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1.
Peat bogs play a large role in the global sequestration of C, and are often dominated by different Sphagnum species. Therefore, it is crucial to understand how Sphagnum vegetation in peat bogs will respond to global warming. We performed a greenhouse experiment to study the effect of four
temperature treatments (11.2, 14.7, 18.0 and 21.4°C) on the growth of four Sphagnum species: S. fuscum and S. balticum from a site in northern Sweden and S. magellanicum and S. cuspidatum from a site in southern Sweden. In addition, three combinations of these species were made to study the effect of temperature
on competition. We found that all species increased their height increment and biomass production with an increase in temperature,
while bulk densities were lower at higher temperatures. The hollow species S. cuspidatum was the least responsive species, whereas the hummock species S. fuscum increased biomass production 13-fold from the lowest to the highest temperature treatment in monocultures. Nutrient concentrations
were higher at higher temperatures, especially N concentrations of S. fuscum and S. balticum increased compared to field values. Competition between S. cuspidatum and S. magellanicum was not influenced by temperature. The mixtures of S. balticum with S. fuscum and S. balticum with S. magellanicum showed that S. balticum was the stronger competitor, but it lost competitive advantage in the highest temperature treatment. These findings suggest
that species abundances will shift in response to global warming, particularly at northern sites where hollow species will
lose competitive strength relative to hummock species and southern species. 相似文献
2.
Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological
mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NPmax), maximum efficiency of photosystem II [variable fluorescence (F
v)/maximum fluorescence yield (F
m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NPmax did not differ between control (0.2 g N m−2 year−1) and high N (3.0 g N m−2 year−1), but was higher in the mid N treatment (1.5 g N m−2 year−1). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F
v/F
m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had
no significant effect on NPmax or F
v/F
m. Addition of 2 g S m−2 year−1 showed a weak negative effect on NPmax and F
v/F
m. Our results suggest a unimodal response of NPmax to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g−1. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects
on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences
in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes. 相似文献
3.
Angela Breeuwer Monique M. P. D. Heijmans Bjorn J. M. Robroek Frank Berendse 《Ecosystems》2010,13(5):712-726
A large proportion of northern peatlands consists of Sphagnum-dominated ombrotrophic bogs. In these bogs, peat mosses (Sphagnum) and vascular plants occur in an apparent stable equilibrium, thereby sustaining the carbon sink function of the bog ecosystem.
How global warming and increased nitrogen (N) deposition will affect the species composition in bog vegetation is still unclear.
We performed a transplantation experiment in which mesocosms with intact vegetation were transplanted southward from north
Sweden to north-east Germany along a transect of four bog sites, in which both temperature and N deposition increased. In
addition, we monitored undisturbed vegetation in control plots at the four sites of the latitudinal gradient. Four growing
seasons after transplantation, ericaceous dwarf shrubs had become much more abundant when transplanted to the warmest site
which also had highest N deposition. As a result ericoid aboveground biomass in the transplanted mesocosms increased most
at the southernmost site, this site also had highest ericoid biomass in the undisturbed vegetation. The two dominant Sphagnum species showed opposing responses when transplanted southward; Sphagnum balticum height increment decreased, whereas S. fuscum height increment increased when transplanted southward. Sphagnum production did not differ significantly among the transplanted mesocosms, but was lowest in the southernmost control plots.
The dwarf shrub expansion and increased N concentrations in plant tissues we observed, point in the direction of a positive
feedback toward vascular plant-dominance suppressing peat-forming Sphagnum in the long term. However, our data also indicate that precipitation and phosphorus availability influence the competitive
balance between Sphagnum, dwarf shrubs and graminoids. 相似文献
4.
Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient 总被引:1,自引:1,他引:0
Gustaf Granath Joachim Strengbom Angela Breeuwer Monique M. P. D. Heijmans Frank Berendse Håkan Rydin 《Oecologia》2009,159(4):705-715
Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor.
We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north–south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging
from 0.28 g N m−2 year−1 in the north, to 1.49 g N m−2 year−1 in the south. The maximum photosynthetic rate (NPmax) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the photosynthesis,
and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic
factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m−2 year−1, but for S. balticum it seemed to level out at 1.14 g N m−2 year−1. The results for S. balticum suggested that transplants from different origin (with low or intermediate N deposition) respond differently to high N deposition.
