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1.
Vertical profiles of DIN,DOC, and microbial activities in the wetland soil of Kushiro Mire,northeastern Japan 总被引:2,自引:0,他引:2
Yukiko Senga Mikiya Hiroki Yosuke Nakamura Yasushi Watarai Yasunori Watanabe Seiichi Nohara 《Limnology》2011,12(1):17-23
Kushiro Mire is the largest mire in Japan and in 1980 was the first wetland in Japan registered under the Ramsar Convention.
Recent reports indicate an increase in nutrient loading into Kushiro Mire from changes in land use. We measured vertical profiles
of dissolved inorganic nitrogen (DIN; NO3
–, NO2
–, NH4
+), dissolved organic carbon (DOC), and various types of microbial activity in soil samples collected to approximately 1.5 m
deep at two sites in Kushiro Mire. We found an accumulation of NO3
– and DOC in the deeper soil. Denitrifying activity was highest in the shallower soils and decreased drastically with depth,
whereas higher levels of fluoresceindiacetate hydrolysis, β-glucosidase, acid phosphatase, and xylosidase enzyme activity
were found in the deeper layers. We also detected humic-like substances as components of the DOC. These results suggest that
the DOC in the wetland soil cannot be used as a substrate for denitrification, causing denitrification to be suppressed in
the deeper soil. In addition, denitrifying activity would be very low in the deeper layers due to low soil temperature. As
a result, nitrogen input to the mire has resulted in a large accumulation of NO3
– in the deeper soil. This will eventually change the mire ecosystem through effects such as increased eutrophication and acidification. 相似文献
2.
Seasonal Variations of Dissolved Nitrogen and DOC:DON Ratios in an Intermittent Mediterranean Stream
Seasonal variations of dissolved inorganic nitrogen (DIN) (NO3–N and NH4–N) and dissolved organic nitrogen (DON) were determined in Fuirosos, an intermittent stream draining an unpolluted Mediterranean
forested catchment (10.5 km2) in Catalonia (Spain). The influence of flow on streamwater concentrations and seasonal differences in quality and origin
of dissolved organic matter, inferred from dissolved organic carbon to nitrogen ratios (DOC:DON ratios), were examined. During
baseflow conditions, nitrate and ammonium had opposite behaviour, probably controlled by biological processes such as vegetation
uptake and mineralization activity. DON concentrations did not have a seasonal trend. During storms, nitrate and DON increased
by several times but discharge was not a good predictor of nutrient concentrations. DOC:DON ratios in streamwater were around
26, except during the months following drought when DOC:DON ratios ranged between 42 and 20 during baseflow and stormflow
conditions, respectively. Annual N export during 2000–2001 was 70 kg km−1 year−1, of which 75% was delivered during stormflow. The relative contribution of nitrogen forms to the total annual export was
57, 35 and 8% as NO3–N, DON and NH4–N, respectively. 相似文献
3.
Reversibility of Soil Productivity Decline with Organic Matter of Differing Quality Along a Degradation Gradient 总被引:8,自引:0,他引:8
Joseph M. Kimetu Johannes Lehmann Solomon O. Ngoze Daniel N. Mugendi James M. Kinyangi Susan Riha Lou Verchot John W. Recha Alice N. Pell 《Ecosystems》2008,11(5):726-739
In the highlands of Western Kenya, we investigated the reversibility of soil productivity decline with increasing length of
continuous maize cultivation over 100 years (corresponding to decreasing soil organic carbon (SOC) and nutrient contents)
using organic matter additions of differing quality and stability as a function of soil texture and inorganic nitrogen (N)
additions. The ability of additions of labile organic matter (green and animal manure) to improve productivity primarily by
enhanced nutrient availability was contrasted with the ability of stable organic matter (biochar and sawdust) to improve productivity
by enhancing SOC. Maize productivity declined by 66% during the first 35 years of continuous cropping after forest clearing.
