Changes in soil and vegetation on moving sand dunes after exclosure in Horqin Sandy Land, Northern China

In the semiarid Horqin Sandy Land of northern China, land desertification is the main causation in vegetation degradation and formation of moving dunes. A study was conducted from 1996 to 2005 to monitor the changes of vegetation characteristics and soil properties after moving dunes were fenced. The changes were compared between moving sand dunes with exclosure and without exclosure to evaluate the effectiveness of vegetation and soil restoration after exclosure establishment. The results show that exlosure establishment facilitated the colonization and development of plant species by ameliorating stressful environmental conditions. Species diversity, average coverage, and plant density significantly increased after exclosure of moving sand dunes along sequence compared with sand dunes without exclosure. Vegetation recovery on moving sand dunes accelerated by exclosure resulted in significant changes in soil properties including increased silt and clay contents, organic C and total N and decreased sand content, especially at the 0-5 cm depth. The results implied that moving sand dunes can be rapidly fixed by construction of exclosure.     

上海淤泥质潮滩潮锋作用及其形成机制初步探讨*

本文具体讨论了上海淤泥质潮滩的潮锋作用过程,定性给出了潮锋的形成机制,认为潮锋作用及其水体高含沙量现象的本质在于“潮锋带水体水流加速效应”,即,由于潮滩坡面变化平缓的特殊性,涨潮水体前锋沿程存在着一持续时间可达数十分钟的水流加速过程.最后,本文初步探讨了潮锋作用在滩面塑造过程中的地位,并重新定义了潮锋作用的内容.     

城市投资环境的评价模型及应用

本文在对投资单元的量化,评价指标的选择及量化进行探讨的基础上,提出了专家得分和模糊评价二种投资评价模型,并以宁波市为例进行了应用.     

Cluster卫星观测的中高度极隙区中场向电流引起的磁场的扰动变化

本文分析了2002年9月10日Cluster四颗卫星穿越南极和北极极隙区期间的观测资料。这两次穿越是在弱而稳定的南向行星际磁场(IMF)条件下发生的。数据显示极隙区中的场向电流(FACs)引起了大的磁场扰动。本文采用了一种基于卫星多点测量来计算扰动界面方向和运动速度的方法。结果显示界面与磁力线大致平行,而它们的速度在卫星穿越南极极隙区时几乎朝向晨侧,在穿越北极极隙区时几乎朝向昏侧,并且其运动速度与相应卫星的速度相比其值很小。     

Quaternary geomorphological evolution of the Kunlun Pass area and uplift of the Qinghai-Xizang (Tibet) Plateau

There is a set of Late Cenozoic sediments in the Kunlun Pass area, Tibetan Plateau, China. Paleomagnetic, ESR and TL dating suggest that they date from the Late Pliocene to the Early Pleistocene. Analyses of stratigraphy, sedimentary characteristic, and evolution of the fauna and flora indicate that, from the Pliocene to the early Quaternary (about 5–1.1 Ma BP), there was a relatively warm and humid environment, and a paleolake occurred around the Kunlun Pass. The elevation of the Kunlun Pass area was no more than 1500 m, and only one low topographic divide existed between the Qaidam Basin and the Kunlun Pass Basin. The geomorphic pattern in the Kunlun Pass area was influenced by the Kunlun–Yellow River Tectonic Movement 1.1–0.6 Ma BP. The Wangkun Glaciation (0.7–0.5 Ma) is the maximum Quaternary glaciation in the Pass and in other areas of the Plateau. During the glaciation, the area of the glaciers was 3–5 times larger than that of the present glacier in the Pass area. There was no Xidatan Valley that time. The extreme geomorphic changes in the Kunlun Pass area reflect an abrupt uplift of the Tibet Plateau during the Early and Middle Pleistocene. This uplift of the Plateau has significance on both the Plateau itself and the surrounding area.     

Process and mechanism of arable land change in Hebei Province during the past 50 years

1 Introduction Arable land is the core of land resources and its dynamic change seriously affects regional sustainable development. Hebei Province, with a large population, is an agricultural province. With the highspeed economic development, population growth and urbanization, a great amount of arable land has been lost and the land shortage has become more serious. Therefore, arable land change and its driving forces should be studied in order to realize the sustainable agricultural develo…     

黄河流域水循环研究的进展和展望

总结了黄河流域水循环研究的进展,指出缺乏立足于水循环整体的机理过程的探讨及缺乏较成熟的流域水文模型是已有研究的不足。为能更好地模拟水文过程对各种作用力的响应,今后研究的方向将是建立既考虑垂向水分和能量传输(如降水,蒸发,感热),又考虑水平向的地表水分运动(汇流)和地下水基流过程的黄河流域的分布式水文模型。模型将结合遥感信息与地面资料,建立与区域大气环流模式(GCM)的接口,辅之以野外生态试验小区、径流试验场和室内试验的资料,以深入探索黄河流域水循环动力学机制     

低山丘陵区土地利用方式对土壤质量的影响—以河北省遵化市为例

通过调查河北省遵化市低山丘陵区油松林、板栗、草地和坡耕地等典型土地利用方式对土壤养分和土壤容重的影响，土地取样取土壤表层0-20cm，结果表明，森林的砍伐以及随后的耕种显著增加了土壤容重并降低了大部分土壤养分。和林地相比，草地、当年开垦的农地、板栗和耕种3年的农地容重分别增加了13.3%，14.2%,27.5%,39.7%。除全磷外，板栗和耕种3年的农地土壤养分有显著下降，和林地相比，板栗有机质减少了60.7%，全氮减少了35.6%，全钾减少了21.3%，速效钾减少了57%；耕种3年的农地土壤有机质、全氮、全钾和速效钾则分别减少了62.9%,52.6%,31%和60%。土壤退化指数的计算结果表明板栗和耕种3年的农地土壤发生了较为严重的退化。     

阿瓦提县地下水水化学特征及成因初探

在大量的实测资料和参考资料的基础上，从第四纪地质演化史的角度，运用同位素方法理论，详细阐述了该地区地下水的水化学现状特征及在平面上和垂向上的变化规律，并对其水化学特征的形成机理进行了较为深入的分析、研究，得出了该地区地下水化学演化史，从而为当地的地下水资源开发提供了借鉴，并提出了水资源开发中注意的问题。     

1980年夏季我国天气气候反常和St.Helens火山爆发的影响

1980年5月18日St.Helens火山大爆发,大量火山灰喷入平流层,围绕北半球中纬度带飘浮.在30°N以北我国东部各站晴空直接辐射量(S)从6月上旬开始异常偏低,夏季S达到近二十余年来的最低值,夏季中纬度S的经向梯度异常增大;相应地,西太平洋副高及北侧的季风雨带在7-8月异常偏南,形成了我国严重的北旱南涝以及江淮冷夏等反常天气气候.本文现就此作物理分析.