This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NPmax was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the
photosynthetic capacity. 相似文献
5.
To elucidate the impact of high nitrogen (N) deposition on intact bog vegetation, as affected by phosphorus (P) availability, we conducted a 4-year fertilization experiment with N and P at six sites, one with moderate N deposition and five with high N deposition. During the growing season, N (40 kg ha–1 ya–1), P (3 kg ha–1 y–1), or a combination of both elements was applied to the vegetation. The fertilization effects turned out to be additive in nature. Adding P decreased the inorganic N concentration and increased the P concentration in the rhizosphere at two sites. Furthermore, P stimulated Sphagnum growth and Sphagnum net primary productivity (NPP) at two sites; it also seemed to encourage growth at two other sites including the moderate-deposition site. Vascular plant growth remained largely unaffected but was depressed at one high-deposition site. Adding N increased the concentration of inorganic N in the rhizosphere at the moderate-deposition site and at two of the three high-deposition sites; vascular plant growth and litter production were encouraged at three high-deposition sites. The addition of N depressed Sphagnum height increment at four high deposition sites and reduced Sphagnum NPP at two sites. Shading by vascular plants was of minor importance in explaining the negative effects of N on Sphagnum. We conclude that because P alleviates the negative impact N has on Sphagnum by enhancing its capability to assimilate the deposited N, P availability is a major factor determining the impact of N deposition on Sphagnum production and thus on carbon sequestration in bogs. 相似文献
6.
Effects of water level and temperature on performance
of four <Emphasis Type="Italic">Sphagnum</Emphasis> mosses 总被引:1,自引:0,他引:1
Bjorn J.M. Robroek Juul Limpens Angela Breeuwer Matthijs G.C. Schouten 《Plant Ecology》2007,190(1):97-107
To evaluate the effects of changes in water level and temperatures on performance of four Sphagnum mosses, S. magellanicum, S. rubellum, S. imbricatum and S. fuscum were grown at two water levels, −5 cm and −15 cm, and at two temperatures, 15°C and 20°C. These species differ in their
position along the microtopographical gradient and in their geographical distribution. Height increment, subcapitulum bulk
density, biomass production, capitulum water content and cumulative evaporation were measured. Height increment and biomass
production of S. magellanicum was lower at low water table than at high water table, whereas height increment and biomass production of S. rubellum, S. imbricatum and S. fuscum were unaffected. Height increment of S. magellanicum, S. rubellum and S. imbricatum was higher at high temperature than at low temperature. Biomass production of only S. magellanicum and S. rubellum was higher at high temperature than at low temperature, corresponding with their more southern distribution. Cumulative evaporation
of S. magellanicum and S. rubellum was lower at low water table and could be explained by hampered water transport towards the capitula. We conclude that changes
in water table and temperature may alter the Sphagnum composition on raised bogs, which may result in changes to important ecosystem processes. Therefore, it is important that
species composition and changes therein are taken into account when evaluating global change effects on raised bog ecosystems. 相似文献
7.
The effect of increased temperature and nitrogen deposition on decomposition in bogs 总被引:3,自引:0,他引:3
Angela Breeuwer Monique Heijmans Bjorn J. M. Robroek Juul Limpens Frank Berendse 《Oikos》2008,117(8):1258-1268
Despite their low primary production, ombrotrophic peatlands have a considerable potential to store atmospheric carbon as a result of their extremely low litter decomposition rates. Projected changes in temperature and nitrogen (N) deposition may increase decomposition rates by their positive effects on microbial activity and litter quality, which can be expected to result in enhanced mass loss and N release from Sphagnum and vascular plant litter. This is the first study that examines the combined effects of increased temperature and N deposition on decomposition in bogs. We investigated mass loss and N release at four bog sites along a gradient from north Sweden to northeast Germany in which both temperature and N deposition increased from north to south. We performed two litterbag experiments: one reciprocal experiment with Eriophorum vaginatum litter and one experiment using recalcitrant (Sphagnum fuscum) and more degradable (Sphagnum balticum) Sphagnum litter collected from the most northern site. We measured mass loss and N release during two (Sphagnum) and three (E. vaginatum) years. The N concentration and decomposability of the E. vaginatum litter did not differ between the sites. Mass loss from E. vaginatum litter increased over the gradient from north to south, but there was no such effect on Sphagnum litter. N loss of all litter types was affected by collection site, incubation site and time and all interactions between these factors. N release in Sphagnum was positively related to N concentration. We conclude that decomposition of vascular plants and Sphagnum litter is influenced by different environmental drivers, with enhanced temperatures stimulating mass loss of vascular plant litter, but not of Sphagnum. Enhanced N deposition increases Sphagnum litter N loss. As long‐term consequences of climate change will presumably entail a higher vascular plant production, overall litter decomposition rates are likely to increase, especially in combination with increased temperature. 相似文献
8.
