Distribution patterns and stable carbon isotopic composition of alkanes and alkan-1-ols from plant waxes of African rain forest and savanna C3 species     

Angela Vogts  Heiko Moossen  Florian Rommerskirchen  Jürgen Rullkötter 《Organic Geochemistry》2009,40(10):1037-1054

Leaf wax components of terrestrial plants are an important source of biomass in the geological records of soils, lakes and marine sediments. Relevant to the emerging use of plant wax derived biomarkers as proxies for past vegetation composition this study provides key data for C₃ plants of tropical and subtropical Africa. We present analytical results for 45 savanna species and 24 rain forest plants sampled in their natural habitats. Contents and distribution patterns of long chain n-alkanes (n-C₂₅ to n-C₃₅) and n-alkan-1-ols (n-C₂₄ to n-C₃₄) as well as bulk and molecular carbon isotopic data are presented. The variations of the analysed parameters among different growth forms (herb, shrub, liana and tree) are small within the vegetation zones, whereas characteristic differences occur between the signatures of rain forest and savanna plants. Therefore, we provide averaged histogram representations for rain forest and savanna C₃ plants.The findings were compared to previously published data of typical C₄ grass waxes of tropical and subtropical Africa. Generally, trends to longer n-alkane chains and less negative carbon isotopic values are evident from rain forest over C₃ savanna to C₄ vegetation. For n-alkanols of rain forest plants the maximum of the averaged distribution pattern is between those of C₃ savanna plants and C₄ grasses. The averaged presentations for tropical and subtropical vegetation and their characteristics may constitute useful biomarker proxies for studies analysing the expansion and contraction of African vegetation zones.  相似文献   

Extended orbitally forced palaeoclimatic records from the equatorial Atlantic Ceara Rise     

Heiko Plike  Julia Frazier  James C. Zachos 《Quaternary Science Reviews》2006,25(23-24):3138

We extend existing high-resolution Oligocene–Miocene proxy records from Ocean Drilling Program (ODP) Leg 154. The extended record spans the time interval from 17.86 to 26.5 Ma. The data are age calibrated against a new astronomical solution that affords a re-evaluation of the intricate interaction between orbital (“Milankovitch”) forcing of the climate and ocean system, and the fidelity with which this forcing is recorded in oxygen and carbon stable isotope measurements from benthic foraminifera, and associated lithological proxy records of magnetic susceptibility, colour reflectance, and the measured sand fraction. Our records show a very strong continual imprint of the Earth's obliquity cycle, modulate in amplitude every , a very strong eccentricity signal in the carbon isotope records, and a strong, but probably local, imprint of climatic precession on the coarse fraction and magnetic susceptibility records. Our data allowed us to evaluate how the interaction of long, multi-million year beats in the Earth's eccentricity and obliquity are implicated in the waxing and waning of ice-sheets, presumably on Antarctica. Our refined age model confirms the revised age of the Oligocene–Miocene boundary, previously established by analysis of the lithological data, and allows a strong correlation with the geomagnetic time scale by comparison with data from ODP Site 1090, Southern Ocean.  相似文献   

Environmental Governance Meets Reality: A Micro-Scale Perspective on Sustainability Certification Schemes for Oil Palm Smallholders in Jambi,Sumatra     

Katrin Martens  Yvonne Kunz  Ir. Rosyani  Heiko Faust 《社会与自然资源》2020,33(5):634-650

Abstract

Multi-stakeholder sustainability certification schemes have become a favorite instrument for applying good governance, though studies indicate their inefficiency at the producer level. In this study, we used a mixed-method approach to first, map the institutional context of independent oil-palm smallholders in rural Sumatra while, second, reflecting upon the impact of the Smallholder Standard proposed by the Roundtable on Sustainable Palm Oil on smallholder management practices. We hold that non-recognition of micro-scale perspectives within governance processes may partially explain noncompliance with certification principles among smallholders. The Smallholder Standard appears unable to mitigate challenges important for smallholders, who in turn cannot properly comply with it, due to problems including weather instability and high management costs. We suggest that certification schemes need to work on some overlooked but essential preconditions of good governance, namely gaining micro-level visibility and acceptance.  相似文献   

1990 Watershed Management Symposium Durango, Colorado, USA     

Stefan Wagner  Robert Hahn  Herbert Reichl 《GeoJournal》1989,18(4):458

Reports

1990 Watershed Management Symposium Durango, Colorado, USA  相似文献   

A model of the distribution of crustal magnetization in central Europe compatible with the field of magnetic anomalies deduced from Magsat results     

H. J. Nolte  A. Hahn 《Geophysical Journal International》1992,111(3):483-496

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Geo-/Object-Coding for Local-Change Assessment     

