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1.
Impacts of climate and land use on N2O and CH4 fluxes from tropical ecosystems in the Mt. Kilimanjaro region,Tanzania
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Adrian Gütlein Friederike Gerschlauer Imani Kikoti Ralf Kiese 《Global Change Biology》2018,24(3):1239-1255
In this study, we quantify the impacts of climate and land use on soil N2O and CH4 fluxes from tropical forest, agroforest, arable and savanna ecosystems in Africa. To do so, we measured greenhouse gases (GHG) fluxes from 12 different ecosystems along climate and land‐use gradients at Mt. Kilimanjaro, combining long‐term in situ chamber and laboratory soil core incubation techniques. Both methods showed similar patterns of GHG exchange. Although there were distinct differences from ecosystem to ecosystem, soils generally functioned as net sources and sinks for N2O and CH4 respectively. N2O emissions correlated positively with soil moisture and total soil nitrogen content. CH4 uptake rates correlated negatively with soil moisture and clay content and positively with SOC. Due to moderate soil moisture contents and the dominance of nitrification in soil N turnover, N2O emissions of tropical montane forests were generally low (<1.2 kg N ha?1 year?1), and it is likely that ecosystem N losses are driven instead by nitrate leaching (~10 kg N ha?1 year?1). Forest soils with well‐aerated litter layers were a significant sink for atmospheric CH4 (up to 4 kg C ha?1 year?1) regardless of low mean annual temperatures at higher elevations. Land‐use intensification significantly increased the soil N2O source strength and significantly decreased the soil CH4 sink. Compared to decreases in aboveground and belowground carbon stocks enhanced soil non‐CO2 GHG emissions following land‐use conversion from tropical forests to homegardens and coffee plantations were only a small factor in the total GHG budget. However, due to lower ecosystem carbon stock changes, enhanced N2O emissions significantly contributed to total GHG emissions following conversion of savanna into grassland and particularly maize. Overall, we found that the protection and sustainable management of aboveground and belowground carbon and nitrogen stocks of agroforestry and arable systems is most crucial for mitigating GHG emissions from land‐use change. 相似文献
2.
WEIJIN WANG RAM C. DALAL STEVEN H. REEVES KLAUS BUTTERBACH‐BAHL RALF KIESE 《Global Change Biology》2011,17(10):3089-3101
The long‐term effects of conservation management practices on greenhouse gas fluxes from tropical/subtropical croplands remain to be uncertain. Using both manual and automatic sampling chambers, we measured N2O and CH4 fluxes at a long‐term experimental site (1968–present) in Queensland, Australia from 2006 to 2009. Annual net greenhouse gas fluxes (NGGF) were calculated from the 3‐year mean N2O and CH4 fluxes and the long‐term soil organic carbon changes. N2O emissions exhibited clear daily, seasonal and interannual variations, highlighting the importance of whole‐year measurement over multiple years for obtaining temporally representative annual emissions. Averaged over 3 years, annual N2O emissions from the unfertilized and fertilized soils (90 kg N ha?1 yr?1 as urea) amounted to 138 and 902 g N ha?1, respectively. The average annual N2O emissions from the fertilized soil were 388 g N ha?1 lower under no‐till (NT) than under conventional tillage (CT) and 259 g N ha?1 higher under stubble retention (SR) than under stubble burning (SB). Annual N2O emissions from the unfertilized soil were similar between the contrasting tillage and stubble management practices. The average emission factors of fertilizer N were 0.91%, 1.20%, 0.52% and 0.77% for the CT‐SB, CT‐SR, NT‐SB and NT‐SR treatments, respectively. Annual CH4 fluxes from the soil were very small (?200–300 g CH4 ha?1 yr?1) with no significant difference between treatments. The NGGF were 277–350 kg CO2‐e ha?1 yr?1 for the unfertilized treatments and 401–710 kg CO2‐e ha?1 yr?1 for the fertilized treatments. Among the fertilized treatments, N2O emissions accounted for 52–97% of NGGF and NT‐SR resulted in the lowest NGGF (401 kg CO2‐e ha?1 yr?1 or 140 kg CO2‐e t?1 grain). Therefore, NT‐SR with improved N fertilizer management practices was considered the most promising management regime for simultaneously achieving maximal yield and minimal NGGF. 相似文献
3.
