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1.
Nitrogen fixation was measured by the acetylene reduction method in a high Arctic ecosystem at Kongsfjorden, Spitsbergen (79°N,
12°E). The most important source of biologically fixed nitrogen was found in cyanobacteria either as free living colonies
ofNostoc sp. in wet unvegetated or sparsely vegetated grounds or growing as epiphytes on bryophytes. Fixation associated with plant
roots or in soil and peat samples had little or no significance for nitrogen input to the ecosystem. The ability to support
an epiphytic flora of nitrogen-fixing cyanobacteria varied greatly between bryophyte species.Calliergon richardsonii andSanionia uncinata seemed especially well adapted for harbouring epiphytic cyanobacteria, but the extent of nitrogen fixation varied with the
growing location. The rate of nitrogen fixation was greatly influenced by grazing by geese. In a geese-grazing area values
were found with a maximum of 693.6±1.5 nmol C2H4 h−1 g (dry weight)−1 while the maximum value for ungrazed areas was 65.3±16.6 nmol C2H4 h−1 g (dry weight)−1. In the grazed area cyanobacteria were also found fixing nitrogen epiphytically on grass. The high plant productivity, supporting
heavy grazing, clearly indicates an effective transfer of fixed nitrogen to the plant community. Under cliffs harbouring colonies
of birds, the biological nitrogen fixation was inhibited by bird droppings. 相似文献
2.
Loic Charpy Katarzyna A. Palinska Beatriz Casareto Marie José Langlade Yoshimi Suzuki Raeid M. M. Abed Stjepko Golubic 《Microbial ecology》2010,59(1):174-186
Dinitrogen-fixing organisms in cyanobacterial mats were studied in two shallow coral reef ecosystems: La Reunion Island, southwestern
Indian Ocean, Sesoko (Okinawa) Island, and northwestern Pacific Ocean. Rapidly expanding benthic miniblooms, frequently dominated
by a single cyanobacterial taxon, were identified by microscopy and molecular tools. In addition, nitrogenase activity by
these blooms was measured in situ. Dinitrogen fixation and its contribution to mat primary production were calculated using
15N2 and 13C methods. Dinitrogen-fixing cyanobacteria from mats in La Reunion and Sesoko showed few differences in taxonomic composition.
Anabaena sp. among heterocystous and Hydrocoleum majus and Symploca hydnoides among nonheterocystous cyanobacteria occurred in microbial mats of both sites. Oscillatoria bonnemaisonii and Leptolyngbya spp. occurred only in La Reunion, whereas Hydrocoleum coccineum dominated in Sesoko. Other mats dominated by Hydrocoleum lyngbyaceum, Phormidium laysanense, and Trichocoleus tenerrimus occurred at lower frequencies. The 24-h nitrogenase activity, as measured by acetylene reduction, varied between 11 and 324 nmoles
C2H2 reduced μg−1 Chl a. The highest values were achieved by heterocystous Anabaena sp. performed mostly during the day. Highest values for nonheterocystous cyanobacteria were achieved by H. coccineum mostly during the night. Daily nitrogen fixation varied from nine (Leptolyngbya) to 238 nmoles N2 μg−1 Chl day−1 (H. coccineum). Primary production rates ranged from 1,321 (S. hydnoides) to 9,933 nmoles C μg−1 Chl day−1 (H. coccineum). Dinitrogen fixation satisfied between 5% and 21% of the nitrogen required for primary production. 相似文献
3.
