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1.
Richard D. Bowden Mark S. Castro Jerry M. Melillo Paul A. Steudler John D. Aber 《Biogeochemistry》1993,21(2):61-71
Fluxes of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) between soils and the atmosphere were measured monthly for one year in a 77-year-old temperate hardwood forest following
a simulated hurricane blowdown. Emissions of CO2 and uptake of CH4 for the control plot were 4.92 MT C ha−1 y−1 and 3.87 kg C ha−1 y−1, respectively, and were not significantly different from the blowdown plot. Annual N2O emissions in the control plot (0.23 kg N ha−1 y−1) were low and were reduced 78% by the blowdown. Net N mineralization was not affected by the blowdown. Net nitrification
was greater in the blowdown than in the control, however, the absolute rate of net nitrification, as well as the proportion
of mineralized N that was nitrified, remained low. Fluxes of CO2 and CH4 were correlated positively to soil temperature, and CH, uptake showed a negative relationship to soil moisture. Substantial
resprouting and leafing out of downed or damaged trees, and increased growth of understory vegetation following the blowdown,
were probably responsible for the relatively small differences in soil temperature, moisture, N availability, and net N mineralization
and net nitrification between the control and blowdown plots, thus resulting in no change in CO2 or CH4 fluxes, and no increase in N2O emissions. 相似文献
2.
Shigehiro Ishizuka Tadashi Sakata Satoshi Sawata Shigeto Ikeda Hisao Sakai Chisato Takenaka Nobuaki Tamai Shin-ichi Onodera Takanori Shimizu Kensaku Kan-na Nagaharu Tanaka Masamichi Takahashi 《Biogeochemistry》2009,92(3):281-295
To clarify the reason for the higher CH4 uptake rate in Japanese forest soils, twenty-seven sites were established for CH4 flux measurement. The first order rate constant for CH4 uptake was also determined using soil core incubation at 14 sites. The CH4 uptake rate had a seasonal fluctuation, high in summer and low in winter, and the rate correlated with soil temperature at
17 sites. The annual CH4 uptake rates ranged from 2.7 to 24.8 kg CH4 ha−1 y−1 (the average of these rates was 9.7 or 10.9 kg CH4 ha−1 y−1, depending on method of calculation), which is somewhat higher than the uptake rates reported in previous literature. The
averaged CH4 uptake rate correlated closely with the CH4 oxidation rate of the topsoil (0–5 cm) in the study sites. The CH4 oxidation constant of the topsoil was explained by a multiple regression model using total pore volume of the soil, nitrate
content, and C/N ratio (p < 0.05, R
2 = 0.684). This result and comparison with literature data suggest that the high CH4 uptake rate in Japanese forest soils depends on the high porosity probably due to volcanic ash parent materials. According
to our review of the literature, the CH4 uptake rate in temperate forests in Europe is significantly different from that in Asia and North America. A new global CH4 uptake rate in temperate forests was estimated to be 5.4 Tg y−1 (1 SE is 1.1 Tg y−1) on a continental basis. 相似文献
3.
Kristell Hergoualc’h Ute Skiba Jean-Michel Harmand Catherine Hénault 《Biogeochemistry》2008,89(3):329-345
The objective of this study was to evaluate the effect of N fertilization and the presence of N2 fixing leguminous trees on soil fluxes of greenhouse gases. For a one year period, we measured soil fluxes of nitrous oxide
(N2O), carbon dioxide (CO2) and methane (CH4), related soil parameters (temperature, water-filled pore space, mineral nitrogen content, N mineralization potential) and
litterfall in two highly fertilized (250 kg N ha−1 year−1) coffee cultivation: a monoculture (CM) and a culture shaded by the N2 fixing legume species Inga densiflora (CIn). Nitrogen fertilizer addition significantly influenced N2O emissions with 84% of the annual N2O emitted during the post fertilization periods, and temporarily increased soil respiration and decreased CH4 uptakes. The higher annual N2O emissions from the shaded plantation (5.8 ± 0.3 kg N ha−1 year−1) when compared to that from the monoculture (4.3 ± 0.1 kg N ha−1 year−1) was related to the higher N input through litterfall (246 ± 16 kg N ha−1 year−1) and higher potential soil N mineralization rate (3.7 ± 0.2 mg N kg−1 d.w. d−1) in the shaded cultivation when compared to the monoculture (153 ± 6.8 kg N ha−1 year−1 and 2.2 ± 0.2 mg N kg−1 d.w. d−1). This confirms that the presence of N2 fixing shade trees can increase N2O emissions. Annual CO2 and CH4 fluxes of both systems were similar (8.4 ± 2.6 and 7.5 ± 2.3 t C-CO2 ha−1 year−1, −1.1 ± 1.5 and 3.3 ± 1.1 kg C-CH4 ha−1 year−1, respectively in the CIn and CM plantations) but, unexpectedly increased during the dry season. 相似文献
4.