LOUISE BARTON DANIEL V. MURPHY RALF KIESE† KLAUS BUTTERBACH-BAHL† 《Global Change Biology Bioenergy》2010,2(1):1-15
Understanding nitrous oxide (N2O) and methane (CH4) fluxes from agricultural soils in semi‐arid climates is necessary to fully assess greenhouse gas emissions from bioenergy cropping systems, and to improve our knowledge of global terrestrial gaseous exchange. Canola is grown globally as a feedstock for biodiesel production, however, resulting soil greenhouse gas fluxes are rarely reported for semi‐arid climates. We measured soil N2O and CH4 fluxes from a rain‐fed canola crop in a semi‐arid region of south‐western Australia for 1 year on a subdaily basis. The site included N fertilized (75 kg N ha?1 yr?1) and nonfertilized plots. Daily N2O fluxes were low (?1.5 to 4.7 g N2O‐N ha?1 day?1) and culminated in an annual loss of 128 g N2O‐N ha?1 (standard error, 12 g N2O‐N ha?1) from N fertilized soil and 80 g N2O‐N ha?1 (standard error, 11 g N2O‐N ha?1) from nonfertilized soil. Daily CH4 fluxes were also low (?10.3 to 11.9 g CH4‐C ha?1 day?1), and did not differ with treatments, with an average annual net emission of 6.7 g CH4–C ha?1 (standard error, 20 g CH4–C ha?1). Greatest daily N2O fluxes occurred when the soil was fallow, and following a series of summer rainfall events. Summer rainfall increased soil water contents and available N, and occurred when soil temperatures were >25 °C, and when there was no active plant growth to compete with soil microorganisms for mineralized N; conditions known to promote N2O production. The proportion of N fertilizer emitted as N2O, after correction for emissions from the no N fertilizer treatment, was 0.06%; 17 times lower than IPCC default value for the application of synthetic N fertilizers to land (1.0%). Soil greenhouse gas fluxes from bioenergy crop production in semi‐arid regions are likely to have less influence on the net global warming potential of biofuel production than in temperate climates. 相似文献
4.
High retention of 15N‐labeled nitrogen deposition in a nitrogen saturated old‐growth tropical forest
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Geshere Abdisa Gurmesa Xiankai Lu Per Gundersen Qinggong Mao Kaijun Zhou Yunting Fang Jiangming Mo 《Global Change Biology》2016,22(11):3608-3620
The effects of increased reactive nitrogen (N) deposition in forests depend largely on its fate in the ecosystems. However, our knowledge on the fates of deposited N in tropical forest ecosystems and its retention mechanisms is limited. Here, we report the results from the first whole ecosystem 15N labeling experiment performed in a N‐rich old‐growth tropical forest in southern China. We added 15N tracer monthly as 15NH415NO3 for 1 year to control plots and to N‐fertilized plots (N‐plots, receiving additions of 50 kg N ha?1 yr?1 for 10 years). Tracer recoveries in major ecosystem compartments were quantified 4 months after the last addition. Tracer recoveries in soil solution were monitored monthly to quantify leaching losses. Total tracer recovery in plant and soil (N retention) in the control plots was 72% and similar to those observed in temperate forests. The retention decreased to 52% in the N‐plots. Soil was the dominant sink, retaining 37% and 28% of the labeled N input in the control and N‐plots, respectively. Leaching below 20 cm was 50 kg N ha?1 yr?1 in the control plots and was close to the N input (51 kg N ha?1 yr?1), indicating N saturation of the top soil. Nitrogen addition increased N leaching to 73 kg N ha?1 yr?1. However, of these only 7 and 23 kg N ha?1 yr?1 in the control and N‐plots, respectively, originated from the labeled N input. Our findings indicate that deposited N, like in temperate forests, is largely incorporated into plant and soil pools in the short term, although the forest is N‐saturated, but high cycling rates may later release the N for leaching and/or gaseous loss. Thus, N cycling rates rather than short‐term N retention represent the main difference between temperate forests and the studied tropical forest. 相似文献
5.
The temporal variations in CO2, CH4 and N2O fluxes were measured over two consecutive years from February 2007 to March 2009 from a subtropical rainforest in south‐eastern Queensland, Australia, using an automated sampling system. A concurrent study using an additional 30 manual chambers examined the spatial variability of emissions distributed across three nearby remnant rainforest sites with similar vegetation and climatic conditions. Interannual variation in fluxes of all gases over the 2 years was minimal, despite large discrepancies in rainfall, whereas a pronounced seasonal variation could only be observed for CO2 fluxes. High infiltration, drainage and subsequent high soil aeration under the rainforest limited N2O loss while promoting substantial CH4 uptake. The average annual N2O loss of 0.5 ± 0.1 kg N2O‐N ha?1 over the 2‐year measurement period was at the lower end of reported fluxes from rainforest soils. The rainforest soil functioned as a sink for atmospheric CH4 throughout the entire 2‐year period, despite periods of substantial rainfall. A clear linear correlation between soil moisture and CH4 uptake was found. Rates of uptake ranged from greater than 15 g CH4‐C ha?1 day?1 during extended dry periods to less than 2–5 g CH4‐C ha?1 day?1 when soil water content was high. The calculated annual CH4 uptake at the site was 3.65 kg CH4‐C ha?1 yr?1. This is amongst the highest reported for rainforest systems, reiterating the ability of aerated subtropical rainforests to act as substantial sinks of CH4. The spatial study showed N2O fluxes almost eight times higher, and CH4 uptake reduced by over one‐third, as clay content of the rainforest soil increased from 12% to more than 23%. This demonstrates that for some rainforest ecosystems, soil texture and related water infiltration and drainage capacity constraints may play a more important role in controlling fluxes than either vegetation or seasonal variability. 相似文献
6.
