毛乌素沙漠东部边缘中β尺度暴雨和冰雹综合分析

利用多普勒雷达资料、Micaps系统提供的常规观测资料和物理量场,对2006年9月20日发生在毛乌素沙漠东部边缘的一次强对流天气过程进行了分析。结果表明:冰雹和暴雨是由两块呈块状的中β尺度强对流单体造成的;地面能量比中α尺度"Ω"系统的生成,为能量的积聚和集中释放提供了有利条件;地面能量比中β尺度能量比低值舌的生成,为强对流天气的发生提供了抬升触发机制;冰雹和暴雨发生前,涡度场和散度场的耦合、影响雹暴区次级环流的形成,为雹暴的发生维持提供了动力机制;850 hPa等压面上湿正压场和湿斜压场的配合、以及湿位涡的三维空间结构,对雹暴的发生及落区有指示意义;在多普勒雷达径向速度场上,雹暴运动的前方对流层低层有中气旋生成,雹暴运动的后方对流层低层有中反气旋生成,而对流层中高层有辐散生成,且超级单体特征明显。     

塔克拉玛干沙漠公路交通事故趋势预测分析

应用塔克拉玛干沙漠干线公路建成通车以来的交通事故统计数据,在分析交通事故主要指标发展变化特征和分布特征的基础上,建立了适用于沙漠公路交通事故特点的GM(1,1)预测模型,对未来几年内交通事故发展趋势进行了预测。预测结果表明,未来几年沙漠公路交通事故次数、死亡人数、受伤人数以及直接经济损失等4项指数将分别以15.9%,10%,4.5%和5%的年平均增长率快速增长。同时针对预测结果提出了相应的对策。     

沙尘天气多发区民勤县发现多例非职业性尘肺病

为了调查非职业性尘肺在我国沙尘天气多发区的发病情况,采用多阶段随机抽样方法随机抽取沙尘天气多发区甘肃省民勤县6个乡镇从未接触过职业性沙尘的1500名18岁以上的农民为调查对象,对其中自觉呼吸系统不适的480人进行了胸透,其中81人进行了X光拍片,分析非职业性尘肺病的发生.分析结果表明,有8例非职业性尘肺患者.如果假设在所调查的未进行X光拍片的农民中无人患有非职业性尘肺病(实际上漏检的可能性是存在的),其患病率也高达5.33‰,表明长期暴露于沙尘天气可引发非职业性尘肺,且发病率高,症状严重,对当地农民的健康影响很大.对此,应引起高度重视.由此结论:长年暴露于沙尘天气可导致非职业性尘肺病的发生.论文建议,将这种因常年暴露于沙尘天气而引起的非职业性尘肺病定名为"沙漠尘肺"(简称:沙漠肺)。     

不同封育年限荒漠草原土壤呼吸日、季动态变化及其影响因子

围封禁牧措施可以改善退化草地生态环境,是我国退化草地植被恢复的主要措施.为探讨干旱区荒漠草原不同围封禁牧年限的土壤呼吸作用特征及影响因子,在生长季连续观测围封禁牧11 a、7 a、放牧不封育(CK)荒漠草原土壤呼吸速率及环境因子,结果表明:1在日、季尺度上,封育11 a、7 a和CK荒漠草原土壤呼吸速率均具有明显的单峰曲线变化规律,在日尺度上,最大、最小值分别出现在12:00~16:00和00:00~06:00;在季节变化尺度上,最大值出现在降水较多温度适宜的8月,土壤呼吸均值表现为11 a[0.143 g·(m2·h)-1]7 a[0.138 g·(m2·h)-1]CK[0.106 g·(m2·h)-1].2封育与未封育荒漠草原的土壤呼吸速率与空气、土壤温度均呈极显著的指数关系(P0.001),相关性大小为:地表温度(R2:0.408~0.413)空气温度(R2:0.355~0.376)5~20 cm土壤温度(R2:0.263~0.394);温度敏感性系数Q10随着土层的加深逐渐变大,不同封育年限Q10表现为11 a(2.728)7 a(2.436)CK(2.086).3封育11 a、7 a和CK荒漠草原土壤呼吸速率与空气湿度、土壤含水量一元二次模型达到显著水平(P0.05),与空气二氧化碳呈极显著线性负相关(P0.01),与风速呈显著线性正相关(P0.05),与光照强度呈极显著线性正相关(P0.01).4干旱区荒漠草原土壤呼吸作用随着围封禁牧年限的增加而增加,温度敏感性系数亦随之增加,0~20 cm土壤温度和水分是其土壤呼吸的主要影响因子.     