Soluble Organic Nitrogen Pools in Forest soils of Subtropical Australia 总被引:15,自引:0,他引:15
Soil soluble organic N (SON) plays an important role in N biogeochemical cycling. In this study, 22 surface forest soils (0–10 cm)
were collected from southeast Queensland, Australia, to investigate the size of SON pools extracted by water and salt solutions.
Approximately 5–45 mg SON kg−1, 2–42 mg SON kg−1 and 1–24 SON mg kg−1 were extracted by 2 M KCl, 0.5 M K2SO4 and water, on average, corresponding to about 21.1, 13.5 and 7.0 kg SON ha−1 at the 0–10 cm forest soils, respectively. These SON pools, on average, accounted for 39% (KCl extracts), 42% (K2SO4 extracts) and 43% (water extracts) of total soluble N (TSN), and 2.3% (KCl extracts), 1.3% (K2SO4 extracts) and 0.7% (water extracts) of soil total N, respectively. Large variation in SON pools observed across the sites
in the present study may be attributed to a combination of factors including soil types, tree species, management practices
and environmental conditions. Significant relationships were observed among the SON pools extracted by water, KCl and K2SO4 and microbial biomass N (MBN). In general, KCl and K2SO4 extracted more SON than water from the forest soils, while KCl extracted more SON than K2SO4. The SON and soluble organic C (SOC) in KCl, K2SO4 and water extracts were all positively related to soil organic C, total N and clay contents. This indicates that clay and
soil organic matter play a key role in the retention of SON in soil. 相似文献
5.
Eva Ritter 《Plant and Soil》2007,295(1-2):239-251
Afforestation has become an important tool for soil protection and land reclamation in Iceland. Nevertheless, the harsh climate
and degraded soils are growth-limiting for trees, and little is know about changes in soil nutrients in maturing forests planted
on the volcanic soils. In the present chronosequence study, changes in C, N and total P in soil (0–10 and 10–20 cm depth)
and C and N in foliar tissue were investigated in stands of native Downy birch (Betula pubescens Enrh.) and the in Iceland introduced Siberian larch (Larix sibirica Ledeb.). The forest stands were between 14 and 97 years old and were established on heath land that had been treeless for
centuries. Soils were Andosols derived from basaltic material and rhyolitic volcanic ash. A significant effect of tree species
was only found for the N content in foliar tissue. Foliar N concentrations were significantly higher and foliar C/N ratios
significantly lower in larch needles than in birch leaves. There was no effect of stand age. Changes in soil C and the soil
nutrient status with time after afforestation were little significant. Soil C concentrations in 0–10 cm depth in forest stands
older than 30 years were significantly higher than in heath land and forest stands younger than 30 years. This was attributed
to a slow accumulation of organic matter. Soil N concentrations and soil Ptot were not affected by stand age. Nutrient pools in the two soil layers were calculated for an average weight of soil material
(400 Mg soil ha−1 in 0–10 cm depth and 600 Mg soil ha−1 in 10–20 cm depth, respectively). Soil nutrient pools did not change significantly with time. Soil C pools were in average
23.6 Mg ha−1 in the upper soil layer and 16.9 Mg ha−1 in the lower soil layer. The highest annual increase in soil C under forest compared to heath land was 0.23 Mg C ha−1 year−1 in 0–10 cm depth calculated for the 53-year-old larch stand. Soil N pools were in average 1.0 Mg N ha−1 in both soil layers and did not decrease with time despite a low N deposition and the uptake and accumulation of N in biomass
of the growing trees. Soil Ptot pools were in average 220 and 320 kg P ha−1 in the upper and lower soil layer, respectively. It was assumed that mycorrhizal fungi present in the stands had an influence
on the availability of N and P to the trees.
