Feather Moss Pleurozium Schreberi Research Articles

Out of site, out of mind: Changes in feather moss phyllosphere microbiota in mine offsite boreal landscapes.

Plant-microbe interactions play a crucial role in maintaining biodiversity and ecological services in boreal forest biomes. Mining for minerals, and especially the emission of heavy metal-enriched dust from mine sites, is a potential threat to biodiversity in offsite landscapes. Understanding the impacts of mining on surrounding phyllosphere microbiota is especially lacking. To investigate this, we characterized bacterial and fungal communities in the phyllosphere of feather moss Pleurozium schreberi (Brid). Mitt in boreal landscapes near six gold mine sites at different stages of the mine lifecycle. We found that (1) both mining stage and ecosystem type are drivers of the phyllosphere microbial community structure in mine offsite landscapes; (2) Bacterial alpha diversity is more sensitive than fungal alpha diversity to mining stage, while beta diversity of both groups is impacted; (3) mixed and deciduous forests have a higher alpha diversity and a distinct microbial community structure when compared to coniferous and open canopy ecosystems; (4) the strongest effects are detectable within 0.2 km from operating mines. These results confirmed the presence of offsite effects of mine sites on the phyllosphere microbiota in boreal forests, as well as identified mining stage and ecosystem type as drivers of these effects. Furthermore, the footprint was quantified at 0.2 km, providing a reference distance within which mining companies and policy makers should pay more attention during ecological assessment and for the development of mitigation strategies. Further studies are needed to assess how these offsite effects of mines affect the functioning of boreal ecosystems.

Plant and soil nitrogen in oligotrophic boreal forest habitats with varying moss depths: does exclusion of large grazers matter?

The boreal forest consists of drier sunlit and moister-shaded habitats with varying moss abundance. Mosses control vascular plant–soil interactions, yet they all can also be altered by grazers. We determined how 2 decades of reindeer (Rangifer tarandus) exclusion affect feather moss (Pleurozium schreberi) depth, and the accompanying soil N dynamics (total and dissolvable inorganic N, δ15N), plant foliar N, and stable isotopes (δ15N, δ13C) in two contrasting habitats of an oligotrophic Scots pine forest. The study species were pine seedling (Pinus sylvestris L.), bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), and feather moss. Moss carpet was deeper in shaded than sunlit habitats and increased with grazer exclusion. Humus N content increased in the shade as did humus δ15N, which also increased due to exclusion in the sunlit habitats. Exclusion increased inorganic N concentration in the mineral soil. These soil responses were correlated with moss depth. Foliar chemistry varied due to habitat depending on species identity. Pine seedlings showed higher foliar N content and lower foliar δ15N in the shaded than in the sunlit habitats, while bilberry had both higher foliar N and δ15N in the shade. Thus, foliar δ15N values of co-existing species diverged in the shade indicating enhanced N partitioning. We conclude that despite strong grazing-induced shifts in mosses and subtler shifts in soil N, the N dynamics of vascular vegetation remain unchanged. These indicate that plant–soil interactions are resistant to shifts in grazing intensity, a pattern that appears to be common across boreal oligotrophic forests.

The Moss Biomonitoring Method and Neutron Activation Analysis in Assessing Pollution by Trace Elements in Selected Polish National Parks

The concentrations of trace elements in feather moss Pleurozium schreberi (Brid.) Mitt. were used to indicate the relative levels of air pollution by trace elements in Polish national parks. Pleurozium schreberi was collected from nine national parks. The highest concentrations were recorded in the moss samples from the southern and most industrialised part of the country; the lowest from northern and north-eastern Poland. A comparison of data obtained from Polish national parks in the 1970s and 1990s showed a significant decrease in the concentrations of heavy metals. In the linear covariability estimation, the t quantile approach was used for multi-element comparison. A number of positive covariabilities were observed. This is a result of anthropogenic activity and the geochemical characteristics of the local environment, including crust composition to which soil composition is related. The statistical approach of t quantile to study common relationships between element concentrations can be used in the interpretation of biomonitoring research results in similar studies.