Direct and interaction-mediated effects of environmental changes on peatland bryophytes 总被引:1,自引:0,他引:1
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. 相似文献
9.
Acidic Sphagnum peat bogs cover a considerable part of the territory of Russia and are an important natural source of biogenic methane, which is formed in their anaerobic layers. A considerable portion of this methane is consumed in the aerobic part of the bog profile by acidophilic methanotrophic bacteria, which comprise the methane filter of Sphagnum peat bogs and decrease CH4 emission to the atmosphere. For a long time, these bacteria escaped isolation, which became possible only after the elucidation of the optimal conditions of their functioning in situ: pH 4.5–5.5; temperature, from 15 to 20°C; and low salt concentration in the solution. Imitation of these conditions and rejection of earlier used media with a high content of biogenic elements allowed methanotrophic bacteria of two new genera and species—Methylocella palustris and Methylocapsa acidiphila—to be isolated from the peat of Sphagnum peat bogs of European northern Russia and western Siberia. These bacteria are well adapted to the conditions in cold, acidic, oligotrophic Sphagnum peat bogs. They grow in a pH range of 4.2–7.5 with an optimum at 5.0–5.5, prefer moderate temperatures (15–25°C) and media with a low content of mineral salts (200–500 mg/l), and are capable of active dinitrogen fixation. Design of fluorescently labeled 16S rRNA–targeted oligonucleotide probes for the detection of Methylocella palustris and Methylocapsa acidiphila and their application to the analysis of sphagnum peat samples showed that these bacteria represent dominant populations of methanotrophs with a density of 105–106 cells/g peat. In addition to Methylocella and Methylocapsa populations, one more abundant population of methanotrophs was revealed (106 cells/g peat), which were phylogenetically close to the genus Methylocystis. 相似文献
10.
Foliar δ15N, %N and %P in the dominant woody and herbaceous species across nutrient gradients in New Zealand restiad (family Restionaceae)
raised bogs revealed marked differences in plant δ15N correlations with P. The two heath shrubs, Leptospermum scoparium (Myrtaceae) and Dracophyllum scoparium (Epacridaceae), showed considerable isotopic variation (−2.03 to −15.55‰, and −0.39 to −12.06‰, respectively) across the
bogs, with foliar δ15N strongly and positively correlated with P concentrations in foliage and peat, and negatively correlated with foliar N:P
ratios. For L. scoparium, the isotopic gradient was not linked to ectomycorrhizal (ECM) fractionation as ECMs occurred only on higher nutrient marginal
peats where 15N depletion was least. In strong contrast, restiad species (Empodisma minus Sporadanthus ferrugineus, S. traversii) showed little isotopic variation across the same nutrient gradients. Empodisma minus and S. traversii had δ15N levels consistently around 0‰ (means of −0.12‰ and +0.15‰ respectively), and S. ferrugineus, which co-habited with E. minus, was more depleted (mean −4.97‰). The isotopic differences between heath shrubs and restiads were similar in floristically
dissimilar bogs and may be linked to contrasting nutrient demands, acquisition mechanisms, and root morphology. Leptospermum scoparium shrubs on low nutrient peats were stunted, with low tissue P concentrations, and high N:P ratios, suggesting they were P-limited,
which was probably exacerbated by markedly reduced mycorrhizal colonisations. The coupling of δ15N depletion and %P in heath shrubs suggests that N fractionation is promoted by P limitation. In contrast, the constancy in
δ15N of the restiad species through the N and P gradients suggests that these are not suffering from P limitation. 相似文献
11.
