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  • 1
    Language: English
    In: Soil Biology and Biochemistry, Feb, 2014, Vol.69, p.320(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2013.11.014 Byline: Marianne Schutt, Werner Borken, Oliver Spott, Claus Florian Stange, Egbert Matzner Abstract: Climate models predict warmer winter in temperate regions, but little is known about the temperature sensitivity of soil carbon (C) and nitrogen (N) mineralization at low temperatures. Here, we assess the temperature sensitivities of gross ammonification, gross nitrification, C and net N mineralization of top soil horizons, under a European beech and a Norway spruce temperate forest. We tested the hypotheses that (1) substrate quality affects the temperature sensitivity of C and N mineralization and (2) that temperature sensitivity of C mineralization is higher than of gross ammonification. Soil incubations were conducted at constant temperatures of -4, -1, +2, +5 and +8 [degrees]C. Gross ammonification and nitrification were measured by the.sup.15N pool dilution technique. Temperature sensitivities of C, gross and net N mineralization were calculated using the Arrhenius equation and C mineralization was taken as proxy for substrate quality. Gross ammonification and C mineralization was much larger in the beech than in the spruce soil, while gross nitrification was in the same order of magnitude. Gross ammonification, nitrification and C mineralization almost ceased at -4 [degrees]C, but already increased at -1 [degrees]C. Net ammonification in Oi/Oe horizons was low at -4 and -1 [degrees]C and increased strongly between +2 and +8 [degrees]C. Net nitrification was low in both soils, but increased in the spruce soil at temperatures 〉2 [degrees]C whereas no temperature response occurred in the beech soil. Apparent Q.sub.10 values of gross ammonification and C mineralization in the temperature range of -4 to +8 [degrees]C were in the range of 3-18. Q.sub.10 were lowest in soil horizons of low substrate quality. The ratio of C mineralization to gross ammonification varied between 0.5 and 2.9, suggesting preferential mineralization of N rich organic substrates or rapid turnover of the N pool in microbial biomass. Rising winter temperatures might have substantial effects on net N mineralization, but effects decrease with soil depth, likely due to decreasing substrate quality of soil organic matter. Author Affiliation: (a) Department of Soil Ecology, University of Bayreuth, 95448 Bayreuth, Germany (b) Department of Soil Physics, Helmholtz Center for Environmental Research, UFZ, 06120 Halle/Saale, Germany (c) Bundesanstalt fur Geowissenschaften und Rohstoffe, Fachbereich B2.4 "Boden als Ressource - Stoffeigenschaften und -dynamik", 30655 Hannover, Germany Article History: Received 21 June 2013; Revised 7 November 2013; Accepted 14 November 2013
    Keywords: Soil Biology -- Analysis ; Nitrification -- Analysis ; Soil Ecology -- Analysis ; Forest Soils -- Analysis ; Soil Carbon -- Analysis
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Soil Biology and Biochemistry, February 2011, Vol.43(2), pp.333-338
    Description: Changes in the soil water regime, predicted as a consequence of global climate change, might influence the N cycle in temperate forest soils. We investigated the effect of decreasing soil water potentials on gross ammonification and nitrification in different soil horizons of a Norway spruce forest and tested the hypotheses that i) gross rates are more sensitive to desiccation in the Oa and EA horizon as compared to the uppermost Oi/Oe horizon and ii) that gross nitrification is more sensitive than gross ammonification. Soil samples were adjusted by air drying to water potentials from about field capacity to around −1.0 MPa, a range that is often observed under field conditions at our site. Gross rates were measured using the N pool dilution technique. To ensure that the addition of solute label to dry soils and the local rewetting does not affect the results by re-mineralization or preferential consumption of N, we compared different extraction and incubation times. T times ranging from 10 to 300 min and incubation times of 48 h and 72 h did not influence the rates of gross ammonification and nitrification. Even small changes of water potential decreased gross ammonification and nitrification in the O horizon. In the EA horizon, gross nitrification was below detection limit and the response of the generally low rates of gross ammonification to decreasing water potentials was minor. In the Oi/Oe horizon gross ammonification and nitrification decreased from 37.5 to 18.3 mg N kg  soil d and from 15.4 to 5.6 mg N kg  soil d when the water potential decreased from field capacity to −0.8 MPa. In the Oa horizon gross ammonification decreased from 7.4 to 4.0 mg N kg  soil d when the water potential reached −0.6 MPa. At such water potential nitrification almost ceased, while in the Oi/Oe horizon nitrification continued at a rather high level. Hence, only in the Oa horizon nitrification was more sensitive to desiccation than ammonification. Extended drought periods that might result from climate change will cause a reduction in gross N turnover rates in forest soils even at moderate levels of soil desiccation. ► Even small changes of water potential decreased gross N turnover rates in the O horizon. ► Only in the Oa horizon gross nitrification was more sensitive to desiccation than ammonification. ► A reduction in gross N turnover rates can be expected in forest soils even at moderate desiccation.
