# ALBERT

## All Library Books, journals and Electronic Records Telegrafenberg

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• 1
Dissertations
Potsdam
Call number: AWI G6-19-92461
Type of Medium: Dissertations
Pages: XVI, 203 Seiten , Illustrationen, Diagramme
Language: English
Branch Library: AWI Library
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• 2
Electronic Resource
Springer
Commentarii mathematici Helvetici 72 (1997), S. 72-83
ISSN: 1420-8946
Keywords: Key words. Betti number, generic map, Čech homology, Jordan-Brouwer theorem, ANR.
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics
Notes: Abstract. Let $f : M \to N$ be a differentiable map of a closed m-dimensional manifold into an (m + k)-dimensional manifold with k 〉 0. We show, assuming that f is generic in a certain sense, that f is an embedding if and only if the (m - k + 1)-th Betti numbers with respect to the Čech homology of M and f(M) coincide, under a certain condition on the stable normal bundle of f. This generalizes the authors' previous result for immersions with normal crossings [BS1]. As a corollary, we obtain the converse of the Jordan-Brouwer theorem for codimension-1 generic maps, which is a generalization of the results of [BR, BMS1, BMS2, Sae1] for immersions with normal crossings.
Type of Medium: Electronic Resource
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• 3
Electronic Resource
Springer
ISSN: 1678-7714
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics
Notes: Abstract In this work we define the notion of a mapf:X→Y to be ann-equivalence modulo a classC of groups. Then we show an equivalent condition, which is more close to a homological condition, in order to a mapf:X→Y to be ann-equivalence modulo a classC of groups. Finally, at least for a complexK which is finite and is a suspension of a connected space, the notion above is also given in terms of the mapf #: [K, X]→[K, Y].
Type of Medium: Electronic Resource
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• 4
Unknown
PANGAEA
Publication Date: 2014-08-31
Repository Name: EPIC Alfred Wegener Institut
Type: PANGAEA Documentation , NonPeerReviewed
Format: application/pdf
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• 5
Publication Date: 2016-07-07
Description: Arctic peatlands store large stocks of organic carbon which are vulnerable to the climate change but their fate is uncertain. There is increasing evidence that a part of it will be lost as a result of faster microbial mineralization. We studied the vulnerability of 3500–5900 years old bare peat uplifted from permafrost layers by cryogenic processes to the surface of an arctic peat plateau. We aimed to find biotic and abiotic drivers of C LOSS from old peat and compare them with those of adjacent, young vegetated soils of the peat plateau and mineral tundra. The soils were incubated in laboratory at three temperatures (4°C, 12°C and 20°C) and two oxygen levels (aerobic, anaerobic). C LOSS was monitored and soil parameters (organic carbon quality, nutrient availability, microbial activity, biomass and stoichiometry, and extracellular oxidative and hydrolytic enzyme pools) were determined. We found that C LOSS from the old peat was constrained by low microbial biomass representing only 0.22% of organic carbon. C LOSS was only slightly reduced by the absence of oxygen and exponentially increased with temperature, showing the same temperature sensitivity under both aerobic and anaerobic conditions. We conclude that carbon in the old bare peat is stabilized by a combination of physical, chemical and biological controls including soil compaction, organic carbon quality, low microbial biomass and the absence of plants.
Print ISSN: 0168-6496
Electronic ISSN: 1574-6941
Topics: Biology
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• 6
Publication Date: 2012-06-23
Description: In the present experiment, the single and combined effects of elevated temperature and ozone (O 3 ) on four silver birch genotypes (gt12, gt14, gt15 and gt25) were studied in an open-air field exposure design. Above- and below-ground biomass accumulation, stem growth and soil respiration were measured in 2008. In addition, a 13 C-labelling experiment was conducted with gt15 trees. After the second exposure season, elevated temperature increased silver birch above- and below-ground growth and soil respiration rates. However, some of these variables showed that the temperature effect was modified by tree genotype and prevailing O 3 level. For instance, in gt14 soil respiration was increased in elevated temperature alone (T) and in elevated O 3 and elevated temperature in combination (O 3 + T) treatments, but in other genotypes O 3 either partly (gt12) or totally nullified (gt25) temperature effects on soil respiration, or acted synergistically with temperature (gt15). Before leaf abscission, all genotypes had the largest leaf biomass in T and O 3 + T treatments, whereas at the end of the season temperature effects on leaf biomass depended on the prevailing O 3 level. Temperature increase thus delayed and O 3 accelerated leaf senescence, and in combination treatment O 3 reduced the temperature effect. Photosynthetic : non-photosynthetic tissue ratios (P : nP ratios) showed that elevated temperature increased foliage biomass relative to woody mass, particularly in gt14 and gt12, whereas O 3 and O 3 + T decreased it most clearly in gt25. O 3 -caused stem growth reductions were clearest in the fastest-growing gt14 and gt25, whereas mycorrhizal root growth and sporocarp production increased under O 3 in all genotypes. A labelling experiment showed that temperature increased tree total biomass and hence 13 C fixation in the foliage and roots and also label return was highest under elevated temperature. Ozone seemed to change tree 13 C allocation, as it decreased foliar 13 C excess amount, simultaneously increasing 13 C excess obtained from the soil. The present results suggest that warming has potential to increase silver birch growth and hence carbon (C) accumulation in tree biomass, but the final magnitude of this C sink strength is partly counteracted by temperature-induced increase in soil respiration rates and simultaneous O 3 stress. Silver birch populations' response to climate change will also largely depend on their genotype composition.