Responsible Editor: Hans Lambers. 相似文献
6.
Land-Use Change and Biogeochemical Controls of Methane Fluxes in Soils of Eastern Amazonia 总被引:3,自引:0,他引:3
Tropical soils account for 10%–20% of the 15–35 Tg of atmospheric methane (CH4) consumed annually by soils, although tropical deforestation could be changing the soil sink. The objectives of this study
were (a) to quantify differences in soil CH4 fluxes among primary forest, secondary forest, active pasture, and degraded pasture in eastern Amazonia; and (b) to investigate
controlling mechanisms of CH4 fluxes, including N availability, gas-phase transport, and soil respiration. At one ranch, Fazenda Vitória, annual uptake
estimates (kg CH4ha−1 y−1) based on monthly measurements were: primary forest, 2.1; secondary forest, 1.0; active pasture, 1.3; degraded pasture, 3.1.
The lower annual uptake in the active pasture compared with the primary forest was due to CH4 production during the wet season in the pasture soils, which is consistent with findings from other studies. In contrast,
the degraded pasture was never a CH4 source. Expressing uptake as a negative flux and emission as a positive flux, CH4 fluxes were positively correlated with CO2 fluxes, indicating that root and microbial respiration in the productive pastures, and to a lesser extent in the primary
forest, contributed to the formation of anaerobic microsites where CH4 was produced, whereas this productivity was absent in the degraded pasture. In all land uses, uptake rates of atmospheric
CH4 were greater in the dry season than in the wet season, indicating the importance of soil water content and gas transport
on CH4 fluxes. These clay soils had low annual uptake rates relative to reported rates on sandy soils, which also is consistent
with gas transport within the soil being a limiting factor. Nitrogen availability indices did not correlate with CH4 fluxes, indicating that inhibition of CH4 oxidation was not an important mechanism explaining differences among land uses. At another ranch, Fazenda Agua Parada, no
significant effect of pasture age was observed along a chronosequence of pasture ages. We conclude that land-use change can
either increase or decrease the soil sink of CH4, depending on the duration of wet and dry seasons, the effects of seasonal precipitation on gas-phase transport, and the
phenology and relative productivity of the vegetation in each land use. 相似文献
7.
Intercropping cotton (Gossypium hirsutum L.) and cowpea (Vigna unguiculata (L.) Walp) is one of the ways to improve food security and soil fertility whilst generating cash income of the rural poor. A study was carried out to find out the effect of cotton–cowpea intercropping on cowpea N2-fixation capacity, nitrogen balance and yield of a subsequent maize crop. Results showed that cowpea suppressed cotton yields but the reduction in yield was compensated for by cowpea grain yield. Cowpea grain yield was significantly different across treatments and the yields were as follows: sole cowpea (1.6 Mg ha−1), 1:1 intercrop (1.1 Mg ha−1), and 2:1 intercrop (0.7 Mg ha−1). Cotton lint yield was also significantly different across treatments and was sole cotton (2.5 Mg ha−1), 1:1 intercrop (0.9 Mg ha−1) and 2:1 intercrop (1.5 Mg ha−1). Intercropping cotton and cowpea increased the productivity with land equivalence ratios (LER) of 1.4 and 1.3 for 1:1 and 2:1 intercrop treatments, respectively. There was an increase in percentage of N fixation (%Ndfa) by cowpea in intercrops as compared to sole crops though the absolute amount fixed (Ndfa) was lower due to reduced plant population. Sole cowpea had %Ndfa of 73%, 1:1 intercrop had 85% and 2:1 intercrop had 77% while Ndfa was 138 kg ha−1 for sole cowpea, 128 kg ha−1 for 1:1 intercrop and 68 kg ha−1 for 2:1 intercrop and these were significantly different. Sole cowpea and the intercrops all showed positive N balances of 92 kg ha−1 for sole cowpea and 1:1 intercrop, and 48 kg ha−1 for 2:1 intercrop. Cowpea fixed N transferred to the companion cotton crop was very low with 1:1 intercrop recording 3.5 kg N ha−1 and 2:1 intercrop recording 0.5 kg N ha−1. Crop residues from intercrops and sole cowpea increased maize yields more than residues from sole cotton. Maize grain yield was, after sole cotton (1.4 Mg ha−1), sole cowpea (4.6 Mg ha−1), 1:1 intercrops (4.4 Mg ha−1) and 2:1 intercrops (3.9 Mg ha−1) and these were significantly different from each other. The LER, crop yields, %N fixation and, N balance and residual fertility showed that cotton–cowpea intercropping could be a potentially productive system that can easily fit into the current smallholder farming systems under rain-fed conditions. The fertilizer equivalency values show that substantial benefits do accrue and effort should be directed at maximizing the dry matter yield of the legume in the intercrop system while maintaining or improving the economic yield of the companion cash crop. 相似文献
8.
