Photosynthetic traits of Sphagnum and feather moss species in undrained,drained and rewetted boreal spruce swamp forests

In restored peatlands, recovery of carbon assimilation by peat‐forming plants is a prerequisite for the recovery of ecosystem functioning. Restoration by rewetting may affect moss photosynthesis and respiration directly and/or through species successional turnover. To quantify the importance of the direct effects and the effects mediated by species change in boreal spruce swamp forests, we used a dual approach: (i) we measured successional changes in moss communities at 36 sites (nine undrained, nine drained, 18 rewetted) and (ii) photosynthetic properties of the dominant Sphagnum and feather mosses at nine of these sites (three undrained, three drained, three rewetted). Drainage and rewetting affected moss carbon assimilation mainly through species successional turnover. The species differed along a light‐adaptation gradient, which separated shade‐adapted feather mosses from Sphagnum mosses and Sphagnum girgensohnii from other Sphagna, and a productivity and moisture gradient, which separated Sphagnum riparium and Sphagnum girgensohnii from the less productive S. angustifolium, S. magellanicum and S. russowii. Undrained and drained sites harbored conservative, low‐production species: hummock‐Sphagna and feather mosses, respectively. Ditch creation and rewetting produced niches for species with opportunistic strategies and high carbon assimilation. The direct effects also caused higher photosynthetic productivity in ditches and in rewetted sites than in undrained and drained main sites.     

Development of microsatellites for the peat moss Sphagnum capillifolium using ISSR cloning

Sphagnum mosses are major components of peat bogs but populations of many species are under threat due to habitat fragmentation resulting from the cutting of peat for fuel. We have used an intersimple sequence repeat (ISSR)‐based cloning method to develop nine polymorphic nuclear microsatellites for the peat moss species Sphagnum capillifolium. Between three and seven alleles per locus were detected in a sample of 48 haploid gametophytes and levels of gene diversity ranged from 0.5391 to 0.7960. These represent the first microsatellite markers developed for this important genus and most also exhibited cross‐species amplification across a range of common Sphagnum species.     

Direct and interaction-mediated effects of environmental changes on peatland bryophytes

Ecosystem processes of northern peatlands are largely governed by the vitality and species composition in the bryophyte layer, and may be affected by global warming and eutrophication. In a factorial experiment in northeast China, we tested the effects of raised levels of nitrogen (0, 1 and 2 g m⁻² year⁻¹), phosphorus (0, 0.1 and 0.2 g m⁻² year⁻¹) and temperature (ambient and +3°C) on Polytrichum strictum, Sphagnum magellanicum and S. palustre, to see if the effects could be altered by inter-specific interactions. In all species, growth declined with nitrogen addition and increased with phosphorus addition, but only P. strictum responded to raised temperature with increased production of side-shoots (branching). In Sphagnum, growth and branching changed in the same direction, but in Polytrichum, the two responses were uncoupled: with nitrogen addition there was a decrease in growth (smaller than in Sphagnum) but an increase in branching; with phosphorus addition growth increased but branching was unaffected. There were no two-way interactions among the P, N and T treatments. With increasing temperature, our results indicate that S. palustre should decrease relative to P. strictum (Polytrichum increased its branching and had a negative neighbor effect on S. palustre). With a slight increase in phosphorus availability, the increase in length growth and production of side-shoots in P. strictum and S. magellanicum may give them a competitive superiority over S. palustre. The negative response in Sphagnum to nitrogen could favor the expansion of vascular plants, but P. strictum may endure thanks to its increased branching.     

