TY - GEN A1 - Hoppert, Michael A1 - Reimer, Rudolph A1 - Kemmling, Anne A1 - Schröder, Annekatrin A1 - Günzl, Bettina A1 - Heinken, Thilo T1 - Structure and reactivity of a biological soil crust from a xeric sandy soil in Central Europe N2 - The investigation was designed to explore the structure, composition and activity of a biological soil crust on an acidic, sandy soil from a temperate climate. The crust covers several hundreds of square meters on the hilltop of a large terminal moraine. The conjugate alga Zygogonium ericetorum forms the essential matrix for the crust, a dense web of algal filaments with interspersed lichens and mosses. The crust is composed of three layers, with an uppermost layer consisting nearly entirely of a dense algal mat. In lower layers, a parasitic fungus, penetrating the algal cells, is another important component of the crust community. In this soil crust, photosynthetic and respiratory activity is stabilized at low water activities. KW - biological soil crust KW - desiccation tolerance KW - electron microscopy KW - Fusarium oxysporum KW - Zygogonium ericetorum Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5872 ER - TY - GEN A1 - Köchy, Martin A1 - Wilson, Scott D. T1 - Variation in nitrogen deposition and available soil nitrogen in a forest–grassland ecotone in Canada N2 - Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local-scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha⁻¹ yr⁻¹). N deposition was on average higher ton clayrich luvisols than on brunisols, and areas burned 1 – 15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition. KW - fire KW - grazing KW - vegetation type KW - soil type KW - shrubland KW - forest invasion KW - subboreal KW - aspen parkland KW - Canada Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5768 ER - TY - GEN A1 - Ginoux, Nicolas T1 - Une nouvelle estimation extrinsèque du spectre de l'opérateur de Dirac T1 - A new extrinsic estimate for the spectrum of the Dirac operator N2 - Nous établissons une nouvelle majoration optimale pour les plus petites valeurs propres de l'opérateur de Dirac sur une hypersurface compacte de l'espace hyperbolique. N2 - We prove a new upper bound for the smallest eigenvalues of the Dirac operator on a compact hypersurface of the hyperbolic space. KW - bounds KW - Eigenvalues Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5644 ER - TY - GEN A1 - Ginoux, Nicolas T1 - Remarques sur le spectre de l'opérateur de Dirac T1 - Remarks on the spectrum of the Dirac operator N2 - Nous décrivons un nouvelle famille d'exemples d'hypersurfaces de la sphère satisfaisant le cas d'égalité de la majoration extrinsèque de C. Bär de la plus petite valeur propre de l'opérateur de Dirac. N2 - We describe a new family of examples of hypersurfaces in the sphere satisfying the limitingcase in C. Bär's extrinsic upper bound for the smallest eigenvalue of the Dirac operator. KW - 1st Eigenvalue KW - Submanifolds KW - Bounds KW - Space Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5630 ER - TY - GEN A1 - Ginoux, Nicolas T1 - Dirac operators on Lagrangian submanifolds N2 - We study a natural Dirac operator on a Lagrangian submanifold of a Kähler manifold. We first show that its square coincides with the Hodge - de Rham Laplacian provided the complex structure identifies the Spin structures of the tangent and normal bundles of the submanifold. We then give extrinsic estimates for the eigenvalues of that operator and discuss some examples. KW - Dirac operators KW - Global Analysis KW - Spectral Geometry KW - Spin Geometry KW - Lagrangian submanifolds Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5627 ER - TY - GEN A1 - Degkwitz, Andreas A1 - Andermann, Heike T1 - Angebots-, Nutzungs- und Bezugsstrukturen elektronischer Fachinformation in Deutschland N2 - Mit dem Übergang zum digitalen Medium haben sich die Bezugsstrukturen und das Angebot an elektronischer Fachinformation in den Bibliotheken nachhaltig verändert. In den vorliegenden Untersuchungen wird das Angebot elektronischer Zeitschriften und Datenbanken und die Nutzung elektronischer Zeitschriften in fünf ausgewählten Fachgebieten und in unterschiedlichen Bibliothekstypen dargelegt. Darüber hinaus werden die derzeitigen Bezugsstrukturen beschrieben sowie die Ergebnisse einer Befragung der Konsortien zu Zielsetzungen, Vertragsformen und Geschäftsmodellen dargestellt. Chancen und Risiken der konsortialen Bezugsform werden erörtert. N2 - With the transition to the digital medium the structures for purchasing digital information and the offer of scientific information in the libraries changed strongly. In the available examination the offer of electronic journals and databases and the usage of electronic journals in five selected disciplines and in different types of libraries is evaluated. Further more the current purchasing structures and the results of interviews with consortia in regard to objectives, forms of contracts and pricing models are described. Chances and risks of consortia purchasing are discussed. KW - elektronische Zeitschriften KW - Datenbanken KW - Konsortien KW - Bezugsstrukturen KW - electronic journals KW - databases KW - consortia KW - purchasing structures Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-672 ER -