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1.
Emissions of nitrous oxide from three tropical forests in Southern China in response to simulated nitrogen deposition 总被引:2,自引:0,他引:2
Wei Zhang Jiangming Mo Guirui Yu Yunting Fang Dejun Li Xiankai Lu Hui Wang 《Plant and Soil》2008,306(1-2):221-236
Emissions of nitrous oxide (N2O) from the soil following simulated nitrogen (N) deposition in a disturbed (pine), a rehabilitated (pine and broadleaf mixed)
and a mature (monsoon evergreen broadleaf) tropical forest in southern China were studied. The following hypotheses were tested:
(1) addition of N will increase soil N2O emission in tropical forests; and (2) any observed increase will be more pronounced in the mature forest than in the disturbed
or rehabilitated forest due to the relatively high initial soil N concentration in the mature forest. The experiment was designed
with four N treatment levels (three replicates; 0, 50, 100, 150 kg N ha−1 year−1 for C (Control), LN (Low-N), MN (Medium-N), and HN (High-N) treatment, respectively) in the mature forest, but only three
levels in the disturbed and rehabilitated forests (C, LN and MN). Between October 2005 to September 2006, soil N2O flux was measured using static chamber and gas chromatography methodology. Nitrogen had been applied previously to the plots
since July 2003 and continued during soil N2O flux measurement period. The annual mean rates of soil N2O emission in the C plots were 24.1 ± 1.5, 26.2 ± 1.4, and 29.3 ± 1.6 μg N2O–N m−2 h−1 in the disturbed, rehabilitated and mature forest, respectively. There was a significant increase in soil N2O emission following N additions in the mature forest (38%, 41%, and 58% when compared to the C plots for the LN, MN, and
HN plots, respectively). In the disturbed forest a significant increase (35%) was observed in the MN plots, but not in the
LN plots. The rehabilitated forest showed no significant response to N additions. Increases in soil N2O emission occurred primarily in the cool-dry season (November, December and January). Our results suggest that the response
of soil N2O emission to N deposition in tropical forests in southern China may vary depending on the soil N status and land-use history
of the forest. 相似文献
2.
Contribution of plants to N
2
O emissions in soil-winter wheat ecosystem: pot and field experiments 总被引:1,自引:0,他引:1
Outdoor pot and field experiments were conducted to assess the role of growing plants in agricultural ecosystem N2O emissions. N2O emissions from plants were quantified as the difference in soil-crop system N2O emissions before and immediately after cutting plants during the main growth stages in 2001–02 and 2002–03 winter wheat
seasons. Emissions of N2O from plants depended on biomass within the same plant developmental status. Field results indicated that the seasonal contribution
of N2O emissions from plants to ecosystem fluxes averaged 25%, ranging from 10% at wheat tillering to 62% at the heading stage.
The fluxes of N2O emissions from plants varied between 0.3 and 3.9 mg N2O-N m−2 day−1 and its seasonal amount was equivalent to 0.23% of plant N released as N2O. A N2O emission coefficient (N2OE, mg N2O-N g−1 C day−1), defined as N2O-N emission in milligrams from per gram carbon of plant dry matter within a day, was represented by a 5-fold variation ranging
from 0.021 to 0.004 mg N2O-N g C−1 day−1. A linear relationship (y=0.4611x+0.0015, r
2=0.9352, p < 0.001) between N2OE (y) and plant dark respiration rate (x, mg CO2-C g C−1 day−1) suggested that in the absence of photosynthesis, some N2O production in plant N assimilation was associated with plant respiration. Although this study could not show whether N2O was produced or transferred by winter wheat plants, these results indicated an important role for higher plant in N2O exchange. Identifying its potential contribution is critical for understanding agricultural ecosystem N2O sources. 相似文献
3.