Heiner Benking Dipl.-Ing  Heiko Schmidt v. Braun 《GeoJournal》1990,20(2):167-173

Missing availability of reliable and specific landscape data may pose substantial restrictions to successful exploitation of remote sensing data and fast implementation of GIS (Geo-Information Systems). The possibilities to document conditions with high spacial resolution at a given time and to review changing aspects by different disciplines represent opportunities for complex environmental programs.The article covers: geodata acquisition and processing, research, execution, and ergonomical/cognitive aspects. Application in inpenetrable terrain for research, landuse, and engineering requirements proved the feasibility especially in areas with high demand for timely, accurate, and comprehensive surveys.Airborne close-range sensing was developed to survey localities and regions. It is no competition to global-change monitoring and large area are mapping programs possible with remote sensing. Substituting only the bulk of field-work, leaving time for in-depth review in the field or in the office, the system provides a possibility to restudy points of interest.Exploitation of advanced metric cameras, specialized airborne platforms, and spatial overlay, recognition, and discrimination techniques form the backbone of the TOPOGRAMM approach. Multi-sectoral, multi-temporal, multi-spectral survey and processing methods rely basically on enlarged image scales additional to conventional aero-photogrammetry and analytic plotting. Measurements and identification, not primarily interpretation, allow to establish high-fidelity and high resolution geo-frameworks. Focussing on micro- and mesoscales, no emphasis is given to highest geometric accuracy used for geodetic surveys. Drawing near to the object allows extraction of thematical and semantical information, dimensions, and phenomelogy of objects hitherto only singularily available.

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Fluid-structure interaction effects for offshore structures     

A. S. Veletsos  A. M. Prasad  G. Hahn 《地震工程与结构动力学》1988,16(5):631-652

Comprehensive analyses are made of the differences in the responses of simple models of offshore structures computed by the standard and extended versions of Morison's equation for the hydrodynamic forces, and of the effects and relative importance of the numerous parameters involved. The responses also are evaluated by the equivalent linearization technique and Penzien's decoupling technique, and the interrelationship and accuracy of these approaches are elucidated. The results are displayed graphically in the form of response spectra for absolute maximum displacement employing dimensionless parameters that are easy to interpret and use. In addition, the decoupling technique is generalized to include consideration of a current of constant velocity, and a simple modification is proposed which improves the accuracy of this approach. A particularly simple approximation is included for the hydrodynamic modal damping values of multi-degree-of-freedom, stick-like systems.  相似文献   

Neotectonic basin and landscape evolution in the Eastern Cordillera of NW Argentina,Humahuaca Basin (~24°S)     

Heiko Pingel  Manfred R. Strecker  Ricardo N. Alonso  Axel K. Schmitt 《Basin Research》2013,25(5):554-573

The intermontane Quebrada de Humahuaca Basin (Humahuaca Basin) in the Eastern Cordillera of the southern Central Andes of NW Argentina (23°–24°S) records the evolution of a formerly contiguous foreland‐basin setting to an intermontane depositional environment during the late stages of Cenozoic Andean mountain building. This basin has been and continues to be subject to shortening and surface uplift, which has resulted in the establishment of an orographic barrier for easterly sourced moisture‐bearing winds along its eastern margin, followed by leeward aridification. We present new U–Pb zircon ages and palaeocurrent reconstructions suggesting that from at least 6 Ma until 4.2 Ma, the Humahuaca Basin was an integral part of a largely contiguous depositional system that became progressively decoupled from the foreland as deformation migrated eastward. The Humahuaca Basin experienced multiple cycles of severed hydrological conditions and subsequent re‐captured drainage, fluvial connectivity with the foreland and sediment evacuation. Depositional and structural relationships among faults, regional unconformities and deformed landforms reveal a general pattern of intrabasin deformation that appears to be associated with different cycles of alluviation and basin excavation in which deformation is focused on basin‐internal structures during or subsequent to phases of large‐scale sediment removal.  相似文献   

Application of satellite remote sensing to observe and analyse temporal changes of cocoa plantation in Ondo State,Nigeria     

Dada  Emmanuel  Hahn  Michael 《GeoJournal》2022,87(1):231-246

GeoJournal - This study examined the changes in the area of land occupied by cocoa plantation in Ondo state in order to provide useful information for effective agricultural policy to increase...  相似文献   

Social learning towards a more adaptive paradigm? Reducing flood risk in Kristianstad municipality,Sweden     

Åse Johannessen  Thomas Hahn 《Global Environmental Change》2013,23(1):372-381

Social learning is often treated as an intervention, a designed process facilitated or even initiated by a third party. We investigated how a social learning process emerged spontaneously from inside Kristianstad, one of the most flood-prone municipalities in Sweden. Twenty key persons were interviewed over 8 years, many of them several times, to assess the process. A small action oriented group of technical professionals perceived the flood risk and were key drivers providing strategic innovative capacity. We identified the process attributes that fostered the learning, the knowledge generated and other learning outcomes adapting a model by Schusler et al. (2003). Despite some elements of double loop learning, this process was not able to change the prevailing stationary principle/paradigm, feeling safe behind the embankments and continuing building on low lying land. We argue that building resilience and adaptive capacity would require a mind shift to a paradigm of flood proofing/living with floods and preparing for the unexpected, acknowledging that water cannot be controlled at a certain level. We conclude that knowledge development is inhibited by the Swedish decentralisation approach and we call for a multilevel learning strategy including learning from international experience and emphasising more active coordination at the national level.  相似文献