Acidification of Soil in a Dry Land Winter Wheat-sorghum/corn-fallow Rotation in the Semiarid U.S. Great Plains 总被引:4,自引:0,他引:4
David D. Tarkalson José O. Payero Gary W. Hergert Kenneth G. Cassman 《Plant and Soil》2006,283(1-2):367-379
Soil pH is decreasing in many soils in the semiarid Great Plains of the United States under dry land no-till (NT) cropping
systems. This study was conducted to determine the rate of acidification and the causes of the acidification of a soil cropped
to a winter wheat (Triticum aestivum L.)-grain sorghum [Sorghum bicolor (L.) Moench]/corn (Zea mays L.)-fallow rotation (W-S/C-F) under NT. The study was conducted from 1989 to 2003 on soil with a long-term history of either
continuous NT management [NT(LT)] (1962–2003) or conventional tillage (CT) (1962–1988) then converted to NT [NT(C)] (1989–2003).
Nitrogen was applied as ammonium nitrate (AN) at a rate of 23 kg N ha−1 in 1989 and as urea ammonium nitrate (UAN) at an average annual rate of 50 kg N ha−1 from 1990 to 2003 for both NT treatments. Soil samples were collected at depth increments of 0–5, 5–10, 10–15, and 15–30 cm
in the spring of 1989 and 2003. Acidification rates for the NT(LT) and NT(C) treatments were 1.13 and 1.48 kmol H+ ha−1 yr−1 in the 0–30 cm depth, respectively. The amount of CaCO3 needed to neutralize the acidification is 57 and 74 kg ha−1 yr−1 for the NT(LT) and NT(C) treatments, respectively. A proton budget estimated by the Helyar and Porter [1989, Soil Acidity
and Plant Growth, Academic Press] method indicated that NO3− leaching from the 30 cm depth was a primary cause of long-term acidification in this soil. Nitrate leaching accounted for
59 and 66% of the H+ from the acid causing factors for NT(LT) and NT(C) treatments, respectively. The addition of crop residues to the soil neutralized
62 and 47% of the acidity produced from the leaching of NO3−, and 37 and 31% of the acid resulting from NO3− leaching and the other acid-causing constituents for the NT(LT) and NT(C) treatments, respectively. These results document
that surface soils in dry land W-S/C-F rotations under NT are acidifying under current management practices. Improved management
to increase nitrogen uptake efficiency from applied fertilizer would help reduce the rate of acidification. The addition of
lime materials to prevent negative impacts on grain yields may be necessary in the future under current management practices.
A contribution of the university of Nebraska Agricultural Research Division, Lincoln, NE 68583. Journal series No. 15120 相似文献
9.
