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1.
Deepa Dhital Yuichiro Yashiro Toshiyuki Ohtsuka Hibiki Noda Yoko Shizu Hiroshi Koizumi 《Journal of plant research》2010,123(4):519-530
The ecosystem carbon budget was estimated in a Japanese Zoysia japonica grassland. The green biomass started to grow in May and peaked from mid-July to September. Seasonal variations in soil CO2 flux and root respiration were mediated by changes in soil temperature. Annual soil CO2 flux was 1,121.4 and 1,213.6 g C m−2 and root respiration was 471.0 and 544.3 g C m−2 in 2007 and 2008, respectively. The root respiration contribution to soil CO2 flux ranged from 33% to 71%. During the growing season, net primary production (NPP) was 747.5 and 770.1 g C m−2 in 2007 and 2008, respectively. The biomass removed by livestock grazing (GL) was 122.1 and 102.7 g C m−2, and the livestock returned 28.2 and 25.6 g C m−2 as fecal input (FI) in 2007 and 2008, respectively. The decomposition of FI (DL, the dry weight loss due to decomposition)
was very low, 1.5 and 1.4 g C m−2, in 2007 and 2008. Based on the values of annual NPP, soil CO2 flux, root respiration, GL, FI, and DL, the estimated carbon budget of the grassland was 1.7 and 22.3 g C m−2 in 2007 and 2008, respectively. Thus, the carbon budget of this Z. japonica grassland ecosystem remained in equilibrium with the atmosphere under current grazing conditions over the 2 years of the
study. 相似文献
2.
Makoto Sampei Hiroshi Sasaki Ryosuke Makabe Alexandre Forest Hiroshi Hattori Jean-��ric Tremblay Yves Gratton Mitsuo Fukuchi Louis Fortier 《Polar Biology》2011,34(4):501-511
Regional variability in the annual fluxes of particulate organic carbon (POC) and biogenic silica (Si) at the periphery of
the Mackenzie Shelf (Beaufort Sea) was investigated using eight long-term sediment traps moored at ~100-m depth. Relatively
high autochthonous POC and Si fluxes were recorded in the Mackenzie Trough (4.1 and 8.9 g m−2 year−1 respectively) and off Cape Bathurst (6.6 and 79 g m−2 year−1), two areas where upwelling events are frequently observed. Diatomaceous new production was minimum on the mid-slope of the
Mackenzie Shelf (2.8 g C m−2 year−1), moderate in the Mackenzie Trough (14.5 g C m−2 year−1), and highest off Cape Bathurst (128.7 g C m−2 year−1). High annual autochthonous POC flux corresponded to high diatom production. Among sites, the vertical attenuation of the
POC flux increased with diatomaceous new production. Hence, the retention of autochthonous POC in the surface layer (<100 m)
was highest (95%) at the highly productive site off Cape Bathurst, intermediate (72%) in the moderately productive Mackenzie
Trough, and low (4%) at the unproductive mid-slope of the shelf. Our results indicate that, on Arctic shelves, upwelling and
the production of diatoms increase the fraction of the POC which is retained in the surface layer and diverted to the pelagic
food web. In the relatively unproductive waters of the Arctic Ocean, biological hot spots such as the one identified off Cape
Bathurst where the food web promotes retention rather than vertical export could be disproportionately important as feeding
grounds for higher trophic levels. 相似文献
3.
Wyatt F. Cross Emma J. Rosi-Marshall Kathrine E. Behn Theodore A. Kennedy Robert O. HallJr. A. Elizabeth Fuller Colden V. Baxter 《Biological invasions》2010,12(9):3033-3043
Species invasions are often associated with large-scale human alteration of ecosystems. One classic example is the increasing
dominance of non-native taxa below and above dams on large rivers. These dams substantially alter the physical template of
river ecosystems, and exotic taxa often proliferate with potentially large impacts on coexisting taxa and ecosystem processes.
