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21.
科尔沁沙地巴克窑地区近150年的环境演变* 总被引:3,自引:1,他引:3
在沉积和花粉分析的基础上,对科尔沁沙地东南部巴克窑地区过去150年的植被和环境演变进行了重建。巴克窑等湖泡的诞生时间是在上个世纪前期,约1837年前后。这个时间也正是科尔沁沙地东南部地区首次大规模人口移入和垦荒年代。突然增加的人类活动导致了沙丘植被的迅速破坏,而植被减少和沙丘活化引起区域水文循环的重新调整,即原来通过植物蒸腾作用输出的水量明显减弱,致使地下潜水位上升,形成一系列湖泡。以后,沙地系统的演化主要是在人类活动、气候和系统内部反馈机制的共同作用下完成的。 相似文献
22.
将区域地球化学资料应用于农业问题的研究,是扩大区域地球化学资料应用领域的重要方面之一。通过土壤中Cu、Zn、Fe、Mn、Co元素的全量、有效量、pH值、有机质与作物产量之间关系的研究,发现元素有效量与土壤中元素全量呈正相关,与pH值呈负相关,与有机质呈正相关,而作物产量与元素有效量呈正相关 相似文献
23.
熔体及其活动在造山带的演化中发挥了重要作用。熔体活动发迹了地壳应力作用方式而诱发形成剪切带或断层;熔体活动调整块体间的位移而影响造山带的变形; 相似文献
24.
我国北方农牧交错带的环境演变 总被引:60,自引:2,他引:60
中国北方农牧交错带在10~8.5kaB.P.经历了三次阶段性增暖后进入全新世暖期。8.5~8.0kaB.P.和4~3.5kaB.P.暖期的开始与结束事件中降水变化落后于温度变化300~500a;暖期盛期时的年均温较现代高2~3℃,降水多100mm左右;暖期中存在多次短期寒冷事件,年均温最冷时较现代低3℃以上。3.5kaB.P.以来冷干趋势之上叠加着大致由300a稳定与500a波动构成的约800a的周期性变化。全新世暖期原始农业文化的阶段性发展与暖期内环境波动相对应;暖期结束时发生了由农业向牧业文化转换的事件;暖期以后的冷干期为农牧交错文化时期,农业经济随冷干程度的变化而兴衰 相似文献
25.
26.
基于MapGIS构建上海及邻近海域地震和新构造活动数据库。该数据库由空间和属性两大数据库组成。其中,空间数据库包括地理底图库及地震、活动断裂、新生代盆地、岩浆岩分布多个专题图库;属性数据库主要针对专题图库而建立,有地震属性库、活动断裂属性库及新生代盆地属性库。通过图形数据结构和属性数据结构共有的标识码实现图形数据库和属性数据库之间的连接。为方便查询检索,对重要的属性数据如断裂走向、地震震级等以编码方式表示。该数据库的建立为定量研究和评价本区地震与新构造活动的关系,以及防震减灾提供了重要的科学依据。 相似文献
27.
Water and water related matters are important issues in water scarce countries like the Republic of South Africa. This is
especially true for the agricultural sector that relies heavily on the availability of water for irrigation to ensure a secure
food supply. In South Africa, present day irrigation projects rely on government subsidies and are usually large undertakings
beyond the reach of individuals or small communities. The sustainability of such large irrigation projects is still a matter
of debate. A 100 years ago a different set of rules applied. Irrigation could only be achieved by hand-dug furrows that supplied
water in relatively small quantities to small farming communities. This paper investigated such a small community, the Leeukloof
farming community in the Western Cape Province of the Republic of South Africa. For the past 93 years this community has maintained
a furrow that supplies water not only to farms bordering the Perdeberg River, which supplies the furrow with water, but also
to farms not bordering the river. The authors try to reconstruct the changes in agricultural practices brought about by the
furrow, methods of water extraction during each phase, as well as the development and role of the furrow system. The perception
by the community of the necessity of this method of water extraction from the river system is also investigated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
28.
The seasonal and interannual variations of Beijing urban heat island (UHI) are investigated in this paper using the temperature data from 1960 to 2000 at 20 meteorological stations in the Beijing region, and then the relationship between the intensity and spatial scale of UHI and Beijing urbanization indices is analyzed and discussed. Main conclusions are the followings. First, Beijing UHI shows obvious seasonal variations, and it is strongest in winter, next in spring and autumn, and least in summer. The seasonal variation of the UHI mainly occurs in the urban area. The UHI intensity at the center of Beijing is more than 0.8℃ in winter, and only 0.5℃ in summer. Second, the intensity of Beijing HUI exhibits a clear interannual warming trend with its mean growth rate (MGR) being 0.3088℃/10 a. The MGR of HUI is largest in winter, next in spring and autumn, and least in summer, and the urban temperature increase makes a major contribution to the growth of HUI intensity. Third, since the Reform and Opening, the urbanization indices have grown several ten times or even one hundred times, the intensity of HUI has increased dramatically, and its spatial scale also expanded distinctively along with the expansion of urban architectural complexes. Fourth, the interannual variation of urbanization indices is very similar with that of HUI intensity, and their linear correlation coefficients are significant at a more than 0.001 confidence level. 相似文献
29.
This paper describes palynological evidence for what appears to be comparatively large-scale human impact in the catchment of the Sungai Niah in the wet tropical lowland swamp forests of Sarawak, Malaysian Borneo close to the Great Cave of Niah. Pollen associated with cleared landscapes and rice cultivation is evident in the sedimentary record from before 6000 cal yr B.P. Human activity seems to have been associated with changes in sedimentary regime, with peat-dominated environments being replaced diachronously by clay-dominated deposition. This may reflect anthropogenic soil erosion in the catchment of the Sungai Niah. 相似文献
30.