Katja Walter Axel Don Roland Fuß Jürgen Kern Julia Drewer Heinz Flessa 《Global Change Biology Bioenergy》2015,7(6):1260-1271
Oilseed rape is one of the leading feedstocks for biofuel production in Europe. The climate change mitigation effect of rape methyl ester (RME) is particularly challenged by the greenhouse gas (GHG) emissions during crop production, mainly as nitrous oxide (N2O) from soils. Oilseed rape requires high nitrogen fertilization and crop residues are rich in nitrogen, both potentially causing enhanced N2O emissions. However, GHG emissions of oilseed rape production are often estimated using emission factors that account for crop‐type specifics only with respect to crop residues. This meta‐analysis therefore aimed to assess annual N2O emissions from winter oilseed rape, to compare them to those of cereals and to explore the underlying reasons for differences. For the identification of the most important factors, linear mixed effects models were fitted with 43 N2O emission data points deriving from 12 different field sites. N2O emissions increased exponentially with N‐fertilization rates, but interyear and site‐specific variability were high and climate variables or soil parameters did not improve the prediction model. Annual N2O emissions from winter oilseed rape were 22% higher than those from winter cereals fertilized at the same rate. At a common fertilization rate of 200 kg N ha?1 yr?1, the mean fraction of fertilizer N that was lost as N2O‐N was 1.27% for oilseed rape compared to 1.04% for cereals. The risk of high yield‐scaled N2O emissions increased after a critical N surplus of about 80 kg N ha?1 yr?1. The difference in N2O emissions between oilseed rape and cereal cultivation was especially high after harvest due to the high N contents in oilseed rape's crop residues. However, annual N2O emissions of winter oilseed rape were still lower than predicted by the Stehfest and Bouwman model. Hence, the assignment of oilseed rape to the crop‐type classes of cereals or other crops should be reconsidered. 相似文献
7.
Long‐term impacts of manure amendments on carbon and greenhouse gas dynamics of rangelands
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Livestock manure is applied to rangelands as an organic fertilizer to stimulate forage production, but the long‐term impacts of this practice on soil carbon (C) and greenhouse gas (GHG) dynamics are poorly known. We collected soil samples from manured and nonmanured fields on commercial dairies and found that manure amendments increased soil C stocks by 19.0 ± 7.3 Mg C ha?1 and N stocks by 1.94 ± 0.63 Mg N ha?1 compared to nonmanured fields (0–20 cm depth). Long‐term historical (1700–present) and future (present–2100) impacts of management on soil C and N dynamics, net primary productivity (NPP), and GHG emissions were modeled with DayCent. Modeled total soil C and N stocks increased with the onset of dairying. Nitrous oxide (N2O) emissions also increased by ~2 kg N2O‐N ha?1 yr?1. These emissions were proportional to total N additions and offset 75–100% of soil C sequestration. All fields were small net methane (CH4) sinks, averaging ?4.7 ± 1.2 kg CH4‐C ha?1 yr?1. Overall, manured fields were net GHG sinks between 1954 and 2011 (?0.74 ± 0.73 Mg CO2 e ha?1 yr?1, CO2e are carbon dioxide equivalents), whereas nonmanured fields varied around zero. Future soil C pools stabilized 40–60 years faster in manured fields than nonmanured fields, at which point manured fields were significantly larger sources than nonmanured fields (1.45 ± 0.52 Mg CO2e ha?1 yr?1 and 0.51 ± 0.60 Mg CO2e ha?1 yr?1, respectively). Modeling also revealed a large background loss of soil C from the passive soil pool associated with the shift from perennial to annual grasses, equivalent to 29.4 ± 1.47 Tg CO2e in California between 1820 and 2011. Manure applications increased NPP and soil C storage, but plant community changes and GHG emissions decreased, and eventually eliminated, the net climate benefit of this practice. 相似文献
8.
Impacts of natural factors and farming practices on greenhouse gas emissions in the North China Plain: A meta‐analysis
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Requirements for mitigation of the continued increase in greenhouse gas (GHG ) emissions are much needed for the North China Plain (NCP ). We conducted a meta‐analysis of 76 published studies of 24 sites in the NCP to examine the effects of natural conditions and farming practices on GHG emissions in that region. We found that N2O was the main component of the area‐scaled total GHG balance, and the CH 4 contribution was <5%. Precipitation, temperature, soil pH , and texture had no significant impacts on annual GHG emissions, because of limited variation of these factors in the NCP . The N2O emissions increased exponentially with mineral fertilizer N application rate, with y = 0.2389e0.0058x for wheat season and y = 0.365e0.0071x for maize season. Emission factors were estimated at 0.37% for wheat and 0.90% for maize at conventional fertilizer N application rates. The agronomic optimal N rates (241 and 185 kg N ha?1 for wheat and maize, respectively) exhibited great potential for reducing N2O emissions, by 0.39 (29%) and 1.71 (56%) kg N2O‐N ha?1 season?1 for the wheat and maize seasons, respectively. Mixed application of organic manure with reduced mineral fertilizer N could reduce annual N2O emissions by 16% relative to mineral N application alone while maintaining a high crop yield. Compared with conventional tillage, no‐tillage significantly reduced N2O emissions by ~30% in the wheat season, whereas it increased those emissions by ~10% in the maize season. This may have resulted from the lower soil temperature in winter and increased soil moisture in summer under no‐tillage practice. Straw incorporation significantly increased annual N2O emissions, by 26% relative to straw removal. Our analysis indicates that these farming practices could be further tested to mitigate GHG emission and maintain high crop yields in the NCP . 相似文献
9.
