63,967 research outputs found
Intensive field measurements of nitrous oxide emissions from a tropical agricultural soil
No full textThe amount of nitrous oxide (N2O) continues to increase in the atmosphere. Agricultural use of nitrogen fertilizers in the tropics is thought to be an important source of atmospheric N2O. High frequency, highly precise measurements of the N2O flux were made with an automated system deployed in N fertilized and unfertilized agricultural plots of papaya and corn in Costa Rica for an entire corn crop growth to harvest cycle. N2O fluxes were as high as 64 ng N-N2O cm(-2) h(-1) from fertilized versus 12 ng N-N2O cm(-2) h(-1) from unfertilized corn and 28 ng N-N2O cm(-2) h(-1) from fertilized versus 4.6 ng N-N2O cm(-2) h(-1) from unfertilized papaya. Fertilized corn released more N2O than fertilized papaya over the 125 days of the crop cycle, 1.83 kg N ha(-1) versus 1.37 kg N ha(-1). This represents a loss as N2O of 1.1 and 0.9% of the total N applied as ammonium nitrate to the corn and papaya, respectively. As has often been observed, N2O fluxes were highly variable. The fastest rates of emission were associated with fertilization and high soil moisture. A diurnal cycle in the fluxes was not evident probably due to the minimal day/night temperature fluctuations. Each chamber was measured between 509 and 523 times over the course of the experiment. This allows us to evaluate the effect on constructed mean fluxes of lowered sampling frequencies. Sampling each collar about once a day throughout the crop cycle (25% of the data set) could result in a calculated mean flux from any individual chamber that can vary by as much as 20% even though the calculated mean would probably be within 10% of the mean of the complete data set. The uncertainty increases very rapidly at lower sampling frequencies. For example, if only 10% of the data set were used which would be the equivalent of sampling every other day, a very high sampling frequency in terms of manual measurements, the calculated mean flux could vary by as much as 40% or more at any given site
Fluxes of nitrous oxide and methane in commercial soybean, rice, and maize crops on the Santarem-Belterra plateau, Para State.
No full textThe west region of Para State, principally the municipality of the Belterra and Santarém, has tried since 2000 an expressive increase in their grain crops areas, specifically soybean, rice and, in 2007, corn. In 2005 the farmers planted 110,000ha of these crops. This brought a no avoid fertilizers applications, where nitrogen has contributed in the formulas to planting and cover application. After 2003, were installed throughfall and precipitation collectors (bulk deposition) to monitoring nutrients cycles in these planted areas on the forest and superficial water (rivers and streams), besides collect gas samples with static chambers in agricultural areas. Using liquid and gas chromatography were analyzed nitrate and ammonium, and nitrous oxide. The results shown that precipitation and throughfall waters have high nitrogen content, in which ammonium is prevalent in the precipitation and nitrate in throughfall, with richest factor of the 3.9 to nitrate and -0.2 to ammonium. Also, the fluxes values to nitrogen (monthly average) according to 3.4 kg N.ha-1 in throughfall, and 3.1 kg N.ha-1 in precipitation. The fluxes of the nitrous oxide were (average) 2.59 ng N.cm-2.hour-1 (conventional soybean), while in no till system this fluxes were 3.2 ng N.cm-2.hour-1. In the superficial waters were observed light undulation during seedbed period (rainy season), with average value of the 0.24 ppm, in the six rivers and streams studied. The principal conclusion is that nitrogen fertilizers used in the crops are going to the forest and the forest is using this nitrogen to supply its necessity to grown
Nitrous oxide, nitric oxide, and methane fluxes from soils following clearing and burning of tropical secondary forest
No full textFluxnet Product from Stordalen grassland
No full textSubset of half-hourly Fluxes and Meteo measurements processed with the international standard FLUXNET procedure (ONEFlux suite) for fast plotting purposes. Full data available in the Archive product.
Crill, P., Friborg, T., Jammet, M., Jansen, J. (2024). Fluxnet Product from Stordalen grassland, 2011-12-31–2019-12-31, FLUXNET, https://hdl.handle.net/11676/9r8BeQrUuOcdRyO3VV7k0Jx
Fluxnet Archive Product from Stordalen grassland
No full textArchive Product for Ecosystem Measurements. Fluxes, Meteo and ancillary measurements processed with the International standard FLUXNET procedure (ONEFlux suite) with different time aggregations.