Old growth forest soils are large C reservoirs, but the impacts of tree-fall gaps on soil C in these forests are not well
understood. The effects of forest gaps on soil C dynamics in old growth northern hardwood–hemlock forests in the upper Great
Lakes region, USA, were assessed from measurements of litter and soil C stocks, surface C efflux, and soil microbial indices
over two consecutive growing seasons. Forest floor C was significantly less in gaps (19.0 Mg C ha−1) compared to gap-edges (39.5 Mg C ha−1) and the closed forest (38.0 Mg C ha−1). Labile soil C (coarse particulate organic matter, cPOM) was significantly less in gaps and edges (11.1 and 11.2 Mg C ha−1) compared to forest plots (15.3 Mg C ha−1). In situ surface C efflux was significantly greater in gaps (12.0 Mg C ha−1 y−1) compared to edges and the closed forest (9.2 and 8.9 Mg C ha−1 y−1). Microbial biomass N (MBN) was significantly greater in edges (0.14 Mg N ha−1) than in the contiguous forest (0.09 Mg N ha−1). The metabolic quotient (qCO2) was significantly greater in the forest (0.0031 mg CO2 h−1 g−1/mg MBC g−1) relative to gaps or edges (0.0014 mg CO2 h−1 g−1/mg MBC g−1). A case is made for gaps as alleviators of old growth forest soil C saturation. Relative to the undisturbed closed forest,
gaps have significantly less labile C, significantly greater in situ surface C efflux, and significantly lower decreased qCO2 values. 相似文献
10.
The two non-CO2 greenhouse gases (GHGs) nitrous oxide (N2O) and methane (CH4) comprise 54.8% of total New Zealand emissions. Nitrous oxide is mainly generated from mineral N originating from animal dung and urine, applied fertiliser N, biologically fixed N2, and mineralisation of soil organic N. Even though about 96% of the anthropogenic CH4 emitted in New Zealand is from ruminant animals (methanogenesis), methane uptake by aerobic soils (methanotrophy) can significantly contribute to the removal of CH4 from the atmpsphere, as the global estimates confirm. Both the net uptake of CH4 by soils and N2O emissions from soils are strongly influenced by changes in land use and land management. Quantitative information on the fluxes of these two non-CO2 GHGs is required for a range of land-use and land-management ecosystems to determine their contribution to the national emissions inventory, and for assessing the potential of mitigation options. Here we report soil N2O fluxes and CH4 uptake for a range of land-use and land-management systems collated from published and unpublished New Zealand studies. Nitrous oxide emissions are highest in dairy-grazed pastures (10–12 kg N2O–N ha?1 year? 1), intermediate in sheep-grazed pastures, (4–6 kg N2O–N ha?1 year?1), and lowest in forest, shrubland and ungrazed pasture soils (1–2 kg N2O–N ha?1 year?1). N deposited in the form of animal urine and dung, and N applied as fertiliser, are the principal sources of N2O production. Generally, N2O emissions from grazed pasture soils are high when the soil water-filled pore-space is above field capacity, and net CH4 uptake is low or absent. Although nitrification inhibitors have shown some promise in reducing N2O emissions from grazed pasture systems, their efficacy as an integral part of farm management has yet to be tested. Methane uptake was highest for a New Zealand Beech forest soil (10–11 kg CH4 ha?1 year?1), intermediate in some pine forest soils (4–6 kg CH4 ha?1 year?1), and lowest in most pasture (<1 kg CH4 ha?1 year?1) and cropped soils (1.5 kg CH4 ha?1 year?1). Afforestation /reforestation of pastures results in increases in soil CH4 uptake, largely as a result of increases in soil aeration status and changes in the population and activities of methanotrophs. Soil CH4 uptake is also seasonally dependent, being about two to three times higher in a dry summer and autumn than in a wet winter. There are no practical ways yet available to reduce CH4 emissions from agricultural systems. The mitigation options to reduce gaseous emissions are discussed and future research needs identified. 相似文献
11.