Productivity remained at a low level of 3.0 t grain ha-1 across the chronosequence stretching up to 105 years of continuous cultivation despite full N–phosphorus (P)–potassium (K)
fertilization (120–100–100 kg ha−1). Application of organic resources reversed the productivity decline by increasing yields by 57–167%, whereby responses to
nutrient-rich green manure were 110% greater than those from nutrient-poor sawdust. Productivity at the most degraded sites
(80–105 years since forest clearing) increased in response to green manure to a greater extent than the yields at the least
degraded sites (5 years since forest clearing), both with full N–P–K fertilization. Biochar additions at the most degraded
sites doubled maize yield (equaling responses to green manure additions in some instances) that were not fully explained by
nutrient availability, suggesting improvement of factors other than plant nutrition. There was no detectable influence of
texture (soils with either 11–14 or 45–49% clay) when low quality organic matter was applied (sawdust, biochar), whereas productivity
was 8, 15, and 39% greater (P < 0.05) on sandier than heavier textured soils with high quality organic matter (green and animal manure) or only inorganic
nutrient additions, respectively. Across the entire degradation range, organic matter additions decreased the need for additional
inorganic fertilizer N irrespective of the quality of the organic matter. For low quality organic resources (biochar and sawdust),
crop yields were increasingly responsive to inorganic N fertilization with increasing soil degradation. On the other hand,
fertilizer N additions did not improve soil productivity when high quality organic inputs were applied. Even with the tested
full N–P–K fertilization, adding organic matter to soil was required for restoring soil productivity and most effective in
the most degraded sites through both nutrient delivery (with green manure) and improvement of SOC (with biochar). 相似文献
4.
Ecological indicators of nutrient enrichment, freshwater wetlands, Midwestern United States (U.S.) 总被引:2,自引:0,他引:2
Vegetation and soil indicators of nutrient condition were evaluated in 30 wetlands, 10 each in 3 Nutrient Ecoregions (NE) (VI-Corn Belt and Northern Great Plains, VII-Mostly Glaciated Dairy Region, IX-Temperate Forested Plains and Hills) of the Midwestern United States (U.S.) to identify robust indicators for assessment of wetland nutrient enrichment and eutrophication. Nutrient condition was characterized by surface water inorganic N (NH4-N, NO3-N) and P (PO4-P) concentrations measured seasonally for 1 year, plant available and total soil N and P, and aboveground biomass, leaf N and P and species composition of emergent vegetation measured at the end of the growing season. Aboveground biomass, nutrient uptake and species composition were positively related to surface water NH4-N (N) but not to PO4-P or NO3-N. Aboveground biomass and biomass of aggressive species, Typha spp. plus Phalaris arundinacea, increased asymptotically with surface water N whereas leaf P, senesced leaf N and senesced leaf P increased linearly with N. And, species richness declined with surface water N. Soil total P was positively related to surface water PO4-P but it was the only soil indicator related to wetland nutrient condition. Individual regressions for each NE generally were superior to a single regression for all NEs. In NE VI (Corn Belt), few indicators were related to surface water N because of the high degree of anthropogenic disturbance (85% of the landscape is cleared) as compared to NEs VII and IX (24–53% cleared). Of the indicators evaluated, stem height (r2 = 0.42 for all NEs, r2 = 0.56 for NE VII + IX) and percent biomass of aggressive species, Typha spp. plus Phalaris, (r2 = 0.46 for all NEs, r2 = 0.54 for NE VII + IX), were the best predictors of wetland nutrient enrichment. Vegetation-based indicators are a promising tool for assessment of wetland nutrient condition but they may not be effective in NEs where landscape disturbance is intense and widespread. 相似文献
5.
Anu Vikman Sakari Sarkkola Harri Koivusalo Tapani Sallantaus Jukka Laine Niko Silvan Hannu Nousiainen Mika Nieminen 《Hydrobiologia》2010,641(1):171-183
We studied the nitrogen retention capacity of six peatland buffer areas constructed in forested catchments in southern and
central Finland. The buffers (0.1–4.9% of the total catchment area) were either undrained mires or drained peatlands rewetted
4–7 years before the present study. The N retention capacity was studied by adding ammonium nitrate (NH4NO3–N) solution into the inflow waters of the buffers once (one area) or twice (five areas) during a period of 4–6 years. Except
for the first N addition in one area, the three largest buffer areas (relative size > 1%) retained the added inorganic N almost
completely; their retention efficiencies during the year of addition were >93% for both NO3–N and NH4–N. Two of the three small buffers (relative size < 0.25%) were also able to reduce inorganic N from the through-flow waters
effectively; their retention capacities for inorganic nitrogen varied between 58 and 89%. However, one small buffer area had
a retention capacity of only <20%. The factors contributing to efficient N retention were hydrological load during N addition,
relative size of the buffer area, and its length, i.e. the distance between the inflow and outflow points. If there was any
release of the added N, it mostly occurred within a relatively short-time period (<100 days) after the treatment. The buffer
areas appeared to be efficient and long-term sinks for inorganic nitrogen because the release of N during the 2–4 years after
N addition was minor. 相似文献
6.