Range change evolution of peat mosses (Sphagnum) within and between climate zones

Peat mosses (Sphagnum) hold exceptional importance in the control of global carbon fluxes and climate because of the vast stores of carbon bound up in partially decomposed biomass (peat). This study tests the hypothesis that the early diversification of Sphagnum was in the Northern Hemisphere, with subsequent range expansions to tropical latitudes and the Southern Hemisphere. A phylogenetic analysis of 192 accessions representing the moss class Sphagnopsida based on four plastid loci was conducted in conjunction with biogeographic analyses using BioGeoBEARS to investigate the tempo and mode of geographic range evolution. Analyses support the hypothesis that the major intrageneric clades of peat‐forming species accounting for >90% of peat moss diversity originated and diversified at northern latitudes. The genus underwent multiple range expansions into tropical and Southern Hemisphere regions. Range evolution in peat mosses was most common within latitudinal zones, attesting to the relative difficulty of successfully invading new climate zones. Allopolyploidy in Sphagnum (inferred from microsatellite heterozygosity) does not appear to be biased with regard to geographic region nor intrageneric clade. The inference that Sphagnum diversified in cool‐or cold‐climate regions and repeatedly expanded its range into tropical regions makes the genus an excellent model for studying morphological, physiological, and genomic traits associated with adaptation to warming climates.     

Experimental warming alters the community composition,diversity, and N2 fixation activity of peat moss (Sphagnum fallax) microbiomes

Sphagnum‐dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole‐ecosystem warming on the Sphagnum moss microbiome, focusing on N₂ fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next‐generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N₂ fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N₂ fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N₂ fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands.     

Estimation of stand-level leaf area for boreal bryophytes

Bryophytes dominate the carbon and nitrogen cycling of many poorly drained terrestrial ecosystems and are important in the vegetation-atmosphere exchange of carbon and water, yet few studies have estimated their leaf area at the stand scale. This study quantified the bryophyte-specific leaf area (SLA) and leaf area index (LAI) in a group of different-aged boreal forest stands in well and poorly drained soils. Species-specific SLA (for three feather mosses, four Sphagnum spp. and Aulacomnium palustre mixed with Tomentypnum nitens) was assessed by determining the projected area using a flatbed scanner and cross-sectional geometry using a dissecting microscope. The hemisurface leaf area was computed as the product of SLA and live biomass and was scaled by coverage data collected at all stands. Pleurozium schreberi dominated the spatial coverage, biomass and leaf area in the well-drained stands, particularly the oldest, while S. fuscum and A. palustre were important in the poorly drained stands. Live moss biomass ranged from 47 to 230 g m⁻² in the well-drained stands dominated by feather mosses and from 102 to 228 g m⁻² in the poorly drained stands. Bryophyte SLA varied between 135 and 473 cm² g⁻¹, for A. palustre and S. capillifolium, respectively. SLA was strongly and significantly affected by bryophyte species, but did not vary between stands; in general, there was no significant difference between the SLA of non-Sphagnum mosses. Bryophyte LAI increased with stand age, peaking at 3.1 and 3.7 in the well and poorly drained stands, respectively; this represented approximately 40% of the overstory LAI in the well-drained stands and 100–1,000% in the poorly drained stands, underscoring the important role bryophytes play in the water and carbon budgets of these boreal forests.     

Post‐fire bryophyte establishment in a continental bog

Questions : What is the mechanism of bog ground layer colonization post‐fire? Is species colonization stochastic or does facilitation occur? Location : Boreal bog peatland near Crow Lake, Alberta, Canada. Methods : Diaspore‐addition treatments were applied in 2003 to autoclaved peat samples from high and low microtopographic positions within a recently burned bog. Colonization was assessed within the plots in 2005 and compared to control plots to determine treatment success and patterns of colonization. Results : A significant degree of ground layer colonization was found two years after fire, with Polytrichum strictum dominating the site. Colonization was greater in low (wet) plots, although only P. strictum and Sphagnum angustifolium had significant colonization. No effect of diaspore addition was observed and Sphagnum was only found in conjunction with P. strictum. Conclusions : Environmental conditions and species life history strategy are more important than diaspore availability for post‐fire colonization. True mosses (e.g. P. strictum) appearto facilitate Sphagnum colonization.     