Winter and summer nitrous oxide and nitrogen oxides fluxes from a seasonally snow-covered subalpine meadow at Niwot Ridge,Colorado 总被引:4,自引:3,他引:1
Gianluca Filippa Michele Freppaz Mark W. Williams Detlev Helmig Daniel Liptzin Brian Seok Brad Hall Kurt Chowanski 《Biogeochemistry》2009,95(1):131-149
The soil emission rates (fluxes) of nitrous oxide (N2O) and nitrogen oxides (NO + NO2 = NO
x
) through a seasonal snowpack were determined by a flux gradient method from near-continuous 2-year measurements using an
automated system for sampling interstitial air at various heights within the snowpack from a subalpine site at Niwot Ridge,
Colorado. The winter seasonal-averaged N2O fluxes of 0.047–0.069 nmol m−2 s−1 were ~15 times higher than observed NO
x
fluxes of 0.0030–0.0067 nmol m−2 s−1. During spring N2O emissions first peaked and then dropped sharply as the soil water content increased from the release of snowpack meltwater,
while other gases, including NO
x
and CO2 did not show this behavior. To compare and contrast the winter fluxes with snow-free conditions, N2O fluxes were also measured at the same site in the summers of 2006 and 2007 using a closed soil chamber method. Summer N2O fluxes followed a decreasing trend during the dry-out period after snowmelt, interrupted by higher values related to precipitation
events. These peaks were up to 2–3 times higher than the background summer levels. The integrated N2O-N loss over the summer period was calculated to be 1.1–2.4 kg N ha−1, compared to ~0.24–0.34 kg N ha−1 for the winter season. These wintertime N2O fluxes from subniveal soil are generally higher than the few previously published data. These results are of the same order
of magnitude as data from more productive ecosystems such as fertilized grasslands and high-N-cycling forests, most likely
because of a combination of the relatively well-developed soils and the fact that subnivean biogeochemical processes are promoted
by the deep, insulating snowpack. Hence, microbially mediated oxidized nitrogen emissions occurring during the winter can
be a significant part of the N-cycle in seasonally snow-covered subalpine ecosystems. 相似文献
4.
Tillage and Nitrogen Application Effects on Nitrous and Nitric Oxide Emissions from Irrigated Corn Fields 总被引:3,自引:0,他引:3
A 2-year study was conducted to investigate the potential of no-till cropping systems to reduce N2O and NO emissions under different N application rates in an irrigated corn field in northeastern Colorado. Flux measurements
were begun in the spring of 2003, using vented (N2O) and dynamic (NO) chambers, one to three times per week, year round, within plots that were cropped continuously to corn
(Zea mays L.) under conventional-till (CT) and no-till (NT). Plots were fertilized at planting in late April with rates of 0, 134 and
224 kg N ha−1 and corn was harvested in late October or early November each year. N2O and NO fluxes increased linearly with N application rate in both years. Compared with CT, NT did not significantly affect
the emission of N2O but resulted in much lower emission of NO. In 2003 and 2004 corn growing seasons, the increase in N2O-N emitted per kg ha−1 of fertilizer N added was 14.5 and 4.1 g ha−1 for CT, and 11.2 and 5.5 g ha−1 for NT, respectively. However, the increase in NO-N emitted per kg ha−1 of fertilizer N added was only 3.6 and 7.4 g ha−1 for CT and 1.6 and 2.0 g ha−1 for NT in 2003 and 2004, respectively. In the fallow season (November 2003 to April 2004), much greater N2O (2.0–3.1 times) and NO (13.1–16.8 times) were emitted from CT than from NT although previous N application did not show
obvious carry-over effect on both gas emissions. Results from this study reveal that NT has potential to reduce NO emission
without an obvious change in N2O emission under continuous irrigated corn cropping compared to CT. 相似文献
5.
Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China 总被引:3,自引:0,他引:3
J. Holst C. Liu Z. Yao N. Brüggemann X. Zheng X. Han K. Butterbach-Bahl 《Plant and Soil》2007,296(1-2):209-226
The aim of the present work was to estimate the contribution of different point and diffuse sources to the regional N2O emission strength of steppe in the Xilin river catchment, Inner Mongolia, People’s Republic of China. Transect studies showed
that the topographic effect on N2O emissions from upland soils was negligible and that upland steppe is only a very weak net source of N2O during the growing season (0.8 ± 0.4 μg N2O–N m−2 h−1). Slightly higher emissions were found for riparian areas (1.8 ± 0.3 μg N2O–N m−2 h−1), which cover ∼4% of the landscape. Even faeces or urine additions stimulated N2O emissions from steppe soils only weakly (<2.5 μg N2O–N m−2 h−1 for a 5 days period). Due to low moisture contents, N2O emissions from dung heaps were also rather low (6.2 ± 0.8 μg N2O–N kg−1 dry matter h−1). In contrast, three orders of magnitude higher N2O emissions were found at sheepfolds (2.45 mg N2O–N m−2 h−1 on average). By calculating N2O emissions on a landscape scale, we show that point sources, and especially sheepfolds, become the dominating regional N2O source during the growing season if stocking rates are >1 sheep ha−1. Our results indicate that the common grazing management in the Xilin river region leads to a translocation of nitrogen from
large source areas towards defined spots. This finding is further supported by measurements of NH3 concentrations at different sites. Since most of the nitrogen accumulated in these hot spots is finally lost through burning
of the dried excrements by the farmers for heating and cooking purposes, the ecosystem faces a significant human perturbation
of regional N cycling, which may contribute to an accelerated degradation of steppe in the Xilin river region.