Dissolved Nitrogen, Phosphorus, and Sulfur forms in the Ecosystem Fluxes of a Montane Forest in Ecuador 总被引:1,自引:0,他引:1
Rainer Goller Wolfgang Wilcke Katrin Fleischbein Carlos Valarezo Wolfgang Zech 《Biogeochemistry》2006,77(1):57-89
The N, P, and S cycles in pristine forests are assumed to differ from those of anthropogenically impacted areas, but there
are only a few studies to support this. Our objective was therefore to assess the controls of N, P, and S release, immobilization,
and transport in a remote tropical montane forest. The study forest is located on steep slopes of the northern Andes in Ecuador.
We determined the concentrations of NO3-N, NH4-N, dissolved organic N (DON), PO4-P, dissolved organic P (DOP), SO4-S, dissolved organic S (DOS), and dissolved organic C (DOC) in rainfall, throughfall, stemflow, lateral flow (in the organic
layer), litter leachate, mineral soil solution, and stream water of three 8–13 ha catchments (1900–2200 m a.s.l.). The organic
forms of N, P, and S contributed, on average, 55, 66, and 63% to the total N, P, and S concentrations in all ecosystem fluxes,
respectively. The organic layer was the largest source of all N, P, and S species except for inorganic P and S. Most PO4 was released in the canopy by leaching and most SO4 in the mineral soil by weathering. The mineral soil was a sink for all studied compounds except for SO4. Consequently, concentrations of dissolved inorganic and organic N and P were as low in stream water (TDN: 0.34–0.39 mg N l−1, P not detectable) as in rainfall (TDN: 0.39–0.48 mg N l−1, P not detectable), whereas total S concentrations were elevated (stream water: 0.04–0.15, rainfall: 0.01–0.07 mg S l−1). Dissolved N, P, and S forms were positively correlated with pH at the scale of soil peda except inorganic S. Soil drying
and rewetting promoted the release of dissolved inorganic N. High discharge levels following heavy rainstorms were associated
with increased DOC, DON, NO3-N and partly also NH4-N concentrations in stream water. Nitrate-N concentrations in the stream water were positively correlated with stream discharge
during the wetter period of the year. Our results demonstrate that the sources and sinks of N, P, and S were element-specific.
More than half of the cycling N, P, and S was organic. Soil pH and moisture were important controls of N, P, and S solubility
at the scale of individual soil peda whereas the flow regime influenced the export with stream water. 相似文献
7.
8.
Understanding how the concentration and chemical quality of dissolved organic matter (DOM) varies in soils is critical because
DOM influences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation–emission fluorescence
spectroscopy, specific UV absorbance (SUVA254) and biodegradable dissolved organic carbon (BDOC) incubations to investigate the chemical quality of DOM in soil water collected
from 25 cm piezometers in four different wetland and forest soils: bog, forested wetland, fen and upland forest. There were
significant differences in soil solution concentrations of dissolved organic C, N, and P, DOC:DON ratios, SUVA254 and BDOC among the four soil types. Throughout the sampling period, average DOC concentrations in the four soil types ranged
from 9–32 mg C l−1 and between 23–42% of the DOC was biodegradable. Seasonal patterns in dissolved nutrient concentrations and BDOC were observed
in the three wetland types suggesting strong biotic controls over DOM concentrations in wetland soils. PARAFAC modeling of
excitation–emission fluorescence spectroscopy showed that protein-like fluorescence was positively correlated (r
2 = 0.82; P < 0.001) with BDOC for all soil types taken together. This finding indicates that PARAFAC modeling may substantially improve
the ability to predict BDOC in natural environments. Coincident measurements of DOM concentrations, BDOC and PARAFAC modeling
confirmed that the four soil types contain DOM with distinct chemical properties and have unique fluorescent fingerprints.
DOM inputs to streams from the four soil types therefore have the potential to alter stream biogeochemical processes differently
by influencing temporal patterns in stream heterotrophic productivity. 相似文献
9.
