Late glacial environment and climate development in northeastern China derived from geochemical and isotopic investigations of the varved sediment record from Lake Sihailongwan (Jilin Province)

Total organic carbon (TOC) content, total nitrogen (TN) content, stable nitrogen isotope (δ¹⁵N) and stable organic carbon isotope (δ¹³C_org) ratios were continuously analysed on a high resolution sediment profile from Lake Sihailongwan (SHL), covering the time span between 16,500 and 9,500 years BP. Strong variations of the investigated proxy parameters are attributed to great climatic fluctuations during the investigated time period. Variations in organic carbon isotope ratios and the ratio of TOC/TN (C/N ratio) are discussed with respect to changing proportions of different organic matter (OM) sources to bulk sedimentary OM. Phases of high TOC content, high TN content, depleted δ¹³C_org values and high δ¹⁵N values are interpreted as times with increased productivity of lacustrine algae in relation to input of terrigenous organic matter. Two distinct phases of enriched nitrogen isotope ratios from 14,200 to 13,700 and 11,550 to 11,050 years BP point towards a reduced phytoplankton discrimination against ¹⁵N due to a diminished dissolved inorganic nitrogen pool. The combination of geochemical (TOC, TN, C/N ratio) and isotopic (δ¹³C_org, δ¹⁵N) proxy parameters points to a division of climate development into four stages. A cold and dry stage before 14,200 years BP, a warm optimum stage with high phytoplankton productivity from 14,200 to 12,450 BP, a colder and drier stage from 12,450 to 11,600 BP and a stage of climatic amelioration with high variability in TOC and TN contents after 11,600 BP. These results are discussed in relation to monsoon variability and Northern Hemisphere climate development of the late glacial.     

Community strategies to promote sustainable wetland-based food security in rural areas of Zimbabwe

This article explores the various strategies rural households employ to sustain wetland use and conservation in the context of the restrictions imposed by the existing legal framework in Zimbabwe. Wetland cultivation is a common feature of the rural landscape and is mainly triggered by subsistence households endeavouring to stabilize their food security, especially in semi-arid and arid environments of the developing countries. Data was collected through a household questionnaire survey, key informant interviews, document review and direct observations. Quantitative data was analysed using ANOVA, Spearman Correlation Coefficient and Wilcoxon in Statistical Package for Social Scientists, whereas qualitative data was subjected to thematic analysis. The results revealed that most households adjacent to wetlands were food secure as wetland conditions enable the provision of a wide range of crops and natural products, contributing almost half of the food directly consumed and 48.2 % of average annual household total cash income. It was also observed that various soil and water conservation practices were adopted and local institutional arrangements were put in place to oversee their effective implementation. Thus, the general result has been increased wetland productivity, improved livelihoods and ecosystem protection. This has largely rendered the impact of legislation restricting wetland cultivation subtle in the local context. The study concluded that there is a need to promote participatory wetland management based on low-cost approaches sensitive to local conditions and the needs and practices of the local communities.     

Neubenennungen lithostratigraphischer Einheiten in der Helvetischen Kreide

In September 2007 Föllmi and coauthors requested the approval of four lithostratigraphic terms of the Swiss Committee of Stratigraphy (SCS). These terms were to be used in their publication on the Cretaceous in the Helvetic realm (Föllmi et al. 2007). At its meeting on October 18, 2007, the SCS decided the following: The Tierwis Formation (replacing the Drusberg Formation) was accepted, with the reserve that a section at Tierwis should be published in the near future. For the former “Lower Orbitolina Beds” the term Rawil Member was accepted, but here too a better type section than the one at Rawil Pass should be published. The term Rohrbachstein bed should not be used as a formal unit because it describes only a minor lithologic variation within the Grünten Member. The term Plaine Morte bed for a thin condensed horizon can not be accepted due to the fact that its definition is based mainly on biostratigraphy. Furthermore, the duplication a locality term which is in use for a previously established lithostratigraphic unit should be avoided.     

末次盛冰期和全新世大暖期中国北方沙地气候定量重建初探

中国北方典型沙地处于东亚季风边缘区半干旱气候带,对气候变化响应敏感.本文对已有的该区域古气候记录文献资料进行整理分析和评估,对末次盛冰期与全新世大暖期两个特征时间段的古温度与古降雨量空间格局进行定量化重建,获得了其分布特征.结果表明,在末次盛冰期(约26 ～ 16ka)温度降低了5～11℃,变率为60％～200％,降温极值在黄土高原南缘;降雨量减少180 ～ 350mm,变率为50％左右,东北地区降雨量变化不大.在全新世大暖期(约9 ～ 5ka),温度升高了1.0 ～3.5℃,变率为20％～130％;降雨量增加了30 ～ 400mm,变率为10％ ～120％,其中存在一些需剔除的奇异点,从东部沿海向西北内陆降雨量增幅有加大趋势.上述结果为进一步探讨中国北方干旱-半干旱区古气候变化机理、检验东亚季风区古气候数值模拟结果等提供了定量化数据.     

The solar constant

A detailed compilation of the most recent values of the solar constant is given (13 values published from 1967 to 1970). The most probable value seems to be 1.95 cal cm^–2 min^–1 or 1.36 kW m^–2 with a formal rms error of ± 0.3%. The corresponding effective temperature is 5770K.Systematic errors of the order of ± 1%, but also a possible variability of the same order cannot be excluded.     

Compression of α-MnS (alabandite) and a new high-pressure phase

The compressibility of -Mns (alabandite) was determined by x-ray analysis using a Mao-Bell type diamond anvil cell. The zero pressure bulk modulus (K₀) is 74±2 GPa with the pressure derivative of the bulk modulus (K_o) fixed at four. Allowing (K_o) to vary yielded a statistically better fit with K₀ = 88±6 GPa and k₀ = 2.2±0.6. Our data combined with the data of McCammon (1991) gave K_o = 73±1 GPa with k_o fixed at four. A fit with k_o allowed to vary yielded k_o = 75±2 GPa and k_o = 3.7±0.4. Alabandite transformed from the B1 structure (NaCl-type) to an unknown high-pressure phase at 26 GPa. The high-pressure phase has lower than hexagonal symmetry and it is stable to at least 46±4 GPa.Also affiliated with the James Franck Institute, University of Chicago     

On the wavelength dependency of solar limb darkening (λλ303 to 1099 nm)

The limb-darkening data published by Neckel and Labs (1994) (5th-order polynomials P ₅(), = cos ) are used to represent the limb darkening by the functions L _n(), proposed first by Kourganoff (1949a). When plotted against wavelength, the coefficients of these functions show a rather low scatter and appear to be linear functions of either ^–1 or ^#x2212;5.     

Improved data of solar spectral irradiance from 0.33 to 1.25μ

The conversion of our centre of disk intensities published in 1968/70 into mean disk intensities has been repeated, using more accurate data for the centre-to-limb variation of both continuous radiation and strong absorption lines.The random observational mean error of the new irradiance data very likely is not larger than 1.5% in the UV and not larger than 1% in the visible and infrared. Comparison with the fluxes of Sun-like stars observed by Hardorp (1980) confirms these errors and seems to exclude the possibility of a systematic, wavelength-dependent scale error which would correspond to a temperature difference larger than 50 K.The resulting integral value of the irradiance between 0.33 and 1.25 is 1.060, the corresponding value of the solar constant lies between 1.368 and 1.377 kWm^-2.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.