Kimberly H. Brown Elizabeth M. Bach Rhae A. Drijber Kirsten S. Hofmockel Elizabeth S. Jeske John E. Sawyer Michael J. Castellano 《Global Change Biology》2014,20(4):1339-1350
Global maize production alters an enormous soil organic C (SOC) stock, ultimately affecting greenhouse gas concentrations and the capacity of agroecosystems to buffer climate variability. Inorganic N fertilizer is perhaps the most important factor affecting SOC within maize‐based systems due to its effects on crop residue production and SOC mineralization. Using a continuous maize cropping system with a 13 year N fertilizer gradient (0–269 kg N ha?1 yr?1) that created a large range in crop residue inputs (3.60–9.94 Mg dry matter ha?1 yr?1), we provide the first agronomic assessment of long‐term N fertilizer effects on SOC with direct reference to N rates that are empirically determined to be insufficient, optimum, and excessive. Across the N fertilizer gradient, SOC in physico‐chemically protected pools was not affected by N fertilizer rate or residue inputs. However, unprotected particulate organic matter (POM) fractions increased with residue inputs. Although N fertilizer was negatively linearly correlated with POM C/N ratios, the slope of this relationship decreased from the least decomposed POM pools (coarse POM) to the most decomposed POM pools (fine intra‐aggregate POM). Moreover, C/N ratios of protected pools did not vary across N rates, suggesting little effect of N fertilizer on soil organic matter (SOM) after decomposition of POM. Comparing a N rate within 4% of agronomic optimum (208 kg N ha?1 yr?1) and an excessive N rate (269 kg N ha?1 yr?1), there were no differences between SOC amount, SOM C/N ratios, or microbial biomass and composition. These data suggest that excessive N fertilizer had little effect on SOM and they complement agronomic assessments of environmental N losses, that demonstrate N2O and NO3 emissions exponentially increase when agronomic optimum N is surpassed. 相似文献
10.
Long‐term nitrous oxide fluxes in annual and perennial agricultural and unmanaged ecosystems in the upper Midwest USA
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Ilya Gelfand Iurii Shcherbak Neville Millar Alexandra N. Kravchenko G. Philip Robertson 《Global Change Biology》2016,22(11):3594-3607
Differences in soil nitrous oxide (N2O) fluxes among ecosystems are often difficult to evaluate and predict due to high spatial and temporal variabilities and few direct experimental comparisons. For 20 years, we measured N2O fluxes in 11 ecosystems in southwest Michigan USA: four annual grain crops (corn–soybean–wheat rotations) managed with conventional, no‐till, reduced input, or biologically based/organic inputs; three perennial crops (alfalfa, poplar, and conifers); and four unmanaged ecosystems of different successional age including mature forest. Average N2O emissions were higher from annual grain and N‐fixing cropping systems than from nonleguminous perennial cropping systems and were low across unmanaged ecosystems. Among annual cropping systems full‐rotation fluxes were indistinguishable from one another but rotation phase mattered. For example, those systems with cover crops and reduced fertilizer N emitted more N2O during the corn and soybean phases, but during the wheat phase fluxes were ~40% lower. Likewise, no‐till did not differ from conventional tillage over the entire rotation but reduced emissions ~20% in the wheat phase and increased emissions 30–80% in the corn and soybean phases. Greenhouse gas intensity for the annual crops (flux per unit yield) was lowest for soybeans produced under conventional management, while for the 11 other crop × management combinations intensities were similar to one another. Among the fertilized systems, emissions ranged from 0.30 to 1.33 kg N2O‐N ha?1 yr?1 and were best predicted by IPCC Tier 1 and ΔEF emission factor approaches. Annual cumulative fluxes from perennial systems were best explained by soil pools (r2 = 0.72) but not so for annual crops, where management differences overrode simple correlations. Daily soil N2O emissions were poorly predicted by any measured variables. Overall, long‐term measurements reveal lower fluxes in nonlegume perennial vegetation and, for conservatively fertilized annual crops, the overriding influence of rotation phase on annual fluxes. 相似文献
11.