Rheum palaestinum (desert rhubarb), a self-irrigating desert plant

The rare plant Rheum palaestinum (Polygonaceae) is a perennial hemicryptophyte that grows during the rainy winter in desert mountainous areas in Israel and Jordan that receive an average annual rainfall of ca. 75 mm. It produces between one and four large round leaves that are tightly attached to the ground and form large rosettes of up to 1 m². These leaves differ markedly from the typical small leaves of most desert plants. Moreover, they have a unique 3D morphology resembling a scaled-down mountainous area with well-developed steep drainage systems, raising the question which selective agents were involved in their evolution. We propose that the large leaves collect rainwater that then infiltrates the soil surrounding the root. We measured the seasonal course of leaf growth, examined the area of wet soil surrounding the root after actual and simulated rain, and modeled the water harvesting capacity using the plant leaf area and the weekly precipitation. We show that even in the slightest rains, water flows above the veins to the leaf’s base where it irrigates the vertical root. A typical plant harvests more than 4,100 cm³ of water per year, and enjoys a water regime of about 427 mm/year, equivalent to the water supply in a Mediterranean climate. This is the first example of self-irrigation by large leaves in a desert plant, creating a leaf-made mini oasis. All authors contributed equally to this paper.     

不同放牧制度下短花针茅荒漠草原植物种群作用和种间关系分析

以短花针茅荒漠草原植物种群为研究对象,采用2×2列联表法和灰色关联分析方法,探讨植物种群地位和作用及种间关系在不同放牧制度下的变化。结果表明,放牧会使建群种短花针茅（Stipa breviflora Griseb.）重要值增大,使碱韭(Allium polyrhizum Turcz. ex Regel)的重要值减小;轮牧有利于无芒隐子草(Cleistogenes songorica (Roshev.) Ohwi)在群落中的地位和作用增加,自由放牧则相反。植物群落种间关系正联结强度表现为禁牧区(CK)>划区轮牧区(RG)>自由放牧区(CG),负联结种对数的多少表现为CK相似文献   

荒漠草原4种典型植物群落夏季土壤呼吸及枯枝落叶分解释放CO2贡献量

采用动态密闭气室分析法测定了沙蒿（Artemisia desertorum）群落、赖草（Leymus secalinus）群落、甘草（Glycyrrhizauralensis）群落和冰草（Agropyron crisatum）群落4种典型荒漠草原植物群落土壤呼吸和枯落物分解的CO2释放速率（RS＋L）、土壤呼吸CO2释放速率（RS）,利用推导法估算得到了枯落物分解的CO2释放速率（RL）及其对总释放的贡献。得到了如下结论：（1）4种群落的RS＋L差异较大,其平均值大小排序分别为冰草群落〉赖草群落〉甘草群落〉沙蒿群落,且各群落的RS＋L在1 d中是不稳定的,均表现为不对称的单峰曲线形式;土壤基础呼吸大小排序分别为冰草群落〉甘草群落〉赖草群落〉沙蒿群落,且土壤基础呼吸高的土壤,其土壤养分状况较好。（2）RS相对于气温具有时滞性,4个群落的平均值大小为冰草群落〉赖草群落〉沙蒿群落〉甘草群落。（3）RL平均值大小排序分别为冰草群落〉甘草群落〉赖草群落〉沙蒿群落;对RS＋L的贡献率大小排序为甘草群落〉冰草群落〉沙蒿群落〉赖草群落,表明RL值大的,其对RS＋L的贡献率不一定大,两者之间不存在正相关关系。不同植物群落枯落物对土壤呼吸的贡献与枯落物量、温度因子的相关关系并未表现出一致性,但与15 cm处的地温相关性最高。夏季RL对RS＋L的平均贡献量（以CO2计）在0.05~0.16 g.m-2.h-1之间,平均贡献率在12.88%~35.33%,是大气CO2的一个重要的排放源。     