Biofilms growing on ice and benthic mats are among the most conspicuous biological communities in Antarctic landscapes and
harbour a high diversity of organisms. These communities are consortia that make important contributions to carbon and nitrogen
input in non-marine Antarctic ecosystems. Here, we study the effect of increasing temperatures on the carbon and nitrogen
metabolism of two benthic communities on Byers Peninsula (Livingston Island, Maritime Antarctica): a biofilm dominated by
green algae growing on seasonal ice, and a land-based microbial mat composed mainly of cyanobacteria. Inorganic carbon photoassimilation,
urea and nitrate uptake and N2-fixation (acetylene reduction activity) rates were determined in situ in parallel at five different temperatures (0, 5, 10,
15, 25°C) using thermostatic baths. The results for the cyanobacterial mat showed that photosynthesis and N2-fixation responded positively to increased temperatures, but urea and NO3− uptake rates did not show a significant variation related to temperature. This microbial mat exhibits relatively low activity
at 0°C whereas at higher temperatures (up to 15°C), N2-fixation rate increased significantly. Similarly, the maximum photosynthetic activity increased in parallel with temperature
and showed no saturation up to 25°C. In contrast, the ice biofilm displayed higher photosynthetic activity at 0°C than at
the other temperatures assayed, and it showed elevated photoinhibition at warmer temperatures. 相似文献
4.
The distributions of carbon, nitrogen and phosphorus in a moss community-soil system developed on a naked region in Rundvågskollane (69050'S, 39009'E), East Antarctica, were investigated in order to analyze the flow of matter in an Antarctic terrestrial ecosystem.
- The moss community was formed from many moss blocks of different sizes and was composed ofBryum pseudotriquetrum (Hedw.) Gaertn., Meyer et Scherb.,Ceratodon purpureus (Hedw.) Brid. andGrimmia lawiana J. H. Willis. The surface of the community was covered with cyanobacteria.
- It was estimated that nitrogen fixed by cyanobacteria flowed from these organisms to the moss and that little nitrogen was transported within the moss body.
- A large amount of phosphorus existed in the soil. The moss community had a high phosphorus content although the amount itself was relatively little due to the small phytomass.
- It seems that absorption of phosphorus from soil is difficult for moss, because of the paucity of water necessary for the movement of phosphorus and the suppressed growth of moss due to the arid conditions.
5.
Summary
Daviesia mimosoides is a common understorey legume in Eucalyptus forests of the Brindabella Range in southeastern Australia, capable of fixing
atmospheric nitrogen. Rates of N fixation were measured by the acetylene-reduction technique over a growing season in the
field. Pot trials under controlled conditions were also carried out to elucidate effects of soil moisture, temperature, and
light.
Average rates in the field varied from about 1–5 μ mol C2H4/g/h (wet weight of nodule), but rates up to 14 μ mol C2H4/g/h were measured in optimum controlled conditions. Annual N-fixation rates approximate 4.5–7.0 kg/ha.
In pot trials, rate of acetylene reduction decreased with soil moisture to about−10 MPa tension, with a marked depression
at about−6 MPa, but within the normal field range of soil moisture there was little correlation of moisture with average acetylene
reduction rate. Rates were similar in the temperature range of 20–30°C, but were depressed by either low or high temperature
(<10 or >30°C). Diurnal fluctuations in acetylene reduction rates were not correlated with solar radiation, but rates were
limited by high mid-day temperatures. 相似文献
6.
Summary The seasonal patterns of nodulation, acetylene reduction, nitrogen uptake and nitrogen fixation were studies for 11 pigeonpea
cultivars belonging to different maturity groups grown on an Alfisol at ICRISAT Center, Patancheru, India. In all cultivars
the nodule number and mass increased to a maximum around 60–80 days after sowing and then declined. The nodule number and
mass of medium- and late-maturing cultivars was greater than that of early-maturing cultivars. The nitrogenase activity per
plant increased to 60 days after sowing and declined thereafter, with little activity at 100 days when the crop was flowering.
At later stages of plant growth nodules formed down to 90 cm below the soil surface but those at greater depth appeared less
active than those near the surface.
All the 11 cultivars continued to accumulate dry matter until 140 days, with most biomass production by the late-maturing
cultivars (up to 11 t ha−1) and least by the early-maturing determinate cultivars (4 t ha−1). Total nitrogen uptake ranged from 69 to 134 kg ha−1. Nitrogen fixation by pigeonpea was estimated as the difference in total nitrogen uptake between pigeonpea and sorghum and
could amount to 69 kg N ha−1 per season, or half the total nitrogen uptake. Fixation by pigeonpea increased with crop duration, but there were differences
within each maturity group. The limitations of the methods used for estimating N2 fixation by pigeonpea are discussed.