Here we document the invasion of New Zealand mud snails (Potamopyrgus antipodarum) in the Colorado River directly below Lake Powell in Glen Canyon, Arizona, USA. We also quantified the magnitude and variability
in growth and secondary production of P. antipodarum during 2006–2007 to gain a functional measure of their role in the ecosystem. Snails were first detected in Glen Canyon in
1995, and have since become a dominant component of the invertebrate fauna. Throughout the invasion of P. antipodarum, biomass of other dominant taxa was variable and did not appear to be positively or negatively influenced by the presence
of P. antipodarum. Specific growth rates of P. antipodarum were moderate (0.001–0.030 day−1) and strongly related to body size. Mean annual habitat-weighted biomass and production were relatively high (biomass: 4.4 g/m2; secondary production: 13.3 g m−2 year−1) and similar among habitats. Mean monthly biomass and daily secondary production were much more variable, with highest values
occurring in autumn. We show that invasion of a productive aquatic consumer to a highly disturbed river ecosystem had little
detectable influence on the biomass of other invertebrate taxa. However, additional research will be necessary to fully understand
and predict effects of P. antipodarum on coexisting taxa. 相似文献
4.
The economic value of ecosystem services of vegetated habitats (seagrass and macroalgal beds) has been estimated to be among
the highest of the various ecosystems on earth. However, fish production has not been included in the evaluations due to the
difficulty of quantitative estimation of fish production in the field. In the present study, annual production and economic
value of wild juvenile black rockfish, Sebastes cheni, a dominant fish species in seagrass and macroalgal beds in the central Seto Inland Sea were estimated. Juvenile S. cheni migrated into vegetated habitats at about 20 mm total length (TL) and grew up to about 60 mm TL by late May. Juvenile abundance
was highest in April (2007) or March (2008). Eight cohorts with the same extrusion period (each cohort covering a 10-day period)
were identified using otolith daily increments. The annual estimates of S. cheni juvenile production were 13,080 g ha−1 year−1 in 2007 and 18,360 g −1 year−1 in 2008. Based on the unit price of artificially raised S. cheni juveniles, the economic value of the annual wild juvenile production was converted to 654,000 JPY (Japanese yen: 100 JPY = ca.
1 USD) ha−1 year−1 for 2007 and 918,000 JPY ha−1 year−1 for 2008. Analyses of stomach contents and stable isotope (δ13C or δ15N) showed that juvenile S. cheni were highly dependent on copepods. The planktonic trophic pathway originating from phytoplankton supports the majority of
the juvenile black rockfish production during the post-migration period (20–60 mm TL) in the seagrass and macroalgal beds
through the production of copepod zooplankton. The total economic value of the ecosystem services of the vegetated habitat
is suggested to be much higher than estimates in previous studies if the provisioning and regulating services which originate
from fish production were included in the estimates. 相似文献
5.
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
6.
Alchichica is a warm-monomictic, oligotrophic lake whose phytoplanktonic biomass is dominated by large size (average ca. 55 μm) diatoms. The fast sinking phytoplankton leads to silica, and other nutrient exportation out of the productive zone
of the lake. The aim of the present study was to identify and measure the sedimentation fluxes of the diatom species and their
temporal dynamics to better understand the magnitude of silica and carbon fluxes. Sediment-traps were exposed at three different
depths and collected monthly. A total of 13 diatom species were observed in the traps. The maximum diatom flux was in February
(304 × 106 cells m−2 day−1) related to the winter diatom bloom. The diatom silica (DSi) fluxes varied from 2.2 to 2,997 mg m−2 day−1 and the diatom carbon (DC) fluxes from 1.2 to 2,918 mg m−2 d−1. Cyclotella alchichicana was the main contributor (>98%) to the total DSi and DC fluxes. The annual diatom (15 × 109 cells m−2 year−1), DSi (147 g m−2 year−1) and DC (92 g m−2 year−1) fluxes are higher than in other aquatic ecosystems of similar or even higher trophic conditions. Our findings in Alchichica
are indicative of the relevance of the phytoplankton type and size in understanding the role tropical and oligotrophic lakes
play regarding silica and carbon fluxes. In addition, our results support previous findings suggesting that inland aquatic
ecosystems are more important than formerly thought in processing carbon, and can, therefore, affect regional carbon balances. 相似文献
7.
