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  • Elsevier (CrossRef)  (28)
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  • 1
    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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  • 2
    Language: English
    In: Soil Biology and Biochemistry, July 2017, Vol.110, pp.1-7
    Description: Previous work has shown that the drying/rewetting (D/W) of soils mobilizes phosphorus (P), and that the effect of D/W on P release likely depends on the soil microbial community composition. We tested the hypotheses that (i) P release after D/W from fungi is lower than from bacteria and that (ii) gram-positive bacteria are less susceptible to D/W than gram-negative bacteria. We investigated the release of dissolved organic (DOP) and inorganic phosphorus (DIP) from bacterial and fungal biomass after rewetting of an artificial soil that was desiccated to different degrees. For this purpose, sterilized soil amended with growth medium was inoculated separately with one of two bacterial strains ( gram-negative and gram-positive) or with one fungal strain ( ). The bacterial strains were grown for 7 days, the fungus for 25 days at 50% soil water holding capacity. After the pre-incubation period, microbial biomass P (Pmic) was determined by chloroform fumigation extraction, and soils were desiccated at 20 °C for 5–8 days until pF 6 (−100 MPa) was reached, while the controls were kept permanently at 50% water holding capacity. At different degrees of desiccation, samples were destructively harvested and soils were extracted with water to measure the release of DIP and DOP. The net release of total dissolved P per unit Pmic following D/W was in the order  =  In case of , net release started already after desiccation to pF 4 (−1.0 MPa) and increased with further desiccation. For and , a tendency for net release was only observed after severe desiccation up to pF 6. Our results suggest that the effect of D/W on P release from microbial biomass depends largely on the microbial community composition, with fungi and gram-positive bacteria being less susceptible to D/W than gram-negative bacteria.
    Keywords: Drying–Rewetting ; Dissolved Phosphorus ; Soil Microbial Biomass ; Saprotrophic Fungi ; Gram-Positive Bacteria ; Gram-Negative Bacteria ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 3
    Language: English
    In: Forest Ecology and Management, 15 December 2013, Vol.310, pp.110-119
    Description: Climate models predict increasing frequency and intensity of summer drought events for Central Europe. In a field experiment, we investigated the response of young beech ( L.) to extreme and repeated summer drought and the modulation of drought response patterns along the natural gradient of light availability at the study site. In autumn 2008, two-year-old, nursery derived beech – as used for forest conversion practices – was planted under a Norway spruce stand primarily opened through winter storm. Precipitation was manipulated in the growing seasons of 2009 through 2011, inducing a pronounced gradient of water availability. Individual drought-stress doses (DSD) and light doses (LD) were calculated for each beech sapling during the three growing seasons. Plant growth, CO -assimilation rate and stomatal conductance were reduced with increasing drought stress, but facilitated by increasing light availability. Progressive acclimation to water and light limitation during the three years of the experiment led to a decreased drought and shade sensitivity of diameter growth. Water-use efficiency, root/shoot ratio and rooting depth, were increased with decreasing water availability. Mean fine root diameter and specific fine root length correlated positively with both DSD and LD. Proceeding low-light acclimation was indicated by progressively increasing specific leaf area and reduced leaf dark-respiration. Present results suggest that nursery-induced high-light acclimation of the beech saplings, exacerbated light limitation upon transplant and hence productivity decline under co-occurring water limitation.
