荒漠生态系统C、N、P生态化学计量研究进展

生态化学计量学是通过研究生物有机体主要元素含量及其比值的变化关系,揭示生态系统各组分间元素循环规律的一门学科,生态化学计量也是荒漠生态系统研究的重要内容。因此,综合掌握水分和养分限制环境下C、N、P生态化学计量的关系对揭示荒漠生态系统植物的限制性元素、土壤营养的供给能力、养分的有效性等都具有重要的意义。基于此,回顾和分析了国内外荒漠生态系统C、N、P生态化学计量最新研究和动态,分别从植物、凋落物、土壤、土壤微生物、土壤酶进行较为系统的评述,讨论了植物-土壤-微生物-酶四者的关系,提出了荒漠生态系统C、N、P生态化学计量的未来研究方向,期望为全面理解固沙植被的演变过程、稳定性维持机制及其科学管理提供理论指导。     

Relationship Between Land Cover Ratio and Urban Heat Island from Remote Sensing and Automatic Weather Stations Data

Urban heat island (UHI) effect has a close relation to land covers type. This paper investigates the relationship between land cover ratio and UHI in Guangzhou, south of China using remote sensing and automatic weather stations data. The temperature data were obtained by Automatic weather stations (AWS) of Guangzhou in October, 2004, at the same time with the CBERS remote sensing image acquired. Firstly, the hourly mean temperature was computed from hourly AWS data. Secondly, the CBERS remote sensing image was classified using support vector machine (SVM) and land covers classification were output. Thirdly, the classification result was overlapped with a round buffer with 1.5 KM radius centered on the AWS, and then the land cover ratio, Edge Density (ED) and Mean Fractal Dimension (MFRACT) of buffers were computed out. Finally, the correlation coefficient between hourly mean temperature and land cover ratio, ED and MFRACT was calculated. It concluded that UHI intensity was heavier during nighttime than daytime. Stations with higher vegetation ratio and higher ED had lower heat island effect. On the contrary, stations with higher impervious ratio and lower ED had more serious heat island effect. The positive–negative of correlation coefficient between hourly mean temperature and vegetation ratio during 11:00–17:00 h (local time) was opposite to that during other time. ED was negatively correlated with hourly mean temperature except during 11:00–17:00 h. On the contrary, MFRACT was positively correlated with hourly mean temperature. It implied that fragmentations of patches were favorable to UHI alleviation, and complexities of patch were unfavorable factors.     

近30年来国外国家公园研究进展与启示

国家公园是自然保护和旅游研究领域的重要内容之一。本文以Web of Science数据库收录的近30年国外国家公园相关文献为基础,对筛选的451篇英文文献运用可视化软件CitespaceⅢ及系统综述的方法,从资源评估、环境影响、发展模式、规划、运营管理5个方面对国外国家公园研究主要内容进行述评,并对研究方法进行系统分析。最后,从国家公园立法、发展模式构建、管理内容与方法、社区参与模式与机制、环境监测与评估5个方面提出未来中国国家公园的研究方向。总体上看,国外有关国家公园的研究具有研究对象复杂、视角多元、方法综合的特征。在构建国家公园体制的大背景下,借鉴国际经验构建中国国家公园研究体系将对完善中国保护地相关研究、指导国家公园建设具有重要意义。     

常量元素氧化物含量及其比值揭示的中晚全新世以来玛曲高原的环境演变

对玛曲高原具有代表性的黄土-古土壤-风成砂剖面(OL剖面)常量元素氧化物含量及其比值的地球化学特征分析表明:(1)常量元素氧化物总含量为91.93%且SiO₂(67.93%) >Al₂O₃(11.2%) >Fe₂O₃(3.97%) >CaO(3.76%)>K₂O(2.16%) >Na₂O(1.81%) >MgO(1.1%);(2)玛曲高原处于较弱的脱Ca、Na初级风化阶段,并伴有碳酸盐的淋失;(3)玛曲高原的气候经历了冷干-凉润-温湿-凉干的冷暖旋回。依据常量元素氧化物含量及其比值揭示的环境特征并结合¹⁴C测年将玛曲高原中晚全新世以来的环境演变划分为4.6 ka BP以前的风沙活动强烈期、4.6～4.3 ka BP的风沙活动较弱期、4.3～0.3 ka BP的固结成壤期和0.3 ka BP至今的风沙活动增强期4个阶段。     

Distribution of the indigenous microorganisms and mechanisms of their orientational activation in Daqing Oilfield

