Land Degradation on Barren Hills: A Case Study in Northeast Vietnam

The term "barren hills" has been a keyword for land degradation in the uplands of Vietnam for over a decade. Nevertheless, the "barren" land is still not adequately ecologically characterized. In this work, we analyze land use-induced changes in vegetation and soil properties along a sequence of barren hills types formed on one physiotope. The study is undertaken in the Bac Kan province, one of the poorest upland regions where livestock plays an important role. A transition from an old-growth laurel forest to a sparse manmade grassland is characterized by a total of 177 species, rapid species turnover, and discrete dominants, and an overwhelming effect of disturbance history on both soil and vegetation patterning. Land degradation is most apparent in land use-induced maintenance of arrested successions, and the regeneration course is shifted towards drier formations. We hypothesize a conceptual model as an aid to understanding the process of early fallow differentiation in response to the patterned, fine-scale disturbances. The larger-scale implications of the observed trends in regeneration potentials deviation, and, in particular, the effect of water buffaloes in halting fallow successions, are discussed.     

Assessing the spatial distribution of grassland age in a marginal European landscape

Grassland age is increasingly recognised to be an indicator for present-day biodiversity, e.g. plant species richness, and is also important for other landscape functions. We developed a methodological approach to systematically assess the spatial distribution of grassland age in marginal European landscapes. This approach - applied to the Lahn-Dill Highlands (1270 km(2)), a marginal landscape in Hesse, Germany - comprises three steps: (1) in a two-stage stratification process, we pre-stratified the study area according to recent land-cover patterns and their changes between 1955 and 1995 (stratification I) and classified grassland types by combining data on soil moisture, base-richness, and elevation (stratification II). From 50 grassland types, we randomly selected 1000 representative grassland patches. (2) We determined the age of these patches by means of aerial photograph interpretation of a chronosequence dating back to 1953 and classified each patch with respect to the age classes young (<18 years), mid-aged (18-47 years), and old (>47 years). (3) Based on this information, we calculated grassland type-specific probabilities for grassland patches to belong to the respective age classes. These probabilities were projected to districts by direct extrapolation. An exemplary validation of extrapolation results for two test areas was performed. The results revealed that 49% of the investigated patches were old grassland. The remaining patches were mid-aged (36%) or young grassland (15%). The extrapolation results indicated accordingly a predominance of old grassland at the district scale. Occurrences of mid-aged grassland were concentrated in districts with a pronounced land-cover change, whereas young grassland is apparently evenly distributed across the study area. Validation results suggest that our approach is suitable for a realistic estimation of grassland age in marginal European landscapes. The method may be applied in landscape models of various disciplines that rely on large-scale information on grassland age.     

Assessment of heavy metal releases from the use phase of road transport in Europe

An emission inventory was compiled for heavy metal air emissions from road transport in Europe (EU-40). For the database, country-specific data was taken such as the diesel and gasoline fuel consumption per country, the content of Pb in gasoline and diesel fuel and the share of different vehicle types. For tyre and brake wear emissions, average wear rates and heavy metal contents of different materials were used to develop emission factors for tyre and brake wear. It covers exhaust emissions (Pb from gasoline and diesel) as well as non-exhaust emissions (As, Cd, Cr, Ni and Pb from the wear of brake linings and vehicle tyres). The base year is 2000, and two scenarios were developed for 2010, a business as usual (BAU) scenario and a maximum feasible technical reduction (MFTR) scenario. Both result in a remarkable decrease in Pb exhaust emissions and a rising share of non-exhaust emissions. To assess the results, the inventory is (a) compared to an inventory compiled with a top-down approach that covers the same area and years but only emissions from combustion processes and (b) added to an inventory covering all sectors for heavy metal air emissions.     

On-road and laboratory investigation of low-level PM emissions of a modern diesel particulate filter equipped diesel passenger car

