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1.
A spatial and temporal investigation of dissolved inorganic nitrogen (DIN; NO 3, NO 2 and NH 4) was conducted under various water discharge conditions in Lanyang-Hsi, a subtropical mountainous stream, which drains through distinct degrees of agriculture-influenced sub-watersheds. In both the cultivated and non-cultivated sub-watersheds, NO 3 was the most abundant species accounting for >80% of total DIN, while NH 4 and NO 2 accounted for <15% and=" 5%=" of=" din,=" respectively.=" agricultural=" activities=" along=" the=" riverbank=" led=" to=" significantly=" higher=">15%> 3 concentrations (13–246 M) and DIN yields (1300–3800 kg N km –2 yr –1) in main channel when compared to those of non-cultivated tributaries (9–38 M for NO 3 and 550–740 kg N km –2 yr –1 for yield). The much lower and less variable DIN yields observed in tributary stations (mean = 660 ± 120 kg N km –2 yr –1) are considered as the present day background of DIN yield, which is significantly higher than those of most natural watersheds in other regions. Elevated atmospheric DIN deposition is likely the cause for the high background DIN yield. Human activity within the watershed results in additional DIN yield, which accounted for 49% of total N export. However, the reported atmospheric DIN input in northern Taiwan (1800 kg N km –2 yr –1) is much higher than the background DIN yield implying that a major fraction (70%) of atmospheric inputs are retained or processed within the watershed. A dilution pattern occurred in the main channel where high NO 3 concentrations from the upstream sources decreased significantly in downstream direction due to inputs of NO 3-diluted water from non-cultivated areas. We adopted a two-source mixing model to predict the NO 3 dilution pattern. This model revealed a third yet not recognized N source in the lower part of watershed. Model results also indicated the importance of water discharge rate in regulating the relative contribution to total DIN export among these sources. 相似文献
2.
Steam chemistry was investigated from May 1991 through April 1992 for 13 Japanese forested watersheds and from May 1990 through August 1994 for two of these watersheds. Nine watersheds were treated over different periods (1983–1991) with different amounts of N (nitrogen) fertilizer as urea and ammonium salts. Total N additions ranged from 20 to 375 kg ha -1. There were no distinct seasonal differences in stream NO 3 - concentrations in either the treated or untreated watersheds, but concentrations tended to be somewhat higher during periods of high discharge. The annual average NO 3 - concentrations in streams had a significant, positive (p < 0.001, r = 0.84) relationship to the total amount of N applied from 1985–1991. The application of 330 kg N ha -1 raised annual average stream NO 3 - concentration to about 300 μeq L -1 compared to less than 160 μeq L -1 in untreated watersheds. The concentrations of K +, Ca 2+, and Mg2+ in stream water also increased in those watersheds with high rates of N fertilizer as a result of nitrification that increased the generation of the mobile nitrate anion. The lack of seasonality in stream NO 3 - concentrations and the large rates of N loss with N addition both suggest that these watersheds were ‘nitrogen saturated’ 相似文献
3.
The aim of this study was to investigate how electromagnetic induction can be used to improve the characterization of N dynamics in a 1.2 ha pasture. The soil apparent electrical conductivity (ECa) was measured by electromagnetic induction using an EM38DD. At 116 locations, soil samples were taken according to a clustered sampling design, three times during one winter, and analyzed for the NO 3––N content in the topsoil (0–60 cm). Management zones were delineated using a fuzzy k-means classification of the interpolated ECa measurements. Two ECa zones were found, reflecting mainly differences in soil texture. Since the mean NO 3––N content was different for the two ECa zones (24 and 65 kg/ha in November 2002), the residuals were interpolated using stratified simple kriging. This allowed evaluating the NO 3– dynamics during the winter in both zones; one ECa zone showed a higher risk for NO 3– losses than the other calling for a site-specific N management. As a validation, NO 3––N was interpolated using ordinary kriging without stratification. This resulted in similar zones confirming the usefulness of the ECa measurements to assess N-specific management zones, even within small fields. 相似文献
4.
