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1

Electronic Resource

Influx and efflux of K+ in sunflower roots after transfer between solutions with different K+ concentrations (1990)

Pettersson, Sune ; Kasimir-Klemedtsson, Åsa

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 79 (1990), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: It was investigated whether K+ efflux, like K+ influx, is affected when roots are transferred between solutions with different K+ concentrations. Sunflower plants (Hehanthus annuus L. cv. Uniflorus) were grown on complete nutrient solutions with 0.1, 1.0, 10 or 25 mM K+. This produced plants with K+ concentrations in the roots varying between 9 and 110 μmol (g fresh weight)–1. At the beginning of the experiments the plants were transferred to an 86Rb-labelled experimental solution initially containing 0.1 mM K+. At intervals during 6.5 h samples were removed from the solution and analyzed for K+ and radioactivity. Based on the analyses K+ (86Rb) influx, K+ net uptake and K+ efflux could be computed. In‘low K+’roots, K+(86Rb) influx and K+ net uptake agreed, suggesting a very low K+ efflux. This was contrary to‘high K+’roots, where K+ efflux was initially higher than K+(86Rb) influx. After about 4 h, K+ efflux declined to a low value also in these roots. When 2-4-dinitrophenol was included in the experimental solution, K+ (86Rb) influx was generally depressed, whereas K+ efflux was high throughout the experiment and directly proportional to the K+ status of the roots. Our hypothesis is that after transfer of‘high K+’roots to a solution with low K+ concentration, the K+ efflux from the vacuoles of root cells transiently increases, until a new electrochemical equilibrium is attained.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1990.tb00045.x

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2

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Nitrous oxide production in a forest soil at low temperatures – processes and environmental controls (2004)

Öquist, Mats G. ; Nilsson, Mats ; Sörensson, Fred ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology ecology 49 (2004), S. 0

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ISSN: 1574-6941

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Recent investigations have highlighted the relative importance of the winter season for emissions of N2O from boreal soils. However, our understanding of the processes and environmental controls regulating these emissions is fragmentary. Therefore, we investigated the potential for, and relative importance of, N2O formation at temperatures below 0 °C in laboratory experiments involving incubations of a Swedish boreal forest soil. Our results show that frozen soils have a high potential for N2O formation and subsequent emission. Net N2O production rates at −4 °C equaled those observed at +10 to +15 °C at moisture contents 〉60% of the soil's water-holding capacity. The source of this N2O was found to be denitrification occurring in anoxic microsites in the frozen soil and temperature per se did not control the denitrification rates at temperatures around 0 °C. Furthermore, both net nitrogenmineralisation and nitrification were observed in the frozen soil samples. Based on these findings we propose a conceptual model for the temperature response of N2O formation in soils at low temperatures.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1016/j.femsec.2004.04.006

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3

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Emission of NH3 and N2O after spreading of pig slurry by broadcasting or band spreading (1999)

Ferm, M. ; Kasimir-Klemedtsson, Å. ; Weslien, P. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 15 (1999), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract. The recommended method of reducing the emission of NH3 while spreading manure is to plough or harrow the manure into the soil. This in turn increases the possibility of N2O emission. At two sites in southern Sweden emissions of NH3 and N2O were measured after spreading pig slurry by broadcasting and band spreading. The band spreading technique can be used in growing crops i.e. when nitrogen is most needed, and it is thought that the NH3 emission is smaller with this technique compared to broadcasting. The average NH3 loss was 50% of applied NH4+ during warm/dry conditions and 10% during cold/wet conditions. The N2O emission was always less than 1% of applied NH4+. When the NH3 emission decreased, the direct N2O emission increased. However, when taking into account the indirect N2O emission due to deposition of NH3 outside the field, the spreading techniques all produced similar total N2O emissions. The ammonia emission was not much lower for the band spreading technique compared to broadcasting, when compared on seven occasions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.1999.tb00059.x