Submitted as J.A. No. 552 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). 相似文献
7.
Yoshio Ino 《Ecological Research》1990,5(2):195-205
Net photosynthesis and dark respiration (CO2 flux) of Antarctic mosses were measured at Langhovde, East Antarctica, from 9 to 17 January 1988. Moss blocks were taken
from communities in the Yukidori Valley (69°14′30″S, 39°46′00″E) at Langhovde. Each block was composed ofCeratodon purpureus andBryum pseudotriquetrum, orB. pseudotriquetrum. The upper part of the block was used to measure net photosynthesis and dark respiration. The net photosynthesis of each
sample was measured in the field for one or three days with two infrared CO2 gas analyzers and an assimilation chamber. The relationships of net photosynthetic rate and dark respiration rate, to the
water content of the sample, the intensity of solar radiation and the moss temperature were estimated from the field data.
The maximum rate of net photosynthesis was about 4 μmol CO2 m−2s−1 at saturating radiation intensity and at optimum temperature, about 10°C. Environmental features of moss habitats in the
Yukidori Valley are discussed in relation to these results. 相似文献
8.
Various types of sub-aerially exposed microbial mats, including emergent mats, beach sand, beach rock and Kopara mats, are
widespread on the 78 km (25 km2) of rim surrounding the Tikehau atoll lagoon. These mats form laminated accretions or diffuse microbial communities growing
under high insolation and temperatures, and are therefore subject to desiccation. Both heterocystous and non-heterocystous
cyanobacteria occur in these mats. Using acetylene reduction techniques, nitrogenase activity was observed at all sites over
a period of 5 years and was 3–17 times higher during daylight than at night in all communities except for beach rock. 15N2 measurements indicated a molar ratio of acetylene reduction to N2 fixed of 1.6 for all exposed communities. Estimated N2 fixation ranged from 1.44 to 8.0 mg N m−2 day−1 in these exposed communities (mean of 4.66 mg N m−2 day−1) with beachrock showing the highest rates. For the whole reef rim, daily N2 fixation amounted to 98.42 kg N day−1 which represents 28% of the rate of fixation in the entire lagoon (area 400 km2). 相似文献
9.
Microclimatic parameters influencing nitrogen fixation in the phyllosphere in a Costa Rican premontane rain forest 总被引:1,自引:0,他引:1
Elke Freiberg 《Oecologia》1998,117(1-2):9-18
The acetylene reduction method was used to measure nitrogen fixation in the phyllosphere of attached leaves of different
phorophytes under natural conditions in a premontane rain forest in Costa Rica. Maximum rates of nitrogen fixation (26 ng N · cm−2 leaf area · h−1) – mainly due to the activity of two species of Scytonema (Cyanobacteria) – were measured in the rainy season in bright sunlight. Rates of nitrogen fixation were correlated with the
leaf area covered by Scytonema. In periods without precipitation the fixation activity decreased to zero within 2–3 days. As long as the epiphylls were sufficiently
supplied with water, other microclimatic factors like temperature and light intensity also influenced nitrogen fixation rates,
but to a lesser extent. Relative humidity and species of phorophyte showed no direct influence. It was concluded that the
most important factor for nitrogen fixation in the phyllosphere was the availability of liquid water. Linking these results
to meteorological data, the input of nitrogen by biological nitrogen fixation in the phyllosphere in the investigation area
was estimated to be as much as 1.6 ± 0.8 kg N · ha−1 · year−1 per unit of leaf area index (LAI). For an LAI of 2 for the understory the nitrogen input would vary between 2 and 5 kg N ·
ha−1 · year−1. This work also demonstrates the importance of detailed knowledge of variation in microclimate throughout the year as a basis
for extrapolation of the annual nitrogen input.
Received: 21 December 1997 / Accepted: 14 June 1998 相似文献
10.