    Keywords: European Beech ; Drought ; Light ; Restoration ; Acclimation ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, December 2016, Vol.103, pp.380-387
    Description: Hydraulic redistribution (HR) of water from wet to dry soil compartments by non-differentiated mycelium was recently shown for the saprotrophic fungus . The redistributed water triggered the carbon (C) mineralization in the dry soil. The potential of other saprotrophic fungal species and their mycelia networks for HR in soils is unknown. Here, we tested the potential for HR of the mycelial cord forming species compared it to capillary water transport in a sandy soil and assessed the impact of HR on C mineralization and enzyme activities in mesocosm experiments with dry and wet soil compartments using labeled water ( H) and labeled organic substrate ( C, N). Further, we determined nitrogen (N) translocation between the soil compartments by the mycelium of and . The flow velocity of redistributed water in single hyphae of was about 0.43 cm min which is 1.5–2 times higher than in hyphae of , suggesting that cords enhance fungal HR. The amount of redistributed water was similar to capillary transport in the sterile sandy soil. Despite greater potential for HR, only slightly increased C mineralization and enzyme activity in the dry soil within 7 days. translocated N towards the organic substrate in the dry soil and used it for hyphal growth whereas redistributed N within the mycelial network towards the wet soil. Our results suggest that fungal hyphae have the potential to overcome capillary barriers between dry and wet soil compartments via HR and that the impact of fungal HR on C mineralization and N translocation is related to the foraging strategy and the resource usage of the fungus species.
    Keywords: Saprotrophic Fungi ; Hydraulic Redistribution ; Drought ; Carbon Mineralization ; Nitrogen Translocation ; Foraging Strategy ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    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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  • 6
    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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  • 7
    Language: English
    In: Forest Ecology and Management, 15 October 2016, Vol.378, pp.181-192
    Description: Decomposition rates of coarse woody debris (CWD) have been investigated in many studies, however data on fungal biomass and the related enzymatic activities in decomposing CWD are scarce. Here, we investigated the relations between fungal biomass, enzyme activities and CWD properties in sap- and heartwood of decomposing logs of 13 different temperate European tree species, exposed for 6 years on the ground. Fungal biomass was significantly higher in sapwood than in heartwood and higher in deciduous than in coniferous species, and represented 0.3–4.4% of CWD dry mass. In deciduous sapwood, fungal biomass may represent up to 29% of the total N stock in CWD. Fungal biomass correlated positively with the N content of CWD and, in heartwood, negatively with extractives. Enzyme activities were higher in deciduous than in coniferous CWD and for hydrolases higher in sapwood than in heartwood. Correlations between enzyme activities and the ergosterol content were generally weak. Hydrolytic enzymes were frequently found in all decaying tree species, whereas ligninolytic oxidoreductases showed high variability specifically in deciduous wood. Fungal biomass and enzymatic activities confirm the assumption that, in the initial stage, the decomposition of deciduous CWD is faster than of coniferous CWD under comparable conditions.
    Keywords: Dead Wood Decomposition ; Temperate Forests ; Lignocellulolytic Enzymes ; Nitrogen Content ; Deciduous and Coniferous Trees ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 8
    Language: English
    In: Soil Biology and Biochemistry, 2011, Vol.43(8), pp.1742-1745
    Description: Dissolved organic nitrogen (DON) plays a key role in the N cycle of many ecosystems, as DON availability and biodegradation are important for plant growth, microbial metabolism and N transport in soils. However, biodegradation of DON (defined as the sum of mineralization and microbial immobilization) is only poorly understood. In laboratory incubations, biodegradation of DON and dissolved organic carbon (DOC) from Oi and Oa horizons of spruce, beech and cypress forests ranged from 6 to 72%. Biodegradation of DON and DOC was similar in most samples, and mineralization of DON was more important than microbial immobilization. Nitrate additions (0–10 mg N L ) never influenced either DON immobilization by microorganisms or mineralization. We conclude that soil microorganisms do not necessarily prefer mineral N over DON for meeting their N demand, and that biodegradation of DON seems to be driven by the microbial demand for C rather than N. Quantifying the dynamics of DON in soils should include consideration of both C and N demands by microbes. ► Biodegradation of dissolved organic nitrogen (DON) and carbon (DOC) was similar. ► Mineralization of DON was more important than microbial immobilization. ► Nitrate additions never influenced either DON immobilization or mineralization. ► DOC and DON they should be considered as a single pool of dissolved organic matter.