The present study was carried out to understand whether fine root growth and N mineralization are synchronized in such a manner that helps to conserve N in the humid subtropical forest ecosystem, and to assess whether or not these processes are influenced by human disturbance. The study was conducted in two pairs of undisturbed and disturbed stands of subtropical humid forest in the Jaintia hill district of Meghalaya, northeast India. The amount of fine root (540–754 g m –2) and coarse root (307–387 g m –2) mass in the protected stands was higher than those recorded (fine root 422–466 g m –2, coarse root 247–305 g m –2) in the unprotected stands. The total annual root production was also higher in the protected stands (1,102–1,242 g m –2) than the unprotected stands (890–940 g m –2). The mean concentration of NH 4+–N and NO 3––N was higher in the protected stands than in the unprotected stands. The inorganic-N (NH 4+–N and NO 3––N) concentration was markedly high during the dry period and low during the wet period in all the stands. Inorganic-N concentration, nitrification and N mineralization rates were significantly ( P<0.01) higher in the surface (0–10 cm) than the subsurface (10–20 cm) layer. The low and high N mineralization rates observed during the dry and wet periods, respectively, coincided with the lean and peak periods of fine root mass. Disturbance in the forests caused a reduction in fine root mass as well as in N mineralization. 相似文献
5.
In the coastal sage scrub (CSS) community of southern California, Artemisia californica and other native shrubs are gradually being replaced by invasive annual grasses, especially Bromus madritensis ssp. rubens. This decline may be attributed, in part, to local atmospheric N deposition, which causes elevated soil NO 3
–. Unaffected soils have low N with a relatively higher concentration of NH 4
+ than NO 3
–. The objectives in this study were: (1) to compare the short-term uptake of 15NO 3
– and 15NH 4
+ by B. madritensis and A. californica and (2) to discern whether 15NO 3
– or 15NH 4
+ uptake is influenced by the mycorrhizal status of either plant species. Analysis of 15N concentrations indicated that both A. californica and B. madritensis took up more 15NO 3
– than 15NH 4
+, but overall, B. madritensis took up 6–15 times more of both forms of 15N than A. californica. Mycorrhizal A. californica had an increased 15NH 4
+ concentration in roots but not shoots. In B. madritensis, the only mycorrhizal response was a reallocation of 15NO 3
–, with mycorrhizal plants retaining a higher proportion of 15NO 3
– in roots. Overall, arbuscular mycorrhizae had a small effect on 15N uptake in this short-term study. However, the ability of B. madritensis to take up so much 15N may explain in part why it has been so successful in replacing A. californica in CSS. 相似文献
6.
Under semiarid subtropical field conditions, denitrification was measured from the arable soil layer of an irrigated wheat–maize cropping system fertilized with urea at 50 or 100 kg N ha –1 year –1 (U 50 and U 100, respectively), each applied in combination with 8 or 16 t ha –1 year –1 of farmyard manure (FYM) (F 8 and F 16, respectively). Denitrification was measured by acetylene inhibition/soil core incubation method, also taking into account the N 2O entrapped in soil cores. Denitrification loss ranged from 3.7 to 5.7 kg N ha –1 during the growing season of wheat (150 days) and from 14.0 to 30.3 kg N ha –1 during the maize season (60 days). Most (up to 61%) of the loss occurred in a relatively short spell, after the presowing irrigation to maize, when the soil temperature was high and a considerable NO 3–-N had accumulated during the preceding 4-month fallow; during this irrigation cycle, the lowest denitrification rate was observed in the treatment receiving highest N input (U 100+F 16), mainly because of the lowest soil respiration rate. Data on soil respiration and denitrification potential revealed that by increasing the mineral N application rate, the organic matter decomposition was accelerated during the wheat-growing season, leaving a lower amount of available C during the following maize season. Denitrification was affected by soil moisture and by soil temperature, the influence of which was either direct, or indirect by controlling the NO 3– availability and aerobic soil respiration. Results indicated a substantial denitrification loss from the irrigated wheat–maize cropping system under semiarid subtropical conditions, signifying the need of appropriate fertilizer management practices to reduce this loss. 相似文献
7.