Responsible Editor: Per Ambus. 相似文献
6.
Christian Brümmer Nicolas Brüggemann Klaus Butterbach-Bahl Ulrike Falk Jörg Szarzynski Konrad Vielhauer Reiner Wassmann Hans Papen 《Ecosystems》2008,11(4):582-600
In a combined field and laboratory study in the southwest of Burkina Faso, we quantified soil-atmosphere N2O and NO exchange. N2O emissions were measured during two field campaigns throughout the growing seasons 2005 and 2006 at five different experimental
sites, that is, a natural savanna site and four agricultural sites planted with sorghum (n = 2), cotton and peanut. The agricultural fields were not irrigated and not fertilized. Although N2O exchange mostly fluctuated between −2 and 8 μg N2O–N m−2 h−1, peak N2O emissions of 10–35 μg N2O–N m−2 h−1 during the second half of June 2005, and up to 150 μg N2O–N m−2 h−1 at the onset of the rainy season 2006, were observed at the native savanna site, whereas the effect of the first rain event
on N2O emissions at the crop sites was low or even not detectable. Additionally, a fertilizer experiment was conducted at a sorghum
field that was divided into three plots receiving different amounts of N fertilizer (plot A: 140 kg N ha−1; plot B: 52.5 kg N ha−1; plot C: control). During the first 3 weeks after fertilization, only a minor increase in N2O emissions at the two fertilized plots was detected. After 24 days, however, N2O emission rates increased exponentially at plot A up to a mean of 80 μg N2O–N m−2 h−1, whereas daily mean values at plot B reached only 19 μg N2O–N m−2 h−1, whereas N2O flux rates at plot C remained unchanged. The calculated annual N2O emission of the nature reserve site amounted to 0.52 kg N2O–N ha−1 a−1 in 2005 and to 0.67 kg N2O–N ha−1 a−1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 kg N2O–N ha−1 a−1 and 0.20 kg N2O–N ha−1 a−1 in 2005 and 2006, respectively. In a laboratory study, potential N2O and NO formation under different soil moisture regimes were determined. Single wetting of dry soil to medium soil water
content with subsequent drying caused the highest increase in N2O and NO emissions with maximum fluxes occurring 1 day after wetting. The stimulating effect lasted for 3–4 days. A weaker
stimulation of N2O and NO fluxes was detected during daily wetting of soil to medium water content, whereas no significant stimulating effect
of single or daily wetting to high soil water content (>67% WHCmax) was observed. This study demonstrates that the impact of land-use change in West African savanna on N trace gas emissions
is smaller—with the caveat that there could have been potentially higher N2O and NO emissions during the initial conversion—than the effect of timing and distribution of rainfall and of the likely
increase in nitrogen fertilization in the future. 相似文献
7.
The Impact of Nitrogen Placement and Tillage on NO, N2O, CH4 and CO2 Fluxes from a Clay Loam Soil 总被引:4,自引:0,他引:4
Xuejun J. Liu Arvin R. Mosier Ardell D. Halvorson Fusuo S. Zhang 《Plant and Soil》2006,280(1-2):177-188
To evaluate the impact of N placement depth and no-till (NT) practice on the emissions of NO, N2O, CH4 and CO2 from soils, we conducted two N placement experiments in a long-term tillage experiment site in northeastern Colorado in 2004.
Trace gas flux measurements were made 2–3 times per week, in zero-N fertilizer plots that were cropped continuously to corn
(Zea mays L.) under conventional-till (CT) and NT. Three N placement depths, replicated four times (5, 10 and 15 cm in Exp. 1 and 0,
5 and 10 cm in Exp. 2, respectively) were used. Liquid urea–ammonium nitrate (UAN, 224 kg N ha−1) was injected to the desired depth in the CT- or NT-soils in each experiment. Mean flux rates of NO, N2O, CH4 and CO2 ranged from 3.9 to 5.2 μg N m−2 h−1, 60.5 to 92.4 μg N m−2 h−1, −0.8 to 0.5 μg C m−2 h−1, and 42.1 to 81.7 mg C m−2 h−1 in both experiments, respectively. Deep N placement (10 and 15 cm) resulted in lower NO and N2O emissions compared with shallow N placement (0 and 5 cm) while CH4 and CO2 emissions were not affected by N placement in either experiment. Compared with N placement at 5 cm, for instance, averaged
N2O emissions from N placement at 10 cm were reduced by more than 50% in both experiments. Generally, NT decreased NO emission
and CH4 oxidation but increased N2O emissions compared with CT irrespective of N placement depths. Total net global warming potential (GWP) for N2O, CH4 and CO2 was reduced by deep N placement only in Exp. 1 but was increased by NT in both experiments. The study results suggest that
deep N placement (e.g., 10 cm) will be an effective option for reducing N oxide emissions and GWP from both fertilized CT-
and NT-soils. 相似文献
8.
