Large‐scale patterns of fish diversity and assemblage structure in the longest tropical river in Asia

Although the Mekong River is one of the world's 35 biodiversity hot spots, the large‐scale patterns of fish diversity and assemblage structure remain poorly addressed. This study aimed to investigate the fish distribution patterns in the Lower Mekong River (LMR) and to identify their environmental determinants. Daily fish catch data (i.e. from December 2000 to November 2001) at 38 sites distributed along the LMR were related to 15 physicochemical and 19 climatic variables. As a result, four different clusters were defined according to the similarity in assemblage composition and 80 indicator species were identified. While fish species richness was highest in the Mekong delta and lowest in the upper part of the LMR, the diversity index was highest in the middle part of the LMR and lowest in the delta. We found that fish assemblages changed along the environmental gradients and that the main drivers affecting the fish assemblage structure were the seasonal variation of temperature, precipitation, dissolved oxygen, pH and total phosphorus. Specifically, upstream assemblages were characterised by cyprinids and Pangasius catfish, well suited to low temperature, high dissolved oxygen and high pH. Fish assemblages in the delta were dominated by perch‐like fish and clupeids, more tolerant to high temperatures, and high levels of nutrients (nitrates and total phosphorus) and salinity. Overall, the patterns were consistent between seasons. Our study contributes to establishing the first holistic fish community study in the LMR.     

土壤种子库的研究进展

文章对土壤种子库的形成分布、组成和大小、分类方法、研究方法进行了系统的分析,并阐述了土壤种子库与地上植被的关系,土壤种子库的时间动态及研究土壤种子库的意义。     

干旱区地下水埋深空间分布对天然植被覆盖度影响研究—以塔里木河下游为例

以塔里木河下游输水河畔的植被覆盖度和地下水埋深为研究对象,建立遥感反演模型获取研究区植被覆盖度的空间分布,建立地下水数值模型模拟与覆盖度同时段的埋深空间分布,采用空间分析方法对覆盖度和埋深的空间分布数据进行分析,获取不同埋深区间所对应的植被覆盖度,并得出以下结论：研究区植被覆盖度在地下水0～20m的埋深区间上呈阶梯状分...     

密集烘烤不同装烟方式对下部烟叶质量的影响

[目的]研究不同装烟方式对下部叶质量的影响。[方法]试验设置散叶插扦、散叶打捆、散叶筐篮、常规挂杆4种装烟方式,研究各装烟方式对下部烤后烟叶外观质量和经济性状的影响。[结果]挂杆烘烤烤后烟叶橘黄烟比例、中等烟比例、烟叶均价均好于散叶插扦、散叶打捆、散叶筐篮装烟方式。在下部叶烘烤时采用常规挂杆烘烤,中上部叶烘烤时再使用散叶插扦、散叶打捆、散叶筐篮等装烟方式进行散叶烘烤。[结论]研究可为提高下部烟叶烘烤质量提供参考。     

几种特殊情况下索书号的给定

阐述了图书出版的几种特殊情况，并结合沈阳化工大学图书馆工作实践，对索书号的给出进行了探讨，以方便读者检索利用。     

沿黄河下游湿地不同土地利用方式植物多样性

以沿黄河下游湿地林下草本,滩地中的花生地、玉米地,水稻田及湖滨湿地为研究对象,以样方法调查各利用方式下的植物群落,分析各个利用方式下的物种组成、优势种变化、植物多样性及群落物种相似度.结果表明,不同利用方式下的湿地由85个植物物种组成,分别隶属于26科66属,其中林地物种数最丰富,湖滨湿地次之；不同利用方式下除花生地与...     

学科影响指标在期刊评价中的作用探讨

对学科影响指标反映期刊学术影响力的情况、与其他评价指标之间的联系、在期刊学科分类工作中的作用及其存在的局限性进行了初步分析和探讨。     

网式散叶密集烘烤下部烟叶失水规律与烘烤效应关系研究

为明确网式散叶密集烘烤过程中不同装烟层烟叶的失水规律及其与烟叶烘烤效应的关系,采用称重器对气流上升式密集烤房网式烟框装烟下部叶烘烤过程中失水量进行了实时测定,并考查烘烤过程中烟叶外观性状变化及烤后烟叶质量性状。结果表明:(1)烘烤过程中上、中、下三层烟叶失水率均呈Logistic曲线变化规律,在干筋期以前烟叶失水率下层明显大于中层,中层明显大于上层;(2)不同层次烟叶失水速率均呈"先上升后下降"的"∧"型变化趋势,全炕烟叶的平均失水率与中层烟叶接近;(3)各层烟叶失水变化规律及烟叶外观性状变化与烘烤过程中温湿度变化、烘烤时间的关系密切,对烟叶外观质量和内在质量都有影响。     

Water-table modelling to estimate irrigation losses: application to the Lower Durance, France

The consumption of water by irrigation in agriculture is very large and thus the effects of the management of irrigation systems on aquifers are very important. The basis of this preliminary study into the reduction of this consumption is to improve our understanding of the losses resulting from water transport and deep seepage inside the irrigated areas of cultivation (parcels) at the regional level (100 km) by studying water-table variations with reference to anthropogenic contributions. The use of a hydrodynamic model that incorporates adjustment of the quantity of irrigation water by a reduction coefficient enables actual water-table behaviour to be simulated. Losses can thus be deduced from the quantity of irrigation water flowing into the irrigation system and from hydrometeorological parameters.

Application of the technique in the Lower Durance (France) indicates that, in this region, 53% of the water remains in the irrigation network and 19% is lost by deep seepage, leaving only 28% of the water supplied for use by plants.