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1.
Chanjuan Guo Judy Simon Rainer Gasche Pascale Sarah Naumann Carolin Bimüller Rodica Pena Andrea Polle Ingrid Kögel-Knabner Bernd Zeller Heinz Rennenberg Michael Dannenmann 《Plant and Soil》2013,369(1-2):657-668
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
15N-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 15N into the mineral soil already 21 days after tracer application with soil microbial biomass initially representing the dominant litter-N sink. However, 15N recovery in non-extractable soil N pools strongly increased over time and subsequently became the dominant 15N sink. Recovery in plant biomass accounted for only 0.025 % of 15N excess after 876 days. After three growing seasons, 15N 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 15N recovery in beech seedlings suggests a high importance of other N sources such as root litter for N nutrition of beech understorey. 相似文献2.
Chanjuan Guo Michael Dannenmann Rainer Gasche Bernd Zeller Hans Papen Andrea Polle Heinz Rennenberg Judy Simon 《Plant and Soil》2013,368(1-2):519-534
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 15N recovery rates in plant and soil N pools by adding 15N-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 15N recovery from litter in seedlings thereby affecting root N nutrition. 15N 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. 相似文献3.
Medinets Sergiy Gasche Rainer Kiese Ralf Rennenberg Heinz Butterbach-Bahl Klaus 《Plant and Soil》2019,445(1-2):335-348
Plant and Soil - Soils are known to be significant sources of atmospheric nitric oxide (NO), a key compound in atmospheric chemistry. NO is a key regulating substance for inter- and intra-species... 相似文献
4.
Defective Cu,Zn-superoxide dismutase (SOD1) is responsible for some types of amyotrophic lateral sclerosis, and ventral horn motor neurons (VMN) have been shown to die through a mitochondria-dependent apoptotic pathway after chronic exposure to high levels of reactive oxygen species (ROS). VMN are also selectively vulnerable to mild spinal cord injury (SCI); however, the involvement of SOD1, ROS, and apoptosis in their death has not been clarified. Mild compression SCI was induced in SOD1-overexpressing transgenic rats and wild-type littermates. Superoxide production, mitochondrial release of cytochrome c, and activation of caspase-9 were examined, and apoptotic DNA injury was also characterized. In the wild-type animals, increased superoxide production, mitochondrial release of cytochrome c, and cleaved caspase-9 were observed exclusively in VMN after SCI. Subsequently, a majority of VMN (75%) selectively underwent delayed apoptotic cell death. Transgenic animals showed less superoxide production, mitochondrial cytochrome c release, and caspase-9 activation, resulting in death of only 45% of the VMN. These results suggest that the ROS-initiated mitochondrial signaling pathway possibly plays a pivotal role in apoptotic VMN death after SCI and that increased levels of SOD1 in VMN reduce oxidative stress, thereby attenuating the activation of the pathway and delayed cell death. 相似文献
5.
The effects of site exposure (microclimate) and forest management (thinning) on fungal-to-bacterial (F:B) respiratory ratio
and N2O emission from forest floor and Ah layer samples were studied at untreated and thinned beech forests. Microclimate effects
were studied by selecting sites facing north-east (NE) or south-west (SW). The F:B respiratory ratio was estimated using substrate-induced
respiration in combination with inhibitors either affecting fungi or bacteria. N2O production was evaluated after moistening samples initially pre-incubated at different moisture levels to 100% of the water
holding capacity (WHC). F:B respiratory ratios were significantly affected by microclimate and thinning, with site exposure
having the strongest effect on fungal-to-bacterial ratio and N2O production both for the forest floor and the Ah layer. Significantly more N2O was produced from soils pre-incubated under low (15% WHC) moisture conditions as compared to soils pre-incubated under air
dry (5% WHC) or wet conditions (30–60% WHC). A positive correlation between N2O emission and F:B respiratory ratio for Ah layer samples and a negative correlation between bacterial substrate induced respiration
(SIR) and N2O emission for both Ah layer and forest floor samples indicated that net N2O production was the result of predominantly fungal N2O production and predominantly bacterial N2O consumption. The latter hypothesis was further supported by increased N2O emission from samples treated with bacterial inhibitor. 相似文献
6.
B. Matejek C. Huber M. Dannenmann M. Kohlpaintner R. Gasche H. Papen 《Plant and Soil》2010,337(1-2):93-110
Microbial N turnover processes were investigated in three different forest soil layers [organic (O) layer, 0–10 cm depth (M1), 10–40 cm depth (M2)] after the clear cutting of a nitrogen (N) saturated spruce stand at the Höglwald Forest (Bavaria, Germany). The aim of the study was to provide detailed insight into soil-layer specific microbial production and the consumption of inorganic N within the main rooting zone. Furthermore, we intended to clarify the relevance of each soil layer investigated in respect of the observed high spatial variation of seepage water nitrate (NO 3 ? ) concentration at a depth of 40 cm. The buried bag and the 15N pool dilution techniques were applied to determine the net and gross N turnover rates. In addition, soil pH, C:N ratio, pool sizes of soil ammonium (NH 4 + ) and NO 3 ? , as well as quantities of microbial biomass carbon (Cmic) and nitrogen (Nmic) were determined. The 40 cm thick upper mineral soil was found to be the main place of NO 3 ? production with a NO 3 ? supply or net nitrification three times higher than in the considerably thinner O layer. Nevertheless, O layer nitrification processes determined via in situ field experiments showed significant correlation with seepage water NO 3 ? . An improved correlation noted several months after the cut may result from a transport-induced time shift of NO 3 ? with downstream hydrological pathways. In contrast, the soil laboratory incubation experiments found no indication that mineral soil is relevant for the spatial heterogeneity of seepage water NO 3 ? . The results from our study imply that in situ experiments may be better suited to studies investigating N turnover in relation to NO 3 ? loss via seepage water in similar ecosystems in order to gain representative data. 相似文献
7.