N2O, CH4 and CO2 emissions from seasonal tropical rainforests and a rubber plantation in Southwest China 总被引:2,自引:1,他引:1
Christian Werner Xunhua Zheng Janwei Tang Baohua Xie Chunyan Liu Ralf Kiese Klaus Butterbach-Bahl 《Plant and Soil》2006,289(1-2):335-353
The main focus of this study was to evaluate the effects of soil moisture and temperature on temporal variation of N2O, CO2 and CH4 soil-atmosphere exchange at a primary seasonal tropical rainforest (PF) site in Southwest China and to compare these fluxes with fluxes from a secondary forest (SF) and a rubber plantation (RP) site. Agroforestry systems, such as rubber plantations, are increasingly replacing primary and secondary forest systems in tropical Southwest China and thus effect the N2O emission in these regions on a landscape level. The mean N2O emission at site PF was 6.0 ± 0.1 SE μg N m−2 h−1. Fluxes of N2O increased from <5 μg N m−2 h−1 during dry season conditions to up to 24.5 μg N m−2 h−1 with re-wetting of the soil by the onset of first rainfall events. Comparable fluxes of N2O were measured in the SF and RP sites, where mean N2O emissions were 7.3 ± 0.7 SE μg N m−2 h−1 and 4.1 ± 0.5 SE μg N m−2 h−1, respectively. The dependency of N2O fluxes on soil moisture levels was demonstrated in a watering experiment, however, artificial rainfall only influenced the timing of N2O emission peaks, not the total amount of N2O emitted. For all sites, significant positive correlations existed between N2O emissions and both soil moisture and soil temperature. Mean CH4 uptake rates were highest at the PF site (−29.5 ± 0.3 SE μg C m−2 h−1), slightly lower at the SF site (−25.6 ± 1.3 SE μg C m−2 h−1) and lowest for the RP site (−5.7 ± 0.5 SE μg C m−2 h−1). At all sites, CH4 uptake rates were negatively correlated with soil moisture, which was also reflected in the lower uptake rates measured in the watering experiment. In contrast to N2O emissions, CH4 uptake did not significantly correlate with soil temperature at the SF and RP sites, and only weakly correlated at the PF site. Over the 2 month measurement period, CO2 emissions at the PF site increased significantly from 50 mg C m−2 h−1 up to 100 mg C m−2 h−1 (mean value 68.8 ± 0.8 SE mg C m−2 h−1), whereas CO2 emissions at the SF and RP site where quite stable and varied only slightly around mean values of 38.0 ± 1.8 SE mg C m−2 h−1 (SF) and 34.9 ± 1.1 SE mg C m−2 h−1 (RP). A dependency of soil CO2 emissions on changes in soil water content could be demonstrated for all sites, thus, the watering experiment revealed significantly higher CO2 emissions as compared to control chambers. Correlation of CO2 emissions with soil temperature was significant at the PF site, but weak at the SF and not evident at the RP site. Even though we demonstrated that N and C trace gas fluxes significantly varied on subdaily and daily scales, weekly measurements would be sufficient if only the sink/ source strength of non-managed tropical forest sites needs to be identified. 相似文献
9.
Compared to upland forests, riparian forest soils have greater potential to remove nitrate (NO3) from agricultural runoff through denitrification. It is unclear, however, whether prolonged exposure of riparian soils to nitrogen (N) loading will affect the rate of denitrification and its end products. This research assesses the rate of denitrification and nitrous oxide (N2O) emissions from riparian forest soils exposed to prolonged nutrient runoff from plant nurseries and compares these to similar forest soils not exposed to nutrient runoff. Nursery runoff also contains high levels of phosphate (PO4). Since there are conflicting reports on the impact of PO4 on the activity of denitrifying microbes, the impact of PO4 on such activity was also investigated. Bulk and intact soil cores were collected from N-exposed and non-exposed forests to determine denitrification and N2O emission rates, whereas denitrification potential was determined using soil slurries. Compared to the non-amended treatment, denitrification rate increased 2.7- and 3.4-fold when soil cores collected from both N-exposed and non-exposed sites were amended with 30 and 60 μg NO3-N g−1 soil, respectively. Net N2O emissions were 1.5 and 1.7 times higher from the N-exposed sites compared to the non-exposed sites at 30 and 60 μg NO3-N g−1 soil amendment rates, respectively. Similarly, denitrification potential increased 17 times in response to addition of 15 μg NO3-N g−1 in soil slurries. The addition of PO4 (5 μg PO4-P g−1) to soil slurries and intact cores did not affect denitrification rates. These observations suggest that prolonged N loading did not affect the denitrification potential of the riparian forest soils; however, it did result in higher N2O emissions compared to emission rates from non-exposed forest soils. 相似文献
10.