Secondary production and diet of an invasive snail in freshwater wetlands: implications for resource utilization and competition 总被引:1,自引:0,他引:1
Invasive species can monopolize resources and thus dominate ecosystem production. In this study we estimated secondary production
and diet of four populations of Pomacea canaliculata, a freshwater invasive snail, in wetlands (abandoned paddy, oxbow pond, drainage channel, and river meander) in monsoonal
Hong Kong (lat. 22°N). Apple snail secondary production (ash-free dry mass [AFDM]) ranged from 165.9 to 233.3 g m−2 year−1, and varied between seasons. Production was lower during the cool dry northeast monsoon, when water temperatures might have
limited growth, but fast growth and recruitment of multiple cohorts were possible throughout much (7–10 months) of the year
and especially during the warm, wet southwest monsoon. The diet, as revealed by stomach-content analysis, consisted mainly
of detritus and macrophytes, and was broadly consistent among habitats despite considerable variation in the composition and
cover of aquatic plants. Apple snail annual production was >10 times greater than production estimates for other benthic macroinvertebrates
in Hong Kong (range 0.004–15 g AFDM m−2 year−1, n = 29). Furthermore, annual production estimates for three apple snail populations (i.e. >230 g AFDM m−2 year−1) were greater than published estimates for any other freshwater snails (range 0.002–194 g AFDM m−2 year−1, n = 33), regardless of climatic regime or habitat type. High production by P. canaliculata in Hong Kong was attributable to the topical climate (annual mean ~24°C), permitting rapid growth and repeated reproduction,
together with dietary flexibility including an ability to consume a range of macrophytes. If invasive P. canaliculata can monopolize food resources, its high productivity indicates potential for competition with other macroinvertebrate primary
consumers. Manipulative experiments will be needed to quantify these impacts on biodiversity and ecosystem function in wetlands,
combined with management strategies to prevent further range extension by P. canaliculata. 相似文献
8.
This paper attempts to establish linkages between growth by a keystone wetland plant, Panicum hemitomon Schultes, and the independent and interactive effect of nutrient and hydrologic regime to inform management and rehabilitation
of thick-mat floating marsh (TMFM). To do so a manipulative glasshouse experiment employing created TMFM similar to that under
consideration for field trials and two levels each of N, P and hydrology was conducted. P. hemitomon grew vigorously under saturated (flooding level with the surface of the mat) when compared to inundated (+15 cm flooding)
hydrologic conditions, and under enriched (50 g m−2 year−1) when compared to non-enriched (25 g m−2 year−1) N. Further, and as inferred from net CO2 assimilation, shoot biomass and rhizome biomass and length, N-enriched conditions seemed to lessen inundation stress. For
all variables the interaction between N and hydrology was non-significant and there was no observable effect of P. We were
unable to infer root or mat buoyancy from root specific gravity measurements but it was evident at harvest that saturation
or minimal flooding is required for vigorous root and rhizome growth. This study provides insight to the notion that decreased
mat buoyancy (and increased flooding level) resulting from sediment deposition associated with Mississippi River diversions
could adversely affect TMFM sustainability, but more clearly demonstrates the need to maintain saturated hydrologic conditions
for achieving the type of root and rhizome growth we feel is required for TMFM rehabilitation. 相似文献
9.
This article reviews historical changes in the total phosphorus (TP) inputs to Loch Leven, Scotland, UK. Data derived from
palaeolimnological records suggest that inputs in the early 1900s were about 6 t TP year−1 (0.45 g TP m−2 year−1). By 1985, this had risen to about 20 t TP year−1 (1.5 g TP m−2 year−1) due to increases in runoff from agricultural land and discharges from point sources. By the late 1970s, increased TP inputs
were causing serious degradation of lake water quality. Most noticeably, there had been an increase in cyanobacterial blooms.
A catchment management plan was implemented in the early 1990s. This resulted in a 60% reduction in the annual TP input between
1985 (20 t TP year−1/1.5 g TP m−2 year−1) and 1995 (8 t TP year−1/0.6 g TP m−2 year−1). The main reduction was associated with better control of point source discharges, but attempts were also made to reduce
inputs from diffuse sources. The reduction in external TP loading to the lake led to a marked decline in TP retention by the
lake each year. 相似文献
10.
