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  • Dannenmann, Michael  (10)
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  • 1
    Language: English
    In: Applied and environmental microbiology, March 2010, Vol.76(6), pp.1831-41
    Description: The relationships between plant carbon resources, soil carbon and nitrogen content, and ectomycorrhizal fungal (EMF) diversity in a monospecific, old-growth beech (Fagus sylvatica) forest were investigated by manipulating carbon flux by girdling. We hypothesized that disruption of the carbon supply would not affect diversity and EMF species numbers if EM fungi can be supplied by plant internal carbohydrate resources or would result in selective disappearance of EMF taxa because of differences in carbon demand of different fungi. Tree carbohydrate status, root demography, EMF colonization, and EMF taxon abundance were measured repeatedly during 1 year after girdling. Girdling did not affect root colonization but decreased EMF species richness of an estimated 79 to 90 taxa to about 40 taxa. Cenococcum geophilum, Lactarius blennius, and Tomentella lapida were dominant, colonizing about 70% of the root tips, and remained unaffected by girdling. Mainly cryptic EMF species disappeared. Therefore, the Shannon-Wiener index (H') decreased but evenness was unaffected. H' was positively correlated with glucose, fructose, and starch concentrations of fine roots and also with the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC/DON), suggesting that both H' and DOC/DON were governed by changes in belowground carbon allocation. Our results suggest that beech maintains numerous rare EMF species by recent photosynthate. These EM fungi may constitute biological insurance for adaptation to changing environmental conditions. The preservation of taxa previously not known to colonize beech may, thus, form an important reservoir for future forest development.
    Keywords: Biodiversity ; Fagus -- Microbiology ; Fungi -- Classification ; Mycorrhizae -- Classification
    ISSN: 00992240
    E-ISSN: 1098-5336
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  • 2
    In: PLoS ONE, 2014, Vol.9(12)
    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, N 2 -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 N 2 O.
    Keywords: Research Article ; Biology And Life Sciences ; Ecology And Environmental Sciences
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: Soil Biology and Biochemistry, March 2013, Vol.58, pp.323-331
    Description: Our main objective was to trace and to quantify the stabilization of nitrogen released from litter decomposition in different functional soil organic matter fractions. To identify the fate of nitrogen in a free-range experiment, N-labeled beech litter was deposited on the bare soil surface of three 2 m × 2 m plots on a Rendzic Leptosol under beech ( L.) with mull humus form near Tuttlingen (Swabian Jura, Germany). The N composition of bulk soil and soil fractions was monitored for three years by sampling the litter layer and the Ah horizon (0–5, 5–10 cm) after 140, 507, and 876 d. A combined density and particle size fractionation procedure allowed the isolation of different functional soil organic matter fractions: free light fraction, occluded organic matter, and organo-mineral associations. The first flush in the N enrichment was observed in the bulk soil within 140 d, due to plant debris transferred to the free light fraction by probably bioturbation and soluble compounds being leached from the litter directly to the clay fractions. The observed rates within the first 140 d indicated a quick transfer of N-enriched compounds from litter into the free light fraction, with a rate of 0.07 μg kg  d , and to the clay fractions, with a rate of 0.31 μg kg  d . In contrast, transfer to the occluded light fractions was delayed, with rates of 0.01 μg kg  d (〉 20 μm) and 0.001 μg kg  d (〈 20 μm), respectively. After 876 d, we recovered 9% of the added label in the 0–10 cm soil horizon, of which more than 4% was found in the organo-mineral fraction (0–5 cm), nearly 3% in the light fractions (0–5 cm), and another 2% unspecified in the bulk soil of 5–10 cm depth. We therefore conclude that the clay fractions act as the main sink for the recovered N. The rapid incorporation and the high preservation of N in the clay fractions revealed the dominant role of organo-mineral associations in the stabilization of nitrogen in the investigated soil. ► Rapid transfer of N from litter into the clay fractions completed within 140 days. ► Dominant role of fine organo-mineral associations for stabilization of nitrogen. ► Occluded organic matter is protected by slow aggregate turnover. ► After 876 d, we recovered 9% of the added N label in the mineral soil (0–10 cm).