Jean-Michel Harmand Hector Ávila Etienne Dambrine Ute Skiba Sergio de Miguel Reina Vanessa Renderos Robert Oliver Francisco Jiménez John Beer 《Biogeochemistry》2007,85(2):125-139
Nitrogen fertilization is a key factor for coffee production but creates a risk of water contamination through nitrate (NO3−) leaching in heavily fertilized plantations under high rainfall. The inclusion of fast growing timber trees in these coffee
plantations may increase total biomass and reduce nutrient leaching. Potential controls of N loss were measured in an unshaded
coffee (Coffea arabica L.) plot and in an adjacent coffee plot shaded with the timber species Eucalyptus deglupta Blume (110 trees ha−1), established on an Acrisol that received 180 kg N ha−1 as ammonium-nitrate and 2,700 mm yr−1 rainfall. Results of the one year study showed that these trees had little effect on the N budget although some N fluxes
were modified. Soil N mineralization and nitrification rates in the 0–20 cm soil layer were similar in both systems (≈280 kg N ha−1 yr−1). N export in coffee harvest (2002) was 34 and 25 kg N ha−1 yr−1 in unshaded and shaded coffee, and N accumulation in permanent biomass and litter was 25 and 45 kg N ha−1 yr−1, respectively. The losses in surface runoff (≈0.8 kg mineral N ha−1 yr−1) and N2O emissions (1.9 kg N ha−1 yr−1) were low in both cases. Lysimeters located at 60, 120, and 200 cm depths in shaded coffee, detected average concentrations
of 12.9, 6.1 and 1.2 mg NO3−-N l−1, respectively. Drainage was slightly reduced in the coffee-timber plantation. NO3− leaching at 200 cm depth was about 27 ± 10 and 16 ± 7 kg N ha−1 yr−1 in unshaded and shaded coffee, respectively. In both plots, very low NO3− concentrations in soil solution at 200 cm depth (and in groundwater) were apparently due to NO3− adsorption in the subsoil but the duration of this process is not presently known. In these conventional coffee plantations,
fertilization and agroforestry practices must be refined to match plant needs and limit potential NO3− contamination of subsoil and shallow soil water. 相似文献
12.
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
13.
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
14.
Hizbullah Jamali Stephen J. Livesley Samantha P. Grover Tracy Z. Dawes Lindsay B. Hutley Garry D. Cook Stefan K. Arndt 《Ecosystems》2011,14(5):698-709
Termites produce methane (CH4) as a by-product of microbial metabolism of food in their hindguts, and are one of the most uncertain components of the regional
and global CH4 exchange estimates. This study was conducted at Howard Springs near Darwin, and presents the first estimate of CH4 emissions from termites based on replicated in situ seasonal flux measurements in Australian savannas. Using measured fluxes
of CH4 between termite mounds and the atmosphere, and between soil and the atmosphere across seasons we determined net CH4 flux within a tropical savanna woodland of northern Australia. By accounting for both mound-building and subterranean termite
colony types, and estimating the contribution from tree-dwelling colonies it was calculated that termites were a CH4 source of +0.24 kg CH4-C ha−1 y−1 and soils were a CH4 sink of −1.14 kg CH4-C ha−1 y−1. Termites offset 21% of CH4 consumed by soil resulting in net sink strength of −0.90 kg CH4-C ha−1 y−1 for these savannas. For Microcerotermes nervosus (Hill), the most abundant mound-building termite species at this site, mound basal area explained 48% of the variation in
mound CH4 flux. CH4 emissions from termites offset 0.1% of the net biome productivity (NBP) and CH4 consumption by soil adds 0.5% to the NBP of these tropical savannas at Howard Springs. 相似文献
15.