Polytrichum Strictum as a Solution to Frost Heaving in Disturbed Ecosystems: A Case Study with Milled Peatlands

Substrate instability is a common problem in many disturbed ecosystems. In the case of milled harvested peatlands, the pioneer moss Polytrichum strictum is commonly found; it is well adapted to tolerate the harsh microclimatic conditions and peat instability of these sites. A field experiment was used to determine the effectiveness of P. strictum against frost heaving, a major type of disturbance on bare peat. Wooden dowels and fir trees (Abies balsamea) placed in a P. strictum carpet experienced almost no frost heaving, whereas heaving was severe on bare peat. Reintroduced P. strictum fragments thinly spread on bare peat reduced but did not eliminate frost heaving. Straw mulch (a protective cover often required in peatland restoration) effectively reduced heaving in the fall, but was less effective in the spring because it had partially decomposed. The P. strictum carpet, P. strictum fragments, and straw mulch reduced frost heaving by reducing the number of freeze–thaw cycles, by slowing the rate of ground thaw in the spring, and by reducing the unfrozen water content of the peat during the spring thaw. Different species of Polytrichum mosses should be considered for the restoration or regeneration of disturbed ecosystems where soil stability is problematic.     

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

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

     

Mosses modify effects of warmer and wetter conditions on tree seedlings at the alpine treeline

Climate warming enables tree seedling establishment beyond the current alpine treeline, but to achieve this, seedlings have to establish within existing tundra vegetation. In tundra, mosses are a prominent feature, known to regulate soil temperature and moisture through their physical structure and associated water retention capacity. Moss presence and species identity might therefore modify the impact of increases in temperature and precipitation on tree seedling establishment at the arctic‐alpine treeline. We followed Betula pubescens and Pinus sylvestris seedling survival and growth during three growing seasons in the field. Tree seedlings were transplanted along a natural precipitation gradient at the subarctic‐alpine treeline in northern Sweden, into plots dominated by each of three common moss species and exposed to combinations of moss removal and experimental warming by open‐top chambers (OTCs). Independent of climate, the presence of feather moss, but not Sphagnum, strongly supressed survival of both tree species. Positive effects of warming and precipitation on survival and growth of B. pubescens seedlings occurred in the absence of mosses and as expected, this was partly dependent on moss species. P. sylvestris survival was greatest at high precipitation, and this effect was more pronounced in Sphagnum than in feather moss plots irrespective of whether the mosses had been removed or not. Moss presence did not reduce the effects of OTCs on soil temperature. Mosses therefore modified seedling response to climate through other mechanisms, such as altered competition or nutrient availability. We conclude that both moss presence and species identity pose a strong control on seedling establishment at the alpine treeline, and that in some cases mosses weaken climate‐change effects on seedling establishment. Changes in moss abundance and species composition therefore have the potential to hamper treeline expansion induced by climate warming.     

A climatic threshold triggers the die‐off of peat mosses during an extreme heat wave

Heat waves, which are projected to be more frequent and intense in a warmer climate, could become a serious threat to plants that rely on water surplus availability, such as bryophytes. Here, I take the advantage of the European summer 2003 climate anomaly to assess the impact of an extreme heat wave on peat mosses of the genus Sphagnum, a group of bryophytes forming the bulk of living and dead biomass in peatlands. With this aim, 20 selected bogs in the Italian Alps were checked for Sphagnum survival in the years following the heat wave. Over the study area, the period May–September 2003 was characterized by higher mean monthly air temperature (13.5 °C) and lower mean monthly precipitation (87 mm) compared with normal climatic conditions (11.5 °C and 117 mm, respectively) so that the heat wave coincided with a drought spell. As a consequence of the unusual water stress, I documented an increased mortality of peat mosses forming high hummocks. In particular, at habitat scale, the distribution of desiccated peat mosses was restricted to the hummock face receiving the greatest amount of solar irradiation. However, at regional scale, the present study identified a climatic threshold, simply defined by the ratio of precipitation to temperature (P : T), which triggered an irreversible desiccation of peat mosses when mean monthly P : T dropped below 6.5 (mm : °C) during May–September 2003. The absence of any sign of recovery after 4 years since the drought must be seen as a harbinger of the deleterious effects of extreme heat waves on organisms not adapted to cope with abrupt climate anomaly.     