Indicators for nitrogen status and leaching in subtropical forest ecosystems,South China 总被引:7,自引:1,他引:6
The deposition of nitrogen (N) is high in subtropical forest in South China and it is expected to increase further in the
coming decades. To assess effects of increasing deposition on N cycling, we investigated the current N status of two selected
40–45-year-old masson pine-dominated Chinese subtropical forest stands at Tieshanping (TSP, near Chongqing City) and Caijiatang
(CJT in Shaoshan, Hunan province), and explored the applicability of several indicators for N status and leaching, suggested
for temperate and boreal forest ecosystems. Current atmospheric N deposition to the systems is from 25 to 49 kg ha−1 year−1. The concentration of total N in the upper 15 cm of the soil is from as low as 0.05% in the B2 horizon to as high as 0.53% in the O/A horizon. The concentration of organic carbon (C) varies from 0.74 (B2) to 9.54% (O/A). Pools of N in the upper 15 cm of the soils range from 1460 to 2290 kg N ha−1, where 25–55% of the N pool is in the O/A horizon (upper 3 cm of the soil). Due to a lack of a well-developed continuous
O horizon (forest floor), the C/N ratio of this layer cannot be used as an indicator for the N status, as is commonly done
in temperate and boreal forests. The net N mineralization rate (mg N g−1 C year−1) in individual horizons correlates significantly with the C/N ratio, which is from as high as 18.2 in the O/A horizon to
as low as 11.2 in the B2 horizon. The N2O emission flux from soil is significantly correlated with the KCl extractable NH4+–N in the O/A horizon and with the net nitrification in the upper 15 cm of the soil. However, the spatial and temporal variation
of the N2O emission rate is high and rates are small and often difficult to detect in the field. The soil flux density of mineral N,
defined as the sum of the throughfall N input rate and the rate of in situ net N mineralization in the upper 15 cm of the
soil, i.e., the combination of deposition input and the N status of the system, explains the NO3− leaching potential at 30 cm soil depth best. The seasonality of stream water N concentration at TSP and CJT is climatic and
hydrologically controlled, with highest values commonly occurring in the wet growing season and lowest in the dry dormant
season. This is different from temperate forest ecosystems, where N saturation is indicated by elevated NO3− leaching in stream water during summer. 相似文献
11.
Nitrous oxide (N2O) emissions from grazed grasslands are estimated to be approximately 28% of global anthropogenic N2O emissions. Estimating the N2O flux from grassland soils is difficult because of its episodic nature. This study aimed to quantify the N2O emissions, the annual N2O flux and the emission factor (EF), and also to investigate the influence of environmental and soil variables controlling
N2O emissions from grazed grassland. Nitrous oxide emissions were measured using static chambers at eight different grasslands
in the South of Ireland from September 2007 to August 2009. The instantaneous N2O flux values ranged from -186 to 885.6 μg N2O-N m−2 h−1 and the annual sum ranged from 2 ± 3.51 to 12.55 ± 2.83 kg N2O-N ha−1 y−1 for managed sites. The emission factor ranged from 1.3 to 3.4%. The overall EF of 1.81% is about 69% higher than the Intergovernmental
Panel on Climate Change (IPCC) default EF value of 1.25% which is currently used by the Irish Environmental Protection Agency
(EPA) to estimate N2O emission in Ireland. At an N applied of approximately 300 kg ha−1 y−1, the N2O emissions are approximately 5.0 kg N2O-N ha−1 y−1, whereas the N2O emissions double to approximately 10 kg N ha−1 for an N applied of 400 kg N ha−1 y−1. The sites with higher fluxes were associated with intensive N-input and frequent cattle grazing. The N2O flux at 17°C was five times greater than that at 5°C. Similarly, the N2O emissions increased with increasing water filled pore space (WFPS) with maximum N2O emissions occurring at 60–80% WFPS. We conclude that N application below 300 kg ha−1 y−1 and restricted grazing on seasonally wet soils will reduce N2O emissions. 相似文献
12.
