TY - BOOK A1 - Rolfes, Manfred A1 - Weith, Thomas A1 - Aehnelt, Reinhard A1 - Schreiber, Karsten A1 - Schultz, Heiko A1 - Werth, Manfred A1 - Neumann, Uwe A1 - Wilhelm, Jan Lorenz A1 - Jessel, Beate A1 - Herberg, Alfred A1 - Kaether, Johann A1 - Zillmer, Sabine A1 - Wiechmann, Thorsten ED - Rolfes, Manfred ED - Weith, Thomas T1 - Evaluation in der Praxis: : Aktuelle Beispiele aus der Stadt-, Regional- und Umweltentwicklung T3 - Praxis Kultur- und Sozialgeographie | PKS - 33 Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-53069 SN - 978-3-937786-50-6 ER - TY - JOUR A1 - Neumann-Cosel, Luisa A1 - Zimmermann, Beate A1 - Hall, Jefferson S. A1 - van Breugel, Michiel A1 - Elsenbeer, Helmut T1 - Soil carbon dynamics under young tropical secondary forests on former pastures-A case study from Panama JF - Forest ecology and management N2 - Secondary forests are gaining increased importance in tropical landscapes and have recently been reported to act as potential belowground carbon sinks. While economic interest in the management of secondary forests to mitigate carbon emissions is rising, the dynamics of soil carbon stocks under these ecosystems remain poorly understood. Recent studies report conflicting results concerning soil carbon trends as well as multiple confounding factors (e.g. soil type, topography and land-use history) affecting these trends. In this study, organic carbon stocks were measured in the mineral soil up to 20 cm depth of at 24 active pastures, 5-8-year-old, and 12-15-year-old secondary forest sites on former pastures. Additionally, we estimated carbon stocks under a 100-year-old secondary forest and compared them to those of nearby mature forests. Abiotic conditions in the study area were homogenous, enabling us to isolate the effect of land-use change on soil organic carbon stocks. Contrary to our expectations, soil carbon stocks in the top 10 cm did not change with young secondary forest development. Pasture soils stored 24.8 +/- 2.9 Mg ha(-1) carbon (mean +/- standard error) in the top 10 cm, and no accumulation of soil carbon was apparent during the first 15 years of secondary succession. Soil carbon stocks under 100-year-old secondary forests, averaging 43.0 +/- 7.9 Mg ha(-1) (mean +/- standard error), were clearly higher than those recorded at younger sites and approached levels of soil carbon stocks under mature forests. These data indicate that soil carbon stocks in this region of Panama are not affected by the land-use transition from pasture to young secondary regrowth. However, an increase of soil carbon storage might be possible over a longer period of time. Our results support trends observed in other tropical areas and highlight the importance of environmental conditions such as soil properties rather than land-use transitions on soil carbon dynamics. While our understanding of organic carbon dynamics in tropical soils remains limited, these results underscore the challenges of undertaking short-term reforestation projects with the expectation of increasing soil carbon sequestration. KW - Soil carbon KW - Secondary forest KW - Pasture KW - Land-use change KW - C sequestration KW - Panama Y1 - 2011 U6 - https://doi.org/10.1016/j.foreco.2010.07.023 SN - 0378-1127 VL - 261 IS - 10 SP - 1625 EP - 1633 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdissa, Negera A1 - Heydenreich, Matthias A1 - Midiwo, Jacob O. A1 - Ndakala, Albert A1 - Majer, Zsuzsanna A1 - Neumann, Beate A1 - Stammler, Hans-Georg A1 - Sewald, Norbert A1 - Yenesew, Abiy T1 - A xanthone and a phenylanthraquinone from the roots of Bulbine frutescens, and the revision of six seco-anthraquinones into xanthones JF - Phytochemistry letters N2 - Phytochemical investigation of the dichloromethane/methanol (1:1) extract of the roots of Bulbine frutescens led to the isolation of a new xanthone, 8-hydroxy-6-methylxanthone-1-carboxylic acid (1) and a new phenylanthraquinone, 6',8-O-dimethylknipholone (2) along with six known compounds. The structures were elucidated on the basis of NMR and MS spectral data analyses. The structure of compound 1 was confirmed through X-ray crystallography which was then used as a reference to propose the revision of the structures of six seco-anthraquinones into xanthones. The isolated compounds were evaluated for cytotoxicity against human cervix carcinoma KB-3-1 cells with the phenylanthraquinone knipholone being the most active (IC50 = 0.43 mu M). Two semi-synthetic knipholone derivatives, knipholone Mannich base and knipholone-1,3-oxazine, were prepared and tested for cytotoxic activity; both showed moderate activities (IC50 value of 1.89 and 2.50 mu M, respectively). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. KW - Bulbine frutescens KW - Xanthone KW - seco-Anthraquinone KW - Phenylanthraquinone KW - Cytotoxicity KW - Structure revision Y1 - 2014 U6 - https://doi.org/10.1016/j.phytol.2014.04.004 SN - 1874-3900 SN - 1876-7486 VL - 9 SP - 67 EP - 73 PB - Elsevier CY - Amsterdam ER -