    Keywords: 15n ; Physical Fractionation ; Light Fraction ; Organo-Mineral Fraction ; Clay ; Fagus Sylvatica L ; Nitrogen Storage ; Field Experiment ; Transfer Rates ; Decomposition ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, January 2014, Vol.68, pp.241-251
    Description: Prolonged summer droughts are projected to occur as a consequence of climate change in Central Europe. The resulting reduced soil water availability may lead to alterations in rates of soil processes such as nitrogen partitioning among soil organic matter fractions and stabilization within soil. To study the effect of climate change-induced drought on (1) the distribution of nitrogen among soil organic matter fractions and (2) nitrogen stabilization, we performed a space-for-time climate change experiment. We transferred intact plant–soil–microbe mesocosms of a Rendzic Leptosol with a young beech tree from a slope with northwestern exposure in southern Germany characterized by a cool-moist microclimate across a narrow valley to a slope with southwestern exposure with a warm-dry microclimate, which reflects projected future climatic conditions. A control transfer was also done on the northwest-facing slope within the same area of origin. We combined a homogenous N labeling approach using ammonium nitrate with a physical fractionation procedure and chemical soil extraction protocols. Our aim was to follow the partitioning of N in different soil organic matter fractions, i.e. light fractions, organo-mineral fractions, and extractable soil fractions including microbial biomass, ammonium, nitrate, and dissolved organic nitrogen. Within less than one growing season, we observed a modified partitioning of recently applied inorganic N between different soil fractions in relation to drier summer conditions, with attenuated nitrogen turnover under drought and consequently significantly higher N concentrations in the relatively labile light fractions. We ascribed this effect to a decelerated mineralization immobilization turnover. We conclude that prolonged summer droughts may alter the stabilization dynamics because the induced inactivity of microorganisms may reduce the transfer of nitrogen to stabilization pathways. A retarded stabilization in organo-mineral associations enhances the risk of nitrogen losses during extreme rainfall events, which are projected to increase in the 21st century predicted by future climate change scenarios for Central Europe.
    Keywords: Nitrogen Stabilization ; Density Fractionation ; 15n Labeling ; Climate Change ; Fagus Sylvatica L ; Field Experiment ; Light Fraction ; Microbial Biomass ; Mineralization Immobilization Turnover ; Transplant Study ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    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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  • 6
    Language: English
    In: PLoS ONE, 01 January 2016, Vol.11(7), p.e0158823
    Description: European beech forests growing on marginal calcareous soils have been proposed to be vulnerable to decreased soil water availability. This could result in a large-scale loss of ecological services and economical value in a changing climate....
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 7
    Language: English
    In: Agriculture, Ecosystems and Environment, 01 August 2019, Vol.280, pp.118-128
    Description: Grassland management and climate change may have profound effects on soil organic carbon (SOC) storage in temperate grasslands, but to date only limited information on the long-term SOC development derived from grassland monitoring sites is available. In 1986, the established 20 long-term grassland soil monitoring sites in the state of Bavaria, Germany. We analyzed SOC changes and their main controlling factors in these monitoring sites between 1989 and 2016 in four intervals using the machine learning algorithm conditional random forest. The results showed that changes of SOC stocks in grassland monitoring sites were affected by the multifactorial and interactive nature of changing climate conditions, pedogenic-topographic factors and management practices. Seasonal climate variables explained the highest variability of SOC stock changes in long-term grassland sites, followed by organic fertilizer application. Increasing autumn precipitation led to decreased SOC stocks, whereas increasing spring and summer precipitation led to increased SOC stocks on sites at high elevations with low slopes. Furthermore, we observed that the organic fertilizer application resulted in an increase and/or preservation of SOC stocks, whereas conventional farming with a low degree of organic fertilization resulted in SOC stock decreases. Regarding the acceleration of climate change and the complex interactions between site conditions, changing climate and management, there is an urgent need to collect improved management data in future long-term studies.