Crill, P., Friborg, T., Jammet, M., Jansen, J. (2024). Fluxnet Archive Product from Stordalen grassland, 2012–2019, FLUXNET, https://hdl.handle.net/11676/rCgmB4gNdPswoiZzrZqCFXb
Constraining the rate and extent of mantle serpentinization from seismic and petrological data: implications for chemosynthesis and tectonic processes
No full textWe used seismic velocity as a proxy for serpentinization of the mantle, which occurred beneath thinned but laterally continuous continental crust during continental break up, prior to opening of the Atlantic Ocean. The serpentinized sub-continental mantle is now exhumed, beneath the Iberia Abyssal Plain and was accessed by scientific drilling on Ocean Drilling Program legs 149 and 173. Chromatographic modelling of kinetically limited transport of the serpentinization front yields a front displacement of 2197 ± 89 m, a time-integrated fluid flux of 1098 ± 45 m3 m2 and a Damköhler number of 6.0 ± 0.2. Whether either surface reaction or chemical transport limit the rate of reaction, we calculate timescales for serpentinization of approximately 105–106 years. This yields time-average fluid flux rates for H2O, entering and reacting with the mantle, of 60–600 mol m2 a1 and for CH4, produced as a by-product of oxidation of Fe++ to magnetite and exiting the mantle, of 0.55–5.5 mol m2 a1. This equates to a CH4-flux of 0.18–1.8 Tg a1 for coeval serpentinization of the mantle that was exhumed west of Iberia. This represents 0.03–0.3% of the present-day annual CH4-flux from all sources and a higher fraction of pre-anthropogenic (lower) CH4 levels. CH4 released by serpentinization at or beneath the seafloor could provide substrate for biological chemosynthesis and/or promote gas-hydrate formation. Finally, noting its volumetric extent and rapidity (<106 years), we interpret serpentinization to be a reckonable component of tectonic processes, contributing both diapiric and expansional forces and helping to 'lubricate' extensional processes. Given its anisotropic permeability, actively deforming serpentinite might impede melt migration which may be of interest, given the apparent lack of melt in some rifted margins
Fluxnet Archive Product from Abisko-Stordalen Palsa Bog
No full textArchive Product for Ecosystem Measurements. Fluxes, Meteo and ancillary measurements processed with the International standard FLUXNET procedure (ONEFlux suite) with different time aggregations.
Lundin, E., Crill, P., Grudd, H., Holst, J., Kristoffersson, A., Meire, A., Molder, M., Rakos, N. (2025). Fluxnet Archive Product from Abisko-Stordalen Palsa Bog, 2022–2024, FLUXNET, https://hdl.handle.net/11676/gROMoDY5jMLhMTRejjKXtC-
Fluxnet Product from Abisko-Stordalen Palsa Bog
No full textSubset of half-hourly Fluxes and Meteo measurements processed with the international standard FLUXNET procedure (ONEFlux suite) for fast plotting purposes. Full data available in the Archive product.
Lundin, E., Crill, P., Grudd, H., Holst, J., Kristoffersson, A., Meire, A., Molder, M., Rakos, N. (2025). Fluxnet Product from Abisko-Stordalen Palsa Bog, 2021-12-31–2024-12-31, FLUXNET, https://hdl.handle.net/11676/ryLKIsi4Dq3_U0P_6loTDZM
Nitrous oxide fluxes and nitrogen cycling along a pasture chronosequence in Central Amazonia, Brazil
No full textWe studied nitrous oxide (N2O) fluxes and soil nitrogen (N) cycling following forest conversion to pasture in the central Amazon near Santarém, Parö, Brazil. Two undisturbed forest sites and 27 pasture sites of 0.5 to 60 years were sampled once each during wet and dry seasons. In addition to soil-atmosphere fluxes of N2O we measured 27 soil chemical, soil microbiological and soil physical variables. Soil N2O fluxes were higher in the wet season than in the dry season. Fluxes of N2O from forest soils always exceeded fluxes from pasture soils and showed no consistent trend with pasture age. At our forest sites, nitrate was the dominant form of inorganic N both during wet and dry season. At our pasture sites nitrate generally dominated the inorganic N pools during the wet season and ammonium dominated during the dry season. Net mineralization and nitrification rates displayed large variations. During the dry season net immobilization of N was observed in some pastures. Compared to forest sites, young pasture sites (=2 years) had low microbial biomass N and protease activities. Protease activity and microbial biomass N peaked in pastures of intermediate age (4 to 8 years) followed by consistently lower values in older pasture (10 to 60 years). The C/N ratio of litter was low at the forest sites (~25) and rapidly increased with pasture age reaching values of 60-70 at pastures of 15 years and older. Nitrous oxide emissions at our sites were controlled by C and N availability and soil aeration. Fluxes of N2O were negatively correlated to leaf litter C/N ratio, NH4+-N and the ratio of NO3--N to the sum of NO3--N + NH4+-N (indicators of N availability), and methane fluxes and bulk density (indicators of soil aeration status) during the wet season. During the dry season fluxes of N2O were positively correlated to microbial biomass N, ß-glucosidase activity, total inorganic N stocks and NH4+-N. In our study region, pastures of all age emitted less N2O than old-growth forests, because of a progressive decline in N availability with pasture age combined with strongly anaerobic conditions in some pastures during the wet season
ETC L2 Meteosens from Abisko-Stordalen Palsa Bog
No full textHalf-hourly meteorological variables for each single sensor calculated by the ICOS ETC starting from the raw data.
Lundin, E., Crill, P., Grudd, H., Gustafsson, J., Holst, J., Kristoffersson, A., Meire, A., Molder, M., Rakos, N. (2025). ETC L2 Meteosens from Abisko-Stordalen Palsa Bog, 2021-12-31–2025-09-30, ICOS RI, https://hdl.handle.net/11676/bARy1xGy-62woCMzQKdG5RM
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