Evaluating the influence of wetland vegetation on chemical residence time in Mississippi Delta drainage ditches

The presence of emergent vegetation within channelized aquatic environments has the capacity to provide a number of biological functions as well as alter the hydrology of the system. Vegetation within the channel exerts roughness, drag and friction on flowing water, reducing flow rates, increasing water depths and increasing hydraulic retention time. By increasing the hydraulic retention time, chemical residence time (CRT) is increased, thus improving the potential of pollutant mitigation. The study compared two geomorphologically similar drainage ditches, one vegetated and one non-vegetated to evaluate the effect obligate, in-stream wetland vegetation had on CRT. A fluoride (F⁻) tracer was amended to both ditches with nutrients and sediments to simulate stormwater runoff event. The measured CRT of the vegetated drainage ditch was at least twice that of the non-vegetated ditch. These results suggest that with the presence of vegetation increasing CRT, chemical removal rates will improve, and as a result increase the possibility of microbial transformation, adsorption, and macrophyte assimilation. By dredging or clear-scraping ditches and removing the vegetative component, farmers and managers alike will increase water flows, decrease CRT and potentially increase pollutant loads into aquatic receiving systems.     

明沟排水条件下盐碱地改良优化配水模式

分析了盐碱地改良传统冲洗模式的弊端,对土壤水的盐分运动进行了活塞流简化。取对称半田面,建立了基于淡化时间的分区灌水数学模型,通过室内试验对冲洗条件下的土壤水盐运动进行了模拟分析,最后利用试验数据求解分区灌水模型得到了盐碱地改良优化配水方案。结果表明,较之传统模式,分区灌水模式下水资源用量明显减少,二分区和三分区模式比较合理,并分别确定了这二种方案最佳的分区位置。     

从中国茶叶博物馆馆藏文物看茶风西渐

茶叶于17世纪初传入西方社会,日后逐渐成为海上丝绸之路的大宗贸易商品,且贸易数量多、价值大.饮茶习俗在西方社会的形成,促进了中国瓷器的外销.本文尝试通过中国茶叶博物馆现藏的文物中的外销茶叶、茶具以及纸质文物,研究、并证明茶叶在传入西方之后的几个世纪对西方社会的文化、经济,尤其是对茶业和陶瓷业所产生的影响.     

乌兰布和沙漠沙尘天气的气象条件分析

运用中国林业科学研究院沙漠林业实验中心野外定位观测站（1983-2004年）和内蒙古磴口县气象站有关资料（1954-2003年），分析乌兰布和沙漠沙尘天气的年际和季节变化特征，研究沙尘天气与气象条件的相关关系。结果表明：该区沙尘天气主要出现在2-6月份，占全年的58．5％，冬季次之，秋季最少，4月份发生频率最高；该区20世纪80年代沙尘天气活动频繁，1983-1987年每年扬沙日数都在100d以上（1986年高达164d）；90年代初期沙尘天气显著下降，中期至末期处于低值；21世纪初，沙尘天气的发生又有所回升。该区充足的沙源为沙尘天气的发生提供了物质来源，当具备了起沙风的动力条件时，极易发生沙尘天气。2～6月沙尘暴、浮尘和扬沙日数与风速呈显著正相关；沙尘暴和扬沙日数与大气相对湿度呈极显著负相关，与蒸发量呈极显著正相关；扬沙、沙尘暴日数与气温和地温呈极显著正相关；浮尘天气与地面相对湿度呈负相关，与蒸发量呈正相关，与气温和地温呈正相关。     

皖西大别山区野生食果资源及其开发应用研究

首次报道了该地区有野生食果资源植物46科、96属、201种(含1亚种、17变种、1变型),并对每种野果分布、数量、食用方法及其综合利用价值进行了详细的调查,将为进一步开发利用这一宝贵资源提供借鉴。     

哀牢山西坡蚂蚁物种及优势种的研究

运用样地调查法对哀牢山自然保护区西坡4个垂直地段28块样地140个样方中的蚂蚁进行调查,共采集蚂蚁标本57 345号,分属9亚科49属172种.切叶蚁亚科的毛切叶蚁属L asiomy rm ex T erayam a etY am ane为中国新记录属.优势亚科为切叶亚科、蚁亚科、猛蚁亚科、臭蚁亚科,优势种有43个.优势种数目随地段或海拔的变化缺乏一致的规律性,优势种百分比随海拔变化有一定的规律.在海拔2 000 m(北段1 750 m)处及以上海拔,蚂蚁群落均由1~3种蚂蚁占绝对优势,甚至只包含1~2种蚂蚁.2 000 m以下蚂蚁优势种数目增加或优势百分比降低.此外,讨论了哀牢山与太白山蚂蚁物种丰富度差异大的原因.     

闽西尾巨桉造林及其生长效果分析

对闽西尾巨桉造林成效进行全面调查,分析了现有林分的生长特点,探讨了不同地理位置、海拔高度、立地质量等级以及施肥次数等因素对尾巨桉生长的影响,总结了尾巨桉造林失败的原因,并提出了闽西今后发展尾巨桉造林的看法。     

生态维护与贫困治理--论"退耕还林"等政策的可持续发展意义

欠发达地区的“生态破坏”与“贫困”是同源性的问题,所以要根本性地消除“贫困”,必须与“生态维护”活动结合起来,才能取得成效。通过分析“退耕还林”政策、“休耕制度”、“世行西部扶贫项目”等实例,对“生态维护”与“贫困治理”相结合的发展思路进行了阐述,并提出了相应的主张。     

中国西部沙漠化与沙尘风暴问题探讨

我国西部地表植被向恶性循环方向发展，土地沙漠化面积迅速增长，沙尘风暴日趋频繁。分析中国西部沙漠化和沙尘风暴存在的主要问题，进一步探讨沙漠化和沙尘风暴形成的原因和对国民经济发展所造成的危害，因地制宜提出了相应的治理对策     

Research on the Ecology Benefit Compensate System of Water of West China

The ecological environment of west region is an important part of the whole ecological environment system of China. The west region has plentiful water resource. But the ecology of water is anxious, it is urgent to protect the water. A consummation ecology benefit compensate of water has significances for west China. This paper summaries the positive role of the ecology benefit compensate system for west China , and analyze the present situation of ecology benefit compensate system in west China, giving some suggestion on its establishment and consummation.