Forest mosses sensitively indicate nitrogen deposition in boreal background areas

Mosses take up nitrogen (N) mainly from precipitation through their surfaces, which makes them competent bioindicators of N deposition. We found positive relationships between the total N concentration (mossN%) of common terrestrial moss species (feather mosses Pleurozium schreberi and Hylocomium splendens, and a group of Dicranum species) and different forms of N deposition in 11–16 coniferous forests with low N deposition load in Finland. The mosses were collected either inside (Dicranum group) or both inside and outside (feather mosses) the forests. Deposition was monitored in situ as bulk deposition (BD) and stand throughfall (TF) and detected for ammonium (NH4+-N), nitrate (NO3−-N), dissolved organic N (DON), and total N (Ntot, kg ha−1yr−1). Ntot deposition was lower in TF than BD indicating that tree canopies absorbed N from deposition in N limited boreal stands. However, mossN% was higher inside than outside the forests. In regression equations, inorganic N in BD predicted best the mossN% in openings, while DON in TF explained most variation of mossN% in forests. An asymptotic form of mossN% vs. TF Ntot curves in forests and free NH4+-N accumulation in tissues in the southern plots suggested mosses were near the N saturation state already at the Ntot deposition level of 3–5 kg ha−1yr−1. N leachate from ground litterfall apparently also contributed the N supply of mosses. Our study yielded new information on the sensitivity of boreal mosses to low N deposition and their response to different N forms in canopy TF entering moss layer. The equations predicting the Ntot deposition with mossN% showed a good fit both in forest sites and openings, especially in case of P. schreberi. However, the open site mossN% is a preferable predictor of N deposition in monitoring studies to minimize the effect of tree canopies and N leachate from litterfall on the estimates.

Genome Sequencing of Pleurozium schreberi: The Assembled and Annotated Draft Genome of a Pleurocarpous Feather Moss

The pleurocarpous feather moss Pleurozium schreberi is a ubiquitous moss species which plays a fundamental role in many terrestrial ecosystems, for instance within the boreal forest, the Earth’s largest terrestrial biome, this species plays a significant role in driving ecosystem nitrogen and carbon inputs and fluxes. By hosting dinitrogen (N2)-fixing cyanobacteria, the moss-cyanobacteria symbiosis constitutes the main nitrogen input into the ecosystem and by the high productivity and the low decomposability of the moss litter, P. schreberi contributes significantly to build-up soil organic matter, and therefore long-term C sequestration. Knowledge on P. schreberi genome will facilitate the development of ‘omics’ and system’s biology approaches to gain a more complete understanding of the physiology and ecological adaptation of the moss and the mechanisms underpinning the establishment of the symbiosis. Here we present the de novo assembly and annotation of P. schreberi genome that will help investigating these questions. The sequencing was performed using the HiSeq X platform with Illumina paired-end and mate-pair libraries prepared with CTAB extracted DNA. In total, the assembled genome was approximately 318 Mb, while repetitive elements account for 28.42% of the genome and 15,992 protein-coding genes were predicted from the genome, of which 84.23% have been functionally annotated. We anticipate that the genomic data generated will constitute a significant resource to study ecological and evolutionary genomics of P. schreberi, and will be valuable for evo-devo investigations as well as our understanding of the evolution of land plants by providing the genome of a pleurocarpous moss.

Symplasmic and apoplasmic transport inside feather moss stems of Pleurozium schreberi and Hylocomium splendens.