PurposeThis study aimed to investigate the benefits of retaining harvest residues on the dynamics of soil C and N pools following clear-cut harvesting of a slash pine plantation in South East Queensland of subtropical Australia. Materials and methodsImmediately following clear-cut harvesting, macro-plots (10?×?10 m) were established on a section of the plantation in a randomised complete block design with four blocks and three treatments: (1) residue removal (RR0), (2) single level of residue retention (RR1) and (3) double level of residue retention (RR2). Soils were sampled at 0, 6, 12, 18 and 24 months following clear-cutting and analysed for total C and N, microbial biomass C (MBC) and N (MBN), hot water–extractable organic C (HWEOC), hot water–extractable organic N (HWEON), NH4+–N and NOx?–N. Results and discussionThe study showed that although soil total C decreased in the first 12 months following clear-cutting, harvest residue retention increased soil total C and N by 45% (p?<?0.001) and 32% (p?<?0.001), respectively, over the 12–24 months. NH4+–N, HWEOC, HWEON and MBC showed initial surges in the first 6 months irrespective of residue management, which declined after the 6th month. However, residue retention significantly increased HWEOC and HWEON over the 12–24 months (p?<?0.001). ConclusionsThis study demonstrated that harvest residue retention during the inter-rotation period can minimise large changes in C and nutrient pools, and can even increase soil C and nutrient pools for the next plantation rotation. 相似文献
8.
This paper focuses on N balance in a paddy field planted with whole crop rice ( Oryza sativa cv. Kusahonami). The experiment was conducted with two treatments during two rice-growing seasons: one was fertilized with N (160 kg N ha –1; 16N plot) and the other unfertilized (0N plot); both plots were fertilized with P and K. The N input from precipitation was 15 and 12 kg N ha –1 in 2002 and 2003, respectively. The N input from irrigation water reached as much as 123 and 69 kg N ha –1 in 2002 and 2003, respectively. This was because irrigation water contained higher NO 3– concentrations ranging from 4 to 8 mg N l –1. The N uptake by rice plants was the major output: 118 and 240 kg N ha –1 in the 0N and 16N plots in 2002 and 103 and 238 kg N ha –1 in 2003, respectively. N losses by leaching were 4.8–5.3 and 6.5–7.3 kg N ha –1 in 2002 and in 2003, respectively. Laboratory experiments were carried out to estimate the amounts of N 2 fixation and denitrification. Amount of N 2 fixation was 43 and 0 kg N ha –1 in the 0N and 16N plots, respectively. Denitrification potential was quite high in both the plots, and 90% of the N input through irrigation water was lost through denitrification. Collectively, the total N inputs were relatively large due to irrigation water contaminated with NO 3–, but N outflow loading, expressed as leaching–(irrigation water + precipitation + fertilizer), showed large negative values, suggesting that the whole crop rice field might serve as a constructed wetland for decreasing N. 相似文献
9.
Summary The nitrogen metabolism of wheat plants inoculated with various Azospirillum brasilense strains and nitrate reductase negative (NR –) mutants was studied in two monoxenic test tube experiments. The spontaneous mutants selected with chlorate under anaerobic conditions with nitrite as terminal electron acceptor fixed N 2 in the presence of 10 m M NO 3
– and were stable after the plant passage. One strain (Sp 245) isolated from surface-sterilized wheat roots produced significant increases in plant weight at both NO 3 levels (1 and 10 m M) which were not observed with the NR – mutants or with the two other strains. Similar effects were observed in a pot experiment with soil on dry weight and total N incorporation but only at the higher N fertilizer level. In the monoxenic test tube experiments plants inoculated with the mutants showed lower nitrogenase activities than NR + strains at the low NO 3
– level (1 = m M) but maintained the same level of activity with 10 m M NO 3
– where the activity of all NR + strains was completely repressed. The nitrate reductase activity of roots increased with the inoculation of the homologous strains and with the mutants at both NO 3
– levels. At the low NO 3
– level this also resulted in increased activity in the shoots, but at the high NO 3
– level the two homologous strains produced significantly lower nitrate reductase activity in shoots while the mutants more than doubled it. The possible role of the bacterial nitrate reductase in NO 3
– assimilation by the wheat plant is discussed. 相似文献
10.