Catabolic diversity of periphyton and detritus microbial communities in a subtropical wetland 总被引:1,自引:0,他引:1
The catabolic diversity of wetland microbial communities may be a sensitive indicator of nutrient loading or changes in environmental
conditions. The objectives of this study were to assess the response of periphyton and microbial communities in water conservation
area-2a (WCA-2a) of the Everglades to additions of C-substrates and inorganic nutrients. Carbon dioxide and CH4 production rates were measured using 14 days incubation for periphyton, which typifies oligotrophic areas, and detritus,
which is prevalent at P-impacted areas of WCA-2a. The wetland was characterized by decreasing P levels from peripheral to
interior, oligotrophic areas. Microbial biomass and N mineralization rates were higher for oligotrophic periphyton than detritus.
Methane production rates were also higher for unamended periphyton (80 mg CH4-C kg−1 d−1) than detritus (22 mg CH4-C kg−1 d−1), even though the organic matter content was higher for detritus (80%) than periphyton (69%). Carbon dioxide production for
unamended periphyton (222 mg CO2-C kg−1 d−1) was significantly greater than unamended detritus (84 mg CO2-C kg−1 d−1). The response of the heterotrophic microbial community to added C-substrates was related to the nutrient status of the wetland,
as substrate-induced respiration (SIR) was higher for detritus than periphyton. Amides and polysaccharides stimulated SIR
more than other C-substrates, and methanogenesis was greater contributor to SIR for periphyton than detritus. Inorganic P
addition stimulated CO2 and CH4 production for periphyton but not detritus, indicating a P limitation in the interior areas of WCA-2a. Continued nutrient
loading into oligotrophic areas of WCA-2a or enhanced internal nutrient cycling may stimulate organic matter decomposition
and further contribute to undesirable changes to the Everglades ecosystem caused by nutrient enrichment. 相似文献
10.
Nutrient cycling and energy flow in ecosystems are tightly linked through the metabolic processes of organisms. Greater uptake
of inorganic nutrients is expected to be associated with higher rates of metabolism [gross primary production (GPP) and respiration
(R)], due to assimilatory demand of both autotrophs and heterotrophs. However, relationships between uptake and metabolism
should vary with the relative contribution of autochthonous and allochthonous sources of organic matter. To investigate the
relationship between metabolism and nutrient uptake, we used whole-stream and benthic chamber methods to measure rates of
nitrate–nitrogen (NO3–N) uptake and metabolism in four headwater streams chosen to span a range of light availability and therefore differing rates
of GPP and contributions of autochthonous carbon. We coupled whole-stream metabolism with measures of NO3–N uptake conducted repeatedly over the same stream reach during both day and night, as well as incubating benthic sediments
under both light and dark conditions. NO3–N uptake was generally greater in daylight compared to dark conditions, and although day-night differences in whole-stream
uptake were not significant, light–dark differences in benthic chambers were significant at three of the four sites. Estimates
of N demand indicated that assimilation by photoautotrophs could account for the majority of NO3–N uptake at the two sites with relatively open canopies. Contrary to expectations, photoautotrophs contributed substantially
to NO3–N uptake even at the two closed-canopy sites, which had low values of GPP/R and relied heavily on allochthonous carbon to
fuel R. 相似文献
11.
The influence of land use on potential fates of nitrate (NO3
−) in stream ecosystems, ranging from denitrification to storage in organic matter, has not been documented extensively. Here,
we describe the Pacific Northwest component of Lotic Intersite Nitrogen eXperiment, phase II (LINX II) to examine how land-use
setting influences fates of NO3
− in streams. We used 24 h releases of a stable isotope tracer (15NO3-N) in nine streams flowing through forest, agricultural, and urban land uses to quantify NO3
− uptake processes. NO3
− uptake lengths varied two orders of magnitude (24–4247 m), with uptake rates (6.5–158.1 mg NO3-N m−2 day−1) and uptake velocities (0.1–2.3 mm min−1) falling within the ranges measured in other LINX II regions. Denitrification removed 0–7% of added tracer from our streams.
In forest streams, 60.4 to 77.0% of the isotope tracer was exported downstream as NO3
−, with 8.0 to 14.8% stored in wood biofilms, epilithon, fine benthic organic matter, and bryophytes. Agricultural and urban
streams with streamside forest buffers displayed hydrologic export and organic matter storage of tracer similar to those measured
in forest streams. In agricultural and urban streams with a partial or no riparian buffer, less than 1 to 75% of the tracer
was exported downstream; much of the remainder was taken up and stored in autotrophic organic matter components with short
N turnover times. Our findings suggest restoration and maintenance of riparian forests can help re-establish the natural range
of NO3
− uptake processes in human-altered streams. 相似文献
12.