The ubiquitous feather mosses Pleurozium schreberi and Hylocomium splendens form a thick, continuous boundary layer between the soil and the atmosphere, and play important roles in hydrology and nutrient cycling in tundra and boreal ecosystems. The water fluxes among these mosses and environmental factors controlling them are poorly understood. The aim of this study was to investigate whether feather mosses are capable of internal transport and to provide a better understanding of species-specific morphological traits underlying this function. The impacts of environmental conditions on their internal transport rates were also investigated. Cells involved in water and food conduction in P. schreberi and H. splendens were identified by transmission electron microscopy. Symplasmic and apoplasmic fluorescent tracers were applied to the moss stems to determine the routes of internal short- and long-distance transport and the impact of air humidity on the transport rates. Symplasmic transport over short distances occurs via food-conducting cells in both mosses. Pleurozium schreberi is also capable of apoplasmic internal long-distance transport via a central strand of hydroids. These are absent in H. splendens. Reduced air humidity significantly increased the internal transport of both species, and the increase was significantly faster for P. schreberi than for H. splendens. Pleurozium schreberi and Hylocomium splendens are capable of internal transport but the pathway and conductivity differ due to differences in stem anatomy. These results help explain their varying desiccation tolerance and possibly their differing physiology and autecology and, ultimately, their impact on ecosystem functioning.

Nitrogen fixation rates associated with the feather mosses Pleurozium schreberi and Hylocomium splendens during forest stand development following clear-cutting

Pleurocarpous feather mosses host di-nitrogen (N2) fixing cyanobacteria, and this association serves as an important source of N input to late-successional natural boreal forests. However, little is known about how forest management affects feather mosses and their associated N2-fixation rates, or how these rates change during post-logging stand development. We established a chronosequence of 32 forest stands used for commercial wood production to better understand how stand development after clear-cutting drives changes in biomass and N2-fixation rates of the two dominant feather mosses, Pleurozium schreberi and Hylocomium splendens. These stands included eight replicate stands of each of four stand types: (1) recently clear-cut and newly planted stands (CC, 4years); (2) pre-commercial thinning stands (PCT, 16years); (3) first thinning stands (T1, 34years); and (4) mature uncut forest (MF, 123years), all dominated by Pinus sylvestris. We found that clear-cutting did not reduce moss biomass relative to the uncut forest. Further, biomass of P. schreberi (but not of H. splendens) increased twofold from CC stands to PCT stands, and remained high throughout the T1 stands. Di-nitrogen fixation capacity, determined as the amount of N fixed per unit moss mass, was ca. six and three times larger in PCT stands compared to the other stand types for P. schreberi and H. splendens respectively. Correlation analyses showed that N2-fixation capacity associated with both moss species increased with increasing Empetrum hermaphroditum biomass, and that N2-fixation capacity of P. schreberi declined with increasing NH4+ availability. Further, correlation analysis showed that N2-fixation capacity of H. splendens declined with increasing tree biomass and decreasing light transmission. The total amount of N fixed at the stand level was highest in the PCT stands (1.0kgha−1year−1 of N), and was associated with both high moss biomass and high N2-fixation capacity. The contribution of N2-fixation to total N accrual per hectare during stand development was ca. 9%, and across the chronosequence N2 was fixed on average at rates of 0.4kgha−1year−1. Our results show that N2-fixation rates in feather moss communities were promoted by the conditions at the PCT stands approximately 16years after clear-cutting, while N2-fixation rates were lowest under conditions at the newly clear-cut and mature stands. Further, it suggests that mosses and associated N2-fixation can be important in maintaining a long-term N balance, and that this source of N input should be accounted for when modeling N balance in N-limited managed boreal forests.

Moss-nitrogen input to boreal forest soils: Tracking 15N in a field experiment

Cyanobacteria living epiphytically on mosses in pristine, unpolluted areas fix substantial amounts of atmospheric nitrogen (N) and therefore represent a primary source of N in N-limited boreal forests. However, the fate of this N is unclear, in particular, how the fixed N2 enters the soil and becomes available to the ecosystem. In this study, we applied 15N-ammonium chloride (15N-NH4Cl) onto carpets of the feather moss Pleurozium schreberi and traced the 15N label into green (living) and brown (senescent) moss and into the upper soil layer over time. Further, we placed filters between moss and soil to assess the role of moss-associated fungi for N-transfer to the soil. The experiment was conducted at endpoints of a N2 fixation gradient in Northern Sweden. Feather moss retained the applied N in the green moss parts for up to 1 year and no increase of excess 15N was found in the brown moss parts or in the soil within that same time frame. The filter treatment did not alter the 15N-distribution in moss or soil. Nitrogen retention in the moss was similar regardless of position along the N2 fixation gradient. Our results suggest that mosses represent a short-term inorganic N sink and that transfer of N to the soil is not facilitated by fungal hyphae.

