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1.
Pascal Badiou Rhonda McDougal Dan Pennock Bob Clark 《Wetlands Ecology and Management》2011,19(3):237-256
North American prairie pothole wetlands are known to be important carbon stores. As a result there is interest in using wetland
restoration and conservation programs to mitigate the effects of increasing greenhouse gas concentration in the atmosphere.
However, the same conditions which cause these systems to accumulate organic carbon also produce the conditions under which
methanogenesis can occur. As a result prairie pothole wetlands are potential hotspots for methane emissions. We examined change
in soil organic carbon density as well as emissions of methane and nitrous oxide in newly restored, long-term restored, and
reference wetlands across the Canadian prairies to determine the net GHG mitigation potential associated with wetland restoration.
Our results indicate that methane emissions from seasonal, semi-permanent, and permanent prairie pothole wetlands are quite
high while nitrous oxide emissions from these sites are fairly low. Increases in soil organic carbon between newly restored
and long-term restored wetlands supports the conclusion that restored wetlands sequester organic carbon. Assuming a sequestration
duration of 33 years and a return to historical SOC densities we estimate a mean annual sequestration rate for restored wetlands
of 2.7 Mg C ha−1year−1 or 9.9 Mg CO2 eq. ha−1 year−1. Even after accounting for increased CH4 emissions associated with restoration our research indicates that wetland restoration would sequester approximately 3.25 Mg
CO2 eq. ha−1year−1. This research indicates that widescale restoration of seasonal, semi-permanent, and permanent wetlands in the Canadian prairies
could help mitigate GHG emissions in the near term until a more viable long-term solution to increasing atmospheric concentrations
of GHGs can be found. 相似文献
2.
F. Kansiime E. Kateyo H. Oryem-Origa P. Mucunguzi 《Wetlands Ecology and Management》2007,15(6):453-467
Wetlands in Uganda experience different forms of human pressure ranging from drainage for agriculture and industrial development
to over harvesting of wetland products. In order to develop sustainable management tools for wetland ecosystems in Uganda
and the Lake Victoria Region, water quality analyses were carried out in a rural undisturbed (pristine) wetland (Nabugabo
wetland in Masaka) and two urban wetlands that are experiencing human and urban development pressure (the Nakivubo wetland
in Kampala and Kirinya wetland in Jinja). The former wetland forms the main inflow into Lake Nabugabo while the other two
border the northern shore of Lake Victoria, Uganda. Nabugabo wetland buffers Lake Nabugabo against surface runoff from the
catchment, while Nakivubo and Kirinya wetlands provides a water treatment function for wastewater from Kampala City and Jinja
town respectively, in addition to buffering Lake Victoria against surface runoff. Water quality was assessed in all the wetland
sites, and in addition nutrient content and storage was investigated in the main plant species (papyrus, Phragmites, Miscanthidium and cocoyam) in Nakivubo and Kirinya wetlands. A pilot experiment was also carried out to assess the wastewater treatment
potential of both the papyrus vegetation and an important agricultural crop Colocasia esculenta (cocoyam). Low electrical conductivity, ammonium–nitrogen and ortho-phosphate concentrations were recorded at the inflow
into Nabugabo wetland (41.5 μS/cm; 0.91 mg/l and 0.42 mg/l respectively) compared to the Nakivubo and Kirinya wetlands (335 μS/cm;
31.68 mg/l and 2.83 mg/l and 502 μS/cm; 10 mg/l and 1.87 mg/l respectively). The papyrus vegetation had higher biomass in
Nakivubo and Kirinya wetlands (6.7 kg DW m−2; 7.2 kg DW m−2 respectively), followed by Phragmites (6.5, 6.7), cocoyams (6.4, 6.6) and Miscanthidium (4.0, 4.2). The papyrus vegetation also exhibited a higher wastewater treatment potential than the agricultural crop (cocoyam)
during the pilot experiment (maximum removal degree of ammonium–nitrogen being 95% and 67% for papyrus and yams). It was concluded
that urbanisation pressure reduces natural wetland functioning either through the discharge of wastewater effluent or the
degradation of natural wetland vegetation. It is recommended that wetland vegetation be restored to enhance wetland ecosystem
functioning and for wetlands that are not yet under agricultural pressure, efforts should be made to halt any future encroachment. 相似文献
3.