Nitrogen removal in a wastewater treatment plant through biofilters: nitrous oxide emissions during nitrification and denitrification 总被引:1,自引:0,他引:1
In order to estimate N2O emissions from immersed biofilters during nitrogen removal in tertiary treatments at urban wastewater treatment plants (WWTPs), a fixed culture from the WWTP of “Seine Centre” (Paris conurbation) was subjected to lab-scale batch experiments under various conditions of oxygenation and a gradient of methanol addition. The results show that during nitrification, N2O emissions are positively related to oxygenation (R
2 = 0.99). However, compared to the rates of ammonium oxidation, the percentage of emitted N2O is greater when oxygenation is low (0.5–1 mgO2 L−1), representing up to 1% of the oxidized ammonium (0.4% on average). During denitrification, the N2O emission reaches a significant peak when the quantity of methanol allows denitrification of between 66% and 88%. When methanol concentrations lead to a denitrification of close to 100%, the flows of N2O are much lower and represent on average 0.2% of the reduced nitrate. By considering these results, we can estimate, the emissions of N2O during nitrogen removal, at the “Seine Centre” WWTP, to approximately 38 kgN-N2O day−1. 相似文献
13.
Nitrous oxide (N2O) is a major greenhouse gas, heavily contributing to global warming. N2O is emitted from various sources such as wastewater treatment plants, during the nitrification and denitrification steps.
ASM models, which are commonly used in wastewater treatment, usually consider denitrification as a one-step process (NO3
− directly reduced to N2) and are as such unable to provide values for intermediate products of the reaction like N2O. In this study, a slightly modified ASM1 model was implemented in the GPS-X™ software to simulate the concentration of such
intermediate products (NO2
−, NO and N2O) and to estimate the amounts of gaseous N2O emitted by the denitrification stage (12 biofilters) of the Seine-Centre WWTP (SIAAP, Paris). Simulations running on a 1-year
period have shown good agreements with measured effluent data for nitrate and nitrite. The calculated mean value for emitted
N2O is 4.95 kgN–N2O/day, which stands in the typical range of estimated experimental values of 4–31 kgN–N2O/day. Nitrous oxide emissions are usually not measured on WWTPs and so, as obtained results show, there is a certain potential
for using models that quantify those emissions using traditionally measured influent data. 相似文献
14.
Effects of Elevated Atmospheric CO2 Concentrations on CH4 and N2O Emission from Rice Soil: An Experiment in Controlled-environment Chambers 总被引:1,自引:0,他引:1
The effects of elevated concentrations of atmospheric CO2 on CH4 and N2O emissions from rice soil were investigated in controlled-environment chambers using rice plants growing in pots. Elevated
CO2 significantly increased CH4 emission by 58% compared with ambient CO2. The CH4 emitted by plant-mediated transport and ebullition–diffusion accounted for 86.7 and 13.3% of total emissions during the flooding
period under ambient level, respectively; and for 88.1 and 11.9% of total emissions during the flooding period under elevated
CO2 level, respectively. No CH4 was emitted from plant-free pots, suggesting that the main source of emitted CH4 was root exudates or autolysis products. Most N2O was emitted during the first 3 weeks after flooding and rice transplanting, probably through denitrification of NO3− contained in the experimental soil, and was not affected by the CO2 concentration. Pre-harvest drainage suppressed CH4 emission but did not cause much N2O emission (< 10 μg N m−2 h−1) from the rice-plant pots at both CO2 concentrations. 相似文献
15.
Jirko Holst Chunyan Liu Nicolas Brüggemann Klaus Butterbach-Bahl Xunhua Zheng Yuesi Wang Shenghui Han Zhisheng Yao Jin Yue Xingguo Han 《Ecosystems》2007,10(4):623-634
Gross rates of N mineralization and nitrification, and soil–atmosphere fluxes of N2O, NO and NO2 were measured at differently grazed and ungrazed steppe grassland sites in the Xilin river catchment, Inner Mongolia, P. R.
China, during the 2004 and 2005 growing season. The experimental sites were a plot ungrazed since 1979 (UG79), a plot ungrazed
since 1999 (UG99), a plot moderately grazed in winter (WG), and an overgrazed plot (OG), all in close vicinity to each other.
Gross rates of N mineralization and nitrification determined at in situ soil moisture and soil temperature conditions were
in a range of 0.5–4.1 mg N kg−1 soil dry weight day−1. In 2005, gross N turnover rates were significantly higher at the UG79 plot than at the UG99 plot, which in turn had significantly
higher gross N turnover rates than the WG and OG plots. The WG and the OG plot were not significantly different in gross ammonification
and in gross nitrification rates. Site differences in SOC content, bulk density and texture could explain only less than 15%
of the observed site differences in gross N turnover rates. N2O and NO
x
flux rates were very low during both growing seasons. No significant differences in N trace gas fluxes were found between
plots. Mean values of N2O fluxes varied between 0.39 and 1.60 μg N2O-N m−2 h−1, equivalent to 0.03–0.14 kg N2O-N ha−1 y−1, and were considerably lower than previously reported for the same region. NO
x
flux rates ranged between 0.16 and 0.48 μg NO
x
-N m−2 h−1, equivalent to 0.01–0.04 kg NO
x
-N ha−1 y−1, respectively. N2O fluxes were significantly correlated with soil temperature and soil moisture. The correlations, however, explained only
less than 20% of the flux variance. 相似文献
16.