Denitrification efficiency for defining critical loads of carbon in shallow coastal ecosystems 总被引:2,自引:2,他引:0
Denitrification efficiency [DE; (N2 − N/(DIN + N2 − N) × 100%)] as an indicator of change associated with nutrient over-enrichment was evaluated for 22 shallow coastal ecosystems
in Australia. The rate of carbon decomposition (which can be considered a proxy for carbon loading) is an important control
on the efficiency with which coastal sediments in depositional mud basins with low water column nitrate concentrations recycle
nitrogen as N2. The relationship between DE and carbon loading is due to changes in carbon and nitrate (NO3) supply associated with sediment biocomplexity. At the DE optimum (500–1,000 μmol m−2 h−1), there is an overlap of aerobic and anaerobic respiration zones (caused primarily by the existence of anaerobic micro-niches
within the oxic zone, and oxidized burrow structures penetrating into the anaerobic zone), which enhances denitrification
by improving both the organic carbon and nitrate supply to denitrifiers. On either side of the DE optimum zone, there is a
reduction in denitrification sites as the sediment loses its three-dimensional complexity. At low organic carbon loadings,
a thick oxic zone with low macrofauna biomass exists, resulting in limited anoxic sites for denitrification, and at high carbon
loadings, there is a thick anoxic zone and a resultant lack of oxygen for nitrification and associated NO3 production. We propose a trophic scheme for defining critical (sustainable) carbon loading rates and possible thresholds
for shallow coastal ecosystems based on the relationship between denitrification efficiency and carbon loading for 17 of the
22 Australian coastal ecosystems. The denitrification efficiency “optimum” occurs between carbon loadings of about 50 and
100 g C m−2 year−1. Coastal managers can use this simple trophic scheme to classify the current state of their shallow coastal ecosystems and
for determining what carbon loading rate is necessary to achieve any future state.
Guest editors: J. H. Andersen & D. J. Conley
Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of
Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark 相似文献
13.
Spatial variability in nutrient concentration and biofilm nutrient limitation in an urban watershed 总被引:1,自引:0,他引:1
Nutrient enrichment threatens river ecosystem health in urban watersheds, but the influence of urbanization on spatial variation
in nutrient concentrations and nutrient limitation of biofilm activity are infrequently measured simultaneously. In summer
2009, we used synoptic sampling to measure spatial patterns of nitrate (NO3
−), ammonium (NH4
+), and soluble reactive phosphorus (SRP) concentration, flux, and instantaneous yield throughout the Bronx River watershed
within New York City and adjacent suburbs. We also quantified biofilm response to addition of NO3
−, phosphate (PO4
3−), and NO3
− + PO4
3− on organic and inorganic surfaces in the river mainstem and tributaries. Longitudinal variation in NO3
− was low and related to impervious surface cover across sub-watersheds, but spatial variation in NH4
+ and SRP was higher and unrelated to sub-watershed land-use. Biofilm respiration on organic surfaces was frequently limited
by PO4
3− or NO3
− + PO4
3−, while primary production on organic and inorganic surfaces was nutrient-limited at just one site. Infrequent NO3
− limitation and low spatial variability of NO3
− throughout the watershed suggested saturation of biological N demand. For P, both higher biological demand and point-sources
contributed to greater spatial variability. Finally, a comparison of our data to synoptic studies of forested, temperate watersheds
showed lower spatial variation of N and P in urban watersheds. Reduced spatial variation in nutrients as a result of biological
saturation may represent an overlooked effect of urbanization on watershed ecology, and may influence urban stream biota and
downstream environments. 相似文献
14.