4.
During the last 15–20 years, re-establishment of freshwater riparian wetlands and remeandering of streams and rivers have
been used as a tool to mitigate nutrient load in downstream recipients in Denmark. The results obtained on monitoring four
different streams and wetland restoration projects are compared with respect to hydrology, i.e. flow pattern and discharge
of ground or surface water, retention of phosphorus (P), and removal of nitrogen (N). Furthermore, the monitoring strategies
applied for quantifying the post-restoration nutrient retention are evaluated. The four wetland restoration projects are the
Brede River restoration (including river valley groundwater flow, remeandering and inundation), Lyngbygaards River restoration
(groundwater flow, irrigation with drainage water, inundation with river water and remeandering), Egeskov fen (fen re-establishment
and stream remeandering) and Egebjerg Meadows (fen restoration and hydrological reconnection to Store Hansted River). Retention
of phosphorus varied between 0.13 and 10 kg P ha−1 year−1, while the removal of nitrogen varied between 52 and 337 kg N ha−1 year−1. The monitoring strategy chosen was not optimal at all sites and would have benefitted from a knowledge on local hydrology
and water balances in the area to be restored before planning for the final monitoring design. Furthermore, the outcome concerning
P retention would have benefitted from a more frequent sampling strategy. 相似文献
5.
Highly productive papyrus (Cyperus papyrus L.) wetlands dominate many permanently flooded areas of tropical East Africa; however, the cycling of carbon and water within
these ecosystems is poorly understood. The objective of this study was to utilise Eddy Covariance (EC) techniques to measure
the fluxes of carbon dioxide and water vapour between papyrus vegetation and the atmosphere in a wetland located near Jinja,
Uganda on the Northern shore of Lake Victoria. Peak, midday rates of photosynthetic CO2 net assimilation were approximately 40 μmol CO2 m−2 s−1, while night time losses through respiration ranged between 10 and 20 μmol CO2 m−2 s−1. Numerical integration of the flux data suggests that papyrus wetlands have the potential to sequester approximately 0.48 kg C m−2 y−1. The average daily water vapour flux from the papyrus vegetation through canopy evapotranspiration was approximately 4.75 kg
H2O m−2 d−1, which is approximately 25% higher than water loss through evaporation from open water. 相似文献
6.
William J. Mitsch Amanda Nahlik Piotr Wolski Blanca Bernal Li Zhang Lars Ramberg 《Wetlands Ecology and Management》2010,18(5):573-586
This paper summarizes the importance of climate on tropical wetlands. Regional hydrology and carbon dynamics in many of these
wetlands could shift with dramatic changes in these major carbon storages if the inter-tropical convergence zone (ITCZ) were
to change in its annual patterns. The importance of seasonal pulsing hydrology on many tropical wetlands, which can be caused
by watershed activities, orographic features, or monsoonal pulses from the ITCZ, is illustrated by both annual and 30-year
patterns of hydrology in the Okavango Delta in southern Africa. Current studies on carbon biogeochemistry in Central America
are attempting to determine the rates of carbon sequestration in tropical wetlands compared to temperate wetlands and the
effects of hydrologic conditions on methane generation in these wetlands. Using the same field and lab techniques, we estimated
that a humid tropical wetland in Costa Rica accumulated 255 g C m−2 year−1 in the past 42 years, 80% more than a similar temperate wetland in Ohio that accumulated 142 g C m−2 year−1 over the same period. Methane emissions averaged 1,080 mg-C m−2 day−1 in a seasonally pulsed wetland in western Costa Rica, a rate higher than methane emission rates measured over the same period
from humid tropic wetlands in eastern Costa Rica (120–278 mg-C m−2 day−1). Tropical wetlands are often tuned to seasonal pulses of water caused by the seasonal movement of the ITCZ and are the most
likely to be have higher fire frequency and changed methane emissions and carbon oxidation if the ITCZ were to change even
slightly. 相似文献
7.
