Investigating source areas of eroded sediments transported in concentrated overland flow using rare earth element tracers

Rare earth element oxides (REOs) have excellent potential for use as tracers in erosion studies. Using laboratory and field experiments we aimed to develop and test a simple application method for spreading REOs and to use REOs to determine the source of sediment to concentrated overland flow paths.     

稀土元素对植物生物学作用机制的研究进展

稀土元素在农业上得到了广泛的应用,产生了显著的经济效益。人们对稀土元素生物学效应 的作用机制进行了很多研究,提出了许多论点。从稀土元素在植物体内的赋存、稀土元素对植物光合 作用的影响机制、稀土元素对细胞中Ca的竞争取代机制、稀土元素对生物体内自由基的清除机制和 稀土与生物大分子的紧密结合及在细胞水平的定位五个方面综合分析了稀土元素对于植物体作用 机制的最新研究成果,为稀土农用技术的研究提供新的思路。     

稀土元素的生理机制与烤烟生产

为推广稀土在贵州省烤烟种植方面的应用提供依据,提高烟叶的产量和质量,从稀土元素在烟株体内的分布、对烟叶叶绿素形成的促进作用、对叶绿体结构的影响、以及稀土对烟叶光合作用中的RuBPcase、过氧化物酶、硝酸还原酶等影响效应等方面综述了稀土元素生理机制与烤烟生产关系的研究成果。     

Demographic analysis of a rare columnar cactus (Neobuxbaumia macrocephala) in the Tehuacan Valley, Mexico

In this study we used population projection matrices to evaluate the conservation status of Neobuxbaumia macrocephala, a columnar cactus endemic to a small region in the Tehuacan Valley, in central Mexico. Demographic data included 2-year observations on growth, fecundity and survival of individuals classified by size. Our results indicate that the population is comprised of 70% juveniles. Population growth rate was 0.979 and 0.994 for the 1997/1998 and the 1998/1999 periods, respectively. The slight increase in λ in 1998/1999 was a result of increased fecundity and seedling survival. The highest elasticity values correspond to the survival of large/old individuals. Numerical simulations were performed by changing the value of particular matrix entries and directly evaluating their effect on λ. Population growth rate reached values above unity only when either fecundity or seedling survival probability were increased 10-fold. Given these limitations for population growth, along with its limited distribution range and low population densities, we propose N. macrocephala to be classified as a rare species and to promote its conservation by favoring management practices aimed to increase germination and seedling establishment success.     

广东省珍稀濒危植物观赏特性及其开发利用

广东省共有珍稀濒危植物75种,占我国珍稀濒危植物总数的19 3%。在分析这些珍稀濒危植物的观赏特性的基础上,对其开发利用提出了一些建议。     

云南金平分水岭国家级自然保护区珍稀濒危植物种类

云南金平分水岭国家级自然保护区共有68种国家重点保护的野生珍稀濒危植物。分析了这些植物资源的基本特点，指出了存在的问题，提出了保护和合理利用方面的建议。     

伏牛山自然保护区珍稀濒危植物资源现状与保护对策

本文论述了伏牛山自然保护区珍稀濒危植物资源现状、区系特征,分析了珍稀濒危植物产生的原因,提出了保护珍稀濒危植物资源相应对策。     

红壤性水稻土稀土元素组分分布与变异性研究

测定了具有代表性的 4种母质发育、3种水育型的红壤性水稻土及起源土壤的∑REE、∑LREE和∑HREE ,分析了其分布特点和剖面变异性 ,表明 :(1)红壤性水稻土的∑REE平均水平和离散性均大于全国水稻土平均水平 :(2 )不同母质发育的供试土壤的∑REE和∑LREE的平均水平依玄武岩母质土壤系列 >石英闪长岩母质土壤系列 >黑云母花岗岩母质土壤系列 >凝灰岩母质土壤系列顺序递减 ;(3 )土壤剖面稀土组分体系的变异程度为 :∑LREE >∑HREE >∑REE ;而在不同水育类型上则依起源土壤、潜育型水稻土、渗育型水稻土、潴育型水稻土顺序增大。 (4 )∑LREE和∑HREE在渗育型水稻土的E层和潴育型水稻土的Br层具有显著的分馏作用     

Assessing limitations on population growth in two critically endangered Acacia taxa

Flowering phenology, soil seedbank and the impact of fire, weeds and grazing were investigated in two rare Acacia taxa restricted to the agricultural district north of Perth Western Australia. Acacia aprica is known from six extant populations and one extinct population. Five of the extant populations are restricted to linear road reserves with the sixth population located in a small native vegetation remnant. Acacia cochlocarpa ssp. cochlocarpa is known from a single population also situated on a road verge. Size class structure, levels of canopy death and an absence of juveniles indicated that all populations are in decline. Flowering intensity and success varied between populations and years in A. aprica and between years in A. cochlocarpa ssp. cochlocarpa. Seed bank analysis indicated that seeds were patchily distributed while experimental fires demonstrated that such events could break seed dormancy and promote germination. Both taxa have similar germination physiologies and showed increased germination after seeds were exposed to heat. Following emergence, however, competition with annual weeds had a negative impact on seedling growth and survival in both taxa. While vertebrate grazing had some influence, weeds were the major inhibitory influence on recruitment. Reduced fire frequencies since fragmentation may be responsible for population decline in both taxa but other site specific factors such as weeds and grazing may affect the establishment of seedlings following fire.     

稀土钕对中国兰花品种线粒体酶活力及其同工酶的影响

采用不同浓度的NdCl3营养液,对中国蕙兰进行根、叶表面喷施培养,分析了蕙兰根部线粒体抗氧化酶SOD、呼吸代谢酶COX活性及同工酶的变化,结果表明:营养液中NdCl3浓度分别为60、80、100 mg/L时,COX-5同工酶被激活,NdCl3浓度为60 mg/L时的COX活性最高;营养液中NdCl3浓度分别为80、10...