N2O emission from soil following combined application of fertiliser-N and ground weed residues 总被引:1,自引:0,他引:1
Emissions of N2O and CO2 were measured following combined applications of 15N-labelled fertiliser (100 μg N g−1; 10 atom % excess 15N) and organic olive crop weed residues (Avena sativa, Ononis viscosa, Ridolfia segetum and Olea europea; 100 μg N g−1) to a silt loam soil under controlled environment conditions. The objective was to determine the effect of varying combinations
of inorganic fertiliser and plant residues on these emissions and soil mineral N dynamics. Emissions were generally increased
following application of residues alone, with 23 ng N2O–N g−1 soil (2 ng N2O–N g−1 soil mg−1 biomass) and 389 μg CO2–C g−1 soil (39 μg CO2–C g−1 soil mg−1 biomass) emitted over 28 days after addition of the Ridolfia residues in the absence of fertiliser-N. N2O emissions from these residue-only treatments were strongly negatively correlated with residue lignin content (r = −0.91; P < 0.05), total carbon content (r = −0.90; P < 0.05) and (lignin + polyphenol)-to-N ratio (r = −0.70; P < 0.1). However, changes in the net input of these compounds through application of 25:75, 50:50 and 75:25 proportional mixtures
of Avena and Ononis residues had no effect on emissions compared to their single (0:100 or 100:0) applications. Addition of fertiliser-N increased
emissions (by up to 30 ng N2O–N g−1 28 days−1; 123%), particularly from the low residue-N treatments (Avena and Ridolfia) where a greater quantity of biomass was applied, resulting in emissions above that of the sum from the unfertilised residue
and fertilised control treatments. In contrast, fertiliser application had no impact on emissions from the Olea treatment with the highest polyphenol (2%) and lignin (11%) contents due to strong immobilisation of soil N, and the 15N–N2O data indicated that residue quality had no effect on the denitrification of applied fertiliser-N. Such apparent inconsistencies
mean that before the potential for manipulating N input (organic + inorganic) to lower gaseous N losses can be realised, first
the nature and extent of interactions between the different N sources and any interactions with other compounds released from
the residues need to be better understood. 相似文献
17.
Maria Ernfors Karin von Arnold Johan Stendahl Mats Olsson Leif Klemedtsson 《Biogeochemistry》2008,89(1):29-41
Total emissions of N2O from drained organic forest soils in Sweden were estimated using an equation linking the C:N ratio of the soil to N2O emissions. Information on soil C:N ratios was derived from a national database. It was estimated that the emissions from
Histosols amount to 2,820 tonnes N2O a−1. This is almost five times the value calculated for the same soils using the method suggested by the Intergovernmental Panel
on Climate Change: 580 tonnes N2O a−1. The higher value in the present study can mainly be explained by improved accuracy of estimates of N2O emissions from nutrient-rich soils, including former agricultural soils. In Sweden, in addition to 0.94 Mha of drained Histosols,
there are 0.55 Mha of other types of drained organic soils. The annual emissions from these soils were estimated to amount
to 1,890 tonnes of N2O. The total emission value calculated for drained organic forest soils was thus 4,700 tonnes N2O a−1, which, if added, would increase the current estimate of the Swedish anthropogenic N2O source strength by 18%. Of these emissions, 88% occur from sites with C:N ratios lower than 25. The exponential relationship
between C:N ratio and N2O emissions, in combination with a scarcity of data, resulted in large confidence intervals around the estimates. However,
by using the C:N ratio-based method, N2O emission estimates can be calculated from a variable that is readily available in databases. Also, the recent findings that
there are exceptionally large emissions of N2O from the most nitrogen-rich drained organic forest soils are taken into account.
This article has previously been published in 84/2 under doi: . 相似文献
18.