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
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.
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
10.
Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden 总被引:1,自引:0,他引:1
Dan Berggren Kleja Magnus Svensson Hooshang Majdi Per-Erik Jansson Ola Langvall Bo Bergkvist Maj-Britt Johansson Per Weslien Laimi Truus Anders Lindroth Göran I. Ågren 《Biogeochemistry》2008,89(1):7-25
This paper presents an integrated analysis of organic carbon (C) pools in soils and vegetation, within-ecosystem fluxes and
net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured
2001–2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for
the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold,
respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from
fine roots (<1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference
in total litter input rate between the sites almost disappeared (190–233 g C m−2 year−1). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter
than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter
input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding
figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the
differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging
from −8 g C m−2 year−1 in the north to +9 g C m−2 year−1 in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m−2 year−1.
An erratum to this article can be found at 相似文献
11.
《Ecological Engineering》2005,24(4):267-278
Nitrate-nitrogen retention as a result of river water diversions is compared in experimental wetland basins in Ohio for 18 wetland-years (9 years × 2 wetland basins) and a large wetland complex in Louisiana (1 wetland basin × 4 years). The Ohio wetlands had an average nitrate-nitrogen retention of 39 g-N m−2 year−1, while the Louisiana wetland had a slightly higher retention of 46 g-N m−2 year−1 for a similar loading rate area. When annual nitrate retention data from these sites are combined with 26 additional wetland-years of data from other wetland sites in the Basin Mississippi River (Ohio, Illinois, and Louisiana), a robust regression model of nitrate retention versus nitrate loading is developed. The model provides an estimate of 22,000 km2 of wetland creation and restoration needed in the Mississippi River Basin to remove 40% of the nitrogen estimated to discharge into the Gulf of Mexico from the river basin. This estimated wetland restoration is 65 times the published net gain of wetlands in the entire USA over the past 10 years as enforced by the Clean Water Act and is four times the cumulative total of the USDA Wetland Reserve Program wetland protection and restoration activity for the entire USA. 相似文献
12.
P. W. Inglett E. M. D’Angelo K. R. Reddy P. V. McCormick S. E. Hagerthey 《Wetlands Ecology and Management》2009,17(2):131-144
The use of periphyton nitrogenase activity (biological N2 fixation) as an indicator of wetland P impact was assessed using patterns of nutrient content (C, N, P, Ca, Mg, K, Fe, and
Mn) and acetylene reduction (AR) in floating cyanobacterial periphyton mat (metaphyton) communities of a P-enriched portion
of the Florida Everglades, USA (Water Conservation Area-2A, WCA-2A). Spatial patterns of nutrients indicate the enrichment
of floating mat periphyton N, P, Fe, and K, and the reduction of Mn and TN:TP in enriched marsh areas. In highly enriched
areas, floating mat periphyton AR was approximately threefold greater than that in less enriched, interior marsh zones. Multiple
regression models indicated AR dependence on P in eutrophic WCA-2A areas while the AR of more interior marsh periphyton mats
was more closely related to tissue levels of Ca and Fe. Nitrogenase activity of floating mat periphyton from P-loaded mesocosms
revealed a significant enhancement of N2 fixation in samples receiving approximately 2–3 mg P m−2 of cumulative P dosing or with biomass TP content of 100–300 mg kg−1. At P contents above the optimum, mat periphyton AR was suppressed possibly as a result of changes in species composition
or increased levels of NH4+. After 3 years of dosing, consistently high AR occurred only at low rates of P enrichment (0.4–0.8 g P m−2 yr−1), and the patterns appeared to be seasonal. These findings agree with the hypothesis that P availability is a key determinant
of nitrogenase activity in aquatic systems, and thus, may support the use of periphyton nitrogenase to indicate P impacts
in P-limited systems. These results also demonstrate the potential existence of a P threshhold for biogeochemical alteration
of periphyton mat function in the Everglades, and that cumulative loading of limiting nutrients (i.e., P), rather than instantaneous
concentrations, should be considered when evaluating nutrient criteria. 相似文献
13.