We used ionic tracers to estimate the volume of old (soil and ground) water interacting with snowmelt in eleven Adirondack, NY watersheds. The contribution of old water varied from 66 to 90%, with no general relationship between old water % and soil depth to till. This approach also discriminated between watershed retention and release of particular ions to lake outlet water during snowmelt. Most watersheds released NO 3 ? during snowmelt, in addition to the snowpack NO 3 ?. Nitrification of snowpack NH 4 + explained part of the additional NO 3 ? in lake out outlet water, but some NO 3 ? was likely mineralized nitrogen from soil organic matter. All watersheds retained NH 4 + as well. Nitrogen release was greatest in the acidic watersheds in the southwestern Adirondacks, a region thought to be impacted by anthropogenic deposition. During snowmelt, Ca 2+ and Mg 2+ ions (presumably from soil exchange sites) were also released from most watersheds. In watersheds with acidic (minimum pH<4.6) lake outlet water, Al was also released during snowmelt. Thus, lake outlet water acidification during snowmelt was both buffered by cation release, and intensified by NO 3 ? release. If the soil exchangeable cation pools were not replenished prior to snowmelt, or NO 3 ? mobilization were increased, acidification during snowmelt would intensify. 相似文献
11.
Summary The chloroform fumigation-incubation method (CFIM) was used to measure the microbial biomass of 17 agricultural soils from Punjab Pakistan which represented different agricultural soil series. The biomass C was used to calculate biomass N and the changes occurring in NH 4
+-N and NO 3
–-N content of soils were studied during the turnover of microbial biomass or added C source. Mineral N released in fumigated-incubated soils and biomass N calculated from biomass C was correlated with some N availability indexes.The soils contained 427–1240 kg C as biomass which represented 1.2%–6.9% of the total organic C in the soils studied. Calculations based on biomass C showed that the soils contained 64–186 kg N ha –1 as microbial biomass. Immobilization of NCO 3
–-N was observed in different soils during the turnover of microbial biomass and any net increase in mineral N content of fumigated incubated soils was attributed entirely to NH 4
+-N.Biomass N calculated from biomass C showed non-significant correlation with different N availability indexes whereas mineral N accumulated in fumigated-incubated soils showed highly significant correlations with other indexes including N uptake by plants. 相似文献
12.
In this paper we try to interpret results from different investigations where an ecosystem with Norway spruce was manipulated with increased N and S deposition via the soil system. The site, in Skogaby in Southwest Sweden, had 1989–93 an annual deposition of 9 kg NH 4-N; 7 kg NO 3-N and 20 kg SO 4-S ha –1. The stand was treated during 6 years with 100 kg N and 114 kg S ha – y –1 in the form of ammonium sulphate (NS treatment). The stand reacted with increased above ground production of 31% after 3 years of treatment. The uptake above ground of N was 155 kg ha –1 higher than in the control. Those trends were even stronger after 6 years of treatment. There were no decreases in the uptake of P, K, Ca or Mg (but for B) after 3 or 6 years of NS-treatment. Needle macro nutrient concentrations in relation to N decreased for several nutrients due to dilution effects. As result of the NS treatment pH increased markedly in the litter layer, and less, but significantly, in the humus layer. A decrease in pH value by about 0.3 units was found in the rest of the soil profile down to 50 cm. Dry mass of needle litter fall and litter layer both increased as a result of 6 years of NS-treatment. After three years of treatment 77–80% of all living fine roots in both control and NS treatment were found in the humus layer and the upper 10 cm of the mineral soil. The amount of living fine roots in the humus layer of NS-treated trees decreased to about one third of the control, and the amount of dead fine roots increased by 150% compared with untreated trees after 6 years of treatment. It is argued that the decreased amount of living and increased amount of dead fine roots not necessarily are indications of decreased root vitality. It can also be explained by increased root turnover rate and decreased decomposition rates of N rich new and old fine root litter. No inorganic N was leached from the control plots whereas the NS treated plots started to leach NO 3 the second year of treatment. During 1989–1993 a total of 44 kg NO 3-N and 30 kg NH 4-N per ha was lost from the system which means that 88% of the N supplied was retained by the ecosystem. At first SO 4 was adsorbed in the soil, but after five years of treatment the output was almost equal to the input. 相似文献
13.
The total deposition of sulphur (S) and nitrogen (N) components in Norway during the period 1988–1992 has been estimated on the basis of measurement data of air- and precipitation chemistry from the national monitoring network. There are large regional variations in depositions with highest values in the southwestern part of Norway. Time series analysis of annual mean concentrations of sulphur dioxide (SO 2) and sulphate (SO 4
––) in air, non marine SO 4
––, nitrate (NO 3
–) and ammonium (NH 4
+) in precipitation, shows a significant reduction in the S concentrations both in air and precipitation. In precipitation the concentrations are reduced by 30–45 percent in Southern Norway and 45–55 percent in Central and Northern Norway. Even larger reductions are observed in air concentrations with 50–65 percent reduction in Southern Norway and 65–88 percent reduction further north. For N components there are generally no significant trends in concentration levels nor in precipitation or air. The observed trends are comparable with reported trends in emission. 相似文献
14.