Exposure to nitrogen does not eliminate N2 fixation in the feather moss Pleurozium schreberi (Brid.) Mitt.

Background and aims The feather moss Pleurozium schreberi (Brid.) Mitt. is colonized by cyanobacteria, which fix substantial amounts of atmospheric nitrogen (N) in pristine and N-poor ecosystems. Cyanobacterial N2 fixation is inhibited by N deposition. However, the threshold of N input that leads to the inhibition of N2 fixation has not been adequately investigated. Further, the ability of N2 fixation to recover in mosses from high N deposition areas has not been studied to date.

The cyanobacterial role in the resistance of feather mosses to decomposition--toward a new hypothesis.

Cyanobacteria-plant symbioses play an important role in many ecosystems due to the fixation of atmospheric nitrogen (N) by the cyanobacterial symbiont. The ubiquitous feather moss Pleurozium schreberi (Brid.) Mitt. is colonized by cyanobacteria in boreal systems with low N deposition. Here, cyanobacteria fix substantial amounts of N2 and represent a potential N source. The feather moss appears to be resistant to decomposition, which could be partly a result of toxins produced by cyanobacteria. To assess how cyanobacteria modulated the toxicity of moss, we measured inhibition of bacterial growth. Moss with varying numbers of cyanobacteria was added to soil bacteria to test the inhibition of their growth using the thymidine incorporation technique. Moss could universally inhibit bacterial growth, but moss toxicity did not increase with N2 fixation rates (numbers of cyanobacteria). Instead, we see evidence for a negative relationship between moss toxicity to bacteria and N2 fixation, which could be related to the ecological mechanisms that govern the cyanobacteria – moss relationship. We conclude that cyanobacteria associated with moss do not contribute to the resistance to decomposition of moss, and from our results emerges the question as to what type of relationship the moss and cyanobacteria share.

The effect of altered macroclimate on N-fixation by boreal feather mosses

Plant productivity is predicted to increase in boreal forests owing to climate change, but this may depend on whether N inputs from biological N-fixation also increases. We evaluated how alteration of climatic factors affects N input from a widespread boreal N-fixer, i.e. cyanobacteria associated with the feather moss Pleurozium schreberi. In each of 10 forest stands in northern Sweden, we established climate-change plots, including a control (ambient climate) plot and three plots experiencing a +2°C temperature increase, an approximately threefold reduction in precipitation frequency, and either 0.07, 0.29 or 1.16 times normal summer precipitation. We monitored N-fixation in these plots five times between 2007 and 2009, and three times in 2010 after climate treatments ended to assess their recovery. Warmer temperatures combined with less frequent precipitation reduced feather moss moisture content and N-fixation rates regardless of total precipitation. After climate treatments ended, recovery of N-fixation rates occurred on the scale of weeks to months, suggesting resilience of N-fixation to changes in climatic conditions. These results suggest that modelling of biological N-inputs in boreal forests should emphasize precipitation frequency and evaporative water loss in conjunction with elevated temperature rather than absolute changes in mean precipitation.