This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast
of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km−2 year−1, with an overall area-weighted average of 1,870 kg N km−2 year−1. In 2002, the range of inputs was 490–10,875 kg N km−2 year−1, averaging 2,158 kg N km−2 year−1. Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km−2 year−1 (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km−2 year−1 (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken
at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km−2 year−1 (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated
with variations in streamflow (export = 0.94 × streamflow − 5.65, R
2 = 0.66), with N inputs explaining an additional 16% of the variance (export = 1.06 × streamflow + 0.06 × input − 227.78,
R
2 = 0.82). The percentage of N input that is exported averaged 12%. Percent export was also related to streamflow (%export = 0.05 × streamflow − 2.61,
R
2 = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes
that control watershed N export are not yet completely understood. 相似文献
14.
Modelling soil C sequestration in spruce forest ecosystems along a Swedish transect based on current conditions 总被引:1,自引:1,他引:0
The change of current pools of soil C in Norway spruce ecosystems in Sweden were studied using a process-based model (CoupModel).
Simulations were conducted for four sites representing different regions covering most of the forested area in Sweden and
representing annual mean temperatures from 0.7°C to 7.1°C. The development of both tree layer and field layer (understory)
was simulated during a 100-year period using data on standing stock volumes from the Swedish Forest Inventory to calibrate
tree growth using different assumptions regarding N supply to the plants. The model successfully described the general patterns
of forest stand dynamics along the Swedish climatic transect, with decreasing tree growth rates and increasing field layer
biomass from south to north. However, the current tree growth pattern for the northern parts of Sweden could not be explained
without organic N uptake and/or enhanced mineralisation rates compared to the southern parts. Depending on the assumption
made regarding N supply to the tree, different soil C sequestration rates were obtained. The approach to supply trees with
both mineralised N and organic N, keeping the soil C:N ratio constant during the simulation period was found to be the most
realistic alternative. With this approach the soils in the northern region of Sweden lost 5 g C m−2 year−1, the soils in the central region lost 2 g C m−2 year−1, and the soils in the two southern regions sequestered 9 and 23 g C m−2 year−1, respectively. In addition to climatic effects, the feedback between C and N turnover plays an important role that needs
to be more clearly understood to improve estimates of C sequestration in boreal forest ecosystems. 相似文献
15.
Mark S. Castro Keith N. Eshleman Louis F. Pitelka Geoff Frech Molly Ramsey William S. Currie Karen Kuers Jeffrey A. Simmons Bob R. Pohlad Carolyn L. Thomas David M. Johnson 《Biogeochemistry》2007,84(3):333-348
The objective of this study was to evaluate the nitrogen (N) biogeochemistry of an 18–22 year old forested watershed in western
Maryland. We hypothesized that this watershed should not exhibit symptoms of N saturation. This watershed was a strong source
of nitrate (NO3
−) to the stream in all years, with a mean annual export of 9.5 kg N ha−1 year−1 and a range of 4.4–18.4 kg N ha−1 year−1. During the 2001 and 2002 water years, wet deposition of inorganic N was 9.0 kg N ha−1 year−1 and 6.3 kg N ha−1 year−1, respectively. Watershed N export rates in 2001 and 2002 water years were 4.2 kg N ha−1 year−1 and 5.3 kg N ha−1 year−1, respectively. During the wetter water years of 2003 and 2004, the watershed exported 15.0 kg N ha−1 year−1 and 18.4 kg N ha−1 year−1, rates that exceeded annual wet deposition of N by a factor of two (7.5 kg N ha−1 year−1 in 2003) and three (5.5 kg N ha−1 year−1 in 2004). Consistent with the high rates of N export, were high concentrations (2.1–3.3%) of N in foliage, wood (0.3%) and
fine roots, low C:N ratios in the forest floor (17–24) and mineral soil (14), high percentages (83–96%) of the amount of mineralized
N that was nitrified and elevated N concentrations (up to 3 mg N l−1) in soil solution. Although this watershed contained a young aggrading forest, it exhibited several symptoms of N saturation
commonly observed in more mature forests. 相似文献
16.
