communities (∑P v ) over the same year. In spring (March-May), when vascular plant leaves are not fully developed, ∑P B for P. piliferum was 3 x ∑P V 4. Model sensitivity analysis indicated that bryophyte turf water content does not significantly affect (March-November) ∑P B for P. piliferum and S. fuscum, at least for periods without sustained lack of precipitation. However, we find that seasonal changes in bryophyte photosynthetic capacity are important in determining ∑P B for both bryophyte species. 5. Our study implies that models of C dynamics in the Arctic must include a bryophyte component if they are intended to predict the effects of changes in the timing of the growing season, or of changes in vegetation composition, on Arctic C balance.

Bryophytes and lichens are ubiquitous in subarctic ecosystems, but their roles in controlling energy fluxes are rarely studied at the species level despite large, recent observed shifts in subarctic vegetation. We quantified the surface and subsurface temperatures and spectral reflectance of common moss and lichen species at field sites in Alaska and Sweden. We also used MODIS observations to determine if the removal of Cladonia spp. by reindeer overgrazing impacts land surface albedo and temperature. Radiometric surface temperature of a feather moss (Pleurozium schreberi) exceeded 50 °C on occasion when dry, up to 20 °C higher than co-located Sphagnum fuscum or C. rangiferina. Spectral reflectance of S. fuscum was on average higher than Polytrichum piliferum across the 350–1400 nm range, with substantial within-species variability. MODIS albedo was significantly higher on the Norwegian (relatively undisturbed) side versus the Finnish (disturbed) side of a border reindeer fence by an average of 1% during periods without snow cover. MODIS nighttime land surface temperatures were often significantly higher on the Norwegian side of the fence by an average of 0.7 °C despite higher albedo, likely due to poor conductance of heat to the subsurface as observed in C. rangiferina in the field. Changes to bryophyte and lichen community composition alter the surface energy balance, and future work must determine how to best incorporate these effects into Earth system models.

Background and aims Two inland dunes in the Netherlands receiving low (24) and high (41 kg N ha⁻¹ yr⁻¹) nitrogen (N) deposition were compared for N dynamics and microbial activity to investigate the potential effect of N on succession rate of the vegetation and loss of pioneer habitats. Methods Primary succession stages were sampled, including bare sand, and vegetation dominated by Polytrichum piliferum, Campylopus introflexus, lichens and grasses respectively, representing a series of vegetation types in undisturbed drift sand sites with succession starting on bare sand containing virtually no organic matter. Microbial characteristics and potential N mineralization were analysed in a laboratory experiment. Results Organic matter accumulated during succession, resulting in a lower pH and in higher microbial biomass (bacteria and fungi), respiration and net N mineralization. The increase in respiration and N mineralization was largely due to the development of an ectorganic layer in the middle stages of succession. The observed effects of N deposition were (1) decrease of microbial biomass, (2) higher net N mineralization per m², (3) higher levels of free nitrogen in the soil, and (4) a higher microbial N:P ratio. Conclusions Elevated N deposition leads to higher N availability which may cause accelerated succession.

Question: Does the neophyte moss Campylopus introflexus invade more often in drift sand pioneer vegetations under high nitrogen (N) deposition? Location: Fourteen inland dune reserves in The Netherlands over a gradient of atmospheric N deposition. Methods: A transect study, dispersal experiment and culture experiment were carried out. In the transect study, the establishment of C. introflexus and lichens was measured in pure mats of Polytrichum piliferum, an early succession stage. The overall presence of C. introflexus in the area was also estimated. In the dispersal experiment, fragments of C. introflexus and lichen species were sown in P. piliferum mats at two sites with high and low N deposition. In the culture experiment C. introflexus fragments were grown on soil with different carbon (C) content and N dose. Results: The Campylopus:lichen ratio was positively correlated (r2=0.61) with the atmospheric ammonia concentration. Campylopus began to dominate at an ammonia air concentration of 7 micrograms m-3, correlated with the overall presence of the species in the sites investigated. Survival of sown Campylopus fragments was significantly higher and the endangered lichen Cladonia strepsilis significantly lower in the site with a high ammonia concentration. Survival of Cladonia coccifera and Cladonia portentosa was high at both sites. Experimental growing of C. introflexus showed significant responses to both C content and N, although C content showed the strongest effect. Conclusions: Growth of C. introflexus is affected by soil C content and N deposition. Inland dune reserves under high N deposition risk loss of lichen-dominated vegetations because of moss encroachment.