    Keywords: 15n Pool Dilution Technique ; Norway Spruce ; Forest Soil ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 3
    Language: English
    In: Soil Biology and Biochemistry, February 2014, Vol.69, pp.320-327
    Description: Climate models predict warmer winter in temperate regions, but little is known about the temperature sensitivity of soil carbon (C) and nitrogen (N) mineralization at low temperatures. Here, we assess the temperature sensitivities of gross ammonification, gross nitrification, C and net N mineralization of top soil horizons, under a European beech and a Norway spruce temperate forest. We tested the hypotheses that (1) substrate quality affects the temperature sensitivity of C and N mineralization and (2) that temperature sensitivity of C mineralization is higher than of gross ammonification. Soil incubations were conducted at constant temperatures of −4, −1, +2, +5 and +8 °C. Gross ammonification and nitrification were measured by the N pool dilution technique. Temperature sensitivities of C, gross and net N mineralization were calculated using the Arrhenius equation and C mineralization was taken as proxy for substrate quality. Gross ammonification and C mineralization was much larger in the beech than in the spruce soil, while gross nitrification was in the same order of magnitude. Gross ammonification, nitrification and C mineralization almost ceased at −4 °C, but already increased at −1 °C. Net ammonification in Oi/Oe horizons was low at −4 and −1 °C and increased strongly between +2 and +8 °C. Net nitrification was low in both soils, but increased in the spruce soil at temperatures 〉2 °C whereas no temperature response occurred in the beech soil. Apparent values of gross ammonification and C mineralization in the temperature range of −4 to +8 °C were in the range of 3–18. were lowest in soil horizons of low substrate quality. The ratio of C mineralization to gross ammonification varied between 0.5 and 2.9, suggesting preferential mineralization of N rich organic substrates or rapid turnover of the N pool in microbial biomass. Rising winter temperatures might have substantial effects on net N mineralization, but effects decrease with soil depth, likely due to decreasing substrate quality of soil organic matter.
    Keywords: Winter Soil Temperatures ; Gross and Net N Mineralization ; Co2 Production ; Forest Soil ; Q10 ; Substrate Quality ; Substrate Availability ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, October 2014, Vol.77, pp.315-315
    Keywords: Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Source: ScienceDirect Journals (Elsevier)
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  • 5
    Language: English
    In: Wetlands, 2012, Vol.32(3), pp.579-587
    Description: Changes of water table level and oxygen supply affect the nitrogen (N) and carbon (C) mineralization of fen soils with potential consequences for the N and C sink and sources function of fens. Here we studied the response of gross N mineralization and CO 2 emissions to water table fluctuations in an acidic minerotrophic fen. In a laboratory study lasting 117 days, undisturbed soil cores were either a) permanently flooded or b) subject to flooding, water table drawdown and reflooding. In the permanently flooded cores the CO 2 emissions were constantly low, but gross ammonification and immobilization of NH 4 + increased after a lag phase of about 30 and 70 days, respectively. In the fluctuated cores, gross ammonification and NH 4 + immobilization first remained constant but then increased after water table drawdown of 30 days. Emission of CO 2 peaked immediately after water table drawdown, followed by a decrease and a second maximum after about 30 days. Following re-flooding, gross ammonification and immobilization of NH 4 + first decreased but recovered after about 30 days to the level of the permanently flooded cores. In contrast, the CO 2 emissions decreased immediately and permanently after re-flooding. The cumulative gross ammonification was larger in the permanently flooded cores than in the fluctuated cores. Rates of gross nitrification and immobilization of NO 3 − were generally low and did not respond to the treatments. The ratios of CO 2 emission/gross ammonification were in the range of 1 to 4 under anoxic condition which seems to be caused by fast N turnover in the microbial biomass pool and low rates of C-mineralization of soil organic matter. Our results indicate that water table fluctuations in fen soils affect N and C mineralization differently. Changes of water table of a few days likely have a bigger effect on C-mineralization than on gross N mineralization.
    Keywords: Gross ammonification ; C mineralization ; Wetland ; Fen soil ; Water table
    ISSN: 0277-5212
    E-ISSN: 1943-6246
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  • 6
    Language: English
    In: Journal of Plant Nutrition and Soil Science, August 2014, Vol.177(4), pp.566-572
    Description: In temperate forest soils, N net mineralization has been extensively investigated during the growing season, whereas N cycling during winter was barely addressed. Here, we quantified net ammonification and nitrification during the dormant season by and laboratory incubations in soils of a temperate European beech and a Norway spruce forest. Further, we compared temperature dependency of N net mineralization in field incubations with those from laboratory incubations at controlled temperatures. From November to April, N net mineralization of the organic and upper mineral horizons amounted to 10.9 kg N (ha · 6 months) in the spruce soil and to 44.3 kg N (ha · 6 months) in the beech soil, representing 65% (beech) and 26% (spruce) of the annual above ground litterfall. N net mineralization was largest in the Oi/Oe horizon and lowest in the A and EA horizons. Net nitrification in the beech soil [1.5 kg N (ha · 6 months)] was less than in the spruce soil [5.9 kg N (ha · 6 months)]. In the range of soil temperatures observed in the field (0–8°C), the temperature dependency of N net mineralization was generally high for both soils and more pronounced in the laboratory incubations than in the incubations. We suggest that homogenization of laboratory samples increased substrate availability and, thus, enhanced the temperature response of N net mineralization. In temperate forest soils, N net mineralization during the dormant season contributes substantially to the annual N cycling, especially in deciduous sites with large amounts of litterfall immediately before the dormant season. High Q values of N net mineralization at low temperatures suggest a huge effect of future increasing winter temperature on the N cycle in temperate forests.
    Keywords: Winter ; Net Ammonification ; Net Nitrification ; Incubation ; Norway Spruce ; European Beech
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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