J. Kipkemboi C. M. Kilonzi A. A. van Dam N. Kitaka J. M. Mathooko P. Denny 《Wetlands Ecology and Management》2010,18(4):471-483
We present the findings of a participatory experiment on integrated aquaculture-agriculture systems (Fingerponds) at the Lake
Victoria wetlands, Kenya. Fingerponds are flood-based lacustrine or floodplain wetland fishponds. The aim of the study was
to explore, within a wetland/floodplain interface environment, the potential of semi-intensive fish production to enhance
the wetland fishery and protect the natural ecosystem from wide-scale, destructive encroachment. The ponds were stocked naturally
by flood water. After flood recession, livestock manure was added to the ponds and the effects of manuring on water and sediment
quality and fish yields were studied. Manuring had positive effects on the nitrogen, phosphorous and chlorophyll a concentrations
of the pond water. Regression analysis results indicated that site, manuring and environmental and climatic variables explained
58–70% of the variation in dissolved nitrogen and phosphorous, and 71% of the variation in chorophyll a. Manuring enhanced the total phosphorus concentration in the sediment but it only had marginal effects on total nitrogen.
Although the net fish yields were highly variable between sites and seasons, ranging from 402 to 1069 kg ha−1, the data showed that manuring was advantageous. The duration of the culture period, site variability and manuring explained
82% of the variation in fish yields. We conclude that Fingerponds fertilized with livestock manure from abutting riparian
subsistence agriculture can improve fish production, enhance food diversity and security and contribute to more efficient
use of papyrus wetlands for food production. This in turn may reduce large-scale conversion of wetlands to agriculture. 相似文献
17.
David Bryan Dail David Y. Hollinger Eric A. Davidson Ivan Fernandez Herman C. Sievering Neal A. Scott Elizabeth Gaige 《Oecologia》2009,160(3):589-599
In N-limited ecosystems, fertilization by N deposition may enhance plant growth and thus impact C sequestration. In many N
deposition–C sequestration experiments, N is added directly to the soil, bypassing canopy processes and potentially favoring
N immobilization by the soil. To understand the impact of enhanced N deposition on a low fertility unmanaged forest and better
emulate natural N deposition processes, we added 18 kg N ha−1 year−1 as dissolved NH4NO3 directly to the canopy of 21 ha of spruce-hemlock forest. In two 0.3-ha subplots, the added N was isotopically labeled as
15NH4
+ or 15NO3
− (1% final enrichment). Among ecosystem pools, we recovered 38 and 67% of the 15N added as 15NH4
+ and 15NO3
−, respectively. Of 15N recoverable in plant biomass, only 3–6% was recovered in live foliage and bole wood. Tree twigs, branches, and bark constituted
the most important plant sinks for both NO3
− and NH4
+, together accounting for 25–50% of 15N recovery for these ions, respectively. Forest floor and soil 15N retention was small compared to previous studies; the litter layer and well-humified O horizon were important sinks for
NH4
+ (9%) and NO3
− (7%). Retention by canopy elements (surfaces of branches and boles) provided a substantial sink for N that may have been
through physico-chemical processes rather than by N assimilation as indicated by poor recoveries in wood tissues. Canopy retention
of precipitation-borne N added in this particular manner may thus not become plant-available N for several years. Despite
a large canopy N retention potential in this forest, C sequestration into new wood growth as a result of the N addition was
only ~16 g C m−2 year−1 or about 10% above the current net annual C sequestration for this site. 相似文献
18.