Carbon (C) allocation and turnover in arctic bryophytes is largely unknown, but their response to climatic change has potentially significant impacts on arctic ecosystem C budgets. Using a combination of pulse-chase experiments and a newly developed model of C turnover in bryophytes, we show significant differences in C turnover between two contrasting arctic moss species (Polytrichum piliferum and Sphagnum fuscum). ¹³C abundance in moss tissues (measured up to 1 year) and respired CO₂ (traced over 5 days) were used to parameterise the bryophyte C model with four pools representing labile and structural C in photosynthetic and stem tissue. The model was optimised using an Ensemble Kaiman Filter to ensure a focus on estimating the confidence intervals (CI) on model parameters and outputs. The ratio of aboveground NPP:GPP in Polytrichum piliferum was 23% (CI 9-35%), with an average turnover time of 1.7 days (CI 1.1-2.5 days). The aboveground NPP:GPP ratio in Sphagnum fuscum was 43% (CI 19-65%) with an average turnover time of 3.1 days (CI 1.6-6.1 days). These results are the first to show differences in C partitioning between arctic bryophyte species in situ and highlight the importance of modelling C dynamics of this group separately from vascular plants for a realistic representation of vegetation in arctic C models.

Question: To which extent do external ecological factors effect Corynephorus grassland vegetation? Location: Central Netherlands. Methods: We implemented different treatments (sand deposition, litter deposition, nitrogen input, mechanical disturbance, control) in permanent plots representing different successional phases in Corynephorus grassland. Plots were recorded just before the treatments and during the subsequent two years. Vegetation changes were analysed by Redundancy Analysis for repeated measurements and Correspondence Analysis, changes in single species abundances by ANOVA. Results: Species composition hardly changed during the observation period. Several single species abundances showed significant responses to different treatments, most often decrements as direct effects of cover, removal, or dieback. However, Corynephorus canescens and Polytrichum piliferum benefited from sand deposition, the exotic moss Campylopus introflexus from litter deposition. In the colonization phase Polytrichum, Campylopus and Cladonia diversa increased irrespective treatment. Therophytes such as Spergula morisonii showed the strongest negative response to drought, grasses (e.g. Corynephorus canescens) and bryophytes (e.g. Polytrichum piliferum) were less susceptible. Most lichens did not respond at all. Conclusions: The experiment confirms the high stability of Corynephorus grassland vegetation. Most vegetation changes are in accordance with the hypothetical series of successional phases. In contrast, changes in abundance of single species express considerable dynamics within the vegetation. Species responses also depend on extreme weather conditions as well as on the successional phase of the grassland vegetation and therefore on the competition situation. Abbreviations: CA = Correspondence Analysis; RDA = Redundancy Analysis. Nomenclature: Wisskirchen & Haeupler (1998) for vascular plants; Koperski et al. (2000) for bryophytes; van Herk & Aptroot (2004) for lichens; Ettl & Gärtner (1995) for algae.

