Middle Westphalian plant fossils from the West Cumberland Coalfield,UK

Twenty-six form-species of plant macrofossils occur in the Coal Measures exposed in the Howgill Head Quarry, Whitehaven, Cumbria, UK. They belong to the Neuropteris semireticulata Subzone in the lower part of the Paripteris linguaefolia Zone, indicating the uppermost Duckmantian. They confirm that the sandstones exposed in this part of the West Cumberland Coalfield are part of the Whitehaven Sandstone Formation, and not a stratigraphically lower unit as previously suggested. The Howgill head fossils represent the only well documented example of a N. semireticulata Subzone assemblage in Britain, although comparable assemblages are known from coeval strata in northern France, Belgium, northern Germany and Poland.     

Sediment transport under the presence and absence of emergent vegetation in a natural alluvial channel from Brazil

Studies regarding the influence of emergent vegetation on sediment transport are scarce and have mainly focused on flume conditions. To fill this gap and also meet the international need, we aimed to evaluate the influence of emergent vegetation (Echinodorus macrophyllus) on sediment transport of Capibaribe River, Brazil. Bedload and suspended sediment measurements were carried out using the US BLH 84 and US DH 48 samplers, respectively. Measurements of stem diameter, stem spacing and plant density were performed in conjunction with flow and sediment field measurements. Based on our results, 0.45 m s ? 1 was the threshold of mean flow velocity supported by E. macrophyllus under field conditions. This value can be helpful for other rivers with gravel-bed river to armoured layer ratio (AR ? D50-surface)/D50-subsurface ? 12.50) – natural conditions observed in Capibaribe River – or where the vegetation can provide positive effects, such as increase the bed stability, assist water restoration/rehabilitation and decrease water turbidity. Our results can hopefully be used in engineering practice and ecosystem management. In general, both the drag coefficient and drag force varied inversely and directly with the mean flow velocity and vegetation density, respectively. The vegetation resistance force was inversely proportional to the bedload transport owing to the resistance caused by emergent vegetation. This finding was supported by the clear decoupling between nonvegetated and emergent vegetated conditions indicated by cluster analysis. The study results provided a reasonable understanding of the interaction between emergent vegetation, water flow and sediment transport in the Capibaribe River.&2016 International Research and Training Centre on Erosion and Sedimentation/the World Association     

降雨冲刷对黄土公路边坡植物防护影响的试验研究

通过对裸露黄土公路边坡、厚层基材植草公路边坡、三维网植草公路边坡以及平台植树公路边坡的现场降雨冲刷试验,阐述了不同防护型式的公路黄土边坡在降雨条件下的坡面径流、含泥量以及坡面冲刷情况,得出了降雨对边坡坡面的侵蚀过程,首先是从雨滴直接打击土体开始,进而引起溅蚀,分散土粒,紧接着发生超渗径流造成坡面冲刷。以及对坡面破坏最大的是坡顶上方来水等重要结论。验证了坡面植物防护以及平台植树等防护方法可以有效降低降雨冲刷对坡面的侵蚀破坏,为黄土地区公路边坡植物防护的设计施工以提供了可靠的依据。     

溪洛渡地下洞室群地震响应的二维及三维数值模型比较分析研究

验证了显示有限差分方法进行地震波衍射分析的可行性,并基于此方法分别建立了二维（2D）及三维（3D）数值模型,对溪洛渡地下洞室群的地震安全性进行了分析与讨论。研究表明,在唐山余震天津医院地震波作用下洞室群处于安全状态。对比2D及3D数值计算结果可以发现,2D数值模型计算效率远远高于3D数值计算模型;对于建造于完整性较好、强度较高的岩体介质中地下洞室群而言,可以采用2D数值模型粗略估算洞身部分的地震响应,而洞室端面的动力响应则必须通过建立3D模型来进行分析。     

污水处理系统中活性污泥细菌多样性研究

采用分子生物学手段16S rDNA克隆文库方法对北京高碑店污水处理厂回流污泥中的细菌进行了多样性研究。结果表明,活性污泥系统中细菌群落具有高度多样性,所有克隆子分属5个不同的细菌类群,优势细菌类群为变形菌(proteobacteria),占克隆文库的76.7%;细菌类群优势依次为β-变形菌类群(β-proteobac-teria,占39.8%)、不可培养菌类群(uncultured bacteria,占22.33%)、γ-变形菌类群(γ-proteobacteria,占20.15%)、α-变形菌类群(α-proteobacteria,占6.79%)和δ-变形菌类群(δ-proteobacteria,占4.85%);活性污泥中起硝化作用的主要是亚硝化单胞菌(Nitrosomonas sp.,占1.94%)和硝化螺旋菌(uncultured Nitrospirae bacterium,占11.65%),由于这2种硝化菌自身生长缓慢,难以与异养细菌竞争,以致其在文库中的比例较低;而作为反硝化细菌的陶厄氏菌属在文库中的比例却高达27.18%,可见该活性污泥具有较强的反硝化能力;克隆文库中还发现了少量的玫瑰单胞菌属(占4.85%),推测它的存在和有机磷的降解有关。     

大气中CO_2含量增长后的温室效应对我国未来农业生产的可能影响

大气中CO_2含量升高引起的气候变化是目前人们十分关注的问题,地球变暖是不少科学家的共同看法.本文根据赵宗慈估算的CO_2含量增加1倍时对我国气候的可能影响,分析了这种变化对农业热量资源及农业生产的可能影响.结果表明:积温将增加无霜期延长,种植界线向北推移,对我国粮食产量的影响区域间差异较大,三北地区为增产趋势,华南为减产趋势.     

Response of the mean global vegetation distribution to interannual climate variability

The impact of interannual variability in temperature and precipitation on global terrestrial ecosystems is investigated using a dynamic global vegetation model driven by gridded climate observations for the twentieth century. Contrasting simulations are driven either by repeated mean climatology or raw climate data with interannual variability included. Interannual climate variability reduces net global vegetation cover, particularly over semi-arid regions, and favors the expansion of grass cover at the expense of tree cover, due to differences in growth rates, fire impacts, and interception. The area burnt by global fires is substantially enhanced by interannual precipitation variability. The current position of the central United States’ ecotone, with forests to the east and grasslands to the west, is largely attributed to climate variability. Among woody vegetation, climate variability supports expanded deciduous forest growth and diminished evergreen forest growth, due to difference in bioclimatic limits, leaf longevity, interception rates, and rooting depth. These results offer insight into future ecosystem distributions since climate models generally predict an increase in climate variability and extremes. CCR Contribution # 941     

交通运输对道路两侧土壤及植物的影响研究展望

针对我国汽车工业的快速发展和机动车保有量迅速增加的状况,结合国内外相关研究成果,介绍了交通运输污染物的分类与来源,概述了交通运输对道路周围土壤及植物的影响。根据我国道路交通的实际,探讨了相关领域未来的研究方向,提出应以开发清洁替代能源和深入研究污染物在各环境介质中的迁移转化规律,进而减少污染物对人类的健康损害及筛选对交通运输特征污染物高富集的树种以阻断污染物的迁移为主。