Distribution and development of necroticSphagnum patches in two Estonian raised bogs

Sphagnum mosses dominate the plant cover of boreal bogs and accumulate carbon as peat. However, discoloured necroticSphagnum patches are also common in bogs. NecroticSphagnum inhibits peat accumulation, and consequently these areas may sink with respect to their surroundings with healthy mosses and continuing peat accumulation. Therefore, necrotic patches in the moss carpet could have an important role in triggering the succession ofSphagnum communities and the differentiation of bog microtopography. Our main aim was to find out how necroticSphagnum patches are distributed on a microtopographic gradient and amongSphagnum species. Based on these results we discuss the development and likely role of necrotic patches. It was found that necrotic patches occur on all types of bog microforms and contain the most of commonSphagnum species. Necrotic patches were more common and larger in wet hollows. The development of necrotic patches depends on their location on the microtopographic gradient. Necrotic patches on higher microforms usually re-vegetate, whereas those in hollows can result in mud-bottom hollows.     

The fate of 15N-nitrate in a northern peatland impacted by long term experimental nitrogen, phosphorus and potassium fertilization

Information about the impact of nitrogen (N) deposition on the fate of deposited N in peatland ecosystems is lacking. Thus we investigated the fate of experimentally added ¹⁵N in long-term N-fertilized treatments in a Sphagnum-dominated ombrotrophic bog. Fertilization significantly stimulated vascular plant and suppressed Sphagnum and Polytrichum moss growth. N content in peat, mosses, and vascular plants was raised by the fertilizer addition and reached a maximum at 3.2 g m^?2 N input level with phosphorus (P) and potassium (K) addition. Most of N was retained in the vegetation and upper 10 cm of the peat. When N deposition equalled 1.6 g m^?2 and less, or 3.2 g m^?2 N with P and K addition, no inorganic N leaching was observed on the plots. This result indicates that co-fertilization with P and K raised the N retention capacity and that critical N loads with respect to N saturation depend on P and K availability. Most of the deposited ¹⁵N was recovered in the bulk peat, which may be related to a rapid immobilization of inorganic N by microorganisms and mycorrhizal assimilation. Increase of N, P, and K fertilization increased the contribution of vascular plants to N retention significantly and reduced those of mosses. The increase was mainly related to enhanced productivity, vascular biomass and N content in tissues; the reduced retention by mosses resulted from both reduced moss biomass and assimilation. The study shows that the N filter function of ombrotrophic bogs will be influenced by interactions with other nutrients and shifts in plant community structure.     

The moss dwelling testacean fauna of Île de la Possession

An ecological study of the moss dwelling testacean fauna (Protozoa, Rhizopoda) on Île de la Possession (Crozet Archipelago, sub-Antarctica) revealed 83 taxa, belonging to 21 genera. The moss flora was dominated by cosmopolitan and ubiquitous taxa, such as Trinema lineare, T. enchelys, Euglypha laevis and E. rotunda. A cluster analysis and a correspondence analysis identified three communities: (1) a Corythion dubium assemblage found in a drier, slightly acidic terrestrial moss vegetation, (2) the Arcella arenaria, and (3) the Difflugiella crenulata assemblages, both characteristic of wetter, circumneutral habitats. The latter typified submerged mosses growing in running water, while the A. arenaria assemblage seemed to prefer mosses in standing waterbodies. Moisture conditions appeared to play a key role in determining the distribution pattern of testacean communities, while pH was only a secondary factor. A logistic regression emphasised the effect of the habitat type in controlling the variance in testacean assemblages. Moreover, the close relationship between bryophyte species and habitat type had a significant influence on the distribution pattern of the testate amoebae. Weighted averaging and calibration were used to estimate moisture optima and tolerances of the testate amoebae.     

