3,156 research outputs found
Mit einem Beitrag zur ersten Ägyptenreise 1864 von Georg Schweinfurth (1836-1925)
No full textSoftcover, 17x24Die vorliegende Arbeit beschäftigt sich mit der Katalogisierung der Holzsammlung des Albrecht-von-Haller-Instituts für Pflanzenwissenschaften der Universität Göttingen, die heute in der Abteilung für Ökologie und Ökosystemforschung aufbewahrt wird. Über einen langen Zeitraum hinweg wurden Gehölzproben verschiedenster Herkunft gesammelt. Da dies jedoch ohne eine bestimmte Ordnung geschah, kann zum Zeitpunkt vor der Katalogisierung eher von einer Holzansammlung gesprochen werden. Ziel der Arbeit war es, den Bestand der gesammelten Objekte zu erfassen und zu erschließen, um diese effektiv für weitere Studien nutzen zu können. Die Arbeit beinhaltet die Daten der gesamten Holzsammlung. Vertiefend werden Belege des Sammlers Georg Schweinfurth, die in der Sammlung enthalten sind, genauer beschrieben. An ihnen wird deutlich, welche hohe Aussagekraft alte Gehölzproben in der heutigen Zeit für die historische Biodiversitätsforschung haben.
Prof. Dr. Volker Wissemann ist Professor für Spezielle Botanik an der Justus-Liebig-Universität Gießen, Direktor des Instituts für Botanik incl. Herbarium, Kondirektor der Hermann-Hoffmann-Akademie und wissenschaftlicher Leiter des botanischen Gartens Gießen. Er ist Mitglied der Akademie der Wissenschaften zu Göttingen und Alumnus der Georgia Augusta.
Denise Jahn ist Lehrerin am Markland College in den Niederlanden. Sie hat ihren Masterabschluss an der Friedrich-Schiller-Universität in Jena in den Fächern Geographie und Biologie erworben, und sich im Rahmen ihrer Masterarbeit mit der Holzsammlung am Albrecht-von-Haller Institut der Georgia Augusta befasst.
Prof. Dr. Christoph Leuschner ist Professor für Pflanzenökologie und Ökosystemforschung am Albrecht-von-Haller Institut der Georg-August Universität Göttingen, sowie Direktor des Botanischen Gartens der Georgia Augusta, Sektion Experimentelle Ökologie (Neuer Botanischer Garten). Er ist Mitglied der Akademie der Wissenschaften zu Göttingen
Monospecific and mixed stands of Fagus and Nothofagus species in the temperate zones of the world
No full textMonospecific and mixed stands of Fagus and Nothofagus species in the temperate zones of the world
No full textδ13C signature of tree rings and radial increment of Fagus sylvatica trees as dependent on tree neighborhood and climate
Full text linkWe conducted dendroecological analyses in 80-year-long tree ring chronologies to detect neighborhood effects (competition intensity, species identity) on the delta C-13 signature of tree rings and radial stem increment of Fagus sylvatica trees growing either in monospecific or mixed patches of a temperate forest. We hypothesized that tree ring delta C-13 is a more sensitive indicator of neighborhood effects and the impact of climate variability on growth than is ring width. We found a closer correlation of summer precipitation to delta C-13 than to ring width. While the ring width showed a decline over the test period (1926-2005), the mean curve of delta C-13 increased until the mid of the 1970s, remained high until about 1990, and markedly decreased thereafter. Possible explanations related to ontogeny and environmental change ('age effect' due to canopy closure; elevated atmospheric SO2 concentrations in the 1960s-1980s) are discussed. Beech target trees surrounded by many allospecific trees had a significantly lower mean delta C-13 in the period 1926-1975 than beech with predominantly or exclusively conspecific neighborhood, possibly indicating a more favorable water supply of beech in diverse stands. Contrary to expectation, trees subject to more intense competition by neighboring trees (measured by Hegyi's competition index) had lower delta C-13 values in their tree rings, which is thought to reflect denser canopies being linked to increased shading. We conclude that tree ring delta C-13 time series represent combined archives of climate variability, stand history and neighborhood effects on tree physiology and growth that may add valuable information to that obtained from conventional tree ring analysis
Temperate forest herbs are adapted to high air humidity — evidence from climate chamber and humidity manipulation experiments in the field
No full textHow growth and morphology of wild plants are controlled by the water vapor saturation deficit of the air (vapor pressure deficit, VPD) is not sufficiently understood. We tested the hypothesis that VPD acts on temperate woodland herbs independently from soil moisture by exposing two species (Mercurialis perennis L. and Stachys sylvatica Toff.) to variable VPD levels in climate chambers and in open-top chambers on the forest floor. A decrease in air humidity from 85% to 40% in the climate chamber experiment, which simulates a microclimate change after canopy gap creation, resulted in a 40% decrease in biomass production of both species when grown in hydroponic culture. This result is supported by the more realistic open-top chamber experiment, which showed a productivity decrease by approximately 25% when plants were continuously exposed to an atmosphere with 15% lower air humidity than ambient. Elevated VPD levels reduced biomass production through either a reduced leaf expansion rate or a lower number of formed leaf buds. We conclude that many woodland herbs require sufficiently high air humidity for optimal growth; permanently decreased air humidity, as may occur in a future drier climate, after gap creation, or after clear-cutting of the forest, may threaten the vitality and survival of woodland herbs.German Federal Environmental Foundatio
Belowground competition in a broad-leaved temperate mixed forest: pattern analysis and experiments in a four-species stand
No full textWe investigated fine root biomass and distribution patterns in a species-rich temperate Carpinus-Quercus-Fagus-Tilia forest and searched for experimental evidence of symmetry or asymmetry in belowground competition. We conducted extensive root coring and applied the recently introduced in situ-root growth chamber technique for quantifying fine root growth under experimentally altered intra- and interspecific root neighbourhoods in the intact stand. In 75% of all soil cores, fine roots of more than two tree species were present indicating a broad overlap of the root systems of neighbouring trees. Quercus trees had more than ten times less fine root biomass in relation to aboveground biomass or productivity (stem growth) and a much higher leaf area index/root area index ratio than Carpinus, Fagus and Tilia trees. The root growth chamber experiments indicated a high belowground competitive ability of Fagus in interspecific interactions, but a low one of Quercus. We conclude that (1) interspecific root competition is ubiquitous in this mixed stand, (2) root competition between trees can be clearly asymmetric, and (3) tree species may be ranked according to their belowground competitive ability. Fagus was found to be the most successful species in belowground competition which matches with its superiority in aboveground competition in this forest community
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