Background concentrations of elements in surface soils and their changes as affected by agriculture use in the desert-oasis ecotone in the middle of Heihe River Basin,North-west China

The concentrations of twenty four chemical elements in the surface layer of natural desert soils and the cultivated farmland soils were measured at a desert-oasis ecotone in the middle of Heihe river basin, north-west China. Background values were estimated for (a) major elements (Si 335.3 g kg^− 1, Al 49.4 g kg^− 1, Fe 19.1 g kg^− 1, Ca 29.4 g kg^− 1, Mg 8.9 g kg^− 1, K 20.1 g kg^− 1, Na 17.5 g kg^− 1 and P 0.338 g kg^− 1), (b) heavy metals and non-metals (Cr 55.8 mg kg^− 1, Mn 404.8 mg kg^− 1, Ni 17.7 mg kg^− 1, Cu 5.1 mg kg^− 1, Zn 33.7 mg kg^− 1, Pb 15.5 mg kg^− 1 and As 5.2 mg kg^− 1) and (c) other trace elements (Ti 2.0 mg kg^− 1, V 55.3 mg kg^− 1, Co 5.7 mg kg^− 1, Rb 82.4 mg kg^− 1, Sr 232.9 mg kg^− 1, Y 14.7 mg kg^− 1, Zr 194.9 mg kg^− 1, Nb 7.8 mg kg^− 1 and Ba 720.6 mg kg^− 1). After natural desert soil was cultivated for agricultural use, significant changes in element concentrations occurred under tillage, irrigation and fertilisation management. Compared to natural soil, the for the levels of Si, K, Na, Sr, Zr and Ba decreased, and no changes were observed for Rb, while the values of the other 17 elements increase in agricultural soil from 1.2 to 3.5 times. However, their absolute concentrations are still low, suggesting that the arable soil in this region remains comparatively a clean soil. The increased silt, clay and organic carbon content, under long-term irrigation, enriched the fine-grained materials, and application of fertilisers and manure contributed to the accumulation of most elements in arable soil. The accumulation of elements in agricultural soil increased with increasing cultivation years and extent of soil development.     

The Migif–Hafafit gneissic complex of the Egyptian Eastern Desert: fold interference patterns involving multiply deformed sheath folds

The Wadi Hafafit Complex (WHC) is an arcuate belt of orthogneisses, migmatites and other high-grade metamorphic rocks, which marks the boundary between the Central Eastern and the South Eastern Deserts of Egypt. In the WHC, gneissic meta-gabbro outlines macroscopic fold interference patterns characterized by elliptical to irregular culminations cored by gneissic meta-tonalite to meta-trondhjemite. The five main culminations of the WHC have previously been labeled A (most northerly), B, C, D and E (most southerly). A detailed structural investigation of B, C, D and E reveals that these structures are a result of the interference of four macroscopic fold phases, the first three of which may represent a single deformation event. The first folding involved sheath-like fold nappes, which were transported to the N or NW, assisted by translation on gently dipping mylonite zones. The regional gneissosity and mineral extension lineations formed during this folding event. The fold nappes were deformed by mainly open upright small macroscopic and mesocopic folds with approximately NE-trending hinges. As a probable continuation of the latter folding, the sheaths were buckled into large macroscopic folds and monoclines with the same NE-trends. The fourth macroscopic folding resulted from shortening along the NE–SW direction, producing mainly NW–SE-trending upright gently plunging folds. Gravitative uplift is disputed as a component of the deformation history of the WHC. The peculiarities of the fold interference pattern result from the interesting behaviour of sheath folds during their refolding.     