Long-term changes in the chemistry of precipitation (1978–94) and 16 lakes (1982–94) were investigated in the Adirondack region of New York, USA. Time-series analysis showed that concentrations of SO 4
2–, NO 3
–, NH 4
+ and basic cations have decreased in precipitation, resulting in increases in pH. A relatively uniform rate of decline in SO 4
2– concentrations in lakes across the region (1.81±0.35 eq L –1 yr –1) suggests that this change was due to decreases in atmospheric deposition. The decrease in lake SO 4
2– was considerably less than the rate of decline anticipated from atmospheric deposition. This discrepancy may be due to release of previously deposited SO 4
2– from soil, thereby delaying the recovery of lake water acidity. Despite the marked declines in concentrations of SO 4
2– in Adirondack lakes, there has been no systematic increase in pH and ANC. The decline in SO 4
2– has corresponded with a near stoichiometric decrease in concentrations of basic cations in low ANC lakes. A pattern of increasing NO 3
– concentrations that was evident in lakes across the region during the 1980's has been followed by a period of lower concentrations. Currently there are no significant trends in NO 3
– concentrations in Adirondack lakes. 相似文献
15.
The restoration of drained peat bogs in Northwest (NW) Europe is an important task of soil protection, but needs to cope with warmer and drier summers. Our examination took place in the Pietzmoor bog (Schneverdingen, NW Germany) that had been drained for fuel peat extraction until the 1970s and rewetted since then. We determined carbon dioxide (CO 2) efflux in situ and in laboratory incubations. Also, we analyzed pore water for dissolved organic carbon (DOC), total and dissolved organic N (DON), nitrate (NO 3–) and ammonium (NH 4+) concentration. In Schneverdingen, the summer 2003 was record-breaking hot (mean temperature June to August elevated > 3 K compared to long-term average) and dry (precipitation during the same period < 59% of long-term average). In July 2003, the water table in the Pietzmoor subsided to > 42 cm below the surface in July 2003, when in situ soil CO 2 efflux was up to 23.4 g m –2 d –1 compared to 15.7 g m –2 d –1 in September. Prior to March 2003, DOC concentrations in pore water were < 180 mg l –1 and NH 4+ was the dominant fraction of mineral N. In July 2003, DOC concentration rose to 249 g l –1, DON concentrations more than doubled, and NO 3– became the dominant fraction of mineral N. Due to the increased future likelihood of hot and dry summers in NW Germany, peat bog restoration efforts need take care that a water table close to the surface is maintained. 相似文献
16.
Core lysimeters containing undisturbed coarse sandy soil (from grassland) were amended with a high rate of anaerobically digested sewage sludge (equivalent to >1,000 t ha –1). Water, at a rate equivalent to the mean weekly rainfall for the soil, was applied to amended and control lysimeters for 30 weeks and the leachate analysed for anions and cations. Lysimeters were also destructively sampled at intervals throughout the experiment and soil samples were analysed for extractable NH 4+-N, NO 3–-N and PO 43–-P. Ammonium N leached for about 11 weeks from the amended lysimeters, then abruptly stopped. A similar amount of NO 3–-N leached, but leaching was continuing when the experiment finished. The control lysimeters leached as much NO 3–-N as those that were amended, but no NH 4+-N. The amended lysimeters also leached NO 2–-N. Negligible PO 43–-P, but large amounts of SO 42– were leached from the amended lysimeters. Concentrations of extractable NH 4+-N and PO 43–-P were very high in the amended soils, but NO 3–-N concentrations remained low throughout the experiment, indicating that nitrification rates were low and/or that denitrification rates were high. 相似文献
17.
