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  • 1
    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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  • 2
    Language: English
    In: Plant and Soil, 2013, Vol.364(1), pp.287-301
    Description: Background and aims: Nitrous oxide (N sub(2)O) and methane (CH sub(4)) can be emitted from surfaces of riparian plants. Data on the emission of these greenhouse gases by upland trees are scarce. We quantified CH sub(4) and N sub(2)O emissions from stems of Fagus sylvatica, an upland tree, and Alnus glutinosa, a riparian tree. Methods: The gas fluxes were investigated in mesocosms under non-flooded control conditions and during a flooding period using static chamber systems and gas chromatographic analyses. Results: Despite differences in the presence of an aerenchyma system, both tree species emitted N sub(2)O and CH sub(4) from the stems. Flooding caused a dramatic transient increase of N sub(2)O stem emissions by factors of 740 (A. glutinosa) and even 14,230 (F. sylvatica). Stem emissions of CH sub(4) were low and even deposition was determined (F. sylvatica controls). The results suggest that CH sub(4) was transported mainly through the aerenchyma, whereas N sub(2)O transport occurred in the xylem sap. Conclusions: For the first time it has been demonstrated that upland trees such as F. sylvatica clearly significantly emit N sub(2)O from their stems despite lacking an aerenchyma. If this result is confirmed in adult trees, upland forests may constitute a new and significant source of atmospheric N sub(2)O.
    Keywords: Methane ; Nitrous oxide ; Soil and stem emission ; Alnus glutinosa ; Fagus sylvatica ; Flooding
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 3
    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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  • 4
    Language: English
    In: Environmental Pollution, Oct, 2011, Vol.159(10), p.2467(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.envpol.2011.06.025 Byline: Xing Wu (a)(b), Nicolas Bruggemann (c), Rainer Gasche (a), Hans Papen (a), Georg Willibald (a), Klaus Butterbach-Bahl (a) Abstract: Based on multi-year measurements of CH.sub.4 exchange in sub-daily resolution we show that clear-cutting of a forest in Southern Germany increased soil temperature and moisture and decreased CH.sub.4 uptake. CH.sub.4 uptake in the first year after clear-cutting (-4.5 [+ or -] 0.2 [mu]g C m.sup.-2 h.sup.-1) was three times lower than during the pre-harvest period (-14.2 [+ or -] 1.3 [mu]g C m.sup.-2 h.sup.-1). In contrast, selective cutting did not significantly reduce CH.sub.4 uptake. Annual mean uptake rates were -1.18 kg C ha.sup.-1 yr.sup.-1 (spruce control), -1.16 kg C ha.sup.-1 yr.sup.-1 (selective cut site) and -0.44 kg C ha.sup.-1 yr.sup.-1 (clear-cut site), respectively. Substantial seasonal and inter-annual variations in CH.sub.4 fluxes were observed as a result of significant variability of weather conditions, demonstrating the need for long-term measurements. Our findings imply that a stepwise selective cutting instead of clear-cutting may contribute to mitigating global warming by maintaining a high CH.sub.4 uptake capacity of the soil. Author Affiliation: (a) Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Kreuzeckbahnstrasse 19, Garmisch-Partenkirchen, Germany (b) State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, 100085 Beijing, China (c) Forschungszentrum Julich GmbH, Agrosphere Institute (IBG-3), Leo-Brandt-Strasse, 52425 Julich, Germany Article History: Received 14 February 2011; Revised 10 June 2011; Accepted 19 June 2011
    Keywords: Weather ; Global Warming ; Methane
    ISSN: 0269-7491
    E-ISSN: 18736424
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Environmental Pollution, October 2011, Vol.159(10), pp.2467-2475
    Description: Based on multi-year measurements of CH exchange in sub-daily resolution we show that clear-cutting of a forest in Southern Germany increased soil temperature and moisture and decreased CH uptake. CH uptake in the first year after clear-cutting (−4.5 ± 0.2 μg C m  h ) was three times lower than during the pre-harvest period (−14.2 ± 1.3 μg C m  h ). In contrast, selective cutting did not significantly reduce CH uptake. Annual mean uptake rates were −1.18 kg C ha  yr (spruce control), −1.16 kg C ha  yr (selective cut site) and −0.44 kg C ha  yr (clear-cut site), respectively. Substantial seasonal and inter-annual variations in CH fluxes were observed as a result of significant variability of weather conditions, demonstrating the need for long-term measurements. Our findings imply that a stepwise selective cutting instead of clear-cutting may contribute to mitigating global warming by maintaining a high CH uptake capacity of the soil. ► Long-term, sub-daily measurements of CH exchange at differently managed forest sites. ► Inter-annual variability in CH uptake is affected by annual precipitation. ► Clear-cutting reduces the CH sink strength of forest soils, whereas thinning has no significant effect. ► Sink strength changes due to clear cutting are long-term and were still present approx. nine years following forest harvest. Forest management affects the soil CH sink strength, with clear-cutting reducing uptake rates for at least eight years.