Nitrogen deposition interacts with climate in affecting production and decomposition rates in Sphagnum mosses 总被引:1,自引:0,他引:1
RENATO GERDOL ALESSANDRO PETRAGLIA† LUCA BRAGAZZA PAOLA IACUMIN‡ LISA BRANCALEONI 《Global Change Biology》2007,13(8):1810-1821
Increasing rates of atmospheric nitrogen (N) deposition may reduce growth and accelerate decomposition of Sphagnum mosses in bogs. Sphagnum growth and rates of Sphagnum litter decomposition may also vary because of climate change as both processes are controlled by climatic factors. The initial purpose of this study was to assess if growth and litter decomposition of hummock and lawn Sphagnum species varied with increasing N input in a factorial mid‐term (2002–2005) experiment of N and phosphorus (P) addition, in a bog on the southern Alps of Italy. However, as the experimental period was characterized by an exceptional heat wave in summer 2003, we also explored the interacting effects of fertilization and strongly varying climate on growth and decomposition rates of Sphagnum. The heat wave implied strong dehydration of the upper Sphagnum layer even if precipitation in summer 2003 did not differ appreciably from the overall mean. Sphagnum production was somewhat depressed by high levels (3 g m−2 yr−1) of N addition without concomitant addition of P presumably because of nutrient imbalance in the tissues, but production rates were much lower than the overall means in 2003, when no effect of nutrient addition could be observed. Adding N at high level also increased the potential decay of Sphagnum litter. Higher CO2 emission from N‐fertilized litter was due to amelioration of litter chemistry showing lower C/N quotients in the N‐fertilized treatments. Rates of CO2 emission from incubated litter also were more strongly affected by water content than by nutrient status, with practically no CO2 emission detected when litter was dry. We conclude that higher rates of atmospheric N availability input may depress Sphagnum growth because of P, and presumably potassium, (co‐)limitation. Higher N availability is also expected to promote potential decay of Sphagnum litter by ameliorating litter chemistry. However, both effects are less pronounced if the growing Sphagnum apex and the underlying senescing tissues dry out. 相似文献
12.
MARCEL R. HOOSBEEK NICO VAN BREEMEN HARRI VASANDER† ALEXANDRE BUTTLER§ FRANK BERENDSE‡ 《Global Change Biology》2002,8(11):1130-1138
The free air carbon dioxide enrichment (FACE) and N deposition experiments on four ombrotrophic bogs in Finland, Sweden, the Netherlands and Switzerland, revealed that after three years of treatment: (1) elevated atmospheric CO2 concentration had no significant effect on the biomass growth of Sphagnum and vascular species; and (2) increased N deposition reduced Sphagnum growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum, while vascular plant biomass growth was not affected. This paper focuses on water chemistry, plant nutrient content, and litter decomposition rates. Potassium limitation, or low supply of K and P, may have prevented a significant increase of Sphagnum growth under elevated CO2 and N deposition. Vascular plant growth under elevated CO2 and N deposition was also limited by K, or by K in combination with P or N (N in CO2 experiment). Elevated CO2 and N deposition had no effect on decomposition rates of Sphagnum and vascular plant litter. Aside from a possible effect of N deposition on light competition between species, we expect that elevated atmospheric CO2 and N deposition concentrations will not affect Sphagnum and vascular plant growth in bogs of north‐west Europe due to K‐, or K in combination with N‐ or P‐, limited growth. For the same reason we expect no effect of elevated CO2 and N deposition on litter decomposition. Net primary production of raised ombrotrophic bogs that are at or close to steady state, is regulated by input of nutrients through atmospheric deposition. Therefore, we hypothesize that the expected increase of plant growth under elevated CO2 and N deposition is diminished by current levels of K (and to some extent P and N) in atmospheric deposition. 相似文献
13.
Vegetation shifts towards wetter site conditions on oceanic ombrotrophic bogs in southwestern Sweden
Question: Is ombrotrophic bog vegetation in an oceanic region of southwestern Sweden changing in the same direction over a five year period (1999 ‐ 2004) as northwest European bogs in the last 50 years, i.e. towards drier and more eutrophic vegetation? Location: The province of Halland, southwestern Sweden. Methods: Changes in species composition were monitored in 750 permanently marked plots in 25 ombrotrophic bogs from 1999 to 2004. Changes in species occurrences and richness were analysed and a multivariate statistical method (DCA) was used to analyse vegetation changes. Results: The species composition changed towards wetter rather than drier conditions, which is unlike the general pattern of vegetation change on bogs in northwestern Europe. Species typical of wetter site conditions including most Sphagnum species increased in abundance on the bogs until 2004. The total number of species per plot increased, mostly due to the increased species richness of Sphagnum species. Nitrogen‐demanding (eutrophic) species increased in occurrence. Conclusions: Ombrotrophic bog vegetation in an oceanic region in Sweden became wetter and was resilient to short‐term climatic shifts, after three years of below normal precipitation followed by several years with normal precipitation levels. Shifts towards more nitrogen demanding species were rapid in this region where the deposition levels have been high for several decades. 相似文献
14.