    Keywords: Dissolved Organic Nitrogen ; Dissolved Organic Carbon ; Nitrate ; Biodegradation ; Mineralization ; Microbial Immobilization ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 9
    Language: English
    In: Science of the Total Environment, 2007, Vol.377(2), pp.308-318
    Description: The fate and behaviour of total arsenic (As) and of As species in soils is of concern for the quality of drinking water. To estimate the relevance of organic As species and the mobility of different As species, we evaluated the vertical distribution of organic and inorganic As species in two uncontaminated and two contaminated upland soils. Dimethylarsinic acid (up to 6 ng As g ), trimethylarsine oxide (up to 1.5 ng As g ), 4 unidentified organic As species (up to 3 ng As g ) and arsenobetaine (up to 15 ng As g ), were detected in the forest soils. Arsenobetaine was the dominant organic As species in both unpolluted and polluted forest soils. No organic As species were detected in the contaminated grassland soil. The organic As species may account for up to 30% of the mobile fraction in the unpolluted forest floor, but never exceed 9% in the unpolluted mineral soil. Highest concentrations of organic As species were found in the forest floors. The concentrations of extractable arsenite were highest in the surface horizons of all soils and may represent up to 36% of total extractable As. The concentrations of extractable arsenate were also highest in the Oa layers in the forest soils and decreased steeply in the mineral soil. In conclusion, the investigated forest soils contain a number of organic As species. The organic As species in forest soils seem to result from throughfall and litterfall and are retained mostly in the forest floor. The relative high concentrations of extractable arsenite, one of the most toxic As species, and arsenate in the forest floor point to the risk of their transfer to surface water by superficial flow under heavy rain events.
    Keywords: Arsenic Speciation ; Forest Soil ; Forest Floor ; Grassland Soil ; Mobility ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 10
    Language: English
    In: Geoderma, 15 January 2018, Vol.310, pp.163-169
    Description: The release of dissolved organic matter (DOM) in forest floors is a dynamic component of organic carbon transformations in forest soils. The biogeochemical processes driving the production and release of dissolved organic carbon and nitrogen (DOC and DON) in forest floors are strongly affected by hydroclimatic conditions during rainfall events. We conducted an exhaustive percolation experiment to examine the pool size and sustained production of mobilizable DOC and DON in Oi, Oe and Oa layers of spruce, larch and beech forest floors. The percolation experiment with small reconstructed soil columns was conducted at 5 and 15 °C for 25 days with a percolation volume equal to 36 mm d , adding up to a total percolation volume of 900 mm. Percolates were collected at an interval of 5 days and analyzed for DOC and DON. Simultaneously to the periodic analysis of percolates, the CO release was measured. The sustained release of DOM during the last leaching period from day 20 to 25, after 720 mm of percolation, was defined as the . The cumulative release of DOM was large: in case of the 15 °C treatment, the total amount of DOM extracted for 25 days was on average 1.6% and 2.2% of the total C and N stock, respectively. The largest cumulative release of DOM and CO was observed for the beech samples. The ratio of cumulative CO /cumulative DOC release ranged from 1 to 3 for Oi and Oe samples but was 〈 0.2 for spruce Oa. No changes in DOC/DON ratios as a result of percolation amount were detected. The production rates indicated a rapid replenishment of DOM pools after leaching. The Q values for the DOM production rates ranged from 2 to 4 and were similar to those for CO production. The positive correlation between DOM and CO production rates in Oi and Oe samples highlights the importance of microbial activity for DOM release. The pool of mobilizable DOM in forest floors seems large enough to provide a sustained rate of DOM release throughout precipitation events under field conditions although the actual rate of mobilization may vary in the field, depending on antecedent conditions and the duration and intensity of the rainfall event.
    Keywords: Dissolved Organic Carbon (Doc) ; Dissolved Organic Nitrogen (Don) ; Forest Floor ; Soil Respiration ; Q10 ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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