Nubbins of the coral Acropora aspera were artificially bleached and nitrogen fixation (acetylene reduction) rates were measured on the developing epilithic communities.
Seasonal comparisons were made between corals that died in summer of heat stress and corals that died in winter from natural
cold stress. Rates of acetylene reduction from artificially bleached corals peaked at 26.66 nmol cm−2 h−1 2 weeks after summer mortality, while rates from natural winter mortality peaked at 18.07 nmol cm−2 h−1 12 days after coral death. Comparative rates of acetylene reduction taken from live corals and coral rubble ranged between
0.56 and 1.16 nmol cm−2 h−1, and 0.15 and 12.77 nmol cm−2 h−1, respectively. N2-fixation rates from dead corals were up to 30 times greater than those measured on live corals. The observed increase in
N2-fixation from dead corals may increase the availability of nitrogen for use in trophic processes within the reef for an extended
period following the initial mortality event. If the spatial scale over which coral mortality has occurred in past thermal
bleaching events is considered the ramifications of such an increase may be substantial. 相似文献
11.
This study reports the effect of salinity and inoculation on growth, ion uptake and nitrogen fixation byVigna radiata. A soil ECe level of 7.5 dS m−1 was quite detrimental causing about 60% decline in dry matter and grain yield of mungbean plants whereas a soil ECe level of 10.0 dS m−1 was almost toxic. In contrast most of the studied strains of Rhizobium were salt tolerant. Nevertheless, nodulation, nitrogen
fixation and total nitrogen concentration in the plant was drastically affected at high salt concentration. A noticeable decline
in acetylene reduction activity occurred when salinity level increased to 7.5 dS m−1. 相似文献
12.
N fixation in feather moss carpets is maximized in late secondary successional boreal forests; however, there is limited understanding
of the ecosystem factors that drive cyanobacterial N fixation in feather mosses with successional stage. We conducted a reciprocal
transplant experiment to assess factors in both early and late succession that control N fixation in feather moss carpets
dominated by Pleurozium schreberi. In 2003, intact microplots of moss carpets (30 cm × 30 cm × 10–20 cm deep) were excavated from three early secondary successional
(41–101 years since last fire) forest sites and either replanted within the same stand or transplanted into one of three late
successional (241–356 years since last fire) forest sites and the transverse was done for late successional layers of moss.
Moss plots were monitored for changes in N-fixation rates by acetylene reduction (June 2003–September 2005) and changes in
the presence of cyanobacteria on moss shoots by microscopy (2004). Forest nutrient status was measured using ionic resin capsules
buried in the humus layer. Late successional forests exhibit high rates of N fixation and consistently high numbers of cyanobacteria
on moss shoots, but low levels of available N. Conversely, early successional forests have higher N availability and have
low rates of N fixation and limited presence of cyanobacteria on moss shoots. Transplantation of moss carpets resulted in
a significant shift in presence and activity of cyanobacteria 1 year after initiation of the experiment responding to N fertility
differences in early versus late successional forests. 相似文献
13.
The ability of the benthic cyanobacterium Lyngbya wollei to fix nitrogen was studied using field samples and axenic cultures. L. wollei was collected and isolated from Lake Okeechobee, Florida, where it forms extensive mats. Rates of acetylene reduction up
to 39.1 nmol mg dry wt−1 h−1 were observed for field samples. The maximum observed rate of acetylene reduction in axenic laboratory cultures was 200 nmol
mg dry wt−1 h−1. Aerobic conditions limited nitrogen fixation activity, but dark/light cycles promoted the development of activity. Reduced
oxygen levels appeared to be required for the development of significant levels of nitrogenase activity. The level of irradiance
also had a significant impact on the level of activity. The potential significance of nitrogen fixation to Lyngbya production is discussed. 相似文献
14.