Maria Ernfors Karin von Arnold Johan Stendahl Mats Olsson Leif Klemedtsson 《Biogeochemistry》2007,84(2):219-231
Total emissions of N2O from drained organic forest soils in Sweden were estimated using an equation linking the C:N ratio of the soil to N2O emissions. Information on soil C:N ratios was derived from a national database. It was estimated that the emissions from
Histosols amount to 2,820 tonnes N2O a−1. This is almost five times the value calculated for the same soils using the method suggested by the Intergovernmental Panel
on Climate Change: 580 tonnes N2O a−1. The higher value in the present study can mainly be explained by improved accuracy of estimates of N2O emissions from nutrient-rich soils, including former agricultural soils. In Sweden, in addition to 0.94 Mha of drained Histosols,
there are 0.55 Mha of other types of drained organic soils. The annual emissions from these soils were estimated to amount
to 1,890 tonnes of N2O. The total emission value calculated for drained organic forest soils was thus 4,700 tonnes N2O a−1, which, if added, would increase the current estimate of the Swedish anthropogenic N2O source strength by 18%. Of these emissions, 88% occur from sites with C:N ratios lower than 25. The exponential relationship
between C:N ratio and N2O emissions, in combination with a scarcity of data, resulted in large confidence intervals around the estimates. However,
by using the C:N ratio-based method, N2O emission estimates can be calculated from a variable that is readily available in databases. Also, the recent findings that
there are exceptionally large emissions of N2O from the most nitrogen-rich drained organic forest soils are taken into account. 相似文献
19.
Katja Pörtl Sophie Zechmeister-Boltenstern Wolfgang Wanek Per Ambus Torsten W. Berger 《Plant and Soil》2007,295(1-2):79-94
Natural 15N abundance measurements of ecosystem nitrogen (N) pools and 15N pool dilution assays of gross N transformation rates were applied to investigate the potential of δ15N signatures of soil N pools to reflect the dynamics in the forest soil N cycle. Intact soil cores were collected from pure
spruce (Picea abies (L.) Karst.) and mixed spruce-beech (Fagus sylvatica L.) stands on stagnic gleysol in Austria. Soil δ15N values of both forest sites increased with depth to 50 cm, but then decreased below this zone. δ15N values of microbial biomass (mixed stand: 4.7 ± 0.8‰, spruce stand: 5.9 ± 0.9‰) and of dissolved organic N (DON; mixed stand:
5.3 ± 1.7‰, spruce stand: 2.6 ± 3.3‰) were not significantly different; these pools were most enriched in 15N of all soil N pools. Denitrification represented the main N2O-producing process in the mixed forest stand as we detected a significant 15N enrichment of its substrate NO3− (3.6 ± 4.5‰) compared to NH4+ (−4.6 ± 2.6‰) and its product N2O (−11.8 ± 3.2‰). In a 15N-labelling experiment in the spruce stand, nitrification contributed more to N2O production than denitrification. Moreover, in natural abundance measurements the NH4+ pool was slightly 15N-enriched (−0.4 ± 2.0 ‰) compared to NO3− (−3.0 ± 0.6 ‰) and N2O (−2.1 ± 1.1 ‰) in the spruce stand, indicating nitrification and denitrification operated in parallel to produce N2O. The more positive δ15N values of N2O in the spruce stand than in the mixed stand point to extensive microbial N2O reduction in the spruce stand. Combining natural 15N abundance and 15N tracer experiments provided a more complete picture of soil N dynamics than possible with either measurement done separately. 相似文献
20.
Greenhouse Gas Budget of a Cool-Temperate Deciduous Broad-Leaved Forest in Japan Estimated Using a Process-Based Model 总被引:1,自引:0,他引:1
A terrestrial ecosystem model, called the Vegetation Integrative Simulator for Trace gases model (VISIT), which fully integrates
biogeochemical carbon and nitrogen cycles, was developed to simulate atmosphere–ecosystem exchanges of greenhouse gases (CO2, CH4, and N2O), and to determine the global warming potential (GWP) taking into account the radiative forcing effect of each gas. The
model was then applied to a cool-temperate deciduous broad-leaved forest in Takayama, central Japan (36°08′N, 137°25′E, 1420 m
above sea level). Simulations were conducted at a daily time step from 1948 to 2008, using time-series meteorological and
nitrogen deposition data. VISIT accurately captured the carbon and nitrogen cycles of this typical Japanese forest, as validated
by tower and chamber flux measurements. During the last 10 years of the simulation, the model estimated that the forest was
a net greenhouse gas sink, having a GWP equivalent of 1025.7 g CO2 m−2 y−1, most of which (1016.9 g CO2 m−2 y−1) was accounted for by net CO2 sequestration into forest biomass regrowth. CH4 oxidation by the forest soil made a small contribution to the net sink (11.9 g CO2-eq. m−2 y−1), whereas N2O emissions were a very small source (3.2 g CO2-eq. m−2 y−1), as expected for a volcanic soil in a humid climate. Analysis of the sensitivity of GWP to changes in temperature, precipitation,
and nitrogen deposition indicated that warming temperatures would decrease the size of the sink, mainly as a result of increased
CO2 release due to increased ecosystem respiration. 相似文献