Relationships among shoot tissue, canopy and photosynthetic characteristics in the feathermoss Pleurozium schreberi

Abstract In bryophytes, rates of net photosynthesis vary among populations. How this variation is shaped by shoot biochemical or structural traits has not been established, yet would be essential to develop useful models of forest floor function in the boreal zone. The objectives of this study were to characterize functional trait relationships in the widespread feathermoss Pleurozium schreberi, to develop an empirical model to predict net photosynthesis in this species, and to compare the performance of a surface model that incorporates the shoot system's average properties with a canopy model that accounts for the vertical distribution of light and shoot area. Maximal rates of net photosynthesis (Amax) and dark respiration (Rd) were measured (n = 25) using gas exchange at optimal water contents. Shoot system concentrations of chlorophyll (a+b), carotenoids and nitrogen were measured in addition to the water content, surface roughness (Lr), canopy height, and the vertical distribution of shoot area and l...

Response of feather moss associated N2 fixation and litter decomposition to variations in simulated rainfall intensity and frequency

Feather mosses in boreal forests form a dense ground‐cover that is an important driver of both nutrient and carbon cycling. While moss growth is highly sensitive to moisture availability, little is known about how moss effects on nutrient and carbon cycling are affected by the dynamics of moisture input to the ecosystem. We experimentally investigated how rainfall regimes affected ecosystem processes driven by the dominant boreal feather moss Pleurozium schreberi by manipulating total moisture amount, frequency of moisture addition and moss presence/absence. Moisture treatments represented the range of rainfall conditions that occur in Swedish boreal forests as well as shifts in rainfall expected through climate change. We found that nitrogen (N) fixation by cyanobacteria in feather mosses (the main biological N input to boreal forests) was strongly influenced by both moisture amount and frequency, and their interaction; increased frequency had greater effects when amounts were higher. Within a given moisture amount, N fixation varied up to seven‐fold depending on how that amount was distributed temporally. We also found that mosses promoted vascular litter decomposition rates, concentrations of litter nutrients, and active soil microbial biomass, and reduced N release into soil solution. These effects were usually strongest under low moisture amount and/or frequency, and revealed a buffering effect of mosses on the decomposer subsystem under moisture limitation. These results highlight that both the amount and temporal distribution of rainfall, determine the effect of feather mosses on ecosystem N input and the decomposer subsystem. They also emphasize the role of feather mosses in mediating moisture effects on decomposer processes. Finally, our results suggest that projected shifts in precipitation in the Swedish boreal forest through climate change will result in increased moss growth and N2 fixation but a reduced dependency of the decomposer subsystem on feather moss cover for moisture retention.

Enhanced soil fertility under Juniperus communis in arctic ecosystems

Patches of common juniper (Juniperus communis L.) shrubs potentially facilitate the formation of fertile islands in heath tundra ecosystems thereby influencing the long-term resilience of these ecosystems. Although the role of juniper in the formation of such ‘islands of fertility’ has been studied in semiarid landscapes, there has been little attention paid to the importance of juniper in other ecosystems. In this study we contrast the soil fertility and rates of N fixation under juniper shrubs with that in open heath tundra in northern Sweden. Plots were established at several individual sites in alpine heath tundra in Northern Sweden and mineral soils to a depth of 10 cm were characterized for available N and P and total C, N, P, Ca, Mg, K, Fe, Mn, Zn, and Cu. Nitrogen fixation rates were measured by acetylene reduction in feather mosses under juniper canopies and contrasted with N fixation in both feather mosses and surface soils in the open heath. Soils under juniper had concentrations of total P greatly in excess of P in open heath, furthermore, juniper islands had the highest concentrations of bioavailable P. Nitrogen fixation rates in the feather moss Pleurozium schreberi (Bird.) Mitt were approximately 150 μmol acetylene reduced m−2 d−1 under the juniper canopy compared to less than 10 μmol acetylene reduced m−2 d−1 in the open heath. Feather mosses under the juniper canopy also fixed N at a significantly higher rate (on an aerial basis) than that of surface cores from the open heath that included lichen, mosses, and soil crusts. Juniper facilitates the formation of islands of soil fertility that may in turn facilitate the growth of other plants and positively influence the long term recovery of heath tundra ecosystems following disturbance.