A macrozoobenthic community study was conducted in an East Greenlandic fjord (Young Sound, 74°18′N; 20°15′W) during the ice-free
period from July to August in 1996. Grab samples as well as underwater photography were used for quantifying the macrozoobenthos
at water depths between 20 and 85 m. Abundance decreased with depth from 2700 ind. · m−2 at 20 m to 900 ind. · m−2 at 85 m. At a time series station at 35 m, abundance increased from 700 ind. · m−2 in mid-July to 1400 ind. · m−2 in mid-August. Polychaetes dominated in grab samples but bivalves constituted an important part of the benthic fauna, especially
at the shallow part of the depth gradient. Photographs revealed high abundances of large epifaunal species, especially brittle
stars. Diversity was generally high, with around 45 species per 201 individuals, as calculated by Hurlbert's rarefaction term.
A gradual change in community structure with depth was observed, which could be related to variation in sediment composition
and disturbance intensity.
Accepted: 20 May 2000 相似文献
15.
Kume Atsushi Nagafuchi Osamu Akune Suguru Nakatani Nobutake Chiwa Masaaki Tetsuka Kenshi 《Ecological Research》2010,25(1):233-243
With the industrialization in East Asia, greater amounts of ozone and acidic aerosols are transported to Japan. Yakushima
Island (30°20′N, 130°31′E) is affected directly by long-range transboundary air pollution from the continent because there
are no industrial areas and sources of pollution between the continent and the island. Recently, there has been a significant
decline of Pinus amamiana in the island and the actual condition of air pollution was investigated. A significant amount of air pollutants were detected
in winter. The daily mean tropospheric O3 concentration was nearly 100 ppb in winter. A large amount of non-sea salt sulfate (nss-SO4
2−) was deposited on the needle surfaces in the northwest part of the island and dry deposition rates of SO4
2− were remarkably higher in February than in November. About half of the increase in SO4
2− was nss-SO4
2− and the rate in February was over four to five times as high as that in November. The load of dry deposition on the crown
of trees was strongly influenced by the topographic position of the slope. The amount of deposited SO4
2− was larger on trees growing on ridges and the tendency of P. amamiana to grow on ridges where it sticks out over 20 m enhances the load of dry deposition and O3 on the needle surfaces. The potassium leakage and ethylene emission from needles were remarkably increased and the needle
mass per area decreased from November to February. It was suggested that the additional input of nss-SO4
2− acidifies the needle surface and accelerates leaf surface deterioration and leaching from needles and soils. 相似文献
16.
Effect of Mineral Phosphate Solubilization on Biological Nitrogen Fixation by Diazotrophic Cyanobacteria 总被引:4,自引:0,他引:4
The ability of two diazotrophic cyanobacteria Westiellopsis prolifica and Anabaena variabilis were examined to solubilize extracellular insoluble tricalcium phosphate (TCP) and Mussorie rock phosphate (MRP). The two
strains exhibited a differential response to insoluble forms of phosphorus used. W. prolifica showed better growth in presence of MRP while A. variabilis proliferated better in presence of TCP. Biological nitrogen fixation measured in terms of acetylene reduction (AR) activity
showed significant variation among the concentrations of TCP or MRP and time of incubation. W. prolifica and A. variabilis showed maximum AR activity on 14 and 21 days of incubation respectively. In general AR activity in presence of MRP was always
less than that in presence of TCP at all concentrations. Among the two cyanobacteria A. variabilis was best in terms of P-solubilization and nitrogen fixation and TCP (20 mg P l−1) was the best source of insoluble P rather than MRP or K2HPO4. 相似文献
17.