The deposition and cycling of carbon and nitrogen in carbonate sediments located between coral reefs on the northern and central
sections of the Great Barrier Reef were examined. Rates of mass sediment accumulation ranged from 1.9 kg m−2 year−1 (inshore reefs) to 2.1–4.9 kg m−2 year−1 (between mid-shelf reefs); sedimentation was minimal off outer-shelf reefs. Rates of total organic carbon decomposition ranged
from 1.7 to 11.4 mol C m−2 year−1 and total nitrogen mineralization ranged from 77 to 438 mmol N m−2 year−1, declining significantly with distance from land. Sediment organic matter was highly reactive, with mineralization efficiencies
ranging from 81 to 99% for organic carbon and 64–100% for nitrogen, with little C and N burial. There was no evidence of carbonate
dissolution/precipitation in short-term incubation experiments. Rates of sulfate reduction (range 0–3.4 mmol S m−2 day−1) and methane release (range 0–12.8 μmol CH4 m−2 day−1) were minor or modest pathways of carbon decomposition. Aerobic respiration, estimated by difference between total O2 consumption and the sum of the other pathways, accounted for 55–98% of total carbon mineralization. Rates of ammonification
ranged from 150 to 1,725 μmol NH4 m−2 day−1, sufficient to support high rates of denitrification (range 30–2,235 μmol N2 m−2 day−1). N2O release was not detected and rates of NH4
+ and NO2
− + NO3
− efflux were low, indicating that most mineralized N was denitrified. The percentage of total N input removed via denitrification
averaged ≈75% (range 28–100%) with little regenerated N available for primary producers. Inter-reef environments are therefore
significant sites of energy and nutrient flow, especially in spatially complex reef matrices such as the Great Barrier Reef. 相似文献
19.
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
20.
Because nitrogen and phosphorus are primary resources for plant, algal, and microbial production, increases in nutrient inputs
can markedly alter aquatic ecosystems. Coastal wetland plots at Belle W. Baruch Marine Field Laboratory (South Carolina, USA)
have been amended with nitrogen and phosphorus for ~20 years to determine the effects of nutrient loading on coastal wetlands.
We conducted a survey of δ15N and δ13C natural abundance in coastal wetland organic pools (sediment, vegetation) with long-term nutrient amendments (control, no
addition; nitrogen; phosphorus; and nitrogen + phosphorus additions). Additionally, we conducted laboratory assays to quantify
pore water nutrient availability and nitrification rates. Marsh vegetation (Spartina alterniflora) had enriched δ13C values (mean −14‰) relative to bulk sediment samples (mean −18‰). Nitrogen-amended plots (alone and in combination with
phosphorus) had enriched δ13C values in the surface sediment (0–5 cm; mean −16.1‰) relative to control (mean −16.5‰) and phosphorus-amended plots (mean
−16.8‰). Nitrogen-amended plots also had depleted δ15N in S. alterniflora leaf tissues (−3.3‰) and surface sediment samples (mean 2.1‰) relative to leaf tissues (mean 2.1‰) or sediment samples (mean
5.8‰) from control or phosphorus-only amended plots. Nitrate availability (as increased pore water concentration) was higher
in N-amended plots although ammonium availability did not differ. Phosphorus availability was higher only in phosphorus-only
amended plots. Overall, we found that long-term nutrient amendments to coastal wetlands significantly altered nutrient availability
and uptake rates as well as natural abundance of δ13C and δ15N in multiple organic matter sources. 相似文献