NITROGEN FIXATION INCREASES WITH SUCCESSIONAL AGE IN BOREAL FORESTS

There is little understanding of successional dynamics of N fixation in northern boreal forests. Recent evidence suggests that N fixation by cyanobacteria in association with the common feather moss Pleurozium schreberi contributes to a significant proportion of the total N economy. The purpose of the work herein was to determine how time since last fire influences N fixation rates in boreal forests. We evaluated seasonal N fixation rates on a total of 12 natural forest preserves varying in time since last fire (35–355 years). Each site was monitored for N fixation activity using a calibrated acetylene reduction assay. Nitrogen fixation rates were found to increase linearly with time since fire. This increase in N fixation with succession is likely a function of degree of colonization by cyanobacteria and site factors such as presence of available N. Surface applications of 4.5 kg N·ha−1·yr−1 as NH4NO3 were found to eliminate N fixation while applications of P resulted in only a slight and temporary increase of N fixation rates. In contrast to common observation our findings suggest that N fixation in boreal forests becomes more important in late succession. Limited N availability in late succession is clearly one of the primary drivers of N fixation rates in boreal forest ecosystems. These findings may help to explain the origin of high rates of net N accumulation in soil unaccounted for at northern boreal sites.

Survey of heavy metal deposition in Poland using mosses as indicators

Concentration of heavy metals in the feather moss Pleurozium schreberi (Brid.) Mitt., a common moss species, were used to indicate relative levels of air pollution by seven heavy metals: Cd, Cr, Cu, Fe, Ni, Pb and Zn in Poland. Pleurozium was sampled from 297 localities regularly distributed throughout the country. Significant differences in heavy metal levels in Pleurozium which are representative of particular localities were found. The highest concentrations were recorded in the moss samples from the southern and most industrialized part of the country, the lowest from northern and north-eastern Poland. A comparison of data obtained from identical localities in Poland (1990, 1995) showed a significant decrease in the concentrations of heavy metals in Pleurozium between 1990 and 1995. The decrease over 20 years (1975–1995) in 12 national parks which are fairly evenly distributed over an area of Poland was even more evident. The heavy metal concentrations found in mosses of Poland in the mid 1990s were generally similar to those reported from other countries of central Europe.

Experiments on the effects of water availability and exclusion of fungal hyphae on nutrient uptake and establishment of Pinus sylvestris seedlings in carpets of the moss Pleurozium schreberi

The feathermoss Pleurozium schreberi has the capacity to suppress tree seedling regeneration in late successional northern boreal forests. We investigated, through a field experiment in a P. schreberi-dominated old-growth Norway spruce forest in northern Sweden, the effects of three precipitation regimes representing the range of natural July precipitation amounts (28, 112 and 256 mm), and extra influences of temporary exclusion of fungal hyphae in senescent shoots of P. schreberi, on seedling establishment, growth and nutrient acquisition of Pinus sylvestris. Seedling establishment of Pinus sylvestris was enhanced by increased amounts of artificial precipitation. Seedlings in plots with the lowest precipitation had a much lower mortality and significantly higher total nutrient content, higher specific absorption rate (SAR) and lower nutrient use efficiency (NUE) compared to seedlings grown in plots with the highest precipitation. Seedling nutrient (especially N and P) content was also significantly higher when fungal hyphae were excluded, and this was most evident in treatments with the intermediate precipitation level. Seedlings in plots without hyphal isolation but with intermediate precipitation levels had much lower total contents of N, P and Mg after one growing season than were initially present in the seeds, indicative of a net nutrient loss during the early establishment phase. Possible rhizosphere interactions, causing immobilisation of nutrients and seedling nutrient losses are discussed in relation to results from greenhouse experiments where no such nutrient losses were found in seedlings. We hypothesize that P. schreberi, in association with ericaceous plants and fungal hyphae, is a powerful controller of tree regeneration from seeds over wide precipitation gradients, due to its inhibition of seedling establishment and strong interference with nutrient acquisition of new seedling cohorts.