The distribution of indigenous microorganisms was surveyed in Block 1 of Daqing Oilfield. Based on this survey, the indigenous microorganisms in the formation water were activated with different activator systems at the simulated stratum ecological environment. The changes of the number of bacteria of various physiological groups were determined during the process of activation. Also changes of pH value and composition of gas productions were analyzed at the end of culturing. The results showed that the selected block formation water contained a great number of saprophytic bacteria, hydrocarbon-oxidizing bacteria, fermentative bacteria, methane-producing bacteria and sulfate-reducing bacteria. Under the conditions that the growth of sulfate-reducing bacteria was controlled the block had the potential to enhance oil recovery by activating beneficial bacteria. The growth of sulfate-reducing bacteria can be inhibited through the activation of nitrate-reducing bacteria. The number of nitrate-reducing bacteria reached 10⁶–10⁷ cells/mL, but sulfate-reducing bacteria reached only 0–45 cells/mL in A system. Methane-producing bacteria can be activated by C, D activators. The relative content of biological methane in the light hydrocarbon gas reached 80% in C, D systems. B activator was conducive to the propagation of acid-producing bacteria, so that the pH value of the culture medium decreased from 7.5 to around 5.0. Hydrocarbon-oxidizing bacteria can be activated by various activator systems. There was low molecular light hydrocarbon in gas production according to the analysis of gas chromatograph. According to the content of methane and the number of methane-producing bacteria, methane only can be generated through activating methane-producing bacteria. By choosing different activator systems, various populations of indigenous microorganisms can be activated accordingly.     

西藏羌塘南部地区的冰海杂砾岩及其成因

青藏高原及邻区广泛分布的漂砾层、杂砾岩、含砾板岩是一种特殊的冰海相沉积岩，称为冰海杂砾岩（Ｉｃｅ－ｓｅａＭｉｘ－ｃｏｎｇｌｏｍｅｒａｔｅｓ）。它们和一起产出的冷水型动物群、耐冷植物群视为这一地区冈瓦纳相最典型的标志，代表着冈瓦纳大陆上塔尔切尔（Ｔａｌｃｈｉｒ）冰期所影响的时间和空间。除“标准型”冰海杂砾岩外，羌塘腹地发现了蛇绿质和钙质冰海杂砾岩。这两种冰海杂砾岩的发现，不但丰富了冰海杂砾岩的家族成员，同时也为冰海沉积、物质来源问题、冈瓦纳大陆北界及特提斯演化研究提供了新的信息。经研究，冰海杂砾岩中的砾石来自印度半岛──冈瓦纳大陆本体，以冰筏为载体融冰落石成因。     

河西走廊最近一次强沙尘暴的调查分析

1996年5月29~31日在甘肃河西走廊又出现了一次强沙尘暴天气。从这次强沙尘暴和1993年"5·5"强沙尘暴的比较分析可知,春季在河西走廊周围易形成以沙漠为中心的高温低压区,与西西伯利亚向东南方向移动的高压冷气流形成明显的气压梯度,这就是大风的动力源。大风前期,在气温、压温比等方面有明显的预兆,由此可进行强沙尘暴的预测预报。     

Potential promoted productivity and spatial patterns of medium- and low-yield cropland land in China

With a continuously increasing population and better food consumption levels, improving the efficiency of arable land use and increasing its productivity have become fundamental strategies to meet the growing food security needs in China. A spatial distribution map of medium- and low-yield cropland is necessary to implement plans for cropland improvement. In this study, we developed a new method to identify high-, medium-, and low-yield cropland from Moderate Resolution Imaging Spectroradiometer (MODIS) data at a spatial resolution of 500 m. The method could be used to reflect the regional heterogeneity of cropland productivity because the classification standard was based on the regionalization of cropping systems in China. The results showed that the proportion of high-, medium-, and low-yield cropland in China was 21%, 39%, and 40%, respectively. About 75% of the low-yield cropland was located in hilly and mountainous areas, and about 53% of the high-yield cropland was located in plain areas. The five provinces with the largest area of high-yield cropland were all located in the Huang-Huai-Hai region, and the area amounted to 42% of the national high-yield cropland area. Meanwhile, the proportion of high-yield cropland was lower than 15% in Heilongjiang, Sichuan, and Inner Mongolia, which had the largest area allocated to cropland in China. If all the medium-yield cropland could be improved to the productive level of high-yield cropland and the low-yield cropland could be improved to the level of medium-yield cropland, the total productivity of the land would increase 19% and 24%, respectively.     

东南极埃默里冰架东缘赖茵博尔特丘陵构造变形过程及其构造意义

对赖茵博尔特丘陵地区的构造变形过程分析表明,该地区发育4期主要构造变形.D1期主要是区域性近EW向片麻理形成阶段,其变形时代为＞970 Ma;D2期是在正片麻岩形成了近EW向轴面陡立韧性剪切褶皱,以及剪切面理上发育的各种紧闭不对称褶皱和低角度拉伸线理,其变形时代为新元古代早期.D3期变形发生在寒武纪早期,以构造抬升至地...     

基于小波分析的汾河河津站径流与输沙的多时间尺度特征

基于汾河流域19个气象台站1959~2005年的月均降水量、河津站的径流量和输沙量资料,借助小波分析方法研究了降水、径流与输沙序列的多时间尺度特征及它们的耦合关系。结果表明:降水、径流与输沙量具有2~4a、14~18 a左右2个不同尺度的周期变化,且三者的主周期基本一致,即3 a和16 a;3 a尺度上,3个要素曲线的正、负位相交替频繁,突变点较多,且曲线变化除个别时段发生紊乱外基本上保持同步性;16 a尺度上,突变点较少,3条曲线的正、负位相交替相应减少且出现不同步现象。降水、径流与输沙量曲线发生趋势变化及出现不同步现象的原因包括自然因素和人类活动,而后者是其主要影响因素。