    Keywords: Methane ; Clear-Cutting ; Selective Cutting ; Soil Temperature ; Wfps ; Inter-Annual Variability ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 6
    Language: English
    In: Plant and Soil, 2006, Vol.287(1), pp.279-300
    Description: The effects of forest management (thinning) on gross and net N conversion, the balance of inorganic N production and consumption, inorganic N concentrations and on soil microbial biomass in the Ah layer were studied in situ during eight intensive field measuring campaigns in the years 2002–2004 at three beech ( Fagus sylvatica L.) forest sites. At all sites adjacent thinning plots (“T”) and untreated control plots (“C”) were established. Since the sites are characterized either by cool-moist microclimate (NE site and NW site) or by warm-dry microclimate (SW site) and thinning took place in the year 1999 at the NE and SW sites and in the year 2003 at the NW site the experimental design allowed to evaluate (1) short-term effects (years 1–2) of thinning at the NW site and (2) medium-term effects (years 4–6) of thinning under different microclimate at the SW and NE site. Microbial biomass N was consistently higher at the thinning plots of all sites during most of the field campaigns and was overall significantly higher at the SWT and NWT plots as compared to the corresponding untreated control plots. The size of the microbial biomass N pool was found to correlate positively with both gross ammonification and gross nitrification as well as with extractable soil NO 3 − concentrations. At the SW site neither gross ammonification, gross nitrification, gross ammonium (NH 4 + ) immobilization and gross nitrate (NO 3 − ) immobilization nor net ammonification, net nitrification and extractable NH 4 + and NO 3 − contents were significantly different between control and thinning plot. At the NET plot lower gross ammonification and gross NH 4 + immobilization in conjunction with constant nitrification rates coincided with higher net nitrification and significantly higher extractable NO 3 − concentrations. Thus, the medium-term effects of thinning varied with different microclimate. The most striking thinning effects were found at the newly thinned NW site, where gross ammonification and gross NH 4 + immobilization were dramatically higher immediately after thinning. However, they subsequently tended to decrease in favor of gross nitrification, which was significantly higher at the NWT plot as compared to␣the␣NWC plot during all field campaigns after␣thinning except for April 2004. This increase␣in␣gross nitrification at the NWT plot (1.73 mg N kg −1  sdw day −1 versus 0.48 mg N kg −1 sdw day −1 at the NWC plot) coincided with significantly higher extractable NO 3 − concentrations (4.59 mg N kg −1 sdw at the NWT plot versus 0.96 mg N kg −1  sdw at the NWC plot). Pronounced differences in relative N retention (the ratio of gross NH 4 + immobilization + gross NO 3 − immobilization to gross ammonification + gross nitrification) were found across the six research plots investigated and could be positively correlated to the soil C/N ratio ( R  = 0.94; p  = 0.005). In sum, the results obtained in this study show that (1) thinning can lead to a shift in the balance of microbial inorganic N production and consumption causing a clear decrease in the N retention capacity in the monitored forest soils especially in the first two years after thinning, (2)␣the resistance of the investigated forest ecosystems to disturbances of N cycling by thinning may vary with different soil C contents and C/N ratios, e. g. caused by differences in microclimate, (3) thinning effects tend to decline with the growth of understorey vegetation in the years 4–6 after thinning.
    Keywords: Beech ; Immobilization ; Microbial biomass N ; Nitrification ; N mineralization ; Thinning ; C/N ratio
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 7
    Language: English
    In: Journal of Geophysical Research: Atmospheres, 08/20/1999, Vol.104(D15), pp.18487-18503
    ISSN: Journal of Geophysical Research: Atmospheres
    E-ISSN: 01480227
    Source: American Geophysical Union (via CrossRef)
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  • 8
    Language: English
    In: Journal of Geophysical Research: Atmospheres, 08/20/1999, Vol.104(D15), pp.18505-18520
    Description: For 3 years we followed the complete annual cycles of NO and NO sub(2) flux rates from soil of a spruce control site, a limed spruce site, and a beech site at the Hoglwald Forest, Bavaria, Germany, with high temporal resolution in order to gain detailed information about (1) the impacts of forest type, liming, and atmospheric N input by wet deposition on the magnitude of NO and NO sub(2) flux rates and (2) the microbial processes involved in NO production and emission. In addition to identification of seasonal variations of flux rates the huge database allowed calculation of annual mean NO and NO sub(2) fluxes with high accuracy and identification of interannual variations of fluxes. The long-term annual mean NO sub(x) emission was 61.7 mu g NO sub(x) N m super(-) super(2) h super(-) super(1) for the spruce control site, 17.3 mu g NO sub(x) N m super(-) super(2) h super(-) super(1) for the limed spruce site, and 4.0 mu g NO sub(x) N m super(-) super(2) h super(-) super(1) for the beech site. These extremely high soil NO sub(x) emissions from a temperate forest most likely reflect the status of N saturation of the Hoglwald Forest as a consequence of year-long heavy atmospheric N input. Multiple regression analyses revealed the following sequence of importance of environmental factors on NO flux: soil temperature to water-filled pore space to soil NO sub(3) super(-) concentrations to soil NH sub(4) super(+) concentrations. Nitrification was the dominating biotic modulator of NO emission at all sites: 〉60% of the variation of NO emission rates were associated with variations of net nitrification rates. There was a strong positive correlation between amount of in situ N input by wet deposition and magnitude of in situ NO flux rates. Approximately 15% and 7% of the actual N input was lost as NO from the soil stocked with spruce and beech, respectively. Liming resulted in 49% reduction of NO emissions as compared to an unlimed spruce control site. The results indicate that the reduction in NO emission was due to an increase in NO consumption within the limed soil. In contrast to NO flux, NO sub(2) flux was modulated by physico-chemical rather than biological factors. Using the data of this study, we estimate that the contribution of N-affected temperate coniferous and deciduous forests to the global NO sub(x) release is 0.3 Tg NO sub(x) N yr super(-) super(1) .