Mercury accumulation in transplanted moss and lichens at high elevation sites in Quebec

Mercury deposition was monitored at two mountain sites in Quebec using transplanted lichens and moss. The terricolous lichen species Cladina rangiferina, the epiphytic lichen species Hypogymnia physodes, and the feather moss Pleurozium schreberi were transplanted from a northern Ontario boreal site to the bases and summits of Roundtop Mountain and Mt. Tremblant in southern Quebec. After 12 months, transplants of C. rangiferina sited at the base and summit of Roundtop mountain and the summit of Mt. Tremblant showed a significant increase in mercury concentration over controls (p < 0.05). The largest difference occurred at the summit of Roundtop mountain where mercury concentration was 81.4 ± 10.9 ppb as compared to 45.6 + 10.6 ppb at the control site. No significant increases in mercury concentration in P. schreberi were seen after 12 months at any site althought trends of increase were apparent. After 20 months, further significant increases in Hg content were observed in both the terricolous lichen and the feather moss at both the Roundtop Mountain base and summit sites. A significant increase in Hg content of P. schreberi was also noted at the Mt. Tremblant summit site. Over the length of the study the greatest mercury concentration increases were observed in the feather moss at the Roundtop Mountain summit site (with a 248.3 ± 30.0 ppb mercury concentration as compared to 108.3 ± 30.0 ppb in controls). No significant change in mercury concentration in the epiphyte H. physodes was found during the study. These data indicate that mercury deposition is occurring, especially to higher elevation sites. While mercury inputs at the summits may be increased by the effects of fog, increases in mercury at the base sites cannot be accounted for the same way, but may represent the importance of dry deposition processes.

Ectomycorrhizas and nutrient transfer in conifer – feather moss ecosystems

Conifer–feather moss ecosystems dominate large areas of the boreal forest regions of the world, but the interrelations between these two components of the system are poorly understood. Mycorrhizal roots of the trees grow in close association with the mosses. The possibility that nutrients can be transferred from moss shoots to trees through mycorrhizal fungi was investigated using the feather moss Pleurozium schreberi and mycorrhizal seedlings of Pinus contorta. Shoots of the moss were divided into three categories, viz. green, senescent, and dead, and nutrient contents of aqueous leachates from the segments were measured before and after drying. Significant quantities of nitrogen and phosphorus were released from moss shoots especially after drying. Senescing segments consistently released more N than those that were dead and generally released more than did the green segments. All categories of segments released some protein nitrogen, and drying induced leakage of glucose, fructose, and sucrose. Leachates of entire moss shoots were capable of supporting growth of three mycorrhizal fungi in pure culture. Moss shoots added to chambers containing mycorrhizal plants were colonized by the fungal associates of the plants, particularly intensive growth occurring in the senescent region of the moss shoots. Phosphate (32P) and carbon (14C), previously fed to the moss shoots, was absorbed by mycorrhizal mycelia and transferred over distances of centimetres to infected roots of pine plants and then to their shoots. The significance of these uptake and transfer processes for nutrient cycling in boreal forest ecosystems is discussed. Key words: leachate, nitrogen, phosphorus, sugars, protein, radioisotope.

Geobotanical and biogeochemical exploration for gold in the Sattasvaara volcanic complex, Finnish Lapland

Abstract Gold mineralization is commonly associated with carbonatized and mica-altered rocks. These altered rocks are characterized by high density of vegetation and a wide variety of plant species in the conifer-dominant belt of Finnish Lapland. Gold contents of juniper ( Juniperus communis ), crowberry ( Empetrum nigrum ), and feather mosses ( Hylocomium splendens and Pleurozium schreberi ) associated with auriferous and background areas are discussed. Gold is enriched in the topmost of podsols overlying the mineralized bedrock at the sites, where plant species also show anomalous Au contents. The highest anomaly in ashed juniper is 70 ppb Au and in crowberry 410 ppb Au.