The effects on growth, quality and N uptake by turfgrass (Cynodon dactylon L.) during sod production of four fertiliser types applied at three application rates (100, 200 or 300 kg N ha−1 per ‘crop’) under two irrigation treatments (70% and 140% daily replacement of pan evaporation) were investigated. The fertiliser
types were: water-soluble (predominately NH4NO3), control-release, pelletised poultry manure, and pelletised biosolids; and the experiment was conducted on a sandy soil
in a Mediterranean-type climate. Plots were established from rhizomes, with the turfgrass harvested as sod every 16–28 weeks
depending upon the time of the year. Four crops were produced during the study. Applying water-soluble and control-release
fertilisers doubled shoot growth and improved turfgrass greenness by up to 10% in comparison with plots receiving pelletised
poultry manure and pelletised biosolids. Nitrogen uptake into the shoots after four crops (averaged across irrigation treatments
and N rates) was 497 kg N ha−1 for the water-soluble fertiliser, 402 kg N ha−1 for the control-release, 188 kg N ha−1 for the pelletised poultry manure and 237 kg N ha−1 for the pelletised biosolids. Consequently, the agronomic nitrogen-use efficiency (NAE, kg DM kg−1 N applied) of the inorganic fertilisers was approximately twice that of the organic fertilisers. Increasing irrigation from
70% to 140% replacement of pan evaporation was detrimental to turfgrass growth and N uptake for the first crop when supplied
with the water-soluble fertiliser. Under the low irrigation treatment, inorganic N fertilisers applied at 200–300 kg N ha−1 were adequate for production of turfgrass sod.
Section Editor: P. J. Randall 相似文献
16.
Drainage of peatlands for forestry starts a succession of ground vegetation in which mire species are gradually replaced by forest species. Some mire plant communities vanish quickly following the water-level drawdown; some may prevail longer in the moister patches of peatland. Drainage ditches, as a new kind of surface, introduce another component of spatial variation in drained peatlands. These variations were hypothesized to affect methane (CH4) fluxes from drained peatlands. Methane fluxes from different plant communities and unvegetated surfaces, including ditches, were measured at the drained part of Lakkasuo mire, Central Finland. The fluxes were found to be related to peatland site type, plant community, water-table position and soil temperature. At nutrient-rich fen sites fluxes between plant communities differed only a little: almost all plots acted as CH4 sinks (−0.9 to −0.4 mg CH4 m−2 d−1), with the exception of Eriophorum angustifolium Honck. communities, which emitted 0.9 g CH4 m−2 d−1. At nutrient-poor bog site the differences between plant communities were clearer. The highest emissions were measured from Eriophorum vaginatum L. communities (29.7 mg CH4 m−2 d−1), with a decreasing trend to Sphagna (10.0 mg CH4 m−2 d−1) and forest moss communities (2.6 mg CH4 m−2 d−1). CH4 emissions from different kinds of ditches were highly variable, and extremely high emissions (summertime averages 182–600 mg CH4 m−2 d−1) were measured from continuously water-covered ditches at the drained fen. Variability in the emissions was caused by differences in the origin and movement of water in the ditches, as well as differences in vegetation communities in the ditches. While drainage on average greatly decreases CH4 emissions from peatlands, a great spatial variability in fluxes is emerged. Emissions from ditches constantly covered with water, may in some cases have a great impact on the overall CH4 emissions from drained peatlands. 相似文献
17.
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
18.
Urbanization can accelerate climate change by increasing soil N2O emission while reducing CH4 uptake
Yang Zhan Zhisheng Yao Peter M. Groffman Junfei Xie Yan Wang Guangtao Li Xunhua Zheng Klaus Butterbach-Bahl 《Global Change Biology》2023,29(12):3489-3502
Urban land-use change has the potential to affect local to global biogeochemical carbon (C) and nitrogen (N) cycles and associated greenhouse gas (GHG) fluxes. We conducted a meta-analysis to (1) assess the effects of urbanization-induced land-use conversion on soil nitrous oxide (N2O) and methane (CH4) fluxes, (2) quantify direct N2O emission factors (EFd) of fertilized urban soils used, for example, as lawns or forests, and (3) identify the key drivers leading to flux changes associated with urbanization. On average, urbanization increases soil N2O emissions by 153%, to 3.0 kg N ha−1 year−1, while rates of soil CH4 uptake are reduced by 50%, to 2.0 kg C ha−1 year−1. The global mean annual N2O EFd of fertilized lawns and urban forests is 1.4%, suggesting that urban soils can be regional hotspots of N2O emissions. On a global basis, conversion of land to urban greenspaces has increased soil N2O emission by 0.46 Tg N2O-N year−1 and decreased soil CH4 uptake by 0.58 Tg CH4-C year−1. Urbanization driven changes in soil N2O emission and CH4 uptake are associated with changes in soil properties (bulk density, pH, total N content, and C/N ratio), increased temperature, and management practices, especially fertilizer use. Overall, our meta-analysis shows that urbanization increases soil N2O emissions and reduces the role of soils as a sink for atmospheric CH4. These effects can be mitigated by avoiding soil compaction, reducing fertilization of lawns, and by restoring native ecosystems in urban landscapes. 相似文献
19.