Photoinhibition as a control on photosynthesis and production of Sphagnum mosses

The effect of high light intensity on photosynthesis and growth of Sphagnum moss species from Alaskan arctic tundra was studied under field and laboratory conditions. Field experiments consisted of experimental shading of mosses at sites normally exposed to full ambient irradiance, and removal of the vascular plant canopy from above mosses in tundra water track habitats. Moss growth was then monitored in the experimental plots and in adjacent control areas for 50 days from late June to early August 1988. In shaded plots total moss growth was 2–3 times higher than that measured in control plots, while significant reductions in moss growth were found in canopy removal plots. The possibility that photoinhibition of photosynthesis might occur under high-light conditions and affect growth was studied under controlled laboratory conditions with mosses collected from the arctic study site, as well as from a temperate location in the Sierra Nevada, California. After 2 days of high-light treatment (800 mol photons m^–2 s^–1) in a controlled environmental chamber, moss photosynthetic capacity was significantly lowered in both arctic and temperate samples, and did not recover during the 14-day experimental period. The observed decrease in photosynthetic capacity was correlated (r ²=0.735, P<0.001) with a decrease in the ratio of variable to maximum chlorophyll fluorescence (F _v/F _m) in arctic and temperate mosses. This relationship indicates photoinhibition of photosynthesis in both arctic and temperate mosses at even moderately high light intensities. It is suggested that susceptibility to photoinhibition and failure to photoacclimate to higher light intensities in Sphagnum spp. may be related to low tissue nitrogen levels in these exclusively ombrotrophic plants. Photoinhibition of photosynthesis leading to lowered annual carbon gain in Sphagnum mosses may be an important factor affecting CO₂ flux at the ecosystem level, given the abundance of these plants in Alaskan tussock tundra.     

Sphagnum in peatlands of Australasia: Their distribution,utilisation and management

In comparison to the northern hemisphere, Sphagnum peatlands are an unusual andinfrequent component of the Australasianlandscape. Most peatlands in Australasiaare primarily composed of eitherRestionaceous or Cyperaceous peats. Sphagnum peatlands in Australia and PapuaNew Guinea/Irian Jaya (now West Papua) arelargely located in montane and alpineenvironments, but also occur down to sealevel in New Zealand and as moss patches onsome subantarctic islands. Fire is a majordeterminant of the characteristics ofpeatlands in Australasia. Peatlandmanagement in Australasia is hindered bythe need for increased understanding ofpeatland processes to enable a sustainablebalance of conservation of a small resourcewith localised utilisation. Themanagement focus in Australasia has largelybeen on ensuring ecologically sustainable Sphagnum moss harvesting, withlimited peat mining. We have found thatgeneral recovery of Sphagnum after moss harvesting canbe enhanced by harvesting larger peatlands,and by leaving one-third of the acrotelm toregenerate. The largest upland peat swampin mainland Australia, Wingecarribee Swamp,suffered a major collapse in 1998 followingpeat mining. Environmental and managementconsequences of this collapse have majorramifications for rehabilitation options. Sphagnum peatlands in Australasia arelikely to be adversely affected bydrainage, burning, grazing, trampling,global warming and peat mining.     

Effects of nutrient addition on vegetation and carbon cycling in an ombrotrophic bog

We measured net ecosystem CO₂ exchange (NEE), plant biomass and growth, species composition, peat microclimate, and litter decomposition in a fertilization experiment at Mer Bleue Bog, Ottawa, Ontario. The bog is located in the zone with the highest atmospheric nitrogen deposition for Canada, estimated at 0.8–1.2 g N m⁻² yr⁻¹ (wet deposition as NH₄ and NO₃). To establish the effect of nutrient addition on this ecosystem, we fertilized the bog with six treatments involving the application of 1.6–6 g N m⁻² yr⁻¹ (as NH₄NO₃), with and without P and K, in triplicate 3 m × 3 m plots. The initial 5–6 years have shown a loss of first Sphagnum, then Polytrichum mosses, and an increase in vascular plant biomass and leaf area index. Analyses of NEE, measured in situ with climate‐controlled chambers, indicate that contrary to expectations, the treatments with the highest levels of nutrient addition showed lower rates of maximum NEE and gross photosynthesis, but little change in ecosystem respiration after 5 years. Although shrub biomass and leaf area increased in the high nutrient plots, loss of moss photosynthesis owing to nutrient toxicity, increased vascular plant shading and greater litter accumulation contributed to the lower levels of CO₂ uptake. Our study highlights the importance of long‐term experiments as we did not observe lower NEE until the fifth year of the experiment. However, this may be a transient response as the treatment plots continue to change. Higher levels of nutrients may cause changes in plant composition and productivity and decrease the ability of peatlands to sequester CO₂ from the atmosphere.     

