中国大陆地磁场Z分量日变幅的时空特征分析

In this paper, we use the daily ranges of the vertical magnetic intensity of approximately 76 geomagnetic stations from January 1, 2008 to December 31, 2010 to analyze the spatial and temporal characteristics of Z ranges. The results are summarized as follows: (1) Temporally, we use regressive analysis and FFT analysis to analyze the data. The results show that the Z component daily ranges of all stations have an obvious cyclical variation, the computed Fourier spectra of all data sets have clearly resolved the required periodicities in the data, in the form of distinct peaks at days 365, 183, 22, and 73, and the power spectra of day 365 is the highest in all periods. (2) In terms of spatial variation, the daily ranges show nonlinear variation with latitude in China. The results show the existence of a point of inflexion (maximal value point) nearby at about 25°N, the daily ranges of Z rise from 15°~25°N and have a good linear decrease variation along with 25°~50°N. (3) Compared with the spatial and temporal variations of Z daily ranges with the Sq current inversion, we found that the spatial and temporal characteristics of Z ranges are decided mainly by the spatio-temporal evolution of the Sq current system. (4) If the latitudes of the maximum amplitudes of variation of the vertical component in the geomagnetic quiet days are roughly taken as the latitudes corresponding to the foci of Sq overhead current system, we can see that these latitudes of foci become higher in summer, are lowest in winter and highest during Equinoxes, displaying conspicuous monthly and daily variations. For two successive geomagnetic quiet days, the latitudes of foci may vary ten degrees.     

Assessing regional differences in predation of endangered species: Implications from Texas populations of the endangered star cactus (Astrophytum asterias)

Understanding threats to endangered species is one of the most critical components of implementing a successful recovery plan. For the endangered star cactus Astrophytum asterias, both mammalian and insect herbivory have been documented as a major threat to populations in Mexico. Herein, we focus on populations of A. asterias in Texas, examining how mortality threats differ from populations found in Mexico as well as among sites within Texas. Our study supports insect and mammalian herbivory as a major threat to A. asterias in Texas, with reductions in population sizes ranging between 16 and 54%. However, our study highlights that both regional and local differences can influence rates of mortality even in a range-restricted species such as A. asterias and highlights the need to assess threats at both of these levels for effective development and implementation of endangered species recovery plans.     

The effects of enclosures and land-use contracts on rangeland degradation on the Qinghai–Tibetan plateau

Rangeland degradation on the Qinghai–Tibetan Plateau is a growing concern, often attributed to climate change and overgrazing. A minority of researchers have suggested instead that degradation may be caused by changes in land management, particularly enclosures and the contracting of long-term rangeland use rights to households. However, these claims have been hampered by a lack of empirical evidence. This field experiment is the first to compare rangeland conditions over time in the case of different management regimes on the Qinghai–Tibetan Plateau, specifically single-household versus multi-household management. A survey of vegetation properties in Maqu County, Gansu province in 2009, and repeated in 2011, examined the differences between single- and multi-household management in terms of vegetation biomass, cover, and species richness. In 2009, the biomass of the sedge group under multi-household management was significantly higher than that under single-household management. In 2011, biomass, vegetation cover, and species richness were all significantly higher under multi-household management than single-household management. These data suggest the flaws of the tragedy of the commons assumptions underlying single-household management.     

湖南境内沅水鱼类资源现状与多样性分析

基于2010年1月-2011年12月对湖南境内沅水鱼类资源的连续调查,系统研究了沅水鱼类物种资源现状及群落多样性特征.结果表明,沅水现有鱼类99种(不含引进种),隶属8目19科63属.在沅水的怀化、五强溪水库和常德江段,鱼类物种数分别为69、66和77种,鱼类多样性春、夏季高于秋、冬季,常德江段高于其它两个江段.五强溪水库与怀化、常德江段之间鱼类群落为中等相似,怀化与常德江段之间为中等不相似.生态类型方面,沅水鱼类以定居性、杂食性和底栖性为主;各江段渔获物组成存在一定差异,渔获物产量和规格以五强溪水库较高,其它江段鱼类小型化明显.对比历史资料显示,沅水鱼类物种多样性已明显下降.     

中国岩石圈三维结构雏型

根据岩石圈的流变习性,可以将中国岩石圈分成3层,即:弹性上地壳、塑性下地壳和岩石圈地幔.它们的构造各不相同,并且各层间呈现复杂的关系.在新疆地区,上地壳推覆叠置形成以三山四盆为特点的盆山构造,驮伏在一系列东西走向的条带状背型构造与向型构造的下地壳之上.在强烈隆升中的西藏地区,它的周边是差异隆升,但它的腹部地区的弹性上地壳完整未遭破坏.这是因为它的腹部的下地壳和岩石圈地幔发生局部熔融,上地壳被局部熔融的下地壳和岩石圈地幔顶托,以液压的方式整体抬升.华北地区,则是软流圈上升破坏了岩石圈地幔,形成新生地幔与残留地幔并存的蘑菇云岩石圈地幔构造.并由于软流圈的上升,使地壳拉张减薄形成裂谷盆地.中国大陆下除了东北吉辽地区太平洋板块向大陆俯冲外,东部其他地区都没有发现太平洋板块俯冲的证据.中生代以来中国东部发生的岩石圈巨变不是太平洋板块向中国大陆的俯冲而造成的,而是软流圈物质上涌的结果.因此,中国大陆当今的构造动力,是西部由印度板块俯冲推挤和东部东亚-西太平洋软流圈上升构成的二元系统.这两个动力系统的分界是南北地震带.在南北地震带以西整体处在压缩环境中:南北地震带以东,则处在拉张环境中.正是由于应力场由压缩转变成拉张产生的剪应力造成了南北地震带.华北地区所以成为地震活动地区是因为它的岩石圈地幔已被强烈的改造成为蘑菇云构造.热流上升,弹性层急剧减薄,弹性极限下降所致.     