Background, Aims and Scope. Pollution by heavy metals over large areas and long periods of time may cause chronic damage to living organisms and must be carefully controlled. One way to determine the extent of environmental contamination is by measuring the levels of contaminants in plants. The use of mosses as biomonitors is a convenient method to determine levels of (atmospheric) deposition, as terrestrial mosses obtain most of their supply of mineral elements from precipitation and dry deposition of airborne particles. Mosses have therefore received increasing attention as a suitable tool for monitoring regional patterns of elemental deposition from the atmosphere in large-scale studies in various countries, in areas close to industrial installations as well as in areas not expected to be contaminated. Although this technique is widely known, ecological studies of this type have rarely been done in Portugal. The aim of this paper is to evaluate and compare the spatial distribution of heavy metals in Hypnum cupressiforme, Pleurozium schreberi, Dicranum scoparium and Polytrichum piliferum collected from the Serra da Estrela natural park in Portugal and in the Veluwezoom natural park in the Netherlands. The selected species are the most widely used bryophytes for biomonitoring in the boreal region. The popularity of these species for this purpose is due to their wide ecological amplitude and distribution. Methods. At 54 sampling sites in both nature parks, samples of Hypnum cupressiforme, Pleurozium schreberi, Dicranum scoparium and Polytrichum piliferum were collected. Plant digests were analyzed for Al, Ba, Ca, Cr, Fe, K, Mg, Mn, Ni, Sr, V, Zn, Pb, Cu, Cd, N and P. Differentiations between sampling sites in terms of concentrations of elements in mosses were evaluated by ANOVA and the least significant difference was calculated. The normality of the analyzed features was checked with the chi square test. After standardization, the matrix of 54 samples and 10 heavy metals was subjected to numerical classification to detect groups of samples with similar patterns of metal concentrations. The clustering algorithm was prepared with Wards method, and the City Block Manhattan method was used for the similarity measure. Metals and samples were also subjected to ordination to reveal possible gradients of heavy metal levels, using PCA. Correlations were calculated between concentrations of metals and factors 1 and 2, allowing the dependence between the concentration of metals and factors (factor loading) to be estimated. Results and Discussion. All species examined in both areas contained elevated levels of Mn and Pb. For each particular species, concentrations of N, P and Pb were significantly higher at Serra da Estrela, while concentrations of Cu were significantly higher at the Veluwezoom. Mosses from Portugal and the Netherlands differed significantly mainly in the concentrations of Al, Ba, Cr, Fe, Mn, Ni, Pb and V. This differentiation did not exceed that within the mosses from Portugal. Conclusions. Mosses from Portugal and the Netherlands differ significantly mainly in the concentrations of Al, Ba, Cr, Fe, Mn, Ni, Pb and V. This differentiation does not exceed the differentiation within the mosses from Portugal. Recommendation and Outlook. Further research is required into the origin and deposition of the polluting elements in other environmental compartments.

The composition of the soil organic matter in soil developing under the influence of vegetation during the primary succession in the poor sandy area was investigated. The Curie-point pyrolysis method coupled with gas chromatographic separation and mass spectrometric identification of pyrolysates was applied during the investigation. A comparison of occurrence and diversity in composition of organic compounds in plant tissues and humus horizon of soils under the communities of coniferous forest series in the initial stages and phases was carried out. A large diversity of organic compounds under Algae-Cyanophyta communities, biological soil crusts and Polytrichum piliferum was noticed. A clear differentiation in the composition of the soil organic matter at different phases of succession under predominating communities with cryptogamous and vascular plants was observed. The analysis of organic compounds in plant tissues was found to facilitate the determination of origin of various groups of organic compounds in the soil. The results obtained from the Curie point pyrograms in the humus horizon (A) under grasses ( Corynephorus canescens, Koeleria glauca ) differed from the pyrolysates obtained under Algae-Cyanophyta communities. The polysaccharide derivates are more frequent in the pyrolysis products under algae, grasses ( Corynephorus canescens, Koeleria glauca ) and mosses than under Pinus sylvestris . In the beginning of the terminal stage of succession, lignin, phenols and aliphatic substances, prevailed over the polysaccharide derivates in the humus horizon.