Qing Liu Huajun Yin Jinsong Chen Chunzhang Zhao Xinying Cheng Yunyan Wei Bo Lin 《Ecological Research》2011,26(3):637-648
The impacts of global climatic change on belowground ecological processes of terrestrial ecosystems are still not clear. We
therefore conducted an experiment in the subalpine coniferous forest ecosystem of the eastern edges of the Tibetan Plateau
to study roots of Picea asperata seedlings and rhizosphere soil responses to soil warming and nitrogen availability from April 2007 to December 2008. The
seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0 or 25 g m−2year−1 N). We used a free air temperature increase from an overhead infrared heater to raise both air and soil temperature by 2.1
and 2.6°C, respectively. The results showed that warming alone significantly increased total biomass, coarse root biomass
and fine root biomass of P. asperata seedlings. Both total biomass and fine root biomass were increased, but coarse root biomass was significantly decreased by
nitrogen fertilization and warming combined with nitrogen fertilization. Warming induced a prominent increase in soil organic
carbon (SOC) and NO3
−-N of rhizosphere soil, while nitrogen fertilization significantly decreased SOC and NH4
+-N of rhizosphere soil. The warming, fertilization and warming × N fertilization interaction decreased soil microbial C significantly,
but substantially increased soil microbial N. These results suggest that nitrogen deposition combined with warmer temperatures
under future climatic change possibly will have no effect on fine root production of P. asperata seedlings, but could enhance the nitrification process of their rhizosphere soils in subalpine coniferous forests. 相似文献
11.
Marko Herrmann José E. F. Alfaya Mauro L. Lepore Pablo E. Penchaszadeh Wolf E. Arntz 《Helgoland Marine Research》2011,65(3):285-297
The yellow clam Mesodesma mactroides (Bivalvia: Mesodesmatidae) was once the most abundant intertidal species on the Atlantic coast of northern Argentina and
an important commercial resource in South America. This study of a population inhabiting the intertidal zone of the sheltered-dissipative
sandy beach Santa Teresita documents the species’ population biology, including demographic structure, growth and production
during December 2004 and December 2006, and adumbrates the critical state of M. mactroides at present. A total of 3,015 M. mactroides were collected and measured, whereas individuals were found with an anterior–posterior shell length between 2 and 64 mm.
A von Bertalanffy growth function with an asymptotic length (L
∞) of 85 mm and a growth constant (K) of 0.47 year−1 was established from length–frequency distributions. The longevity of the species is estimated at approximately 6 years,
and instantaneous mortality rate was about three times higher than 40 years ago. Besides, this study confirmed that the overall
growth performance index (OGP) is habitat-specific and can be used to group M.
mactroides and M.
donacium from different areas into temperate and upwelling species. Furthermore, OGP is inversely correlated with the latitudinal distribution of Mesodesma populations. The intertidal biomass ranged between 0.06 and 0.07 g AFDM m−2 year−1. Individual production was observed to be highest at 47 mm length (0.35 g AFDM m−2 year−1), and annual production ranged between 0.12 and 0.19 g AFDM m−2 year−1, resulting in productivity values (P/B) between 1.84 and 2.93. The comparison of the results of the present study with those of growth studies conducted on M.
mactroides 40 years ago revealed the following considerable differences in the population structure of M.
mactroides, indicating the conservation status of this intertidal bivalve as endangered: (1) present growth rates are faster, but that
the maximum length attained has decreased, (2) the numbers of individuals per square metre were many times higher in the past
than in the present, (3) bivalves from the present work never reached the ‘commercial size’ of 60 mm and (4) 40 years ago,
the population of M.
mactroides was composed of up to three cohorts, whereas in this study, there was only one single cohort visible. 相似文献
12.
Martin Emil Blicher Lars Maltha Rasmussen Mikael Kristian Sejr Flemming Ravn Merkel S?ren Rysgaard 《Polar Biology》2011,34(8):1105-1116
The number of common eiders (Somateria
mollissima borealis) in west Greenland declined dramatically during the twentieth century, supposedly because of human activities. However, their
sensitivity to alternative drivers of variation, such as climate conditions, diseases or food availability, remains unstudied.
In this study, we describe prey availability and assess the trophic coupling between eiders and their macrobenthic prey in
a shallow inlet, Nipisat Sound; a key wintering habitat in the south-west Greenland Open Water Area. Macrobenthic species
abundance and biomass were studied, and annual production was estimated by an empirical model, including environmental characteristics,
fauna composition and individual biomass. In spring 2008, average macrozoobenthic abundance and biomass were 6,912 ind m−2 and 28.4 g ash-free dry mass (AFDM) m−2 (647 kJ m−2), respectively. Annual production was estimated at 13.9 g AFDM m−2 year−1 (317 kJ m−2 year−1). During the winters of 2008–2010, we monitored the number of common eiders (S. mollissima borealis) and king eiders (Somateria spectabilis) and observed a distinct peak in abundance during winter with up to 15.000 birds in Nipisat Sound. Based on physiological
costs of different activities in combination with the observed behavioural pattern, we obtained an estimate of the energy
required for eiders to balance their costs of living, which amounted to 58% of the estimated total annual production of macrobenthos
in Nipisat Sound. This result suggests that eider predation affects macrobenthic species composition and biomass and demonstrates
the potential importance of variations in prey availability for the population dynamics of eiders in Greenland. 相似文献
13.