The Status and Characteristics of Eutrophication in the Yangtze River (Changjiang) Estuary and the Adjacent East China Sea, China 总被引:19,自引:0,他引:19
Eutrophication has become increasingly serious and noxious algal blooms have been of more frequent occurrence in the Yangtze
River Estuary and in the adjacent East China Sea. In 2003 and 2004, four cruises were undertaken in three zones in the estuary
and in the adjacent sea to investigate nitrate (NO3–N), ammonium (NH4–N), nitrite (NO2–N), soluble reactive phosphorus (SRP), dissolved reactive silica (DRSi), dissolved oxygen (DO), phytoplankton chlorophyll
a (Chl a) and suspended particulate matter (SPM). The highest concentrations of DIN (NO3–N+NH4–N+NO2–N), SRP and DRSi were 131.6, 1.2 and 155.6 μM, respectively. The maximum Chl a concentration was 19.5 mg m−3 in spring. An analysis of historical and recent data revealed that in the last 40 years, nitrate and SRP concentrations increased
from 11 to 97 μM and from 0.4 to 0.95 μM, respectively. From 1963 to 2004, N:P ratios also increased from 30–40 up to 150. In parallel with the N and P enrichment,
a significant increase of Chl a was detected, Chl a maximum being 20 mg m−3, nearly four times higher than in the 1980s. In 2004, the mean DO concentration in bottom waters was 4.35 mg l−1, much lower than in the 1980s. In comparison with other estuaries, the Yangtze River Estuary was characterized by high DIN
and DRSi concentrations, with low SRP concentrations. Despite the higher nutrient concentrations, Chl a concentrations were lower in the inner estuary (Zones 1 and 2) than in the adjacent sea (Zone 3). Based on nutrient availability,
SPM and hydrodynamics, we assumed that in Zones 1 and 2 phytoplankton growth was suppressed by high turbidity, large tidal
amplitude and short residence time. Furthermore, in Zone 3 water stratification was also an important factor that resulted
in a greater phytoplankton biomass and lower DO concentrations. Due to hydrodynamics and turbidity, the open sea was unexpectedly
more sensitive to nutrient enrichment and related eutrophication processes. 相似文献
15.
Landscape Controls on Organic and Inorganic Nitrogen Leaching across an Alpine/Subalpine Ecotone,Green Lakes Valley,Colorado Front Range 总被引:5,自引:0,他引:5
Here we report measurements of organic and inorganic nitrogen (N) fluxes from the high-elevation Green Lakes Valley catchment
in the Colorado Front Range for two snowmelt seasons (1998 and 1999). Surface water and soil samples were collected along
an elevational gradient extending from the lightly vegetated alpine to the forested subalpine to assess how changes in land
cover and basin area affect yields and concentrations of ammonium-N (NH4-N), nitrate-N (NO3-N), dissolved organic N (DON), and particulate organic N (PON). Streamwater yields of NO3-N decreased downstream from 4.3 kg ha−1 in the alpine to 0.75 kg ha−1 at treeline, while yields of DON were much less variable (0.40–0.34 kg ha−1). Yields of NH4-N and PON were low and showed little variation with basin area. NO3-N accounted for 40%–90% of total N along the sample transect and was the dominant form of N at all but the lowest elevation
site. Concentrations of DON ranged from approximately 10% of total N in the alpine to 45% in the subalpine. For all sites,
volume-weighted mean concentrations of total dissolved nitrogen (TDN) were significantly related to the DIN:DON ratio (R
2 = 0.81, P < 0.001) Concentrations of NO3-N were significantly higher at forested sites that received streamflow from the lightly vegetated alpine reaches of the catchment
than in a control catchment that was entirely subalpine forest, suggesting that the alpine may subsidize downstream forested
systems with inorganic N. KCl-extractable inorganic N and microbial biomass N showed no relationship to changes in soil properties
and vegetative cover moving downstream in catchment. In contrast, soil carbon–nitrogen (C:N) ratios increased with increasing
vegetative cover in catchment and were significantly higher in the subalpine compared to the alpine (P < 0.0001) Soil C:N ratios along the sample transect explained 78% of the variation in dissolved organic carbon (DOC) concentrations
and 70% of the variation in DON concentrations. These findings suggest that DON is an important vector for N loss in high-elevation
ecosystems and that streamwater losses of DON are at least partially dependent on catchment soil organic matter stoichiometry.
Received 26 July 2001; accepted 6 May 2002. 相似文献
16.
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
17.
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
18.