Habitat, occurrence and conservation of Saharo-Arabian-Turanian element Forsskaolea tenacissima L. in the Iberian Peninsula

The aim of this study is to assess the Iberian populations of Forsskaolea tenacissima L. according to its biogeographical interest, habitat, geographical range and conservation status. Results point out that they are restricted to gravel wadis of Tabernas Desert (SE Spain), are scarcely included in protected areas and represent historically isolated populations with relict behaviour. We also describe a new association, Senecioni-Forsskaoleetum tenacissimae. Conservation status of species is cause for concern and two conservation actions must be carried out. Firstly, protected areas should house Forsskaolea populations and secondly, phytosociological characterization of a community allows inventorying its habitat and directing conservation efforts to community level.     

乌兰布和沙漠东北边缘植物群落物种多样性及其生态环境

应用群落多样性指数（Ｄ）、均匀度（Ｊ）、生态优势度（Ｃ）等指标，对乌兰布和沙漠东北边缘不同生境（荒漠区、绿洲外围、绿洲内）的天然植物群落进行了研究，结果表明这三种指标值能有效地表征群落的组成结构特征及生境的优劣；荒漠植物群落多样性指数（Ｄ＝０．６０３～２．９８４）和均匀度（Ｊ＝０．３３７～０．６９１）都较低，而生态优势度（Ｃ＝０．７２４～０．１９５）较高，说明荒漠植被生态环境的脆弱性，群落结构越复杂，多样性指数越高；多样性与生态环境关系密切，Ｄ和Ｊ随生境渐好而递增，Ｃ随生境渐好而递减，可作为环境评价指标；多样性在一定程度上体现了群落的发展阶段和稳定程度，越接近顶级阶段，多样性越高，且环境的改善有助于群落演替进程的加速；干旱区弃耕撩荒地次生演替植被，在弃耕初期多样性随弃耕年限增大而减小，后期处于一个较稳定的水平，且各演替阶段植物组成变化较大。     

Vegetation change,erosion risk and land management on the Nullarbor Plain,Australia

 Arid karst landscapes that have been degraded by human activities provide a challenge for rehabilitation and an opportunity to test ideas about the stability and resilience of limestone ecosystems. The Nullarbor Plain is the largest arid karst area in Australia (220 000 km²) and is divided into extensive closed karstic depressions separated by low rocky ridges, while the dominant vegetation is chenopod shrubland. Since European settlement there has been considerable change in the vegetation, with significant reduction in shrub and grass cover over large areas of the plain. These changes are related to a state and transition model of vegetation dynamics which incorporates climatic variability, fire history and grazing pressure from sheep, kangaroos and rabbits. A partial sediment budget using ¹³⁷Cs inventories reveals local and regional patterns of soil redistribution within this arid karst landscape. Rehabilitation of eroded soil in pastoral lands has been accomplished at several sites but is labour intensive and vulnerable to climatic fluctuations. Given the low stock numbers, limited number of people involved, and poor economic returns, it would be sensible to make pastoral activities on the Nullarbor secondary to conservation priorities. This would necessitate a change in land ethic to stewardship, with emphasis on rehabilitation and control of feral animals. Management of increased numbers of visitors to the caves and karst also requires that resource inventories and management plans for each area be drawn up and used. Received: 1 June 1995 · Accepted: 4 December 1995     

沙漠沙丘污水处理系统:原理、方法和效果

“沙漠沙丘系统(DDS)”是以地球化学工程学原理为指导的特殊水处理系统,它利用沙漠沙作为滤料,通过“机械过滤”、“化学作用”和“生物作用”净化污染水,一方面可使沙丘变得湿润而不再移动,以固定移动沙漠;另一方面又能净化污染水,最终起到“以害克害、固沙治水、一举多得”的良好综合生态环境效应。DDS是绿色的水处理系统,所需的原料和生成物都属于自然界存在的物质,无二次污染的发生。在DDS设计中,要注意的主要因素应包括:滤料的种类、湿干时间比、微生物培养方式、滤料层厚度、进水水质、时间、温度和pH等。DDS可以把官厅水库水由V类和超V类处理成2~3类水,从而恢复官厅水库的饮用水功能。     

The precipitation infiltration and runoff recharging experiment observation in the Taklimakan Desert