Late-successional forests in the upper Great Lakes region are susceptible to nitrogen (N) saturation and subsequent nitrate
(NO3−) leaching loss. Endemic wind disturbances (i.e., treefall gaps) alter tree uptake and soil N dynamics; and, gaps are particular
susceptible to NO3− leaching loss. Inorganic N was measured throughout two snow-free periods in throughfall, forest floor leachates, and mineral
soil leachates in gaps (300–2,000 m2, 6–9 years old), gap-edges, and closed forest plots in late-successional northern hardwood, hemlock, and northern hardwood–hemlock
stands. Differences in forest water inorganic N among gaps, edges, and closed forest plots were consistent across these cover
types: NO3− inputs in throughfall were significantly greater in undisturbed forest plots compared with gaps and edges; forest floor leachate
NO3− was significantly greater in gaps compared to edges and closed forest plots; and soil leachate NO3− was significantly greater in gaps compared to the closed forest. Significant differences in forest water ammonium and pH
were not detected. Compared to suspected N-saturated forests with high soil NO3− leaching, undisturbed forest plots in these late-successional forests are not losing NO3− (net annual gain of 2.8 kg ha−1) and are likely not N-saturated. Net annual NO3− losses were observed in gaps (1.3 kg ha−1) and gap-edges (0.2 kg ha−1), but we suspect these N leaching losses are a result of decreased plant uptake and increased soil N mineralization associated
with disturbance, and not N-saturation. 相似文献
20.
Impact of long-term nitrogen addition on carbon stocks in trees and soils in northern Europe 总被引:4,自引:2,他引:2
The aim of this study was to quantify the effects of fertiliser N on C stocks in trees (stems, stumps, branches, needles,
and coarse roots) and soils (organic layer +0–10 cm mineral soil) by analysing data from 15 long-term (14–30 years) experiments
in Picea abies and Pinus sylvestris stands in Sweden and Finland. Low application rates (30–50 kg N ha−1 year−1) were always more efficient per unit of N than high application rates (50–200 kg N ha−1 year−1). Addition of a cumulative amount of N of 600–1800 kg N ha−1 resulted in a mean increase in tree and soil C stock of 25 and 11 kg (C sequestered) kg−1 (N added) (“N-use efficiency”), respectively. The corresponding estimates for NPK addition were 38 and 11 kg (C) kg−1 (N). N-use efficiency for C sequestration in trees strongly depended on soil N status and increased from close to zero at
C/N 25 in the humus layer up to 40 kg (C) kg−1 (N) at C/N 35 and decreased again to about 20 kg (C) kg−1 (N) at C/N 50 when N only was added. In contrast, addition of NPK resulted in high (40–50 kg (C) kg−1 (N)) N-use efficiency also at N-rich (C/N 25) sites. The great difference in N-use efficiency between addition of NPK and
N at N-rich sites reflects a limitation of P and K for tree growth at these sites. N-use efficiency for soil organic carbon
(SOC) sequestration was, on average, 3–4 times lower than for tree C sequestration. However, SOC sequestration was about twice
as high at P. abies as at P. sylvestris sites and averaged 13 and 7 kg (C) kg−1 (N), respectively. The strong relation between N-use efficiency and humus C/N ratio was used to evaluate the impact of N
deposition on C sequestration. The data imply that the 10 kg N ha−1 year−1 higher deposition in southern Sweden than in northern Sweden for a whole century should have resulted in 2.0 ± 1.0 (95% confidence
interval) kg m−2 more tree C and 1.3 ± 0.5 kg m−2 more SOC at P. abies sites in the south than in the north for a 100-year period. These estimates are consistent with differences between south
and north in tree C and SOC found by other studies, and 70–80% of the difference in SOC can be explained by different N deposition. 相似文献