高州水库优势轮虫的种群分布

高州水库(1988)发现的44种轮虫中有8种为优势种。它们是螺形龟甲轮虫、针簇多肢轮虫、圆筒异尾轮虫、奇异巨腕轮虫、裂痕龟纹轮虫、卡顿圆筒异尾轮虫、卵形彩胃轮虫和真翅多肢轮虫。它们中除奇异巨腕轮虫、裂痕龟纹轮虫和真翅多肢轮虫外,其余的种类全年出现。8种的种群密度为46.1个/升。它们的个体数量占轮虫总量的83.8%。一年中以夏、秋密度最高,分别占41.2%和39.6%,而春、冬密度最低,各为10.7%和8.5%。文中还讨论了这八种轮虫各种高峰形成的量适温幅以及它们的分布与水质的关系。     

Distribution and species composition of mass occurrences of large-sized sponges in the northeast Atlantic

The geographic and bathymetric distribution of “ostur”, that is mass occurrences of large-sized astrophorid demosponges, first recognized at the Faroe Islands during the internordic BIOFAR programme (Marine Benthic Fauna of the Faroe Islands), are mapped for the northeast Atlantic. This is done on the basis of information obtained during the sampling of the BIOICE programme (Benthic Invertebrates in Icelandic Waters) as well as during cruises at Karmoy (southwest Norway), the Trondheim Fjord (middle Norway), the Koster area (southwest Sweden) and the Denmark Strait (southeast Greenland). In addition, information has been acquired from Nordic and German biologists and fishermen regarding the occurrence of “ostur”. These data together with the sparse information in the literature show that the geographic distribution of the “ostur” areas follows two band-shaped arcs, defined by the Norwegian Atlantic Current and the Irminger Current. The local occurrence of “ostur” is, however, to a great extent dependent on areas of variable topography where a hard bottom is present.The results show that two main types of “ostur” can be recognized in the northeast Atlantic. Firstly a boreal “ostur” which is dominated by Geodia barretti, Geodia macandrewi, Geodia atlantica, Isops phlegraei, Stryphnus ponderosus and Stelletta normani, and occurs around the Faroe Islands, Norway, Sweden, parts of the western Barents Sea and south of Iceland. Secondly a cold water “ostur” characterized by the same genera but represented by different species, viz. Geodia mesotriaena, Isops phlegraei pyriformis and Stelletta rhaphidiophora, which is found north of Iceland, in most of the Denmark Strait, off East Greenland and north of Spitzbergen. A number of hexactinellid species are also represented in the cold water “ostur”, the most frequently occurring being Schaudinnia rosea.Suggestions are given regarding the possible causes for observed changes in the distribution of “ostur” as well as to the biological importance of these areas.     

中国绿球藻目的新种和新变种

饶钦止和沈国华等人于１９５０、１９５２、１９５５和１９９０年自湖北、江苏、广西和黑龙江等地采得标本，经鉴定表明，它们为中国绿球藻目，分隶于６属的８个新种和４个新变种，模式标本保存于中国科学院水生生物研究所藻类标本室。     

厦门及其邻近地区虾池浮游动物的组成及分布

分析了1999年8月至2000年7月逐月采自厦门及其附近地区（厦门杏林、龙海角美、漳浦前亭）4个虾池的浮游动物样品345份、鉴定出浮游动物36种（类），本文初步报道浮游动物的种类组成，浮游动物的种类数和浮游动物的总个体数量的季节分布，并对不同地区的虾池浮游动物的若干生态特征做了比较。     

Desert grassland canopy arthropod species richness: temporal patterns and effects of intense, short-duration livestock grazing

Arthropods living in the canopies of two woody shrub species (a sub-shrub (Gutierrezia sarothrae) and a large shrub (Prosopis glandulosa)) and perennial grasses plus associated herbaceous species, were sampled on 18, 0.5 hectare plots in a Chihuahuan Desert grassland for five consecutive years. Mesquite shrubs were removed from nine plots, six plots were grazed by yearling cattle in August and six plots were grazed in February for the last 3 years of the 5 year study. Arthropod species richness ranged between 154 and 353 on grasses, from 120 to 266 on G. sarothrae, and from 69 to 116 on P. glandulosa. There was a significant relationship between the number of families of insects on grass and G. sarothrae and growing season rainfall but species richness was not a function of growing season rainfall on any of the plants. Several of the arthropod families that were the most species rich in this grassland were found on all of the plants sampled, i.e. Salticid spiders, Bruchid and Curculionid beetles, Cicadellid and Psyllid homopterans, and ants (Formicidae). There were more species rich families that were shared by grasses and the sub-shrub G. sarothrae than with mesquite. The absence of a relationship between growing season rainfall and species richness was attributed to variation in life history characteristics of arthropods and to the non-linear responses of annual and perennial desert grassland plants to rainfall.There were no significant differences in insect family or species richness on any of the plant types as a result of removal of mesquite (P. glandulosa) from selected plots. Intense, short duration (24 h) grazing by livestock during in late summer resulted in reduced species richness in the grass-herb vegetation layer but had no effect on insect species richness on snakeweed or mesquite shrubs. Livestock grazing in winter had no effect on insect species richness on any of the vegetation sampled.