Large Loss of Dissolved Organic Nitrogen from Nitrogen-Saturated Forests in Subtropical China 总被引:5,自引:0,他引:5
Yunting Fang Weixing Zhu Per Gundersen Jiangming Mo Guoyi Zhou Muneoki Yoh 《Ecosystems》2009,12(1):33-45
Dissolved organic nitrogen (DON) has recently been recognized as an important component of terrestrial N cycling, especially
under N-limited conditions; however, the effect of increased atmospheric N deposition on DON production and loss from forest
soils remains controversial. Here we report DON and dissolved organic carbon (DOC) losses from forest soils receiving very
high long-term ambient atmospheric N deposition with or without additional experimental N inputs, to investigate DON biogeochemistry
under N-saturated conditions. We studied an old-growth forest, a young pine forest, and a young mixed pine/broadleaf forest
in subtropical southern China. All three forests have previously been shown to have high nitrate (NO3−) leaching losses, with the highest loss found in the old-growth forest. We hypothesized that DON leaching loss would be forest
specific and that the strongest response to experimental N input would be in the N-saturated old-growth forest. Our results
showed that under ambient deposition (35–50 kg N ha−1 y−1 as throughfall input), DON leaching below the major rooting zone in all three forests was high (6.5–16.9 kg N ha−1 y−1). DON leaching increased 35–162% following 2.5 years of experimental input of 50–150 kg N ha−1 y−1. The fertilizer-driven increase of DON leaching comprised 4–17% of the added N. A concurrent increase in DOC loss was observed
only in the pine forest, even though DOC:DON ratios declined in all three forests. Our data showed that DON accounted for
23–38% of total dissolved N in leaching, highlighting that DON could be a significant pathway of N loss from forests moving
toward N saturation. The most pronounced N treatment effect on DON fluxes was not found in the old-growth forest that had
the highest DON loss under ambient conditions. DON leaching was highly correlated with NO3− leaching in all three forests. We hypothesize that abiotic incorporation of excess NO3− (through chemically reactive NO2−) into soil organic matter and the consequent production of N-enriched dissolved organic matter is a major mechanism for the
consistent and large DON loss in the N-saturated subtropical forests of southern China.
Dr. YT Fang performed research, analyzed data, and wrote the paper; Prof. WX Zhu participated in the initial experimental
design, analyzed data, and took part in writing the paper; Prof. P Gundersen conceived the study and took part in writing;
Prof. JM Mo and Prof. GY Zhou conceived study; Prof. M Yoh analyzed part of the data and contributed to the development of
DON model. 相似文献
19.
This study examined changes in dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) in coastal seawater
after exposure to sand along a high energy beach face over an annual cycle between April 2004 and July 2005. Dissolved organic
nitrogen, NO3
−, and NH4
+ were released from sand to seawater in laboratory incubation experiments clearly demonstrating that they are a potential
source of N to underlying groundwater or coastal seawater. DON increases in seawater, after exposure to surface sands in laboratory
experiments, were positively correlated with in situ water column DON concentrations measured at the same time as sand collection.
Increase in NO3
− and NH4
+ were not correlated with their in situ concentrations. This suggests that DON released from beach sands is relatively more
recalcitrant while NO3
− and NH4
+ are utilized rapidly in the coastal ocean. The release of N was seasonal with carbon to nitrogen ratios indicating that
recent primary productivity was responsible for the largest fluxes in summer while more degraded humic material contributed
to lower fluxes in winter. Fluxes of total dissolved nitrogen (DON and DIN) from surface sand (2.1 × 10−4 mol m−2 h−1) were similar to that of groundwater and more than an order of magnitude larger than rain deposition indicating the potential
importance of surface sand derived nitrogen to the coastal zone with a corresponding impact on primary productivity. 相似文献
20.
José A. Zertuche-González Víctor F. Camacho-Ibar Isaí Pacheco-Ruíz Alejandro Cabello-Pasini Luis A. Galindo-Bect José M. Guzmán-Calderón Víctor Macias-Carranza Julio Espinoza-Avalos 《Journal of applied phycology》2009,21(6):729-736
Bahía San Quintín is a coastal lagoon with large Ulva biomass and upwelling influence. Previous observations suggest that Ulva has increased recently as a result of oyster cultivation. To evaluate the possible role of Ulva as a temporary nutrient sink, biomass and tissue C, N, and P were determined seasonally. Maximum biomass was present during
spring and early summer (1,413–1,160 t (dry)) covering about 400 ha. However, the biomass decreased to 35 t (dry) by winter.
The mean annual percentage of Ulva C, N, and P was 28%, 2%, and 0.14%, respectively. This study shows that Ulva can store up to 28 t of N and 2 t of P in Bahía San Quintín during spring–summer. Ulva may be displacing the seagrass Zostera marina subtidal beds. A partial removal of the seaweed would reduce the risk of eutrophication and the displacement of eelgrass
beds. 相似文献