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Berlin Brandenburg

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  • 1
    Language: English
    In: Plant and Soil, 2011, Vol.343(1), pp.5-15
    Description: Fire is a major disturbance in shrubland ecosystems of the Mediterranean basin, with high potential to alter ecosystem nitrogen (N) stocks and N cycling. However, postfire effects on gross rates of soil N turnover (ammonification, nitrification, microbial immobilization, denitrification) have rarely been investigated. We determined gross rates of N turnover including nitrous oxide fluxes and dinitrogen emissions in the mineral soil of unburned and burned shrublands of Southern Italy 6 months after a natural fire. In soil of burned plots, both gross ammonification and gross nitrification were significantly higher than in soil of unburned plots (2.2 ± 0.3 versus 0.6 ± 0.1 mg N kg −1 sdw day −1 for ammonification and 1.1 ± 0.1 versus 0.5 ± 0.1 mg N kg −1 sdw day −1 for nitrification). Microbial immobilization, in particular of nitrate, could not compensate for the increase in inorganic N production, therefore soil nitrate concentrations were considerably higher at the burned plots. Soil microbial biomass carbon and nitrogen concentrations were significantly lower in soils of burned plots than in soils of unburned plots. Dinitrogen was the dominant end product of denitrification and emitted at higher rates from the unburned plots than from the burned plots (0.094 ± 0.003 versus 0.004 ± 0.002 mg N kg −1 sdw day −1 , while there was no net nitrous oxide flux (burned plots) or slight net nitrous oxide uptake (control plots). These results show that postfire patterns of gross N turnover in soil can exhibit a significant reduction of both microbial N retention and N gas losses via denitrification.
    Keywords: Maquis ; Fire ; N cycling ; Ammonification ; Nitrification ; Denitrification ; Nitrous oxide ; Dinitrogen ; Microbial biomass ; He flow soil core technique
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: PloS one, 2014, Vol.9(12), pp.e114278
    Description: Ongoing climate change will lead to more extreme weather events, including severe drought periods and intense drying rewetting cycles. This will directly influence microbial nitrogen (N) turnover rates in soil by changing the water content and the oxygen partial pressure. Therefore, a space for time climate change experiment was conducted by transferring intact beech seedling-soil mesocosms from a northwest (NW) exposed site, representing today's climatic conditions, to a southwest (SW) exposed site, providing a model climate for future conditions with naturally occurring increased soil temperature (+0.8°C in average). In addition, severe drought and intense rainfall was simulated by a rainout shelter at SW and manual rewetting after 39 days drought, respectively. Soil samples were taken in June, at the end of the drought period (August), 24 and 72 hours after rewetting (August) and after a regeneration period of four weeks (September). To follow dynamics of bacterial and archaeal communities involved in N turnover, abundance and activity of nitrifiers, denitrifiers, N2-fixing microbes and N-mineralizers was analyzed based on marker genes and the related transcripts by qPCR from DNA and RNA directly extracted from soil. Abundance of the transcripts was reduced under climate change with most pronounced effects for denitrification. Our results revealed that already a transfer from NW to SW without further treatment resulted in decreased cnor and nosZ transcripts, encoding for nitric oxide reductase and nitrous oxide reductase, respectively, while nirK transcripts, encoding for nitrite reductase, remained unaffected. Severe drought additionally led to reduced nirK and cnor transcripts at SW. After rewetting, nirK transcripts increased rapidly at both sites, while cnor and nosZ transcripts increased only at NW. Our data indicate that the climate change influences activity pattern of microbial communities involved in denitrification processes to a different extend, which may impact emission rates of the greenhouse gas N2O.
    Keywords: Climate Change ; Soil ; Archaea -- Metabolism ; Bacteria -- Metabolism ; Fagus -- Metabolism ; Nitrogen -- Metabolism
    E-ISSN: 1932-6203
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  • 3
    In: New Phytologist, July 2013, Vol.199(2), pp.520-528
    Description: The spatiotemporal dynamics of, and interspecific differences in, the acquisition of litter‐derived nitrogen (N) by natural assemblages of ectomycorrhizal root tips are poorly understood. Small cylindrical mesh bags containing 15N‐labelled beech (Fagus sylvatica) leaf litter that permit hyphal but not root ingrowth were inserted vertically into the top soil layer of an old‐growth beech forest. The lateral transfer of 15N into the circumjacent soil, roots, microbes and ectomycorrhizas was measured during an 18‐month exposure period. Ectomycorrhial fungi (EMF) showed large interspecific variation in the temporal pattern and extent of 15N accumulation. Initially, when N was mainly available from the leachate, microbes were more efficient at N immobilization than the majority of EMF, but distinct fungal species also showed significant 15N accumulation. During later phases, the enrichment of 15N in Tomentella badia was higher than in microbes and other EMF species. Roots and soil accumulated 15N with a large delay compared with microbes and EMF. Because approximately half of the studied fungal species had direct access to N from leaf litter and the remainder to N from leached compounds, we suggest that EMF diversity facilitates the N utilization of the host by capturing N originating from early‐released solutes and late degradation products from a recalcitrant source.