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｌｏｃａｌｐｒｅｃｉｐｉｔａｔｉｏｎｉｓｍｏｓｔｉｍｐｏｒｔａｎｔａｖａｉｌａｂｌｅｆｒｅｓｈｗａｔｅｒｓｏｕｒｃｅｉｎｄｅｓｅｒｔｓ．ＴｈｅＴａｋｌｉｍａｋａｎＤｅｓｅｒｔｂｅｌｏｎｇｓｔｏａｎｅｘｔｒｅｍｅａｒｉｄｂｅｌｔ．Ａｃｃｏｒｄｉｎｇｔｏａｆｅｗｙｅａｒｓ’ｌｉｍｉｔｅｄｏｂｓｅｒｖａｔｉｏｎｄａｔａ,ｉｔｉｓｅｓｔｉｍａｔｅｄｔｈａｔｔｈｅｐｒｅｃｉｐｉｔａｔｉｏｎｓｈｏｕｌｄｂｅｉｎｔｈｅｒａｎｇｅｏｆ３０－５０ｍｍａｎｎｕａｌｌｙ．Ｈｏｗｅｖ…     

利用探地雷达观测分析早春融雪前后沙丘表层土壤含水量的时空分布

积雪融水是古尔班通古特沙漠春季植物发育的重要水源, 快速获取早春沙丘的土壤水分变化具有十分重要的生态学意义. 2010年3、 4月分别使用探地雷达进行了多次测量实验, 结果显示: 1)融雪初期, 沙丘顶部土壤的自由水含量最大, 阳坡次之, 且融雪水在重力作用下沿坡面侧向缓慢流动, 在坡底汇集, 主导了融雪初期乃至整个春季沙丘表层土壤水分的分布格局; 2)融雪后期, 由于阴坡积雪和冻土消融相对滞后, 表层土壤含水量略高于阳坡, 而沙丘顶部由于融雪最早且融雪期间水分转移最多而表面最为干燥; 3)通过与时域反射仪的同步测量结果对比, 探地雷达的测量精度被有效控制在0.03范围内, 且探地雷达提供的连续数据更有利于从细节上把握土壤含水量的变化趋势, 为中小尺度土壤水分的动态研究提供了一种科学、 有效的技术手段.     

毛乌素沙漠地震勘探历程及效果

总结陕西省煤田地质局物探测量队在毛乌素沙漠开展地震勘探攻关的三个阶段及各阶段取得的成果,认为该区虽然表浅层地震地质条件复杂,地震勘探难度较大,但勘探精度基本上可以达到解释5m断层的的精度。并以国家重大产业技术开发专项的依托工程,内蒙古鄂托克前旗新上海庙地区SZT井田三维地震勘探为例,对地震激发、接收技术进行改进,并采取精细静校、地表一致性振幅补偿等处理手段,结合多参数信息,进行资料精细解释。成果表明：依托工程野外原始资料甲级率达到70％以上,获得的三维数据体信噪比高,构造及煤层解释成果可靠、准确。     

150kaBP以来巴丹吉林沙漠东南区域地层序列的新研究

巴丹吉林沙漠东南部边缘查格勒布鲁剖面中更新统/上更新统下部、上更新统下部/上更新统上部和上更新统上部/全新统的地质界线依次发生在59AGS/60L、39FD/40G和9L/10FD之沉积界面上。其时限依次大致为150kaBP、75kaBP和10kaBP,该剖面记录了150kaBP以来25个旋回的沙漠与湖相等沉积交替变更的历史过程。通过该剖面粒度和SiO₂、Al₂O₃、Fe₂O₃、FeO在地层中的分布特征、软体动物化石指示的古生态等综合研究表明,所述这些沉积旋回是自那时以来,在北半球冰期间冰期气候波动影响下,冬夏古季风往复更迭所导致的非季风沙区沙漠期与间沙漠期多次正逆交替演变的结果。