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4

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Nitrogen losses following application of pig slurry to arable land (1998)

Weslien, P. ; Klemedtsson, L. ; Svensson, L. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 14 (1998), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract. Emissions of ammonia (NH3) and nitrous oxide (N2O), and nitrate (NO-3) leaching were measured in two field experiments following application of pig slurry at rates corresponding to 83–96 kg NH4-N ha-1 before sowing. In spring and in autumn 1994, slurry was applied by four methods: trenching (T), shallow injection (S), band spreading immediately followed by harrowing (B/H) and band spreading (B). NH3 emission measurements were made during the first week after application in both experiments. In the spring experiment N2O emissions and NO-3 leaching were measured during 6 and 52 weeks after spreading respectively, and during 11 and 33 weeks after spreading in the autumn experiment. In spring, the increased N2O emissions (i.e. control subtracted) ranged from 0.27% (T) to 0.45% (B/H), and in the autumn study from 0.92% (T) to 1.14% (B/H), of applied NH4-N, although showing no statistically significant differences. In order to validate the chamber measurements, a ‘megachamber’(21 m2) was used together with an infrared spectrometer. The emissions agreed well for (B/H), while (B) resulted in lower emissions compared with the smaller chambers. Emissions of NH3 were about one order of magnitude higher. In spring, (B) gave the highest emission, reaching 19.5% of applied NH4-N, whereas (S), and (B/H) gave the lowest emissions, reaching 1.2 and 3.5% of applied NH4-N, respectively. NH3 emissions in autumn were 15–20% lower compared with spring. In spring the increased nitrate leaching ranged from 10.1 (T) to 24.9 kg ha-1 (B/H) and from 29.5 (B) to 37.8 kg ha-1 (T) in the autumn experiment, showing no statistically significant differences. Estimations of indirect N2O emissions due to ammonia deposition and nitrate leaching, suggested that the N2O contribution from NH3 deposition was relatively small, while the indirect N2O emissions from NO-3 leaching were of the same order of magnitude or higher than the direct N2O emissions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.1998.tb00150.x

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5

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Greenhouse gas emissions from farmed organic soils: a review (1997)

Kasimir-Klemedtsson, Å. ; Klemedtsson, L. ; Berglund, K. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 13 (1997), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00595.x

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6

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Oxidation of atmospheric methane in Northern European soils, comparison with other ecosystems, and uncertainties in the global terrestrial sink (2000)

Smith, K. A. ; Dobbie, K. E. ; Ball, B. C. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Global change biology 6 (2000), S. 0

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ISSN: 1365-2486

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography

Notes: This paper reports the range and statistical distribution of oxidation rates of atmospheric CH4 in soils found in Northern Europe in an international study, and compares them with published data for various other ecosystems. It reassesses the size, and the uncertainty in, the global terrestrial CH4 sink, and examines the effect of land-use change and other factors on the oxidation rate.Only soils with a very high water table were sources of CH4; all others were sinks. Oxidation rates varied from 1 to nearly 200 μg CH4 m−2 h−1; annual rates for sites measured for ≥1 y were 0.1–9.1 kg CH4 ha−1 y−1, with a log-normal distribution (log-mean ≈ 1.6 kg CH4 ha−1 y−1). Conversion of natural soils to agriculture reduced oxidation rates by two-thirds –- closely similar to results reported for other regions. N inputs also decreased oxidation rates. Full recovery of rates after these disturbances takes 〉 100 y. Soil bulk density, water content and gas diffusivity had major impacts on oxidation rates. Trends were similar to those derived from other published work. Increasing acidity reduced oxidation, partially but not wholly explained by poor diffusion through litter layers which did not themselves contribute to the oxidation. The effect of temperature was small, attributed to substrate limitation and low atmospheric concentration.Analysis of all available data for CH4 oxidation rates in situ showed similar log-normal distributions to those obtained for our results, with generally little difference between different natural ecosystems, or between short-and longer-term studies. The overall global terrestrial sink was estimated at 29 Tg CH4 y−1, close to the current IPCC assessment, but with a much wider uncertainty range (7 to 〉 100 Tg CH4 y−1). Little or no information is available for many major ecosystems; these should receive high priority in future research.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2486.2000.00356.x