Modern diesel particulate filter (DPF) systems are very effective in reducing particle emissions from diesel vehicles. In this work low-level particulate matter (PM) emissions from a DPF equipped EURO-4 diesel vehicle were studied in the emission test laboratory as well as during real-world chasing on a high-speed test track. Size and time resolved data obtained from an engine exhaust particle sizer (EEPS) and a condensation particle counter (CPC) are presented for both loaded and unloaded DPF condition. The corresponding time and size resolved emission factors were calculated for acceleration, deceleration, steady state driving and during DPF regeneration, and are compared with each other. In addition, the DPF efficiency of the tested vehicle was evaluated during the New European Driving Cycle (NEDC) by real time pre-/post-DPF measurements and was found to be 99.5% with respect to PM number concentration and 99.3% for PM mass, respectively. PM concentrations, which were measured at a distance of about 10 m behind the test car, ranged from 1 to 1.5 times background level when the vehicle was driven on the test track under normal acceleration conditions or at constant speeds below 100 kmh^?1. Only during higher speeds and full load accelerations concentrations above 3 times background level could be observed. The corresponding tests in the emission laboratory confirmed these results. During DPF regeneration the total PM number emission of nucleation mode particles was 3–4 orders of magnitude higher compared to those emitted at the same speed without regeneration, while the level of the accumulation mode particles remained about the same. The majority of the particles emitted during DPF regeneration was found to be volatile, and is suggested to originate from accumulated sulfur compounds.     

Cu and Zn mobilization in soil columns percolated by different irrigation solutions

We investigated the effects of different concentrations of nitrate and ammonium in irrigation water on the mobilization of Zn and Cu in repacked soil columns with a metal-polluted topsoil and unpolluted subsoils over two and a half years. Soil solution samples were collected by suction cups installed at vertical distances of a few centimeters and analyzed for dissolved organic carbon (DOC), Cu, and Zn (total and labile). During high N treatments the pH decreased and the presence of exchangeable cations resulted in Zn mobilization from the surface soil. The nitrogen input stimulated the biological activity, which affected both concentration and characteristics of DOC and consequently Cu speciation. Metal leaching through the boundary between the polluted topsoil and the unpolluted subsoils increased soil-bound and dissolved metals within the uppermost 2 cm in the subsoils. Our study shows that agricultural activities involving nitrogen fertilization can have a strong influence on metal leaching and speciation.     

干旱胁迫下5种三叶草的生理反应(英文)

为了解三叶草属抗旱的生理机理,寻找适宜干旱地区种植的三叶草品种,比较了地三叶草(Trifoliumsubterraneum L.)、大花三叶草(T.michelianum Savi)、白三叶草(T.repens L.)、高加索三叶草(T.ambiguum M.Bieb.)和草莓三叶草(T.fragiferum L.)在人工干旱条件下4 wk的生长和生理反应.结果表明,干旱处理下大花三叶草、草莓三叶草和白三叶草地上部分干重严重减少,分别降低了70%、66%和64%,而高加索三叶草和地三叶草减少不到50%;高加索三叶草叶片水势降低到-2.0 MPa以下,而其他4种三叶草只降低到-1.5MPa左右;高加索三叶草和草莓三叶草叶片光合速率降低25%,而地三叶草、白三叶草和大花三叶草下降35%~63%.此外,干旱条件下,5种供试三叶草叶片中游离脯氨酸含量普遍增加,其中高加索三叶草和白三叶草分别增加到2.5倍和3.1倍.研究显示高加索三叶草在多项重要生长和生理指标中表现出很强的抗旱性,因此认为其可作为干旱地区栽培白叶草的补充或替代种.图1表3参22     

Stability and self-organization of proteins

X-ray crystallography and NMR provide insight into the three-dimensional structure of proteins at high resolution yielding a relatively small number of stable "topologies". Their free energies of stabilization are minute compared to the total molecular energy. Molecular adaptation to extremes of physical conditions at the protein level refers to marginal alterations of the intramolecular interactions; clearcut predictions with respect to the correlation of protein structure and protein stability are at present not possible. The acquisition of the native structure of proteins is determined by the kinetically accessible minimum of potential energy. The overall mechanism may be described as a hierarchical condensation with elements of secondary/super-secondary structure and subdomains/domains as intermediate stages. In the case of oligomeric and multimeric proteins, folding and association of subunits follow a consecutive uni-bimolecular mechanism, the kinetics of which can be simulated with high precision. The "code of protein folding" is still unknown.     

Die Technik der Nukleinsäurehybridisierung und ihre Bedeutung für diagnostische Fragestellungen

Nucleic acid hybridization techniques (e.g., Southern blotting and in situ hybridization) gain increasing importance in laboratory medicine, as demonstrated by examples in this paper. The molecular basis of this approach to detect nucleic acids homologous to known DNA probes is explained. It is concluded that this technique has advantages in the detection of pathogens compared to other methods used in laboratory medicine.