    Keywords: ‐Labelled Leaf Litter ; Deciduous Forest ; Ectomycorrhiza ; Microbes ; Nitrogen Uptake ; Roots ; Soil ; Stable Isotopes
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 4
    In: Nature, 2010, Vol.464(7290), p.881
    Description: Atmospheric concentrations of the greenhouse gas nitrous oxide ([N.sub.2]O) have increased significantly since pre-industrial times owing to anthropogenic perturbation of the global nitrogen cycle (1,2), with animal production being one of the main contributors (3). Grasslands cover about 20 per cent of the temperate land surface of the Earth and are widely used as pasture. It has been suggested that high animal stocking rates and the resulting elevated nitrogen input increase [N.sub.2]O emissions (4-7). Internationally agreed methods to upscale the effect of increased livestock numbers on [N.sub.2]O emissions are based directly on per capita nitrogen inputs (8). However, measurements of grassland [N.sub.2]O fluxes are often performed over short time periods (9), with low time resolution and mostly during the growing season. In consequence, our understanding of the daily and seasonal dynamics of grassland [N.sub.2]O fluxes remains limited. Here we report year-round [N.sub.2]O flux measurements with high and low temporal resolution at ten steppe grassland sites in Inner Mongolia, China. We show that short-lived pulses of [N.sub.2]O emission during spring thaw dominate the annual [N.sub.2]O budget at our study sites. The [N.sub.2]O emission pulses are highest in ungrazed steppe and decrease with increasing stocking rate, suggesting that grazing decreases rather than increases [N.sub.2]O emissions. Our results show that the stimulatory effect of higher stocking rates on nitrogen cycling (4,7) and, hence, on [N.sub.2]O emission is more than offset by the effects of a parallel reduction in microbial biomass, inorganic nitrogen production and wintertime water retention. By neglecting these freeze-thaw interactions, existing approaches may have systematically overestimated [N.sub.2]O emissions over the last century for semi-arid, cool temperate grasslands by up to 72 per cent.
    Keywords: Biogeochemical Cycles -- Observations ; Nitrous Oxide -- Environmental Aspects ; Atmospheric Carbon Dioxide -- Properties ; Grasslands -- Natural History ; Greenhouse Gases -- Properties ; Livestock Industry -- Environmental Aspects ; Air Pollution Research -- Methods;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 5
    Language: English
    In: Applied and Environmental Microbiology, Sept 1, 2015, Vol.81(17), pp.5957-5967
    Description: Study is conducted to test the hypothesis that ectomycorrhizal communities and the free-living rhizosphere microbes from beech trees from sites with two distinct climatic conditions shows differences in N acquisition. To test these hypotheses, young trees from dryer conditions and also from cooler, moist climate conditions are transplanted and it concluded that the ectomycorrhizal community influences N transfer to its host and fungal community from dry condition are efficient in N acquisition.
    Keywords: Mycorrhizae – Research ; Mycorrhizae – Physiological Aspects ; Beeches – Research ; Beeches – Physiological Aspects
    ISSN: 0099-2240
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Forest Ecology and Management, 2011, Vol.262(2), pp.105-114
    Description: ► Competition for N between young and adult beech is reduced by seasonal timing. ► Beech seedlings favour N uptake in spring, adult beech trees in autumn. ► Removal of vegetation components does not play a role in this competition. ► Competition between plants and soil microorganisms is, therefore, not avoided. Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e., seedlings, mature trees, other woody and herbaceous understorey). This study investigated in a field experiment whether the competition for N between different vegetation components in beech forests was prevented via seasonal timing of N uptake and affected by microbial N use. For this purpose, a removal approach was used to study the seasonal effects on N uptake and N metabolites in adult beech trees and beech natural regeneration, as well as soil microbial processes of inorganic N production and utilisation. We found that the competition for N between beech natural regeneration and mature beech trees was reduced by seasonal avoidance strategies (“good parenting”) of N uptake regardless of the N sources used. In spring, organic and inorganic N uptake capacity was significantly higher in beech seedlings compared to adult beech trees, whereas in autumn mature beech trees showed the highest N uptake rates. Removal of vegetation components did not result in changes in soil microbial N processes in the course of the growing season. Thus, N resources released by the removal of vegetation components were marginal. This consistency in soil microbial N processes indicates that competition between plants and soil microorganisms for N was not avoided by timing of acquisition during the vegetation period, but existed during the entire growing season. In conclusion, N nutrition in the studied forest ecosystem seems to be optimally attuned to European beech.