《Journal of bryology》2013,35(2):83-90
AbstractNitrogen deposition may cause shifts in the Sphagnum species composition of bogs, ultimately affecting the conservation value of these systems. We studied the effects of N and P on the expansion of S. fallax and S. flexuosum in bogs. We related historical census data of S. fallax, S. flexuosum, and four of their accompanying species to changes in N deposition. In addition, we conducted two fertilization experiments with N and P; one at a low deposition site with S. flexuosum and one at two high deposition sites with S. fallax. Finally, we related existing data on capitulum N and P concentrations of S. fallax to its abundance in the field.A relative increase in observed frequency of S. fallax coincided with an historical increase in N deposition in the Netherlands. There was no indication that S. fallax consistently outcompeted one of the other five Sphagnum species; the observed frequency of the Sphagnum species analysed was rather stable with time. The census data on S. flexuosum did not indicate a response to N deposition, but the species expanded at the low N deposition site when extra N was applied. In contrast, the expansion of S. fallax at the high deposition sites was limited by P. Organic nutrient concentrations suggested that when S. fallax can maintain a capitulum N concentration of 7 mg g-1 or higher and a P concentration of 0.7 mg g-1 or higher the species can grow to dominate.We conclude that S. fallax will gradually colonize an increasing number of new habitats in areas with a low, albeit increasing, N deposition, but will only grow to dominate when P supply is adequate. Then, the expansion of S. fallax may lead to ousting of the other Sphagnum species present. 相似文献
15.
John McCallum Noel Porter Bruce Searle Martin Shaw Bodhi Bettjeman Michael McManus 《Plant and Soil》2005,269(1-2):151-158
Although glasshouse studies have conclusively demonstrated that S nutrition can affect onion (Allium cepaL.) pungency this has been rarely observed in field-based studies due to difficulties in controlling S nutrition and lack
of efficient methods for measurement of flavour bioactives. We have developed a rapid automated method for determination of
onion lachrymatory factor ((Z, E)-thiopropanal-S-oxide; LF) based on juice extraction into dichloromethane and gas chromatography (GC) analysis with flame photometric detection.
We evaluated this in a field trial of a mild (cv. ‘Encore’) and a pungent (cv. ‘Kojak’) onion cultivar grown on a low S soil
with and without S addition, under high or low N treatments. No treatments significantly affected bulb fresh weight but S
fertilisation significantly increased bulb total S, sulfate, pungency, LF and flavour precursor levels in both varieties.
Analysis of bulb flavour precursors by HPLC confirmed that juice LF levels paralleled levels of the flavour precursor S-1-propenyl cysteine sulfoxide. The pungent cultivar also exhibited significant N main effects on bulb LF, total S and sulfate.
We also assayed the key S-assimilatory enzyme, APS reductase (APR) in leaves before and during bulbing. Specific activities
in the range of 1 to 11 nmol mg−1·min−1 were observed in youngest leaves, but only the milder cultivar exhibited significant stage × N × S effects. These findings
suggest that sulfur metabolism of mild and pungent onions respond differently to N fertility, and that GC of LF is practical
for field-based studies of onion flavour. 相似文献
16.
S. A. Käärmelahti R. J. M. Temmink G. van Dijk A. Prager M. Kohl G. Gaudig A. H. W. Koks W. Liu R. J. E. Vroom K. Gerwing C. J. H. Peters M. Krebs C. Fritz 《Plant biology (Stuttgart, Germany)》2023,25(5):715-726
- 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.
17.
