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The nightingale Luscinia megarhynchos has undergone population decline and range contraction at the north-western limit of its distribution in England during the last 25 years. We examine patterns of habitat occupancy and habitat availability across sites with a range of population histories to see whether habitat loss is a plausible explanation for these declines. The number of singing males in 1999 correlated with area of primary nightingale habitat in the East Midlands (where the species has declined), but not in East Anglia (where the population has been stable). Change in population size between 1980 and 1999 and current habitat availability were weakly correlated in the East Midlands but not in East Anglia. These results are consistent with habitat loss having contributed to the decline of the nightingale in the East Midlands, but suggest that other, wider-scale, factors may be at least partially responsible for determining the abundance of the species within England as a whole.  相似文献   
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以珍稀濒危植物毛柄小勾儿茶(Berchemiella wilsonii(Schneid.)Nakai var.pubipetiolata H.Qian)嫩梢为外植体进行组织培养实验,结果表明:以1/2 MS+6-BA0.5mg/L+NAA 0.05mg/L为芽诱导培养基、MS+6-BA0.5mg/L+NAA 0.05mg/L为增殖培养基,可以得到大量的毛柄小勾儿茶试管苗。  相似文献   
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N. Luchi    P. Capretti    G. Surico    C. Orlando    M. Pazzagli    P. Pinzani 《Journal of Phytopathology》2005,153(1):37-42
Pinus nigra (Austrian pine) is a tree widely planted in central and southern Europe in the reforestation of areas with poor soils. One of the major constrains of P. nigra is a fungal disease caused by Sphaeropsis sapinea which causes shoot tip dieback and tree mortality. This paper describes a real‐time quantitative PCR assay based on the partial sequence of the small subunit ribosomal RNA of S. sapinea to detect and quantify DNA of the fungal pathogen in S. sapinea inoculated shoots. The study found that real‐time quantitative PCR was a reliable technique to diagnose this disease and suggests that it can also be used to study fungal behaviour in host tissue and particularly to quantify fungal growth in the latent or endophytic phase.  相似文献   
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Goal, Scope and Background To strengthen the evaluative power of LCA, life cycle interpretation should be further developed. A previous contribution (Heijungs & Kleijn 2001) elaborated five examples of concrete methods within the subset of numerical approaches towards interpretation. These methods were: contribution analysis, perturbation analysis, uncertainty analysis, comparative analysis, and discernibility analysis. Developments in software have enabled the possibility to apply the five example methods to explore the much-used Ecoinvent”96 database.Discussion of Methods The numerical approaches implemented in this study include contribution analysis, perturbation analysis, uncertainty analysis, comparative analysis, discernibility analysis and the newly developed key issue analysis. The data used comes from a very large process database: Ecoinvent’96, containing 1163 processes, 1181 economic flows and 571 environmental flows. Conclusions Results are twofold: they serve as a benchmark to the usefulness and feasibility of these numerical approaches, and they shed light on the question of stability and structure in an often-used large system of interconnected processes. Most of the approaches perform quite well: computation time on a moderate PC is between a few seconds a few minutes. Only Monte Carlo analyses may require much longer, but even then it appears that most questions can be answered within a few hours. Moreover, analytical expressions for error propagation are much faster than Monte Carlo analyses, while giving almost identical results. Despite the fact that many processes are connected to each other, leading to the possibility of a very unstable system and very sensitive coefficients, the overall results show that most results are not extremely uncertain. There are, however, some exceptions to this positive message.  相似文献   
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