高立式沙障不同叠加模式的阻沙量对比分析

为了解决尼龙阻沙网在沙埋情况下的防风阻沙,采用不同叠加模式的尼龙阻沙网进行防护。设置3种高立式沙障叠加模式方案,叠加位置分别位于迎风坡、阻沙网、背风坡,迎风坡与背风坡叠加的尼龙阻沙网与原有阻沙障距离和长度均相同,叠加的阻沙网高度为沙埋原有阻沙障的一半,且叠加的尼龙阻沙网需高出原有尼龙阻沙障。选择高1.2 m的沙埋阻沙障进行叠加,迎风与背风坡叠加的位置距原有阻沙障水平距离约45 cm。通过野外观测发现：① 不同叠加模式的高立式沙障阻沙量不同,即阻沙网＞迎风坡＞背风坡;② 3种不同叠加模式的积沙量都随着阻沙网的不断叠加而增加,且增加的阻沙量越来越大;③ 随着阻沙网的不断叠加,3种不同叠加模式的单位阻沙成本不断变化。迎风坡与阻沙网模式的单位阻沙成本不断降低,最后趋于平稳;背风坡模式有所不同,其单位阻沙成本先有所增加,然后再下降,最终趋于平稳。阻沙成本为：阻沙网<迎风坡<背风坡。     

1958～2000年黄土高原沙尘天气基本特征分析

分析了黄土高原1958～2000年57个气象监测站记录的沙尘天气资料,分析显示:(1)黄土高原沙尘天气主要发生在西部地区,沙尘暴、扬沙和浮尘发生频率的最大值分别为19.2天/年、86.1天/年和45.7天/年;(2)春季为沙尘天气的频发期,62.7%沙尘暴、53.5%扬沙和56.3%浮尘发生在春季,4月是沙尘天气发生最多的月份,29.8%沙尘暴21.3%扬沙22.8%浮尘发生在4月;(3)近43年黄土高原沙尘天气呈减少趋势,1958年是沙尘暴天气最多的一年,1966年是扬沙和浮尘天气最多的一年;(4)强沙尘暴也呈减少的趋势,1966年是强沙尘暴最多的一年;(5)黄土高原57个站43年间只有23条特强沙尘暴记录,其中11条在宁夏;(6)沙尘暴大多开始于10时至17时之间约占71%;(7)持续时间大于t的沙尘暴次数N满足:lg(N)=a-bt,b值为0.1662 hr-1。     

Effects of phosphate,nitrate and chloride on calcium,magnesium and manganese content of cigar‐wrapper tobacco

Abstract

Nutrient solutions containing three levels of phosphate, nitrate, and chloride were applied to cigar‐wrapper tobacco (Nicotiana tabacum L.) plants growing in sand culture for a period of 18 days. Concentrations of other nutrient elements in the nutrient solutions were held constant and the solutions were applied to pots as needed to maintain favorable moisture conditions for plant growth. Plants were in the two leaf stage when transplanted and were maintained on a single nutrient solution for 38 days before treatments were started. At the end of an eight weeks growing period, plant leaves were harvested and analyzed for Ca, Mg, and Mn. Dry matter yield was significantly (P=0.01) increased when 2 mM/1 of Ca(NO₃)₂ replaced an equivalent amount of Ca(H₂PO₄)₂ or CaCl₂ in the nutrient solution. Nitrate significantly (P=0.05) increased Ca and Mg content and decreased Mn concentration in leaf tissue in comparison to chloride. Calcium and Mg content were significantly (P=0.05) decreased and Mn content of tobacco leaves was increased by phosphate in comparison to nitrate and chloride.     

辽西北沙地植被恢复的问题与对策

在简要介绍辽宁省沙化土地现状及危害基础上,以阜新为例,从农业、水利、畜牧业、林业4个领域系统总结制约沙地植被恢复与建设中存在的诸多问题.同时,为了科学恢复重建沙地植被,提高已退化的生态系统的生产力,优化当地的生态环境,针对近10年来气候变化、人为不合理经济活动造成新沙源等问题,从有效预防、科学恢复、提高建设水平、提升经营水平、加强研究示范5方面提出相应对策:1)有效预防,要转变生产方式,严于执法,积极推进立法和新机制的执行力;2)科学恢复,优先采取恢复天然植被,建设人工植被时提倡适度造林;3)提高建设水平,要努力提高生态建设和生态经济水平,探索生态移民等植被建设的新模式;4)提升经营水平,正确评价现有人工植被,找出科学经营的方法;5)研究示范,研究主要生态修复技术,建立主要植被恢复的软、硬件示范.提出的对策可为有关部门和人员合理恢复、高效建设、科学经营沙区人工与天然植被提供参考.     

Tomato growth and mineral composition as influenced by nitrogen form and light intensity

Abstract

Tomato plants were grown in sand culture with NH⁺ ₄, and NO^? ₃, forms of N and three levels of light. Plants supplied with NH⁺ ₄, nutrition under high light intensity had symptoms of stunting, leaf roll, wilting, interveinal chlorosis of the older leaves, and one third the dry weight of N0₃‐fed plants. In contrast, growth of plants receiving NH⁺ ₄, nutrition under shade appeared normal although dry weight was reduced. NH₄‐N nutrition suppressed K, Ca and Mg accumulation in tissues and increased P contents as compared to NO₃‐N nutrition.     