Lucy J. Sheppard Ian D. Leith Toshie Mizunuma John Neil Cape Alan Crossley Sarah Leeson Mark A. Sutton Netty van Dijk David Fowler 《Global Change Biology》2011,17(12):3589-3607
Although the effects of atmospheric nitrogen deposition on species composition are relatively well known, the roles of the different forms of nitrogen, in particular gaseous ammonia (NH3), have not been tested in the field. Since 2002, we have manipulated the form of N deposition to an ombrotrophic bog, Whim, on deep peat in southern Scotland, with low ambient N (wet + dry = 8 kg N ha?1 yr?1) and S (4 kg S ha?1 yr?1) deposition. A gradient of ammonia (NH3, dry N), from 70 kg N ha?1 yr?1 down to background, 3–4 kg N ha?1 yr?1 was generated by free air release. Wet ammonium (NH4+, wet N) was provided to replicate plots in a fine rainwater spray (NH4Cl at +8, +24, +56 kg N ha?1 yr?1). Automated treatments are coupled to meteorological conditions, in a globally unique, field experiment. Ammonia concentrations were converted to NH3‐N deposition (kg N ha?1) using a site/vegetation specific parameterization. Within 3 years, exposure to relatively modest deposition of NH3, 20–56 kg NH3‐N ha?1 yr?1 led to dramatic reductions in species cover, with almost total loss of Calluna vulgaris, Sphagnum capillifolium and Cladonia portentosa. These effects appear to result from direct foliar uptake and interaction with abiotic and biotic stresses, rather than via effects on the soil. Additional wet N by contrast, significantly increased Calluna cover after 5 years at the 56 kg N dose, but reduced cover of Sphagnum and Cladonia. Cover reductions caused by wet N were significantly different from and much smaller than those caused by equivalent dry N doses. The effects of gaseous NH3 described here, highlight the potential for ammonia to destroy acid heathland and peat bog ecosystems. Separating the effects of gaseous ammonia and wet ammonium deposition, for a peat bog, has significant implications for regulatory bodies and conservation agencies. 相似文献
12.
Effects of seasonality,transport pathway,and spatial structure on greenhouse gas fluxes in a restored wetland
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Gavin McNicol Cove S. Sturtevant Sara H. Knox Iryna Dronova Dennis D. Baldocchi Whendee L. Silver 《Global Change Biology》2017,23(7):2768-2782
Wetlands can influence global climate via greenhouse gas (GHG) exchange of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Few studies have quantified the full GHG budget of wetlands due to the high spatial and temporal variability of fluxes. We report annual open‐water diffusion and ebullition fluxes of CO2, CH4, and N2O from a restored emergent marsh ecosystem. We combined these data with concurrent eddy‐covariance measurements of whole‐ecosystem CO2 and CH4 exchange to estimate GHG fluxes and associated radiative forcing effects for the whole wetland, and separately for open‐water and vegetated cover types. Annual open‐water CO2, CH4, and N2O emissions were 915 ± 95 g C‐CO2 m?2 yr?1, 2.9 ± 0.5 g C‐CH4 m?2 yr?1, and 62 ± 17 mg N‐N2O m?2 yr?1, respectively. Diffusion dominated open‐water GHG transport, accounting for >99% of CO2 and N2O emissions, and ~71% of CH4 emissions. Seasonality was minor for CO2 emissions, whereas CH4 and N2O fluxes displayed strong and asynchronous seasonal dynamics. Notably, the overall radiative forcing of open‐water fluxes (3.5 ± 0.3 kg CO2‐eq m?2 yr?1) exceeded that of vegetated zones (1.4 ± 0.4 kg CO2‐eq m?2 yr?1) due to high ecosystem respiration. After scaling results to the entire wetland using object‐based cover classification of remote sensing imagery, net uptake of CO2 (?1.4 ± 0.6 kt CO2‐eq yr?1) did not offset CH4 emission (3.7 ± 0.03 kt CO2‐eq yr?1), producing an overall positive radiative forcing effect of 2.4 ± 0.3 kt CO2‐eq yr?1. These results demonstrate clear effects of seasonality, spatial structure, and transport pathway on the magnitude and composition of wetland GHG emissions, and the efficacy of multiscale flux measurement to overcome challenges of wetland heterogeneity. 相似文献
13.
Are the benefits of yield responses to nitrogen fertilizer application in the bioenergy crop Miscanthus × giganteus offset by increased soil emissions of nitrous oxide?
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Brendan Roth John M. Finnan Mike B. Jones James I. Burke Michael L. Williams 《Global Change Biology Bioenergy》2015,7(1):145-152
A field trial was carried out on a 15 year old Miscanthus stand, subject to nitrogen fertilizer treatments of 0, 63 and 125 kg‐N ha?1, measuring N2O emissions, as well as annual crop yield over a full year. N2O emission intensity (N2O emissions calculated as a function of above‐ground biomass) was significantly affected by fertilizer application, with values of 52.2 and 59.4 g N2O‐N t?1 observed at 63 and 125 kg‐N ha?1, respectively, compared to 31.3 g N2O‐N t?1 in the zero fertilizer control. A life cycle analyses approach was applied to calculate the increase in yield required to offset N2O emissions from Miscanthus through fossil fuel substitution in the fuel chain. For the conditions observed during the field trial yield increases of 0.33 and 0.39 t ha?1 were found to be required to offset N2O emissions from the 63 kg‐N ha?1 treatment, when replacing peat and coal, respectively, while increases of 0.71 and 0.83 t ha?1 were required for the 125 kg‐N ha?1 treatment, for each fuel. These values are considerably less than the mean above‐ground biomass yield increases observed here of 1.57 and 2.79 t ha?1 at fertilization rates 63 and 125 kg‐N ha?1 respectively. Extending this analysis to include a range of fertilizer application rates and N2O emission factors found increases in yield necessary to offset soil N2O emissions ranging from 0.26 to 2.54 t ha?1. These relatively low yield increase requirements indicate that where nitrogen fertilizer application improves yield, the benefits of such a response will not be offset by soil N2O emissions. 相似文献
14.
Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh
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Rose M. Martin Cathleen Wigand Elizabeth Elmstrom Javier Lloret Ivan Valiela 《Ecology and evolution》2018,8(10):4958-4966
Salt marshes may act either as greenhouse gas (GHG) sources or sinks depending on hydrological conditions, vegetation communities, and nutrient availability. In recent decades, eutrophication has emerged as a major driver of change in salt marsh ecosystems. An ongoing fertilization experiment at the Great Sippewissett Marsh (Cape Cod, USA) allows for observation of the results of over four decades of nutrient addition. Here, nutrient enrichment stimulated changes to vegetation communities that, over time, have resulted in increased elevation of the marsh platform. In this study, we measured fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in dominant vegetation zones along elevation gradients of chronically fertilized (1,572 kg N ha?1 year?1) and unfertilized (12 kg N ha?1 year?1) experimental plots at Great Sippewissett Marsh. Flux measurements were performed using darkened chambers to focus on community respiration and excluded photosynthetic CO2 uptake. We hypothesized that N‐replete conditions in fertilized plots would result in larger N2O emissions relative to control plots and that higher elevations caused by nutrient enrichment would support increased CO2 and N2O and decreased CH4 emissions due to the potential for more oxygen diffusion into sediment. Patterns of GHG emission supported our hypotheses. Fertilized plots were substantially larger sources of N2O and had higher community respiration rates relative to control plots, due to large emissions of these GHGs at higher elevations. While CH4 emissions displayed a negative relationship with elevation, they were generally small across elevation gradients and nutrient enrichment treatments. Our results demonstrate that at decadal scales, vegetation community shifts and associated elevation changes driven by chronic eutrophication affect GHG emission from salt marshes. Results demonstrate the necessity of long‐term fertilization experiments to understand impacts of eutrophication on ecosystem function and have implications for how chronic eutrophication may impact the role that salt marshes play in sequestering C and N. 相似文献
15.
Shuang Wu Cheng Ji Yi Sun Yaguo Jin Shuqing Li Zhaofu Li Jianwen Zou 《Global Change Biology》2017,23(6):2520-2532
Soils are among the important sources of atmospheric nitric oxide (NO) and nitrous oxide (N2O), acting as a critical role in atmospheric chemistry. Updated data derived from 114 peer‐reviewed publications with 520 field measurements were synthesized using meta‐analysis procedure to examine the N fertilizer‐induced soil NO and the combined NO+N2O emissions across global soils. Besides factors identified in earlier reviews, additional factors responsible for NO fluxes were fertilizer type, soil C/N ratio, crop residue incorporation, tillage, atmospheric carbon dioxide concentration, drought and biomass burning. When averaged across all measurements, soil NO‐N fluxes were estimated to be 4.06 kg ha?1 yr?1, with the greatest (9.75 kg ha?1 yr?1) in vegetable croplands and the lowest (0.11 kg ha?1 yr?1) in rice paddies. Soil NO emissions were more enhanced by synthetic N fertilizer (+38%), relative to organic (+20%) or mixed N (+18%) sources. Compared with synthetic N fertilizer alone, synthetic N fertilizer combined with nitrification inhibitors substantially reduced soil NO emissions by 81%. The global mean direct emission factors of N fertilizer for NO (EFNO) and combined NO+N2O (EFc) were estimated to be 1.16% and 2.58%, with 95% confidence intervals of 0.71–1.61% and 1.81–3.35%, respectively. Forests had the greatest EFNO (2.39%). Within the croplands, the EFNO (1.71%) and EFc (4.13%) were the greatest in vegetable cropping fields. Among different chemical N fertilizer varieties, ammonium nitrate had the greatest EFNO (2.93%) and EFc (5.97%). Some options such as organic instead of synthetic N fertilizer, decreasing N fertilizer input rate, nitrification inhibitor and low irrigation frequency could be adopted to mitigate soil NO emissions. More field measurements over multiyears are highly needed to minimize the estimate uncertainties and mitigate soil NO emissions, particularly in forests and vegetable croplands. 相似文献
16.