The effects of environmental factors on seasonal and annual variations in soil respiration were examined in the cool temperate
Zoysia japonica grassland of Japan. Field measurements of soil respiration were conducted using a closed chamber method with an infrared
gas analyzer at monthly intervals in the snow-free seasons from May 2007 to December 2009. There was an exponential relationship
between soil respiration and soil temperature, and the soil temperature accounted for 85–86% of seasonal soil respiration
variability. Moreover, a positive linear relationship between soil respiration and soil water content was detected in summer
(R
2 = 0.55, p < 0.001), but not in spring or autumn. Annual soil respiration was estimated at 755, 719, and 1,037 g C m−2 year−1 in 2007, 2008, and 2009, respectively. These interannual variations in soil respiration might be influenced by the strength
of precipitation during rainy seasons and the timing of each snow-melt. Our results suggest that the effects of rainfall and
snow-melt events on soil respiration might be important factors to understand carbon dynamics in grassland ecosystem in Japan. 相似文献
14.
Conversion of secondary broadleaved forest into Chinese fir plantation alters litter production and potential nutrient returns 总被引:2,自引:0,他引:2
Litter production, litter standing crop, and potential nutrient return via litterfall to soil were studied during a 4-year
period (January 2004–December 2007) in a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantation and a secondary broadleaved forest in Hunan Province in subtropical China. Mean annual litterfall
in the sampling sites varied from 358 g m−2 in the pure plantation to 669 g m−2 in the secondary broadleaved forest. Total litterfall followed a bimodal distribution pattern for both forests. Amount of
litterfall was also related to the air temperature in both forests. During the period under this study, annual variation in
the total litterfall in the pure plantation was significantly higher than that in the secondary broadleaved forest. Litterfall
was markedly seasonal in the both forests. Leaf proportions of litterfall in the pure plantation and secondary broadleaved
forest were 58.1 and 61.7%, respectively. Total potential nutrient returns to the soil through litterfall in the pure plantation
were only 46.2% of those in the secondary broadleaved forest. Total litter standing crop was 913 and 807 g m−2 in the pure plantation and secondary broadleaved forest, respectively. Our results confirm that conversion from a secondary
broadleaved forest into a pure coniferous plantation changes the functioning of the litter system. 相似文献
15.
Biomass, primary production and nutrient budgets associated to Sarcocornia perennis subspecies (ssp.) alpini were studied in the Palmones River estuary salt marsh (Southern Spain) to evaluate the nutrient sequestration capacity of the low marsh. Above- and belowground living and dead biomass, as well as carbon, nitrogen and phosphorus content were monitored during 1 year. Additionally, the fate of aboveground detritus was evaluated in an experiment on litter decomposition. The detritus production of S. perennis ssp. alpini was almost equivalent to its annual primary production indicating a rapid turnover of biomass. We calculated that only 12% of the aboveground detritus was exported out of the low marsh while the rest was decomposed in the sediment with a rate of 0.8 year−1. Changes in concentrations of total carbon, nitrogen and phosphorus in the sediment showed patterns related to S. perennis ssp. alpini belowground biomass. Our results suggested that the sediment functions as a net sink for nutrients accumulating 550 g C m−2 year−1, 55 g N m−2 year−1, and 13 g P m−2 year−1. 相似文献
16.
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
17.
Akiko Sasaki Yu Hagimori Ichiro Yuasa Takayuki Nakatsubo 《Landscape and Ecological Engineering》2012,8(1):107-114
To quantify organic matter mineralization at estuarine intertidal flats, we measured in situ sediment respiration rates using
an infrared gas analyzer in estuarine sandy intertidal flats located in the northwestern Seto Inland Sea, Japan. In situ sediment
respiration rates showed spatial and seasonal variations, and the mean of the rates is 38.8 mg CO2-C m−2 h−1 in summer. In situ sediment respiration rates changed significantly with sediment temperature at the study sites (r
2 = 0.70, p < 0.05), although we did not detect any significant correlations between the rates and sediment characteristics. We prepared
a model for estimating the annual sediment respiration based on the in situ sediment respiration rates and their temperature
coefficient (Q
10 = 1.8). The annual sediment respiration was estimated to be 92 g CO2-C m−2 year−1. The total amount of organic carbon mineralization for the entire estuarine intertidal flats through sediment respiration
(43 t C year−1) is equivalent to approximately 25% of the annual organic carbon load supplied from the river basin of the estuary. 相似文献
18.