    Keywords: Random Forest ; Climate Change ; Seasonal Carbon Change ; Grassland Management ; Long-Term Experiments ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
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  • 8
    Language: English
    In: Functional plant biology FPB, 2010, Vol.37(9), pp.879-889
    Description: The goal of this work was to increase the understanding of factors regulating nitrogen (N) competition between roots and soil microbes. For this purpose, root assimilate supply was diminished or abolished in beech (Fagus sylvatica L.) seedlings by girdling, drought stress or a combination of both factors. This was revealed by ¹³C tracer abundance in root tips after ¹³CO₂ pulse labelling of the shoots. Analysis of different root tip fractions revealed that only 6% were ectomycorrhizal. Carbon (C) allocation to ectomycorrhizal and vital non-mycorrhizal root tips was ~26% higher than to distorted root tips. Drought resulted in ~30% increased ammonium (NH₄⁺) and amino acid concentrations in roots and ~65% increased soil NH₄⁺ concentrations, probably because of lower consumption of NH₄⁺ by free-living microorganisms. Root uptake of glutamine of 13nmolg⁻¹ fresh mass h⁻¹ decreased 2-fold with drought, although the number of vital root tips did not decrease. Carbon content in biomass of free-living microbes increased with glucose application regardless of drought, resulting in significant depletion in soil nitrate (NO₃⁻), root NH₄⁺ and amino acid concentrations. Our results suggest that the root-soil system of young beech trees was C-limited, and this prevented amino acid metabolism in roots and microbial NO₃⁻ consumption in the soil, thereby exerting feedback inhibition on uptake of inorganic N by roots. We suggest that rhizodeposition is a key link in regulating the plant-microbial N balance. ; Includes references ; p. 879-889.
    Keywords: Root Tips ; Nutrient Availability ; Amino Nitrogen ; Mycorrhizal Fungi ; Soil Fertility ; Roots ; Rhizosphere ; Nitrate Nitrogen ; Fagus Sylvatica ; Forest Trees ; Phloem ; Photosynthates ; Stable Isotopes ; Ammonium Nitrogen ; Nitrogen ; Drought ; Soil Microorganisms ; Amino Acids ; Glucose ; Nutrient Uptake ; Girdling ; Ectomycorrhizae ; Plant Nutrition ; Plant-Microorganism Interactions
    ISSN: 1445-4408
    E-ISSN: 14454416
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  • 9
    Language: English
    In: Soil Biology and Biochemistry, 2009, Vol.41(8), pp.1622-1631
    Description: Nitrogen (N) cycling in terrestrial ecosystems is complex since it involves the closely interwoven processes of both N uptake by plants and microbial turnover of a variety of N metabolites. Major interactions between plants and microorganisms involve competition for the same N species, provision of plant nutrients by microorganisms and labile carbon (C) supply to microorganisms by plants via root exudation. Despite these close links between microbial N metabolism and plant N uptake, only a few studies have tried to overcome isolated views of plant N acquisition or microbial N fluxes. In this study we studied competitive patterns of N fluxes in a mountainous beech forest ecosystem between both plants and microorganisms by reducing rhizodeposition by tree girdling. Besides labile C and N pools in soil, we investigated total microbial biomass in soil, microbial N turnover (N mineralization, nitrification, denitrification, microbial immobilization) as well as microbial community structure using denitrifiers and mycorrhizal fungi as model organisms for important functional groups. Furthermore, plant uptake of organic and inorganic N and N metabolite profiles in roots were determined. Surprisingly plants preferred organic N over inorganic N and nitrate (NO ) over ammonium (NH ) in all treatments. Microbial N turnover and microbial biomass were in general negatively correlated to plant N acquisition and plant N pools, thus indicating strong competition for N between plants and free living microorganisms. The abundance of the dominant mycorrhizal fungi was negatively correlated to total soil microbial biomass but positively correlated to glutamine uptake by beech and amino acid concentration in fine roots indicating a significant role of this mycorrhizal fungus in the acquisition of organic N by beech. Tree girdling in general resulted in a decrease of dissolved organic carbon and total microbial biomass in soil while the abundance of remained unaffected, and N uptake by plants was increased. Overall, the girdling-induced decline of rhizodeposition altered the competitive balance of N partitioning in favour of beech and its most abundant mycorrhizal symbiont and at the expense of heterotrophic N turnover by free living microorganisms in soil. Similar to tree girdling, drought periods followed by intensive drying/rewetting events seemed to have favoured N acquisition by plants at the expense of free living microorganisms.
    Keywords: N Mineralization ; Nitrification ; Denitrification ; Microbial Immobilization ; Plant N Uptake ; Amino Acid ; Beech ; Competition ; N Metabolite Profiling ; Mycorrhiza ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 10
    Language: English
    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 DANN and RNA directly extracted from soil. Abundance of the transcripts was reduced under climate change with most pronounced effects for denitrification. Our results...
    Source: DataCite
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