Effects of both substrate and nitrogen and phosphorus fertilizer on <Emphasis Type="Italic">Sphagnum palustre</Emphasis> growth in subtropical high-mountain regions and implications for peatland recovery

Human activities have recently caused severe destruction of Sphagnum wetlands in subtropical high-mountain regions, calling for urgent efforts to restore Sphagnum wetlands. Through a greenhouse experiment in western Hubei, China, we studied the effects of different substrate types (peat and mountain soil) and different levels of nitrogen (N) (0, 2, 4, 6, 10 g m^?2 year^?1) and phosphorus (P) (0, 0.2, 0.5, 1, 2 g m^?2 year^?1) on the growth of Sphagnum palustre, which was evaluated by four growth indicators: length growth, number of capitula, coverage change and biomass. We aimed to determine the optimal nutrient conditions for S. palustre growth, which would contribute to the rapid colonization and restoration of Sphagnum wetlands. The results showed that the different substrates significantly influenced S. palustre growth. Compared with those of peat, the acidic properties of the local yellow brown soil in the subtropical high-mountain regions were more favorable for S. palustre growth. As N addition increased, the four growth indicators responded inconsistently to the different substrates. While the number of capitula markedly increased, the other three indicators significantly decreased in the mountain soil or exhibited no definitive changes in the peat. The addition of P markedly promoted S. palustre growth in both substrates. However, a threshold for P fertilization existed; the highest productivity occurred at P additions of 0.2 and 0.5 g m^?2 year^?1 in the peat and mountain soil, respectively. The N and P contents in the capitula increased in parallel as the N and P fertilization rates increased, suggesting that these nutrients were absorbed proportionately and were used during the growth of S. palustre.     

Higher acidification rates in fens with phosphorus enrichment

Question: Why is bryophyte succession in eutrophicated fens faster than in natural fens? Location: Mineral‐rich fens in The Netherlands and NW Europe. Methods: Literature review on the ecology of four bryophyte species in various successional types as observed in Dutch fens. Results: Bryophyte succession in eutrophicated fens from the brown moss Calliergonella cuspidata to Sphagnum squarrosum is much faster than in natural fens with species shifts from Scorpidium scorpioides to Sphagnum subnitens. Under P‐poor conditions, the brown moss stage is stabilized as long as mineral‐rich water is supplied. This is because S. scorpioides is tolerant of rainwater, is a strong competitor and can counteract acidification to some extent while S. subnitens is intolerant to groundwater and has low growth rates and low acidification capacity. In contrast, the Sphagnum stage is stable after rapid succession from rich‐fen mosses under P‐rich conditions. Calliergonella cuspidata has suboptimal growth in rainwater, possibly due to ammonium toxicity, while the high growth rates of S. squarrosum in nutrient‐rich and highly acidic groundwater allow early establishment and rapid expansion. Conclusions: If measures to improve fen base status occur in environments of increased nutrient (P) availability, the management may not lead to the desired restoration of brown moss stages, but instead to rapid acidification by S. squarrosum.     

Growth depends on neighbours: experiments with three Sphagnum L. species

Abstract

Our aim was to search for reasons why some peat mosses (Sphagnum), despite having wide distribution areas, consistently occur in small and distantly scattered populations. The effect of interspecific interactions was proposed as the main hypothesis. Three Sphagnum species exhibiting different distribution frequencies (S. wulfianum Girg., S. teres (Schimp.) Ångstr., and S. magellanicum Brid.) were selected, and two experiments in controlled conditions were established. In the first experiment, the peat mosses were grown in mono-species, two-species, and three-species mixtures. Only the growth of the species with the most restricted distribution (S. wulfianum) responded significantly to the presence of the other Sphagnum species. In the second experiment, shoots of S. wulfianum were watered with the exudates and extracts of the other two species. Significant effects were observed on the growth of S. wulfianum. We conclude that neighbour species can suppress the growth of some bryophyte species and possibly limit their natural distribution.