    Keywords: Fagus Sylvatica ; N Uptake ; N Metabolites ; Soil Microorganisms ; Soil N Processes ; Removal Approach ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 7
    In: PLoS ONE, 2015, Vol.10(5)
    Description: Bioturbation contributes to soil formation and ecosystem functioning. With respect to the active transport of matter by voles, bioturbation may be considered as a very dynamic process among those shaping soil formation and biogeochemistry. The present study aimed at characterizing and quantifying the effects of bioturbation by voles on soil water relations and carbon and nitrogen stocks. Bioturbation effects were examined based on a field set up in a luvic arenosol comprising of eight 50 × 50 m enclosures with greatly different numbers of common vole ( Microtus arvalis L., ca. 35–150 individuals ha –1 mth –1 ). Eleven key soil variables were analyzed: bulk density, infiltration rate, saturated hydraulic conductivity, water holding capacity, contents of soil organic carbon (SOC) and total nitrogen (N), CO2 emission potential, C/N ratio, the stable isotopic signatures of 13 C and 15 N, and pH. The highest vole densities were hypothesized to cause significant changes in some variables within 21 months. Results showed that land history had still a major influence, as eight key variables displayed an additional or sole influence of topography. However, the δ 15 N at depths of 10–20 and 20–30 cm decreased and increased with increasing vole numbers, respectively. Also the CO2 emission potential from soil collected at a depth of 15–30 cm decreased and the C/N ratio at 5–10 cm depth narrowed with increasing vole numbers. These variables indicated the first influence of voles on the respective mineralization processes in some soil layers. Tendencies of vole activity homogenizing SOC and N contents across layers were not significant. The results of the other seven key variables did not confirm significant effects of voles. Thus overall, we found mainly a first response of variables that are indicative for changes in biogeochemical dynamics but not yet of those representing changes in pools.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 8
    Language: English
    In: Plant and Soil, 2013, Vol.368(1), pp.519-534
    Description: Background and aims: Litter decomposition is regulated by e.g. substrate quality and environmental factors, particularly water availability. The partitioning of nutrients released from litter between vegetation and soil microorganisms may, therefore, be affected by changing climate. This study aimed to elucidate the impact of litter type and drought on the fate of litter-derived N in beech seedlings and soil microbes. Methods: We quantified super(15)N recovery rates in plant and soil N pools by adding super(15)N-labelled leaf and/or root litter under controlled conditions. Results: Root litter was favoured over leaf litter for N acquisition by beech seedlings and soil microorganisms. Drought reduced super(15)N recovery from litter in seedlings thereby affecting root N nutrition. super(15)N accumulated in seedlings in different sinks depending on litter type. Conclusions: Root turnover appears to influence (a) N availability in the soil for plants and soil microbes and (b) N acquisition and retention despite a presumably extremely dynamic turnover of microbial biomass. Compared to soil microorganisms, beech seedlings represent a very minor short-term N sink, despite a potentially high N residence time. Furthermore, soil microbes constitute a significant N pool that can be released in the long term and, thus, may become available for N nutrition of plants.
    Keywords: Litter types ; Root litter ; Leaf litter ; Decomposition ; Microbial biomass ; Plant N metabolism ; Soil N pools ; N recovery
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 9
    Language: English
    In: Soil Biology and Biochemistry, April 2016, Vol.95, pp.8-10
    Description: Both storage and sieving of soil samples are still common practices but may alter rates of gross N mineralization and nitrification. In this study, gross N turnover rates of stored (ambient temperature) and incubated intact and sieved soil from an African tropical lower montane forest were compared. Our results revealed that sieving increases N mineralization and storage stimulates nitrification. Therefore, we conclude that for tropical soils storage under ambient temperature conditions as well as sieving of soil samples can cause large biases in measured gross N turnover rates and ratios, limiting cross-site comparisons.
    Keywords: Gross N Mineralization ; Gross Nitrification ; 15n Pool Dilution ; Tropical Forest ; Soil N Cycling ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 10
    Language: English
    In: Plant and Soil, 2013, Vol.369(1), pp.657-668
    Description: Aims: Our aims were to characterize the fate of leaf-litter-derived nitrogen in the plant-soil-microbe system of a temperate beech forest of Southern Germany and to identify its importance for N nutrition of beech seedlings. Methods: super(15)N-labelled leaf litter was traced in situ into abiotic and biotic N pools in mineral soil as well as into beech seedlings and mycorrhizal root tips over three growing seasons. Results: There was a rapid transfer of super(15)N into the mineral soil already 21 days after tracer application with soil microbial biomass initially representing the dominant litter-N sink. However, super(15)N recovery in non-extractable soil N pools strongly increased over time and subsequently became the dominant super(15)N sink. Recovery in plant biomass accounted for only 0.025 % of super(15)N excess after 876 days. After three growing seasons, super(15)N excess recovery was characterized by the following sequence: non-extractable soil N〉〉extractable soil N including microbial biomass〉〉plant biomass〉ectomycorrhizal root tips. Conclusions: After quick vertical dislocation and cycling through microbial N pools, there was a rapid stabilization of leaf-litter-derived N in non-extractable N pools of the mineral soil. Very low super(15)N recovery in beech seedlings suggests a high importance of other N sources such as root litter for N nutrition of beech understorey.
    Keywords: Nitrogen cycling ; Beech ; 15N-labelled leaf litter ; 15N tracing ; Microbial biomass ; Ectomycorrhiza
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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