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7

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Compartmental analysis of efflux of K+(86Rb+) and Rb+(86Rb+) from roots of intact plants of barley (Hordeum vulgare) of high and low K+ status, and after excision of the shoot (1991)

Kasimir-Klemedtsson, Åsa ; Pettersson, Sune

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 83 (1991), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The classic compartment analysis of ion efflux from roots is often applied with the assumption that there is a system of 3 compartments in series. However, complex ion transport across the root tissues, as well as influences from the shoot, may complicate the picture. The present experiments were performed to study the immediate effects that excision of the shoot before the experiment exerts on the efflux of Rb+(86Rb+) and of K+(86Rb+) from 9-day-old roots of plants of barley (Hordeum vulgare L. cv. Salve). The efflux from high K+ and low K+ roots of intact and detopped plants were compared. After excision of the shoot of high K+ plants, a marked increase in efflux was observed after 2.5 h with a maximum at about 7 h. The increase in efflux was seen as a peak in plots of efflux versus time. Excision of the shoot from low K+ roots did not give rise to a consistent increase in efflux. Regular K+ ion efflux curves were observed from roots of intact plants of high or low K+ status. Furthermore, after a pulse treatment of 9-day-old roots of intact plants of high or low K+ status with a solution containing Rb+(86Rb+), the Rb+(86Rb+) transport to the shoots was not reduced during the following 3 h in unlabelled solution. It is suggested that both the peak appearing in the efflux plots and the maintained tracer transport to the shoots after transfer of the roots to an unlabelled solution indicate the existence of a K+/Rb+ transport system in the symplasm of the roots that has only a slow exchange with the bulk cytoplasm and vacuoles.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb00128.x

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8

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Ammonia and nitrous oxide emissions from grass and alfalfa mulches (1998)

Larsson, Lisbeth ; Ferm, Martin ; Kasimir-Klemedtsson, Asa ; [et al.]

Springer

Nutrient cycling in agroecosystems 51 (1998), S. 41-46

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ISSN: 1573-0867

Keywords: closed chambers ; micrometeorological technique ; NH3 ; N-2O

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Ammonia (NH3) and nitrous oxide (N-2O) emissions were measured in the field for three months from three different herbage mulches and from bare soil, used as a control. The mulches were grass with a low N-content (1.15% N in DM), grass with a high N-content (2.12% N in DM) and alfalfa with a high N-content (4.33% N in DM). NH3 volatilization was measured using a micrometeorological technique. N-2O emissions were measured using closed chambers. NH3 and N-2O emissions were found to be much higher from the N-rich mulches than from the low-N grass and bare soil, which did not differ significantly. Volatilization losses of NH3 and N-2O occurred mainly during the first month after applying the herbage and were highest from wet material shortly after a rain. The extent of NH3-N losses was difficult to estimate, due to the low frequency of measurements and some problems with the denuder technique, used on the first occasions of measurements. Nevertheless, the results indicate that NH3-N losses from herbage mulch rich in N can be substantial. Estimated losses of NH3-N ranged from the equivalent of 17% of the applied N for alfalfa to 39% for high-N grass. These losses not only represent a reduction in the fertilizer value of the mulch, but also contribute appreciably to atmospheric pollution. The estimated loss of N-2O-N during the measurement period amounted to 1% of the applied N in the N-rich materials, which is equivalent to at least 13 kg N-2O-N ha-1 lost from alfalfa and 6 kg ha-1 lost from high-N grass. These emission values greatly exceed the 0.2 kg N-2O-N ha-1 released from bare soil, and thus contribute to greenhouse gas emissions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009799126377

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