Allozyme electrophoresis was used to determine amount and structure of genetic variation within and between five congeneric haploid moss species: Polytrichum formosum , P. commune , P. uliginosum , P. piliferum and P. juniperinum . For the different species, gene diversity within populations ( H S ) ranged from very low (0.025) to moderate values (0.127), being, on average, lower than those observed for vascular plants and many other moss species. Polytrichum piliferum and P. juniperinum showed significantly higher levels of H S than the other species examined, which possibly might be explained by sexual reproduction being more prevalent in these two species, that often live in more dynamic habitats, where turnover of individuals is more frequent. Genetic variability was observed to be structured in contrasting ways at different levels. At the intraspecific level genetic differentiation among populations of most Polytrichum species was low, F ST ≤ 0.1, indicating a considerable degree of gene flow by wind-dispersed spores over substantial distances. At the interspecific level strong divergence, genetic identities being on average I =0.222, was observed between most species studied, despite low levels of divergence at the morphological level. These I -values are significantly lower than observed for congeneric vascular plant species and most congeneric bryophyte species. This suggests that the morphological conservatism is not due to lack of genetic variability and evolutionary potential.

Pollution by heavy metals over large areas and long periods of time may cause chronic damage to living organisms and must be carefully controlled. One way to determine the extent of environmental contamination is by measuring the levels of contaminants in plants. The use of mosses as biomonitors is a convenient method to determine levels of (atmospheric) deposition, as terrestrial mosses obtain most of their supply of mineral elements from precipitation and dry deposition of airborne particles. Mosses have therefore received increasing attention as a suitable tool for monitoring regional patterns of elemental deposition from the atmosphere in large-scale studies in various countries, in areas close to industrial installations as well as in areas not expected to be contaminated. Although this technique is widely known, ecological studies of this type have rarely been done in Portugal. The aim of this paper is to evaluate and compare the spatial distribution of heavy metals in Hypnum cupressiforme, Pleurozium schreberi, Dicranum scoparium and Polytrichum piliferum collected from the Serra da Estrela natural park in Portugal and in the Veluwezoom natural park in the Netherlands. The selected species are the most widely used bryophytes for biomonitoring in the boreal region. The popularity of these species for this purpose is due to their wide ecological amplitude and distribution. At 54 sampling sites in both nature parks, samples of Hypnum cupressiforme, Pleurozium schreberi, Dicranum scoparium and Polytrichum piliferum were collected. Plant digests were analysed for Al, Ba, Ca, Cr, Fe, K, Mg, Mn, Ni, Sr, V, Zn, Pb, Cu, Cd, N and P. Differentiations between sampling sites in terms of concentrations of elements in mosses were evaluated by ANOVA and the least significant difference was calculated. The normality of the analysed features was checked with the chi square test. After standardization, the matrix of 54 samples and 10 heavy metals was subjected to numerical classification to detect groups of samples with similar patterns of metal concentrations. The clustering algorithm was prepared with Ward's method, and the City Block Manhattan method was used for the similarity measure. Metals and samples were also subjected to ordination to reveal possible gradients of heavy metal levels, using PCA. Correlations were calculated between concentrations of metals and factors 1 and 2, allowing the dependence between the concentration of metals and factors (factor loading) to be estimated. All species examined in both areas contained elevated levels of Mn and Pb. For each particular species, concentrations of N, P and Pb were significantly higher at Serra da Estrela, while concentrations of Cu were significantly higher at the Veluwezoom. Mosses from Portugal and the Netherlands differed significantly mainly in the concentrations of Al, Ba, Cr, Fe, Mn, Ni, Pb and V. This differentiation did not exceed that within the mosses from Portugal. Mosses from Portugal and the Netherlands differ significantly mainly in the concentrations of Al, Ba, Cr, Fe, Mn, Ni, Pb and V. This differentiation does not exceed the differentiation within the mosses from Portugal. Further research is required into the origin and deposition of the polluting elements in other environmental compartments.