LOUISE BARTON RALF KIESE† DAVID GATTER‡ KLAUS BUTTERBACH-BAHL† RENEE BUCK CHRISTOPH HINZ DANIEL V. MURPHY 《Global Change Biology》2008,14(1):177-192
Understanding nitrous oxide (N2O) emissions from agricultural soils in semi‐arid regions is required to better understand global terrestrial N2O losses. Nitrous oxide emissions were measured from a rain‐fed, cropped soil in a semi‐arid region of south‐western Australia for one year on a sub‐daily basis. The site included N‐fertilized (100 kg N ha?1 yr?1) and nonfertilized plots. Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (?1.8 to 7.3 g N2O‐N ha?1 day?1) and culminated in an annual loss of 0.11 kg N2O‐N ha?1 from N‐fertilized soil and 0.09 kg N2O‐N ha?1 from nonfertilized soil. Over half (55%) the annual N2O emission occurred from both N treatments when the soil was fallow, following a series of summer rainfall events. At this time of the year, conditions were conducive for soil microbial N2O production: elevated soil water content, available N, soil temperatures generally >25 °C and no active plant growth. The proportion of N fertilizer emitted as N2O in 1 year, after correction for the ‘background’ emission (no N fertilizer applied), was 0.02%. The emission factor reported in this study was 60 times lower than the IPCC default value for the application of synthetic fertilizers to land (1.25%), suggesting that the default may not be suitable for cropped soils in semi‐arid regions. Applying N fertilizer did not significantly increase the annual N2O emission, demonstrating that a proportion of N2O emitted from agricultural soils may not be directly derived from the application of N fertilizer. ‘Background’ emissions, resulting from other agricultural practices, need to be accounted for if we are to fully assess the impact of agriculture in semi‐arid regions on global terrestrial N2O emissions. 相似文献
17.
Bärbel Tiemeyer Elisa Albiac Borraz Jürgen Augustin Michel Bechtold Sascha Beetz Colja Beyer Matthias Drösler Martin Ebli Tim Eickenscheidt Sabine Fiedler Christoph Förster Annette Freibauer Michael Giebels Stephan Glatzel Jan Heinichen Mathias Hoffmann Heinrich Höper Gerald Jurasinski Katharina Leiber‐Sauheitl Mandy Peichl‐Brak Niko Roßkopf Michael Sommer Jutta Zeitz 《Global Change Biology》2016,22(12):4134-4149
Drainage has turned peatlands from a carbon sink into one of the world's largest greenhouse gas (GHG) sources from cultivated soils. We analyzed a unique data set (12 peatlands, 48 sites and 122 annual budgets) of mainly unpublished GHG emissions from grasslands on bog and fen peat as well as other soils rich in soil organic carbon (SOC) in Germany. Emissions and environmental variables were measured with identical methods. Site‐averaged GHG budgets were surprisingly variable (29.2 ± 17.4 t CO2‐eq. ha?1 yr?1) and partially higher than all published data and the IPCC default emission factors for GHG inventories. Generally, CO2 (27.7 ± 17.3 t CO2 ha?1 yr?1) dominated the GHG budget. Nitrous oxide (2.3 ± 2.4 kg N2O‐N ha?1 yr?1) and methane emissions (30.8 ± 69.8 kg CH4‐C ha?1 yr?1) were lower than expected except for CH4 emissions from nutrient‐poor acidic sites. At single peatlands, CO2 emissions clearly increased with deeper mean water table depth (WTD), but there was no general dependency of CO2 on WTD for the complete data set. Thus, regionalization of CO2 emissions by WTD only will remain uncertain. WTD dynamics explained some of the differences between peatlands as sites which became very dry during summer showed lower emissions. We introduced the aerated nitrogen stock (Nair) as a variable combining soil nitrogen stocks with WTD. CO2 increased with Nair across peatlands. Soils with comparatively low SOC concentrations showed as high CO2 emissions as true peat soils because Nair was similar. N2O emissions were controlled by the WTD dynamics and the nitrogen content of the topsoil. CH4 emissions can be well described by WTD and ponding duration during summer. Our results can help both to improve GHG emission reporting and to prioritize and plan emission reduction measures for peat and similar soils at different scales. 相似文献
18.