Print ISSN: 0829-318X
Electronic ISSN: 1758-4469
Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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• 7
Unknown
Wiley
Publication Date: 2011-05-05
Print ISSN: 1354-1013
Electronic ISSN: 1365-2486
Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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• 8
Unknown
Copernicus
Publication Date: 2012-08-01
Print ISSN: 1810-6277
Electronic ISSN: 1810-6285
Topics: Biology , Geosciences
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• 9
Unknown
Copernicus
Publication Date: 2015-08-26
Description: Methane (CH4) fluxes were investigated in a subarctic Russian tundra site in a multi-approach study combining plot scale data, ecosystem scale eddy covariance (EC) measurements and fine resolution land cover classification scheme for regional upscaling. The flux data as measured by the two independent techniques resulted in a seasonal (May–October 2008) cumulative CH4 emission of 2.4 (EC) and 3.7 g CH4 m−2 (manual chambers) for the source area representative of the footprint of the EC instruments. Upon upscaling for the entire study region of 98.6 km2, the chamber measured flux data yielded a regional flux estimate of 6.7 g CH4 m−2 yr−1. Our upscaling efforts accounted for the large spatial variability in the distribution of the various land cover types (LCTs) predominant at our study site. In particular, wetlands with emissions ranging from 34 to 53 g CH4 m−2 yr−1 were the most dominant CH4 emitting surfaces. Emissions from thermokarst lakes were an order of magnitude lower, while the rest of the landscape (mineral tundra) was a weak sink for atmospheric methane. Vascular plant cover was a key factor in explaining the spatial variability of CH4 emissions among wetland types, as indicated by the positive correlation of emissions with the leaf area index (LAI). As elucidated through a stable isotope analysis, the plant transport was the dominant CH4 release pathway that discriminates against heavier δ13C-CH4. The methane released from wetlands was lighter than that in the surface porewater and δ13C in the emitted CH4 correlated with the vascular plant cover (LAI) implying that the plant-mediated CH4 release dominates. A mean value of δ13C obtained here for the emitted CH4, −68.2 ± 2.0 ‰, is within the range of values from other wetlands, thus reinforcing the use of inverse modeling tools to better constrain the CH4 budget. Based on the IPCC A1B emission scenario, a temperature increase of 7 °C has been predicted for the tundra region of European Russia by the end of the 21st Century. A regional warming of this magnitude will have profound effects on the permafrost distribution leading to considerable changes in the regional landscape with a potential for an increase in the areal extent of methane emitting wet surfaces. We estimate that a projected increase in air temperature of 7 °C with a mere 10 % associated increase in the combined areal coverage of willow stands, fens and lakes in the region will lead to a 51 % higher amount of CH4 being emitted into the atmosphere by the end of this century.
Print ISSN: 1810-6277
Electronic ISSN: 1810-6285
Topics: Biology , Geosciences
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• 10
Unknown
Copernicus
Publication Date: 2013-01-24
Description: We report here the carbon dioxide (CO2) budget of a 98.6 km2 subarctic tundra area in northeast European Russia based on measurements at two different scales and two independent upscaling approaches. Plot-scale measurements (chambers on terrestrial surfaces, gas gradient method and bubble collectors on lakes) were carried out from July 2007 to October 2008. The landscape-scale eddy covariance (EC) measurements covered the snow-free period of 2008. The annual net ecosystem exchange (NEE) of different land cover types ranged from −251 to 84 g C m−2. Leaf area index (LAI) was an excellent predictor of the spatial variability in gross photosynthesis (GP), NEE and ecosystem respiration (ER). The plot-scale CO2 fluxes were first scaled up to the EC source area and then to the whole study area using two data sets: a land cover classification and a LAI map, both based on field data and a 2.4 m pixel-sized QuickBird satellite image. The good agreement of the CO2 balances for the EC footprint based on the different measuring techniques (−105 to −81 g C m−2 vs. −79 g C m−2; growing season 2008) justified the integration of the plot-scale measurements over the larger area. The regional CO2 balance based on area-integrated plot-scale measurements was −41 or −79 g C m−2 yr−1 according to the two upscaling methods, the land cover classification and the LAI map, respectively. Due to the heterogeneity of tundra, the effect of climate change on CO2 uptake will vary strongly according to the land cover type and, moreover, likely changes in their relative coverage in the future will have great impact on the regional CO2 balance.
Print ISSN: 1726-4170
Electronic ISSN: 1726-4189
Topics: Biology , Geosciences