    Keywords: Hoeglwald Forest, Germany ; Nitric Oxide Emissions From Soil ; Nitrogen Dioxide Emission From Soil ; Physical Properties/Composition ; 546.172.6 ; 546.174;
    ISSN: Journal of Geophysical Research: Atmospheres
    E-ISSN: 01480227
    Source: American Geophysical Union (via CrossRef)
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  • 9
    In: New Phytologist, May 1998, Vol.139(1), pp.71-86
    Description: High loads of nitrogen to spruce and beech forests can result in a complete inhibition of NO uptake by the roots of the trees. This conclusion is based on () a comparison of a field site continuously exposed to high loads of N and a N‐limited site, () the results of N fertilization of a N‐limited field site, and () laboratory experiments under controlled environmental conditions. From fertilization experiments in the field it appears that NH uptake might become inhibited subsequent to an excessive uptake of NH. Apparently, the inhibition of NO uptake by high loads of N to forests is a consequence of an accumulation of organic amino compounds in the roots originating from phloem transport from the shoot to the roots. These amino compounds seem to signal the N demand of the shoot to the roots. At present this function cannot be attributed to an individual organic amino compound in beech or spruce, but Gln is a likely candidate in both species among other compounds, e.g. Glu in spruce or Asp in beech trees. Direct inhibition of NO uptake by NH can be excluded from the present studies. The mechanism(s) by which elevated levels of particular organic amino compounds interact with NO uptake remains to be elucidated. This (these) mechanism(s) seem to affect NO influx rather than NO efflux. As a consequence of this (these) mechanism(s), spruce and beech trees can prevent, within a certain physiological window, N over‐nutrition when the roots are exposed to excessive amounts of inorganic N. However, inhibition of NO and NH uptake by the roots makes more N available for leaching into the ground water and, in addition, for soil microbial processes that result in the production and re‐emission of volatile N compounds into the atmosphere. At the ‘Höglwald’ site, continuously exposed to high loads of N, 〉20% of the N input from throughfall into the spruce and beech plots is re‐emitted as NO and NO. However, the NO to NO ratio is highly dependent on the tree species, with a preference for NO in the spruce and a preference for NO in the beech plot. Since at least part of the NO emitted from the soil will be converted inside the canopy in the presence of ozone to NO that might then be absorbed by the leaves, the portion of the N in the throughfall that will be released from the forest by gaseous N emission is higher in the beech than in the spruce plot. Leaching of NO into the ground water is high in the spruce, but minute in the beech plot. However, this positive effect of beech on ground water quality is achieved at the expense of an enhanced release of radiatively active N gases into the troposphere.
    Keywords: Atmospheric Pollution ; Forest Ecosystem ; Nitrogen Allocation ; Nitrogen Fluxes ; Regulation ; Nitrogen Oxides ; Ammonia
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 10
    In: Geophysical Research Letters, May 2009, Vol.36(9), pp.n/a-n/a
    Description: Despite a considerable knowledge of the significant role of termites in the global methane budget, very little is known about their contribution to the global nitrous oxide (NO) budget. Release of NO from termite () mounds was measured at a natural savanna site in the southwest of Burkina Faso from May to September 2006. Termite NO emissions were around 20 g NO‐N m h at the end of the dry season, and up to two orders of magnitude higher than NO emissions from the surrounding termite‐free soil after the onset of the rainy season. The average NO emission rate from termite mounds during the observation period was 204 g NO‐N m h, and termite mounds contributed 3.0% to total NO emissions from this savanna ecosystem. However, in other tropical terrestrial ecosystems with other termite species and/or higher termite density this share might be significantly higher.
    Keywords: Cubitermes Fungifaber ; Dry Season ; No ; Near‐Natural Savanna ; Rainy Season ; Tropical Grassland
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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