Janaina Braga do Carmo Solange Filoso Luciana C. Zotelli Eraclito R. de Sousa Neto Leonardo M. Pitombo Paulo J. Duarte‐Neto Vitor P. Vargas Cristiano A. Andrade Glauber J. C. Gava Raffaella Rossetto Heitor Cantarella André E. Neto Luiz A. Martinelli 《Global Change Biology Bioenergy》2013,5(3):267-280
Bioethanol from sugarcane is becoming an increasingly important alternative energy source worldwide as it is considered to be both economically and environmentally sustainable. Besides being produced from a tropical perennial grass with high photosynthetic efficiency, sugarcane ethanol is commonly associated with low N fertilizer use because sugarcane from Brazil, the world's largest sugarcane producer, has a low N demand. In recent years, several models have predicted that the use of sugarcane ethanol in replacement to fossil fuel could lead to high greenhouse gas (GHG) emission savings. However, empirical data that can be used to validate model predictions and estimates from indirect methodologies are scarce, especially with regard to emissions associated with different fertilization methods and agricultural management practices commonly used in sugarcane agriculture in Brazil. In this study, we provide in situ data on emissions of three GHG (CO2, N2O, and CH4) from sugarcane soils in Brazil and assess how they vary with fertilization methods and management practices. We measured emissions during the two main phases of the sugarcane crop cycle (plant and ratoon cane), which include different fertilization methods and field conditions. Our results show that N2O and CO2 emissions in plant cane varied significantly depending on the fertilization method and that waste products from ethanol production used as organic fertilizers with mineral fertilizer, as it is the common practice in Brazil, increase emission rates significantly. Cumulatively, the highest emissions were observed for ratoon cane treated with vinasse (liquid waste from ethanol production) especially as the amount of crop trash on the soil surface increased. Emissions of CO2 and N2O were 6.9 kg ha?1 yr?1 and 7.5 kg ha?1 yr?1, respectively, totaling about 3000 kg in CO2 equivalent ha?1 yr?1. 相似文献
19.
Nitrous oxide emissions during establishment of eight alternative cellulosic bioenergy cropping systems in the North Central United States
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Lawrence G. Oates David S. Duncan Ilya Gelfand Neville Millar G. Philip Robertson Randall D. Jackson 《Global Change Biology Bioenergy》2016,8(3):539-549
Greenhouse gas (GHG) emissions from soils are a key sustainability metric of cropping systems. During crop establishment, disruptive land‐use change is known to be a critical, but under reported period, for determining GHG emissions. We measured soil N2O emissions and potential environmental drivers of these fluxes from a three‐year establishment‐phase bioenergy cropping systems experiment replicated in southcentral Wisconsin (ARL) and southwestern Michigan (KBS). Cropping systems treatments were annual monocultures (continuous corn, corn–soybean–canola rotation), perennial monocultures (switchgrass, miscanthus, and poplar), and perennial polycultures (native grass mixture, early successional community, and restored prairie) all grown using best management practices specific to the system. Cumulative three‐year N2O emissions from annuals were 142% higher than from perennials, with fertilized perennials 190% higher than unfertilized perennials. Emissions ranged from 3.1 to 19.1 kg N2O‐N ha?1 yr?1 for the annuals with continuous corn > corn–soybean–canola rotation and 1.1 to 6.3 kg N2O‐N ha?1 yr?1 for perennials. Nitrous oxide peak fluxes typically were associated with precipitation events that closely followed fertilization. Bayesian modeling of N2O fluxes based on measured environmental factors explained 33% of variability across all systems. Models trained on single systems performed well in most monocultures (e.g., R2 = 0.52 for poplar) but notably worse in polycultures (e.g., R2 = 0.17 for early successional, R2 = 0.06 for restored prairie), indicating that simulation models that include N2O emissions should be parameterized specific to particular plant communities. Our results indicate that perennial bioenergy crops in their establishment phase emit less N2O than annual crops, especially when not fertilized. These findings should be considered further alongside yield and other metrics contributing to important ecosystem services. 相似文献
20.
Can intensification reduce emission intensity of biofuel through optimized fertilizer use? Theory and the case of oil palm in Indonesia
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Closing yield gaps through higher fertilizer use increases direct greenhouse gas emissions but shares the burden over a larger production volume. Net greenhouse gas (GHG) footprints per unit product under agricultural intensification vary depending on the context, scale and accounting method. Life cycle analysis of footprints includes attributable emissions due to (i) land conversion (‘fixed cost’); (ii) external inputs used (‘variable cost’); (iii) crop production (‘agronomic efficiency’); and (iv) postharvest transport and processing (‘proportional’ cost). The interplay between fixed and variable costs results in a nuanced opportunity for intermediate levels of intensification to minimize footprints. The fertilizer level that minimizes the footprint may differ from the economic optimum. The optimization problem can be solved algebraically for quadratic crop fertilizer response equations. We applied this theory to data of palm oil production and fertilizer use from 23 plantations across the Indonesian production range. The current EU threshold requiring at least 35% emission saving for biofuel use can never be achieved by palm oil if produced: (i) on peat soils, or (ii) on mineral soils where the C debt due to conversion is larger than 20 Mg C ha?1, if the footprint is calculated using an emission ratio of N2O–N/N fertilizer of 4%. At current fertilizer price levels in Indonesia, the economically optimized N fertilizer rate is 344–394 kg N ha?1, while the reported mean N fertilizer rate is 141 kg N ha?1 yr?1 and rates of 74–277 kg N ha?1 would minimize footprints, for a N2O–N/N fertilizer ratio of 4–1%, respectively. At a C debt of 30 Mg C ha?1, these values are 200–310 kg N ha?1. Sustainable weighting of ecology and economics would require a higher fertilizer/yield price ratio, depending on C debt. Increasing production by higher fertilizer use from current 67% to 80% of attainable yields would not decrease footprints in current production conditions. 相似文献