Sylvia Toet Johannes H. C. Cornelissen Rien Aerts Richard S. P. van Logtestijn Miranda de Beus Rob Stoevelaar 《Plant Ecology》2006,182(1-2):27-40
We studied the effects of elevated CO2 (180–200 ppmv above ambient) on growth and chemistry of three moss species (Sphagnum palustre, S. recurvum and Polytrichum commune) in a lowland peatland in the Netherlands. Thereto, we conducted both a greenhouse experiment with both Sphagnum species and a field experiment with all three species using MiniFACE (Free Air CO2 Enrichment) technology during 3 years. The greenhouse experiment showed that Sphagnum growth was stimulated by elevated CO2 in the short term, but that in the longer term (≥1 year) growth was probably inhibited by low water tables and/or down-regulation
of photosynthesis. In the field experiment, we did not find significant changes in moss abundance in response to elevated
CO2, although CO2 enrichment appeared to reduce S. recurvum abundance. Both Sphagnum species showed stronger responses to spatial variation in hydrology than to increased atmospheric CO2 concentrations. Polytrichum was insensitive to changes in hydrology. Apart from the confounding effects of hydrology, the relative lack of growth response
of the moss species may also have been due to the relatively small increase in assimilated CO2 as achieved by the experimentally added CO2. We calculated that the added CO2 contributed at most 32% to the carbon assimilation of the mosses, while our estimates based on stable C isotope data even
suggest lower contributions for Sphagnum (24–27%). Chemical analyses of the mosses showed only small elevated CO2 effects on living tissue N concentration and C/N ratio of the mosses, but the C/N ratio of Polytrichum was substantially lower than those of the Sphagnum species. Continuing expansion of Polytrichum at the expense of Sphagnum could reduce the C sink function of this lowland Sphagnum peatland, and similar ones elsewhere, as litter decomposition rates would probably be enhanced. Such a reduction in sink
function would be driven mostly by increased atmospheric N deposition, water table regulation for agricultural purposes and
land management to preserve the early successional stage (mowing, tree and shrub removal), since these anthropogenic factors
will probably exert a greater control on competition between Polytrichum and Sphagnum than increased atmospheric CO2 concentrations. 相似文献
18.
19.
Mineral nutrient economy in competing species of Sphagnum mosses 总被引:1,自引:0,他引:1
Bog vegetation, which is dominated by Sphagnum mosses, depends exclusively on aerial deposition of mineral nutrients. We studied how the main mineral nutrients are distributed
between intracellular and extracellular exchangeable fractions and along the vertical physiological gradient of shoot age
in seven Sphagnum species occupying contrasting bog microhabitats. While the Sphagnum exchangeable cation content decreased generally in the order Ca2+ ≥ K+, Na+, Mg2+ > Al3+ > NH4
+, intracellular element content decreased in the order N > K > Na, Mg, P, Ca, Al. Calcium occurred mainly in the exchangeable
form while Mg, Na and particularly K, Al and N occurred inside cells. Hummock species with a higher cation exchange capacity
(CEC) accumulated more exchangeable Ca2+, while the hollow species with a lower CEC accumulated more exchangeable Na+, particularly in dead shoot segments. Intracellular N and P, but not metallic elements, were consistently lower in dead shoot
segments, indicating the possibility of N and P reutilization from senescing segments. The greatest variation in tissue nutrient
content and distribution was between species from contrasting microhabitats. The greatest variation within microhabitats was
between the dissimilar species S. angustifolium and S. magellanicum. The latter species had the intracellular N content about 40% lower than other species, including even this species when
grown alone. This indicates unequal competition for N, which can lead to outcompeting of S. magellanicum from mixed patches. We assume that efficient cation exchange enables Sphagnum vegetation to retain immediately the cationic nutrients from rainwater. This may represent an important mechanism of temporal
extension of mineral nutrient availability to subsequent slow intracellular nutrient uptake. 相似文献
20.
Two Sphagnum moss species occupying hummock areas (Sphagnum capillifolium) and wetter hollows (Sphagnum recurvum) on a raised bog in north east Scotland were treated every two weeks with NH4NO3 solutions to supply 3g N m–2 yr–1. Although S. recurvum moss contained a greater concentration of total P than S. capillifolium the amounts and N:P ratios were similar in both species. Larger amounts of total dissolved P (TDP) and molybdate reactive P (MRP) were extracted from beneath S. recurvum to 25 cm below the moss. Additions of N both increased and decreased the amounts of TDP at different times, and decreased MRP. The MRP fraction accounted for about 20 per cent of TDP and the difference was assumed to be in organic forms (DOP). Nitrogen addition had no effect on the amounts of DOP, but C:P ratios of this fraction changed with species, depth and N addition. Microbial P accounted for as much as 70 per cent of total P and showed seasonal variations, but no differences between the two moss species and N addition. 相似文献