In the central highlands of Mexico, mesquite ( Prosopis laevigata) and huisache ( Acacia schaffneri), N 2-fixing trees or shrubs, dominate the vegetation and are currently used in a reforestation program to prevent erosion. We investigated how natural vegetation or cultivation of soil affected oxidation of CH 4, and production of N 2O. Soil was sampled under the canopy of mesquite (MES treatment) and huisache trees (HUI treatment), outside their canopy (OUT treatment) and from fields cultivated with maize (ARA treatment) at three different sites while production of CO 2, and dynamics of CH 4, N 2O and inorganic N (NH 4+, and NO 3–) were monitored in an aerobic incubation. The production of CO 2 was 2.3 times higher and significantly greater in the OUT treatment, 3.0 times higher in the MES treatment and 4.0 times higher in the HUI treatment compared to the ARA treatment. There was no significant difference in oxidation of CH 4 between the treatments, which ranged from 0.019 g CH 4–C kg –1 day –1 for the HUI treatment to 0.033 CH 4–C kg –1 day –1 for the MES treatment. The production of N 2O was 30 g N 2O–N kg –1 day –1 in the MES treatment and >8 times higher compared to the other treatments. The average concentration of NO 3– was 2 times higher and significantly greater in the MES treatment than in the HUI treatment, 3 times greater than in the OUT treatment and 10 times greater than in the ARA treatment. It was found that cultivation of soil decreased soil organic matter content, C and N mineralization, but not oxidation of CH 4 or production of N 2O. 相似文献
18.
Availability and leaching of dissolved inorganic N (DIN = NH 4+ + NO 3-) in soil were measured in a periodically flooded forest of the Central Amazon floodplain (várzea) during one terrestrial phase. Special emphasis was on the effects of a legume and a non-legume tree species. NH 4+-N accounted for more than 85% of DIN even at the end of the terrestrial phase although it decreased throughout the experimental period. While extractable NO 3–-N was always low in the soil (less than 15% of DIN), the amount of leached NO 3–-N was in the same range as NH 4+-N. Under the legume trees mean DIN contents of the topsoil were higher than under the non-legume trees. DIN leaching from the topsoil (0–20 cm) was significantly higher under the legume trees than at the other sites, also indicating a higher N availability. Therefore, despite considerable leaching legume trees may be an important source of N supporting a high biomass production of the várzea forest. 相似文献
19.
Alternative silvicultural systems were introduced in Coastal Western Hemlock forests of British Columbia, Canada, to reduce
disturbance incurred by conventional clear-cutting and to maintain the forest influence on soil nutrient cycling. As we hypothesized,
in situ pools and net mineralization of NH 4
+ were lower under no and low disturbance (old-growth forest and shelterwood) compared to clear-cuts (high disturbance); in
situ pools and net production of NO 3
− were very low across all treatments. Gross transformation rates of NH 4
+ increased while those of NO 3
− decreased with increasing disturbance, suggesting that these processes were uncoupled. We conclude that shelterwood harvesting
reduces the impact on forest floor NH 4
+ cycling compared to clear-cutting, and that neither low nor high disturbance intensity results in substantial NO 3
− accumulation, as what occasionally occurs in other ecosystems. We hypothesize that the uncoupling of NH 4
+ and NO 3
− dynamics may be due to the predominance of heterotrophic nitrification by lignin-degrading fungi that oxidize organic N rather
than NH 4
+–N, and whose activities are suppressed at high NH 4
+ concentrations. 相似文献
20.
Summary Nitrous oxide (N 2O) fluxes at the soil surface and concentrations at 0.1, 0.2, and 0.3 m were determined in a 40-year-old planted tallgrass (XXX) prairie, a 40-year-old white pine ( Pinus strobus) plantation, and field plots treated annually for 18 years either with 33 metric tons of manure ha –1 (330 kg N ha –1) and NH 4NO 3 (80 kg N ha –1) or with only NH 4NO 3 (control). Nitrous oxide fluxes from the prairie, forest, manure-amended, and control sites from 13 May to 10 November 1980 ranged from 0.2 to 1.3, 3.5 to 19.5, 3.7 to 79.0, and 1.7 to 24.8 ng N 2O-N m –2s –1, respectively. We observed periods when there was no apparent relationship between the N 2O flux from the surface and N 2O concentrations in the soil profile. This was generally the case in the prairie and in the field sites following the application of N fertilizer. The N 2O concentrations in the soil profile increased markedly and coincided with increased soil water content following periods of heavy rainfall for all sites except the prairie. Nitrous oxide concentration gradients indicate that following heavy rainfalls the site of N 2O production was moved from the surface deeper into the soil profile. We suggest that the source of N 2O production near the surface is nitrification and that N 2O is produced by denitrification of NO 3 leached into the soil following heavy rainfall. 相似文献
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