Matteo Campioli Anders Michelsen Andreas Demey Annemie Vermeulen Roeland Samson Raoul Lemeur 《Ecosystems》2009,12(5):760-776
Mesic–dry tundras are widespread in the Arctic but detailed assessments of net primary production (NPP) and ecosystem carbon
(C) stocks are lacking. We addressed this lack of knowledge by determining the seasonal dynamics of aboveground vascular NPP,
annual NPP, and whole-ecosystem C stocks in five mesic–dry tundras in Northern Sweden with contrasting microtopography, altitude,
and dominant species. Those measurements were paralleled by the stock assessments of nitrogen (N), the limiting nutrient.
The vascular production was determined by harvest or in situ growing units, whereas the nonvascular production was obtained
from average species growth rates, previously assessed at the sites. Results showed that aboveground vascular NPP (15–270 g m−2), annual NPP (214–282 g m−2 or 102–137 g C m−2) and vegetation biomass (330–2450 g m−2) varied greatly among communities. Vegetation dominated by Empetrum hermaphroditum is more productive than Cassiope tetragona vegetation. Although the large majority of the apical NPP occurred in early-mid season (85%), production of stems and evergreen
leaves proceeded until about 2 weeks before senescence. Most of the vascular vegetation was belowground (80%), whereas most
of the vegetation production occurred aboveground (85%). Ecosystem C and N stocks were 2100–8200 g C m−2 and 80–330 g N m−2, respectively, stored mainly in the soil turf and in the fine organic soil. Such stocks are comparable to the C and N stocks
of moister tundra types, such as tussock tundra.
Author Contributions Matteo Campioli, Anders Michelsen, Roeland Samson, Raoul Lemeur—conceived and designed study, Matteo Campioli, Anders Michelsen,
Andreas Demey, Annemie Vermeulen—performed research, Matteo Campioli—analyzed data, and Matteo Campioli—wrote the paper. 相似文献
19.
The invasive soft-shell clam Mya arenaria was recorded for the first time in the Tagus estuary, central Portugal. Propagules of the soft-shell clam were probably unintentionally
introduced into the Tagus estuary through ballast water. Mya arenaria was observed in muddy sands in the upper intertidal zone. The assemblage in which the soft-shell clam was observed was composed
of typical estuarine species such as the gastropod Hydrobia ulvae, the bivalve Scrobicularia plana and several polychaete species. The population density of Mya arenaria in the finding area was 40 ind m−2 with a fresh biomass of 163.5 g FW m−2. 相似文献
20.
Aspects of the biology of Abra segmentum were investigated at low salinities in a Mediterranean coastal lagoon (Monolimni Lagoon, Northern Aegean Sea). Monthly samples
were collected during the period from February 1998 to January 1999. Recruitment occurred from mid-spring to early autumn
(0.3–5.7 psu) and recruits grew during summer and autumn (1.2–5.7 psu), while a major part vanished during next autumn, displaying
a maximum life span of about 20 months. A positive correlation was found between the percentage of individuals having a shell
length of ≤3.5 mm and temperature; age group 0 showed a growth rate of 0.97 mm per month, and the largest individual collected
had a 19.76 mm shell length. The population density sharply increased during late spring (0.3–1.2 psu); this increase was
followed by a decline during summer and, afterwards, a gradual increase up to late autumn. Secondary production calculated
by the size–frequency method gave a mean annual density (n) of 3,357 individuals m−2, a mean annual biomass (B) of 21.98 g DW m−2, an annual production (P) of 73.72 g DW m−2 and a P:B ratio of 3.35. A comparison of the present data with available data of A. segmentum populations from higher salinity habitats revealed that this bivalve in the study area showed a life history pattern similar
to that of other populations of the species and a comparatively high growth rate, maximum body size, n, B, P and P:B ratio. Our findings suggest that the studied aspects of A. segmentum biology could not be markedly affected by low salinities. 相似文献