Localized Tetrazolium Reduction in Relation to N2 Fixation, CO2 Fixation, and H2 Uptake in Aquatic Filamentous Cyanobacteria 总被引:3,自引:2,他引:1 下载免费PDF全文
The aquatic filamentous cyanobacteria Anabaena oscillarioides and Trichodesmium sp. reveal specific cellular regions of tetrazolium salt reduction. The effects of localized reduction of five tetrazolium salts on N2 fixation (acetylene reduction), 14CO2 fixation, and 3H2 utilization were examined. During short-term (within 30 min) exposures in A. oscillarioides, salt reduction in heterocysts occurred simultaneously with inhibition of acetylene reduction. Conversely, when salts failed to either penetrate or be reduced in heterocysts, no inhibition of acetylene reduction occurred. When salts were rapidly reduced in vegetative cells, 14CO2 fixation and 3H2 utilization rates decreased, whereas salts exclusively reduced in heterocysts were not linked to blockage of these processes. In the nonheterocystous genus Trichodesmium, the deposition of reduced 2,3,5-triphenyl-2-tetrazolium chloride (TTC) in the internal cores of trichomes occurs simultaneously with a lowering of acetylene reduction rates. Since TTC deposition in heterocysts of A. oscillarioides occurs contemporaneously with inhibition of acetylene reduction, we conclude that the cellular reduction of this salt is of use in locating potential N2-fixing sites in cyanobacteria. The possible applications and problems associated with interpreting localized reduction of tetrazolium salts in cyanobacteria are presented. 相似文献
18.
Summary Tillage has been shown to affect the uptake of phosphorus (P) and yield of soybeans, [Glycine max (L.) Merr.], but there is little information concerning the effects of P fertilization on nitrogen (N2) fixation in soybeans under no-tillage. Two field experiments were conducted in 1980 and 1981 to determine the effects of
soil P on N2 fixation under no-tillage and to study the interaction of P fertilization and tillage of N2 fixation, nutrient uptake, and yield of soybeans. In Exp. I, P was applied in 1977 at five rates up to 384 kg P ha−1 and the effects of residual soil P were evaluated in 1980 and 1981 under no-tillage management. Nitrogen fixation rates,
as measured by acetylene reduction assay, were significantly affected by soil P in Exp. I, but the assay proved to be a poor
technique for estimating total plant N in these tests. Acetylene reduction rates and plant P increased rapidly as soil P increased
from 2 to 20 mg kg−1, with little additional increase above 20 mg P kg−1.
In Exp. II, rates (0, 32, 64, and 128 kg P ha−1) and time (fall, spring and fall plus spring) of P application were compared under conventional tillage and no tillage. However,
plant P increased with increasing levels of applied P. Applied P had no affect on acetylene reduction rates but rates were
greater for no-tillage than conventional tillage at the V9 and R5 stages of growth in 1981. Plant uptake of P was more efficient
under no-tillage than under conventional tillage in 1980 and 1981. Application of 64 kg P ha−1 under no-tillage resulted in equivalent plant P levels as the 128 kg P ha−1 applied under conventional tillage. 相似文献
19.
Jan Pilarski 《Acta Physiologiae Plantarum》2002,24(1):29-36
It has been demonstrated that during the whole year the stems are photosyntheticaly active and capable of assimilating atmospheric
CO2. The intensity of photosynthesis varies. During the vegetation period the registered net photosynthesis lasted up to 13 hours
per day, and in the leafless period for 2–3 hours a day. Photosynthesis was registered also at temperatures below zero (−3
°C) as a reduced CO2 evolution in light in comparison with darkness. The maximal net photosynthesis values during the vegetation period amounted
to 6 up 8 μmol (CO2)·m−2·s−1, and in the leafless period 0.5 – 1 μmol (CO2)·m−2·s−1, and they were close to being up to twice as big as the values obtained of darkness respiration. An increase of the photosynthetic
activity of stems preceded the spring development of the leaves. 相似文献
20.
Nitrogenase activity (C2H2 reduction) ofNostoc commune isolated from Schirmacher Oasis (Antarctica) was compared withNostoc muscorum, N. calcicola, Anabaena doliolum andGloeocapsa sp. The temperature profile of acetylene reduction (5–30 °C) forN. commune revealed (a) that the highest rate of nitrogenase activity was at 25±1 °C, (b) that it was low (69 %) in comparison withN. muscorum, and (c) that nitrogenase activity continued at lower temperatures, which was not evident for other cyanobacteria. The results suggest
thatN. commune is adapted to lower temperatures in terms of nitrogen fixation. 相似文献