The influence of different soil substrates on the service life of Scots pine sapwood and oak heartwood in ground contact

Abstract

The durability of wood in ground contact is affected by numerous influences, such as substrate quality, climate and microflora of the soil, which need to be considered for the prediction of service life of wooden components to be used in the ground. In this study the influence of different soil substrates on the service life of Scots pine sapwood (Pinus sylvestris L.) and oak heartwood (Quercus petraea Liebl.) was investigated. Mini-stakes were exposed in six different soils at the test site of the Federal Research Centre for Forestry and Forest Products (BFH) in Hamburg, Germany. The effect of partly embedding the test samples in concrete or polyethylene films was also examined. After 3 years of exposure the decay rates for both wood species differed significantly between the soil substrates. Compost soil and fertilized test field soil induced the highest decay activity, whereas in pure sand the lowest decay rates were observed. Surprisingly, exposure in gravel also led to higher decay ratings than sand. Protective measures by means of concrete embedding and polyethylene films performed well during the first 2 years of exposure, but showed increasing decay rates in the third year. The overall decay rating for all soil types was higher for oak heartwood than for pine sapwood. The meaning of different soils, independent of other site influences, for service life prediction of wood is discussed, and the need for further studies on this topic is highlighted.     

木槿插条的悬空水培研究

为探讨木槿的有效繁殖技术,促进其生产和推广应用,以木槿为材料,采用悬空水培法和沙培法进行扦插繁殖研究。结果表明:悬空水培法插条4d后有愈伤组织发生,7d后有不定根发生;生根率为100%,生根系数为38.6,根长为22mm,叶片绿色,生长良好。与悬空水培的相比,沙培插条形成愈伤组织和生根时间分别延迟4和8d,生根率、生根系数和根长明显降低,叶片发黄。     

呼伦贝尔沙地樟子松树轮对气候变化的响应1）

在呼伦贝尔沙地中部鄂温克巴彦嵯岗和红花尔基地区共采集沙地樟子松（ Pinus sylvestris var．mon-golica）树轮样芯69个,成功建立了鄂温克、红花尔基两地樟子松轮宽差值年表,用相关函数分析了沙地樟子松的气候限制因子及气候变化对其径向生长的影响。结果表明：气温和降水量同时影响该地区樟子松的径向生长,鄂温克与单一的气候因子均不相关。红花尔基树轮宽度分别与当年6、9月份的气温呈显著负相关;分别与6、9月份的最高温度呈显著负相关;分别与6、8月份的最低温度呈负相关关系;红花尔基树轮指数还与前一年12月份降水量呈显著负相关。鄂温克树轮宽度仅分别与当年7、8月份的帕默尔干旱指数（ PD,S,I ）呈显著负相关;红花尔基樟子松树轮宽度也与当年秋季（8、9、10月份）的PD,S,I显著相关。这表明水分可利用性是沙地樟子松径向生长的最重要影响因子。特征年分析进一步验证了响应分析的结果,即6月份的高温少雨不利于沙地樟子松的生长。     

塔克拉玛干沙漠腹地人工绿地条件下微量元素变化规律研究

在极端干旱的塔克拉玛干沙漠腹地,利用4～5 g@L-1的咸水建立人工植被,改善了生态环境促进了风沙土的成土发育.在成土过程中,土壤微量元素的含量分布具有一定的规律性.研究表明:①人工绿地中的土壤全量微量元素与流沙对照相比变化不大,各处理有效态微量元素大于流沙对照,风沙土成土发育仍处于初级阶段.②流沙中各微量元素含量较低是各处理土壤微量元素含量低的决定因素.③各样地土壤剖面有效态微量元素分布规律为表层明显大于中层及下层.④相同植被类型条件下,人工植被生长年限越长土壤微量元素含量越高.⑤相同年限条件下,草地由于水分和养分条件优于其它处理,各微量元素含量均高于其它植被类型的样地.     

Cu/Pb/Zn/Cd在石英砂中的迁移实验及模拟

通过稳定流混合置换实验,研究了孔隙水流速和pH变化对Cu/Pb/Zn/Cd在石英砂中迁移行为的影响,获得了示踪剂Br-和Cu/Pb/Zn/Cd的穿透曲线(BTCs);并通过室内批量平衡实验获得吸附系数,进而计算出阻滞因子Rd。基于这些实验结果,借助CXTFIT2.1软件,用平衡CDE模型拟合了Br-的BTCs,得到了弥散系数D;在此基础上应用CDE非平衡模型拟合Cu/Pb/Zn/Cd在不同流速和pH条件下的BTCs,并预测了平行实验和不同埋深处Cu/Pb/Zn/Cd浓度的动态变化。结果表明,Cu/Pb/Zn/Cd的迁移能力随流速的增大而增强,而随pH的增大而降低;化学非平衡的两点模型能较好地模拟本文实验条件下Cu/Pb/Zn/Cd的迁移过程。