增温对荒漠草原植物群落组成及物种多样性的影响

以短花针茅荒漠草原为研究对象,通过采用远红外线辐射器模拟增温的方法,探讨了增温对荒漠草原植物群落结构及生物量和物种多样性的影响。结果表明：由于远红外线辐射器的增温作用,在2012年整个生长季内,增温样地10、20、30 cm土壤平均温度与对照样地相比,平均增加了0.39、0.38、0.31℃;各土层土壤含水量较对照平均减少0.76%、0.73%、0.60%。受温度升高及土壤含水量减少的影响,模拟增温6个生长季后,与对照样地相比,群落的高度整体增加,密度、盖度、频度表现为部分物种增加和部分物种减少的趋势,冷蒿（Artemisia frigida）等物种的重要值下降,阿氏旋花（Convolvulus ammanii）等物种的重要值上升,但是增温没有明显改变植物群落的组成。同时,增温处理使荒漠草原禾草的盖度减少,杂类草的盖度增加,半灌木和一两年生植物分盖度未发生明显变化;增温使地上地下生物量出现了不同程度的减少,在0~30 cm土壤深度地下生物量分配中,增温样地0~10 cm分配比例（81.23%）小于对照（86.07%）,10~20 cm分配比例（11.55%）大于对照（9.16%）;20~30 cm 分配比例（7.22%）大于对照（4.77%）,增温使得地下生物量分配格局向深层转移。增温后,增温样地植物Shnnon-Winener指数降低,Pielou均匀度指数升高,温度升高使荒漠草原植物群落的均匀度增加,但并没有提高草地植物的物种多样性。     

Potential Mortality Effects of Off-Highway Vehicles on the Flat-Tailed Horned Lizard (<Emphasis Type="Italic">Phrynosoma mcallii</Emphasis>): A Manipulative Experiment

Southern California desert public lands receive especially high levels of off-highway recreation due to large population centers nearby and popular riding environments such as sand dunes. Controversy has developed over the flat-tailed horned lizard (Phrynosoma mcallii), previously a candidate for listing under the Endangered Species Act. Some evidence suggests lower lizard abundance in areas of higher recreational use than in areas with low or no use. We designed a manipulative experiment to ensure maximum inference in evaluating the direct impact of recreational riding of off-highway vehicles on lizards. Thirty-six lizards, in situ, were treated with an off-highway vehicle treatment during hibernation season in three treatment groups: high impact, low impact, and control. Treatments consisted of timed riding by off-highway vehicles. In all treatment groups survival was 100%, despite hibernation of lizards at very shallow depths. Consequently, indirect effects of off-highway vehicles deserve increased attention. The relative importance of direct versus indirect (i.e., degradation of lizard habitat) impacts caused by off-highway vehicles remains unknown. These indirect effects may include the altering of vegetation, substrate, and prey. We recommend that a manipulative approach be adopted to investigate these possibilities.     

A System to Monitor Climate Change with Epilithic Lichens

The issue of biological monitoring of the local consequences of anticipated global climate change is considered for the Central Negev Highlands, Israel. Epilithic lichens are suggested as biological monitors. The proposed methodology of such monitoring consists of a sampling scheme, including lichen measurement along transects on flat calcareous rocks, and construction of a trend detection index (TDI). TDI is a sum of lichen species cover with coefficients chosen so as to ensure maximum ability to detect global climate trends. Coefficients have been estimated in a study of lichens along an altitudinal gradient from 500 to 1000 m a.s.l. The gradient study demonstrated that the TDI index is performed better than other integrated indices. Recommendations on this system to monitor climate change with epilthic lichens are given. Measuring, for instance, a hundred transects in fifty plots (two transet per plot scheme) allows one to detect a climate-driven change in the epilithic lichen community corresponding to a 0.8 °C shift in annual mean temperature. Such resolution appears sufficient in view of global warming of 2.5 °C considered by the Intergovernmental Panel on Climate Change as a realistic prediction for the end of the next century.