Mouse astrocytes deficient in the mitochondrial form of superoxide dismutase do not grow in culture under 20% atmospheric O2 levels. By flow cytometry, immunocytochemistry, and enzymatic analysis we have shown that the oxygen block of cell division is due to a decrease in the number of cells entering the S phase of the cell cycle and is concomitant with higher DNA oxidation and impairment of mitochondrial functions. Seeding the cells under 5% O2 until the cultures become confluent can circumvent this problem. An initial hypoxic environment increases the resistance of manganese superoxide dismutase-deficient astrocytes to superoxide radicals artificially produced by paraquat treatment, preserves respiratory activity, and allows normoxic division during a subsequent passage. DNA oxidation is then not higher than in wild-type control cells. However, the adaptation of the cells is not due to compensation by other enzymes of the antioxidant defense system and is specific to cells totally lacking manganese superoxide dismutase. Alteration of the phenotype by prior hypoxia exposure in the SOD2-deficient mutant provide a unique model to study adaptative mechanisms of cellular resistance to oxygen toxicity. 相似文献
8.
Ecosystems are usually complex, nonlinear and strongly influenced by poorly known environmental variables. Among these systems, marine ecosystems have high uncertainties: marine populations in general are known to exhibit large levels of natural variability and the intensity of fishing efforts can change rapidly. These uncertainties are a source of risks that threaten the sustainability of both fish populations and fishing fleets targeting them. Appropriate management measures have to be found in order to reduce these risks and decrease sensitivity to uncertainties. Methods have been developed within decision theory that aim at allowing decision making under severe uncertainty. One of these methods is the information-gap decision theory. The info-gap method has started to permeate ecological modelling, with recent applications to conservation. However, these practical applications have so far been restricted to simple models with analytical solutions. Here we implement a deterministic approach based on decision theory in a complex model of the Eastern English Channel. Using the ISIS-Fish modelling platform, we model populations of sole and plaice in this area. We test a wide range of values for ecosystem, fleet and management parameters. From these simulations, we identify management rules controlling fish harvesting that allow reaching management goals recommended by ICES (International Council for the Exploration of the Sea) working groups while providing the highest robustness to uncertainties on ecosystem parameters. 相似文献
9.
Gidday JM Gasche YG Copin JC Shah AR Perez RS Shapiro SD Chan PH Park TS 《American journal of physiology. Heart and circulatory physiology》2005,289(2):H558-H568
Results of recent studies reveal vascular and neuroprotective effects of matrix metalloproteinase-9 (MMP-9) inhibition and MMP-9 gene deletion in experimental stroke. However, the cellular source of MMP-9 produced in the ischemic brain and the mechanistic basis of MMP-9-mediated brain injury require elucidation. In the present study, we used MMP-9-/- mice and chimeric knockouts lacking either MMP-9 in leukocytes or in resident brain cells to test the hypothesis that MMP-9 released from leukocytes recruited to the brain during postischemic reperfusion contributes to this injury phenotype. We also tested the hypothesis that MMP-9 promotes leukocyte recruitment to the ischemic brain and thus is proinflammatory. The extent of blood-brain barrier (BBB) breakdown, the neurological deficit, and the volume of infarction resulting from transient focal stroke were abrogated to a similar extent in MMP-9-/- mice and in chimeras lacking leukocytic MMP-9 but not in chimeras with MMP-9-containing leukocytes. Zymography and Western blot analysis from these chimeras confirmed that the elevated MMP-9 expression in the brain at 24 h of reperfusion is derived largely from leukocytes. MMP-9-/- mice exhibited a reduction in leukocyte-endothelial adherence and a reduction in the number of neutrophils plugging capillaries and infiltrating the ischemic brain during reperfusion; microvessel immunopositivity for collagen IV was also preserved in these animals. These latter results document proinflammatory actions of MMP-9 in the ischemic brain. Overall, our findings implicate leukocytes, most likely neutrophils, as a key cellular source of MMP-9, which, in turn, promotes leukocyte recruitment, causes BBB breakdown secondary to microvascular basal lamina proteolysis, and ultimately contributes to neuronal injury after transient focal stroke. 相似文献
10.
Bernard Favrat Katharina Balck Christian Breymann Michael Hedenus Thomas Keller Anna Mezzacasa Christoph Gasche 《PloS one》2014,9(4)